Experimental Study of the Productive Bed Filtration Mode Changed by an Unsteady Action on the Host Rock Blocks

A laboratory study including physical modeling of filtration processes in porous beds with similarity criteria satisfied is performed. It is demonstrated that weak dynamic actions on stressed host rock blocks can initiate repacking of the system of blocks, leading to an increase in pressure in the productive bed and in oil recovery. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 131–138, January–February, 2006.     

Influence of organoclay dispersed state of poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/organoclay nanocomposites on their characteristics

This work prepared poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG)/organoclay nanocomposites via a melt intercalation process and investigated the influences of organoclay aspect ratio and organoclay content on the dispersed state, mechanical, thermal, gas barrier, and heat recovery properties of PETG/organoclay nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopic analyses showed that the organoclay dispersed in the polymer matrix with intercalation in the nanometer scale range. Differential scanning calorimetry (DSC) analysis demonstrated that all of the obtained nanocomposites were amorphous, indicating that the addition of organoclay did not affect the amorphous nature of PETG. The gas barrier properties of the nanocomposites improved with organoclay content and the properties were also affected by the organoclay aspect ratio. Water vapor and oxygen transmission rates (OTRs) of PETG/organoclay nanocomposites containing 3 phr Cloisite 15A, and 3 phr modified polymer grade Na‐montmorillonites (MPGN) were the lowest among the samples tested, and were 41.7 and 44.3%, respectively, of those of neat PETG. Similar organoclay content‐ and aspect ratio‐related effects were observed in the mechanical and heat recovery properties of the tested nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.     

基于特殊路径的局内车辆路径问题混合策略研究

针对运输途中遇到的某一或一系列无法预知的堵塞事件对决策者路径选择策略的影响,考虑堵塞只发生在一条特殊路径上且可恢复的情况,采用局内竞争分析的思想,建立了局内车辆路径问题的数学模型,对车辆到达堵塞点时堵塞恢复时间未知这一情形下的路径选择问题,提出了两种混合策略,给出了相应的竞争比,并对其竞争性能进行了理论分析。     

A cycle for validating a learning progression illustrated with an example from the concept of function

A learning progression, or learning trajectory, describes the evolution of student thinking from early conceptions to the target understanding within a particular domain. As a complex theory of development, it requires conceptual and empirical support. In earlier work, we proposed a cycle for the validation of a learning progression with four steps: 1) Theory Development, 2) Examination of Empirical Recovery, 3) Comparison to Competing Models, and 4) Evaluation of Instructional Efficacy. A group of experts met to discuss the application of learning sciences to the design, use, and validation of classroom assessment. Learning progressions, learning trajectories, and how they can support classroom assessment were the main focuses. Revisions to the cycle were suggested. We describe the adapted cycle and illustrate how the first third of it has been applied towards the validation of a learning progression for the concept of function.     

Superconvergent Cluster Recovery Method for the Crouzeix-Raviart Element

In this paper, we propose and numerically investigate a superconvergent cluster recovery (SCR) method for the Crouzeix-Raviart (CR) element. The proposed recovery method reconstructs a $C^0$ linear gradient. A linear polynomial approximation is obtained by a least square fitting to the CR element approximation at certain sample points, and then taken derivatives to obtain the recovered gradient. The SCR recovery operator is superconvergent on uniform mesh of four patterns. Numerical examples show that SCR can produce a superconvergent gradient approximation for the CR element, and provide an asymptotically exact error estimator in the adaptive CR finite element method.     

电商平台主导的E-闭环供应链定价、服务决策与回收模式

E-闭环供应链(E-CLSC)管理须有科学的定价与服务决策支撑。针对集中和分散回收模式,构建电商平台主导的Stackelberg博弈模型,研究E-CLSC定价与平台服务决策。通过对产品销售价格、平台服务水平等均衡策略分析,揭示回收主体投资有效性、回收转移价格等对E-CLSC均衡策略影响。研究表明:集中回收模式优于分散回收模式;在分散回收模式下,若回收主体投资有效性相同,制造商、平台均偏好制造商回收模式;平台回收与第三方回收模式相比,产品销售价格、平台服务水平相同,前者回收渠道效率较高;平台回收模式下,单位佣金与回收转移价格负相关,产品销售价格、平台服务水平、废旧产品回收率均与回收转移价格无关;若回收主体投资有效性差异程度较大,制造商回收模式并非总是最优的,回收主体投资有效性差异显著影响产品销售价格、回收渠道效率、平台服务水平和E-CLSC各成员利润。上述结论通过数值仿真进行了验证。     

A novel image tamper localization and recovery algorithm based on watermarking technology

In this paper, an effective self-embedding fragile watermarking scheme is presented. The watermark is generated by encoding the DCT coefficients of each 2 × 2 block and embedded into another block according to the block mapping. A non-linear chaotic sequence is used for generating the block mapping which can enhance the security of the algorithm. An improved tamper localization and recovery algorithm are performed. The experiment results show that the watermarked image has a high average peak signal-to-noise ratio. Furthermore, the tamper region can be successfully localized and exactly recovered, even if for the content-only tampering.     

First-return integrals

Properties of first-return integrals of real functions defined on the unit interval are explored. In particular, first-return integrals are shown to be continuous but not absolutely continuous.