Search results for: stress transfer

Authors: Ramona-Niculina Jurcau, Ioana-Marieta Jurcau, Dong Hun Kwak, Nicolae-Alexandru Colceriu

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Background: Stress management (SM) is a topic of great academic interest and equally a task to accomplish. In addition, it is recognized the beneficial role of unconventional therapies (UCT) in stress modulation. Aims: The aim was to evaluate medical (MS) versus non-medical students’ (NMS) opinions about academic stress management (ASM) using UCT. Methods: MS (n=103, third year males and females) and NMS (n=112, males and females, from humanities faculties, different years of study), out of their academic program, voluntarily answered to a questionnaire concerning: a) Classification of the four most important academic stress factors; b) The extent to which their daily life influences academic stress; c) The most important SM methods they know; d) Which of these methods they are applying; e) the UCT they know or about which they have heard; f) Which of these they know to have stress modulation effects; g) Which of these UCT, participants are using or would like to use for modulating stress; and if participants use UTC for their own choose or following a specialist consultation in those therapies (SCT); h) If they heard about the following UCT and what opinion they have (using visual analogue scale) about their use (following CST) for the ASM: Phytotherapy (PT), apitherapy (AT), homeopathy (H), ayurvedic medicine (AM), traditional Chinese medicine (TCM), music therapy (MT), color therapy (CT), forest therapy (FT). Results: Among the four most important academic stress factors, for MS more than for NMS, are: busy schedule, large amount of information taught; high level of performance required, reduced time for relaxing. The most important methods for SM that MS and NMS know, hierarchically are: listen to music, meeting friends, playing sport, hiking, sleep, regularly breaks, seeing positive side, faith; of which, NMS more than MS, are partially applying to themselves. UCT about which MS and less NMS have heard, are phytotherapy, apitherapy, acupuncture, reiki. Of these UTC, participants know to have stress modulation effects: some plants, bee’s products and music; they use or would like to use for ASM (the majority without SCT) certain teas, honey and music. Most of MS and only some NMS heard about PT, AT, TCM, MT and much less about H, AM, CT, TT. NMS more than MS, would use these UCT, following CST. Conclusions: 1) Academic stress is similarly reflected in MS and NMS opinions. 2) MS and NMS apply similar but very few UCT for stress modulation. 3) Information that MS and NMS have about UCT and their ASM application is reduced. 4) It is remarkable that MS and especially NMS, are open to UCT use for ASM, following an SCT.

Keywords: academic stress, stress management, stress modulation, medical students, non-medical students, unconventional therapies

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Authors: Niveen M. Hassan-Abbas

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The COVID-19 pandemic created a range of stressors, among them difficulties related to work conditions, financial changes, lack of childcare, and confinement or isolation due to social distancing. Among families and married individuals, these stressors were often expressed in additional daily hassles, with an influence on mental health. This study examined two moderated mediation models based on Bodenmann’s systemic-transactional stress model. Specifically, the models tested the hypothesis that intra-dyadic stress mediates the association between extra-dyadic stress and mental health, while two measures of family functioning, cohesion, and flexibility, moderate the relationship between extra and intra-dyadic stress. Participants were 480 heterosexual married Palestinians from Israel who completed self-report questionnaires. The results showed partial mediation patterns supporting both models, indicating that family cohesion and flexibility weakened the mediating effect of intra-dyadic stress on the relationship between extra-dyadic stress and mental health. These findings increase our understanding of the variables that affected mental health during the pandemic and suggested that when faced with extra-dyadic stress, married individuals with good family environments are less likely to experience high levels of intra-dyadic stress, which is in turn associated with preserved mental health. Limitations and implications for planning interventions for couples and families during the pandemic are discussed.

Keywords: Palestinian families in Israel, COVID-19 pandemic, family cohesion and flexibility, extra-dyadic stress, intra-dyadic stress, mental health

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Authors: Jung Hyun Kim, Gyo Woo Lee

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In this study, heat release performances of the three extruded-type heat sinks can be used in the inverter for solar power generation were evaluated. Numbers of fins in the heat sinks (namely E-38, E-47 and E-76) were 38, 47 and 76, respectively. Heat transfer areas of them were 1.8, 1.9 and 2.8 m2. The heat release performances of E-38, E-47, and E-76 heat sinks were measured as 79.6, 81.6, and 83.2%, respectively. The results of heat release performance show that the larger amount of heat transfer area the higher heat release rate. While on the other, in this experiment, variations of the mass flow rates caused by different cross-sectional areas of the three heat sinks may not be the major parameter of the heat release. Despite the 47.4% increment of heat transfer area of E-76 heat sink than that of E-47 one, its heat release rate was higher by only 2.0%; this suggests that its heat transfer area need to be optimized.

Keywords: solar Inverter, heat sink, forced convection, heat transfer, performance evaluation

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Authors: Gurjit Singh, Gurmail Singh

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The shape of microchannels in microchannel heat sinks can have a significant impact on both heat transfer and fluid flow properties. Heat Transfer, pressure drop, and Some effects of microchannel shape on these properties. The shape of microchannels can affect the heat transfer performance of microchannel heat sinks. Channels with rectangular or square cross-sections typically have higher heat transfer coefficients compared to circular channels. This is because rectangular or square channels have a larger wetted perimeter per unit cross-sectional area, which enhances the heat transfer from the fluid to the channel walls. The shape of microchannels can also affect the pressure drop across the heat sink. Channels with a rectangular cross-section usually have higher pressure drop than circular channels. This is because the corners of rectangular channels create additional flow resistance, which leads to a higher pressure drop. Overall, the shape of microchannels in microchannel heat sinks can have a significant impact on the heat transfer and fluid flow properties of the heat sink. The optimal shape of microchannels depends on the specific application and the desired balance between heat transfer performance and pressure drop.

Keywords: heat transfer, microchannel heat sink, pressure drop, chape of microchannel

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Authors: Susan K. Steele-Moses, Aimee Badeaux

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Background Literature: Nurse anesthesia education placed high demands on students both personally and professionally. High levels of anxiety affect student’s mental, emotional, and physical well-being, which impacts their student success. Whereas more research has focused on the health and well-being of graduate students, far less has focused specifically on nurse anesthesia students (SNRAs), who may experience higher levels of anxiety due to the rigor of their academic program. Current literature describes stressors experienced by SRNAs that cause anxiety and affect their performance, including personal, academic, clinical, interpersonal, emotional, and financial. Sample: DNP-NA 2025 and DNP-NA 2024 cohorts (N = 36). Eighteen (66.7%) students participated in the study. Instrumentation: The DASS-21 was used to measure stress (7 items; α = .87) and anxiety (7 items; α = .74) from the participants. Intervention: The mind-shift meditation app, based on cognitive behavioral therapy, is being used daily before clinical and exams to decrease nurse anesthesia students’ stress and anxiety over time. Results: At baseline, the students exhibited a moderate level of stress, but their anxiety levels were low. The range of scores was 4-21 (out of 28) for stress (M = 12.88; SD = 5.40) and 0-16 (out of 28) for anxiety (M = 6.81; SD = 5.04). Both stress and anxiety were normally distributed [SW = .242 (stress); SW = .210 (anxiety)] without any outliers. There was a significant difference between their stress and anxiety levels (t = 5.55; p < .001) at baseline. Stress and anxiety will be measured over time, with the change analyzed using repeated measures ANOVA. Implications for Practice: The use of purposeful mindfulness meditation has been shown to decrease stress and anxiety in nursing students.

Keywords: mindfulness, meditation, graduate nursing education, nursing education

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Authors: Yakup Sahin, Naim Suleyman Ting, Ismail Aksoy

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A 1 kW power factor correction boost converter with an active snubber cell is presented in this paper. In the converter, the main switch turns on under zero voltage transition (ZVT) and turns off under zero current transition (ZCT) without any additional voltage or current stress. The auxiliary switch turns on and off under zero current switching (ZCS). Besides, the main diode turns on under ZVS and turns off under ZCS. The output current and voltage are controlled by the PFC converter in wide line and load range. The simulation results of converter are obtained for 1 kW and 100 kHz. One of the most important feature of the given converter is that it has direct power transfer as well as excellent soft switching techniques. Also, the converter has 0.99 power factor with the sinusoidal input current shape.

Keywords: power factor correction, direct power transfer, zero-voltage transition, zero-current transition, soft switching

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Authors: Misagh Irandoost Shahrestani, Hossein Shokouhmand, Mohammad Kalteh, Behrang Hasanpour

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In this paper, nanofluid conjugate heat transfer through a microtube with viscous dissipation effect is investigated numerically. The fluid flow is considered as a laminar regime. A constant heat flux is applied on the microtube outer wall and the two ends of its wall are considered adiabatic. Conjugate heat transfer problem is solved and investigated for this geometry. It is shown that viscous dissipation effect which is induced by shear stresses can not be neglected in microtubes. Viscous heating behaves as an energy source in the fluid and affects the temperature distribution. The effect of Reynolds number, particle volume fraction and the nanoparticles diameter on the energy source are investigated and an attempt on establishing suitable equations for assessing the value of the energy source based on Re, Dp and Φ is performed and they are depicted as 3D diagrams. Finally, the significance of viscous dissipation and the influence of these parameters on convective heat transfer coefficient are studied.

Keywords: convective heat transfer coefficient, heat transfer, microtube, nanofluid, viscous dissipation

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Authors: Zerubabel Mihret

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Background: Work-related stress is a pattern of reactions to work demands unmatched by worker’s knowledge, skills, or abilities. Healthcare institutions are considered high-risk and intensive work areas for work-related stress. However, there is the nonexistence of clear and strong data about the magnitude of work-related stress on sanitation workers in hospitals in Ethiopia. The aim of this study was to determine the magnitude of work-related stress among sanitation workers in public hospitals during COVID-19 in Addis Ababa, Ethiopia. Methods: Institution-based cross-sectional study was conducted from October 2021 to February 2022 among 494 sanitation workers who were selected from 4 hospitals. HSE (Health and Safety Executive of UK) standard data collection tool was used, and an interviewer-administered questionnaire was used to collect the data using KOBO collect application. The collected data were cleaned and analyzed using SPSS version 20.0. Both binary and multivariable logistic regression analyses were done to identify important factors having an association with work-related stress. Variables with p-value ≤ 0.25 in the bivariate analysis were entered into the multivariable logistic regression model. A statistically significant level was declared at a p-value ≤ 0.05. Results: This study revealed that the magnitude of work-related stress among sanitation workers was 49.2% (95% CI 45-54). Significant proportions (72.7%) of sanitation workers were dissatisfied with their current job. Sex, age, experience, and chewing khat were significantly associated with work-related stress. Conclusion: Work-related stress is significantly high among sanitation workers. Sex, age, experience, and chewing khat were identified as factors associated with work-related stress. Intervention program focusing on the prevention and control of stress is desired by hospitals.

Keywords: work-related stress, sanitation workers, Likert scale, public hospitals, Ethiopia

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Authors: P. Zamani, S. Mohajerzadeh, R. Masoudinejad, K. Farhangdoost

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The riveting process is one of the important ways to keep fastening the lap joints in aircraft structures. Failure of aircraft lap joints directly depends on the stress field in the joint. An important application of riveting process is in the construction of aircraft fuselage structures. In this paper, a 3D finite element method is carried out in order to optimize residual stress field in a riveted lap joint and also to estimate its fatigue life. In continue, a number of experiments are designed and analyzed using design of experiments (DOE). Then, Taguchi method is used to select an optimized case between different levels of each factor. Besides that, the factor which affects the most on residual stress field is investigated. Such optimized case provides the maximum residual stress field. Fatigue life of the optimized joint is estimated by Paris-Erdogan law. Stress intensity factors (SIFs) are calculated using both finite element analysis and experimental formula. In addition, the effect of residual stress field, geometry, and secondary bending are considered in SIF calculation. A good agreement is found between results of such methods. Comparison between optimized fatigue life and fatigue life of other joints has shown an improvement in the joint’s life.

Keywords: fatigue life, residual stress, riveting process, stress intensity factor, Taguchi method

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Authors: Sara Santos, Maria João Santos

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Thisarticleanalyzesthethemeofwork-family conflict and professional stress among financial workers and their relationships with burnout syndrome. This also studieshowthesocio demographicandworkingcharacteristicsoftheseprofessionalsinfluencetheirlevelsofburnout. Weadopted a mixedmethodbasedontheanalysisof 255 surveysand 24 interviewscarriedoutwith financial sector professionals. Thekeyresultsincludeverificationofhowtheseprofessionalsregister a positive relationshipbetweenwork-familyconflictandburnoutsyndrome as well as betweenprofessional stress andburnout. Thestudycontributes to a betterunderstandingoftheimpactsthatwork-familyconflictsandprofessional stress haveon financial professionalsandhowtheycontribute to thevariationsprevailingintheirrespectivelevelsofburnout.

Keywords: burnout syndrome, financial area, conflict, stres

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Authors: G.S. Patel

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In this research paper the discussion have been made on teachers work mental stress and coping strategies. Stress Measurement scale was developed for school teachers. All the scientific steps of test construction was followed. For this test construction, different factors like teachers workplace, teachers' residential area, teachers' family life, teachers' ability and skills, economic factors and other factors to construct teachers stress measurement scale. In this research tool, situational statements have been made and teachers have to give a response in each statement on five-point rating scale what they experienced in their daily life. Special features of the test also established like validity and reliability of this test and also computed norms for its interpretation. A sample of 320 teachers of school teachers of Gujarat state was selected by Cluster sampling technique. t-test was computed for testing null hypothesis. The main findings of the present study are Urban area teachers feel more stressful situation compare to rural area teachers. Those teachers who live in the joint family feel less stress compare to teachers who live in a nuclear family. This research work is very useful to prepare list of activities to reduce teachers mental stress.

Keywords: stress measurement scale, level of stress, validity, reliability, norms

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Authors: Mustafa Jahanara

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The present research was carried out in order to investigate the relationship between meaning in life and hope with depression, anxiety and stress in Afghan Refugees in Alborz province in Iran. In this research, method of study is a descriptive correlation type. One hundred and fifty-eight Afghan refugees (64 male, 94 female) participated in this study. All participants completed the Meaning in Life Questionnaires (MLQ), Hope Scale (HS), and The Depression Anxiety Stress Scales (DASS-21). The results revealed that Meaning in Life was positively associated with hope, presence of meaning, search of meaning, and negatively associated with depression and anxiety. Hope was positively associated with presence of meaning and search of meaning, and hope was negatively associated with depression, anxiety, and stress. Depression, anxiety, and stress were positively correlated with each other. Meaning in life and hope could influence on mental health.

Keywords: Afghan refugees, meaning of life, hope, depression, anxiety and stress

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Authors: Prathuang Usaborisut, Dithaporn Thungsotanon

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Soil compaction induced by a tractor towing trailer becomes a major problem associated to sugarcane productivity. Soil beneath the tractor’s tire is not only under compressing stress but also shearing stress. Therefore, in order to help to understand such effects on soil, this research aimed to determine stress state in soil and predict compaction of soil under a tractive tire. The octahedral stress ratios under the tires were higher than one and much higher under higher draft forces. Moreover, the ratio was increasing with increase of number of tire’s passage. Soil compaction model was developed using data acquired from triaxial tests. The model was then used to predict soil bulk density under tractive tire. The maximum error was about 4% at 15 cm depth under lower draft force and tended to increase with depth and draft force. At depth of 30 cm and under higher draft force, the maximum error was about 16%.

Keywords: draft force, soil compaction model, stress state, tractive tire

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Authors: Gulcan Ozerim, Gunay Anlas

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In shape memory alloys, upon loading, stress increases around crack tip and a martensitic phase transformation occurs in early stages. In many studies the stress distribution in the vicinity of the crack tip is represented by using linear elastic fracture mechanics (LEFM) although the pseudo-elastic behavior results in a nonlinear stress-strain relation. In this study, the HRR singularity (Hutchinson, Rice and Rosengren), that uses Rice’s path independent J-integral, is tried to formulate the stress distribution around the crack tip. In HRR approach, the Ramberg-Osgood model for the stress-strain relation of power-law hardening materials is used to represent the elastic-plastic behavior. Although it is recoverable, the inelastic portion of the deformation in martensitic transformation (up to the end of transformation) resembles to that of plastic deformation. To determine the constants of the Ramberg-Osgood equation, the material’s response is simulated in ABAQUS using a UMAT based on ZM (Zaki-Moumni) thermo-mechanically coupled model, and the stress-strain curve of the material is plotted. An edge cracked shape memory alloy (Nitinol) plate is loaded quasi-statically under mode I and modeled using ABAQUS; the opening stress values ahead of the cracked tip are calculated. The stresses are also evaluated using the asymptotic equations of both LEFM and HRR. The results show that in the transformation zone around the crack tip, the stress values are much better represented when the HRR singularity is used although the J-integral does not show path independent behavior. For the nodes very close to the crack tip, the HRR singularity is not valid due to the non-proportional loading effect and high-stress values that go beyond the transformation finish stress.

Keywords: crack, HRR singularity, shape memory alloys, stress distribution

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Authors: Imen Debbabi, Hédi BelHadjSalah

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The Improved Element Free Galerkin (IEFG) method is presented to treat the steady states and the transient heat transfer problems. As a result of a combination between the Improved Moving Least Square (IMLS) approximation and the Element Free Galerkin (EFG) method, the IEFG's shape functions don't have the Kronecker delta property and the penalty method is used to impose the Dirichlet boundary conditions. In this paper, two heat transfer problems, transient and steady states, are studied to improve the efficiency of this meshfree method for 2D heat transfer problems. The performance of the IEFG method is shown using the comparison between numerical and analytic results.

Keywords: meshfree methods, the Improved Moving Least Square approximation (IMLS), the Improved Element Free Galerkin method (IEFG), heat transfer problems

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Authors: Sérgio S. de Jesus, Aline Santana, Rubens Maciel Filho

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Global oxygen transfer coefficient (kLa) was characterized in a mechanically agitated airlift bio reactor. The experiments were carried out in an airlift bio reactor (3.2 L) with internal re circulation (a concentric draft-tube airlift vessel device); the agitation is carried out through a turbine Rushton impeller located along with the gas sparger in the region comprised in the riser. The experiments were conducted using xanthan gum (0.6%) at 250 C and a constant rotation velocity of 0 and 800 rpm, as well as in the absence of agitation (airlift mode); the superficial gas velocity varied from 0.0157 to 0.0262 ms-1. The volumetric oxygen transfer coefficient dependence of the rotational speed revealed that the presence of agitation increased up to two times the kLa value.

Keywords: aeration, mass transfer, non-Newtonian fluids, stirred airlift bioreactor

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Authors: Hao Xiaohong, Wu Zongxiang, Chen Xuefeng

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With the high power density and high integration of electronic devices, their heat flux has been increasing rapidly. Therefore, an effective cooling technology is essential for the reliability and efficient operation of electronic devices. Liquid cooling is studied increasingly widely for its higher heat transfer efficiency. Serpentine channels are superior in the augmentation of single-phase convective heat transfer because of their better channel velocity distribution. In this paper, eight different frame sizes water-cooled serpentine channel heat sinks are designed to study the heat transfer and pressure drop characteristics. With water as the working fluid, experiment setup is established and the results showed the effect of different channel width, fin thickness and number of channels on thermal resistance and pressure drop.

Keywords: heat transfer, experiment, serpentine heat sink, pressure drop

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Authors: B. Chetti, W. A. Crosby

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This paper presents a numerical analysis for the dynamic performance of a finite journal bearing lubricated with couple stress fluid taking into account the effect of the deformation of the bearing liner. The modified Reynolds equation has been solved by using finite difference technique. The dynamic characteristics in terms of stiffness coefficients, damping coefficients, critical mass and whirl ratio are evaluated for different values of eccentricity ratio and elastic coefficient for a journal bearing lubricated with a couple stress fluids and a Newtonian fluid. The results show that the dynamic characteristics of journal bearings lubricated with couple stress fluids are improved compared to journal bearings lubricated with Newtonian fluids.

Keywords: journal bearing, elastohydrodynamic, stability, couple stress

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Authors: Mohita Singh, Sunil Sachdev, Amrita Singh

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Background and Aim: Physical aerobic exercises promote positive changes in one’s mental health, intelligence, and ability to cope with stressful encounters. The present study was designed to explore the correlation between intelligence and stress parameters and to assess the correlation between the same parameters after the practice of one month of moderate-intensity physical exercise. Method: The study was conducted on thirty-five healthy male volunteer students to assess the correlation between stress parameters in subjects with varying level of general intelligence (GI) and emotional intelligence (EI). Correlation studies were again conducted after one month between the same parameters to evaluate the effect of moderate-intensity physical exercise (MIPE). Baseline values were recorded using standard scales. Result: IQ and EQ correlated negatively with both acute and chronic stress parameters and positively with each other. A positive correlation was found between acute and chronic stress. With the practice of one month of moderate-intensity physical exercise, there was significant increment between the parameters under study and hence improved results. Conclusion: MIPE improved correlation between GI, EI, stress parameters, and thus reduced stress and improved intelligence.

Keywords: emotional intelligence, general intelligence, moderate intensity physical exercise, stress response

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Authors: K. S. Agrawal

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The performance of jet ejector was studied in detail by different authors. Several authors have studied mass transfer characteristics like interfacial area, mass transfer coefficients etc. In this paper, we have made an attempt to develop PDE model by considering bubble properties and apply Lattice-Boltzmann technique for PDE model. We may present the results for the interfacial area which we have obtained from our numerical simulation. Later the results are compared with previous work.

Keywords: jet ejector, mass transfer characteristics, numerical simulation, Lattice-Boltzmann technique

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Authors: Rafik Bouakkaz

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A finite-volume method simulation is used to investigate two dimensional unsteady flow of nanofluids and heat transfer characteristics past a square cylinder inclined with respect to the main flow in the laminar regime. The computations are carried out of nanoparticle volume fractions varying from 0 ≤ ∅ ≤ 5% for an inclination angle in the range 0° ≤ δ ≤ 45° at a Reynolds number of 100. The variation of stream line and isotherm patterns are presented for the above range of conditions. Also, it is noticed that the addition of nanoparticles enhances the heat transfer. Hence, the local Nusselt number is found to increase with increasing value of the concentration of nanoparticles for the fixed value of the inclination angle.

Keywords: copper nanoparticles, heat transfer, square cylinder, inclination angle

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Authors: Rizwana Amin, Afshan Afroze Bhatti

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The study was a quasi-experimental pre-post test design including two groups. Data was collected from 127 students through non-probability random sampling from Bahaudin Zakariya University Multan. The groups were given pre-test using perceived stress scale and information about academic achievement was taken by self-report. After screening, 27 participants didn’t meet the criterion. Remaining 100 participants were divided into two groups (experimental and control). Further, 4 students of experimental group denied taking intervention. Then 46 understudies were separated into three subgroups (16, 15 and 15 in each) for training. The experimental groups were given the stress management training, each of experimental group attended one 3-hour training sessions separately while the control group was only given pre-post assessment. The data were analyzed using ANCOVA method (analysis of covariance) t–test. Results of the study indicate that stress training will lead to increased emotional intelligence and academic achievement of students.

Keywords: stress, stress management, academic achievement, students

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Authors: Sperisa Distantina, Rieke Ulfha Noviyanti, Sri Sutriyani, Fadilah Fadilah, Mujtahid Kaavessina

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In this research, carrageenan extracted from seaweed Eucheuma cottonii was mixed with polyvinyl alcohol (PVA) and then crosslinked using glutaraldehyde (GA). The obtained hydrogel films were applied to control the drug release rate of paracetamol. The aim of this research was to develop a mathematical model that can be used to describe the mass transfer rate of paracetamol from the hydrogel film into buffer solution. The effect of weight ratio carrageenan-PVA (5: 0, 1: 0.5, 1: 1, 1: 2, 0: 5) on the parameters of the mathematical model was investigated also. Based on the experimental data, the proposed mathematical model could describe the mass transfer rate of paracetamol. The weight ratio of carrageenan-PVA greatly affected the amount of paracetamol absorbed in the hydrogel film and the mass transfer rate of paracetamol.

Keywords: carrageenan-PVA, crosslinking, glutaraldehyde, hydrogel, paracetamol, mass transfer

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Authors: Basavaraj R. Endigeri, Shriharsh Desphande

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Optimization and reduction of stress concentration around holes in a uniaxially loaded plate is one of the important design criteria in many of the engineering applications. These stress risers will lead to failure of the component at the region of high stress concentration which has to be avoided by means of providing auxiliary holes on either side of the parent hole. By literature survey it is known that till date, there is no analytical solution documented to reduce the stress concentration by providing auxiliary holes expect for fever geometries. In the present work, plate with a hole subjected to uniaxial load is analyzed with the numerical method to determine the optimum sizes and locations for the auxillary holes for different center hole diameter to plate width ratios. The introduction of auxiliary holes at a optimum location and radii with its effect on stress concentration is also represented graphically. The finite element analysis package ANSYS 8.0 is used to carry out analysis and optimization is performed to determine the location and radii for optimum values of auxiliary holes to reduce stress concentration. All the results for different diameter to plate width ratio are presented graphically. It is found from the work that introduction of auxiliary holes on either side of central circular hole will reduce stress concentration factor by a factor of 19 to 21 percentage.

Keywords: finite element method, optimization, stress concentration factor, auxiliary holes

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Authors: Hamidreza Mansouri

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In the construction industry, the lifespan of a metal structure is directly related to the quality of welding. In most metal structures, the welded area is considered critical and is one of the most important factors in design. To date, many fracture incidents caused by these types of cracks have occurred. Various methods exist to increase the lifespan of welds to prevent failure in the welded area. Among these methods, the application of ultrasonic peening, in addition to the stress relief process, can manually and more precisely adjust the geometry of the weld toe and prevent stress concentration in this part. This research examined Gas Tungsten Arc Welding (GTAW) on common structural steels and 316 stainless steel, which require precise welding, to predict the optimal condition. The GTAW method was used to create residual stress; two samples underwent ultrasonic stress relief, and for comparison, two samples underwent thermal stress relief. Also, no treatment was considered for two samples. The residual stress of all six pieces was measured by X-Ray Diffraction (XRD) method. Then, the two ultrasonically stress-relieved samples and two untreated samples were exposed to a corrosive environment to initiate cracking and determine the effectiveness of the ultrasonic stress relief method. Thus, the residual stress caused by GTAW in the samples decreased by 3.42% with thermal treatment and by 7.69% with ultrasonic peening. Furthermore, the results show that the untreated sample developed cracks after 740 hours, while the ultrasonically stress-relieved piece showed no cracks. Given the high costs of welding and post-welding zone modification processes, finding an economical, effective, and comprehensive method that has the least limitations alongside a broad spectrum of usage is of great importance. Therefore, the impact of various ultrasonic peening stress relief parameters and the selection of the best stress relief parameter to achieve the longest lifespan for the weld area is highly significant.

Keywords: GTAW welding, stress corrosion cracking(SCC), thermal method, ultrasonic peening.

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Authors: Devinder Singh, Rajneesh Kumar, Arvind Kumar

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The present investigation deals with the deformation of micropolar generalized thermoelastic solid subjected to thermo-mechanical loading due to a thermal laser pulse. Laplace transform and Fourier transform techniques are used to solve the problem. Thermo-mechanical laser interactions are taken as distributed sources to describe the application of the approach. The closed form expressions of normal stress, tangential stress, coupled stress and temperature are obtained in the domain. Numerical inversion technique of Laplace transform and Fourier transform has been implied to obtain the resulting quantities in the physical domain after developing a computer program. The normal stress, tangential stress, coupled stress and temperature are depicted graphically to show the effect of relaxation times. Some particular cases of interest are deduced from the present investigation.

Keywords: pulse laser, integral transform, thermoelastic, boundary value problem

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Authors: Kotaro Miura, Makoto Sakamoto, Yuji Tanabe

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We focus on internal stress and displacement of an elastic axisymmetric contact problem for indentation of a layer-substrate body. An elastic layer is assumed to be perfectly bonded to an elastic semi-infinite substrate. The elastic layer is smoothly indented with a flat-ended cylindrical indenter. The analytical and exact solutions were obtained by solving an infinite system of simultaneous equations using the method to express a normal contact stress at the upper surface of the elastic layer as an appropriate series. This paper presented the numerical results of internal stress and displacement distributions for hard-coating system with constant values of Poisson’s ratio and the thickness of elastic layer.

Keywords: indentation, contact problem, stress distribution, coating materials, layer-substrate body

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Authors: Aboussalih Amira, Zarza Tahar, Fedaoui Kamel, Hammoudi Saleh

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This work focuses on the simulation of the prediction of the behaviour of austenitic stainless steel (SS) 304L under complex loading in stress and imposed strain. The Chaboche model is a cable to describe the response of the material by the combination of two isotropic and nonlinear kinematic work hardening, the model is implemented in the ZébuLon computer code. First, we represent the evolution of the axial stress as a function of the plastic strain through hysteresis loops revealing a hardening behaviour caused by the increase in stress by stress in the direction of tension/compression. In a second step, the study of the ratcheting phenomenon takes a key place in this work by the appearance of the average stress. In addition to the solicitation of the material in the biaxial direction in traction / torsion.

Keywords: damage, 304L, Ratcheting, plastic strain

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Authors: A. S. Haruna, M. L. Mayanchi

Abstract:

Pre Nigeria Certificate in Education otherwise called Pre-NCE is an intensive two semester course designed to assist candidates who could not meet the requirements for admission into NCE programme. The task of coping with the stressors in the course can interfere with the students’ ability to regulate attention skills and stay organized. The main objectives of the study were to find out the prevalence of stress; determine the association between stress and ADD and reveal gender difference in the prevalence of ADD among stressed pre-NCE students. Cross–Sectional Correlation Design was employed in which 333 (Male=65%; Female=35%) students were proportionately sampled and administered Stress Assessment Scale [SAS r=0.74) and those identified with stress were thereafter rated with Cognitive Processing Inventory [CPI]. Data collected was used to analyze the three null hypotheses through One-sample Kolmogorov-Smirnov (K-S) Z-score, Pearson Product Moment Correlation Coefficients (PPMCC) and t-test statistics respectively at 0.05 confidence level. Results revealed significant prevalence of stress [Z-calculated =2.24; Z-critical = ±1.96], and a positive relationship between Stress and ADD among Pre-NCE students [r-calculated =0.450; r-critical =0.138]. However, there was no gender difference in the prevalence of ADD among stressed Pre-NCE students in the college [t-calculated =1.49; t-critical =1.645]. The study concludes that while stress and ADD prevail among pre-NCE students, there was no gender difference in the prevalence of ADD. Recommendations offered suggest the use of Learners Assistance Programs (LAP) for stress management, and Teacher-Students ratio of 1:25 be adopted in order to cater for stressed pre-NCE students with ADD.

Keywords: attention deficit disorder, pre-NCE students, stress, Pearson Product Moment Correlation Coefficients (PPMCC)

Procedia PDF Downloads 214

Authors: Sumara Khanzada

Abstract:

This research investigated how much stress is induced by various study-related factors, in undergraduate students belonging to a renowned university in Karachi along with the unhealthy coping strategy the students use to manage the stress. The study related factors considered for the purpose of the study were curriculum and instruction based stress, teacher-student relationship, assessment system and different components related to academic work. A survey in which questionnaires were administered to hundred students was conducted. The data were analyzed quantitatively to determine the percentages of stress induced by the various factors. The study found that student-teacher relationship is the strongest factor that causes stress in the undergraduate students specifically when teachers do not deliver the lectures effectively and give assignments and presentations to students without clear guidelines and instructions. The second important factor that causes stress was the different components of academic life, such as, parental expectations and pressures to achieve one's goals. Assessment system was found to be the third key factor inducing stress and affecting students' cognitive and psychological functioning. The most commonly used unhealthy coping strategy for stress management was procrastination. In light of the findings, it is recommended that importance be given to teacher training to ensure that instruction is proper and healthy teacher student relationship exists. Effective support programs, workshops, seminars, and different awareness programs should be arranged for promoting awareness regarding mental health in educational institutions. Moreover, additional zero credit courses should be offered to teach students how to learn stress management and healthy coping skills. Sumara Khanzada Clinical Psychologist [email protected]

Keywords: Stress, coping stretigies, acadamic stress, relationship

Procedia PDF Downloads 45