• The Journal of Korea Robotics Society
• /
• v.4 no.1
• /
• pp.43-48
• /
• 2009

Generally, underwater vehicle type of propeller shows low efficiency about 50%-55%. However, the efficiency of swimming mechanism of a fish is 60%-70%, more efficient about 20% than screw propellers. Recently, research of underwater vehicle type of fish increase due to its good efficiency and is regarded as a typical bio-mimical robot. In this research, a new algorithm and mechanism that show low energy consumption imitating swimming mechanism of fish proposed increasing speed and running time in field trial.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1412-1414
• /
• 2009

It is suggested that the light extraction efficiency of the display device can be improved by adoption of periodic array of sub-wavelength scale structures. The relief of the total reflection has been investigated using the rigorous coupled wave analysis (RCWA). Various shape of the sub-wavelength scale structure allowed to have non vanishing transmittance for the light rays with the incident angle bigger than the critical angle.

• International Journal of Railway
• /
• v.6 no.2
• /
• pp.33-44
• /
• 2013

In recent years, energy consumption in the transportation sector by expanding motorization continues to increase in almost every country in the world. Moreover, the growth rate of the transportation energy consumption is significantly higher than those of the civilian and industrial sectors. Therefore, every country strives to reduce its dependence on private transport, which is the main contributor to the transportation energy consumption. In many countries, concepts such as Transit Oriented Development (TOD) or New Urbanism, which controls road traffic by increasing the proportion of the public transportation significantly, have been implemented to encourage a modal shift to public transport. However, the level of change required for eliminating environmental problems is a challenging task. Minimizing transportation energy consumption by controlling the increase of the traffic demand and maintaining the level of urban mobility simultaneously is a pressing dilemma for each city. Grasping the impact of the diversity of the urban transport and infrastructure is very important to improve transportation energy efficiency. However, the potential for reducing urban transportation energy consumption has often been ineffectively demonstrated by the diversity of cities. Therefore, the accuracy of evaluating the current efficiency rate of the urban energy consumption is necessary. Nevertheless, quantitative analyses related to the efficiency of transportation energy consumption are scarce, and the research on the current condition of consumption efficiency based on international quantitative analysis is almost nonexistent. On the basis of this background problem definitions, this research first built a database of the transportation energy consumption of private modes in 119 cities, with an attempt to reflect individual travel behaviors calculated by Person Trip data. Subsequently, Data Envelopment Analysis (DEA) was used as an assessment method to evaluate the efficiency of transportation energy consumption by considering the diversity of the urban traffic features in the world cities. Finally, we clarified the current condition of consumption efficiency by attempting to propose a target values for improving transportation energy consumption.

• Journal of Korea Trade
• /
• v.25 no.1
• /
• pp.169-183
• /
• 2021

Purpose - This paper analyzes the effect of the agricultural export market for Korea's new southern countries in consideration of logistics efficiency. In order to expand Korean agricultural exports, the logistics performance index, national income, per capita income, consumer price index, distance and FTA are included. Through empirical analysis, the impact of logistics efficiency on Korean agricultural exports is derived and measures are proposed to expand exports in the future. Design/methodology - The analytical model of this study takes into account the import demand factors of the new southern countries for Korean agricultural exports. A research model was established based on prior research based on the gravity model, which is widely used in international trade effect analysis. In particular, logistics efficiency measures the effect on Korean agricultural exports using the logistics performance index and examines the effect by deriving factors for export expansion. Findings - The main findings of this study can be summarized as follows: The higher the logistics efficiency of the new southern countries in exporting Korean agricultural products, the more directly they have an effect on expanding exports. In addition, it was analyzed that the expansion of Korean agricultural exports has a positive effect on the other countries' national income, per capita income, consumer price index, population, and FTA. Based on these results, the importance of efficient logistics management in agricultural exports has been emphasized. Originality/value - There are not many studies on the export of agricultural products by logistics efficiency. However, prior studies that have adapted to manufacturing and other areas suggest that logistics efficiency has a direct effect on exports. This study suggests that Korean agricultural products are directly effective in exporting to new southern countries in terms of logistics efficiency. This can be an important time point in recognizing that logistics capabilities are important to ensure new books and the safety of agricultural products.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.9
• /
• pp.5425-5433
• /
• 2014

This study examined the effects of the key parameters on the power efficiency of the waste heat power plant using the EES program to obtain data for the design of the 20kW Kalina power plant. The parameters include the ammonia mass fraction, vapor pressure, heat source temperature, and the cooling water temperature. According to the analyses, a lower ammonia mass fraction and a higher vapor pressure increase the efficiency, in general. On the other hand, this study shows that there is a specific region with a very low ammonia mass fraction, where the efficiency decreases with ammonia mass fraction. Regarding the vapor pressure at the turbine inlet, the power efficiency increases with increasing vapor pressure. In addition, it was found that the influence of the vapor pressure on the efficiency increases with increasing ammonia mass fraction. Finally, the optimal condition for the maximum power efficiency is defined in this study, i.e., the maximum efficiency was 15% with a 25bar vapor pressure, $160^{\circ}C$ heat source temperature, $10^{\circ}C$ cooling water temperature, and 0.4 ammonia mass fraction.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.42 no.3
• /
• pp.35-49
• /
• 2017

The main objective of this paper is to empirically analyze the efficiency effects of mergers on Korean pharmaceutical firms and suggests managerial or policy implications for managers or policy makers. This study selects non-merging control firms close to the size of merging firms, as well as a set of merging firms, and measures the effects of mergers on efficiency three years before and after the merger using the non-parametric data envelopment analysis (DEA) method. To compare the differences of efficiency means among several groups, Wilcoxon rank sum test or Wilcoxon signed rank test is used. It showed that the long-term effects after the merger appeared partially. Furthermore, it was observed that there was no difference statistically in the efficiency between merging and non-merging firms. Also, there was no difference statistically in the efficiency between the pre- and post-merger periods. In conclusion, there was not any observed synergy effect through group (or affiliated) mergers between affiliates or related mergers for Korean pharmaceutical firms.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.21-21
• /
• 2003

To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

• Journal of Navigation and Port Research
• /
• v.29 no.3 s.99
• /
• pp.195-201
• /
• 2005

This paper presents the measurement of efficiency for container ports. Data envelopment analysis(DEA), as it is called, has particular applicability in the service sector. Applying mathematical programming techniques, DEA enables relative efficiency ratings to be derived within a set of analysed units. This paper investigates the efficiency employing DEA Model on data for 53 container ports covering 1995-2001 in the world and the change in efficiency for 7 years. As a results, port of Busan was evaluated as inefficiency port compare with major ports of the world except 1995year and 1996year. But After 1997year, efficiency of Busan port is increasing somewhat better every year.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.39 no.3
• /
• pp.23-40
• /
• 2014

This paper measures the operational efficiency of domestic online game companies and analyze its trends and patterns by using data envelopment analysis (DEA). DEA is a non-parametric approach to measuring the relative efficiency of decision-making units (DMUs) with multiple inputs and outputs. 14 online game companies are selected as DMUs and three inputs (number of employees, capital and asset) and three outputs (sales, operating profit and net profit) are selected as DEA variables. First, the output-oriented BCC model and super-efficiency model are employed to measure the static operational efficiency of the online game companies from 2003 to 2012. We also conduct the dynamic analysis with DEA window model to capture the trends of their operational efficiency influenced by internal and external environmental changes. The results are expected to provide fruitful implications for strategic decision making of online game companies and policy making for the online game industry.

• Journal of the military operations research society of Korea
• /
• v.36 no.2
• /
• pp.85-106
• /
• 2010

Recently, government is endeavoring for Defense Ministry unit's efficiency improvement according as requires low cost, high effectiveness continuously about public sector. But, by real condition that measuring analysis about logistical corps'(LOG) efficient operation is not, this study was done to present method to estimate efficient management availability of logistical corps(LOG). Presents choosing variable that is suitable in Quartermaster Corps' efficiency estimation for this through existing virtue study investigation, and takes advantage of DEA (Data Envelopment Analysis) technique that divert in public sector efficiency measurement, I wish to present plan for inefficient organization's efficiency improvement after evaluate efficiency to Quartermaster Corps.