• Structural Engineering and Mechanics
• /
• 제55권1호
• /
• pp.29-46
• /
• 2015

A three-dimensional (3-D) method of analysis is presented for determining the natural frequencies of a truncated shallow and deep conical shell with linearly varying thickness along the meridional direction free at its top edge and clamped at its bottom edge. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_r$, $u_{\theta}$, and $u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Strain and kinetic energies of the truncated conical shell with variable thickness are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated. The frequencies from the present 3-D method are compared with those from other 3-D finite element method and 2-D shell theories.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권3호
• /
• pp.11-18
• /
• 1996

Liquid droplets of water and argon surrounded by their vapor have been simulated by the milecular dynamics method. To explore the surface phenomena of clusters, each molecule is classified into 'liquid', 'surface', or 'vapor' with respect to the number of neighbor molecules. The contribution of a 'surface' molecule of the water cluster to the far infrared spectrum is almist the same as that of the 'liquid' molecule. Hence, the liquid-vapor interface is viewed as geometrically and temporally varying boundary of 'liquid' molecules with only a single layer of 'surface' molecules that might have different characteristics from the 'liquid' molecules. The time scale of the 'phase change' of each molecule is estimated for the argon cluster by observing the instantancous kinetic and potential energies of each molecule. To compare the feature of clusters with macroscopic droplets, the temperature dependence of the surface tension of the argon cluster is estimated.

• Bulletin of the Korean Chemical Society
• /
• 제33권12호
• /
• pp.4098-4102
• /
• 2012

The potential energy surface (PES) for the loss of HCN from the pyrimidine molecular ion has been explored using quantum chemical calculations. Possible reaction pathways to form five $C_3H_3N^{+{\bullet}}$ isomers have been obtained with Gaussian 4 model calculations. The rate constant for the HCN loss and the product branching ratio have been calculated using the Rice-Ramsperger-Kassel-Marcus theory on the basis of the obtained PES. The resultant rate constant agrees with the previous experimental result. By a kinetic analysis, it is proposed that the formation of $CH=CHC{\equiv}NH^{+{\bullet}}$ is favored near the dissociation threshold, while the formation of $CH=CHN{\equiv}CH^{+{\bullet}}$ is favored at high energies.

• 한국군사과학기술학회지
• /
• 제15권2호
• /
• pp.138-146
• /
• 2012

Using Shear-free Ship wake theory it was predicted the detectable submarine's turbulent wake on the sea surface was about 12km long when there was no breaking waves on the sea surface. It means that there are sufficient detectable turbulent kinetic energies on the sea surface as well as in the water. In this paper, we have proposed some concepts of non acoustic anti-submarine surveillance systems; SAR for sea surface surveillance, LIDAR for sub-surface surveillance and propelled gliders for under -water surveillance.

• 한국안전학회지
• /
• 제26권3호
• /
• pp.29-33
• /
• 2011

Experimental studies were performed to investigate the injury potential of BB pellets through gelatine based simulants. In order to record BB pellet movements penetrating into the target simulant, a high-speed video camera was used. In this study the first investigation involved the effects on concentrations, homogeneity and gelation times of the gelatine simulant. The second investigation involved the penetration depth of the pellets to the simulant by different distances between the BB gun and the simulant. The final one is associated with impact velocity, threshold velocity and penetration depth of the pellets by different kinetic energies of the BB gun. Results provided the basis in assessing the injury potential of BB pellets.

• Bulletin of the Korean Chemical Society
• /
• 제12권4호
• /
• pp.387-392
• /
• 1991

We present a theoretical investigation of the inelastic atom-surface phonon scattering for a model He-Si(100) system by the classical trajectory-quantum forced oscillator(DECENT) method. Single and multi-phonon transition probabilities of normal modes are calculated for several initial beam orientations and several initial kinetic energies. In order to understand surface structure effects, the calculation has been done on both reconstructed and unreconstructed surfaces of the He/Si(100) system. The origin of mode specificity for energy transfer is discussed. The contribution of one, two, and multi-phonon events to the total energy transfer between 0 and 600 K is also given.

• Structural Engineering and Mechanics
• /
• 제72권1호
• /
• pp.71-81
• /
• 2019

The objective of this paper is to develop a size-dependent nonlinear model of beams for fluid-conveying nanotubes with an initial deflection. The nonlinear frequency response of the nanotube is analysed via an Euler-Bernoulli model. Size influences on the behaviour of the nanosystem are described utilising the nonlocal strain gradient theory (NSGT). Relative motions at the inner wall of the nanotube is taken into consideration via Beskok-Karniadakis model. Formulating kinetic and elastic energies and then employing Hamilton's approach, the nonlinear motion equations are derived. Furthermore, Galerkin's approach is employed for discretisation, and then a continuation scheme is developed for obtaining numerical results. It is observed that an initial deflection significantly alters the frequency response of NSGT nanotubes conveying fluid. For small initial deflections, a hardening nonlinearity is found whereas a softening-hardening nonlinearity is observed for large initial deflections.

• Bulletin of the Korean Chemical Society
• /
• 제13권2호
• /
• pp.187-192
• /
• 1992

The classical trajectory method, previously applied to the reactions of polyatomic molecules with fcc structured metal solids[S. C. Park, C. H. Cho, and C. H. Rhee, Bull. Kor. Chem. Soc., 11, $1(1990)]^1$ is extended to the collision energy dependence of the reaction of the Al solid by $SiCl_4$ molecules. We have calculated etching yields, degrees of anisotropy, kinetic energy distributions, and angular distributions for the reactions of the Al solid and compared with those for the reactions of the Cu solid. Over the range of collision energies we considered, the reactions of the Al soIid show higher etching yield and better anisotropy than the reactions of the Cu solid. Details of reaction mechanisms and the relevance of these calculations for the dry etching of CuAl alloy are discussed.

• Bulletin of the Korean Chemical Society
• /
• 제6권5호
• /
• pp.270-272
• /
• 1985

The rate constants of the hydrogen-deuterium exchange of 8-CH groups in 5'-rAMP and 5'-GMP were measured by laser Raman spectroscopy. The Arrhenius activation energies calculated from the rate constants measured as a function of temperature were similar for both compounds. However, the effects of pD on exchange rate constants were different for the two compounds. Our kinetic data support the exchange reaction mechanism involving an ylide type intermediate.

• Bulletin of the Korean Chemical Society
• /
• 제11권4호
• /
• pp.290-296
• /
• 1990

Ion-surface collision studies at low kinetic energies (1-100 eV) provide a unique opportunity for investigating reactions and collision dynamics at surfaces. A special ion optics system for generating an energy- and mass-selected ion beam of this energy is designed and constructed. An ultrahigh vacuum (UHV) reaction chamber, in which the ions generated from the beamline collide with a solid surface, is equipped with Auger electron spectroscopy (AES) and thermal desorption spectrometry (TDS) as in-situ surface analytical tools. The resulting beam from the system has the following characteristics : ion current of 5-50 nA, energy spread < 2eV, current stability within ${\pm}5%,$ and unit mass resolution below 20 amu. The performance of the instrument is illustrated with data representing the implantation behavior of $Ar^+$ into a graphite (0001) surface.