• Education of Primary School Mathematics
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• v.18 no.2
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• pp.155-173
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• 2015

The purpose of this study is to offer the implication for elementary school mathematics teaching by analyzing teachers' reflection on the cognitive demands of mathematical tasks they give in class. During the setup phase and the implementation phase in math class, the researchers analyzed the change of cognitive demands on mathematical tasks and the factors which had influence on such changes. After teachers' reflection on teaching, the researchers analyzed the change of cognitive demands on mathematical tasks and the factors which had influence on such changes in math classes. As a result, before teachers' reflection on the cognitive demands of mathematical tasks, the higher-level demands of mathematical tasks had a tendency to decline. However, after teachers' reflection on the cognitive demands of mathematical tasks, higher-level demands of mathematical tasks were maintained.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.283-292
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• 2011

This paper proposed a new multi-level inverter topology based on a H-bridge with two switches and two diodes connected to the DC-link. The output voltage of the proposed topology is quite closer to a sinusoidal waveform compared with a typical single phase inverter. The proposed multi-level inverter is applicable to a power conditioning system for renewable energy sources, and it can be also used as a building block of a cascaded multi-level inverter for a high voltage application. In case of conventional H-bridge type or NPC type multi-level inverter, 8 controllable switches are used to obtain a 5 level output voltage, but the proposed multi-level inverter requires only 6 controllable switches. Thus the circuit configuration is quite simple, reliable and cost-effective implementation is possible. The efficiency can be improved owing to the reduction of the switching loss. A new PWM method based on POD modulation is suggested which requires only one carrier signal. The switching sequence to make the capacitor voltage balanced is also considered. The feasibility is studied through simulation and experiment.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.59-64
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• 2006

The broadband power detector for power amplitude envelope detection of the direct-conversion Six-port output signal was designed and implemented in this paper. The power detector should be linearly operated to produce the linear amplitude and phase signal for input RF signals in required broadband frequency range. The power detector should be designed under conditions of matching circuit with low VSWR, which protect unbalanced phase signal from reflection signal due to mismatch between the output port of a six-port and the input port of a power detector. The designed power detectors, which were implemented in L-band with 50 ohm matching and Ku-band with multiple LC matching circuits and isolator, respectively, were analyzed in viewpoints of the utilization as a power detector of direct conversion Six-port. The dynamic range of designed power detectors were also measured and rvaluated as a power detector of Six-port circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.420-429
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• 2004

This paper proposes a novel current control strategy on active power filters using PQR instantaneous power theory which can compensate the line current harmonics and the neutral line current under the unbalanced and/or distorted source conditions in three-phase four-wire systems. The characteristics of the inverter ac filters are analyzed and a novel digital controller are proposed to overcome the inherent time delay problem in digital controllers with designed control gain in this paper. The proposed current control method is based on a sinusoidal PWM for fully-digital implementation compared with a conventional hysteresis PWM. PSiM simulation results verify the good performance of the proposed current control strategy on shunt type APFs.

• The KIPS Transactions:PartD
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• v.11D no.2
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• pp.259-268
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• 2004

For supporting Interoperability among heterogeneous data sources in different geographic information systems, it is required to use open API like OGIS OLE DB Proposed in OGC. The OLE/COM Implementation Specification of OGIS only provides interfaces to discover and access spatial data, but does not support interfaces for updating distributed spatial data. To solve this problem, we propose and add interfaces for updating spatial objects distributed over heterogeneous data sources and examining the consistency of spatial relationships between updated objects. We also devise a 2-phase commit protocol based on spatial relationships in order to guarantee the consistency of updated objects. To justify the update scheme using the proposed Interfaces and 2-phase commit prototype we design and implement a prototype system for updating distributed spatial objects.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.5
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• pp.503-510
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• 2011

This paper presents a method of optimizing the blade pitch and generator torque controllers which have been already designed for an existing wind turbine generator system. Since the highly nonlinear and uncertain characteristics of the wind turbine generator can not be fully considered in the controller design phase, some parameters such as control gains must be tuned during the field implementation phase. In this paper, nonlinear simulation software, which is based high fidelity wind turbine model, and optimization technique are effectively combined and used to tune a set of gains for the blade pitch and the generator torque controllers. Simulation results show that the baseline controllers can be effectively optimized to reduce the errors in wind turbine rotor speed and generator power output controls as well as twisting of the high and low speed shafts.

• The Journal of the Korea Contents Association
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• v.17 no.5
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• pp.221-233
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• 2017

To survive in the ever-changing environment, organizations need to improve or innovate their business processes. As a result, to attain this objective, BPM (Business Process Management) concept is widely adopted in modern enterprises. BPM life cycle consists of diagnosis, design, implementation and enactment. Conventionally, diagnosis of business process within the BPM life cycle is usually conducted by manual methods such as interviews, questionnaires and direct observations of process. And (re)designing business processes is also usually done manually under supervision of business experts from scratch. It is time-consuming and error-prone tasks. The objective of this research is to integrate the diagnosis and (re)design phase of BPM life cycle by sharing automatically generated process model and basic statistics in the diagnosis phase based on the process mining method. Eventually, this approach will lead to automate the tasks of diagnosis and design of business process. To implement and to show the usefulness of the proposed framework, two case studies were conducted in this research.

• Journal of KIISE:Software and Applications
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• v.33 no.3
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• pp.301-315
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• 2006

In component-based system, the qualities of components as reusable units are the most important to success the component-based development. Therefore, before software implementation phase, the designed components should be measurable to improve the qualities of the components and the measured results should be reflected in the component-based development phase. In addition, the qualities of the components should be measured accurately. Accordingly, this paper proposes cohesion and coupling metrics applying static and dynamic dependency characteristics by the interdependence between classes. We prove the theoretical soundness of the proposed metrics by the axiom of briand et al. A case study and a comparison with the conventional metrics verify the practicality of the proposed metrics. The development times and endeavors to design the components is reduced, because the proposed metrics measure the qualities of components accurately.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.209-216
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• 1999

KITSAT-3, the third satellite of KITSAT series which has been developed for the last four and half years with purely Korean design and implementation technology, was launched successfully at last. All subsystems were tested and validated during the initial operation of the satellite. During the initaial operation phase, the Earth imaging camera on board KITSAT-3 acquisited several tens of scenes all over the world and transmitted the image data to ground station. The quality of images and the reliability of data transmission-reception system were tested qualititively and quantititively, respectively. In this paper, we summarize the camera, data handling, on-board memory, and image data transmission system of KITSAT-3 as well as the image receiving and archiving system in ground station. The error rate of image data transmission and reception was tested during the initial operation phase. The average data transmission error rate satisfied the initial requirement of less than 1%. The error rate will be reduced through the continuous work of test and stabilization of the ground system hardware.

• The Research Journal of the Costume Culture
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• v.28 no.6
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• pp.771-786
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• 2020

This study aims to develop a life-friendly, wrap-one-piece style dance sports practice wear considering the physical characteristics of middle-aged, abdominally obese women. These types of practice wear allow people to enjoy exercise easily and to wear these garments as daily wear while meeting the requirements for dance sports wear. The three participants selected for this study were all women with five or more years of dance sports experience and were all average sized on Korea's abdominal obesity scale. In the first phase of the study, practice wear was created in a total of nine styles with three different styles of neckline depths for three different styles of dress skirt lengths. In the second phase of the study, the practice wear was created in 15 styles with five different styles of sleeve lengths for three different styles of waistline heights. After analyzing the design preferences of the participants, the fit preferences of the designs were evaluated and the final appearance was analyzed in order to suggest a pattern. The results of the subjects' first and second preference evaluations showed a preference for a 10 centimeter neckline depth, for high waistlines, and for elbow to wrist-length sleeves. The implementation of this research is expected to be extensive, as its results can be used as basic data for making lifestyle dance sports practice wear that covers the physical insecurities of middle-aged, abdominally obese women and enables them to enjoy their leisure time.