nils-herrmann/clean_scirepeval huggingface dataset:
Distributed backup scheduling: Modeling and optimization

Recent years have seen rapid growth in data storage, magnifying the importance of ensuring data safety by performing regular backups. However, traffic created by such backups can be a significant burden on the underlying communication network. In the present paper we address the tradeoff between frequent backups (increased safety) and reducing the network peak load. We address the problem of shifting backup traffic from peak hours to off-peak hours within the constraints imposed by user connectivity. Backups are scheduled using a distributed protocol characterized by a set of probabilities that indicate the likelihood of a user initiating a backup during a given hour. Given these probabilities, we study the network capacity by investigating the rate at which users can generate data while retaining stable backlog processes. We then derive explicit expressions for the stationary behavior of the backup process, and discuss how to choose the backup probabilities that strike the right balance between a low peak load and data safety. Via simulation experiments we show that this approach is highly successful in reducing costs.
An Enhanced $Ka$ -Band Reflector Focal-Plane Array Using a Multifeed EBG Structure

This letter presents a first step toward the design of an enhanced multifeed EBG structure that serves as a focal-plane array for a Ka-band reflector for space applications in the 29.5-30-GHz band. The desired Earth coverage is the starting point for the antenna design. As shown in this letter, significant coupling can deteriorate the performance of the multifeed EBG antenna. In order to demonstrate this, the results are compared to those of the single-feed reflector antenna. Filters are then connected to the multifeed antenna ports to control the coupling in a constructive way and obtain good radiation characteristics. Finally, the global feed architecture (EBG structure + filters) is used to illuminate a reflector antenna in order to characterize the antenna performance (C/I ratio, EoC gain).
Conversion of free-viewpoint 3D multi-view video for stereoscopic displays

This paper presents our ongoing research on view synthesis of free-viewpoint 3D multi-view video for 3DTV. With the emerging breakthrough of stereoscopic 3DTV, we have extended a reference free-viewpoint rendering algorithm to generate stereoscopic views. Two similar solutions for converting free-viewpoint 3D multi-view video into a stereoscopic vision have been developed. These solutions take into account the complexity of the algorithms by exploiting the redundancy in stereo images, since we aim at a real-time hardware implementation. Both solutions are based on applying a horizontal shift instead of double execution of the reference free-viewpoint rendering algorithm for stereo generation (FVP stereo generation), so that the rendering time can be reduced by as much as 30–40 %. The trade-off however, is that the rendering quality is 0.5–0.9 dB lower than when applying FVP stereo generation. Our results show that stereoscopic views can be efficiently generated from 3D multi-view video by using unique properties in stereoscopic views, such as identical orientation, similarities in textures and small baseline.
Impact of Mutual Coupling in Leaky Wave Enhanced Imaging Arrays

The impact of mutual coupling between neighboring radiators in an imaging array configuration in the presence of a dielectric super-layer is investigated. The super-layer generally aims at increasing the directivity of each element of the array. However, here it is shown that the directivity of the embedded element patterns are reduced by a high level of mutual coupling. Thus a trade off between directivity enhancement and close packing of the array elements must be found depending on the bandwidth and the pattern requirements.
Reflections inside an elliptical dielectric lens antenna

The reflections inside the elliptical lens of a typical millimetre wave antenna are investigated. In particular, it is seen that these reflections may significantly affect the input impedance of a radiating element which is located at the lens focus, owing to the presence there of a point caustic of doubly reflected rays. The presence of a caustic prevents the field prediction inside the lens by a direct application of geometrical optics. Consequently, the field inside the lens is calculated by means of the physical optics currents associated with singly and doubly reflected rays.
CMOS low-voltage operational amplifiers with constant-G/sub m/ rail-to-rail input stage

Two 3-V CMOS low-voltage operational amplifiers (op-amps) with constant transconductance (g/sub m/) rail-to-rail input stages are presented. The constant g/sub m/ ensures a constant unity-gain frequency within the whole common-mode input range. Two new methods to control the g/sub m/ of the input stage are introduced. The op-amps contain the same class-AB output stage with rail-to-rail output swing. The common-mode input voltage swing extends the positive supply rail by 600 mV and the negative supply rail by 200 mV. The output voltage can reach the supply rails within 130 mV. The output current of the op-amps was limited to +or-2 mA, voltage gain was 85 dB, and the unity-gain frequency was 165 kHz. The op-amps were integrated in a semicustom CMOS process with transistor lengths of 10 mu m.<<ETX>>
GPU-accelerated real-time free-viewpoint DIBR for 3DTV

Multi-view 3D video may succeed stereo 3DTV in multimedia and TV applications. The MPEG committee has installed a special task force to establish a standard for multiview 3D video coding. Enabling free-viewpoint selection by the consumer is one of the major purposes of multi-view 3D encoded data. One focal point of our research work concerns an efficient implementation of the rendering part of stereoscopic free-viewpoint visualization, which is a computationally expensive task and significantly determines the final image quality. The free-viewpoint DIBR algorithm that is described in this article is implemented with an off-theshelf GPU that can be integrated in advanced 3DTV systems. We present the principal steps of a representative freeviewpoint DIBR, based on image warping and image artifact reduction techniques, and show the key differences between the reference software and our GPU implementation. One of those differences is the joint execution of signal processing blocks to share memory usage. Using a combination of the highly parallel programming architecture CUDA and a graphics API, we have achieved real-time performance executing 1080p HD multi-view video with a rendering quality that is comparable to the software implementation.
Beamforming in the Presence of Mutual Coupling Based on Constrained Particle Swarm Optimization

Two approaches towards beamforming based on constrained particle swarm optimization (PSO) are presented. One approach relies on the penalty function method, for which a new mathematical expression to select the penalty factors is derived. The other method uses a new PSO strategy for solving constrained optimization problems. To maximize performance of the beamforming procedure, the optimal system parameters for the PSO algorithm are derived. Mutual coupling and platform effects are fully accounted for by using the measured active element radiation patterns. The new PSO strategy is compared with a standard genetic algorithm. Using the measured radiation patterns of a seven-element antenna array, a real-life example is presented that demonstrates the possibilities of the new approach.
Issues Dealing with Non-Functional Requirements across the Contractual Divide

Agreement on Non-Functional Requirements between customer and supplier is crucial to a successful IT solution delivery project. In an ideal world, stakeholders and architects cooperate to achieve their common goals in a win-win situation. In a commercial setting, however, one dominant feature often introduces powerful forces from outside the technical realm. That feature is the customer/supplier relationship, usually formalized in bidding rules or as a delivery contract. Formal customer/supplier relationships often place severe limitations on information exchange between stakeholders and architects. In this paper, we explore the effect of such limitations on the interaction of architectural design with the quantification of Non-Functional Requirements, and explore a number of avenues to deal with them.
Transmission enhancement between rectangular waveguides by means of left-handed media

Results showing the experimental verification of the transmission improvement when a left-handed material (LHM) is placed in between rectangular waveguides are presented. This improvement has been characterised by means of measuring the increase of transmission (S/sub 21/ parameter) and is related to the enhancement of the radiating features of an open-ended waveguide caused by the use of the LHM as superstrate.
Efficient reflector illumination by an EBG enhanced aperture

This paper deals with the use of EBG super-layers to improve the shape of the illumination function of a center- fed reflector. Following an investigation of the leaky wave pole singularities of the EBG Green's function, the shape of the radiation patterns of small apertures in ground planes are optimized by properly tuning the super layers geometrical parameters. A prototype of such feed has been designed, manufactured and tested. The results indicate that the inclusion of the EBG provides an aperture efficiency of the feed+reflector system with values higher than 80%, over a 10% bandwidth.
Early Human Visual Cortex Encodes Surface Brightness Induced by Dynamic Context

Visual scene perception owes greatly to surface features such as color and brightness. Yet, early visual cortical areas predominantly encode surface boundaries rather than surface interiors. Whether human early visual cortex may nevertheless carry a small signal relevant for surface perception is a topic of debate. We induced brightness changes in a physically constant surface by temporally modulating the luminance of surrounding surfaces in seven human participants. We found that fMRI activity in the V2 representation of the constant surface was in antiphase to luminance changes of surrounding surfaces (i.e., activity was in-phase with perceived brightness changes). Moreover, the amplitude of the antiphase fMRI activity in V2 predicted the strength of illusory brightness perception. We interpret our findings as evidence for a surface-related signal in early visual cortex and discuss the neural mechanisms that may underlie that signal in concurrence with its possible interaction with the properties of the fMRI signal.
Real-time face recognition for smart home applications

We propose a near real-time face recognition system for consumer/embedded applications. The system is embedded in an interconnected home environment and enables intelligent servicing by automatic identification of users. It consists of four processing steps: (1) face detection by stepwise pruning, (2) model-based facial feature extraction, (3) face normalization by affine warping, and (4) face recognition by discrimination analysis. The system has been applied in daily life rooms using ordinary cameras. Under these conditions, it achieves over 95% recognition rate and 4 frames/s processing speed.
An approximation method for a processor sharing queue with controlled arrivals and a waitbuffer

Consider a stored program controlled telephone exchange that is offered two different types of jobs, viz. call request and operator tasks. The main objective of the telephone company would be to handle as many call requests as possible. Accepting all incoming call requests however, would lead to very long sojourn times when the arrival rate of these jobs is high. One can prevent this by restricting the maximum number of call requests that can be in service. Call requests that arrive when the number of call requests in service is equal to the maximum, are rejected and considered lost. At the same time the exchange has to deal with the operator tasks that are necessary for the correct operation of the exchange. The jobs can not be rejected but delayed for some time. To guarantee a correct behaviour of the exchange this delay must not be too large. An approximation method is presented for a queueing model in which operator tasks are not allowed to be rejected. Approximate formulas are derived for the probability that an operator task is delayed, and for the mean and variance of the waiting times for delayed tasks. Numerical results are presented, showing that the approximation is accurate (relative errors smaller than 5%) under certain conditions.<<ETX>>
Optimized basis functions for slot antennas excited by coplanar waveguides

A method is proposed for the analysis of slot antennas excited by coplanar waveguides. First, a standard integral equation for the continuity of the magnetic field is formulated. Then the appropriate equivalent magnetic currents of the method of moments are represented in terms of entire-domain basis functions which synthesize the resonant behavior of the slot and the field in proximity of the feeding source and of the bends. In order to define these basis functions, canonical geometries are identified, whose Green's functions have been found analytically. The accuracy and the effectiveness of the method in terms of convergence rate and number of unknowns is demonstrated by comparison with a standard fine meshing full-wave analysis.
RF-CMOS Performance Trends

The impact of scaling on the analog performance of MOS devices at RF frequencies was studied. Trends in the RF performance of nominal gate length NMOS devices from 350-nm to 50-nm CMOS technologies are presented. Both experimental data and circuit simulations with an advanced validated compact model (MOS Model 11) have been used to evaluate the RF performance. RF performance metrics such as the cutoff frequency, maximum oscillation frequency, power gain, noise figure, linearity, and 1 noise were included in the analysis. The focus of the study was on gate and drain bias conditions relevant for RF circuit design. A scaling methodology for RF-CMOS based on limited linearity degradation is proposed.
Experiments with patch-based object classification

We present and experiment with a patch-based algorithm for the purpose of object classification in video surveillance. A feature vector is calculated based on template matching of a large set of image patches, within detected regions-of-interest (ROIs, also called blobs), of moving objects. Instead of matching direct image pixels, we use Gabor-filtered versions of the input image at several scales. We present results for a new typical video surveillance dataset containing over 9,000 object images. Additionally, we show results for the PETS 2001 dataset and another dataset from literature. Because our algorithm is not invariant to the object orientation, the set was split into four subsets with different orientation. We show the improvements, resulting from taking the object orientation into account. Using 50 training samples or higher, our resulting detection rate is on the average above 95%, which improves with the orientation consideration to 98%. Because of the inherent scalability of the algorithm, an embedded system implementation is well within reach.
Facial feature extraction using a cascade of model-based algorithms

We present a cascaded framework for robust and accurate facial feature extraction. In this framework, we propose the following three model-based algorithms: (1) constrained global deformation using a sparse feature representation; (2) component texture fitting using direct parameter estimation by SVR, and (3) component feature refinement by direct optimization. The algorithms capture different characteristics of facial features, giving various extraction performances in terms of robustness (convergence) and accuracy. To achieve both high accuracy and robustness, we cascade these algorithms into a chain, where each algorithm progressively 'pulls' the model closer to the correct position. Experiments show that the combined algorithm achieves a large convergence area and high accuracy.
Color transformation for improved traffic sign detection

This paper considers large scale traffic sign detection on a dataset consisting of high-resolution street-level panoramic photographs. Traffic signs are automatically detected and classified with a set of state-of-the-art algorithms. We introduce a color transformation to extend a Histogram of Oriented Gradients (HOG) based detection algorithm to further improve the performance. This transformation uses a specific set of reference colors that aligns with traffic sign characteristics, and measures the distance of each pixel to these reference colors. This results in an improved consistency on the gradients at the outer edge of the traffic sign. In an experiment with 33, 400 panoramic images, the number of misdetections decreased by 53.6% and 51.4% for red/blue circular signs, and by 19.6% and 28.4% for yellow speed bump signs, measured at a realistic detector operating point.
Content-adaptive image enhancement, based on sky and grass segmentation

Current TV image enhancement functions employ globally controlled settings. A more flexible system can be achieved if the global control is extended to incorporate semantic-level image content information. In this paper, we present a system that extends existing TV image enhancement functions with control signals that are adaptive to grass and sky areas in the image. We investigate whether this content-adaptive control can offer higher levels of enhancement compared to the current global control approach. Our simulations on 117 natural images show that the mean square pixel value difference from optimally enhanced images reduces with 60%, when content-adaptive control is employed instead of a global controlled approach.
Guided Rule-Based Multi-objective Optimization for Real-Time Distributed Systems

Automated optimization of real-time architectures with respect to cost, performance, robustness and safety has received considerable attention in the last decade. In this paper, we present an automated Design Space Exploration (DSE)method based on both a multi-objective genetic algorithm and a heuristic particle-swarm-optimization technique. The optimization process is guided to desired solutions by weight coefficients that are assigned to the system objectives. The proposed method automatically generates architecture alternatives by changing hardware topology and mapping the tasks on different nodes, CPUs and by modifying their execution priority. Based on multiple quality objectives, the optimization method concludes to the Pareto-optimal solution set of the architecture alternatives. Moreover, in this paper we present an addition to the pre-existing optimization heuristics, targeting the reduction of the exploration time and maintaining a high-quality Pareto-optimal solution set. Finally, we compare the NSGA-II algorithm against the OMOPSO and their "Rule-Based Initial Population versions", for the convergence speed and the quality of their solutions, by comparing the hyper volume and the epsilon quality indicators. The proposed DSE approach has been applied to an autonomously navigating robot system consisting of several processing nodes (real-time distributed system) and resulting into better optimized and balanced solutions when compared to the proposed system architecture by an architect specialist.
Thin AMC Structure for Radar Cross-Section Reduction

A thin artificial magnetic conductor (AMC) structure is designed and breadboarded for radar cross-section (RCS) Reduction applications. The design presented in this paper shows the advantage of geometrical simplicity while simultaneously reducing the overall thickness (for the current design ). The design is very pragmatic and is based on a combination of AMC and perfect electric conductor (PEC) cells in a chessboard like configuration. An array of Sievenpiper's mushrooms constitutes the AMC part, while the PEC part is formed by full metallic patches. Around the operational frequency of the AMC-elements, the reflection of the AMC and PEC have opposite phase, so for any normal incident plane wave the reflections cancel out, thus reducing the RCS. The same applies to specular reflections for off-normal incidence angles. A simple basic model has been implemented in order to verify the behavior of this structure, while Ansoft-HFSS software has been used to provide a more thorough analysis. Both bistatic and monostatic measurements have been performed to validate the approach.
A 250 GHz Subharmonic Mixer Design Using EBG Technology

The design, manufacture and characterization of a sub-harmonic mixer operating in the millimeter wavelength range is described. The mixer combines for the first time electromagnetic band gap (EBG) technology (which improves the radiation features of the dipole antenna used to couple radiation to the mixer), with conventional local oscillator (LO) waveguide circuitry. The mixer is designed to operate in an RF frequency band around 250 GHz when supplied with a LO frequency between 115 and 135 GHz. The fixed IF frequency spans 2.5-3.5 GHz. Performance predictions were made using a combination of the finite elements (FE) method to compute the embedding impedance of the diodes and the harmonic balance analysis (HBA) to predict the noise temperature. A prototype mixer has been fabricated and tested. Best mixer performance (double side band (DSB) mixer noise temperature and conversion loss of 3000 K and 11.5 dB, respectively) was measured with a LO power level of about 5 mW. Good agreement is observed with the predicted performance.
Automated Generation of Road Marking Maps from Street-level Panoramic Images

Accurate maps of road markings are useful for many applications, such as road maintenance, improving navigation, and prediction of upcoming road situations within autonomously driving vehicles. This paper introduces a generic and learning-based system for the recognition of road markings from street-level panoramic images. This system starts with an Inverse Perspective Mapping, followed by segmentation to retrieve road marking candidates. The contours of all found segments are classified, after which a Markov Random Field is applied to adjust the resulting probabilities based on the surrounding context. Finally, the spatial placement of the found individual markings (e.g. shark teeth) is analyzed to retrieve the traffic situations (e.g. priority situations). This system is evaluated for priority, block, striped lines and pedestrian crossing markings, and is able to recognize 80-95% of the individual markings, and about 90% of the occurring situations (e.g. pedestrian crossings).
A high power 270 GHz frequency tripler featuring a Schottky diode parallel pair

A high output power millimetre wave frequency tripler is reported. Important features of the diode mount include a planar waveguide probe which facilitates the parallel combination of two Schottky varactor diodes and provides them with a more ideal embedding impedance. This approach allows for higher power production and handling ability than a similar device using a single diode. Maximum output power at 271 GHz is 15 mW with a flange to flange efficiency of /spl ap/5%.