• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.980-992
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• 2024

Steam line break accident (SLB) in the nuclear reactor is one of the representative Non-LOCA accidents in which thermal-hydraulics and neutron kinetics are strongly coupled each other. Thus, the multi-scale and multi-physics approach is applied in this study in order to examine a realistic safety margin. An entire reactor coolant system is modelled by system scale node, whereas sub-channel scale resolution is applied for the region of interest such as the reactor core. Fuel performance code is extended to consider full core pin-wise fuel behaviour. The MARU platform is developed for easy integration of the codes to be coupled. An initial stage of the steam line break accident is simulated on the MARU platform. As cold coolant is injected from the cold leg into the reactor pressure vessel, the power increases due to the moderator feedback. Three-dimensional coolant and fuel behaviour are qualitatively visualized for easy comprehension. Moreover, quantitative investigation is added by focusing on the enhancement of safety margin by means of comparing the minimum departure from nucleate boiling ratio (MDNBR). Three factors contributing to the increase of the MDNBR are proposed: Various geometric parameters, realistic power distribution by neutron kinetics code, Radial coolant mixing including sub-channel physics model.

• Radiation Oncology Journal
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• v.27 no.1
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• pp.35-41
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• 2009

Purpose: This study was designed to determine the optimum radiotherapy technique for internal mammary node (IMN) irradiation after breast-conserving surgery. Materials and Methods: We selected ten cases of early stage partial mastectomy for plan comparison. Five of the patients were treated to the right-side breast and the rest of the patients were treated to the left-side breast. For each case, four different treatment plans were made to irradiate the entire breast, IMNs and supraclavicular lymph nodes (SCLs). The four planning techniques include a standard tangential field (STF), wide tangential field (WTF), partially wide tangential field (PWT) and a photon-electron mixed field (PEM). We prescribed a dose of 50.4 Gy to the SCL field at a 3 cm depth and isocenter of the breast field. Results: The dose distribution showed clear characteristics depending on the technique used. All of the techniques covered the breast tissue well. IMN coverage was also good, except for the STF, which was not intended to cover IMNs. For the cases of the left-side breasts, the volume of the heart that received more than 30 Gy was larger (in order) for the WTF, PWT, PEM and STF. For radiation pneumonitis normal tissue complication probability (NTCP), the PWT showed the best results followed by the STF. Conclusion: Despite the variety of patient body shapes, the PWT technique showed the best results for coverage of IMNs and for reducing the lung and heart dose.

• Radiation Oncology Journal
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• v.25 no.1
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• pp.16-25
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• 2007

[ $\underline{Purpose}$ ]: Breast conserving surgery (BCS) followed by chemotherapy (CTx.) and radiation therapy (RT) is widely performed for the treatment of early breast cancer. This retrospective study was undertaken to evaluate our interim results in terms of failure patterns, survival and relative risk factors. $\underline{Materials\;and\;Methods}$: From January 1999 through December 2003, 129 patients diagnosed with invasive breast cancer and treated with BCS followed by RT were subject to retrospective review. The median age of the patients was 45 years (age distribution, $27{\sim}76$ years). The proportions of patients according to their tumor, nodes, and metastases (TNM) stage were 65 (50.4%) in stage I, 41 (31.7%) in stage IIa, 13 (10.1%) in stage IIb, 9 (7.0%) in stage III, and 1 patient (0.8%) in stage IIIc. For 32 patients (24.8%), axillary node metastasis was found after dissection. BCS consisted of quadrantectomy in 115 patients (89.1%) and lumpectomy in 14 patients (10.6%). Axillary node dissection at axillary level I and II was performed for 120 patients (93%). For 7 patients (5.4%), only sentinel node dissection was performed with BCS. For 2 patients (1.6%) axillary dissection of any type was not performed. Postoperative RT was given with 6 MV X-rays. A tumor dose of 50.4 Gy was delivered to the entire breast area using a tangential field with a wedge compensator. An aditional dose of $9{\sim}16\;Gy$ was given to the primary tumor bed areas with electron beams. In 30 patients (23.3%), RT was delivered to the supraclavicular node. Most patients had adjuvant CTx. with $4{\sim}6$ cycles of CMF (cyclophosphamide, methotrexate, 5-fluorouracil) regimens. The median follow-up period was 50 months (range: $17{\sim}93$ months). $\underline{Results}$: The actuarial 5 year survival rate (5Y-OSR) was 96.9%, and the 5 year disease free survival rate (5Y-DFSR) was 93.7%. Local recurrences were noted in 2 patients (true: 2, regional node: 1) as the first sign of recurrence at a mean time of 29.3 months after surgery. Five patients developed distant metastases as the first sign of recurrence at $6{\sim}33$ months (mean 21 months). Sites of distant metastatic sites were bone in 3 patients, liver in 1 patient and systemic lesions in 1 patient. Among the patients with distant metastatic sites, two patients died at 17 and 25 months during the follow-up period. According to stage, the 5Y-OSR was 95.5%, 100%, 84.6%, and 100% for stage I, IIa, IIb, and III respectively. The 5Y-DFSR was 96.8%, 92.7%, 76.9%, and 100% for stage I, IIa, IIb, and III respectively. Stage was the only risk factor for local recurrence based on univariate analysis. Ten stage III patients included in this analysis had a primary tumor size of less than 3 cm and had more than 4 axillary lymph node metastases. The 10 stage III patients received not only breast RT but also received posterior axillary boost RT to the supraclavicular node. During the median 53.3 months follow-up period, no any local or distant failure was found. Complications were asymptomatic radiation pneumonitis in 10 patients, symptomatic pneumonitis in 1 patient and lymphedema in 8 patients. $\underline{Conclusion}$: Although our follow up period is short, we had excellent local control and survival results and reaffirmed that BCS followed by RT and CTx. appears to be an adequate treatment method. These results also provide evidence that distant failure occurs earlier and more frequent as compared with local failure. Further studies and a longer follow-up period are needed to assess the effectiveness of BCS followed by RT for the patients with less than a 3 cm primary tumor and more than 4 axillary node metastases.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.1
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• pp.9-15
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• 2006

Purpose: Previous studies have not showed consistent results for the level of expression of sodium/iodide symporter (NIS) in thyroid diseases, especially malignant tumor. We undertook this study to evaluate the distribution of NIS expression in malignant thyroid diseases and compare with that in benign thyroid disease. Materials and Methods: Total patients were 119 cases (Men 15, $48{\pm}13$ yrs). Total number of samples were 205 pieces. In malignant thyroid disease, there were 153 samples: 90 in papillary carcinoma, 4 in follicular carcinoma, 2 in medullary carcinoma and 57 in metastatic lymph node. In benign thyroid disease, there were 52 samples: 36 in goiter/cyst, 11 in thyroiditis and 5 in follicular adenoma. Using immunohistochemical methods, we probed 205 samples with monoclonal anti-NIS Ab. Grading of staining was stored as 0 (negative or absent), 1 (weakly positive), 2 (moderately positive) or 3 (strongly positive). Expression rate (ER) of NIS positivity in individual disease entity was expressed as percentage of total number divided by number in 2 plus 3 grade. Results: ERs of malignant thyroid diseases were 63% in papillary carcinoma, 81% in metastatic lymph node, 71% in follicular carcinoma and 100% in medullary carcinoma. ERs of benign thyroid disease were 53% in goiter/cyst, 64% in thyroiditis and 40% in follicular adenoma. ER of malignant thyroid diseases was higher than benign thyroid diseases (71% vs 54%). Grading of NIS expression in papillary carcinoma or goiter/cyst was heterogeneously distributed in considerable cases. Normal tissue also showed heterogeneous distribution of NIS expression, which was not correlated with that of primary lesion. Conclusion: In papillary thyroid carcinoma, distribution of NIS expression was heterogeneous and increased, and not different compared with that of benign thyroid disease.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.266-272
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• 2010

Purpose: The purpose of this study was to investigate the effects of the surface morphology of the implant neck on marginal bone stress measured by using finite element analysis in six implant models. Materials and methods: The submerged type rescue implant system (Dentis co., Daegu, Korea) was selected as an experimental model. The implants were divided into six groups whose implant necks were differently designed in terms of height (h, 0.4 and 1.0 mm) and width (platform width, w = 3.34 + 2b [b, 0.2, 0.3 and 0.4 mm]). Finite element models of implant/bone complex were created using an axisymmetric scheme. A load of 100 N was applied to the central node on the top of crown in parallel with the implant axis. The maximum compression stress was calculated and compared. Results: Stress concentration commonly observed around dental implants did not occur in the marginal bone around all six test implant models. Marginal bone stress varied according to the implant neck bevel which had different width and height. The stress was affected more markedly by the difference in height than in width. Conclusion: This result indicates that the implant neck bevel may play an important role in improving stress distribution in the marginal bone area.

• Pediatric Infection and Vaccine
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• v.18 no.1
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• pp.54-60
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• 2011

Purpose : In this study, we listed common diseases in pediatric inpatients and evaluated the distribution of diseases by period and age group, in order to estimate the epidemiologic trend. Methods : Patients who were admitted to the Department of Pediatrics between 1997 and 2008 were included. Demographic characteristics, date of admission, and International Classification of Diseases (ICD) code of patients were indentified. Study period was divided into two; early (1997-2002) and late (2003-2008), and age of patients were grouped into four; infancy, early childhood, late childhood, and adolescence. Results : A total of 33,513 patients were admitted for 12 years. In the list of ICD code, Pneumonia (J12-J18; 21.2%) was the most prevalent, followed by gastroenteritis (A00-A09; 17.8%), bronchiolitis (J21; 11.9%), and so on. Common diseases ranked from 1 to 10 comprised the majority (79.1%) of all the inpatients. There was increase in the number of inpatients with respiratory infectious disease (bronchiolitis, otitis media, and sinusitis), enlarged lymph node, or impetigo/cellulitis, but decrease in the number of inpatients with aseptic meningitis, intussusceptions, measles, or nephritic/nephrotic syndrome. The distribution of diseases also showed age group-specific difference. Conclusion : The distribution of diseases by period and age group was different. The epidemiologic trend should be considered in developing the management of strategy for the Department of Pediatrics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.51-56
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• 2016

In this paper, we propose an Arduino-based plant monitoring system. The proposed system is based on the Arduino platform, using an environmental sensor and a pressure sensor for measuring temperature, humidity and illuminance in order to monitor the state of the environment and the facilities of the plant. Monitoring data are transmitted to a ZigBee coordinator connected to a server through a radio frequency transceiver. When using a pressure sensor and the environment sensor data stored on the host server, checking the pressure in the environment of the plant and equipment is intended to report any alarm status to the administrator. Using a grid line-based key distribution scheme, the authentication node dynamically generates a data key to protect the monitoring information. Applying a ZigBee wireless sensor network does not require additional wiring for the actual implementation of a plant monitoring system. Possible working-environment monitoring of an efficient plant can help analyze the cause of any failure by backtracking the working environment when a failure occurs. In addition, it is easy to expand or add a sensor function using the Arduino platform and an expansion board.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.3
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• pp.166-171
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• 2023

Efficient energy management is a very important factor in sensor networks with limited resources, and cluster techniques have been studied a lot in this respect. However, a problem may occur in which energy use of the cluster header is concentrated, and when the cluster header is not evenly distributed over the entire area but concentrated in a specific area, the transmission distance of the cluster members may be large or very uneven. The transmission distance can be directly related to the problem of energy consumption. Since the energy of a specific node is quickly exhausted, the lifetime of the sensor network is shortened, and the efficiency of the entire sensor network is reduced. Thus, balanced energy consumption of sensor nodes is a very important research task. In this study, factors for balanced energy consumption by cluster headers and sensor nodes are analyzed, and a balancing distribution clustering method in which cluster headers are balanced distributed throughout the sensor network is proposed. The proposed cluster method uses multi-hop routing to reduce energy consumption of sensor nodes due to long-distance transmission. Existing multi-hop cluster studies sets up a multi-hop cluster path through a two-step process of cluster setup and routing path setup, whereas the proposed method establishes a hierarchical cluster routing path in the process of selecting cluster headers to minimize the overhead of control messages.

• Korean Journal of Environmental Biology
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• v.30 no.3
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• pp.164-172
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• 2012

In this study, samples were collected from Lake Soyang in Kangwon-do in order to isolate novel Flavobacterium sp. strains. Totally, 21 strains of Flavobacterium showing 97%~98% similarity in 16S rRNA were selected and thoroughly investigated individual characteristics and ecological differences. As results, we could categorize Flavobacterium isolated from Lake Soyang into four major node groups, where most of Flavobacterium belonged to single group. Next, fatty acid analyses were performed demonstrating similar pattern of the majority of fatty acids as either iso $C_{15:0}$ or summed feature 3 (comprised $C_{16:1}$ ${\omega}7c$ and/or $C_{16:1}$ ${\omega}6c$) of the other Flavobacterium. However, other phenotypic data were different from the other Flavobacterium sp. Group. Our data showed that genetically related species of Flavobacterium have been distributed in Lake Soyang. Those Flavobacterium strains were phenotypically different from previously reported genus of Flavobacterium species. Taken together, we speculated that isolated Flavobacterium strains from Lake Soyang might be ecologically important members to maintain ecosystem.

• The KIPS Transactions:PartC
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• v.14C no.6
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• pp.519-524
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• 2007

One of the most important issues on the sensor network with resource limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long lived sensor network is the clustering mechanism which can be further classified into the single hop mode and the multi hop mode. The single hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head(CH) via single hop md, in the multi hop mode, sensor nodes communicate with the CH with the help of other Intermediate nodes. One of the most critical factors that impact on the performance of the existing multi hop clustering mechanism is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non uniformly, the fixed size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic size multi hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed size clustering mechanisms by carrying out numerical analysis and simulations.