Verification of System Level Model Transformations

This paper presents Model Algebra (MA), a formalism for representing SoC designs at system level. We define the objects and composition rules of MA and show how system level models can be represented as expressions in this formalism. The formalism is applied to a system level design methodology, where design decisions are used to gradually transform the functional specification model of the system to a transaction level model with components and communication structure. Each transformation is represented as a manipulation of a model algebraic expression, and proven for correctness using the laws of model algebra. These laws are based on the well defined execution semantics and notion of functional equivalence for MA models. Our approach promises significant savings in the verification of system level models because only the first model needs to be verified using conventional techniques. All transformations of this model, derived using MA laws, are proven to be functionally equivalent.     

New method to determine the mechanical properties of heat treated steels

A new numerical approach to indentation problems is developed for hardened materials. A relationship between load, displacement, flow stress and strain hardening exponent of heat treated materials with a hard film, is given.This method is based on the minimisation of the error between the experimental curve (load–displacement of the indenter) and the theoretical curve, function of the mechanical and geometrical properties of the studied materials.Comparison of the numerical results with those experimentally obtained from known materials confirms the interest of the method proposed.     

Multi-criteria decision-making for controller placement in software-defined wide-area networks

The Journal of Supercomputing - Software-defined networks have many benefits such as more control over the control plane and reduced operating costs through separating the control plane from the...     

Comparison and Extension of Existing 3D Propagation Models with Real-World Effects Based on Ray-Tracing

The next generation of cellular network deployment is heterogeneous and temporally changing in order to follow the coverage and capacity needs. Active Antenna Systems allows fast deployment changes by cell shaping and tilt adaptation which have to be controlled in self-organized manner. However, such kind of automated and flexible network operations require a Self Organizing Network (SON) algorithm that works based on network performance parameters being partly derived from the radio measurements. Thus, appropriate radio propagation models are not only needed for network planning tools but also for simulative lab tests of the developed SON algorithm controlling the flexible deployment changes enabled by Active Antenna Systems. In this paper, an extension of the existing 3D propagation model is proposed in order to incorporate the propagation condition variation effects, not considered so far, by changing antenna beam orientation like antenna tilting or when users are distributed in the third dimension (height) in multi-floor scenarios. Ray tracing based generated propagation maps that show the realistic propagation effect are used as 3D real world reference for investigation and model approval.     

A New Analysis Method of the Dry Sliding Wear Process Based on the Low Cycle Fatigue Theory and the Finite Element Method

In the present work, a combination of a dynamic explicit finite element model and the low cycle fatigue theory is used to simulate the steady-state abrasive wear occurring between an as-cast eutectoid steel and a carbide-tungsten disk. While the low cycle fatigue theory has been used to model wear in softer non-ferrous alloys, this work shows its applicability and accuracy for use in harder alloys, such as the eutectoid steel used in this research which is strengthened with added chromium. The novelty of this work lies in calculating the Manson-Coffin relation constants from a coupled finite element model with experimental tests instead of the previously used Slip line method. The D Manson-Coffin constant, obtained around 2, is in agreement with previous works given in the literature showing that the low cycle fatigue is a general wear mechanism in the steady-state wear of the alloy tested in this work.     

Self-assembled micelles of well-defined pentaerythritol-centered amphiphilic A4B8 star-block copolymers based on PCL and PEG for hydrophobic drug delivery

Biodegradable star-shaped poly(?-caprolactone) (PCL) with four arms were synthesized by ring-opening polymerization (ROP) from a symmetric pentaerythritol core via the ‘‘core-first’’ strategy. Subsequently, two samples of the amphiphilic A₄B₈ star-block copolymers with symmetrical topologies [4s(PCL-b-2sPEG)] were synthesized by a macromolecular coupling reaction between carboxyl-terminated poly(ethylene glycol) (PEG) and 4-arm star-shaped PCL macromers with eight -OH end groups. The latter was prepared by attaching 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (HHMPA) to 4sPCL using a simple two-step reaction sequence. The in vitro cytotoxicity test indicated no apparent cytotoxicity. The amphiphilic star-block copolymers are capable of self-assembling into spherical micelles in water at room temperature, and they possess low critical micelle concentrations (CMCs) of 2∼8 mg/L in aqueous solution which was determined by fluorescence spectroscopy using pyrene as a probe. Transmission electron microscopy (TEM) measurement demonstrated that the micelles exhibit a spherical shape with a size range of 30∼50 nm in diameter. In addition, the hydrophobic and anticancer drug, quercetin, is loaded effectively in the polymeric micelles, suggesting that these new materials are appropriate candidates as hydrophobic drug nanocarriers.     

Compatibilization of poly(methyl methacrylate) and cellulose nanocrystals through co-continuous phase to enhance the thermomechanical properties

The present study focuses on enhancing the thermomechanical properties of poly(methyl methacrylate) (PMMA), a transparent and biocompatible polymer known for its high strength but limited toughness. The approach involves the development of PMMA/cellulose nanocrystals (CNCs) composites. To improve the interfacial compatibility between PMMA and CNCs, a two-step process is employed. Initially, the CNCs undergo oxidation using sodium periodate, followed by the introduction of amino groups through reductive amination. The aminated CNCs are then covalently bonded to PMMA via an amidation reaction using the “grafting onto” approach. Subsequently, the grafted CNCs are incorporated into the PMMA matrix using the solvent casting method. The resulting composites are extruded into filaments. Elemental composition analysis confirms CNC modification, revealing the presence of 1.6% nitrogen. The modified CNCs exhibit a higher degradation temperature than unmodified CNCs, showing a 50°C increase. The composites' dynamic mechanical analysis (DMA) reveals a 20% improvement in storage modulus (E′) upon incorporating 1.5% of the grafted CNCs into the PMMA matrix. This enhancement is attributed to the formation of co-continuous phases in the composite structure.     

Sunscreen Ingredient Octocrylene’s Potency to Disrupt Vitamin D Synthesis

Octocrylene is a widely used ingredient in sunscreen products, and it has been observed that the use of sunscreen has been increasing over the last few decades. In this paper, we investigated the way in which sunscreen’s ingredient octocrylene may disrupt normal vitamin D synthesis pathway, resulting in an imbalance in vitamin D levels in the body. The key techniques used for this insilico investigation were molecular docking, molecular dynamic (MD) simulation, and MMPBSA-based assessment. Vitamin D abnormalities have become very common in human health. Unknown exposure to chemicals may be one of the important risk factors. In molecular docking analysis, octocrylene exhibited a binding energy of −11.52 kcal/mol with vitamin D binding protein (1KXP) and −11.71 for the calcitriol native ligand. Octocrylene had a binding potency of −11.152 kcal/mol with the vitamin D receptor (1DB1), and calcitriol had a binding potency of −8.73 kcal/mol. In addition, octocrylene has shown binding energy of −8.96 kcal/mol with CYP2R1, and the calcitriol binding energy was −10.36 kcal/mol. Regarding stability, the root-mean-square deviation (RMSD), the root-mean-square fluctuation (RMSF), the radius of gyration, hydrogen bonding, and the solvent-accessible surface area (SASA) exhibited that octocrylene has a stable binding pattern similar to calcitriol. These findings revealed that incessant exposure to octocrylene may disrupt normal vitamin D synthesis.     

Maximum power point tracking of a proton exchange membrane fuel cell system using PSO-PID controller

Fuel cells output power depends on the operating conditions, including cell temperature, oxygen partial pressure, hydrogen partial pressure, and membrane water content. In each particular condition, there is only one unique operating point for a fuel cell system with the maximum output. Thus, a maximum power point tracking (MPPT) controller is needed to increase the efficiency of the fuel cell systems. In this paper an efficient method based on the particle swarm optimization (PSO) and PID controller (PSO-PID) is proposed for MPPT of the proton exchange membrane (PEM) fuel cells. The closed loop system includes the PEM fuel cell, boost converter, battery and PSO-PID controller. PSO-PID controller adjusts the operating point of the PEM fuel cell to the maximum power by tuning of the boost converter duty cycle. To demonstrate the performance of the proposed algorithm, simulation results are compared with perturb and observe (P&O) and sliding mode (SM) algorithms under different operating conditions. PSO algorithm with fast convergence, high accuracy and very low power fluctuations tracks the maximum power point of the fuel cell system.