• Wind and Structures
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• v.25 no.6
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• pp.551-567
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• 2017

Studies of unsymmetrical blade H-Darrieus rotors at low wind speeds in terms of starting time, static torque, and power performances for different blade parameters: thickness-to-chord (t/c), camber position, and solidity are scarce. However these are required for knowing insights of rotor performances to obtain some design guidelines for the selection of these rotors. Here, an attempt is made to quantify the effects of these blade parameters on the performances of three different H-Darrieus rotors at various low wind streams. Different blade profiles, namely S815, EN0005 (both unsymmetrical), and NACA 0018 (symmetrical blade for comparison) are considered. The rotors are investigated rigorously in a centrifugal blower apparatus. Firstly the dynamic and static performances of the rotors are evaluated to determine the best performing rotor and their optimum solidity. Generalised performance equations are developed based on selected blade parameters which are validated for the unsymmetrical rotors. Further, the starting time is quantified with respect to the rotor inertia to determine the suitable range of inertia that helps the unsymmetrical blade rotor to self-start earlier than the symmetrical one. This study can work as a benchmark for the selection of optimum blade parameters while designing an unsymmetrical blade rotor at low wind speeds.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.128-136
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• 1995

The problem addressed in this paper is that of the on-line computational burden of time-optimal control laws for quick, strongly nonlinear systems like revolute robots. It will be demonstrated that a large amount of off-line computation can be substituted for most of the on-line burden in cases of time optimization with constrained inputs if differential point-to- point specifications can be relaxed to cell-to-cell transitions. These cells result from a coarse discretization of likely swaths of state space into a set of nonuniform, contiguous volumes of relatively simple shapes. The cell boundaries approximate stream surfaces of the phase fluid and surfaces of equal transit times. Once the cells have been designed, the bang- bang schedules for the inputs are determined for all likely starting cells and terminating cells. The scheduling process is completed by treating all cells into which the trajectories might unex- pectedly stray as additional starting cells. Then an efficient-to-compute control law can be based on the resulting table of optimal strategies.

• International Journal of Advanced Culture Technology
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• v.9 no.4
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• pp.18-28
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• 2021

This study surveyed how retirees' evaluation of starting food service business affects the effectiveness their new business and quality of life, based on personal factors such as entrepreneurship and business-starting capability and environmental factors by using questionnaires. Bootstrapping was carried out in order to find out factors affecting rapidly changing new business environments and retirees' initial intent to start a business so as to verify basic hypothesis about relation between retirees' evaluation of starting food service business (social, economic, and psychological effects) and the effectiveness of their new business and quality of life and confirm whether the effectiveness of the new business acts as a medium between the evaluation of starting food service business and quality of life. In addition, PLS-MGA was performed in order to verify whether the correlations among test factors can be varied according to the kind of job the target retirees had. Having examined the basic thesis, it was found that social and economic factors had significant positive effect on the effectiveness of the new business, and social and psychological factors had significant positive effect on the quality of life. Having analyzed whether the effectiveness of new business acted as a media between evaluation of starting food service business and quality of life, there was no significant effect as a medium. Having studied whether the kind of job of the retirees controlled or affected the relations among evaluation of starting food service business, effectiveness of new business and quality of life, the results were as follows: in the office job retiree group, the greater economic factor led to increase of effectiveness of new business, while social and psychological factors influenced the quality of life; In the physical labor group, the higher social factor resulted in higher effectiveness of new business, which showed significant positive effect on the quality of life. Having researched about which element is considered to be most important in starting food service business, the most important element was found to be dish/menu, followed by staff management, accounting management, business management, and service education. Having analyzed relation between accomplishment and important consideration for starting food service business, "managers with entrepreneurship," "appropriate distribution of time to prepare for starting business," and "operation of practical field education programs" showed higher importance compared to the degree of satisfaction, so it is needed to more concentrate on the above matters. This study intends to raise retirees' awareness of starting business and help them live better life based on the analysis results, and further suggest detailed mechanism and specific operations of factors affecting retirees' decision making on starting business, such that they can use the information as basic materials to make better choices that can lead to successful business.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.321-322
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• 2006

In many manufacturing processes such as web formation, manufacturing of paper and nonwoven, fabric weaving, etc., planar sheets are transported and at the same time appropriate tension is imposed. The input material rolled up on beams is fed by unwinding the beam and the processed is then taken up on beams by winding it. While processed, the planar sheets are thrown under the processing load of impulse form, which causes irregular thickness of the processed sheet. To improve the quality of the product, a dynamic model is needed and the dynamic characteristics is to be analyzed by simulation. This study shows that density variation dynamics of the in-process-sheet in the machine direction can be described at each moment of disturbing impacts in forms of difference equations, while the impacts and tension, the time-dependency of the material properties were taken into account. Simulation showed the most serious variation of the density occurred in the process starting phase. The starting velocity curve with step form showed the least variation of the density. As the time order of the function of the starting velocity cure becomes higher, the density variation gets greater.

• Child Health Nursing Research
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• v.8 no.1
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• pp.55-66
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• 2002

It is an important task to give adequate nutritions to infants and to wean properly for rapid growth. This study was conducted to survey on doing the weaning activities of the first-time mother. This study was to provide basic data of health teaching and nursing intervention for the promotion of ideal weaning activities. Survey was done from January to February in 2001. Total 444 mothers who have first-time baby under twelve month old were interviewed in five community health center around contry (Seoul, Choung-ju, Asan, Cheon-an, Jeju). The results are summarized as follows; Starting time of weaning was common in four month old(40.4%). Most common daily weaning times by age showed once(under 3 months), twice(4 to 7 months), three times(8 to 12 months). The younger, the more commercial weaning products(p<0.01). Education level showed relatively positive relation with home-made weaning food(p<0.05). Items showed low scores in 4 to 7 months group were starting new food item, waiting at least one week interval to new food, feeding by milk bottle, allowing grasping spoon, consulting pediatrician for problems after weaning, starting from morning, regular schedule. Items showed low scores in 8 to 12 months group were feeding whole egg rather than yolk only up to 12 months, keeping weaning interval were increased, feeding by milk bottle, trying various cooking method, not giving commerical cooking and instant food and unproper raw milk feeding. In weaning activities by general factors, mother age, health status, marriage duration, monthly income were statistically significant (p<0.05). To improve good weening activities, targetting on low maternal age and poor health status, and low income group, developing teaching materials and training program for items showed low scores and proper weaning time, type of easy home-made food and easy cooking method should be provided. Further study on effect of nursing intervention to improve weaning activities are needed.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.837-843
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• 2012

Asynchronous motors are widely used in many fields. The various starting methods have been developed for the asynchronous motors which have large power compared to source power. The most popular ways to start the motors are to reduce the voltage of motor's stator or change the resistance fed rotor. It is needed to the specific time to reduce the voltage and change the resistance at a specific step. We call it the switching time. It is very difficult to know the switching time exactly. It varies with different types of motors as well as load characteristics. Thus, this paper focuses on the design and development for the mathematical models of motor and load. And then it is implemented in SIMULINK in order to calculate this time. The simulation results are both compared and discussed in detail so that it can be applied for new system with various motors and loads.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.4
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• pp.399-408
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• 2000

This study evaluated the SO2 adsorption characteristics using a continous moving bed system. Natural manganese oxide (NMO) reaction condition such as L/D the starting time of the NMO feed, feed rate, and flow rate of simulated flue gas, and NMO size were tested. The results showed that optimum L/D was 1.0 in this moving bed system. The higher the feeding rate was the higher the SO2 removal efficiency was and the higher the flow rate of simulated flue gas was the shorter the time to reach the euqilibirum concentration was. The final SO2 con-centration when it reaches the equilibrium concentration was not affected by the starting time of the NMO feed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.802-808
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• 1992

To investigate degradation procedure and life time of the oxidized PE and the unoxidized PE, alternative voltage is applied to the CIGRE Method-II (CM-II) electrode system, which is loaded artificial void, and measures the distribution of partial discharging generation. From the results, the samples etched by oxidation had wide degradation area of dielectric strength. Furthermore, discharge starting voltage was shifted to low voltage, the discharge generation frequency was high and consequently, the quantity of mean charge becomes small. Also, life time of the oxdized sample is shortened according as the oxidation time is longer.

• Korean Journal of Applied Biomechanics
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• v.28 no.3
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• pp.151-158
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• 2018

Objective: In this study, we analyzed kinematic changes in the start phase of speed skating before and after physical training. Method: We introduced a new strength training program (2017) that was improved in terms of exercise type and intensity [%, one repetition maximum (1RM)] compared with the previous strength training program (2016). The new program was applied to elite speed skating athletes (four males and four females). To determine the improvement in starting technique, we recorded race images during the start phase of the 500-m race held in 2016 and 2017. The race images were collected using five high-speed cameras and kinematic characteristics of the start phase were analyzed by three-dimensional image analysis. Results: The 1RMs were improved by 11% on an average after the strength training. In 2017, records of four out of the eight athletes were shortened in terms of the initial lap time (100 m), and 500-m records were shortened in six athletes. The time to nine strokes was shortened in five athletes, and the ratio of correct kinetic chain was increased or maintained at a high level in six athletes. Conclusion: In this study, the new strength training program (2017), applied to elite speed skating athletes, showed a positive effect on starting technique and reduced the record times.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.191-199
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• 2008

The purpose of this study was to analyze movement of inline skate players at inline roller skate T300m start so that we can find effective starting movement, and provide basic and scientific materials in improving performance of inline roller skaters for T300m inline roller skating. In doing so, five Korean national representative inline skaters who elected in 2008 Korean National Inline Roller Skating Cup were taped during the cup and analyzed through 3D viewing in terms of their starting movement Conclusions of the analysis were as follows: First, the better the record of starting phase is the shorter average of contact time on track. Second, to improve starting speed, players raised their body just like running instead of lowering them when gliding. players could shorten their strike and moved faster in order to accelerate, and it was more effective to speed up when they quickly switched from running to gliding. Third, the five country-representative players speeded up by bending their knees to a greater degree in order to improve stability. And then the most effective way was believed to minimize track connection of skating at starting in each phase.