• Journal of radiological science and technology
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• v.27 no.4
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• pp.55-60
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• 2004

The purpose of this study was to examine both patient exposure dose during mammography and the utility status of mammograpy equipments. The data of this study were collected through questionnaire survey for 278 medical facilities registered at Korean Hospital Association and finally 161 medical facilities's data were analyzed. According to data analysis, medical facilities of 14.9% used the average glandular dose of less than 0.5 mGy, $0.51{\sim}1.0\;mGy$ 8.6%, $1.01{\sim}1.5\;mGy$ 14.9%, $1.51{\sim}2.0\;mGy$ 11.1%, $2.01{\sim}2.5\;mGy$ 9.8%, $2.51{\sim}3.0\;mGy$ 33.3%, and 7.4% more than 3.01 mGy. It was found that medical facilities of 92.6% used less than 3 mGy, showing that this figure is similar to the limit value of 3 mGy recommended by Korea Food & Drug Administration(KFDA). Recently, international organizations such as ICRP associated with radiation protection suggests that less than 3 mGy of average mammary gland dose be used during mammography in case of using Mo target+Mo filter, film/screen system and craniocaudal projection with the breast pressed to 4.2 cm. The standard dose is being strictly observed and that of the limits is going down to 2 mGy or 1.5 mGy. The major results of this study indicate that interests and a counterplan to reduce patient dose during mammography should be considered. Based on this study, the authors of this study will continue to measure exposure dose to set a new standard for patient exposure dose during mammography.

• Journal of IKEEE
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• v.25 no.3
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• pp.511-516
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• 2021

The electrical characteristics of AlGaN/GaN/HEMT and MOSHFETs with NiO were studied. The threshold voltage of NiO MOSHFET revealed positive shift of +1.03 V than the -3.79 V of HEMT and negative shift of -1.73 V for SiO₂ MOSHFET. Also, NiO MOSHFET showed better linearity in drain current corresponding to gate voltage and higher transconductance at positive gate voltage than the others. The response of gate pulse with base voltage of -5 V was different for both transistors as HEMT showed 20 % drain current decrease at the frequency range of 0.1 Hz~10 Hz and NiO MOSHFET decreased continuously above 10 Hz.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.11
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• pp.1741-1749
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• 2015

The purpose of this study was to investigate parents' perception and satisfaction of school food materials and supplier performance in Mokpo. To achieve these research objectives, a questionnaire was distributed to parents at 66 schools, and a total of 589 were used in the final analysis. The results of this study were as follows. First, satisfaction of school foodservice, showed the following scores: overall was 3.75, quality of food materials was 3.84, reliability of food suppliers was 3.80, education was 3.53, and information was 3.50. Second, 38.5% of parents participated in receiving school materials. Exactly 80.6% of parents showed intentions to participate. The most difficult thing for receiving materials was comparing quality of food materials (46.3%). Third, the most important factor cited for school food supplier was quality (62.3%) and sanitation and safety (24.1%). Forth, most parents were positive about the possibility of replacing foods used at school with environment friendly products. Local foods were cited for use in school foodservice (92.2%). The reasons were good quality (39.9%) and contribution to the local community (28.5%). In conclusion, parent's perception of school foodservice should increase to improve food material quality of school foodservice. Institutions for certifying are needed to offer high quality food materials at school foodservice and improved communication and education tool between the school and parents.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.71-75
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• 2009

A compact electric field probe sensor incorporating two different electro-optic materials of $LiNbO_3$ and GaAs was proposed and fabricated, and it was used to measure the strength of the horizontal and vertical fields generated by a microstrip ring-resonator filter. The sensitivities of the sensors in $LiNbO_3$ and GaAs were $9.315{\mu}V/\sqrt{Hz}$ and ${\sim}49.346{\mu}V/\sqrt{Hz}$ respectively, and their signal to noise ratios were approximately ${\sim}50\;dB$ and ${\sim}40\;dB$ respectively. And the operating frequency range was up to ${\sim}1.2\;GHz$. The electric field profile for the test circuit was scanned and found to be in good agreement with that obtained by using the HFSS simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.2
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• pp.47-55
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• 2003

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz,5MHz) and different channel environments (rural, urban) in wideband multipath channel. For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipath is within one chip are distingushed into each one and the strongest signal is selected, DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.22-28
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• 2003

This paper describes the frequency dependence of the grounding impedance. In order to propose the evaluation method of the transient response of powered grounding systems, the grounding impedances were measured with varying the frequency of incoming currents by way of the variable frequency inverter and band pass filter. The magnitude and phase of the grounding impedance were analyzed in the frequency range of 20 [Hz]∼2.1[kHz]. The grounding impedance were increased with increasing the frequency of the test current. The grounding impedance at the frequency of 2[kHz] in the actual 22.9[kV] substation grounding system was approximately 3 times as large as the 60[Hz] grounding impedance. It was found that the frequency dependence of the grounding impedance is mainly subject to the inductive reactance of the grounding conductors. As a result, it is critical to determine the shape and size of grounding grid reducing the resultant inductance in grounding systems for lightning surge protection.

• Progress in Medical Physics
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• v.16 no.1
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• pp.10-15
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• 2005

IAEA's guidance levels have been provided for western people to the end. Guidance levels lower than the IAEA'S will be necessary in view of Korean people's proportions. Therefore, we need to develope the standard doses for Korean people. And we conducted a nationwide survey of patient dose from x-ray examinations in Korea. In this study, the 278 institutions were selected from Members Book of Korean Hospital Association. The valid response rate was approximately 57.9%. Doses were calculated from the questionnaires by NDD method. We obtained the results were as follows; 1) General radiographic equipments were distributed for 42.0%, fluoroscopic equipments 29.4%, dental equipments 13.2%, CT units 8.1 % and mamographic units 7.2%. 2) According to classification by rectification, three-phase equipments were 29.9%, inverter-type generators 29.5%, single-phase equipments 25.5%, constant voltage units 9.0% and unknown units 6.0%. 3) According to classification by receptor system, film-screen types were 46.8%, CR types 26.8%, DR types 17.7% and unknown types 8.9%. 4) The number of examinations were chest 49.2%, spine 16.8% and abdomen 12.7%. 5) Patient doses were head AP 3.44 mGy, abdomen AP 4.25 mGy and chest PA 0.39 mGy.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.92-101
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• 2012

Three-dimensional finite-difference simulation in a small-scale half-sphere basin with planar free-surface is performed for an arbitrary shear-dislocation point source. A new scheme to deal with free-surface boundary condition is presented. Then basin parameters are examined to understand main characteristics on ground-motion response in the basin. To analyze the frequency content of ground motion in the basin, spectral amplitudes are compared with each other for four sites inside and outside the basin. Also particle motions for those sites are examined to find which kind of wave plays a dominant role in ground-motion response. The results show that seismic energy is concentrated on a marginal area of the basin far from the source. This focusing effect is mainly due to constructive interference of the direct Swave with basin-edge induced surface waves. Also, ground-motion amplification over the deepest part of the basin is relatively lower than that above shallow basin edge. In the small-scale basin with relatively simple bedrock interface, therefore, the ground-motion amplification may be more related to the source azimuth or direction of the incident waves into the basin rather than depth of it.

• Journal of dental hygiene science
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• v.8 no.4
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• pp.247-253
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• 2008

The purpose of this study is to evaluate the outcomes of the specialized elective course program to be designed to help dental hygiene student to pursue the career by providing the opportunities of attendance to the diverse social settings. Students participating the specialized elective course were required to attend one of the related dental or dental hygiene institutes of their own choice during 2 weeks. After that to evaluate satisfaction of the specialized elective course, 70 of 103 students who have graduated dental hygiene school in Yonsei University responded questionnaire that consist of satisfaction on the specialized elective course, influence on career, change of attitude for career etc. The most students satisfied the specialized elective course(very good 21.4%, good 47.1%, and neutral 24.3%) and satisfaction on this program was significant among related dental institutes. The majority of students(87.1%) responded the specialized elective course to have Influence on their career. Aspect to change of attitude for career, 63 percent of students started serious consideration making a decision on career. This findings indicate that the most students satisfy the specialized elective course, and this program providing the opportunity of attendance to the diverse social settings seems to help dental hygiene student to pursue the career.

• Therapeutic Science for Rehabilitation
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• v.10 no.2
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• pp.95-108
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• 2021

Objective : This study aimed to develop prototypes of "smart stacking cones" by combining ICT to evaluate and train the upper extremity function and dual task performance in patients with central nervous system impairment, and to identify the complementary point to the completion of the device through a usability test. Methods : This prototype comprised of a hardware and software system that enabled the evaluation and training of patients and the management of data obtained from patients' performance. Specific measurement variables were established so that patient performance could be measured correctly. Based on the measurement variables, a the prototype included a 'single task evaluation modes', 'dual task evaluation mode', 'single task training mode', and 'dual task training modes'. Additionally, a usability test was conducted to assess clinical applicability and overall satisfaction for the prototype. Results : The results of the usability test were generally found to be appropriate. The 'content adequacy' in the usability test was the area with the highest level of adequacy and the lowest level of inadequacy. Additionally, overall 'satisfaction' in the usability test was the area with the highest appropriate and inappropriate levels. Hence, the overall satisfaction results were unstable. Conclusion : Future studies should be conducted to identify the clinical effectiveness of the device by applying an upgraded smart stacking cone to an actual patient group.