Showing papers by "Philips published in 2005"

Electrowetting: from basics to applications

Abstract: Electrowetting has become one of the most widely used tools for manipulating tiny amounts of liquids on surfaces. Applications range from 'lab-on-a-chip' devices to adjustable lenses and new kinds of electronic displays. In the present article, we review the recent progress in this rapidly growing field including both fundamental and applied aspects. We compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high. We discuss in detail the origin of the electrostatic forces that induce both contact angle reduction and the motion of entire droplets. We examine the limitations of the electrowetting equation and present a variety of recent extensions to the theory that account for distortions of the liquid surface due to local electric fields, for the finite penetration depth of electric fields into the liquid, as well as for finite conductivity effects in the presence of AC voltage. The most prominent failure of the electrowetting equation, namely the saturation of the contact angle at high voltage, is discussed in a separate section. Recent work in this direction indicates that a variety of distinct physical effects?rather than a unique one?are responsible for the saturation phenomenon, depending on experimental details. In the presence of suitable electrode patterns or topographic structures on the substrate surface, variations of the contact angle can give rise not only to continuous changes of the droplet shape, but also to discontinuous morphological transitions between distinct liquid morphologies. The dynamics of electrowetting are discussed briefly. Finally, we give an overview of recent work aimed at commercial applications, in particular in the fields of adjustable lenses, display technology, fibre optics, and biotechnology-related microfluidic devices.

Tomographic imaging using the nonlinear response of magnetic particles

Abstract: The use of contrast agents and tracers in medical imaging has a long history. They provide important information for diagnosis and therapy, but for some desired applications, a higher resolution is required than can be obtained using the currently available medical imaging techniques. Consider, for example, the use of magnetic tracers in magnetic resonance imaging: detection thresholds for in vitro and in vivo imaging are such that the background signal from the host tissue is a crucial limiting factor. A sensitive method for detecting the magnetic particles directly is to measure their magnetic fields using relaxometry; but this approach has the drawback that the inverse problem (associated with transforming the data into a spatial image) is ill posed and therefore yields low spatial resolution. Here we present a method for obtaining a high-resolution image of such tracers that takes advantage of the nonlinear magnetization curve of small magnetic particles. Initial 'phantom' experiments are reported that demonstrate the feasibility of the imaging method. The resolution that we achieve is already well below 1 mm. We evaluate the prospects for further improvement, and show that the method has the potential to be developed into an imaging method characterized by both high spatial resolution as well as high sensitivity.

Low-cost and nanoscale non-volatile memory concept for future silicon chips.

Abstract: Non-volatile 'flash' memories are key components of integrated circuits because they retain their data when power is interrupted. Despite their great commercial success, the semiconductor industry is searching for alternative non-volatile memories with improved performance and better opportunities for scaling down the size of memory cells. Here we demonstrate the feasibility of a new semiconductor memory concept. The individual memory cell is based on a narrow line of phase-change material. By sending low-power current pulses through the line, the phase-change material can be programmed reversibly between two distinguishable resistive states on a timescale of nanoseconds. Reducing the dimensions of the phase-change line to the nanometre scale improves the performance in terms of speed and power consumption. These advantages are achieved by the use of a doped-SbTe phase-change material. The simplicity of the concept promises that integration into a logic complementary metal oxide semiconductor (CMOS) process flow might be possible with only a few additional lithographic steps.

Polynomial time algorithms for multicast network code construction

Abstract: The famous max-flow min-cut theorem states that a source node s can send information through a network (V, E) to a sink node t at a rate determined by the min-cut separating s and t. Recently, it has been shown that this rate can also be achieved for multicasting to several sinks provided that the intermediate nodes are allowed to re-encode the information they receive. We demonstrate examples of networks where the achievable rates obtained by coding at intermediate nodes are arbitrarily larger than if coding is not allowed. We give deterministic polynomial time algorithms and even faster randomized algorithms for designing linear codes for directed acyclic graphs with edges of unit capacity. We extend these algorithms to integer capacities and to codes that are tolerant to edge failures.

AEthereal network on chip: concepts, architectures, and implementations

Abstract: The continuous advances in semiconductor technology enable the integration of increasing numbers of IP blocks in a single SoC. Interconnect infrastructures, such as buses, switches, and networks on chips (NoCs), combine the IPs into a working SoC. Moreover, the industry expects platform-based SoC design to evolve to communication-centric design, with NoCs as a central enabling technology. In this article, we introduce the AEthereal NoC. The tenet of the AEthereal NoC is that guaranteed services (GSs) - such as uncorrupted, lossless, ordered data delivery; guaranteed throughput; and bounded latency - are essential for the efficient construction of robust SoCs. To exploit the NoC capacity unused by the GS traffic, we provide best-effort services.

IEEE 802.22: the first worldwide wireless standard based on cognitive radios

Abstract: In November/2004, we witnessed the formation of the first worldwide effort to define a novel wireless air interface standard based on cognitive radios (CRs): the IEEE 802.22 working group (WG). The IEEE 802.22 WG is chartered with the development of a CR-based wireless regional area network (WRAN) physical (PHY) and medium access control (MAC) layers for use by license-exempt devices in the spectrum that is currently allocated to the television (TV) service. Since 802.22 is required to reuse the fallow TV spectrum without causing any harmful interference to incumbents (i.e., the TV receivers), cognitive radio techniques are of primary importance in order to sense and measure the spectrum and detect the presence/absence of incumbent signals. On top of that, other advanced techniques that facilitate coexistence such as dynamic spectrum management and radio environment characterization could be designed. In this paper, we provide a detailed overview of the 802.22 architecture, its requirements, applications, and coexistence considerations that not only form the basis for the definition of this groundbreaking wireless air interface standard, but that will also serve as foundation for future research in the promising area of CRs

High-performance solution-processed polymer ferroelectric field-effect transistors

Abstract: We demonstrate a rewritable, non-volatile memory device with flexible plastic active layers deposited from solution. The memory device is a ferroelectric field-effect transistor (FeFET) made with a ferroelectric fluoropolymer and a bisalkoxy-substituted poly(p-phenylene vinylene) semiconductor material. The on- and off-state drain currents differ by several orders of magnitude, and have a long retention time, a high programming cycle endurance and short programming time. The remanent semiconductor surface charge density in the on-state has a high value of 18 mC m−2, which explains the large on/off ratio. Application of a moderate gate field raises the surface charge to 26 mC m−2, which is of a magnitude that is very difficult to obtain with conventional FETs because they are limited by dielectric breakdown of the gate insulator. In this way, the present ferroelectric–semiconductor interface extends the attainable field-effect band bending in organic semiconductors.

Unified Description of Charge-Carrier Mobilities in Disordered Semiconducting Polymers

Abstract: From a numerical solution of the master equation for hopping transport in a disordered energy landscape with a Gaussian density of states, we determine the dependence of the charge-carrier mobility on temperature, carrier density, and electric field. Experimental current-voltage characteristics in devices based on semiconducting polymers are excellently reproduced with this unified description of the mobility. At room temperature it is mainly the dependence on carrier density that plays an important role, whereas at low temperatures and high fields the electric field dependence becomes important. Omission in the past of the carrier-density dependence has led to an underestimation of the hopping distance and the width of the density of states in these polymers.

Highly efficient all‐nitride phosphor‐converted white light emitting diode

Abstract: In the Editor's Choice [1] the development and demonstration of a highly efficient warm-white all-nitride phosphor-converted light emitting diode (pc-LED) is presented utilizing a GaN based quantum well blue LED and two novel nitrogen containing luminescent materials doped with Eu2+. These novel LEDs are superior to both incandescent and fluorescent lamps and may therefore become the next generation of general lighting sources. The cover picture is an artist's view of the 2-pc-LED: On a copper slug and underneath a plastic lens a ‘flip-chip’ is soldered to metal contacts; ‘flip-chip’ meaning the substrate on which the stack of GaN and InGaN layers has been deposited is used as light exit, the (bottom) p-contacts being highly reflective. The color converting phosphors are placed on top of the chip, embedded in silicone. Primary blue as well as color-converted red and green photons are emitted. The first author, Regina Mueller-Mach, manages the Charac-terization Laboratory at Lumileds which runs R&D work on phosphor converted LEDs in close cooperation with Philips Research Laboratories and the Department of Chemistry and Biochemistry of the University of Munich.

LED package methods and systems

Abstract: Methods and systems are provided for LED modules that include an LED die integrated in an LED package with a submount that includes an electronic component for controlling the light emitted by the LED die. The electronic component integrated in the submount may include drive hardware, a network interface, memory, a processor, a switch-mode power supply, a power facility, or another type of electronic component.

Tunable supercurrent through semiconductor nanowires

Abstract: Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.

Dimmable LED-based MR16 lighting apparatus methods

Abstract: Methods and apparatus for providing controllable power via an A.C. power source to LED-based lighting devices having an MR16 configuration. In one example, LED-based MR16 lighting devices may be coupled to A.C. power circuits that are controlled by conventional dimmers (i.e, “A.C. dimmer circuits”). In yet other aspects, one or more parameters relating to the light generated by LED-based light sources (e.g., intensity, color, color temperature, temporal characteristics, etc.) may be conveniently controlled via operation of a conventional A.C. dimmer and/or other signals present on the A.C. power circuit.

Liquid crystal display device and method of fabricating the same

Abstract: A liquid crystal display device includes a substrate, a black matrix layer on the substrate and having a first plurality of openings, a color filter layer on the black matrix layer and having a second plurality of openings, and a plurality of column spacers each contacting the substrate through the first plurality and second plurality of openings.

Analog circuits in ultra-deep-submicron CMOS

Abstract: Modern and future ultra-deep-submicron (UDSM) technologies introduce several new problems in analog design. Nonlinear output conductance in combination with reduced voltage gain pose limits in linearity of (feedback) circuits. Gate-leakage mismatch exceeds conventional matching tolerances. Increasing area does not improve matching any more, except if higher power consumption is accepted or if active cancellation techniques are used. Another issue is the drop in supply voltages. Operating critical parts at higher supply voltages by exploiting combinations of thin- and thick-oxide transistors can solve this problem. Composite transistors are presented to solve this problem in a practical way. Practical rules of thumb based on measurements are derived for the above phenomena.

Abdominal CT with low tube voltage: preliminary observations about radiation dose, contrast enhancement, image quality, and noise.

Abstract: PURPOSE: To prospectively investigate the effect of low tube voltage on radiation dose, contrast enhancement, image quality, and image noise at abdominal dynamic computed tomography (CT). MATERIALS AND METHODS: The institutional review board approved this study. Prior informed consent was obtained from all patients. Forty patients (24 women, 16 men; mean age, 62 years) underwent initial abdominal CT at 120 kV with 100 mL of contrast material (protocol A). Then all patients were randomly assigned to one of two protocols (protocol B, CT at 90 kV with 100 mL contrast material; protocol C, CT at 90 kV with 80 mL contrast material). The CT numbers of their abdominal organs were assessed quantitatively and qualitatively. Statistical analysis was performed by using the two-tailed paired t test, Kruskal-Wallis test, and κ test of interobserver agreement. The radiation dose was measured with a phantom that consisted of glass-rod dosimeters. RESULTS: Quantitative analysis revealed that protocols B and C yielded sig...

Liquid crystal display device and fabricating method thereof

Abstract: A method for fabricating a liquid crystal display (LCD) device comprises forming an active pattern and a data line on a substrate, the active pattern including a source, a drain, and a channel regions; a first insulation film on a portion of the substrate; forming a gate electrode in a portion of the active pattern where the first insulation film is formed; a second insulation film on the substrate; forming a plurality of first contact holes exposing a portion of the source and drain regions and a second contact hole exposing a portion of the data line; forming a source electrode from a transparent conductive material connected to a source region within the respective first contact hole and a data line within the second contact hole; and forming a pixel and a drain electrodes from the transparent conductive material connected to a drain region within the respective first contact hole.

Spectrum agile radios: utilization and sensing architectures

Abstract: Today, the largest and most desirable portion of the radio spectrum is allocated to licensed services, which has resulted in the well-known profound scarcity of this resource for emerging applications. With the rapid growth of wireless technologies, current spectrum scarcity has become a serious problem as more and more wireless applications compete for very little spectrum. On the other hand, the licensed spectrum allocated to applications such as television, cellular telephony and public safety show very little usage over time at different geographical locations. This has, therefore, seriously impaired the evolution of newer technologies because of current regulatory constraints on the operation in licensed spectrum, such as TV bands, and is being addressed by FCC through recent rule makings. With the goal of ubiquitous communication in mind, we look into spectrum agile radios as a new technology enabled by such emerging regulatory rulings and study its advantages over conventional radios. Initially, we provide a simple mathematical modeling to understand the utilization that is achievable by spectrum agile radios. Next, we investigate several issues related to spectrum sensing, as it is one of the key pillars to realize spectrum agile radios. Through sensing, the spectrum agile radio identifies the so-called "white-spaces" in the spectrum and then decides whether to occupy those white spaces opportunistically to transmit data. We also discuss the concept of interference temperature introduced by the FCC, and propose a spectrum-aware sensor network as a way to address it Finally, we extend this spectrum-aware sensor networks to introduce a new sensing architecture to identify and locate white spaces in the spectrum

A Review of Audio Fingerprinting

Abstract: An audio fingerprint is a compact content-based signature that summarizes an audio recording. Audio Fingerprinting technologies have attracted attention since they allow the identification of audio independently of its format and without the need of meta-data or watermark embedding. Other uses of fingerprinting include: integrity verification, watermark support and content-based audio retrieval. The different approaches to fingerprinting have been described with different rationales and terminology: Pattern matching, Multimedia (Music) Information Retrieval or Cryptography (Robust Hashing). In this paper, we review different techniques describing its functional blocks as parts of a common, unified framework.

Charge-carrier concentration dependence of the hopping mobility in organic materials with Gaussian disorder

Abstract: It has recently been demonstrated that the hopping mobility in semiconducting organic materials depends on the charge-carrier concentration. We have analyzed this effect within the framework of six existing semianalytical models, for the case of a Gaussian density of states (DOS). These models were either not applied earlier to the case of a Gaussian DOS, or are shown to require a major modification. The mobility is constant below a certain concentration, which decreases with increasing ratio $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{s}$ of the width of the DOS over the thermal energy ${k}_{B}T$, and it increases for larger concentrations. At very high concentrations final state effects limit this increase or even give rise to a decrease. An analytical expression is given for the mobility, $\ensuremath{\mu}$, in the form of the product of the mobility in the low concentration limit times a concentration $(c)$ and $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{s}$-dependent enhancement factor. Depending on $c$, $\mathrm{ln}(\ensuremath{\mu})$ varies approximately linearly with $1∕T$ or with $1∕{T}^{2}$. This finding may lead to a solution for the long-standing controversy between polaron-based and disorder-based hopping models.

Unifying Ultrafast Magnetization Dynamics

Abstract: We present a microscopic model that successfully explains the ultrafast equilibration of magnetic order in ferromagnetic metals at a time scale tau(M) of only a few hundred femtoseconds after pulsed laser excitation. It is found that tau(M) can be directly related to the so-called Gilbert damping factor sigma that describes damping of GHz precessional motion of the magnetization vector. Independent of the spin-scattering mechanism, an appealingly simple equation relating the two key parameters via the Curie temperature T(C) is derived, tau(M) approximately c(0)h/k(B)T(C)sigma, with h and k(B) the Planck and Boltzmann constants, respectively, and the prefactor c(0) approximately 1/4). We argue that phonon-mediated spin-flip scattering may contribute significantly to the sub-ps response.

Active matrix display devices

Abstract: An active matrix LED display has a light-dependent device for detecting the brightness of the display element and threshold voltage measurement circuitry for measuring a threshold voltage of a pixel the drive transistor. Compensation for ageing of the display element is thus provided by an optical feedback path, and compensation for drive transistor threshold variations is provided by measurement of the threshold voltage. This provides a reliable compensation scheme for the threshold voltage variations, whilst also providing ageing compensation.

Imaging anisotropic and viscous properties of breast tissue by magnetic resonance-elastography

Abstract: MR-elastography is a new technique for assessing the viscoelastic properties of tissue. One current focus of elastography is the provision of new physical parameters for improving the specificity in breast cancer diagnosis. This analysis describes a technique to extend the reconstruction to anisotropic elastic properties in terms of a so-called transversely isotropic model. Viscosity is treated as being isotropic. The particular model chosen for the anisotropy is appealing because it is capable of describing elastic shear anisotropy of parallel fibers. The dependence of the reconstruction on the particular choice of Poisson's ratio is eliminated by extracting the compressional displacement contribution using the Helmholtz-Hodge decomposition. Results are presented for simulations, a polyvinyl alcohol breast phantom, excised beef muscle, and measurements in two patients with breast lesions (invasive ductal carcinoma and fibroadenoma). The results show enhanced anisotropic and viscous properties inside the lesions and an indication for preferred fiber orientation.

Practical biometric authentication with template protection

Abstract: In this paper we show the feasibility of template protecting biometric authentication systems In particular, we apply template protection schemes to fingerprint data Therefore we first make a fixed length representation of the fingerprint data by applying Gabor filtering Next we introduce the reliable components scheme In order to make a binary representation of the fingerprint images we extract and then quantize during the enrollment phase the reliable components with the highest signal to noise ratio Finally, error correction coding is applied to the binary representation It is shown that the scheme achieves an EER of approximately 42% with secret length of 40 bits in experiments

A capacitor cross-coupled common-gate low-noise amplifier

Abstract: The conventional common-gate low-noise amplifier (CGLNA) exhibits a relatively high noise figure (NF) at low operating frequencies relative to the MOSFET f/sub T/, which has limited its adoption notwithstanding its superior linearity, input matching, and stability compared to the inductively degenerated common-source LNA (CSLNA). A capacitor cross-coupled g/sub m/-boosting scheme is described that improves the NF and retains the advantages of the CGLNA topology. The technique also enables a significant reduction in current consumption. A fully integrated capacitor cross-coupled CGLNA implemented in 180-nm CMOS validates the g/sub m/-boosting technique. It achieves a measured NF of 3.0 dB at 6.0 GHz and consumes only 3.6 mA from 1.8 V; the measured input-referred third-order intercept ( IIP3) value is 11.4 dBm. The capacitor cross-coupled g/sub m/-boosted CGLNA is attractive for low-power fully integrated applications in fine-line CMOS technologies.

Smart video surveillance: exploring the concept of multiscale spatiotemporal tracking

Abstract: Situation awareness is the key to security. Awareness requires information that spans multiple scales of space and time. Smart video surveillance systems are capable of enhancing situational awareness across multiple scales of space and time. However, at the present time, the component technologies are evolving in isolation. To provide comprehensive, nonintrusive situation awareness, it is imperative to address the challenge of multiscale, spatiotemporal tracking. This article explores the concepts of multiscale spatiotemporal tracking through the use of real-time video analysis, active cameras, multiple object models, and long-term pattern analysis to provide comprehensive situation awareness.

Variable focus lens

Abstract: A variable focus lens comprising a first fluid (A) and a second, non-miscible, fluid (B) in contact over a meniscus. A first electrode (2) separated from the fluid bodies by a fluid contact layer (10), and a second electrode (12) in contact with the first fluid to cause an electrowetting effect whereby the shape of the meniscus is altered. The fluid contact layer has a substantially cylindrical inner wall.

Large amplitude light-induced motion in high elastic modulus polymer actuators

Abstract: Well-defined gradients in molecular alignment have been used as tools to generate large amplitude, light-induced deformations in stiff polymer networks. These systems are reversible, monolithic and based on a simple one-step self-assembly process. To fabricate the actuators, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diacrylate hosts and photopolymerized in a twisted configuration. The resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa. Regardless of the temperature with respect to the glass transitions, subsequent exposure to UV radiation induced anisotropic expansion/contraction, and simple variations in geometry were used to generate uniaxial bending or helical coiling deformation modes. Because mechanical energy is directly related to elastic modulus, these systems are expected to provide significantly greater work output than contemporary polymer actuator materials.