利用iGPS进行大尺寸空间坐标测量的不确定度评估

iGPS是一种基于激光旋转扫描定位的网络式大尺寸空间坐标测量系统。为分析系统的空间坐标测量不确定度,建立空间坐标测量模型,分析影响系统测量精度的误差源,利用蒙特卡罗法进行了仿真。针对其典型的四站网络测量系统,对系统的测量不确定度进行评估,获得系统的误差分布规律,为iGPS现场大尺寸精密测量系统的具体应用提供有利的支撑。     

Synthesis and characterization of stannane-terminated poly(silole-co-germole) for the evaluation of luminescent polymeric light-emitting diode

Codehydrocoupling (with various inorganic hydrides) followed by stannane-capping (with Ph2SnHCI) of 1,1-dihydrotetraphenylsilole (1) and 1,1-dihydrotetraphenylgermole (2) (9:1 mol ratio) produces electroluminescent stannane-terminated poly(silole-co-germole)s (3) in high yield. The polymerization yield and molecular weight with Selectride increase in the order L-Selectride < N-Selectride < K-Selectride. The molecular weights increase in the order L-Selectride < Red-Al < N-Selectride < K-Selectride < Super-Hydride. The copolymer 3, a good candidate for PLED fabrication, emits at 523 nm and are electroluminescent at 521 nm. The fluorescence quantum yield of 3 in toluene is (1.61 +/- 0.29) x 10(-2). The emission color is green. The maximum brightness of the device is 3,750 cd/m2 with a luminous power efficiency of 0.67 Im/W.     

Designing light-emitting diode arrays for uniform near-field irradiance

We analyze the first-order design of light sources consisting of multiple light-emitting diodes (LEDs) to uniformly illuminate a near target plane by considering each single LED as an imperfect Lambertian emitter. Simple approximate equations and formulas are derived for the optimum LED-to-LED spacing, i.e., the optimum packaging density, of several array configurations to achieve uniform near-field irradiance.     

坐标测量机孔径测量的不确定度评定模型研究

以坐标测量机测量孔径为例,阐述测量过程中影响测量结果的不确定度来源,根据测量模型建立孔径测量的GUM法不确定度评定模型;利用对坐标测量机的测量系统量值特性指标分析的方法 ,给出基于量值特性分析法的各标准不确定度分量的评定模型。通过对汽车空调压缩机后缸体的孔径测量,比较两种方法评定的扩展不确定度。实例分析可以看出:对于坐标测量机复杂的非线性测量模型,GUM法在计算灵敏系数时,运算量较大且获得的是近似结果,因此其可操作性不强;量值特性分析法通过对测量系统整体的分析,基于大量的实验数据对测量结果进行测量不确定度评定,其流程和操作性更为便捷、有效。     

Sinusoidal phase-modulating interferometer insensitive to intensity modulation of a laser diode for displacement measurement

In sinusoidal phase-modulating laser diode interferometers, an injection current of a laser diode is sinusoidally modulated to scan the laser wavelength. However, the modulation of the injection current also involves an intensity modulation of the light, which increases the measurement error if a conventional signal processing is used. A novel signal processing for displacement measurement is proposed to eliminate the influence of the intensity modulation. Numerical simulation results and experimental results make it clear that an optimal depth of the sinusoidal phase modulation exists that can reduce the measurement error to a few nanometers.     

质量比较仪测量结果的不确定度评定

本文依据GJB3756-99（测量不确定度的表示及评定》和JJF1059-1999《测量不确定度评定与表示》，以CC500型质量比较仪为例，对质量比较仪测量结果不确定度进行了定性分析和定量分析。     

Hybrid normal-reverse prism coupler for light-emitting diode backlight systems

For the first time to our knowledge, a hybrid normal-reverse prism coupler was formed on the bottom surface of a light guide in a LED backlight system to achieve a thin, lightweight, LED backlight system. The hybrid prism coupler (HPC) simultaneously exhibits two functions: extraction of guided light from the light guide and focusing the radiated light from the light guide, corresponding to the optical functions of the prism and diffusive sheets used in conventional LED backlight systems. Therefore, using a HPC eliminates the prism and diffusive sheets that have been indispensable optical elements in conventional LED backlight systems, which consequently reduces the thickness of the LED backlight system by 40% compared with conventional systems.     

叶栅试验器气流角度测量不确定度评定

基于GJB 1179——1991《高速和低速风洞流场品质规范》和探针自动跟踪系统的具体特点和应用环境,该文阐述平面叶栅试验器探针自动跟踪测量系统的组成和工作原理,分析在流场测量中气流角度测量不确定度的影响因素。结合叶栅流场实测数据,阐述使用探针自动对向测量叶栅气流角度不确定度评定方法和步骤,并提出减小不确定度和叶栅流场精细化测量的相关措施。结果表明:自动对向测量在实际应用中优势明显,测量气流角度不确定度评定可为流场精细化测量提供数据参考。     

Partially coherent light-emitting diode illumination for video-rate in-line holographic microscopy

The light of a light-emitting diode or a common thermal source, such as a tungsten filament lamp, is known to be quasi-incoherent. We generated partially coherent light of these sources with a volume of coherence in the micrometer range of 5-100 μm3 by spatial and spectral filtering. The corresponding degree of partial coherence was adapted for microscopic interference setups, such as a digital in-line holographic microscope. The practicability of the sources was determined by the spectral emittance and the resulting signal-to-noise ratio (SNR) of the detector. The microscale coherence in correlation with the SNR and its resolution for microscopy were analyzed. We demonstrate how low-light-level, non-laser sources enable holographic imaging with a video frame rate (25 frames/s), an intermediate SNR of 8 dB, and a volume of coherence of 3.4×10(4) μm3. Holograms of objects with a lateral resolution of 1 μm were achieved using a microscope lens (50×/NA=0.7) and a CCD camera featuring a 4-12 bit dynamic range.     

Nitrogen doping of ZnTe for the preparation of ZnTe/ZnO light-emitting diode

Nitrogen-doped p-type zinc telluride (p-ZnTe) films are prepared by sputtering in a mixture of nitrogen/argon plasma. The effect of doping level N (ratio of N₂ flow rate to that for the mixed gas) in the range 0–10 % on the films properties is investigated. Heterojunction diodes are prepared on stainless steel flexible substrate from the p-ZnTe (doping level, N = 5 %) and solution-grown n-ZnO films. The junction parameters and light-emission properties of diodes are investigated. Doping level beyond N = 1 %, changes the cubic crystal structure of ZnTe to hexagonal and reduces the size of crystallites. At the doping level N = 2–4 %, films with the highest hole density of 2.5 × 10¹⁸ cm^?3 and lowest band gap energy of 1.4 eV are obtained. The diodes junction built-in potential and the donor density in n-ZnO films are found to be in the range 0.4–0.7 V and 1.5 × 10¹⁷–1.4 × 10¹⁸ cm^?3, respectively. Diodes exhibit electroluminescence in the UV and visible regions due to the band edge and defect emissions in ZnO.     

Automated optimization of an aspheric light-emitting diode lens for uniform illumination

In this paper, an automated optimization method in the sequential mode of ZEMAX is proposed in the design of an aspheric lens with uniform illuminance for an LED source. A feedback modification is introduced in the design for the LED extended source. The user-defined merit function is written out by using ZEMAX programming language macros language and, as an example, optimum parameters of an aspheric lens are obtained via running an optimization. The optical simulation results show that the illumination efficiency and uniformity can reach 83% and 90%, respectively, on a target surface of 40 mm diameter and at 60 mm away for a 1×1 mm LED source.     

Separated carbon nanotube macroelectronics for active matrix organic light-emitting diode displays

Active matrix organic light-emitting diode (AMOLED) display holds great potential for the next generation visual technologies due to its high light efficiency, flexibility, lightweight, and low-temperature processing. However, suitable thin-film transistors (TFTs) are required to realize the advantages of AMOLED. Preseparated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose because of their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report, for the first time, the demonstration of AMOLED displays driven by separated nanotube thin-film transistors (SN-TFTs) including key technology components, such as large-scale high-yield fabrication of devices with superior performance, carbon nanotube film density optimization, bilayer gate dielectric for improved substrate adhesion to the deposited nanotube film, and the demonstration of monolithically integrated AMOLED display elements with 500 pixels driven by 1000 SN-TFTs. Our approach can serve as the critical foundation for future nanotube-based thin-film display electronics.     

Spin Rabi flopping in the photocurrent of a polymer light-emitting diode

Electron spin is fundamental in electrical and optical properties of organic electronic devices. Despite recent interest in spin mixing and spin transport in organic semiconductors, the actual spin coherence times in these materials have remained elusive. Measurements of spin coherence provide impartial insight into spin relaxation mechanisms, which is significant in view of recent models of spin-dependent transport and recombination involving high levels of spin mixing. We demonstrate coherent manipulation of spins in an organic light-emitting diode (OLED), using nanosecond pulsed electrically detected electron spin resonance to drive singlet-triplet spin Rabi oscillations. By measuring the change in photovoltaic response due to spin-dependent recombination, we demonstrate spin control of electronic transport and thus directly observe spin coherence over 0.5 s. This surprisingly slow spin dephasing underlines that spin mixing is not responsible for magnetoresistance in OLEDs. The long coherence times and the spin manipulation demonstrated are crucially important for expanding the impact of organic spintronics.     

气相色谱法测定室内空气中TVOC的不确定度评定

根据GB／T18883—2002附录C建立气相色谱法测定室内空气中TVOC的不确定度数学模型,从测试程序分析了不确定度的来源,并计算各不确定度分量,得出合成标准不确定度和扩展不确定度。从中可以直观地发现测量TVOC不确定度的主要来源,从而在运用该检测方法时,可以从仪器本身和实验操作过程尽量减少一些不必要的不确定度,使检测结果更加准确。     

Mechanism of droplet generation in silver thin films for organic light-emitting diode displays

Thin silver film is widely used as the cathode in organic light-emitting diode displays and it is generally fabricated using the thermal evaporation method. But during the evaporation process, there is an inevitable outgassing problem and this creates high viscosity bubbles in melted silver. When the bubbles break, the high energy released scatters silver droplets which damage the silver surface. In this study, we were able to decrease the number of droplets from 6,171 to 278 with a degassing process of 400 °C for 6 h before proceeding with a thermal evaporation process.     

Localized surface plasmon-induced emission enhancement of a green light-emitting diode

The output enhancement of a green InGaN/GaN quantum-well (QW) light-emitting diode (LED) through the coupling of a QW with localized surface plasmons (LSPs), which are generated on Ag nanostructures on the top of the device, is demonstrated. The suitable Ag nanostructures for generating LSPs of resonance energies around the LED wavelength are formed by controlling the Ag deposition thickness and the post-thermal-annealing condition. With a 20?mA current injected onto the LED, enhancements of up to 150% in electroluminescence peak intensity and of 120% in integrated intensity are observed. By comparing this with a similar result for a blue LED previously published, it is confirmed that surface plasmon coupling for emission enhancement can be more effective for an InGaN/GaN QW of lower crystal quality, which normally corresponds to the emission of a longer wavelength.     

Thermal analysis of an 80 W light-emitting diode street lamp

Light-emitting diode (LED) street lamps rely heavily on successful thermal management, which strongly affects the optical extraction and the reliability/durability of the LED lamp. A thermal analysis of an 80 W LED street lamp was done. Sixteen thermocouples were used to measure the temperatures at 16 different positions of the street lamp. The results demonstrated that the temperature of the frame and the heat sink of the 80 W LED street lamp remained stable at about 42degC after several hours of lighting at a room temperature of 11degC, and the bulk material resistance of the heat sink could be neglected. Numerical simulation was also used to analyse the temperature distribution of the lamp. The reliability of the numerical model was proven by a comparison of simulation results with the experimental data. Through simulations and the corresponding analyses it was found that the tested 80 W LED street lamp would have poor reliability at an environment temperature of 45degC.     

Nanotexturing of GaN light-emitting diode material through mask-less dry etching

We describe a new technique for random surface texturing of a gallium nitride (GaN) light-emitting diode wafer through a mask-less dry etch process. This involves depositing a sub-monolayer film of silica nanospheres (typical diameter of 200 nm) and then subjecting the coated wafer to a dry etch process with enhanced physical bombardment. The silica spheres acting as nanotargets get sputtered and silica fragments are randomly deposited on the GaN epi-layer. Subsequently, the reactive component of the dry etch plasma etches through the exposed GaN surface. Silica fragments act as nanoparticles, locally masking the underlying GaN. The etch rate is much reduced at these sites and consequently a rough topography develops. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) inspections show that random topographic features at the scale of a few tens of nanometres are formed. Optical measurements using angle-resolved photoluminescence show that GaN light-emitting diode material thus roughened has the capability to extract more light from within the epilayers.     

有效值法交流共模抑制比测量不确定度评定

为解决影响工业现场的数据采集系统精度的共模干扰问题,以波形分析方式研究了交流共模干扰的表现形式,揭示了其同时含有直流偏移叠加交流波动和本底噪声的典型特征。提出以波形有效值幅度进行干扰强度表征,并进行共模抑制比的定量表述;同时使用有效值叠加模型对系统本底噪声的影响予以剔除,提高了共模抑制比的测量精度。基于该方法与流程讨论了其主要的不确定度来源—信号源误差、数据采集系统增益误差、幅度测量误差、幅度分辨力误差以及测量重复性等。进行了测量不确定度分析和评价,结合实例给出了通道共模抑制比的不确定度评价结果,验证了所述方法的实用性与可行性。