Multiwalled Carbon Nanotubes Functionalized by Hyperbranched Poly(urea‐urethane)s by a One‐Pot Polycondensation

Summary: Hyperbranched poly(urea‐urethane)‐functionalized multiwalled carbon nanotubes (MWNT‐HPUs) have been synthesized by a one‐pot polycondensation of tolylene 2,4‐diisocyanate and diethanolamine in the presence of MWNTs terminated with multiple hydroxy groups. FT‐IR, Raman, ¹H NMR, and ¹³C NMR spectra reveal that the HPU trees are covalently grafted onto the MWNT surfaces. After a high density of HPU trees (83.5 wt.‐%) is attached to the MWNTs, core‐shell nanostructures with MWNTs as the core and the HPU trees as the shell are formed. A loose and uniform nanotube network can be observed by TEM, SEM, and AFM. The resulting MWNT‐HPUs are soluble in polar solvents such as dimethylformamide, dimethylacetamine, 1‐methyl‐2‐pyrrolidinone, and dimethyl sulfoxide.

Hyperbranched poly(urea‐urethane)s functionalized multiwalled carbon nanotubes.     

关于一类非线性微分方程的稳定性向题

本文研究了一类非线性微分方程的稳定性,所得结果推广了某些已知结论,并得到一些新结果.     

Study of interfering nuclear reactions in determination of platinum group elements by neutron activation analysis

Eighteen interfering nuclear reactions that likely occur in neutron activation analysis of platinum group elements are studied. Their degrees are calculated by the basic principle of activation analysis. The calculation results indicate that most of the nuclear interferences become significant only if the interfering elements exist in major amount and the elements of interest in trace amount. However, the second-order interference to platinum analysis from gold and the fission interference to analysis of ruthenium and palladium from uranium cannot be neglected even if the gold and uranium exist as trace constituents in samples. Project supported by the National Natural Science Foundation of China (Grant No. 19392100) and the China Postdoctoral Science Foundation.     

A study of six elements daily dietary intake of Chinese people

Neutron activation analysis (NAA) was used to determine the concentrations of 6 elements Cr, Co, Rb, Cl, Br and I in 12 kinds of Chinese diets. The daily dietary intakes of these elements in 4 areas groups of China were investigated and the analytical results were compared with other countries and WHO recommended dietary intakes.     

Measurement of the 158Sm mass excess by the (18O, 20Ne) reaction

A Q- value of 4.046 ±0.102 MeV has been determined for the two protons transfer reaction ¹⁶⁰Gd(¹⁸O, ²⁰Ne) ¹⁵⁸Sm at 98.95 MeV. This result yields a first experimental measured value of ? 65.738 ± 0.102 MeV for the mass excess of ¹⁵⁸Sm, the nucleus far from stability. The result is compared with current theoretical predictions.     

二次自催化反应系统的极限环

本文用广义旋转向量场的方法,证明了系统(1)在B≤A~2时,全平面无极限环;从而与文[1]的结论合在一起,完整地解决系统(1)极限环的存在性问题。     

卷积差技术在ESR和ESR成像中的应用

该文将卷积差技术应用于提高ESR谱的分辨率和在ESR成像过程中扣除固有线宽介绍了卷积差过程,对比了卷积差前后ESR谱的变化.     

小型宽带短波对数周期天线的设计

利用对数周期天线（LPDA）设计的基本理论和电磁场数值方法，详细分析了LPDA各参数与电性能之间的关系．针对传统方法设计LPDA纵向长度大和频带超过10个倍频程后次激励区明显破坏其宽带性能的问题，采用增大LPDA张角的方法来缩短纵向长度，提出了两种抑制次激励区的方法。同时寻找最佳的结构参数优化LPDA的性能．结合工程实际要求设计了一副1．5～30MHz的大张角LPDA．计算机模拟结果表明；该天线在20：1的超宽频带内驻波比小、方向图不分裂，纵向长度比传统方法设计的LPDA缩短一半以上．     

A Robust, Real-Time Voice Activity Detection Algorithm for Embedded Mobile Devices

When an Automatic Speech Recognition (ASR) system is applied in noisy environments, Voice Activity Detection (VAD) is crucial to the performance of the overall system. The employment of the VAD for ASR on embedded mobile systems will minimize physical distractions and make the system convenient to use. Conventional VAD algorithm is of high complexity, which makes it unsuitable for embedded mobile devices; or of low robustness, which holds back its application in mobile noisy environments. In this paper, we propose a robust VAD algorithm specifically designed for ASR on embedded mobile devices. The architecture of the proposed algorithm is based on a two-level decision making strategy, where there is an interaction between a lower features-based level and subsequent decision logic based on a finite-state machine. Many discriminating features are employed in the lower level to improve the robustness of the VAD. The two-level decision strategy allows different features to be used in different states and reduces the cost of the algorithm, which makes the proposed algorithm suitable for embedded mobile devices. The evaluation experiments show the proposed VAD algorithm is robust and contribute to the overall performance gain of the ASR system in various acoustic environments.     

Optimizing match on optical aperture and wave aberration in a small aberration system

Some formulae on correlative match of both optical aperture and wave aberration to determine image quality are derived in this paper. The optimizing match zone on optical aperture and wave aberration were found both theoretically and experimentally. The results are importantly different from traditional criteria for image quality.