• 한국통신학회논문지
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• 제34권8A호
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• pp.575-582
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• 2009

본 논문에서는 RSS(Received Signal Strength) 기반 무선 센서네트워크에서의 거리 식별코드를 이용한 거리측정 알고리즘(LAtu)을 제안하고 이를 기반으로 위치인식시스템을 설계 및 구현하였다. 또한 제안한 거리측정 알고리즘의 Ranging 정확도 성능과, 제안한 거리측정 알고리즘을 적용해서 개발한 위치인식시스템(System(LAtu))의 위치측정 오차 성능을 실제 위치인식 실험을 통해 IEEE 802.15.4 표준규격의 채널모델(LAieee)을 적용한 위치인식 시스템(System(LAieee))과 비교분석하였다. 성능분석의 결과, Ranging 정확도의 성능은 이동모듈과 비콘모듈간의 거리($D_{MM-BM}$)가 2m의 경우는 LAtu가 IEEE 802.15.4 표준규격의 채널모델(LAieee) 보다 34%정도 더 우수하였고, $D_{MM-BM}$가 5m 이상인 경우에서도 LAtu가 LAieee 보다 평균 5% 정도 더 정확하였다. System(LAtu)의 위치측정 오차 성능은 System(LAieee)에 비해 강당에서 1cm, 강의실에서 4cm 정도로 근소하게 낮았다.

• 한국산학기술학회논문지
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• 제10권6호
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• pp.1275-1280
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• 2009

최근 교량설계에서 외부 프리스트레스를 도입한 장지간 및 효율적인 단면활용 등과 같은 연구가 활발하게 진행되고 있다. 강구조물에 프리스트레스를 도입하면 큰 하중에서 탄성변형의 극한값이 증가하게 되어, 강재량을 줄일 수 있고, 비용의 측면에서 경제성이 있는 것으로 평가 되었다. 이러한 이유 때문에 우리나라에서도 최근 가설교량 시공시 프리스트레스를 도입하여 응력보정 및 처짐보정이 가능하고, 비교적 작은 단면으로 장지간 교량을 시공할 수 있어 통수단면을 충분히 할 수 있는 여러 가지 공법이 개발되고 있다. 따라서 본 논문에서는 가설 강교량에 프리스트레스 도입방법 및 고강도 텐던의 배치에 따른 영향, 강판과 고강도 텐던의 복합구조에 대한 효과를 기존 가설공법과 비교하여 검증 하고자 한다.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.343-363
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• 2017

The objective of this work was finding out the most advisable testing conditions for an effective and robust characterization of the tensile strength (TS) of concrete disks. The independent variables were the loading geometry, the angle subtended by the contact area, disk diameter and thickness, maximum aggregate size, and the sample compression strength (CS). The effect of the independent variables was studied in a three groups of experiments using a factorial design with two levels and four factors. The likeliest location where failure beginning was calculated using the equations that account for the stress-strain field developed within the disk. The theoretical outcome shows that for failure beginning at the geometric center of the sample, it is necessary for the contact angle in the loading setup to be larger than or equal to a threshold value. Nevertheless, the measured indirect tensile strength must be adjusted to get a close estimate of the uniaxial TS of the material. The correction depends on the loading geometry, and we got their mathematical expression and cross-validated them with the reported in the literature. The experimental results show that a loading geometry with a curved contact area, uniform load distribution over the contact area, loads projected parallel to one another within the disk, and a contact angle bigger of $12^{\circ}$ is the most advisable and robust setup for implementation of BT on concrete disks. This work provides a description of the BT carries on concrete disks and put forward a characterization technique to study costly samples of cement based material that have been enabled to display new and improved properties with nanomaterials.

• 대한통합의학회지
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• 제10권1호
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• pp.49-60
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• 2022

Purpose : The purpose of this study was to identify whether gym-ball exercise in standing position was an effective intervention for improving muscle strength, balance, gait, and fall efficacy in stroke patients. Methods : Twenty-four stroke patients were randomized into three groups: experimental group 1 (n=8), experimental group 2 (n=8), and control group (n=8). Experimental groups 1, 2 and the control group performed the gym-ball exercise in standing position, same exercise without a gym-ball, and general physical therapy for 4 weeks, five times a week in 30-minute sessions. Muscle strength, balance, gait, and fall efficacy were assessed using a handheld dynamometer, the Berg Balance Scale (BBS), the wearable BTS G-WALK® sensor, and the Korean version of the Falls Efficacy Scale (K-FES), before and after training, respectively. Comparisons within and between groups were analyzed using the Wilcoxon signed rank test, Kruskal Wallis H test, and Mann-Whitney U test. Bonferroni correction was performed when significant differences between groups were identified (p<.017, .05/3). Results : Regarding muscle strength, BBS score, cadence and FES-K were significantly improved after intervention in all three groups. The weight bearing rate, gait speed and step length in experimental group 1 and 2 were significantly improved after the intervention. The stride length in experimental group 1 were significantly improved after the intervention. Experimental group 1 had significantly improved BBS score and stride length after intervention than experimental group 2 and control group. Experimental group 1 and 2 improved muscle strength, weight bearing rate, and FES-K score more than the control group. Experimental group 1 showed significant improvement in cadence, gait speed, and step length after the intervention than control group. Conclusion : This study showed that exercise with gym-ball in standing position can be an effective intervention to improve balance and gait in stroke patients than the same exercise without gym-ball.

• Computers and Concrete
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• 제19권6호
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• pp.631-639
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• 2017

This study experimentally investigated the flexural capacity of a concrete beam reinforced with a newly developed GFRP bar that overcomes the lower modulus of elasticity and bond strength compared to a steel bar. The GFRP bar was fabricated by thermosetting a braided pultrusion process to form the outer fiber ribs. The mechanical properties of the modulus of elasticity and bond strength were enhanced compared with those of commercial GFRP bars. In the four-point bending test results, all specimens failed according to the intended failure mode due to flexural design in compliance with ACI 440.1R-15. The effects of the reinforcement ratio and concrete compressive strength were investigated. Equations from the code were used to predict the deflection, and they overestimated the deflection compared with the experimental results. A modified model using two coefficients was developed to provide much better predictive ability, even when the effective moment of inertia was less than the theoretical $I_{cr}$. The deformability of the test beams satisfied the specified value of 4.0 in compliance with CSA S6-10. A modified effective moment of inertia with two correction factors was proposed and it could provide much better predictability in prediction even at the effective moment of inertia less than that of theoretical cracked moment of inertia.

• 한국통신학회논문지
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• 제38C권2호
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• pp.181-188
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• 2013

본 논문은 GPS 신호를 수신할 수 없는 대형선박의 내부에서 현재 위치를 정확하게 측정하기 위해서, GPS 신호를 대신하여 선박내부에 설치되어 있는 Wireless AP (Access Point)에서 발신되는 RSSI (Received signal strength indication)를 이용하였다. 선박내부에서 수신되는 RSSI 신호 중 신호세기가 가장 강한 3곳의 AP에서 발신되는 RSSI를 Friis 공식을 통해 거리로 환산 후, 삼각측량법을 통해 위치로 변환하였다. 그리고 AP에서 발신되는 신호에는 노이즈가 발생되기 때문에 신호세기가 불규칙하게 변함으로써 정확한 위치를 얻기 힘들다. 그래서 칼만필터를 통해 실시간으로 위치를 보정하고, 보정된 위치는 서버 DB에 저장된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.315-322
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• 2003

Cyclic simple shear tests were performed to find out the effect of preshear on dynamic strength of the sandy soil. Tests were performed for the specimens with 40% and 60% of relative density, under three different effective vertical stress of 50, 100 and 200kPa. For 50 and 100kPa, preshear ratios 0.00, 0.08, 0.12 and 0.16 were given, respectively, For low and high relative densities, two different results are shown in dynamic tests. Under the dense conditions, the maximum shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) and the cyclic shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) causing a certain shear strain increase with augmenting preshear ratio(${\alpha}$). However, the maximum shear stress ratio and the cyclic shear stress ratio increase or decrease with increasing preshear ratio under the loose conditions. Correction factor(K$\_$${\alpha}$/) for preshear increases at an early stage and then decreases with increasing preshear ratio at loose condition and increase with increasing preshear ratio at dense condition. Correction factor (K$\_$${\alpha}$,Max/) for preshear increases with the increasing preshear ratio irrespective of relative density, and the value of has same behavior as K$\_$${\alpha}$/.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제35권3호
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• pp.184-188
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• 2013

Post-traumatic enophthalmos is a relatively common problem following orbitozygomatic fractures. Bony-volume expansion and soft tissue atrophy are considered the main etiological causes of this condition. Enophthalmos is corrected mostly through reducing the enlarged orbit volume. Autogenous graft and various alloplastic materials are used for this purpose. Porous polyethylene is highly biocompatible, durable, and remarkably stable. Also, the titanium plate embedded in a porous polyethylene sheet provides radiographic visibility and increased sheet strength and contour retention. We present experiences of titanium reinforced porous polyethylene for correction of the traumatic enophthalmos with literature review.

• 한국운동역학회지
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• 제28권2호
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• pp.119-125
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• 2018

Objective: The purpose of this study was to compare the effect of different 12-week exercise programs for posture correction on postural alignment in elderly women. Method: The study included 36 elderly women who were randomly divided into 3 groups: Group A (core exercise, n=12), Group B (combined exercise, n=12), and Group C (Pilates exercise, n=12). Postural alignment was measured using 6 variables in frontal and sagittal planes. Two-way mixed analysis of variance was used to compare the effect of exercise program types on postural alignment and a paired t-test was used to compare differences in postural alignment after exercise. Results: The core exercise group showed statistically significant improvement (p<.05) in multiple upper and lower body postural alignment measurements. The combined exercise and Pilates exercise groups showed statistically significant improvement (p<.05) in upper body measurements alone. Conclusion: Core exercise, combined exercise, and Pilates exercise improved postural alignment in elderly woman through improvement in muscle strength and ligament flexibility around the spine and pelvis.

• 한국통신학회논문지
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• 제35권9C호
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• pp.721-728
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• 2010

재귀적 구조의 SPCPC (single parity check product code)인 CAMC (constant amplitude multi-code) 는 반복적 복호를 행할 때 SPCPC에 비하여 오류 정정 성능이 우수하다. 본 논문에서는 대역확산 신호인 CAMC의 처리 이득이 성능 향상에 미치는 영향을 분석한다. 일반적인 곱 부호에서는 반복적 복호로 오류 정정 과정이 종료되지만, CAMC 는 반복적 복호 후의 역확산 과정에서 추가적으로 오류가 정정된다. 잔존하는 비트 오류의 수가 ($\sqrt{N}/2-1$)개 이하인 경우에는 (N은 코드워드의 길이), 역확산 과정에서 그 오류들은 모두 정정된다. 반복적 복호에서 EI (extrinsic information)의 분포 형태를 관찰한 결과, 초기의 EI 분포는 대체로 랜덤하나, 몇 회의 iteration 후에는 ($-E_{max}$) 혹은 ($+E_{max}$)의 이진 값으로 수렴한다. EI의 분포가 오류 정정의 진행 사항을 반영하는 점을 이용하는 iteration 제어 방법을 실험한 결과 Eb/No 에서 약 0.2 dB의 이득을 얻었다.