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991.
The question of nonemptiness of the intersection of a nested sequence of closed sets is fundamental in a number of important
optimization topics, including the existence of optimal solutions, the validity of the minimax inequality in zero sum games,
and the absence of a duality gap in constrained optimization. We consider asymptotic directions of a sequence of closed sets,
and introduce associated notions of retractive, horizon, and critical directions, based on which we provide new conditions
that guarantee the nonemptiness of the corresponding intersection. We show how these conditions can be used to obtain simple
and unified proofs of some known results on existence of optimal solutions, and to derive some new results, including a new
extension of the Frank–Wolfe Theorem for (nonconvex) quadratic programming. 相似文献
992.
Chien-Sheng Kuo Yao-Hsuan Tseng Chia-Hung Huang Yuan-Yao Li 《Journal of molecular catalysis. A, Chemical》2007,270(1-2):93-100
Ultraviolet and visible-light-responsive titania was synthesized and employed in the NOx photomineralization. A thermal decomposition reaction of titanium isopropoxide was carried out with a metal-organic chemical vapor deposition (MOCVD), enabling continuous production of TiO2 nanoparticles. Carbon-containing titanium dioxide with the anatase phase prepared at 500 °C under nitrogen atmosphere exhibited high photocatalytic activity for NO oxidation under visible-light illumination. Experimental results indicate that up to 48% removal of NOx can be achieved in a continuous flow type of reaction system under visible-light illumination (green LED). The chamber temperature in this MOCVD process plays an important role in lattice structure formation, and also affected TiO2 carbon content. The carbonaceous species on the TiO2 surface, shown by X-ray diffractometry (XRD), and Raman, UV–vis, and X-ray photoelectron spectroscopies (XPS), is important to the visible-light absorption and visible-light-catalytic mineralization of NOx. 相似文献
993.
This paper explores a case of flexible facility layout, in which the layout process can be carried out in a dynamic manner responding to changing demands. We consider a facility such as an office building that needs to partition its interior space into units of different sizes and allocate them to different users. Facing different demands, each of which requires a different space size, the management of the facility needs to constantly exercise managerial real options, such as partitioning a big unit to small units and merging small units to a big one. Modelling the demand uncertainties as stochastic processes, we use the Monte Carlo simulation and solve rolling two-stage stochastic programs over time to value the flexible interior layout. Through numerical tests, we demonstrate that effectively and timely exercising the managerial options can significantly increase profit and service quality. Focusing on the dynamic behaviour of the facility interior layout, the proposed options-based approach aims to improve facility management by proactive decision strategies. The approach may also be extended to facility expansion, maintenance and rehabilitation to increase service life and maintain service quality. 相似文献
994.
A parallel-type, pump-shared (PTPS) scheme linear-cavity laser array (LCLA) is proposed and numerically studied. Power-equalization of multiwavelength fiber lasers can be achieved by varying the pumping power ratio, length of the erbium-doped fiber or reflectivity of grating reflector for the individual channels. Before and after power-equalization, the maximum power variation among seven equal-spaced channels, ranging from 1530 to 1560 nm, is 5.8 and 0.2 dB, respectively. 相似文献
995.
996.
997.
Lead-free (Na0.5K0.5)NbO3-xmol% ScTaO4 (x=0-1.5) ceramics are prepared using the conventional solid-state reaction method and their properties are investigated in detail. The results indicate that the piezoelectric properties and density are improved by the introduction of ScTaO4. Due to the high orthorhombic-tetragonal phase transition temperature TO-T (around 200°C), stable piezoelectric properties against temperature are obtained. In a wide temperature range of 15-160°C, kp of the (Na0.5K0.5)NbO3-0.5mol% ScTaO4 ceramic remains almost unchanged and d31 increases slightly from 59pC/N to 71pC/N. The deliquescent problem is effectively solved by the addition of ScTaO4. The piezoelectric properties of ScTaO4 modified (Na0.5K0.5)NbO3 ceramics show no obvious reduction and dielectric loss increases slightly after 120h of immersion. From the analysis, it is suggested that the density is an important factor that improves the humidity resistance of the specimens. 相似文献
998.
The advancement of communication technology and growth of internet traffic have continuously driven the fast evolution of
networks. Compared to the traditional optoelectronic switch, all-optical switch provides high throughput, rich routing functionalities,
and excellent flexibility for rapid signal exchange in fiber optical network. Among various all-optical switches, thermal
actuated ring switch provides the advantages of high accuracy, easy actuation, and reasonable switching speed. However, when
scale up, thermal ring switch may encounter issues related to fabrication error, non-accurate wavelength response, and large
terminal numbers in the control circuit. In this research, we propose the employment of an integrated CMOS control circuit
to compensate the fabrication error and tune as well as lock the wavelength in a thermal-actuated ring-type optical switch
through a frequency modulation scheme. Additional functionalities can also be added in this circuit by tailoring externally
the roundtrip loss or coupling constants of the ring. The design concept can be easily scaled up for large array optical switch
system without much change in the terminal numbers thanks to the three-dimensional hierarchy of control circuit design, which
effectively reduces the terminal numbers into the cubic root of the total control unit numbers. The integrated circuit has
been designed, simulated, as well as fabricated, and demonstrated a decent performance with free spectral range (FSR) equal
to 1.5 nm at 1534 nm and very accurate wavelength modulation to 0.3 nm within 0.01 nm fluctuation for thermal actuated ring
type optical switch. 相似文献
999.
Kai-Wei Tang Chien-Chih Ke Chih-Hua Tseng Yeh-Long Chen Cherng-Chyi Tzeng Yi-Jin Chen Chia-Chi Hsu Hsiao-Ting Tai Ya-Ju Hsieh 《Molecules (Basel, Switzerland)》2021,26(16)
Pterostilbene, a natural metabolite of resveratrol, has been indicated as a potent anticancer molecule. Recently, several pterostilbene derivatives have been reported to exhibit better anticancer activities than that of the parent pterostilbene molecule. In the present study, a series of pterostilbene derivatives were designed and synthesized by the hybridization of pterostilbene, chalcone, and cinnamic acid. The cytotoxic effect of these hybrid molecules was determined using two oral cancer cell lines, HSC-3 and OECM-1. (E)-3-(2-((E)-4-Hydroxystyryl)-4,6-dimethoxyphenyl)-1-(2-methoxyphenyl)prop-2-en-1-one (4d), with IC50 of 16.38 and 18.06 μM against OECM-1 and HSC-3, respectively, was selected for further anticancer mechanism studies. Results indicated that compound 4d effectively inhibited cell proliferation and induced G2/M cell cycle arrest via modulating p21, cyclin B1, and cyclin A2. Compound 4d ultimately induced cell apoptosis by reducing the expression of Bcl-2 and surviving. In addition, cleavage of PARP and caspase-3 were enhanced following the treatment of compound 4d with increased dose. To conclude, a number of pterostilbene derivatives were discovered to possess potent anticancer potentials. Among them, compound 4d was the most active, more active than the parent pterostilbene. 相似文献
1000.
The optical properties of Au nanoparticles deposited on thermochromic thin films of VO2 are investigated using spectroscopy. A localized modification on the transmittance spectrum of VO2 film is formed due to the presence of Au nanoparticles which exhibit localized surface plasmon resonance (LSPR) in the visible-near IR region. The position of the modification wavelength region shows a strong dependence on the Au mass thickness and shifts toward the red as it increases. On the other hand, it was found that the LSPR of Au nanoparticles can be thermally tunable because of the thermochromism of the supporting material of VO2. The LSPR wavelength, λSPR, shifts to the blue with increasing temperature, and shifts back to the red as temperature decreases. A fine tuning is achieved when the temperature is increased in a stepwise manner. 相似文献