Variation In Step Research Articles

Implementasi Fast Fourier Transform dalam Penyelesaian Persamaan Difusi Panas Satu Dimensi

The Fast Fourier Transform (FFT) method for solving the 1-D heat diffusion equation offers an efficient approach for resolving partial differential equations (PDEs) with various time steps . FFT is used to transform the 1-D heat diffusion equation into the frequency domain and back to the time domain through inverse FFT. Using mathematical modeling with initial and Dirichlet boundary conditions, the numerical solutions produced by FFT are compared with analytical solutions. The accuracy of the method is validated using MAE and MSE calculated in Matlab. At several time intervals , the obtained MAE and MSE values indicate a good agreement between the numerical and analytical solutions, with very small errors. Numerical stability analysis confirms the reliability of the FFT method across various The variation in time step has a significant impact on the accuracy and stability of the solution. Smaller time steps improve accuracy and stability but require longer computation times. The optimal time step selected in this study is Increasing the number of discretization points also enhances accuracy but implies an increase in computational load and memory usage. The FFT method demonstrates good numerical consistency with increasing

Death-birth adaptive dynamics: modeling trait evolution.

Here, we derive stochastic adaptive dynamics from the microscopic death-birth process by explicitly modeling the trait variation from offspring to parent in each reproductive event, thereby accounting for a highly polymorphic population. This generalization enables the construction of a quantitative model that can be subjected to empirical validation. Our mathematical analysis furnishes a formula for estimating the trait variation in the reproductive step by exclusively observing the current trait variation in the population. In addition, we provide a straightforward approach to obtain the fitness function associated with a particular trait by examining its actual evolutionary trajectory, which can be employed to forecast the continued evolution of the trait.

Enhancing low‐temperature energy harvesting by lead‐free ferroelectric Ba(Zr0.1Ti0.9)O3

AbstractThe energy‐harvesting ability of the lead‐free ferroelectric Ba(Zr,Ti)O3 was investigated and greatly enhanced using the Kim novel electrothermodynamic cycle for low‐temperature application. Ba(Zr,Ti)O3 was synthesized with a Zr:Ti ratio of 10:90 (BZT10) by hot‐press sintering, which exhibited a mix relaxor‐ferroelectric behavior. For power generation using the Kim cycle with low and high temperatures of TL = 25°C, TH = 120°C, the most optimized temperature pattern occurred for a heating time of 12.5 s and a cooling time of 22.5 s. Under these conditions, the electric field increased during the novel isodisplacement process, and the displacement variation in the isoelectric step reached the highest value and maximized the BZT10 cycle loop area. Applying these conditions while lowering TL to 20°C, an energy density ND = 504 mJ/cm3 was achieved. This value is the highest obtained energy density in a practical test for lead‐free ferroelectric bulk material in the BaTiO3 family.

Concentric Approximation for Fast and Accurate Numerical Evaluation of Nonadiabatic Coupling with Projector Augmented-Wave Pseudopotentials.

We develop an efficient and accurate method for numerical evaluation of nonadiabatic (NA) coupling in the Kohn-Sham representation with projector augmented-wave (PAW) pseudopotentials that are commonly used in electronic structure calculations on nanoscale, condensed matter, and molecular systems. Without additional cost, the method provides an order of magnitude improvement in accuracy compared to the current technique, while it is 3-4 orders of magnitude faster than the exact evaluation. Atomic displacements over typical time steps in molecular dynamics (MD) simulations are much smaller than the size of the PAW core region, and therefore, evaluation of the NA in the core is simplified. The accuracy is demonstrated with three condensed matter systems. The method is robust to variation in the MD time step. The accurate NA coupling evaluation also helps in maintaining phase-consistency of the NA coupling and identifying trivial crossings of adiabatic states. The approach stimulates NAMD applications to modeling of modern materials and processes.

Manipulating electronic delocalization of Mn3O4 by manganese defects for oxygen reduction reaction

Manganese-based oxides are promising in electrocatalytic oxygen reduction reaction, but the activity and conductivity need further improvement. Herein manganese defected Mn3O4 was fabricated by solvothermal synthesis of manganese glycerate and then thermal calcination. The experimental and computational results reveal that manganese defects in Mn3O4 modify the electronic structure to improve conductivity and electronic delocalization, which helps to expose more surface Mn3+ as major active site, thereby facilitating O2 activation and OH* desorption, and reducing the Gibbs free energy variation in the rate-limiting step of ORR. Accordingly, the onset potential, half-wave potential and limiting current density of manganese defected Mn3O4 are 0.87 V, 0.65 V and 5.0 mA cm-2, better than that of normal Mn3O4 (0.77 V, 0.62 V and 2.6 mA cm-2). This work provides an effective approach to tune the defects and electronic structures of Mn3O4 for better electrochemical activity.

Direct Measurement of Stepping Dynamics of E. coli UvrD Helicase

UvrD is a prototypical Superfamily 1 (SF1) helicase from E. coli involved in DNA repair. We report herein the directmeasurement of the stepping behavior of UvrD at thesingle-molecule level as it unwinds and re-zips a DNA hairpin usinghigh-resolution optical tweezers. We measure an averageunwinding and re-zipping step size of ∼3 base pairs, but also observe large variation in step size.Analysis of the step size distribution reveals the presence of multiple sub-steps smaller than 3 bp,suggesting that 3 bp is not the elemental unit of step sizefor UvrD.

Reducing of weight variation in soaking step of shrimp processing: effects of iced storage time and soaking equipment

The aim of shrimp soaking is to improve functional properties and yield of a shrimp product. The weight variation in the soaking step in actual production is larger than that in the laboratory due to many uncontrollable factors that have not been identified. The objective of this work, therefore, was to investigate the causes that provoke the difference in yield calculation between the laboratory and the real production conditions to improve the soaking process of shrimp within the regulated time. First, the effect of storage time in ice (0 and 24 h) on soaking yield variation was studied. Then, the effect of soaking equipment, i.e. flat bottom tank with rod impeller and cone bottom tank with paddle blade impeller, on weight variation was determined. The result revealed that the iced storage time and the design of soaking equipment had no significant effect on the variations of yield and weight (p ≥ 0.05). Nevertheless, water holding capacities after soaking and cooking were significantly influenced by the iced storage period (p < 0.05). The result revealed that the 24-h iced storage significantly reduced the yields of soaking, cooking, and freezing.

Revisiting Tractable Strategies to Determine the Activity/Inactivity of Electrocatalysts towards O2/•OH Production

The measurement of the electroactivity of anode materials toward the generation of hydroxyl radicals or oxygen evolution from water oxidation is overriding to develop novel catalysts with tuned electrocatalytic applications. Thus, this work experimentally revisits chemical and electrochemical characterization techniques with the aims of establishing a comparison of the electrochemical performance of typical IrO2, RuO2, SnO2-Sb, and Boron doped diamond (BDD) electrodes toward H2O oxidation under feasible experimental conditions, and highlighting those conditions where variability cannot be removed. Tafel slopes corrected for ohmic resistance and active areas are 127, 175, 42, 48 mV dec−1 for BDD, SnO2-Sb, IrO2 and RuO2, respectively; while in the same order, the onset potential for water oxidation is: 2.49, 2.29, 1.47, 1.38 V vs SHE, measured at a current density of 0.5 mA cm−2. Additionally, a new interpretation is presented for the analysis of electrochemical impedance spectroscopy (EIS), and its connection with the OER mechanism: in the potential zone where Tafel is applicable is possible to appreciate the dielectric properties of the substrate for non-active anodes and elucidating the variation in the rate-determining step of water oxidation. EIS results suggest the possibility to use the time-constant associated with this stage as a parameter of the active or non-active behavior of the above electrodes. The advantages and drawbacks of different trapping molecules used to detect the •OH generation in electrocatalysis is discussed. The photoluminescence of coumarin could be used as a fast and reliable method for the evaluation of the electrocatalyst activity toward the •OH production.

The Design and Development of Prediction Models for Maximizing Students’ Academic Achievement

To enable early identification and intervention for students at risk for academic failure and for failure on the USMLE Step 1 Examination, three predictive models (pre-matriculation, end of M1, and end of M2) were developed that include both behavioral attributes (Learning and Study Strategies Inventory: LASSI subscale scores) and performance measures (internal examinations and National Board of Medical Examiners [NBME] Comprehensive Basic Science Examination [CBSE] progress tests). Pearson product moment correlation coefficients and multivariate regression modeling were used to determine optimal combinations of independent variables. The pre-matriculation prediction model includes MCAT scores and undergraduate overall GPA. The end of M1 model includes the progress test scores on the NBME CBSE administered at the end of first year medical school (M1), LASSI subscale scores, and weighted performance on M1 internal examinations. Finally, the end of M2 model includes CBSE progress test scores at the end of M1 and second year medical school (M2), LASSI subscale scores, and weighted performance on M1 and M2 internal examinations. Our pre-matriculation, end of M1, and end of M2 models explain 24, 62, and 81% of the variation in USMLE Step 1 performance, respectively. The inclusion of LASSI subscale scores improves the end of M1 model from 60 to 62% and end of M2 model from 79 to 81% in explaining variation in USMLE Step 1 scores. Continuous monitoring of student performance based on these multiple measures supports a holistic perspective on progress, areas of ongoing weakness, and potentially, identification of yet-undetected weakness for targeted interventions.

Modelling spatial trends in sorghum breeding field trials using a two-dimensional P-spline mixed model

Key messageA flexible and user-friendly spatial method called SpATS performed comparably to more elaborate and trial-specific spatial models in a series of sorghum breeding trials.Adjustment for spatial trends in plant breeding field trials is essential for efficient evaluation and selection of genotypes. Current mixed model methods of spatial analysis are based on a multi-step modelling process where global and local trends are fitted after trying several candidate spatial models. This paper reports the application of a novel spatial method that accounts for all types of continuous field variation in a single modelling step by fitting a smooth surface. The method uses two-dimensional P-splines with anisotropic smoothing formulated in the mixed model framework, referred to as SpATS model. We applied this methodology to a series of large and partially replicated sorghum breeding trials. The new model was assessed in comparison with the more elaborate standard spatial models that use autoregressive correlation of residuals. The improvements in precision and the predictions of genotypic values produced by the SpATS model were equivalent to those obtained using the best fitting standard spatial models for each trial. One advantage of the approach with SpATS is that all patterns of spatial trend and genetic effects were modelled simultaneously by fitting a single model. Furthermore, we used a flexible model to adequately adjust for field trends. This strategy reduces potential parameter identification problems and simplifies the model selection process. Therefore, the new method should be considered as an efficient and easy-to-use alternative for routine analyses of plant breeding trials.

A new partitioned staggered scheme for flexible multibody interactions with strong inertial effects

In generic flexible multibody interaction problems, the differences in the mass, damping and stiffness of the bodies can be very large. Of particular interest is a small change in the higher mass structure which triggers relatively large inertial effects on the lower mass structure. In this work, a new partitioned staggered time integration scheme is developed and its applicability is extended to the problems involving low mass ratios in coupled multibody problems. The equation of motion of body with larger inertia is integrated by implicit Newmark method, whereas the smaller inertia is solved using a robust self-starting explicit integration procedure. The coupled formulation includes explicit correction terms that adjusts the amount of interfacial velocity, which plays a key role in the stability and accuracy of the simulations. A wide range of mass (10−6–10−1), damping and stiffness (10−3–103) ratios are chosen to assess the stability and accuracy characteristics of the proposed scheme. The closed-form expressions for the coupling parameter have been constructed for both matching and non-matching time stepping through the Godunov–Ryabenkii normal mode analysis. The stability of the proposed method is observed as a function of the relative properties and temporal discretisation of the coupled system. The time step of the heavier body significantly influences the stability more than the lighter body. To maintain the staggering error minimal, an optimal range of the coupling parameter is identified. The error computed with uniform variation in the time step revealed that the present method is more accurate than the existing methods. The partitioned method is an energy preserving integration method for the dynamic analysis of multibody systems. As a potential application of this scheme, flexible multibody problems in the field of offshore engineering, viz., wave energy converter and floater–mooring systems are presented and validated with experimental measurements.

A Study on Overvoltage Distribution Across the High Voltage Winding of an Electric Power Transformer

The main objective of this paper is to represent effects of overvoltage on a transformer winding by analysis and modelling with special attention given to the voltage distribution across the winding. The authors have considered both approaches in modelling the winding: windings with distributed electrical parameters, and secondly disk coils with concentrated parameters. All known models are assembled in a general model based upon distributed parameters, while the excitation voltages display sinusoidal variation in time (commutation) or step. Both induced and commutation voltages, applied across the transformer winding, will generate free oscillations which are analyzed further on. According to the model, the transformer’s windings are divided in several disk coils with concentrated known parameters. This results in a complete electrical network used for simulations. All simulations have been performed using the software package SYSEG (SYmbolic State Equation Generation). Using SYSEG package, from the state equations assembled in terms of the disk coils voltages, one can obtain the overvoltage across the transformer winding as function of time. If the frequency of the commutation voltage and the frequency of the free oscillations are in close range, then the voltage across the disk coils shows a non-uniform distribution. An important aspect of this paper is accounting for asymmetry of the transformer by modelling the reinforced insulation of the first turns of the disk coils of the transformer’s high voltage winding. This affects the value of the inter-turn capacitance of these coils, and is an aspect which is treated in our simulations.

Relationship Between Performance on the NBME® Comprehensive Clinical Science Self-Assessment and USMLE® Step 2 Clinical Knowledge for USMGs and IMGs

Background: The Comprehensive Clinical Science Self-Assessment (CCSSA) is a web-administered multiple-choice examination that includes content that is typically covered during the core clinical clerkships in medical school. Because the content of CCSSA items resembles the content of the items on Step 2 Clinical Knowledge (CK), CCSSA is intended to be a tool for students to help assess whether they are prepared for Step 2 CK and to become familiar with its content, format, and pacing. Purposes: This study examined the relationship between performance on the National Board of Medical Examiners® CCSSA and performance on the United States Medical Licensing Examination® Step 2 CK for U.S./Canadian (USMGs) and international medical school students/graduates (IMGs). Methods: The study included 9,789 participants who took CCSSA prior to their first Step 2 CK attempt. Linear and logistic regression analyses investigated the relationship between CCSSA performance and performance on Step 2 CK for both USMGs and IMGs. Results: CCSSA scores explained 58% of the variation in first Step 2 CK scores for USMGs and 60% of the variation for IMGs; the relationship was somewhat different for the two groups as indicated by statistically different intercepts and slopes for the regression lines based on each group. Logistic regression results showed that examinees in both groups with low scores on CCSSA were at a higher risk of failing their first Step 2 CK attempt. Conclusions: Results suggest that CCSSA can provide students with a valuable practice tool and a realistic self-assessment of their readiness to take Step 2 CK.

OPTIMIZATION OF TIME STEP AND CFD STUDY OF COMBUSTION IN DI DIESEL ENGINE

Study of Combustion is one of the complicated phenomenon which involves a chemical reaction at certain elements of fuel like Hydrogen and Carbon combine with Oxygen liberating heat energy and causing and increase in temperature of the gases, within the engine cylinder. IC engines involve complex fluid dynamic interactions between air flow, fuel injection, moving geometries, and combustion. Fluid dynamics phenomena like jet formation, wall impingement with swirl and tumble, and turbulence production are critical for high efficiency engine performance and meeting emissions criteria. The design problems that are encountered include port-flow design, combustion chamber shape design, variable valve timing, injection and ignition timing, and design for low or idle speeds. In Internal combustion Engines CFD may be useful to study one of the most complicated process of combustion in Engines. In this paper a CFD in-cylinder combustion analysis are carried out on a single cylinder four stroke Direct Injection (DI) Engine. The engine is 661cc Kirloskar engine. One of the main process in CFD Analysis is the Grid Generation and defining Time step for solving the problem. Proper and improve grids will give better and accurate results, Grid Independence study has been carried out. The optimum grid is find out in previous work current work is to find optimum time step for CFD analysis three cases are studied with variation in time step from TS 1, TS 0.5 and TS 0.25 the computed data is validated with Experimental data available which are in good agreement.

Tuning an rf-SQUID flux qubit system's potential with magnetic flux bias

At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop (Φf) and the small dc-SQUID (Φfcjj), respectively, the potential shape of the system can be fully controlled in situ. Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon.

Coupling of kinesin ATP turnover to translocation and microtubule regulation: one engine, many machines

The cycle of ATP turnover is integral to the action of motor proteins. Here we discuss how variation in this cycle leads to variation of function observed amongst members of the kinesin superfamily of microtubule associated motor proteins. Variation in the ATP turnover cycle among superfamily members can tune the characteristic kinesin motor to one of the range of microtubule-based functions performed by kinesins. The speed at which ATP is hydrolysed affects the speed of translocation. The ratio of rate constants of ATP turnover in relation to association and dissociation from the microtubule influence the processivity of translocation. Variation in the rate-limiting step of the cycle can reverse the way in which the motor domain interacts with the microtubule producing non-motile kinesins. Because the ATP turnover cycle is not fully understood for the majority of kinesins, much work remains to show how the kinesin engine functions in such a wide variety of molecular machines.

Relationship Between Performance on the NBME Comprehensive Basic Sciences Self-Assessment and USMLE Step 1 for U.S. and Canadian Medical School Students

This study examined the relationship between performance on the National Board of Medical Examiners Comprehensive Basic Science Self-Assessment (CBSSA) and performance on United States Medical Licensing Examination Step 1. The study included 12,224 U.S. and Canadian medical school students who took CBSSA prior to their first Step 1 attempt. Linear and logistic regression analyses investigated the relationship between CBSSA performance and performance on Step 1, and how that relationship was related to interval between exams. CBSSA scores explained 67% of the variation in first Step 1 scores as the sole predictor variable and 69% of the variation when time between CBSSA attempt and first Step 1 attempt was also included as a predictor. Logistic regression results showed that examinees with low scores on CBSSA were at higher risk of failing their first Step 1 attempt. Results suggest that CBSSA can provide students with a realistic self-assessment of their readiness to take Step 1.

Initial weight loss is the best predictor for success in obesity treatment and sociodemographic liabilities increase risk for drop-out

Objective To identify pre-treatment factors related to weight loss in obesity treatment. Methods Weight-related and psychological factors were tested in relation to three different weight loss phases: spontaneous weight loss after screening visit (Pre-treatment), weight loss after a preparatory 5-week series of lectures (Step I) and after group treatment lasting two semesters (Step II) in 247 obesity patients. Results The strongest factor for predicting weight loss in the Step II treatment was initial Step I weight loss. At least 1 kg weight loss in Step I predicted 13% of the variation in Step II weight loss. Spontaneous pre-treatment weight loss after screening and a history of more weight losses were also related to more Step II weight loss. Psychological encumbrances such as eating disorders and mental distress were not related to weight loss, neither were self-reported motivation nor weight locus of control. The overall attrition rate was 63% and associated with lower education, being an immigrant, lack of occupation, fewer previous weight losses and higher body dissatisfaction. Conclusion Initial weight loss is the most certain factor for predicting treatment outcome. Practice implication A treatment design including an introductory phase with a minimum weight loss criterion for continuing treatment is suggested.

A Bayesian approach to the alignment of mass spectra

The need to align spectra to correct for mass-to-charge experimental variation is a problem that arises in mass spectrometry (MS). Most of the MS-based proteomic data analysis methods involve a two-step approach, identify peaks first and then do the alignment and statistical inference on these identified peaks only. However, the peak identification step relies on prior information on the proteins of interest or a peak detection model, which are subject to error. Also numerous additional features such as peak shape and peak width are lost in simple peak detection, and these are informative for correcting mass variation in the alignment step. Here, we present a novel Bayesian approach to align the complete spectra. The approach is based on a parametric model which assumes that the spectrum and alignment function are Gaussian processes, but the alignment function is monotone. We show how to use the expectation-maximization algorithm to find the posterior mode of the set of alignment functions and the mean spectrum for a patient population. After alignment, we conduct tests while controlling for error attributable to multiple comparisons on the level of the peaks identified from the absolute mean spectra difference of two patient populations. cavanr@biostat.umn.edu.

Simulation on Temperature Distribution in Chemical Mechanical Polishing

Temperature rise has two-edged influences on chemical mechanical polishing (CMP) process: temperature-rise facilitates the chemical activity and the motion of the nano particles contained in the slurry through which material removal ratio (MRR) is enhanced; to the other side of the same coin, however, it will soften the pad surface and subsequently reduce the MRR. Thus the research on temperature distribution of CMP process will be conducive to discovering the mechanism of polishing, and acquiring stable MRR and improving surface quality. With the help of the knowledge of tribology, hydrodynamics, and thermodynamics, flow equation considering the temperature variation in the fine step of CMP process, wherein high surface quality is the main concern and usually operates in contact free state, is set up, based on which the temperature field in contact is investigated in detail by taking advantage of the simulation technique, and the heat energy production and transition relations are obtained. Due to the slurry used, a small viscous heating effect is acknowledged by simulated results, and the temperature rise is negligible in contact-free flows, which is very conducive to the promotion of the final polished wafer/disk surfaces. The research will surely shed some lights in the mechanism of CMP and lay a feasible foundation for possible future utilization.