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1.
流变学研究的若干问题 总被引:1,自引:0,他引:1
本文综述了1988年8月第10届国际流变学会议部分大会邀请报告及分组报告的下列几个领域内容:①分子动力学;②光学流变测量;⑧血液的动态测量;④数值仿真;⑤钻探油井;⑥强化采油;⑦减阻;⑧聚合物挤压成形加工;⑨食品流变学. 相似文献
2.
《Particuology》2015
There is increasing recognition that some nanomaterials may pose a risk to human health and the environment. Moreover, the industrial use of the novel engineered nanomaterials (ENMs) increases at a higher rate than data generation for hazard assessment; consequently, many of them remain untested. The large number of nanomaterials and their variants (e.g., different sizes and coatings) requiring testing and the ethical pressure towards nonanimal testing means that in a first instance, expensive animal bioassays are precluded, and the use of (quantitative) structure–activity relationships ((Q)SARs) models as an alternative source of (screening) hazard information should be explored. (Q)SAR modelling can be applied to contribute towards filling important knowledge gaps by making best use of existing data, prioritizing the physicochemical parameters driving toxicity, and providing practical solutions for the risk assessment problems caused by the diversity of ENMs. This paper covers the core components required for successful application of (Q)SAR methods to ENM toxicity prediction, summarizes the published nano-(Q)SAR studies, and outlines the challenges ahead for nano-(Q)SAR modelling. It provides a critical review of (1) the present availability of ENM characterization/toxicity data, (2) the characterization of nanostructures that meet the requirements for (Q)SAR analysis, (3) published nano-(Q)SAR studies and their limitations, (4) in silico tools for (Q)SAR screening of nanotoxicity, and (5) prospective directions for the development of nano-(Q)SAR models. 相似文献
3.
Polystyrene (PSt) microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate (KPS) as initiator in ethanol-water mixed solvents.Emulsifier-free seeded emulsion copolymerization of styrene (St) with acrylonitrile (AN) was carried out in the presence of poly(ethylene glycol) monomethoxymonomethacrylate (PEGm)macromonomer as reactive stabilizer and 2,2'-azobisisobutyronitrile (AIBN) as initiator to obtain submicron-sized PEGm graft poly(styrene-co-acrylonitrile) (PEGm-g-PSAN) composite particles with unique morphology.Scanning electron microscopy (SEM) indicated that St and AN together contributed to forming the unusual morphology.The concentration of St and AN,total monomer concentration,initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles. 相似文献
4.
《Journal of Fluids and Structures》2006,22(6-7):741-755
A number of occurrences of flow-induced vibration in the power-generating industry are presented, many in nuclear plant where all incidents/problems have to be reported. Specifically, cases of (i) vortex-induced vibration (VIV), (ii) fluidelastic instability in cylinder arrays, (iii) axial and (iv) annular-flow-induced vibration, (v) leakage-flow instability and (vi) shell-type ovalling are discussed. For items (ii), (v) and (vi), a few words on the mechanisms underlying the vibration are provided. 相似文献
5.
Marvin A. Hamstad 《Experimental Mechanics》1986,26(1):7-13
The technique of acoustic emission has two broad applications areas. The first is nondestructive evaluation. The second is
as a tool in studies or research which are not fundamentally directed towards acoustic emission. It is this second application
with which we are concerned here. Acoustic emission is a very useful tool in this role because of its high sensitivity, real-time
capability, volume-monitoring approach, and sensitivity to any process or mechanism which generates sound waves. This paper
presents a comprehensive review of areas where acoustic emission (AE) has been used for materials studies on composite materials.
The following fields, among others, will be covered: (1) time-dependent composite properties, (2) impact studies, (3) correlation
of AE with stress level, (4) application to matrix cure studies, (5) relationship of AE-detected damage to other measures
of damage, (6) studies of the effects of matrix material, (7) application to differences in second phase, (8) interface studies,
(9) AE and dimensional stability, (10) AE applied to orientation studies, and (11) environmental effects. This review will
emphasize the roles that AE can play as a tool for the materials scientist: (1) discovery of damage mechanisms, (2) characterization
of damage progression with increasing time or stress, (3) optimization of fabrication variables, and (4) reduction in the
numbers of test specimens required in various studies. 相似文献
6.
On the boundedness and the stability properties of solution of certain fourth order differential equations 总被引:1,自引:1,他引:0
This paper investigates equation(1)in two cases:(i)P≡0,(ii)P(≠O)satisfies|P(t,x,y,z,ω)|≤(A |y| |z| |ω|)q(t),where q(t)is a nonnegative function of t.For case(i)the asymptotic stability in the large of the trivial solution x=0 is investigatedand for case(ii)the boundedness result is obtained for solutions of equation(1).Theseresults improve and include several well-known results. 相似文献
7.
This paper discusses scaling of mixing during miscible flow in heterogeneous porous media. In large field systems dispersivity appears to depend on system length due to heterogeneities. Three types of scaling are discussed to investigate the heterogeneous effects. Dimensional analysis of mixing during flow through geometerically scaled heterogeneous models is illustrated using measured dispersion. Fractal analysis of mixing in statistically scaled heterogeneous porous media is discussed. Analog scaling of pressure transients in heterogeneous porous media is suggested as an in-situ method of estimating dispersion.Notation L
Length
- M
mass
- t
time, (1) indicates dimensionless
- a
dispersivity (L)
- V
local velocity (L/t)
- c
concentration (l).
- v
velocity (L/t)
- C1
fluid compressibility (Lt2/M)
- v
time averaged velocity (LJt)
- D
dispersion VA)
- W
width (L)
- D
fractional dimension (1)
- x
coordinate (L)
- d
Euclidean dimension (1)
- Y
Y=In \-k (l)
- \-d
average particle size (L)
- y
coordinate (L)
- g
acceleration due to gravity (L/t2)
- c
fractal cutoff (L)
- \-k
average permeability (L2)
-
viscosity (LM/t)
- L
length (L)
-
porosity (1)
- L
correlation scale (1/L)
-
density (N/L3)
- N
Number of sites (l)
- 2
variance (dimension depends on variable)
- p
pressure (W/t2L)
-
spectral exponent (l)
- [R]
randomnumber (1)
- r
radius (L)
- t
time (t) 相似文献
8.
9.
Hong Chu Hongyan Wang Zhongbin Ni Xiaoya Liu Mingqing Chen 《Particuology》2008,6(5):369-375
Polystyrene (PSt) microspheres with diameter of 375 nm to be used as the seeds for seeded emulsion polymerization were prepared via emulsion polymerization using potassium persulfate (KPS) as initiator in ethanol-water mixed solvents. Emulsifier-free seeded emulsion copolymerization of styrene (St) with acrylonitrile (AN) was carried out in the presence of poly(ethylene glycol) monomethoxymonomethacrylate (PEGm) macromonomer as reactive stabilizer and 2,2'-azobisisobutyronitrile (AIBN) as initiator to obtain submicron-sized PEGm graft poly(styrene-coacrylonitrile) (PEGm-g-PSAN) composite particles with unique morphology. Scanning electron microscopy (SEM) indicated that St and AN together contributed to forming the unusual morphology. The concentration of St and AN, total monomer concentration, initiator type and the monomer adding method remarkably affected the morphology of the composite polymer particles. 相似文献
10.
《Particuology》2015,(4)
There is increasing recognition that some nanomaterials may pose a risk to human health and the environment.Moreover,the industrial use of the novel engineered nanomaterials(ENMs) increases at a higher rate than data generation for hazard assessment;consequently,many of them remain untested.The large number of nanomaterials and their variants(e.g.,different sizes and coatings) requiring testing and the ethical pressure towards nonanimal testing means that in a first instance,expensive animal bioassays are precluded,and the use of(quantitative) structure-activity relationships((Q)SARs) models as an alternative source of(screening) hazard information should be explored.(Q)SAR modelling can be applied to contribute towards filling important knowledge gaps by making best use of existing data,prioritizing the physicochemical parameters driving toxicity,and providing practical solutions for the risk assessment problems caused by the diversity of ENMs.This paper covers the core components required for successful application of(Q)SAR methods to ENM toxicity prediction,summarizes the published nano-(Q)SAR studies,and outlines the challenges ahead for nano-(Q)SAR modelling.It provides a critical review of(1) the present availability of ENM characterization/toxicity data,(2) the characterization of nanostructures that meet the requirements for(Q)SAR analysis,(3) published nano-(Q)SAR studies and their limitations,(4)in silico tools for(Q)SAR screening of nanotoxicity,and(5) prospective directions for the development of nano-(Q)SAR models. 相似文献
11.
For the system of differential equations x=r(t)y,y=-a(t)f(x)g(y) where a(t)>0, r(t)>0 for t≥t; f(x) >0 and is decreasing for x>0 g(y)>0, we give necessary and sufficient condition of the existence of a proper solution, a bounded proper solution or solutions of two kinds of boundary value problems on an infinite interval [c,∞] c≥tg. Several examples are given to illustrate the conditions of these results. 相似文献
12.
We re-examine the large amplitude transverse oscillations of axisymmetric disks spinning near a critical speed resonance as considered by Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139). Averaged equations in traveling wave based coordinates are shown to provide a transparent explanation for certain bifurcations presented in Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139). The theoretical results in Raman and Mote (Int. J. Non-linear Mech. 34 (1) (1999) 139) are proved analytically, and an enhanced interpretation of their results is presented. 相似文献
13.
Lead sulfide (PbS) nanostructures with different morphologies and particle sizes were obtained via a simple hydrothermal reaction between lead (II) salicylate (Pb(Hsal)2) and thiourea (tu). Reaction products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) and Fourier transform infrared (FT-IR) spectroscopy. Morphology of the product, varying from star-like to dendritic, depends on the mole ratio of tu to (Pb(Hsal)2), pH, and reaction time. 相似文献
14.
通过试验, 本文就游离氧化铁在粘性土尤其是红土中富积含量的变化对土体工程地质性质产生的影响及其规律性做了初步研究。 相似文献
15.
Overview of Identification Methods of Mechanical Parameters Based on Full-field Measurements 总被引:6,自引:1,他引:5
Stéphane Avril Marc Bonnet Anne-Sophie Bretelle Michel Grédiac François Hild Patrick Ienny Félix Latourte Didier Lemosse Stéphane Pagano Emmanuel Pagnacco Fabrice Pierron 《Experimental Mechanics》2008,48(4):381-402
This article reviews recently developed methods for constitutive parameter identification based on kinematic full-field measurements,
namely the finite element model updating method (FEMU), the constitutive equation gap method (CEGM), the virtual fields method
(VFM), the equilibrium gap method (EGM) and the reciprocity gap method (RGM). Their formulation and underlying principles
are presented and discussed. These identification techniques are then applied to full-field experimental data obtained on
four different experiments, namely (i) a tensile test, (ii) the Brazilian test, (iii) a shear-flexural test, and (iv) a biaxial
test. Test (iv) features a non-uniform damage field, and hence non-uniform equivalent elastic properties, while tests (i),
(ii) and (iii) deal with the identification of uniform anisotropic elastic properties. Tests (ii), (iii) and (iv) involve
non-uniform strain fields in the region of interest.
Working group “Identification” of the French CNRS research network (GDR 2519) “Mesures de champs et identification en Mécanique
des Solides / Full-field Measurements and Identification in Solid Mechanics”. 相似文献
16.
Layered ,α-cobalt hydroxides Co(OH) 1.65Cl0.35.0.5H2O (1), Co(OH) 1.75(NO3)0.25.0.1H2O (2) with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-diffusion method. The materials have thin film morphologies and were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). 相似文献
17.
Samples of cellulose acetate butyrate (CAB) hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) are contrasted with commercial (atactic) polystyrene (PS) and isotactic polypropylene (PP) in studies of (i) differential scanning calorimetry, (ii) quiescent polarized light microscopy (iii) optical retardation variation following an imposed stress field. It is concluced that HPC and EC are thermotropic liquid crystals, while CAB behaves in a manner similar to a vitrifying isotropic melt such as PS. Studies of the shear viscosity and dynamic viscosity indicate HPC and EC exhibit yield values while CAB shows a zero shear viscosity and Vinogradov-Malkin reduced viscosity curve identical to PS. The normal stress and extrudate swell behavior of CAB are also similar to PS. The HPC and EC exhibit substantially reduced extrudate swell. Measurement of the principal normal stress difference behavior of the HPC melt is troubled by the existence of yield values. 相似文献
18.
19.
Presently, we develop a simplified corticothalamic(SCT) model and propose a single-pulse alternately resetting stimulation(SARS) with sequentially applying anodic(A, "+") or cathodic(C, "-") phase pulses to the thalamic reticular(RE) nuclei,thalamus-cortex(TC) relay nuclei, and cortical excitatory(EX) neurons, respectively.Abatement effects of ACC-SARS of RE, TC, and EX for the 2 Hz–4 Hz spike and wave discharges(SWD) of absence seizures are then concerned. The m∶n on-off ACC-SARS protocol is shown to effectively reduce the SWD with the least current consumption. In particular, when its frequency is out of the 2 Hz–4 Hz SWD dominant rhythm, the desired seizure abatements can be obtained, which can be further improved by our proposed directional steering(DS) stimulation. The dynamical explanations for the SARS induced seizure abatements are lastly given by calculating the averaged mean firing rate(AMFR)of neurons and triggering averaged mean firing rates(TAMFRs) of 2 Hz–4 Hz SWD. 相似文献
20.
A Boundary Element Method (BEM)-based inverse algorithm utilizing the iterative regularization method, i.e. the Conjugate
Gradient Method (CGM), is used to solve the Inverse Heat Conduction Problem (IHCP) of estimating the unknown transient boundary
heat flux in a multi-dimensional domain with arbitrary geometry.
Results show that the advantages of applying the CGM in the inverse calculations lie in that the major difficulties in (i)
choosing a suitable quadratic norm, (ii) determining a proper regularization order and (iii) determining the optimal smoothing
(or regularization) coefficient in the conventional Regularization Method (RM) are avoided.
Received on 27 October 1997 相似文献