• Atmosphere
• /
• v.27 no.3
• /
• pp.317-329
• /
• 2017

Ocean mixed layer (OML) depth affects diurnal cycle of sea surface temperature (SST) induced by change of solar radiation absorption and heat budget in ocean. The diurnal SST variation can lead to convection over the ocean, which can impact on localized precipitation both over coastal and inland. In this study, we investigate the OML characteristics affecting the diurnal cycle of SST for the Korean Peninsula and surrounding areas. To analyze OML characteristics, HYCOM oceanic mixed layer depth (MLD) and wind field at 10 m from ERA-interim during 2008~2016 are used. In the winter, MLD is deeply formed when the strong wind field is located on perpendicular to continental slope over deep seafloor areas. Besides, cooling SST-induced vertical mixing in OML is reinforced by dry cold air originated from Siberia. The OML in summer is shallowly distributed about 20 m. In order to estimate the impact of OML model in high resolution NWP model, four experimental simulations are performed. At this time, the prognostic scheme of skin SST is applied in NWP to simulate diurnal SST. The simulation results show that CNTL (off-OML) overestimates diurnal cycle of SST, while EXPs (on-OML) indicate similar results to observations. The prediction performance for precipitation of EXPs shows improvement compared with CNTL over coastal as well as inland. This results suggest that the application of the OML model in summer season can contribute to improving the prediction for performance of SST and precipitation over coastal area and inland.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.515-518
• /
• 2007

Gas hydrates are ice-like crystalline compounds that form under low temperature and elevated pressure conditions. Recently, gas hydrates present a novel means for natural gas storage and transportation with potential applications in a wide variety of areas. An important property of hydrates that makes them attractive for use in gas storage and transportation is their very high gas-to-sol id ratio. In addition to the high gas content, gas hydrates are remarkably stable. The main barrier to development of gas hydrate technology is the lack of an effective mass production method of gas hydrate in solid form. In this study, some performance comparison among several cases classified by different volume sizes of solution were carried to identify the characteristics due to the volume increment. And it is found that one of the main reasons disturbing hydrate formation is related to the lack of cooling heat transfer due to the volume increase of the solution. So, three kinds of heat transfer plates which have different shapes and cross sectional areas were made and tested for the performance comparison following to the shape and area of each plate. Finally it is clarified that the heat transfer is one of the major factors effecting hydrate formation performance and the installation of heat transfer plate can enhance the formation performance especially not in terms of the quantity but the speed.

• Korean Journal of Food Science and Technology
• /
• v.52 no.4
• /
• pp.357-362
• /
• 2020

This study was conducted to investigate the effects of mushroom composition (0, 4, 8, and 12%) on the quality characteristics of an extruded meat analog. The meat analog blend was isolated soy protein, wheat gluten, and corn starch (50:40:10). The extrusion condition was set to 55% feed moisture, 170℃ barrel temperature, and 150 screw speed by high moisture extrusion using a twin-screw extruder equipped with a cooling die. The integrity index, hardness, cohesiveness, springiness, chewiness, and cutting strength of the meat analog increased with the increasing mushroom content, while its water holding capacity and nitrogen solubility index (NSI) decreased. The protein digestibility decreased with the increasing mushroom content, while the DPPH radical scavenging activity significantly increased. In conclusion, the incorporation of mushrooms into the investigated meat analog enhanced its texture and antioxidant level.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.4 s.193
• /
• pp.115-122
• /
• 2007

Recently, remarkable progress has been made in both technology and production of optical elements including aspheric lens. Especially, requirements for machining glass materials have been increasing in terms of limitation on using environment, flexibility of material selection and surface accuracy. In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical GMP process was developed with an eye to mass production of precision optical glass parts by molding press. This GMP process can produce with precision and good repeatability special form lenses such as camera, video camera, aspheric lens for laser pickup, $f-\theta$ lens for laser printer and prism, and me glass parts including diffraction grating and V-grooved base. GMP process consist a succession of heating, forming, and cooling stage. In this study, as a fundamental study to develop molds for GMP used in fabrication of glass lens, we conducted a glass lens forming simulation. In prior to, to determine flow characteristics and coefficient of friction, a compression test and a compression farming simulation for PBK40, which is a material of glass lens, were conducted. Finally, using flow stress functions and coefficient of friction, a glass lens forming simulation was conducted.

• Korean Journal of Optics and Photonics
• /
• v.22 no.2
• /
• pp.96-101
• /
• 2011

Operational and thermal characteristics of a thin disk Yb:YAG crystal with a thickness of 0.8 mm were studied using as a pumping source a fiber-coupled 930 nm laser diode. The heat generated in the crystal was dissipated by placing both surfaces in contact with copper plates with central hole, and the dependence of the temperature change in the illuminated spot on hole size was investigated by measuring the spectral change of the lasing peaks. The slope efficiency and optical-to-optical efficiency with respect to the LD pump power were as high as 42.2% and 34.8%, respectively. The temperature at the illuminated spot increased with diode current and with increasing hole size of the copper plate. When the hole size considerably exceeded the crystal thickness, the temperature rise deviated from the linear increase at high pump power.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.12
• /
• pp.1007-1016
• /
• 2006

Although the advance in electronic technology enables a large number of circuity to be packed in a small volume, it is simultaneously required to remove the high heat load produced by them. In this study, the heat transfer and pressure drop characteristics of a mini-channel heat exchanger, which is designed for liquid cooling of electronic components, are investigated by varying operating conditions. Water and FC-72 were used as working fluids. The mini-channel heat exchanger was made with circular shape channels having din-meters of 2, 3, and 4 mm in regular intervals, and the channel length was 100 mm. The header and inlet guide pathway to provide uniform inflow were attached at the inlet of the test section. Copper block including the heaters was attached at the sidewall of the test section as a heat source, which provided the heat flux from 5 to $15W/cm^2$. The entrance effects enhanced the heat transfer coefficient in the mini-channel significantly. In addition, the single-phase pressure drop in the mini-channel was very similar to that predicted by the laminar flow correlation except that the transition Re decreased due to flow instability in the entrance region.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.6
• /
• pp.120-130
• /
• 2013

A study was conducted for the performance characteristics of methane taking recently the limelight in the world as a next-generation propellant, with the survey for state of the art in the development of methane/oxygen rocket engine being accompanied. Liquid methane as a rocket fuel has the favorable characteristics such as non-toxic, low cost, regenerative cooling capability, and potential for in-situ resource utilization (ISRU). The combination of liquid methane and liquid oxygen also provides the excellent performance including high specific impulse and low system mass. For these reasons, many researches have been actively carried out on the methane/oxygen engine, nevertheless, its technology readiness level is not that high enough just yet. Therefore, it is judged that it is the time to mitigate the technical gap with the space technology of advanced countries through a swift onset of the development of methane rocket engine.

• Journal of Welding and Joining
• /
• v.30 no.1
• /
• pp.64-71
• /
• 2012

The characteristics of high heat input (342kJ/cm) EG (Electro Gas Arc) welded joint of EH36-TM steel has been investigated. The weld metal microstructure consisted of fine acicular ferrite (AF), a little volume of polygonal ferrite (PF) and grain boundary ferrite (GBF). Charpy impact test results of the weld metal and heat affected zone (HAZ) met the requirement of classification rule (Min. 34J at $-20^{\circ}C$). In order to evaluate the relationship between the impact toughness property and the grain size of HAZ, the austenite grain size of HAZ was measured. The prior austenite grain size in Fusion line (F.L+0.1 mm) was about $350{\mu}m$. The grain size in F.L+1.5 mm was measured to be less than $30{\mu}m$ and this region was identified as being included in FGHAZ(Fine Grain HAZ). It is seen that as the austenite grain size decreases, the size of GBF, FSP (Ferrite Side Plate) become smaller and the impact toughness of HAZ increases. Therefore, the CGHAZ was considered to be area up to 1.3mm away from the fusion line. Results of TEM replica analysis for a welded joint implied that very small size ($0.8\sim1.2{\mu}m$) oxygen inclusions played a role of forming fine acicular ferrite in the weld metal. A large amount of (Ti, Mn, Al)xOy oxygen inclusions dispersed, and oxides density was measured to be 4,600-5,300 (ea/mm2). During the welding thermal cycle, the area near a fusion line was reheated to temperature exceeding $1400^{\circ}C$. However, the nitrides and carbides were not completely dissolved near the fusion line because of rapid heating and cooling rate. Instead, they might grow during the cooling process. TiC precipitates of about 50 ~ 100nm size dispersed near the fusion line.

• Applied Chemistry for Engineering
• /
• v.21 no.5
• /
• pp.522-526
• /
• 2010

Heat storage application techniques can be categorized into the sensible heat storage and the latent heat storage according to the method of heat storage. Heat storage is the way of saving remaining heat when heating and cooling loads are light, and then using it when the heating and cooling loads are heavy. Latent heat storage is defined as the method of saving heat by using substances which have high potential heat when phase change is in the range of a certain temperature and when heat storage space is small, compared to those of sensible heat storage and it is possible that absorption and emission of heat at a certain temperature. This study is conducted to save energy when either air-conditioning or heating is operated in a building. We have tried to find out the essential properties of matter and the optimum mixing rate about cement and gypsum for building materials, which have been widely used for proper phase change materials (PCM), when thermal environment property is applied. So we obtained the result of the cooling delay effect about 19% with heat storage mortar containing 3 wt% of PCM.

• Design & Manufacturing
• /
• v.13 no.2
• /
• pp.17-21
• /
• 2019

In this study, selective laser sintered 3D printing mold core and metal core were used to investigate the difference of the thickness shrinkage from the gate of the injection molded part at a constant interval. SLS 3D printing mold core was made of nylon-based PA2200 powder and the metal core was manufactured by conventional machining method. As the PA2200 powder material has low strength, thermal conductivity and high specific heat characteristics compared with metal, molding conditions were set with the consideration of molten temperature and injection pressure. Crystalline resin(PP) and amorphous resin(PS) with low melting temperature and viscosity were selected for the injection molding experiment. Cooling time for processing condition was selected by checking the temperature change of the cores with a cavity temperature sensor. The cooling time of the 3D printing core was required a longer time than that of the metal core. The thickness shrinkage of the molded part compared to the core depth was measured from the gate by a constant interval. It was shown that the thickness shrinkage of the 3D printing core was 2.02 ~ 4.34% larger than that of metal core. In additions, in the case of metal core, thickness shrinkage was increased with distance from the gate, on the contrary, in the case of polymer core showed reversed aspect.