Lifting Coefficients Research Articles

Identification of particular hydrodynamic parameters for a modular type 4 DOF underwater vehicle by means of CFD method

PurposeThe development of robust control algorithms for the position, velocity and trajectory control of unmanned underwater vehicles (UUVs) depends on the accuracy of their mathematical models. Accuracy of the model is determined by precise estimation of the UUV hydrodynamic parameters. The purpose of this study is to determine the hydrodynamic forces and moments acting on an underwater vehicle with complex body geometry and moving at low speeds and to achieve the accurate coefficients associated with them.Design/methodology/approachA three-dimensional (3D) computer-aided design (CAD) model of UUV is designed with one-to-one dimensions. 3D fluid flow simulations are conducted using computational fluid dynamics (CFD) software programme in the solution of Navier Stokes equations for laminar and turbulent flow analysis. The coefficients depending on the hydrodynamic forces and moments are determined by the external flow analysis using the CFD programme. The Flow Simulation k-ε turbulence model is used for the transition from laminar flow to turbulent flow. Hydrodynamic properties such as lift and drag coefficients and roll and yaw moment coefficients are calculated. The parameters are compared with the coefficient values found by experimental methods.FindingsAlthough the modular type UUV has a complex body geometry, the comparative results of the experiments and simulations confirm that the defined model parameters are accurate and close to the actual experimental values. In the proposed k-ε method, the percentage error in the estimation of drag and lifting coefficients is decreased to 4.2% and 8.39%, respectively.Practical implicationsThe model coefficients determined in this study can be used in high-level control simulations which leads to the development of robust real-time controllers for complex-shaped modular UUVs.Originality/valueThe Lucky Fin UUV with 4 degrees of freedom is a specific design and its CAD model is first extracted. Verification of simulation results by experiments is generally less referenced in studies. However, it provides more precise parameter identification of the model. Proposed study offers a simple and low-cost experimental measurement method for verification of the hydrodynamic parameters. The extracted model and coefficients are worthwhile references for the analysis of modular type UUVs.

Experimental investigation of wind pressure characteristics and aerodynamic optimization of a large-span cantilevered roof

Cantilevered roof is particularly vulnerable to wind because high suction loads often occur on the rooftop due to flow separation. However, wind load characteristics associated with cantilevered roof have not been fully understood. In this paper, a 1/100 scale model of a cantilevered roof, over a grandstand, has been tested in a turbulent boundary layer flow, with particular emphasis on characterizing the wind pressure distribution on the cantilevered roof, and assessing the performance of several aerodynamic optimization devices. The results indicate that large wind suction generally occurs near the windward edge on rooftop surface. The effect of approaching wind direction is evident, which can influence the distribution pattern and value of wind pressure. For the effect of roof inclination, the down-sloping roof is found to be more appropriate since it results in most significant reduction in mean wind pressure, as well as the net lifting and bending moment coefficients. Furthermore, it is shown that adding a vented leading edge slot can effectively reduce the rooftop wind suctions. The maximum reduction in mean and peak suction loads is respectively 30% and 45%.

Power-aware VLSI design of reversible watermarking for access control

A lifting based reversible data hiding is introduced here. The low–high subband is subdivided into little blocks of size (4 × 4), to generate a content dependent watermark. Then the access management is done by permutation of the content dependent watermark by a user-specific covert key. The permuted watermark is employed to modulate the lifting coefficients of the low–high subband. The modulation causes degradation of the visual quality of the host image. That plays an important role in access management through inverse method. Lastly, a low-power ‘very-large-scale-integration’ architectural hardware of this scheme is designed and synthesized on a ‘field programmable gate array’. The experiment is conducted over a variety of benchmark images and the results establish the superiority of the method. It is also observed that in real-time processing, the scheme consumes 63.26% less power than the related implementation found in the literature, for watermarking encoder and decoder at a maximum operating frequency of 130.186 MHz for the processing of (512 × 512) sized images.

On Boeing 737 – 300 Wing Aerodynamics Calculations Based on VLM Theory

<p>In this paper, aerodynamics coefficients of Boeing 737-300 were calculated using VLM (vortex lattice method) theory. The wing was assumed to be planar and was divided into 6×6 panels, which were in the trapezoid shape. Aerodynamics lifting and moment coefficients were calculated. Also, center of pressure location was found using data from VLM and wing geometry. Comparisons between literature, finite wing theory and VLM theory were done. It was found that maximum lifting coefficient error between literature and VLM was about 4.0%. Moreover, that between finite wing theory and VLM was about 2.2%. Center of pressure location error between finite wing theory and VLM was about 0.5%.</p>

The (not so) trivial lifting in two dimensions

When generating cutting-planes for mixed-integer programs from multiple rows of the simplex tableau, the usual approach has been to relax the integrality of the non-basic variables, compute an intersection cut, then strengthen the cut coefficients corresponding to integral non-basic variables using the so-called trivial lifting procedure. Although of polynomial-time complexity in theory, this lifting procedure can be computationally costly in practice. For the case of two-row relaxations, we present a practical algorithm that computes trivial lifting coefficients in constant time, for arbitrary maximal lattice-free sets. Computational experiments confirm that the algorithm works well in practice.

Lower Complexity Lifting Structures for Hierarchical Lapped Transforms Highly Compatible With JPEG XR Standard

This paper presents lifting structures for hierarchical lapped transforms (HLTs) that are highly compatible with the Joint Photographic Experts Group (JPEG) eXtended Range (XR) standard and that are lower in complexity in terms of the number of operations and lifting steps than the existing HLT in JPEG XR. Two structures ( $ \text {T}_{RR}$ and $ \text {T}_{HH}$ ), called Householder-lifting structures, are obtained using a lifting factorization followed by a Householder factorization of a non-separable 2D transform of rotation matrices. The third structure ( $ \text {T}_{HR}$ ) is simply derived from a combination of a Hadamard transform ( $ \text {T}_{HH}$ ) and two rotation matrices. The floating-point lifting coefficients are approximated as dyadic values, as in the existing structures of JPEG XR, because doing so costs less, thanks to the structures having only adders and shifters without multipliers. Although the new $ \text {T}_{HH}$ does not outperform the existing structure, the new $ \text {T}_{RR}$ has one fewer adder, one fewer shifter, and four fewer lifting steps than the existing one. Moreover, the new $ \text {T}_{HR}$ not only has one fewer adder, three fewer shifters, and two fewer lifting steps, but also can reuse $ \text {T}_{HH}$ , i.e., it can be used to make a more stylish codec. We show that these lower complexity HLTs are comparable in performance to the existing HLT at lossy-to-lossless image coding and at the same time highly compatible with JPEG XR.

Boson condensation in topologically ordered quantum liquids

Boson condensation in topological quantum field theories (TQFT) has been previously investigated through the formalism of Frobenius algebras and the use of vertex lifting coefficients. While general, this formalism is physically opaque and computationally arduous: analyses of TQFT condensation are practically performed on a case by case basis and for very simple theories only, mostly not using the Frobenius algebra formalism. In this paper we provide a new way of treating boson condensation that is computationally efficient. With a minimal set of physical assumptions, such as commutativity of lifting and the definition of confined particles, we can prove a number of theorems linking Boson condensation in TQFT with chiral algebra extensions, and with the factorization of completely positive matrices over the nonnegative integers. We present numerically efficient ways of obtaining a condensed theory fusion algebra and S matrices; and we then use our formalism to prove several theorems for the S and T matrices of simple current condensation and of theories which upon condensation result in a low number of confined particles. We also show that our formalism easily reproduces results existent in the mathematical literature such as the noncondensability of 5 and 10 layers of the Fibonacci TQFT.

A polyhedral study on 0–1 knapsack problems with set packing constraints

We investigate the 0–1 knapsack problem with additional set packing constraints. First, we introduce a family of facet-defining clique inequalities. Then, we focus on lifted cover inequalities and we define upper and lower bounds on the lifting coefficients. We also introduce a family of lifted cover inequalities where some of the lifting coefficients are set to their upper bound, and the remaining ones are set at their lower bound. Finally, we specialize our results to the knapsack problem with generalized upper bound constraints, where the set packing constraints must be non-overlapping.

A fingerprint-based hybrid gender classification system using genetic algorithm

In this article, a multilevel hybrid approach which gives better accuracy for gender classification is presented. The first level uses discrete wavelet transform (DWT), singular value decomposition (SVD) and principal component analysis (PCA) techniques to derive three independent sets of feature vectors for simultaneous gender classification by three independent neural networks. Coefficients similar to cdf9/7 DWT lifting coefficients and optimum values of initial seeds for the classifiers are evolved using genetic algorithm (GA), for obtaining better feature vectors. Use of lifting coefficients causes faster evolution. In the second stage, the output is derived by decision formulated based on the outputs of the individual classifiers. With a database consisting left thumb impressions of 100 males and 100 females, an overall success rate of 93.94% and an average improvement of 5.24% accuracy over the existing classifiers is achieved. Use of feature vectors having lesser number of elements enhances the speed of operation of the classifier as well.

A fingerprint-based hybrid gender classification system using genetic algorithm

In this article, a multilevel hybrid approach which gives better accuracy for gender classification is presented. The first level uses discrete wavelet transform DWT, singular value decomposition SVD and principal component analysis PCA techniques to derive three independent sets of feature vectors for simultaneous gender classification by three independent neural networks. Coefficients similar to cdf9/7 DWT lifting coefficients and optimum values of initial seeds for the classifiers are evolved using genetic algorithm GA, for obtaining better feature vectors. Use of lifting coefficients causes faster evolution. In the second stage, the output is derived by decision formulated based on the outputs of the individual classifiers. With a database consisting left thumb impressions of 100 males and 100 females, an overall success rate of 93.94% and an average improvement of 5.24% accuracy over the existing classifiers is achieved. Use of feature vectors having lesser number of elements enhances the speed of operation of the classifier as well.

Supermodular covering knapsack polytope

The supermodular covering knapsack set is the discrete upper level set of a non-decreasing supermodular function. Submodular and supermodular knapsack sets arise naturally when modeling utilities, risk and probabilistic constraints on discrete variables. In a recent paper Atamtürk and Narayanan (2009) study the lower level set of a non-decreasing submodular function.In this complementary paper we describe pack inequalities for the supermodular covering knapsack set and investigate their separation, extensions and lifting. We give sequence-independent upper bounds and lower bounds on the lifting coefficients. Furthermore, we present a computational study on using the polyhedral results derived for solving 0–1 optimization problems over conic quadratic constraints with a branch-and-cut algorithm.

Lifting for mixed integer programs with variable upper bounds

We investigate the convex hull of the set defined by a single inequality with continuous and binary variables, which are additionally related by variable upper bound constraints. First we elaborate on general sequence dependent lifting for this set and present a dynamic program for calculating lifting coefficients. Then we study variable fixings of this set to knapsack covers and to the single binary variable polytope. We explicitly give lifting coefficients of continuous variables when lifting the knapsack cover inequality. We provide two new families of facet-defining inequalities for the single binary variable polytope and we prove that combined with the trivial inequalities they give a full description of this polytope.

Sequential Lifting of General Integer Variables for Integer Programs

Lifting integer variables is a widely used technique to create strong cutting planes. In 1975, Wolsey introduced a method to compute the exact sequential lifting coefficients of bounded integer variables by solving many integer programs. This paper presents a new technique to perform exact sequentially up and down lifting of general integer variables. The technique requires solving only a single branching tree. Some computational results demonstrate that this new sequential lifting technique performed approximately 11 times faster than Wolsey?s technique.

Medical Image Compression using Lifting based New Wavelet Transforms

In this paper, the construction of new lifting based wavelets by a new method of calculating lifting coefficients is presented. First of all, new basis functions are utilized to ease new orthogonal traditional wavelets. Then by using the decomposing poly-phase matrix the lifting steps are calculated using a simplified method. The interesting feature of lifting scheme is that the construction of wavelet is derived in spatial domain only; hence the difficulty in the design of traditional wavelets is avoided. Lifting scheme was used to generate second generation wavelets which are not necessarily translation and dilation of one particular function. Short and sharp basis functions are chosen so as to obtain the non-uniform nature of usual image classes. Implemented wavelets are applied on a number of medical images. It was found that the compression ratio (CR) and Peak Signal to Noise Ratio (PSNR) are far ahead of that are obtained with the popular traditional wavelets as well as the successful 5/3 and 9/7 lifting based wavelets. Set Partitioning in Hierarchical Trees (SPIHT) is used to incorporate compression. DOI: http://dx.doi.org/10.11591/ijece.v4i5.5969

The construction of second generation wavelet-based multivariable finite elements for multiscale analysis of beam problems

A design method of second generation wavelet (SGW)-based multivariable finite elements is proposed for static and vibration beam analysis. An important property of SGWs is that they can be custom designed by selecting appropriate lifting coefficients depending on the application. The SGW-based multivariable finite element equations of static and vibration analysis of beam problems with two and three kinds of variables are derived based on the generalized variational principles. Compared to classical finite element method (FEM), the second generation wavelet-based multivariable finite element method (SGW-MFEM) combines the advantages of high approximation performance of the SGW method and independent solution of field functions of the MFEM. A multiscale algorithm for SGW-MFEM is presented to solve structural engineering problems. Numerical examples demonstrate the proposed method is a flexible and accurate method in static and vibration beam analysis.

Faster techniques to evolve wavelet coefficients for better fingerprint image compression

In this article, techniques have been presented for faster evolution of wavelet lifting coefficients for fingerprint image compression (FIC). In addition to increasing the computational speed by 81.35%, the coefficients performed much better than the reported coefficients in literature. Generally, full-size images are used for evolving wavelet coefficients, which is time consuming. To overcome this, in this work, wavelets were evolved with resized, cropped, resized-average and cropped-average images. On comparing the peak- signal-to-noise-ratios (PSNR) offered by the evolved wavelets, it was found that the cropped images excelled the resized images and is in par with the results reported till date. Wavelet lifting coefficients evolved from an average of four 256 × 256 centre-cropped images took less than 1/5th the evolution time reported in literature. It produced an improvement of 1.009 dB in average PSNR. Improvement in average PSNR was observed for other compression ratios (CR) and degraded images as well. The proposed technique gave better PSNR for various bit rates, with set partitioning in hierarchical trees (SPIHT) coder. These coefficients performed well with other fingerprint databases as well.

Two-dimensional integer wavelet transform with reduced influence of rounding operations

If a system for lossless compression of images applies a decorrelation step, this step must map integer input values to integer output values. This can be achieved, for example, using the integer wavelet transform (IWT). The non-linearity, introduced by the obligatory rounding steps, is the main drawback of the IWT, since it deteriorates the desired filter characteristic. This paper discusses different methods for reducing the influence of rounding in 5/3 and 9/7 filter banks. A novel combination of two-dimensional implementations of the JPEG2000 9/7 filter bank with new filter coefficients is proposed and the effects of the methods on lossless image compression are investigated. In addition, these filter banks are compared to the 9/7 Deslauriers-Dubuc filter bank (97DD). The analysed two-dimensional implementations generally perform better than their one-dimensional counterparts in terms of compression ratio for natural images. On average, the 2D 97DD filter bank performs best. In addition, it has been found that the compression results cannot be improved by simply reducing the number of lifting steps via 2D implementations of the JPEG2000 9/7 filter bank. Only the 2D implementation with a minimum number of lifting steps, in combination with modified lifting coefficients, leads to fewer bits per pixel than the separable implementation on average for a selected set of images.

A second-generation wavelet-based finite element method for the solution of partial differential equations

A new second-generation wavelet (SGW)-based finite element method is proposed for solving partial differential equations (PDEs). An important property of SGWs is that they can be custom designed by selecting appropriate lifting coefficients depending on the application. As a typical problem of SGW algorithm, the calculation of the connection coefficients is described, based on the equivalent filters of SGWs. The formulation of SGW-based finite element equations is derived and a multiscale lifting algorithm for the SGW-based finite element method is developed. Numerical examples demonstrate that the proposed method is an accurate and effective tool for the solution of PDEs, especially ones with singularities.

Design and Factorization of Two-Channel Perfect Reconstruction Filter Banks with Causal-Stable IIR Filters

In this paper, new design and factorization methods of two-channel perfect reconstruction (PR) filter banks (FBs) with casual-stable IIR filters are introduced. The polyphase components of the analysis filters are assumed to have an identical denominator in order to simplify the PR condition. A modified model reduction is employed to derive a nearly PR causal-stable IIR FB as the initial guess to obtain a PR IIR FB from a PR FIR FB. To obtain high quality PR FIR FBs for carrying out model reduction, cosine-rolloff FIR filters are used as the initial guess to a nonlinear optimization software for solving to the PR solution. A factorization based on the lifting scheme is proposed to convert the IIR FB so obtained to a structurally PR system. The arithmetic complexity of this FB, after factorization, can be reduced asymptotically by a factor of two. Multiplier-less IIR FB can be obtained by replacing the lifting coefficients with the canonical signal digitals (CSD) or sum of powers of two (SOPOT) coefficients.

A polyhedral study on [formula omitted] knapsack problems with disjoint cardinality constraints: Facet-defining inequalities by sequential lifting

In this paper, we study the polyhedral structure of the set of 0 – 1 integer solutions to a single knapsack constraint and multiple disjoint cardinality constraints (MCKP). This set is a generalization of the classical 0 – 1 knapsack polytope (KP) and the 0 – 1 knapsack polytope with generalized upper bounds (GUBKP). For MCKP, we extend the traditional concept of a cover to that of a generalized cover. We then introduce generalized cover inequalities and present a polynomial algorithm that can lift them into facet-defining inequalities of the convex hull of MCKP. For the case where the knapsack coefficients are non-negative, we derive strong bounds on the lifting coefficients and describe the maximal set of generalized cover inequalities. Finally, we show that the bound estimates we obtained strengthen or generalize the known results for KP and GUBKP.