An approach to instruction set compiled simulator development based on a target processor C compiler back-end design

Many instruction set simulation approaches place the retargetability and/or cycle-accuracy as the key features for easier architectural exploration and performance estimation early in the hardware development phase. This paper describes an approach in which importance of speed and controllability is placed above the cycle-accuracy and retargetability, thus providing a better platform for software development. The main idea behind this work is to associate the compiled simulator effort with the development of the C language compiler for the target embedded processor, using the knowledge related to compilers and reusing some common software elements. Through the prototype design of a compiled simulator for the Cirrus Logic Coyote DSP architecture, many implementation aspects are presented showing that this approach has great potential.     

Calculated and experimental analysis of cause of the appearance of cracks in the running bogie frame of diesel multiple units of Serbian railways

In this paper an analysis of possible causes of crack occurrence on reconstructed diesel multiple units (DMU) exploited on sideline in Serbia was performed. Analyzed DMU were designed in the sixties of the last century in accordance with standards and UIC regulations of that time. During exploitation cracks appeared on the frame of the running bogie and they were locally repaired. With the purpose of eliminating this negative occurrence that has been reducing the availability of DMU, reconstruction of primary suspension and reconstruction of the DMU running bogie frame was performed. The new construction solution of primary suspension is with rubber springs. In the designing of the new running bogie frame fatigue loads were taken into account. After approximately two and a half years of exploitation, cracks appeared again on frames of the running bogie of DMU and they are the subject of this work. This work gives an analysis of the cause of crack occurrence and investigates links between specific exploitation conditions on tracks of Serbian railways and calculations/investigations performed using currently valid UIC regulations. The analysis also includes other influential factors such as welding quality, track quality, DMU and track maintenance quality.     

Influence of Impeller Diameter on Crystal Growth Kinetics of Borax in a Mixed Dual‐Impeller Batch‐Cooling Crystallizer

The influence of impeller diameter on crystal growth kinetics of borax decahydrate in a batch‐cooling crystallizer of non‐standard aspect ratio was evaluated. The dual‐impeller configuration consisted of a pitched‐blade turbine which was mounted below a straight‐blade turbine on a single shaft. Three different impeller‐to‐tank diameter ratios were investigated. In all experiments, mixing was conducted at just‐suspended impeller speed. To examine hydrodynamic conditions, mixing times were measured. The fluid flow pattern and velocity distribution were determined by computational fluid dynamics. Results showed that the smallest but also more regularly shaped crystals were produced in a system with standard diameter impellers. Product yield and power consumption were highest in this case.     

Automated construction activity monitoring system

Building activities are inadequately monitored during construction projects when attempting to satisfy the need for information, especially in those cases of unforeseen events and conditions on-site. Many IT-supported methods have been introduced, but so far none has been able to deliver satisfactory and reliable information. This paper presents a combined method, consisting of three components: an automated activity tracking subsystem based on image recognition, an automated material tracking subsystem, and a mobile computing supported communication environment. All subsystems are based on the same 4D model of a building.     

Variable neighborhood search and local branching

In this paper we develop a variable neighborhood search (VNS) heuristic for solving mixed-integer programs (MIPs). It uses CPLEX, the general-purpose MIP solver, as a black-box. Neighborhoods around the incumbent solution are defined by adding constraints to the original problem, as suggested in the recent local branching (LB) method of Fischetti and Lodi (Mathematical Programming Series B 2003;98:23–47). Both LB and VNS use the same tools: CPLEX and the same definition of the neighborhoods around the incumbent. However, our VNS is simpler and more systematic in neighborhood exploration. Consequently, within the same time limit, we were able to improve 14 times the best known solution from the set of 29 hard problem instances used to test LB.     

Single development project

An often-cited problem in undergraduate software engineering courses states that some topics are difficult to teach in a university setting and, although laboratory work is a useful supplement to the lectures, it is difficult to make projects realistic and relevant. In recognition of this problem, and based on our past experience, we started preparing a new course by examining the pedagogies and curricular aspects of software engineering that are important for the Net Generation of software engineers.The course project described in this paper concentrates on those aspects that can be dealt with effectively within the environment, i.e., the software lifecycle, system interdependences, teamwork, and realistic yet manageable project dynamics, all supported by various means of communication. The workload per students must be balanced with their lack of knowledge and skills, so that their unpreparedness to deal with complex issues does not abate their motivation.The approach was tested on six large projects over the period of one semester. We believe that the results reflect the students’ strong interest and commitment, and demonstrate their ability to stay focused and work at a level that is well above the obvious.     

Variable neighborhood search for the Vertex Separation Problem

The Vertex Separation Problem belongs to a family of optimization problems in which the objective is to find the best separator of vertices or edges in a generic graph. This optimization problem is strongly related to other well-known graph problems; such as the Path-Width, the Node Search Number or the Interval Thickness, among others. All of these optimization problems are NP-hard and have practical applications in VLSI (Very Large Scale Integration), computer language compiler design or graph drawing. Up to know, they have been generally tackled with exact approaches, presenting polynomial-time algorithms to obtain the optimal solution for specific types of graphs. However, in spite of their practical applications, these problems have been ignored from a heuristic perspective, as far as we know. In this paper we propose a pure 0-1 optimization model and a metaheuristic algorithm based on the variable neighborhood search methodology for the Vertex Separation Problem on general graphs. Computational results show that small instances can be optimally solved with this optimization model and the proposed metaheuristic is able to find high-quality solutions with a moderate computing time for large-scale instances.     

Electrospun PEO/rGO Scaffolds: The Influence of the Concentration of rGO on Overall Properties and Cytotoxicity

Reduced graphene oxide (rGO) is one of the graphene derivatives that can be employed to engineer bioactive and/or electroactive scaffolds. However, the influence of its low and especially high concentrations on scaffolds’ overall properties and cytotoxicity has yet to be explored. In this study, polyethylene oxide (PEO)-based scaffolds containing from 0.1 to 20 wt% rGO were obtained by electrospinning. Morphological, thermal and electrical properties of the scaffolds were characterized by SEM, Raman spectroscopy, XRD, DSC and electrical measurements. The diameter of the fibers decreased from 0.52 to 0.19 µm as the concentration of rGO increased from 0.1 wt% to 20 wt%. The presence of rGO above the percolation threshold (5.7 wt%) resulted in a significantly reduced electrical resistivity of the scaffolds. XRD and Raman analysis revealed delamination of the graphene layers (interlayer spacing increased from 0.36 nm to 0.40–0.41 nm), and exfoliation of rGO was detected for the samples with an rGO concentration lower than 1 wt%. In addition, an evident trend of increasing cell viability as a function of the rGO concentration was evidenced. The obtained results can serve as further guidance for the judicious selection of the rGO content incorporated into the PEO matrix for constructing electroactive scaffolds.