Corner Zone Research Articles

Analyzing movement behavior of zebrafish in different sized confined areas

Movement behavior of zebrafish (Danio rerio) was analysed according to different sizes of observation arena (four sizes:and ). The observation arena was separated into corner, boundary and central areas based on experimental data. The results showed that the shapes of the corner, boundary and central areas were accordingly different in different sizes of the arena. Individuals stayed in the boundary zone for a substantial proportion (approximately 55-58 %) of the observation period while in the corner zone they stayed for the shortest time period (approximately 12-14 %). Movement parameters (speed, acceleration, etc.) of each individual varied in different areas on different sizes and speed was highest in the size of while acceleration was highest in the size of . These reveal that the movement behaviors of zebrafish were affected by different sizes of arenas, at larger sizes they move more actively compared to smaller sizes. However, Transition probability matrices (TPMs) of moving between different areas in the observation were stable. These findings imply that there is a stereotypic inner state that maintains basic behaviors in animals. Information from this work would provide backgrounds of real-life process mechanism and would be useful for monitoring in response to environmental changes in practical aspect and be applicable to a wide range of fields including pharmacology, neurology, and genetics.

Machine Learning Based Visible Light Indoor Positioning With Single-LED and Single Rotatable Photo Detector

In recent years, visible light positioning (VLP) systems have attracted considerable attention because they do not require additional infrastructures. However, most existing researches on the VLP ignore the impact of wall diffuse reflection, which can lead to the dramatical decrease of the position accuracy performance near the indoor walls and corners. In this paper, we design an indoor VLP system with one single light-emitting diode (LED) and a rotatable photodetector (PD), and then propose an indoor VLP algorithm based on machine learning (ML) methods with concern for the indoor reflection of the optical propagation. The proposed positioning process is implemented via two stages: area classification and positioning. During the area classification stage, by using the random forest (RF) algorithm, the entire room is divided into one interior area and four wall or corner zones. In the interior area, the rotatable PD is directly used to determine the target location. In the four wall or corner zones, a hybrid positioning algorithm based on the extreme learning machine (ELM) and the density-based spatial clustering of applications with noise (DBSCAN) is developed to improve localization accuracy near the indoor walls and corners. Simulation results show that by using the proposed indoor VLP system with the rotatable PD and the hybrid algorithm, the maximum and averaged positioning errors of wall or corner zones drop from 137.96 cm and 15.63 cm, to 38.34 cm and 1.43 cm, respectively, and the averaged positioning error of the whole room decreases from 11.97 cm to 1.74 cm.

Numerical and experimental study of the size effect on deformation behavior and quality of microembossed multi-channel structures

With an uptrend of product miniaturization and precision manufacturing, the microembossing process of sheet metal has been widely used, and the corresponding researches have been conducted from the aspects of both experimental and theoretical explorations. Many unknowns, however, remain, such as size effect and it-induced scatters of deformation behaviors and product qualities. In this research, the multi-channel structures with various thicknesses made by a microembossing system using pure copper sheets were employed as case studies. The crystal plasticity finite element method simulations and experiments were conducted to study the effects of grain size and sheet thickness on the process and product of microembossing in terms of load-stroke relation, dimensional accuracy, and surface quality. From both the experimental and numerical results, it is revealed that the grain size effect causes deviated load and non-uniformity in deformation. The dimensional accuracy designated by the variations in thickness and height is affected by both grain size and sheet thickness. As grain size increases, the thickness reduction becomes more dramatic, and the thinnest location is at the corner zone. The height of the channel bottom increases with grain size, while the peak height fluctuation due to grain size is relatively minor. In addition, various surface defects on the surface of the embossed multi-channel structure were observed, including microvoids and micro scratches on the sidewalls, and wrinkles and grooves on the peak and bottom surfaces. From the inner to outer of the structures, microvoids gradually change to micro scratches, which become denser and longer as grain size increases in 100 μm thick copper sheets and also more severe with the increasing sheet thickness. All of these enrich the understanding of sheet metal microembossing and facilitate design solution generation in the optimization of the microembossing process and the quality of the embossed structures.

Experimental evaluation of the coefficients of thermal expansion in a composite laminate using digital image correlation

A procedure for measuring simultaneously the coefficients of thermal expansion (CET) in the in-plane and the thickness directions in L-shaped composite laminated samples is presented. Measurements are carried out using digital image correlation, from which the displacements in one of the faces of the samples are measured when de sample undergoes a temperature increment inside an oven. From the in-plane displacement measurements, the in-plane strain tensor components and the corresponding CTE are determined. Results show that the presented technique is capable of determining these CTE with high accuracy. Displacement measurements in the direction normal to the face, enables determining the rotation of the face and consequently the difference between the CTE in the thickness direction and the CTE in the in-plane direction affected by the curvature. Results obtained for the CTE in the thickness direction show, first, values significantly higher than the CTE of the material in the in-plane direction normal to the fibres and, second, a high dispersion from one stacking sequence to another. These discrepancies were expected and are caused by the misalignment of the fibres in the corner zone of the samples.

Prenatal Trimethyltin Exposure Induces Long-Term DNA Methylation Changes in the Male Mouse Hippocampus.

Trimethyltin (TMT) is an irreversible neurotoxicant. Because prenatal TMT exposure has been reported to induce behavioral changes, this study was conducted to observe gender differences and epigenetic changes using a mouse model. In behavioral testing of offspring at 5 weeks of age, the total times spent in the center, corner, or border zones in the male prenatal TMT-exposed mice were less than those of control unexposed mice in the open-field test. Female TMT-exposed mice scored lower on total numbers of arm entries and percentages of alternations than controls in the Y-maze test with lower body weight. We found that only TMT-exposed males had fewer copies of mtDNA in the hippocampus and prefrontal cortex region than controls. Additional epigenetic changes, including increased 5-methyl cytosine/5-hydroxymethyl cytosine levels in the male TMT hippocampus, were observed. After methylation binding domain (MBD) sequencing, multiple signaling pathways related to metabolism and neurodevelopment, including FoxO signaling, were identified by pathway analysis for differentially methylated regions (DMRs). Increased FOXO3 and decreased ASCL1 expression were also observed in male TMT hippocampi. This study suggests that sex differences and epigenetics should be more carefully considered in prenatal toxicology studies.

Study of the Bimetallic Joint CuCrZr/316L(N)

In this work, a study of the cases of destruction of the CuCrZr / 316L (N) bimetallic joint (BMJ) obtained by diffusion welding under conditions of hot isostatic pressing (HIP) was carried out. The identified defects are cracks propagating in the BMJ zone in the corner zone of the mock-ups of the heat-sink elements (HE). The analysis of the causes of destruction of the BMJ was carried out and the factors leading to the weakening of the BMJ zone are analyzed. The analysis of the thermal and stress-strain state of the HE mock-up during the manufacturing process was carried out. The study of the elements of the HE mock-up were carried out by methods of non-destructive testing (ultrasonic testing (UT)) and destructive testing (metallography; fractography; energy-dispersive X-ray spectroscopy; tensile tests). The inclusion of brittle phases in the zone of the BMJ was revealed and an assumption was made about the chemical composition of these phases. It was revealed that this line of brittle phases is a crack propagation zone in all cases of destruction of the BMJ in the HE mock-ups. The temperature range is revealed at which the effect of "ductility failure" of the CuCrZr is observed during the tensile testing of the samples.

Failure behaviors of 3D braided composites with defects in different locations under low-velocity impact compression

This paper aims to investigate the effects of the impurity defects in different locations on the transverse compressive behaviors of three-dimensional (3D) braided carbon fiber/epoxy composites under low-velocity impact. The composites with defects in different locations were prepared by placing polytetrafluoroethylene particles at the bottom surface, corner and center parts, respectively. The compression test was implemented with the drop-weight impact method. The failure morphologies were characterized using high-speed photography and micro computed tomography (Micro-CT). A mesoscale finite element model considering the defect was developed to enhance the physical understanding of the compression process. It is found that defects located at the corner zone and the central zone have a greater impact on the compression behavior of the 3D braided composite than the defect located at the bottom surface part. The defects at the corner and center zones reduce the compressive strength of the composite, increase the failure area, and cause severe damage to both the yarn and resin. In addition, the defect causes local stress concentration on the surrounding yarns. The defects in different locations cannot change the main shear failure mode of the 3D braided composite. It is shown that great attention should be given during the manufacturing or detection process to avoid such a deterioration effect of defects located in those zones on composite strength.

Zoning Lubricant Die Application for Improving Formability of Box-Shaped Deep Drawn Parts

The ‘formability’ of sheet metal is a major keyword referring to process design in the sheet metal forming industry. Higher formability could reflect lower production costs and time. Many studies have been carried out to improve formability in various ways, by using the finite element method and experimental approaches. In the present research, a new zoning lubricant technique is proposed. The stainless steel SUS304 square deep drawn box is used as an investigative model. Based on the material flow analysis, we found that zoning lubricant die application could reduce the difference in material flow velocity between wall and corner zones. This material flow characteristic resulted in decreased nonconcurrent plastic deformation during the deep drawing process, as well as decreased stretching in the cup wall and the delaying of the fracture. In the present research, the design of the zoning lubricant die was strictly concerned with achieving functionality related to the friction coefficient, area of zoning, and blank-holder pressure. A smaller friction coefficient positioned in the corner zone and larger friction coefficient positioned in the wall zone are recommended. It was revealed that, by appropriate zoning lubricant die application, formability could be increased in terms of box height by approximately 7 mm or 10%.

Provisions and comparison of Chinese wind load standard for roof components and cladding

This paper presents the main theoretical foundation and innovation of winad load provisions for wind loads on components and cladding in the newly-revised Standard for Wind Loads on Roof Structures (JGJ/T 481-2019). Generally, by introducing the concept of peak wind pressure coefficients, a more reasonable and convenient wind load determination for roof components and cladding can be obtained for structural designers. Moreover, based on extensive wind tunnel test data of external wind pressures on components and cladding of typical roofs, the corresponding peak external wind pressure coefficients are proposed, with more specific wind load zones. Regarding those large-span curved roofs, innovative external wind pressure coefficient values on detailed roof zones are firstly presented. In addition, according to comparisons, it is seen that the roof zones in the Chinese standard are similar to those in the Canada wind load code. The resulting peak external wind pressure coefficients in corner, edge and interior zones reach the international advanced level. Finally, optional three methods to determine peak wind pressure coefficient are also clearly specified, which are applicable to cases with different wind pressure time history lengths. All the development and improvement of the standard provide necessary supplement and reference for the international and Chinese wind-resisting design.

Study on the mechanism and therapeutic effect of Antelope horn treatment on cerebral ischemia reperfusion injury of mouse

To the mechanism and therapeutic effect of Antelope horn treatment on cerebral ischemia reperfusion injuries under different levels of concentration. The process is as follows: (1) establish MCAO mouse model, test the modelling using traction and open field experiments, use TTC staining to detect the protective effect of Antelope horn treatment on cerebral ischemia reperfusion injury; (2) after 48 h of MCAO, use Nissl staining to measure the extent of hippocampal neuron damage in each group. The hippocampus corner 1 sector and dentate gyrus corner zone of hippocampal neurons of ischemia reperfusion group mouse suffered severe damages under Nissl staining detection. However, the hippocampal neurons of the medicated mouse show obvious alleviation. Western Blot results showed that, compared to the ischemic control group, the Bcl-2, Hsp 27, Hsp 27 expressions of the medicated group were significantly increased, while the Bax expression was dramatically reduced. Immunofluorescence outcome showed obvious reduction of TUNEL and FJB positive cells in the medicated group. That Antelope horn can reduce focal cerebral ischemia reperfusion injury. The reduction of degeneration and apoptosis suggests the correlation between the therapeutic effect of Antelope horn on ischemia reperfusion injury and its anti-apoptotic protective effect.

Amygdala dynorphin/κ opioid receptor system modulates depressive-like behavior in mice following chronic social defeat stress.

Major depression disorder is a severe and recurrent neuropsychological disorder characterized by lowered mood and social activity and cognitive impairment. Owing to unclear molecular mechanisms of depression, limited interventions are available in clinic. In this study we investigated the role of dynorphin/κ opioid receptor system in the development of depression. Mice were subjected to chronic social defeat stress for 14 days. Chronic social defeat stress induced significant social avoidance in mice characterized by decreased time duration in the interaction zone and increased time duration in the corner zone. Pre-administration of a κ opioid receptor antagonist norBNI (10 mg/kg, i.p.) could prevent the development of social avoidance induced by chronic social defeat stress. Social avoidance was not observed in κ opioid receptor knockout mice subjected to chronic social defeat stress. We further revealed that social defeat stress activated c-fos and ERK signaling in the amygdala without affecting the NAc, hippocampus and hypothalamus, and ERK activation was blocked by systemic injection of norBNI. Finally, the expression of dynorphin A, the endogenous ligand of κ opioid receptor, was significantly increased in the amygdala following social defeat stress; microinjection of norBNI into the amygdala prevented the development of depressive-like behaviors caused by social defeat stress. The present study demonstrates that upregulated dynorphin/κ opioid receptor system in the amygdala leads to the emergence of depression following chronic social defeat stress, and sheds light on κ opioid receptor antagonists as potential therapeutic agents for the prevention and treatment of depression following chronic stress.

Numerical investigation of plastic flow and residual stresses generated in hydroformed tubes

During tube hydroforming process, the friction conditions between the tube and the die have a great importance on the material plastic flow and the distribution of residual stresses of the final component. Indeed, a three-dimensional finite element model of a tube hydroforming process in the case of square section die has been performed, using dynamic and static approaches, to study the effect of the friction conditions on both plastic flow and residual stresses induced by the process. First, a comparative study between numerical and experimental results has been carried out to validate the finite element model. After that, various coefficients of friction were considered to study their effect on the thinning phenomenon and the residual stresses distribution. Different points have been retained from this study. The thinning is located in the transition zone cited between the straight wall and the corner zones of hydroformed tube due to the die–tube contact conditions changes during the process. In addition, it is clear that both die–tube friction conditions and the tube bending effects, which occurs respectively in the tube straight wall and corner zones, are the principal causes of the obtained residual stresses distribution along the tube cross-section.

МОДЕЛЬ КРИТЕРИЯ ТРЕЩИНОСТОЙКОСТИ И ПРОЧНОСТИ ПЛОСОКНАПРЯЖЕННЫХ КОНСТРУКЦИЙ ИЗ ВЫСОКОПРОЧНОГО ФИБРОБЕТОНА И ФИБРОЖЕЛЕЗОБЕТОНА

A variant of the crack resistance criterion and the strength criterion of plane-stressed structures made of high-strength fiber-reinforced concrete, fiber-reinforced concrete is proposed. The criteria are based on the theory of plasticity of concrete and reinforced concrete G.A. Genieva. In general, the condition for crack resistance of a plane-stressed fiber-reinforced concrete element is presented in the form of an ellipse with jumps on the coordinate axes of the main reduced stresses. The strength condition of a fiber-reinforced concrete element is described by a complex figure that takes into account cracking in the element under a plane stress state. The characteristic points on the coordinate axes are calculated from the physical and mechanical characteristics of concrete strength, obtained as a result of testing high-strength fiber-reinforced concrete for uniaxial compression and uniaxial tension with “dissolved” fiber in the concrete body and reinforcement reduced to concrete. The results of a comparative analysis of the criteria for crack resistance and strength of high-strength concrete and high-strength fiber-reinforced concrete are given, depending on the percentage of fiber in the concrete body and the type of fiber used. The proposed analytical dependences can be used to analyze the crack resistance and strength of plane-stressed reinforced concrete beams-walls reinforced with fiber, corner zones of shallow shells and other plane-stressed structures made of high-strength fiber-reinforced concrete and fiber-reinforced concrete.

Features of the stress-strain state in the corner zones of structures

Corner regions of structures are characterized by a complex stress-strain state (SSS), caused by both the shape of the boundary or the “geometric factor”, and the finite rupture of the specified forced deformations, mechanical properties that go to the contact surface of the elements of composite structures. The relevance of the work consists in the analysis of local SSS in the corner zone of the region boundary with various study approaches: theoretical, experimental. For the theoretical analysis of the SSS of the region, we consider the resolving system of equations of the problem of the theory of elasticity in the zone of the cutout of the boundary and elements of the similarity theory; the photoelasticity method is used for experimental studies. An experimental solution was obtained on polymer composite models with an angle cut of the boundary under the action of forced deformations in one of the regions. The analysis of possibilities of theoretical, experimental approaches of SSS studies in zones with irregular point of border allows to reveal zones of applicability of solutions of linear elasticity problem.

Experimental research on deformation and dimensional accuracy of rectangular-section tubular part during open die hydro-pressing process

To solve the problems involving in the open die hydro-pressing process, such as different corner radii and bigger dimensional deviation, an open die hydro-pressing process was proposed and an experiment was conducted on hydro-pressing process of DP590 steel tubular part with rectangular-section. The effects of pressing sequence and supporting pressure on cross-sectional shape and corner filling were discussed. An analysis was conducted to reveal the reason for uneven deformation of the section corners. It is illustrated that the values of corner radii of the tubular part are obviously different under the condition of one pressing step, and the corner nearby the fixed die is larger than that nearby the pressing punch. The reason is that a difference exists in the circumferential force between the four corners due to the existence of the friction, which results in the uneven deformation on the section corner zone. The deviation of the cross-sectional dimension can be effectively improved by multi pressing steps, but too great a number of pressing steps also reduces the forming efficiency. Under the condition of two pressing steps, a rectangular-section tubular part with high dimensional accuracy was obtained by a reasonable pressure loading path. Its relative corner radius is only 2.5, which exceeds the limiting value of that formed by conventional tube hydroforming.

Wind loads on low-slope roofs of buildings with large plan dimensions

Wind load provisions in the North American codes and standards incorporate the results of wind tunnel studies and the full-scale measurements of wind loads. These studies examined wind effects on buildings with regular plan size, i.e. less than 60 m. This fact emphasizes the importance of testing large buildings in the wind tunnel and highlights the necessity of investigating the applicability of the North American code and standard provisions to large buildings. In the present study, three building models were constructed at a length scale of 1:400 with identical plan dimensions (equivalent to 118 m × 118 m) and different heights (equivalent to 5 m, 10 m and 20 m). The models were tested in simulated open country and suburban exposures. The experimental results were compared with full-scale data and the wind provisions of the North American codes and standards. It was found that the external peak pressure coefficients recommended by ASCE 7-16 (2017) are much higher than the experimental findings whereas those recommended by ASCE 7-10 (2010) are consistent with the experimental results. However, the experimental results indicate that the corner zone should be better defined as an L-shape for large buildings of 8 m height or more and the wind loads developed on the roof corner are approximately equal to those on the edge zone for large buildings of height less than 8 m.

Assessment of the pit influence area on the stress state foundations of the nearby buildings

The article solves the problem of the stress state of a heavy half-plane, weakened by a semicircular recess (modeling a foundation pit) and under the influence of a uniformly distributed load (modeling weight from a nearby building). The solution was obtained in a closed form. Visual calculations results in the form of diagrams and isolines of the total voltage are presented. The resulting solution made it possible to consider two practical problems. In the first statement, to assess the pit parameters’ influence on the components of the additional voltage in the corner zone of the distributed load. In the second statement, to assess the distance influence from the pit to the load on the additional voltage components. The analysis of the obtained solutions is carried out. The quantitative character of the change in the additional stress components, on which the dimensions of the influence zone of the construction pit and the existing buildings foundations’ deformation is of particular practical interest.

Experimental Studies on the Stress-Strain State under Drawing Aluminum–Copper Bimetal Parts Rectangular in Plan

The stress-strain state has been studied for a flange of a semiproduct made of an aluminum–copper bimetal under drawing boxes rectangular in plan. These studies are carried out using a grid method, assuming that the material is isotropic and incompressible; the deformation within each cell is uniform; the deformation occurs monotonically; and the stressed state is plane and the deformed state is bulk, but the elastic deformations are negligible. In order to minimize the measurement errors of coordinate grids and reduce the time required for processing information, a CAD software package is used for simulation The billets are rectangles with explosion-welded A4 aluminum and a M4 copper layers subjected to preliminary heat treatment before the operation of drawing. The rectangular billets have been successively drawn to a height of 10 mm; after drawing, the grid and the thickness of the sample under study are measured. The samples of billets have been photographed at an identical focal length and loaded into the application program. In the program, coordinate points are applied to the grid nodes to measure the distances and coordinates of these points before and after deformation. The measurement results show that the greatest deformation is experienced by the corner zones of the billet, where the compressive stresses exhibit an increase from the angle bisector to the walls. These stresses lead to bimetallic billet delamination, as well as to occurring corrugations throughout the copper layer. The drawing is performed for 20 billets and, in each case, the corrugation on the flange surface is observed. Varying the clamping pressure in the range from 0.25 to 0.5 MPa does not lead to any positive results. The end part of the box flange experiences the greatest strain rate, whereas, when approaching the matrix hole, the strain rate exhibits a 20% decrease. The action of angular shear stresses leads to transition-zone discontinuity, which is characterized by the presence of an intermetallic layer having reduced plastic properties.

Korean Red Ginseng reduces chronic social defeat stress-induced mood disorders via N-methyl-D-aspartate receptor modulation in mice

BackgroundA chronic social defeat stress (CSDS) model has been proposed as relevant to stress-induced behavioral change in humans. In this study, we examined the effect of Korean Red Ginseng (KRG) on CSDS-induced mood disorders and protein expression in an animal model. MethodsTo evaluate the effect of KRG on social defeat stress, test mice were exposed in the resident aggressor's home cage compartment for 14 days beginning 1 h after KRG treatment (10, 20, and 40 mg/kg, per oral (p.o.)). After the exposure, behavioral tests to measure anxiety, social interaction, and depression-like behavior were performed. To investigate the underlying mechanism, N-methyl-D-aspartate receptor expression levels in CSDS-induced mice were evaluated using Western blot analysis. ResultsCSDS induced anxiety-like behaviors by decreasing central activity in the open-field test and open-arm approach in the elevated plus maze test and led to social avoidance behavior in the social interaction test. CSDS mice showed upregulated NR1, NR2A, and NR2B expression in the hippocampus. KRG 20 and 40 mg/kg ameliorated anxiety-like activities and KRG 20 mg/kg alleviated social avoidance by decreasing time in the corner zone. KRG treatment recovered CSDS-induced NR1, NR2A, and NR2B protein levels in the hippocampus. ConclusionThese results indicate that KRG has a therapeutic effect on CSDS-induced mood disorder by alleviating N-methyl-D-aspartate receptor overexpression in the hippocampus.

Control and Entropy Analysis of Corner Flow Separation in a Compressor Cascade Using Streamwise Grooves

Flow separation, which often occurs at the junction of blades and endwalls and seriously limits the aerodynamic performance of turbomachinery, is caused mainly by the boundary layer mixing on the blades and endwall surfaces and the transverse secondary flow. Focusing on a linear diffusion cascade with 42° turning angle, the transverse secondary flow is found to be the dominant factor for flow separation, based on detailed analysis. Therefore, controlling the secondary flow to reduce the flow separation is very important. Based on the investigations, the flow separation can be controlled by cutting off the secondary flow. Therefore, nine kinds of streamwise grooves were designed and analyzed herein. Grooves at the endwall substantially inhibited the transverse secondary flow, but the flow structure varied over different spans. An optimum combination of groove width and height was identified, with the height being more important. A detailed flow analysis of the best scheme (with a smaller width and moderate height) was conducted. The loss reduction mechanism was obtained by 3D flow field and entropy analysis. This configuration can reduce the corner zone separation effect, energy loss coefficient, and flow loss.