• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.601-604
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• 2004

Precise position and attitude control of pico-satellite requires huge number of impulses of the order of 10$^{-6}$ Ns. MEMS solid rocket array is a promising propulsion system but the higher degree of miniaturization causes unreliable operation mainly due to quenching. In order to breakthrough this situation, a novel design of solid micro-rocket is proposed, which generates tiny impulses repetitively from a single rocket not from array. This unique micro-rocket is based on the utilization of quenching, which causes propellant reaction to sustain only in a small area. A test chip of a micro solid propellant tank and micro heater array is fabricated and ignition test is conducted. Obtained results show the feasibility of this concept and future direction of this quenching-based propulsion is discussed.

• The Journal of Asian Finance, Economics and Business
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• 제7권1호
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• pp.239-247
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• 2020

Technological convergence is yielding new values and affecting various fields not by single technology but by convergence between technologies. This study aims to analyze the IT -BT-NT convergence and differences between technologies in respect of collaboration within (inventor) and between (assignee) organizations. Among the main technologies leading the technological convergence, IT is the most active of converging with other fields. BT is knowledge-intensive and strong cooperative networks are important in this area. NT is applied in various industrial fields upon the basic technology. Using the data on applied and granted patents by Korean applicants in the U.S., this study conducted quantitative analysis and ANOVA to gain the following results. First, the degree of convergence in between IT-BT-NT is continuously increasing since 2002. Second, BT is where the collaboration within and between organizations is the most active among IT-BT-NT. Third, there were certain differences in the degree of convergence according to the years and the fields of technologies in all the IT-BT-NT. Organizations cooperate with other institutions to sustain their competitiveness with limited internal resources. Companies in these fields are recommended to perform diverse strategies to pursue further collaboration with the outside.

• Journal of Power Electronics
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• 제11권4호
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• pp.464-470
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• 2011

In this paper, the feasibility of applying a position sensorless control technique to hybrid electric vehicles (HEVs) is practically evaluated. The proposed position estimator has a straightforward structure with properties that combines the model and the saliency tracking-based rotor position estimation for interior permanent magnet synchronous motors (IPMSMs). The proposed method can be used in the event of sensor loss or sensor recovery to sustain continuity of operations. The developed system takes into account the estimated position transition between two distinct sensorless methods. The transition is enhanced by introducing a synchronized transition algorithm based on a single tracking observer. Extensive experimental results are presented to verify the principles and show a reliable estimation performance over the entire speed range including standstill under 150% load conditions.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.385-390
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• 2004

An unique ceramic material produced through unidirectional solidification with eutectic composition of two-phase oxides was introduced recently. This composite material has the microstructure of coupled networks of two single crystals interpenetrate each other without grain boundaries. Depending on this microstructure this material, called Melt Growth Composite (MGC), can sustain its room temperature strength up to 1$700^{\circ}C$ (near its melting point) and offer strong oxidization-resistant ability, making its characteristics quite ideal for the gas turbine application. The research project on MGC started in 2001 with the objective of establishing component technologies for MGC application to the high temperature components of the gas turbine engine. MGC turbine nozzles are expected to improve efficiency of gas turbine. However, reduction of the thermal stress is required since high thermal stress is easily generated in MGC turbine nozzles due to temperature distribution. Firstly, the hollow nozzle shape was optimized to reduce thermal stress using numerical analysis. From the results of the first hot gas flow tests, the thermal stress due to span-wise temperature distribution was required to be reduced, and separated nozzle to three pieces was designed. This was tested in hot gas flow at 140$0^{\circ}C$ level, and temperature distributions on the nozzle surface were obtained and stress field was evaluated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권1호
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• pp.334-349
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• 2022

The effectiveness of Wi-Fi networks is greatly influenced by the optimization of contention window (CW) parameters. Unfortunately, the conventional approach employed by IEEE 802.11 wireless networks is not scalable enough to sustain consistent performance for the increasing number of stations. Yet, it is still the default when accessing channels for single-users of 802.11 transmissions. Recently, there has been a spike in attempts to enhance network performance using a machine learning (ML) technique known as reinforcement learning (RL). Its advantage is interacting with the surrounding environment and making decisions based on its own experience. Deep RL (DRL) uses deep neural networks (DNN) to deal with more complex environments (such as continuous state spaces or actions spaces) and to get optimum rewards. As a result, we present a new approach of CW control mechanism, which is termed as contention window threshold (CW_Threshold). It uses the DRL principle to define the threshold value and learn optimal settings under various network scenarios. We demonstrate our proposed method, known as a smart exponential-threshold-linear backoff algorithm with a deep Q-learning network (SETL-DQN). The simulation results show that our proposed SETL-DQN algorithm can effectively improve the throughput and reduce the collision rates.

• 한국통신학회논문지
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• 제35권3B호
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• pp.503-516
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• 2010

본 논문에서는 유무선 통합 환경에서 융합 미디어 서비스를 제공하기 위한 통합 프로파일 및 인증 제어 기술로써, 시스템 구현을 통한 결과를 제시한다. 가입자의 접속, 서비스, 이동성, 방송형 프로파일을 관리하고 개방형 API(Application Program Interface)를 통해서 제3사업자에게 가입자 프로파일 정보를 PUSH/PULL 방식으로 제공하는 방안을 제안한다. 이때 개방형 API는 웹 서비스, REST(Representational State Transfer) 기반으로 구현하여 제3사업자가 쉽게 서비스를 제공할 수 있는 방식을 제안한다. 또한, 한번 접속 인증에 성공하면 액세스 망이 변하거나 혹은 IMS(IP Multimedia Subsystem) 기반의 서비스 망에 접속하게 될 때 동일한 인증 정보를 유지할 수 있는 SSO(Single Sign-On) 기능을 제안한다. 제안된 방식은 CUPS(Converged User Profile Server) 시험 네트워크 구현 연구를 통하여 기능 검증 및 성능 분석을 수행하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.95-102
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• 2018

This paper proposes a dual lifting and its cooperative control system with two different kinds of floating cranes. The Mega-erection and Giga-erection in the ship building are used to handle heavier and wider blocks and modules as ships and off-shore platforms are enlarged. However, there is no equipment to handle such Tera-blocks. In order to overcome the limit on performance of existing floating cranes, the dual lifting is proposed in this research. In the dual lifting, two floating cranes are well-coordinated to add up the lift capabilities of both cranes without any loss such that virtually a single crane is lifting, maneuvering and unloading. Two main constraints for the dual lifting are as follows: First, two barges of floating cranes should be constrained as a rigid body not to cause a relative motion between two barges and main hooks of the two cranes should be controlled as main hooks of a single crane. In order words, it is necessary to develop the cooperative control of two floating cranes in order to sustain a center of gravity of the module and minimize the tilting angle during the lifting and unloading by the two floating cranes. Two floating cranes are handled as a master-slave system. The master crane is able to gather information about all working conditions and make a decision to control the individual hook speed, which communicates the slave crane by TCP/IP. The developed control system has been embedded in the real floating crane systems and the dual lifting has been demonstrated five times at SHI shipyard in 2015. The moving angles of the lifting module are analyzed and verified to be suitable for hoisting control. It is verified that the dual lifting can be applied for many heavier and wider blocks and modules to shorten the construction time of ships and off-shore platforms.

• Asian-Australasian Journal of Animal Sciences
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• 제15권10호
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• pp.1469-1474
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• 2002

This study was designed to evaluate the influence of a single or double dose of Fe dextran with organic trace mineral supplementation on the performance of piglets from dams fed diets with either inorganic (ITM) or organic trace minerals (OTM). It also determined the effect of the source of the trace minerals on the reproductive performance of sows. The trace mineral premixes were prepared using metal proteinates and the corresponding inorganic salts for the OTM and the ITM, respectively. Each mineral premix provided 100 ppm Fe/175 ppm Fe, 35 ppm Cu/170 ppm Cu, 90 ppm Zn/120 ppm Zn, and 40 ppm Mn/35 ppm Mn when added at 0.20% in sows /weaned pigs' diets, respectively. The first dose of Fe dextran was administered to piglets at 3 d and the second dose at 10 d after birth. One dose of Fe dextran supplied 100 mg of Fe. A total of 16 gestating sows (Landrace${\times}$Yorkshire) in parities 2 to 4 were randomly allocated to four treatments: 1) diet with ITM/one dose of Fe dextran to piglets, 2) diet with ITM/two doses of Fe dextran to piglets, 3) diet with OTM/one dose of Fe dextran to piglets, and 4) diet with OTM/two doses of Fe dextran to piglets. The total born alive, weaned, body weight at birth and at weaning were not affected by the sow's dietary treatment. Although organic trace mineral supplementation tended to increase the milk Fe content (p<0.10) at 7 d postpartum, piglets in all treatments performed equally from birth to weaning. The double doses of Fe dextran neither improved the average daily gain (ADG) nor influenced the survival of piglets from birth to weaning (21 d). Results suggest that a single dose of Fe dextran given to suckling pigs is adequate to sustain their needs for growth throughout the lactation period (21 d). Furthermore, there was a 21% improvement in both the ADG and the average daily feed intake (ADFI) (p<0.05) in weaned pigs fed diets with OTM. Cu and Fe in the liver (p<0.01), and Zn in both the bone (p<0.01) and the serum (p<0.01) were higher in piglets fed OTM than in those fed ITM. It would be concluded that single dose of Fe dextran administration with organic trace mineral supplementation show similar growth performance compared to 2 dose Fe dextran administration with inorganic mineral supplementation in young pigs.

• 한국수정란이식학회지
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• 제28권2호
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• pp.87-93
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• 2013

The efficiency of artificial insemination (AI) for horses remains unsatisfactory. It is mainly because each process of AI causes a detrimental effect on semen quality. To sustain quality of semen properly, several factors including libido of stallions and sperm damage during sperm processing and preservation should be considered. Stallions with decent libido produce a high ratio of sperm to seminal plasma in their ejaculates, which is the ideal semen composition for maintaining sperm quality. Thus, to maximize the fertility rate upon AI, stallions should be appropriately managed to enhance their libido. Seminal plasma should have a positive effect on horse fertility in the case of natural breeding, whereas the effects of seminal plasma on both sperm viability and quality in the context of AI remain controversial. Centrifugation of semen is performed during semen processing to remove seminal plasma and to isolate fine quality sperm from semen. However, the centrifugation process can also result in sperm loss and damage. To solve this problem, several different centrifugation techniques such as Cushion Fluid along with dual and single Androcoll-E$^{TM}$ were developed to minimize loss of sperm and to damage at the bottom of the pellet. Most recently, a new technique without centrifugation was developed with the purpose of separating sperm from semen. AI techniques have been advanced to deliver sperm to optimal region of female reproductive tract at perfect timing. Recombinant equine luteinizing hormone (reLH) and low dose insemination techniques have been developed to maximize both fertility rate and the efficiency of AI. Horse breeders should consider that the entire AI procedure should be optimized for each stallion due to variation in individual horses for a uniformed AI protocol.

• Asian Pacific Journal of Cancer Prevention
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• 제15권21호
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• pp.9225-9232
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• 2014

Ensuring adherence to chemotherapy is important to prevent disease progression, prolong survival and sustain good quality of life. Capecitabine is a complex chemotherapeutic agent with many side effects that might affect patient adherence to treatment. This cross sectional study aimed to determine adherence to capecitabine and its contributing factors among cancer outpatients in Malaysia. One hundred and thirteen patients on single regime capecitabine were recruited from Hospital Sultan Ismail and Hospital Kuala Lumpur from October 2013 to March 2014. Adherence was determined based on adherence score using validated Medication Compliance Questionnaire. Patient socio-demographics, disease, and treatment characteristics were obtained from medical records. Satisfaction score was measured using the validated Patient Satisfaction with Healthcare questionnaire. The mean adherence score was 96.1% (standard deviation: 3.29%). The significant contributing factors of adherence to capecitabine were Malay ethnicity [${\beta}=1.3$; 95% confidence interval (CI): 0.21, 2.43; p value=0.020], being female [${\beta}=1.8$; 95%CI: 0.61, 2.99; p value=0.003]), satisfaction score [${\beta}=0.08$; 95%CI: 0.06, 1.46; p value=0.035], presence of nausea or vomiting [${\beta}=2.3$; 95%CI: 1.12, 3.48; p value <0.001] and other side effects [${\beta}=1.45$; 95%CI: 0.24, 2.65; p value=0.019]. Adherence to capecitabine was generally high in our local population. Attention should be given to non-Malay males and patients having nausea, vomiting or other side effects. Sufficient information, proactive assessment and appropriate management of side effects would improve patient satisfaction and thus create motivation to adhere to treatment plans.