• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.4
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• pp.177-187
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• 2018

The purpose of this study is to investigate the influence of learning flow, learning interest, and academic achievement by dividing the time when class was taught by Havruta. The Havruta teaching method is a traditional Jewish method of learning, with a one-on-one discussion with a partner that has a positive impact on each other. Havruta teaches learners through various perspectives and perspectives, helping them to improve their learning ability by attracting new ideas and solutions. In the computer lab, there is a big difference between the students according to the learner's abilities. Therefore, it is thought that the Havruta teaching method will help the learners who have lost interest in learning and improve the learning ability in the conventional way which does not consider personal abilities. do. In this paper, based on the friendship teaching model of the Havruta teaching style, the experimental group was taught through the Havruta practice and the play. Through the pre- and post-test, the students who taught the class with the help of the verbal method improved the learning flow, the learning interest and the academic achievement.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.411-416
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• 1999

The measurement of unsteady flow rate is of vital importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and system. There is also demand for a real time flow sensor of ability to measure unsteady flow rate with high accuracy and fast response to realize feedback control of flow rate in fluid power systems. In this paper, we propose an approach for estimating unsteady flow rate through a pipeline and components under high pressure condition. In the method, unsteady flow rate is estimated by using hydraulic pipeline dynamics and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-checking functions of the method, the validity is investigated by comparison with the measured and estimated pressure waveforms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate waveforms and theroetical those under unsteady laminar flow conditions. the method proposed here is useful in estimating unsteady flow rate through an arbitray cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.995-1002
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• 2012

In a refrigerator, many food boxes are stored, so the flow of chilly air has very complicate stream paths inside the room of a refrigerator. Moreover, on some occasions, there is no flow of chilly air in a space due to blocking flow paths by food boxes, which is an important issue to be settled for improving the ability of food storage with fresh states. One of methods to solve this problem is to redesign the flow-pattern of chilly air to be uniform flow inside room, if possible. In this work, we have tried to design the duct-structure for the uniform flow of a chilly air using a FE-analysis method. And we conducted real commercial tests using a refrigerator having the redesigned duct. The results showed that good agreements with general requirements.

• Journal of Engineering Education Research
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• v.20 no.4
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• pp.61-66
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• 2017

Automatic flow control system composed by hardware and software was designed and fabricated to be used as teaching tool of feedback control theory in university experimental class. This system includes hardwares like data acquisition board, flow measuring device, transmitters, and the pneumatic valve, and software like LabView program for the monitoring and control of flow rates. The system was designed as the student can see the control effect of not only set point but also disturbance changes. Also the LabView program was composed for the calculation of controller parameters of both Ziegler-Nichols and Cohen-Coon tuning. The students can apply both tuning constants and compare the control performances. This system will provide the easy way for the students to understand the function and specification of control hardwares, and to raise the programing ability of control software.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1586-1592
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• 2017

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.757-761
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• 2009

Axial-flow cyclone separator cluster can be used for a dust removal device inside a heating, ventilation, and air conditioning(HVAC) system of subway station. In this study, 3-dimensional computational fluid dynamics(CFD) analysis was performed to compare single unit axial-flow cyclone with couple unit axial-flow cyclone cluster. It is shown that the performance of cyclone separator is not influenced by number of single units but influenced by ability of single unit.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.3
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• pp.315-320
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• 1998

In this paper, we present the PID control method for the controlling flow rate of highly complicated nonlinear Left Ventricular Assist Device(LVAD) with pneumatically driven mock circulatory system. Beat Rate (BR), Systole-Diastole Rate (SDR) and flow rate are used as the main variables of the LVAD system. System modeling is completed using the neural network with input variables (BR, SDR, their derivatives, actual flow) and an output valiable(actual flow). Then, as the basis of this model, we perform the simulation of PID control to predict the performance and tendency of the system and control the flow rate of LVAD system using the PID controller. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated through computer simulation and experiments.

• Journal of Practical Engineering Education
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• v.9 no.2
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• pp.91-98
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• 2017

To produce highly creative students, engineering education must develop both problem recognition skills and the ability to solve problems independently. Chonnam National University has been developing a creativity program in which students identify and solve problems themselves. Initially, the primary focus was on solving problems, but this was unsuccessful at attracting the students' interest. To overcome this, we adopted Csikszentmihalyi's flow theory in our creativity program, much like the way this theory is used in computer games. As a result of adopting flow theory, we achieved our goal. Thus, in this paper, we will introduce Chonnam National University's creativity program (designed based on flow theory), which we will call the Self-Directed Creativity-Upgrade Program. Furthermore, we will discuss the impact of this program based on statistical analyses.

• Journal of Pharmaceutical Investigation
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• v.37 no.3
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• pp.137-148
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• 2007

Using a strain-controlled rheometer [Rheometrics Dynamic Analyzer (RDA II)], the steady shear flow properties of a semi-solid ointment base (vaseline) have been measured over a wide range of shear rates at temperature range of $25{\sim}60^{\circ}C$. In this article, the steady shear flow properties (shear stress, steady shear viscosity and yield stress) were reported from the experimentally obtained data and the effects of shear rate as well as temperature on these properties were discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters (yield stress, consistency index and flow behavior index). Main findings obtained from this study can be summarized as follows : (1) At temperature range lower than $40^{\circ}C$, vaseline is regarded as a viscoplastic material having a finite magnitude of yield stress and its flow behavior beyond a yield stress shows a shear-thinning (or pseudo-plastic) feature, indicating a decrease in steady shear viscosity as an increase in shear rate. At this temperature range, the flow curve of vaseline has two inflection points and the first inflection point occurring at relatively lower shear rate corresponds to a static yield stress. The static yield stress of vaseline is decreased with increasing temperature and takes place at a lower shear rate, due to a progressive breakdown of three dimensional network structure. (2) At temperature range higher than $45^{\circ}C$, vaseline becomes a viscous liquid with no yield stress and its flow character exhibits a Newtonian behavior, demonstrating a constant steady shear viscosity regardless of an increase in shear rate. With increasing temperature, vaseline begins to show a Newtonian behavior at a lower shear rate range, indicating that the microcrystalline structure is completely destroyed due to a synergic effect of high temperature and shear deformation. (3) Over a whole range of temperatures tested, the Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have an almostly equivalent ability to quantitatively describe the steady shear flow behavior of vaseline, whereas the Bingham, Casson,and Vocadlo models do not give a good ability.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.269-278
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• 2020

The purpose of this study is to verify the effectiveness of problem-based learning on self-directed learning ability and learning flow of junior college students. The study was conducted on 248 students from five departments who participated in the faculty learning community program, which was supported by the Center for Teaching and Learning Development at D University in Busan. The effectiveness of the survey conducted before and after the application of the problem-based learning method was examined to show statistically significant changes in both self-directed learning ability and learning flow. A survey on satisfaction with the problem-based learning method showed that 66.2% of all students were satisfied with their classes overall, and 64% of the respondents said that the problem-based learning method helped them understand the course, which allowed them to verify the effectiveness of the study method. This research is meaningful in that it can be used as a basic data for the search for learner-centered education methods required by the era of the fourth industrial revolution.