On the spectral density of a class of chaotic time series

The purpose of this paper is to show explicitly the spectral density function of the stationary stochastic process determined by a certain class of two-dimensional maps F_α defined below (α is a parameter in (0, 1)), the random variable φ(x, y) = x and the invariant probability described below. We first define the transformation T_α: [0, 1]←[0, 1] given by T _α(x) = {x/α if 0 ≤x < α and (α(x?α)/1 ?α) if α≤x≤ 1 where α∈ (0, 1) is a constant. The map T_α describes a model for a particle (or the probability of a certain kind of element in a given population) that moves around, in discrete time, in the interval [0, 1]. The results presented here can be stated either for T_α or for F_α but we prefer the latter. The results for T_α can be obtained from the more general setting described by F_α. The map F_α is defined from K = ([0, 1]× (0, α)) ∨ ([0, α]×[α, 1]) ?;R;² to itself and is given by F_α(x, y) = (T_α(x), G_α(x, y)) for (x, y) ∈K, where G _α(x, y) = {αy if 0 ≤x < α and α + ((1 ?α)/α)y if α≤x < 1. The spectral density function of the stationary process with probability ν (invariant for F_α and absolutely continuous with respect to the Lebesgue measure) Z_t = X_t + ξ_t = φ{F^t_α(X₀, Y₀)} + ξ_t for t∈Z where (X₀, Y₀) ∈R² and ξ_t}_t∈Z is a white noise process, is given explicitly (Theorem 1) by f _Z (λ) = f_X(λ) + (σ²_ξ/2π) = (1/2πvar(X_t))[γ{exp(iλ)}?C(0)] + (σ²/2π) for all λ∈[0, 2π), where var(X_t) = (α²?α + 1)(α²? 5α + 5){12(2 ?α)²}^?1, γ is given by Equation (2.10) of Proposition 5 and C(0) = (1 + α²?α³){3(2 ?α)}^?1. We also estimate the parameter α based on a time series.     

振动频率和振动时间对粉料填充密度的影响

将Si粉(粒度≤0.044mm)和聚乙烯醇水溶液(聚乙烯醇质量分数为5%)按一定比例混匀,过筛造粒后,振动装料,研究了振动频率(14～50Hz)和振动时间(10～230s)对粉料填充密度的影响。研究表明:振动频率对粉料的填充密度有着显著的影响,当振动频率≤29Hz时,粉料不产生“沸腾”和颗粒分层现象,且振动一定时间后,粉料填充密度会趋于恒定,并且随振动频率的增加,振实速度加快;当振动频率在29～50Hz时,粉料产生“沸腾”和颗粒分层现象,导致粉料填充不均匀,并且随频率的增大,“沸腾”和颗粒分层现象加剧。     

Mixing of miscible liquids with density differences: Effect of volume and density of the tracer fluid

The effect on the mixing time of the density difference between the tracer fluid and the bulk, the type and geometry of the impeller, and the amount of the fluid added as a tracer, has been investigated in a tank with diameter of 0.31 m. The amount of tracer pulse has been varied in the range of 2 to 8% of the bulk volume and the density difference between two fluids has been varied in the range of 54 to 145 kg/m³. A generalized correlation has been developed for the prediction of dimensionless mixing time (Nθ) in terms of amount of the tracer fluid, density differences between the bulk and the tracer liquid and the pumping effectiveness of the impeller. A pitched blade downflow turbine with diameter as small as possible is the most energy efficient among the impellers studied in this work.     

聚丙烯腈纤维体积密度影响因素研究

应用X射线衍射仪并结合密度梯度法,考察了纺丝干燥致密化工序对聚丙烯腈纤维的体积密度的影响.结果表明,在聚合组分不变的情况下,随着纺丝干燥致密化工序的变化,聚丙烯腈纤维的体积密度也随之而变化,聚合组分为AN-co-IA、MA三元共聚物体系,纺丝干燥致密化温度在125℃,热拉伸倍率为0.03时,聚丙烯腈纤维的体积密度达到最大值为1.219 g/cm3.     

颗粒尺寸分布对SiC-Si粉体体系密度的影响

研究了两种粒径颗粒的级配对SiC粉体自由堆积密度的影响 ,并与理论模型进行比较 ,发现当粗细颗粒的粒径比 >3且粗颗粒的质量分数在6 0 %～ 70 %之间时 ,体系的自由堆积密度较大。探讨了SiC -Si混合料中SiC的颗粒尺寸分布和Si粉含量对自由堆积密度、压实密度和压缩比的影响 ,表明Si粉量为 30 %时体系的较佳压实密度为2 .0 9g·cm- 3。     

二乙烯基苯对低密度聚苯乙烯密度及尺寸的影响

研究了悬浮聚合法合成氏密度聚苯乙烯（LDPS）微粒子过程中，二乙烯基苯（DVB）的加入对树脂粒径及密度的影响。结果表明，二乙烯基苯从单体分散阶段开始影响单体液滴的分散尺寸，加入DVB后，单体液滴尺寸变小，最终产物粒径变小。且在实验条件下，随DVB量增加，最终LDPS粒径减小，当用明胶做分散剂，二乙烯基苯与苯乙烯之比（DVB／St）大于1时，粒径减小变化趋于平缓；当有致孔剂存在时，LDPS的密度随DVB量增加而减小。     

Effect of storage time on the antimicrobial properties of chitosan

Chitosan (CS) is well known as one of the natural polymers. It is one of the familiar antibacterial materials owing to its safety, non-toxicity and biocompatibility. However, its prolonged capability to act as an antibacterial agent is not yet investigated in detail. i.e., as to how much time it can withstand its ability as an antibacterial agent is very significant for practical purposes. Hence, in the present study, CS solution and thin films in different ratios were prepared and were stored up to 24 months. Later observations were carried on different samples after storage time to assess its potential toward antimicrobial activity. It was noted that CS thin films had superior properties even after storage time of 24 months when compared to solution and powder forms. In addition to the above, morphology of the nanofilms and the presence of functional groups were also studied in detail.     

超声能量密度对污泥脱水性能的影响

<正>引言近年来,生物法在城市污水处理中得到广泛的应用,然而在处理过程中产生了大量的污泥,污泥中含有50%～70%的有机物和较多的氮、磷等营养成分以及致病菌、寄生虫卵等有害物质。其化学     

Effect of composting time on phosphate exchangeability

Because of their high concentrations in organic matter and nutrients, composts have been used as soil amendments for years. However, information on their P availability is scarce. The effect of the composting time on phosphate exchangeability of composts was assessed on three substrates (House Refuse Compost, HRC; Sewage Sludge Compost, SSC; and Food Waste Compost, FWC) using the isotopic exchange kinetic method proposed by Fardeau (1996). Results were then interpreted by a pluricompartmental analysis and compared to those yielded by a sequential extraction. Preliminary results confirmed that the isotopic exchange kinetic method was appropriate to assess phosphate exchangeability of composts. Composts were shown to have a low buffering capacity (r(1)/R) for inorganic P (P_i) and high concentration in water extractable P_i (Cp) and in P_i isotopically exchangeable within 1 min (E_1min) compared to soils. Their concentra tion in P_i isotopically exchangeable between 1min and 3 months (E_{i1min–3months}) and in P_i which cannot be exchanged within three months (E_>3months) was a function of their origin. Composting of HRC, SSC, and FWC, systematically led to decreases in Cp and E_1min with time and in some cases to increases in E_{i1min–3months} and/or in E_>3months. These changes were related to the leaching of water soluble P_i from the HRC and FWC composts and, for the SSC and FWC composts, to the formation of phosphate precipitates with Ca, Mg and/or Fe during composting. Most of the changes in P_i exchangeability occurred during the first month of composting, i.e., during the most intense period of organic matter mineralisation. The slight increase in total organic P content observed after 180 d of composting in FWC and SSC indicates that the immobilisation of P in orga nic forms was not a major pathway for P transformation.     

Influence of irradiation crosslinking on time dependences of conduction and self‐heating in acetylene carbon black filled high‐density polyethylene composites

The time dependences of electrical conduction and self‐heating in high‐density polyethylene/acetylene carbon black composites crosslinked with electron beam irradiation at three different dosages are studied in relation to voltage and ambient temperature. The characteristic decay current constant (τ_i) and the exponential growth time constant for self‐heating (τ_g) are determined for the samples under voltages (U) above the onset voltage (U_c) of self‐heating. The influence of crosslinking on the current decay dynamics, self‐heating process, and amplitude of the resistance switching under field action are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4418–4422, 2006     

两类水滑石对环氧树脂体系凝胶时间的影响

采用水滑石降低环氧树脂/低分子质量聚酰胺固化体系的凝胶时间。考察了水滑石和丙氨酸交换后的水滑石及其加入量对体系凝胶时间的影响,发现水滑石的加入有利于凝胶时间的降低;当低分子质量聚酰胺∶环氧树脂的质量比值>0.7时,比未改性水滑石更有利于凝胶时间的降低;丙氨酸交换后水滑石的加入量越高,凝胶时间越短。     

烟气脱硫灰对水泥凝结时间的影响

研究了亚硫酸钙含量较多的脱硫灰对C_3A和C_4AF含量不同的水泥熟料凝结时间的影响。研究结果表明:亚硫酸钙对C_4AF有缓凝作用,而对C_3A基本不具缓凝作用;对于中间相含量较多、C_3A含量较高,自身凝结时间短的熟料,在水泥中SO_3≤3.5%的条件下,亚硫酸钙不起缓凝作用;对于中间相含量较少、C_3A含量较低而C_4AF含量较高、自身凝结时间较长的熟料,亚硫酸钙有缓凝作用,但终凝时间比掺二水硫酸钙延长;含亚硫酸钙、碳酸钙、粉煤灰和氢氧化钙的脱硫灰与等量的亚硫酸钙对不同种类熟料的水泥凝结时间的影响类同,脱硫灰中所含的亚硫酸钙对水泥凝结时间影响起主要作用。     

Effect of crosslink density on transport of industrial solvents through polyether based polyurethanes

Polyurethanes based on PPG 2000 with variable concentrations of TDI and TMP were prepared and used for sorption studies, employing homologous series of hydrocarbons such as benzene, toluene and xylene. The sorption was observed to be non-Fickian in nature. The solubility parameter of the polyurethane series was observed to be 9·7(calcm^-3)^1/2. The polymer solvent interaction parameter χ was found to be lowest in benzene, suggesting higher interaction with it. The sorption and diffusion coefficients were observed to increase with a decrease in the degree of crosslinking. Molecular weights between crosslinks were calculated using the Flory–Rehner equation and compared with those obtained theoretically. © 1998 Society of Chemical Industry     

Effect of current density and polytetrafluoroethylene on the properties of micro-arc oxide coating of pure aluminum

Micro-arc oxidation (MAO) is a surface treatment technology that enhances the surface properties of valves by creating a ceramic oxide layer on the metal surface. The goal of this study is to investigate the influence of current density on the properties of aluminum coatings during preparation and to improve the tribological properties of MAO/PTFE self-lubricating films on the coating surface. The characterization of the coating was performed using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectra, and energy dispersive spectroscopy. The roughness, hardness, and elastic modulus of the coatings were tested using atomic force microscopy and nanoindentation. Tribological experiments were conducted to evaluate the tribological properties of the coatings. The experimental results show that the friction coefficient (COF), roughness, hardness, and elastic modulus of the MAO coating increase with the increase of current density. Additionally, the friction coefficient of the MAO composite coating significantly decreases after the addition of polytetrafluoroethylene (PTFE), improving the service life and application range of the metal coating. These findings are expected to promote the development of valve metal in various application fields.     

Effect of fluid density on flow in bagged electrowinning cells

In bagged electrowinning cells where there is gas evolution at the anode, such as the NiCl₂ system, flow across a porous diaphragm bag is observed to occur predominantly from the bottom of the cell. A model based on a hydrostatic argument is proposed which can account for this phenomenon on the basis of bulk density difference between the catholyte and anolyte. Experimental evidence by means of visualization through acid-base reactions shows good agreement with the model.     

时间参数对VPSA分离CH_4/N_2效果影响

为提升VPSA分离煤层气CH4/N2吸附效果和改善吸附剂再生程度,在传统三塔PSA装置基础上,利用时间继电器增加均压工艺,利用真空泵增加抽真空工艺,分别测试不同吸附时间、均压时间和抽真空时间对脱附气或尾气中CH4浓度的影响。     

Effect of torrefaction on the density and volume changes of coarse biomass particles

This work provides preliminary data on the effect of torrefaction on the apparent density of biomass. It also examines how the shape of wood is affected by torrefaction. Experiments conducted on cylinders of poplar wood showed that torrefaction reduced both density and volume of the wood, and the extent of reduction increased with increase in severity of torrefaction. The shape of the wood appears to have some effect on the extent of density change. The shrinkage in radial direction was 3–4%, while reduction in longitudinal direction was 6.5–8.8%. The mass yield decreased with torrefaction severity. © 2013 Canadian Society for Chemical Engineering     

Effect of foam density on the properties of water blown rigid polyurethane foam

Density is an important parameter that influences the properties and performances of rigid polyurethane foam (PUF). Rigid PUF with different densities were prepared by varying the amount of distilled water as blowing agent. This investigation reports the mechanical, morphological, water absorption, thermal conductivity, and thermal behavior of rigid PUF varying with the density, which controls the foam architecture. The density of the PUF decreased from 116 to 42 kg/m³ with an increase in the amount of water from 0.1 to 3.0 parts per hundred polyol by weight (phr), respectively. It was found that the mechanical properties of the PUFs changed with the foam density. The results of water absorption of the PUFs showed that water absorption increased with decrease in density, due to increase in the cell size and decrease in the cell‐wall thickness. The thermal conductivity measurements showed that the thermal conductivity decreased with increase in density. It was due to the decrease in cell size. The thermal analysis of the PUFs shows that the glass transition temperature increases with the decrease in foam density, but the thermal stability decreases with the decrease in foam density. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

振动时间、比压等参数对炭阳极质量影响的研究

通过采用动态过程优化程序,对预焙阳极成型参数(振动时间、振动频率、振动比压、激振力和振幅)进行优化,探索出一套适宜多品种预焙阳极均质生产的方法。     

Effect of gamma irradiation on the dielectric relaxation of uniaxially oriented low density polyethylene

The dielectric loss tangent of unirradiated and irradiated low density polyethylene (LDPE) samples was measured as a function of temperature, from 50 K to room temperature, in directions normal and parallel to that of drawing. The influence of drawing and irradiation on the β‐relaxation and γ‐relaxation are related to the changes in the structure of the amorphous phase and lamellae distribution, and to the radiation‐induced processes of degradation and crosslinking. © 1999 Society of Chemical Industry