In this research, carbon sources (Resin Phenolic, Carbon Black and Graphite) and Boron Carbide (B4C) were used to improve the mechanical properties of Silicon Carbide (SiC) composite. For this purpose, carbon sources of 0.5, 0.75, 1, 1.5, 2, 2.5, 3, and 5 wt% as well as 0.5 wt% B4C were added to SiC powder, respectively. The sample containing SiC—2.5 wt% Resin Phenolic—0.5 wt% B4C had the best properties with relative density, hardness, and fracture toughness values of 98.5%, 2820 GPa, and 3.9 MPa.√m, respectively. Examination of SEM images showed that by increasing carbon from 0.5 to 2.5 wt%, the fracture changes from intergranular to transgranular. 相似文献
Actual fatigue life of an existing offshore platform typically deviates from that intended by its designer because aging platforms commonly experience some degradations, mechanical damages, repairs and modifications, and come across demands for the service extension. The current multidisciplinary paper focuses on different aspects of the remaining fatigue life assessment of an aging offshore platform. In the course of a case study, it describes a hindcasting technique for quantitative estimation of the long-term wave climatology, methods for geotechnical/structural modelling of the platform foundation to evaluate the piles fatigue damages accumulated during their driving and in-place service and the outlines for a spectral fatigue modelling and analysis of the fatigue damages to welded structural joints. Potential limitations in the available codes of practice, regarding the fatigue life assessment of existing offshore structures, are highlighted. The reliability of the fatigue life evaluations, possible remedy measures and some fatigue integrity monitoring techniques are discussed. 相似文献
In this paper, a hybrid method is proposed to damp frequency and power oscillations in the power system equipped with unified power flow controller (UPFC) and power system stabilizer (PSS) controllers. The method is robust with respect to operating point’s changes. This hybrid method consists of two stages: offline and online. In the offline stage, the coefficients of PSS and UPFC controllers for different operating points have been found by PSO algorithm; then in the second stage, online new fuzzy controller is proposed to select the best PSS and UPFC coefficients according to operating point. The proposed method is simulated for single machine infinite bus system-associated PSS and UPFC for three different operating points in MATLAB software, and results of proposed method simulation are investigated and compared with conventional PSS (CPSS) + UPFC, CPSS controllers. Simulation results show that the proposed method has a better performance.
This paper presents a low cost fault-tolerant technique so called OWHR (Operand Width Aware Hardware Reuse) to ALU design in embedded processors. The OWHR technique is motivated by two facts: (1) Many of the produced and consumed values are narrow-width values in the embedded processors, i.e. they have leading zeros or ones in their most significant bits. This indicates that only a fraction of the circuit is performing useful operations when a particular arithmetic or logic circuit in the ALU is operating on narrow-width values; (2) other circuits of the ALU are not used, when a particular arithmetic or logic circuit is being utilized to perform a specific operation in the ALU in the embedded processors. To exploit the first fact for fault tolerance purpose, the unused parts of a particular arithmetic or logic circuit can be used to provide redundant computations. The second fact also offers us assisting the other unused arithmetic circuits of the ALU to provide redundant computation while a particular arithmetic circuit is being used to perform a specific operation. In this paper, we have implemented a 32-bit ALU protected by the OWHR technique using VHDL and we have extracted the results of power and performance overheads using Synopsis Design and Power Compiler. To do this, we have profiled the input operands of the adder and multiplier units by running some programs of MiBench embedded suite benchmark on an ARM processor performance mode. We have then applied the profiled operands to the implemented ALU to extract the power and performance overheads. The simulation results show that the proposed technique is capable of correcting about 56% of errors in the adder circuit and about 88% of errors in multiplier circuit while having the ability of detecting 100% of errors in the both of the circuits. Beside its high level of reliability, it offers the benefits of low power, and area overheads. 相似文献
This article designs and studies the approximate performance of robust dispersion charts, namely, MAD chart, Sn chart, and Qn chart, in Phase I analysis (recently developed in the literature). The proposed limits are based on false alarm probability for monitoring the dispersion of a process in Phase I analysis. The charting constants are determined to achieve the required nominal FAP (FAP0). The performance of these structures is evaluated in (i) the attained false alarm rate and (ii) the probability of signals for out‐of‐control situations. The analysis shows that the proposed design of Phase I robust dispersion charts correctly controls the FAP and shows a good performance in detecting the shifts in the process variation. An illustrative example is used to explain the practical implementation of these limits. 相似文献
Modern public transport networks provide an efficient medium for the spread of infectious diseases within a region. The ability to identify components of the public transit system most likely to be carrying infected individuals during an outbreak is critical for public health authorities to be able to plan for outbreaks, and control their spread. In this study we propose a novel network structure, denoted as the vehicle trip network, to capture the dynamic public transit ridership patterns in a compact form, and illustrate how it can be used for efficient detection of the high risk network components. We evaluate a range of network-based statistics for the vehicle trip network, and validate their ability to identify the routes and individual vehicles most likely to spread infection using simulated epidemic scenarios. A variety of outbreak scenarios are simulated, which vary by their set of initially infected individuals and disease parameters. Results from a case study using the public transit network from Twin Cities, MN are presented. The results indicate that the set of transit vehicle trips at highest risk of infection can be efficiently identified, and are relatively robust to the initial conditions of the outbreak. Furthermore, the methods are illustrated to be robust to two types of data uncertainty, those being passenger infection levels and travel patterns of the passengers. 相似文献