圆周上带希尔伯特核的柯西奇异积分方程的数值解(英文)

本文研究了圆周上带希尔伯特核的柯西奇异积分的复合梯型公式.利用连续的分片线性函数逼近被积函数,得到积分公式的误差估计;然后用积分公式构造求解对应奇异积分方程的两种格式;最后给出数值实验验证理论分析结果.     

驱蚊原理的化学解读

介绍了蚊子的嗅觉系统、气味分子与气味结合蛋白和嗅觉受体蛋白作用的原理,并扼要介绍常用驱避剂DEET驱蚊原理的一种假说以及蚊虫驱避剂的发展前景。     

Multiple color-image fusion and watermarking based on optical interference and wavelet transform

A novel multiple color-image fusion and watermarking using optical interference and wavelet transform is proposed. In this method, each secret color image is encoded into three phase-only masks (POMs). One POM is constructed as user identity key and the other two POMs are generated as user identity key modulated by corresponding secret color image in gyrator transform domain without using any time-consuming iterative computations or post-processing of the POMs to remove inherent silhouette problem. The R, G, and B channels of different user identity keys POM are then individually multiplied to get three multiplex POMs, which are exploited as encrypted images. Similarly the R, G, and B channels of other two POMs are independently multiplied to obtain two sets of three multiplex POMs. The encrypted images are fused with gray-level cover image to produce the final encrypted image as watermarked image. The secret color images are shielded by encrypted images (which have no information about secret images) as well as cover image (which reveals no information about encrypted images). These two remarkable features of the proposed system drastically reduce the probability of the encrypted images to be searched and attacked. Each individual user has an identity key and two phase-only keys as three decryption keys besides transformation angles regarded as additional keys. Theoretical analysis and numerical simulation results validate the feasibility of the proposed method.     

In vivo bone regeneration using a novel porous bioactive composite

Many commercial bone graft substitutes (BGS) and experimental bone tissue engineering scaffolds have been developed for bone repair and regeneration. This study reports the in vivo bone regeneration using a newly developed porous bioactive and resorbable composite that is composed of bioactive glass (BG), collagen (COL), hyaluronic acid (HYA) and phosphatidylserine (PS), BG-COL-HYA-PS. The composite was prepared by a combination of sol-gel and freeze-drying methods. A rabbit radius defect model was used to evaluate bone regeneration at time points of 2, 4 and 8 weeks. Techniques including radiography, histology, and micro-CT were applied to characterize the new bone formation. 8 weeks results showed that (1) nearly complete bone regeneration was achieved for the BG-COL-HYA-PS composite that was combined with a bovine bone morphogenetic protein (BMP); (2) partial bone regeneration was achieved for the BG-COL-HYA-PS composites alone; and (3) control remained empty. This study demonstrated that the novel BG-COL-HYA-PS, with or without the grafting of BMP incorporation, is a promising BGS or a tissue engineering scaffold for non-load bearing orthopaedic applications.     

基于语义相似度与XGBoost算法的英语作文智能评价框架研究

作文智能评分和评语智能生成能极大减轻评阅专家的工作量、节约人力成本。目前,评分和评语结果的准确性与公平性尚不高。近年来,机器学习和自然语言处理等技术的快速发展,在一定程度上提升了文本分类、机器翻译等任务的性能,但仍有许多新的研究成果尚未应用于作文智能评价。本研究综合了词向量(word2vec)、段落向量(paragraph2vec)、词性向量(pos2vec)和LDA (latent dirichlet allocation)等特征,共同组合为作文的语义表示向量;采用基于kNN (k nearest neighbors)算法的语义相似度模型,得到作文的评语标签;采用基于XGBoost(extreme gradient boosting)的回归模型计算英语作文的评分值;并以900篇大学生英语作文为样本,构造算例进行验证。最后表明,提出的智能评价框架在英语作文自动评分和评语生成的准确性上,都要高于传统方法。     

Crystal structure of a new lithium indium borate Li3InB2O6

Single crystals of synthetic Li₃InB₂O₆ were obtained by heating a mixture of Li₂CO₃, In₂O₃ and B₂O₃; its formula was determined by the resolution of the structure from X-ray diffraction data. The compound is monoclinic, space group P2₁/n; the unit cell parameters are a=5.168(5) Å, b=8.899(9) Å, c=10.099(10) Å, β=91.112(17)°; Z=4. The crystal structure was solved from 669 reflections until R=0.0249; it exhibits a three-dimensional framework of vertex-sharing InO₅ trigonal bipyramids and BO₃ triangles, which isolates Li ions in channels. This structure is characterized by unusual oxygenated environments of In cations and of one of the three Li cations, which are forming more or less regular trigonal bipyramids. This compound melts incongruently at 827 °C; the powder may be obtained by annealing at 750 °C a mixture of Li₂CO₃, In₂O₃ and B₂O₃.     

An Improved Slice Reconciliation Protocol for Continuous-Variable Quantum Key Distribution

Reconciliation is an essential procedure for continuous-variable quantum key distribution (CV-QKD). As the most commonly used reconciliation protocol in short-distance CV-QKD, the slice error correction (SEC) allows a system to distill more than 1 bit from each pulse. However, the quantization efficiency is greatly affected by the noisy channel with a low signal-to-noise ratio (SNR), which usually limits the secure distance to about 30 km. In this paper, an improved SEC protocol, named Rotated-SEC (RSEC), is proposed through performing a random orthogonal rotation on the raw data before quantization, and deducing a new estimator for the quantized sequences. Moreover, the RSEC protocol is implemented with polar codes. The experimental results show that the proposed protocol can reach up to a quantization efficiency of about 99%, and maintain at around 96% even at the relatively low SNRs (0.5,1), which theoretically extends the secure distance to about 45 km. When implemented with the polar codes with a block length of 16 Mb, the RSEC achieved a reconciliation efficiency of above 95%, which outperforms all previous SEC schemes. In terms of finite-size effects, we achieved a secret key rate of 7.83×10−3 bits/pulse at a distance of 33.93 km (the corresponding SNR value is 1). These results indicate that the proposed protocol significantly improves the performance of SEC and is a competitive reconciliation scheme for the CV-QKD system.