A test of various computational solvation models on a set of “difficult” organic compounds

2009 ◽  
Vol 87 (8) ◽  
pp. 1154-1162 ◽  
Author(s):  
J. Peter Guthrie ◽  
Igor Povar
Keyword(s):  
Large Set ◽  
Aromatic Rings ◽  
Halogen Compounds ◽  
Solvation Energies ◽  
Polyfunctional Compounds ◽  
Solvation Models ◽  
Rms Error ◽  
Definition Of ◽  
Dielectric Continuum ◽  
Rms Errors

Various dielectric continuum models in Gaussian 03, based on the SCRF approach, PCM, CPCM, DPCM, IEFPCM, IPCM, and SCIPCM, have been tested on a set of 54 highly polar, generally polyfunctional compounds for which experimental solvation energies are available. These compounds span a range of 13 kcal/mol in ΔGt. The root-mean-square (RMS) errors for the full set of compounds range from 2.48 for DPCM to 1.77 for IPCM. For each method, classes of compounds which were not handled well could be identified. If these classes of compounds were omitted, the performance improved, and ranged from 1.58 (PCM, 39 compounds) to 1.02 (IPCM, 42 compounds). Models in the PCM family (PCM, CPCM, DPCM, and IEFPCM) with the recommended UAHF or UAKS sets of radii rely on a highly parameterized definition of the solvent cavity. Where this parameterization was inadequate, the calculated solvation energies were less reliable. This has been demonstrated by devising a new parameterization for PCM and halogen compounds, which markedly improves performance for polyhalogen compounds. The effective radius for the portion of the cavity centered on a halogen atom was assumed to be linear in the electron-withdrawing or -donating properties of the rest of the molecule as measured by Hammett σ (for halogens on aromatic rings) or Taft σ* (for halogens on aliphatic carbons). This new parameterization for PCM was tested on a set of 45 aliphatic and 22 aromatic polyhalogen compounds and shown to do well. IPCM, which was already the best of the methods in Gaussian, can be considerably improved by a parameterization to allow for cavitation, dispersion, and hydrogen bonding. A large set of compounds was used for the parameterization to have multiple examples for each parameter and as far as possible to have molecules with multiple instances of each structural feature. In the end, 15 parameters were found to be defined by the data for 241 compounds. With this parameter set, the RMS error for the set used for fitting was 0.81 kcal/mol, and the RMS error for the original set of 54 compounds was 0.85. With this new parameterization, IPCM is clearly the best of the methods available in Gaussian 03.

Using Multiple Surrogates for Minimization of the RMS Error in Meta-Modeling

2008 ◽  
Author(s):  
Felipe A. C. Viana ◽  
Raphael T. Haftka
Keyword(s):  
Cross Validation ◽  
Weighted Average ◽  
Large Set ◽  
High Dimensions ◽  
Engineering Problems ◽  
Cross Validation Error ◽  
Data Points ◽  
Meta Modeling ◽  
Rms Error ◽  
Rms Errors

Surrogate models are commonly used to replace expensive simulations of engineering problems. Frequently, a single surrogate is chosen based on past experience. Previous work has shown that fitting multiple surrogates and picking one based on cross-validation errors (PRESS in particular) is a good strategy, and that cross validation errors may also be used to create a weighted surrogate. In this paper, we discuss whether to use the best PRESS solution or a weighted surrogate when a single surrogate is needed. We propose the minimization of the integrated square error as a way to compute the weights of the weighted average surrogate. We find that it pays to generate a large set of different surrogates and then use PRESS as a criterion for selection. We find that the cross validation error vectors provide an excellent estimate of the RMS errors when the number of data points is high. Hence the use of cross validation errors for choosing a surrogate and for calculating the weights of weighted surrogates becomes more attractive in high dimensions. However, it appears that the potential gains from using weighted surrogates diminish substantially in high dimensions.

scholarly journals Evaluation and Recommendations for Improving the Accuracy of an Inexpensive Water Temperature Logger

2013 ◽  
Vol 30 (7) ◽  
pp. 1576-1582 ◽  
Author(s):  
S. J. Lentz ◽  
J. H. Churchill ◽  
C. Marquette ◽  
J. Smith
Keyword(s):  
Surface Layer ◽  
Solar Radiation ◽  
Water Temperature ◽  
Solar Heating ◽  
Bias Error ◽  
Mean Square ◽  
Temperature Logger ◽  
Accurate Temperature ◽  
Rms Error ◽  
Rms Errors

Abstract Onset's HOBO U22 Water Temp Pros are small, reliable, relatively inexpensive, self-contained temperature loggers that are widely used in studies of oceans, lakes, and streams. An in-house temperature bath calibration of 158 Temp Pros indicated root-mean-square (RMS) errors ranging from 0.01° to 0.14°C, with one value of 0.23°C, consistent with the factory specifications. Application of a quadratic calibration correction substantially reduced the RMS error to less than 0.009°C in all cases. The primary correction was a bias error typically between −0.1° and 0.15°C. Comparison of water temperature measurements from Temp Pros and more accurate temperature loggers during two oceanographic studies indicates that calibrated Temp Pros have an RMS error of ~0.02°C throughout the water column at night and beneath the surface layer influenced by penetrating solar radiation during the day. Larger RMS errors (up to 0.08°C) are observed near the surface during the day due to solar heating of the black Temp Pro housing. Errors due to solar heating are significantly reduced by wrapping the housing with white electrical tape.

Modelling spatial reasoning systems with shape algebras and formal logic

1997 ◽  
Vol 11 (4) ◽  
pp. 273-285 ◽  
Author(s):  
Scott C. Chase
Keyword(s):  
Spatial Reasoning ◽  
Predicate Logic ◽  
Spatial Relations ◽  
Large Set ◽  
First Order ◽  
Reasoning Systems ◽  
Geometric Objects ◽  
Small Set ◽  
Definition Of ◽  
High Level

AbstractThe combination of the paradigms of shape algebras and predicate logic representations, used in a new method for describing designs, is presented. First-order predicate logic provides a natural, intuitive way of representing shapes and spatial relations in the development of complete computer systems for reasoning about designs. Shape algebraic formalisms have advantages over more traditional representations of geometric objects. Here we illustrate the definition of a large set of high-level design relations from a small set of simple structures and spatial relations, with examples from the domains of geographic information systems and architecture.

Computer-Aided Design Synthesis Using Syntactic Solid Modeling

1994 ◽  
Author(s):  
Vassilios E. Theodoracatos ◽  
Xiaogang Guan
Keyword(s):  
Computer Aided Design ◽  
Solid Modeling ◽  
Large Set ◽  
Complex Structures ◽  
Design Synthesis ◽  
Computer Aided ◽  
Grammar Rules ◽  
Small Set ◽  
Definition Of ◽  
Aided Design

Abstract This paper presents a new Computer-Aided Design (CAD) synthesis model which uses Plex Grammar as structural relationship descriptors and NURBS surface representation for constructing standard and non-standard solid entities. Here, the designer uses a syntactic design methodology for early topological and geometrical definition of the structure of concept alternatives resulting from the design process. This syntactic scheme provides the capability of describing a large set of complex structures by using a small set of simple entities. The recursive nature of the grammar and the hierarchical representation of the structure makes the description of complex structures simple and under the direct control of the designer. An object structure constructive tree is generated and subsequently translated into Plex Grammar production rules in order to form an Interconnection Matrix (ICM) expressing. The resulting Plex structure defined in the ICM expresses the topological information among entities which form the specific types of objects. By modifying the Plex grammar rules, various objects with different geometry and topology can easily be reconstructed. Compared to conventional solid modeling techniques, this approach provides more systematic object generation, easy manipulation and modification, control over congruity and the ability to represent sculptured shapes. Several examples of syntactic solid modeling applied in design synthesis will be presented for further usage in downstream applications.

Analytical Method for the Calculation of J Parameter in Cracked Components: Presentation of the RSE-M/RCC-MR Procedure and Benchmark Proposal

2010 ◽  
Author(s):  
S. Marie ◽  
B. Drubay ◽  
P. Le Delliou ◽  
S. Chapuliot ◽  
H. Deschanels ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power ◽  
Strain Curve ◽  
Equivalent Material ◽  
Large Set ◽  
Stress Strain Curve ◽  
Weld Joints ◽  
Joint Geometry ◽  
Material Component ◽  
Definition Of

RSE-M and RCC-MR codes provide flaw assessment methodologies and related tools for Nuclear Power Plant. For these two codes, AREVA, CEA and EDF developed a large set of compendia for the calculation of the parameter J for various components (plates, pipes, elbows, …) and various defect geometries. The last step of these developments deals with the weld joints: since 2004, a methodology have been developed to calculate the J parameter for a defect located in a weld, less conservative than usual methods. This methodology is based on the definition of an equivalent material that leads to the same J value (with same loading conditions and defect geometry) than the bi-material component. The stress-strain curve of this equivalent material is deduced from a combination of the tensile curves of the base metal and of the weld metal. The weigth coefficients applied are specifically defined for the J calculation and generalized to deal with any weld joint geometry.

scholarly journals Comparison of MLC Positioning Deviations Using Log Files and Establishment of Specific Assessment Parameters for Different Accelerators With IMRT and VMAT

2021 ◽  
Author(s):  
Xiutong Lin ◽  
Tao Sun ◽  
Xiao Liu ◽  
Guifang Zhang ◽  
Yong Yin
Keyword(s):  
Influencing Factor ◽  
Similar Data ◽  
Position Errors ◽  
Positioning Errors ◽  
Log Files ◽  
Average Maximum ◽  
Treatment Plans ◽  
Specific Assessment ◽  
Rms Error ◽  
Rms Errors

Abstract Background and purpose: The study evaluated the differences in leaf positioning deviations by the log files of three advanced accelerators with two delivery techniques, and established specific assessment parameters of leaf positioning deviations for different types of accelerators.Methods: A total of 300 treatment plans with 5 consecutive treatment log files were collected from the Trilogy, TrueBeam and Halcyon accelerators. 50 IMRT and 50 VMAT plans were selected randomly on each accelerator. The log files information was parsed by SunCheck software from Sun Nuclear Corporation. The maximum leaf RMS errors, 95th percentile errors and percentages of different leaf positioning errors were statistically analyzed. The correlations between these evaluation parameters and accelerator performance parameters (maximum leaf speed, mean leaf speed, gantry and arc angle) were analyzed.Results: The average maximum leaf RMS errors of the Trilogy in the IMRT and VMAT plans were 0.45±0.1mm and 0.80±0.07mm, respectively, which were higher than the TrueBeam's 0.03±0.01mm, 0.03±0.01 mm and the Halcyon's 0.06±0.01 mm, 0.07±0.01mm. Similar data results were shown in the 95th percentile error. The maximum leaf RMS errors were strongly correlated with the 95th percentile errors. The leaf positioning deviations in VMAT were higher than those in IMRT for all accelerators. In TrueBeam and Halcyon, leaf position errors above 1 mm were not found in IMRT and VMAT plans. The main influencing factor of leaf positioning deviation was the leaf speed, which has no correlation with gantry and arc angles.Conclusions: Compared with the quality assurance guidelines, the MLC positioning deviations tolerances of the three accelerators should be tightened. For both IMRT and VMAT techniques, the 95th percentile error and the maximum RMS error are suggested to be tightened to 1.5 mm and 1 mm for the Trilogy accelerator respectively. In TrueBeam and Halcyon accelerators, the 95th percentile error and maximum RMS error of 1 mm and 0.5 mm, respectively, are considered appropriate.

Consumers experiencing vulnerability: a state of play in the literature

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Aimee Riedel ◽  
Dana Messenger ◽  
David Fleischman ◽  
Rory Mulcahy
Keyword(s):  
Text Mining ◽  
Systematic Approach ◽  
Descriptive Analysis ◽  
Age Factors ◽  
Sexual Exploitation ◽  
Large Set ◽  
Subjective Experiences ◽  
Content Type ◽  
Interpretative Bias ◽  
Definition Of

Purpose The purpose of this paper is to provide a state-of-the-art review of research on consumers experiencing vulnerability to describe the current situation of the consumers experiencing vulnerability literature and develop an up-to-date synthesised definition of consumers experiencing vulnerability. Design/methodology/approach This systematic review, guided by the PRISMA framework, takes a multi-disciplinary approach to identify 310 articles published between 2010 and 2019 examining consumers experiencing vulnerability. Descriptive analysis of the data is undertaken in combination with a thematic and text mining approach using Leximancer software. Findings A definition of consumers experiencing vulnerability is developed- “unique and subjective experiences where characteristics such as states, conditions and/or external factors lead to a consumer experiencing a sense of powerlessness in consumption settings”. The findings reveal consumers experiencing vulnerability have often been classified using a uni-dimensional approach (opposed to a multi-dimensional), focussing on one factor of vulnerability, the most prevalent of these being economic and age factors. A lack of research has examined consumers experiencing vulnerability based upon geographical remoteness, gender and sexual exploitation. Originality/value This paper is one of the first to examine consumers experiencing vulnerability using a systematic approach and text mining analysis to synthesise a large set of articles, which subsequently reduces the potential for researchers’ interpretative bias. Further, it is the first to generate a data-driven definition of consumers experiencing vulnerability. It provides targeted recommendations to allow further scholarly, policy and practical contributions to this area.

scholarly journals Sustainable Evolution for Global Business: A Synthetic Review of the Literature

2016 ◽  
Vol 6 (1) ◽  
pp. 1 ◽  
Author(s):  
S. J. Chang
Keyword(s):  
Corporate Sustainability ◽  
Theoretical Development ◽  
Large Set ◽  
Business And Society ◽  
Global Business ◽  
Business Sustainability ◽  
The Public ◽  
Sustainability Issue ◽  
Sustainability Measurement ◽  
Definition Of

<p>This paper reviews the recent literature on business sustainability. While it is almost impossible to give a universally agreeable definition of “sustainability” due to its scope, depth, and inclusive nature, this paper reviews a fairly large set of research efforts, both empirical and normative, that examine the sustainability issue in regards to the theoretical development, the interface between business and society, the interrelationships among firms, markets, and the public interest, sustainability measurement and assessment, as well as the changes, developments, and evolution in recent years along those lines. The uniqueness of the study is to review the literature by following the developmental and evolutionary sequences in business sustainability in order to shed light on how the concept of corporate sustainability has evolved from the traditional shareholders-focused neoclassical view and how it is advanced from the ideas of environmentalism, stakeholder theory, and CSR.</p>

Modeling Subcooled Flow Film Boiling in a Vertical Tube

2010 ◽  
Vol 2 (2) ◽  
Author(s):  
Meamer El Nakla ◽  
D. C. Groeneveld ◽  
Shui-Chih Cheng
Keyword(s):  
Heat Transfer ◽  
Film Boiling ◽  
Average Error ◽  
Parallel Plates ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Rms Error ◽  
Rms Errors ◽  
Flow Film Boiling

A two-fluid one-dimensional model has been developed to predict the wall temperature of an internally heated tube during inverted annular flow film boiling (IAFB). The model is derived using basic conservation equations of mass, momentum, and energy. To simplify the derivation of the constitutive heat transfer relations, flow between two parallel plates is assumed. The model features shear stress and interfacial relations that make it accurately predict the parametric effects and heat transfer characteristics of IAFB over a wide range of flow conditions. The model predicts wall temperatures of R-134a-cooled tubes with an average error of −1.21% and a rms error of 6.37%. This corresponds to average and rms errors in predicted heat transfer coefficients of 1.33% and 10.07%, respectively. Using water data, the model predicts wall temperatures with an average error of −1.76% and a rms error of 7.78%, which corresponds to average and rms errors in predicted heat transfer coefficients of 4.16% and 15.06%, respectively.

Analytical Method for the Calculation of J Parameter for Surface Cracks in Piping Welds

2008 ◽  
Author(s):  
S. Marie ◽  
Y. Kayser ◽  
B. Drubay ◽  
P. Le Delliou ◽  
P. Gilles ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Strain Curve ◽  
Equivalent Material ◽  
Large Set ◽  
Surface Cracks ◽  
Stress Strain Curve ◽  
Weld Joints ◽  
Joint Geometry ◽  
Material Component ◽  
Definition Of

RSE-M and RCC-MR codes provide flaw assessment methodologies and related tools for Nuclear Power Plant. AREVA, CEA and EDF developed in particular a large set of compendia for the calculation of the parameter J for various components (plates, pipes, elbows, ...) and various defect geometries. The last step of these developments deals with the weld joints : since 2004, the partners are developing a methodology to calculate the J parameter for a defect located in a weld, less conservative than usual methods. This methodology is based on the definition of an equivalent material that leads to the same J value (with same loading conditions and defect geometry) than the bi-material component. The stress-strain curve of this equivalent material is deduced from a combination of the tensile curves of the base metal and of the weld metal. The weigth coefficients applied are specifically defined for the J calculation and generalized to deal with any weld joint geometry.

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