Search results for: Poincaré section

Authors: Ephrem Getahun, Shengwen Qi, Songfeng Guo, Yu Zou, Melesse Alemayehu

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Residual shear characteristics of slide soil profile sections (SSPS) were examined using ring shear tests to know the relative residual shear behaviors among the sections of slide soil. The multistage-multiphase shearing techniques were employed to perform the experiment for each soil specimen continuously towards large displacements. The grain distribution analysis of SSPS samples was characterized by coarsening upward from bottom slip to the top sections; however, the slip surface was considered as a sheared zone that endorses their low shear resistance for failure. There is an average range of 1-2.5 mm axial displacement on each stage of loadings and phases of shearing that depicts the significant effect of dilation and compression of soil specimen. The middle section has the largest consolidation percentage (10-29%), and vertical displacement compared to other sections and showed high shear strengthening behavior having maximum shear stress of 189kPa at 240kPa loading compared to basal and top sections. It is found that the middle section of SSPS has relatively high shear resistance behavior for large displacement shearing. The residual shear assessment indicates that there is a significant influence of large displacement and rate on the friction coefficient behaviors; it resulted in shear weakening effect to attain their residual condition.

Keywords: comparison, displacements, residual shear stress, shear behavior, slide soils

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Authors: Bartosz Olszanski, Zbigniew Nosal, Jacek Rokicki

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An experimental study of cold-jet (nitrogen) reaction control jet system has been carried out to investigate the flow control efficiency for low to moderate jet pressure ratios (total jet pressure p0jet over free stream static pressure in the wind tunnel p∞) and different angles of attack for infinite Mach number equal to 2. An investigation of jet influence was conducted on a flat plate geometry placed in the test section of intermittent supersonic wind tunnel of Department of Aerodynamics, WUT. Various convergent jet nozzle geometries to obtain different jet momentum ratios were tested on the same test model geometry. Surface static pressure measurements, Schlieren flow visualizations (using continuous and photoflash light source), load cell measurements gave insight into the supersonic crossflow interaction for different jet pressure and jet momentum ratios and their influence on the efficiency of side jet control as described by the amplification factor (actual to theoretical net force generated by the control nozzle). Moreover, the quasi-steady numerical simulations of flow through the same wind tunnel geometry (convergent-divergent nozzle plus test section) were performed using ANSYS Fluent basing on Reynolds-Averaged Navier-Stokes (RANS) solver incorporated with k-ω Shear Stress Transport (SST) turbulence model to assess the possible spurious influence of test section walls over the jet exit near field area of interest. The strong bow shock, barrel shock, and Mach disk as well as lambda separation region in front of nozzle were observed as images taken by high-speed camera examine the interaction of the jet and the free stream. In addition, the development of large-scale vortex structures (counter-rotating vortex pair) was detected. The history of complex static pressure pattern on the plate was recorded and compared to the force measurement data as well as numerical simulation data. The analysis of the obtained results, especially in the wake of the jet showed important features of the interaction mechanisms between the lateral jet and the flow field.

Keywords: flow visualization techniques, pressure measurements, reaction control jet, supersonic cross flow

Procedia PDF Downloads 299

Authors: Gangacharyulu Dasaroju, Sumeet Sharma, Sanjay Singh

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Heat pipe is characterised as superconductor of heat because of its excellent heat removal ability. The operation of several engineering system results in generation of heat. This may cause several overheating problems and lead to failure of the systems. To overcome this problem and to achieve desired rate of heat dissipation, there is need to study the performance of heat pipe with annular fins under free convection at different inclinations. This study demonstrates the effect of different mass flow rate of hot fluid into evaporator section on the condenser side heat transfer coefficient with annular fins under natural convection at different inclinations. In this study annular fins are used for the experimental work having dimensions of length of fin, thickness of fin and spacing of fin as 10 mm, 1 mm and 6 mm, respectively. The main aim of present study is to discover at what inclination angles the maximum heat transfer coefficient shall be achieved. The heat transfer coefficient on the external surface of heat pipe condenser section is determined by experimental method and then predicted by empirical correlations. The results obtained from experimental and Churchill and Chu relation for laminar are in fair agreement with not more than 22% deviation. It is elucidated the maximum heat transfer coefficient of 31.2 W/(m²-K) at 25˚ tilt angle and minimal condenser heat transfer coefficient of 26.4 W/(m²-K) is seen at 45˚ tilt angle and 200 ml/min mass flow rate. Inclination angle also affects the thermal performance of heat pipe. Beyond 25^o inclination, heat transport rate starts to decrease.

Keywords: heat pipe, annular fins, natural convection, condenser heat transfer coefficient, tilt angle

Procedia PDF Downloads 154

Authors: Mokhtari Karchegani Amir, Maboudi Samad, Azadi Reza, Dastanian Raoof

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Marun's petrochemical cracking furnaces have a very comprehensive operating control system for combustion and related equipment, utilizing advanced instrument circuits. However, after several years of operation, numerous problems arose in the pyrolysis furnaces. A team of experts conducted an audit, revealing that the furnaces were over-designed, leading to excessive consumption of air and fuel. This issue was related to the burners' shutter settings, which had not been configured properly. The operations department had responded by increasing the induced draft fan speed and forcing the instrument switches to counteract the wind effect in the combustion chamber. Using Fluent and Gambit software, the furnaces were analyzed. The findings indicated that this situation elevated the convection part's temperature, causing uneven heat distribution inside the furnace. Consequently, this led to overheating in the convection section and excessive cracking within the coils in the radiation section. The increased convection temperature damaged convection parts and resulted in equipment blockages downstream of the furnaces due to the production of more coke and tar in the process. To address these issues, corrective actions were implemented. The excess air for burners and combustion chambers was properly set, resulting in improved efficiency, reduced emissions of environmentally harmful gases, prevention of creep in coils, decreased fuel consumption, and lower maintenance costs.

Keywords: furnace, coke, CFD analysis, over cracking

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Authors: Dana J. Abed, Mu'tasim S. Abdel-Jaber, Nasim K. Shatarat

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In this paper, an experimental study on twelve square columns was conducted to investigate the influence of cross-sectional size on axial compressive capacity of carbon fiber reinforced polymers (CFRP) wrapped square reinforced concrete (RC) short columns subjected to eccentric loadings. The columns were divided into three groups with three cross sections (200×200×1200, 250×250×1500 and 300×300×1800 mm). Each group was tested under two different eccentricities: 10% and 20% of the width of samples measured from the center of the column cross section. Four columns were developed in each arrangement. Two columns in each category were left unwrapped as control samples, and two were wrapped with one layer CFRP perpendicular to the specimen surface. In general; CFRP sheets has enhanced the performance of the strengthened columns compared to the control columns. It was noticed that the percentage of compressive capacity enhancement was decreased by increasing the cross-sectional size, and increasing loading eccentricity generally leads to reduced load bearing capacity in columns. In the same group specimens, when the eccentricity increased the percentage of enhancement in load carrying capacity was increased. The study concludes that the optimum use of the CFRP sheets for axial strength enhancement is for smaller cross-section columns under higher eccentricities.

Keywords: CFRP, columns, eccentric loading, cross-sectional

Procedia PDF Downloads 175

Authors: Hamid Reza Mahdipoor, Mehdi Bahrami, Mohammad Bodaghi, Seyed Ali Akbar Mansoori

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Nowadays, with stricter limitations to reduce emissions, considerable penalties are imposed if pollution limits are exceeded. Therefore, refineries, along with focusing on improving the quality of their products, are also focused on producing products with the least environmental impact. The duty of the sulfur recovery unit (SRU) is to convert H₂S gas coming from the upstream units to elemental sulfur and minimize the burning of sulfur compounds to SO₂. The Claus process is a common process for converting H₂S to sulfur, including a reaction furnace followed by catalytic reactors and sulfur condensers. In addition to a Claus section, SRUs usually consist of a tail gas treatment (TGT) section to decrease the concentration of SO₂ in the flue gas below the emission limits. To operate an SRU properly, the flow rate of combustion air to the reaction furnace must be adjusted so that the Claus reaction is performed according to stoichiometry. Accurate control of the air demand leads to an optimum recovery of sulfur during the flow and composition fluctuations in the acid gas feed. Therefore, the major control system in the SRU is the air demand control loop, which includes a feed-forward control system based on predetermined feed flow rates and a feed-back control system based on the signal from the tail gas online analyzer. The use of online analyzers requires compliance with the installation and operation instructions. Unfortunately, most of these analyzers in Iran are out of service for different reasons, like the low importance of environmental issues and a lack of access to after-sales services due to sanctions. In this paper, an SRU in Iran was simulated and calibrated using industrial experimental data. Afterward, the effect of the malfunction of the online analyzer on the performance of SRU was investigated using the calibrated simulation. The results showed that an increase in the SO₂ concentration in the tail gas led to an increase in the temperature of the reduction reactor in the TGT section. This increase in temperature caused the failure of TGT and increased the concentration of SO₂ from 750 ppm to 35,000 ppm. In addition, the lack of a control system for the adjustment of the combustion air caused further increases in SO₂ emissions. In some processes, the major variable cannot be controlled directly due to difficulty in measurement or a long delay in the sampling system. In these cases, a secondary variable, which can be measured more easily, is considered to be controlled. With the correct selection of this variable, the main variable is also controlled along with the secondary variable. This strategy for controlling a process system is referred to as inferential control" and is considered in this paper. Therefore, a sensitivity analysis was performed to investigate the sensitivity of other measurable parameters to input disturbances. The results revealed that the output temperature of the first Claus reactor could be used for inferential control of the combustion air. Applying this method to the operation led to maximizing the sulfur recovery in the Claus section.

Keywords: sulfur recovery, online analyzer, inferential control, SO₂ emission

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Authors: Mclee Kerolle

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For more than 50 years, the state of Hawaii has had the beginnings of a burgeoning commercial aerospace presence statewide. While Hawaii provides the aerospace industry with unique assets concerning geographic location, lack of range safety issues and other factors critical to aerospace development, Hawaii’s strategy and commitment for aerospace have been unclear. For this reason, this paper presents a comparative analysis of Hawaii’s space sector with two of the world’s leading space sectors, Colorado and the Netherlands, in order to provide a strategic plan that establishes a firm position going forward to support Hawaii’s aerospace development statewide. This plan will include financial and other economic incentives legislatively supported by the State to help grow and diversify Hawaii’s aerospace sector. The first part of this paper will examine the business model adopted by the Colorado Space Coalition (CSC), a group of industry stakeholders working to make Colorado a center of excellence for aerospace, as blueprint for growth in Hawaii’s space sector. The second section of this paper will examine the business model adopted by the Netherlands Space Business Incubation Centre (NSBIC), a European Space Agency (ESA) affiliated program that offers business support for entrepreneurs to turn space-connected business ideas into commercial companies. This will serve as blueprint to incentivize space businesses to launch and develop in Hawaii. The third section of this paper will analyze the current policies both CSC, and NSBIC implores to promote industry expansion and legislative advocacy. The final section takes the findings from both space sectors and applies their most adaptable features to a Hawaii specific space business model that takes into consideration the unique advantage and disadvantages found in developing Hawaii’s space sector. The findings of this analysis will show that the development of a strategic plan based on a comparative analysis that creates high technology jobs and new pathways for a trained workforce in the space sector, as well as elicit state support and direction, will achieve the goal of establishing Hawaii as a center of space excellence. This analysis will also serve as a signal to the federal, private sector and international community that Hawaii is indeed serious about developing its’ aerospace industry. Ultimately this analysis and subsequent aerospace development plan will serve as a blueprint for the benefit of all space-faring nations seeking to develop their space sectors.

Keywords: Colorado, Hawaii, Netherlands, space policy

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Authors: Pyi Phyo Maung

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In the study, the calculations of the permeability coefficient, values of the volume and porosity of a unit cell of a woven fabric before and after deformation based on the geometrical parameters are presented. Two types of carbon woven fabric structures were investigated: standard type, which integrated the filament, has a cross sectional shape of a cylinder and spread tow type, which has a rectangular cross sectional shape. The space antennas reflector, which distinctive feature is the presence of the surface of double curvature, is considered as the object of the research. Modeling of the kinetics of the process of impregnation of the reflector for the two types of carbon fabric’s unit cell structures was performed using software RAM-RTM. This work also investigated the influence of the grid angle between warp and welt of the unit cell on the duration of impregnation process. The results showed that decreasing the angle between warp and welt of the unit cell, the decreasing of the permeability values were occurred. Based on the results of calculation samples of the reflectors, their quality was determined. The comparisons of the theoretical and experimental results have been carried out. Comparison of the two textile structures (standard and spread tow) showed that the standard textiles with circular cross section were impregnated faster than spread tows, which have a rectangular cross section.

Keywords: vacuum assistant resin infusion, impregnation time, shear angle, reflector and modeling

Procedia PDF Downloads 273

Authors: Kamaljit Singh Sokhal, Gangacharyulu Dasoraju, Vijaya Kumar Bulasara

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Biopolymers are popular in many areas, like petrochemicals, food industry and agriculture due to their favorable properties like environment-friendly, availability, and cost. In this study, a biopolymer gum Arabic was used to find its effect on the pressure drop at various concentrations (100 ppm – 300 ppm) with various Reynolds numbers (10000 – 45000). A rheological study was also done by using the same concentrations to find the effect of the shear rate on the shear viscosity. Experiments were performed to find the effect of injection of gum Arabic directly near the boundary layer and to investigate its effect on the maximum possible drag reduction. Experiments were performed on a test section having i.d of 19.50 mm and length of 3045 mm. The polymer solution was injected from the top of the test section by using a peristaltic pump. The concentration of the polymer solution and the Reynolds number were used as parameters to get maximum possible drag reduction. Water was circulated through a centrifugal pump having a maximum 3000 rpm and the flow rate was measured by using rotameter. Results were validated by using Virk's maximum drag reduction asymptote. A maximum drag reduction of 62.15% was observed with the maximum concentration of gum Arabic, 300 ppm. The solution was circulated in the closed loop to find the effect of degradation of polymers with a number of cycles on the drag reduction percentage. It was observed that the injection of the polymer solution in the boundary layer was showing better results than premixed solutions.

Keywords: drag reduction, shear viscosity, gum arabic, injection point

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Authors: M. N. Yahaya, K. A. Salako, U. Z. Magawata

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Vertical electrical sounding (VES) method was used to investigate the groundwater potential at the southern part of Gulumbe district, Kebbi State, north-western part of Nigeria. The study was carried out with the aim of determining the subsurface layer’s parameters (resistivity and thickness) and uses the same to characterize the groundwater potential of the study area. The Schlumberger configuration was used for data acquisition. A total number of thirty-three (33) sounding points (VES) were surveyed over six profiles. The software IPI2WIN was used to obtain n-layered geo-electric sections. The geo-electric section drawn from the results of the interpretation revealed that three subsurface layers could be delineated, which comprise of top soil, sand, sandstone, coarse sand, limestone, and gravelly sand. The results of the resistivity sounding were correlated with the lithological logs of nearby boreholes that expose cross-section geologic units around the study area. We found out that the area is dominated by three subsurface layers. The coarse sand layers constituted the aquifer zones in the majority of sounding stations. Thus, this present study concluded that the depth of any borehole in the study area should be located between the depth of 18.5 to 39 m. The study further classified the VES points penetrated based on their conductivity content as highly suitable, suitable, moderately suitably, and poor zones for groundwater exploration. Hence, from this research, we recommended that boreholes can be sited in high conductivity zones across VES 2, 11, 13, 16, 20, 21, 27, and 33, respectively.

Keywords: vertical electrical sounding, resistivity, geo-electric, resistivity, aquifer and groundwater

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Authors: Marijan KovačIć, Davor Pavelić, Darko Tibljaš, Ivo Galić, Frane Marković, Ivica PavičIć

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The North Croatian Basin (NCB) occupies the southwestern part of the Pannonian Basin System and belongs to the Central Paratethys realm. In a quarry near the village of Poljanska, on the southern slopes of Mt. Papuk in eastern Croatia, a 40-meter-thick section is exposed, consisting of well-bedded, mixed, carbonate-siliciclastic deposits with occurrences of pyroclastics. Sedimentological investigation indicates that a salina lake developed in the central NCB during the late early Miocene. Field studies and mineralogical and petrological analyses indicate that alternations of laminated crypto- characterize the lower part of the section to microcrystalline dolomite and analcimolite (sedimentary rocks composed essentially of authigenic analcime) associated with tuffites and marls. The pyroclastic material is a product of volcanic activity at the end of the early Miocene, while the formation of analcime, the zeolite group mineral, is a result of an alteration of pyroclastic material in an alkaline lacustrine environment. These sediments were deposited in a shallow, hydrologically closed lake that was controlled by an arid climate during the first phase of its development. The middle part of the section consists of dolomites interbedded with analcimolites and sandstones. The sandstone beds are a result of the increased supply of clastic material derived from the locally uplifted metamorphic and granitoid basement. The emplacement of sandstones and dolomites reflects a distinct alternation of hydrologically open and closed lacustrine environments controlled by the frequent alternation of humid and arid climates, representing the second phase of lake development. The siliciclastics of the third phase of lake development were deposited during the Middle Miocene in a hydrologically mostly open lake. All lacustrine deposition coincides with the Miocene Climatic Optimum, which was characterized by a hot and warm climate. The sedimentological data confirm the mostly wet conditions previously identified by paleobotanical studies in the region. The exception is the relatively long interval of arid climate in the late early Miocene that controlled the first phase of lake evolution, i.e., the salina-type lake.

Keywords: early Miocene, Pannonian basin System, pyroclastics, salina-type lake

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Authors: Hafsat Iyabo Sa'adu

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A salient feature of the Nigerian Tax Law is the right of the taxpayer to demand for a refund where excess tax is paid. Section 23 of the Federal Inland Revenue Service (Establishment) Act, 2007 vests Federal Inland Revenue Services with the power to make tax refund as well as set guidelines and requirements for refund process from time to time. In addition, Section 61 of the Federal Inland Revenue Service (Establishment) Act, 2007, empowers the Federal Inland Revenue Services to issue information circular to acquaint stakeholders with the policy on the refund process. A Circular was issued to that effect to correct the position that until after the annual audit of the Service before such excess can be paid to the claimant/taxpayer. But it is amazing that such circular issuance does not feature under the states’ laws. Hence, there is an inconsistencies in the tax paying system in Nigeria. This study, therefore, sets an objective, to examine the trending concept of tax refund in Nigeria. In order to achieve this set objective, a doctrinal study went under way, wherein both federal and states laws were consulted including journals and textbooks. At the end of the research, it was revealed that the law should be specific as to the time frame within which to make the refund. It further revealed that it is essential to put up a legal framework for the tax system to recognize excess payment as debt due from the state. This would provide a foundational framework for the relationship between taxpayers and Federal Inland Revenue Service as well as promote effective tax administration in all the states of the federation. Several Recommendations were made especially relating to legislative passage of ‘’Refund Circular Bill at the states levels’ pursuant to the Federal Inland Revenue Service (Establishment) Act, 2007.

Keywords: claim, Nigeria, refund, right

Procedia PDF Downloads 118

Authors: Chee Wai Ku, Pui See Chin

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As an emerging alternative to hysterectomy, uterine artery embolization (UAE) has been widely used in the management of fibroids and in controlling postpartum hemorrhage (PPH) unresponsive to other therapies. Research has shown UAE to be a safe, minimally invasive procedure with few complications and minimal effects on future fertility. We present two cases highlighting the use of UAE in preventing PPH in a patient with a large fibroid at the time of cesarean section and in the treatment of secondary PPH refractory to other therapies in another patient. We present a 36-year primiparous woman who booked at 18+6 weeks gestation with a 13.7 cm subserosal fibroid at the lower anterior wall of the uterus near the cervix and a 10.8 cm subserosal fibroid in the left wall. Prophylactic internal iliac artery occlusion balloons were placed prior to the planned classical midline cesarean section. The balloons were inflated once the baby was delivered. Bilateral uterine arteries were embolized subsequently. The estimated blood loss (EBL) was 400 mls and hemoglobin (Hb) remained stable at 10 g/DL. Ultrasound scan 2 years postnatally showed stable uterine fibroids 10.4 and 7.1 cm, which was significantly smaller than before. We present the second case of a 40-year-old G2P1 with a previous cesarean section for failure to progress. There were no antenatal problems, and the placenta was not previa. She presented with term labour and underwent an emergency cesarean section for failed vaginal birth after cesarean. Intraoperatively extensive adhesions were noted with bladder drawn high, and EBL was 300 mls. Postpartum recovery was uneventful. She presented with secondary PPH 3 weeks later complicated by hypovolemic shock. She underwent an emergency examination under anesthesia and evacuation of the uterus, with EBL 2500mls. Histology showed decidua with chronic inflammation. She was discharged well with no further PPH. She subsequently returned one week later for secondary PPH. Bedside ultrasound showed that the endometrium was thin with no evidence of retained products of conception. Uterotonics were administered, and examination under anesthesia was performed, with uterine Bakri balloon and vaginal pack insertion after. EBL was 1000 mls. There was no definite cause of PPH with no uterine atony or products of conception. To evaluate a potential cause, pelvic angiogram and super selective left uterine arteriogram was performed which showed profuse contrast extravasation and acute bleeding from the left uterine artery. Superselective embolization of the left uterine artery was performed. No gross contrast extravasation from the right uterine artery was seen. These two cases demonstrated the superior efficacy of UAE. Firstly, the prophylactic use of intra-arterial balloon catheters in pregnant patients with large fibroids, and secondly, in the diagnosis and management of secondary PPH refractory to uterotonics and uterine tamponade. In both cases, the need for laparotomy hysterectomy was avoided, resulting in the preservation of future fertility. UAE should be a consideration for hemodynamically stable patients in centres with access to interventional radiology.

Keywords: fertility preservation, secondary postpartum hemorrhage, uterine embolization, uterine fibroids

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Authors: Sara Bilal, Abdi Omar Shuriye, Raihan Othman

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Numerical Methods is a course that can be conducted using workshops and group discussion. This study has been implemented on undergraduate students of level two at the Faculty of Engineering, International Islamic University Malaysia. The Numerical Method course has been delivered to two Sections 1 and 2 with 44 and 22 students in each section, respectively. Systematic steps have been followed to apply the student centered learning approach in teaching Numerical Method course. Initially, the instructor has chosen the topic which was Euler’s Method to solve Ordinary Differential Equations (ODE) to be learned. The students were then divided into groups with five members in each group. Initial instructions have been given to the group members to prepare their subtopics before meeting members from other groups to discuss the subtopics in an expert group inside the classroom. For the time assigned for the classroom discussion, the setting of the classroom was rearranged to accommodate the student centered learning approach. Teacher strength was by monitoring the process of learning inside and outside the class. The students have been assessed during the migrating to the expert groups, recording of a video explanation outside the classroom and during the final examination. Euler’s Method to solve the ODE was set as part of Question 3(b) in the final exam. It is observed that none of the students from both sections obtained a zero grade in Q3(b), compared to Q3(a) and Q3(c). Also, for Section 1(44 students), 29 students obtained the full mark of 7/7, while only 10 obtained 7/7 for Q3(a) and no students obtained 6/6 for Q3(c). Finally, we can recommend that the Numerical Method course be moved toward more student-centered Learning classrooms where the students will be engaged in group discussion rather than having a teacher one man show.

Keywords: teacher centered learning, student centered learning, mathematic, numerical methods

Procedia PDF Downloads 366

Authors: Jin Liang, James H. Liu, Ti-Jun Xiao

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It is known that there exist many physical phenomena where abrupt or impulsive changes occur either in the system dynamics, for example, ad-hoc network, or in the input forces containing impacts, for example, the bombardment of space antenna by micrometeorites. There are many other examples such as ultra high-speed optical signals over communication networks, the collision of particles, inventory control, government decisions, interest changes, changes in stock price, etc. These are impulsive phenomena. Hence, as a combination of the traditional initial value problems and the short-term perturbations whose duration can be negligible in comparison with the duration of the process, the systems with impulsive conditions (i.e., impulsive systems) are more realistic models for describing the impulsive phenomenon. Such a situation is also suitable for the delay systems, which include some of the past states of the system. So far, there have been a lot of research results in the study of impulsive systems with delay both in finite and infinite dimensional spaces. In this paper, we investigate the periodicity of solutions to the nonautonomous impulsive evolution equations with infinite delay in Banach spaces, where the coefficient operators (possibly unbounded) in the linear part depend on the time, which are impulsive systems in infinite dimensional spaces and come from the optimal control theory. It was indicated that the study of periodic solutions for these impulsive evolution equations with infinite delay was challenging because the fixed point theorems requiring some compactness conditions are not applicable to them due to the impulsive condition and the infinite delay. We are happy to report that after detailed analysis, we are able to combine the techniques developed in our previous papers, and some new ideas in this paper, to attack these impulsive evolution equations and derive periodic solutions. More specifically, by virtue of the related transition operator family (evolution family), we present a Poincaré operator given by the nonautonomous impulsive evolution system with infinite delay, and then show that the operator is a condensing operator with respect to Kuratowski's measure of non-compactness in a phase space by using an Amann's lemma. Finally, we derive periodic solutions from bounded solutions in view of the Sadovskii fixed point theorem. We also present a relationship between the boundedness and the periodicity of the solutions of the nonautonomous impulsive evolution system. The new results obtained here extend some earlier results in this area for evolution equations without impulsive conditions or without infinite delay.

Keywords: impulsive, nonautonomous evolution equation, optimal control, periodic solution

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Authors: Robel Wondimu Alemayehu, Sihwa Jung, Manwoo Park, Young K. Ju

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Following the aftermath of the 1994 Northridge earthquake, intensive research on beam to column connections is conducted, leading to the current design basis. The current design codes require the use of either a prequalified connection or a connection that passes the requirements of large-scale cyclic qualification test prior to use in intermediate or special moment frames. The second alternative is expensive both in terms of money and time. On the other hand, the maximum beam depth in most of the prequalified connections is limited to 900mm due to the reduced rotation capacity of deeper beams. However, for long span beams the need to use deeper beams may arise. In this study, a beam to column connection detail suitable for deep beams is presented. The connection detail comprises of thicker-tapered beam flange adjacent to the beam to column connection. Within the thicker-tapered flange region, two reduced beam sections are provided with the objective of forming two plastic hinges within the tapered-thicker flange region. In addition, the length, width, and thickness of the tapered-thicker flange region are proportioned in such a way that a third plastic hinge forms at the end of the tapered-thicker flange region. As a result, the total rotation demand is distributed over three plastic zones. Making it suitable for deeper beams that have lower rotation capacity at one plastic hinge. The effectiveness of this connection detail is studied through finite element analysis. For the study, a beam that has a depth of 1200mm is used. Additionally, comparison with welded unreinforced flange-welded web (WUF-W) moment connection and reduced beam section moment connection is made. The results show that the rotation capacity of a WUF-W moment connection is increased from 2.0% to 2.2% by applying the proposed moment connection detail. Furthermore, the maximum moment capacity, energy dissipation capacity and stiffness of the WUF-W moment connection is increased up to 58%, 49%, and 32% respectively. In contrast, applying the reduced beam section detail to the same WUF-W moment connection reduced the rotation capacity from 2.0% to 1.50% plus the maximum moment capacity and stiffness of the connection is reduced by 22% and 6% respectively. The proposed connection develops three plastic hinge regions as intended and it shows improved performance compared to both WUF-W moment connection and reduced beam section moment connection. Moreover, the achieved rotation capacity satisfies the minimum required for use in intermediate moment frames.

Keywords: connections, finite element analysis, seismic design, steel intermediate moment frame

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Authors: Bruno Coelho Lima, Joao F.A. Martos, Paulo G. P. Toro, Israel S. Rego

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The shock tube is a ground-facility widely used in aerospace and aeronautics science and technology for studies on gas dynamic and chemical-physical processes in gases at high-temperature, explosions and dynamic calibration of pressure sensors. A shock tube in its simplest form is comprised of two separate tubes of equal cross-section by a diaphragm. The diaphragm function is to separate the two reservoirs at different pressures. The reservoir containing high pressure is called the Driver, the low pressure reservoir is called Driven. When the diaphragm is broken by pressure difference, a normal shock wave and non-stationary (named Incident Shock Wave) will be formed in the same place of diaphragm and will get around toward the closed end of Driven. When this shock wave reaches the closer end of the Driven section will be completely reflected. Now, the shock wave will interact with the boundary layer that was created by the induced flow by incident shock wave passage. The interaction between boundary layer and shock wave force the separation of the boundary layer. The aim of this paper is to make an analysis of influences of separation of the boundary layer in the reservoir pressure in the shock tube. A comparison among CDF (Computational Fluids Dynamics), experiments test and analytical analysis were performed. For the analytical analysis, some routines in Python was created, in the numerical simulations (Computational Fluids Dynamics) was used the Ansys Fluent, and the experimental tests were used T1 shock tube located in IEAv (Institute of Advanced Studies).

Keywords: boundary layer separation, moving shock wave, shock tube, transient simulation

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Authors: Chintan Chandrachud

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When primary legislation is challenged for breaching fundamental rights, many courts around the world adopt interpretive techniques to avoid finding such legislation incompatible or invalid. In the UK, these techniques find sanction in section 3 of the Human Rights Act 1998, which directs courts to interpret legislation in a manner which is compatible with European Convention rights, ‘so far as it is possible to do so’. In India, courts begin with the interpretive presumption that Parliament intended to comply with fundamental rights under the Constitution of 1949. In comparing rights-compliant interpretation of primary legislation under the Human Rights Act and the Indian Constitution, this paper makes two arguments. First, that in the absence of a section 3-type mandate, Indian courts have a smaller range of interpretive tools at their disposal in interpreting primary legislation in a way which complies with fundamental rights. For example, whereas British courts frequently read words into statutes, Indian courts consider this an inapposite interpretive technique. The second argument flows naturally from the first. Given that Indian courts have a smaller interpretive toolbox, one would imagine that ceteris paribus, Indian courts’ power to strike down legislation would be triggered earlier than the declaration of incompatibility is in the UK. However, this is not borne out in practice. Faced with primary legislation which appears to violate fundamental rights, Indian courts often reluctantly uphold the constitutionality of statutes (rather than striking them down), as opposed to British courts, which make declarations of incompatibility. The explanation for this seeming asymmetry hinges on the difference between the ‘strike down’ power and the declaration of incompatibility. Whereas the former results in the disapplication of a statute, the latter throws the ball back into Parliament’s court, if only formally.

Keywords: constitutional law, judicial review, constitution of India, UK Human Rights Act

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Authors: Jaejun Jong

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Fake news has recently become a serious international problem. Therefore, researchers and policymakers worldwide have sought to understand fake news and develop strategies to combat it. This study consists of two primary parts: (1) a literature review of how surveys were used to understand fake news and identify problems caused by fake news, and (2) a discussion of how surveys were used to fight back against fake news in educational settings. This second section specifically analyzes surveys used to evaluate a South Korean elementary school program designed to improve students’ metacognition and critical thinking. This section seeks to identify potential problems that may occur in the elementary school setting. The literature review shows that surveys can help people to understand fake news based on its traits rather than its definition due to the lack of agreement on the definition of fake news. The literature review also shows that people are not good at identifying fake news or evaluating their own ability to identify fake news; indeed, they are more likely to share information that aligns with their previous beliefs. In addition, the elementary school survey data shows that there may be substantial errors in the program evaluation process, likely caused by processing errors or the survey procedure, though the exact cause is not specified. Such a significant error in evaluating the effects of the educational program prevents teachers from making proper decisions and accurately evaluating the program. Therefore, identifying the source of such errors would improve the overall quality of education, which would benefit both teachers and students.

Keywords: critical thinking, elementary education, program evaluation, survey

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Authors: Tawanda Mushiri, Charles Mbohwa

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When an external load is applied to one of its ends, a pipe’s bends cross section tends to deform significantly both in and out of its end plane. This shell type behaviour characteristic of pipe bends and mainly due to their curves geometry accounts for their greater flexibility. This added flexibility is also accompanied by stressed and strains that are much higher than those present in a straight pipe. The primary goal of this research is to study the elastic-plastic behaviour of pipe bends under out of plane moment loading. It is also required to study the effects of changing the value of the pipe bend factor and the value of the internal pressure on that behaviour and to determine the value of the limit moments in each case. The results of these analyses are presented in the form of load deflection plots for each load case belonging to each model. From the load deflection curves, the limit moments of each case are obtained. The limit loads are then compared to those computed using some of the analytical and empirical equation available in the literature. The effects of modelling parameters are also studied. The results obtained from small displacement and large displacement analyses are compared and the effects of using a strain hardened material model are also investigated. To better understand the behaviour of pipe elbows under out of plane bending and internal pressure, it was deemed important to know how the cross section deforms and to study the distribution of stresses that cause it to deform in a particular manner. An elbow with pipe bend factor h=0.1 to h=1 is considered and the results of the detailed analysis are thereof examined.

Keywords: elasto-plastic, finite element analysis, pipe bends, simulation

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Authors: Abdulrahman Abdulrahman

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A side weir is a hydraulic structure set into the side of a channel. This structure is used for water level control in channels, to divert flow from a main channel into a side channel when the water level in the main channel exceeds a specific limit and as storm overflows from urban sewerage system. Computation of water surface over the side weirs is essential to determine the flow rate of the side weir. Analytical solutions for water surface profile along rectangular side weir are available only for the special cases of rectangular and trapezoidal channels considering constant specific energy. In this paper, a rectangular side weir located in a combined (trapezoidal with exponential) channel was considered. Expanding binominal series of integer and fraction powers and the using of reduction formula of cosine function integrals, a general analytical formula was obtained for water surface profile along a side weir in a combined (trapezoidal with exponential) channel. Since triangular, rectangular, trapezoidal and parabolic cross-sections are special cases of the combined cross section, the derived formula, is applicable to triangular, rectangular, trapezoidal cross-sections as analytical solution and semi-analytical solution to parabolic cross-section with maximum relative error smaller than 0.76%. The proposed solution should be a useful engineering tool for the evaluation and design of side weirs in open channel.

Keywords: analytical solution, combined channel, exponential channel, side weirs, trapezoidal channel, water surface profile

Procedia PDF Downloads 237

Authors: Raju K. Thadikkaran

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Introduction: The IPR have come to the centre stage of development discourse today for a variety of reasons: It ranges from the arbitrariness in the enforcement, overlapping and mismatch with various international agreements and conventions, divergence in the definition, nature and content and the duration as well as severe adverse consequences to technologically weak developing countries. In turn, the IPR have acquired prominence in the foreign policy making as well as in the relations among nations. Quite naturally, there is ample scope for an examination of the correlation between Technology, IPR and International Relations in the contemporary world. Nature and Scope: A cursory examination of the realm of IPR and its protection shall reveals the acute divergence that exists in the perspectives, on all matters related to the very definition, nature, content, scope and duration. The proponents of stronger protection, mostly technologically advanced countries, insist on a stringent IP Regime whereas technologically weak developing countries seem to advocate for flexibilities. From the perspective of developing countries like India, one of the most crucial concerns is related to the patenting of life forms and the protection of TK and BD. There have been several instances of Bio-piracy and Bio-prospecting of the resources related to BD and TK from the Bio-rich Global South. It is widely argued that many provisions in the TRIPS are capable of offsetting the welcome provisions in the CBD such as the Access and Benefit Sharing and Prior Informed Consent. The point that is being argued out is as to how the mismatch between the provisions in the TRIPS Agreement and the CBD could be addressed in a healthy manner so that the essential minimum legitimate interests of all stakeholders could be secured thereby introducing a new direction to the international relations. The findings of this study reveal that the challenges roused by the TRIPS Regime over-weigh the opportunities. The mismatch in the provisions in this regard has generated various crucial issues such as Bio-piracy and Bio-prospecting. However, there is ample scope for managing and protecting IP through institutional innovation, legislative, executive and administrative initiative at the global, national and regional levels. The Indian experience is quite reflective of the same and efforts are being made through the new national IPR policy. This paper, employing Historical Analytical Method, has Three Sections. The First Section shall trace the correlation between the Technology, IPR and international relations. The Second Section shall review the issues and potential concerns in the protection and management of IP related to the BD and TK in the developing countries in the wake of the TRIPS and the CBD. The Final Section shall analyze the Indian Experience in this regard and the experience of the bio-rich Kerala in particular.

Keywords: IPR, technology and international relations, bio-diversity, traditional knowledge

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Authors: Farid Adisaputra Gumilang

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Kucing Liar Underground Mine is a future mine of PT Freeport Indonesia PTFI that is currently being developed. In the development process, problems were found when blasting the tunnels; there were overbreak, and void occur caused by geological contact or poor rock conditions. Geotechnical engineers must evaluate not only the remnant capacity of ground support systems but also investigate the depth of rock mass yield within pillars. To prevent the potential hazard caused by void zones, geotechnical engineers must ensure the planned drift is mined in the best location where people can work safely. GPR, or Ground penetrating radar, is a geophysical method that can image the subsurface. This non-destructive method uses electromagnetic radiation and detects the reflected signals from subsurface structures. The GPR survey measurements are conducted 48 meters along the drift that has a poor ground condition with 150MHz antenna with several angles (roof, wall, and floor). Concern grounds are determined by the continuity of reflector/low reflector in the radargram section. Concern grounds are determined by the continuity of reflector/low reflector in the radargram section. In this paper, processing data using instantaneous amplitude to identify the void zone. In order to have a good interpretation and result, it combines with the geological information and borehole camera data, so the calibrated GPR data allows the geotechnical engineer to determine the safe location to change the drift location.

Keywords: underground mine, ground penetrating radar, reflectivity, borehole camera

Procedia PDF Downloads 81

Authors: Nour Aladdin

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This paper explores the interconnectedness of belonging, space, and identity in Anglo Arab literature, particularly Saleem Haddad’s Guapa and Hasan Namir’sGod in Pink. This paper suggest that Rasa and Ramy, the queer Arab characters respectively, do not belong in either the Middle East or the West. Using Amin Maalouf’s analysis of the Arab identity, specifically his argument that an individual identifies strongly with the aspect of their identity that is under attack, this paper argues that all of Rasa and Ramy’s spaces are politically charged - a term that denotes that all values and beliefs instilled in Arabs and their spaces are heavily influenced by Arab politics, culture, and, often times religion. Therefore, the politically charged environments Rasa and Ramy inhabit will always be against one part of their identity, which is why they cannot identify as queer and Arab simultaneously. For Rasa, the unnamed Middle Eastern country, his home environment, as well as the so-called safe space nightclub, condemn his queerness, leading him to connect more to his sexual orientation. However, Rasa associates himself with his Arab roots when he migrates to America, a different form of politically charged space that minoritizes his ethnicity. Similarly, Ramy’s spaces are naturally religiopolitical after Islam heightened in Iraq during the Iraq War; as a result, Ramy’s home environment, Sheikh Ammar’s house, the mosque, and the nightclub are influenced by the religiopolitics and bombard his ability to identify as not only a queer Arab but a queer Arab Muslim. Ultimately, because Rasa and Ramy are constantly in movement, their identity attributes are also in movement. This paper is divided into three sections. The first section focuses on Guapa and the Arab Spring’s politics, mainly its influence on queer Arabs in and around the Middle East. Drawing from a number of queer and Arab gender theories, I analyze all of Rasa’s spaces as politically charged that prevent him from the means to be queer and Arab. The second section examines God in Pink in close connection to the 2003 invasion of Iraq. Ramy’s spaces are religiopolitically charged, that prevent him to embrace all of his identity attributes – nationality, ethnicity, sexual orientation, and religious affiliation – concomitantly. The last section considers the rapid use of technology and social media in the Middle East as a means to provide deviant heterotopic spaces for queer Arabs. With the rise of subtle and covert queer heterotopias, there is a slow and steady shift of queer tolerance in the Arab world.

Keywords: belonging, identity, spaces, queer, arabness, middle east, orientalism

Procedia PDF Downloads 114

Authors: Tapiwa Shumba

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The right to fairness and access to appeals and reviews enshrined under the South African Constitution seeks to ensure that justice is served. In essence, the constitution and the law have put in place mechanisms to ensure that a miscarriage of justice through wrongful convictions does not occur. However, once convicted and sentenced on appeal the procedural safeguards seem to resign as if to say, the accused has met his fate. The challenge with this construction is that even within an ideally perfect legal system wrongful convictions would still occur. Therefore, it is not so much of the failings of a legal system that demand attention but mechanisms to redress the results of such failings where evidence becomes available that a wrongful conviction occurred. In this context, this paper looks at the South African criminal procedural mechanisms for litigating innocence post-conviction. The discussion focuses on the role of section 327 of the South African Criminal Procedure Act and its apparent shortcomings in providing an avenue for victims of miscarriages to litigate their innocence by adducing new evidence at any stage during their wrongful incarceration. By looking at developments in other jurisdiction such as the United Kingdom, where South African criminal procedure draws much of its history, and the North Carolina example which in itself was inspired by the UK Criminal Cases Review Commission, this paper is able to make comparisons and draw invaluable lessons for the South African criminal justice system. Lessons from these foreign jurisdictions show that South African post-conviction criminal procedures need reform in line with constitutional values of human dignity, equality before the law, openness and transparency. The paper proposes an independent review of the current processes to assess the current post-conviction procedures under section 327. The review must look into the effectiveness of the current system and how it can be improved in line with new substantive legal provisions creating access to DNA evidence for post-conviction exonerations. Although the UK CCRC body should not be slavishly followed, its operations and the process leading to its establishment certainly provide a good point of reference and invaluable lessons for the South African criminal justice system seeing that South African law on this aspect has generally followed the English approach except that current provisions under section 327 are a mirror of the discredited system of the UK’s previous dispensation. A new independent mechanism that treats innocent victims of the criminal justice system with dignity away from the current political process is proposed to enable the South African criminal justice to benefit fully from recent and upcoming advances in science and technology.

Keywords: innocence, forensic law, post-conviction remedies, South African criminal justice system, wrongful conviction

Procedia PDF Downloads 236

Authors: Faycal Boughalleb, Raoudha Abdellaoui

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The effect of NaCl stress on root and leaf anatomy was investigated in three Astragalus species grown in 0-300 mM NaCl for 30 days under greenhouse conditions. Root cross section and cortex thickness was reduced under salt stress in both species while A. tenuifolius showed thinner cortex and the root cross section was unchanged. The epidermis stele thickness was unaffected by salinity in A. armatus and A. tenuifolius and was reduced in A. mareoticus with smaller xylem vessel size. In addition, vessel density and wall thickness of xylem was increased under salt conditions in the studies species. The entire lamina and mesophyll of the three species were thinner in salt-stressed plants. A. armatus and A. tenuifolius showed the higher thickness with increased size of the lower epidermis. NaCl (300 mM) reduced leaf water content by 41.5 % in A. mareoticus while it was unchanged in the other species. The size of the vascular bundle increased under salinity in A. tenuifolius leaves and it was unchanged in the other ones. A longer distance between leaf vascular bundle was occurred in A. mareoticus. The effects of NaCl on root and leaf ultrastructure are discussed in relation to the degree of salt resistance of these species. The unchanged biomass production under salt stress confirmed the higher tolerance oft A. tenuifolius to salinity. A. armatus was moderately salt tolerant with decrease of biomass production by 14.2 % while A. mareoticus was considered as salt sensitive plant when the decrease in biomass production reached 56.8%.

Keywords: Astragalus species, leaf ultrastructure, root anatomy, salt stress

Procedia PDF Downloads 393

Authors: Jackqueline Uy, Hannah Miriam Verano, Crysler Luis Verbo, Irene Gueco

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Educational tours are part of the curriculum of the College of Tourism and Hospitality Management, De La Salle University-Dasmarinas. They are highly significant to the students, especially Tourism students. The purpose of this study was to determine how effective educational tours were as a learning tool using the Experiential Learning Theory by David Kolb. This study determined the demographic profile of the third year tourism students in terms of gender, section, educational tours joined, and monthly family income and lastly, this study determined if there is a significant difference between the demographic profile of the respondents and their assessment of educational tours as a learning tool. The researchers used a historical research design with the third-year students of the bachelor of science in tourism management as the population size and used a random sampling method. The researchers made a survey questionnaire and utilized statistical tools such as weighted mean, frequency distribution, percentage, standard deviation, T-test, and ANOVA. The result of the study answered the profile of the respondents such as the gender, section, educational tour/s joined, and family monthly income. The findings of the study showed that the 3rd year tourism management students strongly agree that educational tours are a highly effective learning tool in terms of active experimentation, concrete experience, reflective observation, and abstract conceptualisation based on the data gathered from the respondents.

Keywords: CTHM, educational tours, experiential learning theory, De La Salle University Dasmarinas, tourism

Procedia PDF Downloads 173

Authors: Apeng Dong, Shu Li, Wenguo Zhu, Ming Qi, Qiuyi Xu

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The primary objective of this paper is to focus on the elasticity properties of three-dimensional full five directional (3Df5d) braided composite. A large body of research has been focused on the 3D four directional (4d) and 3D five directional (5d) structure but not much research on the 3Df5d material. Generally, the influence of the yarn shape on mechanical properties of braided materials tends to be ignored, which makes results too ideal. Besides, with the improvement of the computational ability, people are accustomed to using computers to predict the material parameters, which fails to give an explicit and concise result facilitating production and application. Based on the traditional mechanics, this paper firstly deduced the functional relation between elasticity properties and braiding parameters. In addition, considering the actual shape of yarns after consolidation, the longitudinal modulus is modified and defined practically. Firstly, the analytic model is established based on the certain assumptions for the sake of clarity, this paper assumes that: A: the cross section of axial yarns is square; B: The cross section of braiding yarns is hexagonal; C: the characters of braiding yarns and axial yarns are the same; D: The angle between the structure boundary and the projection of braiding yarns in transverse plane is 45°; E: The filling factor ε of composite yarns is π/4; F: The deformation of unit cell is under constant strain condition. Then, the functional relation between material constants and braiding parameters is systematically deduced aimed at the yarn deformation mode. Finally, considering the actual shape of axial yarns after consolidation, the concept of technology factor is proposed and the longitudinal modulus of the material is modified based on the energy theory. In this paper, the analytic solution of material parameters is given for the first time, which provides a good reference for further research and application for 3Df5d materials. Although the analysis model is established based on certain assumptions, the analysis method is also applicable for other braided structures. Meanwhile, it is crucial that the cross section shape and straightness of axial yarns play dominant roles in the longitudinal elastic property. So in the braiding and solidifying process, the stability of the axial yarns should be guaranteed to increase the technology factor to reduce the dispersion of material parameters. Overall, the elastic properties of this materials are closely related to the braiding parameters and can be strongly designable, and although the longitudinal modulus of the material is greatly influenced by the technology factors, it can be defined to certain extent.

Keywords: analytic solution, braided composites, elasticity properties, technology factor

Procedia PDF Downloads 237

Authors: Ciara Pienaar, J. W. Odendaal, J. Joubert, J. C. Smit

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Radar cross section (RCS) of dielectric objects play an important role in many applications, such as low observability technology development, drone detection, and monitoring as well as coastal surveillance. Various materials are used to construct the targets of interest such as metal, wood, composite materials, radar absorbent materials, and other dielectrics. Since simulated datasets are increasingly being used to supplement infield measurements, as it is more cost effective and a larger variety of targets can be simulated, it is important to have a high level of confidence in the predicted results. Confidence can be attained through validation. Various computational electromagnetic (CEM) methods are capable of predicting the RCS of dielectric targets. This study will extend previous studies by validating full-wave and asymptotic RCS simulations of dielectric targets with measured data. The paper will provide measured RCS data of a number of canonical dielectric targets exhibiting different material properties. As stated previously, these measurements are used to validate numerous CEM methods. The dielectric properties are accurately characterized to reduce the uncertainties in the simulations. Finally, an analysis of the sensitivity of oblique and normal incidence scattering predictions to material characteristics is also presented. In this paper, the ability of several CEM methods, including method of moments (MoM), and physical optics (PO), to calculate the RCS of dielectrics were validated with measured data. A few dielectrics, exhibiting different material properties, were selected and several canonical targets, such as flat plates and cylinders, were manufactured. The RCS of these dielectric targets were measured in a compact range at the University of Pretoria, South Africa, over a frequency range of 2 to 18 GHz and a 360° azimuth angle sweep. This study also investigated the effect of slight variations in the material properties on the calculated RCS results, by varying the material properties within a realistic tolerance range and comparing the calculated RCS results. Interesting measured and simulated results have been obtained. Large discrepancies were observed between the different methods as well as the measured data. It was also observed that the accuracy of the RCS data of the dielectrics can be frequency and angle dependent. The simulated RCS for some of these materials also exhibit high sensitivity to variations in the material properties. Comparison graphs between the measured and simulation RCS datasets will be presented and the validation thereof will be discussed. Finally, the effect that small tolerances in the material properties have on the calculated RCS results will be shown. Thus the importance of accurate dielectric material properties for validation purposes will be discussed.

Keywords: asymptotic, CEM, dielectric scattering, full-wave, measurements, radar cross section, validation

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Authors: Jaan Lellep, Shahid Mubasshar

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A numerical solution is developed for simply supported nanoarches based on the non-local theory of elasticity. The nanoarch under consideration has a step-wise variable cross-section and is weakened by crack-like defects. It is assumed that the cracks are stationary and the mechanical behaviour of the nanoarch can be modeled by Eringen’s non-local theory of elasticity. The physical and thermal properties are sensitive with respect to changes of dimensions in the nano level. The classical theory of elasticity is unable to describe such changes in material properties. This is because, during the development of the classical theory of elasticity, the speculation of molecular objects was avoided. Therefore, the non-local theory of elasticity is applied to study the vibration of nanostructures and it has been accepted by many researchers. In the non-local theory of elasticity, it is assumed that the stress state of the body at a given point depends on the stress state of each point of the structure. However, within the classical theory of elasticity, the stress state of the body depends only on the given point. The system of main equations consists of equilibrium equations, geometrical relations and constitutive equations with boundary and intermediate conditions. The system of equations is solved by using the method of separation of variables. Consequently, the governing differential equations are converted into a system of algebraic equations whose solution exists if the determinant of the coefficients of the matrix vanishes. The influence of cracks and steps on the natural vibration of the nanoarches is prescribed with the aid of additional local compliance at the weakened cross-section. An algorithm to determine the eigenfrequencies of the nanoarches is developed with the help of computer software. The effects of various physical and geometrical parameters are recorded and drawn graphically.

Keywords: crack, nanoarches, natural frequency, step

Procedia PDF Downloads 128