• Smart Structures and Systems
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• 제24권4호
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• pp.475-490
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• 2019

The detection of structural damage without a priori information on the healthy state is challenging. In order to address the issue, the study presents a baseline-free approach to detect damage in beam structures based on an actual influence line. In particular, a multi-segment function-fitting calculation is developed to extract the actual deflection influence line (DIL) of a damaged beam from bridge responses due to a passing vehicle. An intact basis function based on the measurement position is introduced. The damage index is defined as the difference between the actual DIL and a constructed function related to the intact basis, and the damage location is indicated based on the local peak value of the damage index curve. The damage basis function is formulated by using the detected damage location. Based on the intact and damage basis functions, damage severity is quantified by fitting the actual DIL using the least-square calculation. Both numerical and experimental examples are provided to investigate the feasibility of the proposed method. The results indicate that the present baseline-free approach is effective in detecting the damage of beam structures.

• Korean Journal of Radiology
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• 제23권2호
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• pp.159-171
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• 2022

Objective: This study aimed to investigate the impact of baseline values and temporal changes in body composition parameters, including skeletal muscle index (SMI) and visceral adipose tissue area (VAT), measured using serial computed tomography (CT) imaging on the prognosis of operable breast cancers in Asian patients. Materials and Methods: This study retrospectively included 627 Asian female (mean age ± standard deviation [SD], 53.6 ± 8.3 years) who underwent surgery for stage I-III breast cancer between January 2011 and September 2012. Body composition parameters, including SMI and VAT, were semi-automatically calculated on baseline abdominal CT at the time of diagnosis and follow-up CT for post-treatment surveillance. Serial changes in SMI and VAT were calculated as the delta values. Multivariable Cox regression analysis was used to evaluate the association of baseline and delta SMI and VAT values with disease-free survival. Results: Among 627 patients, 56 patients (9.2%) had breast cancer recurrence after a median of 40.5 months. The mean value ± SD of the baseline SMI and baseline VAT were 43.7 ± 5.8 cm²/m² and 72.0 ± 46.0 cm², respectively. The mean value of the delta SMI was -0.9 cm²/m² and the delta VAT was 0.5 cm². The baseline SMI and VAT were not significantly associated with disease-free survival (adjusted hazard ratio [HR], 0.983; 95% confidence interval [CI], 0.937-1.031; p = 0.475 and adjusted HR, 1.001; 95% CI, 0.995-1.006; p = 0.751, respectively). The delta SMI and VAT were also not significantly associated with disease-free survival (adjusted HR, 0.894; 95% CI, 0.766-1.043; p = 0.155 and adjusted HR, 1.001; 95% CI, 0.989-1.014; p = 0.848, respectively). Conclusion: Our study revealed that baseline and early temporal changes in SMI and VAT were not independent prognostic factors regarding disease-free survival in Asian patients undergoing surgery for breast cancer.

• Smart Structures and Systems
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• 제4권4호
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• pp.391-406
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• 2008

This study attempts to develop a real-time debonding monitoring system for carbon fiber-reinforced polymer (CFRP) strengthened structures by continuously inspecting the bonding condition between the CFRP layer and the host structure. The uniqueness of this study is in developing a new concept and theoretical framework of nondestructive testing (NDT), in which debonding is detected without relying on previously-obtained baseline data. The proposed reference-free damage diagnosis is achieved based on the concept of time reversal acoustics (TRA). In TRA, an input signal at an excitation point can be reconstructed if the response signal measured at another point is reemitted to the original excitation point after being reversed in the time domain. Examining the deviation of the reconstructed signal from the known initial input signal allows instantaneous identification of damage without requiring a baseline signal representing the undamaged state for comparison. The concept of TRA has been extended to guided wave propagations within the CFRP-strengthened reinforced concrete (RC) beams to improve the detectibility of local debonding. Monotonic and fatigue load tests of large-scale CFRP-strengthened RC beams are conducted to demonstrate the potential of the proposed reference-free debonding monitoring system. Comparisons with an electro-mechanical impedance method and an inferred imaging technique are provided as well.

• Journal of Astronomy and Space Sciences
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• 제14권2호
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• pp.347-354
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• 1997

GPS(Global Positioning System) 위성에서 수신된 L1(1575.42MHz) 반송파 위상자료를 이용하여 지표면의 두 지점의 기선 백터와 기선거리를 계산할 수 있는 S/W는 크게 네 부분으로 구성된다. 첫째는 위성의 위치를 계산하는 부분, 둘째는 단일 차분 방정식을 구성하는 부분 셋째는 이중 차분을 구성하는 부분, 그리고 마지막으로 상관관계를 계산하는 부분이다. 개발한 S/W의 정확도를 검증하기 위하여, 대전 천문대의 GPS 관측소($N37^{circ}.75,E127^{circ}.37,H77.61m$)를 중심으로 약 2.7, 42.1, 81.1, 146.6km 떨어진 네 지점에서 Trimble 수신기를 이용하여 동시에 GPS 위성으로부터 관측자료를 획득하였다. 획득한 관측자료를 이 연구에서 개발한 S/W로 처리하였고, 그 결과를 Trimble사의 자료처리 S/W인 GPS Survey에 GPS 위성의 방송 궤도력을 적용하여 L1/L2 ION-Free 기법으로 계산한 결과와 비교 하였다. 두 S/W 시스템으로 산출한 기선 백터의 각 성분은 약 50cm내외에서 잘 일치하였고 기선 거리는 약 10cm내외에서 서로 일치하였다.

• 천문학회지
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• 제38권4호
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• pp.371-384
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• 2005

Self-referencing method in revised-OTFTOOL is a new method in On-The-Fly(OTF) observation mode. It uses the source free regions of the observed frame as references instead of the OFFs references. We already analyzed and discussed its proprieties and advantages in the previous paper. In this paper, we make a statistical study about the self-referencing method by applying it to OTF mapping data of 27 Virgo spiral galaxies. We found that the self-referencing method solves the crooked baseline problem for every datacube. It straightens the baseline, and conserves the emissions. Compared with other data processing, the median filtering task 'mwflt' in AIPS, to use self-referencing method is more effective and safe not only to straighten the baseline but also to conserve the emission. For the strong CO galaxies, the data obtained by self-referencing method shows scarcely any difference from those reduced by conventional OFFs references and AIPS median filtering in the range of uncertainties. Undetected CO emissions in datacubes of conventional OFFs references are also not detected in those of self-referencing method. The self-referencing method is expected to save the observing time and simplify data reduction processes. Besides this, using self-referencing method will offer emission-free references more safely.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.347-351
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• 2010

판과 같은 구조물의 손상 감지를 위해, 손상 전 구조물의 임피던스 신호를 기저신호(Baseline impedance signal)로 이용하여 직접적으로 비교하지 않는 새로운 개념의 무기저 손상진단 기법(Reference-free impedance method)을 제시한다. 박막 압전소자(이하 PZT)를 판의 상하 표면에 부착시킨 한 쌍의 병치 PZT를 이용하여 손상으로 인해 모드변환을 일으키는 전기역학적 신호(Electro Mechanical Signatures ; 이하 EMS)를 추출한다. 이 연구에서는 스펙트럼 요소법(Spectral Element Method ; 이하 SEM)을 이용하여 주파수 영역에서 병치된 PZT의 EMS를 파악하기 위한 수치해석을 수행한다. 특히, 손상에 의해 발생된 모드변환 EMSMC를 병치된 PZT의 극성에 기인한 신호분해 기법을 적용하여 추출하고, 분해된 모드변환 EMSMC가 손상의 위치와 크기에 따라 받는 영향을 추가로 분석한다.

• 비파괴검사학회지
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• 제30권3호
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• pp.261-270
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• 2010

This paper presents an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional side bands that contain the time-of-flight information on the defect location. One of the side band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free detection of a defect, so that experimental studies are needed to verify the proposed method and to be applied to real structure.

• Nutrition Research and Practice
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• 제8권6호
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• pp.695-704
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• 2014

BACKGROUND/OBJECTIVES: The type of sweet snack incorporated into an energy-restricted diet (ERD) may produce differential effects on metabolic improvements associated with body weight (BW) loss. This study compared effects of incorporating either twice daily energy-controlled dark chocolate snacks plus once daily sugar-free cocoa beverage (DC) to non-chocolate snacks plus sugar-free non-cocoa beverage (NC) into an ERD on BW loss and metabolic outcomes. MATERIALS/METHODS: In an 18-week randomized comparative trial, 60 overweight/obese premenopausal women were assigned to DC (n = 30) or NC group (n = 30). Dietary intake was measured at baseline and week 18, and BW, anthropometrics, blood pressure (BP) and serum glucose, insulin and lipid concentrations were measured at baseline, and weeks 6, 12 and 18. Data were analyzed using repeated measures ANOVA. RESULTS: Using intention-to-treat analysis, women in DC and NC groups reduced energy intake (both P < 0.001) and lost $4.4{\pm}0.6kg$ and $5.0{\pm}0.9kg$ (both P < 0.001), respectively. Both groups lowered systolic and diastolic BP [DC = 2.7 (P < 0.05), 2.7 (P < 0.01); NC = 3.4 (P < 0.01), 4.2 (P < 0.01) mmHg, respectively]. Glucose and insulin concentrations decreased by 0.72 mmol/L (P < 0.001) and 13.20 pmol/L (P < 0.01) in DC group and by 0.83 mmol/L (P < 0.001) and 13.20 pmol/L (P < 0.01), respectively, in NC group. Total cholesterol increased in NC group (P < 0.05), with no significant lipid changes in DC group. There were no significant differences in biomarker outcomes between groups. CONCLUSIONS: Overweight/obese premenopausal women following an 18-week ERD that included either DC or NC sweet snack and sugar-free beverage lost equivalent amounts of BW and improved BP measurements and glucose and insulin concentrations.

• Journal of Astronomy and Space Sciences
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• 제23권3호
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• pp.269-288
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• 2006

We revised the OTFTOOL which was developed in Five College Radio Astronomy Observatory (FCRAO) for the On-The-Fly (OTF) observation. Besides the improvement of data resampling function of conventional OTFTOOL, we added a new SELF referencing mode and data pre-reduction function. Since OTF observation data have a large redundancy, we can choose and use only good quality samples excluding bad samples. Sorting out the bad samples is based on the floating level, rms level, antenna trajectory, elevation, $T_{sys}$, and number of samples. And, spikes are also removed. Referencing method can be chosen between CLASSICAL mode in which the references are taken from the OFFs observation and ELLIPSOIDAL mode in which the references are taken from the inner source free region (this is named as SELF reference). Baseline is subtracted with the source free channel windows and the baseline order chosen by the user. Passing through these procedures, the raw OTF data will be an FITS datacube. The revised-OTFTOOL maximizes the advantages of OTF observation by sorting out the bad samples in the earliest stage. And the new self-referencing method, the ELLIPSOIDAL mode, is very powerful to reduce the data. Moreover since it is possible to see the datacube at once without moving them into other data reduction programs, it is very useful and convenient to check whether the data resampling works well or not. We expect that the revised-OTFTOOL can be applied to the facilities of the OTF observation like SRAO, NRAO, and FCRAO.

• 한국해양공학회지
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• 제34권1호
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• pp.1-12
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• 2020

Although there are many kinds of advanced ballast water management systems, pioneering studies for ballast-water free ship and minimal ballast water ship concepts are in progress. In this study, the existing alternatives of ballast water are reviewed and a new design concept is studied on the basis of the existing bulk carrier hull form. To develop a new design alternative which has minimal ballast for ballast water discharge free operation, the new concept should have technical feasibilities that are related to the role of the ballast water, berth access, loading constraints, etc. For this purpose, a simplified systems engineering basis design approach is adopted using a business model as the system analysis and control tool. To check the performance feasibility of the new concept, ship resistance performance is reviewed based on a model scale ship resistance performance analysis.