New directions in commercial fluorescent lighting

It is shown how compact fluorescent lamps and smaller luminaires using deeper shielding can now meet, better than traditional commercial lighting approaches, the requirements of lighting the newer space configurations and seeing tasks that did not exist a few years ago. Design approaches are shown that will optimize lighting cost and effectiveness in matching the new hardware and the new lighting needs. Luminaire patterns are shown in various room and furniture configurations. Their effectiveness in delivering light into panelled workstations and practical methods of predicting the delivered light are discussed     

Synthesis of Imidazole‐Based AIEgens with Wide Color Tunability and Exploration of their Biological Applications

Research on aggregation‐induced emission (AIE) has become increasingly popular recently and various AIE luminogens (AIEgens) have been developed based on tetraphenylethene, hexaphenylsilole, distyrylanthracene, tetraphenylpyrazine, etc. However, facile tuning of the AIEgen emissions in a wide range remains challenging. Herein, a novel series of AIEgens is reported, based on imidazole‐cored molecular rotors, with facile synthesis and emission colors covering the whole visible spectrum. Moreover, these imidazole derivatives exhibit biological functions unique among the AIEgens, including mitochondria‐specific imaging and antifungal activity. Benefiting from the easy preparation and the tunable emission, the imidazole derivatives are expected to not only diversify the family of AIEgens but also enrich their biological applications.     

Fundamental properties of radiation from a leaky mode excited on a planar transmission line

By using a specific normalization, it is shown that the TM/sub 0/ radiation field from a leaky mode that is excited by a source on any printed-circuit structure can be represented in a unified manner. The general properties of the normalized leaky-mode radiation field are examined in detail for a variety of phase and attenuation constants, as well as distances from the source, and for different types of source excitations. The normalized leaky-mode radiation field is compared to similarly normalized geometrical-optics and far-field radiation expressions to provide further insight into the nature of the radiation fields in the near- and far-field regions. The results provide a general view of leaky-mode radiation properties independent of the type of planar transmission line or background structure.     

On the Performance of a Two-User MIMO Downlink System in Heavy Traffic

A multiple-input multiple-output (MIMO) downlink system in which data is transmitted to two users over a common wireless channel is considered. The channel is assumed to be fixed for all transmissions over the period of interest and the ratio of anticipated average arrival rates for the two users, also known as the relative traffic rate, is the system design parameter. A packet-based traffic model is considered where data for each user is queued at the transmit end. A queueing analog for this system leads to a coupled queueing system for which a simple policy is known to be throughput-optimal under Markovian assumptions. Since an exact expression for the performance is not available, as a measure of performance (in heavy traffic), a diffusion approximation is established. This diffusion process is a two-dimensional (2-D) Semimartingale Reflecting Brownian Motion (SRBM) living in the positive quadrant of 2-D space     

Adaptive Network Overload Controls

Network overloads can seriously degrade the quality or availability of telecommunications services if they are not effectively controlled. This paper explains why overload controls are required and how they should behave for both today's and future networks. The requirements of overload controls are presented, in terms of the conditions under which they must operate and the behaviour they should exhibit. Good design principles are proposed, which include identifying the controlled variable, the control structure, convergence and stability, and parameter configuration, while ensuring that different implementations work together. Relevant network standards are highlighted, and the paper stresses the crucial importance that these standards adequately specify the behaviour of overload controls.     

A Methodology to Measure the Environmental Impact of ICT Operating Systems across Different Device Platforms

A new methodology was created to measure the energy consumption and related green house gas (GHG) emissions of a computer operating system (OS) across different device platforms. The methodology involved the direct power measurement of devices under different activity states. In order to include all aspects of an OS, the methodology included measurements in various OS modes, whilst uniquely, also incorporating measurements when running an array of defined software activities, so as to include OS application management features. The methodology was demonstrated on a laptop and phone that could each run multiple OSs, results confirmed that OS can significantly impact the energy consumption of devices. In particular, the new versions of the Microsoft Windows OS were tested and highlighted significant differences between the OS versions on the same hardware. The developed methodology could enable a greater awareness of energy consumption, during both the software development and software marketing processes.     

Optical properties of pseudomorphic Si1-xGexfor Si-based waveguides at the λ=1300-nm and 1550-nmtelecommunications wavelength bands

The index of refraction for pseudomorphic Si_1-xGe_x layers grown on Si has been measured at wavelengths λ=1310 mn and λ=1550 nm. The refractive index values were obtained from waveguide mode profile measurements on a series of Si-Si_1-xGe _x-Si waveguides with Ge_x concentrations between x=0.01 and x=0.1. The index of refraction, n, is significantly larger for light polarized parallel to the growth direction than for light polarized in the plane of the epilayer. This birefringence is consistent with the anisotropic index change predicted using photoelastic theory, given the biaxial strain present in the pseudomorphic Si_1-xGe _x layers. At all wavelengths and polarizations, n varies linearly with the Ge concentration. The pseudomorphic Si_1-xGe _x waveguides layer are stable against lattice relaxation during short anneals at 950°C, but exhibit partial relaxation after annealing at 1200°C     

A NOVEL PASSIVE DUAL ENERGY RECOVERY SNUBBER FOR HIGH POWER GTO CONVERTERS

A novel passive dual energy recovery snubber circuit is presented where energy trapped in the snubber inductor and capacitor is recovered into the both DC rail and load, without any active devices or resistors. The maximum over-shoot voltage on the switch is fixed, peak switch current is low, circuit reset is fast and the operational range of load current is wide. This circuit is suitable for use in high frequency, single ended power gate turn-off (GTO) thyrister choppers. Main design equations, some simulations and practical results are included.     

Jitter reduction through feedback for picosecond pulsed InGaAsPlasers

Following a comparison of picosecond-pulse generation techniques, feedback schemes are reported for the generation of picosecond pulse trains with improved jitter for both multicontact and conventional single-contact InGaAsP-InP lasers. Subpicosecond jitter is achieved for Q-switched laser sources using a novel optoelectronic feedback scheme. The use of resonant electrical feedback is shown to improve the timing jitter of gain-switched pulses by up to six times. Pulse-to-pulse timing jitter as low as 250 fs is demonstrated for a hybrid of optical and electrical feedback schemes. Limits for timing jitter in diode lasers are established for optoelectronic, electrical, and optical feedback schemes, and the key picosecond pulse generation schemes are compared in terms of timing jitter for the first time     

Millimeter-wave components and subsystems built using microstriptechnology

The author describes the evaluation of microstrip as a transmission medium for components and subsystems operating in the millimeter wavebands. The manufacturing process for thin-film MICs on single-crystal quartz is described. The microwave integrated circuit (MIC) manufacturing process is suitable for high-value manufacturing of highly integrated subsystems since manufacturing costs for the circuits are almost independent of the number of circuit functions. Designs for various circuit elements are discussed, and an integrated subsystem is described in which MIC techniques are used to produce a miniature millimeter-wave distance-measuring sensor. Range measurement results for the miniature sensor are presented