• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.389-394
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• 1994

The lattice filter formed transfer function has the advantage of computer simulation in the analysis of muffler. The transfer function is derived by using z-transformation for perforated elements in through-flow, cross-flow and reverse-flow type. A computer program for the prediction of the performance of automotive mufflers is developed using the transfer functions for uniform tube, open termination, expansion element, perforated elements, etc. The analytical results are verified by comparing with the experimental results for the transmission loss of a muffer. The effect of geometric configuration change of the muffler was invesigated in order to improve the performance of noise attenuation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1202-1204
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• 2006

Various types of perforated sheets have been applied on the surface of porous absorptive materials in order to protect dust and to enhance interior design. This study examines experimentally influences on absorptive characteristics according to the shape of perforation which includes rectangular and resonator type as well as circular holes. The measured results shows that the resonance frequency can be changed by the shape of perforation as well as the eccentricity of holes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.849-854
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• 2001

A study on performance of the sound absorbing noise barrier is presented. Noise barrier of sound absorbing type is composed of the front panel, sound absorbing material, and back panel. For allowing sound path, front panel is usually perforated. The performance of the noise barrier is governed by the opening ratio of the perforated panel, sound absorption coefficient of the sound absorbing material. In this study, the effects of the opening ratio, diameter of the hole, thickness of the sound absorbing material are investigated. It is found that the thickness of the sound absorbing material must be at least 50 mm to ensure the required minimum NRC value 0.70, and the opening ratio is greater than 0.2. It is shown that the thickness of the back panel is crucial in providing required STL (Sound Transmission Loss) value. The performance of the developed noise barrier is measured, where its sound absorbing coefficient and sound transmission loss satisfy the criteria.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.59-66
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• 2013

Lack of the space in many diesel vehicles make it difficult to design and install the catalytic muffler to reduce emissions. For this reason, inlet part of the catalytic muffler is made of L-type which has lower flow uniformity than conventional I-type, and catalytic muffler has complex internal structure by various insertions, which affect the flow uniformity and pressure drop of the systems. In this work, the flow characteristics such as flow uniformity and pressure drop have been numerically investigated by changing such various geometries as inlet shape, porosity, and outlet shape inside the muffler with the three-dimensional turbulent incompressible flow solver. Total 4 different cases are considered in order to find optimal configurations of the catalytic muffler in view of high flow uniformity and low pressure drop. The results show that Case 2 which has no induction cone and outlet perforated pipe has higher uniformity index and lower pressure drop than others considered in this work.

• 한국구조물진단유지관리공학회 논문집
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• 제3권1호
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• pp.171-178
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• 1999

Despite of decrease in shear and moment strengths, most steel structural designers use web openings in beams because of economical benefit and requirement. The purpose of this study is to suggest the method of reinforcement of H-shape steel beams with a rectangular web opening. If shear predominates over bending, it is necessary to consider all possible combinations of shear force and bending moment acting at the opening. In this paper, the ultimate strength and behavior of perforated beams have been investigated according to parameters (ratio of M/V, opening width within opening height ratio D/h, various reinforcing types A/B/C/D/M/N/W). The results of this study are as follows ; 1. Deformation of H-shape steel beams with a rectangular web opening was greatly affected by not only bending but also shear. 2. SB1-2/3 series have little difference in the reinforced efficiency, but SB1-2E/3E series have difference in the reinforced efficiency according to the reinforcement type. 3. Efficiency of SB1-2E/3E series is determined by reinforcing types, which RB1-2E-B/M/C and RB1-3E-M/D/C specimens have good efficient. Reinforcing type of perforated beams chooses efficient method according to ratio of M/V and D/h.

• Korean Chemical Engineering Research
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• 제62권2호
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• pp.191-199
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• 2024

A study was conducted on a tubular heat exchanger to improve its heat transfer rate by using a novel baffle plate design with discontinuous swirling patterns. The design consisted of perforated baffle plates with rectangular air deflectors positioned at varying angles. The tubes in the heat exchanger were arranged in a consistent alignment with the airflow direction and exposed to a uniform heat flux on their surfaces. Each baffle plate included sixteen deflectors inclined at the same angle and arranged in a clockwise pattern. This arrangement induced a swirling motion of the air inside a circular duct where the heated tubes were located, leading to increased turbulence and improved heat transfer on the tube surfaces. The spacing between the baffle plates was adjusted at different pitch ratios, and the Reynolds number was controlled within a range of 16,000 to 29,000. The effects of pitch ratios and inclination angles on the heat exchanger's performance were analyzed. The results indicated that using a baffle plate with rectangular deflectors inclined at 30° and a pitch ratio of 1.2 resulted in an average increase of 1.29 in the thermal enhancement factor.

• Journal of Korean Society for Atmospheric Environment
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• 제15권E호
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• pp.17-28
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• 1999

Gas-liquid contact tests above a perforated-plate were conducted with air and water at flooding gas-flow conditions in order to study two-phase flow characteristics in a limestone-gypsum SO2 absorber. Gas layers were in the form of air pockets and confined to the limited areas around each duct pipe, while the remaining tary area were in the wet condition. The liquid above the tray was always in the flooded and even fluidized conditions at gas flows over the range studied, although vigorous bubbly or churn-turbulent two-phase regime was only observed in the immediate vicinity of the gas hole exit at low gas loads. The froth zone was extremely active to provide intimate contact between gas and liquid so that the necessary mass transfer operation can take place, which is the primary purpose of high-performance SO2 absorbers. Howefer, the absorber $\Delta$P was 250mmH2O for the initial water level at 150mm, which is an important issue to be resolved for economical operation of the SO2 absorber. It was seen in the liquid level-and gas flow-transient tests that changes in the absorber liquid inventory were much more pronounced for intimate gas-liquid contact than changes in the gas flow. Based on the 4- and 8-duct pipe test results, grouping the duct pipes near the center of the test tray seemed to promote better recirulation of liquid from gas-liquid contact zone back to the reaction tank so that the absorbed SO2 can be neutralized.

• 한국해안·해양공학회논문집
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• 제36권3호
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• pp.116-127
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• 2024

부잔교는 연안에 설치되는 대표적인 부유식 구조물로 선박의 접안 및 계류시설로 주로 활용되고 있으나, 파랑제어 및 파력발전 구조체와 같은 다양한 목적으로 활용하려는 시도가 계속되고 있다. 본 연구에서는 상하동요와 제한된 횡동요만을 허용하는 말뚝계류 부잔교를 대상으로 부유체의 유공구조 및 몰수판 부착에 따른 반사특성 및 동요특성을 실험적으로 검토하였다. 수리실험결과, 말뚝계류된 부잔교의 반사특성과 동요특성은 뷰유체의 유공구조 유무에 비해 몰수판의 설치 유무와 설치수심에 크게 의존함을 확인하였다. 특히, 몰수판의 설치는 단주기 파랑에서 반사계수를 증가시키고, 부유체의 상하동요 및 횡동요를 감소시키는 효과가 있었다.

• Journal of Gastric Cancer
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• 제2권2호
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• pp.85-90
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• 2002

Purpose: Perforated gastric cancer (PGC) is rare and occurs in $1\∼4\%$ of all gastric cancers. Possible dissemination of tumor cells at the time of perforation of the gastric carcinoma has been a matter of concern. The intraoperative determination of what kind of operation should be done and how extensive the lymphnode dissection should be still remains controversial. The purpose of this study is to evaluate the factors influencing the survival and to determine the optimal treatment for PGC. Materials and Methods: A total of 42 patients were operated on for a perforated gastric carcinoma at Soonchunhyang University Chunan Hospital from 1983 to 2000. the age and the sexes of the patients, the location of perforation, the diameter of perforation, the histologic type of the tumor, the depth of wall invasion, the absence or presence of lymph node metastasis / distant metastasis, the stage of disease, the type of operation, and the outcomes were examined. Statistically significant differences were analyzed by using Fisher's exact test. Results: The stage distributions according to the UICC classification were 1 case of stage I, 6 cases of stage II, 17 cases of stage III, and 11 cases of stage IV. An emergency gastrectomy was done in 26 patients ($61.9\%$), with a 5-yr survival rate of $44\%$. The survival of patients was significantly influenced by the depth of wall invasion, the lymphnode metastasis, distant metastasis, the stage of disease, and the type of operation. Conclusions: an emergency gastrectomy is the treatment of choice for most patients with resectable PGC. Choosing more a optimistic surgical approach for potentially curative cases of PGC should be one way to increase the patient's survival rate.

• Journal of the Korean Wood Science and Technology
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• 제30권1호
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• pp.25-33
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• 2002

파티클보드의 두께방향으로 밀도경사와 흡음성 개선을 위한 새로운 열압방식개발을 위하여 본 과제를 수행하였다. 적용한 열압방식으로는 기존의 평판가열식 열압방식(A-type pressing), 성형장치내 열압방식(B-type pressing), 그리고 성형장치내 요철카울을 설치한 열압방식(C-type pressing)을 적용하였다. 원료목질은 낙엽송 세이빙을 사용하였으며, 접착제로는 수용성 페놀-포름알데하이드 접착제를 사용하였다. 흡음성 개선을 위한 보드는 열압시 요철카울에 의하여 보드 이면에 계단형 공극을 생성하였다. 열압방식별 제조된 보드의 물리적 및 기계적 성질을 측정하였는 바, 성형장치내 열압을 함으로써 강도적 성능을 향상시킬 수 있는 것으로 나타났으며, 보드의 두께방향 밀도경사 역시 평균밀도에 대한 최소밀도의 비율이 90% 이상을 나타내어 기존의 평판가열식으로 제조한 보드 보다 크게 개선시킬 수 있는 것으로 나타났다. 또한 열압시 요철카울에 의하여 천공을 해 줌으로써 파티클보드의 흡음계수를 향상시킬 수 있는 것으로 나타남으로써 향후 저밀도 후판보드 제조가능성과 흡음재 등 새로운 건축내장재료로의 사용가능성을 확인하였다.