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1.
Dov Katz Arun Venkatraman Moslem Kazemi J. Andrew Bagnell Anthony Stentz 《Autonomous Robots》2014,37(4):369-382
Autonomous manipulation in unstructured environments will enable a large variety of exciting and important applications. Despite its promise, autonomous manipulation remains largely unsolved. Even the most rudimentary manipulation task—such as removing objects from a pile—remains challenging for robots. We identify three major challenges that must be addressed to enable autonomous manipulation: object segmentation, action selection, and motion generation. These challenges become more pronounced when unknown man-made or natural objects are cluttered together in a pile. We present a system capable of manipulating unknown objects in such an environment. Our robot is tasked with clearing a table by removing objects from a pile and placing them into a bin. To that end, we address the three aforementioned challenges. Our robot perceives the environment with an RGB-D sensor, segmenting the pile into object hypotheses using non-parametric surface models. Our system then computes the affordances of each object, and selects the best affordance and its associated action to execute. Finally, our robot instantiates the proper compliant motion primitive to safely execute the desired action. For efficient and reliable action selection, we developed a framework for supervised learning of manipulation expertise. To verify the performance of our system, we conducted dozens of trials and report on several hours of experiments involving more than 1,500 interactions. The results show that our learning-based approach for pile manipulation outperforms a common sense heuristic as well as a random strategy, and is on par with human action selection. 相似文献
2.
Mehdi Bidabadi Farzad Faraji Dizaji Hossein Beidaghy Dizaji Moslem Safari Ghahsareh 《中南工业大学学报(英文版)》2014,(1):326-337
In this work, the effect of various effective dimensionless numbers and moisture contents on initiation of instability in combustion of moisty organic dust is calculated. To have reliable model, effect of thermal radiation is taken into account. One- dimensional flame structure is divided into three zones: preheat zone, reaction zone and post-flame zone. To investigate pulsating characteristics of flame, governing equations are rewritten in dimensionless space-time ((, r/, ~) coordinates. By solving these newly achieved governing equations and combining them, which is completely discussed in body of article, a new expression is obtained. By solving this equation, it is possible to predict initiation of instability in organic dust flame. According to the obtained results by increasing Lewis number, threshold of instability happens sooner. On the other hand, pulsating is postponed by increasing Damk6hler number, pyrolysis temperature or moisture content. Also, by considering thermal radiation effect, burning velocity predicted by our model is closer to experimental results. 相似文献
3.
A resource investment problem with discounted cash flows (RIPDCF) is a project-scheduling problem in which (a) the availability levels of the resources are considered decision variables and (b) the goal is to find a schedule such that the net present value of the project cash flows optimizes. In this paper, the RIPDCF in which the activities are subject to generalized precedence relations is first modeled. Then, a genetic algorithm (GA) is proposed to solve this model. In addition, design of experiments and response surface methodology are employed to both tune the GA parameters and to evaluate the performance of the proposed method in 240 test problems. The results of the performance analysis show that the efficiency of the proposed GA method is relatively well. 相似文献
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5.
Antimicrobial effects of Zataria multiflora essential oil and Lactobacillus acidophilus on Escherichia coli O157 stability in the Iranian probiotic white‐brined cheese
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6.
Simulation of Propane Dehydrogenation to Propylene in a Radial‐Flow Reactor over Pt‐Sn/Al2O3 as the Catalyst
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Seyed M. Miraboutalebi Leila Vafajoo Mohammad Kazemeini Moslem Fattahi 《化学工程与技术》2015,38(12):2198-2206
Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial‐flow reactor over Pt‐Sn/Al2O3 as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a reversal of this trend was also revealed when the feed temperature was enhanced or when argon was added into the feed as an inert gas. 相似文献
7.
Aiming for the simultaneous realization of constant gain, accurate input and output impedance matching and minimum noise figure (NF) over a wide frequency range, the circuit topology and detailed design of wide broadband low noise amplifier (LNA) are presented in this paper. A novel 2.5–3.1 GHz wide-band LNA with unique characteristics has been presented. Its design and layout are done by TSMC 0.18 \(\upmu \hbox {m}\) technology. Common gate stage has been used to improve input matching. In order to enhance output matching and reduce the noise as well, a buffer stage is utilized. Mid-stages which tend to improve the gain and reverse isolation are exploited. The proposed LNA achieves a power gain of 15.9 dB, a NF of 3.5 dB with an input return loss less than \(-\) 11.6, output return loss of \(-\) 19.2 to \(-\) 19 and reverse isolation of \(-\) 38 dB. The LNA consumes 54.6 mW under a supply voltage of 2 V while having some acceptable characteristics. 相似文献
8.
Fracture mechanics‐based progressive damage modelling of adhesively bonded fibre‐reinforced polymer joints
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Aida Cameselle‐Molares Roohollah Sarfaraz Moslem Shahverdi Thomas Keller Anastasios P. Vassilopoulos 《Fatigue & Fracture of Engineering Materials & Structures》2017,40(12):2183-2193
A quasi‐static progressive damage model for prediction of the fracture behaviour and strength of adhesively bonded fibre‐reinforced polymer joints is introduced in this paper. The model is based on the development of a mixed‐mode failure criterion as a function of a master R‐curve derived from the experimental results obtained from standard fracture mechanics joints. Consequently, the developed failure criterion is crack‐length and mode‐mixity dependent, and it takes into account the contribution of the fibre‐bridging effect. Energy release rate values for adhesively bonded double‐lap joints are obtained by using the virtual crack closure technique method in a finite element model, and the numerically obtained strain energy release rate is compared to the critical strain energy release rate given by the mixed‐mode failure criterion. The entire procedure is implemented in a numerical algorithm, which was successfully used for predicting the strength and R‐curve response of adhesively bonded double‐lap structural joints made of pultruded glass fibre‐reinforced polymers and epoxy adhesives. 相似文献
9.
A series of polyamides were prepared by direct polyamidation of the p-Xylylene glycol with various commercially available dinitriles via Ritter reaction. All the synthesized polyamides showed
good solubility in amide type solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and dimethyl sulfoxide. They exhibited inherent viscosities in the range of 0.25–0.62 dl/g. Elemental
analysis, differential scanning calorimetry, thermogravimetric analysis, infrared and H1-NMR spectroscopies were used to characterize the polymers. According to the DSC analysis, the glass transition temperatures
of the polyamides were found to be 95–174°C. Thermogravimetric analysis indicated that the polymers show the 10% weight loss
temperatures in the range of 250–350°C. 相似文献
10.
An industrial scale propylene production via oxidative dehydrogenation of propane(ODHP)in multi-tubular reactors was modeled.Multi-tubular fixed-bed reactor used for ODHP process,employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows.Herein,a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence ole fin over V_2O_5/γ-Al_2O_3catalyst was presented.Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions,gas process and coolant temperatures,as well as other parameters affecting the reactor performance such as pressure.Furthermore,the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%.The optimized length of the reactor needed to reach 100%conversion of the oxygen was theoretically determined.For the single-bed reactor the optimized length of 11.96 m including 0.5m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72m for the first and 7.32 m for the second reactor were calculated.Ultimately,the use of a distributed oxygen feed with limited number of injection points indicated a signi ficant improvement on the reactor performance in terms of propane conversion and propylene selectivity.Besides,this concept could overcome the reactor runaway temperature problem and enabled operations at the wider range of conditions to obtain enhanced propylene production in an industrial scale reactor. 相似文献