Recent Advances in Electrocatalysts for Efficient Nitrate Reduction to Ammonia

Ammonia as an irreplaceable chemical has been widely demanded to keep the sustainable development of the modern society. However, its industrial production consumes huge energy and releases extraordinary green-house gases, leading to various environmental issues. To achieve the green production of ammonia is a great challenge that has been extensively pursued recently. In the review, a most promising strategy, electrochemical nitrate reduction reaction (e-NO₃RR) for the purpose is comprehensively investigated to give a full understanding of its development and mechanism and provide guidance for future directions. Particularly, the development of electrocatalysts is focused to realize the high ammonia yield rate and Faraday efficiency for industrial applications. The recent-developed catalysts, including noble metallic materials, alloys, metal compounds, single-metal-atom catalysts, and metal-free materials, are systematically discussed to review the effects of various factors on the catalytic performance in e-NO₃RR. Accordingly, the strategies, including defects engineering, coordination environment modulating, surface controlling, and hybridization, are carefully discussed to improve the catalytic performance, such as the intrinsic activity and selectivity. Finally, perspectives and challenges are given out. This review shall provide insightful guidance on the development of advanced catalytic systems for the production of green ammonia efficiently in the industry.     

Three‐dimensional vibration analysis of rectangular thick plates on Pasternak foundation

The free‐vibration characteristics of rectangular thick plates resting on elastic foundations have been studied, based on the three‐dimensional, linear and small strain elasticity theory. The foundation is described by the Pasternak (two‐parameter) model. The Ritz method is used to derive the eigenvalue equation of the rectangular plate by augmenting the strain energy of the plate with the potential energy of the elastic foundation. The Chebyshev polynomials multiplied by a boundary function are selected as the admissible functions of the displacement functions in each direction. The approach is suitable for rectangular plates with arbitrary boundary conditions. Convergence and comparison studies have been performed on square plates on elastic foundations with different boundary conditions. It is shown that the present method has a rapid convergent rate, stable numerical operation and very high accuracy. Parametric investigations on the dynamic behaviour of clamped square thick plates on elastic foundations have been carried out in detail, with respect to different thickness–span ratios and foundation parameters. Some results found for the first time have been given and some important conclusions have been drawn. Copyright © 2004 John Wiley & Sons, Ltd.     

Hybrid‐stress six‐node prismatic elements

This paper presents three novel hybrid‐stress six‐node prismatic elements. Starting from the element displacement interpolation, the equilibrating non‐constant stress modes for the first element are identified and orthogonalized with respect to the constant stress modes for higher computational efficiency. For the second element, the non‐constant stress modes are non‐equilibrating and chosen for the sake of stabilizing the reduced‐integrated element. The first two elements are intended for three‐dimensional continuum analysis with both passing the patch test for three‐dimensional continuum elements. The third element is primarily intended for plate/shell analysis. Shear locking is alleviated by a new assumed strain scheme which preserves the element accuracy with respect to the twisting load. Furthermore, the Poisson's locking along the in‐plane and out‐of‐plane directions is overcome by using the hybrid‐stress modes of the first element. The third element passes the patch test for plate/shell elements. Unless the element assumes the right prismatic geometry, it fails the patch test for three‐dimensional continuum elements. It will be seen that all the proposed elements are markedly more accurate than the conventional fully integrated element. Copyright © 2004 John Wiley & Sons, Ltd.     

Real-time networked control of an industrial robot manipulator via discrete-time second-order sliding modes

This article presents the networked control of a robotic anthropomorphic manipulator based on a second-order sliding mode technique, where the control objective is to track a desired trajectory for the manipulator. The adopted control scheme allows an easy and effective distribution of the control algorithm over two networked machines. While the predictability of real-time tasks execution is achieved by the Soft Hard Real-Time Kernel (S.Ha.R.K.) real-time operating system, the communication is established via a standard Ethernet network. The performances of the control system are evaluated under different experimental system configurations using, to perform the experiments, a COMAU SMART3-S2 industrial robot, and the results are analysed to put into evidence the robustness of the proposed approach against possible network delays, packet losses and unmodelled effects.     

ACPI and SMI handlers: some limits to trusted computing

Trusted computing has been explored through several international initiatives. Trust in a platform generally requires a subset of its components to be trusted (typically, the CPU, the chipset and a virtual machine hypervisor). These components are granted maximal privileges and constitute the so called Trusted Computing Base (TCB), the size of which should be minimal. The rest of the platform is only granted limited privileges and cannot perform security-critical operations. A few initiatives aim at excluding the BIOS from the TCB in particular (e.g., Intel^® TxT and AMD SVM/SKINIT). However, the BIOS is responsible for providing some objects that need to be trusted for the computer to work properly. This paper focuses on two of these objects, the SMI handler and the ACPI tables, which are responsible for the configuration and the power management of the platform. We study to what extent these two components shall reasonably be trusted. Despite the protections that are implemented, we show that an attacker can hide functions in either structure to escalate privileges. The main contributions of our work are to present an original mechanism that may be used by attackers to alter the SMI handler, and to describe how rogue functions triggered by an external stimulus can be injected inside ACPI tables (in our case, the attacker will plug and unplug the power supply twice in a row). We also explore the countermeasures that would prevent such modifications.     

A framework for testing DBMS features

Testing a specific feature of a DBMS requires controlling the inputs and outputs of the operators in the query execution plan. However, that is practically difficult to achieve because the inputs/outputs of a query depend on the content of the test database. In this paper, we propose a framework to test DBMS features. The framework includes a database generator called QAGen so that the generated test databases are able to meet the test requirements defined on the test queries. The framework also includes a set of tools to automate test case constructions and test executions. A wide range of DBMS feature testing tasks can be facilitated by the proposed framework.     

Estimating farfield organic chemical exposures,intake rates and intake fractions to human age classes

This study describes the development and application of the Farfield Human Exposure (FHX) model. This screening level model brings together information on chemical partitioning, degradation, environmental fate and transport, and food web bioaccumulation for assessing human age class-specific exposures from chemicals released to the environment. The Level III model calculates steady-state concentrations in multimedia compartments such as air, water, and soil, and various food groups including fruits, vegetables, milk, dairy, fish, and meats based on a unit emission rate. Human multimedia intake and ingestion rates determine unit emission based chemical exposures, intake rates and intake fractions for various age classes representing the general population. The FHX model is generally applicable to regional areas and is designed to use readily available chemical input data for screening level and priority setting evaluations. In the present study the model is parameterized for an evaluative regional area using Health Canada exposure factors to determine multimedia intake rates for seven selected age classes. The model outputs, human chemical intake rates and human intake fractions are described for four case study chemicals. Biotransformation and biomagnification processes in food webs are highlighted as key factors influencing human exposure. Future research needs to improve the model are discussed.     

草酸盐沉淀法合成超细Y2O3粉末工艺和机理研究

通过对传统草酸盐法沉淀反应过程的机理研究，提出了改良草酸盐法。该法能根本上加快沉淀反应过程，最终制备出高纯、超细、分散性好、粒径分布窄、近球形颗粒状的Ｙ２Ｏ３粉末。     

IEEE 802.21-based seamless multicast streaming with dynamic playback control

With the explosion of video streaming available on the Internet, online multimedia applications become more popular in our days and the video quality of the Internet multimedia applications is directly affected by the network transmission state, which will be worse while switching the ongoing network connection from one wireless interface to another heterogeneous wireless technology, such as IEEE 802 families, UMTS (universal mobile telecommunications system) network and 3GPP LTE (3rd generation partnership project-long term evolution). In order to perform seamless handover between heterogeneous wireless networks, IEEE group proposed the “IEEE 802.21 standard” and defined a middleware function called “media independent handover function (MIHF)” to smooth the handover. In this paper, a dynamic playback control for multicasting streaming based on IEEE 802.21 is proposed to reduce the influence of handover between heterogeneous networks. In addition, we evaluate three different rate modes for seamless multicasting streams. The simulation results show that different playback frame rate modes, including the usual, incremental and linear modes, can achieve different video quality and can extend the playing time for handover video playback.