• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.51-62
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• 2015

Shear behavior obtained by direct shear tests is dependent on shear box and boundary condition. The objective of this study is to analyze problems of conventional direct shear test (type-A) and provide the reliable results by developing type-C direct shear apparatus. Experimental tests are carried out for Ulleung sand by using type-A and -C direct shear devices. The soil specimens, which are prepared at the relative density of 60%, and are applied to vertical confining stresses of 50, 100, 200, 300, and 400 kPa, are sheared at a constant shear strain rate of 0.5 mm/min. By comparing the results obtained by type-A and -C direct shear apparatus under constant normal load (CNL) condition, the performance of new one is verified. In addition, two constrained conditions including constant normal load (CNL) and constant pressure (CP) are applied to type-C one. Experimental results show that type-A direct shear apparatus has some problems such as rotating of loading plate and upper shear box, and the frictional forces between soil and inner wall of upper shear box. Thus, the shear strengths obtained by type-A device are overestimated or underestimated depending on shear box and boundary condition. On the other hand, type-C device produces clear and consistent test results regardless of constrained conditions. This study represents that type-C direct shear apparatus not only can solve the problems of type-A direct shear apparatus but provide the reliable results.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.301-309
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• 2015

Purpose: The aim of this study was to evaluate the clinical performance of screw- and cement-retained implant prosthesis (SCP) design in terms of retained preload of abutment screws and cement washout. Materials and methods: Patients with the partial posterior edentulous areas comprised the study group. Implants were placed, and SCPs were delivered after 3 to 6 months healing. Follow-up examinations were performed. The implant survival rate and the prosthetic success rate were evaluated. The retained preload ratio of abutment screws and the prosthetic decementation ratio were measured. Results: Twenty one SCPs (forty three implants)in twenty patients were followed up to 64 months. All of the implants survived during the follow-up period (mean follow-up: 34 months). The prosthetic success rate was 100 % considering no abutment, screw, porcelain or metal frame fractures, as well as no screw loosening. The retained preload ratio of SCPs at the end of follow-up period was 97.61% (${\pm}16.29$) and the decementation ratio was 9.5 %. Conclusion: Within the limitations of this clinical study, SCP design showed favorable short-term clinical performances in respect of screw loosening and cement washout.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.6
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• pp.50-59
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• 2015

This study aimed at suggesting Willingness To Pay (WTP) for introduction of the Traffic Accident emergency Call (TAC) system by using Contingent Valuation Method (CVM) which is a general valuation method. As the method, this study suggested a WTP estimation method of the TAC system with the double-bound dichotomous choice model. In previous studies, the data are processed differently according to the type of questions and analysis models used for the calculation of willingness to pay. Therefore, we re-organized the model by the cases using the truncated data sets, and showed the difference in WTPs. The dataset was developed by more than 500 questionnaire obtained from online and offline survey with the consideration of composition ratio by age group referring housing census in 2010 to mitigate regional bias of samples. At last, this study applied various statistical methods, survival analysis, multiple regression, and Tobit model for better interpretation of the questionnaires.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.1
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• pp.70-80
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• 1999

In this paper, a new hierarchical image segmentation algorithm based on human visual system(HVS) characteristic is proposed which can efficiently reduce and control transmission information quantity without the degradation of the subjective and objective image quality. It consists of image segmentation based on mathematical morphology and region merging considering HVS characteristic for the pairs of two adjacent regions at each level of the hierarchy. Image segmentation is composed of 3-level hierarchical structure. In the region merging structure of each level, we extract the pairs of two adjacent regions which human vision can't discriminate, and then merge them. The proposed region merging method extracts pairs of two neighbor regions to be merged and performs region merging according to merging priority based on HVS characteristics. The merging priority for each adjacent pair is determined by the proposed merging priority function(MPF). First of all, the highest priority pair is merged. The information control factor is used to regulate the transmission information at each level. The proposed segmentation algorithm can efficiently improve bottleneck problem caused by excessive contour information at region-based very low bit rate coding. And it shows that it is more flexible structure than that of conventional method. In experimental results, though PSNR and the subjective image quality by the proposed algorithm is similar to that of conventional method, the contour information quantity to be transmitted is reduced considerably. Therefore it is an efficient image segmentation algorithm for region-based very low bit rate coding.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.64-69
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• 2007

Motion control of the system is a position control of motor. Motion control of an uncertain robot system is considered as one of the most important and fundamental research directions in the robotics. Some distinguished works using linear control, adaptive control, robust control strategies based on computed torque methodology have been reported. However, it is generally recognized within the control community that these strategies suffer from the following problems : the exact robot dynamics are needed and hard to implement, the adaptive control cannot guarantee the performance during the transient period for adaptation under the variation, the robust control algorithms such as the sliding mode control need information on the bounds of the possible uncertainty and disturbance. And it produces a large control input as well. In this dissertation, a motion control for the unmanned intelligent robot system using disturbance observer is studied. This system is affected with an impact vibration disturbance. This paper describes a stable motion control of the system with the consideration of external disturbance. To obtain the stable motion independently against the external disturbance, the disturbance rejection is strongly required. To address the above issue, this paper presents a Disturbance OBserver(DOB) control algorithm. The validity of the suggested DOB robust control scheme is confirmed by several computer simulation results. And the experiments with a motor system is performed to give the validity of applicability in the industrial field. This results make the easier implementation of the controller possible in the field.

• Journal of Convergence for Information Technology
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• v.7 no.4
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• pp.83-89
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• 2017

This study aims to investigate the impact of a mobile-based human coaching healthcare service provided for diabetic patients by nurses on their self-management ability. This study collected data from 311 persons who were diagnosed with diabetes from all over the country, and the collected data were analyzed through SPSS Win 23. The results of the study are summarized as follows: First, it was found that the utilization of a glucose meter by the provision of the mobile-based human coaching healthcare service was men group, and there was a statistically significant difference (${\chi}^2=6.059$, p= .048*). Second, there was a positive correlation in the utilization between the glucose meter and an activity tracker band by the provision of the mobile-based human coaching healthcare service, which was statistically significant (r=.660, p< .001). Third, as a result of checking the changes of the utilization of the glucose meter by the provision of the mobile-based human coaching healthcare service, it was maintained between 79% and 41% from Week 1 through 49. In conclusion, this study partially confirmed that the mobile-based human coaching health service was easily accessible and cost-effective in enhancing the participants'self-healthcare ability.

• Journal of Preventive Medicine and Public Health
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• v.30 no.2 s.57
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• pp.428-436
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• 1997

Objectives : The purpose of this paper is to estimate the completeness of the Korean Medical Insurance Data in childhood asthma. Methods : Capture-recapture method was used to estimate the prevalence of childhood asthma and case ascertainment rate(completeness) of Korean Medical Insurance Data using two source model, 'Korean Medical Insurance Committee Data (KMICD)' and 'Nationwide Study of Asthma and Allergies in Korean Children'. The asthma cases were restricted to those who were born from 1981 to 1989 and were identified by their Resident Register Number. Asthma cases in Korean Medical Insurance Data were defined as cases coded by ICD-9 493 and ICD-10 J45. In 'Nationwide Study of Asthma and Allergies in Korean Children', asthma cases were defined as the children who had been diagnosed asthma and had experienced symptoms of asthma during the past 12 months. The defined cases in two data sources were matched by 13 digits Resident Register Number. The numbers of matched patients in two data sources were 245 of 32,825 eligible total subjects. Chapman and Wittes' nearly unbiased estimation was used for capture-recapture analysis of two data sources. Results : Observed prevalence rate of childhood asthma was 5.3% and estimated prevalence rate by capture-recapture analysis was 11.6%. The highest prevalence rate was observed in 6-7 age group and the older the rate decreased. The completeness (the proportion of cases ascertained by KMICD to the total observed cases by two data sources) was 20.6%, and ranged form 10.8% to 28.8% by area. Conclusions : Invalid diagnosis of cases might overestimate the prevalence of child-hood asthma and might underestimate the completeness of Korean Medical Insurance Committee Data in this study.

• Journal of Environmental Health Sciences
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• v.35 no.3
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• pp.153-161
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• 2009

The purpose of this paper is to evaluate 1) blood lead levels of workers at auto repair shops as Biological Exposure Indices (BEI) of toxic substances such as lead and toluene that are produced during automotive painting process, 2) the differences depending on personal characteristics of workers who have been exposed to toluene by using urine hippuric acid concentration as a marker and 3) the correlation between the concentration of hazardous chemicals in each workplace and the BEL. All subjects were male with a mean age of 36.2 years. In terms of age, most were in the 30 to 40 age group (13 persons, 48.1%). In relation to the length of work experience, the highest proportion had experience of 10 years of less (18 persons, 66.7%). Twenty three workers were cigarette smokers (85.2%) while 4 (14.8%) were non-smokers. In addition, more than 80% of the workers drank alcohol. Dust concentration and toluene exposure during automotive painting showed no significant difference with age, length of work experience, smoking and drinking while a significant difference (p<0.05) has been detected between lead concentration and smoking. The geometric mean of dust concentration, lead concentration and toluene concentration were $0.38mg/m^3,\;0.0021mg/m^3$ and 1.08ppm respectively. In addition, the geometric mean of blood lead levels and urine hippuric acid concentration were $1.70{\mu}g/dl$ and 0.25g/g respectively, which were lower than the standard levels suggested by the Ministry of Labor. To determine the influential factors on blood lead and urine hippuric acid concentrations, a correlation analysis has been conducted with variables of air, lead and toluene concentrations, age, length of work experience and amount of cigarette smoking. According to the analysis, a relatively high correlation (p<0.01) has been observed between air lead concentration and biological sample concentration.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.6
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• pp.947-958
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• 2008

To study the effect of a washing machine with silver nano technology on its detergency, the discoloring of the dyed clothes and the staining of standards adjacent fabrics were examined. As the laundry specimen, cotton fabric dyed with reactive dyes and Polyester fabric dyed with disperse dyes were chosen; and as the adjacent fabrics, undyed cotton. polyester and nylon fabrics were chosen. The colorfastness was evaluated after washing under conditions that those washing temperature, liquor ratio, detergency concentration and the type of water were varied. When the clothes were washed with the tap water contains silver ion, the deposition of silver compounds into the washed clothes was measured. As a results, after the washing in the various conditions, discoloring of the dyed clothes was not intense. The higher the washing temperature and the lower the liquor ratio, the larger the staining appeared on the white fabrics; especially for the white nylon fabrics. The concentration of detergent and the type of water affected hardly the colorfastness. After the repeated washing with the water contains silver, whiteness of the cotton and the nylon fabrics were lower than the result after the washing with the tap water, and a quantity of silver ions was found on the washed clothes.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.123-132
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• 2000

To overcome problems of conventional glass ionomers, resin components have been added to glass ionomers. On a continuum between glass ionomers and composites are a variety of blends, employing different proportions of acid-base and free radical reactions to bring about cure. Popular groups defined between the ends are resin-modified glass-ionomers(RMGIs), polyacid-modified composite resins(Compomers) and ionomer modified resins. These groups show different clinical properties, and in selecting these materials for a restoration, one should sufficiently understand these different setting properties. In this study, some difference in the setting characteristics of different groups of hybrid ionomers were examined. Two RMGIs (Fuji2 LC,GC / Vitremer, 3M), three Compomers (Dyract AP, Dentsply / F2000, 3M / Elan, Kerr) were involved in this study. The identification of the setting characteristics of different groups was achieved by a two-stage study. First, thermal analysis was performed by a differential scanning calorimeter, and then the hardness of each group at different depth and time were measured by a micro-hardness tester. Thermal analysis was performed to identify the inorganic filler content and to record the heat change during setting process. The setting process was progressed for each material by chemical set mode and light-cured mode. In the hardness test, samples of materials were prepared with a 6mm-diameter metal ring, and the hardness was measured at the top, and 1mm, 2.5mm, 4mm below at just after a 40 second-cure, and after 10 minutes, 24 hours, and 7 days. Statistical analysis was performed by Mann-Whitney rank sum test to assess significant differences between set modes and types of materials, and by ANOVA and T-test to evaluate the statistical meanings of data at different times and depths of each materials. Followings are findings and conclusions derived from this study. Thermal analysis; 1. Compomers show no evidence of chemical setting while RMGIs exhibit heat output during the process of chemical setting. 2. Heat of cure of RMGIs exceed Compomers. 3. The net heat output of RMGIs through light-cured mode is higher than through chemically set mode. Hardness test; 1. Initial hardness of RMGIs immediately after light cure is relatively low, but the hardness increases as time goes by. On the contrary, Comomers do not show evident increase of the hardness following time. 2. Compomers show a marked decrease of setting degree as the depth of the material increases. In RMGIs, the setting degree at different depths does not significantly differ.