浅谈脱硫液中PDS质量浓度测定方法

提出了在以PDS催化剂作为单一的脱硫催化剂时,脱硫循环液中贫富液的PDS质量浓度的测定方法,可有效地指导在脱硫工序投加PDS的操作及生产运行,为确保出脱硫工序煤气中H2S含量稳定控制在20mg/L以内奠定了基础。     

Change of short-term memory effect in acute ischemic ventricular myocardium: A computational study

The ionic mechanism of change in short-term memory (STM) during acute myocardial ischemia has not been well understood. In this paper, an advanced guinea pig ventricular model developed by Luo and Rudy was used to investigate STM property of ischemic ventricular myocardium. STM response was calculated by testing the time to reach steady-state action potential duration (APD) after an abrupt shortening of basic cycling length (BCL) in the pacing protocol. Electrical restitution curves (RCs), which can simultaneously visualize multiple aspects of APD restitution and STM, were obtained from dynamic and local S1S2 restitution portrait (RP), which consist of a longer interval stimulus (S1) and a shorter interval stimulus (S2). The angle between dynamic RC and local S1S2 RC reflects the amount of STM. Our results indicated that compared with control (normal) condition, time constant of STM response in the ischemic condition decreased significantly. Meanwhile the angle which reflects STM amount is less in ischemic model than that in control model. By tracking the effect of ischemia on intracellular ion concentration and membrane currents, we declared that changes in membrane currents caused by ischemia exert subtle influences on STM; it is only the decline of intracellular calcium concentration that give rise to the most decrement of STM.     

Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid

3‐Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0–20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06–1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu)₄NBF₄ (1.92 V vs Ag/AgCl). Poly(3‐chlorothiophene) (PCT) films with conductivities of 0.1–2 S cm^?1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 502–509, 2003     

Carbon dioxide reforming of methane to synthesis gas over supported Ni catalysts

Carbon dioxide reforming of methane to synthesis gas has been investigated over supported Ni catalysts in the temperature range of 500–850°C. Addition of CaO (10mol%) promoter to the Ni/γ-Al₂O₃ resulted in an increase of reaction rate and an improvement of catalyst stability, which may be related to enhanced reducibility of the promoted catalyst. The kinetic studies show that the overall reaction can be described by a Langmuir-Hinshelwood mechanistic scheme, assuming that methane dissociation is the rate determining step. In addition to adsorbed CO and formate species, three types of carbonaceous species, C, C_β and C_γ, were found to exist on the Ni catalyst. While the active C, species is suggested to be responsible for CO formation, the less active C_β and C_γ species are attributed to causing catalyst deactivation.     

A binary approximating method for graspable region determination of biped climbing robots

For a biped pole-climbing robot (BiPCR) with grippers, it is an essential demand to determine the target grasp configuration for climbing and transiting between poles, with the graspable region as a priori knowledge. The graspable region on the target pole is critically important for climbing path planning and motion control. To efficiently compute the graspable region for a BiPCR, we propose a novel binary approximating method in this paper. This method may also be applied to generate the three-dimensional (3-D) workspace of a manipulator with constant orientation. The grasping problem and the concept of graspable region for a BiPCR are first introduced. The binary approximating method and the corresponding algorithms are then presented to generate the graspable region. Additional constraints on a biped climbing robot with five degrees of freedom (DoFs) are presented as a supplement to the algorithm. A series of comprehensive simulations are conducted with the five-DoF and six-DoF climbing robots to verify the effectiveness of the proposed method. Finally, the dexterity of biped climbing robots with different DoFs is discussed.     

A novel method for camera external parameters online calibration using dotted road line

On board camera is the most important information source for driver assistant application which is based on computer vision. One problem for on board camera is that the external parameters are easy to be changed when moving on the road. Traditional method either calibrates external parameters offline or calibrates external parameters semi-online, which both need human intervention. By observation, it is found that corner connection of dotted road lane can form two groups of parallel lines. Using this geometric characteristics and through theoretical derivation, a novel online camera external parameter calibration method is proposed which focus on the situation when vehicle is moving. The pro of this method is that it maintains relatively high calculation accuracy and more important, it does not require any human intervention in whole calibration process. Experimental and comparison results show that this method is simple and have accurate results which fully meet the requirements of practical application.     

Internet Studies and Development Discourses: The Cases of China and India

This paper investigates Internet studies in two leading developing countries (i.e. China and India) and finds that the Chinese scholarly community relies on the discourse of liberation from the state as a form of critique, whereas Indian Internet studies question the discourse of modernization to contemplate about the success and failure factors of information and communication technologies in development. The difference generally reflects the academic responses to the development discourses embraced by the two governments. We suggest that Internet studies should not only respond to the realities but also transcend the contextual constraints to direct attention to the often neglected dimensions of development, which are to make actual impacts through allowing the people and the communities to define their own development discourses as well as building research institutions that are oriented to influence policy-making.     

Adaptive Neural Network Finite-Time Control for Uncertain Robotic Manipulators

An adaptive neural network finite-time controller (NNFTC) for a class of uncertain nonlinear systems is proposed by using the backstepping method, which employs an adaptive neural network (NN) system to approximate the structure uncertainties and uses a variable structure term to compensate the approximation errors, thus improving the robustness of the system to external disturbances. The controller is then applied to uncertain robotic manipulators, with a control objective of driving the system state to the original equilibrium point. It is proved that the closed-loop system is finite-time stable. Moreover, simulated and experimental results indicate that the proposed NNFTC is effective and robust.     

Unmanned Ground Vehicle Navigation in Coordinate-Free and Localization-Free Wireless Sensor and Actuator Networks

We present a set of algorithms for the navigation of Unmanned Ground Vehicles (UGVs) towards a set of pre-identified target nodes in coordinate-free and localization-free wireless sensor and actuator networks. The UGVs are equipped with a set of wireless listeners that provide sensing information about the potential field generated by the network of actuators. Two main navigation scenarios are considered: single-UGV, single-destination navigation and multi-UGV, multi-destination navigation. For the single-UGV, single-destination case, we present both centralized and distributed navigation algorithms. Both algorithms share a similar two-phase concept. In the first phase, the system assigns level numbers to individual nodes based on their hop distance from the target nodes. In the second phase, the UGV uses the potential field created by the network of actuators to move towards the target nodes, requiring cooperation between triplets of actuator nodes and the UGV. The hop distance to the target nodes is used to control the main moving direction while the potential field, which can be measured by listeners on the UGV, is used to determine the UGV’s movement. For the multi-UGV, multi-destination case, we present a decentralized allocation algorithm such that multiple UGVs avoid converging to the same destination. After each UGV determines its destination, the proposed navigation scheme is applied. The presented algorithms do not attempt to localize UGVs or sensor nodes and are therefore suitable for operating in GPS-free/denied environments. We also present a study of the communication complexity of the algorithms as well as simulation examples that verify the proposed algorithms and compare their performances.     

A new parallel algorithm for vertex priorities of data flow acyclic digraphs

Data flow acyclic directed graphs (digraph) are widely used to describe the data dependency of mesh-based scientific computing. The parallel execution of such digraphs can approximately depict the flowchart of parallel computing. During the period of parallel execution, vertex priorities are key performance factors. This paper firstly takes the distributed digraph and its resource-constrained parallel scheduling as the vertex priorities model, and then presents a new parallel algorithm for the solution of vertex priorities using the well-known technique of forward–backward iterations. Especially, in each iteration, a more efficient vertex ranking strategy is proposed. In the case of simple digraphs, both theoretical analysis and benchmarks show that the vertex priorities produced by such an algorithm will make the digraph scheduling time converge non-increasingly with the number of iterations. In other cases of non-simple digraphs, benchmarks also show that the new algorithm is superior to many traditional approaches. Embedding the new algorithm into the heuristic framework for the parallel sweeping solution of neutron transport applications, the new vertex priorities improve the performance by 20 % or so while the number of processors scales up from 32 to 2048.