• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).

• Journal of the Korean Institute of Landscape Architecture
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• v.41 no.2
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• pp.69-82
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• 2013

The purpose of this study is to evaluate the effect of Dulegil in Bukhansan National Park in dispersing peak climbing hikers, characterize each section of Dulegil and suggest ideas of improvement. This study was conducted based on the survey completed by visitors in all 21 sections of Dulegil. After the construction of Dulegil, the number of visit to Dulegil grew and it was analyzed that Dulegil attracted new visitors given that the rate of young people(aged 19~30) who visited for the first time was quite high. Regarding the frequency of peak climbing, 7.6% of the respondents said "decreased" and 46.2% said "increased", showing that Dulegil's effect to disperse peak climbing hikers is nominal. Seven qualities were evaluated regarding Dulegil's level of satisfaction. Out of those seven, the quality of recreational place and taking a walk achieved high scores of 3.74 and 3.61 respectively. The quality of culture and history scored the lowest with 3.09. The analysis on the characteristic of each section of Dulegil, reason of visit, and the visitors' level of satisfaction showed that Dulegil is now regarded as a place where they can improve their health through light exercise and walking. In addition, a positive effect can be expected for a long time since there are different ways of utilizing the resources of the National Park, such as getting in touch with nature, preserving ecology, learning history and enjoying beautiful landscapes. If infrastructure and programs specific to each section of Dulegil were improved in a long-term perspective, it would be effective to encourage peak climbers and enjoy the lower parts of the mountain.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.5
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• pp.105-115
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• 2015

This study examined what effect the educational satisfaction level in the grey job project had on the business effectiveness and verified the effect the participant education satisfaction level had on the project business effectiveness ultimately by influencing the job satisfaction. This study utilized the source data of the senior job project old participant status survey of the Korea senior manpower development center which was conducted in 2013, and the non-proportional stratification sample extracting method was used which considered the project type, regional size, and cities/provinces. Sejong City was excluded from the survey target and the survey targeted 2,005 persons except for non-response or response-irrelevant persons concerning this study question. The collected material was analyzed by using SPSS WIN 21.0 program. The frequency and percentage were calculated to apprehend the general characteristic of the study target. Also, the regression analysis was conducted to examine the effect the educational satisfaction level had on the business effectiveness of the senior job project, and the hierarchical regression analysis was conducted in order to examine the mediated effect of the job satisfaction level in the effect the educational satisfaction level had on the business effectiveness of the senior job project. The main result of this study is as follows. First, among the effects the educational satisfaction level had on the business effectiveness, both interest level of educational contents and the job utilization of education had a significant effect on the psychological effect, and the interest level of the educational contents had a significant level on the physical/social effect, and the job utilization of education had a significant effect on the economic effect. Second, in the effect the educational satisfaction level had on the business effectiveness, the job satisfaction level was confirmed the job satisfaction level had a partial mediated effect in the effect the educational satisfaction level had on the psychological/physical/social effect. The job satisfaction level was confirmed the job satisfaction level had a complete mediated effect in the effect the educational satisfaction level had on the economic effect. Also, The job satisfaction level was confirmed the job satisfaction level had a partial mediated effect in the effect the educational satisfaction level had on the business effectiveness. Consequently, the educational contents according with the demand of job participants will have to be developed and the exclusive manpower must be arranged to conduct the education effectively. Also, making participants feel a pride on the job fully will largely contribute to raising the business effectiveness because the job satisfaction level has a positive effect on the business effectiveness.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.759-769
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• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.279-286
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• 2005

Purpose : There are two modalities, those are small bowel series(SBS) and abdominal pelvic computed tomography(CT), for diagnosis of small bowel disease. The aim of this study is to lend radiological technologists who are doing the two modalities assistance in the understanding characteristic of disease by comparing the two results. Meterials and method : 284 patients were examined the two SBS and abdominal pelvic CT together from 1999 to 2003. 250 ml $BaSO_4$ suspension 40 w/v% and 600ml carboxy methyl cellulose 0.5 w/v% were used for SBS. Abdominal Pelvic CT was examined in one hour before taking 450 ml $BaSO_4$ suspension 1.5 w/v%. The CT scan was done in 72 sec after 150 ml contrast media injection. the used protocol was helical mode 5:5 mm pitch 1.375:1, speed 27.50, exposure 120 kv, 240 mA, tube rotation time 0.5 sec. the statistic analysis was conducted with statistical program SPSS 10 version with frequency and crossing analysis. P-value less than 0.05 were considered significant. Results : In the results of SBS, normal findings were 131 patients(46.1%), inflammatory bowel disease(IBD) 64(22.9%), ischemia+ileocolitis+vasculitis 22(7.7%), Obstruction+stricture 21(7.7%) and Others 45(15.9%). In the results of abdominal pelvic CT, normal findings were 103 patients(36.3%), inflammatory bowel disease 65(22.9%), wall thickening+lymphadenopathy 42(14.8%), Fluid collection 17(6%), and Others 57case(20%). The same results of the two were 130patients(45.8%). 30patients(10.6%) of normal finding in SBS were diagnosed as wall thickening+lymphadenopathy and IBD in CT, and 15patients(5.3%) of normal finding in CT were diagnosed as ischemia+ileocolitis+vasculitis, mass and IBD in SBS(p<0.05). Transit time delay was diagnosed in 10patients(3.5%) on only SBS, wall thickening+lymphadenopathy was diagnosed in 20patients(7%) in only CT(p<0.05). Conclusion : We think that proper examination method will be selected in the small bowel disease, if we understand the characteristics of the disease and method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.5-9
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• 2004

In this paper, we studied the OCT(Optical Coherence Tomography) system which it has been extensively studied because of having some advantages such as high resolution cross-sectional images, low cost, and small size configuration. A basic principle of OCT system is Michelson interferometer. The characteristics of light source determine the resolution and the transmission depth. As a results, the light source have a commercial SLD with a central wavelength of 1,285 nm and FWHM(Full Width at Half Maximum) of 35.3 nm. The optical delay line part is necessary to equal of the optical path length with scattered light or reflected light from sample. In order to equal the optical path length, the stage which is attached to reference mirror is moved linearly by step motor And the interferometer is configured with the Michelson interferometer using single mod fiber, the scanner can be focused of the sample by using the reference arm. Also, the 2-dimensional cross-sectional images were measured with scanning the transverse direction of the sample by using step motor. After detecting the internal signal of lateral direction at a paint of sample, scanner is moved to obtain the cross-sectional image of 2-demensional by using step motor. Photodiode has been used which has high detection sensitivity, excellent noise characteristic, and dynamic range from 800 nm to 1,700 nm. It is detected mixed small signal between noise and interference signal with high frequency After filtering and amplifying this signal, only envelope curve of interference signal is detected. And then, cross-sectional image is shown through converting this signal into digitalized signal using A／D converter. The resolution of the OCT system is about 30$\mu\textrm{m}$ which corresponds to the theoretical resolution. Also, the cross-sectional image of ping-pong ball is measured. The OCT system is configured with Michelson interferometer which has a low contrast because of reducing the power of feedback interference light. Such a problem is overcomed by using the improved inteferometer. Also, in order to obtain the cross-sectional image within a short time, it is necessary to reduce the measurement time for improving the optical delay line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.248-256
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• 2007

In this paper, we propose a selective DFT spreading method to solve a high PAPR problem in uplink OFDMA system. A selective characteristic is added to the DFT spreading, so the DFT spreading method is mixed with SLM method. However, to minimize increment of computational complexity, differently with common SLM method, our proposed method uses only one DFT spreading block. After DFT, several copy branches are generated by multiplying with each different matrix. This matrix is obtained by linear transforming the each phase rotation in front of DFT block. And it has very lower computational complexity than one DFT process. For simulation, we suppose that the 512 point IFFT is used, the number of effective sub-carrier is 300, the number of allowed sub-carrier to each user's is 1/4 and 1/3 and QPSK modulation is used. From the simulation result, when the number of copy branch is 4, our proposed method has more than about 5.2 dB PAPR reduction effect. It is about 1.8 dB better than common DFT spreading method and 0.95 dB better than common SLM which uses 32 copy branches. And also, when the number of copy branch is 2, it is better than SLM using 32 copy branches. From the comparison, the proposed method has 91.79 % lower complexity than SLM using 32 copy branches in similar PAPR reduction performance. So, we can find a very good performance of our proposed method. Also, we can expect the similar performance when all number of sub-carrier is allocated to one user like the OFDM.

• Tuberculosis and Respiratory Diseases
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• v.41 no.6
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• pp.624-631
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• 1994

Background: Genus of Aspergilli are ubiquitous saprophytic molds in nature, but its change from a saprophytic fungus to a pathogenic organism has occurred since the use of various antibiotics. The fungus affects the chronically ill and debilitated population. Recently frequency of the fungal infection is increasing in Korea with abuse of antibiotics and glucocorticoids. Method: We analyzed medical records of 52 patients with pulmonary aspergillosis seen at Hanyang University Hospital from 1980 to 1994. The results were as follows; Results: 1) Ages ranged between second to eighth decades with majority(50%) in the fourth to fifth decades. The male to female ratio was 1.1:1. 2) Hemoptysis and productive cough, the leading symptoms, occurred in 42.3% and 25% respectively. 3) On chest X-ray fingings, the characteristic "fungus ball" pattern were observed in 53.8% of the 52cases. 4) Sputum culture for aspergilli were positive in 21.6% of the cases. We performed fine needle aspiration in 22 patients and the diagnostic yield was 100%. 5) Thirty-six patients had history of treatment with antituberculous drugs under diagnosis of pulmonary tuberculosis for an average of 27.3 months. But sputum analysis for acid-fast bacilli were positive in 5.6%(2cases of 36cases), and postoperative pathologic findings showed that 38.9%(12 cases of 28cases) were combined with tuberculosis. 6) Right upper and left upper lobes were predominantly involved(34.6% and 19.2% respectively) and lobectomies were performed in 21 cases. 7) Underlying diseases were present in 47 cases and 48.9% of them were pulmonary tuberculosis. Conclusion: These results showed that pulmonary aspergillosis usually develops in patients with open cavitary pulmonary tuberculosis. And we must consider the possibility of pulmonary aspergillosis in a patient with hemoptysis and cavitary lung lesion.

• Computational Structural Engineering
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• v.7 no.3
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• pp.95-103
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• 1994

The safety related components in the nuclear power plant should be designed to withstand the seismic load. Among these components the integrity of reactor internals under earthquake load is important in stand points of safety and economics, because these are classified to Seismic Class I components. So far the modelling methods of reactor internals have been investigated by many authors. In this paper, the dynamic behaviour of reactor internals of Yong Gwang 1&2 nuclear power plants under SSE(Safe Shutdown Earthquake) load is analyzed by using of the simpled Global Beam Model. For this, as a first step, the characteristic analysis of reactor internal components are performed by using of the finite element code ANSYS. And the Global Beam Model for reactor internals which includes beam elements, nonlinear impact springs which have gaps in upper and lower positions, and hydrodynamical couplings which simulate the fluid-filled cylinders of reactor vessel and core barrel structures is established. And for the exciting external force the response spectrum which is applied to reactor support is converted to the time history input. With this excitation and the model the dynamic behaviour of reactor internals is obtained. As the results, the structural integrity of reactor internal components under seismic excitation is verified and the input for the detailed duel assembly series model could be obtained. And the simplicity and effectiveness of Global Beam Model and the economics of the explicit Runge-Kutta-Gills algorithm in impact problem of high frequency interface components are confirmed.

• Progress in Medical Physics
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• v.25 no.4
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• pp.271-280
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• 2014

Recently, digital breast tomosynthesis (DBT) has been investigated to overcome the limitation of conventional mammography for overlapping anatomical structures and high patient dose with cone-beam computed tomography (CBCT). However incomplete sampling due to limited angle leads to interference on the neighboring slices. Many studies have investigated to reduce artifacts such as interference. Moreover, appropriate filters for tomosynthesis have been researched to solve artifacts resulted from incomplete sampling. The primary purpose of this study is finding appropriate filter scheme with FBP reconstruction for DBT system to reduce artifacts. In this study, we investigated characteristics of various filter schemes with simulation and prototype digital breast tomosynthesis under same acquisition parameters and conditions. We evaluated artifacts and noise with profiles and COV (coefficinet of variation) to study characteristic of filter. As a result, the noise with parameter 0.25 of Spectral filter reduced by 10% in comparison to that with only Ramp-lak filter. Because unbalance of information reduced with decreasing B of Slice thickness filter, artifacts caused by incomplete sampling reduced. In conclusion, we confirmed basic characteristics of filter operations and improvement of image quality by appropriate filter scheme. The results of this study can be utilized as base in research and development of DBT system by providing information that is about noise and artifacts depend on various filter schemes.