Water‐absorption characteristics of organic–inorganic composite superabsorbent polymers and its effect on summer maize root growth

Adding inorganic materials in SAPs to synthesize organic–inorganic composite superabsorbent polymers (OICSAPs) can effectively improve salt‐tolerance, gel strength, thermal stability, and water retention. However, most researches mainly focus on synthesizing process optimization and new multifunctional products, lacking reports on how ions affected water‐absorption characteristics and mechanism of OICSAPs and its influence on summer maize root growth. On the basis of these, we set up laboratory experiments and field cultivation experiment, using environmental scanning electron microscopy (ESEM) and fractal theory to study the questions above. Results show that OICSAPs have better salt‐tolerance, while cations and concentration affected its water‐absorption characteristics significantly. With higher cation valence, larger ionic radius, and concentration, its water‐absorption rate reduced remarkably as Na⁺ < K⁺ < Mg²⁺ < Ca²⁺ < Fe²⁺ < Fe³⁺ < Al³⁺ < Cu²⁺, while the effects of anions could be neglected. The OICSAPs presented typical honeycomb membrane‐like 3D crosslinked network structure, but Ca²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Al³⁺, and Cu²⁺ would damage the structure (Cu²⁺ with the most significant effect) in local microdomain, and changed the complexity of pores. In the experiment, higher concentration could reduce water‐absorption rate without changing micromorphological characteristics. Applying OICSAPs will reduce total length, surface area, and volume of summer maize root, while promoting absorbing and transmitting ability by larger root diameter and the proportion of root <0.5 cm. All these results will provide a theoretical basis on application, marketing, and product development of OICSAPs. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of Li doping on the morphological evolution and optical & electrical properties of SnO2 nanomaterials and SnO2/Li2SnO3 composite nanomaterials

SnO₂ nanomaterials and SnO₂/Li₂SnO₃ composite nanomaterials doped with different Li contents were synthesized via a simple one-step thermal evaporation method. X-ray diffraction patterns showed that with the increase of Li doping, the intensity of Li₂SnO₃ diffraction peaks gradually increased, while that of SnO₂ diffraction peaks gradually decreased. With the increase of Li doping, the width of nanobelts gradually increased, with the morphology changing from banded structure to standard hexagonal sheet structure. The Raman scattering spectra indicated that with the increase of Li doping, the peak of Li₂SnO₃ at 588.8 cm^?1 kept increasing, and the strongest vibration mode A_1g in SnO₂ gradually weakened. X-ray photoelectron spectroscopy revealed that with the increase of Li doping, the surface electrophilic oxygen species in SnO₂/Li₂SnO₃ composite nanomaterials greatly increased. Under the condition of light irradiation with a wavelength of 505 nm, the bright current of the Li-doped SnO₂ samples was higher than the dark current, while that of the SnO₂/Li₂SnO₃ composite nanomaterials was higher than the dark current, which was mainly due to more oxygen vacancies in SnO₂/Li₂SnO₃ composite nanomaterials than electrons excited by light. Consequently, positive photoconductivity gradually weakened, and even the negative photoconductivity emerged.     

Generalized analytical solution to wave interaction with submerged multi-layer horizontal porous plate breakwaters

This study deals with the flow induced by a rigid flat plate of finite length, initially touching a horizontal water surface, when it starts to move upwards with constant acceleration. In the present model, negative hydrodynamic pressures on the lower (wetted) surface of the plate are allowed, and thus, the water follows the plate due to the resulting suction force. The acceleration of the plate and the plate length are such that gravity, surface tension and viscous effects can be neglected during the early stages of the motion. Under these assumptions, the initial two-dimensional, potential flow caused by the plate lifting is obtained by using the small-time expansion of the velocity potential. This small-time solution is not valid close to the plate edges, as it predicts there singular flow velocities and unbounded displacements of the water-free surface. It is shown that close to the plate edges the flow is nonlinear and self-similar to leading order. This nonlinear flow is computed by the boundary-element method combined with a time-marching scheme. The numerical time-dependent solution approaches the self-similar local solution with time.     

基于不均等分层分簇的无线传感器网络协议

针对不均等分簇协议中节点竞选半径和簇头的选取机制存在缺陷问题,提出了不均等分层分簇协议,将网络覆盖区域进行分层处理,降低了簇头簇内负担,提高了能量使用效率,并采用Matlab软件进行了仿真实验。仿真结果表明,UHC协议有效降低了簇内节点密度,且延长了网络使用寿命。     

基于全年动态负荷分析的冷热源方案设计

以北京某酒店为例,对该建筑进行全年逐时动态负荷计算分析。根据计算分析结果,确定制冷季梯级利用离心式冷水机组、螺杆机组和空气源热泵机组作为空调系统冷源,供热季利用板式换热器和空气源热泵机组作为空调系统热源,以达到系统节能的目的。     

一种用于电流型电化学传感器的CMOS模拟前端芯片

本文提出了一种用于电流型电化学传感器的CMOS模拟前端芯片,芯片具有高度可编程性,其内部集成了可通过I2C接口总线与外部控制芯片通信的可配置数字模块电路。结合incremental型sigma-delta模数转换器与数字域相关双采样技术,提出并实现了一种新的两次采样的系统架构。该芯片基于华虹宏力0.18μm标准CMOS工艺流片,消耗芯片面积为1.3 mm × 1.9 mm,测试结果表明：该芯片16位数字输出具有高精度,高线性度特性,可检测溶液中磷酸根离子浓度的精度为0.01 mg/L。     

1000 MW机组锅炉汽动引风机运行试验分析

为节约厂用电、减少设备维护成本、简化引风机的DCS控制方式,对某1000 MW机组进行了引风机与脱硫增压风机合并后采用小汽轮机驱动引风机的改造。在汽动引风机调试过程中进行汽动引风机并入运行、最大出力试验,并对启动过程中的风机抢风现象给出了操作建议。     

静电式空气净化器放电保护现象研究分析

静电式空气净化器在不同湿度中使用,控制器应能根据湿度准确调节高压模块输出电压。若输出电压偏差较大,高压发生极就会出现放电打火并伴有异常声响。若放电频繁,可能会导致极板或塑料件局部损坏。本文通过实验研究放电现象,对该现象如何控制进行分析。     

永磁扰动检测有限元分析及优化设计

永磁扰动检测是一种新型无损检测技术,通过永磁扰动传感器在铁磁构件表面扫查并拾取受缺陷影响下静磁场变化情况来判别缺陷尺寸大小。本文深入分析了永磁体与缺陷的扰动机制,并针对传感器设计理论不足、永磁扰动检测信号微弱等问题,提出了采用环绕式体线圈探测永磁体内产生的磁扰动及采用螺旋线圈探测永磁体与缺陷间的外磁扰动,并在此基础上探究感应线圈及永磁体的几何参数对永磁扰动检测效率的影响。通过有限元模型多参数化扫描及正交试验设计方法对永磁扰动传感器进行了优化设计,该方法能够有效地提高永磁扰动内、外感应电压的幅值。     

应用事故树分析矿井通风系统不可靠问题

对矿井通风系统不合理的表现特征进行了分析,制订了事故树编号规则,依据《煤矿安全规程》《煤矿安全监察条例》和《矿山安全法》等有关国家法律法规和标准,采用事故树分析法对"矿井通风系统不可靠"问题进行深入分析和评价,求出其最小径集,根据结构重要度的直观判断准则,得出各个基本事件的结构重要度排序,最大限度地找出影响矿井通风系统稳定性和可靠性的危害因素,从而采取相应措施加强防范和控制。