Self-assembly of nanoparticle-rich interphases in fiber reinforced polymeric composites using migrating agents

Thermoplastic additives, known as migrating agents, can be added to nanoparticle loaded thermosetting resins to form self-assembled nanoparticle structures. Most notably, in fiber reinforced thermosetting composites, self-assembled nanoparticle rich fiber-matrix interphases can be formed. While the self-assembly mechanism remains unclear, depletion interaction correctly describes the types of self-assembled structures formed. Formulations containing modest concentrations of migrating agent form self-assembled fiber-matrix interphases without causing aggregation in the bulk. Slight overdoses of migrating agent can lead to the formation of nanoparticle aggregates in the bulk phase, which can ultimately reduce the mechanical properties of the composite. Even larger overdoses of migrating agent cause the formation of large and open nanoparticle aggregates, indicative of rapid aggregation. Depletion theory predicts that larger molecular weight migrating agents should induce greater attractive forces, thus reducing the concentrations required to form these self-assembled structures. In this study, the migrating agent molecular weight dependence on the self-assembly and aggregation phenomenon are investigated. As predicted by depletion theory, larger molecular weights led to the formation of self-assembled interphases and aggregates at lower concentrations.     

Hydrodynamic Phonon Transport Perpendicular to Diffuse-Gray Boundaries

In this paper, we examine the application of an ideal phonon-hydrodynamic material as the heat transfer medium between two diffuse-gray boundaries with a finite temperature difference. We use the integral-equation approach to solve a modified phonon Boltzmann transport equation with the displaced Bose–Einstein distribution as the equilibrium distribution between two boundaries perpendicular to the heat transfer direction. When the distance between the boundaries is smaller than the phonon normal scattering mean free path, our solution converges to the ballistic limit as expected. In the other limit, we find that, although the local thermal conductivity in the bulk of the hydrodynamic material approaches infinity, the thermal boundary resistance at the interfaces becomes dominant. Our study provides insights into both the steady-state thermal characterization of phonon-hydrodynamic materials and the practical application of phonon-hydrodynamic materials for thermal management.     

Thumb push forces exertable by free-standing subjects

This study assessed the maximum pushing force that could be exerted by freestanding subjects, using thumbs only, on a small surface located in one of three horizontal positions at nine heights ranging from 13·5 to 169·9 cm above the floor. Each of 102 subjects made nine force exertion trials. Data are given on the cumulative percentages of subjects who could exert various forces at each of the 27 locations. An analysis of variance showed a highly significant effect due to location of the surface and highly significant interactions of location of the surface and trial presentation direction (top-down or bottom-up); of location of the surface and trial presentation pattern; and of location of the surface, trial presentation direction and trial presentation pattern. Maximum forces are exerted at about waist height and are increasingly reduced with increasing distances above and below the optimum location. Right-sided access to pushing surfaces is favoured over left-sided access.     

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

A set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η ], translational diffusion D and flotation in a centrifugal field s ) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses M _sD were determined. The Mark–Kuhn–Houwink equations for the range of M _sD from 2240 to 15 300 g mol^?1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry     

Transient Pressure and Temperature Field Measurements in a Lightly Loaded Circumferential Groove Journal Bearing from Startup to Steady-State Thermal Stabilization

The fluid film pressure and temperature fields have been measured simultaneously under laboratory conditions at one land of a circumferential groove journal bearing (CGJB), together with friction torque and oil flow rate, during a time span from stand-still startup to the development of a thermally stabilized steady operating regime.A very fine measurement grid—that is, 216 pressure and 180 temperature points spread across the axial and circumferential directions—has been obtained by joining and synchronizing measurements from separate test runs while rigorously re-creating the test conditions.The study confirmed that the pressure field is established faster than the temperature field, that film rupture occurs both from cavitation nuclei downstream the minimum film thickness and through air ingestion from the environment. Furthermore, the high pressures in the convergent zone stabilize relatively quickly, whereas the low pressures in the divergent zone cavitated region require a longer time to stabilize. The cavitated region reverse flow appearance has been identified thermally through upstream-oriented isotherms. This study is the first to present the transient evolutions of pressure and temperature fields.     

Mathematical modeling and numerical simulation of flow characteristics in an upflow reactor

Abstract

Determining and modeling of the extent of a treatment process in a reactor require knowledge of the flow characteristics. Residence time distribution (RTD), hydrodynamic dispersion coefficients, and velocity distribution are three important terms. Velocity distribution can be measured by a laser doppler anemometer (LDA) accurately, but RTD and hydrodynamic dispersion coefficients must be analyzed by mathematical modeling and dye testing. In this paper, the mathematical modeling and numerical simulation of a upflow reactor are developed. Rhodamine B and a fluorometer are used in laboratory testing. By applying the Euler FTCS (forward‐time‐center‐space) finite‐difference method, the results of dye tests and convection‐dispersion models are compared. The relationship between hydro‐dynamic dispersion coefficients and flow rates is discussed.     

Evaluation of the Missouri River shallow water habitat using a 2D‐hydrodynamic model

Many of the Upper Missouri River dikes have been notched to create additional shallow water habitat (SWH, operationally defined as areas in the stream with depth < 1.5 m, and velocity < 0.75 m s^?1) for fish populations. The goal of this study was to quantify the additional SWH gained from notching these dikes and to evaluate their performance under different flow conditions. A coupled field and numerical study was performed on a reach of the Missouri River, near Nebraska City, NE, which contains a number of dikes notched in 2004. The numerical simulations showed that the SWH criterion for depth was more difficult to satisfy in the study reach than the SWH criterion for velocity. Notching the dikes resulted in a slight shift of the bankline due to local erosion in the vicinity of the dikes and the formation of scour holes downstream of the notches. Results from the study suggested that notching the dikes had limited impact on the SWH because the area gained from the bankline shift was offset by the area lost from the scour holes formation. The performance of the notched dikes in sustaining the minimum habitat suitability conditions for the Missouri River ecosystem was also investigated. These conditions corresponded to discharges < 709 m³ s^?1 for the period from mid‐July to mid‐August, or equivalently SWH areas > 5225 m² dike^?1 during the same period. Analysis of the Missouri River annual discharge records at the study site showed that the dikes can provide the minimum required SWH for mean annual discharges < 667 m³ s^?1. For mean annual discharges > 667 m³ s^?1, new alternative structures or restoration facilities were needed, in addition to the existing dikes, to sustain the minimum required SWH. The dikes were not effective in providing any SWH for mean annual discharges > 2000 m³ s^?1. Copyright © 2010 John Wiley & Sons, Ltd.     

基于SolidWorks软件下进行螺杆压缩机转子受力计算

利用螺杆压缩机的型线端面数据点及型线的接触线数据点,通过给定螺杆压缩机转子参数,在Solid Works里绘制出对应的三维模拟。利用Solid Works里面自带的Simulation模块,对螺杆压缩机进行有限元分析,计算出转子静态下的气体轴向力和径向力,对螺杆压缩机的设计及轴承选型提供很好的理论依据。本文以一种双螺杆制冷压缩机转子为例,利用本方法计算出螺杆压缩机阴阳转子吸排气端的气体径向及排气端气体轴向力。     

Examination of the Causes of Instability of Soy Protein Isolate During Storage Through Probing of the Heat‐Induced Aggregation

This study investigated the mechanism of instability of soy protein isolate (SPI) as influenced by thermal aggregation during SPI preparation. Samples with different degrees of aggregation but similar protein solubility were prepared by heating native SPI (5 % w/v) at 80 or 90 °C for different times before spray‐drying. The samples were then stored at 37 °C for up to 12 weeks and analyzed periodically by atomic force microscopy, gel permeation chromatography, and SDS–PAGE. All SPI samples underwent remarkable protein solubility decreases during the first 8 weeks of storage. The rates of solubility loss were positively correlated with the amounts and/or sizes of soluble aggregates contained in the initial samples (time zero), suggesting their nucleation and activation effects. Solubility tests in SDS–urea solutions and disulfide analysis indicated that non‐covalent interactions were the main driving forces for protein storage instability. Conversely, disulfide bonds and protein carbonyls were abundant in soluble aggregates, and their content increased markedly during storage. This effect suggested that covalent linkages acted as blockers for hydrophobic aggregation.     

青岛市土地利用动态变化及驱动力探究

以青岛市1990-2006年土地利用统计资料和卫星图片等相关资料为基础,通过土地利用的时空变化模型分析,归纳出了其动态变化规律,即：居民点及工矿用地面积、林地面积、交通用地面积和其他农用地面积大幅度增加,耕地、园地和未利用地则表现为不同程度的减少.在此基础上,进一步分析得出了影响青岛市土地利用类型动态变化的几种主要因素,分别是：地形地貌、区域位置、经济发展、城镇化和工业化以及中央和地方各级政府的宏观政策.