Osmotic Dehydration of Apple Cylinders: I. Conventional Batch Processing Conditions

Osmotic drying was carried out, with cylindrical samples of apple cut to a diameter-to-length ratio of 1:1, in a well-agitated large tank containing the osmotic solution at the desired temperature. The solution-to-fruit volume ratio was kept greater than 30. A modified central composite rotatable design (CCRD) was used with five levels of sucrose concentrations (34–63°Brix) and five temperatures (34–66°C). Kinetic parameters weight reduction (WR), moisture loss (ML), solids gain (SG) were considered. A polynomial regression model was developed to relate moisture loss and solids gain to process variables. A conventional diffusion model involving a finite cylinder was also used for moisture loss and solids gain, and the associated diffusion coefficients were computed. The calculated moisture diffusivity ranged from 8.20 × 10^?10 to 24.26 × 10^?10 m²/s and the solute diffusivity ranged from 7.82 × 10^?10 to 37.24 × 10^?10 m²/s. Suitable ranges of main parameters were identified for OD kinetics further study.     

精馏过程中气-液比条件的工程意义

精馏生产技术的关键是确保过程中气-液比如何接近最优条件,通过各技术参数和气-液比之间的关系,研究了如何判断气-液比条件,如何调节气-液比条件的方法和技术措施。     

Viscoelastic behavior of nanotube-filled polycarbonate: Effect of aspect ratio and interface chemistry

A combined experimental and modeling study on the solid-state rheology of multi-walled carbon nanotube (MWNT)/polycarbonate composites as a function, independently, of MWNT aspect ratio and interface chemistry was carried out. Shorter aspect ratio nanotubes lead to greater broadening of the loss modulus peak in frequency space, but there was no effect of aspect ratio on the glass transition temperature. The breadth of the loss modulus peak was found to correlate with the free space parameter, a measure of the spacing between the MWNTs. A new model that accounts for the aspect ratio and distribution in a representative volume element was developed to study these parameters in a controlled setting where morphology was precisely known. Micromechanics modeling was found to correlate well with experimental data. These results shed light on the separate impacts of aspect ratio, dispersion, and interface modification on the solid-state rheology of nanofilled polymers.     

改进型卡塞格林光学系统的设计

普通的卡塞格林光学系统,其主次镜分别由抛物面和双曲面组合而成,非球面镜的加工难度大、成本高,针对这些特点对卡塞格林光学系统进行了改进。改进型的卡塞格林光学系统与传统的卡塞格林光学系统对比具有加工难度小、成本低等特点,通过在系统最前面附加前校正组,使得主次镜可以由球面面型实现,通过在像面前设置后校正组使视场也得到了提高,与传统的卡塞格林光学系统20＇相比,它的视场可以拓宽到1.3°。系统设计结果通过传递函数与点列图的分析与衍射极限非常接近,为中等口径卡塞格林光学系统的设计提供了一个新的思考方法。     

三联供系统中逐时冷热电负荷的模拟计算

在进行冷热电三联供系统设计时,冷热负荷与电负荷的逐时对应关系直接影响到三联供系统的配置与运行,逐时负荷的准确计算是三联供系统优化配置与运行分析的基础。本文基于对建筑冷热电负荷调查研究的基础上,采用日本三联供设计手册中的相关数据,利用“逐时能源负荷分摊比例”的方法,以宾馆建筑为例,模拟计算了该宾馆的全年逐时冷热电负荷,为三联供系统的优化设计与系统配置奠定了一定的基础。     

利用电阻法原理测算高岭石的径厚比

高岭石的径厚比,在高岭土的许多应用领域都是一个重要参数,目前尚未有很好的仪器和技术对其进行精确测量。以电阻法为原理对颗粒粒度的测量,反映了电阻的变化与颗粒体积和形貌之间的关系,可以此为基础进行高岭石径厚比计算。通过对以电阻法为工作原理的库尔特仪测试输出数据和图形的详细分析,发现其输出的电脉冲高度反映颗粒的体积,电脉冲宽度反映通过小孔的颗粒长度,并通过与标准球形颗粒脉冲数据进行对比,建立了高岭石径厚比测算公式AR=3/2(n+W-Wn/Wn+1-Wn/L)3通过实例分析,验证了该方法的精确性。     

高温煅烧石油焦排料过程余热回收

为了实现煅烧石油焦在排料过程中余热的高效回收利用, 本文利用自行搭建的高温煅烧石油焦余热回收试验系统, 研究了煅后焦当量排料速度、换热管类型、换热器当量入口流速等参数变化对余热回收性能的影响规律。试验结果表明:利用余热回收换热器既可实现煅后焦余热的高效回收, 平均余热回收效率为78.9%, 又能实现煅后焦的均匀冷却, 温度不均匀系数仅为0.0757;随着煅后焦当量排料速度的增加, 内换热器和外换热器的传热系数均逐渐增加, 余热回收效率先增加后降低;翅片型换热器比光管型换热器的换热性能明显提高, 余热回收效率提高了7.4%, 同时换热器出口处煅后焦的温度不均匀系数减少了32.6%;随着当量入口流速的增加, 外换热器和内换热器的传热系数均逐渐增加。     

CHARACTERISTICS OF MICROCUTTING FORCE VARIATION IN ULTRAPRECISION DIAMOND TURNING

An investigation of the characteristics of microcutting forces in diamond turning of crystalline materials is presented. The characteristics of the cutting forces were extracted and analyzed using statistical and spectrum analysis methods. A series of cutting experiments were done on a copper alloy and copper single crystals with different crystallographic orientations. Experimental results indicate that there exists a dominant frequency component and a periodicity of fluctuation of the cutting forces per workpiece revolution in the diamond turning of a single crystal material. The periodicity is closely related to the crystallographic orientation of the material being cut. As the depth of cut increases, the influence of crystallographic orientation of the single-crystal materials on microcutting forces is found to be more pronounced. Moreover, the cutting force ratio between the mean thrust force and the mean cutting force is found to vary with the depth of cut, and a large ratio was observed at a small depth of cut. These findings help to explain quantitatively the periodic fluctuations of microcutting forces (and hence the materials-induced vibration) in ultraprecision diamond turning, which are not encountered in conventional machining.     

Weighted least squares estimation of background in EELS imaging

In quantitative Electron Energy Loss Spectrometry, a weighted least squares estimation should theoretically be used to estimate the background law below core edge energy, since the variances of the data vary. However, it is found that proper weighting makes the above edge signal-to-noise ratio decrease rather than increase. This result is discussed, and the influence of the bias introduced by the logarithmic transformation of the data is quantified.     

设计压比和转速变化对对转压气机性能的影响研究

以自行设计的双排轴流对转压气机为研究对象,采用流线曲率法对对转压气机的气动性能及流场结构进行了探索性研究,着重分析了转速调节分别对两排转子出口速度、出气角以及扩散因子的影响,结果表明:两排转子的转速互相依赖,在量级上不宜相差的过大,否则流场极易发生分离或畸变;另外,可通过适当调整各排转子的压比来平衡两转子的加功量,以降低流场畸变的可能性,以上研究结论对对转压气机的设计与应用有着重要的理论意义和工程应用价值。