• 대한기계학회논문집A
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• 제27권6호
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• pp.1020-1027
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• 2003

A traditional mold design has been conducted by an experience-based trial and error, whereby the mold designer would decide the gate locations and processing conditions based on the caring characteristics and its functional requirements. The paper suggests an optimal gate location and processing conditions in the injection molding using a global search method referred to as micro genetic algorithm( ${\mu}$ GA). ${\mu}$ GA yields the optimal solution with a small size of population without respect to design variables for saving time that is needed to calculate the fitness of many individuals. Due to the reason, the paper uses a commercial analysis package of injection molding(CAPA) to analysis a state of flux. In addition to that, axiomatic approach .is applied in the beginning of design. It is a useful method to draw a well-organized and reasonable idea to handle a problem.

• 한국분말재료학회지
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• 제26권3호
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• pp.220-224
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• 2019

The aluminum (Al)/copper oxide (CuO) complex is known as the most promising material for thermite reactions, releasing a high heat and pressure through ignition or thermal heating. To improve the reaction rate and wettability for handling safety, nanosized primary particles are applied on Al/CuO composite for energetic materials in explosives or propellants. Herein, graphene oxide (GO) is adopted for the Al/CuO composites as the functional supporting materials, preventing a phase-separation between solvent and composites, leading to a significantly enhanced reactivity. The characterizations of Al/CuO decorated on GO(Al/CuO/GO) are performed through scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping analysis. Moreover, the functional bridging between Al/CuO and GO is suggested by identifying the chemical bonding with GO in X-ray photoelectron spectroscopy analysis. The reactivity of Al/CuO/GO composites is evaluated by comparing the maximum pressure and rate of the pressure increase of Al/CuO and Al/CuO/GO. The composites with a specific concentration of GO (10 wt%) demonstrate a well-dispersed mixture in hexane solution without phase separation.

• Nonlinear Functional Analysis and Applications
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• 제28권2호
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• pp.497-520
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• 2023

Numerous problems in science and engineering defined by nonlinear functional equations can be solved by reducing them to an equivalent fixed point problem. Fixed point theory provides essential tools for solving problems arising in various branches of mathematical analysis, such as split feasibility problems, variational inequality problems, nonlinear optimization problems, equilibrium problems, complementarity problems, selection and matching problems, and problems of proving the existence of solution of integral and differential equations.The theory of fixed is known to find its applications in many fields of science and technology. For instance, the whole world has been profoundly impacted by the novel Coronavirus since 2019 and it is imperative to depict the spread of the coronavirus. Panda et al. [24] applied fractional derivatives to improve the 2019-nCoV/SARS-CoV-2 models, and by means of fixed point theory, existence and uniqueness of solutions of the models were proved. For more information on applications of fixed point theory to real life problems, authors should (see [6, 13, 24] and the references contained in).

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1218-1242
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• 2002

Photochemical reactions of aromatic carbonyl compounds with silyl ketene acetals have been explored. Irradiation of acetonitrile or benzene solutions containing aryl aldehydes or ketones in the presence of silyl ketene acetals is observed to promo te formation of ${\beta}-hydroxyester$, 2,2-dioxyoxetane and 3,3-dioxyoxetane products. The ratios of these photoproducts, which arise by competitive single electron transfer (SET) and classical Paterno-Buchi mechanistic pathways, is found to be dependent on the degree of methyl-substitution on the vinyl moieties of the ketene acetals in a manner which reflects expected alkyl substituent effects on the oxidation potentials of these electron rich donors. An analysis of the product distribution arising by irradiation of a solution containing butyrophenone (6) and the silyl ketene acetal 9, derived from methyl isobutyrate, provides an estimate of the rate constants for the competitive Norrish type Ⅱ, SET and Paterno-Buchi processes occuring. Finally, sequences involving silyl ketene acetal-aryl aldehyde or ketone photoaddition followed by 2,2-dioxyoxetane hydrolysis represent useful procedures for Claisen-condensation type, ${\beta}-hydroxyester$ synthesis.

• 한국재료학회지
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• 제22권6호
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• pp.275-279
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• 2012

(3-mercaptopropyl)trimethoxysilane (MPTMS) was used as a silylation agent, and modified silica nanoparticles were prepared by solution polymerization. 2.0 g of silica nanoparticles, 150 ml of toluene, and 20 ml of MPTMS were put into a 300 ml flask, and these mixtures were dispersed with ultrasonic vibration for 60 min. 0.2 g of hydroquinone as an inhibitor and 1 to 2 drops of 2,6-dimethylpyridine as a catalyst were added into the mixture. The mixture was then stirred with a magnetic stirrer for 8 hrs. at room temperature. After the reaction, the mixture was centrifuged for 1 hr. at 6000rpm. After precipitation, 150 ml of ethanol was added, and ultrasonic vibration was applied for 30 min. After the ultrasonic vibration, centrifugation was carried out again for 1 hr. at 6000rpm. Organo-modification of silica nanoparticles with a ${\gamma}$-methacryloxypropyl functional group was successfully achieved by solution polymerization in the ethanol solution. The characteristics of the ${\gamma}$-mercaptopropyl modified silica nanoparticles (MPSN) were examined using X-ray photoelectron spectroscopy (XPS, THERMO VG SCIENTIFIC, MultiLab 2000), a laser scattering system (LSS, TOPCON Co., GLS-1000), Fourier transform infrared spectroscopy (FTIR, JASCO INTERNATIONL CO., FT/IR-4200), scanning electron microscopy (SEM, HITACHI, S-2400), an elemental analysis (EA, Elementar, Vario macro/micro) and a thermogravimetric analysis (TGA, Perkin Elmer, TGA 7, Pyris 1). From the analysis results, the content of the methacryloxypropyl group was 0.98 mmol/g and the conversion rate of acrylamide monomer was 93%. SEM analysis results showed that the organo-modification of ultra-fine particles effectively prevented their agglomeration and improved their dispensability.

• 대한환경공학회지
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• 제35권2호
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• pp.131-136
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• 2013

본 연구의 목적은 고온 처리된 납석을 흡착제로 이용하여 불소 제거를 연구하는 것이었다. 본 연구에서는 흡착제양, 반응시간, 초기불소농도 그리고 용액pH가 불소제거에 미치는 영향을 관찰하기 위하여 회분조건에서 흡착실험을 수행하였다. 실험에는 다양한 온도에서 열처리한 납석[무처리 (P-U), $400^{\circ}C$ (P-400), $600^{\circ}C$ (P-600)]을 사용하였다. 실험결과, 불소흡착능은 P-400 > P-U > P-600 순으로 나타났다. XRD 분석결과, P-U와 P-400은 석영, 디카이트, 엽납석으로 구성된 반면, P-600은 석영으로만 구성된 것으로 나타났다. BET 분석결과, 비표면적은 P-600 > P-400 > P-U 순으로 나타났다. 동역학적 실험결과, P-400에서의 불소흡착은 24시간 이내에 평형에 도달하였다. 평형흡착 실험결과, P-400의 최대 불소흡착능은 0.957 mg/g이었다. 또한, P-400에 의한 불소제거는 pH 4-10범위에서 용액 pH의 영향을 받지 않았지만, 강산성(pH < 4)과 강염기성(pH > 10) 조건에서는 불소제거가 크게 감소하였다. 본 연구에 의하면, 납석은 저가 흡착제로써 수용액상의 불소제거에 이용될 수 있을 것으로 판단된다.

• 한국식품위생안전성학회지
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• 제36권1호
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• pp.34-41
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• 2021

본 연구는 조제유류 중 지방산에 대해 최신 분석법을 마련하고자 수행하였다. 조제유류 중 지방산 함량 분석을 위해 GC를 이용한 분석법을 확립하고 시중에 유통 중인 제품을 대상으로 적용성을 검토하였다. 분석법 검증은 특이성, 직선성, 검출한계 및 정량한계, 정확성, 정밀성에 대해 수행되었다. Linoleic acid 및 α-linolenic acid의 0.1-5 mg/mL 농도범위에서 R2=0.999 이상의 우수한 직선성을 확인할 수 있었다. Linoleic acid 및 α-linolenic acid의 LOD는 각각 0.06 mg/mL, 0.01 mg/mL, LOQ는 각각 0.16 mg/mL, 0.03 mg/mL였다. 표준인증물질 분석을 통해 정확성을 검토하였으며, linoleic acid 및 α-linolenic acid의 회수율은 각각 100.8%와 101.1%로 확인하였다. 정밀성을 검토한 결과 시료 채취량에 따른 반복성은 linoleic acid 1.4-2.9%, α-linolenic acid 1.1-2.7%이었고, 실험실간 재현성은 각각 2.8%, 1.5%임을 확인하였다. 본 연구에서 확립된 분석법을 적용하여 국내 유통 중인 조제유류 및 조제식 제품 12건에 대해 적용성 검토를 실시한 결과 전체 시료에서 분석이 용이하였으며, 모두 기준·규격에 적합함을 확인하였다. 본 결과로부터 확립된 GC를 이용한 분석법은 조제유류 중 지방산 함량을 확인하기에 적합함을 확인하였으며 국내 식품 영양성분의 관리 기반을 강화하는데 기여할 것으로 사료된다.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2016-2024
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• 2005

In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the cross section stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.

• Nonlinear Functional Analysis and Applications
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• 제26권2호
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• pp.225-236
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• 2021

In this paper, we determine position vector of a line of curvature of a regular surface which is relatively normal-slant helix, with respect to Darboux frame. Then, a vector differential equation is established by means Darboux formulas, in the case of the geodesic torsion is vanishes. In terms of solution, we determine the parametric representation of a line of curvature which is relatively normal-slant helix, with respect to standard frame in Euclidean 3-space. Thereafter, we apply this result to find the position vector of a line of curvature which is isophote curve.

• Structural Engineering and Mechanics
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• 제28권2호
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• pp.129-152
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• 2008

This paper considers the solution of the stochastic differential equations (SDEs) with random operator and/or random excitation using the spectral SFEM. The random system parameters (involved in the operator) and the random excitations are modeled as second order stochastic processes defined only by their means and covariance functions. All random fields dealt with in this paper are continuous and do not have known explicit forms dependent on the spatial dimension. This fact makes the usage of the finite element (FE) analysis be difficult. Relying on the spectral properties of the covariance function, the Karhunen-Loeve expansion is used to represent these processes to overcome this difficulty. Then, a spectral approximation for the stochastic response (solution) of the SDE is obtained based on the implementation of the concept of generalized inverse defined by the Neumann expansion. This leads to an explicit expression for the solution process as a multivariate polynomial functional of a set of uncorrelated random variables that enables us to compute the statistical moments of the solution vector. To check the validity of this method, two applications are introduced which are, randomly loaded simply supported reinforced concrete beam and reinforced concrete cantilever beam with random bending rigidity. Finally, a more general application, randomly loaded simply supported reinforced concrete beam with random bending rigidity, is presented to illustrate the method.