Near Real Time Heading Drift Correction for indoor pedestrian tracking based on sequence detection

Indoor positioning is currently a research hotspot. In recent years, Pedestrian Dead Reckoning (PDR) has been widely used in indoor positioning. However, the positioning error caused by heading drifts will accumulate as the walking distance increases, so some methods need to be used to correct the heading angle. Heuristic Drift Elimination (HDE) is an effective heading correction algorithm, which only uses the information of a building’s dominant directions to reduce the heading error, but it does not apply to the non-dominant direction condition. In this paper, we propose a heading drift suppressing method for the limitation of HDE. Firstly, the method constructs membership functions to judge the pedestrian’s motion according to the result of comprehensive evaluation. Then, it further determines by a threshold condition whether the pedestrian walks along the dominant directions, and a heading error measurement is introduced for heading correction. Finally, we verify by experiments that the proposed method can correct heading angles properly for different conditions, which indicates an adaptability to the environment.

Recently, electromagnetic environments and electromagnetic compatibility (EMC) in relation to electrical equipment have become important issues. In 2008, the European Union established the EN 50500 standard, which provides measurement and calculation methods for determining magnetic fields emitted from electrical equipment on railways. The major frequency components of the electric and magnetic fields generated from such equipment are in the low range, such as D.C., 16.7 Hz, 50 Hz, 60 Hz and their low-order harmonics. According to the EN 50500 standard, magnetic fields are dominant around this kind of equipment. This paper describes the physical characteristics and analytical methods of low-frequency magnetic fields emitted from electrical equipment in railway substations, and proposes abatement measures and model substation designs based on the above results.

In most previous provocation studies subjects suffering from "electric hypersensitivity" have not been able to determine correctly whether or not they have been subjected to a sham or true provocation to magnetic or electric fields. However, an often-discussed weakness is that most of the earlier provocation studies have been performed in a laboratory situation, often with simulated fields, which may not be representative of conditions prevailing in the homes or workplaces of the patients. Criticism has also been put forth about neglect of the long latency period of symptoms. Therefore, a provocation study was performed in the homes or workplaces of the patients, where we also studied the symptoms and on-off answer 24 hours after the exposure. Fifteen subjects selected as having fast and distinct reactions from electric equipment were provoked on 4 occasions: mainly 2 true and 2 sham provocations. The intervals between exposure were a few or more days in order to provide the subjects with an opportunity to recover before the next provocation. A control group of healthy subjects with normal hearing and vision verified that the provocations were performed in a blind manner. The patients suffering from "electric hypersensitivity" were no better than the control group in deciding whether or not they were exposed to electric and magnetic fields. Exposure to electric and magnetic fields per se does not seem to be a sufficient cause of the symptoms experienced by this patient group.

Problem statement. In electric and hybrid transport, passengers sit very close to the electrical system of considerable power, usually for a considerable time. People are concerned about the level of frequency, intensity of electromagnetic radiation, and the time spent in transport. The relatively high currents achieved in these systems and the short distances between power devices and passengers mean that the latter can be exposed to the corresponding magnetic fields. This means that there is a need to assess the electromagnetic environment inside these vehicles before they are put on the market. When designing electric and hybrid vehicles and their components, it is necessary to take into account the hazards of magnetic field exposure to drivers, passengers and the environment. The aim is to study the effect of electromagnetic radiation on people and improve the efficiency of vehicle operation by assessing the electromagnetic safety of electric and hybrid vehicles at the stage of their operation, as well as to improve methods for assessing electromagnetic radiation depending on operating conditions. Methodology. Methods are a systematic approach to research, protection against electromagnetic radiation in transport, conducting measurements of electromagnetic radiation in electric and hybrid transport, finding out the spatially strong inhomogeneity of the magnetic field and building 3D topology using numerous uniformly distributed magnetic field sensors in the vehicle interior, i.e. by a differential phase-gradient method for the study of ultra-low frequency amplifiers from 0.001 - 100 Hz of geomagnetic variations, a method of testing magnetic fields. This method allows using three three-component magnetic sensors arranged in a triangle at a short distance from each other (magnetic gradiometer) to construct a vector of gradients and phase velocities of magnetic variations for any of the three components of magnetic fields. As a result, the phase-gradient method has found its application for measuring magnetic fields in electric and hybrid vehicles, as well as for detecting the topology of magnetic fields, taking into account their extreme spatial heterogeneity, the sensors in the cabin should be located quite densely, i.e., the number of sensors should be at least 10-20 (evenly at a distance of ten centimeters at floor level, at head level of drivers and passengers, etc.). Scientific novelty: the study of electrical equipment in electric and hybrid transport has shown that the source of electromagnetic fields, which have a strong temporal and spatial heterogeneity in the frequency range from 0 to hundreds of megahertz, that they are a superposition of fields from many sources (from electric motors, traction batteries, live elements, various electrical equipment (starting and braking resistance, group switches, rheostat units, electrical circuits for ventilation, lighting, heating, etc.). Practical relevance. The problems of determining the moment of occurrence of electromagnetic hazards in electric and hybrid vehicles are considered. It is established that electronic devices on board are usually higher in frequency than magnetic fields, which is associated with changes in traffic modes. Safety measures against electromagnetic radiation in electric and hybrid modes of transport are presented.

Power Transformer being essential and costlier equipment in the power sector, maintaining its healthiness is a crucial task. Condition monitoring of transformers can help in predicting the kinds of fault and prevent the mishap. It can be achieved through Dissolved Gas Analysis. But interpretation of DGA to find the nature of fault that has occurred within transformer is a difficult job. There are many conventional methods like key gas method, Rogers ratio method, Duval triangle etc. These methods may not provide accurate and precise results in desired time. Therefore, modern heuristic methods can be helpful in reducing the computation time. One on such heuristic method is Artificial Bee Colony algorithm. The results of this method are validated by comparing with the Fuzzy Inference System method on the basis of accuracy, precision, specificity and sensitivity.

This paper presents the modelling and simulation of a protection system for equipment in the oil and gas industry with various RF grids and enclosures against 500 MHz electromagnetic interference (EMI). COMSOL Multiphysics®Modelling software was used in this study. Electric and magnetic fields distributions were determined by using the Generalized Minimal Residual Method (GMRES) which was integrated into COMSOL Multiphysics® Modelling software. Simulation results indicated that larger RF grid size contributed to the higher electric and magnetic field on equipment. Furthermore, without RF grid, electric and magnetic fields on the equipment were increased significantly (up to 100x). The maximum electric and magnetic fields were found to be near resonance enclosure size (299 mm for 500 MHz frequency source). The results showed that the presence of the RF grid for the EMI protection system was essential.

The attenuation of magnetic fields is important in many cases in order to protect living beings and electrical equipment from its harmful effect. This paper deals with the DC magnetic field reduction by shielding. A finite element method is applied to study the efficiency and reliability of various shield geometries, placed coaxially with a long current carrying wire, in order to decrease the magnetic field outside the shield. The impact of different combinations of permeability and thicknesses of applied ferromagnetic material is investigated. Calculating the shielding effectiveness, defined as the ratio of magnetic flux density magnitude without and with the shield, the most effective shields can be determined. The obtained results show that a partial shield can be good protection in many practical cases.

Comparisons are made between the average magnetic flux density as would be measured with a three-axis coil probe and the flux density at the center of the probe. Probability distributions of the differences between the two quantities are calculated assuming a dipole magnetic field and are found to be asymmetric. The distributions allow estimates of uncertainty for resultant magnetic field measurements made near some electrical appliances and other electrical equipment.

The ambient electric and magnetic fields as well as the electromagnetic fields associated with video display terminals (VDTs) at 150 offices are measured. The aim of the study is to determine the general level of the various electromagnetic parameters in offices and establish a technical base for a case referent study of skin symptoms among VDT workers. The median value of the 50-Hz background field in the 150 offices is 0.07 mu T. Seven of the offices have background levels higher than 0.5 mu T, which is high enough to cause distortion of the picture on the screen. The dominant source for electric fields in the ELF range is electric equipment in the office, not the VDTs. The equivalent surface potential is less than 0.5 kV for 63% of the measured VDTs. The computer monitor is a major source of magnetic fields in the offices. The median value of the magnetic field in the ELF range in front of the VDT is 0.21 mu T, and in the VLF range it is 0.03 mu T.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The watershed algorithm belongs to classical algorithms in mathematical morphology. Lotufo et al. published a principle of the watershed computation by means of an Image Foresting Transform (IFT), which computes a shortest path forest from given markers. The algorithm itself was described for a 2D case (image) without a detailed discussion of its computation and memory demands for real datasets. As IFT cleverly solves the problem of plateaus and as it gives precise results when thin objects have to be segmented, it is obvious to use this algorithm for 3D datasets taking in mind the minimizing of a higher memory consumption for the 3D case without loosing low asymptotical time complexity of O(m+C) (and also the real computation speed). The main goal of this paper is an implementation of the IFT algorithm with a priority queue with buckets and careful tuning of this implementation to reach as minimal memory consumption as possible. The paper presents five possible modifications and methods of implementation of the IFT algorithm. All presented implementations keep the time complexity of the standard priority queue with buckets but the best one minimizes the costly memory allocation and needs only 19-45% of memory for typical 3D medical imaging datasets. Memory saving was reached by an IFT algorithm simplification, which stores more elements in temporary structures but these elements are simpler and thus need less memory. The best presented modification allows segmentation of large 3D medical datasets (up to 512x512x680 voxels) with 12-or 16-bits per voxel on currently available PC based workstations.

Pseudoknots are folded structures in RNA molecules that perform essential functions as part of cellular transcription machinery and regulatory processes. The prediction of these structures in RNA molecules has important implications in antiviral drug design. It has been shown that the prediction of pseudoknots is an NP-complete problem. Practical structure prediction algorithms based on free energy minimization employ a restricted problem class and dynamic programming. However, these algorithms are computationally very expensive, and their accuracy deteriorates if the input sequence containing the pseudoknot is too long. Heuristic methods can be more efficient, but do not guarantee an optimal solution in regards to the minimum free energy model. We present KnotSeeker, a new heuristic algorithm for the detection of pseudoknots in RNA sequences as a preliminary step for structure prediction. Our method uses a hybrid sequence matching and free energy minimization approach to perform a screening of the primary sequence. We select short sequence fragments as possible candidates that may contain pseudoknots and verify them by using an existing dynamic programming algorithm and a minimum weight independent set calculation. KnotSeeker is significantly more accurate in detecting pseudoknots compared to other common methods as reported in the literature. It is very efficient and therefore a practical tool, especially for long sequences. The algorithm has been implemented in Python and it also uses C/C++ code from several other known techniques. The code is available from http://www.csse.uwa.edu.au/~datta/pseudoknot.

This paper proposes novel approaches for checking and correcting spelling errors in Sinhala essays written by candidates of grade five scholarship examination. They don't have a proper mechanism to identify their spelling mistakes in essays by themselves. Spelling errors by such students may occur due to the violation of spelling rules, missing or adding of letters, missing modifiers, inaccurate spelling in a similar structure, and similar sound letters]. To mitigate such challenges, the Sinhala corpus file has been developed to identify the accurate and inaccurate spellings of the written words. The role of this application is to identify the correct and incorrect words which are entered by the user and generate the most correct words as suggestions for the incorrect words. This paper introduces three new novel approaches to detect the correctly spelled words in Sinhala essays namely object word checker method, suffixes checker method and similar word checker method. With addition to that this paper discusses three approaches to generate accurate suggestions including one novel approach. When evaluating the accuracy of the spelling error detection and correction module the overall results for precision, recall, and the f -measure were recorded as 83.05%, 85.57%, and 86.62% respectively.

Condition monitoring is playing an increasingly important role within electrical power networks, where its use can help to reduce maintenance costs, improve supply reliability, and permit increased utilization of equipment capacity by providing a measure of actual operating conditions as an alternative to relying on more stringent “worst case scenario” assumptions. In this context, energy harvesting may have a role to play in that it offers the possibility of realizing autonomous, self-powering sensors that communicate their data wirelessly. In the vicinity of electrical transmission and distribution equipment, alternating magnetic fields at the power frequency offer a potential source of energy that does not require hard-wiring or batteries. There are many potentially useful locations for sensors where the level of magnetic flux density may be sufficient to provide enough power for a low-power wireless sensor node. This paper describes a free-standing inductive harvester for use in positions where there is an ambient magnetic field due to conductors that are remote and/or inaccessible. Using data from surveys of magnetic flux density levels at two substations, optimum core and coil designs for the harvester are obtained through theoretical analyses and experiments. A demonstrator is then constructed in which a wireless sensor becomes self-powering when immersed in a 50-Hz magnetic field. Laboratory results show that this system can deliver a useful average power of 300 μW when placed in a magnetic flux density of 18 μ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Trms</i> .

Partial discharges are a clear ageing agent on insulating materials used in high voltage electrical machines. For this reason, there is increasing interest in measuring this phenomenon in an effort to forecast unexpected failures in electrical equipment. Despite the fact that normalized tests have been carried out for years, the effect of leakage magnetic fluxes in transformers and rotating machines stator windings has not yet been considered. The authors show that common stray fluxes in typical high voltage machines modify partial discharge activity, so the interaction between ionization processes and magnetic fields is analysed. This might have a clear effect on the results extracted from on-line and off-line partial discharge measurements.

A circuit model and an ad hoc computer program were set up to evaluate electromagnetic interference in the vicinity of protective structures struck by lightning. This program permits the evaluation of the impulsive magnetic fields by calculating the impulse current distribution in different parts of such structures. It also allows the evaluation of the electromagnetic interference induced on susceptible victim circuits to which electric equipment may be connected. To validate the approach, a series of impulse tests was performed in the laboratory on conductive structures designed to highlight the features of the program and to make evident the dependence of the impulse current distributions on some particular phenomena that need simplified modeling, such as the effect of induced or return currents through the ground.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>