4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.     

Study of electrochemical performances of multi-doped spinel Li1.1Mn1.85Co0.075Ni0.075O4 at 4.3 and 5 V

Li_1.1Mn_2???2x Co _x Ni _x O₄ (x?=?0, 0.075) spinel powders were successfully synthesized using a liquid stirred tank reactor method. The electrochemical performances of the undoped and doped spinels at 4.3 and 5 V were investigated by X-ray diffraction, field-emission scanning electron microscopy, and electrochemical impedance spectroscopy. The capacity of Li_1.1Mn_2???2x Co _x Ni _x O₄ could be divided into two parts, with 4.3 V as the dividing line in the 3–5 V charge–discharge range. Low capacity and good cyclic performance were obtained when cycled in the 3–4.3 V range for the multi-doped Li_1.1Mn_2???2x Co _x Ni _x O₄ spinel. In comparison with multi-doped spinel at 4.3 V, the results of the cyclic performance worsened at 5 V because the structure underwent further shrinkage, the charge transfer resistance rose and the electrolyte decomposed.     

Acoustic damping characterization and microstructure evolution in nickel-based superalloy during creep

We studied the microstructure evolution of a nickel-based superalloy, Waspaloy, subjected to tensile creep at 1073 K through monitoring of shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). Contactless transduction based on the Lorentz force mechanism is the key to establishing a monitor for microstructural change in the bulk of the metals with a high sensitivity. There is a clear relationship between the attenuation and the life fraction. In the interval, 35 to 40% of the creep life, attenuation experiences a peak, being independent of the applied stress. This novel phenomenon is interpreted in terms of drastic change in dislocation mobility and the coarsening of γ′-precipitates, which is supported by SEM and TEM observations. At this period, dense dislocations start tangling to γ′-precipitates and the coarsening and condensation of γ′-precipitates become saturated. The EMAR has a potential to assess the damage advance and to predict the remaining creep life of metals.     

用硫化助熔剂法合成红外上转换材料的研究

本文采用一种优化的硫化助熔剂方法合成了红外上转换材料,这种材料能够在室温下将红外光转换成可见光。这种新工艺在反应效率、生产成本、环境保护、工艺难度等方面均优于传统的热熔工艺。文章给出了红外上转换材料的激励光谱和发射光谱。     

How to deal with potentially huge dimensional state space: The meta-dynamics approach—application to a model of the co-evolution of bacterio-phage populations

In many problems coming from the “complexity sciences”, the presence of high-dimensional state spaces and non-linear equations renders traditional mathematical objects useless. To deal with these issues, several approaches have recently been studied, most of them presenting the particularity of splitting the dynamical events in two categories; an upper level in which the events describe how the structure of the system changes (the meta-dynamics) and a lower level with the events describing the evolution of the elements in the structure (the dynamics). The state space is then not defined in extenso but unfolds or contracts during the evolution of the system. In term of simulation, this view allows us to deal with only a small part of the state space at each step avoiding the time and memory limitations.     

皮秒扫描相机在半导体激光管输出特性研究中的应用

本工作用Picotron 200型扫描相机和液态氮冷却的CCD摄相机系统对半导体激光二极管LTO22 MC的输出特性进行了测量,其最短输出脉冲宽度为2.1ps。这种半导体激光二极管的发射波长为780nm,连续工作条件下,其输出功率为3mW到5mW。     

由藜芦醛合成娃儿藤碱

以藜芦醛(1)、3,4-二甲氧基苯乙酸(2)、(S)-L-脯氨酸(6)等为原料,经8步反应,合成了一种抗肿瘤活性(s)-( )-娃儿藤碱。先由化合物1和2在乙酸酐/三乙胺催化下反应得到3,4-二甲氧基一反式-α-(3′, 4′-二甲氧基苯基)．肉桂酸(3),在0℃、三氟乙酸存在下用VOF_3对其关环成2,3,6,7-四甲氧基-9-羧基菲(4),然后用喹啉作介质,在230℃、无水CuSO_4催化下脱去羧基,得到2,3,6,7-四甲氧基菲(5),再和(S)-N- (三氟乙酰)-L-脯氨酰氯(6b)傅-克反应得到(S)-N-(三氟乙酰基)-2,3,6,7-四甲氧基-9-L-脯氨酰基菲(7),并对产物进行了柱纯化,所得产物在三氟化硼乙醚存在下用三乙基硅烷还原羰基,然后脱去三氟乙酰保护基,最后在盐酸存在下用甲醛闭环得到目标产物(10)。用NMR和MS表征了中间体和目标产物的结构。该合成反应条件温和,总收率为3．5％,产品纯度98．5％(HPLC)。     

Application of ICP-MS as a multi-element detector for sulfur and metal hydride impurities in hydrocarbon matrices

Maturation of inductively coupled plasma-mass spectrometry (ICP-MS) in terms of size, reliability, and cost has had a significant impact on its consideration as a viable detector for gas chromatography. Its generally excellent sensitivity for those elements it can measure has been a contributing factor. A method for sulfur speciation in various hydrocarbon products is investigated, as well as sulfur and metal hydride contaminants in high purity hydrocarbon feed stocks. Detection limits for sulfur species in hydrocarbon liquids and gases are approximately 5 and 10 ppb, respectively, as sulfur. Lower detection limits on the order of 100 parts per trillion are achieved for arsine. The use of collision cell technology (CCT) is exploited to remove interferences. CCT has been described elsewhere (1) using helium or helium-hydrogen mixtures for suppression of (16)O(16)O(+) interference with (32)S. In this work, a novel approach is investigated which uses oxygen to remove this interference by shifting it in a comprehensive fashion. The advantage of operating the system at full power with a tandem gas and liquid interface is also discussed.     

Dehydration performance of a hydrophobic DD3R zeolite membrane

The all silica DDR membrane turns out to be well suited to separate water from organic solvents under pervaporation conditions, despite its hydrophobic character. All-silica zeolites are chemically and hydrothermally more stable than aluminum containing ones and are therefore preferred for membrane applications, including for dehydration, even though these type of membranes are hydrophobic. Permeation of water, ethanol and methanol through an all-silica DDR membrane has been measured at temperatures ranging from 344 to 398 K. The hydrophobic membrane shows high water fluxes (up to 20 kg m⁻² h⁻¹). The pure water permeance is insensitive to temperature and is well described assuming weak adsorption. Excellent performance in dewatering ethanol (N=2$N=2$ kg m⁻² h⁻¹and _αw=1500${\alpha }_{\text{w}}=1500$ at 373 K and _xw=0.18$x_{\text{w}}=0.18$) is observed and the membrane is also able to selectively remove water from methanol (N=5$N=5$ kg m⁻² h⁻¹ and _αw=9${\alpha }_{\text{w}}=9$). Water could also be removed from methanol/ethanol/water (_αwater_/EtOH=1500${\alpha }_{\text{water}/\text{EtOH}}=1500$, _αMeOH_/EtOH=70${\alpha }_{\text{MeOH}/\text{EtOH}}=70$ at 373 K) mixtures, even at water feed concentrations below 1.5 mol%.     

Direct sampling time-of-flight mass spectrometers for technological analysis

The practicability of direct sampling time-of-flight mass spectrometers for routine technological analysis is considered. The discussed set incorporates two TOF instruments together covering analysis of solid, liquid, and gas samples without the need for time consuming sample preparation. Both an electron ionization reflectron TOF mass analyzer designed for the analysis of gas and liquid samples and a laser ionization axial electrostatic TOF mass analyzer designed for analysis of solid and powder samples use a single system for data acquisition, collection and processing. These instruments achieve ng/g range sensitivity and mass resolution exceeding 1000. Because of its compact design the system also can be realized as a mobile laboratory for on-site analysis. Prospects for applying the instruments to different technological applications are discussed. Received: 17 July 1997 / Revised: 28 November 1997 / Accepted: 22 December 1997