水中产气荚膜梭菌在不同过滤培养体系中的表型特征的研究

目的比较水中的产气荚膜梭菌在2种不同孔径滤膜和2种培养基上的计数结果,并探讨其机理。方法用0.22μm和0.45μm 2种不同孔径的滤膜过滤添加产气荚膜梭菌的矿泉水后,将滤膜贴在亚硫酸盐-多粘菌素-磺胺嘧啶琼脂培养基(sulfite-polymyxin-sulfadiazine agar,SPS)和胰胨-亚硫酸盐-环丝氨酸琼脂培养基(tryptose sulfite cycloserine agar,TSC)上,36℃±1℃厌氧培养24 h,观察菌落形态并进行菌落计数。用扫描电镜观察0.22μm和0.45μm2种滤膜表面的开口大小。结果水样经过2种不同孔径的滤膜过滤后,产气荚膜梭菌在TSC和SPS上的计数结果无显著性差异(P0.05)。但与SPS相比,产气荚膜梭菌在TSC上更易形成特征性黑色菌落;与孔径为0.22μm滤膜相比,在孔径为0.45μm滤膜上生长的菌落更大。电镜扫描发现,0.22μm滤膜和0.45μm滤膜的平均表面开口分别为2 5μm、4 0μm,后者的表面开口更大。结论水样通过0.45μm孔径滤膜过滤,贴在TSC琼脂上培养,更适用于矿泉水中产气荚膜梭菌的检验。     

A united model for predicting pressure wave speeds in oil and gas two-phase pipeflows

A pressure wave, caused by unsteady operations such as a shutdown or restart, pigging, slug flow or input flow rate transient changes during an oil–gas pipeline transmission, could cause a safety hazard to the whole pipeline system. Because of the compressibility of the gas phase, the changes of interface between the gas and liquid, the momentum and energy transfer between the two-phase and the single-phase to the wall, all make it complicated for predicting the pressure wave speeds for oil and gas two-phase flow in long-distance pipelines. On the basis of the gas–liquid two-fluid model, this paper analyzes the pressure wave propagation for the two-phase flow. Pressure sources of gas–liquid momentum equations are described as the function of the gas–liquid flow velocities, gas void fraction, void fraction gradient and their differentiations, which make the two-fluid model hyperbolic. With the introduction of virtual mass force, the united model for prediction of the pressure wave speeds has been developed. And the gas–liquid Equations of State (EOS) has also been used in the united model, which can analyze the effects of the different system pressures. Important factors, such as the virtual mass coefficient and the gas void fraction, are also discussed. The developed model fits well with the experimental data, and can be used to predict wave speeds for different flow patterns, such as stratified flow, dispersed bubble flow and slug flow.     

提高轻质碳酸钙产品质量的几点建议

根据我国轻质碳酸钙 (PCC)产品质量现状 ,提出了提高PCC质量的几点建议 :一是采用间歇式或直烧式煅烧、连续碳化、高效干燥等新工艺新设备 ,提高工艺及设备水平 ;二是选用适宜的表面处理剂及改性工艺 ,对PCC进行表面处理 ,使其表面能减小 ,增加分散性和相容性 ;三是在碳化前后采用增白技术以提高PCC白度     

焦炭强度检验在不同取样点的试验对比

介绍了焦炭强度检验在不同取样点的试验情况,对试验结果进行了对比分析,说明了不同取样点对焦炭强度的影响.     

食品微生物检验及实验室质量控制

食品是人类赖以生存的基础,食品微生物检验对于确保食品安全具有重要作用。食品微生物检测是保证食品质量安全的重要手段,随着人类生活质量不断提高,食品安全已经成为社会各界关注的重点。微生物检测工作的科学开展能够有效提升食品安全,对我国现代食品行业发展具有不可或缺的重要价值。本文主要介绍了食品微生物检验的主要内容及特点、检测技术及方法、食品微生物实验室质量控制措施等,为本行业工作人员提供可靠的理论依据。     

Effect of Solution Treatment on the Microstructure and Mechanical Properties of Sand-Cast Mg–9Gd–4Y–0.5Zr Alloy

Sand-cast Mg–9Gd–4Y–0.5 Zr(wt%) alloy was solution-treated at 500–565 ℃ in the time range of 0.5–30 h in air or vacuum to investigate its microstructure evolution and mechanical properties. The results showed that solution treatment temperature had a significant influence on the dissolving rate of eutectic phase and grain growth. Taken both of them into consideration, 510–520 ℃ was considered to be the optimum solution treatment temperature range for this alloy.It should be noted that the trace(0.4–0.9 vol%) and insoluble cuboid-shaped phase precipitated during solution treatment was identified to be YH2, of which the hydrogen was thought to come from both the melting and solution heating process.In addition, the 3D morphology and dissolving process of Mg24(Gd,Y)5 eutectic phases in the as-cast alloy were also discussed via in-situ observation under X-ray tomography.     

杭州市“共建共享国家食品安全城市微信文章创作大赛”成效分析

目的分析杭州市"共建共享国家食品安全城市微信文章创作大赛"的成效。方法在2016年4~9月举办杭州市"共建共享国家食品安全城市微信文章创作大赛",对参赛单位、参赛作者职业、作品主题、读者关注主题等相关内容进行统计,对活动成效进行分析。结果 342名选手参赛,收到有效作品322篇,200多篇入围,发布期间阅读人数12万多人次,单篇最高阅读数12900,最高点赞数5974。从作品来源分布看,在杭各高校是主要来源,其次为市场监督管理局各辖区县局;从参赛者职业看,高校大学生和研究生、中小学生是参加大赛的主力军;从作品主题及读者关注主题看,"食品安全知识科普"和"共创食安城市"获得了远超其他主题的高关注度。结论本次大赛达到了用微信传播食品安全科学知识和法律法规知识,开展食品安全风险交流的效果,是自媒体时代食品安全宣传工作的有效创新。     

一种面向图神经网络安卓恶意代码检测的通用解释定位方法

面对不断涌现的安卓恶意应用,虽然大量研究工作采用图神经网络分析代码图实现了准确高效的恶意应用检测,但由于未提供应用内恶意代码的具体位置信息,难以对后续的人工复核工作提供有效帮助.可解释技术的出现为此问题提供了灵活的解决方法,在基于不同类型神经网络及代码特征表示实现的检测模型上展示出了较好的应用前景.本研究聚焦于基于图神经网络的安卓恶意代码检测模型上,使用可解释技术实现安卓恶意代码的准确定位:（1）提出了基于敏感API及多关系图特征的敏感子图提取方法.根据敏感API,控制流逻辑以及函数调用结构三类特征与恶意代码子图分布的关联性,细致刻画恶意代码特征,精简可解释技术关注的代码图规模;（2）提出了基于敏感子图输入的可解释技术定位方法.使用基于扰动原理的可解释技术,在不改变检测模型结构的情况下对代码图边缘进行恶意性评分,为各类基于图神经网络安卓恶意代码检测提供解释定位;（3）设计实验验证敏感子图提取对于与恶意代码特征的刻画效果以及基于敏感子图提取的解释定位效果.实验结果显示,本文的敏感子图提取方法相较于MsDroid固定子图半径的方法更为精确,能够为可解释技术提供高质量的输入;基于此方法改进后得到的可解释技术定位方法相较于GNNExplainer通用解释器及MsDroid定位方法,在保证定位适用性和效率的同时,恶意代码平均定位准确率分别提高了8.8%和2.7%.     

Investigations of the EPR parameters and substitutional sites of Ni ions in CuGaS2 and AgGaS2 ternary semiconductors

The electronic paramagnetic resonance (EPR) parameters (g factors g_//, g and zero-field splitting D) of Ni³⁺ ions at both M⁺ (M = Cu, Ag) and Ga³⁺ sites in MGaS₂ ternary semiconductors are calculated from the high-order perturbation formulas based on the two spin-orbit (SO) coupling parameter model for 3d⁷ ions in tetragonal symmetry. The calculated results suggest that Ni³⁺ ions replace the monovalent M⁺ ions in MGaS₂ crystals. This point is contrary to the previous assumption that Ni³⁺ ions substitute for the isovalent Ga³⁺ ions to attain the charge neutrality. The reasonableness of the suggestion is discussed.     

两亲性纳米SiO2复合材料的合成

以3-缩水甘油醚氧丙基三甲氧基硅烷改性过的纳米SiO2作为原料,通过季铵化反应得到两亲性的纳米SiO2复合材料.利用傅里叶红外(FTIR)、热失重分析(TGA)、X射线光电子能谱(XPS)等检测手段研究了合成材料的结构;通过透射电镜(TEM)对合成的尺寸及微观形貌进行了分析;利用其在水/甲苯混合体系中的分散探讨了合成材料的两亲性.结果表明,合成的纳米SiO2复合材料表面接枝的有机成分约为11wt%,该纳米SiO2复合材料具有很好的两亲性.