• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.65-67
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• 2017

Various combustion modeling approaches have been developed and verified in a combustion system such as rockets, gas turbines, and so on. This study introduces basic theory and recent research activities on 1D network model where a system is divided into a series of acoustic element and mass/momemtum/energy conservations are applied in the component. Each component is connected to the neighboring ones with proper jump conditions. Flame transfer function and acoustic transfer function are determined and effects of the each function on the system instability is investigated.

• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.589-598
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• 2018

To maintain safety and reliability of reactors, redundant sensors are usually used to measure critical variables and estimate their averaged time-dependency. Nonhealthy sensors can badly influence the estimation result of the process variable. Since online condition monitoring was introduced, the online cross-calibration method has been widely used to detect any anomaly of sensor readings among the redundant group. The cross-calibration method has four main averaging techniques: simple averaging, band averaging, weighted averaging, and parity space averaging (PSA). PSA is used to weigh redundant signals based on their error bounds and their band consistency. Using the consistency weighting factor (C), PSA assigns more weight to consistent signals that have shared bands, based on how many bands they share, and gives inconsistent signals of very low weight. In this article, three approaches are introduced for improving the PSA technique: the first is to add another consistency factor, so called trend consistency (TC), to include a consideration of the preserving of any characteristic edge that reflects the behavior of equipment/component measured by the process parameter; the second approach proposes replacing the error bound/accuracy based weighting factor ($W^a$) with a weighting factor based on the Euclidean distance ($W^d$), and the third approach proposes applying $W^d$, TC, and C, all together. Cold neutron source data sets of four redundant hydrogen pressure transmitters from a research reactor were used to perform the validation and verification. Results showed that the second and third modified approaches lead to reasonable improvement of the PSA technique. All approaches implemented in this study were similar in that they have the capability to (1) identify and isolate a drifted sensor that should undergo calibration, (2) identify a faulty sensor/s due to long and continuous missing data range, and (3) identify a healthy sensor.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.340-350
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• 2015

This paper proposes strain-based acceptance criteria for assessing plastic instability of the safety class 1 nuclear components made of ferritic steel during level D service loads. The strain-based criteria were proposed with two approaches: (1) a section average approach and (2) a critical location approach. Both approaches were based on the damage initiation point corresponding to the maximum load-carrying capability point instead of the fracture point via tensile tests and finite element analysis (FEA) for the notched specimen under uni-axial tensile loading. The two proposed criteria were reviewed from the viewpoint of design practice and philosophy to select a more appropriate criterion. As a result of the review, it was found that the section average approach is more appropriate than the critical location approach from the viewpoint of design practice and philosophy. Finally, the criterion based on the section average approach was applied to a simplified reactor pressure vessel (RPV) outlet nozzle subject to SSE loads. The application shows that the strain-based acceptance criteria can consider cumulative damages caused by the sequential loads unlike the stress-based acceptance criteria and can reduce the overconservatism of the stress-based acceptance criteria, which often occurs for level D service loads.

• The Mathematical Education
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• v.41 no.1
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• pp.91-100
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• 2002

The purpose of this study is to help the students understand the concepts for the series and calculate the sum of series with diverse methods --- a) High School Algebraic Technique, b) Using Bernoulli Number, c) Integral Method, d) Euler Formular, e) Fourier Series

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.4
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• pp.295-301
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• 2002

In this paper, solenoid-type 3-D passives (inductors and transformers) have been designed, fabricated, and characterized by using electroplating techniques, wire bonding techniques, multi-layer thick photoresist, and low temperature processes which are compatible with semiconductor circuitry fabrication. Two different fabrication approaches are performed to develop the solenoid-type 3-D passives and relationship of performance characteristics and geometry is also deeply investigated such as windings, cross-sectional area of core, spacing between windings, and turn ratio. Fully integrated inductor has a quality factor of 31 at 6 GHz, an inductance of 2.7 nH, and a self resonant frequency of 15.8 GHz. Bonded wire inductor has a quality factor of 120, an inductance of 20 nH, and a self resonant frequency of 8 GHz. Integrated transformers with turn ratios of 1:1 and n:l have the minimum insertion loss of about 0.6 dB and the wide bandwidth of a few GHz.

• Earthquakes and Structures
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• v.8 no.1
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• pp.225-251
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• 2015

This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

• The Plant Pathology Journal
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• v.19 no.1
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• pp.34-42
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• 2003

The ascomycete Magnaporthe grisea is a pathogen of rice blast and is known to form specialized infection structures called appressoria for successful infection into host cells. To understand the molecular mechanism underlying infection process, appressorium-related genes were identified through global approaches including EST sequencing, differential hybridization, and sup-pression subtractive hybridization. EST database was generated on >2,000 cDNA clones randomly selected from appressorium stage cDNA library. Large number of ESTs showed homology to known proteins possibly involved in infection-related cellular development (attachment, germination, appressorium formation, and colonization) of rice blast fungus. The 1051 ESTs showing significant homology to known genes were assigned to 11 functional categories. Differential hybridization and suppression subtractive hybridization were applied to identify genes showing an appressorium stage specific expression pattern. A number of genes were selected as up-regulated during appressorium formation compared with the vegetative growing stage. Clones from various cDNA libraries constructed in different developmental stages were arrayed on slide glass for further expression profiling study. functional characterization of genes identified from these global approaches may lead to a better understand-ing of the infection process of this devastating plant disease, and the development of novel ways to protect host plant.

• Research in Mathematical Education
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• v.27 no.1
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• pp.25-47
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• 2024

Mathematical modeling activities are gaining popularity in K-12 mathematics education curricula worldwide. These activities serve dual purposes by aiding students in making sense of real-world situations intertwined with social justice while acquiring mathematical knowledge. Despite efforts to prepare teacher candidates for instructing in mathematical modeling within a single country, little attention has been given to teacher candidates' approaches to mathematical modeling on a social justice issue from different countries. This article employs an in-depth, small-scale comparative study to examine the approaches of U.S. and Korean teacher candidates in solving a justice-oriented mathematics task. Our findings reveal that, although both U.S. and Korean teacher candidates identified certain variables as key when constructing a mathematical model, Korean teacher candidates formulated a more nuanced model than U.S. candidates by considering diverse variables. However, U.S. teacher candidates exhibited a heightened engagement in linking the task to social justice issues, whereas Korean teacher candidates barely perceived real-world problems in relation to social justice concerns. This study serves as a valuable tool to inform the roles and limitations of teacher education programs, shaped within specific educational contexts.

• Journal of the Korea Institute of Building Construction
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• v.10 no.3
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• pp.71-81
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• 2010

In 1994, Korean construction research and development (R&D) projects received investments amounting to 1.2 billion KRW, an amount that rose to 164.8 billion KRW in 2007. Under the current system, construction researchers submit the application records of Construction Research and Development (R&D) in construction projects to the Korea Institute of Construction & Transportation Technology Evaluation and Planning. The performance of Construction R&D projects has thus been dependent on the subjective reporting of the results by the researchers themselves. For this reason, it is difficult to secure confidence in the records of Construction Research and Development. Therefore, this research suggested measures for revitalizing Construction Research and Development, analyzed approaches to cost-saving in Construction Research and Development, and analyzed economic effectiveness in the results of construction R&D.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5253-5256
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• 2015

Background: A number of randomized trials addressing alternative operative and multimodality approaches to gastric cancer have characterized early postoperative morbidity and mortality rates. The aim of this study was to compare mortality and morbidity and disease free survival after D1 and D2 gastrectomy for adenocarcinomas of the stomach Materials and Methods: From June 2006 to January 2012, patients were selected according to information of the cancer administrator center of Ahvaz Jundishapur Medical University. The inclusion criteria were age between 20-85 years and histologically proven adenocarcinoma of the stomach without evidence of distant metastasis. Patients were excluded if they had previous or coexisting cancer or disability disease. In this research, D1 was compared to D2 gastrectomy. Results: 131 patients were randomised, 49 allocated to D1 and 82 to D2 gastrectomy. The two groups were comparable for age, sex, site of tumors, and type of resection performed. The overall post-operative morbidity rate was 17.5%. Complications developed in 14.2% of patients after D1 and in 19.5% of patients after D2 gastrectomy (p=0.07). Postoperative mortality rate was 0.8% (one death); it was 2% after D1 and 0% after D2 gastrectomy. In this research disease free-survival after 3 years was 71.2 % with 63.2% after D1 and 76.8% after D2 gasterctomy. Conclusions: This study indicates that D2 gastrectomy with pancreas preservation is not followed by significantly higher morbidity and mortality than D1 resection. Based on the results of present study, D2 resection should be recommended as the standard surgical approach for resectable gastric cancer.