• 한국재료학회지
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• 제16권2호
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• pp.85-91
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• 2006

The fraction of $\varepsilon\;and\;\gamma$'-iron nitride in compound layer is predicted by x-ray diffraction using direct comparison method. The validity of formulation models was checked by comparing calculated results with metallographic analysis of iron nitride compound layer grown on steel S45C by gas nitriding. The fraction of $\varepsilon$ calculated by the three phase model, porous-$Fe_3N$/ dense-$Fe_3N$/ mixed layer with $Fe_3N\;and\;Fe_4N$, is 80 percent of that analyzed by etching technique. The $\varepsilon$ fraction predicted by mixed layer model is 122 percent of that measured by microscope.

• Structural Engineering and Mechanics
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• 제70권5호
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• pp.551-562
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• 2019

In the present study, a suitable mathematical model considering parabolic transverse shear strains for dynamic analysis of laminated composite skew plates under different types of impulse and spatial loads was presented for the first time. The proposed mathematical model satisfies zero transverse shear strain at the top and bottom of the plate. On the basis of the cubic variation of thickness coordinate in in-plane displacement fields of the present mathematical model, a 2D finite element (FE) model was developed including skew transformations in the mathematical model. No shear correction factor is required in the present formulation and damping effect was also incorporated. This is the first FE implementation considering a cubic variation of thickness coordinate in in-plane displacement fields including skew transformations to solve the forced vibration problem of composite skew plates. The effect of transverse shear and rotary inertia was incorporated in the present model. The Newmark-${\beta}$ scheme was adapted to perform time integration from step to step. The $C^0$ FE formulation was implemented to overcome the problem of $C^1$ continuity associated with the cubic variation of thickness coordinate in in-plane displacement fields. The numerical studies showed that the present 2D FE model predicts the result close to the analytical results. Many new results varying different parameter such as skew angles, boundary conditions, etc. were presented.

• Structural Engineering and Mechanics
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• 제8권6호
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• pp.623-637
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• 1999

This paper presents a four-noded quadrilateral $C^0$ strain plate element for the analysis of thick laminated composite plates. The element formulation is based on: 1) the third-order shear deformation theory; 2) assumed strain element formulation; and 3) interrelated edge displacements and rotations along element boundaries. Unlike the existing displacement-type composite plate elements based on the third-order theory, which rely on the $C^1$-continuity formulation, the present plate element is of $C^0$-continuity, and its element stiffness matrix is evaluated explicitly. Because of the third-order expansion of the in-plane displacements through the thickness, the resulting theory and hence elements do not need shear correction factors. The explicit element stiffness matrix makes the present element more computationally efficient than the composite plate elements using numerical integration for the analysis of thick layered composite plates.

• 식물병연구
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• 제8권3호
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• pp.184-188
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• 2002

Botrytis cinerea에 의한 들깨 잿빛곰팡이병의 생물학적 방제를 위해 선발한 Bacillus lirheniformis Nl 글주를 제제화하여 미생물농약을 제조하고 이의 방제 효과를 검정하였다. Nl균주의 길항력에 미치는 탄소원과 질소원의 영향을 실험한 결과 탄소원으로는 glucose, 질소원으로는 tryptone이 가장 높은 효과를 보였다. 또한 Nl 균주를 이들 glucose와 tryptone을 첨가한 NB배지에 대량배양하고 그 배양액에 콩가루, 쌀가루, glucose, FeSo$_4$~7$H_2O$ 및 MnCl$_2$. 4$H_2O$ 을 첨가하여 수화형 미생물농약 Soy제제로제조하고,이 병원균에 대한 방제효과를 하우스내에서 폿트 검정한 결과 방제가가 93.1%로서 유의성은 없으나 베노밀 수화제에 의한 86.1%보다 높았다.

• 복합신소재구조학회 논문집
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• 제3권3호
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• pp.22-30
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• 2012

This study deals with an enhanced assumed strain (EAS) three-dimensional element for free vibration analysis of laminated composite and sandwich structures. The three-dimensional finite element (FE) formulation based on the EAS method for composite structures shows excellence from the standpoints of computational efficiency, especially for distorted element shapes. Using the EAS FE formulation developed for this study, the effects of side-to-thickness ratios, aspect ratios and ply orientations on the natural frequency are studied and compared with the available elasticity solutions and other plate theories. The numerical results obtained are in good agreement with those reported by other investigators. The new approach works well for the numerical experiments tested, especially for complex structures such as sandwich plates with laminated composite faces.

• Advances in aircraft and spacecraft science
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• 제4권3호
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• pp.219-235
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• 2017

The large container ships and fast patrol boats are complex marine structures. Therefore, their global mechanical behaviour has long been modeled mostly by refined beam theories. Important issues of cross section warping and bending-torsion coupling have been addressed by introducing special functions in these theories with inherent assumptions and thus compromising their robustness. The 3D solid Finite Element (FE) models, on the other hand, are accurate enough but pose high computational cost. In this work, different marine vessel structures have been analysed using the well-known Carrera Unified Formulation (CUF). According to CUF, the governing equations (and consequently the finite element arrays) are written in terms of fundamental nuclei that do not depend on the problem characteristics and the approximation order. Thus, refined models can be developed in an automatic manner. In the present work, a particular class of 1D CUF models that was initially devised for the analysis of aircraft structures has been employed for the analysis of marine structures. This class, which was called Component-Wise (CW), allows one to model complex 3D features, such as inclined hull walls, floors and girders in the form of components. Realistic ship geometries were used to demonstrate the efficacy of the CUF approach. With the same level of accuracy achieved, 1D CUF beam elements require far less number of Degrees of Freedom (DoFs) compared to a 3D solid FE solution.

• Architectural research
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• 제16권1호
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• pp.27-35
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• 2014

Nonlinear analysis of reinforced concrete structures is carried out by using Reissner-Mindlin (RM) shell finite element (FE). The brittle inelastic characteristic of concrete material is represented by using the elasto-plastic fracture (EPF) material model with the relevant material models such as cracking criteria, shear transfer model and tension stiffening model. In particular, assumed strains are introduced in the formulation of the present shell FE in order to avoid element deficiencies inherited in the standard RM shell FE. The arc-length control method is used to trace the full load-displacement path of reinforced concrete structures. Finally, four benchmark tests are carried out and numerical results are provided as future reference solutions produced by RM shell element with assumed strains.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.49-52
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• 1998

Preparation of hexagonal strontium-ferrite by modified spray co-roasting(MSC:H) which is expected to shorkn the length of the process and to elevate the magnetic properties of hard ferrite was studied. We prapared $Fe_2O_3/SrCO_3$ mixture powders by MSCR after stirring ionized $FeCI_2$ in distilled water with solid state $SrCO_3$. And then calcined the mixture powders up to $1150^{\circ}C$ for Sr-ferrite powders It is possible to prepare hexaferrite powders with high saturation magnetization (Ms > 69 emu/g) , coercivity (Hc > 4000 Oe) The nlagnetic values of saturation magnetization iire higher than those achieved by the conventional technique.

• Steel and Composite Structures
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• 제23권1호
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• pp.41-51
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• 2017

A $C^0$ FE model developed based on an efficient higher order zigzag theory is used for hygrothermal analysis of laminated composite plates. The $C^0$ FE model satisfies the inter-laminar shear stress continuity at the interfaces and zero transverse shear stress conditions at plate top and bottom. In this model the first derivatives of transverse displacement have been treated as independent variables to circumvent the problem of $C^1$ continuity associated with the above plate theory. In the present theory the above mentioned $C^0$ continuity of the present element is compensated in the stiffness matrix formulation by using penalty parameter approach. In order to avoid stress oscillations observed in the displacement based finite element, the stress field derived from temperature/moisture fields (initial strains) must be consistent with total strain field. Special steps are introduced by field consistent approach (e.g., sampling at gauss points) to compensate this problem. A nine noded $C^0$ continuous isoparametric element is used in the proposed FE model. Comparison of present numerical results with other existing solutions shows that the proposed FE model is efficient, accurate and free of locking.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.157-163
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• 2010

CRT 용 shadow mask의 생산속도 향상을 위해 첨가제를 투입한 염화제이철 수용액을 개발하였고 이를 shadow mask의 식각속도 향상에 적용하였다. $Fe(ClO_4)_3$ 첨가제를 종래의 식각용액인 염화제이철 수용액에 투입한 결과, shadow mask의 식각속도가 크게 향상되었으며, 이때 첨가제의 농도가 증가할수록 식각속도가 증가함을 알 수 있었다. 또한 첨가제가 투입된 식각용액으로 순수 니켈과 철-니켈 합금(Invar 강)의 식각속도를 비교한 결과, 대부분의 공정조건에서 둘 사이의 식각속도 차이가 작음을 알 수 있었고, 이는 첨가제의 투입에 따라 니켈과 철의 식각속도가 모두 향상된 결과로 해석되었다. 첨가제의 주입에 따라 식각속도가 증가하는 이유는, 첨가제 내의 음이온인 $ClO^{4-}$가 염화제이철 수용액 내의 $Cl^-$에 비해 전자를 이동하는 가교로서의 역할이 우수하여 전자를 더 빠르게 이동시킬 수 있기 때문인 것으로 추정된다.