• ETRI Journal
• /
• 제35권2호
• /
• pp.336-339
• /
• 2013

To enhance the symbol error rate (SER) performance of the two-way relay channels with physical layer network coding, this letter proposes a relay selection scheme, in which the relay with the maximal minimum distance between different points in its constellation among all relays is selected to assist two-way transmissions. We give the closed-form expression of minimum distance for binary phase-shift keying and quadrature phase-shift keying. Additionally, we design a low-complexity method for higher-order modulations based on look-up tables. Simulation results show that the proposed scheme improves the SER performance for two-way relay networks.

• 산업경영시스템학회지
• /
• 제28권1호
• /
• pp.55-63
• /
• 2005

This paper is to analyze the travel distance and the transport size of the vehicle when the AGV carries multiple-load in the tandem automated guided vehicle systems. The size of multiple-load represents the number of load that the AGV can carry simultaneously. The AGV can carry simultaneously multiple-load that load types are different. The transport system of the manufacturing system is a tandem configuration automated guided vehicle system, which is based on the partitioning of all the stations into several non-overlapping single closed loops. Each loop divided has only one vehicle traveling unidirectionally around it. The AGV of each loop has to have sufficient transport capacity that can carry all loads for given unit time. In this paper, the average loaded travel distance and the size of feasible multiple-load of the vehicle are analyzed. A numerical example is shown.

• Imaging Science in Dentistry
• /
• 제36권1호
• /
• pp.41-48
• /
• 2006

Purpose : To evaluate the reliability and clinical usefulness of ultrasonography in the temporomandibular joint (TMJ). Materials and Methods : Parasagittal and paracoronal 1.5 T MR images and 7.5 MHz ultrasonographs of 40 TMJs in 20 asymptomatic volunteers were obtained. Disc position using MR imaging was evaluated and the distance between the lateral surface of mandibular condyle and the articular capsule using MR image and ultrasonograph of 27 TMJs with normal disc position was measured and compared. Intraobserver and interobserver measurements reliability was evaluated by using interclass correlation coefficients (ICC) and measurement error. Also, the distance measured on ultrasonographs was compared, according to mouth position and disc postion. Results : The normal disc position was found in 27 of 40 asymptomatic joints. At the intraobserver reliability of measurement, ICC at the closed and open mouth position were 0.89 and 0.91. The measurement error was 0.4% and 0.5%. At the interobserver reliability, ICC at the closed and open mouth position were 0.92 and 0.81. The measurement error was 0.4% and 0.7%. At the TMJ with normal disc position, the distances between the lateral surface of mandibular condyle and the articular capsule measured on MR images and ultrasonographs were $2.0{\pm}0.7mm,\;1.8{\pm}0.5mm$, respectively (p<0.05). On the ultrasonographs, the distances at open mouth position were $1.2{\pm}0.5mm$ (p<0.05). At the TMJ with medially displaced disc, the distances at the closed and open mouth position were $1.3{\pm}0.3\;mm\;and\;0.9{\pm}0.2\;mm$ (p<0.05). Conclusion : The results suggest ultrasonography of TMJ is a reliable imaging technique for assessment of normal disc position.

• 지구물리와물리탐사
• /
• 제14권3호
• /
• pp.185-190
• /
• 2011

해양전자탐사의 모델링에서 1차장은 송수신 간격이 넓어지면 크게 감소하기 때문에 기존의 선형필터로서는 정확한 계산이 어려워진다. 그러나 균질 반무한공간의 경우 TM 모드의 Hankel 변환에는 해석해가 존재하므로 이를 이용하면 Hankel 변환의 계산을 위한 선형필터의 정확도를 검토할 수 있다. 그 결과 송수신 간격이 커짐에 따라서 전자기장이 반대수 그래프에서 선형적으로 감소하는 경우는 총 36가지 송수신 조합 중 9가지 뿐이며, 나머지 조합에서는 전자기장이 0 이거나 아니면 공기층의 영향을 받아 전자기장의 감소가 크지 않다. 다행히 이 9가지 조합에는 해석해가 존재하고, 나머지 조합에서는 전자기장의 극단적인 감소가 나타나지 않으므로 비교적 길이가 짧은 필터로도 Hankel 변환의 정확한 계산이 가능하다. 이상의 결과를 토대로 이 논문에서는 균질 반무한공간 모델에 대한 전자기장 계산법으로서 TM 모드의 Hankel 변환에는 해석해를 쓰고 TE 모드 계산에는 그 계수가 61개인 필터를 쓰는 방식을 제안한다.

• 대한물리의학회지
• /
• 제7권1호
• /
• pp.59-67
• /
• 2012

Purpose : This study was somatosensory less in patients with idiopathic scoliosis somatosensory input to the lumbar stabilization exercises carried out to determine the most effective treatment method to be stable and unstable in terms of supporting the lumbar stabilization exercises the patient's torso length and postural sway by comparing the distance from a standing position and looked for differences in effect on the balance. Methods : The subjects of the study were 18 patients who showed the symptom of scoliosis. The study classified the patients into two experimental groups, one using an unstable surface and one a fixed surface, and the patients were required to do a lumbar stabilization exercise a total of 12 times for 60 minutes per session, three times a week for four weeks. The study carried out a paired comparison t-test so as to compare differences between measurement values in each experimental group before and after the exercise. Results : Superior iliac spine on the left, there was a significant reduction in the group doing the lumbar stabilization exercise on an unstable surface (p<0.05). Regarding change in sway distance to the left and right directions in the group doing the lumbar stabilization exercise on the unstable surface, there was a significant decrease in both the condition of closed eyes or open eyes (p<0.05). As for change in sway distance in forward-and-backward direction, there was a significant reduction in the condition of either closed eyes or open eyes (p<0.05). Conclusion : The lumbar stabilization exercise on an unstable surface improved the trunk posture of patients with scoliosis symmetrically, and the static balance ability in a standing posture was discovered to be improved. In the future, the lumbar stabilization exercise on an unstable surface may be used as a posture correction and balance increase exercise for patients with scoliosis.

• 대한족부족관절학회지
• /
• 제24권1호
• /
• pp.14-18
• /
• 2020

Purpose: Chronic ankle instability is a very common abnormality of the ankle, but there is still controversy regarding its evaluation criteria. The stress view has difficulties in reflecting the patient's symptoms and treatment progress. Therefore, this study examined the relationship between the center of pressure (COP) measured by a pedobarograph and the symptoms of the patient. Materials and Methods: Thirty patients with chronic ankle instability from February to August 2018 were included. Each patient was surveyed with the foot and ankle outcome score (FAOS). The COP was measured with a foot pressure scanner, and the travel distance and ellipse area of the COP were calculated. Each patient was measured on one foot and on two feet with his or her eyes closed and open. The relationship between the COP measurement and FAOS score was analyzed using the Pearson correlation coefficient. Results: The participants were consisted of 21 male and nine female, with a mean age of 30 years, mean weight of 72 kg, and mean foot size of 259 mm. With the eyes open, the correlation coefficient between the FAOS and travel distance of the affected side was -0.394 (p<0.05) and that between the FAOS and the ellipse area of the affected side was -0.425 (p<0.05). On the other hand, no significant correlations were found between the travel distance and ellipse area of the affected side when patients closed their eyes. Conclusion: Measurement of the COP using foot pressure scanner could evaluate objectively patients with chronic ankle instability, with measurements in patients with their eyes open being more significant. Based on the findings of this study, an analysis of the COP with the patients with their eyes open and standing on one foot may help determine the management strategy and assess the progress of the patients.

• International Journal of Computer Science & Network Security
• /
• 제21권8호
• /
• pp.308-316
• /
• 2021

During the past two years, the education systems in the world witnessed unprecedented turmoil due to the coronavirus (Covid-19) pandemic, as most schools and universities in the world closed their doors to more than 1.5 billion students, or more than 90% of the total learners, according to recent figures issued by the UNESCO Institute for Statistics. Education experts have agreed that post- coronavirus education will not be the same as before, especially with the increasing use of modern technology in education. One of the most important new patterns with a structure digital in education is distance education, this style has been used, in many countries of the world, as an alternative to traditional education, since the beginning of the pandemic. In Saudi Arabia, this type of education has been used in all educational institutions, starting from kindergarten until the postgraduate level, as an alternative to face-to-face education to preserve the health and safety of students and workers in educational institutions. This study aimed to explore the level of satisfaction of preparatory year students on distance learning in their first year of study at Umm Al-Qura University. The findings of this study showed that students in the preparatory year were satisfied with their online learning experience. In addition, the results revealed that there was no effect for gender and location of study on students' level of satisfaction. Saudi universities should continue to work to create a suitable learning environment for students at the e-learning level.

• Journal of Power Electronics
• /
• 제9권3호
• /
• pp.499-506
• /
• 2009

In this paper, the initial pole-position estimation of a surface (non-salient) permanent magnet synchronous motor is mathematically analyzed and surveyed on the basis of simulation analysis, and developed for accurate servo motor drive. This algorithm is well carried out under the full closed-loop position control without any pole sensors and is completely insensitive to any motor parameters. This estimation is based on the principle that the initial pole-position is simply calculated by the reverse trigonometric function using the two feedback currents in the full closed-loop position control. The proposed algorithm consists of the predefined reference position profile, the information of feedback currents, speed, and relative position, and the reverse trigonometric function for the initial-pole position estimation. Comparing with the existing researches, the mathematical analysis is introduced to get a more accurate initial pole-position of the surface permanent magnet motor under the closed-loop position control. It is found that the proposed algorithm can be easily applied in servo drive applications because it satisfies the following user's specifications; accuracy and moving distance.

• 태양에너지
• /
• 제6권2호
• /
• pp.43-53
• /
• 1986

The objective of this study is to report on the characterics of convective flow and heat transfer during metling process in order to provide design information for thermal energy storage systems which use phase change material. In present study, flow and heat transfer characteristics of the Phase Change Material in the Open Top Model (O.T.M) and in the Closed Top Model (C.T.M) were studied numerically by the control volume formulation using the algebraic non-orthogonal coordinate transformation. For the calculation procedure, the physical properties of fluid are assumed to be constant except density which is linely dependent on temperature in the bouyancy term of momentum equations. At start of melting process, the thickness of melting layer is assumed from the Stefan Problem assumption. The heat transfer results of Open Top Model and Closed Top Model are compared with the parameters of Grashof number and aspect ratio. It was found that heat transfer phenomena in melted region was greatly affected by buoyancy-driven natural convection and the melting distance of Open Top Model at the upper region is greater than that of Closed Top Model.

• 지구물리와물리탐사
• /
• 제25권1호
• /
• pp.44-49
• /
• 2022

이 논문에서는 선형 이상체에 대한 벡터 중력과 중력 변화율 텐서 반응식을 유도하였다. 축대칭성을 가지는 이상체를 멀리서 관측하면 선형 이상체로 근사가 가능하므로 선형 이상체에 대한 중력 및 중력 변화율 해석해가 필요하다. 선형 이상체에 대한 중력 퍼텐셜을 1차원 적분식으로 정의하고 이를 직교 좌표계에서 미분하여 벡터 중력을 유도한다. 중력 변화율 텐서 반응식은 벡터 중력을 직교 좌표계에서 한번 더 미분하여 유도한다.