Implementation of shading effect for reconstruction of smooth layerbased 3D holographic images

A holographic rendering algorithm using a layer-based structure with angular tiling supports view-dependent shading and accommodation cues. This approach also has the advantages of rapid computation speed and visual reduction of layer gap artefacts compared to other approaches. Holograms rendered with this algorithm are displayed using an SLM to demonstrate view-dependent shading and occlusion. © 2013 SPIE-IS&T.

Modelling of free-space optoelectronic switching with MPLS for storage area networks (SANs)

Low-cost optical switches based on SLMs have conventionally been considered unsuitable for packet switching due to slow reconfiguration time. In this paper, we demonstrate that the constraint of SLM reconfiguration time in a hybrid three-stage electronic/optical switching node architecture can be compensated through the utilization of MPLS label switching mechanism to achieve the best performance for SAN applications. © 2012 SEE.

Demonstration of multi-casting in a 1 × 9 LCOS wavelength selective switch

A multi-functional 1 × 9 wavelength selective switch based on liquid crystal on silicon (LCOS) spatial light modulator technology and anamorphic optics was tested at a channel spacing of 100 and 200 GHz, including dynamic data measurements on both single beam deflection and multi-casting to two ports. The multi-casting holograms were optimized using a modified Gerchberg-Saxton routine to design the core hologram, followed by a simulated annealing routine to reduce crosstalk at non-switched ports. The effect of clamping the magnitude of phase changes between neighboring pixels during optimization was investigated, with experimental results for multi-casting to two ports resulting in a signal insertion loss of-7.6 dB normalized to single port deflection, a uniformity of ±0.6%, and a worst case crosstalk of-19.4 dB, which can all be improved further by using a better anti-reflection coating on the LCOS SLM coverplate and other measures. © 2013 IEEE.

Using different carrier gases to control AlN film stress and the effect on morphology, structural properties and optical properties

On the metalorganic chemical vapour deposition growth of AlN, by adjusting H-2+N-2 mixture gas components, we can gradually control island dimension. During the Volmer - Weber growth, the 2-dimensional coalescence of the islands induces an intrinsic tensile stress. Then, this process can control the in-plane stress: with the N-2 content increasing from 0 to 3 slm, the in-plane stress gradually changes from 1.5 GPa tensile stress to - 1.2GPa compressive stress. Especially, with the 0.5 slm N-2 + 2.5 slm H-2 mixture gas, the in-plane stress is only 0.1 GPa, which is close to the complete relaxation state. Under this condition, this sample has good crystal and optical qualities.

A novel ultra-narrow transmission-band fiber Bragg grating and its application in a single-longitudinal-mode fiber laser with improved efficiency

A novel design approach to ultra-narrow transmission-band fiber Bragg grating (FBG) is proposed and demonstrated for the first time. The new grating consists of multiple identical distributed-Bragg reflector (DBR) cavities and a it-phase-shifted gap, and hence, the proposed laser is constructed by the cascade of these identical DBR fiber lasers. By manufacturing the proposed grating in a piece of Er-Yb codoped fiber, a single-wavelength single-longitudinal-mode (SLM) fiber laser with improved efficiency is demonstrated experimentally. The experimental results show that the pump-to-signal conversion efficiency of the proposed laser is improved by a factor of two in comparison with the optimized distributed-feedback (DFB) fiber lasers. (c) 2007 Elsevier B.V. All rights reserved.

Effect of Carrier Gas Flux on ZnO Nanorod Arrays Grown by MOCVD

ZnO nanorod arrays with different morphologies were grown by metalorganic chemical vapor deposition （MOCVD）. The diameters of nanorods range from 150 nm to 20 nm through changing the carrier gas flux during the growth process. Measurements such as scanning electron microscope （SEM）, X-ray diffraction （XRD）, Raman scattering and photoluminescence （pL） spectrum were employed to analyze the differences of these nanorods. It was found that when both carrier gas flux of Zn and O reactant are 1 SLM, we can obtain the best vertically aligned and uniform nanorods. Furthermore, the PL spectrum reveals a blueshift of UV emission peak, which may be assigned to the increase of surface effect.

稳定可调谐的单纵模多环形腔掺铒光纤激光器

提出了一种多环形腔(MRC)结构的稳定可调的单纵模(SLM)掺铒光纤激光器,多环形腔结构由双环形有源腔和两个次级无源腔组成。这种激光器是利用光纤法布里-珀罗可调滤波器(FFP-TF)以及光学光栅滤波器(OGF)两种滤波器和多环形腔结构相结合来共同选模。可实现波长调节范围为1528～1565 nm,在整个波长调节范围内边模抑制比大于44.53 dB,在1554 nm附近边模抑制比可以达到最大值51.18 dB, 输出功率为-8.84 dBm,通过应用多环型腔结构,激光器的输出很稳定,在18 min的观察时间内,中心波长的变化小于0.02 nm,输出功率的变化小于0.04 dBm,实现了稳定且可调谐的单纵模输出。

单纵模多环形腔掺铒光纤激光器及其稳定性

介绍了一种多环形腔结构(MRC)的单纵模(SLM)掺铒光纤激光器(EDFL)。这种激光器通过在主环形腔中插入充当模式滤波器的三个长度不等的无源次级环形腔, 并结合腔内光纤布拉格光栅(FBG)形成多环形腔掺铒光纤激光器结构, 多环形谐振腔可保证激光器的单纵模输出。讨论了使激光器运行在单纵模状态的谐振腔理论。同时, 为了提高系统输出的频率稳定性, 采用外光注入方法有效地抑制了模式跳变和拍噪声, 改善了输出谱特性。实验得到在1550.225 nm处输出功率约3.6 dBm, 信噪比(SNR)>35 dB的单纵模输出光, 且测得线宽小于500 Hz。

Effect of Nozzle Temperature on the Performance of a 1 kW H2-N2 Arcjet Thruster

A 1 kW-class arcjet thruster was ¯red in a vacuum chamber at a pressure of 18 Pa. A gas mixture of H2 : N2 = 2.8 : 1.5 in volume at a total °ow rate of 4.3 slm was used as the propellant with an input power ¯xed at 860 W. The time-dependent thrust, nozzle temperature and inlet pressure of the propellant were measured simultaneously. Results showed that with the increase in nozzle temperature the thrust decreased and various losses increased. The physical mechanisms involved in these effects are discussed.

Volt-ampere characteristics, nozzle temperature and thruster performances in a low power argon arcjet

Argon gas with simple atomic structure and favorite arcing stability at low input power was used as the propellant. The thruster with a regeneratively cooled nozzle were tested in a vacuum system capable of keeping the chamber pressure at about 10 Pa at a propellant feeding rate of 5 slm. Arc current, arc voltage, thrust, nozzle temperature and propellant feeding rate were measured in situ simultaneously. Effects of the working parameters such as the propellant feeding rate and arc current on the thruster performances, mainly the produced thrust, specific impulse and thrust efficiency, were examined. The variation of arc volt-ampere characteristics with running time and the effect of nozzle temperature on thruster property are discussed.

电离层垂直TEC映射函数的实验观测与统计特性

When used in the determining the total electron content (TEC), which may be the most important ionospheric parameter, the worldwide GPS observation brings a revolutionary change in the ionospheric science. There are three steps in the data processing to retrieve GPS TEC: (1) to estimate slant TEC from the measurements of GPS signals; (2) to map the slant TEC into vertical; and (3) to interpolate the vertical TEC into grid points. In this scientific dissertation we focus our attention on the second step, the mapping theory and method to convert slant TEC into vertical. This is conventionally done by multiplying on the slant TEC a mapping function which is usually determined by certain models of electron density profile. Study of the vertical TEC mapping function is of significance in GPS TEC measurement. This paper first reviews briefly the three steps in GPS TEC mapping process. Then we compare the vertical TEC mapping function which were respectively calculated from the electron density profiles of the ionospheric model and retrieved from the observation of worldwide GPS TEC. We also perform the statistical analysis on the observational mapping functions. The main works and results are as follows: 1. We calculated the vertical TEC mapping functions for both SLM and Chapman models, and discussed the modulation of the ionosphere height to the mapping functions. We use two simple models, single layer model (SLM) and Chapman models, of the ionospheric electron density profiles to calculate the vertical TEC mapping function. In the case of the SLM, we discuss the control of the ionospheric altitude, i.e., the layer height hipp, to the mapping function. We find that the mapping function decreases rapidly as hipp increases. For the Chapman model we study also the control mapping function by both ionospheric altitude indicated by the peak electron density height hmF2, and the scale height, H, which present the thickness of the ionosphere. It is also found that the mapping function decreases rapidly as hmF2 increases. and it also decreases as H increases. 2. Then we estimate the mapping functions from the GPS observations and compare them with those calculated from the electron density models. We first, proposed a new method to estimate the mapping functions from GPS TEC data. This method is then used to retrieve the observational mapping function from both the slant TEC (TECS) provided by International GPS Service (IGS）and vertical TEC provide by JPL Global Ionospheric Maps (GIMs). Then we compare the observational mapping function with those calculated from the electron density models, SLM and Chapman. We find that the values of the observational mapping functions are much smaller than that from the model mapping functions, when the zenith angle is large enough. We attribute this to the effect of the plasmasphere which is above about 1000 km. 3. We statistically analyze the observational mapping functions and reveal their climatological changes. Observational mapping functions during 1999-2007 are used in our statistics. The main results are as follows. (1) The observational mapping functions decrease obviously with the decrement of the solar activity which is represented by the F10.7 index; (2) In annual variations of the observational mapping functions, the semiannual component is found at low-latitudes, and the remarkable seasonal variations at mid- and high-latitudes. (3) The diurnal variation of the observational mapping functions is that they are large in daytime and small at night, they become extremely small in the early morning before sunrise. (4) The observational mapping functions change with latitudes that they are smaller at lower latitudes and larger at higher. All of the above variations of the observational mapping functions are explained by the existence of the plasmasphere, which changes more slowly with time and more rapidly with latitude than the ionosphere does . In summary, our study on the vertical TEC mapping function imply that the ionosphere height has a modulative effect on the mapping function. We first propose the concept of the 'observational mapping functions' , and provide a new method to calculate them. This is important in improving the TEC mapping. It may also possible to retrieving the plasmaspheric information from GPS observations.

Absolute Atomic Oxygen Density Distributions in the Effluent of a Micro Scale Atmospheric Pressure Plasma Jet

The coplanar microscale atmospheric pressure plasma jet (µ-APPJ) is a capacitively coupled radio frequency discharge (13.56 MHz, ~15W rf power) designed for optimized optical diagnostic access. It is operated in a homogeneous glow mode with a noble gas flow (1.4 slm He) containing a small admixture of molecular oxygen (~0.5%). Ground state atomic oxygen densities in the effluent up to 2 × 1014 cm-3 are measured by two-photon absorption laser-induced fluorescence spectroscopy (TALIF) providing space resolved density maps. The quantitative calibration of the TALIF setup is performed by comparative measurements with xenon. A maximum of the atomic oxygen density is observed for 0.6% molecular oxygen admixture. Furthermore, an increase in the rf power up to about 15W (depending on gas flow and mixture) leads to an increase in the effluent’s atomic oxygen density, then reaching a constant level for higher powers.

Absolute atomic oxygen density profiles in the discharge core of a microscale atmospheric pressure plasma jet

The micro atmospheric pressure plasma jet is an rf driven (13.56 MHz, ~20 W) capacitively coupled discharge producing a homogeneous plasma at ambient pressure when fed with a gas flow of helium (1.4 slm) containing small admixtures of oxygen (~0.5%). The design provides excellent optical access to the plasma core. Ground state atomic oxygen densities up to 3x1016 cm-3 are measured spatially resolved in the discharge core by absolutely calibrated two-photon absorption laser-induced fluorescence spectroscopy. The atomic oxygen density builds up over the first 8 mm of the discharge channel before saturating at a maximum level. The absolute value increases linearly with applied power.

Design and Development of a Performance Evaluation Prototype for IT Organizations in the Context of Outsourcing

The present study shows design and development of a performance evaluation prototype for IT organizations in the context of outsourcing. The main objective of this research is to help an IT organization in the context of outsourcing to realize its current standing, so it can take corrective steps where ever necessary and strive for continuous improvement. Service level management (SLM) process plays a crucial role in controlling the quality provision for IT service. Out sourcing is the process of entrusting the responsibility of providing certain goods and services to an external party. We have tried to identify as many as twenty complexities and categorized in to four headings. Complexities associated with contracts and SLAs,SLM process,SLM organization and complexities due to intrinsic characteristics. In this study it is possible to measure the quality of the performance of an IT organization in an outsourcing environment effectively

Modellbasiertes Service Level Management verteilter Anwendungssysteme

Zur Senkung von Kosten werden in vielen Unternehmen Dienstleistungen, die nicht zur Kernkompetenz gehören, an externe Dienstleister ausgelagert. Dieser Prozess wird auch als Outsourcing bezeichnet. Die dadurch entstehenden Abhängigkeiten zu den externen Dienstleistern werden mit Hilfe von Service Level Agreements (SLAs) vertraglich geregelt. Die Aufgabe des Service Level Managements (SLM) ist es, die Einhaltung der vertraglich fixierten Dienstgüteparameter zu überwachen bzw. sicherzustellen. Für eine automatische Bearbeitung ist daher eine formale Spezifikation von SLAs notwendig. Da der Markt eine Vielzahl von unterschiedlichen SLM-Werkzeugen hervorgebracht hat, entstehen in der Praxis Probleme durch proprietäre SLA-Formate und fehlende Spezifikationsmethoden. Daraus resultiert eine Werkzeugabhängigkeit und eine limitierte Wiederverwendbarkeit bereits spezifizierter SLAs. In der vorliegenden Arbeit wird ein Ansatz für ein plattformunabhängiges Service Level Management entwickelt. Ziel ist eine Vereinheitlichung der Modellierung, so dass unterschiedliche Managementansätze integriert und eine Trennung zwischen Problem- und Technologiedomäne erreicht wird. Zudem wird durch die Plattformunabhängigkeit eine hohe zeitliche Stabilität erstellter Modelle erreicht. Weiteres Ziel der Arbeit ist, die Wiederverwendbarkeit modellierter SLAs zu gewährleisten und eine prozessorientierte Modellierungsmethodik bereitzustellen. Eine automatisierte Etablierung modellierter SLAs ist für eine praktische Nutzung von entscheidender Relevanz. Zur Erreichung dieser Ziele werden die Prinzipien der Model Driven Architecture (MDA) auf die Problemdomäne des Service Level Managements angewandt. Zentrale Idee der Arbeit ist die Definition von SLA-Mustern, die konfigurationsunabhängige Abstraktionen von Service Level Agreements darstellen. Diese SLA-Muster entsprechen dem Plattformunabhängigen Modell (PIM) der MDA. Durch eine geeignete Modelltransformation wird aus einem SLA-Muster eine SLA-Instanz generiert, die alle notwendigen Konfigurationsinformationen beinhaltet und bereits im Format der Zielplattform vorliegt. Eine SLA-Instanz entspricht damit dem Plattformspezifischen Modell (PSM) der MDA. Die Etablierung der SLA-Instanzen und die daraus resultierende Konfiguration des Managementsystems entspricht dem Plattformspezifischen Code (PSC) der MDA. Nach diesem Schritt ist das Managementsystem in der Lage, die im SLA vereinbarten Dienstgüteparameter eigenständig zu überwachen. Im Rahmen der Arbeit wurde eine UML-Erweiterung definiert, die eine Modellierung von SLA-Mustern mit Hilfe eines UML-Werkzeugs ermöglicht. Hierbei kann die Modellierung rein graphisch als auch unter Einbeziehung der Object Constraint Language (OCL) erfolgen. Für die praktische Realisierung des Ansatzes wurde eine Managementarchitektur entwickelt, die im Rahmen eines Prototypen realisiert wurde. Der Gesamtansatz wurde anhand einer Fallstudie evaluiert.