蠕动进给碳化钨砂轮高速磨削实验研究

描述了在蠕动进给碳化钨砂轮磨削时的磨削应力和磨损的实验研究 ,这项实验是在热固性树脂结合剂砂轮的工作台移动速度从 0 .0 2 m/ min到 0 .4 m/ min和磨削速度从 32 m/ s到 5 8m/ s的条件下进行的 ,当磨削速度提高到 5 8m/ s且工作台移动速度小于 0 .1m/ min时 ,磨削力达到稳定状态 ,并且不会随着磨除率的增加而增大 ,砂轮磨损降低 ,这时可得到良好的磨削效果。

浅析铝合金轮毂和新型碳纤维轮毂

按照材质来分,轮毂可以分为钢质轮毂、铝合金轮毂和碳纤维轮毂,钢质轮毂与铝合金轮毂各有特点,碳纤维轮毂是一种新兴的汽车轮毂,它的质量轻、强度高、噪声小,随着技术的进步,如果能得到更广的应用,将对汽车的轻量化和节能减排做出突出的贡献。

PAB优质莫来石结合的碳化硅窑具

ＰＡＢ优质莫来石结合的碳化硅窑具Ｓ．谬勒（德国宝成公司）本文所介绍的是有关碳化硅窑具的新技术，有关内容曾在１９９４年６月２日北京陶瓷工业展览会期间报告过。在耐火材料中，合成碳化硅具有高导热性和低热膨胀性的优点早已为大家所熟知，问题在于如何将很硬很脆的...

浅谈汽车轮毂的材质问题

作为汽车上最重要的零部件之一,轮毂的材质直接影响汽车的整体性能。目前已成功应用在民用汽车上的轮毂材质主要包括钢和铝合金,碳纤维轮毂作为一种性能优异的新型复合材料轮毂,也具有很大的技术和市场开发潜力。

满足轻量化自行车应用的T700级湿喷湿纺碳纤维预浸料性能研究

采用恒神自制EM134树脂体系分别匹配T700级恒神湿喷湿纺HF30F碳纤维和东丽干喷湿纺T700SC碳纤维,制备出两种预浸料。通过对EM134树脂体系凝胶时间、升温DSC曲线、恒温DSC曲线,合理优化固化温度和固化时间。同时通过实际过程中模具温度变化及预浸料树脂EM134的升温流变优化制造轮毂制件的固化工艺,并对比两种纤维对应层压板及后端制件的性能。

谈X光机自藕变压器的故障及检修

本文将自藕变压器的基本原理与日常故障等相结合,论述了X射线机自藕变压器在工作中可能出现的故障,并结合故障的特点,分析故障的现象、原因,在实践中总结解决的方法,为医院工程师解决X射线机自藕变压器故障提供参考。

FSK302-1A型程控机摄影kV采样电路故障分析

本文介绍了程控X线机的特点,详细分析了FSK302-1A型程控机摄影kV采样与调整的工作流程及故障排除方法。

Dynamic analysis on carbon accumulation of a plantation in Qianyanzhou based on tree ring data

The authors developed a model to estimate annual tree growth based on tree-ring data (Abbr. TGTRing model) derived from the trunk at 0.5,1.3 and 2.5 m height. This model was applied to estimate the annual biomass and carbon accumulation of a plantation in Qianyanzhou Red-Soil Hill Comprehensive Development Experimental Station of CAS in Taihe County,Jiangxi Province (Abbr. Qianyanzhou). The results showed that the inflexion points of the biomass and carbon accumulation curves occur at 17 and 18 years of age,respectively,in masson pine,whilst both inflexion points occurred at 15 years in slash pine and Chinese fir. The biomass and carbon accumulation in Chinese fir proved to be greater in the last 20 years than in the other species,with 171.697 t/hm2 and 92.29 tc/hm2,respectively. masson pine,with a biomass of 133.84 t/hm2 and a carbon accumulation of 73.92 tc/hm2 was the lowest whilst slash pine was intermediate with a biomass of 147.639 t/hm2 (unturpentined) and 135.743 t/hm2 (turpentined),and a carbon accumulation of 80.18 tc/hm2 (unturpentined) and 73.72 tc/hm2 (turpentined). In 2006,the total biomass and carbon storage of the tree stratum of masson pine in Qianyanzhou was 3324.43 t and 14,156.64 tc,respectively,whilst the values for Chinese fir were 1326.97 t and 713.27 tc. For slash pine the total biomass was 14,156.64 t (unturpentined) and 13,015.97 t (turpentined),and the total carbon storage was 7 688.21 tc (unturpentined) and 7068.78 tc (turpentined). Following the shaving of slash pine for resin,the total biomass was reduced by 1140.67 t and the total carbon storage fell by 619.43 tc.

Systematic Analysis of Carbon Dioxide Activation of Waste Tire by Factorial Design

In this study, waste tire was used as raw material for the production of activated carbons through pyrolysis. ＇Fire char was first produced by carbomzation at 550℃ under nitrogen. A two tactortal design was used to optimize the production of activated carbon from tire char. The effects of several factors controlling the activation process, such as temperature （.830-930℃）, time （2-6h） and percentage ot carbon dioxide （70%-100%） were investigated. The production was described mathematically as a function of these three factors. First order modeling equations were developed for surface area, yield and mesopore volume. It was concluded that the yield, BET surface area and mesopore volume of activated carbon were most sensitive to activation temperature and time while percentage of carbon dioxide in the activation gas was a less significant factor.

Cloud Point Extraction of Polycyclic Aromatic Hydrocarbons in Aqueous Solution with Silicone Surfactants

Cloud point extraction （CPE） processes with two silicone surfactants, Dow Coming DC-190 and DC-193, were studied as preconcentration and treatment for the water polluted by three trace polycyclic aromatic hydrocarbons （PAHs）： anthracene, phenanthrene and pyrene. For all cases, the volumes of surfactant-rich phase obtained by two silicone surfactants were very small, i.e. a lower water content in the surfactant-rich phase was obtained. For example, less than 3% of the initial solution was obtained in a 1% （by mass） surfactant solution, which was much smaller than that of TX-114 in the same surfactant concentration. And TX-114 is known as a high compact surfactant-rich phase among most nonionic surfactants, thus the comparison showed that an excellent enrichment was ensured in the analysis application by the CPE process with the silicone surfactants, and the lower water content obtained in the surfactant-rich phase is also important in the large scale water treatment. The influences of additives and phase separation methodology on the recovery of PAHs were discussed. Comparing with DC-193, DC-190 has a lower cloud point and a higher recovery （near 100%） of all the three PAHs in same surfactant concentration, which was required for application as a preconcentration process prior to HPLC system. However the DC-190 solution is hard to be phase separated only by heating, whereas DC-193 has a relative higher phase separating speed by heating, but a high cloud point （around 360K） limits its application. Due to the phase separation by heating is the only method of CPE suitable to the large scale water treatment, the mixtures of two silicone surfacrants solutions were investigated in this study. A solution containing 1% of mixed DC-190 and DC-193 （in the ratio of 90 ： 10） removed anthracene, phenanthrene and pyrene near 100% with a relative low cloud point and quick phase separating speed.

Grinding Characteristics Of Directionally Aligned SiC Whisker Wheel - Comparison With A12O3 Fiber Wheel

A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.

Nitrogen Recoveries and Yields Improvement in Cowpea sorghum and Fallow sorghum Rotations in West Africa Savannah

The effects of previous cowpea （Vignaunguiculata） and annual fallow on N recoveries, succeeding sorghum yields and soil properties were studied using a 5-year-old （1995-1999） field experiment at Kouar6 （11°59′ North, 0°19′ West and 850 m altitude） in Burkina Faso. A 3 4 factorial design in a split plot arrangement with three rotation treatments and four fertilizer treatments was used. Total N uptake by succeeding sorghum increased from 26 kg N ha~ in mono cropping of sorghum to 31 and 48 kg N ha~ when sorghum was rotated with fallow or cowpea respectively. Nitrogen derived from fertilizer increased from 10% in mono cropping of sorghum to 22% and 26% when sorghum was rotated with fallow or cowpea respectively. While fallow did not increase N derived from soil, cowpea doubled the quantity of N derived from soil （Ndfs）. Sorghum grain yields increased from 75% and 100% when sorghum was rotated with fallow or cowpea respectively. All rotations treatments decreased soil organic C and N but soil organic C was the highest in fallow-sorghum rotation. It was concluded that cowpea-sorghum rotation was more effective than fallow-sorghum rotation and five management options were suggested to improve traditional system productivity.

Application of Supercritical CO2 Gas Turbine for the Fossil Fired Thermal Plant

A supercritical CO2 gas turbine cycle can produce power at high efficiency and the gas turbine is compact compared with the steam turbine. Therefore, it is very advantageous power cycle for the medium temperature range less than 650 ℃. The purpose of this paper is to show how it can be effectively applied not only to the nuclear power but also to the fossil fired power plant. A design of 300 MWe plant has been carried out, where thermal energy of flue gas leaving a CO2 heater is utilized effectively by means of economizer and a high cycle thermal efficiency of 43.4 % has been achieved. Since the temperature and the pressure difference of the CO2 heater are very high, the structural design becomes very difficult. It is revealed that this problem can be effectively solved by introducing a double expansion turbine cycle. The component designs of the CO2 heater, the economizer, supercritical CO2 turbines, compressors and the recuperators are given and it is shown that these components have good performances and compact sizes.

Brayton Power Cycles for Electricity Generation from Fusion Reactors

Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configurations, hindering use of a recuperator in Helium cycles and conditioning the outlet turbine temperature in CO2 ones. In both cycles, it is possible to take advantage of the exhaust thermal energy by coupling the Brayton to a Rankine cycle, with an organic fluid in the helium case （iso-butane has been investigated） and steam in the CO2 case. The highest efficiency achieved with Helium cycle is 38.5% using Organic Rankine Cycle and 32.6% with Helium alone. The efficiency changes from 46.7% using Rankine cycle to 41% with CO2 alone. The Helium cycle is highly sensitive to turbine efficiency and in a moderate way to compressor efficiency and pressure drops, being nearly insensitive to thermal effectiveness in heat exchangers. On the other hand, CO2 is nearly insensitive to all the parameters.

Tire Manufacturer Fighting Climate Changes

This paper presents methods and strategy promoted by an operator of tire rubber manufacturer in order to reduce CO2 emissions. This paper presents calculation methods of GHG emissions and data on production activities, as well as fuel consumption, energy, etc. This example shows that environmental investments are effective primarily in the environmental aspect, but they can become profitable （the carbon trading market of GHG allowances and by providing alternative energy in national energy system, resulting in ＂green certificates＂）.

Design principle for parameters and interferences of tungsten carbide insert interface on roller bits

The lifetime of roll-bits with inserted tooth will be obviously decreased while drilling in strata and the tungsten carbide can be integrally separated from the roll-cone,which will need more trip out time to replace the roller bit.This study provides an entire analysis on stress as well as strength for teeth and tooth holes in loaded conditions.Qualities of tooth drop from matrix within roller bit.The optimized interferences of teeth inserted into the bit can be reasonably obtained by the critical interference derived from some relevant influence factors on the tooth-fixing quality of roller bits.

Experimental Study of Operation Performance for Hydrocarbon Fuel Pump with Low Specific Speed

In this paper, a small flow rate hydrocarbon turbine pump was used to pressurize the fuel supply system of scramjet engine. Some experiments were carried out to investigate the characteristics of turbine pump driven by nitrogen or combustion gas under different operating conditions. A experimental database with regard to the curves of the rotational speed, mass flow rate and net head with regard to centrifugal pump were plotted. These curves were represented as functions of the pressure and temperature at turbine inlet/outlet and the throttle diameter at downstream of centrifugal pump. A sensitivity study has been carried out based on design of experiments. The experimental was employed to analyze net head of centrifugal and throttle characteristics. The research results can accumulate foundations for the close loop control system of turbine pump.

Dynamics and Availability of Different Pools of Manganese in Semiarid Soils as Affected by Cropping System and Fertilization

Manganese(Mn) deficiencies are common in soils on the Loess Plateau of China. This research provided essential information on improving Mn availability in semiarid soils through agricultural practices. Twelve cropping system and fertilization treatments were designed in a 28-year experiment. The cropping systems included long-term fallow, continuous winter wheat cropping, pea(1 year)-winter wheat(2 years)-millet(1 year) rotation(crop-legume rotation) cropping, and continuous alfalfa cropping. The fertilizer treatments under the cropping systems included no-fertilizer control(CK), application of P fertilizer(P), application of N and P fertilizers(NP), and application of N and P fertilizers and manure(NPM), but the NP treatment was excluded in the continuous alfalfa cropping system. Available Mn and Mn fractions of soil samples(0–20 and 20–40 cm depths) were measured and further analyzed quantitatively using path analyses. Results showed that the crop-legume rotation and continuous alfalfa cropping systems significantly increased available Mn compared with the fallow soil. Compared with the no-fertilizer control, manure application increased available Mn in soil of the continuous wheat cropping system. Across all treatments, the averaged content of mineral-, oxide-, carbonateand organic matter-bound and exchangeable Mn accounted for 42.08%, 38.59%, 10.05%, 4.59%, and 0.09% of the total Mn in soil,respectively. Cropping significantly increased exchangeable Mn in soil and the highest increase was 185.7% in the continuous wheat cropping system at 0–20 cm depth, compared with the fallow soil. Fertilization generally increased exchangeable and carbonate-bound Mn in soil. Carbonate-bound Mn was the main and direct source of available Mn in soil, followed by exchangeable and organic matterbound Mn. These results indicated that crop-legume rotation cropping, continuous alfalfa cropping and application of manure, have the potential to promote Mn availability in soils of rainfed farmlands.

Sorption and Leaching Potential of Isoproturon and Atrazine in Low Organic Carbon Soil of Pakistan Under a Wheat-Maize Rotation

Pesticide leaching is a great threat in low organic carbon soils when subjected to improper irrigation scheduling.Limited data are available on the sorption and leaching potential of pesticides in agricultural soils of Pakistan with low soil organic carbon(SOC).Lysimeter and field studies were conducted with and without manure application at two irrigation levels in a wheat-fallowmaize rotation in Faisalabad,Punjab,Pakistan.Isoproturon was applied to wheat 55 d after sowing at 1 kg active ingredient(a.i.)ha^(-1),while atrazine was sprayed on maize 30 d after sowing at 0.774 kg a.i.ha^(-1).Soil was sampled from three depths(0-35,35-70,and 70-110 cm) for the field study and four depths(0-35,35-70,70-115,and 115-160 cm) for the lysimeter study,280 and 65 d after application of isoproturon and atrazine,respectively.The soil-water partition coefficients(K_d) of isoproturon and atrazine ranged from 0.3 to 1.2 and 0.4 to 1.5 L kg^(-1),respectively,and increased linearly with increase in SOC contents.The organic carbon-normalized soil-water partition coefficient(K_(oc)) of isoproturon and atrazine averaged 246.1 and 184.9 L kg^(-1),respectively,being higher with low spiking concentration.Isoproturon residues measured 280 d after application ranged from 2.1% to 3.6% of the applied mass in the lysimeter study and from 1.5% to 3.1% under field conditions.Atrazine residues 65 d after application ranged from only 0.62% to 0.78% and from 0.88% to 0.82% in the lysimeter and field studies,respectively.The lowest levels of residues for both pesticides were observed with frequent irrigation applied to manure-amended soil.A pesticide leaching risk screening tool,the ground water ubiquity score(GUS),indicated that in the absence of manure under both irrigation levels,isoproturon has a leaching potential(GUS = 2.8),while with the application of manure it has a very low leaching risk.Atrazine GUS ranged from 1.7 to 1.9,indicating a very low risk of leaching.