• Journal of Communications and Networks
• /
• 제12권2호
• /
• pp.103-113
• /
• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• 한국태양에너지학회 논문집
• /
• 제37권3호
• /
• pp.33-45
• /
• 2017

Crystalline silicon photovoltaic module certification began in 2007. "Renewable Energy Equipment Certification Scheme" was implemented until July 28, 2015. Then, the scheme was changed to "KS Certification Scheme" since July 29, 2015. A total of 2,331 models have been certified by 2016. The proportion of multi crystalline modules in certified products is higher than that of mono crystalline modules, and Korean modules account for 78% of the total certification modules. Chinese solar cells account for the highest percentage of 40% of the total modules and 62.4% of modules certified in 2016 use Chinese solar cells. With the development of technology, module power is continuously increasing, and efficiency is also rising. The average efficiency of mono crystalline module is 0.74% higher than the average of multi crystalline module. As a result of comparing domestic module with Chinese module, the highest efficiency of mono crystalline module and multi crystalline module and the average efficiency of mono crystalline module are higher than those of Chinese module, but the average efficiency of multi crystalline module is similar to that of Chinese module.

• 대한기계학회논문집B
• /
• 제23권9호
• /
• pp.1113-1120
• /
• 1999

Leakage vortices fonned near the blade tip cause an increase of total pressure loss near the casing endwall region and as a result, the efficiency of rotor decreases. The reduction of rotor efficiency is related to the size of tip clearance. In this study, the three-dimensional flow fields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The effects of tip clearance and the of attack on the leakage vortex and overall performance, and the los9 distributions were investigated through numerical calculations. In this study, tip leakage flow rate and total pressure loss due to the tip clearance were evaluated using numerical results and approximate equations were presented to evaluate the reduction of rotor efficiency due to the tip leakage flow.

• 한국사회복지학
• /
• 제52권
• /
• pp.117-141
• /
• 2003

본 연구는 부산지역 사회복지관의 투입 요소와 산출 요소간의 효율성의 관계를 분석한 연구이다. 사회복지관의 효율성 평가를 위해 비영리기관에서 많이 활용되고 있는 자료포락분석(DEA)을 사용하였으며, 자료는 2001년 부산광역시에 제출한 사업보고 자료를 활용하였다. 본 연구에서는 4가지 다른 모델을 설정하여 부산지역 전체 45개 기관을 전수조사 하였다. 4가지 모델을 보면, 전 모델의 산출은 연간 프로그램 이용자의 연인원을 중심으로 투입의 변수에 따라 모델을 구분하였다. 모델 1; 투입에 사회복지사의 인력 수와 사회복지사 인건비, 모델 2; 투입에 총 직원 수, 연간 총 운영비, 모델 3; 투입에 총 직원 수, 연간 자원봉사자 수, 운영기간, 모델 4; 투입에 총 직원 수, 연간 자원봉사자 수, 운영기간, 연간 총 운영비를 설정하여 효율성을 분석하였다. 본 연구의 결과는 다음과 같다. (1) 전체 45개 사회복지관에서 35-55%만이 상대적으로 효율적인 사회복지관으로 평가되고 있는 것으로 나타났다. 각 모델별로 평균 효율치를 살펴보면, 모델 1은 .8735, 모델 2는 .7048, 모델 3은 .4941, 모델4는 .5097로 나타났다. (2) 모든 기관이 효율이 가장 높은 효율점수 1이 되기 위해서 어떻게 변화되어야 하는가를 산출물을 기준으로 하여 모델 1, 2, 3, 4로서 살펴보았다. 사회복지기관에서 주요한 투입변수인 인력과 예산부분에 있어서 어느 정도의 변화가 필요한지를 모델 1, 2, 3, 4를 전체적으로 살펴본 결과 인력과 예산부분에 있어서 변화가 필요한 기관이 전체 45곳 중 41곳이었으며 이 기관은 모두 현재보다 인력이나 예산부분의 증가를 요구되는 것으로 나타났다. 이 중에서도 인력적인 부분과 예산부분의 증가가 모두 필요한 기관은 보강이 필요한 41기관 중 60%에 해당하는 25곳이었으며, 예산의 증액만 요청되는 기관은 6곳, 인력의 보강만 필요한 기관은 10곳으로 나타났다. 따라서 부산지역의 대부분의 사회복지기관이 현재의 산출량에 대해 가장 효율적으로 운영되기 위해서는 개별기관별로 예산과 인력의 보강이 필요한 것으로 나타났다.

• 한국병원경영학회지
• /
• 제21권1호
• /
• pp.43-50
• /
• 2016

The public medical centers are required to make efficient and profitable operation. The efficiency is usually measured by DEA(data envelopment analysis), and profitability is measured by medical income rate. But DEA is measured by relative, not absolute value. So, profitability rate is used alternatively for DEA. This study want to analyze the interchangeability between DEA ranking and medical income rate ranking among public medical centers. The return on total assets is same ranking with DEA on bed number, employee number and total asset, but 60-70% relationship with DEA on bed number and employee number, as input resources. The operating margin is similar ranking with DEA on bed number and employee number, but 50-60% relationship with DEA on bed number, employee number and total asset, as input resources.

• Applied Science and Convergence Technology
• /
• 제26권1호
• /
• pp.1-5
• /
• 2017

The spurt vacuum pump is widely used to transfer sludge and slurry, and to control flow rate in a variety of processing fields, such as the oil, chemical, and fiber industries. The efficiency of the pump depends on the design parameters of the impeller, such as the number of blades, and the blade angle. In this study, the effect of the configuration of the impeller discharge angle of a spurt vacuum pump, which influences total head, shaft power, and efficiency, was numerically investigated using the commercial code, ANSYS CFX ver. 16.1. In addition, the performance of the pump was evaluated on the basis of the correlations between the total head, pump efficiency, and pressure distribution.

• 보건행정학회지
• /
• 제20권4호
• /
• pp.45-57
• /
• 2010

Background : If different cost efficiency indexes were informed to the same clinic depending on the inclusion or exclusion of pharmacy cost, it may impair the reliability of provider-profiling system. This study aimed to investigate whether the omission of pharmacy cost affects cost-efficiency rankings in medical clinics. Methods : Data for ambulatory care cost at 23,112 medical clinics were collected from the claims database, which was constructed after review by the Health Insurance Review and Assessment Service (HIRA) of Korea in April 2007. We calculated two types of cost efficiency indexes by inclusion or exclusion of pharmacy cost for a medical clinic. The agreement between the decile rankings of the two indexes was also assessed using the weighted kappa statistic of Landis and Koch. Results : When the cost efficiency index for total cost including pharmacy cost was compared with the index for total cost excluding it, the agreement between the two indexes was only 55%. The agreements between the two indexes were relatively low within specialties which have larger pharmacy volume of total cost and lower correlation between total cost with or without pharmacy cost included than the average level of all the specialties. Conclusion : These results suggest that the omission of pharmacy cost may result in contradictory outcomes that may be confusing to a medical institution and may impair the reliability of provider-profiling systems. It is very important to standardize profiling criteria for the reliability of provider profiling system.

• 자원ㆍ환경경제연구
• /
• 제14권3호
• /
• pp.595-626
• /
• 2005

본 연구의 목적은 투입물 효율함수를 이용하여 한국농가의 소득계층을 대상으로 기술효율, 환경효율, 규모효율을 측정하고, Tobit 모형으로 그 결정요인을 분석하는 것이다. 본 연구는 비모수적(nonparametric) 방법에 의존하여 재화의 가격이나 최적화 행동에 관한 가정없이 투입요소와 산출량에 의존하여 기술효율을 계측한다. 생산기술은 바람직한 재화와 바람직하지 못한 오염물의 결합생산을 모형화한다. 규모불변과 강처분 하에서 평균 기술효율 수준은 0.437 이었다. 기술비효율의 원인은 순수기술비효율이 47.7%, 규모비효율은 11.3%, 환경비효율 3.2%의 순이다. 규모체증 상태에서 생산농가는 전체농가의 70%를 점유하고 규모체감 상태에서 생산농기는 전체농가의 27%에 이른다. 효율성을 결정하는 요인으로 소득계층이 높을수록 중장기 부채가 높을수록 단위면적당 질소배출량이 높을수록 기술효율은 높았고, 경지면적당 농업경영비가 높을수록 기술효율은 저하되었다. 환경효율에서는 BOD 배출량, 단위면적당 기계도입, 자본의 생산성 유의적이고 음(-)으로 나타나, 청정기술이 아닌 단순한 기계화의 확대는 환경효율을 악화시키는데 영향을 주고 있음을 시사한다.

• KIEAE Journal
• /
• 제6권3호
• /
• pp.43-48
• /
• 2006

This paper aims to suggest ways of institutionally improving standards that must be applied when installing Water Reclamation/Reuse (WRR) system based on efficiency analysis. Currently, the standard for WRR system establishment requires that the system should treat more than 10% of used water in the building of over $60,000m^2$ in total area of all floors, but our research has found that it would be more effective to change the standard to $150-m^3-per-day$ reclaimed water or the total area of all floors of $30,000m^2$ ($50,000m^2$ in the case of an office building). In other words, what this paper suggests is not a one-size-fits-all standard based on the total area of all floors, but a reasonable and flexible standard that takes into account efficiency and a unit water usage according to a building's purpose. Furthermore, this paper recommends a new WRR standard that can be applied to large-scale land development for housinglots, like the New Town. The recommendation is based on the economic analysis that the WRR system will ensure efficiency only if the amount of reclaimed water is over 4,000 tons per day, which corresponds to 4 millions square meters of housinglots. Regarding the size of the established facility, this paper suggests changing the standard, which is now set at over 10% of water usage, to what is relative to the total amount of use of reclaimed water in order to ensure efficiency and promote use of reclaimed water. In addition, this paper proposes that governmental support should be offered not only to facility owners, who are recipients at present, but also to facility builders. By doing so, those who donate a facility to the government, central or local, after building it, can be provided with substantial aid. Therefore, the application of the institutional improvement suggested in this paper is expected to create environment-friendly living conditions and boost the quality of life by encouraging people to secure water resources efficiently in buildings, and in a wider range, in cities.

• 한국물환경학회지
• /
• 제31권4호
• /
• pp.418-427
• /
• 2015

This study was carried out to evaluate the performance of a lab-scale novel septic tank system for improving the conventional septic tank in the developing countries of water shortages. The lab-scale novel septic tank system consists of sepetic tank, aeration tank with HBC-ring, and sand filter. Optimum HRT was reguired about 1.5days to get a total COD removal efficiency of 90%, COD, BOD and SS removal efficiency was about 70%, 60%, and 85% in sepetic tank only. The structure of sepetic tank with two stages results in the high removal efficiency of organic matter. When sepetic tank, aeration tank, and sand filter were more than HRT 1.5days, 18hrs, and 12hrs, respectively, final effluent was less than 20 mg/L of BOD, 14 mg/L of SS, so that there is a high potential of its use for reusing water in flush toilet. There is no significant effect of HRT change on nutrient removal. Total nitrogen removal efficiency was about 40%, final effluent was 30~40 mg/L of TN, total phosphorus removal efficiency was about 11~25%, final effluent was 9~12 mg/L of TP. Because there is very small amounts of organic nitrogen and phosphorus in effluent, it was possible to reuse water for agricultural use.