Topology optimization based on reduction methods with applications to multiscale design and additive manufacturing

Advanced manufacturing processes such as additive manufacturing offer now the capability to control material placement at unprecedented length scales and thereby dramatically open up the design space. This includes the considerations of new component topologies as well as the architecture of material within a topology offering new paths to creating lighter and more efficient structures. Topology optimization is an ideal tool for navigating this multiscale design problem and leveraging the capabilities of advanced manufacturing technologies. However, the resulting design problem is computationally challenging as very fine discretizations are needed to capture all micro-structural details. In this paper, a method based on reduction techniques is proposed to perform efficiently topology optimization at multiple scales. This method solves the design problem without length scale separation, i.e., without iterating between the two scales. Ergo, connectivity between space-varying micro-structures is naturally ensured. Several design problems for various types of micro-structural periodicity are performed to illustrate the method, including applications to infill patterns in additive manufacturing.     

Recent developments in the application of oil palm fibers in cement composites

Fibers obtained from different parts of the oil palm tree (Elaeis guineensis) have been under investigation for possible use in construction. Studies have been carried out investigating the engineering properties and possible applications of these fibers. However, the experimental methods employed and the values of mechanical and physical properties recorded by various authors are inconsistent. It has therefore become necessary to organize information which would be useful in the design of oil palm fiber cement composites and help researchers and engineers make informed decisions in further research and application. This review provides information about fibers from different parts of the oil palm, their properties, enhancement techniques, current and potential application in cement composites.     

Effect of Co-Mo catalyst preparation and CH4/H2 flow on carbon nanotube synthesis

Abstract

Supported Co-Mo catalysts with a given ratio of metals were prepared from polyoxomolybdate Mo₁₂O₂₈(μ₂-OH)₁₂{Со(H₂O)₃}₄ using impregnation and combustion methods. Effects of the type of catalyst and the ratio and flow of methane and hydrogen gases on the structure of carbon nanotubes (CNTs) synthesized by catalytic chemical vapor deposition (CCVD) method were studied using transmission electron microscopy and Raman spectroscopy. The catalyst prepared by combustion method yielded mainly individualized CNTs, while the CNTs were highly entangled or bundled when impregnation method was used. In both cases, addition of hydrogen to methane led to reduction of the CNT yield. The samples synthesized using two different catalysts and the same CH₄/H₂ ratio and flow of gases were tested in electrochemical capacitors. A higher specific surface area of the CNTs grown over impregnation-prepared catalyst caused a better performance at scan rates from 2 to 1000?mV/s.     

Labour market effects of urban riots: An experimental assessment

We measure the effects of urban riots on the labour market prospects of workers in the case of the French riots of 2007. The town of Villiers-le-Bel is our treatment unit while two other towns serve as control groups, Sarcelles and Enghien-les-Bains. Using the technique of correspondence testing, we are able to discern disparities in call-back rates for fictitious candidates who respond to actual job postings over four dimensions: gender, ethnic origin, locality of residence (advantaged vs. disadvantaged), and the degree of media exposure during the riots. We implement an empirical approach to measure discrimination across several dimensions that integrates a set of relevant parameters into one unified system of equations. We find statistically significant negative estimates of a media exposure effect. People residing in the area which received negative publicity were 3.2 percentage points less likely to receive a callback. The group of workers who tend to be the most associated with the riots, namely, men of North African origin (at least in terms of perceptions), are the least affected by potential discrimination by region of residence, while women of French origin are the most affected.     

Network intrusion detection based on deep learning model optimized with rule-based hybrid feature selection

ABSTRACT

Network Intrusion Detection System (NIDS) is often used to classify network traffic in an attempt to protect computer systems from various network attacks. A major component for building an efficient intrusion detection system is the preprocessing of network traffic and identification of essential features which is essential for building robust classifier. In this study, a NIDS based on deep learning model optimized with rule-based hybrid feature selection is proposed. The architecture is divided into three phases namely: hybrid feature selection, rule evaluation and detection. Several search methods and attribute evaluators were combined for features selection to enhance experimentation and comparison. The results obtained showed that the number of selected features will not affect the detection accuracy of the feature selection algorithms, but directly proportional to the performance of the base classifier. Results from the performance comparison proved that the proposed method outperforms other related methods with reduction of false alarm rate, high accuracy rate, reduced training and testing time of 1.2%, 98.8%, 7.17s and 3.11s, respectively. Finally, the simulation experiments on standard evaluation metrics showed that the proposed method is suitable for attack classification in NIDS.     

Computational Analysis of Choices in the Design of Smoke Extraction Duct Systems (SEDS) for Compartment Fires

Fire Technology - Large Eddy Simulations (LES) of smoke extraction duct system (SEDS) in single compartments of different volumes (i.e., 128 m $$^3$$ , 512 m $$^3$$ and 2400 m $$^3$$ ) with FDS...     

Designing and developing smart production planning and control systems in the industry 4.0 era: a methodology and case study

Journal of Intelligent Manufacturing - In furtherance of emerging research within smart production planning and control (PPC), this paper prescribes a methodology for the design and development of...