Optimal Frequency Selection Research Articles

A game-theoretic approach to analyse inter-modal competition between high-speed rail and airlines in the Indian context

ABSTRACTIn this paper, a game-theoretic framework is applied in order to model the competition scenario between high-speed rail (HSR) and airlines in the Indian context and assess the impact of speed and passengers’ characteristics on the equilibrium of the game. The competition is modelled in terms of the fare and frequency offered by the operators to maximize their profits. The speed of HSR is taken as an additional strategic variable in the game with three levels of high speed: low, medium, high. A three-stage game is formulated with the entrant playing its speed strategy in the first stage followed by optimal fare and frequency selection by both the modes. Passengers are considered to be heterogeneous in nature by assuming a continuous distribution of the value of time. Numerical simulations indicate that the dominant strategy for airlines and HSR is based on accommodation and medium speed, respectively.

Development of an energy-based approach for optimized frequency selection for fatigue testing on polymers – Exemplified on polyamide 6

Polymers and composite materials show temperature-dependent material properties. Therefore, the frequency resembles a critical part in fatigue testing, due to its influence on the self-heating of the polymeric material and thereby on the number of cycles to failure. The aim of this paper is the development of a testing method, which allows comparable results with varying frequencies. To minimize the self-heating effect on the fatigue behavior, a model was established for selecting optimized frequencies regarding the load-specific temperature increase of the specimen. A new energy-parameter, the induced energy-rate, was introduced and correlated to the load-specific increase in temperature in multiple and constant amplitude tests at ambient conditions. With this approach, it was possible to determine a threshold value for the newly defined induced energy-rate. A stress-specific model was developed and a limit frequency was calculated. The results were verified in multiple and constant amplitude tests and S/N-curves.

Modeling and Diagnosis of Joints in High Voltage Electrical Transmission Lines

In this paper a new method is developed and described, aimed at the modeling and diagnosis of the joints connecting the ends of two cables on a high voltage electricity pylon. Identifying the anomalous joint behaviour through the line frequency response analysis is the first objective of the work. For this reason, it is necessary to model the whole overhead line with a lumped circuit and studying the joint electrical parameter variation. The problem is approached in multiple steps: modelling, testability analysis of the model, optimal frequency selection, identification of the possible failures. Some simulated cases are included in order to show the potentialities of the method.

Automatic look-up table based real-time phase unwrapping for phase measuring profilometry and optimal reference frequency selection

For temporal phase unwrapping in phase measuring profilometry, it has recently been reported that two phases with co-prime frequencies can be absolutely unwrapped using a look-up table; however, frequency selection and table construction has been performed manually without optimization. In this paper, a universal phase unwrapping method is proposed to unwrap phase flexibly and automatically by using geometric analysis, and thus we can programmatically build a one-dimensional or two-dimensional look-up table for arbitrary two co-prime frequencies to correctly unwrap phases in real time. Moreover, a phase error model related to the defocus effect is derived to figure out an optimal reference frequency co-prime to the principal frequency. Experimental results verify the correctness and computational efficiency of the proposed method.

Modified CRLB Based Optimal Sampling Frequency Selection in Phase and Frequency Estimation

Modified CRLB Based Optimal Sampling Frequency Selection in Phase and Frequency Estimation

A Multispectral Bayesian Classification Method for Increased Acoustic Discrimination of Seabed Sediments Using Multi-Frequency Multibeam Backscatter Data

Multi-frequency backscatter data collected from multibeam echosounders (MBESs) is increasingly becoming available. The ability to collect data at multiple frequencies at the same time is expected to allow for better discrimination between seabed sediments. We propose an extension of the Bayesian method for seabed classification to multi-frequency backscatter. By combining the information retrieved at single frequencies we produce a multispectral acoustic classification map, which allows us to distinguish more seabed environments. In this study we use three triple-frequency (100, 200, and 400 kHz) backscatter datasets acquired with an R2Sonic 2026 in the Bedford Basin, Canada in 2016 and 2017 and in the Patricia Bay, Canada in 2016. The results are threefold: (1) combining 100 and 400 kHz, in general, reveals the most additional information about the seabed; (2) the use of multiple frequencies allows for a better acoustic discrimination of seabed sediments than single-frequency data; and (3) the optimal frequency selection for acoustic sediment classification depends on the local seabed. However, a quantification of the benefit using multiple frequencies cannot clearly be determined based on the existing ground-truth data. Still, a qualitative comparison and a geological interpretation indicate an improved discrimination between different seabed environments using multi-frequency backscatter.

Error analysis and frequency selection guidelines for three-frequency correction in MOS capacitors

The three-frequency correction method is used to extract the model parameters in a five-element model which includes MOS capacitance C, parallel resistance Rp, interface layer (IL) capacitance Ci, IL resistance Ri, and series resistance Rs. A method for the error analysis of these model parameters has been developed, using error propagation of measured capacitance Cm and resistance Rm. We have applied this error analysis method to a 0.3 mm × 0.3 mm Al/ZrO2/IL/n-Si MOS capacitor with dielectric thickness 35.9 nm. Accumulation capacitances and their errors at various frequency combinations have been calculated to study suitable frequency selection. The errors in the three-frequency correction method depend on selection of the three frequencies (f1 > f2 > f3) and dissipation factor Dm. For large differences between frequencies f1 and f3 (f3/f1 ∼ 0.05– 0.2), the f2 value should be equal to or a little larger than the average value (f3 + f1)/2 to ensure a small error (less than 4%) in spite of large Dm ∼ 0.20–0.31 at f1 = 1.0–1.6 MHz. For three close f1 and f3 (f3/f1 ∼ 0.25–0.6), small ratios for f2/f1 < ∼ 2/3 and f3/f2 < ∼ 2/3 (f3/f1 < 0.44), f2 = (f3 + f1)/2 and small Dm less than ∼0.20 have been suggested to ensure error less than 4%. Considering the error and possible dispersion, the difference between f1 and f3 should be moderate, i.e. f3/f1 = 0.05 ∼ 0.44. For optimal frequency selection, we suggest f3/f1 = ∼0.10 and f2 = (f3 + f1)/2. The frequency selection is not critical for most MOS capacitors, e.g. this sample Al/ZrO2/IL/n-Si capacitor. The three-frequency correction method together with error analysis is effective in extracting accurate accumulation capacitance.

For More Energy-Efficient Dual-Hop DF Relaying Power-Line Communication Systems

Energy efficiency in multihop cooperative power-line communication (PLC) systems has recently received considerable attention in the literature. In order to make such systems more energy efficient, this paper proposes a relaying technique equipped with energy-harvesting capabilities. More specifically, we consider a dual-hop decode-and-forward (DF) broadband PLC relaying system in which the relay exploits the high noise inherent in PLC channels to further enhance energy efficiency; this system will be referred to as DF with energy harvesting (DF-EH). This study deploys, particularly, the time-switching relaying protocol for energy harvesting. An accurate analytical expression for the energy efficiency and a closed-form expression for the average outage probability of the proposed system are derived and then verified with Monte Carlo simulations. For the sake of comparison and to highlight the achievable gains, we also analyze the energy-efficiency performances and the average outage probabilities of the conventional DF relaying system, i.e., without energy harvesting, as well as that of the direct-link approach. Furthermore, various frequency selection and power allocation strategies, namely, optimal frequency selection, random frequency selection, and equal power allocation, exploiting the multiple power cables, are studied. Then, the impact of several system parameters such as the energy-harvesting time factor, various idle power consumption profiles, relay location, power allocation as well as different noise scenarios are examined. The results reveal that the proposed DF-EH system is able to provide energy efficiency improvements of more than 30% compared to the conventional DF relaying scheme. It is also shown that the proposed system with optimal frequency selection performs better at low SNR, whereas at high SNR the equal power allocation based system will have the best performance.

Detection of Anomalous Noise Events on Low-Capacity Acoustic Nodes for Dynamic Road Traffic Noise Mapping within an Hybrid WASN.

One of the main aspects affecting the quality of life of people living in urban and suburban areas is the continuous exposure to high road traffic noise (RTN) levels. Nowadays, thanks to Wireless Acoustic Sensor Networks (WASN) noise in Smart Cities has started to be automatically mapped. To obtain a reliable picture of the RTN, those anomalous noise events (ANE) unrelated to road traffic (sirens, horns, people, etc.) should be removed from the noise map computation by means of an Anomalous Noise Event Detector (ANED). In Hybrid WASNs, with master-slave architecture, ANED should be implemented in both high-capacity (Hi-Cap) and low-capacity (Lo-Cap) sensors, following the same principle to obtain consistent results. This work presents an ANED version to run in real-time on Controller-based Lo-Cap sensors of a hybrid WASN, discriminating RTN from ANE through their Mel-based spectral energy differences. The experiments, considering 9 h and 8 min of real-life acoustic data from both urban and suburban environments, show the feasibility of the proposal both in terms of computational load and in classification accuracy. Specifically, the ANED Lo-Cap requires around of the computational load of the ANED Hi-Cap, while classification accuracies are slightly lower (around 10%). However, preliminary analyses show that these results could be improved in around 4% in the future by means of considering optimal frequency selection.

An optimal operating frequency selection scheme for maximizing inductive power link efficiency

AbstractImproving the efficiency of the inductive wireless power transfer (WPT) is an effective way to increase the power transfer distance, reduce the power exposure, and popularize the WPT application. If the geometrical sizes of the transmitting and receiving coils and the distance between them have been determined, an operating frequency exists to maximize the power transfer efficiency. In this work, a method to find this optimal frequency is introduced by virtue of analytical models of self‐ and mutual‐inductances and parasitic resistances and capacitances of the coils, and verified via simulations and measurements.

Performance Standards for Quality Control Systems

<h3>ABSTRACT</h3> Standard statistical quality control (QC) has been around since its introduction in 1950 by Levey and Jennings. Today, while most laboratories use standard statistical QC processes, with or without Westgard multi-rules to evaluate quality, few incorporate performance standards in their QC systems. With performance standards, the quality level of each test is determined on a sigma scale. This guides the selection of optimal QC frequency and rules to monitor the analytical system. QC rules are selected based on the sigma score and are specific to each test. While a single rule (1_3s) is sufficient to efficiently monitor tests with sigma quality at or above 6, a more stringent rule (1_3s/2_2s/R_4s/4_1s) is required for those performing at four sigma. The comparison of analytical total error (TE) to the total error allowable (TEa) helps ensure that the system is operating within the defined quality specifications; therefore, accurate patient results are produced.

Online Optimal Switching Frequency Selection for Grid-Connected Voltage Source Inverters

Enhancing the performance of the voltage source inverters (VSIs) without changing the hardware structure has recently acquired an increased amount of interest. In this study, an optimization algorithm, enhancing the quality of the output power and the efficiency of three-phase grid connected VSIs is proposed. Towards that end, the proposed algorithm varies the switching frequency (fsw) to maintain the best balance between switching losses of the insulated-gate-bipolar-transistor (IGBT) power module as well as the output power quality under all loading conditions, including the ambient temperature effect. Since there is a contradiction with these two measures in relation to the switching frequency, the theory of multi-objective optimization is employed. The proposed algorithm is executed on the platform of Altera® DE2-115 field-programmable-gate-array (FPGA) in which the optimal value of the switching frequency is determined online without the need for heavy offline calculations and/or lookup tables. With adopting the proposed algorithm, there is an improvement in the VSI efficiency without degrading the output power quality. Therefore, the proposed algorithm enhances the lifetime of the IGBT power module because of reduced variations in the module’s junction temperature. An experimental prototype is built, and experimental tests are conducted for the verification of the viability of the proposed algorithm.

Robust and efficient multi-frequency temporal phase unwrapping: optimal fringe frequency and pattern sequence selection.

Temporal phase unwrapping (TPU) is an essential algorithm in fringe projection profilometry (FPP), especially when measuring complex objects with discontinuities and isolated surfaces. Among others, the multi-frequency TPU has been proven to be the most reliable algorithm in the presence of noise. For a practical FPP system, in order to achieve an accurate, efficient, and reliable measurement, one needs to make wise choices about three key experimental parameters: the highest fringe frequency, the phase-shifting steps, and the fringe pattern sequence. However, there was very little research on how to optimize these parameters quantitatively, especially considering all three aspects from a theoretical and analytical perspective simultaneously. In this work, we propose a new scheme to determine simultaneously the optimal fringe frequency, phase-shifting steps and pattern sequence under multi-frequency TPU, robustly achieving high accuracy measurement by a minimum number of fringe frames. Firstly, noise models regarding phase-shifting algorithms as well as 3-D coordinates are established under a projector defocusing condition, which leads to the optimal highest fringe frequency for a FPP system. Then, a new concept termed frequency-to-frame ratio (FFR) that evaluates the magnitude of the contribution of each frame for TPU is defined, on which an optimal phase-shifting combination scheme is proposed. Finally, a judgment criterion is established, which can be used to judge whether the ratio between adjacent fringe frequencies is conducive to stably and efficiently unwrapping the phase. The proposed method provides a simple and effective theoretical framework to improve the accuracy, efficiency, and robustness of a practical FPP system in actual measurement conditions. The correctness of the derived models as well as the validity of the proposed schemes have been verified through extensive simulations and experiments. Based on a normal monocular 3-D FPP hardware system, our method enables high-precision unambiguous 3-D shape measurement with the highest fringe frequency up to 180 by using only 7 fringe patterns achieving a depth precision ∼ 38μm across a field of view of 400 × 300 × 400 mm.

Connectivity of magnetic induction-based ad hoc networks

Magnetic induction (MI) has been proven to be an efficient wireless communication technique for overcoming the transmission challenges in some very harsh propagation environments, such as underground, underwater, etc. For a random distributed MI ad hoc network in a 3-D space composed of uniform medium, we propose a method for determining the required node density and transmitting power that creates an almost surely fully connected network. For which we involve an MI path-loss model and consider the effect of eddy currents, the effective coverage space and the expected node degree of an MI node are then calculated by a Lambert W-function-based integration. Finally, we propose optimized frequency selection methods for improving the connectivity of MI networks. In addition to an ideal frequency-switching optimization method, we provide for engineering applications a practical frequency-fixed optimization method, which is based on the gradient descent algorithm, where an improved initialization is used to reduce iterations.

Optimal frequency selection of multi-channel O2-band different absorption barometric radar for air pressure measurements

Through theoretical analysis, optimal selection of frequencies for O2 differential absorption radar systems on air pressure field measurements is achieved. The required differential absorption optical depth between a radar frequency pair is 0.5. With this required value and other considerations on water vapor absorption and the contamination of radio wave transmission, frequency pairs of present considered radar system are obtained. Significant impacts on general design of differential absorption remote sensing systems are expected from current results.

MATHEMATICAL MODELING OF SPATIAL AND TEMPORAL DISTRIBUTION OF ELECTRON CONCENTRATION IN IONOSPHERE FOR EVALUATION OF ALGORITHMS OF ADAPTATION TO GEOPHYSICAL AND INTERFERENCE CONDITIONS

The paper discusses the algorithms of synthesis of the passive interference structure in the vicinity of MUF (maximal usable frequency) paths with varying length and orientation. Modeling of the space-time structure of the ionosphere has been performed. Estimates have been obtained for possibilities of adaptation to geophysical and interference conditions. Simplified methods have been investigated for selection of optimal jam-proof operating frequencies in DR channel. Algorithms have been developed for synthesis of passive interference structure, principles of the ionosphere model correction and requirements to speed of algorithms and programs.

Frequency agility in cognitive radios: A new measurement algorithm for optimal operative frequency selection

The wide diffusion of multimedia services delivered also on mobile terminals (smart-phone, tablets and so on), is causing a fast and continuous increasing of spectrum usage demand. Nevertheless, several studies have demonstrated that portions of radio spectrum are not in use for significant periods of time. This waste of spectrum shows the necessity to design a more flexible way to manage this resource with respect to the traditional frequency allocation policy.In this context, cognitive radios play a crucial role, because they are thought to enable such flexible spectrum allocation by suitably changing their operating frequency without interfering with other transmitters. As a consequence, they have to implement a method to dynamically select the appropriate operating frequency based on the sensing of signals from other transmitters. This capability is usually called frequency agility.Several spectrum sensing methods have been proposed in literature, whereas few studies have been focused on the development of methods for satisfying the frequency agility capability.In this framework, the paper proposes a novel measurement algorithm able to meet those requirements. It is based on two sequential steps: the former performs a preliminary spectrum sensing aimed at excluding the frequency ranges surely occupied by primary users, while the latter performs a more refined analysis, restricted to frequency intervals not excluded by the previous stage, with the aim of selecting an operating frequency for the cognitive radio terminal that minimizes potential interferences with primary users. It has been designed for operating in scenarios involving signals based on OFDM or which present spectrum shapes and slopes similar to ones shown by OFDM.A key feature of the proposal is the ability to operate even in scenarios characterized by low signal-to-noise ratios as confirmed also by the experimental campaign.

Queue-Aware Optimal Frequency Selection for Energy Minimization in Wireless Networks

Queue-Aware Optimal Frequency Selection for Energy Minimization in Wireless Networks

Frequency-specific alterations of large-scale functional brain networks in patients with Alzheimer's disease.

Background:Previous studies have indicated that the cognitive deficits in patients with Alzheimer's disease (AD) may be due to topological deteriorations of the brain network. However, whether the selection of a specific frequency band could impact the topological properties is still not clear. Our hypothesis is that the topological properties of AD patients are also frequency-specific.Methods:Resting state functional magnetic resonance imaging data from 10 right-handed moderate AD patients (mean age: 64.3 years; mean mini mental state examination [MMSE]: 18.0) and 10 age and gender-matched healthy controls (mean age: 63.6 years; mean MMSE: 28.2) were enrolled in this study. The global efficiency, the clustering coefficient (CC), the characteristic path length (CpL), and “small-world” property were calculated in a wide range of thresholds and averaged within each group, at three different frequency bands (0.01–0.06 Hz, 0.06–0.11 Hz, and 0.11–0.25 Hz).Results:At lower-frequency bands (0.01–0.06 Hz, 0.06–0.11 Hz), the global efficiency, the CC and the “small-world” properties of AD patients decreased compared to controls. While at higher-frequency bands (0.11–0.25 Hz), the CpL was much longer, and the “small-world” property was disrupted in AD, particularly at a higher threshold. The topological properties changed with different frequency bands, suggesting the existence of disrupted global and local functional organization associated with AD.Conclusions:This study demonstrates that the topological alterations of large-scale functional brain networks in AD patients are frequency dependent, thus providing fundamental support for optimal frequency selection in future related research.

Wireless Communication of Intraoral Devices and Its Optimal Frequency Selection.

This paper explores communication methods and frequencies for wireless intraoral electronic devices, by using an intraoral tongue drive system (iTDS) as a practical example. Because intraoral devices do not meet the operating conditions of the body channel communication, we chose radio frequency communication. We evaluated and compared three frequencies in industrial, scientific, and medical bands (27 MHz, 433.9 MHz, and 2.48 GHz) in terms of their data link performance based on path loss and radiation patterns over horizontal and vertical planes. To do so, we dynamically minimize the impedance mismatch caused by the varying oral environment by applying the adaptive impedance matching technique to 433.9 MHz and 2.48 GHz bands. Experimental results showed that 27 MHz has the smallest path loss in the near-field up to 39 cm separation between transmitter and receiver antennas. However, 433.9 MHz shows the best performance beyond 39 cm and offers a maximum operating distance of 123 cm with 0 dBm transmitter output power. These distances were obtained by a bit error rate test and verified by a link budget analysis and full functionality test of the iTDS with computer access.