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Sample records for asymmetric coherent transmission

  1. Asymmetric coherent transmission for single particle diode and gyroscope

    OpenAIRE

    S. Yang; Song, Z; Sun, C.P.

    2009-01-01

    We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The g...

  2. Asymmetric coherent transmission for single particle diode and gyroscope

    CERN Document Server

    Yang, S; Sun, C P

    2009-01-01

    We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The general result is also valid for a neutral particle system since the effective magnetic flux may be implemented by a globe rotation. This observation means that the three-site system can serve as an orientation measuring gyroscope due to the approximate linear dependence of the current difference of two output leads on the rotational angular velocity.

  3. Terahertz metamaterial with asymmetric transmission

    CERN Document Server

    Singh, R; Menzel, C; Rockstuhl, C; Azad, A K; Cheville, R A; Lederer, F; Zhang, W; Zheludev, N I

    2009-01-01

    We show for the first time that a planar metamaterial, an array of coupled metal split-ring resonators with a unit cell lacking mirror symmetry, exhibits asymmetric transmission of terahertz radiation propagating through it in opposite directions. This intriguing effect, that is compatible with Lorentz reciprocity and time-reversal, depends on a directional difference in conversion efficiency of the incident circularly polarized wave into one of opposite handedness, that is only possible in lossy low-symmetry planar chiral metamaterials. We show that asymmetric transmission is linked to excitation of enantiomerically sensitive plasmons, these are induced charge-field excitations that depend on the mutual handedness of incident wave and metamaterial pattern. Various bands of positive, negative and zero phase and group velocities have been identified indicating the opportunity to develop polarization sensitive negative index and slow light media based on such metamaterials.

  4. Asymmetric acoustic transmission in multiple frequency bands

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Hong-xiang, E-mail: jsdxshx@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Shou-qi, E-mail: Shouqiy@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Zhang, Shu-yi [Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  5. Asymmetric DSL Technology of Signal Transmission

    Directory of Open Access Journals (Sweden)

    Dražen Kovačević

    2005-05-01

    Full Text Available Asymmetric flow of information is the key feature of theADSL (Asymmetric Digital Subscriber Loop technology, i.e.higher data transmission rate towards the user than from theuser towards the network. Characteristic is the short messagesending by the user with a certain request to the se!Ver. These!Ver responds to the request by a significantly longer messageof various electronic forms (data, digitized speech, pictures orvideo. Therefore, this technology is most often used by smalland medium users. ADSL is currently the only commerciallyavailable DSL technology which is still experiencing the breakthroughon the seiVice market. It enables faster access to theInternet, LAN (Local Area Network, videoconferencing, VoD(Video on Demand and interactive multimedia. In order tostandardize such se/Vices, the !TU (International TelecommunicationsUnion G. 992.1 (standardized DMT-discrete multi-tone line coding technology and ANSJ (American NationalStandards Institution Tl.413-95!98 are used for ADSL. DMT(Discrete Multi Tone, as the more popular one, uses the linecoding technique, which splits a certain frequency range intoseveral sub-channels. Most of these sub-channels are used forupstream and downstream transmission of speech and data,whereas some are used as pilot signals or kept in rese/Ve. Suchmodulation technique expands the frequency spectrum, allowingthe usage ofbroadband se/Vices per one pair of wires. In thisway the sharing of speech and data se/Vice transmission is realized.

  6. Asymmetric acoustic transmission in graded beam

    Science.gov (United States)

    Jing, Li; Wu, Jiu Hui; Guan, Dong; Lu, Kuan; Gao, Nansha; Songhua, Cao

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  7. Asymmetric transmission: a generic property of lossy periodic interfaces

    CERN Document Server

    Plum, E; Zheludev, N I

    2010-01-01

    Asymmetric transmission of circularly polarized waves is a well-established property of lossy, anisotropic, two-dimensionally chiral patterns. Here we show that asymmetric transmission can be observed for oblique incidence onto any lossy periodically structured plane. Our results greatly expand the range of natural and artificial materials in which directionally asymmetric transmission can be expected making it a cornerstone electromagnetic effect rather than a curiosity of planar chiral metamaterials. Prime candidates for asymmetric transmission at oblique incidence are rectangular arrays of plasmonic spheres or semiconductor quantum dots, lossy double-periodic gratings and planar metamaterial structures.

  8. Role of Asymmetric Clusters in Desynchronization of Coherent Motion

    DEFF Research Database (Denmark)

    Popovych, O.; Maistrenko, Y.; Mosekilde, Erik

    2002-01-01

    The transition from full synchronization (coherent motion) to two-cluster dynamics is studied for a system of N globally coupled logistic maps. When increasing the nonlinearity parameter of the individual map, new periodic and strongly asymmetric two-cluster states are found to emerge in the same...... order as the periodic windows arise in the logistic map. These strongly asymmetric two-cluster states are generally first to stabilize when reducing the coupling strength. Similar phenomena are also observed for a system of globally coupled Henon maps.......The transition from full synchronization (coherent motion) to two-cluster dynamics is studied for a system of N globally coupled logistic maps. When increasing the nonlinearity parameter of the individual map, new periodic and strongly asymmetric two-cluster states are found to emerge in the same...

  9. Narrowband coherent data transmission-mobile

    OpenAIRE

    Bateman, A.; McGeehan, JP

    1987-01-01

    The authors investigate the practical realization of pilot-based channel equalization systems, their integration into coherent data demodulation techniques, and their performance as compared with coherent data systems utilizing the data signal alone. Most of the analysis is associated with the land mobile environment, which is arguably the most hostile environment for data transmission. However many of the results and remarks made are equally applicable to the aeronautical, sea, and satellite...

  10. Complete polarimetry on the asymmetric transmission through subwavelength hole arrays.

    Science.gov (United States)

    Arteaga, Oriol; Maoz, Ben M; Nichols, Shane; Markovich, Gil; Kahr, Bart

    2014-06-02

    Dissymmetric, periodically nanostructured metal films can show non-reciprocal transmission of polarized light, in apparent violation of the Lorentz reciprocity theorem. The wave vector dependence of the extraordinary optical transmission in gold films with square and oblique subwavelength hole arrays was examined for the full range of polarized light input states. In normal incidence, the oblique lattice, in contrast to square lattice, showed strong asymmetric, non-reciprocal transmission of circularly polarized light. By analyzing the polarization of the input and the output with a complete Mueller matrix polarimeter the mechanisms that permits asymmetric transmission while preserving the requirement of electromagnetic reciprocity is revealed: the coupling of the linear anisotropies induced by misaligned surface plasmons in the film. The square lattice also shows asymmetric transmission at non-normal incidence, whenever the plane of incidence does not coincide with a mirror line.

  11. Study of Rayleigh-backscattering induced coherence collapse in an asymmetric DFB FL sensor

    Science.gov (United States)

    Liu, Wen; Ma, Lina; Hu, Zhengliang; Feng, Ying; Yang, Huayong

    2016-09-01

    Rayleigh-back scattering induced coherence collapse of an asymmetric distributed feedback fiber laser (DFB FL) sensor is investigated using a composite cavity model. The coherence collapse threshold condition of the asymmetric DFB FL sensor is measured. The DFB FL sensor shows different dynamic behaviors in different pump configurations. According to the asymmetric behavior to the external optical feedback, a novel method to find the actual phase shift position of the asymmetric DFB FL sensor is presented.

  12. Design and Transmission Analysis of an Asymmetrical Spherical Parallel Manipulator

    DEFF Research Database (Denmark)

    Wu, Guanglei; Caro, Stéphane; Wang, Jiawei

    2015-01-01

    This paper presents an asymmetrical spherical parallel manipulator and its transmissibility analysis. This manipulator contains a center shaft to both generate a decoupled unlimited-torsion motion and support the mobile platform for high positioning accuracy. This work addresses the transmission ...

  13. Multiband Asymmetric Transmission of Airborne Sound by Coded Metasurfaces

    Science.gov (United States)

    Xie, Boyang; Cheng, Hua; Tang, Kun; Liu, Zhengyou; Chen, Shuqi; Tian, Jianguo

    2017-02-01

    We present the design, characterization, and theoretical and experimental demonstration of multiband asymmetric transmission of airborne sound using an ultrathin coded metasurface formed by an alternating arrangement of the coding elements 0 and 1. The asymmetric transmission effect can be easily controlled to selectively achieve off and on by coding different patterns. Both frequency- and angle-selective transmission is discussed. The proposed multiband asymmetric transmission stems from the constructive and destructive interferences of acoustic-wave coupling between the coded elements. The experimental results are in relative agreement with numerical simulations. This work opens an alternative path for ultrathin acoustic-device design and shows promise for application in acoustic rectification and noise control.

  14. Transmission of asymmetric coupling double-ring resonator

    Science.gov (United States)

    Zhao, C. Y.; Tan, W. H.

    2015-02-01

    Based on the asymmetry between waveguide and double ring, the transmission and phase characteristics of coupled double-ring resonators are analyzed systemically. It is shown that the initial detuning determines the shape of transmission spectrum. The transmission spectrum of all-optical analog to electromagnetic inducted transparency (EIT) is controlled by tuning the asymmetric coupled parameter and loss. With the increasing of asymmetric coupled parameter, the transmission spectrum changes from EIT-like profile to Lorenz profile. The EIT-like transmission spectrum results from the interference between two Lorenz profiles. With the increasing of the loss, the transmission spectrum full frequency width at half-maximum broadens and its peak declines. The detuning and loss also make significant influences on the phase profile.

  15. Performance of JPEG Image Transmission Using Proposed Asymmetric Turbo Code

    Directory of Open Access Journals (Sweden)

    Siddiqi Mohammad Umar

    2007-01-01

    Full Text Available This paper gives the results of a simulation study on the performance of JPEG image transmission over AWGN and Rayleigh fading channels using typical and proposed asymmetric turbo codes for error control coding. The baseline JPEG algorithm is used to compress a QCIF ( "Suzie" image. The recursive systematic convolutional (RSC encoder with generator polynomials , that is, (13/11 in decimal, and 3G interleaver are used for the typical WCDMA and CDMA2000 turbo codes. The proposed asymmetric turbo code uses generator polynomials , that is, (13/11; 13/9 in decimal, and a code-matched interleaver. The effect of interleaver in the proposed asymmetric turbo code is studied using weight distribution and simulation. The simulation results and performance bound for proposed asymmetric turbo code for the frame length , code rate with Log-MAP decoder over AWGN channel are compared with the typical system. From the simulation results, it is observed that the image transmission using proposed asymmetric turbo code performs better than that with the typical system.

  16. Performance of JPEG Image Transmission Using Proposed Asymmetric Turbo Code

    Directory of Open Access Journals (Sweden)

    Mohamad Yusoff Alias

    2007-01-01

    Full Text Available This paper gives the results of a simulation study on the performance of JPEG image transmission over AWGN and Rayleigh fading channels using typical and proposed asymmetric turbo codes for error control coding. The baseline JPEG algorithm is used to compress a QCIF (176×144 “Suzie” image. The recursive systematic convolutional (RSC encoder with generator polynomials (1,D3+D2+1/D3+D+1, that is, (13/11 in decimal, and 3G interleaver are used for the typical WCDMA and CDMA2000 turbo codes. The proposed asymmetric turbo code uses generator polynomials (1,D3+D2+1/D3+D+1;D3+D2+1/D3+1, that is, (13/11; 13/9 in decimal, and a code-matched interleaver. The effect of interleaver in the proposed asymmetric turbo code is studied using weight distribution and simulation. The simulation results and performance bound for proposed asymmetric turbo code for the frame length N=400, code rate r=1/3 with Log-MAP decoder over AWGN channel are compared with the typical system. From the simulation results, it is observed that the image transmission using proposed asymmetric turbo code performs better than that with the typical system.

  17. Digital processing optical transmission and coherent receiving techniques

    CERN Document Server

    Binh, Le Nguyen

    2013-01-01

    With coherent mixing in the optical domain and processing in the digital domain, advanced receiving techniques employing ultra-high speed sampling rates have progressed tremendously over the last few years. These advances have brought coherent reception systems for lightwave-carried information to the next stage, resulting in ultra-high capacity global internetworking. Digital Processing: Optical Transmission and Coherent Receiving Techniques describes modern coherent receiving techniques for optical transmission and aspects of modern digital optical communications in the most basic lines. The

  18. Asymmetrical coupled coplanar-type transmission lines with anisotropic substrates

    Science.gov (United States)

    Kitazawa, T.; Hayashi, Y.; Mittra, R.

    1986-07-01

    Various types of transmission lines with anisotropic substances were investigated for use in microwave and millimeter wave integrated circuits. These include single and coupled striplines, slot lines, and coplanar-type transmission lines. The coplanar-type transmission lines (CTLs) are promising because of their easy adaptation to shunt element connections. The application of coupled coplanar-type transmission lines (C-CTLs) were studied based on the quasistatic and hybrid mode formulations and accurate numerical values are available for the cases with isotropic and/or anisotropic substrates. However, most of them assume structural symmetry. The theoretical approach for the asymmetrical version is available only for the propagation constant of the case with a single isotropic substrate. The analytical method for the general structure of asymmetrical C-CTLs with an anisotropic substrate. This method includes both the hybrid mode and the quasistatic formulations and is useful for accurately computing the characteristics impedances as well as propagation constants of various types of assymetrical C-CTLs.

  19. Optical nonreciprocal transmission in an asymmetric silicon photonic crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zheng; Chen, Juguang; Ji, Mengxi; Huang, Qingzhong; Xia, Jinsong; Wang, Yi, E-mail: yingwu2@126.com, E-mail: ywangwnlo@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wu, Ying, E-mail: yingwu2@126.com, E-mail: ywangwnlo@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2015-11-30

    An optical nonreciprocal transmission (ONT) is realized by employing the nonlinear effects in a compact asymmetric direct-coupled nanocavity-waveguide silicon photonic crystal structure with a high loaded quality factor (Q{sub L}) of 42 360 and large extinction ratio exceeding 30 dB. Applying a single step lithography and successive etching, the device can realize the ONT in an individual nanocavity, alleviating the requirement to accurately control the resonance of the cavities. A maximum nonreciprocal transmission ratio of 21.1 dB as well as a working bandwidth of 280 pm in the telecommunication band are obtained at a low input power of 76.7 μW. The calculated results by employing a nonlinear coupled-mode model are in good agreement with the experiment.

  20. Asymmetric transmission of surface plasmon polaritons on planar gratings

    CERN Document Server

    Kuzmiak, Vladimir

    2016-01-01

    We describe a surface structure consisting of a metal-air interface where the metallic part consists of two metallic segments with a periodic modulation of the interface between them. Such a structure possesses a different transmissivity for a surface plasmon polariton incident on it from one side of it than it has for a surface plasmon polariton incident on it from the opposite side. This asymmetric transmission of a surface plasmon polariton is based on the suppression of the zero-order Bragg beam which, for a certain value of the modulation depth, is not transmitted through the structure, while the diffraction efficiencies of the +1 and -1 Bragg beams can be modified by varying the period of grating and/or the angle of incidence. For a certain range of the incidence angle one can observe asymmetry in transmittance for the -1 mode while the +1 mode is completely suppressed. By varying the material and geometrical parameters of the diffractive structure one can control the contrast transmission that characte...

  1. Asymmetric Return and Volatility Transmission in Conventional and Islamic Equities

    Directory of Open Access Journals (Sweden)

    Zaghum Umar

    2017-03-01

    Full Text Available Abstract: This paper analyses the interdependence between Islamic and conventional equities by taking into consideration the asymmetric effect of return and volatility transmission. We empirically investigate the decoupling hypothesis of Islamic and conventional equities and the potential contagion effect. We analyse the intra-market and inter-market spillover among Islamic and conventional equities across three major markets: the USA, the United Kingdom and Japan. Our sample period ranges from 1996 to 2015. In addition, we segregate our sample period into three sub-periods covering prior to the 2007 financial crisis, the crisis period and the post-crisis period. We find weak support for the decoupling hypothesis during the post-crisis period.

  2. Damage Detection and Quantification Using Transmissibility Coherence Analysis

    Directory of Open Access Journals (Sweden)

    Yun-Lai Zhou

    2015-01-01

    Full Text Available A new transmissibility-based damage detection and quantification approach is proposed. Based on the operational modal analysis, the transmissibility is extracted from system responses and transmissibility coherence is defined and analyzed. Afterwards, a sensitive-damage indicator is defined in order to detect and identify the severity of damage and compared with an indicator developed by other authors. The proposed approach is validated on data from a physics-based numerical model as well as experimental data from a three-story aluminum frame structure. For both numerical simulation and experiment the results of the new indicator reveal a better performance than coherence measure proposed in Rizos et al., 2008, Rizos et al., 2002, Fassois and Sakellariou, 2007, especially when nonlinearity occurs, which might be further used in real engineering. The main contribution of this study is the construction of the relation between transmissibility coherence and frequency response function coherence and the construction of an effective indicator based on the transmissibility modal assurance criteria for damage (especially for minor nonlinearity detection as well as quantification.

  3. Broadband Coherent Enhancement of Transmission and Absorption in Disordered Media

    CERN Document Server

    Hsu, Chia Wei; Bromberg, Yaron; Stone, A Douglas; Cao, Hui

    2015-01-01

    We study the optimal diffusive transmission and absorption of broadband or polychromatic light in a disordered medium. By introducing matrices describing broadband transmission and reflection, we formulate an extremal eigenvalue problem where the optimal input wavefront is given by the corresponding eigenvector. We show analytically that a single wavefront can exhibit strongly enhanced total transmission or total absorption across a bandwidth that is orders of magnitude broader than the spectral correlation width of the medium, due to long-range correlations in coherent diffusion. We find excellent agreement between the analytic theory and numerical simulations.

  4. Coherent data transmission with microresonator Kerr frequency combs

    CERN Document Server

    Pfeifle, Joerg; Wegner, Daniel; Brasch, Victor; Herr, Tobias; Hartinger, Klaus; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J; Koos, Christian

    2013-01-01

    Optical frequency combs enable coherent data transmission on hundreds of wavelength channels and have the potential to revolutionize terabit communications. Generation of Kerr combs in nonlinear integrated microcavities represents a particularly promising option enabling line spacings of tens of GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr combs may exhibit strong phase noise and multiplet spectral lines, and this has made high-speed data transmission impossible up to now. Recent work has shown that systematic adjustment of pump conditions allows generating low phase-noise Kerr combs with singlet spectral lines. Here, by employing an integrated Si3N4 microresonator, we demonstrate that Kerr combs are suited for coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the optical source. In our experiment, we encode a data stream of 392 Gbit/s on subsequent lines of a Kerr comb using quadrature phase shift keying (...

  5. Reflection and transmission calculations in a multilayer structure with coherent, incoherent, and partially coherent interference, using the transmission line method.

    Science.gov (United States)

    Stathopoulos, N A; Savaidis, S P; Botsialas, A; Ioannidis, Z C; Georgiadou, D G; Vasilopoulou, M; Pagiatakis, G

    2015-02-20

    A generalized transmission line method (TLM) that provides reflection and transmission calculations for a multilayer dielectric structure with coherent, partial coherent, and incoherent layers is presented. The method is deployed on two different application fields. The first application of the method concerns the thickness measurement of the individual layers of an organic light-emitting diode. By using a fitting approach between experimental spectral reflectance measurements and the corresponding TLM calculations, it is shown that the thickness of the films can be estimated. The second application of the TLM concerns the calculation of the external quantum efficiency of an organic photovoltaic with partially coherent rough interfaces between the layers. Numerical results regarding the short circuit photocurrent for different layer thicknesses and rough interfaces are provided and the performance impact of the rough interface is discussed in detail.

  6. Multi-band asymmetric acoustic transmission in a bended waveguide with multiple mechanisms

    Science.gov (United States)

    Huang, Yu-lei; Sun, Hong-xiang; Xia, Jian-ping; Yuan, Shou-qi; Ding, Xin-lei

    2016-07-01

    We report the realization of a multi-band device of the asymmetric acoustic transmission by placing a phononic crystal inside a bended waveguide immersed in water, as determined both experimentally and numerically. The asymmetric acoustic transmission exists in three frequency bands below 500 kHz induced by multiple mechanisms. Besides the band gap of the phononic crystal, we also introduce the deaf mode and interaction between the phononic crystal and waveguide. More importantly, this asymmetric transmission can be systematically controlled by mechanically rotating the square rods of the phononic crystal. The device has the advantages of multiple band, broader bandwidth, and adjustable property, showing promising applications in ultrasonic devices.

  7. Tunable asymmetric transmission of THz wave through a graphene planar chiral structure

    CERN Document Server

    Zhao, Junyang; Zhu, Zhihong; Yuan, Xiaodong; Qin, Shiqiao

    2015-01-01

    In this letter, we show that asymmetric transmission of circularly polarized waves through a nanostructured planar chiral graphene film can be observed in terahertz range. The asymmetric transmission effect of monatomic layer graphene closely resembles that of metallic planar chiral nanostructures which has previously been demonstrated. And the relative enantiomeric difference in the total transmission varies with the change of graphene's Fermi level. The plasmonic excitation in the graphene nanostructure is the enantiometically sensitive which is asymmetric for opposite propagating directions. This phenomenon will deepen our understanding of light-matter interactions in planar chiral structures and may find applications in polarization-sensitive devices, sensors, detectors and other areas.

  8. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial

    Science.gov (United States)

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-02-01

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities.

  9. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial

    Science.gov (United States)

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-01-01

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities. PMID:28202903

  10. Loss Aversion and the Asymmetric Transmission of Monetary Policy

    DEFF Research Database (Denmark)

    Santoro, Emiliano; Petrella, Ivan; Pfajfar, Damjan

    2014-01-01

    There is widespread evidence that monetary policy exerts asymmetric effects on output over contractions and expansions in economic activity, while price responses display no sizeable asymmetry. To rationalize these facts we develop a dynamic general equilibrium model where households’ utility...

  11. Asymmetric acoustic transmission through near-zero-index and gradient-index metasurfaces

    Science.gov (United States)

    Shen, Chen; Xie, Yangbo; Li, Junfei; Cummer, Steven A.; Jing, Yun

    2016-05-01

    We present a design of acoustic metasurfaces yielding asymmetric transmission within a certain frequency band. The design consists of a layer of gradient-index metasurface and a layer of low refractive index metasurface. Incident waves are controlled in a wave vector dependent manner to create strong asymmetric transmission. Numerical simulations show that the approach provides high transmission contrast between the two incident directions within the designed frequency band. This is further verified by experiments. Compared to previous designs, the proposed approach yields a compact and planar device. Our design may find applications in various scenarios such as noise control and therapeutic ultrasound.

  12. Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yuan; Deng, Li [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Chen, Aixi, E-mail: aixichen@ecjtu.jx.cn [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Institute for Quantum Computing, University of Waterloo, Ontario N2L 3G1 (Canada)

    2015-02-15

    We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

  13. Influence of partial coherence on analyzer-based imaging with asymmetric Bragg reflection.

    Science.gov (United States)

    Modregger, Peter; Lübbert, Daniel; Schäfer, Peter; Richter, Jane; Köhler, Rolf; Baumbach, Tilo

    2009-07-06

    Image magnification via twofold asymmetric Bragg reflection (a setup called the "Bragg Magnifier") is a recently established technique allowing to achieve both sub-micrometer spatial resolution and phase contrast in X-ray imaging. The present article extends a previously developed theoretical formalism to account for partially coherent illumination. At a typical synchrotron setup polychromatic illumination is identified as the main influence of partial coherence and the implications on imaging characteristics are analyzed by numerical simulations. We show that contrast decreases by about 50% when compared to the monochromatic case, while sub-micrometer spatial resolution is preserved. The theoretical formalism is experimentally verified by correctly describing the dispersive interaction of the two orthogonal magnifier crystals, an effect that has to be taken into account for precise data evaluation.

  14. Transmission Probability of an Ultracold Atom in the Presence of Atomic Coherence

    Institute of Scientific and Technical Information of China (English)

    熊锦; 储开芹; 张智明

    2002-01-01

    We investigate the transmission probability of an ultracold V-type three-level atom passing through a micromaser cavity, in the presence of atomic coherence which is established by a coherent driving field. We show that the transmissibility of this micromaser system with the atomic coherence is better than that of the ordinary micromaser system without atomic coherence. When the driving field is strong enough, for any cavity length the ultracold atom can pass through the micromaser cavity freely.

  15. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    Science.gov (United States)

    Chen, Jung-San; Chang, I.-Ling; Huang, Wan-Ting; Chen, Lien-Wen; Huang, Guan-Hua

    2016-09-01

    This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  16. Robust determination of asymmetric side wall angles by means of coherent scanning Fourier scatterometry

    Science.gov (United States)

    Gödecke, M. L.; Peterhänsel, S.; Frenner, K.; Osten, W.

    2016-04-01

    Optical metrology of grating parameters with small scattering volumes, such as side wall angles (SWAs), is an indispensable prerequisite for accurate process control in modern semiconductor lithography. However, current scatterometric technologies suffer from low sensitivity towards SWA and hence, large measurement uncertainties. In order to overcome this deficit, we propose an interferometric sensor design which enables the precise determination of asymmetric SWAs with values that deviate by less than 1° from the ideal 90°. Our measurement technique is based on coherent scanning Fourier scatterometry, extended by a reference arm in Mach-Zehnder/Linnik configuration, a spatially-structured aperture stop in the object arm, and a self-referencing shearing element in front of the detector. We demonstrate the validity and advantages of our approach by presenting rigorous simulations of an exemplary silicon line grating with a grating period of 800 nm. Each grating line consists of a fine sub-grating with 40 nm pitch and 20 nm critical dimension. A variation of the major grating parameters height and critical dimension highlights the robustness of the method. Although our simulation study focuses on the determination of asymmetric SWAs, it should be noted that the presented technique features high sensitivity towards all kinds of structural asymmetries, such as floor tilt or asymmetric bottom roundings.

  17. ASYMMETRIC PRICE TRANSMISSION MODELING: THE IMPORTANCE OF MODEL COMPLEXITY AND THE PERFORMANCE OF THE SELECTION CRITERIA

    Directory of Open Access Journals (Sweden)

    Henry de-Graft Acquah

    2013-01-01

    Full Text Available Information Criteria provides an attractive basis for selecting the best model from a set of competing asymmetric price transmission models or theories. However, little is understood about the sensitivity of the model selection methods to model complexity. This study therefore fits competing asymmetric price transmission models that differ in complexity to simulated data and evaluates the ability of the model selection methods to recover the true model. The results of Monte Carlo experimentation suggest that in general BIC, CAIC and DIC were superior to AIC when the true data generating process was the standard error correction model, whereas AIC was more successful when the true model was the complex error correction model. It is also shown that the model selection methods performed better in large samples for a complex asymmetric data generating process than with a standard asymmetric data generating process. Except for complex models, AIC's performance did not make substantial gains in recovery rates as sample size increased. The research findings demonstrate the influence of model complexity in asymmetric price transmission model comparison and selection.

  18. An asymmetric resonant coupling wireless power transmission link for Micro-Ball Endoscopy.

    Science.gov (United States)

    Sun, Tianjia; Xie, Xiang; Li, Guolin; Gu, Yingke; Deng, Yangdong; Wang, Ziqiang; Wang, Zhihua

    2010-01-01

    This paper investigates the design and optimization of a wireless power transmission link targeting Micro-Ball Endoscopy applications. A novel asymmetric resonant coupling structure is proposed to deliver power to an endoscopic Micro-Ball system for image read-out after it is excreted. Such a technology enables many key medical applications with stringent requirements for small system volume and high power delivery efficiency. A prototyping power transmission sub-system of the Micro-Ball system was implemented. It consists of primary coil, middle resonant coil, and cube-like full-direction secondary receiving coils. Our experimental results proved that 200mW of power can be successfully delivered. Such a wireless power transmission capability could satisfy the requirements of the Micro-Ball based endoscopy application. The transmission efficiency is in the range of 41% (worst working condition) to 53% (best working condition). Comparing to conventional structures, Asymmetric Resonant Coupling Structure improves power efficiency by 13%.

  19. Underwater asymmetric acoustic transmission structure using the medium with gradient change of impedance

    Science.gov (United States)

    Bo, Hu; Jie, Shi; Sheng-Guo, Shi; Yu, Sun; Zhong-Rui, Zhu

    2016-02-01

    We propose an underwater asymmetric acoustic transmission structure comprised of two media each with a gradient change of acoustic impedance. By gradually increasing the acoustic impedances of the media, the propagating direction of the acoustic wave can be continuously bent, resulting in allowing the acoustic wave to pass through along the positive direction and blocking acoustic waves from the negative one. The main advantages of this structure are that the asymmetric transmission effect of this structure can be realized and enhanced more easily in water. We investigate both numerically and experimentally the asymmetric transmission effect. The experimental results show that a highly efficient asymmetric acoustic transmission can be yielded within a remarkable broadband frequency range, which agrees well with the numerical prediction. It is of potential practical significance for various underwater applications such as reducing vibration and noise. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204049 and 11204050), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1228), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20122304120023 and 20122304120011).

  20. Turbulent phase noise on asymmetric two-way ground-satellite coherent optical links

    Science.gov (United States)

    Robert, Clélia; Conan, Jean-Marc; Wolf, Peter

    2015-10-01

    Bidirectional ground-satellite laser links suffer from turbulence-induced scintillation and phase distortion. We study how turbulence impacts on coherent detection capacity and on the associated phase noise that restricts clock transfer precision. We evaluate the capacity to obtain a two-way cancellation of atmospheric effects despite the asymmetry between up and down link that limits the link reciprocity. For ground-satellite links, the asymmetry is induced by point-ahead angle and possibly the use, for the ground terminal, of different transceiver diameters, in reception and emission. The quantitative analysis is obtained thanks to refined end-to-end simulations under realistic turbulence and wind conditions as well as satellite cinematic. Simulations make use of the reciprocity principle to estimate both down and up link performance from wave-optics propagation of descending plane waves. These temporally resolved simulations allow characterising the coherent detection in terms of time series of heterodyne efficiency for different system parameters. We show Tip/Tilt correction on ground is mandatory at reception for the down link and as a pre-compensation of the up link. Good correlation between up and down phase noise is obtained even with asymmetric apertures of the ground transceiver and in spite of pointing ahead angle. The reduction to less than 1 rad2 of the two-way differential phase noise is very promising for clock transfer.

  1. A short model excitation of an asymmetric force free superconducting transmission line magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wake, M.; Sato, H.; /KEK, Tsukuba; Carcagno, R.; Foster, W.; Hays, S.; Kashikhin, V.; Oleck, A.; Piekarz, H.; Rabehl, R,; /Fermilab

    2005-09-01

    A short model of asymmetric force free magnet with single beam aperture was tested at Fermilab together with the excitation test of VLHC transmission line magnet. The design concept of asymmetric force free superconducting magnet was verified by the test. The testing reached up to 104 kA current and no indication of force imbalance was observed. Since the model magnet length was only 10cm, A 0.75m model was constructed and tested at KEK with low current to ensure the validity of the design. The cool down and the excitation at KEK were also successful finding very small thermal contraction of the conductor and reasonable field homogeneity.

  2. Focusing, refraction, and asymmetric transmission of elastic waves in solid metamaterials with aligned parallel gaps.

    Science.gov (United States)

    Su, Xiaoshi; Norris, Andrew N

    2016-06-01

    Gradient index (GRIN), refractive, and asymmetric transmission devices for elastic waves are designed using a solid with aligned parallel gaps. The gaps are assumed to be thin so that they can be considered as parallel cracks separating elastic plate waveguides. The plates do not interact with one another directly, only at their ends where they connect to the exterior solid. To formulate the transmission and reflection coefficients for SV- and P-waves, an analytical model is established using thin plate theory that couples the waveguide modes with the waves in the exterior body. The GRIN lens is designed by varying the thickness of the plates to achieve different flexural wave speeds. The refractive effect of SV-waves is achieved by designing the slope of the edge of the plate array, and keeping the ratio between plate length and flexural wavelength fixed. The asymmetric transmission of P-waves is achieved by sending an incident P-wave at a critical angle, at which total conversion to SV-wave occurs. An array of parallel gaps perpendicular to the propagation direction of the reflected waves stop the SV-wave but let P-waves travel through. Examples of focusing, steering, and asymmetric transmission devices are discussed.

  3. Transmission probability of the two-mode mazer with injected atomic coherence

    Institute of Scientific and Technical Information of China (English)

    袁春华; 张智明

    2005-01-01

    The transmission probability of the two-mode mazer injected with V-type three-level atoms is studied, and the effects of the atomic coherence on it are examined. It is shown that the atomic coherence can affect the transmission probability. In the plots of the atomic transmission probability versus the dimensionless centre-of-mass momentum, there are resonance peaks and non-resonance platforms. The heights of these resonance peaks and non-resonance platforms can be adjusted by the atomic coherence parameter and by the relative coupling strength of the two transition channels.

  4. Route-asymmetrical light transmission of a fiber-chip-fiber optomechanical system

    DEFF Research Database (Denmark)

    Liu, Li; Ding, Yunhong; Cai, Xinlun;

    2016-01-01

    In this paper, we proposed and experimentally demonstrated a route-asymmetrical light transmission scheme based on the thermal radiative effect, which means that forward and backward propagations of an optical device have different transmittances provided they are not present simultaneously......-wave (CW) light but also 10 Gbit/s on-off-keying (OOK) digital signals. Above mentioned unique features can be mostly attributed to the significant characteristics of the thermal radiative effect, which could cause a fiber displacement up to tens of microns. The powerful and significant thermal radiative...... effect opens up a new opportunity and method for route-asymmetrical light transmission. Moreover, this research may have important applications in all-optical systems, such as the optical limiters and ultra-low loss switches....

  5. The Transmission Interfaces Contribute Asymmetrically to the Assembly and Activity of Human P-glycoprotein.

    Science.gov (United States)

    Loo, Tip W; Clarke, David M

    2015-07-01

    P-glycoprotein (P-gp; ABCB1) is an ABC drug pump that protects us from toxic compounds. It is clinically important because it confers multidrug resistance. The homologous halves of P-gp each contain a transmembrane (TM) domain (TMD) with 6 TM segments followed by a nucleotide-binding domain (NBD). The drug- and ATP-binding sites reside at the interface between the TMDs and NBDs, respectively. Each NBD is connected to the TMDs by a transmission interface involving a pair of intracellular loops (ICLs) that form ball-and-socket joints. P-gp is different from CFTR (ABCC7) in that deleting NBD2 causes misprocessing of only P-gp. Therefore, NBD2 might be critical for stabilizing ICLs 2 and 3 that form a tetrahelix bundle at the NBD2 interface. Here we report that the NBD1 and NBD2 transmission interfaces in P-gp are asymmetric. Point mutations to 25 of 60 ICL2/ICL3 residues at the NBD2 transmission interface severely reduced P-gp assembly while changes to the equivalent residues in ICL1/ICL4 at the NBD1 interface had little effect. The hydrophobic nature at the transmission interfaces was also different. Mutation of Phe-1086 or Tyr-1087 to arginine at the NBD2 socket blocked activity or assembly while the equivalent mutations at the NBD1 socket had only modest effects. The results suggest that the NBD transmission interfaces are asymmetric. In contrast to the ICL2/3-NBD2 interface, the ICL1/4-NBD1 transmission interface is more hydrophilic and insensitive to mutations. Therefore the ICL2/3-NBD2 transmission interface forms a precise hydrophobic connection that acts as a linchpin for assembly and trafficking of P-gp.

  6. Tunable hard X-ray spectrometer utilizing asymmetric planes of a quartz transmission crystal.

    Science.gov (United States)

    Seely, John F; Henins, Albert; Feldman, Uri

    2016-05-01

    A Cauchois type hard x-ray spectrometer was developed that utilizes the (301) diffraction planes at an asymmetric angle of 23.51° to the normal to the surface of a cylindrically curved quartz transmission crystal. The energy coverage is tunable by rotating the crystal and the detector arm, and spectra were recorded in the 8 keV to 20 keV range with greater than 2000 resolving power. The high resolution results from low aberrations enabled by the nearly perpendicular angle of the diffracted rays with the back surface of the crystal. By using other asymmetric planes of the same crystal and rotating to selected angles, the spectrometer can operate with high resolution up to 50 keV.

  7. Asymmetric operation of AC power transmission systems : the key to optimizing power system reliability and economics

    Energy Technology Data Exchange (ETDEWEB)

    Marceau, R.J. [University of Ontario Inst. of Technology, Oshawa, ON (Canada); McGillis, D.T. [McGill Univ., Montreal, PQ (Canada). Dept. of Electrical and Computer Engineering]|[Concordia Univ., Montreal, PQ (Canada). Dept. of Electrical and Computer Engineering; Sana, A.R.

    2006-07-01

    This book provides an invaluable tool for professionals working in the field of electrical engineering and applied science. It presents a simple and cost-effective strategy to operate alternating current (AC) power transmission systems more reliably and economically. Typically, bulk power transmission systems are operated symmetrically. When a problem such as a short-circuit occurs on a 3-phase line on an individual phase, all 3 phases are taken out of service. Such a strategy is fundamentally inefficient, given that most faults are single-line-to-ground faults. The more effective operating strategy presented in this book is based on the concept of asymmetric operation, which defines the operation of a 3-phase AC transmission line as 3 independently operated entities. As such, a 3-phase line can be operated with 1 or 2 phases out of service for single-line transmission corridors or with 1 , 2 or 3 phases out of service in the case of multiple-line corridors. This approach also maintains 3-phase symmetrical operation at its extremities, thereby protecting loads and power plants from undesirable voltages and currents. The overall integrity of 3-phase transmission is maintained in terms of power delivery, balanced voltages and currents even in the event of failures in part of the transmission system. The result is improved security. 67 refs., 42 tabs., 73 figs., 2 appendices.

  8. Broadband Impedance Transformer Based on Asymmetric Coupled Transmission Lines in Nonhomogeneous Medium

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Krozer, Viktor; Meincke, Peter

    2007-01-01

    A new broadband quarter-wavelength impedance transformer based on an asymmetric coupled line section is presented. The bandwidth of the coupled line transformer is extended with the help of an interconnecting transmission line. An analytical model for the transformer is developed. The analysis...... of the structure reveals that a fractional bandwidth of more than 100% at –20 dB reflection level can be achieved with such a structure. An experimental transformer circuit has been designed, fabricated and tested. Theoretical and experimental results are fair agreement and confirm the established theory...

  9. Nonlinear phase noise in coherent optical OFDM transmission systems.

    Science.gov (United States)

    Zhu, Xianming; Kumar, Shiva

    2010-03-29

    We derive an analytical formula to estimate the variance of nonlinear phase noise caused by the interaction of amplified spontaneous emission (ASE) noise with fiber nonlinearity such as self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) in coherent orthogonal frequency division multiplexing (OFDM) systems. The analytical results agree very well with numerical simulations, enabling the study of the nonlinear penalties in long-haul coherent OFDM systems without extensive numerical simulation. Our results show that the nonlinear phase noise induced by FWM is significantly larger than that induced by SPM and XPM, which is in contrast to traditional WDM systems where ASE-FWM interaction is negligible in quasi-linear systems. We also found that fiber chromatic dispersion can reduce the nonlinear phase noise. The variance of the total phase noise increases linearly with the bit rate, and does not depend significantly on the number of subcarriers for systems with moderate fiber chromatic dispersion.

  10. Coherent Detection for 1550 nm, 5 Gbit/s VCSEL Based 40 km Bidirectional PON Transmission

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee; Rodes Lopez, Roberto; Zibar, Darko;

    2011-01-01

    Coherent detection of directly modulated 1550nm VCSELs in 5Gbit/s bidirectional 40km SSMF PON-links is presented. Receiver sensitivity of –37.3dBm after transmission is achieved with 30dB system margin, corresponding to 1:1024 passive powersplitting.......Coherent detection of directly modulated 1550nm VCSELs in 5Gbit/s bidirectional 40km SSMF PON-links is presented. Receiver sensitivity of –37.3dBm after transmission is achieved with 30dB system margin, corresponding to 1:1024 passive powersplitting....

  11. Giant and broadband circular asymmetric transmission based on two cascading polarization conversion cavities

    Science.gov (United States)

    Ji, Ruonan; Wang, Shao-Wei; Liu, Xingxing; Lu, Wei

    2016-04-01

    In this paper, a three-layered sandwiched metamaterial is proposed to achieve giant and broadband asymmetric transmission of circularly polarized waves at the near-infrared communication band. The metamaterial consists of two layers of identical 45° tilted chiral S-shaped metasurfaces sandwiched with a subwavelength metallic grating. Based on the delicate combination of broadband polarization conversion and a cavity-enhanced effect, the asymmetric parameter can reach a maximum value of 0.87 and over 0.6 in a wide range from 1.2 to 2.0 μm, which has not been found in previous reports. Furthermore, a perfect robustness to misalignments is obtained as the effect originated from function-independent cascading cavities, which effectively reduce the requirement of alignment precision in layer-by-layer photolithography processes. The proposed nanostructure has a great potential to be used as a circular polarization rotator or diode-like device in optical communication systems.In this paper, a three-layered sandwiched metamaterial is proposed to achieve giant and broadband asymmetric transmission of circularly polarized waves at the near-infrared communication band. The metamaterial consists of two layers of identical 45° tilted chiral S-shaped metasurfaces sandwiched with a subwavelength metallic grating. Based on the delicate combination of broadband polarization conversion and a cavity-enhanced effect, the asymmetric parameter can reach a maximum value of 0.87 and over 0.6 in a wide range from 1.2 to 2.0 μm, which has not been found in previous reports. Furthermore, a perfect robustness to misalignments is obtained as the effect originated from function-independent cascading cavities, which effectively reduce the requirement of alignment precision in layer-by-layer photolithography processes. The proposed nanostructure has a great potential to be used as a circular polarization rotator or diode-like device in optical communication systems. Electronic supplementary

  12. Waveform over fiber: DSP-aided coherent fiber-wireless transmission using millimeter and terahertz waves

    Science.gov (United States)

    Kanno, Atsushi; Tien Dat, Pham; Kuri, Toshiaki; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Kitayama, Ken-ichi

    2015-01-01

    In this paper, we describe seamless networks based on millimeter and terahertz wave radio links using waveform transfer over optical fibers. Coherent optical transceivers with digital signal processing provide transmission impairment compensation in both optical and radio sections, where devices for the signal processing are implemented at edges of the links. Waveforms, which include the modulation formats, the symbol rates, etc., are maintained in the entire links, to reduce transmission latency and energy consumption in the network.

  13. Ultrabroadband Design for Linear Polarization Conversion and Asymmetric Transmission Crossing X- and K- Band

    Science.gov (United States)

    Zhang, Linbo; Zhou, Peiheng; Chen, Haiyan; Lu, Haipeng; Xie, Haiyan; Zhang, Li; Li, En; Xie, Jianliang; Deng, Longjiang

    2016-09-01

    In this work, a high-efficiency and broadband reflective converter using ultrathin planar metamaterial (MM) composed of single-layered SRR is firstly realized. Numerical and experimental results demonstrate that the cross-polarization conversion reflectance above 0.84 is achieved from 8.6 to 18.6 GHz for linearly polarized (LP) incident waves under normal incidence. Subsequently, a multi-layered MM based on SRR enables a dramatic improvement of the recently demonstrated asymmetric transmission (AT) effect. Theoretical and measured results present that strong one-way transmission of two orthogonally polarized waves crossing C- and K- band has been observed. These two separated AT pass-bands have a function of selective polarization filter, which can be switched on/off by changing the polarization state of incident waves. The physical mechanisms are elucidated by taking advantage of electric fields and current distributions. Considering the broad bandwidth and the dual band, we believe that these two structures will be beneficial for designing polarization-controlled and selective transmission converter.

  14. Assessment of Corneal Epithelial Thickness in Asymmetric Keratoconic Eyes and Normal Eyes Using Fourier Domain Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    S. Catalan

    2016-01-01

    Full Text Available Purpose. To compare the characteristics of asymmetric keratoconic eyes and normal eyes by Fourier domain optical coherence tomography (OCT corneal mapping. Methods. Retrospective corneal and epithelial thickness OCT data for 74 patients were compared in three groups of eyes: keratoconic (n=22 and normal fellow eyes (n=22 in patients with asymmetric keratoconus and normal eyes (n=104 in healthy subjects. Areas under the curve (AUC of receiver operator characteristic (ROC curves for each variable were compared across groups to indicate their discrimination capacity. Results. Three variables were found to differ significantly between fellow eyes and normal eyes (all p<0.05: minimum corneal thickness, thinnest corneal point, and central corneal thickness. These variables combined showed a high discrimination power to differentiate fellow eyes from normal eyes indicated by an AUC of 0.840 (95% CI: 0.762–0.918. Conclusions. Our findings indicate that topographically normal fellow eyes in patients with very asymmetric keratoconus differ from the eyes of healthy individuals in terms of their corneal epithelial and pachymetry maps. This type of information could be useful for an early diagnosis of keratoconus in topographically normal eyes.

  15. Coherent optical DFT-spread OFDM transmission using orthogonal band multiplexing.

    Science.gov (United States)

    Yang, Qi; He, Zhixue; Yang, Zhu; Yu, Shaohua; Yi, Xingwen; Shieh, William

    2012-01-30

    Coherent optical OFDM (CO-OFDM) combined with orthogonal band multiplexing provides a scalable and flexible solution for achieving ultra high-speed rate. Among many CO-OFDM implementations, digital Fourier transform spread (DFT-S) CO-OFDM is proposed to mitigate fiber nonlinearity in long-haul transmission. In this paper, we first illustrate the principle of DFT-S OFDM. We then experimentally evaluate the performance of coherent optical DFT-S OFDM in a band-multiplexed transmission system. Compared with conventional clipping methods, DFT-S OFDM can reduce the OFDM peak-to-average power ratio (PAPR) value without suffering from the interference of the neighboring bands. With the benefit of much reduced PAPR, we successfully demonstrate 1.45 Tb/s DFT-S OFDM over 480 km SSMF transmission.

  16. Magnons coherent transmission and its heat transport at ultrathin insulating ferromagnetic nanojunctions

    Directory of Open Access Journals (Sweden)

    Ghantous M. Abou

    2012-06-01

    Full Text Available A model calculation is presented for the magnons coherent transmission and corresponding heat transport at magnetic insulating nanojunctions. The system consists of a ferromagnetically ordered ultrathin insulating junction between two semi-infinite ferromagnetically ordered leads. Spin dynamics are analyzed using the equations of motion for the spin precession displacements, valid for the range of temperatures of interest. Coherent scattering cross-sections at the junction boundary are calculated using the phase field matching theory, for all the incidence angles on the boundary from the lead bands, for arbitrary angles of incidence, at variable temperatures, and for different nano thicknesses of the ultrathin junction. The model is general; it is applied in particular to the Fe/Gd/Fe system with a sandwiched ferromagnetic Gd junction. It yields also the thermal conductivity due to the magnons coherent transmission between the two leads when these are maintained at slightly different temperatures. The calculation is carried out for state of the art values of the exchange constants, and elucidates the relation between the coherent scattering transmission of magnons and their thermal conductivity, for different thicknesses.

  17. Asymmetric lateral coherence of betatron radiation emitted in laser-driven light sources

    Science.gov (United States)

    Paroli, B.; Chiadroni, E.; Ferrario, M.; Petrillo, V.; Potenza, M. A. C.; Rossi, A. R.; Serafini, L.; Shpakov, V.

    2015-08-01

    We show that the radiation emitted by betatron oscillations of a high-energy electron beam undergoing wake-field acceleration is endowed with peculiar coherence properties which deliver quantitative information about the electron trajectories. Such results are achieved by means of accurate numerical simulations and a simple geometrical model gives a clear physical interpretation.

  18. Influence of Even-Order Dispersion on Super-Sech Soliton Transmission Quality under Coherent Crosstalk

    Directory of Open Access Journals (Sweden)

    Aleksandra Panajotovic

    2008-01-01

    Full Text Available The transmission speed of optical network strongly depends on the impact of higher order dispersion. In presence of coherent crosstalk, which cannot be otherwise controlled by optical filtering, the impact of higher order dispersions becomes more pronounced. In this paper, the general expressions, that describe pulse deformation due to second- and fourth-order dispersions in a single-mode fiber, are given. The responses for such even-order dispersions, in presence of coherent crosstalk, are characterized by waveforms with long trailing edges. The transmission quality of optical pulses, due to both individual and combined influence of second- and fourth-order dispersions, is studied in this paper. Finally, the pulse shape and eye diagrams are obtained.

  19. Impact of turbulent phase noise on frequency transfer with asymmetric two-way ground-satellite coherent optical links

    Science.gov (United States)

    Robert, Clélia; Conan, Jean-Marc; Wolf, Peter

    2016-06-01

    Bidirectional ground-satellite laser links suffer from turbulence-induced scintillation and phase distortion. We study how turbulence impacts on coherent detection capacity and on the associated phase noise that restricts clock transfer precision. We evaluate the capacity to obtain a two-way cancellation of atmospheric effects despite the asymmetry between up and down link that limits the link reciprocity. For ground-satellite links, the asymmetry is induced by point-ahead angle and possibly the use, for the ground terminal, of different transceiver diameters, in reception and emission. The quantitative analysis is obtained thanks to refined end- to-end simulations under realistic turbulence and wind conditions as well as satellite cinematic. These temporally resolved simulations allow characterizing the coherent detection in terms of time series of heterodyne efficiency for different system parameters. We show that Tip/Tilt correction on ground is mandatory at reception for the down link and as a pre-compensation of the up link. Good correlation between up and down phase noise is obtained even with asymmetric apertures of the ground transceiver and in spite of pointing ahead angle. The reduction to less than 1 rad2 of the two-way differential phase noise is very promising for clock comparisons.

  20. Coherent Polarization Control of THz Waves Generated from Asymmetrically Ionized Gases

    Energy Technology Data Exchange (ETDEWEB)

    Dai Jianming; Zhang, X-C [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Karpowicz, Nicholas, E-mail: zhangxc@rpi.edu [Max-Planck Institute for Quantum Optics, Garching (Germany)

    2011-02-01

    Unlike polarization control of optical waves, lossless control over the polarization of broadband terahertz waves remained challenging. We recently found that the polarization of terahertz waves generated from gas plasma excited by femtosecond fundamental pulse ({omega}) and its second harmonic (2{omega}) could be coherently controlled by changing the relative phase between the {omega} and 2{omega} pulses. In particular, when the {omega} and 2{omega} pulses are both circularly polarized (or close to it), the photo-excited electrons exhibit different trajectories as the relative phase between the two optical pulses changes, and subsequently terahertz polarization angle can be controlled arbitrarily through the relative phase while the intensity of the emitted terahertz wave is kept constant. This new finding may enable fast terahertz wave modulation and coherent control of nonlinear responses excited by intense terahertz waves with controllable polarization.

  1. Analogical optical modeling of the asymmetric lateral coherence of betatron radiation.

    Science.gov (United States)

    Paroli, B; Chiadroni, E; Ferrario, M; Potenza, M A C

    2015-11-16

    By exploiting analogical optical modeling of the radiation emitted by ultrarelativistic electrons undergoing betatron oscillations, we demonstrate peculiar properties of the spatial coherence through an interferometric method reminiscent of the classical Young's double slit experiment. The expected effects due to the curved trajectory and the broadband emission are accurately reproduced. We show that by properly scaling the fundamental parameters for the wavelength, analogical optical modeling of betatron emission can be realized in many cases of broad interest. Applications to study the feasibility of future experiments and to the characterization of beam diagnostics tools are described.

  2. Enhanced coherent OTDR for long span optical transmission lines containing optical fiber amplifiers

    Science.gov (United States)

    Furukawa, Shin-Ichi; Tanaka, Kuniaki; Koyamada, Yahei; Sumida, Masatoyo

    1995-05-01

    We have newly constructed an enhanced coherent optical time domain reflectometer (C-OTDR) for use in testing optical cable spans in transmission lines containing erbium-doped fiber amplifiers (EDFA's), which is based on heterodyne detection using acousto-optic (AO) switches. In order to avoid any optical surges in the EDFA's in the transmission lines, optical dummy pulses were added between the signal pulses by an AO switch to keep the probe power from the C-OTDR as uniform as possible. We achieved a large single-way dynamic range of 42 dB with 5 dBm less probe power. The measurable portion of the fiber spans was more than 80 km in optical transmission lines containing EDFA's. This is twice the previously reported value.

  3. Asymmetric transmission and optical low-pass filtering in a stack of random media with graded transport mean free path

    Science.gov (United States)

    Bingi, J.; Hemalatha, M.; Anita, R. W.; Vijayan, C.; Murukeshan, V. M.

    2015-11-01

    Light transport and the physical phenomena related to light propagation in random media are very intriguing, they also provide scope for new paradigms of device functionality, most of which remain unexplored. Here we demonstrate, experimentally and by simulation, a novel kind of asymmetric light transmission (diffusion) in a stack of random media (SRM) with graded transport mean free path. The structure is studied in terms of transmission, of photons propagated through and photons generated within the SRM. It is observed that the SRM exhibits asymmetric transmission property with a transmission contrast of 0.25. In addition, it is shown that the SRM works as a perfect optical low-pass filter with a well-defined cutoff wavelength at 580 nm. Further, the photons generated within the SRM found to exhibit functionality similar to an optical diode with a transmission contrast of 0.62. The basis of this functionality is explained in terms of wavelength dependent photon randomization and the graded transport mean free path of SRM.

  4. Coherent light transmission properties of commercial photonic crystal hollow core optical fiber.

    Science.gov (United States)

    Cranch, G A; Miller, G A

    2015-11-01

    Photonic crystal hollow core fiber (PC-HCF) has enabled many exciting new applications in nonlinear optics and spectroscopy. However, to date there has been less impact in coherent applications where preservation of optical phase over long fiber lengths is crucial. This paper presents characteristics of three commercially available PC-HCFs relevant to coherent applications including higher-order mode analysis, birefringence and polarization-dependent loss, and their impact on coherent light transmission in PC-HCF. Multipath interference due to higher-order mode propagation and Fresnel reflection is shown to generate excess intensity noise in transmission, which can be suppressed by up to 20 dB through high frequency phase modulation of the source laser. To demonstrate the potential of PC-HCF in high performance sensing, a Mach-Zehnder interferometer (MZI) incorporating 10 m of PC-HCF in each arm is characterized and demonstrates a phase resolution (59×10(-9)  rad/Hz(1/2) at 30 kHz) close to the shot noise limit, which is better than can be achieved in a MZI made with the same length of single mode solid core fiber because of the limit set by fundamental thermodynamic noise (74×10(-9)  rad/Hz(1/2) at 30 kHz).

  5. A study of direct solar radiation transmission in asymmetrical multi-span greenhouses using scale models and simulation models

    Energy Technology Data Exchange (ETDEWEB)

    Soriano, T.; Morales, M.I.; Castilla, N. [CIFA, Granada (Spain); Montero, J.I.; Anton, A. [IRTA, Barcelona (Spain); Sanchez-Guerrero, M.C.; Medrano, E. [CIFA, Almeria (Spain); Hernandez, J. [University of Almeria (Spain)

    2004-06-01

    Direct solar radiation transmission inside scale models of greenhouses with different roof slopes was measured and the results compared with calculations from a simulation model. Seven different roof slopes were tested, which had symmetrical and asymmetrical roof shapes: 8{sup o}-18{sup o}; 18{sup o}-8{sup o}; 27{sup o}-27{sup o}; 27{sup o}-45{sup o}; 36{sup o}-55{sup o}; 45{sup o}-27{sup o}; 55{sup o}-36{sup o} (8{sup o}-18{sup o} denoting that the south-facing slope was 8' and the north-facing one was 18{sup o}). Radiation transmission in scale models was quantified using linear solarimeters that integrated solar radiation along the cross-section of the span. The correlation between measured and calculated hourly and daily mean transmission values was good. Minor differences were attributed to the accumulation of dust and condensation on the scale models, two conditions that were not taken into account in the simulation model. The results of the study showed that direct solar radiation transmission increased considerably as slope increased, up to a value close to 30{sup o}, especially in the winter months in which radiation was most limited. Asymmetrical greenhouses did not always transmit more than symmetrical ones with similar slopes. In the cases studied, the scale model with 27{sup o}-27{sup o} symmetrical roof had the highest winter transmission. The use of scale models allowed different greenhouse structures to be characterised with respect to direct radiation transmission. This method can produce considerable savings of time and money and provides a realistic simulation of radiation transmission in full-scale greenhouses. (author)

  6. The use of wavenumber normalization in computing spatially averaged coherencies (KRSPAC) of microtremor data from asymmetric arrays

    Science.gov (United States)

    Asten, M.W.; Stephenson, William J.; Hartzell, Stephen

    2015-01-01

    The SPAC method of processing microtremor noise observations for estimation of Vs profiles has a limitation that the array has circular or triangular symmetry in order to allow spatial (azimuthal) averaging of inter-station coherencies over a constant station separation. Common processing methods allow for station separations to vary by typically ±10% in the azimuthal averaging before degradation of the SPAC spectrum is excessive. A limitation on use of high-wavenumbers in inversions of SPAC spectra to Vs profiles has been the requirement for exact array symmetry to avoid loss of information in the azimuthal averaging step. In this paper we develop a new wavenumber-normalised SPAC method (KRSPAC) where instead of performing averaging of sets of coherency versus frequency spectra and then fitting to a model SPAC spectrum, we interpolate each spectrum to coherency versus k.r, where k and r are wavenumber and station separation respectively, and r may be different for each pair of stations. For fundamental mode Rayleigh-wave energy the model SPAC spectrum to be fitted reduces to Jo(kr). The normalization process changes with each iteration since k is a function of frequency and phase velocity and hence is updated each iteration. The method proves robust and is demonstrated on data acquired in the Santa Clara Valley, CA, (Site STGA) where an asymmetric array having station separations varying by a factor of 2 is compared with a conventional triangular array; a 300-mdeep borehole with a downhole Vs log provides nearby ground truth. The method is also demonstrated on data from the Pleasanton array, CA, where station spacings are irregular and vary from 400 to 1200 m. The KRSPAC method allows inversion of data using kr (unitless) values routinely up to 30, and occasionally up to 60. Thus despite the large and irregular station spacings, this array permits resolution of Vs as fine as 15 m for the near-surface sediments, and down to a maximum depth of 2.5 km.

  7. Digital pilot aided carrier frequency offset estimation for coherent optical transmission systems.

    Science.gov (United States)

    Zhao, Donghe; Xi, Lixia; Tang, Xianfeng; Zhang, Wenbo; Qiao, Yaojun; Zhang, Xiaoguang

    2015-09-21

    We present a digital pilot aided carrier frequency offset estimation (FOE) method for coherent optical transmission systems. Unlike the conventional pilot tone insertion scheme, the pilot of the proposed method is generated in a digital manner and can serve as a good FOE indicator. Aided by this kind of digital pilot, the FOE is implemented by determining the location of the digital pilot in the spectrum. Theoretical analysis and numerical simulations show that the proposed method has the advantages in wide range, high accuracy, modulation formats independent, no need to remove the modulation, and high tolerance to the residual chromatic dispersion (CD) and polarization mode dispersion (PMD).

  8. Laser-based space debris removal: design guidelines for coherent coupling power transmission

    Science.gov (United States)

    Kästel, Jürgen; Speiser, Jochen

    2016-10-01

    Space debris presents an increasing threat to the lifetime of commercial and military space assets. Laser-based space debris removal systems could potentially mitigate this threat by targeting debris objects in the cm-range. In order to reach this goal a minimum fluence of a few J/cm² on the debris object and a pulse repetition rate of several 10 Hz are necessary. These requirements can be met by coupling 1000-2000 independent 10 J laser sources coherently and employing a sending telescope with a diameter of 5 m. We analyze which parameters are critical to the effectiveness of the transmission system and deduce design guidelines. In particular the effects of non-optimum filling factors, secondary mirror size, emitter intensity distribution and phase jitter of the individual emitters are discussed and compared.

  9. Coherent, non-planar illumination of a defocused specimen: consequences for transmission electron microscopy

    Science.gov (United States)

    Patwardhan, Ardan

    The objective of this study has been to examine the imaging properties of transmission electron microscopes when coherent non-planar illumination is used in conjunction with defocused specimens. This situation is reminiscent of what is commonly the case in electron microscopic phase-contrast studies of biologically relevant macromolecules, using a field emission gun as a coherent electron source. For the sake of simplicity, the imaging system has been idealized as a thin lens with properties that can be described by the Fresnel approximation of the Huygens-Fresnel principle. The resulting expressions show that the system magnification has a defocus dependent factor, as do the contrast transfer functions. These factors are normally not taken into account in conventional derivations. The defocus dependent factor can be minimized by using planar illumination. The factor approaches infinity as the crossover moves closer to the specimen, and it is in the region close to the specimen that this factor is most significant. These results can have serious implications for high-resolution single-particle cryo electron microscopy as this technique often relies on combining data taken at a range of defocus values.

  10. Breaking the symmetry: immune enhancement increases persistence of dengue viruses in the presence of asymmetric transmission rates.

    Science.gov (United States)

    Mier-y-Teran-Romero, Luis; Schwartz, Ira B; Cummings, Derek A T

    2013-09-07

    The dengue viruses exist as four antigenically distinct serotypes. These four serotypes co-circulate and interact with each other through multiple immune-mediated mechanisms. Though the majority of previous efforts to understand the transmission dynamics of dengue have assumed identical characteristics for these four serotypes, empirical data suggests that they differ from one another in important ways. Here, we examine dynamics and persistence in models that do not assume symmetry between the dengue viruses. We find that for serotype transmission rates that are only slightly asymmetric, increased transmissibility of secondary infections through immune enhancement increases the persistence of all dengue viruses in opposition to findings in symmetric models. We identify an optimal magnitude of immune enhancement that maximizes the probability of persistence of all four serotypes. In contrast to other pathogen systems where heterogeneity between serotypes in transmissibility facilitates competitive exclusion (Bremmermann and Thieme, 1989), here we find that in the presence of Antibody Dependent Enhancement (ADE) heterogeneity can increase the persistence of multiple serotypes of dengue.

  11. Baecklund Transformation and Localized Coherent Structure for the (2+1)—Dimensional Asymmetric Nizhnik—Novikov—Veselov Equation

    Institute of Scientific and Technical Information of China (English)

    张解放; 刘宇陆

    2002-01-01

    This article is concerned with the extended homogeneous balance method for studying the abundant lacalized solution structure of the (2+1)-dimensional asymmetric Nizhnik-novikov-Veselov equation.A Baecklund transformation was first obtained.and then the richness of the localized coherent structures was found,which was caused by the entrance of two variable-separated arbitrary functions,in the model.For some spectial choices of the arbitrary functions,it is shown that the localized structures of the model may be dromions,lumps,and rinmg solitons.

  12. Diodelike asymmetric transmission in hybrid plasmonic waveguides via breaking polarization symmetry

    Science.gov (United States)

    Zhang, Heran; Zhang, Fengchun; Liang, Yao; Huang, Xu-Guang; Jia, Baohua

    2017-04-01

    The ability to control the asymmetric propagation of light in nanophotonic waveguides is of fundamental importance to optical communications and on-chip signal processing. However, in most studies so far, the design of such structures has been based on asymmetric mode conversion where multi-mode waveguides are involved. Here we propose a hybrid plasmonic structure that performs optical diode behavior via breaking polarization symmetry in single mode waveguides. The exploited physical mechanism is based on the combination of polarization rotation and selection. The whole device is ultra-compact with a footprint of 2.95  ×  14.18 µm2, and whose dimension is much smaller than the device previously proposed for a similar function. The extinction ratio is greater than 11.8 dB for both forward and backward propagation at λ  =  1550 nm (19.43 dB for forward propagation and 11.8 dB for the backward one). The operation bandwidth of the device is as great as 70 nm (form 1510 to 1580 nm) for extinction  >10 dB. These results may find important applications in the integrated devices where polarization handling or unidirectional propagation is required.

  13. Dynamic Simulation of Asymmetric Involute Spur Gear Transmission with ADAMS%基于ADAMS的非对称渐开线齿轮动力学仿真

    Institute of Scientific and Technical Information of China (English)

    朱旭辉

    2014-01-01

    根据渐开线齿轮啮合原理,推导了基于某一坐标系统的非对称渐开线齿轮齿廓曲线方程。利用Autodesk Inventor软件的VBA二次开发技术,对非对称齿轮的三维实体模型进行了构建。通过对非对称齿轮动力学模型等价变换,利用ADAMS虚拟样机技术,对非对称齿轮动态啮合传动过程进行了仿真,并与对称齿轮仿真结果进行了对比研究。%On the basis of the gear meshing theory, the curve equation of asymmetric involute tooth profile was derived. And the three-dimensional entity model of asymmetric involute gear was created by using the secondary development technology of VBA within the software of Autodesk Inventor. In order to get the dynamic model of asymmetric gear transmission, an equivalent transformation method was proposed. Whereafter, dynamic characteristics of asymmetric involute spur gear transmission were researched by simulating the virtual prototype model with ADAMS. Meanwhile, the dynamic characteristics of symmetric involute spur gear transmission were compared,to prove whether the asymmetric gear is better in the dynamic meshing process.

  14. Asymmetric sound transmission in a passive non-blocking structure with multiple ports

    Science.gov (United States)

    Zhu, Yi-Fan; Gu, Zhong-Ming; Liang, Bin; Yang, Jing; Yang, Jun; Yin, Lei-lei; Cheng, Jian-Chun

    2016-09-01

    We present the mechanism for breaking the symmetry in sound transmission between any two neighboring ports in a passive multi-port system. Numerical simulations and experimental measurements verify that by using judiciously designed metastructures to provide an extra wavevector without blocking the sound path, the propagating wave will travel along a preset direction at each port instead of splitting to both directions. We have also demonstrated the flexibility of this scheme to adjust the location of each port. Our design advances further the concept of one-way manipulation in passive two-port systems and may enable novel sound-steering devices for more versatile applications.

  15. Bidirectional and Asymmetric Controlled Quantum Information Transmission via Five-qubit Brown State

    Science.gov (United States)

    Fang, Sheng-hui; Jiang, Min

    2017-02-01

    We put forward a new protocol of deterministic controlled bidirectional quantum information transmission, using a five-qubit Brown state. That is to say Alice wants to teleport an arbitrary single-qubit state to Bob and Bob wants to remotely prepare a known state for Alice via the control of the supervisor Charlie. In terms of physical implementations, only a CNOT gate, one Bell-state measurement and one qubit measurement are used in our protocol. Compared with previous study for solely bidirectional quantum teleportation and solely bidirectional remote state preparation schemes, our protocol is a kind of hybrid approach of information communication which makes the quantum channel multipurpose, i.e., no matter whether the transmitted state is known or unknown, the state information can be transmitted with each other via a five-qubit Brown state under the control of the third party as a supervisor.

  16. Asymmetric transmission in planar chiral split-ring metamaterials: Microscopic Lorentz-theory approach

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Galynsky, Vladimir M.; Zhukovsky, Sergei

    2012-01-01

    The electronic Lorentz theory is employed to explain the optical properties of planar split-ring metamaterials. Starting from the dynamics of individual free carriers, the electromagnetic response of an individual split-ring meta-atom is determined, and the effective permittivity tensor...... of the metamaterial is calculated for normal incidence of light. Whenever the split ring lacks in-plane mirror symmetry, the corresponding permittivity tensor has a crystallographic structure of an elliptically dichroic medium, and the metamaterial exhibits optical properties of planar chiral structures. Its...... transmission spectra are different for right-handed versus left-handed circular polarization of the incident wave, so the structure changes its transmittance when the direction of incidence is reversed. The magnitude of this change is shown to be related to the geometric parameters of the split ring...

  17. Asymmetric Dual Axis Energy Recovery Linac for Ultra-High Flux sources of coherent X-ray/THz radiation: Investigations Towards its Ultimate Performance

    CERN Document Server

    Ainsworth, R; Konoplev, I V; Seryi, A

    2015-01-01

    Truly compact and high current, efficient particle accelerators are required for sources of coherent high brightness and intensity THz and X-Ray radiation to be accepted by university or industrial R&D laboratories. The demand for compactness and efficiency can be satisfied by superconducting RF energy recovery linear accelerators (SRF ERL) allowing effectively minimising the footprint and maximising the efficiency of the system. However such set-ups are affected by regenerative beam-break up (BBU) instabilities which limit the beam current and may terminate the beam transport as well as energy recuperation. In this paper we suggest and discuss a SRF ERL with asymmetric configuration of accelerating and decelerating cavities resonantly coupled. In this model of SRF ERL we propose an electron bunch passing through accelerating and decelerating cavities each once and we show that in this case the regenerative BBU instability can be minimised allowing high currents to be achieved. We study the BBU start curr...

  18. Measurement of the penetration depth and coherence length of MgB2 in all directions using transmission electron microscopy

    DEFF Research Database (Denmark)

    Loudon, J. C.; Yazdi, Sadegh; Kasama, Takeshi

    2015-01-01

    the crystallographic a axis. A new method was developed to simulate these images that accounted for vortices with a nonzero core in a thin, anisotropic superconductor and a simplex algorithm was used to make a quantitative comparison between the images and simulations to measure the penetration depths and coherence......We demonstrate that images of flux vortices in a superconductor taken with a transmission electron microscope can be used to measure the penetration depth and coherence length in all directions at the same temperature and magnetic field. This is particularly useful for MgB2, where these quantities...... gives Lambda(ab) = 107 +/- 8 nm, Lambda(c) = 120 +/- 15 nm, xi(ab) = 39 +/- 11 nm, and xi(c) = 35 +/- 10 nm, which agree well with measurements made using other techniques. The experiment required two days to conduct and does not require large-scale facilities. It was performed on a very small sample...

  19. Spatiotemporal coherent control of light through a multiply scattering medium with the Multi-Spectral Transmission Matri

    CERN Document Server

    Mounaix, Mickael; Defienne, Hugo; Volpe, Giorgio; Katz, Ori; Grésillon, Samuel; Gigan, Sylvain

    2015-01-01

    We report broadband characterization of the propagation of light through a multiply scattering medium by means of its Multi-Spectral Transmission Matrix. Using a single spatial light modulator, our approach enables the full control of both spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control and imaging.

  20. 120 Gbit/s injection-locked homodyne coherent transmission of polarization-multiplexed 64 QAM signals over 150 km.

    Science.gov (United States)

    Wang, Yixin; Kasai, Keisuke; Yoshida, Masato; Nakazawa, Masataka

    2014-12-15

    We describe an injection-locked 64 QAM homodyne coherent transmission, which is the highest QAM multiplicity realized with an injection locking technique. The frequency locking range of the local oscillator (LO) was as wide as 1 GHz. The phase noise was only 0.2 deg, which is 1/3 of that obtained with our previous OVCO-based OPLL (0.6 deg.). As a result, a 120 Gbit/s polarization-multiplexed 64 QAM signal was successfully transmitted over 150 km with a simple receiver configuration and low DSP complexity.

  1. Digital signal processing approaches for semiconductor phase noise tolerant coherent transmission systems

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Pang, Xiaodan; Schatz, Richard;

    2015-01-01

    We discuss about digital signal processing approaches that can enable coherent links based on semiconductor lasers. A state-of-the art analysis on different carrier-phase recovery (CPR) techniques is presented. We show that these techniques are based on the assumption of lorentzian linewidth, whi...

  2. Indoor RF signal distribution using a coherence multiplexed/subcarrier multiplexed optical transmission system

    NARCIS (Netherlands)

    Taniman, Robert; Meijerink, Arjan; Etten, van Wim; Haartsen, Jaap

    2003-01-01

    A Radio over Fiber (RoF) distribution network based on single-mode fiber (SMF) and a combination of coherence multiplexing (CM) and subcarrier multiplexing (SCM) is proposed. CM is a relatively unknown and potentially inexpensive form of photonic code-division multiplexing, and is used here as a mea

  3. Equalization of nonlinear transmission impairments by maximum-likelihood-sequence estimation in digital coherent receivers.

    Science.gov (United States)

    Khairuzzaman, Md; Zhang, Chao; Igarashi, Koji; Katoh, Kazuhiro; Kikuchi, Kazuro

    2010-03-01

    We describe a successful introduction of maximum-likelihood-sequence estimation (MLSE) into digital coherent receivers together with finite-impulse response (FIR) filters in order to equalize both linear and nonlinear fiber impairments. The MLSE equalizer based on the Viterbi algorithm is implemented in the offline digital signal processing (DSP) core. We transmit 20-Gbit/s quadrature phase-shift keying (QPSK) signals through a 200-km-long standard single-mode fiber. The bit-error rate performance shows that the MLSE equalizer outperforms the conventional adaptive FIR filter, especially when nonlinear impairments are predominant.

  4. Ultrafast transmission electron microscopy using a laser-driven field emitter: femtosecond resolution with a high coherence electron beam

    CERN Document Server

    Feist, Armin; da Silva, Nara Rubiano; Danz, Thomas; Möller, Marcel; Priebe, Katharina E; Domröse, Till; Gatzmann, J Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha; Ropers, Claus

    2016-01-01

    We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the G\\"ottingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9 {\\AA} focused beam diameter, 200 fs pulse duration and 0.6 eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free electron beams.

  5. Digital signal processing approaches for semiconductor phase noise tolerant coherent transmission systems

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Pang, Xiaodan; Schatz, Richard

    2015-01-01

    We discuss about digital signal processing approaches that can enable coherent links based on semiconductor lasers. A state-of-the art analysis on different carrier-phase recovery (CPR) techniques is presented. We show that these techniques are based on the assumption of lorentzian linewidth, which...... does not hold for monolithically integrated semiconductor lasers. We investigate the impact of such lineshape on both 3 and 20 dB linewidth and experimentally conduct a systematic study for 56-GBaud DP-QPSK and 28-GBaud DP-16QAM systems using a decision directed phase look loop algorithm. We show how...... carrier induced frequency noise has no impact on linewidth but a significant impact on system performance; which rises the question on whether 3-dB linewidth should be used as performance estimator for semiconductor lasers....

  6. 2.56 Tbit/s/ch (640 Gbaud) polarization-multiplexed DQPSK non-coherent Nyquist pulse transmission over 525 km.

    Science.gov (United States)

    Harako, Koudai; Seya, Daiki; Suzuki, Daiki; Hirooka, Toshihiko; Nakazawa, Masataka

    2015-11-30

    We demonstrate a single-channel 2.56 Tbit/s polarization-multiplexed DQPSK transmission using 640 Gbaud non-coherent optical Nyquist pulses. By virtue of a large tolerance to polarization-mode dispersion, the detrimental depolarization-induced crosstalk was reduced by 3.8 dB compared with RZ pulses. As a result, the transmission distance was substantially extended to 525 km compared with the distance of 300 km obtained with a Gaussian pulse.

  7. Adaptive 4~64 QAM real-time coherent optical transmission over 320 km with FPGA-based transmitter and receiver.

    Science.gov (United States)

    Yoshida, Masato; Hirooka, Toshihiko; Kasai, Keisuke; Nakazawa, Masataka

    2014-06-30

    We demonstrate the first real-time adaptive optical coherent QAM transmission with variable multiplicities (4-, 16- and 64-QAM) using an FPGA-based transmitter and receiver. Rate-variable transmission (20~60 Gbit/s) was successfully achieved with a polarization multiplexing scheme at 5 Gsymbol/s over 320 km, where the OSNR margins were increased by 9 and 17 dB, respectively, by changing the modulation level from 64 to 16 and 4.

  8. 107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing.

    Science.gov (United States)

    Shieh, W; Yang, Q; Ma, Y

    2008-04-28

    Coherent optical OFDM (CO-OFDM) has emerged as an attractive modulation format for the forthcoming 100 Gb/s Ethernet. However, even the spectral-efficient implementation of CO-OFDM requires digital-to-analog converters (DAC) and analog-to-digital converters (ADC) to operate at the bandwidth which may not be available today or may not be cost-effective. In order to resolve the electronic bandwidth bottleneck associated with DAC/ADC devices, we propose and elucidate the principle of orthogonal-band-multiplexed OFDM (OBM-OFDM) to subdivide the entire OFDM spectrum into multiple orthogonal bands. With this scheme, the DAC/ADCs do not need to operate at extremely high sampling rate. The corresponding mapping to the mixed-signal integrated circuit (IC) design is also revealed. Additionally, we show the proof-of-concept transmission experiment through optical realization of OBM-OFDM. To the best of our knowledge, we present the first experimental demonstration of 107 Gb/s QPSK-encoded CO-OFDM signal transmission over 1000 km standard-single- mode-fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated system employs 2x2 MIMO-OFDM signal processing and achieves high electrical spectral efficiency with direct-conversion at both transmitter and receiver.

  9. Coupled cavity QED for coherent control of photon transmission (II): Slowing light in coupled resonator waveguide doped with $\\Lambda $ Atoms

    CERN Document Server

    Zhou, L; Sun, C P; Lu, Jing; Zhou, Lan

    2006-01-01

    In the first paper of our series of articles on photon transmission in the coupled resonator optical waveguide (CROW), we used the two time Green function approach to study the physical mechanism for the coherent control by doping two-level atoms. In present paper, we propose and study a hybrid mechanism for photon transmission in the CROW by incorporating the electromagnetically induced transparency (EIT) effect in the doping artificial atoms and the band structure of the CROW. Here, the configuration setup of system, similar to that in the first paper, consists of a CROW with homogeneous couplings and the artificial atoms with $\\Lambda$-type three levels doped in each cavity. Unlike the stimulated Raman process used in the first paper to reduce the three level systems into the two level ones, the roles of three levels are completely considered based on a kind of mean field approach where the collection of three-level atoms collectively behave as two-mode spin waves. Then the total system is reduced into an ...

  10. Transmission and full-band coherent detection of polarization-multiplexed all-optical Nyquist signals generated by Sinc-shaped Nyquist pulses.

    Science.gov (United States)

    Zhang, Junwen; Yu, Jianjun; Chi, Nan

    2015-09-01

    All optical method is considered as a promising technique for high symbol rate Nyquist signal generation, which has attracted a lot of research interests for high spectral-efficiency and high-capacity optical communication system. In this paper, we extend our previous work and report the fully experimental demonstration of polarization-division multiplexed (PDM) all-optical Nyquist signal generation based on Sinc-shaped Nyquist pulse with advanced modulation formats, fiber-transmission and single-receiver full-band coherent detection. Using this scheme, we have successfully demonstrated the generation, fiber transmission and single-receiver full-band coherent detection of all-optical Nyquist PDM-QPSK and PDM-16QAM signals up to 125-GBaud. 1-Tb/s single-carrier PDM-16QAM signal generation and full-band coherent detection is realized, which shows the advantage and feasibility of the single-carrier all-optical Nyquist signals.

  11. Single-channel 1.92 Tbit/s, Pol-Mux-64 QAM coherent Nyquist pulse transmission over 150 km with a spectral efficiency of 7.5 bit/s/Hz.

    Science.gov (United States)

    Otuya, David Odeke; Kasai, Keisuke; Yoshida, Masato; Hirooka, Toshihiko; Nakazawa, Masataka

    2014-10-01

    Coherent Nyquist pulses have been used for optical time division multiplexed (OTDM) digital coherent transmission, and a single-channel 1.92 Tbit/s, Pol-Mux-64 QAM coherent Nyquist pulse transmission over 150 km is demonstrated. The ability to considerably reduce the spectral bandwidth of the data signal enabled us to increase the spectral efficiency from 3.2 bit/s/Hz to 7.5 bit/s/Hz when using a Gaussian pulse train.

  12. The Way of Reducing Current Values in Optical Ground Wires at Asymmetrical Faults on Overhead Transmission Lines

    Directory of Open Access Journals (Sweden)

    Egamnazarov Georgiy

    2016-12-01

    Full Text Available Given the fact that the installing costs of an optical ground wire on overhead lines directly depend on its cross-section, which in turn depends on the level of fault current it should withstand, in order to reduce these current values in the optical ground wire, I suggested performing its isolated descents from the end towers of the line with its transition to an optical cable. The research was carried out on the example of a 500 kV overhead line in the National Electric Power Grid. The Method of Symmetrical Components for calculating asymmetrical fault currents was not used; therefore, calculations were carried out on the base of presenting the line as a multi-wire system for the considered case as a five-wire system (optical ground wire, steel ground wire, and three phase wires. Such approach allows taking into account the initial asymmetry of the line parameters and modeling any kind of asymmetrical faults. The analyses of calculated results were performed. The conclusive evidence that the optical ground wire isolated descents from the end towers of the line give the possibility of reducing the level of maximal fault current distribution values in it and therefore its cross section, is presented.

  13. (2+1)-维反对称Nizhnik-Novikov-Veselov方程的Bcklund变换和局域相干结构%Backlund Transformation and Localized Coherent Structure for the(2+1)-Dimensional Asymmetric Nizhnik-Novikov-Veselov Equation

    Institute of Scientific and Technical Information of China (English)

    张解放; 刘宇陆

    2002-01-01

    This article is concerned with the extended homogeneous balance method for studying the abundant localized solution structure of the (2 + 1)-dimensional asymmetric Nizhnik-Novikov-Veselov equation. A Backlund transformation was first obtained, and then the richness of the localized coherent structures was found, which was caused by the entrance of two variable-separated arbitrary functions, in the model. For some special choices of the arbitrary functions, it is shown that the localized structures of the model may be dromions, lumps, and ring solitons.

  14. Optical 16-QAM-52-OFDM transmission at 4 Gbit/s by directly modulating a coherently injection-locked colorless laser diode.

    Science.gov (United States)

    Chi, Yu-Chieh; Li, Yi-Cheng; Wang, Huai-Yung; Peng, Peng-Chun; Lu, Hai-Han; Lin, Gong-Ru

    2012-08-27

    Coherently injection-locked and directly modulated weak-resonant-cavity laser diode (WRC-FPLD) for back-to-back optical 16-quadrature-amplitude-modulation (QAM) and 52-subcarrier orthogonal frequency division multiplexing (OFDM) transmission with maximum bit rate up to 4 Gbit/s at carrier frequency of 2.5 GHz is demonstrated. The WRC-FPLD transmitter source is a specific design with very weak-resonant longitudinal modes to preserve its broadband gain spectral characteristics for serving as a colorless WDM-PON transmitter. Under coherent injection-locking, the relative-intensity noise (RIN) of the injection-locked WRC-FPLD can be suppressed to ?105 dBc/Hz and the error vector magnitude of the received optical OFDM data is greatly reduced with the amplitude error suppressed down 5.5%. Such a coherently injection-locked single-mode WRC-FPLD can perform both the back-to-back and the 25-km-SMF 16-QAM-52-OFDM transmissions with a symbol rate of 20-MSa/s in each OFDM subcarrier. After coherent injection locking, the BER of the back-to-back transmitted 16-QAM-52-OFDM data is reduced to 2.5 × 10(-5) at receiving power of ?10 dBm. After propagating along a 25-km-long SMF, a receiving power sensitivity of ?7.5 dBm is required to obtain a lowest BER of 2.5 × 10(-5), and a power penalty of 2.7 dB is observed when comparing with the back-to-back transmission.

  15. Real-time optical wireless transmissions of digital TV signals using white InGaN LEDs grown with an asymmetric quantum barrier.

    Science.gov (United States)

    Tsai, Chia-Lung; Chen, Yen-Jen

    2015-10-19

    The feasibility of using InGaN LEDs grown with asymmetric barrier layer (ABL) as transmitters in visible light communications is investigated experimentally. Compared with normal LEDs, the improvement in the spontaneous emission rate due to enhanced carrier localization and better uniformity of carrier distribution in ABL-containing MQWs leads to the fabricated LEDs can exhibit a 32.6% (@ 350 mA) increase in emission intensity and a 10.5% increase in modulation bandwidth. After eliminating the slow-responding phosphorescent components emitting from the phosphor-converted white LEDs, an open eye-diagram at 180 Mb/s is demonstrated over a distance of 100 cm in directed line-of-sight optical links. With the use of proposed LEDs, real-time transmissions of digital TV signals over a moderate distance (~100 cm) in free space is shown to be available in a 150 Mbit/s white LED-based optical link with conventional on-off keying modulation.

  16. An Application of the Two-Regime Threshold Vector Error Correction Model to Analyze Asymmetric Price Transmission of Milk in Zanjan Province of Iran

    Directory of Open Access Journals (Sweden)

    Moharram Ainollahi

    2015-09-01

    Full Text Available I n this paper asymmetric price transmission mechanism and nonlinear adjustment between producer and retail prices of milk were examined in Zanjan Province of Iran. For this purpose, a Two-Regime Threshold Vector Error Correction Model (TVECM and a Sup-LM Test developed by Hansen and Seo (2002 were employed for checking presence of a threshold effect. Application of unit root tests indicated that both wholesale and retail prices are I (1, and Johansen test verified cointegration of the series in the long-run. Results of the Sup-LM test confirmed threshold adjustment of product price towards the long-run equilibrium. Furthermore, results obtained from TVECM revealed that the coefficient of ECT is significant only in the first regime of retailing equation implying that retailers significantly respond to the decreasing deviations from the long-run equilibrium. While adjustment coefficient is not significant for wholesale equation in both regimes to imply that there is not significant inclination to react to deviations from the long-run equilibrium among the wholesalers despite the retailers.

  17. Experimental demonstration of high spectral-efficiency transmission with a novel non-interferometric vector modulator and custom DSP algorithms for coherent PON architectures

    Science.gov (United States)

    Lazarou, I.; Spatharakis, C.; Katopodis, V.; Dris, S.; Bakopoulos, P.; Schrenk, B.; Avramopoulos, H.

    2013-12-01

    We demonstrate a flexible multi-format vector modulator for coherent passive optical network (PON) architectures based on a non-interferometric cascade of a Semiconductor Optical Amplifier (SOA) and an Electro-Absorption Modulator (EAM) that exhibits increased simplicity and high energy-efficiency at low cost. 12- and 16- Quadrature Amplitude Modulation (QAM) constellations are generated, achieving modulation efficiencies of 3.6 and 4 bits/symbol respectively. The presented results demonstrate successful transmission over 25 km of fiber below the Forward Error Correction (FEC) limit, with sufficient compatible loss-budgets, making the proposed modulator concept an attractive candidate for urban network deployments, where high user density demands spectrally efficient formats. In addition, we describe the operation principle of the proposed modulator in detail and finally, the complete set of the digital signal processing (DSP) functionalities and algorithms that follow the standard coherent detection scheme is given, emphasizing on novel methods for QAM signal demodulation with uncommon constellation diagrams.

  18. Upstream WDM-PON transmission scheme based on PDM-OOK modulation and digital coherent detection with dual-modulus algorithm.

    Science.gov (United States)

    Zhu, Paikun; Li, Juhao; Zhou, Peng; Lin, Bangjiang; Chen, Zhangyuan; He, Yongqi

    2015-05-18

    Wavelength-division-multiplexing passive optical network (WDM-PON) is a promising architecture for next-generation access networks because of its large bandwidth, protocol transparency and scalability. In this paper, we propose a cost-effective, high-speed upstream WDM-PON scheme adopting polarization division multiplexed (PDM) on-off keying (OOK) modulation at the optical network unit (ONU) and digital coherent/self-coherent detection with a novel blind dual-modulus equalization algorithm at the optical line terminal (OLT). As such, the upstream capacity can be directly enhanced at low ONU expenditure, and receiver sensitivity as well as power budget can be also improved. Enabled by the scheme, 40-Gb/s upstream transmission in 80-km WDM-PON is experimentally demonstrated.

  19. Asymmetric Price Transmission in Food Supply Chains: Impulse Response Analysis by Local Projections Applied to U.S. Broiler and Pork Prices

    NARCIS (Netherlands)

    Kuiper, W.E.; Oude Lansink, A.G.J.M.

    2013-01-01

    In this article, the author's set out Jordà's (2005) method of local projections by which nonlinear/ asymmetric impulse responses can be computed without the need to specify and estimate the underlying nonlinear/asymmetric dynamic system. The method is used to compute price-reaction functions that s

  20. 非对称一致性风险测度及其应用%Asymmetric Coherent Risk Measure and its Application

    Institute of Scientific and Technical Information of China (English)

    张一喆; 安实; 徐照宇

    2012-01-01

    In order to reflect the risk attitude of investors more completely and rationally, this paper defines an asymmetric risk measure. The new risk measure describes the different attitudes towards bilateral volatility of return through local concavity and local convexity, weakens the properties of translation invariance and zero risk assuming the existence of multiple reference points, which improves the existing axiomatics of risk measure. This paper brings forward a generalized form of asymmetric risk measure, based on which a portfolio optimization model is proposed and corresponding empirical analysis is carried out. The result shows that the asymmetric risk measure defined in this paper and the related portfolio optimization model are reasonable and feasible in practice.%为了更加充分合理地反映投资者的风险态度,文章提出非对称一致性风险测度。这一风险测度在多参考点的情形下通过局部凹性和局部凸性分别描述了投资者对收益双向波动的不同风险态度,并弱化了平移不变性、零风险性等方面的要求,实现了对已有风险测度公理体系的补充与完善。进一步给出一类非对称一致性风险测度的函数形式,并以其为基础构建了投资组合优化模型,同时结合具体数据进行实证研究,结果表明非对称一致性风险测度及相应的投资组合优化模型在实践中是合理可行的。

  1. Coherent Detection of Electron Dephasing

    NARCIS (Netherlands)

    Strambini, E.; Chirolli, L.; Giovanetti, V.; Taddei, F.; Fazio, R.; Piazza, V.

    2010-01-01

    We show that an Aharonov-Bohm ring with asymmetric electron injection can act as a coherent detector of electron dephasing. The presence of a dephasing source in one of the two arms of a moderately-to-highly asymmetric ring changes the response of the system from total reflection to complete transmi

  2. Review of Composite Asymmetric Spur Gear

    OpenAIRE

    Sandeep C. Dhaduti; Dr. S. G. Sarganachari

    2015-01-01

    Gears made from composite materials are widely used in many power and motion transmission applications. Due to lower weight to stiffness ratio, composite gears may be replaced by conventional material gears in power transmission systems. Design of gears with asymmetric teeth enables to increase load capacity, reduce weight, size and vibration level. This article includes a summary of asymmetric gear design parameters, new developments of asymmetric spur gear and their ...

  3. VCSEL Based Coherent PONs

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee; Rodes, Roberto; Caballero Jambrina, Antonio;

    2014-01-01

    We present a review of research performed in the area of coherent access technologies employing vertical cavity surface emitting lasers (VCSELs). Experimental demonstrations of optical transmission over a passive fiber link with coherent detection using VCSEL local oscillators and directly modula...

  4. Directly modulated and fully tunable hybrid silicon lasers for future generation of coherent colorless ONU.

    Science.gov (United States)

    de Valicourt, G; Le Liepvre, A; Vacondio, F; Simonneau, C; Lamponi, M; Jany, C; Accard, A; Lelarge, F; Make, D; Poingt, F; Duan, G H; Fedeli, J-M; Messaoudene, S; Bordel, D; Lorcy, L; Antona, J-C; Bigo, S

    2012-12-10

    We propose and demonstrate asymmetric 10 Gbit/s upstream--100 Gbit/s downstream per wavelength colorless WDM/TDM PON using a novel hybrid-silicon chip integrating two tunable lasers. The first laser is directly modulated in burst mode for upstream transmission over up to 25 km of standard single mode fiber and error free transmission over 4 channels across the C-band is demonstrated. The second tunable laser is successfully used as local oscillator in a coherent receiver across the C-band simultaneously operating with the presence of 80 downstream co-channels.

  5. Asymmetric synthesis v.4

    CERN Document Server

    Morrison, James

    1984-01-01

    Asymmetric Synthesis, Volume 4: The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers describes the practical methods of obtaining chiral fragments. Divided into five chapters, this book specifically examines initial chiral transmission and extension. The opening chapter describes the so-called chiral carbon pool, the readily available chiral carbon fragments used as building blocks in synthesis. This chapter also provides a list of 375 chiral building blocks, along with their commercial sources, approximate prices, and methods of synthesis. Schemes involving

  6. Both asymmetric mitotic segregation and cell-to-cell invasion are required for stable germline transmission of Wolbachia in filarial nematodes

    Directory of Open Access Journals (Sweden)

    Frédéric Landmann

    2012-04-01

    Parasitic filarial nematodes that belong to the Onchocercidae family live in mutualism with Wolbachia endosymbionts. We developed whole-mount techniques to follow the segregation patterns of Wolbachia through the somatic and germline lineages of four filarial species. These studies reveal multiple evolutionarily conserved mechanisms that are required for Wolbachia localization to the germline. During the initial embryonic divisions, Wolbachia segregate asymmetrically such that they concentrate in the posteriorly localized P2 blastomere, a precursor to the adult germline and hypodermal lineages. Surprisingly, in the next division they are excluded from the germline precursor lineage. Rather, they preferentially segregate to the C blastomere, a source of posterior hypodermal cells. Localization to the germline is accomplished by a distinct mechanism in which Wolbachia invade first the somatic gonadal cells close to the ovarian distal tip cell, the nematode stem cell niche, from the hypodermis. This tropism is associated with a cortical F-actin disruption, suggesting an active engulfment. Significantly, germline invasion occurs only in females, explaining the lack of Wolbachia in the male germline. Once in the syncytial environment of the ovaries, Wolbachia rely on the rachis to multiply and disperse into the germ cells. The utilization of cell-to-cell invasion for germline colonization may indicate an ancestral mode of horizontal transfer that preceded the acquisition of the mutualism.

  7. Robustness of a coherence vortex.

    Science.gov (United States)

    Alves, Cleberson R; Jesus-Silva, Alcenisio J; Fonseca, Eduardo J S

    2016-09-20

    We study, experimentally and theoretically, the behavior of a coherence vortex after its transmission through obstacles. Notably, we find that such a vortex survives and preserves its effective topological charge. Despite suffering changes on the modulus of the coherence function, these changes disappear during propagation.

  8. Effect of the degree of phase-correlation of laser sources on the transmission and optical coherent detection in radio-over-fibre systems

    Science.gov (United States)

    Maldonado-Basilio, Ramón; Li, Ran; Abdul-Majid, Sawsan; Nikkhah, Hamdam; Leong, Kin-Wai; Hall, Trevor J.

    2013-01-01

    The deployment of high capacity Radio-over-Fiber (RoF) systems rely, among many aspects, on the capability to efficiently generate, transport, and detect millimeter-wave carriers modulated at high data rates. Photonic approaches based on the heterodyne beating of two free-running laser sources have been proposed as an alternative to generate multi-Gbps quadrature phase modulated signals imposed on millimeter wave carriers. Implementing photonic approaches in the down-link avoids the need for electronic generation of high frequency carriers and decreases the requirements at the base band electronics. In addition, implementing complex modulation formats overcomes some of the typical issues found in intensity modulation direct detection approaches such as non­ linearity, receiver sensitivity and dynamic range. In this work, the performance improvement of a coherent RoF system carrying 10 Gbps QPSK signals is numerically analyzed in terms of both the frequency linewidth and the degree of phase correlation between the lasers utilised at the down-link (for the optical heterodyne beating) and at the up-link (for the optical coherent detection). Relative to phase correlated lasers featuring linewidths of 5 MHz, the peak power of the 60 G Hz carrier generated at the down-link is reduced by 8 dB for un-correlated lasers. In addition, the error vector magnitude of the received signal at the up-link is improved from over 20% (for un-correlated lasers and linewidths of 5 MHz) to around 15% (for correlated lasers) at an optical received power of -30 dBm. The results obtained reinforce the idea of using coherent comb laser sources with phase correlated modes located at the Central Office. It also motivates the eventual deployment of techniques to control the degree of phase correlation between the lasers used as signal and local oscillator at the optical coherent receivers.

  9. Asymmetric Ashes

    Science.gov (United States)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  10. Shape-dependence of transmission, reflection and absorption eigenvalue densities in disordered waveguides with dissipation

    CERN Document Server

    Yamilov, A; Sarma, R; Cao, H

    2015-01-01

    The universal bimodal distribution of transmission eigenvalues in lossless diffusive systems un- derpins such celebrated phenomena as universal conductance fluctuations, quantum shot noise in condensed matter physics and enhanced transmission in optics and acoustics. Here, we show that in the presence of absorption, density of the transmission eigenvalues depends on the confinement geometry of scattering media. Furthermore, in an asymmetric waveguide, densities of the reflection and absorption eigenvalues also depend of the side from which the waves are incident. With increas- ing absorpotion, the density of absorption eigenvalues transforms from single-peak to double-peak function. Our findings open a new avenue for coherent control of wave transmission, reflection and absorption in random media.

  11. Improvement of the chromatic dispersion tolerance in coherent optical OFDM systems using shifted DFT windows for ultra-long-haul optical transmission systems.

    Science.gov (United States)

    Sung, Minkyu; Kim, Hoon; Lee, Jaehoon; Jeong, Jichai

    2014-09-22

    In a high-capacity ultra-long-haul optical coherent orthogonal frequency-division multiplexing (CO-OFDM) system, the dispersion tolerance is determined by the length of cyclic extension (CE). In this paper, we propose a novel scheme to substantially improve the dispersion tolerance of CO-OFDM systems without increasing the CE length. Multiple time-shifted discrete Fourier transform (DFT) windows are exploited at the receiver, each demodulating only a part of the subcarriers. Effectively, the proposed scheme reduces the bandwidth of the OFDM signals under demodulation. Numerical simulations are performed to show the improved dispersion tolerance of the proposed scheme in comparison with the conventional CO-OFDM system. We show that the dispersion tolerance improves by a factor equal to the number of DFT windows. The tradeoff between the improved dispersion tolerance and increased receiver complexity is also presented.

  12. Step-size selection for split-step based nonlinear compensation with coherent detection in 112-Gb/s 16-QAM transmission

    Institute of Scientific and Technical Information of China (English)

    Chien-Yu Lin; Rameez Asif; Michael Holtmannspoetter; Bernhard Schmauss

    2012-01-01

    Non-uniform step-size distribution is implemented for split-step based nonlinear compensation in single-channel 112-Gb/s 16 quadrature amplitude modulation (QAM) transmission. Numerical simulations of the system including a 20x80 km uncompensated link are performed using logarithmic step size distribution to compensate signal distortions. 50% of reduction in number of steps with respect to using constant step sizes is observed. The performance is further improved by optimizing nonlinear calculating position (NLCP) in case of using constant step sizes while NLCP optimization becomes unnecessary when using logarithmic step sizes, which reduces the computational effort due to uniformly distributed nonlinear phase for all successive steps.%Non-uniform step-size distribution is implemented for split-step based nonlinear compensation in singlechannel 112-Gb/s 16 quadrature amplitude modulation (QAM) transmission.Numerical simulations of the system including a 20×80 km uncompensated link are performed using logarithmic step size distribution to compensate signal distortions.50% of reduction in number of steps with respect to using constant step sizes is observed.The performance is further improved by optimizing nonlinear calculating position (NLCP) in case of using constant step sizes while NLCP optimization becomes unnecessary when using logarithmic step sizes,which reduces the computational effort due to uniformly distributed nonlinear phase for all successive steps.

  13. Asymmetric-Structure Analysis of Carbon and Energy Markets

    Science.gov (United States)

    Xu, Wei; Cao, Guangxi

    2016-02-01

    This study aimed to investigate the asymmetric structure between the carbon and energy markets from two aspects of different trends (up or down) and volatility-transmission direction using asymmetric detrended cross-correlation analysis (DCCA) cross-correlation coefficient test, multifractal asymmetric DCCA (MF-ADCCA) method, asymmetric volatility-constrained correlation metric and time rate of information-flow approach. We sampled 1283 observations from January 2008 to December 2012 among pairs of carbon and energy markets for analysis. Empirical results show that the (1) asymmetric characteristic from the cross-correlation between carbon and returns in the energy markets is significant, (2) asymmetric cross-correlation between carbon and energy market price returns is persistent and multifractral and (3) volatility of the base assets of energy market returns is more influential to the base asset of the carbon market than that of the energy market.

  14. Integrated asymmetric vertical coupler pressure sensors

    Science.gov (United States)

    Kiyat, Isa; Kocabas, Askin; Akcag, Imran; Aydinli, Atilla

    2004-08-01

    Design and analysis of a novel pressure sensor based on a silicon-on-insulator asymmetric integrated vertical coupler is presented. The coupler is composed of a single mode low index waveguide and a thin silicon slab. Wavelength selective optical modulation of asymmetric vertical coupler is examined in detail. Its potential for sensing applications is highlighted as an integrated optical pressure sensor which can be realized by standard silicon micro-fabrication. Sensitivity of transmission of such couplers on refractive index change of silicon slab ensures that they are good candidates for applications requiring high sensitivities.

  15. Electroencephalograpic coherence

    Directory of Open Access Journals (Sweden)

    Simon Brežan

    2004-08-01

    Full Text Available Different brain areas process various aspects of information in parallel as well as segregated way. It is not known, how is this information integrated into a unitary percept or action. The binding problem is one of the key problems in understanding brain function. Synchronized oscillatory activity of neurons is one possible mechanism of the functional integration of different communicating brain areas. The binding has been well-studied in the visual system, but it could also serve as a mechanism in visuomotor integration or functional coupling present with other brain processes and behavioural modes (perception, complex motor behaviour, selective attention, learning, working memory, etc.. Interregional synchronization of the electroencephalographic (EEG signal can be determined by EEG coherence analysis. In the article we present a research example of coherence changes in a visuomotor task. During this task, coherence between visual and motor brain areas increased. This might reflect functional coupling between those areas, but it could also be influenced by other cognitive processes (e.g. selective attention. Coherence analysis is suitable for studying integrative brain function. Because it measures only one of the possible mechanisms of integration, it offers promise especially when combined with other electrophysiological and functional imaging methods.

  16. Coherence and Sense of Coherence

    DEFF Research Database (Denmark)

    Dau, Susanne

    2014-01-01

    Constraints in the implementation of models of blended learning can be explained by several causes, but in this paper, it is illustrated that lack of sense of coherence is a major factor of these constraints along with the referential whole of the perceived learning environments. The question...... of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections upon these terms...... and conditions if the student shall be able acquire the necessary competencies....

  17. Coherence, Pseudo-Coherence, and Non-Coherence.

    Science.gov (United States)

    Enkvist, Nils Erik

    Analysis of the factors that make a text coherent or non-coherent suggests that total coherence requires cohesion not only on the textual surface but on the semantic level as well. Syntactic evidence of non-coherence includes lack of formal agreement blocking a potential cross-reference, anaphoric and cataphoric references that do not follow their…

  18. Coherence and Sense of Coherence

    DEFF Research Database (Denmark)

    Dau, Susanne

    2014-01-01

    of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections upon these terms...... and conditions if the student shall be able acquire the necessary competencies....

  19. Impact and Use of the Asymmetric Property in Bi-directional Cooperative Relaying under Asymmetric Traffic Conditions

    Science.gov (United States)

    Saeki, Takaaki; Yamamoto, Koji; Murata, Hidekazu; Yoshida, Susumu

    Cooperative relaying (CR) is a promising technique to provide spatial diversity by combining multiple signals from source and relay stations. In the present paper, the impact and use of the asymmetric property in bi-directional CR under asymmetric traffic conditions are discussed assuming that CR involves one communication pair and one relay station in a time division duplex (TDD) system. The asymmetric property means that the average communication quality differs for each transmission direction because of the difference in signal power between the combined signals for each direction. First, numerical results show the asymmetric property of bi-directional CR. Next, in order to evaluate the impact of the asymmetric property, the optimal relay position and resource allocation are compared to those in simple multi-hop relaying, which does not have the asymmetric property. Numerical results show that, in order to maximize the overall quality of bi-directional communication, the optimal relay position in CR depends on the offered traffic ratio, which is defined as the traffic ratio of each transmission direction, while the offered traffic ratio does not affect the optimal relay position in multi-hop relaying. Finally, the asymmetric property is used to enhance the overall quality. Specifically, a high overall quality can be achieved by, for example, opportunistically switching to the transmission direction with higher quality. Under asymmetric traffic conditions, weighted proportionally fair scheduling (WPFS), which is proposed in the context of downlink scheduling in a cellular network, is applied to transmission direction switching. Numerical results reveal that WPFS provides a high overall quality and that the quality ratio is similar to the offered traffic ratio.

  20. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  1. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Yueh [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Chang, Wei-Tse; Chen, Yi-Sheng; Hwu, En-Te; Chang, Chia-Seng; Hwang, Ing-Shouh, E-mail: ishwang@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Hsu, Wei-Hao [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This work demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.

  2. Asymmetrical international attitudes

    NARCIS (Netherlands)

    Van Oudenhoven, JP; Askevis-Leherpeux, F; Hannover, B; Jaarsma, R; Dardenne, B

    2002-01-01

    In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain asymmet

  3. Asymmetric reactions in continuous flow

    Directory of Open Access Journals (Sweden)

    Xiao Yin Mak

    2009-04-01

    Full Text Available An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed.

  4. Asymmetric catalysis with helical polymers

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2011-01-01

    Inspired by nature, the use of helical biopolymer catalysts has emerged over the last years as a new approach to asymmetric catalysis. In this Concept article the various approaches and designs and their application in asymmetric catalysis will be discussed.

  5. Characteristic of involute slope modification of asymmetric spur gear

    Institute of Scientific and Technical Information of China (English)

    DENG Xiao-he; HUA Lin; HAN Xing-hui

    2015-01-01

    The meshing characteristic of asymmetric involute spur gear was studied, the equations of the geometric shape of the asymmetric gear for both sides were deduced, and the equations of contact ratio and the key points of contact were also obtained. Meanwhile, an involute slope modification method considering the effects of static transmission errors was proposed based on the meshing properties. The characteristic of the involute slope modification was analyzed by changing different modification parameters. The mesh stiffness and synthetic mesh stiffness of unmodified and modified asymmetric spur gears were investigated. Furthermore, the spectrums of synthetic mesh stiffness under different modification parameters were compared. Research results showed that the modification parameters influence the meshing performance of gear pairs, and the proposed modification method was feasible to improve the transmission performance of gear pairs with appropriate modification parameters.

  6. Optical Coherence Tomography

    DEFF Research Database (Denmark)

    Fercher, A.F.; Andersen, Peter E.

    2017-01-01

    Optical coherence tomography (OCT) is a technique that is used to peer inside a body noninvasively. Tissue structure defined by tissue absorption and scattering coefficients, and the speed of blood flow, are derived from the characteristics of light remitted by the body. Singly backscattered light...... used in the medical field, in particular, in ophthalmology. Owing to the high transmissivity of ocular media, the depth penetration is considerable. Corresponding applications in dermatology are somewhat hindered by the strong scattering of epidermic tissue (μs ≈ 102 mm−1). As OCT provides images...... for intraoperative monitoring, and in microsurgical intervention. Optical biopsy based on OCT also provides diagnostic information by differentiating the architectural morphology of urological tissue, gastrointestinal tissue, and respiratory tissue....

  7. Asymmetric information and economics

    Science.gov (United States)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  8. Asymmetric extractions in orthodontics

    OpenAIRE

    Camilo Aquino Melgaço; Mônica Tirre de Souza Araújo

    2012-01-01

    INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portugue...

  9. Asymmetric Evolutionary Games.

    Directory of Open Access Journals (Sweden)

    Alex McAvoy

    2015-08-01

    Full Text Available Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.

  10. Asymmetric extractions in orthodontics

    Directory of Open Access Journals (Sweden)

    Camilo Aquino Melgaço

    2012-04-01

    Full Text Available INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portuguese and the EndNote 9 program was used for data base search in PubMed, Web of Science (WSc and LILACS. The selected articles were case reports, original articles and prospective or retrospective case-control studies concerning asymmetrical extractions of permanent teeth for the treatment of malocclusions. CONCLUSION: According to the literature reviewed asymmetric extractions can make some specific treatment mechanics easier. Cases finished with first permanent molars in Class II or III relationship in one or both sides seem not to cause esthetic or functional problems. However, diagnosis knowledge and mechanics control are essential for treatment success.

  11. Asymmetric flow networks

    OpenAIRE

    Olaizola Ortega, María Norma; Valenciano Llovera, Federico

    2012-01-01

    This paper provides a new model of network formation that bridges the gap between the two benchmark models by Bala and Goyal, the one-way flow model, and the two-way flow model, and includes both as particular extreme cases. As in both benchmark models, in what we call an "asymmetric flow" network a link can be initiated unilaterally by any player with any other, and the flow through a link towards the player who supports it is perfect. Unlike those models, in the opposite direction there is ...

  12. Effect of asymmetric molecule-electrode coupling and molecular bias on rectification in molecular junctions

    Science.gov (United States)

    Kaur, Rupan Preet; Sawhney, Ravinder Singh; Engles, Derick

    2016-12-01

    In this research work, we compare the rectification trends of two symmetrical and one asymmetrical molecular junction formed with gold and silver electrodes bridging benzenedithiol molecule. The origin of rectification is attributed to both molecular bias drop and asymmetric molecule-electrode coupling. The electronic transport properties are computed by using semi-empirical extended Huckel method combined with non-equilibrium Green's function framework. The results are fully rationalized by analysing the distribution of molecular orbitals with changing bias voltage, available density of states and area of transmission spectra spanned within bias window, transmission eigenstates and transmission pathways. We deduce through this work that the molecular rectification is not only the property of asymmetric molecule-metal coupling, but molecular bias also plays vital role in stemming asymmetric I- V characteristics. Our results suggest how to realize molecular rectification by using different electrode materials which act as Schottky barriers in molecular junctions that emulate p-n junction diode in semiconductor electronics.

  13. Additive Effects on Asymmetric Catalysis.

    Science.gov (United States)

    Hong, Liang; Sun, Wangsheng; Yang, Dongxu; Li, Guofeng; Wang, Rui

    2016-03-23

    This review highlights a number of additives that can be used to make asymmetric reactions perfect. Without changing other reaction conditions, simply adding additives can lead to improved asymmetric catalysis, such as reduced reaction time, improved yield, or/and increased selectivity.

  14. Overlapped optics induced perfect coherent effects

    Science.gov (United States)

    Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

    2013-12-01

    For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

  15. The asymmetric sandwich theorem

    CERN Document Server

    Simons, Stephen

    2011-01-01

    We discuss the asymmetric sandwich theorem, a generalization of the Hahn-Banach theorem. As applications, we derive various results on the existence of linear functionals that include bivariate, trivariate and quadrivariate generalizations of the Fenchel duality theorem. Most of the results are about affine functions defined on convex subsets of vector spaces, rather than linear functions defined on vector spaces. We consider both results that use a simple boundedness hypothesis (as in Rockafellar's version of the Fenchel duality theorem) and also results that use Baire's theorem (as in the Robinson-Attouch-Brezis version of the Fenchel duality theorem). This paper also contains some new results about metrizable topological vector spaces that are not necessarily locally convex.

  16. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  17. Partially coherent imaging and spatial coherence wavelets

    CERN Document Server

    Castaneda, R

    2003-01-01

    A description of spatially partially coherent imaging based on the propagation of second order spatial coherence wavelets and marginal power spectra (Wigner distribution functions) is presented. In this dynamics, the spatial coherence wavelets will be affected by the system through its elementary transfer function. The consistency of the model with the both extreme cases of full coherent and incoherent imaging was proved. In the last case we obtained the classical concept of optical transfer function as a simple integral of the elementary transfer function. Furthermore, the elementary incoherent response function was introduced as the Fourier transform of the elementary transfer function. It describes the propagation of spatial coherence wavelets form each object point to each image point through a specific point on the pupil planes. The point spread function of the system was obtained by a simple integral of the elementary incoherent response function.

  18. On Longitudinal Spectral Coherence

    DEFF Research Database (Denmark)

    Kristensen, Leif

    1979-01-01

    It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between...

  19. Improving performance of resonant tunneling devices in asymmetric structures

    Science.gov (United States)

    Shi, Jun-jie; Sanders, Barry C.; Pan, Shao-hua; Goldys, E. M.

    2001-06-01

    Based on the global coherent tunneling model, we present a self-consistent calculation and show that structural asymmetry of double barrier resonant tunneling structures (DBRTSs) significantly modifies the current-voltage characteristics compared to the symmetric structures. Within the framework of the dielectric continuum model, we further investigate the phonon-assisted tunneling (PAT) current in symmetric and asymmetric DBRTSs. Both the interface modes and the confined bulk-like longitudinal-optical phonons are considered. The results indicate that the four higher-frequency interface phonon modes (especially the one which has the largest electron-phonon interaction at either interface of the emitter barrier) dominate the PAT processes. We show that a suitably designed asymmetric structure can produce much larger peak current and absolute value of the negative differential conductivity than its commonly used symmetric counterpart.

  20. Research on the Design and Modification of Asymmetric Spur Gear

    Directory of Open Access Journals (Sweden)

    Xiaohe Deng

    2015-01-01

    Full Text Available A design method for the geometric shape and modification of asymmetric spur gear was proposed, in which the geometric shape and modification of the gear can be obtained directly according to the rack-cutter profile. In the geometric design process of the gear, a rack-cutter with different pressure angles and fillet radius in the driving side and coast side was selected, and the generated asymmetric spur gear profiles also had different pressure angles and fillets accordingly. In the modification design of the gear, the pressure angle modification of rack-cutter was conducted firstly and then the corresponding modified involute gear profile was obtained. The geometric model of spur gears was developed using computer-aided design, and the meshing process was analyzed using finite element simulation method. Furthermore, the transmission error and load sharing ratio of unmodified and modified asymmetric spur gears were investigated. Research results showed that the proposed gear design method was feasible and desired spur gear can be obtained through one time rapid machining by the method. Asymmetric spur gear with better transmission characteristic can be obtained via involute modification.

  1. Complex fermion coherent states

    CERN Document Server

    Tyc, T; Sanders, B C; Oliver, W D; Tyc, Tomas; Hamilton, Brett; Sanders, Barry C.; Oliver, William D.

    2005-01-01

    Whereas boson coherent states provide an elegant, intuitive and useful representation, we show that the desirable features of boson coherent states do not carry over very well to fermion fields unless one is prepared to use exotic approaches such as Grassmann fields. Specifically, we identify four appealing properties of boson coherent states (eigenstate of annihilation operator, displaced vacuum state, preservation of product states under linear coupling, and factorization of correlators) and show that fermion coherent states, and approximations to fermion coherent states, defined over the complex field, do not behave well for any of these four criteria.

  2. Morphology and Crystallization of Thin Films of Asymmetric Organic-Organometallic Diblock Copolymers of Isoprene and Ferrocenyldimethylsilane

    NARCIS (Netherlands)

    Lammertink, Rob G.H.; Hempenius, Mark A.; Vancso, G. Julius

    2000-01-01

    The morphology of thin films of asymmetric block copolymers of poly(isoprene-block-ferrocenyldimethylsilane) was studied using atomic force microscopy, transmission electron microscopy, and optical microscopy. Block copolymers with the organometallic (ferrocenylsilane) phase between 20 and 28 vol %

  3. Asymmetric Hardware Distortions in Receive Diversity Systems: Outage Performance Analysis

    KAUST Repository

    Javed, Sidrah

    2017-02-22

    This paper studies the impact of asymmetric hardware distortion (HWD) on the performance of receive diversity systems using linear and switched combining receivers. The asymmetric attribute of the proposed model motivates the employment of improper Gaussian signaling (IGS) scheme rather than the traditional proper Gaussian signaling (PGS) scheme. The achievable rate performance is analyzed for the ideal and non-ideal hardware scenarios using PGS and IGS transmission schemes for different combining receivers. In addition, the IGS statistical characteristics are optimized to maximize the achievable rate performance. Moreover, the outage probability performance of the receive diversity systems is analyzed yielding closed form expressions for both PGS and IGS based transmission schemes. HWD systems that employ IGS is proven to efficiently combat the self interference caused by the HWD. Furthermore, the obtained analytic expressions are validated through Monte-Carlo simulations. Eventually, non-ideal hardware transceivers degradation and IGS scheme acquired compensation are quantified through suitable numerical results.

  4. Asymmetric Gepner Models (Revisited)

    CERN Document Server

    Gato-Rivera, B

    2010-01-01

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as th...

  5. Magnetically Modified Asymmetric Supercapacitors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  6. Asymmetric de Finetti Theorem for Infinite-dimensional Quantum Systems

    CERN Document Server

    Niu, Murphy Yuezhen

    2016-01-01

    The de Finetti representation theorem for continuous variable quantum system is first developed to approximate an N-partite continuous variable quantum state with a convex combination of independent and identical subsystems, which requires the original state to obey permutation symmetry conditioned on successful experimental verification on k of N subsystems. We generalize the de Finetti theorem to include asymmetric bounds on the variance of canonical observables and biased basis selection during the verification step. Our result thereby enables application of infinite-dimensional de Finetti theorem to situations where two conjugate measurements obey different statistics, such as the security analysis of quantum key distribution protocols based on squeezed state against coherent attack.

  7. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  8. On Asymmetric Quantum MDS Codes

    CERN Document Server

    Ezerman, Martianus Frederic; Ling, San

    2010-01-01

    Assuming the validity of the MDS Conjecture, the weight distribution of all MDS codes is known. Using a recently-established characterization of asymmetric quantum error-correcting codes, linear MDS codes can be used to construct asymmetric quantum MDS codes with $d_{z} \\geq d_{x}\\geq 2$ for all possible values of length $n$ for which linear MDS codes over $\\F_{q}$ are known to exist.

  9. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation-binding catalysis was recently expanded to silicon-based reagents, enabling...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...

  10. Asymmetric transmission in planar chiral metamaterials: microscopic explanation

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Zhukovsky, S. V.

    2011-01-01

    Lorentz electron theory is a powerful approach for description of macroscopic parameters of a medium based on microscopic characteristics of the individual electron. For a planar array of chiral metallic split rings, we determine the averaged electron’s characteristics in a sprit ring and apply...... them to derive the permittivity tensor of the homogenized medium. The effective material parameters obtained describe anisotropic dichroic material, where electromagnetic waves are governed by enantiomeric and directional asymmetry – the signature property of planar chiral metamaterials....

  11. Research and Transmission

    Directory of Open Access Journals (Sweden)

    Denise Pumain

    2001-01-01

    Full Text Available The present situation provides a challenge for us to reconsider the necessary link between science and pedagogy, between research and the transmission of knowledge. The Ministry of National education has just inaugurated a broad consultation of teachers on every level with a view to modernising and giving coherence to the programs of secondary education. Armand Frémont will head the group of experts responsible for history and geography. Is this a coincidence? The changeover in the jury for t...

  12. On -Coherent Endomorphism Rings

    Indian Academy of Sciences (India)

    Li-Xin Mao

    2008-11-01

    A ring is called right -coherent if every principal right ideal is finitely presented. Let $M_R$ be a right -module. We study the -coherence of the endomorphism ring of $M_R$. It is shown that is a right -coherent ring if and only if every endomorphism of $M_R$ has a pseudokernel in add $M_R; S$ is a left -coherent ring if and only if every endomorphism of $M_R$ has a pseudocokernel in add $M_R$. Some applications are given.

  13. Coherent Raman spectroscopy

    CERN Document Server

    Eesley, G L

    1981-01-01

    Coherent Raman Spectroscopy provides a unified and general account of the fundamental aspects of nonlinear Raman spectroscopy, also known as coherent Raman spectroscopy. The theoretical basis from which coherent Raman spectroscopy developed is described, along with its applications, utility, and implementation as well as advantages and disadvantages. Experimental data which typifies each technique is presented. This book is comprised of four chapters and opens with an overview of nonlinear optics and coherent Raman spectroscopy, followed by a discussion on nonlinear transfer function of matter

  14. Application Coherency Manager Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes an Application Coherency Manager that implements and manages the interdependencies of simulation, data, and platform information. It will...

  15. Price Transmission Analysis in Iran Chicken Market

    Directory of Open Access Journals (Sweden)

    Seyed Safdar Hosseini

    2012-12-01

    Full Text Available Over the past three decades vertical price transmissionanalysis has been the subject of considerable attention inapplied agricultural economics. It has been argued that theexistence of asymmetric price transmission generates rents formarketing and processing agents. Retail prices allegedly movefaster upwards than downwards in response to farm level pricemovements. This is an important issue for many agriculturalmarkets, including the Iranian chicken market. Chicken is animportant source of nutrition in Iranian society and many ruralhouseholds depend on this commodity market as a source of income.The purpose of this paper is to analyze the extent, if any,of asymmetric price transmission in Iran chicken market usingthe Houck, Error Correction and Threshold models. The analysisis based on weekly chicken price data at farm and retail levelsover the period October 2002 to March 2006. The results oftests on all three models show that price transmission in Iranianchicken market is long-run symmetric, but short-run asymmetric.Increases in the farm price transmit immediately to the retaillevel, while decreases in farm price transmit relatively moreslowly to the retail level. We conjecture the asymmetric pricetransmission in this market is the result of high inflation ratesthat lead the consumers to expect continual price increases anda different adjustment costs in the upwards direction comparedto the downwards direction for the marketing agents and a noncompetitiveslaughtering industry and that looking for ways tomake this sector of the chicken supply chain more competitivewill foster greater price transmission symmetry and lead towelfare gains for both consumers and agricultural producers.

  16. Fifth-Order Harmonic Generation using a Coherent Controlled Two-Pulsed Optical Field

    Institute of Scientific and Technical Information of China (English)

    刘婷婷; 王大威; 陆伟新; 孙泉; 杨宏; 蒋红兵; 龚旗煌

    2002-01-01

    We have experimentally studied the characteristics of fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase. The intensities of harmonic generation are found to increase vith the coherent degree. In one optical period, the temporal variation of harmonics exhibits an asymmetric characteristic, vhich is interpreted in terms of ionization theory and the deformation of the wave packets of fundamental field contribution to harmonic generation.

  17. Nonlinear effects in asymmetric catalysis.

    Science.gov (United States)

    Satyanarayana, Tummanapalli; Abraham, Susan; Kagan, Henri B

    2009-01-01

    There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non-enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis.

  18. Asymmetric distances for binary embeddings.

    Science.gov (United States)

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2014-01-01

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.

  19. Spectral coherent-state quantum cryptography.

    Science.gov (United States)

    Cincotti, Gabriella; Spiekman, Leo; Wada, Naoya; Kitayama, Ken-ichi

    2008-11-01

    A novel implementation of quantum-noise optical cryptography is proposed, which is based on a simplified architecture that allows long-haul, high-speed transmission in a fiber optical network. By using a single multiport encoder/decoder and 16 phase shifters, this new approach can provide the same confidentiality as other implementations of Yuen's encryption protocol, which use a larger number of phase or polarization coherent states. Data confidentiality and error probability for authorized and unauthorized receivers are carefully analyzed.

  20. Asymmetric Flexible Supercapacitor Stack

    Directory of Open Access Journals (Sweden)

    Leela Mohana Reddy A

    2008-01-01

    Full Text Available AbstractElectrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM, transmission electron microscopy (TEM and HRTEM. An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.

  1. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  2. Reverse Coherent Information

    Science.gov (United States)

    García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.

    2009-05-01

    In this Letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well-known coherent information. This leads to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.

  3. VCSELs for coherent PON

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee; Rodes, Roberto; Cheng, Ning;

    2015-01-01

    Recent advances and research on coherent technologies for access networks are discussed and put into context of user demands and standardization work.......Recent advances and research on coherent technologies for access networks are discussed and put into context of user demands and standardization work....

  4. Understanding Causal Coherence Relations

    NARCIS (Netherlands)

    Mulder, G.

    2008-01-01

    The research reported in this dissertation focuses on the cognitive processes and representations involved in understanding causal coherence relations in text. Coherence relations are the meaning relations between the information units in the text, such as Cause-Consequence. These relations can be m

  5. Channel Coding over Multiple Coherence Blocks with Queueing Constraints

    CERN Document Server

    Qiao, Deli; Velipasalar, Senem

    2010-01-01

    This paper investigates the performance of wireless systems that employ finite-blocklength channel codes for transmission and operate under queueing constraints in the form of limitations on buffer overflow probabilities. A block fading model, in which fading stays constant in each coherence block and change independently between blocks, is considered. It is assumed that channel coding is performed over multiple coherence blocks. An approximate lower bound on the transmission rate is obtained from Feintein's Lemma. This lower bound is considered as the service rate and is incorporated into the effective capacity formulation, which characterizes the maximum constant arrival rate that can be supported under statistical queuing constraints. Performances of variable-rate and fixed-rate transmissions are studied. The optimum error probability for variable rate transmission and the optimum coding rate for fixed rate transmission are shown to be unique. Moreover, the tradeoff between the throughput and the number of...

  6. Digital coherent transceiver for optical communications: from design to implementation

    OpenAIRE

    Anzuola Valencia, Esdras

    2012-01-01

    Establishing the basis of optical coherent transmission and detection which exploit digital signal processing (DSP) to optimize the performance of optical communication systems. [ANGLÈS] In this project we analyze the theoretical models of optical coherent communication systems as well as the front-end arquitectures used to implement them. Key concepts as balanced photo detection and quantum limit are explained and studied. Complex modulation schemes maximize spectral efficiency and power ...

  7. Orthogonal wavelet analysis of counter gradient transport phenomena in turbulent asymmetric channel flow

    Institute of Scientific and Technical Information of China (English)

    Jianbo Jiang; Xiang Qiu; Zhiming Lu; Yulu Liu

    2005-01-01

    In this paper four families of orthogonal wavelets are applied to analyze the turbulent counter gradient transport phenomena in fully developed asymmetric channel flows,The results show that: (1) In the instance of counter gradient transport, the principal scale of the coherent structure is responsible for the strong local counter gradient transport; (2)Counter gradient transport phenomena have a strong effect on the intermittency of turbulence; (3) Non-Gaussian part of the principal coherent structure is essential for counter gradient transport phenomena.

  8. Tunneling-Induced Transient Gain in an Asymmetric Double Quantum Well

    Institute of Scientific and Technical Information of China (English)

    XU Wei-Hua; WU Jin-Hui; GAO Jin-Yue

    2004-01-01

    @@ We investigate the transient behaviour of a weak probe in asymmetric double quantum well structures, where two excited states are coupled by resonant tunnelling through a thin barrier in a three-level system of electronic subbands. There is no external coherent coupling field applied, and we find that probe gain can be achieved during the transient process, which is induced by the coherent coupling of the upper states via the resonant tunnelling.We show that the transient behaviour of the probe depends on the coupling strength and the dephasing rate and can be tuned by changing the width of the tunnelling barrier.

  9. Synthesis of Asymmetric Propanetriol Analogues

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    From natural tartaric acid, (R)-2-benzyloxy-3-(2-tetrahydropyranyloxy) propanol 3 was designed and synthesized, and (R)-2-benzyloxy-3-(4-methoxybenzyloxy) propanol 7 was prepared in a new method. They can be used as chiral synthons of lysophosphatidic acid and other compounds with asymmetric propanetriol backbone.

  10. Catalytic Asymmetric Bromocyclization of Polyenes.

    Science.gov (United States)

    Samanta, Ramesh C; Yamamoto, Hisashi

    2017-02-01

    The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

  11. Wakefields in Coherent Synchrotron Radiation

    Science.gov (United States)

    Billinghurst, Brant E.; Bergstrom, J. C.; Baribeau, C.; Batten, T.; Dallin, L.; May, Tim E.; Vogt, J. M.; Wurtz, Ward A.; Warnock, Robert L.; Bizzozero, D. A.; Kramer, S.; Michaelian, K. H.

    2016-06-01

    When the electron bunches in a storage ring are sufficiently short the electrons act coherently producing radiation several orders of magnitude more intense than normal synchrotron radiation. This is referred to as Coherent Syncrotron Radiation (CSR). Due to the potential of CSR to provide a good source of Terahertz radiation for our users, the Canadian Light Source (CLS) has been researching the production and application of CSR. CSR has been produced at the CLS for many years, and has been used for a number of applications. However, resonances that permeate the spectrum at wavenumber intervals of 0.074 cm-1, and are highly stable under changes in the machine setup, have hampered some experiments. Analogous resonances were predicted long ago in an idealized theory. Through experiments and further calculations we elucidate the resonance and wakefield mechanisms in the CLS vacuum chamber. The wakefield is observed directly in the 30-110 GHz range by rf diodes. These results are consistent with observations made by the interferometer in the THz range. Also discussed will be some practical examples of the application of CSR for the study of condensed phase samples using both transmission and Photoacoustic techniques.

  12. Coherent diffractive {rho} production

    Energy Technology Data Exchange (ETDEWEB)

    Hyett, N.M.; Tovey, S.N. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1995-12-31

    Coherent diffractive {rho} production by neutrinos occurs at low four-momentum transfer and high energy transfer. These interactions are generally understood to occur via the coupling of the weak charged current to the vector meson, which scatters diffractively from the target nucleus. Since coherent events are those in which the nucleus interacts as a whole, ie without breakup, and with small recoil energy, these events have a very sharp |t|-distribution. This presentation deals mostly with the Monte Carlo simulation of the coherent diffractive production of the {rho} production and in particular with the reconstruction algorithm (description and efficiency) and the |t| distribution. 4 refs., 1 fig.

  13. The Coherent Curriculum

    Institute of Scientific and Technical Information of China (English)

    Michael Thomas

    2005-01-01

    @@ What makes a coherent EFL curriculum? How can curriculum planners avoid a mismatch between policy and pragmatics to produce an effective decision-making process? In The Second Language Curriculum, Johnson describes the coherent curriculum as one in which decision outcomes from the various stages of development are mutually consistent and complementary,and learning outcomes reflect curriculum aims.The achievement of coherence is said to depend crucially in most educational contexts upon the formalisation of decision-making processes and products. This formalisation facilitates consensus among those involved and is a prerequisite for effective evaluation and subsequent renewal (1994: xiii)

  14. The Puzzle of Coherence

    DEFF Research Database (Denmark)

    Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;

    2016-01-01

    of coherence in treatment and patient pathways. The aim of our study is to explore the role of health care providers in furthering coherence. Our ambition is to identify areas for improvement or change of collaborative practice between health care providers in municipalities, hospitals and general practice...... initiatives in health care. The present study will generate new, valuable insight into the areas of cross-sectorial health care collaboration. Our findings may facilitate change in current practice and improve the quality and coherence in patient pathways of EPCD. The findings of this study will be useful...

  15. 100-Gbps hybrid optical fiber-wireless transmission

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Caballero Jambrina, Antonio; Deng, Lei;

    2013-01-01

    We present experimental results on using optical transmission technologies such as I&Q modulators, digital coherent receivers, heterodyne up-conversion in fast photodiodes, to generate, transmit and detect high capacity wireless transmission. Both OFDM and QAM modulation formats are tested in the......-achieving capacities up to 100-Gbps with seamless optical fiber-wireless conversion.......We present experimental results on using optical transmission technologies such as I&Q modulators, digital coherent receivers, heterodyne up-conversion in fast photodiodes, to generate, transmit and detect high capacity wireless transmission. Both OFDM and QAM modulation formats are tested in the W...

  16. Tunable bistability and asymmetric line shape in ring cavity-coupled Michelson interferometer

    Science.gov (United States)

    Li, Li; Zhang, Xinlu; Chen, Lixue

    2008-01-01

    A novel configuration of ring cavity-coupled Michelson interferometer is proposed to create sharp asymmetric multiple-resonance line shape, in which a ring cavity is side-coupled to one arm and a phase shifter is introduced into the other arm for static phase compensation. Such asymmetric line shape allows the tuning of the system between zero and complete transmission, with a phase offset much narrower than the full width of the cavity resonance itself. As tuning between resonance peak and notch of such asymmetric profile, optical transmission becomes much more sensitive to the round-trip phase shift of ring cavity than that in the case of symmetric Lorentzian line shape. By cooperating Kerr nonlinearity and cavity feedback, novel hysteresis loops and intrinsic bistability are achievable by adjusting incident power. The shapes of hysteresis curves associated with asymmetric resonance line shape are different from those arising from symmetric line shape. By adjusting the static phase compensation of phase shifter, tunable hysteresis loop and asymmetric multiple-resonance transmission can be easy performed. The simply constructed device is a good reference for sensitive optical switch, filter and sensor.

  17. Optical Code Generating Device Using 1×N Asymmetric Hollow Waveguide Couplers

    Institute of Scientific and Technical Information of China (English)

    Abang Annuar EHSAN; Sahbudin SHAARI; Mohd Kamil ABD.RAHMAN; Kee Mohd Rafique KEE ZAINAL ABIDIN

    2008-01-01

    An optical code generating device for security access system application is presented. The code generating device constructed using asymmetric hollow optical waveguide coupler design provides a unique series of output light intensities which are successively used as an optical code. The design of the waveguide is made using two major components which are asymmetric Y-junction splitter and a linear taper. Waveguiding is done using a hollow waveguide structure. Construction of higher level 1×N hollow waveguide coupler is done utilizing a basic 1×2 asymmetric waveguide coupler design together with a cascaded design scheme. Non-sequential ray tracing of the asymmetric hollow optical waveguide couplers is performed to predict the optical transmission properties of the waveguide. A representation of the code combination that can be generated from the device is obtained using combinatory number theory.

  18. Asymmetric Multilevel Diversity Coding and Asymmetric Gaussian Multiple Descriptions

    CERN Document Server

    Mohajer, Soheil; Diggavi, Suhas N

    2009-01-01

    We consider the asymmetric multilevel diversity (A-MLD) coding problem, where a set of $2^K-1$ information sources, ordered in a decreasing level of importance, is encoded into $K$ messages (or descriptions). There are $2^K-1$ decoders, each of which has access to a non-empty subset of the encoded messages. Each decoder is required to reproduce the information sources up to a certain importance level depending on the combination of descriptions available to it. We obtain a single letter characterization of the achievable rate region for the 3-description problem. In contrast to symmetric multilevel diversity coding, source-separation coding is not sufficient in the asymmetric case, and ideas akin to network coding need to be used strategically. Based on the intuitions gained in treating the A-MLD problem, we derive inner and outer bounds for the rate region of the asymmetric Gaussian multiple description (MD) problem with three descriptions. Both the inner and outer bounds have a similar geometric structure t...

  19. Coherence for Modalities

    CERN Document Server

    Dosen, K

    2008-01-01

    Positive modalities in systems in the vicinity of S4 and S5 are investigated in terms of categorial proof theory. Coherence and maximality results are demonstrated, and connections with mixed distributive laws and Frobenius algebras are exhibited.

  20. Coherence in Industrial Transformation

    DEFF Research Database (Denmark)

    Jørgensen, Ulrik; Lauridsen, Erik Hagelskjær

    2003-01-01

    The notion of coherence is used to illustrate the general finding, that the impact of environmental management systems and environmental policy is highly dependent of the context and interrelatedness of the systems, procedures and regimes established in society....

  1. Genuine Quantum Coherence

    CERN Document Server

    Streltsov, Alexander

    2015-01-01

    The basis of any quantum resource theory are free states and free operations, these are states and operations which can be created or performed at no cost. In the resource theory of quantum coherence free states are states which are diagonal in a fixed reference basis. This choice is natural in many experimental scenarios where the reference basis is singled out by the unavoidable decoherence. The corresponding free operations are called incoherent, they can be implemented as a generalized measurement which does not create any coherence. However, a general quantum operation admits different experimental realizations, and a quantum operation which seems incoherent in one experimental realization might create coherence in another. Starting from this observation, we propose the framework of genuine quantum coherence. This approach is based on a simple principle: we demand that a genuinely incoherent operation preserves all incoherent states. This simple condition automatically guarantees that the operation is in...

  2. Coherence-Enhanced Spaser

    CERN Document Server

    Dorfman, Konstantin E; Voronine, Dmitri V; Genevet, Patrice; Capasso, Federico; Scully, Marlan O

    2012-01-01

    We investigate surface plasmon amplification in a silver nanoshell coupled to an externally driven three-level gain medium, and show that quantum coherence significantly enhances the generation of surface plasmons. Surface plasmon amplification by stimulated emission of radiation is achieved in the absence of population inversion on the spasing transition, which reduces the pump requirements. The coherent drive allows us to control the dynamics, and holds promise for quantum control of nanoplasmonic devices.

  3. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size-asymmetric ......A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size...

  4. Cyclodextrins in Asymmetric and Stereospecific Synthesis

    Directory of Open Access Journals (Sweden)

    Fliur Macaev

    2015-09-01

    Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.

  5. Power efficient and colorless PON upstream system using asymmetric clipping optical OFDM and TDMA technologies

    Science.gov (United States)

    Zhao, Yuan; Qiao, Yaojun; Ji, Yuefeng

    2012-04-01

    Asymmetric clipping optical orthogonal frequency division multiplexing (ACO-OFDM) based time division multiple access (TDMA) Passive Optical Network (PON) upstream transmission architecture is proposed. The system features low power consumption, colorless, and cost effectiveness. Performance and validity of 10 Gb/s upstream transmission are studied and confirmed by simulation. Performance degradation due to interference from rogue Optical Network Unit (ONU) is also studied.

  6. Genuine quantum coherence

    Science.gov (United States)

    de Vicente, Julio I.; Streltsov, Alexander

    2017-01-01

    Any quantum resource theory is based on free states and free operations, i.e. states and operations which can be created and performed at no cost. In the resource theory of coherence free states are diagonal in some fixed basis, and free operations are those which cannot create coherence for some particular experimental realization. Recently, some problems of this approach have been discussed, and new sets of operations have been proposed to resolve these problems. We propose here the framework of genuine quantum coherence. This approach is based on a simple principle: we demand that a genuinely incoherent operation preserves all incoherent states. This framework captures coherence under additional constrains such as energy preservation and all genuinely incoherent operations are incoherent regardless of their particular experimental realization. We also introduce the full class of operations with this property, which we call fully incoherent. We analyze in detail the mathematical structure of these classes and also study possible state transformations. We show that deterministic manipulation is severely limited, even in the asymptotic settings. In particular, this framework does not have a unique golden unit, i.e. there is no single state from which all other states can be created deterministically with the free operations. This suggests that any reasonably powerful resource theory of coherence must contain free operations which can potentially create coherence in some experimental realization.

  7. Dirac Particle for the Position Dependent Mass in the Generalized Asymmetric Woods-Saxon Potential

    Directory of Open Access Journals (Sweden)

    Soner Alpdoğan

    2014-01-01

    Full Text Available The one-dimensional Dirac equation with position dependent mass in the generalized asymmetric Woods-Saxon potential is solved in terms of the hypergeometric functions. The transmission and reflection coefficients are obtained by considering the one-dimensional electric current density for the Dirac particle and the equation describing the bound states is found by utilizing the continuity conditions of the obtained wave function. Also, by using the generalized asymmetric Woods-Saxon potential solutions, the scattering states are found out without making calculation for the Woods-Saxon, Hulthen, cusp potentials, and so forth, which are derived from the generalized asymmetric Woods-Saxon potential and the conditions describing transmission resonances and supercriticality are achieved. At the same time, the data obtained in this work are compared with the results achieved in earlier studies and are observed to be consistent.

  8. Coherence vortices of partially coherent beams in the far field

    Institute of Scientific and Technical Information of China (English)

    Liu Pu-Sheng; Lü Bai-da

    2007-01-01

    Based on the propagation law of cross-spectral density function, studied in this paper are the coherence vortices of partially coherent, quasi-monochromatic singular beams with Gaussian envelope and Schell-model correlator in the far field, where our main attention is paid to the evolution of far-field coherence vortices into intensity vortices of fully coherent beams. The results show that, although there are usually no zeros of intensity in partially coherent beams with Gaussian envelope and Schell-model correlator, zeros of spectral degree of coherence exist. The coherence vortices of spectral degree of coherence depend on the relative coherence length, mode index and positions of pairs of points.If a point and mode index are kept fixed, the position of coherence vortices changes with the increase of the relative coherence length. For the low coherent case there is a circular phase dislocation. In the coherent limit coherence vortices become intensity vortices of fully coherent Laguerre-Gaussian beams.

  9. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  10. Asymmetrical Γ-Source Inverters

    DEFF Research Database (Denmark)

    Wei, Mo; Poh Chiang, Loh; Blaabjerg, Frede

    2014-01-01

    , inverters with coupled transformers have been introduced, but they usually lead to high turns ratio, and hence many winding turns, at high gain. An alternative would then be the asymmetrical Γ-source inverters proposed in this paper, whose gain is raised by lowering their turns ratio toward unity. The input...... current drawn by the proposed inverters is smoother and, hence, more adaptable by the source. Theories and experimental results have been presented in this paper for validating the concepts proposed....

  11. Up-down asymmetric tokamaks

    CERN Document Server

    Ball, Justin

    2016-01-01

    Bulk toroidal rotation has proven capable of stabilising both dangerous MHD modes and turbulence. In this thesis, we explore a method to drive rotation in large tokamaks: up-down asymmetry in the magnetic equilibrium. We seek to maximise this rotation by finding optimal up-down asymmetric flux surface shapes. First, we use the ideal MHD model to show that low order external shaping (e.g. elongation) is best for creating up-down asymmetric flux surfaces throughout the device. Then, we calculate realistic up-down asymmetric equilibria for input into nonlinear gyrokinetic turbulence analysis. Analytic gyrokinetics shows that, in the limit of fast shaping effects, a poloidal tilt of the flux surface shaping has little effect on turbulent transport. Since up-down symmetric surfaces do not transport momentum, this invariance to tilt implies that devices with mirror symmetry about any line in the poloidal plane will drive minimal rotation. Accordingly, further analytic investigation suggests that non-mirror symmetri...

  12. Stimulated coherent transition radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hung-chi Lihn

    1996-03-01

    Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed.

  13. SAR image effects on coherence and coherence estimation.

    Energy Technology Data Exchange (ETDEWEB)

    Bickel, Douglas Lloyd

    2014-01-01

    Radar coherence is an important concept for imaging radar systems such as synthetic aperture radar (SAR). This document quantifies some of the effects in SAR which modify the coherence. Although these effects can disrupt the coherence within a single SAR image, this report will focus on the coherence between separate images, such as for coherent change detection (CCD) processing. There have been other presentations on aspects of this material in the past. The intent of this report is to bring various issues that affect the coherence together in a single report to support radar engineers in making decisions about these matters.

  14. High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback

    DEFF Research Database (Denmark)

    Thestrup, B.; Chi, M.; Sass, B.;

    2003-01-01

    In this letter, we show that polarization coupling and asymmetric diode-laser feedback can be used to combine two diode-laser beams with low spatial coherence into a single beam with high spatial coherence. The coupled laser source is based on two similar laser systems each consisting of a 1 mumx...... lasers are 29+/-1 and 34+/-1, respectively. (C) 2003 American Institute of Physics.......In this letter, we show that polarization coupling and asymmetric diode-laser feedback can be used to combine two diode-laser beams with low spatial coherence into a single beam with high spatial coherence. The coupled laser source is based on two similar laser systems each consisting of a 1 mumx......200 mum broad area laser diode applied with a specially designed feedback circuit. When operating at two times threshold, 50% of the freely running system output power is obtained in a single beam with an M-2 beam quality factor of 1.6+/-0.1, whereas the M-2 values of the two freely running diode...

  15. Reconfigurable Digital Coherent Receiver for Hybrid Optical Fiber/Wireless Metro-Access Networks

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Guerrero Gonzalez, Neil; Caballero Jambrina, Antonio;

    Single reconfigurable DSP coherent receiver is experimentally demonstrated for mixed-format and bit-rates including QPSK, OFDM, IR-UWB for wireline and wireless signal types. Successful transmission and detection over a deployed fiber link is achieved.......Single reconfigurable DSP coherent receiver is experimentally demonstrated for mixed-format and bit-rates including QPSK, OFDM, IR-UWB for wireline and wireless signal types. Successful transmission and detection over a deployed fiber link is achieved....

  16. Coherent Detection of Wavelength Division Multiplexed Phase-Modulated Radio-over-Fibre Signals

    DEFF Research Database (Denmark)

    Zibar, Darko; Yu, Xianbin; Peucheret, Christophe

    2008-01-01

    A WDM phase-modulated Radio-over-Fibre link using digital coherent detection is experimentally demonstrated. 3 times 50 Mb/s WDM transmission of a BPSK modulated 5 GHz RF carrier is achieved over 25 km.......A WDM phase-modulated Radio-over-Fibre link using digital coherent detection is experimentally demonstrated. 3 times 50 Mb/s WDM transmission of a BPSK modulated 5 GHz RF carrier is achieved over 25 km....

  17. Super-Resonant Intracavity Coherent Absorption

    Science.gov (United States)

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.

    2016-07-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.

  18. Super-Resonant Intracavity Coherent Absorption

    CERN Document Server

    Malara, P; Giorgini, A; Avino, S; De Natale, P; Gagliardi, G

    2016-01-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption. We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot-ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy...

  19. Asymmetric Schiff bases derived from diaminomaleonitrile and their metal complexes

    Science.gov (United States)

    Yang, Jianjie; Shi, Rufei; Zhou, Pei; Qiu, Qiming; Li, Hui

    2016-02-01

    Asymmetric Schiff bases, due to its asymmetric structure, can be used as asymmetric catalyst, antibacterial, and mimic molecules during simulate biological processes, etc. In recent years, research on synthesis and properties of asymmetric Schiff bases have become an increase interest of chemists. This review summarizes asymmetric Schiff bases derived from diaminomaleonitrile (DAMN) and DAMN-based asymmetric Schiff bases metal complexes. Applications of DAMN-based asymmetric Schiff bases are also discussed in this review.

  20. Dynamic coherent backscattering mirror

    Energy Technology Data Exchange (ETDEWEB)

    Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu [Physics Department, Fairfield University, Fairfield, CT 06824 (United States)

    2016-02-15

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

  1. Coherence for Monoidal Endofunctors

    CERN Document Server

    Dosen, K

    2009-01-01

    The goal of this paper is to prove coherence results with respect to relational graphs for monoidal endofunctors, i.e. endofunctors of a monoidal category that preserve the monoidal structure up to a natural transformation that need not be an isomorphism. These results are proved first in the absence of symmetry in the monoidal structure, and then with this symmetry. In the later parts of the paper the coherence results are extended to monoidal endofunctors in monoidal categories that have diagonal or codiagonal natural transformations, or where the monoidal structure is given by finite products or coproducts. Monoidal endofunctors are interesting because they stand behind monoidal monads and comonads, for which coherence will be proved in a sequel to this paper.

  2. Coherence in Microchip Traps

    CERN Document Server

    Treutlein, P; Steinmetz, T; Hänsch, T W; Reichel, J; Treutlein, Philipp; Hommelhoff, Peter; Steinmetz, Tilo; H\\"ansch, Theodor W.; Reichel, Jakob

    2003-01-01

    We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $4-130 \\mu$m from the microchip surface. The coherence lifetime in the microtrap is independent of atom-surface distance and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum information processing, we propose to use microwave near-fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.

  3. Dynamic coherent backscattering mirror

    Science.gov (United States)

    Xu, M.

    2016-01-01

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation. PMID:26937296

  4. Optical coherent and envelope detection for photonic wireless communication links

    DEFF Research Database (Denmark)

    Prince, Kamau; Zibar, Darko; Yu, Xianbin;

    We present two novel optical detection techniques for radio over fiber (RoF) communication links. Firstly, we present recent results obtained with optical digital coherent detection of optical phase-modulated ROF signals supporting error-free transmission over 25 km standard SMF with BPSK and QPSK...

  5. Maintaining Web Cache Coherency

    Directory of Open Access Journals (Sweden)

    2000-01-01

    Full Text Available Document coherency is a challenging problem for Web caching. Once the documents are cached throughout the Internet, it is often difficult to keep them coherent with the origin document without generating a new traffic that could increase the traffic on the international backbone and overload the popular servers. Several solutions have been proposed to solve this problem, among them two categories have been widely discussed: the strong document coherency and the weak document coherency. The cost and the efficiency of the two categories are still a controversial issue, while in some studies the strong coherency is far too expensive to be used in the Web context, in other studies it could be maintained at a low cost. The accuracy of these analysis is depending very much on how the document updating process is approximated. In this study, we compare some of the coherence methods proposed for Web caching. Among other points, we study the side effects of these methods on the Internet traffic. The ultimate goal is to study the cache behavior under several conditions, which will cover some of the factors that play an important role in the Web cache performance evaluation and quantify their impact on the simulation accuracy. The results presented in this study show indeed some differences in the outcome of the simulation of a Web cache depending on the workload being used, and the probability distribution used to approximate updates on the cached documents. Each experiment shows two case studies that outline the impact of the considered parameter on the performance of the cache.

  6. Apparent diffusion behaviour of intermolecular double-quantum coherence modulated by a distant dipolar field in solution NMR

    Institute of Scientific and Technical Information of China (English)

    Shen Gui-Ping; Cai Cong-Bo; Cai Shu-Hui; Chen Zhong

    2009-01-01

    A modified correlated spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence was designed to investigate the influence of diffusion behaviour on intermolecular double-quantum coherence signal attenuation during the pre-acquisition period. Theoretical formulas were deduced and experimental measurements and simulations were performed. It is found that the diffusion behaviour of intermolecular double-quantum coherence in the pre-acquisition period may be different from that of conventional single-quantum coherence, depending on the relative orientation of diffusion weighting gradients to coherence selection gradients. When the orientation of the diffusion weighting gradients is parallel or anti-parallel to the orientation of the coherence selection gradients, the diffusion is modulated by the distant dipolar field. This study is helpful for understanding the signal properties in intermolecular double-quantum coherence magnetic resonance imaging.

  7. Coherent states measurement entropy

    CERN Document Server

    Kwapien, J; Zyczkowski, K; Kwapien, Jaroslaw; Slomczynski, Wojciech; Zyczkowski, Karol

    1996-01-01

    Coherent states (CS) quantum entropy can be split into two components. The dynamical entropy is linked with the dynamical properties of a quantum system. The measurement entropy, which tends to zero in the semiclassical limit, describes the unpredictability induced by the process of a quantum approximate measurement. We study the CS--measurement entropy for spin coherent states defined on the sphere discussing different methods dealing with the time limit n \\to \\infty. In particular we propose an effective technique of computing the entropy by iterated function systems. The dependence of CS--measurement entropy on the character of the partition of the phase space is analysed.

  8. Coherent light microscopy

    CERN Document Server

    Ferraro, Pietro; Zalevsky, Zeev

    2011-01-01

    This book deals with the latest achievements in the field of optical coherent microscopy. While many other books exist on microscopy and imaging, this book provides a unique resource dedicated solely to this subject. Similarly, many books describe applications of holography, interferometry and speckle to metrology but do not focus on their use for microscopy. The coherent light microscopy reference provided here does not focus on the experimental mechanics of such techniques but instead is meant to provide a users manual to illustrate the strengths and capabilities of developing techniques. Th

  9. Coherent terahertz photonics.

    Science.gov (United States)

    Seeds, Alwyn J; Fice, Martyn J; Balakier, Katarzyna; Natrella, Michele; Mitrofanov, Oleg; Lamponi, Marco; Chtioui, Mourad; van Dijk, Frederic; Pepper, Michael; Aeppli, Gabriel; Davies, A Giles; Dean, Paul; Linfield, Edmund; Renaud, Cyril C

    2013-09-23

    We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications.

  10. On the wake flow of asymmetrically beveled trailing edges

    Science.gov (United States)

    Guan, Yaoyi; Pröbsting, Stefan; Stephens, David; Gupta, Abhineet; Morris, Scott C.

    2016-05-01

    Trailing edge and wake flows are of interest for a wide range of applications. Small changes in the design of asymmetrically beveled or semi-rounded trailing edges can result in significant difference in flow features which are relevant for the aerodynamic performance, flow-induced structural vibration and aerodynamically generated sound. The present study describes in detail the flow field characteristics around a family of asymmetrically beveled trailing edges with an enclosed trailing-edge angle of 25° and variable radius of curvature R. The flow fields over the beveled trailing edges are described using data obtained by particle image velocimetry (PIV) experiments. The flow topology for different trailing edges was found to be strongly dependent on the radius of curvature R, with flow separation occurring further downstream as R increases. This variation in the location of flow separation influences the aerodynamic force coefficients, which were evaluated from the PIV data using a control volume approach. Two-point correlations of the in-plane velocity components are considered to assess the structure in the flow field. The analysis shows large-scale coherent motions in the far wake, which are associated with vortex shedding. The wake thickness parameter yf is confirmed as an appropriate length scale to characterize this large-scale roll-up motion in the wake. The development in the very near wake was found to be critically dependent on R. In addition, high-speed PIV measurements provide insight into the spectral characteristics of the turbulent fluctuations. Based on the time-resolved flow field data, the frequency range associated with the shedding of coherent vortex pairs in the wake is identified. By means of time-correlation of the velocity components, turbulent structures are found to convect from the attached or separated shear layers without distinct separation point into the wake.

  11. Asymmetric propagation of electromagnetic waves through nanoscale spirals

    Science.gov (United States)

    Hu, Jingpei; Lin, Yu; Zhu, Aijiao; Zhao, Xiaonan; Wang, Chinhua

    2016-10-01

    In this paper, we report that normal incidence transmission of different circularly polarized waves through the 2D Archimedes' nanoscale spirals is asymmetric. The structures consist of raised spiral ridge and two layers metal film covered on the substrate and the ridge. The finite difference time domain method was used to design the structure and perform the simulation. The device can distinguish the different circularly polarized wave across the transmission intensity compare with the common Archimedes' nanoscale spirals which just exhibit the bright or dark modes in the light field. We confirmed that the device provide about 10% circular dichroism in 3.85um-6.0um broadband region. The circular dichroism in the wavelength 3.95 um can reach 13%. This ultracompact device could prove useful for remote sensing and advanced telecommunication applications.

  12. Coherency matrix formulation for partially coherent imaging to evaluate the degree of coherence for image.

    Science.gov (United States)

    Yamazoe, Kenji

    2012-08-01

    This paper defines a matrix from which coherence property of imaging by partially coherent Koehler illumination is determined. The matrix termed coherency matrix in imaging system is derived by the space average of a product of a column vector and its transpose conjugate where each row of the column vector represents mutually incoherent light. The coherency matrix in imaging system has similar properties to the polarization matrix that is utilized for calculating the light intensity and degree of polarization of polarized light. The coherency matrix in imaging system enables us to calculate not only image intensity but also degree of coherence for image. Simulation results of the degree of coherence for image given by the coherency matrix in imaging system correspond to the complex degree of coherence obtained by the van Cittert-Zernike theorem.

  13. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  14. The asymmetric Goos-H\\"anchen effect

    OpenAIRE

    Araujo, Manoel P.; Carvalho, Silvânia A.; De Leo, Stefano

    2013-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the inc...

  15. Coherence Constraints and the Last Hidden Optical Coherence

    CERN Document Server

    Qian, Xiao-Feng; Vamivakas, A Nick; Eberly, Joseph H

    2016-01-01

    We have discovered a new domain of optical coherence, and show that it is the third and last member of a previously unreported fundamental triad of coherences. These are unified by our derivation of a parallel triad of coherence constraints that take the form of complementarity relations. We have been able to enter this new coherence domain experimentally and we describe the novel tomographic approach devised for that purpose.

  16. 冷原子介质中基于相干诱导高反射带和高透射带的全光路由控制%All-optical routing control based on coherently induced high reflection band and high transmission band in a medium of cold atoms

    Institute of Scientific and Technical Information of China (English)

    国秀珍; 侯丽新; 尹昭泰; 吴金辉

    2011-01-01

    On the basis of coherently induced photonic gap structures,a new all-optical routing control scheme is proposed to simultaneously control the propagation dynamics of two weak light signals.With the transfer-matrix method to describe the coherent scattering of light waves in periodic media and the density-matrix equations to describe the resonant interaction between monochromatic laser fields and multi-level atoms,the steady reflection and transmission spectra are calculated for a coherently driven ultra-cold atomic ensemble as the control medium.The results show that,by changing the spatial patterns,intensity,and frequencies of two strong laser fields,a pair of special frequency bands(with 95% reflectivity or 95% transmissivity) can be first established near the probe resonance and then be manipulated at any time to induce two weak light signals of different frequencies into the desired network channels.This scheme well satisfies the basic requirements of low-deformation and low-loss for all-optical routing control of weak light signals in the field of quantum information processing.%以相干诱导光子带隙结构为工作基础,提出了一种可对两个弱光信号的传播路径同时进行动态调控的新型全光路由控制方案。利用描述光波在空间周期介质中相干散射的传输矩阵理论,结合描述单频激光与多能级原子共振相互作用的密度矩阵方程,计算了作为控制媒介的相干驱动超冷原子系综的稳态反射光谱和稳态透射光谱。结果表明,通过改变两个较强相干激光的空间模式、强度和频率等参数,可在探测跃迁共振频率附近建立反射率约为95%或者透射率约为95%的两个特殊频带。对这样的相干诱导高反射带和高透射带进行了实时动态调控,可根据需要引导两个不同频率的弱光信号进入指定的网络通道。该方案很好地满足了在量子信息处理领域对弱光信号进行全光路由控制时的低损耗和低形变要求。

  17. Throughput Analysis of Full Duplex Communication with Asymmetric Traffic in Small Cell Systems

    DEFF Research Database (Denmark)

    Mahmood, Nurul Huda; Berardinelli, Gilberto; Mogensen, Preben Elgaard;

    2015-01-01

    in this contribution using network analysis tools from stochastic geometry. The analytical findings are further confirmed through computer-based Monte-Carlo simulations. Asymmetric downlink/uplink traffic pattern and the increased network interference stemming from full duplex transmissions are found to limit its......Full duplex communication promises a 100% throughput gain by enabling simultaneous transmission and reception. However, such simultaneous communication leads to a corresponding increase in the network interference. In addition, full duplex communication can only be exploited when traffic...... is available in both uplink and downlink directions; while, cellular network traffic tend to be downlink heavy in practice. The potential throughput gains of full duplex communication over conventional half duplex transmission in a small cell network with asymmetric traffic conditions are investigated...

  18. Research on the efficiency of coherent balanced detection

    Science.gov (United States)

    Liu, Hongyang; Ai, Yong; Yang, Xiaobo; Chen, Yang; Ji, Fengzhu; Zhao, Xiaodan

    2016-10-01

    In the spatial coherent optical communication, after long distance transmission, the receiver needs to detect and extract the weak signal, and the balanced detection technology is the key technology in the coherent detection. Using balanced detection technology, not only can further improve the receiving sensitivity of coherent optical detection, but also can suppress the common mode intensity noise, so as to improve the output signal to noise ratio of the system. But the problems are (1) due to external causes (polarization control, input optical power loss error, atmospheric turbulence caused by decay, and so on),at both ends of the balanced detector's input signal can not keep consistent (2) two arms of balanced detector electronic devices (including photodiode and amplifier electronic components) are difficult to achieve perfectly matched. The paper is based on the principle of coherent optical detection, firstly, the advantage of balanced detection compared to single detection is detailed analysis, it is shown that balanced detector used in coherent optical communication system and with the improvement of communication rate, this advantage will more obvious. The theoretical and experimental results have verified several important factors that affect the efficiency of coherent balanced detection, namely, the consistency of the detection response, the atmospheric turbulence and the tracking jitter. It is of reference significant to study the balance detection technology in the spatial coherent optical communication.

  19. HIV Transmission

    Science.gov (United States)

    ... Abroad Treatment Basic Statistics Get Tested Find an HIV testing site near you. Enter ZIP code or city Follow HIV/AIDS CDC HIV CDC HIV/AIDS See RSS | ... on HIV Syndicated Content Website Feedback HIV/AIDS HIV Transmission Language: English Transmisión del VIH Recommend on ...

  20. The asymmetric Goos-H\\"anchen effect

    CERN Document Server

    Araujo, Manoel P; De Leo, Stefano

    2014-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the incoming gaussian beam, it can be also used to determine one of these parameters. Multiple peaks interference is an additional phenomenon seen in the presence of such asymmetric effects.

  1. Delay-enhanced coherence of spiral waves in noisy Hodgkin-Huxley neuronal networks

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qingyun [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China) and School of Statistics and Mathematics, Inner Mongolia Finance and Economics College, Huhhot 010051 (China)], E-mail: nmqingyun@163.com; Perc, Matjaz [Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska cesta 160, SI-2000 Maribor (Slovenia); Duan Zhisheng [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Chen Guanrong [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China)

    2008-08-25

    We study the spatial dynamics of spiral waves in noisy Hodgkin-Huxley neuronal ensembles evoked by different information transmission delays and network topologies. In classical settings of coherence resonance the intensity of noise is fine-tuned so as to optimize the system's response. Here, we keep the noise intensity constant, and instead, vary the length of information transmission delay amongst coupled neurons. We show that there exists an intermediate transmission delay by which the spiral waves are optimally ordered, hence indicating the existence of delay-enhanced coherence of spatial dynamics in the examined system. Additionally, we examine the robustness of this phenomenon as the diffusive interaction topology changes towards the small-world type, and discover that shortcut links amongst distant neurons hinder the emergence of coherent spiral waves irrespective of transmission delay length. Presented results thus provide insights that could facilitate the understanding of information transmission delay on realistic neuronal networks.

  2. The Coherence of Autism

    Science.gov (United States)

    Hobson, R. Peter

    2014-01-01

    There is a growing body of opinion that we should view autism as fractionable into different, largely independent sets of clinical features. The alternative view is that autism is a coherent syndrome in which principal features of the disorder stand in intimate developmental relationship with each other. Studies of congenitally blind children…

  3. Coherently combining antennas

    Science.gov (United States)

    Dybdal, Robert B. (Inventor); Curry, Samuel J. (Inventor)

    2009-01-01

    An apparatus includes antenna elements configured to receive a signal including pseudo-random code, and electronics configured to use the pseudo-random code to determine time delays of signals incident upon the antenna elements and to compensate the signals to coherently combine the antenna elements.

  4. Multiphoton coherent population oscillation

    CERN Document Server

    Sharypov, A V

    2014-01-01

    We study the bichromatic driving of a two-level system which displays long-lived coherent population oscillations (CPO). We show that under certain conditions, multiphoton parametric interaction leads to the appearance of CPO resonances at the subharmonic frequencies. In addition, in the region of the CPO resonances, there is strong parametric interaction between the weak sideband components of the electromagnetic field.

  5. Coherence without Additivity.

    OpenAIRE

    2002-01-01

    The Dutch book argument is a coherence condition for the existence of subjective probabilities. This note gives a general framework of analysis for this argument in a nonadditive probability setting. Particular cases are given by comonotonic and affinely related Dutch books that lead to Choquet expectations and Min expectations.

  6. Bicartesian Coherence Revisited

    CERN Document Server

    Dosen, K

    2007-01-01

    A survey is given of results about coherence for categories with finite products and coproducts. For these results, which were published previously by the authors in several places, some formulations and proofs are here corrected, and matters are updated. The categories investigated in this paper formalize equality of proofs in classical and intuitionistic conjunctive-disjunctive logic without distribution of conjunction over disjunction.

  7. Dental Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Kun-Feng Lin

    2013-07-01

    Full Text Available This review paper describes the applications of dental optical coherence tomography (OCT in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.

  8. Optical Coherence Tomography

    DEFF Research Database (Denmark)

    Andersen, Peter E.

    2015-01-01

    Optical coherence tomography (OCT) is a noninvasive imaging technique that provides real-time two- and three-dimensional images of scattering samples with micrometer resolution. Mapping the local reflectivity, OCT visualizes the morphology of the sample, in real time or at video rate. In addition...

  9. Thin lenses of asymmetric power

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2009-12-01

    Full Text Available It is generally supposed that thin systems, including refracting surfaces and thin lenses, have powers that are necessarily symmetric.  In other words they have powers which can be represented assymmetric dioptric power matrices and in the familar spherocylindrical form used in optometry and ophthalmology.  This paper shows that this is not correct and that it is indeed possible for a thin system to have a power that is not symmetric and which cannot be expressed in spherocylindrical form.  Thin systems of asymmetric power are illustratedby means of a thin lens that is modelled with small prisms and is chosen to have a dioptric power ma-trix that is antisymmetric.  Similar models can be devised for a thin system whose dioptric power matrix is any  2 2 ×  matrix.  Thus any power, symmetric, asymmetric or antisymmetric, is possible for a thin system.  In this sense our understanding of the power of thin systems is now complete.

  10. Excitons in asymmetric quantum wells

    Science.gov (United States)

    Grigoryev, P. S.; Kurdyubov, A. S.; Kuznetsova, M. S.; Ignatiev, I. V.; Efimov, Yu. P.; Eliseev, S. A.; Petrov, V. V.; Lovtcius, V. A.; Shapochkin, P. Yu.

    2016-09-01

    Resonance dielectric response of excitons is studied for the high-quality InGaAs/GaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances. A standard approach for the phenomenological analysis of the profiles is generalized by introducing different phase shifts for the light waves reflected from the QWs at different exciton resonances. Good agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to reliably obtain parameters of the exciton resonances: the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of the Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

  11. Asymmetric Laguerre-Gaussian beams

    Science.gov (United States)

    Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.

    2016-06-01

    We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.

  12. Asymmetric acoustic propagation of wave packets via the self-demodulation effect

    CERN Document Server

    Devaux, Thibaut; Richoux, Olivier; Pagneux, Vincent

    2015-01-01

    This article presents the experimental characterization of nonreciprocal elastic wave transmission in a single-mode elastic waveguide. This asymmetric system is obtained by coupling a selection layer with a conversion layer: the selection component is provided by a phononic crystal, while the conversion is achieved by a nonlinear self-demodulation effect in a 3D unconsolidated granular medium. A quantitative experimental study of this acoustic rectifier indicates a high rectifying ratio, up to $10^6$, with wide band (10 kHz) and an audible effect. Moreover, this system allows for wave-packet rectification and extends the future applications of asymmetric systems.

  13. Coherent states in quantum mechanics

    CERN Document Server

    Rodrigues, R D L; Fernandes, D

    2001-01-01

    We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out.

  14. Coherent hybrid electromagnetic field imaging

    Science.gov (United States)

    Cooke, Bradly J.; Guenther, David C.

    2008-08-26

    An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.

  15. Modeling of Multilayer Transmission Lines for High-Speed Digital Interconnects

    Directory of Open Access Journals (Sweden)

    Sarhan M. Musa,

    2015-08-01

    Full Text Available In this paper, we consider the finite element modeling of multilayer transmission lines for high-speed digital interconnects. We mainly focused on the modeling of the transmission structures with both cases of symmetric and asymmetric geometries. We specifically designed asymmetric coupled microstrips and four-line symmetric coupled microstrips with a two-layer substrate. We computed the capacitance matrix for asymmetric coupled microstrips and the capacitance, inductance, and impedance matrices for four-line symmetric coupled microstrips on a two-layer substrate. We also provide the potential distribution spectrums of the models and their meshing analysis.

  16. Accurate Modeling of Multilayer Transmission Lines for High-Speed Digital Interconnects

    Directory of Open Access Journals (Sweden)

    Sarhan M. Musa

    2014-03-01

    Full Text Available In this paper, we consider the finite element modeling of multilayer transmission lines for high-speed digital interconnects. We mainly focused on the modeling of the transmission structures with both cases of symmetric and asymmetric geometries. We specifically designed asymmetric coupled microstrips and four-line symmetric coupled microstrips with a two-layer substrate. We computed the capacitance matrix for asymmetric coupled microstrips and the capacitance, and inductance matrices for four-line symmetric coupled microstrips on a twolayer substrate. We also provide the potential distribution spectrums of the models.

  17. Temporal coherence and correlation of counterpropagating twin photons

    CERN Document Server

    Gatti, Alessandra; Brambilla, Enrico

    2015-01-01

    This work analyses the temporal coherence and correlation of counterpropagating twin photons generated in a quasi-phase matched nonlinear cristal by spontaneous parametric-down conversion. We find out different pictures depending on the pump pulse duration relative to two characteristic temporal scales, determined respectively by the temporal separation between the counter-propagating and the co-propagating wavepackets. When the pump duration is intermediate between the two scales, we show a transition from a highly entangled state to an almost separable state, with strongly asymmetric spectral properties of the photons.

  18. Transcending Transmission

    DEFF Research Database (Denmark)

    Schoeneborn, Dennis; Trittin, Hannah

    2013-01-01

    Purpose – Extant research on corporate social responsibility (CSR) communication primarily relies on a transmission model of communication that treats organizations and communication as distinct phenomena. This approach has been criticized for neglecting the formative role of communication...... in the emergence of organizations. This paper seeks to propose to reconceptualize CSR communication by drawing on the “communication constitutes organizations” (CCO) perspective. Design/methodology/approach – This is a conceptual paper that explores the implications of switching from an instrumental...

  19. Asymmetric catalysis : ligand design and microwave acceleration

    OpenAIRE

    Bremberg, Ulf

    2000-01-01

    This thesis deals partly with the design and synthesis ofligands for use in asymmetric catalysis, and partly with theapplication of microwave heating on metal-based asymmetriccatalytic reactions. Enantiomerically pure pyridyl alcohols and bipyridylalcohols were synthesized from the chiral pool for future usein asymmetric catalysis. Lithiated pyridines were reacted withseveral chiral electrophiles, yielding diastereomeric mixturesthat could be separated without the use of resolutiontechniques....

  20. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  1. Renewable resource management under asymmetric information

    DEFF Research Database (Denmark)

    Jensen, Frank; Andersen, Peder; Nielsen, Max

    2013-01-01

    Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis. I...

  2. The Catalytic Asymmetric Intramolecular Stetter Reaction.

    Science.gov (United States)

    de Alaniz, Javier Read; Rovis, Tomislav

    2009-05-01

    This account chronicles our efforts at the development of a catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows.

  3. Vertical price transmission analysis: The case of milk in the slovak dairy sector

    OpenAIRE

    Lajdová, Zuzana; Bielik, Peter

    2013-01-01

    Testing for nature price transmission and calculating elasticities of price transmission are important areas of research for providing insights into market efficiency issues. Symmetric or asymmetric price transmission has been the subject of considerable attention in agricultural economics. The concept of the price transmission is an important area of the research particularly in relation to the assessment of impact on the welfare of the vertical entities. The main goal of the paper is an ana...

  4. Optical Coherence and Quantum Optics

    CERN Document Server

    Mandel, Leonard

    1995-01-01

    This book presents a systematic account of optical coherence theory within the framework of classical optics, as applied to such topics as radiation from sources of different states of coherence, foundations of radiometry, effects of source coherence on the spectra of radiated fields, coherence theory of laser modes, and scattering of partially coherent light by random media. The book starts with a full mathematical introduction to the subject area and each chapter concludes with a set of exercises. The authors are renowned scientists and have made substantial contributions to many of the topi

  5. Condensation on Slippery Asymmetric Bumps

    CERN Document Server

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  6. Quantum coherence: Reciprocity and distribution

    Science.gov (United States)

    Kumar, Asutosh

    2017-03-01

    Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation-which we refer to as additivity relation-between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same.

  7. Spectral coherence in windturbine wakes

    Energy Technology Data Exchange (ETDEWEB)

    Hojstrup, J. [Riso National Lab., Roskilde (Denmark)

    1996-12-31

    This paper describes an experiment at a Danish wind farm to investigate the lateral and vertical coherences in the nonequilibrium turbulence of a wind turbine wake. Two meteorological masts were instrumented for measuring profiles of mean speed, turbulence, and temperature. Results are provided graphically for turbulence intensities, velocity spectra, lateral coherence, and vertical coherence. The turbulence was somewhat influenced by the wake, or possibly from aggregated wakes further upstream, even at 14.5 diameters. Lateral coherence (separation 5m) seemed to be unaffected by the wake at 7.5 diameters, but the flow was less coherent in the near wake. The wake appeared to have little influence on vertical coherence (separation 13m). Simple, conventional models for coherence appeared to be adequate descriptions for wake turbulence except for the near wake situation. 3 refs., 7 figs., 1 tab.

  8. Asymmetric Directional Multicast for Capillary Machine-to-Machine Using mmWave Communications.

    Science.gov (United States)

    Kwon, Jung-Hyok; Kim, Eui-Jik

    2016-01-01

    The huge demand for high data rate machine-to-machine (M2M) services has led to the use of millimeter Wave (mmWave) band communications with support for a multi-Gbps data rate through the use of directional antennas. However, unnecessary sector switching in multicast transmissions with directional antennas results in a long delay, and consequently a low throughput. We propose asymmetric directional multicast (ADM) for capillary M2M to address this problem in mmWave communications. ADM provides asymmetric sectorization that is optimized for the irregular deployment pattern of mulicast group members. In ADM, an M2M gateway builds up asymmetric sectors with a beamwidth of a different size to cover all multicast group members with the minimum number of directional transmissions. The performance of ADM under various simulation environments is evaluated through a comparison with legacy mmWave multicast. The results of the simulation indicate that ADM achieves a better performance in terms of the transmission sectors, the transmission time, and the aggregate throughput when compared with the legacy multicast method.

  9. Coherent Transient Systems Evaluation

    Science.gov (United States)

    1993-06-17

    manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints...for governmental purposes. 1.0 Introduction The continuous optical correlator presented here is based on the phenomena of coherent transients, also...Gating the Continuous Processor Programming the continuous processor is accomplished by illuminati , n, the material with ,.’ modulated light pulses: a

  10. Coherent laser vision system

    Energy Technology Data Exchange (ETDEWEB)

    Sebastion, R.L. [Coleman Research Corp., Springfield, VA (United States)

    1995-10-01

    The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.

  11. Coherent electron cooling

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko,V.

    2009-05-04

    Cooling intense high-energy hadron beams remains a major challenge in modern accelerator physics. Synchrotron radiation is still too feeble, while the efficiency of two other cooling methods, stochastic and electron, falls rapidly either at high bunch intensities (i.e. stochastic of protons) or at high energies (e-cooling). In this talk a specific scheme of a unique cooling technique, Coherent Electron Cooling, will be discussed. The idea of coherent electron cooling using electron beam instabilities was suggested by Derbenev in the early 1980s, but the scheme presented in this talk, with cooling times under an hour for 7 TeV protons in the LHC, would be possible only with present-day accelerator technology. This talk will discuss the principles and the main limitations of the Coherent Electron Cooling process. The talk will describe the main system components, based on a high-gain free electron laser driven by an energy recovery linac, and will present some numerical examples for ions and protons in RHIC and the LHC and for electron-hadron options for these colliders. BNL plans a demonstration of the idea in the near future.

  12. Price Transmission in the Cocoa-Chocolate Chain

    OpenAIRE

    Catherine ARAUJO BONJEAN; Brun, Jean-François

    2011-01-01

    Etudes & documents; There is a common perception among consumers that the retail prices respond faster to an increase in the price of raw material than to a decrease. This paper aims at testing the existence of such asymmetric price transmission in the cocoa-chocolate chain on the French market. Two types of asymmetry are suspected: asymmetry in the transmission of positive and negative shocks that may reflect non-competitive behaviour in the chocolate industry and asymmetry in the transmissi...

  13. On the Asymmetric Effect of Vertical Transmission of Vegetable Prices in China---An Empirical Study Based on PVAR Model%我国蔬菜价格垂直传导的非对称性研究--基于面板VAR模型的实证

    Institute of Scientific and Technical Information of China (English)

    刘玲

    2015-01-01

    运用面板向量自回归模型(PVAR)对我国蔬菜的生产价格、批发价格和零售价格的垂直传导机制进行实证研究,结果表明我国蔬菜三种价格的波动幅度和增长速度自上而下呈依次增强的特征;价格的正向传导顺畅,逆向传导存在一到两期的滞后,传导强度上存在正向传递强度明显高于逆向传递的非对称现象;生产价格在整个价格波动的传导链中占主导地位,蔬菜价格的稳定在很大程度上依赖于蔬菜的生产环节。%Based on PVAR,this paper analyzes the vertical transmission mechanism of the production price,wholesale price and retail price of five major vegetables in China.The results have the following indications:fluctuation range and growth rate of the three prices of major vegetables strengthen sequentially;the forward transmission of vegetable prices is smooth,while the reverse transmission lags for one or two periods;transmission strength is also nonsymmetrical,forward transmission strength being obviously higher than reverse transmission strength.Vegetable production price dominates the price transmission link.The stability of vegetable price depends to a larger extent on the production of vegetables.

  14. A resistance formula for coherent multi-barrier structures

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Chen; Yang Jian-Hong

    2007-01-01

    Using the Landauer formula and the quantum S-matrix scattering theory, we derive a resistance formula for multi-barrier structure under phase coherent transmission condition. This formula shows that when the transport is coherent, the potential wells of the structure are just like conductors contributing to the overall resistance. And because the resistance formula is derived based on the scattering theory, the barrier resistance will change with the number of scattering centres (i.e. the number of barriers) in the structure.

  15. Method and apparatus for coherent burst ranging

    Science.gov (United States)

    Wachter, E.A.; Fisher, W.G.

    1998-04-28

    A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time. 12 figs.

  16. Holographic microscopy in low coherence

    Science.gov (United States)

    Chmelík, Radim; Petráček, Jiří; Slabá, Michala; Kollárová, Věra; Slabý, Tomáš; Čolláková, Jana; Komrska, Jiří; Dostál, Zbyněk.; Veselý, Pavel

    2016-03-01

    Low coherence of the illumination substantially improves the quality of holographic and quantitative phase imaging (QPI) by elimination of the coherence noise and various artefacts and by improving the lateral resolution compared to the coherent holographic microscopy. Attributes of coherence-controlled holographic microscope (CCHM) designed and built as an off-axis holographic system allowing QPI within the range from complete coherent to incoherent illumination confirmed these expected advantages. Low coherence illumination also furnishes the coherence gating which constraints imaging of some spatial frequencies of an object axially thus forming an optical section in the wide sense. In this way the depth discrimination capability of the microscope is introduced at the price of restricting the axial interval of possible numerical refocusing. We describe theoretically these effects for the whole range of illumination coherence. We also show that the axial refocusing constraints can be overcome using advanced mode of imaging based on mutual lateral shift of reference and object image fields in CCHM. Lowering the spatial coherence of illumination means increasing its numerical aperture. We study how this change of the illumination geometry influences 3D objects QPI and especially the interpretation of live cells QPI in terms of the dry mass density measurement. In this way a strong dependence of the imaging process on the light coherence is demonstrated. The theoretical calculations and numerical simulations are supported by experimental data including a chance of time-lapse watching of live cells even in optically turbid milieu.

  17. Asymmetric stem cell division: lessons from Drosophila.

    Science.gov (United States)

    Wu, Pao-Shu; Egger, Boris; Brand, Andrea H

    2008-06-01

    Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between the misregulation of asymmetric cell division and cancer. What we are learning from Drosophila as a model system has implication both for stem cell biology and also cancer research.

  18. On-chip asymmetric microcavity optomechanics.

    Science.gov (United States)

    Soltani, Soheil; Hudnut, Alexa W; Armani, Andrea M

    2016-12-26

    High quality factor (Q) optical resonators have enabled rapid growth in the field of cavity-enhanced, radiation pressure-induced optomechanics. However, because research has focused on axisymmetric devices, the observed regenerative excited mechanical modes are similar. In the present work, a strategy for fabricating high-Q whispering gallery mode microcavities with varying degrees of asymmetry is developed and demonstrated. Due to the combination of high optical Q and asymmetric device design, two previously unobserved modes, the asymmetric cantilever and asymmetric crown mode, are demonstrated with sub-mW thresholds for onset of oscillations. The experimental results are in good agreement with computational modeling predictions.

  19. Regenerating a symmetry in asymmetric dark matter.

    Science.gov (United States)

    Buckley, Matthew R; Profumo, Stefano

    2012-01-06

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe.

  20. Absolute Asymmetric Synthesis Using A Cocrystal Approach

    Institute of Scientific and Technical Information of China (English)

    H.Koshima

    2007-01-01

    1 Results Absolute asymmetric synthesis by means of solid-state reaction of chiral crystals self-assembled from achiral molecules is an attractive and promising methodology for asymmetric synthesis because it is not necessary to employ any external chiral source like a chiral catalyst.In order to design reliably absolute asymmetric syntheses in the solid state,it is inevitable to prepare and predict the formation of chiral crystals from achiral compounds.We have prepared a number of chiral cocrystals co...

  1. Asymmetric dark matter in braneworld cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [School of Engineering and Physical Sciences, James Cook University, Townsville, 4811 Australia (Australia)

    2014-06-01

    We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.

  2. Enantiopure sulfoxides: recent applications in asymmetric synthesis.

    Science.gov (United States)

    Carreño, M Carmen; Hernández-Torres, Gloria; Ribagorda, María; Urbano, Antonio

    2009-11-07

    Sulfoxides are nowadays recognised as powerful chiral auxiliaries that may participate in a wide range of asymmetric reactions. Their high configurational stability, the existence of several efficient methods allowing the access to both configurations as well as their synthetic versatility are characteristic features offering a tremendous potential to develop new applications. Significant recent advances leading to high asymmetric inductions in carbon-carbon and carbon-oxygen bond forming reactions, and applications of homochiral sulfoxides to atroposelective synthesis and asymmetric catalysis are discussed. New uses of sulfoxides in the design of chiroptical switches are also shown.

  3. Adiabatic asymmetric scattering of atoms in the field of a standing wave

    CERN Document Server

    Hakobyan, M V; Ishkhanyan, A M

    2015-01-01

    A model of the asymmetric coherent scattering process (caused by initial atomic wave-packet splitting in the momentum space) taking place at the large detuning and adiabatic course of interaction for an effective two-state system interacting with a standing wave of laser radiation is discussed. We show that the same form of initial wave-packet splitting may lead to different, in general, diffraction patterns for opposite, adiabatic and resonant, regimes of the standing-wave scattering. We show that the scattering of the Gaussian wave packet in the adiabatic case presents refraction (a limiting form of the asymmetric scattering) in contrast to the bi-refringence (the limiting case of the high-order narrowed scattering) occurring in the resonant scattering.

  4. Modified Quasi-Steady State Model of DC System for Transient Stability Simulation under Asymmetric Faults

    Directory of Open Access Journals (Sweden)

    Jun Liu

    2015-01-01

    Full Text Available As using the classical quasi-steady state (QSS model could not be able to accurately simulate the dynamic characteristics of DC transmission and its controlling systems in electromechanical transient stability simulation, when asymmetric fault occurs in AC system, a modified quasi-steady state model (MQSS is proposed. The model firstly analyzes the calculation error induced by classical QSS model under asymmetric commutation voltage, which is mainly caused by the commutation voltage zero offset thus making inaccurate calculation of the average DC voltage and the inverter extinction advance angle. The new MQSS model calculates the average DC voltage according to the actual half-cycle voltage waveform on the DC terminal after fault occurrence, and the extinction advance angle is also derived accordingly, so as to avoid the negative effect of the asymmetric commutation voltage. Simulation experiments show that the new MQSS model proposed in this paper has higher simulation precision than the classical QSS model when asymmetric fault occurs in the AC system, by comparing both of them with the results of detailed electromagnetic transient (EMT model of the DC transmission and its controlling system.

  5. Asymmetrically Compressed Stereoscopic 3D Videos: Quality Assessment and Rate-Distortion Performance Evaluation.

    Science.gov (United States)

    Wang, Jiheng; Wang, Shiqi; Wang, Zhou

    2017-03-01

    Objective quality assessment of stereoscopic 3D video is challenging but highly desirable, especially in the application of stereoscopic video compression and transmission, where useful quality models are missing, that can guide the critical decision making steps in the selection of mixed-resolution coding, asymmetric quantization, and pre- and post-processing schemes. Here we first carry out subjective quality assessment experiments on two databases that contain various asymmetrically compressed stereoscopic 3D videos obtained from mixed-resolution coding, asymmetric transform-domain quantization coding, their combinations, and the multiple choices of postprocessing techniques. We compare these asymmetric stereoscopic video coding schemes with symmetric coding methods and verify their potential coding gains. We observe a strong systematic bias when using direct averaging of 2D video quality of both views to predict 3D video quality. We then apply a binocular rivalry inspired model to account for the prediction bias, leading to a significantly improved full reference quality prediction model of stereoscopic videos. The model allows us to quantitatively predict the coding gain of different variations of asymmetric video compression, and provides new insight on the development of high efficiency 3D video coding schemes.

  6. Topological Properties of Spatial Coherence Function

    Institute of Scientific and Technical Information of China (English)

    REN Ji-Rong; ZHU Tao; DUAN Yi-Shi

    2008-01-01

    The topological properties of the spatial coherence function are investigated rigorously.The phase singular structures(coherence vortices)of coherence function can be naturally deduced from the topological current,which is an abstract mathematical object studied previously.We find that coherence vortices are characterized by the Hopf index and Brouwer degree in topology.The coherence flux quantization and the linking of the closed coherence vortices are also studied from the topological properties of the spatial coherence function.

  7. Radio over fiber link with adaptive order n‐QAM optical phase modulated OFDM and digital coherent detection

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Borkowski, Robert; Guerrero Gonzalez, Neil

    2011-01-01

    Successful digital coherent demodulation of asynchronous optical phase‐modulated adaptive order QAM (4, 16, and 64) orthogonal frequency division multiplexing signals is achieved by a single reconfigurable digital receiver after 78 km of optical deployed fiber transmission....

  8. Optimally Coherent Kerr Combs Generated with Crystalline Whispering Gallery Mode Resonators for Ultrahigh Capacity Fiber Communications

    Science.gov (United States)

    Pfeifle, Joerg; Coillet, Aurélien; Henriet, Rémi; Saleh, Khaldoun; Schindler, Philipp; Weimann, Claudius; Freude, Wolfgang; Balakireva, Irina V.; Larger, Laurent; Koos, Christian; Chembo, Yanne K.

    2015-03-01

    Optical Kerr frequency combs are known to be effective coherent multiwavelength sources for ultrahigh capacity fiber communications. These combs are the frequency-domain counterparts of a wide variety of spatiotemporal dissipative structures, such as cavity solitons, chaos, or Turing patterns (rolls). In this Letter, we demonstrate that Turing patterns, which correspond to the so-called primary combs in the spectral domain, are optimally coherent in the sense that for the same pump power they provide the most robust carriers for coherent data transmission in fiber communications using advanced modulation formats. Our model is based on a stochastic Lugiato-Lefever equation which accounts for laser pump frequency jitter and amplified spontaneous emission noise induced by the erbium-doped fiber amplifier. Using crystalline whispering-gallery-mode resonators with quality factor Q ˜109 for the comb generation, we show that when the noise is accounted for, the coherence of a primary comb is significantly higher than the coherence of their solitonic or chaotic counterparts for the same pump power. In order to confirm this theoretical finding, we perform an optical fiber transmission experiment using advanced modulation formats, and we show that the coherence of the primary comb is high enough to enable data transmission of up to 144 Gbit /s per comb line, the highest value achieved with a Kerr comb so far. This performance evidences that compact crystalline photonic systems have the potential to play a key role in a new generation of coherent fiber communication networks, alongside fully integrated systems.

  9. Assisted distillation of quantum coherence

    CERN Document Server

    Chitambar, E; Rana, S; Bera, M N; Adesso, G; Lewenstein, M

    2015-01-01

    We introduce and study the task of assisted coherence distillation. This task arises naturally in bipartite systems where both parties work together to generate the maximal possible coherence on one of the subsystems. Only incoherent operations are allowed on the target system while general local quantum operations are permitted on the other, an operational paradigm that we call local quantum-incoherent operations and classical communication (LQICC). We show that the asymptotic rate of assisted coherence distillation for pure states is equal to the coherence of assistance, a direct analog of the entanglement of assistance, whose properties we characterize. Our findings imply a novel interpretation of the von Neumann entropy: it quantifies the maximum amount of extra quantum coherence a system can gain when receiving assistance from a collaborative party. Our results are generalized to coherence localization in a multipartite setting and possible applications are discussed.

  10. Quantum Coherence as a Resource

    CERN Document Server

    Streltsov, Alexander; Plenio, Martin B

    2016-01-01

    The coherent superposition of states, in combination with energy quantization, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in many-body systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics. In recent years, research on the presence and functional role of quantum coherence in biological systems has also attracted a considerable interest. Despite the fundamental importance of quantum coherence, the development of a rigorous theory of quantum coherence as a physical resource has only been initiated recently. In this Colloquium we discuss and review the development of this rapidly growing research field that encompasses the characterization, quantification, manipulation, dynamical evolution, and operational application of quantum coherence.

  11. Volitional Control of Neuromagnetic Coherence

    Directory of Open Access Journals (Sweden)

    Matthew D Sacchet

    2012-12-01

    Full Text Available Coherence of neural activity between circumscribed brain regions has been implicated as an indicator of intracerebral communication in various cognitive processes. While neural activity can be volitionally controlled with neurofeedback, the volitional control of coherence has not yet been explored. Learned volitional control of coherence could elucidate mechanisms of associations between cortical areas and its cognitive correlates and may have clinical implications. Neural coherence may also provide a signal for brain-computer interfaces (BCI. In the present study we used the Weighted Overlapping Segment Averaging (WOSA method to assess coherence between bilateral magnetoencephalograph (MEG sensors during voluntary digit movement as a basis for BCI control. Participants controlled an onscreen cursor, with a success rate of 124 of 180 (68.9%, sign-test p < 0.001 and 84 out of 100 (84%, sign-test p < 0.001. The present findings suggest that neural coherence may be volitionally controlled and may have specific behavioral correlates.

  12. Asymmetric transport of light in arrow-shape photonic crystal waveguides

    Science.gov (United States)

    Rahal, H.; AbdelMalek, F.

    2017-03-01

    In this paper, we report a design of an asymmetric light propagation based on the Photonic Crystal (PC) structure. The proposed PC is constructed of an arrow-shaped structure integrating different rows of air holes which offer more than 65% transmission in one direction and less than 1% in the opposite direction. The proposed PC is based on the use of two parallel PC waveguides with different air holes in a single platform. The design, optimization and performance of the PC waveguide devices are carried out by employing in-house accurate 2D Finite Difference Time Domain (2D FDTD) computational techniques. Our preliminary numerical simulation results show that complete asymmetric transmission can be achieved in the proposed single structure which would play a significant contribution on realization of high-volume nanoscale photonic integrated circuitry.

  13. Enhanced hybrid asymmetrically clipped orthogonal frequency division multiplexing for optical wireless communications

    Science.gov (United States)

    Guan, Rui; Huang, Nuo; Wang, Jin-Yuan; Wang, Houyu; Chen, Ming

    2016-05-01

    This paper presents an enhanced hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (EHACO-OFDM) scheme, which benefits from the simultaneous transmission of ACO-OFDM, pulse-amplitude-modulated discrete multitone modulation, and direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM). Since the entire available bandwidth is utilized for data modulation, this scheme can achieve higher spectral efficiency than HACO-OFDM and ACO-OFDM. Moreover, as a smaller DC bias is introduced in our scheme, it is more power efficient than asymmetrically clipped DC-biased optical OFDM (ADO-OFDM) and DCO-OFDM. A modified receiver is also designed for this system, taking advantage of an iterative algorithm and a pairwise averaging. It has been shown by simulation that our three-path simultaneous transmission scheme can surpass the existing mixed OFDM-based schemes at high data rates. In addition, compared with the noniterative receiver, the modified receiver exhibits significant gains.

  14. Asymmetric dark matter bound state

    Science.gov (United States)

    Bi, Xiao-Jun; Kang, Zhaofeng; Ko, P.; Li, Jinmian; Li, Tianjun

    2017-02-01

    We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U (1 )d symmetry which is broken at a low scale and provides a light gauge boson X . The dark gauge coupling is strong and then ADM can annihilate away into X -pair effectively. Therefore, the ADM can form a bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with b b ¯. The resulting signature at the LHC depends on the decays of X . In this paper we consider a case of particular interest: p p →b b ¯ +ADMonium followed by ADMonium→2 X →2 e+e- where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC.

  15. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  16. Force on an Asymmetric Capacitor

    CERN Document Server

    Bahder, T B; Bahder, Thomas B.; Fazi, Chris

    2002-01-01

    When a high voltage (~30 kV) is applied to a capacitor whose electrodes have different physical dimensions, the capacitor experiences a net force toward the smaller electrode (Biefeld-Brown effect). We have verified this effect by building four capacitors of different shapes. The effect may have applications to vehicle propulsion and dielectric pumps. We review the history of this effect briefly through the history of patents by Thomas Townsend Brown. At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes: ballistic ionic wind and ionic drift. The calculations indicate that ionic wind is at least three orders of magnitude too small to explain the magnitude of the observed force on the capacitor. The ionic drift transport assumption leads to the correct order of magnitude for the force, however, it is difficult to see how ionic dr...

  17. Asymmetric total synthesis of vindoline.

    Science.gov (United States)

    Kato, Daisuke; Sasaki, Yoshikazu; Boger, Dale L

    2010-03-24

    A concise asymmetric total synthesis of (-)-vindoline (1) is detailed based on a tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which the tether linking the initiating dienophile and oxadiazole bears a chiral substituent that controls the facial selectivity of the initiating Diels-Alder reaction and sets absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduces three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. Implementation of the approach also required the development of a unique ring expansion reaction to provide a six-membered ring suitably functionalized for introduction of the Delta (6, 7)-double bond found in the core structure of vindoline and defined our use of a protected hydroxymethyl group as the substituent used to control the stereochemical course of the cycloaddition cascade.

  18. Objective Eulerian Coherent Structures

    CERN Document Server

    Serra, M

    2015-01-01

    We define objective Eulerian Coherent Structures (OECSs) in two-dimensional, non-autonomous dynamical systems as instantaneously most influential material curves. Specifically, OECSs are stationary curves of the averaged instantaneous material stretching-rate or material shearing-rate functionals. From these objective (frame-invariant) variational principles, we obtain explicit differential equations for hyperbolic, elliptic and parabolic OECSs. As illustration, we compute OECSs in an unsteady ocean velocity data set. In comparison to structures suggested by other common Eulerian diagnostic tools, we find OECSs to be the correct short-term cores of observed trajectory deformation patterns.

  19. Coherent laser beam combining

    CERN Document Server

    Brignon, Arnaud

    2013-01-01

    Recently, the improvement of diode pumping in solid state lasers and the development of double clad fiber lasers have allowed to maintain excellent laser beam quality with single mode fibers. However, the fiber output power if often limited below a power damage threshold. Coherent laser beam combining (CLBC) brings a solution to these limitations by identifying the most efficient architectures and allowing for excellent spectral and spatial quality. This knowledge will become critical for the design of the next generation high-power lasers and is of major interest to many industrial, environme

  20. Diffraction coherence in optics

    CERN Document Server

    Françon, M; Green, L L

    2013-01-01

    Diffraction: Coherence in Optics presents a detailed account of the course on Fraunhofer diffraction phenomena, studied at the Faculty of Science in Paris. The publication first elaborates on Huygens' principle and diffraction phenomena for a monochromatic point source and diffraction by an aperture of simple form. Discussions focus on diffraction at infinity and at a finite distance, simplified expressions for the field, calculation of the path difference, diffraction by a rectangular aperture, narrow slit, and circular aperture, and distribution of luminous flux in the airy spot. The book th

  1. Optical coherence refractometry.

    Science.gov (United States)

    Tomlins, Peter H; Woolliams, Peter; Hart, Christian; Beaumont, Andrew; Tedaldi, Matthew

    2008-10-01

    We introduce a novel approach to refractometry using a low coherence interferometer at multiple angles of incidence. We show that for plane parallel samples it is possible to measure their phase refractive index rather than the group index that is usually measured by interferometric methods. This is a significant development because it enables bulk refractive index measurement of scattering and soft samples, not relying on surface measurements that can be prone to error. Our technique is also noncontact and compatible with in situ refractive index measurements. Here, we demonstrate this new technique on a pure silica test piece and a highly scattering resin slab, comparing the results with standard critical angle refractometry.

  2. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  3. The Puzzle of Coherence

    DEFF Research Database (Denmark)

    Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;

    2016-01-01

    in general practice, outpatient clinics, home care and physiotherapy. Furthermore, field observations are conducted in general practice, home care and rehabilitation settings. Perspectives Knowledge about the practice of cross-sectorial collaboration is crucial to the future planning of collaborating...... initiatives in health care. The present study will generate new, valuable insight into the areas of cross-sectorial health care collaboration. Our findings may facilitate change in current practice and improve the quality and coherence in patient pathways of EPCD. The findings of this study will be useful...

  4. Coherent signal processing in optical coherence tomography

    Science.gov (United States)

    Kulkarni, Manish Dinkarrao

    1999-09-01

    Optical coherence tomography (OCT) is a novel method for non-invasive sub-surface imaging of biological tissue micro-structures. OCT achieves high spatial resolution ( ~ 15 m m in three dimensions) using a fiber-optically integrated system which is suitable for application in minimally invasive diagnostics, including endoscopy. OCT uses an optical heterodyne detection technique based on white light interferometry. Therefore extremely faint reflections ( ~ 10 fW) are routinely detected with high spatial localization. The goal of this thesis is twofold. The first is to present a theoretical model for describing image formation in OCT, and attempt to enhance the current level of understanding of this new modality. The second objective is to present signal processing methods for improving OCT image quality. We present deconvolution algorithms to obtain improved longitudinal resolution in OCT. This technique may be implemented without increasing system complexity as compared to current clinical OCT systems. Since the spectrum of the light backscattered from bio-scatterers is closely associated with ultrastructural variations in tissue, we propose a new technique for measuring spectra as a function of depth. This advance may assist OCT in differentiating various tissue types and detecting abnormalities within a tissue. In addition to depth resolved spectroscopy, Doppler processing of OCT signals can also improve OCT image contrast. We present a new technique, termed color Doppler OCT (CDOCT). It is an innovative extension of OCT for performing spatially localized optical Doppler velocimetry. Micron-resolution imaging of blood flow in sub-surface vessels in living tissue using CDOCT is demonstrated. The fundamental issues regarding the trade- off between the velocity estimation precision and image acquisition rate are presented. We also present novel algorithms for high accuracy velocity estimation. In many blood vessels velocities tend to be on the order of a few cm

  5. Review of Entangled Coherent States

    CERN Document Server

    Sanders, Barry C

    2011-01-01

    We review entangled coherent state research since its first implicit use in 1967 to the present. Entangled coherent states are important to quantum superselection principles, quantum information processing, quantum optics, and mathematical physics. Despite their inherent fragility they have produced in a conditional propagating-wave quantum optics realization. Fundamentally the states are intriguing because they are entanglements of the coherent states, which are in a sense the most classical of all states of a dynamical system.

  6. A novel asymmetric synthesis of cinacalcet hydrochloride

    OpenAIRE

    Arava, Veera R; Laxminarasimhulu Gorentla; Pramod K. Dubey

    2012-01-01

    A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  7. A novel asymmetric synthesis of cinacalcet hydrochloride

    Directory of Open Access Journals (Sweden)

    Veera R. Arava

    2012-08-01

    Full Text Available A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  8. A novel asymmetric synthesis of cinacalcet hydrochloride

    Science.gov (United States)

    Gorentla, Laxminarasimhulu; Dubey, Pramod K

    2012-01-01

    Summary A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described. PMID:23019473

  9. Catalytic Asymmetric Synthesis of Phosphine Boronates

    NARCIS (Netherlands)

    Hornillos, Valentin; Vila, Carlos; Otten, Edwin; Feringa, Ben L.

    2015-01-01

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of ,-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good y

  10. Asymmetric Swiss-cheese brane-worlds

    CERN Document Server

    Gergely, L A; K\\'{e}p\\'{\\i}r\\'{o}, Ibolya

    2006-01-01

    We consider Swiss-cheese brane universes embedded asymmetrically into the bulk. Neither the junction conditions between the Schwarzschild spheres and the sorrounding Friedmann brane regions with cosmological constant $\\Lambda $, nor the evolution of the scale factor are changed with respect to the symmetric case. The universe expands and decelerates forever. The asymmetry however has a drastic influence on the evolution of the cosmological fluid. Instead of the two branches of the symmetric case, in the asymmetric case four branches emerge. Moreover, the future pressure singularity arising in the symmetric case only for huge values of $\\Lambda $ becomes quite generic in the asymmetric case. Such pressure singularities emerge also when $\\Lambda=0$ is set. Then they are due entirely to the asymmetric embedding. For generic values of $\\Lambda $ we introduce a critical value of a suitably defined asymmetry parameter, which separates Swiss-cheese cosmologies with and without pressure singularities.

  11. Congenital asymmetric crying face: a case report

    Directory of Open Access Journals (Sweden)

    Semra Kara

    2011-12-01

    Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.

  12. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  13. Converting Coherence to Quantum Correlations.

    Science.gov (United States)

    Ma, Jiajun; Yadin, Benjamin; Girolami, Davide; Vedral, Vlatko; Gu, Mile

    2016-04-22

    Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.

  14. Coherent states on the circle

    CERN Document Server

    Chadzitaskos, G; Tolar, J

    2011-01-01

    We present a possible construction of coherent states on the unit circle as configuration space. In our approach the phase space is the product Z x S^1. Because of the duality of canonical coordinates and momenta, i.e. the angular variable and the integers, this formulation can also be interpreted as coherent states over an infinite periodic chain. For the construction we use the analogy with our quantization over a finite periodic chain where the phase space was Z_M x Z_M. Properties of the coherent states constructed in this way are studied and the coherent states are shown to satisfy the resolution of unity.

  15. Perspective: Quantum or classical coherence?

    Science.gov (United States)

    Miller, William H

    2012-06-07

    Some coherence effects in chemical dynamics are described correctly by classical mechanics, while others only appear in a quantum treatment--and when these are observed experimentally it is not always immediately obvious whether their origin is classical or quantum. Semiclassical theory provides a systematic way of adding quantum coherence to classical molecular dynamics and thus provides a useful way to distinguish between classical and quantum coherence. Several examples are discussed which illustrate both cases. Particularly interesting is the situation with electronically non-adiabatic processes, where sometimes whether the coherence effects are classical or quantum depends on what specific aspects of the process are observed.

  16. Alignment, vibronic level splitting, and coherent coupling effects on the pump-probe polarization anisotropy.

    Science.gov (United States)

    Smith, Eric R; Jonas, David M

    2011-04-28

    The pump-probe polarization anisotropy is computed for molecules with a nondegenerate ground state, two degenerate or nearly degenerate excited states with perpendicular transition dipoles, and no resonant excited-state absorption. Including finite pulse effects, the initial polarization anisotropy at zero pump-probe delay is predicted to be r(0) = 3/10 with coherent excitation. During pulse overlap, it is shown that the four-wave mixing classification of signal pathways as ground or excited state is not useful for pump-probe signals. Therefore, a reclassification useful for pump-probe experiments is proposed, and the coherent anisotropy is discussed in terms of a more general transition dipole and molecular axis alignment instead of experiment-dependent ground- versus excited-state pathways. Although coherent excitation enhances alignment of the transition dipole, the molecular axes are less aligned than for a single dipole transition, lowering the initial anisotropy. As the splitting between excited states increases beyond the laser bandwidth and absorption line width, the initial anisotropy increases from 3/10 to 4/10. Asymmetric vibrational coordinates that lift the degeneracy control the electronic energy gap and off-diagonal coupling between electronic states. These vibrations dephase coherence and equilibrate the populations of the (nearly) degenerate states, causing the anisotropy to decay (possibly with oscillations) to 1/10. Small amounts of asymmetric inhomogeneity (2 cm(-1)) cause rapid (130 fs) suppression of both vibrational and electronic anisotropy beats on the excited state, but not vibrational beats on the ground electronic state. Recent measurements of conical intersection dynamics in a silicon napthalocyanine revealed anisotropic quantum beats that had to be assigned to asymmetric vibrations on the ground electronic state only [Farrow, D. A.; J. Chem. Phys. 2008, 128, 144510]. Small environmental asymmetries likely explain the observed absence

  17. Optical diode behavior of photonic crystal structure with asymmetric Kerr defect

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Optical diode behavior of asymmetric one-dimensional photonic crystal with Kerr defect is numerically investigated using nonlinear transfer matrix method. In the linear case, the intensity and the phase of transmitted field are the same for the forward and backward operations. In the nonlinear case, however, the transmitted intensities are much different for the two operations, which display diode characteristic. Physical origin of the anisotropic transmission lies in the different localizations in the defect layer of the two operations.

  18. DOES VOLATILITY RESPOND ASYMMETRIC TO PAST SHOCKS?

    OpenAIRE

    Claudiu Botoc

    2014-01-01

    The main aim of the paper is to examine if the stock market volatility exhibits asymmetric or an asymmetric response to past shocks, for certain CEE countries (Romania,Hungary, Bulgaria, Poland) over the period May 2004 - September 2014. For the stock marketsfrom East Europe the results are in line with the symmetric volatility, i.e. volatility is similaraffected by both positive and negative returns with the same magnitude. For the stock marketsfrom Central Europe the results are consistent ...

  19. Digital signal processing techniques for coherent optical communication

    Science.gov (United States)

    Goldfarb, Gilad

    Coherent detection with subsequent digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in various fiber-optic transmission scenarios. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservaton of full information of the incoming field. These benefits include high receiver sensitivity, the ability to achieve high spectral-efficiency and the use of advanced modulation formats. With the immense advancements in DSP speeds, many of the problems hindering the use of coherent detection in optical transmission systems have been eliminated. Most notably, DSP alleviates the need for hardware phase-locking and polarization tracking, which can now be achieved in the digital domain. The complexity previously associated with coherent detection is hence significantly diminished and coherent detection is once gain considered a feasible detection alternative. In this thesis, several aspects of coherent detection (with or without subsequent DSP) are addressed. Coherent detection is presented as a means to extend the dispersion limit of a duobinary signal using an analog decision-directed phase-lock loop. Analytical bit-error ratio estimation for quadrature phase-shift keying signals is derived. To validate the promise for high spectral efficiency, the orthogonal-wavelength-division multiplexing scheme is suggested. In this scheme the WDM channels are spaced at the symbol rate, thus achieving the spectral efficiency limit. Theory, simulation and experimental results demonstrate the feasibility of this approach. Infinite impulse response filtering is shown to be an efficient alternative to finite impulse response filtering for chromatic dispersion compensation. Theory, design considerations, simulation and experimental results relating to this topic are presented. Interaction between fiber dispersion and nonlinearity remains the last major challenge

  20. Coherence for weak units

    CERN Document Server

    Joyal, André

    2009-01-01

    We define weak units in a semi-monoidal 2-category $\\CC$ as cancellable pseudo-idempotents: they are pairs $(I,\\alpha)$ where $I$ is an object such that tensoring with $I$ from either side constitutes a biequivalence of $\\CC$, and $\\alpha: I \\tensor I \\to I$ is an equivalence in $\\CC$. We show that this notion of weak unit has coherence built in: Theorem A: $\\alpha$ has a canonical associator 2-cell, which automatically satisfies the pentagon equation. Theorem B: every morphism of weak units is automatically compatible with those associators. Theorem C: the 2-category of weak units is contractible if non-empty. Finally we show (Theorem E) that the notion of weak unit is equivalent to the notion obtained from the definition of tricategory: $\\alpha$ alone induces the whole family of left and right maps (indexed by the objects), as well as the whole family of Kelly 2-cells (one for each pair of objects), satisfying the relevant coherence axioms.

  1. Fermionic coherent states

    Science.gov (United States)

    Combescure, Monique; Robert, Didier

    2012-06-01

    The aim of this paper is to give a self-contained and unified presentation of a fermionic coherent state theory with the necessary mathematical details, discussing their definition, properties and some applications. After defining Grassmann algebras, it is possible to get a classical analog for the fermionic degrees of freedom in a quantum system. Following the basic work of Berezin (1966 The Method of Second Quantization (New York: Academic); 1987 Introduction to Superanalysis (Dordrecht: Reidel Publishing Company)), we show that we can compute with Grassmann numbers as we do with complex numbers: derivation, integration, Fourier transform. After that we show that we have quantization formulas for fermionic observables. In particular, there exists a Moyal product formula. As an application, we consider explicit computations for propagators with quadratic Hamiltonians in annihilation and creation operators. We prove a Mehler formula for the propagator and Mehlig-Wilkinson-type formulas for the covariant and contravariant symbols of ‘metaplectic’ transformations for fermionic states. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

  2. Asymmetric pallidal neuronal activity in patients with cervical dystonia

    Directory of Open Access Journals (Sweden)

    Christian KE eMoll

    2014-02-01

    Full Text Available The origin of asymmetric clinical manifestation of symptoms in patients suffering from cervical dystonia (CD is hitherto poorly understood. Dysregulated neuronal activity in the basal ganglia has been suggested to have a role in the pathophysiology of CD. Here, we re-assessed the question to what extent relative changes occur in the direct versus indirect basal ganglia pathway in CD, whether these circuit changes are lateralized, and how these alterations relate to CD symptoms. To this end, we recorded ongoing single cell and local field potential (LFP activity from the external (GPe and internal pallidal segment (GPi of thirteen CD patients undergoing microelectrode-guided stereotactic surgery for deep brain stimulation in the GPi. We compared pallidal recordings from CD patients operated under local anaesthesia (LA with those obtained in CD patients operated under general anaesthesia (GA. In awake patients, mean GPe discharge rate (52 Hz was lower than that of GPi (72 Hz. Mean GPi discharge ipsilateral to the side of head turning was higher than contralateral and correlated with torticollis symptom severity. Lateralized differences were absent at the level of the GPe and in recordings from patients operated under GA. Furthermore, in the GPi of CD patients there was a subpopulation of theta-oscillatory cells with unique bursting characteristics. Power and coherence of GPe- and GPi-LFPs were dominated by a theta peak and also exhibited band-specific interhemispheric differences. Strong cross-frequency coupling of low-gamma amplitude to theta phase was a feature of pallidal LFPs recorded under LA, but not GA. These results indicate that CD is associated with an asymmetric pallidal outflow. Based on the finding of symmetric neuronal discharges in the GPe, we propose that an imbalanced interhemispheric direct pathway gain may be involved in CD pathophysiology.

  3. Transmission de PME : du diagnostic au pilotage stratégique

    OpenAIRE

    Van Caillie, Didier; Santin, Sarah

    2007-01-01

    This communication proposes and discusses an original methodology allowing to move in a coherent perspective from a structured initial diagnosis of a SME confrontated with a transmission process to a true strategic monitoring of the transfer process.

  4. Fourier phase in Fourier-domain optical coherence tomography.

    Science.gov (United States)

    Uttam, Shikhar; Liu, Yang

    2015-12-01

    Phase of an electromagnetic wave propagating through a sample-of-interest is well understood in the context of quantitative phase imaging in transmission-mode microscopy. In the past decade, Fourier-domain optical coherence tomography has been used to extend quantitative phase imaging to the reflection-mode. Unlike transmission-mode electromagnetic phase, however, the origin and characteristics of reflection-mode Fourier phase are poorly understood, especially in samples with a slowly varying refractive index. In this paper, the general theory of Fourier phase from first principles is presented, and it is shown that Fourier phase is a joint estimate of subresolution offset and mean spatial frequency of the coherence-gated sample refractive index. It is also shown that both spectral-domain phase microscopy and depth-resolved spatial-domain low-coherence quantitative phase microscopy are special cases of this general theory. Analytical expressions are provided for both, and simulations are presented to explain and support the theoretical results. These results are further used to show how Fourier phase allows the estimation of an axial mean spatial frequency profile of the sample, along with depth-resolved characterization of localized optical density change and sample heterogeneity. Finally, a Fourier phase-based explanation of Doppler optical coherence tomography is also provided.

  5. Electronic Transmission Properties of Two-Dimensional Quasi-Lattice

    Institute of Scientific and Technical Information of China (English)

    侯志林; 傅秀军; 刘有延

    2002-01-01

    In the framework of the tight binding model, the electronic transmission properties of two-dimensional Penrose lattices with free boundary conditions are studied using the generalized eigenfunction method (Phys. Rev. B 60(1999)13444). The electronic transmission coefficients for Penrose lattices with different sizes and widths are calculated, and the result shows strong energy dependence because of the quasiperiodic structure and quantum coherent effect. Around the Fermi level E = 0, there is an energy region with zero transmission amplitudes,which suggests that the studied systems are insulating. The spatial distributions of several typical electronic states with different transmission coefficients are plotted to display the propagation process.

  6. Atomistic observation of a crack tip approaching coherent twin boundaries.

    Science.gov (United States)

    Liu, L; Wang, J; Gong, S K; Mao, S X

    2014-03-18

    Coherent twin boundaries (CTBs) in nano-twinned materials could improve crack resistance. However, the role of the CTBs during crack penetration has never been explored at atomic scale. Our in situ observation on nano-twinned Ag under a high resolution transmission electron microscope (HRTEM) reveals the dynamic processes of a crack penetration across the CTBs, which involve alternated crack tip blunting, crack deflection, twinning/detwinning and slip transmission across the CTBs. The alternated blunting processes are related to the emission of different types of dislocations at the crack tip and vary with the distance of the crack tip from the CTBs.

  7. Quantum coherence of steered states

    Science.gov (United States)

    Hu, Xueyuan; Milne, Antony; Zhang, Boyang; Fan, Heng

    2016-01-01

    Lying at the heart of quantum mechanics, coherence has recently been studied as a key resource in quantum information theory. Quantum steering, a fundamental notion originally considered by Schödinger, has also recently received much attention. When Alice and Bob share a correlated quantum system, Alice can perform a local measurement to ‘steer’ Bob’s reduced state. We introduce the maximal steered coherence as a measure describing the extent to which steering can remotely create coherence; more precisely, we find the maximal coherence of Bob’s steered state in the eigenbasis of his original reduced state, where maximization is performed over all positive-operator valued measurements for Alice. We prove that maximal steered coherence vanishes for quantum-classical states whilst reaching a maximum for pure entangled states with full Schmidt rank. Although invariant under local unitary operations, maximal steered coherence may be increased when Bob performs a channel. For a two-qubit state we find that Bob’s channel can increase maximal steered coherence if and only if it is neither unital nor semi-classical, which coincides with the condition for increasing discord. Our results show that the power of steering for coherence generation, though related to discord, is distinct from existing measures of quantum correlation.

  8. Dynamics of generalized coherent states

    CERN Document Server

    De Martino, S; Illuminati, F; De Martino, S; De Siena, S; Illuminati, F

    1995-01-01

    We show that generalized coherent states follow Schr\\"{o}dinger dynamics in time-dependent potentials. The normalized wave-packets follow a classical evolution without spreading; in turn, the Schr\\"{o}dinger potential depends on the state through the classical trajectory. This feedback mechanism with continuous dynamical re-adjustement allows the packets to remain coherent indefinetely.

  9. COHERENT LIGHT-RECORDING TECHNIQUES.

    Science.gov (United States)

    On the basis of diffraction theory, quantum-mechanics and information theory, it is shown that the principle of coherent light recording is the...mechanical, magnetic or electric approaches. Photographic coherent light recording tests were made by the dynamic sweep tests on 16 mm Recordak Micro-File

  10. COHERENT-LIGHT RECORDING TECHNIQUES.

    Science.gov (United States)

    The purpose of this report is to summarize, define and demonstrate techniques necessary for the application of coherent light to the problems of...Investigations into such areas as the coherent light source itself, modulation, deflection or scanning techniques, readout techniques and the evaluation of recording media are reported.

  11. Coherence and correspondence in medicine

    Directory of Open Access Journals (Sweden)

    Thomas G. Tape

    2009-03-01

    Full Text Available Many controversies in medical science can be framed as tension between a coherence approach (which seeks logic and explanation and a correspondence approach (which emphasizes empirical correctness. In many instances, a coherence-based theory leads to an understanding of disease that is not supported by empirical evidence. Physicians and patients alike tend to favor the coherence approach even in the face of strong, contradictory correspondence evidence. Examples include the management of atrial fibrillation, treatment of acute bronchitis, and the use of Vitamin E to prevent heart disease. Despite the frequent occurrence of controversy stemming from coherence-correspondence conflicts, medical professionals are generally unaware of these terms and the philosophical traditions that underlie them. Learning about the coherence-correspondence distinction and using the best of both approaches could not only help reconcile controversy but also lead to striking advances in medical science.

  12. Coherent Scatter Imaging Measurements

    Science.gov (United States)

    Ur Rehman, Mahboob

    In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.

  13. Coherent imaging without phases

    CERN Document Server

    Moscoso, Miguel; Papanicolaou, George

    2015-01-01

    In this paper we consider narrow band, active array imaging of weak localized scatterers when only the intensities are recorded at an array with N transducers. We consider that the medium is homogeneous and, hence, wave propagation is fully coherent. This work is an extension of our previous paper, where we showed that using linear combinations of intensity-only measurements imaging of localized scatterers can be carried out efficiently using MUSIC or sparsity promoting optimization. Here we show the same strategy can be accomplished with only 3N-2 illuminations, therefore reducing enormously the data acquisition process. Furthermore, we show that in the paraxial regime one can form the images by using six illuminations only. In particular, this paraxial regime includes Fresnel and Fraunhofer diffraction. The key point of this work is that if one controls the illuminations, imaging with intensity-only can be easily reduced to a imaging with phases and, therefore, one can apply standard imaging techniques. Det...

  14. The Puzzle of Coherence

    DEFF Research Database (Denmark)

    Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten

    2016-01-01

    Background During the past decade, politicians and healthcare providers have strived to create a coherent healthcare system across primary and secondary healthcare sectors in Denmark. Nevertheless, elderly patients with chronic diseases (EPCD) continue to report experiences of poor-quality care...... to an acute care ward to discharge and later in meetings with healthcare providers in general practice, outpatient clinics, home care and physiotherapy. Furthermore, field observations were conducted in general practice, home care and rehabilitation settings. Research design An explorative design based...... on an interactionistic approach was used. As a consequence, the focus of data collection is the production of meaning happening between human beings in social interaction in the field of cross-sectorial collaboration. Research questions The research questions reflect the interactionistic approach as they concentrate...

  15. Optical coherence in astrophysics

    CERN Document Server

    Moret-Bailly, Jacques

    2013-01-01

    Many physicists and most astrophysicists assume that the photon is a small particle which, in a very low pressure gas can only interact with a single molecule. Thus, the interaction of light with this gas is incoherent. W. E.Lamb Jr, W. P. Schleich, M. O. Scully and C. H. Townes (Reviews of Modern Physics 71, S263, 1999) have criticized this view: In accordance with quantum electrodynamics the photon is a pseudo-particle resulting from the quantization of a deterministic exchange of energy between identical molecules and a normal mode of electromagnetic field. Following Lamb et al., we study models in which some variables have an unusual value for a spectroscopist: extremely low pressure hydrogen, but huge light paths, extremely hot sources. However, the magnitudes of the spectral radiances and column densities can be similar in astrophysics and in a laboratory using lasers. Thus, several coherent effects must be taken into account: superradiance, multiphoton interactions, impulsive stimulated Raman scatterin...

  16. Quantum information and coherence

    CERN Document Server

    Öhberg, Patrik

    2014-01-01

    This book offers an introduction to ten key topics in quantum information science and quantum coherent phenomena, aimed at graduate-student level. The chapters cover some of the most recent developments in this dynamic research field where theoretical and experimental physics, combined with computer science, provide a fascinating arena for groundbreaking new concepts in information processing. The book addresses both the theoretical and experimental aspects of the subject, and clearly demonstrates how progress in experimental techniques has stimulated a great deal of theoretical effort and vice versa. Experiments are shifting from simply preparing and measuring quantum states to controlling and manipulating them, and the book outlines how the first real applications, notably quantum key distribution for secure communication, are starting to emerge. The chapters cover quantum retrodiction, ultracold quantum gases in optical lattices, optomechanics, quantum algorithms, quantum key distribution, quantum cont...

  17. Optical Coherence Tomography

    Science.gov (United States)

    Huang, David

    Optical coherence tomography (OCT) is a new method for noninvasive cross-sectional imaging in biological systems. In OCT, the longitudinal locations of tissue structures are determined by measuring the time-of-flight delays of light backscattered from these structures. The optical delays are measured by low coherence interferometry. Information on lateral position is provided by transverse scanning of the probe beam. The two dimensional map of optical scattering from internal tissue microstructures is then represented in a false-color or grayscale image. OCT is the optical analog of ultrasonic pulse-echo imaging, but with greatly improved spatial resolutions (a few microns). This thesis describes the development of this new high resolution tomographic imaging technology and the demonstration of its use in a variety of tissues under both in vitro and in vivo conditions. In vitro OCT ranging and imaging studies were performed using human ocular and arterial tissues, two clinically relevant examples of transparent and turbid media, respectively. In the anterior eye, precise measurements of cornea and anterior chamber dimensions were made. In the arterial specimens, the differentiation between fatty -calcified and fibromuscular tissues was demonstrated. In vivo OCT imaging in the retina and optic nerve head in human subjects was also performed. The delineation of retinal layers, which has not been possible with other noninvasive imaging techniques, is demonstrated in these OCT images. OCT has high spatial resolution but limited penetration into turbid tissue. It has potential for diagnostic applications where high resolution is needed and optical access is available, such as in the eye, skin, surgically exposed tissues, and surfaces that can be reached by various catheters and endoscopic probes. In particular, the measurement of fine retinal structures promises improvements in the diagnosis and management of glaucoma, macular edema and other vitreo-retinal diseases

  18. Asymmetric tandem organic solar cells

    Science.gov (United States)

    Howells, Thomas J.

    where it is used to predict the short-circuit current (Jsc) generation of the sub-cells, which is not accessible experimentally. Current-matching is then used to predict the Jsc of the complete tandem device. . As a support to the optical modelling, ellipsometry measurements of thin films of ClAlPc are presented. These films of known thickness are analysed to extract the complex refractive index for use in optical modelling calculations. A dependence of the complex refractive index on film thickness and substrate is also noted. Finally, the external quantum efficiency (EQE) technique is considered as applied to solar cells, and an additional method is proposed to characterise current balancing in asymmetric tandem cells under illumination. This technique is verified experimentally by two separate sets of data..

  19. Ptychographic coherent x-ray diffractive imaging in the water window

    OpenAIRE

    Giewekemeyer, K.; Beckers, M.; Gorniak, T.; Grunze, M.; Salditt, T.; Rosenhahn, A.

    2011-01-01

    Coherent x-ray diffractive microscopy enables full reconstruction of the complex transmission function of an isolated object to diffraction-limited resolution without relying on any optical elements between the sample and detector. In combination with ptychography, also specimens of unlimited lateral extension can be imaged. Here we report on an application of ptychographic coherent diffractive imaging (PCDI) in the soft x-ray regime, more precisely in the so-called water wi...

  20. Price Transmission Analysis in the Fresh Vegetable Supply Chain of Saudi Arabia

    OpenAIRE

    Alhashim, Jawad; Saghaian, Sayed

    2015-01-01

    Price transmission studies focus on how price variation at one marketing level affects the prices at other levels, either vertically or horizontally. Price movement among farms, wholesale, and retail levels is indicative of vertical price transmission. Any change in the farmer’s price is reflected in the final consumer’s price. Asymmetric price transmission (APT) can occur anywhere along the supply chain. The objective of this study is to explore the existence of APT for selected fresh vegeta...

  1. Control of apoptosis by asymmetric cell division.

    Directory of Open Access Journals (Sweden)

    Julia Hatzold

    2008-04-01

    Full Text Available Asymmetric cell division and apoptosis (programmed cell death are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well.

  2. Electronic coherence and the kinetics of inter-complex energy transfer in light-harvesting systems.

    Science.gov (United States)

    Huo, Pengfei; Miller, Thomas F

    2015-12-14

    We apply real-time path-integral dynamics simulations to characterize the role of electronic coherence in inter-complex excitation energy transfer (EET) processes. The analysis is performed using a system-bath model that exhibits the essential features of light-harvesting networks, including strong intra-complex electronic coupling and weak inter-complex coupling. Strong intra-complex coupling is known to generate both static and dynamic electron coherences, which delocalize the exciton over multiple chromophores and potentially influence the inter-complex EET dynamics. With numerical results from partial linearized density matrix (PLDM) real-time path-integral calculations, it is found that both static and dynamic coherence are correlated with the rate of inter-complex EET. To distinguish the impact of these two types of intra-complex coherence on the rate of inter-complex EET, we use Multi-Chromophore Förster Resonance Energy Transfer (MC-FRET) theory to map the original parameterization of the system-bath model to an alternative parameterization for which the effects of static coherence are preserved while the effects of dynamic coherence are largely eliminated. It is then shown that both parameterizations of the model (i.e., the original that supports dynamic coherence and the alternative that eliminates it), exhibit nearly identical EET kinetics and population dynamics over a wide range of parameters. These observations are found to hold for cases in which either the EET donor or acceptor is a dimeric complex and for cases in which the dimeric complex is either symmetric or asymmetric. The results from this study suggest that dynamic coherence plays only a minor role in the actual kinetics of inter-complex EET, whereas static coherence largely governs the kinetics of incoherent inter-complex EET in light-harvesting networks.

  3. Tunnelling of Two-Level Atoms in Two-Photon Mazer:Atomic Coherence Effect and Statistics of Cavity Fields

    Institute of Scientific and Technical Information of China (English)

    何小灵; 杜四德; 周鲁卫; 汪启胜; 陈灏

    2004-01-01

    Tunnelling of a two-level atom is investigated in the two-photon mazer when the atom is initially prepared in a coherent superposition state and the cavity in various quantum states. For a strong coherent field, the tunnelling exhibits more regular oscillations but less remarkable switch effect than that in the one-photon mazer. It is discovered that in the presence of atomic coherence, the transmission probabilities in the ultracold regime are significantly different when the cavity field is initially in coherent, squeezed vacuum, even cat and odd cat states,respectively.

  4. Coherent electron transport in a helical nanotube

    Science.gov (United States)

    Liang, Guo-Hua; Wang, Yong-Long; Du, Long; Jiang, Hua; Kang, Guang-Zhen; Zong, Hong-Shi

    2016-09-01

    The quantum dynamics of carriers bound to helical tube surfaces is investigated in a thin-layer quantization scheme. By numerically solving the open-boundary Schrödinger equation in curvilinear coordinates, geometric effect on the coherent transmission spectra is analysed in the case of single propagating mode as well as multimode. It is shown that, the coiling endows the helical nanotube with different transport properties from a bent cylindrical surface. Fano resonance appears as a purely geometric effect in the conductance, the corresponding energy of quasibound state is obviously influenced by the torsion and length of the nanotube. We also find new plateaus in the conductance. The transport of double-degenerate mode in this geometry is reminiscent of the Zeeman coupling between the magnetic field and spin angular momentum in quasi-one-dimensional structure.

  5. On Linear Coherent Estimation with Spatial Collaboration

    CERN Document Server

    Kar, Swarnendu

    2012-01-01

    We consider a power-constrained sensor network, consisting of multiple sensor nodes and a fusion center (FC), that is deployed for the purpose of estimating a common random parameter of interest. In contrast to the distributed framework, the sensor nodes are allowed to update their individual observations by (linearly) combining observations from neighboring nodes. The updated observations are communicated to the FC using an analog amplify-and-forward modulation scheme and through a coherent multiple access channel. The optimal collaborative strategy is obtained by minimizing the cumulative transmission power subject to a maximum distortion constraint. For the distributed scenario (i.e., with no observation sharing), the solution reduces to the power-allocation problem considered by [Xiao, TSP08]. Collaboration among neighbors significantly improves power efficiency of the network in the low local-SNR regime, as demonstrated through an insightful example and numerical simulations.

  6. Adaptive GOP structure based on motion coherence

    Science.gov (United States)

    Ma, Yanzhuo; Wan, Shuai; Chang, Yilin; Yang, Fuzheng; Wang, Xiaoyu

    2009-08-01

    Adaptive Group of Pictures (GOP) is helpful for increasing the efficiency of video encoding by taking account of characteristics of video content. This paper proposes a method for adaptive GOP structure selection for video encoding based on motion coherence, which extracts key frames according to motion acceleration, and assigns coding type for each key and non-key frame correspondingly. Motion deviation is then used instead of motion magnitude in the selection of the number of B frames. Experimental results show that the proposed method for adaptive GOP structure selection achieves performance gain of 0.2-1dB over the fixed GOP, and has the advantage of better transmission resilience. Moreover, this method can be used in real-time video coding due to its low complexity.

  7. [Development of new methods in asymmetric reactions and their applications].

    Science.gov (United States)

    Node, Manabu

    2002-01-01

    Several novel methods using chiral reagents and biocatalysts for asymmetric reactions are described. Among those reactions, asymmetric reduction via a novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction of acyclic alpha,beta-unsaturated ketones using a chiral mercapto alcohol, asymmetric synthesis of allene-1,3-dicarboxylate via crystallization induced asymmetric transformation, and improved asymmetric nitroolefination of lactones and lactames at alpha-carbon using new chiral reagents were developed. In the reactions using biocatalysts, asymmetric dealkoxycarbonylation of bicyclic beta-keto diesters having sigma-symmetry with lipase or esterase to give optically active beta-keto esters, the asymmetric reduction of bicyclic 1,3-diketones having sigma-symmetry with Baker's yeast to give optically active keto alcohols, and the asymmetric aldol reaction of glycine with threonine aldolase were also developed. The above mentioned products were effectively utilized as chiral building blocks for the asymmetric synthesis of natural products and drugs.

  8. Continuous-Variable Measurement-Device-Independent Multipartite Quantum Communication Using Coherent States

    Science.gov (United States)

    Zhou, Jian; Guo, Ying

    2017-02-01

    A continuous-variable measurement-device-independent (CV-MDI) multipartite quantum communication protocol is designed to realize multipartite communication based on the GHZ state analysis using Gaussian coherent states. It can remove detector side attack as the multi-mode measurement is blindly done in a suitable Black Box. The entanglement-based CV-MDI multipartite communication scheme and the equivalent prepare-and-measurement scheme are proposed to analyze the security and guide experiment, respectively. The general eavesdropping and coherent attack are considered for the security analysis. Subsequently, all the attacks are ascribed to coherent attack against imperfect links. The asymptotic key rate of the asymmetric configuration is also derived with the numeric simulations illustrating the performance of the proposed protocol.

  9. Heteronuclear intermolecular single-quantum coherences in liquid nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Chen Song; Zhu Xiao-Qin; Cai Shu-Hui; Chen Zhong

    2008-01-01

    This paper analyses the heteronuclear Cosy Revamped by Asymmetric Z-gradient Echo Detection pulse sequence.General theoretical expressions of the pulse sequence with arbitrary flip angles were derived by using dipolar field treatment and signals originating from heteronuclear intermolecular single-quantum coherences (iSQCs) in highly-polarized two spin-1/2 systems were mainly discussed in order to find the optimal flip angles.The results show that signals from heteronuclear iSQCs decay slower than those from intermolecular double-quantum coherences or intermolecular zero-quantum coherences. Magical angle experiments validate that the signals are from heteronuclear iSQCs and insensitive to the imperfection of radio-frequency flip angles. All experimental observations are in excellent agreement with theoretical predictions. The quantum-mechanical treatment leads to similar predictions to the dipolar field treatment.

  10. Coherence Properties of the LCLS

    Energy Technology Data Exchange (ETDEWEB)

    Ocko, Samuel

    2010-08-25

    The LINAC Coherent Light Source (LCLS), an X-Ray free-electron laser(FEL) based on the self amplified spontaneous emission principle, has recently come on-line. For many users it is desirable to have an idea of the level of transverse coherence of the X-Ray beam produced. In this paper, we analyze the output of GENESIS simulations of electrons traveling through the FEL. We first test the validity of an approach that ignores the details of how the beam was produced, and instead, by assuming a Gaussian-Schell model of transverse coherence, predicts the level of transverse coherence simply through looking at the beam radius at several longitudinal slices. We then develop a Markov chain Monte Carlo approach to calculating the degree of transverse coherence, which offers a {approx}100-fold speedup compared to the brute-force algorithm previously in use. We find the beam highly coherent. Using a similar Markov chain Monte Carlo approach, we estimate the reasonability of assuming the beam to have a Gaussian-Schell model of transverse coherence, with inconclusive results.

  11. Excitonic effects on coherent phonon dynamics in single-wall carbon nanotubes

    Science.gov (United States)

    Nugraha, A. R. T.; Rosenthal, E. I.; Hasdeo, E. H.; Sanders, G. D.; Stanton, C. J.; Dresselhaus, M. S.; Saito, R.

    2013-08-01

    We discuss how excitons can affect the generation of coherent radial breathing modes in the ultrafast spectroscopy of single-wall carbon nanotubes. Photoexcited excitons can be localized spatially and give rise to a spatially distributed driving force in real space which involves many phonon wave vectors of the exciton-phonon interaction. The equation of motion for the coherent phonons is modeled phenomenologically by the Klein-Gordon equation, which we solve for the oscillation amplitudes as a function of space and time. By averaging the calculated amplitudes per nanotube length, we obtain time-dependent coherent phonon amplitudes that resemble the homogeneous oscillations that are observed in some pump-probe experiments. We interpret this result to mean that the experiments are only able to see a spatial average of coherent phonon oscillations over the wavelength of light in carbon nanotubes and the microscopic details are averaged out. Our interpretation is justified by calculating the time-dependent absorption spectra resulting from the macroscopic atomic displacements induced by the coherent phonon oscillations. The calculated coherent phonon spectra including excitonic effects show the experimentally observed symmetric peaks at the nanotube transition energies, in contrast to the asymmetric peaks that would be obtained if excitonic effects were not included.

  12. Fuzzy Random Walkers with Second Order Bounds: An Asymmetric Analysis

    Directory of Open Access Journals (Sweden)

    Georgios Drakopoulos

    2017-03-01

    Full Text Available Edge-fuzzy graphs constitute an essential modeling paradigm across a broad spectrum of domains ranging from artificial intelligence to computational neuroscience and social network analysis. Under this model, fundamental graph properties such as edge length and graph diameter become stochastic and as such they are consequently expressed in probabilistic terms. Thus, algorithms for fuzzy graph analysis must rely on non-deterministic design principles. One such principle is Random Walker, which is based on a virtual entity and selects either edges or, like in this case, vertices of a fuzzy graph to visit. This allows the estimation of global graph properties through a long sequence of local decisions, making it a viable strategy candidate for graph processing software relying on native graph databases such as Neo4j. As a concrete example, Chebyshev Walktrap, a heuristic fuzzy community discovery algorithm relying on second order statistics and on the teleportation of the Random Walker, is proposed and its performance, expressed in terms of community coherence and number of vertex visits, is compared to the previously proposed algorithms of Markov Walktrap, Fuzzy Walktrap, and Fuzzy Newman–Girvan. In order to facilitate this comparison, a metric based on the asymmetric metrics of Tversky index and Kullback–Leibler divergence is used.

  13. Dc SQUIDs with asymmetric shunt resistors

    Energy Technology Data Exchange (ETDEWEB)

    Rudolph, Matthias; Nagel, Joachim; Kemmler, Matthias; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISAplus, Universitaet Tuebingen (Germany); Meckbach, Johannes Maximilian; Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2013-07-01

    We have investigated asymmetrically shunted Nb/Al-AlO{sub x}/Nb dc SQUIDs. Simulations based on the coupled Langevin equations predict that the optimum energy resolution ε, and thus also the noise performance of such an asymmetric SQUID, can be 3-4 times better than that of its symmetric counterpart. While keeping the total resistance R identical to a comparable symmetric SQUID with R{sup -1} = R{sub 1}{sup -1} + R{sub 2}{sup -1}, we shunted only one of the two Josephson junctions with R = R{sub 1,2}/2. Both types of SQUIDs were characterized with respect to their transport and noise properties at temperature T = 4.2 K, and we compared the experimental results with numerical simulations. Experiments yielded ε ∼ 32 ℎ for an asymmetric SQUID with an inductance L = 22 pH, whereas a comparable symmetric device achieved ε = 110 ℎ.

  14. External Electro-optic Sampling Utilizing an Asymmetric Fabry-Pérot Film of Poled Electro-optical Polymer

    Institute of Scientific and Technical Information of China (English)

    陈开鑫; 杨罕; 张大明; 张红波; 衣茂斌

    2001-01-01

    External electro-optic sampling has been first demonstrated using a poled electro-optical polymer asymmetricFabry-Pérot film, placed freely on the indium-tin oxide coplanar waveguide transmission line and used as anelectro-optic probe tip. Only one laser beam is required due to the fact that the asymmetric Fabry-Pérot film isutilized to convert the phase modulation to amplitude modulation. A 1.2 GHz microwave signal is sampled, andthe voltage sensitivity of about 2 m V/Hz is obtained. The results are promising for technical applications inhigh-speed electronic devices and monolithic microwave integrated circuits research.

  15. International workshop on phase retrieval and coherent scattering. Coherence 2005

    Energy Technology Data Exchange (ETDEWEB)

    Nugent, K.A.; Fienup, J.R.; Van Dyck, D.; Van Aert, S.; Weitkamp, T.; Diaz, A.; Pfeiffer, F.; Cloetens, P.; Stampanoni, M.; Bunk, O.; David, C.; Bronnikov, A.V.; Shen, Q.; Xiao, X.; Gureyev, T.E.; Nesterets, Ya.I.; Paganin, D.M.; Wilkins, S.W.; Mokso, R.; Cloetens, P.; Ludwig, W.; Hignette, O.; Maire, E.; Faulkner, H.M.L.; Rodenburg, J.M.; Wu, X.; Liu, H.; Grubel, G.; Ludwig, K.F.; Livet, F.; Bley, F.; Simon, J.P.; Caudron, R.; Le Bolloc' h, D.; Moussaid, A.; Gutt, C.; Sprung, M.; Madsen, A.; Tolan, M.; Sinha, S.K.; Scheffold, F.; Schurtenberger, P.; Robert, A.; Madsen, A.; Falus, P.; Borthwick, M.A.; Mochrie, S.G.J.; Livet, F.; Sutton, M.D.; Ehrburger-Dolle, F.; Bley, F.; Geissler, E.; Sikharulidze, I.; Jeu, W.H. de; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Naryanan, S.; Sinha, S.K.; Lal, J.; Naryanan, S.; Sinha, S.K.; Lal, J.; Robinson, I.K.; Chapman, H.N.; Barty, A.; Beetz, T.; Cui, C.; Hajdu, J.; Hau-Riege, S.P.; He, H.; Stadler, L.M.; Sepiol, B.; Harder, R.; Robinson, I.K.; Zontone, F.; Vogl, G.; Howells, M.; London, R.; Marchesini, S.; Shapiro, D.; Spence, J.C.H.; Weierstall, U.; Eisebitt, S.; Shapiro, D.; Lima, E.; Elser, V.; Howells, M.R.; Huang, X.; Jacobsen, C.; Kirz, J.; Miao, H.; Neiman, A.; Sayre, D.; Thibault, P.; Vartanyants, I.A.; Robinson, I.K.; Onken, J.D.; Pfeifer, M.A.; Williams, G.J.; Pfeiffer, F.; Metzger, H.; Zhong, Z.; Bauer, G.; Nishino, Y.; Miao, J.; Kohmura, Y.; Yamamoto, M.; Takahashi, Y.; Koike, K.; Ebisuzaki, T.; Ishikawa, T.; Spence, J.C.H.; Doak, B

    2005-07-01

    The contributions of the participants have been organized into 3 topics: 1) phase retrieval methods, 2) X-ray photon correlation spectroscopy, and 3) coherent diffraction imaging. This document gathers the abstracts of the presentations and of the posters.

  16. Coherence in Linear Predicate Logic

    CERN Document Server

    Dosen, K

    2007-01-01

    Coherence with respect to Kelly-Mac Lane graphs is proved for categories that correspond to the multiplicative fragment without constant propositions of classical linear first-order predicate logic without or with mix. To obtain this result, coherence is first established for categories that correspond to the multiplicative conjunction-disjunction fragment with first-order quantifiers of classical linear logic, a fragment lacking negation. These results extend results published in previous two books by the authors, where coherence was established for categories of the corresponding fragments of propositional classical linear logic, which are related to proof nets, and which could be described as star-autonomous categories without unit objects.

  17. Coherent control of quantum dots

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Lodahl, Peter; Hvam, Jørn Märcher

    In recent years much effort has been devoted to the use of semiconductor quantum dotsystems as building blocks for solid-state-based quantum logic devices. One importantparameter for such devices is the coherence time, which determines the number ofpossible quantum operations. From earlier...... measurements the coherence time of the selfassembledquantum dots (QDs) has been reported to be limited by the spontaneousemission rate at cryogenic temperatures1.In this project we propose to alter the coherence time of QDs by taking advantage of arecent technique on modifying spontaneous emission rates...

  18. Asymmetric gear rectifies random robot motion

    Science.gov (United States)

    Li, He; Zhang, H. P.

    2013-06-01

    We experimentally study the dynamics of centimetric robots and their interactions with rotary gears through inelastic collisions. Under the impacts of self-propelled robots, a gear with symmetric teeth diffuses with no preferred direction of motion. An asymmetric gear, however, rectifies random motion of nearby robots which, in return, exert a torque on the gear and drive it into unidirectional motion. Rectification efficiency increases with the degree of gear asymmetry. Our work demonstrates that asymmetric environments can be used to rectify and extract energy from random motion of macroscopic self-propelled particles.

  19. Homogeneous asymmetric catalysis in fragrance chemistry.

    Science.gov (United States)

    Ciappa, Alessandra; Bovo, Sara; Bertoldini, Matteo; Scrivanti, Alberto; Matteoli, Ugo

    2008-06-01

    Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide, Phenoxanol, Citralis, and Citralis Nitrile, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol, Citralis, and Citralis Nitrile were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.

  20. Asymmetric catalysis with short-chain peptides.

    Science.gov (United States)

    Lewandowski, Bartosz; Wennemers, Helma

    2014-10-01

    Within this review article we describe recent developments in asymmetric catalysis with peptides. Numerous peptides have been established in the past two decades that catalyze a wide variety of transformations with high stereoselectivities and yields, as well as broad substrate scope. We highlight here catalytically active peptides, which have addressed challenges that had thus far remained elusive in asymmetric catalysis: enantioselective synthesis of atropoisomers and quaternary stereogenic centers, regioselective transformations of polyfunctional substrates, chemoselective transformations, catalysis in-flow and reactions in aqueous environments.

  1. Asymmetric localization in disordered Landau bands

    Energy Technology Data Exchange (ETDEWEB)

    Nita, M [Institute of Physics and Technology of Materials, PO Box MG7, Bucharest-Magurele (Romania); Aldea, A [Institute of Physics and Technology of Materials, PO Box MG7, Bucharest-Magurele (Romania); Zittartz, J [Institute of Theoretical Physics, Cologne University, 50937 Cologne (Germany)

    2007-06-06

    We show that, due to band mixing, the eigenstate localization within the disordered Landau bands gets an asymmetric structure: the degree of localization increases in the lower part of the band and decreases in the upper one. The calculation is performed for a two-dimensional lattice with the Anderson disorder potential and we prove that this effect is related to the upper shift of the extended states within the band and is enhanced by the disorder strength. The asymmetric localization and the energy shift disappear when the interband coupling is switched off.

  2. Asymmetric multiscale behavior in PM2.5 time series: Based on asymmetric MS-DFA

    Science.gov (United States)

    Zhang, Chen; Ni, Zhiwei; Ni, Liping

    2016-11-01

    Particulate matter with an aerodynamic diameter of 2.5 mm or less (PM2.5) is one of the most serious air pollution, considered most harmful for people by World Health Organisation. In this paper, we utilized the asymmetric multiscale detrended fluctuation analysis (A-MSDFA) method to explore the existence of asymmetric correlation properties for PM2.5 daily average concentration in two USA cities (Fresno and Los Angeles) and two Chinese cities (Hong Kong and Shanghai), and to assess the properties of these asymmetric correlations. The results show the existences of asymmetric correlations, and the degree of asymmetric for two USA cities is stronger than that of two Chinese cities. Further, most of the local exponent β(n) are smaller than 0.5, which indicates the existence of anti-persistent long-range correlation for PM2.5 time series in four cities. In addition, we reanalyze the asymmetric correlation by the A-MSDFA method with secant rolling windows of different sizes, which can investigate dynamic changes in the multiscale correlation for PM2.5 time series with changing window size. Whatever window sizes, the correlations are asymmetric and display smaller asymmetries at small scales and larger asymmetries at large scales. Moreover, the asymmetries become increasingly weaker with the increase of window sizes.

  3. Survey of Transmission Cost Allocation Methodologies for Regional Transmission Organizations

    Energy Technology Data Exchange (ETDEWEB)

    Fink, S.; Porter, K.; Mudd, C.; Rogers, J.

    2011-02-01

    The report presents transmission cost allocation methodologies for reliability transmission projects, generation interconnection, and economic transmission projects for all Regional Transmission Organizations.

  4. Vertical price transmission in the Danish food chain

    DEFF Research Database (Denmark)

    Jensen, Jørgen Dejgård; Møller, Anja Skadkær

    2005-01-01

    This purpose of this paper is to investigate price transmission patterns through selected Danish food chains – from primary production to processing, from processing to wholesale and from wholesale to retail prices. Specifically, the study addresses the following research questions: To what extent...... are commodity prices transmitted from one stage to another in the food chain? What is the time horizon in the price transmission? Is price transmission symmetric – in the short run and in the long run? Is the degree of price transmission affected by the degree of concentration in the supply and demand stage...... considered? These questions are analysed theoretically and empirically using econometric analysis. 6 food chains are investigated: pork, chicken, eggs, milk, sugar and apples. Preliminary empirical results suggest that for most commodities, price transmission tends to be upward asymmetric, i.e. stronger...

  5. Coherent Radio Emission from Pulsars

    CERN Document Server

    Mitra, Dipanjan; Gil, Janusz

    2015-01-01

    We review a physical model where the high brightness temperature of 10$^{25}-10^{30}$ K observed in pulsar radio emission is explained by coherent curvature radiation excited in the relativistic electron-positron plasma in the pulsar magnetosphere.

  6. Coherent Control of Bond Making

    CERN Document Server

    Levin, Liat; Rybak, Leonid; Kosloff, Ronnie; Koch, Christiane P; Amitay, Zohar

    2014-01-01

    We demonstrate for the first time coherent control of bond making, a milestone on the way to coherent control of photo-induced bimolecular chemical reactions. In strong-field multiphoton femtosecond photoassociation experiments, we find the yield of detected magnesium dimer molecules to be enhanced for positively chirped pulses and suppressed for negatively chirped pulses. Our ab initio model shows that control is achieved by purification via Franck-Condon filtering combined with chirp-dependent Raman transitions. Experimental closed-loop phase optimization using a learning algorithm yields an improved pulse that utilizes vibrational coherent dynamics in addition to chirp-dependent Raman transitions. Our results show that coherent control of binary photo-reactions is feasible even under thermal conditions.

  7. Pairing versus quarteting coherence length

    CERN Document Server

    Delion, Doru S

    2015-01-01

    We systematically analyse the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar...

  8. Coherence matrix of plasmonic beams

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Lavrinenko, Andrei

    2013-01-01

    We consider monochromatic electromagnetic beams of surface plasmon-polaritons created at interfaces between dielectric media and metals. We theoretically study non-coherent superpositions of elementary surface waves and discuss their spectral degree of polarization, Stokes parameters, and the for...... of the spectral coherence matrix. We compare the polarization properties of the surface plasmonspolaritons as three-dimensional and two-dimensional fields concluding that the latter is superior....

  9. (Inter)textuality, Semantics, and Coherence.

    Science.gov (United States)

    Weiser, Irwin

    Although the concept of coherence is elusive, explorations of the historical, theoretical, and empirical discussions of coherence can illuminate, though not eliminate, the concept's elusiveness. There are three inter-related and overlapping ways that readers make coherence. Intratextuality, the notion that readers perceive a text as coherent if it…

  10. Coherence Studies for Synthetic Aperture Sonar

    Science.gov (United States)

    2014-09-30

    TITLE AND SUBTITLE Coherence Studies for Synthetic Aperture Sonar 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-13-1-0020 5c. PROGRAM...systematic look at, coherence. 15. SUBJECT TERMS Synthetic; Aperture Sonar , Coherence, Seafloor Scatter, Propagation Variability 16. SECURITY...reconstruction of the document. Coherence Studies for Synthetic Aperture Sonar Anthony P. Lyons The Pennsylvania State University Applied Research

  11. A Construal Model Perspective on Discourse Coherence

    Science.gov (United States)

    Yang, Hongyan

    2015-01-01

    Discourse coherence is a common phenomenon in linguistic studies, and plays an important role in discourse analysis. As a common and extremely important type of language phenomena, discourse coherence has drawn more and more scholars' attention, but they emphasis on partial discourse coherence, paying a little attention to holistic coherence. The…

  12. Coherence evolution of partially coherent beams carrying optical vortices propagating in non-Kolmogorov turbulence.

    Science.gov (United States)

    Qin, Zhiyuan; Tao, Rumao; Zhou, Pu; Xu, Xiaojun; Liu, Zejin

    2013-11-20

    Based on partially coherent Bessel-Gaussian beams (BGBs), the coherence evolution of the partially coherent beams carrying optical vortices in non-Kolmogorov turbulence is investigated in detail. The analytical formulas for the spatial coherence length of partially coherent BGBs with optical vortices in non-Kolmogorov turbulence have been derived by using the combination of a coherence superposition approximation of decentered Gaussian beams and the extended Huygens-Fresnel principle. The influences of beam and turbulence parameters on spatial coherence are investigated by numerical examples. Numerical results reveal that the coherence of the partially coherent laser beam with vortices is independent of the optical vortices, and the spatial correlation length of the beams does not decrease monotonically during propagation in non-Kolmogorov turbulence. Within a certain propagation distance, the coherence of the partially coherent beam will improve, and the improvement of the coherence of the partially coherent beams is closely related to the beam and turbulence parameters.

  13. Spin squeezing in nonlinear spin coherent states

    OpenAIRE

    Wang, Xiaoguang

    2001-01-01

    We introduce the nonlinear spin coherent state via its ladder operator formalism and propose a type of nonlinear spin coherent state by the nonlinear time evolution of spin coherent states. By a new version of spectroscopic squeezing criteria we study the spin squeezing in both the spin coherent state and nonlinear spin coherent state. The results show that the spin coherent state is not squeezed in the x, y, and z directions, and the nonlinear spin coherent state may be squeezed in the x and...

  14. THz operation of asymmetric-nanochannel devices

    NARCIS (Netherlands)

    Balocco, C.; Halsall, M.; Vinh, N. Q.; Song, A. M.

    2008-01-01

    The THz spectrum lies between microwaves and the mid-infrared, a region that remains largely unexplored mainly due to the bottleneck issue of lacking compact, solid state, emitters and detectors. Here, we report on a novel asymmetric-nanochannel device, known as the self-switching device, which can

  15. Asymmetric conditional volatility in international stock markets

    Science.gov (United States)

    Ferreira, Nuno B.; Menezes, Rui; Mendes, Diana A.

    2007-08-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the SP 500, FTSE 100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.

  16. Dynamic Conditional Correlations for Asymmetric Processes

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2010-01-01

    textabstractThe paper develops two Dynamic Conditional Correlation (DCC) models, namely the Wishart DCC (WDCC) model and the Matrix-Exponential Conditional Correlation (MECC) model. The paper applies the WDCC approach to the exponential GARCH (EGARCH) and GJR models to propose asymmetric DCC models.

  17. Weak chaos in the asymmetric heavy top

    CERN Document Server

    Barrientos, M; Ranada, A F

    1995-01-01

    We consider the dynamics of the slightly asymmetric heavy top, a non-integrable system obtained from the Lagrange top by breaking the symmetry of its inertia tensor. It shows signs of weak chaos, which we study numerically. We argue that it is a good example for introducing students to non-integrability and chaos. (author)

  18. Catalytic Asymmetric Synthesis of Phosphine Boronates.

    Science.gov (United States)

    Hornillos, Valentín; Vila, Carlos; Otten, Edwin; Feringa, Ben L

    2015-06-26

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds.

  19. Beam-beam issues in asymmetric colliders

    Energy Technology Data Exchange (ETDEWEB)

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e{sup +}- e{sup -} colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II).

  20. Three dimensional force balance of asymmetric droplets

    Science.gov (United States)

    Kim, Yeseul; Lim, Su Jin; Cho, Kun; Weon, Byung Mook

    2016-11-01

    An equilibrium contact angle of a droplet is determined by a horizontal force balance among vapor, liquid, and solid, which is known as Young's law. Conventional wetting law is valid only for axis-symmetric droplets, whereas real droplets are often asymmetric. Here we show that three-dimensional geometry must be considered for a force balance for asymmetric droplets. By visualizing asymmetric droplets placed on a free-standing membrane in air with X-ray microscopy, we are able to identify that force balances in one side and in other side control pinning behaviors during evaporation of droplets. We find that X-ray microscopy is powerful for realizing the three-dimensional force balance, which would be essential in interpretation and manipulation of wetting, spreading, and drying dynamics for asymmetric droplets. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01007133).

  1. Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts

    NARCIS (Netherlands)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G.; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-01-01

    The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N-benzylated 3-substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh-JosiPhos catalyst reduced a range of pyridinium salts with ee

  2. Nucleation Process in Asymmetric Nuclear Matter

    CERN Document Server

    Peres-Menezes, D

    1998-01-01

    An extended version of the non linear Walecka model, with rho mesons and eletromagnetic field is used to investigate the possibility of phase transitions in hot (warm) nuclear matter, giving rise to droplet formation. Surface properties of asymmetric nuclear matter as the droplet surface energy and its thickness are also examined.

  3. Integrated Optical Asymmetric Coupler Pressure Sensor

    Science.gov (United States)

    Kiyat, Isa; Kocabas, Coskun; Aydinli, Atilla

    2004-05-01

    Analysis of a novel pressure sensor based on a silicon-on-insulator (SOI) asymmetric vertical coupler is presented. The integrated optical component is a coupler composed of a single mode (SM) low index waveguide and a thin silicon slab. High sensitivities of about 0.14 rad.kPa-1 should be achieved.

  4. Asymmetric relationships between proteins shape genome evolution.

    NARCIS (Netherlands)

    Notebaart, R.A.; Kensche, P.R.; Huynen, M.A.; Dutilh, B.E.

    2009-01-01

    BACKGROUND: The relationships between proteins are often asymmetric: one protein (A) depends for its function on another protein (B), but the second protein does not depend on the first. In metabolic networks there are multiple pathways that converge into one central pathway. The enzymes in the conv

  5. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    2012-01-01

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical differentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  6. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical dierentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  7. Advanced Equalization Techniques for Digital Coherent Optical Receivers

    DEFF Research Database (Denmark)

    Arlunno, Valeria

    This PhD thesis addresses the design and performance evaluation of advanced Digital Signal Processing (DSP) algorithms for coherent optical fiber transmission systems. The research results presented in this thesis report on transmission of highly spectrally efficient optical communication systems...... employing multiplexing techniques with polarization multiplexing and multi-level modulations format. Advanced digital signal processing techniques offer robustness and flexibility for next generation high capacity optical fibre networks and are therefore considered as key building blocks in next generation...... format detection. Feedback equalization structure have been investigated in high order modulation formats transmission, when combined with coding techniques, and for closed spaced multiplexing scenario. Highlight results presented in this PhD thesis include evaluation and implementation of a novel...

  8. Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Pier Alberto Testoni

    2007-01-01

    Full Text Available Optical coherence tomography (OCT is an optical imaging modality that performs high-resolution, cross-sectional, subsurface tomographic imaging of the microstructure of tissues. The physical principle of OCT is similar to that of B-mode ultrasound imaging, except that it uses infrared light waves rather than acoustic waves. The in vivo resolution is 10–25 times better (about 10 µm than with high-frequency ultrasound imaging, but the depth of penetration is limited to 1–3 mm, depending on tissue structure, depth of focus of the probe used, and pressure applied to the tissue surface. In the last decade, OCT technology has evolved from an experimental laboratory tool to a new diagnostic imaging modality with a wide spectrum of clinical applications in medical practice, including the gastrointestinal tract and pancreatico-biliary ductal system. OCT imaging from the gastrointestinal tract can be done in humans by using narrow-diameter, catheter-based probes that can be inserted through the accessory channel of either a conventional front-view endoscope, for investigating the epithelial structure of the gastrointestinal tract, or a side-view endoscope, inside a standard transparent ERCP (endoscopic retrograde cholangiopancreatography catheter, for investigating the pancreatico-biliary ductal system. The esophagus and esophagogastric junction have been the most widely investigated organs so far; more recently, duodenum, colon, and the pancreatico-biliary ductal system have also been extensively investigated. OCT imaging of the gastrointestinal wall structure is characterized by a multiple-layer architecture that permits an accurate evaluation of the mucosa, lamina propria, muscularis mucosae, and part of the submucosa. The technique may therefore be used to identify preneoplastic conditions of the gastrointestinal tract, such as Barrett's epithelium and dysplasia, and evaluate the depth of penetration of early-stage neoplastic lesions. OCT imaging

  9. Charge Asymmetric Cosmic Rays as a probe of Flavor Violating Asymmetric Dark Matter

    DEFF Research Database (Denmark)

    Masina, Isabella; Sannino, Francesco

    2011-01-01

    The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown...... component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lepton...... flavor violation and asymmetric dark matter are both required to have a charge asymmetry in the cosmic ray lepton excesses. Therefore, an experimental evidence of charge asymmetry in the cosmic ray lepton excesses implies that dark matter is asymmetric....

  10. Vertical-Cavity Surface-Emitting Lasers: Advanced Modulation Formats and Coherent Detection

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto

    transmission link with real-time demodulation. Furthermore, advanced modulation formats are considered in this thesis to expand the state-of-the-art in high-speed short-range data transmission system based on VCSELs. First, directly modulation of a VCSEL with a 4-level pulse amplitude modulation (PAM-4) signal......This thesis expands the state-of-the-art in coherent detection for optical fiber access networks employing vertical-cavity surface-emitting lasers (VCSELs) as light sources. Bit rates up to 10 Gb/s over 25 km single-mode fibre (SMF) transmission distance have been achieved supporting a passive...... generation optical fiber access networks regarding long reach, high splitting ratio, no optical amplification, no external modulation, and use of a single fiber for upstream and downstream transmission. An important contribution of this thesis is the novel concept of chirpassisted coherent detection...

  11. Coherent states and applications in mathematical physics

    CERN Document Server

    Combescure, Monique

    2012-01-01

    This book presents the various types of coherent states introduced and studied in the physics and mathematics literature and describes their properties together with application to quantum physics problems. It is intended to serve as a compendium on coherent states and their applications for physicists and mathematicians, stretching from the basic mathematical structures of generalized coherent states in the sense of Perelomov via the semiclassical evolution of coherent states to various specific examples of coherent states (hydrogen atom, quantum oscillator, ...).

  12. Coherent detection and digital signal processing for fiber optic communications

    Science.gov (United States)

    Ip, Ezra

    The drive towards higher spectral efficiency in optical fiber systems has generated renewed interest in coherent detection. We review different detection methods, including noncoherent, differentially coherent, and coherent detection, as well as hybrid detection methods. We compare the modulation methods that are enabled and their respective performances in a linear regime. An important system parameter is the number of degrees of freedom (DOF) utilized in transmission. Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency as it uses all four available DOF contained in the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Software based receivers benefit from the robustness of DSP, flexibility in design, and ease of adaptation to time-varying channels. Linear impairments, including chromatic dispersion (CD) and polarization-mode dispersion (PMD), can be compensated quasi-exactly using finite impulse response filters. In practical systems, sampling the received signal at 3/2 times the symbol rate is sufficient to enable an arbitrary amount of CD and PMD to be compensated for a sufficiently long equalizer whose tap length scales linearly with transmission distance. Depending on the transmitted constellation and the target bit error rate, the analog-to-digital converter (ADC) should have around 5 to 6 bits of resolution. Digital coherent receivers are naturally suited for the implementation of feedforward carrier recovery, which has superior linewidth tolerance than phase-locked loops, and does not suffer from feedback delay constraints. Differential bit encoding can be used to prevent catastrophic receiver failure due

  13. Coherence measurements and coherent diffractive imaging at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Vartanyants, I A; Mancuso, A P; Singer, A; Yefanov, O M; Gulden, J, E-mail: ivan.vartaniants@desy.d [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany)

    2010-10-14

    We present an overview of recent experiments performed at the free-electron laser (FEL) FLASH at DESY in Hamburg. Experiments were focused on coherence measurements and coherent x-ray diffractive imaging (CXDI) of periodic and non-periodic biological samples. Young's double slit experiment was performed at FLASH to measure its coherence properties at a fundamental wavelength of 13.7 nm. Additionally, a uniformly redundant array was used to measure the coherence properties of the third harmonic (2.7 nm) of an 8 nm fundamental wavelength at FLASH. Coherent imaging of a two-dimensional (2D) finite crystal structure using a single pulse train of FLASH radiation was demonstrated. We show that the structure is reconstructed to the detector-limited resolution of 220 nm, given an adequate signal to noise ratio. We have also employed CXDI in a non-destructive regime to compare the images of a biological sample using single, femtosecond pulses of FLASH radiation. We have verified that images reconstructed using CXDI are similar for statistically different FEL pulses. We have also demonstrated Fourier transform holography of the same biological sample and present diffraction data measured at the third harmonic of FLASH, reaching into the water window.

  14. Coherent DWDM technology for high speed optical communications

    Science.gov (United States)

    Saunders, Ross

    2011-10-01

    The introduction of coherent digital optical transmission enables a new generation of high speed optical data transport and fiber impairment mitigation. An initial implementation of 40 Gb/s coherent systems using Dual Polarization Quadrature Phase Shift Keying (DP-QPSK) is already being installed in carrier networks. New systems running at 100 Gb/s DP-QPSK data rate are in development and early technology lab and field trial phase. Significant investment in the 100 Gb/s ecosystem (optical components, ASICs, transponders and systems) bodes well for commercial application in 2012 and beyond. Following in the footsteps of other telecommunications fields such as wireless and DSL, we can expect coherent optical transmission to evolve from QPSK to higher order modulations schemes such as Mary PSK and/or QAM. This will be an interesting area of research in coming years and poses significant challenges in terms of electro-optic, DSP, ADC/DAC design and fiber nonlinearity mitigation to reach practical implementation ready for real network deployments.

  15. Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates

    Science.gov (United States)

    Song, Gian; Sun, Zhiqian; Li, Lin; Xu, Xiandong; Rawlings, Michael; Liebscher, Christian H.; Clausen, Bjørn; Poplawsky, Jonathan; Leonard, Donovan N.; Huang, Shenyan; Teng, Zhenke; Liu, Chain T.; Asta, Mark D.; Gao, Yanfei; Dunand, David C.; Ghosh, Gautam; Chen, Mingwei; Fine, Morris E.; Liaw, Peter K.

    2015-01-01

    There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L21-Ni2TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures. PMID:26548303

  16. Controllable soliton propagation based on phase-front curvature in asymmetrical nonlocal media

    Science.gov (United States)

    Zhang, Huafeng; Lü, Hua; Luo, Jianghua; Sun, Lihui

    2016-08-01

    The influence of phase-front curvature on the dynamical behavior of the fundamental mode soliton during its transmission in asymmetrical nonlocal media is studied in detail and the phase-front curvature can be imposed on the fundamental mode soliton by reshaping or phase imprinting technologies. By changing the phase-front curvature or its imposed position, controllable soliton propagation in asymmetrical nonlocal media can be achieved. Project supported by the National Natural Science Foundation of China (Grants Nos. 11547007 and 11304024), the Innovation Personnel Training Plan for Excellent Youth of Guangdong University Project (Grant No. 2013LYM_0023), and the Yangtze Fund for Youth Teams of Science and Technology Innovation (Grant No. 2015cqt03).

  17. Mid/far-infrared photo-detectors based on graphene asymmetric quantum wells

    Science.gov (United States)

    Ben Salem, E.; Chaabani, R.; Jaziri, S.

    2016-09-01

    We conducted a theoretical study on the electronic properties of a single-layer graphene asymmetric quantum well. Quantification of energy levels is limited by electron-hole conversion at the barrier interfaces and free-electron continuum. Electron-hole conversion at the barrier interfaces can be controlled by introducing an asymmetry between barriers and taking into account the effect of the interactions of the graphene sheet with the substrate. The interaction with the substrate induces an effective mass to carriers, allowing observation of Fabry-Pérot resonances under normal incidence and extinction of Klein tunneling. The asymmetry, between barriers creates a transmission gap between confined states and free-electron continuum, allowing the large graphene asymmetric quantum well to be exploited as a photo-detector operating at mid- and far-infrared frequency regimes.

  18. Counteracting 16-QAM Optical Fiber Transmission Impairments With Iterative Turbo Equalization

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Caballero Jambrina, Antonio; Borkowski, Robert;

    2013-01-01

    -division-multiplexing 16 quadrature amplitude modulation impairments in dispersion uncompensated coherent transmission links. Gains exceeding one order of magnitude in terms of bit error rate are obtained in experimental validation up to 497 km-standard single mode fiber link transmission....

  19. Periodic coupling strength-dependent multiple coherence resonance by time delay in Newman-Watts neuronal networks.

    Science.gov (United States)

    Wu, Yanan; Gong, Yubing; Xu, Bo

    2013-12-01

    Recently, multiple coherence resonance induced by time delay has been observed in neuronal networks with constant coupling strength. In this paper, by employing Newman-Watts Hodgkin-Huxley neuron networks with time-periodic coupling strength, we study how the temporal coherence of spiking behavior and coherence resonance by time delay change when the frequency of periodic coupling strength is varied. It is found that delay induced coherence resonance is dependent on periodic coupling strength and increases when the frequency of periodic coupling strength increases. Periodic coupling strength can also induce multiple coherence resonance, and the coherence resonance occurs when the frequency of periodic coupling strength is approximately multiple of the spiking frequency. These results show that for periodic coupling strength time delay can more frequently optimize the temporal coherence of spiking activity, and periodic coupling strength can repetitively optimize the temporal coherence of spiking activity as well. Frequency locking may be the mechanism for multiple coherence resonance induced by periodic coupling strength. These findings imply that periodic coupling strength is more efficient for enhancing the temporal coherence of spiking activity of neuronal networks, and thus it could play a more important role in improving the time precision of information processing and transmission in neural networks.

  20. Spatial Coherence of Synchrotron Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Marchesini, S; Coisson, R

    2003-10-30

    Synchrotron Radiation (SR) has been widely used since the 80's as a tool for many applications of UV, soft X rays and hard X rays in condensed matter physics, chemistry and biology. The evolution of SR sources towards higher brightness has led to the design of low-emittance electron storage rings (emittance is the product of beam size and divergence), and the development of special source magnetic structures, as undulators. This means that more and more photons are available on a narrow bandwidth and on a small collimated beam; in other words there is the possibility of getting a high power in a coherent beam. In most applications, a monochromator is used, and the temporal coherence of the light is given by the monochromator bandwidth. With smaller and smaller sources, even without the use of collimators, the spatial coherence of the light has become appreciable, first in the UV and soft X ray range, and then also with hard X rays. This has made possible new or improved experiments in interferometry, microscopy, holography, correlation spectroscopy, etc. In view of these recent possibilities and applications, it is useful to review some basic concepts about spatial coherence of SR, and its measurement and applications. In particular we show how the spatial coherence properties of the radiation in the far field can be calculated with simple operations from the single-electron amplitude and the electron beam angular and position spreads. The gaussian approximation will be studied in detail for a discussion of the properties of the far field mutual coherence and the estimate of the coherence widths, and the comparison with the VanCittert-Zernike limit.

  1. Detection and spectral measurements of coherent synchrotron radiation at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Behrens, Christopher

    2010-02-15

    The operation of high-gain free-electron laser (FEL) underlies tremendous demands on high quality electron beams with high peak currents. At the Free-Electron-Laser in Hamburg (FLASH), two magnetic bunch compressors are used to compress the electron bunches longitudinally. In the bunch compressor magnets, these short electron bunches generate coherent synchrotron radiation (CSR). This CSR contains information on the longitudinal bunch profile, which is relevant for driving an FEL. In order to investigate coherent synchrotron radiation at the second bunch compressor BC3 at FLASH, a new setup behind the last dipole was installed. For the detection of coherent synchrotron radiation, which is emitted in the infrared regime, pyroelectric detectors were used. These pyroelectric detectors have been calibrated at the free-electron laser FELIX in the wavelength range from 5 {mu}m to 110 {mu}m. For characterisation of the emitted radiation, a transverse scanning device was used to measure the transverse intensity distribution. Various transmission filters were used to obtain additional information about the spectral content. In order to get spectral information with high resolution over a wide wavelength range, a rotating mirror spectrometer using reflective blazed gratings was installed. Using this spectrometer, the first spectral measurements of coherent synchrotron radiation at FLASH in a wavelength range from 10 {mu}m to 160 {mu}m were done. (orig.)

  2. Transmission Of Power Via Combined Laser Beams

    Science.gov (United States)

    Kwon, Jin H.; Lee, Ja H.

    1992-01-01

    Laser Diode Array (LDA) appears to be most efficient means of transferring power from Earth to satellites and between satellites, in terms of mass and size, of various laser configurations. To form large-scale-array amplifier (LSAA), element LDA's must generate well-defined diffraction-limited beams. Coherent matching of phases among LDA's enables system to generate good beam pattern in far field over thousands of kilometers. By passing beam from master laser through number of LDA amplifiers simultaneously, one realizes coherence among amplified output beams. LSAA used for transmission of power with efficiency of approximately 80 percent into receiver of moderate size at 5,000 km. Also transmits data at high rates by line-of-sight rather than fiber optics.

  3. Coherent states in quantum physics

    CERN Document Server

    Gazeau, Jean-Pierre

    2009-01-01

    This self-contained introduction discusses the evolution of the notion of coherent states, from the early works of Schrödinger to the most recent advances, including signal analysis. An integrated and modern approach to the utility of coherent states in many different branches of physics, it strikes a balance between mathematical and physical descriptions.Split into two parts, the first introduces readers to the most familiar coherent states, their origin, their construction, and their application and relevance to various selected domains of physics. Part II, mostly based on recent original results, is devoted to the question of quantization of various sets through coherent states, and shows the link to procedures in signal analysis. Title: Coherent States in Quantum Physics Print ISBN: 9783527407095 Author(s): Gazeau, Jean-Pierre eISBN: 9783527628292 Publisher: Wiley-VCH Dewey: 530.12 Publication Date: 23 Sep, 2009 Pages: 360 Category: Science, Science: Physics LCCN: Language: English Edition: N/A LCSH:

  4. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging

    Science.gov (United States)

    Cua, Michelle; Wahl, Daniel J.; Zhao, Yuan; Lee, Sujin; Bonora, Stefano; Zawadzki, Robert J.; Jian, Yifan; Sarunic, Marinko V.

    2016-09-01

    Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems.

  5. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging.

    Science.gov (United States)

    Cua, Michelle; Wahl, Daniel J; Zhao, Yuan; Lee, Sujin; Bonora, Stefano; Zawadzki, Robert J; Jian, Yifan; Sarunic, Marinko V

    2016-09-07

    Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems.

  6. Coherent optical communication using polarization multiple-input-multiple-output.

    Science.gov (United States)

    Han, Yan; Li, Guifang

    2005-09-19

    Polarization-division multiplexed (PDM) optical signals can potentially be demultiplexed by coherent detection and digital signal processing without using optical dynamic polarization control at the receiver. In this paper, we show that optical communications using PDM is analogous to wireless communications using multiple-input-multiple-output (MIMO) antennae and thus algorithms for channel estimation in wireless MIMO can be ready applied to optical polarization MIMO (PMIMO). Combined with frequency offset and phase estimation algorithms, simulations show that PDM quadrature phase-shift keying signals can be coherently detected by the proposed scheme using commercial semiconductor lasers while no optical phase locking and polarization control are required. This analogy further suggests the potential application of space-time coding in wireless communications to optical polarization MIMO systems and relates the problem of polarization-mode dispersion in fiber transmission to the multi-path propagation in wireless communications.

  7. Quantum memory receiver for superadditive communication using binary coherent states

    CERN Document Server

    Klimek, Aleksandra; Wasilewski, Wojciech; Banaszek, Konrad

    2015-01-01

    We propose a simple architecture based on multimode quantum memories for collective readout of classical information keyed using a pair coherent states, exemplified by the well-known binary phase shift keying format. Such a configuration enables demonstration of the superadditivity effect in classical communication over quantum channels, where the transmission rate becomes enhanced through joint detection applied to multiple channel uses. The proposed scheme relies on the recently introduced idea to prepare Hadamard sequences of input symbols that are mapped by a linear optical transformation onto the pulse position modulation format [Guha, S. {\\em Phys. Rev. Lett.}\\ {\\bf 2011}, {\\em 106}, 240502]. We analyze two versions of readout based on direct detection and an optional Dolinar receiver which implements the minimum-error measurement for individual detection of a binary coherent state alphabet.

  8. A passive transmitter for quantum key distribution with coherent light

    CERN Document Server

    Curty, Marcos; Pruneri, Valerio; Mitchell, Morgan W

    2011-01-01

    Signal state preparation in quantum key distribution schemes can be realized using either an active or a passive source. Passive sources might be valuable in some scenarios; for instance, in those experimental setups operating at high transmission rates, since no externally driven element is required. Typical passive transmitters involve parametric down-conversion. More recently, it has been shown that phase-randomized coherent pulses also allow passive generation of decoy states and Bennett-Brassard 1984 (BB84) polarization signals, though the combination of both setups in a single passive source is cumbersome. In this paper, we present a complete passive transmitter that prepares decoy-state BB84 signals using coherent light. Our method employs sum-frequency generation together with linear optical components and classical photodetectors. In the asymptotic limit of an infinite long experiment, the resulting secret key rate (per pulse) is comparable to the one delivered by an active decoy-state BB84 setup wit...

  9. Quantum memory receiver for superadditive communication using binary coherent states.

    Science.gov (United States)

    Klimek, Aleksandra; Jachura, Michał; Wasilewski, Wojciech; Banaszek, Konrad

    2016-11-12

    We propose a simple architecture based on multimode quantum memories for collective readout of classical information keyed using a pair coherent states, exemplified by the well-known binary phase shift keying format. Such a configuration enables demonstration of the superadditivity effect in classical communication over quantum channels, where the transmission rate becomes enhanced through joint detection applied to multiple channel uses. The proposed scheme relies on the recently introduced idea to prepare Hadamard sequences of input symbols that are mapped by a linear optical transformation onto the pulse position modulation format [Guha, S. Phys. Rev. Lett.2011, 106, 240502]. We analyze two versions of readout based on direct detection and an optional Dolinar receiver which implements the minimum-error measurement for individual detection of a binary coherent state alphabet.

  10. Coherent fiber supercontinuum for biophotonics.

    Science.gov (United States)

    Tu, Haohua; Boppart, Stephen A

    2013-09-01

    Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging.

  11. Coherent infrared imaging camera (CIRIC)

    Energy Technology Data Exchange (ETDEWEB)

    Hutchinson, D.P.; Simpson, M.L.; Bennett, C.A.; Richards, R.K.; Emery, M.S.; Crutcher, R.I.; Sitter, D.N. Jr.; Wachter, E.A.; Huston, M.A.

    1995-07-01

    New developments in 2-D, wide-bandwidth HgCdTe (MCT) and GaAs quantum-well infrared photodetectors (QWIP) coupled with Monolithic Microwave Integrated Circuit (MMIC) technology are now making focal plane array coherent infrared (IR) cameras viable. Unlike conventional IR cameras which provide only thermal data about a scene or target, a coherent camera based on optical heterodyne interferometry will also provide spectral and range information. Each pixel of the camera, consisting of a single photo-sensitive heterodyne mixer followed by an intermediate frequency amplifier and illuminated by a separate local oscillator beam, constitutes a complete optical heterodyne receiver. Applications of coherent IR cameras are numerous and include target surveillance, range detection, chemical plume evolution, monitoring stack plume emissions, and wind shear detection.

  12. Coherent controlization using superconducting qubits.

    Science.gov (United States)

    Friis, Nicolai; Melnikov, Alexey A; Kirchmair, Gerhard; Briegel, Hans J

    2015-01-01

    Coherent controlization, i.e., coherent conditioning of arbitrary single- or multi-qubit operations on the state of one or more control qubits, is an important ingredient for the flexible implementation of many algorithms in quantum computation. This is of particular significance when certain subroutines are changing over time or when they are frequently modified, such as in decision-making algorithms for learning agents. We propose a scheme to realize coherent controlization for any number of superconducting qubits coupled to a microwave resonator. For two and three qubits, we present an explicit construction that is of high relevance for quantum learning agents. We demonstrate the feasibility of our proposal, taking into account loss, dephasing, and the cavity self-Kerr effect.

  13. Performance analysis of multihop coherent OFDM free-space optical communication systems

    Science.gov (United States)

    Wang, Yi; Wang, Deli; Ma, Jing

    2016-10-01

    This paper proposes a multihop coherent orthogonal frequency division multiplexing free space optical (OFDM-FSO) communication system model based on a relay transmission mode of decode and forward (DF) with the Gamma-Gamma channel. In the study of atmospheric statistical model, mainly considering the combined action by the following three aspects, they are the light intensity scintillation caused by the atmospheric turbulence, the pointing error caused the transmitter and the receiver without aiming at each other and the path loss. We derived closed-form expressions of outage probability and symbol error rate of the multihop coherent OFDM-FSO system with serial DF relay transmission. We simulated and analyzed the influence of the atmospheric turbulence, the modulation order, the beam width and the jitter factor on the communication interruption performance and bit error performance of the multihop coherent OFDM-FSO system with different number of hops.

  14. Defect modes properties in periodic lossy multilayer containing negative index materials with symmetric and asymmetric geometric structures

    CERN Document Server

    Aghajamali, Alireza; Barati, Mahmood; Wu, Chien-Jang

    2014-01-01

    In this paper the characteristic matrix method is used to study the propagation of electromagnetic waves through one-dimensional lossy photonic crystals composed of negative and positive refractive index material layers with symmetric and asymmetric geometric structures with a defect layer at the center of the structure. First, the positive index material defect layer is considered, and the effects of the polarization and the angle of incidence on the defect mode in the transmission spectra of the both structures are investigated. The results show that the number of the defect modes in the transmission spectra depends on the geometry (symmetric or asymmetric) of the structure. In addition, it is shown that the defect mode frequency increases as the angle of incidence increases. This property is independent of the geometry of the structure. Then, for normal incidence, the negative index material defect layer is considered, and the properties of defect modes for both structures are investigated. The results can...

  15. Real time 1.55 μm VCSEL-based coherent detection link

    DEFF Research Database (Denmark)

    Rodes Lopez, Roberto; Parekh, D.; Jensen, Jesper Bevensee;

    2012-01-01

    This paper presents an experimental demonstration of VCSEL-based PON with simplified real-time coherent receiver at 2.5 Gbps. Receiver sensitivity of −37 dBm is achieved proving splitting ratio up to 2048 after 17 km fiber transmission....

  16. Coherent versus incoherent dynamics in InAs quantum-dot active wave guides

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, W.; Hvam, Jørn Märcher;

    2001-01-01

    Coherent dynamics measured by time-resolved four-wave mixing is compared to incoherent population dynamics measured by differential transmission spectroscopy on the ground-state transition at room temperature of two types of InAs-based quantum dots with different confinement energies. The measure...

  17. Digital coherent receiver for subcarrier multiplexed phase modulated radio-over-fibre signals

    DEFF Research Database (Denmark)

    Zibar, Darko; Larsen, Knud J.; Tafur Monroy, Idelfonso

    2009-01-01

    Digital coherent detection of multi-channel subcarrier multiplexed optically phase-modulated radio-over-fibre signals is experimentally demonstrated. Successful detection after transmission over a 40 km long fibre link of four or five 25 Mbaud BPSK/QPSK subcarrier channels in 5 GHz bandwidth...... is demonstrated using offline digital signal processing....

  18. Enhancing molecule fluorescence with asymmetrical plasmonic antennas.

    Science.gov (United States)

    Lu, Guowei; Liu, Jie; Zhang, Tianyue; Shen, Hongming; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gu, Ying; He, Yingbo; Wang, Yuwei; Gong, Qihuang

    2013-07-21

    We propose and justify by the finite-difference time-domain method an efficient strategy to enhance the spontaneous emission of a fluorophore with a multi-resonance plasmonic antenna. The custom-designed asymmetrical antenna consists of two plasmonic nanoparticles with different sizes and is able to couple efficiently to free space light through multiple localized surface plasmon resonances. This design simultaneously permits a large near-field excitation near the antenna as well as a high quantum efficiency, which results in an unusual and significant enhancement of the fluorescence of a single emitter. Such an asymmetrical antenna presents intrinsic advantages over single particle or dimer based antennas made using two identical nanostructures. This promising concept can be exploited in the large domain of light-matter interaction processes involving multiple frequencies.

  19. Design of Asymmetric Peptide Bilayer Membranes.

    Science.gov (United States)

    Li, Sha; Mehta, Anil K; Sidorov, Anton N; Orlando, Thomas M; Jiang, Zhigang; Anthony, Neil R; Lynn, David G

    2016-03-16

    Energetic insights emerging from the structural characterization of peptide cross-β assemblies have enabled the design and construction of robust asymmetric bilayer peptide membranes. Two peptides differing only in their N-terminal residue, phosphotyrosine vs lysine, coassemble as stacks of antiparallel β-sheets with precisely patterned charged lattices stabilizing the bilayer leaflet interface. Either homogeneous or mixed leaflet composition is possible, and both create nanotubes with dense negative external and positive internal solvent exposed surfaces. Cross-seeding peptide solutions with a preassembled peptide nanotube seed leads to domains of different leaflet architecture within single nanotubes. Architectural control over these cross-β assemblies, both across the bilayer membrane and along the nanotube length, provides access to highly ordered asymmetric membranes for the further construction of functional mesoscale assemblies.

  20. Asymmetric dark matter models in SO(10)

    Science.gov (United States)

    Nagata, Natsumi; Olive, Keith A.; Zheng, Jiaming

    2017-02-01

    We systematically study the possibilities for asymmetric dark matter in the context of non-supersymmetric SO(10) models of grand unification. Dark matter stability in SO(10) is guaranteed by a remnant Z2 symmetry which is preserved when the intermediate scale gauge subgroup of SO(10) is broken by a {126} dimensional representation. The asymmetry in the dark matter states is directly generated through the out-of-equilibrium decay of particles around the intermediate scale, or transferred from the baryon/lepton asymmetry generated in the Standard Model sector by leptogenesis. We systematically classify possible asymmetric dark matter candidates in terms of their quantum numbers, and derive the conditions for each case that the observed dark matter density is (mostly) explained by the asymmetry of dark matter particles.

  1. Asymmetric Dark Matter Models in SO(10)

    CERN Document Server

    Nagata, Natsumi; Zheng, Jiaming

    2016-01-01

    We systematically study the possibilities for asymmetric dark matter in the context of non-supersymmetric SO(10) models of grand unification. Dark matter stability in SO(10) is guaranteed by a remnant $\\mathbb{Z}_2$ symmetry which is preserved when the intermediate scale gauge subgroup of SO(10) is broken by a ${\\bf 126}$ dimensional representation. The asymmetry in the dark matter states is directly generated through the out-of-equilibrium decay of particles around the intermediate scale, or transferred from the baryon/lepton asymmetry generated in the Standard Model sector by leptogenesis. We systematically classify possible asymmetric dark matter candidates in terms of their quantum numbers, and derive the conditions for each case that the observed dark matter density is (mostly) explained by the asymmetry of dark matter particles.

  2. Cosmological signatures of time-asymmetric gravity

    CERN Document Server

    Cortês, Marina; Smolin, Lee

    2016-01-01

    We develop the model proposed by Cort\\^es, Gomes & Smolin, to predict cosmological signatures of time-asymmetric extensions of general relativity they proposed recently. Within this class of models the equation of motion of chiral fermions is modified by a torsion term. This term leads to a dispersion law for neutrinos that associates a new time-varying energy with each particle. We find a new neutrino contribution to the Friedmann equation resulting from the torsion term in the Ashtekar connection. In this note we explore the phenomenology of this term and observational consequences for cosmological evolution. We show that constraints on the critical energy density will ordinarily render this term unobservably small, a maximum of order $10^{-25}$ of the neutrino energy density today. However, if the time-asymmetric dark energy is tuned to cancel the cosmological constant, the torsion effect may be a dark matter candidate.

  3. Steerability of Quantum Coherence in Accelerated Frame

    CERN Document Server

    Mondal, Debasis

    2015-01-01

    The interplay between steering and quantum coherence is studied in a scenario, where two atoms move through an external massless scalar field. We show that just like entanglement, the steering induced coherence of the equilibrium state may increase or decrease with acceleration depending on the initial condition of the state. We also investigate the condition for coherence steerability - as opposed to simple state steerability. Interestingly, we find that the quantum coherence of the equilibrium state cannot be steered, even when the steering induced coherence is non-zero. We argue that under any condition, gravity prohibits the coherence steering of the equilibrium state.

  4. Venture Capital Contracting Under Asymmetric Information

    OpenAIRE

    Jeffrey Trester

    1993-01-01

    The author develops a model of venture capital contracting in which the entrepreneur and venture capitalist contract under symmetric information. A condition of asymmetric information may arise subsequent to the first contract. The author shows that this condition makes debt contracts infeasible and leads to the use of preferred equity contracts. The author notes that discussions of the relation between venture capital and capital structure are rare. This paper expands the literature by addre...

  5. Fluorous Mixture Synthesis of Asymmetric Dendrimers

    Science.gov (United States)

    Jiang, Zhong-Xing; Yu, Yihua Bruce

    2010-01-01

    A divergent fluorous mixture synthesis (FMS) of asymmetric fluorinated dendrimers has been developed. Four generations of fluorinated dendrimers with the same fluorinated moiety were prepared with high efficiency, yield and purity. Comparison of the physicochemical properties of these dendrimers provided valuable information for their application and future optimization. This strategy has not only provided a practical method for the synthesis and purification of dendrimers, but also established the possibility of utilizing the same fluorinated moiety for FMS. PMID:20170088

  6. Asymmetric k-Center with Minimum Coverage

    DEFF Research Database (Denmark)

    Gørtz, Inge Li

    2008-01-01

    In this paper we give approximation algorithms and inapproximability results for various asymmetric k-center with minimum coverage problems. In the k-center with minimum coverage problem, each center is required to serve a minimum number of clients. These problems have been studied by Lim et al. [A....... Lim, B. Rodrigues, F. Wang, Z. Xu, k-center problems with minimum coverage, Theoret. Comput. Sci. 332 (1–3) (2005) 1–17] in the symmetric setting....

  7. New electric field in asymmetric magnetic reconnection.

    Science.gov (United States)

    Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

    2013-09-27

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

  8. Asymmetric Information – Adverse Selection Problem

    Directory of Open Access Journals (Sweden)

    Dumitru MARIN

    2007-01-01

    Full Text Available The present paper makes an introduction in the contract theory starting with the definitions of asymmetric information and some of the problems that generate: moral hazard and adverse selection. We provide an insight of the latest empirical studies in adverse selection in different markets. An adverse selection model, based on Rothchild and Stiglitz is also present to give a perspective of the theoretical framework.

  9. Interference due to coherence swapping

    Indian Academy of Sciences (India)

    Arun Kumar Pati; Marek Zukowski

    2001-02-01

    We propose a method called ‘coherence swapping’ which enables us to create superposition of a particle in two distinct paths, which is fed with initially incoherent, independent radiation. This phenomenon is also present for the charged particles, and can be used to swap the effect of flux line due to the Aharonov–Bohm effect. We propose an optical version of experimental set-up to test the coherence swapping. The phenomenon, which is simpler than entanglement swapping or teleportation, raises some fundamental questions about the true nature of wave-particle duality, and also opens up the possibility of studying the quantum erasure from a new angle.

  10. Quantum entanglement and coherence in molecular magnets

    Science.gov (United States)

    Shiddiq, Muhandis

    Quantum computers are predicted to outperform classical computers in certain tasks, such as factoring large numbers and searching databases. The construction of a computer whose operation is based on the principles of quantum mechanics appears extremely challenging. Solid state approaches offer the potential to answer this challenge by tailor-making novel nanomaterials for quantum information processing (QIP). Molecular magnets, which are materials whose energy levels and magnetic quantum states are well defined at the molecular level, have been identified as a class of material with properties that make them attractive for quantum computing purpose. In this dissertation, I explore the possibilities and challenges for molecular magnets to be used in quantum computing architecture. The properties of molecular magnets that are critical for applications in quantum computing, i.e., quantum entanglement and coherence, are comprehensively investigated to probe the feasibility of molecular magnets to be used as quantum bits (qubits). Interactions of qubits with photons are at the core of QIP. Photons can be used to detect and manipulate qubits, after which information can then be transferred over long distances. As a potential candidate for qubits, the interactions between Fe8 single-molecule magnets (SMMs) and cavity photons were studied. An earlier report described that a cavity mode splitting was observed in a spectrum of a cavity filled with a single-crystal of Fe8 SMMs. This splitting was interpreted as a vacuum Rabi splitting (VRS), which is a signature of an entanglement between a large number of SMMs and a cavity photon. However, find that large absorption and dispersion of the magnetic susceptibility are the reasons for this splitting. This finding highlights the fact that an observation of a peak splitting in a cavity transmission spectrum neither represents an unambiguous indication of quantum coherence in a large number of spins, nor a signature of

  11. Coherent detection of position errors in inter-satellite laser communications

    Science.gov (United States)

    Xu, Nan; Liu, Liren; Liu, De'an; Sun, Jianfeng; Luan, Zhu

    2007-09-01

    Due to the improved receiver sensitivity and wavelength selectivity, coherent detection became an attractive alternative to direct detection in inter-satellite laser communications. A novel method to coherent detection of position errors information is proposed. Coherent communication system generally consists of receive telescope, local oscillator, optical hybrid, photoelectric detector and optical phase lock loop (OPLL). Based on the system composing, this method adds CCD and computer as position error detector. CCD captures interference pattern while detection of transmission data from the transmitter laser. After processed and analyzed by computer, target position information is obtained from characteristic parameter of the interference pattern. The position errors as the control signal of PAT subsystem drive the receiver telescope to keep tracking to the target. Theoretical deviation and analysis is presented. The application extends to coherent laser rang finder, in which object distance and position information can be obtained simultaneously.

  12. Practical methods for the measurement of spatial coherence-A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Maunders, C. [Dept. of Materials Engineering, Monash University, VIC 3800 (Australia); Dwyer, C., E-mail: christian.dwyer@monash.edu [Dept. of Materials Engineering, Monash University, VIC 3800 (Australia); Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia); Tiemeijer, P.C. [FEI Electron Optics, PO Box 80066, 5600 KA Eindhoven (Netherlands); Etheridge, J. [Dept. of Materials Engineering, Monash University, VIC 3800 (Australia); Monash Centre for Electron Microscopy, Monash University, VIC 3800 (Australia)

    2011-07-15

    Two new methods for the measurement of transverse spatial coherence in a transmission electron microscope (TEM) are developed and applied to measure the spatial coherence in a field emission gun TEM. Measurements are made under different illumination and operating conditions, illustrating the effect of these conditions on the spatial coherence. The relative merits and limitations of these methods are discussed and compared, together with the previously described 'Ronchigram' method. -- Highlights: {yields} Three methods for measuring the spatial coherence in a TEM are compared. {yields} The methods use different electron-optical configurations, applicable to STEM and HRTEM. {yields} One of these methods, applicable to STEM, is presented here for the first time. {yields} The methods are demonstrated to access different contributions to the effective source.

  13. Applications of Telecommunication Transceiver Architectures in All-Fiber Coherent Detection Lidars

    DEFF Research Database (Denmark)

    Abari, Cyrus F.

    to exist between the two. In this thesis, I have presented some of the advances in fiber-optic transceivers, originally developed for high-speed data transmission, and shown how they can be integrated in micropulse and continuous-wave all-fiber coherent detection lidars. The presented technologies not only...... enable the possibility for performance improvements in existing lidars but also pave the way for the application of coherent detection lidars in areas where their presence was neither plausible nor easy to realize. This thesis, composed of an introduction and four scientific paper and one manuscript......, specifically presents the adoption of some of the contemporary fiber-optic communications transceiver architectures in coherent detection lidars. In paper I a new short-range all-fiber coherent Doppler lidar employing an image-reject homodyne receiver is described and demonstrated. In Paper II two different...

  14. Coherent broadband light source for parallel optical coherence tomography

    NARCIS (Netherlands)

    Rivier, S.; Laversenne, L.; Bourquin, S.; Salathé, R.P.; Pollnau, M.; Grivas, C.; Shepherd, D.P.; Eason, R.W.; Flury, M.; Philipoussis, I.; Herzig, H.P.

    2004-01-01

    A Ti:sapphire planar waveguide is rib structured by Ar ion milling to provide parallel channel waveguides. By coupling high-power pump light through a microlens array into the waveguides, a novel broadband luminescent parallel emitter is demonstrated as a light source for parallel optical coherence

  15. Asymmetric threat data mining and knowledge discovery

    Science.gov (United States)

    Gilmore, John F.; Pagels, Michael A.; Palk, Justin

    2001-03-01

    Asymmetric threats differ from the conventional force-on- force military encounters that the Defense Department has historically been trained to engage. Terrorism by its nature is now an operational activity that is neither easily detected or countered as its very existence depends on small covert attacks exploiting the element of surprise. But terrorism does have defined forms, motivations, tactics and organizational structure. Exploiting a terrorism taxonomy provides the opportunity to discover and assess knowledge of terrorist operations. This paper describes the Asymmetric Threat Terrorist Assessment, Countering, and Knowledge (ATTACK) system. ATTACK has been developed to (a) data mine open source intelligence (OSINT) information from web-based newspaper sources, video news web casts, and actual terrorist web sites, (b) evaluate this information against a terrorism taxonomy, (c) exploit country/region specific social, economic, political, and religious knowledge, and (d) discover and predict potential terrorist activities and association links. Details of the asymmetric threat structure and the ATTACK system architecture are presented with results of an actual terrorist data mining and knowledge discovery test case shown.

  16. Asymmetric Conditional Volatility in International Stock Markets

    CERN Document Server

    Ferreira, N B; Menezes, R; Ferreira, Nuno B.; Mendes, Diana A.; Menezes, Rui

    2006-01-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the S&P 500, FTSE100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of chan...

  17. Multiple Traveling Salesmen in Asymmetric Metrics

    CERN Document Server

    Friggstad, Zachary

    2011-01-01

    We consider some generalizations of the Asymmetric Traveling Salesman Path problem. Suppose we have an asymmetric metric G = (V,A) with two distinguished nodes s,t. We are also given a positive integer k. The goal is to find k paths of minimum total cost from s to t whose union spans all nodes. We call this the k-Person Asymmetric Traveling Salesmen Path problem (k-ATSPP). Our main result for k-ATSPP is a bicriteria approximation that, for some parameter b >= 1 we may choose, finds between k and k + k/b paths of total length O(b log |V|) times the optimum value of an LP relaxation based on the Held-Karp relaxation for the Traveling Salesman problem. On one extreme this is an O(log |V|)-approximation that uses up to 2k paths and on the other it is an O(k log |V|)-approximation that uses exactly k paths. Next, we consider the case where we have k pairs of nodes (s_1,t_1), ..., (s_k,t_k). The goal is to find an s_i-t_i path for every pair such that each node of G lies on at least one of these paths. Simple appro...

  18. Traceless Synthesis of Asymmetrically Modified Bivalent Nucleosomes.

    Science.gov (United States)

    Lechner, Carolin C; Agashe, Ninad D; Fierz, Beat

    2016-02-18

    Nucleosomes carry extensive post-translational modifications (PTMs), which results in complex modification patterns that are involved in epigenetic signaling. Although two copies of each histone coexist in a nucleosome, they may not carry the same PTMs and are often differently modified (asymmetric). In bivalent domains, a chromatin signature prevalent in embryonic stem cells (ESCs), namely H3 methylated at lysine 4 (H3K4me3), coexists with H3K27me3 in asymmetric nucleosomes. We report a general, modular, and traceless method for producing asymmetrically modified nucleosomes. We further show that in bivalent nucleosomes, H3K4me3 inhibits the activity of the H3K27-specific lysine methyltransferase (KMT) polycomb repressive complex 2 (PRC2) solely on the same histone tail, whereas H3K27me3 stimulates PRC2 activity across tails, thereby partially overriding the H3K4me3-mediated repressive effect. To maintain bivalent domains in ESCs, PRC2 activity must thus be locally restricted or reversed.

  19. SPECT using asymmetric pinholes with truncated projections

    Energy Technology Data Exchange (ETDEWEB)

    Lin Jianyu; Meikle, Steven R, E-mail: jianyu.lin@curtin.edu.au [Ramaciotti Imaging Centre, Brain and Mind Research Institute, University of Sydney (Australia)

    2011-07-07

    Tomographic systems employing truncated projections have been developed for parallel and fan beam collimation and for cone beam CT but the idea has not been extensively explored in pinhole single photon emission computed tomography (SPECT). In this paper, we explore the sampling requirements and system performance of SPECT systems with asymmetric pinhole collimators and truncated projections. We demonstrate that complete 3D sampling can be achieved by using multiple detectors with truncated asymmetric pinholes, offset axially from each other, and a spiral orbit. The use of truncated projections can be exploited in the design of pinhole SPECT systems by moving the pinholes closer to the subject, resulting in increased sensitivity and improved spatial resolution. Truncated and untruncated pinhole systems were evaluated using the contrast-to-noise ratio (CNR) calculated from the linearized local impulse response as a figure of merit. The CNR for the truncated pinhole system was up to 60% greater than that for the untruncated system at matched resolution for a source voxel near the centre of a uniform phantom and 30% greater at the edge. We conclude that an object can be reconstructed from asymmetric pinholes with truncated projections, which leads to potentially important design considerations and applications in single- and multi-pinhole SPECT.

  20. Transmission electron microscopy in micro-nanoelectronics

    CERN Document Server

    Claverie, Alain

    2013-01-01

    Today, the availability of bright and highly coherent electron sources and sensitive detectors has radically changed the type and quality of the information which can be obtained by transmission electron microscopy (TEM). TEMs are now present in large numbers not only in academia, but also in industrial research centers and fabs.This book presents in a simple and practical way the new quantitative techniques based on TEM which have recently been invented or developed to address most of the main challenging issues scientists and process engineers have to face to develop or optimize sem

  1. Measuring optical transmission matrices by wavefront shaping

    CERN Document Server

    Yoon, Jonghee; Park, Jongchan; Park, YongKeun

    2015-01-01

    We introduce a simple but practical method to measure the optical transmission matrix (TM) of complex media. The optical TM of a complex medium is obtained by modulating the wavefront of a beam impinging on the complex medium and imaging the transmitted full-field speckle intensity patterns. Using the retrieved TM, we demonstrate the generation and linear combination of multiple foci on demand through the complex medium. This method will be used as a versatile tool for coherence control of waves through turbid media.

  2. Optical refractometer based on an asymmetrical twin-core fiber Michelson interferometer.

    Science.gov (United States)

    Zhou, Ai; Zhang, Yanhui; Li, Guangping; Yang, Jun; Wang, Yuzhuo; Tian, Fengjun; Yuan, Libo

    2011-08-15

    We report and demonstrate an optical refractometer based on a compact fiber Michelson interferometer. The Michelson interferometer is composed of an asymmetrical twin-core fiber containing a central core and a side core. By chemically etching a segment of the twin-core fiber until the side core is exposed, the effective index of the side core in the etched region is sensitive to the environmental refractive index, which leads to a shift of the transmission spectrum of the Michelson interferometer. The experimental results show that such a device has a refractive index resolution of more than 800 nm/refractive index unit in the range of 1.34-1.37.

  3. Optical refractometer based on an asymmetrical twin-core fiber Michelson interferometer

    Science.gov (United States)

    Zhou, Ai; Zhang, Yanhui; Li, Guangping; Yang, Jun; Wang, Yuzhuo; Tian, Fengjun; Yuan, Libo

    2011-08-01

    We report and demonstrate an optical refractometer based on a compact fiber Michelson interferometer. The Michelson interferometer is composed of an asymmetrical twin-core fiber containing a central core and a side core. By chemically etching a segment of the twin-core fiber until the side core is exposed, the effective index of the side core in the etched region is sensitive to the environmental refractive index, which leads to a shift of the transmission spectrum of the Michelson interferometer. The experimental results show that such a device has a refractive index resolution of more than 800nm/refractive index unit in the range of 1.34--1.37.

  4. Coherent multiple imaging by means of pupil plane filtering

    Science.gov (United States)

    Erdelyi, Miklos; Kroyan, Armen; Osvay, Karoly; Bor, Zsolt; Wilson, William L., Jr.; Smayling, Michael C.; Tittel, Frank K.

    1999-07-01

    A resolution enhancement technique suitable for Deep-UV microlithography based on coherent multiple imaging (CMI) will be described. We showed recently that a Fabry-Perot etalon inserted between the mask and the projection lens in an optical stepper is able to simultaneously enhance the resolution and depth of focus of an aerial image. Since the multiple images of the mask pattern created by the etalon are added together coherently, the final image profile is very sensitive to the initial phase conditions. It is possible to simulate this coherent multiple imaging techniques using a simulation model which either superimposes separate output electric fields or by applying an appropriate transmission-phase pupil plane filter in the simulator. The first approach, however, requires a modification of the simulation software which allows output of the electric field profile, while the second approach can be used with a conventional commercial lithography simulator. In this paper computer simulations for isolated and extended contact hole arrays are used to demonstrate that the CMI method can enhance resolution by 18 percent while maintaining or even increasing the DOF of the aerial image. It is also shown that the high intensity side lobes generated by the filter nc abe eliminated by means of a phase shifting mask or by reducing the spatial coherence of the illumination source. The optimum value of spatial coherence was found to be 0.28. In this case the side lobes disappear, and the intensity of the main peaks doubles. The impact of this technique on image intensity is also discussed.

  5. Writing Quality, Coherence, and Cohesion.

    Science.gov (United States)

    McCulley, George A.

    1985-01-01

    Using a random sample of 493 persuasive papers written by 17-year-olds during the 1978-79 National Assessment of Educational Progress writing evaluation, a study investigated the relationships among features of textual cohesion and primary trait assessments of writing quality and coherence, with manuscript length held statistically constant. (HOD)

  6. Correspondence and coherence in science

    Directory of Open Access Journals (Sweden)

    Neal V. Dawson

    2009-03-01

    Full Text Available This paper introduces historical aspects of the concepts correspondence and coherence with emphasis on the nineteenth century when key aspects of modern science were emerging. It is not intended to be a definitive history of the concepts of correspondence and coherence as they have been used across the centuries in the field of inquiry that we now call science. Rather it is a brief history that highlights the apparent origins of the concepts and provides a discussion of how these concepts contributed to two important science related controversies. The first relates to aspects of evolution in which correspondence and coherence, as competing theories of truth, played a central role. The controversy about evolution continues into the beginning of the twenty-first century in forms that are recognizably similar to those of the middle of the nineteenth century. The second controversy relates to the etiology of blood-born infections (sepsis during childbirth (childbed fever. In addition to correspondence and coherence, the authors introduce other theories of truth and discuss an evolutionarily cogent theory of truth, the pragmatic theory of truth.

  7. Localized coherence of freak waves

    Science.gov (United States)

    Latifah, Arnida L.; van Groesen, E.

    2016-09-01

    This paper investigates in detail a possible mechanism of energy convergence leading to freak waves. We give examples of a freak wave as a (weak) pseudo-maximal wave to illustrate the importance of phase coherence. Given a time signal at a certain position, we identify parts of the time signal with successive high amplitudes, so-called group events, that may lead to a freak wave using wavelet transform analysis. The local coherence of the critical group event is measured by its time spreading of the most energetic waves. Four types of signals have been investigated: dispersive focusing, normal sea condition, thunderstorm condition and an experimental irregular wave. In all cases presented in this paper, it is shown that a high correlation exists between the local coherence and the appearance of a freak wave. This makes it plausible that freak waves can be developed by local interactions of waves in a wave group and that the effect of waves that are not in the immediate vicinity is minimal. This indicates that a local coherence mechanism within a wave group can be one mechanism that leads to the appearance of a freak wave.

  8. Coherent state quantization of quaternions

    Energy Technology Data Exchange (ETDEWEB)

    Muraleetharan, B., E-mail: bbmuraleetharan@jfn.ac.lk, E-mail: santhar@gmail.com [Department of Mathematics and Statistics, University of Jaffna, Thirunelveli (Sri Lanka); Thirulogasanthar, K., E-mail: bbmuraleetharan@jfn.ac.lk, E-mail: santhar@gmail.com [Department of Computer Science and Software Engineering, Concordia University, 1455 De Maisonneuve Blvd. West, Montreal, Quebec H3G 1M8 (Canada)

    2015-08-15

    Parallel to the quantization of the complex plane, using the canonical coherent states of a right quaternionic Hilbert space, quaternion field of quaternionic quantum mechanics is quantized. Associated upper symbols, lower symbols, and related quantities are analyzed. Quaternionic version of the harmonic oscillator and Weyl-Heisenberg algebra are also obtained.

  9. String effect and QCD coherence

    Energy Technology Data Exchange (ETDEWEB)

    Azimov, Ya.I.; Dokshitzer, Yu.L.; Khoze, V.A.; Troyan, S.I.

    1985-12-19

    In the framework of the idea of local parton-hadron duality we discuss the asymptotic predictions of QCD perturbation theory for angular distributions of hadron flows in the three-jet events, e/sup +/e/sup -/->qanti qg->hadrons. The coherence of soft gluon emission provides the QCD explanation of the string effect observed in experiments. (orig.).

  10. Optical coherent control in semiconductors

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher

    2001-01-01

    of quantum control including the recent applications to semiconductors and nanostructures. We study the influence of inhomogeneous broadening in semiconductors on CC results. Photoluminescence (PL) and the coherent emission in four-wave mixing (FWM) is recorded after resonant excitation with phase...

  11. Neutrino production coherence and oscillation experiments

    CERN Document Server

    Akhmedov, Evgeny; Smirnov, Alexei

    2012-01-01

    Neutrino oscillations are only observable when the neutrino production, propagation and detection coherence conditions are satisfied. In this paper we consider in detail neutrino production coherence, taking \\pi\\to \\mu \

  12. Coherent states, wavelets, and their generalizations

    CERN Document Server

    Ali, Syed Twareque; Gazeau, Jean-Pierre

    2014-01-01

    This second edition is fully updated, covering in particular new types of coherent states (the so-called Gazeau-Klauder coherent states, nonlinear coherent states, squeezed states, as used now routinely in quantum optics) and various generalizations of wavelets (wavelets on manifolds, curvelets, shearlets, etc.). In addition, it contains a new chapter on coherent state quantization and the related probabilistic aspects. As a survey of the theory of coherent states, wavelets, and some of their generalizations, it emphasizes mathematical principles, subsuming the theories of both wavelets and coherent states into a single analytic structure. The approach allows the user to take a classical-like view of quantum states in physics.   Starting from the standard theory of coherent states over Lie groups, the authors generalize the formalism by associating coherent states to group representations that are square integrable over a homogeneous space; a further step allows one to dispense with the group context altoget...

  13. Coherent detection of orbital angular momentum in radio

    CERN Document Server

    Daldorff, L K S; Bergman, J E S; Isham, B; Al-Nuaimi, M K T; Forozesh, K; Carozzi, T D

    2015-01-01

    The angular momentum propagated by a beam of radiation has two contributions: spin angular momentum (SAM) and orbital angular momentum (OAM). SAM corresponds to wave polarisation, while OAM-carrying beams are characterized by a phase which is a function of azimuth. We demonstrate experimentally that radio beams propagating OAM can be generated and coherently detected using ordinary electric dipole antennas. The results presented here could pave the way for novel radio OAM applications in technology and science, including radio communication, passive remote sensing, and new types of active (continuous or pulsed transmission) electromagnetic measurements.

  14. Dynamically encircling an exceptional point for asymmetric mode switching

    Science.gov (United States)

    Doppler, Jörg; Mailybaev, Alexei A.; Böhm, Julian; Kuhl, Ulrich; Girschik, Adrian; Libisch, Florian; Milburn, Thomas J.; Rabl, Peter; Moiseyev, Nimrod; Rotter, Stefan

    2016-09-01

    Physical systems with loss or gain have resonant modes that decay or grow exponentially with time. Whenever two such modes coalesce both in their resonant frequency and their rate of decay or growth, an ‘exceptional point’ occurs, giving rise to fascinating phenomena that defy our physical intuition. Particularly intriguing behaviour is predicted to appear when an exceptional point is encircled sufficiently slowly, such as a state-flip or the accumulation of a geometric phase. The topological structure of exceptional points has been experimentally explored, but a full dynamical encircling of such a point and the associated breakdown of adiabaticity have remained out of reach of measurement. Here we demonstrate that a dynamical encircling of an exceptional point is analogous to the scattering through a two-mode waveguide with suitably designed boundaries and losses. We present experimental results from a corresponding waveguide structure that steers incoming waves around an exceptional point during the transmission process. In this way, mode transitions are induced that transform this device into a robust and asymmetric switch between different waveguide modes. This work will enable the exploration of exceptional point physics in system control and state transfer schemes at the crossroads between fundamental research and practical applications.

  15. Blind equalization for dual-polarization two-subcarrier coherent QPSK-OFDM signals.

    Science.gov (United States)

    Li, Fan; Zhang, Junwen; Yu, Jianjun; Li, Xinying

    2014-01-15

    Dual-polarization two-subcarrier coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission and reception is successfully demonstrated with blind equalization. A two-subcarrier quadrature phase shift keyed OFDM (QPSK-OFDM) signal can be equalized as a 9-ary quadrature amplitude modulation signal in the time domain with the cascaded multimodulus algorithm equalization method. The nonlinear effect resistance and transmission distance can be enhanced compared with the traditional CO-OFDM transmission system based on frequency equalization with training sequence.

  16. The automotive transmission book

    CERN Document Server

    Fischer, Robert; Jürgens, Gunter; Najork, Rolf; Pollak, Burkhard

    2015-01-01

    This book presents essential information on systems and interactions in automotive transmission technology and outlines the methodologies used to analyze and develop transmission concepts and designs. Functions of and interactions between components and subassemblies of transmissions are introduced, providing a basis for designing transmission systems and for determining their potentials and properties in vehicle-specific applications: passenger cars, trucks, buses, tractors, and motorcycles. With these fundamentals the presentation provides universal resources for both state-of-the-art and future transmission technologies, including systems for electric and hybrid electric vehicles.

  17. Correlation singularities in partially coherent electromagnetic beams

    NARCIS (Netherlands)

    Raghunathan, S.B.; Schouten, H.F.; Visser, T.D.

    2012-01-01

    We demonstrate that coherence vortices, singularities of the correlation function, generally occur in partially coherent electromagnetic beams. In successive cross sections of Gaussian Schell-model beams, their locus is found to be a closed string. These coherence singularities have implications for

  18. On Radar Resolution in Coherent Change Detection.

    Energy Technology Data Exchange (ETDEWEB)

    Bickel, Douglas L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    It is commonly observed that resolution plays a role in coherent change detection. Although this is the case, the relationship of the resolution in coherent change detection is not yet defined . In this document, we present an analytical method of evaluating this relationship using detection theory. Specifically we examine the effect of resolution on receiver operating characteristic curves for coherent change detection.

  19. Coherent destruction of tunneling in two-level system driven across avoided crossing via photon statistics

    Science.gov (United States)

    Miao, Qiang; Zheng, Yujun

    2016-06-01

    In this paper, the nature of the multi-order resonance and coherent destruction of tunneling (CDT) for two-level system driven cross avoided crossing is investigated by employing the emitted photons and the Mandel’s Q parameter based on the photon counting statistics. An asymmetric feature of CDT is shown in the spectrum of Mandel’s Q parameter. Also, the CDT can be employed to suppress the spontaneous decay and prolong waiting time noticeably. The photon emission pattern is of monotonicity in strong relaxation, and homogeneity in pure dephasing regime, respectively.

  20. Coherent destruction of tunneling in two-level system driven across avoided crossing via photon statistics.

    Science.gov (United States)

    Miao, Qiang; Zheng, Yujun

    2016-06-29

    In this paper, the nature of the multi-order resonance and coherent destruction of tunneling (CDT) for two-level system driven cross avoided crossing is investigated by employing the emitted photons 〈N〉 and the Mandel's Q parameter based on the photon counting statistics. An asymmetric feature of CDT is shown in the spectrum of Mandel's Q parameter. Also, the CDT can be employed to suppress the spontaneous decay and prolong waiting time noticeably. The photon emission pattern is of monotonicity in strong relaxation, and homogeneity in pure dephasing regime, respectively.

  1. Parity-Time Symmetry in Coherently Coupled Vertical Cavity Laser Arrays

    CERN Document Server

    Gao, Zihe; Thompson, Bradley J; Carney, P Scott; Choquette, Kent D

    2016-01-01

    Parity-time (PT) symmetry in optics has been demonstrated in a variety of passive or optically pumped platforms. Here we discuss the notion of PT symmetry in the context of electrically pumped coherently coupled vertical cavity surface emitting laser arrays. Effects of both asymmetric gain distribution and local frequency detuning are considered using temporal coupled mode theory. It is shown theoretically that beam steering, mode evolution and mode hopping are all related to PT symmetry. Experimentally we observed the predicted mode evolution, mode hopping and PT symmetry breaking with quantitative agreement with the theory.

  2. Hyperspectral image compression using low complexity integer KLT and three-dimensional asymmetric significance tree

    Science.gov (United States)

    Huang, Jing; Zhu, Rihong

    2009-08-01

    A lossy to lossless three-dimensional (3D) compression of hyperspectral images is presented. On the spectral dimension, a low complexity reversible integer Karhunen-Loève transform (KLT) is used to fully exploit the spectral redundancy, while two-dimensional spatial combinative lifting algorithm (SCLA)-based integer wavelet transform is applied on the spatial dimension. At the low complexity KLT, the calculation processing of covariance matrix is carried out on a subset of vectors that is pseudorandomly selected from the complete set of spectral vectors. The transform matrix is factorized into triangular elementary reversible matrices (TERM) for reversible integer mapping and the lifting scheme is applied to implement integer KLT. The 3D asymmetric significance tree structure is then constructed from the 3D asymmetric orientation tree in 3D transformed domain. Each coefficient is then encoded by the significance test of the 3D asymmetric significance tree node at each bitplane instead of ordered lists to track the significance status of the tree or block sets and coefficients. This algorithm has low complexity and can be applied to lossy to lossless progressive transmission.

  3. Bordetella pertussis transmission.

    Science.gov (United States)

    Trainor, Elizabeth A; Nicholson, Tracy L; Merkel, Tod J

    2015-11-01

    Bordetella pertussis and B. bronchiseptica are Gram-negative bacterial respiratory pathogens. Bordetella pertussis is the causative agent of whooping cough and is considered a human-adapted variant of B. bronchiseptica. Bordetella pertussis and B. bronchiseptica share mechanisms of pathogenesis and are genetically closely related. However, despite the close genetic relatedness, these Bordetella species differ in several classic fundamental aspects of bacterial pathogens such as host range, pathologies and persistence. The development of the baboon model for the study of B. pertussis transmission, along with the development of the swine and mouse model for the study of B. bronchiseptica, has enabled the investigation of different aspects of transmission including the route, attack rate, role of bacterial and host factors, and the impact of vaccination on transmission. This review will focus on B. pertussis transmission and how animal models of B. pertussis transmission and transmission models using the closely related B. bronchiseptica have increased our understanding of B. pertussis transmission.

  4. Output voltage calculations in double barrier magnetic tunnel junctions with asymmetric voltage behavior

    KAUST Repository

    Useinov, Arthur

    2011-10-22

    In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR-V curves, output voltages and I-V characteristics for negative and positive values of applied voltages were carried out using MTJs with CoFeB/MgO interfaces as an example. Asymmetry of the experimental TMR-V curves is explained by different values of the minority and majority Fermi wave vectors for the left and right sides of the tunnel barrier, which arises due to different annealing regimes. Electron tunneling in DMTJs was simulated in two ways: (i) Coherent tunneling, where the DMTJ is modeled as one tunnel system and (ii) consecutive tunneling, where the DMTJ is modeled by two single barrier junctions connected in series. © 2012 Elsevier B.V. All rights reserved.

  5. Polarization Drift Channel Model for Coherent Fibre-Optic Systems

    CERN Document Server

    Czegledi, Cristian B; Agrell, Erik; Johannisson, Pontus

    2015-01-01

    A theoretical framework is introduced to model the dynamical changes of the state of polarization during transmission in coherent fibre-optic systems. The model generalizes the one-dimensional phase noise random walk to higher dimensions, accounting for random polarization drifts. The model is described in the Jones, Stokes and real 4-dimensional formalisms, and the mapping between them is derived. Such a model will be increasingly important in simulating and optimizing future optical systems, which to a higher and higher degree rely on transmission and detection on both polarizations jointly using sophisticated digital signal processing. Such analysis cannot be carried out using the more rudimentary polarization drift models in use today, which only account for deterministic effects. The proposed polarization drift model is the first of its kind and will likely be useful in a wide-range of photonics applications where stochastic polarization fluctuation is an issue.

  6. Observation of intermolecular double-quantum coherence signal dips in nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Shen Gui-Ping; Cai Cong-Bo; Cai Shu-Hui; Chen Zhong

    2011-01-01

    The correlated spectroscopy revamped by asymmetric Z-gradient echo detection (CRAZED) sequence is modified to investigate intermolecular double-quantum coherence nuclear magnetic resonance signal dips in highly polarized spin systems.It is found that the occurrence of intermolecular double-quantum coherence signal dips is related to sample geometry,field inhomogeneity and dipolar correlation distance.If the field inhomogeneity is refocused,the signal dip occurs at a fixed position whenever the dipolar correlation distance approaches the sample dimension.However,the position is shifted when the field inhomogeneity exists.Experiments and simulations are performed to validate our theoretic analysis.These signal features may offer a unique way to investigate porous structures and may find applications in biomedicine and material science.

  7. Linear algebraic theory of partial coherence: continuous fields and measures of partial coherence.

    Science.gov (United States)

    Ozaktas, Haldun M; Gulcu, Talha Cihad; Alper Kutay, M

    2016-11-01

    This work presents a linear algebraic theory of partial coherence for optical fields of continuous variables. This approach facilitates use of linear algebraic techniques and makes it possible to precisely define the concepts of incoherence and coherence in a mathematical way. We have proposed five scalar measures for the degree of partial coherence. These measures are zero for incoherent fields, unity for fully coherent fields, and between zero and one for partially coherent fields.

  8. Simple model of a coherent molecular photocell

    Science.gov (United States)

    Ernzerhof, Matthias; Bélanger, Marc-André; Mayou, Didier; Nemati Aram, Tahereh

    2016-04-01

    Electron transport in molecular electronic devices is often dominated by a coherent mechanism in which the wave function extends from the left contact over the molecule to the right contact. If the device is exposed to light, photon absorption in the molecule might occur, turning the device into a molecular photocell. The photon absorption promotes an electron to higher energy levels and thus modifies the electron transmission probability through the device. A model for such a molecular photocell is presented that minimizes the complexity of the problem while providing a non-trivial description of the device mechanism. In particular, the role of the molecule in the photocell is investigated. It is described within the Hückel method and the source-sink potential approach [F. Goyer, M. Ernzerhof, and M. Zhuang, J. Chem. Phys. 126, 144104 (2007)] is used to eliminate the contacts in favor of complex-valued potentials. Furthermore, the photons are explicitly incorporated into the model through a second-quantized field. This facilitates the description of the photon absorption process with a stationary state calculation, where eigenvalues and eigenvectors are determined. The model developed is applied to various generic molecular photocells.

  9. Electrically tunable Fano-type resonance of an asymmetric metal wire pair.

    Science.gov (United States)

    Fu, Quanhong; Zhang, Fuli; Fan, Yuancheng; He, Xuan; Qiao, Tong; Kong, Botao

    2016-05-30

    We theoretically and experimentally investigate the electrically tunable Fano-type resonance of asymmetric metal wire pair loaded with varactor diodes. It is illustrated that Fano-type transmission spectrum with high quality factor Q appears as a result of interference between the dipole and quadrupole modes. The ohmic loss of series resistance in varactor diode makes major contribution to absorption. At the Fano-type resonance frequency, both the two metal wires exhibit the strongest electric resonance simultaneously, and the Fano-type resonance manifests a large group delay. As the bias voltage ranges from 0 V to 8 V, the Fano-type resonance frequency exhibits a prominent blueshift of 0.16 GHz and the transmission experiences a modulation with a modulation depth of 97%.

  10. Quantum optics of lossy asymmetric beam splitters

    Science.gov (United States)

    Uppu, Ravitej; Wolterink, Tom A. W.; Tentrup, Tristan B. H.; Pinkse, Pepijn W. H.

    2016-07-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  11. Improved DFIG Capability during Asymmetrical Grid Faults

    DEFF Research Database (Denmark)

    Zhou, Dao; Blaabjerg, Frede

    2015-01-01

    the natural component of the Doubly-Fed Induction Generator (DFIG) stator flux during the fault period, their effects on the rotor voltage can be investigated. It is concluded that the phase-to-phase fault has the worst scenario due to its highest introduction of the negative stator flux. Afterwards......, the capability of a 2 MW DFIG to ride through asymmetrical grid faults can be estimated at the existing design of the power electronics converter. Finally, a control scheme aimed to improve the DFIG capability is proposed and the simulation results validate its feasibility....

  12. Resonance phenomena for asymmetric weakly nonlinear oscillator

    Institute of Scientific and Technical Information of China (English)

    钱定边

    2002-01-01

    We establish the coexistence of periodic solution and unbounded solution, the infinity of largeamplitude subharmonics for asymmetric weakly nonlinear oscillator x" + a2x+ - b2x- + h(x) = p(t) with h(±∞) - 0 and xh(x) → +∞(x →∞), assuming that M(τ ) has zeros which are all simple and M(τ ) 0respectively, where M(τ ) is a function related to the piecewise linear equation x" + a2x+ - b2x- = p(t).``

  13. Dynamic Conditional Correlations for Asymmetric Processes

    OpenAIRE

    Asai, Manabu; McAleer, Michael

    2011-01-01

    The paper develops two Dynamic Conditional Correlation (DCC) models, namely the Wishart DCC (wDCC) model. The paper applies the wDCC approach to the exponential GARCH (EGARCH) and GJR models to propose asymmetric DCC models. We use the standardized multivariate t-distribution to accommodate heavy-tailed errors. The paper presents an empirical example using the trivariate data of the Nikkei 225, Hang Seng and Straits Times Indices for estimating and forecasting the wDCC-EGARCH and wDCC-GJR mod...

  14. On asymmetric causal relationships in Petropolitics

    Directory of Open Access Journals (Sweden)

    Balan Feyza

    2016-01-01

    Full Text Available The aim of this paper is to examine whether the First Law of Petropolitics denominated by Friedman in 2006 is valid for OPEC countries. To do this, this paper analyses the relationship between political risk and oil supply by applying the asymmetric panel causality test suggested by Hatemi-J (2011 to these countries for the period 1984-2014. The results show that the First Law of Petropolitics is valid for Angola, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, and the UAE, given that positive oil supply shocks significantly lead to negative political stability shocks, and negative oil supply shocks significantly lead to positive shocks in political stability.

  15. Quantum optics of lossy asymmetric beam splitters

    CERN Document Server

    Uppu, Ravitej; Tentrup, Tristan B H; Pinkse, Pepijn W H

    2016-01-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  16. Asymmetric chemical reactions by polarized quantum beams

    Science.gov (United States)

    Takahashi, Jun-Ichi; Kobayashi, Kensei

    One of the most attractive hypothesis for the origin of homochirality in terrestrial bio-organic compounds (L-amino acid and D-sugar dominant) is nominated as "Cosmic Scenario"; a chiral impulse from asymmetric excitation sources in space triggered asymmetric reactions on the surfaces of such space materials as meteorites or interstellar dusts prior to the existence of terrestrial life. 1) Effective asymmetric excitation sources in space are proposed as polarized quantum beams, such as circularly polarized light and spin polarized electrons. Circularly polarized light is emitted as synchrotron radiation from tightly captured electrons by intense magnetic field around neutron stars. In this case, either left-or right-handed polarized light can be observed depending on the direction of observation. On the other hand, spin polarized electrons is emitted as beta-ray in beta decay from radioactive nuclei or neutron fireballs in supernova explosion. 2) The spin of beta-ray electrons is longitudinally polarized due to parity non-conservation in the weak interaction. The helicity (the the projection of the spin onto the direction of kinetic momentum) of beta-ray electrons is universally negative (left-handed). For the purpose of verifying the asymmetric structure emergence in bio-organic compounds by polarized quantum beams, we are now carrying out laboratory simulations using circularly polarized light from synchrotron radiation facility or spin polarized electron beam from beta-ray radiation source. 3,4) The target samples are solid film or aqueous solution of racemic amino acids. 1) K.Kobayashi, K.Kaneko, J.Takahashi, Y.Takano, in Astrobiology: from simple molecules to primitive life; Ed. V.Basiuk; American Scientific Publisher: Valencia, 2008. 2) G.A.Gusev, T.Saito, V.A.Tsarev, A.V.Uryson, Origins Life Evol. Biosphere. 37, 259 (2007). 3) J.Takahashi, H.Shinojima, M.Seyama, Y.Ueno, T.Kaneko, K.Kobayashi, H.Mita, M.Adachi, M.Hosaka, M.Katoh, Int. J. Mol. Sci. 10, 3044

  17. RHIC operation with asymmetric collisions in 2015

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Aschenauer, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Atoian, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brown, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Bruno, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Connolly, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ottavio, T. D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Drees, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gu, X. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hayes, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Huang, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Laster, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Luo, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Makdisi, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marr, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Meot, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Michnoff, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Morris, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Narayan, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nayak, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nemesure, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pile, P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Poblaguev, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Robert-Demolaize, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Roser, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schmidke, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schoefer, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Severino, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Shrey, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Steski, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tsoupas, N. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); White, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yip, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zeno, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zhang, S. Y. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-08-07

    To study low-x shadowing/saturation physics as well as other nuclear effects [1], [2], proton-gold (p-Au, for 5 weeks) and proton-Aluminum (p-Al, for 2 weeks) collisions were provided for experiments in 2015 at the Relativistic Heavy Ion Collider (RHIC), with polarized proton beam in the Blue ring and Au/Al beam in the Yellow ring. The special features of the asymmetric run in 2015 will be introduced. The operation experience will be reviewed as well in the report.

  18. Photoresponse of silicon with asymmetric area contacts

    Science.gov (United States)

    Rabbani, M. Golam; Sundararajan, Jency P.; Verma, Amit; Nekovei, Reza; Khader, Mahmoud M.; Darling, R. B.; Patil, Sunil R.

    2017-01-01

    We report on high performance metal-semiconductor-metal (MSM) photosensors based on asymmetric metal pad areas. The reported devices require a single-step metal deposition, and exhibit large photo response even under zero-bias. Moreover the devices offer fast and stable light switching behavior. Device fabrication and electrical characterization results are presented that are further analyzed with TCAD modeling and simulation. Device simulations show that contact asymmetry along with surface recombination and barrier lowering plays an important role in the MSM I-V characteristics.

  19. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  20. Analysis of Asymmetric Piezoelectric Composite Beam

    CERN Document Server

    Chen, J -S; Wu, K -C

    2008-01-01

    This paper deals with the vibration analysis of an asymmetric composite beam composed of glass a piezoelectric material. The Bernoulli's beam theory is adopted for mechanical deformations, and the electric potential field of the piezoelectric material is assumed such that the divergence-free requirement of the electrical displacements is satisfied. The accuracy of the analytic model is assessed by comparing the resonance frequencies obtained by the analytic model with those obtained by the finite element method. The model developed can be used as a tool for designing piezoelectric actuators such as micro-pumps.

  1. Asymmetric Synthesis of Both Enantiomers of Disparlure

    Institute of Scientific and Technical Information of China (English)

    王志刚; 郑剑峰; 黄培强

    2012-01-01

    Starting from propargyl alcohol (12), and on the basis of Zhou's modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure (+)-8 and its enantiomer (-)-8 have been synthesized, each in six steps, with overall yields of 29% for (+)-8 and 27% for (-)-8 (ee〉98%). The use of the sequential coupling tactic renders the method flexible, which is applicable to the synthesis of other cis-epoxy pheromones.

  2. Nanotribology of Symmetric and Asymmetric Liquid Lubricants

    Directory of Open Access Journals (Sweden)

    Shinji Yamada

    2010-03-01

    Full Text Available When liquid molecules are confined in a narrow gap between smooth surfaces, their dynamic properties are completely different from those of the bulk. The molecular motions are highly restricted and the system exhibits solid-like responses when sheared slowly. This solidification behavior is very dependent on the molecular geometry (shape of liquids because the solidification is induced by the packing of molecules into ordered structures in confinement. This paper reviews the measurements of confined structures and friction of symmetric and asymmetric liquid lubricants using the surface forces apparatus. The results show subtle and complex friction mechanisms at the molecular scale.

  3. Neuronal Alignment On Asymmetric Textured Surfaces

    CERN Document Server

    Beighley, Ross; Sekeroglu, Koray; Atherton, Timothy; Demirel, Melik C; Staii, Cristian

    2013-01-01

    Axonal growth and the formation of synaptic connections are key steps in the development of the nervous system. Here we present experimental and theoretical results on axonal growth and interconnectivity in order to elucidate some of the basic rules that neuronal cells use for functional connections with one another. We demonstrate that a unidirectional nanotextured surface can bias axonal growth. We perform a systematic investigation of neuronal processes on asymmetric surfaces and quantify the role that biomechanical surface cues play in neuronal growth. These results represent an important step towards engineering directed axonal growth for neuro-regeneration studies.

  4. An Asymmetric Block Dynamic Conditional Correlation Multivariate GARCH Model

    OpenAIRE

    Vargas, Gregorio A.

    2006-01-01

    The Block DCC model for determining dynamic correlations within and between groups of financial asset returns is extended to account for asymmetric effects. Simulation results show that the Asymmetric Block DCC model is competitive in in-sample forecasting and performs better than alternative DCC models in out-of-sample forecasting of conditional correlation in the presence of asymmetric effect between blocks of asset returns. Empirical results demonstrate that the model is able to capture ...

  5. Asymmetric joint multifractal analysis in Chinese stock markets

    Science.gov (United States)

    Chen, Yuwen; Zheng, Tingting

    2017-04-01

    In this paper, the asymmetric joint multifractal analysis method based on statistical physics is proposed to explore the asymmetric correlation between daily returns and trading volumes in Chinese stock markets. The result shows asymmetric multifractal correlations exist between return and trading volume in Chinese stock markets. Moreover, when the stock indexes are upward, the fluctuations of returns are always weaker than when they are downward, whether the trading volumes are more or less.

  6. Asymmetric Campaigning as a Rational Choice: Planning Considerations

    Science.gov (United States)

    2006-06-01

    Maslow identified five levels: survival, safety, belonging, esteem, and self-actualization. He presented his theory as a pyramid with five layers...to be sustained by actions of the asymmetric opponent. For the media-fed frenzy over constraints and protraction to continue, the asymmetric...lot of people. The reason for this is twofold. First, the actor needs sufficient support to exist and to sustain an asymmetric campaign. Second, the

  7. Characterisation of dispersive systems using a coherer

    Directory of Open Access Journals (Sweden)

    Nikolić Pantelija M.

    2002-01-01

    Full Text Available The possibility of characterization of aluminium powders using a horizontal coherer has been considered. Al powders of known dimension were treated with a high frequency electromagnetic field or with a DC electric field, which were increased until a dielectric breakdown occurred. Using a multifunctional card PC-428 Electronic Design and a suitable interface between the coherer and PC, the activation time of the coherer was measured as a function of powder dimension and the distance between the coherer electrodes. It was also shown that the average dimension of powders of unknown size could be determined using the coherer.

  8. Coherence depression in stochastic excitable systems with two-frequency forcing

    Science.gov (United States)

    Yu, Na; Longtin, André

    2011-12-01

    We study the response of two generic neuron models, the leaky integrate-and-fire (LIF) model and the leaky integrate-and-fire model with dynamic threshold (LIFDT) (i.e., with memory) to a stimulus consisting of two sinusoidal drives with incommensurate frequency, an amplitude modulation ("envelope") noise and a relatively weak additive noise. Spectral and coherence analysis of responses to such naturalistic stimuli reveals how the LIFDT model exhibits better correlation between modulation and spike train even in the presence of both noises. However, a resonance-induced synchrony, occurring when the beat frequency between the sinusoids is close to the intrinsic neuronal firing rate, decreases the coherence in the dynamic threshold case. Under suprathreshold conditions, the modulation noise simultaneously decreases the linear spectral coherence between the spikes and the whole stimulus, as well as between spikes and the stimulus envelope. Our study shows that the coefficient of variation of the envelope fluctuations is positively correlated with the degree of coherence depression. As the coherence function quantifies the linear information transmission, our findings indicate that under certain conditions, a transmission loss results when an excitable system with adaptive properties encodes a beat with frequency in the vicinity of its mean firing rate.

  9. Quantity Discount Scheme in Supply Chain under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    LI Ji-bin; PENG Zuo-he

    2007-01-01

    Quantity discount scheme plays an important role in supply chain management. The different quantity discount schemes under symmetric (full) information and asymmetric information, are analyzed by using principal-agent and optimal control theory. As a result, the research reveals that the optimal quantity discount solution under symmetric information is a special case of that under asymmetric information. At the same price, the critical value of quantity discount under asymmetric information is much lower than that under asymmetric information. Therefore, this leads to less cost for retailers and smaller profit for their supplier.

  10. Energy cost of creating quantum coherence

    Science.gov (United States)

    Misra, Avijit; Singh, Uttam; Bhattacharya, Samyadeb; Pati, Arun Kumar

    2016-05-01

    We consider physical situations where the resource theories of coherence and thermodynamics play competing roles. In particular, we study the creation of quantum coherence using unitary operations with limited thermodynamic resources. We find the maximal coherence that can be created under unitary operations starting from a thermal state and find explicitly the unitary transformation that creates the maximal coherence. Since coherence is created by unitary operations starting from a thermal state, it requires some amount of energy. This motivates us to explore the trade-off between the amount of coherence that can be created and the energy cost of the unitary process. We also find the maximal achievable coherence under the constraint on the available energy. Additionally, we compare the maximal coherence and the maximal total correlation that can be created under unitary transformations with the same available energy at our disposal. We find that when maximal coherence is created with limited energy, the total correlation created in the process is upper bounded by the maximal coherence, and vice versa. For two-qubit systems we show that no unitary transformation exists that creates the maximal coherence and maximal total correlation simultaneously with a limited energy cost.

  11. A universal coherent source for quantum key distribution

    Institute of Scientific and Technical Information of China (English)

    ZHANG ShengLi; ZOU XuBo; LI ChuanFeng; JIN ChenHui; GUO GuangCan

    2009-01-01

    We propose a concept of universal coherent source for quantum key distribution. The weak coherent pulse (WCP) and heralded single photon source (HSPS) are the most common photon sources for state-of-art quantum key distribution (QKD). However, there exists a prominent crossover between the maximal secure distance and the secure key generating rate in short and middle distance if one applies these two sources in a practical decoy state quantum key distribution. It is shown that by combining the heralded pair coherent state (HPCS) photon source and the practical decoy state method together, one can not only strengthen the maximal secure transmission distance, but also improve key generat-ing rate at short and medium distance. Moreover, the advancement in key generating is not confined in the particular protocol utilized and can be easily checked for both BB84 and SARG protocol. Finally, we clearly demonstrate how the HPCS-based decoy method works effectively and feasibly by proposing an efficient HPCS-based "1 signal+2 decoy" state method.

  12. Continuous-variable quantum network coding for coherent states

    Science.gov (United States)

    Shang, Tao; Li, Ke; Liu, Jian-wei

    2017-04-01

    As far as the spectral characteristic of quantum information is concerned, the existing quantum network coding schemes can be looked on as the discrete-variable quantum network coding schemes. Considering the practical advantage of continuous variables, in this paper, we explore two feasible continuous-variable quantum network coding (CVQNC) schemes. Basic operations and CVQNC schemes are both provided. The first scheme is based on Gaussian cloning and ADD/SUB operators and can transmit two coherent states across with a fidelity of 1/2, while the second scheme utilizes continuous-variable quantum teleportation and can transmit two coherent states perfectly. By encoding classical information on quantum states, quantum network coding schemes can be utilized to transmit classical information. Scheme analysis shows that compared with the discrete-variable paradigms, the proposed CVQNC schemes provide better network throughput from the viewpoint of classical information transmission. By modulating the amplitude and phase quadratures of coherent states with classical characters, the first scheme and the second scheme can transmit 4{log _2}N and 2{log _2}N bits of information by a single network use, respectively.

  13. Vibrational and coherence dynamics of molecules

    CERN Document Server

    Zhang, Zhedong

    2015-01-01

    We {\\it analytically} investigate the population and coherence dynamics and relaxations in the vibrational energy transport in molecules. The corresponding two time scales $t_1$ and $t_2$ are explored. Coherence-population entanglement is found to considerably promote the time scale $t_2$ for dephasing and the amplitude of coherence. This is attributed to the suppression of the environment-induced drift force by coherence. Moreover the population imbalance (magnetization) is shown to be significantly amplified with the coherence-population entanglement. Contrary to the previous studies, we exactly elucidate a coherent process by showing $t_1coherence effect on the heat current at the macroscopic level.

  14. How coherent are Josephson junctions?

    CERN Document Server

    Paik, Hanhee; Bishop, Lev S; Kirchmair, G; Catelani, G; Sears, A P; Johnson, B R; Reagor, M J; Frunzio, L; Glazman, L; Schoelkopf, R J

    2011-01-01

    Attaining sufficient coherence is a requirement for realizing a large-scale quantum computer. We present a new implementation of a superconducting transmon qubit that is strongly coupled to a three-dimensional superconducting cavity. We observe a reproducible increase in the coherence times of qubit (both $T_1$ and $T_2$ > 10 microseconds) and cavity ($T_{cav}$ ~ 50 microseconds) by more than an order of magnitude compared to the current state-of-art superconducting qubits. This enables the study of the stability and quality of Josephson junctions at precisions exceeding one part per million. Surprisingly, we see no evidence for $1/f$ critical current noise. At elevated temperatures, we observe the dissipation due to a small density (< 1 - 10 ppm) of thermally-excited quasiparticles. The results suggest that the overall quality of Josephson junctions will allow error rates of a few $10^{-4}$, approaching the error correction threshold.

  15. Neutrino induced coherent pion production

    CERN Document Server

    Hernández, E; Valverde, M; Vicente-Vacas, M J

    2009-01-01

    We discuss different parameterizations of the $C_5^A(q^2)$ $N\\Delta$ axial form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low $q^2$ behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses of some of the approximations in that model that lead to very large cross sections as well as to the wrong shapes for differential ones. Finally we show that models based on the partial conservation of the axial current hypothesis are not fully reliable for differential cross sections that depend on the angle formed by the pion and the incident neutrino.

  16. Coherent phase argument for inflation

    Energy Technology Data Exchange (ETDEWEB)

    Scott Dodelson

    2004-03-17

    Cosmologists have developed a phenomenally successful picture of structure in the universe based on the idea that the universe expanded exponentially in its earliest moments. There are three pieces of evidence for this exponential expansion--inflation--from observations of anisotropies in the cosmic microwave background. First, the shape of the primordial spectrum is very similar to that predicted by generic inflation models. Second, the angular scale at which the first acoustic peak appears is consistent with the flat universe predicted by inflation. Here the author describes the third piece of evidence, perhaps the most convincing of all: the phase coherence needed to account for the clear peak/trough structure observed by the WMAP satellite and its predecessors. The author also discusses alternatives to inflation that have been proposed recently and explain how they produce coherent phases.

  17. Detecting coherent structures using braids

    CERN Document Server

    Allshouse, Michael R

    2011-01-01

    The detection of coherent structures is an important problem in fluid dynamics, particularly in geophysical applications. For instance, knowledge of how regions of fluid are isolated from each other allows prediction of the ultimate fate of oil spills. Existing methods detect Lagrangian coherent structures, which are barriers to transport, by examining the stretching field as given by finite-time Lyapunov exponents. These methods are very effective when the velocity field is well-determined, but in many applications only a small number of flow trajectories are known, for example when dealing with oceanic float data. We introduce a topological method for detecting invariant regions based on a small set of trajectories. In the method we regard the two-dimensional trajectory data as a braid in three dimensions, with time being the third coordinate. Invariant regions then correspond to trajectories that travel together and do not entangle other trajectories. We detect these regions by examining the growth of hypo...

  18. Photoelectric converters with quantum coherence.

    Science.gov (United States)

    Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can

    2016-05-01

    Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency η_{CA}. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to η_{CA} through manipulation of carefully controlled quantum coherences.

  19. Photoelectric converters with quantum coherence

    Science.gov (United States)

    Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can

    2016-05-01

    Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency ηCA. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to ηCA through manipulation of carefully controlled quantum coherences.

  20. Coherent optical methods for metallography

    Energy Technology Data Exchange (ETDEWEB)

    Pechersky, M.J.

    1991-01-01

    Numerous methods based on coherent optical techniques have been developed over the past two decades for nondestructive evaluation, vibration analysis and experimental mechanics. These methods have a great deal of potential for the enhancement of metallographic evaluations and for materials characterization in general. One such technique described in this paper is the determination of the material damping factors in metals. Damping loss factors as low as 10-5 were measured on bronze and aluminum specimens using a technique based on laser vibrometry. Differences between cast and wrought bronze were easily distinguishable as well as the difference between the bronze and aluminum. Other coherent optical techniques may be used to evaluate residual stresses and to locate and identify microcracking, subsurface voids and other imperfections. These techniques and others can serve as a bridge between microstructural investigations and the macroscopic behavior of materials.

  1. Coherent optical methods for metallography

    Energy Technology Data Exchange (ETDEWEB)

    Pechersky, M.J.

    1991-12-31

    Numerous methods based on coherent optical techniques have been developed over the past two decades for nondestructive evaluation, vibration analysis and experimental mechanics. These methods have a great deal of potential for the enhancement of metallographic evaluations and for materials characterization in general. One such technique described in this paper is the determination of the material damping factors in metals. Damping loss factors as low as 10-5 were measured on bronze and aluminum specimens using a technique based on laser vibrometry. Differences between cast and wrought bronze were easily distinguishable as well as the difference between the bronze and aluminum. Other coherent optical techniques may be used to evaluate residual stresses and to locate and identify microcracking, subsurface voids and other imperfections. These techniques and others can serve as a bridge between microstructural investigations and the macroscopic behavior of materials.

  2. Remote creation of quantum coherence

    Science.gov (United States)

    Ma, Teng; Zhao, Ming-Jing; Fei, Shao-Ming; Long, Gui-Lu

    2016-10-01

    We study remote creation of coherence (RCC) for a quantum system, A, with the help of quantum operations on another system, B, and one-way classical communication. We show that all the nonincoherent quantum states are useful for RCC and all the incoherent-quantum states are not. The necessary and sufficient conditions of RCC for the quantum operations on system B are presented for pure states. The upper bound of average RCC is derived, giving a relation among the entanglement (concurrence), the RCC of the given quantum state, and the RCC of the corresponding maximally entangled state. Moreover, for two-qubit systems we find a simple factorization law for the average remote-created coherence.

  3. The global coherence initiative: creating a coherent planetary standing wave.

    Science.gov (United States)

    McCraty, Rollin; Deyhle, Annette; Childre, Doc

    2012-03-01

    The much anticipated year of 2012 is now here. Amidst the predictions and cosmic alignments that many are aware of, one thing is for sure: it will be an interesting and exciting year as the speed of change continues to increase, bringing both chaos and great opportunity. One benchmark of these times is a shift in many people from a paradigm of competition to one of greater cooperation. All across the planet, increasing numbers of people are practicing heart-based living, and more groups are forming activities that support positive change and creative solutions for manifesting a better world. The Global Coherence Initiative (GCI) is a science-based, co-creative project to unite people in heart-focused care and intention. GCI is working in concert with other initiatives to realize the increased power of collective intention and consciousness. The convergence of several independent lines of evidence provides strong support for the existence of a global information field that connects all living systems and consciousness. Every cell in our bodies is bathed in an external and internal environment of fluctuating invisible magnetic forces that can affect virtually every cell and circuit in biological systems. Therefore, it should not be surprising that numerous physiological rhythms in humans and global collective behaviors are not only synchronized with solar and geomagnetic activity, but disruptions in these fields can create adverse effects on human health and behavior. The most likely mechanism for explaining how solar and geomagnetic influences affect human health and behavior are a coupling between the human nervous system and resonating geomagnetic frequencies, called Schumann resonances, which occur in the earth-ionosphere resonant cavity and Alfvén waves. It is well established that these resonant frequencies directly overlap with those of the human brain and cardiovascular system. If all living systems are indeed interconnected and communicate with each other

  4. Asymmetrical TWDM-PON with 4 × 25-Gb/s downstream DSB OFDM and 4 × 10-Gb/s upstream OOK modulations

    Science.gov (United States)

    Lin, Bangjiang; Li, Yiwei; Zhang, Shihao; Tang, Xuan

    2015-12-01

    We propose and experimentally demonstrate an asymmetrical time wavelength division multiplexing passive optical network (TWDM-PON) scheme with 100-Gb/s downstream and 40-Gb/s upstream capacity using four pairs of wavelengths. Double sideband (DSB) orthogonal frequency division multiplexing (OFDM) with 16-QAM mapping is used for downstream transmission, while on-off keying (OOK) modulation is used for upstream transmission. The experimental results show that the power budget for bidirectional transmission is more than 35.5-dB. This scheme can be a promising solution for 100-Gb/s TWDM-PON with high power budget.

  5. Hanle effect in coherent backscattering

    CERN Document Server

    Labeyrie, G; Müller, C A; Sigwarth, O; Delande, D; Kaiser, R

    2002-01-01

    We study the shape of the coherent backscattering (CBS) cone obtained when resonant light illuminates a thick cloud of laser-cooled rubidium atoms in presence of a homogenous magnetic field. We observe new magnetic field-dependent anisotropies in the CBS signal. We show that the observed behavior is due to the modification of the atomic radiation pattern by the magnetic field (Hanle effect in the excited state).

  6. Scattering and coherence in EUVL

    Science.gov (United States)

    Milster, Tomas D.; Beaudry, Neil A.

    1998-06-01

    We illustrate the importance of considering scattering from the illuminator in extreme UV lithography systems. Our results indicate that a significant amount of amplitude modulation noise is present in the aerial image if scatter is present in a Koehler illuminator. The effect depends on the spatial frequency of the pattern on the mask, the numerical aperture of the projection camera, the coherence factor, and placement of the plane in the illuminator where the scattering occurs.

  7. Spin coherence time analytical estimations

    CERN Document Server

    Orlov, Yuri

    2015-01-01

    Section I presents a variety of analytical estimations related to spin coherence time (SCT) in a purely electric frozen-spin ring. The main result is that, in the case of m > 0 and vertical oscillations only, the kinetic energy equilibrium shift equals zero, that is, SCT does not depend on these oscillations. Section II contains additional information on this case concerning terminology, electric field definition and vertical oscillations.

  8. Reliable and Efficient Broadcasting in Asymmetric Mobile Ad Hoc Networks Using Minimized Forward Node List Algorithm

    Directory of Open Access Journals (Sweden)

    Marimuthu Murugesan

    2011-01-01

    Full Text Available Problem statement: Network wide broadcasting is a fundamental operation in ad hoc networks. In broadcasting, a source node sends a message to all the other nodes in the network. Unlike in a wired network, a packet transmitted by a node in ad hoc wireless network can reach all neighbors. Therefore, the total number of transmissions (Forwarding nodes used as the cost criterion for broadcasting. Approach: This study proposes a reliable and efficient broadcasting algorithm using minimized forward node list algorithm which uses 2-hop neighborhood information more effectively to reduce redundant transmissions in asymmetric Mobile Ad hoc networks that guarantees full delivery. Among the 1-hop neighbors of the sender, only selected forwarding nodes retransmit the broadcast message. Forwarding nodes are selected such a way that to cover the uncovered 2-hop neighbors. Results: Simulation results show that the proposed broadcasting algorithm provides high delivery ratio, low broadcast forward ratio, low overhead and minimized delay. Conclusion: In this study, reliable and efficient broadcasting algorithm in asymmetric Mobile Ad Hoc Networks using minimized forward node list algorithm has been proposed which provides low forward ratio, high delivery ratio while suppressing broadcast redundancy.

  9. Quantum learning of coherent states

    Energy Technology Data Exchange (ETDEWEB)

    Sentis, Gael [Universitat Autonoma de Barcelona, Fisica Teorica: Informacio i Fenomens Quantics, Barcelona (Spain); Guta, Madalin; Adesso, Gerardo [University of Nottingham, School of Mathematical Sciences, Nottingham (United Kingdom)

    2015-12-15

    We develop a quantum learning scheme for binary discrimination of coherent states of light. This is a problem of technological relevance for the reading of information stored in a digital memory. In our setting, a coherent light source is used to illuminate a memory cell and retrieve its encoded bit by determining the quantum state of the reflected signal. We consider a situation where the amplitude of the states produced by the source is not fully known, but instead this information is encoded in a large training set comprising many copies of the same coherent state. We show that an optimal global measurement, performed jointly over the signal and the training set, provides higher successful identification rates than any learning strategy based on first estimating the unknown amplitude by means of Gaussian measurements on the training set, followed by an adaptive discrimination procedure on the signal. By considering a simplified variant of the problem, we argue that this is the case even for non-Gaussian estimation measurements. Our results show that, even in absence of entanglement, collective quantum measurements yield an enhancement in the readout of classical information, which is particularly relevant in the operating regime of low-energy signals. (orig.)

  10. Quantum learning of coherent states

    CERN Document Server

    Sentís, Gael; Adesso, Gerardo

    2014-01-01

    We develop a quantum learning scheme for binary discrimination of coherent states of light. This is a problem of technological relevance for the reading of information stored in a digital memory. In our setting, a coherent light source is used to illuminate a memory cell and retrieve its encoded bit by determining the quantum state of the reflected signal. We consider a situation where the amplitude of the states produced by the source is not fully known, but instead this information is encoded in a large training set comprising many copies of the same coherent state. We show that an optimal global measurement, performed jointly over the signal and the training set, provides higher successful identification rates than any learning strategy based on first estimating the unknown amplitude by means of Gaussian measurements on the training set, followed by an adaptive discrimination procedure on the signal. By considering a simplified variant of the problem, we argue that this is the case even for non-Gaussian es...

  11. Asymmetric disassembly and robustness in declining networks.

    Science.gov (United States)

    Saavedra, Serguei; Reed-Tsochas, Felix; Uzzi, Brian

    2008-10-28

    Mechanisms that enable declining networks to avert structural collapse and performance degradation are not well understood. This knowledge gap reflects a shortage of data on declining networks and an emphasis on models of network growth. Analyzing >700,000 transactions between firms in the New York garment industry over 19 years, we tracked this network's decline and measured how its topology and global performance evolved. We find that favoring asymmetric (disassortative) links is key to preserving the topology and functionality of the declining network. Based on our findings, we tested a model of network decline that combines an asymmetric disassembly process for contraction with a preferential attachment process for regrowth. Our simulation results indicate that the model can explain robustness under decline even if the total population of nodes contracts by more than an order of magnitude, in line with our observations for the empirical network. These findings suggest that disassembly mechanisms are not simply assembly mechanisms in reverse and that our model is relevant to understanding the process of decline and collapse in a broad range of biological, technological, and financial networks.

  12. Algebraic Davis Decomposition and Asymmetric Doob Inequalities

    Science.gov (United States)

    Hong, Guixiang; Junge, Marius; Parcet, Javier

    2016-09-01

    In this paper we investigate asymmetric forms of Doob maximal inequality. The asymmetry is imposed by noncommutativity. Let {({M}, τ)} be a noncommutative probability space equipped with a filtration of von Neumann subalgebras {({M}_n)_{n ≥ 1}}, whose union {bigcup_{n≥1}{M}_n} is weak-* dense in {{M}}. Let {{E}_n} denote the corresponding family of conditional expectations. As an illustration for an asymmetric result, we prove that for {1 spaces {{H}_p^r({M})} and {{H}_p^c({M})} respectively. In particular, this solves a problem posed by the Defant and Junge in 2004. In the case p = 1, our results establish a noncommutative form of the Davis celebrated theorem on the relation betwe en martingale maximal and square functions in L 1, whose noncommutative form has remained open for quite some time. Given {1 ≤ p ≤ 2}, we also provide new weak type maximal estimates, which imply in turn left/right almost uniform convergence of {{E}_n(x)} in row/column Hardy spaces. This improves the bilateral convergence known so far. Our approach is based on new forms of Davis martingale decomposition which are of independent interest, and an algebraic atomic description for the involved Hardy spaces. The latter results are new even for commutative von Neumann algebras.

  13. An asymmetric B factory based on PEP

    Energy Technology Data Exchange (ETDEWEB)

    1991-02-01

    In this report we describe a design for a high-luminosity Asymmetric B Factory to be built in the PEP tunnel on the SLAC site. This proposal, a collaborative effort SLAC, LBL, and LLNL, is the culmination of more than two years of effort aimed at the design and construction of an asymmetric e{sup +}e{sup {minus}} collider capable of achieving a luminosity of L = 3 {times} 10{sup 33} cm{sup {minus}2} s{sup {minus}1}. The configuration adopted utilizes two storage rings, and electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of the B Factory. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two B Factory storage rings.

  14. Evolutionary stability in the asymmetric volunteer's dilemma.

    Directory of Open Access Journals (Sweden)

    Jun-Zhou He

    Full Text Available It is often assumed that in public goods games, contributors are either strong or weak players and each individual has an equal probability of exhibiting cooperation. It is difficult to explain why the public good is produced by strong individuals in some cooperation systems, and by weak individuals in others. Viewing the asymmetric volunteer's dilemma game as an evolutionary game, we find that whether the strong or the weak players produce the public good depends on the initial condition (i.e., phenotype or initial strategy of individuals. These different evolutionarily stable strategies (ESS associated with different initial conditions, can be interpreted as the production modes of public goods of different cooperation systems. A further analysis revealed that the strong player adopts a pure strategy but mixed strategies for the weak players to produce the public good, and that the probability of volunteering by weak players decreases with increasing group size or decreasing cost-benefit ratio. Our model shows that the defection probability of a "strong" player is greater than the "weak" players in the model of Diekmann (1993. This contradicts Selten's (1980 model that public goods can only be produced by a strong player, is not an evolutionarily stable strategy, and will therefore disappear over evolutionary time. Our public good model with ESS has thus extended previous interpretations that the public good can only be produced by strong players in an asymmetric game.

  15. At Low SNR Asymmetric Quantizers Are Better

    CERN Document Server

    Koch, Tobias

    2012-01-01

    We study the capacity of the discrete-time Gaussian channel when its output is quantized with a one-bit quantizer. We focus on the low signal-to-noise ratio (SNR) regime, where communication at very low spectral efficiencies takes place. In this regime a symmetric threshold quantizer is known to reduce channel capacity by 2/pi, i.e., to cause an asymptotic power loss of approximately two decibels. Here it is shown that this power loss can be entirely avoided by using asymmetric threshold quantizers and asymmetric signaling constellations. We prove that in order to avoid this power loss flash-signaling input-distributions are essential. Consequently, one-bit output quantization of the Gaussian channel reduces spectral efficiency. Threshold quantizers are not only asymptotically optimal: as we prove, at every fixed SNR, a threshold quantizer maximizes capacity among all one-bit output quantizers. The picture changes on the Rayleigh-fading channel. In the noncoherent case we show that a one-bit output quantizer ...

  16. Instability of asymmetric continuous shaft system

    Science.gov (United States)

    Srinath, R.; Sarkar, Abhijit; Sekhar, A. S.

    2016-11-01

    In this work, the governing equation of asymmetric continuous shaft in inertial frame of reference is studied. In particular, determination of the parameter ranges for the stability or instability of the shaft response is the focus of the present work. The governing equations are a fourth-order coupled partial differential equations containing time dependent coefficients. The equations are non-dimensionalized in terms of two parameters related to the average moment of inertia and the difference of moments of inertia about the principal axes. Using the latter as the asymptotic parameter and employing modal superposition, a formal methodology based on perturbation methods is developed to ascertain the stability and instability characteristics. The methodology is applicable to shafts subjected to some of the classical boundary conditions viz. simply supported, cantilever, and fixed-fixed. Similar stability curves are obtained for each mode for these different boundary conditions. The novel non-dimensionalization scheme chosen leads to the stability boundaries as well as the loci of varying speeds to be in the form of straight lines. The intersection of these lines determine the stable and unstable speed ranges of different asymmetric shafts. The results are generalized for different material and geometric properties of the shaft.

  17. Asymmetric transition disks: Vorticity or eccentricity?

    CERN Document Server

    Zsom, A; Ghanbari, J

    2013-01-01

    Context. Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young host stars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: they have lopsided shapes. It has been speculated that these rings act as dust traps, which would make them important laboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk with a strong viscosity jump strikingly resembles the observed asymmetric rings. Aims. We aim to study a similar behavior for a disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) a giant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one can observationally distinguish between them. This is important because only a vortex can trap particles both radially and azimuthally, while the eccentric ring can only trap particles in radial direction. Method...

  18. Properties of asymmetrically evolved community networks

    Institute of Scientific and Technical Information of China (English)

    Cui Di; Gao Zi-You; Zheng Jian-Feng

    2009-01-01

    This paper studies a simple asymmetrically evolved community network with a combination of preferential at-tachment and random properties. An important issue about community networks is to discover the different utility increments of two nodes, where the utility is introduced to investigate the asymmetrical effect of connecting two nodes. On the other hand, the connection of two nodes in community networks can be classified as two nodes belonging to the same or to different communities. The simulation results show that the model can reproduce a power-law utility distribution P(u)~ u-σ,σ=2+ 1/p, which can be obtained by using mean-field approximation methods. Furthermore, the model exhibits exponential behaviour with respect to small values of a parameter denoting the random effect in our model at the low-utility region and a power-law feature with respect to big values of this parameter at the high-utility region, which is in good agreement with theoretical analysis. This kind of community network can reproduce a unique utility distribution by theoretical and numerical analysis.

  19. Survey of Reflection-Asymmetric Nuclear Deformations

    Science.gov (United States)

    Olsen, Erik; Cao, Yuchen; Nazarewicz, Witold; Schunck, Nicolas

    2016-09-01

    Due to spontaneous symmetry breaking it is possible for a nucleus to have a deformed shape in its ground state. It is theorized that atoms whose nuclei have reflection-asymmetric or pear-like deformations could have non-zero electric dipole moments (EDMs). Such a trait would be evidence of CP-violation, a feature that goes beyond the Standard Model of Physics. It is the purpose of this project to predict which nuclei exhibit a reflection-asymmetric deformation and which of those would be the best candidates for an EDM measuring experiment. Using nuclear Density Functional Theory along with the new computer code AxialHFB and massively parallel computing we calculated ground state nuclear properties for thousands of even-even nuclei across the nuclear chart: from light to superheavy and from stable to short-lived systems. Six different Energy Density Functionals (EDFs) were used to assess systematic errors in our calculations. These results are to be added to the website Massexplorer (http://massexplorer.frib.msu.edu/) which contains results from earlier mass table calculations and information on single quasiparticle energies.

  20. Understanding ebola virus transmission.

    Science.gov (United States)

    Judson, Seth; Prescott, Joseph; Munster, Vincent

    2015-02-03

    An unprecedented number of Ebola virus infections among healthcare workers and patients have raised questions about our understanding of Ebola virus transmission. Here, we explore different routes of Ebola virus transmission between people, summarizing the known epidemiological and experimental data. From this data, we expose important gaps in Ebola virus research pertinent to outbreak situations. We further propose experiments and methods of data collection that will enable scientists to fill these voids in our knowledge about the transmission of Ebola virus.