Summation Technique Research Articles

Two-dimensional Wigner crystals of classical Lennard-Jones particles

The ground-state of two-dimensional (2D) systems of classical particles interacting pairwisely by the generalized Lennard-Jones potential is studied. Taking the surface area per particle A as a free parameter and restricting oneself to periodic Bravais lattices with one particle per unit cell, Bétermin (2018 Nonlinearity 31 3973) proved that the hexagonal, rhombic, square and rectangular structures minimize successively the interaction energy per particle as A increases. We show here that the second-order transitions between the rhombic/square and square/rectangular phases are of mean-field type. The aim of this paper is to extend Bétermin’s analysis to periodic 2D lattices with more than one particle per elementary cell. Being motivated by previous works dealing with other kinds of models, we propose as the ground-state the extensions of the 2D rectangular (one-chain) lattice, namely the ‘zig-zag’ (two-chain), three-chain, four-chain, etc structures possessing 2, 3, 4, etc particles per unit cell, respectively. By using a recent technique of lattice summation we find for the standard Lennard-Jones potential that their ground-state energy per particle approaches systematically as the number of particles per unit cell increases to the one of a phase separated state (the optimal hexagonal lattice). We analyze analytically the low-density limit and the limiting hard-core case of the generalized Lennard-Jones potential.

Multiple Ion Transition Summation of Isotopologues for Improved Mass Spectrometric Detection of N-Acetyl-S-(1,2-dichlorovinyl)-L-cysteine.

Multiple ion transition summation of isotopologues (MITSI) is an adaptable and easy-to-implement methodology for improving analytical sensitivity, especially for halogenated compounds and otherwise abundant isotopologues. This novel application of signal summing was applied to measure and quantitate the two most abundant ion transitions of two isotopologues of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (1DCV), a urinary metabolite of trichloroethylene (TCE). Because 1DCV is dichlorinated, only approximately half of the total potential signal is quantifiable when the monoisotopic ion transition (i.e., m/z 256 → 127 for 35Cl2) is monitored. By summing the intensity of a separate and high-abundance 1DCV isotopologue ion transition (i.e., m/z 258 → 129 to include 35Cl and 37Cl), overall signal intensity increased by over 70%. This summation technique improved the analytical sensitivity and limit of detection (LOD) by factors of 2.3 and 2.9, respectively, compared to monitoring the two transitions separately, without summation. Separation and detection were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in negative-ion mode with scheduled selected reaction monitoring. This approach was verified for accuracy and precision using two quality control materials. In addition, we derived a modified signal summation equation to calculate predicted signal enhancements specific to the MITSI approach. Graphical Abstract .

Ab initio quantum mechanics/molecular mechanics method with periodic boundaries employing Ewald summation technique to electron-charge interaction: Treatment of the surface-dipole term.

We have developed a combined quantum mechanics/molecular mechanics (QM/MM) method with periodic boundary condition (PBC) treatment of explicit electron-charge interactions in a theoretically rigorous manner, for an accurate description of electronic structures for molecules in the condensed phase. The Ewald summation technique is employed for the calculation of the one-electron Hamiltonian in an ab initio framework. We decompose the Coulomb interactions into two components: those within the same cell and those between different cells. The former is calculated in the same way as the conventional QM/MM calculation for isolated systems; this article focuses on our novel method for calculating the latter type of Coulomb interactions. The detailed formulation of the Hamiltonian of this new QM/MM-PBC method, as well as the necessary one-electron integrals and their gradients, is given. The novel method is assessed by applying it to the dilute water system and a system with a coumarin molecule in water solvent; it successfully reproduces the electronic energies, frontier orbital energies, and Mulliken population charge of the real-space limit calculated by QM/MM using large isolated systems. We investigated the contribution from each term of the Hamiltonian and found that the surface-dipole term in the Ewald summation technique is indispensable for QM/MM-PBC calculations. The newly developed QM/MM-PBC method is promising for tackling chemical reactions and excited states of molecules in the condensed phase.

A Gaussian random field model for de-speckling of multi-polarized Synthetic Aperture Radar data

Synthetic Aperture Radar (SAR) data have gained interest for a variety of remote sensing applications, given the capability of SAR sensors to operate independent of solar radiation and day/night conditions. However, the radiometric quality of SAR images is hindered by speckle noise, which affects further image processing and interpretation. As such, speckle reduction is a crucial pre-processing step in many remote sensing studies based on SAR imagery. This study proposes a new adaptive de-speckling method based on a Gaussian Markov Random Field (GMRF) model. The proposed method integrates both pixel-wised and contextual information using a weighted summation technique. As a by-product of the proposed method, a de-speckled pseudo-span image, which is obtained from the least-squares analysis of the de-speckled multi-polarization channels, is also produced. Experimental results from the medium resolution, fully polarimetric L-band ALOS PALSAR data demonstrate the effectiveness of the proposed algorithm compared to other well-known de-speckling approaches. The de-speckled images produced by the proposed method maintainthe mean value of the original image in homogenous areas, while preserving the edges of features in heterogeneous regions. In particular, the equivalent number of look (ENL) achieved using the proposed method improves by about 15% and 47% compared to the NL-SAR and SARBM3D de-speckling approaches, respectively. Other evaluation indices, such as the mean and variance of the ratio image also reveal the superiority of the proposed method relative to other de-speckling approaches examined in this study.

Calculation of the interfacial tension of the graphene-water interaction by molecular simulations.

We report the calculation of the solid-liquid interface tension of the graphene-water interaction by using molecular simulations. Local profiles of the interfacial tension are given through the mechanical and thermodynamic definitions. The dependence of the interfacial tension on the graphene area is investigated by applying both reaction field and Ewald summation techniques. The structure of the interfacial region close to the graphene sheet is analyzed through the profiles of the density and hydrogen bond number and the orientation of the water molecules. We complete this study by plotting the profiles of the components of the pressure tensor calculated by the Ewald summation and reaction field methods. We also investigate the case of a reaction field version consisting in applying a damped shifted force in the case of the calculation of the pressure components.

Критическое поведение систем с конкуренцией между близкодействием и дальнодействием

Critical behaviour of a range of ferromagnetic materials deviates from the predictions of the Ising, XY and Heisenberg models. Additional long-range forces competing with regular exchange interaction may explain this deviation. These competing interactions lead to new universality classes of critical behaviour. The paper uses the field theory approach to investigate critical behaviour in those systems in which long-range and short-range forces compete. We consider the case when a power function of distance r-D-σ, when 1.5 < σ < 2.0, can describe the long-range forces. There exists a distinctive critical behaviour mode for these values. We derived vertex functions using a two-loop approximation directly in three-dimensional space (D = 3) and, for all values, obtained a linear approximation of asymptotic series in terms of long-range interaction parameters. We applied the Pade --- Borel summation technique to these asymptotic series. We computed stable fixed points and critical exponents as functions of long-range interaction parameters for low relativeefficiency of the long-range interaction. We investigated how critical exponents depend on the factor in the power law and relative long-range interaction intensity. We compared our results to the critical exponent values found experimentally for manganites. We used the experimental critical exponent γ values to compute long-range interaction parameters and then used the long-range interaction parameters to derive the ß exponent values, which we then compared to the experimental values. We show good agreement between our theoretical results and experimental data.

Factorial Transformation for Some Classical Combinatorial Sequences

Factorial transformation known from Euler’s time is a very powerful tool for summation of divergent power series. We use factorial series for summation of ordinary power generating functions for some classical combinatorial sequences. These sequences increase very rapidly, so OGFs for them diverge and mostly unknown in a closed form. We demonstrate that factorial series for them are summable and expressed in known functions. We consider among others Stirling, Bernoulli, Bell, Euler and Tangent numbers. We compare factorial transformation with other summation techniques such as Pade approximations, transformation to continued fractions, and Borel integral summation. This allowed us to derive some new identities for GFs and express their integral representations in a closed form.

Identifying appropriate aggregation technique for incinerability index

A technique to quantify the incinerability of municipal solid waste (MSW) called incinerability index or i‐Index has been developed. Eight input parameters incorporate the 3‐E concept that is, environmental impact, energy recovery, and economy of operation into the index structure, to facilitate the feasibility assessment of waste incineration. Analytic hierarchy process (AHP) gives the relative weightage of the input parameters and normalization of the parameters is performed using rating curves. One of the most crucial stages in the formulation of a composite indicator is the choice of the aggregation technique. While formulating i‐Index, besides ambiguity and eclipsing, the degree of information loss and sensitivity analysis are also considered to choose an aggregation function, which ensures minimal distortion in the output. From the 16 aggregation functions, six are chosen for detailed sensitivity analyses and quantifying the information loss. Based on these studies, the weighted summation technique is concluded to quantify the incinerability of MSW effectively while incorporating the parameter weightages. The incinerability of MSW generated in high‐income, upper‐middle‐income, lower middle‐income, and low‐income countries are subsequently quantified using this function, which amounted to 73, 62.4, 58.4, and 51.2, respectively, on a scale of 0–100. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13068, 2019

Assessment Practices in Mathematics: Local to Global Contexts

The main purpose of this paper is to explore the present mathematics assessment practices in local and global contexts. For this, I decisively review educational policies, practices, curricular documents and contemporary researches. In doing so, I select the Finland, China, USA, as they have stood in the significant positions in an international comparative study such as TIMSS, PISA and Nepal. It reveals that the assessment practices in mathematics are not an isolated phenomenon that have been executed by an external authority at the end of the academic sessions to quantify the individual attributes relating to mathematical performances. It is largely embedded in educational activities from the very beginning and simultaneously works throughout the programme for enriching mathematical outcomes and performances of students. I capture two major trends of assessment practices of these countries; post-positivist approaches of assessment and integral approaches of assessment. The post/positivist perspective incorporates summative evaluation techniques and assessment of learning whereas integral perspectives concentrate on assessment for learning as having broad goals of reconstructing, reframing and transforming the entire programs. These trends of assessment practice largely blend with philosophy of mathematics education. The comparing and contrasting views of assessment practices would be helpful for the policy makers, educators, mathematicians and other related personnel for critically re-evaluate their respective assessment practices and thus encourage to transform the deep-rooted conventional assessment practice that is one of the major hindrance to sanction the mathematics education within the positivistic paradigm. The Sapta Gandaki JournalVol. IX, 2018 Feb. Page: 1-16

Detection of (2,2) quasinormal mode from a population of black holes with a constructive summation method

The quasi normal modes (QNMs) associated with gravitational-wave signals from binary black hole (BBH) mergers can provide deep insight into the remnant's properties. Once design sensitivity is achieved, present ground-based gravitational wave interferometers could detect potentially hundreds of BBH signals in the coming years. For most, the ringdown phase will have a very weak signal-to-noise ratio (SNR). Signal summation techniques allow information extraction from the weak SNR ringdowns. We propose a method to constructively sum the (2,2) QNM from different BBH signals by synchronizing and rescaling them. The parameter space adopted to test the method is presently limited to mass ratio $q\leq3$, initially non-spinning black holes with face-on orientation. Moreover, since the synchronisation procedure fails for the weakest signals, we select all ringdowns with SNR above 2.6. Under these conditions, we show that for different BBH populations, 40 to 70% of all the potential detections could be used for the summation while still ensuring a summed SNR of $\sim$80% of the maximal achievable SNR (i.e. for ideally synchronized signals).

The 1895 Ljubljana earthquake: can the intensity data points discriminate which one of the nearby faults was the causative one?

The earthquake (Mw 6 from the SHEEC defined by the MDPs) that occurred in the central part of Slovenia on 14 April, 1895, affected a broad region, causing deaths, injuries, and destruction. This event was much studied but not fully explained; in particular, its causative source model is still debated. The aim of this work is to contribute to the identification of the seismogenic source of this destructive event, calculating peak ground velocity values through the use of different ground motion prediction equations (GMPEs) and computing a series of ground motion scenarios based on the result of an inversion work proposed by Jukić in 2009 and on various fault models in the surroundings of Ljubljana: Vič, Želimlje, Borovnica, Vodice, Ortnek, Mišjedolski, and Dobrepolje faults. The synthetic seismograms, at the basis of our computations, are calculated using the multi-modal summation technique and a kinematic approach for extended sources, with a maximum peak ground velocity value of 1 Hz. The qualitative and quantitative comparison of these simulations with the macroseismic intensity database allows us to discriminate between various sources and configurations. The quantitative validation of the seismic source is done using ad hoc ground motion to intensity conversion equations (GMICEs), expressly calculated for this study. This study allows us to identify the most probable causative source model of this event, contributing to the improvement of the seismotectonic knowledge of this region. The candidate fault that has the lowest values of average differences between observed and calculated intensities and chi-squared is a strike slip fault with a toward-north rupture as the Ortnek fault.

Evaluation of ground motion and site-specific response spectrum for different parts of India by the method of semi-empirical Green’s function

A synthesis of ground motion and corresponding design response spectrum is presented here. A semi-empirical Green’s function approach based on envelope summation technique is used to model ground motion for evaluation of expected peak ground acceleration (PGA) from future large earthquake in Garhwal Himalaya, northeast (NE) and south India. The synthetic site-specific response spectra for the single degree of freedom (SDOF) structures corresponding to the synthetic ground motion records are obtained for both rock and soil conditions for engineering design of reservoir and nuclear power plant in different parts of India. The predicted PGA for NE India is found to be ~ 3.5 m/s2 at 60 km, decaying to ~ 0.1 m/s2 at 500 km distance, while it is ~ 3.0 m/s2 at 15 km, decaying to ~ 1.4 m/s2 at 80 km distance for Garhwal Himalaya. These PGA estimates are in good agreement with those obtained from the Global Seismic Hazard Assessment Program (GSHAP) exercise. The response spectrum attains its maximum relatively earlier for rock site than for soil site. The response spectra decay gradually at periods later than 0.5 s and approach asymptotically constant values at longer periods. The synthetic ground motions are used to perform seismic response analysis of engineering structures. For such analysis, a PGA of 0.027 g is estimated for the Tail pond reservoir in south India for a target earthquake of M 6.5 at 50 km distance, while a PGA of 0.015 g is found for the Gorakhpur nuclear power plant in north India for similar magnitude and distance. The difference in the PGA estimates between the two is mostly attributed to regional difference in attenuation and site response. The findings of this study are expected to facilitate the seismic design of engineered structures, safe from seismic hazard, in regions where strong motion data are sparse.

Response spectra analysis of the modal summation technique verified by observed seismometer and accelerometer waveform data of the M6.5 Pidie Jaya Earthquake

Wave vibration confined in the boundary will produce stationary wave solution in discrete states called modes. There are many physics applications related to modal solutions such as air column resonance, string vibration, and emission spectrum of the atomic Hydrogen. Naturally, energy is distributed in several modes so that the complete calculation is obtained from the sum of the whole modes called modal summation. The modal summation technique was applied to simulate the surface wave propagation above crustal structure of the earth. The method is computational because it uses 1D structural model which is not necessary to calculate the overall wave propagation. The simulation results of the magnitude 6.5 Pidie Jaya earthquake show the response spectral of the Summation Technique has a good correlation to the observed seismometer and accelerometer waveform data, especially at the KCSI (Kotacane) station. On the other hand, at the LASI (Langsa) station shows the modal simulation result of response is relatively lower than observation. The lower value of the reaction spectral estimation is obtained because the station is located in the thick sedimentary basin causing the amplification effect. This is the limitation of modal summation technique, and therefore it should be combined with different finite simulation on the 2D local structural model of the basin.

Correction: Learning curve and competence for volumetric laser endomicroscopy in Barrett’s esophagus using cumulative sum analysis

Background and study aims Little is known about the learning curve for image interpretation in volumetric laser endomicroscopy (VLE) in Barrett’s esophagus (BE). The goal of this study was to calculate the learning curve, competence of image interpretation, sensitivity, specificity, and accuracy of VLE among novice users. Methods 31 novice users viewed 96 VLE images electronically at three academic institutions after a brief training session. There were 24 images of each histologic type: normal gastric cardia, normal esophageal squamous epithelium, non-neoplastic BE, and neoplastic BE. The users were asked to identify the correct tissue type and level of confidence. The cumulative summation (CUSUM) technique was used to construct a learning curve. Results 22 (71 %) of the physicians achieved VLE interpretation competency during their 96-slide review. Half of the physicians achieved competency at 65 images (95 % confidence interval [CI] 45 – 85). There was a statistically significant association between confidence in diagnosis and selecting the correct histologic tissue type (P Conclusion The majority of novice users achieved competence in image interpretation of VLE for BE, using a pre-selected image set, with a favorable learning curve after a brief training session. An electronic review of VLE images, prior to real-time use of VLE, is encouraged.

Migration-based automated rebar picking for condition assessment of concrete bridge decks with ground penetrating radar

Automatic identification and localization of rebar from ground penetrating radar (GPR) data has been a research topic of great interest. This paper presents an automated rebar picking algorithm for GPR data of concrete bridge decks. The algorithm is based on the Limited and Simplified Hyperbolic Summation (LSHS) technique in which the width of migration is limited and a counter is used to check if a hyperbolic signature exist in a sub-region of GPR image. More specifically, after a time-zero correction, each pixel in the raw GPR image with a positive amplitude will be migrated, as it is usually done with the conventional hyperbolic summation (HS) technique. However, for each pixel to be migrated, the width of migration is limited in the horizontal direction and a unit value will be used for migration, instead of the true amplitude values of the pixels. In the obtained image, the pixels containing rebar peaks will normally have the intensity values close to the number of pixels corresponding to the width of migration and, therefore, can be picked. Whereas the method is rather straightforward and simple to develop, its implementation on GPR data of two concrete bridge decks has shown good results. First, the GPR condition maps obtained from the proposed algorithm were in a good agreement with those developed by the manual method of rebar picking. Second, the accuracy of the picking algorithm was 98.09% and 99.21% for the two decks, respectively.

Verification Modal Summation Technique for Synthetic and Observation Seismogram for Pidie Jaya Earthquake M6.5

Neo-Deterministic Seismic Hazard Assessment (NDSHA) method is a seismic hazard assessment method that has an advantage on realistic physical simulation of the source, propagation, and geological-geophysical structure. This simulation is capable on generating the synthetics seismograms at the sites that being observed. At the regional NDSHA scale, calculation of the strong ground motion is based on 1D modal summation technique because it is more efficient in computation. In this article, we verify the result of synthetic seismogram calculations with the result of field observations when Pidie Jaya earthquake on 7 December 2016 occurred with the moment magnitude of M6.5. Those data were recorded by broadband seismometers installed by BMKG (Indonesian Agency for Meteorology, Climatology and Geophysics). The result of the synthetic seismogram calculations verifies that some stations well show the suitability with observation while some other stations show the discrepancies with observation results. Based on the results of the observation of some stations, evidently 1D modal summation technique method has been well verified for thin sediment region (near the pre-tertiary basement), but less suitable for thick sediment region. The reason is that the 1D modal summation technique excludes the amplification effect of seismic wave occurring within thick sediment region. So, another approach is needed, e.g., 2D finite difference hybrid method, which is a part of local scale NDSHA method.

Advanced dynamic statistical parametric mapping with MEG in localizing epileptogenicity of the bottom of sulcus dysplasia

ObjectiveTo investigate whether advanced dynamic statistical parametric mapping (AdSPM) using magnetoencephalography (MEG) can better localize focal cortical dysplasia at bottom of sulcus (FCDB). MethodsWe analyzed 15 children with diagnosis of FCDB in surgical specimen and 3 T MRI by using MEG. Using AdSPM, we analyzed a ±50 ms epoch relative to each single moving dipole (SMD) and applied summation technique to estimate the source activity. The most active area in AdSPM was defined as the location of AdSPM spike source. We compared spatial congruence between MRI-visible FCDB and (1) dipole cluster in SMD method; and (2) AdSPM spike source. ResultsAdSPM localized FCDB in 12 (80%) of 15 children whereas dipole cluster localized six (40%). AdSPM spike source was concordant within seizure onset zone in nine (82%) of 11 children with intracranial video EEG. Eleven children with resective surgery achieved seizure freedom with follow-up period of 1.9 ± 1.5 years. Ten (91%) of them had an AdSPM spike source in the resection area. ConclusionAdSPM can noninvasively and neurophysiologically localize epileptogenic FCDB, whether it overlaps with the dipole cluster or not. SignificanceThis is the first study to localize epileptogenic FCDB using MEG.

Youth information-seeking behavior and online government information

PurposeThe purpose of this paper is to focus on middle-school-aged young people’s information-seeking behavior and the knowledge and perceptions they have of and about federal government websites.Design/methodology/approachThe case study included 37 youth across four middle schools in the mid-Atlantic USA who all participated in a research-focused after-school program. During these sessions, they participated in several data collection activities, including an interview, a survey, a word association activity, an evaluation of the homepage of a government website, and card-sorting. Using conventional, directed, and summative content analysis techniques, the narratives from each data collection activity were coded using in vivo and theory-based terms.FindingsThe study finds that the majority of participants viewed government websites favorably, but were frequently unsure of what government websites are or who is responsible for their creation. Perhaps more significantly, participants’ views of information-related policies frequently were raised during discussions about government websites. The perceptions reflected the youth information-seeking behaviors and information literacy gaps.Originality/valueOverall, these findings shed light on the opinions of an understudied population in e-government research and inform both policy makers and educators on how to best disseminate government information to youth.

Finite Maxwell field and electric displacement Hamiltonians derived from a current dependent Lagrangian

ABSTRACTIn the common Ewald summation technique for the evaluation of electrostatic forces, the average electric field E is strictly zero. Finite uniform E can be accounted for by adding it as a new degree of freedom in an extended Lagrangian. Representing the uniform polarization P as the time integral of the internal current and E as the time derivative of a uniform vector field A, we define such an extended Lagrangian coupling A to the total current jt (internal plus external) and hence derive a Hamiltonian resembling the minimal coupling Hamiltonian of electrodynamics. Next, applying a procedure borrowed from nonrelativistic molecular electrodynamics the jt · A coupling is transformed to P · D form where D is the electric displacement acting as an electrostatic boundary condition. The resulting Hamiltonian is identical to the constant-D Hamiltonian obtained by Stengel, Spaldin and Vanderbilt (SSV) using thermodynamic arguments. The corresponding SSV constant-E Hamiltonian is derived from an alternative extended Lagrangian.

Nonlinear Summation of Power Series and Exact Solutions of Evolution Equations

The technique of quadratic and cubic summation of power series in the perturbation method was first used for finding exact solutions to nonlinear evolution equations. The series were construction with the use of exponential partial solutions to linearized equations. The solution of both classic and modified nonintegrable Korteweg-de Vries equations, the modified Burgers equation, and the Fisher one allows one to demonstrate specific features of the mentioned method. We obtain exact solitary wave solutions to the mentioned equations in the form of a wave impulse and a wave front and show that summation parameters depend on the pole orders of the desired solutions.