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101.
Natural ventilation systems may have multiple steady states in the combined buoyancy and wind driven mode in a single space. In this paper, dynamical system analysis is applied both graphically and quantitatively to investigate the multiple steady state behavior of such a natural ventilation system. 相似文献
102.
103.
Hyongsuk Kim Tmas Roska Leon O. Chua Frank Werblin 《International Journal of Circuit Theory and Applications》2003,31(4):329-346
A high speed target detection and tracking algorithm for a CNN‐UM chip is presented in this paper. The target confidence value is computed based on the fusion of target existence probabilities of features using products of weighted sums. The target decision is done with such a confidence value and target initiation is done through the temporal accumulation of the confidence. The probability of the target existence for each feature is created in the region of influence depending on the reliability and the strength of the feature. By virtue of the analogic parallel processing structure of the CNN‐UM (Roska T, Chua LO. The CNN universal machine: an analogic array computer. IEEE Trans. Circuits Systems II 1993; CAS‐40 : 163–173), real time tracking can be achieved with presently available technologies with the speed of several kilo‐frames per second. Due to the utilization of multiple features of target, robust target detection is possible via the proposed algorithm. On‐chip experiments of the proposed target‐tracking algorithm have been done and properties of the proposed approach are disclosed through the various experiments. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
104.
Leon O. Chua Chwen-Cher Chang 《International Journal of Circuit Theory and Applications》1988,16(2):157-190
Circuit models for both long-base and short-base p-n junction diodes which are valid for non-linear high-speed and high-frequency operations are presented. the diode model consists of a parallel connection of higher-order dynamic elements and includes the conventional diffusion model as a special case. the new dynamic model can be used for simulating arbitrary p-n junction diode circuits under all operating conditions. In particular, it is capable of simulating realistically the diode's reverse transient behaviour and providing an increasingly accurate approximation to the diffusion equation as the order of the model gets higher. the model is also shown to be capable of reproducing the frequency-dependent small-signal characteristics of p-n junction diodes. The model is based mainly upon the device's physical operating principles. Perhaps the most significant implication of the model is the fact that it illustrates the important roles played by higher-order and dynamic elements in highspeed and high-frequency non-linear device modelling. 相似文献
105.
Hsiu-Li Lin Wen-Horng Liu Kun-Sheng Shen T. Leon Yu Chien-Horng Cheng 《Journal of Polymer Research》2003,10(3):171-179
Thermal transition of PVA-borax aqueous gels with a PVA concentration of 60 g/L and a borax concentration of 0.28 M was investigated at temperatures ranging from 15 to 60C using static light scattering (SLS), dynamic light scattering (DLS), and dynamic viscoelasticity measurements. Three relaxation modes, i.e. two fast and one slow relaxation modes, were observed from DLS measurements. Two fast relaxation modes located around 10–3101 sec, with one fast mode (f1) being scattering vector q-dependent and the other fast mode (f2, with f2>f1) being q-independent. The f1 mode was attributed to the gel mode whilst the f2 mode could be due to the hydrodynamics of intra-molecular hydrophobic domains formed by uncharged segments of polymer backbones. The slow relaxation mode with relaxation time located around 101103 sec in DLS data was due to the motion of aggregated clusters and was observed only at temperatures above 40C. The amplitude and relaxation time of slow mode decrease as temperature is increased from 40 to 60C. At temperatures below 40C, no slow relaxation mode was observed. The SLS measurements showed PVA-borax-water system had fractal dimensions D
f2.4 and D
f2.0 as temperature was below and above 40C, respectively. The simple tilting test indicated gel behaviour for the PVA-borax aqueous system at temperatures below 40C with a creep flow after a long time exposure in the gravity field. But the dynamic viscoelasticity measurements demonstrated a solution behaviour for PVA/borax/water at temperatures below 40C, the critical gel point behaviour for G() and G() was not observed in this system as those reported for chemical crosslinked gels. These results suggest that the PVA-borax aqueous system is a thermoreversible weak gel. 相似文献
106.
Patricia A. Ignacio-de Leon Alexis E. Abelow Julie A. Cichelli Arkady Zhukov Ivan I. Stoikov Ilya Zharov 《Israel journal of chemistry》2014,54(5-6):767-773
Robust mesoporous membranes composed of silica spheres were surface-modified with chiral selector moieties, including small molecules, macrocycles, and polymers. Diffusion rates of enantiomers of a chiral dye through the resulting asymmetrically modified colloidal membranes were measured and the corresponding permselectivities were calculated. The membranes showed enantioselectivities in the range of 1.2–1.8, which were not significantly affected by the structure of the surface-immobilized chiral electors. This selectivity is on par with most reported polymer-based solid membranes and bulk liquid membranes. The enantioselectivity results from the surface-facilitated mechanism of transport of enantiomers through the mesopores. 相似文献
107.
Dr.‐Ing. Andrea Ohle Michael Obst Prof. Dr.‐Ing. Norbert Mollekopf Prof. Dr.‐Ing. Leon Urbas 《化学,工程师,技术》2014,86(5):640-648
Modularization has been identified as one of the research fields of the ?50 % idea”?. A development methodology for modules must consider both the economies of scale for investment costs and costs of operation and maintenance. In this paper, the impact of an absorber module, which is offered as discretized diameter scaling, on the total process is investigated at the example of the CO2 separation from biogas. The simulation shows the effect of this approach to the stripper diameter and the energy demand of the process. The calculations form the basis for applying cost models. 相似文献
108.
An experimental procedure was developed to study directly the process by which liquid bridges between small particles in a granule form and solidify. The evolution of saturated solutions of such pharmaceutical excipients as lactose and mannitol in a liquid bridge was studied on a system situated on a microscope slide. Solidification and crystallization kinetics and phase composition during and immediately following bridge formation were observed directly. It was shown that bridges on the microscope slide and in the granule behave very much the same regardless of the different length and diffusion-scales of the two systems.We found that solid bridge formation takes place in several consecutive but distinct steps. In the case of lactose, considerable shrinkage of the initial liquid bridge takes place prior to the onset of crystallization. Further bridge solidification at ambient conditions occurs via simultaneous crystallization and vitrification within minutes. As a result, a “solid” bridge usually contains both a crystalline and a non-crystalline phase, the crystalline phase being predominately α-lactose monohydrate. Most of the non-crystalline phase eventually converts to crystalline β-lactose but the process may take many hours or even days. Results for this process are compared for samples obtained from different manufacturers of commercially available lactose. In the case of mannitol, different polymorphic forms crystallize as the drying/crystallization process progresses. A formed “solid” bridge usually contains several polymorphs of mannitol. The relevance of the behavior of the two model systems (pure lactose and pure mannitol) to a real granulation and tabletting process is discussed. 相似文献
109.
Prediction of plasticity‐controlled failure in polyamide 6: Influence of temperature and relative humidity 下载免费PDF全文
In this study, the influence of temperature and relative humidity on the plasticity controlled failure of polyamide 6 was investigated. Uniaxial tensile tests were performed at several temperatures, strain rates, and relative humidity; creep tests were performed at different relative humidity and applied load. In order to describe and predict the yield kinetics, the Ree–Eyring equation was employed and modified to include the effect of relative humidity. Subsequently, by the introduction of the concept of critical amount of accumulated plastic strain, the yield kinetics were successfully translated to predictions of time‐to‐failure. A good agreement between predictions and experimental results is obtained, showing that the model is a suitable and versatile tool to evaluate mechanical performance of a temperature and moisture sensitive material such as polyamide 6. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45942. 相似文献
110.
The physical properties of 5 wt% poly(NIPAM) (Mv=3.22×105) semi-dilute solutions in H2O, D2O, and THF (tetrahydrofuran) solvents were studied using dynamic light scattering (DLS) and dynamic shear viscosity (DSV) measurements. The DLS data showed that there were poly(NIPAM) slow mode inter-polymer chains associations in H2O and D2O solvents. However, no DLS slow mode was observed in poly(NIPAM)/THF solutions. The DSV data showed that there are shear thickening behavior in these three poly(NIPAM) solutions, resulting in a maximum shear viscosity ηpeak in the viscosity η′(ω) versus shear frequency ω curve. The slow mode hydrodynamic radius 〈Rhs〉 of DLS measurements and the zero shear rate viscosity η0 and maximum viscosity ηpeak data of DSV measurements from poly(NIPAM)/H2O and poly(NIPAM)/D2O solutions show two critical transition temperatures with Tcr1=30-32 °C and Tcr2=32-34 °C. Poly(NIPASM)/D2O has higher Tcr1 and Tcr2 than poly(NIPASM)/H2O. However, no transition temperatures of poly(NIPAM)/THF solution were observed. The different temperature dependencies of these three solutions were attributed to the ‘solubility’ and ‘hydrogen bonding’ effects between poly(NIPAM) with H2O, D2O, and THF solvents. Without considering the polymer-solvent hydrogen bonding, the solubility of poly(NIPAM) in solvents decreases in the following sequence: THF>H2O>D2O and the degree of polymer-solvent hydrogen bonding increases in the following sequence: THF<H2O<D2O. The effects of the degree of ‘hydrogen bonding’ and the ‘solubility’ of polymer in solvents on the physical properties of poly(NIPAM) solutions are discussed. 相似文献