• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.6
• /
• pp.263-268
• /
• 2014

Eskilson's g-function, a well-known geothermal heat response factor, is widely used for sizing of the ground heat exchangers. Unlike the Eskilson's original model that uses common temperature boundaries for all boreholes and along the borehole height, an analytical-solution-based g-function uses a uniform heat transfer rate over the height with variable heat transfer rates for respective boreholes. To evaluate the impact of such a boundary difference on g-function and the design length, a simple case study was carried out on the cooling-dominant commercial buildings. The results show that the design lengths given by the boundary of uniform heat transfer rates are longer than those given by Eskilson's boundary for all cases tested. The difference in length is more important when the bore field is composed of more boreholes with shorter length of each borehole.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.2
• /
• pp.78-85
• /
• 2010

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.11
• /
• pp.621-628
• /
• 2009

The objectives of this study are to analyze the performance of a river water-source heat pump and to carry out economic assessment for the heat pump. The COP of the river water-source heat pump was 3-21% higher than that of the air-source heat pump because river water provides stable operating temperature compared with air temperature throughout the year. The economic analysis was carried out by comparing the initial and operating cost of the river water-source heat pump with those of the conventional air-source heat pump. The ratio of the life cycle operating cost to the life cycle cost increased with the increase of building capacity. The payback period was found to be less than 3.5 years when the capacity of the river water-source heat pump was larger than 10 RT.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.11
• /
• pp.1060-1067
• /
• 2004

To apply an analysis method of life cycle cost when assessing economics of equipment system, we should basically set up preconditions such as useful life, price escalation rate, interest rate, etc. as well as consider a calculation algorism of source energy and heat source system, which is a complex process for life cycle costing. For this reason, equipment designers tend to plan heat source systems, without a thorough investigation on economics of alternative systems at the pre-design phase. In this process, architectural designers should adopt a proper heat source system, which is one of the most important factors for planning an appropriate architectural design, through a discussion with equipment designers in a short time. In order to offer an evaluation method for equipment designers to analyze economics of an alternative heat source system easily at the pre-design phase, this research would define the simplified economics, evaluation method through analysis of existing papers for economics evaluation, and examine validity through comparison of simplified method values ($LCC_{EC}$) and life cycle costing values ($LCC_{15}$) for six alternative heat source systems.

• Journal of the Korean Solar Energy Society
• /
• v.25 no.4
• /
• pp.69-76
• /
• 2005

The performance of water-to-water heat pump system coupled with the ground source vertical heat exchanger is presented in this paper. The CAP program of Florida Heat Pump Co. is used to predict the heat pump performances while the EED program calculates the borehole fluid temperature. It is shown that COPH increases with decreasing the temperature of output water for the operation of heating mode and COPR increases with increasing temperature of output water for the operation of cooling mode. The value of specific heat extraction rate must be moderate to insure the reasonable installation cost of borehole system. With $1^{\circ}C$decrease of $T_{wo}$ the average COPH increase is estimated as about $0.06/^{\circ}C$(for $T_{wo}\;=\;45{\sim}60^{\circ}C$ range) while with $1^{\circ}C$ increase of $T_{wo}$ the estimation of COPR increase is about $0.13/^{\circ}C$(for $T_{wo}\;= \;5{\sim}11^{\circ}C$ range) at the specific heat extraction rate of 30W/m.

• Journal of the Korean Academy of Clinical Electrophysiology
• /
• v.11 no.1
• /
• pp.39-44
• /
• 2013

Purpose : The purpose of present study is to evaluate the joint angles of legs in the standing posture for six patients with unilateral knee osteoarthritis. Methods : The participants underwent unilateral total knee replacement. A motion analysis was used to measure the joint angles of the hip, knee, and ankle. The measurements were taken before the surgery, one week and two weeks after the surgery. Both sides of the legs were evaluated. Results : This result showed that after a certain healing period, both hip joint angles showed a significant difference while there was no significant difference in the knee and ankle joint angles. After surgery, the angle of ankle dorsiflexion was smaller on the operated side than the opposite side compared to the pre-surgery measurements. Conclusion : After surgery, the asymmetry in a standing position left unchanged due to contracture of the knee joint and tightness in the hamstring muscle. Therefore, when physiotherapists plan an initial exercise programs for TKR patients, it is essential to apply adequate exercises which consider the contracture of the leg joints.

• Journal of the Korean Academy of Clinical Electrophysiology
• /
• v.11 no.1
• /
• pp.21-29
• /
• 2013

Purpose : The purpose of this study was to determine the changes in ultrasound imaging of the lower limbs in patients with degenerative osteoarthritis who received a total knee replacement (TKR). Methods : The participants for the study were ten patients who were to receive a total knee replacement. Measurements were taken a total of three times: before receiving a total knee replacement, and one week and two weeks after receiving a total knee replacement. The vastus medialis, rectus femoris muscle, tibialis anterior and gastrocnemius muscle were measured using ultrasound imaging. Results : Muscle thickness of the vastus medialis, rectus femoris muscle, tibialis anterior and gastrocnemius muscle had no significant interaction over time whether surgery was performed or not. White area index (WAI) and density of vastus medialis, rectus femoris muscle, tibialis anterior and gastrocnemius muscle had no significant interaction over time whether surgery was performed or not. Conclusion : In conclusion, lower quality muscles were due to a decrease in muscle fiber and an increase in fat fiber. Therefore, initial physical therapy after total knee replacement should consider this point and be designed appropriately as a therapeutic approach for total knee replacement patients.

• Journal of the Korean Academy of Clinical Electrophysiology
• /
• v.11 no.1
• /
• pp.1-6
• /
• 2013

Purpose : The purpose of this study was to examine the effect of bobath treatment on the balance and gait in adult hemiplegia. Methods : The study was performed with patients of hemiparesis caused by cerebral stroke. The participants were based on random sampling method. The hemiplegia patient received Bobath therapy. Each rehabilitation program lasted 40 minutes a day, 5 days a week, for 6 weeks. Pertinent indicators Berg's balance scale (BBS), gait velocity, and static balance analysis were recorded before and after the programs, as well as every 2 weeks during the rehabilitation programs. Results : There was showed a significantly increase of BBS score. Static open and close showed statistically significant in interaction by time and groups. There was significant difference of gait velocity. Conclusion : These findings in this study that the Bobath therapy was effective therapy in improving dynamic balance and gait velocity.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.2 no.2
• /
• pp.53-62
• /
• 1992

In Zone Melting Recrystallization(ZMR) of SOl structure, thin silicon films have been recrystallized by artificial control of beam intensity profile which was obtained by tilting of upper elliptical reflector. Temperature profiles and gradients near solidification interface were calculated by numerical simulation for analysis of asymmetric line heating effect. The larger the tilting angle of the upper reflector, the larger the degree of supercooling at liquid and the interdefect spacing in thin silicon films. Major defects were continuous subgrainboundaries. Isolated threading dislocations were observed in the case of the film having low defect density. We have found that the thin silicon films were recrystallized into (100) textured single crystals by cross-sectional TEM and thin film X-ray diffraction analysis.

• Korean Journal of Child Studies
• /
• v.36 no.5
• /
• pp.115-134
• /
• 2015

The main purpose of this study is to explore the relationship between latent classes of childhood maltreatment and depression anxiety and aggression from childhood to adolescence. 1,785 participants in a sample form Seoul Panel Study of Children were used in this study. Using latent class analysis, three classes of child maltreatment were identified: 'low maltreatment'(89.2%), 'physical+emotional abuse+neglect'(1.9%), 'physical+emotional abuse'(8.9%). Three developmental trajectories of depression anxiety were classified: 'low depression anxiety'(72.3%), 'moderate depression anxiety'(23.3%), 'high depression anxiety'(4.4%). Two developmental trajectories of aggression were revealed: 'low aggression'(89.3%), 'high aggression'(10.7%). As estimated by latent transition probability, the multiple maltreatment classes were more likely to have higher levels of depression anxiety or aggression than the no maltreatment class. There appeared to be distinct profiles of maltreatment among adolescents that had differential associations to measures of internal and external problems. The implications for both practice and policy implications are also discussed.