• Solar Energy
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• v.8 no.2
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• pp.26-38
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• 1988

If proper design and selection of the working fluid are made the power generation system of temperature difference could achieve more efficient results than others. This paper is to analysis the production of its power generation due to several parameters. Making the power generation system, the characteristics of power output are investigated to obtain its basic data for design. This results of this experiment are as follows. 1. The most proper working fluid in the system is Freon-22 having high stability and difference between the outlet pressure, $P_E$ of evaporator and outlet pressure, $P_c$ of Condenser. 2. With the increase of temperature difference between evaporator and condenser, the output in the system increases linearly. 3. The generation efficiency is largely dependent on the type or form of propeller, nozzle and optimum design of heat exchanger.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.894-904
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• 2005

The flow structure inside the intake head greatly affects the working efficiency of a vacuum cleaner such as suction power and aero-acoustic noise. In this study, the flow inside intake heads of a vacuum cleaner was investigated using qualitative flow visualization and quantitative PIV (Particle Image Velocimetry) techniques. The aerodynamic power, suction efficiency and noise level of the intake heads were also measured. In order to improve the performance of the vacuum cleaner, inner structure of the flow paths of the intake head, such as trench height and shape of connection chamber were modified. The flow structures of modified intake heads were compared with that of the original intake head. The aero-acoustic noise caused by flow separation was reduced and the suction efficiency was also changed due to flow path modification of intake head. In this paper, the variations of flow fields for different intake heads are presented and discussed together with results of aerodynamic power, suction efficiency and noise level.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.3
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• pp.236-241
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• 1993

Recently, with the ourdoor air pollution, the indoor air pollution devided into living environment and working environment are raised as the problem of indoor space. Also, the more time lived in indoor space, the larger the influence of indoor air pollution. Therefore in this study, the spatial variation of ventilation efficiency was estimated through the experiment using a physical model. The experiment using a physical model. The experiment was conducted in two category; the central zone of ventilated air flow and the corner zone. As the result of experiment, high ventilation efficiency (90$\sim$108%) was shown in the central zone of ventilated air flow. Whereas low ventilation efficiency (46$\sim$77%) was shown in the corner zone. In conclusion, when the designing of ventilation was planned, the zone showed low ventilation efficiency should be considered.

• International Journal of Fluid Machinery and Systems
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• v.9 no.3
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• pp.205-212
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• 2016

The performance of a prototype pump converted from that of its model pump shows an increase in efficiency brought about by a decrease in friction loss. As the friction force working on impeller blades causes partial peripheral motion on the outlet flow from the impeller, the increase in the prototype's efficiency causes also a decrease in its input power. This paper discusses results of analyses on the behavior of the theoretical head or input power of a prototype pump. The equation of friction-drag coefficient for a flat plate was applied for the analysis of hydraulic loss in impeller blade passages. It was revealed that the friction-drag of a flat plate could be, to a certain degree, substituted for the friction drag of impeller blades, i.e. as a means for analyzing the relationship between a prototype pump's efficiency increase and input power decrease.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.69-79
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• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.221-224
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• 2002

The analysis of characteristics of pumping in the small tube well for agriculture were surveyed. Study area was located at the Galsinri in Yesangun near the yedang reservoir. Agricultural electricity using rates for pumping, ground water level and volume of pumping was monitored every week. Pump working ratio and pump efficiency during period of transplanting of rice showed 48.5%, 58.4% respectively.

• Current Optics and Photonics
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• v.4 no.6
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• pp.571-575
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• 2020

Optical wireless power transmission (OWPT) is a good candidate for long-distance underwater wireless power transmission. In this work we investigate the transmission efficiency of underwater OWPT, depending on the operating wavelength. We consider four operating wavelengths: infrared, red, green, and blue. We also consider the cases of pure water and sea water for the working conditions. Our results show that it is necessary to select the operating wavelength of underwater OWPT according to the transmission distance and water type of the target application.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.379-390
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• 2011

Purpose: This study was conducted to improve the working conditions of dental technicians, through survey for working conditions related to perform one's duty, the extent of personal exposure to substances hazardous and complaint rate and factor of job stress and subjective symptom on musculoskeletal disorders. Methods: Using four types of structured questionnaires: social and demographic factor; the actual conditions of working space; working conditions; and characteristics of dental technicians, respondents filled in the questionnaires and the results were analyzed statistically. Results: The evaluation of comfort in working place found that satisfaction level on indoor noise was the lowest with 2.6 on a five-point scale and privacy space followed 2.8 point. In reasons for dissatisfaction with job, over workload ranked the highest by 25.4% and role overload had the highest by 39.5% in job stress factors. Based on the results, we could draw conclusion that dental technicians were unsatisfied with role overload and heavy workload a day. In reasons for musculoskeletal symptom prevalence, long-patient work was the highest by 24.1%. It was thought to cause dental technicians need deep procession and long-patient work due to the nature of their job. Conclusion: In conclusion, noise reduction and privacy space are required to improve job efficiency of dental technicians. In addition; we need to think of ways to increase the job satisfaction with adequate rest while deep procession and long-patient working.

• Geomechanics and Engineering
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• v.36 no.5
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• pp.427-440
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• 2024

This study concentrates on the 301 comprehensive caving working face, notable for its considerable mining height. The roof model is established by integrating prior geological data and the latest borehole rock stratum's physical and mechanical parameters. This comprehensive approach enables the determination of lithology, thickness, and mechanical properties of the roof within 50 m of the primary mining coal seam. Utilizing the transfer rock beam theory and incorporating mining pressure monitoring data, the study delves into the geometric parameters of the direct roof, basic roof movement, and roof pressure during the initial mining process of the 301 comprehensive caving working face. The direct roof of the mining working face is stratified into upper and lower sections. The lower direct roof consists of 6.0 m thick coarse sandstone, while the upper direct roof comprises 9.2 m coarse sandstone, 2.6 m sandy mudstone, and 2.8 m medium sandstone. The basic roof stratum, totaling 22.1 m in thickness, includes layers such as silty sand, medium sandstone, sandy mudstone, and coal. The first pressure step of the basic roof is 61.6 m, with theoretical research indicating a maximum roof pressure of 1.62 MPa during periodic pressure. Extensive simulations and analyses of roof subsidence and advanced abutment pressure under varying working face lengths. Optimal roof control effect is observed when the mining face length falls within the range of 140 m-155 m. This study holds significance as it optimizes the working face length in thick coal seams, enhancing safety and efficiency in coal mining operations.

• Explosives and Blasting
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• v.23 no.1
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• pp.31-39
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• 2005

This study is based on the reseach about conte. track$(Dugso\~wonju)$ double line electric railway tunnel. Authors conducted test blasting to examine the effect of blasting pollution. To be conducted safe and effective work by using this result studies sailable substitution excavation method. No-vibration section generates continuously the vibration of breaker working to go abreast necessarily secondary fragmentation working and according to judging that application is actually difficult in case of the condition of study site, the period of construction, the cost of construction, the efficiency of construction, pre-heavy caliber horizontally boring working + line drilling method + vibration control secondary blasting method excavation working is possible from level within blast vibration standard.