• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.759-765
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• 2013

This study proposes the characteristics of the pressure drop in a compressible fluid through porous media for application to a porous injector in a liquid rocket engine in order to improve the uniformity of the drop size distribution and the mixing performance of shear coaxial injectors. The fluid through the porous media is a Non-Darcy flow that shows a Nonlinear relation between the pressure drop and the velocity at high speed and high mass flow rate. The pressure drop of the Non-Darcy flow can be derived using the Forchheimer equation that includes the losses of viscous and inertia resistance. The permeability and Ergun coefficient represented as a function of the pressure drop and pore size can be applied to the porous injector, where the fluid through the porous media is compressible. A generalized correlation between the pressure drop in relation to the pore size was derived.

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.3
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• pp.391-401
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• 1999

For proper communication among manufactures in various countries and for consumers' convenience in purchasing garments imported from foreign countries the ISO revised the size designation system in 1969. Since 1970's various countries have revised their standard sizing system by adapting the ISO system . The purpose of this study is (1) to satisfy domestic consumer's needs by developing a sizing system based on that of ISO for Korean women in their early twenties and (2) to contribute to entering the international fashion market by manufacturing high quality apparel products The results were as follows: (1) By measuring and analyzing of 464 female between the ages for 18 and 24 the data indicated that body height could be divided into following three groups. S(Short) : 152cm (19.2%) R(Regular) : 160cm (57.8%) L(Long) : 165cm(22.6%) (2) According to the results to analyzing body type of this study the medium hip(drop 6) is 47.4% the large hip(over drop 12) is 42.7% the 2 types covers 90.3% (3) Comparing Korean women's size with foreign women's size DOB size code is 17 JIS size code is 9AR, FNOR size codes are 36n. 38n. and Italian size cods are 40, 42

• Membrane Journal
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• v.6 no.3
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• pp.166-172
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• 1996

For the preparation of polybutadiene latexes with suitable particle size, membrane e$$\mu$sification, which is capable of easy and uniform control of particle size, was used in this study. The parameters were the type and amount of surfactants, amount of additive and pressure. Particle size and distribution of prepared latexes were measured and compared with those of e$$\mu$sion prepared by homogenizer. To investigate the membrane e$$\mu$sification mechanism, theoretical drop size was calculated by Harkins-Brown equation. When the amount of surfactant with more than 0.2 wt%(based on DDI water) was added in the continuous phase, the stable e$$\mu$sion was prepared. Other parameters showed little relationship with particle size and distribution. In this membrane e$$\mu$sification, the essential factor for determining the particle size was the pore size of the membrane.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.21-27
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• 1996

This experimental study was to investigate spray angles and drop sizes in an external mixed twin-fluid swirl jet nozzle. Twin-fluid swirl jet nozzle with swirlers designed four swirl angles such as $0^{\circ},\;22.5^{\circ},\;45^{\circ},\;64.2^{\circ}$ was employed. A PDA system was utilized for the measurement of drop size and mean velocity. Water and air were used as the working fluids in this experiment. The mass flow rate of water was fixed as 0.03 kg/min, and air flow rates were controlled to have the air/liquid mass ratio from 1.0 to 6.0. As a result, swirl angle controlled to spray angles and drop sizes. It was found that swirl angle was increased with spray angle and with decreased SMD. However, the effect of swirl angle was reduced at large air/liquid mass ratio(Mr=6.0).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.225-231
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• 2012

Drop simulations of the board level in the flip chips with solder joints have been highlighted for years, recently. Also, through the study on the life prediction of thermal fatigue in the flip chips considering underfill, its importance has been issued greatly. In this paper, dynamic analysis using the implicit method in the Finite Element Analysis (FEA) is carried out to assess the factors effecting on flip chips considering underfill. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard is modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. Modal analysis is simulated to find out the relation between drop impact and vibration of the board system.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.3
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• pp.335-344
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• 2000

The purpose of this study was to set up sizing system for knit trainning wears. Sample size was 198 females and their age range was from 15 to 24 years old. The body types for sizing system for knit trainning wears were divided by height and drop values. The results were as follows. 1. The height could be divided into three groups and they covered 97.5%. The Short(152cm) covered 27.8%, the Regular(160cm) 51.0% and the Tall(168cm) 18.7%. 2. The Medium hip(drop value 6) and the Large hip(drop value 12)had the high coverage rate of 45.5% and 46%, and the Small hip(drop value 0) had the low coverage rate of 8.6%. 3. For sizing system for knit trainning wears, the intervals of bust girth and hip girth were 5cm and 4cm. In the same size of bust girth, the intervals of hip high girth and waist girth were 1cm, the intervals of back waist length and sleeve length were 2cm and the interval of slacks length was 4∼5cm according to three height groups.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.172-177
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• 2011

In order to investigate spray characteristics of gas-centered swirl coaxial injectors, a phase detection optical probe is employed to obtain the spatial evolution of the drop size and velocity. From the study on the optical probe responses under various impact angles, it is demonstrated that the drop size and velocity can be measured with an uncertainty less than 15% when the probe axis remains within about ${\pm}15^{\circ}$ of the drop velocity direction. This typical uncertainty is in good agreement with a previous study. It is also shown that the drop sizes measured by the optical probe are in accord with those evaluated by image processing techniques. Finally, the experiments with the optical probe are performed in dense sprays, as it were, in the near field of gas-centered swirl coaxial injectors. Some experimental results are presented and discussed to be of help to understanding of spray characteristics of the injectors.

• Journal of the Korean Solar Energy Society
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• v.23 no.1
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• pp.9-16
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• 2003

For the study of an effect that fin thickness and shape of heat exchanger have on the elevation of heat transfer efficiency, we make models of plate fin type heat exchanger and louvered fin type heat exchanger which was given a transformation of fin thickness in plate f)n type heat exchanger and louvered fin type heat exchanger which are often used now. And the effect of fin thickness on pressure drop and characteristics of heat transfer was experimented and analysed when air velocity and temperature of plate heating was a variable. The results of experiment shows below. Pressure drop shows larger in louvered fin type exchanger than in plate fin type exchanger, size of pressure drop shows like this order that fin thickness is 0.3mm, 0.2mm, 0.1mm. Mean heat transfer coefficient shows higher in louvered fin type exchanger than in plate fin type exchanger, size of mean heat transfer coefficient by fin thickness shows same in both case in louvered fin type heat exchanger and plate fin type exchanger like this order that fin thickness is 0.1mm, 0.2mm, 0.3mm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1445-1449
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• 2007

This paper presents the DOD (Drop-On-Demand) characteristic using the electrostatic field induced inkjet printing system. In order to achieve the DOD characteristic of electrostatic field induced inkjet printing, applied the bias voltage of 1.4 kV and the pulse voltage of $2.0\;kV\;{\sim}\;2.7\;kV$ using high voltage pulse generator. Electrostatic field induced droplet ejection is directly observed using a high-speed camera and for investigated DOD characteristic, CNT ink used. The electrostatic field induced inkjet head system has DOD characteristic using pulse generator which can be applied pulse voltage. The bias voltage has a good condition which form meniscus and has micro dripping mode for small size micro droplet. Also, the droplet size decreases with increasing the applied pulse voltage. This paper shows DOD characteristic at electrostatic field induced inkjet head system, Therefore. electrostatic DOD inkjet head system will be applied industrial area comparing conventional electrostatic inkjet head system.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.588-599
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• 2019

This research presents a structural design of high-level waste (HLW) container using ultra-high performance fiber reinforced concrete (UHP-FRC) material. The proposed design aims to overcome the drawbacks of the existing concrete containers which are heavy, difficult to fabricate, and expensive. In this study, the dry storage container (DSC) that commonly used at Canadian Nuclear facilities is selected to present the proposed design. The design has been performed such that the new UHP-FRC alternative has a structural stiffness equivalent to the existing steel-concrete-steel container under various loading scenarios. Size optimization technique is used with the aim of maximizing stiffness, and minimizing the cost while satisfying both the design stresses and construction requirements. Then, the integrity of the new design has been evaluated against accidental drop-impact events based on realistic drop scenarios. The optimization results showed: the stiffness of the UHP-FRC container (300 mm wall thick) is being in the range of 1.35-1.75 times the stiffness of existing DSC (550 mm wall thick). The use of UHP-FRC leads to decrease the container weight by more than 60%. The UHP-FRC container showed a significant enhancement in performance in comparison to the existing DSC design under considered accidental drop impact scenarios.