• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.61-65
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• 2005

Existing test methods for thick-section specimens ( 4mm) have not provided precise compressive properties to date for the analysis and design of thick structure. A survey of the failure behaviour of such thick specimens revealed that the failure initiated at the top corner of the specimen and propagated down and across the width of the specimen as premature failure, not typically reported for thin compression specimens. In the current study, the premature failure was successfully avoided during compressive testing and the failure mode was quite similar regardless of increasing specimen thickness and specimen volume. Failure mode was similar regardless of increasing specimen thickness and specimen volume, i.e. brooming failure mode combined with longitudinal splitting, interlaminar cracking, fibre breakage and kinkband formation (fibre microbuckling). Nevertheless, average failure strengths of the specimens decreased with increasing specimen thicnkiness from 2mm to 8mm with the T800/924C system (36% strength reduction) and specimen volumes from scaling factor I to scaling factor 4 with the IM7/8552 system (46% strength reduction). It was revealed from the literature$^{11}$ that the thickness effect and scaling effect arc caused by manufacturing defects such as void content and fibre waviness.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.51-60
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• 2016

PURPOSES : The applicability of the mechanics-based similarity concept (suggested by Feng et al.) for determining scaled variables, including length and load, via laboratory-scale tests and discrete element analysis, was evaluated. METHODS: Several studies on the similarity concept were reviewed. The exact scaling approach, a similarity concept described by Feng, was applied in order to determine an analytical solution of a free-falling ball. This solution can be considered one of the simplest conditions for discrete element analysis. RESULTS : The results revealed that 1) the exact scaling approach can be used to determine the scale of variables in laboratory tests and numerical analysis, 2) applying only a scale factor, via the exact scaling approach, is inadequate for the error-free replacement of small particles by large ones during discrete element analysis, 3) the level of continuity of flowable materials such as SCC and cement mortar seems to be an important criterion for evaluating the applicability of the similarity concept, and 4) additional conditions, such as the kinetics of particle, contact model, and geometry, must be taken into consideration to achieve the maximum radius of replacement particles during discrete element analysis. CONCLUSIONS : The concept of similarity is a convenient tool to evaluate the correspondence of scaled laboratory test or numerical analysis to physical condition. However, to achieve excellent correspondence, additional factors, such as the kinetics of particles, contact model, and geometry, must be taken into consideration.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.15 no.4
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• pp.267-275
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• 2011

This paper proposes a new quickly convergent pattern search quasi-Newton algorithm that employs the multi-step version of the Symmetric Rank One (SRI). The new algorithm works on the factorizations of the inverse Hessian approximations to make available a sequence of convergent positive bases required by the pattern search process. The algorithm, in principle, resembles that developed in [1] with multi-step methods dominating the dervation and with numerical improvements incurred, as shown by the numerical results presented herein.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.3
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• pp.429-439
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• 1995

The Interior point method in linear programming is classified into two categories the affine-scaling method and the logarithmic barrier method. In this paper, we integrate those methods and implement them in one shared module. First, we analyze the procedures of two interior point methods and then find a unified formula in finding directions to improve the current solution and conditions to terminate the procedure. Second, we build the shared modules which can be used in each interior point method. Then these modules are experimented in NETLIB problems.

• Journal of Periodontal and Implant Science
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• v.50 no.2
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• pp.83-96
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• 2020

Purpose: The present study aimed to evaluate the clinical benefit of additional toothbrushing accompanying non-surgical periodontal treatment on oral and general health in patients with type 2 diabetes mellitus (T2DM). Methods: We conducted a doubled-blind randomized controlled trial in 60 T2DM patients between June 2013 and June 2014. The patients were randomly assigned to the scaling and root planing (SRP) group; the scaling and root planing with additional toothbrushing (SRPAT) group, in which additional toothbrushing was performed by toothpick methods; or the control group. Microbiological and oral examinations were performed for up to 12 weeks following treatment. Non-surgical treatment was conducted in the experimental groups. The SRP group received scaling and root planing and the SRPAT group received additional toothbrushing with the Watanabe method once a week from the first visit through the fifth visit. The primary outcomes were changes in haemoglobin A1c (or glycated haemoglobin; HbA1c) levels, serum endotoxin levels, and interleukin-1 beta levels. Periodontal health status was measured by periodontal pocket depth, the calculus index, and bleeding on probing (BOP). Results: Both the SRP and SRPAT groups showed improvements in periodontal health and HbA1c, but the SRPAT group showed significantly less BOP than the SRP group. Furthermore, only the SRPAT group showed a statistically significant decrease in serum endotoxin levels. Conclusions: Non-surgical periodontal treatment was effective in improving HbA1c and serum endotoxin levels in T2DM patients. Furthermore, non-surgical treatment with additional tooth brushing had a more favourable effect on gingival bleeding management. Trial RegistrationClinical Research Information Service Identifier: KCT000416.

• Korean Journal of Biological Psychiatry
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• v.19 no.1
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• pp.65-69
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• 2012

Objectives : Much is still unknown about the neurophysiological mechanisms or dynamics of the sleep onset process. Detrended fluctuation analysis (DFA) is a new tool for the analysis of electroencephalography (EEG) that may give us additional information about electrophysiological changes. The purpose of this study is to analyze long-range correlations of electroencephalographic signals by DFA and their changes in the sleep onset process. Methods : Thirty channel EEG was recorded in 61 healthy subjects (male:female=34:27, age=$27.2{\pm}3.0$ years). The scaling exponents, alpha, were calculated by DFA and compared between four kinds of 30s sleep-wakefulness states such as wakefulness, transition period, early sleep, and late sleep (stage 1). These four states were selected by the distribution of alpha and theta waves in O1 and O2 electrodes. Results : The scaling exponents, alpha, were significantly different in the four states during sleep onset periods, and also varied with the thirty leads. The interaction between the sleep states and the leads was significant. The means (${\pm}$ standard deviation) of alphas for the states were 0.94 (${\pm}0.12$), 0.98 (${\pm}0.12$), 1.10 (${\pm}0.10$), 1.07 (${\pm}0.07$) in the wakefulness, transitional period, early sleep and late sleep state respectively. The mean alpha of anterior fifteen leads was greater than that of posterior fifteen leads, and the two regions showed the different pattern of changes of the alpha during the sleep onset periods. Conclusions : The characteristic findings in the sleep onset period were the increasing pattern of scaling exponent of DFA, and the pattern was slightly but significantly different between fronto-temporal and parieto-occipital regions. It suggests that the long-range correlations of EEG have a tendency of increasing from wakefulness to early sleep, but anterior and posterior brain regions have different dynamical process. DFA, one of the nonlinear analytical methods for time series, may be a useful tool for the investigation of the sleep onset period.

• Journal of the Korea Society of Computer and Information
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• v.10 no.1 s.33
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• pp.181-188
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• 2005

Chinese Postman Problem (CPP) is a problem that finds a shortest tour traversing all edges or arcs at least once in a given network. The Chinese Postman Problem on Mixed networks (MCPP) is a Practical generalization of the classical CPP and it has many real-world applications. The MCPP has been shown to be NP-complete. In this paper, we transform a mixed network into a symmetric network using virtual arcs that are shortest paths by Floyd's algorithm. With the transformed network, we propose a Genetic Algorithm (GA) that converges to a near optimal solution quickly by a multi-directional search technique. We study the chromosome structure used in the GA and it consists of a path string and an encoding string. An encoding method, a decoding method, and some genetic operators that are needed when the MCPP is solved using the Proposed GA are studied. . In addition, two scaling methods are used in proposed GA. We compare the performance of the GA with an existing Modified MDXED2 algorithm (Pearn et al. , 1995) In the simulation results, the proposed method is better than the existing methods in case the network has many edges, the Power Law scaling method is better than the Logarithmic scaling method.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.25-34
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• 2016

OBJECTIVES : This is a basic research for the domestic production of airport-airside deicers. This research selected basic materials for deicers appropriate for the pavement of domestic airports by evaluating the deicing performances of basic materials used in international-standard airport deicers and their impacts on pavements. METHODS : Laboratory investigation was conducted to evaluate the asphalt surface tensile strength, concrete scaling impact, ASR impact, and deicing performances of sodium formate (NaFm), potassium formate (KFm), sodium acetate (NaAc), and potassium acetate (KAc), which are the basic de-icing materials commonly used at international airports, approved by the FAA. In addition, the analyses were also performed on the airside deicer urea, which is currently used in domestic airports. RESULTS : Laboratory investigation confirmed that sodium formate, potassium formate, sodium acetate, and potassium acetate had superior surface tensile strength, concrete scaling impact, and deicing performance compared to airside urea, but they also had greater impacts on concrete ASR. Among these materials, sodium formate had the best asphalt surface tensile strength, concrete scaling impact, and deicing performance, while also having the greatest impact on ASR; hence, mitigation plans for ASR were needed, if it were to be used as airport-airside deicer. CONCLUSIONS : It is necessary to consider additional additives to prevent ASR of concrete pavements when developing airport-airside deicers using sodium formate, potassium formate, sodium acetate, and potassium acetate.

• Journal of Korean society of Dental Hygiene
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• v.18 no.3
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• pp.269-280
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• 2018

Objectives: The purpose of this study was to investigate the change in the posture of dental hygiene students and clinical dental hygienists when implementing dental scaling before and after posture correction training using the rapid upper limb assessment (RULA) method and 3D motion analysis. Methods: Thirty-two healthy volunteers performed dental scaling to remove artificial calculus on dental manikin. The movement and angle of the joints were verified by RULA and 3D motion analysis during the procedure. The subjects were also photographed for 1 minute during the procedure for 10 minutes while the calculus was removed. After the removal of the calculus, the subject and the instructor checked the video together. Posture correction training was conducted by the instructor so that the subject could perform the calculus removal operation in the correct posture. Artificial calculus of the adjacent teeth was then removed for the same period of time, and the change in posture was reviewed. Results: The total score of the posture change using RULA was $5.72{\pm}0.58$ before training and $4.31{\pm}0.10$ after training, showing a significant decrease after training (p<0.001), and upper arm, lower arm, wrist position, neck and waist position showed significant decrease after training. The three-dimensional motion analysis showed significant differences according to the criteria measured at all measurement sites except the left shoulder (p<0.05) Conclusions: It was confirmed through RULA and 3D motion analysis that postural correction training using calculus removal images was effective, and that correct postural education is essential to preventing musculoskeletal diseases caused by removal of calculus.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.15 no.2
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• pp.141-148
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• 2011

Objectives: In comparison with functional dyspepsia, food accumulation is known to have wider concept. On this study, we will make a proposal on the concept of food accumulation by a statistical comparison between pyungweesan questionnaire and health related questionnaires. Methods: We studied the similarities between six factors of pyungweesan questionnaire and four health related questionnaires(Rome II criteria of functional dyspepsia, subjective symptoms of fatigue test, beck depression inventory, state-trait anxiety inventory, etc.) using multidimensional scaling. Results and Conclusions: 1. Physical-emotional axis and acute-chronic axis were labelled in a two-dimensional scaling solution. 2. Seup-dam(濕痰) factor and sik-che(食滯) factor of food accumulation were closely related to fatigue. 3. Bi-seup(脾濕) factor of food accumulation was closely related to depression and anxiety. 4. The findings suggest that a concept of food accumulation reflects some aspects of physical fatigue and emotional depression as well as dyspepsia.