Permanent deformation of asphaltic materials has a major Contribution to rutting. Under static loading, the steady-state deformation of asphaltic materials is the key component of the permanent deformation. The steady-state deformation behaviour of a standard 70/100 penetration grade pure bitumen and two types of asphaltic mixtures used in the UK pavements, namely a 10mm Dense Bitumen Macadam (DBM), which is a dense graded mixture, and a 30/10 Hot Rolled Asphalt (HRA), which is a gap graded mixture have been studied. Using Dynamic Shear Rheometer (DSR) Constant stress creep tests were conducted on the bitumen at 10 degrees C and 20 degrees C over a range of stress levels. Uniaxial creep and constant strain rate tests have been conducted over a range of stress levels, strain rates and temperatures, and triaxial creep tests have been conducted over a range of stress levels and confining pressures on the mixtures. The steady-state deformation behaviour of the bitumen is found to be linear at stress levels less than 100 kPa and non-linear power law creep with a power exponent of 2.6 at stress levels higher than 500 kPa. The steady-state deformation behaviour of both mixtures is found to be well captured by the Modified Cross Model which predicts linear viscous behaviour at low stress levels and non-linear viscous behaviour at high stress levels. The steady-state deformation behaviour of the DBM mixture is found to be more sensitive to the stress level. The temperature dependency of the steady-state deformation behaviour is found to be well captured by the Williams-Landel-Ferry (WLF) equation. It is found that confinement has a stiffening effect on the steady-state deformation behaviour of the mixtures. The stiffening effect of the confining stress is found to be higher for the DBM mixture.
Bidding is a strategic decision that helps contractor firms to survive. Traditionally, bidding behaviors are highly unstructured in construction companies. This paper discusses the issues involved in evaluating a tender to assist the managers of a firm in making reliable and sound decisions. The emphasis of the work is on developing a logical decision making framework that covers organizational, environmental, risky and financial considerations.The model takes advantage of well-known decision making methods such as the analytical hierarchy process and the simple additive weighting. The model's input would be the linguistic description of each project's value with respect to the decision criteria, and the output would be the value of each project proposed to decision makers considering its correlation with existing projects. By means of a case study, the model has been implemented. The proposed decision making model is found to yield substantially improved solutions when large size contractors are concerned.
This paper reports on the capability of nonlinear quasi-static finite element modeling in simulating the hysteretic behavior of FRP-retrofitted reinforced concrete (RC) exterior beam-column joints under cyclic loads. For the purposes of our investigation, three concrete beam-to-column joint specimens (un-strengthened and FRP-strengthened) were selected. The ANSYS finite element software was used for modeling RC exterior joints. The specimens were loaded using a step-by- step load increment procedure to simulate the cyclic loading regime employed in testing. Additionally, an automatically reforming stiffness matrix strategy was used to simulate the actual seismic performance of the RC members after cracking, steel yielding, and concrete crushing during the push and pull loading cycles. The results show that the hysteretic simulation is satisfactory for both un-strengthened and FRP-strengthened specimens. Furthermore, when FRP strengthening is employed, strengthened beam-column joints exhibit a better structural performance than the un-strengthened specimens.
We present a new and efficient method for identifying the modulation type of a butrsty QAM signal in the presence of additive white Gaussian noise (AWGN) in umknown fading channels and with umknown carrier phase. Outr approach is based on an iterative combination of blind equalization and soft-clustering techniques, utilizes the constant modulus algorithm (CMA) for an initial reconstruction of the received signal constellation, and employs a nonpmametric soft clustering method to identify a small set of possible modulations based on the partition coefficient (PC) criterion. We then use an iterative approach in utilizing the decision adjusted modulus algorithm (DAMA) to refine om choices until we reach two hypotheses. Besides, we propose a parallel implementation of the proposed method, and provide an asymptotic analysis as well as simulation results to demonstrate the validity and usefidness of the proposed method. Simudatinn results indicate that outr proposed method achieves a significant gain as compared to the cmmdant-based approach for butrst mode transmissions in lading channels.
This paper presents the effect of preload, as one of the design parameters, on nonlinear dynamic behavior of a rigid rotor supported by gas-lubricated noncircular journal bearings. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using the Runge–Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under different operating conditions, dynamic trajectory, power spectra, Poincare maps, and bifurcation diagrams are used. Results of this study reveal how the complex dynamic behavior of two types of noncircular bearing systems comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center varies with changes in preload value.
To determine a safe substation grounding grid in power systems, it is important to compute the split factor for earth fault current including the proximity influences among the grid and the earthing systems of the incoming/outgoing transmission lines' towers. In this paper, a novel, simple and accurate method is developed for computing this factor that can correctly take into account the proximity effects. The results are compared with those that have been published (for the cases that they are able to compute) which show good agreement and accuracy.
Generation expansion planning is one of the major modules of power system planning studies, normally performed for the next 10-30 years. Optimal generation expansion planning is a non-linear and limited optimization problem. All solutions are compared to each other in order to reach final optimal solution. Some simplifications are made to reduce the problem dimensions which will not lead to unreal results. In this paper, WASP software package, one of the well known power expansion planning softwares, is used to optimize lran generation expansion planning. For modeling the power system, WASP uses the probabilistic simulation, while for optimization the dynamic programming method is used. In this paper, the generation system expansion planning is performed from 2009 till 2024 (a duration of 16 years). Finally, the sensitivity analysis is performed on the capital cost and the fuel cost of power plants.
Safety-critical systems such as medical and avionic ones are the systems in which failure to satisfy the user requirements may put man's life and resources in jeopardy. Since the adequate reliability of the software of such systems may be unobtainable via formal methods and the software testing approach single-handedly, verification of run-time behavior of software against user requirements violation is considered as a complementary approach. However, the synthesis of such a run-time verifier, hereafter we have called it a monitor, is confronted with the challenging problem of verifying low-level run-time behavior of target software against high-level user requirements violation. To solve this problem, we propose an approach in two phases. In the first phase, we obtain user requirements and then specify their violation formally. This formal specification is a high-level version of user requirements violations and should be mapped to a low-level one. To this end, in the second phase we extract a tabular automaton from the formal specification of user requirements violations in order to determine a state-based specification of the violations. This low-level specification, which constitutes the core of the monitor, determines those states which target software should not reach. To show the effectiveness of our approach, we apply it to the synthesis of a monitor for verifying behavior of the Continuous Insulin infusion Pump (CIIP) system.
Fluid flow and heat transfer are computed through a rib-roughened duct of square cross-section. The staggered ribs are attached along the two opposite walls of the channel to augment heat transfer. Simulations are performed with an incompressible SIMPLEC finite volume collocated code. Five different versions of k-ω and k-ε turbulence models are employed. The molecular Prandtl number is 0.71 and the Reynolds number based on the bulk velocity and the height of the channel is 100000. The predicted flow field and heat transfer show a relatively good agreement with the experimental results for different employed turbulence models, although the predicted flow field results are much better than the heat transfer results. Employing a variable turbulent Prandtl number according to the Kays and Crawford relation shows only a small difference in the estimated turbulent heat transfer fluxes. The influence of constant turbulent Prandtl numbers ranging from 0.5 to 0.92 is also examined and it is found that it has a significant effect on the simulation results of the heat transfer.
Thickness of compound layers formed on the surface of pure iron during the nitriding process was analytically calculated and compared with experimental data in the gaseous and plasma nitriding. Plasma nitriding was carried out on a high purity iron substrate at a temperature of 550°C in an atmosphere of 75 vol. % H2 and 25 vol. % N2 for various nitriding times. The thickness of compound layers was evaluated by several characterization techniques including optical microscopy, SEM and XRD. Using the Fick's first diffusion law and a mass conservation rule, two separate equations were developed for predicting the thickness of the binary compound layers; epsilon (ε) and gamma prime (γ′), in terms of the nitriding process parameters. The results of modelling indicated good agreement with the experimental data, provided that appropriate correction factors are applied. The flexibility and reliability of the models were increased by introducing two factors, Kε and Kγ′; the calculated curves corresponded well with both gaseous and plasma nitriding experimental data.
Phase variation of potential field data can be used as an interpretation method. This idea appears in edge detection with tilt angle or phase angle. The advantages of this quantity are its independency to body magnetization direction and also its easy computations. In this paper variations of this quantity termed local wave number are used for source parameter estimation such as body depth and susceptibility, which can be used without any prior information about source geometry. This method was applied on synthetic magnetic data and on the real magnetic data of an area in the Sar-Cheshme region. Using this method, causative body depth varies from 15 to 100 meters in different locations of the studied area, which is in agreement with the existing drilling information and forward modeling.
Enormous loss of production time in machining, handling and assembly operations is caused mainly by resources' unavailability. For this reason companies, both large and small, should optimize the production processes with the detection and elimination in advance of the majority of possible mistakes and disturbances that could cause deadlocks in the production process. The optimization tools which are available on the market are usually too expensive for smaller companies, which search for their competitive position in small quantity production. Therefore, a low cost simulation tool for the optimization of the resource present management is presented in this paper, where resources are treated as one of the main parameters in the production process and which could also enable smaller companies to optimize their production processes from the resource presence viewpoint.
The secondary suspension of most new EMU and DMU rail vehicles is equipped with air springs, to offer a good ride comfort to passengers. Air springs are a very important isolating component, which guarantees good ride comfort during the trip. In most rail-vehicle models developed by researchers, the thermo-dynamical effects of air springs in the rail-vehicle dynamics are not considered and secondary suspension is modeled by simple springs and dampers. As the performance of suspension components, especially for air springs, have significant effects on rail-vehicle dynamics and the ride comfort of passengers, a complete nonlinear thermo-dynamical air spring model, which is a combination of two different models, is introduced. Results from field tests show remarkable agreement between the proposed model and experimental data. Effects of air reservoir volume and the connecting pipes' length and diameter on the system performances are investigated here.
Bree's cylinder was used to show different material behaviors under constant mechanical and cyclic thermal gradient loadings. Bree showed different behaviors with the help of a diagram known by his name as Bree's diagram. In this research, the problem was reconsidered without his simplified hypothesis. The used material model is nonlinear kinematic hardening. The two dimensional problem and the Poisson's effect were considered. In order to obtain the Bree's diagram, return mapping algorithm was used. The results showed that the one dimensional model of Bree is conservative and the bi-dimensional Bree's diagram does not correspond to the complete model.
In the present paper, the effect of heat treatment on the surface roughness of AISI 4140 steel has been investigated by use of paired t-test and one way analysis of variance (ANOVA). The paired t-test was performed to determine the differences between the means before and after heat treatment. One way ANOVA was used to further evaluate the effect of heat treatment on the difference in variances between two groups. According to the statistical analysis, it was concluded that heat treatment has decreased the surface roughness at the 95% confidence level. The improvement of surface roughness varies from 37% to 45% with various combinations of experimental parameters.
In this study, loss of concrete-steel bond strength of lightweight and ordinary concrete under monotonic and cyclic loading is examined for plain and deformed steel bars. Here, lightweight and ordinary concrete-steel bond strength is determined by pull-out test for a variety of specimens in various configurations. For each specimen, a bond strength-slip curve is obtained through monotonic loading. Following this process, an identical specimen is subjected to cyclic loading under similar conditions using the same test setup. These examinations reveal several insights. Lightweight concrete-steel bond strength is greater than the ordinary concrete-steel bond strength for plain steel bars under monotonic loading. Ordinary concrete-steel bond strength is greater than lightweight concrete-steel bond strength under both monotonic and cyclic loading for deformed steel bars. The loss of concrete-steel bond strength is greater in plain bars than in deformed bars. Keywords– Concrete-steel bond, bond strength, lightweight concrete, ordinary concrete, monotonic and cyclic loading, plain and deformed bars, slip
Recently, several types of Distributed Generators (DGs) have been connected together to form a small power system called a micro grid (MG). MG usually operates in normal connecting mode and is connected to the main grid. If a fault occurs in the main grid, MG will transfer immediately to the islanding mode. This paper developed a complete model which can simulate, in detail, the dynamic performance of the MG during and subsequent to islanding occurrence. The developed model is used to investigate the effect of using storage batteries for enhancing MG dynamic performance during all modes. Two cases are studied, the first case discusses the effect of the islanding process on the frequency, voltages and active powers of all micro sources when there are no storage batteries installed inside the MG. The second studied case investigates the effect of islanding occurrence on the MG performance when MG is equipped with two storage batteries. In the two studied cases, wind speed and irradiance vary continuously. Results proved that the existence of storage batteries led to dramatic improvement in the dynamic performance of the MG during subsequent islanding occurrence. Also, MG performance, when exposed to a severe disturbance, led to an unacceptable frequency drop is studied and load shedding strategy activation during this situation is also highlighted.
This paper relates to rail mounted wide span gantry cranes and especially to the design of anti-skewing controller. The hereby presented algorithm provides skew elimination according to a simple, efficient and practically applicable method based on two absolute encoders and a skew controller realized in PLC. A safe and reliable operation, even in the case of components failure requires an additional compensator with minimal hardware requirements. Design points are outlined and characteristic results are shown. The proposed solution is experimentally verified in different industry branches.
Although Polypropylene (PP) fibers have advantageous characteristics, the weak bond with the cement matrix as a result of their smooth surface and chemical inertness remains a large limitation. It has been demonstrated that the fiber-matrix bond strongly affects the ability of fibers to stabilize crack propagation in the matrix. As the bond between fiber and matrix is mainly mechanical, it seems that incorporating nano-SiO2 into fiber reinforced cement composites provides a better bond with the matrix through pore refinement and better distribution of the hydration products. Hence, in this paper an effort was made to study the effect of PP fibers on the mechanical and physical properties of mortars incorporating nano-SiO2. Four fiber volume fractions, 0, 0.1%, 0.3% and 0.5% were considered. Compressive and flexural strength, water absorption and shrinkage of mortars were reported. SEM observation was also conducted to evaluate the effect of nano-SiO2 on the microstructure of cement paste. Results showed that nanoSiO2 significantly improved the mechanical and water absorption characteristics of mortars. It was observed that the microstructural characteristics of cement paste can be effectively improved by incorporating nano-SiO2, as the presence of nano-SiO2 enhanced the PP fibers effectiveness in strengthening mortar properties. Keywords– Cement mortar, nano-SiO2, silica fume, mechanical properties, shrinkage, SEM
This article deals with the problem of choosing the best possible shipping alternative among, a set of transportation modes based on four decision criteria. An Analytic Hierarchy Process (AHP)-like model was used to solve the problem. The developed model was run on a combination of rail road sea transportation, for Turkey. Instead of considering different commodity types, just the textile sector was modeled and studied for simplicity. The proposed model was shown to be very flexible with the considered criteria. Because of time and financial limitations the study area was restricted to Istanbul city. A short poll was conducted to find out the most important decision criterion for shippers. Subsequently, the first four most preferred criteria of the respondents were chosen to be embodied into the model. Finally, the model validity was proven by almost seventy percent accuracy along with the real life choices of the shippers.
