A novel diffractive backlight concept for mobile displays

Abstract— Power‐efficiency demands on mobile communications device displays have become severe with the emergence of full‐video‐capable cellular phones and mobile telephony services such as third‐generation (3G) networks. The display is the main culprit for power consumption in the mobile‐phone user interface and the backlight unit (BLU) of commonly used active‐matrix liquid‐crystal displays (AMLCDs) is the main power drain in the display. One way of reducing the power dissipation of a mobile liquid‐crystal display is to efficiently distribute and outcouple the light available in the backlight unit to direct the primary wavelength bands in a spectrum‐specific fashion through the respective color subpixels. This paper describes a diffractive‐optics approach for a novel backlight unit to realize this goal. A model grating structure was fabricated and the distribution of outcoupled light was studied. The results verify that the new BLU concept based on an array of spectrum‐specific gratings is feasible.     

Automatic time-step adaptation of the forward Euler method in simulation of models of ion channels and excitable cells and tissue

The forward Euler method is commonly used to simulate models of ion channels and excitable cells and tissue. We show that the computational efficiency of these simulations could be significantly improved with automatic time-step adaptation. For this purpose a new easy-to-implement time-step adaptation method was developed.     

Modelling local bubble size distributions in agitated vessels

Photography and capillary suction probe were used to measure local bubble size distributions (BSDs) from Rushton turbine agitated (14/200 L) air-tap water and CO₂-n-butanol dispersions. A multiblock stirred tank model with population balances (PBs) for bubbles was created to describe local BSDs in agitated vessels. Unknown parameters in breakage and coalescence models were adjusted by comparing the predicted and measured local BSDs. The BSDs from both investigated systems and varying vessel-operating conditions were included simultaneously to the fitting. The adjusted models were incorporated to MUSIG PB model in CFX-5.7 and tested for the laboratory stirred tanks. The multiblock model showed to be an optimal trade-off between the accuracy and CPU time for the investigation of gas-liquid hydrodynamics and validation of closure models. As a result of fitting, the adjusted model seems to describe local BSDs more accurately in agitated vessels than the model of Lehr et al. [2002. Bubble-size distributions and flow fields in bubble columns. A.I.Ch.E. Journal 48, 2426-2443], which has been successful in bubble column studies. This shows that phenomenological breakage and coalescence closures need experimental validation for various flow environments.     

A BiCMOS Differential Amplifier and Timing Discriminator for the Receiver of a Laser Radar

A differential BiCMOS amplifier channel with gain control circuitry and a timing discriminator has been designed for a pulsed time-of-flight laser radar. The measured bandwidth of the amplifier channel is 160 MHz and its gain can be controlled with a variable R-2R ladder attenuator in 7 discrete steps from 0.44 to 23. A peak detector, used for gain control, can detect the peak of a single 10 ns pulse, the amplitude of which varies from 50 mV to 3.5 V. The timing discriminator produces accurately timed logic level pulses from noisy analog output pulses of the amplifier channel. The distance measurement result of the designed timing discriminator varies +/– 4 mm with an input amplitude range of 55 mV – 3.3 V. The single shot resolution with SNR = 250 is better than 6 mm. Measurement results suggest that a cm-level distance measurement accuracy can be realized using integrated ASICs.     

Modeling linguistic qualifiers of uncertainty in a fuzzy database

In this contribution an interpretation of linguistic qualifiers of uncertainty is proposed in the context of fuzzy databases; these qualifiers are defined in the framework of possibility theory to express incomplete knowledge on the represented world. The uncertain and vague information represented in a fuzzy database is formalized based on the notion of prioritized constraints with safeguard. © 2000 John Wiley & Sons, Inc.     

Colloidal properties and gelation of aqueous dispersions of conductive poly(benzimidazobenzophenanthroline) derivatives

Poly(benzimidazobenzophenanthroline), BBL, is a practically insoluble conductive polymer. It can be gradually dispersed in water, however by dialysis and sonication, i.e. during the purification and dilution right after synthesis. Dispersions with higher solids content and colloidal stability were prepared by first turning the polymer amphiphilic adding poly(ethylene oxide), PEO, into BBL chain ends (BBL–PEO). Dynamic light scattering and zeta potential measurements showed that the dispersions consist of negatively-charged particles with a broad size distribution. These dispersions were found to be sensitive to ionic strength. Salting out occurred within a NaCl concentration range of 0.5–4 mM and some samples showed re-entrant behavior with redispersion upon further salt addition. Addition of a non-ionic surfactant was found to enhance the stability of BBL–PEO dispersions against salting-out. Upon increasing the polymer concentration the dispersions form gels upon resting. The strength of the gels depends on the total polymer concentration as well as the proportions of BBL and PEO in the BBL–PEOs. The gel formation was attributed to a formation of a network of nano-wire-type aggregates, which was verified with electron cryo-microscopy.     

A Single Chip 160 Mbit/s Cable Communication Circuit Including a Gain Controlled Equalizer and a Data Regenerating PFLL

In this paper a single chip transmitter and receiver interface circuit for 160 Mbit/s CMI-coded data transmission is presented. The receiver circuit includes a 12 dB cable equalizer to compensate for nonconstant cable attenuations. There is also a PFLL for data regeneration and to extract a 320 MHz oscillator clock signal. The frequency characteristics of the equalizer are controlled with an automatic gain control loop (AGC). The PFLL is a combination of two separate control loops, the purpose of which is to keep the integrated oscillator on the narrow locking range of the data loop. The frequency loop has been designed with a frequency detector to avoid interferences between the two control loops. The transmitter includes a cable driver supplying a stable 1 Vpp signal amplitude to the transmission line and also a PLL to extract a 320 MHz clock signal.     

BOOTSTRAP 3.0—A SPICE1 Conformant Software Process Assessment Methodology

BOOTSTRAP methodology was initially developed in an ESPRIT project together with European industry. After February 1993, the methodology has been managed and further developed by a European Economic Interest Group, called BOOTSTRAP Institute. BOOTSTRAP methodology version 3.0 was released in September 1997. It is compliant with the ISO/IEC software engineering standard number 15504, the emerging standard on software process assessment. The core of the methodology consists of an assessment model and method. The assessment model of the methodology version 3.0 was updated to align with the ISO 12207 life-cycle and 15504 reference model requirements. In addition to the Process and Capability dimensions, it contains a Technology dimension. The Process dimension contains 33 different processes organised in six clusters: Organisation, Life Cycle Dependent, Management, Support, Customer-Supplier, and Process Related. The Capability dimension consists of six levels, each level consisting of one or more process attributes, adopted from ISO 15504. An assessment is conducted at SPU and project levels. The BOOTSTRAP Institute organises and co-ordinates assessor training and registration scheme. BOOTSTRAP methodology is being used in two European projects: SPAM and PROFES.     

K-means properties on six clustering benchmark datasets

This paper has two contributions. First, we introduce a clustering basic benchmark. Second, we study the performance of k-means using this benchmark. Specifically, we measure how the performance depends on four factors: (1) overlap of clusters, (2) number of clusters, (3) dimensionality, and (4) unbalance of cluster sizes. The results show that overlap is critical, and that k-means starts to work effectively when the overlap reaches 4% level.