Local Parameter Values Research Articles

Laser spectroscopy of thermal plasma

Thermal plasma, due to its applications, is a research field of great importance, but reliable diagnostics of such plasma remains a challenging task. Spatially resolved methods, which provide local values of plasma parameters, are crucial for understanding the underlying physics. This can be achieved using pump–probe techniques. Two methods applicable and useful for thermal plasma diagnostics—four-wave mixing and scattering of laser beams—are discussed in this paper. Experimental examples of their application, namely four-wave mixing in argon arc plasma and scattering of laser light by laser-induced plasma, are presented.

Weak symmetry breaking in two-dimensional topological insulators

We show that there exist two dimensional (2D) time reversal invariant fractionalized insulators with the property that both their boundary with the vacuum and their boundary with a topological insulator can be fully gapped without breaking time reversal or charge conservation symmetry. This result leads us to an apparent paradox: we consider a geometry in which a disk-like region made up of a topological insulator is surrounded by an annular strip of a fractionalized insulator, which is in turn surrounded by the vacuum. If we gap both boundaries of the strip, we naively obtain an example of a gapped interface between a topological insulator and the vacuum that does not break any symmetries -- an impossibility. The resolution of this paradox is that this system spontaneously breaks time reversal symmetry in an unusual way, which we call \emph{weak symmetry breaking}. In particular, we find that the only order parameters that are sensitive to the symmetry breaking are nonlocal operators that describe quasiparticle tunneling processes between the two edges of the strip; expectation values of local order parameters vanish exponentially in the limit of a wide strip. Also, we find that the symmetry breaking in our system comes with a ground state degeneracy, but this ground state degeneracy is topologically protected, rather than symmetry protected. We show that this kind of symmetry breaking can also occur at the edge of 2D fractional topological insulators.

Active Mode Recognition of Switched Nonlinear Systems: Application to Fault Detection and Isolation

AbstractRobust switching detection and active mode recognition are addressed for switched nonlinear systems. The nonlinear modes are represented by Takagi‐Sugeno (TS) models where the weighting functions are supposed to be online computable. The proposed switching detection technique and the active mode recognition method lie on indicator signals that are generated using a data‐driven projection technique. The main advantage of this method is that it does not need the knowledge of local model parameter values. Only input‐output data and the weighting functions of the TS model are used to generate these indicator signals. A numerical example is provided to illustrate the proposed approach.

Vertical heterogeneities of hydraulic aquitard parameters: preliminary results from laboratory and in situ monitoring

A borehole is developed in a shallow multi-layered aquifer and used to derive the porosity, specific storage and hydraulic conductivity of the aquitard. Local values of hydrodynamical parameters are estimated from petrophysical analysis of core samples, and the empirical relationship between porosity and permeability. Vertical diffusivity is determined from the response of the aquitard to a loading cyclic signal using pressure records at different depths. Hydraulic conductivities deduced from the petrophysical analysis ranged from 10−8 to 10−10 m s−1 and are comparable with those of facies of marine/lacustrine clay observed in samples. The permeability values calculated based on diffusivity are within the range 10−9 to 10−11 m s−1 with a quasi-systematic bias of one order of magnitude. These values are average for a larger part of the aquitard and correspond to an integrated value. The methodology retained for the aquitard characterization is discussed with emphasis on the implications for the management of a complex aquifer system. Citation Larroque, F., Cabaret, O., Atteia, O., Dupuy, A., and Franceschi, M., 2013. Vertical heterogeneities of hydraulic aquitard parameters: preliminary results from laboratory and in situ monitoring. Hydrological Sciences Journal, 58 (4), 912–929.

Local parameter for armor weight estimation

Yoo, D.H., Yoon, J.J., Yoo, J., Lim, H.S., Choi, J.Y., 2013. Local parameter for armor weight estimationA new surf parameter called the ‘wave action slope' is introduced to represent local wave conditions in shallow waters by employing local values of wave length or wave celerity and wave height. The use of wave theory on a flat bed of depth at the front of the breakwater might be considered far superior to the simple adoption of the deep water wave length for characterizing surfing waves at a shoaling depth. The wave action slope is formed by the product of the breakwater slope and the ratio of the celerity to the wave height. The optimum or minimum weight of the armor unit is related to the wave action slopes, which are employed for developing new empirical equations. Analyzing the laboratory data of van der Meer revealed that the armor weights are closely related to the wave action slope. By using the new surf parameter given with local parameter values, we suggest a simple but accurate equation to estimate the breakwater armor weight. Several empirical equations are applied to cases of failure experienced along the eastern coast of Korea. The values given by the Hudson equation are satisfactory for 26 of the 57 total failure cases. The number of satisfactory cases decreases by using recent empirical equations; of the 57 failure cases, the number of satisfactory cases yielded is 17 for the van der Meer/de Jong equation and 13 for the equation of the present study considering local parameters. The reduced number of satisfactory cases may indicate improvement of the new empirical equations over the Hudson equation.

A Novel Image Registration Approach With SIFT Algorithm and Tangent-Cross-Point Feature

By the aid of Tangent-Cross-Point feature, a novel improved SIFT algorithm is proposed in this paper. This method is more efficient and reliable in some cases, since it adopts Tangent-Cross-Point feature to improve the efficiency and robustness of SIFT algorithm. With a pair of matching feature points and a pair of curves nearby, it’s very easy to estimate the values of local transformation parameters and validate the correctness of this matching by the aid of Tangent-Cross-Point feature.

Automated Regularization Parameter Selection in Multi-Scale Total Variation Models for Image Restoration

Multi-scale total variation models for image restoration are introduced. The models utilize a spatially dependent regularization parameter in order to enhance image regions containing details while still sufficiently smoothing homogeneous features. The fully automated adjustment strategy of the regularization parameter is based on local variance estimators. For robustness reasons, the decision on the acceptance or rejection of a local parameter value relies on a confidence interval technique based on the expected maximal local variance estimate. In order to improve the performance of the initial algorithm a generalized hierarchical decomposition of the restored image is used. The corresponding subproblems are solved by a superlinearly convergent algorithm based on Fenchel-duality and inexact semismooth Newton techniques. The paper ends by a report on numerical tests, a qualitative study of the proposed adjustment scheme and a comparison with popular total variation based restoration methods.

Polynomial-time interior-point algorithm based on a local self-concordant finite barrier function

The choice of self-concordant functions is the key to efficient algorithms for linear and quadratic convex optimizations, which provide a method with polynomial-time iterations to solve linear and quadratic convex optimization problems. The parameters of a self-concordant barrier function can be used to compute the complexity bound of the proposed algorithm. In this paper, it is proved that the finite barrier function is a local self-concordant barrier function. By deriving the local values of parameters of this barrier function, the desired complexity bound of an interior-point algorithm based on this local self-concordant function for linear optimization problem is obtained. The bound matches the best known bound for small-update methods.

FDS simulation of the fuel fireball from a hypothetical commercial airliner crash on a generic nuclear power plant

In the aftermath of 9/11 events it became clear that the impact of a fast flying commercial airliner hitting the NPP could no longer be excluded as a potential external hazard threatening the nuclear power plant (NPP) safety. One of the potential consequences of the impact is the occurrence of a fireball, large enough to engulf the entire NPP. The knowledge about fireballs from air crashes is rather poor since it is only based on footage shot by chance. From careful physical and chemical examinations using first principles, it can be concluded that the physics and chemistry of the kerosene fireball are similar to BLEVE fireballs in gas tank accidents which have been studied during the last decades. The knowledge from these analyses can be applied to air crash fireball analysis. In order to obtain an adequate understanding of the potential hazards to a NPP engulfed by a fireball a detailed analysis of the fireball is necessary. It is only by a detailed analysis that the effect of the NPP structures on the evolution of the fireball can be derived. Though the safety-relevant parts of the NPP are strong concrete structures, according to IAEA regulations the hypothesized entry of combustion products into ventilation or air supply systems and the entry of fuel into buildings through normal openings have to be analyzed in detail. This requires local transient values of the safety-relevant fireball parameters. With the NPP being a very large structure an adequately detailed simulation requires large computing grids and substantial computing power. With the release of Version 5 of the Fire Dynamic Simulator (FDS) from NIST in 2007 a simulation tool is now available which is capable to perform simulations of large fireballs on sufficiently large computing grids. These fireball simulations can be performed also by any other CFD code in which the relevant models have been implemented. The FDS fireball simulation capabilities were validated with the help of a well-documented fireball event, in which 5.9 to of propane were burnt during a BLEVE impact experiment conducted by the German BAM in 1999. To demonstrate the applicability of FDS to nuclear safety analysis a simulation of the impact of a 90 to fireball on a generic NPP was performed. The results are presented in this paper and show that FDS release Version 5 is an adequate tool to analysis the effect of a fireball on a NPP, even if the largest possible amount of kerosene involved in the crash is assumed. The work presented in this paper is based on codes, papers, footage and material that are freely available on the Internet. The paper does not use any information that is not freely available on the Internet.

Determining acoustical parameters using cochlear modeling and auditory masking

The acoustical qualities of a concert hall or any other room are generally expressed using acoustical parameters determined from impulse responses. From microphone array measurements it turned out that these parameters can fluctuate severely over small distances, whereas the perceptual cues for which these parameters are supposed to be a measure remain constant. This means that a local parameter value has a very low predictive value for acoustic quality. In this research, cochlear modeling techniques and simulations of auditory masking effects have been applied to model human hearing. These techniques together model various stages in the auditory path, like the movement of the basilar membrane inside the cochlea and mechanisms inside the brains. It turns out that determining acoustical parameters using this representation leads to results which show much less spatial fluctuations, and are closer to human perception.

Dependence of mechanical compressive strength on local variations in microarchitecture in cancellous bone of proximal human femur

Human cancellous bone is a heterogeneous material. Despite this, most of the published studies report correlations between mechanical properties and morphometric parameters averaged on the whole specimen. This work investigated whether local variations in morphometric parameters were linked to the localized failure regions of cancellous bone. Additionally, it was examined whether local values of morphometric parameters can predict the ultimate stress better than the average bone volume fraction (BV/TV). Cylindrical cancellous bone specimens extracted along the primary compressive group of human femoral heads were studied. These were microCT-imaged to assess the morphometric parameters, compressed to determine the ultimate stress, and rescanned by microCT to visualize the failure region. Failure involved slightly less than half of the free height of the specimens. Significant differences were found in the morphometric parameters calculated in the failure and in the non-failure regions. The cross-sections containing minimum BV/TV values were those most often located inside the failure region (83%, p<0.001). Regression analysis confirmed that variations in BV/TV best describe variations in ultimate stress ( R 2=0.84) out of the averaged morphometric parameters. The prediction of ultimate stress increased when minimum or maximum values of the morphometric parameters were taken, with the highest prediction found by considering the minimum BV/TV ( R 2=0.95). In conclusion, due to the heterogeneity of cancellous bone, there may exist regions characterized by a different microarchitecture, where the bone is weaker and consequently is more likely to fail. These regions mostly contain minimum values in BV/TV, which were found to predict ultimate stress better than average BV/TV.

Inverse groundwater modelling in the Willunga Basin, South Australia

A new inverse technique for modelling groundwater flow, based on a functional minimization technique, has been used to calibrate a groundwater flow model of a subregion of the Port Willunga aquifer within the Willunga Basin in South Australia. The Willunga Basin is the location of extensive viticulture, irrigated primarily by groundwater, the levels and quality of which have declined significantly over the last 40 years. The new method is able to generate estimates of transmissivity, storativity and groundwater recharge over the whole subregion as a time-varying continuous surface; previous methods estimate local discrete parameter values at specific times. The new method has also been shown to produce accurate head values for the subregion and very good estimates of groundwater recharge. Its ultimate goal will be to provide a new and invaluable tool for significantly improved groundwater resource management.

Biophysical effects of electric fields on membrane water interfaces: a mini review

Lipid-water interfaces are dielectric transition regions. Their local organizations are highly sophisticated. They are sensitive to electric field with dramatic consequences on the global membrane organization and function. The importance of using local values of parameters (e.g. dielectric constant) near water-solution interface due to hydration and different electrostatic effects is often neglected in the description of cellular functions. Structural changes in the lipid layer are induced by minute changes in the electric properties of the interface. They bring alterations in the structure and oligomerization of membrane proteins.

A probe diagnostics for high-speed flows of rarefied partially dissociated plasma

A procedure of probe diagnostics of supersonic flows of rarefied partially dissociated plasma has been developed. It is shown that the use of a single cylindrical Langmuir probe and a pressure probe allows determination of the complete set of the local values of plasma parameters and the degrees of dissociation, nonisothermality, and flow ionization.

Optimization technique for simple reconstruction of the index modulation profile of symmetric fiber Bragg gratings from their reflective spectrum

We propose a new and simple method to reconstruct the refractive-index modulation of a symmetric fiber Bragg grating (FBG) from its magnitude reflection spectrum (i.e., phase information is not required). The reconstruction method uses an FBG model based on some known parameters of the fabricated FBG (grating length, number of subgratings, and grating period) and an optimization technique, namely, the Quasi-Newton method, to find the local parameter values of the FBG. To our knowledge, this is the first time that the reconstruction of FBG is experimentally realized by an optimization technique. Compared with other reconstruction methods, the proposed method is so simple that it requires only the reflection spectrum of the fabricated FBG.

Characterization of a laser-induced plasma by spatially resolved spectroscopy of neutral atom and ion emissions.: Comparison of local and spatially integrated measurements

The local values of the parameters that characterize a laser-induced plasma (temperature, electron density, relative number densities of neutral atoms and ions) have been obtained by spatially resolved emission spectroscopy, including the deconvolution of the measured intensity spectra. The plasma has been generated using a Nd:YAG laser with a Fe–Ni alloy in air at atmospheric pressure, and the emission in the time window 3.0–3.5 μs has been detected. The temperature values obtained from neutral atom and ion emissions have been compared in the cases of local and spatially-integrated measurements. Local Boltzmann and Saha–Boltzmann plots with high correlation to linear fittings have been obtained using two broad sets of optically thin neutral atom and ion lines (21 Fe I lines and 15 Fe II lines), resulting in local values of the electronic temperature that coincide within the error. These results of local measurements contrast with those of spatially integrated measurements, for which two different temperatures are obtained from the Boltzmann plots of neutral atoms (9100±150 K) and ions (13 700±300 K). This difference is explained according to the measured distributions of the electronic temperature and the neutral atom and ion number densities, that result in separated emissivity (or population) distributions of neutral atom and ion lines, leading to different neutral atom and ion apparent temperatures (population-averages of the local electronic temperature). Local values of the plasma parameters have been obtained at all the positions with significant emission, including the determination of the electronic temperature from Saha–Boltzmann or Boltzmann plots. The ionization degree is high- and low-varying at the inner part of the plasma, decaying only near the plasma front. The maximum of the ion density does not coincide with the temperature maximum; on the contrary, the axial variation of both the neutral atom and ion densities (that decrease towards the sample surface) is opposite to that of the temperature, a behaviour that is interpreted to result from the plasma expansion process.

Recent Developments in Tissue-Type Imaging (TTI) for Planning and Monitoring Treatment of Prostate Cancer

Because current methods of imaging prostate cancer are inadequate, biopsies cannot be effectively guided and treatment cannot be effectively planned and targeted. Therefore, our research is aimed at ultrasonically characterizing cancerous prostate tissue so that we can image it more effectively and thereby provide improved means of detecting, treating and monitoring prostate cancer. We base our characterization methods on spectrum analysis of radiofrequency (rf) echo signals combined with clinical variables such as prostate-specific antigen (PSA). Tissue typing using these parameters is performed by artificial neural networks. We employed and evaluated different approaches to data partitioning into training, validation, and test sets and different neural network configuration options. In this manner, we sought to determine what neural network configuration is optimal for these data and also to assess possible bias that might exist due to correlations among different data entries among the data for a given patient. The classification efficacy of each neural network configuration and data-partitioning method was measured using relative-operating-characteristic (ROC) methods. Neural network classification based on spectral parameters combined with clinical data generally produced ROC-curve areas of 0.80 compared to curve areas of 0.64 for conventional transrectal ultrasound imaging combined with clinical data. We then used the optimal neural network configuration to generate lookup tables that translate local spectral parameter values and global clinical-variable values into pixel values in tissue-type images (TTIs). TTIs continue to show cancerous regions successfully, and may prove to be particularly useful clinically in combination with other ultrasonic and nonultrasonic methods, e.g., magnetic-resonance spectroscopy.

Photoelectrical measurements of the local value of the contact potential difference in the metal–insulator semiconductor (MIS) structures

In this work the local values of contact potential difference (CPD) and their distributions in the plane of the metal–insulator-semiconductor (MIS) structure's gate have been determined for the first time. This has been achieved by application of a focused beam of UV radiation from a laser source. The less than 20-μm diameter of UV radiation beam allows determination of distributions of local CPD values in the plane of the gate. The CPD distribution is such that its values are highest far away from the gate edge regions, lower in the vicinity of gate edges and still lower in the vicinity of gate corners. In this paper the method and the optical setup used to determine local values of CPD are described and example measurement results are given. The CPD distributions obtained have been confirmed by a series of independent measurements by other methods. It is believed that the CPD distributions obtained (as well as distributions of local values of other parameters) are due to the mechanical stress distributions under the gate of a MIS system.

Time to Reduction: Factors Influencing Management Efficacy in Sterilizing Overabundant White-Tailed Deer

In managing overabundant white-tailed deer (Odocoileus virginianus), fertility control frequently is regarded as a viable alternative to lethal strategies. However, little information is available concerning expected duration of fertility control. Our objectives were to create a flexible model for application in a diverse array of environmental conditions, determine the extent to which various parameters contributed to population growth, and assess the time necessary to reduce a population to a given level. The modeled population was assumed geographically closed without density dependence. Using prospective perturbation analysis on a linear time-invariant Lefkovitch matrix model, survival rates contributed to overall population growth nearly twice that of birth rates. Using numerical analysis, a general relationship between annual sterilization rate, desired population reduction, and time to that reduction was determined. This relationship was nonlinear and showed decreased efficiency per unit effort. Depending on local parameter values, we determined that a population could be reduced by 30% to 60% in 4-10 years if a manager could sterilize 25-50% of available fertile females annually. Thus, sterilization may be a viable option for communities with the financial resources and political will to sterilize.

Onset of neoclassical tearing modes on JET

A detailed study has been made of the onset and behaviour of (m = 3, n = 2) neoclassical tearing modes (NTMs) on JET, validating many of the underlying concepts in NTM physics. In particular, fitting onset thresholds in terms of the correctly motivated physics parameters produces scalings closer to theoretical expectations. The use of such locally measured parameters also removes previous inconsistencies in the data between different divertor configurations. The evolution of island size with β confirms the predicted levels of bootstrap current, and highlights the role of small island size stabilization terms, which give rise to a seeding requirement for NTMs from some other instability. This seeding requirement is confirmed, and is generally provided by sawteeth in the cases studied here. Although there are a variety of possible seeding mechanisms, for the particular cases studied here, it appears doubtful that the seeds are induced by magnetic coupling. In particular the NTM always appears well below the n = 2 sawtooth precursor harmonic frequency—although they often lock together once the NTM has grown close to saturation. Also, while plasma rotation profiles are favourable for a three wave interaction involving (4, 3) and n = 1 modes, with irregular matches to the appropriate mode frequency condition, there is no clear correlation between such matches and (3, 2) NTM growth rates. Thus, other seeding models should be considered—we have discussed two possibilities: a temporary change to classical tearing stability due to the sawtooth, and flow variation leading to a change in ion polarization current polarity, but neither of these are yet confirmed by the data. A complete resolution of this issue is essential if a predictive theory of NTMs is to be obtained, but it requires further, more detailed experimental measurements, and development of theoretical models. Finally, the nature of the (4, 3) NTM has also been explored. This mode also requires a seed perturbation to be triggered (in these cases supplied by a sawtooth), and occurs at similar local parameter values as the (3, 2) NTM, but with lower heating powers and βN. A cascade process emerges in which successively lower mode number NTMs occur as β is raised.