bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface-mediated structural transformation in CdTe nanoparticles dispersed in SiO2 thin films
Authors: Dayal P. Babu , Mehta B. R. , Aparna Y. , Shivaprasad S. M.
Published: November 2002

Cadmium telluride nanoparticles dispersed in silicon dioxide thin films have been grown by magnetron sputtering technique followed by thermal annealing. The effect of thermal annealing conditions on the structure of the surface layer and the nanoparticle core has been studied. A structural transformation in the nanoparticle core mediated solely by surface effects has been observed for the first time in any nanoparticle system. The presence of a crystalline cadmium tellurium oxide layer modifies the crystal structure of the cadmium telluride nanoparticle core by introducing a large concentration of stacking faults.
A simple neutron microscope using a compound refractive lens
Authors: Beguiristain H. R. , Anderson I. S. , Dewhurst C. D. , Piestrup M. A. , Cremer J. T. , Pantell R. H.
Published: November 2002

Images obtained with a high-magnification simple neutron microscope using a compound refractive lens are presented in this letter. The short focal length of the stack of Al biconcave lenses facilitated the setup of a simple neutron microscope at the D22 small angle scattering beam line at the Institut Laue Langevin, Grenoble, France that achieved a 35× magnification and a 214 μm resolution. Higher-resolution images could be obtained using improved neutron lens systems that enhance beam delivery from neutron sources and produce high-quality images in combination with higher resolution two-dimensional neutron detectors.
Resonant interband tunneling spin filter
Authors: Ting David Z.-Y. , Cartoixà Xavier
Published: November 2002

We propose an InAs/GaSb/AlSb-based asymmetric resonant interband tunneling diode as a spin filter. The interband design exploits large valence band spin–orbit interaction to provide strong spin selectivity, without suffering from fast hole spin relaxation. Spin filtering efficiency is also enhanced by the reduction of tunneling through quasibound states near the zone center, where spin spitting vanishes and spin selectivity is difficult. Our calculations show that, when coupled with an emitter or collector capable of lateral momentum selectivity, the asymmetric resonant interband tunneling diode can achieve significant spin filtering in conventional nonmagnetic semiconductor heterostructures under zero magnetic field.
Single-shot supercontinuum spectral interferometry
Authors: Kim K. Y. , Alexeev I. , Milchberg H. M.
Published: November 2002

We have developed a single-shot spectral interferometer using the supercontinuum pulse generated by self-focusing in atmospheric pressure air. The diagnostic can be used to measure ultrafast refractive index transients either in a direct frequency-to-time mapping mode or in a full Fourier transform mode. In the direct mapping mode, temporal resolution is shown to be strongly restricted by the pulse chirp. In the transform mode, the ultimate temporal resolution is limited by the supercontinuum pulse bandwidth and the maximum pump-induced phase shift.
Heterodyne near-field scattering
Authors: Brogioli Doriano , Vailati Alberto , Giglio Marzio
Published: November 2002

We describe an optical technique based on the statistical analysis of the random intensity distribution due to the interference of the near-field scattered light with the strong transmitted beam. It is shown that, from the study of the two-dimensional power spectrum of the intensity, one derives the scattered intensity as a function of the scattering wave vector. Near-field conditions are specified and discussed. The substantial advantages over traditional scattering technique are pointed out, and is indicated that the technique could be of interest for wavelengths other than visible light.
Polymer-based red, green, and blue emitting devices fabricated by reductive photopatterning
Authors: Trattnig Gernot , Pogantsch Alexander , Langer Gregor , Kern Wolfgang , Zojer Egbert
Published: November 2002

Using a color tuning approach reliant on reductive photopatterning, we present red-green-blue electroluminescence from a single layer polymer light-emitting device. To be able to cover the full color range, we employ a single emissive layer consisting of a blue emitter (the host polymer), as well as green and red emitting guest polymers. The energy transfer between the host and the various guest compounds is tuned via a reductive photoinitiated process in the presence of gaseous hydrazine. This process is compatible with regular film casting techniques such as spin coating, and therefore can be regarded as a promising alternative to the more complex, traditional patterning approaches.
Si rings, Si clusters, and Si nanocrystals—different states of ultrathin SiOx layers
Authors: Yi L. X. , Heitmann J. , Scholz R. , Zacharias M.
Published: November 2002

Amorphous SiO/SiO2 superlattices were prepared by reactive evaporation of SiO powder in an oxygen atmosphere. Infrared absorption and photoluminescence spectra were measured as a function of annealing temperature. Three photoluminescence emission bands were observed. A band centered at 560 nm is present in as-prepared samples and vanishes for annealing above 700 °C. The second band around 760 nm to 890 nm is detected for annealing temperatures above 500 °C. A strong red luminescence is observed for annealing temperatures above 900 °C. The origin of the different photoluminescence bands and different states of the phase separation of ultrathin SiOx layers is discussed.
Synthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrix
Authors: Kumar D. , Pennycook S. J. , Lupini A. , Duscher G. , Tiwari A. , Narayan J.
Published: November 2002

Single domain magnetic nickel nanocrystals were embedded in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out at the atomic level using scanning transmission electron microscopy with atomic number contrast (STEM-Z) in conjunction with electron energy loss spectroscopy have revealed that the Ni particles are well separated and have interfaces with the host matrix that are atomically sharp and free of any oxide layer. An excellent correlation was found between particle sizes determined theoretically from magnetization versus field data and experimentally using STEM-Z which indicates the absence of any magnetically dead layers on the Ni nanoparticles within an experimental error of 0.1 monolayer.
Porosity effect on the dielectric constant and thermomechanical properties of organosilicate films
Authors: Liu Junjun , Gan Dongwen , Hu Chuan , Kiene Michael , Ho Paul S. , Volksen Willi , Miller Robert D.
Published: November 2002

This letter reports a study of the porosity effect on material properties of methylsilsesquioxane films, including the dielectric constant, thermal conductivity, and thermal stress behavior. In a porosity range from 0% to 50%, both the dielectric constant and thermal conductivity decreased with increasing porosity and no significant change was observed at the percolation point where pores became interconnected. In comparison, the stress–temperature slope also decreased with porosity, but as the porosity approached the percolation point, the slope showed a large drop of 40%, indicating a significant degradation of the thermomechanical properties due to percolation of pores. Assuming the coefficients of thermal expansion remain at 17 ppm/°C within the porosity range, the change in the stress–temperature slope corresponds to a decrease of the biaxial modulus from 7 to 5 GPa around the percolation point.
Enhanced photoconductive gain in quantum-well infrared photodetectors
Authors: Gadir M. A. , Harrison P. , Soref R. A.
Published: November 2002

A quantum-mechanical scattering theory approach is taken to evaluate the capture probability from the continuum into the quantum wells in quantum-well infrared photodetectors. The calculations show that the capture probability is dependent on the well width, the barrier height, and bias. An additional tunnel barrier is introduced to disturb the continuum levels near the top of the quantum well. It is shown that this can be optimized to reduce the capture probability and thus increase the photoconductive gain of the device.
Procedure to induce a persistent current in superconducting cylinders or rings
Authors: González-Jorge H. , Peleteiro J. , Carballo E. , Romanı́ L. , Domarco G.
Published: November 2002

A procedure to induce a persistent current in superconducting cylinders or rings was developed using a coil and a ferromagnetic core. Using the field cooling method, the current is induced from the combined effect of the coil magnetic field and the core magnetization. The proposed method was checked using four Bi-2223 samples. The main usefulness seems to be that a high persistent current can be induced using small both probe currents and coils.
Degradation of ferroelectric properties in integrated Pt/SrBi2Ta2O9/Pt capacitor by impurity diffusion from interlevel dielectric layer
Authors: Oh Sang-Hyun , Hong Suk-Kyoung , Kim Jin Gu , Seong Jin Yong , Park Young-Jin , Lee Deok-Won
Published: November 2002

The ferroelectric properties of integrated Pt/SrBi2Ta2O9 (SBT)/Pt capacitors with boron (B)- and phosphorus (P)-doped silicate glass (BPSG) as an interlevel dielectric layer were investigated. After annealing at 800 °C to densify the BPSG, a significant reduction in remanent polarization was observed. Both transmission electron microscopy and nanoprobe energy dispersive spectroscopy analysis showed bismuth (Bi) and P interdiffusion across the interface between the SBT and BPSG layers. This strongly suggests that Pt/SBT/Pt capacitor degradation results from Bi loss in the surface region of the SBT layer, which is induced by P diffusion into the SBT. The degradation in ferroelectric properties was prevented by inserting a thin undoped silicate glass (USG) layer between the SBT and the BPSG, which blocked P diffusion. From the USG thickness dependence of the remanent polarization, P-induced degradation was also verified.
Silicon tip arrays with ultrathin amorphous diamond apexes
Authors: She J. C. , Xu N. S. , Huq S. E. , Deng S. Z. , Chen Jun
Published: November 2002

Silicon (Si) tip emitter arrays with uniform, smooth, and ultrathin (∼2 nm) amorphous diamond (a-D) apexes were fabricated. Aqueous buffer hydrofluoric acid and H2/Ar plasma have been employed to remove the native oxide layer of Si tips, prior to the a-D film deposition. Scanning electron microscopy study showed that uniform a-D coatings were highly localized on the apex of individual Si tips. Study using high-resolution transmission electron microscopy and x-ray energy dispersive spectroscopy confirmed that the Si/a-D junction is free from the oxide interlayer. Field-emission measurements demonstrated that the removal of the native oxide layer and the a-D apex coating are important to stabilize and enhance the electron emission from Si field emitters.
Thickness dependence on the thermal stability of silver thin films
Authors: Kim H. C. , Alford T. L. , Allee D. R.
Published: November 2002

This study investigates the dependence of Ag resistivity on film thickness during temperature ramping as a means to access thermal stability. In situ van der Pauw four-point probe analysis is used to determine the onset temperature; the temperature when the electrical resistivity deviates from linearity during the temperature ramp. At that point, the silver thin films become unstable due to void formation and growth during thermal annealing. The thermal stability of Ag thin films on SiO2 in a vacuum is greatest when thicknesses are greater than 85 nm. Using an Arrhenius relation in terms of onset temperature and film thickness, an activation energy (0.32±0.02 eV) for the onset of agglomeration in Ag thin films on SiO2 ramped at a rate of 0.1 °C/s is determined. This value is consistent with the activation energy for surface diffusion of silver in a vacuum, which is believed to be the dominant mechanism for agglomeration of silver thin film.
Tunable multichannel optical filter based on silicon photonic band gap materials actuation
Authors: Yi Yasha , Bermel Peter , Wada Kazumi , Duan Xiaoman , Joannopoulos J. D. , Kimerling L. C.
Published: November 2002

A Si-based tunable omnidirectional reflecting photonic band gap structure with a relatively large air gap defect is fabricated and measured. Using only one device, low-voltage tuning around two telecom wavelengths of 1.55 and 1.3 μm by electrostatic force is realized. Four widely spaced resonant modes within the photonic band gap are observed, which is in good agreement with numerical simulations. The whole process is at low temperature and can be compatible with current microelectronics process technology. There are several potential applications of this technology in wavelength division multiplexing devices.
Holographic recording in TiO2 nanoparticle-dispersed methacrylate photopolymer films
Authors: Suzuki Naoaki , Tomita Yasuo , Kojima Takashi
Published: November 2002

We demonstrate permanent holographic storage in the green with high diffraction efficiency and recording sensitivity in TiO2 nanoparticle-dispersed methacrylate photopolymer films. It is shown that the diffraction efficiency as well as the recording sensitivity significantly increase with an increase of nanoparticle concentration. It is also found that volumetric shrinkage during holographic exposure is noticeably suppressed by inclusion of the nanoparticles.
Suppression of silicidation in ZrO2/SiO2/Si structure by helium annealing
Authors: Muraoka Kouichi
Published: November 2002

Suppression of silicidation in ZrO2/SiO2/Si structure by high-temperature helium (He) gas annealing was demonstrated. Comparison of ultrahigh vacuum, 1 Torr N2 and He annealing with controlled oxygen partial pressure (PO2) at 920 °C revealed that the optimal PO2 range in He at which the thermal stability of the layered structure can be achieved is over one order wider than that in N2. This result suggests that He gas physically obstructs SiO removal through the quenching of atomic vibration and the occupation of SiO diffusion path in the ZrO2/SiO2 layer, thus impeding the contact of ZrO2, SiO, and Si effectively, which is the trigger of silicidation. Moreover, rapid thermal He annealing is found to be the most effective means of suppressing transition of interface structure.
Grain-boundary and crack effects on the dielectric response of high-permittivity films and ceramics
Authors: Rychetský I. , Petzelt J. , Ostapchuk T.
Published: November 2002

Grain-boundary and crack effects on the dielectric response of high-permittivity films and ceramics were analyzed using the generalized effective-medium approximation. It was demonstrated that the brick-wall and coated spheres models, which become equivalent for a small porosity, best describe the strong reduction of the dielectric response and hardening of the soft-mode frequency recently revealed in SrTiO3 films and PbZrO3 ceramics.
Effects of Co-doping level on the microstructural and ferromagnetic properties of liquid-delivery metalorganic-chemical-vapor-deposited Ti1−xCoxO2 thin films
Authors: Seong Nak-Jin , Yoon Soon-Gil , Cho Chae-Ryong
Published: November 2002

Polycrystalline Ti1−xCoxO2 thin films on SiO2 (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition, and the microstructure and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed Ti1−xCoxO2 thin films with x⩽0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the Ti1−xCoxO2 (TCO) phases. On the other hand, in case of thin films above x=0.05, Co1−xTix clusters having a soft magnetic (SM) property formed in a homogeneous Ti1−xCoxO2 phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and SMCo–Ti. Co1−xTix clusters with about 150 nm size decreased the value of Hc (coercive field) and increased the saturation magnetic field.
Enhanced thermal stability of strong gratings written in H-loaded tin-phosphosilicate optical fibers
Authors: Brambilla Gilberto
Published: November 2002

Enhanced photosensitivity has been observed in hydrogen-loaded tin-phosphosilicate fibers by using a 248 nm excimer laser. Isothermal measurements up to 860 K demonstrated significant advantages over fiber gratings written in conventional H-loaded fibers.
Patterning organic light-emitting diodes by cathode transfer
Authors: Rhee Jungsoo , Lee Hong H.
Published: November 2002

A technique is presented for patterning the metal cathode of organic light-emitting diodes that allows for cathode engineering. The technique involves transferring pretreated and prepatterned metal on a substrate onto the surface of organic layers of the device by pressing, utilizing a difference in the adhesion strength of the metal between the substrate and the underlying organic layer. This cathode transfer technique is applied to fabricating a 20×10 passive matrix display with a pixel size of 250 μm by 250 μm.
Blue cathodoluminescence from Ba2B5O9Cl:Eu phosphor thin films on glass substrates
Authors: Hao Jianhua , Cocivera Michael
Published: November 2002

Spray pyrolysis was used to deposit thin films of Ba2B5O9Cl:Eu from aqueous solutions containing Eu3+. Blue cathodoluminescence due to the abnormal reduction of Eu3+→Eu2+ in as-grown thin films was observed at the growth temperatures from 140 °C to 500 °C. Significant line narrowing was found as the growth temperature increased. Using either conventional or rapid thermal annealing of thin films in air enhanced the transition of the emission spectrum from several peaks to a sharp single peak. Our results also provide the possibility of tuning the blue emission at temperatures suitable for the use of glass substrates in flat panel applications.
Phosphorescent light-emitting electrochemical cell
Authors: Chen Fang-Chung , Yang Yang , Pei Qibing
Published: November 2002

Due to the harvest of singlet and triplet excitons, highly-efficient phosphorescent polymer light-emitting diodes have been demonstrated. However, the driving voltage of these devices remains high because of the carrier trapping at the dopant sites. To achieve high power efficiency, a phosphorescent light-emitting electrochemical cell, which consists of bis[2-(2′-benzothienyl)-pyridinato-N,C3′]iridium(acetylacetonate) as the dopant, poly[9,9-bis(3,6-dioxaheptyl)-fluorene-2,7-diyl] as the host polymer, and lithium trifluoromethane sulfonate has been demonstrated in this letter. The turn-on voltage for light emission was as low as the band gap of the host material (2.8 eV). Compared with the light-emitting diode with a similar device structure, a sixfold enhancement in power efficiency has been achieved.
Investigation of localized states in cadmium zinc telluride crystals by scanning photodielectric spectroscopy
Authors: Komar V. K. , Migal V. P. , Chugai O. N. , Puzikov V. M. , Nalivaiko D. P. , Grebenyuk N. N.
Published: November 2002

A method of scanning photodielectric spectroscopy of crystals has been suggested. It is based on the measurements of small increments of the real Δε′ and imaginary Δε″ parts of effective dielectric permittivity at a smooth variation of the photoexcitation wavelength λ. The spectral functions Δε′(λ) and Δε″(λ) are presented in a complex plane, that is, in parametric view, and their characteristic points are determined. Application of this method on Cd1−xZnxTe crystals showed a possibility of determining the energy position of the localized states generated in the forbidden zone by the intrinsic structure defects.
A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu
Authors: Han S-J. , Song J. W. , Yang C.-H. , Park S. H. , Park J.-H. , Jeong Y. H. , Rhie K. W.
Published: November 2002

Successful synthesis of room-temperature ferromagnetic semiconductors, Zn1−xFexO, is reported. The essential ingredient in achieving room-temperature ferromagnetism in bulk Zn1−xFexO was found to be additional Cu doping. A transition temperature as high as 550 K was obtained in Zn0.94Fe0.05Cu0.01O; the saturation magnetization at room temperature reached a value of 0.75μB per Fe. A large magnetoresistance was also observed below 100 K.
Modeling of Si 2p core-level shifts at Si–(ZrO2)x(SiO2)1−x interfaces
Authors: Giustino Feliciano , Bongiorno Angelo , Pasquarello Alfredo
Published: November 2002

We model Si 2p core-level shifts at Si–(ZrO2)x(SiO2)1−x interfaces for varying Zr content x. Using a first-principles approach, we calculate Si 2p shifts for a model interface and for cluster models, and establish the validity of a linear dependence of these shifts on both the number of second-neighbor Zr atoms and the O coordination of these Zr atoms. Applying this relation to model structures of amorphous Zr silicates generated by classical molecular dynamics, we find that the Si 2p line shifts to lower binding energies with increasing Zr content x, in accord with experimental data.
Measurement of relaxation between polarization eigenstates in single quantum dots
Authors: Stievater T. H. , Li Xiaoqin , Cubel T. , Steel D. G. , Gammon D. , Katzer D. S. , Park D.
Published: November 2002

Low temperature relaxation of excitons between polarization eigenstates in single interface fluctuation quantum dots is studied using copolarized and cross-polarized transient differential transmission spectroscopy. The measured spin relaxation times are on the order of ∼100 ps. Such a spin relaxation time is longer than the reported times for thin quantum wells, but considerably shorter than the predicted times for interface fluctuation quantum dots.
Horizon 2010: Biophysics at Future High-intensity Neutron Sources
Authors: Middendorf H.D. , Hayward R.L.
Published: November 2002

Third-generation neutron facilities are expected to provide the flux levels and dedicated instruments needed to exploit more fully the rich information content of energy-resolved neutron scattering from biomolecular systems. This paper reviews applications of quasielastic and inelastic neutron scattering to problems in molecular biophysics and discusses likely directions of future work.
Neutron Inelastic Scattering Spectrometer for Protein Dynamics Analysis: DYANA
Authors: Niimura Nobuo , Shibata Kaoru , Dieter Middendorf H.
Published: November 2002

In this paper we describe the underlying scientific motivation and the design of DYANA, a new neutron spectrometer dedicated to biology, biomaterials, and related soft-matter studies.
The Design and Performance of the Indirect Geometry Spectrometer TOSCA
Authors: Parker Stewart F.
Published: November 2002

The design, performance, philosophy, lessons learned and advantages of the indirect geometry spectrometer, TOSCA, at ISIS, are described.
What can TOF–NSE Contribute?
Authors: Farago Bela
Published: November 2002

Neutron spin echo (NSE) is the method which can achieve the highest energy resolution in quasielastic neutron scattering. It is now well established at different steady state neutron sources. It appears that the next generation neutron sources will all be of pulsed spallation type. IN15, the high resolution NSE at the ILL in Grenoble, has a chopper system to work in Time of Flight mode and has demonstrated the technical feasibility and tested the possible advantages of operating in this mode. In soft matter and biological studies, in the great majority of cases, the samples have some characteristics which happen to be very favorable for TOF–NSE and this is what we will try to demonstrate.
Simulation of Virtual SANS Spectrometers at IBR-2 Reactor
Authors: Belushkin A.V. , Manoshin S.A.
Published: November 2002

The experience gained in the last 15 years of experimental studies of large-scale structures with the SANS instrument at the IBR-2 pulsed reactor in Dubna shows that some parameters of the spectrometer can be improved. In particular, it concerns reduction of the fast neutron and gamma backgrounds that limit the possibilities of studying weakly scattering objects. Another direction of improvement is to reduce a minimum momentum transfer value Qmin to study objects with larger characteristic dimensions. The paper investigates several configurations of the SANS machine at IBR-2. The Monte Carlo codes are used to calculate the parameters of such virtual instruments. An optimal instrument structure is proposed.
A Monte Carlo Model for Simulation of Neutron-induced Elastic Recoil Spectra
Authors: Abdurakhmanov A.H. , Artemov S.V. , Zhukovskaya E.V. , Radyuk G.A. , Ulanov V.G. , Jakushev V.P.
Published: November 2002

A procedure for simulation of the energy spectrum and angular distribution of the recoil nuclei from the (n, 1,2,3H) reaction on a thick target is described. The model is based on the Monte Carlo technique and analytic geometry tools. It takes into account the main processes of neutron generation, their interaction with hydrogen in the specimen, the passage of the hydrogen recoil through matter, and the subsequent recording of the recoil. Comparison with calculated spectra of the experimental recoil spectra obtained by the NERD method for various geometric and thermodynamics conditions makes it possible to obtain the depth profile of the concentration of hydrogen isotopes in the specimens.
Hardware Architectures for the Orthogonal and Biorthogonal Wavelet Transform
Authors: Knowles G.
Published: November 2002

In this note, optimal hardware architectures for the orthogonal and biorthogonal wavelet transforms are presented. The approach used here is not the standard lifting method, but takes advantage of the symmetries inherent in the coefficients of the transforms and the decimation/interpolation operators. The design is based on a highly optimized datapath, which seamlessly integrates both orthogonal and biorthogonal transforms, data extension at the edges and the forward and inverse transforms. The datapath design could be further optimized for speed or low power. The datapath is controlled by a small fast control unit which is hard programmed according to the wavelet or wavelets required by the application.

Example circuits are given, including one for the Daubechies 9‐7 wavelet which requires only 2.5 multipliers for each input data value, when the equivalent for lifting is 3.
A Dynamically Reconfigurable Video Compression Scheme Using FPGAs with Coarse‐grain Parallelism
Authors: Ramachandran S. , Srinivasan S.
Published: November 2002

A dynamically reconfigurable scheme for video encoder to switch among many different applications is presented. The scheme is suitable for FPGA implementation and conforms to JPEG, MPEG‐1, MPEG‐2, and H.263 standards. The scheme has emerged as an efficient and cost‐effective solution for video compression as a result of innovative design using well‐partitioned algorithms, highly pipelined architecture and coarse‐grain parallelism. The reconfiguration time of the video encoder is less than 320 μs while switching from one standard to another. Although the dynamic reconfiguration scheme is presented for a video encoder, the same design methodology may be applied effectively for any other application.
A Combined Coefficient Segmentation and Block Processing Algorithm for Low Power Implementation of FIR Digital Filters
Authors: Erdogan A. T. , Arslan T.
Published: November 2002

A combined coefficient segmentation and block processing algorithm for low power implementation of FIR digital filters is described in this paper. The algorithm processes data and coefficients in blocks of fixed sizes. During the manipulation of each block, coefficients are segmented into two primitive components. The accumulative effect of processing a sequence of blocks and segmentation results in up to 80% reduction in power consumption in the multiplier circuit compared to conventional filtering. The paper describes the implementation of the algorithm, its constituent components, and the power evaluation environment developed. Simulations are performed using eight practical digital filter examples with various filter orders and data/coefficient wordlengths. In addition, the algorithm is compared with conventional filtering implementations and those using block processing and coefficient segmentation algorithms alone.
Minimizing Spurious Switching Activities with Transistor Sizing
Authors: Wróblewski Artur , Schimpfle Christian V. , Schumacher Otto , Nossek Josef A.
Published: November 2002

In combinatorial blocks of static CMOS circuits transistor sizing can be applied for delay balancing as to guarantee synchronously arriving signal slopes at the input of logic gates, thereby avoiding glitches. Since the delay of logic gates depends directly on transistor sizes, their variation allows equalizing different path delays without influencing the total delay of the circuit. Unfortunately, not only the delay, but also power consumption circuits depend on the transistor sizes. To achieve optimal results, transistor lengths have to be increased, which results in both increased gate capacitances and area. Splitting the long transistors counteracts this negative influence.
Timing Challenges for Very Deep Sub‐Micron (VDSM) IC
Authors: Lin Ichiang , Chen Chien-In Henry
Published: November 2002

Many IC design houses failed to be market leaders because they miss the market window due to timing closure problems. Compared to half‐micron designs, the amount of time spent on timing verification has greatly increased. Cell delays can be accurately estimated during logic synthesis. However, interconnect delays are unknown until the wire geometry is defined in physical design. Logic synthesis using the cell library models for interconnect delay estimates may be statistically accurate, but can not predict the delay of individual nets accurately. Delay estimates for individual nets (global nets, long wires, large fan‐outs, buses), which matter most for the critical paths can be inaccurate and cause a design failure. Inaccurate timing verification causes silicon failure in shipped products that results in the loss of millions of dollars spent designing a high‐performance product and potentially larger costs due to lost market share. Full‐chip, sign‐off verification with silicon‐accuracy will allow these problems to be discovered and fixed before tape‐out.
Energy Efficient Signaling in Deep‐submicron Technology
Authors: Dhaou Imed Ben , Parhi Keshab K. , Tenhunen Hannu
Published: November 2002

In deep‐submicron technology, global interconnect capacitances have started reaching several orders of magnitude greater than the intrinsic capacitances of the CMOS gates. The dynamic power consumption of a CMOS gate driving a global wire is the sum of the power dissipated due to (dis)charging (i) the intrinsic capacitance of the gate, and (ii) the wire capacitance. The latter is referred to as on‐chip signaling power consumption.

In this paper, a scheme has been proposed for combating crosstalk noise and reducing power consumption while driving the global wire at an optimal delay. This scheme is based on reduced voltage‐swing signaling combined with buffer‐insertion and resizing. The buffers are inserted and resized to compensate for the speed degradation caused by scaling the supply voltage and eradicating the crosstalk noise. A new buffer insertion algorithm called VIJIM has been described here, along with accurate delay and crosstalk‐noise estimation algorithms for distributed RLC wires.

The experimental results show that the VIJIM algorithm inserts fewer buffers into non‐critical nets than does the existing buffer‐insertion algorithms. In a 0.25 mm CMOS process, the experimental results show that energy savings of over 60% can be achived if the supply voltage is reduced from 2.5 to 1.5 V.
Accurate Coupling‐centric Timing Analysis Incorporating Temporal and Functional Isolation
Authors: Arunachalam Ravishankar , Blanton Ronald DeShawn , Pileggi Lawrence T.
Published: November 2002

Neighboring line switching can contribute to a large portion of the delay of a line for today′s deep submicron designs. The impact of this switching on delay is usually estimated by scaling the coupling capacitances (often by a factor of 2) and modeling them as grounded. This simple approach has been shown to be overly pessimistic in some cases, while somewhat optimistic in others. Apart from the delay modeling inaccuracies, the temporal and functional isolation of the aggressors can contribute to the pessimism. This paper introduces TACO, a timing analysis approach that addresses both these issues. TACO captures the provably worst‐and best‐case delays as a function of the timing‐window inputs to the gates. We then present a comprehensive ATPG‐based approach that uses functional information to identify valid interactions between coupled lines. Our algorithm accounts for glitches on aggressors that can be caused by static and dynamic hazards in the circuit. Results on industrial examples and benchmark circuits show the value of our approach.
Improving the Timing of Extended Finite State Machines Via Catalyst
Authors: Huang Shi-Yu
Published: November 2002

We propose a timing optimization technique for a complex finite state machine that consists of not only random logic but also data operators. In such a design, the timing critical path often forms a cycle and thus cannot be cut down easily by popular techniques such as pipelining or retiming. The proposed technique, based on the concept of catalyst, adds a functionally redundant block—which includes a piece of combinational logic and several other registers—to the circuits under consideration so that the timing critical paths are divided into stages. During this transformation, the circuit′s functionality is not affected, while the speed is improved significantly. This technique has been successfully applied to an industrial application—a Built‐In Self‐Test (BIST) circuit for static random access memories (SRAMs). The synthesis result indicates a 47% clock cycle time reduction.
Two‐valley Hydrodynamical Models for Electron Transport in Gallium Arsenide: Simulation of Gunn Oscillations
Authors: Anile A. Marcello , Hern Simon D.
Published: November 2002

To accurately describe non‐stationary carrier transport in GaAs devices, it is necessary to use Monte Carlo methods or hydrodynamical (or energy transport) models which incorporate population transfer between valleys.We present here simulations of Gunn oscillations in a GaAs diode based on two‐valley hydrodynamical models: the classic Bløtekjær model and two recently developed moment expansion models. Scattering parameters within the models are obtained from homogeneous Monte Carlo simulations, and these are compared against expressions in the literature. Comparisons are made between our hydrodynamical results, existing work, and direct Monte Carlo simulations of the oscillator device.
An Analytical Study of Smooth Solutions of the Bløtekjær Hydrodynamic Model of Electron Transport
Authors: Jerome Joseph W.
Published: November 2002

We study the Bløtekjær hydrodynamic model from the standpoint of local well‐posedness. We employ analytical methods, originally introduced by T. Kato for complex systems, to obtain the existence of unique local smooth solutions of the Cauchy problem, with smooth initial data. The time interval is invariant with respect to vanishing heat flux. The model is self‐consistent, and is developed for onevalley electron carriers only. A symmetrizer is introduced for the system, and regularization is employed to avoid the formation of singularities due to vacuum regions. In the regime studied, it is not possible for shocks to form.
Frequency Domain Kernel Estimation for 2nd‐order Volterra Models Using Random Multi‐tone Excitation
Authors: Bicken G. , Carey G. F. , Stearman R. O.
Published: November 2002

We consider the problem of frequency domain kernel estimation using random multi‐tone (harmonic) excitation for 2nd‐order Volterra models. The basic approach is based on least squares minimization of model output error, and results for the Volterra kernel estimations with random multi‐tone inputs and random Gaussian input are compared. We show that kernel estimation with multi‐tones are very accurate and efficient compared to the latter. As an illustration, the proposed method is applied to a discrete input–output system obtained from the numerical simulation of a representative hydrodynamic system for modeling semiconductor device transport. We also consider the effect of noise in the kernel estimation.
Comparison of Single‐Particle Monte Carlo Simulation with Measured Output Characteristics of an 0.1µm n‐MOSFET
Authors: Bufler F. M. , Schenk A. , Zechner C. , Inada N. , Asahi Y. , Fichtner W.
Published: November 2002

A comparison between non‐selfconsistent single‐particle Monte Carlo (MC) simulations and measurements of the output characteristics of an 0.1 µm n‐MOSFET is presented. First the bulk MC model, which features a new simplified treatment of inelastic acoustic intravalley scattering, is validated by comparison with experimental literature data for mobilities and velocities. The dopant distribution of the MOSFET is obtained from a 2D process simulation, which is calibrated with SIMS and electrical measurements and fine‐tuned by a comparison of the measured transfer characteristics in the subthreshold regime with a coupled Schro¨dinger drift‐diffusion (DD) simulation. Then the quantum effect is replaced by a shift of the work function and the DD, hydrodynamic (HD) and MC models are adjusted to reproduce the measured drain current in the linear regime. The results of the three models in the non‐linear regime are compared without further adjustment to the measured output characteristics. While good agreement is found for the MC model, the on‐current is significantly overestimated by the HD model and underestimated by the DD model.
Getting the measure of freshwater fish habitat in New Zealand
Authors: McDowall R. M.
Published: November 2002

New Zealand has prolific, cool, clear fresh water of high quality, found in numerous medium to small rivers and streams and low elevation to high country lakes. These waterways carry a highly endemic fish fauna of low diversity (36 indigenous species, 21 exotic species). The indigenous fauna is dominated by Galaxiidae (20 species), whereas the most diverse exotic groups are Salmonidae and Cyprinidae (7 species of each). The steep topography of the country means that the rivers and streams tend to be swiftly flowing, with coarse gravel and cobble, substrates of hard rock, and a high proportion of the indigenous species live within these substrates. About half the indigenous species are diadromous, undertaking regular, seasonally-timed migrations to and from the sea. Fisheries based on the indigenous fauna include modest commercial anguillid eel and galaxiid whitebait fisheries, but probably the chief form of freshwater fisheries exploitation (in overall economic terms) is for New Zealand's world-renowned, recreational angling fisheries for salmonids. Research on the fauna is broadly spread across diverse fields, from studies of the place of freshwater fishes in the community ecology of river and stream biotas as a whole, to focussed studies on habitats of threatened species, design of fish passage facilities for migratory fishes, the effects of introduced exotic species on the indigenous fauna, the impacts of human stream perturbation on aquatic values including fish, and understanding the local ecology of species introduced to New Zealand from other lands.
Stream Fish Habitat Science and Management in Japan: A Review
Authors: Taniguchi Yoshinori , Inoue Mikio , Kawaguchi Yoichi
Published: November 2002

Japanese freshwater fish habitats can be generally categorized into 1) rivers and streams, 2) ponds and lakes, and 3) rice fields and small irrigation channels connecting them. Of these, reviewing studies on stream fish habitat is the primary objective of this paper. Streams in Japan have widely received severe habitat alterations through construction of artificial instream structures as well as modification of riparian vegetations. As a result, streamdwelling fishes that require natural flow regimes, substrates, and riparian vegetation have declined their populations in great deal in many parts of the country. Recent studies have found riparian forests control water temperature and provide woody debris creating cover structures for the stream fishes resulting in enhancing their carrying capacity. Differences in riparian vegetation types (forest versus grass) played an important role in determining the local distribution of salmonids. Also, experiments removing concrete-lined channel and installing log-drop structures demonstrated that such the treatment greatly improved fish habitat.

As the general public became aware of the serious degradation of aquatic habitats, river management policy has gradually shifted to include conservation and improvement of river environment as habitat for wildlife during the last two decades. For fish migration, installation of fishway on dams has been prevailing, and research efforts have been made to design more effective fishway and passable weirs. In many cases, however, such restoration work lacks ecological data for assessment of their effectiveness. When such knowledge on fish habitat are accumulated, a vital issue will be how it is accounted into actual management. Future studies on fish habitat should shift toward treating habitat network at larger spatial scales to seek better designs for distributing appropriate habitats over a whole catchment. Such studies should also include clarifying the habitat requirements of endangered species and effects of non-native on native species.
Freshwater fish habitat science and management in Greece
Authors: Bobori D. C. , Economidis P. S. , Maurakis E. G.
Published: November 2002

Objectives are to (1) characterize the current status of and threats to freshwater fish habitats, native fishes, and fisheries in Greece; (2) canvas the states and priorities of fisheries science, legislation, and regulations for freshwater habitats and their fishes/fisheries; (3) indicate priority gaps in freshwater fish habitat management; and (4) comment on planning and managing strategies for freshwater aquatic resources and fishes in Greece. Freshwater fishes total 126 species (58 % endemic), 19 of which are introductions. Inland fishery production (about 700 t in 1999) has steadily decreased (due to overfishing, habitat alteration, and pollution) for the past 40 years while marine fisheries have increased from ∼12000 to 30000 t in 30 years (1964-1994). Population declines and extirpation of fish species and their habitats have been related to dam construction and operation, stream channelization, canalization, pollution, and stream desiccation, a result of water abstraction for crop irrigation and diversion of river and stream waters for potable waters supplies of urban and rural areas. Published information on habitat requirements (i.e., spawning habitat, spawning behavior, nursery areas, foraging ranges, vegetative cover, and migration) of freshwater fishes in Greece is limited. Absence of coordination among ministries and an increased market-based economy have resulted in low conservation priorities and investments for freshwater environs. Conservation programs and action plans have been implemented in Greece only recently for two endemic fish species (Pungitius hellenicus and Ladigesocypris ghigii) compared to 14 for other vertebrate species. Regardless of environmental statues and presidential decrees since 1970, there is no current established national action plan to improve and integrate aquatic environments and natural habitat management in a growing market-based economic strategic plan. Recommendations for the creation of an integrated, national action plan that incorporates environmental costs of protecting freshwater aquatic habitats and fish communities in sustainable economic policies and goals of Greece, an European fringe country experiencing significant competition in the international marketplace are presented.
Status of freshwater fish habitat science in Great Britain
Authors: Hughes S. , Aprahamian M. , Armstrong J. D. , Gardiner R. , Milner N.
Published: November 2002

The general understanding of how habitats influence populations of freshwater fishes in Great Britain is reviewed briefly as a component of a Europe-wide comparison. Great Britain, an island of temperate climate in the north west of Europe comprising the countries England, Scotland and Wales, has diverse aquatic habitats but a relatively impoverished freshwater fish fauna. Recreational rod-and-line fisheries for certain salmonids and non-salmonids termed coarse fish are valuable components of the economies of the countries comprising Great Britain. In some cases, distribution and abundance of fish species and their population sizes are constrained by habitat degradation. There is a growing awareness of the multidimensional importance of habitat management to develop and maintain high quality fisheries. Current knowledge of fish habitat requirements is patchy; progress has been made on salmonids and some coarse fish species. Fish habitat science has an important role in integrated river catchment management, which is reflected in recent national and international legislation.
Freshwater Fish Habitat: Science, Management, and Conservation in France
Authors: Souchon Y. , Keith P.
Published: November 2002

Characteristics of French water bodies and fish fauna are described with special reference to physically altered streams. Recent researches on fish physical habitat have produced new insights on: models of probability of fish distributions at a watershed scale, fish ecology, in particular about their habitat preferences, hydraulic statistical modelling with simplification of data collection, models of impacts of flow or modifications to stream morphology, and coupling physics and biology. These models have been validated at fish population (trout) or assemblage (Rhône river) level.

Other complementary researches are dealing with fluvial dynamics necessary to maintain habitat or with ecological dynamic linked to flows and morphology (especially substrate).

For the legal point of view, Fishing law (1984 in FCE a), Water law (1992 in FCE b), and the last European Water Framework Directive (2000) defined the limits of hydrosystems utilization. They defended the principle of an equilibrium between hydrosystems utilization.

It is also necessary to better link streams and their watersheds. Waterbodies regionalization will be a good way to reduce the natural variability of physical and biological situations in order to better manage ecological entities with respect of their sensitivity. The setting of a national survey of fish communities is fundamental.

National conservation programmes with main protected areas of France has not been very successful at protecting freshwater fish. Rehabilitation plans of some emblematic fish species Salmon, Sturgeon, Eel, Shad have helped to coordinate actions in large heavily anthropised rivers. In other numerous aquatic systems, it is better to restore the functioning of the first key compartments, hydrology and morphology. Fish communities are in these cases good measures of the benefits of rehabilitation actions.

Future research will deal with different interfaces between physics and biology, in order to better manage channels, sediments, flows, and riparian vegetation.