LPNN-based approach for LASSO problem via a sequence of regularized minimizations

In compressive sampling theory, the least absolute shrinkage and selection operator (LASSO) is a representative problem. Nevertheless, the non-differentiable constraint impedes the use of Lagrange programming neural networks (LPNNs). We present in this article the -LPNN model, a novel algorithm that tackles the LASSO minimization together with the underlying theory support. First, we design a sequence of smooth constrained optimization problems, by introducing a convenient differentiable approximation to the non-differentiable -norm constraint. Next, we prove that the optimal solutions of the regularized intermediate problems converge to the optimal sparse signal for the LASSO. Then, for every regularized problem from the sequence, the -LPNN dynamic model is derived, and the asymptotic stability of its equilibrium state is established as well. Finally, numerical simulations are carried out to compare the performance of the proposed -LPNN algorithm with both the LASSO-LPNN model and a standard digital method.     

Constructing malware normalizers using term rewriting

A malware mutation engine is able to transform a malicious program to create a different version of the program. Such mutation engines are used at distribution sites or in self-propagating malware in order to create variation in the distributed programs. Program normalization is a way to remove variety introduced by mutation engines, and can thus simplify the problem of detecting variant strains. This paper introduces the “normalizer construction problem” (NCP), and formalizes a restricted form of the problem called “NCP=”, which assumes a model of the engine is already known in the form of a term rewriting system. It is shown that even this restricted version of the problem is undecidable. A procedure is provided that can, in certain cases, automatically solve NCP= from the model of the engine. This procedure is analyzed in conjunction with term rewriting theory to create a list of distinct classes of normalizer construction problems. These classes yield a list of possible attack vectors. Three strategies are defined for approximate solutions of NCP=, and an analysis is provided of the risks they entail. A case study using the virus suggests the approximations may be effective in practice for countering mutated malware. R. Mathur is presently at McAfee AVERT Labs.     

Experimental characterization and performance study of an ammonia–water–hydrogen refrigerator

We present in this paper an experimental study of a commercial diffusion-absorption refrigeration machine (DAR) operating on the Platen and Munters cycle. The temperatures at the inlet and outlet of every component of the machine, as well as the cabinet and ambient temperature are measured continuously. The tests are repeated for various electric power inputs to the refrigerator. The global heat transfer coefficient of the cabinet (UA)_cab is determined using both theoretical and experimental methods. This coefficient is found equal to 0.2 W/°C. The global heat transfer coefficient of the evaporator (UA)_evap is deduced using dynamic and steady state methods. This global heat transfer coefficient (UA)_evap is found equal to 0.3 W/°C. Finally the cooling capacity of the unit and the coefficient of performance are evaluated. The heating power supply to the generator necessary to ensure the desired state of this machine is found to be in the range of 35 W–45 W.     

Two La0.5Ag0.1Ca0.4MnO3 Manganite Nanoparticles Synthesized via Sol–Gel and Solid-State Methods–Structural,Magnetic, and Magnetocaloric Properties

Journal of Superconductivity and Novel Magnetism - La0.5Ag0.1Ca0.4MnO3 manganite nanoparticles are synthesized via two different ways, namely, a solid-state reaction (S1) and the sol–gel...     

Deflection Prediction of Steel and FRP-Reinforced Concrete-Filled FRP Tube Beams

This paper presents the results of experimental and theoretical investigations that study the flexural behavior of reinforced concrete-filled fiber-reinforced polymer (FRP) tubes (RCFFTs) beams. The experimental program consists of 10 circular beams [6 RCFFT and 4 control reinforced concrete (RC) beams] with a total length of 2,000?mm, tested under four-point bending load. The experimental results were used to review and verify the applicability of various North American code provisions and some available equations in the literature to predict deflection of RCFFT beams. The measured deflections and the experimental values of the effective moment of inertia were analyzed and compared with those predicted using available models. The results of the analysis indicated that the behavior of steel and FRP-RCFFT beams under the flexural load was significantly different than that of steel and FRP-RC members. This is attributed to the confining effect of the FRP tubes and their axial contribution. This confining behavior in turn enhanced the overall flexural behavior and improved the tension stiffening of RCFFT beams. For that, the predicted tension stiffening of steel and FRP-RCFFT beams using the conventional equations (steel or FRP-RC member) underestimates the flexural response; therefore, the predicted deflections are overestimated. Based on the analysis of the test results, the Branson’s equation for the effective moment of inertia of RC structures is modified, and new equations are developed to accurately predict the deflection of concrete-filled FRP tube (CFFT) beams reinforced with steel or FRP bars.     

Physicochemical characterization of low sulfonated polyether ether ketone/Smectite clay composite for proton exchange membrane fuel cells

Polyether ether ketone (PEEK) with a low sulfonation degree was blended using different proportions of sodium rich Smectite clay (3 and 6 wt%) to use as an electrolyte membrane for fuel cell application. The structural functionalities, surface morphologies, and the thermal stability of the resultant composite membranes were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, atom force microscopy, and thermo-gravimetric analysis. FT-IR showed that no chemical reactions take place between the sulfonated polyether ether ketone (SPEEK) and the clay with different ratios. XRD diffractograms illustrated a lower degree of crystallinity of the blended SPEEK than pristine SPEEK. The elaborated composite membranes proved to have a higher thermal stability than SPEEK. Furthermore, the SPEEK/clay composite membranes with 3 and 6 wt% in clay loading had higher water uptake and lower methanol uptake than those in pristine SPEEK It was also shown that, the incorporation of sodium ions rich Smectite clay layers between the clusters in SPEEK improved the conductivity to 2 × 10⁻² S/cm at 140°C (for 6 wt% in clay) without compromising the dimensional stability of the composite membranes. These results propose the composite membranes as a potential candidate for methanol fuel cells at temperatures above 120°C making SPEEK composite membrane competitive to that of Nafion membrane.     

Crystallographic Orientation in Pure and Aluminum-Doped Zinc Oxide Thin Films Prepared by Sol–Gel Technique

Novel sol–gel processes for the preparation of grain-oriented thin films of pure and aluminum-doped zinc oxide (AZO) are reported. Using various stabilizing ligands, oxide films with different degree of c -axis orientation could be prepared on amorphous substrates. The origin of orientation in sol–gel-derived ZnO and AZO films is investigated. The texture selection of ZnO films is independent of the heat-treatment schedule but sensitive to the precursor system. The electrical properties of the films do not depend significantly on the crystallographic orientation. The film visible transmittance remained higher than 90% even after vacuum annealing.     

Low-temperature processing and characterization of single-phase PZT powders by sol-gel method

A new sol-gel system using acetoin was developed and employed for the fabrication of PZT powders and films with compositions near the morphotropic phase boundary Pb(Zr_0.52Ti_0.48)O₃. Acetoin was used as chelating agent to replace the highly toxic methoxyethanol used in previous formulations. This route simplified the chemical processing of PZT-based solutions. Powders were completely crystallized by about 450 °C and contained the ferroelectric perovskite single phase. The firing temperature and time were to be the most important variables. Metallic lead formed only when excess Pb was incorporated. The precursor and the heat-treated powders have been characterized by using thermal analysis and X-ray diffractometry (XRD) studies. The average particle size, as measured from X-ray line broadening, was ∼35 nm.     

Optimization of submerged Aspergillus oryzae S2 α-amylase production

Food Science and Biotechnology - Use of 4 agro-industrial by products and organic materials as nitrogen sources for production of Aspergillus oryzae S2 α-amylase in liquid culture was...     

Thermal effects on GFRP rebars: experimental study and analytical analysis

The bond mechanism between Glass Fiber Reinforced Polymer (GFRP) bars and concrete is investigated through experimental testing and analytical modeling. This bond depends on several parameters such as temperature. The present paper studies the thermal effect, under high temperature up to 80°C, on bond behaviour at the interface GFRP bars/concrete through pullout-testing. These tests are conducted on specimens after 24 h of exposure at various temperatures. The thermal effect on an average short-term bond strengths and the pullout-load versus end-slip behaviours are compared to untreated specimens (20°C). Some pullout-tests on steel bars/concrete are also performed for the comparison. Experimental results show no significant change in the average bond strength for specimens subjected to temperatures up to +60°C. On the other hand at 80°C, there is a decrease of bond strength of about 22 and 28% for the 8 mm and the 16 mm diameter rods, respectively. An analytical model of the bond stress-slip response of a GFRP/concrete bar has been proposed. The results show good accuracy between the model and the experimental results.