• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.930-938
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• 2023

Maritime English is a specialized language system designed for ship operations, maritime safety, and external and internal communication onboard. According to the International Maritime Organization's (IMO) International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW), it is imperative that navigational officers engaged in international voyages have a thorough understanding of Maritime English including the use of Standard Marine Communication Phrases (SMCP). This study measured students' proficiency in Maritime English using a learning and testing platform that includes voice recognition, translation, and word entry tasks to evaluate the resulting improvement in Maritime English exam scores. Furthermore, the study aimed to investigate the level of platform use needed for cadets to qualify as junior navigators. The experiment began by examining the correlation between students' overall English skills and their proficiency in SMCP through an initial test, followed by the evaluation of improvements in their scores and changes in exam duration during the mid-term and final exams. The initial test revealed a significant dif erence in Maritime English test scores among groups based on individual factors, such as TOEIC scores and self-assessment of English ability, and both the mid-term and final tests confirmed substantial score improvements for the group using the platform. This study confirmed the efficacy of a learning platform that could be extensively applied in maritime education and potentially expanded beyond the scope of Maritime English education in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.843-856
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• 2023

The global surge in maritime traffic has resulted in an increased number of ship collisions, leading to significant economic, environmental, physical, and human damage. The causes of these maritime accidents are multifaceted, often arising from a combination of crew judgment errors, negligence, complexity of navigation routes, weather conditions, and technical deficiencies in the vessels. Given the intricate nuances and contextual information inherent in each incident, a methodology capable of deeply understanding the semantics and context of sentences is imperative. Accordingly, this study utilized the SentenceBERT model to analyze maritime safety tribunal decisions over the last 20 years in the Busan Sea area, which encapsulated data on ship collision incidents. The analysis revealed important keywords potentially responsible for these incidents. Cluster analysis based on the frequency of specific keyword appearances was conducted and visualized. This information can serve as foundational data for the preemptive identification of accident causes and the development of strategies for collision prevention and response.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.200-208
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• 2024

The occurrence a fire on a training ship with a large number of people on board can lead to severe casualties. Hence the Seafarers' Act and Safety Life At Sea(SOLAS) emphasizes the importance of the abandon ship drill. Therefore, in this study, the training ship of Mokpo National Maritime University, Segero, which has a large number of people on board, was selected as the target ship and the likelihood and severity of fire accidents on each deck were predicted through the preliminary hazard analysis(PHA) qualitative risk assessment. Additionally, assuming a fire in a high-risk area, a simulation of evacuation time and population density was performed to quantitatively predict the risk. The the total evacuation time was predicted to be the longest at 501s in the meal time scenario, in which the population distribution was concentrated in one area. Depending on the scenario, some decks had relatively high population densities of over 1.4pers/m², preventing stagnation in the number of evacuees. The results of this study are expected to be used as basic data to develop training scenarios for training ships by quantifying evacuation time and population density according to various evacuation scenarios, and the research can be expanded in the future through comparison of mathematical models and experimental values.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.275-282
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• 2023

Workers in nuclear power plants are likely to be exposed to radiation from various geometrical sources. In order to evaluate the exposure level, the point-kernel method can be utilized. In order to perform a dose assessment based on this method, the radiation source should be divided into point sources, and the number of divisions should be set by the evaluator. However, for the general public, there may be difficulties in selecting the appropriate number of divisions and performing an evaluation. Therefore, the purpose of this study is to develop an algorithm for dose assessment for arbitrary shaped sources based on the point-kernel method. For this purpose, the point-kernel method was analyzed and the main factors for the dose assessment were selected. Subsequently, based on the analyzed methodology, a dose assessment algorithm for arbitrary shaped sources was developed. Lastly, the developed algorithm was verified using Microshield. The dose assessment procedure of the developed algorithm consisted of 1) boundary space setting step, 2) source grid division step, 3) the set of point sources generation step, and 4) dose assessment step. In the boundary space setting step, the boundaries of the space occupied by the sources are set. In the grid division step, the boundary space is divided into several grids. In the set of point sources generation step, the coordinates of the point sources are set by considering the proportion of sources occupying each grid. Finally, in the dose assessment step, the results of the dose assessments for each point source are summed up to derive the dose rate. In order to verify the developed algorithm, the exposure scenario was established based on the standard exposure scenario presented by the American National Standards Institute. The results of the evaluation with the developed algorithm and Microshield were compare. The results of the evaluation with the developed algorithm showed a range of 1.99×10^-1~9.74×10^-1 μSv hr^-1, depending on the distance and the error between the results of the developed algorithm and Microshield was about 0.48~6.93%. The error was attributed to the difference in the number of point sources and point source distribution between the developed algorithm and the Microshield. The results of this study can be utilized for external exposure radiation dose assessments based on the point-kernel method.

• Journal of Korea Port Economic Association
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• v.40 no.3
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• pp.61-78
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• 2024

This study centered on labor demand between ship officers and ratings in the maritime sector, focusing on human capital theory. Ship officers bear the primary responsibilities in ship operations, including navigation, compliance with safety procedures, crew and resource management, and strategic decision-making, necessitating high levels of education and experience. Conversely, ratings execute various tasks aboard ships under the guidance of officers, contributing to daily operations. Using a multifactor Cobb-Douglas production function, the study evaluated the productivity of ship officers and ratings and analyzed the segmentation of their respective labor markets. The analysis revealed that globalization did not significantly impact either ship officers or ratings. However, technological advancements notably adversely affected the labor demand for ratings, highlighting its role in widening wage gaps and exacerbating job insecurity among less skilled workers within broader economic and social contexts. The study concludes by emphasizing the need for appropriate employment policies responsive to fluctuations in labor demand for ship officers and ratings due to economic changes. It also underscores the importance of flexible responses to the impacts of technological progress on different job sectors, advocating for policy approaches that prioritize worker education and training.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.83-91
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• 2017

Objectives: The purpose of this study was to evaluate the error of the leaf position accuracy of the MLC due to the gravity effect according to the gantry angle by using picket fence test using EPID and GafChromic EBT3 film. Materials and Methods: A 5 cm solid phantom was placed on the table and the SAD was set to 100 cm. The EBT3 film was placed exactly over the solid phantom and covered a 1.5 cm solid phantom and the picket fence test was performed. The EPID was measured under the same conditions as the EBT3 film at SID 100 cm. The gantry angles were measured at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$ in order to evaluate the position of the MLC according to the gantry angle. For the geometric evaluation of the MLC, the leaf position accuracy of the MLC was analyzed using the analysis program. Results: In case of EPID, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.18 mm, 0.31 mm, 0.20 mm, 0.26 mm on the average and the maximum values of the errors were respectively 0.44 mm, 0.54 mm, 0.34 mm, 0.44 mm. In case of EBT3 film, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.19 mm, 0.21 mm, 0.19 mm, 0.31 mm on the average and the maximum values of the errors were respectively 0.35 mm, 0.45 mm, 0.36 mm, 0.48 mm. Conclusion: In this study, we analyzed the position error of the leaf of the MLC according to the gantry angle, and confirmed the position error of the leaf by gravity effect. As a result of comparing the leaf position accuracy using EPID and EBT3 film according to the variation of gantry angle, a larger error occurred in the error analysis method using EPID than that of EBT3 film. Therefore, in the case of IMRT based on MLC, as well as verification of accurate dosimetry should be conducted, it is considered that the quality control and verification for the precise operation of the MLC will be needed. and it is necessary to compare and verify the method of analysis.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.742-749
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• 2009

The use of cone-beam computed tomography(CBCT) has been proposed for guiding the delivery of radiation therapy. A kilovoltage imaging system capable of radiography, fluoroscopy, and cone-beam computed tomography(CT) has been integrated with a medical linear accelerator. A standard clinical linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) with an on-board electronic portal imager can be used to treat palliative patient and verify the patient's position prior to treatment. On-board CBCT images are used to generate patient geometric models to assist patient setup. The image data can also, potentially, be used for dose reconstruction in combination with the fluence maps from treatment plan. In this study, the accuracy of Hounsfield Units of CBCT images as well as the accuracy of dose calculations based on CBCT images of a phantom and compared the results with those of using CT simulator images. Phantom and patient studies were carried out to evaluate the achievable accuracy in using CBCT and CT stimulator for dose calculation. Relative electron density as a function of HU was obtained for both planning CT stimulator and CBCT using a Catphan-600 (The Phantom Laboratory, USA) calibration phantom. A clinical treatment planning system was employed for CT stimulator and CBCT based dose calculations and subsequent comparisons. The dosimetric consequence as the result of HU variation in CBCT was evaluated by comparing MU/cCy. The differences were about 2.7% (3-4MU/100cGy) in phantom and 2.5% (1-3MU/100cGy) in patients. The difference in HU values in Catphan was small. However, the magnitude of scatter and artifacts in CBCT images are affected by limitation of detector's FOV and patient's involuntary motions. CBCT images included scatters and artifacts due to In addition to guide the patient setup process, CBCT data acquired prior to the treatment be used to recalculate or verify the treatment plan based on the patient anatomy of the treatment area. And the CBCT has potential to become a very useful tool for on-line ART.)

• Radiation Oncology Journal
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• v.3 no.2
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• pp.95-101
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• 1985

From July 1979 through March 1985,112 patients with carcinoma of the uterine cervix were treated by whole pelvis irradiation and intracavitary radiation with Cs-137. The treatment consisted of 3600rad-5200rad to the whole pelvis by parallel opposing portals, 5 days per week, 180-200rad per day. Parametrial boost with 400-800rad was given in 60 patients. 2 intracavitary Cs-137 radiation using TAO applicator were done with 7-10 days interval. Total treatment times were 40-65 days with average 52 days. Total dose of radiation to point A varied from 6820 to 10500rad with average 8388rad and to point B from 4850 to 6899ra0 with average 5898rad. All patients had follow up from 6 months to 75 months and median follow up of 31 months. $9(8\%)$ had stage $14(12.5\%)$ had stage IIa, $50(44.6\%)$ had stage IIb, $33(29.5\%)$ had stage III, $6(5.4\%)$ had stage IV. 110 patients had squamous cell carcinoma and 2 patients had adenocarcinoma. 5 year actuarial survival rates were $61.8\%$ for the entire group, $84.6\%$ for stage Ib,$77.8\%$ for stage IIa, $56.7\%$ for stage IIb, $60\%$ for stage III, $33.3\%$ for stage IV. RT dose to medial parametrium (point A) below 8000rad resulted in $7/18(38.9\%)$ failure (=death) in contrast to 25/94 $(26.5\%)$ failure with dose over 8000rad. RT dose to lateral parametrium (point B) below 6000ra0 yielded 20/63 $(34.9\%)$ failure compared to $10/49(20.4\%)$ failure with dose over 6000rad. Poor survival group of age were between 40-49 years with failure of $14/41(34.1\%)$. There was no increased failure rate below age of 40 with failure of $2111(13.9\%)$. The results suggest that survival is as good as other published data, and that higher doses over 8000rad to point A and 6000rad to point B should be delivered.

• Progress in Medical Physics
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• v.17 no.3
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• pp.173-178
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• 2006

The purpose of this study was to evaluate the radiation dose for clinical PET/CT protocols in clinical environments using Alderson phantom and TLDs. Radiation doses were evaluated for both Philips GEMINI 16 slice PET/CT system and GE DSTe 16 slice PET/CT system. Specific organ doses with $^{137}Cs$ transmission scan, high quality CT scan and topogram in philips GEMINI PET/CT system were measured. Specific organ doses with CT scan for attenuation map, CT scan for diagnosis and topogram in GE DSTe PET/CT system were also measured. The organs were selected based on ICRP60 recommendation. The TLDs used for measurements were selected for within an accuracy of ${\pm}5%$ and calibrated in 10 MV X-ray radiation field. The effective doses for $^{137}Cs$ transmission scan, high qualify scan, and topogram in Philips GEMINI PET/CT system were $0.14{\pm}0.950,\;29.49{\pm}1.508\;and\;0.72{\pm}0.032mSv$ respectively. The effective doses for CT scan to make attenuation map, CT scan to diagnose and topogram in GE DSTe PET/CT system were $20.06{\pm}1.003,\;24.83{\pm}0.805\;and\;0.27{\pm}0.008mSv$ respectively. We evaluated the total effective dose by adding effective dose for PET Image. The total PET/CT doses for Philips GEMINI PET/CT (Topogram+$^{137}Cs$ transmission scan+PET, Topogram+high qualify CT+PET) and GE DSTe PET/CT (Topogram +CT for attenuation map+ PET, Topogram+diagnostic CT+ PET) are $7.65{\pm}0.951,\;37.00{\pm}1.508,\;27.12{\pm}1.003\;and\;31.89{\pm}0.805mSv$ respectively. Further study may be needed to be peformed to find optimal PET/CT acquisition protocols for reducing the patient exposure with good image qualify.

• Journal of Radiation Protection and Research
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• v.10 no.1
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• pp.50-63
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• 1985

A derivation of new release limit, named Derived Release Limit(DRL), into the atomsphere from a reference nuclear power plant has been performed on the basis of the new system of dose limitation recommended by the ICRP, instead of the (MPC)a limit which has been currently used until now as a general standard for radioactive effluents in Korea. In DRL Calculation, a Concentration Factor Method was applied, in which the concentrations of long-term routinely released radionuclides were in equilibrium with dose in environment under the steady state condition. The analytical model used in the exposure pathway analysis was the one which has been suggested by the USNRC and the exposure limits applied in this analysis were those recommended by the USEPA lately. In the exposure pathway analysis, all of the pathways are not considered and some may be excluded either because they are not applicable or their contribution to the exposure is insignificant compared with other pathways. In case, the environmental model developed in this study was applied to the Kori nuclear power plant as the reference power plant, the highest DRL value was calculated to be as $9.10{\times}10^6Ci/yr$ for Kr-85 in external whole body exposure from the semi-infinite radioactive cloud, while the lowest DRL value was observed 3.64Ci/yr for Co-60 in external whole body exposure from the contaminated ground, by the radioactive particulates. The most critical exposure pathway to an individual in the unrestricted area of interest (Kilchun-Ri, 1.3 km to the north of the release point) seems to be the exposure pathway from the contaminated ground and the most critical radionuclide in all pathways appears to be Co-60 in the same pathway. When comparing the actual release rate from KNU-l in 1982 with the DRL's obtained here the release of radionuclides from KNU-1 were much lower than the DRL's and it could be conclued that the exposure to an individual had been kept below the exposure limits recommended by the USEPA.