• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 추계 학술논문 발표대회
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• pp.1-5
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• 2008

In this study, batcher plant composition test and mock-up test were carried out to conduct comparison and analysis on flow behavior and strength properties of concrete at early age. As a result, it was found that slump and amount of air in batcher plant composition test reached the target range. As for compressive strength, composition using HESPC showed the most excellent strength development. In mock-up test which was carried out to find out the strength properties, two methods with specimen and core test body both revealed HESPC as the most excellent composition. However, strength estimation with ultrasonic survey presented less reliable data. As a result of the previously conducted indoor composition test and the mock-up test in this study, target performance of concrete at early age was 4day/cycle. It was found that the optimum conditions that meet the required strength, 5MPa/18hr and 14MPa/36hr in mullion and transom are; curing temperature above 15℃, W/B 45%, unit-water 165kg/㎥ and CHC cement.

• 수산해양기술연구
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• 제50권4호
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• pp.427-434
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• 2014

Although ex situ target strength (TS) measurements using dual- and split-beam systems have become the primary approach of estimating fish abundance, theoretical model estimation is a powerful tool for verifying the measurements, as well as for providing values when making direct measurements is difficult. TS values for 20 samples of live bambooleaf wrasse (Pseudolabrus japonicus) whose target length (TL) ranged between 13.7 and 21.3 cm were estimated theoretically using the Kirchhoff-ray mode model, and the TS values for 18 live fish samples were additionally measured at ${\sim}0^{\circ}$ tilt angle to the swimming aspect using a tethered method at a frequency of 120 kHz to verify the theoretical values. The digitizing intervals used to extract the fish body and swim bladder morphology in the X-ray photographs significantly affected the calculated TS patterns, but variations based on the speed of sound and density ratio values for the general range of fish flesh were relatively small (within 1 dB). Close agreement was observed between the measured and theoretical TS values, and the correlation between the average TS and body length of the fish could be calculated accurately as <$TS_{120kHz}$>= 20logTL (cm) -71.6 using the theoretical method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.812-819
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• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. This research provides the time pattern of TS in time domain, which is applicable to pulse modulated acoustic pressure field. If the time pattern of TS is predicted by using TS equation in frequency domain, it takes long time and difficult since time function pulsed acoustic wave may be decomposed into their frequency domain components. But TS equation in time domain has a convenience. If the expression for pulsed acoustic field has been obtained, the problem can be solved. Furthermore this paper introduces about mathematical equivalence quantities between EM wave and Acoustic Wave.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.568-571
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• 2004

This research estimated the physical. mechanical characteristic and the character of sound absorption according to target void ratio of porous concrete and the mixing ratio of recycled aggregate for the valid utilization of recycled aggregate using waste concrete and sound reduction out of a road, a railway, a residential street, and a downtown area. As a result of the test, compressive strength tended to be a radical strength fall when target void ratio was $25\%$ and contents of recycled aggregate exceeded over $50\%$. Also, the character of sound absorption of porous concrete which used recycled aggregate using waste concrete was the most excellent when target void ratio was $25\%$, and the influence by contents of recycled aggregate was trivial. Therefore, when the strength and the character of sound absorption of porous concrete are considered, it is proved valid that proper target void ratio was $25\%$ and contents of recycled aggregate using waste concrete was $50\%$ or so.

• 전산구조공학
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• 제10권4호
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• pp.281-290
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• 1997

현행 내진설계 규준에서 사용하고 있는 반응수정계수는 설계지진하중과 유사한 지진발생시 구조물이 비선형 거동을 하도록 탄성응답에서 요구되는 밑면전단력 값을 낮추는 계수라 할 수 있다. 따라서 반응수정계수는 하중저감계수(force reduction factor)라고 할 수 있으며, 이러한 값들은 경험적으로 결정된 것이어서 예상지진에 대하여 구조설계자가 설계한 건물이 어느정도의 비선형 거동을 할지는 예측하기가 힘들다. 본 연구에서는 목표가 되는 연성비(target ductility ratio)에 따라 요구되는 밑면전단력의 값을 구하고 이를 규준에서 요구하는 값과 비교할 것이다. 만약 요구되는 값이 규준 값 보다 크다면 이는 구조물이 가지는 부가강도(overstrength)나 잉여력(redundancy)이 담당해야 한다. 모멘트연성골조 건물을 설계한 후 이를 push-over 해석에 의하여 부가강도를 찾아 보아 요구강도와 비교할 것이다.

• 한국건축시공학회지
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• 제8권3호
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• pp.85-91
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• 2008

Out of all the nondestructive test (NDT) methods, the pullout test is one of the most reliable techniques for estimating the strength of concrete under construction. However the pullout test inevitably produces significant surface damage because of the inherent test mechanism and costs too much for using measurement devices. In the view of construction engineers and inspectors, the main purpose of NDT methods for concrete is to verify whether the concrete strength of structure members exceeds the target strength or not. In this paper, a new pullout test method, which involves a pre-installed breaking bolt, with pre-determined breaking torques corresponding to the target strength of concrete, is introduced with related test data. The three types of test, the rebound hammer test, the pullout test, and the new pullout test with breaking bolt, were carried out on wall specimen with three types of concrete strengths. Our results show that concrete strength as evaluated by the pullout test with breaking bolt was similar with cylinder test results. Therefore it can be said that the new pullout test with breaking bolt is a useful method for checking the concrete strength without any surface damages in construction site.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.177-178
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• 2023

In this study, the mass production process was simulated using a 1m³ batcher plant to evaluate the application of high-strength fire resistance concrete. The strength ranges of concrete were set to 50, 60, 70, and 80 MPa, and each concrete mix proportions was selected through preliminary experiments in the laboratory. For the selected concrete mix proportions, after the mixer load value was stabilized in the batcher plant, the slump flow and air content of the fresh concrete were evaluated, and the compressive strength was evaluated up to 56 days. As a result of the experiment, both the slump flow and air content of the fresh concrete satisfied the target performance, and in the case of compressive strength, 50 and 60 MPa satisfied the target performance at 28 days and 70 and 80 MPa at 56 days.

• 한국군사과학기술학회지
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• 제4권1호
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• pp.93-103
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• 2001

고주파를 주로 사용하는 능동소나에서 반사신호는 물체표면의 거울면 반사와 내부의 여러 등가적인 산란자로 형성되며, 이는 물체에 공간적으로 분포된 하이라이트에 의해 특징 된다. 본 연구에서는 기존의 모의표적에 대한 반사신호 합성모델 즉, 랜덤분포 모델, 등간격분포 모델 및 MUTAHID 모델에 대하여 분석하고, 합성된 반사신호 결과특성을 여러 조건에서 비교하였다. 이러한 하이라이트 분포 모델들은 수중표적의 반사신호 합성을 필요로 하는 각종 실시스템의 모의표적 신호 합성에 유용하게 적용될 수 있으리라 생각된다.

• 대한건축학회논문집:구조계
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• 제34권2호
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• pp.29-40
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• 2018

Strength design wind loads for the wind resistance design of structures shall be evaluated by the product of wind loads calculated based on the basic wind speed with 100 years return period and the wind load factor 1.3 specified in the provisions of load combinations in Korean Building Code (KBC) 2016. It may be sure that the wind load factor 1.3 in KBC(2016) had not been determined by probabilistic method or empirical method using meteorological wind speed data in Korea. In this paper, wind load factors were evaluated by probabilistic method and empirical method. The annual maximum 10 minutes mean wind speed data at 69 meteorological stations during past 40 years from 1973 to 2012 were selected for this evaluation. From the comparison of the results of those two method, it can be found that the mean values of wind load factors calculated both probability based method and empirical based method were similar at all meteorological stations. When target level of reliability index is set up 2.5, the mean value of wind load factors for all regions should be presented about 1.35. When target level of reliability index is set up 3.0, wind load factor should be presented about 1.46. By using the relationship between importance factor(conversion factor for return period) and wind load factor, the return periods for strength design were estimated and expected wind speeds of all regions accounting for strength design were proposed. It can be found that return period to estimate wind loads for strength design should be 500 years and 800 years in according to target level of reliability index 2.5 and 3.0, respectively. The 500 years basic wind speed map for strength design was suggested and it can be used with a wind load factor 1.0.

• 한국해양공학회지
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• 제19권1호
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• pp.64-70
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• 2005

Target Strength(TS) is an important factor for the detection of the target in an active sonar system: thus the numerical model for the prediction of TS is widely being developed. For the frequency range of several kHz, the most important scattering mechanism is known to be specular reflection, which is largely affected by the geometrical shape of the target. In this paper, a numerical algorithm to predict TS is developed based on the Kirchhoff approximation which is computationally efficient. The developed algorithm is applied to the canonical targets of simple shapes, for which the analytical solutions exist. The numerical results show good agreement with the analytical solutions. Also, the algorithm is applied to more complex scatterers, and is compared with the experimental data obtained in the water tank experiment for the purpose of verifying the developed numerical model. Discussions on the effect of spatial sampling and other aspects of numerical m odeling are presented.