• 한국자동차공학회논문집
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• 제16권6호
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• pp.115-120
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• 2008

There are many typesof accelerometer sensor. There was mainly used high-g accelerometer to obtain data for vehicle in crash test. Accelerometer was mounted on test vehicle with mounting blocks. Test result can be influenced by condition of mounting i.e. bonding material and type of block. These influences can be evaluated to variation of sensitivity in calibration test. In this paper, Calibration test were carried out for 3 types of bonding material i.e. stud, beewax and double side tape. Other factor was taken into consideration by 3-types for mounting block. All test was conducted by sinusoidal signal vibrator up to 4500Hz. In order to investigate influence for sensitivity from different input voltage in the calibrator, the same test was repeated. Test results were compared with standard accelerometer data. Relative sensitivities and phases were showed small difference in sensitivity for bonding materials with one block, but significant one for another block and different input voltage below 1000Hz.

• 한국방사선학회논문지
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• 제13권2호
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• pp.313-318
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• 2019

민감도 향상을 위해 블록형 섬광체를 사용한 검출기를 개발하였다. 픽셀형 섬광체는 섬광체에서 발생된 빛을 최대한 광센서로 이동시키기 위해 픽셀 사이에 반사체가 위치하며, 반사체 부분으로 민감도 손실이 발생한다. 민감도를 향상시키고 픽셀형 섬광체의 특징을 가지게 하기 위해 블록형 섬광체를 레이저 각인을 통해 픽셀 형태의 섬광체로 가공하였다. 본 섬광체를 위치민감형 광전증배관과 결합하여 평면 영상을 획득하였고, 각 픽셀별 에너지 스펙트럼과, 에너지 분해능을 측정하였으며, GATE 시뮬레이션을 통해 블록형 섬광체와 픽셀 섬광체의 민감도 분석을 수행하였다. 측정된 전체 에너지 분해능은 20.7%를 보였으며, 민감도는 픽셀 섬광체에 비해 18.5% 높은 결과를 나타내었다. 본 검출기를 감마카메라 및 양전자방출단층촬영기기 등의 영상화 기기에 활용할 경우 높은 민감도 향상을 통해 촬영시간의 단축 및 적은 방사선원 사용으로 환자의 피폭선량 감소를 이룰 수 있을 것이다.

• 한국안전학회지
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• 제18권1호
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• pp.8-13
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• 2003

This study proposes integrity evaluation method of weld zone in rails using high precision distance amplitude characteristics curve(DACC) and ultrasonic signals. For these purposes, the ultrasonic signals for defects(porosity and crack) of weld zone in rails are acquired in the type of time series data and echo strength. 6 lines in the DACC indicated damage evaluation standard of weld zone in rails. The aquired ultrasonic signals agree fairly well with the mesured results of reference block and sensitivity block(defect location, beam propagation distance, echo strength, etc). The proposed high precision DACC in this study can be used for integrity evaluation of weld zone in rails.

• 한국안전학회지
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• 제23권4호
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• pp.7-12
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• 2008

This study proposes integrity evaluation method of weld zone in titanium using titanium distance amplitude characteristics curve(TDACC) and ultrasonic signals. For these purposes, the ultrasonic signals for porosity defects of weld zone in titanium are acquired in the type of time series data and echo strength. 4 lines in the DACC indicated damage evaluation standard of weld zone in titanium. The acquired ultrasonic signals agree fairly well with the measured results of reference block and sensitivity block(defect location, bean1 propagation distance, echo strength, etc). The proposed TDACC in this study agree fairy well with the measured results of weld zone in titanium(weld defects as porosity). The proposed TDACC in this study can be used for integrity evaluation of weld zone in titanium.

• 한국안전학회지
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• 제20권1호
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• pp.30-35
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• 2005

This study proposes construction of through transmission for weld defects detection of rail weld zone from ultrasonic signals. For these purposes, the ultrasonic signals for defects(porosity and crack) of weld zone in rails are acquired in the type of time series data and echo strength. 6 lines in the distance amplitude characteristics curve(DACC) indicated damage evaluation standard of weld zone in rails. The acquired ultrasonic signals agree flirty well with the mesured results of reference block and sensitivity block(defect location beam propagation distance, echo strength, etc). The proposed construction of through transmission in this study can be used for weld defects detection of rail weld zone.

• Macromolecular Research
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• 제15권5호
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• pp.437-442
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• 2007

Poly(ethylene glycol) methyl ether (PEG)-poly(${\beta}$-amino ester) (PAE) block copolymers were synthesized using a Michael-type step polymerization, and the construction of pH-sensitive polymeric micelles (PM) investigated. The ${\beta}$-amino ester block of the block copolymers functioned as a pH-sensitive moiety as well as a hydrophobic block in relation to the ionization of PAE, while PEG acted as a hydrophilic block, regardless of ionization. The synthesized polymers were characterized using $^1H-NMR$, with their molecular weights measured using gel permeation chromatography. The $pK_b$ values of the pH-sensitive polymers were measured using a titration method. The pH-sensitivity and critical micelle concentration (CMC) of the block copolymers in PBS solution were estimated using fluorescence spectroscopy. The pH dependent micellization behaviors with various bisacrylate esters varied within a narrow pH range. The critical micelle concentration at pH 7.4 decreased from 0.032 to 0.004 mg/mL on increasing the number of methyl group in the bisacrylate from 4 to 10. Also, the particle size of the block copolymer micelles was determined using dynamic light scattering (DLS). The DLS results revealed the micelles had an average size below 100 nm. These pH-sensitive polymeric micelles may be good carriers for the delivery of an anticancer drug.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.560-568
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• 1998

Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.326-332
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• 1997

Recently to develop an automobile with better prosperities, many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weights of the engine without changing the dynamic characteristics. At first we perform the vibration analysis by the Substructure Synthesis Method and execute the exciting test for the engine model, and observe the coincidences of two results to confirm the reliability of the analyzing tools used. The weight minimization is performed by the Sensitivities of the Natural frequencies of the engine block. To decrease the engine weight ideally, the parts of the sensitivity zero are to be cut mainly, and the changing quantity of natural frequency by the cut is to be recovered by the structural modification for the parts with the good sensitivity. But, as actually the mathematical solution for the homogeneous problem(i.e. 0 object function) do not exist, we hereby redesign the block with much thinner thickness and recover the natural frequencies and natural modes to original structure's by the sensitivity analysis. And the Frequency Response Functions(FRF) are to be observed for the interesting points. In this analysis, the original thickness of the engine model has 8 mm of thickness, and the thickness redesigned is 5 mm and 6 mm. And we are to try to recover the 1, 2, 4, and 5 lower natural frequencies interested.

• Structural Engineering and Mechanics
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• 제23권3호
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• pp.309-323
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• 2006

In this paper, seismic response of a free-standing ship located in a dry dock and supported by an arrangement of n keel blocks due to base excitation is addressed. Formulation of the problem including derivation of governing equations in various modes of motion as well as transition conditions from one mode to another is given in Moghaddasi and Bargi (2006) by same authors. On the base of numerical solution for presented formulation, several numbers of analyses are conducted to study sensitivity of system's responses to some major contributing parameters. These parameters include friction coefficients between contacting surfaces, block dimensions, peak ground acceleration, and the magnitude of vertical ground acceleration. Finally, performance of a system with usual parameters normally encountered in design is investigated.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권7호
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• pp.434-441
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• 2003

This paper proposes a new quantitative and objective image quality metric which is essential to verify the performance of block-based DCT image coding. The proposed metric considers not only global distortion of coded image such as spatial frequency sensitivity and channel masking using HVS based multi-channel model, but also structural distortions caused block-based coding. The experimental results show a strong correlation between proposed metric and subjective metric.