• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• 한국통신학회논문지
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• 제16권6호
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• pp.556-565
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• 1991

A가 nxn 삼중대각행렬인 선형방정식 Ax=b를 WZ분해 알고리즘을 이용하여 해석하고 이 알고리즘을 CAM Systolic Array 로 구현했다. 그리고 이 어레이를 평가하기위하여 LU분해 알고리즘을 제시하고 이를 W, D, Z분해 알고리즘과 비교 고찰한 결과 LU분해 알고리즘 보다 WZ분해 알고리즘이 1/4정도 가까운 시간으로 실행시간이 단축될 수 있었다. CAM Systolic Array에서 실행되는 각 단계를 1 time stpe으로 가정하면 2n+1 times이 필요하고 CAM의 데이타 워드는 메트릭스 원소의 값과 행번호, 연산의 형태 및 상태에 관한 정보를 포함하고 pipeline식으로 각 프로세서를 systolic processing하므로서 중앙제어가 필요없고, data brodcasting도 피할 수 있다.

• 한국음향학회지
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• 제31권5호
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• pp.332-339
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• 2012

빔공간 변환(beamspace transform) 기법은 공간 영역의 신호를 입사각 혹은 그 사인함수의 영역으로 변환하는 기법으로, MUSIC과 같은 음원 정위 및 추적(source localization and tracking) 문제나 적응 빔형성(adaptive beamforming)과 같은 문제에서 많이 사용되는 기법이다. 다채널 음원 분리 기법에 사용될 때에는, 음원의 정보 뿐만아니라 해당 음원의 이미지(image)를 재구성하여야 하므로 역변환 기법 또한 중요하다. 본 논문에서는 멀티 채널 음원 분리 기법을 위한 빔공간 변환 기법과 그 역변환 기법에 대하여 고찰하였으며, 특히 빔공간-영역 다채널 비음수 행렬 분해 기법에 적용되었을 때 그 성능에 미치는 영향을 중점적으로 살펴보았다.

• Archives of Pharmacal Research
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• 제5권2호
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• pp.79-86
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• 1982

Sulfisoxazole, $C-{11}H_{13}N_{3}S$, crystallized in the orthohombic system, space group Pbca, with a = 14.492(1), b = 11.563(1), c = 14.900(2) $\AA$ and Z = 8. Intensities for 1867(1360 observed) unique reflections were measured on a four-circle diffractometer wirh CuKa radiation ($\lambda$ = 1.5418$\AA$). The structure was solved by heavy atom methods and refined by full-matrix least-squares procedures to a final R of 0.094. The benzene ring plane makes an angle of $68^{\circ}C$ with the plane of the isoxazole ring, which is plannar. The conformational angle formed by the torsional angle C(4)-S-N(2)-C(7) is $54^{\circ}C$. There are two intermolecular hydrogen bonds in the structure. One of them is of the type N-H...H with the length 2.915$\AA$. Thus two dimensional networks of hydrogen bonds form infinite moelcular sheets parallel to the (001) plane. Adjacent sheets are bound together by van der Waals forces.

• Current Applied Physics
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• 제18권11호
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• pp.1289-1293
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• 2018

The influence of crystallization treatment on the structure, magnetic properties and magnetocaloric effect of $Gd_{71}Ni_{29}$ melt-spun ribbons has been investigated in detail. Annealing of the melt-spun samples at 610 K for 30 min, a majority phase with a $Fe_3C$-type orthorhombic structure (space group, Pnma) and a minority phase with a CrB-type orthorhombic structure (space group, Cmcm) were obtained in the amorphous matrix. The amorphous melt-spun ribbons undergo a second-order ferromagnetic to paramagnetic phase transition at 122 K. For the annealed samples, two magnetic phase transitions caused by amorphous matrix and $Gd_3Ni$ phases occur at 82 and 100 K, respectively. The maximum magnetic entropy change $(-{\Delta}S_M)^{max}$ is $9.0J/(kg{\cdot}K)$ (5T) at 122 K for the melt-spun ribbons. The values of $(-{\Delta}S_M)^{max}$ in annealed ribbons are 1.0 and $5.7J/(kg{\cdot}K)$, corresponding to the two adjacent magnetic transitions.

• Steel and Composite Structures
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• 제45권3호
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• pp.331-348
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• 2022

The main goal of this article is to develop the finite element formulation based on the nonlocal strain gradient and the refined higher-order deformation theory employing a new function f(z) to investigate the static bending and free vibration of functionally graded porous (FGP) nanobeams. The proposed model considers the simultaneous effects of two parameters: nonlocal and strain gradient coefficients. The nanobeam is made by FGP material that exists in un-even and logarithmic-uneven distribution. The governing equation of the nanobeam is established based on Hamilton's principle. The authors use a 2-node beam element, each node with 8 degrees of freedom (DOFs) approximated by the C¹ and C² continuous Hermit functions to obtain the elemental stiffness matrix and mass matrix. The accuracy of the proposed model is tested by comparison with the results of reputable published works. From here, the influences of the parameters: nonlocal elasticity, strain gradient, porosity, and boundary conditions are studied.

• Korean Chemical Engineering Research
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• 제54권4호
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• pp.574-581
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• 2016

본 연구에서는 탄소나노튜브에 다양한 아미노산과 알데히드의 1,3-dipolar cycloaddition 반응을 통해 pyrrolidine 고리를 도입하여 기능화된 탄소나노튜브를 합성하였다. 기능화된 탄소나노튜브에 메탈로센 촉매를 담지하였고 in-situ 에틸렌 중합을 통해 탄소나노튜브/폴리에틸렌 복합체를 합성하였다. 글리신과 벤즈알데히드로 기능화된 탄소나노튜브(Gly+BA-CNT)에 담지된 메탈로센 촉매는 낮은 지르코늄 함량에도 불구하고 높은 지르코늄 함량을 나타내는 N-benzyloxycarbonylglycine과 파라포름알데히드로 기능화된 탄소나노튜브(Z-Gly+PFA-CNT)에 담지된 촉매와 유사한 중합 활성을 보였다. N-Benzyloxycarbonylglycine과 파라포름알데히드로 기능화된 탄소나노튜브(Z-Gly+PFA-CNT)에 담지된 메탈로센 촉매의 경우 촉매 활성점의 분포가 조밀하여 에틸렌 중합 시 활성점으로 에틸렌 모노머와 공촉매 MAO가 확산하는데 입체적 방해를 주기 때문이다. 균일계 메탈로센 촉매로 생성된 폴리에틸렌과 비교하여 표면 기능화된 탄소나노튜브에 메탈로센을 담지한 촉매로 생성된 CNT/PE 복합체는 높은 분해 개시 온도($T_{onset}$)와 최대 중량 감소 온도($T_{max}$)를 가진다. 이는 pyrrolidine 고리가 기능화된 CNT는 PE 매트릭스 내에 균일하게 분산되고 CNT와 고분자 간의 강한 상호작용으로 인해 열적 안정성이 향상된 것으로 판단된다.

• Smart Structures and Systems
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• 제9권3호
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• pp.231-251
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• 2012

The stochastic optimal control for a piezoelectric spherically symmetric shell subjected to stochastic boundary perturbations is constructed, analyzed and evaluated. The stochastic optimal control problem on the boundary stress output reduction of the piezoelectric shell subjected to stochastic boundary displacement perturbations is presented. The electric potential integral as a function of displacement is obtained to convert the differential equations for the piezoelectric shell with electrical and mechanical coupling into the equation only for displacement. The displacement transformation is constructed to convert the stochastic boundary conditions into homogeneous ones, and the transformed displacement is expanded in space to convert further the partial differential equation for displacement into ordinary differential equations by using the Galerkin method. Then the stochastic optimal control problem of the piezoelectric shell in partial differential equations is transformed into that of the multi-degree-of-freedom system. The optimal control law for electric potential is determined according to the stochastic dynamical programming principle. The frequency-response function matrix, power spectral density matrix and correlation function matrix of the controlled system response are derived based on the theory of random vibration. The expressions of mean-square stress, displacement and electric potential of the controlled piezoelectric shell are finally obtained to evaluate the control effectiveness. Numerical results are given to illustrate the high relative reduction in the root-mean-square boundary stress of the piezoelectric shell subjected to stochastic boundary displacement perturbations by the optimal electric potential control.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.513-533
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• 1994

The smooth surface after polishing of composite resin contributes to the patient's comfort, and appearance and longevity of the restoration. This study was performed for the quantitative analysis of the effects of the various finishing and polishing instruments on the surface roughness and reflectivity of the microfill, and hybrid composite resins. Cylindrical specimens 2mm thick and 10mm in diameter of Silux Plus, Durafill VS ; Z100, Prisma TPH, Brilliant, and Herculite XR composite resin were polymerized under the matrix strip. 18 specimens for each composite resin materials were divided into 6 groups ; 5 experimental groups were abraded with # 600 sand paper to remove resin-rich layer, except control. Thereafter, using diamond bur(Mani Dia-Burs), carbide bur(E. T. carbide set 4159), rubber point(Composite polishing kit), aluminum-oxide disk(Sof-Lex disk), polishing paste(Enhance system) ; each specimen was polished to its best achievable surface according to manufacturer's directions. Final polished surfaces were evaluated for the surface roughness with profilometer(${\alpha}$-step 200, Tencor instruments, USA) and for the reflectivity with image analyser(Omniment Image Analyser, Buehler, USA). The results were as follows. 1. Polishing paste or aluminum-oxide disk finish in the microfill, and hybrid composite resins was as smooth as matrix strip finish on the surface roughness test. 2. Polishing paste or aluminum-oxide disk finish in the microfill ; polishing paste finish in the hybrid composite resins was as reflective as matrix strip finish on the refectivity test. 3. For the polishing paste, there were no significant differences between the composite resin materials on the surface roughness and refectivity tests. 4. For the aluminum-oxide disk, the best result was obtained with the microfill composite resin on the surface roughness and reflectivity test. 5. Diamond bur, carbide bur, and rubber point were inappropriate for the final polishing instruments.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
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• pp.128-128
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• 1998

Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteases that degrade extracellular matrix and basement membrane. These enzymes are play important roles in tumor cell invasion and metastasis, as well as angiogenesis and other connective tissue diseases. In our screening program for inhibitors of MMP-2 from fungal metabolites, we have isolated novel non-peptidic inhibitors of MMPs, designated gelastatin A and B from the culture broth of Westerdykella multispora F50733. The structures of gelastatin A and B were determined to be 3-(5E-hexa-2E,4E-dienylidene-2-oxo-5,6-dihydro-2H-pyran-3yl)-propanoic acid and 3-(5Z-hexa-2E,4E-dienylidene-2-oxo-5,6-dihydro-2H-pyran-3yl)-propanoic acid, respectively. Gelastatin A and B exist as a mixture of two stereoisomers in a ratio of 2: 1. The 2: 1 mixture of gelastatin A and B inhibited activated MMP-2 and MMP-9 with an IC$\sub$50/ value of 0.63, 5.29 ${\mu}$M, respectively. They inhibited the invasion of B16F10 melanoma cells through basement membrane Matrigel with dose dependent.