• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.9
• /
• pp.24-32
• /
• 2020

A self-blast type gas circuit breaker has been studied in this study to improve efficiency of interrupting performance of short line fault(SLF). Hot gas flows of gas circuit breaker have been simulated to evaluate interruption performance using CFD. Design parameters such as various types of expansion chamber and nozzles are suggested by using simulation results. Simulated results and experimental ones are compared with previous (ones that of in under development and with capacitor) GCB. Modified new shape of an expansion chamber and nozzle has been suggested to improve the efficiency of gas flow and to provide guidelines for designing self-blast breaker with a higher interruption capability.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.3
• /
• pp.1785-1801
• /
• 2017

In recent years, image encryption algorithms have been developed rapidly in order to ensure the security of image transmission. With the assistance of our previous work, this paper proposes a novel chaotic image encryption algorithm based on self-adaptive model and feedback mechanism to enhance the security and improve the efficiency. Different from other existing methods where the permutation is performed by the self-adaptive model, the initial values of iteration are generated in a novel way to make the distribution of initial values more uniform. Unlike the other schemes which is on the strength of the feedback mechanism in the stage of diffusion, the piecewise linear chaotic map is first introduced to produce the intermediate values for the sake of resisting the differential attack. The security and efficiency analysis has been performed. We measure our scheme through comprehensive simulations, considering key sensitivity, key space, encryption speed, and resistance to common attacks, especially differential attack.

• Journal of Internet Computing and Services
• /
• v.7 no.6
• /
• pp.131-141
• /
• 2006

In many papers, item difficulty does apply to the E-Learning system for advance learning effect. But there have to need item revision difficulty for more correct item difficulty. Also, there have to support self-directed learning process which learner can make plan and operate learning progress. In this research, I developed self-directed E-Learning system using item revision difficulty. For efficiency of system development, il is implemented and composited by component based development. In the applied result, it was able to support more correct item revision difficulty to learner. And I displayed efficiency of operation the component based self-directed learning system.

• Korean Journal of Childcare and Education
• /
• v.6 no.2
• /
• pp.117-133
• /
• 2010

The purpose of this research is to find out whether children's self-efficacy can be improved by sensory activities devised to encourage spirituality. The survey involved 36 children aged 4 to 5. To measure the subjects' self-efficacy, Jeon Inok(1996)'s tool was used. The 18 members of the experimental group attended a program which was dedicated to promoting spirituality by using sensory activities. The program was administered three times a week for four weeks, totaling 12 sessions, each of which contained a type of activity and lasted about fifty minutes. To the 18 members of the control group, the standard child care curriculum was applied. The levels of the subjects' self-efficacy were measured twice, both in the same way, before and after the children participated in the program. The finding reveals that the program which was designed to boost children's spirituality through sensory activities has positive effect on children's self-efficiency - cognitively, socially, emotionally, and physically. The self-efficiency level in the experimental group significantly increased by t=7.17(df=34, p<.001) compared to the control group. So, it can be said that the program dedicated to improving spirituality using sensory activities is more effective than the standard child care curriculum.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.13 no.4
• /
• pp.295-300
• /
• 2015

The precise determination of the activity for each radionuclide in environmental samples requires the self-absorption correction factor. In this research, we derived the self-absorption correction factor for three p-type high purity germanium detectors using the Monte Carlo code MCNPX. These detectors have different characteristics such as crystal diameter, height and size of the core. We compared the calculated full-energy peak efficiency with the experimental value using a standard sample with $1g/m^3$ density and verified the modeling. We simulated the dependency of the full-energy peak efficiency on the 0.3, 0.6, 0.9, 1.0, 1.2 and $1.5g/m^3$ samples and obtained the corresponding self-absorption correction factor. The self-absorption correction factors calculated for the three detectors differ by less than 1% over most of the energy range and sample densities considered. This indicates that the self-absorption correction factors are independent of the crystal characteristics of HPGe detector.

• Journal of Convergence for Information Technology
• /
• v.9 no.10
• /
• pp.144-153
• /
• 2019

The purpose of this study is to investigate the structural correlation between career decision making self-efficacy, major satisfaction and occupation value of beauty major students by questionnaire collection and statistical analysis. Major satisfaction was found to be statistically significant at the significance level of .05 with respect to coccupation value and career decision making self-efficacy at p<.001. Occupation value was found to be statistically significant at p<.001 for career decision and job decision of career decision making self-efficacy and significance level .05. Therefore, it has been confirmed that the major satisfaction and job value are the factors that play a significant role in the self-efficiency of career decisions, and it is believed that continuous research on various variables that affect the self-efficiency of career decisions of beauty major university students is necessary.

• Journal of Ship and Ocean Technology
• /
• v.10 no.4
• /
• pp.1-11
• /
• 2006

The finite volume based multi-block RANS code, WAVIS developed at MOERI is applied to the numerical self-propulsion test. WAVIS uses the cell-centered finite volume method for discretization of the governing equations. The realizable $k-{\epsilon}$ turbulence model with a wall function is employed for the turbulence closure. The free surface is captured with the two-phase level set method and body forces are used to model the effects of a propeller without resolving the detail blade flow. The propeller forces are obtained using an unsteady lifting surface method based on potential flow theory. The numerical procedure followed the self-propulsion model experiment based on the 1978 ITTC performance prediction method. The self-propulsion point is obtained iteratively through balancing the propeller thrust, the ship hull resistance and towing force that is correction for Reynolds number difference between the model and full scale. The unsteady lifting surface code is also iterated until the propeller induced velocity is converged in order to obtain the propeller force. The self-propulsion characteristics such as thrust deduction, wake fraction, propeller efficiency, and hull efficiency are compared with the experimental data of the practical container ship. The present paper shows that hybrid RANS and potential flow based numerical method is promising to predict the self-propulsion parameters of practical ships as a useful tool for the hull form and propeller design.

• Journal of IKEEE
• /
• v.25 no.1
• /
• pp.206-211
• /
• 2021

This paper proposes a Self-Reset Zero-Current Switching (ZCS) Circuit for thermoelectric energy harvesting. The Self-Reset ZCS circuit minimizes the operating current consumed by the voltage comparator, thereby reduces the power consumption of the energy harvesting circuit and improves the energy conversion efficiency by adding the self-reset function to the comparator. The Self-Reset ZCS circuit shows 3.4% of improvement in energy efficiency compared to the energy harvesting system with the conventional analog comparator ZCS for the output/input voltage ratio of 5.5 as a result of circuit simulation. The proposed circuit is useful for improving the performance of the wearable and bio-health-related harvesting circuits, where low-power and energy-efficient thermoelectric energy harvesting is needed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.21 no.5
• /
• pp.474-481
• /
• 1997

Waterjet propulsion generally refers to propulsion of ships by internally mounted pumps with proper ducting. This arrangement of the actuator component of the system leads to the fundamental differences with respects to screw propeller system. In this paper, the basic hydrodynamic characteristics of waterjet propulsion was outlined to clarify the application consideration and proposal for carrying out model self-propulsion tests with waterjet propelled models was presented. The results of model self-propulsion tests carried out in the Hyundai Maritime Research Institute towing tank with catamaran ship were presented.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.807-810
• /
• 1998

This paper presents BIST (Built-in self-test) techniques for detection of path delay faults in digital circuits. In the proosed BIST schemes, the shift registers make possible to concurrently generate and compact the latched test data. Therefore the test time is reduced efficiently. By reordering the elements of th shifte register based on the information of the hamming distance of each memory elements in CUt, it is possible to increase the number of path delay faults detected robustly/non-robustly. Experimental results for ISCAS'89 benchmark circuits show the efficiency of the proposed BIST techniques.