Minimal Stress Research Articles

Nonlinear relationship between early life stress exposure and subsequent resilience in monkeys

Retrospective correlational studies of humans suggest that moderate but not minimal or substantial early life stress exposure promotes the development of stress inoculation-induced resilience. Here we test for a nonlinear relationship between early life stress and resilience by comparing varying “doses” of early life stress. Juvenile squirrel monkeys underwent one of five treatment conditions between 17–27 weeks of age: Stress inoculation (SI) with continuous access to mother (SI + Mom; one stress element), SI without continuous access to mother (SI; two stress elements), SI without continuous access to mother and with alprazolam injection pretreatments (SI + Alz; three stress elements), SI without continuous access to mother and with vehicle injection pretreatments (SI + Veh; three stress elements), or standard housing (No SI; zero stress elements). Alprazolam was used to test whether anxiolytic medication diminished SI effects. Subjects exposed to one or two early life stressors subsequently responded with fewer indications of anxiety (e.g., decreased maternal clinging, increased object exploration, smaller cortisol increases) compared to No SI subjects. Subjects exposed to three early life stressors did not differ on most measures from one another or from No SI subjects. These findings provide empirical support for a nonlinear J-shaped relationship between early life stress exposure and subsequent resilience.

Intra-Annual Variability in Responses of a Canopy Forming Kelp to Cumulative Low Tide Heat Stress: Implications for Populations at the Trailing Range Edge.

Anthropogenic climate change is driving the redistribution of species at a global scale. For marine species, populations at trailing edges often live very close to their upper thermal limits and, as such, poleward range contractions are one of the most pervasive effects of ongoing and predicted warming. However, the mechanics of processes driving such contractions are poorly understood. Here, we examined the response of the habitat forming kelp, Laminaria digitata, to realistic terrestrial heatwave simulations akin to those experienced by intertidal populations persisting at the trailing range edge in the northeast Atlantic (SW England). We conducted experiments in both spring and autumn to determine temporal variability in the effects of heatwaves. In spring, heatwave scenarios caused minimal stress to L.digitata but in autumn all scenarios tested resulted in tissue being nonviable by the end of each assay. The effects of heatwave scenarios were only apparent after consecutive exposures, indicating erosion ofresilience over time. Monthly field surveys corroborated experimental evidence as the prevalence of bleaching (an indication of physiological stress and tissue damage) in natural populations was greatest in autumn and early winter. Overall, our data showed that L.digitata populations in SW England persist close to their upper physiological limits for emersion stress in autumn. As the intensity of extreme warming events is likely to increase with anthropogenic climate change, thermal conditions experienced during periods of emersion will soon exceed physiological thresholds and will likely induce widespread mortality and consequent changes at the population level.

Investigation of the detrimental effect of the rotational speed on gas holdup in non-Newtonian fluids with Scaba-anchor coaxial mixer: A paradigm shift in gas-liquid mixing

Our research findings challenge the paradigm that a high rotational speed of impellers can intensify the gas dispersion. Interestingly, we observed the deterioration in the gas holdup at the higher rotational speeds. Electrical resistance tomography (ERT) and computational fluid dynamics (CFD) were extensively utilized to shed light on the hydrodynamics of Scaba-anchor coaxial mixer and its impact on the aeration efficiency in non-Newtonian fluids, for the first time. The working fluid was 1 wt% carboxymethyl cellulose solution, which is a non-Newtonian fluid and obeys the power law model. At a fixed central impeller speed of 290 rpm, as the anchor impeller speed was increased from 15 to 50 rpm, the decrease in the local gas holdup was attributed to the decline in the Scaba impeller pumping capacity and its aerated power consumption. On the other hand, at a constant anchor impeller speed of 10 rpm, when the Scaba rotational speed was increased from 290 to 430 rpm, the gas holdup decreased surprisingly even with an increasing Scaba’s pumping capacity at higher rotational speed. The sharp drop in the local gas holdup was the consequence of a poor axial gas dispersion. With a minimal fluid shear stress at low agitation speed, our research findings hold promise to optimize energy savings while enhancing the aeration efficiency in non-Newtonian fluids at low Reynolds numbers.

Advances in Hermetic Projection Weld Sealing

Abstract In this article, we describe a novel process for hermetic projection weld sealing of semiconductor devices, considered by many to be an important legacy technology from decades gone bye, but not particularly relevant in today's arsenal of sealing technologies. We will demonstrate that with appropriate modifications to be described, this technology can used to seal various high power devices as well as high reliability semiconductors, crystals, hybrid packages, medical electronics, photonic devices, automotive electronics, etc. Its features primarily stem from the fact that it can be used to quickly and efficiently produce true hermetic seals in components. The welding is so rapid, that it is essentially a room temperature technology and the equipment is small enough that it can be housed in an atmosphere controlled chamber filled with any gas that is not explosive. Air, Nitrogen, Argon, Helium and their mixtures are the most commonly utilized gasses. The process is so adiabatic that it can be used to seal many liquids also. In some applications the technology competes against pulsed laser welding, but unlike laser welding the entire seal takes place in a few milliseconds because it is a single discharge, component-shaped spot/projection weld, which means that the entire seam is made in a single high speed discharge. So, in the same time that it takes a laser welding machine to make one of the many small overlapping spot welds required to make a seal, the projection welder has completed the entire operation. This process results in minimal stress and distortion, and maximum hermetic properties, strength and reliability, without requiring electroplating or preforms. Because the weld involves the localized high speed melting of metals, it among the highest energy density processes. A concern with the earlier resistance welding technologies has been the expulsion of particulates, both out of, and into the seal. This expulsion has been systemic and becomes progressively worse as the package size increases. In the course of this presentation we will demonstrate how this concern has been dealt with and corrected. Internal dew points can be held to −40 degrees, or lower if required. Other common applications for this technology include sealing and welding of nuts and studs for hermetic applications and sealing of devices for medical applications that must endure autoclave sterilization. In the course of this presentation, we will take you back to the roots of the original resistance welding process as taught by the early process developers so that you will understand how things have changed, and the reasons for the changes.

Development and optimization of the laser-assisted bonding process for a flip chip package

In a fine pitch flip chip package, a laser-assisted bonding (LAB) technology has recently been developed to overcome several reliability and throughput issues in the conventional mass reflow (MR) and thermal compression bonding technology. This study investigated the LAB process for a flip chip package with a copper (Cu) pillar bump using numerical heat transfer and thermo-mechanical analysis. During the LAB process, the temperature of the silicon die was uniform across the entire surface and increased to 280 °C within a few seconds; this was high enough to melt the solder. The heat in the die was quickly conducted to the substrate through the Cu pillar bumps. Meanwhile, the substrate temperature was low and remained constant. Therefore, a stable solder interconnection was quickly achieved with minimal stress and thermal damage to the package. The substrate thickness, the number of Cu bumps, and the bonding stage temperature were found to be important factors affecting the heat transfer behavior of the package. The temperature of the die decreased when a thinner substrate, a higher number of Cu bumps, and a lower bonding stage temperature were used. If the temperature of the die was not sufficiently high, insufficient heat was transferred to the solder to melt it, resulting in incomplete solder joint formation. Thermo-mechanical analysis also showed that the LAB process produced lower warpage and thermo-mechanical strain than the conventional MR process. These results indicated that a LAB process using a selective local heating method would be beneficial in reducing thermo-mechanical stress and increasing throughput for the fine pitch flip chip packages.

Stress distribution along the cruciform geometry under pure in-plane biaxial loading condition

The present paper aims at designing a novel cruciform geometry which could effectively demonstrate the biaxial behavior of aluminum A1050-H14. A cruciform geometry with two geometric shapes milled about the center region on the basic cross-shaped geometry is considered for the present study. The geometric shapes include a double-armed cruciform and a circle but with different depths (geometric-shaped CS-I). An FEA tool is used to study the biaxial behavior of these geometries under two biaxial loading conditions: (1) biaxial tension (TT) and (2) biaxial compression–tension (CT). Along with the above-mentioned geometry, two more geometries are even analyzed to end up with a better geometry for the in-plane biaxial testing. The other two geometries are (1) modified cruciform with spline cut at the cross-arms of the sample and with a straight arm (CS-II), and (2) modified CS-I geometry by tapering the arms (CS-III). The geometry producing (1) uniform von Mises stress, (2) zero or minimal shear stress along the gauge section and (3) initiation of failure about the gauge section is considered.

Three-button gateway smart home interface (TrueSmartface) for elderly: Design, development and deployment

With the growing age, the older adults experience gradual health, physical as well cognitive, declining. Oftentimes, the degree of developed health concerns is severe enough for the inevitable need of most likely a permanent caregiver or resource-rich but overly expensive assisted or nursing facility. The increasingly technical richness of the science advancements helps elevate at least most aspects of human life and the existence of smart home is one such outcome that has attained popularity, maturity and acceptability over the short period of time, especially in the communities of seniors, where it promises them an independent daily living. The smart home is an intelligent, technical, and automated cyber-physical infrastructure, which consists of a number of appliances and devices embedded or attached in physical environment. Some of them will be contextually-triggered, however, there is also a potential need for an efficient interface (graphical or non-graphical) to operate some. The design of such graphical interfaces is not so rudimentary, rather ought to be a comprehensive human-centered design that imposes very minimal physical and cognitive stress on a senior inhabitant. In this research work, we design and develop one such graphical interface (apt for desktop, laptop and mobile devices), which is based on some newly devised hypotheses, validated through literature and informal surveys. At every stage of the design, a three-button constraint is precisely persevered and the interface is successfully deployed into the Smart Home Lab at Iowa State University.

Behavioral and adrenocortical responses of captive white rhino adolescents to the introduction of a new calf

Changes in group composition are not exclusive to zoos and conservation breeding centers. The recent increase in poaching of African rhino species has accelerated the arrival of orphan calves at rehabilitation centers. Introducing new members into an existing group is often stressful for many mammal species. However, when young animals are involved, such responses may be reduced or absent. The goal of the present study was to evaluate the effect of introducing orphan calves on the stress responses of young orphan rhino from existing groups. The behavior and fecal glucocorticoid metabolite (fGCM) concentrations of eight orphan southern white rhinoceros (Ceratotherium simum simum) were assessed 1 month before and after the introduction of a new calf. From the 10 variables measured, only the response to humans and submissive behaviors showed significant changes. Stereotypies were not observed during the course of the study, and adrenocortical activity, monitored by means of fGCM concentrations, did not increase after the introductions, showing values within the range observed in free-ranging white rhino. However, strong individual differences were evident in most variables. Our results suggest that the introduction of white rhino calves into an existing group of young rhinos caused minimal stress in existing group members. Although these findings should be treated with caution when generalizing to other captive populations due to the small and heterogeneous sample, our findings may have management implications for rhino orphanages as well as zoos and breeding centers where non-breeding pairs are frequently maintained.

Optimized capacitive active ripple compensation topology for a 3.7 kW single-phase high power density on-board charger of electric vehicles

In this paper, a comprehensive investigation of the capacitive active ripple compensation (ARC) techniques is made to conclude which one is optimal to be used in on-board chargers of electric vehicles. Crucial aspects in such an application are: lifetime, volumetric and specific power density (including components’ size and the needed cooling solution), and overall efficiency of the charger. As presented in this paper, all capacitive ARC topologies (buck, boost, and buck–boost) have successfully diverted the low-frequency ripple from the dc side with a maximized power density. The ARC circuit consists of two additional switches, a smoothing auxiliary inductor, and a storage auxiliary capacitor. Finally, the buck capacitive ARC topology proves to be the optimal ARC technique for on-board chargers because of its maximal power density, minimal loss behavior and voltage stress, and long lifetime capability as it requires a downsized capacitance to the extent, where film capacitors or ceramic capacitors can replace the normally used bulky electrolytic capacitors. The performance of the three capacitive ARC techniques is proved by simulation results.

Self‐similarity analysis of vehicle driver's electrodermal activity

AbstractThis paper characterizes stress levels via a self‐similarity analysis of the electrodermal activity (EDA) collected in a real‐world driving context. To characterize the EDA richness over scales, the fractional Brownian motion (FBM) process and its corresponding exponent H, estimated via a wavelet‐based approach, are used. Specifically, an automatic scale range selection is proposed in order to detect the linearity in a log scale diagram. The procedure is applied to the EDA signals, from the open database drivedb, originally captured on the foot and the hand of the drivers during a real‐world driving experiment, designed to evoke different levels of arousal and stress. The estimated Hurst exponent H offers a distinction in stress levels when driving in highway versus city, with a reference to restful state of minimal stress level. Specifically, the estimated H values tend to decrease when the driving environmental complexity increases. In addition, the estimated H values on the foot EDA signals allow a better characterization of the driving task than that of hand EDA. The self‐similarity analysis was applied to various physiological signals in literature but not to the EDA so far, a signal which was found to correlate most with human affect. The proposed analysis could be useful in real‐time monitoring of stress levels in urban driving spaces, among other applications.

Comparative Assessment of Three Microimplant Assisted Biomechanical Strategies for the Simultaneous Intrusion and Retraction of Anterior Teeth in Relation to Alveolar Bone Stress and Change in Incisor Inclinations – A 3D Finite Element Analysis Study

Microimplants are widely used to provide absolute anchorage in cases with bimaxillary dentoalveolar protrusion especially in those that require simultaneous retraction and intrusion of anterior teeth. The position of the microimplant significantly affects the build up of stress in the alveolar bone as well as the incisor inclinations, and is therefore a critical factor in treatment plannning. Keeping this in mind, this finite element method(FEM) study was taken up to identify the most suitable combination of implant placement sites for cases in which en-masse anterior retraction is done along with intrusion. The geometric model was constructed from a CBCT scan of the maxilla of an adult patient with full permanent dentition.The images were saved as DICOM files and were later exported to the 3D image processing software (Mimics,version 17). The center of resistance for the 6 anterior teeth was 9 mm superiorly and 13.5 mm posteriorly from the midpoint of crown tip of central incisors. The working archwires were assumed to be 0.019 / 0.025-in stainless steel. The three mini-implant placement sites compared were – S1- Midline micro implant between the maxillary central incisors with two placed posteriorly between maxillary 2nd premolar 1st molar roots. S2 – Micro implant placed between the lateral incisor and canine along with posterior mini implants as above. S3- Micro implant placed high up between the maxillary second premolar and first molar roots. The amount of tooth displacement after finite element analysis was compared with central and lateral incisor and canine axis graphs. For the system S1, intrusive components were seen on the archwire mainly in the anterior region with maximum displacement between central incisors and gradually decreasing away from point of force application. In S2, the intrusive component of force was more evenly distributed. In S3, pattern of intrusive component was similar to S2 but the maximum displacement was slightly lower. Greatest value of minimal principal stress was seen on cervical and apical third of central incisors as well as apical third of lateral incisors in S1; and cervical third of lateral incisors and apical and cervical third of canines in S2. Maximum retraction of anterior teeth was seen in S3. In all of the three systems of force application, tooth inclinations were maintained. Maxillary anterior teeth showed more tendency towards retraction in the case where two micro implants were placed posteriorly high up above the roots of maxillary premolars and molars such that the force is directed diagonally having both horizontal and vertical components, and hence eliminating the need for anterior implants. Greater intrusion tendency was seen when implants were placed between the roots of maxillary central incisors.

Reflecting on the research encounter for people in the early stages of dementia: Lessons from an embedded qualitative study.

Gathering meaningful data from people with dementia presents challenges to researchers involved in both qualitative and quantitative studies. Careful planning and implementation are required, including skilful and sympathetic management by the researcher who must pay attention to the cognitive challenges experienced by the person with dementia. These challenges are particularly evident when conducting structured interviews using standardised measures. This paper presents the findings of an embedded qualitative study undertaken within a pragmatic randomised controlled trial. The novel method involves nesting a qualitative analysis within a quantitative study by recording incidental conversation during structured interviews, requiring no additional data collection. The method shone a light on the formal interview process itself, something rarely revealed outside the interview setting. It provided a unique insight into the challenges posed by research participation for people in early-stage dementia. Analysis revealed three main themes relating to dementia as a condition and to the research design. First, people with dementia contributed very few conversational comments during the structured interviews. Second, the context of the interview, that is: managing the conversational interchange, responding to direct and often sensitive questions and making decisions about day-to day-feelings and experiences was difficult for participants to manage. Third, people in early stage dementia struggled with the content of the structured interviews due to their linguistic and cognitive demands. The findings raise questions about how people with dementia are included in research and the methods employed to gather accurate data with minimal inconvenience and stress for research participants.

A Bottom Up Perspective to Understanding the Dynamics of Team Roles in Mission Critical Teams.

There is a long history, dating back to the 50 s, which examines the manner in which team roles contribute to effective team performance. However, much of this work has been built on ad hoc teams working together for short periods of time under conditions of minimal stress. Additionally, research has been conducted with little attention paid to the importance of temporal factors, despite repeated calls for the importance of considering time in team research (e.g., Mohammed et al., 2009). To begin to understand team roles and how temporal aspects may impact the types of team roles employed when teams are working in extreme mission critical environments, the current manuscript uses a data-driven, bottom-up approach. Specifically, we employ the use of retrospective historical data as our input and a historiometric approach (Simonton, 2003). Source documents consist primarily of autobiographies, memoires, biographies, and first-hand accounts of crew interaction during spaceflight. Critical incidents regarding team interaction were extracted from these source documents and independently coded for team roles by two trained raters. Results of the study speak to the importance of task and social roles within teams that are predominantly intact and operating in extreme environments where mistakes can be life threatening. Evidence for the following task (i.e., coordinator, boundary spanner, team leader, evaluator, critic, information provider, team player, and innovator) and social roles (i.e., team builder, nurturer, harmonizer, entertainer, jokester, and the negative roles of attention seeker and negativist) were found. While it is often task roles that receive the greatest attention, results point to the importance of not neglecting the socioemotional health of the team (and the corresponding roles). Results also indicated that while some roles were consistently enacted independent of temporal considerations (e.g., mission length), the degree to which others were enacted varied across missions of differing lengths. Additionally, based on the current sample we see the following trends: (1) increased enactment of the team builder role as mission duration increases, (2) prominence of the entertainer role, and (3) increased emphasis on the visionary/problem solver role on missions over 2 years.

Depression, Anxiety, and Stress in Parents of Patients With Retinoblastoma

To assess depression, anxiety, and stress in parents of patients with retinoblastoma and to evaluate the impact of unifocal vs multifocal retinoblastoma. A cross-sectional, self-reported psychological assessment of parents of patients with retinoblastoma at a tertiary care ocular oncology center was performed. The Beck Depression Inventory-II (BDI), Beck Anxiety Inventory (BAI), The Parental Stress Index 4-Short Form, and a retinoblastoma Knowledge Assessment questionnaire were administered. Descriptive statistics for outcomes and comparative analyses were made. There were 138 parents of children with retinoblastoma (unifocal: n= 77, multifocal: n= 61). Overall, parents displayed mild, moderate, or severe depression (BDI) (n= 37, 26.7%); mild, moderate, or severe anxiety (BAI) (n= 49, 35.8%), and stress scores within normal limits (n= 138, 100%). A comparison (unifocal vs multifocal) revealed parents of children with multifocal retinoblastoma with severe depression (1.4% vs 10.2%, P < .02), and no differences in anxiety or stress. Factors associated with moderate or severe parental depression included previous history of depression (30.0% vs 3.9%, P < .001) and factors for moderate or severe anxiety included previous history of depression (33.3% vs 8.6%, P < .001), parent highest level of education at high school or less vs college or beyond (29.2% vs 10.9%, P= .031), and parental report of "child developmental delay" (31.5% vs 11.3%, P= .019). The majority of parents displayed minimal depression (73.3%), anxiety (64.2%), or stress (100%). However, severe depression is more often found in those whose children have multifocal disease, and previous history of depression and less education can impact psychological function. NOTE: Publication of this article is sponsored bythe American Ophthalmological Society.

Bemessungskonzept für Druckschächte bei Nutzung des passiven Gebirgswiderstands

AbstractThe proposed method can be seen as an adaption of the ”Seeber“ concept considering developments in geomechanics, calculation methods and steel technology over the last decades. When exposed to inner pressure, the cracking condition is transgressed and steel linings will not protect the rock mass against cracking. Accordingly, the post‐failure behaviour of the rock mass is an essential basis for structural design. The effects of crack water pressure on radial displacements and the width of gaps are considered. The resistant behaviour of the rock mass is determined by its minor primary principal stress. Under mountain ridges and slopes, there is no correlation between the minor stresses and the height of overburden. Obviously damage cases in concrete lined tunnels are the result of inappropriate assessment of principal stresses. A better approach is proposed based on fundamental considerations and FE calculations. Crack water pressure close to the level of the minimal principal stress will induce progressive hydraulic fracturing in the rock mass, which requires safe waterproofing sealing of the shaft. Grouting the coaxial gap in rock mass is a firm part of any design concept. In shafts sealed by membranes, the capability to bridge fissures must be proved by tests. In steel lined shafts, the usable passive resistance of rock mass is determined by the acceptable radial displacement.

Biomechanical Evaluation of Zygomatic Implant Use in Patients With Different Buccal Maxillary Defect Levels.

The purpose of this study was to examine the biomechanics of zygomatic implants that were planned on an atrophic maxilla with five different buccal defect types and two different bone types. Three-dimensional models of zygomatic implants, human skulls, and maxillary prostheses were modeled with SolidWorks software. Ten finite element models of skulls with five different buccal defect types and two different bone types were constructed to mimic various clinical scenarios. Two bilateral zygomatic implants and two anterior dental implants were inserted into all models. The data were processed by ANSYS Workbench software. 150-N vertical occlusal and 300-N masseteric loads were simulated on a modeled prosthesis. The stresses on and deformations of the bones and implants were then observed and compared. Maximum Von Mises stress was found in skulls modeled with a type 4 defect and D3 bone type. Minimal stress values were found in the skull model with a type 1 buccal bone defect and D2 bone type. Displacement values were correlated with stress values. Cortical bone anchorage and bone type of zygomatic implants positively affect their biomechanics. Alveolar crest support has an effective role in the biomechanics of zygomatic implants.

Flow stress of open-celled aluminum foams based on current density and the optimal foam for energy absorption

Aiming to reveal a fundamental property of open-celled foams under large plastic deformation, the present study proposes and examines a hypothesis, that is, a piece of open-celled foam after being compressed to a certain strain without wall fracture can be regarded as a fresh piece of foam characterized by its current density. As an immediate deduction of this hypothesis, the mechanical property of open-celled foam is completely determined by its current density regardless its initial density. The proposed hypothesis is successfully verified by our experimental data. It is shown that the plastic flow stress (expressed in true stress) of a piece of open-celled foam is independent of its initial density and can be predicted by a power function of its current relative density. Based on the power function, the specific energy absorbed by the aluminum foam can be predicted merely from the initial and the final densities of the foam, instead of integrating the measured stress-strain curve, which greatly simplifies the material design for engineering applications. Then an optimization method is proposed to determine the foam with the optimal initial density for absorbing a specified energy. The optimal foam will produce the minimal stress during the energy absorption compared to those with other magnitudes of density. All the analytical predictions are verified by the experimental results.

Numerical study of Bingham flow in macroscopic two dimensional heterogeneous porous media

The flow of non-Newtonian fluids is ubiquitous in many applications in the geological and industrial context. We focus here on yield stress fluids (YSF), i.e. a material that requires minimal stress to flow. We study numerically the flow of yield stress fluids in 2D porous media on a macroscopic scale in the presence of local heterogeneities. As with the microscopic problem, heterogeneities are of crucial importance because some regions will flow more easily than others. As a result, the flow is characterized by preferential flow paths with fractal features. These fractal properties are characterized by different scale exponents that will be determined and analyzed. One of the salient features of these results is that these exponents seem to be independent of the amplitude of heterogeneities for a log-normal distribution. In addition, these exponents appear to differ from those at the microscopic level, illustrating the fact that, although similar, the two scales are governed by different sets of equations.

Teacher Self-Efficacy for Teaching Students With Autism Spectrum Disorder: Associations with Stress, Teacher Engagement, and Student IEP Outcomes Following COMPASS Consultation

Although teachers reporting high teaching self-efficacy demonstrate positive teaching behaviors, minimal stress, and superior classroom management techniques, surprisingly few studies have demonstrated a relationship between teacher self-efficacy and student outcomes. This study explored self-efficacy specific to teaching students with autism spectrum disorder (ASD), and examined relationships with stress, teacher engagement, and student individualized education program (IEP) outcomes. Special education teachers ( N = 44) were recruited as part of a larger study examining a consultation intervention. Results indicated that self-efficacy for teaching students with ASD was significantly and positively correlated with teacher engagement and student outcomes, and negatively correlated with teacher stress. Furthermore, teachers who received the consultation intervention reported higher levels of self-efficacy for teaching students with ASD. This is the first study to report a direct association between teacher self-efficacy and student IEP outcomes and the potential positive impact of a teacher consultation intervention on the teacher intrapersonal factor of self-efficacy.

Optimal mechanical and thermal architecture of high-conductivity inserts for cooling an electronic piece

Highly conductive inserts improve heat removal from electronic components remarkably; however, using these inserts is associated with a side effect: the mechanical strength deterioration of the piece. In this research, based on the constructal theory, the architecture of these inserts is optimized in such a way that the lowest maximum temperature and highest mechanical strength of the disc-shaped piece are achieved. Here, three patterns for the configuration of inserts embedded in the disc are studied, namely radial, dendritic with one level of pairing and dendritic with two levels of pairing. The total amount of high-conductivity inserts material is fixed, while the geometrical parameters of the inserts like length, the bifurcating locations and the angles of bifurcations are considered as degrees of freedom. It was observed that when 16 inserts were invoked, maximum temperature and stress were minimized. Results showed that changing the structure from radial to dendritic with one bifurcation causes a decrease in the maximum temperature and stress of about 17% and 3.2%, respectively. Also, it was seen that increasing the complexity of the structure by increasing the number of bifurcations from one to two leads to 5.6% reduction and 1% increment in minimal maximum temperature and optimal maximum stress, respectively.