Experimental investigation of dispersion during flow of multi-walled carbon nanotube/polymer suspension in fibrous porous media

We prepared three types of multi-walled carbon nanotubes (MWNT)/vinyl ester resin suspensions with different degrees of initial MWNT dispersion. Each suspension was injected into a mold cavity to saturate a stationary random glass fiber preform. High shear rates were not encountered in the non-uniform porous media. The quality of dispersion of the MWNT caused by the interaction between the MWNT with glass fiber media was characterized by examining the sections of the cured composites using scanning electron microscope (SEM) and transmission electron microscope (TEM). The results revealed that the final MWNT/Glass fiber structure is a strong function of the initial state of the MWNT dispersion in the suspension and the porous media structure.     

Optimizing processes based on censored data obtained in repetitious experiments using grey prediction

The design of experiment (DOE) has been extensively adopted to increase the efficiency of designing new products and developing manufacturing processes in industry. However, some designed experiments cannot be completed for some uncontrollable reasons, such as cost and time restrictions or power damage during the experiment. Under such circumstances, incomplete data obtained in the experiment are referred to as censored data. Conventional approaches to analyzing censored data are computationally complex and frequently depend on assumptions of the normality of data. This study presents a procedure for analyzing the censored data obtained in repetitious experiments using the grey system theory. The proposed procedure does not make any statistical assumption and is less conceptual and computationally complex than current methods. Two experiments – one conventional experiment with type II censoring and one Taguchi experiment with type I censoring – are performed to demonstrate the effectiveness of the proposed procedure.     

Deployment and validation of out of band IP traceback approach (OBTA) in wireless mesh network

Wireless mesh networks (WMNs) have acquired recently enormous attention and momentum; therefore, security aspects have been a fundamental concern for them. Among catastrophic threats on WMNs, Denial‐of‐Service attacks that have become a severe danger because of their plug‐and‐play structural design. Unfortunately, preventing a Denial‐of‐Service attack presents a challenging issue. This fact is induced with the appearance of the source IP addresses spoofing. The resolution key of this issue is to reveal the attack source based on the path through which the attack packet passes. For this, many researchers in IP traceability field propose various methods and techniques to deal with the issue. In this article, we conceive a novel approach named out of band IP traceback approach in WMN (IEEE 802.11s). We create a new architecture using signaling messages for discovering the real source(s) of IP packets. Our solution is based on a security‐oriented signaling protocol. This protocol allows specialized signaling entities to communicate via reliable signaling information. This fact permits us to perform a simple and efficient traceback. In our novel approach, we use 2 radios: the first one transmits normal data packets whereas the second is reserved to exchange IP traceback information. The performance of the proposed scheme is analyzed via simulation analysis using the Network Simulator 3. The simulation results show that our scheme is efficient in dealing with the traceback problem in WMN environments.     

Single‐Atom Engineering of Directional Charge Transfer Channels and Active Sites for Photocatalytic Hydrogen Evolution

Efficiency of layered photocatalysts such as graphitic carbon nitride (g‐CN) is still too low due to the poor utilization of photoexcited‐charge carriers. The major drawback is that the weak van der Waals force among g‐CN layers is unfavorable for the charge transfer between the adjacent layers and the intrinsically π‐conjugated planes with inefficient random in‐plane charge migration. Herein, an atomically dispersed Pd layered photocatalyst with both bridged sites of adjacent layers and surface‐sites of g‐CN is demonstrated, providing directional charge‐transfer channels and targeting active sites for photocatalytic water reduction. Both theoretical prediction and empirical characterizations are conducted to achieve the successful synthesis of single‐atom engineered Pd/g‐CN hybrid and the excellent separation of charge transfer as well as the efficient photocatalytic hydrogen evolution, much better than that of the optimized Pt/g‐CN benchmark. The finding in this work provides a rational way for tailoring the performance and engineering of single‐atomic noble metal.     

On vibration of rotating shaftsSur la vibration des arbres en rotation

Some results on the vibration of elastic and viscoelastic rotating shafts are presented. The cases of the simply supported symmetric and the simply supported unsymmetric shafts are studied. The effects of rotary inertia and transverse shear deformation are included in the analysis and it is seen that there are two types of instabilities: bending and shear, as compared to just the bending type given by the Euler-Bernoulli theory.     

RESEARCH ON AUSTENITIC Cr-Mn-C-N STAINLESS STEELS

本文综合报导了作者对二百余种Cr-Mn-C-N实验钢所进行的有系统研究的主要结果:(1)稳定奥氏体区域.(2)重要相变——马氏体转变、σ相形成及沉淀作用.(3)室温及高温性能及其与钢中化学成分的关系.(4)间隙固溶体强化原理.(5)沉淀作用与高温强度的关系.(6)加入V,W,Mo,Nb,Si及B诸元素的影响.(7)工业上可试用的领域.     

A buyer-vendor EOQ model with changeable lead-time in supply chain

In this paper, we discuss a EOQ model on Stackelberg game in supply chain, that is, a distribution channel system contains one supplier and a single retailer, and the supplier in the channel holds monopolistic status, in which he not only owns cost information about the retailer but also has the decision-making right of the lead time. Under this circumstance, the optimal lead time and order cycle time of the supplier and the retailer, respectively, are investigated, and approximate solutions for then are derived. The analysis is made by numerical data that it’s likely to bring the supplier and the retailer profits and losses by controlling the lead time.     

Using commercial video games in flipped classrooms to support physical concept construction

Based on the flipped‐classroom model and the potential motivational and instructional benefits of digital games, we describe a flipped game‐based learning (FGBL) strategy focused on preclass and overall learning outcomes. A secondary goal is to determine the effects, if any, of the classroom aspects of the FGBL strategy on learning efficiency. Our experiments involved 2 commercial games featuring physical motion concepts: Ballance (Newton's law of motion) and Angry Birds (mechanical energy conservation). We randomly assigned 87 8th‐grade students to game instruction (digital game before class and lecture‐based instruction in class), FGBL strategy (digital game before class and cooperative learning in the form of group discussion and practice in class), or lecture‐based instruction groups (no gameplay). Results indicate that the digital games exerted a positive effect on preclass learning outcomes and that FGBL‐strategy students achieved better overall learning outcomes than their lecture‐based peers. Our observation of similar overall outcomes between the cooperative learning and lecture‐based groups suggests a need to provide additional teaching materials or technical support when introducing video games to cooperative classroom learning activities.     

Single‐phase slack‐based centralized DEA for resource reallocation

Data envelopment analysis (DEA) is an effective method for measuring the relative efficiency of a set of homogeneous decision‐making units (DMUs). Yu et al.’s study proposed an extended centralized DEA (CDEA) model that utilizes a two‐phase process for reallocating resources to project not only in each DMU (e.g., branch company) but also in the central DMU (e.g., headquarters, central authority) on the production frontier. However, evaluating the two‐phase model using the approach of Yu et al. may present some challenges because of inconsistent benchmarks. To solve this issue, we modified a single‐phase slack‐based CDEA that considers transfer‐in and transfer‐out slacks to facilitate the reallocation and adjustment of resources. Our modified single‐phase slack‐based CDEA is demonstrated with a numerical example illustrating input resource reallocation. Results show that the modified single‐phase CDEA model is effective to deal with a more realistic inconsistency reference set and provide much more reallocation ability than the two‐phase approach.     

Efficient algorithms for discovering high utility user behavior patterns in mobile commerce environments

Mining user behavior patterns in mobile environments is an emerging topic in data mining fields with wide applications. By integrating moving paths with purchasing transactions, one can find the sequential purchasing patterns with the moving paths, which are called mobile sequential patterns of the mobile users. Mobile sequential patterns can be applied not only for planning mobile commerce environments but also for analyzing and managing online shopping websites. However, unit profits and purchased numbers of the items are not considered in traditional framework of mobile sequential pattern mining. Thus, the patterns with high utility (i.e., profit here) cannot be found. In view of this, we aim at integrating mobile data mining with utility mining for finding high-utility mobile sequential patterns in this study. Two types of algorithms, namely level-wise and tree-based methods, are proposed for mining high-utility mobile sequential patterns. A series of analyses and comparisons on the performance of the two different types of algorithms are conducted through experimental evaluations. The results show that the proposed algorithms outperform the state-of-the-art mobile sequential pattern algorithms and that the tree-based algorithms deliver better performance than the level-wise ones under various conditions.