WorldWideScience
 
 
1

Small-signal Loudspeaker Impedance Emulator  

DEFF Research Database (Denmark)

Specifying the performance of audio ampliers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterised by the mechanical resonance between the mass of the diaphragm and the compliance of its' suspension which vary from driver to driver. Therefore a loudspeaker emulator capable of adjusting its' impedance to a given driver is in need for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible to emulate the loudspeaker impedance with an electric circuit and that its' resonance frequency can be changed by tuning two resistors.

Knott, Arnold; Iversen, Niels Elkjær

2014-01-01

2

A small - signal stability analysis of DFIG wind generation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper examines the small-signal stability impacts of high penetrations of doubly-fed induction generator (DFIG) wind turbines on power systems. It provides a basic overview of small-signal stability concepts and then examines the response of DFIG generation to two local contingency event. Using the New England 39 bus test system, this paper will demonstrate the stability implications of DFIG turbines utilizing terminal voltage control and fixed power factor control in response...

Vittal, Eknath; O Malley, Mark; Keane, Andrew

2009-01-01

3

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth...

Zhao, Hx; Yoon, Sf; Tong, Cz; Liu, Cy; Wang, R.; Cao, Q.

2010-01-01

4

Power system small signal stability analysis and control  

CERN Document Server

Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system

Mondal, Debasish; Sengupta, Aparajita

2014-01-01

5

Small-Signal Amplifier with MOSFET and BJT in Triple Darlington Configuration  

Directory of Open Access Journals (Sweden)

Full Text Available A new circuit model of a small-signal narrow-band amplifier is proposed and analyzed on the qualitative scale. Proposed amplifier uses two MOSFETs and a BJT in Triple Darlington configuration with two additional biasing resistances in the circuit. With low distortion percentage (1.28%, the proposed circuit successfully amplifies small-signals of 1-10mV range and simultaneously provides high voltage gain (311.593 and current gain (13.971K with narrow bandwidth (9.665KHz. Variations of maximum voltage gain with different biasing resistances and DC supply voltage and the temperature sensitivity of various performance parameters are elaborately studied and discussed in length. Qualitative performance of the proposed amplifier is also compared with the circuit which is having BJT-MOSFET in Darlington pair configuration. The proposed amplifier can be used to process audio range signal excursions and may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in narrow-band low frequency region.

SUSMRITA SRIVASTAVA

2013-02-01

6

Robustness of Supersensitivity to Small Signals in Nonlinear Dynamical Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nonlinear dynamical systems possessing an invariant subspace can display interesting dynamical behavior, such as on-off intermittency and bubbling. This letter shows that a class of such systems have amazing features of (1) supersensitivity to small input signals and (2) robustness of the supersensitivity in the presence of noise. These features make the systems very promising as small signal detectors.

Zhou, Changsong; Lai, C. -h

2000-01-01

7

Carbon dioxide laser system with zero small signal gain  

Energy Technology Data Exchange (ETDEWEB)

The design and performance of a small multipass CO/sub 2/ laser system that has been fully stabilized against parasitic oscillations are described. By the use of a multicomponent gas isolator mixture, the round-trip small-signal gain of the system is reduced to zero, while the output power remains at 40% of its nonstabilized value.

Figueira, J.F.; Nowak, A.V.

1980-02-01

8

Small Signal Dynamic Analysis of the TCSC compensated Transmission Line  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a linearized time-invariant and discrete-time model to analyze the small signal dynamics of the TCSC with minute variations of the conduction angle. In this paper, system considered is a system of one machine connected to an infinite bus through a thyristor controlled series compensated transmission line. Three boundary conditions of the TCSC dynamics and the zero-crossing displacement of the line current are considered to obtain an accurate model. The proposed model for small signal dynamic analysis of the TCSC is verified through the comparison of the analysis results obtained from the periodic state space model. This paper also presents analysis of the eigenvalues of the TCSC using the proposed model. the proposed method is expected to be advantageously used in an accurate analysis of the TCSC dynamics and the designing of the TCSC controller. (author). refs., figs.

Han, Hak Guhn [Dong Yang Technical College (Korea, Republic of); Kim, Kwang Ho [Kang Won National University (Korea, Republic of); Moon, Seung Ill; Park, Jong Keun [Seoul National University (Korea, Republic of); Han, Byung Moon [Myong Ji University (Korea, Republic of)

1998-06-01

9

DFIG turbine representation for small signal voltage control studies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper addresses the representation of a wind power plant, based on wound rotor asynchronous generators, with a centralized voltage controller, by an equivalent transfer function, valid for small signal voltage control studies. This representation allows to investigate the influence of the centralized plant control gain and short circuit ratio on the system stability, for instance, by analyzing the zero-pole placement. Larger percentages of wind power penetration translate to more demandi...

Garcia, Jorge Martinez; Kjær, Philip Carne; Teodorescu, Remus

2010-01-01

10

Small-signal gain in a gas-loaded FEL  

Energy Technology Data Exchange (ETDEWEB)

At present, existing FEL facilities operate in the infrared and visible ranges of wavelengths. Generation of shorter waves (in the VUV and X-ray region) is of great scientific interest, but this would require a very expensive accelerator which could provide a high-current electron beam in the GeV-range of energies. A promising way to relax requirements on electron energy by introduction of a gas into the optical cavity was proposed nearly ten years ago. For small deviations from the vacuum wavelength, the idea was confirmed in experiments performed in Stanford; however, a detailed theory of such a device is still not developed. We present an analysis of the small-signal gain in a gas-loaded free-electron laser. Multiple scattering of electrons by the atoms of the gas inside the optical cavity is shown to lead to two additional effects, as compared to the case of a vacuum FEL: a loss of coherence between different parts of the electron trajectory and an enhancement of the phase {open_quotes}jitter{close_quotes}. Both effects become increasingly important at short wavelengths and significantly reduce the small-signal gain per pass. In 1D approximation analytical expressions are obtained and numerical calculations are made to estimate beam and undulator parameters necessary for lasing in the vacuum ultraviolet. Hydrogen-filled FELs are shown to have good prospects for this at today`s technological level. To operate in the range of wavelengths 125-140 nm, an electron beam should have an energy above 50 MeV and a good quality: a normalised emittance of the order of 5{pi} mm-mrad and an energy spread below 10{sup -3}. All these parameters are achieveable with modern linacs and photoinjectors.

Goloviznin, V.V.; Amersfoort, P.W. van [FOM-Institute for Plasma Physics, Nieuwegein (Netherlands)

1995-12-31

11

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Science.gov (United States)

We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5-50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

Zhao, Hx; Yoon, Sf; Tong, Cz; Liu, Cy; Wang, R.; Cao, Q.

2011-12-01

12

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C. Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

Tong CZ

2011-01-01

13

Thermal Effects and Small Signal Modulation of 1.3-?m InAs/GaAs Self-Assembled Quantum-Dot Lasers  

Science.gov (United States)

We investigate the influence of thermal effects on the high-speed performance of 1.3-?m InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.

2011-01-01

14

Analytical theory of a small signal modulation response of a transistor laser with dots-in-well in the base  

International Nuclear Information System (INIS)

We have developed the theory for the threshold base current, light power output and small signal modulation response of a transistor laser, the base of which contains a quantum well (QW) with a layer of quantum dots (QDs) inserted within it. Our theory involves the solution of the continuity equation for an arbitrary location of the QW in the base, and the solution of coupled rate equations for carriers and photons in the QD. The excitonic recombination model is assumed to be valid in the QD. The estimated threshold base current for InAs QDs embedded in the InGaAs QW is found to be smaller than the value for the InGaAs QW in the GaAs base. The values of the modulation bandwidths for different values of the base current however do not reach the high values obtained for the QW system. (paper)

2012-01-11

15

Modeling and Small-Signal Analysis of Controlled On-time Boost Power Factor Correction Circuit  

Energy Technology Data Exchange (ETDEWEB)

A large-signal average model for the controlled on-time boost power factor correction(PFC) circuit is developed and subsequently linearized resulting in a small-signal model for the PFC circuit. Ac analyses are performed using the small-signal model, revealing new results on small-signal dynamics of the PFC circuit. The analysis results and model predictions are confirmed with experimental measurements on a 200W prototype PFC circuit. (author). refs., figs.

Park, Hyokil [Samsung Electronics Co., Ltd. (Korea); Hong, Sung Soo [Kookmin University (Korea); Choi, Byung Cho [Kyungpook National University (Korea)

2000-05-01

16

The Bandwidth Exchange Architecture  

CERN Document Server

New applications for the Internet such as video on demand, grid computing etc. depend on the availability of high bandwidth connections with acceptable Quality of Service (QoS). There appears to be, therefore, a requirement for a market where bandwidth-related transactions can take place. For this market to be effective, it must be efficient for both the provider (seller) and the user (buyer) of the bandwidth. This implies that: (a) the buyer must have a wide choice of providers that operate in a competitive environment, (b) the seller must be assured that a QoS transaction will be paid by the customer, and (c) the QoS transaction establishment must have low overheads so that it may be used by individual customers without a significant burden to the provider. In order to satisfy these requirements, we propose a framework that allows customers to purchase bandwidth using an open market where providers advertise links and capacities and customers bid for these services. The model is close to that of a commoditi...

Turner, D M; Keromytis, A D; Turner, David Michael; Prevelakis, Vassilis; Keromytis, Angelos D.

2005-01-01

17

Electronic Bandwidth Compression Module.  

Science.gov (United States)

This final report describes the design, construction and operation of a 80 stage, high speed CCD based Bandwidth Compression Module which samples a high speed signal at 400MHz, stores this data, and reads the data out at a 400KHz rate. The module is to be...

K. Petrosky D. Bozanic

1984-01-01

18

P3DB 3.0: From plant phosphorylation sites to protein networks  

Science.gov (United States)

In the past few years, the Plant Protein Phosphorylation Database (P3DB, http://p3db.org) has become one of the most significant in vivo data resources for studying plant phosphoproteomics. We have substantially updated P3DB with respect to format, new datasets and analytic tools. In the P3DB 3.0, there are altogether 47 923 phosphosites in 16 477 phosphoproteins curated across nine plant organisms from 32 studies, which have met our multiple quality standards for acquisition of in vivo phosphorylation site data. Centralized by these phosphorylation data, multiple related data and annotations are provided, including protein–protein interaction (PPI), gene ontology, protein tertiary structures, orthologous sequences, kinase/phosphatase classification and Kinase Client Assay (KiC Assay) data—all of which provides context for the phosphorylation event. In addition, P3DB 3.0 incorporates multiple network viewers for the above features, such as PPI network, kinase-substrate network, phosphatase-substrate network, and domain co-occurrence network to help study phosphorylation from a systems point of view. Furthermore, the new P3DB reflects a community-based design through which users can share datasets and automate data depository processes for publication purposes. Each of these new features supports the goal of making P3DB a comprehensive, systematic and interactive platform for phosphoproteomics research.

Yao, Qiuming; Ge, Huangyi; Wu, Shangquan; Zhang, Ning; Chen, Wei; Xu, Chunhui; Gao, Jianjiong; Thelen, Jay J.; Xu, Dong

2014-01-01

19

Bandwidth in bolometric interferometry  

CERN Document Server

Bolometric Interferometry is a technology currently under development that will be first dedicated to the detection of B-mode polarization fluctuations in the Cosmic Microwave Background. A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers in order to be competitive with imaging experiments. A crucial concern is that interferometers are presumed to be importantly affected by a spoiling effect known as bandwidth smearing. In this paper, we investigate how the bandwidth modifies the work principle of a bolometric interferometer and how it affects its sensitivity to the CMB angular power spectra. We obtain analytical expressions for the broadband visibilities measured by broadband heterodyne and bolometric interferometers. We investigate how the visibilities must be reconstructed in a broadband bolometric interferometer and show that this critically depends on hardware properties of the modulation phase shifters. Using an angular power spectrum estimator ...

Charlassier, R; Hamilton, J -Ch; Kaplan, J; Malu, S

2009-01-01

20

Radio Interferometers with wide bandwidths  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Australia Telescope Compact Array and the Very Large Array are currently being upgraded to operate with wide bandwidths; interferometers dedicated to the measurement of cosmic microwave background anisotropies are being designed with large instantaneous bandwidths for high sensitivity. Interferometers with wide instantaneous bandwidths that do not operate with correlators capable of decomposing the bands into narrow channels suffer from `bandwidth smearing' effects in wi...

Subrahmanyan, Ravi

2003-01-01

 
 
 
 
21

Small-Signal Stability of Wind Power System With Full-Load Converter Interfaced Wind Turbines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants (WPP). In this paper a comprehensive analysis is presented which assesses the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damp...

Knu?ppel, Thyge; Nielsen, Jørgen Nygaard; Jensen, Kim Høj; Dixon, Andrew; Østergaard, Jacob

2012-01-01

22

Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale...

Knu?ppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nyga?rd; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

2009-01-01

23

Small Signal Stability Improvement and Congestion Management Using PSO Based TCSC Controller  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper an attempt has been made to study the application of Thyristor Controlled Series Capacitor (TCSC) to mitigate small signal stability problem in addition to congestion management of a heavily loaded line in a multimachine power system. The Flexible AC Transmission System (FACTS) devices such as TCSC can be used to control the power flows in the network and can help in improvement of small signal stability aspect. It can also provide relief to congestion in the heavily loaded line...

Mondal, D.; Chakrabarti, A.; Sengupta, A.

2011-01-01

24

Estimating Bottleneck Bandwidth using TCP  

Science.gov (United States)

Various issues associated with estimating bottleneck bandwidth using TCP are presented in viewgraph form. Specific topics include: 1) Why TCP is wanted to estimate the bottleneck bandwidth; 2) Setting ssthresh to an appropriate value to reduce loss; 3) Possible packet-pair solutions; and 4) Preliminary results: ACTS and the Internet.

Allman, Mark

1998-01-01

25

Study on Small Signal Stability Improvement by PSS of the Large-Scale Wind Power Integration  

Directory of Open Access Journals (Sweden)

Full Text Available With the increasing penetration of wind energy generation into power system, the impact of wind farms on power grids performance and stability control is of growing concern. Firstly there is a introduction of basic principles related to small signal stability analysis. Then a new method of improving small signal stability is proposed in this paper. The method, based on optimization adjustment of time constant of the phase shift link of PSS, is verified to be effective by an instance analysis of simulation in DIgSILENT/Power Factory. Three-machine Nine Nodes Model is used in this simulation.

Zi Lan Zhao

2013-04-01

26

SMALL-SIGNAL GAIN MEASUREMENTS AT THE CENTER LINE IN A C.W. DF LASER  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Measurements of the small-signal gain of the laser medium produced by a DF combustion-driven continuous wave chemical laser are presented. A low power hydrogen (deuterium) fluoride mixing laser has been developed as probe laser which produces cw radiation on a single line and single TEMooq mode. By applying a saw-tooth voltage to the P.Z.T. crystal modulating the laser cavity length we measured the gain at the center line. The small-signal gain profile along the gas flow direction was observe...

Gastaud, M.; Voignier, F.; Bousselet, P.; Regnier, P.

1980-01-01

27

Linearized Modeling of Single Machine Infinite Bus Power System and Controllers for Small Signal Stability Investigation and Enhancement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Small signal stability investigation is vital as thesystem outage due small signal perturbation being unknown tothe system operators. The small signal disturbance may beinitiating event for large system outage. The Single MachineInfinite Bus (SMIB) power system helps in tuning thecontrollers at one machine without considering the effect ofother machines in the power system. The effect of disturbanceseen by the machine being 100%, whereas in interconnectedpower system the effect gets distribut...

2012-01-01

28

Network Bandwidth Utilization Forecast Model on High Bandwidth Network  

Energy Technology Data Exchange (ETDEWEB)

With the increasing number of geographically distributed scientific collaborations and the scale of the data size growth, it has become more challenging for users to achieve the best possible network performance on a shared network. We have developed a forecast model to predict expected bandwidth utilization for high-bandwidth wide area network. The forecast model can improve the efficiency of resource utilization and scheduling data movements on high-bandwidth network to accommodate ever increasing data volume for large-scale scientific data applications. Univariate model is developed with STL and ARIMA on SNMP path utilization data. Compared with traditional approach such as Box-Jenkins methodology, our forecast model reduces computation time by 83.2percent. It also shows resilience against abrupt network usage change. The accuracy of the forecast model is within the standard deviation of the monitored measurements.

Yoo, Wucherl; Sim, Alex

2014-07-07

29

Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines  

DEFF Research Database (Denmark)

Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale integration of full-load converter interfaced wind turbines on inter-area oscillations in a three generator network. A detailed aggregated wind turbine model is employed which includes all necessary control functions. It is shown that the wind urbines have very low participation in the inter-area power oscillation.

Knüppel, Thyge; Akhmatov, Vladislav

2009-01-01

30

Small-Signal Stability of Wind Power System With Full-Load Converter Interfaced Wind Turbines  

DEFF Research Database (Denmark)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants (WPP). In this paper a comprehensive analysis is presented which assesses the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine (WT) model with all grid relevant control functions is used in the study. The WT is, furthermore, equipped with a park level WPP voltage controller and comparisons are presented. The WT model for this work is a validated dynamic model of the 3.6 MW Siemens Wind Power WT. The study is based on modal analysis which is complemented with time domain simulations on the nonlinear system.

Knüppel, Thyge; Nielsen, Jørgen Nygaard

2012-01-01

31

ANNs in Bias Dependant Small-Signal and Noise Modeling of Microwave FETs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper an efficient procedure for determination of small-signal and noise behavior of microwave transistors for various bias conditions is proposed. An empirical transistor noise model based on an equivalent circuit (improvement of Pospieszalski’s noise model) is considered. Since it is necessary to extract values of the model equivalent circuit for each bias point (which requires the measured data acquiring and repeated time consuming extraction procedures), it is proposed to use an...

Marinkovic?, Z. D.; Pronic?-ranc?ic?, O.; Markovic?, V.

2010-01-01

32

Appropriate placement of series compensators to improve small signal stability of power system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Series FACTS devices like thyristor controlled series capacitors (TCSC) equipped with appropriate supplementary damping controller can improve the small signal stability of power system if they are located properly. In this paper, trajectory sensitivity analysis (TSA) is used to determine the best locations for installing TCSC to damp out the inter-area mode of oscillation. Based on the modal analysis, an equivalent angle is defined by determining critical and non-critical machines, and then ...

Nasri, Amin

2012-01-01

33

High-bandwidth memory interface  

CERN Document Server

This book provides an overview of recent advances in memory interface design at both the architecture and circuit levels. Coverage includes signal integrity and testing, TSV interface, high-speed serial interface including equalization, ODT, pre-emphasis, wide I/O interface including crosstalk, skew cancellation, and clock generation and distribution. Trends for further bandwidth enhancement are also covered.   • Enables readers with minimal background in memory design to understand the basics of high-bandwidth memory interface design; • Presents state-of-the-art techniques for memory interface design; • Covers memory interface design at both the circuit level and system architecture level.

Kim, Chulwoo; Song, Junyoung

2014-01-01

34

On the small-signal theory of stimulated Cherenkov emission in dielectric-lined waveguides  

International Nuclear Information System (INIS)

The growth characteristics of a two-dimensional Cherenkov free-electron laser (CFEL) in the small-signal low gain regime are studied for both single-electron and collective models. In the single-electron regime, for a thick enough beam, we prove that the gain of the CFEL can be increased by a factor of 2 than that obtained for an infinitely thin electron beam. Thus, the Cherenkov laser should be considered as a hybrid longitudinal/transverse free-electron laser device in general. In the collective-regime, we demonstrate the damping effects of Coulomb collisions among electrons on the amplification characteristics of a Cherenkov laser.

2012-05-01

35

State Space Modeling and Small Signal Stability Analysis of Synchronous Generator with Fuzzy based AVR  

Directory of Open Access Journals (Sweden)

Full Text Available

This paper presents a linear mathematical model of a Synchronous Generator with excitation system for small signal stability analysis. This work aims to develop a controller based on fuzzy logic to simulate an Automatic Voltage Regulator (AVR for a synchronous generator. The performance of fuzzy based AVR is tested on Single Machine connected to an Infinite Bus bar system (SMIB in the MATLAB/SIMULINK platform and the results are compared with the IEEE Exciter model.

Selvi K

2012-10-01

36

A transfer function approach to the small-signal response of saturated semiconductor optical amplifiers  

DEFF Research Database (Denmark)

A theoretical analysis of the small-signal frequency response (SSFR) of a wavelength converter based on cross-gain modulation in a semiconductor optical amplifier with a finite waveguide loss is presented. We use a transfer function formalism to explain the resonant behavior of the frequency response. The limitations to the magnitude of the spectral overshoot are also accounted for. Operating with the data and CW signals in a co-propagating configuration, we End that the resonance only exists for a finite waveguide loss. In a counter-propagating scheme, a resonance can exist regardless of the presence of loss.

Nielsen, Mads Lønstrup; Blumenthal, D. J.

2000-01-01

37

LMI Based Wide Area TCSC Controller in Mitigating Small Signal Oscillations  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a Linear Matrix Inequality(LMI based ?? robust controller design employing WideArea Measurement (WAM based stabilizing signals asgenerator speed. A Three-input, Single-output (TISOcontroller is designed for a Thyristor Controlled Seriescompensator (TCSC in order to mitigate small signaloscillations in a multimachine power system. The controllerdesign has been carried out based on the ?? mixed-sensitivityformulation in a LMI framework with pole-placementconstraint. The small signal performance of the test system hasbeen examined employing eigenvalue analysis as well as timedomain response. The designed controller is found to be robustagainst disturbances like varying generations as well as loadpower demand.

D. Mondal

2012-01-01

38

Uncertainty Estimation in SiGe HBT Small-Signal Modeling  

DEFF Research Database (Denmark)

An uncertainty estimation and sensitivity analysis is performed on multi-step de-embedding for SiGe HBT small-signal modeling. The uncertainty estimation in combination with uncertainty model for deviation in measured S-parameters, quantifies the possible error value in de-embedded two-port parameters (Y and Z - parameters). The analysis is applied to a 0.35 μm 60 GHz fT SiGe HBT in frequency range 45 MHz to 26 GHz.

Johansen, Tom Keinicke; Vidkjær, Jens

2005-01-01

39

Comment on ''Small-signal analysis in high-energy physics: A Bayesian approach''  

International Nuclear Information System (INIS)

Prosper's recent paper postulates that, in the absence of any prior information, the distribution of prior probabilities for an experiment should have the same symmetries as the conditional probabilities for the experiment. From this assumption, he derives a unique form for the prior probability distribution in the case of an experiment to measure a small signal above a background. His derivation does not adequately take into account the arbitrary nature of the normalization of the prior probability distribution. Allowing for changes in the normalization, the form of the prior probability distribution is no longer uniquely determined

1988-12-01

40

Small-signal analysis in high-energy physics: A Bayesian approach  

Energy Technology Data Exchange (ETDEWEB)

The statistics of small signals masked by a background of imprecisely known magnitude is addressed from a Bayesian viewpoint using a simple statistical model which may be derived from the principle of maximum entropy. The issue of the correct assignment of prior probabilities is resolved by invoking an invariance principle proposed by Jaynes. We calculate the posterior probability and use it to calculate point estimates and upper limits for the magnitude of the signal. The results are applicable to high-energy physics experiments searching for new phenomena. We illustrate this by reanalyzing some published data from a few experiments.

Prosper, H.B.

1988-03-01

 
 
 
 
41

Small-signal amplifier based on single-layer MoS2  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this letter we demonstrate the operation of an analog small-signal amplifier based on single-layer MoS2, a semiconducting analogue of graphene. Our device consists of two transistors integrated on the same piece of single-layer MoS2. The high intrinsic band gap of 1.8 eV allows MoS2-based amplifiers to operate with a room temperature gain of 4. The amplifier operation is demonstrated for the frequencies of input signal up to 2 kHz preserving the gain higher than 1. Our work shows that MoS2...

2012-01-01

42

Bivariate Instantaneous Frequency and Bandwidth  

CERN Multimedia

The generalizations of instantaneous frequency and instantaneous bandwidth to a bivariate signal are derived. These are uniquely defined whether the signal is represented as a pair of real-valued signals, or as one analytic and one anti-analytic signal. A nonstationary but oscillatory bivariate signal has a natural representation as an ellipse whose properties evolve in time, and this representation provides a simple geometric interpretation for the bivariate instantaneous moments. The bivariate bandwidth is shown to consists of three terms measuring the degree of instability of the time-varying ellipse: amplitude modulation with fixed eccentricity, eccentricity modulation, and orientation modulation or precession. A application to the analysis of data from a free-drifting oceanographic float is presented and discussed.

Lilly, Jonathan M

2010-01-01

43

High bandwidth wall current monitor  

CERN Document Server

Wall Current Monitors (WCM) are commonly used to observe the time profile and spectra of a particle beam by detecting its image current. Within the framework of the EuroTeV Programme, a WCM for CLIC and ILC having a very large bandwidth (100kHz-20GHz) is required and has been developed. A deep study of the field configuration for the device has been necessary. Consequently, the geometrical parameters crucial for a proper functioning of the structure have been found. Three possible geometrical configurations were found. Two of them required a reduction of the geometrical aperture and were therefore rejected. The third one, which was chosen, has been fully characterized both from an electromagnetic and from a mechanical point of view. Furthermore, the very stringent initial requests (bandwidth from 100kHz to 20GHz) were reviewed in a more critical way showing that the low frequency cutoff can be sensibly increased.

D'Elia, A; Søby, L

2009-01-01

44

Algorithms and Requirements for Measuring Network Bandwidth  

Energy Technology Data Exchange (ETDEWEB)

This report unveils new algorithms for actively measuring (not estimating) available bandwidths with very low intrusion, computing cross traffic, thus estimating the physical bandwidth, provides mathematical proof that the algorithms are accurate, and addresses conditions, requirements, and limitations for new and existing algorithms for measuring network bandwidths. The paper also discusses a number of important terminologies and issues for network bandwidth measurement, and introduces a fundamental parameter -Maximum Burst Size that is critical for implementing algorithms based on multiple packets.

Jin, Guojun

2002-12-08

45

PolySac3DB: an annotated data base of 3 dimensional structures of polysaccharides  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Polysaccharides are ubiquitously present in the living world. Their structural versatility makes them important and interesting components in numerous biological and technological processes ranging from structural stabilization to a variety of immunologically important molecular recognition events. The knowledge of polysaccharide three-dimensional (3D structure is important in studying carbohydrate-mediated host-pathogen interactions, interactions with other bio-macromolecules, drug design and vaccine development as well as material science applications or production of bio-ethanol. Description PolySac3DB is an annotated database that contains the 3D structural information of 157 polysaccharide entries that have been collected from an extensive screening of scientific literature. They have been systematically organized using standard names in the field of carbohydrate research into 18 categories representing polysaccharide families. Structure-related information includes the saccharides making up the repeat unit(s and their glycosidic linkages, the expanded 3D representation of the repeat unit, unit cell dimensions and space group, helix type, diffraction diagram(s (when applicable, experimental and/or simulation methods used for structure description, link to the abstract of the publication, reference and the atomic coordinate files for visualization and download. The database is accompanied by a user-friendly graphical user interface (GUI. It features interactive displays of polysaccharide structures and customized search options for beginners and experts, respectively. The site also serves as an information portal for polysaccharide structure determination techniques. The web-interface also references external links where other carbohydrate-related resources are available. Conclusion PolySac3DB is established to maintain information on the detailed 3D structures of polysaccharides. All the data and features are available via the web-interface utilizing the search engine and can be accessed at http://polysac3db.cermav.cnrs.fr.

Sarkar Anita

2012-11-01

46

Time resolved spectroscopy and small signal gain in a flash initiated, pulsed HF laser  

Energy Technology Data Exchange (ETDEWEB)

An experimental and computer modeling investigation of a pulsed, flash photolysis initiated, H/sub 2/ + F/sub 2/ chemical laser was undertaken. Time resolved spectral (TRS) output, time history of small signal gain (SSG) and total pulse energy (TPE) were measured. Several experimental trends were noted. The experimental TRS and SSG results were compared to the calculations resulting from two models. Conclusions reached in this study were: 1) the time scales of SSG and TRS are not the same, SSG having much longer durations; 2) the trends of initiation, termination and peak gain or intensity times are similar for SSG and TRS; 3) computer models are capable of accurately predicting the time resolved characteristics of gain and emission; and 4) further work is necessary to determine the form of V-R,T energy transfer.

Sojka, P.E.

1983-01-01

47

3-D effects on small signal gain for undulators with variable parameters  

International Nuclear Information System (INIS)

A new explanation on the quadrature expression for small signal gain (SSG) in a variable parameter undulator is given in terms of Madey's theorem and analogy between the FEL and a phased antenna array and the spontaneous emission spectrum is derived. The generalization of the SSG expression from one to three dimensions is carried out and the effect on SSG due to the collimation error among the axes of the optical, electron beam and undulator is included as well. It shows at three dimensional effects will reduce SSG severely. The comparison with Boeing's FEL experiment is carried out and it is also pointed out that a better operation condition may be obtained if the first uniform section of the Boeing's undulator is reduced a little to make the optimum energy mismatch shifted towards zero

1992-02-01

48

Cryogenic small-signal conversion with relaxation oscillations in Josephson junctions  

CERN Document Server

Broadband detection of small electronic signals from cryogenic devices, with the option of simple implementation for multiplexing, is often a highly desired, although non-trivial task. We investigate and demonstrate a small-signal analog-to-frequency conversion system based on relaxation oscillations in a single Josephson junction. Operation and stability conditions are derived, with special emphasis on noise analysis, showing the dominant noise sources to originate from fluctuation processes in the junction. At optimum conditions the circuit is found to deliver excellent noise performance over a broad dynamic range. Our simple models successfully apply within the regime of classical Josephson junction and circuit dynamics, which we confirm by experimental results. A discussion on possible applications includes a measurement of the response to a cryogenic radiation detector.

Furlan, M

2006-01-01

49

Small-signal gain diagnostic measurements in a flowing CO2 pin discharge laser  

Science.gov (United States)

Small-signal gain diagnostic measurements were conducted on closed loop, high power, carbon dioxide laser to assess the coupling between gas flow velocity and resonator saturation. Parameters investigated included optical cavity and discharge power. Results of gain measurements within and downstream of the excitation volume are presented for a laser gas composition He:N2:CO2 of 10:7:1 at 90 torr. The gain at constant discharge power was observed to be dependent upon discharge power level and time. An important result of this study is that the effects of gain swept downstream of the discharge region must be considered in the resonator design if efficient extraction of stored optical energy is desired.

Blech, R. A.; Manista, E. J.; Dunning, J. W., Jr.

1977-01-01

50

A New Current-Controlled-Power Technique for Small Signal Applications  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a new current-controlled-power technique for small signal applications is presented. The proposed technique needs no passive devices (a resistor and a capacitor but the well-known SCR technique needs, thus the proposed technique is very suitable for an IC process. An example application as a new current-controlled-power CMOS fullwave rectifier is also given. The example application is simulated by using the SPICE program. Simulation results show that the proposed technique can work well; the controlled-current from 0 µA to 5.5 µA produces the peak area amplitude from 100 mV to 0 mV to the load.

Adisak Monpapassorn

2012-04-01

51

Wide-Area Assessment of Aperiodic Small Signal Rotor Angle Stability in Real-Time  

DEFF Research Database (Denmark)

This paper presents the details of a new real-time stability assessment method. The method assesses a particular mechanism of stability: each generatorâ??s capability to generate sufficient steady state electromechanical torque. The lack of sufficient steady state torque causes aperiodic increase in rotor angle and a loss of synchronism, referred to as aperiodic small signal instability. The paper provides the theoretical background of the method and an analytical assessment criterion. Furthermore, a mathematical mapping of the generatorsâ?? operating points that enables informative visualization of multiple operating points is derived in the paper. Finally, results from time-domain simulation of instability scenarios in the Nordic32 test system are presented and results used for testing the assessment method. The results illustrate the methodâ??s capability to efficiently identify the location of the emerging problem and to quantify margins to stability boundary.

Jóhannsson, Hjörtur; Nielsen, Arne Hejde

2013-01-01

52

A Three-Dimensional Model of Small Signal Free-Electron Lasers  

CERN Document Server

Coherent electron cooling is an ultra-high-bandwidth form of stochastic cooling which utilizes the charge perturbation from Debye screening as a seed for a free-electron laser. The amplified and frequency-modulated signal that results from the free-electron laser process is then used to give an energy-dependent kick on the hadrons in a bunch. In this paper, we present a theoretical description of a high-gain free-electron laser with applications to a complete theoretical description of coherent electron cooling.

Webb, Stephen; Litvinenko, Vladimir

2011-01-01

53

On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind tu...

Knu?ppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nyga?rd; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

2010-01-01

54

Bandwidth enhancement of circular microstrip antennas  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip Antennas have many advantages such as low profile, light weight, can be easily matched with microwave integrated circuits which leads to use this type of antennas in different applications, on the other side, the great disadvantage of these antennas is the narrow bandwidth which is 2 to 5 %. In this paper a single element circular Microstrip antenna has been designed which had a narrow bandwidth and then two methods of bandwidth enhancement had been designed and compared to the single patch, these two techniques gave a bandwidth of 10% and 38 % respectively. The three designs had been simulated using Microwave Office Package.

Ali Hussain Ali Yawer

2010-01-01

55

A methodology for performance evaluation of LEDs based on ac small signal analysis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This paper shows fundamentals and results that support a promising methodology for evaluation in locus of a LED from its own radiating signal, and that allows monitoring of its aging by remote inference on which degradation mechanism is acting internally to the device's structure. It brings out also [...] an alternative route for estimation of parameters of the Shockley's equation directly from small-signal ac analysis in a simple bench circuit. This last approach is shown to be effective and advantageous relatively to methods which take near a hundred points to achieve good estimations, while it uses only two points of the I-V static characteristic. Both approaches __ referred to as remote inference method (RIM) and two-points method (TPM) __ are applied together to show that external quantum efficiency (EQE) can be closely correlated to the injection process assumed to take place in that emitting device, meanwhile overvalued serial resistances due to neutral layers and ohmic contacts in electrodes affect only its electrical performance.

Isnaldo J. Souza, Coêlho; James N. da, Silva.

56

InGaAs/AlGaInAs/InP Laser with Compressively Strained Multiquantum Well Layers for High Speed Modulation Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The modulation frequency response of compressively strained multiquantum well (MQW) lasers grown with an InGaAs/AlGaInAs/InP heterostructure and emitting at the wavelength of 1.55 mm is presented. The laser devices processed with the mushroom-stripe buried structure present a high frequency 3 dB bandwidth above 20 GHz. The frequency response was measured with the small signal modulation technique. The logarithmic subtraction method was employed to extract th...

1997-01-01

57

Improving the Bandwidth Utilization by Recycling the Unused Bandwidth in IEEE 802.16 Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The Physical and MAC layers have been specified in IEEE 802.16 networks. The quality of service is ensured by the bandwidth reservation. The subscriber station should reserve the bandwidth more than its demand. But the bandwidth is fully utilized by SS but not all the time. So the bandwidth has recycled by the process of recycling the unused bandwidth. The main objective of the proposed scheme is to utilize the unused bandwidth by recycling and maintain the QOS service. By recycling the throughput can be improved which maintains the QOS in the proposed scheme. During this recycling process to maintain the QOS services, the amount of reserved bandwidth is not changed. The proposed scheme can utilize the unused bandwidth up to 70% on average. Protocols and the scheduling algorithms are used to improve the utilization and throughput.

Gowri T

2012-03-01

58

Multiple-bandwidth photoacoustic tomography  

Energy Technology Data Exchange (ETDEWEB)

Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal-noise ratio.

Ku Geng [Optical Imaging Laboratory, Department of Biomedical Engineering, Texas A and M University, 3120 TAMU, College Station, TX 77843-3120 (United States); Wang, Xueding [Optical Imaging Laboratory, Department of Biomedical Engineering, Texas A and M University, 3120 TAMU, College Station, TX 77843-3120 (United States); Stoica, George [Department of Pathobiology, Texas A and M University, College Station, TX 77843-5547 (United States); Wang, Lihong V [Optical Imaging Laboratory, Department of Biomedical Engineering, Texas A and M University, 3120 TAMU, College Station, TX 77843-3120 (United States)

2004-04-07

59

Multiple-bandwidth photoacoustic tomography  

International Nuclear Information System (INIS)

Photoacoustic tomography, also referred to as optoacoustic tomography, employs short laser pulses to generate ultrasonic waves in biological tissues. The reconstructed images can be characterized by the convolution of the structure of samples, the laser pulse and the impulse response of the ultrasonic transducer used for detection. Although the laser-induced ultrasonic waves cover a wide spectral range, a single transducer can receive only part of the spectrum because of its limited bandwidth. To systematically analyse this problem, we constructed a photoacoustic tomographic system that uses multiple ultrasonic transducers simultaneously, each at a different central frequency. The photoacoustic images associated with the different transducers were compared and analysed. The system was tested by imaging both mouse brains and phantom samples. The vascular vessels in the brain were revealed by all of the transducers, but the image resolutions differed. The higher frequency detectors provided better image resolution while the lower frequency detectors delineated the major structural traits with a higher signal-noise ratio

2004-04-07

60

47 CFR 2.202 - Bandwidths.  

Science.gov (United States)

...depending on the quality desired Speech and music, M=4000, Bandwidth: 8000 Hz= 8 kHz...depending on the quality desired Speech and music, M=4000, Bandwidth: 4000 Hz= 4 kHz...lowest modulation frequency Speech and music, M=4500, lowest modulation...

2000-10-01

 
 
 
 
61

Adaptable bandwidth planning using reinforcement learning  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In order to improve the bandwidth allocation considering feedback of operational environment, adaptable bandwidth planning based on reinforcement learning is proposed. The approach is based on new constrained scheduling algorithms controlled by reinforcement learning techniques. Different constrained scheduling algorithms,, such as "conflict free scheduling with minimum duration", "partial displacement" and "pattern oriented scheduling" are defined and implemented. The...

2006-01-01

62

Bandwidth Allocation Algorithm of Heterogeneous Network  

Directory of Open Access Journals (Sweden)

Full Text Available In order to reasonable and effective distribute bandwidth to giving full play to the advantages of network resources and improve the efficiency of network data flow in heterogeneous network, this paper puts forward a heterogeneous network bandwidth allocation algorithm. The algorithm is adopted connection bandwidth constraint mechanism in the flow model, starting from the data transmission in the network key topological properties, and combines with routing strategy, using the connection bandwidth allocation to regulate the flow of the network data flow, to achieve ease network congestion, increase network load capacity, at the same time, the qualitatively analyses the process and cause of the change of the flow. Finally in scale-free network and small-world network on the network topology platform made simulating experiment, the experimental results show that: The algorithm optimizes the network bandwidth resource allocation, regulates the network traffic, increased the network load capacity

Zhijun Hu

2014-03-01

63

On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines  

DEFF Research Database (Denmark)

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine model with all grid relevant control functions is used in the study. Furthermore is the wind power plant (WPP) equipped with a WPP voltage controller and comparisons are presented. The models of wind turbine and WPP voltage controller are kindly provided by Siemens Wind Power A/S for this work. The study is based on modal analysis which are complemented with simulations on the nonlinear system.

Knüppel, Thyge; Akhmatov, Vladislav

2010-01-01

64

Center frequency and bandwidth tunable HTS filter  

International Nuclear Information System (INIS)

We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. Several ?-shaped waveguides are placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. Additional electrical pads are placed open ends of the resonators for tuning the center frequency. Pads are also placed around the input/output coupled-line elements to enable the coupling strength between the coupled-line and resonator to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole tunable bandpass filter was designed and analyzed using an electromagnetic simulator based on the moment method. The filter was designed at a center frequency of 5.00 GHz and a bandwidth of 150 MHz. The simulated bandwidth and center frequency of the filter were tuned from 150 to 300 MHz and 4.5-5 GHz without degradation of the insertion loss, respectively.

2011-11-01

65

Bandwidth challenge teams at SC2003 conference  

CERN Multimedia

Results from the fourth annual High-Performance Bandwidth Challenge, held in conjunction with SC2003, the international conference on high-performance computing and networking which occurred last week in Phoenix, AZ (1 page).

2003-01-01

66

High bandwidth control of precision motion instrumentation  

Science.gov (United States)

This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant bandwidth and precision improvements over the feedback controller, and the ability to achieve precision motion control at frequencies higher than multiple system resonances.

Bristow, Douglas A.; Dong, Jingyan; Alleyne, Andrew G.; Ferreira, Placid; Salapaka, Srinivas

2008-10-01

67

Reduction of electromagnetic interference susceptibility in small-signal analog circuits using complementary split-ring resonators  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Low-frequency analog and digital electronic circuits are susceptible to electromagnetic interference in the radiofrequency (RF) range. This disturbance is produced when the coupled RF signal is rectified by the nonlinear behavior of the semiconductors used in the small-signal analog input stage of the electronic system. Circuits based on operational amplifiers are usually employed for such input stages. These circuits present an amplitude modulation demodulation produced ...

Pe?rez Robles, Daniel; Gil Gali?, Ignacio; Gago Barrio, Javier; Ferna?ndez Garci?a, Rau?l; Balcells Sendra, Josep; Gonza?lez Di?ez, David; Berbel Artal, Ne?stor; Mon Gonza?lez, Juan

2012-01-01

68

Gain and noise properties of small-signal erbium-doped fiber amplifiers pumped in the 980-nm band  

DEFF Research Database (Denmark)

The authors have experimentally and theoretically investigated the effects of detuning the pump wavelength on the gain and noise properties of small-signal, erbium-doped fiber amplifiers codirectionally pumped in the 980-nm band. While the pump wavelength can be varied over a wide range with little impact on the gain, a noise penalty is incurred. For amplifiers saturated by amplified spontaneous emission, it is possible to increase the gain by detuning the pump wavelength

Pedersen, B.; Chirravuri, J.

1992-01-01

69

Increase Bandwidth for Circular Microstrip Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a design and performance of acircularly microstrip patch antenna, for the application inWireless Local Area Network (WLAN, are reported here. Theantenna is a proximity coupled microstrip patch antenna wherethe radiating patch is loadedby a V-slot. This miniaturizedmicrostrip antenna has wide bandwidth in the frequency bandof WLAN and exhibits circularly far field with very good axialratio bandwidth. The simulated results using IE3D software areverified by measurement

Sonali Jain,

2012-02-01

70

Optimal spectral bandwidth for long memory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For long range dependent time series with a spectral singularity at frequency zero, a theory for optimal bandwidth choice in non-parametric analysis ofthe singularity was developed by Robinson (1991b). The optimal bandwidths are described and compared with those in case of analysis of a smooth spectrum. They are also analysed in case of fractional ARIMA models and calculated as a function of the self similarity parameter in some special cases. Feasible data dependent approximations to the opt...

1993-01-01

71

Optimal Spectral Bandwidth for Long Memory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For long range dependent time series with a spectral singularity at frequency zero, a theory for optimal bandwidth choice in non-parametric analysis of the singularity was developed by Robinson (1994a). In the present paper, the optimal bandwidths are compared with those in case of a smooth spectrum. They are also analysed in case of fractional ARIMA models and calculated as a function of the self similarity parameter in some special cases. Feasible data-dependent approximations to the optima...

1996-01-01

72

Sampling of communications systems with bandwidth expansion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many communication systems are {\\em bandwidth-expanding}: the transmitted signal occupies a bandwidth larger than the {\\em symbol rate}. The sampling theorems of Kotelnikov, Shannon, Nyquist et al. shows that in order to represent a bandlimited signal, it is necessary to sample at what is popularly referred to as the Shannon or Nyquist rate. However, in many systems, the required sampling rate is very high and expensive to implement. In this work we show that it is possible to get suboptimal...

Kusuma, Julius; Ridolfi, Andrea; Vetterli, Martin

2002-01-01

73

Bandwidth Selection for Weighted Kernel Density Estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the this paper, the authors propose to estimate the density of a targeted population with a weighted kernel density estimator (wKDE) based on a weighted sample. Bandwidth selection for wKDE is discussed. Three mean integrated squared error based bandwidth estimators are introduced and their performance is illustrated via Monte Carlo simulation. The least-squares cross-validation method and the adaptive weight kernel density estimator are also studied. The authors also con...

Wang, Bin; Wang, Xiaofeng

2007-01-01

74

Ultrawide Bandwidth RFID: The Next Generation?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Future advanced radio-frequency identification (RFID) systems are expected to provide both identification and high-definition localization of objects with improved reliability and security while maintaining low power consumption and cost. Ultrawide bandwidth (UWB) technology is a promising solution for next generation RFID systems to overcome most of the limitations of the current narrow bandwidth RFID technology such as: reduced area coverage, insufficient ranging resolution for accurate loc...

Dardari, Davide; D Errico, Raffaele; Roblin, Christophe; Sibille, Alain; Win, Moe Z.

2010-01-01

75

Bandwidth Estimation For Mobile Ad hoc Network (MANET)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we presents bandwidth estimation scheme for MANET, which uses some components of the two methods for the bandwidth estimation: 'Hello Bandwidth Estimation 'Listen Bandwidth Estimation. This paper also gives the advantages of the proposed method. The proposed method is based on the comparison of these two methods. Bandwidth estimation is an important issue in the Mobile Ad-hoc Network (MANET) because bandwidth estimation in MANET is difficult, because each host has imprecise know...

Rabia Ali; Dr. Fareeha Zafar

2011-01-01

76

Small-Signal-Gain and Time-Resolved Spectroscopy of the D2-F2/CO2 Pulsed Chemical Transfer Laser System.  

Science.gov (United States)

The authors report measurements of the small-signal-gain and time-resolved spectral output of a flash-initiated D2-F2/CO2 chemical transfer laser system. Small-signal-gain measurements indicate a possible lack of rotational equilibration among the rotatio...

S. N. Suchard

1974-01-01

77

Wide-bandwidth charge sensitivity with a radio-frequency field-effect transistor  

Science.gov (United States)

We demonstrate high-speed charge detection at room temperature with single-electron resolution by using a radio-frequency field-effect transistor (RF-FET). The RF-FET combines a nanometer-scale silicon FET with an impedance-matching circuit composed of an inductor and capacitor. Driving the RF-FET with a carrier signal at its resonance frequency, small signals at the transistor's gate modulate the impedance of the resonant circuit, which is monitored at high speed using the reflected signal. The RF-FET driven by high-power carrier signals enables a charge sensitivity of 2 × 10-4 e/Hz0.5 at a readout bandwidth of 20 MHz.

Nishiguchi, Katsuhiko; Yamaguchi, Hiroshi; Fujiwara, Akira; van der Zant, Herre S. J.; Steele, Gary A.

2013-09-01

78

12. 5-GHz direct modulation bandwidth of vapor phase regrown 1. 3-. mu. m InGaAsP buried heterostructure lasers  

Energy Technology Data Exchange (ETDEWEB)

A small-signal modulation bandwidth of 12.5 GHz is reported for vapor phase regrown 1.3-..mu..m InGaAsP buried heterostructure (BH) lasers operated at a bias optical power of only 6.9 mW/facet. The bandwidth per square root of bias optical power is a factor of 1.6 higher than previous best results. In addition, the optical modulation amplitude remains flat to 12 GHz in sharp contrast to other types of BH lasers which exhibit signal roll-off at frequencies below the resonance frequency. The wide modulation bandwidth is attained by increasing the p-doping level in the active region and by the choice of short cavity length. The device is grown on a conductive substrate, indicating that it is unnecessary to use a semi-insulating substrate to obtain flat optical response in vapor phase regrown BH lasers.

Su, C.B.; Lanzisera, V.; Powazinik, W.; Meland, E.; Olshansky, R.; Lauer, R.B.

1985-02-15

79

Design and characterization of a 30-GHz bandwidth low-power silicon traveling-wave modulator  

Science.gov (United States)

We present the design and characterization of a silicon PN junction traveling-wave Mach–Zehnder modulator near 1550 nm wavelength. The device shows 30 GHz bandwidth at 1 V reverse bias, with a 2.7 V-cm V?L? and accordingly a 9-V small-signal V?. The insertion loss of the phase shifter is 3.6 dB±0.4 dB. The device performance metrics in combination show significant improvement compared to the state-of-the-art in the sense that lower phase shifter loss and higher bandwidth are achieved for the same V? or vice versa. We demonstrated low modulation power of 640-fJ/bit at 40 Gb/s with a 1.6-Vpp differential-drive and 0-V DC bias, raising the prospect of direct compatibility with CMOS drive-voltages. Critical design tradeoffs are analyzed and design models are validated with measurement results. We proposed a new figure-of-merit (FOM) V?L?RpnC2pn as the junction design merit for high-speed traveling-wave modulators, and utilized 6 implants to achieve an optimal FOM with lower insertion loss. Several key RF design issues are addressed for the first time using simulation and measurement results. In particular, we discussed bandwidth extension using mismatched termination and closely matched experimental results. A bandwidth-limiting RF multi-mode behavior is noted, which also exists in other results in the literature; we suggested a widely applicable design remedy.

Ding, Ran; Liu, Yang; Li, Qi; Yang, Yisu; Ma, Yangjin; Padmaraju, Kishore; Lim, Andy Eu-Jin; Lo, Guo-Qiang; Bergman, Keren; Baehr-Jones, Tom; Hochberg, Michael

2014-06-01

80

Adaptable bandwidth planning using reinforcement learning  

Directory of Open Access Journals (Sweden)

Full Text Available In order to improve the bandwidth allocation considering feedback of operational environment, adaptable bandwidth planning based on reinforcement learning is proposed. The approach is based on new constrained scheduling algorithms controlled by reinforcement learning techniques. Different constrained scheduling algorithms,, such as "conflict free scheduling with minimum duration", "partial displacement" and "pattern oriented scheduling" are defined and implemented. The scheduling algorithms are integrated into reinforcement learning strategies. These strategies include: - Q-learning for selection of optimal planning schedule using Q-values; - Informed Q-learning for exploitation and handling of prior-knowledge (patterns of network behaviour; - Relational Q-learning for improving of bandwidth allocation policies dynamically in operational networks considering actual network performance data. Scenarios based on integration of the scheduling algorithms and reinforcement learning techniques in the experimental monitoring and bandwidth planning system called QORE (QoS and resource optimisation are given. The proposed adaptable bandwidth planning is required for more efficient usage of network resources.

Dirk Hetzer

2006-08-01

 
 
 
 
81

Improved space bandwidth product in image upconversion  

DEFF Research Database (Denmark)

We present a technique increasing the space bandwidth product of a nonlinear image upconversion process used for spectral imaging. The technique exploits the strong dependency of the phase-matching condition in sum frequency generation (SFG) on the angle of propagation of the interacting fields with respect to the optical axis. Appropriate scanning of the phase-match condition (Î?k=0) while acquiring images, allow us to perform monochromatic image reconstruction with a significantly increased space bandwidth product. We derive the theory for the image reconstruction process and demonstrate acquisition of images with >10 fold increase in space bandwidth product, i.e. the number of pixel elements, when compared to upconversion of images using fixed phase-match conditions.

Dam, Jeppe Seidelin; Pedersen, Christian

2012-01-01

82

Amplification of small signals near the threshold of a collective-acoustic instability in a system of parametric nuclear magnons  

International Nuclear Information System (INIS)

Amplification of small signals was observed in a system of parametric nuclear magnons in antiferromagnetic CsMnF3 near the threshold of excitation of elastic vibrations of the crystal. This effect confirmed the predictions of Wiesenfeld and McNamara of the behavior of a dynamic system near a cycle creation bifurcation. A calculation of coupled oscillation of the magnon and phonon subsystems of a crystal, carried out using a model of a collective-acoustic instability proposed by Cherepanov, provided a satisfactory description of the experimental results

1988-01-01

83

Comment on ''Small-signal analysis in high-energy physics: A Bayesian approach''  

Energy Technology Data Exchange (ETDEWEB)

Prosper's recent paper postulates that, in the absence of any prior information, the distribution of prior probabilities for an experiment should have the same symmetries as the conditional probabilities for the experiment. From this assumption, he derives a unique form for the prior probability distribution in the case of an experiment to measure a small signal above a background. His derivation does not adequately take into account the arbitrary nature of the normalization of the prior probability distribution. Allowing for changes in the normalization, the form of the prior probability distribution is no longer uniquely determined.

Williams, D.A.

1988-12-01

84

Critical analysis of the small-signal voltage-decay technique for minority-carrier lifetime measurement in solar cells  

Energy Technology Data Exchange (ETDEWEB)

We have performed a detailed analysis of the Small-Signal Voltage-Decay lifetime measurement technique and we find that for long-based diodes a complementary error function represents the voltage decay more accurately than the commonly assumed exponential dependence. For short-based diodes a series solution is presented for the voltage decay. We also discuss the precautions necessary for proper interpretation of experimental data. Experimental results and computer simulations of the lifetime measurements are presented to support our analysis. (author).

Joardar, K.; Dondero, R.C.; Schroder, D.K. (Arizona State Univ., Tempe, AZ (US). Center for Solid State Electronics Research)

1989-06-01

85

Bypassing the bandwidth theorem with PT symmetry  

CERN Multimedia

The beat time {\\tau}_{fpt} associated with the energy transfer between two coupled oscillators is dictated by the bandwidth theorem which sets a lower bound {\\tau}_{fpt}\\sim 1/{\\delta}{\\omega}. We show, both experimentally and theoretically, that two coupled active LRC electrical oscillators with parity-time (PT) symmetry, bypass the lower bound imposed by the bandwidth theorem, reducing the beat time to zero while retaining a real valued spectrum and fixed eigenfrequency difference {\\delta}{\\omega}. Our results foster new design strategies which lead to (stable) pseudo-unitary wave evolution, and may allow for ultrafast computation, telecommunication, and signal processing.

Ramezani, Hamidreza; Ellis, F M; Guenther, Uwe; Kottos, Tsampikos

2012-01-01

86

Design Of Power System Stabilizer To Improve Small Signal Stability By Using Modified Heffron-Phillip’s Model  

Directory of Open Access Journals (Sweden)

Full Text Available One of the major problems in power system operation is related to small signal instability caused by insufficient damping in the system. The most effective way of countering this instability is to use auxiliary controllers called Power System Stabilizers, to produce additional damping in the system. Generally Heffron-phillip’s Model of a synchronous machine is commonly used for the small signal stability analysis. A Modified Heffron-Phillip’s (KconstantModel is derived for the design of Power System Stabilizers; knowledge of external parameters, such as equivalent infinite bus voltage and external impedance value are required for designing a conventional power system stabilizer, Modified Heffron-Phillip’s Model power system stabilizer. The efficiency of the proposeddesign technique and the performance of the stabilizer has been evaluated over a range of operating and system conditions and the performance of the proposed Modified Heffron-Phillip’s Model is much better than the conventional power system stabilize.. The proposed work describes the ‘Design of Power System Stabilizer by using Modified Heffron-Phillip’s model’ is simulated by using MATLAB/SIMULINK.

G. Sai Sudheer,

2011-06-01

87

Impacts of the SSSC control modes on small-signal and transient stability of a power system  

Energy Technology Data Exchange (ETDEWEB)

In order to accomplish specific compensation objectives a static synchronous series compensator (SSSC) may be controlled by several ways. The most common control modes of the SSSC are: (1) constant voltage mode, (2) constant impedance emulation mode, and (3) constant power control mode. Moreover, to improve the dynamic performance of the system, a SSSC may be equipped with supplementary controllers, such as damping controls. Therefore, this paper investigates the impacts of different SSSC control modes on small-signal and transient stability of a power system. The performance of different input signals to the power oscillation damping (POD) controller is also assessed. The stability analysis and the design of the SSSC controllers are based on modal analysis, non-linear simulations, pole placement technique, and time and frequency response techniques. The results obtained allow to conclude that the usage of the SSSC in the constant impedance emulation mode is the most beneficial strategy to improve both the small-signal and transient stability. (author)

Castro, M.S.; Ayres, H.M.; da Costa, V.F.; da Silva, L.C.P. [Department of Energy Control and Systems, State University of Campinas-Brazil, UNICAMP/FEEC/DSCE, Av. Albert Einstein, 400, Campinas-SP 13083-852 (Brazil)

2007-01-15

88

Consequence and impact of electric utility industry restructuring on transient stability and small-signal stability analysis  

International Nuclear Information System (INIS)

The electric utility industry is undergoing unprecedented changes in its structure worldwide. With the advent of an open market environment and competition in the industry, and restructuring of the industry into separate generation, transmission, and distribution entities, new issues in power system operation and planning are inevitable. One of the major consequences of this new electric utility environment is the greater emphasis on reliability and secure operation of the power system. This paper examines the impact of restructuring on power system dynamic analysis. It specifically addresses issues related to transient stability analysis and small-signal stability analysis. Four major topics to examine the effect on the nature of studies conducted are considered. These topics are (1) system adequacy and security, (2) system modeling data requirements, (3) system protection and control, and (4) system restoration. The consequences and impact of each of these topics on the nature of the studies conducted are examined and discussed. The emphasis on greater reliability has led to a clearer enunciation of standards, measurements, and guides in some countries. These requirements will result in: (1) more measurements on existing systems, (2) rigorous analysis of transient stability and small-signal stability to determine operating limits and plan systems, (3) greater emphasis on studies to verify coordination and proper performance of protection and controls, and (4) development of a detailed plan for system restoration in the case of wide-spread outages

2000-02-01

89

Experiences in Traceroute and Bandwidth Change Analysis  

International Nuclear Information System (INIS)

SLAC has been studying end-to-end WAN bandwidth availability and achievability for 2.5 years via IEPM-BW [1]. IEPM-BW performs network intensive tests every 90 minutes. Based on that experience we have also developed a light weight available bandwidth (ABwE [2]) measurement tool that can make a measurement within a second. We are now extending this to a WAN measurement and detection system (IEPM-LITE) aimed at more quickly detecting and troubleshooting network performance problems and also to be more friendly on lower performance paths. IEPM-LITE uses ping, forward traceroutes, and ABwE sensors to monitor, in close to real-time, Round Trip Times (RTT), changes in available bandwidth and routes to and from target hosts. This paper discusses the experiences, techniques and algorithms used to detect and report on significant traceroute and bandwidth changes. The ultimate aim is to develop a lightweight WAN network performance monitoring system that can detect, in near real time, significant changes and generate alerts

2004-01-01

90

Bandwidth Enhancement Techniques of Dielectric Resonator Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available The paper briefly reviews the historical background of dielectric resonator antenna and its bandwidth enhancement techniques. The main focus is on a compact DRA that can offer broad band operation. It has been illustrated that dual resonance and multi resonance operation can be much effective to give wide band characteristics of DRA.

ARCHANA SHARMA

2011-07-01

91

Small-signal stability analysis of DC-link voltage control system affected by synchronization control in a wind turbine connected to weak grid  

Energy Technology Data Exchange (ETDEWEB)

In this paper, small-signal stability of DC-link voltage control loop, affected by PLL which is also called synchronization control, is researched under weak grid condition. Similar to small-signal stability analysis of the traditional power system, a small-signal model of the grid-connected converter is presented. This model includes DC-link voltage control loop and PLL. It is analyzed in physics that how synchronization control affects small-signal stability of DC-link voltage control system. Influencing factors of small signal stability of DC-link voltage control system is presented and analyzed including DC-link voltage controller parameter, PLL controller parameter, strength of grid and operating point. An improved control strategy is proposed to enhance the small-signal stability of DC-link voltage control system. Simulations on a 1.5-MW full-capacity wind power generation system are conducted in Matlab/Simulink and the feasibility of the proposed control scheme is validated. (orig.)

Huang, Yunhui; Yuan, Xiaoming; Hu, Jiabing [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Laboratory of Advanced Electromagnetic Engineering and Technology

2012-07-01

92

Small-Signal Analysis of Autonomous Hybrid Distributed Generation Systems in Presence of Ultracapacitor and Tie-Line Operation  

Science.gov (United States)

This paper presents small-signal analysis of isolated as well as interconnected autonomous hybrid distributed generation system for sudden variation in load demand, wind speed and solar radiation. The hybrid systems comprise of different renewable energy resources such as wind, photovoltaic (PV) fuel cell (FC) and diesel engine generator (DEG) along with the energy storage devices such as flywheel energy storage system (FESS) and battery energy storage system (BESS). Further ultracapacitors (UC) as an alternative energy storage element and interconnection of hybrid systems through tie-line is incorporated into the system for improved performance. A comparative assessment of deviation of frequency profile for different hybrid systems in the presence of different storage system combinations is carried out graphically as well as in terms of the performance index (PI), ie integral square error (ISE). Both qualitative and quantitative analysis reflects the improvements of the deviation in frequency profiles in the presence of the ultracapacitors (UC) as compared to other energy storage elements.

Ray, Prakash K.; Mohanty, Soumya R.; Kishor, Nand

2010-07-01

93

High Bandwidth Differential Amplifier for Shock Experiments  

Energy Technology Data Exchange (ETDEWEB)

We developed a high bandwidth differential amplifier for gas gun shock experiments/applications. The circuit has a bandwidth > 1 GHz, and is capable of measuring signals of ?1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is approximately 250 V relative to ground. Since the expected voltage change in the target is < 1 V, the differential amplifier must have a large common mode rejection. High pass filters suppress internal ringing of operational amplifiers. Results of bench tests are shown.

Ross, P. W., Tran, V., Chau, R.

2012-04-30

94

Parasitic Microstrip Patch Antenna with Enhanced Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the design and simulation of parasitic microstrip patch antenna with enhanced bandwidth.The microstrip patch antenna becomes very popular day by day because of its ease of analysis low cost, light weight, easy to feed and their attractive characteristics. The bandwidth obtained by the proposed antenna structure is about 58.10%. The antenna is thin and compact which makes it easily portable. A maximum gain of 4dB achieved at 2.88GHz frequency. The VSWR parameter was found to be less than 2 within the operating frequency range. The substrate material with relative permittivity of 4.2 and loss tangent of 0.0013 is used in this proposed antenna. The total simulation is done on IE3D software.

Beena

2013-05-01

95

Embedding spanning bipartite graphs of small bandwidth  

CERN Multimedia

Boettcher, Schacht and Taraz gave a condition on the minimum degree of a graph G on n vertices that ensures G contains every r-chromatic graph H on n vertices of bounded degree and of bandwidth o(n), thereby proving a conjecture of Bollobas and Komlos. We strengthen this result in the case when H is bipartite. Indeed, we give an essentially best-possible condition on the degree sequence of a graph G on n vertices that forces G to contain every bipartite graph H on n vertices of bounded degree and of bandwidth o(n). This also implies an Ore-type result. In fact, we prove a much stronger result where the condition on G is relaxed to a certain robust expansion property. Our result also confirms the bipartite case of a conjecture of Balogh, Kostochka and Treglown concerning the degree sequence of a graph which forces a perfect H-packing.

Knox, Fiachra

2011-01-01

96

Optimal Bandwidth for High Efficiency Thermoelectrics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The thermoelectric figure of merit (ZT) in narrow conduction bands of different material dimensionalities is investigated for different carrier scattering models. When the bandwidth is zero, the transport distribution function (TDF) is finite, not infinite as previously speculated by Mahan and Sofo [ Proc. Natl. Acad. Sci. U.S.A. 93 7436 (1996)], even though the carrier density of states goes to infinity. Such a finite TDF results in a zero electrical conductivity and thus a zero ZT. We point...

Zhou, Jun; Yang, Ronggui; Chen, Gang; Dresselhaus, Mildred

2011-01-01

97

Antenna Bandwidth Optimization with Single Frequency Simulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method to compute antenna Q using an electromagnetic simulation at a single frequency is described. This method can easily be integrated into global optimization algorithms. In this way the optimization time of some antenna parameters, e.g., bandwidth, may be significantly reduced. The method is validated by direct comparison with the physical bound of the analyzed structure. Numerical examples for rectangular antennas and antennas with a rectangular ground plane illustrate the integration ...

Cismasu, Marius; Gustafsson, Mats

2013-01-01

98

Ultra-wide bandwidth piezoelectric energy harvesting  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Here, we present an ultra wide-bandwidth energy harvester by exploiting the nonlinear stiffness of a doubly clamped microelectromechanical systems (MEMSs) resonator. The stretching strain in a doubly clamped beam shows a nonlinear stiffness, which provides a passive feedback and results in amplitude-stiffened Duffing mode resonance. This design has been fabricated into a compact MEMS device, which is about the size of a US quarter coin. Based on the open circuit voltage measurement, it is exp...

Hajati, Arman; Kim, Sang-gook

2011-01-01

99

Wide bandwidth porous silicon coatings for silicon  

Energy Technology Data Exchange (ETDEWEB)

Porous silicon anti-reflection coatings for silicon substrate, with a reflectance of less than 2% in the spectral range of 400-1000 nm, were fabricated. The wide bandwidth operation was realized by introducing a smooth refractive index gradation at the porous silicon-substrate interface to suppress multiple reflection fringes. Low current density anodization was adopted to form the high refractive index layer needed for a smooth refractive index gradation. (orig.)

Uehara, S.; Kurose, K.; Matsubara, T. [Seikei Univ., Tokyo (Japan). Fac. of Eng.

2000-11-16

100

High Quality Geographic Services and Bandwidth Limitations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we provide a critical overview of the state of the art in human-centric intelligent data management approaches for geographic visualizations when we are faced with bandwidth limitations. These limitations often force us to rethink how we design displays for geographic visualizations. We need ways to reduce the amount of data to be visualized and transmitted. This is partly because modern instruments effortlessly produce large volumes of data and Web 2.0 further allows bottom-up ...

Arzu Coltekin; Tumasch Reichenbacher

2011-01-01

 
 
 
 
101

Fixed Innovative Bandwidth Utilization in TDM EPON  

Directory of Open Access Journals (Sweden)

Full Text Available PON can be used by two technologies, which were developed APONs (ATM Passive Optical Networks and EPONs (Ethernet Passive Optical Networks.With the development of services offered by the Internet, the last mile bottleneck problems continue to increase day by day. Many algorithms were developed for making TDM EPON efficient like IPACT, Scheduling, Priority swapping etc. These all algorithms have problems like starvation, QoS, latency and channel under-utilization. We focused the efficient bandwidth utilization in TDM EPON by managing time slots within ONUs and reducing latency, starvation and increasing quality of service. Our Fixed Innovative Bandwidth Algorithm is an intra-ONU bandwidth allocation algorithm, which is used to enhance the network performance by evaluating the parameters like channel underutilization, starvation, delay and Quality of Service. The issues which are lacking in the already made algorithms are being resolved with our proposed solution. The main problem is that the other solutions didn't use the time slots which are guaranteed to their classes efficiently. In FIB Algorithm this issue is being resolved.

Muhammad Bilal

2011-03-01

102

Bandwidth and resolution enhancement through pulse compression.  

Science.gov (United States)

A novel pulse compression technique is developed that improves the axial resolution of an ultrasonic imaging system and provides a boost in the echo signal-to-noise ratio (eSNR). The new technique, called the resolution enhancement compression (REC) technique, was validated with simulations and experimental measurements. Image quality was examined in terms of three metrics: the eSNR, the bandwidth, and the axial resolution through the modulation transfer function (MTF). Simulations were conducted with a weakly-focused, single-element ultrasound source with a center frequency of 2.25 MHz. Experimental measurements were carried out with a single-element transducer (f/3) with a center frequency of 2.25 MHz from a planar reflector and wire targets. In simulations, axial resolution of the ultrasonic imaging system was almost doubled using the REC technique (0.29 mm) versus conventional pulsing techniques (0.60 mm). The -3 dB pulse/echo bandwidth was more than doubled from 48% to 97%, and maximum range sidelobes were -40 dB. Experimental measurements revealed an improvement in axial resolution using the REC technique (0.31 mm) versus conventional pulsing (0.44 mm). The -3 dB pulse/echo bandwidth was doubled from 56% to 113%, and maximum range sidelobes were observed at -45 dB. In addition, a significant gain in eSNR (9 to 16.2 dB) was achieved. PMID:17441586

Oelze, Michael L

2007-04-01

103

Effective File I/O Bandwidth Benchmark  

Energy Technology Data Exchange (ETDEWEB)

The effective I/O bandwidth benchmark (b{_}eff{_}io) covers two goals: (1) to achieve a characteristic average number for the I/O bandwidth achievable with parallel MPI-I/O applications, and (2) to get detailed information about several access patterns and buffer lengths. The benchmark examines ''first write'', ''rewrite'' and ''read'' access, strided (individual and shared pointers) and segmented collective patterns on one file per application and non-collective access to one file per process. The number of parallel accessing processes is also varied and well-formed I/O is compared with non-well formed. On systems, meeting the rule that the total memory can be written to disk in 10 minutes, the benchmark should not need more than 15 minutes for a first pass of all patterns. The benchmark is designed analogously to the effective bandwidth benchmark for message passing (b{_}eff) that characterizes the message passing capabilities of a system in a few minutes. First results of the b{_}eff{_}io benchmark are given for IBM SP and Cray T3E systems and compared with existing benchmarks based on parallel Posix-I/O.

Rabenseifner, R.; Koniges, A.E.

2000-02-15

104

InGaAs/AlGaInAs/InP Laser with Compressively Strained Multiquantum Well Layers for High Speed Modulation Bandwidth  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The modulation frequency response of compressively strained multiquantum well (MQW) lasers grown with an InGaAs/AlGaInAs/InP heterostructure and emitting at the wavelength of 1.55 mm is presented. The laser devices processed with the mushroom-stripe buried structure presen [...] t a high frequency 3 dB bandwidth above 20 GHz. The frequency response was measured with the small signal modulation technique. The logarithmic subtraction method was employed to extract the intrisic frequency response of the MQW active layer, providing the determination of important laser parameters: the differential gain, the nonlinear gain coefficient and the maximum 3 dB frequency bandwidth.

M.T., Furtado; E.J.T., Manganote; A.C.G., Bordeaux-Rêgo; F., Steinhagen; H., Janning; H., Burkhard.

105

An octave bandwidth frequency independent dipole antenna  

CERN Multimedia

Precision measurements of the spectrum of the cosmic radio background require frequency independent antennas of small electrical dimensions. We describe the design of a wide-band fat-dipole antenna with a sinusoidal profile having a frequency independent performance over the octave band 87.5 to 175 MHz. The input return loss exceeds 15 dB and the radiation power pattern is frequency invariant and close to cosine square over the octave bandwidth. The structure has been optimized using electromagnetic modeling, and the design has been validated by constructing a prototype.

Raghunathan, Agaram; Subrahmanyan, Ravi

2013-01-01

106

Bandwidth Partitioning in Decentralized Wireless Networks  

CERN Document Server

This paper addresses the following question, which is of interest in the design of a multiuser decentralized network. Given a total system bandwidth of W Hz and a fixed data rate constraint of R bps for each transmission, how many frequency slots N of size W/N should the band be partitioned into in order to maximize the number of simultaneous links in the network? Dividing the available spectrum results in two competing effects. On the positive side, a larger N allows for more parallel, non-interfering communications to take place in the same area. On the negative side, a larger N increases the SINR requirement for each link because the same information rate must be achieved over less bandwidth, which in turn increases the area consumed by each transmission. Exploring this tradeoff and determining the optimum value of N in terms of the system parameters is the focus of the paper. Using stochastic geometry, the optimal SINR threshold - which directly corresponds to the optimal spectral efficiency - is derived ...

Jindal, Nihar; Weber, Steven

2007-01-01

107

Bandwidth Allocation and Session Scheduling using SIP  

Directory of Open Access Journals (Sweden)

Full Text Available

Session Initiation Protocol (SIP is a new signaling protocol designed to establish multimedia sessions in telecommunication networks. In this paper, we suggest the extension of SIP functionalities to coordinate QoS mechanisms deployed in IP networks, and especially in DiffServ domain. Indeed, the interaction between small and big TCP sessions may have dramatic consequences on small TCP sessions. Hence, we use SIP to achieve QoS management on a session basis, in which the over all activity of the user during the session is considered. The suggested mechanisms deal with two issues: first, session scheduling based on session duration and/or volume, and second bandwidth allocation on a per-flow basis using equivalent bandwidth estimation techniques. The proposed mechanisms are implemented in the SIP proxy server as QoS management algorithms, and they are validated by simulations.

Jean-Marie Garcia

2006-08-01

108

Tunable pulsed narrow bandwidth light source  

Science.gov (United States)

A tunable pulsed narrow bandwidth light source and a method of operating a light source are provided. The light source includes a pump laser, first and second non-linear optical crystals, a tunable filter, and light pulse directing optics. The method includes the steps of operating the pump laser to generate a pulsed pump beam characterized by a nanosecond pulse duration and arranging the light pulse directing optics so as to (i) split the pulsed pump beam into primary and secondary pump beams; (ii) direct the primary pump beam through an input face of the first non-linear optical crystal such that a primary output beam exits from an output face of the first non-linear optical crystal; (iii) direct the primary output beam through the tunable filter to generate a sculpted seed beam; and direct the sculpted seed beam and the secondary pump beam through an input face of the second non-linear optical crystal such that a secondary output beam characterized by at least one spectral bandwidth on the order of about 0.1 cm.sup.-1 and below exits from an output face of the second non-linear optical crystal.

Powers, Peter E. (Dayton, OH); Kulp, Thomas J. (Livermore, CA)

2002-01-01

109

High Quality Geographic Services and Bandwidth Limitations  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we provide a critical overview of the state of the art in human-centric intelligent data management approaches for geographic visualizations when we are faced with bandwidth limitations. These limitations often force us to rethink how we design displays for geographic visualizations. We need ways to reduce the amount of data to be visualized and transmitted. This is partly because modern instruments effortlessly produce large volumes of data and Web 2.0 further allows bottom-up creation of rich and diverse content. Therefore, the amount of information we have today for creating useful and usable cartographic products is higher than ever before. However, how much of it can we really use online? To answer this question, we first calculate the bandwidth needs for geographic data sets in terms of waiting times. The calculations are based on various data volumes estimated by scholars for different scenarios. Documenting the waiting times clearly demonstrates the magnitude of the problem. Following this, we summarize the current hardware and software solutions, then the current human-centric design approaches trying to address the constraints such as various screen sizes and information overload. We also discuss a limited set of social issues touching upon the digital divide and its implications. We hope that our systematic documentation and critical review will help researchers and practitioners in the field to better understand the current state of the art.

Tumasch Reichenbacher

2011-12-01

110

Bandwidth broadening in RF-structure  

International Nuclear Information System (INIS)

Broad bandwidth represents one of the features the most sought after in electron tubes. In linear accelerators, it ensures the insensitiveness of the RF-structure to mechanical error or beam loading. This is commonly achieved by increasing the coupling between accelerating cells. To go further however, coalescence between two passbands or more is being used. The postcoupled Alvarez structure, the side-coupled or resonant slot-coupled cavity chain, as well as the dish-andwasher structure, among others, are well known examples. More generally, coalescence can take place in complex RF-structures such as multiperiodic systems. Presently, the use of mode coalescence is extended to certain types of RF-structures in TWTs in order to avoid band-edge oscillations. The purpose of this paper is to derive rules that mode coalescence obeys

1985-10-01

111

Bandwidth adjustment based on dynamic differential pulse code modulation  

Science.gov (United States)

This paper describes an application in which speech coding and resultant bandwidth usage is dynamically adapted to available network bandwidth. Network feedback concerning available bandwidth and current load is provided by the statistics generated by the real-time protocol which is used to support many audio and video applications running on the Multicast Backbone. This feedback is evaluated and used to control the speech encoding and adaptation. Speech segments are encoded to 16, 12, 10, 8 or 4 bit samples depending on network traffic conditions. Fewer bits are used when current network conditions show a reduction in available bandwidth, and additional bits are used when bandwidth is plentiful. Bit reduction lowers the amount of bandwidth needed to transmit the audio samples, and subsequently, fewer audio data packets are lost. Listening tests were performed to evaluate perceptual quality and to establish an acceptable maximum loss rate and minimum encoding rate.

Christianson, Leann M.; Brown, Kevin A.

1998-12-01

112

Diameter-bandwidth product limitation of isolated-object cloaking  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that cloaking of isolated objects using transformation-based cloaks is subject to a diameter-bandwidth product limitation: as the size of the object increases, the bandwidth of good (small-cross-section) cloaking decreases inversely with the diameter, as a consequence of causality constraints even for perfect fabrication and materials with negligible absorption. This generalizes a previous result that perfect cloaking of isolated objects over a nonzero bandwidth violates causality. Fu...

Joannopoulos, John D.; Mccauley, Alexander Patrick; Hashemi, Hila; Johnson, Steven G.; Qui, Cheng-wei

2012-01-01

113

An Efficient Bandwidth Estimation Schemes used in Wireless Mesh Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

wireless mesh networks (WMNs) has been widely used for the new generation wireless network. The capability of self-organization in WMNs reduces the complexity of wireless network deployment and maintenance. So, the perfect estimation of the bandwidth available of the mesh nodes is the required to admission control mechanism which provides QOs confirmation in wireless mesh networks. The bandwidth estimation of schemes do not give clear output. Here we are proposing bandwidth scheme estimation ...

2012-01-01

114

Variable data driven bandwidth choice in nonparametric quantile regression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The choice of a smoothing parameter or bandwidth is crucial when applying non- parametric regression estimators. In nonparametric mean regression various meth- ods for bandwidth selection exists. But in nonparametric quantile regression band- width choice is still an unsolved problem. In this paper a selection procedure for local varying bandwidths based on the asymptotic mean squared error (MSE) of the local linear quantile estimator is discussed. To estimate the unknown quant...

Abberger, Klaus

2002-01-01

115

Variable data driven bandwidth choice in nonparametric quantile regression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The choice of a smoothing parameter or bandwidth is crucial when applying non- parametric regression estimators. In nonparametric mean regression various meth- ods for bandwidth selection exists. But in nonparametric quantile regression band- width choice is still an unsolved problem. In this paper a selection procedure for local varying bandwidths based on the asymptotic mean squared error (MSE) of the local linear quantile estimator is discussed. To estimate the unknown quantities of the MS...

Abberger, Klaus

2002-01-01

116

Bandwidth limitation of the Fabry Perot cavity antennas  

International Nuclear Information System (INIS)

The bandwidth behavior of the Fabry Perot cavity antennas are considered on the basis of circuit theory. It is shown that the approaches of regenerative amplifier are applicable to resonator antenna. The equations for bandwidth limitation of the matched resonator antennas are obtained. It is experimentally confirmed that bandwidth of the Fabry Perot cavity antennas can be significantly enlarged by using properly selected partially reflective additional superstates

2011-01-01

117

A Priority Based Bandwidth Reservation Protocol for Wireless Mesh Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In wireless mesh networks, when compared with traditional applications, multimedia application requires the need of inflexible Quality of services (QoS) for high speed digital audio and videos. Under such a condition, the need of proper resource allocation is extremely handy. In this paper, we propose to develop a Priority Based Bandwidth Reservation Protocol (PBRP) for wireless mesh networks. Our protocol consists of two phases namely Bandwidth Request phase and Bandwidth Reply phase. In the...

Valarmathi, K.; Malmurugan, N.

2012-01-01

118

A study of Bandwidth Management in Computer Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Bandwidth management is one of the most widely misunderstood subjects in modern networking. Bandwidth Management is a lot like economics, because the complexities of how it works are beyond simple logic. Internet "bandwidth" is not a spectrum; traffic streams are one bit at a time. Bandwidth on the internet can only be conceptualized over time, and the amount of time that you talk about can greatly change the user experience. For reliable data transmission within computer network and internet forms the basis for management and control of bandwidth. Without bandwidth management, an user will not be able to handle all available bandwidth on the networks. It will be impossible to differentiate between various network traffics, and it will also be difficult to control which user or application has priority on the network. Applications which require specific quantity and quality of service may not be predicted in terms of available bandwidth, thus making some applications run poorly due to improper bandwidth allocation. This work focus on the development of an application to combat the challenges facing easy flow of data transmission problems in network design as organization network evolves. Here PHP Script, Apache Server and MySQL are the development tools used.

Devajit Mahanta,

2013-01-01

119

Frequency Bandwidth Optimization of Left-Handed Metamaterial  

Science.gov (United States)

Recently, left-handed metamaterials (LHM s) have been demonstrated with an effective negative index of refraction and with antiparallel group and phase velocities for microwave radiation over a narrow frequency bandwidth. In order to take advantage of these characteristics for practical applications, it will be beneficial to develop LHM s with increased frequency bandwidth response and lower losses. In this paper a commercial three-dimensional electromagnetic simulation code is used to explore the effects of geometry parameter variations on the frequency bandwidth of a LHM at microwave frequencies. Utilizing an optimizing routine in the code, a geometry was generated with a bandwidth more than twice as large as the original geometry.

Chevalier, Christine T.; Wilson, Jeffrey D.

2004-01-01

120

Optimal resource allocation in random networks with transportation bandwidths  

International Nuclear Information System (INIS)

We apply statistical physics to study the task of resource allocation in random sparse networks with limited bandwidths for the transportation of resources along the links. Recursive relations from the Bethe approximation are converted into useful algorithms. Bottlenecks emerge when the bandwidths are small, causing an increase in the fraction of idle links. For a given total bandwidth per node, the efficiency of allocation increases with the network connectivity. In the high connectivity limit, we find a phase transition at a critical bandwidth, above which clusters of balanced nodes appear, characterized by a profile of homogenized resource allocation similar to the Maxwell construction

2009-03-01

 
 
 
 
121

Effects of laser bandwidth on tool to tool CD matching  

Science.gov (United States)

According to the ITRS roadmap, low k1 imaging requires extremely tight control of Critical Dimension (CD). Maintaining the same performance from one exposure to another for new imaging requirements has become increasingly important, particularly for matching dry and wet systems. Tool to tool CD matching depends on many factors, for example, lens aberrations, partial coherence, laser spectral bandwidth and short range flare. We have performed a detailed study of laser bandwidth effects on tool CD matching for typical 65nm node structures exposed on immersion ArF scanners. A high accuracy on-board spectrometer was used to characterize the lithography Laser bandwidth, allowing measurements of both the FWHM and E95 parameters of the laser spectrum. Spectral bandwidth was adjusted over a larger range than normally experienced during wafer exposures using Cymer's Tunable Advanced Bandwidth Stabilization device (T-ABS) to provide controlled changes in bandwidth while maintaining all other laser performance parameters within specification. Measurements of both Lines and Contact Holes on 65nm node structures through all pitches were made and correlated with bandwidth to determine the sensitivity of IDB and C/H to bandwidth variation. We demonstrated that bandwidth can be adjusted for CD matching on different tool using the T-ABS function.

Hsueh, Bo-Yun; Wu, Hung-Yi; Jang, Louis; Yeh, Met; Yang, Chen-Chin; Huang, George K. C.; Yu, Chun-Chi; Chang, Allen

2008-03-01

122

Effective Bandwidth Utilization in IEEE802.11 for VOIP  

CERN Document Server

Voice over Internet protocol (VoIP) is one of the most important applications for the IEEE 802.11 wireless local area networks (WLANs). For network planners who are deploying VoIP over WLANs, one of the important issues is the VoIP capacity. VoIP bandwidth consumption over a WAN is one of the most important factors to consider when building a VoIP infrastructure. Failure to account for VoIP bandwidth requirements will severely limit the reliability of a VoIP system and place a huge burden on the WAN infrastructure. Less bandwidth utilization is the key reasons for reduced number of channel accesses in VOIP. But in the QoS point of view the free bandwidth of atleast 1-5% will improve the voice quality. This proposal utilizes the maximum bandwidth by leaving 1-5% free bandwidth. A Bandwidth Data rate Moderation (BDM) algorithm has been proposed which correlates the data rate specified in IEEE802.11b with the free bandwidth. At each time BDM will calculate the bandwidth utilization before sending the packet to i...

Bhanu, S Vijay; Balakrishnan, V

2010-01-01

123

Schottky Heterodyne Receivers With Full Waveguide Bandwidth  

Science.gov (United States)

Compact THz receivers with broad bandwidth and low noise have been developed for the frequency range from 100 GHz to 1 THz. These receivers meet the requirements for high-resolution spectroscopic studies of planetary atmospheres (including the Earth s) from spacecraft, as well as airborne and balloon platforms. The ongoing research is significant not only for the development of Schottky mixers, but also for the creation of a receiver system, including the LO chain. The new receivers meet the goals of high sensitivity, compact size, low total power requirement, and operation across complete waveguide bands. The exceptional performance makes these receivers ideal for the broader range of scientific and commercial applications. These include the extension of sophisticated test and measurement equipment to 1 THz and the development of low-cost imaging systems for security applications and industrial process monitoring. As a particular example, a WR-1.9SHM (400-600 GHz) has been developed (see Figure 1), with state-of-the-art noise temperature ranging from 1,000-1,800 K (DSB) over the full waveguide band. Also, a Vector Network Analyzer extender has been developed (see Figure 2) for the WR1.5 waveguide band (500 750 GHz) with 100-dB dynamic range.

Hesler, Jeffrey; Crowe, Thomas

2011-01-01

124

Bandwidth tunable filter based on silicon microring-MZI structure  

DEFF Research Database (Denmark)

A novel bandwidth tunable bandpass filter based on a silicon microring-MZI structure is proposed and demonstrated. By thermally tuning the resonance offset between the two microring resonators, and adding the two drop transmissions together, the bandwidth of the microring-MZI filter can be easily linearly tuned with low in-band ripples.

Ding, Yunhong; Pu, Minhao

2010-01-01

125

A Study of Bandwidth Measurement Technique in Wireless Mesh Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Wireless mesh networks (WMNs have been proposed as a key technology for next generation wirelessnetworking to provide last-mile broadband access. Here we have given our observation and study for endto-end bandwidth estimation in WMNs. End-to-end Bandwidth Estimation is an important metric fornetwork management and monitoring. It can also improve the effectiveness of congestion controlmechanism, audio/video stream adoration and dynamic overlay. In recent years, many techniques havebeen developed for bandwidth estimation in the wired as well as the last-hop wireless networks, but theyunder-perform in WMNs. We investigate attributes that can affect the bandwidth estimation in WNMs; wefound existing techniques do not consider the effect of attributes like CSMA/CA-based contending trafficand high interference interference that leads to the error full estimation.In this paper, we present an active bandwidth measurement technique called Bandwidth Probe based on thepacket dispersion principle. It measures the steady state bandwidth of the system while considering theeffects of the FIFO cross and CSMA/CA-based contending traffic. It is also mitigating the effect ofinterference. We also show how to achieve the stationary state behaviour of the system to limit the numberof probe packets. On simulation, Bandwidth Probe gives a accurate estimation of the available bandwidthusing average convergence time and lower intrusiveness.

Ajeet Kumar Singh

2011-10-01

126

One Method of Cloud Computing Bandwidth Allocation Based on Fairness  

Directory of Open Access Journals (Sweden)

Full Text Available In order to solve the bandwidth allocation unfairness problem in the cloud computing network, one method uses fairness congestion control algorithm, access control list (ACL and traffic policing and traffic shaping in the paper. The method can rationally solve the problem after analyzing the reason of cloud computing bandwidth allocation unfairness. For illustration, one network video conference example was utilized to show the method in solving bandwidth allocation unfairness problem.The experimental results show network bandwidths are fairly allocated, packet loss ratio and latency is obvious improvement. The method deals with non-adaptive UDP and TCP adaptive flow congestion and provides the end-to-end quality of service over the differentiated services networks, and the bandwidth allocation problem based on fairness in the cloud computing network is solved well.

Yiquan Kong

2013-02-01

127

A Priority Based Bandwidth Reservation Protocol for Wireless Mesh Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In wireless mesh networks, when compared with traditional applications, multimedia application requires the need of inflexible Quality of services (QoS for high speed digital audio and videos. Under such a condition, the need of proper resource allocation is extremely handy. In this paper, we propose to develop a Priority Based Bandwidth Reservation Protocol (PBRP for wireless mesh networks. Our protocol consists of two phases namely Bandwidth Request phase and Bandwidth Reply phase. In the former Phase, a Bandwidth Request (BREQ message is forwarded from the node that requests the admission of a new traffic flow to its destination. In the later Phase, a Bandwidth Reply (BREP message proceeds backwards, hop-by-hop, from the destination node to the node that originated the request along the path laid down by the corresponding (BREQ message. The destination node precedes the reply according to the priority of traffic classes and reserves the bandwidth on the reply path. By simulation results, we show that our proposed protocol achieves high bandwidth utilization and throughput with reduced delay, when compared with existing technique.

K. Valarmathi

2012-01-01

128

A NOVEL µ-NEGATIVE METAMATERIAL WITH ENHANCED REJECTION BANDWIDTH  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, a novel planar µ-Negative (MNG metamaterial structure based on Split Ring Resonators (SRRs with improved rejection bandwidth is presented. A bridging technique is used to connect two SRR unit cells at the center to emulate a cascaded filter. The proposed structure achieved a -20 dB rejection bandwidth of 15.5% compared to 4.5% for the conventional SRRs which makes it a good candidate for integration with antennas and RF circuits that require large operational bandwidth.

Haider Raad

2013-01-01

129

Energy efficiency in elastic-bandwidth optical networks  

DEFF Research Database (Denmark)

The forecasted growth in the Internet traffic has made the operators and industry to be concerned about the power consumption of the networks, and to become interested in alternatives to plan and operate the networks in a more energy efficient manner. The introduction of OFDM, and its property of elastic bandwidth allocation, opens new horizons in the operation of optical networks. In this paper, we compare the network planning problem in an elastic bandwidth CO-OFDM-based network and a fixed-grid WDM network. We highlight the benefits that bandwidth elasticity and the selection of different modulation formats offer in terms of energy efficiency.

Vizcaino, Jorge Lopez; Ye, Yabin

2011-01-01

130

Phase locking and bandwidth in a gyrotron oscillator  

Science.gov (United States)

For imaging radar and for satellite and space communication (e.g. NASA's deep space network), it is important that the bandwidth be as large as possible. Here we derive a formalism for computing the phase locking bandwidth that can be achieved in a gyrotron oscillator while varying the beam voltage. As an example, a second harmonic TE02/03 gyrotron is considered. For this device, the effective bandwidth can be increased by a factor of about 3 compared with the fixed voltage case by allowing the beam voltage to change together with the input locking signal.

Latham, P. E.; Granatstein, V. L.; Carmel, Y.

1993-01-01

131

Intrinsic transmission bandwidths of graded-index plastic optical fibers.  

Science.gov (United States)

We theoretically demonstrate that microscopic heterogeneous properties can enhance the transmission bandwidths of graded-index plastic optical fibers (POFs) for short-haul communication networks. The heterogeneities of the POF cores are quantitatively correlated with mode couplings by modifying the coupled power equation with consideration of the spatial correlation characteristics of the heterogeneities. Using the modified theory, we clarify that the larger fluctuation size and/or amplitude results in higher bandwidth because of greater forward scattering and/or higher scattering efficiency, respectively. This suggests that the multimode fiber bandwidths can depend on the macroscopically observed index profiles as well as on the microscopic material properties. PMID:22743462

Inoue, Azusa; Sassa, Takafumi; Makino, Kenji; Kondo, Atsushi; Koike, Yasuhiro

2012-07-01

132

Broad-bandwidth Brillouin slow light in optical fibers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We experimentally demonstrate that Brillouin slow light with an arbitrary large bandwidth can be readily obtained in conventional optical fibers using a simple and inexpensive pump spectral broadening technique

Gonzalez Herraez, M.; Song, Kwang-yong; The?venaz, Luc

2006-01-01

133

Bandwidth allocation and pricing problem for a duopoly market  

Directory of Open Access Journals (Sweden)

Full Text Available This research discusses the Internet service provider (ISP bandwidth allocation and pricing problems for a duopoly bandwidth market with two competitive ISPs. According to the contracts between Internet subscribers and ISPs, Internet subscribers can enjoy their services up to their contracted bandwidth limits. However, in reality, many subscribers may experience the facts that their on-line requests are denied or their connection speeds are far below their contracted speed limits. One of the reasons is that ISPs accept too many subscribers as their subscribers. To avoid this problem, ISPs can set limits for their subscribers to enhance their service qualities. This paper develops constrained nonlinear programming to deal with this problem for two competitive ISPs. The condition for reaching the equilibrium between the two competitive firms is derived. The market equilibrium price and bandwidth resource allocations are derived as closed form solutions.

You Peng-Sheng

2011-01-01

134

Image Cipher Technique for Covert and Low Bandwidth Channels  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Security of images during the transmission over covert low bandwidth channel has importance in today's image communications for confidential, integrated and secure real time communication. The major security problems during communication over covert and low bandwidth channel is to reduce no of bits, efficient and secure cryptographic techniques such that output gain and performance may lead towards more secure and efficient mechanism. Thus, in this paper, we have purposed a secure, reliable a...

2011-01-01

135

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A Virtual Private Network (VPN) provides private network connections over a publicly accessible shared network. The effective allocation of bandwidth for VPNs assumes significance in the present scenario due to varied traffic. Each VPN endpoint specifies bounds on the total amount of traffic that it is likely to send or receive at any time. The network provider tailors the VPN so that there is sufficient bandwidth for any traffic matrix that is consistent with these bounds. The approach incor...

Mahalakshmi Chidambara Natarajan; Ramaswamy Muthiah; Alamelu Nachiappan

2010-01-01

136

Bandwidth selection for kernel density estimation with doubly truncated data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several bandwidth selection procedures for kernel density estimation of a random variable that is sampled under random double truncation are introduced and compared. The motivation is based on the fact that this type of incomplete data is often encountered in astronomy and medicine. The considered bandwidth selection procedures are appropriate modifications of the normal reference rule, the least squares cross-validation procedure, two types of plug-in procedures, and a bootstrap based method...

2013-01-01

137

Analysis and implementation of the multiprocessor bandwidth inheritance protocol  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Multiprocessor Bandwidth Inheritance (M-BWI) protocol is an extension of the Bandwidth Inheritance (BWI) protocol for symmetric multiprocessor systems. Similar to Priority Inheritance, M-BWI lets a task that has locked a resource execute in the resource reservations of the blocked tasks, thus reducing their blocking time. The protocol is particularly suitable for open systems where different kinds of tasks dynamically arrive and leave, because it guarantees temporal isolation among indepe...

Faggioli, Dario; Lipari, Giuseppe; Cucinotta, Tommaso

2012-01-01

138

Review of high bandwidth fiber optics radiation sensors  

International Nuclear Information System (INIS)

This paper summarizes the use of fiber optics or guided optical systems for radiation sensors. It is limited a passive systems wherein electrical is not required at the sensor location. However, electrically powered light sources, receivers and/or recorders may still be required for detection and data storage in sensor system operation. This paper emphasizes sensor technologies that permit high bandwidth measurements of transient radiation levels, and will also discuss several low bandwidth applications. 60 refs

1985-08-18

139

Bandwidth-Aware AODV based Routing Protocol in MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available A wireless ad hoc network is a collection of mobile nodes that dynamically form a temporary network and communicate with each other without any physical networking infrastructure . Many real time applications have quality of Service (QoS requirements like bandwidth, end-to-end delay and jitter. So,to support these applications it is important to have QoS mechanism. In this paper we propose a bandwidth-aware routing protocol, which is based on the reactive ad-hoc distance vector (AODV routing protocol therefore we named it BAAODV protocol. In this Protocol, we include one of the important issue of ad hoc networks which is the bandwidth where the bandwidth-aware route discovery process discover a route in which each intermediate node has bandwidth greater than the required bandwidth. We compare our proposed bandwidthaware AODV routing (BA-AODV protocol to the existing traditional AODV routing protocol. The simulation results show the effectiveness and correctness of our proposed method in terms of increased network load in the scenarios consisting of mobile nodes as well as static nodes.

Richa Jain#1 , Chetan Kumar#2, Pankaj Jain

2013-06-01

140

Fuzzy-based adaptive bandwidth control for loss guarantees.  

Science.gov (United States)

This paper presents the use of adaptive bandwidth control (ABC) for a quantitative packet loss rate guarantee to aggregate traffic in packet switched networks. ABC starts with some initial amount of bandwidth allocated to a queue and adjusts it over time based on online measurements of system states to ensure that the allocated bandwidth is just enough to attain the specified loss requirement. Consequently, no a priori detailed traffic information is required, making ABC more suitable for efficient aggregate quality of service (QoS) provisioning. We propose an ABC algorithm called augmented Fuzzy (A-Fuzzy) control, whereby fuzzy logic control is used to keep an average queue length at an appropriate target value, and the measured packet loss rate is used to augment the standard control to achieve better performance. An extensive simulation study based on both theoretical traffic models and real traffic traces under a wide range of system configurations demonstrates that the A-Fuzzy control itself is highly robust, yields high bandwidth utilization, and is indeed a viable alternative and improvement to static bandwidth allocation (SBA) and existing adaptive bandwidth allocation schemes. Additionally, we develop a simple and efficient measurement-based admission control procedure which limits the amount of input traffic in order to maintain the performance of the A-Fuzzy control at an acceptable level. PMID:16252823

Siripongwutikorn, Peerapon; Banerjee, Sujata; Tipper, David

2005-09-01

 
 
 
 
141

Design, Analysis and Implementation of a Small Signal Control Strategy on a 10 kVA STATCOM Prototype Connected to Inductive Load  

Science.gov (United States)

Power factor on the supply side at point of common connection (PCC) can be improved through reactive power compensation using a static synchronous compensator (STATCOM). This approach is becoming increasingly popular in power system applications. In this paper, a small signal model of the STATCOM is practically implemented for maintaining unity power factor on the grid side in presence of inductive loads using a 10 kVA laboratory prototype. The designed controller is first simulated and then experimentally validated on the above laboratory prototype. Excellent agreement between the simulated and experimental results demonstrates the effectiveness of the proposed control strategy and highlights the accuracy of the experiments.

Moharana, J. K.; Sengupta, M.; Sengupta, A.

2013-03-01

142

Wide-bandwidth and high-power 1.3 ?m InGaAsP buried crescent lasers with semi-insulating Fe-doped InP current blocking layers  

International Nuclear Information System (INIS)

By the use of Fe-doped InP layer as the only current blocking layer, 8.3 GHz bandwidth and 30 mw/facet output has been achieved on 1.3 ?m buried crescent lasers. Conventional 1.3 ?m buried crescent lasers are attractive as light sources for optical fiber communication systems because of their high output power, single transverse mode, and good reliability. However, their small signal modulation bandwidth is rather limited due to excess parasitic capacitance from the current blocking reverse-biased p-n junction. Recently, the modulation bandwidth of InGaAsP buried crescent lasers has been extended to 4 GHz by the use of Fe-doped semi-insulating InP blocking layers grown by metal organic vapor phase epitaxy (MOVPE). In this previous work, a stripe geometry contact defined by a SiO/sub 2/ mask in addition to the semi-insulating InP layer was used to restrict the current flow laterally. In the present work, the authors report 1.3 ?m In GaAsP buried crescent lasers using similar semi-insulating InP as the current blocking layer, but without the SiO/sub 2/ current confining layer. The lasers with the broad area metal contacts exhibit both wide bandwidth and high power capabilities simultaneously

1987-01-01

143

Bandwidth-disorder phase diagram of half doped layered manganites  

CERN Document Server

Phase diagrams in the plane of $r_A$ (the average ionic radius, related to one-electron bandwidth $W$) and $\\sigma^2$ (the ionic radius variance, measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'', have been established for perovskite manganites, with three-dimensional (3$D$) Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram of half-doped layered manganites with the two-dimensional (2$D$) Mn-O network, examining in detail the ``mother state'' of the colossal magnetoresistance (CMR) phenomenon in crystals without ferromagnetic instability. The consequences of the reduced dimensionality, from 3$D$ to 2$D$, on the order-disorder phenomena in the charge-orbital sectors are also highlighted.

Mathieu, R; Kaneko, Y; He, J P; Yu, X Z; Kumai, R; Arima, T; Tomioka, Y; Asamitsu, A; Matsui, Y; Tokura, Y

2006-01-01

144

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

Directory of Open Access Journals (Sweden)

Full Text Available A Virtual Private Network (VPN provides private network connections over a publicly accessible shared network. The effective allocation of bandwidth for VPNs assumes significance in the present scenario due to varied traffic. Each VPN endpoint specifies bounds on the total amount of traffic that it is likely to send or receive at any time. The network provider tailors the VPN so that there is sufficient bandwidth for any traffic matrix that is consistent with these bounds. The approach incorporates the use of Ad-hoc On demand Distance Vector (AODV protocol, with a view to accomplish an enhancement in the performance of the mobile networks. The NS2 based simulation results are evaluated in terms of its metrics for different bandwidth allocations, besides analyzing its performance in the event of exigencies such as link failures. The results highlight the suitability of the proposed strategy in the context of real time applications.

Ramaswamy Muthiah

2010-01-01

145

Demonstration of wide bandwidth energy harvesting from vibrations  

International Nuclear Information System (INIS)

We experimentally demonstrate a true wide bandwidth vibration energy harvester based on piezoelectric transduction. Our device is designed to work specifically off-resonance under sinusoidal input vibrations with constant displacement amplitudes. The same device displays wide bandwidth operation under vibrations with constant acceleration amplitudes. We have achieved over 6 nW of wide bandwidth power extraction per active piezoelectric patch between 80–180 Hz for constant 100 µm displacement amplitude, and across 20–90 Hz for constant 3g acceleration amplitude. Simulation of the micro-harvester with optimally fabricated piezoelectric material demonstrates over 1 µW of power across the same frequencies, enabling a fully integrated, self-powered wireless sensor node. (paper)

2012-06-01

146

Optical computing for image bandwidth compression: analysis and simulation.  

Science.gov (United States)

Image bandwidth compression is dominated by digital methods for carrying out the required computations. This paper discusses the general problem of using optics to realize the computations in bandwidth compression. A common method of digital bandwidth compression, feedback differential pulse code modulation (DPCM), is reviewed, and the obstacles to making a direct optical analogy to feedback DPCM are discussed. Instead of a direct optical analogy to DPCM, an optical system which captures the essential features of DPCM without optical feedback is introduced. The essential features of this incoherent optical system are encoding of low-frequency information and generation of difference samples which can be coded with a small number of bits. A simulation of this optical system by means of digital image processing is presented, and performance data are also included. PMID:20203902

Hunt, B R

1978-09-15

147

Enhancement of bandwidth of planar microstrip antenna with meta materials  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we present a planar left-handed material pattern on the rectangular patch antenna mounted on the substrate is designed to enhance its horizontal radiation as well as to broaden its working bandwidth. The parametric study is done to study the effect of the ground plane slots width of 0.3, 0.4 and 0.5 mm respectively on the return loss and bandwidth enhancement, the best value of g is 0.4 mm. Enhancement in the bandwidth is achieved by introducing the meta material phenomena instead of the single patch antenna is about 19.2 times with g = 0.4 mm.

Ahmed Al-Shaheen

2011-09-01

148

Bandwidth selection for smooth backfitting in additive models  

CERN Document Server

The smooth backfitting introduced by Mammen, Linton and Nielsen [Ann. Statist. 27 (1999) 1443-1490] is a promising technique to fit additive regression models and is known to achieve the oracle efficiency bound. In this paper, we propose and discuss three fully automated bandwidth selection methods for smooth backfitting in additive models. The first one is a penalized least squares approach which is based on higher-order stochastic expansions for the residual sums of squares of the smooth backfitting estimates. The other two are plug-in bandwidth selectors which rely on approximations of the average squared errors and whose utility is restricted to local linear fitting. The large sample properties of these bandwidth selection methods are given. Their finite sample properties are also compared through simulation experiments.

Mammen, E; Mammen, Enno; Park, Byeong U.

2005-01-01

149

The bandwidth of optimized nonlinear vibration-based energy harvesters  

Science.gov (United States)

In an attempt to improve the performance of vibration-based energy harvesters, many authors suggest that nonlinearities can be exploited to increase the bandwidths of linear devices. Nevertheless, the complex dependence of the response upon the input excitation has made a realistic comparison of linear harvesters with nonlinear energy harvesters challenging. In a previous work it has been demonstrated that for a given frequency of excitation, it is possible to achieve the same maximum power for a nonlinear harvester as that for a linear harvester, provided that the resistance and the linear stiffness of both are optimized. This work focuses on the bandwidths of linear and nonlinear harvesters and shows which device is more suitable for harvesting energy from vibrations. The work considers different levels of excitation as well as different frequencies of excitation. In addition, the effect of the mechanical damping of the oscillator on the power bandwidth is shown for both the linear and nonlinear cases.

Cammarano, A.; Neild, S. A.; Burrow, S. G.; Inman, D. J.

2014-05-01

150

Large bandwidth, highly efficient optical gratings through high index materials  

CERN Document Server

We analyze the diffraction characteristics of dielectric gratings that feature a high index grating layer, and devise, through rigorous numerical calculations, large bandwidth, highly efficient, high dispersion dielectric gratings in reflection, transmission, and immersed transmission geometry. A dielectric TIR grating is suggested, whose -1dB spectral bandwidth is doubled as compared to its all-glass equivalent. The short wavelength diffraction efficiency is additionally improved by allowing for slanted lamella. The grating surpasses a blazed gold grating over the full octave. An immersed transmission grating is devised, whose -1dB bandwidth is tripled as compared to its all-glass equivalent, and that surpasses an equivalent classical transmission grating over nearly the full octave. A transmission grating in the classical scattering geometry is suggested, that features a buried high index layer. This grating provides effectively 100% diffraction efficiency at its design wavelegth, and surpasses an equivalen...

Rathgen, Helmut

2008-01-01

151

Continuously Variable Bandwidth Sharp FIR Filters with Low Complexity  

Directory of Open Access Journals (Sweden)

Full Text Available In software defined radio (SDR, sharp filters of different bandwidth are required to fine tune the desired channel. This requires different computational resources and large number of filter coefficients. This paper proposes a continuously variable bandwidth sharp finite impulse response (FIR filter with low distortion and low complexity. For this, a fixed length FIR filter is used with two arbitrary sampling rate converters. This system can be used for both the continuous increase as well as decrease of the effective bandwidth of a filter. The low complexity and sharpness are achieved by using the frequency-response masking (FRM approach for the design of the fixed length FIR filter. The sharp transition width leads to maximum rejection to channel interference in SDR.

James T. George

2012-08-01

152

Delivery of very high bandwidth with ATM switches and SONET  

Energy Technology Data Exchange (ETDEWEB)

To deliver high bandwidth, a ubiquitous inter-/intra-building cable plant consisting of single mode and multimode fiber as well as twisted pair copper is required. The selection of the ``glue`` to transport and interconnect distributed LANs with central facility resources over a pervasive cable plant is the focus of this paper. A description of the traditional problems that must be overcome to provide very high bandwidth beyond the narrow confines of a computer center is given. The applicability of Asynchronous Transfer Mode (ATM) switching (interconnection) and Synchronous Optical NETwork (SONET) (transport) for high bandwidth delivery is described using the environment and requirements of Sandia National Laboratories. Other methods for distributing high data rates are compared and contrasted. Sandia is implementing a standards based foundation utilizing a pervasive single mode fiber cable plant, SONET transport, and ATM switching to meet the goals of gigabit networking.

Gossage, S.A.

1993-08-01

153

Performance Investigation of Virtual Private Networks with Different Bandwidth Allocations  

CERN Document Server

A Virtual Private Network (VPN) provides private network connections over a publicly accessible shared network. The effective allocation of bandwidth for VPNs assumes significance in the present scenario due to varied traffic. Each VPN endpoint specifies bounds on the total amount of traffic that it is likely to send or receive at any time. The network provider tailors the VPN so that there is sufficient bandwidth for any traffic matrix that is consistent with these bounds. The approach incorporates the use of Ad-hoc On demand Distance Vector (AODV) protocol, with a view to accomplish an enhancement in the performance of the mobile networks. The NS2 based simulation results are evaluated in terms of its metrics for different bandwidth allocations, besides analyzing its performance in the event of exigencies such as link failures. The results highlight the suitability of the proposed strategy in the context of real time applications.

Natarajan, Mahalakshmi Chidambara; Nachiappan, Alamelu

2010-01-01

154

A novel dynamic wavelength bandwidth allocation scheme over OFDMA PONs  

Science.gov (United States)

With rapid growth of Internet applications, supporting differentiated service and enlarging system capacity have been new tasks for next generation access system. In recent years, research in OFDMA Passive Optical Networks (PON) has experienced extraordinary development as for its large capacity and flexibility in scheduling. Although much work has been done to solve hardware layer obstacles for OFDMA PON, scheduling algorithm on OFDMA PON system is still under primary discussion. In order to support QoS service on OFDMA PON system, a novel dynamic wavelength bandwidth allocation (DWBA) algorithm is proposed in this paper. Per-stream QoS service is supported in this algorithm. Through simulation, we proved our bandwidth allocation algorithm performs better in bandwidth utilization and differentiate service support.

Yan, Bo; Guo, Wei; Jin, Yaohui; Hu, Weisheng

2011-11-01

155

Effective Bandwidth Utilization in IEEE802.11 for VOIP  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Voice over Internet protocol (VoIP) is one of the most important applications for the IEEE 802.11 wireless local area networks (WLANs). For network planners who are deploying VoIP over WLANs, one of the important issues is the VoIP capacity. VoIP bandwidth consumption over a WAN is one of the most important factors to consider when building a VoIP infrastructure. Failure to account for VoIP bandwidth requirements will severely limit the reliability of a VoIP system and place...

Bhanu, S. Vijay; Chandrasekaran, Rm; Balakrishnan, V.

2010-01-01

156

VISA IB Ultra-High Bandwidth, High Gain SASE FEL  

CERN Document Server

The results of a high energy-spread SASE FEL experiment, the intermediary experiment linking the VISA I and VISA II projects, are presented. A highly chirped beam (~1.7%) was transported without correction of longitudinal aberrations in the ATF dogleg, and injected into the VISA undulator. The output FEL radiation displayed an uncharacteristicly large bandwidth (~11%) with extremely stable lasing and measured energy of about 2 microJoules. Start-to-end simulations reproduce key features of the measured results and provide an insight into the mechanisms giving rise to such a high bandwidth. These analyses are described as they relate to important considerations for the VISA II experiment.

Andonian, Gerard; Murokh, Alex; Pellegrini, Claudio; Reiche, Sven; Rosenzweig, J B; Travish, Gil

2004-01-01

157

Small Bandwidth Asymptotics for Density-Weighted Average Derivatives  

DEFF Research Database (Denmark)

This paper proposes (apparently) novel standard error formulas for the density-weighted average derivative estimator of Powell, Stock, and Stoker (1989). Asymptotic validity of the standard errors developed in this paper does not require the use of higher-order kernels and the standard errors are "robust" in the sense that they accommodate (but do not require) bandwidths that are smaller than those for which conventional standard errors are valid. Moreover, the results of a Monte Carlo experiment suggest that the finite sample coverage rates of conâ?¦dence intervals constructed using the standard errors developed in this paper coincide (approximately) with the nominal coverage rates across a nontrivial range of bandwidths.

Cattaneo, Matias D.; Crump, Richard K.

2008-01-01

158

Image Cipher Technique for Covert and Low Bandwidth Channels  

Directory of Open Access Journals (Sweden)

Full Text Available Security of images during the transmission over covert low bandwidth channel has importance in today's image communications for confidential, integrated and secure real time communication. The major security problems during communication over covert and low bandwidth channel is to reduce no of bits, efficient and secure cryptographic techniques such that output gain and performance may lead towards more secure and efficient mechanism. Thus, in this paper, we have purposed a secure, reliable and efficient mechanism using arithmetic coding techniques followed by IMAES (Improved Modified Advanced Encryption standard techniques. The output of encrypted images reveals that proposed technique presents higher performance, quit reliable and robust.

Sangeeta Solanki

2011-05-01

159

Bandwidth-constrained delay optimization for signal systems  

Energy Technology Data Exchange (ETDEWEB)

Over the past decade, a number of computerized techniques have been developed for optimizing signal timing plans for urban signal systems. These techniques very in their criteria employed to reach a desired timing plan. Most use the criterion of either minimizing system delay and stops or maximizing arterial progression bandwidths. Techniques also vary in terms of the traffic variables considered in the optimization process. The purpose of this article is to report on an approach that integrates the best features of the delay/stops optimization and progression bandwidth optimization techniques. Through the integrated approach, all four variables can be explictly optimized in stages.

Liu, C.C.

1988-12-01

160

Extending the Bandwidth of Electric Ring Resonator Metamaterial Absorber  

International Nuclear Information System (INIS)

An efficient method is proposed to extend the bandwidth of a metamaterial absorber with multi-resonance structure. The basic unit cell of a metamaterial absorber consists of the electric ring resonator, dielectric substrate (FR-4) and split-wire. By assembling five sandwiched structures with different geometric dimensions into a unit cell, we obtain the superposition of five different absorption peaks. Finally, the bandwidth of metamaterial absorption is extended and the full width at half maximum is up to 1.3 GHz. The simulated and experimental results are consistent. (fundamental areas of phenomenology(including applications))

2011-03-01

 
 
 
 
161

Ultra Wideband Microstrip Diamond Slotted Patch Antenna with Enhanced Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An Ultra Wideband (UWB) microstrip diamond slotted patch antenna with enhanced bandwidth is presented in this paper. The proposed antenna is simulated in CST Microwave Studio and fabricated for measurements. Its simulated result displays impedance bandwidth from 3.28 GHz to 19.64 GHz, whereas the measured result displays the frequency region from 2.01 GHz to 18.67 GHz. The antenna complies with the return loss of S11 < –10 dB and Voltage Standing Wave Ratio (VSWR) < 2 throughout the i...

Chia Ping Lee; Chandan Kumar Chakrabarty

2011-01-01

162

Bandwidth Enhancement of Probe Fed Microstrip Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antenna becomes verypopular day by day because of its ease of analysis andfabrication, low cost, light weight, easy to feed and theirattractive radiation characteristics. Although patchantenna has numerous advantages, it has also somedrawbacks such as restricted bandwidth, and a potentialdecrease in radiation pattern. Different techniques forbandwidth enhancement of conventional rectangularmicrostrip antenna are proposed in this paper. Byincreasing the height of patch , increasing the substratethickness and decreasing the permittivity of substrate the%bandwidth is increased. HFSS Software is used for thesimulation and design calculation of microstrip patchantenna. The return loss, vswr curve, directivity and gainare evaluated.

Parminder Singh

2013-01-01

163

Determining Bandwidth for Server in Saxess and Genium Trading Platforms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this final study an approximation of how much bandwidth one server requires in Saxess and Genium environment was studied. In Saxess it is possible to trade only in so called cash markets, for other financial instruments there are other programs. In Genium it is possible to trade in cash markets and in all the other markets, for example derivates. For the final results to be comparable only cash market traffic was analyzed in Genium. The goal was to determine how much bandwidth was needed f...

Nyman, Birger

2008-01-01

164

SATELLITE BANDWIDTH ALLOCATION FOR SATELLITE ROUTED SENSOR NETWORKS?  

Directory of Open Access Journals (Sweden)

Full Text Available Next Generation Satellite Routed Sensor Systems is expected to provide disaster detection system with high real time performance. By using Satellite Networks SRSS realizes data collection from multiple sensor terminals deployed in a wide area. However an efficient access control scheme is needed to achieve multiple access from numerous sensor terminals to the satellite with its limited bandwidth. In order to efficiently resolve these problems we propose a new scheme which utilizes a divide and conquer approach for efficient bandwidth allocation. Numerical results demonstrate the effectiveness of proposal.

Ambika Telkar

2014-06-01

165

Design of a Ã?4 subharmonic sub-millimeter wave diode mixer, based on an analytic expression for small-signal conversion admittance parameters  

DEFF Research Database (Denmark)

Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description of the small-signal admittance in a Schottky-diode mixer where the phase can be set arbitrarily. It is shown that only for the case of a fundamental frequency mixer this admittance becomes a purely real valued conductance. To test the theory a Ã?4 subharmonic sub-millimeter wave mixer is designed and simulated. With an RF frequency of 640 GHz, this design achieves a conversion gain of â??13.5 dB with a LO-power of only â??2.5 dBm.

Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke

2013-01-01

166

Fingerprinting: Bounding the Soft-Error Detection Latency and Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fingerprinting summarizes the history of internal processor state updates into a cryptographic signature. The processors in a dual modular redundant pair periodically exchange and compare fingerprints to corroborate each other's correctness. relative to other techniques, fingerprinting offers superior error coverage and significantly reduces the error-detection latency and bandwidth.

Smolens, Jared C.; Gold, Brian T.; Kim, Jangwoo; Falsafi, Babak; Hoe, James C.; Nowatzyk, Andreas G.

2004-01-01

167

Distributed Algorithms for Dynamic Bandwidth Provisioning in Communication Networks  

Directory of Open Access Journals (Sweden)

Full Text Available

Efficient dynamic resource provisioning algorithms are necessary to the development and automation of Quality of Service (QoS networks. The main goal of these algorithms is to offer services that satisfy the QoS requirements of individual users while guaranteeing at the same time an efficient utilization of network resources. In this paper we introduce a new service model that provides quantitative per-flow bandwidth guarantees, where users subscribe for a guaranteed rate; moreover, the network periodically individuates unused bandwidth and proposes short-term contracts where extra-bandwidth is allocated and guaranteed exclusively to users who can exploit it to transmit at a rate higher than their subscribed rate. To implement this service model we propose a dynamic provisioning architecture for intra-domain Quality of Service networks. We develop an efficient bandwidth allocation algorithm that takes explicitly into account traffic statistics to increase the users’ benefit and the network revenue simultaneously. We demonstrate through simulation in several realistic network scenarios that the proposed dynamic provisioning model is superior to static provisioning in providing resource allocation both in terms of total accepted load and network revenue.

Antonio Capone

2006-12-01

168

A Bandwidth Characterization Tool For MPEG-2 File  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes the design and development of MPEG 2 Video Decoder to offer flexible and effective utilization of bandwidth services. The decoder is capable of decoding the MPEG 2 bit stream on a single host machine. The present decoder is designed to be simple, but yet effectively reconstruct the video from MPEG 2 bit stream.

Kugali, Sandeep; Manvi, S. S.; Sutagundar, A. V.

2009-01-01

169

A Preliminary Evaluation of Bandwidth Allocation Model Dynamic Switching  

Directory of Open Access Journals (Sweden)

Full Text Available Bandwidth Allocation Models (BAMs are used in order to define Bandwidth Constraints (BCs in a per-class basis for MPLS/DS-TE networks and effectively define how network resources like bandwidth are obtained and shared by applications. The BAMs proposed (MAM – Maximum Allocation Model, RDM – Russian Dolls Model, G-RDM – Generic RDM and AllocTC-Sharing attempt to optimize the use of bandwidth resources on a per-link basis with different allocation and resource sharing characteristics. As such, the adoption of distinct BAMs and/or changes in network resource demands (network traffic profile may result in different network traffic allocation and operational behavior for distinct BAMs. This paper evaluates the resulting network characteristics (li nk utilization, preemption and flows blocking of using BAMs dynamically with different traffic scenarios. In brief, it is investigated the dynamics of BAM switching with distinct traffic scenarios. The paper presents initially the investigated BAMs in relation to their behavior and resource allocation characteristics. Then, distinct BAMs are compared using different traffic scenarios in order to investigate the impact of a dynamic change of the BAM configured in the network. Finally, the paper shows that the adoption of a dynamic BAM allocation strategy may result in benefits for network operation in terms of link utilization, preemption and flows blocking.

Rafael F. Reale

2014-06-01

170

Effective Distribution of High Bandwidth to the Last Mile.  

Science.gov (United States)

Since the mid 1990s, Internet is revolutionizing the way business is conducted around the globe. Bandwidth- intensive graphics, video and audio applications are becoming more popular and the desire for fast access to information places a huge demand on hi...

D. V. Kwok

2003-01-01

171

High speed and wide bandwidth delta-sigma ADCs  

CERN Document Server

This book describes techniques for realizing wide bandwidth (125MHz) over-sampled analog-to-digital converters (ADCs) in nanometer-CMOS processes.  The authors offer a clear and complete picture of system level challenges and practical design solutions in high-speed Delta-Sigma modulators.  Readers will be enabled to implement ADCs as continuous-time delta-sigma (CT??) modulators, offering simple resistive inputs, which do not require the use of power-hungry input buffers, as well as offering inherent anti-aliasing, which simplifies system integration. The authors focus on the design of high speed and wide-bandwidth ??Ms that make a step in bandwidth range which was previously only possible with Nyquist converters. More specifically, this book describes the stability, power efficiency, and linearity limits of ??Ms, aiming at a GHz sampling frequency.   • Provides overview of trends in Wide Bandwidth and High Dynamic Range analog-to-digital converters (ADCs); • Enables the design of a wide band...

Bolatkale, Muhammed; Makinwa, Kofi A A

2014-01-01

172

Bandwidth enhancement of inner shorted annular microstrip antennas  

Directory of Open Access Journals (Sweden)

Full Text Available An inner shorted annular microstrip antenna was designed using Bessel function relations and then two techniques of bandwidth enhancement has been suggested and designed and the current distribution and the radiation field with the frequency and the feed point location has been studied.

Abdulkareem Abd Ali Mohammed

2009-10-01

173

Integrated Short Range, Low Bandwidth, Wearable Communications Networking Technologies.  

Science.gov (United States)

This report provides a summary of research and development (R&D) activity and accomplishments, with respect to the development of SPARNET, for U.S. Army contract number W911QY-11-C-0012 - Integrated Short Range, Low Bandwidth, Wearable Communications Netw...

D. Barnett

2012-01-01

174

Small signal microwave amplifier design  

CERN Document Server

This book explains techniques and examples for designing stable amplifiers for high-frequency applications in which the signal is small and the amplifier circuit is linear. An in-depth discussion of linear network theory provides the foundation needed to develop actual designs. Examples throughout the book will show you how to apply the knowledge gained in each chapter leading to the complex design of low noise amplifiers. Many exercises at the end of each chapter will help students to practice their skills. The solutions to these design problems are available in an accompanying solutions book

Grosch, Theodore

2000-01-01

175

On Free-Electron Laser Growing Modes and their Bandwidth  

CERN Document Server

Free-electron lasers play an increasing role in science, from generating unique femtosecond X- ray pulses for single short recording of the protein structures to amplifying feeble interactions in advanced cooling systems for high-energy hadron colliders. While modern Free-electron laser codes can describe their amplification mechanism, a deep analytical understanding of the mechanism is of extreme importance for a number of applications. Mode competition, their growth rates and amplification bandwidth are among the most important parameters of a free-electron laser. A dispersion relation, which defines these important characteristics, can be solved analytically only for a very few simple cases. In this letter we show that for a typical bell-shape energy distribution in electron beam there is no more that one growing mode. We also derive an analytical expression which determines the bandwidth of the free-electron laser.

Webb, Stephen; Litvinenko, Vladimir

2011-01-01

176

Plasma density profiles and finite bandwidth effects on electron heating  

International Nuclear Information System (INIS)

Intense, p-polarized microwaves are incident on an inhomogeneous plasma in a cylindrical waveguide. Microwaves are mainly absorbed by resonant absorption near the critical surface (where the plasma frequency, ?/sub pe/, equals the microwave frequency, ?/sub o/). The localized plasma waves strongly modify the plasma density. Step-plateau density profiles or a cavity are created depending on the plasma flow speed. Hot electron production is strongly affected by the microwave bandwidth. The hot electron temperature varies as T/sub H/ is proportional to (? ?/?)-025. As the hot electron temperature decreases with increasing driver bandwidth, the hot electron density increases. This increase is such that the heat flux into the overdense region (Q is proportional to eta/sub H/T/sub H/32) is nearly constant

1980-04-15

177

Long-pulse-width narrow-bandwidth solid state laser  

Science.gov (United States)

A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications.

Dane, C. Brent (Livermore, CA); Hackel, Lloyd A. (Livermore, CA)

1997-01-01

178

BANDWIDTH ENHANCEMENT USING PARASITIC PATCH FOR KU BAND  

Directory of Open Access Journals (Sweden)

Full Text Available - A design of microstrip patch antenna with prime focused of increasing bandwidth using various techniques of probe feed, parasitic patch around the main patch and two layer of substrate. The simulation process has been done using HFSS (High frequency Structural Simulator. In this paper, authors cover six aspect of microstrip antenna designs. The first is analysis of single element narrowband rectangular microstrip antenna which operates at central frequency of 14.3 GHz. The second/third aspect is design of two gap/direct coupled patch along main patch. The fourth/fifth aspect is analysis and design of four gap/direct coupled parasitic patch along main patch and in sixth aspect is analysis and design of two layer of substrate in parasitic patch design. The properties of antenna such as bandwidth, S parameter, VSWR, Gain has been investigated and compared

Kalpesh B. Barad

2014-04-01

179

A Contemporary Methodology for Bandwidth Reservation in Wireless Cellular Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The emerging technologies in wireless communication under the next generation have pulled many scientists and researchers towards them. The wireless cellular network, which is a widely used technology, has various issues regarding Quality of Service (QoS. The major issues that ever attract people are resource reservation, call admission control mechanisms and user mobility patterns. In this paper, various resource reservation schemes with their unique features are discussed and compared. One of the best-suited schemes would be the Tier- Based Bandwidth Reservation Scheme with better resource utilization. The simulation results have shown the better resource utilization and conservation when compared to one of the traditional schemes. The enhancement with the bandwidth borrowing concept is also simulated and the results are compared.

Malathi Balaji

2013-04-01

180

A wide-bandwidth and high-sensitivity robust microgyroscope  

International Nuclear Information System (INIS)

This paper reports a microgyroscope design concept with the help of a 2 degrees of freedom (DoF) sense mode to achieve a wide bandwidth without sacrificing mechanical and electronic sensitivity and to obtain robust operation against variations under ambient conditions. The design concept is demonstrated with a tuning fork microgyroscope fabricated with an in-house silicon-on-glass micromachining process. When the fabricated gyroscope is operated with a relatively wide bandwidth of 1 kHz, measurements show a relatively high raw mechanical sensitivity of 131 µV (° s?1)?1. The variation in the amplified mechanical sensitivity (scale factor) of the gyroscope is measured to be less than 0.38% for large ambient pressure variations such as from 40 to 500 mTorr. The bias instability and angle random walk of the gyroscope are measured to be 131° h?1 and 1.15° h?1/2, respectively

2009-07-01

 
 
 
 
181

Bandwidth and power efficient satellite TDMA demodulator and decoder  

Science.gov (United States)

A proof-of-concept demodulator for TDMA applications requiring high total data rates composed of many low data rate users is proposed. High-spectrum efficiency is obtained via a bandwidth efficient combined modulation and coding system, and low TDMA overhead is obtained via a fast acquiring digital phase lock loop. The system employs a data rate of 200 Mb/s with a bit error rate of better than 5 x 10 to the -7th in the presence of adjacent channel interference 20 dB above the weakest user. The 8-PSK modulation combined with the rate 5/6 forward error correction coding results in a bandwidth efficiency of better than 2 bits/second per Hz.

Ames, Stephen A.; Monte, Paul A.; Hoeber, Christopher F.; Chethik, Frank

1988-01-01

182

IconoNET: a tool for automated bandwidth allocation planning  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Communication networks are expected to offer a wide range of services to an increasingly large number of users, with a diverse range of quality of service. This calls for efficient control and management of these networks. In this paper, we address the problem of quality-of-service routing, more specifically the planning of bandwidth allocation to communication demands. Shortest path routing is the traditional technique applied to this problem. However, this can lead to poor network utilizati...

Frei, C.; Faltings, B.; Melissargos, G.; Pu, P.

2000-01-01

183

Recursive Structure and Bandwidth of Hales-Numbered Hypercube  

CERN Document Server

The Hales numbered $n$-dimensional hypercube and the corresponding adjacency matrix exhibit interesting recursive structures in $n$. These structures lead to a very simple proof of the well-known bandwidth formula for hypercube, whose proof was thought to be surprisingly difficult. A related problem called hypercube antibandwidth, for which Harper proposed an algorithm, is also reexamined in the light of the above recursive structures, and a close form solution is found.

Wang, Xiaohan

2007-01-01

184

Dynamic Bandwidth Provisioning and Malleable Bulk Data Transfer Scheduling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To address the anticipated sporadic terabyte demands generated by high-end time-constrained applications, dynamically reconfigurable optical networks services are envisioned. However, the time and rate granularities of a bandwidth reservation service and those of transfer tasks using the reserved capacity is not necessarly in the same order of magnitude. This may lead to poor resource utilisation and overprovisionning. Transfer request aggregation is able to limit this problem. This paper exp...

2008-01-01

185

Coherent temporal imaging with analog time-bandwidth compression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We introduce the concept of coherent temporal imaging and its combination with the anamorphic stretch transform. The new system can measure both temporal profile of fast waveforms as well as their spectrum in real time and at high-throughput. We show that the combination of coherent detection and warped time-frequency mapping also performs time-bandwidth compression. By reducing the temporal width without sacrificing spectral resolution, it addresses the Big Data problem in ...

Asghari, Mohammad H.; Jalali, Bahram

2013-01-01

186

Transverse flow imaging based on photoacoustic Doppler bandwidth broadening  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a new method to measure transverse flow velocity based on photoacoustic Doppler bandwidth broadening, which is determined by the geometry of the probe-beam and the velocity of the transverse flow. By exploiting pulsed laser excitation and raster motor scanning, three-dimensional structure and flow velocity can be imaged simultaneously. In addition, the flow direction can be determined with bidirectional scanning. In a flowing suspension of red-dyed microspheres (diameter: 6 ?m), t...

Yao, Junjie; Wang, Lihong V.

2010-01-01

187

Effect of Time Bandwidth Product on Cooperative Communication  

Directory of Open Access Journals (Sweden)

Full Text Available Cognitive radios are proposed to be the technique that will ameliorate the problem of spectrum deficiency by using the underutilized radio frequency spectrum opportunistically on non-interfering basis. In this paper, we have analyzed the effect of time bandwidth product in spectrum sensing in AWGN (non fading and Rayleigh fading environment under cooperative environment. For decision statics hard combining rule (k out of n is considered. Simulation results are also given to confirm the analytical results.

Surendra Kumar Singh

2013-03-01

188

Precedence Based Preemption and Bandwidth Reservation Scheme in MANET  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Infrastructures less mobile networks are commonly known as Mobile Ad Hoc Networks (MANET). Quality of Service (QOS) constraints is highly required for multimedia communications with MANET. Providing QOS in MANET is not easy task due to its broadcast and dynamic nature. There are some number of protocols exist which takes care for the QOS. Some of them are Diffserv, Intserv, AQR etc. All have some limitations. This paper propose a protocol Preemption And Bandwidth Reservation Scheme (PBRS) whi...

Sourabh Singh Verma

2012-01-01

189

Exponential Frequency Modulation Bandwidth Criterion for Virtual Analog Applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cross modulation or Exponential FM is a sound synthesis technique associated with modular analog subtractive synthesizers. It differs from the more well-known linear FM synthesis technique in that the modulation is an exponential function of the control voltage. Its spectrum shape is more complex, thus giving it a larger bandwidth with respect to the modulation depth. Thus, the prevention of aliasing distortion requires different conditions than Carson’s rule as used with linear FM. A suita...

2011-01-01

190

Bullet: high bandwidth data dissemination using an overlay mesh  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In recent years, overlay networks have become an effective alternative to IP multicast for efficient point to multipoint communication across the Internet. Typically, nodes self-organize with the goal of forming an efficient overlay tree, one that meets performance targets without placing undue burden on the underlying network. In this paper, we target high-bandwidth data distribution from a single source to a large number of receivers. Applications include large-file transfers and real-time ...

Kostic, D.; Rodriguez, A.; Albrecht, J.; Vahdat, A.

2003-01-01

191

Bandwidth Extension Method Based on Spectral Envelope Estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In current communication system, high quality audio signal is supposed to be provided with low bit rate and low computational complexity. This paper proposed a novel audio coding bandwidth extension method, which can improve decoded audio quality with increasing only a few coding bits per frame and a little computational complexity. This method calculate high-frequency synthesis filter by using codebook mapping method, and transmit only quantified gain corrections in high-frequency part of mu...

Bo Hang; Ruimin Hu; Shi Dong; Ye Ma

2011-01-01

192

Two New Six-Port Reflectometers Covering Very Large Bandwidths  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents two new structures for six-port reflectometers with very large operating bandwidths of more than three decades, using a combination of lumped reflectors and transmission lines. Circuits working over a range of 2 MHz to 1300 MHz and 2 MHz to 2200 MHz have been built using inexpensive passive surface mount elements and Schottky detector diodes. Comparing results obtained from the new proposed structures with those obtained from a commercial network analyzer showed a worst ca...

Hesselbarth, Jan; Wiedmann, Frank; Huyart, Bernard

1997-01-01

193

Modifying the double smoothing bandwidth selector in nonparametric regression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper a modified double smoothing bandwidth selector, ^h MDS , based on a new criterion, which combines the plug-in and the double smoothing ideas, is proposed. A self-complete iterative double smoothing rule ( ^ h IDS ) is introduced as a pilot method. The asymptotic properties of both ^ h IDS and ^ h MDS are investigated. It is shown that ^ h MDS performs asymptotically very well. Moreover, it is asymptotically negatively correlated with h ASE , the minimizer of ...

Beran, Jan; Feng, Yuanhua; Heiler, Siegfried

2000-01-01

194

Managing high-bandwidth real-time data storage  

Energy Technology Data Exchange (ETDEWEB)

There exist certain systems which generate real-time data at high bandwidth, but do not necessarily require the long-term retention of that data in normal conditions. In some cases, the data may not actually be useful, and in others, there may be too much data to permanently retain in long-term storage whether it is useful or not. However, certain portions of the data may be identified as being vitally important from time to time, and must therefore be retained for further analysis or permanent storage without interrupting the ongoing collection of new data. We have developed a system, Mahanaxar, intended to address this problem. It provides quality of service guarantees for incoming real-time data streams and simultaneous access to already-recorded data on a best-effort basis utilizing any spare bandwidth. It has built in mechanisms for reliability and indexing, can scale upwards to meet increasing bandwidth requirements, and handles both small and large data elements equally well. We will show that a prototype version of this system provides better performance than a flat file (traditional filesystem) based version, particularly with regard to quality of service guarantees and hard real-time requirements.

Bigelow, David Db [Los Alamos National Laboratory; Brandt, Scott A [Los Alamos National Laboratory; Bent, John M [Los Alamos National Laboratory; Chen, Hsing - Bung [Los Alamos National Laboratory

2009-01-01

195

Rahul Fixed Priority Enhance Classes Bandwidth Exploitation in TDM EPON  

Directory of Open Access Journals (Sweden)

Full Text Available A Passive Optical Network (PON is a single, collective optical fiber that used low-cost optical splitters to divide the single fiber into split strands feed individual subscribers. PONS are called passive because, other than at the CO (Central Office and subscriber endpoints, there are no active electronics inside the access network. With the development of services offered by the Internet, the "last mile" restricted access problems keep it up to increase step by step. Many algorithms were developed for making TDM EPON efficient similar to Scheduling (No class Solution and Priority Swapping, IPACT etr. These all algorithms have problems like delay, QoS and channel under- utilization. We focused the well-organized bandwidth utilization in TDM EPON by managing time slots within ONUs and reducing latency and increasing quality of service. Our Rahul Fixed Priority Enhance Classes Bandwidth (RFPECB algorithm is an intra-ONU bandwidth allocation algorithm, which is used to enhance the network performance by evaluating the parameters like channel underutilization, delay and Quality of Service. The issues which are lacking in the already made algorithms are being resolved with our RFPECB Algorithm. The main problem time slots management issue solved in RFPECB algorithm.

Muhammad Bilal

2011-09-01

196

Fixed Advance Priority based Bandwidth Utilization in TDM EPON  

Directory of Open Access Journals (Sweden)

Full Text Available PON technology can be used to avoid the placement of electronics in the field by using passive optical filters (splitters to distribute optical circuits to individual customers. They reduced the amount of fiber and local exchange and field equipment. With the development of services offered by the Internet, the last mile bottleneck problems persist to increase step by step. Many algorithms were developed for making TDM EPON efficient similar to Scheduling, Priority swapping etc. These all algorithms have problems like starvation, QoS, latency and channel under- utilization. We focused the efficient bandwidth utilization in TDM EPON by managing time slots within ONUs and reducing latency and increasing quality of service. Our Fixed Advance Priority based Bandwidth Algorithm is an intra-ONU bandwidth allocation algorithm, which is used to enhance the network performance by evaluating the parameters like channel underutilization, delay and Quality of Service. The issues which are lacking in the already made algorithms are being resolved with our proposed solution. The main problem time slots management issue solved in FAPB algorithm.

Muhammad Bilal

2011-05-01

197

Bandwidth Enhancement and Radiation Properties of Slotted Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available The design of low-cost, wideband, printed inverted-F antennas (PIFAs that are suitable for portable devices operating at the 2–3 GHz band is described. The design specifications were extracted according to the constraints of high data rate wireless sensor devices. Reactive tuning through slot loading was applied to enforce degeneration of a higher resonance, and thus double the bandwidth in the band of interest. Three slotted antenna configurations are reported plus a baseline configuration; a thorough numerical characterisation of performance is provided. Fractional bandwidth (FBW in the range 22–34% was achieved, which is almost quadruple that of existing implementations. The antennas exhibit total efficiencies around 80% and are elliptically polarised. A suitable figure-of-merit is suggested for performance comparisons; it attempts to capture overall antenna performance in a single quantity. Antenna performance depends heavily on electrical size, which depends on the size of the ground plane, since the RF ground is an integral part of the total radiator. The ground-effect study showed that wrong choice of size can force resonant modes to vanish. Best performance for a slotted PIFA was obtained with a ground plane measuring 0.20l _ 0.28l, significantly smaller than predicted in prior studies. Bandwidth augmentation through slot loading is supported by measurements. Fabricated antennas with sub-optimal ground plane sizes exhibit FBWs in the range 20–23%

Deenanath Sahu,

2013-04-01

198

High-bandwidth polarimeter for a high density, accelerated spheromak  

Energy Technology Data Exchange (ETDEWEB)

A three-beam heterodyne polarimeter has been built to diagnose the PI-1 plasma injector at General Fusion, Inc. The polarimeter measures plasma density and Faraday rotation, which can provide estimates of magnetic field magnitude and direction. Two important calibration steps are required for the polarimeter to produce reasonable Faraday rotation signals. Beam polarization ellipticity must be measured to ensure there is a linear Faraday rotation response. In addition, the two beams travelling through the plasma must be collinear to reduce error due to differences in plasma density. Once calibrated, the Faraday rotation signals are in much better agreement with other diagnostics. For a null signal, the Faraday rotation measurement noise floor is 0.1° at 0.5 MHz bandwidth. Comparing preliminary spheromak Faraday rotation measurements to a model, the maximum error is about 0.3° at 0.5 MHz bandwidth, which is primarily due to electrical noise during the injector's capacitor discharge and limitations of the model. At a bandwidth of 0.5 MHz, the polarimeter has an axial resolution between 6 cm and 30 cm depending on the speed of the spheromak, which varies between 30 km/s and 150 km/s. The spheromak length ranges from 0.75 m to 2 m. Additional polarimeter chords will be added in future upgrades.

Carle, Patrick J. F.; Morelli, Jordan [Department of Physics, Queen' s University, 99 University Ave., Kingston, Ontario K7L 3N6 (Canada); Howard, Stephen [General Fusion, Inc., 108-3680 Bonneville Pl, Burnaby, British Columbia V3N 4T5 (Canada)

2013-08-15

199

High-bandwidth remote flat panel display interconnect system  

Science.gov (United States)

High performance electronic displays (CRT, AMLCD, TFEL, plasma, etc.) require wide bandwidth electrical drive signals to produce the desired display images. When the image generation and/or image processing circuitry is located within the same line replaceable unit (LRU) as the display media, the transmission of the display drive signals to the display media presents no unusual design problems. However, many aircraft cockpits are severely constrained for available space behind the instrument panel. This often forces the system designer to specify that only the display media and its immediate support circuitry are to be mounted in the instrument panel. A wide bandwidth interconnect system is then required to transfer image data from the display generation circuitry to the display unit. Image data transfer rates of nearly 1.5 Gbits/second may be required when displaying full motion video at a 60 Hz field rate. In addition to wide bandwidth, this interconnect system must exhibit several additional key characteristics: (1) Lossless transmission of image data; (2) High reliability and high integrity; (3) Ease of installation and field maintenance; (4) High immunity to HIRF and electrical noise; (5) Low EMI emissions; (6) Long term supportability; and (7) Low acquisition and maintenance cost. Rockwell Collins has developed an avionics grade remote display interconnect system based on the American National Standards Institute Fibre Channel standard which meets these requirements. Readily available low cost commercial off the shelf (COTS) components are utilized, and qualification tests have confirmed system performance.

Peterson, Darrel G.

1999-08-01

200

An Efficient Bandwidth Estimation Schemes used in Wireless Mesh Networks  

Directory of Open Access Journals (Sweden)

Full Text Available wireless mesh networks (WMNs has been widely used for the new generation wireless network. The capability of self-organization in WMNs reduces the complexity of wireless network deployment and maintenance. So, the perfect estimation of the bandwidth available of the mesh nodes is the required to admission control mechanism which provides QOs confirmation in wireless mesh networks. The bandwidth estimation of schemes do not give clear output. Here we are proposing bandwidth scheme estimation for decreasing the parallel transmission will cause the accurate and it will solve the maximum clique problem in the theory of graph. The hop by hop routing protocol is integrated by the admission control mechanism. Finally the implementation phase was simulated by the mechanism based on BEPTC will effectively control the traffic load and offer QoS guarantee for admitted new flows all these lead the network to accommodate more flows with QOS guarantee and obtain higher system throughput make difference with other conservative approaches.

A.Sandeep Kumar ,Second Author

2012-08-01

 
 
 
 
201

Large-bandwidth data acquisition network for XFEL facility, SACLA  

International Nuclear Information System (INIS)

The SACLA (SPring-8 Angstrom Compact Free Electron Laser) facility consists of an accelerator building, an undulator building and an experimental facility. SACLA is designed to produce X-ray with a wavelength as short as 0.06 nm and with a repetition rate of 60 Hz. X-ray Free-Electron Laser (XFEL) experiments demands large bandwidth network for data acquisition (DAQ). At SACLA the experimental data rate is to be up to 5.8 Giga bit per second (Gbps). Some of the experiments demands preprocessing and on-line analysis by high-performance computers. In order to fulfill these requirements, a dedicated network system for DAQ and data analysis has been developed. A DAQ network consists of a dedicated 10 Gbps Ethernet (10 GbE) physical layer to secure the data bandwidth and a 1 GbE layer for instrument controls. The DAQ network is connected to a primary storage and indirectly to a PC cluster for data preprocessing. A fire-wall system with virtual private network (VPN) features is also implemented in order to secure remote access from off-site institutes. The use of a large-bandwidth data transfer technique allows the efficient transfer of pre-processed data from SACLA to an off-site supercomputer

2011-10-10

202

Improved Radiation and Bandwidth of Triangular and Star Patch Antenna  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents a hexagonal shape Defected Ground Structure (DGS implemented on two element triangular patch microstrip antenna array. The radiation performance of the antenna is characterized by varying the geometry and dimension of the DGS and also by locating the DGS at specific position which were simulated. Simulation and measurement results have verified that the antenna with DGS had improved the antenna without DGS. Measurement results of the hexagonal DGS have axial ratio bandwidth enhancement of 10 MHz, return loss improvement of 35%, mutual coupling reduction of 3 dB and gain enhancement of 1 dB. A new wideband and small size star shaped patch antenna fed capacitively by a small diamond shape patch is proposed. To enhance the impedance bandwidth, posts are incorporated under the patch antenna. HFSS high frequency simulator is employed to analyze the proposed antenna and simulated results on the return loss, the E- and H-plane radiation patterns and Gain of the proposed antenna are presented at various frequencies. The antenna is able to achieve in the range of 4-8.8 GHz an impedance bandwidth of 81% for return loss of less than-10 dB.

M. Ramkumar Prabhu

2012-06-01

203

Dynamic bandwidth allocation algorithms in EPON: a simulation study  

Science.gov (United States)

In this paper we present a dynamic bandwidth allocation algorithm for EPON, which makes use of the Multipoint Control Protocol (MPCP) with threshold reporting and with inter- and intra-ONU priority scheduling. Three varieties of this algorithm are compared, by means of a detailed simulation program, regarding average packet delay for several priorities, delay variation for constant bit rate (CBR) traffic and bandwidth utilization. We show that by introducing a specific intra-ONU priority scheduling algorithm, which takes the reported values into account, the bandwidth can be fully utilized. However, this scheduling algorithm causes an increased packet delay and delay variation for CBR traffic. In order to eliminate this drawback, we combine this scheduling algorithm with a rate-based scheme for the highest priority (CBR) traffic. This combined algorithm provides an interesting tradeoff between the efficiency, which is still near to the optimal, and the delay characteristics of time critical applications. Finally, we also include a comparison with a standard intra-ONU priority scheme.

Nikolova, Dessislava; Van Houdt, Benny; Blondia, Chris L.

2003-10-01

204

Influence of small oxygen additions on the small-signal-gain dynamics in the active medium of a pulsed electron-beam-controlled discharge CO laser  

International Nuclear Information System (INIS)

The method for measuring the rate constants of the VV' exchange between CO and O2 molecules is developed. The method is based on a comparison of the measured and numerically calculated small-signal-gain (SSG) dynamics in the active medium of a pulsed electron-beam-controlled cryogenic CO laser. The SSG dynamics was measured in CO-He-O2 mixtures with the fixed CO:He = 1:4 ratio by varying the oxygen content from 0 to 4%. The SSG dynamics was measured by probing the active medium of the pulsed CO laser by a beam from a tunable cw CO laser. The mathematical model of the CO laser takes into account the influence of oxygen on energy exchange processes. The parameters of the analytic approximation for constants of the near-resonance VV' exchange CO(v)+O2(u=0) ? CO(v-1)+O2(u=1) are determined by the developed method for quantum vibrational numbers v = 18-24. In particular, the rate constant for v = 20 is (3.1±0.5)x10-12 cm3 s-1 at the gas temperature of 150 K. The extrapolation of the obtained analytic expression for rate constants in gases at room temperature gives the reasonable agreement with the measurements performed earlier for v = 12 and 13. (active media. lasers)

2008-09-30

205

Fluorescence and small-signal gain at 2177 and 2163 Angstrom in CIII by resonant photoexcitation with 310 Angstrom MnVI line radiation  

International Nuclear Information System (INIS)

Line radiation at 310 Angstrom from a laser-produced Mn plasma was used to resonantly photoexcite the 2s 1s - 4p 1p0 transition in CIII ions in a vacuum-arc discharge. Enhanced fluorescence, up to a factor of 180, was observed on the 4p-3d line at 2177 Angstrom. Enhanced fluorescence was also observed on other 4-3 lines in CIII, because the photoexcited 4p population is collisionally redistributed among all the n = 4 levels. A 72-level, collisional-radiative model of CIII was constructed, including the resonant photoexcitation. Measured values of electron density and temperature were used in the model. Theoretical predictions of enhanced fluorescence agree well with the measurements. Small-signal gain coefficients of ? 0.1 cm-1 were theoretically predicted. Single-pass gain measurements show gains as high as 0.4 cm-1 on the 4p-3d, 2177 Angstrom line and the 4f-3d, 2163 Angstrom line. This CIII-MnVI photoexcitation scheme is a prototype for soft x-ray lasers, using higher Z, isoelectronic analogs

1986-10-01

206

Bandwidth shaping of microresonator-based frequency combs via dispersion engineering.  

Science.gov (United States)

We investigate experimentally and theoretically the role of group-velocity dispersion and higher-order dispersion on the bandwidth of microresonator-based parametric frequency combs. We show that the comb bandwidth and the power contained in the comb can be tailored for a particular application. Additionally, our results demonstrate that fourth-order dispersion plays a critical role in determining the spectral bandwidth for comb bandwidths on the order of an octave. PMID:24978530

Okawachi, Yoshitomo; Lamont, Michael R E; Luke, Kevin; Carvalho, Daniel O; Yu, Mengjie; Lipson, Michal; Gaeta, Alexander L

2014-06-15

207

Influence of launch-beam distribution on bandwidth in step-index plastic optical fibers.  

Science.gov (United States)

The power-flow equation is employed to calculate bandwidth of step-index plastic optical fibers (POFs) for different launch conditions. The outcome specifies bandwidth as a function of the mean input angle and width of the launch-beam distribution. For small distribution widths, bandwidth is shown to decrease with increasing mean input angle of the launch-beam distribution. For large distribution widths, bandwidth becomes independent of the launch angle. Launch-beam distribution, mode-dependent attenuation, and mode dispersion and coupling in POFs strongly influence the bandwidth of data transmission systems. PMID:23434979

Savovi?, Svetislav; Drlja?a, Branko; Djordjevich, Alexandar

2013-02-20

208

Spacer Optimization and Accurate Small-Signal Modeling of 90nm Gate Underlap SOI-MOSFETs for Low Power GHz Applications  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the significance of gate-source/drain extension region (also known as underlap design optimization in 90nm single gate (SG Silicon-on-Insulator (SOI MOSFET for low power GHz frequency applications. Using an optimal spacer s (? 0.8×LG, where LG is gate length, it has been found that the device exhibits intrinsic gain of ? 25 dB in low-moderate inversion region (VOD =VGS – VTH ? 90 mV, where VOD, VGS and VTH are the overdrive, gate and threshold voltages, respectively at operating frequency of 20 GHz. An accurate (including non-quasi-static and extrinsic parasitics effects small-signal model for the optimized device has been presented. The comparison of Y-parameters of 2D ATLAS with overall modeled value (up to 20 GHz has shown an excellent matching (with an average error of ?5%, whereas results from quasi-static (QS predictive technology model (PTM differ significantly (>20%. Optimized underlap device shows transit frequency fT and maximum frequency of oscillation fMAX, ~108 and ~130 GHz respectively, with noise figure (NF ~2.8 dB and exhibits unilateral power gain (ULG ~38 dB (VOD =90mV, drain-to-source current IDS ? 0.64mA and drain-to-source voltage VDS = 1V at 20 GHz. Comparison with limited measured data suggest that simulated results are in well conformity, which suggest the possibility of use of underlap device technology in the design of key blocks such as low noise amplifier LNA and mixer for GHz applications. Key Words: Gate Underlap, silicon-on-Insulator, Non-Quasi-Static, Transconductance-to-Net-Charge Ratio (TCR, Low Power.

Indra Vijay Singh

2013-02-01

209

Optimizing bandwidth utilization in packet based telemetry systems  

Energy Technology Data Exchange (ETDEWEB)

A consistent theme in spacecraft telemetry system design is the desire to obtain maximum bandwidth utilization given a fixed transmission capability (usually due to cost/weight criteria). Extensions to basic packetization telemetry architectures are discussed which can facilitate a reduction in the amount of actual data telemetered, without loss of data quality. Central to the extensions are the establishment of an ``intelligent`` telemetry process, which can evaluate pending data to be telemetered, and act to compress, discard, or re-formulate data before actual transmission to ground stations.

Kalibjian, J.R.

1995-10-17

210

The Power of Prediction: Cloud Bandwidth and Cost Reduction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we present PACK (Predictive ACKs), a novel end-to-end Traffic Redundancy Elimination (TRE) system, designed for cloud computing customers. Cloud-based TRE needs to apply a judicious use of cloud resources so that the bandwidth cost reduction combined with the additional cost of TRE computation and storage would be optimized. PACK's main advantage is its capability of offloading the cloud-server TRE effort to end-clients, thus minimizing the processing costs induced by the T...

Zohar, Eyal; Cidon, Israel; Mokryn, Osnat

2011-01-01

211

V-305 high-bandwidth analog airborne recorder/reproducer  

Science.gov (United States)

The V-305 High-Bandwidth Analog Airborne Recorder/Reproducer has been specifically developed to satisfy the airborne image recording requirements for various applications including high-resolution airborne reconnaissance, search and rescue operations, and surveillance. In addition, the V-305 has the flexibility to record many other types of signals such as those encountered in E-W, ELINT, and radar applications. As part of this new product's ongoing development and evaluation, NACOUS has recently performed airborne recording of infrared imagery from an AN/AAD-5 RC Infrared Linescanner. This paper describes the V-305 and the in-flight image recording results.

Ludeke, Peter J.

1993-02-01

212

Iterative Available Bandwidth Estimation for Mobile Transport Networks  

DEFF Research Database (Denmark)

Available bandwidth estimation has lately been proposed to be used for end-to-end resource management in existing and emerging mobile communication systems, whose transport networks could end up being the bottleneck rather than the air interface. Algorithms for admission control, handover and adaptive QoS management could take into account such estimations, which may lead to an overall system performance improvement. This paper introduces two new iterative algorithms (Zoom and Adaptive pathChirp) for network load monitoring that can be combined with a linear least squares fitting achieving reliable estimations without causing congestion collapse. Their performance is evaluated in a simulated UTRAN Long Term Evolution backhaul.

Ubeda Castellanos, Carlos; López Villa, Dimas

2007-01-01

213

Low Bandwidth Vocoding using EM Sensor and Acoustic Signal Processing  

Energy Technology Data Exchange (ETDEWEB)

Low-power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference [1]. By combining these data with the corresponding acoustic signal, we've demonstrated an almost 10-fold bandwidth reduction in speech compression, compared to a standard 2.4 kbps LPC10 protocol used in the STU-III (Secure Terminal Unit, third generation) telephone. This paper describes a potential EM sensor/acoustic based vocoder implementation.

Ng, L C; Holzrichter, J F; Larson, P E

2001-10-25

214

Bandwidth Extension Method Based on Spectral Envelope Estimation  

Directory of Open Access Journals (Sweden)

Full Text Available In current communication system, high quality audio signal is supposed to be provided with low bit rate and low computational complexity. This paper proposed a novel audio coding bandwidth extension method, which can improve decoded audio quality with increasing only a few coding bits per frame and a little computational complexity. This method calculate high-frequency synthesis filter by using codebook mapping method, and transmit only quantified gain corrections in high-frequency part of multiplexing coding bit stream. The preliminary test show that this method can provide comparable audio quality with lower bit consumption and computational complexity compared to the high frequency regeneration of AMR-WB+.

Ye Ma

2011-06-01

215

Bandwidth optimization of individual hop for robust data streaming on emergency medical application  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new bandwidth estimation method for individual hop for high-speed, non-invasive, and faster convergence transmission in multiple medical data networks. Available Bandwidth Estimation Technique for individual Hops (ABETH has been developed employing parameters like Hop (H, Capacity (C, Bandwidth (B, Available Bandwidth (AB etc. Bandwidth estimation techniques, tools and methods are considered to develop the technique and it represents an effective combination of different other existing techniques aiming to exploit the positive aspects of them. More precisely, the technique which is implied in the method modifies and integrates the one recent tool SPRUCE which estimates available bandwidth and the IP layer capacity estimation formula which measures capacity. This technique provides a linear combination of capacity versus bandwidth which satisfies the link utilization demand.

A. K. M. Fazlul Haque

2009-10-01

216

Inherent RF linearized bandwidth broadening capability of an ultra-linear optical modulator  

Science.gov (United States)

Almost all existing resonator-based linearized optical modulators suffer from an inherent RF bandwidth narrowing that limit their applications and performance. Here, we show an ultra-linear optical modulator, called IMPACC, (Interferometric Modulator with Phase-modulating And Cavity-modulating Components) that has three unique RF bandwidth characteristics, which are not present in other resonator-based linearized optical modulators. We demonstrate these unique characteristics by contrasting IMPACC's performance to the Resonator-Assisted Mach Zehnder Interferometer (RAMZI) modulator. First, IMPACC can enhance its linearized RF bandwidth up to ~ 20% of central RF frequency (compared to ~1% for RAMZI). Second, unlike RAMZI, the RF bandwidth enhancement has a near-flat response characteristic across this bandwidth window. Third, IMPACC can maintain an excellent spurious free dynamic range (SFDR) capability (>130 dB at 1Hz bandwidth) across this window. The wide linear bandwidth capability is also demonstrated for modulation frequencies up to 75GHz.

Dingel, Benjamin B.; Prescod, Andru; Madamopoulos, Nicholas

2011-01-01

217

The Effect of Pulse Shaping QPSK on Bandwidth Efficiency  

Science.gov (United States)

This research investigates the effect of pulse shaping QPSK on bandwidth efficiency over a non-linear channel. This investigation will include software simulations and the hardware implementation. Three kinds of filters: the 5th order Butterworth filter, the 3rd order Bessel filter and the Square Root Raised Cosine filter with a roll off factor (alpha) of 0.25,0.5 and 1, have been investigated as pulse shaping filters. Two different high power amplifiers, one a Traveling Wave Tube Amplifier (TWTA) and the other a Solid State Power Amplifier (SSPA) have been investigated in the hardware implementation. A significant improvement in the bandwidth utilization (rho) for the filtered data compared to unfiltered data through the non-linear channel is shown in the results. This method promises strong performance gains in a bandlimited channel when compared to unfiltered systems. This work was conducted at NMSU in the Center for Space Telemetering, and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering Department and is supported by a grant from the National Aeronautics and Space Administration (NASA) NAG5-1491.

Purba, Josua Bisuk Mubyarto; Horan, Shelia

1997-01-01

218

Series-fed circularly polarized microstrip antennas with broad bandwidth  

Science.gov (United States)

A new series-fed circularly polarized antenna (SFCPA) in microstrip configuration, which consists of a traveling-wave-type crank-line antenna (CLA) and a resonant-type square-ring slot antenna (SRSA), is developed. Unlike the conventional crank-line (CL) antenna array with an open end or a resistive load, the proposed SFCPA uses the SRSA at the termination of the CLA and thus exhibits not only a broad circularly polarized (CP) bandwidth but also a large antenna gain. The characteristics of the SFCPA, including the leaky-wave radiation and the circular polarization, are examined in terms of the dispersion diagram and the current distribution. The SFCPA with the two-cell CLA and the terminated SRSA is fabricated and measured to demonstrate the 10-dB return loss and 3-dB axial ratio (AR) bandwidths of 34.3% and 30.5%, respectively. The frequency-scanning radiation patterns with a 5-7 dBi antenna gain are also presented in the operating band.

Mao, Shau-Gang; Chen, Shiou-Li; Yeh, Jen-Chun; Lin, Tien-Min

2007-08-01

219

X-ray FEL with a meV bandwidth  

Science.gov (United States)

A new design for a single pass X-ray Self-Amplified Spontaneous Emission (SASE) FEL was proposed by Feldhaus et al. (Opt. Commun. 140 (1997) 341) and named "two-stage SASE FEL". The scheme consists of two undulators and an X-ray monochromator located between them. For the Angström wavelength range the monochromator can be realized using Bragg reflections from crystals. We propose a scheme of monochromator with a bandwidth of 20 meV for the 14.4 keV X-ray SASE FEL being developed in the framework of the TESLA linear collider project. The spectral bandwidth of the radiation from the two-stage SASE FEL ( 20 meV) is determined by the finite duration of the electron pulse. The shot-to-shot fluctuations of energy spectral density are dramatically reduced in comparison with the 100% fluctuations in a SASE FEL. The peak and average brilliance are three orders of magnitude higher than the values which could be reached by a conventional X-ray SASE FEL.

Saldin, E. L.; Schneidmiller, E. A.; Shvyd'ko, Yu. V.; Yurkov, M. V.

2001-12-01

220

Modulator-Based, High Bandwidth Optical Links for HEP Experiments  

CERN Document Server

As a concern with the reliability, bandwidth and mass of future optical links in LHC experiments, we are investigating CW lasers and light modulators as an alternative to VCSELs. These links will be particularly useful if they utilize light modulators which are very small, low power, high bandwidth, and are very radiation hard. We have constructed a test system with 3 such links, each operating at 10 Gb/s. We present the quality of these links (jitter, rise and fall time, BER) and eye mask margins (10GbE) for 3 different types of modulators: LiNbO3-based, InP-based, and Si-based. We present the results of radiation hardness measurements with up to ~1012 protons/cm2 and ~65 krad total ionizing dose (TID), confirming no single event effects (SEE) at 10 Gb/s with either of the 3 types of modulators. These optical links will be an integral part of intelligent tracking systems at various scales from coupled sensors through intra-module and off detector communication. We have used a Si-based photonic transceiver to...

Underwood, D G; Fernando, W S; Stanek, R W

2012-01-01

 
 
 
 
221

Bandwidth Extension of Telephone Speech Aided by Data Embedding  

Directory of Open Access Journals (Sweden)

Full Text Available A system for bandwidth extension of telephone speech, aided by data embedding, is presented. The proposed system uses the transmitted analog narrowband speech signal as a carrier of the side information needed to carry out the bandwidth extension. The upper band of the wideband speech is reconstructed at the receiving end from two components: a synthetic wideband excitation signal, generated from the narrowband telephone speech and a wideband spectral envelope, parametrically represented and transmitted as embedded data in the telephone speech. We propose a novel data embedding scheme, in which the scalar Costa scheme is combined with an auditory masking model allowing high rate transparent embedding, while maintaining a low bit error rate. The signal is transformed to the frequency domain via the discrete Hartley transform (DHT and is partitioned into subbands. Data is embedded in an adaptively chosen subset of subbands by modifying the DHT coefficients. In our simulations, high quality wideband speech was obtained from speech transmitted over a telephone line (characterized by spectral magnitude distortion, dispersion, and noise, in which side information data is transparently embedded at the rate of 600 information bits/second and with a bit error rate of approximately 3?10?4. In a listening test, the reconstructed wideband speech was preferred (at different degrees over conventional telephone speech in 92.5% of the test utterances.

David Malah

2007-01-01

222

Bandwidth Extension of Telephone Speech Aided by Data Embedding  

Directory of Open Access Journals (Sweden)

Full Text Available A system for bandwidth extension of telephone speech, aided by data embedding, is presented. The proposed system uses the transmitted analog narrowband speech signal as a carrier of the side information needed to carry out the bandwidth extension. The upper band of the wideband speech is reconstructed at the receiving end from two components: a synthetic wideband excitation signal, generated from the narrowband telephone speech and a wideband spectral envelope, parametrically represented and transmitted as embedded data in the telephone speech. We propose a novel data embedding scheme, in which the scalar Costa scheme is combined with an auditory masking model allowing high rate transparent embedding, while maintaining a low bit error rate. The signal is transformed to the frequency domain via the discrete Hartley transform (DHT and is partitioned into subbands. Data is embedded in an adaptively chosen subset of subbands by modifying the DHT coefficients. In our simulations, high quality wideband speech was obtained from speech transmitted over a telephone line (characterized by spectral magnitude distortion, dispersion, and noise, in which side information data is transparently embedded at the rate of 600 information bits/second and with a bit error rate of approximately . In a listening test, the reconstructed wideband speech was preferred (at different degrees over conventional telephone speech in of the test utterances.

Sagi Ariel

2007-01-01

223

An Exponential Time 2-Approximation Algorithm for Bandwidth  

CERN Document Server

The bandwidth of a graph G on n vertices is the minimum b such that the vertices of G can be labeled from 1 to n such that the labels of every pair of adjacent vertices differ by at most b. In this paper, we present a 2-approximation algorithm for the bandwidth problem that takes worst-case O(1.9797^n) time and uses polynomial space. This improves both the previous best 2- and 3-approximation algorithms of Cygan et al. which have an O(3^n) and O(2^n) worst-case time bounds, respectively. Our algorithm is based on constructing bucket decompositions of the input graph. A bucket decomposition partitions the vertex set of a graph into ordered sets (called buckets) of (almost) equal sizes such that all edges are either incident on vertices in the same bucket or on vertices in two consecutive buckets. The idea is to find the smallest bucket size for which there exists a bucket decomposition. The algorithm uses a simple divide-and-conquer strategy along with dynamic programming to achieve this improved time bound.

Fürer, Martin; Kasiviswanathan, Shiva Prasad

2009-01-01

224

Crystallographic data collection using a 0.22% bandwidth multilayer.  

Science.gov (United States)

To bridge the gap between traditional multilayer and crystal optics a high-resolution multilayer monochromator with a bandwidth of 0.22% has been designed and installed on a bending-magnet beamline (F3) at the Cornell High Energy Synchrotron Source (CHESS) to provide an unfocused monochromatic X-ray beam for protein crystallography experiments. Crystallographic data of excellent quality from a medium-sized protein, Concanavalin A, were collected and processed using standard crystallographic programs. The data were successfully used for a structure solution and refinement. The flux from the multilayer monochromator is enhanced, relative to that from a flat Si(111) monochromator, by a factor of 5; consequently, data collection is faster and/or smaller samples may be used. At the same time, the bandwidth is narrow enough to avoid streaked spots. This experiment suggests that multilayer optics may play a valuable role in satisfying the demands of the structural biology community for rapid X-ray data collection, particularly at under-utilized bending-magnet beamlines. PMID:15840920

Englich, Ulrich; Kazimirov, Alexander; Shen, Qun; Bilderback, Don H; Gruner, Sol M; Hao, Quan

2005-05-01

225

Propagation of wide bandwidth signals in a tropospheric ducting system  

Science.gov (United States)

The propagation properties of wide bandwidth signals transmitted through a tropospheric ducting medium are examined analytically. A flat earth model with a perfect surface conductivity (sea surface) is taken. The refractive index profile n(h) is assumed a stepwise function of the height h. Horizontal and vertical polarized waves are treated in parallel by employing similar procedures. The corresponding boundary value problems are solved by using spectral representations for the primary antenna and induced fields. Guided and radiated mode contributions are then computed by applying approximate asymptotic integration techniques under a continuous wave (CW) excitation. The behavior of wide bandwidth signals propagating in a tropospheric duct is examined in terms of the inverse Fourier transformation of the CW field expressions. Several geometries are considered such as both transmitting and receiving antennas being inside the tropospheric waveguide or the opposite. Particular attention is given to the case when the communication path crosses the waveguide ceiling. In order to determine the influence of the multipath propagation, occurring inside the ducting medium, into a real communication link a phase shift keying modulation is considered. Numerical results are given for several tropospheric ducting media in terms of the bit error rate.

Uzunoglu, N. K.

1984-10-01

226

Extending the bandwidth of optical-tweezers interferometry  

International Nuclear Information System (INIS)

High-resolution force and displacement measurements by laser interferometry, combined with optical tweezers in a light microscope, are frequently based on near-infrared lasers. With common silicon PN photodiodes the bandwidth of detection was found to be limited to about 5 kHz at 1064 nm laser wavelength. This is caused by the fact that silicon becomes increasingly transparent for wavelengths approaching the band gap energy, leading to the generation of charge carriers outside the depletion zone of the diode for wavelengths longer than about 850 nm. These charges have to diffuse before they can contribute to the photocurrent. In this technical note we demonstrate experimentally that the detection bandwidth can be extended to at least 100 kHz, either by using wavelengths below 850 nm, or by using different detectors at longer wavelengths: InGaAs PIN photodiodes or special-purpose fully depleted p-type silicon photodiodes. We measured the well-known power spectral density of the Brownian motion of micron-sized beads in optical tweezers and show that the optimized detectors do not cause attenuation within experimental noise. They are indeed linear enough to detect the weak inertial effects of the watery solvent on the power spectral density of the Brownian motion

2003-07-01

227

A Bandwidth Allocation Model Provisioning Framework with Autonomic Characteristics  

Directory of Open Access Journals (Sweden)

Full Text Available The Bandwidth Allocation Models (MAM, RDM, G-RDM and AllocTC-Sharing are managementalternatives currently available which propose different resource (bandwidth allocation strategies inmultiservice networks. The BAM adoption by a network is typically a management choice andconfiguration task executed by the network operations and management system setup in a static or nearlystatic way. This paper proposes and explores the alternative ofallowing BAM definition and configurationon a more dynamic way. In effect, one of the basic motivations towards BAM dynamic allocation is the factthat multiservice networks characteristics (traffic loadmay change considerably in daily networkoperation and, as such, some dynamics in BAM allocation should be introduced in order to improveperformance. A framework is presented supporting BAM dynamicallocation. The framework adopts anOpenFlow-based software-defined networking (SDN implementation approach in order to supportscalability issues with a centralized controller and managementnetwork view. The framework architecturealso supports the implementation of some autonomic characteristics which, in brief, look for improving andfacilitating the decision-making process involved with BAM provisioning in a multiservice network. Aproof of concept is presented evaluating different BAM performance under different traffic loads in order todemonstrate the framework strategy adopted.

Rafael F. Reale

2013-11-01

228

3-DB, 3-D Multigroup Diffusion, X-Y-Z, R-Theta-Z, Triangular-Z Geometry, Fast Reactor Burnup  

International Nuclear Information System (INIS)

1 - Description of problem or function: 3DB is a three-dimensional (x-y-z, r-theta-z, triangular-z) multigroup diffusion code for use in detailed fast-reactor criticality and burnup analysis. The code can be used to - (a) compute keff and perform criticality searches on time absorption, reactor composition, and reactor dimensions by means of either a flux or an adjoint model, (b) compute material burnup using a flexible material shuffling scheme, and (c) compute flux distributions for an arbitrary extraneous source. 2 - Method of solution: Eigenvalues are computed by standard source- iteration techniques. Group re-balancing and successive over-relaxation with line inversion are used to accelerate convergence. Adjoint solutions are obtained by inverting the input data and redefining the source terms. Material burnup is by reactor zone. The burnup rate is determined by the zone and energy-averaged cross sections which are recomputed after each time-step. The isotopic chains, which can contain any number of isotopes are formed by the user. The code does not contain built- in or internal chains. 3 - Restrictions on the complexity of the problem: Since variable dimensioning is employed, no simple bounds can be stated

1974-01-01

229

1092 Channel 2-D Array Demultiplexer for Ultralarge Data Bandwidth  

Science.gov (United States)

We demonstrate 1 x 1092 channel wavelength demultiplexing with 50-GHz channel pitch and a 600-nm total bandwidth. Outputs from 1 x 40 channel arrayed waveguide gratings operating with multiple orders enter a free-space optical grating demultiplexer which separates the orders into a 2-D spot array, where the light can be coupled into discrete output fibers or operated on by a surface normal device (i.e., microelectromechanical system switch or detector array). Supercontinuum source input from 1140 to 1750 nm produced a 28 x 39 spot array at the output plane. The insertion loss for light is coupled into a single mode fiber ranged from 7 to 18 dB with less than 10-dB loss in channels between 1300 and 1750 nm. Bit-error-rate measurements show a negligible 0.1-dB power penalty at 10 GB/s.

Chan, Trevor K.; Karp, Jason; Jiang, Rui; Alic, Nikola; Radic, Stojan; Marki, Christopher F.; Ford, Joseph E.

2007-03-01

230

Ce impurities in superconductors: Zero-bandwidth limit  

International Nuclear Information System (INIS)

The effect of the continuous demagnetization of Ce on the superconductivity of the matrix is studied with a simple, exactly solvable model obtained as a zero-conduction-bandwidth limit of the Mueller-Hartmann and Zittartz and of the Wiecko-Lopez models. Phase diagrams are obtained from the exact free energies. This phase diagrams agree, within the limitations of the model, with those previously calculated by Mueller-Hartmann and Zittartz and by Wiecko and Lopez. The exact calculation of the free energy allows us to extend the Wiecko-Lopez results and to predict a normal phase at low temperatures which has not been observed before. The characteristic features observed in LaCe and (La/sub x/Th/sub 1-x/)Ce are reproduced. The phenomenon of reentrance emerges with a clear physical meaning as a competition for stability between two states with different occupation number of the ''conduction'' electrons which have different degeneracy

1981-02-01

231

Stripline network drives 32 elements to wide bandwidths  

Science.gov (United States)

The use of passive L-band Butler matrices using simple 180-deg hybrids and passive phase shifters is proposed for driving linear arrays of 32 vertical dipole antennas over broad bandwidths. The stripline component design for a network incorporating a Butler matrix reduced from the standard 32 x 32 to 8 x 32 for the considered application is discussed. Results of the network's performance evaluation are presented, and the performance is found to be in good agreement with that predicted by computer simulation. The use of passive phase shifters is shown to provide high reliability at low cost, and optimization at the design stage eliminates the need for trimming in production units. The network can also be used in direction-finding applications by connecting an antenna array to the outputs of the matrix and detecting the amplitude of the signals at the input ports.

Macnamara, Thereza M.; Cahill, Robert; Foti, Stephen J.

1989-05-01

232

Optical preparation and measurement of atomic coherence at gigahertz bandwidth  

International Nuclear Information System (INIS)

We detail a method for the preparation of atomic coherence in a high-density atomic vapour of 87Rb, utilizing a coherent preparation scheme of off-resonant gigahertz bandwidth pulses. The scheme is found to be faster and more effective than techniques based on resonant interaction, such as coherent population trapping and population inversion. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing coherent states is found to be close to unity at the entrance to the medium. The medium is then probed non-invasively with a laser field, the polarization of which is dependent upon the relative phase of the atomic coherence produced by the preparation fields. (paper)

2012-06-28

233

Very low bandwidth, unattended imager for surveillance applications  

Energy Technology Data Exchange (ETDEWEB)

The need arises in certain vehicular surveillance applications for an electronic imager that can perform without human interaction and can transmit definitive images over very low bandwidth channels. The investigators have found that line scan imagers offer particular advantages toward these ends. Specifically, the use of a line scan imager facilitates the following processing steps: (1) segmentation of the vehicle from the background, (2) automatic exposure control, (3) light level equalization prior to quantization, and (4) implementation of an adaptive sampling scheme. These processing steps together with the source encoder may be implemented on a relatively low throughput processor and achieve near real time operation. The specific encoding method used here is an extended differential pulse code modulation (DPCM). A prototype system has been developed, producing medium resolution images at less than 10K bits per frame.

Eichel, P.H.; Jakowatz, C.V. Jr.

1986-01-01

234

Wide-Bandwidth Capture of Wire-Scanner Signals  

International Nuclear Information System (INIS)

Integrated charge collected on the sense wires of wire-scanner systems utilized to determine beam profile is generally the parameter of interest. The LANSCE application requires capturing the charge information macropulse-by-macropulse with macropulse lengths as long as 700 (micro)s at a maximum macropulse rate of 120 Hz. Also, for the LANSCE application, it is required that the integration be performed in a manner that does not require integrator reset between macropulses. Due to the long macropulse which must be accommodated and the 8.33 ms minimum pulse period, a simple R-C integrator cannot be utilized since there is insufficient time between macropulses to allow the integrator to adequately recover. The application of wide analog bandwidth to provide accurate pulse-by-pulse capture of the wire signals with digital integration of the wire signals to determine captured charge at each macropulse in applications with comparatively long macropulses and high pulse repetition rates is presented.

2012-05-20

235

Enhanced Gain and Bandwidth of Patch Antenna Using EBG Substrates  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antenna becomes very popular day by day because of its ease of analysis andfabrication, low cost, light weight, easy to feed and their attractive radiation characteristics. Althoughpatch antenna has numerous advantages, it has also some drawbacks such as restricted bandwidth, lowgain and a potential decrease in radiation pattern. In recent years, attention to use Electromagnetic BandGap (EBG substrates to overcome the limitations of patch antenna. In this paper, we propose arectangular microstrip patch antenna with EBG substrates and compare the performance of the proposedantenna with a conventional patch antenna in the same physical dimension. Due to the presence of theEBG structure in the dielectric substrates, the electromagnetic band gap is created that reduces thesurface waves considerably. As a result, the performance of the proposed antenna is better comparing theconventional existing microstrip patch antenna.

Mst. Nargis Aktar

2011-02-01

236

Coherence Bandwidth Effects on Underwater Image Transmission in Multipath Channel  

Science.gov (United States)

The performance of an underwater acoustic communication system in shallow water is strongly affected by the water surface and the seabed acoustical properties. Time-variant water surface scattering and grazing-angle-dependent bottom reflection limit the received signal coherency. Consequently, the performance of underwater acoustic communication systems is degraded, and high-speed digital communication is disrupted. In this study, the authors consider two different multipath channels, such as a water tank and a river, and conduct experiments to quantify these effects on the image transmission using binary frequency shift keying (BFSK) modulation. The quality of the received image in a water tank experiment is shown to be affected by water surface scattering. In the 9-m-deep Nakdong river experiment, it is shown to be affected by grazing-angle-dependent bottom reflection. The analysis is based on the coherence bandwidth of the multipath channel response.

Kim, Jongwook; Park, Kyu-Chil; Park, Jihyun; Yoon, Jong Rak

2011-07-01

237

Auction-based Bandwidth Allocation Mechanisms for Wireless Future Internet  

CERN Document Server

An important aspect of the Future Internet is the efficient utilization of (wireless) network resources. In order for the - demanding in terms of QoS - Future Internet services to be provided, the current trend is evolving towards an "integrated" wireless network access model that enables users to enjoy mobility, seamless access and high quality of service in an all-IP network on an "Anytime, Anywhere" basis. The term "integrated" is used to denote that the Future Internet wireless "last mile" is expected to comprise multiple heterogeneous geographically coexisting wireless networks, each having different capacity and coverage radius. The efficient management of the wireless access network resources is crucial due to their scarcity that renders wireless access a potential bottleneck for the provision of high quality services. In this paper we propose an auction mechanism for allocating the bandwidth of such a network so that efficiency is attained, i.e. social welfare is maximized. In particular, we propose a...

Dramitinos, Emmanouil

2010-01-01

238

Research on the Fair Assignment of Router’s Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available The problem of providing a fair allocation between responsible flows (such as TCP and non-responsible (such as UDP is investigated. A core stateless fair queuing algorithm with high throughput is presented. In the algorithm, the same packet loss strategies that are based on the calculated probability p are used to all of the flows without distinction. And it does not make into account the sensitivity of TCP. So this paper proposes a new algorithm VCSFQ do the different packet loss strategy. The algorithm can protect TCP flows against UDP flows and improves the fairness of bandwidth allocation. The algorithm performs better than CSFQ for getting high throughput. Simulation shows that it is effective and efficient.

Zifen Yang

2010-10-01

239

Frequency, bandwidth, and information transfer in B-mode imaging  

Science.gov (United States)

Center frequency and bandwidth are two generic parameters used to characterize transmitted pulse profiles in B-mode ultrasonic imaging. Increasing either is generally thought to improve spatial resolution in the final image, but at a potential cost of lower signal-to-noise ratio, with no general understanding of where they are optimal. In this work we investigate their role in converting the acquired radio-frequency signal from a linear array into an envelope image. Statistics of the backscattered signal, based on Rayleigh-Sommerfeld diffraction theory, are used in an ideal observer calculation that quantifies the task-relevant information contained in the radio-frequency (RF) signal. We then compare two approaches to computing an envelope image. The first is a standard B-mode envelope from the complex analytic signal. The second approach processes RF through a Wiener filter before forming an analytic signal. Effects of envelope detection are measured by computing the ideal observer in the envelope domain using Smith-Wagner approximations. Over frequencies ranging from 3-15MHz and fractional bandwidths ranging from 20% to 80%, we find that information transfer in the envelope varies widely with task. There is a substantial loss of information in all conditions in the formation of a standard envelope. Efficiency relative to the RF ranges from 60% to less than 5%. The Weinerfiltered envelope images substantially improve efficiency in two of the three tasks investigated. In the third task, the results are mixed, but we argue that the Weiner filter may be improved substantially by retuning it to the interior of a lesion.

Abbey, Craig K.; Nguyen, Nghia Q.; Insana, Michael F.

2012-02-01

240

A Survey of Dynamic-centric Bandwidth Allocation Technique for Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Objective of the study is to study and analyze the dynamic-centric metrics of bandwidth allocation and estimation for wireless networks. We also extend the objective to probe Quality of Service (QoS provisioning guarantee for infeasible packet routing networking protocols. This study signifies the bandwidth sharing scheme for real time and non-real time based. So far, the researchers have not examined this signification to have a good impact on throughput rate, packet reception rate, packet dropping rate and packet delay. Nowadays, the network technologies have been focused much on dynamic bandwidth allocation for achieving effective bandwidth utilization, good service rate and improving service satisfaction. Thus, we study a lot of routing strategies to analyze the metrics of bandwidth. In the study, we find the convex optimization technique as suitable to enhance the network throughput performance, providing bandwidth issue is negotiated on network.

Bakkiam David Deebak

2014-01-01

 
 
 
 
241

Netest: A Tool to Measure the Maximum Burst Size, Available Bandwidth and Achievable Throughput  

Energy Technology Data Exchange (ETDEWEB)

Distinguishing available bandwidth and achievable throughput is essential for improving network applications' performance. Achievable throughput is the throughput considering a number of factors such as network protocol, host speed, network path, and TCP buffer space, where as available bandwidth only considers the network path. Without understanding this difference, trying to improve network applications' performance is like ''blind men feeling the elephant'' [4]. In this paper, we define and distinguish bandwidth and throughput, and debate which part of each is achievable and which is available. Also, we introduce and discuss a new concept - Maximum Burst Size that is crucial to the network performance and bandwidth sharing. A tool, netest, is introduced to help users to determine the available bandwidth, and provides information to achieve better throughput with fairness of sharing the available bandwidth, thus reducing misuse of the network.

Jin, Guojun; Tierney, Brian

2003-01-31

242

Bandwidth Enhancement in Chaotic Semiconductor Lasers with Strong Chaotic Optical Injection  

Science.gov (United States)

The bandwidth properties of chaotic signals generated by semiconductor lasers subject to strong chaotic optical injection (COI) are investigated numerically. The chaotic output of an injection master laser (ML) is injected into the slave laser (SL). The effects of feedback strength, injection strength and bias current on the bandwidth properties are discussed in detail. Some novel results are found, the bandwidth for SL increases with the injection strength firstly until reaches a maximum, and then decrease to approach the bandwidth of ML due to the injection-locking chaos synchronization. Large feedback strength and bias current contributes to higher maximum chaotic bandwidth in the range of injection strength. That is to say, for given parameters, optimal injection strength exists contributing to highest chaotic bandwidth, and moves to a large value for a large feedback strength and bias current, which is extremely useful for increasing the transmission rate of the optical chaotic communication system.

Yang, Hui-Min

243

Bandwidth Enhancement of Antenna Arrays Utilizing Mutual Coupling between Antenna Elements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The mutual coupling effect between antenna elements on an array's bandwidth is investigated using scattering parameters instead of the mutual impedance. First, an approximate expression is derived for matched voltage standing wave ratio (VSWR) bandwidth of a tuned antenna, which reveals that the bandwidth is inversely proportional to the magnitude |?0'(?0)| of the frequency derivative of the reflection coefficient. Next, considering linear antenna arrays with corporat...

Min Wang; Wen Wu; Zhongxiang Shen

2010-01-01

244

Quality of Service in Mobile Ad Hoc Networks using Bandwidth Estimation Method in AODV and AOMDV  

Directory of Open Access Journals (Sweden)

Full Text Available Bandwidth Estimation is an important issue in MANETs, because the path of the nodes in the network can change dynamically. Due to predefined infrastructure and bandwidth constraint the Quality of Service (QOS is challenging assignment in Mobile Ad hoc network. In this paper we propose bandwidth estimation mechanisms using AODV and AOMDV protocol. The performance shows that increase packet delivery ratio and throughput and also reduce end - to - end delay.

Mrs.D.Maheshwari

2013-06-01

245

The evolution and limits of spectral bandwidth in free electron lasers  

International Nuclear Information System (INIS)

We study the bandwidths in free electron lasers (FELs) under different circumstances; for weakly saturated FELs in storage rings, the bandwidth is given be the formula derived in the super mode theory, while it is given by the Fourier transform of the electron pulse length in the strongly saturated FELs in linacs. The limiting bandwidth for the case of a DC beam is given by a Schawlow-Townes formula, but the approach to the limit is very slow. 14 refs

1990-09-17

246

The evolution and limits of spectral bandwidth in free electron lasers  

Energy Technology Data Exchange (ETDEWEB)

We study the bandwidths in free electron lasers (FELs) under different circumstances; for weakly saturated FELs in storage rings, the bandwidth is given be the formula derived in the super mode theory, while it is given by the Fourier transform of the electron pulse length in the strongly saturated FELs in linacs. The limiting bandwidth for the case of a DC beam is given by a Schawlow-Townes formula, but the approach to the limit is very slow. 14 refs.

Kim, K.J.

1990-11-01

247

High-Bandwidth Mesh-based Overlay Multicast in Heterogeneous Environments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we present MeshCast, a peer-to-peer (p2p) multicast protocol for applications requiring high bandwidth (such as live video streaming) from a server to a large number of receivers. Traditional tree-based approaches to overlay multicast inefficiently utilise the outgoing bandwidth of participating nodes and poorly adapt to node membership churn. In contrast, MeshCast is based on Chainsaw meshbased approach to data delivery that better utilises bandwidth and...

Meier, Rene

2006-01-01

248

Numerical models of broad-bandwidth nanosecond optical parametric oscillators  

International Nuclear Information System (INIS)

We present three new methods for modeling broad-bandwidth, nanosecond optical parametric oscillators in the plane-wave approximation. Each accounts for the group-velocity differences that determine the operating linewidth of unseeded optical parametric oscillators, and each allows the signal and the idler waves to develop from quantum noise. The first two methods are based on split-step integration methods in which nonlinear mixing and propagation are calculated separately on alternate steps. One method relies on Fourier transforming the fields between t and ? to handle propagation, with mixing integrated over a ?z step; the other transforms between z and kz in the propagation step, with mixing integrated over ?t. The third method is based on expansion of the three optical fields in terms of their respective longitudinal empty cavity modes, taking into account the cavity boundary conditions. Equations describing the time development of the mode amplitudes are solved to yield the time dependence of the three output fields. These models exclude diffraction and group-velocity dispersion but can be readily extended to include them. copyright 1999 Optical Society of America

1999-04-01

249

Mechanism of bandwidth improvement in passively cooled SMA position actuators  

International Nuclear Information System (INIS)

The heating of shape memory alloy (SMA) materials leads to a thermally driven phase change which can be used to do work. An SMA wire can be thermally cycled by controlling electric current through the wire, creating an electro-mechanical actuator. Such actuators are typically heated electrically and cooled through convection. The thermal time constants and lack of active cooling limit the operating frequencies. In this work, the bandwidth of a still-air-cooled SMA wire controlled with a PID controller is improved through optimization of the controller gains. Results confirm that optimization can improve the ability of the actuator to operate at a given frequency. Overshoot is observed in the optimal controllers at low frequencies. This is a result of hysteresis in the wire's contraction–temperature characteristic, since different input temperatures can achieve the same output value. The optimal controllers generate overshoot during heating, in order to cause the system to operate at a point on the hysteresis curve where faster cooling can be achieved. The optimization results in a controller which effectively takes advantage of the multi-valued nature of the hysteresis to improve performance

2009-09-01

250

Bandwidths for the perception of head orientation decrease during childhood.  

Science.gov (United States)

Adults use the orientation of people's heads as a cue to the focus of their attention. We examined developmental changes in mechanisms underlying sensitivity to head orientation during childhood. Eight-, 10-, 12-year-olds, and adults were adapted to a frontal face view or a 20° left or right side view before judging the orientation of a face at or near frontal. After frontal adaptation, there were no age differences in judgments of head orientation. However, after adaptation to a 20° left or right side view, aftereffects were larger and sensitivity to head orientation was lower in 8- and 10-year-olds than in adults, with no difference between 12-year-olds and adults. A computational model indicates that these results can be modeled as a consequence of decreasing neural tuning bandwidths and decreasing additive internal noise during childhood, and/or as a consequence of increasing inhibition during childhood. These results provide the first evidence that neural mechanisms underlying sensitivity to head orientation undergo considerable refinement during childhood. PMID:24674736

Vida, Mark D; Wilson, Hugh R; Maurer, Daphne

2014-05-01

251

High Bandwidth Short Stroke Rotary Fast Tool Servo  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the design and performance of a new rotary fast tool servo (FTS) capable of developing the 40 g's tool tip acceleration required to follow a 5 micron PV sinusoidal surface at 2 kHz with a planned accuracy of 50 nm, and having a full stroke of 50 micron PV at lower frequencies. Tests with de-rated power supplies have demonstrated a closed-loop unity-gain bandwidth of 2 kHz with 20 g's tool acceleration, and we expect to achieve 40 g's with supplies providing {+-} 16 Amp to the Lorentz force actuator. The use of a fast tool servo with a diamond turning machine for producing non-axisymmetric or textured surfaces on a workpiece is well known. Our new rotary FTS was designed to specifically accommodate fabricating prescription textured surfaces on 5 mm diameter spherical target components for High Energy Density Physics experiments on the National Ignition Facility Laser (NIF).

Montesanti, R C; Trumper, D L

2003-08-22

252

A scanning SQUID microscope with 200 MHz bandwidth  

Science.gov (United States)

We developed a scanning DC SQUID microscope with novel readout electronics capable of wideband sensing of RF magnetic fields from 50 to 200 MHz and simultaneously providing closed-loop response at kHz frequencies. To overcome the 20 MHz bandwidth limitation of traditional closed-loop SQUIDs, a flux-modulated closed-loop simultaneously locks the SQUID quasi-static flux and flux-biases the SQUID for amplification of the RF flux up to ?0/4 in amplitude. Demodulating the SQUID voltage with a double lock-in technique yields a signal representative of both the amplitude and phase of the RF flux. This provides 80 dB of a linear dynamic range with a flux noise density of 4 ??0 Hz?1/2 at 200 MHz for a Y Ba2Cu3O7 bi-crystal SQUID at 77 K. We describe the electronics’ performance and present images for RF magnetic field of the travelling wave in a coplanar waveguide, the standing wave in an open-circuited microstrip, and a surface mounted device antenna.

Talanov, Vladimir V.; Lettsome, Nesco M., Jr.; Borzenets, Valery; Gagliolo, Nicolas; Cawthorne, Alfred B.; Orozco, Antonio

2014-04-01

253

Review of single transient oscillographic recorders with gigahertz bandwidth  

Energy Technology Data Exchange (ETDEWEB)

In laser driven inertial confinement fusion research, at Livermore, we are diagnosing many phenomena that occur in a time frame that exceeds the capabilities of even the most advanced, present day oscillographic recording instruments. Many of the by-products of the interaction between the laser beam and fuel pellet are monitored to determine the specifics of the fusion process. By the use of appropriate detectors, we convert the information contained in the radiated by-products to electrical signals which are recorded on high bandwidth oscillographic recorders. Our present range of recording capabilities for one x-ray diagnostic measurement in use at Livermore is shown. A commonly used configuration consists of an XRD-31 x-ray detector connected to a direct access Tektronix R7912 transient digitizer using 1/2 in. diameter air dielectric coaxial cable. This configuration gives a system fwhm of approximately 335 ps. Our premier configuration, on the other hand, consists of an improved response detector and a French Thomson-CSF TSN-660 oscilloscope with a shorter length of coaxial cable (typically 20 feet). The system fwhm in this case is less than 120 ps which is our fastest oscillographic recording system at the present time.

Campbell, D.E.

1982-10-20

254

Model Based Bandwidth Scavenging for Device Coexistence in Wireless LANs  

Science.gov (United States)

Dynamic Spectrum Access in a Wireless LAN can enable a set of secondary users' devices to access unused spectrum, or whitespace, which is found between the transmissions of a set of primary users' devices. The primary design objectives for an efficient secondary user access strategy are to be able to "scavenge" spatio-temporally fragmented bandwidth while limiting the amount of interference caused to the primary users. In this paper, we propose a secondary user access strategy which is based on measurement and modeling of the whitespace as perceived by the secondary users in a WLAN. A secondary user continually monitors and models its surrounding whitespace, and then attempts to access the available spectrum so that the effective secondary throughput is maximized while the resulting interference to the primary users is limited to a pre-defined bound. We first develop analytical expressions for the secondary throughput and primary interference, and then perform ns2 based simulation experiments to validate the effectiveness of the proposed access strategy, and evaluate its performance numerically using the developed expressions.

Plummer, Anthony; Taghizadeh, Mahmoud; Biswas, Subir

255

Agent based Bandwidth Reservation Routing Technique in Mobile Ad Hoc Networks  

Directory of Open Access Journals (Sweden)

Full Text Available In mobile ad hoc networks (MANETs, inefficient resource allocation causes heavy losses to the service providers and results in inadequate user proficiency. For improving and automating the quality of service of MANETs, efficient resource allocation techniques are required. In this paper, we propose an agent based bandwidth reservation technique for MANET. The mobile agent from the source starts forwarding the data packets through the path which has minimum cost, congestion and bandwidth. The status of every node is collected which includes the bottleneck bandwidth field and the intermediate node computes the available bandwidth on the link. At the destination, after updating the new bottleneck bandwidth field, the data packet is feedback to the source. In resource reservation technique, if the available bandwidth is greater than bottleneck bandwidth, then bandwidth reservation for the flow is done. Using rate monitoring and adjustment methodologies, rate control is performed for the congested flows. By simulation results, we show that the resource allocation technique reduces the losses and improves the network performance.

Vishnu Kumar Sharma,

2011-12-01

256

Design and fabrication of bandwidth tunable HTS transmit filter using ?-shaped waveguides  

International Nuclear Information System (INIS)

We have developed a method for tuning the bandwidth of a high-temperature superconducting (HTS) microstrip filter. Several ?-shaped waveguides are placed between the resonators, and the bandwidth is tuned in discrete steps by changing the switch states of the waveguides, which changes the coupling coefficient between the resonators. The filter contains 3-pole half-wavelength straight-line resonators and two ?-shaped waveguides for bandwidth tuning. It also has several electrical pads distributed around the feed lines for trimming after tuning. The filter was fabricated by depositing YBa2Cu3O7 thin film on an MgO substrate and has a measured center frequency of 5.17 GHz and bandwidth of 220 MHz. Use of the ?-shaped waveguides to adjust the coupling coefficients and the electrical pads to adjust the external quality factors resulted in 80-MHz bandwidth tuning without increased insertion loss.

2010-11-01

257

Dynamic Bit Allocation for Object Tracking in Bandwidth Limited Sensor Networks  

CERN Document Server

In this paper, we study the target tracking problem in wireless sensor networks (WSNs) using quantized sensor measurements under limited bandwidth availability. At each time step of tracking, the available bandwidth $R$ needs to be distributed among the $N$ sensors in the WSN for the next time step. The optimal solution for the bandwidth allocation problem can be obtained by using a combinatorial search which may become computationally prohibitive for large $N$ and $R$. Therefore, we develop two new computationally efficient suboptimal bandwidth distribution algorithms which are based on convex relaxation and approximate dynamic programming (A-DP). We compare the mean squared error (MSE) and computational complexity performances of convex relaxation and A-DP with other existing suboptimal bandwidth distribution schemes based on generalized Breiman, Friedman, Olshen, and Stone (GBFOS) algorithm and greedy search. Simulation results show that, A-DP, convex optimization and GBFOS yield similar MSE performance, w...

Masazade, Engin; Varshney, Pramod K

2011-01-01

258

Design and enhancement bandwidth rectangular patch antenna using single trapezoidal slot technique  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antennas has some drawbacks of low efficiency, narrow bandwidth (3-6 % of the central frequency, its bandwidth is limited to a few percent which is not enough for most of the wireless communication systems nowadays. In this paper one of the efficient methods used for the enhancement of patch antenna Bandwidth is the loading of microstrip patch Antenna with a trapezoidal slot. Microstrip patch antenna that meets the requirement of operation at 2.4 GHZ, the proposed configurations is simulated and analyzed using (CST- 2010 software package. The VSWR, input impedance‚ radiation patterns and S11 performance are used for the analysis of the different configurations. The simulated results for trapezoidal slot give bandwidth of 287.2 MHZ (11.93% fractional bandwidth. Feed point on the patch that gives a good Match of 50 ohm.

Karim A. Hamad

2012-03-01

259

Broad-Bandwidth FPGA-Based Digital Polyphase Spectrometer  

Science.gov (United States)

With present concern for ecological sustainability ever increasing, it is desirable to model the composition of Earth s upper atmosphere accurately with regards to certain helpful and harmful chemicals, such as greenhouse gases and ozone. The microwave limb sounder (MLS) is an instrument designed to map the global day-to-day concentrations of key atmospheric constituents continuously. One important component in MLS is the spectrometer, which processes the raw data provided by the receivers into frequency-domain information that cannot only be transmitted more efficiently, but also processed directly once received. The present-generation spectrometer is fully analog. The goal is to include a fully digital spectrometer in the next-generation sensor. In a digital spectrometer, incoming analog data must be converted into a digital format, processed through a Fourier transform, and finally accumulated to reduce the impact of input noise. While the final design will be placed on an application specific integrated circuit (ASIC), the building of these chips is prohibitively expensive. To that end, this design was constructed on a field-programmable gate array (FPGA). A family of state-of-the-art digital Fourier transform spectrometers has been developed, with a combination of high bandwidth and fine resolution. Analog signals consisting of radiation emitted by constituents in planetary atmospheres or galactic sources are downconverted and subsequently digitized by a pair of interleaved analog-to-digital converters (ADCs). This 6-Gsps (gigasample per second) digital representation of the analog signal is then processed through an FPGA-based streaming fast Fourier transform (FFT). Digital spectrometers have many advantages over previously used analog spectrometers, especially in terms of accuracy and resolution, both of which are particularly important for the type of scientific questions to be addressed with next-generation radiometers.

Jamot, Robert F.; Monroe, Ryan M.

2012-01-01

260

Fuzzy Logic Bandwidth Prediction and Policing in a DiffServ-Aware Network  

Directory of Open Access Journals (Sweden)

Full Text Available

Differentiated Services (DiffServ-aware network potentially can provide the next generation platform for multimedia support in the Internet. In this work we look at improving bandwidth allocation in such a network. We study how to implement bandwidth predicting and policing in a DiffServ aware network using fuzzy logic. A token bucket fuzzy logic bandwidth predictor for real time variable bit rate traffic class is proposed. Here, the AF traffic class is associated with real time variable bit rates traffic. The fuzzy logic bandwidth predictor facilitates bandwidth predicting and dynamic policing based on the class based packet aggregates. This improves the admission control of connections to the network. A simulation study was performed for the fuzzy logic predictor using Network Simulator-2. The simulation results show that the fuzzy logic predictor gave commendable bandwidth prediction value compared to a deterministic bandwidth allocation for the traffic class.

Norsheila Fisal

2008-05-01

 
 
 
 
261

Suitability of Data Intensive Application in a Bandwidth Constrained Global Grid Network  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: To check the suitability of real time data intensive applications in a global grid network. Approach: With improved bandwidth availability, taking the grid to the internet is becoming a reality. However issues regarding the security and bandwidth utilization needs to be understood as these factors become crucial to the success of the grid as a commercial model. Results: Here in this research work we investigate the effect of data intensive applications running in a grid with different number of nodes under constrained bandwidth. Conclusion/Recommendations: Our simulation shows that increasing node count does not guarantee improved quality of service.

T. R. Srinivasan

2011-01-01

262

Increasing the bandwidth of resonant gravitational antennas: the case of explorer.  

Science.gov (United States)

Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG Collaboration, has been upgraded with a new readout. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its center operating frequency of 919 Hz the spectral sensitivity is better than 10(-20) Hz(-1/2). We describe the detector and its sensitivity and discuss the foreseeable upgrades to even larger bandwidths. PMID:14525411

Astone, P; Babusci, D; Bassan, M; Carelli, P; Cavallari, G; Coccia, E; Cosmelli, C; D'Antonio, S; Fafone, V; Fauth, A C; Federici, G; Giordano, G; Marini, A; Minenkov, Y; Modena, I; Modestino, G; Moleti, A; Pallottino, G V; Pizzella, G; Quintieri, L; Rocchi, A; Ronga, F; Terenzi, R; Torrioli, G; Visco, M

2003-09-12

263

Evidence of non-bolometric mixing in the bandwidth of a hot-electron bolometer  

International Nuclear Information System (INIS)

The gain bandwidth of a superconducting NbN hot-electron mixer was measured at local oscillator (LO) frequencies 2.5, 0.6 and 0.3 THz and compared to values from presently known bolometric mixer models. At 2.5 THz variations of the bandwidth with the LO power agree rather with the hot-spot mixer model than with any of the homogeneous bolometric models, whereas an increase of the bandwidth at low LO frequencies plausibly evidences non-bolometric direct interaction of magnetic vortices with the radiation field

2006-10-01

264

Evidence of non-bolometric mixing in the bandwidth of a hot-electron bolometer  

Science.gov (United States)

The gain bandwidth of a superconducting NbN hot-electron mixer was measured at local oscillator (LO) frequencies 2.5, 0.6 and 0.3 THz and compared to values from presently known bolometric mixer models. At 2.5 THz variations of the bandwidth with the LO power agree rather with the hot-spot mixer model than with any of the homogeneous bolometric models, whereas an increase of the bandwidth at low LO frequencies plausibly evidences non-bolometric direct interaction of magnetic vortices with the radiation field.

Semenov, A. D.; Il'in, K.; Siegel, M.; Smirnov, A.; Pavlov, S.; Richter, H.; Hübers, H.-W.

2006-10-01

265

Evidence of non-bolometric mixing in the bandwidth of a hot-electron bolometer  

Energy Technology Data Exchange (ETDEWEB)

The gain bandwidth of a superconducting NbN hot-electron mixer was measured at local oscillator (LO) frequencies 2.5, 0.6 and 0.3 THz and compared to values from presently known bolometric mixer models. At 2.5 THz variations of the bandwidth with the LO power agree rather with the hot-spot mixer model than with any of the homogeneous bolometric models, whereas an increase of the bandwidth at low LO frequencies plausibly evidences non-bolometric direct interaction of magnetic vortices with the radiation field.

Semenov, A D [German Aerospace Center, 12489 Berlin (Germany); Il' in, K [Institute of Micro-and Nanosystems, University of Karlsruhe, 76187 Karlsruhe (Germany); Siegel, M [Institute of Micro-and Nanosystems, University of Karlsruhe, 76187 Karlsruhe (Germany); Smirnov, A [State Pedagogical University, 119435 Moscow (Russian Federation); Pavlov, S [German Aerospace Center, 12489 Berlin (Germany); Richter, H [German Aerospace Center, 12489 Berlin (Germany); Huebers, H-W [German Aerospace Center, 12489 Berlin (Germany)

2006-10-15

266

Low noise and wide bandwidth of NbN hot-electron bolometer mixers  

Science.gov (United States)

We report a record double sideband noise temperature of 600 K (5h?/kB) offered by a NbN hot-electron bolometer receiver at 2.5 THz. Allowing for standing wave effects, this value was found to be constant in the intermediate frequency range 1-7 GHz, which indicates that the mixer has an unprecedentedly large noise bandwidth in excess of 7 GHz. The insight into this is provided by gain bandwidth measurements performed at the superconducting transition. They show that the dependence of the bandwidth on the mixer length follows the model for an HEB mixer with diffusion and phonon cooling of the hot electrons.

Tretyakov, Ivan; Ryabchun, Sergey; Finkel, Matvey; Maslennikova, Anna; Kaurova, Natalia; Lobastova, Anastasia; Voronov, Boris; Gol'Tsman, Gregory

2011-01-01

267

A bandwidth-optimized WENO scheme for the effective direct numerical simulation of compressible turbulence  

Science.gov (United States)

Two new formulations of a symmetric WENO method for the direct numerical simulation of compressible turbulence are presented. The schemes are designed to maximize order of accuracy and bandwidth, while minimizing dissipation. The formulations and the corresponding coefficients are introduced. Numerical solutions to canonical flow problems are used to determine the dissipation and bandwidth properties of the numerical schemes. In addition, the suitability and accuracy of the bandwidth-optimized schemes for direct numerical simulations of turbulent flows is assessed in decaying isotropic turbulence and supersonic turbulent boundary layers.

Martín, M. P.; Taylor, E. M.; Wu, M.; Weirs, V. G.

2006-12-01

268

A Low Cross-Polarization Smooth-Walled Horn with Improved Bandwidth  

Science.gov (United States)

Corrugated feed horns offer excellent beam symmetry, main beam efficiency, and cross-polar response over wide bandwidths, but can be challenging to fabricate. An easier-to-manufacture smooth-walled feed is explored that approximates these properties over a finite bandwidth. The design, optimization and measurement of a monotonically-profiled, smooth-walled scalar feedhorn with a diffraction-limited approx. 14deg FWHM beam is presented. The feed was demonstrated to have low cross polarization (<-30 dB) across the frequency range 33-45 GHz (30% fractional bandwidth). A power reflection below -28 dB was measured across the band.

Zeng, Lingzhen; Bennette, Charles L.; Chuss, David T.; Wollack, Edward J.

2009-01-01

269

Breaking the energy-bandwidth limit of electro-optic modulators: theory and a device proposal  

CERN Document Server

In this paper, we quantitatively analyzed the trade-off between energy per bit for switching and modulation bandwidth of classical electro-optic modulators. A formally simple energy-bandwidth limit (Eq. 10) is derived for electro-optic modulators based on intra-cavity index modulation. To overcome this limit, we propose a dual cavity modulator device which uses a coupling modulation scheme operating at high bandwidth (> 200 GHz) not limited by cavity photon lifetime and simultaneously features an ultra-low switching energy of 0.26 aJ, representing over three orders of magnitude energy consumption reduction compared to state-of-the-art electro-optic modulators.

Lin, Hongtao; Liu, Jifeng; Zhang, Lin; Michel, Jurgen; Hu, Juejun

2013-01-01

270

Bandwidth and unpredictability properties of semiconductor ring lasers with chaotic optical injection  

Science.gov (United States)

The bandwidth and unpredictability properties of chaotic semiconductor ring lasers (SRLs) are numerically investigated. The SRL is brought to chaotic behaviors by utilizing chaotic optical injection from a master laser with optical feedback. The bandwidth and unpredictability degree of chaotic signal are examined for parameter regions of injection strength and frequency detuning. The chaos unpredictability degree is evaluated quantitatively by permutation entropy (PE). It is shown that, chaos can be obtained in large parameter regions, and simultaneous enhancement of bandwidth and unpredictability degree could be achieved for proper injection parameters. Such results are important for carrying out chaos-based communications and fast random number generations (RNGs).

Li, Nianqiang; Pan, Wei; Xiang, Shuiying; Yan, Lianshan; Luo, Bin; Zou, Xihua; Zhang, Liyue

2013-12-01

271

High-Density, High-Bandwidth, Multilevel Holographic Memory  

Science.gov (United States)

A proposed holographic memory system would be capable of storing data at unprecedentedly high density, and its data transfer performance in both reading and writing would be characterized by exceptionally high bandwidth. The capabilities of the proposed system would greatly exceed even those of a state-of-the art memory system, based on binary holograms (in which each pixel value represents 0 or 1), that can hold .1 terabyte of data and can support a reading or writing rate as high as 1 Gb/s. The storage capacity of the state-of-theart system cannot be increased without also increasing the volume and mass of the system. However, in principle, the storage capacity could be increased greatly, without significantly increasing the volume and mass, if multilevel holograms were used instead of binary holograms. For example, a 3-bit (8-level) hologram could store 8 terabytes, or an 8-bit (256-level) hologram could store 256 terabytes, in a system having little or no more size and mass than does the state-of-the-art 1-terabyte binary holographic memory. The proposed system would utilize multilevel holograms. The system would include lasers, imaging lenses and other beam-forming optics, a block photorefractive crystal wherein the holograms would be formed, and two multilevel spatial light modulators in the form of commercially available deformable-mirror-device spatial light modulators (DMDSLMs) made for use in high speed input conversion of data up to 12 bits. For readout, the system would also include two arrays of complementary metal oxide/semiconductor (CMOS) photodetectors matching the spatial light modulators. The system would further include a reference-beam sterring device (equivalent of a scanning mirror), containing no sliding parts, that could be either a liquid-crystal phased-array device or a microscopic mirror actuated by a high-speed microelectromechanical system. Time-multiplexing and the multilevel nature of the DMDSLM would be exploited to enable writing and reading of multilevel holograms. The DMDSLM would also enable transfer of data at a rate of 7.6 Gb/s or perhaps somewhat higher.

Chao, Tien-Hsin

2008-01-01

272

Uniform-in-bandwidth consistency for kernel-type estimators of Shannon's entropy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We establish uniform-in-bandwidth consistency for kernel-type estimators of the differential entropy. We consider two kernel-type estimators of Shannon's entropy. As a consequence, an asymptotic 100% confidence interval of entropy is provided.

Bouzebda, Salim; Elhattab, Issam

2008-01-01

273

THz Tube Waveguides With Low Loss, Low Dispersion, and High Bandwidth  

DEFF Research Database (Denmark)

We propose, model and experimentally characterize a novel class of terahertz hollow-core tube waveguides with high-loss cladding material, resulting in propagation with low loss, low dispersion, and high useful bandwidth.

Bao, Hualong; Nielsen, Kristian

2014-01-01

274

Coherence bandwidth characterization in an urban microcell at 62.4 GHz  

DEFF Research Database (Denmark)

Results of experiments made at 62.4 GHz in an urban mobile radio environment to characterize the coherence bandwidth are presented. The correlation coefficients between signal envelopes separated in frequency are measured and expressed as functions of distance from the base station. Due to the high variation of this coefficient with distance and in order to provide accurate estimates of the coherence bandwidth in the microcell, the correlation coefficient has to be measured over large sections. Two methods to calculate the coherence bandwidth are presented and compared. It is shown that estimating this parameter from the frequency correlation function obtained at each position may yield incorrect results. The coherence bandwidths for correlation levels of 0.5, 0.7, and 0.9 are given. A ray-tracing tool has been used to assist in interpreting experimental results.

Sánchez, M. G.; Hammoudeh, A. M.

2000-01-01

275

Multi-Hop Bandwidth Management Protocol for Mobile Ad Hoc Networks  

CERN Document Server

An admission control scheme should play the role of a coordinator for flows in a data communication network, to provide the guarantees as the medium is shared. The nodes of a wired network can monitor the medium to know the available bandwidth at any point of time. But, in wireless ad hoc networks, a node must consume the bandwidth of neighboring nodes, during a communication. Hence, the consumption of bandwidth by a flow and the availability of resources to any wireless node strictly depend upon the neighboring nodes within its transmission range. We present a scalable and efficient admission control scheme, Multi-hop Bandwidth Management Protocol (MBMP), to support the QoS requirements in multi-hop ad hoc networks. We simulate several options to design MBMP and compare the performances of these options through mathematical analysis and simulation results, and compare its effectiveness with the existing admission control schemes through extensive simulations. KEYWORDS

Pattanayak, Binod Kumar; Jagadev, Alok Kumar; Nayak, Manojranjan

2010-01-01

276

Bandwidth Reduction of Digital Telecommunication Channels Reduction de Bande Passante des Canaux de Telecommunications Numeriques.  

Science.gov (United States)

The possibility of bandwidth reduction in the case of high speed digital signal transmission under white Gaussian noise constraints was investigated. It is shown that the application of Dirac shape pulse transmission and detection principles to signaling ...

A. Ribes J. Cazemajou N. Lannelongue

1976-01-01

277

Design of a Wide Slot Antenna for Bandwidth Enhancement for Wireless Communication Application  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we are proposing a brief description about Microstrip printed wide slot antenna with a fork like tuning stub for bandwidth enhancement. By applying fork like tuning stub to the microstrip wide slot antenna instead of line feed, it is experimentally found that operating bandwidth can be enhanced. Experimental results indicate that the impedance bandwidth, defined by -10Db return loss, of the proposed wide slot antenna can reach operating bandwidth of 3.1 GHz at operating frequency about 2GHz which is 6 times greater than conventional wide slot antenna. A comprehensive parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the designed antenna.

Manish Kumar Rajput

2013-03-01

278

New scintillators for fiber optics: system sensitivity and bandwidth as a function of fiber length  

Energy Technology Data Exchange (ETDEWEB)

Long-wavelength liquid scintillators have been developed for fiber-optic plasma-diagnostic experiments. Relative system sensitivity and bandwidth data as a function of fiber length for several scintillator systems will be presented.

Lutz, S.; Franks, L.A.; Flournoy, J.M.; Lyons, P.B.

1981-01-01

279

A Bandwidth-Aware Job Grouping-Based Scheduling on Grid Environment  

Directory of Open Access Journals (Sweden)

Full Text Available This study explores the feasibility of job scheduling strategies and extend the job grouping-based approach using the idea of bandwidth-awareness. As today`s best-effort network generally experiences low bandwidth and high delay, we aim to maximize the Grid resource utilization and reduce the delay by considering the bandwidth criterion. A simulation environment using GridSim is developed to model job scheduling process. Exploiting the simulation environment, a job scheduling strategy that encompasses the job grouping concept coupled together with bandwidth-aware scheduling is proposed and evaluated. The proposed scheduling strategy focuses on grouping independent jobs with small processing requirements into suitable jobs with larger processing requirements and schedules them in accordance with indeterminist network conditions. The simulation result demonstrates that the proposed strategy succeeds in minimizing the total processing time by at most 82% as compared to its counterpart.

T.F. Ang

2009-01-01

280

A wide bandwidth analog front-end circuit for 60-GHz wireless communication receiver  

Science.gov (United States)

This paper presents an analog front-end circuit for a 60-GHz wireless communication receiver. The feature of the proposed analog front-end circuit is a bandwidth more than 1-GHz wide. To expand the bandwidth of a low-pass filter and a voltage gain amplifier, a technique to reduce the parasitic capacitance of a transconductance amplifier is proposed. Since the bandwidth is also limited by on-resistance of the ADC sampling switch, a switch separation technique for reduction of the on-resistance is also proposed. In a high-speed ADC, the SNDR is limited by the sampling jitter. The developed high resolution VCO auto tuning effectively reduces the jitter of PLL. The prototype is fabricated in 65nm CMOS. The analog front-end circuit achieves over 1-GHz bandwidth and 27.2-dB SNDR with 224 mW Power consumption.

Furuta, M.; Okuni, H.; Hosoya, M.; Sai, A.; Matsuno, J.; Saigusa, S.; Itakura, T.

2014-03-01

 
 
 
 
281

Managing Bandwidth and Traffic via Bundling and Filtration in Large- Scale Distributed Simulations.  

Science.gov (United States)

Research has shown that bandwidth can be a limiting factor in the performance of distributed simulations. The Air Force's Distributed Mission Operations Center (DMOC) periodically hosts one of the largest distributed simulation events in the world. The en...

R. C. Sanchez

2006-01-01

282

Generalized Bandwidth Adaptive System for Multimedia Transmission in Multi-Cell Wireless Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, a novel system, which adapts a bandwidth by dynamic extracting the excess bandwidth not only from one cell but also from other cells in the cellular wireless networks, is presented. The proposed system manages the multimedia sessions to redistribute the new QoS parameters values in case of notable changes or network starvation. The performance analysis shows that our proposed system impacts the old trials and decreases the drop probability of new and handoff calls in multi-cell...

Said, O.; Tolba, A.

2011-01-01

283

GBAS: Generalized Bandwidth Adaptation System for Enhancing Multimedia Transmission Over Multi-Cell Wireless Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nowadays, multimedia Quality of Services (QoS) is considered a very important research issue. In cellular infrastructure wireless networks, a user can move from one cell to another. Hence; a large number of handoff events may occur during a typical session. In case of running multimedia applications with a limited bandwidth, new, handoff, and waiting calls may be dropped. This paper proposes enhancements for the Generalized Bandwidth Adaptation System which is used for multimedia transmission...

Omar Said

2012-01-01

284

Ultranarrow bandwidth moiré reflecting Bragg gratings recorded in photo-thermo-refractive glass.  

Science.gov (United States)

An experimental demonstration of a moiré reflecting Bragg grating in photo-thermo-refractive glass is carried out. This narrowband filter is obtained by the recording of two reflecting Bragg gratings with different periods. Filters with central wavelength at 1550 nm, bandwidth of 50 pm, and transmission higher than 95% are demonstrated. The methods to decrease bandwidth to 1 pm are finally investigated. PMID:20160828

Smirnov, Vadim; Lumeau, Julien; Mokhov, Sergiy; Zeldovich, Boris Ya; Glebov, Leonid B

2010-02-15

285

Tuning gain and bandwidth of traveling wave tubes using metamaterial beam-wave interaction structures  

CERN Document Server

We employ metamaterial beam-wave interaction structures for tuning the gain and bandwidth of short traveling wave tubes. The interaction structures are made from metal rings of uniform cross section, which are periodically deployed along the length of the traveling wave tube. The aspect ratio of the ring cross sections are adjusted to control both gain and bandwidth. The frequency of operation is controlled by the filling fraction of the ring cross section with respect to the period.

Lipton, Robert

2014-01-01

286

Bandwidth statistics from the eigenvalue moments for the Harper-Hofstadter problem  

CERN Document Server

I propose a method for studying the product of bandwidths for the Harper-Hofstader model. This method requires knowledge of the moments of the midband energies. I conjectured a general formula for these moments. I computed the asymptotic representation for the product of bandwidths in the limit of a weak magnetic flux using Szego's theorem for Hankel matrices. I then give a first approximation for the edge of the butterfly spectrum and discuss its connection with P. Levy's formula for Brownian motion .

Lipan, O

2000-01-01

287

The Parameters affecting on Raman Gain and Bandwidth for Distributed Multi-Raman Amplifier  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to the benefits of Raman amplifier for Long-Haul UW-WDM Optical Communications Systems, we interest in this paper to investigate the parameters affecting on Raman gain and bandwidth, and also we are analyzed four and eight Raman pumping of special pump power and pumping wavelengths to show the effect of this parameters on gain and bandwidth. The model equations are numerically handled and processed via specially cast software (Matlab). The gain is computed over the spectral optical wavele...

Mustafa, Fathy M.; Khalaf, Ashraf A.; El-geldawy, F. A.

2012-01-01

288

Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber amplifiers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A theoretical analysis of the Raman amplification in optical fibers and the pump-to-signal relative intensity noise (RIN) transfer has been performed in the spectral domain. An efficient Raman amplification of a monochromatic signal beam by a large-bandwidth pump beam has been demonstrated for a pump bandwidth much smaller than the Raman linewidth. Under the same approximation the pump-to-signal RIN transfer has been calculated in both cases of copropagating and counterpropagating beams in th...

Kei?ta, Kafing; Delaye, Philippe; Frey, Robert; Roosen, Ge?rald

2006-01-01

289

Improving Accuracy in Available Bandwidth Estimation for 802.11-based Ad Hoc Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we propose an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks. This method is based on a mechanism to predict the synchronisation of ilde periods and an estimation of collision probability on wireless link. We evaluate our solution on different scenarios. We also provide a comparison with different QoS routing protocols, BRuIT, AAC and QoS-AODV, based on different available bandwidth estimation techniques.

Sarr, Cheikh; Chaudet, Claude; Chelius, Guillaume; Gue?rin Lassous, Isabelle

2006-01-01

290

Transmission Bandwidth Tunability of a Liquid-Filled Photonic Bandgap Fiber  

International Nuclear Information System (INIS)

A temperature tunable photonic bandgap fiber (PBGF) is demonstrated by an index-guiding photonic crystal fiber filled with high-index liquid. The temperature tunable characteristics of the fiber are experimentally and numerically investigated. Compression of transmission bandwidth of the PBGF is demonstrated by changing the temperature of part of the fiber. The tunable transmission bandwidth with a range of 250 nm is achieved by changing the temperature from 30°C to 90°C

2009-04-01

291

Ultrabroad-bandwidth electro-optic modulator based on a cascaded Bragg grating.  

Science.gov (United States)

It is shown that the bandwidth of a traveling-wave electro-optical modulator can be greatly increased by matching of the group velocities of the optical and rf waves in the waveguides with cascaded Bragg gratings. A LiNbO>(3) Mach-Zehnder modulator with 1-V half-wave voltage and a bandwidth in excess of 100 GHz is proposed and its performance evaluated. PMID:18059785

Khurgin, J B; Kang, J U; Ding, Y J

2000-01-01

292

Performance of PPM Multipath Synchronization in the Limit of Large Bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The acquisition, or synchronization, of the multipath profile for an ultrawideband pulse position modulation (PPM) communication systems is considered. Synchronization is critical for the proper operation of PPM based For the multipath channel, it is assumed that channel gains are known, but path delays are unknown. In the limit of large bandwidth, W, it is assumed that the number of paths, L, grows. The delay spread of the channel, M, is proportional to the bandwidth. The r...

Porrat, Dana; Mitra, Urbashi

2005-01-01

293

A plug-in rule for bandwidth selection in circular density estimation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new plug-in rule procedure for bandwidth selection in kernel circular density estimation is introduced. The performance of this proposal is checked throughout a simulation study considering a variety of circular distributions exhibiting multimodality, peakedness and/or skewness. The plug-in rule behaviour is also compared with other existing bandwidth selectors. The method is illustrated with two classical datasets of cross-beds layers and animal orientation.

Oliveira, M.; Crujeiras, R. M.; Rodri?guez-casal, A.

2012-01-01

294

The benefits of bimodal hearing: effect of frequency region and acoustic bandwidth.  

Science.gov (United States)

We examined the effects of acoustic bandwidth on bimodal benefit for speech recognition in adults with a cochlear implant (CI) in one ear and low-frequency acoustic hearing in the contralateral ear. The primary aims were to (1) replicate Zhang et al. [Ear Hear 2010;31:63-69] with a steeper filter roll-off to examine the low-pass bandwidth required to obtain bimodal benefit for speech recognition and expand results to include different signal-to-noise ratios (SNRs) and talker genders, (2) determine whether the bimodal benefit increased with acoustic low-pass bandwidth and (3) determine whether an equivalent bimodal benefit was obtained with acoustic signals of similar low-pass and pass band bandwidth, but different center frequencies. Speech recognition was assessed using words presented in quiet and sentences in noise (+10, +5 and 0 dB SNRs). Acoustic stimuli presented to the nonimplanted ear were filtered into the following bands: full, nonfiltered bandwidth). The primary findings were: (1) the minimum acoustic low-pass bandwidth that produced a significant bimodal benefit was meaning multiple frequency regions contain useful cues for bimodal benefit. Clinical implications are that (1) all aidable frequencies should be amplified in individuals with bimodal hearing, and (2) verification of audibility at 125 Hz is unnecessary unless it is the only aidable frequency. © 2014 S. Karger AG, Basel. PMID:24556850

Sheffield, Sterling W; Gifford, René H

2014-01-01

295

Bandwidth Enhancement of Antenna Arrays Utilizing Mutual Coupling between Antenna Elements  

Directory of Open Access Journals (Sweden)

Full Text Available The mutual coupling effect between antenna elements on an array's bandwidth is investigated using scattering parameters instead of the mutual impedance. First, an approximate expression is derived for matched voltage standing wave ratio (VSWR bandwidth of a tuned antenna, which reveals that the bandwidth is inversely proportional to the magnitude |?0'(?0| of the frequency derivative of the reflection coefficient. Next, considering linear antenna arrays with corporate feed as an example, closed-form expressions of the reflection coefficient are derived at the input port of the feeding network, which shows that the active reflection coefficient of an array is the linear superposition of elements' passive reflection coefficient S11 and the mutual coupling coefficient S12 from adjacent elements. The VSWR bandwidth expressions for an array imply that bandwidth enhancement of the overall array can be achieved when the element passive reflection coefficient S11 and mutual coupling S12 are cancelled, as well as the frequency derivatives S11' and S12' also cancel each other. Slot arrays and a two-element Vivaldi array are investigated to verify the validity of our theoretical analysis. Numerical and experimental results are presented to successfully demonstrate the bandwidth enhancement of antenna arrays utilizing mutual coupling effect.

Zhongxiang Shen

2010-01-01

296

Improved scheme for estimating T-CONT bandwidth demand in status reporting DBA for NG-PON  

Science.gov (United States)

A scheme for estimating T-CONT bandwidth demand within dynamic bandwidth allocation (DBA) for next-generation passive optical network (NG-PON) is proposed and evaluated. Estimating T-CONT bandwidth demand is considered as a main challenge in gigabit-capable passive optical network (GPON) DBA. The proposed minimum guaranteed T-CONT content (MGTC) scheme allows for a more conservative estimate of bandwidth demand. It is shown that at high load significant improvements in delay, jitter and bandwidth utilization can be achieved with the proposed scheme. For light loads the conventional scheme shows better delay performance. However, this may be overcome by controlled overgranting in the MGTC scheme.

Skubic, Björn; Chen, Biao; Chen, Jiajia; Ahmed, Jawwad; Wosinska, Lena

2009-11-01

297

Density estimation and adaptive bandwidths: A primer for public health practitioners  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Geographic information systems have advanced the ability to both visualize and analyze point data. While point-based maps can be aggregated to differing areal units and examined at varying resolutions, two problems arise 1 the modifiable areal unit problem and 2 any corresponding data must be available both at the scale of analysis and in the same geographic units. Kernel density estimation (KDE produces a smooth, continuous surface where each location in the study area is assigned a density value irrespective of arbitrary administrative boundaries. We review KDE, and introduce the technique of utilizing an adaptive bandwidth to address the underlying heterogeneous population distributions common in public health research. Results The density of occurrences should not be interpreted without knowledge of the underlying population distribution. When the effect of the background population is successfully accounted for, differences in point patterns in similar population areas are more discernible; it is generally these variations that are of most interest. A static bandwidth KDE does not distinguish the spatial extents of interesting areas, nor does it expose patterns above and beyond those due to geographic variations in the density of the underlying population. An adaptive bandwidth method uses background population data to calculate a kernel of varying size for each individual case. This limits the influence of a single case to a small spatial extent where the population density is high as the bandwidth is small. If the primary concern is distance, a static bandwidth is preferable because it may be better to define the "neighborhood" or exposure risk based on distance. If the primary concern is differences in exposure across the population, a bandwidth adapting to the population is preferred. Conclusions Kernel density estimation is a useful way to consider exposure at any point within a spatial frame, irrespective of administrative boundaries. Utilization of an adaptive bandwidth may be particularly useful in comparing two similarly populated areas when studying health disparities or other issues comparing populations in public health.

Tanski Susanne

2010-07-01

298

An impact excitation system for repeatable, high-bandwidth modal testing of miniature structures  

Science.gov (United States)

Miniature components and devices are increasingly seen in a myriad of applications. In general, the dynamic behavior of miniature devices is critical to their functionality and performance. However, modal testing of miniature structures poses many challenges. This paper presents a design and evaluation of an impact excitation system (IES) for repeatable, high-bandwidth, controlled-force modal testing of miniature structures. Furthermore, a dynamic model of the system is derived and experimentally validated to enable the identification of the system parameters that yield single-hit impacts with desired bandwidth and force magnitude. The system includes a small instrumented impact tip attached to a custom designed flexure-based body, an automated electromagnetic release mechanism, and various precision positioners. The excitation bandwidth and the impact force magnitude can be controlled by selecting the system parameters. The dynamic model of the system includes the structural dynamics of the flexure-based body, the electromagnetic force and the associated eddy-current damping, and the impact event. A validation study showed an excellent match between the model simulations and experiments in terms of impact force and bandwidth. The model is then used to create process maps that relate the system parameters to the number of hits (single vs. multiple), the impact force magnitudes and the excitation bandwidths. These process maps can be used to select system parameters or predict system response for a given set of parameters. A set of experiments is conducted to compare the performances of the IES and a (manual) miniature impact hammer. It is concluded that the IES significantly improves repeatability in terms of the impact bandwidth, location, and force magnitude, while providing a high excitation-bandwidth and excellent coherence values. The application of the IES is demonstrated through modal testing of a miniature contact-probe system.

Bediz, Bekir; Korkmaz, Emrullah; Burak Ozdoganlar, O.

2014-06-01

299

Design and fabrication of center frequency and bandwidth tunable HTS filter  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? We have developed a bandwidth and a center frequency tunable HTS filter. ? A tunable passband ratio of 1.8:1 was achieved. ? An 8% of center frequency tuning at 5 GHz was achieved. ? Adjustment of external quality factors improves the filter response after tuning. -- Abstract: We have developed a bandwidth and a center frequency tuning method for use in high-temperature superconducting microstrip filters. A pair of waveguide is placed between the resonators, and the bandwidth is adjusted by changing the switch states of the waveguides. Additional electrical pads are placed open ends of the resonators for tuning the center frequency. Pads are also placed around the input/output coupled-line elements to enable the external quality factors to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole tunable bandpass filter was fabricated by depositing YBa{sub 2}Cu{sub 3}O{sub 7} thin film on an MgO substrate and has a measured center frequency of 4.83 GHz and bandwidth of 121 MHz. Use of the waveguides to adjust the coupling coefficients, the electrical pads to adjust the effective lengths of the resonators and the pads to adjust the external quality factors resulted in 120-MHz bandwidth tuning and 400-MHz center frequency tuning without increased insertion loss.

Sekiya, N., E-mail: nsekiya@yamanashi.ac.jp [Department of Electrical Engineering, Yamanashi University, Kakio-Sekiya Laboratory, 4-3-11 Takeda, Kofu 400-8511 (Japan); Harada, H.; Kakio, S. [Department of Electrical Engineering, Yamanashi University, Kakio-Sekiya Laboratory, 4-3-11 Takeda, Kofu 400-8511 (Japan); Ohshima, S. [Yamagata University, 4-3-16 Johnan, Yonezawa 992-8510 (Japan)

2013-01-15

300

Studies of bandwidth dependence of laser plasma instabilities driven by the Nike laser  

Science.gov (United States)

Experiments at the Nike laser facility of the Naval Research Laboratory are exploring the influence of laser bandwidth on laser plasma instabilities (LPI) driven by a deep ultraviolet pump (248 nm) that incorporates beam smoothing by induced spatial incoherence (ISI). In early ISI studies with longer wavelength Nd:glass lasers (1054 nm and 527 nm),footnotetextObenschain, PRL 62(1989);Mostovych, PRL 62(1987);Peyser, Phys. Fluids B 3(1991). stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (??/?˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). The current studies will compare the emission signatures of LPI from planar CH targets during Nike operation at large bandwidth (??˜1THz) to observations for narrower bandwidth operation (??˜0.1-0.3THz). These studies will help clarify the relative importance of the short wavelength and wide bandwidth to the increased LPI intensity thresholds observed at Nike. New pulse shapes are being used to generate plasmas with larger electron density scale-lengths that are closer to conditions during pellet implosions for direct drive inertial confinement fusion.

Weaver, J.; Kehne, D.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Oh, J.; Lehmberg, R. H.; Brown, C. M.; Seely, J.; Feldman, U.

2012-10-01

 
 
 
 
301

Optimization of Inter-network Bandwidth Resources for Large-Scale Data Transmission  

Directory of Open Access Journals (Sweden)

Full Text Available In order to solve problems such as low resources utilization of data center backbone bandwidth and expensive daily expenses caused by the tidal effect in the transition of large-scale network data, the new optimization method of bandwidth resource for bulk data transfer is proposed. This method finishes the bulk data transfer by taking full advantage of the idle channel bandwidth. Firstly, the dynamic idle network bandwidth resource was switched into the static flow network; and then the max-min fair multi-commodity flow model is built on the basis of static network; finally, the iterative technique is used to solve the programming model for getting the maximum transport flows and the corresponding transmission path of bulk data transfer. The simulation method was used to test this optimization project. The results show that the optimization method proposed by the paper can significantly improve the utilization of data center backbone bandwidth resource, and the maximum amount of data transmission and the speed of data transfer have been obviously increased

Mu Zhang

2014-03-01

302

ENHANCEMENT OF BANDWIDTH OF RECTANGULAR PATCH ANTENNA USING TWO SQUARE SLOTS TECHNIQUES  

Directory of Open Access Journals (Sweden)

Full Text Available The research in wireless communication has spurred the development of extra ordinary range of antennas, each with its own advantage and limitations. There are many applications where space is at premium, and where there is an urgent need for an antenna with the flexibility to efficiently combine the capabilities of multiple antennas. In fact rapidly developing market in personal communication systems (PCS, mobile satellite communications, direct broadband television (DBS wireless local area networks (WLANs suggest that demand for Microstrip antennas and array will increase even further. Conventional Microstrip patch antennas has some drawbacks of low efficiency, narrow bandwidth (3-6% of the central frequency, its bandwidth is limited to a few percent which is not enough for most of the wireless communication systems nowadays. In this paper one of the efficient methods used for the enhancement of patch antenna bandwidth is the loading of rectangular microstrip patch antenna with two square slots across its side surface. This type of Microstrip patch antenna meets the requirement of operation for wireless applications. The proposed configuration is simulated and analyzed using GENESYS software package. The VSWR, input impedance‚ and S11 performance are used for the analysis of the different configurations. The simulated results for square slots antenna structure give bandwidth of 311 MHZ. Feed point on the patch that gives a good match of 50 ohm. The results of the fabricated microstrip antenna give the bandwidth of 286 MHz.

Patil V. P.

2012-10-01

303

Analysis of Design Optimization of Bandwidth and Loss Performance of Reflectarray Antennas Based on Material Properties  

Directory of Open Access Journals (Sweden)

Full Text Available An investigation for the enhancement strategy of bandwidth performance and analysis of different types of losses associated with reflectarray antennas is presented in this paper. Studies are carried out using different commercially available dielectric materials with dielectric permittivity (?r values ranging from 2.08 to 13 and loss tangent (tan? ranging from 0.0003 to 0.025. The performance of different dielectric materials for the design of infinite reflectarray is analyzed in terms of bandwidth, reflection loss and Figure of Merit (FOM. Bandwidths at different levels are observed and it has been noticed that 10% bandwidth varies from 84 MHz to 360MHz and 20% bandwidth varies from 126 MHz to 540MHz based on the selection of dielectric substrate for reflectarray antenna design. Moreover it has been demonstrated that the reflection loss of the reflectarray antenna can be factorized into dielectric loss and conductor loss which depends on the material properties used for the design. Detailed numerical analysis is carried out in order to verify the acquired results.

Muhammad Yusof Ismail

2009-12-01

304

High-bandwidth quantum memory protocol for storing single photons in rare-earth doped crystals  

International Nuclear Information System (INIS)

We present a detailed analysis of a high-bandwidth quantum memory protocol for storing single photons in a rare-earth-ion doped crystal. The basic idea is to benefit from a coherent free-induced decay type re-emission which occurs naturally when a photon with a broadband spectrum is absorbed by a narrow atomic transition in an optically dense ensemble. This allows for a high-bandwidth memory for realistic material parameters. Long storage time and on-demand readout are obtained by means of spin states in a lambda-type configuration, through the transfer of the optical coherence to a spin coherence (so-called spin-wave storage). We give explicit formulae and show numerical results which make it possible to gain insight into the dependence of the memory efficiency on the optical depth and on the width and the shape of stored photons. We present a feasibility study in rare-earth doped crystals and show that high efficiencies and high bandwidth can be obtained with realistic parameters. High-bandwidth memories using spin-wave storage offers the possibility of very high time-bandwidth products, which is important for experiments where high repetition rates are needed. (paper)

2013-09-01

305

On NoC Bandwidth Sharing for the Optimization of Area Cost and Test Application Time  

Science.gov (United States)

Current NoC test scheduling methodologies in the literature are based on a dedicated path approach; a physical path through the NoC routers and interconnects are allocated for the transportation of test data from an external tester to a single core during the whole duration of the core test. This approach unnecessarily limits test concurrency of the embedded cores because a physical channel bandwidth is typically larger than the scan rate of any core-under-test. We are proposing a bandwidth sharing approach that divides the physical channel bandwidth into multiple smaller virtual channel bandwidths. The test scheduling is performed under the objective of co-optimizing the wrapper area cost and the resulting test application time using two complementary NoC wrappers. Experimental results showed that the area overhead can be optimized (to an extent) without compromising the test application time. Compared to other NoC scheduling approaches based on dedicated paths, our bandwidth sharing approach can reduce the test application time by up to 75.4%.

Hussin, Fawnizu Azmadi; Yoneda, Tomokazu; Fujiwara, Hideo

306

GBAS: Generalized Bandwidth Adaptation System for Enhancing Multimedia Transmission Over Multi-Cell Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Nowadays, multimedia Quality of Services (QoS is considered a very important research issue. In cellular infrastructure wireless networks, a user can move from one cell to another. Hence; a large number of handoff events may occur during a typical session. In case of running multimedia applications with a limited bandwidth, new, handoff, and waiting calls may be dropped. This paper proposes enhancements for the Generalized Bandwidth Adaptation System which is used for multimedia transmission over multi-cell wireless networks and demonstrated by the author in a previous work. Our proposed extended system monitors the multimedia sessions to create the new bandwidth values in case of significant changes or calls starvation. The enhancement criteria are done over three interlocutors. The first one is to add some new features such as distance between cells, waiting calls, starved calls bandwidth considerations and call prioritization technique. The second one is to recover some drawbacks such as huge number of management messages. The third one is to make some old issues more scalable such as normal degree division to be multi-values and starting with minimum degree bandwidth. Also, statistical analysis for the enhanced version is demonstrated. Furthermore, a simulation environment to test our proposed system is constructed. Finally, comparing these results with the old trials results is demonstrated to make sure that our proposed system enhances other old trials.

Omar Said

2012-05-01

307

Non-stationary 1D Thin Bed Model for Non-stationary Frequency Bandwidth Expansion Algorithms  

Directory of Open Access Journals (Sweden)

Full Text Available Seismic resolution has always been a quest of a geophysicist to obtain detailed structural and stratigraphic information from the seismic data. New algorithm developed for frequency bandwidth expansion are usually tested on stationary thin bed models before their implementation on real seismic data. These models are created by using the Ricker or Rayleigh criterion. But seismic wavelet is non-stationary, which changes its shape, amplitude and frequency contents as the wave propagates subsurface. A new technique is presented in this paper to create non-stationary thin bed model where the frequency bandwidth of the seismic wavelet decreases smoothly. The study describes the comprehensive mathematical formulation of new technique and testing of new bandwidth expansion algorithms like Differential Resolution and Short Time Fourier Transform Half Cepstrum for their effectiveness for non-stationary and stationary thin bed models.

M. Sajid

2014-01-01

308

Power-Bandwidth Tradeoff in Dense Multi-Antenna Relay Networks  

CERN Document Server

We consider a dense fading multi-user network with multiple active multi-antenna source-destination pair terminals communicating simultaneously through a large common set of $K$ multi-antenna relay terminals in the full spatial multiplexing mode. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the power- bandwidth tradeoff) in meaningful asymptotic regimes of signal-to-noise ratio (SNR) and network size. We design linear distributed multi-antenna relay beamforming (LDMRB) schemes that exploit the spatial signature of multi-user interference and characterize their power-bandwidth tradeoff under a system wide power constraint on source and relay transmissions. The impact of multiple users, multiple relays and multiple antennas on the key performance measures of the high and low SNR regimes is investigated in order to shed new light on the possible reduction in power and bandwidth requirements through the usage of such practical relay cooperation...

Oyman, Ozgur

2007-01-01

309

Magnetic properties of the two-band Hubbard model with different bandwidths  

Energy Technology Data Exchange (ETDEWEB)

We investigate magnetic properties of the two-band Hubbard model with different bandwidths. By means of dynamical mean-field theory combined with the hybridization expansion continuous time quantum Monte Carlo method, we discuss how the difference in the bandwidths affects the magnetism at low temperatures. It is found that the nature of the magnetic phase transition is not affected by the difference in the bandwidths at half filling and thus a single phase transition occurs at the same critical temperature. By contrast, the introduction of holes induces an orbital-selective insulator-metal transition. The characteristic properties of the intermediate phase with one orbital localized and the other itinerant are also discussed.

Koyama, Yohta, E-mail: yohta@scphys.kyoto-u.ac.j [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Koga, Akihisa; Kawakami, Norio [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Werner, Philipp [Columbia University, 538 West, 120th Street, New York, NY 10027 (United States)

2009-10-15

310

BECPA : Bandwidth Efficient Cluster Based Packet Aggregation in Wireless Sensor Network  

DEFF Research Database (Denmark)

In recent years, energy consumption and data gathering is a foremost concern in many applications of wireless sensor networks (WSN). The major issue in WSN is effective utilization of the resource as energy and bandwidth with a large gathering of data from the monitoring and control applications. This paper proposes novel bandwidth efficient cluster based packet aggregation algorithm (BECPA) for heterogeneous WSN. It combines the idea of variable packet generation rate of each node with random data. The nodes are randomly distributed with different energy level with equal in numbers. It uses the perfectly compressible aggregation function at cluster head based on the correlation of packets and data generated by nodes. The aggregation functions prevent transmission of redundant packets. Compare to state-of-the-art solutions, the algorithm shows significant energy saving by reducing the number of packets at the sink with better bandwidth utilization in packet aggregation than data aggregation.

Dnyaneshwar, Mantri; Prasad, Neeli R.

2013-01-01

311

Amplifying modeling for broad bandwidth pulse in Nd:glass based on hybrid-broaden mechanism  

International Nuclear Information System (INIS)

In this paper, the cross relaxation time is proposed to combine the homogeneous and inhomogeneous broaden mechanism for broad bandwidth pulse amplification model. The corresponding velocity equation, which can describe the response of inverse population on upper and low energy level of gain media to different frequency of pulse, is also put forward. The gain saturation and energy relaxation effect are also included in the velocity equation. Code named CPAP has been developed to simulate the amplifying process of broad bandwidth pulse in multi-pass laser system. The amplifying capability of multi-pass laser system is evaluated and gain narrowing and temporal shape distortion are also investigated when bandwidth of pulse and cross relaxation time of gain media are different. Results can benefit the design of high-energy PW laser system in LFRC, CAEP

2008-05-01

312

A Distributed Cluster Scheme For Bandwidth Management In Multi-hop MANETs  

CERN Document Server

Electronic collaboration among devices in a geographically localized environment is made possible with the implementation of IEEE 802.11 based wireless ad hoc networks. Dynamic nature of mobile ad hoc networks(MANETs) may lead to unpredictable intervention of attacks or fault occurrence, which consequently may partition the network, degrade its performance, violate the QoS requirements and most importantly, affect bandwidth allocation to mobile nodes in the network. In this paper, we propose a new distributed cluster scheme for MANETs, especially in harsh environments, based on the concept of survivability to support QoS requirements and to protect bandwidth efficiently. With the incorporation of clustering algorithms in survivability technology, we employ a simple network configuration and expect to reduce occurrences of faults in MANETs. At the same time, we address the scalability problem, which represents a great challenge to network configuration. We do expect a simplification of accessing bandwidth allo...

Pattanayak, Binod Kumar; Mishra, Manoj Kumar; Nayak, Manoj Ranjan

2010-01-01

313

Bandwidth-enhanced polarization-insensitive microwave metamaterial absorber and its equivalent circuit model  

Science.gov (United States)

In this paper, a bandwidth-enhanced polarization-insensitive ultra-thin metamaterial absorber has been presented. A simple equivalent circuit model has been proposed describing the absorption phenomenon to estimate the frequency of absorption of the proposed microwave absorber. The basic structure consists of concentric rings embedded one inside another to enhance bandwidth by incorporating the scalability property of the metamaterials. Simulation results show that the structure has enhanced bandwidth response with full width at half maxima (FWHM) of 1.15 GHz (9.40-10.55 GHz) with two absorption peaks at 9.66 and 10.26 GHz (96% and 92.5% absorptivity, respectively). The structure is symmetric in design giving rise to polarization-insensitivity and can achieve high absorption for oblique incidence up to 40°. The proposed absorber has been fabricated and measured in anechoic chamber, showing that experimental results agree well with the simulated responses.

Ghosh, Saptarshi; Bhattacharyya, Somak; Kaiprath, Yadunath; Vaibhav Srivastava, Kumar

2014-03-01

314

Sequential Data-Adaptive Bandwidth Selection by Cross-Validation for Nonparametric Prediction  

CERN Multimedia

We consider the problem of bandwidth selection by cross-validation from a sequential point of view in a nonparametric regression model. Having in mind that in applications one often aims at estimation, prediction and change detection simultaneously, we investigate that approach for sequential kernel smoothers in order to base these tasks on a single statistic. We provide uniform weak laws of large numbers and weak consistency results for the cross-validated bandwidth. Extensions to weakly dependent error terms are discussed as well. The errors may be {\\alpha}-mixing or L2-near epoch dependent, which guarantees that the uniform convergence of the cross validation sum and the consistency of the cross-validated bandwidth hold true for a large class of time series. The method is illustrated by analyzing photovoltaic data.

Steland, Ansgar

2010-01-01

315

Performance analysis of bandwidth limited coherent time spreading OCDMA system employing DPSK format and turbo code  

Science.gov (United States)

Differential phase shift keying (DPSK) data format is employed to combat noise in the bandwidth limited coherent time spreading (TS) optical code division multiplexing access (OCDMA) system. In addition, the performance of DPSK-OCDMA system with turbo coding is analysed and simulated. Theoretical results show that performance degradation due to bandwidth limitation could be effectively restrained by the DPSK-OCDMA scheme, and further performance improvement could be achieved by incorporating turbo coding into OCDMA system. It is confirmed that the number of active users is increased from K = 11 to K = 25 in bandwidth limited OCDMA system by employing DPSK format and turbo code for a given BER of 10-6.

Chen, Xiaogang; Yuan, Xiuhua

2008-11-01

316

Bandwidth Enhancement of UWB Microstrip Antenna with a Modified Ground Plane  

Directory of Open Access Journals (Sweden)

Full Text Available This article presents a bandwidth enhancing technique using a modified ground plane with diagonal edges, rectangular slot, and T-shape cut for the design of compact antennas. The proposed low-cost, compact-size circular patch antenna on 3?cm × 5.1?cm printed circuit board (FR-4 is designed and validated through simulations and experiments. Results show that the T-shaped ground plane with the presence of the diagonal cuts at the top corners and the rectangular slots can increase the bandwidth. Return losses of ?19 and ?26?dB for the first and second resonant frequencies, respectively, can be achieved when the depth of the diagonal cut is 5?mm, the dimension of each rectangular slot is 5×3?mm, and the T-shaped size is 8×4?mm, providing a 28.67% wider bandwidth than FCC standard.

N. Prombutr

2009-01-01

317

Design and Simulation of Microstrip E-shaped Patch Antenna for Improved Bandwidth and Directive Gain  

Directory of Open Access Journals (Sweden)

Full Text Available Despite the many advantages of microstrip patch antennas, they do have some considerable drawbacks. One of the main limitations with patch antennas is their inherently narrowband performance due to its resonant nature. With bandwidth as low as a few percent; broadband applications using conventional patch designs are limited. So for the antenna miniaturization and bandwidth improvement E-shaped microstrip patch antenna used. In this paper, authors cover two aspects of microstrip antenna designs. The first is the analysis of single element narrowband rectangular microstrip antenna which operates at the central frequency of 6.5GHz. The second aspect is the analysis and design of slot cut E-shaped microstrip antenna. The simulation process has been done through high frequency structure simulator (HFSS. The properties of antenna such as bandwidth, return loss, VSWR has been investigated and compared between a single element rectangular and E-shaped microstrip antenna.

Prof. Jaikaran Singh

2014-03-01

318

Density of states of the lowest exciton band and the exciton bandwidth in coronene single crystals  

International Nuclear Information System (INIS)

The thermo-absorption spectra of coronene single crystals were investigated over the temperature range between 193 and 287 K. The density of states and the exciton bandwidth of the lowest exciton band were obtained from the thermo-absorption spectra for the 0-1 absorption band region. The density of states function of the lowest exciton band, we observed in coronene has double peaks, as is expected for the one-dimensional model. The peak-to-peak energy separation gives the exciton a bandwidth of 490 cm-1. The bandwidth obtained (490 cm-1) is larger compared with the magnitude 370 cm-1 reported for coronene at 10 K. This difference can be explained in terms of the structural phase change that occurs at 140-180 K

2005-04-01

319

Density of states of the lowest exciton band and the exciton bandwidth in coronene single crystals  

Energy Technology Data Exchange (ETDEWEB)

The thermo-absorption spectra of coronene single crystals were investigated over the temperature range between 193 and 287 K. The density of states and the exciton bandwidth of the lowest exciton band were obtained from the thermo-absorption spectra for the 0-1 absorption band region. The density of states function of the lowest exciton band, we observed in coronene has double peaks, as is expected for the one-dimensional model. The peak-to-peak energy separation gives the exciton a bandwidth of 490 cm{sup -1}. The bandwidth obtained (490 cm{sup -1}) is larger compared with the magnitude 370 cm{sup -1} reported for coronene at 10 K. This difference can be explained in terms of the structural phase change that occurs at 140-180 K.

Totoki, R. [Department of Physics, Konan University, Okamoto, Kobe 658-8501 (Japan); Aoki-Matsumoto, T. [Department of Physics, Konan University, Okamoto, Kobe 658-8501 (Japan); Mizuno, K. [Department of Physics, Konan University, Okamoto, Kobe 658-8501 (Japan)]. E-mail: mizuno@konan-u.ac.jp

2005-04-15

320

Bandwidth-adjustable dynamic grating in erbium-doped fiber by synthesis of optical coherence function.  

Science.gov (United States)

We present an approach for bandwidth-adjustable optical filter with the dynamic grating in erbium-doped fiber (EDF). The dynamic grating is introduced by the interference of two coherent light beams counter-propagating in the pumped EDF per the phenomenon of gain saturation. The bandwidth of the grating is determined by the length of the grating, i.e., the length of the interference region. With the technique of synthesis of optical coherence function (SOCF), we localize the interference into a range at an arbitrary position along the fiber by modulating the frequency of the two interfering light beams. The length of the range is controlled by adjusting the frequency modulation parameter. In this way, the length of the dynamic grating is controlled and its reflection bandwidth then adjusted. The experimental demonstration is given. PMID:19498578

Fan, Xinyu; He, Zuyuan; Mizuno, Yosuke; Hotate, Kazuo

2005-07-25

 
 
 
 
321

Near-perfect absorber with ultrawide bandwidth in infrared region using a periodically chirped structure  

Science.gov (United States)

We propose a near-perfect absorber with ultrawide bandwidth in infrared region using a periodically chirped subwavelength structure implemented in both one-dimensional (1D) and two-dimensional (2D) schemes. The structure is composed of an array of chirped metal-insulator-metal resonators made of a metal/dielectric two-layer grating sitting on a uniform metal layer. Each resonator harvests the photon via the SPP localization at its own resonance wavelength which exhibits linear distribution due to the linearly chirped structure. A near-perfect absorption in wide bandwidth is realized with an appropriate design under the restriction of phase-matching and subwavelength dimension. A stop-band with a FWHM of 3 ?m at central wavelength of ˜9 ?m and a high absorption efficiency of up to 92% is achieved simultaneously. This provides a novel method in designing and implementing flexible thin-film devices with wide bandwidth and high absorption efficiency.

Song, Yanqin; Wang, Chinhua; Lou, Yimin; Cao, Bing; Li, Xiaofeng

2013-09-01

322

A high-bandwidth amplitude estimation technique for dynamic mode atomic force microscopy  

International Nuclear Information System (INIS)

While often overlooked, one of the prerequisites for high-speed amplitude modulation atomic force microscopy is a high-bandwidth amplitude estimation technique. Conventional techniques, such as RMS to DC conversion and the lock-in amplifier, have proven useful, but offer limited measurement bandwidth and are not suitable for high-speed imaging. Several groups have developed techniques, but many of these are either difficult to implement or lack robustness. In this contribution, we briefly outline existing amplitude estimation methods and propose a new high-bandwidth estimation technique, inspired by techniques employed in microwave and RF circuit design, which utilizes phase cancellation to significantly improve the performance of the lock-in amplifier. We conclude with the design and implementation of a custom circuit to experimentally demonstrate the improvements and discuss its application in high-speed and multifrequency atomic force microscopy

2014-02-01

323

Comparison of Available Bandwidth Estimation Techniques in Packet-Switched Mobile Networks  

DEFF Research Database (Denmark)

The relative contribution of the transport network towards the per-user capacity in mobile telecommunication systems is becoming very important due to the ever increasing air-interface data rates. Thus, resource management procedures such as admission, load and handover control can make use of information regarding the available bandwidth in the transport network, as it could end up being the bottleneck rather than the air interface. This paper provides a comparative study of three well known available bandwidth estimation techniques, i.e. TOPP, SLoPS and pathChirp, taking into account the statistical conditions of the available bandwidth and assessing the variability of their estimations. Simulation-based studies on a mobile transport network show that pathChirp outperforms TOPP and SLoPS, both in terms of accuracy and efficiency.

López Villa, Dimas; Ubeda Castellanos, Carlos

2006-01-01

324

Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers.  

Science.gov (United States)

Capacitive micromachined ultrasonic transducers (cMUT) have large bandwidths, but they typically have low conversion efficiencies. This paper defines a performance measure in the form of a gain-bandwidth product and investigates the conditions in which this performance measure is maximized. A Mason model corrected with finite-element simulations is used for the purpose of optimizing parameters. There are different performance measures for transducers operating in transmit, receive, or pulse-echo modes. Basic parameters of the transducer are optimized for those operating modes. Optimized values for a cMUT with silicon nitride membrane and immersed in water are given. The effect of including an electrical matching network is considered. In particular, the effect of a shunt inductor in the gain-bandwidth product is investigated. Design tools are introduced, which are used to determine optimal dimensions of cMUTs with the specified frequency or gain response. PMID:16463487

Olcum, Selim; Senlik, Muhammed N; Atalar, Abdullah

2005-12-01

325

Local intelligent electronic device (IED) rendering templates over limited bandwidth communication link to manage remote IED  

Science.gov (United States)

The present disclosure provides systems and methods for remote device management. According to various embodiments, a local intelligent electronic device (IED) may be in communication with a remote IED via a limited bandwidth communication link, such as a serial link. The limited bandwidth communication link may not support traditional remote management interfaces. According to one embodiment, a local IED may present an operator with a management interface for a remote IED by rendering locally stored templates. The local IED may render the locally stored templates using sparse data obtained from the remote IED. According to various embodiments, the management interface may be a web client interface and/or an HTML interface. The bandwidth required to present a remote management interface may be significantly reduced by rendering locally stored templates rather than requesting an entire management interface from the remote IED. According to various embodiments, an IED may comprise an encryption transceiver.

Bradetich, Ryan; Dearien, Jason A; Grussling, Barry Jakob; Remaley, Gavin

2013-11-05

326

Wide-bandwidth and high-power InGaAsP distributed feedback lasers  

Energy Technology Data Exchange (ETDEWEB)

The fabrication and performance characteristics of a wide-bandwidth InGaAsP laser diode structure are described. The wide bandwidth is achieved using semi-insulating Fe-doped InP current blocking layers around the active region. The lasers have a bandwidth of 18 GHz at 20 mW, emit 50 mW in a single transverse and longitudinal mode, have rise and fall times of less than 40 ps, have low chirp (FWHM{lt}1 A) under modulation, and exhibit harmonic distortion characteristics in agreement with fundamental calculations using a rate equation model. Error-free transmission with no dispersion penalty has been obtained using these lasers in a transmission experiment at 8 Gb/s over 76 km of fiber.

Dutta, N.K.; Wang, S.J.; Piccirilli, A.B.; Karlicek, R.F. Jr.; Brown, R.L.; Washington, M.; Chakrabarti, U.K. (AT T Bell Laboratories, Murray Hill, New Jersey 07974 (USA)); Gnauck, A. (AT T Bell Laboratories, Crawford Hill, New Jersey 07733 (USA))

1989-11-15

327

Narrow Bandwidth 850-nm Fiber Bragg Gratings in Few-Mode Polymer Optical Fibers  

DEFF Research Database (Denmark)

We report on the inscription and characterization of narrow bandwidth fiber Bragg gratings (FBGs) with 850-nm resonance wavelength in polymer optical fibers (POFs). We use two fibers: an in-house fabricated microstructured POF (mPOF) with relative hole size of 0.5 and a commercial step-index POF, which supports six modes at 850 nm. The gratings have been written with the phase-mask technique and a 325-nm HeCd laser. The mPOF grating has a full-width at half-maximum (FWHM) bandwidth of 0.29 nm and the step-index POF has a bandwidth of 0.17 nm. For both fibers, the static tensile strain sensitivity is measured to be 0.71 pm/$muvarepsilon$ at 850 nm and 1.3 pm/$muvarepsilon$ at 1550 nm.

Stefani, Alessio; Yuan, Wu

2011-01-01

328

Composite-CMOS integrated photonics for high bandwidth WDM optical interconnects  

Science.gov (United States)

Bandwidth requirements continue to drive the need for low-power, high speed interconnects. Harnessing the mature CMOS technology for high volume manufacturing, Silicon Photonics is a top candidate for providing a viable solution for high bandwidth, low cost, low power, and high packing density, optical interconnects. The major drawback of silicon, however, is that it is an indirect bandgap material, and thus cannot produce coherent light. Consequently, different integration schemes of III/V materials on silicon are being explored. An integrated CMOS tunable laser is demonstrated as part of a composite-CMOS integration platform that enables high bandwidth optical interconnects. The integration platform embeds III-V into silicon chips using a metal bonding technique that provides low thermal resistance and avoids lattice mismatch problems. The performance of the laser including side mode suppression ratio, relative intensity noise, and linewidth is summarized.

Creazzo, Timothy; Marchena, Elton; Krasulick, Stephen B.; Yu, Paul K. L.; Van Orden, Derek; Spann, John Y.; Blivin, Christopher C.; He, Lina; Cai, Hong; Dallesasse, John M.; Stone, Robert J.; Mizrahi, Amit

2014-03-01

329

Estimating individual listenersâ?? auditory-filter bandwidth in simultaneous and non-simultaneous masking  

DEFF Research Database (Denmark)

Frequency selectivity in the human auditory system is often measured using simultaneous masking of tones presented in notched noise. Based on such masking data, the equivalent rectangular bandwidth (ERB) of the auditory filters can be derived by applying the power spectrum model of masking and assuming a rounded-exponential filter shape. If a forward masking paradigm is used instead of simultaneous masking, filter estimates typically show significantly sharper tuning. This difference in frequency selectivity has commonly been related to spectral suppression mechanisms observed in the cochlea. Considering bandwidth estimates from previous studies based on forward masking, only average data across a number of subjects have been considered. The present study is concerned with bandwidth estimates in simultaneous and forward masking in individual normal-hearing subjects. In order to investigate the reliability of the individual estimates, a statistical resampling method is applied. It is demonstrated that a ratherlarge set of experimental data is required to reliably estimate auditory filter bandwidth, particularly in the case of simultaneous masking. The poor overall reliability of the filter estimates was found to be mainly related to the very short tone duration (i.e., 10 ms) that was chosen. Applying 300-ms long tones in simultaneous masking drastically improved the reliability of the filter estimates. The tone duration in forward masking had to be very short to elicit a sufficient amount of masking. Based on extensive data for three subjects, the difference between forward and simultaneous masking es-timates of auditory filter bandwidth was found to be even larger than previously reported, with a bandwidth decrease by a factor of about 1.8 rather than 1.4. The results of the study can be used to optimize the measures of frequency selectivity which is particularly useful when studying consequences of (individual) hearing impairment.

Buchholz, Jörg; Strelcyk, Olaf

2010-01-01

330

An efficient Bandwidth Demand Estimation for Delay Reduction in IEEE 802.16j MMR WiMAX Networks  

Directory of Open Access Journals (Sweden)

Full Text Available IEEE 802.16j MMR WiMAX networks allow the number of hops between the user andthe MMR-BS to be more than two hops. The standard bandwidth request procedure inWiMAX network introduces much delay to the user data and acknowledgement of theTCP packet that affects the performance and throughput of the network. In this paper,we propose a new scheduling scheme to reduce the bandwidth request delay in MMRnetworks. In this scheme, the MMR-BS allocates bandwidth to its direct subordinate RSswithout bandwidth request using Grey prediction algorithm to estimate the requiredbandwidth of each of its subordinate RS. Using this architecture, the access RS canallocate its subordinate MSs the required bandwidth without notification to the MMR-BS.Our scheduling architecture with efficient bandwidth demand estimation able to reducedelay significantly.

Fath Elrahman Ismael

2010-01-01

331

Confidentiality & Authentication Mechanism for Biometric Information Transmitted over Low Bandwidth & Unreliable channel  

CERN Document Server

The security of bio-metric information - finger print, retina mapping, DNA mapping and some other chemical and biological modified genes related information - transfer through low bandwidth and unreliable or covert channel is challenging task. Therefore, Security of biometric information is essential requirement in this fast developing communication world. Thus, in this paper, we propose efficient and effective mechanism for confidentiality and authentication for biometric information transmitted by using arithmetic encoding representation over low bandwidth and unreliable channel. It enhances the speed of encryption, decryption and authentication process. It uses arithmetic encoding scheme and public key cryptography e.g. modified version of RSA algorithm called RSA-2 algorithm.

Singh, Raju

2011-01-01

332

Photon Number Statistics in Resonance Fluorescence with Excitation of Finite Bandwidth  

Science.gov (United States)

Exact closed form expressions are derived for the photon number distribution functions and the factorial moments in resonance fluorescence from a two-level atom that is driven on or near resonance by a laser beam of finite bandwidth. Derivation procedure that was used by Lenstra in the theory of photon number statistics for limited cases is applied to our generalized problem with help of the theory of resonance fluorescence with excitation of finite bandwidth. All of the results are presented in a fully suitable form for practical analyses of statistical features of resonance fluorescence.

Kaminishi, Katsuji

1984-03-01

333

Why is the bandwidth of sodium observed to be narrower in photoemission experiments?  

CERN Document Server

The experimentally predicted narrowing in the bandwidth of sodium is interpreted in terms of the non-local self-energy effect on quasi-particle energies of the electron liquid. The calculated self-energy correction is a monotonically increasing function of the wavenumber variable. The usual analysis of photo-emission experiments assumes the final state energies on the nearly-free-electron-like model and hence it incorrectly ascribes the non-local self-energy correction to the final state energies to the occupied state energies, thus leading to a seeming narrowing in the bandwidth.

Yasuhara, H; Higuchi, M

1999-01-01

334

Increased pump acceptance bandwidth in spontaneous parametric downconversion process using Bragg reflection waveguides  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we show that by suitably tailoring the dispersion characteristics of a Bragg reflection waveguide (BRW) mode, it is possible to achieve efficient photon pair generation over a large pump bandwidth while maintaining narrow signal bandwidth. The structure proposed consists of a high index core BRW with a periodically poled GaN core and periodically stratified cladding made up of alternate layers of Al0.02Ga0.98N and Al0.45Ga0.55N. Such photon-pair generators should find applicatio...

Thyagarajan, Krishna; Das, Ritwick; Alibart, Olivier; Micheli, Marc; Ostrowsky, Daniel Barry; Tanzilli, Se?bastien

2008-01-01

335

A high-speed, wide-bandwidth, amplification and peak-holding circuit  

International Nuclear Information System (INIS)

A high-speed, wide-bandwidth, amplification and peak-holding circuit is introduced briefly in this paper. This circuit was developed for beam position monitor electronics, it is a key front-end device of the system. It consists of amplifying circuit and peak-holding circuit. It can be used to amplify small, fast voltage signals. In order to keep phase excursion as low as possible, dc coupling mode was adopted to construct the amplifying circuit. Moreover, the authors take differential amplifier and low-pass filter to restrain the dc excursion. Bandwidth of the circuit is ?70 MHz, gains?700. (authors)

2006-07-01

336

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth  

CERN Document Server

We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135$^\\circ$ phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wide variety of applications requiring precision control of optical lengths, including laser frequency stabilization, optical interferometers, and optical communications.

Briles, Travis C; Cingoz, Arman; Schibli, Thomas; Ye, Jun

2010-01-01

337

Simple piezoelectric-actuated mirror with 180 kHz servo bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a high bandwidth piezoelectric-actuated mirror for length stabilization of an optical cavity. The actuator displays a transfer function with a flat amplitude response and greater than 135$^\\circ$ phase margin up to 200 kHz, allowing a 180 kHz unity gain frequency to be achieved in a closed servo loop. To the best of our knowledge, this actuator has achieved the largest servo bandwidth for a piezoelectric transducer (PZT). The actuator should be very useful in a wi...

Briles, Travis C.; Yost, Dylan C.; Cingoz, Arman; Schibli, Thomas; Ye, Jun

2010-01-01

338

Efficient Bandwidth Allocation for Integrated Services in Broadband Wireless ATM Networks  

DEFF Research Database (Denmark)

An efficient bandwidth allocation scheme is proposed for supporting intergrated services in wireless ATM networks. These include CBR, VBR amd ABR types of traffic. The proposed scheme is based om A-PRMA for carrying ATM traffic in a dynamic TDMA type access system. It allows mobile users to adjust the reserved bandwidth according to their current demands and the wireless channel status. Extensive simulation results show that the proposed scheme can provide QoS guarantees with low cell transfer delay, high channel utilization (more than 70 %) and short buffer length requirements.

Liu, Hong; Dittmann, Lars

1999-01-01

339

Bandwidth Impacts of Localizing Peer-to-Peer IP Video Traffic in Access and Aggregation Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper examines the burgeoning impact of peer-to-peer (P2P) traffic IP video traffic. High-quality IPTV or Internet TV has high-bandwidth requirements, and P2P IP video could severely strain broadband networks. A model for the popularity of video titles is given, showing that some titles are very popular and will often be available locally; making localized P2P attractive for video titles. The bandwidth impacts of localizing P2P video to try and keep traffic within a broadband access netw...

2008-01-01

340

Confidentiality & Authentication Mechanism for Biometric Information Transmitted over Low Bandwidth & Unreliable channel  

Directory of Open Access Journals (Sweden)

Full Text Available The security of bio-metric information – finger print, retina mapping, DNA mapping and some otherchemical and biological modified genes related information - transfer through low bandwidth andunreliable or covert channel is challenging task. Therefore, Security of biometric information is essentialrequirement in this fast developing communication world. Thus, in this paper, we propose efficient andeffective mechanism for confidentiality and authentication for biometric information transmitted by usingarithmetic encoding representation over low bandwidth and unreliable channel. It enhances the speed ofencryption, decryption and authentication process. It uses arithmetic encoding scheme and public keycryptography e.g. modified version of RSA algorithm called RSA-2 algorithm.

Raju Singh

2011-03-01

 
 
 
 
341

Bandwidth Optimization Design of a Multi Degree of Freedom MEMS Gyroscope  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new robust multi-degree of freedom (multi-DOF) MEMS gyroscope is presented in this paper. The designed gyroscope has its bandwidth and amplification factor of the sense mode adjusted more easily than the previous reported multi-DOF MEMS gyroscopes. Besides, a novel spring system with very small coupling stiffness is proposed, which helps achieve a narrow bandwidth and a high amplification factor for a 2-DOF vibration system. A multi-DOF gyroscope with the proposed weak spring system is desi...

Chaowei Si; Guowei Han; Jin Ning; Fuhua Yang

2013-01-01

342

A Scheduling Discipline for Latency and Bandwidth Guarantees in Asynchronous Network-on-Chip  

DEFF Research Database (Denmark)

Guaranteed services (GS) are important in that they provide predictability in the complex dynamics of shared communication structures. This paper discusses the implementation of GS in asynchronous Network-on-Chip. We present a novel scheduling discipline called Asynchronous Latency Guarantee (ALG) scheduling, which provides latency and bandwidth guarantees in accessing a shared media, e.g. a physical link shared between a number of virtual channels. ALG overcomes the drawbacks of existing scheduling disciplines, in particular the coupling between latency and bandwidth guarantees. A 0.12 &956;m CMOS standard cell implementation of an ALG link has been simulated. The operation speed of the design was 702 MDI/s.

Bjerregaard, Tobias; Sparsø, Jens

2005-01-01

343

Gain bandwidth characterization of surface-emitting quantum well laser gain structures for femtosecond operation.  

Science.gov (United States)

We present a method to experimentally characterize the gain filter and calculate a corresponding parabolic gain bandwidth of lasers that are described by "class A" dynamics by solving the master equation of spectral condensation for Gaussian spectra. We experimentally determine the gain filter, with an equivalent parabolic gain bandwidth of up to 51 nm, for broad-band InGaAs/GaAs quantum well gain surface-emitting semiconductor laser structures capable of producing pulses down to 60 fs width when mode-locked with an optical Stark saturable absorber mirror. PMID:20941029

Barnes, M E; Mihoubi, Z; Wilcox, K G; Quarterman, A H; Farrer, I; Ritchie, D A; Garnache, A; Hoogland, S; Apostolopoulos, V; Tropper, A C

2010-09-27

344

Absorption line shape recovery beyond the detection bandwidth limit: application to the Boltzmann constant determination  

CERN Document Server

A theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate line parameters. The theoretical model is validated by experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy. Particular emphasis is put on the detection bandwidth adjustments required to perform a spectroscopic determination of the Boltzmann constant at the 1 ppm level of accuracy.

Rohart, François; Sow, Papa Lat Tabara; Tokunaga, Sean K; Chardonnet, Christian; Darquié, Benoît; Dinesan, H; Fasci, E; Castrillo, A; Gianfrani, L; Daussy, Christophe

2014-01-01

345

Bandwidth and wavelength-tunable optical bandpass filter based on silicon microring-MZI structure  

DEFF Research Database (Denmark)

A novel and simple bandwidth and wavelength-tunable optical bandpass filter based on silicon microrings in a Mach-Zehnder interferometer (MZI) structure is proposed and demonstrated. In this filter design, the drop transmissions of two microring resonators are combined to provide the desired tunability. A detailed analysis and the design of the device are presented. The shape factor and extinction ratio of the filter are optimized by thermally controlling the phase difference between the two arms of the MZI. Simultaneous bandwidth and wavelength tunability with in-band ripple control is demonstrated by thermally tuning the resonance offset between the two microring resonators.

Ding, Yunhong; Pu, Minhao

2011-01-01

346

A large bandwidth photonic delay line using passive cascaded silicon-on-insulator microring resonators  

International Nuclear Information System (INIS)

This paper investigated the design and the characterization of a photonic delay line based on passive cascaded silicon-on-insulator (SOI) microrings. We considered the compromise of group delay, bandwidth and insertion loss. A 3-stage double channel side-coupled integrated spaced sequence of resonator (SCISSOR) device was optimized by shifting the resonance of each microring and fabricated with electron beam lithography and dry etching. The group delay was measured to be 17 ps for non-return-to-zero signals at different bit rates and the bandwidth of 78 GHz was achieved. The experiment result agreed well with our simulation. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

2011-07-01

347

Low Voltage CMOS Fully Differential Current Feedback Amplifier with Controllable 3-dB Bandwidth  

International Nuclear Information System (INIS)

This paper presents a new CMOS fully differential current feedback operational amplifier with controllable 3-dB bandwidth suitable for analog data processing and acquisition applications. The FDCFOA has the advantage of a wide range controllable 3-dB bandwidth (?57 MHz to 500 MHz) without changing the feedback resistance this guarantee the stability of the circuit. The FDCFOA has a standby current of 320?A. PSpice simulations of the FDCFOA block were given using 0.25?m CMOS technology from AMI MOSIS and dual supply voltages ±0.75 V

2008-02-11

348

Optical slotted circuit switched network: a bandwidth efficient alternative to wavelength-routed network  

Science.gov (United States)

Wavelength-routed networks have received enormous attention due to the fact that they are relatively simple to implement and implicitly offer Quality of Service (QoS) guarantees. However, they suffer from a bandwidth inefficiency problem and require complex Routing and Wavelength Assignment (RWA). Most attempts to address the above issues exploit the joint use of WDM and TDM technologies. The resultant TDM-based wavelength-routed networks partition the wavelength bandwidth into fixed-length time slots organized as a fixed-length frame. Multiple connections can thus time-share a wavelength and the grooming of their traffic leads to better bandwidth utilization. The capability of switching in both wavelength and time domains in such networks also mitigates the RWA problem. However, TMD-based wavelength-routed networks work in synchronous mode and strict synchronization among all network nodes is required. Global synchronization for all-optical networks which operate at extremely high speed is technically challenging, and deploying an optical synchronizer for each wavelength involves considerable cost. An Optical Slotted Circuit Switching (OSCS) architecture is proposed in this paper. In an OSCS network, slotted circuits are created to better utilize the wavelength bandwidth than in classic wavelength-routed networks. The operation of the protocol is such as to avoid the need for global synchronization required by TDM-based wavelength-routed networks.

Li, Yan; Collier, Martin

2007-12-01

349

A low-noise PLL design achieved by optimizing the loop bandwidth  

International Nuclear Information System (INIS)

This paper describes a low-noise phase-locked loop (PLL) design method to achieve minimum jitter. Based on the phase noise properties extracted from the transistor, and the low-pass or high-pass transfer characteristics of different noise sources to the output, an optimal loop bandwidth design method, derived from a continuous-time PLL model, further improves the jitter characteristics of the PLL. The described method not only finds the optimal loop-bandwidth to minimize the overall PLL jitter, but also achieves optimal loop-bandwidth by changing the value of the resistor or charge pump current. In addition, a phase-domain behavioral model in ADS is presented for accurately predicting improved jitter performance of a PLL at system level. A prototype PLL designed in a 0.18?m CMOS technology is used to investigate the accuracy of the theoretical predictions. The simulation shows significant performance improvement by using the proposed method. The simulated RMS and peak-to-peak jitter of the PLL at the optimal loop-bandwidth are 10.262 ps and 46.851 ps, respectively. (semiconductor integrated circuits)

2009-08-01

350

Maximizing the bandwidth of supercontinuum generation in As2Se3 chalcogenide fibers.  

Science.gov (United States)

We describe in detail a procedure for maximizing the bandwidth of supercontinuum generation in As(2)Se(3) chalcogenide fibers and the physics behind this procedure. First, we determine the key parameters that govern the design. Second, we find the conditions for the fiber to be endlessly single-mode; the fiber should be endlessly single-mode to maintain high nonlinearity and low coupling loss. We find that supercontinuum generation in As(2)Se(3) fibers proceeds in two stages--an initial stage that is dominated by four-wave mixing and a later stage that is dominated by the Raman-induced soliton self-frequency shift. Third, we determine the conditions to maximize the Stokes wavelength that is generated by four-wave mixing in the initial stage. Finally, we put all these pieces together to maximize the bandwidth. We show that it is possible to generate an optical bandwidth of more than 4 microm with an input pump wavelength of 2.5 microm using an As(2)Se(3) fiber with an air-hole-diameter-to-pitch ratio of 0.4 and a pitch of 3 microm. Obtaining this bandwidth requires a careful choice of the fiber's waveguide parameters and the pulse's peak power and duration, which determine respectively the fiber's dispersion and nonlinearity. PMID:20389694

Hu, Jonathan; Menyuk, Curtis R; Shaw, L Brandon; Sanghera, Jasbinder S; Aggarwal, Ishwar D

2010-03-29

351

Optimization model for memory bandwidth usage in x-ray image enhancement  

Science.gov (United States)

In Cardiovascular minimal invasive interventions, physicians require low-latency X-ray imaging applications, as their actions must be directly visible on the screen. The image-processing system should enable the simultaneous execution of a plurality of functions. Because dedicated hardware lacks flexibility, there is a growing interest in using off-the-shelf computer technology. Because memory bandwidth is a scarce parameter, we will focus on optimization methods for bandwidth reduction within multiprocessor systems at the chip level. We create a practical realistic model of required compute and memory bandwidth for a given set of image-processing functions. Similar modeling is applied for the available system resources. We concentrate in particular on X-ray image processing based on multi-resolution decomposition, noise reduction and image-enhancement techniques. We derive formulas for which we can optimize the mapping of the application onto processors, cache and memory for different configurations. The data-block granularity is matched to the memory hierarchy, so that caching will be optimized for low latency. More specifically, we exploit the locality of the signal-processing functions to streamline the memory communication. A substantial performance improvement is realized by a new memorycommunication model that incorporates the data dependencies of the image-processing functions. Results show a memory-bandwidth reduction in the order of 60% and a latency reduction in the order of 30-60% compared to straightforward implementations.

Albers, Rob; Suijs, Eric; de With, Peter H. N.

2008-03-01

352

Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser  

Science.gov (United States)

The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987);Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (??/?˜0.03-0.19%) pulses irradiated targets at moderate to high intensities (10^14-10^15 W/cm^2). Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (??˜1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets.

Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

2011-11-01

353

Hyper-Branched PON Development for High-Bandwidth Demanding Access Networks  

DEFF Research Database (Denmark)

This paper presents the merit and business applications of an hyper-branched optical access network providing 10Gbit/s bandwidth. We also present the development and experimental results of a high-speed semiconductor optical amplifier gain control to fulfill the extra-insertion losses of such network.

Vegas Olmos, Juan José; Sugawa, Jun

2012-01-01

354

Log based Pipelined Backoff for Bandwidth Estimation in QoS enabled Multipath Routing for MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available QoS enabled routing makes the utilization of resources more efficient by minimizing the unnecessary control messages and should not allow the transmissions that cannot meet the given QoS requirements. Due to the limited bandwidth constraint and dynamic topology of MANETS, supporting QoS is a challenging task. To improve the amount of unconsumed bandwidth and to reduce the overhead associated with the channel contention in MAC (Medium Access Control layer, log based pipelined concept is applied to backoff procedure. Due to this logarithmic pipelined concept, channel waiting time is reduced. This modified method is integrated with a multipath routing protocol called enhanced link disjoint AOMDV(Adhoc Ondemand Multipath Distance Vector which allows the establishment of multiple paths between a single source and destination node. Multiple paths can be useful in improving the effective bandwidth of communication pairs. This approach is implemented in NS2 simulator. Performance of this method is evaluated in terms of throughput, packet delivery ratio, effective bandwidth utilization, energy consumption.

N.SUMATHI,

2010-11-01

355

The research of methods to improve the control bandwidth for liquid crystal beam steering system  

Science.gov (United States)

The liquid crystal beam steering technology with low driving voltage, high diffraction efficiency and without the effect of mechanical inertia?is regard as a potential technology in the field of non-mechanical beam steering. Liquid crystal spatial light modulator (LCSLM) can be applied as a beam steering control device in laser communication, and it can realize the programmable control in real time. And compared with fast steering mirror (FSM), which is widely used at present, LCSLM is smaller, lighter and lower power consumptive in a non-mechanical way, so it's convenient to control. But the system bandwidth is a restricted problem in the research. In this article, the principle of beam steering with LCSLM is introduced firstly. A beam steering bench is set up using reflective pure-phase LCSLM from BNS. The offset of beam spot is detected by the CCD and a classic PI close-loop control experiment is designed to test the system bandwidth. And then the factors which restricted the control bandwidth are analyzed. Considering the effect of the CCD' frame rate, the PSD with higher frame rate is used in the control system and the data model of the liquid crystal is tested. A controller is designed based on the data model and the bandwidth is improved observably.

Hao, Ya-jing; Huang, Yong-mei; Wu, Qiong-yan; Xiao, Wen-ben

2013-08-01

356

In vivo photoacoustic imaging of transverse blood flow using Doppler broadening of bandwidth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new method is proposed to measure transverse blood flow using photoacoustic Doppler broadening of bandwidth. By measuring bovine blood flowing through a plastic tube, the linear dependence of the broadening on the flow speed was validated. The blood flow of the microvasculature in a mouse ear and a chicken embryo (stage 16) was also studied.

Yao, Junjie; Maslov, Konstantin I.; Shi, Yunfei; Taber, Larry A.; Wang, Lihong V.

2010-01-01

357

Delay-Bandwidth and Delay-Loss Limitations for Cloaking of Large Objects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that the difficulty of cloaking is fundamentally limited by delay-loss and delay-bandwidth limitations that worsen as the size of the object to be cloaked increases relative to the wavelength, using a simple model of ground-plane cloaking. These limitations must be considered when scaling experimental cloaking demonstrations up from wavelength-scale objects.

2010-01-01

358

BANDWIDTH ENHANCED E- SHAPED MICROSTRIP ANTENNA WITH PAIR OF WIDE SLITS  

Directory of Open Access Journals (Sweden)

Full Text Available A single-layer single-patch wideband microstrip antenna could be developed, and impedance bandwidth greater than 30% can easily be achieved for a microstrip antenna with a probe feed, A broad-band design of a probe-fed rectangular patch antenna with a pair of wide slits is studied, and the simulated, radiation characteristics are studied. The proposed design is with an air substrate of thickness about 8% of the wavelength of the center operating frequency, the proposed antenna have an impedance bandwidth about 31.32%, with respect to center frequency. For frequencies within the impedance bandwidth, good radiation characteristics are also observed, with a peak antenna gain about 9.3 dBi.  in this paper the wide slits are inserted at one of the radiating edges of the rectangular patch and increasing the length, width of slits and reducing the distance between them upto the specific limit the, proposed design has achieved the wide impedance bandwidth and good radiation characteristics details of the proposed antenna and Some simulation results obtained by IE3D and are given.

Yogesh Sharma

2012-12-01

359

Hazard rate estimation under random censoring with varying kernels and bandwidths.  

Science.gov (United States)

We discuss the estimation of hazard rates under random censoring with the kernel method. Two practically relevant problems that occur when applying unmodified kernel estimators are boundary effects near the endpoints of the support of the hazard rate, and a substantial increase in the variance from left to right over the range of abscissae where the hazard rate is estimated. A new class of boundary kernels is proposed for the first problem. Explicit formulas for these kernels are developed, and it is shown that this boundary correction works well in practice. A data-adaptive varying bandwidth selection procedure is proposed for the second problem. This procedure generally will lead to increasing bandwidths near the left endpoint and toward the right endpoint, and will lead to smaller integrated mean squared error of the hazard rate estimator as compared to a fixed bandwidth method. A practically feasible method incorporating the new boundary kernels and local bandwidth choices is implemented and illustrated with survival data from a leukemia study. PMID:8086616

Müller, H G; Wang, J L

1994-03-01

360

Technique for tuning center frequency of HTS microstrip filters without significantly changing bandwidth  

Energy Technology Data Exchange (ETDEWEB)

We have developed a technique for tuning high-temperature superconducting (HTS) microstrip filters in which additional electric pads are placed at the open ends of the resonators for tuning the center frequency. Pads are placed along one side of the open ends of the resonators to enable the effective lengths of the resonators to be adjusted, thereby shifting the center frequency. Pads are also placed around the I/O coupled-line elements to enable the coupling strength between the coupled-line and resonator to be adjusted, thereby reducing the insertion loss caused by tuning. The pads consist of line-and-space patterns. The former are electrically connected to the resonators, and the latter are electrically connected to the coupled-line elements. Simulated application of this technique to a 3-pole superconducting microstrip combline bandpass filter with half-wavelength resonators, a 5.0-GHz center frequency, and a 120-MHz 3-dB bandwidth shifted the bandwidth 500 MHz. However, the 3-dB bandwidth was reduced about 14 MHz. Use of a modified 3-pole microstrip interdigital bandpass filter mitigated the reduction to 2 MHz. Using this modified filter with additional electric pads is thus an effective way to tune the center frequency of HTS bandpass filters without significantly changing the bandwidth.

Sekiya, N., E-mail: nsekiya@yamanashi.ac.j [University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Nakagawa, Y. [University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Saito, A.; Ohshima, S. [Yamagata University, 4-3-16 Johnan, Yonezawa 992-8510 (Japan)

2009-10-15

 
 
 
 
361

Performance of a High-Concentration Erbium-Doped Fiber Amplifier with 100 nm Amplification Bandwidth  

International Nuclear Information System (INIS)

Increasing demand for higher bandwidth has driven the need for higher Wavelength Division Multiplexing (WDM) channels. One of the requirements to achieve this is a broadband amplifier. This paper reports the performance of a broadband, compact, high-concentration and silica-based erbium-doped fiber amplifier. The amplifier optimized to a 2.15 m long erbium-doped fiber with erbium ion concentration of 2000 ppm. The gain spectrum of the amplifier has a measured amplification bandwidth of 100 nm using a 980 nm laser diode with power of 150 mW. This silica-based EDFA shows lower noise figure, higher gain and wider bandwidth in shorter wavelengths compared to Bismuth-based EDFA with higher erbium ion concentration of 3250 ppm at equivalent EDF length. The silica-based EDF shows peak gain at 22 dB and amplification bandwidth between 1520 nm and 1620 nm. The lowest noise figure is 5 dB. The gain is further improved with the implementation of enhanced EDFA configurations.

2010-07-07

362

Effects of frequency and bandwidth on diagnostic information transfer in ultrasonic B-mode imaging.  

Science.gov (United States)

Transmitted pressure pulses in ultrasonic B-mode imaging systems are commonly characterized by their center frequency and bandwidth. Both parameters are associated with tradeoffs in spatial resolution and signal-to-noise in ultrasonic system design, with no general understanding of where they are optimal when applied to specific clinical exams. We use the ideal observer and simple psychophysical studies with human observers to evaluate the efficiency of information transfer in B-mode imaging as a function of the transmitted pulse center frequency and fractional bandwidth. Our approach uses a statistical model of backscatter relevant to breast imaging, and a 2-D model of pulse propagation based on Rayleigh-Sommerfeld diffraction theory. The statistics of the backscattered signal are combined in an ideal observer calculation that quantifies the task-relevant information contained in the radio-frequency (RF) signal after delay-and-sum beamforming. This is followed by a psychophysical evaluation of observer performance on B-mode envelope-detected images in three simple tasks. This experimental design allows us to track the flow of diagnostic information through RF acquisition and subsequent reading of the envelope image. In a low-contrast detection task and a high-contrast boundary discrimination task, optimal efficiency for human observers is observed at the highest center frequencies tested (15 MHz) and at moderate bandwidth (40%). For detection of scattering material in a high-contrast hypoechoic lesion, optimal efficiency was observed at lower center frequencies (5 MHz) and higher bandwidth (80%). The ideal observer analysis shows that this task dependence does not arise in the acquisition stage, where efficiency is maximized at 15 MHz with bandwidths of 60% or greater, but rather in the subsequent processing and reading of the envelope image. In addition, at higher frequencies more information is lost in the processing and reading than in the acquisition of reflected signals. PMID:22711407

Abbey, Craig K; Nguyen, Nghia Q; Insana, Michael F

2012-06-01

363

Low Voltage, High Bandwidth & Input Impedance CMOS Differential Amplifier at NANO Scale  

Directory of Open Access Journals (Sweden)

Full Text Available Since analog circuits have proved primarily essential in many of today’s high complex performance systems. This paper demonstrate designing and simulation of low power CMOS technology based differential amplifier at nano scale of different channel length(45nm,32nm,22nm via applying various supply voltages i.e. 1.1V, 0.95V , 0.9V respectively. Here the high input impedance, low power dissipation circuit is mainly characterized in terms of common mode rejection ratio (CMRR, voltage gain and gain band width product .The input impedance calculated are in the range of 190 G? (giga ohm, cut off frequency (-3db approximately greater than 50 MHz (mega hertz and average power dissipation in the order of less than 130 ?w (micro watt. The simulation result shows that all transistors are operated in saturation region, with this unique behavior of MOSFET transistor operating in this region not only allows a designer to work at a low voltage but also at a high frequency. Finally, the analog design consists of low operating voltages via very deep sub micron (nano scale technology.. The simulation is carried out using PTM Low Power 45nm, 32nm, & 22nm Metal Gate / High-K / Strained-Si technology with H-spice. A Matlab tool is also used to plot the graph of various parameters at different channel length in two dimensions (2-D.

Adil Zaidi

2013-05-01

364

All-optical characterization of large-signal modulation bandwidth of a monolithically integrated DFB-EA  

DEFF Research Database (Denmark)

We use an all-optical method to characterize the modulation bandwidth of a DFB-EA designed for 100 Gb/s Ethernet. In a large-signal wavelength conversion set-up, we show the device has an all-optical bandwidth of 83 GHz.

Blaaberg, Søren; Mulvad, Hans Christian Hansen

2009-01-01

365

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure  

Energy Technology Data Exchange (ETDEWEB)

An improved ultra-high bandwidth helical coil deflection structure for a cathode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Dunham, M.E.; Hudson, C.L.

1991-05-15

366

Cavity resonance absorption in ultra-high bandwidth CRT deflection structure by a resistive load  

Energy Technology Data Exchange (ETDEWEB)

An improved ultra-high bandwidth helical coil deflection structure for a hode ray tube is described comprising a first metal member having a bore therein, the metal walls of which form a first ground plane; a second metal member coaxially mounted in the bore of the first metal member and forming a second ground plane; a helical deflection coil coaxially mounted within the bore between the two ground planes; and a resistive load disposed in one end of the bore and electrically connected to the first and second ground planes, the resistive load having an impedance substantially equal to the characteristic impedance of the coaxial line formed by the two coaxial ground planes to inhibit cavity resonance in the structure within the ultra-high bandwidth of operation. Preferably, the resistive load comprises a carbon film on a surface of an end plug in one end of the bore.

Dunham, Mark E. (Santa Cruz, NM); Hudson, Charles L. (Santa Barbara, CA)

1993-01-01

367

Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths  

Energy Technology Data Exchange (ETDEWEB)

We investigate the ground-state properties of the one-dimensional two-band Hubbard model with different bandwidths. The density-matrix renormalization group method is applied to calculate the averaged electron occupancies n as a function of the chemical potential mu. Both at quarter and half fillings, 'charge plateaux' appear in the n-mu plot, where dmu/dn diverges and the Mott insulating states are realized. To see how the orbital polarization in the one-quarter charge plateau develops, we apply the second-order perturbation theory from the strong-coupling limit at quarter filling. The resultant Kugel-Khomskii spin-orbital model includes a magnetic field coupled to orbital pseudo-spins. This field originates from the discrepancy between the two bandwidths and leads to a finite orbital pseudo-spin magnetization.

Miyashita, Satoshi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Yamashita, Yasufumi; Yonemitsu, Kenji [Institute for Molecular Science, Okazaki 444-8585 (Japan); Koga, Akihisa; Kawakami, Norio, E-mail: satoshi@ims.ac.j [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

2009-03-01

368

Interference and Bandwidth Adjusted (ETX) in Wireless Multi-hop Networks  

CERN Document Server

In this paper, we propose a new quality link metric, interference and bandwidth adjusted ETX (IBETX) for wireless multi-hop networks. As MAC layer affects the link performance and consequently the route quality, the metric therefore, tackles the issue by achieving twofold MAC-awareness. Firstly, interference is calculated using cross-layered approach by sending probes to MAC layer. Secondly, the nominal bit rate information is provided to all nodes in the same contention domain by considering the bandwidth sharing mechanism of 802.11. Like ETX, our metric also calculates link delivery ratios that directly affect throughput and selects those routes that bypass dense regions in the network. Simulation results by NS-2 show that IBETX gives 19% higher throughput than ETX and 10% higher than Expected Throughput (ETP). Our metric also succeeds to reduce average end-to-end delay up to 16% less than Expected Link Performance (ELP) and 24% less than ETX.

Javaid, Nadeem; Djouani, Karim

2010-01-01

369

A Novel Optical Vector Spectral Analysis Technique Employing a Limited-Bandwidth Detector  

Directory of Open Access Journals (Sweden)

Full Text Available A new technique for obtaining frequency-dependent magnitude and phase information across an optical channel is presented using tunable allpass optical filters and a detector with a small bandwidth relative to the full channel width. This technique has application to optical monitoring of intersymbol interference distortions, including chromatic and polarization-mode dispersion effects, and thus can provide vector information for input to the control of adaptive optical filters. A method for generating a test signal spanning the spectrum of a modulated data signal without introducing intersymbol interference is discussed. This technique can also be used to characterize an optical pulse source and does not scale in complexity or cost as the bandwidth of the source increases.

Madsen CK

2005-01-01

370

Pickup design for high bandwidth bunch arrival-time monitors in free-electron lasers  

International Nuclear Information System (INIS)

The increased demands for low bunch charge operation mode in the free-electron lasers (FELs) require an upgrade of the existing synchronization equipment. As a part of the laser-based synchronization system, the bunch arrival-time monitors (BAMs) should have a sub-10 femtosecond precision for high and low bunch charge operation. In order to fulfill the resolution demands for both modes of operation, the bandwidth of such a BAM should be increased up to a cutoff frequency of 40 GHz. In this talk, we present the design and the realization of high bandwidth cone-shaped pickup electrodes as a part of the BAM for the FEL in Hamburg (FLASH) and the European X-ray free-electron laser (European XFEL). The proposed pickup was simulated with CST STUDIO SUITE, and a non-hermetic model was built up for radio frequency (rf) measurements.

2012-03-02

371

Bandwidth smearing in optical interferometry: Analytic model of the transition to the double fringe packet  

CERN Multimedia

Bandwidth smearing is a chromatic aberration due to the finite frequency bandwidth. In long-baseline optical interferometry terms, it is when the angular extension of the source is greater than the coherence length of the interferogram. As a consequence, separated parts of the source will contribute to fringe packets that are not fully overlapping; it is a transition from the classical interferometric regime to a double or multiple fringe packet. While studied in radio interferometry, there has been little work on the matter in the optical, where observables are measured and derived in a different manner, and are more strongly impacted by the turbulent atmosphere. We provide here the formalism and a set of usable equations to model and correct for the impact of smearing on the fringe contrast and phase, with the case of multiple stellar systems in mind. The atmosphere is briefly modeled and discussed.

Lachaume, Régis

2012-01-01

372

Enhancing the Bandwidth of a Microstrip Patch Antenna using Slots Shaped Patch  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, three different geometry shapes, the U, E and H are developed from a rectangular patch of the width (W = 32mm and length (L = 24mm. The proposed antennas are simulated using Sonnet software and the results compared with the conventional rectangular patch antenna. The results obtained clearly show that, bandwidth of conventional rectangular microstrip antenna can be enhanced from 4.81% (100MHz to 28.71% (610 MHz, 28.89% (630MHz and 9.13% (110MHz respectively using U, E and H-patch over the substrate. The E-shaped patch antenna has the highest bandwidth followed by U-shaped patch antenna and Hshaped patch antenna. The substrate material used for the proposed antennas is Alumina 96%, with the dielectric constant of 9.4 and loss tangent of 4.0e-4. The proposed antennas may find applications in Wireless Local Area Network (WLAN.

Atser A. Roy

2013-09-01

373

Improving bandwidth rectangular patch antenna using different thickness of dielectric substrate  

Directory of Open Access Journals (Sweden)

Full Text Available Microstrip patch antenna has some drawbacks of low efficiency, narrow band (<5%, and surface wave losses. In this paper the solution method was used different thickness of dielectric substrate (h= 4, 6 and 8 mm to increase bandwidth, the simulated results for rectangular give bandwidth of (200 MHZ in case (h=6mm.A rectangular micro strip patch antenna that meets the requirement of operation at (2.4 GHZ, the proposed configurations are simulated and analyzed using microwave office 2000 software package. The VSWR, input impedance, radiation patterns and S11 performance are used for the analysis of the different configurations. Feed point on the patch that gives a good match of 50 ohm, input impedance was found by a method of trial and error.

Karim A. Hamad

2011-04-01

374

BANDWIDTH AND GAIN INCREMENT OF MICROSTRIP PATCH ANTENNA WITH SHIFTED ELLIPTICAL SLOT  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the increment in Bandwidth and Gain of Rectangular Microstrip Patch antenna with Shifted Elliptical slot. First we have designed a Rectangular microstrip patch antenna. After that an elliptical slot is cut inside a rectangular patch which is shifted towards right. The results of both the designs are compared and it was found that an increase in the bandwidth of 21% and gain of 7.21 dBi is being achieved as that of a simple Rectangular microstrip patch antenna. Microstrip patch antenna is designed on a Duroid 5880 substrate with a dielectric constant of 2.2. The antenna is fed by a Coaxial probe feed. The antenna designs and performances are analyzed using Zealand IE3D software. The antenna can be used for many modern communication systems.

ISHA PURI

2011-07-01

375

A novel microstrip patch antenna with large impedance bandwidth in VHF/UHF range  

Energy Technology Data Exchange (ETDEWEB)

In this paper a novel antenna is presented. This antenna, employing microstrip circular disc as radiator is seen to perform over a large impedance bandwidth ( 130MHz to 876 MHz). The disk resonator is loaded with L-C-R circuit across a selective location in the disk via a thin shorting pin. The theoretical modeling predicts TM01 mode of operation. Therefore the beam pattern shows a null in the broadside direction. The said antenna is proposed to be developed for end use in coal mine where the antenna can be flush mounted on coal strata. Thus it will be able to measure the angle of arrival of any reflective component due to presence of waterbed at a distance. The measured as well as simulated results regarding impedance bandwidth and beam pattern agrees well. The simulated efficiency using IE3D is 48% whereas measured efficiency is nearly 45%. 7 refs., 5 figs., 1 tab.

Chakravarty, T.; Roy, S.M.; Sanyal, S.K.; De, A. [Durgapur Institute for Advanced Technology & Management, Rajbandh (India)

2005-07-01

376

Metamaterial absorber and extending absorbance bandwidth based on multi-cross resonators  

Science.gov (United States)

In this paper, we report the design, simulation, and measurements of a broadband metamaterial absorber (MA) based on a periodic array of multi-layer cross-structure resonators. A perfect narrowband MA consists of cross-structure resonator, dielectric substrate, and continuous metal films, and the absorption frequency can be tunable by changing the geometrical parameters based on L- C resonance circuit theory. Furthermore, the absorption band of our design is effectively extended by simply stacking several such structural layers with different geometrical dimensions. Finally, the 4-layer cross-structure MA is only 2 mm, which can achieve a full width at half maximum (FWHM) bandwidth of 2 GHz by numerical simulations, and 90 % bandwidth of 1.9 GHz by experiments.

Cheng, Yongzhi; Nie, Yan; Gong, Rongzhou

2013-05-01

377

A Tandem Communication Network with Dynamic Bandwidth Allocation and Modified Phase Type Transmission having Bulk Arrivals  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with the performance evaluation of a two node communication network with dynamic bandwidth allocation and modified phase type transmission having bulk arrivals. The performance of the statistical multiplexing is measured by approximating with the compound Poisson process and the transmission completions with Poisson processes. It is further assumed that the transmission rate at each node are adjusted depending upon the content of the buffer which is connected to it. The packets transmitted through the first node may be forwarded to the buffer connected to the second node or get terminated with certain probabilities. The performance measures of the network like, mean content of the buffers, mean delays, throughput, transmitter utilization etc. are derived explicitly under transient conditions. Sensitivity analysis with respect to the parameters is also carried through numerical illustration. It is observed that the dynamic bandwidth allocation and batch size distribution of arrivals has a tremendous influence on the performance measures.

Kuda Nageswara Rao

2010-07-01

378

Pickup design for high bandwidth bunch arrival-time monitors in free-electron lasers  

Energy Technology Data Exchange (ETDEWEB)

The increased demands for low bunch charge operation mode in the free-electron lasers (FELs) require an upgrade of the existing synchronization equipment. As a part of the laser-based synchronization system, the bunch arrival-time monitors (BAMs) should have a sub-10 femtosecond precision for high and low bunch charge operation. In order to fulfill the resolution demands for both modes of operation, the bandwidth of such a BAM should be increased up to a cutoff frequency of 40 GHz. In this talk, we present the design and the realization of high bandwidth cone-shaped pickup electrodes as a part of the BAM for the FEL in Hamburg (FLASH) and the European X-ray free-electron laser (European XFEL). The proposed pickup was simulated with CST STUDIO SUITE, and a non-hermetic model was built up for radio frequency (rf) measurements.

Angelovski, Aleksandar; Penirschke, Andreas; Jakoby, Rolf [TU Darmstadt (Germany). Institut fuer Mikrowellentechnik und Photonik; Kuhl, Alexander; Schnepp, Sascha [TU Darmstadt (Germany). Graduate School of Computational Engineering; Bock, Marie Kristin; Bousonville, Michael; Schlarb, Holger [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Weiland, Thomas [TU Darmstadt (Germany). Institut fuer Theorie Elektromagnetischer Felder

2012-07-01

379

Single-Shot Rotational Raman Thermometry for Turbulent Flames Using a Low-Resolution Bandwidth Technique  

Science.gov (United States)

An alternative optical thermometry technique that utilizes the low-resolution (order 10(exp 1)/cm) pure-rotational spontaneous Raman scattering of air is developed to aid single-shot multiscalar measurements in turbulent combustion studies. Temperature measurements are realized by correlating the measured envelope bandwidth of the pure-rotational manifold of the N2/O2 spectrum with a theoretical prediction of a species-weighted bandwidth. By coupling this thermometry technique with conventional vibrational Raman scattering for species determination, we demonstrate quantitative spatially resolved, single-shot measurements of the temperature and fuel/oxidizer concentrations in a high-pressure turbulent Cf4-air flame. Our technique provides not only an effective means of validating other temperature measurement methods, but also serves as a secondary thermometry technique in cases where the anti-Stokes vibrational N2 Raman signals are too low for a conventional vibrational temperature analysis.

Kojima, Jun; Nguyen, Quang-Viet

2007-01-01

380

Linear and Nonlinear Analysis of Magnetic Bearing Bandwidth Due to Eddy Current Limitations  

Science.gov (United States)

Finite element analysis was used to study the bandwidth of alloy hyperco50a and silicon iron laminated rotors and stators in magnetic bearings. A three dimensional model was made of a heteropolar bearing in which all the flux circulated in the plane of the rotor and stator laminate. A three dimensional model of a plate similar to the region of a pole near the gap was also studied with a very fine mesh. Nonlinear time transient solutions for the net flux carried by the plate were compared to steady state time harmonic solutions. Both linear and quasi-nonlinear steady state time harmonic solutions were calculated and compared. The finite element solutions for power loss and flux bandwidth were compared to those determined from classical analytical solutions to Maxwell's equations.

Kenny, Andrew; Palazzolo, Alan

2000-01-01

 
 
 
 
381

High Bandwidth Atomic Magnetometery with Continuous Quantum Non-demolition Measurements  

CERN Document Server

We describe an experimental study of spin-projection noise in a high sensitivity alkali-metal magnetometer. We demonstrate a four-fold improvement in the measurement bandwidth of the magnetometer using continuous quantum non-demolition (QND) measurements. Operating in the scalar mode with a measurement volume of 2 cm$^{3}$ we achieve magnetic field sensitivity of 22 fT/sqrt{Hz}$^{1/2}$ and a bandwidth of 1.9 kHz with a spin polarization of only 1%. Our experimental arrangement is naturally back-action evading and can be used to realize sub-fT sensitivity with a highly polarized spin-squeezed atomic vapor.

Shah, V; Romalis, M V

2009-01-01

382

The multiplet cavity: A buncher for broad-bandwidth klystron amplifiers  

Energy Technology Data Exchange (ETDEWEB)

The bandwidth of a klystron output cavity scales (approximately) as {wp}{sup 0.8} P{sup 0.2}, where {wp} is the beam perveance and P is the beam power. For high-perveance ({wp} > 10 {micro}pervs) high-power (P > 10 kW) electron beams, it is relatively straightforward to design a broad-band output cavity. However, the design of the input cavity of the broad-band klystron is in some ways more difficult. The purpose of the input cavity is to produce a velocity-modulated amplitude that will optimize the bandwidth of the entire klystron system, while providing a magnitude of velocity modulation large enough to minimize the length of the klystron. This paper shows how a multiplet (multiple cavity) buncher cavity can be designed to provide broad-band (>20%) operation while keeping short the drift section length of the klystron.

Bromborsky, A. [Army Research Lab., Adelphi, MD (United States)

1996-06-01

383

Compositional and thermal treatment effects on Raman gain and bandwidth in nanostructured silica based glasses  

Science.gov (United States)

Investigations of new materials possessing both higher Raman gain and larger spectral bandwidth than fused silica are becoming mandatory in order to satisfy increasing telecommunications demands. Herein, silica-niobia based glasses have been prepared and characterized by ellipsometry and Raman spectroscopy. A fine glass structural characterization of bulk system has been performed and the Raman gain has been quantified. Our silica-based glass system (K2O-Nb2O5-SiO2 (KNS)) provides via thermal treatment a nanocomposite material of easy and cheap fabrication. In our glass composition a strong Raman gain (up to 30 times higher than fused silica) and a large bandwidth have been measured and demonstrated to be related to nanostructured material domains.

Sirleto, Luigi; Aronne, Antonio; Gioffrè, Mariano; Fanelli, Esther; Righini, Giancarlo C.; Pernice, Pasquale; Vergara, Alessandro

2013-12-01

384

Real-Time Multi-path Tracking of Probabilistic Available Bandwidth  

CERN Document Server

Applications such as traffic engineering and network provisioning can greatly benefit from knowing, in real time, what is the largest input rate at which it is possible to transmit on a given path without causing congestion. We consider a probabilistic formulation for available bandwidth where the user specifies the probability of achieving an output rate almost as large as the input rate. We are interested in estimating and tracking the network-wide probabilistic available bandwidth (PAB) on multiple paths simultaneously with minimal overhead on the network. We propose a novel framework based on chirps, Bayesian inference, belief propagation and active sampling to estimate the PAB. We also consider the time evolution of the PAB by forming a dynamic model and designing a tracking algorithm based on particle filters. We implement our method in a lightweight and practical tool that has been deployed on the PlanetLab network to do online experiments. We show through these experiments and simulations that our app...

Thouin, Frederic; Rabbat, Michael

2010-01-01

385

Experimental demonstration of an improved EPON architecture using OFDMA for bandwidth scalable LAN emulation  

DEFF Research Database (Denmark)

We propose and demonstrate an improved Ethernet passive optical network (EPON) architecture supporting bandwidth-scalable physical layer local area network (LAN) emulation. Due to the use of orthogonal frequency division multiple access (OFDMA) technology for the LAN traffic transmission, there is no need to change the existing EPON architecture. Only one receiver at each optical network unit (ONU) is required to detect both LAN traffic and EPON downstream traffic, which makes the proposed system simple and cost-effective. Moreover, flexible assignment of LAN traffic bandwidth is realized by allocating different number of subcarriers or using different modulation formats. The 250Mb/s 4-quadrature amplitude modulation (4-QAM) and 500Mb/s 16-QAM OFDM LAN traffic are successfully emulated with the EPON traffic in our experiment.

Deng, Lei; Zhao, Ying

2011-01-01

386

Dynamic Bandwidth Allocation Based on Online Traffic Prediction for Real-Time MPEG-4 Video Streams  

Directory of Open Access Journals (Sweden)

Full Text Available The distinct characteristics of variable bit rate (VBR video traffic and its quality of service (QoS constraints have posed a unique challenge on network resource allocation and management for future integrated networks. Dynamic bandwidth allocation attempts to adaptively allocate resources to capture the burstiness of VBR video traffic, and therefore could potentially increase network utilization substantially while still satisfying the desired QoS requirements. We focus on prediction-based dynamic bandwidth allocation. In this context, the multiresolution learning neural-network-based traffic predictor is rigorously examined. A well-known-heuristic based approach RED-VBR scheme is used as a baseline for performance evaluation. Simulations using real-world MPEG-4 VBR video traces are conducted, and a comprehensive performance metrics is presented. In addition, a new concept of renegotiation control is introduced and a novel renegotiation control algorithm based on binary exponential backoff (BEB is proposed to efficiently reduce renegotiation frequency.

Mei Han

2007-01-01

387

Optimal Resource Allocation and Relay Selection in Bandwidth and Time Exchange Based Cooperative Forwarding  

CERN Document Server

In this paper, we investigate joint optimal relay selection and resource allocation that are fundamental to the understanding of bandwidth exchange (BE) and time exchange (TE) enabled incentivized cooperative forwarding in wireless networks. We consider a network where N nodes transmit data in the uplink to an access point (AP) or base station (BS). We first consider the scenario where each node gets an initial amount (equal, optimal or arbitrary) of resource in the form of bandwidth or time, and uses this resource as a flexible incentive for two hop relaying. We focus on ?-fair network utility maximization (NUM) and total power minimization in this environment. For both BE and TE, we show the concavity or convexity of the resource allocation problem for a fixed relay set. Defining the link weights of each relay pair as the utility gain due to cooperation (over noncooperation), we show that the optimal relay selection, often a combinatorially cumbersome problem, reduces to the maximum weighted matching (MWM) ...

Islam, Muhammad Nazmul; Kompella, Sastry

2011-01-01

388

Advances in broad bandwidth light sources for ultrahigh resolution optical coherence tomography  

International Nuclear Information System (INIS)

Novel ultra-broad bandwidth light sources enabling unprecedented sub-2 ?m axial resolution over the 400 nm-1700 nm wavelength range have been developed and evaluated with respect to their feasibility for clinical ultrahigh resolution optical coherence tomography (UHR OCT) applications. The state-of-the-art light sources described here include a compact Kerr lens mode locked Ti:sapphire laser (?c = 785 nm, ?? = 260 nm, Pout = 50 mW) and different nonlinear fibre-based light sources with spectral bandwidths (at full width at half maximum) up to 350 nm at ?c = 1130 nm and 470 nm at ?c = 1375 nm. In vitro UHR OCT imaging is demonstrated at multiple wavelengths in human cancer cells, animal ganglion cells as well as in neuropathologic and ophthalmic biopsies in order to compare and optimize UHR OCT image contrast, resolution and penetration depth

2004-04-07

389

High resolution Raman study of phonon and vibron bandwidths in isotopically pure and natural benzene crystal  

Science.gov (United States)

The frequency and the bandwidth of the 12 Raman active lattice modes and of more than 45 internal vibrons of natural and 12C isotopically pure benzene have been measured under high resolution with the aid of a tandem interferometer-spectrometer system or alternatively of a two meter focal length grating Sopra spectrometer. For five lattice phonons and for several vibrons the measurements were extended to a sufficient temperature range to study the relaxation processes in terms of anharmonic phonon-phonon and phonon-vibron coupling processes. The effect of the isotopic impurities on the phonon lifetime has been shown to be very important for some vibrons, in particular, for those resonant with the impurity level. The bandwidth evolution with temperature has been interpreted in terms of down- and up- three- and four-phonon as well as of dephasing processes.

Pinan, J. P.; Ouillon, R.; Ranson, P.; Becucci, M.; Califano, S.

1998-10-01

390

A NEW DATA TRANSFER SCHEME BASED ON BANDWIDTH ALLOCATION FOR VIRTUAL PRIVATE NETWORKS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper attempts to develop a data transfer scheme with a view to sufficiently provision the hose model of the Virtual Private Network (VPN and accomplish the desired degree of performance. The basic ideais to extract a service comparable to that of a private dedicated network with leased lines for the endpoints of the VPN. The service providers are expected to guarantee the required bandwidth, in order to address Quality of Service (QoS issues while employing a VPN over a shared network. Thus a tree based mechanism is generated through which well defined resource management procedures are devised to optimize the available bandwidth. The data packets forwarded through such predetermined paths serve to ensure secure communication betweencustomer sites. The NS2 based simulation results are included to demonstrate the merits of the designed approach and highlight the suitability of VPN for real time applications.

Mahalakshmi C

2010-05-01

391

High-bandwidth fiber-optic system using laser-diode transmitters  

International Nuclear Information System (INIS)

A system has been developed to transmit analog signals through 1-km-long fiber-optic cables having bandwidths up to 1.5 GHz. Semiconductor injection laser-diode transmitters operating at a wavelength of about 815 nm are directly modulated by electrical signals from radiation detectors. Graded-index optical fibers transmit the optical signals to a remote facility, where they are recorded on a single streak camera

1985-08-18

392

High-bandwidth fiber-optic system using laser-diode transmitters  

Energy Technology Data Exchange (ETDEWEB)

A system has been developed to transmit analog signals through 1-km-long fiber-optic cables having bandwidths up to 1.5 GHz. Semiconductor injection laser-diode transmitters operating at a wavelength of about 815 nm are directly modulated by electrical signals from radiation detectors. Graded-index optical fibers transmit the optical signals to a remote facility, where they are recorded on a single streak camera.

Pruett, B.L.; Roeske, F.; Jones, R.A.; Hagans, K.G.

1985-07-01

393

Potential Upgrade of the CMS Tracker Analog Readout Optical Links Using Bandwidth Efficient Digital Modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The potential application of advanced digital communication schemes in a future upgrade of the CMS Tracker readout optical links is currently being investigated at CERN. We show experimentally that multi-Gbit/s data rates are possible over the current 40 MSamples/s analog optical links by employing techniques similar to those used in ADSL. The concept involves using one or more digitally-modulated sinusoidal carriers in order to make efficient use of the available bandwidth.

Dris, Stefanos; Foudas, Costas; Gill, Karl; Grabit, Robert; Ricci, Daniel; Troska, Jan; Vasey, Francois

2010-01-01

394

Sensitivity to temporal modulation rate and spectral bandwidth in the human auditory system: MEG evidence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Slow acoustic modulations below 20 Hz, of varying bandwidths, are dominant components of speech and many other natural sounds. The dynamic neural representations of these modulations are difficult to study through noninvasive neural-recording methods, however, because of the omnipresent background of slow neural oscillations throughout the brain. We recorded the auditory steady-state responses (aSSR) to slow amplitude modulations (AM) from 14 human subjects using magnetoencephalography. The r...

Wang, Yadong; Ding, Nai; Ahmar, Nayef; Xiang, Juanjuan; Poeppel, David; Simon, Jonathan Z.

2012-01-01

395

On Bandwidth Efficient Modulation for High-Data-Rate Wireless LAN Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We address the problem of high-data-rate orthogonal frequency division multiplexed (OFDM) systems under restrictive bandwidth constraints. Based on recent theoretic results, multiple-input multiple-output (MIMO) configurations are best suited for this problem. In this paper, we examine several MIMO configurations suitable for high rate transmission. In all scenarios considered, perfect channel state information (CSI) is assumed at the receiver. In constrast, availability of CSI at the...

Terry John D; Heiskala Juha; Stolpman Victor; Fozunbal Majid

2002-01-01

396

A Novel Optical Vector Spectral Analysis Technique Employing a Limited-Bandwidth Detector  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new technique for obtaining frequency-dependent magnitude and phase information across an optical channel is presented using tunable allpass optical filters and a detector with a small bandwidth relative to the full channel width. This technique has application to optical monitoring of intersymbol interference distortions, including chromatic and polarization-mode dispersion effects, and thus can provide vector information for input to the control of adaptive optical filters. A meth...

Ck, Madsen

2005-01-01

397

Broad bandwidth of perceptual learning in the visual system of adults with anisometropic amblyopia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent studies have demonstrated that training adult amblyopes in simple visual tasks leads to significant improvements of their spatial vision. One critical question is: How much can training with one particular stimulus and task generalize to other stimuli and tasks? In this study, we estimated the bandwidth of perceptual learning in teenage and adult observers with anisometropic amblyopia and compared it to that of normal observers. We measured and compared contrast sensitivity functions?...

Huang, Chang-bing; Zhou, Yifeng; Lu, Zhong-lin

2008-01-01

398

BANDWIDTH ENHANCED E- SHAPED MICROSTRIP ANTENNA WITH PAIR OF WIDE SLITS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A single-layer single-patch wideband microstrip antenna could be developed, and impedance bandwidth greater than 30% can easily be achieved for a microstrip antenna with a probe feed, A broad-band design of a probe-fed rectangular patch antenna with a pair of wide slits is studied, and the simulated, radiation characteristics are studied. The proposed design is with an air substrate of thickness about 8% of the wavelength of the center operating frequency, the proposed antenna ha...

Shushant Kumar Jain; Asha Singh Kushwah; Avnish Sharma; Yogesh Sharma

2012-01-01

399

Banding together for bandwidth: An analysis of survey results from wireless community network participants  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using a resource mobilization framework, this study attempts to better understand the factors motivating people to join wireless community networks that enable members to share bandwidth. In addition, the research illuminates ties between this kind of peer-to-peer networking and civic engagement at a broader level. An in depth survey completed by 43 respondents from throughout Europe and North America found that participants in this movement felt a stronger sense of community, as well as were...

Shaffer, Gwen University Of California

2011-01-01

400

Interference and Bandwidth Adjusted (ETX) in Wireless Multi-hop Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we propose a new quality link metric, interference and bandwidth adjusted ETX (IBETX) for wireless multi-hop networks. As MAC layer affects the link performance and consequently the route quality, the metric therefore, tackles the issue by achieving twofold MAC-awareness. Firstly, interference is calculated using cross-layered approach by sending probes to MAC layer. Secondly, the nominal bit rate information is provided to all nodes in the same contention dom...

Javaid, Nadeem; Bibi, Ayesha; Djouani, Karim

2010-01-01

 
 
 
 
401

A Flexible Bandwidth Reservation Framework for Bulk Data Transfers in Grid Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In grid networks, distributed resources are interconnected by wide area network to support compute and data-intensive applications, which require reliable and efficient transfer of gigabits (even terabits) of data. Different from best-effort traffic in Internet, bulk data transfer in grid requires bandwidth reservation as a fundamental service. Existing reservation schemes such as RSVP are designed for real-time traffic specified by reservation rate, transfer start time but with unknown lifet...

Chen, Bin Bin; Primet, Pascale

2006-01-01

402

Connectivity aware routing - a method for finding bandwidth constrained paths over a variety of network topologies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multimedia traffic and real-time e-commerce applications can experience quality degradation in traditional networks such as the Internet. These difficulties can be overcome in networks which feature dynamically set up paths with bandwidth and delay guarantees. The problem of selecting such constrained paths is the task of quality of service (QoS) routing. Researchers have proposed several ways of implementing QoS routing, preferring either mechanisms which distribute network load or algorithm...

Kowalik, Karol; Collier, Martin

2003-01-01

403

Experimental characterization of the radio channel for systems with large bandwidth and multiple antennas  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wireless communications have become essential in our society [Rappaport, 1996], [Parsons, 2000]. Nowadays, people need to be connected everywhere and at any time, and demand faster and enhanced communications every day. New applications requires higher data rates and, therefore, higher bandwidths. On the one hand, Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher data rates and optimize the use of the spectrum. On the other hand, more recently, syst...

Garci?a Pardo, Concepcio?n

2011-01-01

404

Bandwidth Improvement in Large Reflectarrays by Using True-Time Delay  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A significant improvement in the bandwidth of large reflectarrays is demonstrated using elements which allow true-time delay. Two identical, large reflectarrays have been designed using different phase distributions to generate a collimated beam. In the former, the phase distribution is truncated to 360deg as is usual in reflectarray antennas, while in the second, the true phase delay is maintained (three cycles of 360deg). The chosen phase-shifter elements are based on previously measured an...

2008-01-01

405

Limited Bandwidths and Correlation Ambiguities: Do They Co-Exist in Galileo Receivers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Galileo is the Global Navigation Satellite System that Europe is building and it is planned to be operational in the next 3-5 years. Several Galileo signals use split-spectrum modulations, such as Composite Binary Offset Carrier (CBOC) modulation, which create correlation ambiguities when processed with large or infinite front-end bandwidths (i.e., in wideband receivers). The correlation ambiguities refer to the notches in the correlation shape (i.e., in the envelope of the correlation betwee...

Elena Simona Lohan

2011-01-01

406

Influence of carrier dynamics on the modulation bandwidth of quantum-dot based nanocavity devices  

DEFF Research Database (Denmark)

We theoretically investigate the modulation response of quantum-dot based nanocavity light emitting devices. For high Purcell enhancement factors, our theory predicts the possibility of decreasing the modulation bandwidth with increasing scattering rate into the lasing quantum-dot state. This counterintuitive effect is investigated using a microscopic semiconductor model. The resulting guidelines for possible optimizations of quantum-dot based nanocavity laser devices are given.

Lorke, Michael; Nielsen, Torben Roland

2010-01-01

407

Gas-filled cell as a narrow bandwidth bandpass filter in the VUV wavelength range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a method for spectrally filtering radiation in the VUV wavelength range by means of a monochromator constituted by a cell filled with a resonantly absorbing rare gas. Around particular wavelengths, the gas exhibits narrow-bandwidth absorbing resonances following the Fano profile. In particular, within the photon energy range 60 eV - 65 eV, the correlation index of the Fano profiles for the photo-ionization spectra in Helium is equal to unity, meaning that the mini...

Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

2011-01-01

408

Investigation of Bandwidth Requirement of Smart Meter Network Using OPNET Modeler  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Smart meter networks are the backbone for smart electrical distribution grid. Smart meter network requires the bidirectional communications medium and interoperability capability. As thousands of meters are interconnected in the smart meter network, it is vital to select an appropriate communication bandwidth to facilitate real-time two-way information flows and this will also allow further uptake of greenhouse-friendly technology options and enhance energy security. Optimized Network Enginee...

2013-01-01

409

Laser-induced acoustic point source for accurate impulse response measurements within the audible bandwidth.  

Science.gov (United States)

Laser induced air breakdown is proposed as a sound source for accurate impulse response measurements. Within the audible bandwidth, the source is repeatable, broadband, and omnidirectional. The applicability of the source was evaluated by measuring the impulse response of a room. The proposed source provides a more accurate temporal and spatial representation of room reflections than conventional loudspeakers due to its omnidirectionality, negligible size and short pulse duration. PMID:24907837

Gómez Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville; Eskelinen, Joona; Hæggström, Edward

2014-06-01

410

Single passband microwave photonic filter with wideband tunability and adjustable bandwidth.  

Science.gov (United States)

A new and simple structure for a single passband microwave photonic filter is presented. It is based on using an electro-optical phase modulator and a tunable optical filter and only requires a single wavelength source and a single photodetector. Experimental results are presented that demonstrate a single passband, flat-top radio-frequency filter response without free spectral range limitations, along with the capability of tuning the center frequency and filter bandwidth independently. PMID:23164884

Chen, Tong; Yi, Xiaoke; Li, Liwei; Minasian, Robert

2012-11-15

411

On egress router selection for inter-domain traffic with bandwidth guarantees  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As the Internet has grown in size and diversity of applications, the next generation is designed to accommodate flows that span over multiple domains with quality of service guarantees, and in particular bandwidth. In that context, a problem emerges when destinations for inter-domain traffic may be reachable through multiple egress routers. Selecting different egress routers for traffic flows can have diverse effects on network resource utilization. In this paper, we address a critical provis...

Ho, Kh; Wang, N.; Trimintzios, P.; Pavlou, G.; Howarth, Mp

2004-01-01

412

An Efficient Dynamic Bandwidth Allocation Algorithm for Quality of Service Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Efficient dynamic resource provisioning algorithms are necessary to the development and automation of Quality of Service (QoS) networks. The main goal of these algorithms is to offer services that satisfy the QoS requirements of individual users while guaranteeing at the same time an efficient utilization of network resources. In this paper we introduce a new service model that provides quantitative per-flow bandwidth guarantees, where users subscribe for a guaranteed rate; moreover, the netw...

Elias, Jocelyne; Martignon, Fabio; Capone, Antonio

2006-01-01

413

Amplified spontaneous emission in N2 lasers: Saturation and bandwidth study  

Science.gov (United States)

A complete ASE analysis in a 3-level laser system based on the model of the geometrically dependent gain coefficient (GDGC) is presented. For the study, the photon density/intensity rate equation in the saturated and unsaturated conditions, along with reported experimental measurements on the ASE output energy and spectral bandwidth for N2-lasers were utilized. It was found that the GDGC model is able to explain the ASE output energy behavior and gain profiles correctly. In addition, the model was used to predict the spontaneous emission bandwidth ??0 and consequently the stimulated emission cross-section for the C?B transition of nitrogen molecule at 337.1 nm. In this work, for example, ??0 was found to be 766 GHz (2.9 Å) which is consistent with the earliest experimental observation on the ASE bandwidth reduction in a N2-laser as reported to be ~3. This is the first theoretical result that explains the spontaneous emission bandwidth which is different from the commonly used value of ~1 Å obtained from measurements of N2-lasers output spectra. The method was also applied for a filament N2 laser for the C?B transition produced in atmosphere, and a good consistency between the laboratory and filament lasers was obtained. Details of the calculations for this study are presented. The results obtained from 3-level systems confirm further the potential of applying the GDGC model for the ASE study in different laser systems and is unifying lasers of the same active medium.

Hariri, A.; Sarikhani, S.

2014-05-01

414

Overcoming Modal Bandwidth Limitation in Radio-over-Multimode Fiber Links  

DEFF Research Database (Denmark)

Employing the optical frequency multiplication method, the theoretical modal bandwidth limitation of multimode fiber (MMF) can be overcome in radio-over-fiber links. The principle is analyzed theoretically and supported experimentally by generation and transmission of microwave carriers up to 40 GHz and 16- and 64-level quadrature-amplitude-modulated (QAM) radio signals in the 24- to 30-GHz band over 4.4-km MMF link

Larrode, M. Carcía; Koonen, A.M.J.

2006-01-01

415

A novel bandwidth allocation scheme for QoS routing in mobile ad hoc networks  

Science.gov (United States)

The main purpose of this paper is to propose a novel bandwidth allocation scheme for facilitating quality of service (QoS) routing in mobile ad hoc networks (MANETs). In a MANET using time division multiple access (TDMA), each node communicates with its neighbors in the same time slot. In general, finding a route with the maximum end-to-end bandwidth subject to the constraint of collision-free transmission is an NP-complete problem. This paper proposed a sub-optimal solution to this problem. The solution is based on a centrally controlled bandwidth allocation scheme to properly assign the available time slots to each intermediate link. The advantage of our proposed scheme is that the resource utilization of MANET is maximized and the end-to-end QoS is guaranteed during the route establishment period. Performance analyses show that when using the proposed scheme with AODV to perform QoS routing, it achieves about 25% throughput higher than its best-effort counterpart if the node is moving at 5mps speed.

Wu, Bin; Kuo, Geng-Sheng

2004-10-01

416

Time Slot Assignment for Maximum Bandwidth in a Mobile Ad Hoc Network  

Directory of Open Access Journals (Sweden)

Full Text Available

Time slot assignment is essential to provide the calculated bandwidth in a TDMA (Time Division Multiple Access-based mobile ad hoc network (MANET, which is a focus of attention of this paper because of its collision-free packet transmission with QoS(Quality of Service support. In this paper, a new time slot assignment algorithm-SAGO (Slot Assignment by Global Overview is proposed, by which more available bandwidth can be obtained than conventional approximate solutions. SAGO assigns time slots from a global overview, that is, time slot assignment is based on the usage of global information such as finding of bottleneck of a route, tentative bandwidth evaluation of a route and assignment of time slot according to the order of their free times in the concerned links. In addition, SAGO’s effectiveness is proved by simulation results.

Yasushi Wakahara

2007-11-01

417

Contrast-enhanced intravascular ultrasound pulse sequences for bandwidth-limited transducers.  

Science.gov (United States)

We demonstrate two methods for vasa vasorum imaging using contrast-enhanced intravascular ultrasound, which can be performed using commercial catheters. Plaque neovascularization was recognized as an independent marker of coronary artery plaque vulnerability. IVUS-based methods to image the microvessels available to date require high bandwidth (-6 dB relative frequency bandwidth >70%), which are not routinely available commercially. We explored the potential of ultraharmonic imaging and chirp reversal imaging for vasa vasorum imaging. In vitro recordings were performed on a tissue-mimicking phantom using a commercial ultrasound contrast agent and a transducer with a center frequency of 34 MHz and a -6 dB relative bandwidth of 56%. Acoustic peak pressures <500 kPa were used. A tissue-mimicking phantom with channels down to 200 ?m in diameter was successfully imaged by the two contrast detection sequences while the smallest channel stayed invisible in conventional intravascular ultrasound images. Ultraharmonic imaging provided the best contrast agent detection. PMID:23384459

Maresca, David; Renaud, Guillaume; van Soest, Gijs; Li, Xiang; Zhou, Qifa; Shung, K Kirk; de Jong, Nico; van der Steen, Antonius F W

2013-04-01

418

Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz  

DEFF Research Database (Denmark)

We present a metamaterial, consisting of a cross structure and a metal mesh filter, that forms a composite with greater functional bandwidth than any terahertz (THz) metamaterial to date. Metamaterials traditionally have a narrow usable bandwidth that is much smaller than common THz sources, such as photoconductive antennas and difference frequency generation. The composite structure shown here expands the usable bandwidth to exceed that of current THz sources. To highlight the applicability of this combination, we demonstrate a series of bandpass filters with only a single pass band, with a central frequency (f) that is scalable from 0.86â??8.51 THz, that highly extinguishes other frequencies up to >240 THz. The performance of these filters is demonstrated in experiment, using both air biased coherent detection and a Fourier transform infrared spectrometer (FTIR), as well as in simulation. We present equationsâ??and discuss their scaling lawsâ??which detail the f and full width at half max (Î?f) of the pass band, as well as the required geometric dimensions for their fabrication using standard UV photolithography and easily achievable fabrication linewidths. With these equations, the geometric parameters and Î?f for a desired frequency can be quickly calculated. Using these bandpass filters as a proof of principle, we believe that this metamaterial composite provides the key for ultra-broadband metamaterial design.

Strikwerda, Andrew; Zalkovskij, Maksim

2014-01-01

419

Metamaterial composite bandpass filter with an ultra-broadband rejection bandwidth of up to 240 terahertz  

Science.gov (United States)

We present a metamaterial, consisting of a cross structure and a metal mesh filter, that forms a composite with greater functional bandwidth than any terahertz (THz) metamaterial to date. Metamaterials traditionally have a narrow usable bandwidth that is much smaller than common THz sources, such as photoconductive antennas and difference frequency generation. The composite structure shown here expands the usable bandwidth to exceed that of current THz sources. To highlight the applicability of this combination, we demonstrate a series of bandpass filters with only a single pass band, with a central frequency (f0) that is scalable from 0.86-8.51 THz, that highly extinguishes other frequencies up to >240 THz. The performance of these filters is demonstrated in experiment, using both air biased coherent detection and a Fourier transform infrared spectrometer (FTIR), as well as in simulation. We present equations—and discuss their scaling laws—which detail the f0 and full width at half max (?f) of the pass band, as well as the required geometric dimensions for their fabrication using standard UV photolithography and easily achievable fabrication linewidths. With these equations, the geometric parameters and ?f for a desired frequency can be quickly calculated. Using these bandpass filters as a proof of principle, we believe that this metamaterial composite provides the key for ultra-broadband metamaterial design.

Strikwerda, Andrew C.; Zalkovskij, Maksim; Lund Lorenzen, Dennis; Krabbe, Alexander; Lavrinenko, Andrei V.; Uhd Jepsen, Peter

2014-05-01

420

Extremely large bandwidth and ultralow-dispersion slow light in photonic crystal waveguides with magnetically controllability  

DEFF Research Database (Denmark)

A line-defect waveguide within a two-dimensional magnetic-fluid-based photonic crystal with 45o-rotated square lattice is presented to have excellent slow light properties. The bandwidth centered at $$ \\lambda_{0} $$ = 1,550 nm of our designed W1 waveguide is around 66 nm, which is very large than that of the conventional W1 waveguide as well as the corresponding optimized structures based on photonic crystal with triangular lattice. The obtained group velocity dispersion $$ \\beta_{2} $$ within the bandwidth is ultralow and varies from â??1,191$$ a/(2\\pi c^{2} ) $$ to 855$$ a/(2\\pi c^{2} ) $$ (a and c are the period of the lattice and the light speed in vacuum, respectively). Simultaneously, the normalized delay-bandwidth product is relatively large and almost invariant with magnetic field strength. It is indicated that using magnetic fluid as one of the constitutive materials of the photonic crystal structures can enable the magnetically fine tunability of the slow light in online mode. The concept and resultsof this work may give a guideline for studying and realizing tunable slow light based on the external-stimulus-responsive materials.

Pu, Shengli; Wang, Haotian

2013-01-01

 
 
 
 
421

A Real-time Data Compression for Massive Data Transmission Over High Delay-bandwidth Network  

Directory of Open Access Journals (Sweden)

Full Text Available Packet dropout and retransmission have become a more and more serious problem in high delay-bandwidth network, it is difficult for traditional streaming compression to deal with reorder packets, people have to use stateless compression, but it can only achieve very low compression ratio. In this study, we introduce a novel Orderless Tolerance Compression Algorithm (OTCA. The algorithm works effectively with orderless packets which is caused by the packet retransmission, through allowing variable delay in the dictionary construction. OTCA performs better compression ratio than stateless compression and low decoding latency than that of streaming compression and excels delay-dictionary compression in both compression ratio and decoding latency especially in high bandwidth network. We conduct extensive experiments to establish the potential improvement for packet compression techniques, using many data files including the Calgary corpus and the Canterbury corpus. Experimental results of the OTCA show that it is a good compromise proposal for transfer massive data over high delay-bandwidth networks.

Zheng Chen

2013-01-01

422

Bandwidth Enhancement and Size Reduction of Microstrip Patch Antenna by Magnetoinductive Waveguide Loading  

Directory of Open Access Journals (Sweden)

Full Text Available A planar magnetoinductive (MI waveguide loaded rectangular microstrip patch antenna is presented and discussed. The MI waveguide consists of two planar metamaterial split squared ring resonators (SSRRs placed in between two microstrip lines. The backward wave propagation takes place through this structure. The rectangular microstrip patch antenna is magnetically coupled to the MI waveguide. The unloaded rectangular microstrip patch antenna resonates at 37.10 GHz. When loaded with planar MI waveguide, its resonant frequency is reduced to 9.38 GHz with the bandwidth and gain of 44% and 4.16 dBi respectively. In loaded condition, the dimension of antenna is 12.50 mm × 3.70 mm (0.390 ? × 0.115 ?. The appreciable bandwidth is achieved in such a small size antenna. The pass band frequency of MI waveguide is predicted by using the theoretical model of dispersion equation. The effective medium theory is used to verify the metamaterial characteristics of SSRR. The simulated results and theoretical calculations are also presented. The results show that the proposed method can be used to design compact and high bandwidth microstrip patch antennas.

Swapna Devi

2011-04-01

423

Bandwidth Analysis of Bootstrap Transimpedance Amplifier for Optical Free Space Receiver  

Directory of Open Access Journals (Sweden)

Full Text Available Free Space Optic (FSO or optical wireless link operates in high noise environments. On the other hand, theperformance is subjected to several atmospheric factors like environmental temperature, fog, smoke, haze and rain. Signalto-noise ratio (SNR can vary radically with the distance and ambient noise. A good sensitivity and a broad bandwidth willhabitually use a small photodetection area where the aperture is small. However, FSO optical receiver requires a largeaperture and accordingly, to have a large collection area, which possibly will be achieved by using a large area photodetectorand large filter. Consequently, large area photodetector produces a high input capacitance that will be reduced thebandwidth. Hence, techniques to reduce the effective detector capacitance are required in order to achieve a low noise aswell as wide bandwidth design. In this paper, modeling and analysis of the series and shunt with floating source: and seriesshuntbootstrap transimpedance amplifier (BTA of front-end receiver for input capacitance reduction will be presented. Theresult shows that the technique improved the conventional transimpedance amplifier (TIA bandwidth up to 1000 times withan effective capacitance reduction technique for optical wireless detector.

A. Ramli

2008-06-01

424

Multi-path Probabilistic Available Bandwidth Estimation through Bayesian Active Learning  

CERN Document Server

Knowing the largest rate at which data can be sent on an end-to-end path such that the egress rate is equal to the ingress rate with high probability can be very practical when choosing transmission rates in video streaming or selecting peers in peer-to-peer applications. We introduce probabilistic available bandwidth, which is defined in terms of ingress rates and egress rates of traffic on a path, rather than in terms of capacity and utilization of the constituent links of the path like the standard available bandwidth metric. In this paper, we describe a distributed algorithm, based on a probabilistic graphical model and Bayesian active learning, for simultaneously estimating the probabilistic available bandwidth of multiple paths through a network. Our procedure exploits the fact that each packet train provides information not only about the path it traverses, but also about any path that shares a link with the monitored path. Simulations and PlanetLab experiments indicate that this process can dramatical...

Thouin, Frederic; Rabbat, Michael

2010-01-01

425

Automatic high-bandwidth calibration and reconstruction of arbitrarily sampled parallel MRI.  

Science.gov (United States)

Today, many MRI reconstruction techniques exist for undersampled MRI data. Regularization-based techniques inspired by compressed sensing allow for the reconstruction of undersampled data that would lead to an ill-posed reconstruction problem. Parallel imaging enables the reconstruction of MRI images from undersampled multi-coil data that leads to a well-posed reconstruction problem. Autocalibrating pMRI techniques encompass pMRI techniques where no explicit knowledge of the coil sensivities is required. A first purpose of this paper is to derive a novel autocalibration approach for pMRI that allows for the estimation and use of smooth, but high-bandwidth coil profiles instead of a compactly supported kernel. These high-bandwidth models adhere more accurately to the physics of an antenna system. The second purpose of this paper is to demonstrate the feasibility of a parameter-free reconstruction algorithm that combines autocalibrating pMRI and compressed sensing. Therefore, we present several techniques for automatic parameter estimation in MRI reconstruction. Experiments show that a higher reconstruction accuracy can be had using high-bandwidth coil models and that the automatic parameter choices yield an acceptable result. PMID:24915203

Aelterman, Jan; Naeyaert, Maarten; Gutierrez, Shandra; Luong, Hiep; Goossens, Bart; Pižurica, Aleksandra; Philips, Wilfried

2014-01-01

426

Optimal apparent damping as a function of the bandwidth of an array of vibration absorbers.  

Science.gov (United States)

The transient response of a resonant structure can be altered by the attachment of one or more substantially smaller resonators. Considered here is a coupled array of damped harmonic oscillators whose resonant frequencies are distributed across a frequency band that encompasses the natural frequency of the primary structure. Vibration energy introduced to the primary structure, which has little to no intrinsic damping, is transferred into and trapped by the attached array. It is shown that, when the properties of the array are optimized to reduce the settling time of the primary structure's transient response, the apparent damping is approximately proportional to the bandwidth of the array (the span of resonant frequencies of the attached oscillators). Numerical simulations were conducted using an unconstrained nonlinear minimization algorithm to find system parameters that result in the fastest settling time. This minimization was conducted for a range of system characteristics including the overall bandwidth of the array, the ratio of the total array mass to that of the primary structure, and the distributions of mass, stiffness, and damping among the array elements. This paper reports optimal values of these parameters and demonstrates that the resulting minimum settling time decreases with increasing bandwidth. PMID:23927106

Vignola, Joseph; Glean, Aldo; Judge, John; Ryan, Teresa

2013-08-01

427

The effective I/O bandwidth benchmark (b{_}eff{_}io)  

Energy Technology Data Exchange (ETDEWEB)

The effective I/O bandwidth benchmark (b{_}eff{_}io) covers two goals: (1) to achieve a characteristic average number for the I/O bandwidth achievable with parallel MPI-I/O applications, and (2) to get detailed information about several access patterns and buffer lengths. The benchmark examines ''first write'', ''rewrite'' and ''read'' access, strided (individual and shared pointers) and segmented collective patterns on one file per application and non-collective access to one file per process. The number of parallel accessing processes is also varied and wellformed I/O is compared with non-wellformed. On systems, meeting the rule that the total memory can be written to disk in 10 minutes, the benchmark should not need more than 15 minutes for a first pass of all patterns. The benchmark is designed analogously to the effective bandwidth benchmark for message passing (b{_}eff) that characterizes the message passing capabilities of a system in a few minutes. First results of the b{_}elf{_}io benchmark are given for IBM SP and Cray T3E systems and compared with existing benchmarks based on parallel Posix-I/O.

Koniges, A E; Rabehseifner, R

2000-02-17

428

The effect of squeeze film constriction on bandwidth improvement in interferometric accelerometers  

International Nuclear Information System (INIS)

This paper studies the effects of a constricted squeeze film on the performance of an optical microelectromechanical system accelerometer. Squeeze films are shown to extend the sensor frequency range (bandwidth) in accelerometers without decreasing the mechanical sensitivity by retarding the resonate response. By restricting the venting of a squeeze film, this preferential behavior is observed at lower frequencies than is expected for ideally vented accelerometers. Due to this effect, constricted squeeze films may be used to improve the bandwidth performance of devices of lower natural frequencies and higher inertial sensitivities. A model, extended from the existing squeeze film theory, is developed for the squeeze film formed between circular plates with generalized mixed boundary pressure conditions to describe the boundary flow resistance. These effects are experimentally observed in a parallel plate Fabry–Pérot interferometric accelerometer through frequency response characterization at mechanical resonance under pressure variation. The analytical results for the constricted squeeze film are used to predict the performance gains due to the frequency-dependent squeeze film parameters. These results are experimentally confirmed by demonstrating improved bandwidth performance due to the constricted squeeze film

2008-05-01

429

Bandwidth Enhancement of A Micro strip Line Fed Hexagonal Wide-Slot Antenna Using Fork-like Tuning Stub  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a printed hexagonal wide slot antenna, fed by a microstrip line with fork like tuning stub for bandwidth enhancement is proposed and experimentally investigated. The impedance, radiation and gain characteristics of this antenna are studied. Simulation and experimental results indicate that a 1.5:1 VSWR bandwidth, of about 1 GHz and 2:1 VSWR bandwidth of 1.34 GHz is achieved at operating frequency around 2.5 GHz, which is about three times larger than a microstrip line fed hexagonal wide slot antenna, with normal tuning stub, considered as reference antenna.

Krishnendu Chattopadhyay

2012-05-01

430

Application of inexpensive, low-cost, low-bandwidth silhouette profiling UGS systems to current remote sensing operations  

Science.gov (United States)

Low cost, power and bandwidth UGS can be used to fill the growing need for surveillance in remote environments. In particular, linear and 2D thermal sensor systems can run for up to months at a time and their deployment can be scaled to suit the size of the mission. Thermal silhouette profilers like Brimrose's SPOT system reduce power and bandwidth requirements by performing elementary classification and only transmitting binary data using optimized compression methods. These systems satisfy the demands for an increasing number of surveillance operations where reduced bandwidth and power consumption are mission critical.

Haskovic, Emir Y.; Walsh, Sterling; Cloud, Glenn; Winkelman, Rick; Jia, Yingqing; Vishnyakov, Sergey; Jin, Feng

2013-05-01

431

Demonstration of an X-Band Multilayer Yagi-Like Microstrip Patch Antenna With High Directivity and Large Bandwidth  

Science.gov (United States)

The feasibility of obtaining large bandwidth and high directivity from a multilayer Yagi-like microstrip patch antenna at 10 GHz is investigated. A measured 10-dB bandwidth of approximately 20 percent and directivity of approximately 11 dBi is demonstrated through the implementation of a vertically-stacked structure with three parasitic directors, above the driven patch, and a single reflector underneath the driven patch. Simulated and measured results are compared and show fairly close agreement. This antenna offers the advantages of large bandwidth, high directivity, and symmetrical broadside patterns, and could be applicable to satellite as well as terrestrial communications.

Nessel, James A.; Zaman, Afroz; Lee, Richard Q.; Lambert, Kevin

2005-01-01

432

Low-delay, high-bandwidth frequency-locking loop of resonator integrated optic gyro with triangular phase modulation.  

Science.gov (United States)

A frequency-locking loop affects the bandwidth and output of the resonator integrated optic gyro (RIOG). A low-delay, high-bandwidth frequency-locking loop is implemented on a single field-programmable gate array with triangular phase modulation. The signal processing delay is reduced to less than 1 ?s. The loop model is set up, and the influences of loop parameters on the bandwidth and unit step response are analyzed; the bandwidth of 10 kHz is obtained with the optimized loop parameters. As a result, the accuracy of the frequency-locking loop is reduced to 1.37 Hz (10 s integrated time). It is equivalent to a rotation rate of 0.005??deg/s, which is close to the ultimate sensitivity of the RIOG. Moreover, the bias stability of the RIOG is improved to 0.45??deg/s (10 s integrated time) based on the frequency-locking loop. PMID:24513753

Zhi, Yinzhou; Feng, Lishuang; Lei, Ming; Wang, Kunbo

2013-11-20

433

Microwave Mixing and IF Bandwidth In Sub-Micron Long High-T(sub c) Hot-Electron Bolometers  

Science.gov (United States)

We have systematically measured both the length and temperature dependence of the intermediate frequency (IF) bandwidth of hot-electron bolometer (HEB) mixer made form a high-T(sub c) superconductor (HTS).

Harnack, O.; Karasik, B.; McGrath, W.; Kleinsasser, A.; Barner, J.

1999-01-01

434

Performance Evaluation of Two Node Tandem Communication Network with Dynamic Bandwidth Allocation having Two Stage Direct Bulk Arrivals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A two node tandem communication network with dynamic bandwidth allocation (DBA) having two stage direct bulk arrivals is developed and analyzed. The messages arriving to the source are packetized and stored in the buffers for forward transmission. Dynamic bandwidth allocation strategy is proposed by adjusting the transmission rate at every node just before transmission of each packet. The arrival and transmission processes at each node are characterized through compound Poisson and Poisson pr...

Srinivasa Rao, K.; Kuda Nageswara Rao; Srinivasa Rao, P.

2011-01-01

435

Deficit Round-Robin-Based ISP Traffic Control Scheme Enabling Excess Bandwidth Allocation in Shared Access Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In shared access, shaping subscriber traffic based on token bucket by ISPs results in waste of network resources when there are few active subscribers, because it cannot allocate excess bandwidth in the long term. To address it, a traffic control scheme based on core-stateless fair queueing (CSFQ) and token bucket meters (TBMs) has been recently proposed, which can allocate excess bandwidth among active subscribers proportional to their token generation rates. The use of FIF...

Kim, Kyeong Soo

2014-01-01

436

Frequency response of an InGaAsP vapor phase regrown buried heterostructure laser with 18 GHz bandwidth  

Energy Technology Data Exchange (ETDEWEB)

The frequency response of a 1.3-..mu..m InGaAsP vapor phase regrown buried heterostructure laser with an 18-GHz cw bandwidth is analyzed in detail. The intrinsic bandwidth of the device is shown to be 22 GHz and the 3-dB R-italicC-italic roll-off frequency due to electrical parasitics is found to be 10 GHz.

Olshansky, R.; Lanzisera, V.; Su, C.B.; Powazinik, W.; Lauer, R.B.

1986-07-21

437

Rectangular Microstrip Antenna on Ridge Ground Plane to Control the Resonant Modes for Improved Bandwidth using Transverse Resonance Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A single layer single element rectangular microstrip antenna on ridge ground plane for improved bandwidth is theoretically investigated with a view to develop a concrete physical insight in to the phenomenon. The simple single element probe fed rectangular microstrip antenna fabricated on conventional PTFE (Poly Tetra Fluride Ethelene) substrate have many advantages except its narrow bandwidth. The present study proposes the technique to control the resonant modes of a microstrip antenna for ...

Sudip Kumar Ghosh; Abhijyoti Ghosh; Dia Ghosh; Sudipta Chattopadhyay; Sandip Banerjee

2012-01-01

438

High frequency bandwidth polarization and strain control using a fractional derivative inverse model  

International Nuclear Information System (INIS)

The present paper proposes an inverse dynamical model based on fractional derivatives in order to simulate the electrical field versus the polarization field E(P) as well as the electrical field versus the mechanical strain E(S) of ferroelectric hysteresis. By considering a fractional derivative term, the frequency bandwidth of the inverse model is greatly increased. As a consequence, the model became suited for the usual inverse model applications, such as adaptive inverse control of piezoelectric actuators, high-speed positioning or high precision positioning. The proposed high-accuracy inverse model rendered it possible to avoid standard feedback mechanisms that usually exhibit restrain frequency bandwidths due mainly to high frequency noise. Starting from a quasi-static inverse model, and based on a simple mechanism related to the dry-friction concept, a polarization fractional derivative term was added in order to take into account the dynamical effects. The order of the fractional derivative was, using a direct model P(E) and experimental data on a large frequency bandwidth (10?3 Hz 2 Hz), found to be equal to 0.5. A quadratic relation was used to link the ferroelectric strain and the polarization field. Moreover, a dynamical strain control based on an inverse dynamic polarization field contribution was proposed. Experimental procedures were developed to verify the accuracy of the polarization as well as of the strain control. Good results were obtained and exposed for sinus and triangular polarization-imposed waveforms. Various frequencies and amplitudes were tested in both cases

2010-04-01

439

Self-seeding scheme with gas monochromator for narrow-bandwidth soft X-ray FELs  

International Nuclear Information System (INIS)

Self-seeding schemes, consisting of two undulators with a monochromator in between, aim at reducing the bandwidth of SASE X-ray FELs. We recently proposed to use a new method of monochromatization exploiting a single crystal in Bragg transmission geometry for self-seeding in the hard X-ray range. Here we consider a possible extension of this method to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake. In fact, the FEL pulse forces the gas atoms to oscillate in a way consistent with a forward-propagating, monochromatic radiation beam. The radiation power within this wake is much larger than the equivalent shot noise power in the electron bunch. Further on, the monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements. These are the gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation. In this paper we assess the features of gas monochromator based on the use of He and Ne.We analyze the processes in the monochromator gas cell and outside it, touching upon the performance of the differential pumping system as well. We study the feasibility of using the proposed self-seeding technique to generate narrow bandwidth soft X-ray radiation in the LCLS-II soft X-ray beam line. We present conceptual design, technical implementation and expected performances of the gas monochromator self-seeding scheme. (orig.)

2011-01-01

440

Self-seeding scheme with gas monochromator for narrow-bandwidth soft X-ray FELs  

Energy Technology Data Exchange (ETDEWEB)

Self-seeding schemes, consisting of two undulators with a monochromator in between, aim at reducing the bandwidth of SASE X-ray FELs. We recently proposed to use a new method of monochromatization exploiting a single crystal in Bragg transmission geometry for self-seeding in the hard X-ray range. Here we consider a possible extension of this method to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake. In fact, the FEL pulse forces the gas atoms to oscillate in a way consistent with a forward-propagating, monochromatic radiation beam. The radiation power within this wake is much larger than the equivalent shot noise power in the electron bunch. Further on, the monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements. These are the gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation. In this paper we assess the features of gas monochromator based on the use of He and Ne.We analyze the processes in the monochromator gas cell and outside it, touching upon the performance of the differential pumping system as well. We study the feasibility of using the proposed self-seeding technique to generate narrow bandwidth soft X-ray radiation in the LCLS-II soft X-ray beam line. We present conceptual design, technical implementation and expected performances of the gas monochromator self-seeding scheme. (orig.)

Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2011-03-15

 
 
 
 
441

Time Slot Assignment for Maximum Bandwidth in a Mobile Ad Hoc Network  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Time slot assignment is essential to provide the calculated bandwidth in a TDMA (Time Division Multiple Access)-based mobile ad hoc network (MANET), which is a focus of attention of this paper because of its collision-free packet transmission with QoS(Quality of Service) support. In this paper, a new time slo...

Jianping Li; Yasushi Wakahara

2007-01-01

442

Integrated Synthesis of Control and Bandwidth Scheduling on Networked Control Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many Networked Control Systems (NCS) comprise several control loops that are closed over a network of computation nodes. In those systems, periodic, sporadic and non-periodic packets