• Journal of Applied Reliability
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• v.17 no.2
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• pp.112-121
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• 2017

Purpose: The most previous works on designing accelerated life tests (ALTs) are focused on the application of a single stress. Because of the difficulty to obtain the sufficient information in a reasonable duration using single stress only, there is needed in practice to use multiple-stress ALTs frequently. This paper presents new practical plans with two stresses for Weibull distribution. Methods: The four-level practical plans based on rectangle test region are proposed and compared with the corresponding three-level statistically optimal plans. Sensitivity analyses for assumed design parameters and life-stress relationship are conducted. Results: A procedure to choose practical ALT plans is illustrated with a numerical example and guidelines for planning two-stress ALTs are provided. Conclusion: The proposed two-stress ALT plans on practical constraints to assess a quantile of Weibull lifetime distribution at the use condition are efficient and robust.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.143-150
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• 2003

This study deals with the stress-strain-strain rate behaviour of overconsolidated clay. Consolidated-drained stress path tests were performed on the stress-time dependent condition. Stress history consists of rotation angle of stress path, overconsolidation ratio, and magnitude of length of recent stress path. Time history includes loading rate of recent and current stress path. Test results show that all influence factors have an increasing strain rate with time, and the strain rate varies with the change of the rotation angle of stress path. With the increase of overconsolidation ratio and loading rate of current stress path, the strain rate also increases. For the stress history, correlation between stress-strain and strain rate is indicated but the time history is not.

• Journal of Oral Medicine and Pain
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• v.23 no.4
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• pp.309-326
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• 1998

In general, the major causative factor of halitosis is thought to be a sulfated compounds. Clusterin, a sulfated glycoprotein-2(SGP-2), is frequently found in diabetic conditions and cold stress conditions. The same result is werum glucose level to diabeteic and cold stress conditions that founded Clusterin. Therefore, this study was performed to examine Clusterin in the slivary glands under stress conditions before insulin injection I.M. Fourty rats were diveded into 3 groups ; 1) 10 rats of gorup I were selected as a control 2) 15 rats beloning to group II were bathed in cold water for 30 seconds twice a day 3) 15 rats in group III received cold stress and injected I.M. with insulin. The rats were sacrifeced at day 0, 3, 5, 7 and 10 of the experiment and the submandibular glands and parotid galnds were removed. RNAs were purified from the salivary of the salivary glands were subjected to Hematoxillin-Eosin stainings and examined under the light microscope. The obtained results were as follows : 1. With immunohistochemistric method, in normal control goup, Clusterin was moderately stained in the intercalated ductal cell of the submandibualr glands, mild stained in the striated ductal cell of the submandibular glands, heavily stained on the cytoplasm of the intercalated ductal cell in the mucous submandibular glands nad slightrly stained in the intercalated ductal cell of the paroted gland, expressed negativity in the acina cell. 2. With immunohistochemistric method, Clusterin slightly increased in the acina cell of the submandibular glands under stress condition at 3 days after experement, moderately stained at 5 days after experiment so revealed positive response. And hearily in the intercalated ductal cell and mildly lin the acina celluar eytoplasm of the parotid glands under stress condition at 3 days experiment. 3. With immunohistochemistric method, no remarkable differences are found between the normal control group and stress conditioned group that insulin administration was performed before. 4. In the stressor-giving group, Clusterin mRNA was porminently expressed in submandibular gland after 5 days after experiment, in parotid gland after 3 days after experiment, performed in immunoelectrophoresis method. 5. In the insulin-injected nad stressor-giving group, Clusterin mRNA was not observed in all experimental submandibular and parotid gland, performed in immunoelectrophoresis method.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.237-248
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• 2000

Based on the preliminary results from the therm analysis, which is currently carrying, three-dimensional computer simulations using a finite element code, ABAQUS Ver. 5.8, were designed to determine the mechanically stable cavern and deposition hole spacing. Linear elastic modeling for the cases with different cavern and deposition hole spacing were carried out under three different in situ stress conditions. From the simulations, the response of the rock to the stress redistribution after the excavation of the openings could be investigated. Also the optimum cavern and deposition hole spacing could be estimated based on the factor of safety. When the in situ stress determined from the actual stress measurements in Korea were used, the case with cavern spacing of 40m and deposition hole spacing of 3m was in very stable condition, because the factor of safety was calculated as 3.42., When the in situ stress conditions for Sweden and Canada were used, the previous case, they seem to be in stable condition, since the factors of safety are still higher than 1.0. From these results, it was concluded that the rock will not fail even after the stress redistribution.

• Journal of Korean Academy of Nursing
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• v.14 no.1
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• pp.1-20
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• 1984

This study was attempted to evaluate and explain the correlation between stress and utilization of Dispensary, Frequency of absence, Frequency of accident as the health condition of bluecollared workers. The subjects for this study were 260 workers selected conveniently from 360 workers working at one chemical manufacturer located in Seoul. The dataas measure the Stress was collected through SRRS (The Social Readjustment Rating Scale) which is developed by Holmes ＆ Rahe (1976) from 27th July to 10th August, 1983. The data of Utilization of Dispensary and Frequency of Accident were brought out from the record of Dispensary during past 8 months. The Frequency of Abscence from January to August were collected through diligence and indolence cards of each department. All collected data were analysed based on the SPSS (Statistical Package for the Social Science) program. The results of the study are as follows: 1. The average of Utilization of Dispensary was 7.4, Frequency of abscence 14.6, frequency of Accident 0.4. 2. The average score of Stress was 134 (minimum : 0, maximum : 593, Standard deviation : 109. 3) It can be considered as a slight stressed group by the requlations of Holmes and Rahe. 3. According to the analysed results of correlation between Stress and the Utilization of Dispensary, Frequency of Absence, frequency of Accident, the Utilization of dispensary and stress were significantly related (r= .1955, p<.001), the Frequency of Absence (r=.0284, p >, 05), and the Frequency of Absence (r=.0284, p>.05), and the Frequency of Accident (r= .0831, p>.05) were not significantly related with Stress. 4. In the relation between general characters of subjects and the Utilization of Dispensary, 20 to 25 aged group, women, single, christian, lent-house dwelling, 1 to 5 years employed group used at a high ratio. 5. In the relation between general character of subjects and the Frequency of Absence, men, 51 to 55 aged group, 21 to 25 years employed group indicated high Frequency, and other char-noters were not significantly related. 6. In the relation between general characters of subjects and the Frequency of Accident, women. single, 20 to 25 aged group, catholic, lent-house dwelling, below 1 year employed group showed high frequency. 7. Stress showed a significant difference only with a religion. Catholic group represented mode-rate stressed scored 209.67, and not significantly related with other general characters.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.1
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• pp.37-53
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• 2006

Purpose: The purpose of this study was to investigate the influences of the jaw dimension on the bone stress. Materials and Methods: Root analogue implant of Frialit-2 Synchro model in the jaw bone of various thickness from 8mm to 13mm were modelled axisymmetrically for a series of finite element analyses. As load conditions, non-axisymmetric lateral load of 20N and an oblique load of 50N, as well as an axisymmetric vertical load of 50N were taken into consideration. Results: The cervical area of implant under the axisymmetric load and the base cortical bone under the non axisymmetric load condition were the areas of main concern where the higher level of stress were likely to be obtained. Conclusion: The results indicated that at the two concerned areas drastically different stress distribution could take place as a function of the load conditions. Under the vertical load, the lower level of stress was observed for the narrow jaw bone at the cervical cortical bone whereas stress at the base cortical bone remained virtually unchanged. Under the non axisymmetric load condition, however, the stress at the base cortical bone increased very rapidly as the jaw bone width increased without inducing any significant change in the stress level at the cervical area.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.5-15
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• 2011

In this study, centrifuge model tests were performed to investigate stress concentration ratio, stress characteristics of soft clay ground improved by granular compaction piles with changes of piles type, loading condition and area replacement ratio. From the results of rigid loading tests, while vertical stresses acting on clay ground is similar, vertical stresses acting on GCP is larger than those acting on SCP with same replacement ratio. Also, average stress concentration ratio is increased proportionally with increasing the area replacement ratio of GCP and SCP. It was evaluated that average stress concentration ratio of soft clay ground improved by GCP is larger than that of SCP. As a result of flexible loading tests, stress concentration ratio is the highest when replacement ratio of GCP and SCP is 40%. Average stress concentration ratio of soft clay ground improved by GCP is a little more higher than is improved by SCP.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.332-337
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitative evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and friction condition on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the heights of the boss and rib. In addition, the effect of flow stress was also investigated on the deformation patterns through FE simulations.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.132-135
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• 2004

High-performance concrete (HPC) may be expected to differ from usual concrete with respect to shrinkage behavior, and it shows high autogenous shrinkage due to the use of very low water-binder ratio (w/b) and various admixtures. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structure, volumetric change of HPC should be understood. In this study, small prisms made of HPC with w/b of 0.32 and blast-furnace slag content of $0\%,\;30\%,\;and\;50\%$ were prepared to measure the volumetric changes such as autogenous shrinkage, drying shrinkage, and swelling under three different curing conditions. It was observed that the concrete cured. sealed condition showed only autogenous shrinkage while the concrete let to dry condition at temperature of $20^{\circ}C$ and relative humidity of $60\%$ during the test period showed both autogenous and drying shrinkage. Moreover, the concrete exposed to dry condition after 2-day water curing swelled and then started to shrink with age. The total shrinkage (autogenous+drying) of this concrete was smaller than that of the concrete cured dry condition, especially at early-age. Therefore, the early-age moisture curing is very effective to control or minimize the volumetric change and its induced stress of HPC.

• International journal of advanced smart convergence
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• v.11 no.1
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• pp.94-100
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• 2022

It is common for commercial vehicles to make the top part according to the use after making the bear chassis, and to connect various devices with the bear chassis. Various brackets used in bear chassis for the development of all automobiles, including commercial vehicles, play a role of connecting the components required for driving and operating the car to the car body. In commercial vehicles, components necessary for operation are installed in the bear chassis; that is, the bear chassis of commercial vehicles is a space where the devices required for driving and operating the vehicle are installed. The devices required for the configuration of the vehicle are drive, brake, exhaust and steering, etc. These devices are basically connected to the body, the front axis, or the rear axis. The part interlinking the apparatuses required for the vehicle drive to the car body or axis is bracket. In this study, we analyzed the boundary conditions to evaluate the stability of the three brackets that connect the components of the car to the front axis of the new type of 30-seater bus in the development process. In order to analyze the boundary conditions, the boundary conditions according to the driving condition of the vehicle were classified. For stress analysis to evaluate the stability of brackets according to the driving state of the vehicle, it is reasonable to give the bracket a boundary condition of harsh conditions.