• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.59-65
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• 2019

In this study, optimal design of direct-drive VCMs (Voice Coil Motor) for a missile fin actuator is carried out. The torque performance and the characteristics of the VCM are predicted by commercial electromagnetic analysis software, ANSYS Maxwell. The optimal design is obtained at the minimum and maximum actuating angles where the aerodynamic load acting on the fin is the largest in the operating range. The critical variables of the actuator is designed and the RSM (Response Surface Method) is used for the optimization. The response surface model consists of second-order functions and its experimental points are selected by a central composite design. This design is widely used for fitting a second-order response surface. The adjustment regression coefficients is computed for adequacy checking of the response surface model. Finally, the torque values obtained by the RSM and the ANSYS Maxwell are shown in good agreement.

• Journal of Family Relations
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• v.22 no.1
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• pp.23-40
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• 2017

Objectives: The major purpose of the study is to examine structural relation among teenager's perception of parenting attitudes, peer attachment, resilience and meaning in life. In order to achieve purpose of the study, we will develop reliable criterion which can measure variable. Method: We will set up structural relational model from relationship between internal and external variables that can influence teenager's meaning in life and we will examine the relationship between variables through structural equation analysis. we will find structural relationship among parenting attitudes, peer attachment, resilience and meaning in life. Results: We analyzed structural relationship among variables targeting 744 middle school and high school students. Teenager's perception of parenting attitudes have positive influence on peer attachment. This shows that teenager perception of fostering attitude have a positive influence even though teenager percepts parent's foster attitude as overprotective or compassionate. However, if teenager percept fostering attitude as overprotective, teenager perception of parenting attitudes doesn't have influence on resilience. Parent's compassionate attitude not only directly influence resilience but also influence resilience through peer attachment. This validates that individual psychological factor, such as how teenager accept and interpret surrounding environment can influence resilience. Peer attachment relationship not only directly influence resilience but also influence meaning of life through resilience. The resilience has direct effect on meaning in life. Conclusions: When one of education goal is to help teenager to find meaning in life and to reach self-realization, We need to have interest in resilience which is known factor for contributing meaning in life. As previous teenager studies has approached this problem, such as maladjustment, delinquency, and depression, it is significant that this study is examined in positive a psychological perspective which focus on healthy adjustment, such as meaning in life based on teenager's resilience and happiness.

• Journal of the Korean Society of Safety
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• v.36 no.1
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• pp.36-43
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• 2021

Effective leadership in safety performance, such as safety leadership, has received attention as a factor that greatly affects safety performance in various high-risk industrial environments. Based on prior research, this study aims to analyze the impact relationship between safety leadership, safety observance, safety education, and safety culture to reveal the effectiveness of safety leadership. In addition, this study will examine the effects of safety leadership on safety observance and safety education to identify the effects of safety understanding. For this purpose, a survey was conducted with employees of an aviation manufacturing company in Gyeongnam. For verification, a positive factor analysis, correlation analysis, and structural equation analysis were conducted using the AMOS 21.0 program. This study's findings show that, first, safety leadership has a positive and significant impact on safety observance and safety education. Second, safety leadership was found to have a direct impact on organizations' safety culture. Third, although safety observance has significant positive effects on safety culture, safety education has often been rejected. Finally, after verifying the control effect of safety understanding, this study uncovered the presence of an adjustment effect in the effect of safety leadership on safety observance. Therefore, based on the results of this study, theoretical and practical implications suggest that through the exercise of safety leadership, managers can improve their organizations' safety culture by increasing organizations' compliance with safety observance and/or acceptance of safety education.

• Advances in nano research
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• v.13 no.6
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• pp.513-525
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• 2022

In this study, it was aimed to evaluate direct oxidation of aqueous solution containing cefalexin antibiotic with new generation Sn/Sb/Ni: 500/8/1 anode. The fact that there is no such a study on treatment of cefalexin with these new anode made this study unique. According to the operating parameters evaluation COD graphs showed clearer results compared to TOC and CLX and thus, it was it was chosen as major parameter. Furthermore, pseudo-first degree kd values were calculated from CLX results to show more accurate and specific results. Experimental results showed that after 60 min of electrochemical oxidation, complete removal of COD and TOC was accomplished with 750 mg L^-1 KCl, at pH 7, 50 mA cm^-2 current density and 1 cm anode-cathode distance. Also, the stability of the Sn/Sb/Ni anode was evaluated by taking SEM and AFM images and XRD analysis before and after of electrochemical oxidation processes. According to the results, it was not occurred too much change on the anode surface even after 300 h of electrolysis. Thus, it was thought that the anode material was not corroded to a large extent. Furthermore, the removal efficiencies were very high for almost all the time and conditions. According to the results of the study, electrochemical oxidation with new generation Sn/Sb/Ni anodes for the removal of cefalexin antibiotic was found very successful and applicable due to require less reaction time complete mineralization and doesn't require pH adjustment step compared to other studies in literature. In future studies, different antibiotic types should be studied with this anode and maybe with real wastewaters to test applicability of the process in treatment of pharmaceutical wastewaters containing antibiotics, in a better way.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.154-160
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• Smart Structures and Systems
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• v.29 no.5
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• pp.661-675
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• 2022

In this paper, an electric vehicle drives with efficient control and low cost hardware using four quadrant DC converter with Permanent Magnet Direct Current (PMDC) motor fed by DC boost converter is presented. The main idea of this work is to improve the energy efficiency of the conversion chain of an electric vehicle by inserting a boost converter between the battery and the four quadrant-DC motor chopper assembly. Consequently, this method makes it possible to maintain the amplification gain of the 4 quadrant chopper constant regardless of the battery voltage drop and even in the presence of a fault in the battery. One of the most important control problems is control under heavy uncertainty conditions. The higher order sliding mode control technique is introduced for the adjustment of DC bus voltage and mechanical motor speed. To implement the proposed approach in the automotive field, experimental tests were carried out. The performances obtained show the usefulness of this system for a better energy management of an electric vehicle and an ideal control under different operating conditions and constraints, mostly at nominal operation, in the presence of a load torque, when reversing the direction of rotation of the motor speed and even in case of battery chamber failure. The whole system has been tested experimentally and its performance has been analyzed.

• Korea Trade Review
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• v.48 no.2
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• pp.1-26
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• 2023

The purpose of this study is to demonstrate how internal capability adjustments made by subsidiaries in response to local market adaption and market changes, together with the use of internal and external networks, have an impact on the investment performance of such subsidiaries. From the empirical results, it was proven that the larger the extent of internal capability adjustment made by subsidiaries, and the more quickly and flexibly it is implemented, the more positive the investment performance is. The empirical findings also showed that in this process, the use of internal/external network embeddedness has a positive mediating impact on the investment performance. Additionally, the results of statistical analysis support the research hypothesis that external embeddedness has a greater mediating influence on multinational manufacturing companies entering Chinese market than internal embeddedness. It implies to the top managers of subsidiaries that the subsidiary should actively utilize external embeddedness to create a new locational competitive advantage in the local region, as well as develop a strategy to reduce foreignness costs such as cost of adapting to the local system.

• Journal of the Korean School Mathematics Society
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• v.17 no.4
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• pp.717-746
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• 2014

The study aimed to explore how to improve mathematical thinking through metacognitive learning by stressing metacognitive abilities as a core strategy to increase mathematical creativity and problem-solving abilities. Theoretical exploration was followed by an analysis of correlations between metacognitive abilities and various ways of mathematical thinking. Various metacognitive teaching and learning methods used by many teachers at school were integrated for sharing. Also, the methods of learning application and assessment of metacognitive thinking were explored. The results are as follows: First, metacognitive abilities were positively related to 'reasoning, communication, creative problem solving and commitment' with direct and indirect effects on mathematical thinking. Second, various megacognitive ability-applied teaching and learning methods had positive impacts on definitive areas such as 'anxiety over Mathematics, self-efficacy, learning habit, interest, confidence and trust' as well as cognitive areas such as 'learning performance, reasoning, problem solving, metacognitive ability, communication and expression', which is a result applicable to top, middle and low-performance students at primary and secondary education facilities. Third, 'metacognitive activities, metaproblem-solving process, personal strength and weakness management project, metacognitive notes, observation tables and metacognitive checklists' for metacognitive learning were suggested as alternatives to performance assessment covering problem-solving and thinking processes. Various metacognitive learning methods helped to improve creative and systemic problem solving and increase mathematical thinking. They did not only imitate uniform problem-solving methods suggested by a teacher but also induced direct experiences of mathematical thinking as well as adjustment and control of the thinking process. The study will help teachers recognize the importance of metacognition, devise and apply teaching or learning models for their teaching environments, improving students' metacognitive ability as well as mathematical and creative thinking.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.1032-1041
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• 2007

The global navigation satellite system (GNSS), which is the core technique for the location based service, adopts the direct sequence/spread spectrum (DS/SS) as its modulation method. The success of a DS/SS system depends on the synchronization between the received and locally generated pseudo noise (PN) signals. As a step in the synchronization process, the tacking scheme performs fine adjustment to bring the phase difference between the two PN signals to zero. The most widely used tracking scheme is the delay locked loop with early minus late discriminator (EL-DLL). In the ideal case, the EL-DLL is the best estimator among various DLL. However, in the band-limited multipath environment, the EL-DLL has tracking bias. In this paper, the timing offset range of correlation function is divided into advanced offset range (AOR) and delayed offset range (DOR) centering around the correct synchronization time point. The tracking bias results from the following two reasons: symmetry distortion between correlation values in AOR and DOR, and mismatch between the time point corresponding to the maximum correlation value and the synchronization time point. The former and latter are named as the type I and type II tracking bias, respectively. In this paper, when the receiver has finite bandwidth in the presence of multipath signals, it is shown that the type II tracking bias becomes a more dominant error factor than the type I tracking bias, and the correlation values in AOR are not almost changed. Exploiting these characteristics, we propose a novel tracking bias mitigation scheme and demonstrate that the tracking accuracy of the proposed scheme is higher than that of the conventional scheme, both in the presence and absence of noise.

• Applied Microscopy
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• v.34 no.1
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• pp.13-21
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• 2004

The high voltage electron microscope (HVEM) newly installed in KBSI is an advanced transmission electron microscope capable of atomic resolution (${\leq}1.2{\AA}$ point-to-point resolution) together with high titling function (${\pm}60^{\circ}$), which are suitable to do 3-dimensional atomic imaging of a specimen. In addition, the instrument can be controlled by remote operation system, named as 'FasTEM' for the HVEM, which is favorable to overcome some environmental obstacles resulting from the direct operation. The FasTEM remote operation system has been established between the headquarter of KBSI in Daejeon and the Seoul branch. The server system in the headquarter has been connected with a portable client console system in the Seoul branch using an advanced internet resource, 'KOREN' of 155 Mbps grade. Most of the HVEM functions essential to do remote operation are available on the portable client console. The experiment to acquire the high resolution image of [001] Au has been achieved by excellent transmission of control signals and communication with the HVEM. Real-time reaction like direct operation, such as controls of the illumination and projection parameters, acquisition and adjustment of each detector signal, and electrical steering of each motor-driven system has been realized in remote site. It is positively anticipated that the first remote operation of HVEM in conjunction with IT infraengineering plays a important role in constructing the network based e-Science Grid in Korea for national user s facilities.