• Journal of Korea Multimedia Society
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• v.5 no.1
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• pp.68-76
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• 2002

Multicast in mobile host has the problem of hast mobility, multicast decision, triangle routing, tunnel convergence, implosion of retransmission, and bandwidth waste. In particular, the bandwidth waste in radio is a definite factor that decreases transmission rate. To solve the problems, this paper proposes a new multicast transmission protocol called FIM(Forward Error Correction Integrated Multicast), which supports reliable packet recovery mechanism by integrating If Mobility Support for the host mobility, IGMP(Interned Group Management Protocol) for the group management, and DVMRP(Distance Vector Multicast Routing Protocol) for the multicast routing, and it also uses FEC and the local recovery method based on receiver. The performance measurement is performed by dividing the losses into the homogeneous independent loss, the heterogeneous independent loss, and the shared source link loss model.. The result shows that the performances improves in proportion to the size of local areal group when the size of transmission group exceeds designated size. This indicates FIM is effective in the environment where there are much of data and many receivers in the mobile host.

• Smart Structures and Systems
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• v.15 no.1
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• pp.135-150
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• 2015

Large concrete structures are prone to cracks and damages over time from human usage, weathers, and other environmental attacks such as flood, earthquakes, and hurricanes. The health of the concrete structures should be monitored regularly to ensure safety. A reliable method of real time communications can facilitate more frequent structural health monitoring (SHM) updates from hard to reach positions, enabling crack detections of embedded concrete structures as they occur to avoid catastrophic failures. By implementing an unconventional mode of communication that utilizes guided stress waves traveling along the concrete structure itself, we may be able to free structural health monitoring from costly (re-)installation of communication wires. In stress-wave communications, piezoelectric transducers can act as actuators and sensors to send and receive modulated signals carrying concrete status information. The new generation of lead zirconate titanate (PZT) based smart aggregates cause multipath propagation in the homogeneous concrete channel, which presents both an opportunity and a challenge for multiple sensors communication. We propose a time reversal based pulse position modulation (TR-PPM) communication for stress wave communication within the concrete structure to combat multipath channel dispersion. Experimental results demonstrate successful transmission and recovery of TR-PPM using stress waves. Compared with PPM, we can achieve higher data rate and longer link distance via TR-PPM. Furthermore, TR-PPM remains effective under low signal-to-noise (SNR) ratio. This work also lays the foundation for implementing multiple-input multiple-output (MIMO) stress wave communication networks in concrete channels.

• The Mathematical Education
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• v.57 no.4
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• pp.329-352
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• 2018

This study analyzed each process of demand analysis(A), design(D), development(D), implementation(I) and evaluation(E) of the program to support mathematics learning of students with under-achievement of math in high school. To analyze the demand, a survey was conducted on 235 high school math teachers and 334 high school students who were under-achieved in mathematics. To design and develope the program, this study linked middle school math to high school math so that the students with poor math learning could easily participate in mathematics learning. The programs developed in this study were implemented in three high schools, where separate classes were organized and run for students with poor math learning. The evaluation of the programs developed in this study was done in two ways. One was a quantitative evaluation conducted by five experts, and the other was a qualitative evaluation conducted through interviews with teachers and students participating in the program. This study found that students with poor mathematics learning were more motivated to learn, started to do mathematics, and encouraged to be confident when using learning materials that included easy problems and detailed solutions that they could solve themselves. From these results, the following three implications can be derived in developing a program to support students who are experiencing poor mathematics learning in high school. First, we should develop learning materials that link middle school mathematics to high school mathematics so that students can supplement middle school mathematics related to high school mathematics. Second, we need to develop learning materials that include detailed solutions to basic examples and include homogeneous problems that can be solved while looking at the basic example's solution process. Third, we should avoid the challenge of asking students who are under-achieving to respond too openly.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.158-162
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• 2014

Purpose: Reference material (RM) is defined as material that is safe and homogeneous enough about specified characteristic that is made with a purpose of using test of measurement or nominal characteristic. Certified reference material (CRM), which is issued by authorized organization, is defined as reference material that provides characteristic value, link uncertainty and retroactivity. The purpose of this paper was to evaluate recovery of radioimmunoassay by Certified Reference Material enclosed with a certificate and therefore to enhance reliability of test. Materials and Methods: WHO certified reference material is purchased from NIBSC (National Institute for Biological Standard and Control, United Kingdom) and made of 3 levels that are C-1 (low concentration), C-2 (medium concentration) and C-3 (high concentration) and measured for kit at the Seoul National University Hospital. Recovery rate is evaluated after measurement at four different days. Results: Recovery rate results using WHO certified reference material are T4 90%, Ferritin 88%, PSA 94%, Prolactin 99%, AFP 94% and TSH 93%. Conclusion: A procedure that appropriate accuracy, precision, specificity, sensitivity, reproducibility, and validate on the subject of kit for radioimmunoassay is essential. Recovery rate assay as extraction efficiency of analysis process is percent about already measuring results of analysis result after all measuring process. This is very important assessment standards of performance evaluation of immunoassay kit. Recovery rate results of 6 type used WHO CRM are satisfactory to 88~99%. This demonstrates that the radioimmunoassay is a very accurate measurement, which is very effectively utilized in clinical practice.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.145-152
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• 2010

The gel polymer electrolyte(GPE) were prepared by in-situ thermal cross-linking reaction of homogeneous precursor solution of perfluorinated phosphate-based cross-linker and liquid electrolyte. Ionic conductivities and electrochemical properties of the prepared gel polymer electrolyte with the various contents of liquid electrolytes and perfluorinated organophosphate-based cross-linker were examined. The stable gel polymer electrolyte was obtained up to 97 wt% of the liquid electrolyte. Ionic conductivity and electrochemical properties of the gel polymer electrolytes with the various chain length of perfluorinated ethylene oxide and different content of liquid electrolytes were examined. The maximum ionic conductivity of liquid electrolyte was measured to be $1.02\;{\times}\;10^{-2}\;S/cm$ at $30^{\circ}C$ using the cross-linker($PFT_nGA$). The electrochemical stability of the gel polymer electrolyte was extended to 4.5 V. The electrochemical performances of test cells composed of the resulting gel polymer electrolyte were also studied to evaluate the applicability on the lithium polymer batteries. The test cell carried a discharge capacity of 136.11mAh/g at 0.1C. The discharge capacity was measured to be 91% at 2C rate. The discharge capacity decreased with increase of discharge rate which was due to the polarization. After 500th charge/discharge cycles, the capacity of battery decreased to be 70% of the initial capacity.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.209-217
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• 2006

The major continental blocks in NE-Asia are the North China Block and the South China Blo, which have collided, starting from the Korean peninsula. The suture zone in NE China between two blocks is well defined from the QinIing-Dabie-Orogenic Belt to the Jiaodong (Sulu) Belt by the geological and geophysical interpretation. The discovery of high pressure metamorphic rocks in the Hongsung area of the Korean peninsula can be used to estimate the suture zone. This indicates that the suture zone in the Jiaodong Belt might be extended to Hongsung area. However, due to the lack of geological and geophysical data over the Yellow sea, the extension of the suture zone to the Korean peninsula across the Yellow Sea is obscure. To find out the tectonic relationship between NE China and the Korean peninsula it is necessary to complete U-ie homogeneous geophysical dataset of NE Asia, which can be provided by satellite observations. The CHAMP lithospheric magnetic field (MF3) and CHAMP-GRACE gravity field, combined with surface measured data, allow a much more accurate in-ference of tectonic structures than previously available. The CHAMP magnetic anomaly map reveals significant magnetic lows in the Yellow Sea near Nanjing and Hongsung, where are characterized by gravity highs on U-ie CHAMP-GRACE gravity anomaly map. To evaluate the depth and location of poten-tial field anomaly causative bodies, the Euler Deconvolution method is implemented. After comparing the two potential field solutions with the simplified geological map containing tectonic lines and the distribution of earthquakes epicenters, it is found that the derived structure boundaries of both are well coincident with the seismic activities as well as with the tectonic lineaments. The interpretation of the CHAMP satellite magnetic and GRACE satellite gravity datasets reveal two tectonic boundaries in U-ie Yellow Sea and the Korean peninsula, indicating U-ie norttiern and southern margins of the suture zone between the North China Block and the South China Block. The former is extended from the Jiaodong Belt in East China to the Imjingang Belt on the Korean peninsula, the later from Nanjing, East China, to Hongsung, the Korean peninsula. The tectonic movement in or near the suture zone might be responsible for the seismic activities in the western region of the Korean Peninsula and the development of the Yellow Sea sedimentary basin.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.628-636
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• 2019

In various industrial processes, piping serves as a link between unit processes and is an essential installation for internal flow. Therefore, the optimum design of the piping system is very important in terms of safety and cost, which requires the estimation of the pressure drop, flow rate, pipe size, etc. in the piping system. In this study, we developed a software that determines pressure drop, flow rate, and pipe size when any two of these design variables are known. We categorized the flows into single phase, homogeneous two phase, and separated two phase flows, and applied suitable calculation models accordingly. We also constructed a system library for the calculation of the pipe material, relative roughness, fluid property, and friction coefficients to minimize user input. We further created a costing library according to the piping material for the calculation of the investment cost of the pipe per unit length. We implemented all these functions in an integrated environment using a graphical user interface for user convenience, and C # programming language. Finally, we verified the accuracy of the software using literature data and examples from an industrial process with obtained deviations of 1% and 8.8% for the single phase and two-phase models.