Segmentation Of Strings Research Articles

Evolution of semilocal string networks. II. Velocity estimators

We continue a comprehensive numerical study of semilocal string networks and their cosmological evolution. These can be thought of as hybrid networks comprised of (non-topological) string segments, whose core structure is similar to that of Abelian Higgs vortices, and whose ends have long--range interactions and behaviour similar to that of global monopoles. Our study provides further evidence of a linear scaling regime, already reported in previous studies, for the typical length scale and velocity of the network. We introduce a new algorithm to identify the position of the segment cores. This allows us to determine the length and velocity of each individual segment and follow their evolution in time. We study the statistical distribution of segment lengths and velocities for radiation- and matter-dominated evolution in the regime where the strings are stable. Our segment detection algorithm gives higher length values than previous studies based on indirect detection methods. The statistical distribution shows no evidence of (anti)correlation between the speed and the length of the segments.

Searching for cosmic strings in CMB anisotropy maps using wavelets and curvelets

We use wavelet and curvelet transforms to extract signals of cosmic strings from simulated cosmic microwave background (CMB) temperature anisotropy maps, and to study the limits on the cosmic string tension which various ongoing CMB temperature anisotropy experiments will be able to achieve. We construct sky maps with size and angular resolution corresponding to various experiments. These maps contain the signals of a scaling solution of long string segments with a given string tension G μ, the contribution of the dominant Gaussian primordial cosmological fluctuations, and pixel by pixel white noise with an amplitude corresponding to the instrumental noise of the various experiments. In the case that we include white noise, we find that using curvelets we obtain lower bounds on the string tension than with wavelets. For maps with Planck specification, we obtain bounds comparable to what was obtained by the Planck collaboration [1]. Experiments with better angular resolution such as the South Pole Telescope third generation (SPT-3G) survey will be able to yield stronger limits. For maps with a specification of SPT-3G we find that string signals will be visible down to a string tension of G μ = 1.4 × 10−7.

Segmentation and recognition system for unknown-length handwritten digit strings

The segmentation of handwritten digit strings into isolated digits remains a challenging task. The difficulty for recognizing handwritten digit strings is related to several factors such as sloping, overlapping, connecting and unknown length of the digit string. Hence, this paper aims to propose a segmentation and recognition system for unknown-length handwritten digit strings by combining several explicit segmentation methods depending on the configuration link between digits. Three segmentation methods are combined based on histogram of the vertical projection, the contour analysis and the sliding window Radon transform. A recognition and verification module based on support vector machine classifiers allows analyzing and deciding the rejection or acceptance each segmented digit image. Moreover, various submodules are included leading to enhance the robustness of the proposed system. Experimental results conducted on the benchmark dataset show that the proposed system is effective for segmenting handwritten digit strings without prior knowledge of their length comparatively to the state of the art.

An Improved Bandgap Reference with Curvature-Compensated and High Power Supply Rejection

This paper presents a bandgap reference (BGR) with the characteristics of curvature-compensation and high power supply rejection ratio (PSRR). To achieve a better performance, the base current of BJT is injected to a small segment of resistor string to flatten the temperature variation, and a pre-regulator of the power supply is implemented to improve the PSRR. The circuits, designed in 0.18[Formula: see text][Formula: see text]m BCD technology, exhibit an average voltage of 1.212[Formula: see text]V with temperature coefficient of 2.0[Formula: see text]ppm/[Formula: see text] in the range from [Formula: see text] to 110[Formula: see text] at typical condition, and a power supply rejection ratio of [Formula: see text][Formula: see text]dB at low frequency. After 4-bit trimming, Monte Carlo simulation results show that the proposed design gets an accuracy of 0.29%, with a variation of [Formula: see text][Formula: see text]mV. The active design area is 160[Formula: see text][Formula: see text]m, and the power supply current is about 8.2[Formula: see text][Formula: see text]A.

MEMORY-Based Hardware Architectures to Detect ClamAV Virus Signatures with Restricted Regular Expression Features

We aim to implement a single-chip hardware detection engine for virus scanning. Our study is based on the ClamAV virus database, which contains 88.9K strings and 9.6K extended hex-signatures with restricted regular expression (regex) features. We have previously presented cost-effective hardware architectures to detect the 88.9K strings and 3.2K regex patterns that are composed of multiple string segments. In this paper, we shall present hardware architectures to detect the remaining 6.4K regex patterns. Our method is based on the information reduction approach. We transform the byte-oriented matching problem to a token-based matching problem. A regex pattern contains one or more segments, and a segment may be subdivided into multiple non-trivial tokens. In general, a token is associated with one or a few regexes only. The input byte-stream is converted into a token-stream using dedicated hardware units, where the number of tokens is much less than the number of bytes. The token-stream is processed by a NFA-based aggregation unit to determine if any segment can be found. Detected segments are further processed by a scoreboard to determine if any multi-segment pattern can be found. For proof-of-concept, our method is implemented on a Virtex-6 FPGA which consumes 1.84 MB on-chip memory.

Segmentation and Recognition of Handwritten Digit Numeral String Using a Multi Layer Perceptron Neural Networks

Segmentation and Recognition of Handwritten Digit Numeral String Using a Multi Layer Perceptron Neural Networks

Handwritten Courtesy Amount and Signature Recognition on Bank Cheque using Neural Network

Bank cheques are used not only in our country but also all over the world for financial transactions. Still now Bank cheques are processed manually everyday in both developed and developing countries. The proposed system presents a recognition system of both handwritten courtesy amount and signature .To read the courtesy amount and signature, the system uses the scanned image of Bank cheque. The proposed system divided into several stages that focus on: Image preprocessing; the detection of block of courtesy amount and signature; the post processing; the segmentation of string into characters; Feature extraction of courtesy amount and signature; Neural Network recognition. At first, scanned image is converted into gray image and then it is filtered. Then detection of the courtesy amount and signature is performed using image cropping method. The cropped images are post-processed to ensure correct recognition. Then courtesy amount is segmented using the segmentation method. The segmentation module has been implemented as a recursive process. Then segmented digit and binary image of signature are passed through the feature extraction process. A rotation, translation, scaling and orientation invariant feature extraction method has been used to extract the features of the input images based on moment feature extraction method. And finally, a back propagation learning algorithm is used to train up the network and tested the performance. Overall success rate of the system is tested in different sorts of numeral and the experimental result shows satisfactory performance.

Pauses enhance chunk recognition in song element strings by zebra finches.

When learning a language, it is crucial to know which syllables of a continuous sound string belong together as words. Human infants achieve this by attending to pauses between words or to the co-occurrence of syllables. It is not only humans that can segment a continuous string. Songbirds learning their song tend to copy ‘chunks’ from one or more tutors’ songs and combine these into their own song. In the tutor songs, these chunks are often separated by pauses and a high co-occurrence of elements, suggesting that these features affect chunking and song learning. We examined experimentally whether the presence of pauses and element co-occurrence affect the ability of adult zebra finches to discriminate strings of song elements. Using a go/no-go design, two groups of birds were trained to discriminate between two strings. In one group (Pause-group), pauses were inserted between co-occurring element triplets in the strings, and in the other group (No-pause group), both strings were continuous. After making a correct discrimination, an individual proceeded to a reversal training using string segments. Segments were element triplets consistent in co-occurrence, triplets that were partly consistent in composition and triplets consisting of elements that did not co-occur in the strings. The Pause-group was faster in discriminating between the two strings. This group also responded differently to consistent triplets in the reversal training, compared to inconsistent triplets. The No-pause group did not differentiate among the triplet types. These results indicate that pauses in strings of song elements aid song discrimination and memorization of co-occurring element groups.

Segmentation of Handwritten Chinese Character Strings Based on improved Algorithm Liu

Algorithm Liu attracts high attention because of its high accuracy in segmentation of Japanese postal address. But the disadvantages, such as complexity and difficult implementation of algorithm, etc. have an adverse effect on its popularization and application. In this paper, the author applies the principles of algorithm Liu to handwritten Chinese character segmentation according to the characteristics of the handwritten Chinese characters, based on deeply study on algorithm Liu.In the same time, the author put forward the judgment criterion of Segmentation block classification and adhering mode of the handwritten Chinese characters.In the process of segmentation, text images are seen as the sequence made up of Connected Components (CCs), while the connected components are made up of several horizontal itinerary set of black pixels in image. The author determines whether these parts will be merged into segmentation through analyzing connected components. And then the author does image segmentation through adhering mode based on the analysis of outline edges. Finally cut the text images into character segmentation. Experimental results show that the improved Algorithm Liu obtains high segmentation accuracy and produces a satisfactory segmentation result.

Research on the Piano String Sound Reconstruction and its Implementation Based on the Theory of String Vibration

The vibration of the string is a series of different frequency and different amplitude and phase of harmonic vibration superposition. These different frequencies are including fundamental frequency, double or triple frequency, and more integer time’s frequency. It is composed of string segment of vibration. The piano sound is spread by the string vibration, through the string to the soundboard that is by the soundboard to air, and then is introduced to the process of the human ear. String vibration is sound energy generated link, its energy is the key to the size of the sound vibration energy; therefore, the sound propagation attenuation problem in the first part is crucial, how to improve the strings attenuation becomes a key problem to be solved. This article aim is that the application of the string vibration theory in the piano strings sound reconstruction and its implementation are discussed.

Research on the Piano String Sound Reconstruction with Computer Technology Based on the Theory of String Vibration

The vibration of the string is a series of different frequency and different amplitude and phase of harmonic vibration superposition. These different frequencies are including fundamental frequency, double or triple frequency, and more integer time’s frequency. It is composed of string segment of vibration. The piano sound is spread by the string vibration, through the string to the soundboard that is by the soundboard to air, and then is introduced to the process of the human ear. String vibration is sound energy generated link, its energy is the key to the size of the sound vibration energy; therefore, the sound propagation attenuation problem in the first part is crucial, how to improve the strings attenuation becomes a key problem to be solved. This article aim is that the application of the string vibration theory in the piano strings sound reconstruction and its implementation are discussed.

On the number of cosmic strings

The number of cosmic strings in the observable Universe is relevant in determining the probability of detecting such cosmic defects through their gravitational signatures. In particular, we refer to the observation of gravitational lensing events and anisotropy in the cosmic microwave background (CMB) radiation induced by cosmic strings. In this article, a simple method is adopted to obtain an approximate estimate of the number of segments of cosmic strings crossing the particle horizon that fall inside the observed part of the Universe. We show that there is an appreciable difference in the expected number of segments that differentiates cosmic strings arising in Abelian Higgs and Nambu–Goto models and that a different choice of setting for the cosmological model can lead to significant differences in the expected number of cosmic string segments. Of this number, the fraction that are realistically detectable may be considerably smaller.

CMB ISW-lensing bispectrum from cosmic strings

We study the effect of weak lensing by cosmic (super-)strings on the higher-order statistics of the cosmic microwave background (CMB). A cosmic string segment is expected to cause weak lensing as well as an integrated Sachs-Wolfe (ISW) effect, the so-called Gott-Kaiser-Stebbins (GKS) effect, to the CMB temperature fluctuation, which are thus naturally cross-correlated. We point out that, in the presence of such a correlation, yet another kind of the post-recombination CMB temperature bispectra, the ISW-lensing bispectra, will arise in the form of products of the auto- and cross-power spectra. We first present an analytic method to calculate the autocorrelation of the temperature fluctuations induced by the strings, and the cross-correlation between the temperature fluctuation and the lensing potential both due to the string network. In our formulation, the evolution of the string network is assumed to be characterized by the simple analytic model, the velocity-dependent one scale model, and the intercommutation probability is properly incorporated in order to characterize the possible superstringy nature. Furthermore, the obtained power spectra are dominated by the Poisson-distributed string segments, whose correlations are assumed to satisfy the simple relations. We then estimate the signal-to-noise ratios of the string-induced ISW-lensing bispectra and discuss the detectability of such CMB signals from the cosmic string network. It is found that in the case of the smaller string tension, Gμ << 10-7, the ISW-lensing bispectrum induced by a cosmic string network can constrain the string-model parameters even more tightly than the purely GKS-induced bispectrum in the ongoing and future CMB observations on small scales.

Conformational changes of a single magnetic particle string within gels

Magnetorheological (MR) gels consist of micron sized magnetic particles inside a gel matrix. Before physical cross-linking, the suspension is subjected to a small magnetic field which creates a particle string structure. After cross-linking, the string is kept within the gel at room temperature. Under an external homogeneous magnetic field and mechanical deformation, the soft swollen gel matrix allows the string to largely rearrange at microscopic scales. With the help of two homemade magneto cells mounted on an optical microscope, we were able to follow the conformational change and instabilities of a single magnetic particle string under the combined influence of shear (or stretch) and the magnetic field. In the absence of mechanical deformation, an external magnetic field, applied in the perpendicular direction to the string, breaks it into small pieces generating periodic structures like sawteeth. When an external magnetic field is applied parallel to the pre-aligned string, it exhibits a length contraction. However, under shear strain perpendicular to the original pre-structured string (and magnetic field), the string breaks and short string segments tilt, making an angle with the original direction that is smaller than that of the applied shear (non-affine). The difference in tilt angle scales with the inverse length of the small segments L-1 and the magnetic flux density B, reflecting the ability of the gel matrix to expel solvents under local stress.

Jets, Bulk Matter, and their Interaction in Heavy Ion Collisions at the LHC

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The physical picture of our approach is the following: Initial hard scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the pt of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes, flows, and finally hadronizes) and jets, according to some criteria based on partonic energy loss. High energy flux tube segments will leave the fluid, providing jet hadrons via the usual Schwinger mechanism of flux-tube breaking caused by quark-antiquark production. But the jets may also be produced at the freeze-out surface. Here we assume that the quark-antiquark needed for the flux tube breaking is provided by the fluid, with properties (momentum, flavor) determined by the fluid rather than the Schwinger mechanism. Considering transverse fluid velocities up to 0.7c, and thermal parton momentum distributions, one may get a "push" of a couple of GeV to be added to the transverse momentum of the string segment. This will be a crucial effect for intermediate pt jet hadrons.

Probabilistic estimates of the number of cosmic strings

The dependences of the mean expected number of cosmic strings on their redshift up to the surface of last scattering have been derived. The calculations are based on the geometric probability of a straight string segment crossing a given field and on information about the absence of strings when they are searched for via their gravitational lensing effects in optical catalogs. It is shown that there are no strings for redshifts 0 < z < 1.954, but the expected number of strings for 0 < z < 5 can be no more than 2.1 × 103 at the 95% confidence level. The expected number of strings for redshifts up to z = 1100 can be no more than 2.4 × 104 at the 95% confidence level. The latter estimate is sensitive to a priori information about the absence of cosmic strings in the redshift range 0 < z < 1.954 in a field of 4.48 square degrees in optical catalogs; it is smaller than the estimate without allowance for this information by 6%.

Separating jets from bulk matter in heavy ion collisions at the LHC

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The physical picture of our approach is the following: Initial hard scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the pt of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes, flows, and finally hadronizes) and jets, according to some criteria based on partonic energy loss. High energy flux tube segments will leave the fluid, providing jet hadrons via the usual Schwinger mechanism of flux-tube breaking caused by quark-antiquark production. But the jets may also be produced at the freeze-out surface. Here we assume that the quark-antiquark needed for the flux tube breaking is provided by the fluid, with properties (momentum, flavor) determined by the fluid rather than the Schwinger mechanism. Considering transverse fluid velocities up to 0.7c, and thermal parton momentum distributions, one may get a "push" of a couple of GeV to be added to the transverse momentum of the string segment. This will be a crucial effect for intermediate pt jet hadrons.

Lambda-to-Kaon Ratio Enhancement in Heavy Ion Collisions at Several TeV

We introduced recently a new theoretical scheme which accounts for hydrodynamically expanding bulk matter, jets, and the interaction between the two. Important for the particle production at intermediate values of transverse momentum (p(t)) are jet hadrons produced inside the fluid. They pick up quarks and antiquarks (or diquarks) from the thermal matter rather than creating them via the Schwinger mechanism-the usual mechanism of hadron production from string fragmentation. These hadrons carry plasma properties (flavor, flow) but also the large momentum of the transversely moving string segment connecting quark and antiquark (or diquark). They therefore show up at quite large values of p(t), not polluted by soft particle production. We will show that this mechanism leads to a pronounced peak in the Lambda-to-kaon ratio at intermediate p(t). The effect increases substantially with centrality, which reflects the increasing transverse size with centrality.

Jets, bulk matter, and their interaction in heavy ion collisions at several TeV

We discuss a theoretical scheme that accounts for bulk matter, jets, and the interaction between the two. The aim is a complete description of particle production at all transverse momentum (${p}_{t}$) scales. In this picture, the hard initial scatterings result in mainly longitudinal flux tubes, with transversely moving pieces carrying the ${p}_{t}$ of the partons from hard scatterings. These flux tubes constitute eventually both bulk matter (which thermalizes and flows) and jets. We introduce a criterion based on parton energy loss to decide whether a given string segment contributes to the bulk or leaves the matter to end up as a jet of hadrons. Essentially low ${p}_{t}$ segments from inside the volume will constitute the bulk, high ${p}_{t}$ segments (or segments very close to the surface) contribute to the jets. The latter ones appear after the usual flux tube breaking via q-qbar production (Schwinger mechanism). Interesting is the transition region: Intermediate ${p}_{t}$ segments produced inside the matter close to the surface but having enough energy to escape, are supposed to pick up q-qbar pairs from the thermal matter rather than creating them via the Schwinger mechanism. This represents a communication between jets and the flowing bulk matter (fluid-jet interaction). Also very important is the interaction between jet hadrons and the soft hadrons from the fluid freeze-out. We employ this picture to investigate Pb-Pb collisions at 2.76 TeV. We discuss the centrality and ${p}_{t}$ dependence of particle production and long-range dihadron correlations at small and large ${p}_{t}$.

Weak lensing of CMB by cosmic (super-)strings

We study the effect of weak lensing by cosmic (super-)strings on the anisotropies of cosmic microwave background (CMB). In developing a method to calculate the lensing convergence field due to strings, and thereby temperature and polarization angular power spectra of CMB, we clarify how the nature of strings, characterized by the intercommuting probability, can influence these CMB anisotropies. Assuming that the power spectrum is dominated by Poisson-distributed string segments, we find that the convergence spectrum peaks at low multipoles and is mostly contributed from strings located at relatively low redshifts. As the intercommuting probability decreases, the spectra of the convergence and hence the lensed temperature and polarizations are gained because the number density of string segments becomes larger. An observationally important feature of the string-induced CMB polarizations is that the string-lensed spectra decay more slowly on small scales compared with primordial scalar perturbations from standard inflation.