基于长度可调T形光声腔和掺铒光纤激光器的光声光谱气体浓度测量系统

应用光声光谱原理设计了气体浓度测量系统。针对C2H2气体运用了掺铒光纤激光器作为光源。光声腔为新型长度可调T形一阶纵向共振式光声腔，调制频率为1099Hz。将成熟的二次谐波检测技术作为信号处理的基本原理，采用三角波调制并得到受调制后光源输出信号曲线。将二次谐波系数与一次谐波系数的比值作为系统输出，并得到影响其因素的曲线关系。对不同浓度的乙炔气体的实验结果表明，该系统的检测灵敏度为9．634×10-6，信噪比为41.52dB。

基于插值样条的数控运动轨迹描述及平滑处理

为了更好地描述工程中复杂的数控加工运动轨迹,实现轨迹段间的平滑过渡,提出了一种基于特殊基函数的可调形三次三角插值样条曲线。该曲线具有C1连续性,可以精确表示直线、圆弧及自由曲线等常见工程曲线。给定控制点信息,改变调形系数,可以得到不同形状的插值样条曲线;通过在数控运动相邻加工段拐角处附近选择合适的控制点及调形系数,可以实现拐角的平滑过渡,从而保证运动路径的平稳、进给速度的连续。

基于三次三角插值样条的数控运动路径规划

为了更好地描述工程中复杂的数控加工运动轨迹,实现轨迹段间的平滑过渡,提出了一种基于特殊基函数的可调形三次三角插值样条曲线。该曲线具有一阶(C1)连续性,可以精确表示直线、圆弧及三次抛物线等常见工程曲线。给定控制点信息,改变调形系数,可以得到不同形状的插值样条曲线;通过在数控运动相邻加工段拐角处附近选择合适的控制点及调形系数,可以实现拐角的平滑过渡,从而保证运动路径的平稳、进给速度的连续,降低对机床的冲击。

自制可调角度楔形垫板在精确放疗摆位中的应用

目的比较自制可调角度楔形垫板（楔形垫板组）、负压真空垫（负压真空垫组）、普通软枕（普通软枕组）分别联合热塑头颈肩膜体位固定技术，在脊柱后凸畸形头颈部位肿瘤（含原发和继发）患者精确放疗摆位中的重复性。方法选择2014年6月-2016年4月期间入住本院的48例头颈部肿瘤患者．随机数字表法均分为3组，分别联合热塑头颈肩膜体位固定，以颅骨有茎突尖足方向末层中心点为参考点，对左茎突尖足方向末层中心点、定位坐标系原点在患者左右、头足、腹背（x、y、z）方向位置变化测量分析。结果与负压真空垫组相比，楔形垫板组摆位误差与坐标系转移误差结果差异无统计学意义（P〉0．05）；与普通软枕组相比，其他两组的三维摆位误差均有统计学意义（t=-6．99～-2．69，P〈0．05）；与普通软枕组相比，其他两组的三维坐标系转移误差均有统计学意义（t=-5．13～-2．71，P〈0．05）。结论自制可调角度楔形垫板在脊柱后凸畸形头颈部位肿瘤患者放疗摆位中简便且重复性好。

On approximating multifractal traffic burstiness with Markov modulated Poisson processes

We investigate the approximating capability of Markov modulated Poisson processes (MMPP) for modeling multifractal Internet traffic. The choice of MMPP is motivated by its ability to capture the variability and correlation in moderate time scales while being analytically tractable. Important statistics of traffic burstiness are described and a customized moment-based fitting procedure of MMPP to traffic traces is presented. Our methodology of doing this is to examine whether the MMPP can be used to predict the performance of a queue to which MMPP sample paths and measured traffic traces are fed for comparison respectively, in addition to the goodness-of-fit test of MMPP. Numerical results and simulations show that the fitted MMPP can approximate multifractal traffic quite well, i.e. accurately predict the queueing performance.

Adjustable transmission properties through ring-shaped nanotube arrays using finite-difference time-domain method

Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain （FDTD） method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra offing-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.

Design of Arbitrary Waveform Generator Based on Virtual Instrument Technology

A desiga of arbitrary waveform generator using NI PXI- 5412 module （an arbitrary waveform generator） was provided in this paper, based on virtual instrument technology and LabVIEW. The generator can produce standard function waveforms, such as sine, triangle, square wave with adjustable amplitude and frequency. It can also produce arbitrary waveforms of different data files importing by Analog Waveform Geaemtor Software. A heart dectric wavefonn was set as an example of arbitrary waveform generation. It has practical value, because the standard functions and heart electric waveforms generated by the generator can be used in laboratories.

Femtosecond Stimulated Raman Line Shapes:Dependence on Resonance Conditions of Pump and Probe Pulses

Resonance enhancement has been increasingly employed in the emergent felntosecond stimu- lated Raman spectroscopy （FSRS） to selectively monitor molecular structure and dynamics with improved spectral and temporal resolutions and signal-to-noise ratios. Such joint eflforts by the technique- and application-oriented scientists and engineers have laid the foundation for exploiting the tunable FSRS methodology to investigate a great variety of photosensitive systems and elucidate the underlying functional mechanisms on molecular time scales. Dur- ing spectral analysis, peak line shapes remain a major concern with an intricate dependence on resonance conditions. Here, we present a comprehensive study of line shapes by tuning the Rarnan pump wavelength from red to blue side of the ground-state absorption band of the fluorescent dye rhodarnine 6G in solution. Distinct line shape patterns in Stokes and anti-Stokes FSRS as well as from the low to high-frequency modes highlight the competition between multiple third-order and higher-order nonlinear pathways, governed by difl^rent res- onance conditions achieved by Raman pump and probe pulses. In particular, the resonance condition of probe wavelength is revealed to play an important role in generating circular line shape changes through oppositely phased dispersion via hot luminescence （HL） pathways. Meanwhile, on-resonance conditions of the Rarnan pump could promote excited-state vibrational modes which are broadened and red-shifted from the coincident ground-state vibrational modes, posing challenges for spectral analysis. Certain strategies in tuning the Raman pump and probe to characteristic regions across an electronic transition band are discussed to improve the FSRS usability and versatility as a powerful structural dynamics toolset to advance chemical, physical, materials, and biological sciences.

Hierarchical 3D mechanical parts matching based-on adjustable geometry and topology similarity measurements

A hierarchical scheme of feature-based model similarity measurement was proposed,named CSG_D2,in which both geometry similarity and topology similarity were applied.The features of 3D mechanical part were constructed by a series of primitive features with tree structure,as a form of constructive solid geometry(CSG) tree.The D2 shape distributions of these features were extracted for geometry similarity measurement,and the pose vector and non-disappeared proportion of each leaf node were gained for topology similarity measurement.Based on these,the dissimilarity between the query and the candidate was accessed by level-by-level CSG tree comparisons.With the adjustable weights,our scheme satisfies different comparison emphasis on the geometry or topology similarity.The assessment results from CSG_D2 demonstrate more discriminative than those from D2 in the analysis of precision-recall and similarity matrix.Finally,an experimental search engine is applied for mechanical parts reuse by using CSG_D2,which is convenient for the mechanical design process.

Resultant linear acceleration of an instrumented head form does not differ between junior and collegiate taekwondo athletes' kicks

Objective： The purpose of this study was to compare the effects of various taekwondo kicks and age （school level） in absolute terms and relative body mass on the resultant linear acceleration （RLA） of an instrumented head form. Methods： Forty-eight male （middle school： 16; high school： 16; university： 16） taekwondo athletes were recruited for this study. Subjects performed 10 turning, 10 jump spinning hook, and 10 jump back kicks on a Hybrid II head mounted on a height-adjustable frame. Results： A 2-way （School x Kick） MANOVA was used to determine the differences in RLA between schools （age groups） by type of kick. There was no univariate School main effect for absolute RLA （η2 = 0.06） and RLA relative to body mass （η2 = 0.06）. No univariate Kick main effects were found for absolute （η2 = 0.06） and relative RLA （η2 = 0.06）. Conclusion： It is of concern that RLA did not significantly differ between school levels, implying that young taekwondo athletes generate similar forces to their adult counterparts, possibly exposing young athletes to an increased risk for head ir^iuries.

Fabrication of ZnO with tunable morphology through a facile treatment of Zn-based coordination polymers

The morphology and structure of zinc oxide(ZnO), one of the important semiconductors, are relevant to its properties and applications. The preparation of ZnO with tunable morphology and desired structure is an attractive topic in the field of material synthesis. This work reports a facile method for the synthesis of Zn O with controllable morphology and crystal orientation using Zn-based coordination polymer particles(Zn-CPP) as precursors. Using hydrothermal method, Zn-CPP with morphologies of microrod, nanoplate, flower-like, arrow-tipped microsheet, and square cylinder were successfully synthesized via the coordination between metal ions Zn2+ and organic ligand 1,4,5,8-naphthalenetetracarboxylic dianhydride in aqueous solution. Subsequent thermal treatment of the Zn-CPP successfully resulted in the formation of porous Zn O with similar morphology to Zn-CPP. It is also found that the Zn O with enhanced(002) orientation could be obtained from Zn-CPP with preferred(002) orientation. This strategy could be extended for the preparation of other metal oxides with desired shape and structure.

A switchable and tunable ytterbium-doped fiber ring laser with a Sagnac loop mirror

A switchable and tunable ytterbium-doped fiber ring laser(YDFL) is reported and demonstrated. Employing a Sagnac loop mirror fabricated by an 85-cm-long polarization-maintaining fiber(PMF), the proposed YDFL can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1 064 nm. Both stable dual-wavelength lasing and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the proposed fiber laser with two different operation modes is rather stable at room temperature.