• 설비공학논문집
• /
• 제4권4호
• /
• pp.360-369
• /
• 1992

A heat pump system is constructed to evaluate its performance and heat transfer characteristics with mixtures of R22/R142b as working fluids. The heat transfer in the evaporator and the overall performance are measured and analyzed in terms of the compositions and relevant variables. Possibility of capacity modulation by changing composition is observed without degradation of heat transfer coefficients and coefficient of performance. The cooling capacity is varied continuously within 200 percent based on minimum capacity at constant compressor speed. For similar cooling capacity, COP is improved by mixing two refrigerants and shows maximum value at 60％ mass fraction of R22. Average heat transfer coefficients of mixtures decrease in comparison with pure refrigerants at similar cooling capacity and mass flow rate. However, the overall heat transfer coefficients decrease moderately. A cycle simulation is performed in order to manifest the advantages of using refrigerant mixtures, considering experimentally observed heat transfer characteristics.

• 지식경영연구
• /
• 제17권1호
• /
• pp.135-154
• /
• 2016

Absorptive capacity has been increasingly thought of as a potential source of innovation. From the knowledge management perspective, absorptive capacity is composed of a set of activities dealing with acquisition, assimilation, transformation, and exploitation of external and internal knowledge. This study investigates what relationship the absorptive capacity of individuals who have technical knowledge in the organization has with process innovation and product innovation. Mobile based survey was conducted from the employees working for the largest electronics manufacturer in Korea. The analyzed data was based on 156 responses from 199 participants. The analysis result shows that four phases of absorptive capacity such as acquisition, assimilation, transformation and exploitation have different effects on process innovation and product innovation, respectively. Specifically, transformation is found to be most critical in leading to innovation.

• KDI Journal of Economic Policy
• /
• 제41권2호
• /
• pp.41-58
• /
• 2019

Health capacity to work for the elderly is an essential piece of information for designing social policies in an aging society. Here, we assess the health capacity to work of older men in South Korea and provide a cross-country comparison. Following the methodology proposed by Milligan and Wise (2012), which uses the cohort mortality rate as a proxy for overall health status, we quantify the additional employment capacity of current older men in reference to the mortality-employment relationship of a generation ago. Despite the high employment rate of older men in South Korea, we find substantial additional employment capacity among older men (those aged 55 or more) as of 2016 comparable in size to those found in other advanced countries. We also find evidence that older men are not merely capable of working but are also willing to work, and many of them are increasingly combining pension income and work. These findings suggest that labor supply disincentives for older men embedded in public pension systems in South Korea need to be thoroughly reexamined and adjusted accordingly lest they should inhibit the labor supply of older workers.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.776-781
• /
• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1MW organic Rankine cycle system was designed and developed. The exhaust gases of $175^{\circ}C$ at two 100MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1MW as designed but only 670kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• 태양에너지
• /
• 제20권2호
• /
• pp.85-96
• /
• 2000

When the liquid with the additive of ppm unit of a polymer flows, the pressure drop can be manifestly decreased compared to that of pure liquid: that's the drag reduction. This method is that a small amount of a polymer which doesn't make the transformation of the properties of the working fluid is dissolved into the working fluid, the links of chains of the polymer do a buffer action to the molecules of the working fluid which come out between near the wall of the pipe and the interface, so that the pressure drop is dramatically decreased. When we transport the fluid, therefore, we can save a lot of pumping power, or we can increase the transportation capacity with using the same transportation equipment. But when a polymer solution is also flowing in the fluid transportation system, the degradation which have a very close relation with the phenomena of the drag reduction occurs necessarily. When adding polymer to reduce the drag in two phase flow system, It is impossible to find some studies. This study is focussing on a searching examination for the experimental study considering the mechanical degradation in the closed tow phase system to find out the conditions which could improve the pump capacity.

• 한국안전학회지
• /
• 제14권3호
• /
• pp.127-133
• /
• 1999

One of the major malodorous gas at the working place is hydrogen sulfide and impregnated activated carbon fiber(ACF) was used as a adsorbent to remove this gas. ACF is treated and impregnated with chemicals to increase the adsorption capacity. The experiments showed that the adsorption efficiency for hydrogen sulfide was increased in case of impregnation with $Na_2CO_3$ or KI. Also, by the surface treatment with NaOH, the adsorption efficiency was increased however not so much as impregnation. KI was the best impregnant for this purpose and the optimum concentration was 9wt%. The adsorption capacity of hydrogen sulfide was more than 500mg/g ACF.

• 한국식생활문화학회지
• /
• 제3권3호
• /
• pp.293-299
• /
• 1988

34 packaged meal (Dosirak) manufacturing establishments were assessed in terms of working environment, production and transportation practices. Questionnaires and facility check-lists were developed. Most establishments were small in business, and production personnel as well as production facilities were insufficient compared with production capacity of establishments. Mean production capacity for packaged meals in terms of optimum and maximum levels were 6,500 and 15,166 meals in large sized establishments; 2,662 and 8,301 in medium; and 2,112, and 4,733 in small respectively. Those figures indicate potentially hazardous practices in production especially in small and medium sized establishments. Most meals were produced to order. Transportation facility and kitchen space were assessed as insufficient.

• 한국수학교육학회지시리즈D:수학교육연구
• /
• 제17권3호
• /
• pp.199-220
• /
• 2013

The main objective of this study is to explore the relationship between psychological factors (i.e. math anxiety, attention, attitude, Working Memory Capacity (WMC), and Field dependency) and students' mathematics problem solving based on Revised Bloom Taxonomy. A sample of 169 K11 school girls were tested on (1) The Witkin's cognitive style (Group Embedded Figure Test). (2) Digit Span Backwards Test. (3) Mathematics Anxiety Rating Scale (MARS). (4) Modified Fennema-Sherman Attitude Scales. (5) Mathematics Attention Test (MAT), and (6) Mathematics questions based on Revised Bloom Taxonomy (RBT). Results obtained indicate that the effect of these items on students mathematical problem solving is different in each cognitive process and level of knowledge dimension.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 춘계학술대회 논문집
• /
• pp.886-892
• /
• 2007

This paper presents examples of trolley wire resistance influential on the movement of tensioning devices. Therefore, this study is on the examples of trolley wire resistance which keep tensioning devices from working properly to the expansion and contraction in accordance with temperature change of overhead trolley wire system such as messenger wire and contact wire. Trolley wire resistance interrupts the working of tensioning device and drops the capacity of trolley wire. Reduced trolley wire capacity lowers the performance of current collection and has a bad effect on electrical train operation. So it is desirable to reduce the factors increasing trolley wire resistance to the minimum from the designing and construction stage of overhead trolley wire system. This study will introduce this problem and suggest the solution.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제6권
• /
• pp.80-92
• /
• 1998

A third-order simulation model of a Vuilleumier{VM) heat pump has been developed. This model takes into account the major losses such as the heat conduction losses through regenerators and displacers, the pumping losses and the wall-to-gas heat transfer losses in active volumes, in addition to the heat exchanger and regenerator losses. The working volume was divided into 12 control volumes and the conservation equations of mass and energy were applied to each control volume. Pressure drops were considered in regenerators only. Thermodynamic behavior of the working gas in a VM heat pump was investigated and effects of the major losses and operating conditions on the performance of a VM heat pump were shown.