nils-herrmann/clean_scirepeval huggingface dataset:
3D TWT modeling and experimental validation

The ability to fully simulate the 3D effects of RF and space charge forces on the electron beam of a helix TWT during energy extraction is important for TWT design and optimization. A helix TWT simulator, CHRISTINE3D, has been developed to achieve this capability. Validation of code results is an important step to address before the code can be reliably used for TWT design. CHRISTINE3D has been used to compute the output power and efficiency of a C-Band TWT as a function of frequency and input drive power and showed excellent agreement with experimental results. The greatest value of the model, however, lies in its ability to calculate the full set of phase space information of all particles as they travel along the length of the simulation. This allows the determination of such parameters as beam expansion and spent beam distribution which can then be used to determine magnetic field profiles and collector design. This information is not available in a 1 D simulation and is critical for overall TWT design optimization. The TWT used for the validation exhibits forward helix intercept current for certain magnetic field configurations and is a good vehicle to test the beam expansion predictions of the simulator. Comparison of computed results with experimental data will be reported for several experimental configurations. Also, several spent beam distributions were computed for varying values of circuit efficiency. These distributions were also measured for comparison with prediction. The results presented will show good correlation between experiment and simulation for the wide range of magnetic field and distribution functions studied. These results give confidence in the predictive capability of the CHRISTINE3D TWT simulator and in the ability to understand and to continually improve TWT performance through simulation.
Cyclic Pursuit of mobile robots: A linear approach

Cyclic Pursuit is a distributed control law wherein competitive or non-cooperative local interactions among agents are used to achieve cooperative global behaviors. Due to their inherent nonlinear dynamics, unicycle models are widely used in designing cyclic pursuit control laws for mobile robots. This paper introduces a simplified technique for design of linear, distributed control laws for achieving cyclic pursuit among a group of differential drive mobile robots. The control laws discussed in this paper can be used to design simple yet fully functional cyclic pursuit algorithms. The efficacy of these linear control laws for mobile robots featuring nonlinear dynamics was verified through V-REP simulations.
Cell shunt resistance and photovoltaic module performance

The shunt resistance of solar cells in photovoltaic modules can affect module power output and could indicate flawed manufacturing processes and reliability problems. The authors describe a two-terminal diagnostic method to directly measure the shunt resistance of individual cells in a series-connected module nonintrusively, without de-encapsulation. Peak power efficiency vs. light intensity was measured on a 12-cell, series-connected, single crystalline PV module having relatively high cell shunt resistances. The module was remeasured with 0.5-, 1-, and 2-ohm resistors attached across each cell to simulate shunt resistances of several emerging technologies. Peak power efficiencies decreased dramatically at lower light levels. Using the PSpice circuit simulator, the authors verified that cell shunt and series resistances can indeed be responsible for the observed peak power efficiency vs. intensity behavior. They discuss the effect of basic cell diode parameters, i.e., shunt resistance, series resistance, and recombination losses, on PV module performance as a function of light intensity.
Channel allocation, power budget and bit error rate in hierarchical optical ring interconnection network (HORN)

Recent advances in computer processing speeds have resulted in a parallel processing environment in which the interconnection networks (INs) themselves are the limiting factor in terms of performance. Larger and faster INs can be implemented optically subject to the current limitation in the number of wavelengths imposed by optical switch and filter technology if the INs are arranged hierarchically, i.e. if the processing nodes are arranged in clusters and these clusters are connected together special routing nodes at one or more higher levels. HORN uses optically connected rings as the basic building blocks and connects these rings using an optical tree. Three key issues facing HORN are addressed in this paper: dynamic channel allocation (DCA), optical power budget (OPE) and bit error rate (BER). Four approaches to DCA are evaluated and a design trade-off is performed between them. The first two are taken from the literature while the last two are proposed here and exploit the multiple paths available in a hierarchical network. The evaluation of OPE and BER shows that HORN is feasible and practical when optical amplification is used at the initial signal insertion point for transmissions at higher levels in the hierarchy.
CHRISTINE 3D: a 3D multi-frequency large signal simulation code for helix traveling wave tubes

A generalization of the theory and implementation of the original CHRISTINE code to three dimensions will be described. The beam is treated as a collection of rays, rather than as disks as in 1D codes like CHRISTINE, and the complete 3D trajectories are followed by the code. This treatment permits the computation of helix intercept current and transverse beam distributions at the entrance to the collector-important design data that are unavailable from a 1D code. The beam may be initialized either by an internal parametric model, including transverse beam current distribution and beam temperature, or by importation of initial data from a gun code. The magnetic focusing field may also be represented by simple parametric models or by actual magnetic field data that is imported from a magnetics code. The RF fields supported by the helix are represented by modal expansion; the full (Bessel function) radial dependence is included. As in the original CHRISTINE, the new code employs models for sheath and tape helices that may be used in parametric studies. Alternatively, the code accepts a table of user-provided data for the circuit dispersion and interaction impedance. Also as in the original 1D code, the new code allows for tapered circuit properties, and for user specified attenuation profiles.
Design and deployment of a blood safety monitoring tool

Blood is a scarce resource critical to the management of a variety of life-threatening medical conditions. It can also be a medium for the transmission of infections, including HIV. Monitoring the quality and quantity of available blood, essential to utilizing it as effectively as possible, has been a challenge in many developing countries. This paper describes the design and implementation of a web-based tool to monitor the collection, screening and distribution of blood in developing countries. This project was conducted under the auspices of the US President's Emergency Plan for AIDS Relief (PEPFAR), which funds blood safety projects in 14 countries in Africa and the Caribbean. We report results from a usability study, formulate relevant design principles and discuss prospects for long-term sustainability.
Circuit Design for Surface Electromyography Data Acquisition

This paper presents a circuit design for data acquisition of Surface-Electromyographic Signals together with a description of the main signal characteristics. The proposed circuit is developed with integrated circuits, an instrumentation amplifier and active filters using operation amplifiers. This paper also demonstrates all the steps for deriving transfer functions and equations necessary for specifying the components. Simulations and experimental results, as well as signal capture with electrodes, are presented in order to validate the theoretical analyses carried out. Lastly, as it becomes clear within the text, the circuit shows an adequate behavior, being an interesting solution for data acquisition in Surface Electromyographic Systems.
Cross Correlation Characteristics of Large Scale Parameters in Urban Macro Cell

Extensive analysis of channel measurement data for the investigation of new channel models plays a fundamental role in designing and evaluating todays wireless communication systems. Besides the knowledge of the parameters and their distribution functions, the cross correlation between them is of great interest and can be exploited for more sophisticated channel simulations. In this contribution the cross correlation characteristics of the large scale parameters (LSP) in the power and delay domain are investigated for different parameter estimation procedures (taking the spatial filtering due to directional antennas into account or neglecting it), for various distance ranges between base station (BS) and mobile station (MS) as well as for different antenna heights.
Development of a fault tolerant distributed database via inference

The authors report on the experience of building a knowledge-based distributed database testbed on top of a commercial relational database to experiment with semantics for fault tolerance. This work sets out to test the philosophy that not only can syntactic redundancy (replication) be exploited to improve fault tolerance, but that most data are correlated, containing redundant information at the semantic level as well. The database must be engineered to make use of the inference engine to infer the inaccessible from the accessible data. The authors provide an overview of the architecture and discuss the data inference system, the knowledge schema, caching, the commercial database server, and database error handling.<<ETX>>
Edge-sensitive image restoration using order-constrained least squares methods

In this paper we consider a novel technique for the restoration of noise corrupted images, using order-constrained least squares methods. The restoration process uses a moving cross-shaped filter window, within which two operations are combined. The first operation consists of simple hypothesis tests for the presence of an edge of some minimal height δ, crossing the center of the window. The second operation computes the window output as the order-constrained least squares fit of the windowed values (if an edge is deemed to be present), or simply the average (if no edge is present). The new technique is applied to some actual noise corrupted images, and the results are compared to the results of applying similarly configured median and averaging filters. Some computational considerations and comparisons are discussed at the end of the paper.
A General Framework to Detect Unsafe System States From Multisensor Data Stream

This paper proposes a general framework for detecting unsafe states of a system whose basic real-time parameters are captured by multiple sensors. Our approach is to learn a danger-level function that can be used to alert the users of dangerous situations in advance so that certain measures can be taken to avoid the collapse. The main challenge to this learning problem is the labeling issue, i.e., it is difficult to assign an objective danger level at each time step to the training data, except at the collapse points, where a definitive penalty can be assigned, and at the successful ends, where a certain reward can be assigned. In this paper, we treat the danger level as an expected future reward (a penalty is regarded as a negative reward) and use temporal difference (TD) learning to learn a function for approximating the expected future reward, given the current and historical sensor readings. The TD learning obtains the approximation by propagating the penalties/rewards observable at collapse points or successful ends to the entire feature space following some constraints. This avoids the labeling issue and naturally allows a general framework to detect unsafe states. Our approach is applied to, but not limited to, the application of monitoring driving safety, and the experimental results demonstrate the effectiveness of the approach.
Adaptive compression of teleconference sequences using the LMS Algorithm

The Least Mean Squares (LMS) adaptive algorithm is applied to the problem of reducing the mean square power of the information sequence required for transmission of video or teleconferencing image sequences. The results of processing actual teleconferencing sequences are presented and compared with the results of using a fixed coefficient predictive algorithm. Operating on actual teleconferencing sequences averaging 2% - 12% moving area, the LMS adaptive filter is shown to provide approximately 1-4 dB reduction in transmitted sequence power when compared to a fixed coefficient filter. Further, the performance of the LMS adaptive system is shown to be quite insensitive to the value of the feedback gain parameter, α, for a wide range of α. This allows the user to achieve a substantial performance gain (compared to the fixed coefficient system) without encountering problems of adaptive filter stability.
Characterisation of Channel Measurements at 70GHz in Indoor Femtocells

A wideband, fully polarimetric and directional radio channel sounding campaign conducted at 70 GHz is presented. Measurement site was chosen as an entrance hall, featuring femtocell size. Transmitter and receiver were placed according to an access-point scenario. Initial large-scale parameters like excess-delay, delay-spread and angular spread are derived for channel characterisation. It is not the paper's goal to describe a new channel model. The main focus is the identification of propagation effects and characteristics, which have to be considered in future modelling. It was found, that first more specular than diffuse components occur and second the channel is spatially sparse.
Constructing finite state machines for fast gesture recognition

Proposes an approach to 2D gesture recognition that models each gesture as a finite state machine (FSM) in the spatial-temporal space. The model construction works in a semi-automatic way. The structure of the model is first manually decided based on the observation of the spatial topology of the data. The model is refined iteratively between two stages: data segmentation and model training. We incorporate a modified Knuth-Morris-Pratt algorithm recognition procedure to speed up recognition. The computational efficiency of the FSM recognizers allows real-time online performance to be achieved.
A flexible simulation tool for estimating data loss risks in storage arrays

It characterizes each array by five numbers, namely, the size n of the array, the number nf of simultaneous disk failures the array will always tolerate without data loss, and the respective fractions f1, f2 and f3 of simultaneous failures of nf + 1, nf + 2 and nf + 3 disks that will not result in a data loss. As with any simulation tool, Proteus imposes no restriction on the distributions of failure and repair events. Our measurements have shown a surprisingly good agreement with the results obtained through analytical techniques and no measurable difference between values obtained assuming deterministic repair times and those assuming exponential repair times.
Analytical theory of low frequency oscillations in gyrotrons

Low frequency oscillations attributed to reflected electrons bouncing adiabatically between the electron gun and the interaction space have been observed in many gyrotrons. An analytical model is considered which allows one to apply space-charge wave theory to the analysis of these oscillations. In the framework of the small signal theory, the regions of low frequency oscillations, the oscillation frequency and the temporal and spatial growth rates of low frequency oscillations are determined in the parameter relevant space. These results are consistent with some experimental data. They also allow recommending some means for suppressing low frequency oscillations.
A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress Within Arteriovenous Grafts

A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by dialysis needle flow impingement within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear stress. Preliminary in vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Both the simulations and the qualitative flow visualization measurements demonstrate that the adapter reduces the severity of the dialysis needle flow impingement on the vascular access graft.
Comparative analysis of the Curnow and Malykhin-Konnov-Komarov (MKK) circuits as representations of coupled-cavity slow-wave structures

Two lumped element models of coupled-cavity slow-wave structures, one due to Curnow (1965) and another due to Malykhin, Konnov, and Komarov (MKK) (2003), are compared. The basis of comparison is the level of accuracy with which the models reproduce the cold circuit phase velocity and characteristic impedance of the structures as functions of frequency, as obtained from numerical solutions of Maxwell's field equations. Two distinct types of coupled-cavity structure are analyzed using these two models. These are a C-band double staggered ladder circuit and an L-band slot coupled "Hughes-type" structure. We find for the C-band case, both the Curnow and MKK models give excellent representations of both the cavity and slot bands, but for the L-band case the Curnow model has no solution when an attempt is made to fit both the cavity and slot bands, while the MKK model accurately represents both bands in this case.
Deploying high penetration photovoltaic systems — A case study

Photovoltaic (PV) system capacity penetration, or simply “penetration,” is often defined as the rated power output of the aggregate PV systems on a distribution circuit segment divided by the peak load of that circuit segment. Industry experts agree that a single value defining high penetration is not universally applicable. However, it is generally agreed that a conservative value to designate high penetration is the condition when the ratio of aggregate PV systems ratings to peak load exceeds 15%. This case study illustrates the case of a distribution feeder which is able to accommodate a traditional capacity penetration level of 47%, and perhaps more. New maximum penetration levels need to be defined and verified and enhanced definitions for penetration on a distribution circuit need to be developed. The new penetration definitions and studies will help utility engineers, system developers, and regulatory agencies better agree what levels of PV deployment can be attained without jeopardizing the reliability and power quality of a circuit.
Dense spatio-temporal motion segmentation for tracking multiple self-occluding people

In this paper, we describe a new dense spatio-temporal motion segmentation algorithm with application to tracking of people in crowded environments. The algorithm is based on state-of-the-art motion and image segmentation algorithms. We specifically make use of a mean shift image segmentation algorithm and two graph based motion segmentation algorithms. The resulting motion segmentation is on the one hand accurate and on the other hand computationally efficient. In addition our method is capable of handling mutual occlusions. This shows that motion segmentation can efficiently be used to simultaneously detect, track and segment moving objects. We apply this to tracking people in surveillance videos, but the algorithm is not limited to this class of scenes.
Direct Torque Control with duty cycle control strategy for permanent magnet motors with non-sinusoidal back EMF

Direct Torque Control (DTC) of brushless DC (BLDC) motor having trapezoidal back emf with a reduced torque ripple is presented in this paper. Unlike conventional six step PWM technique, a quasi square wave current is obtained by selecting the voltage vectors from the pre defined switching table, which results in faster torque response compared to the conventional scheme. A back emf versus position look up table is used to avoid the low frequency oscillations as a result of which, a better torque response is obtained while the amplitude of stator flux linkage is deliberately kept constant by ignoring the flux control in constant torque region. The conventional DTC fails to concentrate on the torque ripple problem due to the variation in switching frequency. By adjusting the duty ratio of the active vector selected from the switching table, the torque ripple can be reduced and it causes significant change in the torque response without deteriorating the overall performance of the system. In this paper the validity of the scheme is verified from the simulation results.
Efficient distortion metrics calculation for hyperspectral waveforms in broadband nonlinear amplifiers with memory

We present a method for efficient, physics-based calculation of distortion metrics for hyperspectral waveforms (i.e. wide-band, with large number of frequency components) in broadband nonlinear amplifiers with memory. It leverages the acceleration potential of our recently developed framework for massively parallel frequency-domain simulation of hyperspectral waveforms . We introduce a generalized distortion metric that accounts for memory effects, such as dispersion and wave reflections, and we study the effect of varying the parallelization parameters on the accuracy of the distortion calculation.
Estimating Human Age by Manifold Analysis of Face Pictures and Regression on Aging Features

Extensive recent studies on human faces reveal significant potential applications of automatic age estimation via face image analysis. Due to the temporal features of age progression, aging face images display sequential pattern of low-dimensional distribution. Through manifold analysis of face pictures, we developed a novel age estimation framework. The manifold learning methods are applied to find a sufficient embedding space and model the low-dimensional manifold data with a multiple linear regression function. Experimental results on a large size age database demonstrate the effectiveness of the framework. To our best knowledge, this is the first work involving the manifold ways of age estimation.
Electrical and thermal performance of a hybrid high-power density inverter phase switch

The authors describe the construction and the electrical and thermal performance of a hybrid 600 V, 1200 A inverter phase switch designed for aerospace applications. Two sealed hermetic packages are used for the phase switch. Each module contains 44 mm bipolar transistor dies connected in a Darlington configuration, base current steering diodes and 22 mm fast recovery rectifier dies, and is mated with an integral air-to-air heat exchanger. A compression clamp secures all components and exerts the required clamping force on the large-area semiconductor. The design concept incorporates the compression dies and contact systems as utilized within a compression style semiconductor package and interconnected these dies to form an inverter phase switch in two hermetically sealed cans.<<ETX>>
Design issues for a trusted electronic document management system

This paper describes the issues related to the design of a trusted electronic document management system (TEDMS). The computer security issues and background research that lead to the final design of a TEDMS application are also discussed. The major component of an electronic document management system (EDMS) is the database in which the documents' metadata are kept. In a TEDMS, this database becomes a multilevel secure (MLS) database. The challenge of this design is to regroup MLS database design and trusted application design in one homogeneous application.