Single Ground Research Articles

Distributed relay protection for distribution network based on hybrid power method and current method

The distributed power supply is gradually connected to the distribution network, the original single power source radiant network pattern of the distribution network no longer exists. The topology of the distribution network is characterized by variable topology and multi-power supply, and the traditional fault detection and protection actions cannot adapt to the new distribution network topology. Based on failure probability of the highest single phase ground fault in distribution network by the power differential method and differential current method to deal with failure, installed the reclosing device, and through the simulink simulation, verify the effectiveness of the proposed scheme, can effectively deal with the distribution network fault, to deal with instant fault and permanent fault, effectively reduce misoperation. In this paper, the scheme of setting the setting value independently is adopted, which can quickly restore the power supply in non-fault area and improve the continuity of power supply. It has very broad engineering application scenarios.

Spinal fracture reveals an accident episode in Eremotherium laurillardi shedding light on the formation of a fossil assemblage

The Toca das Onças cave is one of the most important Quaternary mammal deposits of Brazil. Two different hypotheses have been proposed to explain the preservation mode of its skeletal remains: either the animals climbed down into the cave, or it could have functioned as a natural trap. Evaluation of pathological modifications on three articulated vertebrae of a single adult giant ground sloth Eremotherium laurillardi reveals a particular type of bone fracture caused by compressive force on the vertebral column, which split the vertebral bodies in the sagittal plane. This diagnosis suggests that the animal accidentally fell into the cave, in accordance with the second hypothesis proposed to the incorporation mode of skeletal remains into the cave.

Experimental study on compressive strength and frost resistance of steam cured concrete with mineral admixtures

The study of frost resistance and mechanical properties of steam cured concrete is helpful to understand the state of precast concrete elements in a complex environment. In this paper, the compressive strength of concrete under 10 working conditions, such as standard cured system, steam cured system, no mineral admixtures, single ground granulated blast furnace slag (GGBS) and fly ash (FA) mixed with GGBS, was tested at the age of 180d. It is found that the compressive strength of concrete under standard cured system is 4.71% to 18.46% higher than that under steam cured system, although steam cured improves the strength at the initial stage. The addition of FA and GGBS can make up 14% to 16% strength defects caused by steam cured system. The compressive strength of steam cured concrete (ZF40℃) is the highest when the steam cured temperature is 40℃ and the mixture ratio of FA and GGBS is 2:3. On this basis, the frost resistance of ZF40℃ specimens was studied. The results showed that the surface degradation degree of steam cured concrete gradually deepened with the increase of freeze–thaw (F-T) cycles, and the extracted surface roughness ranged from 0.066 ∼ 0.505 mm. The relative dynamic elastic modulus and mass loss rate decreased with the increase of F-T cycles, and the maximum loss rate were 69.4% and 1.41%, respectively. In addition, the compressive strength test, acoustic emission (AE) signal monitoring and acquisition of pore structure characteristics were carried out to understand the mechanical properties of steam cured concrete under F-T cycles conditions. The results show that the compressive strength decreases with the increase of F-T cycles, and the strength loss rate is within 10% per 50 cycles. The overall activity of AE signal decreases with the increase of F-T cycles, andthe damage form gradually changes from the initial tensile damage to the later shear damage. Porosity and pore size range basically increase with the increase of F-T cycles. Pore deterioration is the main reason for the decrease of compressive strength of steam cured concrete under F-T environment.

Probabilistic seismic analysis of bridges through machine learning approaches

Probabilistic seismic demands of bridge components such as bridge column and deck are conventionally expressed as a power-law function of a single ground motion intensity measure. This unidimensional probabilistic seismic demand model (PSDM) was introduced more than two decades ago, and since then, it was commonly used to estimate seismic demands. Over the recent years, an extensive body of research has been evolved to propose alternative PSDMs, but none has been proved to be dominantly superior over other approaches. There yet remains a milestone to enrich predictions provided by PSDMs and expanding their application beyond certain methodology, particular functional form, and corresponding assumptions on the distribution of the demands. Given the advancements in computational technologies which lead to the growth of diverse analytically-driven data, machine learning (ML) approaches have a tremendous potential to revolutionize predictions of seismic demands. This study presents a comprehensive appraisal of ML-based PSDMs to further expand the research advances in this domain and leverage the efficiency and advantages that ML methods offer compared to the unidimensional model. To this end, the efficiency of a variety of parametric and non-parametric ML algorithms with different degrees of flexibility are explored to estimate the demands associated with the primary bridge components. Moreover, by applying ML-based variable selection techniques, this study assesses the level of influence of the random variables on the generated PSDMs. These variables are used for the treatment of inherent uncertainties in material, geometric, structural, and ground motion parameters. As part of the appraisal, a ranking is provided for the investigated 39 models, such as Generalized Linear Models, Multi-order regressions, Bagging and Boosting, and Kernel-based models, according to their statistical performance in estimating the individual demands.

Dealing with Disagreements: Looking Beyond the Majority Vote in Subjective Annotations

AbstractMajority voting and averaging are common approaches used to resolve annotator disagreements and derive single ground truth labels from multiple annotations. However, annotators may systematically disagree with one another, often reflecting their individual biases and values, especially in the case of subjective tasks such as detecting affect, aggression, and hate speech. Annotator disagreements may capture important nuances in such tasks that are often ignored while aggregating annotations to a single ground truth. In order to address this, we investigate the efficacy of multi-annotator models. In particular, our multi-task based approach treats predicting each annotators’ judgements as separate subtasks, while sharing a common learned representation of the task. We show that this approach yields same or better performance than aggregating labels in the data prior to training across seven different binary classification tasks. Our approach also provides a way to estimate uncertainty in predictions, which we demonstrate better correlate with annotation disagreements than traditional methods. Being able to model uncertainty is especially useful in deployment scenarios where knowing when not to make a prediction is important.

Forecasting Geomagnetic activity (Dst Index) using the ensemble kalman filter

ABSTRACT A novel Ensemble Kalman Filter (EnKF) method is adopted to make reliable forecasts of geomagnetic activity (Dst index) for real-time applications. In this method, an educated estimate (forecast) of Disturbance storm time (Dst) is made based on the ring current dynamics like injection and decay rates. This estimated Dst is further updated with the assimilation of real-time Dst values or ∆H values from a single ground based magnetometer observations. The forecasted Dst values by this EnKF method are validated with the true Dst during the severely disturbed period that consists of 2 super (Dst< -250 nT), 8 intense (Dst< -100 nT), and 13 moderate geomagnetic storms (Dst< -50 nT). It is found that the EnKF method implemented in this work offers the best accurate forecast of Dst with a root mean square error (RMSE) and regression coefficient (R) of 4.3 nT and 0.99, respectively.

Analytical models for heat transfer around a single ground heat exchanger in the presence of both horizontal and vertical groundwater flow considering a convective boundary condition

Ground heat exchanges (GHEs) are widely applied in the ground source heat pump (GSHP) system for exploration of shallow geothermal energy. Heat transfer around a single GHE in the presence of both horizontal and vertical groundwater flow under a convective boundary condition is investigated. To describe the heat transfer process, three typical GHE models including the solid cylindrical heat source (SCS) model, the ring coil heat source (RCS) model and the finite line source (FLS) model are improved by incorporating the effect of horizontal and vertical groundwater flow and considering convection between the air and the ground surface. After introducing a new variable, analytical solutions for the three improved models are established using the Green's function method. Comparison between the analytical solution and a numerical solution of COMSOL is made, and the agreement between the two solutions confirms the derivation and programming process of the analytical solution. Effects of horizontal and vertical groundwater flow on the temperature increment caused by a SCS are investigated using the analytical solution. For situations with high velocities of horizontal groundwater flow, the curve relating the temperature increment and the depth has a depth-independent segment, and the temperature increment for locations near the mid-depth of heat source remains unchanged with the velocity of vertical groundwater flow changing; the variation of average temperature increment of pipe wall with the variation of vertical groundwater velocity is negligible. For situations with low velocities of horizontal groundwater flow (Pex = 10), strong vertical groundwater flow (Pez = 100) makes the aforementioned depth-independent segment disappear, and the temperature increment at a downstream location increases from 0.58 °C to 7.79 °C with the depth increasing from 0 to lc. With Pez increasing from 10 to 100, the average temperature increment of pipe wall decreases from 10.14 °C to 6.92 °C, which reduces the thermal resistance of ground and improves the economic performance of the GSHP system.

Study on the correlations of different clinical types with imaging findings at initial diagnosis and clinical laboratory indexes in COVID-19 patients.

Objectives:To investigate the correlations of initial lab and imaging findings in COVID-19 patients of different clinical types.Methods:We retrospective analyzed patients confirmed with COVID-19 in the Fifth Medical Center of the People’s Liberation Army (PLA) General Hospital between February to April 2020, selected a total of 58 (N) patients with lab and imaging examinations that met the study criteria, using Artificial intelligence (AI) software to calculate the percentage of COVID-19 lesions in the volume of the whole lung, then the correlations of general information, initial chest CT examination after admission and laboratory examinations were analyzed.Results:The 58 (N) COVID-19 patients were divided into mild group [41(n) cases]: and severe group [17(n) cases]: according to patient’s condition. CT findings of the severe group and mild group mainly included single or multiple ground glass opacity (GGO), with lesions mainly distributed in the periphery of lungs or GGO mixed with consolidation, with lesions involved in peripheral and central areas of both lungs, accompanied other signs. A significant difference in CRP, IL-6, D-D, GGT was observed between the two groups (p < 0.05). The ratios regarding lymphocyte abnormality and neutrophil abnormality in the severe group were higher than those in the mild group (p < 0.05).Conclusion:The CT features at initial diagnosis of COVID-19 were mainly characterized by multiple GGO with or without partial consolidation in both lungs, with the lesions mainly distributed at the subpleural regions. Some lab test indexes were correlated with the clinical types of COVID-19.

Single Channel SAR Ground Moving Target Detection Algorithm Based on Subband Interferometry

Traditional synthetic aperture radar (SAR) ground moving target detection (GMTD) technology mostly relies on multichannel data, which requires higher complexity of the radar system. This letter proposes a subband interferometry (SBI)-based algorithm for single-channel SAR GMTD. First, the echo signal is divided into high and low bands containing overlapping parts before the imaging process, then the subbands are imaged separately, and the SBI algorithm is used to achieve the interferometric phase of the subbands. It can be observed that the moving target has the characteristics of phase reversal in the interferometric phase image, and graphics operations such as median filtering or morphological processing can be used to detect the moving target. In this letter, the relationship between the subbands coincidence, the correlation coefficient (CC) of SBI, and the phase of moving target after SBI processing are derived. The real airborne SAR data verify the feasibility and effectiveness of the algorithm.

Chirp form selection to produce intense and broad harmonic spectra and attosecond pulses in the presence of single and superposition initial states

The chirp form selection for producing intense and broad high-order harmonic spectra has been investigated when the initial state is chosen to be the single or superposition states. It is found that, for the case of a single ground initial state, the down-chirp is much better for extending the harmonic cutoff with the stronger emission intensity. Moreover, the multi-color combined field is beneficial to produce the larger harmonic cutoff and higher harmonic intensity. After the control of laser waveform, the combination of 3-color down-chirps with a proper UV pulse is the best condition to obtain the intense X-ray spectral continuum and the isolated attosecond pulse. For the case of superposition initial state, both the up-chirp and down-chirp are beneficial to generate the high-intensity spectral regions. However, with the combination of multi-color field, only the harmonic cutoff can be further extended, and the harmonic intensity presents almost no changes for the superposition initial state case. Finally, by properly choosing the 3-color up-chirps or 3-color down-chirps combined pulses, the stronger intensity harmonic spectra covering the X-ray region can be obtained, which can produce the isolated pulses of 37 as.

Antiferromagnetic Ordering and Uncoupled Spins in CaFe2O4 Thin Films Probed by Spin Hall Magnetoresistance

AbstractCaFe2O4 is a uniaxial antiferromagnet displaying two coexisting magnetic orderings, A and B, characterized by ↑↑↓↓ and ↑↓↑↓ spin modulation, respectively, and the emergence of a net magnetization in a limited temperature range, which is not yet understood. The spin Hall magnetoresistance (SMR) is probed at the interface between Pt and CaFe2O4 and the crystallographic domain structure of thin film samples is exploited to perform single‐ and multi‐domain scale measurements. The SMR response, upon rotating the magnetic field along three orthogonal planes, shows little effect of the strong magnetocrystalline and shape anisotropies. Together with the response to a varying magnetic field strength, the modulations in the SMR signal allow to extract two contributions: one corresponds to the long‐range antiferromagnetic ordering, supporting a single ground state scenario; while the second contribution originates from uncompensated, non‐interacting spins. These are expected to exist at the antiphase boundaries between antiferromagnetic domains. Here, it is shown that these are also uncoupled from the antiferromagnetic ordering. Nonetheless, the long range correlations that emerge in the proximity of the critical antiferromagnetic transition can give rise to ordering of the uncompensated spins and be responsible for the net magnetization observed in this antiferromagnet.

Novel Methodology for Sizing a Single U-Tube Ground Heat Exchanger Useful at the Early Design Stage

Renewable energy system (RES) is an environmentally friendly source of energy. A suitable design of RES is crucial to implement an energy-efficient building such as a zero energy building (ZEB). The significance of appropriate decision-making for the successful implementation of energy-efficient buildings has been increasing. In addition, the identification of the sizing of RES is equally important for architects or HVAC engineers. In this study, a novel sizing method for a single U-tube ground heat exchanger (GHE) is proposed. A transient thermal analysis for a single GHE is performed by considering ground temperature recovery effect as well as other major design parameters. The results are used to design the proposed sizing method and were verified by transient simulations for different design cases. Additionally, it was observed that the coefficient of variation of root mean square error (CV(RMSE)) for all ten design cases was lower than 15% during the heating and cooling seasons. Thus, the proposed design method can be used for sizing a GHE in the early design stage.

Key Trends Regarding the Effects of Site Geometry on Lateral Spreading Displacements

Nonlinear, effective stress finite-element analyses are used to model earthquake-induced displacements at lateral spread sites near a free face. The numerical analyses consist of 132 models with model geometries selected to isolate the influence of the height of the free face, the thickness of liquefiable layers, sloping ground behind the free face, and the presence of a topographic terrace on lateral spread displacement patterns. Each model is analyzed in the context of how the geometric factors influence the maximum horizontal displacement, the inland extent of displacements, and the shape of the displacement profile between the free face and the inland extent. For sites with flat ground behind the free face and with no terrace present, the dominant factor controlling the displacement pattern is the combined thickness of the free face and underlying liquefiable soil. Lateral spread displacements are significantly affected by the presence of sloping ground behind the free face, with the inland extent affected more significantly than the maximum displacement. The presence of a topographic terrace several hundred meters from a free face can increase appreciably the displacements in the area between the free face and terrace. A bilinear surface model is proposed as a framework for predicting displacement patterns at a free-face lateral spread site and used to model the displacements from the numerical simulations. The observations in this study are based only on a single input ground motion, but the framework can be extended with additional analyses utilizing a range of earthquake ground motions.

Design and Simulation of Smart Communication System for Unmanned Arial Vehicles

In recent years, the use of drones has drastically increased as the evolution of drone use in commercial sectors and reduced costs of the hardware. Earlier drone services were mostly used for military operations but nowadays the Unmanned Arial Vehicles (UAV) system is very advanced and its applications are not limited to military operations. The recent years have also witnessed a network evolution of UAVs from single ground to air network to multi-UAV network systems along with usage of wireless public networks like LTE which can act as UAV communication channel. In the proposed project, a communication system used in the UAS system is simulated to analyze the UAV behavior under different conditions with respect to mission planning and the communication networks used. A comprehensive study is done on communication networks used in controlling UAVs. For a safer approach, the proposed model is simulated using available software instead of hardware implementations. ArduPilot SITL, MAVProxy and Mission Planner are used to simulate the UAV system virtually. Whereas network simulations of Wi-Fi and LTE network are done with the help of NS-3 on a separate platform. Various network parameters like network delay, throughput, etc., are graphically represented.

Dual Symmetrical Slots Single Slit Partial Ground Dual Notch Rectangular Monopole Microstrip Antenna for Broadband Applications

The worldwide wireless communication technology’s rapid growth requires broadband antennas with multiple applications simultaneously for various applications such as television, mobile phones, GPS, Wi-Fi and 4G. The design and development of Microstrip Antenna Technology fulfills these features. A simple compact Dual Symmetrical Slots Single Slit Partial Ground Dual Notch Rectangular Monopole Microstrip Antenna is designed and proposed for Broad Band Applications in this paper. The proposed antenna is fabricated on modify Epoxy substrate material of εr = 4.2, h=1.6mm at 3 GHz of dimension 50X50 mm2. The impedance bandwidth covers the range from 1.15-8.12 GHz with respective bandwidth of 150.30% for the magnitude of return loss&lt;-10dB and VSWR&lt;=2 with multiple resonant frequencies..The designed and proposed antenna has nearly omnidirectional radiation pattern and maximum gain at 4GHz. The Proposed antenna is most suitable for wireless communications including ISM (2.4-2.5 GHz)/ (6.765-6.795GHz), WLAN IEEE 802.11 g/a (5.15-5.35 GHz and 5.725-5.825 GHz) and C Band (4-8 GHz) applications.

Thermal performance of a single U-tube ground heat exchanger: A parametric study

Thermal performance of a single U-tube ground heat exchanger: A parametric study

Impact of 3D radiative transfer on airborne NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; imaging remote sensing over cities with buildings

Abstract. Airborne imaging remote sensing is increasingly used to map the spatial distribution of nitrogen dioxide (NO2) in cities. Despite the small ground-pixel size of the sensors, the measured NO2 distributions are much smoother than one would expect from high-resolution model simulations of NO2 over cities. This could partly be caused by 3D radiative transfer effects due to observation geometry, adjacency effects and effects of buildings. Here, we present a case study of imaging a synthetic NO2 distribution for a district of Zurich using the 3D MYSTIC (Monte carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres) solver of the libRadtran radiative transfer library. We computed NO2 slant column densities (SCDs) using the recently implemented 3D-box air mass factors (3D-box AMFs) and a new urban canopy module to account for the effects of buildings. We found that for a single ground pixel (50 m × 50 m) more than 50 % of the sensitivity is located outside of the pixel, primarily in the direction of the main optical path between sun, ground pixel, and instrument. Consequently, NO2 SCDs are spatially smoothed, which results in an increase over roads when they are parallel to the optical path and a decrease otherwise. When buildings are included, NO2 SCDs are reduced on average by 5 % due to the reduced sensitivity to NO2 in the shadows of the buildings. The effects of buildings also introduce a complex pattern of variability in SCDs that would show up in airborne observations as an additional noise component (about 12 µmol m−2) similar to the magnitude of typical measurement uncertainties. The smearing of the SCDs cannot be corrected using 1D-layer AMFs that assume horizontal homogeneity and thus remains in the final NO2 map. The 3D radiative transfer effects by including buildings need to be considered to compute more accurate AMFs and to reduce biases in NO2 vertical columns obtained from high-resolution city-scale NO2 remote sensing.

Single line to ground fault detection and location in medium voltage distribution system network based on neural network

&lt;p&gt;The aim of this project was to detect and locate the single ground failure lines that occurs in medium voltage (MV) networks on the transmission lines (TL). Compared with anther faults, single line-to-ground (SLG) is the most frequent. The neural network (NN) algorithm was advanced in order to discover and locate SLG faults. The network is simulated through simulated numerous defects at various locations, as well as changing earth resistance from (or 100 Ω) to TL to gather all of the data. In the electromagnetic transients’ program (EMTP) program software, the existing fault have been measured. In addition, the waves were evaluated by utilize MATLAP's fastfourier-transform to calculate the waves of top three of them, On the MV network are fifty hundred faults are simulated all data in the neural network at MATLAB were trained and examined to improve the NN algorithm according to this data. Comparing all the simulated location faults that have been applied with those all locations detected in the NN algorithm, the overall error between them has been found to be very low and not to exceed 0.7. The Simulink circuit was created from this algorithm and checked in order to predict each failure could occur in the future in the MV network.&lt;/p&gt;

Retrieving Doppler Frequency via Local Correlation Method of Segmented Modeling

The high accuracy radio Doppler frequency is critical for navigating a deep space probe and for planetary radio science experiments. In this paper, we propose a novel method based on the local correlation of segmented modeling to retrieve Doppler frequency by processing an open-loop radio link signal from one single ground station. Simulations are implemented, which prove the validity of this method. Mars Express (MEX) and Tianwen-1 observation experiments were carried out by Chinese Deep Space Stations (CDSS). X-band Doppler frequency observables were retrieved by the proposed method to participate in orbit determination. The results show that the accuracy of velocity residuals of orbit determination in open-loop mode is from 0.043 mm/s to 0.061 mm/s in 1 s integration; the average accuracy of Doppler frequency is about 3.3 mHz in 1 s integration and about 0.73 mHz in 60 s integration. The Doppler accuracy here is better than that of the digital baseband receiver at CDSS. The algorithm is efficient and flexible when the deep space probe is in a high dynamic mode and in low signal to noise ratio (SNR). This will benefit Chinese deep space exploration missions and planetary radio science experiments.

Formation control of nonholonomic unmanned ground vehicles via unscented Kalman filter-based sensor fusion approach

This paper investigates the formation control of nonholonomic unmanned ground vehicles via unscented Kalman filter-based sensor fusion approach. According to the kinematic model of single unmanned ground vehicle, the formation model of multiple unmanned ground vehicles is established. Note that the physical leader is considered instead of a virtual leader, which is more realistic. The formation control problem is converted to the stability problem of an error dynamic system. An asymptotic stability condition of the error dynamic system is derived by designing an appropriate Lyapunov function. The leader-following formation is well formed through designing effective control vectors and utilizing unscented Kalman filter-based state estimation algorithm for each follower. Some simulation examples are provided to verify the effectiveness of the proposed formation control algorithm.