• Transactions on Control, Automation and Systems Engineering
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• 제4권1호
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• pp.62-74
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• 2002

The tracking of a reference temperature trajectory in a polymerization batch reactor is a common problem and has critical importance because the quality control of a batch reactor is usually achieved by implementing the trajectory precisely. In this study, only energy balances around a reactor are considered as a design model for control synthesis, and material balances describing concentration variations of involved components are treated as unknown disturbances, of which the effects appear as time-varying parameters in the design model. For the synthesis of a tracking controller, a method combining the input-output linearization of a time-variant system with the parameter estimation is proposed. The parameter estimation method provides parameter estimates such that the estimated outputs asymptotically follow the measured outputs in a specified way. Since other unknown external disturbances or uncertainties can be lumped into existing parameters or considered as another separate parameters, the method is useful in practices exposed to diverse uncertainties and disturbances, and the designed controller becomes robust. And the design procedure and setting of tuning parameters are simple and clear due to the resulted linear design equations. The performances and the effectiveness of the proposed method are demonstrated via simulation studies.

• Journal of Microbiology and Biotechnology
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• 제11권2호
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• pp.329-332
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• 2001

It has been known that, in enzymatic synthesis of cephalexin, the conversion yield was reduced by high loading of ampicillin acylase. In order to elucidate this phenomena, pH-controlled synthesis of cephalexin was examined using a purified Acetobacter turbidans acylase. When the pH of the reaction mixture was maintained at $6.20{\pm}0.04$, the reduction of the maximal conversion rate was not observed even with high enzyme loading. The kinetic parameters also suggest that pH drop during the enzymatic synthesis of cephalexin was mainly attributed to the rapid hydrolysis of D-${\alpha}$-phenylglycine methyl ester to D-${\alpha}$-phenylglycine, rather than the disappearance of 7-amino-3-deacetoxycephalosporanic acid for cephalexin synthesis. At higher molar ratio of two substrates, [D-${\alpha}$-phenylglycine methyl ester]/[7-amino-3-deacetoxycephalosporanic acid], the conversion rate was also elevated under pH-controlled enzymatic synthesis, which implies that the main reason for the pH drop is due to the production of D-${\alpha}$-phenylglycine methyl easter, the effect of a water-methanol cosolvent system on the ester, the effect of a water-methanol cosolvent system on the conversion profile was also examined. Even the though the conversion rate was increased in 10% methanol solution, a higher than 16% methanol in the reaction mixture caused an inactivation of enzyme.

• 한국음향학회지
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• 제14권4호
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• pp.89-95
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• 1995

파형부호화법은 음성신호에서 잉여성분 제거과정을 통해 유용한 파형의 꼴을 단순히 보존하는 방법이다. 음성합성분야에서 고음질의 파형부호화법은 분석에 의한 합성방식으로 주로 적용된다. 그렇지만 이러한 부호화법에서 파라미터들은 여기용과 성도 여파기용으로 분리되지 않기 때문에 이 파형부호화법을 규칙에 의한 합성 방식으로 사용하기는 어렵다. 파형부호화합을 규칙합성에 적용하려면 운율조절을 위해 피치변경법이 필요하다. 본 논문에서는 시간축 스케일링과 주파수상에서의 스펙트럼 보정을 통해 파형부호화법에서 피치를 변경할 수 있는 새로운 피치변경법을 제안하였다. 이 방식은 파형의 위상성분을 보존하는 시간-주파수 혼성법이고, 50%의 피치변경을 수행하였을 때 2.5%정도의 스펙트럼 왜곡을 나타내었다.

• 한국분말재료학회지
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• 제15권4호
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• pp.314-319
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• 2008

Nano-sized tungsten disulfide ($WS_2$) powders were synthesized by chemical vapor condensation (CVC) process using tungsten carbonyl ($W(CO)_6$) as precursor and vaporized pure sulfur. Prior to the synthesis of tungsten disulfide nanoparticles, the pure tungsten nanoparticles were produced by same route to define the optimum synthesis parameters, which were then successfully applied to synthesize tungsten disulfide. The influence of experimental parameters on the phase and chemical composition as well as mean size of the particles for the produced pure tungsten and tungsten disulfide nanoparticles, were investigated.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.680-688
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• 2001

In this paper, we propose a reliable method for searching the optimally performing generalized brain-state-in-a-box (GBSB) neural associative memory using an evolution program (EP) given a set of prototype patterns to be stored as stable equilibrium points. First, we exploit some qualitative guidelines necessary to synthesize the GBSB model. Next, we parameterize the solution space utilizing the limited number of parameters to represent the solution space. Then, we recast the synthesis of GBSB neural associative memories as two constrained optimization problems, which are equivalent to finding a solution to the original synthesis problem. Finally, we employ an evolution program (EP), which enables us to find an optimal set of parameters related to the size of domains of attraction (DOA) for prototype patterns. The validity of this approach is illustrated by a design example and computer simulations.

• 소음진동
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• 제6권1호
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• pp.71-82
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• 1996

The finite element analysis for rotor bearing systems has been an essential tool for design, identification, and diagnosis of rotating machinery. Among others, the unbalance response analysis is fundamental in the vibration analysis of rotor bearing systems because rotating unbalance is recognized as a common sourve of vibration in rotating machinery. However there still remains a problem in the aspect of computational efficiency for unbalance response analysis of large rotor bearing systems. Gyroscopic terms and local bearing parameters in rotor bearing systems often make matters worse in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and/or anisotropy. The present paper proposes an efficient method for unbalance responses of multi-span rotor bearing systems. An improved substructure synthesis scheme is introduced which makes it possible to compute unbalance responses of the system by coupling unbalance responses of substructures that are of self adjoint problem with small order matrices. The present paper also suggests a scheme to easily deal with gyroscopic tems and local, coupling or bearing parameters. The proposed method causes no errors even though the computational effort is reduced drastically. The present method is demonstrated through three test examples.

• 한국표면공학회지
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• 제49권5호
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• pp.472-476
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• 2016

The nano-array of the vertically aligned rod-like particles grown on ZnO coated glass-substrates was obtained via hydrothermal process. ZnO thin film coatings were prepared on the glass substrates using a MOD (metallorganic deposition) dip-coating method with zinc chloride dihydrate as starting material and 2-ethylhexanol as solvent. ZnO nanorods were synthesized on the seeded substrates by hydrothermal method at $80^{\circ}C$ using zinc-nitrate hexahydrate as a Zn source and sodium hydroxide as a mineralizer. Under the hydrothermal condition, the rod-like nanocrystals were easily attaching on the already ZnO seeded (coated) glass surface. It has been shown that the hydrothermal synthesis parameters are key factors in the nucleation and growth of ZnO crystallites. By controlling of hydrothermal parameters, the ZnO particulate morphology could be easily tailored. Rod-shaped ZnO arrays on the glass substrates consisted of elongated crystals having 6-fold symmetry were predominantly developed at high Zn precursor concentration in the pH range 7~11.

• 한국통신학회논문지
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• 제21권3호
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• pp.612-621
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• 1996

In this paper, we propose the low sidelobe digital FIR doppler filter bank synthesis algorithm through the Gradient Descent method and it can be practially appliable to coherent pulse doppler radar signal processing. This algorithm shows the appropriate calculation of tap coefficients or zeros for FIR transversal fiter which has been employed in radar signal processor. The span of the filters in the filter bank be selected at the desired position the designer want to locate, and the lower sidelobe level that has equal ripple property is achieved than one for which the conventional weithtedwindow is used. Especially, when we implemented filter zeros as design parameters it is possible to make null filter gain at zero frequency intensionally that would be very efficient for the eliminatio of ground clutter. For the example of 10 tap filter synthesis, when filter coefficients or zeros are selected as design parameters the corresponding sidelobelevel is reducedto -70db or -100db respectively and it has good convergent characteristics to the desired sidelobe reference value. The accuracy ofapproach to the reference value and the speed of convergence that show the performance measure of this algorithm are tuned out with some superiority and the fact that the bandwidth of filter appears small with respect to one which is made by conventional weighted window method is convinced. Since the filter which is synthesized by this algorithm can remove the clutter without loss of target signal it strongly contributes performance improvement with which detection capability would be concerned.

• 대한기계학회논문집A
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• 제28권4호
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• pp.378-385
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• 2004

Viscous-driven pumping is a very promising type in microscale applications. However, there exist a few disadvantages such as low efficiency and small volume flow rate. In the present study, a pump with tandem rotating cylinders and its optimum synthesis are proposed fur enhancing pumping performance. First, using an unstructured grid CFD method, we investigate the effects of geometrical parameters and then the performance of the pump with tandem cylinders is evaluated. Next, an optimum design synthesis tool is constructed by combining the aforementioned CFD analysis model with the mathematical optimization model, namely, Modified Method of Feasible Directions (MMFD). This technique is used to optimize the geometrical parameters of the pump, fur maximizing pumping efficiency. From the optimization results, it is believed that the present optimum synthesis is robust and has a potential fur other microfluidic device design.

• 대한음성학회지:말소리
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• 제68권
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• pp.65-74
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• 2008

A statistical parametric speech synthesis system based on the hidden Markov models (HMMs) has grown in popularity over the last few years, because it needs less memory and low computation complexity and is suitable for the embedded system in comparison with a corpus-based unit concatenation text-to-speech (TTS) system. It also has the advantage that voice characteristics of the synthetic speech can be modified easily by transforming HMM parameters appropriately. In this paper, we present experimental results of voice characteristics conversion using the HMM-based Korean speech synthesis system. The results have shown that conversion of voice characteristics could be achieved using a few sentences uttered by a target speaker. Synthetic speech generated from adapted models with only ten sentences was very close to that from the speaker dependent models trained using 646 sentences.