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Experiments on the rectangular prisms with side ratios of 2. 0, 2.5, 3.0, 3.5 and 4. 0 are reported. Wind pressure measurements were carried out on five rectangular prisms for the testing Reynolds number Re ranging from l. 1 x 105 to 6. 8 x 105. The Reynolds number effects on the wind pressure distributions and the base pressure coefficients were studied, then the mechanisms of Reynolds number effects on rectangular prisms were described by analyzing the variation of the flow around the model. The results are summarized as follows; wind pressure distributions of five rectangular prisms are all sensitive to Re, and the Reynolds number affects the wind pressure distributions not only in the reattachment region, but also in the separation bubble. The sensitivity to the Reynolds number effects is changed with the side ratio of the rectangular prism, and the B/D = 4 .0 rectangular prism appears to be the most sensitive to the Re. Its separated shear layer is easier to reattach to the body at high Re, and the flow reattachment point moves towards the leading edge suddenly at the critical Re = 6. 8 x 105. In addition, with the increasing of Re, the absolute value of base pressure coefficient for the B/D =4. 0 prism increases firstly, and then decreases rapidly. [ABSTRACT FROM AUTHOR]

Gable-roofed low-rise buildings with ridges, protruding gable walls and eaves gutters are usually found on the southeastern coast of China, which are often invaded by typhoons. The wind effects due to ridges, protruding gable walls and eaves gutters on low-rise buildings as well as the wind loads on the architectural details themselves have been studied through a series of wind tunnel tests. The mean block pressure coefficient and the negative peak block pressure coefficient on different roof regions were compared, and architectural details' single tap pressure coefficients and drag coefficients were investigated. The study shows that each of the architectural details reduces roof wind load impact to various extents, and their coexistence has a most significant effect on decreasing roof wind loads, up to the reduction of 56% on the 'Ru' windward region for the mean block pressure coefficient, and 47% and 45% on the 'C1' and 'C2' corner regions for the worst negative peak block pressure coefficient, respectively. The worst negative peak pressure at the interior surface of the architectural details occurs when the wind blows obliquely on the exterior surface of the architectural details. This condition leads to very large peak net pressure coefficients. The worst net pressure coefficients of the protruding gable wall, ridge and eaves gutter are about 18.0, 10.5 and 6.7, respectively. Finally, the drag coefficients on the architectural details were also examined, and the results are suitable for engineering application. [ABSTRACT FROM AUTHOR]

Abstract: Stay cables of cable-stayed bridges often experience vibrations with large amplitudes induced by wind or jointly by both wind and rain. To understand the aerodynamic characteristics of the stay cables and excitation mechanics of rain–wind-induced vibration (RWIV), an inclined and yawed circular cylinder with and without an artificial upper rivulet is studied through a series of wind tunnel tests. The impacts of upper rivulet and axial flow on the aerodynamics of the cylinder are investigated. It is found that for an inclined and yawed cylinder without rivulet there exists a non-zero lift force at large wind angle. Furthermore, the wind pressures and aerodynamic forces acting on both the cylinder and the upper rivulet are obtained, which can be used to develop more rational theoretical models for RWIV of stay cables. Results show that the upper rivulet can both enhance and depress Karman vortex shedding depending on the position of the rivulet. As a result, dramatic variations of the aerodynamic forces acting on the cylinder and the rivulet will occur, which may eventually result in RWIV. Also axial flow may have a noticeable influence on the aerodynamic characteristics of the inclined and yawed cylinder. And the presence of the rivulet can enhance such influence from the axial flow. [Copyright &y& Elsevier]

Abstract: Effects of multi-mode coupling should be taken into account in computing the resonant buffeting response of some kinds of flexible structures with low damping and concentrated modes. In this paper, a new concept of “mode coupling factor” for computation of coupling effects between multi-mode resonant responses of the structures is proposed. On the base of the mode coupling factor, a modified SRSS method for computation of the resonant response contributed by multi-modes and their coupling effects of the structures is further raised. The roof structure of Shanghai Southern Railway Station is then taken as the case study to indicate the application and to verify the precision of the mode coupling factor and the modified SRSS method. The computaion results indicate that the mode coupling factor can quantitatively describe the contribution of mode coupling to the resonant response; and the modified SRSS method can make the computation of structural resonant response with consideration of mode coupling effects simpler. [Copyright &y& Elsevier]

The interference effects of neighboring dry-coal sheds and the internal coal stacks within the investigated dry-coal shed probably make the wind-induced responses of the dry-coal shed more complicated. In order to provide a systematic method to study the characteristics of dry-coal sheds with/without interference condition, wind-induced responses are calculated in this paper. The wind-induced dynamic responses are calculated in frequency domain using mode superposition method (CQC method), based on the wind pressure distributions on roof from wind tunnel tests on the rigid models. The wind-induced responses under no-interference conditions are firstly analyzed, and the results show that the responses of some typical nodes are largest when the structure is subjected to skew wind. Through the analysis of interference factors, the characteristics of interference effects under different interference conditions and wind directions are investigated, the cases where the interference effects are stronger are pointed Out. Meanwhile, it is found that interferences only had small effect on the largest total peak displacement for the control condition. [ABSTRACT FROM AUTHOR]

Abstract: We address the problem of board-level multiterminal net assignment in FPGA-based logic emulation. We present a novel mathematical model for this problem. A powerful metaheuristic approach, called scatter search, is adopted. Effective heuristics are incorporated for accelerating the optimization search process. Experimental results demonstrate the promising performance of our approach. [Copyright &y& Elsevier]

Highlights: [•] We design the schematic diagram of solar desalination system with evacuated tube collectors. [•] Mathematical and economic models of the collector and desalination subsystem are proposed. [•] The method of desalination is low temperature multi effect distillation. [•] The cost constitution of solar desalination system is shown. [•] The water cost given appreciate the economic performance of the system. [Copyright &y& Elsevier]

Abstract: PLC is widely used in the field of automatic control. To use formal methods to verify the correctness of PLC programs, semantic characterization of PLC programs are needed. Based on the extended -calculus definition, this paper presents a novel semantic modeling of PLC programs. The results lay the solid underpinnings for theorem proving and modeling checking for PLC systems. [Copyright &y& Elsevier]

Abstract: We report on a method for formally specifying and verifying programmable logic controllers (PLCs) in the specification language TLA+. The specification framework is generic. It separates the description of the environment from that of the controller itself and its structure is consistent with the scan cycle mechanism used by PLCs. Specifications can be parameterized with the number of replicated components. In our experience, the structuring mechanisms of TLA+ help to obtain clear, well-organized, and configurable specifications, finite instances of which are verified by the TLA+ model checker TLC. We have validated our approach on a concrete case study, a controller for fire fighting equipment in a ship dock, and report on the results obtained for this case study. [Copyright &y& Elsevier]

Abstract: Programmable Logic Controllers (PLC) are widely used in industry. Reliable PLC systems are vital to many critical applications. The reliability analysis of PLC is special because the hardware component and embedded software are combined and operated in a specific manner. This paper presents a probabilistic modeling for PLC systems, which considers both the hardware and software components. Three analysis strategies are proposed for probabilistic evaluation of reliability characterization. The first method is an input-based analysis which considers the impact of errors from primary inputs. The second one is an action-based analysis. It extends the first method by considering the impact of software-based processing deviations on primary inputs. The third method is an action-traverse analysis. It computes the reliability characterization in a single topological traverse through the primary inputs during the software execution. Experimental results demonstrate the effectiveness of our approaches when compared to fault tree analysis. [Copyright &y& Elsevier]

By investigating acrosswind forces on rectangular cylinders with various side ratios at normal attack angle in a boundary layer wind tunnel, this paper presents empirical formula of acrosswind force spectra, RMS lift coefficients and Strouhal numbers of rectangular tall buildings, and coherence functions of acrosswind force are also probed. Thus, a complete analytical model of acrosswind dynamic loads on rectangular tall buildings is established. This model is in good agreement with the experimental results obtained by wind tunnel tests; so it is reliable and applicable. A calculation method based on this model can be developed to evaluate wind-induced acrosswind responses of rectangular tall buildings in frequency domain. [Copyright &y& Elsevier]