• The Korean Journal of Applied Statistics
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• v.23 no.4
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• pp.715-724
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• 2010

Recurrent event data occurs when a subject experience the event of interest several times and has been found in biomedical studies, sociology and engineering. Several diverse approaches have been applied to analyze the recurrent events (Cook and Lawless, 2007). In this study, we analyzed the YTOP(Young Traffic Offenders Program) dataset which consists of 192 drivers with conviction dates by speeding violation and traffic rule violation. We consider a subject-specific effect, frailty, to reflect the individual's driving behavior and extend to time-varying frailty effect. Another feature of this study is about the redefinition of risk set. During the study, subject may be under suspension and this period is regarded as non-risk period. Thus the risk variables are reformatted according to suspension and termination time.

• Journal of Information Display
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• v.7 no.1
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• pp.25-29
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• 2006

By the voltage threshold (Vt) close-curve measurement method, the changes in the discharge characteristics such as a firing voltage and IR emission among the three electrodes were examined relative to the low or high panel temperature ranging from -10 to $80^{\circ}$. The variation in the panel temperature was found significantly influence the surface discharge between the MgO surfaces rather than the plate gap discharge between the MgO and phosphor layers. Based on this experimental observation, a modified reset waveform that alleviates the surface discharge during a ramp-up and -down period was deeloped. By adopting the proposed reset waveform, a stable address discharge could be obtained irrespective of the panel temperature variation.

• KSTLE International Journal
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• v.3 no.1
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• pp.68-73
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• 2002

A fretting wear experiment in roam temperature air was performed to evaluate the wear mechanism of fuel rod using a fretting wear tester, which has been developed for experimental study, The main focus was to compare the wear behaviors of fuel rod against support springs with different contact contours (i.e. concave and convex). Wear volume, degree or surface hardening and adhesion tendency of wear particle were examined by the surface roughness tester. The result indicated that with a change of contact condition from contact force of 5 N to 0.1 mm gap, the wear volume of tube increased in the condition of concave spring, but slowly decreased in convex spring. From the results of SEM observation, wear mechanism of each test condition was also dependent on the spring shapes. The wear mechanism of each test condition in room temperature air is discussed.

• Fibers and Polymers
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• v.4 no.4
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• pp.188-194
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• 2003

Phase behavior and spinodal phase separation kinetics in binary blends of a random copolymer of vinylidene fluoride and trifluoroethylene (75/25) [P(VDF/TrFE)] and poly(l,4-butylene adipate) (PBA) have been investigated by means of optical microscopic observation and time-resolved light scattering. The blends exhibited a typical lower critical solution temperature (LCST)∼${34}^{\circ}C$ above the melting temperature of the P(VDF/TrFE) crystals over the entire blend composition range. P(VDF/TrFE) and PBA were totally miscible in the temperature gap between the melting point of P(VDF/TrFE) and the LCST. Temperature jump experiments of the 3/7 P(VDF/TrFE)/PBA blend were carried out on a light-scattering apparatus from a single-phase melt state (${180}^{\circ}C$) to a two-phase region (205∼${215}^{\circ}C$). Since the late stage of spinodal decomposition (SD) is prevalent in the 3/7 blend, SD was analyzed using a power law scheme. Self-similarity was preserved well in the late stage of SD in the 3/7 blend.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.433-438
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• 2012

We have studied on welding dissimilar materials of Carbon steel SCP1-S by using laser beam. In this research we have performed some experiments to know the possibility of welding dissimilar materials using laser beam and magnetic fields by adjusting the power output of 35W laser. Other conditions of the experiments were as follows : the welding speed was varied in the range 10 m/min nitrogen gas was used as shield gas, the flow value of shield gas was ranged 10 L/min. In order to ascertain of the welded surface, we have done the tensile strength testing, the hardness testing and the microscope observation. As a result, we have found that tensile strength was the highest at the condition of the welding speed of 10mm/s, the flow value of 10 L/min, the gap of two materials 0, and the use of nitrogen gas. Above testings have also showed that the tensile strength was generally satisfactory since the penetration of welding was almost complete due to the thinness of the materials. In addition, the formation of the welded area was excellent when it had the highest tensile strength.

• Health Policy and Management
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• v.12 no.2
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• pp.1-22
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• 2002

Since the early 1980s scholars have applied latent structure and other type of finite mixture models from various academic fields. Although the merits of finite mixture model are well documented, the attempt to apply the mixture model to medical service has been relatively rare. The researchers aim to try to fill this gap by introducing finite mixture model and segmenting inpatients DB from one general hospital. In section 2 finite mixture models are compared with clustering, chi-square analysis, and discriminant analysis based on Wedel and Kamakura(2000)'s segmentation methodology schemata. The mixture model shows the optimal segments number and fuzzy classification for each observation by EM(expectation-maximization algorism). The finite mixture model is to unfix the sample, to Identify the groups, and to estimate the parameters of the density function underlying the observed data within each group. In section 3 and 4 we illustrate results of segmenting 4510 patients data including menial and ratio scales. And then, we show AHP can be identify the attractiveness of each segment, in which the decision maker can select the best target segment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.249-251
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• 2015

In this study, the application of biosensor having a large surface area for more effective and AAO (anomic aluminium oxide) template in order to gain concentration and voltage of anodizing process morphology changes to the control of experiments were conducted. The biosensor surface may increase the response characteristics by having a large surface area. So the entrance to a little more efficient wide depth sensing experiment was carried out to obtain a structure body with a branch shape with a large surface area with increasing. Experimental results from the FE-SEM observation was obtained template morphology. As a result, depending on the anodizing time, the depth of the layer of aluminum oxide was found that it was confirmed that the deepening of the pore size changes according to anodizing condition. And measuring the detection performance according to the conditions in the electrolyte and the reaction because of blood using a biosensor measuring sensing property according to the depth of the pore depth is considered that does not have a significant impact.

• Fashion & Textile Research Journal
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• v.12 no.4
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• pp.513-522
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• 2010

The aim of this study is to investigate the actual state for the development of the thermally comfortable uniform for workers on a low temperature storage. Observation, interview and survey were executed focusing on the environment, clothing, and human factors which have effects on the comfort of workers. Of 400 distributed, 253 questionnaires were analyzed through descriptives, frequency, ANOVA, t-test, multi-response analysis, correlation analysis with SPSS 12.0. The results are following. Coming and going between a selling area and cold storages, the workers showed to experience a big temperature gap. They indicated to feel cold on face and hands which were not covered by clothing and have got sick because of low temperature. The workers wanted the uniform made of functional fabrics, especially heat insulation fabrics. Female workers rather than male workers, the older, and the longer their working period were, the more uncomfortable they revealed to feel. The workers who works on the daily products part or mainly on the freezer appeared to feel cold more than any other workers. In conclusion, it was found that the uniform which consider steady state and unsteady state heat transfer together must be developed.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.2
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• pp.383-404
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• 1997

In this study, we tried to compare the effect of glass inserts on marginal leakage of composite resin restoration by comparing with that of several filling methods. The results obtained from this experiment were as follows ; 1. The degree of microleakage measured in glass inserts group was generally lower than that of the other groups. Statistical analysis showed significant intergroup difference between glass inserts and one complete unit, pre-polymerized composite resin ball(P<.05), but no significant difference between groups of glass inserts and increments(P>.05). 2. Scanning electron microscopic observation showed relatively large gap around resin-tooth interface in specimens restored the method of using the one complete unit and pre-polymerized composite resin ball whereas a denser and tighter was observed in increments and glass inserts group. Generally the gingival margin was shown to have better bonds than the occlusal margin in specimen of all groups. 3. In the present experiment, methods using the techniques of glass inserts and increments were evaluated to be superior to those of one complete unit, pre-polymerized composite resin ball in the aspect of microleakage. However, the result of this study could not determine the superiority of the use of glass inserts over incremental method. Besides the physical properties observed in this study, the practical aspect of clinical convenience should be considered in determining the selection of material.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.965-970
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• 2012

Structure and optical properties of cadmium sulphide-zinc oxide composite nanorods have been evaluated by suitable characterization techniques. The X-ray diffraction spectrum contains a series of peaks corresponding to reflections from various sets of lattice planes of hexagonal ZnO as well as CdS. The above observation is supported by the Micro-Raman spectroscopy result. The optical reflectance spectra of CdS-ZnO is compared with that of ZnO where we observe an enhanced absorption and hence diminished reflection from CdS-ZnO compared to that from only ZnO. A very small intensity of the visible photoluminescence peak observed at 550 nm proves that the ZnO nanorods have very low concentrations of point defects such as oxygen vacancies and zinc interstitials. The photocurrent in the visible region has been significantly enhanced due to deposition of CdS on the surface of the ZnO nanorods. CdS acts as a visible sensitizer because of its lower band gap compared to ZnO.