Field Of Nuclear Science Research Articles

FECSG-ML: Feature Engineering for Nuclear Reaction Cross Sections Generation Using Machine Learning

In the field of nuclear science, obtaining and utilizing nuclear data, including nuclear reaction data, nuclear structure information, and radioactive decay data, is crucial. Neutron-induced nuclear reactions, particularly nuclear cross sections data, are essential for various applications, including reactor design. The EXFOR database is the only international repository for storing nuclear reaction experimental measurement information and data. However, experimental measurement data are often scarce, subject to discrepancies, or even errors, requiring human evaluation. This process can be prone to biases and significant uncertainties. To address these challenges, this study proposes a novel framework, Feature Engineering for Nuclear Reaction Cross Section Generation using Machine Learning (FECSG-ML), which employs machine learning methods to generate nuclear cross sections data, serving as a substitute for evaluating nuclear databases. Given the limited size of the EXFOR database, training a model solely on EXFOR data could lead to underfitting. Therefore, the proposed approach utilizes transfer learning, initially pre-training the model using the ENDF/B-VIII.0 dataset and subsequently fine-tuning it with the EXFOR database. This approach ensures high accuracy where real data are available and enables the learning of characteristics of the evaluation dataset where real data are lacking. Moreover, machine learning techniques are employed to transform discrete nuclear cross sections data into a continuous format, accommodating various isotopes and predicting multiple sets of cross sections data. The framework integrates various machine learning methods and utilizes ensemble learning for result optimization. Experimental results demonstrate that the regression curves generated by the FECSG-ML model align well with EXFOR data points, outperforming the ENDF/B-VIII.0 evaluation database. Furthermore, the nuclear cross sections data generated by the FECSG-ML model are applied in the OpenMC Monte Carlo simulation program to simulate pin fuel assemblies and CANDU bundle reactors, confirming the effectiveness of the model. This study underscores the importance of accurate and reliable nuclear cross sections data and provides a method for substituting the evaluation of nuclear databases.

A Vision for the Science of Rare Isotopes

The field of nuclear science has considerably advanced since its beginning just over a century ago. Today, the science of rare isotopes is on the cusp of a new era with theoretical and computing advances complementing experimental capabilities at new facilities internationally. In this article we present a vision for the science of rare isotope beams (RIBs). We do not attempt to cover the full breadth of the field; rather, we provide a perspective and address a selection of topics that reflect our own interests and expertise. We focus in particular on systems near the drip lines, where one often finds nuclei that are referred to as exotic and where the role of the nuclear continuum is only just starting to be explored. An important aspect of this article is its attempt to highlight the crucial connections between nuclear structure and the nuclear reactions required to fully interpret and leverage the rich data to be collected in the next years at RIB facilities. Further, we connect the efforts in structure and reactions to key questions of nuclear astrophysics.

A multiclass classification model for predicting the thermal conductivity of uranium compounds

ABSTRACT Advanced nuclear fuels are designed to offer improved performance and accident tolerance, with an emphasis on achieving higher thermal conductivity. While promising fuel candidates like uranium nitrides, carbides, and silicides have been widely studied, the majority of uranium compounds remain unexplored. To search for potential candidates among these unexplored uranium compounds, we incorporated machine learning to accelerate the material discovery process. In this study, we trained a multiclass classification model to predict a compound’s thermal conductivity based on 133 input features derived from element properties and temperature. The initial training data consist of over 160,000 processed thermal conductivity records from the Starrydata2 database, but a skewed data class distribution led the trained model to underestimate compound’s thermal conductivity. Consequently, we addressed the issue of class imbalance by applying Synthetic Minority Oversampling TEchnique and Random UnderSampling, improving the recall for materials with thermal conductivity higher than 15 W/mK from 0.64 to 0.71. Finally, our best model is used to identify 119 potential advanced fuel candidates with high thermal conductivity among 774 stable uranium compounds. Our results underscore the potential of machine learning in the field of nuclear science, accelerating the discovery of advanced nuclear materials.

Application of machine learning methods for filling and updating nuclear knowledge bases

The paper deals with issues of designing and creating knowledge bases in the field of nuclear science and technology. The authors present the results of searching for and testing optimal classification and semantic annotation algorithms applied to the textual network content for the convenience of computer-aided filling and updating of scalable semantic repositories (knowledge bases) in the field of nuclear physics and nuclear power engineering and, in the future, for other subject areas, both in Russian and English. The proposed algorithms will provide a methodological and technological basis for creating problem-oriented knowledge bases as artificial intelligence systems, as well as prerequisites for the development of semantic technologies for acquiring new knowledge on the Internet without direct human participation. Testing of the studied machine learning algorithms is carried out by the cross-validation method using corpora of specialized texts. The novelty of the presented study lies in the application of the Pareto optimality principle for multi-criteria evaluation and ranking of the studied algorithms in the absence of a priori information about the comparative significance of the criteria. The project is implemented in accordance with the Semantic Web standards (RDF, OWL, SPARQL, etc.). There are no technological restrictions for integrating the created knowledge bases with third-party data repositories as well as metasearch, library, reference or information and question-answer systems. The proposed software solutions are based on cloud computing using DBaaS and PaaS service models to ensure the scalability of data warehouses and network services. The created software is in the public domain and can be freely replicated.

The cross-country evaluation of nuclear science and technology publications

PurposeThe purpose of this study is to measure the quality of nuclear science and technology research using the scientometric indicators, like activity index, attractivity index and publication efficiency index.Design/methodology/approachThe present scientometric study is based on the bibliographic data extracted from the core collection of the Web of Science database from 1989 to 2019. The data was collected using the advanced search feature, with a search string of 28 related terms. The bibliographic data for all the journal articles, excluding all other formats, was downloaded for statistical analysis.FindingsThe present study highlights the growth pattern and the research efforts devoted to the field of nuclear science and technology worldwide, as reflected through the Core Collection of the Web of Science database, for 31 years from 1989 to 2019. The USA has emerged as the topmost producer, with a total share of almost 29% with respect to the world literature followed by Japan, Germany, France and UK. However, the relative citation impact has been the highest for Netherlands followed by the USA, Germany, France and UK, respectively. The study depicted that the activity index, also called as the relative performance indicator, has been the highest for the USA, whereas the attractivity index has been the highest for China, indicating its dominance in attracting citations to its publications in the field of nuclear science and technology. The publication efficiency index, the value has been the maximum for Iran, for which the value has been greater than 1 (1.618). The measure suggests that Iran’s research effectiveness in the field of nuclear science and technology has been more than the research effort devoted to the field.Research limitations/implicationsThe paper was based on the data retrieved from a single database, and the results may vary across other databases. Hence, caution should be taken while generalizing the findings.Originality/valueSeveral scientometric studies have taken place in the field of nuclear science and technology, particularly in its allied branches, but none of the studies has focused on evaluating the research efforts carried out by the countries in terms of activity index, attractivity index and publication efficiency index, and the present study is an attempt to fill the gap.

Progress on nuclear analysis techniques

The nuclear analysis has been of important significance in the field of nuclear science and technology. The developing trends and some frontier topic of nuclear analysis techniques as well as their applications have been presented in this paper. Four categories of nuclear analysis techniques have been mainly reviewed, which include radiochemical analysis, Z-pinch driven dynamic hohlraum for inertial confinement fusion, nuclear reactor analysis method and neutron scattering techniques. The future directions for them have been also summarized and viewed.

Preparation of DMHMP Levextrel resin and separation of zirconium and hafnium by extraction chromatography in HNO3-HCl mixture

Separation of zirconium and hafnium with very similar chemical properties is very important and difficult in the field of nuclear science, technology and engineering. Herein, a novel extraction chromatographic method was developed to quantitative separation of zirconium and hafnium using di-(1-methylheptyl)methylphosphonate (DMHMP) Levextrel resin as the stationary phase and HNO3-HCl mixture as mobile phase. The DMHMP Levextrel resin was prepared by the suspension polymerization technique. The extraction behavior of zirconium and hafnium was systematically investigated by liquid-liquid extraction method from HCl, HNO3 and HNO3-HCl solutions, respectively. It has been found that a high separation factor (SF) of 47 for Zr/Hf can be obtained in 2 M HNO3-2 M HCl solution. Under the optimum conditions, extraction chromatography was performed to separate zirconium and hafnium in different weight ratios. The effects of amount of carriers and interference ions on the chromatographic separation were examined. The recovery and mutual decontamination factor (DF) of both elements were determined. It exhibits Zr and Hf can be completely separated from each other. And the high recovery of 98–102%, mutual decontamination factor (DF) of 104, and high selectivity for both elements against a large excess of interference ions were obtained. This work provides an effective extraction chromatographic procedure to concentration and separation of Zr and Hf.

Determination of Reactor Parameters for Different Subcritical Configurations of the Philippine Research Reactor-1 TRIGA Nuclear Fuel

The Philippine Research Reactor-1 (PRR-1) will be revived as a subcritical assembly for training, education, and research (SATER) in the field of nuclear science and technology. SATER will utilize the existing slightly irradiated nuclear fuel rods that have been maintained in the PRR-1 facility for more than 30 years. A subcritical arrangement for the fuel rods was chosen considering the inherent safety of this configuration. In this paper, we calculate relevant reactor parameters that characterize different annular and hexagonal subcritical configurations of 44 PRR-1 fuel rods. These parameters include the neutron multiplication factor ( ), the effective delayed neutron fraction ( ), and the mean neutron generation time ( ), which are essential quantities to describe reactor behavior. Calculations were performed using the well-validated Monte Carlo radiation transport code MCNP5 v.1.6 together with the ENDF/B- VII.1 evaluated nuclear data library. The maximum value is at 4.0 cm pitch for the chosen annular arrangement, while the maximum value is at 4.3 cm pitch for the chosen hexagonal arrangement. For these configurations, the reactor kinetic parameters were and for the annular arrangement, while and for the hexagonal arrangement. Results demonstrate that with 44 fuel rods, different fuel arrangements remain subcritical with a subcriticality margin that is at least or maximum of 0.97. The key reactor performance characteristics determined in this study can aid in the analysis of transient behavior and safety assessment of subcritical core configurations with TRIGA fuel rods. Our results provide support in expanding the utilization options for irradiated TRIGA fuel rods, even for other TRIGA facilities

AN INITIATIVE FOR THE DEVELOPMENT AND APPLICATION OF OPEN-SOURCE MULTI-PHYSICS SIMULATION IN SUPPORT OF R&D AND E&T IN NUCLEAR SCIENCE AND TECHNOLOGY

Modelling and simulation (M&S) have gradually become irreplaceable tools in the field of Nuclear Science and Technology (NS&T), including nuclear energy systems. This is partly due to growing computational resources and advances in computational science and partly to the difficulties to finance, build and license new experimental facilities. However, the utilization of M&S for research and development (R&D) and education and training (E&T) applications is somewhat hampered by limited accessibility to controlled and sensitive nuclear M&S tools as well as by the desires of the developers of these tools to retain their intellectual property (IP). Open-source software and open-access data are growingly perceived as means to accelerate innovation by promoting synergistic collaborative developments while lowering the barriers associated to code distribution, modification, and sharing. Open-source software development is ideal for R&D and E&T purposes because it permits the enhancement of understanding, the use of advanced computational methods and it promotes the cooperation among researchers and scientists, without rigorous constraints on quality assurance or reliance on proprietary data for technology-specific validation. As a fundamental research tool, this helps to mitigate constraints related to dual use of such technology. It is in this context that an initiative is being launched under the aegis of the International Atomic Energy Agency (IAEA) to promote the development and application of open-source multi-physics simulation in support of R&D and E&T in NS&T. This paper presents scope and objectives of this initiative.

ANALISIS PERLAKUAN AKUNTANSI TERHADAP PENERIMAAN NEGARA BUKAN PAJAK (PNBP) ATAS JASA LAYANAN IPTEK NUKLIR

The mechanism for managing PNBP services in BATAN is guided by Law (Law) Number 20 of 2017 concerning PNBP, Government Regulation (PP) Number 29 of 2011 concerning Types and Rates of PNBP Types that Apply to the National Nuclear Energy Agency, Government Regulation (PP) Number 71 of 2010 concerning Government Accounting Standards (SAP), Technical Bulletin of Government Accounting Standards Number 23 concerning Accounting for Non-Tax Revenue Collection, and Regulation of the Minister of Finance of the Republic of Indonesia (PMK-RI) Number 152 / PMK.02 / 2014 concerning Instructions for the Compilation of PNBP of the State Ministries / Institutions implemented by 16 work units in BATAN for 15 types of Nuclear Science and Technology services. In order to meet the needs of the community for goods / services in the nuclear sector, BATAN provides services in the field of nuclear science and technology (science and technology), one of which is carried out through an application system. In line with bureaucratic reforms which have an impact on changes in governance in various fields, the regulation of PNBP. Law Number 20 Year 1997 concerning PNBP only contains PNBP groups and rules in general, and their implementation is regulated in detail through PP. However, the preparation of legislation requires a long time, while the implementation of PNBP must continue to run. In implementing PNBP, BATAN is increasingly demanded to provide services that are fast, easy, practical and transparent. Service customers do not have to come to the intended work unit to complete administration. With online-based administration all communication with customers can be done both ways. This study uses descriptive analysis, showing the largest percentage of PNBP service use in BATAN out of 15 types of Nuclear Science and Technology services in 2017 conducted by the PSTBM Work Unit (99.64%) and the smallest percentage of use by the PTBGN Work Unit (5.88%) (able seen in the results of the discussion on pages 10-14). Keywords: PNBP, Measurement,Acceptance, Use, Nuclear Science and Technology Services.

Stability analysis of linear FNPK model considering reactivity feedback effects for a research nuclear reactor

Fractional neutron point kinetics (FNPK) model has been known for some researchers in the field of nuclear science and engineering for less than a decade. This modeling has a better approximation and physical interpretation for some phenomena, specially, when large variations of neutron cross sections occur and the dynamic behavior of neutron is different. This paper, for the first time, presents a fractional neutron point kinetics model which consists of three delayed neutron groups and the reactivity feedback effects (temperature feedbacks and poison feedbacks). Also, Stability Analysis of linear FNPK model considering reactivity feedback effects for a Research Nuclear Reactor is done. The model has been linearized around the equilibrium operating point. Then, the closed-loop linear fractional neutron point kinetics model considering reactivity feedback effects is transformed from S-domain to W-domain. For stability evaluation, two strategies have been implemented. The first strategy is the assessment of the region of closed-loop poles in the principal Riemann sheet (PRS) for the transformed system. The second one is the step response evaluation of the linear fractional-order closed-loop model for different values of the model parameters (including relaxation times and anomalous diffusion coefficients). Simulation results demonstrate that the stability of the system depends on the values of these model parameters and for one scenario, the closed-loop poles are located in the unstable region of PRS and the step response is unstable. However, for the others, it is stable and settles at an equilibrium value. In addition, a smaller anomalous diffusion coefficient (α), leads to a more unstable closed-loop model (have poles closer or inside the unstable region). Comparative analysis is shown that reactivity feedback effects are considerable on the stability of the research nuclear reactor. Specially, feedback by xenon has a negative effect on the stability and reduces the stability of system. Also, the stability highly depends on the values of α and τ.

Verification of R-matrix calculations for charged-particle reactions in the resolved resonance region for the 7Be system

R-matrix theory is used to describe nuclear reactions in the resolved resonance region. It uses information on bound states and low energy resonances to accurately parametrize cross sections on the resonances as well as the non-resonant background. Since the seminal work of Lane and Thomas (1958), the approach has been widely used to analyze experimental cross-section data in a broad range of fields spanning nuclear reaction dynamics, nuclear astrophysics, ion beam analysis and their applications. Different R-matrix codes have been developed and used in these different applications with very little communication among the developers or practitioners on the capabilities, achievements or limitations of the codes. A limited comparison among three R-matrix codes on neutron-induced reactions was performed by the International Atomic Energy Agency (IAEA) International Evaluation of Neutron Cross Section Standards project (2007). Since then, significant progress has been made in their implementation of the R-matrix algorithms, and R-matrix codes have enhanced capabilities. In this paper we present, for the first time, the results of a comprehensive effort to verify the most widely used R-matrix codes in the various fields of nuclear science and applications: AMUR, AZURE2, CONRAD, EDA, FRESCO, GECCCOS, and SAMMY. In addition to the description of the capabilities of the codes and their specifications, we discuss the results of a joint exercise which was coordinated by the International Atomic Energy Agency. The aim of the exercise was to compare calculations of charged-particle reaction cross sections for the light composite system 7Be. The calculations were performed by the codes using identical input R-matrix parameters and other specifications and were limited to charged-particle channels.

A review of nuclear data for the k₀-based neutron activation analysis

Nuclear data for the k0-based neutron activation analysis (k0-NAA) including: k0-factors – combination of nuclear constants (atomic mass, isotopic abundance, gamma-ray yield and thermal neutron capture cross section); Q0 – the ratio of the resonance integral to thermal neutron capture cross section; and Er – effective resonance energy, along with the related nuclear data are presented and evaluated in the presentation. Accuracy and capability of k0-NAA depends considerably on the reliability of the above mentioned nuclear data. In general, the evaluation of nuclear data is essential and necessary in the field of nuclear science and technology, and this work is conducted by the nuclear data centers on the world as well as the research institutions where the nuclear data are usedfor R&D. Therefore, the evaluation of the nuclear data used in k0-NAA should also be performed so that some of data may no longer be appropriate should be redetermined. The evaluation of nuclear data in k0-NAA would contribute to the improvement of accuracy and reliability of the method, moreover, it would also contribute to the establishment a nuclear database in Vietnam in the future.

Numerical evaluation of gamma radiation monitoring

Abstract Airborne Gamma Ray Spectrometry (AGRS) with its important applications such as gathering radiation information of ground surface, geochemistry measuring of the abundance of Potassium, Thorium and Uranium in outer earth layer, environmental and nuclear site surveillance has a key role in the field of nuclear science and human life. The Broyden–Fletcher–Goldfarb–Shanno (BFGS), with its advanced numerical unconstrained nonlinear optimization in collaboration with Artificial Neural Networks (ANNs) provides a noteworthy opportunity for modern AGRS. In this study a new AGRS system empowered by ANN-BFGS has been proposed and evaluated on available empirical AGRS data. To that effect different architectures of adaptive ANN-BFGS were implemented for a sort of published experimental AGRS outputs. The selected approach among of various training methods, with its low iteration cost and non-diagonal scaling allocation is a new powerful algorithm for AGRS data due to its inherent stochastic properties. Experiments were performed by different architectures and trainings, the selected scheme achieved the smallest number of epochs, the minimum Mean Square Error (MSE) and the maximum performance in compare with different types of optimization strategies and algorithms. The proposed method is capable to be implemented on a cost effective and minimum electronic equipment to present its real-time process, which will let it to be used on board a light Unmanned Aerial Vehicle (UAV). The advanced adaptation properties and models of neural network, the training of stochastic process and its implementation on DSP outstands an affordable, reliable and low cost AGRS design. The main outcome of the study shows this method increases the quality of curvature information of AGRS data while cost of the algorithm is reduced in each iteration so the proposed ANN-BFGS is a trustworthy appropriate model for Gamma-ray data reconstruction and analysis based on advanced novel artificial intelligence systems.

Knowledge management in radiation protection: The Goiânia accident - Learning in the face of tragedy

A radiological accident usually ends up bringing damage to society. The accident in Goiânia, which turns 30 years in 2017, could not be different. However, the polysemy of the term accident, which usually refers to malfeasance, can also lead to discussion of social issues, thus generating knowledge. In this context, the objective of this work was to present some contributions to the learning in the radioprotection area from this accident. In this case, a thematic workshop was held, together with the students of the Specialization Course in Radiological Protection and Security of Radioactive Sources, offered jointly by the Institute of Radioprotection and Dosimetry (IRD) and the International Atomic Energy Agency (IAEA), focusing on the performance of the IRD during the accident. To do this, some professors of the course made a statement about what was the greatest legacy of the accident for the radioprotection area. From the analysis of the speeches, the workshop was held to discuss the relevance of the accident, focusing on the survey of the scientific advances and lessons learned. Thus, it was sought to evidence the radiological accident as a learning tool in the field of nuclear science, opening space for discussions of a wider knowledge on ionizing radiation. In this way, it is not possible to deny the technological advance or to negate the learning originated from this tragedy in Brazilian soil, understanding that the investigations related to historical aspects of science end up leading to new implications in the teaching of sciences.

Does the superior position of countries in co-authorship networks lead to their high citation performance

The objective of this research was to determine the macro-topological structure and the relationship between citation performance and centrality measures of co-authorship social networks of countries in the field of Nuclear Science and Technology from 2008 to 2010. The present study applied the network analysis method in order to visualize co-authorship networks. Hypothesized relationships were tested using the authors of 24,308 documents cited in the Web of Science. Data relevant to citation performance of a country was based on the articles published by the researchers of the country in a three-year period and the citation data of articles were collected two years after their publication. The investigation of co-authorship social network in the field of Nuclear Science and Technology revealed that the countries which are members of a Nuclear Club hold a prominent position in the network and their influence or power in the network is greater than other countries. Having characteristics like short mean path length, low network diameter (less than or equal to 6) and relatively high clustering coefficient, this network is regarded as a Small World Network. The results of testing the research hypotheses indicated that as the value of centrality of countries rise, the citation performance of researchers in that country is also improved. The analysis of variance confirmed the validity of stepwise regression analysis in predicting the citation performance of researchers (F=816.958 and p>0.000) and through three steps, three components including degree centrality, beta centrality and flow betweenness centrality were concluded to have multiple correlation with citation performance of researchers

Parametric uncertainty analysis of solute transport process using fuzzy lattice Boltzmann scheme

Uncertainty analysis of groundwater flow and solute transport model is important from the point of safety measures in the field of nuclear science and technology. Researchers have already carried out this uncertainty analysis using traditional Monte Carlo simulations. However, in practice, Monte Carlo simulation may not be possible because of lack of data obtained from the field experiments. Therefore, demand is to investigate the uncertainty by using imprecise based method. In order to fulfill this demand, we have carried out the parametric uncertainty analysis of solute transport model using a fuzzy set method. This paper, proposes an innovative methodology for solving advection diffusion equation describing tracer transport through geological media in presence of imprecise measurements of model parameters such as tracer dispersion coefficient and groundwater flow velocity. Measurement around most likely value provides a spread causing an imprecision of the model parameters. Imprecision is addressed as a fuzzy variable and the membership function of each such fuzzy variable is expressed in the form of a triangular fuzzy number. The governing advection dispersion equation is numerically solved using lattice Boltzmann scheme along with fuzzy parameters of the representative model and due to this the present numerical approach is named as fuzzy lattice Boltzmann. Uncertainty quantification of the solute concentration as solution of the governing fuzzy differential equation is carried out and by using this uncertainty modeling, advantage of the fuzzy lattice Boltzmann approach for obtaining the numerical solution of a fuzzy partial differential equation is shown.

Transition energy and half-life determinations of photonuclear reaction products of erbium nuclei

Photon induced reactions are called as photonuclear reactions and used in many research fields of nuclear science and nuclear physics. The photonuclear data are used in many nuclear applications such as radiation shielding and protection, radiation transport analyses, reactor core design, activation analysis and nuclear waste transmutation. In the past, many studies had been devoted to extract photonuclear data covering the isotopic chart. However, there is still lack of existing data. In the present study, we have performed photonuclear reactions on erbium (Er) target by using clinical electron linear accelerators (cLINAC). By using measured residual activity of photonuclear reaction products of Er nuclei, we have determined the half-life of [Formula: see text]Er nucleus and transition energies of [Formula: see text]Ho nucleus. Also, new measurements on gamma-ray energies of the products have been determined accurately. Furthermore, this study shows that repurposed cLINAC with limited budget can contribute to the global nuclear science knowledge.

The Second-Order Adjoint Sensitivity Analysis Methodology for Nonlinear Systems—I: Theory

The use of adjoint methods for computing first-order sensitivities (i.e., functional derivatives) of results (responses) produced by a computational model to the model’s parameters was initiated in the nuclear engineering sciences in the 1940s. The field of nuclear science and engineering also provided pioneering works, during the 1970s, for computing second-order response sensitivities of responses associated with the adjoint neutron and radiation transport and/or diffusion equations. These works generally indicated that the second-order sensitivities of responses such as reaction rates and the system’s effective multiplication factor to cross sections were computationally intensive to obtain, requiring O(Nα2) large-scale computations per response, for a system comprising Nα model parameters, and were considerably smaller than the corresponding first-order sensitivities. These results likely gave rise to the generally held opinion that second-order sensitivities are generally insignificant in reactor physics, which may, in turn, have led to diminishing interest in developing efficient methods for computing second-order sensitivities for nuclear engineering systems.This work presents the second-order adjoint sensitivity analysis methodology (2nd-ASAM) for nonlinear systems, which yields exactly and efficiently the second-order functional derivatives of physical system responses (i.e., system performance parameters) to the system’s model parameters. For a physical system comprising Nα parameters, forward methods require a total of (Nα2/2+3Nα/2) large-scale computations for obtaining all of the first- and second-order sensitivities, for all system responses. In contradistinction, the 2nd-ASAM requires one large-scale computation using the first-level adjoint sensitivity system (1st-LASS) for obtaining all of the first-order sensitivities, followed by at most Nα large-scale computations using the second-level adjoint sensitivity systems, for obtaining exactly all of the second-order sensitivities of a functional-type response. The construction, implementation, and solution of the 2nd-ASAM require very little additional effort beyond the construction of the 1st-LASS needed for computing the first-order sensitivities. Furthermore, because of the symmetry properties of the second-order sensitivities, the 2nd-ASAM comprises the inherent automatic solution verification of the correctness and accuracy of the second-level adjoint functions used for the efficient and exact computation of the second-order sensitivities. The use of the 2nd-ASAM to compute exactly all of the second-order response sensitivities to model input parameters is expected to enable significant advances in related scientific disciplines, particularly the areas of uncertainty quantification and predictive modeling, including model validation, reduced-order modeling, data assimilation, model calibration, and extrapolation.

The Influence of Barium Sulphate and Barium Carbonate on the Portland Cement

Shielding of different types of radiation should be studied these days when there is a great development in the field of nuclear science. Barium ions can shield different type of radiation, therefore, by incorporation of barium ions into the system of Portland clinker, a binder with shielding properties can be made. The work is focused on influence of barium ions on the formation of Portland clinker and its properties. As a source of barium, barium sulphate and barium carbonate were added to raw meal. Clinkers and cements with a different amount of barium were prepared and the effect of barium on the clinker and cement properties respectively was studied. By Rietveld analysis (using X-Ray diffraction) and microscopic point counting method, the ratio of clinker phases was studied. With increasing amount of barium, the alite: belite ratio was decreasing and the amount of free lime was increasing. Sulphate decelerates the decreasing ratio and causes grow of alite crystals to great dimensions. The presence of barium in different phases was observed by SEM with EDS. The highest amount of barium was found in belite and clinker melt. In clinker melt, conglomerations of barium were formed. Furthermore, a difference in formation temperature of clinker phases was observed and some elementary tests were done on prepared cements according to the European standards.