Search results for: failure pressure

Authors: Aniko Babits, Ahmad Daoud

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Introduction: The beach chair position (BCP) is a good approach to almost all types of shoulder procedures. However, moving an anaesthetized patient from the supine to sitting position may pose a risk of cerebral hypoperfusion and potential cerebral ischaemia as a result of significant reductions in blood pressure and cardiac output. Hypocapnia in ventilated patients and impaired blood flow to the vertebral artery due to hyperextension, rotation, or tilt of the head may have an impact too. Co-morbidities that may increase the risk of cerebral ischaemia in the BCP include diabetes with autonomic neuropathy, cerebrovascular disease, cardiac disease, severe hypertension, generalized vascular disease, history of fainting, and febrile conditions. Beach chair surgery requires a careful anaesthetic and surgical management to optimize patient safety and minimize the risk of adverse outcomes. Methods: We describe the necessary steps for optimal patient positioning and the aims of intraoperative management, including anaesthetic techniques to ensure patient safety in the BCP. Results: Regardless of the anaesthetic technique, adequate patient positioning is paramount in the BCP. The key steps to BCP are aimed at optimizing surgical success and minimizing the risk of severe neurovascular complications. The primary aim of anaesthetic management is to maintain cardiac output and mean arterial pressure (MAP) to protect cerebral perfusion. Blood pressure management includes treating a fall in MAP of more than 25% from baseline or a MAP less than 70 mmHg. This can be achieved by using intravenous fluids or vasopressors. A number of anaesthetic techniques could also improve cerebral oxygenation, including avoidance of intermittent positive pressure ventilation (IPPV) with general anaesthesia (GA), using regional anaesthesia, maintaining normocapnia and normothermia, and the application of compression stockings. Conclusions: In summary, BCP is a reliable and effective position to perform shoulder procedures. Simple steps to patient positioning and careful anaesthetic management could maximize patient safety and avoid unwanted adverse outcomes in patients undergoing surgery in BCP.

Keywords: beach chair position, cerebral oxygenation, cerebral perfusion, sitting position

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Authors: M. K. Yusuf, W. O. Hamman, U. E. Umana, S. B. Oladele

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Background: Dilatation of the inferior vena cava (IVC) is used as the ultrasonic diagnostic feature in patients suspected of congestive heart failure. The IVC diameter has been reported to vary among the various body mass indexes (BMI) and body shape indexes (ABSI). Knowledge of these variations is useful in precision diagnoses of CHF by imaging scientists. Aim: The study aimed to establish an equation for predicting the ultrasonic mean diameter of the IVC among the various BMI/ABSI of inhabitants of Azare, Bauchi State-Nigeria. Methodology: Two hundred physically healthy adult subjects of both sexes were classified into under, normal, over, and obese weights using their BMIs after selection using a structured questionnaire following their informed consent for an abdominal ultrasound scan. The probe was placed on the midline of the body, halfway between the xiphoid process and the umbilicus, with the marker on the probe directed towards the patient's head to obtain a longitudinal view of the IVC. The maximum IVC diameter was measured from the subcostal view using the electronic caliper of the scan machine. The mean value of each group was obtained, and the results were analysed. Results: A novel equation {(IVC Diameter = 1.04 +0.01(X) where X= BMI} has been generated for determining the IVC diameter among the populace. Conclusion: An equation for predicting the IVC diameter from individual BMI values in apparently healthy subjects has been established.

Keywords: equation, ultrasonic, IVC diameter, body adiposities

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Authors: Umar Hayatu Sidik

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Application of liquid base petroleum fuel (petrol and diesel) for transportation fuel causes emissions of greenhouse gases (GHGs), while natural gas (NG) reduces the emissions of greenhouse gases (GHGs). At present, compression and liquefaction are the most matured technology used for transportation system. For transportation use, compression requires high pressure (200–300 bar) while liquefaction is impractical. A relatively low pressure of 30-40 bar is achievable by adsorbed natural gas (ANG) to store nearly compressed natural gas (CNG). In this study, adsorbents for high-pressure adsorption of methane (CH4) was prepared from coconut shells and polyetheretherketone (PEEK) using potassium hydroxide (KOH) and microwave-assisted activation. Design expert software version 7.1.6 was used for optimization and prediction of preparation conditions of the adsorbents for CH₄ adsorption. Effects of microwave power, activation time and quantity of PEEK on the adsorbents performance toward CH₄ adsorption was investigated. The adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG) and derivative thermogravimetric (DTG) and scanning electron microscopy (SEM). The ideal CH4 adsorption capacities of adsorbents were determined using volumetric method at pressures of 5, 17, and 35 bar at an ambient temperature and 5 oC respectively. Isotherm and kinetics models were used to validate the experimental results. The optimum preparation conditions were found to be 15 wt% amount of PEEK, 3 minutes activation time and 300 W microwave power. The highest CH4 uptake of 9.7045 mmol CH4 adsorbed/g adsorbent was recorded by M33P15 (300 W of microwave power, 3 min activation time and 15 wt% amount of PEEK) among the sorbents at an ambient temperature and 35 bar. The CH4 equilibrium data is well correlated with Sips, Toth, Freundlich and Langmuir. Isotherms revealed that the Sips isotherm has the best fit, while the kinetics studies revealed that the pseudo-second-order kinetic model best describes the adsorption process. In all scenarios studied, a decrease in temperature led to an increase in adsorption of both gases. The adsorbent (M33P15) maintained its stability even after seven adsorption/desorption cycles. The findings revealed the potential of coconut shell-PEEK as CH₄ adsorbents.

Keywords: adsorption, desorption, activated carbon, coconut shells, polyetheretherketone

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Authors: Sai Hung Cheung, Zhe Shao

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Recent earthquake-induced tsunamis in Padang, 2004 and Tohoku, 2011 brought huge losses of lives and properties. Maintaining vertical evacuation systems is the most crucial strategy to effectively reduce casualty during the tsunami event. Thus, it is of our great interest to quantify the risk to structural dynamic systems due to earthquake-induced tsunamis. Despite continuous advancement in computational simulation of the tsunami and wave-structure interaction modeling, it still remains computationally challenging to evaluate the reliability (or its complement failure probability) of a structural dynamic system when uncertainties related to the system and its modeling are taken into account. The failure of the structure in a tsunami-wave-structural system is defined as any response quantities of the system exceeding specified thresholds during the time when the structure is subjected to dynamic wave impact due to earthquake-induced tsunamis. In this paper, an approach based on a novel integration of the Subset Simulation algorithm and a recently proposed moving least squares response surface approach for stochastic sampling is proposed. The effectiveness of the proposed approach is discussed by comparing its results with those obtained from the Subset Simulation algorithm without using the response surface approach.

Keywords: response surface model, subset simulation, structural reliability, Tsunami risk

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Authors: M. Belén Prendes-Gero, Celestino González-Nicieza, M. Inmaculada Alvarez-Fernández

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Roof collapse is one of the problems with a higher frequency in most of the mines of all countries, even now. There are many reasons that may cause the roof to collapse, namely the mine stress activities in the mining process, the lack of vigilance and carelessness or the complexity of the geological structure and irregular operations. This work is the result of the analysis of one accident produced in the “Mary” coal exploitation located in northern Spain. In this accident, the roof of a crossroad of excavated galleries to exploit the “Morena” Layer, 700 m deep, collapsed. In the paper, the work done by the forensic team to determine the causes of the incident, its conclusions and recommendations are collected. Initially, the available documentation (geology, geotechnics, mining, etc.) and accident area were reviewed. After that, laboratory and on-site tests were carried out to characterize the behaviour of the rock materials and the support used (metal frames and shotcrete). With this information, different hypotheses of failure were simulated to find the one that best fits reality. For this work, the software of finite differences in three dimensions, FLAC 3D, was employed. The results of the study confirmed that the detachment was originated as a consequence of one sliding in the layer wall, due to the large roof span present in the place of the accident, and probably triggered as a consequence of the existence of a protection pillar insufficient. The results allowed to establish some corrective measures avoiding future risks. For example, the dimensions of the protection zones that must be remained unexploited and their interaction with the crossing areas between galleries, or the use of more adequate supports for these conditions, in which the significant deformations may discourage the use of rigid supports such as shotcrete. At last, a grid of seismic control was proposed as a predictive system. Its efficiency was tested along the investigation period employing three control equipment that detected new incidents (although smaller) in other similar areas of the mine. These new incidents show that the use of explosives produces vibrations which are a new risk factor to analyse in a next future.

Keywords: forensic analysis, hypothesis modelling, roof failure, seismic monitoring

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Authors: S. V. Ncube, A. I. O. Jideani, E. T. Gwata

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The plight of food insecurity in developing countries has led to renewed interest in underutilized legumes. Their nutritional versatility, desirable functionality, pharmaceutical value and inherent bioactive compounds have drawn the attention of researchers. This has provoked the development of value added products with the aim of commercially exploiting their full potential. However processing of these legumes leads to changes in nutritional composition as affected by processing variables like pH, temperature and pressure. There is therefore a need for process control and quality assurance during production of the value added products. However, conventional methods for microbiological and biochemical identification are labour intensive and time-consuming. Biosensors offer rapid and affordable methods to assure the quality of the products. They may be used to quantify nutrients and anti-nutrients in the products while manipulating and monitoring variables such as pH, temperature, pressure and oxygen that affect the quality of the final product. This review gives an overview of the types of biosensors used in the food industry, their advantages and disadvantages and their possible application in processing of legumes.

Keywords: legume processing, biosensors, quality control, nutritional versatility

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Authors: Heiko Jessen, Laura Tanus, Slobodan Ruzicic

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Objectives: The efficacy of Stribild®, an integrase strand transfer inhibitor (INSTI) -based STR, has been evaluated in randomized clinical trials and it has demonstrated durable capability in terms of achieving sustained suppression of HIV-1 RNA-levels. However, differences in monitoring frequency, existing selection bias and profile of patients enrolled in the trials, may all result in divergent efficacy of this regimen in routine clinical settings. The aim of this study was to assess the virologic outcomes, safety and tolerability profile of Stribild® in a routine clinical setting. Methods: This was a retrospective monocentric analysis on HIV-1-infected patients, who started with or were switched to Stribild®. Virological failure (VF) was defined as confirmed HIV-RNA>50 copies/ml. The minimum time of follow-up was 24 weeks. The percentage of patients remaining free of therapeutic failure was estimated using the time-to-loss-of-virologic-response (TLOVR) algorithm, by intent-to-treat analysis. Results: We analyzed the data of 197 patients (56 ART-naïve and 141 treatment-experienced patients), who fulfilled the inclusion criteria. Majority (95.9%) of patients were male. The median time of HIV-infection at baseline was 2 months in treatment-naïve and 70 months in treatment-experienced patients. Median time [IQR] under ART in treatment-experienced patients was 37 months. Among the treatment-experienced patients 27.0% had already been treated with a regimen consisting of two NRTIs and one INSTI, whereas 18.4% of them experienced a VF. The median time [IQR] of virological suppression prior to therapy with Stribild® in the treatment-experienced patients was 10 months [0-27]. At the end of follow-up (median 33 months), 87.3% (95% CI, 83.5-91.2) of treatment-naïve and 80.3% (95% CI, 75.8-84.8) of treatment-experienced patients remained free of therapeutic failure. Considering only treatment-experienced patients with baseline VL<50 copies/ml, 83.0% (95% CI, 78.5-87.5) remained free of therapeutic failure. A total of 17 patients stopped treatment with Stribild®, 5.4% (3/56) of them were treatment-naïve and 9.9% (14/141) were treatment-experienced patients. The Stribild® therapy was discontinued in 2 (1.0%) because of VF, loss to follow-up in 4 (2.0%), and drug-drug interactions in 2 (1.0%) patients. Adverse events were in 7 (3.6%) patients the reason to switch from therapy with Stribild® and further 2 (1.0%) patients decided personally to switch. The most frequently observed adverse events were gastrointestinal side effects (20.0%), headache (8%), rash events (7%) and dizziness (6%). In two patients we observed an emergence of novel resistances in integrase-gene. The N155H evolved in one patient and resulted in VF. In another patient S119R evolved either during or shortly upon switch from therapy with Stribild®. In one further patient with VF two novel mutations in the RT-gene were observed when compared to historical genotypic test result (V106I/M and M184V), whereby it is not clear whether they evolved during or already before the switch to Stribild®. Conclusions: Effectiveness of Stribild® for treatment-naïve patients was consistent with data obtained in clinical trials. The safety and tolerability profile as well as resistance development confirmed clinical efficacy of Stribild® in a daily practice setting.

Keywords: ART, HIV, integrase inhibitor, stribild

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Authors: Young Min Kim, Jeong Lak Sohn, Eui Soo Yoon

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This study describes the optimization of supercritical carbon dioxide (S-CO2) power cycle for recovering waste heat from a gas turbine. An S-CO2 cycle that recovers heat from small industrial and aeroderivative gas turbines can outperform a steam-bottoming cycle despite its simplicity and compactness. In using S-CO2 power cycles for waste heat recovery, a split cycle was studied to maximize the net output power by incorporating the utilization efficiency of the waste heat (lowering the temperature of the exhaust gas through the heater) along with the thermal efficiency of the cycle (minimizing the temperature difference for the heat transfer, exergy loss). The cooling condition of the S-CO2 WHR system has a great impact on the performance and the optimum low pressure of the system. Furthermore, the optimum high pressure of the S-CO2 WHR systems for the maximum power from the given heat sources is dependent on the temperature of the waste heat source.

Keywords: exergy loss, gas turbine, optimization, supercritical CO2 power cycle, split cycle, waste heat recovery

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Authors: Marcin Szlachetka, Mateusz Paszko, Grzegorz Baranski

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This paper discusses the AVL EXCITE Designer simulation research into loads applied to main and crank bearings in the compression-ignition two-stroke engine. There was created a model of engine lubrication system which covers the part of this system related to particular nodes of a bearing system, i.e. a connection of main bearings in an engine block with a crankshaft, a connection of crank pins with a connecting rod. The analysis focused on the load given as a distribution of hydrodynamic oil film pressure corresponding different values of radial internal clearance. There was also studied the impact of gas force on minimal oil film thickness in main and crank bearings versus crankshaft rotational speed. Our model calculates oil film parameters, an oil film pressure distribution, an oil temperature change and dimensions of bearings as well as an oil temperature distribution on surfaces of bearing seats. Accordingly, it was possible to select, for example, a correct clearance for each of the node bearings. The research was performed for several values of engine crankshaft speed ranging from 800 RPM to 4000 RPM. Bearing oil pressure was changed according to engine speed ranging between 1 bar and 5 bar and an oil temperature of 90°C. The main bearing clearances made initially for the calculation and research were: 0.015 mm, 0.025 mm, 0.035 mm, 0.05 mm, 0.1 mm. The oil used for the research corresponded the SAE 5W-40 classification. The paper presents the selected research results referring to certain specific operating points and bearing radial internal clearances. Acknowledgement: This work has been realized in the cooperation with The Construction Office of WSK ‘PZL-KALISZ’ S.A. and is part of Grant Agreement No. POIR.01.02.00-00-0002/15 financed by the Polish National Centre for Research and Development.

Keywords: crank bearings, diesel engine, oil film, two-stroke engine

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Authors: Thiago Viana

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Eventually train accidents occur on railways and for some specific cases it is necessary to use a train rescue with a crane positioned under a platform wagon. These tumbled machines are collected and sent to the machine shop or scrap yard. In one of these cranes that were being used to rescue a wagon, occurred a fall of hoist due to fracture of two large pins. The two pins were collected and sent for failure analysis. This work investigates the main cause and the secondary causes for the initiation of the fatigue crack. All standard failure analysis procedures were applied, with careful evaluation of the characteristics of the material, fractured surfaces and, mainly, metallographic tests using an optical microscope to compare the geometry of the peaks and valleys of the thread of the pins and their respective seats. By metallographic analysis, it was concluded that the fatigue cracks were started from a notch (stress concentration) in the valley of the threads of the pin applied to the right side of the crane (pin 1). In this, it was verified that the peaks of the threads of the pin seat did not have proper geometry, with sharp edges being present that caused such notches. The visual analysis showed that fracture of the pin on the left side of the crane (pin 2) was brittle type, being a consequence of the fracture of the first one. Recommendations for this and other railway cranes have been made, such as nondestructive testing, stress calculation, design review, quality control and suitability of the mechanical forming process of the seat threads and pin threads.

Keywords: crane, fracture, pin, railway

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Authors: Nosheen Zareen Khan, Abdul Majeed Siddiqui, Muhammad Afzal Rana

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The steady flow of a second order fluid through constricted tube with slip velocity at wall is modeled and analyzed theoretically. The governing equations are simplified by implying no slip in radial direction. Based on Karman Pohlhausen procedure polynomial solution for axial velocity profile is presented. An expressions for pressure gradient, shear stress, separation and reattachment points and radial velocity are also calculated. The effect of slip and no slip velocity on velocity, shear stress, pressure gradient are discussed and depicted graphically. It is noted that when Reynolds number increases velocity of the fluid decreases in both slip and no slip conditions. It is also found that the wall shear stress, separation and reattachment points are strongly effected by Reynolds number.

Keywords: approximate solution, constricted tube, non-Newtonian fluids, Reynolds number

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Authors: Daniel Thompson, Muhammad Peerbux, Sophie Cerutti, Hansraj Bookun

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Introduction: Dialysis access is a key component of the care of patients with end stage renal failure. In our institution, a combined service of vascular surgeons and nephrologists are responsible for the creation and maintenance of arteriovenous fisultas (AVF), tenckhoff cathethers and Hickman/permcath lines. This poster investigates the last 10 years of dialysis access surgery conducted at St. Vincent’s Hospital Melbourne. Method: A cross-sectional retrospective analysis was conducted of patients of St. Vincent’s Hospital Melbourne (Victoria, Australia) utilising data collection from the Australasian Vascular Audit (Australian and New Zealand Society for Vascular Surgery). Descriptive demographic analysis was carried out as well as operation type, length of hospital stays, postoperative deaths and need for reoperation. Results: 2085 patients with renal failure were operated on between the years of 2011 and 2020. 1315 were male (63.1%) and 770 were female (36.9%). The mean age was 58 (SD 13.8). 92% of patients scored three or greater on the American Society of Anesthiologiests classification system. Almost half had a history of ischaemic heart disease (48.4%), more than half had a history of diabetes (64%), and a majority had hypertension (88.4%). 1784 patients had a creatinine over 150mmol/L (85.6%), the rest were on dialysis (14.4%). The most common access procedure was AVF creation, with 474 autologous AVFs and 64 prosthetic AVFs. There were 263 Tenckhoff insertions. We performed 160 cadeveric renal transplants. The most common location for AVF formation was brachiocephalic (43.88%) followed by radiocephalic (36.7%) and brachiobasilic (16.67%). Fistulas that required re-intervention were most commonly angioplastied (n=163), followed by thrombectomy (n=136). There were 107 local fistula repairs. Average length of stay was 7.6 days, (SD 12). There were 106 unplanned returns to theatre, most commonly for fistula creation, insertion of tenckhoff or permacath removal (71.7%). There were 8 deaths in the immediately postoperative period. Discussion: Access to dialysis is vital for patients with end stage kidney disease, and requires a multidisciplinary approach from both nephrologists, vascular surgeons, and allied health practitioners. Our service provides a variety of dialysis access methods, predominately fistula creation and tenckhoff insertion. Patients with renal failure are heavily comorbid, and prolonged hospital admission following surgery is a source of significant healthcare expenditure. AVFs require careful monitoring and maintenance for ongoing utility, and our data reflects a multitude of operations required to maintain usable access. The requirement for dialysis is growing worldwide and our data demonstrates a local experience in access, with preferred methods, common complications and the associated surgical interventions.

Keywords: dialysis, fistula, nephrology, vascular surgery

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Authors: Miraz Hafiz Rossy

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As part of planning to address shortfalls in fresh water supply for the world, Sea water can be a huge source of fresh water. But Desalinating sea water to get fresh water could require a lots of fossil fuels. To save the fossil fuel in terms of save the green world but meet the up growing need for fresh water, a very useful but energy efficient method needs to be introduced. Vacuum desalination of sea water using only the Renewable energy can be an effective solution to this issue. Taking advantage of sensitivity of water's boiling point to air pressure a vacuum desalination water treatment plant can be designed which would only use sea water as feed water and solar energy as fuel to produce fresh drinking water. The study indicates that reducing the air pressure to a certain value water can be boiled at very low temperature. Using solar energy to provide the condensation and the vacuum creation would be very useful and efficient. Compared to existing resources, desalination is considered to be expensive, but using only renewable energy the cost can be reduced significantly. Despite its very few drawbacks, it can be considered a possible solution to the world's fresh water shortages.

Keywords: desalination, scarcity of fresh water, water purification, water treatment

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Authors: Eun Kyung Kim, Kyehan Rhee

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Viscoelastic wall properties of the arterial plaques change as the disease progresses, and estimation of wall viscoelasticity can provide a valuable assessment tool for plaque rupture prediction. Cross section of the stenotic coronary artery was modeled based on the IVUS image, and the finite element analysis was performed to get wall deformation under pulsatile pressure. The effects of viscoelastic parameters of the plaque on luminal diameter variations were explored. The result showed that decrease of viscous effect reduced the phase angle between the pressure and displacement waveforms, and phase angle was dependent on the viscoelastic properties of the wall. Because viscous effect of tissue components could be identified using the phase angle difference, wall deformation waveform analysis may be applied to predict plaque wall composition change and vascular wall disease progression.

Keywords: atherosclerotic plaque, diameter variation, finite element method, viscoelasticity

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Authors: Aleksandr I. Korobov, Natalia V. Shirgina, Aleksey I. Kokshaiskiy

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The transformation of two types of acoustic waves can occur on a flat interface between two solids at oblique incidence of longitudinal and shear bulk acoustic waves (BAW). This paper presents the results of experimental studies of the properties of reflection and propagation of longitudinal wave and generation of second and third longitudinal and shear harmonics of BAW at oblique incidence of longitudinal BAW on a flat rough boundary between two solids. The experimental sample was a rectangular isosceles pyramid made of D16 aluminum alloy with the plane parallel bases cylinder made of D16 aluminum alloy pressed to the base. The piezoelectric lithium niobate transducer with a resonance frequency of 5 MHz was secured to one face of the pyramid to generate a longitudinal wave. Longitudinal waves emitted by this transducer felt at an angle of 45° to the interface between two solids and reflected at the same angle. On the opposite face of the pyramid, and on the flat side of the cylinder was attached longitudinal transducer with resonance frequency of 10 MHz or the shear transducer with resonance frequency of 15 MHz. These transducers also effectively received signal at a frequency of 5 MHz. In the spectrum of the transmitted and reflected BAW was observed shear and longitudinal waves at a frequency of 5 MHz, as well as longitudinal harmonic at a frequency harmonic of 10 MHz and a shear harmonic at frequency of 15 MHz. The effect of reversing changing of external pressure applied to the rough interface between two solids on the value of the first and higher harmonics of the BAW at oblique incidence on the interface of the longitudinal BAW was experimentally investigated. In the spectrum of the reflected signal from the interface, there was a decrease of amplitudes of the first harmonics of the signal, and non-monotonic dependence of the second and third harmonics of shear wave with an increase of the static pressure applied to the interface. In the spectrum of the transmitted signal growth of the first longitudinal and shear harmonic amplitude and non-monotonic dependence - first increase and then decrease in the amplitude of the second and third longitudinal shear harmonic with increasing external static pressure was observed. These dependencies were hysteresis at reversing changing of external pressure. When pressure applied to the border increased, acoustic contact between the surfaces improves. This increases the energy of the transmitted elastic wave and decreases the energy of the reflected wave. The second longitudinal acoustic harmonics generation was associated with the Hertz nonlinearity on the interface of two pressed rough surfaces, the generation of the third harmonic was caused by shear hysteresis nonlinearity due to dry friction on a rough interface. This study was supported by the Russian Science Foundation (project №14-22-00042).

Keywords: generation of acoustic harmonics, hysteresis nonlinearity, Hertz nonlinearity, transformation of acoustic waves

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Authors: Michel Wakim, Rodrigo Rivera Tinoco

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Supersonic ejector is an economical device that use high pressure vapor to compress a low pressure vapor without any rotating parts or external power sources. Entrainment ratio is a major characteristic of the ejector performance, so the ejector performance is highly dependent on its geometry. The aim of this paper is to design ejector geometry, based on pre-specified operating conditions, and to study the flow behavior inside the ejector by using computational fluid dynamics ‘CFD’ by using ‘ANSYS FLUENT 15.0’ software. In the first section; 1-D mathematical model is carried out to predict the ejector geometry. The second part describes the flow behavior inside the designed model. CFD is the most reliable tool to reveal the mixing process at different parts of the supersonic turbulent flow and to study the effect of the geometry on the effective ejector area. Finally, the results show the effect of the geometry on the entrainment ratio.

Keywords: computational fluids dynamics, ejector, entrainment ratio, geometry optimization, performance

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Authors: Yongseok Kim, Jeong-Min Lee, Hyunwoo Song, Junghan Yun, Jungin Byun, Jae-Mean Koo, Chang-Sung Seok

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Thermal barrier coating(TBC) is applied for gas turbine components to protect the components from extremely high temperature condition. Since metallic substrate cannot endure such severe condition of gas turbines, delamination of TBC can cause failure of the system. Thus, delamination life of TBC is one of the most important issues for designing the components operating at high temperature condition. Thermal stress caused by thermally grown oxide(TGO) layer is known as one of the major failure mechanisms of TBC. Thermal stress by TGO mainly occurs at the interface between TGO layer and ceramic top coat layer, and it is strongly influenced by the thickness and shape of TGO layer. In this study, Isothermal oxidation is conducted on coin-type TBC specimens prepared by APS(air plasma spray) method. After the isothermal oxidation at various temperature and time condition, the thickness and shape(rumpling shape) of the TGO is investigated, and the test data is processed by numerical analysis. Finally, the test data is arranged into a mathematical prediction model with two variables(temperature and exposure time) which can predict the thickness and rumpling shape of TGO.

Keywords: thermal barrier coating, thermally grown oxide, thermal stress, isothermal oxidation, numerical analysis

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Authors: Reinhard Hermawan Lasut, Henki Wibowo Ashadi

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The use of materials in Indonesia's construction sector requires engineers and practitioners to develop efficient construction technology, one of the materials used in cold-formed steel. Generally, the use of cold-formed steel is used in the construction of roof trusses found in houses or factories. The failure of the roof truss structure causes errors in the calculation analysis in the form of cross-sectional dimensions or frame configuration. The roof truss structure, vertical distance effect to the span length at the edge of the frame carries the compressive load. If the span is too long, local buckling will occur which causes problems in the frame strength. The model analysis uses various shapes of roof trusses, span lengths and angles with analysis of the structural stiffness matrix method. Model trusses with one-fifth shortened span and one-sixth shortened span also The trusses model is reviewed with increasing angles. It can be concluded that the trusses model by shortening the span in the compression area can reduce deflection and the model by increasing the angle does not get good results because the higher the roof, the heavier the load carried by the roof so that the force is not channeled properly. The shape of the truss must be calculated correctly so the truss is able to withstand the working load so that there is no structural failure.

Keywords: cold-formed, trusses, deflection, stiffness matrix method

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Authors: E. Rama Devi Jothilingam

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Diabetes mellitus is now one of the most common non communicable diseases globally. India leads the world with largest number of diabetic subjects earning the title "diabetes capital of the world". In order to reduce the mortality rate, a fuzzy expert system is designed to predict the severity of cardiac and renal problems of diabetic patients using fuzzy logic. Since uncertainty is inherent in medicine, fuzzy logic is used in this research work to remove the inherent fuzziness of linguistic concepts and uncertain status in diabetes mellitus which is the prime cause for the cardiac arrest and renal failure. In this work, the controllable risk factors "blood sugar, insulin, ketones, lipids, obesity, blood pressure and protein/creatinine ratio" are considered as input parameters and the "the stages of cardiac" (SOC)" and the stages of renal" (SORD) are considered as the output parameters. The triangular membership functions are used to model the input and output parameters. The rule base is constructed for the proposed expert system based on the knowledge from the medical experts. Mamdani inference engine is used to infer the information based on the rule base to take major decision in diagnosis. Mean of maximum is used to get a non fuzzy control action that best represent possibility distribution of an inferred fuzzy control action. The proposed system also classifies the patients with high risk and low risk using fuzzy c means clustering techniques so that the patients with high risk are treated immediately. The system is validated with Matlab and is used as a tracking system with accuracy and robustness.

Keywords: Diabetes mellitus, fuzzy expert system, Mamdani, MATLAB

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Authors: Yogi Sirodz Gaos, Irvan Wiradinata

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In the 500 kW Organic Rankine Cycle (ORC) power plant in Indonesia, an AFT (according to the Tubular Exchanger Manufacturers Association – TEMA) type shell and tube heat exchanger device is used as a pre-heating system for the ORC’s hot water circulation system. The pre-heating source is a waste heat recovery of the brine water, which is tapped from a geothermal power plant. The brine water itself has 5 MWₜₕ capacities, with average temperature of 170ᵒC, and 7 barg working pressure. The aim of this research is to examine the performance of the heat exchanger in the ORC system in a 500 kW ORC power plant. The data for this research were collected during the commissioning on the middle of December 2016. During the commissioning, the inlet temperature and working pressure of the brine water to the shell and tube type heat exchanger was 149ᵒC, and 4.4 barg respectively. Furthermore, the ΔT for the hot water circulation of the ORC system to the heat exchanger was 27ᵒC, with the inlet temperature of 140ᵒC. The pressure in the hot circulation system was dropped slightly from 7.4ᵒC to 7.1ᵒC. The flow rate of the hot water circulation was 80.5 m³/h. The presentation and discussion of a case study on the performance of the heat exchanger on the 500 kW ORC system is presented as follows: (1) the heat exchange duty is 2,572 kW; (2) log mean temperature of the heat exchanger is 13.2ᵒC; (3) the actual overall thermal conductivity is 1,020.6 W/m².K (4) the required overall thermal conductivity is 316.76 W/m².K; and (5) the over design for this heat exchange performance is 222.2%. An analysis of the heat exchanger detailed engineering design (DED) is briefly discussed. To sum up, this research concludes that the shell and tube heat exchangers technology demonstrated a good performance as pre-heating system for the ORC’s hot water circulation system. Further research need to be conducted to examine the performance of heat exchanger system on the ORC’s hot water circulation system.

Keywords: shell and tube, heat exchanger, organic Rankine cycle, performance, commissioning

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Authors: Polycarp A. Igbojekwe, Chizoba Amajuoyi, Peterson Nwokorie

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The main purpose of this study was to carry out a survey of customer’s aggression towards hotel workers and make contributions on the prevalence and rationale behind customer’s aggression. Data for the study were gathered with a four-point Likert type rating scale. Samples were drawn from frontline hotel employees, managers and customers of twelve (12) hotels selected from three zones of Imo State. Data analyses were conducted using simple percentage, descriptive statistics; and Z-test statistical technique was used to test hypotheses. Among other factors, service failure and verbal abuse by service providers and poor quality product compared to price were identified by customers as the three major factors that can lead to customer aggression. Frontline employees indentified verbal abuse as the most common mode of aggression and that customer aggression causes emotional disturbance in them. The study also revealed that customer aggression is more prevalent in the 1&2 star hotels than it is in 3-5 star hotels. Most of the hotels have not institutionalized systematic approaches needed to effectively face the challenges of customer aggression, thus, customer aggression has become a common feature in the industry. Frontline jobs demand high emotional input. Therefore, we recommend that frontline employees should be given emotional support by their managers and also trained on how to cope with emotional disturbance.

Keywords: customer aggression, emotional disturbance, employee well-being, service failure, verbal abuse

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Authors: A. P. Joshi, H. V. Warrior, J. P. Panda

Abstract:

This paper is a continuation of the work carried out by various turbulence modelers in Oceanography on the topic of oceanic turbulent mixing. It evaluates the evolution of ocean water temperature and salinity by the appropriate modeling of turbulent mixing utilizing proper prescription of eddy viscosity. Many modelers in past have suggested including terms like shear, buoyancy and vorticity to be the parameters that decide the slow pressure strain correlation. We add to it the fact that dissipation anisotropy also modifies the correlation through eddy viscosity parameterization. This recalibrates the established correlation constants slightly and gives improved results. This anisotropization of dissipation implies that the critical Richardson’s number increases much beyond unity (to 1.66) to accommodate enhanced mixing, as is seen in reality. The model is run for a couple of test cases in the General Ocean Turbulence Model (GOTM) and the results are presented here.

Keywords: Anisotropy, GOTM, pressure-strain correlation, Richardson critical number

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Authors: Eunseop Yeom

Abstract:

Many cardiovascular diseases, such as thrombosis and atherosclerosis, can change biochemical molecules in plasma and red blood cell. These alterations lead to excessive increase of blood viscosity contributing to peripheral vascular diseases. In this study, a simple microfluidic-based method is used to measure blood viscosity. Microfluidic device is composed of two parallel side channels and a bridge channel. To estimate blood viscosity, blood samples and reference fluid are separately delivered into each inlet of two parallel side channels using pumps. An interfacial line between blood samples and reference fluid occurs by blocking the outlet of one side-channel. Since width for this interfacial line is determined by pressure ratio between blood and reference flows, blood viscosity can be estimated by measuring width for this interfacial line. This microfluidic-based method can be used for evaluating variations in the viscosity of animal models with cardiovascular diseases under flow conditions.

Keywords: blood viscosity, microfluidic chip, pressure, shear rate

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Authors: Armin Najipour, A. M. Fattahi

Abstract:

The aim of this research was to investigate the effect of the addition of multi walled carbon nanotubes on the mechanical properties of polyethylene/carbon nanotube nanocomposites. To do so, polyethylene and carbon nanotube were mixed in different weight percentages containing 0, 0.5, 1, and 1.5% carbon nanotube in two screw extruder apparatus by fusion. Then the nanocomposite samples were molded in injection apparatus according to ASTM: D6110 standard. The effects of carbon nanotube addition in 4 different levels and injection pressure in 2 levels on the hardness and impact strength of the nanocomposite samples were investigated. The results showed that the addition of carbon nanotube had a significant effect on improving hardness and impact strength of the nanocomposite samples such that by adding 1% w/w carbon nanotube, the impact strength and hardness of the samples improved to 74% and 46.7% respectively. Also, according to the results, the effect of injection pressure on the results was much less than that of carbon nanotube weight percentage.

Keywords: carbon nanotube, injection molding, mechanical properties, nanocomposite, polyethylene

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Authors: Han Kexi, Lv Xuewei, Song Bing

Abstract:

This paper focuses on the preparation of pelletizing with the Panzhihua ilmenite concentrate to satisfy the requirement of smelting titania slag. The effects of the moisture content, mixing time of raw materials, pressure of pellet, roller rotating speed of roller, drying temperature and time on the pelletizing yield and compressive strength were investigated. The experimental results show that the moister content was controlled at 2.0%~2.5%, mixing time at 20 min, the pressure of the ball forming machine at 13~15 mpa, the pelletizing yield can reach up 85%. When the roller rotating speed is 6~8 r/min while the drying temperature and time respectively is 350 ℃ and 40~60 min, the compressive strength of pelletizing more than 1500 N. The preparation of pelletizing can meet the requirement of smelting titania slag.

Keywords: Panzhihua fine ilmenite concentrate, pelletizing, pelletizing yield, compressive strength, drying

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Authors: M. Dezyani, R. Ezzati, H. Mirzaei

Abstract:

The objectives of this study were to determine the effect of pH on chemical, structural, and functional properties of Fetta cheese, and to relate changes in structure to changes in cheese unctionality. Fetta cheese was obtained from a cheese-production facility and stored at 4°C. Ten days after manufacture, the cheese was cut into blocks that were vacuum-packaged and stored for 4 d at 4°C. Cheese blocks were then high-pressure injected one, three, or five times with a 20% (wt/wt) glucono-δ-lactone solution. Successive injections were performed 24 h apart. Cheese blocks were then analyzed after 40 d of storage at 4°C. Acidulant injection decreased cheese pH from 5.3 in the uninjected cheese to 4.7 after five injections. Decreased pH increased the content of soluble calcium and slightly decreased the total calcium content of cheese. At the highest level, injection of acidulant promoted syneresis. Thus, after five injections, the moisture content of cheese decreased from 34 to 31%, which esulted in decreased cheese weight. Lowered cheese pH, 4.7 compared with 5.3, also resulted in contraction of the protein matrix. Acidulant injection decreased cheese hardness and cohesiveness, and the cheese became more crumbly.

Keywords: calcium, high-pressure injection, protein matrix, syneresis

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Authors: Ali Saleh Al-Rafedah, Ahmed Mohammed Al-Quthami, Tariq Jalal Al-Ashawi, Talal Nasser Motar Al-Enez

Abstract:

Introduction: Barodontalgia is essentially dental pain provoked by changes in atmospheric pressure which usually disappear when the affected person reaches normal pressure zone. Barodontalgia has been recognized as a potential cause of aircrew-member vertigo and sudden incapacitation, which could jeopardize the safety of flight. Objective: The current study aimed to investigate the incidence of this phenomena among aircrews in Kingdom of Saudi Arabia. It also aimed to assess the knowledge of dental interns toward this phenomena. Material and Method: A 120 questionnaire consists of 17 questions were distributed to different of Aircrews working in commercial and governmental centers in different areas of KSA. Another questionnaire also distributed to 240 interns in different institutes in KSA. Results: Out of 120 questionnaire distributed to aircrews, 48 has been returned back (40%) and the participants were mainly pilots. The results showed that about 33% of the participants had this pain at least once during flying and the incidence of this pain was not associated with any age group. Most of the pain experience were during descending and at altitude between 10.000-20.000 feet (63%). The pain completely relieved after landing in most of the cases. Regarding pain scores, the majority of the participants reported moderate scores of severity (%65) and about 85% of them had visited the physician or dentist to investigate the existing oral problem. Among dental interns in KSA, our finding indicated lack of knowledge regarding this phenomena since only 23 % of the participants have an idea about this phenomena. Conclusion and recommendation: The incidence of Barodontalgia among aircrews in Saudi Arabia is considerably high and further studies should be carried out for better understanding of this phenomena. Significant lack of knowledge among dental interns about the Barodontalgia has been highlighted and inclusion of it in the teaching of clinical and preclinical curriculum is recommended.

Keywords: Barodontalgia/dental, atmospheric pressure, incapacitation, Saudi Arabia

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Authors: Masood Abdollahi, Seyed Naser Moghaddas Tafreshi

Abstract:

Expanded polystyrene (EPS) geofoam is a cellular geosynthetic material that can be used to protect lifelines (e.g. pipelines, electricity cables, etc.) below ground. Post and beam system is the most recent configuration of EPS blocks which can be implemented for this purpose. It provides a void space atop lifelines which allows settlement of the loading surface with imposing no pressure on the lifelines system. This paper investigates the efficiency of the configuration of post-beam system subjected to static loading. To evaluate the soil surface settlement, beam deformation and transferred pressure over the beam, laboratory tests using two different densities for EPS blocks are conducted. The effect of geogrid-reinforcing the cover soil on system response is also investigated. The experimental results show favorable performance of EPS post and beam configuration in protecting underground lifelines. 

Keywords: beam deformation, EPS block, laboratory test, post-Beam system, soil surface settlement

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Authors: Shahnam Behnam Malekzadeh, Ian Kerr, Tyson Kaempffer, Teague Harper, Andrew Watson

Abstract:

The Site C Hydroelectric dam is currently being constructed in north-eastern British Columbia on sub-horizontal sedimentary strata that dip approximately 15 meters from one bank of the Peace River to the other. More than 615 pressure sensors (Vibrating Wire Piezometers) have been installed on bedding planes (BPs) since construction began, with over 80 more planned before project completion. These pressure measurements are essential to monitor the stability of the rock foundation during and after construction and for dam safety purposes. BPs are identified by their clay gouge infilling, which varies in thickness from less than 1 to 20 mm and can be challenging to identify as the core drilling process often disturbs or washes away the gouge material. Without the use of depth predictions from nearby boreholes, stratigraphic markers, and downhole geophysical data, it is difficult to confidently identify BP targets for the sensors. In this paper, a Case-Based Reasoning (CBR) method was used to develop an empirical model called the Bedding Plane Elevation Prediction (BPEP) to help geologists and geotechnical engineers to predict geological features and bedding planes at new locations in a fast and accurate manner. To develop CBR, a database was developed based on 64 pressure sensors already installed on key bedding planes BP25, BP28, and BP31 on the Right Bank, including bedding plane elevations and coordinates. Thirteen (20%) of the most recent cases were selected to validate and evaluate the accuracy of the developed model, while the similarity was defined as the distance between previous cases and recent cases to predict the depth of significant BPs. The average difference between actual BP elevations and predicted elevations for above BPs was ±55cm, while the actual results showed that 69% of predicted elevations were within ±79 cm of actual BP elevations while 100% of predicted elevations for new cases were within ±99cm range. Eventually, the actual results will be used to develop the database and improve BPEP to perform as a learning machine to predict more accurate BP elevations for future sensor installations.

Keywords: case-based reasoning, geological feature, geology, piezometer, pressure sensor, core logging, dam construction

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Authors: Daniel K. Gameti

Abstract:

The paper explored the effects of active and passive entrepreneurship education methods on the venture creation intention of undergraduate students in Ghana. The study also examined the moderating effect of gender and negative personal characteristics (risk tolerance, stress tolerance and fear of failure) on students’ venture creation intention. Deductive approach was used in collecting quantitative data from 555 business students from one public university and one private university through self-administered questionnaires. Descriptive statistic was used to determine the dominant method of entrepreneurship education used in Ghana. Further, structural equation model was used to test four hypotheses. The results of the study show that the dominant method of education used in Ghana was lectures and the least method used was field trip. The study further revealed that passive methods of education are less effective compared to active methods which were statistically significant in venture creation intention among students. There was also statistical difference between male and female students’ venture creation intention but stronger among male students and finally, the only personal characteristics that influence students’ intention was stress tolerance because risk tolerance and fear of failure were statistically insignificant.

Keywords: entrepreneurship education, Ghana, moderating variables, venture creation intention, undergraduate students

Procedia PDF Downloads 452