High Efficient Methods of Content-based 3D Model Retrieval

Content-based 3D model retrieval is of great help to facilitate the reuse of existing designs and to inspire designers during conceptual design. However, there is still a gap to apply it in industry due to the low time efficiency. This paper presents two new methods with high efficiency to build a Content-based 3D model retrieval system. First, an improvement is made on the ＂Shape Distribution （D2）＂ algorithm, and a new algorithm named ＂Quick D2＂ is proposed. Four sample 3D mechanical models are used in an experiment to compare the time cost of the two algorithms. The result indicates that the time cost of Quick D2 is much lower than that of D2, while the descriptors extracted by the two algorithms are almost the same. Second, an expandable 3D model repository index method with high performance, namely, RBK index, is presented. On the basis of RBK index, the search space is pruned effectively during the search process, leading to a speed up of the whole system. The factors that influence the values of the key parameters of RBK index are discussed and an experimental method to find the optimal values of the key parameters is given. Finally, ＂3D Searcher＂, a content-based 3D model retrieval system is developed. By using the methods proposed, the time cost for the system to respond one query online is reduced by 75% on average. The system has been implemented in a manufacturing enterprise, and practical query examples during a case of the automobile rear axle design are also shown. The research method presented shows a new research perspective and can effectively improve the content-based 3D model retrieval efficiency.

Rapid and efficient method for isolating plant high molecular weight(HMW)DNA with high purity

PREPARATION of HMW DNA (Megabase-size) is the basis for construction of genomic library with large DNA inserts such as bacterial artificial chromosome (BAC) and yeast artificial chromosome (YAC), and for long-range physical mapping. It can also be used for the macro-study of repeat sequences. Since HMW DNA during preparation is inclined to be sheared physically and digested by internal nucleases, it is very difficult to prepare the HMW DNA. Initially, plant HMW DNA was prepared by embedding protoplasts in the low melting-point (LMP) agarose; however, it had several disadvantages: (ⅰ) Culture of protoplasts was time-consuming, costly and tedious. ( ⅱ ) It was only used successfully for limited

A highly efficient method for enriching TALEN or CRISPR/Cas9-edited mutant cells

In recent years,genome editing with site-specific nucleases,such as ZFN（zinc finger nuclease）,TALEN（transcription activatorlike effector nucleases）,and CRISPR/Cas9（the type II bacterial clustered,regularly interspaced,short palindromic repeats-associated protein 9）,has gained popularity for use in cell lines,animals,and plants（Urnov et al.,2010;Miller et al.,2011;Cong et al.

Low-cost method of fabricating large-aperture,high efficiency,Fresnel diffractive membrane optic using a modified moir technique

To reduce the cost and achieve high diffraction efficiency, a modified moir@ technique for fabricating a large- aperture multi-level Fresnel membrane optic by a novel design of alignment marks is proposed. The modified moire fringes vary more sensitively with the actual misalignment. Hence, the alignment accuracy is significantly improved. Using the proposed method, a 20 μm thick, four-level Fresnel diffractive polyimide membrane optic with a 200 mm diameter is made, which exhibits over 62% diffraction efficiency into the ＋1 order, and an efficiency root mean square of 0.051.