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71.
Unsteady-state periodic operations can improve the optimal steady-state performance of nonlinear chemical processes. To examine if the optimal periodic operation is proper and to obtain the optimal forcing functions subject to various control and state constraints it is suggested in this paper to convert the problems into a form which is suitable for constrained nonlinear programming. The adopted numerical optimization method is based on employing the control parametrization technique and is thus capable of dealing with the problem of multiple input forcings and obtaining optimal forcing functions and/or parameters while subject to general constraints. Besides, it provides information about to what extent the process performance can be improved by adopting the optimal periodic control. 相似文献
72.
Yeong-Koo?YeoEmail author Ki-Seok?Hwang Sung?Chul?Yi Hong?Kang 《Korean Journal of Chemical Engineering》2004,21(4):761-766
In this study a model for the drying process in paper production plants was developed based on the mass and heat balances
around drying cycles. Relationships for the heat transfer coefficients between the web and the air as well as between the
drying cylinder and the web were extracted from the closed-loop plant operation data. It was found that the heat transfer
coefficients could be represented effectively in terms of moisture content, basis weight and reel velocity. The effectiveness
of the proposed model was illustrated through numerical simulations. From the comparison with the operation data, the proposed
model represents the paper plant being considered with sufficient accuracy. 相似文献
73.
A novel bismaleimide (BMI), bis(4-maleimidophenoxy-3,5-dimethylphenyl)dicyclopentadiene (DCPDBMI), containing a large dicyclopentadiene (DCPD) and aryl ether linkage, was synthesized from bis(4-aminophenoxy-3,5-dimethylphenyl)dicyclopentadiene and maleic anhydride by the usual two-step procedure that included ring-opening addition to give bismaleamic acid, followed by cyclodehydration to bismaleimide. The monomers were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (NMR), elemental analyses (EA), and mass spectra (MS). A series of bismaleimide-triazine (BT) resins were prepared from synthesized bismaleimide (DCPDBMI) and then cured with 2,6-dimethyl phenol-dicyclopentadiene dicyanate ester (DCPDCY) at various molar ratios. Thermal properties of cured BT resins (DCPDBMI/DCPDCY) were studied using dielectric analyzer (DEA), dynamic mechanical analyzer (DMA) and thermalgravimetric analyzer (TGA). These data were compared with that of commercial bismaleimide (DDMBMI) cured with bisphenol A dicyanate ester (BADCY). The cured DCPDBMI/DCPDCY exhibits lower dielectric constant, dissipation factor and moisture absorption than those of DDMBMI/BADCY. The effects of blend composition on the glass transition temperatures and thermal stability are discussed. 相似文献
74.
Takatoshi Yamada Purayath Robert Vinod Doo-Sup Hwang Hiromichi Yoshikawa Shin-ichi Shikata Naoji Fujimori 《Diamond and Related Materials》2005,14(11-12):2047
This paper describes a self-aligned fabrication process for diamond gated field emitter array (FEA). Utilizing the non-conformal coverage sputtering conditions of silicon oxide, an interesting “sphere on cone” structure is formed on diamond nano tip array, which is the key point of gate hole opening process. This structure causes shadowing at certain regions of side-wall during Ti / Au gate metal deposition. Removal of “sphere” by wet etching leads to the successful fabrication of a single crystalline diamond gated FEA. Scanning electron microscope observations reveal the fabrication of a uniform emitter array with tip radius of curvature (20 nm) and gate hole (1.4 μm). We also confirmed that no noticeable physical damage exists on tip. In field emission characteristics of the fabricated single crystal diamond gated FEA, gate voltage control of field emission current is realized. 相似文献
75.
Kwangryul Hwang Takafumi Noguchi Fuminiro Tomosawa 《Cement and Concrete Research》2004,34(12):697-2276
Based on experimental results concerning the compressive strength development of concrete containing fly ash, the authors derived an estimation equation for compressive strength development. The equation can express coefficient , which indicates the activity of fly ash as a binder, in the form of a function of age, fly-ash content, and Blaine specific surface area of fly ash.
This equation is capable of explaining the increases in the early strength due to fly ash in place of part of fine aggregate, the decreases in the early strength due to fly ash in place of part of cement, the increases in the long-term strength due to pozzolanic reaction, the relationship between the fly-ash replacement ratio and the ratio of strength increase/decrease, and the effect of fly ash's Blaine specific surface area on the strength. 相似文献
76.
This study aims to develop a controller for use in the online simulation of two interacting characters. This controller is capable of generalizing two sets of interaction motions of the two characters based on the relationships between the characters. The controller can exhibit similar motions to a captured human motion while reacting in a natural way to the opponent character in real time. To achieve this, we propose a new type of physical model called a coupled inverted pendulum on carts that comprises two inverted pendulum on a cart models, one for each individual, which are coupled by a relationship model. The proposed framework is divided into two steps: motion analysis and motion synthesis. Motion analysis is an offline preprocessing step, which optimizes the control parameters to move the proposed model along a motion capture trajectory of two interacting humans. The optimization procedure generates a coupled pendulum trajectory which represents the relationship between two characters for each frame, and is used as a reference in the synthesis step. In the motion synthesis step, a new coupled pendulum trajectory is planned reflecting the effects of the physical interaction, and the captured reference motions are edited based on the planned trajectory produced by the coupled pendulum trajectory generator. To validate the proposed framework, we used a motion capture data set showing two people performing kickboxing. The proposed controller is able to generalize the behaviors of two humans to different situations such as different speeds and turning speeds in a realistic way in real time. 相似文献
77.
Yong K. Park Ho K. Lee Nong M. Hwang Houk C. Kwon Jong C. Park Duk N. Yoon 《Journal of the American Ceramic Society》1988,71(6):297-C
Microstructures of Y-Ba-Cu-O superconductor were observed using a polarized microscope. Orthorhombic and tetragonal phases were easily distinguished by the optical etching with cross-polarized light. In the specimen cooled rapidly in oxygen, it was possible to see the path of oxygen diffusion by observing the variation of the twin concentration. At the boundary between transformed and untransformed materials, evidence for diffusion-driven transformation could be clearly seen. 相似文献
78.
Summary Poly[2-(2-(4-(trifluoromethyl)phenyl)ethenyl)-5-methoxy-1,4-phenylenevinylene] (PFEMPV) and a series of PPV copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and third-order nonlinear optical properties were studied. The PFEMPV films could not be doped with I2, but FeCl3-doped films showed an electrical conductivity of 5.0x10-4 S/cm. The conductivities of FeCl3-doped copolymer films ranged from 2.0x10-3 to 2.0 S/cm depending on their copolymer compositions. The third-order nonlinear optical susceptibility, (3)(–;,,–), was also investigated by the degenerate four wave mixing technique at 602 nm. The (3) value of PFEMPV was 6.9x10-11 esu. The photoluminescence spectrum of PFEMPV shows its emission maximum at 550 nm. 相似文献
79.
J.-F. Hwang J. A. Manson R. W. Hertzberg G. A. Miller L. H. Sperling 《Polymer Engineering and Science》1989,29(20):1466-1476
Epoxies toughened with two reactive liquid rubbers, an epoxy-terminated butadiene acrylonitrile rubber (ETBN) and an amino-terminated butadiene acrylonitrile rubber (ATBN), were prepared and studied in terms of their structure property relationships. A two-phase structure was formed, consisting of spherical rubber particles dispersed in an epoxy matrix. A broad distribution of rubber particles was observed in all the materials with most of the particles ranging in size from 1 to 4 μm, but some particles exceeding 20 μm were also found. Impact strength, plane strain fracture toughness (KIC), and fracture energy (GIC) were increased, while Young's modulus and yield strength decreased slightly with increasing rubber content and volume fraction of the dispersed phase. Both GIC and KIC were found to increase with increasing apparent molecular weight between crosslinks and decreasing yield strength. The increased size of the plastic zone at the crack tip associated with decreasing yield strength could be the cause of the increased toughness. An ATBN-toughened system containing the greatest amount of epoxy sub-inclusion in the rubbery phase demonstrated the best fracture toughness in this series. In the present systems, rubber-enhanced shear deformation of the matrix is considered to be the major toughening mechanism. Curing conditions and the miscibility between the liquid rubber and the epoxy resin determine the phase morphology of the resulting two-phase systems. Kerner's equation successfully describes the modulus dependence on volume fraction for the two-phase epoxy materials. 相似文献
80.
An increase in the depolymerization of chitosan was found with an increased concentration of sodium perborate. Acetic anhydride was added to reacetylated chitosan in a molar ratio per gulcosamine unit, and the amide I band of IR spectra changed with the addition of acetic anhydride. Sixteen chitosans with various molecular weights (MWs) and degrees of deacetylation (DODs) were prepared. X‐ray diffraction patterns indicated their amorphous and partially crystalline states. Increases in the chitosan MW and DOD increased the tensile strength (TS). TS of the chitosan films ranged from 22 to 61 MPa. However, the elongation (E) of chitosan films did not show any difference with MW. TS of chitosan films decreased with the reacetylation process. However, E of chitosan films was not dependent on DOD. The water vapor permeabilities (WVPs) of the chitosan films without a plasticizer were between 0.155 and 0.214 ng m/m2 s Pa. As the chitosan MW increased, the chitosan film WVP increased, but the values were not significantly different. Moreover, the WVP values were not different from low DOD to high DOD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3476–3484, 2003 相似文献