• Journal of electromagnetic engineering and science
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• 제11권1호
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• pp.34-41
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• 2011

This paper proposes a systematic design for a precoding codebook for a transmit-ing space-division multiple access (TN-SDMA) sharing spectrum with existing fixed wireless service (FWS). Based on an estimated direction angle of a victim FWS system, an interfering transmitter adaptively constructs a codebook, forming a transmit in the direction angle, while satisfying orthogonal beamforming constraints. Sum throughput results indicate that the throughput loss of TN-SDMA relative to a practical SDMA, called per user unitary and rate control ($PU^2RC$), is lower at larger number of transmission antennas, lower signal-to-noise ratio, or a smaller number of users. In particular, a small loss (12% throughput loss) is provided for practical system parameters. Spectrum sharing results confirm that TNSDMA efficiently shares spectrum with FWS systems by reducing protection distance to more than 66 %. Although a TN-SDMA system always has lower throughput compared to $PU^2RC$ in non-coexistence scenarios; it offers an intriguing opportunity to re-use a spectrum already allocated to an FWS.

• 한국통신학회논문지
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• 제30권6C호
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• pp.551-559
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• 2005

센서 배열을 이용하여 모르는 신호 매개변수들을 추정하는 것에 대한 연구가 광범위하게 진행되어 왔다. 또한 최근에는 셀룰러 시스템의 이동통신 이용자 수가 폭발적으로 증가되어, 다중 사용자로 인한 간섭이 매우 커지고 있다. 이러한 문제를 해결하기 위한 방법으로 채널 용량을 더 증가시키기 위한 안테나 배열기술의 응용이 연구되고 있다. 이 논문에서는 이동국 근처의 국소적 산란 신호의 새로운 모형을 평균 조정 벡터를 이용하여 만들고, 몇 가지 분포에 대한 수학적 유도를 하였다. 이 모델에서 신호 도래각의 추정은 weighted subspace fitting(WSF) 기법에 바탕을 두었고, 통계적 분석과 모의실험을 통해 성능을 보였다.

• Journal of Positioning, Navigation, and Timing
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• 제7권2호
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• pp.61-71
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• 2018

Existing radio positioning systems have a drawback that the attitude of user's tag is difficult to be determined. Although forward link angle of arrival (FLAOA) technology that uses measurements of array antenna arranged in a tag among the angle of arrival (AOA) technologies can estimate attitude and positioning of tags, it cannot extend the estimated results into three-dimensional (3D) results due to complex non-linear model displayed because of the effects of 3D positioning and attitude in tags. This paper proposed a radio navigation technique that determines 3D attitude and positioning via FLAOA / time of arrival (TOA) integration. According to the order of determining attitude and positioning, two integration techniques were proposed. To analyze the performance of the proposed technique, MATLAB-based simulations were used to verify the performance. The simulation results showed that the first proposed method, TOA-FLAOA integrated technique, showed about 0.15 m of positioning error, and $2-3^{\circ}$ of attitude error performances regardless of the positioning space size whereas the second method, differenced FLAOA-TOA integrated technique, revealed a problem that a positioning error became larger as the size of the positioning space became larger.

• 대한기계학회논문집A
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• 제26권10호
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• pp.1961-1970
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• 2002

A laser scanner is widely used fur a device fur acquiring point data in reverse engineering. It is more efficient to generate a surface automatically from the line-typed data than scattered data of points clouds. In the case of a compound model, it is hard to represent all the scanned data into one surface maintaining its original line characteristics. In this paper, a method is presented to generate a surface by the segmentation of measured point data. After forming triangular net, the segmentation is done by the user input such as the angle between triangles, the number of facets to be considered as small segment, and the angle for combining small segment. B-spline fitting is implemented to the point data in each segment. The surface generation through segmentation shows a reliable result when it is applied to the models with curvature deviation regions. An useful algorithm for surface reconstruction is developed and verified by applying an practical model and shows a good tools fur reverse engineering in design modification.

• 한국소음진동공학회논문집
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• 제23권7호
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• pp.669-674
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• 2013

To design the optimized low noise planetary gear sets, a program called pRMC(planetary run many cases) is developed. The pRMC is especially using a combination analysis method for all gear specifications and also able to analyze any type of planetary gear sets. The pRMC is composed of the 5 sections those are generate, setting, evaluate, combine and analysis. After calculating all candidate gear sets, the pRMC could show many results that represent the character of each gear set including the transmission error which is the main gear noise factor, the contact ratios, the bending stress and so on. By comparing the results objectively, user could predict and select the optimized gear set which has quiet noise level and desired durability. The planetary gear designed by pRMC could have reduced noise and vibration level from 5 to 10 dB than previous-designed one.

• 한국의류학회지
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• 제46권6호
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• pp.1074-1087
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• 2022

This study reports an optimization of a 3D printed wrist brace (WB) for various tilting angles (0°, 45°, 90°) of the re-entrant (RE) pattern and thickness (2 mm, 4 mm) using thermoplastic polyurethane (TPU) filaments and thermoplastic elastomer (TPE) filaments. The actual printing time, weight, Poisson's ratio, and tensile property of the manufactured samples were analyzed. The results confirmed that the actual printing time and weight increased with increasing thickness, regardless of the filament type. All tilting angles of the WB showed a negative Poisson's ratio (NPR), the largest of which appeared at 90°. The results of the tensile property analysis showed that a 90° tilting angle also had the largest value of elongation and stress. From these results, we conclude that the most suitable wrist brace is one in which the actual printing time is low, the weight is minimized to a thickness of 2 mm, and the tilting angle of the RE pattern is 90° for good shock absorption. The choice of filaments may be decided upon according to the user's preference, since the TPU is stiff and the TPE is elastic.

• International journal of advanced smart convergence
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• 제11권4호
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• pp.129-140
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• 2022

The purpose of this study to improve the shoulder wheel that is used frequently during shoulder circumduction exercise in a park, to link the shoulder wheel to a game application comprising various shoulder circumduction exercise and shoulder ROM exercise, and to enjoy the game during the exercises. A step motor was added to the shoulder wheel, and the rotating speed and rotating angle, and rotating direction can be controlled. The shoulder height, different for different people, can be controlled as well, so that any user can use this device. The developed application content includes the game elements, to enjoy the repetitive and boring exercise with fun and interest, and the control to adjust the degree of difficulty. This was to help users heighten their desire to rehabilitate by inducing active participation during repetitive shoulder rehabilitation exercise because the game vests users with intrinsic motivation and immersion. If the shoulder wheel and application contents proposed in this study are used, shoulder diseases can be prevented in advance by performing muscle strengthening exercises required in an aging society. This study is expected to contribute to the field of research related to serious games and rehabilitation.

• Physical Therapy Rehabilitation Science
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• 제13권2호
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• pp.240-249
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• 2024

Objective: The objective of this study is to evaluate various research that have examined dynamic knee valgus and to pinpoint a straightforward, clinically practical 2D assessment method for dynamic knee valgus that is user-friendly. Design: A literature review Methods: This literature review was conducted in Pubmed, MEDLINE^® and Google Scholar with the following key words: Knee valgus angle, Knee valgus evaluation, Knee valgus assessment, Dynamic knee valgus. After removing duplicate studies, 53 articles were initially chosen using this method, with 17 studies ultimately meeting the selection criteria. Results: Based on the comprehensive review of various studies, the Single Leg Squat (SLS) was identified as the most popular test method, followed by the Single Leg Landing (SLL) as the next most common test method. The Frontal Plane Projection Angle (FPPA) method was the most representative method for measuring dynamic knee valgus (DKV) during these tests. SLS was found in a total of 10 studies, while SLL was found in 7 studies. Conclusions: The most commonly proposed test for assessing DKV is measuring the SLS using the FPPA method. However, when applied to individuals without knee pathology, the discriminative power of this method may be limited. This suggests the need for further research to explore alternative methods for assessing DKV in this population.

• 한국항행학회논문지
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• 제22권6호
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• pp.610-615
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• 2018

세계적으로 GNSS (global navigation satellite system)는 선진국에서 개발 및 운용 중에 있다. 가장 대표적인 시스템인 GPS (global positioning system)을 시작으로 현재 중국의 Beidou가 빠르게 발전하고 있다. 본 논문에서는 빠르게 변화하는 Beidou의 활용을 위해 현재 시점의 한국지역에서 Beidou 위성의 가시성 분석을 수행한다. 이렇게 수행되는 분석에서 안정적으로 서비스되고 있는 GPS와 비교하며 진행하도록 한다. 가시성분석은 mask angle (저앙각 위성 배제 각도)에 따른 결과, skyplot (사용자 위치에서 위성의 위치를 가시적으로 표현하기 위한 그림)을 통한 결과를 수행하였다. 가시성 분석을 통해 한국지역에서 GPS위성에 비해 Beidou 위성의 고앙각 배치가 많아지는 것을 확인 할 수 있다. 또한 고앙각 배치가 많아지는 것의 효과를 확인하기 위해 GPS와 Beidou의 가용성 및 위치정확도 분석을 수행한다. 수행 결과에 따라 한국지역에서 고앙각 위성을 활용 할 시 GPS보다 Beidou가 더 효과적일 것으로 확인된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.98-100
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• 2005

This paper describes link analysis on the processed data, HRIT (High Rate Information Transmission) and LRIT (Low Rate Information Transmission), for the preliminary design of interface between COMS (Communication, Ocean and Meteorological Satellite) and ground station. At the MODAC (MeteorologicaVOcean Data Application Center), the processed data are transmitted to user station via COMS with normalization and calibration by pre-processing of MI (Meteorological Imager) data. Due to consider satellite as radio relay, overall analysis containing uplink and downlink is needed. Specific link parameters can be obtained with using the outcomes of SRR (System Requirement Review) which was held on 13-14 June 2005, in Toulouse. From the relation between overall link margin and output power of HPA (High Power Amplifier) of MODAC, it is shown that even though the minimum power related with COMS receiving power range is transmitted at MODAC, the obtained link margin of HRIT could be above 3 dB at user station which antenna elevation angle is 10 degree.