• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.189-196
• /
• 2020

When concrete member become large like in high rise buildings, hydration heat makes temperature difference inside and outside and cause cracks. The method of using latent heat material as heat reducer could be more accessible, usable and efficient than other methods. Therefore, many studies using PCM as heat reducer are being conducted. Since heat reducer have different reacting temperature, they may be affected by environmental factors like ambient and concrete mixing temperature but studies issuing this are insignificant. Therefore, this paper attempt to evaluate the hydration heat characteristics and quality of concrete using strontium-based PCM under hot weather conditions. As a result, when the strontium-based hydration heat reducer was mixed 3wt.% and 5wt.% in hot weather condition, hydration heat speed and heating rate could be reduced by 8%, 21%, and 75, 85 minutes compared to OPC, respectively. This is considered to be the phase change reaction is relatively promoted when the temperature is high and cause improve performance than room condition result. Later, comparing the efficiency of other types of P.C.M in hot weather condition, and conduct detailed reviews on the strength development in long-term age.

• Journal of ILASS-Korea
• /
• v.23 no.3
• /
• pp.149-153
• /
• 2018

The present study investigates the heat transfer characteristics of droplet growth during dropwise condensation on the hydrophobic copper surface. We use the copper specimen coated by the self-assembled layer and conduct the real-time measurement of droplet size and spatial distribution of condensates during condensation with the use of the K2 lens (long distance microscope lens) and CMOS camera. The temperatures are measured by three RTDs (resistance temperature detectors) that are located through the holes made in the specimen. The surface temperature is estimated by the measured temperatures with the use of the one-dimensional conduction equation. It is observed that the droplets on the surface are growing up and merging, causing larger droplets. The experimental results show that there are three distinct regimes; in the first regime, individual small droplets are created on the surface in the early stage of condensation, and they are getting larger owing to direct condensation and coalescence with other droplets. In the second and third regimes, the coalescence occurs mainly, and the droplets are detached from the surface. Also, the fall-off time becomes faster as the surface wettability decreases. In particular, the heat transfer coefficient increases substantially with the decrease in wettability because of faster removal of droplets on the surfaces for lower wettability.

• Journal of the Korean Society of Safety
• /
• v.29 no.3
• /
• pp.114-120
• /
• 2014

The purpose of this study is to conduct the study of the combustion and thermal characteristics through transportation oil for the analysis of fire hazard. Transportation oil breaks down into fuels such as diesel for civilian demands, gasoline, DF1(diesel for military), high sulfur diesel(for marine), kerosene and JP1(for aviation), and lubricants like brake fluid, power steering oil, engine oil, and automatic and manual transmission oil. The experiments of flash point, ignition point, flame duration time, heat release rate were carried out using TAG closed cup flash point tester(AFP761), Cleveland open cup auto flash point analyzer(AFP762), KRS-RG-9000 and Dual cone calorimeter. As a result, the fuel's ignition points were lower than lubricants, especially that of gasoline was not conducted as it has below zero one. Gasoline has the highest ignition point of about $600^{\circ}C$, while the other fuels showed $400{\sim}465^{\circ}C$. For flame duration time, lubricants had over 300 seconds, but fuels had less than 300 seconds except high sulfur diesel(350 seconds). Total heat release rate ranged $287{\sim}462kW/m^2$ for lubricants and gasoline showed the highest total heat release rate, $652kW/m^2$.

• Journal of Animal Science and Technology
• /
• v.64 no.2
• /
• pp.330-342
• /
• 2022

We aimed to investigate candidate proteins related to long-term caloric restriction and feed efficiency in bovine longissimus dorsi muscle (LM). A total of 31 Korean native steers were randomly distributed to ad libitum (n = 16) or caloric restriction group (n = 15) to conduct two feeding trials for 13 mon. In the first trial (10-18 mon of age), steers were fed with 100% ad libitum (NE_g = 0.63 Mcal/kg) or caloric restriction (80% of the previous day's feed intake of ad libitum group). In the second trial (18-23 mon of age), the energy value of 100% ad libitum diet was 1.13 Mcal/kg NE_g and those in caloric restriction group diet was 0.72 Mcal/kg NE_g. At the endpoint of this experiment, in each group, 6 animals were selected with high (n = 3) or low feed efficiency (n = 3) to collect muscle tissue samples (6 animals/group). From muscle tissues of 23 mo of age, we excavated 9 and 12 differentially expressed (two-fold or more) proteins in a nutritional group and feed efficiency group using two-dimensional electrophoresis, respectively. Of these proteins, heat shock protein beta-6 was up-regulated in both the caloric restriction and the low feed efficiency group. In bovine embryonic fibroblasts, the mRNA expression of heat shock protein beta-6 increased after adipogenic differentiation, however, decreased after myogenic differentiation. Our data provide that heat shock protein beta-6 may be an adipogenic protein involved in the mechanism of caloric restriction and feed efficiency in the LM of the steer.

• Journal of Energy Engineering
• /
• v.24 no.1
• /
• pp.32-41
• /
• 2015

The Metropolitan Area Green Heat Project (MAGHP), which collects unused heat gathered from power plants, steel works, landfills in western Metropolitan area and distribute it to integrated energy business (IEB) companies, is proposed for the purpose of enhancing energy efficiency and providing low-price heat for IEB companies. Therefore, in order to decide on whether to initiate the MAGHP, the economic feasibility analysis of the project is widely demanded. This paper attempts to consider and measure four economic benefits: heat supply benefit, production cost reduction benefit, greenhouse gas mitigation benefit, and air quality improvement benefit. In addition, the paper tries to conduct the economic feasibility analysis. The project requires three-year investment and thirty-year operation. Three important findings emerge from the analysis. First, its net present value is computed to be 1,269 billion won and more than zero. Second, its benefit/cost ratio is calculated to be 1.72 and bigger than 1.0. Third, its internal rate of return is estimated to be 24.26% and larger than the social rate of return, 5.5%. In conclusion, the MAGHP is socially profitable and should be conducted immediately.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.5 s.236
• /
• pp.762-769
• /
• 2005

This paper presents a method to investigate the characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature considering the variation of the clearance as well as the lubricant viscosity. Iterative finite element analysis of the heat conduction and the thermal deformation is performed to determine the viscosity and clearance of a hydrodynamic bearing due to elevated temperature until the temperature of the bearing area converges. Proposed method is verified by comparing the calculated temperature with the measured one in elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearing of a HDD spindle motor. Once the viscosity and the clearance of a hydrodynamic bearing of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of a hydrodynamic bearing of a HDB spindle motor due to elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration to affect the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor

• Tribology and Lubricants
• /
• v.33 no.3
• /
• pp.112-118
• /
• 2017

Tilting pad journal bearings(TPJBs) are widely used for high speed rotating machinery owing to their rotordynamic stability and thermal management feature. With increase in the rotating speed of such machinery, an increasingly important aspect of TPJB design is the prediction of their thermal behaviors. Researchers have conducted detailed investigations in the last two decades, which provided design tools for the TPJBs. Based on these previous studies, this paper presents a thermohydrodynamic(THD) analysis model for TPJBs. To calculate pressure distribution, we solve the generalized Reynolds equation and to predict the lubricant temperature, we solve the 3D energy equation. We employ the oil mixing theory to calculate pad inlet temperature; further, to consider heat conduction via the pad, we solve the heat conduction equation for the pads. We assume the shaft temperature as the averaged oil film temperature and apply natural convection boundary conditions to the pad side and back surfaces. To validate the analysis model, we compare the predicted pad temperatures with those from previous research. The results show good agreement with previous research. In addition, we conduct parametric studies on a TPJB which was used in a gas turbine simulator system. The predicted results show that film temperature largely depends on the rotating speed and oil supply condition.

• The Journal of Pediatrics of Korean Medicine
• /
• v.15 no.2
• /
• pp.141-165
• /
• 2001

Attention-deficit/hyperactivity disorder(ADHD) is one of the most common childhood-onset psychlatric disorders. It is distinguished by symptoms of inattention, hyperactivity, and impulsivity. ADHD may be accompanied by learning disabilities, depression, anxiety, conduct disorder, and oppositional defiant disorder. The etiology of ADHD is unknown, and the disorder may have several different causes. Individual with ADHD present in childhood and may continue to show symptoms as they enter adolescence and adult life. Public interest in ADHD has increased along with debate in the media concerning the diagnostic process and treatment strategies. The purpose of this study is oriental medical approach to ADHD. This study was progressed for oriental diagnosis and treatment for ADHD. In oriental medicine, the reason of ADHD was deficiency of the kidney, hyperactivity of the liver(腎虛肝亢), deficiency of the heart and the spleen(心脾不足), heart disturbed by phlegm and heat(痰熱擾心). The method of medical treatment was nourishing the kidney and checking exuberance of yang(滋腎潛陽), relieving mental stress and promoting wisdom(寧神益智), nourishing the heart and strengthening the spleen(養心健脾), tranquilzation(安神定志). removing heat-phlegm(淸熱化痰), inducing resuscitation and tranquilzation(開窮安神). The prescription was commonly used as Liuwei Dihuang Wan jiajian(六味地黃丸加減), Guipi Tang he Ganmai Dazao Tang jiajian(歸脾湯合甘麥大棗湯加減), Huanglian Wendan Tang jiawei(溫黃連溫膽湯加味). It should help primary care providers in their assessment of a common child health problem.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.141-146
• /
• 2008

For the efficient use of thermal energy and its related equipments, optimal energy in view of quality and quantity should be timely provided. The core of thermal energy storage technology deals with an energy efficiency for effective energy storage and supply. The relative importance of thermal energy storage technology has been underestimated so far, and the specific projects on this filed have been performed intermittently. For the efficient and systematic approach of the energy supply system projects on thermal energy storage technology, we conduct the survey on the current status of this field. Firstly, classify into the thermal energy storage and describing the recent research for each system. The necessity and importance of thermal energy storage technology is identified through this study. It reveals that the thermal energy storage is the mandatory technology to solve the difference of supply and demand in thermal loads. It would greatly contribute to the combined heat and power(CHP) system. The urgent technologies for the commercial value and the core technologies for the CHP system are classified with this study.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.2 s.233
• /
• pp.224-231
• /
• 2005

The present study investigates flow characteristics in an optical disc drive (ODD). Detailed knowledge of the flow characteristics is essential to analyze flow-induced noise and vibration, forced convection and flow friction loss. The ODD used in a personal computer is used for the experiment and rotating velocity of disc is under the 4500 rpm. Time-resolved velocity component and velocity spectrum are obtained using the laser Doppler anemometry (LDA), and the flow patterns induced by rotating disc in the ODD are calculated by a commercial finite volume method at the same time. The results show that the front holes reduce flow-induced noise and the position of pickup body only affects flow near the window. Furthermore, it is possible for cooling of heat sources in the drive through measuring the flow fields under the tray. In addition, the numerical results are well matched up to the experimental results, therefore, the validation of the numerical results can be achieved. From the validation of numerical results, it is possible to predict the flow characteristics of the region where it is unable to conduct the experiment.