Microstructure and castability of lead‐free silicon brass alloys

Development of lead free brass alloys is an important subject due to the environmental demands and new regulations and standards that restrict lead contamination to decrease the toxicity. Pb‐free Si brasses are interesting alloys for this application, due to economical aspects and promising properties. In this work four Pb‐free brasses prepared with 1, 2, 3 and 4 wt% Si, based on Cu60/Zn40 alloy, are characterized. Their microstructure is examined and phases formed are identified. Castabilty indicated by fluidity and porosity is studied and correlated with the phases formed and their volume fraction.     

Microstructural characterization of pipe bomb fragments

Recovered pipe bomb fragments, exploded under controlled conditions, have been characterized using scanning electron microscopy, optical microscopy and microhardness. Specifically, this paper examines the microstructural changes in plain carbon-steel fragments collected after the controlled explosion of galvanized, schedule 40, continuously welded, steel pipes filled with various smokeless powders. A number of microstructural changes were observed in the recovered pipe fragments: deformation of the soft alpha-ferrite grains, deformation of pearlite colonies, twin formation, bands of distorted pearlite colonies, slip bands, and cross-slip bands. These microstructural changes were correlated with the relative energy of the smokeless powder fillers. The energy of the smokeless powder was reflected in a reduction in thickness of the pipe fragments (due to plastic strain prior to fracture) and an increase in microhardness. Moreover, within fragments from a single pipe, there was a radial variation in microhardness, with the microhardness at the outer wall being greater than that at the inner wall. These findings were consistent with the premise that, with the high energy fillers, extensive plastic deformation and wall thinning occurred prior to pipe fracture. Ultimately, the information collected from this investigation will be used to develop a database, where the fragment microstructure and microhardness will be correlated with type of explosive filler and bomb design. Some analyses, specifically wall thinning and microhardness, may aid in field characterization of explosive devices.     

Development of genetic algorithm-based fuzzy rules design for metal cutting data selection

Fuzzy rules optimization is always a problem for a complex fuzzy model. For a simple 2-inputs-1-output fuzzy model, the designer has to select the most optimum set of fuzzy rules from more than 10 000 combinations. The authors have developed fuzzy models for machinability data selection (Int. J. Flexible Autom. Integrated Manuf. 5 (1 and 2) (1997) 79). There are more than 2×10²⁹ possible sets of rules for each model. The situation would be more complicated if there were a further increase in the number of inputs and/or outputs. The fuzzy rules (Turning Handbook of High-Efficiency Metal Cutting, General Electric Co., Detroit) were selected based on trial and error and/or intuition. Genetic optimization has been suggested in this paper to further optimize the fuzzy rules. The development of a Fuzzy Genetic Optimization algorithm is presented and discussed. An object-oriented library to handle fuzzy rules optimization with genetic optimization has been developed. The effect of constraint rules is also presented and discussed. Comparisons between the results from the optimized models and literature are made.     

Innovative Hetero-Associative Memory Encoder (HAMTE) for Palmprint Template Protection

Many types of research focus on utilizing Palmprint recognition in user identification and authentication. The Palmprint is one of biometric authentication (something you are) invariable during a person’s life and needs careful protection during enrollment into different biometric authentication systems. Accuracy and irreversibility are critical requirements for securing the Palmprint template during enrollment and verification. This paper proposes an innovative HAMTE neural network model that contains Hetero-Associative Memory for Palmprint template translation and projection using matrix multiplication and dot product multiplication. A HAMTE-Siamese network is constructed, which accepts two Palmprint templates and predicts whether these two templates belong to the same user or different users. The HAMTE is generated for each user during the enrollment phase, which is responsible for generating a secure template for the enrolled user. The proposed network secures the person’s Palmprint template by translating it into an irreversible template (different features space). It can be stored safely in a trusted/untrusted third-party authentication system that protects the original person’s template from being stolen. Experimental results are conducted on the CASIA database, where the proposed network achieved accuracy close to the original accuracy for the unprotected Palmprint templates. The recognition accuracy deviated by around 3%, and the equal error rate (EER) by approximately 0.02 compared to the original data, with appropriate performance (approximately 13 ms) while preserving the irreversibility property of the secure template. Moreover, the brute-force attack has been analyzed under the new Palmprint protection scheme.     

Quasi-static crushing behaviour of hybrid and non-hybrid natural fibre composite solid cones

A comprehensive experimental investigation of the quasi-static axial crushing of hybrid and non-hybrid natural fibre/polyester composite solid cones between flat platens has been carried out. The composite solid cones were fabricated from two types of natural fibres namely oil palm fibre and coir fibre and different vertex angles varied from 0° to 60°. Typical load-deformation histories are presented and discussed. Crashworthiness parameters such as load carrying capacity; energy absorption capability and failure mechanism have been discussed. The results presented in this study will help us to understand the behaviour and characteristics of natural fibre composite as a filler material.     

Experimental optimization of composite collapsible tubular energy absorber device

A four-phase program to improve the specific energy absorbed by axially crushed composite collapsible tubular energy absorber devices was undertaken. In the first phase, examining of the crushing behaviour of non-triggered tubes was carried out. The second phase is aimed at obtaining the best position for the triggered wall. The third phase focuses on the effects of material sizing in order to understand the influence of triggered wall length on the responses of composite circular tubes to the axial crushing load. The results of these three phases of the study contribute to the fourth whose objective is to optimize the shape geometry of the cross-section area to further improving in tube energy absorption capability. The experimental results demonstrated the strong potential benefits of optimizing the material distribution. The sizing and shape optimization of composite collapsible tubes exhibited a pronounced effect on their capability to absorb high specific energy under axial compressive load.     

Cross-layer based transmit antenna selection for decision-feedback detection in correlated Ricean MIMO channels

In this paper, we investigate a cross-layer transmit antenna selection (AS) approach for the decision-feedback detector (DFD) over spatially correlated flat Ricean fading multiple-input multiple-output (MIMO) channels. Closed-form expressions for the system throughput with both perfect and imperfect channel estimation are derived. Considering a training-based channel estimation technique, we show that the capacity-based AS is more robust to imperfect channel estimation. However, in all cases, the cross-layer AS delivers higher throughput gains than the capacity-based AS.     

Quasi-static axial and lateral crushing of radial corrugated composite tubes

This paper presents the effect of corrugation geometry on the crushing behavior, energy absorption, failure mechanism, and failure mode of woven roving glass fibre/epoxy laminated composite tube. Experimental investigations were carried out on three geometrical different types of composite tubes subjected to axial and lateral compressive loadings. On the addition to a radial corrugated composite tube, cylindrical composite tube, and corrugated surrounded by cylindrical tube were fabricated and tested under the same condition in order to know the effect of corrugation geometry. The results showed that the loading carrying capability is significantly influenced by corrugation geometry in axial crushing. However, no affect of corrugation geometry was observed for lateral crushing. Load–displacement curve was plotted for all conducted tests, thus clear comparison between different specimen's geometry was achieved. It is also found that radial corrugation could significantly applicable as a stable and effective energy absorber.     

Limitation of the frequency stability by local oscillator phase noise: new investigations and natural improvements

In frequency standards in which the atoms have a continuous interaction with the probe signal, local oscillator phase noise may limit medium term frequency stability. This spurious effect cannot be suppressed whenever there Is any truncation in the spectrum of the resonator response. Nevertheless, a simultaneous processing of the probe signal, similar to that of the NIST, and of the resonator response (by means of an appropriate demodulation) makes it possible to reduce this limiting effect. Previously achieved with a square wave frequency modulation, this result is now extended to various frequency modulations. An uncontrolled distortion in the demodulation waveform may significantly degrade the performance. For the case of a square wave phase modulation, the limiting effect also exists, but it is smaller than for a frequency modulation. When the phase noise of the local oscillator is naturally "not flat", it is possible to easily reduce the spurious effect: using the quasi-static approximation, one can calculate various optimized demodulation waveforms and the corresponding improvements. For the simplest optimized demodulation (f (M), 3f(M)), theoretical predictions are experimentally confirmed for flicker phase noise and flicker frequency noise.     

Code detection in turbo source coding

We consider the lossless compression of binary memoryless sources using a library of turbo codes. The message is compressed by each code and the best result along with the index of the applied code is sent to the decoder. Instead of transmitting the code index, we find a criterion to detect the code index using the transmitted parities. Our method helps to reduce the compression rate of short block length turbo source coders.