Transition Operator Research Articles

β decay and evolution of low-lying structure in Ge and As nuclei

A simultaneous calculation for the shape evolution and the related spectroscopic properties of the low-lying states, and the $\beta$-decay properties in the even- and odd-mass Ge and As nuclei in the mass $A\approx70-80$ region, within the framework of the nuclear density functional theory and the particle-core coupling scheme, is presented. The constrained self-consistent mean-field calculations using a universal energy density functional (EDF) and a pairing interaction determines the interacting-boson Hamiltonian for the even-even core nuclei, and the essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. A rapid structural evolution from $\gamma$-soft oblate to prolate shapes, as well as the spherical-oblate shape coexistence around the neutron sub-shell closure $N=40$, is suggested to occur in the even-even Ge nuclei. The predicted low-energy spectra, electromagnetic transition rates, and $\beta$-decay $\log{ft}$ values are in a reasonable agreement with experiment. The predicted $\log{ft}$ values reflect the structures of the wave functions for the initial and final nuclei of $\beta$ decay, which are, to a large extent, determined by the microscopic input provided by the underlying EDF calculation.

Two-neutrino double- β decay in the mapped interacting boson model

A calculation of two-neutrino double-$\beta$ ($2\nu\beta\beta$) decay matrix elements within the interacting boson model (IBM) that is based on the nuclear density functional theory is presented. The constrained self-consistent mean-field (SCMF) calculation using a universal energy density functional (EDF) and a pairing interaction provides potential energy surfaces with triaxial quadrupole degrees of freedom for even-even nuclei corresponding to the initial and final states of the $2\nu\beta\beta$ decays of interest. The SCMF energy surface is then mapped onto the bosonic one, and this procedure determines the IBM Hamiltonian for the even-even nuclei. The same SCMF calculation provides the essential ingredients of the interacting boson fermion-fermion model (IBFFM) for the intermediate odd-odd nuclei and the Gamow-Teller and Fermi transition operators. The EDF-based IBM and IBFFM provide a simultaneous description of excitation spectra and electromagnetic transition rates for each nucleus, and single-$\beta$ and $\beta\beta$ decay properties. The calculated $2\nu\beta\beta$-decay nuclear matrix elements are compared with experiment and with those from earlier theoretical calculations.

Universal properties of the isotropic Laplace operator on homogeneous trees

Let P be the isotropic nearest neighbor transition operator on a homogeneous tree. We consider the λ-eigenfunctions of P for λ outside its ℓ2-spectrum spec(P), i.e., the eigenfunctions with eigenvalue γ=λ−1 of the Laplace operator Δ=P−I, and also the λ-polyharmonic functions, that is, the union of the kernels of (Δ−γI)n. We prove that, on a suitable Banach space generated by the λ-polyharmonic functions, the operator eΔ−γI is hypercyclic, although Δ−γI is not.

Evaluating the Comprehensive Benefit of Public Transport Service – The Perspective of Three Stakeholders

Most studies investigate the benefit of public trans-port service from either the perspective of the operators or the public individually, failing to bind them together. Furthermore, they have not considered the significance of the government in quantifying the benefit. This pa-per explores the comprehensive benefit of public trans-port service from the perspectives of three stakeholders; namely, the operators, the public, and government. We develop a comprehensive benefit evaluation tool that is able to quantify production efficiency, service effect, and environmental effect, and test the effectiveness of the tool through a case study in 36 central cities of China. A network data envelopment analysis (NDEA) is used to evaluate the efficiency of the production and service sub-process, and comprehensive benefits. The results re-veal the following: (1) during the period 2010–2017, the production efficiency in 36 central cities showed a down-ward trend; (2) the service effectiveness did not change considerably from 2010 to 2013 but declined gradual-ly during the period 2014–2017; (3) the comprehensive benefits rarely changed during the period 2010–2013, but gradually got worse in response to reductions in the production efficiency and service effectiveness during the period 2014–2017. This study offers a robust tool to mea-sure the benefits of public transport in China for better decision-making, in terms of transit operation and man-agement.

Linear dynamics induced by odometers

Weighted shifts are an important concrete class of operators in linear dynamics. In particular, they are an essential tool in distinguishing a variety of dynamical properties. Recently, a systematic study of dynamical properties of composition operators on L p L^p spaces has been initiated. This class of operators includes weighted shifts and also allows flexibility in construction of other concrete examples. In this article, we study one such concrete class of operators, namely composition operators induced by measures on odometers. In particular, we study measures on odometers which induce mixing and transitive linear operators on L p L^p spaces.

Sea trial investigation for dynamic load compensation effect evaluation on novel soft hang-off system

ABSTRACT Offshore drilling activities have been significantly impacted by extreme storm conditions as oil and gas development has moved into deeper water. Under the situation of the imminent arrival of a typhoon, retrieval of the whole drilling riser is time-consuming and tedious. A novel soft hang-off system under hang-off and transit operations is proposed and developed to solve the low-efficiency and time limitation for risers' retrieval. The hang-off joint system suspends the drilling riser and the hydraulic system is designed for dynamic load compensation. Sea trial for enhanced hang-off mode with hang-off joint, non-differential control dynamic load compensation mode at hang-off operation and passive compensation mode at transit operation are conducted to evaluate the load compensation effect equipped with novel soft hang-off system compared with conventional hard hang-off mode. Results on dynamic load compensation effect are discussed. The novel soft hang-off system is of high application value for deepwater drilling engineering.

Transit use reduction following COVID-19: The effect of threat appraisal, proactive coping and institutional trust.

Transit systems suffered from a significant demand decrease during COVID-19. Understanding the psychological motivators underlying reduced transit use can help transit authorities and operators to take proactive action towards returning to the “new normal” and increasing their preparedness towards future pandemics. This study is based on the protection motivation theory to understand the effect of threat appraisal, and coping appraisal and denial mechanisms on transit use reduction for commuting. The behavioral framework is validated by a survey of 856 transit users in Israel during August 2020, three months after the end of the lockdown and before the vaccine administration. The results show that: i) Skepticism, risk ubiquity, and personal immunity beliefs lead to maladaptive threat appraisal; ii) wearing masks and social distancing are antecedents of fear of infection while using transit and reduced transit use; iii) higher perceived threat deters transit use, while trust in transit operators motivates transit use; and iv) in a franchised transit system, trust in transit operators depends on the perceived level-of-service and trust in the ability of government authorities to regulate, monitor and enforce transit operators' preventive and protective actions.

There are no topologically transitive operators in the noncommutative Schwartz space

The aim of this note is to prove that there are no topologically transitive operators in the noncommutative Schwartz space.

An optimization model for planning limited-stop transit operations

An optimization model for planning limited-stop transit operations

Open Quantum Random Walks and Quantum Markov chains on Trees I: Phase transitions

In the present paper, we construct QMC (Quantum Markov Chains) associated with Open Quantum Random Walks such that the transition operator of the chain is defined by OQRW and the restriction of QMC to the commutative subalgebra coincides with the distribution [Formula: see text] of OQRW. However, we are going to look at the probability distribution as a Markov field over the Cayley tree. Such kind of consideration allows us to investigate phase transition phenomena associated for OQRW within QMC scheme. Furthermore, we first propose a new construction of QMC on trees, which is an extension of QMC considered in [10]. Using such a construction, we are able to construct QMCs on tress associated with OQRW. Our investigation leads to the detection of the phase transition phenomena within the proposed scheme. This kind of phenomena appears for the first time in this direction. Moreover, mean entropies of QMCs are calculated.

Development of a Model for Dynamic Station Assignmentto Optimize Demand Responsive Transit Operation

Development of a Model for Dynamic Station Assignmentto Optimize Demand Responsive Transit Operation

Research on Safety Management of Urban Rail Transit Operation Based on BIM

Research on Safety Management of Urban Rail Transit Operation Based on BIM

Calculated Event Rates for Axion Detection via Atomic and Nuclear Processes

The possibility of detection of 5.5 MeV and 14.4 keV solar axions by observing axion-induced nuclear and atomic transitions is investigated. The presence of nuclear transitions between spin orbit partners can be manifested by the subsequent deexcitation via gamma ray emissions. The transition rates can also be studied in the context of radiative axion absorption by a nucleus. The elementary interaction is obtained in the context of the axion-quark couplings predicted by existing axion models. Then, these couplings will be transformed to the nucleon level utilizing reasonable existing models, which lead to effective transition operators. Using these operators, we calculate the needed nuclear matrix elements employing wave functions obtained in the context of the nuclear shell model. With these ingredients, we discuss possibilities of experimental observation of the axion-induced nuclear gamma rays. In the second part, we will examine the axion-induced production of X-rays (axion-photon conversion) or ionization from deeply bound electron orbits. In this case, the axion electron coupling is predicted by existing axion models; no renormalization is needed. The experimental signal is the observation of directly produced electrons and/or the emission of hard X-rays and Auger electrons, following the deexcitation of the final atom. Critical discussion is made on the experimental feasibility of detecting the solar axions by using multiton scale NaI detectors.

Prediction of Train Station Delay Based on Multiattention Graph Convolution Network

Train station delay prediction is always one of the core research issues in high-speed railway dispatching. Reliable prediction of station delay can help dispatchers to accurately estimate the train operation status and make reasonable dispatching decisions to improve the operation and service quality of rail transit. The delay of one station is affected by many factors, such as spatiotemporal factor, speed limitation or suspension caused by strong wind or bad weather, and high passenger flow caused by major holiday. But previous studies have not fully combined the spatiotemporal characteristics of station delay and the impact of external factors. This paper makes good use of the train operation data, proposes the multiattention mechanism to capture the spatiotemporal characteristics of train operation data and process the external factors, and establishes a Multiattention Train Station Delay Graph Convolution Network (MATGCN) model to predict the train delay at high-speed railway stations, so as to provide references for train dispatching and emergency plan. This paper uses real train operation data coming from China high-speed railway network to prove that our model is superior to ANN, SVR, LSTM, RF, and TSTGCN models in the prediction effect of MAE, RMSE, and MAPE.

A Dynamic Choice Model to Estimate the User Cost of Crowding with Large-Scale Transit Data

Abstract Efficient mass transit provision should be responsive to the behaviour of passengers. Operators often conduct surveys to elicit passenger perspectives, but these can be expensive to administer and can suffer from hypothetical biases. With the advent of smart card and automated vehicle location data, operators have reliable sources of revealed preference (RP) data that can be utilized to estimate transit riders’ valuation of service attributes. To date, effective use of RP data has been limited due to modelling complexities. We propose a dynamic choice model (DCM) for population-level longitudinal RP data to address prominent challenges. In the DCM, riders are assumed to follow different decision rules (compensatory and inertia/habit) and temporal switching between decision rules based on experience-based learning is also formulated. We develop an expectation–maximization algorithm to estimate the DCM and apply our model to estimate passenger valuation of crowding. Using large-scale data of 2 months with over four million daily trips by an Asian metro, our DCM estimates show an increase of 47% in passenger’s valuation of travel time under extremely crowded conditions. Furthermore, the average passenger follows the compensatory rule on only 25.5% or fewer trips. These results are valuable for supply-side decisions of transit operators.

Start-up, shutdown, and transition timescale analysis in biomass reactor operations

The time required to achieve steady state operation is an important factor in biomass conversion reactors, especially at a pilot or higher scale. The present work analyses the start-up, shutdown, and transient timescales of the laboratory-scale biomass reactor set-up using theoretical framework, for the case study of biomass torrefaction. The experimental time series temperature data is analyzed to infer the transient behaviors of the reactor, as well as how it changes with reactor scaling. Thermal mass of the reactor played a significant part in the reactor's temporal response to changes, and it was demonstrated to possibly achieve a reasonable temporal response time at scale. A series of start-up and cooling operation strategies are devised to optimize the time and feedstock consumption requirements. The learning is applied to the case of transitioning between two reactor operating conditions where rapid start-up or cooling procedure proved more time-efficient and feedstock-efficient. The insights learned provide a basis for a more comprehensive study of the reactor transitional operations that can be encapsulated into an automated control system to minimize human intervention.

A framework for BEB energy prediction using low-resolution open-source data-driven model

• We proposed a low-resolution open-source data-driven BEB energy prediction model. • The prediction model is applied to one-minute segments and full trips. • A sensitivity analysis is conducted to assess the model performance. • On full trips, the model is very accurate (more than 90% accuracy). • On one-minute segments, the model is acceptable (more than 80% accuracy). The accurate calculation of the energy consumption (E C ) rates of Battery-Electric Buses (BEBs) might be ambiguous due to uncertainties in amassing real-world operation data such as speed profiles, route topology, passenger loading, and weather conditions. Therefore, attaining an extensive validated E C prediction model is essential to surmount the challenges in collecting real-world data. In this respect, this study develops and assesses an open-source low-resolution data-driven framework to estimate BEB's E C in transit operation, using vehicular, operational, topological, and external parameters. Moreover, a three-step validation process is used to assess the proposed framework's performance. The results show that the prediction model provides a reasonable error margin (20%). The validation analyses show a powerful goodness-of-fit where the prediction model can explain more than 90% of the E C variation. The framework can superbly provide transit planners and agencies with an optimal transit operating profile that reinforces the BEB’s energy savings.

Enhancing Dependability Analysis Provisioning in CBTC Wireless Communication System With Age of Information

As a crucial part of the communication-based train control (CBTC) system, the wireless communication subsystem is responsible for transmitting safety-critical information, which directly affects the safe and efficient operation of the urban rail transit. The dependability analysis method for wireless communication in CBTC is critical and necessary to ensure the stable transmission of safety-critical information. However, most of the existing researches in CBTC lack a unified evaluation index to analyze the wireless communication dependability. In this paper, the dependability of wireless communication system in CBTC is established. To be specific, timeliness, integrity, security, and safety are used to describe the dependability of CBTC wireless communication system in our definition. The age of information (AoI) is used to quantitatively analyze the dependability in the CBTC wireless communication system. To verify the effectiveness of the proposed dependability analysis method, we quantitatively introduce the dependability of wireless communication system in CBTC with different scenarios, including packet-drop, re-transmission, handoff, and cyber-attack. Simulation results show that the designed dependability analysis method with quantized AoI can efficiently describe the dependability of CBTC wireless communication system in different scenarios.

Investigating the influence of weather on public transit passenger’s travel behaviour: Empirical findings from Brisbane, Australia

Drawing on transit smart card data allied with local weather station records over a 12-month period, this paper takes Brisbane, Australia as the study context and examines the way in which weather impose influences on public transit passenger’s travel behaviour. In terms of transit passenger’s spatiotemporal origin–destination (OD) information, a new travel behaviour indicator called stickiness is developed to reflect passenger’s travel similarity in using the transit service over a period. By applying a suite of regression models, it shows that weather’s effects on transit passenger’s travel behaviour vary by temporal period and passenger type. In general, weather is shown to exert a stronger effect on passenger’s stickiness during midday off-peak hours in comparison with either AM peak or PM peak. Across all types of passengers, child passengers are found to be most tolerant to weather changes and even be stickier to their regular travel pattern during AM peak. The modelling results also reveal that when it relates to journey-to-work or journey-to-school, weather’s effects on alighting location are much smaller than other three OD-related travel behaviour features (i.e., boarding time, boarding location, and alighting time). In contrast with the postponement during AM peak, transit passengers are prone to bring forward their trip back home during PM peak in response to poor weather conditions. Moreover, this paper verifies that weather parameters are not singly perceived by transit passengers but as an interrelated unity in shaping transit passenger’s travel behaviour. By enriching the weather–travel behaviour scholarship, the empirical findings of this study are helpful to render a holistic understanding of the weather–travel behaviour relationship and have important implications for transit operators in building a more weather-resilient transit system.

Quenching of Gamow-Teller strengths and two-particle–two-hole configurations

We apply the charge-exchange subtracted second random-phase approximation (SSRPA), based on Skyrme functionals, to investigate Gamow-Teller resonances in several closed-shell and closed-subshell nuclei, located in different regions of the nuclear chart. After having discussed the SSRPA findings obtained within different approximation schemes in $^{48}$Ca, we compare our results with {\it{ab-initio}} coupled-cluster predictions available for C and O isotopes, where two-body currents are included. Our integrated strenghts, obtained by using one-body transition operators, are lower compared to the corresponding {\it{ab-initio}} results. This indicates that, within our model, quenching effects are mainly driven by the inclusion of two particle - two hole configurations and that the role of a two-body contribution in the transition operator is less important than in the coupled-cluster approach. By analyzing heavier nuclei, $^{90}$ Zr and $^{132}$Sn, we confirm the same conclusions that we have recently drawn for $^{48}$Ca: the inclusion of two particle - two hole configurations is very effective in our model for providing strengths which are significantly more quenched than in other theoretical models and, thus, in better agreement with the experimental measurements. This occurs because two particle - two hole configurations have a density which strongly increases with the excitation energy. Their inclusion thus pushes a significant amount of the strength to higher energies, compared to what happens in other theoretical models, reducing in this way the cumulative sum of the strength up to excitation energies around 20-30 MeV.