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The particle-in-cell (PIC) method has been widely used for plasma simulation, because of its noise-reduction capability and moderate computational cost. The immersed finite element (IFE) method is efficient for solving interface problems on Cartesian meshes, which is desirable for the PIC method. The combination of these two methods provides an effective tool for plasma simulation with complex interface/boundary. This paper introduces an improved IFE–PIC method that enhances the performance in both IFE and PIC aspects. For the electric field solver, we adopt the newly developed partially penalized IFE method with enhanced accuracy. For PIC implementation, we introduce a new interpolation technique to ensure the conservation of the charge. Numerical examples are provided to demonstrate the features of the improved IFE–PIC method. [ABSTRACT FROM AUTHOR]

This paper presents the results from experiments and numerical simulations on the ballistic impact of 10 mm thick aramid fabric-epoxy composite laminates by a 7.62 mm armor piercing projectile at varying impact velocities. Post perforated residual velocity (RV), contact duration of projectile with the target and ballistic limit (BL) of composite were simulated using a finite element code HyperWorks-Radioss. Interaction of projectile with composite laminates was captured by high speed video. The predicted ballistic parameter from simulation compared well with the precision experimental results. The simulated energy and stress distribution during impact of projectile on composite laminate showed marked difference with variation in impact velocities (SV). The magnitude and duration of stress as well as the contact force was found to increase when projectile impacted at lower SV thus enhancing the extent of delaminating and the core damage area and the trend was reversed for higher SV. The findings corroborate the bullet inflicted damage of composite laminates experimentally determined by ultrasonic C-scan. [ABSTRACT FROM AUTHOR]

A pile is a fundamental part of fixed type platform which commonly used to support superstructure rig in the offshore area. A seamless pipe is usually used as the pile structure. However, this seamless pipe is a high-priced pipe and scarce to find in Indonesia. ERW (Electric Resistant Welded) pipe can be used for an alternative selection of the seamless pipe for piling structure. However, ERW pipe production may have a defect in the form of a cold weld and a hook crack. This paper studies the possibility of ERW pipe utilization as the piling structure. A case study was conducted for ERW pipe NPS 24 and length of 6 m. This research conducted by using eta-FEMB and LS-DYNA software to examine the effective stress of the pile structure during installation. Numerical simulations were carried out on the pile structure with crack modelling and withstand multiple impact loading. The result was compared with failure criterion based on API RP 2A WSD. Those criteria include Axial Allowable Tensile Stress (AATS), Axial Allowable Compressive Stress (AACS) and Critical Hoop Buckling Stress (CHBS). Based on this preliminary analysis, we hypothesize that the ERW pipe with defect length up to 5 mm can be used for the piling structure. However, this analysis need further investigation in order to be a recommendation for substituting seamless pipe for piling structure. [ABSTRACT FROM AUTHOR]

Bars alignment in a Split Hopkinson Pressure Bar influences the quality of signal recorded during experiments, and thus affects the data of material properties being measured. There are some parameters directly related to the bars alignment such as their straightness, the impact face parallelism, and the neutral axis offset. This paper presents the study on the effects of non-straightness of an SHPB bar systems, dome shaped specimen, and striker bar to incident bar offset using numerical simulations. The bar component is made of AISI 4340 material with 10 mm diameter and 1000 mm length. The non-straightness of the bars and dome shaped specimen which occured due to the limitation of manufacturing process and availability of material, were measured by using dial gauges with ring supports in every 100 mm. First the simulation of an SHPB using ideal bar geometries were carried out. The simulations were then repeated by incorporating bar straightness, specimen surface, and striker bar to incident bar offset in the numerical model. From the comparisons of the material properties obtained from all simulations, it can be concluded that dome shaped specimen is the most affecting factor to the results of the SHPB measurement.. [ABSTRACT FROM AUTHOR]

Reliability Block Diagrams (RBDs) allow us to model the failure relationships of complex systems and their sub-components and are extensively used for system reliability, availability and maintainability analyses. Traditionally, these RBD-based analyses are done using paper-and-pencil proofs or computer simulations, which cannot ascertain absolute correctness due to their inaccuracy limitations. As a complementary approach, we propose to use the higher-order logic theorem prover HOL to conduct RBD-based analysis. For this purpose, we present a higher-order logic formalization of commonly used RBD configurations, such as series, parallel, parallel-series and series-parallel, and the formal verification of their equivalent mathematical expressions. A distinguishing feature of the proposed RBD formalization is the ability to model nested RBD configurations, which are RBDs having blocks that also represent RBD configurations. This generality allows us to formally analyze the reliability of many real-world systems. For illustration purposes, we formally analyze the reliability of a generic Virtual Data Center (VDC) in a cloud computing infrastructure exhibiting the nested series-parallel RBD configuration. [ABSTRACT FROM AUTHOR]

Survivability or detecting and predicting failures for humans or animals is a matter of instinct. Unlike for robots, machines, or anything that bases its rationality in software, that assumption is not applicable, yet. In this paper we apply model checking techniques to avoid future complete malfunctioning. Scenarios where non existing states are evaluated in order to find solution to possible future problems. A model checker is used for online evaluation of all the states, including possible non-existing transitions and states. [ABSTRACT FROM AUTHOR]