• 대한안전경영과학회지
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• 제23권4호
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• pp.93-104
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• 2021

In this paper, we propose a method for diagnosing overload and working load of collaborative robots through performance analysis of machine learning algorithms. To this end, an experiment was conducted to perform pick & place operation while changing the payload weight of a cooperative robot with a payload capacity of 10 kg. In this experiment, motor torque, position, and speed data generated from the robot controller were collected, and as a result of t-test and f-test, different characteristics were found for each weight based on a payload of 10 kg. In addition, to predict overload and working load from the collected data, machine learning algorithms such as Neural Network, Decision Tree, Random Forest, and Gradient Boosting models were used for experiments. As a result of the experiment, the neural network with more than 99.6% of explanatory power showed the best performance in prediction and classification. The practical contribution of the proposed study is that it suggests a method to collect data required for analysis from the robot without attaching additional sensors to the collaborative robot and the usefulness of a machine learning algorithm for diagnosing robot overload and working load.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1996년도 추계학술발표회논문집
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• pp.101-103
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• 1996

This Paper describes Peak load forecasting technique of pole transformers with correlation equation. While customers are demanding safe energy supply, current correlation equation that is used for load management of pole transformers has some problems. To get accurate correlation equation. several correlation equation were examined using past data and nu data collected using the measuring instrument developed for this study. It was recognized that the quadratic equation was the most accurate for peak load forecasting from working electrical energy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.585-590
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.170-177
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• 한국농촌생활과학회지
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• 제8권2호
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• pp.119-124
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• 1997

In this study we tried to give a decision on propriety of working conditions, to present ideas on reducing work loads, and to grope for efficiency of agricultural works. For this we examined the actual working conditions of cultivating welsh onion in the summer ground. And we improved harmful factors that affect farmer's health by considering results of previous study and farmer's subjective sensation. And we measured. compared, and analyzed the farmer's work loads before and after improvement. The results of this study are as follows ; 1. According to examine the actual working conditions of cultivating welsh onion in the summer ground, farmers have experienced physical and mental chronic fatigue on the basis of farmer's appel to eye - fatigue and sun - burned skin on hot working environment including excessive ultraviolet rays, the rough ground condition, inconsistent arrangement of working stand and sorter, heavy - weared habits, and unsuitable working posture. 2. When we improved harmful factors that affect farmer's health, conformed the effects on important work efficiency index such as heart rate, electromyovolume, body temperature, and microclimate inside clothing and work loads were decreased by eliminating the hillock and obstacles of ground, decreasing the clothing weight, using proper clothing appliances such as hat and sunglasses, controlling height of working stand and sorter suitably, improving the working postures and methods as using assistant appliances, alloting the working time and sequence effectively and presenting the light gymnastic exercises and rest for fatigue restoration.

• 인지과학
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• 제29권1호
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• pp.39-59
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• 2018

작업기억 부담이 부적 얼굴정서 처리에 미치는 영향을 밝히기 위해, N-back 과제 수행 도중 제시된 부적 얼굴표정에 의해 유발된 ERP성분들을 조사하였다. 한 개씩 순차적으로 제시되는 시각적 사물그림들에 대한 기억을 유지하고 갱신하도록 요구하면서(N-back 과제) 이 사물그림들이 제시되는 사이에 공포표정 또는 중립표정의 얼굴자극을 하나씩 제시하였는데, 작업기억 부담을 0-back 조건(저부담)과 2-back 조건(고부담)으로 조작하였다. N-back과제 수행반응을 분석한 결과, 고부담조건에 비해 저부담조건에서 더 빠르고 정확한 반응이 관찰되었다. 얼굴자극에 의해 유발된 ERP 평균진폭을 분석한 결과, 후두영역에서 측정한 P1 진폭에서는 정서가효과는 유의미하지 않았고 작업기억 부담효과만 유의미하였다(고부담 > 저부담). 후측 후두-측두 영역에서 측정한 N170 진폭에서 얼굴 정서가효과는 전반적으로는 유의미하였지만(부정 > 중립) 세부적으로는 작업기억부담과 반구에 따라 다르게 나타났는데, 정서가효과가 좌반구에서는 저부담조건의 경우에만, 우반구에서는 두 부담조건 모두에서 관찰되었다. 결국, 얼굴표정의 부적 정서가가 N170에 미치는 영향이 좌반구에서는 작업기억 부담에 의해 조절되었지만 우반구에서는 그렇지 않았다. 이러한 결과는, 부적 얼굴 표정의 초기 정서처리가 작업기억의 유지 및 조작 부담이 큰 경우 좌반구에서는 약화되거나 일어나지 않을 수 있는 반면, 우반구에서는 작업기억 부담의 크기에 관계없이 일어남을 보여주는 것으로써, 부적 얼굴정서 처리의 우반구 편재를 시사한다.

• Journal of Biosystems Engineering
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• 제43권2호
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• pp.83-93
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• 2018

Purpose: This study derived the consumed power and load characteristics of a tillage operation performed in an upland field located in Seomyeon, Chuncheon, Rep. Korea, where potatoes and cabbages were cultivated in two crops. Methods: A plow and rotavator were mounted on a tractor with 23.7 kW of rated power to perform the tillage operation. The work conditions were determined, considering the actual working speed of the tillage operation performed by the local farmers. The power consumption of the rear axle, engine, and power take-off (PTO), PTO torque, and tractive force were measured under each work condition. The consumed power and load characteristics were analyzed using their average values. Results: The rotary-tillage operation consumed more engine power than the plow operation for the same tractor-transmission gear condition. The PTO in the rotary-tillage operation and the rear axle in the plow operation consumed the most power. The power consumption of the engine and the PTO for the rotary-tillage operation tended to increase as the transmission gears of the tractor and the PTO became higher. In contrast, the rear-axle power consumption was insignificant. In addition, the PTO torque tended to rise as the tilling pitch increased. For the plow operation, the drawbar power and the rear axle power accounted for 68-90% of the engine power. The engine and rear axle power, drawbar power, and tractive force tended to rise as the working speed increased. Conclusions: The power consumption and load characteristics differed for the plow and rotary-tillage operations. They may also differ depending on the soil conditions. Therefore, the power consumption and load characteristics in various work environments and regions should be analyzed, and reflected in the design of tractors and working implements. The results derived from this study can be used as a reference for such designs.

• 한국산업보건학회지
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• 제16권3호
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• pp.276-283
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• 2006

Work-related musculoskeletal disorders (WMSDs) were a major source of disability and lost work time after 'Foreign Currency Crisis(1998-2000)' in Korea. There is considerable evidence documenting the association between psychosocial risk factors and work disability due to WMSDs. But, there is not much in Korea. The present study aimed to explore the predictive association between the changed working conditions and WMSDs after 'Foreign Currency Crisis' in Korea. A study sample of 8,670 automobile assembly workers were recruited for this study. A structured-questionnaire was used to assess general characteristics, working conditions, and information concerning medical treatment of WMSDs. After adjustment for sociodemographic factors, increased overtime work(OR=1.22), daily work time(OR=1.20), work speed (OR=1.32), number of workers(OR=0.83), supervisory control(OR=1.39), physical load(OR=1.39), and mental load (OR=1.25) were all founded to be significantly associated with WMSDs. This study has shown the importance of changed working conditions in the occurrence of WMSDs. Therefore, it will be necessary to reduce WMSDs with controlling both physical and psychosocial factors.

• 한국초전도ㆍ저온공학회논문지
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• 제14권3호
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• pp.48-52
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• 2012

This paper describes experimental study on the orientation dependence of GM-type pulse tube refrigerator with helium and neon as working gas. A pulse tube refrigerator generates refrigeration work with gas expansion by gas displacer in the pulse tube. The pulse tube is only filled with working gas and there exists secondary flow due to large temperature difference between cold-end and warm-end. The stability of secondary flow is affected by orientation of cold-head and thus cooling performance is deteriorated by gas mixing due to secondary flow. In this study, a single stage GM-type pulse tube with orifice valve as a phase control device is fabricated and tested. The fabricated pulse tube refrigerator is tested with two different working gases of helium and neon. First, optimal valve opening and operating frequency are determined with experimental results of no-load test. And then, the variation of no-load temperature as orientation angle of cold-head is measured for two different working gases. Effect of orientation dependence of cold-head as working gas is discussed with experimental results.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.68-73
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• 2011

An experimental study was conducted to investigate the thermal performance of a medium-temperature heat pipe against the charge amount of working fluid. The container and the wick of the heat pipe were made of stainless steel and the working fluid was Dowtherm-A for medium-temperature applications around $250^{\circ}C$. The diameter and length of the heat pipe were 25.4 mm and 1 m, respectively. The maximum thermal load was 1 kW and the working fluid charge ratio varied from 372% to 420%. The results showed that the thermal resistance ranged from 0.12 to $250^{\circ}C/W$ and the effective thermal conductance ranged from 7,703 to $8,898 W/m{\cdot}K$. Dry-out occurred for the heat pipe with 372% fill-charge at the heat load of 950 W, while the other heat pipes with higher charge amount did not encounter dry-out up to 1060 W.