• 구강회복응용과학지
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• 제23권1호
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• pp.55-68
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• 2007

The purpose of this study was to analyze the distribution of stress in the surrounding bone around implant placed in the first and second molar region. Two different three-dimensional finite element model were designed according to vertical bone level around fixture ($4.0mm{\times}11.5mm$) on the second molar region. A mandibular segment containing two implant-abutments and a two-unit bridge system was molded as a cancellous core surrounded by a 2mm cortical layer. The mesial and distal section planes of the model were not covered by cortical bone and were constrained in all directions at the nodes. Two vertical loads and oblique loads of 200 N were applied at the center of occlusal surface (load A) or at a position of 2mm apart buccally from the center (load B). Von-Mises stresses were analyzed in the supporting bone. The results were as follows; 1. With the vertical load at the center of occlusal surface, the stress pattern on the cortical and cancellous bones around the implant on model 1 and 2 was changed, while the stress pattern on the cancellous bone with oblique load was not. 2. With the vertical load at the center of occlusal surface, the maximum von-Mises stress appeared in the outer distal side of the cortical bone on Model 1 and 2, while the maximum von-Mises stress appeared in the distal and lingual distal side of the cortical bone with oblique load. 3. With the vertical load at a position of 2 mm apart buccally from the center, there was the distribution of stress on the upper portion of the implant-bone interface and the cortical bone except for the cancellous bone, while there was a distribution of stress on the cancellous bones at the apical and lingual sides around the fixture and on the cortical bone with oblique load. 4. With the changes of the supporting bone on the second molar area, the stress pattern on the upper part of the cortical bone between two implants was changed, while the stress pattern on the cancellous bone was not. The results of this study suggest that establishing the optimum occlusal contact considering the direction and position of the load from the standpoint of stress distribution of surrounding bone will be clinically useful.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.145-158
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• 2015

Disposable marine product packaging materials such as wooden, Styrofoam, and corrugated cardboard boxes have a very low reuse rate, thus causing the logistics costs to rise and making it difficult to establish a unit load system for marine products. Disposable packing containers to be discarded are accompanied by resource and environmental issues home and abroad. Transportation vehicles for marine products have to return empty without loading different kinds of products after delivery due to the smell and properties of marine products, thus posing as an obstacle to logistics rationalization. In an effort to overcome those limitations, this study examined the stages of transportation including "producer-wholesale market in the producing area-commission merchant-wholesale market in the consumption area-commission merchant-quasi-wholesale market-consumer" and also analyzed the utilization and distribution of disposable packaging materials currently used in the circulation of marine products including wooden, Styrofoam, and corrugated cardboard boxes. Based on the analysis results, the investigator developed a logistics rationalization model capable of promoting semi-permanent reuse and lowering empty vehicle rate on return routes as an alternative to address environmental issues caused by disposable packaging materials, which have been an obstacle to the logistics rationalization of marine products, packaging costs in the process of repeating packing and unpacking at each stage of marine products circulation, and empty vehicle rates on return routes after marine products delivery.

• International Journal of Precision Engineering and Manufacturing
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• 제2권2호
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• pp.57-64
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• 2001

In recent years, the concern of designing multi-stage gear drives ha increased with more application of them in high-speed and high-load. Until now, however, the researches on the design of gear drives have been focused on single gear pairs. Thus the design practice for multi-stage gear drives has been depended on experiences and expertise of designers and carried out commonly by trial and error. We propose an automation algorithm for the design of two-and three-strage cylindrical gear drives. The two types of dimensional design processes have been proposed to determine gear dimensions in a formal way. The first design process(Process I) uses to total volume of gears to determine gear ration , and uses K factor , unit load and aspect ration to determine gear dimensions, The second one(Process II) makes use of Niemann's formula and center distance to calculate gear ratio and gear dimensions. Process I and Process II employ material date from AGMA and ISO standards, respectively. The configuration design determines the positions of gears with minimizing the volume of gearbox by using a simulated annealing algorithm. The availability of the design algorithm is validated by the design examples to two-and three=stage gear drives.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1709-1718
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• 2017

This paper presents a hybrid stochastic deterministic multi-timescale scheduling (SDMS) approach for generation scheduling of a power grid. SDMS considers flexible resource options including conventional generation flexibility in a chance-constrained day-ahead scheduling optimization (DASO). The prime objective of the DASO is the minimization of the daily production cost in power systems with high penetration scenarios of variable generation. Furthermore, energy storage is scheduled in an hourly-ahead deterministic real-time scheduling optimization (RTSO). DASO simulation results are used as the base starting-point values in the hour-ahead online rolling RTSO with a 15-minute time interval. RTSO considers energy storage as another source of grid flexibility, to balance out the deviation between predicted and actual net load demand values. Numerical simulations, on the IEEE RTS test system with high wind penetration levels, indicate the effectiveness of the proposed SDMS framework for managing the grid flexibility to meet the net load demand, in both day-ahead and real-time timescales. Results also highlight the adequacy of the framework to adjust the scheduling, in real-time, to cope with large prediction errors of wind forecasting.

• 한국정밀공학회지
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• 제17권9호
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• pp.202-209
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• 2000

In recent years the concern of designing multi-stage gear drives increases with the more application of gear drives in high-speed and high-load. until now however research on the gear drive design has been focused on single gear pairs and the design has been depended on experiences and know-how of designers and carried out commonly by trial and error. We propose the automation of the dimensional design of gears and the configuration design for gear arrangement of two-and three-stage cylindrical gear drives. The dimensional design is divided into two types of design processes to determine the dimensions of gears. The first design process(Process I) uses the total volume of gears to determine gear ratio and uses K factor unit load and aspect ratio to determine gear dimensions. The second one(Process II) makes use of Niemann's formula and center distance to calculate gear ratio and dimensions. Process I and II employ material data from AGMA and ISO standards respectively. The configuration design determines the positions of gears to minimize the volume of gearbox by simulated annealing algorithm. Finally the availability of the design algorithm is validated by the design examples of two-and three-stage gear drives.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.334-345
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• 2009

Pumped storage power plants are playing a significant role in the contribution to the stabilization of an electrical grid, above all by stable operation and fast reaction to sudden load respectively frequency changes. Optimized efficiency and smooth running characteristics both in pump and turbine operation, improved stability for synchronization in turbine mode, load control in pump mode operation and also short reaction times may be achieved using adjustable speed power units. Such variable speed power plants are applicable for high variations of head (e.g. important for low head pump-turbine projects). Due to the rapid development of power semiconductors and frequency converter technology, feasible solutions can be provided even for large hydro power units. Suitable control strategies as well as clear design criteria contribute significantly to the optimal usage of the pump turbine and motor-generators. The SIMSEN tool for dynamic simulations has been used for comparative investigations of different configurations regarding the power converter topology, types of semiconductors and types of motor-generators including the coupling to the hydraulic system. A brief overview of the advantages & disadvantages of the different solutions can also be found in this paper. Using this approach, a customized solution minimizing cost and exploiting the maximum usage of the pump-turbine unit can be developed in the planning stage of new and modernization pump storage projects.

• Journal of Biosystems Engineering
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• 제30권6호통권113호
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• pp.347-353
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• 2005

Paper angle, environment friendly packaging material, has been mainly used as an edge protector, But, in the future, paper angle will be applied to package design of heavy product such as strength reinforcement or unit load system (ULS). Therefore. understanding of buckling behavior fur angle itself, compression strength and quality standard are required. The objectives of this study were to characterize the buckling behavior by theoretical and finite element analysis, and to develop compression strength model by compression test for symetric and asymetric paper angle. Based on the result of theoretical and finite element analysis, as applied load level was bigger and/or the length of angle was longer, incresing rate of buckling of asymmetric paper angle was higher than that of symmetric paper angle. Decreasing rate of minimum principal moment of inertia significantly increased as the extent of asymmetric angle increased, and buckling orientation of angle was open- direction near the small web. Incresing rate of maximum compression strength (MCS) for thickness of angle decreased as the web size increased in symmetric angle. MCS of asymmetric angle of 43${\times}$57 and 33${\times}$67 decreased $15{\~}18\%$ and $65{\~}78\%$, and change of buckling increased $12{\~}13\%$ and $62{\~}66\%$, respectively.

• 한국포장학회지
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• 제11권1호
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• pp.1-10
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• 2005

Paper angle, environment friendly packaging material, has been mainly used as an edge protector. But, we have perceived its application to package design of heavy product such as strength reinforcement or unit load system (ULS) in the future. Above all, understanding of buckling behavior for angle itself and compression strength and quality standard have to be accomplished for the paper angle to be used for this purpose. The purpose of this study was to elucidate the buckling behavior through theoretical and finite element analysis, and to develop compression strength model by compression test for symetric and asymetric paper angle. Based on the result of theoretical and finite element analysis, increasing rate of buckling of asymmetric paper angle was higher as applied load level was bigger and/or the length of angle was longer than that of symmetric paper angle. Decreasing rate of minimum principal moment of inertia was remarkably increased as the extent of asymmetric angle is bigger, and buckling orientation of angle was open direction near the small web. Increasing rate of maximum compression strength (MCS) for thickness of angle was smaller as the web size was bigger in symmetric angle. MCS of asymmetric angle of $43{\times}57$ and $33{\times}67$ was decreased $15{\sim}18%$ and $65{\sim}78%$, and change of buckling was increased $12{\sim}13%$ and $62{\sim}66%$, respectively.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.481-490
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• 2021

In the ultrasonic welding machine, when the load fluctuates, the L and C of the piezo element in the oscillation part change. As a result, the resonant frequency is changed, so it is necessary to match the operating frequency of the ultrasonic welding machine to the new resonant frequency. That is, in order to maximize the output of the oscillation unit of the ultrasonic welding machine, it is inevitable to follow the resonance frequency. Accordingly, many methods for following the resonant frequency are being actively studied. In addition, in order to check the effect of external inductance on the operation of the ultrasonic welding machine, The equivalent circuit of the piezo element was analyzed by including the external inductance for resonance in the equivalent circuit of the piezo element, and the method of selecting an appropriate inductance was described. In this paper, we propose a new system that allows the switching frequency of the inverter to tracking the resonance frequency even if the resonance frequency is changed due to the load of the ultrasonic welding machine.

• 설비공학논문집
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• 제24권8호
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• pp.646-655
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• 2012

This study is intended to analyze the thermal performance and evaluate the applicability about non-duct type heat recovery ventilation system integrated with window. Eventually, economic analysis of the system is conducted according to building energy saving ratio of it. As results of the thermal performance, the U-factor of the window conducted on the basis of KS F 2278 appears to $1.8W/m^2K$, and the effective heat exchange efficiency of the ventilator conducted on the basis of KS B 6879 appears 49.95% for cooling, 66.89% for heating. In the applicability evaluated by TRNSYS 16, the caes of applying the heat recovery ventilator integrated with window is found to reduce the cooling or heating load by 2.9% or 13.5% than the non-ventilator case. The results of economic analysis taking a side of consumer is verified as the payback is 3 years, and the accumulated earning is 1,408,133 won in terms of '600,000 won/unit' for initial cost, 10 years for useful life of the system.