• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.98-105
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• 2021

This study presented the results of the static load tests conducted to verify the structural robustness of the composite oxidant tank for a space launch vehicle. First, we introduced the test equipment used in the static load test of the composite oxidant tank, and then described the test requirements that the composite oxidant tank must satisfy. In addition, we presented a test set-up diagram consisting of the static load test fixture, hydraulic pressure, control equipment, and data acquisition equipment, and the load profile of the static load test of the composite oxidant tank consisting of shear, equivalent compression, bending, and combination tests. As a result of load control, we verified the reliability of this test by showing the errors between the input load and the feedback load in each channel according to the increase of the test load, and the feedback error between the channel A and channel B of load cell in each load actuator. As a result of the static load test, the load of the actuator was properly controlled within the allowable error range in each test, and we found that the test specimen did not cause damage or buckling that causes significant structural defects in the required load.

• Journal of Korean Society for Quality Management
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• v.22 no.1
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• pp.169-178
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• 1994

Nonparametric tests for comparing two treatments when data are subject to unequal patterns of censorship are discussed. Best precedence test proposed by Slud can be viewed as a nice alternative test comparing with weighted log-rank tests, not to mention the advantage of short experimental period. This research revises some missing parts of Slud's test and examines the asymptotic power of it under the nonproportional hazard alternatives through the simulation. The simulation studies show best precedence test has reasonable power in the sense of robustness under nonproportional hazard alternatives and could be recommended at such situation.

• The Korean Journal of Applied Statistics
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• v.9 no.1
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• pp.53-73
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• 1996

This paper compares two accelerated life for Weibull distribution. One is the optimum constant stress accelerated life test which minimizes the asymptotic variance of maximum likelihood estimator of a specified quantile at design stress, and the other is corresponding simple step stress test. The models and optimum designs of constant stress and step stress tests are reviewed. Behaviors of asymptotic variances, effects of design parameters to optimum tests, and expected numbers of failures and expected test times of the two tests are investigated. The efficiency of step stress test relative to constant stress test is studied in terms of variance ratio, and robustness to preestimates of design parameters are investigated.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.97-103
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• 2022

An aircraft component can only be mounted on an aircraft if it has been certified to have a structural robustness under flight load conditions. Among the major components of the aircraft, a pylon is a structure that connects external equipment such as an engine, and external attachments with the main wing of an aircraft and transmits the loads acting on it to the main structure of the aircraft. In civil aircraft, when there is an incident of fire in the engine area, the pylon prevents the fire from spreading to the wings. This study presents the results of structural static tests performed to verify the structural robustness of a fuel pylon used to mount external fuel tank in an aircraft. In the main text, we present the test set-up diagram consisting of test fixture, hydraulic pressure unit, load control system, and data acquisition equipment used in the structure static test of the fuel pylon. In addition, we introduce the software that controls the load actuator, and provide a test profile for each test load condition. As a result of the structural static test, it was found that the load actuator was properly controlled within the allowable error range in each test, and the reliability of the numerical analysis was verified by comparing the numerical analysis results and the strain obtained from the structural test at the main positions of the test specimen. In conclusion, it was proved that the fuel pylon covered in this study has sufficient structural strength for the required load conditions through structural static tests.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.4
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• pp.205-214
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• 2018

The reliability test is a crucial step for ensuring robustness of high-cost and complex weapon systems. In this paper, we present a set of quantitative criteria to select critical parts or components in weapon systems for the reliability test, and implement a fuzzy inference system by applying developed criteria to fuzzy theory. We classify the selection criteria of critical parts or components into four fuzzy sets and membership functions. A fuzzy inference rule is proposed based on the AHP (Analytic Hierarchy Process) analysis technique so as to derive a convincing reliability test. The credibility of the fuzzy inference system is confirmed through a case study using actual equipment data exacted from an existent weapon system.

• Smart Media Journal
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• v.10 no.3
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• pp.54-59
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• 2021

Flight data acquired through flight instrumentation equipment during aircraft development play an important role in aircraft development and performance improvement. Therefore, as the reliability of flight instruments is required, inspection systems to check the soundness of flight instruments are very important. In this paper, we analyze the existing test system for flight data instrumentation equipment and present improvements in the hardware and software aspects of the test system. Based on this, we design and implement a test system with improved performance and present test results. Test system with improved performance improves cost savings, flexible application, and maintenance compared to the existing test system. Therefore, the robustness of the instrumentation equipment can be obtained, which can be expected to improve the reliability of flight data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1931-1942
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• 2002

In this paper a formulation of robust optimization is presented and illustrated by a design example of vibratory micro gyroscopes in order to reduce the effect of variations due to uncertainties in MEMS fabrication processes. For the vibratory micro gyroscope considered it is important to match the resonance frequencies of the vertical (sensing) and lateral (driving) modes as close as possible to attain a high sensing sensitivity. A deterministic optimization in which the difference of both the sensing and driving natural frequencies is minimized as an objective function results in highly enhanced performance but apt to be very sensitive to fabrication errors. The formulation proposed is to attain robustness of the performance by including the sensitivity of the response with respect to uncertain variables as a term of objective function to be minimized. This formulation is simple and practically applicable since no detail statistical information on fabrication errors is required. The geometric variables, beam width, length and thickness of vibratory micro gyroscopes are adopted as design variables and at the same time considered as uncertain variables because here occur the fabrication errors. A robustness test in terms of a percentage yield by using the Monte Carlo simulation has shown that the robust optimum produces twice more acceptable designs than the deterministic optimum. Improvement of robustness becomes bigger as the amount of fabrication errors is assumed larger. Considering that the magnitude of fabrication errors and uncertainties in a MEMS structure are comparatively large, the present method is illustrated to be a viable approach for a robust MEMS design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.1
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• pp.23-29
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• 2008

Two high resolution compressive schemes, CICSAM(Ubbink, 1997) and HRIC(Muzaferija & Peric, 1999), in interface capturing method are reviewed briefly with respect to the extended forms suitable for unstructured meshes. And then those are applied to three typical test cases of translation test, shearing flow test and collapsing water problem with an obstacle. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method, which is based on the finite-volume technique and fully conservative. The calculated results show that CICSAM is better than HRIC with respect to accuracy and robustness, although either scheme can be used as a good choice for free surface or two-phase flow simulation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.12
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• pp.716-722
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• 2005

In this paper, we propose the audio watermarking algorithm based on the critical band of HAS(human auditory system) without audibly affecting the quality of the watermarked audio and implement the detecting algorithm on the BSS(broadcast synchronizing system) for testing the proposed algorithm. According to the audio quality test, the SNR(signal to noise ratio) of the watermarked audio objectively is 66dB above. In the robustness test, the proposed algorithm can detect the watermark more than $90\%$ from various compression(MP3, AAC), A/D and D/A conversions, sampling rate conversions and especially asynchronizing attacks. The BSS automatically switches the programs between the key station and the local station in broadcasting system. The result of reliability test of implemented system by using the real broadcasting audio has no false positive error during 30 days. Because of detecting once processing per 0.5 second, we can judge that the false positive error does not occur.

• Journal of the Korean Statistical Society
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• v.11 no.2
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• pp.109-117
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• 1982

In this paper, a preliminary study is performed on the subset selection procedures which are based on the trimmed means and the Hodges-Lehmann estimator derived from the Wilcoxon test. The proposed procedures are compared to the Gupta's rule through a small smaple Monte Carlo study. The results show that the procedures based on the robust estimators are successful in terms of efficiency and robustness.