Determining robust reaction kinetics from limited data

Accurate chemical kinetics are essential for reactor design and operation. However, despite recent advances in “big data” approaches, availability of kinetic data is often limited in industrial practice. Herein, we present a comparative proof-of-concept study for kinetic parameter estimation from limited data. Cross-validation (CV) is implemented to nonlinear least-squares (LS) fitting and evaluated against Markov chain Monte Carlo (MCMC) and genetic algorithm (GA) routines using synthetic data generated from a simple model reaction. As expected, conventional LS is fastest but least accurate in predicting true kinetics. MCMC and GA are effective for larger data sets but tend to overfit to noise for limited data. LS-CV strongly outperforms these methods at much reduced computational cost, especially for significant noise. Our findings suggest that implementation of CV with conventional regression provides an efficient approach to kinetic parameter estimation with high accuracy, robustness against noise, and only minimal increase in complexity.     

平原地区城市湖泊防洪与景观功能协调研究——以枝江市金湖为例

为了使城市湖泊尽可能滞蓄雨洪、发挥景观功能、打造良好的居民"亲水空间",以枝江市金湖为例,根据金湖主要泄洪渠道的实际情况,利用Mike 21模型模拟计算汛限水位值,按照景观水位确定大、小洪水工况下合理的水位。在此基础上,提出传统的静态景观水位与改进的动态景观水位两种方案。结果表明:以50年一遇、30年一遇为代表的大洪水工况下合理景观水位为40.7 m,以20年一遇、10年一遇为代表的小洪水工况合理景观水位为41.3 m;静态方案采用50年一遇洪水计算结果为标准执行,将40.7 m作为金湖固定的景观水位;动态方案水位可在41.3~40.7 m之间波动;金湖适宜采用动态景观水位运行方案,水位可在40.7~41.3 m之间波动;根据短期预报及历史监测资料分析后合理调度,将41.3 m作为金湖常水位,确定预测洪水大小后调整水位迎战洪水。据此,可在充分利用水资源的同时有效协调景观高水位需求与防洪之间的矛盾。     

融合环境因素的有限空间毒气扩散危害程度分析

为探究环境因素对毒气扩散危害程度的影响,通过对比有限空间内外环境差异,了解气体在有限空间内受力情况,并以传统高斯烟羽模型为基础,考虑扩散气体与有限空间边界碰撞产生的反射作用,建立了适用于有限空间气体扩散的改进高斯烟羽模型。深度剖析有限空间气体扩散环境,挖掘气体扩散主要关联因子,构建风速、地表粗糙度对有限空间气体扩散的影响函数;参照有限空间环境特征,分别设置3种不同风速与2种不同地表粗糙度,推求6种不同环境条件下气体扩散面积,阐明风速与地表粗糙度对有限空间气体扩散的影响程度。结果表明:在单一风速条件下,风速越高,地表粗糙度越低,洞室内H2S气体滞留时间越短,洞室内气体的扩散面积越小;风速越低,地表粗糙度越高,洞室内气体的扩散面积越大。     

TG6钛合金冷却过程的块状转变机制研究

在近α型TG6钛合金两相区淬火过程中,对初生α相αP周围形成的块状组织αm进行表征研究,块状组织αm与αP存在明显的界面,合金元素Al、Sn和Zr浓度介于αP和β基体之间,EBSD分析结果表明αm取向与αP保持一致。在冷却过程中,αP周围β基体中合金元素扩散受到限制,进而在局部过渡成分区域通过扩散转变形成αm组织。当固溶温度从1040℃提高至1060℃,同时保温时间从30 min减少为5 min,溶质元素扩散受限,αm体积分数从5.2%提升至30.7%。     

受限空间安全作业管理浅析

受限空间因受作业场所限制,存在的危险因素较多,受限空间安全管理控制措施为:建立许可制,落实责任和措施,做好受限空间作业人员的个体防护,对受限空间作业的安全管理要实行从审批到应急处理全过程的控制。介绍了受限空间的危险特点和事故类型,提出了受限空间作业安全管理的具体措施。     

Graph-based video fingerprinting using double optimal projection

A double optimal projection method that involves projections for intra-cluster and inter-cluster dimensionality reduction are proposed for video fingerprinting. The video is initially set as a graph with frames as its vertices in a high-dimensional space. A similarity measure that can compute the weights of the edges is then proposed. Subsequently, the video frames are partitioned into different clusters based on the graph model. Double optimal projection is used to explore the optimal mapping points in a low-dimensional space to reduce the video dimensions. The statistics and geometrical fingerprints are generated to determine whether a query video is copied from one of the videos in the database. During matching, the video can be roughly matched by utilizing the statistics fingerprint. Further matching is thereafter performed in the corresponding group using geometrical fingerprints. Experimental results show the good performance of the proposed video fingerprinting method in robustness and discrimination.     

复杂膨胀性围岩条件下交岔点支护技术研究

针对复杂膨胀性围岩条件下交岔点高应力集中区围岩稳定性控制和支护技术难题，通过对交岔点围岩变形表现形式、交岔点围岩变形机理的研究分析，提出了交岔点支护难点及重点。基于围岩控制理论分析，提出了“有限让压的柔性支护+全断面封闭抗压的刚性支护技术”，前期柔性支护采用“高强、高预应力锚杆+锚索+喷浆”联合支护有限度控制围岩变形，允许围岩在可控范围内释放围岩应力|后期通过架设异形支架与支撑架组成的联合支护体并喷射混凝土对交岔点围岩进行全断面封闭抗压支护，有效控制巷道交岔点围岩的变形。确保了交岔点围岩变形的整体可控性、稳定性，达到了预期支护效果。     

Effects of different feeding levels during a 14-week preweaning phase in dairy heifer calves on telomere length and mitochondrial DNA copy number in blood

Telomeres cap the ends of eukaryotic chromosomes, and the telomere length (TL) is related to cellular age. The mitochondrial DNA copy number (mtDNAcn) reflects the abundance of mitochondria in a cell. In addition to generating energy, mitochondria are also the main producers of reactive oxygen species, which in turn can accelerate TL attrition and impair mitochondrial function. Nutrition in early life could influence mtDNAcn and TL in later life. In the present study, we investigated the effects of feeding different levels of milk replacer (MR) on TL shortening and energetic status by examining mtDNAcn of heifers during their first year of life. In this study, whole blood samples were obtained from German Holstein heifer calves 36 to 48 h after birth (wk 1) and at wk 12 and wk 16 of life (n = 37), as well as from 31 calves when reaching 1 yr of age. Calves were fed either a high level of MR (14% solids) at 10 L/d (1.4 kg of MR/d; n = 18) or a restrictive low level at 5.7 L/d (0.8 kg of MR/d; n = 19) until linear weaning in wk 13 to 14 of life. Additional whole blood samples were taken from their respective dams 36 to 48 h after calving. Relative TL (qT) and mtDNAcn in cells from whole blood were measured by multiplex quantitative PCR. The greatest qT values were observed in neonates (36–48 h after birth), with decreasing qT values thereafter. Delta qT values were calculated as ΔqT = qT (first year of life) ? initial qT (36–48 h after birth). We found no effect of the feeding regimen on qT values, but qT decreased with age. The mtDNAcn was lowest in neonates, increased until wk 12 of life, and then remained at a constant level until after weaning (wk 16). After the first year of life, mtDNAcn was decreased and returned to levels comparable to those of the neonatal stage. No differences in mtDNAcn were detectable between feeding groups within each time point. When comparing the values of qT and mtDNAcn between the calves and their dams after calving (36–48 h after birth and after calving), greater values were observed in calves than in dams. Delta qT values were negative in all but 2 calves (on the restricted diet), indicating that the change in TL with age was not uniform among individual animals, whereas no difference in mean ΔqT values occurred between the feeding groups. Additional analyses of the correlation between qT, mtDNAcn, and various indicators of oxidative status from birth until wk 16 of life did not indicate major interactions between oxidative status, qT and mtDNAcn. The results of this study support an age-dependent decrease of TL in calves independent of the MR feeding level and show the dynamic changes of mtDNAcn in early life.     

混凝土构件正常使用极限状态的可靠度计算

以混凝土构件混凝土表面出现锈胀裂缝作为混凝土构件的正常使用极限状态 ,建立了混凝土构件在正常使用情况下的极限状态方程 ,应用可靠度程序进行计算 ,讨论了正常使用情况下各个因素对混凝土构件可靠指标的影响     

直连有备用供热系统的限额供热调节

本文分析了直连有备用供热系统限额供热的调节工况，提出了以限额流量系数作为限额供热的计算指标的原则，对直连有备用供热系统进行了实际工况的计算，并给出了主要计算结果。