Rugorous analysis of planar waveguides with two-dimensionally periodic layer

Rigorous analysis of planar waveguides with two-dimensionally periodic (2DP) layer is presented. Characteristic solutions in periodic layer are exactly represented by a double Fourier series known as the Floquet solutions. The vector amplitudes of space harmonics are proved to be governed by five-term recurrence relation in the operator-vector form for sinusoidal modulation. A general transmission-line network representation of two-dimensionally periodic medium and multiport network representation of uniform-periodic-medium interface are introduced. Any layered structures cascading with periodic ones can be analyzed. Numerical results based on the established theory are also presented to illustrate characteristics of 2DP medium and structure.     

空间三重奏

设计的确是一项非常有趣的工作，就如同一位导演运用出色的技巧掌控有限的预算，为观众呈现令人回味的剧情，逼真的音效和异彩纷呈的视觉映像，这无疑是三个紧密相扣的环。     

影响喷气燃料与橡胶相容性的因素

采用几种具有不同初始物理性能及不同丙烯腈含量、不同硫化剂和硫化程度的丁腈橡胶，考察了其配方和物理性能对采用不同工艺条件生产的喷气燃料的相容性。结果表明，喷气燃料与橡胶的相容性不仅与喷气燃料的加工工艺有关，而且与橡胶的组成及其制备工艺有关。采用非加氢工艺生产的喷气燃料与橡胶的相容性好于采用加氢工艺(特别是加氢裂化工艺)生产的喷气燃料。橡胶材料的初始力学性能的好坏并不完全决定其与喷气燃料相容性的好坏，橡胶材料的耐过氧化物侵蚀能力才是影响相容性好坏的主要因素。橡胶的组成和其制备工艺决定了橡胶在喷气燃料中萃取物的数量和组成，不同萃取物的综合作用给相容性带来不同程度的影响。用硫作硫化剂的橡胶虽然原始强度低于用过氧化物作硫化剂的橡胶，但前者与喷气燃料的相容性却远好于后者。     

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Different NMR techniques were combined to obtain the structure and velocity information for a systematic investigation of fixed beds with low aspect ratio (tube diameter to particle diamter, d_t/d_p) in the range 1.4 to 32. The structure of the void space was determined for a variety of packed beds of glass beads or regular and irregular porous pellets by magnetic resonance imaging (MRI). Based on the images the radial distribution of the voids within the bed was obtained. Ordering effects were found even for non‐spherical and polydisperse particles, and a maximum of the fluid density near the tube wall was confirmed for all pellet geometries and sizes. By combining MRI with velocity encoding, velocity profiles and distributions of flow velocity components of a single fluid phase through packed beds have been acquired. The radial velocity distribution follows an oscillatory pattern which largely reflects the ordering of the particles, which can be accessed from the density distribution of the interparticle fluid. Maximum velocities of up to four times the average value were found to occur near the tube wall. This wall effect was observed for all but the smallest particles, where the aspect ratio was d_t/d_p = 32. Moreover, a visualisation of flow pattern in the presence of packed particles was achieved by using a tagging technique, and the stationary flow field could be identified for an experimental time of several hours.     

悬浮床加氢裂化油溶性催化剂与沥青质的作用

在高压釜反应器中对添加了油溶性 Ni 催化剂(UPC-O)和水溶性 Ni 催化剂(UPC-W)的辽河稠油常压渣油(LHAR)进行了悬浮床加氢裂化实验。通过元素分析和傅里叶变换红外光谱(FTIR)分析对抑制反应生焦效果好的 UPC-O 与 LHAR 沥青质的作用进行了研究。元素分析结果显示,在 LHAR 中加入 UPC-O1000μg/g,沥青质和脱沥青质油中 Ni 含量分别出476μg/g和110μg/g 增加到7 559μg/g 和1 024μg/g,表明 UPC-O 在沥青质中有富集的趋势。FTIR 表征结果显示,UPC-O 和沥青质发生了相互作用。UPC-O 可在沥青质原位硫化为活性组分,对沥青质在悬浮床加氢裂化反应中的缩合起到好的抑制作用。     

Nickel and chromium cycles: Stocks and flows project part IV

Nickel and chromium are essential ingredients in alloys increasingly important for energy-efficient, environmentally friendly modern technology. Quantitative assessment of the flows of these metals through the world economy from resource extraction to final disposal informs resource policy, energy planning, environmental science, and waste management. This article summarizes the worldwide technological cycles of nickel and chromium in 2000. Stainless steel is the major use of these metals, but they serve numerous other special needs, as in superalloys for high-temperature service, as plating materials, and in coinage. Because they are used primarily in alloys, novel recycling issues arise as their use becomes more widespread. “... the great New York and St. Louis double track, nickel plated railroad...” — Norwalk, Ohio, Chronicle 10 March 1881 announces arrival of surveyors for the future Nickel Plate Railway “Later [1911] I formed an alloy of Iron and Chromium, which showed remarkable resistance to rust and tarnish ... [It was] rediscovered by an Englishman named Brearley, in 1914.” —Elwood Haynes to Stephen F. Roberts, 17 January 1925     

Influence of the silicon surface treatment by plasma etching and scratching on the nucleation of diamond grown in HFCVD - a comparative study

A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with 1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers. Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332 cm⁻¹ and a peak at ∼1,580 cm⁻¹ for both samples.     

Geotechnical properties of the soft soil in Guangzhou College City

The paper describes some geotechnical properties of the soft soils in Guangzhou College City, China, which are difficult to both sample and test. Laboratory and in situ tests were carried out to assess the physical and mechanical indices of the soils. The data were statistically analyzed and linear regression undertaken such that equations could be developed by which the geotechnical properties of the soft soils can be predicted. The statistical validity of the degree of correlation confirmed that using these equations, the mechanical indices can be estimated from physical indices determined by routine testing.      

Equilibrium and crystallographic measurements of the binary tetrahydrofuran and helium clathrate hydrates

Clathrate compounds are crystalline materials formed by a physical interaction between host and relatively light guest molecules. Various types of nano-sized cages surrounded by host frameworks exist in the highly unique crystalline structures and free guest molecules are entrapped in an open host-guest network. Recently, we reported two peculiar phenomena, swapping and tuning, naturally occurring in the hydrate cages. Helium, one of the smallest light guest molecules, must be the challengeable material in the sense of physics and moreover possesses versatile applications in the field of superconductivity technology and thermonuclear industry. In this regard, we attempted for the first time to synthesize helium hydrates at moderate temperature and pressure conditions. According to inclusion phenomena, helium itself normally cannot form clathrate hydrates due to being too small molecularly without the help of hydrate former molecules (sI, sII, and sH formers). In this study, the hydrate equilibria of the binary clathrate hydrate containing tetrahydrofuran, helium, and water were determined at 2, 3, 5.56 THF mol%. Direct volumetric measurements were also carried out to confirm the exact amount of helium captured in the hydrate cages. Finally, the crystalline structure of the formed mixed hydrates was identified by powder X-ray diffraction, resulting in structure II.