• Smart Structures and Systems
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• v.8 no.4
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• pp.343-365
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• 2011

Structural system identification (SSI) is an inverse problem of difficult solution. Currently, difficulties lie in the development of algorithms which can cater to large size problems. In this paper, a parameter estimation technique based on evolutionary strategy is presented to overcome some of the difficulties encountered in using the traditional system identification methods in terms of convergence. In this paper, a non-traditional form of system identification technique employing evolutionary algorithms is proposed. In order to improve the convergence characteristics, it is proposed to employ immune algorithms which are proved to be built with superior diversification mechanism than the conventional evolutionary algorithms and are being used for several practical complex optimisation problems. In order to reduce the number of design variables, domain decomposition methods are used, where the identification process of the entire structure is carried out in multiple stages rather than in single step. The domain decomposition based methods also help in limiting the number of sensors to be employed during dynamic testing of the structure to be identified, as the process of system identification is carried out in multiple stages. A fifteen storey framed structure, truss bridge and 40 m tall microwave tower are considered as a numerical examples to demonstrate the effectiveness of the domain decomposition based structural system identification technique using immune algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.1
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• pp.9-14
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• 2012

This paper investigates the prediction of the dynamic strain response using acceleration response only. Two methods are proposed for the strain prediction; one is based on beam theory and the other is calculated by the frequency response function between acceleration and strain. First, it is estimated the dynamics of the simple notched beam, including the non-linearity, through the uni-axial vibration testing. Then, the dynamic strain response is predicted under two different methods using acceleration response. The validation of proposed methods is conducted by the comparison between measured strain and predicted values. The comparison reveals that the proposed method based on the FRF between acceleration and strain is more reliable one than that stemmed from beam theory and the maximum relative error is less than 8 %.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2061-2068
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• 1993

Condition monitoring technology is of great importance for the maintenance of complex machinery in view of its early monitoring of the abnormal condition and the protection against failure. Several methods have been used for the detection of failure of journal bearings, one of the main elements of mechanical system. The methods most frequently used are vibration and temperature monitoring, but these are unable to monitor the wear conditions exactly. In this study, an ultrasonic measument method, one of the non-destructive testing methods, was introduced as the monitoring technology. Furtermore a pattem recognition method was applied to analyze the ultrasonic signal. The monitoring system using the pattern recognition method is composed of digital signal processing units and uses Hamming net algorithm for the recognition of ultrasonic waves. From the journal bearing wear test, the occurrence of adhesive wear of the white metal in rubbing contact with the shaft was exactly detected by this system, and the wear status of the journal bearing was monitored by measuring the wear thickness.

• Clinical and Experimental Pediatrics
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• v.51 no.11
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• pp.1165-1171
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• 2008

Purpose : This study aimed to identify the true extent of non-responsiveness in full-term infants born from HBsAg-negative or HBsAg-positive mothers and vaccinated against hepatitis B virus (HBV) at 0, 1, and 6 months of age and to evaluate the effect of revaccination among non-responders. Methods : The study included 716 full-term infants born in 2004-2007. Of 716, 662 infants (A group) were born to HBsAg-negative mothers and 54 infants (B group: 50, except HBsAg-positive infants) were born to HBsAg-positive mothers. All infants were administered DNA recombinant vaccines at 0, 1, and 6 months of age. B group infants received hepatitis B immunoglobulin at birth. Anti-HBs titers were tested at 7-12 and 9-15 months in A and B groups, respectively. Three revaccination doses were administered to non-responders whose anti-HBs titers were under 10 mIU/ml; revaccinated infants were retested at 1-3 months after last vaccination. The association between HBeAg seropositivity of mother and the failure of HBV immunoprophylaxis was evaluated. Results : The seroconversion rates after primary hepatitis B vaccination were higher in A group (94.1%) than in B group (78%, P<0.001). The seroconversion rates were high in revaccinated infants (A group non-responders: 96.9%, B group non-responders: 87.5%). The failure of HBV immunoprophylaxis was significantly associated with maternal HBeAg seropositivity (P<0.001). Conclusion : The seroconversion rates after primary hepatitis B vaccination were low in B group infants. Revaccination of non-responders in B group was very effective. Therefore, anti-HBs testing and revaccination of B group is very important. Revaccination of non-responders in A group was also very effective. Thus, testing the immune status of infants born to HBsAg-negative mothers even after primary hepatitis B vaccination should be considered. However, to realize this, further studies on the cost-effectiveness of anti-HBs testing in healthy full-term infants are necessary.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.2
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• pp.99-105
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• 2017

Many composite materials are used in the aerospace industry because of their excellent mechanical properties. However, the nature of aviation exposes these materials to high temperature and high moisture conditions depending on climate, location, and altitude. Therefore, the molecular arrangement chemical properties, and mechanical properties of composite materials can be changed under these conditions. As a result, surface disruptions and cracks can be created. Consequently, moisture-impregnating defects can be induced due to the crack and delamination of composite materials as they are repeatedly exposed to moisture absorption moisture release, fatigue environment, temperature changes, and fluid pressure changes. This study evaluates the possibility of detecting the moisture-impregnating defects of CFRP and GFRP honeycomb structure sandwich composite materials, which are the composite materials in the aircraft structure, by using an active infrared thermography technology among non-destructive testing methods. In all experiments, it was possible to distinguish the area and a number of CFRP composite materials more clearly than those of GFRP composite material. The highest detection rate was observed in the heating duration of 50 mHz and the low detection rate was at the heating duration of over 500 mHz. The reflection method showed a higher detection rate than the transmission method.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.1-7
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• 2007

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the study on non-destructive testing methods has become an important research area for improving their reliability and safety. AE (acoustic emission) can evaluate the defects by detecting the emitting strain energy when elastic waves are generated by the initiation and growth of crack, plastic deformation, fiber breakage, matrix cleavage, or delamination. In the paper, AE signals generated under uniaxial tension were measured and analyzed using the $8{\times}8$ matrix piezo electric sensor. The electronic circuit to control the transmitting distance of AE signals was designed and constructed. The optical data storage system was also designed to store the AE signal of 64channels using LED (light emitting diode) elements. From the tests, it was shown that the source location and propagation path of AE signals in composite materials could be detected effectively by the $8{\times}8$ matrix piezo electric sensor.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.18
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• pp.7981-7984
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• 2014

Purpose: Colorectal cancer (CRC) screening with fecal occult blood testing (FOBT) has been associated with a reduction in CRC incidence and CRC-related mortality. However, a conventional FOBT requires stool collection and handling, which may be inconvenient for participants. The EZ-Detect$^{TM}$ (Siam Pharmaceutical Thailand) is a FDA-approved chromogen-substrate based FOBT which is basically a self-checked FOBT (no stool handling required). This study aimed to evaluate the accuracy of EZ-Detect for CRC detection. Methods: This prospective study was conducted in the Faculty of Medicine, Siriraj Hospital, Bangkok, Thailand between November 2013 and May 2014. Some 96 patients with histologically-proven CRC and 101 patients with normal colonoscopic findings were invited to perform self-checked FOBT according to the manufacturer's instructions. Results were compared with endoscopic and pathologic findings. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for CRC detection were calculated. Results: The present study revealed the sensitivity, specificity, PPV and NPV of this self-checked FOBT for CRC detection to be 41% (95% CI: 31-51), 97% (95% CI: 92-99), 93% (95% CI: 81-98) and 63% (95% CI: 55-70), respectively. The overall accuracy of the self-checked FOBT for identifying CRC was 70%. The sensitivity for CRC detection based on 7th AJCC staging was 29% for stage I, 32% for stage II and 50% for stage III/IV (P=0.19). The sensitivity was 33% for proximal colon and 42% for distal colon and rectal cancer (P=0.76). Notably, none of nine infiltrative lesions gave a positive FOBT. Conclusions: The self-checked FOBT had an acceptable accuracy of CRC detection except for infiltrative tumors. This home-administrated or 'DIY' do-it-yourself FOBT could be considered as one non-invasive and convenient tool for CRC screening.

• The Journal of Korean Physical Therapy
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• v.19 no.1
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• pp.33-44
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• 2007

Purpose: To investigate and analyze effects of environmental enrichment(EE) and nerve stimulation that follows in application times with change of functional recovery(1, 3, 7 and 14 days). Methods: Focal ischemic brain injury was produced in 100 Sprauge-Dawley rats through middle cerebral artery occlusion(MCAO). Neurobehavioral assessment were selected, such as tilting plane testing, horizontal wire testing, vestibulomotor function testing and complex neuromotor function test, then they were randomly divided into five groups; Group I : Sham group, Group II: MCAO group, Group III: MCAO and ES group, Group IV: MCAO and EE group, Group V: MCAO and EE and ES group. Results: In neurobehavioral assessment, group V were significantly difference from other groups on between-subject effects. Conclusion: Our findings suggest that in focal ishemic brain injury, combined environmental enrichment and peripheral nerve electrical stimulation is more improved that the improvement of exercise function recovery than non treatment group.

• Clinical and Experimental Reproductive Medicine
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• v.51 no.1
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• pp.75-84
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• 2024

Objective: The purpose of this study was to evaluate the impact of preimplantation genetic testing for aneuploidy (PGT-A) on clinical outcomes among high-risk patients. Methods: This retrospective study involved 1,368 patients and the same number of cycles, including 520 cycles with PGT-A and 848 cycles without PGT-A. The study participants comprised women of advanced maternal age (AMA) and those affected by recurrent implantation failure (RIF), recurrent pregnancy loss (RPL), or severe male factor infertility (SMF). Results: PGT-A was associated with significant improvements in the implantation rate (IR) and the ongoing pregnancy rate/live birth rate (OPR/LBR) per embryo transfer cycle in the AMA (39.3% vs. 16.2% [p<0.001] and 42.0% vs. 21.8% [p<0.001], respectively), RIF (41.7% vs. 22.0% [p<0.001] and 47.0% vs. 28.6% [p<0.001], respectively), and RPL (45.6% vs. 19.5% [p<0.001] and 49.1% vs. 24.2% [p<0.001], respectively) groups, as well as the IR in the SMF group (43.3% vs. 26.5%, p=0.011). Additionally, PGT-A was associated with lower overall incidence rates of early pregnancy loss in the AMA (16.7% vs. 34.3%, p=0.001) and RPL (16.7% vs. 50.0%, p<0.001) groups. However, the OPR/LBR per total cycle across all PGT-A groups did not significantly exceed that for the non-PGT-A groups. Conclusion: PGT-A demonstrated beneficial effects in high-risk patients. However, our findings indicate that these benefits are more pronounced in carefully selected candidates than in the entire high-risk patient population.

• The Journal of Korean Society for School & Community Health Education
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• v.20 no.3
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• pp.123-134
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• 2019

Objectives: The purpose of this study is to identify the problems of verbal violence that adolescents face in the post-human age, when the non-face-to-face media is increasing. Methods: A survey was conducted on 305 adolescents, aged 14 to 16 years of middle school and high school students. The data were analyzed with the SPSS 25.0. Results: As a result of conducting multiple regression analysis to identify the type of conversation that affects verbal abuse of adolescents, a model with a conversation with family, conversation with other people, messenger conversation such as KakaoTalk, and video chat conversation was selected. The amount of explanation was 11.4%. (R2 = .114) Of these, non-face-to-face conversations have been shown to increase verbal violence, and face-to-face conversations with family have, in turn, lowered the risk. As a result of t-testing to examine the effect of verbal abuse experience on the verbal violence index, the damage experience was significant in depression (p = .042) and impulsive aggression (p = .021). (P = .000). Conclusion: This study reiterates the importance of family dialogue along with the fact that the development of various non-face-to-face media in the Fourth Industrial Revolution can have a negative impact on adolescent mental health.