• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.277-294
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• 2018

In the space industry, structures undergo several vibration and acoustic tests in order to verify their design and give confidence that they will survive the launch and other critical in-orbit dynamic scenarios. At component level, vibration tests are conducted with the aim to reach local or global interface loads without exceeding the design loads. So, it is often necessary to control and limit the input based on a load criterion. This means the test engineer should be able to assess the interface loads, even when load cannot be measured. This paper presents various approaches to evaluate interface loads using measured accelerations and by referring to mass operators. Various methods, from curve fitting techniques to finite element-based methods are presented. The methods are compared using signals with known imperfection to identify strengths and weaknesses of each mass operator definition.

• 콘크리트학회논문집
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• 제12권2호
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• pp.71-78
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• 2000

This paper presents a study on the flexural rigidity of reinforced high strength concrete beams. Thirty six beams with different compressive strength of concrete, tensile reinforcement ratio, compressive reinforcement ratio, and pattern of loadings(1 point loading and 2 points loading) were tested to evaluate the effective moment of inertia. According to the experimental results, the eqation(1) proposed by ACI code for the effective moment of inertia overestimated that of simply supported reinforced high strength concrete beams. Thus, in this paper, an empirical equation(3) is proposed as a lower bound of 90% confidence limit to estimate the effective moment of inertia of simply supported reinforced high strength concrete beams.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.44-49
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• 2000

Small sonic nozzles (throat diameter $0.28{\~}4.48mm$) were tested in the gas flow standard system. This standard system is composed of two bell provers and 5 column piston provers, compressor, filters, and dehumidifier. The discharge coefficients of small some nozzles are obtained and correlated as a function of throat Reynolds numbers with $0.316\%$ uncertainty at a confidence level $95\%$. The tested high Reynolds number was the lower limit of ISO 9300 specifications. The data are useful as data base for revision of ISO 9300.

• 한국항공운항학회지
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• 제20권4호
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• pp.14-20
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• 2012

A properly determined separation minima applied in Air Traffic Management(ATM) is critical for safe and efficient aircraft operations. The separation minima is primarily determined by the accuracy performance of surveillance system, and, due to the stringent aviation safety standard, the position accuracy of the surveillance system must be estimated with a high level of reliability. This study proposed a method for estimating the position accuracy of surveillance system with a relatively small amount of data by finding upper confidence limit instead of maximum likelihood values of unknown parameters. Through the proposed method, it is possible to determine a required separation minima with a more reliability in the face of data scarcity which often occurs when we implement a new surveillance system such as Automatic Dependent Surveillance-Broadcast (ADS-B).

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.153-158
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• 2004

The security system using optical fiber is a system, circulating infrared rays laser pulse on the optical fiber which is attached on the security fence to prevent invasion, which can show invasion position with visible and audible signal on the situation monitor if an invader cut or pull the security fence with minuteness of 10m. The optical fiber can be also applied for the bed structure stability monitoring system of high speed train as well as security system. To apply this system for high speed railroad bed structures, this system will give an alarm if it detect excessive tension, shrinkage, deflection which is beyond the limit of structure, that will prevent serious railroad accident. In this paper, we like to propose that applying this system for security and structure stability can improve confidence and stability on operation of railways

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.201-206
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• 2003

This study is test for STS304 specimen using bending and torsion state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed If summarize STS304 torsion result of fatigue test, is as following. Fatigue life prediction was available by Weibull statistics distribution, and 50% breakdown probability correlation equation was appeared as following.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.678-683
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• 2003

Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multiregression analysis and phase measurement in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

• Biomolecules & Therapeutics
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• 제9권3호
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• pp.231-235
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• 2001

The single oral toxicity of JG-381 was studied in Sprague-Dawley rats of both sexes. In this study, rats were administrated orally with dosages of 267, 400, 600, 900 and 1350 mg/kg of JG-381. We daily examined number of deaths, clinical signs, body weights and gross findings for 14 days after JG-381 administration. When we administered different doses of 267, 400, 600, 900 and 1350 mg/kg, we found 1, 4, 4, 5 and 5 male rats died and 3, 5, 4, 5 and 5 female rats died within 1 day after administration, respectively. Some clinical signs (decrease locomotor activity, salivation, soft stool, prone position, lacrimation, crouching position, convulsion, ataxic gait, incontinence of urine) were also observed during the experimental period. Our findings suggest that oral L $D_{50s}$ (95% confidence limit) for male and female rats are 327 mg/kg (270~396 mg/kg) and 250 mg/kg (256~264 mg/kg), respectively.y.

• 한국생산제조학회지
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• 제21권5호
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• pp.830-835
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• 2012

A research for application of LDSMC(Low Density Sheet Molding Compound) composite is in progress for lightening the weight. This paper has performed fatigue test and simulation of external panel for Korean commercial vehicle. Before the fatigue test, static test was carried out. From the test, the structural safety was investigated using Goodman diagram. After the static test performance, the fatigue test was conducted at a range of load frequency 5Hz, a stress ratio(R) of 0.05 and an endurance limit of $10^6$ to obtain the S-N curve. The S-N curve is applied to the fatigue analysis of the external panel assembly. The result of FEM analysis was in accord with the experimental result within 83% confidence. It showed that the process to set up the safety range of allowable error is required in process of the design and simulation verification.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.719-721
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• 2011