scholarly journals A new approach to optimize pH buffers

2021 ◽  
Author(s):  
Marc Blétry
Keyword(s):  
Analytical Chemistry ◽  
Parametric Study ◽  
Numerical Optimization ◽  
Practical Interest ◽  
Optimization Techniques ◽  
Ph Gradients ◽  
New Approach ◽  
First Derivative ◽  
Buffer Solutions ◽  
New Strategy

Buffer solutions are pervasive in chemistry, biochemistry, analytical chemistry, etc. A better understanding of buffer properties and what controls them is susceptible to be of interest in many scientific and technological fields. For instance, linear pH gradients are commonly used in electrophoresis and their optimization rests on numerical optimization of the concentrations of various weak species. It is probably generally assumed that no basic progress could be made on optimization approaches. We introduce here a new strategy to buffer optimization, based on a parametric study of the roots of the first derivative of the buffer index. In this way, it is possible to find mathematically optimal sets of parameters (pKa and concentrations). The method is applied to mixtures of 2, 3 and 4 monovalent species, which represent simple cases that do not call for overly elaborate numerical optimization techniques, but are nevertheless of practical interest in various branches of analytical chemistry.

scholarly journals The multilevel ant stigmergy algorithm for numerical optimization

2006 ◽  
Vol 19 (2) ◽  
pp. 247-260 ◽  
Author(s):  
Peter Korosec ◽  
Jurij Silc
Keyword(s):  
Differential Evolution ◽  
Optimization Algorithm ◽  
Numerical Optimization ◽  
Optimization Techniques ◽  
Industrial Case Study ◽  
New Approach ◽  
Collective Work ◽  
Better Than

The Multilevel Ant Stigmergy Algorithm (MASA) is a new approach to solving multi-parameter problems based on stigmergy, a type of collective work that can be observed in nature. In this paper we evaluate the performance of MASA regarding its applicability as numerical optimization techniques. The evaluation is performed with several widely used benchmarks functions, as well as on an industrial case study. We also compare the MASA with Differential Evolution, well-known numerical optimization algorithm. The average solution obtained with the MASA was better than a solution recently found using Differential Evolution.

On-Surface Radical Oligomerisation: A New Approach to STM Tip-Induced Reactions

2018 ◽  
Author(s):  
Gaolei Zhan ◽  
Younes Makoudi ◽  
Judicael Jeannoutot ◽  
Simon Lamare ◽  
Michel Féron ◽  
...  
Keyword(s):  
Sample Surface ◽  
Scanning Tunnelling Microscope ◽  
Transfer Event ◽  
New Approach ◽  
The Past ◽  
Organic Nanostructures ◽  
Scanning Tunnelling ◽  
New Strategy ◽  
Surface Fabrication ◽  
And Control

Over the past decade, on-surface fabrication of organic nanostructures has been widely investigated for the development of molecular electronic devices, nanomachines, and new materials. Here, we introduce a new strategy to obtain alkyl oligomers in a controlled manner using on-surface radical oligomerisations that are triggered by the electrons/holes between the sample surface and the tip of a scanning tunnelling microscope. The resulting radical-mediated mechanism is substantiated by a detailed theoretical study. This electron transfer event only occurs when <i>V</i><sub>s</sub> < -3 V or <i>V</i><sub>s</sub> > + 3 V and allows access to reactive radical species under exceptionally mild conditions. This transfer can effectively ‘switch on’ a sequence leading to formation of oligomers of defined size distribution due to the on-surface confinement of reactive species. Our approach enables new ways to initiate and control radical oligomerisations with tunnelling electrons, leading to molecularly precise nanofabrication.

An Alternative Design Approach for Vehicle Crash Safety Using Crash Pulse Optimization

2000 ◽  
Author(s):  
R. J. Yang ◽  
C. H. Tho ◽  
C. C. Gearhart ◽  
Y. Fu
Keyword(s):  
Time Domain ◽  
Numerical Optimization ◽  
Piecewise Linear ◽  
Linear Representation ◽  
Optimization Techniques ◽  
Safety Requirements ◽  
Crash Safety ◽  
Design Variables ◽  
Piecewise Linear Representation ◽  
Occupant Injury

Abstract This paper presents an approach, based on numerical optimization techniques, to identify an ideal (5 star) crash pulse and generate a band of acceptable crash pulses surrounding that ideal pulse. This band can be used by engineers to quickly determine whether a design will satisfy government and corporate safety requirements, and whether the design will satisfy the requirements for a 5 star crash rating. A piecewise linear representation of the crash pulse with two plateaus is employed for its conceptual simplicity and because such a pulse has been shown to be sufficient for reproducing occupant injury behavior when used as input into MADYMO models. The piecewise linear crash pulse is parameterized with 7 design variables (5 for time domain and 2 for acceleration domain) in the optimization process. A series of sample runs are conducted to validate that pulses falling within the acceptable crash pulse band do in fact satisfy 5 star requirements.

scholarly journals Metal-free visible light photoredox enables generation of carbyne equivalents via phosphonium ylide C–H activation

2019 ◽  
Vol 10 (6) ◽  
pp. 1687-1691 ◽  
Author(s):  
Mrinmoy Das ◽  
Minh Duy Vu ◽  
Qi Zhang ◽  
Xue-Wei Liu
Keyword(s):  
Visible Light ◽  
Bond Formation ◽  
Formation Processes ◽  
New Approach ◽  
Carbon Bond ◽  
Metal Free ◽  
Carbon Carbon Bond ◽  
Carbon Carbon Bonds ◽  
Carbon Bonds ◽  
New Strategy

Phosphonium ylides have shown their synthetic usefulness in important carbon–carbon bond formation processes. Our new strategy employs phosphonium ylides as novel carbyne equivalents and features a new approach for constructing carbon–carbon bonds from alkenes.

scholarly journals Evolutionary Algorithms for Constrained Parameter Optimization Problems

1996 ◽  
Vol 4 (1) ◽  
pp. 1-32 ◽  
Author(s):  
Zbigniew Michalewicz ◽  
Marc Schoenauer
Keyword(s):  
Nonlinear Programming ◽  
Evolutionary Algorithms ◽  
Evolutionary Computation ◽  
Numerical Optimization ◽  
Optimization Problems ◽  
Optimization Techniques ◽  
Test Cases ◽  
Nonlinear Constraints ◽  
Nonlinear Programming Problem ◽  
General Nonlinear Programming

Evolutionary computation techniques have received a great deal of attention regarding their potential as optimization techniques for complex numerical functions. However, they have not produced a significant breakthrough in the area of nonlinear programming due to the fact that they have not addressed the issue of constraints in a systematic way. Only recently have several methods been proposed for handling nonlinear constraints by evolutionary algorithms for numerical optimization problems; however, these methods have several drawbacks, and the experimental results on many test cases have been disappointing. In this paper we (1) discuss difficulties connected with solving the general nonlinear programming problem; (2) survey several approaches that have emerged in the evolutionary computation community; and (3) provide a set of 11 interesting test cases that may serve as a handy reference for future methods.

scholarly journals Combining Analytical Models and Mesh Morphing Based Optimization Techniques for the Design of Flying Multihulls Appendages

2021 ◽  
Vol 6 (01) ◽  
pp. 151-172
Author(s):  
Ubaldo Cella ◽  
Corrado Groth ◽  
Stefano Porziani ◽  
Alberto Clarich ◽  
Francesco Franchini ◽  
...  
Keyword(s):  
Numerical Optimization ◽  
Fluid Dynamic ◽  
Optimization Procedure ◽  
Optimization Techniques ◽  
Analytical Models ◽  
High Fidelity ◽  
Mesh Morphing ◽  
Wide Range ◽  
Global Equilibrium ◽  
Range Of Values

Abstract The fluid dynamic design of hydrofoils involves most of the typical difficulties of aeronautical wings design with additional complexities related to the design of a device operating in a multiphase environment. For this reason, “high fidelity” analysis solvers should be, in general, adopted also in the preliminary design phase. In the case of modern fast foiling sailing yachts, the appendages accomplish both the task of lifting up the boat and to make possible upwind sailing by contributing balance to the sail side force and the heeling moment. Furthermore, their operative design conditions derive from the global equilibrium of forces and moments acting on the system which might vary in a very wide range of values. The result is a design problem defined by a large number of variables operating in a wide design space. In this scenario, the device performing in all conditions has to be identified as a trade-off among several conflicting requirements. One of the most efficient approaches to such a design challenge is to combine multi-objective optimization strategies with experienced aerodynamic design. This paper presents a numerical optimization procedure suitable for foiling multihulls. As a proof of concept, it reports, as an application, the foils design of an A-Class catamaran. The key point of the method is the combination of opportunely developed analytical models of the hull forces with high fidelity multiphase analyses in both upwind and downwind sailing conditions. The analytical formulations were tuned against a database of multiphase analyses of a reference demihull at several attitudes and displacements. An aspect that significantly contributes to both efficiency and robustness of the method is the approach adopted to the geometric parametrization of the foils which was implemented by a mesh morphing technique based on Radial Basis Functions.

scholarly journals Action Research: a Supplementary Source for the English Langauge Teachers

2019 ◽  
Vol 8 (2S11) ◽  
pp. 2883-2885
Keyword(s):  
Action Research ◽  
Learning Outcomes ◽  
English Language ◽  
Teaching Strategy ◽  
Language Teachers ◽  
New Approach ◽  
New Strategy ◽  
Current Scenario ◽  
English Language Teachers ◽  
The Subject

This paper tries to explore that, Action Research is a supplementary source for English Language Teachers to bring out better teaching outcome of the teachers and better learning outcomes of the students. In the current scenario, apart from the syllabus, English Language teachers expect a supplementary source to follow a new strategy in order to satisfy the expectations of the students inside the classroom. They face many challenges in the classroom and one of the important problems is to draw continuous involvement of the students as well as to create good understanding of the subject in the classroom. In this connection, Action Research helps the teachers to explore effective teaching strategy in the classroom. This Action Research is integrated with a new approach called MUSE (Manageable, Urgent, Significant and Engaging), that helps the teachers to plan effectively. Besides, it is an exploratory or activity based classroom research and so it encourages the students to learn effectively and understand clearly with more involvement in the classroom. This study suggests a need for the supplementary source and it also focuses on Action Research to aid the teachers.

Efficient Structural Design Using a Numerical Optimization Technique

2019 ◽  
Author(s):  
Qian Wang ◽  
Lucas Schmotzer ◽  
Yongwook Kim
Keyword(s):  
Structural Design ◽  
Numerical Optimization ◽  
Optimization Technique ◽  
Optimization Method ◽  
Optimization Techniques ◽  
Convergence Criteria ◽  
Efficient Design ◽  
Concrete Building ◽  
Gradient Based ◽  
Structural Responses

<p>Structural designs of complex buildings and infrastructures have long been based on engineering experience and a trial-and-error approach. The structural performance is checked each time when a design is determined. An alternative strategy based on numerical optimization techniques can provide engineers an effective and efficient design approach. To achieve an optimal design, a finite element (FE) program is employed to calculate structural responses including forces and deformations. A gradient-based or gradient-free optimization method can be integrated with the FE program to guide the design iterations, until certain convergence criteria are met. Due to the iterative nature of the numerical optimization, a user programming is required to repeatedly access and modify input data and to collect output data of the FE program. In this study, an approximation method was developed so that the structural responses could be expressed as approximate functions, and that the accuracy of the functions could be adaptively improved. In the method, the FE program was not required to be directly looped in the optimization iterations. As a practical illustrative example, a 3D reinforced concrete building structure was optimized. The proposed method worked very well and optimal designs were found to reduce the torsional responses of the building.</p>

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