• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.81-91
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• 2013

A novel design process of a parallel multi-flow type air-cooled condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated focusing on reduction of the pressure drop inside the micro-tubes. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently. However, the refrigerant has low evaporation temperature enough to recover the waste from engine coolant of about $100^{\circ}C$ but has small saturation enthalpy so that excessive mass flow rate of the LT working fluid, e.g., over 150 g/s, causes enormously large pressure drop of the working fluid to maintain the heat dissipation performance of more than 20 kW. This paper has dealt with the scheme to design the low temperature condenser that has reduced pressure drop while ensuring the required thermal performance. The number of pass, the arrangement of the tubes of each pass, and the positions of the inlet and outlet ports on the header are most critical parameters affecting the flow uniformity through all the tubes of the condenser. For the purpose of the performance predictions and the parametric study for the LT condenser, we have developed a 1-dimensional user-friendly performance prediction program that calculates feasibly the phase change of the working fluid in the tubes. An example is presented through the proposed design process and compared with an experiment.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.320-330
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• 2018

Purpose: The aim of this study was to investigate the harvesting performance of a prototype small combine for buckwheat and adlay. Methods: The prototype small combine was designed and constructed. Its ratio of grain loss, ratio of output components in the grain outlet, and field capacity for harvesting buckwheat and adlay were analyzed through field tests. Results: The prototype small combine required a working width of about 0.6 to 0.7 m to harvest buckwheat. The maximum travel speed was about 0.36 m/. The total ratio of grain loss was about 21.6%, which consisted of 8.8% at the header and 12.8% at the dust outlet. The grain and the material other than grain (MOG) ratios at the grain outlet were 94.1% and 5.9% respectively. In the case of adlay harvest, the maximum working width was about 1.2 m, that is, two rows. The range of maximum travel speed was about 0.45 to 0.46 m/s. When adlay was harvested in one row, the total ratio of grain loss ranged from 36.3 to 42.8% according to the cutting height. The cutting height of 30 cm resulted in a higher total ratio of grain loss than 60 cm and 90 cm. When the cutting height was 60 cm, there was no significant change in the total ratio of grain loss according to the number of working rows and the stage of the primary transmission shift. The total ratio of grain loss ranged from 35.2 to 37.7%. The grain and the MOG ratios at the grain outlet ranged from 93.1 to 95.8% and from 4.2 to 6.9%, respectively. No significant difference was observed in relation to cutting height, number of working rows, and the stage of the primary transmission shift. Conclusions: The prototype small combine for harvesting miscellaneous cereal crops showed good potential for the efficient harvesting of buckwheat and adlay. However, to improve the harvesting performance, there seems to be a need to develop new crop varieties suitable for machine-based harvesting and improve the transmissions, reels, separation/cleaning systems.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.2
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• pp.13-21
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• 2023

In the recent era of the fourth industrial revolution, many industries aim to maximize the efficiency of products and services by introducing cutting-edge technologies such as artificial intelligence and big data. In this situation, organizational culture is changing a lot due to the influx of the MZ generation with strong individualistic tendencies and the decreased face-to-face communication between members. However, active communication with colleagues is still essential to maximize performance, and the margins created by simplifying work processes and automating processes must be used for creating work performance. This requires cooperation and commitment through the job immersion of members who have an active attitude. This study analyzed how the organization's autonomous work environment and trust among members, which are creative work performance conditions, affect job immersion using raw data from the Occupational Safety and Health Research Institute. As a result, it was found that both the organization's autonomous working environment and trust among members significantly effected the members' job immersion. in order to achieve productivity and value improvement in companies, efforts are needed to increase workers' job immersion by building an autonomous working environment and trust among members. The results of this study are expected to contribute significantly to the search for ways to increase workers' job commitment to improve organizational productivity.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.318-327
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• 2002

In this paper, heat transfer and pressure oscillation characteristics on oscillating capillary tube heat pipe(OCHP) according to input heat flux, mixture ratio of working fluid and inclination angle were investigated and were compared single working fluid(R-142b) with binary mixture working fluid(R-142b-Ethano1). OCHP was made to serpentine structure of loop type with 10 turns by drilling the channels of length 220mm, width 1.5mm, and depth 1.5mm on the surface of brass plate. In this study, R-l42b and R-l42b-Ethanol were used as working fluids, the charging ratio of working fluids was 40(vol.%), the input heat flux to evaporating section was changed from 0.3W/㎠ to 1.8W/㎠, and mixture ratio of working fluid was R(100%), R(95%)-E(5%), R(90%)-E(10%), and R(85%)-E(15%). From the experimental results, it was found that the effective thermal conductivity of single working fluid was better than that of binary mixture working fluid. But, in case of binary mixture working fluid, critical heat flux was higher than that of single working fluid. And, the higher the mixture ratios of working fluid, the lower heat transfer performance. In case of pressure oscillation, as the inclination angle was lower, pressure wave was more irregular. These phenomena were more serious when the working fluid was binary mixture. Besides, when mixture ratio was higher, saturated pressure was increased, more irregular wave was observed and the mean amplitude was increased. For the same input heat flux, inclination angle and charging ratio, when pressure oscillation has sinusoidal wave, mean amplitude was small, and saturated pressure was low value, the heat transfer was excellent.

• The Journal of Economics, Marketing and Management
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• v.2 no.1
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• pp.18-28
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• 2014

In this research we investigate the effect return on assets, return on equity, profit margin and earnings per share on working capital management. Current ratio and quick ratio used as proxies for working capital management. The research sample includes 451 year -firm of Tehran Stock Exchange (TSE) listed companies for period 2007-10. The multiple linear regressions were applied to test the research hypotheses. The results showed that, return on assets and earnings per share have a negative impact on working capital management. The results also show that earnings per share and profit margin positively associated with the firm performance.

• Korean Journal of Occupational Health Nursing
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• v.23 no.4
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• pp.254-261
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• 2014

Purpose: The purpose of this study was to investigate the degree of performance of TB control manpower in Korea and to identify the affecting factors associated with it. Methods: This study employed a quantitative observational with cross-sectional design and the subjects were consisted of 189 TB (Tuberculosis) control manpower who were working in both community health centers and private hospitals. Variables included in this study were demographic, social, work-related characteristics, aqhnd self-efficacy. A reliability of the instrument for the performance was Cronbach's ${\alpha}$=.91. Data were analyzed by t-test, ANOVA and multiple regression using SPSS (19th version). Results: The mean value of the degree of work-related performance of TB control manpower was $4.4{\pm}0.49$9 and it was higher than those of general nurses working in any other health care departments. The mean differences in the degree of work-related performance were in self-efficacy, workplace, the number of full charge manpower in TB, the number of participation in in-depth education, and the willingness to job maintenance. In multiple regression analysis, factors associated with TB control manpower' work-related performance were self-efficacy (${\beta}$=.164, p=.025), workplace (${\beta}$=-.186, p=.023), the number of participation in in-depth education(${\beta}$=.339, p<.002), and the willingness to job maintenance (${\beta}$=-.157, p=.036). Conclusion: Results of this study showed that work-related performances of manpower working in private hospital were higher than those of manpower in public health centers. So, it is necessary to enhance nation's active intervention to improve effectiveness and reduction of risk factors in TB policy.

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.185-191
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• 2012

Rear collisions to expressway work trucks result many casualties these days. But, currently, no special measure are being taken except deploying sign trucks behind the working trucks. In the U.S and Europe, trucks with TMA(Truck Mounted Attenuator) are being deployed behind the working truck, which is regarded as the standard method for work area safety, thereby reducing the fatality rates and property damage tremendously. Also, standard for the performance of TMA are established and TMA can be used in the field only when it satisfies the standard. In Korea, neither the standard for nor any guide to the TMA exists. In the situation some manufacturer developed TMA without proper performance evaluation and marketed limited number of TMAs in the field. In the study, NCHRP350, which is the performance standard of expressway safety features of U.S. and materials related to the TMA standard in Europe have been reviewed to establish the Korean performance criteria. Based on the review, and incorporating existing Korean standard for crash cushions, domestic standard for TMA has been proposed and applied in developing Korean TMA and crash tested it to verify the performance. The original design developed was crash tested and modified. The newly proposed design was studied using impact simulation program several times. Modifications were made after each simulation and prototype was built and crash tested as per the newly established TMA performance criteria.

• Journal of the military operations research society of Korea
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• v.24 no.1
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• pp.176-188
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• 1998

In this paper, it is identified that the optimal level of each performance measures (service and inventory level) is not sensitive to an uncertain environment under JIT Kanban system designed by Moeeni. Moreover, it is proposed that the optimal design method considering multiple performance characteristics is the optimal level decision method according to the relative importance differences of each performance when there exist multiple performance characteristics. The result from the simulation analysis shows that the number of Kanban for stage 3 (final process) and stage 2 is increased at the service level. It is found that the expected loss is minimal when the cycle time decreases and the container size increases. However, the stage 1 is not affected by the number and cycle time of Kanban. It is thus important to consider carefully the cycle time and the container size of the Kanban to satisfy the demand in right time. In case of inventory level, the working inventory level decreases when the container size is decreased and the working inventory level also decreases slightly when the cycle time of the Kankban is increased in stage 1 and 2.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.699-707
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• 2017

This study presents a comparative thermodynamic analysis of subcritical and transcritical organic Rankine cycles for the recovery of low-temperature heat sources considering nine substances as the working fluids. The effects of the turbine inlet pressure, source temperature, and working fluid on system performance were all investigated with respect to metrics such as the temperature distribution of the fluids and pinch point in the heat exchanger, mass flow rate, and net power production, as well as the thermal efficiency. Results show that as the turbine inlet pressure increases from the subcritical to the supercritical range, the mismatch between hot and cold streams in the heat exchanger decreases, and the net power production and thermal efficiency increase; however, the turbine size per unit power production decreases.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.3
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• pp.518-528
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• 2010

This study analyzes the work environment and the work clothes wearing conditions of shipyard painters. In addition to this, three types of experimental painting work clothes were evaluated by painters in terms of the material performance and wearing functions. The findings on the harmful painting work environmental factors were organic solvents, noise, heavy dust, high temperatures, and noxious fumes. The body parts damaged during painting operations were the skin, arms, whole body, and face. In general, the satisfaction with the wearing performance of work clothes for painting was low especially in regards to sweat absorbency, sweat permeability, body protection, covering, and the work motion suitability. The satisfaction with the wearing sense of painting working clothes (regardless of the type of material) was high in the order of movement comfort> sensual comfort> physiological comfort. The satisfaction in overall comfort according to the types of material was high in the order of nylon> SMS nonwoven fabric> SF nonwoven fabric.