• 한국추진공학회지
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• 제18권2호
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• pp.60-66
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• 2014

액체로켓엔진 연소기의 연소안정성을 평가하기 위한 방법으로 연소 시 외부 교란을 공급하여 안정성 특성을 확인하는 방법이 사용된다. 본 논문에서는 연소기의 연소안정성 평가시험을 위한 펄스건 기폭시험에 대한 연구를 수행하였다. 비연소조건에서 펄스건 기폭시험을 수행하여 압력파의 강도를 확인함으로써 펄스건의 장약량을 결정하였다. 동일한 연소기 헤드에서 펄스건이 적용되지 않은 14번의 연소시험 동안 연소불안정이 나타나지 않았지만, 펄스건이 적용된 두 번의 탈설계점 조건에서는 연소불안정 현상이 발생하였다. 이로부터 펄스건을 이용한 기폭시험이 연소안정성 평가의 방법이 될 수 있음을 확인하였으며, 연소안정성 판정을 위한 연소시험 횟수를 줄일 수 있는 방법임을 제시하였다.

• 한국추진공학회지
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• 제18권6호
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• pp.68-74
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• 2014

1 N급 단일추진제 추력기 개발모델의 장기수명 연소시험 동안 펄스모드 성능 특성 및 성능 추이를 살펴보았다. 응답 시간의 경우 주입압력조건에 따른 편차가 상대적으로 크지 않았으며, 점화지연, 반응시간, 하강시간이 각각 32-35 ms, 86-91 ms, 89-98 ms인 결과를 보여주었다. 안정화된 펄스 영역에서 주입압력조건에 따라 임펄스 비트는 $3{\sigma}$ 기준 1.41, 1.32, 2.10%의 뛰어난 재현성을 보여주었다. 장기수명 연소시험 동안 임펄스 비트가 다소 감소하지만 그 감소폭은 제한적이며, 따라서 펄스모드 성능이 유지되었다. 추력 중심 지연 또한 장기수명 연소시험 동안 일정한 것을 확인할 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제17권3호
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• pp.445-453
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• 2007

The effect of an electrochemically generated oxidation-reduction potential and electric pulse on ethanol production and growth of Saccharomyces cerevisiae ATCC 26603 was experimented and compared with effects of electron mediators (neutral red, benzyl viologen, and thionine), chemical oxidants (hydrogen peroxide and hypochlorite), chemical reductants (sulfite and nitrite), oxygen, and hydrogen. The oxidation (anodic) and reduction (cathodic) potential and electric pulse activated ethanol production and growth, and changed the total soluble protein pattern of the test strain. Neutral red electrochemically reduced activated ethanol production and growth of the test strain, but benzyl viologen and thionine did not. Nitrite inhibited ethanol production but did not influence growth of the test strain. Hydrogen peroxide, hypochlorite, and sulfite did not influence ethanol production and growth of the test strain. Hydrogen and oxygen also did not influence the growth and ethanol production. It shows that the test strain may perceive electrochemically generated oxidation-reduction potential and electric pulse as an environmental factor.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.427-436
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• 2017

Concrete technologists have used ultrasonic pulse velocity test for decades to evaluate the properties of concrete. However, the presented research work focuses on the use of ultrasonic pulse velocity test to study the degradation in steel-concrete bond subjected to increasing loading. A detailed experimental investigation was conducted by testing five identical beam specimens under increasing loading. The loading was increased from zero till failure in equal increments. From the experimentation, it was found that as the reinforced concrete beams were stressed from control unloaded condition till complete failure, the propagating ultrasonic wave velocity reduced. This reduction in wave velocity is attributed to the initiation, development, and propagation of internal cracking in the concrete surrounding the steel reinforcement. Using both direct and semidirect methods of testing, results of reduction in wave velocity with evidence of internal cracking at steel-concrete interface are presented. From the presented results and discussion, it can be concluded that the UPV test method can be successfully employed to identify zones of poor bonding along the length of reinforced concrete beam. The information gathered by such testing can be used by engineers for localizing repairs thereby leading to saving of time, labor and cost of repairs. Furthermore, the implementation strategy along with real-world challenges associated with the application of the proposed technique and area of future development have also been presented.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.389-392
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• 2000

This paper provide nondestructive test method of concrete by applying ultrasonic pulse test. Whinstone aggregates produced from cheju island are used for coarse aggregate. The purpose of this study is to contribute to the standardization of nondestructive test for estimating compressive strength of concrete manufactured from cheju island. According to experimental results, it is found that compressive strength of Whinstone aggregates concrete shows higher than that of granite stone concrete, whereas ultrasonic pulse of Whinstone aggregates concrete shows lower that of granite concrete Based on the results of this study, estimation formula compressive strength by ultrasonic pulse test are presented in Fig 2.

• Korean Journal of Acupuncture
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• 제28권4호
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• pp.101-112
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• 2011

Objectives : This study was done to investigate the degree of the pulse wave parameter of post-mastectomy women and to identify the relationships between each of them. Methods : Data were obtained from public health center in Busan Metropolitan city. Participants were 82 post-mastectomy women aged 31-82. the data collection was from Oct, 1, 2010 to Oct, 31, 2010. the data were analyzed with descriptive statistics, one-way ANOVA, Duncan test. A p-value less than .05 was considered significant by 2-tailed test. All statistical analyses were performed with SPSS/Win(ver 12.0). Results : As for the difference in the pulse wave by the general characteristics. The pulse energy was showed highly in the order of Chon, Quan and Chuk of left and right pulse respectively. In the pulse energy of left Quan and right Chon, the case of both mastectomy was showed highly and in the pulse energy of left Chuk, the case of right mastectomy was showed highly. Left and right pulse energy of menopause female were significantly higher than normal range except left Chon and Chuk. In h1, h2, h4, h5, t1, t2, AP and Aw, the pulse energy of left Chon was showed the largest significantly. In As, the pulse energy of right Chon was showed the smallest and in Ad, right Chuk was showed the largest. In RAI, right and left Chuk was showed the highest respectively. Conclusions : From these result, we can see that there are relation between women's age, area of operation breast and menopause after mastectomy in pulse wave. The result of this study will become basic data necessary for the Oriental Medicine treatment to reduce or prevent women's functional difficulties, symptomatology after mastectomy.

• 한국구조물진단유지관리공학회 논문집
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• 제5권3호
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• pp.123-130
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• 2001

The purpose of this study is to suggest the non-destructive equation for the estimation of concrete strength by ultrasonic pulse velocity at the Age of 28day compressive strength of $600{\sim}1000kg/cm^2$. For this purpose, selected test variables were water-hinder ratio, replacement ratio of silica fume, binder content, maximum size of coarse aggregate and sand-aggregate ratio. From the results, the average increase or decrease of ultrasonic pulse velocity is 61m/sec for each 1% of moisture content. And the correlation equation between the ultrasonic pulse velocity and the compressive strength of concrete is as follows. $F_c=896.3V_p-3514$ ($R^2$ = 0.81) where, $F_c$ : compressive strength($kgf/cm^2$), $V_p$ : ultrasonic velocity(km/sec).

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.353-356
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• 2011

전파를 수집하고 분석하는 신호수신시스템은 실 운용환경에서 검증되기 전에 정밀한 모의전파신호원을 이용한 정량적인 성능예측 및 실 환경과 유사한 모의전파환경에서 검증되어야한다. 신호수신 시스템은 전파의 주파수(Frequency), 펄스 변조(Pulse Modulation), 스캔 변조(Scan Modulation), 펄스 내 위상변조(Phase Modulation On Pulse), 펄스 내 주파수 변조(Frequency Modulation On Pulse) 등 다양한 신호특성에 대한 측정, 분석능력을 갖는다. 이러한 신호원들은 기본으로 실험실 환경에서 모의발생 되어야 하고 전파가 다수 존재하는 복잡한 전파환경 또한 모의되어야 한다. 본 논문에서는 효과적인 전파신호원의 모의발생, 운용시나리오에 따른 정밀고주파시험신호 모의방법에 관한 연구 결과를 서술한다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.189-193
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• 1999

An experimental study was carried out to improve the cooling capacity and performance of the pulse tube refrigerator. Three buffer pulse tube refrigerator was designed and fabricated, and the experimental apparatus was constructed. This paper presents operating process of three buffer pulse tube refrigerator and results obtained with the performance test. The cooldown characteristics and load characteristics are described. The lowest temperature measured in three pulse tube refrigerator was 88K and the cooling capacity at the optimum operating condition was 27W at 120K.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.601-609
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• 2018

Steel bolts are used in the construction industry for a large variety of applications that range from fixing permanent installations to temporary fixtures. In the past much research has been focused on developing destructive testing techniques to estimate their pull-out load carrying capacity with very little attention to develop non-destructive techniques. In this regards the presented research work details the combined use of ultrasonic pulse velocity and Schmidt hammer tests to identify anchor bolts with faculty installation and to estimate their pull-out strength by relating it to the Schmidt hammer rebound value. From experimentation, it was observed that the load capacity of bolt depends on its embedment length, diameter, bond quality/concrete strength and alignment. Ultrasonic pulse velocity test is used to judge the quality of bond of embedded anchor bolt by relating the increase in ultrasonic pulse transit time to the presence of internal pours and cracks in the vicinity of steel bolt and the surrounding concrete. This information combined with the Schmidt hammer rebound number, R, can be used to accurately identify defective bolts which resulted in lower pull-out strength. 12 mm diameter bolts with embedment length of 70 mm and 50 mm were investigated using constant strength concrete. Pull-out load capacity versus the Schmidt hammer rebound number for each embedment length is presented.