• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.627-634
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• 2004

The purpose of this study is to investigate seismic performance of a bearing wall system for apartment buildings. An 1/3 scale three-story specimen was constructed and tested under cyclic lateral loads. The specimen was consisted of pierced walls and coupling elements as well as floor slabs. The bearing wall system is considered to have a adequate deformation capacity up to $2.0\%$ of roof drift ratio, and the experimental results showed the ductile load-deformation characteristics even though some walls were failed in shear Nonlinear analysis was peformed to compare the load-deformation curve obtained from the experimental program. The result of nonlinear analysis could be useful to predict the actual behavior characteristics of the bearing wall system subjected to lateral loads.

• Journal of Environmental Health Sciences
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• v.36 no.2
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• pp.95-107
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• 2010

Hand-washing is one of the major factors in personal hygiene and public health. This study was undertaken to investigate the hygienic behavior of food-service employees, focusing on awareness of hand washing, hand washing practices, and the load of index microorganisms (aerobic plate count, total and fecal coliforms, Escherichia coli, and Staphylococcus aureus) on the hands of food-service employees. A questionnaire survey completed by direct interview, direct observation of restrooms by the researcher and trained observers, and microbiological examination according to the Food Code of Korea were carried out. In the survey, a positive attitude toward hand washing compliance was reported; however, improper hand washing and poor hand hygiene of the food-service employees were seen under direct observation. Significant differences (p<0.05) were found between the questionnaire survey and the direct observations in hand washing compliance after using the toilet, duration of hand washing, use of hand washing agents, use of hand washing tools, washing of different parts of the hands, hand-drying method, temperature of water, and method of turning off the water. Samples taken from employees' hands before washing showed higher levels of bacteria than those taken during work and/or after washing (p<0.05). Poor hand washing practices were indicated by the positive results for total and fecal coliforms, E. coli, and S. aureus on the hands of some food-service employees. This study showed that there is a marked difference between the food-service employees' awareness of hand-washing and their actual hand-washing practices. The poor hand hygiene of and improper hand washing by the food-service employees should be addressed for improved food safety.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.5-15
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• 2017

Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile. Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1~0.4D (50~200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.55-66
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• 1991

Presented is a study on the realistic determination of design loads and design criteria for bridge structures. The current bridge design code does not consider realistically the uncertainties inherent in loads and resistances and thus the level of safety varies greatly among the bridge spans. The resonable bridge design loads and design criteria which exhibit uniform reliability among various bridge spans are therefore derived in the present paper. The proposed design loads are determined from the analysis of numerous data obtained from actual traffic survey and the design criteria are based on the advanced concept of load and resistance factor format. The live load factors take into account resonably the effects of traffic volume increase. The proposed design loads and design criteria show uniform safety level for various bridge spans and reasonably consider the effects of traffic volume increase. The present study provides useful and valuable data for new version of our bridge design code.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1221-1229
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• 2014

This paper proposes an approach for predicting the fatigue life of a propeller shaft of a forklift truck by an accelerated life test method. The accelerated life test method adopted in this study is the calibrated accelerated life test, which is highly effective in the prediction of the lifetime and enables significant reduction of the test time as well as a quantification of reliability in the case of small sample sizes. First, the fatigue test was performed under two high stress levels, and then, it was performed by setting low stress levels in consideration of the available test time and extrapolation. Major reliability parameters such as the lifetime, accelerated power index, and shape parameter were obtained experimentally, and the experimentally predicted lifetime of the propeller shaft was verified through comparison with results of an analysis of load spectrum data under actual operating conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1105-1112
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• 2013

In this study, a method for predicting heating loads using building characteristic coefficients is proposed for heating system control, and a method for predicting hourly temperature and solar insolation, which mainly affect building heating loads, is also proposed. The temperature and solar insolation are predicted by using a fuzzy theory from forecast information at the meteorological agency, and the building characteristic coefficients for the prediction of heating loads are derived from EnergyPlus. The simulated heating loads of the present study show good agreement with those of EnergyPlus. and the variations of the predicted heating loads using the predicted temperature and solar insolation are similar to those using the actual weather data.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.847-852
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• 2006

A fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that applies heat in the outer diameter of a gear to a suitable range under the tempering temperature and assembles the gear and the shaft made larger than the inner radius of the gear. Its stress depends on the yield strength of a gear. Press fitting is a method that generally squeezes gear toward that of a shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of a shaft. A warm shrink fitting process for an automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by the process produced dimensional change in both outer diameter and profile of the gear so that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of a warm shrink fitting process in which design parameters such as contact pressure according to fitting interference between outer diameter of a shaft and inner diameter of a gear, fitting temperature, and profile tolerance of gear are involved. In this study, an closed form equation to predict the contact pressure and fitting load was proposed in order to develop an optimization technique of a warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, thermal-structural coupled field analysis. Actual loads measured in the field have a good agreement with the results obtained from theoretical and finite element analysis and also the expanded amounts of the outer diameters of the gears have a good agreement with the results.

• Journal of Power Electronics
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• v.11 no.2
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• pp.194-201
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• 2011

The air flow supplied to a fuel cell system is one of the most significant factors in determining fuel efficiency. The conventional method of controlling the air flow is to fix the oxygen supply at an estimated constant rate for optimal efficiency. However, the actual optimal point can deviated from the pre-set value due to temperature, load conditions and so on. In this paper, the maximum efficiency point tracking (MEPT) algorithm is proposed for finding the optimal air supply rate in real time to maximize the net-power generation of fuel cell systems. The fixed step MEPT algorithm has slow dynamics, thus it affects the overall efficiency. As a result, the variable step MEPT algorithm is proposed to compensate for this problem instead of a fixed one. The complete small signal model of a PEM Fuel cell system is developed to perform a stability analysis and to present a design guideline. For a design example, a 1kW PEM fuel cell system with a DSP 56F807 (Motorola Inc) was built and tested using the proposed MEPT algorithm. This control algorithm is very effective for a soft current change load like a grid connected system or a hybrid electric vehicle system with a secondary energy source.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.5
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• pp.635-638
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• 2003

Japanese Black cattle (Wagyu) are fed for a long period to produce high quality beef, however, extended feeding often causes inefficiency and greater environmental load mainly derived from their manure. The objectives of this study were to analyze changes in feeding length by listing breeding values (BVs) at calf markets and the relationships between BVs and carcass characteristics of 4,052 Japanese Black cattle, and to examine the feasibility of optimizing feeding length by referring to listed BVs. BV classes A, B, and C were defined based on BVs of cows in Shimane Prefecture as follows: an upper quarter of BVs was classified as A, a second quarter as B, and under the average as C. For cattle sold at calf markets in the first term of 1996, just before the start of BV listing, the feeding length of cattle with class B BVs for the beef marbling standard (BMS) was longer (p>0.05) than that of class A cattle. However, in the second term of 1996, just after the start of BV listing, the feeding length of class B cattle became shorter (p<0.001) than that of class A cattle. Then, the feeding lengths of both classes showed no significant differences. Feeding lengths of both class A and B BVs for carcass weight (CW) changed similarly to the corresponding BV classes for BMS. The analysis of the relationships among the listed BV classes and the actual carcass characteristics showed that class A cattle had a higher (p<0.001) BMS than class B cattle, and that the higher-class cattle had a heavier CW (p<0.05). On the basis of previous reports, the cattle, particularly those with lower genetic marbling ability, seem to only increase marbling at markedly low efficiency for a few months before slaughter. Therefore, the finding that carcass characteristics corresponded to their class of BVs suggests that an optimum feeding length based on listed BVs not only increases the efficiency of beef production, but also reduces the environmental load.

• Wind and Structures
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• v.25 no.1
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• pp.63-77
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• 2017

When railway vehicles run by towers of long span bridges, the railway vehicles might experience a sudden load-off and load-on phenomenon in crosswind conditions. To ensure the running safety of the railway vehicles and the running comfort of the passengers, some studies were carried out to investigate the impacts of sudden changes of aerodynamic loads on moving railway vehicles. In the present study, the aerodynamic coefficients which were measured in wind tunnel tests using a moving train model are converted into the aerodynamic coefficients in the actual scale. The three-component aerodynamic loads are calculated based on the aerodynamic coefficients with consideration of the vehicle movement. A three-dimensional railway vehicle model is set up using the multibody dynamic theory, and the aerodynamic loads are treated as the inputs of excitation varied with time for kinetic simulations of the railway vehicle. Thus the dynamic responses of the railway vehicle passing by the bridge tower can be obtained from the kinetic simulations in the time domain. The effects of the mean wind speeds and the rail track positions on the running performance of the railway vehicle are discussed. The three-component aerodynamic loads on the railway vehicle are found to experience significant sudden changes when the vehicle passes by the bridge tower. Correspondingly, such sudden changes of aerodynamic loads have a large impact on the dynamic performance of the running railway vehicle. The dynamic responses of the railway vehicle have great fluctuations and significant sudden changes, which is adverse to the running safety and comfort of the railway vehicle passing by the bridge tower in crosswind conditions.