Experience with an On‐board Weighing System Solution for Heavy Vehicles

Mining, construction, and other special vehicles for heavy use are designed to work under high‐performance and off‐road working conditions. The driving and executive mechanisms of the support structures and superstructures of these vehicles frequently operate under high loads. Such high loads place the equipment under constant risk of an accident and can jeopardize the dynamic stability of the machinery. An experimental investigation was conducted on a refuse collection vehicle. The aim of this research was to determine the working conditions of a real vehicle: the kinematics of the waste container, that is, a hydraulic rotate drum for waste collection; the dynamics of the load manipulator (superstructure); the vibrations of the vehicle mass; and the strain (stress) of the elements responsible for the supporting structure. For an examination of the force (weight) on the rear axle of a heavy vehicle, caused by its own weight and additional load, a universal measurement system is proposed. As a result of this investigation, we propose an alternative system for continuous vehicle weighing during waste collection while in motion, that is, an on‐board weighing system, and provide suggestions for measuring equipment designs.     

Influence of imperfect carrier recovery on satellite QPSK communication system performance

The purpose of this paper is to provide the theoretical approach for determining the bit error probability in detecting a coherent quaternary phase-shift-keyed signal transmitted over a soft-limited channel in the presence of the uplink and downlink noise, as well as the noisy carrier reference signal. The uplink noise is considered in the specific way through the envelope variations and the frequency offset of the signal remitted by the satellite station having influence on the variations of the phase-locked loop parameters in the receiving ground station, consequently on the probability density function of the phase error, i.e. the average bit error probability. The downlink noise is also taken into consideration. The determined results are based on the non-linear phase-locked loop model with primary emphasis on the degradations in the system performance produced by the imperfect carrier signal extraction. Copyright © 1999 John Wiley & Sons, Ltd.     

Referees for Volume 25 (2007)

Bidding strategies vary from contractor to contractor, each of which will have different degrees of sensitivity towards the factors affecting their bidding decisions. A competitor analysis using a linear mixed model is proposed for use by contractors as part of a more informed approach in identifying key competitors, and as a basis for formulating bidding strategies. The competitiveness between bids is examined according to: (i) project size, (ii) work sector; (iii) work nature; and (iv) number of bidders. The model was tested empirically by application to a bidding dataset obtained from a large Hong Kong contractor. Allowing for different degrees of sensitivity towards the four bidding variables across competing contractors (i.e. with the model parameters that varied across competing contractors), the results indicate that competitiveness in bidding of this contractor is generally greater than the majority of its competitors.     

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.     

Experimental determination of mechanical properties and short-time creep of AISI 304 stainless steel at elevated temperatures

The high temperature properties of AISI 304 stainless steel were studied.Basic data about the employed experimental equipment,testing procedures,and specimen geometry were given.The experimental setup was used to obtain stress-strain diagrams from tensile tests at room temperature as well as several elevated temperatures.Furthermore,the specimens were subjected to short-time creep tests at various temperatures.Stress levels for creep testing were established as a percentage of yield stress.The results indic...     

Tuning of BiFeO3 multiferroic properties by light doping with Nb

Bulk ceramic samples of BiFeO₃ were light doped (up to 1%) with Nb⁵⁺ in the place of Fe³⁺ (B-site doping) and their multiferroic properties were investigated using XRD, SEM, polarization (PMTS) and magnetization (SQUID) techniques. It is shown that even the small percentages of doping can notably change electric and magnetic behavior. Electric conductivity differs by two orders of magnitude between samples doped with 0.2% and 1% Nb. The ferroelectric behavior strongly depended on conduction mechanism, and transition from space-charge-limited current (SCLC) conduction to trap-filled limited (TFL) conduction regime reflected on a change in hysteresis patterns, particularly for the samples with 0.2% and 0.5% Nb. Separation of ZFC-FC magnetization curves occurred for all Nb concentrations and increased with Nb doping. Weak ferromagnetic behavior and the increase of remnant magnetization with Nb concentration was observed from the hysteresis measurements. Coercive field changed drastically compared to the pure BiFeO₃, namely, the sample with 1% Nb exhibited very high coercive magnetic field of ~ 10?kOe.     

Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor

Photocatalytic phenol dissociation was studied in a microreactor, with a TiO₂ layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015     

Time Domain Verification of Oscillator Circuit Properties

The application of formal methods to analog and mixed signal circuits requires efficient methods for constructing abstractions of circuit behaviors. This paper concerns the verification of properties of oscillator circuits. Generic monitor automata are proposed to facilitate the application of hybrid system reachability computations to characterize time domain features of oscillatory behavior, such as bounds on the signal amplitude and jitter. The approach is illustrated for a nonlinear tunnel-diode circuit model using PHAVer, a hybrid system analysis tool that provides sound verification results based on linear hybrid automata approximations and infinite precision computations.     

Packet error rate analysis of decode-and-forward free-space optical cooperative networks in the presence of random link blockage

This paper analyses end-to-end packet error rate (PER) of a free-space optical decode-and-forward cooperative network over a gamma–gamma atmospheric turbulence channel in the presence of temporary random link blockage. Closed-form analytical expressions for PER are derived for the cases with and without transmission links being prone to blockage. Two cooperation protocols (denoted as ‘selfish’ and ‘pilot-adaptive’) are presented and compared, where the latter accounts for the presence of blockage and adapts transmission power. The influence of scintillation, link distance, average transmitted signal power, network topology and probability of an uplink and/or internode link being blocked are discussed when the destination applies equal gain combining. The results show that link blockage caused by obstacles can degrade system performance, causing an unavoidable PER floor. The implementation of the pilot-adaptive protocol improves performance when compared to the selfish protocol, diminishing internode link blockage and lowering the PER floor, especially for larger networks.     

Human-like behavior of robot arms: general considerations and the handwriting task—Part I: mathematical description of human-like motion: distributed positioning and virtual fatigue

This two-part paper is concerned with the analysis and achievement of human-like behavior by robot arms (manipulators). The analysis involves three issues: (i) the resolution of the inverse kinematics problem of redundant robots, (ii) the separation of the end-effector's motion into two components, i.e. the smooth (low accelerated) component and the fast (accelerated) component, and (iii) the fatigue of the motors (actuators) of the robot joints. In the absence of the fatigue, the human-like performance is achieved by using the partitioning of the robot joints into “smooth” and “accelerated” ones (called distributed positioning—DP). The actuator fatigue is represented by the so-called “virtual fatigue” (VF) concept. When fatigue starts, the human-like performance is achieved by engaging more the joints (motors) that are less fatigued, as does the human arm. Part I of the paper provides the theoretical issues of the above approach, while Part II applies it to the handwriting task and provides extensive simulation results that support the theoretical expectations.