共查询到20条相似文献,搜索用时 31 毫秒
1.
In recent years, high-energy ultrasound has been used as an alternative to improve the functional properties of various proteins, such as from milk, eggs, soy and poultry. The benefits of implementing this technology depend on the inherent characteristics of the protein source and the intensity and amplitude of the ultrasound, as well as on the pH, temperature, ionic strength, time, and all of the variables that have an effect on the physicochemical properties of proteins. Therefore, it is necessary to establish the optimal conditions for each type of food. The use of ultrasound is a promising technique in food technology with a low impact on the environment, and it has thus become known as a green technology. Therefore, this review focuses on the application of high-energy ultrasound to food; its effects on the functional properties of proteins; and how different conditions such as the frequency, time, amplitude, temperature, and protein concentration affect the functional properties. 相似文献
2.
《Journal of Physics and Chemistry of Solids》2001,62(9-10):1899-1910
An ideal structure of zeolite membrane should be a slice of a perfect zeolite crystal attached on a porous metal or ceramic support. To maximize the throughput, the zeolite layer must be very thin, limited only by the cell dimension of zeolite. Separation of a mixture may then be achieved based on the molecular sieving ability of zeolite, which allows only molecules smaller than a critical size to pass through. A variety of methods have been reported for the preparation of zeolite membranes, but so far a perfect epitaxial zeolite layer is still out of reach and only a polycrystalline zeolite membrane can be obtained. The first part of this review focuses on the permeation of gases and vapors through a polycrystalline zeolite membrane as a separation means. The effect of microstructure on permeance will also be discussed, as well as the preparation methods leading to different microstructures. In addition to the usage as a shape-selective membrane, thin films of zeolite and zeolite-like molecular sieves can also serve as hosts for the encapsulation and orientation of guest atoms and molecules and their clusters. In the second part of this review, the production of layers of aligned microporous molecular sieve crystals on supports and the fabrication of supported thin zeolite-like nanoporous silica films as well as their potential applications on the preparation of advanced materials are discussed. 相似文献
3.
The growing interest in sonochemistry as a tool for environmental remediation leads to the need for process optimization. Sonochemistry is a complex process, which depends on physical parameters and also on the process conditions. Physical parameters are interrelated and therefore a systematic approach has to be taken to optimize the process. The effect of physical parameters on the destruction of seven estrogen hormones (17α-estradiol, 17β-estradiol, estriol, 17α-ethinylestradiol, 17α-dihydroequilin, estrone and equilin) is reported in this study. Artificial neural networks (ANN) was used as a tool to identify the correlations between these process parameters. ANN enabled the establishment of relationship between sonication parameters such as power density, power intensity, ultrasound amplitude, as well as the reactor design parameters. The major significance was attributed to the area-specific power density and the volume-specific power intensity. The results of this work provide a sound basis to design pilot and full-scale ultrasound treatment systems. Process optimization lead to a 5-fold decrease in energy consumption as compared to the commercially available reactors, thereby making the process attractive for field applications. 相似文献
4.
For the three-dimensional incompressible Navier–Stokes equations, we present a formulation featuring velocity, vorticity and helical density as independent variables. We find the helical density can be observed as a Lagrange multiplier corresponding to the divergence-free constraint on the vorticity variable, similar to the pressure in the case of the incompressibility condition for velocity. As one possible practical application of this new formulation, we consider a time-splitting numerical scheme based on an alternating procedure between vorticity–helical density and velocity–Bernoulli pressure systems of equations. Results of numerical experiments include a comparison with some well-known schemes based on pressure–velocity formulation and illustrate the competitiveness on the new scheme as well as the soundness of the new formulation. 相似文献
5.
We show that experimental data on inclusive neutrino reactions can be used to obtain general bounds on the coupling constants
of the isovector part of the hadronic weak neutral current provided this isovector current is related to the charged current
by isospin rotation. These bounds are free from the assumption of a specific model for the neutral current as well as any
dynamical assumption on the hadronic structure functions. We derive upper bounds on the coupling constants which involve only
the cross sections for isospin-averaged nucleon target as well as lower bounds which require a knowledge of the cross sections
for proton and neutron separately. 相似文献
6.
Benoit Gars 《哲学杂志》2013,93(11):1390-1421
The effect of a free surface on the Peierls stress of a perfect dislocation, as well as on one of two dislocation partials under a free surface, has been accounted for by considering the Lubarda–Markenscoff variable-core dislocation model (VCM). The VCM dislocation smears the Burgers vector, while producing on the slip plane the Peierls–Nabarro sinusoidal relation between the stress and the slip discontinuity with a variable width. Here the core radius is allowed to depend on the distance to the free surface and the other partial. The Peierls stress is computed as a configurational force by accounting for all the energies and the image stresses to satisfy the traction-free boundary conditions. The results are applied to aluminum and copper and comparisons are made with atomistic calculations in the literature that show that the partials merge as they approach the free surface. 相似文献
7.
The effect of real-time information on the traffic flows of the crossing roads is studied by simulations based on a cellular automaton model. At the intersection, drivers have to enter a road of a shorter trip-time, by making a turn if necessary, as indicated on the information board. Dynamics of the traffic are expressed as a return map in the density-flow space. The traffic flow is classified into six phases, as a function of the car density. It is found that such a behavior of drivers induces too much concentration of cars on one road and, as a result, causes oscillation of the flow and the density of cars on both roads. The oscillation usually results in a reduced total flow, except for the cases of high car density. 相似文献
8.
《Molecular physics》2012,110(11-12):1305-1316
The present study concerns the cycle performance modelling of a particular configuration of an absorption refrigeration machine based on phase separation as well as development of a strategy for computer aided design of absorbents. The model uses predictive methods based on the group contribution concept for the computation of the thermodynamic phase equilibria involved such as liquid–liquid and vapour–liquid as well as enthalpy–concentration diagrams. The proposed absorbents computer-aided design strategy is based on the exploration of a number of structural group combinations obtained from a selected set of functional groups, according to the chemistry laws. The model was tested on four different absorbent–refrigerant pairs reported in the literature, namely (benzyl ethyl amine–glycerol), (water–hexanoic acid), (water–2-hexanone) and (water–ethyl propionate) as well as on pairs where the absorbent compound is generated by the proposed absorbent design strategy and the refrigerant is water. The results show that quite good values of the coefficient of performance (COP) can be obtained, indicating that this cycle configuration is promising and energetically efficient, mainly due to hardware savings, i.e. absence of condenser. However, other working fluid combinations have to be tested using the proposed model. 相似文献
9.
Herein we demonstrate an improved metal-assisted etching method to achieve highly dense and uniform silicon nanowire arrays. A pre-surface treatment was applied on a silicon wafer before the process of metal-assisted etching in silver nitrate and hydrogen fluoride solution. The treatment made silver ion continuously reduce on silver nuclei adherence on the silicon surface, leading to formation of dense silver nanoparticles. Silver nanoparticles acting as local redox centers cause the formation of dense silicon nanowire arrays. In contrast, an H-terminated silicon surface made silver ion reduce uniformly on the silicon surface to form silver flakes. The silicon nanowires fabricated with a pre-surface treatment reveals higher density than those fabricated without a pre-surface treatment. The volume fraction improves from 18 to 38%. This improvement reduces the solar-weighted reflectance to as low as 3.3% for silicon nanowires with a length of only 0.87 μm. In comparison, the silicon nanowires fabricated without a pre-surface treatment have to be as long as 1.812 μm to achieve the same reflectance. 相似文献
10.
High precision wavelength meter with Fabry-Perot optics 总被引:1,自引:0,他引:1
N. Konishi T. Suzuki Y. Taira H. Kato T. Kasuya 《Applied Physics A: Materials Science & Processing》1981,25(3):311-316
A high precision wavelength meter in the visible is described, which is based on a Fabry-Perot interferometer with several
etalons of different resolution. The interference fringe pattern projected on a photo-diode array detector is computationally
processed to give a stepwise refinement of the wavelength value to any adjusted accuracy. The present model intends to provide
digital and real-time values of high precision wavelength for dye-laser spectroscopy, and to serve as a monitor or as a pilot
for wavelength control of a dye-laser source of nanosecond pulses. The model is, therefore, designed with particular emphasis
on its short-pulse capability and on-line mode of operation as well as on its high sensitivity and resolution. Some arrangements
of essential necessity are involved therein, such as to avoid an errorneous wavelength readout for a noisy incidence of pulsed
field. The ultimate accuracy of wavelength measurement is prescribed by the resolving power of the thickest etalon employed.
As applied to the pulsed source, the model determines the wavelength to the accuracy of ±one part in 107 for even a single shot nanosecond incidence of a fraction of μJ energy. The design and performance are described in connection
to pulsed dye-laser incidence. 相似文献
11.
We investigate the effect of curvature on the behaviour of a quantum particle bound to move on a surface shaped as a helical tube. We derive and discuss the governing Schrödinger equation and the corresponding quantum effective potential which is periodic and points to the helical configuration as more energetically favorable as compared to the straight tube. The exhibited periodicity also leads to energy band structure of pure geometrical origin. 相似文献
12.
This paper presents an analytical model of a hydrogenated amorphous silicon (a-Si:H) junction field effect transistor (JFET) based on a p-type/intrinsic/n-type stacked structure. The p-doped layer is connected to the transistor gate electrode, while the n-layer acts as the device channel. The analysis shows the effect of the geometrical and physical parameters of the intrinsic and n-doped layers on the transistor characteristics. In particular, the intrinsic layer thickness plays a central role in determining the depletion region of the n-channel and, as a consequence, the device threshold voltage. The drain current behavior achieved with a modeled parametric analysis is in very good agreement with the experimental drain current measured on fabricated JFET, both in triode and pinch-off regions. This demonstrates the model feasibility as an effective tool to design thin film electronic circuit as a sensor signal amplifier based on a-Si:H p-i-n junction. 相似文献
13.
An optical system based on shearing interference using diffraction grating was applied, to carry out the aberration inspection
process of the pickup lens of a digital versatile disc (DVD) at high speed. An algorithm was devised that processes points
allocated on certain lines on a fringe and fits relations between the distance from basis point to the measurement points,
and phase data of the fringe at these points to an equation of higher degree as curve fitting. Aberration was numerically
estimated as the size of a certain coefficient. Simulation showed that this algorithm could detect all 5th order aberrations
independently. An inspection system developed based on this optical system and algorithm detected aberration as accurately
as a conventional interferometer that has been used as the standard, attaining an inspection time of 1/10-1/20. In comparison
with the spot method, this system has 5th order aberration detecting ability and 1/3 the inspection time. 相似文献
14.
L.C. Fai A. Fomethe V.B. Mborong S.C. Kenfack J.T. Diffo S. Domngang Ashok Mody 《Superlattices and Microstructures》2010
We investigate the effect of plasmon screening on the polaron characteristics following the Feynman variational method and find that the screening considerably reduces the polaron characteristics, as plasmon density increases. We establish that the factor contributing to this screening not only depends on the concentration, but also on the anisotropy of the dielectric permittivities, the temperature, and charge as well as on the layer width. The contribution of the surface effects to the total polaron characteristics are exceedingly small and can therefore be safely neglected. The characteristics are found to be strongly dependent on the screen function referred to as the F-function, and when screening parameters vanish this F-function vanishes and the polaron characteristics reduce to the familiar non-screen ones. The decrease of the polaron characteristics with an increase of the screening parameter is not exactly exponential but mimics that of a pseudoatom which has a much more slow decrease. 相似文献
15.
We study numerically the nature of the diffusion process on a honeycomb and a quasi-lattice, where a point particle, moving along the bonds of the lattice, scatters from randomly placed scatterers on the lattice sites according to strictly deterministic rules. For the honeycomb lattice fully occupied by fixed rotators two (symmetric) isolated critical points appear to be present, with the same hyperscaling relation as for the square and the triangular lattices. No such points appear to exist for the quasi-lattice. A comprehensive comparison is made with the behavior on the previously studied square and triangular lattices. A great variety of diffusive behavior is found, ranging from propagation, superdiffusion, normal, quasi-normal, and anomalous, to absence of diffusion. The influence of the scattering rules as well as of the lattice structure on the diffusive behavior of a point particle moving on the all lattices studied so far is summarized. 相似文献
16.
Sonia Grego Kristin H. Gilchrist Ja-Yeon Kim Min-Ki Kwon M. Saif Islam 《Applied Physics A: Materials Science & Processing》2011,105(2):311-316
We demonstrate bridged nanowires on a non-single-crystal substrate as a versatile fabrication approach to combine active and
passive photonic functionalities on silicon platforms. Silicon nanowires are grown on vertical non-single-crystal surfaces
by a vapor-liquid-solid process and bridge a microtrench obtained by etching an amorphous optical rib waveguide. A pair of
phosphorous-doped polysilicon electrodes is deposited on the walls of the waveguide microtrench for seeding the nanowire synthesis
and for electrical interfacing. The bridged nanowires act as photoconductors and their photoresponse to edge-illumination
from waveguided light is characterized. Taking advantage of crystalline nanowire growth on non-single-crystal substrates may
ultimately lead to substrate-independent integration of best-of-breed semiconductor nanodevices for applications such as photonic
integrated circuits. 相似文献
17.
The main components of cell membranes are phospholipids and proteins. The aim of our study was to examine structural changes of dipalmitoyl-phosphatidylcholine (DPPC) monolayer as a simple model system of a cell membrane in different environments. Pure water, ethanol and methanol solutions were used as subphases of Langmuir films as a membrane models. For detection of changes in charge states of the molecules as well as relation with structural and conformational changes, a contactless method Maxwell's displacement currents (MDC) was used. Behaviour of DPPC molecules on two different subphases is substantialy different. In DPPC monolayer on the subphase of methanol-water, a gradual absorption (incorporation, penetration) of methanol molecules into the layer can appear. In DPPC monolayer on the subphase of ethanol-water adsorption of ethanol molecules on the layer can be observed. The membrane permeability might change. At both subphases (ethanol-water and methanol-water) the elasticity modulus of the monolayer decreases leading to the loss of membrane elasticity. 相似文献
18.
The boundary element method (BEM) is a commonly used method to compute the insertion loss of noise barriers having arbitrary cross-sections. For large scale three-dimensional problems, however, the BEM is not feasible. On the other hand, standardized calculation methods for noise mapping are efficient, but shapes other than the straight barrier cannot be properly calculated. Attempts to merge these two approaches by using BEM to derive correction functions based on geometrical quantities such as source and target angle as well as the path length elongation between source and receiver caused by the barrier were usually focused on a small set of barrier types, dimensions, absorptive configurations, source or receiver positions. The main objective of this study is to investigate which functions based on the most common geometrical parameters are well suited for approximating the efficiency of different types of barriers, dimensions and absorptive configurations. To achieve this, numerous combinations of 7 different barrier types, different heights and widths as well as 3 different absorptive configurations were simulated using the 2D BEM for 8 different source positions. The octave-band-wise efficiency, i.e. the frequency-dependent gain in insertion loss compared to an equally high, fully reflective straight barrier was used as a basis for the correction functions. Linear as well as polynomial models were compared yielding a polynomial of third degree in the source and fourth degree in the target angle as the best model. Effects on the error using uniform sampling in the target angle instead of a uniform receiver grid as a basis for the correction functions are also investigated. Furthermore, wide-band efficiencies based on standardized traffic emission spectra are calculated showing small errors compared to single-band errors, in particular in the high-frequency range. A linear interpolation scheme is suggested to deal with barriers having dimensions not simulated in this work. 相似文献
19.
20.
A. O. Sousa T. Yu-Song M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):115-124
Under synchronous updating and allowing the agents to move
in the lattice or underlying network, we find that the Sznajd model always
reaches a consensus as a steady state, – because agent frustrations are removed
due to their diffusion. Moreover, we succeed in obtaining the well-known
phase transition of the traditional Sznajd model, which depends on the
initial concentration of individuals following an opinion. How the time
for reaching consensus depends on the system size, and on the topology
have been exhaustively investigated. The analyzed topologies were: annealed
and quenched dilution on a square lattice, as well as on a variant of the
well-known Barabási-Albert model, called triad network. 相似文献