Discrete Theory Research Articles

Administrative Discretion: Questions and Answers (Part 1)

This material opens a series of scientific publications planned by the editors of the Siberian Law Review journal, the Authors of which analyze the problem of administrative discretion (discretion), which is very relevant for Russian administrative legal theory and law practice, in the “question-answer” format. The scientific, theoretical and practical significance of the noted problem is predetermined by the fact that the exercise of discretionary powers by the public administration (as opposed to powers strictly bound by law) is fraught with the greatest threat to the rights, freedoms and legitimate interests of citizens, the rights and legitimate interests of organizations. The purpose of the study is to clarify issues related to the concept and essence of administrative discretion, its regulatory legal framework, forms of implementation, ways to establish the limits of discretion of public administration, criteria for assessing the legality of discretionary administrative acts, judicial and agency control over administrative discretion. The subject of the research is normative legal acts, legal principles, administrative and judicial acts, scientific works of Russian and foreign legal scholars. The hypothesis of the study is that, despite the abundance of scientific publications on administrative-discretionary topics, the domestic doctrine of administrative discretion is a motley mixture of judgments that do not agree with each other, often divorced from the needs of administrative and judicial practice, characterized by the absence of a single categorical apparatus. According to Yuri P. Solovey, an important, if not the most important section of administrative discretionary issues, are the limits of judicial control over administrative discretion, which has practically fallen out of the field of view of Russian scholars, despite the fact that it has been thoroughly studied abroad for more than a century and a half. From the point of view of Petr P. Serkov, the domestic science of administrative law has not yet properly answered three fundamental questions, namely: what is administrative discretion, what is it intended for and how is it carried out. The Authors of the publication are unanimous that such a “doctrine” of administrative discretion does not contribute to the development of legislative solutions to bring such discretion to the standards of a legal, democratic state. In the process of research, dialectical, formal-logical, formal-legal, comparative-legal methods of cognition, the method of interpreting law, analysis of materials from administrative and judicial practice are used. The Authors attempt to streamline the categorical apparatus of the theory of administrative discretion, as well as to formulate its main provisions and some proposals for improving the current legislation.

Research on Mesoscopic Characteristics of Limestone Grouting Diffusion Based on Discrete Fracture Network

The limestone stratum has well-developed rock fissures and abundant groundwater. Under extreme rainstorm conditions, tunnel surrounding rock seepage is serious especially. In order to reveal the grouting diffusion mechanism of karst fractured rock mass and realize effective water plugging, in this paper, the basic mechanical parameters of limestone are obtained by laboratory triaxial test, and the porosity distribution of rock mass is obtained by nuclear magnetic resonance test. The PFC2D discrete element software is used to simulate the mechanical characteristics of compressive deformation and fracture propagation pattern of the limestone and compared with the triaxial test results. Discrete fracture network theory is used to establish PFC2D numerical simulation of grouting diffusion model of fractured rock mass. And the filling diffusion mechanism and stress variation rule of cement slurry in fractured limestone under different grouting pressure are studied. The results show that (1) During the grouting process, the micro-cracks expand along the tip of the existing cracks, and extend to the surrounding cracks to finally form through cracks, so as to achieve the effect of grouting reinforcement. (2) With the increase of grouting pressure, the maximum displacement of particles increases continuously, but with the prolongation of grouting time, the maximum displacement of particles reaches a stable state and no longer increases. (3) During the grouting process of the fractured rock mass, with the increase of grouting time, the stress of the fractured rock mass finally reaches a stable state. This study provides an important reference for the setting of grouting parameters of limestone rock mass.

Research on Bucket Loading Resistance Based on Discrete Element Method

Shovel loading resistance is the reaction force of the material on the bucket during the shovel loading process, which contains two parts: the resistance of the bucket insertion stage and the resistance of the lifting stage. The resistance of shovel loading has a great influence on the loading efficiency, so it is important to carry out resistance research. Based on the discrete element theory, this paper applies EDEM software to establish a simulation model of the loading process and realise the simulation of the forward and reverse shovel loading process. Through the simulation, the mechanical characteristics of the shovelling operation are visually analysed, and the obstructing effect of the material on the bucket is clarified; the shovelling resistance of the key parts of the bucket at different stages of the shovelling process is specifically analysed, and the parts where the peak shovelling resistance is located and the stages where it is located are identified. The influence of the shovel angle on the resistance is also analysed.

Atmospheric heat redistribution effect on emission spectra of Hot-Jupiters

Hot Jupiters are the most studied and easily detectable exoplanets for transit observations. However, the correlation between the atmospheric flow and the emission spectra of such planets is still not understood. Due to huge day–night temperature contrast in hot Jupiter, the thermal redistribution through atmospheric circulation has a significant impact on the vertical temperature–pressure structure and on the emission spectra. In the present work, we aim to study the variation of the temperature–pressure profiles and the emission spectra of such planets due to different amounts of atmospheric heat redistribution. For this purpose, we first derive an analytical relation between the heat redistribution parameter f and the emitted flux from the uppermost atmospheric layers of hot Jupiter. We adopt the three possible values of f under isotropic approximation as 14,12 and 23 for full-redistribution, semi-redistribution and no-redistribution cases respectively and calculate the corresponding temperature–pressure profiles and the emission spectra. Next, we model the emission spectra for different values of f by numerically solving the radiative transfer equations using the discrete space theory formalism. We demonstrate that the atmospheric temperature–pressure profiles and the emission spectra both are susceptible to the values of the heat redistribution function. A reduction in the heat redistribution yields a thermal inversion in the temperature–pressure profiles and hence increases the amount of emission flux. Finally, we revisits the hot Jupiter XO-1b temperature–pressure profile degeneracy case and show that a non-inversion temperature–pressure profile best explains this planet’s observed dayside emission spectra.

From PEF to PBF: What difference does the longer alkyl chain make a computational spectroscopy study of poly(butylene 2,5-furandicarboxylate).

This work explores the conformational preferences and the structure-property correlations of poly(butylene 2,5-furandicarboxylate) (PBF), a longer chain analogue of the most well-known biobased polyester from the furan family, poly(ethylene 2,5-furandicarboxylate) (PEF). A thorough computational spectroscopic study-including infrared, Raman and inelastic neutron scattering spectroscopy, combined with discrete and periodic density functional theory calculations-allowed the identification of dominant structural motifs in the amorphous and crystalline regions. Discrete calculations and vibrational spectroscopy of semi-crystalline and amorphous samples strongly support the predominance of gauche, trans, gauche conformations of the butylene glycol fragment in both the crystalline and amorphous domains. In what concerns the furandicarboxylate fragment, amorphous domains are dominated by syn,syn conformations, while in the crystalline domains the anti,anti forms prevail. A possible crystalline structure-built from these conformational preferences and including a network of C-H···O hydrogen bond contacts-was optimized using periodic density functional theory. This proposed crystal structure avoids the unrealistic structural features of the previously proposed X-ray structure, provides an excellent description of the inelastic neutron scattering spectrum of the semi-crystalline form, and allows the correlation between microscopic structure and macroscopic properties of the polymer.

Precise ground state of multiorbital Mott systems via the variational discrete action theory

Determining the ground state of multi-orbital Hubbard models is critical for understanding strongly correlated electron materials, yet existing methods struggle to simultaneously reach zero temperature and infinite system size. The \textit{de facto} standard is to approximate a finite dimension multi-orbital Hubbard model with a $d=\infty$ version, which can then be formally solved via the dynamical mean-field theory (DMFT), though the DMFT solution is limited by the state of unbiased impurity solvers for zero temperature and multiple orbitals. The recently developed variational discrete action theory (VDAT) offers a new approach to solve the $d=\infty$ Hubbard model, with a variational ansatz that is controlled by an integer $\mathcal{N}$, and monotonically approaches the exact solution at an increasing computational cost. Here we propose a decoupled minimization algorithm to implement VDAT for the multi-orbital Hubbard model in $d=\infty$ and study $\mathcal{N}=2-4$ . At $\mathcal{N}=2$, VDAT rigorously recovers the multi-orbital Gutzwiller approximation, reproducing known results. At $\mathcal{N}=3$, VDAT precisely captures the competition between the Hubbard $U$, Hund $J$, and crystal field $\Delta$ in the two orbital Hubbard model over all parameter space, with a negligible computational cost. For sufficiently large $U/t$ and $J/U$, we show that $\Delta$ drives a first-order transition within the Mott insulating regime. In the large orbital polarization limit with finite $J/U$, we find that interactions have a nontrivial effect even for small $U/t$. VDAT will have far ranging implications for understanding multi-orbital model Hamiltonians and strongly correlated electron materials.

Thermodynamics of multipolar Kihara fluids. Results from Monte Carlo simulations and molecular discrete perturbation theory

We present a systematic study of the vapor–liquid equilibria of prolate Kihara fluids embedding both dipole and quadrupole moments Monte Carlo simulations and perturbation theory methods. The agreement between both approaches is good and allows to shed light on some general features of molecular models whose distribution of charge can be modeled as a dipole plus a quadrupole moments. The validation of the equation of state does lead as a byproduct to a rapid, uncommon, and powerful instrument able to widen the frontiers of perturbation theory for molecular fluids and their mixtures.

Robust Operating Room Scheduling Model with Violation Probability Consideration under Uncertain Surgery Duration.

This paper proposes an operating room (OR) scheduling model to assign a group of next-day patients to ORs while adhering to OR availability, priorities, and OR overtime constraints. Existing studies usually consider OR scheduling problems by ignoring the influence of uncertainties in surgery durations on the OR assignment. In this paper, we address this issue by formulating accurate patient waiting times as the cumulative sum of uncertain surgery durations from the robust discrete approach point of view. Specifically, by considering the patients’ uncertain surgery duration, we formulate the robust OR scheduling model to minimize the sum of the fixed OR opening cost, the patient waiting penalty cost, and the OR overtime cost. Then, we adopt the box uncertainty set to specify the uncertain surgery duration, and a robustness coefficient is introduced to control the robustness of the model. This resulting robust model is essentially intractable in its original form because there are uncertain variables in both the objective function and constraint. To make this model solvable, we then transform it into a Mixed Integer Linear Programming (MILP) model by employing the robust discrete optimization theory and the strong dual theory. Moreover, to evaluate the reliability of the robust OR scheduling model under different robustness coefficients, we theoretically analyze the constraint violation probability associated with overtime constraints. Finally, an in-depth numerical analysis is conducted to verify the proposed model’s effectiveness and to evaluate the robustness coefficient’s impact on the model performance. Our analytical results indicate the following: (1) With the robustness coefficient, we obtain the tradeoff relationship between the total management cost and the constraint violation probability, i.e., a smaller robustness coefficient yields remarkably lower total management cost at the expense of a noticeably higher constraint violation probability and vice versa. (2) The obtained total management cost is sensitive to small robustness coefficient values, but it hardly changes as the robustness coefficient increases to a specific value. (3) The obtained total management cost becomes increasingly sensitive to the perturbation factor with the decrease in constraint violation probability.

Geometric Partition Entropy: Coarse-Graining a Continuous State Space

Entropy is re-examined as a quantification of ignorance in the predictability of a one dimensional continuous phenomenon. Although traditional estimators for entropy have been widely utilized in this context, we show that both the thermodynamic and Shannon’s theory of entropy are fundamentally discrete, and that the limiting process used to define differential entropy suffers from similar problems to those encountered in thermodynamics. In contrast, we consider a sampled data set to be observations of microstates (unmeasurable in thermodynamics and nonexistent in Shannon’s discrete theory), meaning, in this context, it is the macrostates of the underlying phenomenon that are unknown. To obtain a particular coarse-grained model we define macrostates using quantiles of the sample and define an ignorance density distribution based on the distances between quantiles. The geometric partition entropy is then just the Shannon entropy of this finite distribution. Our measure is more consistent and informative than histogram-binning, especially when applied to complex distributions and those with extreme outliers or under limited sampling. Its computational efficiency and avoidance of negative values can also make it preferable to geometric estimators such as k-nearest neighbors. We suggest applications that are unique to this estimator and illustrate its general utility through an application to time series in the approximation of an ergodic symbolic dynamics from limited observations.

Couple stresses and discrete potentials in the vertex model of cellular monolayers.

The vertex model is widely used to simulate the mechanical properties of confluent epithelia and other multicellular tissues. This inherently discrete framework allows a Cauchy stress to be attributed to each cell, and its symmetric component has been widely reported, at least for planar monolayers. Here, we consider the stress attributed to the neighbourhood of each tricellular junction, evaluating in particular its leading-order antisymmetric component and the associated couple stresses, which characterise the degree to which individual cells experience (and resist) in-plane bending deformations. We develop discrete potential theory for localised monolayers having disordered internal structure and use this to derive the analogues of Airy and Mindlin stress functions. These scalar potentials typically have broad-banded spectra, highlighting the contributions of small-scale defects and boundary layers to global stress patterns. An affine approximation attributes couple stresses to pressure differences between cells sharing a trijunction, but simulations indicate an additional role for non-affine deformations.

Dualities and flavored indices of M2-brane SCFTs

We study various conjectural dual descriptions of a stack of M2-branes in M-theory including ADHM, ABJ(M), BLG, discrete gauge theories and quiver Chern-Simons (CS) theories and propose several new dualities of the M2-brane SCFTs by analyzing flavored supersymmetric indices in detail. The mapping of local operators, Coulomb, Higgs and mixed branch operators as well as global symmetries under the dualities are obtained from the precise matching of the indices. Furthermore, we find closed form expressions for the Coulomb limit of the indices of the U(N) ADHM theory and the dual quiver CS theory for arbitrary N and propose a refined generating function for plane partitions with trace N. For the quiver CS theories we also find an infinite-sum expression for the Higgs limit of the indices which is more useful than the original expression.

Staged multicluster hydraulic fracture propagation mechanism and its influencing factors in horizontal wells for CBM development

AbstractStaged multicluster fracturing (SMCF) is crucial for the low‐permeability coalbed methane (CBM) reservoirs development. To reveal the fracture propagation mechanism and characteristics in SMCF and select appropriate hydraulic fracturing parameters, this study considers CBM exploitation in the Shizhuang block, Qinshui Basin in China as the engineering background. Then, XSite hydraulic fracturing software based on the discrete lattice theory and synthetic rock mass method is used to construct a three‐dimensional model. The influence mechanisms of the cluster spacing (CS) and lateral pressure coefficient (LPC) on the fractures propagation characteristics were investigated. With an increase in the CS, the stress interference between fractures gradually weakens, and the fracture deflection also decreases. Both the stimulated reservoir area (SRA) and fracture aperture of a single cluster increase with an increase in CS, but the SRA and fracturing efficiency exhibit limited growth when the CS is greater than 15 m. The SRA decreases exponentially with an increase in LPC. When the LPC increases from 0.4 to 1.4, the SRA decreases by 74.2%. The LPC plays a decisive role in the fracture propagation direction. When the LPC reaches 1.4, the fractures propagate along the horizontal direction. With an increase in LPC, the fracturing fluid pressure increases linearly, and the fracturing efficiency decreases exponentially. The results of this study reveal the fracture propagation law of SMCF and can provide a reference for engineering applications. In the SMCF at the 3# coal seam of the Shizhuang block, the CS can be set to approximately 15 m, and the CS can be appropriately reduced when the LPC is large.

Experimental and Numerical Investigation of Energy Evolution Characteristic of Granite considering the Loading Rate Effect

In order to investigate the loading rate effect of energy evolution in granite, the indoor physical simulation test of single face fast unloading-three directions and five faces stress-vertical continuous loading under different loading rates was conducted using a new true triaxial rockbursttest system. The energy accumulation-dissipation-release characteristics in the process of rock deformation and failure were revealed. Based on the three-dimensional discrete element theory and the polycrystalline modeling technique (randomly generated Voronoi mineral grains), the entire process of rockburst inoculation-occurrence-development, as well as the energy evolution characteristics under true triaxial single face unloading conditions, were studied. The test results indicate that the energy transport and conversion of rock samples under different loading rates exhibit distinct stage characteristics. It can be divided into the initial energy accumulation stage, steady energy accumulation stage, rapid energy dissipation stage, and rapid energy release stage. With a rise in loading rate, the specimen in the process of energy accumulation is accompanied by energy dissipation, more external input energy, and elastic strain energy release amount into the kinetic energy of fragments, resulting in the rockburst phenomenon. As the loading rate increases, the elastic strain energy conversion rate (Ue/U) falls, while the dissipative energy conversion rate (Ud/U) increases. The higher the elastic strain energy conversion rate and the lower the dissipative energy conversion rate, the more serious the rockburst occurs. Numerical simulation results show that the entire process of rockburst inoculation-occurrence-development is successfully simulated using the crystal scale fine model (CSFM) considering the grain mineral composition. The ejection failure process can be divided into four stages, including grains ejection, rock spalling into plates, rock shearing into fragments, and rock fragments ejection. The relationships between the peak strength, elastic strain energy of rock samples, and loading rates are obtained, which is consistent with the laboratory test results. The high rate linear growth of kinetic energy evolution between the two inflection points can provide precursor information for rockburst prediction.

Bloch oscillations and matter-wave localization of a dipolar quantum gas in a one-dimensional lattice

Three-dimensional quantum gases of strongly dipolar atoms can undergo a crossover from a dilute gas to a dense macrodroplet, stabilized by quantum fluctuations. Adding a one-dimensional optical lattice creates a platform where quantum fluctuations are still unexplored, and a rich variety of phases may be observable. We employ Bloch oscillations as an interferometric tool to assess the role quantum fluctuations play in an array of quasi-two-dimensional Bose-Einstein condensates. Long-lived oscillations are observed when the chemical potential is balanced between sites, in a region where a macrodroplet is extended over several lattice sites. Further, we observe a transition to a state that is localized to a single lattice plane–driven purely by interactions–marked by the disappearance of the interference pattern in the momentum distribution. To describe our observations, we develop a discrete one-dimensional extended Gross-Pitaevskii theory, including quantum fluctuations and a variational approach for the on-site wavefunction. This model is in quantitative agreement with the experiment, revealing the existence of single and multisite macrodroplets, and signatures of a two-dimensional bright soliton.

Study on mechanical maintenance method of ballasted track of high-speed railway based on nonlinear discrete element theory

Abstract To study the electrical performance of high-speed railway ballasted work and the long running and rotating characteristics of the bed, different design methods are adopted. The longitudinal and transverse resistance of the bed increases with the increase in the ballast grading width. When ballast particle gradation is the lowest interpolation between envelope line and envelope line boundary, the longitudinal and transverse resistance of the bed work according to special requirements. With the increase in the shoulder width, the transverse resistance of running bed increases, while the longitudinal resistance remains constant. When the shoulder width is more than 400 mm, the longitudinal and transverse resistance of the bed works according to the required specifications. Maintenance costs for the various ballasts running on high-speed trains are not cheap. The test results show that the workability can be reduced, and improved by using complete asphalt or stone instead of tussah. Daily cleaning work only accounts for about 10% of the tussah, especially emergency work and special riders should not spend time working. The rubber cushion in sleeper and asphalt concrete cushion in ballast have their advantages and disadvantages in improving the strength of bed. In fact, it should be stipulated in the case file.

Evaluation of the thermal performance of radiant floor heating system with the influence of unevenly distributed solar radiation based on the theory of discretization

Evaluation of the thermal performance of radiant floor heating system with the influence of unevenly distributed solar radiation based on the theory of discretization

Simulation Analysis of Cement-Stabilized Macadam Compaction Processing Based on the Discrete Element Method

The mechanical properties of cement-stabilized macadam (CSM) base mixture are closely related to its forming process. Although the present study investigates the macroscopic effects of molding on cement-stabilized macadam, mesoscopic research analyses of the internal composition’s structural characteristics and change trends after molding lack sufficient intuitiveness. In this study, we built three-dimensional models of cement-stabilized macadam for heavy compaction molding and vibration molding tests based on the discrete element theory. The effects of different molding methods on cement-stabilized macadam’s internal structure were revealed from the mesoscopic perspective by tracking changes in porosity, coordination number, force chain development and internal particle position during the simulation molding process. The simulation results show that (1) the first 10 compactions had a significant influence on the molding effect, and specimens’ height and porosity decreased the fastest; (2) after the simulation experiments, the average coordination number of particles in the vibration molding specimen was 2.3% higher than that of the heavy compaction molding specimen; (3) after the simulation experiments, the vibration molding specimen’s porosity was 2.5% lower than that of the heavy compaction molding specimen; and (4) the vibration molding specimen’s particle distribution was more uniform, whereas the heavy compaction molding specimen’s particle distribution was dense at the top and sparse at the bottom. Overall, the effect of vibration molding is superior to that of heavy compaction molding.

Effects of width-height ratio and roof-floor strength on the mechanical characteristics of cemented gangue backfill pier-column.

Cemented gangue backfill pier-column (CGBP) which was made of coal gangue, fly ash, cement, and water is the supporting component of the goaf in partial backfill mining or constructional backfill mining for controlling the surface subsidence of coal mining. The width-height ratio and roof-floor strength directly affect the bearing capacity of CGBP under axial compression, which is essential for the design of CGBP. Herein, the effect of width-height ratio (1:3-1:1) on the mechanical characteristics of CGBP with different curing ages under uniaxial compression was system studied through experiment, and the damage process was analyzed by ultrasonic equipment and DIC. Based on the experimental results and discrete element theory, a three-phase numerical model for CGBP was established, which considered the real aggregate shape and distribution and the mechanical characteristics of each phase. Then, the effects of the end friction coefficient and the strength ratio of roof-CGBP-floor combination on the strength and failure characteristics of CGBP (large width-height ratio: 1:1-4:1) were investigated. The results show that CGBP shows the width-height ratio effect obviously and the strength and ductility increase with the increase of the width-height ratio, and the width-height ratio effect increases with the increase of curing age and strength ratio. The end friction constraint is the main reason for the width-height ratio effect, and the higher the friction coefficient is, the larger the width-height ratio effect shows, and the width-height ratio effect disappears without end friction constraint. The increase of the width-height ratio of CGBP and the strength ratio of the roof-CGBP-floor combination increases the strength of the combination. Whether the strength of the combination is greater than that of CGBP may have a roof-floor strength threshold or a strength ratio threshold, which are between 31.44-54.11MPa and 3.75-6.44, respectively. When the strength of the roof and floor is different, the strength of the combination is mainly controlled by the weak carrier and increases with the increase of the strength of the weak carrier. The peak strain energy of CGBP and combination increases with the increase of end friction coefficient, width-height ratio, and strength of roof and floor. The experimental and simulation results can be used to guide the design of CGBP in constructional backfill mining or partial backfill mining.

What Makes You Proactive Can Burn You Out: The Downside of Proactive Skill-Building

It is generally assumed that proactivity at work is motivated by positive motivational states and has positive outcomes for employees. However, recent perspectives suggest a downside to proactive behavior, as it may be driven by negative emotions and experienced by employees as depleting. Building on self-determination and discrete emotions theories, we argue that perceived financial precarity starts a motivational chain that leads employees to proactively learn new skills out of fear, and that proactivity driven by precarity and fear creates feelings of burnout. We further argue that the effect of proactivity on burnout will be particularly strong for employees with high impression management motives. We test our hypotheses in a four-wave study of 1,315 employees at a large university in the United States during the COVID-19 pandemic, when employees’ concerns about their finances were heightened and many felt the need to learn new skills. Theoretically, our findings shed light on both the antecedents and consequences of the downside of proactivity. Practically, our findings help to understand both how employees proactively adapt to financial precarity and how those proactive efforts are experienced as draining.

Influences of car sharing and car license plate lottery policy on consumer preference and accessibility in urban mobility system: A stated choice experiment in Beijing

Sustainable mobility is critical to achieve sustainable development goals . Public policy makers worldwide have introduced different policy instruments to motivate sustainable mobility such as promoting car sharing and introducing car license plate lottery. Limited attention has been devoted to studying the effects of these types of policies on consumers' accessibility in urban mobility system, in particular when these policies are intended to achieve the same objective of promoting sustainable mobility. To fill this gap, based on the consumer discrete choice behavioral theory, this paper designs a stated choice experiment and performs discrete choice analysis to investigate how the interactions of these two policies influence consumers’ mobility preferences and consumer surplus-based accessibility. By collecting data in Beijing, as an empirical context, we identify a nested logit model with a hierarchical choice structure, where bus and underground fall in the nest of public transit , while car sharing, private car and taxi are independent alternatives. Consumers who are participating in the car license plate lottery are more likely to choose car sharing, and car sharing can largely compensate for the loss of accessibility caused by the car license plate lottery policy, which implies that car sharing and the car license plate lottery policy are indeed complementary policies. However, the introduction of car sharing can also lead to an unintended consequence of higher total car usage by attracting more public transit users who never intended to buy or drive cars. This study contributes to the literature by proposing and implementing a generic theoretical framework for analyzing consumer preference-based accessibility for developing a sustainable mobility system and provides important practical implications.