Destruction of silica fiber cladding by the fuse effect

The phenomenon of destruction of silica fiber cladding by the fiber fuse effect has been observed for the first time to the authors' knowledge. Experiments on the optical discharge propagation along a fiber were conducted with fibers of decreased cladding thickness. The destruction of fiber cladding led to expansion of the optical discharge plasma and to a decrease of its density. This resulted in the termination of optical discharge propagation. The section of a fiber with decreased cladding thickness can act as a safety device to halt damage propagation.     

Polarization effect produced by the magnetooptical phenomena

The possibility of simultaneous measurement of the Faraday rotation and magnetic induced circular dichroism is discussed. The linearly polarized radiation under the action of the two mentioned phenomena is transformed into elliptically polarized one. The relation between parameters of the polarization ellipse and the parameters of the two studied phenomena is found.     

Tailored Pd-Au layer produced by conventional evaporation process for hydrogen sensing

Here we propose two methods using conventional evaporation process to produce tailored Pd/Au composite thin films for hydrogen sensing. In the first method Pd and Au are evaporated simultaneously using different evaporation rate. In the other, alternated nano-layer of Pd and Au are evaporated. Some characteristics of the thin films and their response to hydrogen when they are deposited over optical fibers are experimentally analyzed. Optical fiber sensors for detection of hydrogen concentration lower than 4% and response time of 10 s approximately are demonstrated. The possibility to precisely control the proportion of the constituents of Pd-alloys thin films to produce optical fiber hydrogen sensors with fast response makes these methods very attractive.     

Frequency selective IR-filter produced by using EB-lithography

This paper reports on the fabrication of Jerusalem cross diplexer by direct write electron beam (EB) lithography followed by reactive ion etching (RIE) on a phosphorus doped polished silicon wafer substrate. Such structures can be used as frequency selective components in visible, microwave and near infra-red wavelength region. Replication of the patterns is accomplished by micron or sub-micron order mould fabricated from the silicon (Si) master. Fourier transform infra-red reflectance (FT-IR) measurements were performed to characterize the structured patterns. The spectral reflectance from these patterns clearly show a reflection dip due to surface plasmon excitation in the near infra-red wavelength at about 1.42 and 2.5 μm, respectively. Potential applications such as antireflection surface (ARS) can be realized.     

Optical switching of fs laser produced Kα-radiation using the Borrmann effect

The Borrmann effect has been demonstrated in GaAs single crystals with ultra-short X-ray bursts from laser-produced plasmas. It was switched on ns time scales in crystals of two different thicknesses. In case of the thinner crystal a change in the line profile was observed while in the thick-crystal case a dramatic drop by 50% of the line intensity occurred. The results can be qualitatively explained by dynamical theory of X-ray diffraction for slightly deformed crystals.     

Validation of an extractive, airborne, compact TDL spectrometer for atmospheric humidity sensing by blind intercomparison

Accuracy, precision, repeatability and long-term stability, are the most important requirements to enable reliable airborne humidity measurements, which are needed for climate models or to validate e.g. remote sensing instrumentation like satellites. However, various hygrometer artifacts which depend on the individual sensor principle and the application profile frequently cause problems and significantly complicate the hygrometer choice. Sensor intercomparisons are one way of providing the information for an optimal choice. In this paper we present the first part of a blind, static, laboratory-based intercomparison of a new, calibration-free, 1.4 μm diode laser-based, optical hygrometer (SEALDH) with the two most important measurement principles for airborne hygrometry (frost-point hygrometers, FPH, and Lyman-alpha fluorescence hygrometers, LAFH). During three days of measurement, the TDL-hygrometer achieved a H₂O resolution of up to 0.5 ppmv (Δt=2 sec) at tropospheric pressure and H₂O concentration levels (100–800 hPa, 10 to 8000 ppmv H₂O). Its absolute accuracy was investigated via blind intercomparison with two reference FPHs and a LAFH. Without any calibration of SEALDH, i.e. without a comparison to a water vapor standard, we achieve an excellent agreement with the reference sensors, with an average systematic offset (over all three days) of ?3.9 %±1.5 %, which is fully consistent with the sensor’s uncertainty bounds. Further we also reevaluated the SEALDH data of day 2 and 3 in a calibrated mode using an independent set of FPH data from the first day and found an 8-fold accuracy improvement, yielding an excellent overall relative deviation of only 0.52 %±1.5 % with respect to a LAFH and a D/FH sensor.     

注意力机制融合前端网络中间层的语声情感识别

为了使机器能够更好地理解人的情感并改善人机交互体验,可对语声特征及分类网络进行融合以提升情感识别性能。本文从网络融合的角度,把基于梅尔倒谱系数和逆梅尔倒谱系数的二维卷积神经网络和基于散射卷积网络系数的长短期记忆网络作为前端网络,提取前端网络的中间层作为话语级的特征表示,利用压缩-激励(SE)通道注意力机制对前端网络的中间层的权重进行调整并融合,然后由深度神经网络后端分类器输出情感分类结果。在汉语情感数据集中进行五折交叉验证的对比实验,实验结果表明,基于SE通道注意力机制的网络融合方式可以有效地利用不同前端网络在语声情感识别任务中的优势,提高语声情感识别的准确率。     

Long-period fiber-gratings produced by exposure with a low-pressure mercury lamp and their sensing characteristics

A new production method of long-period fiber-gratings using neither a laser nor a fine-positioning system was proposed. A low-pressure mercury lamp emitting 254 nm ultraviolet light was used as a light source. Hydrogen-loaded Ge-B co-doped fiber was exposed to the emission of the lamp through an amplitude mask. A coupling loss up to 23 dB was obtained for a grating period of 212 μm. The maximum coupling loss for a grating period of 460 μm was 18 dB. The growth rate of the refractive index change by mercury-lamp exposure was 1.3 × 10⁻⁴/h. The temperature and strain characteristics were measured and compared with those fabricated by excimer-laser exposure. The temperature and strain sensitivities of long-period gratings with a period of 212 μm were higher than those of 460 μm. The temperature and strain sensitivities of those by mercury-lamp exposure were almost equal to those by excimer-laser exposure of the same fiber. The sensitivities of those by excimer-laser exposure of non-loaded fiber were higher than those of hydrogen-loaded fiber by mercury-lamp or excimer-laser exposures except for the temperature sensitivity of a grating period of 460 μm.     

Intense pulses of polarized electrons produced by Fano effect

A pulsed polarized electron source using the Fano effect on cesium is described in detail. A frequency doubled dye laser producing 2 mJ/pulse at 305 nm is used as the source of circularly polarized light. The light beam interacts with an array of 20 atomic beams. The atomic beam oven operates in a closed cycle thereby increasing running time by a factor of 30. Intensities of 3×10⁹ e ^?/0.5 μs with a polarization of 90% have been routinely obtained.     

Distance sensing using dynamic speckles formed by micro-electro-mechanical-systems deflector

We present a novel architecture of dynamic-speckles distance sensors with a micro-electro-mechanical system (MEMS) deflecting mirror for surface scanning. Since the MEMS mirror deflects the beam sinusoidally, the speed of scanning varies during the scan leading to sufficient variations in the signal frequency which is used to evaluate the distance to the object. Nevertheless, this feature does not affect the accuracy of range measurements when the distance is estimated from zero-crossing counts of the signal during a specially chosen time window within the scan. Experimental results indicate that a single 1 ms scan yields 70 μm accuracy of distance measurement. Averaging data from multiple scans of different surface areas during a 1-s measurement can provide approximately 2 mm of accuracy. Precision of the measurements can be further improved by optimization of the optical system. The compactness of the MEMS deflector and simplicity of the suggested signal processing provides a good basis for practical applications of this distance sensor.     

Thermographic measurement of the effect of humidity in mortar porosity

The objective of this analysis is to examine the influence of the moisture in the porosity measurement by means of thermal non-destructive test and ultrasound techniques. It is possible to determine the concrete durability by the calculation of its porosity. Porosity is determined in an indirect way, measuring mortar diffusivity by means of active thermography. Using ultrasound techniques, the porosity is related with the ultrasonic propagation of velocity. The diffusivity has been calculated using the W.J. Parker equation. In the ultrasound technique, using the pulse transmission method, ultrasonic propagation velocity was measured as a function of the water content. The conclusions express the correlation between both methods.     

利用超高速撞击产生的等离子体测量微粒速度的方法研究

超高速微粒在与靶物质撞击时会形成瞬时的等离子体.本文首次设计出两种传感器收集等离子体获取微粒到达传感器的时间,然后通过飞行时间法测量超高速微粒的速度.在等离子体驱动微小碎片加速器上开展了原理实验,采集到了微粒撞击产生的等离子体信号,测量到了超高速微粒的速度,验证了这种时间测量精度高、信噪比高的全新超高速微粒速度的测量方法.     

Relative line intensities in the argon L x-ray emission spectra produced by 0.3 to 3 keV electron impact

This note presents the first measurement of the relative intensities of the radiative processes of the L shell of argon. The partial emission cross sections are deduced. Our data show that the radiative transitions within the excited ion are very sensitive to the incident electron energy.     

Study on the design of ZnO/PANI composites and the mechanism of enhanced humidity sensing properties

ZnO/PANI composite humidity sensor was prepared by hydrothermal method. The first principles of density functional theory study the sensing mechanism. The calculation shows that the oxygen vacancy on ZnO surface is beneficial to the adsorption of water molecules. The {0 0 0‾1} crystal plane with the largest lattice oxygen number in ZnO has a strong adsorption capacity for water molecules, which is also conducive to improving the humidity sensitivity. PANI is easy to be combined on {0 1‾1 0} plane of ZnO, and it indirectly promotes the growth of {0 0 0‾1} plane, increasing the adsorption of water molecules and the proportion of H⁺ and H₃O⁺ ions. In addition, the N–H group in ZnO/PANI enhances the H⁺ conduction, which further improves the performance of the sensor. The results concluded that the proportion of lattice oxygen in humidity sensor is an important factor of humidity sensor sensitive detection.     

One-step method for measuring the effect of humidity on powder resistivity

We present a method for measuring powder resistivity as a function of moisture using a one-step process. The developed new resistivity cell consists of narrow horizontal electrode surrounded by a grounded guard electrode and simultaneous measurement of humidity within the powder bed. The system was modeled using computer simulations. As an example, resistivities of three different lactoses, wheat flour and quartz are presented. Resistivity was found to decrease several orders of magnitude between 10 RH% and 90 RH%. Simulated results showed that if no guard plate is used, measurement errors caused by humidity gradient are of order of magnitude.     

Crosstalk in high-speed WDM produced by refractive index fluctuation nonlinear effect

With the development of the ultra-high speed and large capacity, the channel crosstalk cause by nonlinear effects become more apparent. This paper research the crosstalk produced by refractive index fluctuation nonlinear effects, establish the corresponding mathematical models and physical monitoring models. The experiment simulation results show when the input power is less than 50 mW, the channel crosstalk caused by the nonlinear effects is low and can be ignored; when input power greater than 50 mW, the channel crosstalk caused by the nonlinear effects is more high and affect transmission quality; and with the further increase in power, the channel crosstalk caused by SPM and XPM gradual increase, when the input power is greater than 300 mW, the crosstalk caused by SPM and XPM morn than by FWM.     

Electron acceleration by laser produced wake field: Pulse shape effect

Analytical expressions are obtained for the longitudinal field (wake field: E_x), density perturbations () and the potential () behind a laser pulse propagating in a plasma with the pulse duration of the electron plasma period. A feasibility study on the wake field is carried out with Gaussian-like (GL) pulse, rectangular–triangular (RT) pulse and rectangular–Gaussian (RG) pulse considering one-dimensional weakly nonlinear theory (), and the maximum energy gain acquired by an electron is calculated for all these three types of the laser pulse shapes. A comparative study infers that the RT pulse yields the best results: In its case maximum electron energy gain is 33.5 MeV for a 30 fs pulse duration whereas in case of GL (RG) pulse of the same duration the gain is 28.6 (28.8)MeV at the laser frequency of 1.6 PHz and the intensity of 3.0 × 10¹⁸ W/m². The field of the wake and hence the energy gain get enhanced for the higher laser frequency, larger pulse duration and higher laser intensity for all types of the pulses.     

Damage zone produced by the bombardment of stainless steel using Ti nitride PVD coatings

This paper presents the damage zone and defects produced by TiN thin film deposition on stainless steel using DC magnetron sputtering to produce collisions between the TiN ions and the substrate. The PVD process used a low operative pressure, reducing the bombardment damage on the substrate, in comparison with other methods.Internal friction (IF) and elastic modulus measurements were carried out in TiN-PVD coated AISI 304 stainless steel, using a sub-resonant torsion pendulum (f ≅ 1 Hz) and a vibrant-reed instrument (f ≅ 10³ Hz). Some experiments showed several internal friction peaks, which are attributed to dislocation relaxation and to martensitic transformation from γ to α′. The characterization was carried out with X-ray, AFM and SEM. Analysis of X-ray peaks indicates a residual deformation in the order of 0.0005-0.0009 for γ-phase and 0.0006-0.00204 for α′-phase. Two methods are presented to determine the adhesion energy by IF in coated materials: for the first the enthalpy is determined by means of isochronal IF measurements, while for the second it is determined using isothermal measurements. These produce an image of damage caused by the bombardment on the substrate, especially of the residual defects.     

Dynamic speckle effect induced by an acousto-optic deflector for fast range sensing

A technique for fast distance measurements based on continuous frequency measurements of the power modulation of spatially filtered scattered light is proposed. For what is to our knowledge the first time, it is shown that the technique works when laser beam scanning is performed with an acousto-optic deflector. The most impressive feature of the proposed technique is that it works at very high scanning speed, providing an extremely fast response time. Experimental verification of the technique is demonstrated at a scanning speed as as high as 130 m/s. The proposed method of range sensing allows the design of a distance sensor possessing a response time as fast as 80 ns.