• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.592-597
• /
• 2003

Thrust vector control using a coflow-counterflow concept is achieved by suction and blowing through a slot adjacent to a primary jet which is shrouded by a suction collar. In the present study, the flow characteristics of thrust vectoring is investigated using a numerical method. The nozzle has a design Mach number of 2.0, and the operation pressure ratio is varied to obtain various flow features of the nozzle flow. Test conditions are in the range of the nozzle pressure ratio from 6.0 to 10.0, and a suction pressure from 90kPa to 35kPa. Two-dimensional, compressible Navier-Stokes computations are conducted with RNG ${\kappa}-{\varepsilon}$ turbulence model. The computational results provide an understanding of the detailed physics of the thrust vectoring process. It is found that an increase in the nozzle pressure ratio leads to increased thrust efficiency but reduces the thrust vector angle.

• Polymer(Korea)
• /
• v.29 no.6
• /
• pp.557-564
• /
• 2005

Thermoplastic starch (TPS) was manufactured and blended with poly(butylene adipate-co-succinate) (PBAS), which is one of the most popular biodegradable aliphatic polyesters. The effects of the TPS contents on the mechanical properties, thermal characteristics, and biodegradability of PBAS/TPS blends were investigated. The foaming characteristics of those were also studied. With small amount of TPS, mechanical properties of the blends were largely deteriorated and the variations of them decreased with more addition of TPS. In addition, TPS decreased crystallinity and thermal decomposition temperature of PBAS. The PBAS/TPS foam having maximum blowing ratio was obtained with 20 Phr of TPS, and their blowing ratio decreased with the further increase of TPS.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.3
• /
• pp.338-348
• /
• 2004

The present study is conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with initial crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of tile hole diameter. Initial crossflow passes between the injection and effusion plates, and the square ribs (3mm) are installed on the effusion plate. Both the injection and effusion hole diameters are 10mmand Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effects of rib arrangements, various rib arrangements, such as 90$^{\circ}$transverse and 45$^{\circ}$angled rib arrangements, are used. Also, the effects of flow rate ratio of crossflow to impinging jets are investigated. With the initial crossflow, locally low transfer regions are formed because the wall jets are swept away, and level of heat transfer rate get decreased with increasing flow rate of crossflow. When the ribs are installed on the effusion plate, the local distributions of heat/mass transfer coefficients around the effusion holes are changed. The local heat/mass transfer around the stagnation regions and the effusion holes are affected by the rib positions, angle of attack and rib spacing. For low blowing ratio, the ribs have adverse effects on heat/mass transfer, but for higher blowing ratios, higher and more uniform heat transfer coefficient distributions are obtained than the case without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. Average heat transfer coefficients with rib turbulators are approximately 10% higher than that without ribs, and the higher values are obtained with small pitch of ribs. However, the attack angle of the rib has little influence on the average heat/mass transfer.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.11a
• /
• pp.171-172
• /
• 2014

This is an experimental study on manufacturing of non-cement matrix. Materials like cement and blowing agent in foamed concrete is replaced by by-products from blast furnace slag and paper ash. Sample 43-PS-1 with density showed lowest. The compressive strength test result, showed a similar trend with density. And it showed that compressive strength of the 40-PS-1 was highest.

• Elastomers and Composites
• /
• v.57 no.4
• /
• pp.138-146
• /
• 2022

Research on the reduction of plastic use to prevent environmental pollution is urgently needed. Accordingly, studies on reducing the weight of polyethylene terephthalate (PET) bottles are currently being conducted. PET bottles are fabricated by injection stretch blow molding. In this study, stretch blow molding for fabricating PET bottles using preform studied through a computer simulation. Blowing characteristics are analyzed by varying the start time of the pre-blow, which is one of the process conditions of stretch blow molding. Simulation results and the preform inflation process are presented, and the parameters of stretch ratio, stretching path, thickness distribution, and weight distribution of blown PET bottles are investigated.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.8
• /
• pp.1122-1130
• /
• 2001

Film cooling performance from two rows of holes with opposite orientation angles is evaluated in terms of heat flux ratio. The film cooling hole has a fixed inclination angle of 35°and orientation angle of 45°for the downstream row and -45°for the upstream row. Four film cooling hole arrangements including inline and staggered configurations are investigated. The blowing ratio studied was 1.0. Boundary layer temperature distributions are measured to investigate injectant behaviors and mixing characteristics. Detailed distributions of the adiabatic film cooling effectiveness and the heat transfer coefficient are measured using TLC(Thermochromic Liquid Crystal). For the inline configuration, there forms a downwash flow at the downstream hole exit to make the injectant well attach to the wall, which gives high adiabatic film cooling effectiveness and heat transfer coefficient. The evaluation of heat flux ratio shows that the inline configuration gives better film cooling performance with the help of the downwash flow at the downstream hole exits.

• Elastomers and Composites
• /
• v.38 no.4
• /
• pp.354-362
• /
• 2003

The use of a petaloid design for the bottom of carbonated poly(ethylene terephthalate)(PET) bottles is widely spread. This study investigated the causes of bottom cracks. The tensile yield stress variations of PET according to the crystallinity and stretch ratio were examined, then the stretch ratio and strength in the bottom area of a blown bottle were analyzed. A crack test was also performed to observe the cracking phenomena. The distribution of the effective stress and maximum principal stress were both examined using computer simulation to seek the influence of the bottom design on crack. It was concluded that the bottom cracks occurred because of inadequate material strength due to the insufficient stretching of PET, plus the coarse design of a petaloid bottom. The stretch ratio at the bottom during bottle blowing should be higher than the strain hardening point of PET to produce enhanced mechanical strength. The cracks in the bottom of the PET bottles occurred through crazing below the yield stress. The maximum principal stress was higher in the valleys of the petaloid bottom than in the rest bottom area, and the maximum principal stress had a strong effect on the cracks.

• Journal of the Korean Solar Energy Society
• /
• v.39 no.4
• /
• pp.55-67
• /
• 2019

Recently, as the amount of particulate matter blowing from China increases, the domestic air environment is rapidly deteriorating. This pollution of the atmosphere greatly affects the light energy reaching the ground. Particularly, since the light enters the solar cell module in various forms, the amount of input energy of the solar power generation system may be changed depending on the ratio of direct beam irradiation and diffused horizontal irradiation. In this paper, we analyze how the ratio of direct beam component and diffused component on global horizontal irradiation varies with the atmospheric conditions. In addition, the reliability of the regression equation, designed to decompose the global horizontal irradiation into horizontal direct beam irradiation and diffused horizontal irradiation, was verified according to the level of air pollution. So, we derive the most suitable decomposition model for use in domestic climatic conditions in Korea by comparing the ratio of direct and diffuse component on the horizontal which is calculated with Perez model and Watanabe model using the meteorological weather data observed for 14 months. Finally, to reduce the error of the transposition result, we verified the reliability of the decomposition which depends on the atmospheric environment.

• Korean Journal of Oriental Medicine
• /
• v.14 no.1
• /
• pp.73-83
• /
• 2008

Background : Kigong(氣功) is to develope a nature-therapy by controling and recovering Jinki(眞氣) and it has common features in Yangsaengbeob(養生法), Doinbeob(導引法) and Jeongkisin(精氣神), but it is rarely researched and applied in clinic examine. Objectives : it is compared and contrasted among Kukseondo(國仙道) Yeonjeongwon(硏精院), Seokmunhoheub(石門呼吸). Result : Kukseondo, Yeonjeongwon, Seokmunhoheub have the same point that beginners breath slowly, deeply and naturally. The breathing in each group becomes deeper gradually by mental and physical relaxation although each group has a different breathing method, and it is similar to Jogigyeol(調氣訣) in Dongeuibogam. Ywasik(臥式) is distinguished by the presence of sensation. The breathing in Kukseondo is Yidanhoheub(二段呼吸), the breathing in Yeonjeongwon is Yugi(留氣) and the breathing in Seokmunhoheub is that the ratio of inhaling and blowing are 6 to 4. The breathing in each group is deep and small, Ki also accumulates in the Below-abdomen between blowing and inhaling. This is confirmed by Sinjunapgi(腎主納氣) theory in Oriental-medicine. There is the breath, which is through skin, in Kigonghoheub(氣孔呼吸) of Samhabdanbeop(三合丹法) and Jolidanbeop(造理丹法) in Kukseondo, it is also in Gwiilbeop(歸一法) of Seokmunhoheub. In Kukseondo's case, the breathing is through skin mainly instead of a respiratory organ. In Seokmunhoheub's case, the circulation of Ki is through skin during breathing. In Oriental-medicine, this is called as Pyejupimo(肺主皮毛) which is connected with lung and skin. The breathing coincide with tension and relaxation of body while the breathing through skin and the absorption of Ki spread sensation over the whole body, but the breathing through skin is just a specific ability from a training.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.5
• /
• pp.2979-2984
• /
• 2015

This paper has presented a new foaming technology of selective hybrid-structured polymer film with expanded pores. The porous structure of closed pore was firstly fabricated by applying the 355nm UV-pulsed laser to 0.1mm thick film that was uniformly mixed with PP pellets, copper powder, and CBA (Chemical Blowing Agent). In order to expand pore size of closed-cell shape, LAMO(Laser Aided Micro pore Opening) processing was conducted to heat the copper powder, and then the bigger pore size of closed-cell more than existing pore size was successfully formed because of rapid conduction of heated metal powder. From the experimental results, various process parameters such as laser fluence, intensity, scan rate, spot size and density of powder and CBA were considerably considered to reveal the correlation among the pore characteristics. In the future, a function experiment will be carried out to use the hybrid film of industrial applications.