• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.3
• /
• pp.413-420
• /
• 2017

We investigate the performance of a true time delay(TTD) phase shifter to reduce the beam squint caused by frequency changes of a phased array antenna in wideband communication systems. To design a high gain phased array antenna, we need a long TTD, which causes high RF loss, low resolution and large dimension of TTD phase shifters. To overcome the problems, we propose a schematic of dual TTD phase shifters, which consists of short time delay(STD) in radio frequency(RF) part and long time delay(LTD) in intermediate frequency(IF) part. Our analysis results show that the proposed scheme reduces the required bits and delay time in RF band of the TTD compared to the conventional single TTD scheme.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.3
• /
• pp.234-240
• /
• 2014

We investigated the effects of feeding rate on the growth performance, blood components, and histology of growing olive flounder Paralichthys olivaceus. We determined the optimum feeding rate (initial fish mean weight of $240{\pm}10.9$ g) at the optimum water temperature. Two replicated groups of fish were fed a commercial diet at rates of 0%, 0.5%, 0.75%, and 1.0% body weight (BW) per day, and to satiation. Feeding trial was conducted using a flow-through system with 10 1.2-metric ton aquaria receiving filtered seawater at $19-21^{\circ}C$ for three weeks. Weight gain (WG) for fish fed to satiation was significantly higher than that of unfed fish and fish fed at 0.5% and 0.75% BW per day. The WG of fish fed at 1.0% BW per day was significantly higher than that of unfed fish and of fish fed at 0.5% BW per day. However, there were no significant differences in WG between fish fed at 0.5% BW per day and those fed at 0.75% BW per day, between fish fed at 0.75% BW per day and those fed at 1.0% BW per day, and between fish fed at 1.0% BW per day and those fed to satiation. The specific growth rates of fish fed at 1.0% BW per day and those fed to satiation were significantly higher than those of unfed fish and of fish fed at 0.5% BW per day. Broken-line regression analysis of weight gain showed that the optimum feeding rate of olive flounder weighing 240 g was 1.09% BW per day at the optimum water temperature.

• Journal of Aquaculture
• /
• v.22 no.1
• /
• pp.1-4
• /
• 2009

A 10-week feeding trial was conducted to investigate the effects of feeding rate on growth and body composition of adult flounder during the summer season. Three replicated groups of the fish (initial mean weight of $535{\pm}4.1\;g$) were hand-fed a extruded diet twice a day at the different feeding rates of satiation (100%), 90%, 80% and 70% of satiation for 10 weeks. Mean Water temperature was $19.2{\pm}2.8^{\circ}C$ during the feeding trial. Weight gain and condition factor increased significantly with increase in daily feeding rate (P<0.05), but there was no significant difference in weight gain of fish fed the diet between 100% and 90% of satiation. Survival and feed efficiency were not significantly different among all groups. Proximate composition of dorsal muscle was not significantly affected by feeding rate. Based on the results of this study, optimum feeding rate for growth and condition factor of adult flounder (535-928 g) seemed to be 90% of satiation.

• Journal of The Korean Association of Information Education
• /
• v.6 no.3
• /
• pp.338-346
• /
• 2002

In these days, because of internet activation, each organs of education or istructors develop and manage the web based education system, but component development that used in web based education system development is not ready. When we develop the web education system using component, we can gain the various desired result of reusability, interaction in various computers, expansion, reduction of development time, saving of development expense, etc. Therefore, in this paper we classified the web based education components by the function of web based education system, did modeling for development process of components, and chose the component platform that can reuse components in distributed computing environment that the client/server environment is supported. The induction of these web based education components will be give many assistance to development of the web based education system.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.9
• /
• pp.46-51
• /
• 2013

In this paper, the optimum placement and shape of UHF antenna on the unmanned aerial vehicle (UAV) are analyzed by using the electromagnetic (EM) simulation on the various locations. The FEKO was used for the EM-simulation. In order to reduce the complexity of simulation and minimize the runtime and memory usage, the composite aircraft structure is simplified as the PEC model excluding the radome structure. The simulation was performed on the wing and ventral fin of UAV, and the antenna shape used the monopole, dipole, and bent monopole antennas. When the monopole antenna is mounted under the wing, two antennas need to be mounted under the right and left wings, and those antennas have to be switched as the direction of UAV wing to the line of sight (LOS) data-link (DL) ground antenna. In the case of mounting under the ventral fin, one antenna can be used regardless of the direction of UAV wing to the LOS DL ground antenna. Also, the antenna gain is improved by the blockage reduction. The antenna gain is further improved by using the bent monopole antenna. The optimum solution of UHF antenna placement and shape on UAV is to mount the bent monopole antenna under the ventral fin.

• Culinary science and hospitality research
• /
• v.22 no.1
• /
• pp.96-107
• /
• 2016

The purposes of the study are (1) to explore relationships amongst attitudes to positive/negative tourism impacts, community satisfaction, government trust, and support for tourism development and (2) to provide practical implications for policy makers how they can gain residents' support by increasing community satisfaction and government trust, which are resulted from attitudes to tourism impacts. A questionnaire is self-administered to local residents using a systematic sampling method in Ninh Hai Commune, Hoa Lu District, Ninh Binh Province, Vietnam. The results indicate community satisfaction and government trust are core factors of support for tourism development. The study highlights that to attain community satisfaction and government trust, the policy makers should especially increase positive socio-cultural and environmental impacts and minimize negative economic impacts on the community simultaneously.

• Journal of Information Processing Systems
• /
• v.13 no.3
• /
• pp.518-532
• /
• 2017

Due to the rapid growth of the amount of data, research on bigdata processing has been highlighted. For bigdata processing, CUBRID Shard is able to support query processing in parallel way by dividing the database into a number of CUBRID servers. However, CUBRID Shard can answer a user's query only when the query is required to gain accesses to a single CUBRID server, instead of multiple ones. To solve the problem, in this paper we propose a CUBRID based distributed parallel query processing system that can answer a user's query in parallel and distributed manner. Finally, through the performance evaluation, we show that our proposed system provides 2-3 times better performance on query processing time than the existing CUBRID Shard.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2004.05a
• /
• pp.576-580
• /
• 2004

As technology innovation has become a competitive weapon in the globalized era, firms are engaged in the development of new products to gain competitiveness in the marketplace. One of the main phenomena in a firm's effort to enhance technology development activities is the formation of technology strategy, i.e. the formalization of technology development activities within the firm. This paper explores the practice and management of technology innovation in the Korean manufacturing sector. Based on a survey of over 100 manufacturing firms in Korea, it identifies the contemporary practice of technology planning, and also characterizes the types of relationships that exist among participating interest groups for technology strategy formulation within a firm.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.03a
• /
• pp.143-147
• /
• 1998

As the accuracy of manufactured goods needed high-accuracy processing has made the efficiency of NC and measurment technology develop, the innovation of machine tools has influence the development of the semi-conductor and optical technology. We can mention that a traction role of the acceleration for the development like that depends on the development of the measurement technics - Stylus instrument method, STM, SEM, Laser interferometer method - which are used for measuring the movement accuracy of machine tools. The movement error factors in movement accuracy are expressed as yaw, roll, and pitch etc. Machining center has 21 movement error factors including of 3 axies joint errors because that has 3 axies and has been measured as the standard of the unloaded condition until now inspite of getting static, dynamic, and servo-gain errors in the case of expending the error range. Therefore, this study tries to measure position accuracy according to loading on the X-Y table of the machining center.

• KDI Journal of Economic Policy
• /
• v.37 no.2
• /
• pp.1-21
• /
• 2015

The creation of S&T knowledge and development of S&T- based innovation has spread worldwide from traditionally advanced countries to traditionally developing countries, often under the direction of governments. Korea is an exemplar in this new locus. Korea's burst in Science and Technology during the last three decades has made Korea a substantive player in the global production of S&T knowledge and its application to business. Although Korea still trails the US and other top countries in the quality of research, it has leaped from its 1980s standing as bit player in the knowledge economy to being among the leaders in the early 21st Century. This paper shows that Korea's advance benefited from its active participation in the global market in higher education, in international research collaborations, and its close ties to the U.S. Korea's experience offers lessons for other countries who seek to advance by becoming knowledge economies. Korea proves that a developing country can gain comparative advantage in knowledge production and use; that government policy can stimulate such a development; and that openness to the world of higher education and research is the best way to move forward and overcome the middle income trap.