WorldWideScience
 
 
1

Asymmetric Double Langmuir Probe: Small Signal Application.  

Science.gov (United States)

We discuss the asymmetric double Langmuir probe (ADLP) and demonstrate the possibility of using it to measure plasma temperature T/sub e/ and density n when it is operated in the region of small signal response. The area of one of the ADLP collectors is c...

T. Uckan

1987-01-01

2

Asymmetric double Langmuir probe: Small signal application  

International Nuclear Information System (INIS)

[en] We discuss the asymmetric double Langmuir probe (ADLP) and demonstrate the possibility of using it to measure plasma temperature T/sub e/ and density n when it is operated in the region of small signal response. The area of one of the ADLP collectors is considerably larger than the other. This probe can be operated at a relatively low applied voltage eV/sub a//T/sub e/

1987-01-01

3

Asymmetric double Langmuir probe: Small signal application  

International Nuclear Information System (INIS)

[en] We discuss the asymmetric double Langmuir probe (ADLP) and demonstrate the possibility of using it to measure plasma temperature T/sub e/ and density n when it is operated in the region of small signal response. The area of one of the ADLP collectors is considerably larger than the other. This probe can be operated at a relatively low applied voltage, eV/sub a/T/sub e/

1987-01-01

4

Small-signal analysis of granular semiconductors  

International Nuclear Information System (INIS)

The small-signal ac response of granular n-type semiconductors is calculated analytically using the drift-diffusion theory when electronic trapping at grain boundaries is present. An electrical equivalent circuit (EEC) model of a granular n-type semiconductor is presented. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is very good in a broad frequency range at low dc bias voltages.

2010-11-01

5

Small signal impedance of heart cell membranes.  

UK PubMed Central (United Kingdom)

The electrical impedance of seven-day ventricular embryonic chick heart cell membranes maintained in tissue culture was measured under voltage clamp using the two-microelectrode voltage-clamp technique. Small sinusoidal perturbations were added to the voltage-clamp potential and the amplitude and phase of the steady-state sinusoidal response in current was recorded as a function of mean clamp potential or perturbing frequency. The experimental results are compared with two models of excitability for heart: the MNT model (McAllister, Noble & Tsien, J. Physiol. (London) 251:1-59, (1975) and the BR model (Beeler & Reuter, J. Physiol. (London) 268:177-210, 1977). The small signal impedance of heart cell membranes, in theory and experiment, shows a resonance near 1 Hz and near the threshold potential. The effect of this resonance is to increase the effective length constant of the membrane for these conditions.

Clapham DE; DeFelice LJ

1982-01-01

6

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. Us...

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

7

A New Circuit Model of Small-Signal Sziklai Pair Amplifier  

Directory of Open Access Journals (Sweden)

Full Text Available A new circuit model of RC coupled small-signal Sziklai pair amplifier is proposed and qualitatively analyzed for the first time. The circuit of proposed amplifier uses a Sziklai pair with NPN driver and crops high voltage gain (237.916), moderate bandwidth (15.10KHz), fairly high current gain (712.075) and considerably low THD (0.73%) at 1mV, 1KHz input AC signal. This circuit can be tuned in specific audible frequency range, extending approximately from 1Hz to 20KHz. Tuning performance makes this amplifier circuit suitable to use in Radio and TV receiver stages. The qualitative and tuning performance of the proposed amplifier offers it a flexible application range as high voltage gain, high power gain and tuned amplifier. Tuning performance, variation of voltage gain with frequency and different biasing resistances, input and output noises at operating frequency, temperature dependency of performance parameters and total harmonic distortion of the amplifier are perused for providing wide spectrum to the qualitative studies. The proposed Sziklai pair configuration with NPN driver transistor can be attempted to fabricate a single pack transistor IC version of Sziklai pair. Proposed circuit is also free from poor response problem of small-signal Darlington pair amplifiers at higher frequencies and narrow-band response region for PNP driven small-signal Sziklai pair amplifier.

SachchidaNand Shukla and Susmrita Srivastava

2013-01-01

8

Small-signal Amplifier with Three Dissimilar Active Devices in Triple Darlington Topology  

Directory of Open Access Journals (Sweden)

Full Text Available A new circuit model of a small-signal amplifier is proposed and analyzed on the qualitative scale. Apart from routine biasing components, the proposed amplifier circuit uses two additional biasing resistances and three dissimilar active devices namely MOSFET, JFET and BJT in Triple Darlington configuration. Having a considerably low amount of distortion (0.71%), the proposed circuit successfully amplifies small-signals of 1-5mV range (at 1 KHz frequency) and simultaneously provides high voltage gain (189.846) and high current gain (16.542K) with moderate range bandwidth (369.529KHz). These properties offer a flexible application range to the proposed circuit as high voltage gain or high current gain or high power gain amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are perused to provide a wide spectrum to the qualitative studies. Qualitative performance of the proposed amplifier is also compared with two different circuits which are respectively having BJT-JFET and BJT-MOSFET in Darlington pair configuration. The proposed amplifier may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in audio frequency region.

DR.SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

2013-01-01

9

Small-signal neural models and their applications.  

UK PubMed Central (United Kingdom)

This paper introduces the use of the concept of small-signal analysis, commonly used in circuit design, for understanding neural models. We show that neural models, varying in complexity from Hodgkin-Huxley to integrate and fire have similar small-signal models when their corresponding differential equations are close to the same bifurcation with respect to input current. Three applications of small-signal neural models are shown. First, some of the properties of cortical neurons described by Izhikevich are explained intuitively through small-signal analysis. Second, we use small-signal models for deriving parameters for a simple neural model (such as resonate and fire) from a more complicated but biophysically relevant one like Morris-Lecar. We show similarity in the subthreshold behavior of the simple and complicated model when they are close to a Hopf bifurcation and a saddle-node bifurcation. Hence, this is useful to correctly tune simple neural models for large-scale cortical simulations. Finaly, the biasing regime of a silicon ion channel is derived by comparing its small-signal model with a Hodgkin-Huxley-type model.

Basu A

2012-02-01

10

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; Pérez Serge

2012-01-01

11

Modulation bandwidth of high-power single-mode semiconductor lasers: Effect of intraband gain saturation  

Energy Technology Data Exchange (ETDEWEB)

The effect of intraband gain saturation on the modulation bandwidth of single-mode semiconductor lasers is discussed by using a nonperturbative form of the optical gain that is valid at high-power levels. The small-signal analysis of the modified rate equations is used to predict the power dependence of the modulation bandwidth. The results are used to discuss the ultimate modulation bandwidth of InGaAsP distributed feedback semiconductor lasers and its dependence on various device parameters.

Agrawal, G.P.

1990-07-02

12

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; NARESH KUMAR CHAUDHARY; SACHCHIDANAND SHUKLA

2013-01-01

13

A Novel Circuit Model of Small-Signal Amplifier Developed by Using BJT-JFET-BJT in Triple Darlington Configuration  

Directory of Open Access Journals (Sweden)

Full Text Available Two distinct configurations of small-signal amplifiers, consisting hybrid combination of BJT-FET-BJT in Triple Darlington topology, are proposed and qualitatively analyzed perhaps for the first time. The first proposed amplifier crops high voltage with moderate current gain and bandwidth in 1-15mV input signal range at 1 KHz frequency. However, the second amplifier is configured by creating certain modifications in the first circuit. This amplifier produces about double voltage and current gain than the first amplifier circuit with almost half bandwidth in 1-4mV input-signal-range at 1 KHz frequency. Both the amplifier circuits include two additional biasing resistances. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifiers are also perused. The proposed amplifiers can be successfully implemented as high power gain small-signal amplifiers in audio-frequency-range because of the obtained values of the current and voltage gains which are higher than unity.

SACHCHIDANAND SHUKLA; SUSMRITA SRIVASTAVA

2013-01-01

14

Transient and asymptotic small-signal gain in laser amplifiers  

Energy Technology Data Exchange (ETDEWEB)

The problem of pulse amplification in the small-signal regime of a laser amplifier is investigated theoretically. Analytical solutions to the Maxwell-Bloch equations are obtained. These reconcile the concept of laser gain needed to describe free-electron lasers (and synchronously pumped lasers in general) with earlier concepts that describe pulsed laser amplifiers. We find the latter to be a transient of our solution while the former depends on its asymptotic features.

Hopf, F.A.; Bergou, J.; Varro, S.

1986-12-01

15

High Bandwidth Page  

Science.gov (United States)

The High Bandwidth Page is a good starting point for those who have decided it's time they learn more about all the hoopla surrounding high-bandwidth Internet access, especially to the home. The page provides links to extensive information about cable modems, ISDN, and the newest group of letters to hit the Net: ADSL. Also provided are sections on video telephones and general articles related to high bandwidth. A good individual effort by Gary Zaret.

16

Regulation of Arabidopsis root development by small signaling peptides.  

UK PubMed Central (United Kingdom)

Plant root systems arise de novo from a single embryonic root. Complex and highly coordinated developmental networks are required to ensure the formation of lateral organs maximizes plant fitness. The Arabidopsis root is well-suited to dissection of regulatory and developmental networks due to its highly ordered, predictable structure. A myriad of regulatory signaling networks control the development of plant roots, from the classical hormones such as auxin and cytokinin to short-range positional signaling molecules that relay information between neighboring cells. Small signaling peptides are a growing class of regulatory molecules involved in many aspects of root development including meristem maintenance, the gravitropic response, lateral root development, and vascular formation. Here, recent findings on the roles of regulatory peptides in these aspects of root development are discussed.

Delay C; Imin N; Djordjevic MA

2013-01-01

17

CCD small signal characterization using fluoresce x rays  

Science.gov (United States)

Past and present revelations within scientific imaging have stressed the importance of CCD small signal sensitivity. Current characterization techniques use a Fe55 soft x-ray source to determine charge transfer and noise, however rendering signal sensitivity less than 1620 e- unknown. CCD evolution has brought forth innovative design and fabrication techniques to decrease device noise and increase device sensitivity, enabling low level imaging. This paper presents a simple approach to characterizing the transfer functions, linearity, noise, and output sensitivity at low signal levels, thus confirming the true capabilities of the imager. This characterization technique also validates the quality of the base material and process via low level trap testing. The characterization method uses fluoresce x-rays from target materials to illuminate the imager.

Boggs, Kasey

2006-02-01

18

Small Signal Stability Analysis of Switching Dynamical Systems  

UK PubMed Central (United Kingdom)

Integration of power electronic switchingsystems into electric utility systems and electric motionsystems creates the possibility of new instabilities in thesesystems. The analysis of these systems is a challengingproblem since it is difficult to develop a high fidelityanalytical model that captures the complex dynamicalinteraction of these systems. Averaging models often do notprovide the required accuracy and therefore they cannotalways predict the stability properties of the system. To meetthis challenge, a new small signal stability analysis methodhas been developed. The method is based on computation ofthe transition matrix over a specified time interval. Sincethese systems are generally periodic the time interval isselected equal to one cycle of the fundamental frequency.The method is applicable to any system and it is especiallysuited to switching systems with or without nonlinearelements. In this paper we are interested in systems withPEBB (Power Electronic Building Block)driven motionsubsystems (i.e. any type of electric motors). An applicationexample is presented.

A. P. Meliopoulos; G. J. Cokkinides; R. A. Dougal

19

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

20

Small-signal theory of gyrotrons and gyroklystrons  

International Nuclear Information System (INIS)

Zhurakovskiy's equation of motion for electrons in a steady magnetic field and a time-varying transverse electric field have been used to derive an interaction impedance for an electron beam passing through a TE cavity with one or more one-half sinusoid axial variations of transverse electric field. In a similar fashion an expression for transconductance of a gyroklystron consisting of TE cavities separated by drift spaces has been derived. The expressions contain relativistic corrections which are important above approximately 50 kV but give results identical with those of Hirshfield et al. at lower voltages. In addition, an analytic small-signal, space-charge theory for gyroklystrons utilizing TE/sub o,n/ cavities and a hollow electron beam has been developed. It predicts exponential growth of the modulation on the beam in a drift space free of all fields other than the space-charge fields and the steady magnetic field. The beam loading, transconductance and space-charge theories have been used to predict the stability and gain of Gyrotrons and gyroklystrons for EBT. The tubes operate at 80 kV and have produced up to 250 kW at 28 GHz

1977-10-25

 
 
 
 
21

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

22

The Bandwidth Exchange Architecture  

CERN Multimedia

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

23

Message in a bottle: small signalling peptide outputs during growth and development.  

UK PubMed Central (United Kingdom)

Classical and recently found phytohormones play an important role in plant growth and development, but plants additionally control these processes through small signalling peptides. Over 1000 potential small signalling peptide sequences are present in the Arabidopsis genome. However, to date, a mere handful of small signalling peptides have been functionally characterized and few have been linked to a receptor. Here, we assess the potential small signalling peptide outputs, namely the molecular, biochemical, and morphological changes they trigger in Arabidopsis. However, we also include some notable studies in other plant species, in order to illustrate the varied effects that can be induced by small signalling peptides. In addition, we touch on some evolutionary aspects of small signalling peptides, as studying their signalling outputs in single-cell green algae and early land plants will assist in our understanding of more complex land plants. Our overview illustrates the growing interest in the small signalling peptide research area and its importance in deepening our understanding of plant growth and development.

Czyzewicz N; Yue K; Beeckman T; Smet ID

2013-09-01

24

ABB: active bandwidth broker  

Science.gov (United States)

In this paper, we shall discuss a novel design on the policy-based management for the Internet. This design deploys the concept of active networking. As opposed to the traditional network design, active network empowers network node with the ability to manipulate data and program code in packets, and configure the network properties according to the needs of different applications. The policy-based management can control network routers in order to realize end-to-end Quality of Service (QoS), such as differentiated and integrated services, across the Internet. For the moment, the Internet Engineering Task Force (IETF) has defined the framework of the policy-based management. It employs a simple client/server model that uses Common Open Policy Service (COPS) protocol to facilitate policy management and control. Our design of Active Bandwidth Broker (ABB) belongs to an active application. Our goals are to distribute centralized workload of the policy-based management over multiple active nodes in the active networks, introduce mobility of the bandwidth brokers, and allows load sharing to the policy-based management. This results a network-wide intelligent, highly available, and consistent QoS control that allows performance protection for voice, video and Internet business application while reducing costs for growing networks.

Wong, Kason; Law, Edward

2001-07-01

25

Dynamic Bandwidth Allocation Schemes  

UK PubMed Central (United Kingdom)

Ethernet Passive Optical Networks (EPONs) arean emerging access network technology that provides a lowcost !!solution for fiber-to-the-home (FTTH) and fiber-to-business(FTTB). In this paper, conventional bandwidth allocation schemesin EPON are shown to suffer from poor utilization under nonuniformtraffic conditions, particularly as the number of ONUs,guard time and round-trip time increase. To resolve this problem,we propose a new scheme that allocates a timeslot intelligentlyby considering other ONUs' queue occupancy, instead of strictlyenforcing a maximum timeslot size. The analysis and simulationresults show that the proposed scheme can provide significantlyhigher utilization than conventional schemes and can supportmax-min fairness under non-uniform traffic conditions.

26

Bandwidth enhancement and optical performances of multiple quantum well transistor lasers  

CERN Document Server

A detailed rate-equation-based model is developed to study carrier transport effects on optical and electrical characteristics of the Multiple Quantum Well Heterojunction Bipolar Transistor Laser in time-domain. Simulation results extracted using numerical techniques in small-signal regime predict significant enhancement in device optical bandwidth when multiple quantum wells are used. Cavity length and base width are also modified to optimize the optoelectronic performances of the device. An optical bandwidth of \\approx 60GHz is achieved in the case of 5 quantum wells each of 70A widths and a cavity length of 200um.

Taghavi, Iman; Leburton, Jean-Pierre

2012-01-01

27

Modulation bandwidth of planar waveguide laser with 1D photonic crystal mirrors  

Science.gov (United States)

An analysis of the 3-dB modulation bandwidth in planar waveguide laser based on 1D photonic crystal structures is presented. The theoretical model takes into account the gain saturation effect, transverse and longitudinal field distribution. A small-signal perturbation solution of the coupled laser rate equation is used to obtain relations describing the dynamic operation. In paper, the distributed Bragg resonator DBR created as 1D photonic crystal is considered. The active waveguide is surrounded by 1D photonic crystal mirrors consisting of alternately placed stripes with different refractive indices. In particular, the influence of the photonic crystal parameters on the 3-dB modulation bandwidth is investigated.

Mossakowska-Wyszy?ska, A.

2012-12-01

28

Small signal theory of an open column grating with arbitrarily shaped groove  

Energy Technology Data Exchange (ETDEWEB)

An open column grating with arbitrarily shaped groove is studied in this paper. The small signal analysis is carried out based on a model that an annular electron beam flies near the surface of the column grating. The dispersion equation is established for the slow wave in the way of self-consistent field theory. Through numerical solutions of the dispersion equation, the dispersion relation, frequency characteristic and the small signal gain for various shapes of groove are analyzed, as well as the dependences of the gain on the electron beam and grating parameters are investigated.

Chen Beiran [Vacuum Electronics National Laboratory, University of Electronic Science and Technology of China, Chengdu 610054 (China); Wei Yanyu [Vacuum Electronics National Laboratory, University of Electronic Science and Technology of China, Chengdu 610054 (China)], E-mail: yywei@uestc.edu.cn; Gong Yubin; Lin Juan; Zhao Guoqing; Wang Wenxiang [Vacuum Electronics National Laboratory, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li Dazhi [Institute for Laser Technology, Osaka 565-0871 (Japan)

2008-07-21

29

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; Wen Ying Liu; Xu Bin Han

2013-01-01

30

Small-signal frequency response theory for ideal dc-to-dc converter systems  

Energy Technology Data Exchange (ETDEWEB)

The frequency response problem of a switching dc-to-dc converter system is the problem of computing the small-signal frequency response of the system with respect to its inputs. It arises in the study of the small-signal behavior and in the design of a feedback controller for the dc-to-dc converter system. The analytical solution of the problem is discussed in this thesis. There are previous efforts in developing approximate analytical methods for solving the problem; however, these methods are unsatisfactory. The Small-Signal Frequency Response Theory presented in this thesis is a mathematical theory for the linearization of an ideal dc-to-dc converter system in the vicinity of its steady-state solution. It is developed to overcome the problems encountered in the application of the approximate analytical methods. The theory is exact in the small-signal limit, and the results given by the theory is valid at all frequencies provided that the system model used in the calculation of frequency response is valid at all frequencies. The theory has the best of both the time-domain approach and the frequency domain approach for the analysis of switching dc-to-dc converter systems. The theory results in significant impact in the fields of computer-aided design and modeling and analysis in power electronics.

Lau, B.Y.

1987-01-01

31

Pressure dependence of the small-signal gain and saturation intensity of a copper vapor laser.  

Science.gov (United States)

The small-signal gain coefficient and the saturation intensity of a copper vapor laser have been measured for both 510.6- and 578.2-nm transitions through the implementation of a discharge driven oscillator-amplifier configuration. Pressure dependence of the gain and saturation property of the laser has been investigated. PMID:12617218

Behrouzinia, Saeid; Sadighi, Rasool; Parvin, Parviz

2003-02-20

32

Small-Signal Step Response of Laser Amplifiers and Measurement of CO2 Laser Linewidth.  

Science.gov (United States)

As part of a general program of research on time response of a laser medium to optical transients, the linear (small-signal) response to a rectangular pulse signal input, were studied both theoretically and experimentally. The theory for the case of Loren...

T. J. Bridges H. A. Haus P. W. Hoff

1968-01-01

33

Bandwidth reduction in rectalgular grids  

CERN Document Server

We show that the bandwidth of a square two-dimensional grid of arbitrary size can be reduced if two (but not less than two) edges are deleted. The two deleted edges may not be chosen arbitrarily, but they may be chosen to share a common endpoint or to be non-adjacent. We also show that the bandwidth of the rectangular n by m (m greater or equal to n) grid can be reduced by k, for all k that are sufficiently small, if m-n+2k edges are deleted.

Andreescu, T; Sunik, Z; Sunik, Zoran

2003-01-01

34

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

35

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

36

Analysis of free electron laser small-signal gain for gaussian beams  

International Nuclear Information System (INIS)

A three-dimensional gain expression is presented and analysed for a Gaussian optical beam in small signal case. An asymptotic gain formula is given for a broader electron beam in cross section compared to the optical beam. When electron beam transverse dimension is smaller than the beam waist of the Gaussian mode, an analytic approximate formula is given and the results are in good agreement with numerical simulations

1991-01-01

37

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.

Ramya R; Selvi K

2012-01-01

38

Small signal gain analysis for a wiggler with noncollinear laser wave and electron beam  

CERN Multimedia

The collective and single-electron amplification regimes of a non-collinear free electron laser are analyzed within the framework of dispersion equations. The small-signal gain and the conditions for self-amplified excitations are found. The collective excitations in a free electron laser are shown to be favored by the non-collinear arrangement of the relativistic electrons and the laser wave. Implications for free-electron lasing without inversion are discussed.

Artemiev, A I; Kurizki, G; Poluektov, N P; Shubin, N Y

2004-01-01

39

An EC-branch in the decay of 27-s sup 2 sup 6 sup 3 Db evidence for the isotope sup 2 sup 6 sup 3 Rf  

CERN Multimedia

27-s sup 2 sup 6 sup 3 Db was produced in the sup 2 sup 4 sup 9 Bk ( sup 1 sup 8 O, 4n) reaction at 93 MeV.The activity was transported by a He/KCl-jet to the laboratory where it was collected for 15 min and then subjected to a chemical separation specific for group-4 elements. The activity was dissolved in 0.5 M unbuffered alpha-HiB and eluted from a cation-exchange column. The effluent was made 9 M in HCl and group-4 tetrachlorides were extracted into TBP/Cyclohexane which was evaporated to dryness on a Ta disc. The Ta discs were assayed for alpha and SF activity. A SF activity with a half life on the order of 20 min was observed and assigned to the nuclide sup 2 sup 6 sup 3 Rf. It is formed by electron-capture decay of sup 2 sup 6 sup 3 Db with a decay branch of 3 sup + sup 4 sub - sub 1 %.

Kratz, J V; Rieth, U; Kronenberg, A K; Kuczewski, B; Strub, E; Brüchle, W; Schädel, M; Schausten, B; Türler, A; Gäggeler, H W; Jost, D T; Gregorich, K E; Nitsche, H; Laue, C; Sudowe, R; Wilk, P A

2003-01-01

40

Dynamic bandwidth allocation in GPON networks  

DEFF Research Database (Denmark)

Two Dynamic Bandwidth Allocation algorithms used for coordination of the available bandwidth between end users in a GPON network have been simulated using OPNET to determine and compare the performance, scalability and efficiency of status reporting and non status reporting dynamic bandwidth allocation. Results show that the status reporting is more efficiently using the bandwidth while non-status reporting provides better QoS for real time services.

Ozimkiewiez, J.; Ruepp, Sarah Renée

2009-01-01

 
 
 
 
41

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 (TISO)controller 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; A. Chakrabarti; A. Sengupta

2012-01-01

42

Improvement of modulation bandwidth in multisection RSOA for colorless WDM-PON.  

UK PubMed Central (United Kingdom)

We demonstrated two-section reflective semiconductor optical amplifier (RSOA) with dramatic improvement of small-signal modulation bandwidth above 10 GHz as colorless source for wavelength division multiplexed-passive optical network (WDM-PON). The device provides the fiber-to-fiber gain of 22.8 dB, 3-dB amplified spontaneous emission (ASE) bandwidth of 30 nm, and ripple of 1.5 dB. Good performance at 2.5 Gbps was obtained with an extinction ratio of 8 dB and a power penalty of 2 dB at a 10(-9) bit error rate (BER) up to 20 km transmission.

Kim HS; Choi BS; Kim KS; Kim DC; Kwon OK; Oh DK

2009-09-01

43

Numerical modeling and experimental testing of reflective semiconductor optical amplifier (RSOA) with modulation bandwidth optimization  

Science.gov (United States)

The characteristics of commercial RSOA, i.e. fiber-to-fiber gain and small-signal electro-optical conversion (E/O) response are measured. A numerical model for RSOA including spatial variations of carrier density and ASE noise is established and validated via experimental tests. The auger recombination coefficient and active region bulk of commercial RSOA are determined by fitting the stimulated characteristics to the experimental results numerically. Performance of RSOA with different cross-sectional areas of active region is investigated based on the numerical model. The stimulated results indicate that reducing the cross-sectional area can increase its modulation bandwidth. RSOA 3-dB bandwidth is able to increase to 10.0GHz by optimizing its active region bulk.

Liu, Mingtao; Zhang, Min; Liu, Lei; Zhan, Yueying; Liu, Zhuo; Ye, Peida

2010-12-01

44

Bandwidth requirements for fine resolution squinted SAR  

Energy Technology Data Exchange (ETDEWEB)

The conventional rule-of-thumb for Synthetic Aperture Radar is that an RF bandwidth of c/(2{rho}{sub r}) is required to image a scene at the desired slant-range resolution {rho}{sub r}, and perhaps a little more to account for window functions and sidelobe control. This formulation is based on the notion that the total bandwidth required is the same bandwidth that is required for a single pulse. What is neglected is that efficient processing of an entire synthetic aperture of pulses will often require different frequency content for each of the different pulses that makeup a synthetic aperture. Consequently, the total RF bandwidth required of a Synthetic Aperture Radar may then be substantially wider than the bandwidth of any single pulse. The actual RF bandwidth required depends strongly on flight geometry, owing to the desire for a radar to maintain a constant projection of the Fourier space collection surface onto the {omega}{sub y} axis. Long apertures required for fine azimuth resolution, and severe squint angles with steep depression angles may require total RF bandwidths well beyond the minimum bandwidth required of any single transmitted pulse, perhaps even by a factor of two or more. Accounting for this is crucial to designing efficient versatile high-performance imaging radars. This paper addresses how a data set conducive to efficient processing might increase the total RF bandwidth, and presents examples of how a fixed RF bandwidth might then limit SAR geometries.

DOERRY,ARMIN W.

2000-03-01

45

Influence of Wind Plant Ancillary Frequency Control on System Small Signal Stability  

DEFF Research Database (Denmark)

Since large-scale wind farms are increasingly connected to modern power grids, the transmission system operators put more requirements as part of the grid codes on the integration of wind farms. System frequency control which is normally provided by conventional synchronous generators becomes a common requirement to wind farms. This ancillary frequency control provided by wind farms could have some influence on the system small signal stability. This paper implements an ancillary frequency control strategy on a directdrive- full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation modes within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0.

Su, Chi; Chen, Zhe

2012-01-01

46

Influence of Wind Plant Ancillary Voltage Control on System Small Signal Stability  

DEFF Research Database (Denmark)

As a common tendency, large-scale wind farms are increasingly connected to the transmission system of modern power grids. This introduces some new challenges to the connected power systems, and the transmission system operators (TSOs) have to put some new requirements as part of the grid codes on the integration of wind farms. One common requirement to wind farms is the function of system voltage control which can be implemented in the grid-side convertor controller of a variable speed wind turbine. This ancillary voltage control provided by wind farms could have some influence on the system small signal stability. This paper implements an ancillary voltage control strategy on a direct-drive-full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation mode within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0.

Su, Chi; Chen, Zhe

2012-01-01

47

Comparison Study of Power System Small Signal Stability Improvement Using SSSC and STATCOM  

DEFF Research Database (Denmark)

A static synchronous series compensator (SSSC) has the ability to emulate a reactance in series with the connected transmission line. A static synchronous compensator (STATCOM) is able to provide the reactive power to an electricity network. When fed with some supplementary signals from the connected power system, both SSSC and STATCOM are able to participate in the power system inter-area oscillation damping by changing the compensated reactance or the provided reactive power. This paper analyses the influence of SSSC and STATCOM on power system small signal stability. The damping controller schemes for SSSC and STATCOM are presented and discussed. The IEEE 39-bus New England system model as the test system is built in DIgSIELNT PowerFactory, in which the damping control strategies for both SSSC and STATCOM are validated by time domain simulations and modal analysis. Furthermore, comparison studies show that the SSSC is a better solution in term of equipment capabilities and costs.

Hu, Weihao; Su, Chi

2013-01-01

48

Small-Signal Amplification of Period-Doubling Bifurcations in Smooth Iterated Maps  

CERN Document Server

Various authors have shown that, near the onset of a period-doubling bifurcation, small perturbations in the control parameter may result in much larger disturbances in the response of the dynamical system. Such amplification of small signals can be measured by a gain defined as the magnitude of the disturbance in the response divided by the perturbation amplitude. In this paper, the perturbed response is studied using normal forms based on the most general assumptions of iterated maps. Such an analysis provides a theoretical footing for previous experimental and numerical observations, such as the failure of linear analysis and the saturation of the gain. Qualitative as well as quantitative features of the gain are exhibited using selected models of cardiac dynamics.

Zhao, X; Berger, C M; Gauthier, D J; Zhao, Xiaopeng; Schaeffer, David G.; Berger, Carolyn M.; Gauthier, Daniel J.

2006-01-01

49

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 generator’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 generators’ 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 method’s capability to efficiently identify the location of the emerging problem and to quantify margins to stability boundary.

Jóhannsson, Hjörtur

2013-01-01

50

Small signal stability analysis program package: Version 2. 0 User Manual  

Energy Technology Data Exchange (ETDEWEB)

The Small Signal Stability Package (SSSP) consists of two eigenvalue programs MASS and PEALS along with a data base program. This volume contains two user manuals: one for the programs MASS and PEALS and one for the data base program. The dynamic data and part of the program control data are common to MASS and PEALS and, therefore, a single manual is provided for both programs. Data applicable only to one of the programs is clearly identified in the manual. The MASS-PEALS manual describes the general structure of the dynamic data file for dynamic data supplied in OH, EPRI, IEEE or PECO format. OH dynamic models and their input-data formats are described in detail. The user manual for the data base program, describes the format of the input data required to create a new data base or print data stored in an existing data base. 19 figs., 1 tab.

Rogers, G.J.; Wong, D.Y. (Ontario Hydro, Toronto, ON (Canada))

1990-01-01

51

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

2012-01-01

52

Experimental modulation bandwidth beyond the relaxation oscillation frequency in a monolithic twin-ridge laterally coupled diode laser based on lateral mode locking.  

UK PubMed Central (United Kingdom)

Monolithic twin-ridge laterally coupled diode lasers emitting at 1.3microm are presented that have a small-signal modulation bandwidth beyond the relaxation oscillation frequency of a single ridge. Spectra and spectrally resolved far fields are presented for three bias conditions: only one ridge lasing, both ridges lasing just above threshold, and both ridges lasing at biases well above threshold. In the first two cases the spectrum has single-peaked longitudinal modes, whereas the third cases shows splitting to in-phase and out-of-phase modes. The splitting frequency of the optical spectrum is measured to be 7.7 GHz. Small-signal modulation measurements reveal a strong resonance at 7.7 GHz, demonstrating an effect of lateral mode locking. As a result of this effect, the twin-ridge laser can be made to have a -3-dB bandwidth beyond that associated with its relaxation oscillation frequency.

Lamela H; Roycroft B; Acedo P; Santos R; Carpintero G

2002-03-01

53

A decision weight analysis of transition bandwidths.  

UK PubMed Central (United Kingdom)

A decision weight analysis is used to investigate transition bandwidths [Berg (2007). J. Acoust. Soc. Am. 121, 3639-2645]. The psychophysical task is similar to a standard profile analysis experiment except that the spacing of the tones comprising the stimuli is linear and very narrow (e.g., 20 Hz). An increment in the level of the central tone constitutes the signal. Pitch cues and single channel energy cues are degraded with randomization procedures. Thresholds increase as the number of tones comprising the stimulus (n) increases up to a transition bandwidth and then decrease or stay constant with further increases in n. It is proposed that the transition bandwidth reflects a discrete change in the underlying process, with a temporal process (e.g., envelope processor) dominating for stimulus bandwidths less than the transition bandwidth and a process of spectral profile analysis at wider bandwidths. Estimates of decision weights support the proposal.

Berg BG

2013-03-01

54

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...

2012-10-01

55

BANDWIDTH ENLARGEMENT OF PLANAR EBG ANTENNAS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new structure based on a combination of two PRS (Partially Reflective Surface) is introduced and studied analytically to improve the bandwidth of the FP and EBG antennas. The original procedure developed here leads to a design method for broadening the bandwidth of planar EBG antennas.

Vu, Thai Hung; Mahdjoubi, Kouroch; Tarot, Anne-Claude; Collardey, Sylvain

56

Holographic Bandwidth Compression Using Spatial Subsampling  

UK PubMed Central (United Kingdom)

A novel electro-holographic bandwidth compression technique, fringelet bandwidth compression,is described and implemented. This technique uses spatial subsampling to reduce the bandwidth and complexityof holographic fringe computation for real-time 3-D holographic displays. Fringelet bandwidth compressionis a type of diffraction-specific fringe computation, an approach that considers only the reconstructionprocess in holographic imaging. The fringe pattern is treated as a spectrum that is sampled in space (as holographicelements or "hogels") and in spatial frequency (as "hogel vectors"). Fringelet bandwidth compressionachieves a compression ratio of 16:1 without conspicuously degrading image quality. Further increase in compressionratio and speed is possible with additional image degradation. Fringelet decoding is extremely simple,involving the replication of fringelet sample values. This simplicity enables an overall increase in fringe computationspeed of over 3000 times co...

57

Coupled-cavity semiconductor lasers under current modulation: small-signal analysis  

Energy Technology Data Exchange (ETDEWEB)

The modulation characteristics such as the power response and the chirp (dynamic line broadening) of single-frequency coupledcavity semiconductor lasers are analyzed theoretically. The model is based on the small-signal analysis of a set of generalized rate equations and neglects the lateral variations of the optical field and the carrier density in the two cavity sections. When the controller section is biased below threshold in a three-terminal device the modulation response is not significantly affected by the intercavity coupling. By contrast, new features arise when both sections are biased above threshold. It is found that the chirp can be significantly reduced by a proper combination of the bias levels and the modulation splitting between the two sections. The chirp reduction also depends on the strength of the intercavity coupling and its phase, and the best performance is achieved for the case of in-phase coupling. The calculated results are in qualitative agreement with the reported experimental data and are useful as a guide to optimize the performance of a coupled-cavity device.

Agrawal, G.P.

1985-03-01

58

Linewidth considerations in small signal gain or loss measurements with pulses  

International Nuclear Information System (INIS)

[en] This report discusses the difference between c.w. and pulse small signal gain or loss measurements. The spectrum of the gain or loss medium must be compared to the spectrum of the probe signal. First we discuss the formulation of the problem and apply the results to a Gaussian pulse propagating through a single line Lorentzian gain or loss medium. Second, we calculate the pulse energy gain or loss for the six overlapping lines of the iodine spectrum. (orig.)[de] Die vorliegende Arbeit diskutiert den Unterschied zwischen C.W.- und Kleinsignal-Plusverstaerkungs- oder Verlustmessungen. Das Spektrum des verstaerkenden oder daempfenden Mediums muss mit dem Spektrum des Mess-Signals verglichen werden. Zuerst wird die Formulierung des Problems dargestellt um anschliessend die Ergebnisse auf die Ausbreitung eines Gauss-foermigen Pulses in einem verstaerkenden oder daempfenden Medium mit Lorenenz-foermiger Einliniencharakteristik anzuwenden. Weiterhin wird die Energieverstaerkung oder -Daempfung des Pulses fuer den Fall der sechs ueberlappenden Linien des Iod-Spektrums berechnet. (orig.)

1976-01-01

59

Small signal model for H bridge chopper power supply and digital controller realization based on TMS320F2808  

International Nuclear Information System (INIS)

A brief summary of H bridge non-isolated DC-DC converter and operation principles is presented in this paper. A small signal model of the ideal converter in continuous current mode is proposed and simulation results of the converter are given. The hardware structure of digital power supply controller based on TMS320F2808 MCU is introduced. (authors)

2009-01-01

60

A Method to Simultaneously Extract the Small-Signal Equivalent Circuit and Noise Parameters of Heterojunction Bipolar Transistors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method to extract the elements of the small-signal equivalent circuit and the noise parameters (NPs) of heterojunction bipolar transistors (HBTs) is presented. The extraction is done by simultaneous fitting of the measured S-parameters, noise figure (for a well-matched impedance), and NPs (estimat...

Maya Sánchez, Mª del Carmen; Lázaro Guillén, Antoni; Pradell i Cara, Lluís

 
 
 
 
61

Measurement of the small-signal gain and saturation intensity of a XeF discharge laser.  

Science.gov (United States)

An optical oscillator-amplifier series driven by a Blumlein discharge has been fabricated and optimized for measuring the small-signal gain and saturation intensity of a XeF (B ? X) laser at 352 nm. Pressure dependence of the gain and the saturation property of the laser have been investigated. PMID:18250782

Parvin, P; Zaeferani, M S; Mirabbaszadeh, K; Sadighi, R

1997-02-20

62

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 th...

Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

63

Small signal gain based on analytic models of thin intense electron beams  

Energy Technology Data Exchange (ETDEWEB)

We develop the free-electron laser theory of the effective energy distribution and the small signal gain for a thin electron beam. The assumption of thinness allows us to treat various transverse locations and electron beam trajectory angles as introducing phase shifts that have the same effect as those introduced by a change in energy of the electron. We have extended these ideas in five important ways. The first is the ability to treat electron beams with three different classes of matching or symmetry conditions: (1) electron beams with separate betatron matching in each plane, (2) those with aspect ratio matching, and (3) crossed matched beams. Manifestations of these symmetries include elliptical cross sections and electron beams that have modulated spatial profiles. Second, two emittance parameters for the electron beam are shown to consolidate into a single parameter that describes most of the energy variation of the effective energy distributions. Third, these calculations extend to energy distributions, angular distributions, and spatial distributions that all follow gaussian profiles. Fourth, this model incorporates the description of the incident gaussian optical beam and the above electron beam dynamics into a single influence function kernal. Fifth, three-dimensional profiles of the optical fields are computed. In this work the parameters of the incident optical beam are included. The resulting transverse dependence of the fields may be characterized by an optical beam radius. This optical beam width starts out large compared to the thin electron beam and then, in the example given, contracts to a size that becomes so small that the thin beam assumption is violated. 10 refs., 5 figs.

Elliott, C.J.; McVey, B.; Schmitt, M.

1990-01-01

64

Electron mobility characterization in OLEDs from ac small signal optical modulation  

International Nuclear Information System (INIS)

This paper investigates the field dependence of electron mobility in tris(8-hydroxyquinolinato)aluminium (Alq3) and bathocuproine (BCP) through ac small signal optical modulation on green light (ITO/PEDOT/NPD/Alq3/Ba/Ag) and blue light (ITO/PEDOT/NPD/BCP/Alq3/Ba/Ag) OLED. The electroluminescence (EL) transient time delay for the blue light OLED is much longer than for the green one. The electron mobility in BCP was extracted based on a Poole-Frenkel-like equation and EL transient time delay measurement, which is in the range (7-9) x 10-8 cm2 V-1 s-1 at an external electric field of 1530-1830 (V cm-1)1/2, comparable to the results from other published reports (Muckl et al 2000 Synth. Met. 111-112 91; Barth et al 2001 J. Appl. Phys. 89 3711; Nakamura H et al 1996 Int. Symp. on Inorganic and Organic Electroluminescence ed R H Mauch and H-E Gumlich (Berlin: Wissenschaft und Technik) p 95; Xie et al 2002 Appl. Phys. Lett. 80 1477). The difference in EL transient time delay and electron mobility for green and blue light OLEDs was demonstrated by the results of direct modulation. The electron transit time shows similar field dependence in both Alq3 layers in green and blue OLEDs. Unlike Alq3, the field dependence of electron mobility in BCP did not fit the conventional organic semiconductor characteristics ??exp(?E1/2), and the excitons formation at the NPD/BCP interface for the blue OLEDs was demonstrated through the EL spectrum.

2010-05-19

65

High bandwidth control of precision motion instrumentation.  

UK PubMed Central (United Kingdom)

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 DA; Dong J; Alleyne AG; Ferreira P; Salapaka S

2008-10-01

66

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

67

Consistent static and small-signal physics-based modeling of dye-sensitized solar cells under different illumination conditions.  

Science.gov (United States)

A numerical device-level model of dye-sensitized solar cells (DSCs) is presented, which self-consistently couples a physics-based description of the photoactive layer with a compact circuit-level description of the passive parts of the cell. The opto-electronic model of the nanoporous dyed film includes a detailed description of photogeneration and trap-limited kinetics, and a phenomenological description of nonlinear recombination. Numerical simulations of the dynamic small-signal behavior of DSCs, accounting for trapping and nonlinear recombination mechanisms, are reported for the first time and validated against experiments. The model is applied to build a consistent picture of the static and dynamic small-signal performance of nanocrystalline TiO2-based DSCs under different incident illumination intensity and direction, analyzed in terms of current-voltage characteristic, Incident Photon to Current Efficiency, and Electrochemical Impedance Spectroscopy. This is achieved with a reliable extraction and validation of a unique set of model parameters against a large enough set of experimental data. Such a complete and validated description allows us to gain a detailed view of the cell collection efficiency dependence on different operating conditions. In particular, based on dynamic numerical simulations, we provide for the first time a sound support to the interpretation of the diffusion length, in the presence of nonlinear recombination and non-uniform electron density distribution, as derived from small-signal characterization techniques and clarify its correlation with different estimation methods based on spectral measurements. PMID:23380986

Cappelluti, Federica; Ma, Shuai; Pugliese, Diego; Sacco, Adriano; Lamberti, Andrea; Ghione, Giovanni; Tresso, Elena

2013-08-14

68

Consistent static and small-signal physics-based modeling of dye-sensitized solar cells under different illumination conditions.  

UK PubMed Central (United Kingdom)

A numerical device-level model of dye-sensitized solar cells (DSCs) is presented, which self-consistently couples a physics-based description of the photoactive layer with a compact circuit-level description of the passive parts of the cell. The opto-electronic model of the nanoporous dyed film includes a detailed description of photogeneration and trap-limited kinetics, and a phenomenological description of nonlinear recombination. Numerical simulations of the dynamic small-signal behavior of DSCs, accounting for trapping and nonlinear recombination mechanisms, are reported for the first time and validated against experiments. The model is applied to build a consistent picture of the static and dynamic small-signal performance of nanocrystalline TiO2-based DSCs under different incident illumination intensity and direction, analyzed in terms of current-voltage characteristic, Incident Photon to Current Efficiency, and Electrochemical Impedance Spectroscopy. This is achieved with a reliable extraction and validation of a unique set of model parameters against a large enough set of experimental data. Such a complete and validated description allows us to gain a detailed view of the cell collection efficiency dependence on different operating conditions. In particular, based on dynamic numerical simulations, we provide for the first time a sound support to the interpretation of the diffusion length, in the presence of nonlinear recombination and non-uniform electron density distribution, as derived from small-signal characterization techniques and clarify its correlation with different estimation methods based on spectral measurements.

Cappelluti F; Ma S; Pugliese D; Sacco A; Lamberti A; Ghione G; Tresso E

2013-08-01

69

Kernel bandwidth estimation for nonparametric modeling.  

UK PubMed Central (United Kingdom)

Kernel density estimation is a nonparametric procedure for probability density modeling, which has found several applications in various fields. The smoothness and modeling ability of the functional approximation are controlled by the kernel bandwidth. In this paper, we describe a Bayesian estimation method for finding the bandwidth from a given data set. The proposed bandwidth estimation method is applied in three different computational-intelligence methods that rely on kernel density estimation: 1) scale space; 2) mean shift; and 3) quantum clustering. The third method is a novel approach that relies on the principles of quantum mechanics. This method is based on the analogy between data samples and quantum particles and uses the SchrOdinger potential as a cost function. The proposed methodology is used for blind-source separation of modulated signals and for terrain segmentation based on topography information.

Bors AG; Nasios N

2009-12-01

70

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 (?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

71

Improving Bandwidth of Yagi-Uda Arrays  

Directory of Open Access Journals (Sweden)

Full Text Available A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.

Richard A. Formato

2012-01-01

72

Queueing Delay Guarantees in Bandwidth Packing  

UK PubMed Central (United Kingdom)

This paper proposes a new formulation for the bandwidth packing problem, assuringmaximum service delay in telecommunications networks. The bandwidth packing problem isone of selecting calls, from a list of requests, to be routed in the network. We limit themaximum queueing delay, while maximizing revenues generated from the routed calls. Anefficient Lagrangean relaxation based heuristic procedure for finding bounds and solutions tothe problem is demonstrated, and computational results from a variety of problem instances arereported. We show that the procedure is both efficient and effective in finding good solutions.

Erik Rolland; Ali Amiri

73

Vertical-bandwidth-limited digital holography.  

Science.gov (United States)

Optical scanning holography (OSH) is a promising technique to acquire a big-size digital hologram. However, the acquisition speed is limited by the mechanical scanner. In this Letter we apply the OSH in conjunction with an anisotropic low-pass filtering pupil to acquire vertical-bandwidth-limited (VBL) holograms. The size and the acquisition time of the VBL hologram can be reduced by one order of magnitude while the horizontal resolution remains the same as the conventional scanning hologram. The VBL hologram can be coded as an off-axis hologram without any postfiltering. Meanwhile, the full horizontal bandwidth of the displaying device can be capitalized. PMID:22743459

Liu, Jung-Ping; Lee, Chieh-Cheng; Lo, Ying-Hau; Luo, Dao-Zheng

2012-07-01

74

Vertical-bandwidth-limited digital holography.  

UK PubMed Central (United Kingdom)

Optical scanning holography (OSH) is a promising technique to acquire a big-size digital hologram. However, the acquisition speed is limited by the mechanical scanner. In this Letter we apply the OSH in conjunction with an anisotropic low-pass filtering pupil to acquire vertical-bandwidth-limited (VBL) holograms. The size and the acquisition time of the VBL hologram can be reduced by one order of magnitude while the horizontal resolution remains the same as the conventional scanning hologram. The VBL hologram can be coded as an off-axis hologram without any postfiltering. Meanwhile, the full horizontal bandwidth of the displaying device can be capitalized.

Liu JP; Lee CC; Lo YH; Luo DZ

2012-07-01

75

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

76

Reconfigurable silicon filter with continuous bandwidth tunability.  

UK PubMed Central (United Kingdom)

We present the design and the fabrication of compact tunable silicon-on-insulator bandpass filters based on the integration of a Mach-Zehnder interferometer with ring resonators and activated via thermo-optic phase shifters. The proposed architecture provides wide filter bandwidth tunability from 10% to 90% of the free spectral range preserving the filter off-band rejection. Possible applications are channel subset selection in wavelength division multiplexing optical systems, adaptive filtering to signal bandwidth, and reconfigurable filters for gridless networking.

Orlandi P; Ferrari C; Strain MJ; Canciamilla A; Morichetti F; Sorel M; Bassi P; Melloni A

2012-09-01

77

Users Bandwidth in Air Traffic Management:  

UK PubMed Central (United Kingdom)

This paper focuses on communication and information flowsin the ATC system. We first identify the various informationchannels in ATC. The bandwidth of channels involving ahuman operator is considered a major limitation in theperformance of the overall ATC system. This bandwidthcould be increased, provided that adequate Human MachineInteraction techniques are implemented. Examples based onDigiStrips and other prototypes developed at CENA are thenused to demonstrate how the users bandwidth could bedramatically increased. These prototypes are mainly based ontouch screen technology, simple gestures recognition, graphicdesign, and animations. They enhance system input, andsystem output as well as communications between close ordistant operators.

Christophe Mertz

78

Bandwidth, Broadband, and Planning for Public Access  

Science.gov (United States)

Broadband and bandwidth allocation is an essential technology planning activity that libraries should address on a continual basis. There are five key factors that will impact your network's performance: 1. infrastructure, 2. network load, 3. workstation performance, 4. prioritization of services, and 5. network management. The author thinks it's…

Blowers, Helene

2012-01-01

79

Fast Faraday Cup With High Bandwidth  

Energy Technology Data Exchange (ETDEWEB)

A circuit card stripline Fast Faraday cup quantitatively measures the picosecond time structure of a charged particle beam. The stripline configuration maintains signal integrity, and stitching of the stripline increases the bandwidth. A calibration procedure ensures the measurement of the absolute charge and time structure of the charged particle beam.

Deibele, Craig E [Knoxville, TN

2006-03-14

80

Big Bandwidth Battle: Universal ADSL Looks Ahead.  

Science.gov (United States)

Discusses the new Universal ADSL (Asymmetric Digital Subscriber Line) standard, which promises simple, high-bandwidth access over standard telephone lines. Topics include varieties of DSL; voice and data capacities; adapters and installation for personal computers; Internet backbone capacity; and headend access. (LRW)

Hargadon, Tom

1998-01-01

 
 
 
 
81

Bandwidth reduction for stereoscopic video signals  

Science.gov (United States)

The bandwidth required to transmit stereoscopic video signals is nominally twice that required for standard, monoscopic images. An effective method of reducing the required bandwidth is to code the two video streams asymmetrically. We assessed the impact of this bandwidth- reduction technique on image quality and overall sensation of depth. Images from the right-eye stream were spatially filtered on image quality and overall sensation of depth. Images from the right-eye stream were stream were spatially filtered to half and quarter resolution. Subsequently, the images were processed using an MPEG-2 codec at bit-rates of 6, 2, and 1 Mbit/s. Subjects assessed image quality and depth using a double-stimulus, continuous-quality scale method. It was found that perceived depth was relatively robust to spatial filtering and bit-rate reduction. Image quality was affected more by bit-rate reduction than by spatial filtering and, at the lower bit rates, ratings were much higher for stereoscopic than for non-stereoscopic sequences. The results indicate that asymmetrical coding of stereoscopic sequences can be an effective means of reducing bandwidth for storage and transmission.

Tam, Wa James; Stelmach, Lew B.; Meegan, Daniel V.; Vincent, Andre

2000-05-01

82

Spectral Bandwidth and WEC Performance Assessment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper investigates the dependency of wave energy conversion on the spectral bandwidth of sea-states. To this aim, the performance of an axisymmetrical Wave Energy Converter is assessed in the frequency domain by using a stochastic model in two far different wave climates (Portugal and North Sea...

Saulnier, J.-B.; Ricci, P.; Pontes, M.T.; Falcão, A.F. de O.

83

Experiences in Traceroute and Bandwidth Change Analysis  

International Nuclear Information System (INIS)

[en] 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

84

Improving Ad Hoc Network Performances by Estimating Available Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available The term bandwidth refers to the data rate that a network link or a network path can transfer. Bandwidth is one of the guarantee attribute to measure the performance of the network. Measuring available bandwidth in ad hoc networks is a challenging issue in Mobile Ad hoc Network (MANET). In this paper, the new technique is proposed to evaluate the accurate available bandwidth in ad hocnetworks. This technique considers reducing backoff time, node’s and link’s capability. By these network flows, the amount of bandwidth is wasted. Estimating accurate available bandwidth allows a node to make an optimal decision before sending a packet in networks.

K. Mohideen Vahitha Banu

2010-01-01

85

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

86

Effective Bandwidth Utilization in IEEE802.11 for VOIP  

Directory of Open Access Journals (Sweden)

Full Text Available 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 improve performance and voice quality of VoIP. The bandwidth calculation in BDM can be done by using Erlang and VOIP bandwidth calculator. Finally, ns2 experimental study shows the relationship between bandwidth utilization, free bandwidth and data rate. The paper concludes that marginal VoIP call rate has been increased by BDM algorithm..

S. Vijay Bhanu; RM.Chandrasekaran; V. Balakrishnan

2010-01-01

87

Narrow-bandwidth unstable laser resonator  

Energy Technology Data Exchange (ETDEWEB)

The present invention relates to unstable laser resonators, particularly to unstable laser resonators, and particularly to an unstable laser resonator that produces optical radiation that simultaneously has the high output power diffraction-limited divergence characteristic of an unstable laser resonator and also the narrow bandwidth that can usually be obtained only with a stable laser resonator. Some success was achieved in the frequency narrowing of the laser radiation from an unstable laser resonator cavity by using a diffraction grating. This technique was works best with lasers that have sharp line structure, such as molecular lasers. For example, selection of a single line in a hydrogen-fluoride laser has been reported in several configurations involving the insertion of a diffraction grating into a standard unstable laser resonator cavity. Although currently available, unstable laser resonators have the configuration of choice for producing high-power, low-divergence radiation from laser cavities; they are not compatible with a simultaneous requirement of narrow bandwidth.

Reintjes, J.F.; Tankersley, L.L.; Cooper, D.

1988-10-21

88

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

89

DBAS: A Deployable Bandwidth Aggregation System  

CERN Multimedia

The explosive increase in data demand coupled with the rapid deployment of various wireless access technologies have led to the increase of number of multi-homed or multi-interface enabled devices. Fully exploiting these interfaces has motivated researchers to propose numerous solutions that aggregate their available bandwidths to increase overall throughput and satisfy the end-user's growing data demand. These solutions, however, have faced a steep deployment barrier that we attempt to overcome in this paper. We propose a Deployable Bandwidth Aggregation System (DBAS) for multi-interface enabled devices. Our system does not introduce any intermediate hardware, modify current operating systems, modify socket implementations, nor require changes to current applications or legacy servers. The DBAS architecture is designed to automatically estimate the characteristics of applications and dynamically schedule various connections or packets to different interfaces. Since our main focus is deployability, we fully i...

Habak, Karim; Harras, Khaled A

2012-01-01

90

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.

Hassan Hassan; Jean-Marie Garcia; Olivier Brun

2006-01-01

91

Extended bandwidth management mechanism among multi-OLTs  

Science.gov (United States)

Passive optical networks (PON) is being considered as a promising solution for next generation broadband access network due to the convergence of broad bandwidth and low-cost fiber infrastructure along with its ability to successfully support IP-based multimedia applications. PON system has its individual bandwidth allocation mechanism compared with core network allocating bandwidth based on service priority level. However, no uniform bandwidth allocation mechanism from access network to care network. In this paper we propose a novel method of extended bandwidth allocation mechanism among multi-PON systems; then extended dynamic bandwidth allocation (DBA) algorithm in a Gigabit-capable PON (GPON) system for core network is presented. The bandwidth management mechanism among multi-optical line terminals (OLTs) can provide an end-to-end bandwidth guarantee for data transmission. We conduct detailed simulation experiments to study the performance and validate the effectiveness of the proposed method.

Zhang, Na; Yoshiuchi, Hideya

2007-12-01

92

Dynamic MTW: a dynamic bandwidth distribution scheme in EPON  

Science.gov (United States)

An algorithm to improve the bandwidth utilization for EPON by using dynamic bandwidth distribution is put forward. System performance, such as queuing delay under self-similar traffic, is simulated by using OPNET.

Chen, Hong; Ge, Liangwei; Zeng, Lieguang

2002-08-01

93

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

94

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

Scientific Electronic Library Online (English)

Full Text Available 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 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 (more) 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.

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

1997-12-01

95

Millimeter-wave small-signal modeling with optimizing sensitive-parameters for metamorphic high electron mobility transistors  

Science.gov (United States)

In this paper, we present a simple and reliable technique for determining the small-signal equivalent circuit model parameters of the 0.1 µm metamorphic high electron mobility transistors (MHEMTs) in a millimeter-wave frequency range. The initial eight extrinsic parameters of the MHEMT are extracted using two S-parameter (scattering parameter) sets measured under the pinched-off and zero-biased cold field-effect transistor conditions by avoiding the forward gate biasing. Furthermore, highly calibration-sensitive values of the Rs, Ls and Cpd are optimized by using a gradient optimization method to improve the modeling accuracy. The accuracy enhancement of this procedure is successfully verified with an excellent correlation between the measured and calculated S-parameters up to 65 GHz.

Moon, S.-W.; Oh, J.-H.; Baek, Y.-H.; Han, M.; Rhee, J.-K.; Kim, S.-D.

2010-08-01

96

Small-signal model parameter extraction for microwave SiGe HBTs based on Y- and Z-parameter characterization  

International Nuclear Information System (INIS)

High frequency intrinsic small-signal model parameter extraction for microwave SiGe heterojunction bipolar transistors is studied, with a focus on the main feedback elements including the emitter series resistor, internal and external base-collector capacitors as well as the base series resistor, all of which are important in determining the behavior of the device equivalent circuit. In accordance with the respective features of definition of the Y- and Z-parameters, a novel combined use of them succeeds in reasonably simplifying the device equivalent circuit and thus decoupling the extraction of base-collector capacitances from other model parameters. As a result, a very simple direct extraction method is proposed. The proposed method is applied for determining the SiGe HBT small-signal model parameters by taking numerically simulated Y- and Z-parameters as nominal 'measurement data' with the help of a Taurus-device simulator. The validity of the method is preliminarily confirmed by the observation of certain linear relations of device frequency behavior as predicted by the corresponding theoretical analysis. Furthermore, the extraction results can be used to reasonably account for the dependence of the extracted model parameters on device geometry and process parameters, reflecting the explicit physical meanings of parameters, and especially revealing the distributed nature of the base series resistor and its complex interactions with base-collector capacitors. Finally, the accuracy of our model parameter extraction method is further validated by comparing the modeled and simulated S-parameters as a function of frequency. (semiconductor devices)

2009-01-01

97

Small-signal model parameter extraction for microwave SiGe HBTs based on Y- and Z-parameter characterization  

Energy Technology Data Exchange (ETDEWEB)

High frequency intrinsic small-signal model parameter extraction for microwave SiGe heterojunction bipolar transistors is studied, with a focus on the main feedback elements including the emitter series resistor, internal and external base-collector capacitors as well as the base series resistor, all of which are important in determining the behavior of the device equivalent circuit. In accordance with the respective features of definition of the Y- and Z-parameters, a novel combined use of them succeeds in reasonably simplifying the device equivalent circuit and thus decoupling the extraction of base-collector capacitances from other model parameters. As a result, a very simple direct extraction method is proposed. The proposed method is applied for determining the SiGe HBT small-signal model parameters by taking numerically simulated Y- and Z-parameters as nominal 'measurement data' with the help of a Taurus-device simulator. The validity of the method is preliminarily confirmed by the observation of certain linear relations of device frequency behavior as predicted by the corresponding theoretical analysis. Furthermore, the extraction results can be used to reasonably account for the dependence of the extracted model parameters on device geometry and process parameters, reflecting the explicit physical meanings of parameters, and especially revealing the distributed nature of the base series resistor and its complex interactions with base-collector capacitors. Finally, the accuracy of our model parameter extraction method is further validated by comparing the modeled and simulated S-parameters as a function of frequency. (semiconductor devices)

Fu Jun, E-mail: fujun@mail.tsinghua.edu.c [Tsinghua National Laboratory for Information Science and Technology (TNList), Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

2009-08-15

98

Recycling of Bandwidth in Metropolitan Area Networks(MAN)  

Directory of Open Access Journals (Sweden)

Full Text Available In case of variable bite rate application, the subscriber station requires bandwidth for downlink anduplink of data transmission. As subscriber station cant estimate how much data it wants and to ensurethe QOS guaranteed services, It may reserve more bandwidth than its demand. As a result, the reservedbandwidth may not be fully utilized all the time. Hence there is a wastage of bandwidth. This paperconsists of a scheme named as ‘Bandwidth Recycling’, to recycle the unused bandwidth without changingthe existing bandwidth reservation. In this scheme the subscriber station will used the available unusedbandwidth. By this system throughput can also increase while maintain the same quality of services. Inthis scheme we use mathematical analysis and simulation. And this results in the scheme can recycle35% of unused bandwidth on average. The extension for this project can also be showed by the threescheduling algorithms. Thus the simulation results to improve overall throughput by 40% in a steadynetwork.

Bhargava Devana; Sudharshana Kristipati; Raghava Nirati

2012-01-01

99

Bandwidth Modeling and Estimation in Peer to Peer Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Recent studies have shown that the majority of today’s internet traffic is related to Peer to Peer(P2P) traffic. The study of bandwidth in P2P networks is very important. Because it helps us in more efficientcapacity planning and QoS provisioning when we would like to design a large scale computer networks. In thispaper motivated by the behavior of peers (sources or seeds) that is modeled by Ornstein Uhlenbeck (OU)process, we propose a model for bandwidth in P2P networks. This model is represented with a stochasticintegral. We also model the bandwidth when we have multiple downloads or uploads. The autocovariancestructure of bandwidth in either case is studied and the statistical parameters such as mean, variance andautocovariance are obtained. We then study the queue length behavior of the bandwidth model. The methodsfor generating synthetic bandwidth process and estimation of the bandwidth parameters using maximumlikehood estimation are presented.

Kiarash Mizanian; Mehdi Vasef; Morteza Analoui

2010-01-01

100

Improved access to optical bandwidth in trees  

Energy Technology Data Exchange (ETDEWEB)

We present improved bounds for efficient bandwidth allocation in a WDM optical network whose topology is that of a directed tree of fiber-optic links. The problem of bandwidth allocation is modeled as a coloring problem, where each path in a set of communication requests must be assigned a color (representing a wavelength) in such a way that no two paths using the same link in the same direction are assigned the same color. Letting L be the largest number of paths using any directed link, we show that for an arbitrary set of paths, 7L/4 colors axe sufficient to route all paths. This improves an upper bound of 15L/8 due to Mihail, Kaklamanis and Rao. In addition, we show that a family of problem instances given by Mihail, Kaklamanis and Rao to establish a worst-case lower bound of U/2 for the problem can in most cases be colored with only 5L/4 colors (technically, [5L/4]). Finally, we show that in all cases 5L/4 colors are in fact necessary for this family of instances, yielding a general lower bound of 5L/4.

Kumar, V.; Schwabe, E.J. [Northwestern Univ., Evanston, IL (United States)

1997-06-01

 
 
 
 
101

Polarization based charge density drain current and small-signal model for nano-scale AlInGaN/AlN/GaN HEMT devices  

Science.gov (United States)

In this paper, we present a two-dimensional electron gas (2DEG) charge-control drain current and small-signal model for sheet carrier density in the channel is developed for AlInGaN/AlN/GaN high-electron-mobility transistor with quaternaries band gap calculation model. The sheet carrier density and small signal model used here are accounts for the independence between Fermi level Ef and ns. This physics-based ns model fully depend upon the variation of Ef, the first sub band E0, the second sub band E1, and ns. We present a physics based analytical drain current model using ns with the minimum set of parameters. The analytical results so obtained are comparing them with four samples of short and long gate and analyzed the small signal parameters. A good agreement between the results is obtained, thus validating the model.

Godwinraj, D.; Pardeshi, Hemant; Pati, Sudhansu Kumar; Mohankumar, N.; Sarkar, Chandan Kumar

2013-02-01

102

Bandwidth Extension of Constant-Q Bandpass Filter using Bandwidth Extension Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available CMOS spiral inductors suffer from a number of drawbacks including a low Q factor, a low self- resonant frequency, and a small and non-tunable inductance and require a large chip area. On the other hand active inductor offers many unique advantages over their spiral counterparts including small chip area, large and tunable inductance and high quality factor. These active inductors have been used successfully in many applications such as in radio frequency (RF) front end integrated circuits, filters, and phase shifter and oscillator circuits. The effectiveness of these active inductors is however affected by a number of limitation including small dynamic range, a high noise level and high power consumption. High speed applications such as preamplifier of data transceiver require large bandwidth hence there is a need for technique that achieve larger bandwidth without increased power consumption and design complexity. In this paper, bandwidth extension techniques are used to extend the bandwidth of the bandpass filter. Active inductors are used in the designing of the bandpass filter. A swing independent quality factor, called constant-Q active inductor is used as an active element in the designing of the bandpass filter. Bandpass filter is implemented on both 0.5 µm and 0.35 µm CMOS process. Comparisons are made between resistive compensation technique and inductive series peaking technique. Simulation results shows that the bandwidth is improved by 72%.The operating frequency is also increases from 122.995 MHz to 194.276 MHz at 0.5 µm technology and operating frequency increases from 163.641 MHz to 259.189 MHz at 0.35 µm technology.

Megha Chitranshi; Sudha Radhika; Anand Mishra

2013-01-01

103

Bandwidth Enhancement in Multilayer Microstrip Proximity Coupled Array  

Directory of Open Access Journals (Sweden)

Full Text Available Now days, there is a huge demand for wireless applications. Antennas which are used in these applications require being low profile, light weight, easily mounted and broad bandwidth. The microstrip antenna has all the features mentioned above except for its narrow bandwidth, typically from less than 1% to several percent. This paper introduces an alternative approach in enhancing the bandwidth of the microstrip antenna. The bandwidth enhancement technique which is studied is the Proximity coupled Microstrip Antenna with Air-Gap. By using this technique, a bandwidth enhancement of 14.77% can be achieved and after that we have designed an array of proximity coupled antenna and achieved a bandwidth of 19% at afrequency of 7GHz.

Shubham Gupta; Shilpa Singh

2012-01-01

104

Optimal filter bandwidth for pulse oximetry.  

UK PubMed Central (United Kingdom)

Pulse oximeters contain one or more signal filtering stages between the photodiode and microcontroller. These filters are responsible for removing the noise while retaining the useful frequency components of the signal, thus improving the signal-to-noise ratio. The corner frequencies of these filters affect not only the noise level, but also the shape of the pulse signal. Narrow filter bandwidth effectively suppresses the noise; however, at the same time, it distorts the useful signal components by decreasing the harmonic content. In this paper, we investigated the influence of the filter bandwidth on the accuracy of pulse oximeters. We used a pulse oximeter tester device to produce stable, repetitive pulse waves with digitally adjustable R ratio and heart rate. We built a pulse oximeter and attached it to the tester device. The pulse oximeter digitized the current of its photodiode directly, without any analog signal conditioning. We varied the corner frequency of the low-pass filter in the pulse oximeter in the range of 0.66-15 Hz by software. For the tester device, the R ratio was set to R = 1.00, and the R ratio deviation measured by the pulse oximeter was monitored as a function of the corner frequency of the low-pass filter. The results revealed that lowering the corner frequency of the low-pass filter did not decrease the accuracy of the oxygen level measurements. The lowest possible value of the corner frequency of the low-pass filter is the fundamental frequency of the pulse signal. We concluded that the harmonics of the pulse signal do not contribute to the accuracy of pulse oximetry. The results achieved by the pulse oximeter tester were verified by human experiments, performed on five healthy subjects. The results of the human measurements confirmed that filtering out the harmonics of the pulse signal does not degrade the accuracy of pulse oximetry.

Stuban N; Niwayama M

2012-10-01

105

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,; Majidul Ahmed,; Utpal Jyoti Bora,

2013-01-01

106

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

107

Bandwidth Allocation and Reservation - End-to-End Specification  

CERN Document Server

The Bandwidth Allocation and Reservation (BAR) activity within JRA4 of the EGEE project specified and implemented the necessary components and interfaces to enable the EGEE Grid middleware to request and use guaranteed bandwidth services. This report describes the components and interfaces required for an end-to-end BAR service and how they interact.

Kavoussanakis, K; Palansuriya, C; Patil, A; Scharinger, F; Tziouvaras, C; Phipps, A; Vuagnin, G; Trew, A

2006-01-01

108

Bandwidth Allocation and Reservation - End-to-End Specification  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Bandwidth Allocation and Reservation (BAR) activity within JRA4 of the EGEE project specified and implemented the necessary components and interfaces to enable the EGEE Grid middleware to request and use guaranteed bandwidth services. This report describes the components and interfaces required ...

Kavoussanakis, K

109

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; Jatindra Kr Deka

2011-01-01

110

Absorption bandwidth of isomeric polymethine dyes  

Energy Technology Data Exchange (ETDEWEB)

The authors attempt to study the structural features of dyes that give such a strong influence of isomerism of their heterocyclic rings on their spectra that the absorption bands of the 2-isomers are much broader than those of the 4-isomers. It is determined that in dyes with unsubstituted polymethine chain, which include those considered here, the all-trans isomer predominates and that therefore the difference in the bandwidths of compounds 2- and 4- cannot be attributed to stereoisomerization. It is further determined that the differences also cannot be attributed to solvation effects or to quasidegeneration. It is concluded that the difference in the absorption bandwiths of the isomeric dyes is due to a different degree of vibronic interactions in their molecules. It is further concluded that in the 2-isomers there is a more intense fixation and redistribution of bonds during electronic excitation than in the 4-isomer and this is the main reason for broadening of the absorption bands of the former.

Dyadyusha, G.G.; Derevyanko, N.A.; Ishchenko, A.A.; Tolmachev, A.I.

1985-06-01

111

Bandwidth Calculation in IEEE 802.16 Networks  

Directory of Open Access Journals (Sweden)

Full Text Available IEEE 802.16 standard was designed to support the bandwidth demanding applications with quality of service (QoS).Bandwidth is reserved for each application to ensure the QoS. For variable bit rate (VBR) applications, however, it is difficult for the subscriber station (SS) to predict the amount of incoming data. To ensure the QoS guaranteed services, the SS may calculate more bandwidth. In this paper, we propose a scheme, named Bandwidth Calculation, to calculate the bandwidth without changing the existing unused calculates bandwidth. The idea of the proposed scheme is to allow other SSs to calculate the bandwidth when it is available. Thus, the system through put can be improved while maintaining the same QoS guaranteed services. Mathematical analysis and simulation are used to evaluate the proposed scheme..Simulation and analysis results confirm that the proposed scheme can calculate on average. By analyzing factors affecting the calculating performance, scheduling algorithms are proposed to improve the overall throughput. The simulation results show that our proposed algorithm improves the overall throughput by 40% in a steady network.

Roop Singh Takur; E.Ramkumar

2012-01-01

112

Bandwidth Enhancement for Microstrip Antenna in Wireless Applications  

Directory of Open Access Journals (Sweden)

Full Text Available Antenna is a vital component in wireless application systems. The microstrip antenna can be used for wireless applications as it has features such as light weight, easily mounted and it is easy to mass produce. Although there are many features that suits well for microstrip antenna to be deployed for wireless applications, there is a very serious limitation where it has a very narrow bandwidth. The typical bandwidth of the microstrip antennas is between 1 - 3%. If this limitation is eliminated, the microstrip antenna can be used to its full potential. An alternative bandwidth enhancement technique is studied and then proposed in order to broaden the bandwidth of the microstrip antenna. The wireless application that is selected to be studied is the Wireless Local Area Network (WLAN) based on the IEEE 802.11b standard. In Malaysia, this WLAN band spans from 2.4GHz to 2.48GHz. The bandwidth enhancement technique which is selected is the Identical Dual-Patch Microstrip Antenna with Air-Gap (IDMA). By using this technique, a bandwidth enhancement of about 11% has been achieved. This bandwidth very well covers the required WLAN band with an operating frequency of 2.45GHz.

RSA Raja Abdullah; D Yoharaaj; A Ismail

2009-01-01

113

Brain anatomical structure segmentation by adaptive bandwidth density estimation.  

UK PubMed Central (United Kingdom)

Determination of region in a space of multimodal features of brain MR images requires kernel estimation tecniques with bandwidths that are adapted locally. The bandwidth selection is a critical aspect at the filtering stage of image segmentation. This work presents two methods for determinate the adaptive bandwidth in the application of density estimation, in the segmentation of regions at the feature space of an MRI. Two adaptive methods: sample point and k-nearest neighbors, where applied for real and synthetic data, achieved similarity indexes of 0.68 and 0.71 for gray matter and white matter respectively.

López Palafox GD; Jimenéz Alaníz JR

2012-01-01

114

Optimal Resource Allocation in Random Networks with Transportation Bandwidths  

CERN Document Server

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. We find recursive relations and convert them 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, an interesting profile of the allocated resource is found with features similar to the Maxwell's construction.

Yeung, C H

2008-01-01

115

Broadening the potential bandwidth of piezoelectric transducers by partial depolarization  

International Nuclear Information System (INIS)

[en] Elastic waves are used more and more in a nondestructive way to probe the physical properties of materials. The resolution of the images or the accuracy of the measurements is directly associated with the ultrasonic signal bandwidth and amplitude a system can generate or detect. The authors propose a technique to broaden the potential bandwidth of piezoelectric generators and sensors, which is based on utilizing a nonuniformly-polarized piezoelectric material. Both simulated and experimental responses are shown. They are in good agreement and exhibit a useful bandwidth over several natural harmonics of the piezoelectric transducer. [copyright] 2001 American Institute of Physics

2001-06-18

116

Effects of driver bandwidth upon resonantly heated electrons  

International Nuclear Information System (INIS)

[en] Experimental data are presented which show that increased bandwidth of an electromagnetic driver can reduce the hot electron temperature due to resonant absorption. This work, done at microwave frequencies, shows that T/sub H/a(Dw/w)/sup -0.25/. It was also observed that the hot electron density increases with increasing bandwidth such that the heat flux (Q/sub H/an/sub H/T/sub H//sup ts3/2/) is nearly constant as a function of bandwidth

1981-03-30

117

Evaluation of dynamic bandwidth allocation algorithms in GPON networks  

DEFF Research Database (Denmark)

In this paper, two approaches for Dynamic Bandwidth Allocation in GPON networks are proposed, and validated through simulations in the OPNET modeler. One approach address a Status Reporting scheme, where the bandwidth allocation originates from the client request. The second use a centralized Non Status Reporting scheme. Furthermore, parameters to cope with variances in the traffic pattern is quantified. The results on performance, scalability and efficiency show that Status Reporting is utilizing the bandwidth more efficient while the Non Status Reporting provides better QoS for real time services.

Ozimkiewicz, J.; Ruepp, Sarah Renée

2010-01-01

118

Bandwidth analysis of multimode fiber passive optical networks (PONs)  

Directory of Open Access Journals (Sweden)

Full Text Available The analysis of frequency response in different branches of a multimode fiber based passive optical network is conducted. Both the theoretical and experimental results show that bandwidth of various network paths may be different.

Grzegorz Stepniak; Lukasz Maksymiuk; Jerzy Siuzdak

2009-01-01

119

Continuous-wave nonclassical light with gigahertz squeezing bandwidth.  

UK PubMed Central (United Kingdom)

Squeezed states can be employed for entanglement-based continuous-variable quantum key distribution, where the secure key rate is proportional to the bandwidth of the squeezing. We produced a nonclassical cw laser field at the telecommunication wavelength of 1550 nm, which showed squeezing over a bandwidth of more than 2 GHz. The experimental setup used parametric downconversion via a periodically poled potassium titanyl phosphate crystal. We did not use any resonant enhancement for the fundamental wavelength, which should in principle allow a production of squeezed light over the full phase-matching bandwidth of several nanometers. We measured the squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz limited by the measuring bandwidth of the homodyne detector. The squeezing strength was possibly limited by thermal lensing inside the nonlinear crystal.

Ast S; Samblowski A; Mehmet M; Steinlechner S; Eberle T; Schnabel R

2012-06-01

120

MULTILAYER MICROSTRIP ANTENNA QUALITY FACTOR OPTIMIZATION FOR BANDWIDTH ENHANCEMENT  

Directory of Open Access Journals (Sweden)

Full Text Available The impedance bandwidth, one of the important characteristics of microstrip patch antennas, can be significantly improved by using a multilayer dielectric configuration. In this paper the focus is on bandwidth enhancement technique of a multilayer patch antenna for X-band applications. In order to enhance the bandwidth, antenna losses are contained by controlling those quality factors which can have a significant impact on the bandwidth for a given permittivity and thickness of the substrate. This has been achieved by conformal transformation of the multidielectric microstrip antenna. For the ease of analysis Wheelers transformation is used to map the complex permittivity of a multilayer substrate to a single layer. Method of Moments and Finite Difference Time Domain approaches are used for the computation of results.

SAMIR DEV GUPTA; M.C. SRIVASTAVA

2012-01-01

 
 
 
 
121

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; Lee Chun-Chieh; Hsieh Yi-Chih

2011-01-01

122

Review of high bandwidth fiber optics radiation sensors  

International Nuclear Information System (INIS)

[en] 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

1985-01-01

123

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

2013-01-01

124

Statistical Multiplexing of Homogeneous Streams results in Linear Bandwidth Gains  

Directory of Open Access Journals (Sweden)

Full Text Available Statistical multiplexing of traffic streams results in reduced network bandwidth requirement. The resulting gain increases with the increase in the number of streams being multiplexed together. However, the exact shape of the gain curve, as more and more streams are multiplexed together, is not known. In this paper, we first present the generalized result that the statistical gain of combining homogeneous traffic streams, of any traffic type, is a linear function of the number of streams being multiplexed. That is, given a fixed Quality of Service (QoS) constraint, like percentile delay, D, the bandwidth requirement of n streams to satisfy the delay constraint D is n x R x c where R is the bandwidth requirement of a single stream that satisfies the constraint D and c e (0,1]. We present the linear bandwidth gain result, using an extensive simulation study for video traces, specifically, streaming video (IPTV traces) and interactive video (CISCO Telepresence traces). The linear bandwidth gain result is then verified using analytical tools from two different domains. First, we validate the linearity using Queueing Theory Analysis, specifically using Interrupted Poisson Process (IPP) and Markov Modulated Poisson Process (MMPP) modeling. Second, we formally prove the linear behavior using the Asymptotic Analysis of Algorithms, specifically, the Big-O analysis.

2013-01-01

125

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

126

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.

2013-08-01

127

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; Elizabeth Elias

2012-01-01

128

Bandwidth selection for smooth backfitting in additive models  

CERN Multimedia

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

129

Analysis of bandwidth measurement methodologies over WLAN systems  

CERN Multimedia

WLAN devices have become a fundamental component of nowadays network deployments. However, even though traditional networking applications run mostly unchanged over wireless links, the actual interaction between these applications and the dynamics of wireless transmissions is not yet fully understood. An important example of such applications are bandwidth estimation tools. This area has become a mature research topic with well-developed results. Unfortunately recent studies have shown that the application of these results to WLAN links is not straightforward. The main reasons for this is that the assumptions taken to develop bandwidth measurements tools do not hold any longer in the presence of wireless links (e.g. non-FIFO scheduling). This paper builds from these observations and its main goal is to analyze the interaction between probe packets and WLAN transmissions in bandwidth estimation processes. The paper proposes an analytical model that better accounts for the particularities of WLAN links. The mod...

Portoles-Comeras, Marc; Mangues-Bafalluy, Josep; Domingo-Pascual, Jordi

2009-01-01

130

Gain-switched all-fiber laser with narrow bandwidth  

DEFF Research Database (Denmark)

Gain-switching of a CW fiber laser is a simple and cost-effective approach to generate pulses using an all-fiber system. We report on the construction of a narrow bandwidth (below 0.1 nm) gain-switched fiber laser and optimize the pulse energy and pulse duration under this constraint. The extracted pulse energy is 20 ?J in a duration of 135 ns at 7 kHz. The bandwidth increases for a higher pump pulse energy and repetition rate, and this sets the limit of the output pulse energy. A single power amplifier is added to raise the peak power to the kW-level and the pulse energy to 230 ?J while keeping the bandwidth below 0.1 nm. This allows frequency doubling in a periodically poled lithium tantalate crystal with a reasonable conversion efficiency.

Larsen, Casper; Giesberts, M.

2013-01-01

131

Bandwidth-Conserving Multicast VoIP Teleconference System  

Directory of Open Access Journals (Sweden)

Full Text Available Teleconferencing is an essential feature in any business telephone system. A teleconference allows associates to engage in a group discussion by conducting a virtual meeting while remaining at geographically dispersed locations. Teleconferencing increases productivity while reducing travel costs and saving travel time. In a VoIP telephone system, we face the significant challenge of providing a teleconference feature that can support a large-scale teleconference without using excessive bandwidth. This paper presents a new, bandwidth-efficient way of implementing a real-time VoIP teleconference system. This new method provides all of the features that existing teleconference systems provide, but this new approach consumes considerably less data bandwidth than existing systems require. The new system allows a network with a given capacity to accommodate almost double the number of conference participants that an existing system would allow.

Teck-Kuen Chua; David C. Pheanis

2008-01-01

132

A Modified Adaptive Algorithm for Formant Bandwidth in Whisper Conversion  

Directory of Open Access Journals (Sweden)

Full Text Available The whisper conversion technology is to transform undistinguished whispers with lower SNR into clear normal speech, and it has important application prospect in mobile communication. Because the whisper speech is stirred by the yawp source, its formant position shifts and its bandwidth increases, which induces the problem of formant combination occurs in the whisper conversion. By analyzing the power spectrum, in this article, we proposed a modified adaptive algorithm for formant bandwidth. Based on the rule that the pole power does not change, the algorithm has resolved the problem of formant combination by modifying the formant bandwidth of whisper before implementing formant conversion. The experimental results with six Chinese mandarin monophthong phoneme conversions proved the validity of the algorithm.

Gang Lv; Heming Zhao

2009-01-01

133

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.

Mahalakshmi Chidambara Natarajan; Ramaswamy Muthiah; Alamelu Nachiappan

2010-01-01

134

Correlation and image compression for limited-bandwidth CCD.  

Energy Technology Data Exchange (ETDEWEB)

As radars move to Unmanned Aerial Vehicles with limited-bandwidth data downlinks, the amount of data stored and transmitted with each image becomes more significant. This document gives the results of a study to determine the effect of lossy compression in the image magnitude and phase on Coherent Change Detection (CCD). We examine 44 lossy compression types, plus lossless zlib compression, and test each compression method with over 600 CCD image pairs. We also derive theoretical predictions for the correlation for most of these compression schemes, which compare favorably with the experimental results. We recommend image transmission formats for limited-bandwidth programs having various requirements for CCD, including programs which cannot allow performance degradation and those which have stricter bandwidth requirements at the expense of CCD performance.

Thompson, Douglas G.

2005-07-01

135

Gain-switched all-fiber laser with narrow bandwidth.  

UK PubMed Central (United Kingdom)

Gain-switching of a CW fiber laser is a simple and cost-effective approach to generate pulses using an all-fiber system. We report on the construction of a narrow bandwidth (below 0.1 nm) gain-switched fiber laser and optimize the pulse energy and pulse duration under this constraint. The extracted pulse energy is 20 ?J in a duration of 135 ns at 7 kHz. The bandwidth increases for a higher pump pulse energy and repetition rate, and this sets the limit of the output pulse energy. A single power amplifier is added to raise the peak power to the kW-level and the pulse energy to 230 ?J while keeping the bandwidth below 0.1 nm. This allows frequency doubling in a periodically poled lithium tantalate crystal with a reasonable conversion efficiency.

Larsen C; Giesberts M; Nyga S; Fitzau O; Jungbluth B; Hoffmann HD; Bang O

2013-05-01

136

Cascaded passive silicon microrings for large bandwidth slow light device  

Energy Technology Data Exchange (ETDEWEB)

Slow light devices have important applications in the areas of data buffering, signal processing, and phased array antenna. Cascaded microring resonators structure can obtain large delay and also enhance the bandwidth, which was considered as a potential approach for future on-chip optical buffer. In this paper, we demonstrated a large bandwidth slow light device using cascaded Silicon-on-insulator (SOI) based microring resonators. With carefully designed the gap between the bus and the ring waveguides and the distances between the adjacent rings, a 57 ps group delay was observed and 83 Gbps maximum allowable bit rate is suggested according the measured 3 dB spectral bandwidth in the 8-stage cascaded microrings.

Li Yuntao; Hu Yingtao; Xiao Xi; Li Zhiyong; Yu Yude; Yu Jinzhong, E-mail: ytli@semi.ac.cn [State Key Laboratory of integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, Beijing 100083 (China)

2011-02-01

137

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 con…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

138

Enhancement bandwidth of microstrip antenna using tapered single slot  

Directory of Open Access Journals (Sweden)

Full Text Available A modified rectangular patch antenna design has been proposed in this paper, the bandwidth of this antenna is enhancement using the tapered slot with type of feeding (probe feed). This design is simulated with microwave office 2008 software package. This method is employed for analysis at the frequency band of (1 GHz- -- 3 GHz). When it was changed the location and dimensions of tapered slot. It gives a good VSWR less than (2), return losses (RL) less than (- 10 dB) and impedance bandwidth of the order of (13.1%) at the frequency band of (2.2921GHz- 2.6063) GHz of [2-3] GHz.

Ali A. Dheyab Al-Sajee

2012-01-01

139

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; A.K.Vats; Shikha Maan

2011-01-01

140

Ultrafast pulsed laser utilizing broad bandwidth laser glass  

Energy Technology Data Exchange (ETDEWEB)

An ultrafast laser uses a Nd-doped phosphate laser glass characterized by a particularly broad emission bandwidth to generate the shortest possible output pulses. The laser glass is composed primarily of P.sub.2 O.sub.5, Al.sub.2 O.sub.3 and MgO, and possesses physical and thermal properties that are compatible with standard melting and manufacturing methods. The broad bandwidth laser glass can be used in modelocked oscillators as well as in amplifier modules.

Payne, Stephen A. (Castro Valley, CA); Hayden, Joseph S. (Clarks Summit, PA)

1997-01-01

 
 
 
 
141

SEMICONDUCTOR DEVICES: Small-signal model parameter extraction for microwave SiGe HBTs based on Y- and Z-parameter characterization  

Science.gov (United States)

High frequency intrinsic small-signal model parameter extraction for microwave SiGe heterojunction bipolar transistors is studied, with a focus on the main feedback elements including the emitter series resistor, internal and external base-collector capacitors as well as the base series resistor, all of which are important in determining the behavior of the device equivalent circuit. In accordance with the respective features of definition of the Y- and Z-parameters, a novel combined use of them succeeds in reasonably simplifying the device equivalent circuit and thus decoupling the extraction of base-collector capacitances from other model parameters. As a result, a very simple direct extraction method is proposed. The proposed method is applied for determining the SiGe HBT small-signal model parameters by taking numerically simulated Y- and Z-parameters as nominal “measurement data" with the help of a Taurus-device simulator. The validity of the method is preliminarily confirmed by the observation of certain linear relations of device frequency behavior as predicted by the corresponding theoretical analysis. Furthermore, the extraction results can be used to reasonably account for the dependence of the extracted model parameters on device geometry and process parameters, reflecting the explicit physical meanings of parameters, and especially revealing the distributed nature of the base series resistor and its complex interactions with base-collector capacitors. Finally, the accuracy of our model parameter extraction method is further validated by comparing the modeled and simulated S-parameters as a function of frequency.

Jun, Fu

2009-08-01

142

Efficient Upload Bandwidth Estimation and Communication Resource Allocation Techniques  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we address two problems, for which we present novel, efficient, algorithmic solutions. The first problem is motivated by practical situations and is concerned with the efficient estimation of the upload bandwidth of a machine, particularly in the context of a peer-to-peer content shari...

Andreica, Mugurel Ionut; Tapus, Nicolae

143

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 ...

Bo Hang; Ruimin Hu; Shi Dong; Ye Ma

144

On bandwidth of solar subsecond bursts in cm-range  

Science.gov (United States)

The dependence of subsecond pulse spectral bandwidth on source location has been studied The goal is to study spectral band spreading due to wave scattering in the low corona The data with high spatial spectral and temporal resolution obtained with the Siberian Solar Radio telescope frequency about 5 7 GHz spatial resolution until 15 arc sec time resolution 14 ms were used The data of the spectropolarimeters 5 2-7 6 GHz 6 ms of the National Astronomical Observatories overlap with SSRT observation time including the SSRT working bandwidth Working with a large dataset of observations 22 events we researched relation between spectral width of type III-like pulses and their position on the Sun The mean bandwidth differs significantly from event to event at the same center frequency The results show that there is no intrinsic bandwidth of subsecond pulses suggesting that accidental surrounding source plasma parameters are responsible for the width of the emission Our study opens new possibilities for diagnostics of plasma turbulence parameters in the corona and it permits one to identify the generation mechanism of emission This work was supported by Russian projects of RFBR No 04-02-39003 newline RI-112 001 045 NSH-477 2003 2 05-07-90147 Programme RAN 1 16

Meshalkina, N. S.; Altyntsev, A. T.; Yan, Y.

145

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; Ali Hussain Ali Yawer

2009-01-01

146

Bandwidth invariant feedback automatic gain control systems for sonar  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Feedback Automatic Gain Control (FBAGC) is used to suppress large, slow unwanted variations of a received signal's envelope while passing more rapid required variations. Two ways in which the bandwidth of FBAGC may be kept fixed at the designed value, independent of the input signal are examined. Th...

McGeehan, JP; Burrows, DF; Whipp, SJ

147

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.

Jocelyne Elias; Fabio Martignon; Antonio Capone; Guy Pujolle

2006-01-01

148

Some Reflections on the Design of Bandwidth Efficient Turbo Codes  

UK PubMed Central (United Kingdom)

In this paper we review several approaches to bandwidth efficient turbo coding that have appeared in the recent literature. In addition, some new designs using bit interleaved coded modulation are introduced, including asymmetric designs and low-complexity multiple turbo code designs.

Daniel J. Costello; Adrish Banerjee; Thomas E. Fuja; Peter C. Massey

149

Bandwidth utilization maximization of scientific RF communication systems  

Energy Technology Data Exchange (ETDEWEB)

A method for more efficiently utilizing the frequency bandwidth allocated for data transmission is presented. Current space and range communication systems use modulation and coding schemes that transmit 0.5 to 1.0 bits per second per Hertz of radio frequency bandwidth. The goal in this LDRD project is to increase the bandwidth utilization by employing advanced digital communications techniques. This is done with little or no increase in the transmit power which is usually very limited on airborne systems. Teaming with New Mexico State University, an implementation of trellis coded modulation (TCM), a coding and modulation scheme pioneered by Ungerboeck, was developed for this application and simulated on a computer. TCM provides a means for reliably transmitting data while simultaneously increasing bandwidth efficiency. The penalty is increased receiver complexity. In particular, the trellis decoder requires high-speed, application-specific digital signal processing (DSP) chips. A system solution based on the QualComm Viterbi decoder and the Graychip DSP receiver chips is presented.

Rey, D. [Sandia National Lab., Albuquerque, NM (United States); Ryan, W. [New Mexico State Univ., Las Cruces, NM (United States); Ross, M.

1997-01-01

150

Effective Communication and File-I/O Bandwidth Benchmarks  

Energy Technology Data Exchange (ETDEWEB)

We describe the design and MPI implementation of two benchmarks created to characterize the balanced system performance of high-performance clusters and supercomputers: b{_}eff, the communication-specific benchmark examines the parallel message passing performance of a system, and b{_}eff{_}io, which characterizes the effective 1/0 bandwidth. Both benchmarks have two goals: (a) to get a detailed insight into the Performance strengths and weaknesses of different parallel communication and I/O patterns, and based on this, (b) to obtain a single bandwidth number that characterizes the average performance of the system namely communication and 1/0 bandwidth. Both benchmarks use a time driven approach and loop over a variety of communication and access patterns to characterize a system in an automated fashion. Results of the two benchmarks are given for several systems including IBM SPs, Cray T3E, NEC SX-5, and Hitachi SR 8000. After a redesign of b{_}eff{_}io, I/O bandwidth results for several compute partition sizes are achieved in an appropriate time for rapid benchmarking.

Koniges, A E; Rabenseifner, R

2001-05-02

151

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 inexpens...

Hesselbarth, Jan; Wiedmann, Frank; Huyart, Bernard

152

Bandwidth Selection for Kernel Density Estimation with Doubly Truncated Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work we introduce and compare several bandwidth selection procedures for kernel density estimation of a random variable that is sampled under random double truncation. The work is motivated by the fact that this type of incomplete data is often encountered in studies in astronomy and medicin...

Moreira , Carla; Van Keilegom, Ingrid

153

Scalable Video Coding in Online Video transmission with Bandwidth Limitation  

Directory of Open Access Journals (Sweden)

Full Text Available Resource limitation and variety of network and users cause many obstacles while transmitting data especially online video data through network. Video applications in Internet face by significant growth in several market segments and bandwidth limitation is one of those challenges which consider as a main obstacle in this paper.

Sima Ahmadpour; Salah Noori Saleh; Omar Amer Abouabdalla; Mahmoud Baklizi; Nibras Abdullah

2010-01-01

154

Extraction of the InP/InGaAs metallic collector-up heterojunction bipolar transistor small-signal equivalent circuit  

Science.gov (United States)

An efficient technique for determining the small-signal equivalent-circuit model of a Metal collector-up Heterojunction Bipolar Transistor (C-up MHBT) is presented. The technique employs analytically derived expressions for direct calculation of HBT T-Model equivalent circuit element values in terms of the measured S-parameters. This approach avoids errors due to uncertainty in fitting to large, over determined equivalent circuits and does not require the use of test structures and extra measurement steps to evaluate parasitics. Physically realistic results are demonstrated under various biasing conditions for the n-p-n InP/InGaAs HBT with metallic collector up structure. The agreement between the measured and model-produced data is excellent over the large frequency range and for several polarizations conditions for devices.

Bourguiga, R.; Oudir, A.; Mahdouani, M.; Pardo, F.; Pelouard, J. L.

2008-06-01

155

Bandwidth-aware co-scheduling for clusters  

Directory of Open Access Journals (Sweden)

Full Text Available Cluster computing are the best category of number of off-the-shelf commodity computers and resources that are integrated through hardware, networks and software to behave as a single computer simultaneously. In parallel applications, some processes are in need of executing simultaneously. We cannot be sure that all the processes are independent due to its communication behavior of some processes. Many of the processes are in need of co-scheduling each other. There are various types of co-scheduling available. This paper will focus mainly on the bandwidth and the memory concept mainly. This paper demands for the efficient resource utilization of cluster resources under the parallel execution of jobs using the newer bandwidth-aware co-scheduling concept which is put forth here.

A.Neela madheswari; M.Azath; Dr.R.S.D Wahida Banu

2009-01-01

156

On Free-Electron Laser Growing Modes and their Bandwidth  

CERN Multimedia

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

157

Raman scheme for adjustable-bandwidth quantum memory  

International Nuclear Information System (INIS)

[en] We propose a scenario of quantum memory for light based on Raman scattering. The storage medium is a vapor and the different spectral components of the input pulse are stored in different atomic velocity classes. One uses appropriate pulses to reverse the resulting Doppler phase shift and to regenerate the input pulse, without distortion, in the backward direction. The different stages of the protocol are detailed and the recovery efficiency is calculated in the semiclassical picture. Since the memory bandwidth is determined by the Raman transition Doppler width, it can be adjusted by changing the angle between the input pulse wave vector and the control beams. The optical depth also depends on the beam angle. As a consequence the available optical depth can be optimized depending on the needed bandwidth. The predicted recovery efficiency is close to 100% for large optical depth.

2009-01-01

158

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 (? ?/?)-0 25. 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/3 2) is nearly constant

1980-04-15

159

Available Network Bandwidth Schema to Improve Performance in TCP Protocols  

Directory of Open Access Journals (Sweden)

Full Text Available The TCP congestion control mechanism in standard implementations presents several problems, for example, large queue lengths in network routers and packet losses, a misleading reduce of the transmission rate when there are link failures, among others. This paper proposes a schema to congestion control in TCP protocols, called NGWA, witch is based on the network bandwidth. The NGWA provides information considering the available bandwidth of the network infrastructure to the endpoints of the TCP connection.Hence, it helps in choosing a better transmission rate for TCP improving its performance. Simulation results show superior performance of the proposed scheme when compared to those obtained by TCP New Reno and standard TCP. A physical implementation in the Linux kernel was performed to prove the correct operation of the proposal.

Marcos Talau

2013-01-01

160

Modeling of Bandwidth Aggregation over Heterogeneous Wireless Access Networks  

DEFF Research Database (Denmark)

Motivated by the multihomming capability of the mobile devices and the fact that the heterogeneous wireless access networks overlap in coverage, mobile operators are looking for solutions that will benefit by simultaneous use of the available multiple access interfaces. Multipath or multilink transfer deals with the problem on how to effectively aggregate the bandwidth by simultaneous usage of heterogeneous networks that a host is attached to in order to improve the throughput. This paper deals with a simulation based analysis of bandwidth aggregation techniques and their impact on higher layer applications. The analysis is performed on a multipath model developed with OPNET Modeler, which is an advanced research tool that supports modeling and integration of various kinds of built-in networks.

Popovska Avramova, Andrijana; Dittmann, Lars

2012-01-01

 
 
 
 
161

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; Dr. RD. Balaji; Ramkumar Lakshminarayanan

2013-01-01

162

Precedence Based Preemption and Bandwidth Reservation Scheme in MANET  

Directory of Open Access Journals (Sweden)

Full Text Available 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) which adds more functionalities with AQR and added with AODV. In addition to reserving bandwidth it will also provide preemption scheme. It will minimize number of preemption and will assure that preemption is being done fairly. Case studies between AODV and PBRS shows the added advantage of PBRS over AODV in terms of priority and preemption.

Sourabh Singh Verma

2012-01-01

163

Plasma density profiles and finite bandwidth effects on electron heating  

Energy Technology Data Exchange (ETDEWEB)

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, ..omega../sub pe/, equals the microwave frequency, ..omega../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 (..delta.. ..omega../..omega..)/sup -0/ /sup 25/. 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//sup 3/ /sup 2/) is nearly constant.

Spielman, R.B.; Mizuno, K.; DeGroot, J.S.; Bollen, W.M.; Woo, W.

1980-01-01

164

Anamorphic transformation and its application to time-bandwidth compression.  

UK PubMed Central (United Kingdom)

A general method for compressing the modulation time-bandwidth product of analog signals is introduced. As one of its applications, this physics-based signal grooming, performed in the analog domain, allows a conventional digitizer to sample and digitize the analog signal with variable resolution. The net result is that frequency components that were beyond the digitizer bandwidth can now be captured and, at the same time, the total digital data size is reduced. This compression is lossless and is achieved through a feature selective reshaping of the signal's complex field, performed in the analog domain prior to sampling. Our method is inspired by operation of Fovea centralis in the human eye and by anamorphic transformation in visual arts. The proposed transform can also be performed in the digital domain as a data compression algorithm to alleviate the storage and transmission bottlenecks associated with "big data."

Asghari MH; Jalali B

2013-09-01

165

Anamorphic transformation and its application to time-bandwidth compression.  

Science.gov (United States)

A general method for compressing the modulation time-bandwidth product of analog signals is introduced. As one of its applications, this physics-based signal grooming, performed in the analog domain, allows a conventional digitizer to sample and digitize the analog signal with variable resolution. The net result is that frequency components that were beyond the digitizer bandwidth can now be captured and, at the same time, the total digital data size is reduced. This compression is lossless and is achieved through a feature selective reshaping of the signal's complex field, performed in the analog domain prior to sampling. Our method is inspired by operation of Fovea centralis in the human eye and by anamorphic transformation in visual arts. The proposed transform can also be performed in the digital domain as a data compression algorithm to alleviate the storage and transmission bottlenecks associated with "big data." PMID:24085172

Asghari, Mohammad H; Jalali, Bahram

2013-09-20

166

High-bandwidth/low-latency temporary storage for supercomputers  

Energy Technology Data Exchange (ETDEWEB)

The traditional use of memory and a symmetrical set of registers for storage of temporary results of scientific programs requires more execution time, hardware, and instruction-stream bandwidth than necessary. Novel register organizations that can be easily integrated into traditional supercomputer architectures can reduce all of these requirements. Execution speed can be more than doubled by storing temporary results in an asymmetrical set of general-purpose registers or an asymmetrical set of vector registers, instead of in memory and a small register-set. Faster access and a hardware cost one fourth that of traditional vector registers can be had by using a vector register that incorporates a pipelined, random-access-memory chip. If a large enough set of registers is used, the need to store temporary results in memory and then reload them for alter use can be eliminated; this saves both instruction-stream bandwidth and execution time.

Swensen, J.A.

1987-01-01

167

High-bandwidth/low-latency temporary storage for supercomputers  

Energy Technology Data Exchange (ETDEWEB)

The traditional use of memory and a symmetrical set of registers for storage of temporary results of scientific programs requires more execution time, hardware, and instruction-stream bandwidth than necessary. Novel register organizations that can be easily integrated into traditional supercomputer architectures can reduce all of these requirements. Execution speed can be more than doubled by storing temporary results in an asymmetrical set of general-purpose registers or an asymmetrical set of vector registers, instead of in memory and a small register-set. Faster access and a hardware cost one fourth that of traditional vector registers can be had by using a vector register that incorporates a pipelined, random-access-memory chip. If a large enough set of registers is used, the need to store temporary results in memory and then reload them for later use can be eliminated; this saves both instruction-stream bandwidth and execution time.

Swensen, J.

1987-01-01

168

High-bandwidth/low latency temporary storage for supercomputers  

Energy Technology Data Exchange (ETDEWEB)

The traditional use of memory and symmetrical set of registers for storage of temporary results of scientific programs requires more execution time, hardware, and instruction-stream bandwidth than necessary. Novel register organizations that can be easily integrated into traditional supercomputer architectures can reduce all of these requirements. Execution speed can be more than doubled by storing temporary results in an asymmetrical set of general-purpose registers or an asymmetrical set of vector registers, instead of in memory and a small register-set. Faster access and a hardware cost one fourth that of traditional vector registers can be had by using a vector register that incorporates a pipelines, random-access-memory chip. If a large enough set of registers is used, the need to store temporary results in memory and then reload them for later use can be eliminated; this saves both instruction-stream bandwidth and execution time. 111 refs., 43 figs., 40 tabs.

Swensen, J.A.

1987-12-01

169

Efficient Upload Bandwidth Estimation and Communication Resource Allocation Techniques  

CERN Multimedia

In this paper we address two problems, for which we present novel, efficient, algorithmic solutions. The first problem is motivated by practical situations and is concerned with the efficient estimation of the upload bandwidth of a machine, particularly in the context of a peer-to-peer content sharing and distribution application. The second problem is more of a theoretical nature and considers a constrained communication resource allocation situation.

Andreica, Mugurel Ionut

2010-01-01

170

Effects of radiation on the bandwidth of graded index fibers  

International Nuclear Information System (INIS)

The influence of gamma radiation on the bandwidth of graded index fibers of four different manufacturers is measured at about 840 and 1,300 nm wavelength. Increase as well as decrease is observed, depending on fiber type and wavelength. Differential mode attenuation and mode delay measurements, as well as examination of light emission distribution at the fiber endface before and after irradiation are performed to explain the results.

1996-01-01

171

High bandwidth second-harmonic generation in partially deuterated KDP  

International Nuclear Information System (INIS)

We have experimentally determined the spectrally noncritical phasematching behavior of Type I frequency doubling in KDP and its dependence on deuteration level in partially deuterated KDP. The first order wavelength sensitivity parameter??k/?? for Type I doubling of 1.053 ?m light vanishes for a KD*P crystal with a deuteration level between 10 and 14%. Very high bandwidth frequency doubling of Nd:glass lasers is possible with such a crystal.

1992-01-01

172

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; V. Reji; A. Sivabalan

2012-01-01

173

The feasibility of pulse compression by nonlinear effective bandwidth extension.  

UK PubMed Central (United Kingdom)

Chirp-encoded excitation has been utilized for increased signal-to-noise ratio (SNR) in both linear and harmonic imaging. In either case, it is necessary to isolate the relevant frequency band to avoid artifacts. In contrast, the present study isolates and then combines the fundamental and the higher harmonics, treating them as a single, extended bandwidth. Pulse-inverted sum and difference signals are first used to isolate even and odd harmonics. Matched filters specific to the source geometry and the transmit signal are then separately applied to each harmonic band. Verification experiments are performed using up to the third harmonic resulting from an underwater chirp excitation. Analysis of signal peaks after scattering from a series of steel and nylon wires indicates increased compression using the extended bandwidth, as compared to well-established methods for fundamental and second harmonic chirp compression. Using third harmonic bands, a mean pulse width of 56% relative to fundamental compression and 48% relative to second harmonic compression was observed. Further optimization of the compression by altering the transmission indicated 17% additional reduction in the pulse width and a 47% increase in peak-to-sidelobe ratio. Overall, results establish the feasibility of extended bandwidth signal compression for simultaneously increasing SNR and signal resolution.

Clement GT; Nomura H; Kamakura T

2011-10-01

174

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,; Kartik Dev Bharti,; Mohit Singh,

2013-01-01

175

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

2012-01-01

176

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

2011-01-01

177

Bandwidth Selection in an EM-like algorithm for nonparametric multivariate mixtures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we describe a method to select the bandwidth used in the nonparametric EM (npEM) algorithm of Benaglia et. al. (2008). This method is a generalization of the Silverman's rule of thumb used to select a bandwidth in kernel density estimation, and it results in one bandwidth for each mixt...

Benaglia, Tatiana; Chauveau, Didier; Hunter, David

178

Small signal microwave amplifier design  

CERN Multimedia

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

179

Influence of modal filtering on the bandwidth of multimode optical fibers  

Directory of Open Access Journals (Sweden)

Full Text Available The multimode (MM) optical fiber maximum operational range is defined by the fiber bandwidth (related to the intermodal dispersion) rather than by the fiber attenuation. The relationship between the modal bandwidth of the fiber, the launching condition and mode coupling is fairly complicated. There is presented a theoretical study on the modal bandwidth of the multimode fiber. The theory is based on a numerical solution of the coupled mode diffusion equation that allows the bandwidth of the MM optical fiber to be calculated. It is shown that appropriate modal filtering at the receiver side of the fiber link increases the link bandwidth.

Jerzy SIUZDAK; Grzegorz STEPNIAK

2007-01-01

180

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

UK PubMed Central (United Kingdom)

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.

Savovi? S; Drlja?a B; Djordjevich A

2013-02-01

 
 
 
 
181

Small signal AC-surface photovoltage technique for non-contact monitoring of near surface doping and recombination-generation in the depletion layer[Alternating Current  

Energy Technology Data Exchange (ETDEWEB)

Small signal non-contact ac-SPV method for monitoring near surface doping (NSD) in silicon has recently been introduced in commercial diagnostic tools. High chopping frequency light with a submicron penetration depth is used to generate small SPV signal and this signal is in turn monitored using a transparent pickup electrode. This technique has the advantage of producing fast, non-destructive full wafer measurement. Under certain conditions, the magnitude of this ac-SPV signal is inversely proportional to the depletion layer capacitance. if a depletion layer barrier height is known this allows the calculation of the concentration of ionized donors or acceptors in the depletion layer. NSD measurements by ac-SPV method were typically done for doping concentrations up to about 10{sup 16} cm{sup {minus}3}. Only recently this range has been extended to 10{sup 18} cm{sup {minus}3}, making it a very attractive technique for monitoring low and medium dose implants and especially for wafer scale mapping of implant uniformity and activation efficiency. In addition, the frequency dependence of the SPV signal provides a mean for evaluating the minority carrier lifetime in the near surface region of bulk and epitaxial wafers. The influence of surface/interface traps upon small ac-SPV signal has never been fully understood. This paper quantifies the role of interface traps in the monitoring of NSD. The effect of typical surface treatments such as HF, SC1 and SC1+SC2 wafer cleans are examined.

Marinskiy, D.; Lagowski, J.; Wilson, M.; Savtchouk, A.; Jastrzebski, L.; DeBusk, D.

2000-07-01

182

Request-based Dynamic Bandwidth Allocation of Gigabit Passive Optical Network  

Directory of Open Access Journals (Sweden)

Full Text Available We propose request-based dynamic bandwidth allocation (DBA) of gigabit passive optical network (GPON). The optical line terminal (OLT) in GPON grants bandwidth to optical network units (ONUs). ONUs report request bandwidth which depends on queue lengths of traffic containers (TCONTs) to the OLT. In the OLT, DBA of GPON supports a request-based polling order to allocate bandwidth. Our request-based dynamic bandwidth allocation focuses on weight assignments in the request-based polling order. Weight assignments allocate bandwidth in proportion to guaranteed and request bandwidth. We use the C program to simulate results. Simulated results indicate improved performance in queueing delay when total offered loads are or are not shared uniformly to TCONTs.

Chih-Ta Chiu; Yung-Chung Wang

2013-01-01

183

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; Md. Hanif Ali; M Adnan Kiber

2009-01-01

184

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.

Norashidah Md Din; Norsheila Fisal

2008-01-01

185

Spatial frequency bandwidth of surround suppression tuning curves.  

UK PubMed Central (United Kingdom)

The contrast detection threshold of a grating located in the periphery is increased if a surrounding grating of the same frequency and orientation is present. This inhibition between center and surround has been termed surround suppression. In this work we measured the spatial frequency bandwidth of surround suppression in the periphery for different spatial frequencies (0.5, 1.1, 3, and 5 cycles/deg) of a sinusoidal grating (target) surrounded by a grating with different spatial frequencies (surround). Using a Bayesian adaptive staircase, we measured contrast detection thresholds in an 8AFC detection task in which the target (grating with a 2.3-deg Butterworth window) could appear in one of eight possible positions at 4° eccentricity. The target was surrounded by a grating (with a 18° Butterworth window) with the same or an orthogonal orientation. In each session we fixed the spatial frequency of the target and changed the spatial frequency and the orientation of the surround. When the surround was orthogonal to the target, the thresholds were similar to those obtained without surround, independent of the surrounding spatial frequency. However, when the target and surround had the same orientation and spatial frequency, the contrast threshold was increased by a factor ranging from 3 to 6 across subjects. This suppression reduced rapidly as the spatial frequency of the surround moved away from that of the target. The bandwidth of the suppressive effect depended on spatial frequency, declining from 2.9 octaves at 0.5 c/deg to 1 octave for frequencies above 3 c/deg. This is consistent with the bandwidth of individual simple cells in visual cortex and of spatial frequency channels measured psychophysically, both of which decline with increasing spatial frequency. This suggests that surround suppression may be due to relatively precise inhibition by cells with the same tuning as the target.

Serrano-Pedraza I; Grady JP; Read JC

2012-01-01

186

Low Bandwidth Vocoding using EM Sensor and Acoustic Signal Processing  

International Nuclear Information System (INIS)

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.

2001-01-01

187

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

188

Efficient and Fair Bandwidth Allocation AQM Scheme for Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Heterogeneous Wireless Networks are considered nowadays as one of the potential areas in research and development. The traffic management’s schemes that have been used at the fusion points between the different wireless networks are classical and conventional. This paper is focused on developing a novel scheme to overcome the problem of traffic congestion in the fusion point router interconnected the heterogeneous wireless networks. The paper proposed an EF-AQM algorithm which provides an efficient and fair allocation of bandwidth among different established flows. Finally, the proposed scheme developed, tested and validated through a set of experiments to demonstrate the relative merits and capabilities of a proposed scheme

Rafe Alasem

2010-01-01

189

Systems with selective overflow and change of bandwidth  

DEFF Research Database (Denmark)

We consider a loss system with n channels and a finite or infinite overflow group, which is offered N different services, all having Poisson arrival processes. All calls have same bandwidth demand and mean service time, but the mean service time may be different on the primary group and the overflow group, corresponding to data traffic with different bandwidth allocation on primary (micro-cell = femto-cell) and overflow group (macro-cell = LTE-cell). Then using a result of Wallström we can calculate the Binomial moments of the total overflow traffic. Given a certain number of busy channels on the overflow group, we show by balance equations that the number of calls of each service will be Multinomial distributed with probabilities proportional with the arrival rates. Using a recent result of Newcomer & al, we then find moments (done up to fourth order) of individual overflow streams or any combinations of overflow streams. Thus we can find the correlation between services and for example the moments of some traffic streams which may overflow to one system, whereas other traffic streams may be blocked or overflow to another system.

Iversen, Villy Bæk

2012-01-01

190

Explicit Codes Minimizing Repair Bandwidth for Distributed Storage  

CERN Multimedia

We consider the problem of data storage across n nodes in a distributed manner. A data collector (DC) should be able to reconstruct the entire data by connecting to any k out of the n nodes and downloading all the data stored in them. When a node fails, it has to be regenerated back using the existing nodes. In a recent paper, Wu et al. have obtained an information theoretic lower bound for the repair bandwidth. Recently, there has been additional interest in storing data in systematic form as no post processing is required when DC connects to k systematic nodes. Because of their preferred status there is a need to regenerate back any systematic node quickly and exactly. Replacement of a failed node by an exact replica is termed Exact Regeneration.In this paper, we consider the problem of minimizing the repair bandwidth for exact regeneration of the systematic nodes. The file to be stored is of size B and each node can store alpha = B/k units of data. A failed systematic node is regenerated by downloading bet...

Shah, Nihar B; Kumar, P Vijay; Ramchandran, Kannan

2009-01-01

191

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.

Ariel Sagi; David Malah

2007-01-01

192

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; Malah David

2007-01-01

193

Modulator-Based, High Bandwidth Optical Links for HEP Experiments  

CERN Multimedia

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

194

Impact of Wind Power Plants with Full Converter Wind Turbines on Power System Small-Signal Stability : Inherent Characteristics and Potential for Power Oscillation Damping Control  

DEFF Research Database (Denmark)

Wind power is being developed in power systems all around the world, and already today wind power covers more than 20 % of the electricity consumption in some countries. As the size of each wind power plant (WPP) increases and as the levels of penetration reaches certain magnitudes, the inclusion of the dynamic properties of the WPPs in the power system stability studies become important. The work presented in this report deal with the impact of WPPs based on full converter wind turbines (WTs) on the power system small-signal rotor angle stability. During small disturbances in the power system, the rotor speed of the synchronous machines will eventually return to its steady state if the power system is small-signal stable. The dynamic properties of a WPP are fundamentally dierent from those of a synchronous machine, and the interaction of WPPs with the synchronous machines in power system oscillations has not yet been fully claried. The participation of the WPP in the power system oscillations was investigated for a number of WPP penetration levels and for dierent WPP modes of operation. It was generally found that the inter-area modes were largely unaected by the WPP penetration level and mode of operation. The participation of the WT mechanical system in the inter-area modes were found to be orders of magnitudes smaller than the participation of the synchronous generators. The reactive power controller of the WPP and the WT were found have the highest participation among the WPP and WT states. WPPs based on converter interfaced WTs oer a high degree of controllability due to the rapid response of the converter and the ability to control both the active and the reactive power output. During this project, it has been explored how these properties could be utilized to actively contribute to the modal damping of weakly damped power oscillations through WPP power oscillation damping control (POD). Emphasis has been put on WPP level PODs due to its simplicity as compared to individual WT PODs, and since this oers a single point of access if the operation of the POD is to be controlled by a wide-area measurement system. The ndings encourage that a WPP level POD is feasible, since the WTs in a 150 WT WPP required very similar control signals to optimally contribute to an increased modal damping, and since time domain simulations showed that the interaction between the WTs did not adversely eect the ability of the WTs to generate an aligned WPP response. The theoretical ndings are supported with eld test results on a small 13 WT WPP that has been subject to open-loop tests of both active and reactive power modulations in the frequency range of 0:1 to 1:0 Hz. With the eld tests it has been shown that it was possible to control the WTs to deliver a common WPP response that was consistent in both frequency and phase. This was achieved for both active and reactive power modulation.

Knüppel, Thyge

2012-01-01

195

Dynamic Bandwidth Management in Distributed VoD based on the User Class Using Agents  

CERN Multimedia

This paper proposes a dynamic bandwidth management algorithm in which more bandwidth is allocated for higher class users and also higher priority is given to the videos with higher popularity within a class using agent technology. The popularity and weight profile of the videos which is used for efficiently allocating bandwidth is periodically updated by a mobile agent. The proposed approach allocates more bandwidth for higher class users and gives higher priority for higher weight videos [popular videos] so that they can be served with high QoS, reduces the load on the central multimedia server and maximizes the channel utilization between the neighboring proxy servers and the central multimedia server and lower video rejection ratio. The simulation results prove the reduction of load on central multimedia server by load sharing among the neighboring proxy servers, maximum bandwidth utilization, and more bandwidth allocation for higher class users.

Guruprasad, H S

2009-01-01

196

Performance improvement of bandwidth-flexible reconfigurable optical add/drop multiplexers with wavelength converters  

Science.gov (United States)

In this paper, we propose a novel bandwidth-flexible reconfigurable optical add/drop multiplexer (ROADM) architecture based on coherent optical-orthogonal frequency division multiplexing (CO-OFDM) technology. The bandwidth-flexible ROADM architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. We simulate and compare the blocking performance of bandwidth-flexible ROADM with and without wavelength converters. It is found that wavelength converter could obviously improve the blocking performance of bandwidth-flexible ROADM with different frequency grid. Moreover, the conversion ratios are calculated for different load and channel spacing. Based on the analysis of conversion ratio, we could make an appropriate configuration of wavelength converters in bandwidth-flexible ROADM.

You, S.

2011-11-01

197

A Study of Bandwidth-Perception Management Mechanisms in IEEE 802.16 Networks  

CERN Multimedia

Bandwidth request-grant mechanisms are used in 802.16 networks to manage the uplink bandwidth needs of subscriber stations (SSs). Requests may be sent by SSs to the base station (BS) by means of several mechanisms defined in the standard. Based on the incoming requests, the BS (which handles most of the bandwidth scheduling in the system) schedules the transmission of uplink traffic, by assigning transmission opportunities to the SSs in an implementation-dependent manner. In this paper we present a study of some bandwidth allocation issues, arising from the management of the perception of subscriber stations' bandwidth needs at the base station. We illustrate how the bandwidth perception varies depending on the policy used to handle requests and grants. By means of ns-2 simulations, we evaluate the potential impact of such policies on the system's aggregate throughput when the traffic is composed of Best-Effort TCP flows.

Arcia-Moret, Andres; Montavont, Nicolas; Ros, David

2010-01-01

198

Generalized gene adjacencies, graph bandwidth, and clusters in yeast evolution.  

UK PubMed Central (United Kingdom)

We present a parameterized definition of gene clusters that allows us to control the emphasis placed on conserved order within a cluster. Though motivated by biological rather than mathematical considerations, this parameter turns out to be closely related to the bandwidth parameter of a graph. Our focus will be on how this parameter affects the characteristics of clusters: how numerous they are, how large they are, how rearranged they are, and to what extent they are preserved from ancestor to descendant in a phylogenetic tree. We infer the latter property by dynamic programming optimization of the presence of individual edges at the ancestral nodes of the phylogeny. We apply our analysis to a set of genomes drawn from the Yeast Gene Order Browser.

Zhu Q; Adam Z; Choi V; Sankoff D

2009-04-01

199

Modulator based high bandwidth optical readout for HEP detectors  

Science.gov (United States)

Optical links will be an integral part of future LHC experiments at various scales from coupled sensors to off-detector communication. We are investigating CW lasers and light modulators as an alternative to VCSELs. Light modulators are small, use less power, have high bandwidth, are reliable, have low bit error rates and are very rad-hard. We present the quality of the links at 10Gbps and the results of radiation hardness measurements for the modulators built based on LiNbO3, InP, and Si. Also we present results on modulator-based free space data links, steered by MEMS mirrors and optical feedback paths for the control loop.

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

2013-02-01

200

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

 
 
 
 
201

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; Muhammad Shahin Uddin; Ruhul Amin; Mortuza Ali

2011-01-01

202

Transformation optics for antennas: why limit the bandwidth with metamaterials?  

UK PubMed Central (United Kingdom)

In the last decade, a technique termed transformation optics has been developed for the design of novel electromagnetic devices. This method defines the exact modification of magnetic and dielectric constants required, so that the electromagnetic behaviour remains invariant after a transformation to a new coordinate system. Despite the apparently infinite possibilities that this mathematical tool introduces, one restriction has repeatedly recurred since its conception: limited frequency bands of operation. Here we circumvent this problem with the proposal of a full dielectric implementation of a transformed planar hyperbolic lens which retains the same focusing properties of an original curved lens. The redesigned lens demonstrates operation with high directivity and low side lobe levels for an ultra-wide band of frequencies, spanning over three octaves. The methodology proposed in this paper can be applied to revolutionise the design of many electromagnetic devices overcoming bandwidth limitations.

Quevedo-Teruel O; Tang W; Mitchell-Thomas RC; Dyke A; Dyke H; Zhang L; Haq S; Hao Y

2013-01-01

203

Adapting to Bandwidth Variations in Wide-Area Data Combination  

UK PubMed Central (United Kingdom)

Efficient data combination over wide-area networks is hard as wide-area networks have largevariations in available network bandwidth. In this paper, we examine the utility of changing thelocation of combination operators as a technique to adapt to variations in wide-area networkbandwidth. We try to answer the following questions. First, does relocation of operators providea significant performance improvement? Second, is on-line relocation useful or does a one-timepositioning at start-up time provide most if not all the benefits? If on-line relocation is useful,how frequently should it be done and is global knowledge of network performance required orcan local knowledge and local relocation of operators sufficient? Fourth, does the effectiveness ofoperator relocation depend on the ordering of the combination operations. That is, are certainways of ordering more amenable to adaptation than others? Finally, how do the results changeas the number of data sources change...

Anurag Acharya; Joel Saltz

204

Adapting to Bandwidth Variations in Wide-Area Data Combination  

UK PubMed Central (United Kingdom)

Efficient data combination over wide-area networks is hard as wide-area networks have largevariations in available network bandwidth. In this paper, we examine the utility of changing thelocation of combination operators as a technique to adapt to variations in wide-area networkbandwidth. We try to answer the following questions. First, does relocation of operators providea significant performance improvement? Second, is on-line relocation useful or does a one-timepositioning at start-up time provide most if not all the benefits? If on-line relocation is useful,how frequently should it be done and is global knowledge of network performance required orcan local knowledge and local relocation of operators sufficient? Fourth, does the effectiveness ofoperator relocation depend on the ordering of the combination operations. That is, are certainways of ordering more amenable to adaptation than others? Finally, how do the results changeas the number of data sources changes?1 Intro...

Anurag Acharya; Joel Saltz

205

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

206

Achilles: High Bandwidth, Low Latency, Low Overhead Communication  

UK PubMed Central (United Kingdom)

Achilles provides a system for high performance parallel computingbased on a network of workstations (NoW) with a high bandwidth,low latency, low overhead, 32 bit wide, fast crossbar switchingcircuit router. The host interface adaptors are PCI compliant and capableof maximum PCI transfer rate with low host CPU overhead. Achillesis capable of quickly transferring megabytes of data through a single circuitconnection with low latency. It is particularly suited to NoW parallelprocessing, where for maximum efficiency, the tasks are coarse grain, andlarge amounts of data often need to be shifted between workstations. Asingle Achilles router provides eight concurrent connections and is capableof 128 Mbyte/s throughput per channel, for a total cross sectionalbandwidth over 1 Gbyte/s, with sub microsecond hardware latency. Thecurrent Achilles prototype router and PCI host interface have been measuredproviding 28 Mbyte/s throughput per channel with a hardwarelatency...

Sonny Tham; John Morris; Richard Gregg

207

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

2010-01-01

208

Bandwidth allocation strategy for traffic systems of scale-free network  

Energy Technology Data Exchange (ETDEWEB)

In this Letter, the bandwidth resource allocation strategy is considered for traffic systems of complex networks. With a finite resource of bandwidth, an allocation strategy with preference parameter {alpha} is proposed considering the links importance. The performance of bandwidth allocation strategy is studied for the local routing protocol and the shortest path protocol. When important links are slightly favored in the bandwidth allocation, the system can achieve the optimal traffic performance for the two routing protocols. For the shortest path protocol, we also give a method to estimate the network traffic capacity theoretically.

Ling Xiang [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Hu MaobBin, E-mail: humaobin@ustc.edu.c [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Department of Mathematics and Statistics, Curtin University of Technology, Perth WA6845 (Australia); Du Wenbo [School of Computer Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Jiang Rui [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China); Wu Yonghong [Department of Mathematics and Statistics, Curtin University of Technology, Perth WA6845 (Australia); Wu Qingsong [School of Engineering Science, University of Science and Technology of China, Hefei 230026 (China)

2010-11-01

209

Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration.  

UK PubMed Central (United Kingdom)

We present a scheme to generate a 10 GHz optical frequency comb that is bandwidth reconfigurable on a time scale of tens of nanoseconds via electronic control of the drive signal to a phase modulator. When such a comb is used as the source for a radio-frequency (RF) photonic filter employing dispersive propagation, the RF filter bandwidth varies in inverse proportion to the optical bandwidth. As a result we are able to demonstrate, for the first time to our knowledge, bandwidth-reconfigurable RF filtering with transition times under 20 ns. The reconfiguration speed is determined by the response time of a programmable RF variable attenuator.

Wu R; Song M; Leaird DE; Weiner AM

2013-08-01

210

Improvement of the bandwidth of the transient digitizers in the LIDAR Thomson scattering diagnostic on JET  

International Nuclear Information System (INIS)

The main limitation on the spatial resolution of the LIDAR Thomson scattering diagnostic on the JET tokamak is due to the narrow bandwidth of the detection system. The transient digitizers, Tektronik 7912AD, are the main contributors to the narrow bandwidth. It is shown how the digitizers can be modified to improve the response time from approx. 480 to 410 ps. (author)

1990-01-01

211

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,; Dr. Sarita Singh Bhadauria

2011-01-01

212

Gigabit Passive Optical Networks (GPON) the Ultimate Solution for Large Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available The demand for bandwidth has increased drastically. So optical transmission has got more importance in access networks. The upcoming features like IPTV, High speed internet(HSI), Video on demand(VOD), online gaming are confronting large bandwidth at the customer end.The demand of bandwidth can be satisfied by XDSL, but the distance is restricted by using this type of technique. So we can use optical transmission for achieving large bandwidth by using passive optical networks(PON). One of the most advanced PON solution is Gigabit PON (GPON). This is the most widely used solution where there is a requirement of large bandwidth This paper provides an overview of GPONfeatures, transmission mechanism, optical splitting and power budget.

A.ManikantaSitaram; K. Mohan Swamy,; Akella.Rama Krishna,

2012-01-01

213

Cell Scheduling And Bandwidth Allocation For Heterogeneous Vbr Video Conferencing Traffic  

UK PubMed Central (United Kingdom)

We first propose a new cell loss scheduling scheme,referred to as the QoS-scheme. This scheme can satisfy differentindividual quality of service (QoS) requirements of a group ofvirtual channel connections with minimum required bandwidth.We next derive a simple formula based on Gaussian approximationto allocate bandwidth to heterogeneous VBR video conferencingconnections. Comparing the proposed QoS-scheme withthe simple last-in-first-out (LIFO) scheme, we find that if theLIFO scheme is adopted as the loss scheduling scheme, developingany more efficient bandwidth allocation algorithms can atmost improve bandwidth utilization by about 10%. However, ifthe proposed QoS-scheme is implemented, an efficient allocationalgorithm can improve bandwidth utilization by roughly 20%.I. IntroductionReal-time video (e.g., video conferencing, video-on-demand,and switched broadcasted TV programs) is expected to be one ofthe major services supported by ATM-based B-ISDN. Real-timevideo tra...

Video Conferencing; Traffic Yang; Danny H. K; Tsang Patrick Mccabe

214

Maximizing audibility and speech recognition with nonlinear frequency compression by estimating audible bandwidth.  

UK PubMed Central (United Kingdom)

OBJECTIVE: Nonlinear frequency compression attempts to restore high-frequency audibility by lowering high-frequency input signals. Methods of determining the optimal parameters that maximize speech understanding have not been evaluated. The effect of maximizing the audible bandwidth on speech recognition for a group of listeners with normal hearing is described. DESIGN: Nonword recognition was measured with 20 normal-hearing adults. Three audiograms with different high-frequency thresholds were used to create conditions with varying high-frequency audibility. Bandwidth was manipulated using three conditions for each audiogram: conventional processing, the manufacturer's default compression parameters, and compression parameters that optimized bandwidth. RESULTS: Nonlinear frequency compression optimized to provide the widest audible bandwidth improved nonword recognition compared with both conventional processing and the default parameters. CONCLUSIONS: These results showed that using the widest audible bandwidth maximized speech identification when using nonlinear frequency compression. Future studies should apply these methods to listeners with hearing loss to demonstrate efficacy in clinical populations.

McCreery RW; Brennan MA; Hoover B; Kopun J; Stelmachowicz PG

2013-03-01

215

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

2012-01-01

216

Energy and Bandwidth Constrained QoS Enabled Routing for MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available Mobile adhoc networks are rapid deployable self organizing networks. Their key characteristics aredynamic topology, high node mobility, low channel bandwidth and limited battery power. Hence, it isnecessary to minimize bandwidth and energy consumption. To transmit packets, available bandwidth isknown along the route from sender to receiver. Thus, bandwidth estimation is the main metric to supportQuality of Service (QoS). This work focuses on improving the accuracy of available bandwidth andincorporating a QoS-aware scheme into the route discovery procedure. It is also important to limit theenergy consumed by nodes. Probability based overhearing method is proposed to reduce energy spent onoverhearing nodes. This experiment is implemented in NS2 simulator and the performance of the network isanalyzed in terms of QoS parameters.

N.Sumathi; C.P.Sumathi

2013-01-01

217

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

218

Construction and experimental testing of the constant-bandwidth constant-temperature anemometer.  

UK PubMed Central (United Kingdom)

A classical constant-temperature hot-wire anemometer enables the measurement of fast-changing flow velocity fluctuations, although its transmission bandwidth is a function of measured velocity. This may be a source of significant dynamic errors. Incorporation of an adaptive controller into the constant-temperature system results in hot-wire anemometer operating with a constant transmission bandwidth. The construction together with the results of experimental testing of a constant-bandwidth hot-wire anemometer prototype are presented in this article. During the testing, an approximately constant transmission bandwidth of the anemometer was achieved. The constant-bandwidth hot-wire anemometer can be used in measurements of high-frequency variable flows characterized by a wide range of velocity changes.

Ligeza P

2008-09-01

219

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

220

Simulations of the intermediate bandwidth fluctuations in nanostructured PV  

Science.gov (United States)

The size dispersion and distributions of quantum dot nanoparticles (sizes from 2–5 nm) embedded in the active region of the intermediate band solar cells are important to reach the high efficiencies. An optimized size and regularity can increase the efficiency due largely to avoided non-radiative transitions which can originate from the fluctuations in the bandwidth of the intermediate layer. In this work, we propose all the energy band diagrams possible in the formation of such a cell. Five equivalent band diagrams of the cells with different size dispersions and regularity of quantum dots are considered and compared with the reported experimental profiles in the literature. Furthermore, the degree of the size fluctuation is considered by proposing a fluctuation degree for the band gap and sub-band gaps of the cell. These proposed profiles and the fluctuation theory are exploited to consider the experimental data reported in literature. The optimized size dispersion will increase the photocurrent of the cell. We believe that every quantum dot solar cell will fall into one of the proposed band diagrams. This approach gives foresight to the theoretical studies of such devices and expectation from the energy band structure and band widths since it considers the fluctuation of the band widths for the intermediate band separately.

Mebadi, Ashkan; Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.

2013-09-01

 
 
 
 
221

QoS routing via multiple paths using bandwidth reservation  

Energy Technology Data Exchange (ETDEWEB)

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate. They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete and propose a polynomial-time approximate solution.

Rao, N.S.V.; Batsell, S.G.

1997-11-01

222

QoS routing via multiple paths using bandwidth reservation  

Energy Technology Data Exchange (ETDEWEB)

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate.They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete, and propose a polynomial-time approximately solution.

Rao, N.S.V.; Batsell, S.G.

1998-01-01

223

Automatic Bandwidth Adjustment for Content Distribution in MPLS Networks  

Directory of Open Access Journals (Sweden)

Full Text Available Aggregates of real-time traffic may experience changes in their statistical characteristics often manifesting non stationary behavior. In multi protocol label switching (MPLS) networks this type of the traffic is assigned constant amount of resources. This may result in ineffective usage of resources when the load is below than expected or inappropriate performance when the load is higher. In this paper we propose new algorithm for dynamic resource adaptation to temporarily changing traffic conditions. Assuming that network nodes may reallocate resources on-demand using automatic bandwidth adjustment capability of MPLS framework, the proposed algorithm, implemented at ingress MPLS nodes, dynamically decides which amount of resources is currently sufficient to handle arriving traffic with given performance metrics. This decision is then communicated to interior MPLS nodes along the label switched path. As a basic tool of the algorithm we use change-point statistical test that signals time instants at which statistical characteristics of traffic aggregates change. The major advantage of the proposed approach is that it is fully autonomous, that is, network nodes do not need any support from hosts in terms of resource reservation requests. The proposed algorithm is well suited for traffic patterns experiencing high variability, especially, for non stationary type of the traffic.

D. Moltchanov

2008-01-01

224

Shaped optimal control pulses for increased excitation bandwidth in EPR.  

UK PubMed Central (United Kingdom)

A 1 ns resolution pulse shaping unit has been developed for pulsed EPR spectroscopy to enable 14-bit amplitude and phase modulation. Shaped broadband excitation pulses designed using optimal control theory (OCT) have been tested with this device at X-band frequency (9 GHz). FT-EPR experiments on organic radicals in solution have been performed with the new pulses, designed for uniform excitation over a significantly increased bandwidth compared to a classical rectangular ?/2 pulse of the same B(1) amplitude. The concept of a dead-time compensated prefocused pulse has been introduced to EPR with a self-refocusing of 200 ns after the end of the pulse. Echo-like refocused signals have been recorded and compared to the performance of a classical Hahn-echo sequence. The impulse response function of the microwave setup has been measured and incorporated into the algorithm for designing OCT pulses, resulting in further significant improvements in performance. Experimental limitations and potential new applications of OCT pulses in EPR spectroscopy will be discussed.

Spindler PE; Zhang Y; Endeward B; Gershernzon N; Skinner TE; Glaser SJ; Prisner TF

2012-05-01

225

Satisfying customer bandwidth demand in IP data networks  

Science.gov (United States)

We introduce the notion of customer bandwidth fulfillment in IP data networks and provide a quantitative characterization of the fulfillment using measurements of the router uplink (link connecting a router to the backbone) utilization. The threshold for the uplink utilization is calculated for a given probability of customer fulfillment based on the normal approximation. We use three different stochastic models to prove the normal approximation for the distribution of the uplink utilization. The convergence to the Gaussian diffusion prcess is proved in the framework of the nonstationary exponential Benes buffer model. In a special case of an alternating renewal process, we show that the fulfillment can be evaluated based on measurements of the mean uplink utilization. We also prove that the distribution for the number of busy links in a large generalized Engset model is asymptotically normal that provides another justification of the normal approximation for the uplink utilization. We analyze 5-minutes measurements of the uplink utilization and show that their empirical distribution is close to normal.

Kogan, Yaakov; Kosal, Haluk; Maguluri, Gangaji; Ramachandran, Gomathi

2001-07-01

226

On the Observance of Approximate Invariance of Effective Bandwidth with Finite Number of Sources  

Directory of Open Access Journals (Sweden)

Full Text Available The effective bandwidth is a descriptor in the context of stochastic models for statistical sharing of resources. One of the most interesting properties of effective bandwidth is that it does not change when passing a network node under many sources limiting regime (infinitely many sources). This is referred as the “invariance property” of effective bandwidth. Numerical simulations have suggested that in some cases, the “invariance property” of effective bandwidths holds already for a surprisingly small number of competing flows even in the presence of aggressive TCP traffic. The real question, though, is: how many input processes are needed for reasonable convergence over the scale of interest? This work addresses this question using recent results from the large deviations theory under many sources limiting regime and the theory of statistical network calculus. We also show that as the number of arrival flows increases, the bound on the departure process’ effective bandwidth converges exponentially fast to that of the effective bandwidth of the arrival. The advantage of identifying the minimum number of independent multiplexing flows at each network node to observe approximate invariance of effective bandwidth is that the task of network resources dimensioning can be greatly simplified.

Kishore Angrishi; Ulrich Killat

2009-01-01

227

Real-Time Virtual Instruments for Remote Sensor Monitoring Using Low Bandwidth Wireless Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The development of a peer-to-peer virtual instrumentation system for remote acquisition, analysis and transmission of data on low bandwidth networks is described. The objective of this system is to collect high frequency/high bandwidth data from multiple sensors placed at remote locations and adaptively adjust the resolution of this data so that it can be transmitted on bandwidth limited networks to a central monitoring and command center. This is achieved by adaptively re-sampling (decimating) the data from the sensors at the remote location before transmission. The decimation is adjusted to the available bandwidth of the communications network which is characterized in real-time. As a result, the system allows users at the remote command center to view high bandwidth data (at a lower resolution) with user-aware and minimized latency. This technique is applied to an eight hydrophone data acquisition system that requires a 25.6 Mbps connection for the transmission of the full data set using a wireless connection with 1 – 3.5 Mbps variable bandwidth. This technique can be used for applications that require monitoring of high bandwidth data from remote sensors in research and education fields such as remote scientific instruments and visually driven control applications.

Biruk Gebre; Liwen Guo; Nishit Patel; Kishore Pochiraju

2008-01-01

228

MR-BART: Multi-Rate Available Bandwidth Estimation in Real-Time  

CERN Multimedia

In this paper, we propose Multi-Rate Bandwidth Available in Real Time (MR-BART) to estimate the end-to-end Available Bandwidth (AB) of a network path. The proposed scheme is an extension of the Bandwidth Available in Real Time (BART) which employs multi-rate (MR) probe packet sequences with Kalman filtering. Comparing to BART, we show that the proposed method is more robust and converges faster than that of BART and achieves a more AB accurate estimation. Furthermore, we analyze the estimation error in MR-BART and obtain analytical formula and empirical expression for the AB estimation error based on the system parameters.

Sedighizad, Mahboobeh; Navaie, Keivan

2009-01-01

229

Increased spectral bandwidths in nonlinear conversion processes by use of multicrystal designs.  

UK PubMed Central (United Kingdom)

The fourth-harmonic generation of broadband 243-nm radiation is reported. The broadband radiation is achieved by implementation of a multicrystal design to overcome spectral bandwidth limitations, and a plane-wave analysis is developed that shows increased spectral bandwidths for these designs. The fourth harmonic of a Cr:LiSAF laser operating at 972 nm is generated in beta-barium borate (BBO). The results demonstrate a spectral bandwidth at 243 nm more than five times broader than that which is expected from a single BBO crystal of equivalent length.

Brown M

1998-10-01

230

A MODIFIED SWIFTER START ALGORITHM FOR EVALUATING HIGH BANDWIDTH DELAY PRODUCT NETWORKS  

Directory of Open Access Journals (Sweden)

Full Text Available It is well known that the TCP congestion control algorithm has been remarkably successful in improving the current TCP/IP function better and efficiently. However, it can perform poorly in networks with high Bandwidth Delay Product (BDP) paths. This paper presents modification to the Swifter Start congestion control algorithm, that may helps the TCP better utilize the bandwidth provided by huge bandwidth long delay links. It also presents results to show a comparison of the original Swifter Start algorithm and the modified Swifter Start algorithm, these are promising enough.

Ehab Aziz Khalil

2012-01-01

231

Error-resilient video communications over CDMA networks with a bandwidth constraint.  

Science.gov (United States)

We present an adaptive video transmission scheme for use in a code-division multiple-access network, which incorporates efficient bandwidth allocation among source coding, channel coding, and spreading under a fixed total bandwidth constraint. We derive the statistics of the received signal, as well as a theoretical bound on the packet drop rate at the receiver. Based on these results, a bandwidth allocation algorithm is proposed at the packet level, which incorporates the effects of both the changing channel conditions and the dynamics of the source content. Detailed simulations are done to evaluate the performance of the system, and the sensitivity of the system to estimation error is presented. PMID:17076387

Shen, Yushi; Cosman, Pamela C; Milstein, Laurence B

2006-11-01

232

High bandwidth data recording systems for pulsed power and laser produced plasma experiments  

International Nuclear Information System (INIS)

[en] We present two high bandwidth data transmission and recording systems for the measurement of transient signals during pulsed power and laser produced plasmas. These systems use fiber optic cables to transmit analog data over long distances to high bandwidth digitizing oscilloscopes. One system is based on the direct modulation of a laser diode and has a bandwidth of 1.5 GHz. The other system is based upon a Mach-Zehnder modulator and has a bandwidth of 12 GHz, and is limited by the photoreceiver. The signals are recorded on commercial digitizing oscilloscopes that have approximately six effective bits. The transmission systems use many off-the-shelf components from the telecommunications industry and thus have a high reliability and a moderate cost. Investigation of the reduction in optical transmission of the fibers during exposure to high dose radiation will also be discussed

2006-01-01

233

High Bandwidth Data Recording Systems for Pulsed Power and Laser Produced Plasma Experiments.  

Energy Technology Data Exchange (ETDEWEB)

We present two high bandwidth data transmission and recording systems for the measurement of transient signals during pulsed power and laser produced plasmas. These systems use fiber optic cables to transmit analog data over long distances to high bandwidth digitizing oscilloscopes. One system is based on the direct modulation of a laser diode and has a bandwidth of 1.5 GHz. The other system is based upon a fiber-optic Mach-Zehnder modulator and has a bandwidth of 12 GHz, and is limited by the photo receiver. The signals are recorded on commercial digitizing oscilloscopes that have approximately 6 effective bits. The transmission systems use many off-the-shelf components from the telecommunications industry and thus have a high reliability and a moderate cost. Results from recent measurements will be presented. Investigation of the reduction in optical transmission by the fibers during exposure to high dose radiation will also be discussed.

May, M J; Clancy, T; Fittinghoff, D; Halvorson, C; MIlls, T; Nikitin, A; Perry, T; Roberson, P; Smith, D; Teruya, A; Miller, K; Trainham, C

2006-05-02

234

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; W.K. Ng; T.C. Ling; L.Y. Por; C.S. Liew

2009-01-01

235

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; Divyanshu Prabhav; Chitransh Karade

2013-01-01

236

A Foundation for Stochastic Bandwidth Estimation of Networks with Random Service  

CERN Multimedia

We develop a stochastic foundation for bandwidth estimation of networks with random service, where bandwidth availability is expressed in terms of bounding functions with a defined violation probability. Exploiting properties of a stochastic max-plus algebra and system theory, the task of bandwidth estimation is formulated as inferring an unknown bounding function from measurements of probing traffic. We derive an estimation methodology that is based on iterative constant rate probes. Our solution provides evidence for the utility of packet trains for bandwidth estimation in the presence of variable cross traffic. Taking advantage of statistical methods, we show how our estimation method can be realized in practice, with adaptive train lengths of probe packets, probing rates, and replicated measurements required to achieve both high accuracy and confidence levels. We evaluate our method in a controlled testbed network, where we show the impact of cross traffic variability on the time-scales of service availab...

Lübben, Ralf; Liebeherr, Jörg

2010-01-01

237

Experimental Demonstration of a Bandwidth Scalable LAN Emulation over EPON Employing OFDMA  

DEFF Research Database (Denmark)

We propose a novel EPON system supporting bandwidth scalable local area network emulation by using orthogonal frequency division multiplexing access technology. Added to the EPON traffic, 250Mbps and 500Mbps OFDM LAN traffics are experimentally emulated.

Deng, Lei; Zhao, Ying

2011-01-01

238

Continuous-wave non-classical light with GHz squeezing bandwidth  

CERN Multimedia

Squeezed states can be employed for entanglement-based continuous-variable quantum key distribution, where the secure key rate is proportional to the bandwidth of the squeezing. We produced a non-classical continuous-wave laser field at the telecommunication wavelength of 1550 nm, which showed squeezing over a bandwidth of more than 2 GHz. The experimental setup used parametric down-conversion via a periodically poled potassium titanyl phosphate crystal (PPKTP). We did not use any resonant enhancement for the funda- mental wavelength, which should in principle allow a production of squeezed light over the full phase-matching bandwidth of several nanometers. We measured the squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz limited by the measuring bandwidth of the homodyne detector. The squeezing strength was possibly limited by thermal lensing inside the non-linear crystal.

Ast, Stefan; Mehmet, Moritz; Steinlechner, Sebastian; Eberle, Tobias; Schnabel, Roman

2012-01-01

239

Terahertz bandwidth photonic Hilbert transformers based on synthesized planar Bragg grating fabrication.  

Science.gov (United States)

Terahertz bandwidth photonic Hilbert transformers are proposed and experimentally demonstrated. The integrated device is fabricated via a direct UV grating writing technique in a silica-on-silicon platform. The photonic Hilbert transformer operates at bandwidths of up to 2 THz (?16??nm) in the telecom band, a 10-fold greater bandwidth than any previously reported experimental approaches. Achieving this performance requires detailed knowledge of the system transfer function of the direct UV grating writing technique; this allows improved linearity and yields terahertz bandwidth Bragg gratings with improved spectral quality. By incorporating a flat-top reflector and Hilbert grating with a waveguide coupler, an ultrawideband all-optical single-sideband filter is demonstrated. PMID:23988981

Sima, Chaotan; Gates, J C; Holmes, C; Mennea, P L; Zervas, M N; Smith, P G R

2013-09-01

240

Creating large bandwidth photonic crystal slab waveguide by tailoring the dispersion curve of waveguide mode  

Science.gov (United States)

In the photonic crystal (PhC) slab, a waveguide is typically created by introducing a line defect into the perfect periodic lattice, and the waveguide modes will appear within the photonic band gap. An practical waveguide should possess sufficient single-mode bandwidth and display minimal group velocity dispersion within the bandwidth. By adjusting the air holes adjacent to the line defect, the dispersion curves of waveguide modes can be tailored and the requests above are reached. In this way, an air-bridge slab waveguide gets a single-mode bandwidth of 0.025 c/a, where c is the light speed in vacuum and a is the lattice constant of the photonic crystal. In addition, an SOI (Silicon-on-Insulator) slab waveguide receives a single-mode bandwidth of 0.007 c/a and a frequency window of 0.003 c/a with a nearly constant group velocity of 0.082 c.

Chen, Kan; Yang, Dongxiao; He, Wenjun

2008-12-01

 
 
 
 
241

Terahertz bandwidth photonic Hilbert transformers based on synthesized planar Bragg grating fabrication.  

UK PubMed Central (United Kingdom)

Terahertz bandwidth photonic Hilbert transformers are proposed and experimentally demonstrated. The integrated device is fabricated via a direct UV grating writing technique in a silica-on-silicon platform. The photonic Hilbert transformer operates at bandwidths of up to 2 THz (?16??nm) in the telecom band, a 10-fold greater bandwidth than any previously reported experimental approaches. Achieving this performance requires detailed knowledge of the system transfer function of the direct UV grating writing technique; this allows improved linearity and yields terahertz bandwidth Bragg gratings with improved spectral quality. By incorporating a flat-top reflector and Hilbert grating with a waveguide coupler, an ultrawideband all-optical single-sideband filter is demonstrated.

Sima C; Gates JC; Holmes C; Mennea PL; Zervas MN; Smith PG

2013-09-01

242

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

243

Very broad gain bandwidth parametric amplification in nonlinear crystals at critical wavelength degeneracy.  

UK PubMed Central (United Kingdom)

Gain spectra were calculated at critical wavelength degeneracy (CWD) in a collinear phase-matching geometry optical parametric amplification (OPA) process. The frequency bandwidth available through CWD-OPA is broader compared to the gain bandwidth obtained by the non-collinear OPA geometry. A solution for very broad bandwidth chirped pulse amplification based on partially deuterated DKDP (P-DKDP) crystals, pumped by pulsed green lasers, is proposed. 1.38x10(14) Hz frequency bandwidth and peak intensity gain G approximately 62 were calculated in a 5-mm long 58% deuterated DKDP crystal, pumped by 527-nm wavelength at 64-GW/cm2 intensity. Parametric amplification at CWD in few-mm thin P-DKDP crystals, pumped by picosecond pulses of nearly 100-GW/cm2 intensity, possesses a true potential for generating high energy laser pulses compressible to one-cycle duration.

Dabu R

2010-05-01

244

Very broad gain bandwidth parametric amplification in nonlinear crystals at critical wavelength degeneracy.  

Science.gov (United States)

Gain spectra were calculated at critical wavelength degeneracy (CWD) in a collinear phase-matching geometry optical parametric amplification (OPA) process. The frequency bandwidth available through CWD-OPA is broader compared to the gain bandwidth obtained by the non-collinear OPA geometry. A solution for very broad bandwidth chirped pulse amplification based on partially deuterated DKDP (P-DKDP) crystals, pumped by pulsed green lasers, is proposed. 1.38x10(14) Hz frequency bandwidth and peak intensity gain G approximately 62 were calculated in a 5-mm long 58% deuterated DKDP crystal, pumped by 527-nm wavelength at 64-GW/cm2 intensity. Parametric amplification at CWD in few-mm thin P-DKDP crystals, pumped by picosecond pulses of nearly 100-GW/cm2 intensity, possesses a true potential for generating high energy laser pulses compressible to one-cycle duration. PMID:20589028

Dabu, R

2010-05-24

245

The influence of complex material coverings on the bandwidth of antennas  

CERN Multimedia

The influence of material coverings on the antenna bandwidth is investigated for antennas formed by thin electric or magnetic line sources. It is shown that uniform thin layers of arbitrary passive materials (including Veselago, left-handed, or double-negative materials) cannot help to overcome the bandwidth limitations imposed by the amount of energy stored in the antenna reactive field. Alternative possibilities offered by complex composite materials in the antenna design are identified.

Tretyakov, S A; Sochava, A A; Simovski, C R

2004-01-01

246

Measurements of higher order noise correlations in a quantum dot with a finite bandwidth detector  

CERN Document Server

We present measurements of the fourth and fifth cumulants of the distribution of transmitted charge in a tunable quantum dot. We investigate how the measured statistics is influenced by the finite bandwidth of the detector and by the finite measurement time. By including the detector when modeling the system, we use the theory of full counting statistics to calculate the noise levels for the combined system. The predictions of the finite-bandwidth model are in good agreement with measured data.

Gustavsson, S; Ihn, T; Ensslin, K; Reinwald, M; Wegscheider, W

2006-01-01

247

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

248

Generalized regression neural networks with multiple-bandwidth sharing and hybrid optimization.  

UK PubMed Central (United Kingdom)

This paper proposes a novel algorithm for function approximation that extends the standard generalized regression neural network. Instead of a single bandwidth for all the kernels, we employ a multiple-bandwidth configuration. However, unlike previous works that use clustering of the training data for the reduction of the number of bandwidths, we propose a distinct scheme that manages a dramatic bandwidth reduction while preserving the required model complexity. In this scheme, the algorithm partitions the training patterns to groups, where all patterns within each group share the same bandwidth. Grouping relies on the analysis of the local nearest neighbor distance information around the patterns and the principal component analysis with fuzzy clustering. Furthermore, we use a hybrid optimization procedure combining a very efficient variant of the particle swarm optimizer and a quasi-Newton method for global optimization and locally optimal fine-tuning of the network bandwidths. Training is based on the minimization of a flexible adaptation of the leave-one-out validation error that enhances the network generalization. We test the proposed algorithm with real and synthetic datasets, and results show that it exhibits competitive regression performance compared to other techniques.

Goulermas JY; Zeng XJ; Liatsis P; Ralph JF

2007-12-01

249

The Minimum Bandwidth of Narrowband Spikes in Solar Flare Decimetric Radio Waves  

CERN Document Server

The minimum and the mean bandwidth of individual narrowband spikes in two events in decimetric radio waves is determined by means of multi-resolution analysis. Spikes of a few tens of millisecond duration occur at decimetric/microwave wavelength in the particle acceleration phase of solar flares. A first method determines the dominant spike bandwidth scale based on their scalegram, the mean squared wavelet coefficient at each frequency scale. This allows to measure the scale bandwidth independently of heuristic spike selection criteria, e.g. manual selection. The major drawback is a low resolution in the bandwidth. To overcome this uncertainty, a feature detection algorithm and a criterion for spike shape in the time-frequency plane is applied to locate the spikes. In that case, the bandwidth is measured by fitting an assumed spike profile into the denoised data. The smallest FWHM bandwidth of spikes was found at 0.17 % and 0.41 % of the center frequency in the two events. Knowing the shortest relevant bandwi...

Messmer, P; Messmer, Peter; Benz, Arnold O.

1999-01-01

250

Effects of eluent temperature and elution bandwidth on detection response for aerosol-based detectors.  

UK PubMed Central (United Kingdom)

Aerosol detectors provide generally uniform response for most analytes, independent of their optical properties, and have the advantage of being compatible with elevated temperature mobile phases. Therefore, aerosol detectors present an attractive detection alternative for high temperature liquid chromatography (HTLC) separations. The present study has investigated the effects of HTLC conditions using aqueous mobile phases on the detection response of an evaporative light-scattering detector (ELSD) and a corona-charged aerosol detector (C-CAD). The response of the ELSD was increased up to 5-fold by increasing the separation temperature from 30°C to 180°C. The C-CAD showed much smaller increases in response under the same conditions. This increase in response was found not to result from the increased temperature for the mobile phase but rather from compression of the elution bandwidth at elevated temperature. The effect of bandwidth on detector response was confirmed using flow-injection studies in which the same amount of analyte was introduced into the detector at varying bandwidths. Furthermore, it is shown that a temperature gradient can be used to counteract the effects of varying bandwidths associated with isocratic-isothermal separations, with relatively constant bandwidth and detector response being observed with appropriate temperature gradients. This study demonstrates the necessity to consider the elution bandwidth in HTLC-aerosol detector analysis.

Khandagale MM; Hutchinson JP; Dicinoski GW; Haddad PR

2013-09-01

251

Effects of eluent temperature and elution bandwidth on detection response for aerosol-based detectors.  

Science.gov (United States)

Aerosol detectors provide generally uniform response for most analytes, independent of their optical properties, and have the advantage of being compatible with elevated temperature mobile phases. Therefore, aerosol detectors present an attractive detection alternative for high temperature liquid chromatography (HTLC) separations. The present study has investigated the effects of HTLC conditions using aqueous mobile phases on the detection response of an evaporative light-scattering detector (ELSD) and a corona-charged aerosol detector (C-CAD). The response of the ELSD was increased up to 5-fold by increasing the separation temperature from 30°C to 180°C. The C-CAD showed much smaller increases in response under the same conditions. This increase in response was found not to result from the increased temperature for the mobile phase but rather from compression of the elution bandwidth at elevated temperature. The effect of bandwidth on detector response was confirmed using flow-injection studies in which the same amount of analyte was introduced into the detector at varying bandwidths. Furthermore, it is shown that a temperature gradient can be used to counteract the effects of varying bandwidths associated with isocratic-isothermal separations, with relatively constant bandwidth and detector response being observed with appropriate temperature gradients. This study demonstrates the necessity to consider the elution bandwidth in HTLC-aerosol detector analysis. PMID:23953611

Khandagale, Manish M; Hutchinson, Joseph P; Dicinoski, Greg W; Haddad, Paul R

2013-08-06

252

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.

Carlos Heather A; Shi Xun; Sargent James; Tanski Susanne; Berke Ethan M

2010-01-01

253

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

Science.gov (United States)

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.

Caprara Vivoli, Valentina; Sangouard, Nicolas; Afzelius, Mikael; Gisin, Nicolas

2013-09-01

254

Enhanced Shared-TDD Based Hybrid WDM/TDM-PON with Dynamic Bandwidth Allocation Scheme  

Science.gov (United States)

Although wavelength division multiplexing-passive optical network (WDM-PON) is known as a high-speed transfer, it creates high channel costs per subscriber and low bandwidth utilization due to the fact that a wavelength is dedicated to each subscriber. Thus, it is imperative to reduce channel costs per subscriber and improve the bandwidth utilization. To achieve these, we first adopt a existing WDM-PON, which uses the bidirectional transmission with a single source for cost-efficiency by employing a gain-saturated reflective semiconductor optical amplifier (RSOA). Secondly, based on the existing WDM-PON, we propose an enhanced hybrid WDM/TDM-PON, which can extend the number of subscribers supported in each wavelength with splitters in the physical layer and a shared-time division duplex (TDD) frame format in the media access control (MAC) layer. Moreover, it can adaptively control the bandwidth through a dynamic bandwidth allocation (DBA) scheme according to the volume of traffic. Compared to the non TDD-based hybrid WDM/TDM-PON, it can reduce channel costs per subscriber from the extended number of subscribers supported in each wavelength. Furthermore, due to the DBA, it can improve the total queueing delay and throughput, and thus increase the bandwidth utilization.

Jung, Bokrae; Kim, Min-Gon; Kim, Byong-Whi; Kang, Minho

255

Percentage Based Trust Model with Bandwidth Reservation Technique for Privacy Preserving Routing in MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available Routing in Mobile Ad-Hoc Networks are vulnerable to malicious traffic analysis, harmful attackers can mitigate paths and malicious intermediate nodes breaks security, ineffective reserve of available resources ( utilization of bandwidth ) in node causes losses and as well as anonymity, unobservability of communication is not provided. To detect misbehaviors and effective utilization of resources in trusted nodes the Percentage Based Trust management system, with bandwidth reservation technique is proposed, and for achieving privacy in MANETs the PPRP is proposed. In this paper the scheme called Percentage based Trust management system is defined to allow trustworthy intermediate nodes to participate in path construction with resource reservation technique to allow trusted nodes to select a path which has minimum cost, congestion and bandwidth. In reservation technique, if available bandwidth is greater than traffic jam bandwidth. Using rate monitoring and adjustment methodologies, rate control is performed for the overcrowded flows and then an Privacy Preserving routing Protocol (PPRP) is proposed to offer complete anonymity, unlinkability and unobservabilty for all types of packets. PPRP uses novel combination of group signature and Id based encryption techniques for route discovery. The simulation result shows that this paper achieves trustworthy path construction through intermediate nodes with resource allocation technique and stronger privacy protection is achieved than existing scheme like AODV.

Raghu. R , Gopinathan. B

2013-01-01

256

Manipulation of two-dimensional spectra of excitonically coupled molecules by narrow-bandwidth laser pulses  

International Nuclear Information System (INIS)

Graphical abstract: The full broad-bandwidth photon echo signal can be reconstructed using the set of narrow-bandwidth simulations along with the extraction of specific cross-peaks. - Abstract: Complete expressions within the response function theory are derived for a coherent two-dimensional (2D) signal covering the finite-bandwidth and pulse-overlap effects. Ideal time domain, frequency domain as well as mixed regime are considered. Conditions for the strong pulse-overlap effects are also described and analyzed. As demonstrated for the excitonically coupled dimer, certain configurations of central frequencies allow to extract various peaks in the 2D signal, resembling certain physical processes. In the case of weakly overlapping pulses, the scheme for generating both ultra-broad-bandwidth time-domain signal and frequency-domain spectra from a set of narrow-bandwidth multi-color measurements is presented. Possibility of reconstructing microscopic parameters such as inter-molecular couplings and transition dipole orientations from high-resolution crosspeaks is discussed.

2010-06-16

257

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; Sharifah K. Syed Yusof; Norsheila Fisal

2010-01-01

258

The Relative Importance of Memory Latency, Bandwidth, and Branch Limits to Performance  

UK PubMed Central (United Kingdom)

This study investigates the relative importance of memorylatency, memory bandwidth, and branch predictability in determininglimits to processor performance. We use an aggressivesimulation model with few other limits to study theperformance of SPEC92 benchmarks. Our basic machinemodel assumes a dynamically scheduled processor with a16536 entry instruction window. Up to 16536 instructionsof any type can be issued each cycle, subject to data dependencies.In systems with unlimited memory bandwidth and perfectbranch predictability, we find that memory latency isnot a significant limit to performance until it exceeds 100to 200 cycles. Memory bandwidth is not usually a significantlimit either. In systems with memory latency of 16cycles and perfect branch predictability, many applicationsrequire less than 6 bytes per cycle, while all but one performwell if 100 bytes per cycle are available. Based on currenttrends in the semiconductor industry and current research inpackaging ...

Parthasarathy Ranganathan

259

ANN Based Forecasting of VBR Video Traffic for Dynamic Bandwidth Allocation in ATM Networks  

UK PubMed Central (United Kingdom)

Two time delay neural network (TDNN) based forecasting systems are proposed to performdynamic bandwidth reservation for real-time, variable bit rate (VBR) video service in ATMnetworks. Both multilayered perceptron (MLP) and pi-sigma network (PSN) based systems arefound to give highly reliable predictions even in a nonstationary environment. Their performanceis quantified through simulation experiments on clippings from the movie, "Star Wars".In particular, the PSN-TDNN based dynamic bandwidth reservation achieves high network utilization,loss-free transmission and reasonable delay, and its lower computational requirementsmake it suitable for on-line operation.keywords: ATM network, real-time VBR video, dynamic bandwidth allocation, time delayneural network, pi-sigma network, forecasting.1 IntroductionFuture broadband integrated services digital networks (B-ISDN) will support a wide range of servicesincluding voice, data, video and other modalities in an integrated and un...

Song Chong; San-qi Li; Joydeep Ghosh

260

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

Energy Technology Data Exchange (ETDEWEB)

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.

Sujingqin; Lanqin, L; Wenyi, W; Feng, J; Xiaofeng, W; Xiaomin, Z [Research Center of Laser Fusion, China Academy of Engineering Physics, P. O. Box 919-988, Mianyang, China, 621900 (China); Bin, L [School of Computer and Communication Engineering, Southwest Jiaotong University, Chengdu. China, 610031 (China)], E-mail: sujingqin@tom.com

2008-05-15

 
 
 
 
261

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.

2008-01-01

262

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.

Jianping Li; Yasushi Wakahara

2007-01-01

263

On the Effective Bandwidth in Buffer Design for the Multi-Server Channels  

UK PubMed Central (United Kingdom)

Gibbens and Hunt [3] derive the expression for the effective bandwidths for a uniform arrival and servicemodel of traffic flow offered to a multi-service channel. Their model is based on negative exponentially distributedon-times of the traffic sources. The present study leads to the expression for the effective bandwidthwithout specifying these distributions explicitly. By the results so obtained the influence of the burstiness of theindividual source traffic on its effective bandwidth can be analysed; it is shown that it can be quite substantial.AMS Subject Classification (1991): 90B22, 60K25Keywords & Phrases: effective bandwidth, multi-service channels, instantaneous input, gradual input, maximalbuffer content, M=G=1 model, tail behaviour, burstiness, in-and outflow rate.1. IntroductionIn communication systems for data handling and transport the incoming traffic stream usuallypasses a buffer before it is admitted to the processing network. The buffer transforms the inc...

Copyright Stichting; Mathematisch Centrum; J. W. Cohen

264

Measurement of micro-roughness and effects of detector bandwidth and finite width  

Science.gov (United States)

Surface micro-roughness of grazing incidence optics has long been recognized as a critical parameter in the control of the scattered X-ray intensity and its effects on the point spread function half-energy width. Accurate knowledge of the amplitude of surface micro-roughness is vital to assess optic predicted performance during the final stages of fabrication. This requires not only a knowledge of the spatial bandwidth over which surface features must be measured, but also knowledge of the bandwidth of the measurement instrument. We show that the standard assumption that instruments respond up to their Nyquist limit is an oversimplification which neglects the finite detector size and its bandwidth limiting effects when sampling a real (i.e., two-dimensional) surface.

Reid, P. B.; Glenn, P.

265

Adaptive H.263+ rate control algorithm for interactive video communication with bandwidth renegotiation  

Science.gov (United States)

This paper presents a novel adaptive H.263+ rate control algorithm for interactive video communication under the networks supporting bandwidth renegotiation, which can communicate with end-users to accommodate their time-varying bandwidth requests during data transmission. They are especially suitable for the transmission of non-stationary video traffics. The proposed rate control algorithm communicates with the network to renegotiate the required bandwidth for the underlying video and choose their control strategies according to the renegotiation results. The proposed algorithm treats both the spatial and temporal qualities at the same time to enhance human visual perceptual quality. Experimental results are provided to demonstrate that the proposed rate control algorithms can achieve superior performance with a low computational.

Song, Hwangjun

2002-01-01

266

Design and Bandwidth Analysis of Fault-Tolerant Multistage Interconnection Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The design of a suitable interconnection network for inter-processor communication is one of the key issues of the system performance. In this study a new irregular interconnection network IABN (Irregular Augmented Baseline) has been proposed. IABN is designed by modifying existing ABN (Augmented Baseline Network). ABN is a regular multi-path network with limited fault tolerance. IABN provides three times more paths between any pair of source-destination in comparison to ABN. The ABN and IABN MINs are analyzed and compared in terms of performance parameters namely Bandwidth, Cost and Bandwidth per unit Cost. The proposed network IABN provides much better fault-tolerance and almost double bandwidth at the expanse of little more cost than ABN.

R. Aggarwal; L. Kaur

2008-01-01

267

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

268

Inconsistent channel bandwidth estimates suggest winner-take-all nonlinearity in second-order vision.  

UK PubMed Central (United Kingdom)

The processing of texture patterns has been characterized by a model that postulates a first-stage linear filter to highlight a component texture, a pointwise rectification stage to convert contrast for the highlighted texture into mean response strength, followed by a second-stage linear filter to detect the texture-defined pattern. We estimated the spatial-frequency bandwidth of the second-stage filter mediating orientation discrimination of orientation-modulated second-order gratings by measuring threshold elevation in the presence of filtered noise added to the modulation signal. This experiment yielded no evidence for frequency tuning. A second experiment, in which subjects had to detect similar second-order gratings while judging their modulation frequency, produced bandwidth estimates of 1-1.5 octaves, similar to estimated bandwidths of first-order channels. We propose that an additional dominant-response-selection nonlinearity can account for these apparently contradictory results.

Westrick ZM; Henry CA; Landy MS

2013-04-01

269

Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit  

International Nuclear Information System (INIS)

[en] Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

2010-01-01

270

Optical Sideband Generation: a Longitudinal Electron Beam Diagnostic Beyond the Laser Bandwidth Resolution Limit  

Energy Technology Data Exchange (ETDEWEB)

Electro-optic sampling (EOS) is widely used as a technique to measure THz-domain electric field pulses such asthe self-fields of femtosecond electron beams. We present an EOS-based approach for single-shot spectral measurement that excels in simplicity (compatible with fiber integration) and bandwidth coverage (overcomes the laser bandwidth limitation), allowing few-fs electron beams or single-cycle THz pulses to be characterized with conventional picosecond probes. It is shown that the EOS-induced optical sidebands on the narrow-bandwidth optical probe are spectrally-shifted replicas of the THz pulse. An experimental demonstration on a 0-3 THz source is presented.

Lawrence Berkeley National Laboratory; Tilborg, J. van; Matlis, N. H.; Plateau, G. R.; Leemans, W. P.

2010-06-01

271

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 network area or within a broadband access aggregation network area are examined. Results indicate that such highly localized P2P video can greatly lower core bandwidth usage.

Kenneth Kerpez

2008-01-01

272

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

Directory of Open Access Journals (Sweden)

Full Text Available Abstract 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 network area or within a broadband access aggregation network area are examined. Results indicate that such highly localized P2P video can greatly lower core bandwidth usage.

Kerpez Kenneth

2008-01-01

273

Efficient time-slot assignment algorithms for SS/TDMA systems with variable-bandwidth beams  

Science.gov (United States)

In this paper, we present efficient sequential and parallel algorithms for computation of time-slot assignments in SS/TDMA (satellite-switched /time-division multiple-access) systems with variable-bandwidth beams. These algorithms are based on modeling the time-slot assignment (TSA) problem as a network-flow problem. Our sequential algorithm, in general, has a better time-complexity than a previous algorithm due to Gopal, et al. and generates fewer switching matrices. If M (N) is the number of uplink (downlink) beams, L is the length of any optimal TSA, and alpha is the maximum bandwidth of an uplink or downlink beam, our sequential algorithm takes O ((M x N)(exp 3)) min(MN alpha, L) time to compute an optimal TSA when the traffic-handling capacity of the satellite is of the same order as the total bandwidth of the links.

Chalasani, Suresh; Varma, Anujan

1994-02-01

274

Apparatus and method for increasing the bandwidth of a laser beam  

Energy Technology Data Exchange (ETDEWEB)

A method and apparatus is disclosed that provides a laser output beam having a broad bandwidth and an intensity smooth over time. The bandwidth of the laser output can be varied easily by varying the intensity of a broadband source. The present invention includes an optical modulation apparatus comprising a narrowband laser that outputs a horizontally polarized beam (a "signal beam") and a broadband laser that outputs a vertically polarized beam (a "pump beam") whose intensity varies rapidly. The two beam are coupled into a birefringent laser material so that the respective polarizations coincide with the principal axes of the material. As the two beams travel through the material, the polarization preserving properties of the birefringent material maintain the respective polarizations of the two beam; however there is coupling between the two beams as a result of cross phase modulations, which induces a bandwidth change of the signal beam. The amount of bandwidth change is dependent upon the average intensity of the pump beam. The beams are coupled out from the birefringent material and the modulated signal beam is separated by a polarization selector. The modulated signal beam now has a wider bandwidth, and its shape remains smooth in time. This signal beam can be applied to incoherence inducing systems. The different bandwidths required by these different incoherence inducing systems can be obtained by varying the intensity of the pump beam. The United States Government has rights in this invention pursuant to Contract No. W7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.

Chaffee, Paul H. (Bolina, CA)

1991-01-01

275

Estimating individual listeners’ 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; Caminade, Sabine

2010-01-01

276

Bandwidth-tunable add-drop filters based on micro-electro-mechanical-system actuated silicon microtoroidal resonators.  

UK PubMed Central (United Kingdom)

A bandwidth-tunable filter has been demonstrated based on a micro-electro-mechanical-system (MEMS) actuated single-crystalline silicon microtoroidal resonator. Bandwidth is tuned from 2.8 to 78.4 GHz by voltage control, the largest bandwidth tuning range reported to date to our knowledge in resonator-based filters. A 21.8 dB extinction ratio is attained as a dynamic add-drop filter.

Yao J; Wu MC

2009-09-01

277

QoS Study Based On IEEE 802.16 Bandwidth Scheduling Strategy  

Directory of Open Access Journals (Sweden)

Full Text Available on the basis of presenting the existing problems of the QoS multimedia services in IEEE802.16, this paper analyzes the disadvantage and advantage of current bandwidth scheduling strategy based on IEEE802.16. Then an improvement strategy of IEEE802.16 PMP network model is proposed based on existing strict priority scheduling strategy. Finally, through the simulation data, it proves that the strategy can ensure the QoS performance and fairness of bandwidth allocation between various multimedia communication services.  

Jun Tu; De-hua Li; Yingjiang Zhang; Zhiwei Ye; Wangyu Tong

2012-01-01

278

Tunable Bandwidth Third Order Switched-Capacitor with Multiple Feedbacks Filter for Different Center Frequencies  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes third order tunable bandwidth active Switched-Capacitor filter. The circuit consists of only op-amps and switched capacitors. The circuit is designed for circuit merit factor Q = 10. The proposed circuit implements three filter functions low pass, band pass and high pass simultaneously in single circuit. The filter circuit can be used for both narrow as well as for wide bandwidth. For various values of cut-off frequencies the behaviour of circuit is studied. The circuit works properly only for higher central frequencies, when f0 > 10 kHz.

Ganeshchandra N. Shinde; Sanjay R. Bhagat

2010-01-01

279

A Novel Compact Microstrip Elliptical Patch Resonator Filter with Tunable Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available A novel elliptical patch resonator for a compact bandpass filter with tunable bandwidth is presented. This bandpass filter has the advantage of great flexibility in which the center frequency can be changed easily. The bandwidth of this filter can be modified by simply changing one variable, and this makes the proposed design unique. The order of the elliptical patch resonator can be increased, and three types of different orders of the same design are compared. The proposed filter can be used for future compact advanced wireless communication systems.

Ruwaybih Alsulami; Heather Song

2013-01-01

280

VLSI arrays with limited I/O bandwidth for pattern analysis  

Energy Technology Data Exchange (ETDEWEB)

Two new orthogonally connected triangular arrays for l-u decomposition of a matrix using Court's and Cholesky's methods, respectively, are proposed. To minimize the limited I/O bandwidth or limited I/O pins problem, reconfiguration techniques are used to restructure a computing array, so that it can carry out in succession several distinct functional computations of matrix inversion without the data leaving the array. Computation time for pattern analysis is reduced, since the limited I/O bandwidth affects only the first and last phases of the necessary computations. 17 references.

Liu, P.S.; Young, T.Y.

1983-10-01

 
 
 
 
281

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 wavelengths (1.45m signal 1.65m).

Fathy M. Mustafa; Ashraf A. Khalaf; F. A. El-Geldawy

2012-01-01

282

Power-Bandwidth Efficiency and Capacity of Wireless Feedback Communication Systems  

CERN Multimedia

The paper is devoted to the analysis of problems appearing in optimisation and improvement of the power-bandwidth efficiency of digital communication feedback systems (FCS). There is shown that unlike digital systems, adaptive FCS with the analogue forward transmission allow full optimisation and derivation of optimal transmission-reception algorithm approaching their efficiency to the Shannon boundary. Differences between the forward channel capacity and capacity of adaptive FCS as communication unit, as well as their influence of the power-bandwidth efficiency of transmission are considered.

Platonov, Anatoliy

2011-01-01

283

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

CERN Multimedia

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

284

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

285

Gap-Coupling: A Potential Method for Enhancing the Bandwidth of Microstrip Antennas  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a technical review on gap-coupled microstrip antennas is presented. The gap-coupled microstrip antennas give a large bandwidth as compared to the conventional microstrip antennas. The method of bandwidth enhancement using gap-coupled microstrip antennas has been elaborated. The gap-coupled microstrip antennas also produce two resonances. The dual frequency operation of the gap-coupled microstrip antenna is also described. A research overview of gap-coupled microstrip antennas, challenges, types of gap-coupled microstrip antennas as well as numerical methods of calculating various parameters of the gap-coupled microstrip antennas are discussed in this paper.

P. Kumar; G. Singh

2012-01-01

286

Gain and bandwidth of the gyro-TWT and CARM amplifiers  

International Nuclear Information System (INIS)

[en] Issues concerning the interpretation of gain and bandwidth from the dispersion relation are examined for the gyrotron traveling wave tube (gyro-TWT) and cyclotron autoresonance maser (CARM) amplifiers. A general method for the determination of critical current for oscillation is illustrated. Despite the broad bandwidth predicted for the CARM amplifier by the commonly employed dispersion relation, it is seen in particle simulation that single-particle interaction, rather than collective amplification, prevails over much of the band. Reasons for the discrepancy are analyzed

1988-01-01

287

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; A.K.Vatsa

2011-01-01

288

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects.  

UK PubMed Central (United Kingdom)

We demonstrate an add/drop filter based on coupled vertical gratings on silicon. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with 6 nm channel separation, 3 nm bandwidth, a flat top response with < 0.8 dB ripple within the 3 dB passband, 1 dB insertion loss and 16 dB crosstalk suppression. The device is ultracompact, having a footprint < 2 X 10(-9)/2.

Tan DT; Ikeda K; Zamek S; Mizrahi A; Nezhad MP; Krishnamoorthy AV; Raj K; Cunningham JE; Zheng X; Shubin I; Luo Y; Fainman Y

2011-01-01

289

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects.  

Science.gov (United States)

We demonstrate an add/drop filter based on coupled vertical gratings on silicon. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with 6 nm channel separation, 3 nm bandwidth, a flat top response with < 0.8 dB ripple within the 3 dB passband, 1 dB insertion loss and 16 dB crosstalk suppression. The device is ultracompact, having a footprint < 2 X 10(-9)/2. PMID:21369058

Tan, D T H; Ikeda, K; Zamek, S; Mizrahi, A; Nezhad, M P; Krishnamoorthy, A V; Raj, K; Cunningham, J E; Zheng, X; Shubin, I; Luo, Y; Fainman, Y

2011-01-31

290

Variable bandwidth of dynamic add-drop filters based on coupling-controlled microdisk resonators.  

UK PubMed Central (United Kingdom)

Dynamic add-drop filters with variable bandwidth are demonstrated on microelectromechanical-system (MEMS)-actuated microdisk resonators for what is believed to be the first time. The tuning mechanism is based on a variable power coupling ratio that is controlled by varying the gap spacing between the waveguide and the microdisk through MEMS actuators. The results show wavelength switching with an extinction ratio of 20 dB and a tunable bandwidth ranging from 12 to 27 GHz. These dual functions were realized using the device with the operation voltage varying between 0 and 35 V.

Lee MC; Wu MC

2006-08-01

291

Power and bandwidth studies for W-band free-electron masers  

CERN Multimedia

Power and bandwidth studies for a high power W-band (approx 94 GHz) FEM amplifier is presented for a helical wiggler/cylindrical waveguide configuration using 3D ARACHNE simulation code (H.P. Freund, T.M. Antonsen, Jr., Principles of Free-electron Lasers, 2nd edn., Chapman and Hall, London, 1996, Ch. 5). Using a 300 kV/20 A electron beam with a normalized emittance of 95 mm mrad, a 600 G wiggler field with a 0.88 cm period, and a strong guide field of 20 kG, efficiencies of greater than 8% are possible with a FWHM bandwidth of 4.5 GHz.

Freund, H P; Danly, B G; Levush, B

1999-01-01

292

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 wireless networks.

O Said; A Tolba

2011-01-01

293

Theoretical model of ultranarrow bandwidth Faraday-Zeeman optical filter at 780nm  

Energy Technology Data Exchange (ETDEWEB)

Natural rubidium is a mixture of the two isotopes, {sup 85}Rb and {sup 87}Rb. Taking into account their hyperfine structure, and using a quantum-mechanical treatment of the resonant Faraday effect, the authors calculate the transmission, central frequency shift and pass bandwidth of Rb 780nm Faraday-Zeeman optical filter, as functions of magnetic field strength and atomic cell temperature.

Peng Yufeng [Henan Normal Univ., Xinxiang (China). Dept. of Physics; Ji Yuanming [Pingyuan Univ., Xinxiang (China). Dept. of Technical Engineering

1996-12-31

294

High efficiency resonance-based spectrum filters with tunable transmission bandwidth fabricated using nanoimprint lithography  

Science.gov (United States)

We propose a nanostructured color filter based on a metallic resonant waveguide structure capable of extremely high transmission efficiency. As an experimental demonstration, a blue and a red device were fabricated over a large area using nanoimprint lithography. Achieving transmission as high as 90% with a variable transmission bandwidth, these devices exhibit desirable features for numerous color filter applications.

Kaplan, Alex F.; Xu, Ting; Jay Guo, L.

2011-10-01

295

Tunable Bandwidth Third Order Switched-Capacitor with Multiple Feedbacks Filter for Different Center Frequencies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes third order tunable bandwidth active Switched-Capacitor filter. The circuit consists of only op-amps and switched capacitors. The circuit is designed for circuit merit factor Q = 10. The proposed circuit implements three filter functions low pass, band pass and high pass simultan...

Ganeshchandra N. Shinde; Sanjay R. Bhagat

296

Higher-order effects in bandwidth-limited soliton propagation in optical fibers  

Energy Technology Data Exchange (ETDEWEB)

By means of numerical studies and soliton perturbation theory we examine the effects of higher-order linear and nonlinear terms in bandwidth-limited amplified soliton propagation. We show that these effects are responsible for strong reductions of soliton--soliton interaction in such systems.

Aceves, A.B.; De Angelis, C. (Department of Mathematics and Statistics, University of New Mexico, Albuquerque, New Mexico 87131 (United States)); Nalesso, G.; Santagiustina, M. (Dipartimento di Elettronica e Informatica, Universita di Padova, Via Gradenigo 6/a, 35131 Padova (Italy))

1994-12-15

297

Bandwidth Limitations of Nb/AlN/Nb SIS Mixers Around 700 GHz  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study, using niobium-technology, the bandwidth of SIS mixers operating at frequencies close to the energy-gap frequency. Microstriplines of niobium-silicon dioxide-niobium have different properties for the top and bottom superconductor, which we find to depend on the used fabrication process. Rep...

Lodewijk, C.F.J.; Zijlstra, T.; Zhu, S.; Mena, F.P.; Baryshev, A.M.; Klapwijk, T.M.

298

Bandwidth and power allocation for cooperative relay in cognitive radio networks  

Science.gov (United States)

In this article, we consider a cognitive radio (CR) relay network where one source secondary user (SU) communicates with its corresponding destination SU with the help of relay SUs. Conventionally, equal bandwidth and/or power are allocated to each relay SU, which may not be efficient for the CR with limited bandwidth and power. Therefore, this article presents bandwidth and power allocation with amplify-and-forward (AF) or decode-and-forward (DF) relaying protocol to (1) maximize the sum network throughput; (2) minimize the total transmit power of the CR network with considering the fairness of power drain of relay SUs; (3) maximize the energy efficiency of the CR network. It is shown that DF relaying protocol can achieve better performance when the decoding rate constraint is not considered. In contrast, when considering the decoding rate constraint in DF relaying protocol, we propose the hybrid relaying protocol that combines AF and DF relaying protocols. We formulate the joint bandwidth and power allocation problem with hybrid relaying protocol to maximize the sum network throughput. A greedy algorithm is developed to solve the joint optimization problem, which has much less computational complexity. It is shown that the greedy algorithm has comparable performance to the exhaustive search algorithm. Finally, numerical results are provided to endorse our proposed algorithms.

Yu, Huogen; Tang, Wanbin; Li, Shaoqian

2012-12-01

299

A dynamic bandwidth and phase linearity measurement technique for 4-channel MSK VLF antenna systems  

Science.gov (United States)

This paper presents a method for performing dynamic measurements of antenna bandwidth and phase linearity parameters for VLF transmitter systems. These measurements were undertaken in support of both National and NATO VLF MSK upgrade programs and relate to VLF transmitting antenna characteristics required in order to comply with STANAG 5030.

Harrington, M. D.

1993-05-01

300

On the joint distribution of wave heights and periods: The role of the spectral bandwidth  

Energy Technology Data Exchange (ETDEWEB)

The influence of spectral bandwidth on the probabilistic structure of the joint distribution of wave heights and periods is analyzed by means of simulated wave records. The authors put the emphasis on its effect upon the asymmetric and bimodal structure of the distributions. Moreover, the adequacy of some theoretical models to describe such features is considered.

Rodriguez, R.G.; Rubio, R.F.; Pacheco, M.M.; Martinez, M.A. [Univ. de Las Palmas de Gran Canaria (Spain). Dept. de Fisica

1996-12-31

 
 
 
 
301

Can high bandwidth and latency justify large cache blocks in scalable multiprocessors?  

Energy Technology Data Exchange (ETDEWEB)

An important architectural design decision affecting the performance of coherent caches is the choice of block size. There are two primary factors that influence this choice: The reference behavior of applications and the remote access bandwidth and latency of the machine. Given that we anticipate increases in both network bandwidth and latency (in processor cycles) in scalable shared-memory multiprocessors, the question arises as to what effect these increases will have on the choice of block size. We use analytical modeling and execution-driven simulation of parallel programs on a large-scale shared-memory machine to examine the relationship between cache block size and application performance as a function of remote access bandwidth and latency. We show that even under assumptions of high remote access bandwidth and latency, the best application performance usually results from using cache blocks between 32 and 128 bytes in size. We also show that modifying the program to remove the dominant source of misses may not increase the best performing block size. We conclude that large cache blocks cannot be justified in most realistic scenarios.

Bianchini, R.; LeBlanc, T.J. [Univ. of Rochester, NY (United States)

1994-12-31

302

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 n...

Deng, Lei; Zhao, Ying; Yu, Xianbin; Arlunno, Valeria; Borkowski, Robert; Liu, Deming; Tafur Monroy, Idelfonso

303

A New Bandwidth Interval Based Forecasting Method for Enrollments Using Fuzzy Time Series  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we introduce the concept of (4/3)? bandwidth interval based forecasting. The historical enrollments of the university of Alabama are used to illustrate the proposed method. In this paper we use the new simplified technique to find the fuzzy logical relations.

Hemant Kumar Pathak; Prachi Singh

2011-01-01

304

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

305

An enhanced dynamic wavelength and bandwidth allocation method in WDM-EPON  

Science.gov (United States)

A kind of dynamic wavelength and bandwidth allocation (DWBA) algorithm of WDM-EPON was studied and then improved to guarantee QoS of multiple-services access. MPCP extension with modified REQUEST message and GRANT message are also proposed.The simulation results based on OPNET indicates the improved algorithm performed well in successful QoS assurance.

Zeng, Zhiwei; Ran, Yang; Huang, Hongbin; Liu, Weiping

2009-11-01

306

Bandwidth increase by controlled angular dispersion of signal beam in optical parametric amplification.  

UK PubMed Central (United Kingdom)

Angular dispersion of the signal beam inside the nonlinear media is introduced to improve the non-collinear phase-matching range. Simulations run for BBO crystals predict that bandwidth increase is possible for most of the application spectral range and that it can surpass one order of magnitude in some particular configurations.

Cardoso L; Figueira G

2004-07-01

307

Gain-switched, Yb-doped, all-fiber laser with narrow bandwidth  

DEFF Research Database (Denmark)

We demonstrate that an all-fiber, narrow bandwidth, high pulse energy pulsed laser can be constructed from commercially available components by applying gain-switching. After single-stage amplification the pulses are frequency doubled in ppSLT with high efficiency.

Larsen, Casper; Giesberts, Martin

2013-01-01

308

Finite bandwidth, long wavelength convection with boundary imperfectons: near-resonant wavelength excitation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Finite amplitude thermal convection with continuous finite bandwidth of long wavelength modes in a porous layer between two horizontal poorly conducting walls is studied when spatially nonuniform temperature is prescribed at the lower wall. The weakly nonlinear problem is solved by using multiple sc...

D. N. Riahi

309

Design and fabrication of center frequency and bandwidth tunable HTS filter  

Science.gov (United States)

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 YBa2Cu3O7 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.; Harada, H.; Kakio, S.; Ohshima, S.

2013-01-01

310

QoS Study Based On IEEE 802.16 Bandwidth Scheduling Strategy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

on the basis of presenting the existing problems of the QoS multimedia services in IEEE802.16, this paper analyzes the disadvantage and advantage of current bandwidth scheduling strategy based on IEEE802.16. Then an improvement strategy of IEEE802.16 PMP network model is proposed based on existing s...

Jun Tu; De-hua Li; Yingjiang Zhang; Zhiwei Ye; Wangyu Tong

311

Bandwidth Optimization in 802.15.4 Networks through Evolutionary Slot Assignment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Traditional Wireless Sensor Networks (WSNs) based on carrier sense methods for channel access suffer from reduced bandwidth utilization, increase energy consumptions and latency problems in networks with high traffic. In this work, a novel Evolutionary Slot Assignment (ESA) algorithm has been develo...

Vidya KRISHNAMURTHY; Edward SAZONOV

312

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)-b...

Jianping Li; Yasushi Wakahara

313

Handling Two-Way TCP Traffic in Bandwidth Asymmetric Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The TCP congestion control protocol assumes bandwidth symmetric paths. As two-way asymmetric connections will probably become common case in the future with the widespread use of ADSL and satellites technologies, it will be important to assure that congestion is properly handled in these environment...

Louati, Fatma; Barakat, Chadi; Dabbous, Walid

314

Investigation of bandwidth, efficiency, and quality factor for circular patch antennas with magneto-dielectric substrate  

DEFF Research Database (Denmark)

This article documents an investigation of the effect of a magneto-dielectric substrate on the performance of a circular patch antenna; in particular, the radiation efficiency, the quality factor, and the bandwidth. Both analytical and numerical methods have been used to model the patch antenna. The numerical method is used for lossy substrates, while the analytical method is used for lossless substrates.

Nour, Baqer; Breinbjerg, Olav

2011-01-01

315

The influence of reduced audible bandwidth on asynchronous double-vowel identification.  

UK PubMed Central (United Kingdom)

PURPOSE: In this study, the authors sought to determine whether reduced audible bandwidth associated with hearing loss contributes to difficulty benefiting from an onset asynchrony between sounds. METHOD: Synthetic double-vowel identification was measured for normal-hearing listeners and listeners with hearing loss. One vowel (Target 2) was 250 ms in duration, and one (Target 1) varied in duration. The vowels had the same offset, and an onset asynchrony between the vowels ranged between 0 and 200 ms. Listeners identified both vowels in their perceived order. The scoring metrics used were as follows: Target 1 correctly identified in the correct position, Target 2 correctly identified in the correct position, ordered double-vowel identification, and unordered double-vowel identification. The same experiment was conducted with vowels low-pass filtered at 900 Hz simulating reduced audible bandwidth. RESULTS: For all scoring metrics, increases in onset asynchrony led to better vowel identification. Listeners with hearing loss benefited less from onset asynchrony than normal-hearing listeners only for Target 2 identification. Filtering the vowels reduced onset asynchrony benefit for all scoring categories and for both groups. CONCLUSION: Results implicate reduced audible bandwidth in difficulties of listeners when using onset asynchrony for sound segregation. Therefore, listeners with a reduced audible bandwidth may have communication difficulties in natural environments.

Valentine S; Lentz JJ

2012-12-01

316

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

Science.gov (United States)

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.

Hajireza, P.; Shahabuddin, N. S.; Abbasi-Zargaleh, S.; Emami, S. D.; Abdul-Rashid, H. A.; Yusoff, Z.

2010-07-01

317

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

318

Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a fac...

Baselmans, J.J.A.; Hajenius, M.; Gao, J.R.; Klapwijk, T.M.; De Korte, P.A.J.; Voronov, B.; Gol'tsman, G.

319

Dependency of human neck reflex responses on the bandwidth of pseudorandom anterior-posterior torso perturbations.  

UK PubMed Central (United Kingdom)

The vestibulocollic (VCR) and cervicocollic (CCR) reflexes are essential to stabilize the head-neck system and to deal with unexpected disturbances. This study investigates how neck reflexes contribute to stabilization and modulate with perturbation properties. We hypothesized that VCR and CCR modulate with the bandwidth of the perturbation and that this modulation is maintained across amplitudes and influenced by the eyes being open or closed. Seated subjects were perturbed in an anterior-posterior direction. The perturbations varied in bandwidth from 0.3 Hz to a maximum of 1.2, 2.0, 4.0, and 8.0 Hz, at three amplitudes, and with eyes open and closed. Frequency response functions of head kinematics and neck muscle EMG demonstrated substantial changes with bandwidth and vision and minor changes with amplitude, which through closed-loop identification were attributed to neural (reflexive) modulation. Results suggest that both reflexes were attenuated when perturbations exceeded the system's natural frequency, thereby shifting from a head-in-space to a head-on-trunk stabilization tendency. Additionally, results indicate that reflexive and mechanical stiffness marginally exceed the negative stiffness due to gravity; a stabilization strategy which minimizes effort. With eyes closed, reflexes were attenuated further, presumably due to a reduced ability to discriminate self-motion, driving the system to a head-on-trunk stabilization strategy at the highest bandwidth. We conclude that VCR and CCR modulate with perturbation bandwidth and visual feedback conditions to maintain head-upright posture, but are invariant across amplitude changes.

Forbes PA; de Bruijn E; Schouten AC; van der Helm FC; Happee R

2013-04-01

320

Parallel Computing Applied To Compensate The Effect Of Amplifier Bandwidth In The Design Of Switched Capacitor Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method is described for the extraction of capacitor values for switched capacitor (SC) networks which compensate for the effect of finite amplifier bandwidth in the design of SC networks using optimization. The finite bandwidths of the amplifier distort the response of the network from the require...

Makkey, M. Y.

 
 
 
 
321

Design of zone-based bandwidth management scheme in IEEE 802.16 multi-hop relay networks  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract IEEE 802.16 Wireless Network technology is a hot research issue in recent years. It provides wider coverage of radio and higher speed wireless access, and Quality-of-Service plays an important part in the standard. For mobile multi-hop wireless network, IEEE 802.16j/MR network not only can supply large area wireless deployment, but also can provide high quality network service to mobile users. Although Mobile QoS supporting has been extensively investigated, Mobile QoS supporting in the IEEE 802.16-MR network is relatively unexplored. In this article, the probability of a mobile user who visits a Relay Station (RS) is known beforehand. With the visiting probability at each RS and the system specified size of the range for bandwidth allocation, Base Station (BS) can calculate the required bandwidth to meet the mobile user's demand and allocate appropriate bandwidth for a mobile user roaming in the range of the bandwidth allocation. The range of bandwidth allocation for mobile users is called the Zone in this article, which includes the user's current RS and the nearby RSs. The proposed scheme is therefore called Zone-based bandwidth management scheme. The simulation results demonstrate that Zone-based bandwidth management scheme can reduce QoS degradation and bandwidth re-allocation overhead.

Mai Yi-Ting; Chen Kuo-Yang

2011-01-01

322

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; Divakar veer Vikram singh; Firoz; Dileep Kumar; Veerandra pratap

2013-01-01

323

On the Cell Breathing Technique to Reduce Congestion Applying Bandwidth Limitation  

Directory of Open Access Journals (Sweden)

Full Text Available In order to effectively analyze or evaluate the performance of Wireless Local Area Networks (WLANs), it is important to identify what types of network settings can cause bad performance in the network when analyzing poor network performance, there is an important factor which is responsible for poor performance is when a number of users may obtain a much larger share of the available bandwidth in access point in a limited boundary as provided in the concept of cell breathing technique. In this paper, we proposed a new concept in which we can set bandwidth limitation so that no user can access data more than the specified limit for a particular access point. In this way the different users will get an efficient access over the network.

Parminder Kaur

2012-01-01

324

Design of a smart material electro-hydraulic actuator with improved frequency bandwidth  

Science.gov (United States)

Smart material electro-hydraulic actuators utilize fluid rectification by one-way valves to convert the small, high-frequency, high-force motions of smart materials such as piezoelectrics and magnetostrictives into useful motions of a hydraulic cylinder. These actuators have potential to replace centralized hydraulic pumps and lines with lightweight, compact, power-by-wire systems. This paper presents the design and testing of an improved actuator system. To increase the frequency bandwidth of operation, a lumped-parameter model is developed and validated based on experimental study of a pump with a performance capacity of 18.4 W. The critical parameters for pump performance are identified and their effect on pump performance assessed. The geometry of the hydraulic manifold that integrates the smart material pump and the output hydraulic cylinder is found to be critical for determining the effective system bandwidth.

Larson, John P.; Dapino, Marcelo J.

2012-03-01

325

Bandwidth Allocation Problem in ATM Network Model is NP-Complete  

UK PubMed Central (United Kingdom)

We show that the Bandwidth Allocation problem in the ATM network model is NPComplete.Based on that inference we suggest using the Genetic Algorithm technique toselect a subset of calls from the set of incoming call requests for transmission, so that theavailable network bandwidth is utilized effectively, thus maximizing the revenue generatedwhile preserving the promised QoS.Keywords: ATM, NP-Complete, Genetic Algorithm1 IntroductionThe Asynchronous Transfer Mode (ATM) Network Model has been evolving as the standardfor future networking that is expected to carry voice, real time video and a large volumeof still images in addition to the growing volumes of computer data. ATM networks arepredominently expected to be implemented using optical fiber with very low data error rateand guaranteed Quality of Service (QoS). It works on the assumption that the requiredbandwidth for transmission will be available throughout the connection time; the QoS deterioratesdrastically when the...

Sundararajan Vedantham; S. S. Iyengar

326

A Practical Learning-based Approach for Dynamic Storage Bandwidth Allocation  

UK PubMed Central (United Kingdom)

In this paper, we address the problem of dynamic allocationof storage bandwidth to application classes so as to meet theirresponse time requirements. We present an approach based onreinforcement learning to address this problem. We argue thata simple learning-based approach may not be practical sinceit incurs significant memory and search space overheads. Toaddress this issue, we use application-specific knowledge todesign an efficient, practical learning-based technique for dynamicstorage bandwidth allocation. Our approach can reactto dynamically changing workloads, provide isolation to applicationclasses and is stable under overload. We implementour techniques into the Linux kernel and evaluate it using prototypeexperimentation and trace-driven simulations. Our resultsshow that (i) the use of learning enables the storage systemto to reduce the number of QoS violations by a factor of2.1 and (ii) the implementation overheads of employing suchtechniques in operating system kernels is small.

Vijay Sundaram; Prashant Shenoy

327

Anamorphic Spectrum Transform and its Application to Time-Bandwidth Compression  

CERN Multimedia

A mathematical transform for compressing the time-bandwidth product of analog signals is introduced. As one of its applications, this physics-based signal grooming allows a conventional digitizer to sample and digitize the analog signal with variable resolution. The net result is that frequency components that were beyond the digitizer bandwidth can now be captured and, at the same time, the total digital data volume is reduced. This analog compression is loss-less and is made possible because the proposed transformation, performed prior to sampling, causes more samples to be allocated to higher frequencies, where they are needed, and less to lower frequencies, where they are redundant. Our method is inspired by operation of Fovea centralis in human eye and by anamorphic transformation in visual arts. The proposed transform can also be performed in digital domain as a data compression algorithm to alleviate the storage and transmission bottlenecks of big data.

Asghari, Mohammad H

2013-01-01

328

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.

Liang Yao; Han Mei

2007-01-01

329

Sidelobe suppression in low and high time-bandwidth products of linear FM pulse compression filters  

Science.gov (United States)

Numerical results on the obtainable suppression using the discrete inverse Fourier transform sampling technique and the complex Fresnel integral algorithms in low (50) and high (720) time-bandwidth products (TB) of linear FM pulse compression filters are presented. Peak sidelobe suppression of -38 dB from the main lobe for a high TB at a sampling rate of 512 with broadening in the main lobe, and of -41 dB for a low TB, are shown to be achieved. Sidelobe suppression of unweighted and Hamming externally weighted linear FM pulse compression filters at various TB values is determined for different central frequencies, dispersion times, and bandwidths. Comparison of skirt steepness, sidelobe ripple rejection, Gibbs ripples of the wave spectrum, reduction of the insertion loss, and suppression of Fresnel ripples is also made.

El-Shennawy, Khamies M.; Abdel Alim, Onsy; Ezz-El-Arab, Mohamed A.

1987-09-01

330

Towards Higher Disk Head Utilization: Extracting "Free" Bandwidth From Busy Disk Drives  

Canada Institute for Scientific and Technical Information (Canada)

Freeblock scheduling is a new approach to utilizing more of disks' potential media bandwidths. By filling rotational latency periods with useful media transfers, 20?50% of a never-idle disk's bandwidth can often be provided to background applications with no effect on foreground response times. This paper describes freeblock scheduling and demonstrates its value with two concrete applications: free segment cleaning and free data mining. Free segment cleaning often allows an LFS file system to maintain its ideal write performance when cleaning overheads would otherwise cause up to factor of 3 performance decreases. Free data mining can achieve 45 - 70 full disk scans per day on an active transaction processing system, with no effect on transaction performance.

2000-01-01

331

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

332

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; K. Srinivasa Rao; P. Srinivasa Rao

2010-01-01

333

Overview of IEPM-BW-Bandwidth Testing of Bulk Data Transfer  

Energy Technology Data Exchange (ETDEWEB)

Grid Computing capabilities are needed for the High Energy and Nuclear Physics research of today and in the future. Groups such as the Particle Physics Data Grid are developing tools to meet these needs. An additional challenge is the evaluation and fine tuning of these applications, as well as support for long term monitoring, performance analysis, and troubleshooting. In September 2001, SLAC started the development of an infrastructure for measuring the available bandwidth and actual bandwidth utilization that is achievable by the network and various bulk data transfer applications. The purpose of these active and passive measurements is to understand what throughputs are achievable, the constraints, and how to optimize, and to make the data and predictions available for net-workers and application tuning. This paper discusses the measurement methodology and pathologies, analysis, results, and avenues for future development.

Cottrell, Les

2003-06-19

334

Terahertz bandwidth all-optical Hilbert transformers based on long-period gratings.  

Science.gov (United States)

A novel, all-optical design for implementing terahertz (THz) bandwidth real-time Hilbert transformers is proposed and numerically demonstrated. An all-optical Hilbert transformer can be implemented using a uniform-period long-period grating (LPG) with a properly designed amplitude-only grating apodization profile, incorporating a single ?-phase shift in the middle of the grating length. The designed LPG-based Hilbert transformers can be practically implemented using either fiber-optic or integrated-waveguide technologies. As a generalization, photonic fractional Hilbert transformers are also designed based on the same optical platform. In this general case, the resulting LPGs have multiple ?-phase shifts along the grating length. Our numerical simulations confirm that all-optical Hilbert transformers capable of processing arbitrary optical signals with bandwidths well in the THz range can be implemented using feasible fiber/waveguide LPG designs. PMID:22743469

Ashrafi, Reza; Azaña, José

2012-07-01

335

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

International Nuclear Information System (INIS)

[en] 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

336

High-Fidelity Polarization Storage in a Gigahertz Bandwidth Quantum Memory  

CERN Document Server

We demonstrate a dual-rail optical Raman memory inside a polarization interferometer; this enables us to store polarization-encoded information at GHz bandwidths in a room-temperature atomic ensemble. By performing full process tomography on the system we measure up to 97\\pm1% process fidelity for the storage and retrieval process. At longer storage times, the process fidelity remains high, despite a loss of efficiency. The fidelity is 86\\pm4% for 1.5 \\mu s storage time, which is 5,000 times the pulse duration. Hence high fidelity is combined with a large time-bandwidth product. This high performance, with an experimentally simple setup, demonstrates the suitability of the Raman memory for integration into large-scale quantum networks.

England, D G; Champion, T F M; Reim, K F; Lee, K C; Sprague, M R; Jin, X -M; Langford, N K; Kolthammer, W S; Nunn, J; Walmsley, I A

2011-01-01

337

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

338

Terahertz bandwidth all-optical Hilbert transformers based on long-period gratings.  

UK PubMed Central (United Kingdom)

A novel, all-optical design for implementing terahertz (THz) bandwidth real-time Hilbert transformers is proposed and numerically demonstrated. An all-optical Hilbert transformer can be implemented using a uniform-period long-period grating (LPG) with a properly designed amplitude-only grating apodization profile, incorporating a single ?-phase shift in the middle of the grating length. The designed LPG-based Hilbert transformers can be practically implemented using either fiber-optic or integrated-waveguide technologies. As a generalization, photonic fractional Hilbert transformers are also designed based on the same optical platform. In this general case, the resulting LPGs have multiple ?-phase shifts along the grating length. Our numerical simulations confirm that all-optical Hilbert transformers capable of processing arbitrary optical signals with bandwidths well in the THz range can be implemented using feasible fiber/waveguide LPG designs.

Ashrafi R; Azaña J

2012-07-01

339

Low Latency Wireless Ad-Hoc Networking: Power and Bandwidth Challenges and a Hierarchical Solution  

CERN Multimedia

This paper is concerned with the scaling of the number of hops in a large scale wireless ad-hoc network (WANET), a quantity we call network latency. A large network latency affects all aspects of data communication in a WANET, including an increase in delay, packet loss, required processing power and memory. We consider network management and data routing challenges in WANETs with scalable network latency. On the physical side, reducing network latency imposes a significantly higher power and bandwidth demand on nodes, as is reflected in a set of new bounds. On the protocol front, designing distributed routing protocols that can guarantee the delivery of data packets within scalable number of hops is a challenging task. To solve this, we introduce multi-resolution randomized hierarchy (MRRH), a novel power and bandwidth efficient WANET protocol with scalable network latency. MRRH uses a randomized algorithm for building and maintaining a random hierarchical network topology, which together with the proposed r...

Sarshar, N; Roychowdhury, V P; Sarshar, Nima; Rezaei, Behnam A.; Roychowdhury, Vwani P.

2006-01-01

340

Transmit Signal and Bandwidth Optimization in Multiple-Antenna Relay Channels  

CERN Multimedia

Transmit signal and bandwidth optimization is considered in multiple-antenna relay channels. Assuming all terminals have channel state information, the cut-set capacity upper bound and decode-and-forward rate under full-duplex relaying are evaluated by formulating them as convex optimization problems. For half-duplex relays, bandwidth allocation and transmit signals are optimized jointly. Moreover, achievable rates based on the compress-and-forward transmission strategy are presented using rate-distortion and Wyner-Ziv compression schemes. It is observed that when the relay is close to the source, decode-and-forward is almost optimal, whereas compress-and-forward achieves good performance when the relay is close to the destination.

Ng, Chris T K

2010-01-01

 
 
 
 
341

The large analog bandwidth recorder and digitizer with ordered readout (LABRADOR) ASIC  

Energy Technology Data Exchange (ETDEWEB)

Three generations of full-custom analog integrated circuits designed for low-power, high-speed sampling of Radio-Frequency (RF) transients in excess of the Nyquist minimum have been developed. These 0.25{mu}m CMOS devices are denoted the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) ASICs and finally consist of nine channels of 260 deep sampling. Continuous sampling is provided with common stop capability. Input analog bandwidth is approximately 1 GHz and sampling speeds are adjustable from 0.02 to 3.7 GSa/s. Completely parallel internal conversion supports 12-bit digitization and readout of all 2340 cells in under 50{mu}s.

Varner, G.S. [Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822 (United States)], E-mail: varner@phys.hawaii.edu; Ruckman, L.L. [Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822 (United States); Nam, J.W. [Department of Physics and Astronomy, University of California at Irvine, Frederick Reines Hall, Irvine, CA 92697 (United States); Nichol, R.J. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Cao, J. [NeuroPace Inc., 1375 Shorebird Way, Mountain View, CA 94043 (United States); Gorham, P.W. [Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822 (United States); Wilcox, M. [Oceanit Laboratories Inc., 9565 Kaumualii Hwy., Waimea, HI 96769 (United States)

2007-12-21

342

The large analog bandwidth recorder and digitizer with ordered readout (LABRADOR) ASIC  

International Nuclear Information System (INIS)

[en] Three generations of full-custom analog integrated circuits designed for low-power, high-speed sampling of Radio-Frequency (RF) transients in excess of the Nyquist minimum have been developed. These 0.25?m CMOS devices are denoted the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) ASICs and finally consist of nine channels of 260 deep sampling. Continuous sampling is provided with common stop capability. Input analog bandwidth is approximately 1 GHz and sampling speeds are adjustable from 0.02 to 3.7 GSa/s. Completely parallel internal conversion supports 12-bit digitization and readout of all 2340 cells in under 50?s

2007-12-21

343

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; ARCHANA AGRAWAL

2011-01-01

344

Direction-Aware Time Slot Assignment for Largest Bandwidth in Slotted Wireless Ad Hoc Networks  

Science.gov (United States)

Slotted wireless ad hoc networks are drawing more and more attention because of their advantage of QoS (Quality of Service) support for multimedia applications owing to their collision-free packet transmission. Time slot assignment is an unavoidable and important problem in such networks. The existing time slot assignment methods have in general a drawback of limited available bandwidth due to their local assignment optimization without the consideration of directions of the radio wave transmission of wireless links along the routes in such networks. A new time slot assignment is proposed in this paper in order to overcome this drawback. The proposed assignment is different from the existing methods in the following aspects: a) consideration of link directions during time slot assignment; b) largest bandwidth to be achieved; c) feasibility in resource limited ad hoc networks because of its fast assignment. Moreover, the effectiveness of the proposal is confirmed by some simulation results.

Li, Jianping; Wakahara, Yasushi

345

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

346

Fluid limits for networks with bandwidth sharing and general document size distributions  

CERN Multimedia

We consider a stochastic model of Internet congestion control, introduced by Massouli\\'{e} and Roberts [Telecommunication Systems 15 (2000) 185--201], that represents the randomly varying number of flows in a network where bandwidth is shared among document transfers. In contrast to an earlier work by Kelly and Williams [Ann. Appl. Probab. 14 (2004) 1055--1083], the present paper allows interarrival times and document sizes to be generally distributed, rather than exponentially distributed. Furthermore, we allow a fairly general class of bandwidth sharing policies that includes the weighted $\\alpha$-fair policies of Mo and Walrand [IEEE/ACM Transactions on Networking 8 (2000) 556--567], as well as certain other utility based scheduling policies. To describe the evolution of the system, measure valued processes are used to keep track of the residual document sizes of all flows through the network. We propose a fluid model (or formal functional law of large numbers approximation) associated with the stochastic ...

Gromoll, H Christian; 10.1214/08-AAP541

2009-01-01

347

G. Bauch: A Bandwidth-efficient Scheme for Non-coherent Transmit Diversity, in Proc. of  

UK PubMed Central (United Kingdom)

Differential transmit diversity which can be detectednoncoherently is an attractive alternative to coherentspace-time block codes since channel estimation is more difficultin multi-antenna systems than in single antenna systems. Wefocus on differential space-time block codes from orthogonaldesigns which derive the transmit symbols from an M-PSKconstellation in order to fulfill the requirement that the transmitvectors have unit length. Since PSK is only advantegeous for8, we propose to extend the transmit symbol constellationfor bandwidth-efficient transmission such that multiple levelsare allowed for the length of the transmit vector. Furthermore,we derive a simple soft-output detector which does not requirechannel estimation. The new scheme outperforms the existingunit-length approach at high bandwidth-efficiency, particularly intime-varying channels. Furthermore, it is more flexible in termsof data rate adaptation and has lower detection complexity.

Gerhard Bauch

348

Narrow-bandwidth solar upconversion: design principles, efficiency limits, and case studies  

CERN Document Server

We employ a detailed balance approach to model a single-junction solar cell with a realistic narrow-band, non-unity-quantum-yield upconverter. As upconverter bandwidths are increased from 0 to 0.5 eV, maximum cell efficiencies increase from the Shockley-Queisser limit of 30.58% to over 43%. Such efficiency enhancements are calculated for upconverters with near-infrared spectral absorption bands, readily accessible with existing upconverters. While our model shows that current bimolecular and lanthanide-based upconverting materials will improve cell efficiencies by <1%, cell efficiencies can increase by several absolute percent with increased upconverter quantum yield - even without an increased absorption bandwidth. By examining the efficiency limits of a highly realistic solar cell-upconverter system, our model provides a platform for optimizing future solar upconverter designs.

Briggs, Justin A; Dionne, Jennifer A

2013-01-01

349

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

350

Towards broad-bandwidth polarization-independent nanostrip waveguide ring resonators.  

UK PubMed Central (United Kingdom)

We demonstrate a new method for accessing the broad-bandwidth polarization-independent operation of a microring resonator based on the standard photonic nanostrip waveguides. The method employs the selective application of atomic layer deposition to form highly uniform TiO(2) overlayers with the specific dispersion properties. The wide operation window is achieved by matching the wavelength dependencies of the free spectral ranges of the two orthogonal polarizations.

Erdmanis M; Karvonen L; Säynätjoki A; Tu X; Liow TY; Lo QG; Vänskä O; Honkanen S; Tittonen I

2013-04-01

351

Velocity matched electrode structures on doped semiconductors for large bandwidth optoelectronic modulators  

Energy Technology Data Exchange (ETDEWEB)

High-speed optoelectronic modulators are becoming increasingly important in microwave applications. These devices are necessarily electrically large and hence require velocity matching of the microwave signal to the light. A design methodology for velocity matched electrodes on doped semiconductor devices will be presented. As an example of a successful device design, experimental results on a >10 bandwidth high-efficiency (>15{degrees}/V/mm) Mach Zehnder interferometer will be presented.

Hietala, V.M.; Vawter, G.A.; Fuchs, B.; Armendariz, M.G.; Sullivan, C.T.

1995-12-31

352

Bandwidth Enhancement of a Microstrip Line-Fed Rotated Slot Antenna with a Parasitic Center Patch  

Directory of Open Access Journals (Sweden)

Full Text Available With day to day advancement wireless and communication industry, a single device needs to operate at multi frequency and enormous high bandwidth. Microstrip antenna is only to fit in this. A small rotated square slot antenna with a parasitic patch for bandwidth enhancement is proposed and investigated. A simple 50- microstrip line is used to excite the slot. A rotated square slot resonator with center parasitic patch is considered as reference geometry. The rotated square slot antenna exhibits two resonances .By embedding a parasitic patch into the center of the rotated square slot, the lower resonant frequency is decreased and the higher resonant frequency is increased. Thus, broadband characteristic of the wide-slot antenna is achieved. The measured results demonstrate that this structure exhibits a wide impedance bandwidth, which is over 85% for dB ranging from 2.19 to 5.95 GHz. Also, a stable and Omni directional radiation pattern is observed within the operating bandwidth. In this design, a smaller ground plane is considered compared to the reference antenna (rotated square slot antenna with the parasitic center patch). The proposed antenna has a strong application in UWB and WiMax devices. The IEEE 802.16 working group has been established a new operating band name as Worldwide Interoperability for Microwave access (WiMax). WiMax has three allocated frequency bands. The low band (2.5-2.69 GHz), the middle band (3.2-3.8 GHz) and the upper band (5.2-5.8 GHz).

SHILPA VERMA, SHALINI SHAH, PAURUSH BHULANIA

2013-01-01

353

Bandwidth Enrichment for Micro-strip Patch Antenna Using Pendant Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available A probe feed, slotted hexagonal patch antenna has been proposed. Bandwidth enhancement has been improved by suitably cutting slots into hexagonal patch.Proposed antenna is suitable for various telecoms, LAN, WiFi applications in ISM-band. It is demonstrated that the proposed antenna exhibits resonance in ISM-Band and a peak gain of 6dBi.The antenna structure is described and simulated results are presented.

Dr. D. Bhattacharya, R. Prasanna

2013-01-01

354

Monte Carlo simulation of high-bandwidth Cerenkov detectors for NIF fusion burn measurements  

International Nuclear Information System (INIS)

Measurement of D-T fusion gamma rays with gas Cerenkov detectors is being considered for the National Ignition Facility (NIF). New time-dependent photon/electron/Cerenkov Monte Carlo simulation capability has been developed for such design studies. Gas Cerenkov detection systems are being designed for Omega high-yield capsule proof-of-principle experiments. Ultimately, our designs are intended to achieve >20 GHz bandwidth and provide improved energy selectivity at the NIF. (authors)

2000-01-01

355

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

CERN Document Server

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; Gill, K; Grabit, R; Ricci, D; Troska, J; Vasey, F

2007-01-01

356

Energy efficient OFDM transceiver design based on traffic tracking and adaptive bandwidth adjustment.  

Science.gov (United States)

This paper proposes a novel scheme to reduce energy consumption of digital transceivers with OFDM as the modulation scheme. The energy consumption of transceivers is saved based on two key techniques: 1) adaptively tune the bandwidth and sampling rate of the OFDM signal; 2) selectively power off individual block of parallel modules in the transceiver. Performance analysis illustrate that the newly designed transceiver consumes a significantly less amount of energy as compared to the conventional transceiver. PMID:22274130

Zhang, Jingjing; Hu, Junqiang; Qian, Dayou; Wang, Ting

2011-12-12

357

Energy efficient OFDM transceiver design based on traffic tracking and adaptive bandwidth adjustment.  

UK PubMed Central (United Kingdom)

This paper proposes a novel scheme to reduce energy consumption of digital transceivers with OFDM as the modulation scheme. The energy consumption of transceivers is saved based on two key techniques: 1) adaptively tune the bandwidth and sampling rate of the OFDM signal; 2) selectively power off individual block of parallel modules in the transceiver. Performance analysis illustrate that the newly designed transceiver consumes a significantly less amount of energy as compared to the conventional transceiver.

Zhang J; Hu J; Qian D; Wang T

2011-12-01

358

A Dynamic Bandwidth Assignment Approach Under DDoS Flood Attack  

Directory of Open Access Journals (Sweden)

Full Text Available Distributed denial-of-service (DDoS) attacks are a major threat to the Internet. A lot of research is going on to detect, prevent and trace back DDoS attacks. Most of researchers are busy in post attack forensics which comes after the attack has been occurred but nobody is talking about how to design a system which can tolerate such attacks. In this paper we have suggested a approach for dynamic assignment of bandwidth in order to sustain the server. Basic idea is to examine genuine IP user’s traffic flow based on volume. Divide traffic in two categories of genuine traffic and malicious traffic and assign bandwidth as per category. The idea is to design a system which can give services even when the server is under attack. However some performance will degrades but overall Quality of services will be acceptable. A new formula also has been derived for dynamic bandwidth assignment which is based on number of genuine users and traffic volumes of users and attackers.

Raman Singh; Amandeep Verma

2012-01-01

359

Optimization of Single-Sensor Two-State Hot-Wire Anemometer Transmission Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available Hot-wire anemometric measurements of non-isothermal flows require the use of thermal compensation or correction circuitry. One possible solution is a two-state hot-wire anemometer that uses the cyclically changing heating level of a single sensor. The area in which flow velocity and fluid temperature can be measured is limited by the dimensions of the sensor’s active element. The system is designed to measure flows characterized by high velocity and temperature gradients, although its transmission bandwidth is very limited. In this study, we propose a method to optimize the two-state hot-wire anemometer transmission bandwidth. The method is based on the use of a specialized constanttemperature system together with variable dynamic parameters. It is also based on a suitable measurement cycle paradigm. Analysis of the method was undertaken using model testing. Our results reveal a possible significant broadening of the two-state hot-wire anemometer's transmission bandwidth.

Paweł Ligęza

2008-01-01

360

Bandwidths of micro-twisted-pair cables and fusion-spliced SIMM-GRIN fiber  

Energy Technology Data Exchange (ETDEWEB)

The SLHC is designed to increase the luminosity of the LHC by a factor of 10. In the present ATLAS pixel detector, electrical signals between the pixel modules and the optical modules (opto-boards) are transmitted in {approx}1 m of micro-twisted-pair cables. The optical signals between the opto-boards and the off-detector optical modules are transmitted in fiber ribbons. Each fiber link consists of 8 m of rad-hard/low bandwidth SIMM fiber fusion spliced to 70 m of rad-tolerant/medium bandwidth GRIN fiber. We currently transmit optical signals at 80 Mb/s and expect to transmit signals at 1 Gb/s in the SLHC. For the SLHC optical link, we would like to take advantage of some of the design features of the present pixel optical links and the many years of R and D effort and production experience. If the present architecture can transmit signals at the higher speed required by the SLHC, the constraint of requiring no extra service space is automatically satisfied. We have measured the bandwidths of the transmission lines and our preliminary results indicate that the micro-twisted-pair cables can transmit signals up to {approx}1 Gb/s and the fusion-spliced fiber ribbon can transmit signals up to {approx}2 Gb/s.

Gan, K.K. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States)]. E-mail: gan@mps.ohio-state.edu; Kagan, H.P. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States); Kass, R.D. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States); Smith, D.S. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States)

2007-06-11

 
 
 
 
361

High bandwidth Ge p-i-n photodetector integrated on Si  

International Nuclear Information System (INIS)

The authors present a germanium on silicon p-i-n photodiode for vertical light incidence. For a Ge p-i-n photodetector with a radius of 5 ?m a 3 dB bandwidth of 25 GHz is measured at an incident wavelength of 1.55 ?m and zero external bias. For a modest reverse bias of 2 V, the 3 dB bandwidth increases to 39 GHz. The monolithically integrated devices are grown on Si with solid source molecular beam epitaxy. The complete detector structure consisting of a highly p-doped Ge buried layer, an intrinsic absorption region, and a highly n-doped top contact layer of Ge/Si is grown in one continuous epitaxial run. A low growth temperature sequence was needed to obtain abrupt doping transitions between the highly doped regions surrounding the intrinsic layer. A theoretical consideration of the 3 dB bandwidth of the Ge detector was used to optimize the layer structure. For a photodiode with 5 ?m mesa radius the maximum theoretical 3 dB frequency is 62 GHz with an intrinsic region thickness of 307 nm.

2006-08-14

362

High-Bandwidth Dynamic Full-Field Profilometry for Nano-Scale Characterization of MEMS  

International Nuclear Information System (INIS)

The article describes an innovative optical interferometric methodology to delivery dynamic surface profilometry with a measurement bandwidth up to 10MHz or higher and a vertical resolution up to 1 nm. Previous work using stroboscopic microscopic interferometry for dynamic characterization of micro (opto)electromechanical systems (M(O)EMS) has been limited in measurement bandwidth mainly within a couple of MHz. For high resonant mode analysis, the stroboscopic light pulse is insufficiently short to capture the moving fringes from dynamic motion of the detected structure. In view of this need, a microscopic prototype based on white-light stroboscopic interferometry with an innovative light superposition strategy was developed to achieve dynamic full-field profilometry with a high measurement bandwidth up to 10MHz or higher. The system primarily consists of an optical microscope, on which a Mirau interferometric objective embedded with a piezoelectric vertical translator, a high-power LED light module with dual operation modes and light synchronizing electronics unit are integrated. A micro cantilever beam used in AFM was measured to verify the system capability in accurate characterisation of dynamic behaviours of the device. The full-field seventh-mode vibration at a vibratory frequency of 3.7MHz can be fully characterized and nano-scale vertical measurement resolution as well as tens micrometers of vertical measurement range can be performed.

2006-01-01

363

Optimal bandwidth-aware VM allocation for Infrastructure-as-a-Service  

CERN Multimedia

Infrastructure-as-a-Service (IaaS) providers need to offer richer services to be competitive while optimizing their resource usage to keep costs down. Richer service offerings include new resource request models involving bandwidth guarantees between virtual machines (VMs). Thus we consider the following problem: given a VM request graph (where nodes are VMs and edges represent virtual network connectivity between the VMs) and a real data center topology, find an allocation of VMs to servers that satisfies the bandwidth guarantees for every virtual network edge---which maps to a path in the physical network---and minimizes congestion of the network. Previous work has shown that for arbitrary networks and requests, finding the optimal embedding satisfying bandwidth requests is $\\mathcal{NP}$-hard. However, in most data center architectures, the routing protocols employed are based on a spanning tree of the physical network. In this paper, we prove that the problem remains $\\mathcal{NP}$-hard even when the phys...

Dutta, Debojyoti; Post, Ian; Shinde, Rajendra

2012-01-01

364

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 between incoming signal and reference modulated code) which happen within +/– 1 chip from the main peak. These correlation ambiguities affect adversely the detection probabilities in the code acquisition process and are usually dealt with by using some form of unambiguous processing (e.g., BPSK-like techniques, sideband processing, etc.). In some applications, such as mass-market applications, a narrowband Galileo receiver (i.e., with considerable front-end bandwidth limitation) is likely to be employed. The question addressed in this paper, which has not been answered before, is whether or not this bandwidth limitation can cope inherently with the ambiguities of the correlation function, to which extent, and which the best design options are in the acquisition process (e.g., in terms of time-bin step and ambiguity mitigation mechanisms).

Elena Simona Lohan

2011-01-01

365

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.

S. M. Idrus; S. S. Rais; A. Ramli

2008-01-01

366

Bandwidth provisioning in infrastructure-based wireless networks employing directional antennas  

Energy Technology Data Exchange (ETDEWEB)

Motivated by the widespread proliferation of wireless networks employing directional antennas, we study the problem of provisioning bandwidth in such networks. Given a set of subscribers and one or more access points possessing directional antennas, we formalize the problem of orienting these antennas in two fundamental settings: (1) subscriber-centric, where the objective is to fairly allocate bandwidth among the subscribers and (2) provider-centric, where the objective is to maximize the revenue generated by satisfying the bandwidth requirements of subscribers. For both the problems, we first design algorithms for a network with only one access point working under the assumption that the number of antennas does not exceed the number of noninterfering channels. Using the well-regarded lexicographic max-min fair allocation as the objective for a subscriber-centric network, we present an optimum dynamic programming algorithm. For a provider-centric network, the allocation problem turns out to be NP-hard. We present a greedy heuristic based algorithm that guarantees almost half of the optimum revenue. We later enhance both these algorithms to operate in more general networks with multiple access points and no restrictions on the relative numbers of antennas and channels. A simulation-based evaluation using OPNET demonstrates the efficacy of our approaches and provides us further in insights into these problems.

Hasiviswanthan, Shiva [Los Alamos National Laboratory; Zhao, Bo [PENN STATE UNIV.; Vasudevan, Sudarshan [UNIV OF MASS AMHERST; Yrgaonkar, Bhuvan [PENN STATE UNIV.

2009-01-01

367

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 ?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

368

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

UK PubMed Central (United Kingdom)

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 responses to five AM rates (1.5, 3.5, 7.5, 15.5, and 31.5 Hz) and four types of carrier (pure tone and 1/3-, 2-, and 5-octave pink noise) were investigated. The phase-locked aSSR was detected reliably in all conditions. The response power generally decreases with increasing modulation rate, and the response latency is between 100 and 150 ms for all but the highest rates. Response properties depend only weakly on the bandwidth. Analysis of the complex-valued aSSR magnetic fields in the Fourier domain reveals several neural sources with different response phases. These neural sources of the aSSR, when approximated by a single equivalent current dipole (ECD), are distinct from and medial to the ECD location of the N1m response. These results demonstrate that the globally synchronized activity in the human auditory cortex is phase locked to slow temporal modulations below 30 Hz, and the neural sensitivity decreases with an increasing AM rate, with relative insensitivity to bandwidth.

Wang Y; Ding N; Ahmar N; Xiang J; Poeppel D; Simon JZ

2012-04-01

369

Ultra-wide bandwidth measurement of partial discharge current pulses in SF6  

International Nuclear Information System (INIS)

This paper presents ultra-wide bandwidth measurements of partial discharge (PD) current pulses. Using a 33 GHz bandwidth oscilloscope together with a direct, matched coaxial connection to the PD source, pulses have been characterized with a greater degree of accuracy than has previously been achieved, with a minimum observed rise time of 24 ps. The PD source consists of a sharp protrusion in pressurized sulfur hexaflouride (SF6) with a tip radius of 25 µm. Both positive and negative corona pulses were recorded, revealing previously indistinguishable frequency content and features such as the appearance of groups of multiple component pulses occurring within a nanosecond time scale. The upper bandwidth limitation of the complete measurement set-up was established. This was calculated by cross-correlating current pulses with corresponding pulses filtered at lower frequencies to determine their similarity. The tendency for multiple consecutive pulses to occur within a short time period was evident. The results provide valuable data for researchers investigating fundamental physical phenomena of SF6 ionization and PD activity. (paper)

2012-04-25

370

An Improved Fitness Function and Mutation Operator for Metaheuristic Approaches to the Bandwidth Minimization Problem  

Science.gov (United States)

The Bandwidth Minimization Problem (BMP) is a graph layout problem which is known to be NP-complete. Since 1960, a considerable number of algorithms have been developed for addressing the BMP. At present, meta-heuristics (such as evolutionary algorithms and tabu search) are popular and successful approaches to the BMP. In such algorithms, the design of the fitness function (i.e. the metric that attempts to guide the search towards high-quality solutions) plays a key role in performance; the fitness function, along with the operators, induce the `search landscape', and careful attention to these issues may lead to landscapes that are more amenable to successful search. For example, rather than simply use the most obvious quality measure (in this case, the bandwidth itself), it is often helpful to design a more informative measure, indicating not only a solutions quality, but also encapsulating (for example) an indication of how distant this particular solution is from even better solutions. In this paper, a new fitness function and an associated new mutation operator are presented for BMP. These are incorporated within a simple Evolutionary Algorithm (EA), and evaluated on a set of 27 instances of the BMP (from the Harwell-Boeing sparse matrix collection). The results of this EA are compared with results obtained by using the standard fitness function (used in almost all previous researches on metaheuristics applied to the BMP). The results indicate clearly that the new fitness function and operator performed provide significantly superior results in the reduction of bandwidth.

Koohestani, Behrooz; Corne, David W.

2009-04-01

371

A constant loop bandwidth fractional-N frequency synthesizer for GNSS receivers  

International Nuclear Information System (INIS)

A constant loop bandwidth fractional-N frequency synthesizer for portable civilian global navigation satellite system (GNSS) receivers implemented in a 130 nm 1P6M CMOS process is introduced. Via discrete working regions, the LC-VCO obtains a wide tuning range with a simple structure and small VCO gain. Spur suppression technology is proposed to minimize the phase offset introduced by PFD and charge pumps. The optimized bandwidth is maintained by an auto loop calibration module to adjust the charge pump current when the PLL output frequency changes or the temperature varies. Measurement results show that this synthesizer attains an in-band phase noise lower than ?93 dBc at a 10 kHz offset and a spur less than ?70 dBc; the bandwidth varies by ± 3% for all the GNSS signals. The whole synthesizer consumes 4.5 mA current from a 1 V supply, and its area (without the LO tested buffer) is 0.5 mm2. (semiconductor integrated circuits)

2012-04-01

372

Development of a wide bandwidth heterodyne detector using a photoconductive element  

International Nuclear Information System (INIS)

Studies on a photoconductive detector such as Ge-Ga detector are described. Successful construction of the detector which works for a heterodyne mode detection with a wide bandwidth and low noise represents a progress in the FIR plasma diagnostics. Video detection in a photoconductor, heterodyne detection by a photoconductor, noise in FIR detection, the noise equivalent power (NEP) in the video mode detection (NEP-V), and NEP in the heterodyne mode (NEP-H) were studied. The minimum signal can be detected by using the photoconductive detector. With the experimental data of signal power, LO power, the voltage responsiveness and the correlation coefficient between the signal and the LO beam, the heterodyne voltage signal at the input should be 147 ?V. By using a 100 voltage gain preamplifier, the heterodyne voltage signal of 14.7 mV can be obtained at the output. The signal power at the input is 21.6 PW. The noise power at the input is 10-13 W by setting the bandwidth of 5 MHz. The signal to noise power ratio at the input by setting the bandwidth of 50 Hz is 2.16 x 107. The characteristics of the Ge-Ga detector to be used were determined. It is possible to get information of the limited capability with the fast response by using 10 ?m radiation, which can be easily modulated. (Kato, T.)

1982-01-01

373

MHBCDA: Mobility and Heterogeneity aware Bandwidth Efficient Cluster based Data Aggregation for Wireless Sensor Network  

DEFF Research Database (Denmark)

Wireless Sensor Network (WSN) offers a variety of novel applications for mobile targets. It generates the large amount of redundant sensing data. The data aggregation techniques are extensively used to reduce the energy consumption and increase the network lifetime, although it has the side effect of reduced reliability. In the mobile environment, it is necessary to consider the techniques which minimize the communication cost with efficient bandwidth utilization by decreasing the packet count reached at the sink. This paper proposes the mobility and heterogeneity aware bandwidth efficient Cluster-based Data Aggregation (MHBCDA) algorithm for the randomly distributed nodes. It considers the mobile sink based packet aggregation for the heterogeneous WSN. It uses predefined region for the aggregation at cluster head to minimize computation and communication cost. The MHBCDA is energy and bandwidth efficient. It exploits correlation of data packets generated by varying the packet generation rate. It prevents transmission of redundant data packets by improving energy consumption by 4.11% and prolongs the network life by 34.45% as compared with state-of-the-art solutions.

Dnyaneshwar, Mantri; Prasad, Neeli R.

2013-01-01

374

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; Santanu Das; Sekhar Ranjan Bhadra Chaudhuri

2012-01-01

375

Design of a demonstration experiment on the wide-bandwidth high-power dielectric Cherenkov maser amplifier  

Energy Technology Data Exchange (ETDEWEB)

Bandwidth dependences on the parameters of an electron beam and dielectric-fined waveguide have been calculated from the system dispersion relation, and the optimal set of parameters yielding large value of the bandwidth has been chosen. One-dimensional nonlinear simulations have been carried out. The output power of 60 MW at the peak gain of 27 dB is planned to be achieved. The wide-bandwidth input coupler has been constructed, and the results of microwave transmission measurements through the no-beam system are presented.

Harin, V.; Melnikov, G.; Shlapapkovskii, A. [Tomsk Polytechnical Univ. (Russian Federation)

1995-12-31

376

Modelamiento y análisis de pequeña señal de un generador de inducción y un STATCOM conectados a un sistema de potencia/ Modeling and analysis of a small signal of an induction generator and a STATCOM connected to a power system  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish En este documento se presenta el modelamiento y análisis de pequeña señal de un generador de inducción (IG) y un compensador síncrono estático (STATCOM), conectados a un barraje infinito, que representa un sistema de potencia; el IG es modelado como un sistema de quinto orden y se le acopla un STATCOM que es estudiado como un modelo de primer orden. El comportamiento dinámico fue simulado y comparado usando MATLAB/Simulink, bajo dos condiciones de perturbación: un (more) a variación en el torque de la máquina y una variación en la tensión del barraje infinito debido a un fallo en este punto. Las respuestas obtenidas por el software reflejan que el compensador actúa de forma adecuada, contrarrestando variaciones en potencia y tensión. Cabe resaltar que se debe agregar una etapa de sintonización de parámetros para mejorar las respuestas obtenidas. Abstract in english This paper presents the modeling and small-signal analysis of an induction generator (IG) and a static synchronous compensator (STATCOM) connected to an infinite bus bar, representing a power system, the IG is modeled as ffith-order system and is coupled to a STATCOM is studied as a model of first order. The dynamic behavior was simulated and compared using MATLAB/ Simulink, two conditions of disturbance: a variation in the torque of the machine and a variation in the inf (more) inite bus bar voltage because of a failure at this point. The responses obtained by the software show that the compensator acts appropriately counteracting power and voltage variations. Significantly, it must add a stage of tuning parameters to improve the responses.

Zuluaga Ríos, Carlos David; Alzate Gómez, Alfonso

2011-07-01

377

Multichannel compression hearing aids: effect of channel bandwidth on consonant and vowel identification by hearing-impaired listeners.  

UK PubMed Central (United Kingdom)

Aided consonant and vowel identification was measured in 13 listeners with high-frequency sloping hearing losses. To investigate the influence of compression-channel analysis bandwidth on identification performance independent of the number of channels, performance was compared for three 17-channel compression systems that differed only in terms of their channel bandwidths. One compressor had narrow channels, one had widely overlapping channels, and the third had level-dependent channels. Measurements were done in quiet, in speech-shaped noise, and in a three-talker background. The results showed no effect of channel bandwidth, neither on consonant nor on vowel identification scores. This suggests that channel bandwidth per se has little influence on speech intelligibility when individually prescribed, frequency-varying compressive gain is provided.

Strelcyk O; Li N; Rodriguez J; Kalluri S; Edwards B

2013-03-01

378

A simple photonic generation of linearly chirped microwave pulse with large time-bandwidth product and high compression ratio.  

UK PubMed Central (United Kingdom)

Based on the heterodyne beating between the pre-chirped optical pulse and the continuous wave (CW) light in a wideband photodetector (PD), linearly chirped microwave pulse with time duration of 3.2ns and bandwidth of 33GHz, which yields a large time-bandwidth product (TBWP) of 106 and high compression ratio of 160, is generated in our experiment. Dispersion compensation fiber (DCF) with uniform response across broad bandwidth is used for providing the original linear chirp in our method, which shows the promise to generate linearly chirped microwave pulse with bandwidth of up to THz. The flexibility of the center frequency and the stability of the time-frequency performance are demonstrated by generating different types of linearly chirped microwave pulses. The range resolution of our generated microwave pulse is also verified by off-line processing.

Gao H; Lei C; Chen M; Xing F; Chen H; Xie S

2013-10-01

379

Dependence of satellite pulse occurrence on gain band-width of a passively mode-locked laser  

Energy Technology Data Exchange (ETDEWEB)

A simple analysis is used to show that the occurrence of satellites in a mode locked train of pulses is dependent on the width of the oscillating axial modes of the laser. The method also helps one to predict the position of the satellites in the primary mode locked train if gain bandwidth and average intensity are known. Examples are presented for the cases of gain bandwidths of 40 and 233 cm, and average intensity values of 10, 12 and 14.

Arunkumar, K.A.

1981-01-01

380

Geometrical noise bandwidth: a new tool to characterize the resolving power of analogue and digital imaging devices  

Science.gov (United States)

The electrical noise bandwidth quantifies the transfer of noise in electrical systems. Geometrically, the noise can be interpreted as a circle of confusion. The adaptation of the electrical noise bandwidth to geometrical resolution problems demands a generalization of frequencies in two dimensions. The Geometrical Noise Bandwidth is calculated from the product of all MTF, which give the final picture. Here, the optics, the pixel form and size, the color interpolation and optical low pass filters can be considered. Geometrical Noise Bandwidth is measured in mm-2. It can be calculated by integration for films. In the case of digital imaging devices, the integration limit of spatial frequencies is the Nyquist frequency. The circle of confusion is inverse proportional to the quadratic root of the Geometrical Noise Bandwidth. The results of different imaging devices (photographic film, classical monochrome and color matrices, Fuji Super CCD, several digital-backs, scanners) will be compared using test- pictures of the Siemens star resolution test target. Beyond this, the Geometrical Noise Bandwidth permits comparison of the information contents of classical films and digital matrices. We obtain information to evaluate whether digital imaging devices are better than photographic films.

Schuster, Norbert

2002-04-01

 
 
 
 
381

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

382

Designing and implementing Multibeam Smart Antennas for high bandwidth UAV communications using FPGAs  

Science.gov (United States)

Requirements for high bandwidth UAV communications are often necessary in order to move large amounts of mission information to/from Users in real-time. The focus of this paper is antenna beamforming for point-to-point, high bandwidth UAV communications in order to optimize transmit and receive power and support high data throughput communications. Specifically, this paper looks at the design and implementation of Multibeam Smart Antennas to implement antenna beamforming in an aerospace communications environment. The Smart Antenna is contrasted against Fast Fourier Transform (FFT) based beamforming in order to quantify the increase in both computational load and FPGA resources required for multibeam adaptive signal processing in the Smart Antenna. The paper begins with an overall discussion of Smart Antenna design and general beamforming issues in high bandwidth communications. Important design considerations such as processing complexity in a constrained Size, Weight and Power (SWaP) environment are discussed. The focus of the paper is with respect to design and implementation of digital beamforming wideband communications waveforms using FPGAs. A Multibeam Time Delay element is introduced based on Lagrange Interpolation. Design data for Multibeam Smart Antennas in FPGAs is provided in the paper as well as reference circuits for implementation. Finally, an example Multibeam Smart Antenna design is provided based on a Xilinx Virtex-7 FPGA. The Multibeam Smart Antenna example design illustrates the concepts discussed in the paper and provides design insight into Multibeam Smart Antenna implementation from the point of view of implementation complexity, required hardware, and overall system performance gain.

Porcello, J. C.

383

Investigation of the Bandwidth of GaAs/AlGaAs Quantum Well Infrared Photodetector  

Science.gov (United States)

A GaAs/AlGaAs multi-quantum well (MQW) structure has been grown by solid source molecular beam epitaxy (MBE) and fabricated to detectors. A spectral response curve of the detector with full width at half maximum (FWHM) = 3.78 ?m and peak wavelength = 9.73 ?m has been obtained at a bias of E = 3 × 103 Vcm-1 at T = 77 K. We study the bandwidth of the GaAs/AlGaAs quantum well infrared photodetector (QWIP) by using effective mass approximation. It is found that the transmissivity of the electron through the potential barrier reaches its maximum value (T = 1) on the condition of resonance transmission in a multi-quantum well structure, if the energy state is defined as a conduction state when the transmissivity of electron through the potential barrier on which is bigger than 1/2, then, a series of separated conduction microbands were formed above the barriers which consist of conduction states. Under the influence of an external electric field, the conduction microbands stagger periodically among the quantum wells to form a Wannier-Stark ladder. When optical excitation occurs, electrons not only vertically transit from Fermi level EF in a quantum well to conduction microbands above the well, but also obliquely transit to the conduction microbands above the neighboring well, and the formed photocurrent peaks overlap together; consequently, the bandwidth of the photoresponsive spectrum is improved. The calculated bandwidth of the photocurrent spectrum agrees well with the measured one in our experiment.

Kong, Ling-Min; Zhang, Jian; Cheng, Xing-Kui; Zhang, Cun-Xi; Wang, Rui

384

BANDWIDTH AND EFFICIENT ENCODING SCHEME COMBINING TCM-UGM TO STBC  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a bandwidth efficient encoding scheme is proposed. It combines the modified version of trellis coded-modulation (called trellis coded-modulation with Ungerboeck-Gray mapping, TCM-UGM) to space-time block code (STBC). The performance of this encoding scheme is investigated over memoryless Rayleigh fading (MRF) channel for throughput 2 bits/s/Hz. The simulation result, using 2/3 rate 16-state TCM-UGM encoder, two transmit antennas and two receive antennas, shows clearly that the proposed scheme outperforms the performance of the association TCM/STBC by 0.67 dB at FER=10-2.

MOHAMED BENAISSA; ABDESSELAM BASSOU,; MOHAMMED BELADGHAM; ABDELMOUNAIM MOULAY LAKHDAR

2011-01-01

385

Toward Quantum Processing in Molecules: A THz-Bandwidth Coherent Memory for Light.  

UK PubMed Central (United Kingdom)

The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to ?1??ns, enabling ?10^{4} operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

Bustard PJ; Lausten R; England DG; Sussman BJ

2013-08-01

386

Toward quantum processing in molecules: a THz-bandwidth coherent memory for light.  

UK PubMed Central (United Kingdom)

The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to ~1 ns, enabling ~10(4) operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

Bustard PJ; Lausten R; England DG; Sussman BJ

2013-08-01

387

Computer-generated holograms with optimum bandwidths obtained with twisted-nematic liquid-crystal displays.  

Science.gov (United States)

We discuss a computer-generated hologram for encoding arbitrary complex modulation based on a commercial twisted-nematic liquid-crystal display. This hologram is implemented with the constrained complex modulation provided by the display in a phase-mostly configuration. The hologram structure and transmittance are determined to obtain on-axis signal reconstruction, maximum bandwidth, optimum efficiency, and high signal-to-noise ratio. We employed the proposed holographic code for the experimental synthesis of first-order Bessel beams. PMID:15813265

Arrizón, Victor; González, Luis A; Ponce, Rodrigo; Serrano-Heredia, Alfonso

2005-03-20

388

Increased bandwidth for dielectric spectroscopy of proteins through electrode surface preparation.  

UK PubMed Central (United Kingdom)

Dielectric spectroscopy measurements of liquids are often limited by electrode polarization. The influence of surface polishing and deposition of the conducting polymer polypyrrole/polystyrenesulfonate (PPy/PSS) on the polarization impedance is investigated. A quantitative description of the electrode polarization contribution to the real-valued permittivity spectrum is derived. This description explains the origin of the ?(-const). (const.>1) dependency commonly observed in permittivity measurements. Electrode surface roughness is correlated with both the magnitude and phase of the constant phase element. Generally, rougher electrodes have better performance, and an order of magnitude bandwidth improvement is achieved using PPy/PSS electrodes.

Mellor BL; Cortés EC; Khadka S; Mazzeo BA

2012-01-01

389

Reception frequency bandwidth of a gravitational resonant detector with optical readout  

Energy Technology Data Exchange (ETDEWEB)

A gravitational resonant bar detector with a large scale Fabry-Perot (FP) cavity as an optical readout and a mechanical displacement transformer is considered. We calculate, in a fully analytical way, the final receiver bandwidth in which the potential sensitivity, limited only by the bar thermal noise, is maintained despite the additional thermal noise of the transformer and the additive noise of the optical readout. We also discuss an application to the OGRAN project, where the bar is instrumented with a 2 m long FP cavity.

Gusev, A V; Rudenko, V N; Cheprasov, S A [Sternberg Astronomical Institute of Moscow State University, Moscow (Russian Federation); Bassan, M [Dip. Fisica, Universita Tor Vergata and INFN Roma (Italy)

2008-03-07

390

Space-bandwidth scaling for wide field-of-view imaging.  

Science.gov (United States)

We examine the space-bandwidth product of wide field-of-view imaging systems as the systems scale in size. Our analysis is based on one conducted to examine the behavior of a plano-convex lens imaging onto a flat focal geometry. We extend this to consider systems with monocentric lenses and curved focal geometries. As a means to understand system cost, and not just performance, we also assess the volume and mass associated with these systems. Our analysis indicates monocentric lenses imaging onto a curved detector outperform other systems for the same design constraints but do so at a cost in lens weight. PMID:22307128

Milojkovic, Predrag; Mait, Joseph N

2012-02-01

391

Space-bandwidth scaling for wide field-of-view imaging.  

UK PubMed Central (United Kingdom)

We examine the space-bandwidth product of wide field-of-view imaging systems as the systems scale in size. Our analysis is based on one conducted to examine the behavior of a plano-convex lens imaging onto a flat focal geometry. We extend this to consider systems with monocentric lenses and curved focal geometries. As a means to understand system cost, and not just performance, we also assess the volume and mass associated with these systems. Our analysis indicates monocentric lenses imaging onto a curved detector outperform other systems for the same design constraints but do so at a cost in lens weight.

Milojkovic P; Mait JN

2012-02-01

392

Toward quantum processing in molecules: A THz-bandwidth coherent memory for light  

CERN Multimedia

The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to 1ns, enabling 10,000 operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

Bustard, Philip J; England, Duncan G; Sussman, Benjamin J

2013-01-01

393

Laser-bandwidth-induced fluctuations in the intensity transmitted by a Fabry-Perot interferometer  

Energy Technology Data Exchange (ETDEWEB)

We have measured the power spectrum of the intensity fluctuations of light transmitted by a Fabry-Perot interferometer when the input field is the real Gaussian field. The real Gaussian field is a field characterized by real, random (Gaussian) amplitude fluctuations. The bandwidth of the real Gaussian field was varied, taking on values less than that of the interferometer, as well as greater. Comparisons of the measured spectra with calculated spectra are quite satisfactory. Of special interest is a feature in the spectra centered at the laser-interferometer detuning frequency.

Klimeck, G.; Elliott, D.S. (School of Electrical Engineering, Purdue University, West Lafayette, Indiana (USA)); Hamilton, M.W. (Department of Physics and Applied Physics, University of Strathclyde, Glasgow (G4ONG Scotland))

1991-09-01

394

Exciton bandwidth and coupling to intramolecular phonons in PTCDA[Perylenetetracarboxylic dianhydride  

Energy Technology Data Exchange (ETDEWEB)

A Holstein model is introduced for PTCDA stacks forming a one-dimensional exciton system and analyzed using Merrifield's variational method. The bandwidth and hopping integral V = 0.15 eV are obtained by comparing the absorption, emission, and fluorescence excitation of PTCDA films to solution spectra. PTCDAs crystallize face-to-face with strong {pi}-overlap indicated by the spacing c = 3.38 {angstrom} along the stack, while interstack contacts are van der Waals or longer.

Hennessy, M.H.; Soos, Z.G.; Bulovic, V.; Forrest, S.R.

1998-07-01

395

A Bandwidth-Efficient Service for Local Information Dissemination in Sparse to Dense Roadways  

Directory of Open Access Journals (Sweden)

Full Text Available Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging station advertising system, which takes advantage of the broadcast nature of the network. We have found that reducing the number of total sent packets is important, as it allows for a better use of the available bandwidth. We have designed improvements for a distance-based flooding scheme, so that it can support the advertising application with good results in sparse to dense roadway scenarios.

Estrella Garcia-Lozano; Celeste Campo; Carlos Garcia-Rubio; Alberto Cortes-Martin; Alicia Rodriguez-Carrion; Patricia Noriega-Vivas

2013-01-01

396

A wide bandwidth free-electron laser with mode locking using current modulation.  

Energy Technology Data Exchange (ETDEWEB)

A new scheme for mode locking a free-electron laser amplifier is proposed based on electron beam current modulation. It is found that certain properties of the original concept, based on the energy modulation of electrons, are improved including the spectral brightness of the source and the purity of the series of short pulses. Numerical comparisons are made between the new and old schemes and between a mode-locked free-electron laser and self-amplified spontaneous emission free-electron laser. Illustrative examples using a hypothetical mode-locked free-electron laser amplifier are provided. The ability to generate intense coherent radiation with a large bandwidth is demonstrated.

Kur, E.; Dunning, D. J.; McNeil, B. W. J.; Wurtele, J.; Zholents, A. A. (Accelerator Systems Division (APS)); (Univ. of California at Berkeley); (Univ. of Strathclyde); (STFC Daresbury Lab.); (LBNL)

2011-01-20

397

Two-impurity Anderson model in the zero-bandwidth limit  

Science.gov (United States)

The zero-bandwidth limit of the two-impurity Anderson model is applied to calculate the magnetic correlations between impurities. The model includes two localized orbitals with the same energies ?d and on-site Coulomb repulsions U coupled to two uncorrelated band orbitals with energies at the Fermi level. For large U, when the distance of the impurities is reduced, the model shows that the Kondo energy decreases and ferromagnetic correlations between the impurities take place. For small U, antiferromagnetic correlations are obtained. The results are in a good qualitative agreement with recent experimental data.

Allub, R.

2003-04-01

398

Pulse compression over a 170-THz bandwidth in the visible by use of only chirped mirrors.  

Science.gov (United States)

We report on double-chirped mirrors with custom-tailored dispersion characteristics over a bandwidth of 170 THz in the visible. The mirrors are used in a prismless compressor for a noncollinear optical parametric amplifier in the visible. The compressed pulses, characterized for the what is believed to be first time by use of the spectral phase interferometry for direct electric field reconstruction technique, display a nearly flat phase from 510 to 710 nm and have a duration of 5.7 fs. PMID:18049547

Zavelani-Rossi, M; Cerullo, G; De Silvestri, S; Gallmann, L; Matuschek, N; Steinmeyer, G; Keller, U; Angelow, G; Scheuer, V; Tschudi, T

2001-08-01

399

APEnet+: high bandwidth 3D torus direct network for petaflops scale commodity clusters  

Science.gov (United States)

We describe herein the APElink+ board, a PCIe interconnect adapter featuring the latest advances in wire speed and interface technology plus hardware support for a RDMA programming model and experimental acceleration of GPU networking; this design allows us to build a low latency, high bandwidth PC cluster, the APEnet+ network, the new generation of our cost-effective, tens-of-thousands-scalable cluster network architecture. Some test results and characterization of data transmission of a complete testbench, based on a commercial development card mounting an Altera® FPGA, are provided.

Ammendola, R.; Biagioni, A.; Prezza, O.; Lo Cicero, F.; Lonardo, A.; Paolucci, P. S.; Rossetti, D.; Salamon, A.; Salina, G.; Simula, F.; Tosoratto, L.; Vicini, P.

2011-12-01

400

APEnet+: high bandwidth 3D torus direct network for petaflops scale commodity clusters  

CERN Multimedia

We describe herein the APElink+ board, a PCIe interconnect adapter featuring the latest advances in wire speed and interface technology plus hardware support for a RDMA programming model and experimental acceleration of GPU networking; this design allows us to build a low latency, high bandwidth PC cluster, the APEnet+ network, the new generation of our cost-effective, tens-of-thousands-scalable cluster network architecture. Some test results and characterization of data transmission of a complete testbench, based on a commercial development card mounting an Altera FPGA, are provided.

Ammendola, Roberto; Frezza, Ottorino; Cicero, Francesca Lo; Lonardo, Alessandro; Paolucci, Pier Stanislao; Rossetti, Davide; Salamon, Andrea; Salina, Gaetano; Simula, Francesco; Tosoratto, Laura; Vicini, Piero

2011-01-01

 
 
 
 
401

APEnet+: high bandwidth 3D torus direct network for petaflops scale commodity clusters  

International Nuclear Information System (INIS)

We describe herein the APElink+ board, a PCIe interconnect adapter featuring the latest advances in wire speed and interface technology plus hardware support for a RDMA programming model and experimental acceleration of GPU networking; this design allows us to build a low latency, high bandwidth PC cluster, the APEnet+ network, the new generation of our cost-effective, tens-of-thousands-scalable cluster network architecture. Some test results and characterization of data transmission of a complete testbench, based on a commercial development card mounting an Altera® FPGA, are provided.

2011-12-23

402

Effect of bandwidth on beam smoothing and frequency conversion at the third harmonic of the Nova laser  

Energy Technology Data Exchange (ETDEWEB)

We present the results of experiments performed on the Nova laser system to determine the effect of bandwidth on third harmonic (3{omega}) frequency conversion and beam smoothing by spectral dispersion (SSD). Our experiments utilized a wide bandwidth fiber optic cross-phase modulated (XPM) source and a narrower bandwidth microwave modulated (FM) source, each centered at 1053 nm (1{omega}). The FM source produced {approximately}2 cm{sup {minus}1} of bandwidth, modulated at 3 GHz; the XPM bandwidth was varied from 5 to 15 cm{sup {minus}1}, modulated by the temporally noisy output of a multimode Nd:glass laser ({le} 500 GHz). The FM beam showed no evidence of self-phase modulation in the laser chain produced by intensity fluctuations, and 1{omega} bandwidth was tripled upon conversion to 3{omega} (2--6 cm{sup {minus}1}). The 1{omega} XPM bandwidth increased by {ge} 25% due to self-phase modulation in the laser chain (16--22 cm{sup {minus}1}) due to it`s relative noisy temporal structure. Over 50% of the 1{omega} XPM bandwidth was transferred to the 3{omega} beam (22--36 cm{sup {minus}1}), yielding 0.13% bandwidth at 3{omega}. The maximum intrinsic narrowband 3{omega} frequency conversion obtained using a type-II/type-II KDP crystal array was 62%. The intrinsic efficiency obtained at the Nova 10-beam chamber is typically > 65%. We have developed broadband frequency conversion codes and broadband pulse simulations to model our results, and have obtained good agreement with experiment. Using a random phase plate without bandwidth, we obtained a smoothing level, {sigma}/I {approximately} 0.79, defined by the rms variance normalized with respect to the average intensity. This is less than the theoretically expected value of 1 for an ideal speckle pattern, and could be evidence of polarization smoothing as a result of focus lens birefringence. With spectral dispersion and RPP we demonstrated an excellent level of smoothing with the XPM source.

Pennington, D.M.; Henesian, M.A.; Dixit, S.N.; Powell, H.T.; Thompson, C.E.; Weiland, T.L.

1993-05-01

403

Narrow-bandwidth high-order harmonics driven by long-duration hot spots  

International Nuclear Information System (INIS)

We predict and investigate the emission of high-order harmonics by atoms that cross intense laser hot spots that last for a nanosecond or longer. An atom that moves through a nanometer-scale hot spot at characteristic thermal velocity can emit high-order harmonics in a similar fashion to an atom that is irradiated by a short-duration (picosecond-scale) laser pulse. We analyze the collective emission from a thermal gas and from a jet of atoms. In both cases, the line shape of a high-order harmonic exhibits a narrow spike with spectral width that is determined by the bandwidth of the driving laser. Finally, we discuss a scheme for producing long-duration laser hot spots with intensity in the range of the intensity threshold for high-harmonic generation. In the proposed scheme, the hot spot is produced by a long laser pulse that is consecutively coupled to a high-quality micro-resonator and a metallic nano-antenna. This system may be used for generating ultra-narrow bandwidth extreme-ultraviolet radiation through frequency up-conversion of a low-cost compact pump laser. (paper)

2012-01-01

404

High-bandwidth squeezed light at 1550 nm from a compact monolithic PPKTP cavity  

CERN Document Server

We report the generation of squeezed vacuum states of light at 1550 nm with a broadband quantum noise reduction of up to 4.8 dB ranging from 5 MHz to 1.2 GHz sideband frequency. We used a custom-designed 2.6 mm long biconvex periodically-poled potassium titanyl phosphate (PPKTP) crystal. It featured reflectively coated end surfaces, 2.26 GHz of linewidth and generated the squeezing via optical parametric amplification. Two homodyne detectors with different quantum efficiencies and bandwidths were used to characterize the non-classical noise suppression. We measured squeezing values of up to 4.8 dB from 5 to 100 MHz and up to 3 dB from 100 MHz to 1.2 GHz. The squeezed vacuum measurements were limited by detection loss. We propose an improved detection scheme to measure up to 10 dB squeezing over 1 GHz. Our results of GHz bandwidth squeezed light generation provide new prospects for high-speed quantum key distribution.

Ast, Stefan; Schnabel, Roman

2013-01-01

405

Design optimization for relative bandwidth of left-handed metamaterials with split-ring resonators  

Science.gov (United States)

Due to their special properties, left-handed metamaterials have important potential applications in engineering. When an incident wave propagates through a periodic material with the dimension of its microstructure much smaller than the wavelength, the metamaterial can be regarded as a homogeneous medium, and its effective electromagnetic parameters (permittivity and permeability) in the frequency domain can be obtained with the S-parameters retrieval method. From this perspective, the design of a material with the desired left-handed characteristics becomes possible. By establishing automatic parametric modeling technology, we can study the transmission and reflection properties of left-handed metamaterials with arrays of split-ring resonators. Next, a whole flow chart of design optimization for improving left-handed metamaterial performance is proposed. Finally, the design method is illustrated through a numerical example including the shape and the size design of split-ring resonators to max relative bandwidth, based on parametric analysis of the left-handed relative bandwidths. Sequential quadratic programming and enumeration optimization are applied to solve the optimization problem.

Liu, Shutian; Dong, Yanzhang; Xu, Weikai

2011-01-01

406

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

International Nuclear Information System (INIS)

[en] Scintillators have been employed for several years as ionizing radiation-to-light converters in plasma diagnostic experiments that utilize fiber optics. Until recently, nanosecond and subnanosecond scintillators were available only in the near ultraviolet. However, the bandwidth and transmission properties of fiber optics both strongly favor operation at longer wavelengths. More recently, nanosecond and subnanosecond scintillators with emission peaks around 480 nm have been reported. A time-resolved plasma-imaging experiment using one of these scintillators and 100 channels of graded-index fiber, each 500 m long, has been successfully tested on a nuclear event at the Nevada Test Site. During the past year we have developed several new scintillator systems with emission wavelengths more compatible with fiber optics and with response times in the nanosecond and subnanosecond time region. One scintillator, based on Kodak dye 14567 (DCM), has an emission maximum at 650 nm and a response time (FWHM) of 1.2 ns. Experimental data on system sensitivity and bandwidth versus fiber length are presented for three fluor-fiber systems. Data on fluor formulation, response time, and linearity-of-response are given, and a model for scintillator nonlinearity, based on solvent, radiation-induced, transient absorption, is presented

1981-08-28

407

Self-calibrating ultra-low noise, wide-bandwidth optomechanical accelerometer  

CERN Multimedia

The reflection spectrum of an optical cavity is exquisitely sensitive to length variations, enabling precise and accurate displacement measurements. When combined with mechanical oscillators, such cavities can yield accelerometers of unprecedented resolution. Previously, accelerometer sensitivity enhancements were achieved by lowering the sensor's natural frequency and bandwidth. Detection near the thermal limit was achieved, but at high acceleration levels due to low oscillator mass. We present a novel self-calibrating accelerometer, capable of reaching nano-gn/rtHz sensitivities (micro-Gal/rtHz -- 1gn=9.81 m/s^2 -- equivalent displacement of attometer/rtHz) over a bandwidth of several kHz, and compare its accuracy to a calibrated commercial system. It consists of a compact (10.6 x 15 mm), high-mQ (5kg) fused-silica oscillator that utilizes fiber-optic micro-mirror cavities, for self-calibrated detection of the motions of its test-mass. This device provides a substantial improvement over conventional systems...

Cervantes, Felipe Guzman; Pratt, Jon; Taylor, Jacob

2013-01-01

408

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

CERN Document Server

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 minimum of the cross-section is exactly zero. For sufficiently large column density in the gas cell, the spectrum of the incoming radiation will be attenuated by the background cross-section of many orders of magnitude, except for those wavelengths close to the point where the cross-section is zero. Remarkable advantages of a gas monochromator based on this principle are simplicity, efficiency and narrow-bandwidth. A gas monochromator installed in the experimental hall of a VUV SASE FEL facility would enable the delivery of a single-mode VUV l...

Geloni, Gianluca; Saldin, Evgeni

2011-01-01

409

A 46 GHz Bandwidth Monolithic InP/InGaAs PIN/SHBT-Photoreceiver  

UK PubMed Central (United Kingdom)

A InGaAs PIN-photodetector and a lumped SHBT-transimpedance-preamplifierhave been monolithicallyintegrated and characterized. The preamlifier achieves a transimpedance gain of 44:6dBOmega (170Omega) and the optical/electrical Gamma3dB-bandwidth of the entire receiver is 46 GHz. This is, to thebest of our knowledge, the highest bandwidth for any HBT based photoreceiver reported to date.Introduction: The monolithic integration of photodetectors and preamplifiers in InP-based materialshas been the focus of research in industrial and academic laboratories for its ease of fabrication. Becausethe InGaAs base-collector junction of the HBT can be used for the formation of the photodiode, no additionalepitaxial and processing steps are necessary for this cointegration. Furthermore, the InGaAs-PINdiodeserves as a detector for light at the wavelength of 1:55 ¯m, the interconnection-parasitics betweendiode and preamplifier can be reduced to a minimum and high-performance transistors ...

D. Huber; M. Bitter; T. Morf; C. Bergamaschi; H. Melchior

410

Auditory masking in three pinnipeds: Aerial critical ratios and direct critical bandwidth measurements  

Science.gov (United States)

This study expands the limited understanding of pinniped aerial auditory masking and includes measurements at some of the relatively low frequencies predominant in many pinniped vocalizations. Behavioral techniques were used to obtain aerial critical ratios (CRs) within a hemianechoic chamber for a northern elephant seal (Mirounga angustirostris), a harbor seal (Phoca vitulina), and a California sea lion (Zalophus californianus). Simultaneous, octave-band noise maskers centered at seven test frequencies (0.2-8.0 kHz) were used to determine aerial CRs. Narrower and variable bandwidth masking noise was also used in order to obtain direct critical bandwidths (CBWs). The aerial CRs are very similar in magnitude and in frequency-specific differences (increasing gradually with test frequency) to underwater CRs for these subjects, demonstrating that pinniped cochlear processes are similar both in air and water. While, like most mammals, these pinniped subjects apparently lack specialization for enhanced detection of specific frequencies over masking noise, they consistently detect signals across a wide range of frequencies at relatively low signal-to-noise ratios. Direct CBWs are 3.2 to 14.2 times wider than estimated based on aerial CRs. The combined masking data are significant in terms of assessing aerial anthropogenic noise impacts, effective aerial communicative ranges, and amphibious aspects of pinniped cochlear mechanics.

Southall, Brandon L.; Schusterman, Ronald J.; Kastak, David

2003-09-01

411

Auditory masking in three pinnipeds: aerial critical ratios and direct critical bandwidth measurements.  

UK PubMed Central (United Kingdom)

This study expands the limited understanding of pinniped aerial auditory masking and includes measurements at some of the relatively low frequencies predominant in many pinniped vocalizations. Behavioral techniques were used to obtain aerial critical ratios (CRs) within a hemianechoic chamber for a northern elephant seal (Mirounga angustirostris), a harbor seal (Phoca vitulina), and a California sea lion (Zalophus californianus). Simultaneous, octave-band noise maskers centered at seven test frequencies (0.2-8.0 kHz) were used to determine aerial CRs. Narrower and variable bandwidth masking noise was also used in order to obtain direct critical bandwidths (CBWs). The aerial CRs are very similar in magnitude and in frequency-specific differences (increasing gradually with test frequency) to underwater CRs for these subjects, demonstrating that pinniped cochlear processes are similar both in air and water. While, like most mammals, these pinniped subjects apparently lack specialization for enhanced detection of specific frequencies over masking noise, they consistently detect signals across a wide range of frequencies at relatively low signal-to-noise ratios. Direct CBWs are 3.2 to 14.2 times wider than estimated based on aerial CRs. The combined masking data are significant in terms of assessing aerial anthropogenic noise impacts, effective aerial communicative ranges, and amphibious aspects of pinniped cochlear mechanics.

Southall BL; Schusterman RJ; Kastak D

2003-09-01

412

Towards a Flow-based Internet Traffic Classification for Bandwidth Optimization  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The evolution of the Internet into a large complex service-based network has posed tremendous challenges for network monitoring and control in terms of how to collect the large amount of data in addition to the accurate classification of new emerging applications such as peer to peer, video streaming and online gaming. These applications consume bandwidth and affect the performance of the network especially in a limited bandwidth networks such as university campuses causing performance deterioration of mission critical applications. Some of these new emerging applications are designed to avoid detection by using dynamic port numbers (port hopping), port masquerading (use http port 80) and sometimes encrypted payload. Traditional identification methodologies such as port-based signature-based are not efficient for today’s traffic. In this work machine learning algorithms are used for the classification of traffic to their corresponding applications. Furthermore this paper uses our own customized made training data set collected from the campus, The effect on the amount of training data set has been considered before examining, the accuracy of various classification algorithms and selecting the best. Our findings show that random tree, IBI, IBK, random forest respectively provide the top 4 highest accuracy in classifying flow based network traffic to their corresponding application among thirty algorithms with accuracy not less than 99.33%.

Abuagla Babiker Mohd; Dr. Sulaiman bin Mohd Nor

2009-01-01

413

Power allocation, bit loading and sub-carrier bandwidth sizing for OFDM-based cognitive radio  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The function of the Radio Resource Management module of a Cognitive Radio (CR) system is to evaluate the available resources and assign them to meet the Quality of Service (QoS) objectives of the Secondary User (SU), within some constraints on factors which limit the performance of the Primary User (PU). While interference mitigation to the PU spectral band from the SU's transmission has received a lot of attention in recent literature; the novelty of our work is in considering a more realistic and effective approach of dividing the PU into sub-bands, and ensuring that the interference to each of them is below a specified threshold. With this objective, and within a power budget, we execute the tasks of power allocation, bit loading and sizing the sub-carrier bandwidth for an orthogonal frequency division multiplexing (OFDM)-based SU. After extensively analyzing the solution form of the optimization problems posed for the resource allocation, we suggest iterative algorithms to meet the aforementioned objectives. The algorithm for sub-carrier bandwidth sizing is novel, and not previously presented in literature. A multiple SU scenario is also considered, which entails assigning sub-carriers to the users, besides the resource allocation. Simulation results are provided, for both single and multi-user cases, which indicate the effectiveness of the proposed algorithms in a CR environment.

Thumar Vinay; Nadkar Taskeen; Gopavajhula Tej; Desai Uday; Merchant Shabbir

2011-01-01

414

BHCDA:Bandwidth Efficient Heterogeneity aware Cluster based Data Aggregation for Wireless Sensor Network  

DEFF Research Database (Denmark)

The fundamental challenge in the design of Wireless sensor Network (WSNs) is proper utilization of resources which are scare. One of the critical challenges is to maximize the bandwidth utilization in data gathering from sensor nodes and forward to sink. The main design objective of this paper is to utilize the available bandwidth efficiently with reduced packet delivery ratio and throughput. BHCDA presents the solution for effective data gathering with in-network aggregation. It considers the network with heterogeneous nodes in terms of energy and mobile sink to aggregate the data packets. It embodies the optimal approach by Intra and inter-cluster aggregation on the randomly distributed nodes with variable data generation rate while routing data to sink. It uses the correlation of data within the packet for applying the aggregation function on data generated by nodes. BHCDA shows significant improvement in packet delivery ratio (67.66% & 19.62%) and throughput (37.01 % & 17.16%) as compared with the state-of-the-art solutions (TTCDA and EECDA).

Dnyaneshwar, Mantri; Prasad, Neeli R.

2013-01-01

415

Bisection (Band)Width of Product Networks with Application to Data Centers  

CERN Document Server

The bisection width of interconnection networks has always been important in parallel computing, since it bounds the amount of information that can be moved from one side of a network to another, i.e., the bisection bandwidth. Finding its exact value has proven to be challenging for some network families. For instance, the problem of finding the exact bisection width of the multidimensional torus was posed by Leighton and has remained open for almost 20 years. In this paper we provide the exact value of the bisection width of the torus, as well as of several d-dimensional classical parallel topologies that can be obtained by the application of the Cartesian product of graphs. To do so, we first provide two general results that allow to obtain upper and lower bounds on the bisection width of a product graph as a function of some properties of its factor graphs. We also apply these results to obtain bounds for the bisection bandwidth of a d-dimensional BCube network, a recently proposed topology for data center...

Aroca, Jordi Arjona

2012-01-01

416

Bandwidth Optimization Design of a Multi Degree of Freedom MEMS Gyroscope.  

UK PubMed Central (United Kingdom)

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 designed, and simulations indicate that when the operating frequency is set at 12.59 kHz, the flat frequency response region of the sense mode can be designed as narrow as 80 Hz, and the amplification factor of the sense mode at the operating frequency is up to 91, which not only protects the amplification factor from instability against process and temperature variations, but also sacrifices less performance. An experiment is also carried out to demonstrate the validity of the design. The multi-DOF gyroscope with the proposed weak coupling spring system is capable of achieving a good tradeoff between robustness and the performance.

Si C; Han G; Ning J; Yang F

2013-01-01

417

High-bandwidth squeezed light at 1550 nm from a compact monolithic PPKTP cavity.  

UK PubMed Central (United Kingdom)

We report the generation of squeezed vacuum states of light at 1550 nm with a broadband quantum noise reduction of up to 4.8 dB ranging from 5 MHz to 1.2 GHz sideband frequency. We used a custom-designed 2.6 mm long biconvex periodically-poled potassium titanyl phosphate (PPKTP) crystal. It featured reflectively coated end surfaces, 2.26 GHz of linewidth and generated the squeezing via optical parametric amplification. Two homodyne detectors with different quantum efficiencies and bandwidths were used to characterize the non-classical noise suppression. We measured squeezing values of up to 4.8 dB from 5 to 100 MHz and up to 3 dB from 100 MHz to 1.2 GHz. The squeezed vacuum measurements were limited by detection loss. We propose an improved detection scheme to measure up to 10 dB squeezing over 1 GHz. Our results of GHz bandwidth squeezed light generation provide new prospects for high-speed quantum key distribution.

Ast S; Mehmet M; Schnabel R

2013-06-01

418

Routing Scheme for Bandwidth Guaranteed Traffic in AMC-Enabled Wireless Mesh Networks  

Science.gov (United States)

Backbone network of the mobile networks, i.e. mobile backhaul networks, is an important part of mobile network system. With the decreasing size of mobile network system cells, it is considered next-generation mobile backhaul networks will form mesh topology. Most mobile backhaul networks are formed with microwave radios. To increase data rate, Adaptive Modulation and Coding (AMC) is used for wireless links. However, the data rate of each wireless link changes over time and leads to unexpected packet loss or traffic degradation. This paper proposes a routing scheme and methods for estimating the transmission parameters or modes of wireless links to route bandwidth guaranteed flows over mobile backhaul networks. Proposed routing scheme can reduce degradation of flows caused by unexpected changes of the data rate of wireless links. We evaluate our routing scheme when mode distribution of links follows normal, uniform and Poisson distributions. This paper shows mode estimation using mode history of link to estimate the link quality can route bandwidth guaranteed flows efficiently by choosing more stable links for the path.

Nishioka, Jun; Yamano, Satoru

419

QoS Bandwidth Estimation Scheme for Delay Sensitive Applications in MANETs  

Directory of Open Access Journals (Sweden)

Full Text Available For last few years, MobileAd hoc Networks (MANETs) have attracted a great interest in case of wireless and multimedia technologies. Infrastructure less nature of MANETs makes Quality of Service (QoS) provisioning very challenging and important research aspect. To find a QoS constrained route from source to destination, we should be able to effectively determine the available resources throughout the route. The routing protocol is the most integral part of any type of QoS provisioning. It has to decide which route is able to fulfill the requirement of the desired QoS for specified application. In this paper, modification has been proposed in the existing MANET protocols to get the information about total path bandwidth for delay sensitive applications. It uses modified technique for bandwidth estimation and for route maintenance. The proposed protocol is implemented and simulated using NS-2 simulator. Results of our implementation show that there is much improvement in overheads without any impact on overall end-to-end throughput.

Surjeet   Arun Parkash; Rajeev Tripathi

2013-01-01

420

Bandwidth optimization design of a multi degree of freedom MEMS gyroscope.  

Science.gov (United States)

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 designed, and simulations indicate that when the operating frequency is set at 12.59 kHz, the flat frequency response region of the sense mode can be designed as narrow as 80 Hz, and the amplification factor of the sense mode at the operating frequency is up to 91, which not only protects the amplification factor from instability against process and temperature variations, but also sacrifices less performance. An experiment is also carried out to demonstrate the validity of the design. The multi-DOF gyroscope with the proposed weak coupling spring system is capable of achieving a good tradeoff between robustness and the performance. PMID:23948872

Si, Chaowei; Han, Guowei; Ning, Jin; Yang, Fuhua

2013-08-14

 
 
 
 
421

Investigation of Bandwidth Requirement of Smart Meter Network Using OPNET Modeler  

Directory of Open Access Journals (Sweden)

Full Text Available 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 Engineering Tools (OPNET) Modeler is one of most powerful simulation tools for the analysis of communication networks. In this paper, several models of different structured smart meter networks were developed with network parameters which were connected with different communication links such as 10 BaseT and 100 BaseT in order to measure propagation delay, throughput, and utilization of the network. It was found that the propagation delay decreases with higher bandwidth. The other network parameters, namely network utilization and network throughput were also analysed. Based on the investigation, it is recommended that the 100 BaseT communication link is suitable for the smart meter network. The outcome of this paper provided a guideline to the future smart meter network developer so as to avoid catastrophic challenges faced by some of the distribution companies.

M. Rahman; Amanullah Mto

2013-01-01

422

Supporting Bandwidth Guarantee and Mobility for Real-Time Applications on Wireless LANs  

CERN Multimedia

The proliferation of IEEE 802.11-based wireless LANs opens up avenues for creation of several tetherless and mobility oriented services. Most of these services, like voice over WLAN, media streaming etc., generate delay and bandwidth sensitive traffic. These traffic flows require undisrupted network connectivity with some QoS guarantees. Unfortunately, there is no adequate support built into these wireless LANs towards QoS provisioning. Further, the network layer handoff latency incurred by mobile nodes in these wireless LANs is too high for real-time applications to function properly. In this paper, we describe a QoS mechanism, called Rether, to effectively support bandwidth guarantee on wireless LANs. Rether is designed to support the current wireless LAN technologies like 802.11b and 802.11a with a specific capability of being tailored for QoS oriented technology like 802.11e. We also describe a low-latency handoff mechanism which expedites network level handoff to provide real-time applications with an ad...

Sharma, S; Zhu, N; Peng, G; De, P; Chiueh, T; Sharma, Srikant; Gopalan, Kartik; Zhu, Ningning; Peng, Gang; De, Pradipta; Chiueh, Tzi-cker

2004-01-01

423

Phase loop bandwidth measurements on the advanced photon source 352 MHz rf systems  

Energy Technology Data Exchange (ETDEWEB)

Phase loop bandwidth tests were performed on the Advanced Photon Source storage ring 352-MHz rf systems. These measurements were made using the HP3563A Control Systems Analyzer, with the rf systems running at 30 kilowatts into each of the storage ring cavities, without stored beam. An electronic phase shifter was used to inject approximately 14 degrees of stimulated phase shift into the low-level rf system, which produced measureable response voltage in the feedback loops without upsetting normal rf system operation. With the PID (proportional-integral-differential) amplifier settings at the values used during accelerator operation, the measurement data revealed that the 3-dB response for the cavity sum and klystron power-phase loops is approximately 7 kHz and 45 kHz, respectively, with the cavities the primary bandwidth-limiting factor in the cavity-sum loop. Data were taken at various PID settings until the loops became unstable. Crosstalk between the two phase loops was measured.

Horan, D.; Nassiri, A.; Schwartz, C.

1997-08-01

424

Design of RFID Cloud Services in a Low Bandwidth Network Environment  

Directory of Open Access Journals (Sweden)

Full Text Available The use of Information and Communication Technologies has significantly improved the efficiency of modern supply chains. Existing IT architecture is too rigid to allow new technologies such as RFID technologies to be implemented. With the aid of virtualisation and integrated with cloud services, infrastructure hardware and network devices can be consolidated into a physical device, reducing the cost of ownership. However, for such cloud services model to work correctly, a high speed network is required between each site and the cloud service provider. This poses huge challenges for real?time system such as RFID?enabled supply chains. Since modern supply chains operate on a global platform, it is almost impossible to assure availability of high speed networks across the global supply chain. This paper proposes two solutions to supplement the virtualisation and cloud services model. A sub?cloud services solution, where each service is distributed across multiple hosts across different countries and regions is proposed to enhance accessibility to higher bandwidth networks. The second solution is the Queued Burst Device Compression system incorporates a compression service that compresses RFID data sets into much smaller packages. This solution is proved to work by a multiple?in?single?out queuing model and is suitable for low bandwidth networks such as GPRS and 3G wireless environmenst.

John P.T. Mo; William Lorchirachoonkul

2011-01-01

425

Estimating critical bandwidths of temporal sensitivity to low-frequency amplitude modulation.  

UK PubMed Central (United Kingdom)

Auditory filter bandwidths are measured for a temporal process using an amplitude-modulation detection task. The signal is a 200?Hz wide, sinusoidally amplitude-modulated band of noise centered within an unmodulated notched-noise masker. A modulation rate of 10?Hz is used to avoid possible information loss at more central processing levels for high modulation rates. Threshold functions are obtained for 10-14 notch widths for each of four different center frequencies (0.6, 1, 2, and 4?kHz) to determine the maximum notch width at which the masker has an effect. The ratio of center frequency to maximum notch width is ~2 at all center frequencies. It is proposed that the bandwidths observed in temporal tasks, which are consistently greater than expected from the viewpoint of critical band theory, be characterized as "temporal critical bands." This proposal does not oppose, but provides a complement to the traditional critical band obtained in tasks involving spectral discrimination.

Shim AI; Berg BG

2013-05-01

426

Deterministic Formulization of End-to-End Delay and Bandwidth Efficiency for Multicast Systems  

Directory of Open Access Journals (Sweden)

Full Text Available End-System multicasting (ESM) is a promising application-layer scheme that has been recently proposed for implementing multicast routing in the application layer as a practical alternative to the IP multicasting. Moreover, ESM is an efficient application layer solution where all the multicast functionality is shifted to the end users. However, the limitation in bandwidth and the fact that the message needs to be forwarded from host-to-host using unicast connection, and consequently incrementing the end-to-end delay of the transmission process, contribute to the price to pay for this new approach. Therefore, supporting high-speed real-time applications such as live streaming multimedia, videoconferencing, distributed simulations, and multiparty games require a sound understanding of these multicasting schemes such as IP multicast and ESM and the factors that might affect the end-user requirements. In this paper, we present both the analytical and the mathematical models for formalizing the end-to-end delay and the bandwidth efficiency of both IP and ESM multicast system. For the sake of the experimental verifications of the proposed models, numerical and simulation results are presented in this paper. Finally, the proposed formulization can be used to design and implement a more robust and efficient multicast systems for the future networks

Syed S. Rizvi; Aasia Riasat; Khaled M. Elleithy

2009-01-01

427

Scintillators for fiber optics: system sensitivity and bandwidth as a function of fiber length. [Nuclear explosions  

Energy Technology Data Exchange (ETDEWEB)

Scintillators have been employed for several years as ionizing radiation-to-light converters in plasma diagnostic experiments that utilize fiber optics. Until recently, nanosecond and subnanosecond scintillators were available only in the near ultraviolet. However, the bandwidth and transmission properties of fiber optics both strongly favor operation at longer wavelengths. More recently, nanosecond and subnanosecond scintillators with emission peaks around 480 nm have been reported. A time-resolved plasma-imaging experiment using one of these scintillators and 100 channels of graded-index fiber, each 500 m long, has been successfully tested on a nuclear event at the Nevada Test Site. During the past year we have developed several new scintillator systems with emission wavelengths more compatible with fiber optics and with response times in the nanosecond and subnanosecond time region. One scintillator, based on Kodak dye 14567 (DCM), has an emission maximum at 650 nm and a response time (FWHM) of 1.2 ns. Experimental data on system sensitivity and bandwidth versus fiber length are presented for three fluor-fiber systems. Data on fluor formulation, response time, and linearity-of-response are given, and a model for scintillator nonlinearity, based on solvent, radiation-induced, transient absorption, is presented.

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

1981-01-01

428

Mahanaxar: quality of service guarantees in high-bandwidth, real-time streaming data storage  

Energy Technology Data Exchange (ETDEWEB)

Large radio telescopes, cyber-security systems monitoring real-time network traffic, and others have specialized data storage needs: guaranteed capture of an ultra-high-bandwidth data stream, retention of the data long enough to determine what is 'interesting,' retention of interesting data indefinitely, and concurrent read/write access to determine what data is interesting, without interrupting the ongoing capture of incoming data. Mahanaxar addresses this problem. Mahanaxar guarantees streaming real-time data capture at (nearly) the full rate of the raw device, allows concurrent read and write access to the device on a best-effort basis without interrupting the data capture, and retains data as long as possible given the available storage. It has built in mechanisms for reliability and indexing, can scale to meet arbitrary bandwidth requirements, and handles both small and large data elements equally well. Results from our prototype implementation shows that Mahanaxar provides both better guarantees and better performance than traditional file systems.

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

2010-01-01

429

Fractal-Shaped Balun Using Composite Right/Left-Handed Transmission Line for Bandwidth Enhancement  

Science.gov (United States)

This article presents a fractal-shaped broadband balun based on the lumped-element composite right/left-handed transmission line (CRLH TL). The developed balun involved there -90° Koch-shaped microstrip branches and one +90° CRLH branch, features compact, excellent transmission performance and bandwidth enhancement. Closedform formulae for broadband strategy and general guide lines for fractal implementation are derived. For verification, a balun operated at 1.5 GHz is designed, fabricated and measured. Consistent results between simulation and measurement has validated this concept as well as the developed equations. The fabricated balun, with an occupied area of 17.7 × 24.8 mm2 corresponding to 12% of the area that its conventional counterpart occupies, exhibits a relative bandwidth of 93.3% ranging from 1.03 to 2.43 GHz. Across this frequency region, the return loss is better than 10 dB while the amplitude and phase imbalance varies within 1 dB and 4.2° respectively.

Xu, He-Xiu; Wang, Guang-Ming; Lu, Ke; Chen, Xin

2011-07-01

430

The importance of RF bandwidth for effective tagging in pulsed arterial spin labeling MRI at 9.4T.  

UK PubMed Central (United Kingdom)

The movement towards MRI at higher field strengths (>7T) has enhanced the appeal of arterial spin labeling (ASL) for many applications due to improved SNR of the measurements. Greater field strength also introduces increased magnetic susceptibility effects resulting in marked B(0) field inhomogeneity. Although B(0) field perturbations can be minimised by shimming over the imaging volume, marked field inhomogeneity is likely to remain within the labeling region for pulsed ASL (PASL). This study highlights a potential source of error in cerebral blood flow quantification using PASL at high field. We show that labeling efficiency in flow-sensitive alternating inversion recovery (FAIR) displayed marked sensitivity to the RF bandwidth of the inversion pulse in a rat model at 9.4T. The majority of preclinical PASL studies have not reported the bandwidth of the inversion pulse. We show that a high bandwidth pulse of >?=?15?kHz was required to robustly overcome the field inhomogeneity in the labeling region at high field strength, which is significantly greater than the inversion bandwidth ~2-3?kHz used in previous studies. Unless SAR levels are at their limit, we suggest the use of a high bandwidth labeling pulse for most PASL studies.

Wells JA; Siow B; Lythgoe MF; Thomas DL

2012-10-01

431

Dynamic Bandwidth Allocation for Multiple Traffic Classes in IEEE 802.16e WiMax Networks: A Petrinet Approach  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: WiMAX supports multiple types of traffic such as data, voice and video. Each flow requires a certain minimum bandwidth to achieve its QoS. Bandwidth allocation to traffic classes should be in such a way that fairness criteria is met with. Hence, we propose a dynamic bandwidth allocation mechanism to achieve fair and efficient allocation. Approach: We present a Generalized Stochastic Petri Net (GSPN) approach to model bandwidth allocation in Broadband Wireless Access (BWA) networks with multiple traffic classes. A dynamic weight assignment mechanism is proposed to enable fair bandwidth allocation among the competing traffic classes. Performance of the weight assignment mechanism is analytically evaluated using the GSPN model developed. Results: Results show performance improvement in terms of mean delay and normalized throughput of traffic classes compared to existing mechanisms. Simulation is carried out for different traffic rates. Analytical results are validated using simulations. Conclusion: Performance of the proposed system is evaluated in terms of mean delay and normalized system throughput. The model developed is generic and can be extended to any wireless network with multiple traffic classes.

S. Geetha; R. Jayaparvathy

2011-01-01

432

Wide-bandwidth, wide-beamwidth, high-resolution, millimeter-wave imaging for concealed weapon detection  

Science.gov (United States)

Active millimeter-wave imaging is currently being used for personnel screening at airports and other high-security facilities. The cylindrical imaging techniques used in the deployed systems are based on licensed technology developed at the Pacific Northwest National Laboratory. The cylindrical and a related planar imaging technique form three-dimensional images by scanning a diverging beam swept frequency transceiver over a two-dimensional aperture and mathematically focusing or reconstructing the data into three-dimensional images of the person being screened. The resolution, clothing penetration, and image illumination quality obtained with these techniques can be significantly enhanced through the selection of the aperture size, antenna beamwidth, center frequency, and bandwidth. The lateral resolution can be improved by increasing the center frequency, or it can be increased with a larger antenna beamwidth. The wide beamwidth approach can significantly improve illumination quality relative to a higher frequency system. Additionally, a wide antenna beamwidth allows for operation at a lower center frequency resulting in less scattering and attenuation from the clothing. The depth resolution of the system can be improved by increasing the bandwidth. Utilization of extremely wide bandwidths of up to 30 GHz can result in depth resolution as fine as 5 mm. This wider bandwidth operation may allow for improved detection techniques based on high range resolution. In this paper, the results of an extensive imaging study that explored the advantages of using extremely wide beamwidth and bandwidth are presented, primarily for 10-40 GHz frequency band.

Sheen, David M.; Fernandes, Justin L.; Tedeschi, Jonathan R.; McMakin, Douglas L.; Jones, A. Mark; Lechelt, Wayne M.; Severtsen, Ronald H.

2013-05-01

433

Trade-Off between Bandwidth and Number of Array Elements in the Performance Enhancement of Passive Fathometer  

Directory of Open Access Journals (Sweden)

Full Text Available Improved signal to noise ratio (SNR) and resolution of the ambient noise cross-correlation function (NCF) between two points help in the estimation of bottom profile of the ocean. One of the main requirements of the improvement of the SNR and resolution is collection of a large amount of data. These large amounts of data can be achieved by recording a large bandwidth ambient noise or using an array of hydrophones. This paper evaluates the performance of the array processing and compares it to the large bandwidth technique in terms of SNR and resolution of NCF. It is shown that the large bandwidth technique gives better SNR and resolution compared to the array processing technique under certain conditions. The outcome of this article finds application in the enhanced estimation of the passive fathometer.

Jahangir Alam; E. H. Huntington; M. R. Frater

2013-01-01

434

An Experimental Study of the Printed-Circuit Elliptic Dipole Antenna with 1.5-16 GHz Bandwidth  

Directory of Open Access Journals (Sweden)

Full Text Available Printed-circuit board (PCB) elliptic antennas with useful bandwidth exceeding 10:1 ratio are suitable for wideband radar, wireless ultra wideband (UWB) and other wireless communication applications. We present wideband PCB elliptic dipole antennas which are capable of achieving the bandwidth requirements for all the applications. A set of elliptic dipole antennas with varying eccentricities have been fabricated for demonstration. We find one specific size (specific eccentricity) dipole that can yield an impressive 1.5-16 bandwidth exceeding the currently available. A couple of elliptic dipole antennas suitable for UWB application have been presented. We have measured swept frequency response, impedance and radiation patterns of all dipoles. An empirical formula is given for calculating the starting resonant frequency within the operating band. The calculated values are found in good agreement with measured results.

Chun-Chi LEE; Hsin-Sheng HUANG; Cheng-Da YANG; Chia-Wei WANG

2008-01-01

435

Incident IR Bandwidth Effects on Efficiency and Shaping for Third Harmonic Generation of Quasi-Rectangular UV Longitudinal Profiles  

Energy Technology Data Exchange (ETDEWEB)

The photocathode of the proposed LCLS RF Photoinjector will be irradiated by uv laser light which is generated as the third harmonic of incident fundamental ir laser light. We have investigated quantitatively the effect of input ir spectral bandwidth on the exiting longitudinal intensity profiles, energy conversion efficiencies and spectral bandwidths that characterize the third harmonic generation (THG) process with a pair of crystals. These profiles, efficiencies and bandwidths include the residual fundamental and residual second harmonic light exiting the second crystal. The intrinsic acceptance bandwidth for THG is determined by crystal material and thickness as well as the type of phase matching that is used. For our case of BBO material with type I phase matching these bandwidths are approximately 0.9 nm*cm and 0.1 nm*cm for second and third harmonic generation respectively. Consequently for fixed crystal thicknesses and a fixed input ir longitudinal profile, the specified input ir bandwidth will determine the profiles, efficiencies and bandwidths exiting the second crystal. The results reported here are predictions of the SNLO code that is available as 'freeware' from the Sandia National Laboratories. It has been modified for this work. It is critical to note that this modification has enabled us to generate SNLO predictions of the 'coupled' case in which the output of the first crystal is used as input to the second crystal. Our focus is the dependence of uv longitudinal intensity profile and THG efficiency on the input ir bandwidth and crystal thicknesses. We include here cases that best illustrate input bandwidth effects. The criteria for selection of reported cases are highest efficiency generation of quasi-rectangular uv profiles with proportional intensity ripple less than 5% rms on the plateau of the pulse. Maximizing THG efficiency typically amounts to maximizing the crystal thicknesses with the longitudinal profile constraint. The specified incident ir longitudinal profile is quasi-rectangular (i.e. nonzero risetime and falltime with small intensity variation on the plateau) with a 10 psec pulse duration (FWHM). By assumption, this profile has been established upstream of the crystals at the fundamental ir wavelength. The simplest possible optical configuration is used in this work as shown in figure 1. The first crystal is the site of second harmonic generation (SHG) driven by the incident ir irradiation of central wavelength, 800nm. Downstream of the first crystal, the second crystal is the site of third harmonic generation (THG) which occurs by sum frequency mixing. Inter-crystal optics (such as a half waveplate) are assumed to be lossless at the fundamental and second harmonic wavelengths. As shown in figure 1, a portion of the incident ir irradiation is not sequestered from the first crystal for subsequent THG in the second crystal. Also, quasi-phase matching configurations and other complex compensation schemes have not been investigated at this point. The simplistic geometry better elucidates the intrinsic acceptance bandwidth limitations imposed b