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1.
In this paper, the problem of motion planning for parallel robots in the presence of static and dynamic obstacles has been investigated. The proposed algorithm can be regarded as a synergy of convex optimization with discrete optimization and receding horizon. This algorithm has several advantages, including absence of trapping in local optimums and a high computational speed. This problem has been fully analyzed for two three-DOF parallel robots, ie 3s-RPR parallel mechanism and the so-called Tripteron, while the shortest path is selected as the objective function. It should be noted that the first case study is a parallel mechanism with complex singularity loci expression from a convex optimization problem standpoint, while the second case is a parallel manipulator for which each limb has two links, an issue which increases the complexity of the optimization problem. Since some of the constraints are non-convex, two approaches are introduced in order to convexify them: (1) A McCormick-based relaxation merged with a branch-and-prune algorithm to prevent it from becoming too loose and (2) a first-order approximation which linearizes the non-convex quadratic constraints. The computational time for the approaches presented in this paper is considerably low, which will pave the way for online applications. 相似文献
2.
Arrays of precisely positioned single crystal silicon nanopillars, nanoneedles, and nanoblades with minimum feature sizes as small as 30 nm are fabricated using entirely scalable top-down fabrication techniques. Using the same scalable technologies, devices consisting of electrically connected silicon nanopillars with multiple addressable electrodes for each nanostructure are realized. The arrays of nanopillars, nanoneedles, and nanoblades are shown to exhibit Raman signal enhancement on 1,2-benzenedithiol monolayers, opening a path to nanodevices that manipulate, position, detect and analyze molecules. 相似文献
3.
Adhesion plays an important role in the final properties of nanocomposites. This study explored the surface interaction of
cellulose nanocrystals (CNCs) and the effect of CNC sources on adhesion between individual CNCs and the Si tip of an AFM cantilever
using a force mapping technique called FMap. The adhesion between CNCs and a Si tip from five different sources has been studied:
cotton, Whatman filter paper, hemp, softwood chemical kraft pulp, and softwood-dissolving pulp (alistaple). Mica was used
as the background substrate to act as an internal standard. This study’s findings suggest that adhesion is not the same for
all CNCs. Transmission electron microscopy and atomic force microscopy were used to determine the size and shape of each CNC.
The experimental quantitative data showed that adhesion between CNCs and the Si tip has a close correlation with the diameter
of the CNCs. X-ray photoelectron spectroscopy confirmed the presence of sulfate groups on the surface of the CNCs and a correlation
between adhesion and surface chemistry of the CNCs was observed. 相似文献
4.
Jalalzadeh-Esfahani Mehrnoosh Sedaghat Tahereh Beheshti Azizollah Azadi Roya 《Journal of Porous Materials》2022,29(4):1149-1164
Journal of Porous Materials - Benzimidazole functionalized mesoporous silica nanoparticles immobilized Pd(0)/Pd(II) has been proposed as an efficient catalyst for the one-pot preparation of biaryls... 相似文献
5.
Ahmadi Ameneh Sedaghat Tahereh Azadi Roya 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4126-4140
Journal of Inorganic and Organometallic Polymers and Materials - 3-Chloropropyltrimethoxysilane (CPTMS) was grafted on the surface of silica coated Fe3O4 core (Fe3O4@MCM-41) and then condensed with... 相似文献
6.
Fatemeh Asghari Roya Salehi Marziyeh Agazadeh Effat Alizadeh Khosro Adibkia Mohammad Samiei 《国际聚合物材料杂志》2016,65(14):720-728
The authors aimed to design nanofibrous (NF) scaffolds that facilitate odontogenic and osteogenic differentiation of human dental pulp-derived mesenchymal stem cells (DPSCs) in vitro. For this purpose, hydroxyapatite (HA)–loaded poly (L-lactic acid)/poly (?-caprolactone) (PLLA:PCL 2;1) blend NFs were prepared using the electrospinning method. Alizarin red activity and cell viability were evaluated by MTT assay, and SEM revealed the proliferation properties of NF scaffolds. QRT-PCR results demonstrated that HA-loaded PLLA/PCL can lead to osteoblast/odontoblast differentiation in DPSCs through the up-regulation of related genes, thus indicating that electrospun biodegradable PCL/PLA/HA has remarkable prospects as scaffolds for bone and tooth tissue engineering. 相似文献
7.
H. Sabet K. Ishii S. Matsuyama Y. Kikuchi K. Nakazawa A. Esmaili Torshabi H. Yamazaki 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2009,600(3):678-682
A new method to modify coordinates of detectors in any positron emission tomography (PET) system using a radioactive point source is developed. This method is based on selecting a centered detector in each detector block of PET and measuring coincidence counts between the two centered detectors in opposite detector blocks to find the coordinates of their LOR (Line of Response). Due to slight misalignment of detector positions, measured LORs may not intersect at a single point. Based on the proposed method, the coordinates of detectors can be measured with very high accuracy and the coordinate of the center of the gantry (which is normally the same as the center of field of view) can be defined correctly. The results of the application of our method to a small animal PET system (FinePET), which was recently developed at Tohoku University, Japan, are shown here. The method is expected to contribute to the design and development of PET systems which can realize a very high spatial resolution of less than 1 mm FWHM. 相似文献
8.
Ian Laboriante Maxwell Fisch Amir Payamipour Fang Liu Carlo Carraro Roya Maboudian 《Tribology Letters》2011,44(1):13-17
The evolution of morphology, electrical properties, and chemical composition has been studied in cyclically contacting polycrystalline
silicon (polysilicon) surfaces coated with perfluoroalkylsilane self-assembled monolayer (SAM). The microinstrument used is
a MEMS cantilever that is repeatedly actuated out-of-plane to impact a landing pad and is then moved in-plane to enable nondestructive
in situ inspection of the impacted area. Analyses show that a device with a monolayer coating exhibits signs of surface degradation
after a much higher number of cycles than its uncoated counterpart. A sharp increase in contact resistance between the cantilever
and landing pad is observed at ~10 billion cycles for a coated device, versus ~25 million cycles for an uncoated device. Likewise,
the onset of grain fracture in the landing pad occurs at ~25 billion cycles for the SAM-coated device, versus ~3 billion cycles
for its uncoated counterpart. The effectiveness of the monolayer coating diminishes after more than 100 billion contact cycles
as the SAM layer is removed, and the polysilicon substrate becomes susceptible to adhesive wear. 相似文献
9.
Sitra Esmaili M. E. Bahrololoom C. Zamani 《Surface Engineering and Applied Electrochemistry》2011,47(4):323-327
The giant magnetoresistance of electrodeposited NiFe/Cu multilayers from a single bath under potentiostatic control is studied.
The observed nonsaturating behavior urged us to investigate the probability of the occurrence of superparamagnetic regions
in these multilayers. In this research, for the first time, the presence of super-paramagnetic regions in electrodeposited
NiFe/Cu multilayers is shown and proved via high resolution transmission electron microscopy. The reason was found to be the
existence of a very large anodic transient at the beginning of the copper deposition pulse, which could be eliminated by choosing
a more negative potential. 相似文献
10.
Jaber Jahanbin Sardroodi Seyed Masood Seyed Ahmadian Gholam Reza Pazuki Moayad Hossaini Sadr Mahdi Esmaili 《Calphad》2006
The osmotic coefficient of the solution, activity of the solvent and activity coefficient of the solute in solutions of 1- and 2-naphthol in methanol and ethanol have been measured by the isopiestic method. The experimental osmotic coefficient data were correlated using the Non-Random Two Liquid model (NRTL), the Non-Random Factor model (NRF), the two suffix Margules equation and a polynomial in terms of the molality of the solute. The models give reliable results for the correlation of the osmotic coefficient data. The activity coefficients of 1- and 2-naphthol were evaluated according to the considered methods using the parameters obtained by the correlation of osmotic coefficients. 相似文献