Real-time Representation Research Articles

Real-Time Representations of the Output Gap

Methods are described for the appropriate use of data obtained and analysed in real time to represent the output gap. The methods employ cointegrating VAR techniques to model real-time measures and realizations of output series jointly. The model is used to mitigate the impact of data revisions; to generate appropriate forecasts that can deliver economically meaningful output trends and that can take into account the end-of-sample problems encountered in measuring these trends; and to calculate probability forecasts that convey in a clear way the uncertainties associated with the gap measures. The methods are applied to data for the United States 1965q4–2004q4, and the improvements over standard methods are illustrated.

N-Particle Scattering Matrix for Electrons Interacting on a Quantum Dot

We present a nonperturbative expression for the scattering matrix of N particles interacting inside a quantum dot. Characterizing the dot by its resonances, we find a compact form for the scattering matrix in a real-time representation. We study the transmission probabilities and interaction-induced orbital entanglement of two electrons incident on the dot in a spin-singlet state.

Generation of Reference Material by the Use of Multiple Displacement Amplification (MDA) for the Detection of Genetically Modified Organisms (GMOs)

The identification of genetically modified (GM) organisms (GMOs) in unknown samples by polymerase chain reaction (PCR) requires the use of a positive control sample, containing the target sequence derived from the respective GMO. For this purpose, either DNA extracted from suitable reference material or plasmids bearing the sequence are used. In the case of isolated genomic DNA, the preparation is cost-intensive and time-consuming, and material availability may be limited. Once the sequence is cloned into a plasmid, it may be simpler and less cost-intensive to purify the DNA, but contamination risk is substantially higher. The potential of multiple displacement amplification (MDA) as a new tool to generate reference material for GMO detection was studied taking the GM maize MON810 as a case. MDA yield of maize-specific DNA and amplification efficiency in dependence of the amount of starting material were estimated using real-time PCR. Applicability of the amplified DNA for the use as reference material was tested with regard to real-time PCR performance and MDA bias. Depending on the amount of genomic DNA (gDNA) input into MDA, amplification rates in the range of 30-fold (100 ng input of gDNA) to 23,000-fold (0.1 ng input of gDNA) were achieved. Real-time PCR performance and gene representation of amplified DNA (mdaDNA) are comparable to those of gDNA. Our results demonstrate that the DNA amplified by MDA is suitable for the use as reference material for qualitative GMO analysis.

Real-time representation of multielectrode ablation catheters by integration of computed tomographic geometry with three-dimensional electroanatomic mapping of left atrium and pulmonary veins

t B f s t P l s a S t v A m c t f w t R l A 36-year-old man without apparent structural heart disase was referred for catheter ablation of atrial fibrillation. e had weekly episodes of palpitations that were resistant to iltiazem, propranolol, and flecainide. Short bursts of atrial achycardia and fibrillation were demonstrated on ECGs and 4-hour ambulatory ECG Holter monitoring recorded on ifferent days. The patient underwent 64-detector multislice omputed tomography (CT) of the left atrium and pulmoary veins before the ablation procedure. A 24-pole ring-shaped catheter (yellow in Figure 1) and custom octapolar ablation catheter (white in Figure 1) ere introduced into the left atrium for mapping and abla-

DSA-Visualisation Monitoring and Ranking of System Dynamic Behaviour

The paper presents the application of a software tool to simulate system dynamic behavior together with the possibility to select critical contingencies of an electrical energy system. These cases are visualized and a ranking decision is introduced to support the operators to select critical system states. Insecure operating conditions can be monitored in the time domain using the full system representation in real time or by calculating the eigenvalues of the system to monitored weakly damped system states and stability margins.

Design evaluation and modification of mechanical systems in virtual environments

Design is one of the most important stages in the manufacturing cycle and influences all the subsequent stages of product development. In the context of today’s iterative design methodology, the modification of any design is a process involving many evaluations and improvements to the solutions chosen in earlier stages. For this purpose, in the most recent decade, 3D computer simulations have become common tools used within industry. Whilst virtual reality (VR) technology is seen as the interaction technology of the future, much of the current research in this area is carried out to explore the potential benefits and added value brought by the integration of this into standard software technologies currently used at various stages in manufacturing life cycle. A lot of attention has been given to exploring the usability and benefits of interactive VR for assembly planning, knowledge elicitation and design and simulation. However, little research has focussed on the analytical aspects of the design process, for example in the use of VR as an interface for simulation software in finite element methods and multi-body systems. This paper introduces research focussing on applications of virtual environments (VEs) for interactive design evaluation and modification adapted and used with standard simulation software. The use of such interactive visualisation offers the engineer more realistic real-time representations of the design and advanced facilities to interact with the model during the design process. While design evaluation is based mainly on visualisation; design modification requires interactive changes of the model during the simulation, and the interfaces described here highlights such applications. In this work, two software prototypes have been developed using VR technology. First, a software tool called design evaluation in virtual environments is presented together with an application in civil engineering to illustrate the mode of operation and added value of the use of an interactive visualisation environment. Linking the simulation software with the VE provides real time bi-directional communication of graphical information which can be successfully achieved even within the limits of current computer technology. The tool includes a suite of software modules and a user interface to facilitate the link between the simulation results and the VE. The second tool facilitates the design modification in virtual environments system by providing real time dynamic simulation. Two dynamic approaches are investigated in order to study the real time simulation issues in the context of design modification and system performance: the classic approach based on rigid interconnected bodies, and a new and novel approach developed by the authors based on particles dynamics. Both implementations have been tested and compared on a mechanism application under the same computing conditions. The research applications presented demonstrate the practicality, flexibility and versatility of the visualisation in virtual environment in design evaluation and modification. However, the computer efficiency whilst carrying out real time dynamic simulation is limiting the range of applications to models of moderate size; however, this is an improvement on previous similar applications.

Spin relaxation in a generic two-dimensional spin-orbit coupled system

We study the relaxation of a spin density injected into a two-dimensional electron system with generic spin-orbit interactions. Our model includes the Rashba as well as linear and cubic Dresselhaus terms. We explicitly derive a general spin-charge coupled diffusion equation. Spin diffusion is characterized by just two independent dimensionless parameters which control the interplay between different spin-orbit couplings. The real-time representation of the diffuson matrix (Green's function of the diffusion equation) is evaluated analytically. The diffuson describes space-time dynamics of the injected spin distribution. We explicitly study two regimes: The first regime corresponds to negligible spin-charge coupling and is characterized by standard charge diffusion decoupled from the spin dynamics. It is shown that there exist several qualitatively different dynamic behaviors of the spin density, which correspond to various domains in the spin-orbit coupling parameter space. We discuss in detail a few interesting phenomena such as an enhancement of the spin relaxation times, real space oscillatory dynamics, and anisotropic transport. In the second regime, we include the effects of spin-charge coupling. It is shown that the spin-charge coupling leads to an enhancement of the effective charge diffusion coefficient. We also find that in the case of strong spin-charge coupling, the relaxation rates formally become complex and the spin/charge dynamics is characterized by real time oscillations. These effects are qualitatively similar to those observed in spin-grating experiments [Weber et al., Nature 437, 1330 (2005)].

Low-Cost Telepresence for Collaborative Virtual Environments

We present a novel low-cost method for visual communication and telepresence in a CAVE -like environment, relying on 2D stereo-based video avatars. The system combines a selection of proven efficient algorithms and approximations in a unique way, resulting in a convincing stereoscopic real-time representation of a remote user acquired in a spatially immersive display. The system was designed to extend existing projection systems with acquisition capabilities requiring minimal hardware modifications and cost. The system uses infrared-based image segmentation to enable concurrent acquisition and projection in an immersive environment without a static background. The system consists of two color cameras and two additional b/w cameras used for segmentation in the near-IR spectrum. There is no need for special optics as the mask and color image are merged using image-warping based on a depth estimation. The resulting stereo image stream is compressed, streamed across a network, and displayed as a frame-sequential stereo texture on a billboard in the remote virtual environment.

On algorithmic rate-coded AER generation

This paper addresses the problem of converting a conventional video stream based on sequences of frames into the spike event-based representation known as the address-event-representation (AER). In this paper we concentrate on rate-coded AER. The problem is addressed as an algorithmic problem, in which different methods are proposed, implemented and tested through software algorithms. The proposed algorithms are comparatively evaluated according to different criteria. Emphasis is put on the potential of such algorithms for a) doing the frame-based to event-based representation in real time, and b) that the resulting event streams ressemble as much as possible those generated naturally by rate-coded address-event VLSI chips, such as silicon AER retinae. It is found that simple and straightforward algorithms tend to have high potential for real time but produce event distributions that differ considerably from those obtained in AER VLSI chips. On the other hand, sophisticated algorithms that yield better event distributions are not efficient for real time operations. The methods based on linear-feedback-shift-register (LFSR) pseudorandom number generation is a good compromise, which is feasible for real time and yield reasonably well distributed events in time. Our software experiments, on a 1.6-GHz Pentium IV, show that at 50% AER bus load the proposed algorithms require between 0.011 and 1.14 ms per 8 bit-pixel per frame. One of the proposed LFSR methods is implemented in real time hardware using a prototyping board that includes a VirtexE 300 FPGA. The demonstration hardware is capable of transforming frames of 64 x 64 pixels of 8-bit depth at a frame rate of 25 frames per second, producing spike events at a peak rate of 10(7) events per second.

APB: An Adaptive Playback Buffer Scheme for Wireless Streaming Media

The wireless streaming media communications are fragile to the delay jitter because the conditions and requirements vary frequently with the users' mobility. Buffering is a typical way to reduce the delay jitter of media packets before the playback, however, it will incur a longer end-to-end delay. Our motivation in this paper is to improve the balance between the elimination of delay jitter and the decrease of end-to-end delay. We propose a novel adaptive playback buffer (APB) based on the probing scheme. By utilizing the probing scheme, the instantaneous network situations are collected, and then the delay margin and the delay jitter margin are employed to calculate the step length (sl) which is used to adjust the playback buffer in each time. The adaptive adjustment to the playback buffer in APB enables the continuous and real-time representation of streaming media at the receiver. Unlike the previous studies, the novelty and contributions of the paper are: a) Accuracy: by employing the instantaneous network information, the adjustment to the playback buffer correctly reflects the current network situations and therefore achieves the improved balance between the elimination of delay jitter and the decrease of end-to-end delay; Hence. APB adjustment is accurate in terms of improving such balance; b) Efficiency: by utilizing the simple probing scheme, APB achieves the current network situations without the complex mathematic predictions, which enables the adjustment to be more timely and efficient. Performance data obtained through extensive simulations show that our APB is effective to reduce both delay jitter and playback buffer delay.

Unrestricted TDHF studies of nuclear response in the continuum

The TDHF dynamics in the small-amplitude regime is studied in the real-space and real-time representation. The continuum is taken into account by introducing a suitable complex potential. This is equivalent to the continuum random-phase approximation and applicable to deformed nuclei.

Identification of network-level coding units for real-time representation of episodic experiences in the hippocampus

To examine the network-level organizing principles by which the brain achieves its real-time encoding of episodic information, we have developed a 96-channel array to simultaneously record the activity patterns of as many as 260 individual neurons in the mouse hippocampus during various startling episodes. We find that the mnemonic startling episodes triggered firing changes in a set of CA1 neurons in both startle-type and environment-dependent manners. Pattern classification methods reveal that these firing changes form distinct ensemble representations in a low-dimensional encoding subspace. Application of a sliding window technique further enabled us to reliably capture not only the temporal dynamics of real-time network encoding but also postevent processing of newly formed ensemble traces. Our analyses revealed that the network-encoding power is derived from a set of functional coding units, termed neural cliques, in the CA1 network. The individual neurons within neural cliques exhibit "collective cospiking" dynamics that allow the neural clique to overcome the response variability of its members and to achieve real-time encoding robustness. Conversion of activation patterns of these coding unit assemblies into a set of real-time digital codes permits concise and universal representation and categorization of discrete behavioral episodes across different individual brains.

Virtual Test Track

The virtual test track (VTT) is a real-time vehicle simulator used for powertrain and chassis system development in a virtual environment. The VTT is designed and built based on the rapid control prototyping (RCP) concept. Therefore, different from the conventional vehicle simulator, the VTT can provide many additional benefits, such as ease of use, flexibility of interface with other devices, and ability to easily implement any hardware-in-the-loop system. The VTT consists of a powerful simulation engine to solve the equations of a complicated vehicle dynamics model in real-time and a sophisticated animation engine to provide real-time visual representation of vehicle behavior. It also contains multiple virtual test environments with variable surfaces and weather conditions to provide different types of driving conditions.

Transport theory of interacting mesoscopic systems: A memory-function approach to charge-counting statistics

We address the subtle problem of formulating mesoscopic transport phenomena in the language of many-body physics. We propose a microscopic description in which the whole system (sample, leads, and detectors) is given fully-quantum-mechanical treatments. The dynamics of the system is obtained from the projection, or memory-function, formalism of nonequilibrium statistical mechanics combined with recent prescriptions for measurements that are extended in the time domain. The associated irreversible quantum dynamics contains an intrinsic doubling of the degrees of freedom identical to the real-time path-integral representation of the Keldysh formalism. We derive a simple formula relating the generating function of the charge-counting statistics to the single-particle matrix Green's function of the interacting system, thereby generalizing the Levitov-Lesovik functional determinant formula. We report an interesting sample-leads duality in our description, which has a simple interpretation in the regime of noninteracting particles, thus establishing the equivalence between the Green's-function technique and the random scattering-matrix approach. We discuss the physical conditions, within the present scheme, for the validity of the Landauer-Buttiker description of mesoscopic transport. We conclude by providing an exact solution for the problem of charge transfer into a noninteracting ballistic cavity in the presence of a periodic time-dependent voltage, using the supersymmetry method.

Vector Doppler: spatial sampling analysis and presentation techniques for real time systems

The aim of the vector Doppler (VD) technique is the quantitative reconstruction of a velocity field independent of the ultrasonic probe axis to flow angle. In particular, vector Doppler is useful for studying vascular pathologies related to complex blood flow conditions. Clinical applications require a real-time operating mode and the capability to perform Doppler measurements over a defined volume. The combination of these two characteristics produces a real-time vector velocity map. In previous works we investigated the theory of pulsed-wave (PW) vector Doppler and developed an experimental system capable of producing off-line 3-D vector velocity maps. Afterward, for producing dynamic velocity vector maps, we realized a new 2-D vector Doppler system based on a modified commercial echograph. The measurement and presentation of a vector velocity field requires correct spatial sampling that must satisfy the Shannon criterion. In this work we tackle this problem, establishing a relationship between sampling steps and scanning system characteristics. Another problem posed by the vector Doppler technique is the data representation in realtime that should be easy to interpret for the physician. With this in mind we attempt a multimedia solution that uses both interpolated images and sound to represent the information of the measured vector velocity map. These presentation techniques are tested for real-time scanning on flow phantoms and preliminary measurements in vivo on a human carotid artery.

Petabyte‐class video archive system with large‐scale automatic tape feed robot

AbstractIn order to supply a volume of digital video content in the digitalization of broadcasting, it is necessary to realize a method of storing a large number of videos and of high‐speed content retrieval. This paper describes a petabyte (1015 power) large‐capacity video archive system and its retrieval method. The archive system employs an automatic magnetic tape feed robot that can accommodate 7200 tapes (15,000 hours) in its center, and an HDD server and a DVD server respectively for each purpose, thus making the efficiency of storage and distribution better and realizing retrieval, video delivery, and remote editing from remote sites. Further, a method of detection of scene change points in a video sequence, a method of browsing video production based on the detected scene change points, and a method of visual retrieval by simultaneous playback representation of multiple videos on a screen are also included. In this paper, a large‐scale archive system that has an automatic tape feed robot at its center and a high‐speed and efficient method of retrieval of the target video using the real‐time playback representation of multiple videos are presented. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(8): 30–40, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10064

Real-time flat-panel pixel imaging system and control for X-ray and neutron detection

We present in this paper industrial nondestructive X-ray and neutron testing applications with a real-time digital imaging device and control system X-View based on active matrix flat-panel imager technology. X-View consists of X-ray or neutron converters, arrays of amorphous silicon (a-Si:H) thin-film transistors and photodiodes, a fast real-time electronic system for readout and digitization of images and appropriate computer tools for control, real-time image treatment data representation, and off-line analysis. Some basic image-quality parameters and different objects were assessed for quantitative and qualitative analysis. Results show a wide dynamic range (16 bits ADC resolution) and lack of blooming, a high frame rate (up to 25 fps), and rapid image capture. Images are directly displayed, on-line, on a PC monitor and archived in a digital form for radiography and radioscopy procedures and limitless industrial applications in X-ray and neutron inspections.

Pain and the body schema: evidence for peripheral effects on mental representations of movement.

Some accounts of body representations postulate a real-time representation of the body in space generated by proprioceptive, somatosensory, vestibular and other sensory inputs; this representation has often been termed the 'body schema'. To examine whether the body schema is influenced by peripheral factors such as pain, we asked patients with chronic unilateral arm pain to determine the laterality of pictured hands presented at different orientations. Previous chronometric findings suggest that performance on this task depends on the body schema, in that it appears to involve mentally rotating one's hand from its current position until it is aligned with the stimulus hand. We found that, as in previous investigations, participants' response times (RTs) reflected the degree of simulated movement as well as biomechanical constraints of the arm. Importantly, a significant interaction between the magnitude of mental rotation and limb was observed: RTs were longer for the painful arm than for the unaffected arm for large-amplitude imagined movements; controls exhibited symmetrical RTs. These findings suggest that the body schema is influenced by pain and that this task may provide an objective measure of pain.

Estimate of discrete nonlinearities in a mainly linear dynamic system

The class of system considered is a single degree of freedom undamped vibrating system with a clearance in which the dynamical behavior is described by a state-space representation in real time. The direct identification technique for the estimate of a clearance and other parameters in the system is presented in terms of least squares method and stepby-step iteration approach. For numerical simulation purpose, the simulated data are achieved by corrupting the modeled responses. The mathematical algorithm, which is put forward, has proven to be effective through a practical numerical example.

Computer Vision Detection System for Network Model Validation

A computer vision-based traffic detection system has been developed and tested that is capable of uniquely identifying vehicles in a traffic network from video images and later reidentifying them at other detection sites in the network. This capability may serve as the basis for deterministic validation of microscopic network flow models, origin-destination tables, and travel-time tables. The system is referred to as the video-based vehicle signature analysis and tracking system. With video cameras used as primary sensors, detection modules generate a numeric video signature vector (VSV) for each vehicle and transmit them to a central Internet-connected correlation computer via a public low-power wireless network. The correlation computer attempts to match vehicles, as represented by their VSVs, generated at successive detection sites to enable a sampled real-time microscopic flow representation of a freeway network. Test results indicate 93.6 percent accuracy in correctly reidentifying vehicles at successive sites. The tendency of the system to incorrectly match different vehicles at successive sites was measured at 0.0116 percent. Potential advantages are low cost in widespread deployment, simplicity and reliability of detection, minimal bandwidth and storage requirements for transmission of the VSV, and reasonable identification ability without violation of privacy rights. The primary disadvantages are the requirement to place video cameras above each traffic lane and video imaging limitations related to reliance on ambient illumination.