• Journal of the Korean Mathematical Society
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• v.56 no.2
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• pp.539-558
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• 2019

An ideal of a commutative ring is called a d-ideal if it contains the annihilator of the annihilator of each of its elements. Denote by DId(A) the lattice of d-ideals of a ring A. We prove that, as in the case of f-rings, DId(A) is an algebraic frame. Call a ring homomorphism "compatible" if it maps equally annihilated elements in its domain to equally annihilated elements in the codomain. Denote by $SdRng_c$ the category whose objects are rings in which the sum of two d-ideals is a d-ideal, and whose morphisms are compatible ring homomorphisms. We show that $DId:\;SdRng_c{\rightarrow}CohFrm$ is a functor (CohFrm is the category of coherent frames with coherent maps), and we construct a natural transformation $RId{\rightarrow}DId$, in a most natural way, where RId is the functor that sends a ring to its frame of radical ideals. We prove that a ring A is a Baer ring if and only if it belongs to the category $SdRng_c$ and DId(A) is isomorphic to the frame of ideals of the Boolean algebra of idempotents of A. We end by showing that the category $SdRng_c$ has finite products.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2791-2796
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• 2007

In their long journey through the cardiovascular circuit, erythrocytes are coerced to shape transform and assume different shapes on account of varying flow conditions in different blood vessels. The present work was aimed to visualize these erythrocyte shape transformations by an invitro microcirculatory model, and assess multi-shape erythrocyte deformability. The model uses an in-house fabricated, inexpensive disposable micro flow channel to mimic certain invivo conditions and a fast frame video microscopic system for imaging the shape changes in erythrocytes. Results show the multi-shape transformation of erythrocyte christened as discoidal shape, the asymmetrically deformed 'hat' and 'bullet-like' shapes, and the axially deformed 'slipper' and 'spindle-like' shapes. Specific erythrocyte showed the shape transition and transformation while passing through the observed window. The obtained erythrocyte shapes very analyzed for deformability index using image processing techniques that varied significantly (p <0.001) for different shapes as compared with the resting shape.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.720-724
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• 2004

This paper introduces a new type of driving mechanism for rescue robot that has a variable geometry single-track which satisfies the pre-conditions of rescue robot. This mechanism is a symmetric configuration that has dual directions and prepares against overturn. By using transformation, it can reduce the energy consumption in steering and rotating. And also it maximizes the ability to overcome obstacles, like steps. It is designed to make the size of robot compact and to have the low center of gravity in driving on steps. Finally, we optimized the design variables of components determining the shape of reverse-trapezoid frame to enhance the adaptability to 4 phases of climbing steps.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.17-23
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• 2013

The regulation of currents in a three-phase load is an important issue for electric power systems. The most popular conventional method is a decoupling controller that compensates the coupling terms arising from DQ rotating frame transformation. Although the decoupling controller achieves decent performance in the absence of load parameter uncertainties, the variation of parameters causes performance to degrade intolerably. In this paper, we propose to use disturbance observer based controller to improve the control performance in spite of the parameter uncertainties. The computer simulation study validates the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.6
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• pp.380-386
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• 2000

This paper presents the mathematical modelling analysis of Brushless Synchronous Motor(BLSM). The dynamic and the steady state characteristics of BLSM are simulated and analyzed : electromagnetic torque, speed, line voltage, and current. We used mathematical modelling to model of BLSM with sinusoidal back EMF, namely the shaft transformation referencing rotor frame from a, b, c three to produce constant torque like synchronous motor. The experiment result has already similar to compare with simulation result : torque error about 7%, speed error about 5%. The validity of proposed modelling and analysis was confirmed by the experimental result.

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.348-353
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• 2007

The propagation of a macro-scale crack and the accompanying transformation zone around it was visualized in an Y-TZP ceramic using a mechano-luminescence (ML) technique. The technique allows realistic fractures that take place catastrophically in actual applications to be realistically stimulated. Unlike conventional quasi-static R-curves, the ML technique on a relatively fast time frame permitted a so-called quasi-dynamic R-curve in the crack speed range from 50 to 140 m/sec. to be measured. Effective toughening then commenced and the applied stress intensity factor increased to 27 $MPa{\sqrt{m}}$. The transformation zone height obtained from the ML observations was in good agreement with that predicted by the Marshall model, and coincided with previously observed results for quasi-static conditions by Raman spectorscopy and x-ray analysis.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.197-204
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• 2003

This study proposes a method to reduce errors in scanning object and registration using a laser scanner. The method consists of 3 stages. First, there is an error induced by the difference of the distance between the probe and the object. It is possible to reduce the error by planning a scanning strategy: object setting, scan path. Second, the scan data of the tooling ball affects calculating the tooling ball center. A z-direction compensation is given to calculate more accurate registration points. Third, three points are used to determine a coordinate transformation on each frame. The maximum error usually lies on the third tooling ball in the conventional merging method. LSM (Least Square Method) is applied to a coordinate transformation to reduce the registration error.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.1001-1008
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• 2003

A time-delay compensation method for vector control system is proposed that can compensate for voltage and current distortions resulting from a time delay in the overall system due to the low pass filter, hysteresis control inverter, microprocessor program computation time, and so on. The proposed scheme estimates the time delay using the difference between the Q-axis stator current command and the time-delayed actual Q-axis stator current in a synchronous reference frame, then compensates the time delay in the voltage and current using the angular displacement of a DQ transformation. Accordingly, the proposed scheme can accurately compensate for the time delay related to the overall system, thereby significantly improving the performance of the vector control system, as verified by simulation and experiment.

• Journal of the Korean Society of Visualization
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• v.8 no.4
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• pp.26-30
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• 2010

A PTV algorithm was constructed using a linear transformation, in which the merits of the conventional PIV and PTV were adopted. In PIV calculations, the obtained velocity vectors are affected by the filtering effects by its calculation principle. PTV techniques are widely used for their excellences of measuring small scaled flows, such as nano and bio flows. However, PTVs produce vector errors due to interpolation process. To overcome these problems, a hybrid PTV algorithm was constructed by combining PTVs' and PIVs' benefits using a linear transformation. The Taylor-Green vortex flows were generated for the tests of vorticity calculations. The conventional gray-level cross-correlation PIV technique and 2-Frame PTV technique were tested for the same flows for comparisons with those obtained by the constructed hybrid algorithm. The excellence of the constructed hybrid algorithm was validated through an actual experiment on the cylinder wake.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.145-152
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• 1995

A general stiffener element which includes transverse shear deformation(TSD) is formulated using the p-version of finite element method. Hierarchic C"-shape functions, derived from Integrals of Legendre polynomials, are used to define the assembled stiffness matrix of the stiffener and plate on the basis of 5 D.0.F displacement fields. The stiffness matrix for the stiffener with respect to the local reference frame is transformed to the plate reference system by applying the appropriate transformation matrices in order to insure compatibility of displacements at the junction of the stiffener and plate. The transformation matrices which account for the orientation and the eccentricity effects of the stiffener with respect to the plate reference axes are used to find local behavior at the junction of the stiffener and the relative contributions of the plate and stiffener to the strength of the composite system. The results obtained by the p-version of the finite element method are compared with the results in literatures, especially those by the h-version software, MICROFEAP-II.P-II.