Qu Yingdong

First-principle study on energy gap of CNT superlattice structure

By using the CASTEP modules based on density functional theory, the electronic structures of B/N pair co-doping (5, 5) CNT rings superlattice have been investigated. The calculation results show that the formation energies of B/N pair co-doping CNT rings are negative, indicating that the new type construction will probably be stable. The band structure and state density of the new type construction show that the energy gap is opened by B/N co-doping in (5, 5) metallic CNT and the metallic CNT is changed into a semiconductor. The energy gap of pure CNT is strongly sensitive to the changes of CNT diameter but the energy gap of B/N co-doping CNT rings remains stable when the diameters are in a reasonable scope, which means that the requirements for the production of CNT have been reduced. The compressive deformation effects mean that the energy gaps are narrowed, which is equivalent to enhancing the doping volume concentration. However, the changes of the energy gap under the tensile deformation effect are opposite. Achieving control of the electrical conductivity of CNT has an important significance for electron devices.

Analysis of principle deviation of subpixel Zernike moments operator

In original Zernike moments subpixel edge operator, ideal step edge model is chosen for calculating four parameters of a pixel point, and therefore principle deviation is caused by edge model. In order to discuss the effect of principle deviation on edge location, sampled edge model is chosen for calculating edge parameters, principle deviation of edge translation l is derived based on Zernike moments edge detection theory, and modified formula of l is given for Zernike moments operator with masks of 5 × 5 size. Both theory analysis and testing result demonstrate that principle deviation is zero when edge translation l is limited in central pixel of a sampled window. In another case, the modification of l should be considered, which results in edge location accuracy of non-subpixel level for this subpixel edge operator.

Characteristics of array holes with large aspect ratio in aluminum-based cast alloy

ABSTRACT Array holes were obtained by machining methods or nontraditional machining methods, and casting process was rarely used in the preparation of array holes. In this experiment, stainless steel thin rods coated with alcohol group graphite paint were chosen as cores to prepare array holes on aluminum-based cast alloys, and the roughness and roundness of holes were analyzed. The results show that array holes cast with 2 mm pitch of holes, 0.54 mm diameters, and large aspect ratio of 100 were obtained. The roundness and roughness of holes were influenced by consumption of carbon element from surface of hole core and wettability between molten metal and hole core surface; the lower roughness and the better roundness could be acquired under these experimental conditions. And roughness of holes (Ra) was about 6.3 µm, which is close to that obtained by machining, and the value of hole shape factor (K, characterizing the roundness of the hole) was above 0.7; the shape of the hole approached a circular shape.

Deposit Dimension Control with Using Single Neuron Self-learning PSD Controller During Spray Forming

A single neuron self-learning PSD controller is used to perform deposit dimension control during spray forming process. Simulation results show that control performance of PSD controller is satisfied, override and steady state error are zero at three predetermined target value, and corresponding response time is short too. PSD closed-loop control experimental results show that the average deposit thickness is 5.32mm in steady period, average error is 0.18mm between actual size and target value 5.5mm, maximum error is 0.28mm, and RMS(mean square root) of error is 0.23mm. Both simulation and experiment show that PSD controller is suitable for deposit dimension control owing to its self-learning and intelligent characteristic.