Parameter estimation and prediction uncertainties for multi-response kinetic models with uncertain inputs

Error-in-variables model (EVM) methods are used for parameter estimation when independent variables are uncertain. During EVM parameter estimation, output measurement variances are required as weighting factors in the objective function. These variances can be estimated based on data from replicate experiments. However, conducting replicates is complicated when independent variables are uncertain. Instead, pseudo-replicate runs may be performed where the target values of inputs for repeated runs are the same, but the true input values may be different. Here, we propose a method to estimate output-measurement variances for use in multivariate EVM estimation problems, based on pseudo-replicate data. We also propose a bootstrap technique for quantifying uncertainties in resulting parameter estimates and model predictions. The methods are illustrated using a case study involving n-hexane hydroisomerization in a well-mixed reactor. Case-study results reveal that assumptions about input uncertainties can have important influences on parameter estimates, model predictions and their confidence intervals.     

GC–MS analysis of oxysterols and their formation in cultivated liver cells (HepG2)

Oxysterols play a key role in many (patho)physiological processes and they are potential biomarkers for oxidative stress in several diseases. Here we developed a rapid gas chromatographic-mass spectrometry-based method for the separation and quantification of 11 biologically relevant oxysterols bearing hydroxy, epoxy, and dihydroxy groups. Efficient chromatographic separation (resolution ≥ 1.9) was achieved using a medium polarity 35%-diphenyl/65%-dimethyl polysiloxane stationary phase material (30 m × 0.25 mm inner diameter and 0.25 μm film thickness). Based on thorough analysis of the fragmentation during electron ionization we developed a strategy to deduce structural information of the oxysterols. Optimized sample preparation includes (i) extraction with a mixture of n-hexane/iso-propanol, (ii) removal of cholesterol by solid phase extraction with unmodified silica, and (iii) trimethylsilylation. The method was successfully applied on the analysis of brain samples, showing consistent results with previous studies and a good intra- and interday precision of ≤20%. Finally, we used the method for the investigation of oxysterol formation during oxidative stress in HepG2 cells. Incubation with tert-butyl hydroperoxide led to a massive increase in free radical formed oxysterols (7-keto-chol > 7β-OH-chol >> 7α-OH-chol), while 24 h incubation with the glutathione peroxidase 4 inhibitor RSL3 showed no increase in oxidative stress based on the oxysterol pattern. Overall, the new method described here enables the robust analysis of a biologically meaningful pattern of oxysterols with high sensitivity and precision allowing us to gain new insights in the biological formation and role of oxysterols.     

Quantification of significant volatile components of pacharán

 Pacharán is a traditional drink from Navarra (Spain). This liqueur is obtained by maceration of sloe berries (Prunus spinosa L.) with aqueous ethanol and subsequent addition of sugar and essential oils of anise (Pimpinella anisum L. or Illicium verum H.). The following volatile components of pacharán were identified and quantified: cis-anethol; trans-anethol; anisaldehyde; benzaldehyde; benzyl alcohol; γ-butyrolactone; 1,1-diethoxyethane; ethyl benzoate; ethyl lactate; diethyl malate (hydroxybutanedioic acid diethyl ester); estragol (methyl chavicol); eugenol [2-methoxy-4-(2-propenyl)-phenol]; 2-furaldehyde; linalool; cis-3-hexen-1-ol; (4-methoxyphenyl)propanone; 2-phenylethanol and vanillin. Received: 3 November 1997 / Revised version: 29 December 1997     

我国传统粮食科学技术的量化考察与分析

本文对我国古代粮食科学技术分别从粮食储藏、粮食加工、食品加工和造曲酿酒等四方面进行了量化考察，并作了综合分析，确认量化程度由高到低的序列为：造曲酿酒——食品加工——粮食加工——粮食储藏。在量化考察分析的基础上，得出古代粮食科学技术在发展中的重要教训是，在已取得辉煌成就的基础上，没有从“数量化”的高度进行归纳总结，因而没有得出有意义的结论，使得已有的科学技术成就无法突破并继续提高。文章最后指出了古代粮食科学技术未能实现数学化的三条主要原因。     

基于自然影响因子的长江口港口岸线资源评价

港口航运的发展是关系着上海市能否成为世界物流中心的关键,港口岸线是上海市航运发展的宝贵资源。在分析评价的过程中,将上海市岸线分为河口岸线、海岸线和滩涂岸线,利用近年来的实测自然环境数据并结合社会影响因素,选取了岸前水深、潮差、岸线稳定性、坡度、工程地质、生态环境、海域通航、陆域纵深和交通便捷度共9个主要影响因子进行了研究讨论。根据研讨结果,对上海市港口岸线资源进行了综合评价,并对上海市四大滩涂的建港适宜性分别进行了分析,从而确定了上海市五大主要港口岸线资源,包括河口岸线上海市北岸新陆村-川沙新镇段、长兴岛南沿石沙村-庆丰村段及崇明岛南沿城桥村-奚东沙段;海岸线杭州湾渔业村-芦潮港段;滩涂岸线横沙东滩段。研究结果可为上海市未来港口规划和土地利用提供导向性建议。     

Quantification of the cold worked material inside the deep honing grooves on cylinder liner surfaces and its effect on wear

The increased presence of cold work material on cylinder liners due to the introduction of the diamond honing is undesirable as it seals the oil-bearing honing grooves. The most of it is a smeared metal inside the deep honing grooves (blechmantel) that may break and act as abrasive wear particles increasing the bore wear. An attempt has been made to estimate the extent of removal of blechmantel for different wear regimes present at the middle and top region (near the top dead centre) of the liner surface using the least worn bottom region as a reference for comparison. A number of truck grey iron cylinder liners were axially sectioned after varying periods of engine running under similar conditions of load, engine speed and lubrication. 3D surface measurements were taken at the three regions and a range of standard parameters was extracted. Combining the profile and image analysis, an algorithm was developed to identify and quantify the blechmantel. The algorithm has successfully identified/quantified the blechmantel and can be used for automatic surface quality and process control. It was found that the amount of the blechmantel in the middle section was approximately the same (though slightly lower) as that in the bottom section, while there was a considerable dislocation and removal of blechmantel in the top section and thereby it represents one of the possible causes for wear. Axial wear scratches of different size and distribution were observed not only through the whole stroke area, but also in the bottom region. All engines and liners performed well throughout the tests, and the observed quantities of blechmantel and axial scratches are acceptable for the time being.     

钛合金缺陷相控阵超声衍射波定量方法

针对传统衍射波设置法受散射杂波干扰难以进行钛合金缺陷定量的问题,分析了体积型缺陷和面积型缺陷的超声衍射波信号特点,并通过试验测试了钛合金材料的衍射波信号特征,提出了基于相控阵超声的高信噪比衍射波定量方案。制备了不同尺寸的长横孔试块和通槽试块,分别模拟体积型缺陷和面积型缺陷,测试试验定量。结果表明,采用相控阵超声衍射波定量方法对两种类型缺陷的定量精度均达到了1 mm以内。相控阵超声衍射波定量法操作简单,可为钛合金缺陷定量提供新的思路。     

社交网络用户隐私泄露量化评估方法

社交网络用户隐私泄露的量化评估有利于帮助用户了解个人隐私泄露状况,提高公众隐私保护和防范意识,同时也能为个性化隐私保护方法的设计提供依据.针对目前隐私量化评估方法主要用于评估隐私保护方法的保护效果,无法有效评估社交网络用户的隐私泄露风险的问题,提出了一种社交网络用户隐私泄露量化评估方法.基于用户隐私偏好矩阵,利用皮尔逊...     

生态文明价值范式转换下的城市生态空间 绩效研究

秉承"哲学为基础、科学理论为依据、技术为手段"的评价等级体系,在自然内在价值与外在价值共存的生态价值认知范式下,以生态学理论为依据构建以内、外绩效为主体的城市生态空间绩效评价体系和内、外绩效协调度模型,以及绩效发展强度模型,并在GIS技术支撑下实现量化结果的空间化表达。实例证明可得到城市生态空间绩效与协调性的数量结构特征与时空变化特点,可识别高效的生态空间格局、定位低效空间,能从数量分布与空间分布方面更全面地了解城市生态空间的质量,协助判断城市发展的趋势。以期为城市评价工作提供新的视角,为城市生态空间质量的监督、监测提供一种可更新、可视化的时空量化方法。