Search results for: perceived stress

Authors: H. Dehghan, E. Mahdavi, M. M. Heyhat

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In pressure vessels contain hydrogen, the role of hydrogen will be important because of hydrogen cracking problem. It is difficult to predict what is happened in metallurgical field spite of a lot of studies have been searched. The main role in controlling the mass diffusion as driving force is related to stress. In this study, finite element analysis is implemented to estimate material-s behavior associated with hydrogen embrittlement. For this purpose, one model of a pressure vessel is introduced that it has definite boundary and initial conditions. In fact, finite element is employed to solve the sequentially coupled mass diffusion with stress near a crack front in a pressure vessel. Modeling simulation intergrarnular fracture of AISI 4135 steel due to hydrogen is investigated. So, distribution of hydrogen and stress are obtained and they indicate that their maximum amounts occur near the crack front. This phenomenon is happened exactly the region between elastic and plastic field. Therefore, hydrogen is highly mobile and can diffuse through crystal lattice so that this zone is potential to trap high volume of hydrogen. Consequently, crack growth and fast fracture will be happened.

Keywords: Stress Intensity Factor, Mass Diffusion, FEM, Pressure Vessel

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Authors: R. Thiamsri, N. Ruangkajonmathee, A. Oonsivilaiand B. Marungsri

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This paper presents the experimental results on effect of applied voltage stress frequency to the occurrence of electrical treeing in 22 kV cross linked polyethylene (XLPE) insulated cable.Hallow disk of XLPE insulating material with thickness 5 mm taken from unused high voltage cable was used as the specimen in this study. Stainless steel needle was inserted gradually into the specimen to give a tip to earth plane electrode separation of 2.5
0.2 mm at elevated temperature 105-110°C. The specimen was then annealed for 5 minute to minimize any mechanical stress build up around the needle-plane region before it was cooled down to room temperature. Each specimen were subjected to the same applied voltage stress level at 8 kV AC rms, with various frequency, 50, 100, 500, 1000 and 2000 Hz. Initiation time, propagation speed and pattern of electrical treeing were examined in order to study the effect of applied voltage stress frequency. By the experimental results, initial time of visible treeing decreases with increasing in applied voltage frequency. Also, obviously, propagation speed of electrical treeing increases with increasing in applied voltage frequency.Furthermore, two types of electrical treeing, bush-like and branch-like treeing were observed.The experimental results confirmed the effect of voltage stress frequency as well.

Keywords: Voltage stress frequency, cross-linked polyethylene, electrical treeing, treeing propagation, treeing pattern

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Authors: Felipe V. Díaz, Claudio A. Mammana, Armando P. M. Guidobono, Raúl E. Bolmaro

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Through a proper analysis of residual strain and stress distributions obtained at the surface of high speed milled specimens of AA 6082–T6 aluminium alloy, the performance of an improved indentation method is evaluated. This method integrates a special device of indentation to a universal measuring machine. The mentioned device allows introducing elongated indents allowing to diminish the absolute error of measurement. It must be noted that the present method offers the great advantage of avoiding both the specific equipment and highly qualified personnel, and their inherent high costs. In this work, the cutting tool geometry and high speed parameters are selected to introduce reduced plastic damage. Through the variation of the depth of cut, the stability of the shapes adopted by the residual strain and stress distributions is evaluated. The results show that the strain and stress distributions remain unchanged, compressive and small. Moreover, these distributions reveal a similar asymmetry when the gradients corresponding to conventional and climb cutting zones are compared.

Keywords: Residual strain, residual stress, high speed milling, indentation methods, aluminium alloys.

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Authors: Habtu Alemayehu, G. Radhakrishnamacharya

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The paper presents an analytical solution for dispersion of a solute in the peristaltic motion of a couple stress fluid through a porous medium with slip condition in the presence of both homogeneous and heterogeneous chemical reactions. The average effective dispersion coefficient has been found using Taylor-s limiting condition and long wavelength approximation. The effects of various relevant parameters on the average coefficient of dispersion have been studied. The average effective dispersion coefficient tends to increase with permeability parameter but tends to decrease with homogeneous chemical reaction rate parameter, couple stress parameter, slip parameter and heterogeneous reaction rate parameter.

Keywords: Dispersion, Peristalsis, Couple stress fluid, Porousmedium, Chemical reaction, Slip condition.

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Authors: James Kuria, John Kihiu

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This work presents a numerical model developed to simulate the dynamics and vibrations of a multistage tractor gearbox. The effect of time varying mesh stiffness, time varying frictional torque on the gear teeth, lateral and torsional flexibility of the shafts and flexibility of the bearings were included in the model. The model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the vibration and stress levels on the gears. The first design variable, module, had little effect on the vibration levels but a higher module resulted to higher bending stress levels. The second design variable, pressure angle, had little effect on the vibration levels, but had a strong effect on the stress levels on the pinion of a high reduction ratio gear pair. A pressure angle of 25o resulted to lower stress levels for a pinion with 14 teeth than a pressure angle of 20o. The third design variable, contact ratio, had a very strong effect on both the vibration levels and bending stress levels. Increasing the contact ratio to 2.0 reduced both the vibration levels and bending stress levels significantly. For the gear train design used in this study, a module of 2.5 and contact ratio of 2.0 for the various meshes was found to yield the best combination of low vibration levels and low bending stresses. The model can therefore be used as a tool for obtaining the optimum gear design parameters for a given multistage spur gear train.

Keywords: bending stress levels, frictional torque, gear designparameters, mesh stiffness, multistage gear train, vibration levels.

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Authors: Tejeet Singh, Harmanjit Singh

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Creep behavior of thick-walled functionally graded cylinder consisting of AlSiC and subjected to internal pressure and high temperature has been analyzed. The functional relationship between strain rate with stress can be described by the well known threshold stress based creep law with a stress exponent of five. The effect of imposing non-linear particle gradient on the distribution of creep stresses in the thick-walled functionally graded composite cylinder has been investigated. The study revealed that for the assumed non-linear particle distribution, the radial stress decreases throughout the cylinder, whereas the tangential, axial and effective stresses have averaging effect. The strain rates in the functionally graded composite cylinder could be reduced to significant extent by employing non-linear gradient in the distribution of reinforcement.

Keywords: Functionally Graded Material, Pressure, Steady State Creep, Thick-Cylinder.

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Authors: Fakhruddin Esa, Yusri Yusof

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The confirmatory of Total Quality Management (TQM) implementation is most vital in quality management. This paper focuses on employees' perceptions towards TQM implementation in a local automotive company supplier. The objectives of this study are first and foremost to determine the perception of TQM implementation among the staff, and secondly to ascertain the correlation between the variables, and lastly to identify the relative influence of the 10 TQM variables on the cost of poor quality (COPQ). The TQM implementation is perceived to be moderate. All correlation is found to be significant and five variables having positively moderate to high correlation. Out of 10 variables, quality system improvement, reward and recognition and customer focus influence the perceived COPQ. This study extended a discussion on these three variables contribution to TQM in general and the human resource development in the organization. A significant recommendation to lowering costs of internal error, such as trouble shooting and scraps are also discussed. Certain components of further research that would add value to this study have also been suggested and perhaps could be implemented at policy-level initiatives.

Keywords: Cost of poor quality, correlation, total quality management, variables.

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Authors: A.R. Pazoki, A. H. Shirani Rad, D. Habibi, F. Paknejad, S. Kobraee, N. Hadayat

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In the other to Study of drought stress and Selenium spraying effect on superoxide dismotase (SOD) activity of rapeseed (Brassica napus L.) cultivars in Shahr-e-Rey region, an experiment carried out in Split factorial design in the basis of randomized complete blocks with 4 replications in 2006. Irrigation in two levels: Normal irrigation and irrigation with drought stress when the soil electrical conductivity reached to 60 as main factor and rapeseed cultivars in 3 levels Zarfam, Okapi, Opera and selenium spraying at the beginning of flowering stage in 3 levels: 0, 16 and 21 g/ha as sub factor. The results showed that the simple and interaction effect of irrigation, selenium and cultivars on SOD activity had significant difference. In this case Zarfam cultivar with 2010 u.mg-1 protein and Opera with 1454 u.mg-1 protein produced maximum and minimum amounts of SOD activitiy. Interaction effect of irrigation and variety showed that, normal irrigation in Opera with 1115 u.mg-1 protein and drought stress in Zarfam with 2784 u.mg-1 protein conducted to and minimum and maximum amounts of SOD activity. Interaction effect of irrigation, cultivar and selenium on SOD indicated that drought stress condition and 21 gr/ha selenium spraying in Zarfam variety with 3146 u.mg-1 protein gained to highest activities of SOD.

Keywords: Drought stress, Rapeseed, Selenium, Superoxide dismutase.

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Authors: Chien-Jen Liu, Shu Ching Yang

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Using the technology acceptance model (TAM), this study examined the external variables of technological complexity (TC) to acquire a better understanding of the factors that influence the acceptance of computer application courses by learners at Active Aging Universities. After the learners in this study had completed a 27-hour Facebook course, 44 learners responded to a modified TAM survey. Data were collected to examine the path relationships among the variables that influence the acceptance of Facebook-mediated community learning. The partial least squares (PLS) method was used to test the measurement and the structural model. The study results demonstrated that attitudes toward Facebook use directly influence behavioral intentions (BI) with respect to Facebook use, evincing a high prediction rate of 58.3%. In addition to the perceived usefulness (PU) and perceived ease of use (PEOU) measures that are proposed in the TAM, other external variables, such as TC, also indirectly influence BI. These four variables can explain 88% of the variance in BI and demonstrate a high level of predictive ability. Finally, limitations of this investigation and implications for further research are discussed.

Keywords: Technology acceptance model (TAM), technological complexity, partial least squares (PLS), perceived usefulness.

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Authors: Khadiga Kahwa, Aniza Ismail

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Depression, anxiety, and stress are associated with decreased role functioning, productivity, and quality of life. International students are more prone to psychological distress as they face many stressors while studying abroad. The objectives of the study were to determine the prevalence and associated factors of depression, anxiety, and stress among international students, their help-seeking behavior, and their awareness of the available on-campus mental support services. A cross-sectional study with a purposive sampling method was performed on 280 international students at Universiti Kebangsaan Malaysia (UKM) between the age of 18 and 35 years. The Depression Anxiety Stress Scale-21 (DASS-21) questionnaire was used anonymously to assess the mental health of students. Socio-demographic, help-seeking behavior, and awareness data were obtained. Independent sample t-test, one-way ANOVA test, and multiple linear regression were used to explore associated factors. The overall prevalence of depression, anxiety, and stress among international students were 58.9%, 71.8%, and 53.9%, respectively. Age was significantly associated with depression and anxiety. Ethnicity showed a significant association with depression and stress. No other factors were found to be significantly associated with psychological distress. Only 9.6% of the international students had sought help from on-campus mental support services. Students who were aware of the presence of such services were only 21.4% of the participants. In conclusion, this study addressed the gap in the literature on the mental health of international students and provided data that could be used in intervention programs to improve the mental health of the increasing number of international students in Malaysia.

Keywords: Anxiety, depression, stress, help-seeking behavior, students.

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Authors: J. R. C. Kuntz, Katharina Näswall, Frances Walls

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This study sought to uncover the complex role of stress in the workplace by investigating both positive (eustress) and negative (distress) stress responses. In particular, the study tested a mediation model in which organisational stressors (person-job fit and role overload) influence employee affective wellbeing, both directly and indirectly through stress responses. Participants were recruited from retail and finance organisations in Australia and New Zealand, and asked to complete an anonymous online questionnaire. A total of 140 individuals returned completed questionnaires. The results show that person-job fit influenced eustress, which in turn had a positive effect on employee affective wellbeing; and role overload impacted distress, which in turn held a negative influence on affective wellbeing. These findings indicate that different organisational stressors have unique relationships with eustress and distress responses. Limitations and implications of the study are discussed.

Keywords: Distress, Eustress, Role Overload, Wellbeing.

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Authors: Mohammad Ali Lotfollahi-Yaghin, Hamid Ahmadi

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In the present paper, a set of parametric FE stress analyses is carried out for two-planar welded tubular DKT-joints under two different axial load cases. Analysis results are used to present general remarks on the effect of geometrical parameters on the stress concentration factors (SCFs) at the inner saddle, outer saddle, toe, and heel positions on the main (outer) brace. Then a new set of SCF parametric equations is developed through nonlinear regression analysis for the fatigue design of two-planar DKT-joints. An assessment study of these equations is conducted against the experimental data; and the satisfaction of the criteria regarding the acceptance of parametric equations is checked. Significant effort has been devoted by researchers to the study of SCFs in various uniplanar tubular connections. Nevertheless, for multi-planar joints covering the majority of practical applications, very few investigations have been reported due to the complexity and high cost involved.

Keywords: Offshore jacket structure, Parametric equation, Stress concentration factor (SCF), Two-planar tubular KT-joint

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Authors: Siong W. Lee, Kang H. Tan, En H. Yang

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This paper presents the results of an experimental study undertaken to evaluate the local bond stress-slip response of short embedment of reinforcing bars in normal concrete (NC) and high performance fiber reinforced cement composites (HPFRCC) blocks. Long embedment was investigated as well to gain insights on the distribution of strain, slip, bar stress and bond stress along the bar especially in post-yield range. A total of 12 specimens were tested, by means of pull-out of the reinforcing bars from concrete blocks. It was found that the enhancement of local bond strength can be reached up to 50% and ductility of the bond behavior was improved significantly if HPFRCC is used. Also, under a constant strain at loaded end, HPFRCC has delayed yielding of bars at other location from the loaded end. Hence, the reduction of bond stress was slower for HPFRCC in comparison with NC. Due to the same reason, the total slips at loaded end for HPFRCC was smaller than NC as expected. Test results indicated that HPFRCC has better bond slip behavior which makes it a suitable material to be employed in anchorage zone such as beam-column joints.

Keywords: Bond stress, high performance fiber reinforced cement composites, slip, strain.

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Authors: Majid Toghyani, Abbas Ali Gheisari, Ali Khodami, Mehdi Toghyani, Mohammad Mohammadrezaei, Ramin Bahadoran

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This experiment was conducted to investigate the effect of different levels of dietary chromium yeast (Cr-yeast) on thigh meat quality of broiler chicks reared under heat stress condition. Two hundred and forty Ross male chickens in heat stress condition (33±3°C) were allocated to five treatments in a completely randomized design. Treatments were supplemented with 0 (control), 200, 400, 800 and 1200 μg kg-1 Cr in the form of Cr yeast. Twelve chicks from each treatment were slaughtered at 42 d, to evaluate moisture, protein, lipid, pH and lipid oxidation of thigh meat. Protein, moisture, lipid and pH of thigh meat were not affected by supplemental Cr. Thigh meat lipid tended to decrease in broilers received 1200 μg kg-1. Storage time increased lipid oxidation of meat (P<0.01). Lipid oxidation of thigh muscle for two days of storage were affected by supplemental Cr and decreased (P<0.05). Results of this study showed that dietary Cr-yeast supplementation improved the thigh meat quality of broiler chicks in heat stress condition.

Keywords: Broiler, Heat stress, Chromium yeast, Thigh meat quality.

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Authors: M.Devakar, T.K.V.Iyengar

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In this paper, we investigate the generalized Stokes’ problems for an incompressible couple stress fluid. Analytical solution of the governing equations is obtained in Laplace transform domain for each problem. A standard numerical inversion technique is used to invert the Laplace transform of the velocity in each case. The effect of various material parameters on velocity is discussed and the results are presented through graphs. It is observed that, the results are in tune with the observation of V.K.Stokes in connection with the variation of velocity in the flow between two parallel plates when the top one is moving with constant velocity and the bottom one is at rest.

Keywords: Couple stress fluid, Generalized Stokes’ problems, Laplace transform, Numerical inversion

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Authors: P. Saleh, G. Challita, R. Hazimeh, K. Khalil

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In this paper 3D FEM analysis was carried out on double lap bonded joint with composite adherents subjected to dynamic shear. The adherents are made of Carbon/Epoxy while the adhesive is epoxy Araldite 2031. The maximum average shear stress and the stress homogeneity in the adhesive layer were examined. Three fibers textures were considered: UD; 2.5D and 3D with same volume fiber then a parametric study based on changing the thickness and the type of fibers texture in 2.5D was accomplished. Moreover, adherents’ dissimilarity was also investigated. It was found that the main parameter influencing the behavior is the longitudinal stiffness of the adherents. An increase in the adherents’ longitudinal stiffness induces an increase in the maximum average shear stress in the adhesive layer and an improvement in the shear stress homogeneity within the joint. No remarkable improvement was observed for dissimilar adherents.

Keywords: Adhesive, Composite adherents, Impact shear, Finite element.

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Authors: Meisam Omidi, M. Mirijalili, Mohammadmehdi Choolaei, Z. Sharifi, F. Haghiralsadat, F. Yazdian

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In this work, we have used arrays of micromechanical piezoresistive cantilever with different geometries to detect carcinoembryonic antigen (CEA), which is known as an important biomarker associated with various cancers such as colorectal, lung, breast, pancreatic, and bladder cancer. The sensing principle is based on the surface stress changes induced by antigen–antibody interaction on the microcantilevers surfaces. Different concentrations of CEA in a human serum albumin (HSA) solution were detected as a function of deflection of the beams. According to the experiments, it was revealed that microcantilevers have surface stress sensitivities in the order of 8 (mJ/m). This matter allows them to detect CEA concentrations as low as 3 ng/mL or 18 pM. This indicates the fact that the self-sensing microcantilevers approach is beneficial for pathological tests.

Keywords: Micromechanical biosensors, Carcinoembryonic antigen (CEA), surface stress.

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Authors: Y. Zheng, W. Sun

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This paper describes a new approach which can be used to interpret the experimental creep deformation data obtained from miniaturized thin plate bending specimen test to the corresponding uniaxial data based on an inversed application of the reference stress method. The geometry of the thin plate is fully defined by the span of the support, l, the width, b, and the thickness, d. Firstly, analytical solutions for the steady-state, load-line creep deformation rate of the thin plates for a Norton’s power law under plane stress (b→0) and plane strain (b→∞) conditions were obtained, from which it can be seen that the load-line deformation rate of the thin plate under plane-stress conditions is much higher than that under the plane-strain conditions. Since analytical solution is not available for the plates with random b-values, finite element (FE) analyses are used to obtain the solutions. Based on the FE results obtained for various b/l ratios and creep exponent, n, as well as the analytical solutions under plane stress and plane strain conditions, an approximate, numerical solutions for the deformation rate are obtained by curve fitting. Using these solutions, a reference stress method is utilised to establish the conversion relationships between the applied load and the equivalent uniaxial stress and between the creep deformations of thin plate and the equivalent uniaxial creep strains. Finally, the accuracy of the empirical solution was assessed by using a set of “theoretical” experimental data.

Keywords: Bending, Creep, Miniature Specimen, Thin Plate.

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Authors: M. Stoklasa, H. Starzyczna, K. Matusinska

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This article deals with the perceived quality of regional products in the Moravian-Silesian region in the Czech Republic. Research was focused on finding out what do consumers perceive as a quality product and what characteristics make a quality product. The data were obtained by questionnaire survey andanalysed by IBM SPSS. From the thousands of respondents the representative sample of 719 for MS region was created based on demographic factors of gender, age, education and income. The research analysis disclosed that consumers in MS region are still price oriented and that the preference of quality over price does not depend on regional brand knowledge.

Keywords: Regional brands, quality products, characteristics of quality, quality over price.

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Authors: Isa Ahmadi, Ramin Khamedi

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In this paper, the elasto-plastic and cyclic torsion of a shaft is studied using a finite element method. The Prager kinematic hardening theory of plasticity with the Ramberg and Osgood stress-strain equation is used to evaluate the cyclic loading behavior of the shaft under the torsional loading. The material of shaft is assumed to follow the non-linear strain hardening property based on the Prager model. The finite element method with C¹ continuity is developed and used for solution of the governing equations of the problem. The successive substitution iterative method is used to calculate the distribution of stresses and plastic strains in the shaft due to cyclic loads. The shear stress, effective stress, residual stress and elastic and plastic shear strain distribution are presented in the numerical results.

Keywords: Cyclic Loading, Finite Element Analysis, Prager Kinematic Hardening Model, Torsion of shaft.

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Authors: C. Barreto Carvalho, C. da Motta, M. Sousa, J. Cabral, A. L. Carvalho, E. B. Peixoto

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The aim of the current study was to develop and validate a Response to Stressful Situations Scale (RSSS) for the Portuguese population. This scale assesses the degree of stress experienced in scenarios that can constitute positive, negative and more neutral stressors, and also describes the physiological, emotional and behavioral reactions to those events according to their intensity. These scenarios include typical stressor scenarios relevant to patients with schizophrenia, which are currently absent from most scales, assessing specific risks that these stressors may bring on subjects, which may prove useful in non-clinical and clinical populations (i.e. Patients with mood or anxiety disorders, schizophrenia). Results from Principal Components Analysis and Confirmatory Factor Analysis of two adult samples from general population allowed to confirm a three-factor model with good fit indices: χ2 (144)= 370.211, p = 0.000; GFI = 0.928; CFI = 0.927; TLI = 0.914, RMSEA = 0.055, P(rmsea ≤0.005) = .096; PCFI = .781. Further data analysis of the scale revealed that RSSS is an adequate assessment tool of stress response in adults to be used in further research and clinical settings, with good psychometric characteristics, adequate divergent and convergent validity, good temporal stability and high internal consistency.

Keywords: Assessment, stress events, stress response, stress vulnerability.

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Authors: Olusegun K. Afolabi, Emmanuel B. Oyewo

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Fluoroquinolones are a group of antibiotics widely used because of their broad spectrum activity against both Gram-positive and Gram-negative bacteria. In this study, ciprofloxacin and levofloxacin were administered to rats at therapeutic doses to evaluate their effects on plasma arylesterase activity, as well as, on hepatic advanced oxidized protein products (AOPPs) and malondialdehyde (MDA) levels, as measures of oxidative stress. Ciprofloxacin (80 mg/kg body weight) and levofloxacin (40 mg/kg body weight) were administered to male albino rats for 7 and 14 days. The data obtained demonstrated that plasma arylesterase activity was significantly decreased by both drugs with ciprofloxacin administration inhibiting the activity by 29% and 30% while Levofloxacin treatment resulted in 35% and 30% inhibition, after 7 and 14 days treatment respectively. Hepatic AOPP and MDA levels were both elevated by these antibiotics. This study supplies further evidence that fluoroquinolones at therapeutic doses promote oxidative stress.

Keywords: Arylesterase, Ciprofloxacin, Levofloxacin, Oxidative Stress.

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Authors: Ahmet C. Kutlu, Seçkin Polat

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Organizational structure of the Turkish state universities is a form of bureaucracy, a high efficient system in rational and formal control. According to the dimensional approach bureaucracy can occur in an organization in a degree, as some bureaucracy characteristics can be stronger than others. In addition, the units of an organization due to their different specific characteristic properties can perceive the bureaucracy differently. In the study, Hall-s Organizational Inventory, which was developed for evaluating the degree of bureaucratization from the dimensional perspective, is used to find out if there is a difference in the perception of the bureaucracy between the academicians working in three different departments and two faculties in the same university.

Keywords: Degree of bureaucratization, Hall's Organizational Inventory, perceived bureaucracy.

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Authors: Md Abdullah Al Faruque, Ram Balachandar

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The present study was carried out to understand the extent of effect of roughness and Reynolds number in open channel flow (OCF). To this extent, four different types of bed surface conditions consisting smooth, distributed roughness, continuous roughness, natural sand bed and two different Reynolds number for each bed surfaces were adopted in this study. Particular attention was given on mean velocity, turbulence intensity, Reynolds shear stress, correlation, higher order moments and quadrant analysis. Further, the extent of influence of roughness and Reynolds number in the depth-wise direction also studied. Increasing Reynolds shear stress near rough beds are noticed due to arrays of discrete roughness elements and flow over these elements generating a series of wakes which contributes to the generation of significantly higher Reynolds shear stress.

Keywords: Bed roughness, ejection, sweep, open channel flow, Reynolds Shear Stress, turbulent boundary layer, velocity triple product.

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Authors: Marthese Azzopardi, Liberato Camilleri

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This research was performed to investigate the study habits and level of difficulty perceived by post-secondary students in Biology at Advanced-level topics after completing their first year of study. At the end of a two-year ‘sixth form’ course, Maltese students sit for the Matriculation and Secondary Education Certificate (MATSEC) Advanced-level biology exam as a requirement to pursue science-related studies at the University of Malta. The sample was composed of 23 students (16 taking Chemistry and seven taking some ‘Other’ subject at the Advanced Level). The cohort comprised seven males and 16 females. A questionnaire constructed by the authors, was answered anonymously during the last lecture at the end of the first year of study, in May 2016. The Chi square test revealed that gender plays no effect on the various study habits (c² (6) = 5.873, p = 0.438). ‘Reading both notes and textbooks’ was the most common method adopted by males (71.4%), whereas ‘Writing notes on each topic’ was that mostly used by females (81.3%). The Mann-Whitney U test showed no significant difference in the study habits of students and the mean assessment mark obtained at the end of the first year course (p = 0.231). Statistical difference was found with the One-ANOVA test when comparing the mean assessment mark obtained at the end of the first year course when students are clustered by their Secondary Education Certificate (SEC) grade (p < 0.001). Those obtaining a SEC grade of 2 and 3 got the highest mean assessment of 68.33% and 66.9%, respectively [SEC grading is 1-7, where 1 is the highest]. The Friedman test was used to compare the mean difficulty rating scores provided for the difficulty of each topic. The mean difficulty rating score ranges from 1 to 4, where the larger the mean rating score, the higher the difficulty. When considering the whole group of students, nine topics out of 21 were perceived as significantly more difficult than the other topics. Protein synthesis, DNA Replication and Biomolecules were the most difficult, in that order. The Mann-Whitney U test revealed that the perceived level of difficulty in comprehending Biomolecules is significantly lower for students taking Chemistry compared to those not choosing the subject (p = 0.018). Protein Synthesis was claimed as the most difficult by Chemistry students and Biomolecules by those not studying Chemistry. DNA Replication was the second most difficult topic perceived by both groups. The Mann-Whitney U test was used to examine the effect of gender on the perceived level of difficulty in comprehending various topics. It was found that females have significantly more difficulty in comprehending Biomolecules than males (p=0.039). Protein synthesis was perceived as the most difficult topic by males (mean difficulty rating score = 3.14), while Biomolecules, DNA Replication and Protein synthesis were of equal difficulty for females (mean difficulty rating score = 3.00). Males and females perceived DNA Replication as equally difficult (mean difficulty rating score = 3.00). Discovering the students’ study habits and perceived level of difficulty of specific topics is vital for the lecturer to offer guidance that leads to higher academic achievement.

Keywords: Biology, Perceived difficulty, Post-secondary, Study habits.

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Authors: S. Lecheb, A. Chellil, H. Mechakra, A. Zeggane, H. Kebir

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In this work, repaired crack in 6061- T6 aluminum plate with composite patches presented, firstly we determine the displacement, strain and stress, also the first six mode shape of the plate, secondly we took the same model adding central crack initiation, which is located in the center of the plate, its seize vary from 20 mm to 60 mm and we compare the first results with second. Thirdly we repair various cracks with composite patch (carbon/ epoxy) and for (2 layers, 4 layers). Finally the comparison of stress, strain, displacement and six first natural frequencies between un-cracked specimen, crack propagation and composite patch repair.

Keywords: Composite patch repair, crack growth, aluminum alloy plate, stress.

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Authors: Oleksandr Poliakov, Genadiy Olinichenko, Yevgen Pashkov, Vadym Kramar, Mykhaylo Kalinin

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For maintenance of a spine stability during the postoperative period a transpedicular fixing of its elements is often used. Usually the transpedicular systems are formed of rods which as a result form a design of the frame type, fastening by screws to vertebras. Such design should be rigid and perceive loadings operating from the spine without essential deformations. From the perfection point of view of known designs their stress whole, and each of elements, in particular is of interest. In this study the modeling of the transpedicular screw is performed and estimation of its deformations taking into account interaction with a vertebra body having variable structure is made.

Keywords: Spine, screw, stress-strain state, transpedicular fixation system, vertebra

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Authors: Armando Cartenì, Ilaria Henke

Abstract:

The perceived public transport quality is an important driver that influences both customer satisfaction and mobility choices. The competition among transport operators needs to improve the quality of the services and identify which attributes are perceived as relevant by passengers. Among the “traditional” public transport quality attributes there are, for example: travel and waiting time, regularity of the services, and ticket price. By contrast, there are some “non-conventional” attributes that could significantly influence customer satisfaction jointly with the “traditional” ones. Among these, the beauty/aesthetics of the transport terminals (e.g. rail station and bus terminal) is probably one of the most impacting on user perception. Starting from these considerations, the point stressed in this paper was if (and how munch) the travel experience of the overall travel (e.g. how long is the travel, how many transport modes must be used) influences the perception of the public transport quality. The aim of this paper was to investigate the weight of the terminal quality (e.g. aesthetic, comfort and service offered) within the overall travel experience. The case study was the extra-urban Italian bus network. The passengers of the major Italian terminal bus were interviewed and the analysis of the results shows that about the 75% of the travelers, are available to pay up to 30% more for the ticket price for having a high quality terminal. A travel experience effect was observed: the average perceived transport quality varies with the characteristic of the overall trip. The passengers that have a “long trip” (travel time greater than 2 hours) perceived as “low” the overall quality of the trip even if they pass through a high quality terminal. The opposite occurs for the “short trip” passengers. This means that if a traveler passes through a high quality station, the overall perception of that terminal could be significantly reduced if he is tired from a long trip. This result is important and if confirmed through other case studies, will allow to conclude that the “travel experience impact" must be considered as an explicit design variable for public transport services and planning.

Keywords: Transportation planning, sustainable mobility, decision support system, discrete choice model, design problem.

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Authors: S. J. Higgs, E. Van Eck, K. Heynis, S. H. Broadberry

Abstract:

Engagement with non-human animals is a rapidly-growing field of study within the animal science and social science sectors, with human-interactions occurring in many forms; interactions, encounters and animal-assisted therapy. To our knowledge, there has been a wide array of research published on domestic and livestock human-animal interactions, however, there appear to be fewer publications relating to zoo animals and the effect these interactions have on the animal, human and establishment. The aim of this study was to identify if there were any perceivable benefits from the human-animal interaction for the cheetah, the human and the establishment. Behaviour data were collected before, during and after the interaction on the behaviour of the cheetah and the human participants to highlight any trends with nine interactions conducted. All 35 participants were asked to fill in a questionnaire prior to the interaction and immediately after to ascertain if their perceptions changed following an interaction with the cheetah. An online questionnaire was also distributed for three months to gain an understanding of the perceptions of human-animal interactions from members of the public, gaining 229 responses. Both questionnaires contained qualitative and quantitative questions to allow for specific definitive answers to be analysed, but also expansion on the participants perceived perception of human-animal interactions. In conclusion, it was found that participants’ perceptions of human-animal interactions saw a positive change, with 64% of participants altering their opinion and viewing the interaction as beneficial for the cheetah (reduction in stress assumed behaviours) following participation in a 15-minute interaction. However, it was noted that many participants felt the interaction lacked educational values and therefore this is an area in which zoological establishments can work to further improve upon. The results highlighted many positive benefits for the human, animal and establishment, however, the study does indicate further areas for research in order to promote positive perceptions of human-animal interactions and to further increase the welfare of the animal during these interactions, with recommendations to create and regulate legislation.

Keywords: Acinonyx jubatus, encounters, human-animal interactions, perceptions, zoological establishments.

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Authors: M. Benachour, N. Benachour

Abstract:

Stainless steel has been employed in many engineering applications ranging from pharmaceutical equipment to piping in the nuclear reactors and storage to chemical products. In this attempt, simulation of fatigue crack growth based on experimental results of austenitic stainless steel 304L was presented using AFGROW code when NASGRO mode laws adopted. Double through crack at hole specimen is used in this investigation under constant amplitude loading. Effect of mean stress is highlighted. Results show that fatigue crack growth rate (FCGR) and fatigue life were affected by maximum applied load and dimension of hole. An equivalent of Paris law for this material was estimated.

Keywords: Fatigue crack, stainless steel, mean stress, amplitudeloading.

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