Effects of the number of benzene rings on the properties of single-source ZrC-based liquid precursors and nano zirconium carbide powders thereof

Effects of carbon source in single-source ZrC-based liquid precursors on the properties of the precursors and precursor-derived nano ZrC powders were investigated. The liquid precursors were prepared by directly blending and heating zirconium n-butoxide with either 2,4-pentanedione, benzoyl acetone or 1,3-diphenyl-1,3-propanedione additives which have the same chemical composition and structure except for the number of benzene rings (0, 1 and 2, respectively) in order to control the carbon content in the precursors. The ceramic yield of the precursor decreased as the number of benzene rings in the precursors increased. The stability of the precursors in air and the carbon content of the ceramic powder increased when using 1,3-diphenyl-1,3-propanedione additive. X-ray pure nano zirconium carbide powders with ultra-fine size (30 nm), isotropic shape and homogeneous particle size distribution were synthesized from the liquid precursors containing two benzene rings in the structure. Compared with ZrC powders derived from the precursors containing zero or one benzene ring, the powder from the precursor containing two benzene rings was finer and more homogeneous in size distribution.     

Analysis of color volume of multi‐chromatic displays using gamut rings

There are claims that multi‐chromatic displays can achieve a wider color gamut by the use of additional highly saturated secondary color channels. However, there are other claims that these displays lose lightness and/or color saturation at brighter levels. These apparently divergent views have led to some controversy in the display industry and at standard setting organizations. This study examines the color gamut volume for a variety of simulated and measured multi‐chromatic (sometimes incorrectly referred to as “multi‐primary”) displays using combinations of white and/or secondary color channels, such as cyan, magenta, and yellow. Furthermore, a two‐dimensional gamut representation, referred to as “gamut rings,” is introduced to illustrate that the addition of nonprimary optical color channels to a trichromatic (RGB) display can result in a significant decrease in the chroma at higher lightness levels. The additional saturated color channels can increase the gamut volume only around their hues at darker levels. The results also confirm the validity of comparing the color light output and white light output for revealing the design trade‐offs between the high‐peak white and the color‐image brightness for multi‐chromatic displays.     

旋转叶片电加热防冰系统设计与应用

在开展结冰试验时，结冰风洞风扇叶片前缘有结冰风险，影响风洞安全运行。针对大型旋转叶片结冰问题，提出了旋转叶片电加热防冰系统设计方法，研制了大型结冰风洞旋转叶片电加热防冰系统。首先，研制了内置电加热单元和温度反馈的防冰叶片。针对叶片复杂的工作环境，提出一种新的旋转叶片电加热防冰功率计算方法，通过精确测量和方案优化，设计了基于特殊环境的分半式、大尺寸、高线速度、碳刷自动移开/压紧的导电滑环。最后，采用变结构分级温度闭环和试验参数连锁防冰控制策略解决了旋转叶片结冰问题。该系统已应用于大型结冰风洞，运行中加热电流和叶片温度反馈信号传输连续，所有旋转叶片前缘快速加热且温度分布均匀，防冰效果好。     

Synthesis of ionic liquids based on alkylimidazolium salts and their coal dissolution and dispersion properties

A series of new bis (imidazolium) cation-based ionic liquids, wherein two imidazole rings are tethered by alkyl ether chains (oxygen numbers) of different lengths, were prepared, and their coal dissolution and dispersion properties were studied. It was found these ionic liquids can be used to fragment, disperse, and partially dissolve micrometer-size coal particles by simply mixing ionic liquid/coal dispersions. Dissolution performances and light hydrocarbon production were found to be sensitively increased by increasing the lengths of alkyl ether chains between imidazolium rings.     

Construction of a polynomial invariant annihilation attack of degree 7 for T-310

Abstract

Cryptographic attacks are typically constructed by black-box methods and combinations of simpler properties, for example in [Generalised] Linear Cryptanalysis. In this article, we work with a more recent white-box algebraic-constructive methodology. Polynomial invariant attacks on a block cipher are constructed explicitly through the study of the space of Boolean polynomials which does not have a unique factorisation and solving the so-called Fundamental Equation (FE). Some recent invariant attacks are quite symmetric and exhibit some sort of clear structure, or work only when the Boolean function is degenerate. As a proof of concept, we construct an attack where a highly irregular product of seven polynomials is an invariant for any number of rounds for T-310 under certain conditions on the long term key and for any key and any IV. A key feature of our attack is that it works for any Boolean function which satisfies a specific annihilation property. We evaluate very precisely the probability that our attack works when the Boolean function is chosen uniformly at random.     

Realisation of linear time-varying systems

In this paper, the realisation problem of linear multi-input multi-output, time-varying systems is studied. The approach, based on the theory of non-commutative polynomial rings, yields explicit and simple formulas for computation of the state coordinates as well as for state equations in observable canonical form. The formulas are based on (left) Euclidean polynomial division.     

Radiography and partial tomography of wood with thermal neutrons

The effective high neutron scattering absorption coefficient of hydrogen (48.5 cm²/g) due to the scattering allows neutrons to reveal hydrocarbon structures with more contrast than X-rays, but at the same time limits the sample size and thickness that can be investigated. Many planar shaped objects, particularly wood samples, are sufficiently thin to allow thermal neutrons to transmit through the sample in a direction perpendicular to the planar face but not in a parallel direction, due to increased thickness. Often, this is an obstacle that prevents some tomographic reconstruction algorithms from obtaining desired results because of inadequate information or presence of distracting artifacts due to missing projections. This can be true for samples such as the distribution of glue in glulam (boards of wooden layers glued together), or the course of partially visible annual rings in trees where the features of interest are parallel to the planar surface of the sample. However, it should be possible to study these features by rotating the specimen within a limited angular range. In principle, this approach has been shown previously in a study with fast neutrons [2]. A study of this kind was performed at the Antares facility of FRM II in Garching with a 2.6×10⁷/cm² s thermal neutron beam. The limit of penetration was determined for a wooden step wedge carved from a 2 cm×4 cm block of wood in comparison to other materials such as heavy metals and Lucite as specimens rich in hydrogen. The depth of the steps was 1 cm, the height 0.5 cm. The annual ring structures were clearly detectable up to 2 cm thickness. Wooden specimens, i.e. shivers, from a sunken old ship have been subjected to tomography. Not visible from the outside, clear radial structures have been found that are typical for certain kinds of wood. This insight was impaired in a case where the specimen had been soaked with ethylene glycol. In another large sample study, a planar board made of glulam has been studied to show the glued layers. This study shows not only the limits of penetration in wood but also demonstrates access to structures perpendicular to the surface in larger planar objects by tomography with fast neutrons, even with incomplete sets of projection data that covers an angular range of only 90° or even 60°.     

Spin transport properties in double quantum rings connected in series

A new model of metal/semiconductor/metal double-quantum-ring connected in series is proposed and the transport properties in this model are theoretically studied.The results imply that the transmission coefficient shows periodic variations with increasing semiconductor ring size.The effects of the magnetic field and Rashba spin-orbit interaction on the transmission coefficient for two kinds of spin state electrons are different.The number of the transmission coefficient peaks is related to the length ratio between the upper arm and the half circumference of the ring.In addition,the transmission coefficient shows oscillation behavior with enhanced external magnetic field,and the corresponding average value is related to the two leads’ relative position.     

Frictional behavior of piston rings of small utility two-stroke engine under secondary motion of piston

The secondary motion of the piston head of a motorized engine is captured using two laser displacement sensors to obtain the piston motion and tilt angle. The controlled parameters of the measurement are engine speed, quantity of oil and oil-fuel mixture and its ratio. The reduction in friction force is more significant at dead center at high speed as the quantity of oil supplied increases. Changes in tilt direction of piston head occur at the inlet port. The relationship between the friction force and piston tilt angle showed weak correlation at low speed and increases with the engine speed.     

GCr15钢制轴承套圈渗碳工艺的研究

通过不同炉型进行试验对比,选择出适合GCr15钢制套圈渗碳加工的设备和工艺,开拓了公司的业务范围。