固体雪崩管快脉冲源的研制

固体雪崩管被触发工作在雪崩或二次击穿瞬间时能输出很大的脉冲峰值电流,且触发晃动和上升时间都很小,因此广泛用于制作重复频率低而脉冲功率高的快脉冲源。近几年研制了几种用于纳秒同步机的单管源,应用于产生较宽快沿方波,并且研制出微分波的多管串并联源,应用于纳秒高压产生器中触发氢闸管的多管串联源。     

信息安全中的光学加密技术

光学加密技术作为一种新的加密手段,近年来得到了快速发展,成为现代加密技术的重要研究内容之一.简要概括光学加密技术的产生和发展过程.就影响较大的几种光学加密技术,如双随机相位编码方法、基于分数傅里叶变换的加密方法、基于菲涅耳变换的加密方法、基于联合变换相关器的加密系统、利用离轴数字全息的加密系统和利用相移干涉技术的加密系统以及基于相位恢复算法的加密技术等作了分类评述和讨论.介绍各种加密方案的技术特点和实现方法,讨论实际应用中尚存在的问题,并对其应用前景作了进一步阐述.     

冬虫夏草菌CS.SYSU-Ⅱ深层发酵条件的优化

以菌丝体干质量为评价指标,对冬虫夏草菌(Cordyceps sinensis) CS.SYSU-Ⅱ在5 L发酵罐中的发酵条件进行优化。在单因素试验基础上,选取搅拌转速、通气量和装料系数,采用3因素3水平的正交设计试验,得出最佳发酵条件并验证,最后扩大至20 L发酵罐。结果表明,冬虫夏草菌CS.SYSU-Ⅱ在5 L发酵罐中培养6 d的最佳发酵条件为搅拌转速220 r/min、通气量2.0 vvm和装料系数60%,在此条件下进行验证试验,菌丝体干质量能达到(19.85±0.52) g/L。扩大至20 L发酵罐,可得菌丝体干质量为(16.78±0.06) g/L,发酵结果能达到5 L发酵罐的85%。通过比较摇床与5 L发酵罐的生长曲线,发现pH值能反映菌丝体干质量的变化趋势,可将pH值的变化规律作为发酵结束的判断依据。     

Exploitable biomass status and potential of the Southeastern Anatolia Region,Turkey

In this study, the exploitable biomass potential of nine provinces located in the Southeastern Anatolia region of Turkey was investigated. Animal- and vegetal-derived biomasses were taken into consideration in the analyses. The animal-derived biomass was handled as poultry, small ruminants, and cattle. The vegetal-derived biomass was accounted as field, garden, and vegetable crops. The contribution of each species on the biomass energy potential was studied. The available animal and vegetal residues in the region were estimated to be, respectively, equal to 6.2% and 9.4% of the corresponding residual amount in Turkey. The annual total biomass potential of the region was found to be approximately 83.4 PJ which could meet 15.7% energy demand of the region.     

Water Dynamics in Whey-Protein-Based Composite Hydrogels by Means of NMR Relaxometry

Whey-protein-isolate-based composite hydrogels with encapsulated black carrot (Daucus carota) extract were prepared by heat-induced gelation. The hydrogels were blended with gum tragacanth, pectin and xanthan gum polysaccharides for modulating their properties. ¹H spin-lattice relaxation experiments were performed in a broad frequency range, from 4 kHz to 30 MHz, to obtain insight into the influence of the different polysaccharides and of the presence of black carrot on dynamical properties of water molecules in the hydrogel network. The ¹H spin-lattice relaxation data were decomposed into relaxation contributions associated with confined and free water fractions. The population of the confined water fraction and the value of the translation diffusion coefficient of water molecules in the vicinity of the macromolecular network were quantitatively determined on the basis of the relaxation data. Moreover, it was demonstrated that the translation diffusion is highly anisotropic (two-dimensional, 2D).     

Experimental investigation of extinction cross-section of single vegetation elements using open resonator

The experimental results of investigation of the total cross — section of scattering and absorption (extinction cross — section) σ_t of stalks and strip leaves of grass in millimeter waves range are presented. The investigation was carried out using open quasioptical resonator with spherical mirrors. Measirements were carried out as by absolute method as using the relative method. Experimental results obtained by two different methods showed that in spite of some data differences obtained by absolute and relative methods the latter may be used for estimation of the extinction cross — section σ_t of vegetation elements.     

Prediction of chenille yarn and fabric abrasion resistance using radial basis function neural network models

The abrasion resistance of chenille yarn is crucially important in particular because the effect sought is always that of the velvety feel of the pile. Thus, various methods have been developed to predict chenille yarn and fabric abrasion properties. Statistical models yielded reasonably good abrasion resistance predictions. However, there is a lack of study that encompasses the scope for predicting the chenille yarn abrasion resistance with artificial neural network (ANN) models. This paper presents an intelligent modeling methodology based on ANNs for predicting the abrasion resistance of chenille yarns and fabrics. Constituent chenille yarn parameters like yarn count, pile length, twist level and pile yarn material type are used as inputs to the model. The intelligent method is based on a special kind of ANN, which uses radial basis functions as activation functions. The predictive power of the ANN model is compared with different statistical models. It is shown that the intelligent model improves prediction performance with respect to statistical models.     

Effect of the milling process on the properties of CoFe2O4 pigment

In this study, CoFe₂O₄ pigments were synthesised using both co-precipitation and conventional ceramic methods. Pigment particles prepared using the conventional ceramic method were subsequently milled to submicron size. The effects of the solvent, dispersant and milling type in the milling process were investigated. This study showed that planetary milling in a diethylene glycol (DEG) medium with sodium tripolyphosphate (STPP) was an effective method for producing submicron-sized pigment powders from pigments synthesised using the conventional method. With this method, submicron-sized pigment particles (approximately 190 nm) were obtained after milling for 4 h. Planetary milling was more efficient in reducing particle size compared to attrition milling. Co-precipitated pigment had a more intense black colour, due to the nanoscale particle size (<100 nm). However, conventional ceramic pigments also had an adequately intense black colour that increased after milling compared to unmilled conventional pigments. When considering production of industrial scale submicron-sized pigments, the milling of these pigments to submicron size can be a good alternative method for the production of ink colourants.     

U型钢机器人快速MAG焊接工艺研究

采用机器人对U型钢试件进行快速MAG焊接工艺试验,通过对立缝焊接过程电流、电压、速度等工艺参数及摆动幅度、摆动频率、两侧壁停留时间等机器人运动参数对焊接过程及焊后结果的影响进行分析,结合立角焊接过程熔池受力特性对焊接过程的影响,配合平角及立向弯角焊接,形成一套连贯有效的U型钢快速MAG焊接工艺并能用应用于实际产品。结果表明,在保证焊接稳定性的前提下,焊接电流、电弧电压适当减小,焊接速度适当增加,摆动参数适当减小,有利于焊后焊缝良好成形及效率提高;最终工艺应用在产品上,降本增效,满足生产质效需求。     

Solubility of blue CoAl2O4 ceramic pigments in water and diethylene glycol media

The chemical stability of blue CoAl₂O₄ ceramic pigment in aqueous and non-aqueous suspension was investigated. Distilled water and diethylene glycol (DEG) were used as media. The isoelectric points (IEP) for the commercial and synthesised CoAl₂O₄ pigment were determined to be 4.9 and 8.5, respectively. The IEP shifts toward acidic pH values for the commercial pigment with respect to the synthesised pigment due to the existence of the quartz phase. In water, the cobalt ion concentration was low (2.5 mg dm⁻³), and this concentration did not change with time. However, the aluminium ion concentration was initially high and then decreased to ∼10 mg dm⁻³ at pH 9 and 11 due to the precipitation of Al³⁺ ions as an Al(OH)₃ phase. In DEG, the dissolution of pigment particles with higher ion concentrations (>800 mg dm⁻³) was more significant than that of the aqueous medium, implying that CoAl₂O₄ pigment has insufficient chemical stability in DEG medium with respect to aqueous suspensions.