• Educational Technology International
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• v.6 no.2
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• pp.11-21
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• 2005

The study analyzed the topics and the types of the selected articles from the 20-year-old Journal of Educational Technology(JET), flagship journal of the Korean Society of Educational Technology. Further the results were compared with those of the Educational Technology Research & Development journal. Results indicate that the JET has grown in terms of quantity and quality since its birth 20 years ago. The JET seems to be independent as a young adult. Some issues and concerns were also identified: The articles of the JET are more inclined to Experimental design in terms of research type, and to Design in terms of research topic. Balance across Types and Topics needs be kept for long-term, healthier growth. The emergence of e-Learning and high technology of Korea offered opportunities to the field. However, the monopoly of e-Learning that consumes most of the limited space of the JET raises a red flag. More balanced and quality-oriented endeavors were suggested for another 20 years coming.

• Journal of Gifted/Talented Education
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• v.25 no.1
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• pp.77-93
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• 2015

The purpose of this study was to explore the problem solving strategy for Goldberg machine tasks of the gifted students in elementary science depending on the cognitive style(tendency to field-dependent and field independent). It was aimed to provide suggestions for the features and differences of the problem solving strategies of the gifted students in elementary science according to their cognitive styles. A total of 16 students, from the gifted class of P elementary school in Hwaseong were sampled for the research, cognitive styles Test was conducted to divide the students in teams, and the teams were classified according to cognitive style tendencies to five groups of field-dependent group, weak field-dependent group, mixed group, weak field-independent group and field-independent group. The Goldberg device task given was to make a Goldberg device within the angle framework of (Figure) 1, for a bead to start from the starting point and to reach the final point the last. The results are as follows: First, regarding the plan for producing the device, the stronger the field-independent tendency, they established more specific strategy-reflected plan; the stronger the field-dependent tendency, they established less specific strategy-reflected plan. Second, all cognitive style groups took a limited period of time into consideration, to fabricate the devices for the ball to arrive the last using a fine adjustment rather than many devices. Third, the field-independent group used a lot of logical reasoning; the field-dependent group used a lot of intuitive thinking. Fourth, the field independent group properly utilized strategies such as cooperation and role allocation; the field-dependent group tried to solve the task personally rather than cooperatively with poor role allocation. Fifth, the intermediate mixed group solved the problem better than the inclined groups such as field-dependent or field-independent groups.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1015-1025
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• 2010

In this present study, we experimentally investigated the effects of electric fields on the characteristics of flames spreading over electric-wires with AC fields. The dependence of the rate at which a flame spreads over polyethylene-insulated wires on the frequency and amplitude of the applied AC electric field was examined. The spreading of the flame can be categorized into linear spreading and non-linearly accelerated spreading of flame. This categorization is based on the axial distribution of the field strength of the applied electric field. The rate at which the flame spreads is highly dependent on the inclined direction of the wire fire. It could be possible to explain the spreading of the flame on the basis of thermal balance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2B
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• pp.171-178
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• 2006

The finite element model based on the 2-D advection-dispersion equation incorporating the dispersion tensor that is calculated using velocity field data was developed in order to analyze more accurately 2-D mixing of pollutants for meandering streams. The proposed model was tested using the straight channel that inclined at 45o in the Cartesian coordinate system. The simulation results showed that dispersion tensor model using velocity field data gives an accurate solution. The suitability of the proposed model in analyzing actual pollutant mixing in meandering channels was demonstrated by comparing the simulation results with experimental data obtained from the tracer tests in the laboratory flume. Comparison results showed that the proposed model with dispersion tensor can represents more accurately the mixing phenomena of the pollutants in the meandering channels in which the direction of the primary flow is varying periodically along the channel.

• Journal of Navigation and Port Research
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• v.30 no.10 s.116
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• pp.801-808
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• 2006

To create the value-added in the field of the shipbuilding, we have to vitalize the marine equipment industry. However the competitiveness is inclined to its outward than inward in the field of the shipbuilding in our country. Especially the field of the marine equipment industry needs to acquire the competitiveness as soon as possible in comparison with an advanced country. Therefore, this paper analyzes the characteristics of the marine equipment, the present situation of the marine equipment industry, the present situation of the demand-supply, the localization of the marine equipment, so that it can raise the competitiveness of the marine equipment industry. Based on this paper, it is the purpose of this paper to derive the alternative for acquiring the competitiveness. This paper is trying to find the way to progress the marine equipment industry and suggest well-founded data for acquiring the competitiveness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1919-1932
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• 1991

Experimental studies are conducted to investigate the Flow-Induced Vibration mechanism for cantilever plate model with the angle of attack (.alpha.=10.deg., 20.deg., 30.deg.). Research is divided into two parts. First, the flow fields around two dimensional flat plate model are investigated using LDV system. Second, the vortex shedding frequency and response spectra of cantilever plate are obtained experimentally using gap sensor and hot wire anemometer. Finite element method program was used in order to predict the flow field and pressure field around thin flat plate. And some predicted results were compared with the experimental data. The aspect ration of test model is d/t=25 (d; width, t; thickness). From the measurement of the flow field it was found that in the case of small inclined (.alpha.=10.deg., 20.deg.) relatively, the separated boundary layer at sharp leading edge developed smoothly downstream. With increasing the angle of attack of the plate, stagnation region was appeared on the back side of the plate and separated boundary layer was extended downstream. These trends are a good agreement with the computational results. It was found by analysis of response spectra of cantilever plate that the influences of vortex shedding frequency were important at the large of attack (.alpha.=30.deg.), and two peak values appear in entire test model at 24Hz, 150Hz.

• Journal of the Korean GEO-environmental Society
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• v.22 no.4
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• pp.15-23
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• 2021

Various micropiles have been developed through research related to micropiles, which have been carried out with the increased use of micropiles. Among the micropile construction methods being developed, the triaxial micropile (tmp), which is recently developed for the purpose of increasing the horizontal bearing capacity (seismic resistance), is representative. The three-axis micropile has the advantage of a method that can resist horizontal load more effectively because three micropiles installed inclined on each axis resist horizontal load. However, there is a problem in effectively using this pile method due to insufficient research on the support characteristics of the triaxial group micropile. In order to effectively utilize the triaxial group micropile (tmp), it is required to evaluate the bearing capacity for the factors that affect the horizontal bearing capacity of the pile. Therefore, in this study, field horizontal loading Tests were performed for each load direction, field loading Tests were verified through three-dimensional finite element analysis, behavioral characteristics of triaxial micropiles were evaluated, and appropriate horizontal bearing capacity was analyzed in consideration of horizontal load directions.

• Wind and Structures
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• v.6 no.6
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• pp.485-498
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• 2003

This paper presents a mechanical model of Rain-Wind Induced Vibration (RWIV) of stay cables. It is based on the physical interpretation of the phenomenon as given in Cosentino, et al. (2003, referred as Part I). The model takes into account all the main forces acting on cable, on the upper water rivulet (responsible of the excitation) and the cable-rivulet interaction. It is a simplified (cable cross-sectional and deterministic) representation of the actual (stochastic and three-dimensional) phenomenon. The cable is represented by its cross section and it is subjected to mechanical and aerodynamic (considering the rivulet influence) forces. The rivulet is supposed to oscillate along the cable circumference and it is subjected to inertial and gravity forces, pressure gradients and air-water-cable frictions. The model parameters are calibrated by fitting with experimental results. In order to validate the proposed model and its physical basis, different conditions (wind speed and direction, cable frequency, etc.) have been numerically investigated. The results, which are in very good agreement with the RWIV field observations, confirm the validity of the method and its engineering applicability (to evaluate the RWIV sensitivity of new stays or to retrofit the existing ones). Nevertheless, the practical use of the model probably requires a more accurate calibration of some parameters through new and specifically oriented wind tunnel tests.

• Journal of the Society of Disaster Information
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• v.3 no.2
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• pp.95-117
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• 2007

With rapid changes taking place in every field, the expansion and specialization of various social service activities are one of the characteristics of the modem society. However, the increase of crimes and inefficiency of public police service to cope with this situation have caused discontent and distrust on the service among the public, making people more inclined to solve safety-related problems by themselves. Private Security Service(PSS) and Private Investigation Service(PIS) were introduced to satisfy these needs. In the area of PIS, Public Investigation Service System(PISS) has been established for a quite long time in foreign countries. However in Korea, PIS is being provided by unregulated service providers such as errand service center due to the lack of legal system, causing many problems related with illegal practices by the service providers. This paper is the result of the research on how to adopt a relevant PISS in Korea and develop it in the future. This kind of research is much needed to curb the rising illegal practices of the errand service centers, complement the insufficient operation of public police service, and strengthen the competitiveness of our country by taking more efficient actions in the changing public security environment. Based on the research, this paper also examines positively the possibility of introduction of PIS in Korea. This paper also recommends a prompt enactment of PIS regulation and improvement on the legal environment for such introduction of the relevant and suitable PISS in Korea.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.459-475
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• 2018

In the field of aerospace engineering, accurate control of a spacecraft's orientation is often very important to mission success. Therefore, attitude control is a technically plentiful and extensively studied subject in controls literature during recent decades. This investigation of spacecraft attitude control is assumed to address two important aspects of the problem solutions. One sliding mode anti-disturbance control for utilization of faulty actuator components and another one disturbance observer based control to improve the pointing accuracy in the absence of anti-vibration equipment for the elastic appendages like a solar panel. Simultaneous occurrence of vibration due to flexible appendages and reaction degradation due to failure in attitude actuators complicates this case. The advantage of this method is acquisition proper control by the combination of disturbance observer and sliding mode compensation that form a fault tolerant control for the concerned satellite attitude control system. Furthermore, the proposed composite method indicates that occurrence the failure in actuators and even elastic solar panel vibration effect may be handled directly without reconfiguring the control components or providing piezoelectric devices. It's noteworthy, attitude quaternion and angular velocity commands are robustly tracked via controllers to become inclined to zero.