An Equation for Calculating Nitrogen Density from Measurements of Dielectric Constants

A new equation for determining the density of nonpolar substances based on measurements of dielectric constants is presented. Applying the new equation to nitrogen at a density from 1 to 30 mol·L^–1, the mean deviation of the results calculated from the equation is of the order of 10^–4, which is the same as the uncertainty of the experimental data. Owing to its analytical form, the derived equation can be applied to indicate the density of nonpolar substances with a densitometer, without adding error to the experimental uncertainty. This equation is also capable of determining the mean polarizabilities and molecular diameters, which agree well with results from other investigators. We suggest that the equation derived here can be applied to some other nonpolar substances as well.     

The triangular density to approximate the normal density: decision rules-of-thumb

In this paper we explore the approximation of the normal density function with the triangular density function, a density function that has extensive use in risk analysis. Such an approximation generates a simple piecewise-linear density function and a piecewise-quadratic distribution function that can be easily manipulated mathematically and that produces surprisingly accurate performance under many instances. This mathematical tractability proves useful when it enables closed-form solutions not otherwise possible, as with problems involving the embedded use of the normal density. For benchmarking purposes we compare the basic triangular approximation with two flared triangular distributions and with two simple uniform approximations; however, throughout the paper our focus is on using the triangular density to approximate the normal for reasons of parsimony. We also investigate the logical extensions of using a non-symmetric triangular density to approximate a lognormal density. Several issues associated with using a triangular density as a substitute for the normal and lognormal densities are discussed, and we explore the resulting numerical approximation errors for the normal case. Finally, we present several examples that highlight simple decision rules-of-thumb that the use of the approximation generates. Such rules-of-thumb, which are useful in risk and reliability analysis and general business analysis, can be difficult or impossible to extract without the use of approximations. These examples include uses of the approximation in generating random deviates, uses in mixture models for risk analysis, and an illustrative decision analysis problem. It is our belief that this exploratory look at the triangular approximation to the normal will provoke other practitioners to explore its possible use in various domains and applications.     

A nodal variable method of structural topology optimization based on Shepard interpolant

A method for topology optimization of continuum structures based on nodal density variables and density field mapping technique is investigated. The original discrete‐valued topology optimization problem is stated as an optimization problem with continuous design variables by introducing a material density field into the design domain. With the use of the Shepard family of interpolants, this density field is mapped onto the design space defined by a finite number of nodal density variables. The employed interpolation scheme has an explicit form and satisfies range‐restricted properties that makes it applicable for physically meaningful density interpolation. Its ability to resolve more complex spatial distribution of the material density within an individual element, as compared with the conventional elementwise design variable approach, actually provides certain regularization to the topology optimization problem. Numerical examples demonstrate the validity and applicability of the proposed formulation and numerical techniques. Copyright © 2011 John Wiley & Sons, Ltd.     

n-Hexane Diluted Electrolyte with Ultralow Density enables Li–S Pouch Battery Toward >400 Wh kg−1

Lithium–sulfur (Li-S) batteries are attractive candidates for next generation energy storage devices due to their high theoretical energy density of up to 2600 Wh kg⁻¹. However, the uneven deposition of lithium, the undesired shuttle of lithium polysulfides (LiPSs), and the excess weight fraction of electrolyte severely impair the practical energy density of Li-S batteries. Here, a low concentrated and nonpolar n-hexane (NH)-diluted electrolyte (named as LCDE) with ultralow-density to alleviate the above dilemmas is proposed. The nonpolar NH boosts the diffusion of lithium ion in LCDE, favoring the homogeneous deposition of lithium. This nonpolar effect also reduces the solubilities of LiPSs, promoting a quasi-solid-state transformation of sulfur chemistry, thus tremendously eradicating the shuttle of LiPSs. Most importantly, the ultra-light NH diluent enables the LCDE with an ultralow density of only 0.79 g mL⁻¹, which reduces the weight of LCDE by 32.5% compared with conventional ether-based electrolyte. Owing to all the merits, the Li-S pouch cell achieves a high energy density up to 417 Wh kg⁻¹. The nonpolar NH-diluted electrolyte with multifunction presented in this work provides a new and feasible direction to increase the practical energy density of Li-S batteries.     

石墨烯铝基复合材料的制备及性能分析

采用真空热压烧结工艺制备了石墨烯质量分数分别为0.1%、0.5%和1.0%的添加粘结剂与不加粘结剂的两种6061铝复合材料,对其致密度、硬度和导电性进行了测试分析。结果发现,添加粘结剂的复合材料在石墨烯质量分数为0.1%时就开始出现Al4C3,而不添加粘结剂的复合材料在石墨烯质量分数为0.5%时才开始出现Al4C3,其原因是添加粘结剂的复合材料中的石墨烯先与纳米铝粉混合,使石墨烯更容易与铝发生反应。随着石墨烯质量分数的增加,两种复合材料的致密度和导电性降低,硬度增加。其原因都是随着石墨烯质量分数的增加Al4C3增加,且石墨烯团聚现象也越严重。粘结剂的添加对复合材料的致密度、导电性以及硬度都有较大的影响。     

基于体积扫描容重法的社区垃圾分类系统研究

目的 响应国家垃圾分类政策，通过设计社区生活垃圾分类设备检测系统，提高分类正确率，改善“混投乱投”的现状，从源头提高城市垃圾分类投递的准确性。方法 结合现有针对垃圾容重区间划分方法和多种评价标准，总结归纳各类垃圾的容重阈值划分区间，并将其作为垃圾分类的判断方法。设计体积检测模块，利用激光测距传感器点阵获得待测物切片遮挡图和截面积，并计算待测物体积，结合称重传感器计算待测物容重，并依据容重区间对待测物进行分类判断。结果 根据容重阈值分类标准，对多种随机样本进行检测。绝大多数可回收物和厨余垃圾的容重检测值在各分类的容重阈值内，可以被正确分类；其余样本在混合垃圾容重阈值内，符合边界条件设定和模糊垃圾的样本按其他垃圾标准处理的分选原则，检测结果符合分类要求。结论 基于体积扫描检测容重的社区生活垃圾分类系统可以满足居民前端投递环节中对生活垃圾分类检测的需求，有助于提高源头分类的准确性，能有效推进我国垃圾分类和再生资源利用工作的发展。     

Achieving Ultrahigh Volumetric Energy Storage by Compressing Nitrogen and Sulfur Dual-Doped Carbon Nanocages via Capillarity

High volumetric performance is a challenging issue for carbon-based electrical double-layer capacitors (EDLCs). Herein, collapsed N,S dual-doped carbon nanocages (cNS-CNC) are constructed by simple capillary compression, which eliminates the surplus meso- and macropores, leading to a much increased density only at the slight expense of specific surface area. The N,S dual-doping induces strong polarity of the carbon surface, and thus much improves the wettability and charge transfer. The synergism of the high density, large ion-accessible surface area, and fast charge transfer leads to state-of-the-art volumetric performance under the premise of high rate capability. At a current density of 50 A g⁻¹, the optimized cNS-CNC delivers a high volumetric capacitance of 243 and 199 F cm⁻³ in KOH and EMIMBF₄ electrolyte, with high energy density of 7.9 and 93.4 Wh L⁻¹, respectively. A top-level stack volumetric energy density of 75.3 Wh L⁻¹ (at power density of 0.7 kW L⁻¹) and a maximal stack volumetric power density of 112 kW L⁻¹ (at energy density of 18.8 Wh L⁻¹) are achieved in EMIMBF₄, comparable to the lead–acid battery in energy density but better in power density with 2–3 orders. This study demonstrates an efficient strategy to design carbon-based materials for high-volumetric-performance EDLCs with wide practical applications.     

PVT measurements of liquid ethanol in the temperature range from 310 to 363 k at pressures up to 200 MPa

Density measurements in the compressed liquid phase for ethanol were performed with a metal-bellows variable volumometer for temperatures between 310 and 363 K at pressures from the vapor pressure to 200 MPa. The results cover the high-density region from 737 to 882 kg m_–3. The experimental uncertainties (total errors) of temperature, pressure, and density were estimated to be no greater than 3 mK, 0.1 %, and 0.1 %, respectively. Measurements of saturated liquid density at temperatures of 310, 340, and 360 K are also reported.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

燃煤流化床床料的密度、错位密度和颗粒形貌研究

在两种燃煤颗粒和一种循环流化床锅炉冷渣颗粒形貌测量的基础上,提出了颗粒错位密度的概念,建立了颗粒外接六面体体积充满度与错位密度之间的关系。测量结果显示,采用错位密度处理颗粒形貌数据时,原本分散的测量数据表现出明显的线性化效果。对于实验中的两种煤,将颗粒密度当作常数处理对错位密度几乎没有影响。而对于循环流化床锅炉的冷渣,将颗粒密度当作常数,造成较大偏差。     

彩色胶卷的印片密度

印片密度是彩色胶卷在实用扩印条件下的有效密度，感光测定中都用Ｍ状态密度来表示。本文中用实验方法求取了彩色胶卷的印片密度，并与测定的Ｍ状态密度作了对比。印片密度的实验测定定性地说明了彩色胶卷的特性曲线通常都是黄层的反差最大而青层的反差最小。     

High‐Stacking‐Density,Superior‐Roughness LDH Bridged with Vertically Aligned Graphene for High‐Performance Asymmetric Supercapacitors

The high‐performance electrode materials with tuned surface and interface structure and functionalities are highly demanded for advanced supercapacitors. A novel strategy is presented to conFigure high‐stacking‐density, superior‐roughness nickel manganese layered double hydroxide (LDH) bridged by vertically aligned graphene (VG) with nickel foam (NF) as the conductive collector, yielding the LDH‐NF@VG hybrids for asymmetric supercapacitors. The VG nanosheets provide numerous electron transfer channels for quick redox reactions, and well‐developed open structure for fast mass transport. Moreover, the high‐stacking‐density LDH grown and assembled on VG nanosheets result in a superior hydrophilicity derived from the tuned nano/microstructures, especially microroughness. Such a high stacking density with abundant active sites and superior wettability can be easily accessed by aqueous electrolytes. Benefitting from the above features, the LDH‐NF@VG can deliver a high capacitance of 2920 F g^?1 at a current density of 2 A g^?1, and the asymmetric supercapacitor with the LDH‐NF@VG as positive electrode and activated carbon as negative electrode can deliver a high energy density of 56.8 Wh kg^?1 at a power density of 260 W kg^?1, with a high specific capacitance retention rate of 87% even after 10 000 cycles.     

Ultrahigh‐Energy Density Lithium‐Ion Cable Battery Based on the Carbon‐Nanotube Woven Macrofilms

Moore's law predicts the performance of integrated circuit doubles every two years, lasting for more than five decades. However, the improvements of the performance of energy density in batteries lag far behind that. In addition, the poor flexibility, insufficient‐energy density, and complexity of incorporation into wearable electronics remain considerable challenges for current battery technology. Herein, a lithium‐ion cable battery is invented, which is insensitive to deformation due to its use of carbon nanotube (CNT) woven macrofilms as the charge collectors. An ultrahigh‐tap density of 10 mg cm^?2 of the electrodes can be obtained, which leads to an extremely high‐energy density of 215 mWh cm^?3. The value is approximately seven times than that of the highest performance reported previously. In addition, the battery displays very stable rate performance and lower internal resistance than conventional lithium‐ion batteries using metal charge collectors. Moreover, it demonstrates excellent convenience for connecting electronics as a new strategy is applied, in which both electrodes can be integrated into one end by a CNT macrorope. Such an ultrahigh‐energy density lithium‐ion cable battery provides a feasible way to power wearable electronics with commercial viability.     

纸张性能对不同阶调处印刷品密度的影响

实验结合印刷品质量检测方法和SPSS软件,对在IGT印刷适性仪上的印刷结果进行分析,得到纸张性能与不同阶调处印刷品密度之间的关系.据此数据能够预知密度再现质量情况,可通过比较不同纸张的性能数据判断哪种纸张适合于目标印刷品.     

Generation of non-Gaussian stochastic processes using nonlinear filters

Non-Gaussian stochastic processes are generated using nonlinear filters in terms of Itô differential equations. In generating the stochastic processes, two most important characteristics, the spectral density and the probability density, are taken into consideration. The drift coefficients in the Itô differential equations can be adjusted to match the spectral density, while the diffusion coefficients are chosen according to the probability density. The method is capable to generate a stochastic process with a spectral density of one peak or multiple peaks. The locations of the peaks and the band widths can be tuned by adjusting model parameters. For a low-pass process with the spectrum peak at zero frequency, the nonlinear filter can match any probability distribution, defined either in an infinite interval, a semi-infinite interval, or a finite interval. For a process with a spectrum peak at a non-zero frequency or with multiple peaks, the nonlinear filter model also offers a variety of profiles for probability distributions. The non-Gaussian stochastic processes generated by the nonlinear filters can be used for analysis, as well as Monte Carlo simulation.     

密度对C/C复合材料热力学性能的影响

采用针刺预制体经化学气相沉积与沥青浸渍-高压碳化致密工艺制备C/C复合材料,通过控制沥青浸渍-高压碳化致密次数,获得了密度分别为1.70g/cm~3、1.82g/cm~3、1.89g/cm~3的三种C/C材料,测试材料的力学、热学性能。结果表明材料拉伸强度随密度升高而降低。当密度较低时,纤维/基体界面结合强度相对较低,可以延缓纤维断裂的发生;拉伸断口显示出假塑性断裂特征,有利于材料拉伸强度的提高。材料的压缩强度与剪切性能密切相关,且均随密度升高表现出先升后降的趋势。材料的热膨胀系数随密度升高而增大,材料中微晶之间的空隙在受热过程中可以吸收一部分膨胀量,因此对于C/C材料,降低密度有利于降低热膨胀系数。材料导热系数随密度升高而明显增大,且随密度升高,微晶尺寸增大,有利于晶格振动的传递,从而使得导热系数增大。热应力因子随密度升高而先升后降,作为热结构件使用时,采用密度为1.82g/cm~3的C/C材料可以获得相对较高的抗热震能力。在C/C材料研究开发中,可以综合对材料力学、热学性能的要求来对C/C材料密度指标进行设计。     

一种具有密度梯度的飞片材料的制备

本文作者使用Fe-Al烧结助剂,在1473 K的热压烧结条件下成功制备出了整体致密、密度沿厚度方向呈特定分布的W-Mo-Ti体系密度梯度飞片材料。研究表明,低熔点Al的添加,使部分烧结助剂Fe以液态形式存在,提高了Fe的活化烧结能力。W-Mo,Mo-Ti合金的烧结均为液相烧结过程,W-Mo合金主要通过形成少量粘结相和液相来粘结W,Mo晶粒,而Mo-Ti合金则通过形成部分Mo-Ti固溶体来实现致密化。     

Controlled Fab installation onto polymeric micelle nanoparticles for tuned bioactivity

Abstract

Antibodies and antigen-binding fragments (Fabs) can be used to modify the surface of nanoparticles for enhanced target binding. In our previous work, site-specific conjugation of Fabs to polymeric micelles using conventional methods was limited to approximately 30% efficiency, possibly due to steric hindrance related to macromolecular reactants. Here, we report a new method that enables conjugation of Fabs onto a micelle surface in a controlled manner with up to quantitative conversion of nanoparticle reactive groups. Variation of (i) PEG spacer length in a heterofunctionalized cross-linker and (ii) Fab/polymer feed ratios resulted in production of nanoparticles with a range of Fab densities on the surface up to the theoretical maximum value. The biological impact of variable Fab density was evaluated in vitro with respect to cell uptake and cytotoxicity of a drug-loaded (SN38) targeted polymeric micelle bearing anti-EphA2 Fabs. Fab conjugation increased cell uptake and potency compared with non-targeted micelles, although a Fab density of 60% resulted in decreased uptake and potency of the targeted micelles. Altogether, our findings demonstrate that conjugation strategies can be optimized to allow control of Fab density on the surface of nanoparticles and also that Fab density may need to be optimized for a given cell-surface target to achieve the highest bioactivity.     

Growth of compact arrays of optical quality single crystalline ZnO nanorods by low temperature method

We report the synthesis and optical properties of compact and aligned ZnO nanorod arrays (dia, ∼ 50–200 nm) grown on a glass substrate with varying seed particle density. The suspension of ZnO nanoparticles (size, ∼ 15 nm) of various concentrations are used as seed layer for the growth of nanorod arrays via selfassembly of ZnO from solution. We studied the effect of various growth parameters (such as seeding density, microstructure of the seed layer) as well as the growth time on the growth and alignment of the nanorods. We find that the growth, areal density and alignment of the nanorods depend on the density of seed particles which can be controlled. It is observed that there is a critical density of the seed particles at which nanorod arrays show maximum preferred orientation along [002] direction. The minimum and maximum radius of the aligned nanorods synthesized by this method lie in the range 50–220 nm which depend on the seeding density and time of growth. These nanorods have a bandgap of 3.3 eV as in the case of bulk crystals and show emission in the UV region of the spectrum (∼ 400 nm) due to excitonic recombination and defect related emission in the visible region.     

Preparation and characterization of ultra-low density porous gold foams

We present a simple approach to generate ultra-low density porous gold foams with the density as low as 0.519 gcm^-3. In our work, gold nanoparticles with small grain sizes and good solubility were prepared and used as starting building blocks; afterwards, the freeze-dry technique was employed to prepare gold compound foams. Finally the gold compound foams were sintered to obtain porous gold foams with ultra-low density. The results show that the content of gold element in the foams is close to 99.2%. Even though the density is as low as 0.519 gcm^-3 the foams still have good intensity and can be machined to simple regular shapes. The microstructure analysis results indicate that the gold foams have continuous open structure, the average pores size is about 1-2 μm, and the framework of the gold foams is piled up with gold particles of different sizes. Our approach might give a way to produce low-density gold foams with simple fabrication procedures.