Differential graphical games for H∞ control of linear heterogeneous multiagent systems

Differential graphical games have been introduced in the literature to solve state synchronization problem for linear homogeneous agents. When the agents are heterogeneous, the previous notion of graphical games cannot be used anymore and a new definition is required. In this paper, we define a novel concept of differential graphical games for linear heterogeneous agents subject to external unmodeled disturbances, which contain the previously introduced graphical game for homogeneous agents as a special case. Using our new formulation, we can solve both the output regulation and H_∞ output regulation problems. Our graphical game framework yields coupled Hamilton‐Jacobi‐Bellman equations, which are, in general, impossible to solve analytically. Therefore, we propose a new actor‐critic algorithm to solve these coupled equations numerically in real time. Moreover, we find an explicit upper bound for the overall ‐gain of the output synchronization error with respect to disturbance. We demonstrate our developments by a simulation example.     

Effects of a titanate coupling agent on the mechanical and thermo‐physical properties of talc‐reinforced polyethylene compounds

An experimental study was carried out to investigate the effects of a titanate coupling agent on the mechanical properties, moisture absorption, and thermal conductivity of talc‐filled high‐density polyethylene (HDPE). Talc (0–35 wt %) was used as reinforcement particulate filler in an HDPE matrix and samples were prepared in a micro‐compounder and an injection molding machine. Isopropyl tri(dioctyl)phosphate titanate (0.5 wt %) was used as coupling agent. Composites with and without coupling agent were evaluated for changes in mechanical and thermo‐physical properties, morphology, and void content. Addition of the titanate coupling agent most often resulted in an increase in stiffness and tensile strength. Furthermore, both the void content and the elongation at break of composites were reduced. Results also showed that the coupling agent had no effects on the thermal conductivity, thermal diffusivity, and specific heat capacity of the composites. In addition, it was observed that the coupling agent was more effective at low concentrations of filler. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40449.     

Load Tests on Prestressed Precast Concrete and Timber Piles

This paper presents the results of six pile-load tests performed on timber and prestressed concrete piles. Five axial compressive pile-load tests and one lateral-load test are presented. Comparisons are made between the results of these tests and predictions made using available geotechnical computer software. These comparisons provide an insight into using the Brinch-Hansen method of pile-load test evaluation along with wave equation and other computer analyses to evaluate pile capacities from load test data. This paper demonstrates how wave equation analyses can be used to anticipate and mitigate excess driving stresses during the installation of prestressed concrete piles. This paper also demonstrates that the use of well-established analytical methods can adequately predict the vertical and lateral behavior of timber and prestressed concrete piles. However, the bending rigidity of concrete piles under lateral loading should be carefully selected to obtain a good prediction to the measured data.     

The full cost of high-speed rail: an engineering approach

This paper examines the full costs, defined as the sum of private and social costs, of a high-speed rail system proposed for a corridor connecting Los Angeles and San Francisco in California. The full costs include infrastructure, fleet capital and operating expenses, the time users spend on the system, and the social costs of externalities, such as noise, pollution, and accidents. Comparing these full costs to those of other competing modes contributes to the evaluation of the feasibility of high-speed rail in the corridor. The paper concludes that high-speed rail is significantly more costly than expanding existing air service, and marginally more expensive than auto travel. This suggests that high-speed rail is better positioned to serve shorter distance markets where it competes with auto travel than longer distance markets where it substitutes for air. Received: May 1996 / Accepted in revised form: December 1996     

The effect of microstructure on the slow crack growth resistance in polyethylene resins

The slow crack growth (SCG) in high density polyethylene (HDPE) is a phenomenon dominated by crazing. In this work, the crazing was analyzed from a microstructural point of view. PENT (Pennsylvania Edge Notched Tensile) test was chosen to study the evolution of the craze with time for different resins from PE‐80 up to PE‐100 grades. Two different geometries, the standard and an alternative named CDNT (Circumferentially Deep Notched Tensile), were employed. Failure times were correlated with intercrystalline parameters like tie molecules and the molecular weight between entanglements. Experimental results showed good correlations using both direct SCG test (standard PENT and CDNT geometries). Finally, the strain hardening modulus was correlated with PENT failure times. The results disclosed an outstanding correlation for several polyethylene grades from blow molding up to PE‐80, PE‐100, and higher resistant to crack grades. These results permitted an easy‐classifying and ranking method as much to the old polyethylene grades as to the new generation of HDPE resins with a very high SCG resistance. POLYM. ENG. SCI., 55:1018–1023, 2015. © 2014 Society of Plastics Engineers     

Family of Soft-Switching PWM Converters With Current Sharing in Switches

In this paper, a new family of soft-switching pulsewidth modulation (PWM) converters is introduced. In this family of converters, two switches operate out of phase and share the output current while providing soft-switching condition for each other. A buck converter, from this family of converters, is analyzed and its operating modes are discussed. The adoption of regular PWM control circuit to the proposed converters is presented. A prototype converter is implemented and its experimental results are illustrated.     

Machining simulation and system integration combining FE analysis and cutting mechanics modelling

This work presents a method for machining complex three-dimensional surfaces using only one axis of controlled motion for positioning a cutting tool on a specially designed numerically controlled (NC) machine. This single controlled axis lathe is configured like a lathe, but is used to produce complex sculptured surfaces out of wood. This is accomplished by mechanically linking two axes of motion to produce a fixed helical footprint of a tool path with constant step-over distance. As the linked axes are rotated, their location is measured by an encoder and passed directly to a personal computer (PC). Software running on the PC determines the depth of the computer-controlled axis. The depth information is used to control the depth axis. Several test pieces have been machined out of cedar for evaluating the method.     

A novel analog switch for high‐precision switched‐capacitor applications

The performance of a switched‐capacitor circuit strongly depends on its analog switches. This paper introduces a new technique to design a high‐precision analog metal‐oxide‐semiconductor switch for switched‐capacitor applications. The accuracy of analog switches is a critical parameter to determine overall performance of the discrete‐time analog systems. To satisfy the accuracy requirements of the switch, a novel technique to minimize the charge injection and clock feedthrough errors by using a very simple structure is proposed. Moreover, an innovative approach to increase the OFF resistance of the switch and consequently minimizing its leakage current is presented. To evaluate the performance of the proposed switch, simulations are done in TSMC 0.18μm standard complementary metal‐oxide‐semiconductor technology with BSIM3V3 device models. The ON and OFF resistances of the switch are one of the most important factors that should be considered while investigating analog switches. The ON resistance of the proposed switch is less than 560Ω over entire input signal range which completely satisfies the tracking bandwidth requirements. In addition, since the proposed switch provides an ultrahigh OFF resistance in the range of several GΩs, the leakage current of the proposed switch is negligible. Simulation results also show that switch‐induced errors are significantly eliminated by using the proposed cancellation technique. The output error charge due to charge injection and clock feedthrough over a wide range of input signal variation is very low (less than 1.6 fC). Moreover, simulation results show that the proposed switch achieves signal to noise plus distortion ratio of 80.55 dB, effective number of bits of 13.08, total harmonic distortion of ?81.41 dB, and spurious‐free dynamic range of 87.7 dB for a 2.5‐MHz sinusoidal input of 800‐mV peak‐to‐peak amplitude at 200‐MHz sampling rate with a 1.8‐V supply voltage. Consequently, the simulation results verify that the proposed switch can significantly improve the dynamic and static performances of a switched‐capacitor circuit.