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After having described many different aspects of our team software in previous years, in this paper we take the freedom to describe the magmaChallenge framework provided by the magmaOffenburg team. The framework is used as a benchmark tool to run different challenges like the running challenge in 2014 or the kick accuracy challenge in 2015. This description should serve as a documentation to simplify the maintenance by the community and to add new benchmarks in the future.
Kommentar zu "Intracortical microstimulation of human somatosensory cortex" von Sharlene N. Flesher et al., veröffentlicht in Science Translational Medicine, Vol. 8, No. 361, Seite 361ra141 (DOI: 10.1126/scitranslmed.aaf8083)
A new yield function for lamellar gray cast iron materials is proposed. The new model is able to describe the results of recently performed microstructure-based finite-element computations that resolve the three dimensional yield surface of three different gray cast irons. The yield function requires only the yield stress in tension and compression of the respective material as model parameters. Furthermore, the algorithmic formulation of the new model is assessed for numerical robustness and efficiency.
BACKGROUND:
While hearing aids for a contralateral routing of signals (CROS-HA) and bone conduction devices have been the traditional treatment for single-sided deafness (SSD) and asymmetric hearing loss (AHL), in recent years, cochlear implants (CIs) have increasingly become a viable treatment choice, particularly in countries where regulatory approval and reimbursement schemes are in place. Part of the reason for this shift is that the CI is the only device capable of restoring bilateral input to the auditory system and hence of possibly reinstating binaural hearing. Although several studies have independently shown that the CI is a safe and effective treatment for SSD and AHL, clinical outcome measures in those studies and across CI centers vary greatly. Only with a consistent use of defined and agreed-upon outcome measures across centers can high-level evidence be generated to assess the safety and efficacy of CIs and alternative treatments in recipients with SSD and AHL.
METHODS:
This paper presents a comparative study design and minimum outcome measures for the assessment of current treatment options in patients with SSD/AHL. The protocol was developed, discussed, and eventually agreed upon by expert panels that convened at the 2015 APSCI conference in Beijing, China, and at the CI 2016 conference in Toronto, Canada.
RESULTS:
A longitudinal study design comparing CROS-HA, BCD, and CI treatments is proposed. The recommended outcome measures include (1) speech in noise testing, using the same set of 3 spatial configurations to compare binaural benefits such as summation, squelch, and head shadow across devices; (2) localization testing, using stimuli that rove in both level and spectral content; (3) questionnaires to collect quality of life measures and the frequency of device use; and (4) questionnaires for assessing the impact of tinnitus before and after treatment, if applicable.
CONCLUSION:
A protocol for the assessment of treatment options and outcomes in recipients with SSD and AHL is presented. The proposed set of minimum outcome measures aims at harmonizing assessment methods across centers and thus at generating a growing body of high-level evidence for those treatment options.
n this work a mathematical model for describing the performance of lithium-ion battery electrodes consisting of porous active material particles is presented. The model represents an extension of the Newman-type model, accounting for the agglomerate structure of the active material particles, here Li(Ni1/3Co1/3Mn1/3)O2 (NCM) and Li(Ni1/3Co1/3Al1/3)O2 (NCA). To this goal, an additional pore space is introduced on the active material level. The space is filled with electrolyte and a charge-transfer reaction takes place at the liquid-solid interface within the porous active material particles. Volume-averaging techniques are used to derive the model equations. A local Thiele modulus is defined and provides an insight into the potentially limiting factors on the active material level. The introduction of a liquid-phase ion transport within the active material reduces the overall transport losses, while the additional active surface area within the agglomerate lowers the charge-transfer resistance. As a consequence, calculated discharge capacities are higher for particles modeled as agglomerates. This finding is more pronounced in the case of high C-rates
MITK-OpenIGTLink for combining open-source toolkits in real-time computer-assisted interventions
(2016)
PURPOSE:
Due to rapid developments in the research areas of medical imaging, medical image processing and robotics, computer-assisted interventions (CAI) are becoming an integral part of modern patient care. From a software engineering point of view, these systems are highly complex and research can benefit greatly from reusing software components. This is supported by a number of open-source toolkits for medical imaging and CAI such as the medical imaging interaction toolkit (MITK), the public software library for ultrasound imaging research (PLUS) and 3D Slicer. An independent inter-toolkit communication such as the open image-guided therapy link (OpenIGTLink) can be used to combine the advantages of these toolkits and enable an easier realization of a clinical CAI workflow.
METHODS:
MITK-OpenIGTLink is presented as a network interface within MITK that allows easy to use, asynchronous two-way messaging between MITK and clinical devices or other toolkits. Performance and interoperability tests with MITK-OpenIGTLink were carried out considering the whole CAI workflow from data acquisition over processing to visualization.
RESULTS:
We present how MITK-OpenIGTLink can be applied in different usage scenarios. In performance tests, tracking data were transmitted with a frame rate of up to 1000 Hz and a latency of 2.81 ms. Transmission of images with typical ultrasound (US) and greyscale high-definition (HD) resolutions of [Formula: see text] and [Formula: see text] is possible at up to 512 and 128 Hz, respectively.
CONCLUSION:
With the integration of OpenIGTLink into MITK, this protocol is now supported by all established open-source toolkits in the field. This eases interoperability between MITK and toolkits such as PLUS or 3D Slicer and facilitates cross-toolkit research collaborations. MITK and its submodule MITK-OpenIGTLink are provided open source under a BSD-style licence ( http://mitk.org )
Cardiac resynchronization therapy is an established therapy for heart failure patients. The aim of the study was to evaluate electrical left cardiac atrioventricular delay and interventricular desynchronization in sinus rhythm cardiac resynchronization therapy responder and non-responder. Cardiac electrical desynchronization were measured by surface ECG and focused transesophageal bipolar left atrial and left ventricular ECG before implantation of cardiac resynchronization therapy defibrillators. Preoperative electrical cardiac desynchronization was 195.7 ± 46.7 ms left cardiac atrioventricular delay and 74.8 ± 24.5 ms interventricular delay in cardiac resynchronization therapy responder. Cardiac resynchronization therapy responder New York Heart Association class improved during long term biventricular pacing. Transesophageal left cardiac atrioventricular delay and interventricular delay may be additional useful parameters to improve patient selection for cardiac resynchronization therapy.
Background: Cardiac resynchronization therapy (CRT) is an established therapy for heart failure (HF) patients (P) with reduced left ventricular (LV) ejection fraction and electrical interventricular desynchronization, but not all P improved clinically. The aim of the study was to evaluate electrical interventricular delay (IVD) to LV delay (LVD) ratio in atrial fibrillation (AF) CRT responder (R) and non-responder (NR).
Methods: AF P (n = 18, age 60.6 ± 11.4 years, 1 female, 17 males) with HF New York Heart Association (NYHA) class 3.0 ± 0.2, 25.3 ± 5.9 % LV ejection fraction and 157.8 ± 24.4 ms QRS duration (QRSD) were measured by surface ECG and focused transesophageal bipolar LV ECG before implantation of CRT pacemaker (n = 2) or CRT defibrillator (n = 16). IVD was measured between onset of QRS in the surface ECG and onset of LV signal in the LV ECG. LVD was measured between onset and offset of LV signal in the LV ECG.
Results: Electrical ventricular desynchronization in AF CRT P were 61.9 ± 26.9ms IVD, 80.6 ± 24.3ms LVD, 0.85 ± 0.41 IVD-LVD-ratio (Figure), 3.12 ± 1.89 QRSD-IVD-ratio and 2.07 ± 0.47 QRSD-LVD-ratio. There were 72.2 % AF CRT R (n = 13) with 64.2 ± 24.6ms IVD and 77.8 ± 21.6ms LVD with Pearson correlation to 0.89 ± 0.39 IVD-LVD-ratio (r = 0.87, P < 0.01; r = -0.69, P < 0.01), 2.82 ± 1.32 QRSD-IVD-ratio (r = -0.76, P < 0.01; r = 0.67, P = 0.011) and 2.13 ± 0.46 QRSD-LVD-ratio (r = 0.57, P = 0.041; r = -0.85, P < 0.01). There were 27.8% AF CRT NR (n = 5) with 56.0 ± 34.5ms IVD and 87.8 ± 31.9ms LVD without correlation to 0.74 ± 0.48 IVD-LVD-ratio, 3.88 ± 2.98 QRSD-IVD-ratio and 1.90 ± 0.48 QRSD-LVD-ratio. During 15.3 ± 13.1 month CRT follow-up, the AF CRT R NYHA class improved from 3.0 ± 0.2 to 2.2 ± 0.3 (P < 0.001). During 18.8 ± 20.7 month CRT follow-up, the AF CRT NR NYHA class not improved from 3 to 3.3 ± 0.97.
Electrochemical impedance spectroscopy (EIS) is a widely-used diagnostic technique to characterize electrochemical processes. It is based on the dynamic analysis of two electrical observables, that is, current and voltage. Electrochemical cells with gaseous reactants or products (e.g., fuel cells, metal/air cells, electrolyzers) offer an additional observable, that is, the gas pressure. The dynamic coupling of current and/or voltage with gas pressure gives rise to a number of additional impedance definitions, for which we use the term electrochemical pressure impedance. It also gives rise to different experimental probing approaches. In this article we present a model-based study of electrochemical pressure impedance spectroscopy (EPIS). Possible quantifications and realizations of EPIS are discussed. The study of generic cell geometries consisting of gas reservoir, diffusion layer(s) and electrochemically active layer(s) reveals distinct spiral-shaped features in the Nyquist plot. Using the example of a sodium/oxygen (Na/O2) cell, the dynamic spatiotemporal behavior of the state variables is quantified and interpreted. Results are compared to first experimental EPIS measurements by Hartmann et al. [J. Phys. Chem. C118, 1461, 2014]. A sensitivity analysis highlights the properties of EPIS with respect to geometric, transport, and kinetic parameters. We demonstrate that EPIS is sensitive to transport parameters that are not well-accessible with standard EIS.
Structured Innovation with TRIZ in Science and Industry - Creating Value for Customers and Society
(2016)
Lithium–oxygen cells with nonaqueous electrolyte show high overpotentials during charge, indicating asymmetric charge/discharge reaction mechanisms. We present a kinetic modeling and simulation study of the lithium–oxygen cell cycling behavior. The model includes a multistep reaction mechanism of the cell reaction (2Li + O2 ⇄ Li2O2) forming lithium peroxide by precipitation, coupled to a 1D porous-electrode transport model. We apply the model to study the asymmetric discharge/charge characteristics and analyze the influence of a redox mediator dissolved homogeneously in the liquid electrolyte. Model predictions are compared to experimental galvanostatic cycling data of cells without and with 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) as redox mediator. The predicted discharge behavior shows good agreement with the experimental results. A spatiotemporal analysis of species concentrations reveals inhomogeneous distributions of dissolved oxygen and reaction products within the cathode during discharge. The experimentally observed charge overpotentials as well as their reduction by using a redox mediator can be qualitatively reproduced with a partially irreversible reaction mechanism. However, the proposed models fail to reproduce the particular shape of the experimental charge curve with continuously increasing charge overpotential, which implies that part of the reaction mechanism is still open for investigation in future work.
The M-Bus protocol (EN13757) is in widespread use for metering applications within home area and neighborhood area networks, but lacks a strict specification. This may lead to incompatibilities in real-life installations and to problems in the deployment of new M-Bus networks. This paper presents the development of a novel testbed to emulate physical Metering Bus (M-Bus) networks with different topologies and to allow the flexible verification of real M-Bus devices in real-world scenarios. The testbed is designed to support device manufacturers and service technicians in test and analysis of their devices within a specific network before their installation. The testbed is fully programmable, allowing flexible changes of network topologies, cable lengths and types. Itis easy to use, as only the master and the slaves devices have to be physically connected. This allows to autonomously perform multiple tests, including automated regression tests. The testbed is available to other researchers and developers. We invite companies and research institutions to use this M-Bus testbed to increase the common knowledge and real-world experience.
In contrast to conventional aortic valve replacement, the Transcatheter Aortic Valve Implantation (TAVI) is a new highly specialist alternative to surgical valve replacement for patients with symptomatic severe aortic stenosis and high operative risk. The procedure was performed in a minimally invasive way and was introduced at the university heart centre, Freiburg – Bad Krozingen in 2008. The results have been getting better and better over the years. The aim of the investigation is the analysis of electrocardiogram conduction time and the electrocardiography changes recorded hours and days after the procedure depending on artificial heart valve models, which may lead to pacemaker implantation, even the analysis of the effectiveness of treatment.
Transthoracic impedance cardiography (ICG) is a non-invasive method for determination of hemodynamic parameters. The basic principle of transthoracic ICG is the measurement of electrical conductivity of the thorax over the time. The aim of the study was the analysis of hemodynamic parameters from healthy individuals and the evaluation of various hemodynamic monitoring devices. Fourteen men (mean age 25 ± 4.59 years) and twelve women (mean age 24 ± 3.5 years) were measured during the cardiovascular engineering laboratory at Offenburg University of Applied Sciences, Offenburg, Germany. The ICG recordings were measured with the devices CardioScreen 1000, CardioScreen 2000 and TensoScreen with the corresponding Software Cardiovascular Lab 2.5 (Medis Medizinische Messtechnik GmbH, Illmenau, Germany). In order to create identical frame conditions, all measurements were recorded in the same position and for the same duration. Various positions were simulated from horizontal lying position to vertical standing position. Altogether, more than 30 hemodynamic parameters were measured.
The industry of the agave-derived bacanora, in the northern Mexican state of Sonora, has been growing substantially in recent years. However, this higher demand still lies under the influences of a variety of social, legal, cultural, ecological and economic elements. The governmental institutions of the state have tried to encourage a sustainable development and certain levels of standardization in the production of bacanora by applying different economical and legal strategies. However, a large portion of this alcoholic beverage is still produced in a traditional and rudimentary fashion. Beyond the quality of the beverage, the lack of proper control, by using adequate instrumental methods, might represent a health risk, as in several cases traditional-distilled beverages can contain elevated levels of harmful materials. The present article describes the qualitative spectral analysis of samples of the traditional-produced distilled beverage bacanora in the range from 0 cm−1 to 3500 cm−1 by using a Fourier Transform Raman spectrometer. This particular technique has not been previously explored for the analysis of bacanora, as in the case of other beverages, including tequila. The proposed instrumental arrangement for the spectral analysis has been built by combining conventional hardware parts (Michelson interferometer, photo-diodes, visible laser, etc.) and a set of self-developed evaluation algorithms. The resulting spectral information has been compared to those of pure samples of ethanol and to the spectra from different samples of the alcoholic beverage tequila. The proposed instrumental arrangement can be used the analysis of bacanora.
Flexible Three-dimensional Camera-based Reconstruction and Calibration of Tracked Instruments
(2016)
Navigated instruments commonly include applied parts, e.g. burrs or saw blades, that need to be calibrated with respect to the attached or integrated tracker. Since this calibration has to be very precise, it is often performed by the manufacturer. However, due to the great variety of instruments and the option to exchange the applied parts (e.g. burrs) there is a definite demand for flexible and generic calibration techniques. Furthermore, if we look into the medical field, there is also a need for calibrating sterile instruments. We propose a new and flexible camera-based calibration technique that addresses these demands by working contactlessly, precisely, and generically for a large variety of tracked instruments. This is realized using one or more tracked cameras which are calibrated with respect to an attached or integrated tracker. The tracked instrument is rotated in front of the camera(s) and its 3D geometry and surface are reconstructed from the 2D images in the coordinate system of the attached or integrated tracker. The 3D geometry of the navigated instrument was reconstructed with an accuracy of under 0.2 mm. The radius of a sphere-shaped instrument was reconstructed with an RMS deviation of 0.015mm.
Economic dispatch is a well-known optimization problem in smart grid systems which aims at minimizing the total cost of power generation among generation units while maintaining some system constraints. Recently, some distributed consensus-based approaches have been proposed to replace traditional centralized calculation. However, existing approaches fail to protect privacy of individual units like cost function parameters, generator constraints, output power levels, etc. In this paper, we show an attack against an existing consensus-based economic dispatch algorithm from [16] assuming semi-honest non-colluding adversaries. Then we propose a simple solution by combining a secure sum protocol and the consensus-based economic dispatch algorithm that guarantees data privacy under the same attacker model. Our Privacy Preserving Economic Dispatch (PPED) protocol is information-theoretically secure.
Components of rocket engines as actively cooled combustion chambers must withstand high pressure as well as severe and complex thermal transients. While the thermal transients result in temperature gradients and, thus, in constraint thermal strains, the pressure load induces mean stresses. To assess the mechanical behaviour of such components during design via finite-element calculations, constitutive models are necessary that describe the time- and temperature-dependent plasticity of the material appropriately.
Advanced models account for viscoplastic deformations including isotropic and kinematic hardening, recovery and ratcheting. However, the models contain a relatively large number of temperature-dependent material properties that must be determined on the basis of data of material tests. The determination of the properties is a non-trivial task because it is not clear which loading history must be applied in the tests for a certain material to obtain stable and robust (i.e. objective) material properties. Consequently, the determined properties are depending on the underlying loading history in the tests as well as on the experience and valuation of the person that determined the properties. This results in uncertainties during the assessment of the components that must be faced with conservative designs leading to negative consequences in terms of mass and costs.
It is the aim of this work funded by the European Space Agency ESA to derive a procedure to determine stable and robust material properties of an advanced viscoplastic constitutive model for aerospace materials. To this end, a special loading history is applied in isothermal material tests conducted with copper at different temperatures in the temperature range from 300 to 700 K. To determine the material properties and to assess stability and robustness methods for numerical optimization as well as analytical and statistical methods are used. The determined material properties are validated on the basis of results of thermomechanical material tests also conducted in the temperature range from 300 to 700 K.
The interaural time difference (ITD) is an important cue for the localization of sounds. ITD changes as little as 10 μs can be detected by the human auditory system. By provision of one ear with a cochlear implant (CI) ITD are altered due to the partial replacement of the peripheral auditory system. A hearing aid (HA), in contrast, does not replace but adds a processing delay component to the peripheral auditory system extending ITD. The aim of the present study was to quantify interaural stimulation timing between these different modalities to estimate the need for central auditory temporal compensation in single sided deaf CI users or bimodal CI/HA users. For this purpose, wave V latencies of auditory brainstem responses evoked either acoustically (ABR) or electrically via the CI (EABR) have been measured. The sum of delays consisting of CI signal processing measured in the MED-EL OPUS2 audio processor and EABR wave V latencies evoked on different intracochlear sites allowed an estimation of the entire CI channel-specific delay for MED-EL MAESTRO CI systems. We compared these values with ABR wave V latencies measured in the contralateral normal hearing or HA provided ear in different frequency bands. The results showed that EABR wave V latencies were consistently shorter than those evoked acoustically in the unaided normal hearing ear. Thus, artificial delays within the audio processor can be implemented to adjust interaural stimulation timing. The currently implemented group delays in the MED-EL CI system turned out to be reasonably similar to those of the unaided ear. For adjustment of CI and contralateral HA, in contrast, an adjustable additional across-frequency delay in the range of 1–11 ms implemented in the CI would be required. Especially for bimodal CI/HA users the adjustment of interaural stimulation timing may induce improved binaural hearing, reduced need for central auditory temporal compensation and increased acceptance of the CI/HA provision.
This paper presents an overview of the coding aspects of a GNSS receiver. Coding allows detection and correction of channel-induced errors at the receiver, here the focus is on the mitigation of threats from malicious interferences. Although the effects of interference at different stages of GNSS baseband processing has been deeply analyzed in the literature, little attention was devoted to its impact on the navigation message decoding stage. Theis paper provides an introduction to the various coding schemes employed by current GNSS signals, discussing their performance in the presence of noise in terms of block-error rate. Additionally, the benefits of soft-decoding schemes for navigation message decoding are highlighted when jamming interferences are present. The proposed scheme requires estimating the noise plus interference power, yielding to enhanced decoding performances under severe jamming conditions. Finally, cryptographic schemes as a means of providing anti-spoofing for geosecurity location-based services, and their potential vulnerability are discussed, with particular emphasis on the dependence on the dependence of the scheme on successful navigation message decoding
Wireless Sensor Networks (WSN) have emerged as interesting topic in the research community due to its manifold applications. One of the main challenges of this field is the energy consumption of the nodes, which typically is quite restricted due to the required lifetime of such WSNs. To solve that problem several energy-saving MAC protocols have been developed so far. One of them recently presented by the authors is the so-called SmartMAC as an extension to the IEEE802.15.4 standard. In this paper, we present the implementation details of the porting of the SmartMAC protocol to the discrete event network simulator NS3. We develop this module for NS3 to simulate the performance, multi node execution, and multi node configuration. Along with this model, we also present an energy model for the evaluation of the energy consumption. The current implementation in NS3 is based on the LR-WPAN (Low-Rate Wireless Personal Area Networks) as specified by the IEEE802.15.4 (2006) standard. The simulation results show that the SmartMAC with its sleep and wake-up mechanisms for the transceivers, is significantly more efficient than the current NS3 MAC (Medium Access Control) scheme.
Due to its numerous application fields and benefits, virtualization has become an interesting and attractive topic in computer and mobile systems, as it promises advantages for security and cost efficiency. However, it may bring additional performance overhead. Recently, CPU virtualization has become more popular for embedded platforms, where the performance overhead is especially critical. In this article, we present the measurements of the performance overhead of the two hypervisors Xen and Jailhouse on ARM processors in the context of the heavy load “Cpuburn-a8” application and compare it to a native Linux system running on ARM processors.
The ability to detect a target signal masked by noise is improved in normal-hearing listeners when interaural phase differences (IPDs) between the ear signals exist either in the masker or in the signal. To improve binaural hearing in bilaterally implanted cochlear implant (BiCI) users, a coding strategy providing the best possible access to IPD is highly desirable. In this study, we compared two coding strategies in BiCI users provided with CI systems from MED-EL (Innsbruck, Austria). The CI systems were bilaterally programmed either with the fine structure processing strategy FS4 or with the constant rate strategy high definition continuous interleaved sampling (HDCIS). Familiarization periods between 6 and 12 weeks were considered. The effect of IPD was measured in two types of experiments: (a) IPD detection thresholds with tonal signals addressing mainly one apical interaural electrode pair and (b) with speech in noise in terms of binaural speech intelligibility level differences (BILD) addressing multiple electrodes bilaterally. The results in (a) showed improved IPD detection thresholds with FS4 compared with HDCIS in four out of the seven BiCI users. In contrast, 12 BiCI users in (b) showed similar BILD with FS4 (0.6 ± 1.9 dB) and HDCIS (0.5 ± 2.0 dB). However, no correlation between results in (a) and (b) both obtained with FS4 was found. In conclusion, the degree of IPD sensitivity determined on an apical interaural electrode pair was not an indicator for BILD based on bilateral multielectrode stimulation.
The aim of this data collection is to enforce evidence of SCS effectiveness in treating neuropathic chronic pain and the very low percentage of undesired side effects of complications reported in our case series suggests that all implants should be performed by similarly well-trained and experienced professionals.
A Survey of Channel Measurements and Models for Current and Future Railway Communication Systems
(2016)
Electric arc furnaces (EAF) are complex industrial plants whose actual behavior depends upon numerous factors. Due to its energy intensive operation, the EAF process has always been subject to optimization efforts. For these reasons, several models have been proposed in literature to analyze and predict different modes of operation. Most of these models focused on the processes inside the vessel itself. The present paper introduces a dynamic, physics-based model of a complete EAF plant which consists of the four subsystems vessel, electric system, electrode regulation, and off-gas system. Furthermore the solid phase is not treated to be homogenous but a simple spatial discretization is employed. Hence it is possible to simulate the energy input by electric arcs and fossil fuel burners depending on the state of the melting progress. The model is implemented in object-oriented, equation-based language Modelica. The simulation results are compared to literature data.
Proton Exchange Membrane Fuel Cells (PEMFC) are energy efficient and environmentally friendly alternatives to conventional energy conversion systems in many yet emerging applications. In order to enable prediction of their performance and durability, it is crucial to gain a deeper understanding of the relevant operation phenomena, e.g., electrochemistry, transport phenomena, thermodynamics as well as the mechanisms leading to the degradation of cell components. Achieving the goal of providing predictive tools to model PEMFC performance, durability and degradation is a challenging task requiring the development of detailed and realistic models reaching from the atomic/molecular scale over the meso scale of structures and materials up to components, stack and system level. In addition an appropriate way of coupling the different scales is required.
This review provides a comprehensive overview of the state of the art in modeling of PEMFC, covering all relevant scales from atomistic up to system level as well as the coupling between these scales. Furthermore, it focuses on the modeling of PEMFC degradation mechanisms and on the coupling between performance and degradation models.
This paper focuses on appropriately measuring the accuracy of forecasts of load behavior and renewable generation in micro-grid operation. Common accuracy measures like the root mean square of the error are often difficult to interpret for system design, as they describe the mean accuracy of the forecast. Micro-grid systems, however, have to be designed to handle also worst case situations. This paper therefore suggests two error measures that are based on the maximum function and that better allow understanding worst case requirements with respect to balancing power and balancing energy supply.
IPv6 over resource-constrained devices (6Lo) emerged as a de-facto standard for the Internet of Things (IoT) applications especially in home and building automation systems. We provide results of an investigation of the applicability of 6LoWPAN with RPL mesh networks for home and building automation use cases. The proper selection of Trickle parameters and neighbor reachable time-outs is important in the RPL protocol suite to respond efficiently to any path failure. These parameters were analyzed in the context of energy consumption w.r.t the number of control packets. The measurements were performed in an Automated Physical Testbeds (APTB). The results match the recommendation by RFC 7733 for selecting various parameters of RPL protocol suite. This paper shows the relationship between various RPL parameters and control traffic overhead during network rebuild. Comparative measurement results with Bluetooth Low Energy (BLE) in this work showed that 6Lo with RPL outperformed BLE in this use case with less control traffic overheads.
In this work, we consider a duty-cycled wireless sensor network with the assumption that the on/off schedules are uncoordinated. In such networks, as all nodes may not be awake during the transmission of time synchronization messages, nodes will require to re-transmit the synchronization messages. Ideally a node should re-transmit for the maximum sleep duration to ensure that all nodes are synchronized. However, such a proposition will immensely increase the energy consumption of the nodes. Such a situation demands that there is an upper bound of the number of retransmissions. We refer to the time a node spends in re-transmission of the control message as broadcast duration. We ask the question, what should be the broadcast duration to ensure that a certain percentage of the available nodes are synchronized. The problem to estimate the broadcast duration is formulated so as to capture the probability threshold of the nodes being synchronized. Results show the proposed analytical model can predict the broadcast duration with a given lower error margin under real world conditions, thus demonstrating the efficiency of our solution.
The ability to detect a signal masked by noise is improved in normal-hearing (NH) listeners when interaural phase differences (IPD) between the ear signals exist either in the masker or the signal. We determined the impact of different coding strategies in bilaterally implanted cochlear implant (BiCI) users with and without fine-structure coding (FSC) on masking level differences. First, binaural intelligibility level differences (BILD) were determined in NH listeners and BiCI users using their clinical speech processors. NH subjects (n=8) showed a significant mean BILD of 7.5 dB. In contrast, BiCI users (n=9) without FSC as well as with FSC revealed a barely significant mean BILD (0.4 dB respectively 0.6 dB). Second, IPD thresholds were measured in BiCI users using either their speech processors with FS4 or direct stimulation with FSC. With the latter approach, synchronized stimulation providing an interaural accuracy of stimulation timing of 1.67 µs was realized on pitch matched electrode pairs. The resulting individual IPD threshold was lower in most of the subjects with direct stimulation than with their speech processors. These outcomes indicate that some BiCI users can benefit from increased temporal precision of interaural FSC and adjusted interaural frequency-place mapping presumably resulting in improved BILD.
NEXCODE is a project promoted by the European Space Agency aimed at research design development and demonstration of a receiver chain for telecomm and links in space missions including the presence of new short low-density parity-check codes for error correction. These codes have excellent performance from the error rate viewpoint but also put new challenges as regards synchronization issues and implementation. In this paper after a short review of the results obtained through numerical simulations we present an overview of the breadboard designed for practical testing and the test-plan proposed for the verification of the breadboard and the validation of the new codes and novel synchronization techniques under relevant operation conditions.
This work describes a non-parametric camera-based method for the calibration of Optical See-Through Glasses (OSTG). Existing works model the optical system through perspective projection and parametric functions. In the border areas of the displays such models are often inadequate. Moreover, rigid calibration patterns, that produce only a small amount of non-equidistant point correspondences, are used. In order to overcome these disadvantages every single display pixel is calibrated individually. The error prone user interaction is avoided by using cameras placed behind the displays of the OSTG. The displays show a shifting pattern that is used to calculate the pixels' locations. A camera mounted rigidly on the OSTG is used to find the relations between the system components. The obtained results show better accuracies than in previous works and prove that a second calibration step for user adaptation is necessary for high accuracy applications.
The effect of fluctuating maskers on speech understanding of high-performing cochlear implant users
(2016)
Objective: The present study evaluated whether the poorer baseline performance of cochlear implant (CI) users or the technical and/or physiological properties of CI stimulation are responsible for the absence of masking release. Design: This study measured speech reception thresholds (SRTs) in continuous and modulated noise as a function of signal to noise ratio (SNR). Study sample: A total of 24 subjects participated: 12 normal-hearing (NH) listeners and 12 subjects provided with recent MED-EL CI systems. Results: The mean SRT of CI users in continuous noise was −3.0 ± 1.5 dB SNR (mean ± SEM), while the normal-hearing group reached −5.9 ± 0.8 dB SNR. In modulated noise, the difference across groups increased considerably. For CI users, the mean SRT worsened to −1.4 ± 2.3 dB SNR, while it improved for normal-hearing listeners to −18.9 ± 3.8 dB SNR. Conclusions: The detrimental effect of fluctuating maskers on SRTs in CI users shown by prior studies was confirmed by the current study. Concluding, the absence of masking release is mainly caused by the technical and/or physiological properties of CI stimulation, not just the poorer baseline performance of many CI users compared to normal-hearing subjects. Speech understanding in modulated noise was more robust in CI users who had a relatively large electrical dynamic range.
Nickel cobalt aluminum oxide (NCA) based lithium-ion battery electrodes exhibit a distinct asymmetry in discharge/charge behavior towards high bulk stoichiometry (low state of charge). We show that basic electrochemical relationships, that is, the Nernst equation and the Butler-Volmer equation, are able to reproduce this behavior when a two-step reaction mechanism is assumed. The two-step mechanism consists of (1) lithium-ion adsorption from the electrolyte onto the active material particle surface under electron transfer, and (2) intercalation of surface-adsorbed lithium atoms into the bulk material. The asymmetry of experimental half-cell data of an NCA electrode cycled at 0.1 C-rate can be quantitatively reproduced with this simple model. The model parameters show two alternative solutions, predicting either a saturated (highly-covered) or a depleted surface for high bulk lithiation.
We present a novel scheme for Slotted ALOHA random access systems that combines physical-layer network coding (PLNC) with multiuser detection (MUD). The PLNC and MUD are applied jointly at the physical layer to be able to extract any linear combination of messages experiencing a collision within a slot. The set of combinations extracted from a whole frame is then processed by the receiver to recover the original packets. A simple precoding stage at the transmitting terminals allows the receiver to further decrease the packet loss rate. We present results for the decoding at the physical layer as well as several performance measures at frame level, namely, throughput, packet loss rate, and energy efficiency. The results we present are promising and suggest that a cross-layer approach leveraging on the joint use of PLNC and MUD can significantly improve the performance of random access systems in the presence of slow fading.
Wireless sensor networks have found their way into a wide range of applications among which environmental monitoring systems have attracted increasing interests of researchers. The main challenges for the applications are scalability of the network size and energy efficiency of the spatially distributed motes. These devices are mostly battery-powered and spend most of their energy budget on the radio transceiver module. A so-called Wake-On-Radio (WOR) technology can be used to achieve a reasonable balance among power consumption, range, complexity and response time. In this paper, a novel design for integration of WOR into IEEE802.1.5.4 is presented, which flexibly allows trade-offs in energy consumption between sender and receiver station, between real-time capability and energy consumption. For identical behavior, the proposed scheme is significantly more efficient than other schemes, which were proposed in recent publications, while preserving backward compatibility with standard IEEE802.15.4 transceivers.