Simulation and evaluation of pilot-scale pulsed electric field (PEF) processing

Pulsed electric field (PEF) processing is a novel mild treatment for pumpable foods preservation at low or moderate temperatures. The electric field strength and the temperature distribution in the treatment chamber have been identified as the key processing parameters affecting the treatment efficacy and possibly the sensorial and nutritional quality of the food. A full 3D computational fluid dynamics (CFD) model of a pilot-scale PEF system with co-linear configuration of the electrodes was developed. The model couples the fluid dynamics and the electrical field and can be used to predict the liquid’s flow pattern, electric field distribution, temperature increase, and residence time in the treatment chamber. A total of 48 process conditions with different settings of applied voltage V, pulse length τ, pulse repetition rate (frequency) f and flow rate in combination with four different inlet temperatures were simulated for a model liquid food (NaCl solutions with two different electrical conductivities) and whole milk. The simulated PEF energy dissipated into the liquids was between 4 and 66 kJ/kg and process temperatures ranged from approximately 25 to 80 °C. The predicted temperature data agree well (R² > 0.99) with experimental measurements in five locations of the treatment chamber using fibre optic probes.     

关于影响空心包体应变计地应力测量精度若干因素的讨论

空心包体应变计法测量地应力较其他地应力测量方法具有精度高、一次可测得三维应力的特点。蔡美峰教授对测量探头进行改进对最初的围压率定公式进行修正，大大提高空心包体地应力测量的精度。但是目前，空心包体地应力测量在实际操作、电路情况、温度变化以及率定公式等方面仍然存在一些误差。通过对国内目前使用的两种空心包体应变计探头在测量电路和温度补偿方面产生误差的大小和原因进行综合比较、分析，指出13线探头在电路方面产生的误差较小，而15线探头在温度补偿方面性能更优。详细分析目前使用的围压率定修正公式，指出蔡美峰教授推导的围压率定修正公式虽然较最初的率定公式在精度上有很大提高但未考虑树脂层受压产生抗力的影响，因此与实际情况也存在一定出入，并推导了完整形式的公式。     

基于分段解除的深部空心包体应变计中非线性优化算法

随着浅部资源的日益枯竭,地下开采的深度不断增大,千米级乃至更深的矿产资源开采已成为常态。因此弄清深部岩体原岩应力的赋存环境是至关重要的,目前CSIRO地应力测量作为国际岩石力学学会建议直接测量方法,在世界各地广泛使用。在浅部岩体空心包体应变计地应力测量解析式中,弹性模量和泊松比都是通过室内双轴加载数据拟合获得的常数。进入深部岩体表现出高度的非线性,在对解除岩芯进行高压双轴加卸载试验中发现围压与应变的关系非线性,并且随着围压不断增大非线性关系尤为突出。传统的双轴加载试验设备最大围压加载值试验室内测得20 MPa,不能满足深部岩体解除岩芯的高压双轴试验模拟解除岩石在深部所受的应力环境。因此对传统的设备进行改造,研发了一套高压双轴加载试验装置,所承受的理论最大径向压力为200 MPa以上,目前试验测试的最大围压为100 MPa。对三山岛金矿埋深800 m的解除岩芯进行了高压双轴加卸载试验,分析应力与应变的关系提出一种平均应力与体积模量和剪切模量之间的非线性双曲线模型,明确了模型中3个拟合参数的物理意义,推导出平均应力与应变之间的非线性关系特征公式。基于弹性力学理论原岩应力分量计算在不考虑解除路径时,应用最小二乘法进行计算后获得最大主应力大小为53. 11 MPa,西北312°,倾角为8°。本文提出的考虑解除路径的优化算法,将整个解除过程分成多个阶段,每个阶段的变形模量计算参数与解除岩芯所受应力状态有关,且符合推导的应力与应变的非线性关系公式,各个阶段叠加计算的最大主应力大小为47. 78 MPa,西北311°,倾角为5°。     

Anodic oxidation of some polycyclic bridgehead iodides in anhydrous acetonitrile

The anodic oxidation of some polycyclic bridgehead iodides is reported in 0.5 M solutions of lithium perchlorate in anyhydrous acetonitrile, using rotating glassy-carbon disk electrodes. The ease of abstraction of an electron from the compounds is correlated with the steric strain at the bridgehead positions of the molecules. It is found that anodic acetamidation proceeds efficiently only for compounds of low steric strain.     

Mercury in the river mersey, its estuary and tributaries during 1973 and 1974

Mercury levels found in waters and suspended matter from 53 stations, occupied four times at 3-monthly intervals, showed that most mercury was associated with particulates but the amount varied during the year. In the polluted region between Warrington and Runcorn, where fresh-water and sea-water converge, >80% of the mercury was associated with the particulates. Dissolved mercury concentrations and the mercury load on particulate matter were always greater in freshwater than in tidal waters, except during a flood. A model of partitioning of mercury between particulate and dissolved phases is presented. The River Weaver and the Manchester Ship Canal were grossly polluted with mercury throughout that year due to a Castner-Kelner plant at Runcorn. Dredge spoils and water flow transport 17 (range 8–138) and 1.55 ± 65% tonnes yr⁻¹ respectively of mercury into Liverpool Bay.     

Use of LANDSAT-1 imagery in exploration for keweenawan-type copper deposits

LANDSAT-1 imagery is used to detect and map hydrothermally altered flow tops in a sequence of basic lavas in the Hamersley Basin, Western Australia. The altered flow tops form targets one or two km wide due to shallow dips in the region and may be up to 50km or more in length. The true thickness of the dipping altered layers vary from less than 5 metres up to about 30 metres. Associations of quartz, albite, chlorite, pumpellyite and, in some places, epidote characterise the alteration. The style of alteration in a control area was identified from conventional EROS black and white, and color composite LANDSAT-1 images using a scale of 1:500,000. Strike extension of this alteration was visible for 350km. Even better discrimination between altered and unaltered lava was obtained using first generation contrast stretched prints of MSS bands 4, 5 and 7 enlarged to 1:250,000 scale, and also a color composite of these bands. Topographic problems apparent in this imagery were partly overcome by ratioing MSS band 5 over band 7, interpreting the product as a black and white print at 1:250,000 scale. Computer classification trials block out part of the control area and in places show an improvement in discrimination over the other displays.     

Evaluation of measurement-related uncertainties in the analysis of overcoring rock stress data from Äspö HRL, Sweden: a case study

A re-evaluation of overcoring results from the Borre Probe and the CSIRO HI cell was carried out at the Äspö HRL. The re-analysis revealed a number of measurement-related uncertainties for the two cells, e.g. bonding, temperature effects and identification of elastic parameters. These uncertainties were corrected and the re-analyzed strains were then used to determine the in situ stress field using standard least-squares technique. The results indicate lower stress magnitudes compared to the original interpretations and the results are in good agreement with existing hydraulic fracturing data as well as with theoretical vertical stress. Overall, the re-analysis indicates that the stress field at Äspö HRL is well constrained and relatively consistent with depth.     

地应力测量精度及其全要素量化表征研究

针对行业现状对地应力测量精度定义及其全要素量化表征方法进行了研究。概述了地应力测量方法、常用试验技术及其测量精度方面存在的问题与原因。从闭环测量角度给出了地应力测量及其精度的定义,在对测量精度研究分类和总结的基础上,提出了地应力测量精度表征体系的构成和分层,指出了测量精度研究的意义、测量方法与测量技术的定义及其测量精度问题。阐述了地应力测量精度全要素量化表征的思路和含义、三维物理模型测量精度试验装置、坐标设定和表征程序,给出了平均方式和最大值方式的表征指标,以及二维和三维测量的精度表征公式,对角度误差的计算方法进行了讨论,对表征方式与技术研发要求的对应关系进行了说明。以早期的USBM孔径变形计和CSIRO空心包体应变计物理模型试验结果的测量精度表征为例,展示了测量精度的量化表征过程,与原有测量精度表征指标进行了对比,获得上述试验技术最大值方式单一指标的总体测量误差分别为10%和27%。首次获得了两试验方法的全要素测量精度数据,比较显示前者的总体测量精度大大优于后者。     

基于空心包体应变计的扰动应力云监测系统构建

扰动应力是导致地下工程岩体破坏失稳的原因,扰动应力监测岩体工程稳定性及地下结构应力状态的及时反馈,为地下结构的安全提供重要保障。目前,扰动应力监测使用电磁辐射技术或微震测试技术易受到电磁干扰影响测量精度;钻孔应力监测技术又受到设备长期供电、数据采集复杂等因素制约。本文基于数字化完全温度补偿型的空心包体监测应变计,优化岩石力学实时扰动应力计算方法,通过研发并构建扰动应力云监测系统,实现了对金川镍矿二矿区1 150m水平有轨联络道实验洞段的线上扰动应力长期监测。近416d的应力监测数据表明,该系统数据传输稳定,系统运行过程稳定可靠,实现了远程云端长期采集和数据传输,提高了扰动应力监测的效率,为后续其他项目中应力测量数据和监测数据的实时入网上传提供接口和平台。研究方法和监测方案对同类型工程具有借鉴意义。     

改进空心包体应变计测量裕源井田地应力

山西省河东煤田属于国内储量较大的煤矿之一,矿区地质结构比较复杂,必须进行矿区深部地应力测量,了解其变化规律。采用应力解除法改进型空心包体应变计测量地应力,应用新的温度影响修正技术,研究温度对于测量精度的影响效果,并在围压率定试验中综合考虑树脂弹模和应变片位置的影响,推导出围压率定的修正公式,提高了地应力测量结果的精度。测量结果表明,最大主应力均为近水平方向,为NNW向,各测点测得的主应力大小在14 MPa左右。在同一平面内,同一种地应力在不同点的大小方向有一定的变化,但没有出现突变现象,说明矿区地应力场比较均匀。