• 한국전기전자재료학회논문지
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• 제13권6호
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• pp.472-477
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• 2000

Oxides of the form Mn$_{4}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO present properties that make them useful as power NTC thermistor for current limited. Electrical properties of Mn$_{3}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO power NTC thermistor such as I-V characteristics tim constant activation energy and heat dissipation coefficient measured as a function of temperature and composition. In Mn$_{4}$/O$_{4}$-CuO-Co$_{3}$/O$_{4}$-NiO-ZnO system with the 5wt% addition of Co$_{3}$/O$_{4}$ it can be seen that resistivity and B-constant were increased as the ratio of ZnO/Mn$_{3}$/O$_{4}$ was increased. Heat dissipation constant, I-V characteristics and time constant showed similar behaviour compared with those of conventional thermistors. In particular resistance change ratio ($\Delta$R) the important factor for reliability varied within $\pm$5% indicating the compositions of these products could be available for power thermistor.

• 한국해양공학회지
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• 제34권3호
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• pp.217-226
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• 2020

An offshore plant is an offshore platform that can process oil and gas resources in rough seas with a poor working environment. Moreover, it is a complex structure with different types of offshore facilities and a large amount of outfitting that connects different offshore installations. In particular, an enormous amount of various piping materials is installed in a relatively narrow space, and thus, the difficulty of working is relatively high compared to working in ships or ground plants. Generally, when the 3D detailed design is completed, an offshore plant piping process is carried out at the shipyard with ISO 2D fabrication drawings and ISO 2D installation drawings. If a worker wants to understand the three-dimensional piping composition in the working area, he can only use three-dimensional viewers that provide limited functionality. As offshore plant construction progresses, correlating work with predecessors becomes more complicated and rework occurs because of frequent design changes. This viewer function makes it difficult to identify the 3D piping structure of the urgently needed part. This study deals with the process support method based on a system using a 3D simulator to improve the efficiency of the piping process. The 3D simulator is based on the Unity3D engine and can be simulated by considering the classification and priority of 3D models by the piping process in the system. Further, it makes it possible to visualize progress information of the process. In addition, the punch content can be displayed on the 3D model after the pipe inspection. Finally, in supporting the data in relation to the piping process, it is considered that 3D-simulator-supported piping installing could improve the work efficiency by more than 99% compared to the existing method.

• ETRI Journal
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• 제37권2호
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• pp.359-368
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• 2015

In this paper, we investigate the capture effect through experiments conducted with Iris nodes equipped with AT86RF230 radio transceivers. It is shown that the first arriving packet in a collision can capture the radio channel for equal power transmissions and may be decoded depending on the amount of overlap. A new 3-packet-capture scenario is introduced and implemented. To be able to understand the impact of capture on the throughput performance of wireless sensor networks, we present an analysis of the capture coefficient using our practical results. For real-world implementations, the throughput of pure ALOHA considering a finite number of users is presented in analytical form. The capture coefficient is then applied to pure ALOHA as a case study. Using analytical and practical implementations of the capture effect on ALOHA, a very good match in channel throughput performance enhancement is demonstrated over the non-capture effect case. TinyOS-2.x is used to program the nodes and to observe data exchange on a computer through a base station.

• Environmental Engineering Research
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• 제14권4호
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• pp.200-210
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• 2009

The modern era of water quality modeling in the United States began in the 1960s. Pushed by advances in computer technology as well as environmental sciences, water quality modeling evolved through five broad periods: (1) initial model development with mainframe computers (1960s - mid 1970s), (2) model refinement and generalization with minicomputers (mid 1970s - mid 1980s), (3) model standardization and support with microcomputers (mid 1980s - mid 1990s), (4) better model access and performance with faster desktop computers running Windows and local area networks linked to the Internet (mid 1990s - early 2000s), and (5) model integration and widespread use of the Internet (early 2000s - present). Improved computer technology continues to drive improvements in water quality models, including more detailed environmental analysis (spatially and temporally), better user interfaces and GIS software, more accessibility to environmental data from on-line repositories, and more robust modeling frameworks linking hydrodynamics, water quality, watershed and atmospheric models. Driven by regulatory needs and advancing technology, water quality modeling will continue to improve to better address more complicated water bodies and pollutant types, and more complicated management questions. This manuscript describes historical trends in water quality model development in the United States, reviews current efforts, and projects promising future directions.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2247-2254
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• 2010

The surface structures of copper phthalocyanine (CuPc) thin films deposited on sulphur-passivated and plane perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)-covered InAs(100) surfaces have been studied by low energy electron diffraction (LEED) and van der Waals (vdW) intermolecular interaction energy calculations. The annealing to $300^{\circ}C$ and $450^{\circ}C$ of $(NH_4)_2S_x$-treated InAs(100) substrates produces a ($1{\times}1$) and ($2{\times}1$) S-passivated surface respectively. The CuPc deposition onto the PTCDA-covered InAs(100) surface leads to a ring-like diffraction pattern, indicating that the 2D ordered overlayer exists and the structure is dominantly determined by the intermolecular interactions rather than substrate-molecule interactions. However, no ordered LEED patterns were observed for the CuPc on S-passivated InAs(100) surface. The intermolecular interaction energy calculations have been carried out to rationalise this structural difference. In the case of CuPc unit cells on PTCDA layer, the planar layered CuPc structure is more stable than the $\alpha$-herringbone structure, consistent with the experimental LEED results. For CuPc unit cells on a S-($1{\times}1$) layer, however, the $\alpha$-herringbone structure is more stable than the planar layered structure, consistent with the absence of diffraction pattern. The results show that the lattice structure during the initial stages of thin film growth is influenced strongly by the intermolecular interactions at the interface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.584-586
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• 2004

This paper deals with the development of on-line fault and lightning stroke section locating system for branched overhead transmission line. The section locating algorithm of this system i3 by analyzing the distribution pattern of current flowing through the overhead ground wire. It composes of three parts; current sensors, local remote terminal unit(RTU) and analysis program at surveillance tenter. Double Rogowski coil sensor having integrating amplifier was designed as current sensor. In order for current pattern analysis, the transmitted waves from each sensor wert synchronized by GPS tim c clock in RTU. While, lightning stroke location are judged only by polarity information of lightning currents. This design has a benefit in simplicity of signal processing unit of RTU.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.268-273
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• 2000

Velocity-dependent increase in tonic stretch reflexes is one of the prominent characteristics of spasticity. It is very important to evaluate spasticity objectively and quantitatively before and after treatment for physicians. An accurate quantitative biomechanical evaluation for the spasticity which is caused by the disorder of central nervous system is made in this study. A sudden leg dropper which is designed to generate objective testing environment at every trial gives very effective environment for the test. Kinematic data are archived by the 3-dimensional motion analysis system($Elite^{(R)}$, B.T.S., Italy). Kinematic data are angle and angular velocity of lower limb joints, and length and lengthening velocity of lower limb muscle. A program is also developed to analyze the kinematic data of lower limb, contraction and relaxation length of muscles, and dynamic EMG data at the same tim. To evaluate spasticity quantitatively, total 31 parameters extracted from goniogram, EMG and muscle model are analyzed. Statistical analysis are made for bilateral correlations for all parameters. The described instrumentation and parameters to make quantitative and objective evaluation of spasticity shows good results.

• Steel and Composite Structures
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• 제23권2호
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• pp.205-215
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• 2017

The use of advanced fibre composite materials in bridge engineering offers alternative solutions to structural problems compared to traditional construction materials. Advanced composite or fibre reinforced polymer (FRP) materials have high strength to weight ratios, which can be especially beneficial where dead load or material handling considerations govern a design. However, the reduced weight and stiffness of FRP footbridges results in generally poorer dynamic performance, and vibration serviceability is likely to govern their design to avoid the footbridge being "too lively". This study investigates the dynamic behaviour of the 51.3 m span Wilcott FRP suspension footbridge. The assessment is performed through a combination of field testing and finite element analysis, and the measured performance of the bridge is being used to calibrate the model through an updating procedure. The resulting updated model allowed detailed interpretation of the results. It showed that non-structural members such as the parapets can influence the dynamic behaviour of slender, lightweight footbridges, and consequently their contribution must be included during the dynamic assessment of a structure. The test data showed that the FRP footbridge is prone to pedestrian induced vibrations, although the measured response levels were lower than limits specified in relevant standards.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제14권2호
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• pp.173-194
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• 2010

This study examines the differences and similarities of mathematics teachers' subject matter knowledge among England, the Chinese mainland and Hong Kong. Data were collected from a ten-item test in the SKIMA subject matter audit instrument [Rowland, T.; Martyn, S.; Barber, P. & Heal, C. (2000). Primary teacher trainees' mathematics subject knowledge and classroom performance. In: T. Rowland & C. Morgan (eds.), Research in Mathematics Education, Volume 2 (pp.3-18). ME 2000e.03066] from over 500 participants. Results showed that participants from England performed consistently better, with those from Hong Kong being next and then followed by those from the Chinese mainland. The qualitative data revealed that participants from Hong Kong and the Chinese mainland were fluent in applying routines to solve problems, but had some difficulties in offering explanations or justifications.

• STI Policy Review
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• 제4권1호
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• pp.74-93
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• 2013

Although open innovation (OI) has been an important research theme for over a decade, its theoretical framework has been relatively under-researched. As OI involves a wide range of innovation activities, a firm's capacities in the use of the various firm resources play a critical role in OI implementation. However, it is unclear how they affect firms' performances for little is known of OI capacities. Based on a theoretical framework derived from the literature, this study looks into the relationships between six OI capacities (inventive, absorptive, transformative, connective, innovative, and desorptive) and financial performance using the Korean Innovation Survey (KIS) 2008 data. The research model was tested using structural equation modelling (SEM) while potential differences in capacities between different firm groups were also investigated. The results indicate that 1) OI capacities are significantly associated with firms' financial performance; 2) capacities are highly correlated with one another; and 3) some capacities are differently configured between different types of firms. Findings suggest that policy makers should pay more attention to helping firms enhance OI capacities and attempt to develop relevant policies in order to complement inadequate capacities.