• 대한공업교육학회지
• /
• v.44 no.2
• /
• pp.65-85
• /
• 2019

This study is aimed to analyze vocational high school teachers' different perceptions on implementing High School Credit System in relation to their teaching subjects(the vocational high schooland the specialized subjects). The result indicates that the specialized subject teachers perceive the value of the prerequisites for implementation of High School Credit System more strongly than the common subject teachers. Otherwise, the result reveals that no significant difference exists between the common subject teachers' perceptions and the specialized subject teachers' perceptions of the external environment improvement, the operational modes, the characteristics of vocational high schools and the factors related to successful implementation of High School Credit System.

• Journal of the Korean Society of Safety
• /
• v.28 no.1
• /
• pp.12-17
• /
• 2013

Considering the wind power system and the rotor blades which are composed of much technology, the wind power blade would be the most dangerous part because it revolves at high speed and weighs about dozens of tons, if the accident happens. Therefore, the light weight composite materials have been replacing as substitutional materials. The object of this study is to examine the delamination and damage for CFRP/GFRP hybrid composite that is used for strength improvement of a wind power blade. The influence of the initial crack length and fiber orientation for the interlaminar delamination was exposed for the blade safety. Plain woven CFRP instead of GFRP was inserted into the layer of the box spar for improving the strength and blade life. DCB(Double Cantilever Beam) specimen was used for evaluating fracture toughness and damage evaluation of interlaminar delamination. The material used in the experiment is a commercial material known as CF 3327 EPC in plain woven carbon prepreg(Hankuk Carbon Co.) and UD glass fiber prepreg(Hyundai Fiber Co.). From the results, crack growth rate is not so different according to the variation of the initial crack length. Mode I interlamainar fracture toughness of fiber direction $0^{\circ}$ is higher than that of $45^{\circ}$. Interlaminar fracture has an effect on fiber direction and K decreased with lower value according to increasing initial crack length. Also energy release rate fracture toughness was evaluated because CFRP/GFRP hybrid composite with a different thickness is under the mixed mode loading condition. The interlaminar fracture was almost governed by mode I fracture even though the mixed mode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.12
• /
• pp.29-35
• /
• 2008

In this paper, The author present a load current feed-forward compensator by method that improve voltage controller of Step-down Chopper to get stable output voltage to sudden change of load current. To confirm the characteristics of a presented load current feed-forward compensator compared each transfer function of whole system that load current feed-forward compensator is added with transfer function of whole system that existent voltage controller is included using Mason gains formula in Root locus and Bode diagram. As a result the pole of system is improved, extreme point of the wave and system improves, and size of peak value and phase margin of break frequency in resonance frequency confirmed that is good. Therefore, presented control technique could confirm that reduce influence by perturbation and improves stationary state and dynamic characteristics in output of Step-down Chopper.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.23 no.1
• /
• pp.123-139
• /
• 1995

The megalopolis citizens are reevaluating the expectant value and the perception of leisure aceording to increasing the level of their incomes, The leisure of citizens is increasing in the aspect of quantity and quality of life nowadays In the site planning of leisure, the concrete understanding about people's choice of a leisure site will be the most important thing, not only for the aspect of improvement of the quality of life but also efficiencies of the land use The purposes of chi study are firstly, to find out the factors which are influenced on a choice of Outdoor leisure facilities in neighbourhood unit and to Compare the Characteristics Of Choice models between the three metropolitan areas, secondly, to predict a limitation of use areal according to the change of a needed time based on the metropolitan's standard choice model For the choice model establishment this research used Logit Model which has been used in the field of the traffic, the tourism and the economics. This research made the results which find out the influencing variables with needed times, the accessibility and the percentage of facilities. The lindtations of use areas come out the results which are predicted according to the change of needed times as a most influencing factors. The range of each preferred leisure facility is about 956 meter distant in the neighbourhood park about 644 meter distant in the pocket park about 604 meter distant in the recreation center, about 628 meter distant in the tennis court about 974 meter distant in the private hob by facility and about 528 meter distant in the library from the apartment unit The recreation center and the library are nearer facilities than the other facilities. But these facilities are surveyed to be more or less influenced by an interesting progran, a context of events and the level of useful facilities, etc.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.29 no.4
• /
• pp.34-43
• /
• 2001

Unlike ordinary recreational facilities, an amusement park consists of various entertainment facilities, attractions, food services, souvenir shops and other attribute. The purpose of this study is to survey users´ responses to such attributes and analyze the importance and performance of each attribute, and thereby, ultimately help improve the efficiency of management and operation of the amusement parks. For this purpose, a survey was conducted of Everland users in August, 1999. 420 users were chosen by means of he systematic sampling. All the suers were asked to rate the importance of 14 attributes of Everland at the entrance and all of them were asked to do the same at the exit. As a result, it was found that the attribute rated highest by the users was ´attraction´, followed by ´service´, ´accessibility´ and ´cost´ in that order. On the other hand, it was found that the total average of importance rated for 14 attributes was 3.31, while that of performance was 3.10. As a consequence of analyzing the action grids, it was found that ´appropriateness of the circulation system´ should be improved most urgently. 7 attributes were categorized as ´keeping up good work´, and 6 ones were rated ´low priority´ in terms of improvement. There was no attribute considered to be ´possible overkill´. Meanwhile, as a result of analyzing the difference among groups in order to determine users´ response depending on their demographic and socio-economic variables, it was found that only the ´age´ variable was significant. It is expected that the results that the results of this study would be useful in determining priorities when improving amusement park facilities or their programs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.807-810
• /
• 2005

Constructed network test environment of wireless base for confidentiality guarantee of data and safe transmission that is transmited at Mobile node of Wireless Network environment in this paper. And, progressed research about IKEv2's Multiple-Key Exchange mechanism for efficient security transmission that use IPSec that is built-in to basis to IPv6 of Mobile environment. Have several key to single terminal to solve that is seam at hand off packet transmission process of Mobile Node in Wireless Network and Re-setting for Key and Re-exchange problem that happen frequently and studied technology that move. Key exchange protocol that is used for an experiment loads basically in MIPv6 and used IKEv2 protocol that is used for management and distribution of reliable encryption key between both end. Using network simulator of SSFNet(Scalable Simulation Framework Network Models) in this paper Key exchange delay value of IKEv2's security transmission analyzing comparison Performance measure and studied about problem and improvement way accordingly.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.9
• /
• pp.2169-2175
• /
• 2014

In this paper we have proposed a new distributed architecture of session-based instant message system, in which multiple servers can distribute loads effectively to improve system extendability. The server of session-based instant message system should manage SIP sessions to transfer instant message with multimedia data to each users, and it should process large amount of presence informations from each users. Therefore load of the server should be distributed as the number of users increases. In our system, when server load increases according to large user numbers, the load are distributed by selecting a server with the lowest load value, or new server is created to allocate the message processing. Therefore the overall load of instant message system can be dynamically distributed. A new presence information data format with added elements for controlling server load has been designed for this purpose, and SIP messages exchanging procedure between servers and users has been also suggested. The performance of our proposed system has been analysed by simulation, and showed improvement of performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.4 no.1
• /
• pp.7-12
• /
• 2003

The purpose of testability analysis is to estimate the difficulty of testing a stuck-at fault in logic circuits. A good testability measurement can give an early warning about the testing problem so as to provide guidance in improving the testability of a circuit. There have been researches attempting to efficiently compute the testability analysis. Conventional testability measurements, such as COP and SCOAP, can calculate the testability value of a stuck-at fault efficiently in a tree-structured circuit but may be very inaccurate for a general circuit. The inaccuracy is due to the ignorance of signal correlations for making the testability analysis linear to a circuit size. This paper proposes an efficient method for computing testability analysis, which takes into account signal correlation to obtain more accurate testability. The proposed method includes the algorithm for identifying all reconvergent fanouts in a given n circuit and the gates reachable from them, by which information related to signal correlation is gathered.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7893-7901
• /
• 2015

It is important to the periodic collection and analysis of the maintenance and management information of bridges for a more safe and efficient management of the bridges. To enhance the reliability and ease of acquisition of the bridge inspection information that is the basis for a strategy for safe and economic management using the bridge management system (BMS), this study develops a smart phone application for bridge inspection and ensures the actual applicability of the application. The developed application that is linked with the BMS for life-cycle management of bridges is possible to real-time query, modify and transmit of the maintenance-related information, and the application is able to greatly relieve the time and cost for the bridge inspection through the automatic creation of site inspection reports. The proposed method using the application is directly or indirectly expected to be very high effects of value improvement, such as ease of use, improved accuracy, sustainability of information, and future utilization, compared to conventional inspection method.

• Transactions on Electrical and Electronic Materials
• /
• v.3 no.3
• /
• pp.21-24
• /
• 2002

Two kinds of $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$, the sintering samples and zone melting samples, were heat-treated under pure Ar at 950$^{circ}C$. The substitution of Nd ion for Ba ion in the $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ before and after the heat treatment was investigated by XRD. In order to confirm the effects of the heat treatment, the Tc and Jc of samples with/without the heat treatment under Ar were comparatively studied. $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ samples were oxygenated under pure oxygen at $300^{circ}C$. From the XRD pattern it was found that the sample with x<0.4 was transferred from tetragonal phase to orthorhombic phase after the oxygenation, while the sample with x>0.4 did not show the phase transition even after a long time oxygenation. Therefore, the low oxygen partial pressure (Ar+1 % O$_2$) was used for the ambient atmosphere of the zone-melting samples, which could reduce the melting temperature and depress the substitution of Nd for Ba. After the improvement in the zone-melting process, the Jc value was increased to 2 x $10^4$A/$cm^2$ (0 T, 78 K). The particle orientation and the structure of zone-melted NdBaCuO were studied by the XRD and SEM analysis.