Reverse engineering models of software interfaces

Cyber-physical systems consist of many hardware and software components. Over the lifetime of these systems their components are often replaced or updated. To avoid integration problems, formal specifications of component interface behavior are crucial. Such a formal specification captures not only the set of provided operations but also the order of using them and the constraints on their timing behavior. Usually the order of operations are expressed in terms of a state machine. For new components such a formal specification can be derived from requirements. However, for legacy components such interface descriptions are usually not available. So they have to be reverse engineered from existing event logs and source code. This costs a lot of time and does not scale very well. To improve the efficiency of this process, we present a passive learning technique for interface models inspired by process mining techniques. The approach is based on representing causal relations between events present in an event log and their timing information as a timed-causal graph. The graph is further processed and eventually transformed into a state machine and a set of timing constraints. Compared to other approaches in literature which focus on the general problem of inferring state-based behavior, we exploit patterns of client-server interactions in event logs.

Anisotropic Multicomponent Topology Optimization for Additive Manufacturing With Build Orientation Design and Stress-Constrained Interfaces

This paper presents a multicomponent topology optimization method for designing structures assembled from additively manufactured components, considering anisotropic material behavior for each component due to its build orientation, distinct material behavior, and stress constraints at component interfaces (i.e., joints). Based upon the multicomponent topology optimization (MTO) framework, the simultaneous optimization of structural topology, its partitioning, and the build orientations of each component is achieved, which maximizes an assembly-level structural stiffness performance subject to maximum stress constraints at component interfaces. The build orientations of each component are modeled by its orientation tensor that avoids numerical instability experienced by the conventional angular representation. A new joint model is introduced at component interfaces, which enables the identification of the interface location, the specification of a distinct material tensor, and imposing maximum stress constraints during optimization. Both 2D and 3D numerical examples are presented to illustrate the effect of the build orientation anisotropy and the component interface behavior on the resulting multicomponent assemblies.

Highly efficient inverted hole-transport-layer-free perovskite solar cells

Inverted HTL-free PSCs show high PCE and stability, and will be further improved by component, interface and passivation engineering.

Dry Coupling of Ultrasonic Transducer Components for High Temperature Applications

The viability for dry coupling of piezoelectric ultrasonic transducer components was investigated, using a thin foil of annealed silver as a filler material/coupling agent at each component interface. Criteria used for room temperature evaluation were centered on signal-to-noise ratio (SNR) and echo bandwidth, for a Li-Nb based transducer operating in pulse-echo mode. A normal clamping stress of only 25 MPa, applied repeatedly over three loading cycles on a precisely-aligned transducer stack, was sufficient to yield backwall echoes with a SNR greater than 25 dB, and a 3 dB bandwidth of approximately 65%. This compares to a SNR of 32 dB and a 3 dB bandwidth of 65%, achievable when all transducer interfaces were coupled with ultrasonic gel. The respective roles of a soft filler material, alignment of transducer components, cyclic clamping, component roughness, and component flatness were evaluated in achieving this high efficiency dry coupling, with transducer clamping forces far lower than previously reported. Preliminary high temperature tests indicate that this coupling method is suitable for high temperature and achieves signal quality comparable to that at room temperature with ultrasonic gel.

Modular product design for additive manufacturing of satellite components: maximising product value using genetic algorithms

For space manufacturers, additive manufacturing promises to dramatically reduce weight and costs by means of integral designs achieved through part consolidation. However, integrated designs hinder the ability to change and service components over time – actually increasing costs – which is instead enabled by highly modular designs. Finding the optimal trade-off between integral and modular designs in additive manufacturing is of critical importance. In this article, a product modularisation methodology is proposed for supporting such trade-offs. The methodology is based on combining function modelling with optimisation algorithms. It evaluates product design concepts with respect to product adaptability, component interface costs, manufacturing costs and cost of post-processing activities. The developed product modularisation methodology is derived from data collected through a series of workshops with industrial practitioners from three different manufacturer companies of space products. The implementation of the methodology is demonstrated in a case study featuring the redesign of a satellite antenna.

Anisotropic Multicomponent Topology Optimization for Additive Manufacturing With Build Orientation Design and Stress-Constrained Interfaces

This paper presents a multicomponent topology optimization method for designing structures assembled from additively-manufactured components, considering anisotropic material behavior for each component due to its build orientation and distinct material behavior and stress constraint at component interfaces (i.e., joints). Based upon the multicomponent topology optimization (MTO) framework, the simultaneous optimization of structural topology, its partitioning, and the build orientations of each component is achieved that maximizes an assembly-level structural stiffness performance, subject to a maximum stress constraint at component interfaces. The build orientations of each component are modeled by its orientation tensor that avoids numerical instability often experienced by the angular representation. A new joint model is introduced at component interfaces, which enables identifying the interface region, assigning a distinct tensor for the region, and imposing a maximum stress constraint in the region during optimization. Both 2D and 3D numerical examples are presented to illustrate the effect of the build orientation anisotropy and the component interface behavior on the resulting multicomponent assemblies. The example 3D assembly, optimized for a multi-load condition, is fabricated for the purpose of demonstration.

Automated Test System for Test and Evaluation of C-Band Transmitter Packages for Geosat Spacecrafts

The aim of this paper is to develop an Automated Test System (ATS) for the Test and Evaluation of C-Band Transmitter packages for GEOSAT Space crafts using Virtual Instrumentation. Efficiency, coverage, quality and accuracy for the test and evaluation of Device Under Test (DUT) can be increased by Automated Testing. Minimizing the errors anticipated with manual intervention. Automated Test System using Virtual instrumentation (VI) combines rapid development software and modular, flexible hardware to create user-defined test systems. Here Modular PXI (Peripheral component interface Extensions for Instrumentation) instruments from National Instruments are used with NI-LabVIEW software for realizing the ATS. For characterizing the C-Band Transmitter, Spectrum analyzer & Digital Multimeter (DMM) is configured in PXI form-factor and the Power supply is controlled through GPIB (General Purpose Interface Bus) bus. The complete software is developed using NI LabVIEW which takes care of configuring the test condition and analyzing the DUT performance. The user friendly GUI well takes care of user interaction to the ATS.