• Journal of the Korean Magnetics Society
• /
• v.15 no.1
• /
• pp.7-11
• /
• 2005

A single slab in which one Ni(001) atom layer embedded between two of four Rh layers is considered to examine the oscillation of magnetic moment in each layer. The all electron total-energy full-potential linearized augmented plane wave(FLAPW) method was used to calculate the spin densities, magnetic moments, density of states(DOS), and the number of electrons within each muffin-tin(MT) sphere. The magnetic moment of the center layer Ni(C) in the system of 4Rh/Ni/4Rh is calculated to be 0.34${\mu}_B$, which is 40% have magnetic moment at the interface layers by strong band hybridization with Ni(C) when Ni(001) monolayers is inserted, and the magnetic moment shows a damped oscillation as we go from center Ni(C) layer to the surface Rh(S). From the calculated density of states, it is found that the Fermi level shifts inside the energy band of the Ni(C) in affection of Rh(001).

• Korean Journal of Materials Research
• /
• v.28 no.7
• /
• pp.371-375
• /
• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• Interaction and multiscale mechanics
• /
• v.3 no.1
• /
• pp.55-79
• /
• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.

• Proceedings of KOSOMES biannual meeting
• /
• 2007.05a
• /
• pp.169-174
• /
• 2007

The purpose in having a control rod an a buoy system is to control the motion of it. The system may be composed entirely af a single circular cylinder finder and a lang mooring anchor cable. A control rod has one function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of the effects of mutual interference, then determine the stability characteristics of the body. In this paper, the study of control-rod-attached buoy's 2-dimensional section was accomplished. model tests and numerical simulations had been carried out with different diameters of control rods. and varying the Reynolds number $Re=5,000{\sim}25,000$ based an the cylinder diameter(D=50mm) to. predict the performance af the body and the 2 frame particle tracking method had been used to obtain the velocity distribution in the flaw field 50mm circular cylinder had been used during the whale experiments and measured results had been compared with each other.

• Structural Engineering and Mechanics
• /
• v.29 no.2
• /
• pp.135-154
• /
• 2008

The moving vehicle loads on a bridge deck is one of the most important live loads of bridges. They should be understood, monitored and controlled before the bridge design as well as when the bridge is open for traffic. A MOM-based algorithm (MOMA) is proposed for identifying the timevarying moving vehicle loads from the responses of bridge deck in this paper. It aims at an acceptable solution to the ill-conditioning problem that often exists in the inverse problem of moving force identification. The moving vehicle loads are described as a combination of whole basis functions, such as orthogonal Legendre polynomials or Fourier series, and further estimated by solving the new system equations developed with the basis functions. A number of responses have been combined, some numerical simulations on single axle, two axle and multiple-axle loads, being either constant or timevarying, have been carried out and compared with the existing time domain method (TDM) in this paper. The illustrated results show that the MOMA has higher identification accuracy and robust noise immunity as well as producing an acceptable solution to ill-conditioning cases to some extent when it is used to identify the moving force from bridge responses.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.2
• /
• pp.200-207
• /
• 2017

The purpose in having a control surface on ships is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portions. A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the manoeuvring characteristics of the ship. In this paper, two-dimensional flow characteristics of a flapped rudder and a water-blowing control rudder were accomplished respectively by PIV method in a circulating water channel. Model test has been carried out with different angles of attack of main foil (NACA 0012) and flap's deflection angles to predict the performance of the flapped rudder and the water-blowing control rudder. The 2-frame particle tracking method has been used to obtain the velocity distribution in the flow field. $Re{\fallingdotseq}3.0{\times}10^4$ has been used during the whole experiments and measured results have been compared with each other.

• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.2
• /
• pp.197-206
• /
• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.3
• /
• pp.606-619
• /
• 1998

In this paper, we have tfesigned and ihlplemented ACE(Application sharing Collaboration Engine) which is pessible an application sharing to collaborate among peoples who are geographically dispersed. The application sharing is a technology whereby two or more users collaborate to share the output of single application running on one computer system to the other users, and to provide input to the applications. We defined ASO(Applicatio!1 Sharing Object) object and its behavior to share applications in real time and ACE processes a sharing using ASO object among the distributed systems. ASO is classified into activateASO, updateASO, inputASO, and controlASO. The each ASO's behavior involves both events which occur at specific moments such as keystrokes and mouse clicks and more persistent status which can be observed at any time such as the image on the screen. The implemented ACE can be applied to the data conferencing, distance education, and project collaboration for engineer in distributed environments.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.2
• /
• pp.147-160
• /
• 2007

In this paper, we described the aeroelastic full-bridge model tests that were conducted to investigate the effect of alternative temporary stabilizing measures for thecable-stayed bridge during construction to ensure aerodynamic stability in the event of a typhoon or similar disasters. The effect of alternative temporary stabilizing measures was investigated through various configurations on two cable-stayed bridges with a main span of 475 m and 230 m, respectively. To investigate the bridge's aerodynamic behaviour and dynamic wind force during construction, the deflections at the end of the cantilever, the accelerations atthe top of the pylon and the moments at the lower part of the pylon were measured. As the result, the system with two sets of vertical cables per cantilever seemed to be the overall most effective solution, but the system with single vertical cable may also work. The combined system using the caisson support and vertical cables and the system with two sets of inclined cables per cantilever on the same anchor block may also be a solution. The inclined cables from the caisson to the girder were effective for some early stages of erecting the deck.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.1
• /
• pp.183-193
• /
• 2008

The reliability analysis of simply-supported and continuous composite plate girder and box girder bridges under flexure was performed to provide a basic data for the development of LRFD c ode. The bridges were designed based on LRFD specification with newly proposed design live load which was developed by analyzing traffic statistics from highways and local roads. A performance function for flexural failure was expressed as a function of the flexural resistance of composite section and the design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 domestic structural steel samples were used. Several different values of bias factors for the live load moment from 1.0 to 1.2 were used. Due to the lack of available domestic measured data on the moment by permanent loads, the same statistical properties used in the calibration of ASHTO-LRFD were ap plied. The reliability indices for the composite girder bridges with various span lengths, different live load factors, and bias fact or for the live load were obtained by applying the Rackwitz-Fiessler technique.