• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.692-695
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• 2000

This paper is concerned with Accuracy Design of LM Guide System in Machine Tools. Elastic deformation of bearing is calculated by Hertz contact theory and motion error of LM block is analyzed. A new algorithm using block stiffness is proposed fur the analysis of motion accuracy of the table. The best advantage of this algorithm is fast analysis speed because it isn't necessary iteration processes for satisfying equilibrium equation of the table. Motion errors of the table analyzed under artificial form error of rail theoretically and experimentally. Only one of two rails is bent by putting a thickness gauge into horizontal direction. This form error of rail is measured by gap sensor against the other rail. Then, motion errors of the table are predicted by proposed new algorithm theoretically and measured by laser interferometer. Measurements are carried out by changing the preload and thickness. The results show that the table motion errors are reduced from 1/2 to 1/60 times than form error of rail according to its height and width. And the effect of preloading is almost negligible.

• Journal of Korean Traditional Oncology
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• 제16권1호
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• pp.1-14
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• 2011

Background and Objectives : This study is an observational study of nonequivalent control group based on time lag design in order to determine the effectiveness of gargling Hwangryunhaedok-tang (HRHDT) on stomatitis caused by chemotherapy. Methods : The study period is from July 1st, 2010 to September 30th, 2010. The subjects are 13 patients who fit the profile of the study and who are admitted in the tumor department of the regional cancer center of C University Hospital which is located in Chung-Joo City. When stomatitis occurs after chemotherapy, the level of stomatitis is assessed using oral assessment guide score and oral discomfort score. Then mix 5 g of powered HRHDT and 60 ml of distilled water, and 15 ml of the solution is given to patients 4 times per day to gargle for 1 minute. For the control group, 60 ml of Chlorohexidin gargling solution is used; everyday for one week, 4 times per day, 15 ml per gargle and gargled for 1 minute. Oral Assessment Guide score and Oral Discomfort Score are assessed at same hour everyday. Crosstabulation analysis $X^2$(${\rho}$) was used to examine the demographic characteristics and difference of the two groups by using SPSS/WIN 12.0. For mean and standard deviation, descriptive statistical analysis was used. T-test was used to determine the difference of the oral discomfort scores. Result : The study has shown that the Oral Assessment Guide score of the experimental group has decreased more with more regularity. On the third day, the score of the control group is 20.16 and the score of the experimental group was 18.75, which showed a statistically significant difference with the level of significance of p<0.05. Oral Discomfort Score of the control group's score was 13.60 on the first day and 6.80 on the seventh day and the experimental group's score was 13.00 on the first day and 2.25 on the seventh day. The experimental group's score 2.25 is statistically significantly lower than the control group's score of 6.80 with the level of significance of p<0.05. Conclusions : The HRHDT gargling solution showed more regular effectiveness compared to Chlorohexidin solution on chemotherapy-caused stomatitis. Therefore this study has shown that HRHDT gargling solution can be used as an alternative medicine.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제41권3호
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• pp.161-169
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• 2017

The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was $60^{\circ}$, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio ($e/D_h$) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

• The Journal of Korean Academy of Prosthodontics
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• 제60권2호
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• pp.143-151
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• 2022

Purpose. The purpose of this study was to evaluate the performance efficiency of two different drill combinations according to the heat generated and drilling time. Materials and methods. In this study, cow ribs were used as research materials. To test the specimen, cow bones were rid of fascia and muscles, and a temperature sensor was mounted around the drilling area. The experimental group was divided into a group using a guide drill and a group using a Lindmann drill according to the drill used before the initial drilling. The drilling sequence of the guide drilling group is as follows; guide drill (ø 2.25), initial drill (ø 2.25), twist drill (ø 2.80), and twist drill (ø 3.20). The drilling sequence of the Lindmann drilling group is as follows; Lindmann drill (ø 2.10), initial drill (ø 2.25), twist drill (ø 2.80), and twist drill (ø 3.20). The temperature was measured after drilling. For statistical analysis, the difference between the groups was analyzed using the Mann-Whitney U test and the Friedman test was used (α = .05). Results. The average performance efficiency for each specimen of guide drilling group ranged from 0.3861 to 1.1385 mm³/s and that of Lindmann drilling group ranged from 0.1700 to 0.4199 mm³/s. The two drill combinations contained a guide drill and Lindmann drill as their first drills. The combination using the guide drill demonstrated excellent performance efficiency when calculated using the drilling time (P < .001). Conclusion. Since the guide drill group showed better performance efficiency than the Lindmann drill group, the use of the guide drill was more suitable for the primary drilling process.

• Transactions of the Korean Society of Mechanical Engineers
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• 제19권9호
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• pp.2105-2113
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• 1995

The compressive tests under impact conditions were performed to establish a design guide for impact damage tolerance. The composition of layup was selected for the real cases of composite aircraft structure. The energy level of visible of visible damage threshold was determined as 7 Joules. It was found that the normalized bending stiffnesses in the direction of closely fixed boundary affected the area of damage. Graphite/epoxy used in the tests exhibited 60% reduction in compression strength at the energy level of visible damage threshold. Wet-conditioned specimens represented 9% reduction in residual compressive strength in comparison with room temperature ambient specimens. In this study, a design factor of 2.1 was proposed for the low velocity impact damage.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.27-32
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• 2000

Microearthquake records with magnitude 2.6~3.1 recorded in the southeastern part of the Korean peninsula during 1994~1998 are analyzed. Total of 42 records consisted of 12 events instrumented at 7 stations. The response spectra with the above data shows that the frequency range of the dominant response is about 10~25Hz and are compared with the standard response spectrum. The result implies that the characteristics of the microearthquake ground motion differ from those of standard response spectrum presented in US NRC Reg. Guide 1.60 especially at higher frequencies.

• Journal of the Korean Society of Propulsion Engineers
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• 제17권1호
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• pp.52-60
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• 2013

Ejector-diffuser system makes use of high-pressure primary stream to entrain the low-pressure secondary stream through pure shear action between two streams. In general, the flow field in the ejector-diffuser system is highly complicated due to turbulent mixing, compressibility effects. A fatal drawback of the ejector system is in its low efficiency. Many works have been done to improve the performance of the ejector system, but not yet satisfactory. In the present study, a mixing guide vane was installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A CFD method has been applied to simulate the supersonic flows inside the ejector-diffuser system. The present results obtained were validated with existing experimental data. The mixing guide vane effects are discussed in terms of the entrainment ratio, total pressure loss as well as pressure recovery.

• Transactions of Materials Processing
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• 제20권1호
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• pp.60-63
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• 2011

BLU(back light unit) is one of kernel parts of LCD(liquid crystal display) unit. New 3-D micro-lens pattern for LGP(light guide plate), one of the most important parts of LCD-BLU, had been researched. Instead of dot pattern made by chemical etching or laser ablation, SCS(slanted curved surface) micro-lens pattern was designed with optical CAE simulation. This study introduce the method of design using optical CAE simulation for SCS micro-lens, the new fabrication method of micro-mold with SCS micro-lens pattern.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.637-644
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• 2006

Acceleration time history used in the seismic analysis of nuclear porter plant structure should envelop a target power spectral density (PSD) function in addition to design response spectrum. Current regulation guide defines the target PSD function only for the U.S. URC RG 1.60 Design Response Spectrum. This paper proposes a technical scheme to obtain the target PSD function compatible with generally defined design response spectrum. The scheme includes the methodology for design-spectrum compatible motion history in order to minimize the variation of the derived target PSD function. The PSD calculation procedure follows simple and practical methods allowed within regulation. Effectiveness of the proposed scheme is identified through an example problem. The design response spectrum In the example is based on U.S. NRC RG 1.60 but amplifies the spectral acceleration amplitudes above 9Hz. The target PSD function with little variation can be constructed with the reduced time history ensemble.

• Journal of Korean Elementary Science Education
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• 제30권4호
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• pp.535-552
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• 2011

The purpose of this study was to investigate elementary school teachers' conceptions on the general remarks (GR) in the new science teacher's guide, the teachers' conceptions on inservice training program of the GR, and their opinions of improvement on the GR. Also, the teachers' utilization of the GR was examined. The participants were 152 elementary school teachers who were teaching grade 3~6. A questionnaire was used to collect data. The results of this study are as follows; First, at least 13.2~17.1% of the teachers did not have specific conception of the purpose of the GR, and more than 90% of the teachers expressed that the GR is necessary in the teachers' guide. Second, about 60% of the teachers responded that the training program on the GR is necessary, and when the program is open, their most favorite agency and speaker were a provincial education office and a textbook developer(or author), respectively. Their most favorite time and period of the training program were the vacation and 15~30 hours, respectively. Third, the mean values on the frequency of use were lower than 3 point of the five-point Likert scale at both the GR for grade 3~4 and the GR for grade 5~6, and the teachers' main use of the GR was the planning a science lesson for an open class. Fourth, the teachers suggested various opinions and there was difference between the opinions about the GR for grade 3~4 and the opinions about the GR for grade 5~6.