Search results for: stress testing

Authors: Xuerui Niu, Bolin Wang, Xinchuang Zhang, Xiaohua Ma, Bin Hou, Ling Yang

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The application of discrete GaN-based power switches requires the collaboration of silicon-based peripheral circuit structures. However, the packages and interconnection between the Si and GaN devices can introduce parasitic effects to the circuit, which has great impacts on GaN power transistors. GaN-based monolithic power integration technology is an emerging solution which can improve the stability of circuits and allow the GaN-based devices to achieve more functions. Complementary logic circuits consisting of GaN-based E-mode p-channel heterostructure field-effect transistors (p-HFETs) and E-mode n-channel HEMTs can be served as the gate drivers. E-mode p-HFETs with recessed gate have attracted increasing interest because of the low leakage current and large gate swing. However, they suffer from a poor interface between the gate dielectric and polarized nitride layers. The reliability of p-HFETs is analyzed and discussed in this work. In circuit applications, the inverter is always operated with dynamic gate voltage (VGS) rather than a constant VGS. Therefore, dynamic electrical stress has been simulated to resemble the operation conditions for E-mode p-HFETs. The dynamic electrical stress condition is as follows. VGS is a square waveform switching from -5 V to 0 V, VDS is fixed, and the source grounded. The frequency of the square waveform is 100kHz with the rising/falling time of 100 ns and duty ratio of 50%. The effective stress time is 1000s. A number of stress tests are carried out. The stress was briefly interrupted to measure the linear IDS-VGS, saturation IDS-VGS, As VGS switches from -5 V to 0 V and VDS = 0 V, devices are under negative-bias-instability (NBI) condition. Holes are trapped at the interface of oxide layer and GaN channel layer, which results in the reduction of VTH. The negative shift of VTH is serious at the first 10s and then changes slightly with the following stress time. However, different phenomenon is observed when VDS reduces to -5V. VTH shifts negatively during stress condition, and the variation in VTH increases with time, which is different from that when VDS is 0V. Two mechanisms exists in this condition. On the one hand, the electric field in the gate region is influenced by the drain voltage, so that the trapping behavior of holes in the gate region changes. The impact of the gate voltage is weakened. On the other hand, large drain voltage can induce the hot holes generation and lead to serious hot carrier stress (HCS) degradation with time. The poor-quality interface between the oxide layer and GaN channel layer at the gate region makes a major contribution to the high-density interface traps, which will greatly influence the reliability of devices. These results emphasize that the improved etching and pretreatment processes needs to be developed so that high-performance GaN complementary logics with enhanced stability can be achieved.

Keywords: GaN-based E-mode p-HFETs, dynamic electric stress, threshold voltage, monolithic power integration technology

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Authors: Alexander Matrosov, Guriy Shirunov

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A superposition method based on Lame's idea is used to get a general analytical solution to analyze a stress and strain state of a rectangular isotropjc elastic thick plate. The solution is built by using three solutions of the method of initial functions in the form of double trigonometric series. The results of bending of a thick plate under normal stress on its top face with two opposite sides clamped while others free of load are presented and compared with FEM modelling.

Keywords: general solution, method of initial functions, superposition method, thick isotropic plates

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Authors: Zahra Azizi, Ashkan Karbasi, Farzin Firouzian, Sara Soleimani Asl, Akram Ranjbar

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Background: One of the most often used herbicides in agriculture is paraquat (PQ), which is very harmful to both people and animals. Chitosan is a well-known, non-toxic polymer commonly used in preparing particles via ionotropic gelation facilitated by negatively charged agents such as sodium alginate. This study aimed to compare the effects of PQ and nanoparaquat (PQNPs) on liver function in male rats. Materials & Methods: Rats were exposed to PQ & PQNPs (4 mg/kg/day, intraperitoneally) for seven days. Then, rats were anesthetized, and serum and liver samples were collected. Later, enzymatic activities such as alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) in serum and oxidative stress biomarkers such as lipid peroxidation (LPO), total antioxidant capacity (TAC) and total thiol groups (TTG) levels in liver tissue were measured by colorimetric methods. Also, histological changes in the liver were evaluated. Results: PQ altered the levels of ALT, AST, and ALP while inducing oxidative stress in the liver. Additionally, liver homogenates with PQ exposure had challenged LPO, TAC, and TTG levels. The severe liver damage is indicated by a significant increase in the enzyme activity of AST, ALT, and ALP in serum. According to the results of the current study, PQNPs, as compared to PQ and the control group, lowered ALT, AST, ALP, and LPO levels while increasing TAC and TTG levels. Conclusion: According to biochemical and histological investigations, PQ loaded in chitosan-alginate particles is more efficient than free PQ at reducing liver toxicity.

Keywords: paraquat, paraquat nanoparticles, liver, oxidative stress

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Authors: Constantin Ott, Dietmar Drummer

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The direct encapsulation of electronic components is an effective way of protecting components against external influences. In addition to achieving a sufficient protective effect, there are two other big challenges for satisfying the increasing demand for encapsulated circuit boards. The encapsulation process should be both suitable for mass production and offer a low component load. Injection molding is a method with good suitability for large series production but also with typically high component stress. In this article, two aims were pursued: first, the development of a calculation model that allows an estimation of the occurring forces based on process variables and material parameters. Second, the evaluation of a new approach for stress reduction by means of thermoplastic foam injection molding. For this purpose, simulation-based process data was generated with the Moldflow simulation tool. Based on this, component stresses were calculated with the calculation model. At the same time, this paper provided a model for estimating the forces occurring during overmolding and derived a solution method for reducing these forces. The suitability of this approach was clearly demonstrated and a significant reduction in shear forces during overmolding was achieved. It was possible to demonstrate a process development that makes it possible to meet the two main requirements of direct encapsulation in addition to a high protective effect.

Keywords: encapsulation, stress reduction, foam-injection-molding, simulation

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Authors: Fahad Raj Khan, Suleman Khan

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There is a lack of consensus about the predictive value of raised blood glucose levels in terms of major adverse cardiac events (MACEs) in non-diabetic patients admitted for acute decompensated heart failure. The purpose of this research was to examine the long-term prognosis of acute decompensated heart failure (ADHF) in non-diabetic persons who had increased blood glucose levels, i.e., stress hyperglycemia, at the time of their ADHF hospitalization. The research involved 650 non-diabetic patients. Based on their admission stress hyperglycemia, they were divided into two groups.ie with and without (SHGL). The two groups' one-year outcomes for major adverse cardiac events (MACEs) were compared, and key predictors of MACEs were discovered. For statistical analysis, the two-tailed Mann-Whitney U test, Fisher's exact test, and binary logistic regression analysis were utilized. SHGL was found in 353 (54.3%) individuals. It was more frequent in men than in women. About 27% of patients with SHGL had previously been admitted for ADHF. Almost 62% were hypertensive, whereas 14 % had CKD. MACEs were significantly predicted by SHGL, HTN, prior hospitalization for ADHF, CKD, and cardiogenic shock upon admission. SHGL at the time of ADHF admission, independent of DM status, may be a predictive indication of MACEs.

Keywords: stress hyperglycemia, acute heart failure, major adverse cardiac events, MACEs

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Authors: Farnoush Haghanipour

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Recent research studies relation between coping strategies with stress and mental health situation in flying addicted family of self-introducer and private, Units of Guilan province. For this purpose 251 family (parent, spouse), that referred to private and self-introducer centers to break out of drug are selected in random sampling form. Research method was cross sectional-descriptive and purpose of research was fixing of between kinds of coping strategies with stress and mental health condition with attention to demographic variables. Therefore to collection of information, coping strategies questionnaire (CSQ) and mental health questionnaire (GHQ) was used and finally data analyzed by descriptive statistical methods (average, standard deviation) and inferential statistical correlation coefficient and regression. Study of correlation coefficient between mental healths with problem focused emotional focused and detachment strategies in level more than %99 is confirmed. Also mental health with avoidant focused hasn't correlation in other words relation is between mental health with problem focused strategies (r= 0/34) and emotional focused with mental health (r=0.52) and detachment with mental health (r= 0.18) in meaningful level 0.05. And also relation is between emotional focused strategies and mental health (r= 0.034) that is meaningless in Alpha 0.05. Also relation between problem processed coping strategies and mental health situation with attention to demographic variable is meaningful and relation level verified in confidence level more than 0.99. And result of anticipation equation regression statistical test has most a have in problem focused coping strategy, mental health, but relation of the avoidant emotional, detachment strategy with mental health was meaningless with attention to demographic variables.

Keywords: stress, coping strategy with stress, mental health, self introducer and private

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Authors: Roman Kalvin, Anam Nadeem, Shahab Khushnood

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Differential is an integral part of four wheeled vehicle, and its main function is to transmit power from drive shaft to wheels. Differential assembly allows both rear wheels to turn at different speed along curved paths. It consists of four gears which are assembled together namely pinion, ring, spider and bevel gears. This research focused on the spider gear and its static structural analysis using ANSYS. The main aim was to evaluate the distribution of stresses on the teeth of the spider gear. This study also analyzed total deformation that may occur during its working along with bevel gear that is meshed with spider gear. Structural steel was chosen for spider gear in this research. Modeling and assembling were done on SolidWorks for both spider and bevel gear. They were assembled exactly same as in a differential assembly. This assembly was then imported to ANSYS. After observing results that maximum amount of stress and deformation was produced in the spider gear, it was concluded that structural steel material for spider gear possesses greater amount of strength to bear maximum stress.

Keywords: ANSYS, differential, spider gear, structural steel

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Authors: Shoaei Shahram, Rafiei Felora

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To study the effects of using superabsorbent polymers on physiological of maize in deficit Irrigation condition .an experiment carried out in split plot factorial based on completely Randomized Block design (RCBD) with three replication in 2012years. Deficit Irrigation was applied by three different Irrigation amount. Super absorbent polymers in 3 levels were and two veriety of maize allocated in sub plots. there was significant difference between Irrigation levels in all experimental Traits by increasing in deficit irrigation. Results of this research showed water stress significantly decreased relative water content (RWC) LAI,Ash percentage in both hybrids, and increased Cell membrane percentage and SPAD,ADF percent.whereas the application of super absorbent polymer compensated the negative effect of drought stress, especially in high rates of polymer application .These mentioned rates of polymer had the best effect to all of the studied traits. These findings can be suggested that the irrigation intervals of corn could be increased by application of super absorbent polymer.

Keywords: super absorbent, p hysiological, water stress, zea maize

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Authors: Yong-Kian Lim, Khan Cheung, Xin Dang, Steven Roberts, Xiaotong Wang, Vengatesen Thiyagarajan

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Unprecedented rate of increased CO₂ level in the ocean and the subsequent changes in carbonate system including decreased pH, known as ocean acidification (OA), is predicted to disrupt not only the calcification process but also several other physiological and developmental processes in a variety of marine organisms, including edible oysters. Nonetheless, not all species are vulnerable to those OA threats, e.g., some species may be able to cope with OA stress using environmentally induced modifications on gene and protein expressions. For example, external environmental stressors, including OA, can influence the addition and removal of methyl groups through epigenetic modification (e.g., DNA methylation) process to turn gene expression “on or off” as part of a rapid adaptive mechanism to cope with OA. In this study, the above hypothesis was tested through testing the effect of OA, using decreased pH 7.4 as a proxy, on the DNA methylation pattern of an endemic and a commercially important estuary oyster species, Crassostrea hongkongensis, at the time of larval habitat selection and metamorphosis. Larval growth rate did not differ between control pH 8.1 and treatment pH 7.4. The metamorphosis rate of the pediveliger larvae was higher at pH 7.4 than those in control pH 8.1; however, over one-third of the larvae raised at pH 7.4 failed to attach to an optimal substrate as defined by biofilm presence. During larval development, a total of 130 genes were differentially methylated across the two treatments. The differential methylation in the larval genes may have partially accounted for the higher metamorphosis success rate under decreased pH 7.4 but with poor substratum selection ability. Differentially methylated loci were concentrated in the exon regions and appear to be associated with cytoskeletal and signal transduction, oxidative stress, metabolic processes, and larval metamorphosis, which implies the high potential of C. hongkongensis larvae to acclimate and adapt through non-genetic ways to OA threats within a single generation.

Keywords: adaptive plasticity, DNA methylation, larval metamorphosis, ocean acidification

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Authors: Souad Mouzaoui, Bahia Djerdjouri

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Oxidative stress is one of the main factors involved in the onset and chronicity of inflammatory bowel disease (IBD). In this study, we investigated the beneficial effects of a potent natural antioxidant, curcumin (Cur) on colitis and mitochondrial dysfunction in trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Rectal instillation of the chemical irritant TNBS (30 mg kg-1) induced the disruption of distal colonic architecture and a massive inflammatory cells influx to the mucosa and submucosa layers. Under these conditions, daily administration of Cur (25 mg kg-1) efficiently decreased colitis scores in the inflamed distal colon by reducing leukocyte infiltrate as attested by reduced myeloperoxidase (MPO) activity. Moreover, the levels of nitrite, an end product of inducible NO synthase activity (iNOS) and malonyl dialdehyde (MDA), a marker of lipid peroxidation increased in a time depending manner in response to TNBS challenge. Conversely, the markers of the antioxidant pool, reduced glutathione (GSH) and catalase activity (CAT) were drastically reduced. Cur attenuated oxidative stress markers and partially restored CAT and GSH levels. Moreover, our results expanded the effect of Cur on TNBS-induced colonic mitochondrial dysfunction. In fact, TNBS induced mitochondrial swelling and lipids peroxidation. These events reflected in the opening of mitochondrial transition pore and could be an initial indication in the cascade process leading to cell death. TNBS inhibited also mitochondrial respiratory activity, caused overproduction of mitochondrial superoxide anion (O2-.) and reduced level of mitochondrial GSH. Nevertheless, Cur reduced the extent of mitochondrial oxidative stress induced by TNBS and restored colonic mitochondrial function. In conclusion, our results showed the critical role of oxidative stress in TNBS-induced colitis. They highlight the role of colonic mitochondrial dysfunction induced by TNBS, as a potential source of oxidative damages. Due to its potent antioxidant properties, Cur opens a promising therapeutic approach against oxidative inflammation in IBD.

Keywords: colitis, curcumin, mitochondria, oxidative stress, TNBS

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Authors: Manganyi Patricia Siphiwe

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Work environments are characterised by performance pressure and mechanisation, which lead to job stress and the dehumanisation of work spaces. The personnel’s competence to accomplish job responsibilities and high job demands lead to a substantial load of health. Therefore, providing employees with conducive working environments is essential. In order to attain it, the employer should ensure that responsive and institutional safe systems are in place. The employer’s responses to employees’ needs are of significance to a healthy and developmental work environment. Denying employees a developmental and flourishing workplace is to deprive a workplace of being humane. Stressors coming from various aspects in the workplace can yield undue pressure and undesired responses for the workforces. Against the profiled background, this paper examines the causes and consequences of workplace stress within the Emergency Medical sector. The paper utilised a qualitative methodology and in-depth interviews for data collection with the purposively sampled emergency medical personnel. The findings showed that workplace stress has been associated with high demands and lack of support which has an adverse effect on biopsychosocial wellbeing of employees. This paper, therefore, recommends an engaged involvement of social workers through work organisational initiatives, such as Employee Assistance Programmes (EAP) and related labour relations policy activities to promote positive and developmental working environments.

Keywords: stress, employee, workplace, wellbeing

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Authors: Amy Gooden, Meshandren Naidoo

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Genetic research and transfers of big data are not confined to a particular jurisdiction, but there is a lack of clarity regarding the legal requirements for importing and exporting such data. Using direct-to-consumer genetic testing (DTC-GT) as an example, this research assesses the status of data sharing into and out of South Africa (SA). While SA laws cover the sending of genetic data out of SA, prohibiting such transfer unless a legal ground exists, the position where genetic data comes into the country depends on the laws of the country from where it is sent – making the legal position less clear.

Keywords: cross-border, data, genetic testing, law, regulation, research, sharing, South Africa

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Authors: M. Beusink, E. W. C. Coenen

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The increased application of novel structural materials, such as high grade asphalt, concrete and laminated composites, has sparked the need for a better understanding of the often complex, non-linear mechanical behavior of such materials. The effective macroscopic mechanical response is generally dependent on the applied load path. Moreover, it is also significantly influenced by the microstructure of the material, e.g. embedded fibers, voids and/or grain morphology. At present, multiscale techniques are widely adopted to assess micro-macro interactions in a numerically efficient way. Computational homogenization techniques have been successfully applied over a wide range of engineering cases, e.g. cases involving first order and second order continua, thin shells and cohesive zone models. Most of these homogenization methods rely on Representative Volume Elements (RVE), which model the relevant microstructural details in a confined volume. Imposed through kinematical constraints or boundary conditions, a RVE can be subjected to a microscopic load sequence. This provides the RVE's effective stress-strain response, which can serve as constitutive input for macroscale analyses. Simultaneously, such a study of a RVE gives insight into fine scale phenomena such as microstructural damage and its evolution. It has been reported by several authors that the type of boundary conditions applied to the RVE affect the resulting homogenized stress-strain response. As a consequence, dedicated boundary conditions have been proposed to appropriately deal with this concern. For the specific case of a planar assumption for the analyzed structure, e.g. plane strain, axisymmetric or plane stress, this assumption needs to be addressed consistently in all considered scales. Although in many multiscale studies a planar condition has been employed, the related impact on the multiscale solution has not been explicitly investigated. This work therefore focuses on the influence of the planar assumption for multiscale modeling. In particular the plane stress case is highlighted, by proposing three different implementation strategies which are compatible with a first-order computational homogenization framework. The first method consists of applying classical plane stress theory at the microscale, whereas with the second method a generalized plane stress condition is assumed at the RVE level. For the third method, the plane stress condition is applied at the macroscale by requiring that the resulting macroscopic out-of-plane forces are equal to zero. These strategies are assessed through a numerical study of a thin walled structure and the resulting effective macroscale stress-strain response is compared. It is shown that there is a clear influence of the length scale at which the planar condition is applied.

Keywords: first-order computational homogenization, planar analysis, multiscale, microstrucutures

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Authors: Didik Sugiyanto

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Conditions that often occur in the framework of a particular vehicle at a car is a collision or collision with another object, an example of such damage is to the frame or chassis for the required design framework that is able to absorb impact energy. Characteristics of the material are influenced by the value of the stiffness of the material that need to be considered in choosing the material properties of the material. To obtain material properties that can be adapted to the experimental conditions tested the tensile and compression testing. In this study focused on the chassis at an angle of 150, 300, and 450. It is based on field studies that vehicle primarily for freight cars have a point of order light between 150 to 450. Research methods include design tools, design framework, procurement of materials and experimental tools, tool-making, the manufacture of the test framework, and the testing process, experiment is testing the power of the press to know the order. From this test obtained the maximum force on the corner of 150 was 569.76 kg at a distance of 16 mm, angle 300 is 370.3 kg at a distance of 15 mm, angle 450 is 391.71 kg at a distance of 28 mm. After reaching the maximum force the order will occur collapse, followed by a decrease in the next distance. It can be concluded that the greatest strain energy occurs at an angle of 150. So it is known that the frame at an angle of 150 produces the best level of security.

Keywords: buckling, collapse, body frame, vehicle

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Authors: Dragana Tomic

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This research deals with relations among strategies and styles of coping with stress, social interaction anxiety and the achievement motive of young athletes and non-athletes. The research was conducted on the sample of 402 examinees (197 female and 205 male participants) of the average age of 20.76, divided into three groups: athletes, recreationists, and non-athletes. The COPE-S questionnaire, the Social Interaction Anxiety Scale (SIAS) and the Achievement Motivation Questionnaire (MOP 2002) were used for conducting this research and they had satisfactory reliability. The results of the research indicate that athletes, recreationists and non-athletes are not different when it comes to strategies and styles of coping with stress. Non- athletes have more noticeable social interaction anxiety when compared to athletes (U=5281.5, p=.000) and also when compared to recreationists (U=7573, p=.000). There was a difference among these three groups in the achievement motive (χ2(2)=23,544, p=.000) and the three components of this motive (Competing with others, χ2(2)=31,718, p=.000, Perseverance, χ2(2)=9,415, p=.009 and Planning orientation, χ2(2)=8,171, p=.017). The research also indicates a significant difference in the relation between social interaction anxiety and the achievement motive of examinee subgroups, where the most significant difference is between athletes and non- athletes (q=-.45). Moreover, women more frequently use emotion-focused coping (U=16718, p=.003), while men more frequently use avoidance (U=14895.5, p=.000). Women have a lead when it comes to expressing social anxiety (U=17750.5, p=.036) and the achievement motive (U=17395.5, p=.020). The discussion of the results includes findings of similar previous research and theoretical concepts of the variables which were examined. Future research should be oriented towards examining the background of the differences which were (not) gained as well as towards the influence of personality dimensions on the variables which were examined in order to apply the results in practice in the best way.

Keywords: achievement motivation, athletes, coping with stress, non-athletes, recreationists, social interaction anxiety

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Authors: Zaid A. Janjua, Barbara Turnbull, Kwing-So Choi

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The adhesion of glaze ice on power infrastructure, ships and aerofoils cause monetary and structural damage. Here we investigate the influence of temperature as an important parameter affecting adhesion strength of ice. Two terms are defined to investigate this: 'freezing temperature', the temperature at which glaze ice forms; and 'ambient temperature', the temperature of the surrounding during the test. Using three metal surfaces, the adhesion strength of ice has been calculated as a value of shear stress at the point of detachment on a spinning centrifuge. Findings show that the ambient temperature has a greater influence than the freezing temperature on the adhesion strength of ice. This is because there exists an amorphous liquid-like layer at the ice-surface interface, whose bond with the surface increases in strength at lower ambient temperatures when the substrate conducts heat much faster than the ice and acts as a heat sink. The results will help us to measure the actual adhesion strength of ice to metal surfaces based on data from weather monitoring devices. Future tests envisaged focus on thermally non-conducting substrates and their influence on adhesion strength.

Keywords: ice adhesion, centrifuge, glaze ice, freezing temperature, ambient temperature

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Authors: Janusz Kwaśniewski, Ireneusz Dominik, Krzysztof Lalik

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The knowledge about rock layers thickness, especially above drilled mining pavements are crucial for workers safety. The measuring systems used nowadays are generally imperfect and there is a strong demand for improvement. The application of a new type of a measurement system called Self-Excited Acoustical System is presented in the paper. The system was applied until now to monitor stress changes in metal and concrete constructions. The change in measurement methodology resulted in possibility of measuring the thickness of the rocks above the tunnels as well as thickness of a singular rock layer. The idea is to find two resonance frequencies of the self-exited system, which consists of a vibration exciter and vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which operate in a closed loop with a positive feedback. The resonance with the higher amplitude determines thickness of the whole rock, whereas the lower amplitude resonance indicates thickness of a singular layer. The results of the laboratory tests conducted on a group of different rock materials are also presented.

Keywords: auto-oscillator, non-destructive testing, rock thickness measurement, geotechnic

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Authors: Hanan Al-Khalifa

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There has been an interest in raising poultry in environmentally controlled cages rather than on floor, because poultry raised on floor are more susceptible to environmental stress including pathogens and heat stress. A study was conducted to investigate the effect of managerial environmental conditions on body weight gain of Cobb 500 broiler breed. Broilers were raised in cages and on floor in two separate rooms. Body weight at different ages of the broilers was monitored. It was found that body weight at slaughter age (5weeks) for boilers raised in batteries were significantly higher than those raised on the floor.

Keywords: broilers, cages, floor, poultry

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Authors: Mehdi Soltani Howyzeh, Neda Kardoni, Mani Mojadam

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To evaluate the vigor of wheat seeds and stress of premature aging effects on germination percentage, root length and shoot length of five wheat cultivars that include Vynak, Karkheh, Chamran, Star and Kavir which underwent a period of zero, two, three, four days in terms of premature aging with 41 °C temperature and 100% relative humidity. Seed germination percentage, root length and shoot length in these conditions were measured. This experiment was conducted as a factorial completely randomized design with four replications in laboratory conditions. The results showed that each of aging treatments used in this experiment can be used to detect differences in vigor of wheat varieties. Wheat cultivars illustrated significant differences in germination percentage, root length and shoot length in terms of premature aging. The wheat cultivars; Astar and Vynak had maximum germination percentage and Karkheh, respectively Kavir and Chamran had lowest percentage of seed germination. Reactions of root and shoot length of wheat cultivars was also different. The results showed that the seeds with a stronger vigor affected less in premature aging condition and the difference between the percentage of seed germination under normal conditions and stress was significant and the seeds with the weaker vigor were more sensitive to the premature aging stress and the premature aging had more severe negative impact on seed vigor.

Keywords: wheat cultivars, seed vigor, premature aging effects, germination

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Authors: Vishvas N. Patel, Mehul Chorawala

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Currently, according to the authors best knowledge there are less effective therapeutic agents to limit intestinal mucosa damage associated with inflammatory bowel disease (IBD). Clinical studies have shown beneficial effects of several probiotics in patients of IBD. Probiotics are live organisms; confer a health benefit to the host by modulating immunoinflammation and oxidative stress. Although probiotics in murine and human improve disease severity, very little is known about the specific contribution of cell wall contents of probiotics in IBD. Herein, we investigated the ameliorative potential of cell wall contents of Lactobacillus casei (LC) in lipopolysaccharide (LPS)-induced murine colitis. Methods: Colitis was induced in LPS-sensitized rats by intracolonic instillation of LPS (50 µg/rat) for consecutive 14 days. Concurrently, cell wall contents isolated from 103, 106 and 109 CFU of LC was given subcutaneously to each rat for 21 days, considering sulfasalazine (100 mg/kg, p.o.) as standard. The severity of colitis was assessed by body weight loss, food intake, stool consistency, rectal bleeding, colon weight/length, spleen weight and histological analysis. Colonic inflammatory markers (myeloperoxidase (MPO) activity, C-reactive protein and proinflammatory cytokines) and oxidative stress markers (malondialdehyde, reduced glutathione and nitric oxide) were also assayed. Results: Cell wall contents of isolated from 106 and 109 CFU of LC significantly improved the severity of colitis by reducing body weight loss and diarrhea & bleeding incidence, improving food intake, colon weight/length, spleen weight and microscopic damage to the colonic mucosa. The treatment also reduced levels of inflammatory and oxidative stress markers and boosted antioxidant molecule. However, cell wall contents of isolated from 103 were ineffective. Conclusion: In conclusion, cell wall contents of LC attenuate LPS-induced colitis by modulating immuno-inflammation and oxidative stress.

Keywords: probiotics, Lactobacillus casei, immuno-inflammation, oxidative stress, lipopolysaccharide, colitis

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Authors: Deepak Kumar, Ravi Rajwanshi, Mohd. Aslam Yusuf, Nisha Kant Pandey, Preeti Singh, Mukesh Saxena, Neera Bhalla Sarin

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Global issues are leading to concerns over food security. These include climate change, urbanization, increase in population subsequently leading to greater energy and water demand. Futuristic approach for crop improvement involves gene pyramiding for agronomic traits that empower the plants to withstand multiple stresses. In an earlier study from the laboratory, the efficacy of overexpressing γ-tocopherol methyl transferase (γ-TMT) gene from the vitamin E biosynthetic pathway has been shown to result in six-fold increase of the most biologically active form, the α-tocopherol in Brassica juncea which resulted in alleviation of salt, heavy metal and osmoticum induced stress by the transgenic plants. The glyoxalase I (gly I) gene from the glyoxalase pathway has also been earlier shown by us to impart tolerance against multiple abioitc stresses by detoxification of the cytotoxic compound methylglyoxal in Brassica juncea. Recently, both the transgenes were pyramided in Brassica juncea lines through sexual crosses involving two stable Brassica juncea lines overexpressing γ-TMT and gly I genes respectively. The transgene integration was confirmed by PCR analysis and their mRNA expression was evident by RT-PCR analysis. Preliminary physiological investigations showed ~55% increased seed germination under 200 mM NaCl stress in the pyramided line and 81% higher seed germination under 200 mM mannitol stress as compared to the WT control plants. The pyramided lines also retained more chlorophyll content when the leaf discs were floated on NaCl (200, 400 and 600 mM) or mannitol (200, 400 and 600 mM) compared to the WT control plants. These plants had higher Relative Water Content and greater solute accumulation under stress compared to the parental plants having γ-TMT or the glyI gene respectively. The studies revealed the synergy of two components from different metabolic pathways in enhancing stress hardiness of the transgenic B. juncea plants. It was concluded that pyramiding of genes (γ-TMT and glyI) from diverse pathways can lead to enhanced tolerance to salt and mannitol stress (simulating drought conditions). This strategy can prove useful in enhancing the crop yields under various abiotic stresses.

Keywords: abiotic stress, brassica juncea, glyoxalase I, α-tocopherol

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Authors: Won Jung

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In automotive, propeller shaft is the device for transferring power from engine to axle via transmission, and the slip yoke is one of the main parts in the component. Since the propeller shafts are subject to torsion and shear stress, they need to be strong enough to bear the stress. The purpose of this research is to improve the productivity of slip yoke for automotive propeller shaft. We present how to redesign the component that currently manufactured as a forged single body type. The research was focused on not only reducing processing time but insuring durability of the component simultaneously.

Keywords: automotive, propeller shaft, productivity, durability, slip yoke

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Authors: Lukasz Mierczak, Patrick Denke, Piotr Klimczyk, Stefan Siebert

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Due to the high complexity of the magnetization in electrical machines and influence of the manufacturing processes on the magnetic properties of their components, the assessment and prediction of hysteresis and eddy current losses has remained a challenge. In the design process of electric motors and generators, the power losses of stators and rotors are calculated based on the material supplier’s data from standard magnetic measurements. This type of data does not include the additional loss from non-sinusoidal multi-harmonic motor excitation nor the detrimental effects of residual stress remaining in the motor laminations after manufacturing processes, such as punching, housing shrink fitting and winding. Moreover, in production, considerable attention is given to the measurements of mechanical dimensions of stator and rotor cores, whereas verification of their magnetic properties is typically neglected, which can lead to inconsistent efficiency of assembled motors. Therefore, to enable a comprehensive characterization of motor materials and components, Brockhaus Measurements developed a range of in-line and offline measurement technologies for testing their magnetic properties under actual motor operating conditions. Multiple sets of experimental data were obtained to evaluate the influence of various factors, such as elevated temperature, applied and residual stress, and arbitrary magnetization on the magnetic properties of different grades of non-oriented steel. Measured power loss for tested samples and stator cores varied significantly, by more than 100%, comparing to standard measurement conditions. Quantitative effects of each of the applied measurement were analyzed. This research and applied Brockhaus measurement methodologies emphasized the requirement for advanced characterization of magnetic materials used in electric drives and automotive applications.

Keywords: magnetic materials, measurement technologies, permanent magnets, stator and rotor cores

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Authors: Otokiti Mojeed Jimoh

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This work investigates the possibility of using recycled polyethylene LDPE as a base polymer in production of different products (shoe sole, foot mat, and many more) using carbon black as a filler to improve its mechanical properties, like hardness, tensile stress properties and elongation at break properties, from the result so far gotten there is a possibility that there is an increase in the mechanical properties of the sample compare to natural rubber sample.

Keywords: recycled polyethylene, base polymer, hardness, stress properties

Procedia PDF Downloads 417

Authors: M. Shannag, A. Charif, S. Naser, F. Faisal, A. Karim

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Structural lightweight concrete is used primarily to reduce the dead-load weight in concrete members such as floors in high-rise buildings and bridge decks. With given materials, it is generally desired to have the highest possible strength/unit weight ratio with the lowest cost of concrete. The work presented herein is part of an ongoing research project that investigates the properties of concrete mixes containing locally available Scoria lightweight aggregates and mineral admixtures. Properties considered included: workability, unit weight, compressive strength, and splitting tensile strength. Test results indicated that developing structural lightweight concretes (SLWC) using locally available Scoria lightweight aggregates and specific blends of silica fume and fly ash seems to be feasible. The stress-strain diagrams plotted for the structural LWC mixes developed in this investigation were comparable to a typical stress-strain diagram for normal weight concrete with relatively larger strain capacity at failure in case of LWC.

Keywords: lightweight concrete, scoria, stress, strain, silica fume, fly ash

Procedia PDF Downloads 511

Authors: Kari Bjorn

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Team learning has been studied and modeled as double loop model and its variations. Also, metacognition has been suggested as a concept to describe the nature of team learning to be more than a simple sum of individual learning of the team members. Team learning has a positive correlation with both individual motivation of its members, as well as the collective factors within the team. Team learning of previously very independent members of two teaching teams is analyzed. Applied Science Universities are training future professionals with ever more diversified and multidisciplinary skills. The size of the units of teaching and learning are increasingly larger for several reasons. First, multi-disciplinary skill development requires more active learning and richer learning environments and learning experiences. This occurs on students teams. Secondly, teaching of multidisciplinary skills requires a multidisciplinary and team-based teaching from the teachers as well. Team formation phases have been identifies and widely accepted. Team role stress has been analyzed in project teams. Projects typically have a well-defined goal and organization. This paper explores team stress of two teacher teams in a parallel running two course units in engineering education. The first is an Industrial Automation Technology and the second is Development of Medical Devices. The courses have a separate student group, and they are in different campuses. Both are run in parallel within 8 week time. Both of them are taught by a group of four teachers with several years of teaching experience, but individually. The team role stress scale items - the survey is done to both teaching groups at the beginning of the course and at the end of the course. The inventory of questions covers the factors of ambiguity, conflict, quantitative role overload and qualitative role overload. Some comparison to the study on project teams can be drawn. Team development stage of the two teaching groups is different. Relating the team role stress factors to the development stage of the group can reveal the potential of management actions to promote team building and to understand the maturity of functional and well-established teams. Mature teams indicate higher job satisfaction and deliver higher performance. Especially, teaching teams who deliver highly intangible results of learning outcome are sensitive to issues in the job satisfaction and team conflicts. Because team teaching is increasing, the paper provides a review of the relevant theories and initial comparative and longitudinal results of the team role stress factors applied to teaching teams.

Keywords: engineering education, stress, team role, team teaching

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Authors: Patrizia Bonaventura

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The aim of this study is to analyze the influence of prosody on the acquisition of temporal aspects of V-V anticipatory lingual coarticulation in productions by Italian-speaking children. Two twin 7-years old male children, native Italian speakers, interacted with the same adult, repeating nonsense disyllables containing VtV sequences where V1 = {i, a} and V2 = {a,e, i, o,u}, with different stress patterns (e.g. pi’ta, pi’ta). The duration of the VC F2 transitions and the CV/VC F2 transitions durations ratios in different V2 contexts and stress conditions were measured by spectrographic analysis and compared between pronunciations by each child vs. the adult to test whether the child was able to imitate the duration of the transitions as produced by the adult in different stress conditions. Consequences highlighted a significant difference in durations of VC transitions between children and adult: longer VC transitions durations, indicating a greater amount of coarticulation, were found for one child in every context, and for the other, only in stressed [it] sequences. The data support the hypothesis of the presence of different temporal patterns of anticipatory coarticulation in adults and children, and of a greater amount of coarticulation in children, with different strategies of implementation across different prosodic conditions.

Keywords: speech acquisition, coarticulation, Italian language, prosody

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Authors: Michael Tupý, Vít Petránek

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The paper is focused on testing of the poly(vinyl butyral) (PVB) layer which had the function of a CO2 insulating protection against concrete and mortar carbonation. The barrier efficiency of PVB was verified by the measurement of diffusion characteristics. Two different types of PVB were tested; original extruded PVB sheet and PVB sheet made from PVB dispersion which was obtained from recycled windshields. The work deals with the testing CO2 diffusion when polymer sheets were exposed to a CO2 atmosphere (10% v/v CO2) with 0% RH. The excellent barrier capability against CO2 permeability of original and also recycled types of PVB layers was observed. This application of PVB waste can bring advantageous use in civil engineering and significant environmental contribution.

Keywords: windshield, poly(vinyl butyral), mortar, diffusion, carbonatation, polymer waste

Procedia PDF Downloads 423

Authors: Chanchai Supaartagorn

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Structured Query Language (SQL) is the standard de facto language to access and manipulate data in a relational database. Although SQL is a language that is simple and powerful, most novice users will have trouble with SQL syntax. Thus, we are presenting SQL generator tool which is capable of translating actions and displaying SQL commands and data sets simultaneously. The tool was developed based on Model-View-Controller (MVC) pattern. The MVC pattern is a widely used software design pattern that enforces the separation between the input, processing, and output of an application. Developers take full advantage of it to reduce the complexity in architectural design and to increase flexibility and reuse of code. In addition, we use White-Box testing for the code verification in the Model module.

Keywords: MVC, relational database, SQL, White-Box testing

Procedia PDF Downloads 421

Authors: Samuel Oye Bandele

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A policy is a system of principles to guide activities and strategic decisions of an organisation in order to achieve stated objectives and meeting expected outcomes. A Computer Based Test (CBT) policy is therefore a statement of intent to drive the CBT programmes, and should be implemented as a procedure or protocol. Policies are hence generally adopted by an organization or a nation. The concern here, in this paper, is the consideration and analysis of issues that are significant to evolving the acceptable policy that will drive the new CBT innovation in Nigeria. Public examinations and internal examinations in higher educational institutions in Nigeria are gradually making a radical shift from Paper Based or Paper-Pencil to Computer-Based Testing. The need to make an objective and empirical analysis of Policy issues relating to CBT became expedient. The following are some of the issues on CBT evolution in Nigeria that were identified as requiring policy backing. Prominent among them are requirements for establishing CBT centres, purpose of CBT, types and acquisition of CBT equipment, qualifications of staff: professional, technical and regular, security plans and curbing of cheating during examinations, among others. The descriptive research design was employed based on a population consisting of Principal Officers (Policymakers), Staff (Teaching and non-Teaching-Policy implementors), and CBT staff ( Technical and Professional- Policy supports) and candidates (internal and external). A fifty-item researcher-constructed questionnaire on policy issues was employed to collect data from 600 subjects drawn from higher institutions in South West Nigeria, using the purposive and stratified random sampling techniques. Data collected were analysed using descriptive (frequency counts, means and standard deviation) and inferential (t-test, ANOVA, regression and Factor analysis) techniques. Findings from this study showed, among others, that the factor loadings had significantly weights on the organizational and National policy issues on CBT innovation in Nigeria.

Keywords: computer-based testing, examination, innovation, paper-based testing, paper pencil based testing, policy issues

Procedia PDF Downloads 248