• Korean Journal of Materials Research
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• v.9 no.5
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• pp.491-495
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• 1999

In this study, we focus on Ca contaminant which affects on the roughness Si substrate after thermal process. The initial Si substrates were contaminated intentionally by using a standard Ca solution. The contamination levels of Ca impurity were measured by TXRF and the chemical composition of that was analyzed by AES. Then we gre the thermal oxide to investigate the effect of Ca contaminants. The microroughness of the Si surface, the thermal oxide surface, and the surface after removing the thermal oxide were measured to examine the electrical characteristics. The initial substrates that were contaminated with the standard solution of Ca exhibited the contamination levels of 10\ulcorner~10\ulcorneratoms/$\textrm{cm}^2$ which was measured by TXRF. The Ca contaminants were detected by AES and exhibited the peaks of Ca, SI, C and O.After intentional contamination, the surface microroughness of this initial substrate was increased from $1.5\AA$ to 4$\AA$ as contamination levels became higher. The microroughness of the thermal oxide surfaces of both contaminated and bare Si substrates exhibits similar values. But the microroughness of the contaminated$ Si/SiO_2$ interface was increased as contamination increased. The thermal oxide of contaminated substrate exhibited the small minority carrier diffusion length, low breakdown voltage, and slightly high leakage current.

• Earthquakes and Structures
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• v.1 no.4
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• pp.411-425
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• 2010

The effect of dead loads on dynamic responses of uniform elastic beams is examined by means of a governing equation which takes into account initial bending stress due to dead loads. First, the governing equation of beams which includes the effect of dead loads is briefly presented from the author's paper (Takabatake 1990). In the formulation the effect of dead loads is considered by strain energy produced by conservative initial stresses produced by the dead loads. Second, the effect of dead loads on dynamical responses produced by live loads in simply supported beams and clamped beams is confirmed by the results of numerical computations with the Galerkin method and Wilson-${\theta}$ method. It is shown that the dynamical responses, like dynamic deflections and bending moments produced by dynamic live loads, are decreased in a heavyweight beam when the effect of dead loads is included. Third, an approximate solution for dynamic deflections including the effect of dead loads is presented in closed-form. The proposed solution shows good in agreement with results of numerical computations with the Galerkin method and Wilson-${\theta}$ method. Finally, a method reflecting the effect of dead loads for dynamic responses of beams on the magnitude of live loads is presented by an example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.4
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• pp.82-88
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• 2011

A typical job sequencing problem is studied in this research to improve productivities in manufacturing companies. The problem consists of two-stage parts and assembly processes. Two parts are provided independently each other and then two sequential assembly processes are followed. A new heuristic is developed to solve the new type of sequencing problem. Initial solution is developed in the first stage and then the initial solution is improved in the second stage. In the first stage, a longer part manufacturing time for each job is selected between two, and then a sequence is determined by descending order of the times. This initial sequence is compared with Johnson's sequence obtained from 2-machine assembly times. Any mismatches are tried to switch as one possible alternative and completion time is calculated to determine whether to accept the new sequence or not to replace the current sequence. Searching process stops if no more improvement can be made.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.04a
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• pp.37-46
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• 1998

Several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation by biezocone excess pore water dissipation test in soft clay deposits. However, depending on the assumptions and analytical techniques, the estimated coefficient of consolidation could be in a considerably wide range even for a specific degree of consolidation. These solutions are obtained from an initial excess porewater pressure distribution which can be determined from. either the cavity expansion theory or the strain path method. The 야ssipation of the initial excess porelvater pressure has been usally simulated by means of linear-uncoupled consolidation analysis and then the dissipation curve is normalized by the initial excess porewater pressure for easy use. However. since there is no guidelines or rules on which method gives the best solution for obtaining the coefficient of consolidation from the dissipation curve, the final selection was only based on engineer's extrience and Judgements. Thus, such an arbitrary selection might be inappropriate for a specific site to characterize the consolidation behavior. In this paper, we reviewed various theoretical time factors and, based on this consideration, we mentioned needs for researches in selecting a specific solution that is compatible for Korean clays. Also we listed some source of errors that can be encountered in the procedure of dissipation analysis.

• KSBB Journal
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• v.15 no.5
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• pp.444-451
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• 2000

Nonliving methanotrophic biomass was used as biosorbent to remove lead which is one of representative pollutants in metal-bearing wastewater. Solution pH, maximum uptake, biosorbent dose and ionic strength were considered as major factors for adsorption experiments. The optimum pH range for lead removal was increased 3.8∼11.0 for methanotrophic biomass compared to biosorbent-free control, pH of 8.4∼11.2. Removal efficiency of lead by methanotrophic biomass was pH dependent, but less sensitive than that of control. In isotherm experiments with 0.2g biosorbent/L at initial solution pH 5.0, methanotrophic biomass took up lead from aqueous solutions to the extent of 1085 mg/g biomass. Removal amount of lead increased with an increase of biomass dose. According to biomass dose for initial 1000 mg Pb/L at initial pH 5.0, the optimum amount of biomass for maximum lead removal per unit methanotrophic biomass was 0.2 g biomass/L. As a result of scanning electron microscope (SEM) micrographs equipped with energy dispersive spectroscopy (EDS), lead removal by methanotrophic biomass seemed to be through adsorptions on the surface of methanotrophic biomass and exopolymers around the biomass. EDS spectra confirmed that lead adsorption appeared on the biomass and exopolymers that may be effective to lead removal comparing before and after contact with lead. Removal efficiency of lead was slightly affected by ionic strength up to 2.0 M of NaCl and NaNO$_3$respectively.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.273-277
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• 2023

The biosorption of methylene blue (MB) from aqueous solution was investigated using dried Rhodotorula glutinis as the biosorbent. The effects of pH, initial dye concentration, biosorbent dosage, and kinetic studies were determined to obtain valuable information for biosorption. Results indicated that most of the adsorbed MB bound within 30 minutes of contact and the MB adsorption capacity increased from 21.1 to 101.8 mg/g with the initial MB concentration increased from 50 to 300 mg/L. Additionally, the MB adsorption capacity gradually increased from pH 4.0 to 9.0, reaching its peak at an initial pH of 9.0. As the biomass load was increased from 0.25 to 4.0 g/L, the MB removal efficiency increased from 14.1 to 84.5%. The Langmuir model provided the best fit throughout the concentration range, and the maximum adsorption capacity (q_max) and Langmuir constant (b) were determined to be 135.14 mg/g and 0.026 l/mg, respectively. Furthermore, the biosorbent process of R. glutinis was found to follow pseudo-second-order kinetics and the calculated q_eq,cal value showed good agreement with the experimental q_eq value. Overall, the biosorption of MB by R. glutinis can be characterized as a monolayer, single site type phenomenon, and the rate-limiting step was determined to be the chemical reaction between the adsorbent and the adsorbate.

• Journal of Digital Convergence
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• v.16 no.6
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• pp.197-204
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• 2018

The realistic Visual Effects using fluid simulation in 3D computer graphics are operated as important factors to improve the quality of images. The process of creating realistic motions of water, fire, explosion by controlling each property of fluid is called fluid simulation. In general, the creation of a fluid simulation concentrates on the main simulation work phase, however an effective method for initial set up is important for the main simulation work. The purpose of this study is to analyze the factors involved in the initial emission motion and shape of fluid and propose methods that can efficiently apply this into the initial set up. For the process of the research, first, problems are raised based on related researches, and second, two experiments, 'Dynamic Fluid Emitter Creation' and 'User Design Type Emission Velocity Solution', are conducted for more effective fluid simulation. Through this research, the effective fluid simulation of initial set up phase will be suggested through the user design-type emission control solutions.

• Journal of the Korean Mathematical Society
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• v.54 no.5
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• pp.1483-1504
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• 2017

We consider weak solutions of the instationary Navier-Stokes system in a smooth bounded domain ${\Omega}{\subset}{\mathbb{R}}^3$ with initial value $u_0{\in}L^2_{\sigma}({\Omega})$. It is known that a weak solution is a local strong solution in the sense of Serrin if $u_0$ satisfies the optimal initial value condition $u_0{\in}B^{-1+3/q}_{q,s_q}$ with Serrin exponents $s_q$ > 2, q > 3 such that ${\frac{2}{s_q}}+{\frac{3}{q}}=1$. This result has recently been generalized by the authors to weighted Serrin conditions such that u is contained in the weighted Serrin class ${{\int}_0^T}({\tau}^{\alpha}{\parallel}u({\tau}){\parallel}_q)^s$ $d{\tau}$ < ${\infty}$ with ${\frac{2}{s}}+{\frac{3}{q}}=1-2{\alpha}$, 0 < ${\alpha}$ < ${\frac{1}{2}}$. This regularity is guaranteed if and only if $u_0$ is contained in the Besov space $B^{-1+3/q}_{q,s}$. In this article we consider the limit case of initial values in the Besov space $B^{-1+3/q}_{q,{\infty}}$ and in its subspace ${{\circ}\atop{B}}^{-1+3/q}_{q,{\infty}}$ based on the continuous interpolation functor. Special emphasis is put on questions of uniqueness within the class of weak solutions.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.4
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• pp.631-642
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• 2016

This article deals with one-dimension backward heat conduction problem (BHCP). A new approach based on least squares support vector machines (LS-SVM) is proposed for obtaining their approximate solutions. The approximate solution is presented in closed form by means of LS-SVM, whose parameters are adjusted to minimize an appropriate error function. The approximate solution consists of two parts. The first part is a known function that satisfies initial and boundary conditions. The other is a product of two terms. One term is known function which has zero boundary and initial conditions, another term is unknown which is related to kernel functions. This method has been successfully tested on practical examples and has yielded higher accuracy and stable solutions.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.313-318
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• 2004

We studied a storage of waste-brown seaweed at room temperature and degradation of alginate in seaweed by microorganism DS-02. The seaweeds, mixed with 5.0 wt% DS-02 and sealed in vinyl package without any other treatment, could be stored longer than 1 year without spoilage at room temperature. During the storage process, the alginate of seaweed was decomposed by enzyme of DS-02 and the molecular weight of alginate decreased to about 1/10 of initial quantity. DS-02 growed as fast as it had maximum weight after 24 hour culture and it's enzyme had a maximum activity of alginate degradation at $40^{\circ}C.$ The seaweed sample became particles in DS-02 culture solution and the M. W of alginate decreased to about 1/10 of initial value after 24 hour decomposition. The effect of alginate degradation with DS-02 was similar to that of degradation with 3.0 M HCI solution for 24 hour.