大型结构物自动称重过程的计算机控制技术

大型结构物的称重通过多个千斤顶同步顶升实现。大型结构物往往存在柔度大、重量分布不均、支点跨距大的特点。在称重过程中需要进行计算机同步控制,实现结构物的平稳顶升和下降。大型结构物自动称重以工控机为核心,基于现场总线技术,对压力传感器、位移传感器、状态设置开关、油泵换向阀和油管超高压电磁阀等设备进行网络监控,对多个支点同步协调控制和结构物的精确称重,该系统已在多个油气田工程的建造中得到实际应用。     

透湿膜的透湿机理与膜的研究概况

基于透湿膜的空气除湿是一种比较新颖的空气除湿方法。本文介绍了各种膜在空气除湿领域的应用情况，结合对膜制备工艺的简要介绍，侧重对原除湿原理，亲水性的高分子纤维素膜，凝胶膜和分子筛无机膜在空气除湿领域的研究和进展进行了分析。     

手套箱气氛中氚化水处理的工艺研究

分子筛吸附柱和热金属镁床是手套箱气氛中氚化水 (HTO)搜集和分解处理的一种有效手段。测试了分子筛柱对气氛中水的吸附性能和热金属镁床对HTO的分解性能。结果表明 :分子筛柱对气氛中水的吸附效率 >99 99% ,在空气中水含量为 3 4× 1 0 - 3～ 4 2× 1 0 - 3条件下 ,未发现吸附柱水的贯穿现象 ;热金属镁床对HTO的分解率 >99 9% ,当金属镁的消耗量大于 80 %时 ,未见分解率明显降低。     

Modeling of the bulk free radical polymerization up to high conversion—three stage polymerization model. II. Number-average molecular weight and apparent initiator efficiency

The equations for predicting the number-average molecular weight are derived on the basis of the three stage polymerization model (TSPM) in this paper. By applying the equations, a plotting approach is proposed to determine the apparent initiator efficiency defined as f[(α_td+1)/2] and the constant of chain transfer to monomer, where f is the initiator efficiency and α_td denotes the fraction of the termination rate constants by disproportionation. Using the approach to plot the experimental data in the literature, it is found that the chain transfer to monomer can be neglected for both methylmethacrylate (MMA) and styrene (St) polymerizations, but it can exert a significant effect on ethylmethacrylate (EMA) polymerization. In addition, the apparent initiator efficiency is found to be independent of reaction temperature and initiator concentration at each stage. The values of f[(α_td+1)/2] at gel effect stage are slightly reduced as compared with that at low conversion stage for MMA and EMA polymerizations. However, it decreases significantly at gel effect stage for St polymerization. Using the equations derived and the apparent initiator efficiencies obtained from TSPM plots, the number-average molecular weights at different conversions can be predicted. Comparisons show that the agreement between predictions and experimental data is satisfactory.     

Structure and properties of injection‐molded polypropylenes with different molecular weight distribution and tacticity characteristics

Two series of polypropylenes with different molecular weight distribution and tacticity characteristics were injection molded into flexural test specimens by varying cylinder temperature and the effects of the molecular weight distribution and tacticity on the structure and properties of the moldings were studied. Measured propertied were flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, and mold shrinkage and structures studied were crystallinity, the thickness of skin layer, a*‐axis‐oriented component fraction and crystalline orientation functions. The relations between the structures and properties were also studied. It was found that the molecular weight distribution and tacticity characteristics affect the properties mainly through the molecular orientation and crystallinity, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2142–2156, 2002     

Thermally induced microstructural changes in cotton fibers: A free‐volume study

I measured positron lifetime in natural polymer–cotton fibers as a function of isochronal annealing temperature in the range 27–290°C. The variations in the positron results indicated structural changes occurring in the cotton fibers and determined the glass‐transition temperature as 80°C. Activation energies were measured separately for the crystalline and amorphous regions, indicating the versatility of the technique. These values were close to the O? H bond dissociation energy, suggesting O? H bond dissociation, the most probable process occurring under thermal treatment. As an extension of the positron results, the molecular weight of the cotton fibers was determined to be 1,200,000 based on free volume, which was within the range suggested for cotton. There seemed to be an indication that crosslinking changed the spiral structure of cotton fibers to the network type. However, this needs to be validated by other measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3336–3345, 2002     

Defects in molecular beam epitaxial GaAs grown at low temperatures

We have utilized a variable energy positron beam and infrared transmission spectroscopy to study defects in GaAs epilayers grown at low temperatures (LT-GaAs) by molecular beam epitaxy. We have measured the Doppler broadening of the positron-electron annihilation gamma ray spectra as a function of positron implantation energy. From these measurements, we have obtained results for the depth profiles of Ga monovacancies in unannealed LT-GaAs and Ga monovacancies and arsenic cluster related defects in annealed LT-GaAs. We have also studied the effects of the Si impurities in annealed LT-GaAs. The infrared transmission measurements on unannealed LT-GaAs furnish a broad defect band, related to As antisites, centered at 0.370 eV below the conduction band.     

High uniformity of Al0.3Ga0.7As/ln0.15Ga0.85As doped-channel structures grown by molecular beam epitaxy on 3″ GaAs substrates

Al_0.3Ga_0.7As/ln_0.15Ga_0.85As doped-channel structures were grown by molecular beam epitaxy on 3″ GaAs substrates. The uniformities of electrical and optical properties across a 3″ wafer were evaluated. A maximum 10% variation of sheet charge density and Hall mobility was achieved for this doped-channel structure. A1 μm long gate field-effect transistor (FET) built on this layer demonstrated a peak transconductance of 350 mS/mm with a current density of 470 mA/mm. Compared to the high electron mobility transistors, this doped-channel FET provides a higher current density and higher breakdown voltage, which is very suitable for high-power microwave device applications.     

Investigation of iodine as a donor in MBE grown Hg1−xCdxTe

N-type Hg_1−xCd_xTe layers with x values of 0.3 and 0.7 have been grown by molecular beam epitaxy using iodine in the form of CdI₂ as a dopant. Carrier concentrations up to 1.1 × 10¹⁸ cm⁻³ have been achieved for x = 0.7 and up to 7.6 × 10¹⁷ cm⁻³ for x=0.3. The best low temperature mobilities are 460 cm²/(Vs) and 1.2 × 10⁵ cm²/(Vs) for x=0.7 and x=0.3, respectively. Using CdI₂ as the dopant modulation doped HgTe quantum well structures have been grown. These structures display very pronounced Shubnikov-de Haas oscillations and quantum Hall plateaus. Electron densities in the 2D electron gas in the HgTe quantum well could be varied from 1.9 × 10¹¹ cm⁻² up to 1.4 × 10¹² cm⁻² by adjusting the thicknesses of the spacer and doped layer. Typical mobilities of the 2D electron gas are of the order of 5.0 × 10⁴ cm²/(Vs) with the highest value being 7.8 × 10⁴ cm²/(Vs).     

氨基磺酸系高性能减水剂的研制开发

本文主要讨论了氨基磺酸系高性能减水剂的合成过程及后期混凝土试验情况。通过对反应温度、反应时间、溶液浓度和酸碱度、投料顺序及速度、第四单体的选择等反应条件的控制,合成具有最佳分子结构的最终产物,并通过红外光谱图和核磁共振谱图对合成主产物的分子结构进行了验证。同时,大量的混凝土试验说明氨基磺酸高性能减水剂具有优良的保坍性能。