• Journal of Engineering Education Research
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• v.19 no.1
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• pp.3-10
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• 2016

This study was conducted to identify Korea's TRIZ research trends and to propose implications for setting a direction for future TRIZ research by analyzing TRIZ-related research over the past 15 years, or from 1998 to 2013. The subjects in this study were 256 published studies, including 149 studies in academic journals, 97 master theses, and 10 doctorate theses. This study reached the following conclusion. First, academic journals were the most frequent form of publication of TRIZ-related studies, followed by master's degree theses, and doctorate theses. Second, two or more TRIZ tools were used to solve problems and the most frequently used topic was technical contradiction as the result of frequency analysis for TRIZ research topics. This signified that it was easier to solve problems when various TRIZ tools were used, rather than applying a single TRIZ tool while technical contradiction was considered to be actively used as it allowed the relatively easy understanding of TRIZ. Third, the use of TRIZ research topics had increased and diversified each year. This could be interpreted to be based on the increased understanding of TRIZ. Fourth, case studies and experimental research were the most frequently used methods in TRIZ-related research. This was because various TRIZ tools were applied on problem solving situations, which were directly proposed as the research result. Fifth, the use of TRIZ was increasing in the educational field. Specifically, it was noted that TRIZ was used in creativity education with the use of 40 invention principles in elementary, middle, and high schools.

• Korean Institute of Interior Design Journal
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• v.27 no.2
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• pp.175-185
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• 2018

The purpose of this study is to analyze the concept of 'Gradual Differentiation' in parametric design in terms of pure model logic and thus describe the distinctive feature from the previous design method. To meet the purpose, it explores external cases like gradual factor identified in natural phenomenon and artworks and define the inherent model principles into "Self-similarity', "Correlation', and 'Temporality' by examining these features in terms of algorithm. Meanwhile, it identified the principle of gradual model representation in parametric design within a single system called 'Attractor System' by applying these three concepts into specific methods of parametric design, and by interpreting the logical structure through the association among 'Attractor', 'Field', and 'Differentiation'. The creative utilization of parameter shows that gradual model process in parametric design does not mean a passive "conversion process" merely replacing natural parameter with algorithm; rather, it refers to an active "generating process" creating new meanings and value. By continuing this process of conceptual understanding and insight, creative perspective and practical ability to interpret parameter can be improved.

• Journal of Drive and Control
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• v.13 no.4
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• pp.31-44
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• 2016

In recent hydraulic actuation systems, conventional hydraulic spool valves with pressure compensators are becoming less popular, after the introduction of the independent metering concept for valves. Within this concept, four valves are needed for actuating a single cylinder. Subsequently, this increases the freedom of controlling both chamber pressures of the cylinder, and it then provides for electronically-controlled pressure compensation facilities. Additionally, this has the potential to save valuable energy. The primary focus of this paper is to develop a new generation of hydraulic circuits using the independent metering valve (IMV). This configuration can function well as a conventional IMV circuit while providing better pressure control. We first describe the working principles of five distinct modes of the proposed IMV system. Then, mathematical models for each working mode are presented. Finally, we present numerical simulations that have been carried out to evaluate the system performance, in comparison with that of the conventional IMV configuration. The simulation results demonstrate that the performance of the new IMV configuration is superior to the conventional IMV system in terms of energy savings.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.77-84
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• 2013

In this paper, we review two-dimensional measuring methods referring to target patterns. The patterns consist of two linearly-repeated patterns or is designed repeatedly in two-dimension. The repeated properties are reflectivity, refractivity, air-gapping distance, capacitance, magnetic reluctance, electrical resistance and sloping gradient, etc. However, the optical methods are generally used for high speed processing and density, and their encoding principles are treated here. In case of two-dimensional pattern, as there is not inherently error between single units encoding the pattern except for the metrology frame errors, the end-effector position of an object accompanying the pattern can be measured with respect of the global frame without via error. Therefore, it is regarded as a substitute for laser interferometer with severe environmental constraints and has been applied to the high-accurate planar actuator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.822-829
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• 2015

A transfer matrix method has been developed to determine the more accurate natural frequencies for the bending vibration of Bernoulli-Euler beam with linearly reduced width and a concentrated tip mass. The proposed method can be computed an infinite number of the natural frequencies using a single element. Using the differential equation, shear force, and bending moment in which can be deduced by the diverse variational principles, a transfer matrix is formulated. The roots of the differential equation are computed by the Frobenius method. The effect of the concentrated mass for the natural frequencies of width-tapered beams is examined through a parametric study, and to show the accuracy of the proposed method, the computed results compared with those obtained from commercial finite element analysis program(ANSYS).

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.274-277
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• 2003

The Theory of Constraints (TOC) is an approach and a philosophy that is used to develop specific management techniques. It was first popularized by the novel, The Goal, that applied the principles to operations management. Since 1997 it has found application in two areas within project management. The first application is scheduling of a single project to reduce project duration and simplify project control. there is a further application to allocate resources that are shared by concurrent project. It is the objective of this paper to explore the fundamentals of critical chain and to pursue an application of critical chain method to construction project by a case study.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1015-1026
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• 2018

A family of dual-DC-input (DI) dual-buck inverters (DBIs) is proposed by employing a DI switching cell as the input of traditional DBIs. Three power ports, i.e. a low voltage DC input port, a high voltage DC input port and an AC output port, are provided by the proposed DI-DBIs. A low voltage DC source, whose voltage is lower than the peak amplitude of the AC side voltage, can be directly connected to the DI-DBI. This supplies power to the AC side in single-stage power conversion. When compared with traditional DBI-based two-stage DC/AC power systems, the conversion stages are reduced, and the power rating and power losses of the front-end Boost converter of the DI-DBI are reduced. In addition, five voltage-levels are generated with the help of the two DC input ports, which is a benefit in terms of reducing the voltage stresses and switching losses of switches. The topology derivation method, operation principles, modulation strategy and characteristics of the proposed inverter are analyzed in-depth. Experimental results are provided to verify the effectiveness and feasibility of the proposed DI-DBIs.

• Korean Institute of Interior Design Journal
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• v.24 no.6
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• pp.107-118
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• 2015

Today, The representation of the modern space is experimented with shape and surface of the de-structural point of view to make architecture and space, in terms of not being able to make defined by single regulation. However, it can correspond to the rapidly changing modern, but it is easy to fade of architecture fundamental meaning. Along with the need for the rise of the construction of fundamental space, should be built a 'tectonic' spatial, which is said to be building of logos. Tectonic, as norms for expressing the fundamental meaning of architecture, as to expression of construction, be unfolded with dualism such as science and art, technology and express, structure and formation, and it was introduced into the architecture through the construction expression of space that was a tectonic discussion of 19c german architects. On the other hand Constructivism which is avant-garde formative movement with Russia revolution, constructed 'sculpture' with the formative principles as tectonic. Tectonic's Formative characteristics can draw a conclusion with of tectonic characteristics of constructivism sculpture, space of logos will be realized through its study. Other hand, The pavilion, as symbol space, can be analyzed by tectonic properties, Pavilion, meaning the space is expressed in a variety of tectonic expression. As tectonic construction, fundamental ideology and symbolization of space is revealed metaphorically and visually.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1989-2000
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• 2015

In this paper, digital peak current mode control for single phase H-bridge inverters is developed and implemented. The digital peak current mode control is achieved by directly controlling the PWM signals by cycle-by-cycle current limitation. Unlike the DC-DC converter where the output voltage always remains in the positive region, the output of DC-AC inverter flips from positive to negative region continuously. Therefore, when the inverter operates in negative region, the control should be changed to valley current mode control. Thus, a novel control logic circuit is required for the function and need to be analyzed for the hardware to track the sinusoidal reference in both regions. The problem of sub-harmonic instability which is inherent with peak current mode control is also addressed, and then proposes the digital slope compensation in constant-sloped external ramp to suppress the oscillation. For unipolar PWM switching method, an adaptive slope compensation in digital manner is also proposed. In this paper, the operating principles and design guidelines of the proposed scheme are presented, along with the performance analysis and numerical simulation. Also, a 200W inverter hardware prototype has been implemented for experimental verification of the proposed controller scheme.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.68-74
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• 2004

This paper presents a novel hybrid multilevel inverter using DC-Link voltage combination in order to improve the waveshape of output voltage and reduce harmonics. The proposed multilevel inverter can generate an 11-level output voltage. It employs three H-bridge cell, which consists of single phase full-bridge inverter module. Among them, two modules are used for level generation, and one module performs PWM switching. Nine levels are synthesised by the level inverter, and two levels are added to output by the PWM inverter. As a result, it generates an 11-level. The operational principles are explained in depth, and the validity of the proposed system is verified through the PSpice simulation and experimental results based on a prototype.