Non-systematic Errors Research Articles

Examining credentialing criteria and poor performance indicators for IROC Houston's anthropomorphic head and neck phantom.

To analyze the most recent results of the Imaging and Radiation Oncology Core Houston Quality Assurance Center's (IROC-H) anthropomorphic head and neck (H&N) phantom to determine the nature of failing irradiations and the feasibility of altering credentialing criteria. IROC-H's H&N phantom, used for intensity-modulated radiation therapy credentialing for National Cancer Institute-sponsored clinical trials, requires that an institution's treatment plan agrees within ±7% of measured thermoluminescent dosimeter (TLD) doses; it also requires that ≥85% of pixels pass ±4 mm distance to agreement (7%/4 mm gamma analysis for film). The authors re-evaluated 156 phantom irradiations (November 1, 2014-October 31, 2015) according to the following tighter criteria: (1) 5% TLD and 5%/4 mm, (2) 5% TLD and 5%/3 mm, (3) 4% TLD and 4%/4 mm, and (4) 3% TLD and 3%/3 mm. Failure rates were evaluated with respect to individual film and TLD performance by location in the phantom. Overall poor phantom results were characterized qualitatively as systematic errors (correct shape and position but wrong magnitude of dose), setup errors/positional shifts, global but nonsystematic errors, and errors affecting only a local region. The pass rate for these phantoms using current criteria was 90%. Substituting criteria 1-4 reduced the overall pass rate to 77%, 70%, 63%, and 37%, respectively. Statistical analyses indicated that the probability of noise-induced TLD failure, even at the 5% criterion, was <0.5%. Phantom failures were generally identified by TLD (≥66% failed TLD, whereas ≥55% failed film), with most failures occurring in the primary planning target volume (≥77% of cases). Results failing current criteria or criteria 1 were primarily diagnosed as systematic >58% of the time (11/16 and 21/36 cases, respectively), with a greater extent due to underdosing. Setup/positioning errors were seen in 11%-13% of all failing cases (2/16 and 4/36 cases, respectively). Local errors (8/36 cases) could only be demonstrated at criteria 1. Only three cases of global errors were identified in these analyses. For current criteria and criteria 1, irradiations that failed from film only were overwhelmingly associated with phantom shifts/setup errors (≥80% of cases). This study highlighted that the majority of phantom failures are the result of systematic dosimetric discrepancies between the treatment planning system and the delivered dose. Further work is necessary to diagnose and resolve such dosimetric inaccuracy. In addition, the authors found that 5% TLD and 5%/4 mm gamma criteria may be both practically and theoretically achievable as an alternative to current criteria.

R-SLAM: Resilient localization and mapping in challenging environments

Accurate pose estimation plays an important role in solution of simultaneous localization and mapping (SLAM) problem, required for many robotic applications. This paper presents a new approach called R-SLAM, primarily to overcome systematic and non-systematic odometry errors which are generally caused by uneven floors, unexpected objects on the floor or wheel-slippage due to skidding or fast turns. The hybrid approach presented here combines the strengths of feature based and grid based methods to produce globally consistent high resolution maps within various types of environments.The proposed R-SLAM algorithm improves the pose estimation by positioning some of the particles relative to the features existing in the environment. So instead of assuming unimodal Gaussian distribution of particles, as it is in GMapping method, R-SLAM handles the odometry errors better without increasing the number of particles. R-SLAM approach does not necessitate any pre-defined landmarks, yet makes use of them whenever they exist in the environment. Restricted use of the features keeps the computational complexity suitable for real time applications in large scaled environments.A four wheeled, differential drive mobile robot platform and ROS framework have been used to implement and test the proposed method. Field test results reported in this article are obtained in historical Hagia Sophia museum, Istanbul, which occupies an area of 7500 square meters. To provide analogous results, another set of tests are performed on publicly available datasets and SLAM evaluation toolkit developed at the University of Freiburg is used to compare the results.

Numerical solution of the Sinanoǧlu equation using a multicentre radial-angular grid

ABSTRACTThe pair functions that minimise the correlation energy of second-order many-body perturbation (MP2) theory (the Hylleraas functional) are obtained as solutions to the corresponding Sinanoǧlu equation by expanding them on a six-dimensional, multicentre, radial-angular grid of two electrons. Cusps in the pair functions at the nuclei are described numerically accurately by the multicentre grid. A cusp in each singlet pair function at the coalescence of the two electrons is taken into account analytically by a correlation factor. With a grid of approximately 10,000 points per atom, the MP2 correlation energies for atoms and polyatomic molecules are obtained usually within 0.1 mEh of the complete-basis-set results. The correlation factor, auxiliary basis functions, and a judicious choice of integration algorithms are all necessary to stabilise the grid-based MP2 and underlying Hartree–Fock (HF) calculations. The auxiliary basis set, in particular, largely restores the hermiticity and diagonal dominance of the Fock matrix as well as furnishes virtual orbitals used in a resolution-of-the-identity approximation to lower the dimension of some integrals. The results of the grid-based HF and MP2 calculations without a correlation factor are found to suffer from large, nonsystematic errors frequently.

Diffusion Monte Carlo for Accurate Dissociation Energies of 3d Transition Metal Containing Molecules.

Transition metals and transition metal compounds are important to catalysis, photochemistry, and many superconducting systems. We study the performance of diffusion Monte Carlo (DMC) applied to transition metal containing dimers (TMCDs) using single-determinant Slater-Jastrow trial wavefunctions and investigate the possible influence of the locality and pseudopotential errors. We find that the locality approximation can introduce nonsystematic errors of up to several tens of kilocalories per mole in the absolute energy of Cu and CuH if Ar or Mg core pseudopotentials (PPs) are used for the 3d transition metal atoms. Even for energy differences such as binding energies, errors due to the locality approximation can be problematic if chemical accuracy is sought. The use of the Ne core PPs developed by Burkatzki et al. (J. Chem. Phys. 2008, 129, 164115), the use of linear energy minimization rather than unreweighted variance minimization for the optimization of the Jastrow function, and the use of large Jastrow parametrizations reduce the locality errors. In the second section of this article, we study the general performance of DMC for 3d TMCDs using a database of binding energies of 20 TMCDs, for which comparatively accurate experimental data is available. Comparing our DMC results to these data for our results that compare best with experiment, we find a mean unsigned error (MUE) of 4.5 kcal/mol. This compares well with the achievable accuracy in CCSDT(2)Q (MUE = 4.6 kcal/mol) and the best all-electron DFT results (MUE = 4.5 kcal/mol) for the same set of systems (Truhlar et al. J. Chem. Theory Comput. 2015, 11, 2036-2052). The mean errors in DMC depend less on the exchange-correlation functionals used to generate the trial wavefunction than the corresponding mean errors in the underlying DFT calculations. Furthermore, the QMC results obtained for each molecule individually vary less with the functionals used. These observations are relevant for systems such as molecules interacting with transition metal surfaces where the DFT functionals performing best for molecules (hybrids) do not yield improvements in DFT. Overall, the results presented in this article yield important guidelines for both the assessment of the achievable accuracy with DMC and the design of DMC calculations for systems including transition metal atoms.

Crustal and uppermost mantle structure beneath the United States

AbstractThis paper presents a new model of the shear velocity structure of the crust and uppermost mantle beneath the contiguous U.S. The model is based on more than a decade of USArray Transportable Array (TA) data across the U.S. and derives from a joint Bayesian Monte Carlo inversion of Rayleigh wave group and phase speeds determined from ambient noise and earthquakes, receiver functions, and Rayleigh wave ellipticity (H/V) measurements. Within the Bayesian inverse theoretic framework, a prior distribution of models is posited and a posterior distribution is inferred beneath all of the more than 1800 TA stations across the U.S. The resulting mean and standard deviation of the mean of the posterior distribution at each station summarize the inversion results, which are then interpolated onto a regular 0.25°×0.25° grid across the U.S. to define the final 3‐D model. We present arguments that show that the standard deviation of the posterior distribution overestimates the effect of nonsystematic errors in the final model by a factor of 4–5 and identify uncertainties in density and mantle Q as primary potential sources of remaining systematic error in the final model. The model presents a great many newly resolved structural features across the U.S. that require further analysis and dedicated explication. We highlight here low‐velocity anomalies in the upper mantle that underlie the Appalachians with centers of anomalies in northern Georgia, western Virginia, and, most prominently, New England.

Troubles in the Systematic Prediction of Transition Metal Thermochemistry with Contemporary Out-of-the-Box Methods.

The recently developed DLPNO-CCSD(T) method and seven popular DFT functionals (B3LYP, M06, M06L, PBE, PBE0, TPSS, and TPSSh) with and without an empirical dispersion term have been tested to reproduce 111 gas phase reaction enthalpies involving 11 different transition metals. Our calculations, corrected for both relativistic effects and basis set incompleteness, indicate that most of the methods applied with default settings perform with acceptable accuracy on average. Nevertheless, our calculations also evidenced unexpected and nonsystematic large deviations for specific cases. For group 12 metals (Zn, Cd, Hg), most of the methods provided mean unsigned errors (MUE) less than 5.0 kcal/mol, with DLPNO-CCSD(T) and PBE methods performing excellently (MUE lower 2.0 kcal/mol). Problems started with group 4 metals (Ti and Zr). The best performer for Zr complexes with MUE of 1.8 kcal/mol, PBE0-D3, provides MUE larger than 8 kcal/mol for Ti. DLPNO-CCSD(T) provides a reasonable MUE of 3.3 kcal/mol for Ti reactions but gives MUE a larger than 14.4 kcal/mol for Zr complexes, with all the larger deviations for reactions involving ZrF4. Large and nonsystematic errors have been obtained for group 6 metals (Mo and W), for eight reactions containing Fe, Cu, Nb, and Re complexes. Finally, for the whole set of 111 reactions, the DLPNO-CCSD(T), B3LYP-D3, and PBE0-D3 methods turned out to be the best performers, all providing MUE below 5.0 kcal/mol. Since DFT results cannot be systematically improved and large nonsystematic deviations of 20-30 kcal/mol were obtained even for best performers, our results indicate that current DFT methods are still unable to provide robust predictions in transition metal thermochemistry, at least for the functionals explored in this work. The same conclusion holds for both DLPNO-CCSD(T) and canonical CCSD(T) methods when used entirely as out-of-the-box. However, if careful investigation of core correlation is performed, relativistic effects are properly included and the quality of the reference wave function is properly checked, CCSD(T) methods can still provide good quality results that might even be used to validate DFT methods due to paucity of accurate thermodynamic data for realistic-sized transition metal complexes.

Employer reasons for failing to report eligible workers' compensation claims in the BLS survey of occupational injuries and illnesses.

BackgroundLittle research has been done to identify reasons employers fail to report some injuries and illnesses in the Bureau of Labor Statistics Survey of Occupational Injuries and Illnesses (SOII).MethodsWe interviewed the 2012 Washington SOII respondents from establishments that had failed to report one or more eligible workers’ compensation claims in the SOII about their reasons for not reporting specific claims. Qualitative content analysis methods were used to identify themes and patterns in the responses.ResultsNon‐compliance with OSHA recordkeeping or SOII reporting instructions and data entry errors led to unreported claims. Some employers refused to include claims because they did not consider the injury to be work‐related, despite workers’ compensation eligibility. Participant responses brought the SOII eligibility of some claims into question.ConclusionSystematic and non‐systematic errors lead to SOII underreporting. Insufficient recordkeeping systems and limited knowledge of reporting requirements are barriers to accurate workplace injury records. Am. J. Ind. Med. 59:343–356, 2016. © 2016 The Authors. American Journal of Industrial Medicine Published by Wiley Periodicals, Inc.

Problems, successes and challenges for the application of dispersion-corrected density-functional theory combined with dispersion-based implicit solvent models to large-scale hydrophobic self-assembly and polymorphism

The recent advent of dispersion-corrected density-functional theory (DFT) methods allows for quantitative modelling of molecular self-assembly processes, and we consider what is required to develop applications to the formation of large self-assembled monolayers (SAMs) on hydrophobic surfaces from organic solution. Focus is on application of the D3 dispersion correction of Grimme combined with the solvent dispersion model of Floris, Tomasi and Pascual–Ahuir to simulate observed scanning-tunnelling microscopy (STM) images of various polymorphs of tetraalkylporphyrin SAMs on highly oriented pyrolytic graphite surfaces. The most significant problem is identified as the need to treat SAM structures that are incommensurate with those of the substrate, providing a challenge to the use of traditional periodic-imaging boundary techniques. Using nearby commensurate lattices introduces non-systematic errors into calculated lattice constants and free energies of SAM formation that are larger than experimental uncertainties and polymorph differences. Developing non-periodic methods for polymorph interface simulation also remains a challenge. Despite these problems, existing methods can be used to interpret STM images and SAM atomic structures, distinguishing between multiple feasible polymorph types. They also provide critical insight into the factors controlling polymorphism. All this stems from a delicate balance that the intermolecular D3 and solvent Floris, Tomasi and Pascual–Ahuir corrections provide. Combined optimised treatments should yield fully quantitative approaches in the future.

Modelling noise in second generation sequencing forensic genetics STR data using a one-inflated (zero-truncated) negative binomial model

We present a model fitting the distribution of non-systematic errors in STR second generation sequencing, SGS, analysis. The model fits the distribution of non-systematic errors, i.e. the noise, using a one-inflated, zero-truncated, negative binomial model. The model is a two component model. The first component models the excess of singleton reads, while the second component models the remainder of the errors according to a truncated negative binomial distribution.We estimated the parameters of the model in two ways: (1) we maximised the likelihood using an explicitly calculated gradient function and (2) we used the expectation-maximisation, EM, algorithm. The estimated parameters were used to create dynamic, sample specific thresholds for noise removal using marker specific proportions of the negative binomial distribution.Based on data from dilution series experiments (amounts of DNA ranging from 100pg to 2ng) conducted at The Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark, the method was compared to that of a naïve model that implies the removal of reads with a coverage of less than 5–10% of the total marker coverage. In comparison, our method resulted in three allelic drop-outs (true alleles below threshold), whereas the 10%-threshold induced 12 drop-outs. The non-filtered error reads (e.g. stutters, shoulders and reads with miscalled bases) will subsequently be modelled by different statistical methodologies.

Development of Nonlinear Model Based on Wavelet-ANFIS for Rainfall Forecasting at Klang Gates Dam

Rainfall is one of the most complicated effective hydrologic processes in runoff prediction and water management. Artificial neural networks (ANN) have been found efficient, particularly in problems where characteristics of the processes are stochastic and difficult to describe using explicit mathematical models. However, time series prediction based on ANN algorithms is fundamentally difficult and faces some other problems. For this purpose, one method that has been identified as a possible alternative for ANN in hydrology and water resources problems is the adaptive neuro-fuzzy inference system (ANFIS). Nevertheless, the data arising from the monitoring stations and experiment might be corrupted by noise signals owing to systematic and non-systematic errors. This noisy data often made the prediction task relatively difficult. Thus, in order to compensate for this augmented noise, the primary objective of this paper is to develop a technique that could enhance the accuracy of rainfall prediction. Therefore, the wavelet decomposition method is proposed to link to ANFIS and ANN models. In this paper, two scenarios are employed; in the first scenario, monthly rainfall value is imposed solely as an input in different time delays from the time (t) to the time (t-4) into ANN and ANFIS, second scenario uses the wavelet transform to eliminate the error and prepares sub-series as inputs in different time delays to the ANN and ANFIS. The four criteria as Root Mean Square Error (RMSE), Correlation Coefficient (R2), Gamma coefficient (G), and Spearman Correlation Coefficient (ρ) are used to evaluate the proposed models. The results showed that the model based on wavelet decomposition conjoined with ANFIS could perform better than the ANN and ANFIS models individually.

Getting it (approximately) right (and center and left!): Reliability and uncertainty estimates for the comparative manifesto data

The extensive estimates of party policy preferences produced by the CMP (Comparative Manifesto Project, now MARPOR) have proved robust and valid over a wide variety of research applications. But all estimates carry some error. We demonstrate that one of the two existing assessments of non-systematic error in the CMP data strongly overstates their reliability while the other understates it, leaving much potential for mis-estimation. We develop a new method which extends classical test theory and directly estimates overall data reliability; reliabilities and standard errors of measurement for each party system; and standard errors of measurement for each data-point. These should facilitate use of the CMP policy scores which are usually the only ones available for extended party and policy research.

An efficient approach to pose tracking based on odometric error modelling for mobile robots

SUMMARYOdometric error modelling for mobile robots is the basis of pose tracking. Without bounds the odometric accumulative error decreases localisation precision after long-range movement, which is often not capable of being compensated for in real time. Therefore, an efficient approach to odometric error modelling is proposed in regard to different drive type mobile robots. This method presents a hypothesis that the motion path approximates a circular arc. The approximate functional expressions between the control input of odometry and non-systematic error as well as systematic error derived from odometric error propagation law. Further an efficient algorithm of pose tracking is proposed for mobile robots, which is able to compensate for the non-systematic and systematic error in real time. These experiments denote that the odometric error modelling reduces the accumulative error of odometry efficiently and improves the specific localisation process significantly during autonomous navigation.

Tissue-Point Motion Tracking in the Tongue From Cine MRI and Tagged MRI

PURPOSE Accurate tissue motion tracking within the tongue can help professionals diagnose and treat vocal tract-related disorders, evaluate speech quality before and after surgery, and conduct various scientific studies. The authors compared tissue tracking results from 4 widely used deformable registration (DR) methods applied to cine magnetic resonance imaging (MRI) with harmonic phase (HARP)-based tracking applied to tagged MRI. METHOD Ten subjects repeated the phrase "a geese" multiple times while sagittal images of the head were collected at 26 Hz, first in a tagged MRI data set and then in a cine MRI data set. HARP tracked the motion of 8 specified tissue points in the tagged data set. Four DR methods including diffeomorphic demons and free-form deformations based on cubic B-spline with 3 different similarity measures were used to track the same 8 points in the cine MRI data set. Individual points were tracked and length changes of several muscles were calculated using the DR- and HARP-based tracking methods. RESULTS The results showed that the DR tracking errors were nonsystematic and varied in direction, amount, and timing across speakers and within speakers. Comparison of HARP and DR tracking with manual tracking showed better tracking results for HARP except at the tongue surface, where mistracking caused greater errors in HARP than DR. CONCLUSIONS Tissue point tracking using DR tracking methods contains nonsystematic tracking errors within and across subjects, making it less successful than tagged MRI tracking within the tongue. However, HARP sometimes mistracks points at the tongue surface of tagged MRI because of its limited bandpass filter and tag pattern fading, so that DR has better success measuring surface tissue points on cine MRI than HARP does. Therefore, a hybrid method is being explored.

Improved Approach to Global Localization based on Odometry Error Modeling for Mobile Robots

It is often the odometry accumulative error without bound after long-range movement that decreases the precision of global localization for wheeled mobile robots. Therefore, an efficient a pproach to odometry error modeling is proposed regarding gentle drive type mobile robots. The approximate functional expressions, between process input of odometry and non-systematic error as well as systematic error, are derived based on odometry error propagation law. Further, the odometry error model is applied to the global localization to compensate the accumulative error during long-time navigation. In addition, Because a lot of candidate poses of robots are generated in the process of monocular visual localization, particle swarm optimization is applied to acquire the optimal pose for mobile robots during global localization. The experiments denote that in spite of sacrificing a little computation time, the proposed method decreases odometry accumulative errors, and improves the global localization precision during autonomous navigation efficiently.

An ab Initio Benchmark and DFT Validation Study on Gold(I)-Catalyzed Hydroamination of Alkynes.

High level ab initio calculations have been carried out on an archetypal gold(I)-catalyzed reaction: hydroamination of ethyne. We studied up to 12 structures of possible gold(I)-coordinated species modeling different intermediates potentially present in a catalytic cycle for the addition of a protic nucleophile to an alkyne. The benchmark is used to evaluate the performances of some popular density functionals for describing geometries and relative energies of stationary points along the reaction profile. Most functionals (including hybrid or meta-hybrid) give accurate structures but large nonsystematic errors (4-12 kcal/mol) along the reaction energy profile. The double hybrid functional B2PLYP outperforms all considered functionals and compares very nicely with our reference ab initio benchmark energies. Moreover, we present an assessment of the accuracy of commonly used approaches to include relativistic effects, such as relativistic effective potentials and a scalar ZORA Hamiltonian, by a comparison with the results obtained using a relativistic all-electron four-component Dirac-Kohn-Sham method. The contribution of nonscalar relativistic effects in gold(I)-catalyzed reactions, as we investigated here, is expected to be on the order of 1 kcal/mol.

Design of test track for accurate calibration of two wheel differential mobile robots

Odometry using incremental wheel encoder sensors provides the relative position of a mobile robot. The major drawback of odometry is the accumulation of kinematic modeling errors when travel distance increases. The major systematic error sources are unequal wheel diameters and erroneous wheelbase. The UMBmark test is a practical and useful calibration scheme for systematic odometry errors of two wheel differential mobile robots. We previously proposed an accurate calibration scheme that extends the conventional UMBmark. A calibration experiment was carried out using the robot’s heading errors, and kinematic parameters were derived by considering the coupled effect of the systematic errors on a test track. In this paper, we propose design guidelines of test tracks for odometry calibration. As non-systematic errors constitute a grave problem in practical applications, the test track shape and size should be determined by considering the distributions of systematic and non-systematic errors. Numerical simulations and experiments clearly demonstrate that the proposed scheme results in more accurate calibration results.

Stratospheric lifetimes of CFC-12, CCl&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, CH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;Cl and N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O from measurements made by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS)

Abstract. Long lived halogen-containing compounds are important atmospheric constituents since they can act both as a source of chlorine radicals, which go on to catalyse ozone loss, and as powerful greenhouse gases. The long-term impact of these species on the ozone layer is dependent on their stratospheric lifetimes. Using observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) we present calculations of the stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O. The lifetimes were calculated using the slope of the tracer–tracer correlation of these species with CFC-11 at the tropopause. The correlation slopes were corrected for the changing atmospheric concentrations of each species based on age of air and CFC-11 measurements from samples taken aboard the Geophysica aircraft – along with the effective linear trend of the volume mixing ratio (VMR) from tropical ground based AGAGE (Advanced Global Atmospheric Gases Experiment) sites. Stratospheric lifetimes were calculated using a CFC-11 lifetime of 45 yr. These calculations produced values of 113 + (−) 26 (18) yr (CFC-12), 35 + (−) 11 (7) yr (CCl4), 69 + (−) 65 (23) yr (CH3Cl), 123 + (−) 53 (28) yr (N2O) and 195 + (−) 75 (42) yr (CH4). The errors on these values are the weighted 1σ non-systematic errors. Systematic errors were estimated by recalculating lifetimes using VMRs which had been modified to reflect differences between ACE-FTS retrieved VMRs and those from other instruments. The results of these calculations, including systematic errors, were as follows: 113 + (−) 32 (20) for CFC-12, 123 + (−) 83 (35) for N2O, 195 + (−) 139 (57) for CH4, 35 + (−) 14 (8) for CCl4 and 69 + (−) 2119 (34) yr for CH3Cl. For CH3Cl &amp;amp; CH4 this represents the first calculation of the stratospheric lifetime using data from a space based instrument.

Calibration of omnidirectional wheeled mobile robots: method and experiments

SUMMARYOdometry errors, which occur during wheeled mobile robot movement, are inevitable as they originate from hard-to-avoid imperfections such as unequal wheels diameters, joints misalignment, backlash, slippage in encoder pulses, and much more. This paper extends the method, developed previously by the authors for calibration of differential mobile robots, to reduce positioning errors for the class of mobile robots having omnidirectional wheels. The method is built upon the easy to construct kinematic formulation of omnidirectional wheels, and is capable of compensating both systematic and non-systematic errors. The effectiveness of the method is experimentally investigated on a prototype three-wheeled omnidirectional mobile robot. The validations include tracking unseen trajectories, self-rotation, as well as travelling over surface irregularities. Results show that the method is very effective in improving position errors by at least 68%. Since the method is simple to implement and has no assumption on the sources of errors, it should be considered seriously as a tool for calibrating omnidirectional mobile having any number of wheels.

Benchmark Studies on the Building Blocks of DNA. 3. Watson–Crick and Stacked Base Pairs

Excited states of stacked adenine-thymine and guanine-cytosine pairs as well as the Watson-Crick pair of guanine-thymine have been investigated using the equation of motion coupled-cluster (EOM-CC) method with single and double as well as approximate triple excitations. Transitions have been assigned, and the form of the excitations has been analyzed. The majority of the excitations could be classified as localized on the nucleobases, but for all three studied systems, charge-transfer (CT) transitions could also be identified. The main aim of this study was to compare the performance of lower-level methods (ADC(2) and TDDFT) to the high-level EOM-CC ones. It was shown that both ADC(2) and TDDFT with long-range correction have nonsystematic error in excitation energies, causing alternation of the energetic ordering of the excitations. Considering the high costs of the EOM-CC calculations, there is a need for reliable new approximate methods.

A Methodology for Systematic Geometric Error Compensation in Integrated Inspection and Machining

Evaluation of form errors of machined parts is fundamental in quality inspection to verify their conformance to the expected tolerances. Performance of methods have been reviewed in [1].A methodology for maximizing the adherence to the specified tolerances using an integrated machining and inspection system is presented. Considering thedesired tolerance envelope of the part, an error decomposition technique is developed to model machining errors caused by the systematic and non-systematic errors in the machine tool. The model is used to adaptively plan the final machining cuts, based on inspection feedback, to enhance the geometric accuracy of the final product and is illustrated by an example.