• 한국산학기술학회논문지
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• 제9권4호
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• pp.871-877
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• 2008

Adaptive 아크 로봇 용접을 위한 용접 공정 변수와 용접 부 형상 사이에 상관관계를 조사하는 것은 중요한 일이다. 하지만 맞대기 용접의 공정에 있어 갭으로 인해 정확한 이면비드를 예측하는 것은 어려운 일이다. 본 연구에서는, 먼저 맞대기 용접을 통해 외부 용접 조건과 용접 비드 형상사이 상관관계가 규명되었고, 이를 응용하여 적절한 이면비드를 얻기 위한 개발이 이루어졌고, 이 연구결과는 산업 전 분야에 폭넓게 사용될 수도 있다. 다중회귀분석법이 공정변수 예측을 위한 연구방법으로 적용되었다. 예측방법의 결과들 또한 비교 및 분석이 이루어졌다.

• 지역사회간호학회지
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• 제17권1호
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• pp.17-25
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• 2006

Purpose: The goals of this research are to find out factors influencing the duration of work-related disability and to present implications for policies to prevent delayed recovery. Method: The subjects of this study were 238 workers who had been proved to be industrial disaster victims for occupational low back pain between January 1 2000 and December 31 2003. Kaplan-Meier method was used to estimate the proportion of duration of disability associated with low back pain, and Cox proportional hazards analysis was used to identify factors predicting it. The model distinguished main symptom variables affecting acute(${\leq}90\;days$) and chronic phase of disability (>90 days). Result: Fifty percent of the workers had not recovered in 408 days. The results of Cox regression show that delayed duration of disability was predicted by diagnosis, pain radiation (in chronic phase), sex, the size and labor union of the workplace, scheduled rest, compensation from the company, and operation. Conclusion: Duration of disability associated with compensated low back pain is influenced not only by factors related to the company and compensation system but also by individual factors. Thus, future efforts to reduce duration of disability may need to take into account all these factors.

• 척추신경추나의학회지
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• 제13권1호
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• pp.35-44
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• 2018

Objectives: To determine the effectiveness of Tai-chi in treatinglow back pain. Methods: We searched 9 electronic databases(Pubmed, CAJ, EMBASE, Cochrane Library, Web of Science, KISS, KISTI, NDSL, and RISS) till April 2018 and included randomized controlled trials(RCTs) that used Tai-chi for lower back pain treatment. The methodological quality of each RCT was assessed usingthe Cochrane risk of bias tool. Results: As per the inclusion criteria, 5 RCTswere found to be eligible for our review. These studies were divided into 4 groups and meta-analysis was performed. The meta-analysis of 1 study showed favorable results regardingthe use of Tai-chi. Twostudies showed favorable results regardingthe use of Tai-chi with Tuina rather than Tuina alone. All studies were observed to have a high risk of bias. Conclusions: There is limited evidence available to support the effectiveness of Tai-chi in relieving low back pain;hence, additionalwell-designed RCTs should be encouraged for better evidence.

• 한국운동역학회지
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• 제20권4호
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• pp.487-495
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• 2010

The purpose of this study was conducted to make a comparative biomechanical analysis of X-factor and X-factor stretch during driver and iron swing. The subjects were composed of 10 professional golfers with more than 10 years career. The result was as follows: First, the analysis of the back swing with driver and iron swing showed no differences statistically between both the timing in horizontal rotating of shoulder and hip, the time required for X-factor stretch also showed no differences statistically. Second, the back swing with a driver swing showed more maximum horizontal rotation of shoulder and hip joint than the back swing with an iron swing, but the twist of shoulder and hip that was X-factor stretch angle showed no difference. Third, the GRF of the max value for the left and right foot during shoulder and hip horizontal rotation of back swing showed no differences statistically in the movement of driver and iron swing during the back swing, and the GRF of X-factor stretch for the left and right foot showed no differences statistically in driver and iron swing. Therefore the result of this research showed that the operation of torso(X-factor stretch) and weight shifting were similar although the horizontal rotation of body was different during the driver and iron swing.

• 소성∙가공
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• 제30권1호
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• pp.35-42
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• 2021

Magnesium alloys are used in electronic devices such as laptops due to their lightweight features as well as vibration absorption and electromagnetic shielding properties. However, the precision of electronics is limited by the large number of small and precise ribs, the cost-effective manufacture of which requires appropriate technology. Plate forging is an efficient manufacturing process that can address these challenges. In this study, plate forging of magnesium alloys was investigated specifically for the fabrication of laptop cover. The plate forging process with back-pressure was used for near-net shape formation. Finite element analysis was used to select appropriate variables for back-pressure formation to generate ribs of various sizes and shapes without defects. The reliability of the analysis was verified to manufacture the prototype. The effect of back-pressure can be verified via fabrication of prototypes as well as structure and forming analysis based on finite element method. The process design factor of back-pressure increases formability without defects of under-filling and flow-through. Moreover, the tensile strength was maintained even after high temperature plate forging at 370 ℃, and the elongation was improved.

• 한국지반공학회논문집
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• 제21권3호
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• pp.99-108
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• 2005

지하 구조물을 설계하는데 있어서 가장 중요하면서도 어려운 일은 대상 지반의 정확한 공학적 특성을 파악하는 것이다. 본 논문의 주된 목적은 터널 주변지반의 지반정수 평가를 위한 새로운 터널 역해석 기법의 제안에 있다. 이를 위하여, 초기 예측치와 계측치로부터 예측된 값을 합리적으로 조합할 수 있는 확장 Bayesian 방법(Extended Bayesian Method, EBM)을 적용하였다. 또한 터널 내에서 계측된 터널 상대변위만을 역해석 입력값으로 사용함으로써 터널 절대변위 예측을 위한 수학적 연산 과정에서 발생되는 오차를 제거하였으며, 터널 상대변위 발생 경향을 역해석에 충분히 반영하기 위하여 3차원 수치해석을 적용하였다. 이를 바탕으로 본 논문에서는 터널 상대변위를 이용한 3차원 터널 역해석 기법을 제안하였으며, 가상의 단면에 대한 예제해석을 통해 그 적용성을 검증하였다.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.314-319
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• 2000

Back-face strain compliance (BFS compliance) for the four-point bend specimen has been calibrated for various crack length ratios. Finite element technique was employed to simulate four-point loading and calculate back-face strain of the bend specimen. The numerically determined strain variation along the back face indicates that the sensitivity to gage placement increases with crack length and back-face strain at the gage length less than O.2W, where W is the width of the bend specimen, can be measured within 5% deviation of the maximum BFS. Non-dimensional back-face strain compliance, -E'BCW, was calibrated with FE analysis and experiment. The experimentally determined compliance indicates good agreement with the numerical compliance and can be expressed as a function of crack length ratio.

• Journal of Power Electronics
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• 제12권4호
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• pp.604-614
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• 2012

This paper presents a comparative study of position sensorless control schemes based on back-electromotive force (back-EMF) estimation in permanent magnet synchronous motors (PMSM). The characteristics of the estimated back-EMF signals are analyzed using various mathematical models of a PMSM. The transfer functions of the estimators, based on the extended EMF model in the rotor reference frame, are derived to show their similarity. They are then used for the analysis of the effects of both the motor parameter variations and the voltage errors due to inverter nonlinearity on the accuracy of the back-EMF estimation. The differences between a phase-locked-loop (PLL) type estimator and a Luenberger observer type estimator, generally used for extracting rotor speed and position information from estimated back-EMF signals, are also examined. An experimental study with a 250-W interior-permanent-magnet machine has been performed to validate the analyses.

• 기본간호학회지
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• 제17권3호
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• pp.343-350
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• 2010

Purpose: This study was conducted to identify the factors that influence low back pain in nurses in Intensive Care Units (ICUs). Methods: A descriptive-correlational design was used, with a convenience sample of 116 nurses from one university hospital in Seoul. The data collected were processed using SPSS Window 17.0 Program for actual numbers and percentages, differences in the dependent variable according to general characteristics, and mean, standard deviations, correlation coefficients and multiple regression analysis. Results: The factor influencing low back pain in nurses in ICUs was functional ability (${\beta}$=.652). This one factor explained 41.9% of low back pain in nurses in ICUs. Conclusion: These results show that functional ability was related to nurses' low back pain in nurses in ICUs. These results further suggest that more research is needed to develop program involving functional ability to prevent and management of low back pain in nurses in ICUs.

• 한국전문물리치료학회지
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• 제21권2호
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• pp.74-81
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• 2014

The versions of the Oswestry disability questionnaire (ODQ) is regarded as one of the most extensively used condition-specific instruments measuring disability resulting from low back pain. It has been shown to have adequate psychometrics, reliability, validity, and responsiveness as a whole, yet the summated total score of the instrument often provide little information to rehabilitation clinicians. A keyform analysis based on Rasch measurement model is an innovative way of illustrating the specific test items that an individual may or may not perform. By applying the keyform of the Rasch measurement model to the ODQ, rehabilitation clinicians may able to select more challenging ODQ items matching an individual's ability and document them as attainable treatment goals. The results demonstrated how a keyform analysis assist to setting possible goals for the treatment of individuals with low back pain. Forty-two individuals with low back pain were recruited from rehabilitation clinics in Gainesville, Florida. A series of Rasch analyses on the 10 items of the ODQ were performed using Winsteps software. The performance of two individuals on those 10 items was illustrated on the keyform. The keyform analysis of the Rasch measurement model may be translated into a useful tool for making clinical judgements.