• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.993-996
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• 1993

This paper presents the static thrust of a hybid-type LPM by coenergy method. First, the nonlinealities of the permanent magnet, the primary core and the secondary are interpolated by the cubic spline method. Then the equivalent magnetic circuit including airgap reluctance, which is a function of displacement, modelled by the permeance method is obtained. From the derivative of coenergy with displacement computed by Newton Raphson method, the static thrust is calculated at each displacement with certain exciting current.

• Nonlinear Functional Analysis and Applications
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• v.28 no.2
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• pp.537-555
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• 2023

In this paper, we consider two types of fractional boundary value problems, one of them is an implicit type and the other will be an integro-differential type with nonlocal integral multi-point boundary conditions in the frame of generalized Hilfer fractional derivatives. The existence and uniqueness results are acquired by applying Krasnoselskii's and Banach's fixed point theorems. Some various numerical examples are provided to illustrate and validate our results. Moreover, we get some results in the literature as a special case of our current results.

• Structural Monitoring and Maintenance
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• v.10 no.1
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• pp.63-86
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• 2023

Structural health monitoring and damage detection are essential for assessing, maintaining, and rehabilitating structures. Most of the existing damage detection approaches compare the current state structural response with the undamaged vibrational structural response, which is unsuitable for old and existing structures where undamaged vibrational responses are absent. One of the approaches for existing structures, numerical model updating/inverse modelling, available in the literature, is limited to numerical studies with high-end software. In this study, an attempt is made to study the effectiveness of the model updating technique, simplify modelling complexity, and economize its usability. The optimization-based detection problem is addressed by using programmable open-sourced code, OpenSees^® and a derivative-free optimization code, NOMAD^®. Modal analysis is used for damage identification of beam-like structures with several damage scenarios. The performance of the proposed methodology is validated both numerically and experimentally. The proposed method performs satisfactorily in identifying both locations and intensity of damage in structures.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.1 s.60
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• pp.23-28
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• 2007

Ascorbic acid (vitamin C, AsA) has been known as a strong reducing agent and is supposed to retard the synthesis of melanin pigment. A main problem that arose in using vitamin C in cosmetic formulation was its poor stability and low skin permeability, which result in low lightening efficacy in clinical trials. In this study, iontophoretic gel patch with flexible thin layer battery was employed in order to enhance skin permeation of vitamin c derivative (ascorbyl glucoside, AsAG) and to increase its lightening efficacy. in vitro iontophoretic skin permeation and stability of AsAG, safety and clinical lightening efficacy of iontophoretic patch containing 2% AsAG solution were examined. A optimun current of ionthophoretic patch for korean women was 0.1 mA, considering the skin permeability and skin irritation of consumers. We suggest that iontophoretic gel patch could be a safe system for enhancing the skin permeation of AsAG and lightning efficacy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.456-464
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• 1997

The effect of the additives on the Zn-Ni alloy electrocrystallization from a chloride bath was investigated by means of electrochemical methodes, scanning electron microscopy and measurement of surface appearance, X-ray diffraction patterns. The additives tested were the surfactant of naphtalene-derivative, saccharin and aliphatic alcohol. The resistance of electrodeposit increased by adding the additives, whereas the effect of additives on resistance was different with current density. The nickel content of alloy deposit was increased by the addition of alcohol, while decreased by the surfactant. The surface roughness, appearance and morphology of deposit were also influenced by the type of additive. The fine, compact grains and good surface roughness could be obtained from the surfactant or alcohol -added bath, and the surfactant or saccharin improved the surface appearance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.359-366
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• 2005

Most engineering optimization are based on numerical linear and nonlinear programming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These algorithm, however, reveal a limited approach to complicated real-world optimization problems. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the obtained optimal solution may not necessarily be the global optimum. This paper describes a new harmony search(HS) meta-heuristic algorithm-based approach for structural size optimization problems with continuous design variables. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. Two classical space truss optimization problems are presented to demonstrate the effectiveness and robustness of the HS algorithm. The results indicate that the proposed approach is a powerful search and optimization technique that may yield better solutions to structural engineering problems than those obtained using current algorithms.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.12
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• pp.626-633
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• 2004

In this paper, we present a time domain combined field integral equation (TD-CFIE) formulation to analyze the transient electromagnetic response from three-dimensional dielectric objects. The solution method in this paper is based on the method of moments (MoM) that involves separate spatial and temporal testing procedures. A set of the RWG (Rao, Wilton, Glisson) functions Is used for spatial expansion of the equivalent electric and magnetic current densities and a combination of RWG and its orthogonal component is used as spatial testing. We also investigate spatial testing procedures for the TD-CFIE to select the proper testing functions that are derived from the Laguerre polynomials. These basis functions are also used for temporal testing. Use of this temporal expansion function characterizing the time variable enables one to handle the time derivative terms in the integral equation and decouples the space-time continuum in an analytic fashion. Numerical results computed by the proposed formulation are presented and compared with the solutions of the frequency domain combined field integral equation (FD-CFIE).

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.429-436
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• 2007

In this study, we improved control performance of an EMV (electromechanical valve) system using a PM/EM (permanent magnet/electromagnet) hybrid EMA (electromagnetic actuator) and showed the feasibilities of both soft landing and fast transition of the EMV system using a simple PID control. The conventional EMV systems using only EM show significant nonlinear characteristics. Therefore, it is very difficult to control the valve position and several complex control schemes are used. This paper focused on the control performance improvement using a PM/EM hybrid actuator. In particular, a PM is used as a key design parameter such as a bias current of a magnetic bearing in order to improve the linear characteristic of the actuator, although most PM/EM hybrid actuators use a PM as a power saver during valve-open and -closed states. First, a FE (finite element) analysis was performed to confirm its linear static force characteristics. Then, both a test rig and a valve control system were built in order to prove experimentally the control performance improvement of the actuator. Finally, feasibilities of both soft landing and fast transition of the system were shown experimentally through gain-scheduled PID (proportional derivative integral) control.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.3
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• pp.146-151
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• 2018

In this study, we compared the threshold-voltage extraction methods of accumulation-type JLDG (junctionless double-gate) MOSFETs (metal-oxide semiconductor field-effect transistors). Threshold voltage is the most basic element of transistor design; therefore, accurate threshold-voltage extraction is the most important factor in integrated-circuit design. For this purpose, analytical potential distributions were obtained and diffusion-drift current equations for these potential distributions were used. There are the ${\phi}_{min}$ method, based on the physical concept; the linear extrapolation method; and the second and third derivative method from the $I_d-V_g$ relation. We observed that the threshold-voltages extracted using the maximum value of TD (third derivatives) and the ${\phi}_{min}$ method were the most reasonable in JLDG MOSFETs. In the case of 20 nm channel length or more, similar results were obtained for other methods, except for the linear extrapolation method. However, when the channel length is below 20 nm, only the ${\phi}_{min}$ method and the TD method reflected the short-channel effect.

• KSTLE International Journal
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• v.6 no.1
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• pp.28-32
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• 2005

The electrorheoloRical (ER) fluids are composed of a colloidal dispersion of polarizable particles in insulating oil, and it's the rheological property changes by the applied electric field. These changed are reversible and occur fast within a fewmilliseconds. The ER properties of the ER fluid such as increment of viscosity and yield stress come from the particle chain structure induced by electric fleld. When formulating the ER fluid for a speciflc application, some requirement must besatisfled, which are high yield stress under electric field, rapid response, and dispersion stability. While this characteristic makes valuable ER fluids in valious industrial applications, their lung term and quiescent application has been limited because ofproblems with particle sedimentation. In an effort to overcome sedimentation problem of ER fluids, the anhydrous ER materials of monodispersed hollow polyaniline (PANI) and adipate derivative respectively with submicron-sized suspension providing wide operating temperature range and other advantage were synthesized in a four-step procedure. The ER fluidswere characterized by FT-lR, TGA, DLS, SEM, and TEM. Stability of the suspensions was examined by an UV spectroscopy.The rheological and electrical properties of the suspension were investigated Couette-type rheometer with a high voltagegenerator, current density, and conductivity. And the behavior of ER suspensions was observed by a video camera attached toan optical microscope under 3kV/mm. The suspensions showed good ER properties, durability, and particle dispersion.