• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.216-221
• /
• 2001

The equivalent source method(ESM) is used for the calculation of the internal pressure field for an enclosure which can have arbitrary boundary conditions and may include internal objects which scatter the sound field. The advantage of using ESM is that it requires relatively low computing cost and is easy to model the internal diffracting objects. In the ESM modelling, some of the equivalent positions are chosen to be the same as the first order images of the source inside the enclosure, some are positioned on a spherical surface some distance outside the enclosure. The normal velocity on the surfaces of the enclosure walls is evaluated at a larger number of positions than there are equivalent sources. The sum of the squared difference between this velocity and the expected is minimized by adjusting the strength of the equivalent sources. This study is on the optimal equivalent source positions, the far field sources. Typically, the far field sources are evenly distributed on a surface of a virtual sphere which is centered at the enclosure with a sufficiently large radius. In this study, optimal far field source locations are searched using simulated annealing method and simulation results showed that optimally located sources gave better accuracy even with a smaller number of far field sources.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.143-148
• /
• 2013

Novel titanium containing solid core mesoporous shell silica has been synthesized by using octadecyltrichloro silane and triethylamine. The synthesized material was characterized by various physicochemical techniques. The mesoporous character of the material has been revealed from PXRD studies. The presence of octadecyltrichloro silane and triethylamine in the sample has been confirmed from EDAX studies. TG/DTA analysis reveals the thermal characteristics of the synthesized material. The presence of titanium in the frame work and its coordination state has been studies by UV-vis DR studies and XPS analysis. Chemical environment of Si in the framework of the material has been studied by $^{29}SiMASNMR$ studies. The surface area of the material is found to be around $550\;m^2g^{-1}$ and pore radius is of nano range from BET analysis. The spherical morphology and particle size of the core as well as shell has been found to be 300 nm and 50 nm respectively from TEM analysis. The catalytic application of this material towards the synthesis of caprolactam from cyclohexanone in presence of hydrogen peroxide through ammoxidation reaction has been investigated. The optimum conditions for the reaction have been established. The plausible mechanism for the formation of core silica and conversion of cyclohexanone has been proposed.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.5
• /
• pp.717-724
• /
• 2010

The initial trajectory of a spheroid configuration bobbin for precision guidance has been investigated by analyzing its aerodynamic load and six-degree-of-freedom motion. The effects of changes in the spheroidal head configuration, flow angle and lateral center-of-gravity offset are numerically studied using the commercial software "FLUENT". A wind tunnel test is also conducted to validate the numerical scheme and to examine effect of the Reynolds number on the flow around the bobbin. It is shown that the size of the separation bubble formed on the surface decreases significantly when the Reynolds number is varied between 110,000 and 140,000. At a zero flow angle, an oblate spheroidal head shows relatively moderate rotation while a prolate spheroidal head shows rapid rotation. The bobbin with a spherical head shape has little effect on the flow direction; however, the oblate bobbin is sensitive to the flow angle. The roll motion of the bobbin is greatly influenced by the lateral center-of-gravity offset and maximum dispersion is observed at half of the radius.

• Macromolecular Research
• /
• v.10 no.6
• /
• pp.311-317
• /
• 2002

The quantitative analysis of polymer micelles consisting of amphiphilic block copolymers was carried out by small-angle neutron scattering (SANS). The block copolymers, made of poly(2-ethoxyethyl vinyl ether-b-2-hydroxyethyl vinyl ether)(poly(EOVE-b-HOVE)), exhibited a sharp morphological transition from a homogeneous solution to a micelle structure with increasing temperature. This transition is accompanied by a formation of spherical domains of poly(EOVE) with a radius around 200 $\AA$. The variations of the size and its distribution of the domains were investigated as a function of polymer concentration and temperature. The validity of SANS analysis, including the wavelength- and incident-beam-smearing effects of the SANS instrument, was examined with a pre-calibrated polystyrene latex.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.8
• /
• pp.897-904
• /
• 1999

We have presented the thermodynamic, structural and dynamic properties of liquid pentane isomers - normal pentane, isopentane, and neopentane - using an expanded collapsed atomic model. The thermodynamic properties show that the intermolecular interactions become weaker as the molecular shape becomes more nearly spherical and the surface area decreases with branching. The structural properties are well predicted from the site-site radial, the average end-to-end distance, and the root-mean-squared radius of gyration distribution func-tions. The dynamic properties are obtained from the time correlation functions - the mean square displacement (MSD), the velocity auto-correlation (VAC), the cosine (CAC), the stress (SAC), the pressure (PAC), and the heat flux auto-correlation (HFAC) functions - of liquid pentane isomers. Two self-diffusion coefficients of liquid pentane isomers calculated from the MSD's via the Einstein equation and the VAC's via the Green-Kubo relation show the same trend but do not coincide with the branching effect on self-diffusion. The rotational re-laxation time of liquid pentane isomers obtained from the CAC's decreases monotonously as branching increases. Two kinds of viscosities of liquid pentane isomers calculated from the SAC and PAC functions via the Green-Kubo relation have the same trend compared with the experimental results. The thermal conductivity calculated from the HFAC increases as branching increases.

• Journal of Environmental Science International
• /
• v.30 no.6
• /
• pp.429-439
• /
• 2021

Food waste is both an industrial and residential source of pollution, and there has been a great need for food waste reduction. As a preliminary step in this study, waste reduction is quantitatively modeled. This study presents two models based on kinetics: a simple kinetic model and a mass transport-shrinking model. In the simple kinetic model, the smaller is the reaction rate constant ratio k₁, the lower the rate of conversion from the raw material to intermediate products. Accordingly, the total elapsed reaction time becomes shorter. In the mass transport-shrinking model, the smaller is the microbial decomposition resistance versus the liquid mass transfer resistance, the greater is the reduction rate of the radius of spherical waste particles. Results showed that the computed reduction of waste mass in the second model agreed reasonably with that obtained from a few experimantal trials of biodegradation, in which the microbial effect appeared to dominate. All calculations were performed using MATLAB 2020 on PC.

• Advances in Computational Design
• /
• v.9 no.1
• /
• pp.39-52
• /
• 2024

If the governing differential equation arising from engineering problems is treated as an analytic, continuous and derivable function, it can be expanded by one point as a series of finite numbers. For the function to be zero for each value of its domain, the coefficients of each term of the same power must be zero. This results in a recursive relationship which, after applying the natural conditions or the boundary conditions, makes it possible to obtain the values of the derivatives of the function with acceptable accuracy. The elastoplastic analysis of an inhomogeneous thick sphere of metallic materials with linear variation of the modulus of elasticity, yield stress and Poisson's ratio as a function of radius subjected to internal pressure is presented. The Beltrami-Michell equation is established by combining equilibrium, compatibility and constitutive equations. Assuming axisymmetric conditions, the spherical coordinate parameters can be used as principal stress axes. Since there is no analytical solution, the natural boundary conditions are applied and the governing equations are solved using a proposed new method. The maximum effective stress of the von Mises yield criterion occurs at the inner surface; therefore, the negative sign of the linear yield stress gradation parameter should be considered to calculate the optimal yield pressure. The numerical examples are performed and the plots of the numerical results are presented. The validation of the numerical results is observed by modeling the elastoplastic heterogeneous thick sphere as a pressurized multilayer composite reservoir in Abaqus software. The subroutine USDFLD was additionally written to model the continuous gradation of the material.

• Journal of Sensor Science and Technology
• /
• v.4 no.4
• /
• pp.1-9
• /
• 1995

The ${\gamma}$-ray deposition spectra were calculated by Monte Calro method to obtain the scintillation characteristics of the ${\gamma}$-ray for BGO scintillation detector with the spherical shape of 1.25 cm radius. The code used in calculating the ${\gamma}$-ray deposition spectra was made for personal computer with qbasic language. Also the ${\gamma}$-ray energy spectra of $^{22}Na$, $^{137}Cs$ and $^{207}Bi$ were measured with the detector. The energy dependent resolution below 2000 keV for the detector was determined by estimating the standard deviation of the photopeak fitted with gaussian function, and $X^{2}$ fitting using Nardi's empirical formula. The measured spectra of $^{22}Na$ and $^{137}Cs$ were compared with the broadened spectra which were obtained by broadening the calculated ${\gamma}$-ray deposition spectra with the energy dependent resolution. The absolute efficiency and the intrinsic peak efficiency of the detector were obtained by calculating the ${\gamma}$-ray deposition spectrum with the code.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.2
• /
• pp.267-278
• /
• 2019

Variety of tunnel ahead prediction methods have been performed for safe tunnel construction during tunnel excavation. Pole-pole array among the electrical resistivity survey, which is one of the tunnel ahead prediction method, has been utilized to predict water-bearing sediments or weak zone located within 5 times of tunnel diameter. One of the most important processes is the estimation of virgin ground resistivity and it can be obtained from the following process: 1) calculation of contact area between the electrodes and the medium, and 2) assumption of the electrodes as equivalent spherical electrodes which have a same surface area with the electrodes. This assumption is valid in a small contact area and sufficient distance between the electrodes. Since the measured resistance, in general, varies with the electrode size, shape, and distance between the electrodes, it is necessary to evaluate the influence of these factors. In this study, theoretical equations were derived and experimental tests were conducted considering the electrode size, shape, and distance of cylindrical electrodes which is the most commonly utilized electrode shape. Through this theoretical and experimental study, it is known that one should be careful to use the assumption of the equivalent half-spherical electrode with large ratio between the penetrated depth and radius of the cylindrical electrode, as the error may get larger.

• Journal of the Korean Home Economics Association
• /
• v.37 no.7
• /
• pp.17-27
• /
• 1999

According to the design method for constructing the Korean Men's Jo-go-ri(the traditional Korean jacket)collar, there are differences in form after its completion. In the construction design of the midsection of the gusset as in that of the basic pattern Jo-go-ri, not only was the positioning of the two sides of the collar not smooth, but also, when the collar strip(Dongjung) was attached, there would be an imbalance on one side or the other so that it was difficult to achieve symmetry. Therefore in this project, by applying the pattern design of the gusset midsection to that of the collar midsection, not only did attaching the collar(Kit) and the collar strip create a visual effect by equalizing the lengths of the two sides, but the construction was also easy. This method of construction introduces the three-dimensional aspect of the human form in its conic, spherical and cylindrical aspects, so that, through schematizing the scientific character of Korea's clothing, its appropriateness is verified. As a matter of fact, since there is no standardization of pattern whether for educational use or for mass-produced clothing, so that even the patterns used in computer-assisted design are executed according to the designer's personal skill, the reality is that after completion of construction the quality has not been uniform. For this schematization, inverse calculation of measurements pertaining to the calculation formula and of teaching materials has been referenced. In particular, the partial regulation of the calculation formula pertaining to the basic pattern construction, the method of making the collar midsection, and the construction method of the extreme and mean ratio adjustment, can be adjusted for all measurements, thereby providing the establishment of a design criterion and the possibility of the standardization of construction methods. The production method for the basic pattern design is as follows: 1) The conic angle for the Jo-go-ri's girth, length end neck width is fixed at 70(72) degree. 2) The radius of the cone is sleeve length. 3) The bust girth calculation formula is B/4 + 2.5 cm. 4) The armhole formula is B/4 + 2.5cm. 5) The neck width formula is B/10. 6) The ratio of the collar junction{width of collar(Kit) + width of collar strip(Dongjung) to the gusset length is 5:8. 7) The length of the side seam is a length intersecting the armhole line and the conic radius of sleeve length, that is an arc that exceeds the length of the Jo-go-ri's midsection.