• Smart Structures and Systems
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• v.30 no.3
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• pp.303-315
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• 2022

The degradation of wheel tread may result in serious hazards in the railway operation system. Therefore, timely wheel defect diagnosis of in-service trains to avoid tragic events is of particular importance. The focus of this study is to develop a novel wheel defect detection approach based on the relevance vector machine (RVM) which enables online detection of potentially defective wheels with trackside monitoring data acquired under different running-speed conditions. With the dynamic strain responses collected by a trackside monitoring system, the cumulative Fourier amplitudes (CFA) characterizing the effect of individual wheels are extracted to formulate multiple probabilistic regression models (MPRMs) in terms of multi-kernel RVM, which accommodate both variables of vibration frequency and running speed. Compared with the general single-kernel RVM-based model, the proposed multi-kernel MPRM approach bears better local and global representation ability and generalization performance, which are prerequisite for reliable wheel defect detection by means of data acquired under different running-speed conditions. After formulating the MPRMs, we adopt a Bayesian null hypothesis indicator for wheel defect identification and quantification, and the proposed method is demonstrated by utilizing real-world monitoring data acquired by an FBG-based trackside monitoring system deployed on a high-speed trial railway. The results testify the validity of the proposed method for wheel defect detection under different running-speed conditions.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.199-206
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• 2023

This study presents a novel monitoring technique for underwater high-voltage direct current (HVDC) cables based on the Distributed Acoustic Sensor (DAS). The proposed technique utilizes vibration and acoustic signals generated on HVDC cables to monitor their condition and detect events such as earthquakes, shipments, tidal currents, and construction activities. To implement the monitoring system, a DAS based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) system was designed, fabricated, and validated for performance. For the HVDC cable monitoring experiments, a testbed was constructed on land, mimicking the cable burial method and protective equipment used underwater. Defined various scenarios that could cause cable damage and conducted experiments accordingly. The developed DAS system achieved a maximum measurement distance of 50 km, a distance measurement interval of 2 m, and a measurement repetition rate of 1 kHz. Extensive experiments conducted on HVDC cables and protective facilities demonstrated the practical potential of the DAS system for monitoring underwater and underground areas.

• Annals of Clinical Neurophysiology
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• v.12 no.1
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• pp.21-26
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• 2010

Background: Although quantitative sensory test (QST) is being used with increasing frequency for measuring sensory thresholds in clinical practice and epidemiologic studies, there has been no age-matched normative data in Korean adults. The objective of this study is to evaluate the value of QST in diabetic polyneuropathy with normal range in Korean adults. Methods: The Computer Aided Sensory Examination IV 4,2 (WR Medical Electronics Co., Stillwater, Minnesota, U.S.A.), with 4,2,1 stepping algorithm was used to determine vibration and cold perception threshold in 70 normal controls and 19 patients with diabetic polyneuropathy aged from 21 to 79 years. The data were used to define age-matched upper and lower normal limits and normal range of side to side difference. We also evaluated the duration of diabetes, serum HbA1C level, and findings of nerve conduction study (NCS) and QST in patients with diabetic polyneuropathy. Results: In normal adults, sensory thresholds slightly increased with age, and a slight side-to-side difference was observed. The diagnostic sensitivity of QST was not higher than NCS in patients with diabetic polyneuropathy (36.8% vs. 42.1%, p=0.716), especially among elderly patients. Conclusions: QST might be used as a complementary test for NCS in the diagnosis of diabetic polyneuropathy. Although the QST is a simple method for the evaluation of peripheral nerve function, there are some limitations. Most of all, because the QST measuring is dependent on the subjective response of patients, the degree of concentration and cooperation of the patients can significantly affect the result. And thus, attention should be paid during the interpretation of QST results in patients with peripheral neuropathy.

• Journal of Haehwa Medicine
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• v.12 no.1
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• pp.79-102
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• 2003

It has been believed that the human body can be effected by color, sound, smell, and taste - each of them is based on the original character. Out of these elements, the color can be a mediation that absorbs energy into human body and adapts it to the creatures whose life are definitely based on the solar energy. This thesis makes a study of the possibility of applying the color to the oriental medical science by researching the color psychology and therapy which are studied in the west medical science, the recognition and application of color developed from orientalism, and the opinion of color in the oriental medical science. Color therapy is one of the psychological treatment techniques that are able to recover and maintain the health with the rays of the sun rays and the color. The light and the color have its energy that may relax, harmonize, encourage, or excite a human being. This is because the wavelength and the vibration of each color will take effects to human body. The core energy of absorbing and distributing the color vibration is made in the 7 "chakras" in the body, which are the pith and marrow of bio-energy directly connected with the center of the nervous system. There are several methods in the color therapy - the treatment of solar ray, the color-bath, the water-therapy using color energy, the inducement of the solar energy into the body, the acupuncture, the therapy of crystal and jewel, and the self-suggestion dependent upon the color. The color therapy can help us to keep our balance by changing the emotion into the positive energy that will cure the disease with color. As a result, this method not only must be useful to cure physical disease, or develop into good health but also will be used in conforming itself to the mental disease. The color therapy mainly uses the eight colors, which are made by mixing Red, Yellow and Blue basic colors in the field. They are never used in the treatment, but they will go along with complementary colors. This rule is closely connected with the theory of yin and yang which lies at the root of oriental philosophy, and with the treatment principle of oriental medical science whose field is focused on the balancing the body mentally as well as physically. In the East, it is the Obangsaek - the color of blue, red, yellow, white, and black in the theory of yin and yang and the five elements that have been used in helping people having trouble with their health for a long time. In the view of the oriental medical science, these five colors attached the theory of five-elements have been very useful to the physiology, the pathology, or the diagnosis, and been applied to the medical treatment, combining themselves with a five-taste in medicinal herbs. Since the study of color and human physiology has been made in some different interest and fields these days, it goes to prove that the different function of color we couldn't have got before becomes very useful to the medical science. The color must be worth researching the diversity for applying itself to the oriental medical science.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.130-137
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• 2003

Because of falling-off in power quality by harmonics, obstacles like lowering of capability, noise, vibration of power facilities and so on are occurred. Also generation of harmonics is inevitable and the point at harmonics is seriously gathering strength because energy saving installation using semiconductor circuit as countermeasures to enhance energy efficiency will be broadly spread and the use of energy conversion equipment like motor speed control contrivance, energy keeping installation and so on will increase, in the future. In order to eliminate harmonics obstacle, precision measurement and analysis on voltage, current, power factor, the each ingredient of harmonic order, the percentage of total harmonic distortion, and so forth are needed. In this paper, we developed low-cost measurement system to measure and analyze power quality connected with harmonics and verified it's performance by measuring and analyzing power quality in the three-phase and four-wire system.

• Journal of Oral Medicine and Pain
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• v.23 no.2
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• pp.127-141
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• 1998

This study was performed to investigate the clinical features of internal derangement of temporomandibular joint. For this study, 117 patients with temporomandibular disorders and 81 dental students without any signs and symptoms of temporomandibular disorders were selected as the patients group and as the control group, respectively. Preferred chewing side, Angle's classification, lateral guidance pattern, maximal mouth opening range, and affected side were recorded clinically. Head and shouldeer posture was measured in a groundplate on which square diagram of five centimeters each had been drawn, and cephalograph was also taken for measurement of head and neck posture. Sonopak of Biopak system (Bioresearch inc., USA) was used to record joint vibration for evaluation of internal healthy status of temporomandibular joint. The data collected were analyzed by SAS statistical program. The results of this study were as follows : 1. Frequency of left side chewing subjects was higher in patients than in control group, but there was no difference in distribution of subjects by Angle's classification. Other types was prvalent in patients whereas group function was more in control group for lateral guidance pattern. 2. As to lateral guidance pattern by clinical diagnosis, patients with internal derangement and/or degenerative joint disease showed higher frequency was consistent with the result by Sonopak impression. 3. There was no difference for shoulder height between the two groups, however, tilting of head and backward extension of cervical spine was more frequent in control group. 4. Acromion was positioned more anteriorly in patients with internal derangement and/or degenerative joint disease than in control group and angle between eye and tragus was larger in patients. Patients with degenerative joint disease showed more flexed head posture than control group did in cephalometric profile. 5. Maximal mouth opening range in patients with internal derangement was the least in all subgroups in patients classified by Sonopak impression.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.7 no.4
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• pp.41-47
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• 2012

Railroad rolling stock has long service life and a lot of maintenance cost running on rail by wear and vibration. And it is very important to get optimization of maintenance. This paper want to analyze rolling stock maintenance situation of KORAIL and find out its improvement methods. Especially, the purpose of this paper is to adopt the most effective maintenance period and methods to daily inspection which needs many maintenance manpower in rolling stock. Rolling stock has self-diagnosis function using computer system and the quality of rolling stock has much improved these days but current daily inspection repeat for short period routinely and it is very ineffective. Therefore, the paper adopt improved daily inspection period reflecting the characteristics of rolling stock, and want to secure reliability of rolling stock and minimize maintenance cost.

• Smart Structures and Systems
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• v.22 no.2
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• pp.185-192
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• 2018

Participants in the Asia Pacific Conference of the Prognostics and Health Management Society 2017 (PHMAP 2017) Data Challenge were given measured vibration signals from motor-driven gearboxes used in pulverizers. Using this information, participants were requested to predict failure dates and the faulty components. The measured signals were affected by significant noise and disturbance, as the pulverizers in the provided data worked under actual operating conditions. This paper thus presents a fault prediction method for a motor-driven gearbox in a pulverizer system that can perform under external noise and disturbance conditions. First, two fault features, an RMS value in the higher frequency zones (HRMS) and an amplitude of a period for high-speed shaft in the quefrency domain ($QA_{HSS}$), were extracted based on frequency analysis using the higher and lower sampling rate data. The two features were then applied to each pulverizer based on results of frequency responses to impact loadings. Then, a regression analysis was used to predict the failure date using the two extracted features. A weighted regression analysis was used to compensate for the imbalance of the features in the given period. In addition, the faulty components in the motor-driven gearboxes were predicted based on the modulated frequency components. The score predicted by the proposed approach was ranked first in the PHMAP 2017 Data Challenge.

• Tribology and Lubricants
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• v.30 no.2
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• pp.124-129
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• 2014

The piping system accounts for a large portion of the machinery structure of a plant, and is considered as a very important mechanical structure for plant safety. Accordingly, it is used in most energy plants in the nuclear, gas, and heavy chemical industries. In particular, the piping system for a nuclear plant is generally complicated and uses the reactor and its cooling system. The piping equipment is exposed to diverse loads such as weight, temperature, pressure, and seismic load from pipes and fluids, and is used to transfer steam, oil, and gas. In ultrasound infrared thermography, which is an active thermography technology, a 15-100 kHz ultrasound wave is applied to the subject, and the resulting heat from the defective parts is measured using a thermography camera. Because this technique can inspect a large area simultaneously and detect defects such as cracks and delamination in real time, it is used to detect defects in the new and renewable energy, car, and aerospace industries, and recently, in piping defect detection. In this study, ultrasound infrared thermography is used to detect information for the diagnosis of nuclear equipment and structures. Test specimens are prepared with piping materials for nuclear plants, and the optimally designed ultrasound horn and ultrasound vibration system is used to determine damages on nuclear plant piping and detect defects. Additionally, the detected images are used to improve the reliability of the surface and internal defect detection for nuclear piping materials, and their field applicability and reliability is verified.

• Clinical and Experimental Reproductive Medicine
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• v.21 no.3
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• pp.253-259
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• 1994

A clinical investigation was undertaken on primary male infertility patients of recent 5 years. The results obtained were as follow: 1. Suspective etiologic factors were: 1) testicular failure, 36.1 %; 2) varicocele, 18.7%; 3) endocrine abnormality, 13.5%; 4) obstruction, 13.5%; 5) idiopathic, 10.9%; 6) cryptorchidism, 2.6%; 7) necrospermia, 0.9%. 2. On semen analyses, azoospermia was found in 55.8%, single abnormal parameter in 21.5 %, and multiple/all abnormal parameter in 22.7% of the 163 cases. 3. For the evaluation of the sensitivity and specificity of noninvasive variables in predict in obstruction as the cause of azoospermia in patient who had undergone testicular biopsy, the testicular size and serum follicle-stimulating hormone(FSH) level revealed 100% of sensitivity. 4. Among the 43 patients with a testicular biopsy confirmed diagnosis there was a significant difference in testicular size, ejaculate volume(p<0.0001) and serum FSH(p<0.0001) between patients with testicular failure and those with ductal obstruction. 5. Of 93 treated patients with primary male infertility, 42 were managed by medical treatment including endocrine treament, retrograde ejaculation treatment, infection treatment and observation; 29 were managed by surgical treatment including varicocelectomy, vasovasostomy, vasoepididymostomy and TUR of ejaculatory duct; 20 were managed by sperm preparation treatment including artificial insemination(AI), electroejaculation plus AI and vibration ejaculation plus AI ; 2 were managed by microscopic epididymal sperm aspiration plus IVF, repectively. 6. 42 patients who could be followed-up, 21 patients(50%) impregnated their wives.