• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1680-1688
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• 2017

In this study, analysis is performed on entropy generation during cilia transport of water based titanium dioxide nanoparticles in the presence of viscous dissipation. Moreover, thermal heat flux is considered at the surface of a channel with ciliated walls. Mathematical formulation is constructed in the form of nonlinear partial differential equations. Making use of suitable variables, the set of partial differential equations is reduced to coupled nonlinear ordinary differential equations. Closed form exact solutions are obtained for velocity, temperature, and pressure gradient. Graphical illustrations for emerging flow parameters, such as Hartmann number (Ha), Brinkmann number (Br), radiation parameter (Rn), and flow rate, have been prepared in order to capture the physical behavior of these parameters. The main goal (i.e., the minimizing of entropy generation) of the second law of thermodynamics can be achieved by decreasing the magnitude of Br, Ha and ${\Lambda}$ parameters.

• 한국미생물·생명공학회지
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• 제9권3호
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• pp.165-171
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• 1981

E. coil ATCC 9637의 균체를 젤라틴과 DEAE-cellulose의 혼합 성형 후 글루트알데히드 가교법으로 제조론 고정화 penicillin amidase의 differential column reactor에서의 반응속도를 논의하였다. 이러한 반응조의 최적 조작조건은 효소충진량 1g, 기질농도30mM(0.1M 인산완충액, pH8.0), 유출속도 4 $m\ell$/min, 온도 4$0^{\circ}C$이었다. 이 최적조건에서 고정화효소의 일반적인 성질을 조사하였다. Km 상수는 4.8mM 이었고 specific activity 308 units/g 고정화 효소이 었다. 또한 고정화효소에서는 기질에 의한 효소반응 저해효과가 보이지 않았다. 이러한 differential column reactor에서는 column내에서의 pH 감소효과 및 외부 화산효과가 없어지기 때문에 이러한 외부적 영향을 받지 않는 고정화효소의 반응 속도론적 연구에 적합함을 알았다.

• 한국공작기계학회논문집
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• 제12권2호
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• pp.71-78
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• 2003

This research proposes an implementation method of linearized equations of motion for multibody systems with closed loops. The null space of the constraint Jacobian is first pre-multiplied to the equations of motion to eliminate the Lagrange multiplier and the equations of motion are reduced down to a minimum set of ordinary differential equations. The resulting differential equations are functions of all relative coordinates, velocities, and accelerations. Since the variables are tightly coupled by the position, velocity, and acceleration level coordinates, direct substitution of the relationships among these variables yields very complicated equations to be implemented. As a consequence, the reduced equations of motion are perturbed with respect to the variations of all variables, which are coupled by the constraints. The position velocity and acceleration level constraints are also perturbed to obtain the relationships between the variations of all relative coordinates, velocities, and accelerations and variations of the independent ones. The Perturbed constraint equations are then simultaneously solved for variations of all variables only in terms of the variations of the independent variables. Finally, the relationships between the variations of all variables and these of the independent ones are substituted into the variational equations of motion to obtain the linearized equations of motion only in terms of the independent variables variations.

• 한국전산유체공학회지
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• 제3권1호
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• pp.11-21
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• 1998

A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity now: (ⅰ) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ⅱ) driven only by uniform shear (of the classical type).

• 한국전문물리치료학회지
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• 제19권4호
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• pp.16-23
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• 2012

This study examined the effects of custom-made foot orthotics on the temporal-spatial gait parameters in children with cerebral palsy. Twenty spastic bilateral cerebral palsy (spastic CP) children (11 boys and 9 girls) participated in this study. GAITRite was used to examine the velocity, cadence, step length differential, step length, stride length, stance time, single support time, double support time, base of support, and toe angle while walking with and without foot orthotics. The differences in temporal-spatial parameters were analyzed using paired t-test. The significance level was set at .05. The velocity, cadence, both step lengths, both stride lengths, both bases of support and right toe angle significantly increased when the children with spastic CP with foot orthotics compared to without foot orthotics (p<.05). The step length differential between the two extremities, left stance time and left single support time, significantly decreased with foot orthotics (p<.05). Right stance time, right single support time, both double support times and left toe angle showed little change (p>.05). This study demonstrated that foot orthotics were beneficial for children with spastic CP as a gait assistance tool.

• Journal of Advanced Marine Engineering and Technology
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• 제27권2호
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• pp.272-279
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• 2003

This study aimed to understand the effects of transporting ice slurry Particles through Pipes with branches. The experimental apparatus was constructed as ice slurry mixing tank. vortex pump, manometers for differential pressure measuring. IPF(ice packing factor) measuring instruments and branches as test sections. The experiments were carried out under various conditions. with concentration of water solution ranging between 0∼20wt% and velocity of water solution at the entry ranging between 1.5∼2.5m/s. The differential Pressure and IPF between the pipe entry and exit were measured. and flowing form was checked throughout the experiment. The pressure loss in 3d branches appeared compared with 6d branches so that it was very high. In the pressure loss of the inside and outside of branches. 6d branches was showed the difference. but was agreed in 3d branches The pressure loss according to concentration of water solution, low value appeared at 10wt% in 6d branches, at 20wt% in 3d branches. The pressure loss according to velocity, did not show large difference. The change of IPF at outlet, appeared +15∼-25% in 6d branches and 0∼-20% in 3d branches. The difference of IPF at the inside and outside of branches. appeared 10∼15% in 6d branches and maximum 5% in 3d branches.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.448-448
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• 2000

This paper deals with dynamic behaviour analysis for pipeline inspection gauge (PIG) flow control in natural gas pipeline. The dynamic behaviour of the PIG is depending on the different Pressure between the rear and nose parts, which is generated by injected gas flow behind PIG's tail and expelled gas flow in front of its nose. To analyze the dynamic behaviour characteristics such as gas flow in pipeline, and the PIG's position and velocity, mathematical model is derived as two types of a nonlinear hyperbolic partial differential equation for unsteady flow analysis of the PIG driving and expelled gas, and nonhomogeneous differential equation for dynamic analysis of PIG. The nonlinear equation is solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used when we solve the steady flow equations to get initial flow values and the dynamic equation of PIG. The gas upstream and downstream of PIG are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of PIG with different operational conditions of pipeline.

• 한국생산제조학회지
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• 제7권3호
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• pp.43-50
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• 1998

In the use of CNC machine tool, the unmanned production system has been growing in the manufacturing field. Thus, it is necessary to monitor adequate tool fracture during the cutting process efficiently. This experimental study is intended to investigate the development of flank wear in sysnchronous turning of differential materials(Aℓ/GC) which is used in industrial application and it is acknowledged as a machine to difficult material. In cutting process change of velocity, change of feed, and change of depth of cut were investigated on the effect of flank wear, and slenderness ratio is also investigated. The conclusions of this paper are summarized as follows; 1.Under the high cutting speed condition, the flank wear is affected by the feed and depth of cut. but the influence of feed on the flank wear is larger than the depth of cut and that is reduced when the velocity is low. 2.Under the high cutting speed, as the smaller slenderness ratio is, the shorter tool life is under the lower cutting speed, the effect of slenderness ratio on the flank wear is low. 3.Using the characteristics of cutting force, the flank wear of a tool can be detected 4. Investigating the development of flank wear, there are almost no differences between the characteristics of cutting force and feed force. Finally, these data from the differntial materials cutting process will be used in the basic field of precision and economic cutting process.

• 대한금속재료학회지
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• 제48권7호
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• pp.605-614
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• 2010

Conventional rolling (symmetric) and differential speed rolling (DSR) were both applied to AA1050 sheets at various velocity ratios, from 1 to 2 between the top and bottom rolls. An electron backscatter diffraction (EBSD) technique was used to measure texture inhomogeneity through the thickness direction. After the annealing process, the annealing texture of the DSR processed sheets was different from that of conventionally rolled sheets. The velocity ratio between the top and bottom rolls affected the texture inhomogeneity and macroscopic plastic strain ratio of the AA1050 sheets. A prediction for the macroscopic plastic strain ratio of AA1050 sheets was carried out using a visco-plastic self-consistent (VPSC) polycrystal model. The strain ratio directionality that was predicted using the VPSC polycrystal model was in good agreement with experimental results.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.357-366
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• 2020

This paper addressed a relative navigation method for autonomous rendezvous and docking of cube-satellites using single frequency Differential GPS (DGPS) under the intermittent communication between satellites. Since the ionospheric error of GPS measurement is variable depending on the visible satellites, a few meters error of relative navigation is occurred in the Low-Earth Orbit (LEO) environment. Therefore, it is essential to remove the ionospheric error to perform relative navigation. Besides, an intermittent communication period for receiving GPS measurements of the target satellite is limited for getting information every sampling time. To solve this problem, a method combining range domain DGPS and orbit propagation is proposed in this paper. The proposed method improves the performance of DGPS by using Hatch filter and solves an intermittent communication problem by estimating the relative position and velocity using Hill-Clohessy-Wiltshire Equation. Through the simulation, it is verified that the suggested algorithm provides the relative position error within RMS 0.5 m and the relative velocity error within RMS 3 cm/s. Furthermore, it has the advantage that it is suitable for real-time implementation using single-frequency GPS measurements and is computationally efficient.