• Journal of the Korean Wood Science and Technology
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• 제36권3호
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• pp.61-69
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• 2008

구조부재의 압축성능을 검토하기 위하여 낙엽송 소재에 대해 섬유방향 및 섬유직각방향 압축시험을 행하였다. 시험편의 길이와 가압판의 크기에 따른 압축성능을 검토하였으며 현행 기준의 최소끝면거리의 적정성에 대해 검토하기 위하여 다우얼 지압지점으로부터 시험편의 섬유방향에 대해 변형율 변화를 측정하였다. 가압판의 크기에 따라 압축성능은 다르게 나타났으며, 다우얼형 파스너의 최소끝면거리(end distance)는 내부변형을 고려할 경우 현행 7 D보다 높게 적용하여야 안전한 것으로 나타났다.

• 한국지반신소재학회논문집
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• 제19권3호
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• pp.23-33
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• 2020

대구경 현장타설말뚝의 경우 수평지지특성은 중요한 요소이며 이를 증가시키기 위한 방안은 말뚝의 인접지반을 개량하여 강성을 증가시키는 방법과 말뚝 자체의 강성을 증가시키는 방법이 있다. 이중 말뚝체에 케이싱을 보강하여 강성을 증가시키는 방법이 많이 제안되고 있는 추세이지만 이와 관련된 연구는 거의 이루어지지 않고 있는 실정이다. 따라서 본 연구에서는 지반조건에 따라 대구경 현장타설말뚝의 적정 케이싱 보강길이를 평가하기 위해 비선형해석을 이용하여 지반조건별로 케이싱 보강길이에 따른 수평지지특성을 연구하였다. 그 결과 대구경 현장타설말뚝의 수평지지특성은 케이싱 보강 길이비(κ)가 1.2인 경우 가장 효과적이며 지반조건에 따라서는 느슨한 지반일수록 큰 보강효과를 나타내었다.

• 대한토목학회논문집
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• 제33권4호
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• pp.1523-1528
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• 2013

연약지반에 적용하여 인력 및 장비의 진입을 용이하게 함은 물론 나아가 가시설이나 소형구조물의 기초로서의 역할도 가능한 간편하고 효율적인 공법의 개발이 필요한 실정이다. 본 연구에서는 얕은기초에 설치되는 저면돌출벽의 지내력 증대 효과를 확인하고 간격과 길이에 따라 연약지반상 기초의 지내력이 어떻게 달라지는가를 알아보고자 하였다. 이를 위하여 재하장치가 설치된 토조에 연약지반을 조성하고 다양한 간격과 길이의 저면돌출벽을 가진 모형기초에 대해 재하시험을 실시하여 지지력과 침하량을 측정하였다. 그 결과 연약지반에서 얕은기초에 저면돌출벽을 장치하면 지내력 증대 효과를 얻을 수 있으며 돌출벽의 길이가 길수록, 개수가 증가할수록 전반적으로 지내력은 증가하는 양상을 보였다. 또한 저면돌출벽의 길이 대 폭 비가 1일 때 즉, 돌출벽과 기초 저면이 이루는 형상이 정사각형일 때 최적의 효과를 보이며 이 경우 지내력은 약 25% 증대된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.585-590
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• 2004

Many machine failures are not detected well in advance due to the masking of background noise and attenuation of the source signal through the transmission mediums. Advanced signal processing techniques using adaptive filters and higher order statistics have been attempted to extract the source signal from the measured data at the machine surface. In this paper, blind deconvolution using the eigenvector algorithm (EVA) technique is used to recover a damaged bearing signal using only the measured signal at the machine surface. A damaged bearing signal corrupted by noise with varying signal-to-noise (s/n) was used to determine the effectiveness of the technique in detecting an incipient signal and the optimum choice of filter length. The results show that the technique is effective in detecting the source signal with an s/n ratio as low as 0.21, but requires a relatively large filter length.

• 대한물리치료과학회지
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• 제10권1호
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• pp.7-17
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• 2003

The purpose of this study was to investigate the effect of the involved lower limb weight bearing training on symmetrical weight supporting rate improvement and gait characteristics of patients with hemiplegia including their gait velocity, cadence, stride length, step length of the non affected side, step length of the affected side, foot angle of the non affected side, foot angle of the affected side, base of support, and so on. The subject of the study was 28 men and women patients with hemiplegia from 22 to 77 age, among patients who doctor diagnosed as hemiplegia due to stroke or traumatic brain injury, were possible to do independent gait more than 45m without others assistance, the flexion contracture of hip pint was less than $15^{\circ}$, did not have contracture for knee pint and one more than $5^{\circ}$ for ankle joint, did not have contraindication for exercise or gait did not show visual defect due to brain injury. The patients, the subject of the study, were classified into 14 patients of treatment. group applying continuous involved weight bearing with general therapeutic exercise and 14 patients of control group applying general therapeutic exercise, and then analyzed their gait before and after exercise. Temporal distance gait analysis(Boening, 1977) was used to analyze their gait, and ink foot-print was applied as one of measurement methods. However, it was statistically signifiant in the change rate(%) of gait characteristics, and treatment group's patients with hemiplegia had been highly changed in gait characteristics in comparison with control group. From the above-mentioned results, could find that continuous involved weight bearing training for patients with hemiplegia was effective to improve their gait ability and it could increase the ability in comparison with general exercise.

• Geomechanics and Engineering
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• 제19권2호
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• pp.127-139
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• 2019

Available methods to determine the ultimate bearing capacity of shallow foundations may not be accurate enough owing to the complicated failure mechanism and diversity of the underlying soils. Accordingly, applying new methods of artificial intelligence can improve the prediction of the ultimate bearing capacity. The M5' model tree and the genetic programming are two robust artificial intelligence methods used for prediction purposes. The model tree is able to categorize the data and present linear models while genetic programming can give nonlinear models. In this study, a combination of these methods, called the M5'-GP approach, is employed to predict the ultimate bearing capacity of the shallow foundations, so that the advantages of both methods are exploited, simultaneously. Factors governing the bearing capacity of the shallow foundations, including width of the foundation (B), embedment depth of the foundation (D), length of the foundation (L), effective unit weight of the soil (${\gamma}$) and internal friction angle of the soil (${\varphi}$) are considered for modeling. To develop the new model, experimental data of large and small-scale tests were collected from the literature. Evaluation of the new model by statistical indices reveals its better performance in contrast to both traditional and recent approaches. Moreover, sensitivity analysis of the proposed model indicates the significance of various predictors. Additionally, it is inferred that the new model compares favorably with different models presented by various researchers based on a comprehensive ranking system.

• Tribology and Lubricants
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• 제34권1호
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• pp.16-22
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• 2018

Cylindrical turbine guide bearings (TGBs) with simple plain pads have conventionally been used in vertical hydro-power turbine-generator applications in order to provide turbine runner shafts with smooth rotation guides and supports. To overcome low-load/low-eccentricity performance drawbacks, such as very low film stiffness and lack of design credibility in the stiffness values themselves, of conventional cylindrical TGBs, the introduction of a rotational-directional leading-edge taper to each partitioned pad, simply pad leading-edge taper, has been found to be very effective in enhancing their design-application availability and usefulness. In this study, we investigate the effects of taper angle and length for given taper heights in detail in order to systematically establish the effectiveness of design on the performance improvement of vertical hydro-power application cylindrical TGBs with pad leading-edge tapers. The analysis results with $4-Pad{\times}1-Row$ cylindrical TGBs show that the lubrication performance of the cylindrical TGBs is optimized with an approximate taper angle ratio of 0.8 and taper length ratio of 0.9. We conclude that the introduction of pad leading-edge tapers along with the optimization of taper designs can be very effective in improving the overall operation reliability of cylindrical TGBs and the rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems as well, to which the TGBs are applied.

• 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.

• 한국정밀공학회지
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• 제19권5호
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• pp.139-148
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• 2002

Motion errors of linear motion guideway are analyzed theoretically in this paper. For the analysis, an new algorithm predicting motion errors of bearing and guideway is proposed using the Hertz's elastic deformation theory. Accuracy averaging effect can be calculated quantitatively by analyzing relationship between motion errors of guideway and spatial frequency of rail form error. Influences of design parameters on the motion errors including the number of balls, preload, ball diameter, bearing length and the number of bearings are analyzed. As it is difficult to measure the rail form error, experimental results are compared with results analyzed by the equivalent analysis method which evaluate the motion errors of guideway using the measured errors of bearing. From the experimental results, it is confirmed that the proposed analysis method it effective lo analyze the motion errors of linear motion bearing and guideway.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.691-699
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• 2008

In the design of a foundation, settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a piled-raft foundation system may be adopted using piles as settlement reducing component. In this paper, Disconnected Piled Raft Foundation (DPRF) system, which installs disconnected piles underneath the raft and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical piled-raft foundation system. To this end, large size loading tests were carried out on weathered ground changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 34~87% and the allowable bearing pressure increased by 70% on average from those of the unreinforced original ground, respectively. The correlating formula between the area replacement ratio and the load bearing ratio of piles were derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on one inch settlement criteria.