不同穗型水稻产量与群体生理性状的关系

根据穗倾角穴穗颈节至穗尖的连线与茎秆延长线的夹角雪的大小,将参试的12个品种划分为直立穗型、半弯曲穗型、弯曲穗型3种类型,研究了不同穗型的群体形态生理性状与产量形成的关系。结果表明,弯曲穗型品种抽穗期干物重较高,直立穗型品种抽穗后和成熟期干物重较高,抽穗后干物重占成熟期干物重的百分比也较高,半弯曲穗型上述方面介于二者之间。直立穗型、半弯曲穗型和弯曲穗型的颖花/叶值相近,说明三者单位叶面积所负担的颖花数差异不大。就粒重/叶而言,直立穗型>半弯曲穗型>弯曲穗型。直立穗和半弯曲穗型品种抽穗后单个颖花拥有的干物质越多,成粒率越高。比叶重大的品种,抽穗后群体叶面积衰减缓慢,具有一定的群体叶面积,对干物质生产和产量的形成是十分有利的。     

高强度钢干式铣削替代半精磨的试验研究

采用硬质合金刀片(YW1)和涂层刀片(YB415)进行了高强度钢的干式铣削代替半精磨试验研究。根据试验结果,确定适合加工该型号高强度钢的刀具材料和切削用量。以这两种刀片在不同切削用量条件下的耐用度、加工表面粗糙度和主切削力作为刀具加工性能的评价依据,同时研究了刀片的磨、破损机理和卷、排屑稳定性。试验结果表明:涂层刀片干铣削高强度钢的加工性能优异,工件加工表面质量达到半精磨水平。     

Mode of zero wear in mechanical systems with dry contact

A theoretical and experimental analysis of a mechanical system with dry contact and subject to harmonic excitation is made. The adopted model is a two-degree-of-freedom system representing two sub-structures in dry contacts from their flat ground surfaces. It is theoretically shown that the two sub-structures move in phase with equal amplitudes at a particular frequency of oscillation. This particular frequency is called the frequency of virtual sticking and depends upon the physical properties of the two contacting sub-structures as well as the ratio between the amplitudes of external forces applied on these two structures in the direction of their friction sliding. Zero wear of contact surfaces can thus be established since relative velocity between encountered asperities of sub-structure surfaces becomes zero. It is shown, theoretically and experimentally, that when one of the applied harmonic forces is zero, the frequency of virtual sticking is equal to the natural frequency of the unforced sub-structure. The displacement ratio of the two contacting structures under the effect of harmonic excitation in their sliding direction is investigated within a frequency range up to 400 Hz. The tangential contact stiffness and the dynamic contact rigidity are theoretically determined and experimentally predicted from the measured forced displacement ratio.     

Dry sliding wear response of zinc-based alloy over a range of test speeds and loads: a comparative study with cast iron

This study pertains to the observations made during the sliding wear response of a zinc-based alloy in different test conditions. The effects of sliding speed and load on the wear behaviour of the alloy have been studied. The properties evaluated were wear rate, frictional heating and coefficient of friction. The wear performance of the zinc-based alloy has been compared with that of a conventional cast iron in identical test conditions. The wear rate of the samples increased with applied load and sliding speed while the seizure resistance (load) deteriorated with speed. The zinc-based alloy exhibited less wear rate and reduced frictional heating than that of the cast iron while friction coefficient followed a reverse trend. Observed wear response of the samples has been discussed in terms of specific features like lubricating, load carrying, microcracking and thermal stability of various microconstituents of the samples, and substantiated further through the features of wear surfaces, subsurface regions and debris.     

THERMAL DESIGN FOR HARMON DRY-COOLING SYSTEM IN LARGE POWER STATION

Based on the analysis of air flow and heat transfer in the dry-cooling tower for Harmon system, a combined iteration method is presented to solve the coupled heat transfer and draft equations derived from theoretical and empirical formulas, with the size of the exchangers and the cooling tower or the systematic parameters being determined. Taking the 686 MW unit as an example, the present calculating results are well agreed with those of the real case, and thus the method presented is practical and feasible for reasonable design of Harmon system.     

Entropy generation from hydrogen production of catalytic partial oxidation of methane with excess enthalpy recovery

Catalytic partial oxidation of methane (CPOM) is an important route for producing hydrogen and it is featured by autothermal reaction. To recognize the reaction characteristics of CPOM, H₂ production and entropy generation from CPOM in Swiss-roll reactors are studied numerically. The considered parameters affecting the performance of CPOM include the excess enthalpy recovery, gas hourly space velocity (GHSV), number of turns and atomic O/C ratio. The impact of chemical reactions, heat transfer and friction on entropy generation is also analyzed. The results indicate that preheating reactants through waste heat recovery as well as increasing GHSV or number of turns is conducive to enhancing H₂ yield, whereas the maximum H₂ yield develops at O/C = 1.2. A higher H₂ yield is always accompanied by a higher value of entropy generation, and chemical reactions are the main source of entropy generation, especially from steam methane reforming. In contrast, viscous dissipation almost plays no part on entropy generation, compared to heat transfer and chemical reactions. From the analysis of entropy generation, detailed mechanisms of H₂ production from CPOM can be figured out.     

Effect of [6,6]‐phenyl‐C61‐butyric acid methyl ester on the morphology of poly(3‐hexylthiophene) film

The change of morphology of poly(3‐hexylthiophene) (P3HT) film as a result of blending with [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) was studied using a freeze‐dry method. A porous structure was observed as the P3HT/PCBM solution was freeze‐dried. The pore size decreased as the proportion of PCBM increased in the P3HT/PCBM blended film. Additionally, the freeze‐dried P3HT/PCBM film was more resistant to the formation of PCBM crystals than that prepared by a spin‐coating method during the thermal annealing process. Homogeneous distribution of PCBM in the freeze‐dried P3HT/PCBM film was the main reason for the reduction of large PCBM crystal formation. Copyright © 2011 Society of Chemical Industry     

Effect of dry‐heat treatments on the nutritional value of maize germ

Maize germ is a by‐product of the maize milling process that is characterised by a high nutritional value. Currently, heat treatments are employed to prevent full‐fat maize germ from spoilage. The aim of this research was to study the effect of five dry‐heat treatments on the nutritional value of full‐fat maize germ. The results confirmed that after each dry‐heat treatment, the lipase activity decreases but the use of high temperatures could be detrimental for phytosterol and thiamine concentrations. The main negative effects have been observed after treatments at 140 °C for 30 min and 160 °C for 10 min. No significant difference has been observed for protein, ash or fatty acid contents. The treatment at 140 °C for 20 min resulted an optimal combination between temperature and heating time to inactivate lipase without altering deeply the nutritional value and the colour of maize germ.     

建筑防火设计中脉冲超细干粉灭火技术的应用

脉冲超细干粉灭火技术是灭火技术的一场革命。它优良的灭火效果、安全无毒的特性，使得它在几乎所有场合得到运用。本文提出了脉冲灭火技术在建筑设计中应用的要求，并分析了该技术在建筑消防上的应用。     

Oxidation of potential SOFC interconnect materials,Crofer 22 APU and Avesta 353 MA,in dry and humid air studied in situ by X-ray diffraction

Abstract

Several stainless steels have been developed for the use as interconnect materials in solid oxide fuel cells in order to reduce costs, while maintaining the required performance. The materials however, are subjected to humid air, at high temperatures up to 800°C leading to enhanced oxidation. High temperature X-ray diffraction, combined with field emission – scanning electron microscopy, has been applied to study in situ the influence of water vapour on the chromia scale formation on the ferritic Crofer 22 APU and the austenitic Avesta 353 MA alloys in comparison to their dry air oxidation behaviour. Both materials form at 800°C, during the first 100h exposure, Cr₂O₃ and MnCr₂O₄, the latter mostly in the surface region of the oxide scale. Additionally, Crofer 22 APU forms internal Al₂O₃ precipitates, while on Avesta 353 MA a SiO₂ layer is found beneath the outer oxide scale. High temperature XRD indicates stress formation and relaxation in the Cr₂O₃ scale formed in humid air, especially for Crofer 22 APU.