• 천문학회지
• /
• 제21권2호
• /
• pp.105-116
• /
• 1988

We have investigated hydrodynamical behaviors of spicules by solving numerically the hydrodynamic equations subject to proper boundary conditions using the method of characteristics. We examined the behaviors of MHD slow mode waves propagating through rigid magnetic flux tubes which were excited by the pressure perturbations at the lower boundary. It is found that the spicules are identified as the manifestation of the movement of the transition region being pushed upward by collisions with the shock waves. One of the most important findings is the presence of the rebound shocks and their roles. We interpreted the rebound shocks in terms of the observed recurrent spicules.

• 한국구조물진단유지관리공학회 논문집
• /
• 제5권2호
• /
• pp.137-146
• /
• 2001

The non-destructive tests are widely used to predict the strength of existing structures. The purpose of the present study is to propose the prediction equations for strength evaluation of concrete structures. The present study focuses on the rebound method and ultrasonic pulse velocity method for quartzite aggregate concrete. The major test variables include the water-cement ratio and curing methods. The water-cement ratio are 0.4, 0.5, 0.6, 0.7, respectively and the curing method covers ail-dry condition and standard curing condition. The prediction equations for strength of concrete are proposed from the present test data.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제17권3호
• /
• pp.207-212
• /
• 2017

Purpose: This article provides an efficient cushion molding method for improving reliability of the rotation driving system. Method: Allowable stress level for cushion is calculated by using physical characteristics of the rotation driving system. In addition, various test units are manufactured and used to conduct the rebound resilience, the burst pressure and the alternating load test. Results: Actual allowable stress level and test results of the rebound resilience, the burst pressure and the alternating load test are provided. Conclusion: The cushion manufactured by the compression molding method gives more preferable characteristics for improving the reliability of the rotation driving system.

• 중환자간호학회지
• /
• 제16권3호
• /
• pp.99-108
• /
• 2023

Purpose : This retrospective study aims to provide basic data for intervention to improve clinical outcomes and identify the characteristics of the rebound hyperthermia (RHG) and non-rebound hyperthermia (NRHG) groups by checking body temperature in patients with post-cardiac arrest syndrome. Method : The study involved 118 patients who completed target temperature management (TTM) in an acute-care unit. Data were analyzed for frequency, percentages, mean, standard deviation, median, and quartiles, and compared using the chi-squared test and Mann-Whitney U-test. Results : Rebound hyperthermia (RH) was observed in 74 (62.7%) patients, predominantly male (69.5%), with an average age of 64.54 ± 15.98, and a body mass index of 23.22 ± 4.75kg/m² (overweight). Hypertension (50%) was the most common co-morbidity, followed by diabetes and heart disease (33.1%). Neuron-specific enolase levels were higher in the NRHG 24, 48, and 72 hours after recovery of spontaneous circulation (p = .037, p < .001, p = .008). The APHCHE IV was also higher in the NRHG (p < .001). RH occurred 25.49 (7.28-52.96) hours after TTM completion, lasting for 2 (1-3) hours. Temperature reduction strategies included notifying doctors, administering antipyretics, and nursing intervention, with the latter being the most common at 94.6%. Half of the subjects in the RHG and 77.3% in the NRHG fell into cerebral performance categories 3, 4, and 5 (p = .003). Conclusion : RH is more likely a body mechanism related to CPR and TTM than a result of pathogenic infection. Therefore, we require an active intervention for hyperthermia, and a patient-specific nursing intervention protocol.

• 한국구조물진단유지관리공학회 논문집
• /
• 제1권1호
• /
• pp.97-105
• /
• 1997

The major object of this study is to analyze and investigate experimentally the experimenal equation for the estimate of compressive strength of concrete. The results are as follows. The relation between maturity scaled logarithm and compressive strength of concrete can be expressed in liner equation which show an good correlation. And combined method using rebound number, pulse velocity and water cement ratio also show an excellent correlation. The equation by combined method is same as the conclusions.

• 한국구조물진단유지관리공학회 논문집
• /
• 제6권4호
• /
• pp.91-98
• /
• 2002

Prediction for the compressive strength of concrete by non-destructive tests(NDT) has a tendency to show different outcomes according to various aggregates. The purpose of this study is to develop estimation equation by rebound number, ultrasonic velocity and combined method at concrete structures which used granite as coarse aggregates. The test variable is water/cement ratio(41.1%, 48.6%, 67.6%), curing method(moisture condition, dry condition) and age(7, 14, 28, 56). According to the test variable, new equation was suggested, and compared with the existing equations.

• 콘크리트학회논문집
• /
• 제16권6호
• /
• pp.833-840
• /
• 2004

비파괴 검사에 의한 콘크리트 압축강도 시험법 중에서 반발도법과 초음파 속도법은 가장 널리 사용되는 방법이다. 그러나 국내에서 사용되고 있는 비파괴 강도 시험법은 대부분이 외국의 시험법을 적용하고 있어서 국내의 콘크리트 구조물에 직접 적용하는 데는 무리가 따른다고 할 수 있다. 반발도법의 경우, 일본건축학회 등의 제안에 자라 20개의 타격점을 표준으로 채택하고 있으나 표준편차에 대한 고려를 하지 않고 있는 실정이다. 또한, 초음파 속도법에 의한 시험은 압축강도를 추정하는데 필요한 측정횟수의 규정이 없다 따라서 본 연구에서는 카이검증을 이용하여 비파괴 검사법에 의한 콘크리트 압축강도의 타격횟수의 신뢰도를 검토하고 최소시험 횟수를 제안하였다. 그 결과, 반발도법과 초음파 속도법으로 추정한 콘크리트 압축강도 값이 만족할 만한 신뢰범위에 들기 위한 최소시험횟수는 각각 11회와 7회로 분석되었다. 다만, 실구조물의 품질변동을 고려하여 이상치의 결측처리와 시험군의 격자 배열을 전제로 한다면, 반발도법은 국내의 관행에 따라 20회로, 음파 속도법은 9회로 규정하는 것이 바람직하다고 판단된다.

• 한국안전학회지
• /
• 제32권5호
• /
• pp.62-68
• /
• 2017

It is necessary to analyze on the compressive strength among material properties of concrete for confirming damages of architectures due to large explosion. A non destructive test is known as the representative methods estimating compressive strength and ultrasonic pulse velocity, rebound hardness test are widely used because of their simplicity, convenience. But combined method supplementing two types is applied at now as they are affected by the characteristics of test specimen. In this research to check damages on the members of structure before and after explosion, the characteristics of compressive strength are compared and analyzed through a real explosion test prior to full scale structures. The test results showed that the larger the TNT powder and the shorter the distance, the greater the decrease in strength before and after the explosion and that the largest displacement and moment for the explosive load and the greatest decrease in the strength at the central part. Due to the surface condition and the thickness variation of the concrete specimens, the standard deviation value is the smallest in the combining method of fusion of the ultrasonic method and rebound hardness method. Thus, the combining method can be one of appropriate methods to evaluate the strength in the reinforced concrete structures damaged by the explosion.

• 한국구조물진단유지관리공학회 논문집
• /
• 제3권3호
• /
• pp.157-165
• /
• 1999

The nondestructive testing methods are commonly used to determine the in-situ compressive strength of concrete. The correlation curves to evaluate the effect of aging on the development of concrete strength was proposed. Thirty two ${\Phi}10{\times}20cm$ cylinder specimens were cast from 5 batches having different strength levels. The correlation curves for rebound hammer method, ultrasonic pulse velocity method and combined method were derived from the laboratory tests and multiple regression analysis. To account for the change of condition such as surface hardness, internal moisture contents, the aging coefficients are applied to the correlation curves. From the comparison the nondestructive strength with the core strength taken from the existing reinforced concrete structures, the validity of the proposed correlation curves are verified.

• 한국구조물진단유지관리공학회 논문집
• /
• 제7권1호
• /
• pp.279-288
• /
• 2003

This study is the development of method on repairing concrete structure for progressing the durability of reinforced concrete. This method is wet spray method which compress and conduct mortar pre-mixed with polymer powder to hose by high pressure pump and spray it on the section of concrete structure through nozzle made specially. Characters of this method are that materials are selected with the sort of structure and the cause of deterioration and macro pores are removed in repaired section by conducting with high pressure and spraying with high velocity for progressing the durability of concrete structure. This study has carried out that the minimum capacity of rebound was measured with various condition and physical properties of sample made by spray method were estimated in comparing with sample made by previous hand method. Also, properties of long-term have carried out after this method was applied on site. According to experimental study, the capacity of rebound showed below 5% and physical properties of sample made by spray method were superior to that of sample made by hand method and physical and durable properties of long-term showed excellence.