• 한국항해학회지
• /
• 제13권3호
• /
• pp.21-36
• /
• 1989

The submarine played an active part in military operation during the last of nineteenth century. Today, as an aid to science and technology and technology m the submarine is being utilized in the fields of deep sea investigation and sight-seeing as well as military activities. When the stability and the maneuverability of a submarine is studied, the problems arise on the vertical plane as well as the horizontal plane. However, the horizontal plane has been dealt with in the study of surface vessels. The author attempts to look into the hydrodynamic directional stability at high speeds (above 10knots) on the vertical plane, and to clarify the submarine's depth-rate as related to the factors that affect it : the distance from the center of buoyancy to the center of gravity, the speed of the submarine, and the position and the area ratio of hydroplane. In this study, the author considered the two groups of dimensionless derivatives of submarine. It is confirmed that the depth-rate of a submarine is decreased when the length, of BG is increased under the continuous submerging status. But the depth-rate is increased when the area ratio of hydroplane is enlarged. It is also confirmed that a submarine has only one critical speed in accordance with the shape of its hull, but unconcerned with its speeds.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권10호
• /
• pp.2338-2356
• /
• 2013

In cognitive radio networks, acquiring the position information of the primary user is critical to the communication of the secondary user. Localization of primary users can help improve the efficiency with which the spectrum is reused, because the information can be used to avoid harmful interference to the network while simultaneity is exploited to improve the spectrum utilization. Despite its inherent inaccuracy, received signal strength based on range has been used as the standard tool for distance measurements in the location detection process. Most previous works have employed the path-loss propagation model with a fixed value of the path loss exponent. However, in actual environments, the path loss exponent for each channel is different. Moreover, due to the complexity of the radio channel, when the number of channel increases, a larger number of RSS measurements are needed, and this results in additional energy consumption. In this paper, to overcome this problem, we propose using the Bayesian compressive sensing method with a calibrated path loss exponent to improve the performance of the PU localization method.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2012년도 춘계학술대회
• /
• pp.413-416
• /
• 2012

해를 거듭해 갈수록 정보화는 이젠 쉽게 접 할 수 있는 문화이며 일반화가 되어가고 있다. 이런 사회에서 학원 혹은 학교에서만 배움의 기회를 얻을 수 있었다면, 이젠 인터넷을 이용한 사이버학습이 가능하게 되었고, 이러한 사이버학습을 이용한 컨텐츠들이 많이 생겨나고 있다. 이에 발맞추어 학원과 학교 교육에만 의존하는게 아니라 가정에서도 학습을 할 수 있도록 하는 형태로 변화되어 가고 있다. 이러한 사이버학습에 대해서 알아보고자 한다. 첫째, 사이버 가정학습에 관한 효과는 무엇인가? 둘째, 사이버 가정학습에 대한 문제점은 무엇인가? 이러한 것들을 알아보고 대처방안에 대해 알아보고자 한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.175-177
• /
• 1996

This paper is studied on the numerical analysis of temperature distribution on the Nb-foil due to the eddy current under operating a superconducting power supply. The increase of rotating speed and magnetic flux above critical magnetic field lead to the temperature rising in the normal spot, the heat was distributed in the region of 30% distance from the center of the normal spot, but the most of the heat was transferred to LHe. Under operation of the sc power supply, the increase of rotation speed has the more influence on the temperature rising than that of magnetic flux. we can conclude that the totaling speed of normal spot is the main design consideration of the sc power supply, and get the optimal value of rotating speed.

• 한국환경과학회지
• /
• 제17권1호
• /
• pp.119-128
• /
• 2008

Laboratory analytical results of 22 sets of hydrophobic adsorbent coils containing surface soil-vapor and two soil samples collected by conventional intrusive method from each boring location at two active dry cleaning facilities in the State of Illinois, U.S.A, were presented to evaluate the performance of soil-vapor survey. The most critical factor to determine the effectiveness of soil-vapor survey is the distance from the soil-vapor sampling device to the actual contamination, which is a function of soil porosity, permeability, primary lithology, and other geological and hydrogeological site-specific parameters. Also this factor can be affected by the history of contaminant-generating operations. The laboratory analytical results in this study showed longer dry cleaning operation history (i.e., 50 years) and presence of fine sand at the beneath Site B allow the contaminants to migrate farther and deeper over a fixed time compared to Site A(i.e., 35 years and silty clay) so that the soil-vapor survey is not likely the most effective environmental site investigation method alone for Site B. However, for Site A, the soil-vapor survey successfully screened the site to identify the location reporting the highest soil concentration of chlorinated solvents.

• 한국주거학회논문집
• /
• 제23권3호
• /
• pp.53-61
• /
• 2012

Openness to outside is one of the most critical advantages for high-rise buildings. However, the effect of openness can be decreased if it is blocked by other high-rise buildings, especially built within the building complex of commercial district. The purpose of this study is to identify the horizontal openness of high-rise residential buildings by comparing 3 different cases of building arrangement type. A new method of evaluation has been introduced on the basis of distance to measure the openness including the matter of securing privacy. As a result of this study, comparative analysis was possible and relatively plentiful results of analysis could be drawn out. Through the process of analysis, this study set the evaluation indicators suitable to the analysis of openness of unit households. Thereby, the results of this study are expected to be used as useful basic data in planning high-rise mixed-use buildings.

• 대한기계학회논문집
• /
• 제11권6호
• /
• pp.877-883
• /
• 1987

본 연구에서는 이러한 경험적인면이 최소화되고 물리적 의미가 부여된 후류모 델을 제시하여 일반적인 형상에 대한 계산에 앞서 Celik등의 경우와 같이 원통 주위유 동장을 먼저 다루어 보고자 한다. 다른 방법들과는 달리 후류면의 길이를 조절하지 않고 후류면에서의 와도분포를 점차 감소시켜 후류영향이 자연적으로 감소되게 하였는 데, 이는 물체에서 떨어져 나간 와류(vortex)가 확산에 의해 점차 소멸해가는 점을 모 델링한 것이다. 본 계산은 경계층배제두께의 영향을 무시하고 후류모델에 필요한 박 리점은 실험치를 사용하여 수행하였다. 박리점의 예측은 기존의 경계층해법을 도입 하면 쉽게 해결할 수 있어 큰 문제가 아니라고 생각하며 다만 배제두께 영향은 Reyno- lds수에 따라 계산 결과에 다소 영향을 미칠 수 있게 되는데 이는 뒤에 다시 다루기로 한다.

• 한국항공우주학회지
• /
• 제41권4호
• /
• pp.314-318
• /
• 2013

국내 최초로 개발되는 공대지 유도키트에 대하여 미국의 MIL-HDBK 및 STANDARD를 준용한 시험을 성공적으로 수행하였다. 각종 지상시험을 통하여 유도키트의 작동 성능과 내구성을 검증하였으며, 유도키트를 일반목적폭탄에 장착한 활공탄으로 비행시험을 수행하여 중거리 활공비행성능 및 정확도가 매우 양호함을 확인하였다.

• 한국소음진동공학회논문집
• /
• 제13권3호
• /
• pp.202-209
• /
• 2003

A simply supported beam subjected to a uniformly distributed tangential follower force and the two successively moving spring-mass systems upon it constitute this vibration system. The influences of the velocities of the moving spring-mass system, the distance between two successively moving spring-mass systems and the uniformly distributed tangential follower force have been studied on the dynamic behavior of a simply supported beam by numerical method. The uniformly distributed tangential follower force is considered within its critical value of a simply supported beam without two successively moving spring-mass systems, and three kinds of constant velocities and constant initial displacement of two successively moving spring-mass systems are also chosen. Their coupling effects on the transverse vibration of the simply supported beam are inspected too. In this study the simply supported beam is deflected with small vibration proportional to natural frequency of the moving spring-mass systems. According to the increasing of initial displacement of the moving spring-mass systems the amplitude of the small vibration of the simply supported beam is increased due to the spring force. The velocity of the moving spring-mass system more affect on the transverse deflection of simply supported beam than other factors of the system and the effect is dominant at high velocity of the moving spring-mass systems.

• 조명전기설비학회논문지
• /
• 제28권2호
• /
• pp.70-75
• /
• 2014

A track circuit is a critical piece of equipment that allows the existence of the trains on the track to be detected. Train detection is very important for the signal safety equipment. It allows for the confirmation of a train's location, the locking of switch points, the coordination of safe distance between trains, and the advance notice of a train's arrival. Track circuits can be powered by AC or DC. The DC track circuits are usually used on non-electrified tracks. On these tracks, many signal errors can be caused by lightning or problems with the power source. These problems can also cause damages to the rectifiers which must be repaired or replaced, promptly. This issue is especially problematic in the summer because of the higher frequency of thunderstorms. Issues with track circuits also cause problems for other equipment, such as railroad crossings and switch points. This further disrupts the safe operation of trains. This study aims to enhance maintenance efficiency and improve safety by utilizing parallel operation and multiplexing of a DC track circuit as well as installing an external surge protector. The experimental results on the operation of the proposed method is also presented.