微通道板表面羟基化工艺研究北大核心

研究了3种微通道板基底羟基化的方法,测量了羟基化处理后微通道板基底表面水接触角及通道端面的形貌变化,分析了各种方法中微通道板基底的亲水性和腐蚀情况。实验结果表明:氨水双氧水溶液对基体表面的亲水性能提升不大,NaOH溶液对基体有腐蚀作用,经食人鱼溶液处理的基体表面亲水性明显提高且无腐蚀作用。研究了微通道板在食人鱼溶液中的浸泡时间和浸泡温度对表面亲水性的影响。结果表明:随着浸泡温度的增加,微通道板表面水接触角先减小后增大,当温度为80℃时达到极小值,浸泡时间对微通道板表面的亲水性影响不大。最终确定了微通道板表面羟基化工艺:浸泡温度为80℃,静置时间为20~60 min。     

Exploring contact lens opportunities for patients above the age of 40 years

PurposeContact lenses offer a good option for patients with presbyopia, especially with improved optical designs available in modern multifocal contact lenses. Due to the ageing population there is good opportunity to increase contact lens penetration by managing these patients better. However, multifocal contact lenses achieve low penetration in the market.MethodsA questionnaire was administered to people aged above 40 years, to investigate their perceptions of contact lenses for presbyopia. Only people, with presbyopia, who were existing contact lens wearers or willing to try contact lenses were included. Participants were recruited from United Kingdom (UK), United States of America (USA), Netherlands, Germany, France, Spain and Italy.ResultsData from 1540 participants above the age of 40 years was collected, 57.9% were females and 42.1% males. Overall, 50.8% of the participants wore contact lenses, but contact lens wear was less common amongst older participants. Some data supported earlier studies, such as 6.1% wore gas permeable lenses. However, only 25% of the contact lens wearers used multifocal contact lenses. The reasons the participants wanted to wear contact lenses were similar to younger patient such as sports or cosmesis reasons. Reasons why participants had dropped out of contact lenses included discomfort and dry eye related issues. Poor visual performance with contact lenses was a reason to dropout of contact lenses for the older participants.ConclusionsThe study highlights some failings by eye care practitioners in the management of patients with presbyopia. It seems that patients of this age group are seeking suggestions and recommendations from their eye care practitioner including upgrading contact lenses and dual wear options. The day-to-day problems encountered by the contact lens wearers in this study seem to be, in the main, things that could be easily tackled by additional counselling and instruction from the eye care practitioners.     

超高效液相色谱⁃四极杆⁃飞行时间质谱对含PET食品接触材料中可迁移非挥发性物质的筛查研究

采用超高效液相色谱⁃四极杆⁃飞行时间高分辨质谱（UPLC⁃Q⁃TOF）对4类不同类型的含聚对苯二甲酸乙二醇酯（PET）材质的食品接触材料在4 %乙酸和50 %乙醇模拟物中的迁移出的非挥发性未知物进行筛查解析。结果表明，产品在4 %乙酸模拟物的迁移风险远小于50 %乙醇模拟物，主要迁移物质为聚合单体形成的寡聚物，抗氧剂、润滑剂、胶黏剂等加工助剂以及生产加工、迁移过程中形成的非有意添加物（NIAS）物质；纯PET材质的产品迁移物质较少，多层复合材料迁移物质较多。复合材质的产品中，PET材质可能在生产时添加了己二酸、癸二酸、新戊二醇等物质，进行了改性处理；此外，部分迁移物质会与模拟物中的乙醇发生反应，生成新的NIAS物质。     

Swabbing the surface: critical factors in environmental monitoring and a path towards standardization and improvement

Abstract

Cross-contamination can be broadly defined as the transfer, direct or indirect, of microorganisms from a contaminated product to a non-contaminated product. Events that may result in cross-contamination include inadequate hygiene practices, contaminated equipment surfaces, contamination via food handling personnel, further product processing, or storage abuse All of these niches require consistent environmental surveillance systems to monitor microbial harborage sites to prevent foodborne illnesses via cross-contamination. Environmental surveillance is achieved through routine surface sampling of the food contact surfaces and surrounding areas. To better understand cross-contamination, the role of environmental surface transmission during outbreaks due to the presence and persistence of pathogenic microorganisms on various food contact surfaces must be investigated. However, studies on environmental sampling techniques are rarely performed in an actual food processing environment but rather under controlled variables within a laboratory-setting. Moreover, results and conclusions of studies differ because of the considerable variability across surface sampling tools due to individual operator dependency, low recovery rates, and low reproducibility. Information is also often lacking on environmental sampling tools used within a processing facility, the characterization of these tools, and the optimization of recovery of microorganisms for surface sampling. Thus, this review aims to: (1) discuss and compare factors impacting the recovery of microorganisms and the standardization of surface sampling methods for optimal recovery of microorganisms and (2) examine how research strategies could focus more towards the development of standard methodologies for surface sampling.     

二连盆地乌兰花凹陷特低渗安山岩储层的有效性评价

针对二连盆地乌兰花凹陷安山岩储层的特性认识不清、有效储层划分不准确的问题，利用岩心薄片、黏土矿物分析、物性测试以及核磁共振实验等手段开展了岩石储集空间特征、岩石蚀变程度、测井响应特征分析。在此基础上，重点开展了基于核磁共振实验的安山岩储层有效孔隙度计算模型研究，开发了相适应的测井解释评价模块，并结合常规测井和试油结果建立了安山岩储层的分类标准。结果表明：安山岩储集空间具有发育"微孔"、"杏仁孔"双孔隙的特征，且以微孔为主；根据不同蚀变程度所建立的安山岩有效孔隙度计算模型具有很高的精度，平均绝对误差为0.16%，平均相对误差为19.40%；新测井解释储层分类标准在实际应用中与试油结论具有很好的一致性，有利于乌兰花凹陷安山岩有效储层的精确划分，并为该地区开发方案的设计及可采储量评价提供技术支持。     

基于改进奇异值分解滤波和谱峭度的滚动轴承故障诊断

针对含噪信号的有效奇异值个数难以确定的问题，提出了一种改进的奇异值分解降噪方法--奇异值累积法。该方法通过计算奇异值的实际下降值与奇异值平均下降速度累积量的差值，并取该差值最大值点的位置作为有效奇异值的分界点来确定有效奇异值的个数。在此基础上，提出了一种基于奇异值累积法与快速谱峭度的滚动轴承故障诊断方法。采用奇异值累积法对原信号进行降噪处理，然后利用快速谱峭度确定滤波器中心频率及带宽，通过分析频段包络谱中明显的频率成分来诊断故障。该方法可以有效去除信号中的噪声，使得到的峭度值所反映的故障冲击更接近实际情况。对含内圈、外圈故障的滚动轴承实验数据进行分析，实验结果表明，相比快速谱峭度的故障诊断方法，该方法具有更好的故障识别效果。     

A novel method used to study growth of ash deposition and in situ measurement of effective thermal conductivity of ash deposit

Ash deposition always brings boilers some trouble due to fouling or slagging. In this paper, a completely controlled system was developed to study the growth of ash deposit. A novel sampling probe was designed to online measure the heat flux through ash deposit. Additionally, the thickness of ash deposit can be obtained by an online figure collecting system. The results of this research showed that as the thickness of ash deposit increased, the heat flux decreased. It was also found that at the initial stage of ash deposition when the thickness of ash deposit is approximately 1 mm, the heat flux through ash deposit had a sharp reduction. An effective method was attempted to situ measure the effective thermal conductivity of the ash deposit in the simulated combustion flue gas. It was found that temperature of the ash deposit layer had no obvious effect on its value. It was concluded that the structure of ash deposit had no obvious change in a short deposition time of 30 min with varied surface temperatures of the probe head between 400 °C and 600 °C.     

微间隙共形圆柱接触力模型的适用性分析

针对目前间隙铰接副接触力模型无法有效表述不同材料耗散阻尼效应,以及不适用于微间隙共形接触的问题,分析各种接触力模型中弹性接触力和耗散阻尼力计算方法的优缺点,提出一种普适性的圆柱内接触力分析模型。该模型将接触力描述为接触深度的显式函数,并将其适用范围有效地扩展至微间隙和低恢复系数工况。采用含间隙铰接副的曲柄-滑块机构进行动力学分析,对所提出接触力进行验证,计算结果表明:所提出的普适性接触力模型体现了微间隙时更高的接触刚度和低恢复系数时显著的阻尼效应,从而可为不同材料和间隙尺寸的间隙铰接副力学分析提供更为完备的计算模型。