• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.632-642
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• 2017

This paper presents an improved approach towards reducing the switching loss of insulated gate bipolar transistors (IGBTs) for a medium-capacity-class power conditioning system (PCS). In order to improve the switching performance, the switching operation is analyzed, and based on this analysis, an improved switching method that reduces the switching time and switching loss is proposed. Compared to a conventional gate drive scheme, the switching loss, switching time, and delay are improved in the proposed gate driving method. The performance of the proposed gate driving method is verified through several experiments.

• Journal of Information Technology Applications and Management
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• 제12권4호
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• pp.13-24
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• 2005

The sensor network is a key component of the ubiquitous computing system which is expected to be widely utilized in logistics control, environment/disaster control, medical/health-care services, digital home and other applications. Nodes in the sensor network are small-sized and exposed to adverse environments. They are demanded to perform their missions with very limited power supply only. Also the sensor network is composed of much more nodes than the wireless ad hoc networks are. In case that some nodes consume up their power capacity, the network topology should change, and rerouting/retransmission is necessitated. Communication protocols studied for conventional wireless networks or ad hoc networks are not suited for the sensor network resultantly. Schemes should be devised to control the efficient usage of node power in the sensor network. This paper proposes a medium access protocol to enhance the efficiency of energy consumption in the sensor network node. Its performance is analyzed by simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.454-458
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• 2005

Light railway system has many characteristics of better accessibility, frequency service, low construction cost, reduced air pollution and medium capacity public transport etc. Light railway system as a urban transportation system has been glowing worldwide since the late 20th century. More than 300 cities around the world have light railway systems. Many medium-size cities in domestic site is planning the construction of light railway. This paper reviews the domestic and foreign light railway system.

• Steel and Composite Structures
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• 제6권6호
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• pp.479-491
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• 2006

Structures in seismic regions are designed to dissipate seismic energy input through inelastic deformations. Structural or component failure occurs when the hysteretic energy demand for a structure or component subject to an earthquake ground motion (EQGM) exceeds its hysteretic energy dissipation capacity. This paper presents a study on identifying the hysteretic energy demand and distribution throughout the height of regular steel moment resisting frames (SMRFs) subject to severe EQGMs. For this purpose, non-linear dynamic time history (NDTH) analyses were carried out on regular low-, medium-, and high-rise steel SMRFs. An ensemble of ninety EQGMs recorded on different soil types was used in the study. The results show that the hysteretic energy demand decreases from the bottom stories to the upper stories and for high-rise structures, most of the hysteretic energy is dissipated by the bottom stories. The decrease is quite significant, especially, for medium- and high-rise structures.

• ETRI Journal
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• 제23권2호
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• pp.52-60
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• 2001

In this paper, a medium access control protocol is proposed for integrated voice and data services in wireless local networks. Uplink channels for the proposed protocol are composed of time slots with multiple spreading codes per slot based on slotted code division multiple access (CDMA) systems. The proposed protocol uses spreading code sensing and reservation schemes. This protocol gives higher access priority to delay-sensitive voice traffic than to data traffic. The voice terminal reserves an available spreading code to transmit multiple voice packets during a talkspurt. On the other hand, the data terminal transmits a packet without making a reservation over one of the available spreading codes that are not used by voice terminals. In this protocol, voice packets do not come into collision with data packets. The numerical results show that this protocol can increase the system capacity for voice service by applying the reservation scheme. The performance for data traffic will decrease in the case of high voice traffic load because of its low access priority. But it shows that the data traffic performance can be increased in proportion to the number of spreading codes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.736-741
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• 2004

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal (PES) is becoming smaller and smaller. In order to achieve the high TPI disk drive, it is necessary to improve the writing accuracy during the STW(servo track writing) process through the reduction of TMR sources. Among the main contributors of the NRRO(Non-Repeatable Run-out) PES, the disk vibration and the HSA(head-stack assembly) vibration is considered to be one of the most significant factors. Also the most contributors of RRO(Repeatable Run- out) come from the contributors of NRRO which is written-in at the time of STW(servo track writing) process. In this paper, the experimental test result shows that the effect of NRRO on servo written-in RRO effectively can be reduced through a STW process under low dense medium condition such as semi-vacuum.

• Journal of Plant Biotechnology
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• 제30권3호
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• pp.241-244
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• 2003

Root cluster section culture, showing high efficient Protocorm-like body (PLB) formation capacity, were established in Doritaenopsis hybrids. Three types of root were obtained from excised shoots in 1/2MS medium containing different concentrations of NAA; \circled1normal roots, \circled2multiple roots and \circled3abnormal root clusters. Those were placed on 1/2MS medium supplemented with 0.5 mg/L thidiazuron for PLB regeneration. PLB regeneration rate was greater in root cluster section cultures (77.8%) compare to normal root tip cultures(30%). Number of PLBs regenerated from root cluster sections were counted over 11 per explant (5.3 per normal root tip).High frequency of PLB regeneration was achieved in root cluster section culture. This result can be used as an efficient method for clonal proliferation of Doritaenopsis hybrids.

• 한국미생물·생명공학회지
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• 제23권3호
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• pp.352-358
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• 1995

In this study, authors investigated the cadmium tolerance, the accumulation of cadmium, and the cellular distribution of accumlated cadmium in lactic acid bacteria under the anaerobic condition. Lactic acid bacteria grew fairly well in modified EG medium containing 10 ppm of cadmium but could hardly grow at 50 ppm of cadmium. Tolerance to cadmium of genus Lactobacillus was greater than that of genus Streptococcus, and Lactobacillus acidophilus showed the higest cadmium tolerance amomg the bacteria tested. The capacity of cadmium accumlation (9.304-12.428 mg/g wet cell) of lactic acid bacteria was higher than that (6.775 mg/g wet cell) of Escherichia coli. Lactobacillus casei of them took up the largest amount of cadmium. The cadmium elimination amount (28.46-29.25%) of lactic acid bacteria from modified EG medium containing cadmium were also higher than that (14.43%) of Escherichia coli. Accumulated cadmium in Lactobacillus acidophilus was distributed by 42.41% at cell wall, 28.97% at cytoplasm, and 28.62% at plasma membrane, respectively.

• 미생물학회지
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• 제14권4호
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• pp.167-175
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• 1976

Twenty one strains of Rhodopseudomonas palustris from 7 different regions in Korea have been isolated and identified on the basis of Bergey's Manual in order to study their regional variation. They can use fructose as carbon source (or hydrogen donor). Capacity to produce molecular hydrogen during photosynthesis was tested using liquid medium, modified by omission of $NH_4Cl$ and addition of L0glutamic acid. As nitrogen source nitrate can be used, and isopropanol can be used as hydrogen donor. their pH ranges are 5.9 - 9.1. Their growth are inhibited in the medium that contains 100 units of penicillin G/ml. as for the growing test in dark aerobic condition, the period needed for adptation is longer than that of Korea strain of Rhodopseudomonas gelatinosa.

• Journal of Ginseng Research
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• 제6권2호
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• pp.162-167
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• 1982

Calli and leaflets of ginseng (Panax ginseng C.A. Meyer) were cultured on 1/2MS media supplement. with kinetin, 2 iP, NAA, 2,4-D and IBA to assess their capacity to regenerate embryoids and organs. Root calli produced numerous embryoids and shoots in 1/2MS medium supplemented with 2 mg/l NAA and 2mg/s 2iP, and the combination of 2 iP and NAA was more effective than the combination of kinetin and NAA in induction of embryoid and shoot from root calli. Culture of leaflet in the medium supplemented with IBA resulted in profuse root regeneration.