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Reference intervals (RI) play a decisive role in the interpretation of medical laboratory results. An important step in the determination of RI is age- and sex specific partitioning, which is usually based on an empirical approach by graphical representation. In this study, we evaluate an automated machine learning approach.

This paper examines the transition of lithium-ion batteries from electric vehicles (EVs) to energy storage systems (ESSs), with a focus on diagnosing their state of health (SOH) to ensure efficient and safe repurposing. It compares direct methods, model-based diagnostics, and data-driven techniques, evaluating their strengths and limitations for both EV and ESS applications. This study underscores the necessity of accurate SOH diagnostics to maximize battery reuse, promoting sustainability and circular economy objectives. By providing a comprehensive overview of the battery lifecycle—from manufacturing to recycling—this research offers strategies for effective lifecycle management and cost-effective, environmentally sustainable secondary battery applications. Key findings highlight the potential of second-life EV batteries in ESSs. The integration of the considered diagnostic methods was shown to extend battery lifespan by up to 30%, reduce waste, and optimize resource efficiency, which is crucial for achieving circular economy objectives. This paper's insights are crucial for advancing sustainable energy systems and informing future research on improving diagnostic methods for evolving battery technologies. [ABSTRACT FROM AUTHOR]

Human propulsive forces are a key-factor to enhance swimming performance, but there is scarce knowledge when using direct assessments. The aim of this review was to analyse the evidence about human propulsive forces in competitive swimming measured by direct assessment methods. A search up to 30 June 2020 was performed in Web of Science, PubMed, and Scopus databases. The Downs and Black Quality Assessment Checklist was used to assess the quality index (QI) of the included studies. Out of 2530 screened records, 35 articles met the inclusion criteria. Tethered-swimming and differential pressure sensors allow directly measure propulsive forces. Cross-sectional designs measured peak and mean propulsive force during the front crawl stroke and including men/boys (≥15 years-old) at different competitive levels were mostly reported. Men are more able to show higher propulsive forces than women counterparts. Short- and long-term effects were observed while using dry-land and in-water training programmes. The magnitude of propulsive force is dependent on the type of assessment method, swimming stroke, number of body limbs and gender. While the short-term effects supporting the different training programmes lead to an increase in propulsive force, there is a lack of long-term evidence. [ABSTRACT FROM AUTHOR]

In diffusion kurtosis imaging, it is necessary to know all D-eigenpairs of tensors in order to calculate the mean kurtosis value and the fractional kurtosis anisotropy. It is well known that the D-eigenpairs of tensors are the special cases of the B-eigenpairs of tensors. In order to find all B-eigenpairs (also, D-eigenpairs) of tensors with dimension 2 or 3, we in this paper propose direct methods for calculating them and show that these direct methods are workable by a numerical example. [ABSTRACT FROM AUTHOR]

Direct methods have practically solved the phase problem for small–medium‐size molecules but have substantially failed in macromolecular crystallography. They have two main limitations: a strong dependence on structural complexity and the need to work with atomic‐resolution data. Many attempts have been made to broaden their field of applicability, for example the use of some a priori information to make the estimate of the triplet invariant phases more effective. Unfortunately none of these new approaches allowed the successful application of direct methods to proteins and nucleic acids. Direct methods are still a niche tool in macromolecular crystallography. In a recent publication [Giacovazzo (2019). Acta Cryst. A75, 142–157] the method of joint probability distributions has been modified to take into account new sources of prior information, one of which is relevant to this article: the Patterson map. In practice, it has been shown that with prior knowledge of the interatomic vectors one is able to modify the classic Cochran reliability parameter for estimating the triplet invariant phases. The article was essentially theoretical in nature, and no attempt was described to test the practical usefulness of the new probabilistic formulas. This work is therefore the first application of the new method. It is shown that the use of the Patterson map as prior information substantially improves the Cochran estimate of triplet phases; the phase error distribution for the new estimates, even if it is related to macromolecular structures, becomes similar to that obtained for medium‐size structures. In some ways, it is as if the use of the Patterson information reduces the structural complexity, thus allowing a more general use of direct methods in macromolecular crystallography. Atomic resolution no longer seems to be a necessary ingredient for the applicability of direct methods; tests show that the apparent reduction in structural complexity also occurs in macromolecular structures with experimental data having a resolution of 2.3 Å. A number of test structures have been used to show the potential of the new technique. [ABSTRACT FROM AUTHOR]

Peter Main is remembered. [ABSTRACT FROM AUTHOR]

This paper provides a concise overview of three commonly employed methods for the determination of crystal structures from powder diffraction data, each exemplified with a specific case study. The first method is the single-crystal-like direct methods, leveraging reciprocal space information to construct the structure model. The second approach involves simulated annealing, which performs a global optimization of randomly generated models in real space to identify the structure. The third is the charge flipping method in which modifications to structure factors in reciprocal space and charge densities in real space are made, leading to the determination of the structure model through Fourier cycling switching back and forth between the two spaces. The presented examples are Ba3BPO7, MgSO4.2H2O and MgSO4.2.5H2O, respectively. [ABSTRACT FROM AUTHOR]

The marvel of X-ray crystallography is the beauty and precision of the atomic structures deduced from diffraction patterns. Since these patterns record only amplitudes, phases for the diffracted waves must also be evaluated for systematic structure determination. Thus, we have the phase problem as a central complication, both intellectually for the field and practically so for many analyses. Here, I discuss how we – myself, my laboratory and the diffraction community – have faced the phase problem, considering the evolution of methods for phase evaluation as structural biology developed to the present day. During the explosive growth of macromolecular crystallography, practice in diffraction analysis evolved from a universal reliance on isomorphous replacement to the eventual domination of anomalous diffraction for de novo structure determination. As the Protein Data Bank (PDB) grew and familial relationships among proteins became clear, molecular replacement overtook all other phasing methods; however, experimental phasing remained essential for molecules without obvious precedents, with multi- and single-wavelength anomalous diffraction (MAD and SAD) predominating. While the mathematics-based direct methods had proved to be inadequate for typical macromolecules, they returned to crack substantial selenium substructures in SAD analyses of selenomethionyl proteins. Native SAD, exploiting the intrinsic S and P atoms of biomolecules, has become routine. Selenomethionyl SAD and MAD were the mainstays of structural genomics efforts to populate the PDB with novel proteins. A recent dividend has been paid in the success of PDB-trained artificial intelligence approaches for protein structure prediction. Currently, molecular replacement with AlphaFold models often obviates the need for experimental phase evaluation. For multiple reasons, we are now unfazed by the phase problem. Cryo-EM analysis is an attractive alternative to crystallography for many applications faced by today's structural biologists. It simply finesses the phase problem; however, the principles and procedures of diffraction analysis remain pertinent and are adopted in single-particle cryo-EM studies of biomolecules.

This paper describes an approach to determine a fast-charging profile for a lithium-ion battery by utilising a simplified single-particle electrochemical model and direct collocation methods for optimal control. An optimal control problem formulation and a direct solution approach were adopted to address the problem effectively. The results shows that, in some cases, the optimal current profile resembles the current profile in the Constant Current–Constant Voltage charging protocol. Several challenges and knowledge gaps were addressed in this work, including a reformulation of the optimal control problem that utilises direct methods as an alternative to overcome the limitations of indirect methods employed in similar studies. The proposed formulation considers the minimum-time optimal control case, trade-offs between the total charging time, the maximisation of the lithium bulk concentration, and energy efficiency, along with inequality constraints and other factors not previously considered in the literature, which can be helpful in practical applications. [ABSTRACT FROM AUTHOR]

The strong ellipticity condition (abbr. SE-condition) of the displacement equations of equilibrium for general nonlinearly elastic materials plays an important role in nonlinear elasticity and materials. Existing literature shows that it can be equivalently transformed into the SE-condition of an elasticity tensor, and that the SE-condition of an elasticity tensor holds if and only if all of its M-eigenvalues are positive. In order to judge the strong ellipticity of an elasticity tensor, we in this paper propose a direct method for calculating all M-eigenvalues of an elasticity tensor and show that the direct method is workable by a numerical example. [ABSTRACT FROM AUTHOR]

The production of portland cement is among the major contributors to greenhouse gas emissions that adversely affect the environment. Identifying sustainable materials to partially replace portland cement in concrete, such as pozzolanic materials, is crucial in addressing this issue. These materials mainly consist of silica and alumina that react with the available calcium hydroxide to form strength-bearing phases such as calcium silicate hydrates. Understanding the degree of pozzolanic reactivity of materials using efficient reactivity test methods is an important consideration. The paper thoroughly reviews the available literature related to direct and indirect pozzolanic reactivity test methods that have been utilized over the years. Direct methods quantify the amount of consumed calcium hydroxide, whereas indirect methods assess changes in the physical properties of the specimen due to pozzolanic reactions. The aim of this paper is to identify affordable, time-saving, and effective direct and indirect methods. Based on this study, the Frattini, electrical conductivity, and pH tests are considered the most time-efficient methods to assess pozzolanic materials. Electrical conductivity and pH tests are also easy to perform. In contrast, other methods are more time-consuming. [ABSTRACT FROM AUTHOR]

Abstract Background Pakistan has an inadequate vital event registration system, leading to fewer than half of all births being registered, and this issue is further exacerbated by systematic recall errors and omission of births. This study aims to evaluate direct and indirect methods of fertility estimation to analyze the trends and patterns of fertility rates in Pakistan from 1990 to 2018. Design/methodology/approach Indirect methods are utilized in this study to evaluate the direction and extent of changes in total and age-specific fertility rates, and these findings are compared to direct estimates. The study draws data on livebirths from four waves of the Pakistan Demographic and Health Survey that took place between 1990 and 2018. To ensure the quality of data, graphical methods and Whipple and Myers indices are employed. Additionally, the Brass Relational Gompertz model was used to analyze the data. Results The Relational Gompertz model revealed that total fertility rates (TFRs) were higher than direct estimates by 0.4 children and age-specific fertility rates (ASFR) were higher for all age groups except the oldest. The difference was more significant among younger women aged 15–24, and less so for age groups 29 and above. The gap in estimated fertility between direct and indirect methods decreased with age. Conclusion The indirect method is an invaluable tool in situations where direct measurement of fertility rates is challenging or impossible. By utilizing this method, policymakers can gain important insights into the fertility patterns and trends of a population, which is crucial for making informed decisions on fertility planning.

We consider the coefficient inverse problem for the 2D acoustic equation. The problem is recovering the speed of sound in the medium (which depends only on the depth) and the density (function of both variables). We describe the method, based on the Gelfand–Levitan–Krein approach, which allows us to obtain both functions by solving two sets of integral equations. The main advantage of the proposed approach is that the method does not use the multiple solution of direct problems, and thus has quite low CPU time requirements. We also consider the variation of the method for the 1D case, where the variation of the wave equation is considered. We illustrate the results with numerical experiments in the 1D and 2D case and study the efficiency and stability of the approach. [ABSTRACT FROM AUTHOR]

Background: Pakistan has an inadequate vital event registration system, leading to fewer than half of all births being registered, and this issue is further exacerbated by systematic recall errors and omission of births. This study aims to evaluate direct and indirect methods of fertility estimation to analyze the trends and patterns of fertility rates in Pakistan from 1990 to 2018. Design/methodology/approach: Indirect methods are utilized in this study to evaluate the direction and extent of changes in total and age-specific fertility rates, and these findings are compared to direct estimates. The study draws data on livebirths from four waves of the Pakistan Demographic and Health Survey that took place between 1990 and 2018. To ensure the quality of data, graphical methods and Whipple and Myers indices are employed. Additionally, the Brass Relational Gompertz model was used to analyze the data. Results: The Relational Gompertz model revealed that total fertility rates (TFRs) were higher than direct estimates by 0.4 children and age-specific fertility rates (ASFR) were higher for all age groups except the oldest. The difference was more significant among younger women aged 15–24, and less so for age groups 29 and above. The gap in estimated fertility between direct and indirect methods decreased with age. Conclusion: The indirect method is an invaluable tool in situations where direct measurement of fertility rates is challenging or impossible. By utilizing this method, policymakers can gain important insights into the fertility patterns and trends of a population, which is crucial for making informed decisions on fertility planning. [ABSTRACT FROM AUTHOR]

To determine a substructure from single‐wavelength anomalous diffraction (SAD) data using Patterson or direct methods, the substructure‐factor amplitude (|Fa|) is first estimated. Currently, the absolute value of the Bijvoet difference is widely used as an estimate of |Fa| values for SAD data. Here, an equation is derived from multivariate statistics and tested that takes into account the correlation between the observed positive (F+) and negative (F−) Friedel pairs and Fa along with measurement errors in the observed data. The multivariate estimation of |Fa| has been implemented in a new program, Afro. Results on over 180 test cases show that Afro provides a higher correlation to the final substructure‐factor amplitudes (calculated from the refined, final substructures) than the Bijvoet differences and improves the robustness of direct‐methods substructure detection. [ABSTRACT FROM AUTHOR]

General sparse hybrid solvers are commonly used kernels for solving wide range of scientific and engineering problems. This work addresses the current problems of efficiently solving general sparse linear equations with direct/iterative hybrid solvers on many core distributed clusters. We briefly discuss the solution stages of Maphys, HIPS, and PDSLin hybrid solvers for large sparse linear systems with their major algorithmic differences. In this category of solvers, different methods with sophisticated preconditioning algorithms are suggested to solve the trade off between memory and convergence. Such solutions require a certain hierarchical level of parallelism more suitable for modern supercomputers that allow to scale for thousand numbers of processors using Schur complement framework. We study the effect of reordering and analyze the performance, scalability as well as memory for each solve phase of PDSLin, Maphys, and HIPS hybrid solvers using large set of challenging matrices arising from different actual applications and compare the results with SuperLU_DIST direct solver. We specifically focus on the level of parallel mechanisms used by the hybrid solvers and the effect on scalability. Tuning and Analysis Utilities (TAU) is employed to assess the efficient usage of heap memory profile and measuring communication volume. The tests are run on high performance large memory clusters using up to 512 processors. [ABSTRACT FROM AUTHOR]

Oxidative stability and antioxidant properties significantly impact the quality, shelf-life, and nutritional value of food. However, current methods for studying lipid oxidation and antioxidants face limitations including a lack of real-time monitoring, difficulties in complex food matrix assessment, limited sensitivity, and mechanistic insights. Invasive sample preparation and reliance on model systems further compound these challenges. Overcoming these limitations is essential for advancing food preservation and product development strategies. This review discusses the use of isothermal calorimetry (IC) in food science, particularly for studying lipid oxidation and antioxidant properties. It explains how IC heat flow data can provide valuable kinetic information, revealing the mechanisms of antioxidant action. Moreover, the review evaluates the advantages and limitations of IC in food science, providing insights into its potential for future research and applications. IC enables real-time monitoring of lipid oxidation and antioxidant activity, offering valuable insights into their behavior in the presence of food-based oxidizable substrates. By measuring heat flow over time and applying appropriate data analysis, IC can generate key kinetic parameters that describe the rates of oxidation and the rate constants of both oxidation and inhibition reactions. Additionally, kinetic modeling allows for the assessment of antioxidant efficiency (A.E.) and oxidizability index (O.I.), which are especially useful for complex food matrices such as emulsions, encapsulated powders, and natural extracts. While IC provides direct measurement, high sensitivity, and long-term thermal stability, challenges include the non-specificity of heat flow and the requirement for specialized expertise to set up and interpret experiments accurately. [Display omitted] • Isothermal calorimetry proves to be a reliable technique to study lipid oxidation. • Isothermal calorimetry data provides valuable kinetic information revealing the mechanisms of oxidation reactions. • Kinetic modeling of isothermal calorimetry data allows for the assessment of antioxidant efficiency and oxidizability index. [ABSTRACT FROM AUTHOR]

This paper describes an approach to determine a fast-charging profile for a lithium-ion battery by utilising a simplified single-particle electrochemical model and direct collocation methods for optimal control. An optimal control problem formulation and a direct solution approach were adopted to address the problem effectively. The results shows that, in some cases, the optimal current profile resembles the current profile in the Constant Current–Constant Voltage charging protocol. Several challenges and knowledge gaps were addressed in this work, including a reformulation of the optimal control problem that utilises direct methods as an alternative to overcome the limitations of indirect methods employed in similar studies. The proposed formulation considers the minimum-time optimal control case, trade-offs between the total charging time, the maximisation of the lithium bulk concentration, and energy efficiency, along with inequality constraints and other factors not previously considered in the literature, which can be helpful in practical applications.

The production of portland cement is among the major contributors to greenhouse gas emissions that adversely affect the environment. Identifying sustainable materials to partially replace portland cement in concrete, such as pozzolanic materials, is crucial in addressing this issue. These materials mainly consist of silica and alumina that react with the available calcium hydroxide to form strength-bearing phases such as calcium silicate hydrates. Understanding the degree of pozzolanic reactivity of materials using efficient reactivity test methods is an important consideration. The paper thoroughly reviews the available literature related to direct and indirect pozzolanic reactivity test methods that have been utilized over the years. Direct methods quantify the amount of consumed calcium hydroxide, whereas indirect methods assess changes in the physical properties of the specimen due to pozzolanic reactions. The aim of this paper is to identify affordable, time-saving, and effective direct and indirect methods. Based on this study, the Frattini, electrical conductivity, and pH tests are considered the most time-efficient methods to assess pozzolanic materials. Electrical conductivity and pH tests are also easy to perform. In contrast, other methods are more time-consuming.

The direct transcription method that employs global collocation at Legendre-Gauss-Radau points is addressed and applied to infinite-dimensional dynamic optimization problems in engineering. The formulation of these latter is considered referring to a Bolza-type performance index. A reduced unconstrained form of it is particularly studied in the pseudospectral domain and the continuous-to-discrete conversion is thoroughly discussed. An equivalent finite-dimension nonlinear programming problem is therefore obtained and hints on its numerical implementation are given. Eventually, a few benchmark historical problems in engineering are revisited, stated, numerically solved and compared to literature.

An experimental study of the efficiency of 3D boundary value problem solvers on regular subgrids of quasi-structured parallelepipedal grids is carried out. Five solvers are considered. Three of them are iterative ones: successive over-relaxation, alternating direction implicit, and explicit incomplete factorization with acceleration by conjugate gradients, and two are direct ones: PARDISO and HEMHOLTZ—both from the Intel MKL library. Characteristic features of this study are: 1) each of the subgrids has a small number of nodes; 2) the efficiency is estimated not only for single calculations, but mainly for a series of calculations in each of which a large number of solution cycles is carried out for the problem with different boundary conditions on the same subgrid. The numerical experiments show that the fastest solver under the above conditions is the method of successive over-relaxation. [ABSTRACT FROM AUTHOR]

Abstract Mechanical engineering structures and structural components are often subjected to cyclic thermomechanical loading which stresses their material beyond its elastic limits well inside the inelastic regime. Depending on the level of loading inelastic strains may lead either to failure, due to low cycle fatigue or ratcheting, or to safety, through elastic shakedown. Thus, it is important to estimate the asymptotic stress state of such structures. This state may be determined by cumbersome incremental time-stepping calculations. Direct methods, alternatively, have big computational advantages as they focus on the characteristics of these states and try to establish them, in a direct way, right from the beginning of the calculations. Among the very few such general-purpose direct methods, a powerful direct method which has been called RSDM has appeared in the literature. The method may directly predict any asymptotic state when the exact time history of the loading is known. The advantage of the method is due to the fact that it addresses the physics of the asymptotic cycle and exploits the cyclic nature of its expected residual stress distribution. Based on RSDM a method for the shakedown analysis of structures, called RSDM-S has also been developed. Despite most direct methods for shakedown, RSDM-S does not need an optimization algorithm for its implementation. Both RSDM and RSDM-S may be implemented in any Finite Element Code. A thorough review of both these methods, together with examples of implementation are presented herein.

Let A be an order m dimension n real tensor. Two direct methods are proposed to find all Z-eigenpairs of A with n = 2 or 3. For the convenience of application, the specific form of this direct method is given for m = 3 , 4 or 6, respectively. Finally, two numerical examples are reported to show that these direct methods are workable for a general tensor. [ABSTRACT FROM AUTHOR]

Traditional monocular direct visual odometry (DVO) is one of the most famous methods to estimate the ego-motion of robots and map environments from images simultaneously. However, DVO heavily relies on high-quality images and accurate initial pose estimation during tracking. With the outstanding performance of deep learning, previous works have shown that deep neural networks can effectively learn 6-DoF (Degree of Freedom) poses between frames from monocular image sequences in the unsupervised manner. However, these unsupervised deep learning-based frameworks cannot accurately generate the full trajectory of a long monocular video because of the scale-inconsistency between each pose. To address this problem, we use several geometric constraints to improve the scale-consistency of the pose network, including improving the previous loss function and proposing a novel scale-to-trajectory constraint for unsupervised training. We call the pose network trained by the proposed novel constraint as TrajNet. In addition, a new DVO architecture, called deep direct sparse odometry (DDSO), is proposed to overcome the drawbacks of the previous direct sparse odometry (DSO) framework by embedding TrajNet. Extensive experiments on the KITTI dataset show that the proposed constraints can effectively improve the scale-consistency of TrajNet when compared with previous unsupervised monocular methods, and integration with TrajNet makes the initialization and tracking of DSO more robust and accurate. [ABSTRACT FROM AUTHOR]

Synthesis, X-ray structure, molecular docking, lattice energy and Hirshfeld surface analysis of (E)-2-methoxy-5-(((6-methoxypyridin-3yl)imino)methyl)phenol (MMPIMP) is presented in this paper. The compound crystallizes in the monoclinic space group P21/c with unit cell parameters: a = 5.6149 (2), b = 14.5520 (5), c = 29.9813 (8) Å, β = 94.795 (3) and Z = 8. The asymmetric unit contains two crystallographically independent molecules (A and B) and the structure was solved by direct methods using single-crystal X-ray diffraction data and refined by full-matrix least-squares procedure to a final value of R = 0.050 and wR2 = 0.1231 for 3536 observed reflections. The molecular packing in the unit cell is stabilized via O – H... N and C – H... O intermolecular hydrogen bonds. In the crystal packing, pairs of intermolecular hydrogen bonds of the type O–H...N links the molecules into dimers, forming R 2 2 (20) ring motif. To understand the nature and strength of intermolecular interaction in terms of its energy and their quantitative contributions toward the molecular packing, lattice energy analysis was carried out by using PIXEL software. Molecular docking studies were executed to realize the inhibitory activity of the compound MMPIMP against DprE1 (PDB code: 4KW5). The analysis of the Hirshfeld surface and its associated two dimension fingerprint plots has been carried out to examine the intermolecular contacts in the crystal structure. [ABSTRACT FROM AUTHOR]

The direct transcription method that employs global collocation at Legendre-Gauss-Radau points is addressed and applied to infinite-dimensional dynamic optimization problems in engineering. The formulation of these latter is considered referring to a Bolza-type performance index. A reduced unconstrained form of it is particularly studied in the pseudospectral domain and the continuous-to-discrete conversion is thoroughly discussed. An equivalent finite-dimension nonlinear programming problem is therefore obtained and hints on its numerical implementation are given. Eventually, a few benchmark historical problems in engineering are revisited, stated, numerically solved and compared to literature. [ABSTRACT FROM AUTHOR]

The present paper addresses the robustness and convergence behavior of the direct limit analysis (LA) based methodology developed for the topology design of continuum structures subject to prescribed statically and plastically admissible loads. The design methodology, based on a direct method formulation of the static LA problem, has recently been proposed for continuous topology optimization and its merits were highlighted. One of its remarkable features is the outstanding similarity of the topology design mathematical problem with its underlying direct static form of the LA problem. Subsequently, it has been extended to solve two dimensional discrete, i.e. black-and-white, topology design problems by modifying the objective function into a square root form in a way to penalize the intermediate densities and solving a sequence of conic quadratic programming problems of identical scale and algebraic structure as the continuous design problem, leaving a number of issues to be investigated, pertaining to convergence. In the present work different families of penalization function forms are proposed and assessed as alternatives to the original square root function. The performance is evaluated in terms of robustness, accuracy in the sense of closeness of the final design to a 0–1 topology and efficiency or number of approximate problems required for convergence. Convergence of the discrete topology design is shown to be improved using higher order power functions as well as trigonometric and exponential type penalty functions. The performance of the design method in solving example problems using the various penalization schemes is compared and the factors that affect it are analyzed. [ABSTRACT FROM AUTHOR]

Mechanical engineering structures and structural components are often subjected to cyclic thermomechanical loading which stresses their material beyond its elastic limits well inside the inelastic regime. Depending on the level of loading inelastic strains may lead either to failure, due to low cycle fatigue or ratcheting, or to safety, through elastic shakedown. Thus, it is important to estimate the asymptotic stress state of such structures. This state may be determined by cumbersome incremental time-stepping calculations. Direct methods, alternatively, have big computational advantages as they focus on the characteristics of these states and try to establish them, in a direct way, right from the beginning of the calculations. Among the very few such general-purpose direct methods, a powerful direct method which has been called RSDM has appeared in the literature. The method may directly predict any asymptotic state when the exact time history of the loading is known. The advantage of the method is due to the fact that it addresses the physics of the asymptotic cycle and exploits the cyclic nature of its expected residual stress distribution. Based on RSDM a method for the shakedown analysis of structures, called RSDM-S has also been developed. Despite most direct methods for shakedown, RSDM-S does not need an optimization algorithm for its implementation. Both RSDM and RSDM-S may be implemented in any Finite Element Code. A thorough review of both these methods, together with examples of implementation are presented herein. [ABSTRACT FROM AUTHOR]

In the field of nuclear engineering, Printed Circuit Heat Exchangers (PCHEs) have become increasingly popular and the structural integrity assessment of these key power plant components is crucial. As part of the structural integrity assessment, creep rupture analysis considers the interaction of cyclic plasticity and creep behaviour, which is vital for components subjected to cyclic thermal-mechanical loads. The Linear Matching Method (LMM) framework has included a creep rupture module based on an extended shakedown algorithm, which has been adopted by several researchers. However, the current LMM framework mainly relies on linear extrapolation and requires users to provide a large amount of data points to estimate the rupture stress. This paper introduces a Unified Creep Rupture Equation (UCRE) for characterizing the creep rupture curves of diverse steel types. The UCRE is implemented in an extended shakedown algorithm and integrated into the LMM framework. The numerical method is validated through a comparative analysis, wherein the estimated rupture curves are compared with those provided in the ECCC data sheet, as well as against alternative numerical models. Shakedown and creep rupture analyses are then performed on a PCHE core. The proposed method facilitates the parametric study of changing materials and the process of material selection. Various geometric configurations are also considered and the proposed unitary cell model is verified by comparing the results with ones from full FE models. The UCRE has been proved to be an accurate engineering tool for the prediction of rupture strengths while the LMM framework has gained improved usability and versatility for engineering applications. • A numerical procedure to predict rupture strengths for a wide range of steel. • Proposed method is verified by comparing with alternative numerical models. • Direct method-based creep rupture analysis using the Linear Matching Method framework. • Parametric study on a Printed Circuit Heat Exchanger core based on a unitary cell model. [ABSTRACT FROM AUTHOR]

Over the decades, the constant life diagram has become an important tool for engineering design and assessment. For specific materials, the effect of mean stress and stress amplitude on the fatigue life is considered in traditional constant life diagrams. In this study, the concept of the structural constant creep-fatigue life diagram is proposed for engineering structures subjected to cyclic loads in high-temperature environments. By integrating constant fatigue and creep-fatigue life curves into the traditional Bree diagram, we offer an efficient and reliable approach that enables quick determination of structural life and corresponding failure mechanisms. To provide a one-stop solution for the evaluation of constant fatigue/creep-fatigue life curves, an extended Unified Procedure for Fatigue and Ratchet Analysis (eUPFRA) has been proposed based on the Linear Matching Method (LMM) framework. Case studies on engineering components have also been performed with consideration of the cyclic hardening effect, temperature-dependent material properties and various damage models. The impact of the target life and creep dwell time is further investigated, as well as the creep-fatigue interaction mechanism. Verification against ABAQUS step-by-step inelastic analysis has finally been conducted, confirming the precision and efficiency of the eUPFRA. • The structural constant creep-fatigue life diagram is proposed based on direct methods. • The cyclic hardening effect is considered in the constant low-cycle-fatigue life diagram. • Several failure mechanisms and creep-fatigue interaction mechanisms are discussed. • The proposed two-stage procedure is verified with the ABAQUS step-by-step analysis. [ABSTRACT FROM AUTHOR]

The incorporation of the new peakness‐enhancing fast Fourier transform compatible ipp procedure (ipp = inner‐pixel preservation) into the recently published SM algorithm based on |ρ| [Rius (2020). Acta Cryst A76, 489–493] improves its phasing efficiency for larger crystal structures with atomic resolution data. Its effectiveness is clearly demonstrated via a collection of test crystal structures (taken from the Protein Data Bank) either starting from random phase values or by using the randomly shifted modulus function (a Patterson‐type synthesis) as initial ρ estimate. It has been found that in the presence of medium scatterers (e.g. S or Cl atoms) crystal structures with 1500 × c atoms in the unit cell (c = number of centerings) can be routinely solved. In the presence of strong scatterers like Fe, Cu or Zn atoms this number increases to around 5000 × c atoms. The implementation of this strengthened SM algorithm is simple, since it only includes a few easy‐to‐adjust parameters. [ABSTRACT FROM AUTHOR]

An experimental study of the efficiency of solvers of 2D boundary value problems on subgrids of quasi-structured rectangular grids is carried out. A solver means a solution method and its software implementation. The following three solvers are considered: a direct solver (Buneman's cyclic reduction method) and two iterative ones (the alternative direction method of Peaceman and Rachford and the successive overrelaxation method). Characteristic features of the study are as follows: 1) the subgrids have a small number of nodes, namely 8 × 8, 16 × 16, 32 × 32, and 64 × 64; 2) the efficiency is estimated not only for single calculations, but also for series of calculations; in each of them the problem is repeatedly solved with different boundary conditions on the same subgrid. Based on a series of calculations, a combined method is proposed, and recommendations on using the solvers are given. [ABSTRACT FROM AUTHOR]

Obituary for Professor Dr Hendrik (Henk) Schenk. [ABSTRACT FROM AUTHOR]

Direct methods of measuring the gas content of coal beds, including calculation of the lost gas, are reviewed. In determining the gas content of the coal in productive beds within the Kuznetsk Basin, the distinctive properties of the coal must be taken into account: specifically, its high natural gas content; and hazardous dynamic gas releases in mine workings. That is especially common for valuable coking coal. [ABSTRACT FROM AUTHOR]

In this paper, the optimal control of a continuous type bioreactor with multi-input-multi-output signals is presented for the two active phases: growth and stationary. The underlying criterion to be minimized generalizes the classic quadratic forms to address some crucial objectives in controlling the bioreactor. In particular, the protection of actuators against fast switching in the controller output is considered by including a weighting term of the control signal derivatives. The direct optimal control approach is used to carry out the optimization in the presence of various limiting constraints. Direct methods are based on transcribing the infinite-dimensional problem to a finite-dimensional one. In this manuscript, direct single shooting and trapezoidal collocation methods are used for transcription, and the successive quadratic programming method is employed to solve the resulting nonlinear programming problem. It is shown that the trapezoidal method is an effective method for controlling the bioreactor in all the active phases, whereas the single shooting fails in dealing with the unstable one (i.e., growth). To analyze solutions in a more accurate manner, an auxiliary criterion is defined, and then the cheap control analysis is studied. The convergence to the lowest value of the auxiliary cost function and the effects on the optimal state and control trajectories are then examined by varying cheap parameters. Several numerical simulations support the presented theoretical formulation. [ABSTRACT FROM AUTHOR]

In this work, we have studied the asymptotic behavior of Green's function and the reciprocity relation of the far-field pattern in the stratified ocean waveguide. Moreover, two direct sampling methods (DSM) are proposed to determine the marine sources and scatterers from the far-field data. The direct approaches are fast, easy to implement, and computationally efficient since they involve only scalar product but no matrix inversion. In the numerical simulations, the DSM for the source is capable of identifying the sources from very few observation data, and the DSM for the scatterer can reconstruct the scatterers in different shapes, scales, types, and positions. The effectiveness and robustness of the novel methods are also demonstrated. Thus, the DSM can be viewed as simple and efficient numerical techniques for providing reliable initial approximate locations of the marine sources and scatterers for any existing more refined and advanced but computationally more demanding algorithms to recover the accurate physical profiles. [ABSTRACT FROM AUTHOR]

We propose a parallel sparse triangular linear system solver based on the Spike algorithm. Sparse triangular systems are required to be solved in many applications. Often, they are a bottleneck due to their inherently sequential nature. Furthermore, typically many successive systems with the same coefficient matrix and with different right hand side vectors are required to be solved. The proposed solver decouples the problem at the cost of extra arithmetic operations as in the banded case. Compared to the banded case, there are extra savings due to the sparsity of the triangular coefficient matrix. We show the parallel performance of the proposed solver against the state-of-the-art parallel sparse triangular solver in Intel's Math Kernel Library (MKL) on a multicore architecture. We also show the effect of various sparse matrix reordering schemes. Numerical results show that the proposed solver outperforms MKL's solver in ∼ 80 % of cases by a factor of 2.47, on average. [ABSTRACT FROM AUTHOR]