在均匀颜色空间中实现彩色图像的颜色量化

颜色量化是将原有图像中的多种颜色根据人的视觉效果归类为较少的颜色,从而用这些较少种类的颜色重新生成一幅新的图像,使量化后的图像与原图像的差别即量化误差最小.采用了将RGB非均匀颜色空间变换到L^*a^*b^*为基准的均匀颜色空间的方法,在L^*a^*b^*均匀颜色空间中对彩色图像进行颜色量化,从而解决了量化误差相对人眼不均匀的问题.首先将彩色图像的像素数据保存在单链表中,然后对链表进行扫描,并把本次扫描得到的色差最小的两个节点合并成一个新的节点.经过足够的动态运算后可得到量化处理后的图像调色板.实验结果表明,本方法具有普遍性、唯一性,可以减小量化误差,提高颜色量化的准确性.     

一种新的高分子聚合物光限幅特性的实验研究

报道了一种具有σ-π电子共轭轨道的硅聚合物的光限幅特性.在532nm波长,测量了不同浓度下样品的透射率与光强的关系.实验结果指出该聚合物具有较好的光限幅特性.利用Z扫描方法测定了该样品的有效双光子吸收系数β=3.5×10^-9cm/W.     

全光谱配色的匀色空间权重因子方法

在CIE 1976(L^*a^*b^*)匀色颜色空间中,本文为全光谱匹配方法提供一种权重因子。这种权重因子使∑_j[ΔE(λ_j)]²→min.实验结果表明,使用这种色差型权重因子进行计算机配色比Schmid和Strockash设计的两种权重因子效果好。     

高帧频电视跟踪器

本文介绍了高帧频电视跟踪器的原理及单元电路,提出了一种快速求目标重心的方法。目标重心位置与系统复合光轴的误差脱靶量在场扫描结束后0.1ms的时间内实时输出,采用此跟踪器后.子系统的跟踪精度在最大加速度为20°/s²最大速度为20°/s时可达到20”～30”。本文的最后给出了实验结果。     

CIE1976(L*a*b*)匀色空间颜色变量特性研究

CIE1976(L^*a^*b^*)颜色空间是较理想的匀色空间之一.为了使它获得更广泛合理的应用,人们继续对其进行探讨和改进.本研究利用心理物理评价实验,对该空间的诸变量特性进行了研究.     

Fizeau激光波长计测量脉冲激光波长

详细讨论了采用单片机控制的Fizeau波长计测量脉冲激光波长的两种方法,包括脉冲激光同步测量方法与软件判别捕捉方法,文章最后给出了系统的测量结果,其测量精度与测量连续激光相同,即绝对精度<10^-6,分辨率<10^-7.     

遥感数字图像分类编码软件仿真

图像分类法是一种自适应图像编码方案,文献^[1]提出了向量标量分类方法,对于普通图像进行自适应编码,具有编码辅助信息少编码效率高的特点.在卫星图像分类编码应用中,我们发现其编码效率体现的不明显.依据卫星数字图像边缘信息丰富,频谱中高频分量多的特点,在文献^[1]方法的基础上调整了频率划分的策略,提高了聚类效果.通过应用C++语言在计算机上进行仿真实验,结果表明分类编码效率明显提高.改进方法在卫星数字图像的自适应编码和高码率编码器设计中具有广泛的应用.     

1.0μm掺钕介质全固化调Q脉冲激光技术

以量子阱激光二极管(LD)为泵浦源、三价钕离子(Nd³⁺)晶体为增益介质、发射波长在1.0μm附近的全固体脉冲激光器团结构紧凑、性能可靠,而能够在许多方面得到广泛的应用.本文介绍了近年来这种全固化调Q激光技术的发展与运用,主要有主动(电光、声光)调Q激光器、被动调Q激光器等.实验表明,将Cr⁴⁺:YAG为代表的掺四价铬离子晶体作为被动调Q元件,能够实现这一波段内高重复率和高峰值功率的脉冲运转,为全固化低成本、中小功率/能量输出的脉冲激光器指出了一条具有实际意义的道路.     

像差在临界角方法探焦技术中的影响

分析了在临界角方法探焦技术中像差对测量灵敏度的影响。并给出了对两个显微物镜测量的结果。焦点探测试验精度为±1×10^-2μm.     

Henke型软X射线源的研制与测试

本文叙述了Henke型软X射线源的主要特点及研制、测试工作.我们研制的Henke源采用棱形靶、线焦点、可拆卸式结构.最大阳极电流可达100mA.本文还介绍了70m真空装置上的软X射线接收实验.终端计数率>3×10⁴/s·cm².     

Development of a 2-D flow solver on unstructured and adaptive Cartesian meshes

A two-dimensional flow solver using mixed grids has been developed for accurate and efficient simulation of steady and unsteady flow fields. The flow solver was cast to accommodate two different topologies of computational meshes: unstructured triangular meshes in the near-body region such that complex geometric configurations can be easily modeled, while unstructured adaptive Cartesian meshes are utilized in the off-body region to resolve the flow more accurately with less numerical dissipation by adopting a spatially high-order accurate scheme and solution-adaptive mesh refinement technique. The unstructured adaptive Cartesian meshes can be generated automatically and allow to handle data efficiently via quad-tree data structures. A chimera mesh approach has been employed to link the two flow regimes adopting each mesh topology. A second-order accurate vertex-centered scheme and a 3^rd- or 5^th-order accurate cellcentered WENO scheme has been utilized in the near-body region and in the off-body region, respectively. Validations were made for the unsteady inviscid vortex convection and the steady and unsteady turbulent flows over an NACA0012 airfoil, and the results were compared with other computational and experimental results.     

Adaptive filtering based system for extracting gearbox condition feature from the measured vibrations

Vibration signals measured from a gearbox are complex multi-component signals, generated by tooth meshing, gear shaft rotation, gearbox resonance vibration signatures and a substantial amount of noise. This article presents a novel scheme for extracting gearbox fault features using adaptive filtering techniques for enhancing condition features, meshing frequency sidebands. A modified least mean square (LMS) algorithm is developed and validated using only one accelerometer, instead of using two accelerometers in traditional arrangement, as the main signal and a desired signal is artificially generated from the measured shaft speed and gear meshing frequencies. The proposed scheme is applied to a signal simulated from gearbox frequencies with a numerous values of step size. Findings confirm that 10⁻⁵ step size invariably produces more accurate results and there has been a substantial improvement in signal clarity (better signal-to-noise ratio); which make meshing frequency sidebands more discernible. The developed scheme is validated via a number of experiments carried out using two-stage helical gearbox for a pair of healthy gears and one pair suffering from a tooth breakage with severity fault 1 (25% tooth removal), and fault 2 (50% tooth removal) under loads (0%, and 80% of the total load). The experimental results show remarkable improvements and enhance gear fault features. This paper illustrates that the new approach offers a more effective way to detect early faults.     

Experimental and numerical study of O/W emulsion lubricated strip rolling in mixed film regime

An experimental and numerical study of cold rolling lubricated by O/W emulsion has been carried out. The strip rolling experiment was carried out on a Hille experimental rolling mill with a view to study the performance of emulsion lubrication in terms of practical rolling parameters. Accordingly, rolling parameters such as rolling force and torque were measured. The experimental measurements compare favourably with the computed results from a numerical scheme developed by the authors. The scheme, based on a two-phase lubricant model, is capable of calculating the oil concentration at any point within the inlet zone and work zone, rolling pressure, film thickness, and fractional contact area ratio associated with strip rolling under mixed film lubrication at different rolling speeds. Using this scheme, the intertwined effects of an emulsion’s parameters such as: oil concentration, mean oil droplet size, and rolling speed on strip rolling were investigated. The numerical study encompassed the mixed film regime for speed, S ranges from 10⁻⁴ to 10⁻², supply oil concentration level λ_ds from 1 to 10%, and oil droplet size D _S from 5 to 10. Experimentally, the differences between water, oil and emulsion-lubricated rolling are not discernible except for film thickness. At a low speed of 10 RPM, force and torque of water-lubricated rolling are marginally higher than oil- or emulsion-lubricated ones. However, the difference between emulsion and neat oil is not apparent. The numerical results show the occurrence of a moderate oil concentration increase in the inlet zone followed by a sharp one at the beginning of the work zone. The effect of the concentration process is predominantly seen in the film thickness and the lubricant pressure whilst its effect on the total pressure is less pronounced. The analysis of the results suggests that it is possible to lower the emulsion oil concentration without any adverse effect on the rolling process. This principle can be used to control the outlet lubricant film thickness and hence the surface quality of the rolled strip.     

Shear force near-field optical microscope based on Q-controlled bimorph sensor for biological imaging in liquid

Shear force near‐field microscopy on biological samples in their physiological environment loses considerable sensitivity and resolution as a result of liquid viscous damping. Using a bimorph‐based cantilever sensor incorporating force feedback, as recently developed by us, gives an alternative force detection scheme for biological imaging in liquid. The dynamics and sensitivity of this sensor were theoretically and experimentally discussed. Driving the bimorph cantilever close to its resonance frequency with appropriate force feedback allows us to obtain a quality factor (Q‐factor) of up to 10³ in water, without changing its intrinsic resonance frequency and spring constant. Thus, the force detection sensitivity is improved. Shear force imaging on mouse brain sections and human skin tissues in liquid with an enhanced Q‐factor of 410 have shown a high sensitivity and stability. A resolution of about 50 nm has been obtained. The experimental results suggest that the system is reliable and particularly suitable for biological cell imaging in a liquid environment.     

Investigating material removal rate and surface roughness using multi-objective optimization for focused ion beam (FIB) micro-milling of cemented carbide

Cemented carbide has been investigated as a useful material for the fabrication of micro devices. Focused ion beam (FIB) micro-milling has been found to be one of the most appropriate methods for the fabrication of micro devices. The experimental FIB micro-milling on cemented carbide have been conducted according to the L₁₆ orthogonal array of Taguchi technique. Beam current, extraction voltage, angle of beam incidence, dwell time and percentage overlap between beam diameters have been considered as process variables of FIB micro-milling in experimental design. Material removal rate (MRR) and surface roughness have been determined experimentally for FIB micro-milling of cemented carbide and beam current has been identified as the most significant parameter. The minimum surface roughness of 5.6 nm has been reported on cemented carbide, which is not a usual practice to achieve on such polycrystalline material, and hence it may be considered as a significant research contribution. Maximum MRR of 0.4836 μm³/s has been reported. Moreover, genetic algorithm toolbox of MATLAB has been utilized for multi-objective optimization between MRR and surface roughness. The corresponding optimum values of MRR and surface roughness for multi-objective optimization have been represented by pareto optimum solution generated by genetic algorithm. The research work presented in this paper determines the setting of process parameters of FIB micro-milling for achieving a specific combination of MRR and surface roughness on cemented carbide.     

A new methodology to estimate starvation in ball bearings

In agreement with isothermal EHD theory, increases in speed and lubricant viscosity determine the increase in film thickness. Beyond certain limits, both speed and viscosity lead to a decrease in film thickness, as a result of thermal effects and starvation. To estimate starvation limits and film thickness in high-speed, mist-lubricated ball bearings, a new analytical methodology has been developed. This methodology is based both on the oil flow rate in ball-race contacts and Hamrock and Dowson's starvation theory. This new methodology has been used to estimate minimum film thickness in a 7206C angular contact ball bearing, axially-loaded, and rotated between 0 and 35,000 r/min⁻¹. Good correlation between computed and experimental values of the minimum film thickness have been obtained.     

The complex express evaluation of tribotechnical properties of antifriction aluminum alloys by sclerometric tests

The results of an investigation of experimental aluminum alloys proposed for replacing the highcost bronzes in friction units have been presented. The alloys were preliminarily selected using sclerometric tests based on the criterion of relative shear strength τ/σ_mc as being more informative compared with contact microcutting stress smc. Tribotechnical tests of selected alloys have been performed according to the three pins-on-disc scheme, which imitates the operation of the plane journal bearing. The results of tests confirmed the possibility of using these alloys as bronze substitutes. The structure and chemical composition of the surface of both initial samples and tested samples have been investigated. The influence of the chemical composition of the alloy on the tribotechnical properties of alloys under study has been shown.     

Rheology of Thin Organic Films

This paper deals with the effects of contact pressure and temperature on the shear strength of thin organic films. The experimental method involves depositing the material as thin films (ca. 3 nm to 500 nm) on smooth glass surfaces. The film is sheared by sliding over it indenters of fired glass. By varying the indenter radius from 4 μm to 2.5 mm and the load from 10 mg to 20 g, the contact pressure may be varied from 10⁷ Pa (1.4 × 10³ P.s.i.) to 8 × 10⁹ Pa (12 × 10⁵ p.s.i.). The temperature dependence of the shear strength is also studied. Two types of organic materials have been investigated. These range from simple low molecular weight compounds such as stearates, to more complex high molecular weight polymers, for example P.M.M.A.

The shear strength of these films has been compared with the bulk shear properties and consideration has been given to the molecular processes occurring during shear.     

A Ring Neutron Detector for a Time-of-flight Diffractometer Based on Linear Scintillation Detectors with Silicon Photomultipliers

A ring neutron detector has been developed for a time-of-flight diffractometer based on linear scintillation detectors. Light is transported over an organic glass light guide with a diffuse reflector. This scheme makes it possible to collect more photons than are collected in detectors based on wavelength-shifting fibers and to use avalanche photodiodes (SiPMs) instead of photomultiplier tubes. Testing confirmed that these detectors could be used as an alternative for widely used proportional neutron counters filled with ³He.     

A neutron field monitoring system for collider experiments

A monitoring system for intense (up to 10⁵ neutrons/(cm² s)) neutron fluxes with energies as high as 15 MeV has been developed for long-term operation in strong magnetic and radiation fields of collider experiments. The system is used to monitor the radiation shielding efficiency, estimate the radiation degradation of active elements of experimental setups, and perform additional independent monitoring of the accelerator luminosity. The system has been tested and put into operation at the Compact Muon Solenoid (CMS) experimental setup of the Large Hadron Collider (LHC).