• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.557-564
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• 2009

A combined sewer system can quickly drain both storm water and sewage, improve the living environment and resolve flood measures. A combined sewer system is much superior to separate sewer system in reduction of the non-point source pollutant load. However, during rainfall. it is impossible in time, space and economic terms to cope with the entire volume of storm water. A sewage system that exceeds the capacity of the sewer facilities drain into the river mixed with storm-water. In addition, high concentration of CSOs by first-flush increase pollution load and reduce treatment efficiency in sewage treatment plant. The aim of this study was to develope a processing unit for the removal of high CSOs concentrations in relation to water quality during rainfall events in a combined sewer. The most suitable operational design for processing facilities under various conditions was also determined. With a designed discharge of 19.89 m/min, the removal efficiency was good, without excessive overflow, but it was less effective in relation to underflow, and decreased with decreasing particle size and specific gravity. It was necessary to lessen radius of vortex separator for increasing inlet velocity in optimum range for efficient performance, and removal efficiency was considered to high because of rotation increases through enlargement of comparing height of vortex separator in diameter. By distribution of influent particle size, the actual turbulent flow and experimental results was a little different from the theoretical removal efficiency due to turbulent effect in device.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.111-118
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• 2017

In this paper, combustion tests were performed to investigate performance characteristics of a canted slit-type pintle injector engine which uses kerosene and liquid oxygen as propellants. The number of slits, slit angle and blockage factor were chosen as design variables of the pintle injector. ${\Delta}SR$ was newly defined as the difference of skip ratio caused by both sides of the tip of the canted slit. The experimental results showed that optimal combustion was performed when the blockage factor is about 1 and the difference is less than 0.26.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.6
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• pp.447-456
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• 2007

Suspended particles behavior when they go through a vertical riser with heat transfer is of significant concern to system designers and operators in pneumatic transport, various processes such as in chemical, pharmaceutical and food industries. When it comes with the energy system, that knowledge is critical to the reliable design practices of related equipment as heat exchangers, especially in the phase of system scale-up. Without haying a good understanding of the related physics, many scale-up practices based on their pilot plant experience suffer from unexpected behaviors and problems of unstable fluidization typically associated with excessive pressure drop, pressure fluctuation and even unsuccessful particle circulation. In the present study, we try to explain the observed phenomena with related physics, which may help understanding of our unanswered experiences and to provide the designers with more reliable resources for their work. We selected hot exhaust gas with solid particle that goes through a heat exchanger riser as our model to be considered. The effect of temperature change on the gas velocity, thermodynamic properties, and eventually on the particles motion behavior is reviewed along with some heat transfer analyses. The present study presents an optimal riser length at full scale under given conditions, and also defines the theoretical limiting length of the riser. The field data from the numerical analysis was validated against our experimental results.

• Journal of the Korean Home Economics Association
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• v.27 no.4
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• pp.167-191
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• 1989

The present study was conducted to devlop and appropriate retirement home model for the elderly in terms of clothing and textiles; nutrition, health, and foodservice; housing and environment; and psychological adaptation. Specifically, the purposes of the study were: 1) to provide basic guidelines for clothing by comparing the clothing behavior of the elderly living in the retirement home and those living in their own homes with family, 2) to provide basic guidelines for balanced diet and effective foodservice, 3) to develop an ideal life space and facilities, and 4) to assess the psychological characteristics of the elderly. Questionnaires, observation, experimental method, and survey of literature were used for the study. Clothing behavior showed that the elderly were much concerned about clothing, and they preferred comfortable as well as fashionable designs. The elderly in the retirement homes complained of a lack of quantity and variety in clothing. They preferred natural fiber rather than blended fabrics. Flame resistance, thermal insulation, and flexibility of textile fabrics were found to be prime considerations in manufacturing and selecting clothing materials for the elderly. The health status of the surveyed elderly was generally good, but some poor eating habits were observed. Dietary nutrients intakes were generally sufficient, but several nutrients intakes were insufficient. The level of equipment in the kitchens of the institutions was low. Furthermore, the employment rate of dietitians in institutional settings was extremely low. This resulted in a lack of systematic foodservice management. Residents in the institution were generally satisfied with present life space and facilities but this was mainly because of abandonment, adaptation, and past experience. Optimal allocation of residents per bedroom and an adequate design for storage, bathroom, utility room, and dining room were recommended. The comparison of psychological status of the elderly living at home was more stable than those living in an institution. The emotional state of the elderly living in the institution was characterized by loneliness; they did not have close interpersonal relationships or future plans. An appropriate model for the elderly was developed on the basis of these findings.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.57-63
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• 2009

In this Paper, a novel 622Mbps burst-mode clock and data recovery (CDR) circuit is proposed for passive optical network (PON) applications. The CDR circuit is composed of CDR(Clock and Data Recovery) block and PLL(Phase Locked Loop) block. Lock dynamics is accomplished on the first data transition and data are sampled in the optimal point. The CDR circuit is realized in 0.35um CMOS process technology. With input pseudo-random bit sequences(PRBS) of $2^7-1$, the simulations show 17ps peak-to-peak retimed data jitter characteristics. The experimental results show that the proposed CDR circuits are operating as expected, recovering an incoming 622Mbps burst-mode input data without errors.

• Journal of Forest and Environmental Science
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• v.31 no.2
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• pp.119-125
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• 2015

This study examined the effects of rice straw steaming time and mixing ratio between rice straw and wood particle on the properties of mixed particle board from Acacia mangium Willd wood and rice straw. Rice straw and Acacia mangium Willd wood were collected in Hanoi, Vietnam. The particle board was three-layer particle board with the structural ratio of 1:3:1. The thickness, density and board size of the particle board were 18 mm, $0.7g/cm^3$, and $800{\times}800{\times}18$ (mm, including trimming), respectively. A resin mixture between commercial Urea-formaldehyde (U-F) adhesive and methylene diphenyl isocyanate (MDI) adhesive was used with a dosage of 12% for the core layer and 14% for the surface layer. In this experimental design, the steaming time for rice straw was 15, 30, 45, 60, and 75 minutes at $100^{\circ}C$. The rice straw-wood mixing ratio was 10, 20, 30, 40, and 50%. The results showed that both mixing ratio and steaming time affect the properties of the particleboard, but the mixing ratio has a stronger impact. A higher mixing ratio and a longer steaming time resulted in a better quality of particleboard. The optimal steaming time for rice straw was 46.12 minutes with the straw-wood mixing ratio of 29.85% with the following characteristics of the particle board: the modulus of rupture (MOR) of 14.64 MPa, internal bond strength (IB) of 0.382 MPa, thickness swelling (TS) of 8.83%, and board density of $0.7-0.7g/cm^3$.

• Transactions of the KSME C: Technology and Education
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• v.2 no.1
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• pp.9-13
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• 2014

Nowadays, among several reasons for customers to choose their own cars, NVH performance plays much important role. The concern for the car interior noise is increasing recently, because electric cars and hybrid cars generate less engine noise which was the main noise of traditional cars. According to oversea references, high Lateral Dynamic Stiffness (LDS) of vehicle wheels is described to reduce Structure Bone Noise (SBN) which is being generated while driving cars. However availablet test standards and test results are not enough, in this study the interior noise has been measured after attaching a same tyre to several wheels which has different Lateral Dynamic Stiffness. The test has verified that the interior noise differs depending on Lateral Dynamic Stiffness of wheels. As to this, the reduction of the interior noise can be possible with the optimal design of the wheel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.125-130
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• 2013

According to the law revision of TPMS mounting obligations in Korea, researches about energy harvester which is the alternative of the battery are actively performed by many groups. Because WSN (Wireless Sensor Network) has the proposition of "Install and forget" and the power supplier also has the same performance as the vehicle's lifetime. In this paper, electromagnetic induction type of energy harvester through the relative motion between the rotating wheel and the fixed brake disc is introduced by using the most efficient source as the rotating motion in the view of vehicle's mechanism. The coil on the wheel and the permanent magnet at the brake disc are arranged in several ways. These various arrangements are the number of coil turns are consisted of design variables. By using the orthogonal array to reduce the experimental cost, the optimal composition is verified through the experiment. Finally the validity of the module is considered by measuring the level of storable electrical energy.

• Fire Science and Engineering
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• v.24 no.6
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• pp.139-144
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• 2010

Fire fighting foam is expanded when it mix with many water in mechanical method. It have adaptability, mass production possibility, long-time storage possibility. But foam isn't recommended that it use for extinguish the fire in winter. Because of, expansion ratio is changed according to exterior temperature and environment. In this study, we analysis to effect of expansion according to temperature and develop auto mixing system available for fire engine. As a result of non-standard drug mixture is 3.0% up to 30.08% depending on the temperature of the fire showed that the difference in performance occurs. In addition, analysis of the applicability of automatic mixing system design values and actual experimental data as 0.012% maximum error of the applicability of the system obtained according nataname was judged.

• Earthquakes and Structures
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• v.17 no.6
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• pp.611-621
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• 2019

Precast concrete structure has many advantages, but the assembled seam will affect potentially the overall seismic performance of structure. Based on the sidewall joint located in the bottom of assembled monolithic subway station, the main objectives of this study are, on one hand to present an experimental campaign on the seismic behavior of precast sidewall joint (PWJ) and cast-in-place sidewall joint (CWJ) subjected to low-cycle repeated loading, and on the other hand to explore the effect of shape and position of assembled seam on load carrying capacity and crack width of precast sidewall joint. Two full-scale specimens were designed and tested. The important index of failure pattern, loading carrying capacity, deformation performance and crack width were evaluated and compared. Based on the test results, a series of different height and variably-shape of assembled seam of precast sidewall joint were considered. The test and numerical investigations indicate that, (1) the carrying capacity and deformation capacity of precast sidewall and cast-in-place sidewall were very similar, but the crack failure pattern, bending deformation and shearing deformation in the plastic hinge zone were different obviously; (2) the influence of the assembled seam should be considered when precast underground structures located in the aquifer water-bearing stratum; (3) the optimal assembled seam shape and position can be suggested for the design of precast underground concrete structures according to the analysis results.