Search results for: air force

Authors: Mahdi Almaky, Reda Hassanin, Benjamin Horrocks, Andrew Houlton

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DNA-templated poly(N-substituted pyrrole)bipyridinium nanowires were synthesised at room temperature using the chemical oxidation method. The resulting CPs/DNA hybrids have been characterised using electronic and vibrational spectroscopic methods especially Ultraviolet-Visible (UV-Vis) spectroscopy and FTIR spectroscpy. The nanowires morphology was characterised using Atomic Force Microscopy (AFM). The electrical properties of the prepared nanowires were characterised using Electrostatic Force Microscopy (EFM), and measured using conductive AFM (c-AFM) and two terminal I/V technique, where the temperature dependence of the conductivity was probed. The conductivities of the prepared CPs/DNA nanowires are generally lower than PPy/DNA nanowires showingthe large effect on N-alkylation in decreasing the conductivity of the polymer, butthese are higher than the conductivity of their corresponding bulk films.This enhancement in conductivity could be attributed to the ordering of the polymer chains on DNA during the templating process. The prepared CPs/DNA nanowires were used as templates for the growth of copper nanowires at room temperature using aqueous solution of Cu(NO3)2as a source of Cu2+ and ascorbic acid as reducing agent. AFM images showed that these nanowires were uniform and continuous compared to copper nanowires prepared using the templating method directly onto DNA. Electrical characterization of the nanowires by c AFM revealed slight improvement in conductivity of these nanowires (Cu-CPs/DNA) compared to CPs/DNA nanowires before metallisation.

Keywords: templating, copper nanowires, polymer/DNA hybrid, chemical oxidation method

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Authors: M. M. Bagheri, G. Doudak, M. Gong

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The in-plane rigidity of light frame diaphragms has been investigated by researchers due to the importance of this subsystem regarding lateral force distribution between the lateral force resisting system (LFRS). Where research has lacked is in evaluating the impact of out-of-plane raigidity of the diaphragm on the deflection of shear walls. This study aims at investigating the effect of the diaphragm on the behavior of wood light-frame shear walls, in particular its out-of-plane rigidity was simulated by modeling the floors as beam. The out of plane stiffness of the diaphragm was investigated for idealized (infinitely stiff or flexible) as well as “realistic”. The results showed reductions in the shear wall deflection in the magnitude of approximately 80% considering the out of plane rigidity of the diaphragm. It was also concluded that considering conservative estimates of out-of-plane stiffness might lead to a very significant reduction in deflection and that assuming the floor diaphragm to be infinitely rigid out of plan seems to be reasonable. For diaphragms supported on multiple panels, further reduction in the deflection was observed. More work, particularly at the experimental level, is needed to verify the finding obtained in the numerical investigation related to the effect of out of plane diaphragm stiffness.

Keywords: finite element analysis, lateral deflection, out-of-plane stiffness of the diaphragm, wood light-frame shear wall

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Authors: Djalal Hamed

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The aim of this paper is to perform, by mean of the finite volume method, a numerical solution of the transient natural convection in a narrow rectangular channel between two vertical parallel Material Testing Reactor (MTR)-type fuel plates, imposed under a heat flux with a cosine shape to determine the margin of the nuclear core power at which the natural convection cooling mode can ensure a safe core cooling, where the cladding temperature should not reach a specific safety limits (90 °C). For this purpose, a computer program is developed to determine the principal parameters related to the nuclear core safety, such as the temperature distribution in the fuel plate and in the coolant (light water) as a function of the reactor core power. Throughout the obtained results, we noticed that the core power should not reach 400 kW, to ensure a safe passive residual heat removing from the nuclear core by the upward natural convection cooling mode.

Keywords: buoyancy force, friction force, finite volume method, transient natural convection

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Authors: Joanne Haddad

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The distinctive traits of early settlers at initial stages of institutional development may be crucial for cultural formation. In 1973, the cultural geographer Wilbur Zelinsky postulated this in his doctrine of “first effective settlement”. There is however little empirical evidence supporting the role of early settlers in shaping culture over the long run. This paper tests this hypothesis by relating early settlers’ culture to within state variation in gender norms in the United States. Settlers’ culture is captured using past female labor force participation, women’s suffrage, and financial rights at their place of origin. The paper documents the distinctive characteristics of settlers’ populations and provide suggestive evidence in support of the transmission of gender norms across space and time. Results from this analysis show that women’s labor supply is higher, in both the short and long run, in U.S. counties that historically hosted a larger settler population originating from places with favorable gender attitudes. Findings from this study shed new light on the importance of the characteristics of immigrants and their place of origin for cultural formation in hosting societies.

Keywords: female labor force participation, settlers, gender norms, cultural formation.

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Authors: Nicholas Jensen

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As the effort to create new drugs to treat rare conditions cost-effectively intensifies, there is a need to ensure maximum efficiency in the manufacturing process. This includes the creation of ultracompact treatment forms, which can best be achieved via applications of fundamental laws of physics. This paper reports an experiment exploring the relationship between the forms of Newton's 2ⁿᵈ Law appropriate to linear motion and to transversal architraves. The moment of inertia of three discs was determined by experiments and compared with previous data derived from a theoretical relationship. The method used was to attach the discs to a moment arm. Comparing the results with those obtained from previous experiments, it is found to be consistent with the first law of thermodynamics. It was further found that Newton's 2ⁿᵈ law violates the second law of thermodynamics. The purpose of this experiment was to explore the relationship between the forms of Newton's 2nd Law appropriate to linear motion and to apply torque to a twisting force, which is determined by position vector r and force vector F. Substituting equation alpha in place of beta; angular acceleration is a linear acceleration divided by radius r of the moment arm. The nevrological analogy of Newton's 2nd Law states that these findings can contribute to a fuller understanding of thermodynamics in relation to viscosity. Implications for the pharmaceutical industry will be seen to be fruitful from these findings.

Keywords: Newtonian physics, inertia, viscosity, pharmaceutical applications

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Authors: Ngono Mindzeng Terencia

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Community based tourism, as a sustainable tourism approach, has been adopted as a tool for development among local communities in third world countries with income generation as the main driver. However, an analysis of community based tourism and development brings to light another driving force which is paramount to development strategies in the difficult conditions of third world countries: this driving force is “place revitalization”. This paper seeks to assess the relevance of “place revitalization” to the enhancement of development within the challenging context of developing countries. The research provides a community based tourism model to development in third world countries through a three step process based on awareness, mentoring and empowerment at the local level. It also tries to examine how effectively this model can address the development problems faced by the local communities of third world countries. The case study for this research is the Bamiléké region of Cameroon, the breeding ground of community based tourism initiatives and a region facing the difficulties of third world countries that are great impediments to community based tourism.

Keywords: awareness, empowerment, local communities, mentoring, place revitalization, third world countries

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Authors: Pratyush Vatsala, Sanjay Ahuja

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The national security and human rights are related terms as there is nothing like absolute security or absolute human right. If we are committed to security, human right is a problem and also a solution, and if we deliberate on human rights, security is a problem but also part of the solution. Ultimately, we have to maintain a balance between the two co-related terms. As more and more armed forces are being deployed by the government within the nation for maintaining peace and security, using force against its own citizen, the search for a judicious balance between intent and action needs to be emphasized. Notwithstanding that a nation state needs complete political independence; the search for security is a driving force behind unquestioned sovereignty. If security is a human value, it overlaps the value of freedom, order, and solidarity. Now, the question needs to be explored, to what extent human rights can be compromised in the name of security in Kashmir or Mizoram like places. The present study aims to explore the issue of maintaining a balance between the use of power and good governance as human rights, providing security as a human value. This paper has been prepared with an aim of strengthening the understanding of the complex and multifaceted relationship between human rights and security forces operating for conflict management and identifies some of the critical human rights issues raised in the context of security forces operations highlighting the relevant human rights principles and standards in which Security as human value be respected at all times and in particular in the context of security forces operations in India.

Keywords: Kashmir, Mizoram, security, value, human right

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Authors: Marshal D. Kafle, Jun H. Kim, Hyun W. Been, Kyoung M. Min

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Fluid viscous damping systems are well suited for many air vehicles subjected to shock and vibration. These damping system work with the principle of viscous fluid throttling through the orifice to create huge pressure difference between compression and rebound chamber and obtain the required damping force. One application of such systems is its use in aircraft door system to counteract the door’s velocity and safely stop it. In exigency situations like crash or emergency landing where the door doesn’t open easily, possibly due to unusually tilting of fuselage or some obstacles or intrusion of debris obstruction to move the parts of the door, such system can be combined with other systems to provide needed force to forcefully open the door and also securely stop it simultaneously within the required time i.e.less than 8seconds. In the present study, a hydraulic system called snubber along with other systems like actuator, gas bottle assembly which together known as emergency power assist system (EPAS) is designed, built and experimentally studied to check the magnitude of angular velocity, damping force and time required to effectively open the door. Whenever needed, the gas pressure from the bottle is released to actuate the actuator and at the same time pull the snubber’s piston to operate the emergency opening of the door. Such EPAS installed in the suspension arm of the aircraft door is studied explicitly changing parameters like orifice size, oil level, oil viscosity and bypass valve gap and its spring of the snubber at varying temperature to generate the optimum design case. Comparative analysis of the EPAS at several cases is done and conclusions are made. It is found that during emergency condition, the systemopening time and angular velocity, when snubber with 0.3mm piston and shaft orifice and bypass valve gap of 0.5 mm with its original spring is used,shows significant improvement over the old ones.

Keywords: aircraft door damper, bypass valve, emergency power assist system, hydraulic damper, oil viscosity

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Authors: Abouzar Kaboudian, Ravi Chaithanya Mysa, Boo Cheong Khoo, Rajeev Kumar Jaiman

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Vortex induced vibrations can significantly affect the effectiveness of structures in aerospace as well as offshore marine industries. The oscillatory nature of the forces resulting from the vortex shedding around bluff bodies can result in undesirable effects such as increased loading, stresses, deflections, vibrations and noise in the structures, and also reduced fatigue life of the structures. To date, most studies concentrate on either the free oscillations or the prescribed motion of the bluff bodies. However, the structures in operation are usually subject to the external oscillatory forces (e.g. due to the platform motions in offshore industries). In this work, we present the effects of the external cross-flow forces on the vortex-induced vibrations of an oscillating cylinder. The effects of the amplitude, as well as the frequency of the external force on the fluid-forces on the oscillating cylinder are carefully studied and presented. Moreover, we present the transition of the response to be dominated by the vortex-induced-vibrations to the range where it is mostly dictated by the external oscillatory forces. Furthermore, we will discuss how the external forces can affect the flow structures around a cylinder. All results are compared against free oscillations of the cylinder.

Keywords: circular cylinder, external force, vortex-shedding, VIV

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Authors: Jemal Ebrahim Dessie, Lukács Zsolt

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High-strength aluminum alloys have drawn a lot of attention because of the expanding demand for lightweight vehicle design in the automotive sector. Due to poor formability at room temperature, warm and hot forming have been advised. However, warm and hot forming methods need more steps in the production process and an advanced tooling system. In contrast, since ordinary tools can be used, forming sheets at room temperature in the W temper condition is advantageous. However, springback of supersaturated sheets and their thinning are critical challenges and must be resolved during the use of this technique. In this study, AA6082-T6 aluminum alloy was solution heat treated at different oven temperatures and times using a specially designed and developed furnace in order to optimize the W-temper heat treatment temperature. A U-shaped bending test was carried out at different time periods between W-temper heat treatment and forming operation. Finite element analysis (FEA) of U-bending was conducted using AutoForm aiming to validate the experimental result. The uniaxial tensile and unload test was performed in order to determine the kinematic hardening behavior of the material and has been optimized in the Finite element code using systematic process improvement (SPI). In the simulation, the effect of friction coefficient & blank holder force was considered. Springback parameters were evaluated by the geometry adopted from the NUMISHEET ’93 benchmark problem. It is noted that the change of shape was higher at the more extended time periods between W-temper heat treatment and forming operation. Die radius was the most influential parameter at the flange springback. However, the change of shape shows an overall increasing tendency on the sidewall as the increase of radius of the punch than the radius of the die. The springback angles on the flange and sidewall seem to be highly influenced by the coefficient of friction than blank holding force, and the effect becomes increases as increasing the blank holding force.

Keywords: aluminum alloy, FEA, springback, SPI, U-bending, W-temper

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Authors: Josephine Wanja Nyatia

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The relationship between vegetation and soil erosion deserves attention due to its scientific importance and practical applications. A great deal of information is available about the mechanisms and benefits of vegetation in the control of soil erosion, but the effects of soil erosion on vegetation development and succession is poorly documented. Research shows that soil erosion is the most important driving force for the degradation of upland and mountain ecosystems. Soil erosion interferes with the process of plant community development and vegetation succession, commencing with seed formation and impacting throughout the whole growth phase and affecting seed availability, dispersal, germination and establishment, plant community structure and spatial distribution. There have been almost no studies on the effects of soil erosion on seed development and availability, of surface flows on seed movement and redistribution, and their influences on soil seed bank and on vegetation establishment and distribution. However, these effects may be the main cause of low vegetation cover in regions of high soil erosion activity, and these issues need to be investigated. Moreover, soil erosion is not only a negative influence on vegetation succession and restoration but also a driving force of plant adaptation and evolution. Consequently, we need to study the effects of soil erosion on ecological processes and on development and regulation of vegetation succession from the points of view of pedology and vegetation, plant and seed ecology, and to establish an integrated theory and technology for deriving practical solutions to soil erosion problems

Keywords: soil erosion, vegetation, development, seed availability

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Authors: Emmanuela Ngozi Maduka

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In Nigeria, civil-military relations is at its lowest point as a result of the challenges emanating from incessant initiation of military aid to civil authorities (MACA) for internal security operations. This paper is concerned with the question whether it is appropriate for the military to handle internal security crisis with exception to terrorism and armed militia. It analyses the legal framework for MACA in internal security operations which appear to be in contradiction with military tactical and equipment training. The paper argues that the expectation that transitional re-training of the military for internal security operations will reconcile these inconsistencies specifically on the issue of use of force is not practicable and will always pose challenges for both the military and the citizens. Accordingly, this paper adopts a socio-legal methodology for better clarity on the interactions between the legal framework on MACA and military internal security operations. The paper also identifies the lack of effective and proficient paramilitary within the security design of Nigeria as the key issue which results in incessant initiation of MACA and advocates for the establishment of an effective and proficient paramilitary to effectively handle internal security crisis within Nigeria.

Keywords: civil-military relations, MACA, military training, operational challenges, paramilitary, use of force

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Authors: Karel Šebesta, Jiří Žáček, Matuš Salva, Mohammad Housam

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Drivers of agricultural vehicles are exposed to continuous vibration caused by driving over rough terrain. The long-term effects of these vibrations could start with a decreased level of vigilance at work and could reach the level of several health problems. Therefore, eliminating the vibration to maximize the comfort of the driver is essential for better/longer performance. One of the modern damping systems, which can deal with this problem is the Semi-active (S/A) suspension system featuring a Magnetorheological (MR) damper. With this damper, the damping level can be adjusted using varying currents through the coil. Adjustments of the damping force can be carried out continuously based on the evaluated data (position and acceleration of seat) by the control algorithm. The advantage of this system is the wide dynamic range and the high speed of force response time. Compared to other S/A or active systems, the MR damper does not need as much electrical power, and the system is much simpler. This paper aims to prove the effectiveness of this damping system used in the tractor seat. The vibration testing stand was designed and manufactured specifically for this type of research, which is used to simulate vibrations with constant amplitude at variable frequency.

Keywords: magnetorheological damper, semi-active suspension, seat scissor mechanism, sky-hook

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Authors: M. Fowsia, Dominic Xavier Fernando, Vinojitha, Rahamath Juliyana

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Aerofoil is a primary element to be designed during the initial phase of creating any new aircraft. It is the component that forms the cross-section of the wing. The wing is used to produce lift force that balances the weight which is acting downwards. The lift force is created due to pressure difference over the top and bottom surface which is caused due to velocity variation. At sub-sonic velocities, for a real fluid, we obtain a smooth flow of air over both the surfaces. In this era of high speed travel, commercial aircraft that can travel faster than speed of sound barrier is required. However transonic velocities cause the formation of shock waves which can cause flow separation over the top and bottom surfaces. In the transonic range, shock waves move across the top and bottom surfaces of the aerofoil, until both the shock waves merge into a single shock wave that is formed near the leading edge of theaerofoil. In this paper, a transonic aerofoil is designed and its aerodynamic properties at different velocities in the Transonic range (M = 0.8; 0.9; 1; 1.1; 1.2) are studied with the help of CFD. The Pressure and Velocity distributions over the top and bottom surfaces of aerofoil are studied and the variations of shock patterns, at different velocities, are analyzed. The analysis can be used to determine the effect of drag divergence on the lift created by the aerofoil.

Keywords: transonic aerofoil, cfd, drag divergence, shock formation, viscous flow

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Authors: Mehmet Halkaci, Ekrem Öztürk, Mevlüt Türköz, H. Selçuk Halkacı

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Hydromechanical deep drawing (HMD) process is an advanced manufacturing process used to form deep parts with only one forming step. In this process, sheet metal blank can be drawn deeper by means of fluid pressure acting on sheet surface in the opposite direction of punch movement. High limiting drawing ratio, good surface quality, less springback characteristic and high dimensional accuracy are some of the advantages of this process. The performance of the HMD process is affected by various process parameters such as fluid pressure, blank holder force, punch-die radius, pre-bulging pressure and height, punch diameter, friction between sheet-die and sheet-punch. The fluid pressure and bank older force are the main loading parameters and affect the formability of HMD process significantly. The punch diameter also influences the limiting drawing ratio (the ratio of initial sheet diameter to punch diameter) of the sheet metal blank. In this research, optimal loading (fluid pressure and blank holder force) profiles were determined for AA 5754-O sheet material through fuzzy control algorithm developed in previous study using LS-DYNA finite element analysis (FEA) software. In the preceding study, the fuzzy control algorithm was developed utilizing geometrical criteria such as thinning and wrinkling. In order to obtain the final desired part with the developed algorithm in terms of the punch diameter requested, the effect of punch diameter, which is the one of the process parameters, on loading profiles was investigated separately using blank thickness of 1 mm. Thus, the practicality of the previously developed fuzzy control algorithm with different punch diameters was clarified. Also, thickness distributions of the sheet metal blank along a curvilinear distance were compared for the FEA in which different punch diameters were used. Consequently, it was found that the use of different punch diameters did not affect the optimal loading profiles too much.

Keywords: Finite Element Analysis (FEA), fuzzy control, hydromechanical deep drawing, optimal loading profiles, punch diameter

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Authors: Li Yang, Yang Song, Martin Y. M. Chiang

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Objective: To experimentally substantiate the micromechanical compatibility between cell and scaffold, in the regenerative medicine approach for restoring bone volume, is essential for phenotypic transitions Methods: Through nanotechnology and electrospinning process, nanofibrous scaffolds were fabricated to host dental follicle stem cells (DFSCs). Blends (50:50) of polycaprolactone (PCL) and silk fibroin (SF), mixed with various content of cellulose nanocrystals (CNC, up to 5% in weight), were electrospun to prepare nanofibrous scaffolds with heterogeneous microstructure in terms of fiber size. Colloidal probe atomic force microscopy (AFM) and conventional uniaxial tensile tests measured the scaffold stiffness at the micro-and macro-scale, respectively. The cell elastic modulus and cell-scaffold adhesive interaction (i.e., a chemical function) were examined through single-cell force spectroscopy using AFM. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to determine if the mechanotransduction signal (i.e., Yap1, Wwr2, Rac1, MAPK8, Ptk2 and Wnt5a) is upregulated by the scaffold stiffness at the micro-scale (cellular scale). Results: The presence of CNC produces fibrous scaffolds with a bimodal distribution of fiber diameter. This structural heterogeneity, which is CNC-composition dependent, remarkably modulates the mechanical functionality of scaffolds at microscale and macroscale simultaneously, but not the chemical functionality (i.e., only a single material property is varied). In in vitro tests, the osteogenic differentiation and gene expression associated with mechano-sensitive cell markers correlate to the degree of micromechanical compatibility between DFSCs and the scaffold. Conclusion: Cells require compliant scaffolds to encourage energetically favorable interactions for mechanotransduction, which are converted into changes in cellular biochemistry to direct the phenotypic evolution. The micromechanical compatibility is indeed important to the efficacy of regenerative medicine.

Keywords: phenotype transition, scaffold stiffness, electrospinning, cellulose nanocrystals, single-cell force spectroscopy

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Authors: Ibrahim Arslan

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Since 1984, Turkey has experienced a significant transformation in legal and economic matters. The most consequential examples of this transformation in recent years are the renewal of the Commercial Code and the Check Act. Nowadays, the commercial activity is not limited within the boundaries of the country; on the contrary, as required by the global economy, it has an international dimension. For this reason, unlike some other legal principles, the rules regulating the commercial life should be compatible with the international standards as much as possible. Otherwise the development possibility in the global markets will be limited. The Check Act has been adopted in 2009 and the Commercial Code has been adopted in 2011. The Commercial Code has been entered into force on 1 July 2012. The international dimension of check is in-disputable for it is based on the Geneva Convention. However, the Turkish business life has created a unique application of this legal tool. This application is called “post-date” checks. Indeed the majority of the checks being used in the market are post-dated checks. The holders of these checks have waited the date written on the check for presentation and collection. Thus, the actual situation has occurred. This actual situation has been legitimized via Check Act No. 5941 and post dated checks have gained a legal status. In the preparation of the new the Turkish Commercial Code one of the goals is "to ensure that the Turkish commercial law becomes a part of the international market". To achieve this goal, significant changes have been made especially concerning the independent external audition of the corporations, the board structure and public disclosure regulations. These changes aim to facilitate the internationalization of Turkish corporations as well as intensification of foreign direct investments through foreign capital. Although the target has been determined this way, after the adoption but five days before the entry into force of the Turkish Commercial Code No. 6102, a law made backward going alterations concerning independent external audition and public disclosure regulations. Turkish Commercial Code has been currently in force with its altered status. Both the regulations in the Check Act as well as the changes in the Commercial Code are not compatible with the goals introduced by rationale “to ensure Turkish commercial law to be a part of the international market” as such.

Keywords: Turkish Commercial Code No. 6102, Turkish Check Act, “post-date” checks, legal changes

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Authors: Ibrahim Ercan, Mustafa Arikan

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In recent years, alternative dispute resolution methods have attracted the attention of many country’s legislators. Instead of solving the disputes by litigation, putting the end to a dispute by parties themselves is more important for the preservation of social peace. Therefore, alternative dispute resolution methods (ADR) have been discussed more intensively in Turkey as well as the whole world. After these discussions, Mediation Act was adopted on 07.06.2012 and entered into force on 21.06.2013. According to the Mediation Act, it is only possible to mediate issues arising from the private law. Also, it is not compulsory to go to mediation in Turkish law, it is optional. Therefore, the parties are completely free to choose mediation method in dispute resolution. Mediators need to be a lawyer with experience in five years. Therefore, it is not possible to be a mediator who is not lawyers. Beyond five years of experience, getting education and success in exams about especially body language and psychology is also very important to be a mediator. If the parties compromise as a result of mediation, a document is issued. This document will also have the ability to exercising availability under certain circumstances. Thus, the parties will not need to apply to the court again. On the contrary, they will find the opportunity to execute this document, so they can regain their debts. However, the Mediation Act has entered into force in a period of nearly two years of history; it is possible to say that the interest in mediation is not at the expected level. Therefore, making mediation mandatory for some disputes has been discussed recently. At this point, once the mediation becomes mandatory and good results follows it, this institution will be able to find a serious interest in Turkey. Otherwise, if the results will not be satisfying, the mediation method will be removed.

Keywords: alternative dispute resolution methods, mediation act, mediation, mediator, mediation in Turkey

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Authors: Moiz S. Vohra, Nagalingam Arun Prasanth, Wei L. Tan, S. H. Yeo

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The understanding of generation and collapse of acoustic cavitation bubbles are prerequisites for application of cavitation erosion. Microbubbles generated due to rapid fluctuation of pressure induced by propagation of ultrasonic wave lead to formation of high velocity microjets and or shock waves upon collapse. Due to vast application of ultrasonic, it is important to characterize and understand cavitation collapse pressure under the radiating surface at different conditions. A comparative investigation is carried out to determine impact load and dynamic pressure distribution exerted upon bubble collapse using thin film pressure sensors. Measurements were recorded at different input conditions such as amplitude, stand-off distance, insertion depth of the horn inside the liquid and pulse on-off time of acoustic vibrations. Impact force of 2.97 N is recorded at amplitude of 108 μm and stand-off distance of 1 mm from the sensor film, whereas impulsive force as low as 0.4 N is recorded at amplitude of 12 μm and stand-off distance of 5 mm from the sensor film. The results drawn from the investigation indicated that variety of impact loads can be achieved by controlling generation and collapse of bubbles, making it suitable to use for numerous application.

Keywords: ultrasonic cavitation, bubble collapse, pressure mapping sensor, impact load

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Authors: Apetsi K. Ampiah, Zhao Xin

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Earthquakes over the years have been known to cause devastating damage on buildings and induced huge loss on human life and properties. It is for this reason that engineers have devised means of protecting buildings and thus protecting human life. Since the invention of devices such as the viscous and friction dampers, scientists/researchers have been able to incorporate these devices into buildings and other engineering structures. The viscous damper is a hydraulic device which dissipates the seismic forces by pushing fluid through an orifice, producing a damping pressure which creates a force. In the friction damper, the force is mainly resisted by converting the kinetic energy into heat by friction. Devices such as viscous and friction dampers are able to absorb almost all the earthquake energy, allowing the structure to remain undamaged (or with some amount of damage) and ready for immediate reuse (with some repair works). Comparing these two devices presents the engineer with adequate information on the merits and demerits of these devices and in which circumstances their use would be highly favorable. This paper examines the performance of both viscous and friction dampers under different ground motions. A two-storey frame installed with both devices under investigation are modeled in commercial computer software and analyzed under different ground motions. The results of the performance of the structure are then tabulated and compared. Also included in this study is the ease of installation and maintenance of these devices.

Keywords: friction damper, seismic, slip load, viscous damper

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Authors: M. Kessi

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We investigated the effect of the magnetic field on carrier transport phenomena in the transistor channel region of Double-Gate Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). This explores the Lorentz force and basic physical properties of solids exposed to a constant external magnetic field. The magnetic field modulates the electrons and potential distribution in the case of silicon Tunnel FETs. This modulation shows up in the device's external electrical characteristics such as ON current (ION), subthreshold leakage current (IOF), the threshold voltage (VTH), the magneto-transconductance (gm) and the output magneto-conductance (gDS) of Tunnel FET. Moreover, the channel doping concentration and potential distribution are obtained using the numerical method by solving Poisson’s transport equation in 3D modules semiconductor magnetic sensors available in Silvaco TCAD tools. The numerical simulations of the magnetic nano-sensors are relatively new. In this work, we present the results of numerical simulations based on 3D magnetic sensors. The results show excellent accuracy comportment and good agreement compared with that obtained in the experimental study of MOSFETs technology.

Keywords: single-gate MOSFET, magnetic field, hall field, Lorentz force

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Authors: S. M. Dash, K. B. Lua, T. T. Lim

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This paper presents results of numerical and experimental studies on a two-dimensional (2D) flapping elliptic airfoil in a forward flight condition at Reynolds number of 5000. The study is motivated from an earlier investigation which shows that the deterioration in thrust performance of a sinusoidal heaving and pitching 2D (NACA0012) airfoil at high flapping frequency can be recovered by changing the effective angle of attack profile to square wave, sawtooth, or cosine wave shape. To better understand why such modifications lead to superior thrust performance, we take a closer look at the transient aerodynamic force behavior of an airfoil when the effective angle of attack profile changes gradually from a generic smooth trapezoidal profile to a sinusoid shape by modifying the base length of the trapezoid. The choice of using a smooth trapezoidal profile is to avoid the infinite acceleration condition encountered in the square wave profile. Our results show that the enhancement in the time-averaged thrust performance at high flapping frequency can be attributed to the delay and reduction in the drag producing valley region in the transient thrust force coefficient when the effective angle of attack profile changes from sinusoidal to trapezoidal.

Keywords: two-dimensional flapping airfoil, thrust performance, effective angle of attack, CFD, experiments

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Authors: Itziar Gonzalez, Pilar Carreras, Alberto Pinto, Roque Ruben Andres

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Acoustophoretic separation of plasma from blood is based on a collection process of the blood cells, driven by an acoustic radiation force. The number of cells, their concentration, and the sample hydrodynamics are involved in these processes. However, their influence on the acoustic blood response has not yet been reported in the literature. Addressing it, this paper presents an experimental study of blood samples exposed to ultrasonic standing waves at different hematocrit levels and hydrodynamic conditions. The experiments were performed in a glass capillary (700µm-square cross section) actuated by a piezoelectric ceramic at 1MHz, hosting 2D orthogonal half-wavelength resonances transverse to the channel length, with a single-pressure-node along its central axis where cells collected driven by the acoustic radiation force. Four blood dilutions in PBS of 1:20, 1:10, 1:5, and 1:2 were tested at eight flow rate conditions Q=0:120µL/min. The 1:5 dilution (H=9%) demonstrated to be optimal for the plasmapheresis at any of the flow rates analyzed, requiring the shortest times to achieve plasma free of cells. The study opens new possibilities to optimize processes of plasmapheresis processes by ultrasounds at different hematocrit conditions in future personalized diagnoses/treatments involving blood samples.

Keywords: ultrasounds, microfluidics, flow rate, acoustophoresis, polymeric resonators

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Authors: Masoud Mahdavi

Abstract:

The structure is made using different members and combining them with each other. These members are basically based on technical and engineering principles and are combined in different ways and have their own unique effects on the building. Trusses are one of the most common and important members of the structure, accounting for a large percentage of the power transmission structure in the building. Different types of trusses are based on structural needs and evaluating and making complete comparisons between them is one of the most important engineering analyses. In the present study, four types of trusses have been studied; 1) Hawe truss, 2) Pratt truss, 3) k truss, and 4) warren truss, under cyclic loading for 80 seconds. The trusses are modeled in 3d using st₃₇ steel. The results showed that Hawe trusses had higher values ​​than all other trusses (k, Pratt and Warren) in all the studied indicators. Indicators examined in the study include; 1) von Mises stresses, 2) displacement, 3) support force, 4) velocity, 5) acceleration, 6) capacity (hysteresis curve) and 7) energy diagram. Pratt truss in indicators; Mises stress, displacement, energy have the least amount compared to other trusses. K truss in indicators; support force, speed and acceleration are the lowest compared to other trusses.

Keywords: hawe truss, pratt truss, K truss, warren truss, cyclic loading, finite element method

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Authors: A. Raj Kumar, S. Bilaloglu

Abstract:

Stroke is a leading cause of adult disability worldwide. We depend on our hands for our activities of daily living(ADL). Although many patients regain the ability to walk, they continue to experience long-term hand motor impairments. As the number of individuals with young stroke is increasing, there is a critical need for effective approaches for rehabilitation of hand function post-stroke. Motor relearning for dexterity requires task-specific kinesthetic, tactile and visual feedback. However, when a stroke results in both sensory and motor impairment, it becomes difficult to ascertain when and what type of sensory substitutions can facilitate motor relearning. In an ideal situation, real-time task-specific data on the ability to learn and data-driven feedback to assist such learning will greatly assist rehabilitation for dexterity. We have found that kinesthetic and tactile information from the unaffected hand can assist patients re-learn the use of optimal fingertip forces during a grasp and lift task. Measurement of fingertip grip force (GF), load forces (LF), their corresponding rates (GFR and LFR), and other metrics can be used to gauge the impairment level and progress during learning. Currently ATI mini force-torque sensors are used in research settings to measure and compute the LF, GF, and their rates while grasping objects of different weights and textures. Use of the ATI sensor is cost prohibitive for deployment in clinical or at-home rehabilitation. A cost effective mechatronic device is developed to quantify GF, LF, and their rates for stroke rehabilitation purposes using off-the-shelf components such as load cells, flexi-force sensors, and an Arduino UNO microcontroller. A salient feature of the device is its integration with an interactive gaming environment to render a highly engaging user experience. This paper elaborates the integration of kinesthetic and tactile sensing through computation of LF, GF and their corresponding rates in real time, information processing, and interactive interfacing through augmented reality for visual feedback.

Keywords: feedback, gaming, kinesthetic, rehabilitation, tactile

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Authors: Zhenyu Yang, Qiunan Chen, Xiaocheng Huang

Abstract:

Reliable prediction of tunnel collapse remains a prominent challenge in the field of civil engineering. In this study, leveraging the nonlinear Hoek-Brown failure criterion and the upper-bound theorem, an analytical solution for the collapse surface of shallowly buried circular tunnels was derived, taking into account the coupled effects of surface loads and pore water pressures. Initially, surface loads and pore water pressures were introduced as external force factors, equating the energy dissipation rate to the external force, yielding our objective function. Subsequently, the variational method was employed for optimization, and the outcomes were juxtaposed with previous research findings. Furthermore, we utilized the deduced equation set to systematically analyze the influence of various rock mass parameters on collapse shape and extent. To validate our analytical solutions, a comparison with prior studies was executed. The corroboration underscored the efficacy of our proposed methodology, offering invaluable insights for collapse risk assessment in practical engineering applications.

Keywords: tunnel roof stability, analytical solution, hoek–brown failure criterion, limit analysis

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Authors: A. Boonpratatong, J. Pantong, S. Kiattisaksophon, W. Senavongse

Abstract:

In this study, an integrated sensing and modeling system for manual wheelchair propulsion measurement and propulsion efficiency calculation was used to indicate the level of overuse. Seven subjects participated in the measurement. On the level surface, the propulsion efficiencies were not different significantly as the riding speed increased. By contrast, the propulsion efficiencies on the 15-degree incline were restricted to around 0.5. The results are supported by previously reported wheeling resistance and propulsion torque relationships implying margin of the overuse. Upper limb musculoskeletal injuries and syndromes in manual wheelchair riders are common, chronic, and may be caused at different levels by the overuse i.e. repetitive riding on steep incline. The qualitative analysis such as the mechanical effectiveness on manual wheeling to establish the relationship between the riding difficulties, mechanical efforts and propulsion outputs is scarce, possibly due to the challenge of simultaneous measurement of those factors in conventional manual wheelchairs and everyday environments. In this study, the integrated sensing and modeling system were used to measure manual wheelchair propulsion efficiency in conventional manual wheelchairs and everyday environments. The sensing unit is comprised of the contact pressure and inertia sensors which are portable and universal. Four healthy male and three healthy female subjects participated in the measurement on level and 15-degree incline surface. Subjects were asked to perform manual wheelchair ridings with three different self-selected speeds on level surface and only preferred speed on the 15-degree incline. Five trials were performed in each condition. The kinematic data of the subject’s dominant hand and a spoke and the trunk of the wheelchair were collected through the inertia sensors. The compression force applied from the thumb of the dominant hand to the push rim was collected through the contact pressure sensors. The signals from all sensors were recorded synchronously. The subject-selected speeds for slow, preferred and fast riding on level surface and subject-preferred speed on 15-degree incline were recorded. The propulsion efficiency as a ratio between the pushing force in tangential direction to the push rim and the net force as a result of the three-dimensional riding motion were derived by inverse dynamic problem solving in the modeling unit. The intra-subject variability of the riding speed was not different significantly as the self-selected speed increased on the level surface. Since the riding speed on the 15-degree incline was difficult to regulate, the intra-subject variability was not applied. On the level surface, the propulsion efficiencies were not different significantly as the riding speed increased. However, the propulsion efficiencies on the 15-degree incline were restricted to around 0.5 for all subjects on their preferred speed. The results are supported by the previously reported relationship between the wheeling resistance and propulsion torque in which the wheelchair axle torque increased but the muscle activities were not increased when the resistance is high. This implies the margin of dynamic efforts on the relatively high resistance being similar to the margin of the overuse indicated by the restricted propulsion efficiency on the 15-degree incline.

Keywords: contact pressure sensor, inertia sensor, integrating sensing and modeling system, manual wheelchair propulsion efficiency, manual wheelchair propulsion measurement, tangential force, resultant force, three-dimensional riding motion

Procedia PDF Downloads 290

Authors: Jiazhen Chen, Yue Sun, Joanne Yip, Kit-Lun Yick

Abstract:

The design of sports bras poses a considerable challenge due to the difficulty in accurately predicting the wearing result after computer-aided design (CAD). It needs repeated physical try-on or virtual try-on to obtain a comfortable pressure range during motion. Specifically, in the context of running, the exact support area and force exerted on the breasts remain unclear. Consequently, obtaining an effective method to design the sports bra pads shape becomes particularly challenging. This predicament hinders the successful creation and production of sports bras that cater to women's health needs. The purpose of this study is to propose an effective method to obtain the 3D shape of sports bra pads and to understand the relationship between the supporting force and the 3D shape parameters of the pads. Firstly, the static 3D shape of the sports bra pad and human motion data (Running) are obtained by using the 3D scanner and advanced 4D scanning technology. The 3D shape of the sports bra pad is parameterised and simplified by Free-form Deformation (FFD). Then the sub-models of sports bra and human body are constructed by segmenting and meshing them with MSC Apex software. The material coefficient of sports bras is obtained by material testing. The Marc software is then utilised to establish a dynamic contact model between the human breast and the sports bra pad. To realise the reverse design of the sports bra pad, this contact model serves as a forward model for calculating the inverse problem. Based on the forward contact model, the inverse problem of the 3D shape parameters of the sports bra pad with the target bra-wearing pressure range as the boundary condition is solved. Finally, the credibility and accuracy of the simulation are validated by comparing the experimental results with the simulations by the FE model on the pressure distribution. On the one hand, this research allows for a more accurate understanding of the support area and force distribution on the breasts during running. On the other hand, this study can contribute to the customization of sports bra pads for different individuals. It can help to obtain sports bra pads with comfortable dynamic pressure.

Keywords: sports bra design, breast motion, running, inverse problem, finite element dynamic model

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Authors: Seyed Abbas Tabatabaei, Afshin Ghanbarzadeh, Mehdi Abidizadeh

Abstract:

Nowadays the subject of road traffic accidents and the high social and economic costs due to them is the most fundamental problem that experts and providers of transport and traffic brought to a challenge. One of the most effective measures is to enhance the skid resistance of road surface. This research aims to study the intersection of one case in Ahwaz and the effect of increasing the skid resistance in reducing pedestrian injuries in accidents at intersections. In this research the device was developed to measure the coefficient of friction and tried the rules and practices of it have a high similarity with the Locked Wheel Trailer. This device includes a steel frame, wheels, hydration systems, and force gauge. The output of the device is that the force gauge registers. By investigate this data and applying the relationships relative surface coefficient of friction is obtained. Friction coefficient data for the current state and the state of the new pavement are obtained and plotted on the graphs based on the graphs we can compare the two situations and speed at the moment of collision between the two modes are compared. The results show that increasing the coefficient of friction to what extent can be effective on the severity and number of accidents.

Keywords: intersection, coefficient of friction, skid resistance, locked wheels, accident, pedestrian

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Authors: Chingwen Yeh, Chang Ning Hung

Abstract:

This paper aims to analysis the aesthetic qualities of Dancing Ink (2017) performed by Miao-Hsuan Dance Group in Taiwan. The premiere was performed at Taichung Seaport Art Center Exhibition Hall Room A, in Taichung Taiwan on March 11th, 2017. What calligraphic elements were applied into the contemporary dance choreography was examed by these authors. Although calligraphy and dance are two different art forms, one can see in Dancing Ink that the beauty of Yin Yang force circling; the flow of Chi from inner meditation to the outer physical action are resonated in both art forms. The aesthetic experience was documented through qualitative research methods. In-depth interviews were conducted within a focus group including the calligrapher, the choreographer, the participated professional dancers and the appreciators. Subject matter, movement qualities, characteristic and meaning are the four main areas of interpretation originated from Janet Adshead’s dance analytical theory. Based on all the research data collection and analysis, this research found: 1) Making invisible spirituality visible in relations to creative process, 2) An artistic symbol that transforms from two-dimensional into three-dimensional generates a new aesthetic value, 3) Choreography and calligraphy require different artistic skills and disciplines but expressed the similar dynamic and rhythm in their movement.

Keywords: Chi, Dancing Ink, Miao Hsuan Dance Group, Yin Yang force

Procedia PDF Downloads 405