传热单元操作的基本研究方法

本文通过介绍间壁式换热器中热传导、热对流和工艺计算中的几种基本研究方法,阐述了传热的基本研究方法也是动量和质量传递的基本研究方法,而讨论研究方法的共同性,是把握一个知识体系途径之一.     

同步测量大气湍流折射率结构常数和内尺度的光学方法

 基于不同波长的光闪烁,采用修正的大气湍流Hill谱模型,提出了一种同时反演大气湍流内尺度及折射率结构常数的方法。假定内尺度在某一个范围内取值,对于不同波长的闪烁指数,如果当内尺度取某一定值时,由光传输理论计算的C²_n(λ₁,…)和C²n (λ₂,…)相等,反演成功。根据此原理设计了三波长闪烁计并在某地进行了外场测量。近地面大气湍流的内尺度一般在2~10 mm之间,且随折射率结构常数（其量级为10^-16~10^-13）的变化而变化,两者之间存在一定的正相关;任意两波长组合进行反演得到的内尺度(或折射率结构常数)值具有自洽性,其相关系数的最小值为0.81,因此证明了该方法的可行性。     

Chemically modified multiwalled carbon nanotubes as efficient and selective sorbent for separation and preconcentration of trace amount of Co(II), Cd(II), Pb(II), and Pd(II)

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized by glutaric dihydrazide (GDH) and characterized with FT-IR technique. This new sorbent was used for enrichment and preconcentration of Co(II), Cd(II), Pb(II), and Pd(II) ions. The adsorption was achieved quantitatively on MWCNTs at pH 4.0, and then the retained metal ions on the adsorbent were eluted with 1.5 mol L^?1 HNO₃. The effects of analytical parameters including pH of the solution, eluent type, sample volume, and matrix ions were investigated for optimization of the presented procedure. The adsorption capacity of the adsorbent at optimum conditions was found to be 33.6, 29.2, 22.1, and 36.0 mg g^?1 for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The LOD values of the method were 0.16, 0.19, 0.17, and 0.12 ng mL^?1 (3Sb, n = 10) for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The RSDs values of the method were 0.75, 0.85, 1.16, and 1.30 ng mL^?1 for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The method was applied for the determination of analytes in soil, well water, and wastewater samples with satisfactory results.     

Prediction of particle sticking efficiency for fly ash deposition at high temperatures

The tendency of ash particles to stick under high temperatures is dictated by the ash chemistry, particle physical properties, deposit surface properties and furnace operation conditions. A model has been developed in order to predict the particle sticking efficiency for fly ash deposition at high temperatures. The model incorporates the particle properties relevant to the ash chemistry, particle kinetic energy and furnace operation conditions and takes into consideration the partial sticking behaviour and the deposit layer. To test the model, the sticking behaviours of synthetic ash in a drop tube furnace are evaluated and the slagging formation from coal combustion in a down-fired furnace is modelled. Compared with the measurements, the proposed model presents reasonable prediction performance on the particle sticking behaviour and the ash deposition formation. Through a sensitivity analysis, furnace operation conditions (velocity and temperature), contact angle and particle size have been found to be the significant factors in controlling the sticking behaviours for the synthetic ash particles. The ash chemistry and furnace temperature dictate the wetting potential of the ash particles and the melting ability of the deposit surface; particle size and density not only control the particle kinetic energy, but also affect the particle temperature. The furnace velocity condition has been identified as being able to influence the selective deposition behaviour, where the maximum deposition efficiency moves to smaller particles when increasing the gas velocity. In addition, the thermophoresis effect on the arrival rate of the particles reduces with increasing the gas velocity. Further, increasing the melting degree of the deposit layer could greatly enhance the predicted deposition formation, in particular for the high furnace velocity condition.     

Characterization of dynamical measurement's uncertainty in a two-qubit system coupled with bosonic reservoirs

We study the dynamical characteristics of the entropy-based uncertainty with regard to a pair of incompatible measurements under a bipartite qubit-system suffering from quantum decoherence induced by hierarchical environments. How non-Markovian and Markovian environments affect the dynamical behaviors of the measurement's uncertainty is revealed. We prove that the measured uncertainty of interest demonstrates a non-monotonic behavior, viz., the amount will increase initially and subsequently oscillate periodically with the growth of time in a non-Markovian regime; On the contrary, the uncertainty will inflate firstly and monotonically decrease in a Markovian regime. Noteworthily, we put forward a simple and feasible strategy to suppress the damping of the system and hence be good for decreasing the magnitude of the uncertainty, by virtue of optimal combination of pre-weak measurements and post-filtering operations. Furthermore, we explore the applications of the uncertainty relation investigated on entanglement witness and channel capacity.     

The electronic structures and properties for carbon doped aluminum phosphide

Based on the first-principle method, the effects of carbon dopants on AlP are studied. Our investigations indicate carbons substituting aluminum (C_Al) or phosphorus (C_P) cannot induce the AlP to be magnetic system. The AlP with C_Al defects shows n-type metallic characteristic. As the carbons forming the interstitial doped configurations (C_int), a few percent of C_int could induce the AlP to be a half-metallic ferromagnet, and the half-metallic gaps could reach 0.45∼0.48 eV. Mean field theory predicts the Curie temperature for C_int doped configurations would be above room temperature. Formation energies indicate that C_int, C_Al and C_P defects could be realized experimentally. Positive pair binding energies indicate that carbon would form homogenous distribution in AlP host. This research suggests carbon is a promising dopant, and could be utilized to functionalize the AlP's properties for versatile applications.     

逻辑函数高阶布尔e偏导数求解算法的实现

针对已有方法在求解布尔e偏导数时只能解决小规模电路的问题,提出了一种基于逻辑函数不相交运算的大函数高阶布尔e偏导数的求解算法.该方法将逻辑函数转化为不相交乘积项的集合,用逻辑函数的不相交运算替代布尔e导数运算中的逻辑“与”运算;并将不包含待求导变量的乘积项拆分出来,不参与布尔e导数运算,以达到降低算法复杂度、提高算法速度的目的.提出的算法用C语言编程实现,并用MCNC测试电路进行了测试.实验结果显示,本算法能快速实现大函数高阶布尔e偏导数的求解,求解效率与参与不相交运算的乘积项数量有关,但对输入变量的数量不敏感.     

基于DEA模型的城市地铁交通系统运营效率研究

以20个地铁交通系统已正式投入运营的城市为研究对象,从投入产出方面构建评价城市地铁交通系统运营效率的指标体系,借助数据包络分析模型将20个城市地铁交通系统运营效率划分为高效率水平城市、较高效率水平城市和低效率水平城市3个层级。此外,基于投入产出的视角,分析各城市地铁交通系统当前的投入产出特征,找出当前地铁交通系统存在的不足,为相关部门科学合理地决策提供参考。     

美国致密油开发关键技术

 中国致密油储量丰富, 但目前国内的致密油开发技术还处于探索阶段。美国的致密油开发技术在全球致密油开发技术中最为成熟, 具有非常重要的借鉴意义。从美国致密油开发过程分析看, 可以发现水平井技术和水力压裂技术是推动致密油成功开发的关键, 而与之相配套的技术工艺与工具, 包括水平井布井方式、旋转导向工具、行走式钻机、分级/分段改造工艺及工具等, 是致密油开发技术最重要的组成部分。通过对美国致密油钻井及水力压裂的相关关键技术的认识, 对其开发过程中钻井工艺、配套工具及钻井设备和压裂工艺、分段改造工具及压裂施工参数进行了总结。对比目前中美致密油开发技术, 认为加强国际间技术合作及相关技术的自主研发, 是推动国内致密油高效开发的关键。     

灰色实物型投入产出分析的覆盖解研究

由于国民经济系统的复杂性,人们在使用实物型投入产出分析工具时不可能获得各部门产品的投入与产出的确定值。采用灰色系统理论基本原理提出灰色实物型投入产出分析并给出模型及各种灰色分析系数的覆盖解公式。灰色实物型投入产出分析能处理统计数据为区间的情形,可以使决策者在不确定性情况下对复杂经济系统进行分析、预测和控制,提高人们的抗风险能力。模拟案例验证了模型计算的可行性。