Static Distribution Research Articles

Local biodiversity change reflects interactions among changing abundance, evenness, and richness.

Biodiversity metrics often integrate data on the presence and abundance of multiple species. Yet our understanding of covariation between changes to the numbers of individuals, the evenness of species relative abundances, and the total number of species remains limited. Using individual-based rarefaction curves, we show how expected positive relationships among changes in abundance, evenness and richness arise, and how they can break down. We then examined interdependencies between changes in abundance, evenness and richness in more than 1100 assemblages sampled either through time or across space. As predicted, richness changes were greatest when abundance and evenness changed in the same direction, and countervailing changes in abundance and evenness acted to constrain the magnitude of changes in species richness. Site-to-site differences in abundance, evenness, and richness were often decoupled, and pairwise relationships between these components across assemblages were weak. In contrast, changes in species richness and relative abundance were strongly correlated for assemblages varying through time. Temporal changes in local biodiversity showed greater inertia and stronger relationships between the component changes when compared to site-to-site variation. Overall, local variation in assemblage diversity was rarely due to repeated passive samples from an approximately static species abundance distribution. Instead, changing species relative abundances often dominated local variation in diversity. Moreover, how changing relative abundances combined with changes to total abundance frequently determined the magnitude of richness changes. Embracing the interdependencies between changing abundance, evenness and richness can provide new information to better understand biodiversity change in the Anthropocene.

Inhibition mechanism of static pressure circumferential double-peak distribution using a recirculation device for a centrifugal compressor

The asymmetric volute structure in the turbocharger centrifugal compressor causes a static pressure circumferential double-peak distribution (PD-DP) at small flow rates and affects the circumferential stall position near the impeller inlet. In this study, a recirculation device was added to a prototype compressor, and the effect of the recirculation flow on the PD-DP was studied to reveal the difference in the PD-DP formation mechanism with and without the device. In addition, the influence of the PD-DP difference on the compressor flow stability was investigated. The results show that the PD-DP generated various pressure gradients between the front and rear slots of the recirculation device at different circumferential positions, resulting in a double-peak distribution in the recirculation flow rate. When the recirculation airflow flowed back into the impeller inlet, the two recirculation flow rate peaks were near the circumferential positions occupied by the two static pressure peaks in the prototype compressor. Therefore, the pressure distortion degree near the impeller inlet could be inhibited, weakening the difference in the deflection degree of the tip leakage flow (TLF) in each compressor passage. It should be noted that the circumferential positions with more prominent variation in the TLF corresponded to the passages with more serious flow deterioration in the prototype compressor, and the blockage of these passages near the inlet was reduced to a greater extent, which could better improve the flow stability of the compressor.

Effects of electric field and anisotropy on the mass-radius relationship of a particular class of compact stars

For a static, spherically symmetric, anisotropic and charged distribution of matter, we present a new class of exact solutions to the Einstein-Maxwell system. By assuming specific forms of the electric field and anisotropy, we transform the master equation of the Einstein-Maxwell system to Bessel and modified Bessel differential equations. The subsequent solutions turn out to be generalizations of the isotropic and uncharged stellar model of Finch and Skea (1989), the isotropic and charged stellar model of Hansraj and Maharaj (2006) and the anisotropic and charged stellar model of Maharaj et al. (2017). We analyze the physical viability of the solutions and utilize one particular class of solutions to examine the effects of charge and anisotropy on the mass-radius relationship of compact stars.

Controlled synthesis of hierarchical tungsten oxide hydrates for efficient acetone detection

The detection of acetone is of great significance for environmental safety and human health. Micromorphology control is a feasible pathway to obtaining excellent gas-sensitive materials. In this study, three types of hierarchical WO3·H2O, including nanoplates, hollow spheres and nanospheres, were controlled synthesis by a simple hydrothermal method. Their morphologies and growth mechanisms were studied by various characterization methods, and their acetone sensing performances were tested via a static distribution method. The results indicate that the sensor based on the hierarchical WO3·H2O hollow spheres exhibits higher sensitivity, better selectivity and faster response speed towards acetone than two other morphologies at the optimum operating temperature (300 ℃). Specifically, the response value reaches 21.4–50 ppm acetone, and the response/recovery times are 3.6 s/6.0 s. The superior performance and fast response characteristics of the hollow WO3·H2O are mainly attributed to its high specific surface area, unique pore structure, abundant surface active sites, and suitable energy level structure. This work enlightens some thoughts on the functionalization of tungsten-based gas sensors and efficient detection of acetone.

Dynamic Relief Items Distribution Model with Sliding Time Window in the Post-Disaster Environment

In smart cities, relief items distribution is a complex task due to the factors such as incomplete information, unpredictable exact demand, lack of resources, and causality levels, to name a few. With the development of Internet of Things (IoT) technologies, dynamic data update provides the scope of distribution schedule to adopt changes with updates. Therefore, the dynamic relief items distribution schedule becomes a need to generate humanitarian supply chain schedules as a smart city application. To address the disaster data updates in different time periods, a dynamic optimised model with a sliding time window is proposed that defines the distribution schedule of relief items from multiple supply points to different disaster regions. The proposed model not only considers the details of available resources dynamically but also introduces disaster region priority along with transportation routes information updates for each scheduling time slot. Such an integrated optimised model delivers an effective distribution schedule to start with and updates it for each time slot. A set of numerical case studies is formulated to evaluate the performance of the optimised scheduling. The dynamic updates on the relief item demands’ travel path, causality level and available resources parameters have been included as performance measures for optimising the distributing schedule. The models have been evaluated based on performance measures to reflect disaster scenarios. Evaluation of the proposed models in comparison to the other perspective static and dynamic relief items distribution models shows that adopting dynamic updates in the distribution model cover most of the major aspects of the relief items distribution task in a more realistic way for post-disaster relief management. The analysis has also shown that the proposed model has the adaptability to address the changing demand and resources availability along with disaster conditions. In addition, this model will also help the decision-makers to plan the post-disaster relief operations in more effective ways by covering the updates on disaster data in each time period.

Stochastic Optimization with Decision-Dependent Distributions

Stochastic optimization problems often involve data distributions that change in reaction to the decision variables. This is the case, for example, when members of the population respond to a deployed classifier by manipulating their features so as to improve the likelihood of being positively labeled. Recent works on performative prediction identify an intriguing solution concept for such problems: find the decision that is optimal with respect to the static distribution that the decision induces. Continuing this line of work, we show that, in the strongly convex setting, typical stochastic algorithms—originally designed for static problems—can be applied directly for finding such equilibria with little loss in efficiency. The reason is simple to explain: the main consequence of the distributional shift is that it corrupts algorithms with a bias that decays linearly with the distance to the solution. Using this perspective, we obtain convergence guarantees for popular algorithms, such as stochastic gradient, clipped gradient, prox-point, and dual averaging methods, along with their accelerated and proximal variants. In realistic applications, deployment of a decision rule is often much more expensive than sampling. We show how to modify the aforementioned algorithms so as to maintain their sample efficiency when performing only logarithmically many deployments. Funding: This work was supported by the Division of Computing and Communication Foundations [Grant 1740551] and Division of Mathematical Sciences [Grant 1651851].

Mobile impurity in a one-dimensional gas at finite temperatures

We consider the McGuire model of a one-dimensional gas of free fermions interacting with a single impurity. We compute the static one-body function and momentum distribution of the impurity at finite temperatures. The results involve averages over Fredholm determinants that we further analyse using the effective form factors approach. With this approach, we derive the large-distance behaviour of the one-body function, which takes the form of an averaged exponential decay. This method allows us to study an experimentally important regime of small momenta of the impurity's momentum distribution. We also consider the one-body function at short distances and compute finite temperature Tan's contact.

Fluid Energy Conversion Analysis in Hydraulic Channels of reactor coolant pump under flow coastdown transient

Conversion between dynamic energy and static pressure energy is complex in reactor coolant pump (RCP) hydraulic channel in nuclear plant station, especially under flow coastdown transient. The performance was calculated by numerical simulation. The performance of RCP under flow coastdown is studied, and the energy conversion characteristics of hydraulic components are analyzed. The results investigated show that with increasing of coastdown time head loss decreases sharply from coastdown starting. After the coastdown time of 10 s, the head loss in the channel of impeller, guide vane and volute decrease to 50% below. In the process of coastdown, dynamic pressure head of the inlet flow domain drops rapidly from 6.8 m, and finally decreases to 0 m, while static pressure head gradually increases from −7 m, and closes to 0 m after coastdown time is 140 s. When coastdown starts, dynamic energy above 24.33 m is mainly distributed at the outlet of impeller, the inlet of guide vane and the outlet of volute. When t= 110 s, the dynamic energy in most area is below 12.17 m, and when t= 200 s, the dynamic energy is small, distributed in the range of 0 m∼6.08 m. With coastdown time increasing the dynamic energy on pressure and suction surfaces of impeller and guide vane blade decreases. At t= 90 s, dynamic energy is lower at leading edge of blade than that at trailing of impeller blade, and the maximum energy of guide vane blade is located at the root of leading edge. As the coastdown time increases, static pressure energy of RCP inlet flow domain and impeller inlet continues to increase, while the larger static pressure energy distribution area in the volute gradually decreases.

The Identification and Reservoir Architecture Characterization of Wandering Braided River in Nanpu 1-29 Area, Bohai Bay Basin

Nanpu 1-29 Area of Jidong Oilfield in China is currently in the stage of high water cut and low recovery degree. The remaining oil development and adjustment are difficult because of the complex reservoir heterogeneity and the lack of analysis of the reservoir architecture due to the unclear river type. This study first used sedimentary background, granularity, core, and sand body distribution to determine the river type and believed it belongs to the wandering braided river. Combined with core and logging data, four types of sedimentary architectural elements were found in the study area, namely, channel bar, braided channel, floodplain, and basalt. Based on the scale measurement of many similar modern wandering braided rivers, core data, and empirical formulas, the scales of the braided rivers were determined. The quantitative relationships among the scale of the braided river, the channel bar, and the braided channel were established. With this constraint, the reservoir architecture was anatomized. The results showed two filling types of the braided channels, including sandy filling and muddy filling. The combination patterns of the channel bars and the braided channels could be divided into three types, namely, superimposed, standalone, and contact, and the contact type was the primary type. On the whole, it showed the geometric morphological characteristics of the flat top convex at the bottom of the channel bar and the flat bottom convex at the top of the braided river channel. A careful measure of the architectural element was executed. The length of the single braided flow belts was 365.16-1349.72 m, and the width was 270.57-1160.54 m. The channel bar’s length was distributed 158.89-318.32 m, and the width was distributed 75.97-116.41 m. The braided river’s width was distributed 16.81-180.05 m. The length and width ratio of the channel bar was concentrated between 2 and 4, which manifested wide bar and narrow river channel mode. Finally, the static distribution model and dynamic response curve were compared to verify the correctness of the reservoir architecture characteristics to guide the subsequent development of the oilfield.

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research, mechanical stress, static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented. The kinematic relations are developed based on higher-order sinusoidal shear deformation theory. Thickness stretching formulation is accounted for more accurate analysis. The total transverse deflection is divided into bending, shear and thickness stretching parts in which the third term is responsible for change of deflection along the thickness direction. The axisymmetric formulations are derived through principle of virtual work. A parametric study is presented to investigate variation of stress and strain components along the thickness and longitudinal directions. To explore effect of thickness stretching model on the static results, a comparison between the present results with the available results of literature is presented. As an important output, effect of micro-scale parameter is studied on the static stress and strain distribution.

Response of rigid circular plate in a functionally graded transversely isotropic, half-space under horizontal steady-state excitation

In this paper, a theoretical formulation for lateral translation and impedance function of a rigid foundation in a transversely isotropic functionally graded (TIFG) half-space is presented. Accordingly, the medium is considered linear elastic and the elastic constants of materials vary exponentially along the depth for considering the effect of elastic non-homogeneities. The relax treatment of mixed boundary value problem is formulated by integrating the transformed kernels of Green’s functions over the foundation area with unknown surface traction function, which can be reduced into a Fredholm integral equation. The results represent the impact and treatment of frequency and material anisotropy through the medium. In addition, static and dynamic distribution of tangential shear stress over the foundation for surface and embedded disk extracted and the cutoff frequency is found out explicitly. The proposed solution gives exact concurrence with accessible literature.

Experimental Study of Modal Characteristics for Heated Composite Structures

Aircrafts with high Mach speeds are exposed to severe thermal load, which affect the performance of aircraft components. Although several experimental studies have been performed on the mechanical behavior of aircraft structures subjected to high temperatures, the experimental research on dynamic characteristics of structures under thermal load is limited. In this work, a series of laboratory modal tests have been carried out on carbon fiber reinforced silicon carbide matrix (C/SiC) composite plates under various radiant-heating conditions. High temperatures are achieved using quartz lamps, and their dynamic responses are measured using a scanning laser vibrometer. The modal parameters are evaluated by PolyMAX at several static temperature distributions. The temperatures are acquired by both full-field noncontacting infrared thermography and contacting thermocouples. The flat plates are with both free and constrained boundary conditions and the high temperature modal survey are performed for two kinds of thickness. The stiffened plate with free boundary condition is further studied as a more practical structure. Both the changes of the modal frequency and modal shape as temperature rises are presented. The effects of the thermal loads on the modal characteristics are investigated by test. The results show that the thermal stresses have a much greater effect on the modal characteristics than the change of the material properties due to heating. The test results could provide technical material for the limited database of high-temperature modal testing results.

Visualizing the Surface Photocurrent Distribution in Perovskite Photovoltaics

Defect states play an important role in the photovoltaic performance of metal halide perovskites. Particularly, the passivation of surface defects has made great contributions to high-performance perovskite photovoltaics. This highlights the importance of understanding the surface defects from a fundamental level by developing more accurate and operando characterization techniques. Herein, a strategy to enable the surface carriers and photocurrent distributions on perovskite films to be visualized in the horizontal direction is put forward. The visual image of photocurrent distribution is realized by combining the static local distribution of carriers provided by scanning near-field optical microscopy with the dynamic transporting of carriers achieved via a scanning photocurrent measurement system. Taking a surface passivated molecule as an example, a comprehensive defect scene including static and dynamic as well as local and entire conditions is obtained using this strategy. The comprehensive analysis of the trap states in perovskite films is pioneered vertically and horizontally, which will powerfully promote the deep understanding of defect mechanisms and carrier behavior for the goal of fabricating high-performance perovskite optoelectronic devices.

4D marine conservation networks: Combining 3D prioritization of present and future biodiversity with climatic refugia.

Given the accelerating rate of biodiversity loss, the need to prioritize marine areas for protection represents a major conservation challenge. The three-dimensionality of marine life and ecosystems is an inherent element of complexity for setting spatial conservation plans. Yet, the confidence of any recommendation largely depends on shifting climate, which triggers a global redistribution of biodiversity, suggesting the inclusion of time as a fourth dimension. Here, we developed a depth-specific prioritization analysis to inform the design of protected areas, further including metrics of climate-driven changes in the ocean. Climate change was captured in this analysis by considering the projected future distribution of >2000 benthic and pelagic species inhabiting the Mediterranean Sea, combined with climatic stability and heterogeneity metrics of the seascape. We identified important areas based on both biological and climatic criteria, where conservation focus should be given in priority when designing a three-dimensional, climate-smart protected area network. We detected spatially concise, conservation priority areas, distributed around the basin, that protected marine areas almost equally across all depth zones. Our approach highlights the importance of deep sea zones as priority areas to meet conservation targets for future marine biodiversity, while suggesting that spatial prioritization schemes, that focus on a static two-dimensional distribution of biodiversity data, might fail to englobe both the vertical properties of species distributions and the fine and larger-scale impacts associated with climate change.

Prediction Based Semi-Supervised Online Personalized Federated Learning for Indoor Localization

Fingerprint-based indoor localization has drawn increasing attention with the development of deep learning. Nevertheless, it faces challenges from frequent data collection and the corresponding exposure of privacy. Federated Learning (FL) is introduced into indoor localization recently for overcoming these challenges. However, most of the current FL-based indoor localization studies only focus on the static data distributions and ignore the fact that users have their preferred localization requirements. In this paper, two typical indoor localization scenarios are considered. Clients with various localization demands and data distributions collect online unlabeled data in Scenario I. For Scenario II, only one requesting user (RU) with high mobility applies for the localization service. A Prediction based Semi-supervised Online Personalized Federated Learning (PSO-PFL) is proposed for addressing these problems in the two scenarios. Experiments are conducted based on two real-world datasets. The experiment results show that PSO-PFL achieves higher personalization accuracy than centralized training and Federated Averaging, and utilizes unlabeled data efficiently. The strategy of selecting clients via prediction achieves higher accuracy than the random selection strategy. In brief, the proposed methods protect users’ privacy via FL. And the challenges of dynamical and heterogeneous stream data in indoor localization are addressed by the proposed methods which provide better personalization localization service for users than baseline methods.

A Sensitivity Study of the Thermal Tides in the Venusian Atmosphere: Structures and Dynamical Effects on the Superrotation

AbstractIn order to resolve discrepancy between recent observational and numerical studies on the thermal tides in the Venusian atmosphere, we investigated by means of a general circulation model how the thermal tides are affected by the static stability in and above the upper cloud layer by using three different distributions of the static stability. The results show that the vertical structure of the semidiurnal tide, which propagates vertically, is strongly affected by the static stability. The diurnal tide, which has an equivalent barotropic structure in 62–73 km altitudes, becomes weaker with the higher static stability although its vertical structure is almost unchanged. The horizontal distribution of the thermal tides with the realistic static stability distribution, which is consistent with radio occultation measurements, agrees with the observations at the cloud top. The meridional angular momentum flux associated with the thermal tides is equatorward in low latitudes near the altitude where the equatorial zonal‐mean wind takes its maximum. This result is consistent with the recent Akatsuki UVI observations, suggesting that the thermal tides could contribute to the maintenance of the superrotation in the equatorial region near the cloud top. In the most realistic case, the zonal‐mean zonal wind is effectively accelerated at rates of 0.2–0.5 m s−1 day−1 in low latitudes at altitudes of 52–76 km by both the meridional and vertical angular momentum transports. The thermal tides also induce significant meridional heat flux, which cannot be ignored in the dynamical effect on the zonal‐mean zonal wind.

Anisotropic viable solutions of stellar structures in modified teleparallel gravity

The commitment behind this work is to find the solutions of compact stellar models by using the spherically symmetric static space-time and anisotropic matter distribution in the framework of [Formula: see text] gravity. In this study, we used the new type of metric functions [Formula: see text] and evaluated other functions [Formula: see text] by the well-known Karmarkar condition. In this work, we use the rotated and spinning tetrad named as off-diagonal and most generic function of [Formula: see text] gravity. We find the strange stellar solutions by incorporating the MIT bag equation of state [Formula: see text] to evaluate cosmological constant. Aiming at the simplicity of solutions we utilize the given data for masses and radii of compact objects PSR J1416-2230, 4 U 1608-52, Cen X-3, EXO 1785-248, SMC X-1. By graphical presentation of the core properties of compact models, we show by concluding that our solutions are graphically fit and physically admissible and interesting by having the compatibility with the compact stars study.

Determination of the Required Air Exchange on a Metro Line with a Double-Track Tunnel

The paper investigates the air distribution in the subway tunnel ventilation network with a double-track tunnel, depending on the length of the line under study. The study of static air distribution was carried out in the analytical complex of designing ventilation, air treatment and air conditioning systems of mining enterprises based on the contour flow method. It is shown that when the number of runs on the line is more than two, the provision of air exchange is carried out by the same fans in any mode of operation of tunnel ventilation. At the same time, the maximum parameters of the fans in the normal operation of tunnel ventilation are: 73.8 m/s capacity and 684 Pa pressure, and in emergency mode: 66 m/s capacity and 843 Pa pressure.

Study on Mechanism of Rock Burst in Horizontal Section Mining of a Steeply Inclined Extra-Thick Coal Seam

Abstract With the increase of mining depth, rock burst disasters frequently occur in steeply inclined coal seams. Firstly, this paper analyzes the rock burst of 5521-20 working face in Yaojie No. 3 coal mine and summarizes the characteristics of rock burst in horizontal section mining of steeply inclined extra-thick coal seam (SIETCS). Then, the static load distribution characteristics and the influence of dynamic load in the horizontal section mining of SIETCS are systematically studied by combining theoretical analysis with numerical simulation. On this basis, the mechanism of rock burst in horizontal section mining of SIETCS is put forward, verified by actual measurement. The results show that the SIETCS is “clamped” under the combined action of the same change trend of roof and floor. The maximum principal stress peak values on the roof and floor sides reach 22.0 MPa and 20.5 MPa. The maximum shear stress earned 8.7 MPa and 8.4 MPa, which makes the shear stress concentration in the coal body high and tends to “shear dislocation.” Under this “shear-clamping” action, an approximate “trapezoidal” plastic zone and a “rectangular” stress concentration zone are formed under the section. With the increase of mining depth, the “shear-clamping” action of SIETCS becomes more and more intense. When the roof cantilever reaches the ultimate span and breaks, the intense dynamic load increases the shear stress and failure of coal, which is easy to induce rock burst. The superimposed load greatly affects the area from the roof side to the middle of the working face, and the rock burst is intense. The rock burst is weak on the floor side due to the pressure relief of the surrounding plastic zone. The monitoring results show that the supports pressure and MS events activity on the roof side and near the middle part of the working face is considerable, while the floor side is opposite, which verifies the research results.

A New Approach to the Optimal Placement of the Viscous Damper Based on the Static Force Distribution Pattern

Viscous dampers (VDs) are currently used an effective earthquake risk reduction measure. Due to the high cost of this type of dampers, an optimal damper layout across the stories will specifically improve the seismic response and reduce building costs. This paper introduces a new simple three-stage method to determine the optimal placement of VDs on different stories of reinforced concrete structures. In the first stage, the damping demand of each story was determined using the distribution pattern of earthquake forces by the equivalent static method and the story velocity obtained through time-history analysis. In the second stage, the number of dampers required for the structure was calculated, and the location and damping percentage of dampers were precisely determined through an iterative process in the third stage. An indicator representing all basic structural responses was used to evaluate the multiple choices for the damper layout. This process was evaluated for 4, 8 story concrete frames under a near-field earthquake. The results indicated the efficiency of the proposed method in determining the location and damping of VDs on different stories of the structure.