A new fuzzy-based potential field method is presented in this paper for autonomous mobile robot motion planning with dynamic
environments including static or moving target and obstacles. Two fuzzy Mamdani and TSK models have been used to develop the
total attractive and repulsive forces acting on the mobile robot. The attractive and repulsive forces were estimated using
four inputs representing the relative position and velocity between the target and the robot in the x and y directions, in one hand, and between the obstacle and the robot, on the other hand. The proposed fuzzy potential field motion
planning was investigated based on several conducted MATLAB simulation scenarios for robot motion planning within realistic
dynamic environments. As it was noticed from these simulations that the proposed approach was able to provide the robot with
collision-free path to softly land on the moving target and solve the local minimum problem within any stationary or dynamic
environment compared to other potential field-based approaches. 相似文献
This paper presents the theoretical background for the development of a constitutive model that is used in the simulation of the compaction of asphalt mixtures. The constitutive model is developed to comply with the principles of thermodynamics, and is derived to represent the macroscopic behaviour of an asphalt mixture as a highly compressible viscoelastic material. The paper presents the details of the mathematical formulation and the computational implementation of the model in the finite element package computer-aided pavement analysis 3D. The capabilities of the compaction model and its sensitivity to changes in model's parameters are illustrated using simple numerical applications. In a companion publication, (Masad et al., Finite element modelling of field compaction of hot mix asphalt. Part II: Application, International Journal of Pavement Engineering, Accepted, 2014), the model is verified against field compaction measurements which demonstrate the ability of the model to capture the general trends of the compaction observed in the field. 相似文献
We present here the design of a novel class of RNA inhibitors of the RNase H domain of HIV-1 RT, a ribonuclease activity that is essential for viral replication in vivo. Specifically, we show that small RNA hairpins and dumbbells can selectively inhibit the RNase H activity of HIV-1 RT without affecting other cellular RNases H (e.g., E. coli and human RNase H). These results suggest that the inhibitors do not interact with the nucleic acid binding site of RT RNase H, as this region should be well conserved among the various enzymes. The most potent inhibitors displayed IC50 values in the 3-8 microM range. Remarkably, the DNA polymerase activity, an intrinsic property of HIV RT, was not inhibited by the hairpin and dumbbell aptamers, a property not previously observed for any nucleic acid aptamer directed against RT RNase H. The results described here suggest a noncompetitive binding mechanism, as outlined in the differential inhibitory characteristics of each of the nucleic acid aptamers against the bacterial, human, and viral RNase H homologues. 相似文献
Asphalt concrete is the most widely used material for building the surface layer of pavements. It is a porous material that consists of a non-uniform arrangement of asphalt binder, aggregate particles and air voids. One of the primary factors controlling pavement performance is the fluid flow characteristics within the surface asphalt concrete layer.
This paper focuses on the numerical simulation of fluid flow in the three-dimensional (3-D) microstructure of asphalt concrete, and the calculation of permeability from the flow field. The asphalt concrete microstructure was captured using the non-destructive X-ray computed tomography (CT) technique. X-ray CT images were processed in order to identify and retain interconnected air voids and eliminate isolated voids. This image processing enhanced the efficiency of the model as it does not have to solve for flow in isolated voids that do not contribute to fluid flow. The X-ray CT images were analyzed and the results were used to determine the relationship between air void distribution and permeability directional distribution or anisotropy.
The computed permeability values were found to have good correlation with the experimental measurements. The major and minor principal directions of the permeability tensor were found to correspond to the horizontal and vertical directions, respectively. The results indicated that the non-uniform spatial distribution of air voids created more open flow paths in the horizontal directional than the vertical direction, and hence was the much higher permeability in the horizontal directions. 相似文献
This study presents the characterization of the nonlinearly viscoelastic behavior of hot mix asphalt (HMA) at different temperatures
and strain levels using Schapery’s model. A recursive-iterative numerical algorithm is generated for the nonlinearly viscoelastic
response and implemented in a displacement-based finite element (FE) code. Then, this model is employed to describe experimental
frequency sweep measurements of two asphalt mixes with fine and coarse gradations under several combined temperatures and
shear strain levels. The frequency sweep measurements are converted to creep responses in the time domain using a phenomenological
model (Prony series). The master curve is created for each strain level using the time temperature superposition principle
(TTSP) with a reference temperature of 40°C. The linear time-dependent parameters of the Prony series are first determined
by fitting a master curve created at the lowest strain level, which in this case is 0.01%. The measurements at strain levels
higher than 0.01% are analyzed and used to determine the nonlinear parameters. These parameters are shown to increase with
increasing strain levels, while the time–temperature shift function is found to be independent of strain levels. The FE model
with the calibrated time-dependent and nonlinear material parameters is used to simulate the creep experimental tests, and
reasonable predictions are shown. 相似文献
The generalized stability of families of real matrices and polynomials is considered. (Generalized stability is meant in the
usual sense of confinement of matrix eigenvalues or polynomial zeros to a prescribed domain in the complex plane, and includes
Hurwitz and Schur stability as special cases.) Guardian maps and semiguardian maps are introduced as a unifying tool for the
study of this problem. These are scalar maps which vanish when their matrix or polynomial argument loses stability. Such maps
are exhibited for a wide variety of cases of interest corresponding to generalized stability with respect to domains of the
complex plane. In the case of one- and two-parameter families of matrices or polynomials, concise necessary and sufficient
conditions for generalized stability are derived. For the general multiparameter case, the problem is transformed into one
of checking that a given map is nonzero for the allowed parameter values.
This research was supported in part by the National Science Foundation’s Engineering Research Centers Program, NSFD CDR 8803012,
and was also supported by the NSF under Grants ECS-86-57561, DMC-84-51515, and by the Air Force Office of Scientific Research
under Grant AFOSR-87-0073. 相似文献
Wind penetration into existing diesel systems to meet the load of a remote Jordanian village was assessed. Techno-economical
analysis and thousands of hourly simulations were performed to design an optimal hybrid wind–diesel power plant to serve the
loads of the village. The hybrid plant with 24% of wind-energy penetration, and comprised of five wind turbines and three
diesel generators was found to be the optimal plant and it becomes feasible for wind speeds in the order of 5 m/s and more
regardless of the diesel fuel cost. Utilizing this plant for electricity generation decreased the operational hours of the
diesel generators by 10.3% in comparison with the diesel only situation. This led to a decrease of 21.3% in the diesel consumption.
Consequently, 13.25 tons of greenhouse gas emissions can be avoided annually utilizing the proposed hybrid power plant for
electricity generation in place of the existing diesel only system. Based on the obtained results, the studied village in
particular and the remote Jordanian settlements in general are prospective candidates for deployment of the proposed hybrid
wind–diesel power plant for electricity generation. 相似文献
Moisture damage is a major factor in the deterioration of asphalt pavements. In order to combat this problem, it is essential to understand the effects of moisture on the adhesive and cohesive bonds in asphalt concrete mixtures. These effects can be quantified through the use of surface free energy, which is a thermodynamic material property that has been successfully used to select asphalt binders and aggregates that have the necessary compatibility to firm strong bonds and resist moisture damage.This study aimed at understanding the effects of material characteristics and additives on surface energy and the resulting bond between asphalt binders and aggregates. As such, the study involved measuring the surface free energy of 37 neat and polymer modified asphalt binders and 11 aggregates were measured. In addition, the surface free energy was measured for three asphalt binders after two anti-strip agents were added separately (six binder-anti-strip agent combinations) and for nine asphalt binders that were both short and long-term aged. The study also examined the effect of water pH on surface energy and water-aggregate adhesive bond. It was found that anti-strip agents, in general, reduced the cohesive bond energy of asphalt binder, allowing better wetting and adhesion to aggregates and increase in resistance to moisture damage. Aging of the asphalt either increased or decreased the cohesive bond depending upon the chemical composition of the unaged asphalt binder. Statistical analysis was conducted to rank the moisture resistance of asphalt binders and asphalt–aggregate combinations, respectively. The results showed that the pH of the water increased slightly due to contact with the aggregates, but did not significantly alter the total surface tension of the water or surface free energy components of the asphalt binder. 相似文献
As landfills mature, biodegradable matter in leachate is consumed and remaining compounds are increasingly recalcitrant. In this work, ferrate was compared to Fenton’s reagent for the purpose of removing nonbiodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20- and 12-year-old solid waste cells. Results from this study demonstrated that Ferrate and Fenton’s reagent had similar optimum pH ranges (3–5), but different organic removal capacities, ranging from 54 to 79% of initial leachate organic contents. An advantage of ferrate was that it was effective over a wide pH range. Advantages associated with Fenton’s reagent include that it had higher organic removal capacity, produced more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and produced more biodegradable byproducts (measured as chemical oxygen demand/5-day biochemical oxygen demand). Finally, both treatments were found to attack larger molecules (>1,000?Dalton), as indicated by an increase in smaller molecule contribution to organic carbon. 相似文献