共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
《Ceramics International》2017,43(18):16076-16083
Effect of Nd2O3 concentrations on optical properties and upconversion studies were investigated for oxyfluorosilicate glasses with composition of SiO2-Al2O3-Na2CO3-SrF2-CaF2. The Judd-Ofelt (JO) intensity parameters, Ωλ (λ = 2, 4 and 6) as well as radiative properties for the 4F3/2 level of Nd3+ ion have been evaluated from the absorption spectra of 1.0 mol% Nd2O3-doped glass. For all the glass samples, the strong NIR emissions were observed at 891, 1058 and 1330 nm and have been attributed to 4F3/2 → 4I9/2, 11/2, 13/2 transitions respectively. The stimulated emission cross-section for the 4F3/2 → 4I11/2 transition is evaluated and found to be 4.24 × 10–20 cm2. From the decay curves, experimental lifetimes (τexp) of the 4F3/2 level have been determined and are found to be 363, 340, 205, 134, 122 and 54 μs for 0.1, 0.5, 1.0, 1.5, 2.0 and 3.0 mol% Nd3+ ions doped glasses, respectively. By exciting the prepared glass samples at 808 nm, the upconversion of infrared light into blue, green, yellow and red emission have also observed. These results indicate that the present glasses could be useful for opto-electric devices and solid state laser applications. 相似文献
3.
4.
5.
A sensitive explosive was coated with a less sensitive explosive in order to improve stability while maintaining explosion performance. In this study the sensitive explosive HMX was coated with the less sensitive explosive NTO (3‐nitro‐1, 2, 4‐triazole‐5‐one) by cooling crystallization. The mechanism of coating by crystallization was determined to be an agglomeration and crystal growth phenomenon. The surface morphology and the growth rate of the coating were investigated under various experimental conditions. The surface morphology was predominantly influenced by the solvent type, HMX/NTO ratio, agitation speed, and degree of sub‐cooling. The growth rate of the HMX coating was increased to a certain extent by increasing the concentration ratio of HMX/NTO, but then began to decrease because of high agglomeration. Finally, the optimal conditions to achieve thin and uniform surface coatings on HMX were found experimentally. 相似文献
6.
Waldemar&#x;A. Trzci&#x;ski Stanis&#x;aw Cudzi&#x;o Jzef Paszula 《Propellants, Explosives, Pyrotechnics》2007,32(6):502-508
Research on the effect of aluminium contents and its particle size on free field and confined explosions characteristics of RDX‐based compositions containing 15–60% aluminium was carried out. Parameters of blast waves produced by charges of the investigated explosives detonating in an open space were measured by the use of piezoelectric gauges. Simultaneously, photodiode set‐ups were used to measure light output of the detonating charges. Quasi‐static pressure measurements were conducted in steel chambers of 0.15 and 7 m3 volume filled with air. Moreover, the heat of detonation was measured with a calorimetric set in a 5.6 dm3 bomb filled with argon. The results of QSP and detonation heat measurements were compared with those obtained from thermochemical calculations. 相似文献
7.
The polarisation ratio resulting from the backscattering of linearly polarised incident light by fly ash particles is indicative of the carbon content. Determination of this parameter is useful for characterising the efficiency of coal burning furnaces. This paper describes the development of an instrument to make these measurements, which is designed to be attached furnace ducts. The performance of the instrument is tested in laboratory measurements on a range of ashes from different coals. It is concluded that if the mineral content of the ashes is not known then the carbon mass fraction can be determined to within ±1%. If the mineral content is known then the use of neural network analysis can reduce this to ±0.5%. 相似文献
8.
《Ceramics International》2022,48(11):15755-15761
In this work we detail the preparation of new luminescent Li+ and K+ doped Na2Zn3Si2O8: Er3+ up-conversion phosphors using the high-temperature solid-phase method. We investigate the phosphors phase structure, elemental distribution, up-conversion luminescence characteristics and temperature sensing properties. Our fabricated samples were found to be homogeneous and when excited using 980 nm light, they emitted wavelengths in the green and red visible wavelength bands, which correspond to two major emission bands of Er3+. Doping with Li+ and K+ increased the luminescence intensity of the Na2Zn3Si2O8: Er3+ phosphor at 661 nm by 36 and 21 times respectively. The highest relative temperature sensitivity (Sa) of the fabricated phosphor reached a value of 19.69% K?1 and the highest absolute temperature sensitivity (Sr) reached 1.20% K?1. These values are superior to other materials which utilize up-conversion by Er3+ ions as a tool for temperature sensing. We anticipate that these new phosphors will find significant application as components in optical temperature measurement systems. 相似文献
9.
介绍了挤出机机头中压力的计算方法、测量技术和控制技术的研究进展。采用数值模拟方法计算复杂挤出机机头内的压力降能适合多种情况,是压力降计算方法的发展方向,但计算比较复杂;机头压力的在线测量可以提供连续测量数据,为机头设计提供可靠依据;压力控制精度的提高是制品质量和产量稳定的最终保证。 相似文献
10.
采用美国NI的虚拟仪器技术设计开发了高温高压三维填砂物理模型试验装置的实时测控系统,选用LabVIEW8.6软件开发平台和PXI模块化硬件平台,实现了整个试验过程的自动化,实现了各种试验设备和仪器的自动控制,测量了试验过程中动态三维压力场、饱和度场及分相流量等参数。 相似文献
11.
Equations are established for the pressure increase as a function of time for the self‐decomposition of tetrafluoroethylene (TFE) for both a uniform tube and a sphere. The resting gas is locally ignited at one end of the tube and in the center of the sphere respectively. Buoyancy is ignored. Due to the low κ‐value, major simplifications are justifiably introduced. Apart from the geometrical factors, the pressure increase as a function of time is solely controlled by the pressure increase ratio, Π, and the intrinsic flame speed, vo, thus the equations also are applicable to other gaseous TFE‐mixtures of technical interest. The average flame speed is 0.1–0.3 m/s, which compares well with other explosive gaseous mixtures, and vo lies in the range of the molecular diffusion rate. The self‐decomposition of TFE does not seem to exhibit any specific patterns. 相似文献
12.
D.‐H. Frobese 《化学工程与技术》2000,23(2):182-190
It is a requirement of environmental protection that the vapor/air mixtures formed during the storage, transport and refilling of petrols be collected and that the vapor contained in these mixtures be recovered. By vapor balancing within the distribution chain, the vapor/air mixtures are returned to the distribution depots where they are intermediately stored in vapor tanks, if need be, and processed in vapor recovery and exhaust air cleaning units. The more comprehensive the technical measures of discharging, conveying or processing the vapor/air mixtures of flammable liquids, the greater the problems of explosion protection. In this contribution, petrol will serve as an example to present and elucidate the explosion protection measures to be taken in exhaust air cleaning or vapor recovery units. 相似文献
13.
S. Miyanishi N. Iketani I. Suzuki Y. Murakami K. Kojima A. Takahashi 《Electrochimica acta》2007,53(1):4-6
We fabricated a generator that produces optical near field and magnetic filed in a nanometer area for achievement of thermally assisted magnetic recording. The generator consists of an embedded wire with a bottleneck structure on a SiO2 substrate. The magnetic field is mainly generated around the bottleneck structure by feeding current through the wire. The near field is produced on an edge of the narrow wire by focusing a laser beam on the bottleneck structure through the backside of the substrate. The generator is anticipated as application to control ordering, chirality, and phase transition of diamagnetic materials in a nano-area. We confirmed the three-dimentional localization of near field in the nanometer size around the bottleneck structure by means of a near field scanning optical microscope. 相似文献
14.
15.
This contribution presents a novel approach to investigate entrainment in distillation and absorption columns. An image-based probe allows precise droplet detection at various radial and axial positions above trays. Validations achieve an average error of 6.4 % (monospheres 9.2–114.4 µm) and 3 % (monodisperse droplet stream up to 19 m s−1 and 74.5 µm). Experiments in a DN 450 cold flow test rig show an increasing (decreasing) share of larger droplets with higher gas (liquid) loads. Locally measured droplet sizes depend on probe position as well as tray design and enable an extrapolation to integral entrainment rates. 相似文献
16.
Maximum safe diameters of microcapillaries for a stoichiometric ethene/oxygen mixture 总被引：1，自引：0，他引：1
A method and its corresponding first results are presented for the determination of maximum safe capillary diameters, which may be used to describe the extended safety range of operation conditions for partial gas phase oxidation reactions in microreactor devices. Sections of stainless steel microcapillaries of different inner diameters were mounted between a primary and a secondary chamber. A detonation was ignited in the primary chamber and the propagation of the detonation through the stainless steel microcapillaries was monitored by pressure transducers located between the sections of the microcapillaries. This set-up was used in order to determine explosion velocities inside the capillaries, maximum safe initial pressures, and corresponding maximum safe capillary diameters. Initial investigations were performed with an ideal stoichiometric mixture necessary for complete combustion of ethene with oxygen at room temperature. The measured maximum safe capillary diameters obey an indirect proportionality to the initial pressures. The maximum safe capillary diameter can be estimated on the basis of the λ/3-rule. 相似文献
17.
A comparison on predictive models of gas explosions 总被引：2，自引：0，他引：2
A comparison on existing models of gas explosion predictions has been done. The advantages and drawbacks, and the possibilities and limitations of the different empirical, phenomenological, and computational fluid dynamics assessment models of gas explosions were discussed. Particular attention was paid to CFD models. 相似文献
18.
实验先利用细管实验法确定出本次试验条件下二氧化碳的最小混相压力为26 MPa,再使用人造低渗透岩心并设定驱替压力分别为24 MPa近混相驱压力条件和28 MPa混相驱替压力条件进行驱油实验。结果是二者驱油效率变化基本一致,且混相驱替比近混相驱替最终驱油效率高出1.8个百分点,以期为后续研究二氧化碳驱油提供理论和实验基础。 相似文献
19.
Rani M. Roopa K. Prakasan R. Rudramoorthy 《Polymer-Plastics Technology and Engineering》2013,52(8):762-770
Polyethylene (PE) is an extremely versatile plastic and has the largest sales turnover than other plastics. With new uses for PE, researchers continue to find innovative technologies to process and join the material. Ultrasonic welding is one such process that is rapidly emerging as a major joining process for thermoplastics because of its reliability, ease of operation, fastness, and economic feasibility. Amorphous polymers are ideal materials for ultrasonic welding, but semicrystalline polymers are difficult to weld in the far-field region. This paper deals with the far field welding of semicrystalline polymer/high-density polyethylene (HDPE). The temperature distribution has been modeled for varying lengths of the specimen using Ansys to predict the temperature spikes, which can be related to the performance of the joints achieved. Experimental work studied the temperature at the joint interface and the variation in tensile strength for different lengths of the specimen. 相似文献