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외란관측기를 사용한 복합형능동전력필터의 Deadbeat제어에 관한 연구
우정인,박지호,김영빈,문백영 東亞大學校 2000 東亞論叢 Vol.37 No.-
When LC filter is connected parallel to the Active Power Filter, a problem of the resonance between the Active Power Filter(AF) and LC filter often arises. In this paper, deadbeat control of Hybrid Active Power Filter using Disturbance-observer is introduced to solve this problem. By the estimation of the harmonics disturbance using proposed disturbance observer, the compensation characteristics of the AF is improved and the resonant current is suppressed. The validity of proposed disturbance observer is verified from simulation results using PSIM.
Beak, Seung-Ho,Kang, Tai-Kyung,Park, Wonyoung,Lee, Yoo-Sub Korea Institute of Construction Engineering and Ma 2015 Journal of construction engineering and project ma Vol.5 No.3
Bidding and contract systems are used for public construction projects to select contractors following fair competition principles and to execute national budgets effectively. Many challenges have arisen due to a lack of transparency and fairness and because bidding practices have been luck-based. Few comprehensive or comparative analyses have been conducted on the performance and limitations of bidding and contract systems, and empirical analyses designed to improve policies on and the practice of such systems are lacking. This study empirically analyzed current bidding and contract systems to seek ways of improving them. The study proposes several alternatives to resolve the problems with and irrationalities of the current system: 1) improving bidding and selection systems by changing them from a luck-based price competition into a technical merit- and value-based competition; 2) improving the assessment criteria to meet the current market level of bid and winning prices; 3) adjusting contractual responsibilities and sharing structures to meet the current trend; and 4) strengthening the competitiveness and expanding the social responsibility-based procurement systems of construction companies.
Switchable reflective lens based on cholesteric liquid crystal.
Lee, Jae-Ho,Beak, Ji-Ho,Kim, Youngsik,Lee, You-Jin,Kim, Jae-Hoon,Yu, Chang-Jae Optical Society of America 2014 Optics express Vol.22 No.8
<P>We demonstrated a switchable reflective lens based on choleteric liquid crystal (CLC) with a plano-convex shape. The plano-convex CLC lens was fabricated by assembling a planar substrate and a concave substrate. The reflective CLC lens exhibits wavelength selectivity and handedness sensitivity like the conventional CLC cell. The plano-convex CLC lens acts as a biconvex lens with the same curvature due to the Bragg reflection of the CLC layer. In addition, the reflective CLC lens was defocused by applying external voltage.</P>
HPMC의 입도에 따른 염산벤라팍신 및 카바마제핀 서방성 정제의 용출 특성
백현호(Hyun Ho Beak),차재욱(Jae Uk Cha),차자현(Ja Hyun Cha),홍준기(Jun Kee Hong),이성완(Sung Wan Lee),고원화(Won Hwa Ko) 한국고분자학회 2012 폴리머 Vol.36 No.3
본 연구는 약물의 용해도에 따른 서방성 용출 거동의 특성을 파악하기 위해 수행되었으며, 이에 따라 고 분자의 입도에 따른 염산벤라팍신과 카바마제핀의 정제를 제조하였다. 사용된 고분자는 경구를 통한 서방성 약 물전달 시스템 설계에 가장 널리 사용되는 히드록시 프로필 메틸셀룰로오스(HPMC)이며, HPMC의 입도 분포 에 따른 팽윤 속도의 차이는 중요한 특성으로 약물의 용출에 큰 영향을 미친다. HPMC 입도에 따른 정제 표면 을 분석하기 위해 SEM을 사용하였으며, 결정학적 특성을 파악하기 위해 DSC를 이용하여 분석하였고, 용출 특 성의 주요 메카니즘을 파악하기 위해 용출 모델식을 적용하였다. 본 연구를 통해 약물의 용해도 및 HPMC의 입 도에 따라 약물의 용출 거동을 조절할 수 있었다. The primary objective of this work is to find the properties of sustained release dissolution pattern depending on solubility of drugs, so venlafaxine HCl and carbamazepine tablets were made by using polymer wich various particle size. Hydroxy propyl methyl cellulose (HPMC) has been utilized in this study as an excipient that is one of the most widely used polymers for an oral sustained release formulation, and drug release pattern was strongly influenced by swelling rate depending on particle size of HPMC. Scanning electron microscope (SEM) was employed to investigate the surface of tablets with various HPMC particle size, and differential scanning calorimeter (DSC) was employed to investigate the crystallization of drugs in tablets. The release model equation was applied to analyze the main mechanism of drug release pattern. The results demonstrate that drug release pattern is controlled by the drug solubility and HPMC particle size.
Survey on the Incidence of Reproductive Disorders in Dairy Cattle
Hyun-Joo Lim,Ho-Beak Yoon,Jihoo Park,Yong-il Cho,Harim Im,Yeon-Seop Jeong,Kwang-Seok Ki,Seok-Ki Im 한국수정란이식학회 2015 한국동물생명공학회지 Vol.30 No.1
genetic selection has resulted in modern dairy cow with very high milk yields but reduced fertility, due mainly to an increase in reproductive disorders. The study was conducted to estimate the proportion of reproductive disorders among dairy cattle. The factors analyzed were; milk yield, cow parity, periparturient disorders, and reproductive status. The result of this study showed the incidence of reproductive disorders in high yielding dairy cows was prevalent. Repeat breeding was the major postpartum reproductive problem comprising (42.3%) of the samples. Higher reproductive disorders were also associated with lower parity. These disorders subsequently reduced reproductive performance by prolonged intervals from calving to first artificial insemination and from calving to pregnancy. Abnormalities in the reproductive system such as repeat breeder, silent heat, anestrous and ovarian cysts, as well as lower fertility have been recorded during the summer months (June to August). In conclusion, the study revealed that incidence of repeat breeder is mostly prevalent in dairy cows. Moreover, the incidence of reproductive disorders was higher in summer season and hence appropriate preventive and or therapeutic measures as per the type of abnormalities need to be undertaken.
Relationship between Growth Pattern, Age at First Calving and Next Reproduction in Holstein Heifers
Hyun-Joo Lim,Ho-Beak Yoon,Seok-Ki Im 한국수정란이식학회 2015 한국동물생명공학회지 Vol.30 No.4
Growth rate during rearing, which varies depending on provided nutrition, has been related with age at 1st calving (AFC). This study investigated the effect of upgrowth parameters during the rearing period on the reproduction of nulliparous Holstein heifers. The study comprised 77 successively born heifers from the same herd. Growth rate and fertility traits were measured during rearing and fertility parameters were recorded in lactations 1. Growth parameters (body weight, height, heart girth and body length) were measured at the approximate birth time, 270 and 450 d of age. Reproduction data collected included age at 1st breeding, number of services per conception (S/C), pregnancy rate to 1st artificial insemination, AFC. Animals were subsequently divided into 4 AFC groups for analysis: <23 mo, 23∼ 25 mo, 26∼30 mo and >30 mo. The AFC reflected both upgrowth rate and heifer reproduction, with later calving heifers smaller. Increased skeletal growth (at 270 and 450 d) was related with a reduced AFC (p<0.05). Early calving animals (<23 mo) had the best reproduction as nulliparous heifers, with most conceiving at first service (87.5%). Fertility in the first lactation was the worst in the oldest AFC group (>30 mo). In the 1st lactation period, a number of services per conception (3.1±0.3) increased with increasing AFC (>30 mo). Sub-optimal upgrowth related with an increased AFC could be mitigated by improved monitoring of replacement heifers during the rearing period.