Linear Matching Research Articles

Mid-infrared Raman amplification and wavelength conversion in dispersion engineered silicon-on-sapphire waveguides

Raman amplification based on stimulated Stokes Raman scattering (SSRS) and wavelength conversion based on coherent anti-Stokes Raman scattering (CARS) are theoretically investigated in silicon-on-sapphire (SOS) waveguides in the mid-infrared (IR) region. When the linear phase mismatch Δk is close to zero, the Stokes gain and conversion efficiency drop down quickly due to the effect of parametric gain suppression when the Stokes-pump input ratio is sufficiently large. The Stokes gain increases with the increase of Δk, whereas efficient wavelength conversion needs appropriate Δk under different pump intensities. The conversion efficiency at exact linear phase matching (Δk = 0) is smaller than that at optimal linear phase mismatch by a factor of about 28 dB when the pump intensity is 2 GW cm−2.

The Bree problem with different yield stresses on-load and off-load and application to creep ratcheting

The ratchet boundaries and ratchet strains are derived for the Bree problem and an elastic-perfectly plastic material with different yield stresses on-load and off-load. The Bree problem consists of a constant uniaxial primary membrane stress and a cycling thermal bending stress. The ratchet problem with differing yield stresses is also solved for a modified loading in which both the primary membrane and thermal bending stresses cycle in-phase. The analytic solutions for the ratchet boundaries are compared with the results of deploying the linear matching method (LMM) and excellent agreement is found. Whilst these results are of potential utility for purely elastic–plastic behaviour, since yield stresses will often differ at the two ends of the cycle, the solution is also proposed as a means of assessing creep ratcheting via a creep ductility exhaustion approach.

In-plane shear behavior of corrugated cellular solids and validation of an open-cell corrugated cellular solid

The objective in here is to compare the design of a corrugated wire mesh laminate (CWML) with an open-cell mockup by using a uniaxial shear test. This paper depicts the fabrication of CWML specimens by using a transient liquid phase (TLP) skill at low temperatures and a design of a shear testing frame, and then applying uniaxial shear loading. The material used in the fabrication is a 316 stainless steel woven wire mesh with a 0.22-mm wire diameter and 0.95-mm aperture. Tin-alloy (95%Sn–5%Ag) is used as the bonding material in the TLP method, and the designed shear frames are glued with epoxy. The fabricated samples are tested under a uniaxial condition to determine their shear behaviors. Finite element software is employed to model the CWML and study its reaction to mechanical shear loading. The results of the numerical simulation are confirmed by experimental results for the shear loading behavior. Finally, the CWML is concluded to be of an open-cell foam type, and the results of the numerical model show a reasonably linear match to the experimental results on a log-log scale.

On creep-fatigue endurance of TIG-dressed weldments using the linear matching method

This paper is devoted to parametric study on creep-fatigue endurance of the steel type 316N(L) weldments at 550°C identified as type 3 according to R5 Vol. 2/3 procedure classification. The study is implemented using a direct method known as the Linear Matching Method (LMM) and based upon the creep-fatigue evaluation procedure considering time fraction rule for creep-damage assessment. Seven configurations of the weldment, characterised by particular values of a geometrical parameter ρ, are proposed. Parameter ρ, which represents different grades of TIG dressing, is a ratio between the radius of the fillet of the remelted metal on a weld toe and the thickness of welded plates. For each configuration, the total number of cycles to failure N☆ in creep-fatigue conditions is assessed numerically for different loading cases defined by normalised bending moment M∼ and dwell period Δt. The obtained set of N☆ is extrapolated by the analytic function dependent on M∼,Δt and parameter ρ. Proposed function for N☆ shows good agreement with numerical results obtained by the LMM. Therefore, it is used for the identification of Fatigue Strength Reduction Factors (FSRFs) effected by creep, which are intended for design purposes, and dependent on Δt and ρ.

Minimum income in a transition economy

AbstractThe Albanian Ndihma Ekonomike is one of the first poverty reduction programmes launched in transitional economies. Its record has been judged positively during the recession period of the 1990s and negatively during the more recent growth phase. This article reconsiders the programme using a regression‐adjusted local linear matching estimator first suggested by Heckman et al. (1997, 1998). We find the programme to have a weak targeting capacity and a non‐significant impact on different household outcomes.

Application of linear matching method to creep–fatigue failure analysis of cruciform weldment manufactured of austenitic steel AISI type 316N(L)

This paper presents a creep–fatigue life assessment of a cruciform weldment made of the steel AISI type 316N(L) and subjected to reversed bending and cyclic dwells at 550°C using the linear matching method (LMM) and considering different weld zones. The design limits are estimated by the shakedown analysis using the LMM and elastic–perfectly plastic material model. The creep–fatigue analysis is implemented using the material models: Ramberg–Osgood model for plastic strains under saturated cyclic conditions and power law model in ‘time hardening’ form for creep strains during primary creep stage. The number of cycles to failure N* under creep–fatigue interaction is defined by relation for cycles to fatigue failure N* dependent on total strain range Δϵtot for the fatigue damage ωf, long term strength relation for the time to creep rupture t* dependent on average stress during dwell Δt for the creep damage ωcr and non-linear creep–fatigue interaction diagram for the total damage. Numerically estimated N* for different Δt and Δϵtot shows good quantitative agreement with experiments. A parametric study of different dwell times Δt is used to formulate the functions for N* and residual life L* dependent on Δt and normalised bending moment .

A parametric study on creep–fatigue strength of welded joints using the linear matching method

This paper presents a parametric study on creep–fatigue strength of the steel AISI type 316N(L) weldments of types 1 and 2 according to R5 Vol. 2/3 Procedure classification at 550°C. The study is implemented using the Linear Matching Method (LMM) and is based upon a latest developed creep–fatigue evaluation procedure considering time fraction rule for creep-damage assessment. Parametric models of geometry and FE-meshes for both types of weldments are developed in this way, which allows variation of parameters governing shape of the weld profile and loading conditions. Five configurations, characterised by individual sets of parameters, and presenting different fabrication cases, are proposed. For each configuration, the total number of cycles to failure N☆ in creep–fatigue conditions is assessed numerically for different loading cases including normalised bending moment M∼ and dwell period Δt. The obtained set of N☆ is extrapolated by the analytic function, which is dependent on M∼,Δt and geometrical parameters (α and γ). Proposed function for N☆ shows good agreement with numerical results obtained by the LMM. Thus, it is used for the identification of Fatigue Strength Reduction Factors (FSRFs) intended for design purposes and dependent on Δt, α, γ.

The nonlinear development of the relativistic two-stream instability

The two-stream instability has been mooted as an explanation for a range of astrophysical applications from GRBs and pulsar glitches to cosmology. Using the first nonlinear numerical simulations of relativistic multi-species hydrodynamics we show that the onset and initial growth of the instability are very well described by linear perturbation theory. In the later stages the linear and nonlinear description match only qualitatively, and the instability does not saturate even in the nonlinear case by purely ideal hydrodynamic effects.

Detection and Classification of Multiple Objects using an RGB-D Sensor and Linear Spatial Pyramid Matching

This paper presents a complete system for multiple object detection and classification in a 3D scene using an RGB-D sensor such as the Microsoft Kinect sensor. Successful multiple object detection and classification are crucial features in many 3D computer vision applications. The main goal is making machines see and understand objects like humans do. To this goal, the new RGB-D sensors can be utilized since they provide real-time depth map which can be used along with the RGB images for our tasks. In our system we employ effective depth map processing techniques, along with edge detection, connected components detection and filtering approaches, in order to design a complete image processing algorithm for efficient object detection of multiple individual objects in a single scene, even in complex scenes with many objects. Besides, we apply the Linear Spatial Pyramid Matching (LSPM) [1] method proposed by Jianchao Yang et al for the efficient classification of the detected objects. Experimental results are presented for both detection and classification, showing the efficiency of the proposed design.

Linear Compressed Pattern Matching for Polynomial Rewriting (Extended Abstract)

This paper is an extended abstract of an analysis of term rewriting where the terms in the rewrite rules as well as the term to be rewritten are compressed by a singleton tree grammar (STG). This form of compression is more general than node sharing or representing terms as dags since also partial trees (contexts) can be shared in the compression. In the first part efficient but complex algorithms for detecting applicability of a rewrite rule under STG-compression are constructed and analyzed. The second part applies these results to term rewriting sequences. The main result for submatching is that finding a redex of a left-linear rule can be performed in polynomial time under STG-compression. The main implications for rewriting and (single-position or parallel) rewriting steps are: (i) under STG-compression, n rewriting steps can be performed in nondeterministic polynomial time. (ii) under STG-compression and for left-linear rewrite rules a sequence of n rewriting steps can be performed in polynomial time, and (iii) for compressed rewrite rules where the left hand sides are either DAG-compressed or ground and STG-compressed, and an STG-compressed target term, n rewriting steps can be performed in polynomial time.

Moment matching for nonlinear port Hamiltonian and gradient systems

The problem of moment matching with preservation of port Hamiltonian and gradient structure is studied. Based on the time-domain approach to linear moment matching, we characterize the (subset of) port Hamiltonian/gradient models from the set of parameterized models that match the moments of a given port Hamiltonian/gradient system, at a set of finite points.

The association of complementary and alternative medicine use and health care expenditures for back and neck problems.

Health care costs associated with use of complementary and alternative medicine (CAM) by patients with spine problems have not been studied in a national sample. To estimate the total and spine-specific medical expenditures among CAM and non-CAM users with spine problems. Analysis of the 2002-2008 Medical Expenditure Panel Survey. Adults (above 17 y) with self-reported neck and back problems who did or did not use CAM services. Survey-weighted generalized linear regression and propensity matching to examine expenditure differences between CAM users and non-CAM users while controlling for patient, socioeconomic, and health characteristics. A total of 12,036 respondents with spine problems were included, including 4306 (35.8%) CAM users (40.8% in weighted sample). CAM users had significantly better self-reported health, education, and comorbidity compared with non-CAM users. Adjusted annual medical costs among CAM users was $424 lower (95% confidence interval: $240, $609; P<0.001) for spine-related costs, and $796 lower (95% confidence interval: $121, $1470; P = 0.021) for total health care cost than among non-CAM users. Average expenditure for CAM users, based on propensity matching, was $526 lower for spine-specific costs (P<0.001) and $298 lower for total health costs (P = 0.403). Expenditure differences were primarily due to lower inpatient expenditures among CAM users. CAM users did not add to the overall medical spending in a nationally representative sample with neck and back problems. As the causal associations remain unclear in these cross-sectional data, future research exploring these cost differences might benefit from research designs that minimize confounding.

Signal Recovery on Incoherent Manifolds

Suppose that we observe noisy linear measurements of an unknown signal that can be modeled as the sum of two component signals, each of which arises from a nonlinear submanifold of a high-dimensional ambient space. We introduce successive projections onto incoherent manifolds (SPIN), a first-order projected gradient method to recover the signal components. Despite the nonconvex nature of the recovery problem and the possibility of underdetermined measurements, SPIN provably recovers the signal components, provided that the signal manifolds are incoherent and that the measurement operator satisfies a certain restricted isometry property. SPIN significantly extends the scope of current recovery models and algorithms for low-dimensional linear inverse problems and matches (or exceeds) the current state of the art in terms of performance.

Modeling genetic regulatory networks: a delay discrete dynamical model approach

Modeling genetic regulatory networks is an important research topic in genomic research and computational systems biology. This paper considers the problem of constructing a genetic regulatory network (GRN) using the discrete dynamic system (DDS) model approach. Although considerable research has been devoted to building GRNs, many of the works did not consider the time-delay effect. Here, the authors propose a time-delay DDS model composed of linear difference equations to represent temporal interactions among significantly expressed genes. The authors also introduce interpolation scheme and re-sampling method for equalizing the non-uniformity of sampling time points. Statistical significance plays an active role in obtaining the optimal interaction matrix of GRNs. The constructed genetic network using linear multiple regression matches with the original data very well. Simulation results are given to demonstrate the effectiveness of the proposed method and model.

Unified theory of spin dynamics in a two-dimensional electron gas with arbitrary spin-orbit coupling strength at finite temperature

We study the spin dynamics in the presence of impurity and electron-electron (e-e) scattering in a III-V semiconductor quantum well with arbitrary spin-orbit coupling (SOC) strength and symmetry at finite temperature. We derive the coupled spin-charge dynamic equations in the presence of inelastic scattering and provide a new formalism that describes the spin relaxation and dynamics in both the weak and the strong SOC regimes in a unified way. In the weak SOC regime, as expected, our theory reproduces all previous zero-temperature results, most of which have focused on impurity-scattering induced spin-charge dynamics. In the regime where the strength of the Rashba and linear Dresselhaus SOC match, known as the SU(2) symmetry point, experiments have observed the spin-helix mode with a large spin-lifetime whose unexplained nonmonotonic temperature dependence peaks at around 75 K. As a key test of our theory, we are able to naturally explain quantitatively this nonmonotonic dependence and show that it arises as a competition between the Dyakonov-Perel mechanism, suppressed at the SU(2) point, and the Elliott-Yafet mechanism. In the strong SOC regime, we show that our theory directly reproduces the only previous known analytical result at the SU(2) symmetry point in the ballistic regime. It also explains, as we have shown previously, the rise of damped oscillating dynamics when the electron scattering time is larger than half of the spin precession time due to the SOC. Hence we provide a unified theory of the spin dynamics in two-dimensional electron gases in the full phase diagram experimentally accessible.

STUDY ON OIL-GAS RESERVOIR DETECTING METHODS USING HYPERSPECTRAL REMOTE SENSING

Abstract. Oil-gas reservoir exploration using hyperspectral remote sensing, which based on the theory of hydrocarbon microseepage information and fine spectral response of target, is a new direction for the application of remote sensing technology. In this paper, Qaidam Basin and Liaodong Bay in China were selected as the study areas. Based on the hydrocarbon microseepage theory, the analysis of crude oil in soil in Qaidam Basin and spectral experiment of crude oil in sea water in Liaodong Bay, Hyperion hyperspectral remote sensing images were used to develop the method of oil-gas exploration. The results indicated that the area of oil-gas reservoir in Qaidam Basin could be delimited in two ways: the oil-gas reservoir can be obtained directly by the absorption bands near 1730nm in Hyperion image; and Linear Spectral Unmixing (LSU) and Spectral Angle Matching (SAM) of alteration mineral (e.g. kaolinite, illite) could be used to indirectly detect the target area in Qaidam Basin. In addition, combined with the optimal bands in the region of visible/near-infrared, SAM was used to extract the thin oil slick of microseepage in Liaodong Bay. Then the target area of oil-gas reservoir in Liaodong Bay can be delineated.

Analysis of multi-stage open shop processing systems

We study algorithmic problems in multi-stage open shop processing systems that are centered around reachability and deadlock detection questions. We characterize safe and unsafe system states. We show that it is easy to recognize system states that can be reached from the initial state (where the system is empty), but that in general it is hard to decide whether one given system state is reachable from another given system state. We show that the problem of identifying reachable deadlock states is hard in general open shop systems, but is easy in the special case where no job needs processing on more than two machines (by linear programming and matching theory), and in the special case where all machines have capacity one (by graph-theoretic arguments).

Do unemployed workers benefit from enterprise zones? The French experience

This paper presents an impact evaluation of the French enterprise zone program which was initiated in 1997 to help unemployed workers find employment by granting a significant wage-tax exemption (about one third of total labor costs) to firms hiring at least 20% of their labor force locally. Drawing from a unique geo-referenced dataset of unemployment spells in the Paris region over an extensive period of time (1993–2003), we are able to measure the direct effect of the program on unemployment duration, distinguishing between short- and medium-term effects. This is done by implementing an original two-stage empirical strategy using individual data in the first stage and aggregate data and conditional linear matching techniques in the second stage. We show that although the enterprise zone program tended to “pick winners”, it is likely to be cost-ineffective. It had a small but significant effect on the rate at which unemployed workers find a job (which is increased by a modest 3%). This effect is localized and significant only in the short run (i.e. at best during the 3years that follow the start of the policy).

Comparisons of spectral characteristics of wind noise between omnidirectional and directional microphones

Wind noise reduction is a topic of ongoing research and development for hearing aids and cochlear implants. The purposes of this study were to examine spectral characteristics of wind noise generated by directional (DIR) and omnidirectional (OMNI) microphones on different styles of hearing aids and to derive wind noise reduction strategies. Three digital hearing aids (BTE, ITE, and ITC) were fitted to Knowles Electronic Manikin for Acoustic Research. They were programmed to have linear amplification and matching frequency responses between the DIR and OMNI modes. Flow noise recordings were made from 0° to 360° azimuths at flow velocities of 4.5, 9.0, and 13.5 m/s in a quiet wind tunnel. Noise levels were analyzed in one-third octave bands from 100 to 8000 Hz. Comparison of wind noise revealed that DIR generally produced higher noise levels than OMNI for all hearing aids, but it could result in lower levels than OMNI at some frequencies and head angles. Wind noise reduction algorithms can be designed to detect noise levels of DIR and OMNI outputs in each frequency channel, remove the constraint to switch to OMNI in low-frequency channel(s) only, and adopt the microphone mode with lower noise levels to take advantage of the microphone differences.

A Robust Audio Fingerprinting Method Based on Segmentation Boundaries

A robust audio fingerprinting method is presented based on segmentation boundaries. In order to obtain robustness against linear speed changes, fingerprint extraction and matching are synchronized with the segmentation boundaries. Experimental results show that the proposed method is also robust against other common audio processing steps including low bit-rate compression, equalization, and time-scale modification.