• Journal of Korean Neurosurgical Society
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• v.60 no.6
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• pp.611-619
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• 2017

Objective : In addition to bone bridging inside a cage or graft (intragraft bone bridging, InGBB), extragraft bone bridging (ExGBB) is commonly observed after anterior cervical discectomy and fusion (ACDF) with a stand-alone cage. However, solid bony fusion without the formation of ExGBB might be a desirable condition. We hypothesized that an insufficient contact area for InGBB might be a causative factor for ExGBB. The objective was to determine the minimal area of InGBB by finite element analysis. Methods : A validated 3-dimensional, nonlinear ligamentous cervical segment (C3-7) finite element model was used. This study simulated a single-level ACDF at C5-6 with a cylindroid interbody graft. The variables were the properties of the incorporated interbody graft (cancellous bone [Young's modulus of 100 or 300 MPa] to cortical bone [10000 MPa]) and the contact area between the vertebra and interbody graft (Graft-area, from 10 to $200mm^2$). Interspinous motion between the flexion and extension models of less than 2 mm was considered solid fusion. Results : The minimal Graft-areas for solid fusion were $190mm^2$, $140mm^2$, and $100mm^2$ with graft properties of 100, 300, and 10000 MPa, respectively. The minimal Graft-areas were generally unobtainable with only the formation of InGBB after the use of a commercial stand-alone cage. Conclusion : ExGBB may be formed to compensate for insufficient InGBB. Although various factors may be involved, solid fusion with less formation of ExGBB may be achieved with refinements in biomaterials, such as the use of osteoinductive cage materials; changes in cage design, such as increasing the area of polyetheretherketone or the inside cage area for bone grafts; or surgical techniques, such as the use of plate/screw systems.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1309-1312
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• 2002

The electric power network paralleled with wind turbine generator may have the negative impacts on the protection, operation, and management caused by the operation of wind turbine generator. Therefore, it is necessary to investigate the operating characteristic of wind turbine generator. This paper describes model of a squirrel-cage type wind turbine induction generator and the soft cut-in connection method for reducing the transient state on power network, and simulates various cases of wind turbine operations. The radial distribution network of IEEE 13-bus are modeled and tested by PSCAD/EMTDC.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2558-2562
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• 2007

In the present work, flow characteristics analysis has been performed for steam turbine bypass control valve (single-path type). The numerical analysis is performed by solving three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. Shear stress transport (SST) model is used as turbulence closure. Symmetry condition is applied at the mid plane of the valve while adiabatic condition is used at the outer wall of the cage. Grid independency test is performed to find the optimal number of grid points. The pressure and temperature distributions on the outer wall of the cage are analyzed. Mass flow rate at maximum plug opening condition is compared with the designed mass flow rate.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.527-530
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• The KSFM Journal of Fluid Machinery
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• v.9 no.4 s.37
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• pp.36-42
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.12
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• pp.704-713
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• 2002

This paper describes operational characteristics of wind turbine induction generators interconnected with distribution networks using PSCAD/EMTDC. Due to the simple and durable structure, induction generators are the most common type used in wind Power generation. Generally, induction generators are classified into two groups according to the shape of rotor, one is squirrel-cage type and the other is wound-rotor type. In this study, we simulate the start-up and the output variation of generators interconnected with distribution networks and compare the operational characteristics of squirrel -cage type and wound-rotor type induction generators located in the unfaulted distribution lines about the disturbance occurred on the associated distribution feeders emanated from the substation to which wind turbine generator is connected. In order to obtain the realistic results, we use the radial distribution network of IEEE 13-bus model.

• Journal of Power Electronics
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• v.6 no.3
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• pp.245-252
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• 2006

This paper presents a method based on neural networks to detect the broken rotor bars and end rings of squirrel cage induction motors. At first, detection methods are studied, and then traditional methods of fault detection and dynamic models of induction motors by using winding function model are introduced. In this method, all of the stator slots and rotor bars are considered, thus the performance of the motor in healthy situations or breakage in each part can be checked. The frequency spectrum of current signals is derived by using Fourier transformation and is analyzed in different conditions. In continuation, an analytical discussion and a simple algorithm are presented to detect the fault. This algorithm is based on neural networks. The neural network has been trained by using information of a 1.1 KW induction motor. This system has been tested with a different amount of load torque, and it is capable of working on-line and of recognizing all normal and ill conditions.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.48-50
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• 2008

A wind power system with squirrel-cage induction generator has irregular change of output power according to the sudden change of wind speed. This paper describes the development of a active and reactive power compensator, which is composed of a 3-phase inverter and a bidirectional DC/DC converter with super-capacitor. The operational characteristic was analyzed through simulations with PSCAD/EMTDC and experimental works with a scaled model. The developed system can continuously compensate the active power change with energy storage and the reactive power change with 3-phase inverter.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.99-105
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• 2010

The electrical transport properties of mayenite ($Ca_{12}Al_{14}O_{33}$ or $12CaO{\cdot}7Al_2O_3$; mostly abbreviated as $C_{12}A_7$) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model-despite the complex cage structure: A point defect model based on the assumption that the framework $[Ca_{12}Al_{14}O_{32}]^{2+}$ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with -1/4 slope at temperatures between 800 and $1000^{\circ}C$. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.77-77
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• 1993

약물 내성 (tolerance) 및 의존성 (dependence)은 그 약물이 지니고 있는 여러 가지 약리작용과 관련되어 형성된다. 약물의 반복투여 후, 나타나는 작용이 처음의 반응 (response) 보다 감소되어 나타나는 현상 즉, 내성과, 이와는 반대로 약물반복 투여 후 나타나는 작용이 처음의 반응보다 점점 증가하는 역내성 (reverse tolerance 또는 sensitization) 측정에 있어서 약물에 따라 적절한 검색 방법을 설명한다. 의존성에 있어서 약물 섭취 결과 mood가 변하거나 도취감 또는 만족감을 일으키게 되면 그 감각을 재 경험하고 싶다는 욕구가 일어나게 되는 정신적 의존성(psychic dependence)과, 약물을 반복 투여하다가 갑자기 투여를 중단 했을때 여러가지 생리학적인 또는 행동적인 변화가 급격히 증가하여 금단증상을 나타내는 신체적 의존성 (physical dependence) 측정 방법을 제시한다. 내성과 의존성은 근본적으로 다르지만 대부분의 경우 내성이 형성되면 의존성이 형성된다. 여기서는 주로 morphine과 psychostimulants를 투여한 후 나타나는 약리작용에 대한 내성과 opioids (마약성 진통제)의 의존성 평가 방법에 대한 model을 설명하고자 한다 진통성 내성(analgesic tolerance)에 있어서 진통제의 진통력은 진통력 측정 방법(tail pinch, paw-withdrawal, tail flick, tail-withdrawal, hot plate, writhing, etc)에 따라 차이가 있기 때문에 각각의 진통제의 정합한 내성 측정 방법을 결정할 필요가 있다. 역내성 (roversetolerance)은 cocaine, amphetamine, opioids둥의 만성투여에서 일어난다. 이들 역내성을 측정하는 한 방법으로 자발운동을 측정하는데 locomotor activity cage나 tilting cage를 이용한다. 정신적 의존성(psychic dependence)은 약물 섭취 욕구를 이용한 CPP (conditioned place preference)법을 소개한다. 신체적 의존성 (physical dependence)은 opioids를 만성적으로 투여한 후 naloxone으로 precipitation하여 나타난 여러 가지 금단증상을 측정하고 몇몇 평가 model을 제시한다.