Research on force control system of lead cathode leveler

The flatness of the lead cathode plate affects the electrolytic efficiency of lead and the production efficiency of the whole lead electrolytic industry. However, the dynamic response of the force control system of the leveler is slow, and the anti-interference and robustness are poor. By comparing proportion integration differentiation (PID) control and feedback linearized synovial control two control strategies, MATLAB software was used for modeling and simulation analysis. The results show that the system with feedback linearized sliding mode control has faster response, higher precision and better robustness

Effective video multicast over wireless internet

With the rapid growth of wireless networks and great success of Internet video, wireless video services are expected to be widely deployed in the near future. As different types of wireless networks are converging into all IP networks, i.e., the Internet, it is important to study video delivery over the wireless Internet. This paper proposes a novel end-system based adaptation protocol calledWireless Hybrid Adaptation Layered Multicast (WHALM) protocol for layered video multicast over wireless Internet. In WHALM the sender dynamically collects bandwidth distribution from the receivers and uses an optimal layer rate allocation mechanism to reduce the mismatches between the coarse-grained layer subscription levels and the heterogeneous and dynamic rate requirements from the receivers, thus maximizing the degree of satisfaction of all the receivers in a multicast session. Based on sampling theory and theory of probability, we reduce the required number of bandwidth feedbacks to a reasonable degree and use a scalable feedback mechanism to control the feedback process practically. WHALM is also tuned to perform well in wireless networks by integrating an end-to-end loss differentiation algorithm (LDA) to differentiate error losses from congestion losses at the receiver side. With a series of simulation experiments over NS platform, WHALM has been proved to be able to greatly improve the degree of satisfaction of all the receivers while avoiding congestion collapse on the wireless Internet

The L∞-null controllability of parabolic equation with equivalued surface boundary conditions

In this paper, we obtain the L∞-null controllability of the parabolic equation with equivalued surface boundary conditions in Ω×[0,T]. The control is supported in the product of an open subset of Ω and a subset of [0,T] with positive measure. The main result is obtained by the method of Lebeau-Robbiano iteration, based on a new estimate for partial sum of the eigenfunctions of the elliptic operator with equivalued surface boundary conditions

Nexus of Inter-organizational Trust, Principled Negotiation, and Joint Action for Improved Cost Performance: Survey of Chinese Megaprojects

Drawing on the theory of relational governance, this study determined the nexus of interorganizational trust, principled negotiation, and joint action in cost performance. To this end, five hypotheses were formulated based on established management theories or principles of organizational studies. The study used partial least squares structural equation modeling to analyze the 248 valid questionnaires collected from the analyzed organizations involved in megaprojects. The results show that interorganizational trust has direct and indirect positive effects on improving cost performance. Principled negotiation and joint action can serve as multiple mediating roles between interorganizational trust and cost performance. Contractual governance also has different moderation effects on principled negotiation and joint action toward cost performance. In conclusion, this study contributes to the knowledge on interorganizational trust and its mediating effects on cost performance from the perspective of megaprojects. The results are generalizable to other projects with complicated organizational and working relationships

Numerical simulation of two-phase cross flow in the gas diffusion layer microstructure of proton exchange membrane fuel cells

The cross flow in the under-land gas diffusion layer (GDL) between 2 adjacent channels plays an important role on water transport in proton exchange membrane fuel cell. A 3-dimensional (3D) two-phase model that is based on volume of fluid is developed to study the liquid water-air cross flow within the GDL between 2 adjacent channels. By considering the detailed GDL microstructures, various types of air-water cross flows are investigated by 3D numerical simulation. Liquid water at 4 locations is studied, including droplets at the GDL surface and liquid at the GDL-catalyst layer interface. It is found that the water droplet at the higher-pressure channel corner is easier to be removed by cross flow compared with droplets at other locations. Large pressure difference Δp facilitates the faster water removal from the higher-pressure channel. The contact angle of the GDL fiber is the key parameter that determines the cross flow of the droplet in the higher-pressure channel. It is observed that the droplet in the higher-pressure channel is difficult to flow through the hydrophobic GDL. Numerical simulations are also performed to investigate the water emerging process from different pores of the GDL bottom. It is found that the amount of liquid water removed by cross flow mainly depends on the pore's location, and the water under the land is removed entirely into the lower-pressure channel by cross flow

Sudden stoppage of rotor in a thermally driven rotary motor made from double-walled carbon nanotubes

In a thermally driven rotary motor made from double-walled carbon nanotubes, the rotor (inner tube) can be actuated to rotate within the stator (outer tube) when the environmental temperature is high enough. A sudden stoppage of the rotor can occur when the inner tube has been actuated to rotate at a stable high speed. To find the mechanisms of such sudden stoppages, eight motor models with the same rotor but different stators are built and simulated in the canonical NVT ensembles. Numerical results demonstrate that the sudden stoppage of the rotor occurs when the difference between radii is near 0.34 nm at a high environmental temperature. A smaller difference between radii does not imply easier activation of the sudden rotor stoppage. During rotation, the positions and electron density distribution of atoms at the ends of the motor show that a sp(1) bonded atom on the rotor is attracted by the sp(1) atom with the biggest deviation of radial position on the stator, after which they become two sp(2) atoms. The strong bond interaction between the two atoms leads to the loss of rotational speed of the rotor within 1 ps. Hence, the sudden stoppage is attributed to two factors: the deviation of radial position of atoms at the stator's ends and the drastic thermal vibration of atoms on the rotor in rotation. For a stable motor, sudden stoppage could be avoided by reducing deviation of the radial position of atoms at the stator's ends. A nanobrake can be, thus, achieved by adjusting a sp(1) atom at the ends of stator to stop the rotation of rotor quickly.The authors are grateful for financial support from the National Natural-Science-Foundation of China (Grant Nos. 50908190, 11372100)

Simultaneous Determination of Palladium and Platinum by On-line Enrichment and HPLC with 4-(2-Hydroxynaphthalene- 1-ylmethylene)-thiazolidine-2,5-Dithione as Pre-column Derivatization Reagent

In this paper, a new reagent, 4-(2-hydroxy-naphthalene-1-ylmethylene)-thiazolidine-2,5-dithione (HNMTD) was synthesized. A new method for the simultaneous determination of palladium and platinum ions as metal-HNMTD chelates was developed using high performance liquid chromatography equipped with an on-line enrichment technique. Prior to chromatography the palladium and platinum ions were derivatized with HNMTD to coloured chelate complexes. The Pd-HNMTD and Pt-HNMTD complexes were then enriched on an enrichment column(ZORBAXReversed Phase StableBoundC18, 4.6×10mm,1.8 μm) using a buffer solution of 0.05 mol L–1 sodium acetate-acetic acid buffer (pH 3.8) as mobile phase.After the enrichment was completed, the retained chelates were back-flushed to the analytical column. The separation of chelates on the analytical column (ZORBAX Reversed Phase Stable Bound C18, 4.6 × 50 mm, 1.8 μm) was satisfactory when 72% methanol (containing 0.05 mol L–1 of pH 3.8 sodium acetate-acetic acid buffer salt and 0.1% of TritonX-100) was used as mobile phase. The Pt-HNMTD and Pd-HNMTD chelates were separated completely within 2 min. The detection limits (S/N = 3) for palladium and platinum were 1.2 ng L–1 and 1.4 ng L–1, respectively. The method was applied with good results to the determination of palladium and platinum in water and urine samples.Keywords: Palladium, platinum, 4-(2-hydroxy-naphthalene-1-ylmethylene)-thiazolidine-2,5-dithione, high performance liquid chromatography, on-line enrichment