• 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.

• Clean Technology
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• v.18 no.4
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• pp.390-397
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• 2012

Removal characteristics of lead-contaminated soil at the military shooting range located in the Changwon city were studied experimentally using soil washing process. As a washing solution, hydrogen chloride (HCl) concentrations of 0.001, 0.01, 0.1 and 0.2 N were used, and soil : solution ratios were 1 : 2, 1 : 3, 1 : 4, and 1 : 5. Particle diameter of contaminated soil of 4-0.075 mm, and washing period of 5, 10, 15, 20, 30, 60, and 120 min were used as operating parameters. The optimum concentration of HCl solution was 0.1 N (56.3% of Pb removal efficiency) with 15 minutes operation period in views of economics, and the optimum soil : solution ratio was determined as 1 g : 3 mL for 69.7% of Pb removal efficiency with 0.1 N HCl and 15 minutes washing period. As washing period increased, removal efficiency was increased until 20 min of the removal efficiency of 75.3%, and then almost stable. Pb removal efficiency in soil particle diameters of 0.075 mm or more was ranged from 77.0% to 82.0%, but it was decreased to 52.8% in diameter of less than 0.075 mm. Therefore, the optimum cut-off size of the soil particle diameter was found less than 0.075 mm. Combined HCl solution and ultrasonic washing method showed better removal efficiency compared to only water or HCl washing method for particle sizes above 0.075 mm.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.206-214
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• 2009

Statement of problem: There are common clinical cases in which the mandibular first and second molars are missing unilaterally. Purpose: This study was designed to compare and evaluate the magnitude and distribution of stress produced by four kinds of mandibular unilateral free-end removable partial dentures that could be applied clinically in Kennedy class II cases. Material and methods: Four unilateral free-end removable partial dentures using clasp, Konus crown, resilient attachment, and flexible resin were fabricated on the photoelastic models of the Kennedy class II cases. The vertical load of 6㎏ was applied on the central fossa of the first molar of every removable partial denture in the stress freezing furnace and the photoelastic models were frozen according to the stress freezing cycle. After these models were sliced mesio-distally to a thickness of 6mm, the photoelastic isochromatic white and black lines of the sliced specimens were examined with the transparent photoelastic experiment device and photographs were taken with a digital camera. The fringe order numbers at eight measuring points in the photograph were measured with the naked eye. Results: The maximum fringe order number of each sliced specimen and the fringe order number at the residual ridge just below the loading point were in the decreasing order of the unilateral removable partial dentures using flexible resin followed by clasp, resilient attachment, and Konus crown. The fringe order number at the root apex of the second premolar was in the decreasing order of the unilateral removable partial dentures using clasp followed by flexible resin, Konus crown, and resilient attachment. Conclusion: The removable partial denture using Konus crown showed the most equalized stress distribution to the supporting alveolar bone of abutment teeth and residual ridge under the vertical loads. The removable partial denture using flexible resin can be applied to the case that has a better state of residual ridge than abutment teeth.

• Journal of Chest Surgery
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• v.31 no.9
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• pp.884-892
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• 1998

Background: The gastroepiploic artery is not only an alternative graft but also may be considered an important primary graft for coronary revascularization. However, the long-term patency of the gastroepiploic arterial graft is yet to be determined and the incidence of perioperative spasm and long-term patency of a coronary graft may be affected by the properties of the graft response to certain vasoactive substances. The reactivity of the gastroepiploic artery to vasoactive substances has not been studied extensively and the results of the studies are contradictory. Material and Method: This study was designed to test the reactivity of human gastroepiploic artery to four constrictors and four relaxants. The middle sections of the human gastroepiploic arteries were collected from the patients undergoing gastrectomy and the arterial rings with intact endothelium were suspended in organ baths for isometric tension recording. Result: Epinephrine, norepinephrine, and potassium chloride induced the maximum constriction to higher forces (7.0$\pm$1.1g, 6.6$\pm$0.9g, and 6.5$\pm$1.1g) than 5-hydroxytryptamine did (3.8$\pm$1.7g, p<0.05). Nitroprusside and histamine induced almost full relaxation in the gastroepiploic arteries preconstricted with norepinephrine. There was no significant difference between two relaxants regarding maximum relaxation force. Acetylcholine induced the maximum relaxation to weaker force when compared with nitroprusside and histamine (p<0.05), and isoproterenol was the weakest of the relaxants (p<0.05 compared with acetylcholine). Conclusion: The gastroepiploic artery has a strong capacity of endothelium-dependent relaxation which could have an important influence on long-term patency. The gastroepiploic artery exhibits a potent contractility to catecholamines and the enhanced contractility may facilitate vasospasm in the presence of high circulating levels of catecholamines. Nitroprusside, a potent relaxant in gastroepiploic artery, might be beneficial for the treatment of gastroepiploic arterial graft spasm. The gastroepiploic arterial graft with intact endothelium may respond weakly to beta-adrenoceptor agonist and 5-hydroxytryptamine.

• Fire Science and Engineering
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• v.31 no.5
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• pp.53-62
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• 2017

Electric power which is the energy source of economy and industries requires long distance transportation due to regional difference between its production and consumption, and it is supplied through the multi-loop transmission and distribution system. Prior to its actual use, electric power flows through several transformations by voltage transformers in substations depending on the characteristics of each usage, and a transformer has the structure consisting of the main body, winding wire, insulating oil and bushings. A transformer fire that breaks out in substations entails the primary damage that interrupts the power supply to houses and commercial facilities and causes various safety accidents as well as the secondary economic losses. It is considered that causes of such fire include the leak of insulating oil resulting from the destruction of bottom part of bushings, and the chain reaction of fire due to insulating oil that reaches its ignition point within 1 second. The smoke detector and automatic fire extinguishing system are established in order to minimize fire damage, but a difficulty in securing golden time for extinguishing fire due to delay in the operation of detector and release of gas from the extinguishing system has become a problem. Accordingly, this study was carried out according to needs of active mechanism to prevent the spread of fire and block the leak of insulating oil, in accordance with the importance of securing golden time in extinguishing a fire in its early stage. A bushings fireproof structure was developed by applying the high temperature shape retention materials, which are expanded by flame, and mechanical flame cutoff devices. The bushings fireproof structure was installed on the transformer model produced by applying the actual standards of bushings and flange, and the full scale fire test was carried out. It was confirmed that the bushings fireproof structure operated at accurate position and height within 3 seconds from the flame initiation. It is considered that it could block the spread of flame effectively in the event of actual transformer fire.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.73-81
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• 2018

Purpose : The aims of this study were to compare and assess the effectiveness of Volumetric Modulated Arc Therapy(VMAT) using jaw tracking(JT) and fixed jaw(FJ) in radiation therapy of multiple brain metastasis. Methode and material : Among the patients with Multiple Brain Metastasis treated with jaw tracking, 10 patients with more than 6 tumors and with the size of radiation field $14{\times}14cm^2$ or more were included. Each Treatment plans with jaw tracking(JT) and fixed jaw(FJ) was established with Eclipse (Ver. 13.6 Varian, USA). Gamma Index (3 mm, 3 % confidence interval - 95 %) and maximum dose difference were measured with an electronic portal imaging device(EPID). The $D_{max}$ and $D_{mean}$ of Organ At Risk(OAR) were assessed and compared, and the Conformity Index(CI) and Homogeneity Index(HI) were evaluated. Result : Evaluating jaw tracking(JT) and fixed jaw(FJ) outcomes, in all cases, Gamma Index met the permissible standard of 3 mm, 3 % confidence intervals of 95 %. The maximum dose difference value from the areas with leaf end transmission was measured at a maximum of 98.4 % and an average of 43.6 % in clockwise(CW), and 67.9 % and 41.0 % for each in Counter-Clockwise(CCW). With jaw tracking, the maximum value of $D_{max}$ for each normal organ in OAR decreased in 15.36 %~74.59 % with the average value decreasing in 2.84 %~39.80 %. The maximum value of $D_{mean}$ in OAR decreased in 27.90 %~65.23 %, with the average value decreasing in 7.70 %~41.71 %. No change has been found in Conformity Index and Homogeneity Index values. Conclusion : When Jaw tracking is used in treating patients with multiple brain metastasis with VMAT, the unnecessary exposure due to leakage and transmission of radiation in unspecified areas was reduced, without affecting the dose distribution of the planning target volume(PTV), and the availability of radiation therapy with lower doses in normal organs is expected.

• Journal of Climate Change Research
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• v.3 no.1
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• pp.71-88
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• 2012

The global warming is probably the most significant issue of concern all over the world and according to the report published by the Intergovernmental Panel on Climate Change (IPCC), the average temperature and extent of global warming around the globe have been on the rise and so have the uncertainty for the future. Such effects of global warming have adverse effects on basic foundation of the mankind in numerous ways and water resource is no exception. The researches on water resources assessment for climate change are significant enough to be used as the preliminary data for researches in other fields. In this research, a total of 124 peer-reviewed publications and 57 reports on the subject of research on climate change related to water resources, that has been carried out so far in Korea has been reviewed. The research on climate change in Korea (inclusive of the peer-reviewed articles and reports) has mainly focused on the future projection and assessment. In the fields of hydrometeorology tendency and projection, the analysis has been carried out with focus on surface water, flood, etc. for hydrological variables and precipitation, temperature, etc. for meteorological variables. This can be attributed to the large, seasonal deviation in the amount of rainfall and the difficulty of water resources management, which is why, the analysis and research have been carried out with focus on those variables such as precipitation, temperature, surface water, flood, etc. which are directly related to water resources. The future projection of water resources in Korea may differ from region to region; however, variables such as precipitation, temperature, surface water, etc. have shown a tendency for increase; especially, it has been shown that whereas the number of casualties due to flood or drought decreases, property damage has been shown to increase. Despite the fact that the intensity of rainfall, temperature, and discharge amount are anticipated to rise, appropriate measures to address such vulnerabilities in water resources or management of drainage area of future water resources have not been implemented as yet. Moreover, it has been found that the research results on climate change that have been carried out by different bodies in Korea diverge significantly, which goes to show that many inherent uncertainties exist in the various stage of researches. Regarding the strategy in response to climate change, the voluntary response by an individual or a corporate entity has been found to be inadequate owing to the low level of awareness by the citizens and the weak social infrastructure for responding to climate change. Further, legal or systematic measures such as the governmental campaign on the awareness of climate change or the policy to offer incentives for voluntary reduction of greenhouse gas emissions have been found to be insufficient. Lastly, there has been no case of any research whatsoever on the anticipated effects on the economy brought about by climate change, however, there are a few cases of on-going researches. In order to establish the strategy to prepare for and respond to the anticipated lack of water resources resulting from climate change, there is no doubt that a standardized analysis on the effects on the economy should be carried out first and foremost.

• Journal of Venture Innovation
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• v.5 no.1
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• pp.91-106
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• 2022

Cryptocurrency, stood out the sharp cost rising of Bitcoin has been spotlighted by means of the solution for stagflation because it is decentralized with an existing currency differently. Especially getting into 4th industrial revolution, technologies using block chain and internet of things have been used in the many fields, and the power of influence is also widespread. Nevertheless like a remark of Elon Musk of Tesla CEO, the problems of environmental contamination for cryptocurrency have been pointed out continuously and the most representative of them is an enormous electric usage as the use of fossil fuels. Also the amount generated of carbon dioxide result in the acceleration of global warming mainly based on the climate changes of earth if the existing mining method is continued. On the other hand, review researches have been conducted restrictively as the connection with environmental contamination as the mining of cryptocurrency. In this study, it intended to review problems for environmental contamination as the diversification of ecological system of cryptocurrency concretely. Upon investigation existing prior documents on the putting recent data first, the mining of cryptocurrency has affected on the environmental contamination conflicting with carbon neutrality as increasement of the electric usage and electronic wastes. And POS method without the mining process appeared, but it had a demerit collapsing a decentralization and then we met turning point on appearing various environmental-friendly cryptocurrency. Finally the appearance of cryptocurrency using new renewable energy acted on the opportunity of the usage maximization of energy storage apparatus and the birth of national government intervention. Based on these results, we mention clearly that hereafter cryptocurrency will regress if not go abreast the value of currency as well as environmental approach.

• Journal of the Korean Society of Radiology
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• v.18 no.3
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• pp.293-300
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• 2024

On October 31, 2023, the revision of the Medical Technologist Act made it mandatory to complete field training courses in order to obtain a license as a radiologic technologist. Therefore, we would like to survey the actual situation of field training in medical institutions to inform the revised Medical Technologist Act and propose improvement measures to increase the effectiveness of field training. A survey was conducted from March to April, 2023, among radiologic technologists working in medical institutions. The questionnaire was sent through a form on a domestic portal site, Company N, and 120 respondents completed it. Eighty-two respondents, or 68.3 percent, had experience in educating on-the-job training students. 58% of the respondents were aware of the fact that the amendment to the Act on Medical Technologist etc. made field training mandatory to obtain a radiologic technologist license. In accordance with Article 9 of the Medical Technologist Act, which prohibits unlicensed persons from practicing, 50% of the respondents were aware that those who are in training to complete an education course equivalent to the license they are seeking to obtain at a university or other institution are allowed to practice as medical Technologists. When asked what is currently taught during fieldwork, 6% of respondents said that they are required to perform radiation-generating activities in addition to observing, guiding patients, and positioning and moving patients. When asked about the future direction of education as fieldwork becomes mandatory for licensure, 77% of respondents said that they will teach more than they currently do. When asked about the appropriate total length of fieldwork, 35% said 12 weeks and 480 hours, 33% said 8 weeks and 320 hours, and 27% said 16 weeks and 640 hours. It can be seen that the current on-the-job training is inadequate according to various regulations, and students' satisfaction is low. However, with the revision of the Act on Medical Technologists, field training has become mandatory to obtain a license as a radiologist, and it is necessary to improve the educational conditions of field training. Therefore, it is necessary to comply with the Nuclear Safety Act and the Rules on the Safety Management of Diagnostic Radiation Generating Devices, introduce standardized training objectives and evaluation systems, designate training hospitals and radiologists in charge of training, and introduce extended training periods and simulation exercises to internalize field training.

• Journal of the Korean Society of Radiology
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• v.18 no.3
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• pp.257-265
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• 2024

In this study, we applied AEC(Auto Exposure Control), which is used in many chest examinations, to evaluate whether medical devices inserted into the body affect the dose and image quality of chest images. After attaching three HIMD(Human implantable medical devices) to the ion chamber, the Monte Carlo methodology-based program PCXMC(PC Program for X-ray Monte Carlo) 2.0 was applied to measure the effective dose by inputting the DAP(Dose Ares Product) value derived from the Pacemaker and CRT and Chemoport Additionally, to evaluate image quality, we set three regions of interest and one noise region on the chest and measured SNR and CNR. The final study results showed significant differences in DAP and Effective dose. There was a significant difference between Pacemaker and CRT when AEC was applied and not applied. (p<0.05) When applied, the dose increased by 37% for Pacemaekr and 52% for CRT. Chemoport showed a 10% increase in effective dose depending on whether AEC was applied, but there was no significant difference. (p>0.05) In the image quality evaluation, there was no significant difference in image quality between all HIMD insertions and AEC applied or not. (p>0.05) Therefore, when the HIMD was inserted into the chest during a chest x ray and overlapped with the ion chamber sensor, the effective dose increased, and there was no difference in image quality even at a low dose without AEC. Therefore, when performing a chest X-ray examination of a patient with a HIMD inserted, it is considered that performing the examination without applying AEC is a method that can be considered to reduce the patient's radiation exposure.