Size Of String Research Articles

Improving the construction of ORB through FPGA-based acceleration

Binary descriptors have won their place as efficient and effective visual descriptors in several vision tasks. In this context, one of the most widely used binary descriptors to date is the ORB descriptor. ORB is robust against rotation changes, and it uses a learning procedure to generate sampling pairwise tests to construct the descriptor. However, this construction involves a sequential memory access of as many steps as the binary string size. From the latter and motivated by the fact that modern computer vision tasks may require the construction of thousands, if not millions of binary descriptors, we propose to accelerate the construction process of the ORB descriptor via an FPGA-based hardware architecture. The latter is leveraged with a novel arrangement of pairwise tests, which takes advantage of a dual random access memory scheme achieving an acceleration of up to 17 times when compared against the sequential way. The empirical assessment indicates that ORB descriptors obtained from the proposed approach keep a similar performance to that of the original ORB.

In-place algorithms for exact and approximate shortest unique substring problems

We revisit the exact shortest unique substring (SUS) finding problem, and propose its approximate version where mismatches are allowed, due to its applications in subfields such as computational biology. We design a generic in-place framework that fits to solve both the exact and approximate k-mismatch SUS finding, using the minimum 2n memory words, each of ⌈log2⁡(n)⌉ bits, plus n bytes space, where n is the input string size. By using the in-place framework, we can find the exact and approximate k-mismatch SUS for every string position using a total of O(n) and O(n2) time, respectively, regardless of the value of k. Our framework does not involve any compressed or succinct data structures and thus is practical and easy to implement. Experimental study shows that the peak memory usage of our proposal is consistently 9n bytes for any string of size n, validating the claim that our solution is in-place. Further, our proposal uses much less memory and is much faster than the currently best work that has implementation for exact SUS finding.

Robust Fuzzy C-Means Cluster Algorithm through Energy Minimization for Image Segmentation

Background: The Fuzzy c-means (FCMCA) cluster algorithm with spatial information is adopted for image segmentation. In the direction of acceptable segmentation concert on noisy images, the anticipated technique exemplifies the foreign spatial evidence derived from the image and also inherits appropriateness which correspondingly reflects on the universal fuzzy fitness and fuzzy isolation among the clusters. Methods: Segmentation combines two regions firstly, the physical dimension of the image and contextual data through energy reduction function. Secondly, since the kernel metric value is merged with fuzziness of the energy level, the dynamic delineation progresses is steadily deprived of the reinitialization progress for the level set process. Afterwards generating the bunch of non-conquered clarifications, the concluding clustering elucidation is preferred through Cluster Validity Index (CVI) by consuming the foreign spatial evidence. Additionally, the total number of clusters incorporates the actual oblique mutable string length scheme to encrypt the cluster groups in terms of grouped chromosomes spontaneously. Findings: This novel fuzzy and nonlinear type of energy functionality brands the modernizing of region group’s added strength against the noise and edge of the image. The projected method is undergone with image polluted through noise and likened with fuzzy c & k means, dual FCM cluster based approaches with predefined spatial data and dynamic string size is inherited by fuzzy clustering procedure. Applications/Improvements: The investigational outcome demonstrates that the anticipated technique performs thriving in developing the sum of clusters and procurement in acceptable performance on noise in image segmentation process.

MODELING AND ANALYSIS OF UNSTEADY FLOW BEHAVIOR IN DEEPWATER CONTROLLED MUD-CAP DRILLING

A new mathematical model was developed in this study to simulate the unsteady flow in controlled mud-cap drilling systems. The model can predict the time-dependent flow inside the drill string and annulus after a circulation break. This model consists of the continuity and momentum equations solved using the explicit Euler method. The model considers both Newtonian and non-Newtonian fluids flowing inside the drill string and annular space. The model predicts the transient flow velocity of mud, the equilibrium time, and the change in the bottom hole pressure (BHP) during the unsteady flow. The model was verified using data from U-tube flow experiments reported in the literature. The result shows that the model is accurate, with a maximum average error of 3.56% for the velocity prediction. Together with the measured data, the computed transient flow behavior can be used to better detect well kick and a loss of circulation after the mud pump is shut down. The model sensitivity analysis show that the water depth, mud density and drill string size are the three major factors affecting the fluctuation of the BHP after a circulation break. These factors should be carefully examined in well design and drilling operations to minimize BHP fluctuation and well kick. This study provides the fundamentals for designing a safe system in controlled mud-cap drilling operati.

The kinematical AdS5 × S5 Neumann coefficient

For the case of two particles a solution of the string field theory vertex axioms can be factorized into a standard form factor and a kinematical piece which includes the dependence on the size of the third string. In this paper we construct an exact solution of the kinematical axioms for AdS5xS5 which includes all order wrapping corrections w.r.t. the size of the third string. This solution is expressed in terms of elliptic Gamma functions and ordinary elliptic functions. The solution is valid at any coupling and we analyze its weak coupling, pp-wave and large L limit.

A really simple approximation of smallest grammar

In this paper we present a really simple linear-time algorithm constructing a context-free grammar of size 4glog3/2⁡(N/g) for the input string, where N is the size of the input string and g the size of the optimal grammar generating this string. The algorithm works for arbitrary size alphabets, but the running time is linear assuming that the alphabet Σ of the input string can be identified with numbers from {1,…,Nc} for some constant c. Algorithms with such an approximation guarantee and running time are known, however all of them were non-trivial and their analyses were involved. The here presented algorithm computes the LZ77 factorisation and transforms it in phases to a grammar. In each phase it maintains an LZ77-like factorisation of the word with at most ℓ factors as well as additional O(ℓ) letters, where ℓ was the size of the original LZ77 factorisation. In one phase in a greedy way (by a left-to-right sweep and a help of the factorisation) we choose a set of pairs of consecutive letters to be replaced with new symbols, i.e. nonterminals of the constructed grammar. We choose at least 2/3 of the letters in the word and there are O(ℓ) many different pairs among them. Hence there are O(log⁡N) phases, each of them introduces O(ℓ) nonterminals to a grammar. A more precise analysis yields a bound ℓ+4ℓlog⁡(N/ℓ). As ℓ≤g, this yields the desired bound g+4glog⁡(N/g).

Cyclic interconnection for formation control of 1-D vehicle strings

In this paper, we study a formation control scheme for a 1-D string of vehicles. Each member tracks the movement of its immediate predecessor but also the first vehicle tracks the position of the last member of the string. We discuss conditions for the stability of the full interconnected system and show that if a constant spacing policy is used, the stability of the system is lost after the string size exceeds a certain number depending on the model parameters (vehicles and controllers). Additionally, we study the use of a constant time headway spacing policy. If the associated time headway parameter is greater than a critical value, the interconnected system is stable and string stable for any string size. Finally, we show that if an independent leader vehicle is added to the formation and every follower has access to this leader position, the cyclic formation with a constant spacing policy can be made stable and string stable by appropriately selecting a design parameter.

Stretched string with self-interaction at the Hagedorn point: Spatial sizes and black holes

We analyze the length, mass and spatial distribution of a discretized transverse string in $D_\perp$ dimensions with fixed end-points near its Hagedorn temperature. We suggest that such a string may dominate the (holographic) Pomeron kinematics for dipole-dipole scattering at intermediate and small impact parameters. Attractive self-string interactions cause the transverse string size to contract away from its diffusive size, a mechanism reminiscent of the string-black-hole transmutation. The string shows sizable asymmetries in the transverse plane that translate to primordial azimuthal asymmetries in the stringy particle production in the Pomeron kinematics for current pp and pA collisions at collider energies.

Approximation of grammar-based compression via recompression

In this paper we present a simple linear-time algorithm constructing a context-free grammar of size O(glog⁡(N/g)) for the input string, where N is the size of the input string and g the size of the optimal grammar generating this string. The algorithm works for arbitrary size alphabets, but the running time is linear assuming that the alphabet Σ of the input string can be identified with numbers from {1,…,Nc} for some constant c. Otherwise, additional cost of O(Nlog⁡|Σ|) is needed.Algorithms with such an approximation guarantee and running time are known, the novelty of this paper is a particular simplicity of the algorithm as well as the analysis of the algorithm, which uses a general technique of recompression recently introduced by the author. Furthermore, contrary to the previous results, this work does not use the LZ representation of the input string in the construction, nor in the analysis.

A computerized loop based approach for identification of isomorphism and type of mobility in planar kinematic chains

Some new invariants like chain string, link identification string, loop participation of joint frequency string and loop size frequency string of simple jointed kinematic chains are presented. The first step of the proposed method is to identify all possible loops of a kinematic chain and then these new invariants are developed. A modified loop-joint approach is proposed in this work as compared to the previous work in literature where loop-link matrix is formulated to search all the loops present in a kinematic chain. A computer program has been developed for formulating loop-joint matrix of kinematic chain and its all invariants. This method takes into consideration all the loops present, associated joints and links and is able to test isomorphism among kinematic chains and their inversions and also to detect type of mobility of multi degree of freedom kinematic chains. The proposed method is successfully tested for all kinematic chains upto five independent loops having any number of degree of freedom and no counter example is found. The detailed results of 9-link, M = 2 (mobility) and 10 link, M = 3 kinematic chains are provided with five types of mobility and results are in accordance with the results published in literature. The method is also explained with the help of some complex examples and presented in this paper.

The glass transition of polymers with different side-chain stiffness confined in free-standing thin films.

The effect of confinement on the glass transition temperature Tg of polymeric glass formers with different side chain stiffness is investigated by coarse-grained molecular dynamics simulations. We find that polymer with stiffer side groups exhibits much more pronounced Tg variation in confinement compared to that with relatively flexible side groups, in good agreement with experiments. Our string analysis demonstrates that the polymer species dependence of dynamics can be described by an Adam-Gibbs like relation between the size of cooperatively rearranging regions and relaxation time. However, the primary effect of changing side-group stiffness is to alter the activation barrier for rearrangement, rather than string size. We clarify that free-surface perturbation is the primary factor in determining the magnitude of Tg variation for polymers in confinement: It is more significant for polymers having higher Tg and results in much more pronounced reduction of surface Tg and then the overall Tg of the polymers.

A simple yet time-optimal and linear-space algorithm for shortest unique substring queries

We revisit the problem of finding shortest unique substring (SUS) proposed recently by Pei et al. (2013) [12]. We propose an optimal O(n) time and space algorithm that can find an SUS for every location of a string of size n and thus significantly improve their O(n2) time complexity. Our method also supports finding all the SUSes covering every location, whereas theirs can find only one SUS for every location. Further, our solution is simpler and easier to implement and is more space efficient in practice, since we only use the inverse suffix array and the longest common prefix array of the string, while their algorithm uses the suffix tree of the string and other auxiliary data structures. Our theoretical results are validated by an empirical study with real-world data that shows our method is at least 8 times faster and uses at least 20 times less memory. The speedup gained by our method against Pei et al.'s can become even more significant when the string size increases due to their quadratic time complexity. We also have compared our method with the recent Tsuruta et al.'s (2014) [14] proposal, another independent O(n) time and space algorithm for SUS finding. The empirical study shows that both methods have nearly the same processing speed. However, ours uses at least 4 times less memory for finding one SUS and at least 2 times less memory for finding all SUSes, both covering every string location.

Theoretical studies on the structures of one-dimensional Nin (n = 3, 5, 7) metal string complexes under the effect of electric field

Metal string complexes Ni3(dpa)4C12(1), Ni5(tpda)4Cl2(2) and Ni7(teptra)4Cl2(3), have been investigated with density functional theory BP86 method by considering the effect of an external electric field (EF) along the Nin2n+ chain. With the increasing EF, the negative charge of Cl at the low potential end decreases, while that at the opposite end increases. There is no electron-transfer between the metal chain and the equatorial ligands. The spin densities of Ni and Cl at the high potential end decrease, while increasing at the opposite end. When the EF is larger than 2.056V·nm−1, the spin densities on Ni ions of Ni7(teptra)4Cl2 in the quintet state change significantly due to orbital mixing of δNi–N∗(3) and σ∗. The Ni–Cl distances at the high potential end and the Ni–Ni distances at the low potential end increase, while those at the opposite end decrease. Furthermore, the distributions of frontier occupied orbitals move toward the low potential end and their energies increase, whereas those of the unoccupied orbitals move to the opposite end and their energies decrease. Therefore, the HOMO–LUMO gaps decrease. These features are more pronounced with increasing metal chain length. Tuning the size of the metal string has a profound effect on the electron transport.

On query execution over encrypted data

ABSTRACTTo ensure the confidentiality of the encrypted data in a database‐as‐a‐service model, the sensitive data need to be encrypted. When this encrypted data are queried, complete record has to be decrypted to fetch the actual results. This paper is concentrating on improving the performance of different query operations, that is, non‐aggregate, aggregate, and user‐defined query operations on encrypted data. The performance of these query operations over the encrypted data is compared with that of the available methods in terms of the execution time, and it is found that the efficiency of the proposed approach is better than that of the traditional approach. Effectiveness of different types of non‐aggregate query operations is identified in terms of filter ratio and false ratio. The analysis has shown that the filter ratio increases and the false ratio decreases with increase in size of sensitive string and the reachability matrix generated for non‐aggregate attribute. Copyright © 2014 John Wiley & Sons, Ltd.

Adaptive non-critical alarm reduction using hash-based contextual signatures in intrusion detection

Signature-based intrusion detection systems (IDSs) have been widely deployed in network environments aiming to defend against different kinds of attacks. However, a large number of alarms, especially noncritical alarms could be generated during the detection, which can greatly lower the effectiveness of detection and increase the difficulty in analyzing the generated IDS alarms. The main reason is that the detection capability of a signature-based IDS heavily depends on its signatures, whereas current IDS signatures are short of information related to actual deployment (i.e., lacking of contextual information). In addition, the traditional signature matching is a key limiting factor for IDSs in which the processing burden is at least linear to the size of an input string. To mitigate these issues, in this paper, we propose a novel scheme of hash-based contextual signatures that combines the original intrusion detection signatures with contextual information and hash functions. By using hash functions, our scheme can be used to construct an adaptive hash-based non-critical alarm filter which can further improve the performance of existing contextual signatures in filtering out non-critical alarms. Some examples of contextual information matching are also provided. In the evaluation, we discuss how to choose appropriate hash functions and investigate the performance upon implementation of the scheme with a real dataset and in a real network environment. The experimental results are positive and indicate that our scheme is encouraging and effective in filtering out non-critical alarms.

Legal Briefs: Devastating Consequences From Prolonged Use of an Umbilical Arterial Catheter

A 960-g, 26-3/7 weeks’ gestation male twin B was delivered by normal vaginal spontaneous delivery in the breech position to 31-year-old, healthy, gravida 3 para 1 mother whose pregnancy was complicated by preterm labor and diamniotic dichorionic twins. The mother received antibiotics, a partial course of betamethasone, and magnesium sulfate for tocolysis. At delivery, the infant had a heart rate (HR) less than 100 beats per minute, no respiratory effort, and was blue. The infant was intubated and required resuscitation, including chest compressions for 15 seconds, and 2 doses of epinephrine via an endotracheal tube (ETT). Apgar scores were 2 at 1 minute, 4 at 5 minutes, and 7 at 10 minutes. The infant was then admitted to the NICU, where an umbilical venous catheter (UVC) and an umbilical arterial catheter (UAC) were placed. The UVC was placed in the right atrium, where it remained until its removal several days later, and his UAC was placed appropriately at the seventh thoracic vertebrae and removed on day 13. The infant’s vital signs and blood pressure were normal. He had respiratory distress syndrome, for which he was given 3 doses of surfactant. Initially, the infant required 100% oxygen, but after several hours, the inspired oxygen was weaned to 30%, and the ventilator settings were low. His initial complete blood cell count revealed a white blood cell count (WBC) of 3.1 × 103/uL, a platelet count of 185 × 103/uL, and a hematocrit reading of 51% (0.51). The infant was given ampicillin and gentamicin after blood culture results were obtained, and he was started on low-dose indomethacin for intraventricular hemorrhage prophylaxis. On day 1, the fraction of inspired oxygen (Fio2) and ventilatory settings were low. The blood gas values were normal, with some permissive hypercarbia in the …

Towards adaptive character frequency-based exclusive signature matching scheme and its applications in distributed intrusion detection

Network intrusion detection systems (NIDSs), especially signature-based NIDSs, are being widely deployed in a distributed network environment with the purpose of defending against a variety of network attacks. However, signature matching is a key limiting factor to limit and lower the performance of a signature-based NIDS in a large-scale network environment, in which the cost is at least linear to the size of an input string. The overhead network packets can greatly reduce the effectiveness of such detection systems and heavily consume computer resources. To mitigate this issue, a more efficient signature matching algorithm is desirable. In this paper, we therefore develop an adaptive character frequency-based exclusive signature matching scheme (named ACF-EX) that can improve the process of signature matching for a signature-based NIDS. In the experiment, we implemented the ACF-EX scheme in a distributed network environment, evaluated it by comparing with the performance of Snort. In addition, we further apply this scheme to constructing a packet filter that can filter out network packets by conducting exclusive signature matching for a signature-based NIDS, which can avoid implementation issues and improve the flexibility of the scheme. The experimental results demonstrate that, in the distributed network environment, the proposed ACF-EX scheme can positively reduce the time consumption of signature matching and that our scheme is promising in constructing a packet filter to reduce the burden of a signature-based NIDS.

Adaptive blacklist-based packet filter with a statistic-based approach in network intrusion detection

Network intrusion detection systems (NIDS) are widely deployed in various network environments. Compared to an anomaly based NIDS, a signature-based NIDS is more popular in real-world applications, because of its relatively lower false alarm rate. However, the process of signature matching is a key limiting factor to impede the performance of a signature-based NIDS, in which the cost is at least linear to the size of an input string and the CPU occupancy rate can reach more than 80% in the worst case. In this paper, we develop an adaptive blacklist-based packet filter using a statistic-based approach aiming to improve the performance of a signature-based NIDS. The filter employs a blacklist technique to help filter out network packets based on IP confidence and the statistic-based approach allows the blacklist generation in an adaptive way, that is, the blacklist can be updated periodically. In the evaluation, we give a detailed analysis of how to select weight values in the statistic-based approach, and investigate the performance of the packet filter with a DARPA dataset, a real dataset and in a real network environment. Our evaluation results under various scenarios show that our proposed packet filter is encouraging and effective to reduce the burden of a signature-based NIDS without affecting network security.

The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation

We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the validity of the entropy formulation of the AG theory, constraining the exponent values of the RFOT theory. This constraint, together with the analysis of size scales, enables us to estimate the characteristic exponents of RFOT.

TBA-like equations and Casimir effect in (non-)perturbative AdS/CFT

We consider high spin, s, long twist, L, operators in the planar $ \mathcal{N}=4 $ SYM at strong coupling. Precisely, we compute the minimal anomalous dimensions (from asymptotic Bethe Ansatz) for large ’t Hooft coupling λ to the lowest order of the (string) scaling variable $ \ell \sim L/\left( {\ln\,S\sqrt{\lambda }} \right) $ with GKP string size ~ $ \ln\,S\equiv 2\ln \left( {s/\sqrt{\lambda }} \right) $ . At the leading order (ln S) · ℓ2, we can confirm the O(6) non-linear sigma model description for this bulk term, without boundary term (ln S)0. Going further, we derive, extending the O(6) regime, the exact effect of the size finiteness. In particular, we compute, at all loops, the first Casimir correction ℓ0 / ln S (in terms of the infinite size O(6) NLSM), which reveals only one massless mode (out of five), as predictable once the O(6) description has been extended. Consequently, upon comparing with string theory expansion, at one loop our findings agree for large twist, while reveal for negligible twist, already at this order, the appearance of wrapping. At two loops, as well as for next loops and orders, we can produce predictions, which may guide future string computations.