• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.680-683
• /
• 2007

In dish concentrating system, natural convection heat loss occurs in cavity receiver. Heat loss mechanisms of conduction, convection, and radiation can reduce the system efficiency. To obtain the high efficiency, the receiver is to absorb the maximum of solar energy and transfer to the working fluid with maximum of heat losses. The convection heat loss is an important factor to determine the system performance. Numerical analysis of the convection heat loss of receiver was carried out for varing inclinaton angle from 0$^{\cdot}$ to 70$^{\cdot}$ with temperature range from 400$^{\cdot}C$ to 600$^{\cdot}C$ using the commercial software package, Fluent 6.0. The result of numerical analysis was comparable with convection heat loss model of solar receiver.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.1
• /
• pp.52-60
• /
• 2018

The winding of the motor stator coil is broken due to external stress and various factors. If the proper current is not injected when interturn fault(ITF) occurs, the fault can easily be expanded and the motor can be finally destroyed, resulting in many problems with time costs and safety. In this paper, the power loss limit concept, which is the inherent durability of each motor, is applied to secure safety by controlling the total power loss of the motor within the limits. So, we propose an algorithm that can control maximum torque per minimum power loss based on constant torque curve and power loss limit. To verify the proposed method, the simulation and experimental results with an Interior permanent magnet synchronous motor(IPMSM) having an ITF are shown.

• Structural Engineering and Mechanics
• /
• v.63 no.5
• /
• pp.691-702
• /
• 2017

Clearances are essential for the assemblage of mechanisms to allow the relative motion between the joined bodies. This clearance exists due to machining tolerances, wear, material deformations, and imperfections, and it can worsen the mechanism performance when the precision and smoothly-working are intended. Energy is a subject which is less paid attention in the area of clearance. The effect of the clearance on the energy of a flexible slider-crank mechanism is investigated in this paper. A clearance exists in the joint between the slider and the coupler. The contact force model is based on the Lankarani and Nikravesh model and the friction force is calculated using the modified Coulomb's friction law. The hysteresis damping which has been included in the contact force model dissipates energy in clearance joints. The other source for the energy loss is the friction between the journal and the bearing. Initial configuration and crank angular velocity are changed to see their effects on the energy of the system. Energy diagrams are plotted for different coefficients of friction to see its influence. Finally, considering the coupler as a flexible body, the effect of flexibility on the energy of the system is investigated.

• Journal of Obesity & Metabolic Syndrome
• /
• v.27 no.4
• /
• pp.203-212
• /
• 2018

Dynamic energy balance can give clinicians important answers for why obesity is so resistant to control. When food intake is reduced for weight control, all components of energy expenditure change, including metabolic rate at rest (resting energy expenditure [REE]), metabolic rate of exercise, and adaptive thermogenesis. This means that a change in energy intake influences energy expenditure in a dynamic way. Mechanisms associated with reduction of total energy expenditure following weight loss are likely to be related to decreased body mass and enhanced metabolic efficiency. Reducing calorie intake results in a decrease in body weight, initially with a marked reduction in fat free mass and a decrease in REE, and this change is maintained for several years in a reduced state. Metabolic adaptation, which is not explained by changes in body composition, lasts for more than several years. These are powerful physiological adaptations that induce weight regain. To avoid a typically observed weight-loss and regain trajectory, realistic weight loss goals should be established and maintained for more than 1 year. Using a mathematical model can help clinicians formulate advice about diet control. It is important to emphasize steady efforts for several years to maintain reduced weight over efforts to lose weight. Because obesity is difficult to reverse, clinicians must prioritize obesity prevention. Obesity prevention strategies should have high feasibility, broad population reach, and relatively low cost, especially for young children who have the smallest energy gaps to change.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.831-835
• /
• 2007

Energy Saving is one of worldwide emerging issues. These days, applicable techniques of railway vehicle's regenerative energy are investigating in worldwide railway industries. Energy saving methods are "Downsizing energy loss" and "Re-utilizing kinetic energy". Useful plans for Downsizing energy loss are "adjusting operation table" and "optimizing running pattern". Furthermore, regenerative energy that is produced with decreasing speed and stoping, is an important element with reducing vehicle's weight, raising equipment 's efficiency, decreasing running resistance and re-configurating running pattern. Sustainable energy storage mass : Flywheel, EDLC(electrical double layer capacitor) and Secondary battery are applied in overseas, but these cases are not reported within the country. This research is reported for problems and economical validity that comes from by installing sustainable regenerative energy storage system in korean railway industries.

• Transactions of the Korean hydrogen and new energy society
• /
• v.27 no.4
• /
• pp.404-411
• /
• 2016

To select appropriate oxygen carrier candidates for chemical looping combustion, reduction characteristics of seven oxygen carriers were measured and discussed using three different reduction gases, such as $H_2$, CO, and $CH_4$. Moreover, attrition losses of those oxygen carriers also measured and compared. Among seven oxygen carrier particles, OCN703-1100 and NiO/bentonite particles showed higher oxygen transfer capacity than other particles, but these particles showed more attrition loss than other particles. C14 and C28 particles which used as cheap oxygen carriers in European country showed lower oxygen transfer capacity and less attrition loss. Based on the experimental results, we could select OCN717-R1SU, NC001, and N002 particles as candidates for future works because these oxygen carriers showed enough oxygen transfer capacity and good attrition resistance.

• Journal of the Korean Magnetics Society
• /
• v.10 no.4
• /
• pp.178-182
• /
• 2000

We have constructed a rotational loss measuring system which consists of two yoke system for rotational magnetization and 4-channel transient recording system for Hx, Hy, Bx and By measurements. Using the constructed measuring system, we have mesaured rotational energy loss for non-oriented electrical steel sheets. Rotational energy loss was depending on the angle between B-search coil and H-search coil, and the direction of rotation (clockwise and counter clockwise). The average of the rotational energy losses under clockwise and counter clockwise was independent of the angle between B-search coil and H-search coil, and we could improve measuring uncertainty using the averaged rotational energy losses.

• Advances in Energy Research
• /
• v.8 no.1
• /
• pp.21-39
• /
• 2022

In this study, the first law of thermodynamics was used to establish a one-dimensional (1-D) thermal model for parabolic trough receiver (PTR) taking into account the pressure drop and kinetic energy loss effects of the heat transfer fluid (HTF) flowing inside the absorber tube. The validation of the thermal model with data from the SEGS-LS2 solar collector-test showed a good agreement, which is consistent with the previously established models for the conventional straight and smooth (CSS) receiver where the effects of pressure drop and kinetic energy loss were neglected. Based on the developed model and code, a comparative study of the newly designed parabolic trough S-curved receiver versus the CSS receiver was conducted and solar unit's performances were analyzed. Without any supplementary devices, the S-curved receiver enhances the performance of the parabolic trough module, with a maximum of 0.16% compared to CSS receiver with the same sizes and mass flow rates. Thermal losses were reduced by 7% due to the decrease in the temperature of the outer surface of the receiver tube. In addition, it has been shown that from a mass flow rate of 9.5 kg/s the heat losses of the S-curved receiver remain unchanged despite the improvement in the heat transfer rate.

• Journal of Nutrition and Health
• /
• v.33 no.2
• /
• pp.193-201
• /
• 2000

This study was conducted to investigate the effectiveness of nutrition counseling on the dietary intake and nutritional status cancer patients undergoing radiotherapy treatment. The study was conducted over 6 week period and included 104 patients : 66 received nutrition counseling as the variable group of 42 male and 24 female and 38 patients received no counseling as the control group of 19 male and 19 female. Nutrition counseling was accompanied with the radiation therapy and adminstered via counseling session and distribution of printed material during radiation therapy for 6 weeks. Nutrition counseling aimed at maintaining a balanced diet and preventing weight loss of subjects, guideline used for energy and protein intake were 35kcal/kg IBW and 1.5-2.0g/kg IBW, respectively. Over the course of the study, the counseling group increased significantly in comparison to the control group's energy intake, evidenced by the counseling group's initial mean daily energy intake of 1932.0kcal, and 4 and 6 week mean energy intake values of 2046.6kcal, 2066kcal, respectively. But mean energy values of control group was 1614.3kcal at 4 week. Th energy intake per weight values and protein intake per weight values for initial, 4 and 6 week intervals for counseling group were 33.2kcal/kg, 33.7kcal/kg, 34.0kcal/kg, and 1.48g/kg, 1.58g/kg, 1.59g/kg, respectively. Based on results, nutrition counseling had positive effects on both the variety of diet and energy intake of the variable group, mostly due to an increase in dairy product and egg consumption. In addition, the percentage of counseling group patients who consumed all 5 food group increased from 48.5% to 54.5%. Sufficient energy intake and protein consumption seem to be important factors in weight loss prevention, evidenced by weight gain by subjects in the counseling group who had 36.1kcal/kg/day mean energy intake and 1.77g/kg/day mean protein intake after 4 weeks. Counseling group subjects experiencing weight loss had lower intake and 1.77g/kg/day mean protein intake after 3 weeks. Counseling group subjects experiencing weight loss had lower intakes of 29.3kcal/kg/day for energy and 1.33g/kg/day for protein during the same period. Another significant factor in weight loss prevention of the counseling group could be the variety of diet. The dietary variety scores(DVS) of both counseling and control groups differed significantly : the counseling group had a mean score of 34 while the control group of patients. At the end of the study, the mean percentage of subjects within each group having a DDS 5 was higher in the counseling group (54.5% v.s. 24.0%). In this study, nutrition counseling for cancer patients undergoing radiation therapy proved to be effective in preventing weight loss, a major complication during radiotherapy. Nutrition counseling not only increased protein and energy intake, but also had desirable effects on variety or diversity of diet.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.3
• /
• pp.241-245
• /
• 1994

A method has been developed to estimate the kinetic energy release originating from the reverse critical energy in unimolecular ion dissociation. Contribution from the excess energy was estimated by RRKM theory, the statistical adiabatic model and the modified phase space calculation. This was subtracted from the experimental kinetic energy release distribution (KERD) via deconvolution. The present method has been applied to the KERDs in $H_2$, loss from $C_6H_6^+$ and HF loss from ${CH_2CF_2}^+$. In the present formalism, not only the energy in the reaction coordinate but also the energy in some transitional vibrational degrees of freedom at the transition state is thought to contribute to the experimental kinetic energy release. Details of the methods for treating the transitional modes are found not to be critical to the final outcome. For a reaction with small excess energy and large reverse critical energy. KERD is shown to be mainly governed by the reverse critical energy.