• Investigative Magnetic Resonance Imaging
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• v.23 no.1
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• pp.1-16
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• 2019

Dynamic contrast enhanced (DCE) magnetic resonance (MR) imaging plays an important role in non-invasive detection and characterization of primary and metastatic lesions in the liver. Recently, efforts have been made to improve spatial and temporal resolution of DCE liver MRI for arterial phase imaging. Review of recent publications related to arterial phase imaging of the liver indicates that there exist primarily two approaches: breath-hold and free-breathing. For breath-hold imaging, acquiring multiple arterial phase images in a breath-hold is the preferred approach over conventional single-phase imaging. For free-breathing imaging, a combination of three-dimensional (3D) stack-of-stars golden-angle sampling and compressed sensing parallel imaging reconstruction is one of emerging techniques. Self-gating can be used to decrease respiratory motion artifact. This article introduces recent MRI technologies relevant to hepatic arterial phase imaging, including differential subsampling with Cartesian ordering (DISCO), golden-angle radial sparse parallel (GRASP), and X-D GRASP. This article also describes techniques related to dynamic 3D image reconstruction of the liver from golden-angle stack-of-stars data.

• Current Optics and Photonics
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• v.6 no.5
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• pp.473-478
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• 2022

To overcome the capture-range problem in phase-diversity phase retrieval (PDPR), a geometrical-optics initial-estimate method is proposed to avoid a local minimum and to improve the accuracy of laser-wavefront measurement. We calculate the low-order aberrations through the geometrical-optics model, which is based on the two spot images in the propagation path of the laser, and provide it as a starting guess for the PDPR algorithm. Simulations show that this improves the accuracy of wavefront recovery by 62.17% compared to other initial values, and the iteration time with our method is reduced by 28.96%. That is, this approach can solve the capture-range problem.

• The Pure and Applied Mathematics
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• v.19 no.2
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• pp.147-169
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• 2012

We introduce a Heaviside-function formulation of the interaction between incompressible two-phase fluid and a non-deformable solid. Fluid and solid interact in two ways : fluid satises the Dirichlet boundary condition imposed by the velocity field of solid, and solid is accelerated by the surface traction exerted by fluid. The two-way couplings are formulated by the Heaviside function to the interface between solid and fluid. The cumbersome treatment of interface is taken care of by the Heaviside function, and the interaction is discretized in a simple manner. The discretization results in a stable and accurate projection method.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.363-367
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• 2010

A new two step on-axis digital holography (DH) is proposed without any assumptions, phase shifting, or complicated optical components. A dual-channel Mach-Zehnder interferometer was employed. Using that setup, the object field can be reconstructed requiring only two step measurements. To eliminate position difference between two charge-coupled device (CCD) cameras, a matched filter algorithm was used. Experimental results are compared to those of the traditional phase shifting technique. The proposed approach can also be applied to single-exposure on-axis DH for real time measurement.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.425-428
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• 1999

The radar interferogram represents phase differences between the two synthetic aperture radar observations acquired in slightly different angle. The success of the radar interferometric application largely depends on the quality of the interferogram generated from two or more synthetic aperture radar data sets. We propose here to apply the wavenumber correlation analysis to the in-phase and quadrature phase of the radar interferogram. The wavenumber correlation analysis is to resolve the highly correlated components from the low correlation components by estimating correlation coefficients for each wavenumber component. Through this approach, one can easily distinguish the signal components from the noise components in the wavenumber domain. Therefore, the wavenumber correlation analysis of the radar interferogram can be utilized to design post filter and to estimate the quality of interferogram. We have tested the wavenumber correlation analysis using a Radarsat SAR data pair to demonstrated the effectiveness of

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.485-493
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• 2007

This paper deals with the problem of detection of induction motor incipient faults. Artificial Neural Network (ANN) approach is applied to detect two types of incipient faults (1). Interturn insulation and (2) Bearing wear faults in single-phase induction motor. The experimental data for five measurable parameters (motor intake current, rotor speed, winding temperature, bearing temperature and the noise) is generated in the laboratory on specially designed single-phase induction motor. Initially, the performance is tested with two inputs i.e. motor intake current and rotor speed, later the remaining three input parameters (winding temperature, bearing temperature and the noise) were added sequentially. Depending upon input parameters, the four ANN based fault detectors are developed. The training and testing results of these detectors are illustrated. It is found that the fault detection accuracy is improved with the addition of input parameters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1733-1740
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• 2004

In the transverse flux linear induction motor(TFLIM) with the general secondary composed of conductor and back-yoke, there exists a magnetized force into the normal direction or the air-gap direction of the thrust motion as well as the thrust force. Therefore, the various methodologies have been tried to use the normal force by the two independent control variables of the multi-phase input. But, as the force depends inevitably and strongly on the thrust force, it is essential to decouple both forces for two control index. In this paper, we suggest a novel approach capable of compensating the couple between both forces and the control index by using the DC-biased multi-phase input, and then realizing the independent control of TFLIM.

• Journal of Power Electronics
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• v.9 no.1
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• pp.74-84
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• 2009

The design and implementation of a high performance PID (Proportional Integral & Differential) style controller with zero-phase error tracking property is considered in this article. Unlike a ball screw driven system, the controller in a direct drive system should provide a high level of tracking performance while avoiding the problems due to the absence of the gear system. The stiff mechanical element in a direct drive system allows high precise positioning capability, but relatively high tracking ability with minimal position error is required. In this work, a feasible position controller named 'Unified PID controller' is presented. It will be shown that the function of the closed position loop can be designed into unity gain system in continuous time domain to provide minimal position error. The focus of this work is in two areas. First, easy gain tunable PID position controller without speed control loop is designed in order to construct feasible high performance drive system. Second, a simple but powerful zero phase error tracking strategy using the pre-designed function of the main control loop is presented for minimal tracking error in all operating conditions. Experimental results with a s-curve based position pattern commonly used in industrial field demonstrate the feasibility and effective performance of the approach.

• The Journal of Society for e-Business Studies
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• v.12 no.1
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• pp.73-87
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• 2007

To survive in a global competition, many companies are trying to standardize and visualize Business Process (BP) by implementing Business Process Management (BPM). Recently, enhancing business process efficiency has become one of critical success factors. In this paper, we introduce a two-phase perspective of BP efficiency: Process Engine Perspective (PEP) and Task Performer Perspective (TPP). The former is related to allocation function of BP engine; it is mainly concerned with efficient task allocation to users. The latter phase influences efficiency depending on how users execute tasks assigned to them. Instead of considering each phase separately, we develop a comprehensive method considering the two-phase together, which is more effective for the BP efficiency. We carry out simulation experiment to show the combinational effect of the two phases.

• Journal of Korean Society of Transportation
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• v.6 no.2
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• pp.49-56
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• 1988

Alternate use of lane at a signalized intersection is a quite different control of the operation of an intersection. This control introduces a new stop line and signal before the original stop line. All of the lanes between the two stop lines are used for left turn traffic or through traffic at a time. The purpose of the control is increasing the capacity of a n intersection without widening the approach width. this paper contains a study on the condition of a application, the proper distances between the two stop lines, the reasonable offsets(rear) to guarantee clearing the vehicles of previous phase, the comparison of approach capacity between the existing control and this control. The study results reveals that the offsets(rear) are rather stable showing the range(maximum value minus minimum value) of it's value does not exceed 3.6 seconds according to the field data. The approach capacity will be increased by 27%, 43%, 59%, 84% when the distances between the stop lines are 30.0m respectively. The control might have theoretical limitation to operate in practice. So an experimental application of the control at some suitable intersections prior to expanding it.