Search results for: tensile stress electrical resistivity

Authors: A. Bilek, M. Beldi, T. Cherfi, S. Djebali, S. Larbi

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Finite elements analysis and photoelasticity are used to determine the stress field developed in a double edge notched specimen loaded in tension. The specimen is cut in a birefringent plate. Experimental isochromatic fringes are obtained with circularly polarized light on the analyzer of a regular polariscope. The fringes represent the loci of points of equal maximum shear stress. In order to obtain the stress values corresponding to the fringe orders recorded in the notched specimen, particularly in the neighborhood of the notches, a calibrating disc made of the same material is loaded in compression along its diameter in order to determine the photoelastic fringe value. This fringe value is also used in the finite elements solution in order to obtain the simulated photoelastic fringes, the isochromatics as well as the isoclinics. A color scale is used by the software to represent the simulated fringes on the whole model. The stress concentration factor can be readily obtained at the notches. Good agreements are obtained between the experimental and the simulated fringe patterns and between the graphs of the shear stress particularly in the neighborhood of the notches. The purpose in this paper is to show that one can obtain rapidly and accurately, by the finite element analysis, the isochromatic and the isoclinic fringe patterns in a stressed model as the experimental procedure can be time consuming. Stress fields can therefore be analyzed in three dimensional models as long as the meshing and the limit conditions are properly set in the program.

Keywords: isochromatic fringe, isoclinic fringe, photoelasticity, stress concentration factor

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Authors: Gilbert Omorodion Osayemwenre, Edson Meyer, R. T. Taziwa

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The electrical analysis of single junction amorphous silicon solar modules is carried out using outdoor monitoring technique. Like crystalline silicon PV modules, the electrical characterisation and performance of single junction amorphous silicon modules are best described by its current-voltage (IV) characteristic. However, IV curve has a direct dependence on the type of PV technology and material properties used. The analysis reveals discrepancies in the modules performance parameter even though they are of similar technology. The aim of this work is to compare the electrical performance output of each module, using electrical parameters with the aid of PVPM 100040C IV tracer. These results demonstrated the relevance of standardising the performance parameter for effective degradation analysis of a-Si:H.

Keywords: PVPM 100040C IV tracer, SolarWatt part, single junction amorphous silicon module (a-Si:H), Staebler-Wronski (S-W) degradation effect

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Authors: Aruha Khan, Brynn E. Kankel, Paraskevi Papadopoulou

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In recent years, extensive research upon ‘stress’ has provided insight into its two distinct guises, namely the short–term (fight–or–flight) response versus the long–term (chronic) response. Specifically, the long–term or chronic response is associated with the suppression or dysregulation of immune function. It is also widely noted that the occurrence of cancer is greatly correlated to the suppression of the immune system. It is thus necessary to explore the impact of long–term or chronic stress upon the prevalence and risk of cancer. To what extent can the dysregulation of immune function caused by long–term exposure to stress be controlled or minimized? This study focuses explicitly upon immunosuppression due to its ability to increase disease susceptibility, including cancer itself. Based upon an analysis of the literature relating to the fundamental structure of the immune system alongside the prospective linkage of chronic stress and the development of cancer, immunosuppression may not necessarily correlate directly to the acquisition of cancer—although it remains a contributing factor. A cross-sectional analysis of the survey data from the University of Tennessee Medical Center (UTMC) and Harvard Medical School (HMS) will provide additional supporting evidence (or otherwise) for the hypothesis of the study about whether immunosuppression (caused by the chronic stress response) notably impacts the prevalence of cancer. Finally, a multidimensional framework related to education on chronic stress and its effects is proposed.

Keywords: immune system, immunosuppression, long–term (chronic) stress, risk of cancer

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Authors: Alfi Al Fahreizy

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Yogyakarta is one of the provinces in Indonesia that often get a power outage because of high load electrical consumption. The authors mapped the electrical energy consumption [GWh] for the province of Yogyakarta in 2014-2025 using LEAP (Long-range Energy Alternatives Planning system) software. This paper use BAU (Business As Usual) scenario. BAU scenario in which the projection is based on the assumption that growth in electricity consumption will run as normally as before. The goal is to be able to see the electrical energy consumption in the household sector, industry , business, social, government office building, and street lighting. The data is the data projected statistical population and consumption data electricity [GWh] 2010, 2011, 2012 in Yogyakarta province.

Keywords: LEAP, energy consumption, Yogyakarta, BAU

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Authors: Deepak Bhardwaj, Narendra Tuteja

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Global climate change is impacting large agrarian societies, especially those in countries located near the equator. Agriculture, and consequently, plant-based food, is the hardest hit in tropical and sub-tropical countries such as India due to an increased incidence of drought as well as an increase in soil salinity. One method that holds promise is AMF-rich biofertilizers which assist in activating proteins which in turn help alleviate abiotic stress in plants. In the present study, we identified two important species of (arbuscular mycorrhizal fungus) AMF belonging to Glomus and Gigaspora from the rhizosphere of the important medicinal plant Justicia adathoda. These two species have been found to be responsible for the abundance of Justicia adathoda in the semi-arid areas of the Jammu valley located in northern India, namely, the Union Territory of Jammu and Kashmir. We isolated the species of Glomus and Gigaspora from the rhizosphere of Justicia adathoda and used them as biofertilizers for the tomato plant. Significant improvements in the growth parameters were observed in the tomato plants inoculated with Glomus sp. and Gigaspora sp. in comparison with the tomato plants that were grown without AMF treatments. Tomato plants grown along with Glomus sp. and Gigaspora sp. have been observed to withstand 200 mM of salinity and 25% PEG stress. AMF also resulted in an increased concentration of proline and antioxidant enzymes in tomato plants. We also examined the expression levels of salinity and drought stress-inducible genes such as pea DNA helicase 45 (PDH 45) and genes of G-protein subunits of the tomato plants inoculated with and without AMF under stress and normal conditions. All the stress-inducible genes showed a significant increase in their gene expression under stress and AMF inoculation, while their levels were found to be normal under AMF inoculation without stress. We propose a model of abiotic stress alleviation in tomato plants with the help of external factors such as AMF and internally with the help of proteins like PDH 45 and G-proteins.

Keywords: AMF, abiotic stress, g-proteins, PDH-45

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Authors: Ezgi Yurdakul, Klaus-Alexander Rieder, Richard Sibbick

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Most of the shotcrete projects require compliance with meeting a specified early-age strength target (e.g., reaching 1 MPa in 1 hour) that is selected based on the underground conditions. To meet the desired early-age performance characteristics, accelerators are commonly used as they increase early-age strength development rate and accelerate the setting thereby reducing sagging and rebound. The selection of accelerator type and its dosage is made by the setting time and strength required for the shotcrete application. While alkaline and alkali-free accelerators are the two main types used in wet-mix shotcrete; alkali-free admixtures increasingly substitute the alkaline accelerators to improve the performance and working safety. This paper aims to evaluate the impact of alkali-free accelerators in wet-mix on various tests including set time, early and later-age compressive strength, boiled absorption, and electrical resistivity. Furthermore, the comparison between accelerated and non-accelerated samples will be made to demonstrate the interaction between cement and accelerators. Scanning electron microscopy (SEM), fluorescent resin impregnated thin section and cut and polished surface images will be used to understand the microstructure characterization of mixes in the presence of accelerators.

Keywords: accelerators, chemical admixtures, shotcrete, sprayed concrete

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Authors: P. D. Pedrosa, J. M. A. Rebello, M. P. Cindra Fonseca

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Duplex stainless steels (DSS) exhibit a biphasic microstructure consisting of austenite and delta ferrite. Their high resistance to oxidation, and corrosion, even in H2S containing environments, allied to low cost when compared to conventional stainless steel, are some properties which make this material very attractive for several industrial applications. However, several of these industrial applications imposes cyclic loading to the equipments and in consequence fatigue damage needs to be a concern. A well-known way of improving the fatigue life of a component is by introducing compressive residual stress in its surface. Shot peening is an industrial working process which brings the material directly beneath component surface in a high mechanical compressive state, so inhibiting fatigue crack initiation. However, one must take into account the fact that the cyclic loading itself can reduce and even suppress these residual stresses, thus having undesirable consequences in the process of improving fatigue life by the introduction of compressive residual stresses. In the present work, shot peening was used to introduce residual stresses in several DSS samples. These were thereafter submitted to three different fatigue regimes: low, medium and high cycle fatigue. The evolution of the residual stress during loading were then examined on both surface and subsurface of the samples. It was used the DSS UNS S31803, with microstructure composed of 49% austenite and 51% ferrite. The treatment of shot peening was accomplished by the application of blasting in two Almen intensities of 0.25 and 0.39A. The residual stresses were measured by X-ray diffraction using the double exposure method and a portable equipment with CrK radiation and the (211) diffracting plane for the austenite phase and the (220) plane for the ferrite phase. It is known that residual stresses may arise when two regions of the same material experienced different degrees of plastic deformation. When these regions are separated in respect to each other on a scale that is large compared to the material's microstructure they are called macro stresses. In contrast, microstresses can largely vary over distances which are small comparable to the scale of the material's microstructure and must balance zero between the phases present. In the present work, special attention will be paid to the measurement of residual microstresses. Residual stress measurements were carried out in test pieces submitted to low, medium and high-cycle fatigue, in both longitudinal and transverse direction of the test pieces. It was found that after shot peening, the residual microstress is tensile in the austenite and compressive in the ferrite phases. It was hypothesized that the hardening behavior of the austenite after shot peening was probably due to its higher nitrogen content. Fatigue cycling can effectively change this stress state but this effect was found to be dependent of the shot peening intensity was well as the fatigue range.

Keywords: residual stresses, fatigue, duplex steel, shot peening

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Authors: Ahmad El Hajjar, Joanna Eid, Salima Bouchemella, Tariq Ouahbi, Benoit Duchemin, Said Taibi

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In our present society, raw earth presents an alternative as an energy-saving building material for dealing with climate and environmental issues. Nevertheless, it has a sensitivity to water, due to the presence of fines, which has a direct effect on its consistency. This can be expressed during desiccation, by shrinkage deformations resulting in cracking that begins once the internal tensile stresses developed, due to suction, exceed the tensile strength of the material. This work deals with the evolution of the strain of clay samples, from the beginning of shrinkage until the initiation of crack, using the DIC (Digital Image Correlation) technique. In order to understand the origin of cracking, desiccation is studied for different boundary conditions and depending on the intrinsic characteristics of the material. On the other hand, a study of restrained shrinkage is carried out on the ring test to investigate the ultimate tensile strength from which the crack begins in the dough of clay. The purpose of this test is to find the type of reinforcement adapted to thwart in the cracking of the material. A microscopic analysis of the damaged area is necessary to link the macroscopic mechanisms of cracking to the various physicochemical phenomena at the microscopic scale in order to understand the different microstructural mechanisms and their impact on the macroscopic shrinkage.

Keywords: clayey soil, shrinkage, strain, cracking, digital image correlation

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Authors: Muhammad R. Islam, Mohammad Dalour H. Beg, Saidatul S. Jamari

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Considering palm oil as non-drying oil owing to its low iodine value, an attempt was taken to increase the unsaturation in the fatty acid chains of palm oil for the preparation of alkyds. To increase the unsaturation in the palm oil, sulphuric acid (SA) and para-toluene sulphonic acid (PTSA) was used prior to alcoholysis for the dehydration process. The iodine number of the oil samples was checked for the unsaturation measurement by Wijs method. Alkyd resin was prepared using the dehydrated palm oil by following alcoholysis and esterification reaction. To improve the film properties 0.5 wt% multi-wall carbon nano tubes (MWCNTs) were used to manufacture polymeric film. The properties of the resins were characterized by various physico-chemical properties such as density, viscosity, iodine value, acid value, saponification value, etc. Structural elucidation was confirmed by Fourier transform of infrared spectroscopy and proton nuclear magnetic resonance; surfaces of the cured films were observed by scanning electron microscopy. In addition, pencil hardness and chemical resistivity was also measured by using standard methods. The effect of enhancement of the unsaturation in the fatty acid chain found significant and motivational. The resin prepared with dehydrated palm oil showed improved properties regarding hardness and chemical resistivity testing. The incorporation of MWCNTs enhanced the thermal stability and hardness of the films as well.

Keywords: alkyd resin, nano-coatings, dehydration, palm oil

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Authors: Carla M. Machado, André A. Silva, Armando Bastos, Telmo G. Santos, J. Pamies Teixeira

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Advanced high-strength steels (AHSS) are increasingly being used in automotive components. The use of AHSS sheets plays an important role in reducing weight, as well as increasing the resistance to impact in vehicle components. However, the large-scale use of these sheets becomes more difficult due to the limitations during the forming process. Such limitations are due to the elastically driven change of shape of a metal sheet during unloading and following forming, known as the springback effect. As the magnitude of the springback tends to increase with the strength of the material, it is among the most worrisome problems in the use of AHSS steels. The prediction of strain hardening, especially under non-proportional loading conditions, is very limited due to the lack of constitutive models and mainly due to very limited experimental tests. It is very clear from the literature that in experimental terms there is not much work to evaluate deformation behavior under real conditions, which implies a very limited and scarce development of mathematical models for these conditions. The Bauschinger effect is also fundamental to the difference between kinematic and isotropic hardening models used to predict springback in sheet metal forming. It is of major importance to deepen the phenomenological knowledge of the mechanical and microstructural behavior of the materials, in order to be able to reproduce with high fidelity the behavior of extension of the materials by means of computational simulation. For this, a multi phenomenological analysis and characterization are necessary to understand the various aspects involved in plastic deformation, namely the stress-strain relations and also the variations of electrical conductivity and magnetic permeability associated with the metallurgical changes due to plastic deformation. Aiming a complete mechanical-microstructural characterization, uniaxial tensile tests involving successive cycles of loading and unloading were performed, as well as biaxial tests such as the Erichsen test. Also, nondestructive evaluation comprising eddy currents to verify microstructural changes due to plastic deformation and ultrasonic tests to evaluate the local variations of thickness were made. The material parameters for the stable yield function and the monotonic strain hardening were obtained using uniaxial tension tests in different material directions and balanced biaxial tests. Both the decrease of the modulus of elasticity and Bauschinger effect were determined through the load-unload tensile tests. By means of the eddy currents tests, it was possible to verify changes in the magnetic permeability of the material according to the different plastically deformed areas. The ultrasonic tests were an important aid to quantify the local plastic extension. With these data, it is possible to parameterize the different models of kinematic hardening to better approximate the results obtained by simulation with the experimental results, which are fundamental for the springback prediction of the stamped parts.

Keywords: advanced high strength steel, Bauschinger effect, sheet metal forming, springback

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Authors: Richu J. Babu, Sony Mathew, Sharon Rony Jacob, Soney C. George, Jibin C. Jacob

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Human hair is a non-biodegradable waste available in plenty throughout the world but is rarely explored for applications in engineering fields. Tensile strength of human hair ranges from 170 to 220 MPa. This property of human hair can be made use in the field of making bio-composites[1]. The composite is prepared by commixing the human hair and natural rubber in a two roll mill along with additives followed by vulcanization. Here the concentration of the human hair is varied by fine-tuning the fiber length as 20 mm and sundry tests like tensile, abrasion, tear and hardness were conducted. While incrementing the fiber length up to a certain range the mechanical properties shows superior amendments.

Keywords: human hair, natural rubber, composite, vulcanization, fiber loading

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Authors: Zemour Kamel, Chouhim Kadda Mohamed Amine

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Salinity is one of the most environmental factors limiting crop productivity. It has a negative effect on both germination and plant growth processes (photosynthesis, respiration, and transpiration), nutrient balance, membrane properties and cellular homeostasis, enzymatic and metabolic activities. Among the strategic crops in the world and more mainly in Algeria, durum wheat is very affected by this abiotic stress. For that, this study focuses on an evaluation of salt stress effect on the germination process of durum wheat as well as its response after application of lavender hydrosol and aqueous pistachio extract. The results have shown that all the physicochemical parameters of germination have been affected by this stress. However, lavender hydrosol and aqueous pistachio extract, considered as organic compounds, significantly improved the germination of wheat seeds. Finally, this study has highlighted the importance of using organic products as an ideal alternative to reduce the effect of abiotic stress on durum wheat productivity.

Keywords: salinity, wheat durum, extract, lavender hydrosol, aqueous pistachio

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Authors: V. Hashim, P. N. Dileep

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Stent implantation is being seen as the most successful method to treat coronary artery diseases. Different types of stents are available in the market these days and the success of a stent implantation greatly depends on the proper selection of a suitable stent for a patient. Computer numerical simulation is the cost effective way to choose the compatible stent. Studies confirm that the design characteristics of stent do have great importance with regards to the pressure it can sustain, the maximum displacement it can produce, the developed stress concentration and so on. In this paper different designs of stent were analyzed together with balloon to optimize the stent and balloon system. Commercially available stent Palmaz-Schatz has been selected for analysis. Abaqus software is used to simulate the system. This work is the finite element analysis of the artery stent implant to find out the design factors affecting the stress and strain. The work consists of two phases. In the first phase, stress distribution of three models were compared - stent without balloon, stent with balloon of equal length and stent with balloon of extra length than stent. In second phase, three different design models of Palmaz-Schatz stent were compared by keeping the balloon length constant. The results obtained from analysis shows that, the design of the strut have strong effect on the stress distribution. A design with chamfered slots found better results. The length of the balloon also has influence on stress concentration of the stent. Increase in length of the balloon will reduce stress, but will increase dog boning effect.

Keywords: coronary stent, finite element analysis, restenosis, stress concentration

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Authors: Eda Gök

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Peridynamics is a new modeling concept of non-local interactions for solid structures. The formulations of Peridynamic (PD) theory are based on integral equations rather than differential equations. Through, undefined equations of associated problems are avoided. PD theory might be defined as continuum version of molecular dynamics. The medium is usually modeled with mass particles bonded together. Particles interact with each other directly across finite distances through central forces named as bonds. The main assumption of this theory is that the body is composed of material points which interact with other material points within a finite distance. Although, PD theory developed for discontinuities, it gives good results for structures which have no discontinuities. In this paper, displacement control of the isotropic plate under the effect of tensile and bending loading has been investigated by means of PD theory. A MATLAB code is generated to create PD bonds and corresponding surface correction factors. Using generated MATLAB code the geometry of the specimen is generated, and the code is implemented in Finite Element Software. The results obtained from non-local continuum theory are compared with the Finite Element Analysis results and analytical solution. The results show good agreement.

Keywords: non-local continuum mechanics, peridynamic theory, solid structures, tensile loading, flexural loading

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Authors: Mary Esere, Mogbekeloluwa Fakokunde, Adetoun Idowu

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Background: Working in a military setting could elicit some amount of stressful doses into ones system because of the attendant peculiar characteristics found in the military environment. Thus, this study was carried out to find out the sources of occupational stress among teachers in various Command Secondary Schools within 2 Division of Nigerian Army. Method: The study employed a survey method. Simple random sampling technique was used to select the schools in the Division. A total of 200 respondents participated in the study. Sources of Teachers’ Occupational Stress Questionnaire (STOSQ) was administered to the respondents to collect relevant data. The t-test and Analysis of Variance (ANOVA) statistics were used to test the hypotheses. Findings: From the study, it was discovered that teachers in this setting do experience occupational stress. Their major sources of stress bother on issues relating to salaries and allowances and staff welfare concerns. The findings also revealed that there were no significant differences in the sources of occupational stress among the teachers in respect to gender and marital status. Discussion: Based on these findings, it was recommended that the Appropriate Superior Authority (ASA) should reconstitute the proscribed Armed Forces Schools Management Board (AFSMB) where issues, such as staff salaries and welfare concerns for teachers working in the schools under the three services (Army, Navy, Airforce) will always be addressed. This will go a long way in enhancing the psychological well-being of the teachers.

Keywords: Nigerian army, occupational stress, sources, teachers

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Authors: Regina Bowler

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Rationale & Aims: Complementary interventions such as mindfulness-meditation, gratitude, and self-affirmation are often used by therapists to treat stress. Many studies have been conducted using these interventions either individually or adjunctively with regard to stress. However, there has been little work comparing these interventions to investigate which of them is the most effective in treating stress. This study aims to compare these interventions and to determine which of them has the strongest perceived and physiological impact on stress. Participants: 120 law students preparing to take the bar exam: 3 experimental groups of 30 individuals, 1 control group of 30 individuals. Methods: One day prior to administering the interventions, baseline salivary cortisol samples will be taken, and the participants will complete the perceived stress scale (Cohen et al., 1983). Thirty days prior to the bar exam, each experimental group will be given an intervention to practice. Interventions will be practiced once in the morning after waking and once at night at bedtime. In group one, each participant will do a recorded three-minute mindfulness meditation. In group two, each participant will practice gratitude by writing down three things he/she/they are grateful for. In group three, each participant will practice affirmation by writing three sentences affirming his/her/their core values. The control group will not have an intervention to practice. Starting experimental day 1, upon waking and prior to practicing the intervention, the participants will take a salivary cortisol sample. Then they will practice their given intervention. Every night, before going to bed, the participants will practice their given intervention for a second time. The participants will practice their interventions and take salivary cortisol samples for 28 days. After each seven-day period (days 7, 14, 21, 28), the participants will fill out a brief questionnaire about the effects their intervention has on their stress, daily life, and relationships with themselves and others. On day 29, the participants will take a final salivary cortisol sample and will fill out the Perceived Stress Scale (Cohen et al., 1983). Applications of findings: Findings from this study would inform therapists of best practices when working with clients with stress. Moreover, therapists will gain knowledge of how individuals perceive these interventions and their impact on stress, daily life, somatic symptoms, and relationships with self and others. Thus, therapists will be able to administer these interventions with more precision to the stress-related contexts and issues their clients bring.

Keywords: stress, mindfulness-meditation, gratitude, affirmations, complementary interventions

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Authors: Baishali Deb, Hari Om Pandey, Shrilla Elangbam, Mukesh Singh, Ayon Tarafdar, A. K. S. Tomar, A. K. Pandey, Triveni Dutt

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The goal of the present investigation was to determine the impact of social stress on behavioural characteristics, physiological responses, and haemato-biochemical indicators under various social environments in Tharparkar cattle. Serum cortisol and faecal cortisol metabolites analysis were used to determine the stress level of Tharparkar cattle. Social isolation and social mixing were the two different social circumstances used to evaluate the animals. In both the experiments i.e., social isolation and social mixing, the lying period of animals decreased significantly (p<0.05) while standing period significantly (p<0.05) increased. Frequency and duration of activities like idling, walking, exploration, oral manipulation, and elimination increased significantly (p<0.05) in Tharparkar cattle after being subjected to social isolation and social mixing. Time spent in grooming (self-grooming and allo-grooming) in respect to social isolation significantly increased during isolation and post-reunion, whereas there was a significant (p<0.05) decline in the grooming behaviour especially allo-grooming during mixing of the animals. Feeding and rumination time also decreased significantly (p<0.05) in animals during both the experiments. Physiological parameters such as respiration rate, heart rate and pulse rate increased during the treatment periods. There was no significant difference in the haematological parameters for both the experiments. There was significant (p<0.05) increase in serum cortisol and faecal cortisol metabolites (FCM) concentration in animals subjected to social stress. Therefore, it can be concluded that social stress strongly impacts the behaviour and physiological parameters of the animals, causing stress and nervousness, proving that social stress is a valid psychological stress in animals. The higher concentration of FCM in Tharparkar cattle subjected to social stress, further supported by higher serum cortisol and behaviour manifestations, suggest that FCM could be used to assess stress response as a non-invasive method.

Keywords: social stress, fecal cortisol metabolites, non-invasive, animal welfare, behaviour

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Authors: Amin Alvani

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Multiple sclerosis (MS) is a chronic, often disabling disease in which the immune system attacks the myelin sheath of neurons in the central nervous system. The present study aimed to investigate the Relationship between behavioral inhibition/approach system (BIS-BAS) and perceived stress (PS) whit control white blood cell (WBC). 60 MS patients (male=36.7, female=63.3%; age range=15-65 participated in the study and completed the demographic questionnaire, the count blood cell (CBC) test, the behavioral Activation and behavioral inhibition scale (BIS-BAS), and the perceived stress Questionnaire (PSS-14). The results revealed that Between of BAS-reward responsiveness (BAS-DR) subscale and PS, in more than MS patient (BIS), there are increase WBC.

Keywords: behavioral inhibition/approach system, perceived stress, white blood cell, multiple sclerosis

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Authors: Jaime R. Silva, Gabriel E. Reyes, Marianne Krause

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Background: The two-polarity model of the depressive personality argues that experience is organized around two axes: interpersonal relatedness and self-definition. Differential emphasis on one of these poles defines three types of depressive experience: Anaclitic, Introjective or Mixed pattern. On the one hand, Anaclitic pattern has been conceptually related with exaggerated biological stress sensitivity. On the other hand, the Introjective pattern was linked with anhedonic symptomatology. The general aim of the study was to find empirical support for this relationship. Methods: 101 non-clinical individuals participated in two experimental sessions. During the first session, the biological stress reactivity (cortisol concentration in saliva) and the subjective stress perceived (self-reported) during the Trier Social Stress Test (TSST), were investigated. In the second session, a visual discrimination task with a specific reward system, to study the reinforcement sensitivity (anhedonia), was performed. Results: Results evidenced that participants with Introjective depressive symptoms showed a higher interpersonal sensitivity and a diminished sensitivity to reinforcement. In addition, results also indicated that such a group has a poor psychological detection of its exacerbated reactivity to stress, which is the opposite pattern evidenced amongst the Anaclitic group. Conclusions: In perspective, these results empirically support the two-polarity of the depressive personality model. Clinical implications are discussed.

Keywords: depression, interpersonal stress, personality, trier social stress test

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Authors: Shenghu Feng, Jun Cheng

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The molecular mechanism underlying nonalcoholic fatty liver disease (NAFLD) progression to hepatocellular carcinoma (HCC) remains unknown. In this study, immunohistochemistry staining result showed that NS5ABP37 protein expression decreased as with increasing degree of HCC malignancy. In agreement, NS5ABP37 protein overexpression significantly suppressed cell proliferation, caused G1/S cell cycle arrest, and induced apoptosis by increasing caspase-3/7 activity and cleaved caspase-3 levels. In addition, NS5ABP37 overexpression resulted in decreased intracellular TG and TC contents, with level reduction in SREBPs and downstream effectors. Furthermore, NS5ABP37 overexpression decreased SREBP1c and SREBP2 levels by inducing their respective promoters. Finally, ROS levels and ER-stress were both induced by NS5ABP37 overexpression. These findings together demonstrate that NS5ABP37 inhibits cancer cell proliferation and promotes apoptosis, by altering SREBP-dependent lipogenesis and cholesterogenesis in HepG2 cells and inducing oxidative stress and ER stress.

Keywords: NS5ABP37, liver cancer, lipid metabolism, oxidative stress, ER stress

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Authors: David A. Wallace, Salakjit J. Nilboworn

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Secure and reliable transmission and distribution of electrical power is crucial in today’s ever-increasing demand for electricity. Traditional methods of protecting the electrical grid have relied on relaying systems receiving voltage and current inputs from inductive instruments transformers (IT). This method has provided robust and stable performance throughout the years. Today with the advent of new non-conventional transformers (NCIT) and sensors, the electrical landscape is changing. These new systems have to ability to provide the same electrical performance as traditional instrument transformers with the added features of data acquisition, communication, smaller footprint, lower cost and resistance to GMD/GIC events.

Keywords: non-conventional instrument transformers, digital substations, smart grids, micro-grids

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Authors: Shota Nagata, Kazuya Okubo, Toru Fujii

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The purpose of this study is to investigate the proper condition in extracting carbon fibers as the reinforcement of composite molded by injection method. Recycled carbon fibers were extracted from wasted CFRP by pyrolyzing epoxy matrix of CFRP under air atmosphere at different temperature conditions 400, 600 and 800°C in this study. Recycled carbon fiber reinforced polypropylene (RCF/PP) pellets were prepared using twin screw extruder. The RCF/PP specimens were molded into dumbbell shaped specimens using injection molding machine. The tensile strength of recycled carbon fiber was decreased with rising pyrolysis temperature from 400 to 800°C. However, superior mechanical properties of tensile strength, tensile modulus and fracture strain of RCF/PP specimen were obtained when the extracting temperature was 600°C. Almost fibers in RCF/PP specimens were aligned in the mold filling direction in this study when the extracting temperature was 600°C. To discuss the results, the failure mechanisms of RCF/PP specimens was shown schematically. Finally, it was concluded that the temperature condition at 600°C should be selected in extracting carbon fibers as the reinforcement of RCF/PP composite molded by injection method.

Keywords: CFRP, recycled carbon fiber, injection molding, mechanical properties, fiber orientation, failure mechanism

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Authors: Qingying Liu, S. Liu, L. Hao, B. Zhang, J. D. Yan

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HVDC technology is becoming increasingly popular due to its simplicity in topology and less power loss over long distance of power transmission, in comparison with HVAC technology. However, the dielectric behavior of insulators in the long term under HVDC stress is completely different from that under HVAC stress as a result of charge accumulation in a constant electric field. Insulators used in practical systems are never perfect in their structural conditions. Over time shallow cracks may develop on their surface. The presence of defects can lead to drastic change in their dielectric behaviour and thus increase the probability of surface flashover. In this contribution, experimental investigations have been carried out on the charge accumulation phenomenon on the surface of a rod insulator made of epoxy that is placed between two disk shaped electrodes at different voltage levels and in different gases (SF6, CO2 and N2). Many results obtained, such as, the two-dimensional electrostatic potential distribution along the insulator surface after the removal of the power source following a pre-defined period of application. The probe has been carefully calibrated before each test. Results show that surface charge distribution near the two disk shaped electrodes is not uniform in the circumferential direction, possibly due to the imperfect electrical connections between the embeded conductor in the insulator and the disk shaped electrodes. The axial length of this non-uniform region is experimentally determined, which provides useful information for shielding design. A charge transport model is also used to explain the formation of the long term electrostatic potential distribution under a constant applied voltage.

Keywords: HVDC, power systems, dielectric behavior, insulation, charge accumulation

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Authors: Eiji Nakamachi, Tsuyoshi Eguchi, Sayo Yamamoto, Yusuke Morita, H. Sakamoto

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In this study, we aim to reveal the relationship between the meniscal tearing and the articular cartilage injury of knee joint by using the dynamic explicit finite element (FE) method. Meniscal injuries reduce its functional ability and consequently increase the load on the articular cartilage of knee joint. In order to prevent the induction of osteoarthritis (OA) caused by meniscal injuries, many medical treatment techniques, such as artificial meniscus replacement and meniscal regeneration, have been developed. However, it is reported that these treatments are not the comprehensive methods. In order to reveal the fundamental mechanism of OA induction, the mechanical characterization of meniscus under the condition of normal and injured states is carried out by using FE analyses. At first, a FE model of the human knee joint in the case of normal state – ‘intact’ - was constructed by using the magnetron resonance (MR) tomography images and the image construction code, Materialize Mimics. Next, two types of meniscal injury models with the radial tears of medial and lateral menisci were constructed. In FE analyses, the linear elastic constitutive law was adopted for the femur and tibia bones, the visco-hyperelastic constitutive law for the articular cartilage, and the visco-anisotropic hyperelastic constitutive law for the meniscus, respectively. Material properties of articular cartilage and meniscus were identified using the stress-strain curves obtained by our compressive and the tensile tests. The numerical results under the normal walking condition revealed how and where the maximum compressive stress occurred on the articular cartilage. The maximum compressive stress and its occurrence point were varied in the intact and two meniscal tear models. These compressive stress values can be used to establish the threshold value to cause the pathological change for the diagnosis. In this study, FE analyses of knee joint were carried out to reveal the influence of meniscal injuries on the cartilage injury. The following conclusions are obtained. 1. 3D FE model, which consists femur, tibia, articular cartilage and meniscus was constructed based on MR images of human knee joint. The image processing code, Materialize Mimics was used by using the tetrahedral FE elements. 2. Visco-anisotropic hyperelastic constitutive equation was formulated by adopting the generalized Kelvin model. The material properties of meniscus and articular cartilage were determined by curve fitting with experimental results. 3. Stresses on the articular cartilage and menisci were obtained in cases of the intact and two radial tears of medial and lateral menisci. Through comparison with the case of intact knee joint, two tear models show almost same stress value and higher value than the intact one. It was shown that both meniscal tears induce the stress localization in both medial and lateral regions. It is confirmed that our newly developed FE analysis code has a potential to be a new diagnostic system to evaluate the meniscal damage on the articular cartilage through the mechanical functional assessment.

Keywords: finite element analysis, hyperelastic constitutive law, knee joint injury, meniscal tear, stress concentration

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Authors: Emre Alan, Zafer Cetin

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Electrical steels are widely used as a magnetic core materials in many electrical applications such as transformers, electric motors, and generators. Core loss property of these magnetic materials refers to dissipation of electrical energy during magnetization in service conditions. Therefore, in order to minimize the magnetic core loss, certain precautions are taken from steel producers; “Steel Cleanliness” is one of the major points among them. For obtaining lower core loss values, increasing proper elements in chemical composition such as silicon is a must. Therefore, impurities of these alloys are a key value for producing a cleaner steel. In this study, effects of impurity levels of different FeSi alloying materials to the steel cleanliness will be investigated. One of the important element content in FeSi alloy materials is Calcium. A SEM investigation will be done in order to present if Ca content in FeSi alloy is enough for proper inclusion modification or an additional Ca-treatment is required.

Keywords: electrical steels, FeSi alloy, impurities, steel cleanliness

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Authors: Aviva Lvan, Lipaz Shamoa-Nir

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Recently, has increased the research interest in modern fatherhood especially, the increasing involvement of fathers in the family. However, there is a little research evidence on fathers to children with special needs. Therefore, the purpose of this study was to examine the effects of stress and coping style on involvement in school among fathers to children with special needs in inclusive education. We compared the fathers to children with special needs (N=72) with fathers to non-special needs children (N = 75), and found that higher stress levels, greater educational involvement and greater use of social support coping style, were found among fathers of children with special needs. In addition, mission coping style and emotional coping style predict involvement in the school and emotional coping style predicts high levels of stress. The above findings contribute to the investigation of changes in the perception of the role of fathers and their involvement in their children's lives especially, among fathers to children with special needs. From the applied aspect, the findings may increase the understanding of the role of fathers and their unique contribution to the social, emotional, and academic development of their children.

Keywords: coping style, educational involvement, special needs, stress

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Authors: Shuangxin Wu

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Superalloy ultra-thin-walled components occupy a considerable proportion of aero engines and play an increasingly important role in structural weight reduction and performance improvement. To solve problems such as high deformation resistance and poor formability at room temperature, the introduction of pulse current in the processing process can improve the plasticity of metal materials, but the influence mechanism of pulse current on the forming limit of superalloy ultra-thin sheet is not clear, which is of great significance for determining the material processing window and improving the micro-forming process. The effect of pulse current on the microstructure evolution of superalloy thin plates was observed by optical microscopy (OM) and X-ray diffraction topography (XRT) by applying pulse current to GH3039 with a thickness of 0.2mm under plane strain and uniaxial tensile states. Compared with the specimen without pulse current applied at the same temperature, the internal void volume fraction is significantly reduced, reflecting the non-thermal effect of pulse current on the growth of micro-pores. ED (electrically deforming) specimens have larger and deeper dimples, but the elongation is not significantly improved because the pulse current promotes the void coalescence process, resulting in material fracture. The electro-plastic phenomenon is more obvious in the plane strain state, which is closely related to the effect of stress triaxial degree on the void evolution under pulsed current.

Keywords: pulse current, superalloy, ductile fracture, void damage

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Authors: Nkereke M. Essien

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The intention of this paper is to examine stress in the Educated Nigerian Accent of English (ENAE) with the aim of analyzing stress and rhythmic patterns of Nigerian English. Our aim also is to isolate differences and similarities in the stress patterns studied and also know what forms the accent of these Educated Nigerian English (ENE) which marks them off from other groups or English’s of the world, to ascertain and characterize it and to provide documented evidence for its existence. Nigerian stress and rhythmic patterns are significantly different from the British English stress and rhythmic patterns consequently, the educated Nigerian English (ENE) features more stressed syllables than the native speakers’ varieties. The excessive stressed of syllables causes a contiguous “Ss” in the rhythmic flow of ENE, and this brings about a “jerky rhythm’ which distorts communication. To ascertain this claim, ten (10) Nigerian speakers who are educated in the English Language were selected by a stratified Random Sampling technique from two Federal Universities in Nigeria. This classification belongs to the education to the educated class or standard variety. Their performance was compared to that of a Briton (control). The Metrical system of analysis was used. The respondents were made to read some words and utterance which was recorded and analyzed perceptually, statistically and acoustically using the one-way Analysis of Variance (ANOVA). The Turky-Kramer Post Hoc test, the Wilcoxon Matched Pairs Signed Ranks test, and the Praat analysis software were used in the analysis. It was revealed from our findings that the Educated Nigerian English speakers feature more stressed syllables in their productions by spending more time in pronouncing stressed syllables and sometimes lesser time in pronouncing the unstressed syllables. Their overall tempo was faster. The ENE speakers used tone to mark prominence while the native speaker used stress to mark pronounce, typified by the control. We concluded that the stress pattern of the ENE speakers was significantly different from the native speaker’s variety represented by the control’s performance.

Keywords: accent, Nigerian English, rhythm, stress

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Authors: Rodlyn Remina Hines

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Africans who migrate to the United States (U.S.) go through an acculturation period. When they join the U.S. workforce during the period they are still acquainting to the new geographic area and culture, they may experience work and family conflict in addition to the stressors of acculturation. This study investigated the impact of acculturation stress and work-family conflict on the health and wellbeing of African immigrants in the U.S. using a growing immigrant population. Ghanaian immigrants (n = 100, males= 43%; females= 56%) residing in New York and Massachusetts, United States (U.S.), were recruited via purposive sampling to investigate the role acculturation stress and work-family conflict play on the health and wellbeing of African immigrants in the U.S. Using the Sociocultural theory, three hypotheses were proposed: (1) High acculturation stress will lead to high work-family conflict, (2) High work-family conflict will result in poor health and wellbeing, and (3) Work-family conflict will mediate the relationship between acculturation stress and health and wellbeing. The results fully supported the first hypothesis and partially supported the second and third. High acculturation stress led to high work-family conflict. Although high work-family conflict resulted in poorer health and wellbeing, high family support mediated work-family conflict and health and wellbeing. Participants who reported poor health also reported a lack of family or other support and those who reported strong family or other support also reported excellent health and wellbeing even with high work-family conflict. The latter group did not expect their health and wellbeing to get worse. I draw on these findings to conclude that African immigrants in the U.S. experience significant acculturation stress and work-family conflict resulting in poor health and wellbeing during their acculturation period if there is a lack of family or other support. These findings have implications for practitioners and policymakers.

Keywords: acculturation stress, work-family conflict, Ghanaian immigrants, health and wellbeing

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Authors: Zine Kechrid

Abstract:

This study was carried out to investigate the antioxidant effect of vitamin C on oxidative stress induced by dietary Zn-deficiency in albino diabetic rats. Thirty two males alloxan-diabetic rats divided into two groups of 16 individuals each; the first group was fed a zinc adequate diet (54 mg zinc/kg). The second group had given low zinc diet (1 mg zinc/kg). Then, half of each group was treated with vitamin C (1 g/l) in drinking water. After four weeks, animals were sacrificed and different parameters were determined. The findings showed that dietary deficiency zinc intake significantly increased serum glucose. Zn-deficiency was also led to an increase in oxidative stress, which was indicated by an increase of MDA level and glutathione-S-transferase activity. Meanwhile it was result in a decrease of reduced glutathione (GSH) content, glutathione peroxidase GSH-Px and catalase activities in liver. However, the administration of vitamin C restored all the previous parameters approximately to their normal values. In conclusion, vitamin C probably played a key role strong as antioxidant factor against oxidative stress provoked by dietary zinc inadequate. Therefore, it might be contributed in reduction diabetes complications.

Keywords: vitamin C, oxidative stress, zinc, experimental diabetes, rats

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