The Dynamic Volt-Ampere Characteristics of a Vacuum Arc at Intermediate-Frequency Under a Transverse Magnetic Field

In this study, the changes of a vacuum arc＇s appearance were observed and the volt-ampere characteristics of the vacuum arc at intermediate frequency were analyzed under a transverse magnetic field （TMF）. The TMF and phase shift time were calculated by using the TMF contact model and the large phase shift of the magnetic field at a higher frequency was conductive to the dispersion process of residual plasma. The arc velocity was higher at 800 Hz than at 400 Hz. It can be inferred that TMF will encourage arc movement at 800 Hz. Moreover, the arc movement has an impact on the arc voltage. Because of the increasing length of the arc column with a high arc velocity, the elongated arc causes the arc voltage to increase. Specifically, the volt-ampere characteristics of the vacuum arc are divided into three stages in this paper. The higher the frequency, the greater the initial rate of rise in the arc voltage and the larger the area surrounded by arc volt-ampere characteristics. The correlations between the arc voltage and the amplitude and frequency of the current are also presented.

VOLT-AMPERE CHARACTERISTICS OF CIS-POLY(PHENYL ACETYLENE)

The volt-ampere (Ⅰ-Ⅴ) characteristics of the c/s-poly (phenyl acetylene) (PPA) of cis-transoidal structure has been studied in the temperature range of 253-288K. An ITO/ PPA/ Au sandwich configuration was used for the measurements. Under an applied field of less than 10~5V/ cm it showed ohmic behavior, while the space charge limited current (SCLC) was observed at applied fields above 5×10~5V/ cm. In the ohmic region a conductivity of 1.37×10^(-16)S/ cm was obtained at room temperature with an activation energy of 0.5eV. These data indicate that the conduction is not intrinsic one but is the result of thermal release of trapped carriers. In fact the data in the SCLC region treated according to the theory for a single Gaussian distribution of traps gave a mean trap energy of 0.48 eV with a half-width of 0.4 eV and a total density of trapping states of 5×10^(16)/cm^3.

Luminescent characteristics of Ba_3Y_2(BO_3)_4:Eu^(3+) phosphor for white LED

The Ba3Y2（BO3）4：Eu^3＋ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5D0-TF2 transition of Eu^3＋, under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba3Y2（BO3）n：Eu^3＋ phosphor was effectively excited by ultraviolet （UV） （254, 365 and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the 613 nm emission of the Ba3Y2（BO3）n：Eu^3＋ phosphor was measured. The results showed that the emission intensity increased with increasing Eu^3＋ concentration, and then decreased. The CIE color coordinates of Ba3Y2（BO3）4：Eu^3＋ phosphor were x=0.641 and y=0.359 at 15 mol.% Eu^3＋.

Numerical Simulation on Thermal-Electrical Characteristics and Electrode Patterns of GaN LEDs with Graphene/NiO_x Hybrid Electrode

The thermal-electrical characteristic of a GaN light-emitting diode （LED） with the hybrid transparent conductive layers （TCLs） of graphene （Gr） and NiOx is investigated by a finite element method. It is indicated that the LED with the compound TCL of 3-layer Gr and 1 nm NiOx has the best thermal-electrical performance from the view point of the maximum temperature and the current density deviation of multiple quantum wells, and the maximum temperature occurs near the n-electrode rather than p-electrode. Furthermore, to depress the current crowding on the LED, the electrode pattern parameters including p- and n-electrode length, p-electrode buried depth and the distance of n-electrode to active area are optimized. It is found that either increasing p- or n-electrode length and buried depth or decreasing the distance of n-electrode from the active area will decrease the temperature of the LED, while the increase of the n-electrode length has more prominent effect. Typically, when the n-electrode length increases to 0.8 times of the chip size, the temperature of the GaN LED with the inm NiOx/3-1ayer-Gr hybrid TCLs could drop about 7K and the current density uniformity could increase by 23.8%, compared to 0.4 times of the chip size. This new finding will be beneficial for improvement of the thermal- electrical performance of LEDs with various conductive TCLs such as NiOx/Gr or ITO/Gr as current spreading layers.

Effects of Variable Lighting Intensity on Growth Characteristics and Nutritional Quality of Hydroponically Grown Arugula(Eruca sativa Mill.)

Arugula(Eruca sativa Mill.),as an edible medicinal vegetable of peculiar flavor,is served as uncooked dish.The influence of variable lighting intensity(LI)on the growth characteristics and nutritional quality of hydroponically grown arugula was investigated by using light-emitting diodes(LEDs)to light the hydroponically grown arugula for a reference for industrialized arugula production.The dynamic demands of arugula for LI in the seedling stage,initial growth stage and vigorous growth stage were tested under two light quality conditions including a red/blue light ratio of 7:1 and a light/dark photoperiod of 12 h/12 h.Then,the curves of variable LI-induced changes in the growth indices of arugula in different development periods were drawn.Next,the influence of variable LI on the growth characteristics and nutritional quality of arugula was investigated by measuring the dry/fresh weight ratio,chlorophyll content,vitamin C content and soluble protein content.Variable LI significantly increased the height,stem diameter,leaf width,dry/fresh weight ratio,chlorophyll content and soluble protein content of arugula plant.Plant height,stem diameter,dry/fresh weight ratio,chlorophyll content and soluble protein content were the highest in the group exposed to LI of 200,300 and 300μmol•m^(-2)•s^(-1)during the seedling stage,initial growth stage and vigorous growth stage,respectively.The greatest leaf width was achieved at LI of 100,250 and 350μmol•m^(-2)•s^(-1),respectively.High intensity LI markedly repressed the synthesis of vitamin C.

LED Modulation Characteristics in a Visible-Light Communication System

This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.

Effects of Light-Emitting Diode (LED) Red and Blue Light on the Growth and Photosynthetic Characteristics of <i>Momordica charantia</i>L.

With andromonoecious Momordica charantia L. (bitter gourd) as material, three light qualities (50 μmol·m-2·s-1) including white LED light (WL), blue monochromatic light (B, 465 nm), and red monochromatic light (R, 650 nm) were carried out to investigate their effects on seed germination, physiological and biochemical parameters, sex differentiation and photosynthetic characteristics of bitter gourd. The results showed that compared to the WL treatment, the R treatment significantly promoted seed germination, seedling height elongation and soluble sugar content, the B treatment significantly increased seedling stem diameter, reducing sugar content and soluble protein content, the R and B treatments both significantly reduced sucrose content, but their POD activity showed no significant difference. Compared with the R treatment, the B treatment significantly increased the total female flower number and female flower nod ratio in 30 nods of main stems. The study of photosynthetic characteristics found that the R and B treatments could effectively increase the stomatal conductance (GS) of leaves, significantly improved the net photosynthetic rate (Pn) compared to the WL treatment, and the effect of the B treatment was better. Compared to the R and WL treatments, the B treatment increased the maximum photosynthetic rate (Pmax), apparent quantum efficiency (AQE) and light saturation point (LSP), and reduced the dark respiration rate (Rd) and light compensation point (LCP) of the leaves. Fit light response curves showed that the adaptability and utilization of weak light in bitter gourd were middle or below, but it showed higher adaptability and utilization of strong light. Thus, it suggests that Momordica charantia is a typical sun plan with lower Rd. In summary, it is concluded that blue light has a positive effect on the seed germination, seedling growth, sex differentiation and improving the photosynthetic performance, and this will lay the foundation for artificially regulating optimum photosynthesis using specific LEDs wavelength, and help to elucidate the relationship how light quality influences the sex differentiation of plant.

Preparation and luminescence characteristics of Eu^(2+) activated silicate phosphor

This paper synthesizes the Sr2SiO4：Eu^2＋ phosphor by high temperature solid-state reaction. The emission spectrum of Sr2SiO4 ： Eu^2＋ shows two bands centred at 480 and 547 nm, which agree well with the calculation values of emission spectrum, and the location of yellow emission of Sr2SiO4 ： Eu^2＋ is influenced by the Eu^2＋ concentration. The excitation spectrum for 547 nm emission has two bands at 363 and 402 nm. The emission spectrum of white light emitting diodes （w-LEDs） based on Sr2SiO4 ： Eu^2＋ phosphor ＋ InGaN LED was investigated.

Experimental study on the jet characteristics of a steam plasma torch

Thermal steam plasma jet is promising for applications in environmental industries due to its distinctive characteristics of high enthalpy and high chemical reactivity. However, the performance of the steam plasma torch for its generation is limited by the problems of the large arc voltage fluctuation and serious erosion of the electrodes. In this study, a gas-stabilized steam plasma torch which can operate continuously and stably was designed. Experiments were conducted to reveal the effect of the different working parameters, including the anode diameter, the cooling water temperature, the arc current and the steam flow rate, on its Volt-Ampere characteristics, arc voltage fluctuation, thermal efficiency, jet characteristics and electrodes erosion. Results showed that the use of hot water to cool the electrodes can effectively prevent the condensation of steam on the inner wall of the electrodes, thus significantly reducing the arc voltage fluctuations and electrodes erosion. This is crucial for increasing the working life of the electrodes and ensuring long-term stability of the steam plasma torch. In addition, suitable anode diameter can greatly reduce the arc voltage fluctuation of the steam plasma torch and effectively improve the stability of the steam plasma jet. Furthermore, high arc current can effectively reduce the fluctuations of the arc voltage and increase the length and the volume of the steam plasma jet. Finally, using steam as the plasma forming gas can achieve higher thermal efficiency compared to air. An ideal thermal efficiency can be achieved by properly reducing the arc current and increasing the steam flow rate.

LED光源对小浆果生长发育影响研究进展

LED补光是设施栽培中实现小浆果优质高产的重要手段。近年来,国内外学者在LED光源对蓝莓、草莓、葡萄等小浆果的生长发育影响方面进行了大量研究工作。该文简要地总结了LED光源对小浆果组培苗及壮苗生长发育、光合特性、生理特性等指标的影响研究进展,为LED光源在小浆果及其它植物设施栽培应用方面提供理论依据和技术参考。

交流驱动无电学接触GaN基Micro⁃LED器件光电特性

针对Micro‐LED器件微型化带来的尺寸效应、高速巨量转移、发光器件与驱动背板的高精度键合等问题,本文通过金属有机化学气相沉积和原子层沉积技术制备了一种垂直结构的交流驱动无电学接触型GaN基Micro‐LED器件,研究了其光电特性。结果表明,器件电路模型可等效为RC电路,随着交流驱动信号频率的增大,器件等效阻抗先快速减小后趋于稳定。当频率固定时,器件I⁃V特性呈线性关系,器件等效阻抗稳定,器件亮度随着驱动电压增大而增强。当驱动电压固定时,器件在16~22 MHz频率范围内达到最大亮度,且亮度随频率增加呈现先上升后下降趋势;此外,由于回路呈电容特性,无电学接触型Micro‐LED器件存在发光延迟效应和电流超前效应。对比传统Micro‐LED器件,无电学接触型Micro‐LED器件与外部电极无电学接触,在交流驱动条件下实现内部载流子复合发光,有望解决Micro‐LED芯片微型化带来的技术难题。

Electrical and Optical Characteristics of Electrodeless Lamp

In order to study the methods to enhance the efficacy of electrodeless lamp,volt-ampere characteristics,illuminance and emission spectrum have been investigated in home-built electrodeless lamp experimental system with an electrodeless lamp in shape like QL 85 lamp.The results show that lamp current increases as lamp voltage increases in non-discharge,the current decreases first and then increases as the voltage increases in discharge.The illuminance of electrodeless lamp increases linearly with discharge power increasing,and it decreases linearly with power decreasing.The emission spectrum is different for different bulb and lighting time.The spectrum of Ar 811.5 nm,76.5 nm,750.4 nm and Hg 313.2 nm decrease with lighting time.While the intensity of Hg 407.8 nm increases with lighting time.

不同比例LED光源对生菜生长相关特性的影响

以生菜为试验材料,以LED灯板为人工灯源,探究红、蓝、白、绿光源在3种不同组合和比例下(T_(1),R∶B∶W=3∶1∶3;T_(2),R∶B∶W=3∶1∶1;T_(3),R∶B∶G=8∶3∶1)对生菜水培品质、形态以及光合特性的影响。结果表明,T_(3)模式下生菜地上部重量、地下部重量、叶片数、全株重量高于其他模式。总体而言T_(3)模式下生菜的生长情况最佳;T_(2)模式下的生菜叶绿素a含量、叶绿素b含量、叶绿素总含量、类胡萝卜素含量以及净光合速率高于其他模式,而生菜的胞间二氧化碳浓度T_(3)模式高于其他模式,生菜的蒸腾速率以及气孔导度T_(1)模式高于其他模式,说明T_(2)模式下生菜的光合特性最佳。T_(2)模式下生菜的可溶性蛋白含量最高,T_(3)模式下生菜的可溶性糖含量最高,总体而言T_(3)模式下生菜的品质显著高于其他处理。综合分析得出T_(3)模式(R∶B∶G=8∶3∶1)的光源处理是生菜生产最佳的组合。

高频驱动GaN-LED的频率响应特性研究

高刷新率显示器对氮化镓基发光二极管(GaN-LED)驱动频率提出更高的要求,因此研究GaN-LED的频率响应特性具有重要意义。研究了方波交流电压驱动下GaN-LED发光强度的频率响应特性。结果表明,LED的发光强度波形与电压波形存在固定的迟滞时间(约27 ns),且该迟滞时间不随驱动频率改变。在所施加的交流驱动频率范围内(100 kHz~50 MHz),发光强度呈现四个不同的区域:即随着频率的升高,LED发光强度先保持稳定,随后下降,再次上升,最后衰减直至停止工作。文中阐述了形成四个区域的原因。该研究有望为基于LED的超高帧速率显示器件驱动设计提供依据。

面向可见光通信的LED空间辐射特性仿真实验研究

LED已经广泛渗透到大众生活的照明、指示、通信、定位等众多领域。特别是在可见光通信领域,LED自身的空间辐射特性主导了其在不同可见光通信场景的实际性能。实际上,如何基于不同类别、不同复杂程度的光源辐射特性解析模型,平滑地实现LED光波束三维建模及直观展示,仍然缺少针对性的阐述和讨论。面向各类新型光源应用对LED空间辐射特性的表征实验需求,本文提出了面向LED朗伯辐射特性、对称非朗伯辐射特性以及非对称非朗伯辐射特性空间建模及直观展示的仿真实验方法。该方法能够满足商用迥异LED光波束的三维展示需求,同时能够满足对LED空间辐射特性进行针对性地二维剖析需求。此外,上述工作为后续开展可见光通信组合光波束的优化设计提供了路径和便利。

不同光质对树莓组培苗生长的影响

该研究以树莓‘秋红’为试验材料,探究在红蓝光基础上添加不同单色光质对其组培苗生长及光合特性的影响,筛选有利于树莓组培苗生长的较佳光质。试验结果表明,红蓝光(2∶1)+15%绿光处理更有利于树莓组培苗的生长,其茎粗、生根率、根长、单株鲜重和干重均优于荧光灯和红蓝光(2∶1)处理的,叶绿素含量、净光合速率(Pn)、实际光化学效率(Y[II])、相对电子传递速率(rETR)均表现出较佳的优势,可推荐作为树莓组培苗较优的组培光质。

LED复合光质对洛阳红形态和生理特性的影响

本试验以牡丹年宵花洛阳红品种为试材,研究了不同LED复合光质补光对其形态特征和生理特性的影响。结果表明:对牡丹生长最有利的复合光是红蓝绿复合光,对牡丹开花最有利的复合光是红蓝黄;对牡丹叶片色素积累最有利的复合光是红蓝黄绿紫;红蓝、红蓝黄、红蓝绿复合光最利于牡丹叶片可溶性糖、可溶性蛋白的积累。试验为改良牡丹年宵花的品质提供理论依据。

LED补光对番茄光合特性的影响

为找出适于番茄生长的最佳光谱成分,采用发光二极管(light-emitting diode,LED)研究不同光质处理对番茄‘菜都5号’叶片光合特性的影响。结果表明,补光改变了番茄叶片光合速率日变化规律,使番茄光合速率日变化曲线由"单峰"型变为"双峰"型;LED光源虽然可以延长光合作用时间,但对胞间CO2浓度、气孔导度和蒸腾速率的影响不明显。LED光源对番茄光合速率的影响因光质而异,红灯和蓝灯的光合速率显著大于绿灯,这表明红灯和蓝灯比绿灯更有利于增加番茄的光合速率,促进番茄叶片内有机物质的积累。

LED光质对油茶苗生长和光合特性的影响

[目的]探寻适合油茶苗培育的最佳LED光质配比。[方法]以2年生长林4号油茶扦插苗为试材,LED白光为对照,研究LED红光、蓝光及其复合光对油茶苗生长和光合特性的影响。[结果]表明:L1(红光)处理下,油茶苗高生长量最大,但表观量子效率、光补偿点和胞间CO2浓度最小;L7(蓝光)处理下,油茶苗光补偿点最高,但高生长量、干物质含量、壮苗指数、气孔导度和蒸腾速率最小;L6(10%红光+90%蓝光)处理下,油茶苗地径生长量、干物质含量、壮苗指数、光合色素含量、表观量子效率、最大净光合速率、暗呼吸速率、气孔导度、蒸腾速率、实际光能转换效率和相对电子传递速率均最大;L4(50%红光+50%蓝光)处理下,油茶苗地径生长量、光合色素含量、最大净光合速率、实际光化学效率和相对电子传递速率均最小,且非光化学淬灭系数最大。[结论]与对照及其它处理相比,L6(10%红光+90%蓝光)处理更利于长林4号油茶苗生长和光合能力的提高,是培育油茶壮苗较为理想的光质。

LED光强对不结球小白菜生长与光合特性的影响

【目的】研究LED不同光强对不结球小白菜生长、光合特性及光源能耗的影响,探讨适合不结球小白菜生长的节能高效的光强参数。【方法】以"四季"和"鸡毛"2个不结球小白菜品种为材料,在4个LED光强处理(153,229,287和330μmol/(m2·s))下栽培不结球小白菜,处理48d后测定不结球小白菜的形态指标、生物量、光合指标及LED耗电量。【结果】随光强增加,不结球小白菜茎粗、叶片数、叶面积、生物量均有所增加;株高先降低后增高。除高强光处理(330μmol/(m2·s))外,叶绿素含量均随光强的降低而增加。净光合速率(Pn)、光系统Ⅱ的实际光化学效率(ΦPSⅡ)、光化学量子效率(Fv/Fm)、光化学猝灭系数(qP)和光合电子传递速率(ETR)等指标随光强下降也都呈现减小趋势。光强越低,消耗的电能越小;光强越高,电能转换效率越高。【结论】330μmol/(m2·s)高光强处理增强了光系统Ⅱ反应中心的开放程度和光能转化效率,提高了光合能力,有利于不结球小白菜的正常生长。