• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1997년도 International Symposium on Fire Science and Technology
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• pp.146-153
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• 1997

An experimental study was performed of natural-convection downward smolder spread across a sawdust bed peripherally enclosed with an insulating container, to examine the effect of the open- ing condition at the top end on downward smolder spread. Experiments were conducted by using relatively coarse sawdust and 25-cm-long cylindrical container The variations of temperature profiles along the bed axis with time were determined far different opening conditions and were com-pared with those in smolder spread from open top to open bottom. It was shown that the smolder zone initiated from open top toward closed bottom penetrates the bed with keeping high peak temperature like the case of open top to open bottom spread, although mean spread rate is smaller. This indicates that the downward smolder zone can be sustained stably if sufficient air or oxygen Is supplied from the back of it by natural convection even if upward draft entering from the bottom of the bed is absent. When the top end was partially closed by mounting a cover after stable smolder spread had begun from open top toward open bottom, the temperature at the peak decreased more than 200 K and the smolder zone became to spread with thickening residue. In this case, the shape of temperature profiles continuously changed or decayed until end-effect at the open bottom end enhanced the reaction. The temperature at the shrunk peak, free from the end-effect, was almost identical with the temperature at the exothermic oxidative-degradation zone in smolder spread from open top to open bottom. from these results, it can be inferred for natural-convection downward smolder spread that the oxidation reaction of the char is very sensitive to the oxygen supply by natural convection in the space above the smolder zone, and that the top end opening condition strongly alters the completeness of reactions, structure, and behavior of the smolder zone.

• 한국식생활문화학회지
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• 제34권4호
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• pp.449-455
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• 2019

The purpose of this study was to develop a peach spread premix to increase the usability of peaches with low storage stability. We analyzed the effect of adding different ratio of peach powder (0, 5, 10, 15%) on the physicochemical and sensory quality characteristics of peach spread premix. The result showed that the pH of the spread premix significantly decreased with the addition of greater amounts of peach powder (p<0.05). The total titratable acidity (TTA) and sweetness of the peach spread premix were significantly increased as the amount of added peach powder increased (p<0.05). The redness (a-value) and yellowness (b-value) increased with an increase of the peach powder ratio; however, the lightness (L-value) decreased (p<0.05). The water activity and viscosity of the spread decreased with an increased amount of added peach powder. The results of the sensory test with spread premix prepared with 10% peach powder had the highest score for color, taste, texture, stickiness, and overall acceptability (p<0.05). We suggested that the peach spread premix made with 10% peach powder may be the most desirable for manufacturing spread premix and for improving sensory preference.

• 한국통신학회논문지
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• 제37권6A호
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• pp.426-437
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• 2012

This paper proposes an array antenna assisted Doppler spread compensator with dummy elements which are placed on either end of a monopole array for a digital terrestrial television broadcasting (DTTB) receiver. An array antenna assisted Doppler spread compensator, proposed previously, has a major drawback in performance degradation owing to mutual coupling effect among array elements. In order to solve the mutual coupling problem, dummy elements, placed on both sides of the monopole array mitigate performance degradation of a Doppler spread compensator arising from the mutual coupling among monopole array elements. Computer simulation results show that the dummy elements can reduce this performance degradation as well as expand the operating bandwidth of a Doppler spread compensator.

• The Korean Journal of Pain
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• 제31권2호
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• pp.125-131
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• 2018

Background: The thoracic transforaminal epidural block (TTFEB) is usually performed to treat herpes zoster or postherpetic neuralgia (PHN). Especially, multiple segmental involvements and approximate contrast medium spread range, according to volume, help to choose the proper drug volume in the transforaminal epidural block. This study investigated the contrast medium spread patterns of 1-ml to 3-ml TTFEBs. Methods: A total of 26 patients with herpes zoster or PHN were enrolled in this study. All participants received 1 ml, 2 ml, or 3 ml of contrast medium. Results were divided into Groups A, B and C based on the volume (1, 2, or 3 ml), with n = 26 for each group. After the injection of contrast medium, the spread levels were estimated in both the lateral and anteroposterior (AP) images using fluoroscopy. Results: The cephalad spread of contrast medium in the lateral image as expressed by the median (interquartile range) was 2.00 levels (1.00-2.00) for Group A, 2.50 (2.00-3.00) for Group B, and 3.00 (2.00-4.00) for Group C. The caudal spread level of contrast medium was 1.00 (1.00-2.00) for Group A, 2.00 (2.00-3.00) for Group B, and 2.00 (2.00-3.00) for Group C. There was ventral and dorsal spread of the 3-ml contrast medium injection in 88% (23/26) of cases in the lateral image. Conclusions: Injection of 3 ml of contrast medium through the foramina spread 6 levels in a cephalocaudal direction. Spread patterns revealed a cephalad preference. TTFEB resulted in dorsal and ventral spread in a high percentage of cases. This procedure may be useful for transferring drugs to the dorsal and ventral roots.

• Korean Chemical Engineering Research
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• 제43권1호
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• pp.47-52
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• 2005

미립 금속분체에 대한 산업 수요 증가와 함께, 퇴적 금속분의 착화에 의한 화재, 폭발사고가 증가하고 있다. 본 연구에서는 퇴적 금속분체의 화재, 폭발 위험특성을 조사하기 위하여 새로운 실험장치를 개발하였다. 금속분(Mg, Zr, Ta, Ti) 및 PMMA(polymethyl methacrylate)분진을 사용하여, 연소 거동(소염거리, 화염전파속도) 및 화염전파에 미치는 $N_2$ 치환 분위기 농도의 영향 등을 실험적으로 상세히 조사하였다. 실험결과로부터, 퇴적 금속 분체의 화염전파속도는 PMMA보다 크고, 화염전파속도의 퇴적층 두께에 대한 의존성은 작으며, 질소 치환 분위기에서의 Mg의 한계 산소 농도는 3.6-3.7 vol%로 나타났다. 퇴적금속 분체층의 화염전파속도와 소염거리 역수는 높은 상관관계를 가지고 있으며, 이들 연소성 지표에 있어서 상대적인 위험성의 예측이 가능하다.

• 한국농공학회논문집
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• 제53권1호
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• pp.29-36
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• 2011

HPAI (High pathogenic avian influenza) which is a disease legally designated as an epidemic generally shows rapid spread of disease resulting in high mortality rate as well as severe economic damages. Because Korea is contiguous with China and southeast Asia where HPAI have occurred frequently, there is a high risk for HPAI outbreak. A prompt treatment against epidemics is most important for prevention of disease spread. The spread of HPAI should be considered by both direct and indirect contact as well as various spread factors including airborne spread. There are high risk of rapid propagation of HPAI flowing through the air because of collective farms mostly in Korea. Field experiments for the mechanism of disease spread have limitations such as unstable weather condition and difficulties in maintaining experimental conditions. In this study, therefore, computational fluid dynamics which has been actively used for mass transfer modeling were adapted. Korea has complex terrains and many livestock farms are located in the mountain regions. GIS numerical map was used to estimate spreads of virus attached aerosol by means of designing three dimensional complicated geometry including farm location, road network, related facilities. This can be used as back data in order to take preventive measures against HPAI occurrence and spread.

• 한국정밀공학회지
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• 제29권12호
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• pp.1368-1375
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• 2012

In this paper, a method for prediction of spread is proposed to design proper roll profile taking into account spread in shape rolling of angle bar. The effect of the process variables on spread, such as draught ratio, bending angle and aspect ratio, is analyzed by FE-analysis and response surface method (RSM). Roll profiles for equal angle bar are designed with the spread predicted by the regression equation. Effectiveness of the designed roll profiles are verified by FE-analysis in which the flange length, strain distribution, mean strain and roll torque are compared with those by Geuze. Finally, the proposed method is applied to the design of roll profile for unequal angle bar. As a result, the final product can be obtained within the allowable tolerance of ${\pm}0.5mm$ in length. Therefore, it is found that the prediction of spread can improve the efficiency of design roll profile in shape rolling of angle bar.

• 한국인터넷방송통신학회논문지
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• 제17권5호
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• pp.79-84
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• 2017

본 논문은 다중 경로 다중입력 (Multiple-input multiple-output : MIMO) 채널에서 space alternating generalized expectation-maximization(SAGE) 알고리즘을 이용하여 채널 파라미터 추정 성능을 확인한다. 성능을 비교하기 위해 781 대역의 제주도 측정지역에서의 채널 파라미터로부터 시변 채널 환경 채널 파라미터 추정을 SAGE 알고리즘을 통해 추정하고 원본 데이터와 비교한다. 이를 통해 SAGE 알고리즘의 성능을 확인할 수 있으며 일반적인 파라미터 계산보다 SAGE 알고리즘을 통해 추정하는 것이 지연 확산(Delay Spread), 도래각 확산(Arrive of Angular Spread)이 적어 정확 측면에서 성능이 뛰어나고 안정적이다.

• 소성∙가공
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• 제25권4호
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• pp.235-241
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• 2016

Dimensional accuracy of hot coil is improved by precise control of thickness profiles, flatness, width and winding profile. Especially, precise width control is important because yield could be increased significantly. Precise width control can be improved by predicting the amount of width spread. The purpose of this study is to develop the advanced prediction model for width spread in hot finish rolling for controlling width precisely. FE-simulations were performed to investigate the effect of process variables on width spread such as reduction ratio, forward and backward tension and initial width at each stand. From the statistical analysis of simulated data, advanced model was developed based on the existing models for strip width spread. The experimental hot rolling trials showed that newly developed model provided fairly accurate predictions on the strip width spread during the whole hot finishing rolling process.

• 대한기계학회논문집
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• 제13권5호
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• pp.831-836
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• 1989

본 연구에서는 이에 대한 검토를 하기 위하여, Kato의 속도장을 수정하여 수치게산한 폭 증가율과 알루미늄을 재료로 실험한 결과를 비교하고, 마찰비와 판폭비 및 압하율의 변화에 따른 폭 증가율의 영향에 대하여 고찰하였다.