Standard Moment Research Articles

Generalized orthonormal moment tensor decomposition and its source-type diagram

Moment tensor decomposition is a method for deriving the isotropic (ISO), double-couple (DC), and compensated linear vector dipole (CLVD) components from a seismic moment tensor. Currently, there are two families of methods, namely, standard moment tensor decomposition and Euclidean moment tensor decomposition. Although both methods can usually provide workable solutions, there are some minor inconsistencies between the two methods: an equality inconsistency that occurs in standard moment tensor decomposition and the pure CLVD unity and flip basis inconsistency encountered in Euclidean moment tensor decomposition. Moreover, there is a sign problem when disentangling the CLVD component from a DC-dominated case. To address these minor inconsistencies, we propose a new moment tensor decomposition method inspired by both previous methods. The new method can not only avoid all these minor inconsistencies but also withstand deviations in ISO- or CLVD-dominated cases when using source-type diagrams.

The Dynamics of the Implied Volatility Surface: A Story of Rare Economic Events

We propose a macro-finance model that rationalizes robust features in equity-index option markets. When rare disasters are followed by economic recoveries, the slope of the implied volatility term structure is positive in good times but turns negative in bad times. Additionally, implied volatility decreases with moneyness in bad times (volatility skew), while the shape becomes a smile in good times in the presence of rare economic booms. Our theory contributes to understanding the dynamics of the implied volatility surface while keeping standard asset pricing moments realistic.

The mutual influence of electromagnetic and mechanical processes in dynamic modes of inertial vibrating electric drives

To conduct studies on the mutual influence of electromagnetic and mechanical transient processes of starting inertial vibration drives with an asynchronous motor (IVD-AD), a mathematical model is developed in this work. For this, the analytical dependence of the dynamic mechanical characteristics of the vibrator is determined for various values of the acceleration of the rotor, significantly different from the standard moments of resistance. In the mathematical model, the dynamic mechanical characteristic of an induction motor is used as a torque. Studies on a mathematical model showed that one of the disturbing effects on the dynamic mode of the IVD-AD is a change in the load parameters during operation, another disturbance is a change in the acceleration of the rotor, which leads to a shift in the resonance curves, which must be taken into account when choosing methods and means of tuning control in resonance.

Computer Anxiety as Correlate of Use of Information Technology Tools among Undergraduates of Library and Information Science in Tai Solarin University of Education, Ijagun, Ogun State

The study was designed to investigate computer anxiety as a correlate of use of Information Technology tool by undergraduates of Library and Information Science in Tai Solarin University of Education (TASUED), Ijagun, Ogun State. Descriptive survey design was adopted while Stratified Random Sampling Technique was used to select 169 undergraduates of LIS. A questionnaire designed by the researchers was used for collecting data. Out of the 169 copies of the questionnaire administered 120 copies were returned and used for the analysis. Data was analyzed by Simple percentages, frequency, Mean and Standard Deviation and Pearson product moment correlation. Findings show that the level of computer anxiety among LIS undergraduates is high. The available IT tools among LIS undergraduates are mobile technology, laptops, CD-ROM, printers and internet search engines. The most frequency utilized IT tools among LIS undergraduate are mobile technology and laptops. The impact of computer anxiety on students’ utilization of IT tools is high. The major constraints of computer anxiety towards the utilization of IT tools among LIS undergraduates are level of computer anxiety and lack of conducive environment. A null hypothesis was tested which revealed that there is a significant relationship between computer anxiety and students’ utilization of IT tools among the LIS undergraduates surveyed. The study therefore recommends that the management of TASUED should provide more conducive learning environment, adequate IT infrastructural facilities, computer literacy should be encouraged to help lower anxiety and reduce stress in an IT environment.Keywords: computer anxiety, computer literacy, Tai Solarin University, undergraduates

Improved estimators of correlation and R2 for skewed hydrologic data

ABSTRACTThe coefficient of determination R2 and Pearson correlation coefficient ρ = R are standard metrics in hydrology for the evaluation of the goodness of fit between model simulations and observations, and as measures of the degree of dependence of one variable upon another. We show that the standard product moment estimator of ρ, termed r, while well-behaved for bivariate normal data, is upward biased and highly variable for bivariate non-normal data. We introduce three alternative estimators of ρ which are nearly unbiased and exhibit much less variability than r for non-normal data. We also document remarkable upward bias and tremendous increases in variability associated with r using both synthetic data and daily streamflow simulations from 905 calibrated rainfall–runoff models. We show that estimators of ρ = R accounting for skewness are needed for daily streamflow series because they exhibit high variability and skewness compared to, for example, monthly/annual series, where r should perform well.

A multi-scale modeling approach to predict the impact of clinical interventions on femoral growth in children with cerebral palsy

Selective dorsal rhizotomy aims to reduce spasticity in children with cerebral palsy. Early investigations indicated postoperative weakness, whereas more recent studies showed that selective dorsal rhizotomy either does not change or improves muscle strength. All previous studies assessed muscle strength in a static position, which did not represent the walking situation. The aim of this study was to analyze the influence of selective dorsal rhizotomy on muscle forces during gait.Motion capture data of 25 children with spastic cerebral palsy and 10 typically developing participants were collected. A musculoskeletal OpenSim model was used to calculate joint kinematics, joint kinetics and muscle forces during gait. Static optimization and an electromyography-informed approach to calculate muscle forces were compared. A Muscle-Force-Profile was introduced and used to compare the muscle forces during walking before and after a selective dorsal rhizotomy.Independent of the approach used (electromyography-informed versus static optimization), selective dorsal rhizotomy significantly normalized forces in spastic muscles during walking and did not reduce the contribution of non-spastic muscles.This study showed that selective dorsal rhizotomy improves dynamic muscle forces in children with cerebral palsy and leads to less gait pathology, as shown in the improvement in joint kinematics and joint kinetics. Individual muscle force analyses using the Muscle-Force-Profile extend standard joint kinematics and joint moment analyses, which might improve clinical-decision making in children with cerebral palsy in the future. The reference data of our participants and MATLAB code for the Muscle-Force-Profile are publicly available on simtk.org/projects/muscleprofile.

Data Detection in Multisatellite Communication Systems

This paper deals with the practical aspects of development of multisatellite communication system. Specifically, the problem of data detection in multisatellite communication system is discussed in this paper. All satellites want to communicate to a particular earth station (ES). A novel interference cancellation method is used to obtain the data of different satellites at the ES. Based on the standard moment generating function approach, the proposed system is evaluated by analyzing the symbol error rate, diversity order, and average capacity. It is shown through simulation and analysis that the number of antennas at the ES should be sufficiently large as compared to the number of satellites in order to achieve good performance and improved diversity gain and average capacity. It is also shown that the diversity order of the considered system does not depend upon the shadowing environment. By placing more antennas at the ES, the effect of channel (shadowing) can be compensated.

Statistical fluctuations and quasi phase transition of mesoscopic Bose–Einstein condensation in anharmonic trap

The possibility of quasi phase transition of interacting Bose gas in mesoscopic regime and in the anharmonic trap is studied by a correlated two-body basis function approach. Our methodology accurately describes all measures of statistical fluctuations in anharmonic trap with different anharmonicity. The results addressed here go beyond the mean-field theory, correctly describe finite-sized effect and one unique formalism is valid for entire temperature region. Our main discovery : the lambda-structure in all fluctuation measures near the transition temperature remains same qualitatively in all traps. We also define three characteristic temperatures calculated from the point of inflexion of the lambda-structure of standard deviation, third and fourth central moment. All the three characteristic temperatures smoothly increase with increase in anharmonicity which jointly confirm that the achievement of condensation is more favourable in anharmonic trap. The possibility of true phase transition is ruled out for all traps for the mesoscopic Bose–Einstein condensate. However the additional calculation of transition exponent for the specific heat capacity nicely exhibits that quasi phase transition is more prominent in harmonic trap in comparison with anharmonic traps.

Improved inverse gravity moment term weighting for text classification

Text classification is one of the popular high dimensional classification problems where providing better feature vector representations explicitly improve classification performances. Thus, assigning appropriate weights to features or terms are crucial for obtaining effective feature vector representations. The methods used for weighting terms in text classification are called term weighting schemes. Although there exist some term weighting schemes for text classification, they are not fully effective and researchers still focus on proposing new term weighting schemes. In this study, two novel term weighting schemes namely SQRT_TF-IGMimp and TF-IGMimp derived from standard inverse gravity moment formula are proposed to improve weighting behaviors of existing TF-IGM scheme especially for some extreme cases. The performances of proposed schemes are compared with two standard IGM based schemes and five other state-of-the-art term weighting methods on both unbalanced (Reuters-21578) and balanced (20 Mini Newsgroups and 20 Newsgroups) datasets with KNN, SVM, and NN classifiers. Micro-F1 and macro-F1 are used as success measures. The experiments are conducted with various different feature sizes to examine the effects of the feature size on the success of weighting. The experimental results showed that the proposed SQRT_TF-IGMimp method generally outperformed all schemes including both standard TF-IGM and SQRT_TF-IGM schemes. However, the proposed TF-IGMimp scheme also showed mostly better performance than standard TF-IGM. To demonstrate validity of the proposed weighting scheme having maximum performance, t-test is also used and it can be stated that the performance gains obtained by the proposed SQRT_TF-IGMimp weighting scheme compared to standard SQRT_TF-IGM are statistically significant.

Selective dorsal rhizotomy improves muscle forces during walking in children with spastic cerebral palsy

BackgroundSelective dorsal rhizotomy aims to reduce spasticity in children with cerebral palsy. Early investigations indicated postoperative weakness, whereas more recent studies showed that selective dorsal rhizotomy either does not change or improves muscle strength. All previous studies assessed muscle strength in a static position, which did not represent the walking situation. The aim of this study was to analyze the influence of selective dorsal rhizotomy on muscle forces during gait. MethodsMotion capture data of 25 children with spastic cerebral palsy and 10 typically developing participants were collected. A musculoskeletal OpenSim model was used to calculate joint kinematics, joint kinetics and muscle forces during gait. Static optimization and an electromyography-informed approach to calculate muscle forces were compared. A Muscle-Force-Profile was introduced and used to compare the muscle forces during walking before and after a selective dorsal rhizotomy. FindingsIndependent of the approach used (electromyography-informed versus static optimization), selective dorsal rhizotomy significantly normalized forces in spastic muscles during walking and did not reduce the contribution of non-spastic muscles. InterpretationThis study showed that selective dorsal rhizotomy improves dynamic muscle forces in children with cerebral palsy and leads to less gait pathology, as shown in the improvement in joint kinematics and joint kinetics. Individual muscle force analyses using the Muscle-Force-Profile extend standard joint kinematics and joint moment analyses, which might improve clinical-decision making in children with cerebral palsy in the future. The reference data of our participants and MATLAB code for the Muscle-Force-Profile are publicly available on simtk.org/projects/muscleprofile.

Optimization of compressive loading parameters to mimic in vivo cervical spine kinematics in vitro

The human cervical spine supports substantial compressive load in vivo. However, the traditional in vitro testing methods rarely include compressive loads, especially in investigations of multi-segment cervical spine constructs. Previously, a systematic comparison was performed between the standard pure moment with no compressive loading and published compressive loading techniques (follower load – FL, axial load – AL, and combined load – CL). The systematic comparison was structured a priori using a statistical design of experiments and the desirability function approach, which was chosen based on the goal of determining the optimal compressive loading parameters necessary to mimic the segmental contribution patterns exhibited in vivo. The optimized set of compressive loading parameters resulted in in vitro segmental rotations that were within one standard deviation and 10% of average percent error of the in vivo mean throughout the entire motion path. As hypothesized, the values for the optimized independent variables of FL and AL varied dynamically throughout the motion path. FL was not necessary at the extremes of the flexion–extension (FE) motion path but peaked through the neutral position, whereas, a large negative value of AL was necessary in extension and increased linearly to a large positive value in flexion. Although further validation is required, the long-term goal is to develop a “physiologic” in vitro testing method, which will be valuable for evaluating adjacent segment effect following spinal fusion surgery, disc arthroplasty instrumentation testing and design, as well as mechanobiology experiments where correct kinematics and arthrokinematics are critical.

Development of Paramagnetism Analyze

One of the quantities of fundamental importance in describing magnetic phenomena and materials is the magnetic moment. This research focused on the development of a paramagnetic materials analyzer using locally sourced materials to determine magnetic moment of magnetic materials. This involves the design of a sensing unit. The sensing unit comprised of a colpitts oscillator, preamplifier and shaping circuit, K – type thermocouple sensor, thermocouple amplifier, microcontroller, matrix keypad and a LCD. The developed instrument was calibrated using a known standard magnetic moment value of iron. The instrument was tested and it was able to determine the magnetic moment of available magnetic materials with a standard deviation of 0.0163. The value of magnetic moment obtained for the available known materials fall within the range of values obtained from literature.

Suitability and evaluating wind speed probability distribution models in a hot climate: Djibouti case study

The paper investigates the most reliable numerical method for estimating the Weibull parameters to calculate the wind power density in urban and rural hot regions of the Republic of Djibouti. It is important to mention that no similar studies have been carried out and therefore this is the first study to evaluate and diagnosis the best Weibull distribution method for wind analysis and wind energy potential in the country. Five investigated numerical methods such as Graphical Method (GM), Empirical Method of Justus (EMJ), Energy Pattern Factor Method (EPFM), Standard Deviation Method (SDM) and Moment Method (MM) were adopted to estimate Weibull c and k parameters. Four statistical indicators including root mean square error, index of agreement, coefficient of determination and relative percentage error were used to precisely rank the methods. The study aims to identify the most accurate method to determine the wind power density in four stations which are University of Djibouti, International Airport of Djibouti, Ghoubet and Bara Wein. Then, to provide a complete analysis, the study is performed on monthly, yearly and seasonal scales. The results reveal that GM and EPFM are the most accurate methods for estimating the c and k parameters and are recommended in estimating the wind power density in Djibouti.

High Order Portfolio Optimization Problem with Transaction Costs

This paper studies a high order moments portfolio optimization model with transaction costs. The model takes kurtosis as objective function and takes the skewness, variance, mean and transaction costs as constraints conditions. Since the optimization problem is of high order and non-convex, it brings some difficulties to the solution of the model. Therefore, this paper transforms the optimization problem into a semi-definite matrix optimization problem by using the moment matrix theory, and then solves it. Through the study of four risky assets in China’s securities market, it is found that transaction costs are significant parts in the study of portfolio model. In addition, sensitivity analysis shows that the kurtosis and skewness are positively correlated with the mean and variance invariant. When mean and skewness are constant, kurtosis and variance are positively correlated. When mean and skewness remain unchanged, the fourth order standard central moment and variance are negatively correlated.

Functional convergence for moving averages with heavy tails and random coefficients

We study functional convergence of sums of moving averages with random coefficients and heavy-tailed innovations. Under some standard moment conditions and the assumption that all partial sums of the series of coefficients are a.s. bounded between zero and the sum of the series we obtain functional convergence of the corresponding partial sum stochastic process in the space $D[0,1]$ of cadlag functions with the Skorohod $M_{2}$ topology.

Dynamic Weights Equations for Converting Grayscale Image to RGB Image

The method of converting color images from the RGB color system to grayscale images is a simple operation by using the fixed weights method of conversion, but using the same weights to restore the color of the same images is not an effective operation of all types of images because the grayscale image contains little information and it isn't worthy of conversion operation.
 The basic idea in this paper is to employ the mathematics equations which extracted from the grayscale image in conversion operation, this paper presents the method of coloring the grayscale image by using the weights derived from the characteristics of the grayscale image. Skewness, Mean and Standard deviation moments have been extracted from the features of grayscale images and its adoption the determine weights of the RGB color system. This method proved its success in coloring images compared to the traditional method adoption of fixed weights for coloring images because it relies on fixed weights for converting all grayscale images.

Conservative magnetic moment of runaway electrons and collisionless pitch-angle scattering

Recently, the validity of the guiding-center approach to model relativistic runaway electrons in tokamaks has been challenged by full-orbit simulations that demonstrate the breakdown of the standard magnetic moment conservation. In this paper, we derive a new expression for the magnetic moment of relativistic runaway electrons with , which is conserved significantly better than the standard one. The new result includes one of the second-order corrections in the standard guiding-center theory which, in case of runaway electrons with , can peculiarly be of the same order as the lowest-order term. The better conservation of the new magnetic moment also explains the collisionless pitch-angle-scattering effect observed in full-orbit simulations since it allows momentum transfer between the perpendicular and parallel directions when the runaway electron is accelerated by an electric field. While the derivation of the second-order correction to the magnetic moment in general case would require the full extent of the relativistic second-order guiding-center theory, we exploit the Lie-perturbation method at the limit which simplifies the computations significantly. Consequently, we present the corresponding guiding-center equations applicable to runaway electrons.

Operative Scheme for the Short-range Complex Forecasting of Surface Air Temperature and Humidity

The statistical scheme is proposed for the forecast of surface air temperature and humidity using operative weather forecasts with 3–5-day lead time from the best forecasting hydrodynamic models as well as the archives of forecasts of these models and observational data from 2800 weather stations of Russia, Eastern Europe, and Central Asia. The output of the scheme includes the forecasts of air temperature for the standard observation moments with the period of 6 hours and extreme temperatures with the lead times of 12–120 hours. The accuracy of temperature and humidity forecasts for the period from July 2014 till June 2017 is much higher than that for the forecasts of original hydrodynamic models. The skill scores for extreme temperature forecasts based on the proposed method are compared with the similar results of the Weather Element Computation (WEC) forecasting scheme and forecasts by weathermen.

New set of fluid moment equations describes plasma behavior with greater numerical stability

Researchers find a new anti-symmetric formulation of the standard plasma moment approach with a first-principles numerical stability.

The Nongraded Instructional System And Learners Academic Achievement

The Philippines is continuously seeking the best educational system that would provide the needs of the students, the industry, and to meet the international standards in education. Angelicum College is the only nongraded school in the Philippines that offers a unique system of education to its learners. The very purpose of the study was to find out the assessment of the learners on the nongraded instructional system and their level of achievement in Mathematics, Science, and English. The study used the descriptive-correlational method with the survey questionnaire as which has three (3) major indicators: the Teaching/Learning Approach, Role of Facilitators, and Evaluation System. Descriptive statistics such as mean and standard deviation and Pearson Product Moment or Correlation Analysis were also utilized. The learners assessed that the nongraded instructional system in terms of teaching/learning approach, role of facilitator and evaluation system. A 50-item achievement test in Mathematics, Science, and English was administered to the learners. The assessment of learners on the nongraded instructional system shows that they agree with a mean of 4.05 on the teaching/learning approach; 4.15 on the role of facilitators; and 4.02 on the evaluation system, with standard deviations that show homogeneous responses among learners. The learners agree on the importance of the nongraded instructional system which is categorized by teaching/learning approach, role of facilitator, and evaluation system. The level of achievement of learners show a mean of 30.86 in Mathematics; 29.32 in Science; and 34.11 in English, with standard deviations that show variations of scores by about 6 to 9 points. No significant relationship exists between the assessment of the nongraded instructional system and the learners achievement in Mathematics, Science, and English. It is recommended that the curriculum be retained because individualized instruction is efficient and that constant upgrading and evaluation be conducted to identify its strengths and limitations. The administrators may guide in realizing novel activities or programs that might lead to the vision that through the years, the unique system of instruction in the country would somehow influence for higher achievement of the learners in totality