• 한국안전학회지
• /
• 제32권3호
• /
• pp.8-14
• /
• 2017

This study examined the combustion and thermal characteristics of imported woods for building materials in Korea. Wooden specimens were confirmed by a cone calorimeter according to the KS F ISO 5660-1 standard. The combustion properties of the wooden specimens were measured in terms of the heat release rate (HRR), total heat released (THR), mass lose rate (MLR), and ignition time (time to ignition; TTI). The optical microscope was used for determine the anatomical characteristics of wood pit and structure. Also, the thermal properties were measured by thermogravimetric analysis (TGA) to determine the thermal stability of wooden specimens. The result of this experiment would be useful for fundamentals of guiding the combustion properties and thermal stability using wood application.

• 대한한방내과학회지
• /
• 제19권2호
• /
• pp.451-457
• /
• 1998

This study was performed on the bases of clinical consideration about patient who has malaria. The symptoms of malaria are periodic alternating of chills and fever on everyone, two or three days. The patients feel a chill at the first time of malaria, and have a fever, headache and sweating at the next time. The long cycle of malarial fever such as every 2 or 3 days means that it takes a turn for the worse. In this study, oriental medicine was taken based on the oriental medicine principle such as Dalwonum(達原飮), Sosihotang(小柴胡湯) and Bojungikgitang(補中益氣湯), and the patients take a turn for the better. In the process of treatment if there is no fever in the expected date of the malarial fever, it is sure to have fever in the next expected date. It is favorable that patients lose the chills first and the fever lately in the process of treatment, and we can explain that supporting healthy energy to eliminate evil(扶正祛邪). The long cycle of malarial fever such as every 4, 6 or 9 days means that it is just before the recovery.

• 대한전자공학회논문지
• /
• 제18권1호
• /
• pp.16-24
• /
• 1981

Delay-lock loop(DLL)는 상단관련이 있는 두 파형 사이의 지연차이를 추적하는한 최적장치이다. 본 논문에서는 지연시간이 n- 로 확장된 한 DLL의 구조와 동기상실 주파수등 저역주파수대의 성능이 해석되었다. 본 DLL은 correlator와 개선된 PN 신호장치로 구성되었으며,상관 특성은 확장된 S-커브의 형태를 가지고 있다. 잡음이 크더라도 추적범위와 초기동기시간이 좋은 특성을 가지고 있다. 3- DLL을 1- DLL과 비교하면 직렬동기방식에서 초기동기시간이 3배나 빠르며, doppler shift에 대한 저항이 2배나 큰 것으로 나타났다.

• Journal of Positioning, Navigation, and Timing
• /
• 제5권3호
• /
• pp.157-163
• /
• 2016

Clocks for time synchronization using radio signals such as global navigation satellite system (GNSS) may lose reference signals by intentional or unintentional jamming. This is called as holdover. When holdover occurs, a clock goes into free run in which synchronization performance is degraded considerably. In order to maintain the required precise time synchronization during holdover, accurate estimation on main parameters such as frequency offset and frequency drift is needed. It is necessary to implement an optimum filter through various simulation tests by creating clock noise in accordance with given specifications in order to estimate the main parameters accurately. In this paper, a method that creates clock noise in accordance with given specifications is described.

• 천문학회보
• /
• 제37권1호
• /
• pp.39.1-39.1
• /
• 2012

Nuclear rings in barred galaxies are sites of active star formation (SF). We investigate SF and its feedback effects occurring in barred galaxies, for the first time, using high-resolution grid-based hydrodynamic simulations. The gaseous medium is assumed to be infinitesimally thin, isothermal, and unmagnetized. The SF recipes include a density threshold corresponding to the Jeans condition, a SF efficiency of 1%, and momentum feedback via Type II supernova events together with stellar-wind mass loss. To investigate various environments, we vary the gas sound speed as well as the efficiency of momentum injection in the in-plane direction. We find that when the sound speed is small, the surface density of a ring becomes largely independent of the azimuthal angle, resulting in star-forming regions distributed over the whole length of the ring. When the sound speed is large, on the other hand, the ring achieves the largest density at the contact points between the dust lanes and the ring where SF occurs preferentially, leading to a clear age gradient of star clusters in the azimuthal direction. Since rings shrink with time, a radial age gradient of star clusters naturally develop regardless of sound speed, consistent with observations. SF persists over 200 Myr, with an average rate of ${\sim}1.3M_{\odot}/yr$ similar to observed values. Rings gradually become hostile to SF as they lose gas into stars and turbulent motions dominate.

• 한국콘텐츠학회논문지
• /
• 제6권12호
• /
• pp.177-185
• /
• 2006

문제해결학습을 수행하는데 있어서 가장 큰 문제점은 학생들이 문제 해결에 필요한 학습 정보를 수집하는데 많은 시간과 노력이 필요하다는 점이다. 이는 기존의 웹 기반 검색 시스템이 단순 키워드 매칭 검색 방법을 사용하고 있기 때문이다. 단순 키워드 매칭 검색방법은 단순히 키워드의 매칭 여부만으로 학습 정보를 검색하게 된다. 따라서 학생들이 정보를 찾는데 많은 시간과 노력을 투자하여야 하며, 학습 방향을 잃을 수 있는 문제점들을 안고 있다. 이러한 문제점을 해결하기 위하여 본 논문에서는 온톨로지 기반 검색 시스템을 설계 구 현하고 중학교 사회과 문제해결학습에 적용해 보았다. 그 결과 온톨로지 기반 검색이 기존의 웹 검색보다 더 효과적인 것으로 나타났다.

• 한국운동역학회지
• /
• 제24권3호
• /
• pp.209-216
• /
• 2014

The purpose of this study was to explore the effect of 8 weeks after school classes of track sports on students' start motion through kinematic variables. 30 students in D National university of education participated for this study. These students divided into two groups, 17 students for experimental group and 13 students for control group. The two groups participated in general athletic class as common class, and the experimental group participated in after school class additionally. The general class taught track and jump skill for 3 hours a week, and the after school class taught only athletic running skill for 30 minutes a week. Pre and post test assessed to assess students' kinematic changes. Findings indicated that velocity and step rate were increased, and contact time, step length, displacement of center of mass were decreased in the experimental group. In the control group, early velocity, knee/hip angle velocity were increased, and contact time, step length, displacement of center of mass were decreased. In conclusion, the students who only participated in general class, could not maintain athletic skills obtained from the class. However, students who participated in both general and after school class accomplish athletic start skill. This is because Continuous learning effect helped students keep the skill and did not lose the skill. Thus, in order for students to learn specific sport skills, joining after school class with general class together is recommended.

• 한국축산식품학회지
• /
• 제32권5호
• /
• pp.578-583
• /
• 2012

The purpose of this study was to evaluate the ultrastructural and shear force changes of duck breast and leg meat during aging at $0^{\circ}C$. Pekin ducks (45 d old) purchased from Greemud Co. were used for this experiment, and were stored at $0^{\circ}C$ for 7 d in order to determine the changes of the meat structure using transmission electron microscopy (TEM) and shear force. At day 0, A-band, I-band, M-line and Z-line of sarcomeres were seen clearly, but sarcomeres started to lose structure and become extended in length from day 2. With extended aging periods, myofibrils were destroyed and symptoms of aging became more obvious. In the duck breast meat, some myofibrils were also destroyed at the Z-line, but were mainly destroyed at the M-line. The change in structure of duck leg meat over time was similar to that of breast meat. After five days and seven days of aging, mitochondria size and quantity were determined to be increased between the myofibrils. Shear force was decreased over time. From this study, aging at $0^{\circ}C$ was found to negatively influence the ultrastructure and shear force of duck meat.

• 한국통신학회논문지
• /
• 제32권1A호
• /
• pp.101-108
• /
• 2007

센서 네트워크를 위한 IEEE 802.15.4표준에서는 여러 개의 Full Function Device(FFD)들이 독립적으로 송신하는 비컨들간의 충돌 현상이 존재한다. 이러한 비컨의 충돌은 디바이스간의 타임 동기를 잃게 할 뿐만 아니라, 통신 불능 상태까지 이르게 한다. 이를 개선하기 위해IEEE 802.15.4b 표준안에서는 Post Beacon Period(PBP)를 추가로 정의하여 사용하지만, 역시 다단 토폴로지에서는 비컨충돌의 가능성이 존재할 수 있다. 본 논문에서는 이러한 비컨 충돌의 문제점을 해결하기 위해 FFD가 최초 결합 절차 시 코디네이터가 할당하는 Shor Address 값을 이용하여 비컨 송신 시기를 스스로 결정하는 새로운 비컨 정렬 방식을 제시하였으며, NS-2를 이용하여 제시된 방식의 비컨 충돌 회피 과정을 모의 실험하였다.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권10호
• /
• pp.219-228
• /
• 2021

The study examines the behavior of stock prices after large price changes. It further examines the effect of firm size on stock returns, and the presence of the disposition effect. The study employs the event study methodology using daily price data from Pakistan Stock Exchange (PSX) for the period January 2001 to July 2012. Furthermore, to examine the factors that explain stock price behavior after large price movements, the study employs a two-way fixed-effect model that allows for the analysis of unobservable company and time fixed effects that explain market reversals or continuation. The findings suggest that winners perform better than losers after experiencing large price shocks thus showing a momentum behavior. In addition, the winners remain the winner, while the losers continue to lose more. This suggests that most of the investors in PSX behave rationally. Further, the study finds no evidence of disposition effect in PSX. The investors underreact to new information and the prices continue to move in the direction of initial change. The pooled regression estimates show that firm size is positively related to post-event abnormal returns while the fixed-effect model reveals the presence of unobservable firm-specific and time-specific effects that account for price continuation.