bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the axisymmetric metric generated by a rotating perfect fluid with the vacuum boundary
Authors: Makino Tetu 
Published: May 2021

Abstract
We consider the equations for the coefficients of stationary rotating axisymmetric metrics governed by the Einstein–Euler equations, that is, the Einstein equations together with the energy–momentum tensor of a barotropic perfect fluid. Although the reduced system of equations for the potentials in the co-rotating co-ordinate system is known, we derive the system of equations for potentials in the so called zero angular momentum observer co-ordinate system. We newly give a proof of the equivalence between the reduced system and the full system of Einstein equations. It is done under the assumption that the angular velocity is constant on the support of the density. Also the consistency of the equations of the system is analyzed. On this basic theory we construct on the whole space the stationary asymptotically flat metric generated by a slowly rotating compactly supported perfect fluid with vacuum boundary.
Classical and quantum exact solutions for a FRW in chiral like cosmology
Authors: Socorro J , Pérez-Payán Sinuhé , Hernández-Jiménez Rafael , Espinoza-García Abraham , Díaz-Barrón Luis Rey 
Published: May 2021

Abstract
In this work, first, we study a flat Friedmann–Robertson–Walker Universe with two scalar fields but only one potential term, which can be thought as a simple quintessence plus a K-essence model. Employing the Hamiltonian formalism we are able to obtain the classical and quantum solutions. The second model studied, is also a flat Friedmann–Robertson–Walker Universe with two scalar fields, with the difference that the two potentials are considered as well as the standard kinetic energy and the mixed term (chiral field approach). Regarding this second model, it is shown that setting to zero the coefficient accompanying the mixed momenta term, two possible cases can be studied: a quintom like case (

m

+

12

) and a quintessence like case (

m

−

12

). For both scenarios classical and quantum solutions are presented.
Smart physics with an oscillating beverage can
Authors: Kaps A , Stallmach F 
Published: May 2021

Abstract
A digital learning-teaching environment is introduced in which undergraduate students are challenged to connect the basic physical concepts of oscillation, buoyancy and data analysis via an authentic experiment. The damped oscillation of a cylindrical body swimming upright in water is measured via the MEMS acceleration sensor of a wireless MCU SensorTag. The data are recorded with the app phyphox on a smartphone or tablet. The theoretical oscillation period and the experimentally determined periods obtained via different data analysis roots are found to agree showing an excellent theory-experiment interplay. The proposed experiment is suited for the physics home lab e.g. under the current pandemic situation or for open university courses as well as for physics lab courses.
Designing an instructional module to teach light diffraction by a grating to secondary students applying a STEM-integrated approach
Authors: Chuasontia Itsarapong , Sirirat Tanita 
Published: May 2021

Abstract
This research aimed to design an instructional module to teach light diffraction by a grating to secondary students applying a science, technology, engineering, and mathematics (STEM)-integrated approach. Based on this approach, instructional management integrated the disciplines of physics and mathematics with engineering design process principles, while information searches, assessment, and evaluation drew on technology. The module involved working out a solution to the real-world scientific problem of constructing a spectroscope in the environment of cooperative learning. Upon completion of the module, the students were expected to demonstrate a thorough understanding of light diffraction by the grating as well as problem-solving skills. To evaluate its effectiveness, the module was trialed on thirty 11th grade students in a Thai school in Pathum Thani, Thailand. The findings revealed that the implementation of the module enabled the students to achieve a statistically higher post-test score than that for the pre-test at the significance level of 0.05. As a result of the module, the students also exhibited a high level of academic development, as indicated by the class normalized gain of 0.82. Finally, the module was perceived by the students as being suitable for their level, offering them a chance to apply classroom knowledge to authentic problems and hence accumulating their hands-on experience, enhancing their problem-solving skills through the application of the engineering design process, and improving their team-working ability.
Estimating star distances with a light bulb
Authors: Craig David M , Leslie Lewis R 
Published: May 2021

Abstract
A practical experiment is described to estimate the distance to a star using simple equipment, suitable for secondary or undergraduate students. The brightness of the star is visually matched to a miniature filament lamp, and its distance inferred from the inverse square law. Students gain an appreciation of astronomical units and practice in manipulating powers of 10. By additionally applying knowledge of the H-R diagram and black body radiation, accuracy can be improved to one order of magnitude.
The next-to-leading spin-orbit effects on the general motions in Kerr spacetime
Authors: Yang Bo , He Guansheng , Lin Wenbin 
Published: May 2021

Abstract
We derive the second-and-half post-Newtonian solution for the generally inclined motion of a test particle in Kerr spacetime when the effects of the spin-induced quadrupole are negligible. The next-to-leading order spin-orbit effects on the test particle’s motion are obtained, which are important in fitting the motions of the extremely-mass-ratio-inspiral systems and also calculating the gravitational wave radiated by this kind of systems at the second-and-half post-Newtonian order.
The cosmological evolution of self-interacting dark matter
Authors: Egana-Ugrinovic Daniel , Essig Rouven , Gift Daniel , LoVerde Marilena 
Published: May 2021

Abstract
We study the evolution of cosmological perturbations in dark-matter models with elastic and velocity-independent self interactions. Such interactions are imprinted in the matter-power spectrum as dark acoustic oscillations, which can be experimentally explored to determine the strength of the self scatterings. Models with self interactions have similarities to warm dark matter, as they lead to suppression of power on small scales when the dark-matter velocity dispersion is sizable. Nonetheless, both the physical origin and the extent of the suppression differ for self-interacting dark matter from conventional warm dark matter, with a dark sound horizon controlling the reduction of power in the former case, and a free-streaming length in the latter.
We thoroughly analyze these differences by performing computations of the linear power spectrum using a newly developed Boltzmann code. We find that while current Lyman-α data disfavor conventional warm dark matter with a mass less than 5.3 keV, when self interactions are included at their maximal value consistent with bounds from the Bullet Cluster, the limits are relaxed to 4.4 keV. Finally, we make use of our analysis to set novel bounds on light scalar singlet dark matter.
Novel accelerated Stochastic Progressive Photon Mapping rendering with neural network
Authors: Xing Qiwei , Chen Chunyi , Li Zhihua 
Published: May 2021

Abstract
Recently, deep learning-based approaches have led to dramatic improvements for Monte Carlo rendering at the low sampling rate. Most of these approaches are aimed at path tracing. However, they are not suitable for photon mapping. In this paper, we develop a novel accelerate stochastic progressive photon mapping approaches with neural network. First, our framework utilizes the particle-based rendering and focuses on photon density estimation. We train a neural network to predict a kernel function to aggregate photon contributions at shading point. Then we construct a estimation images with the prediction network. During experiments, we could find that there are spike pixels and noises in estimation images sometimes. So we present the improved denoising network to post-process the estimation images. Finally, we can obtain the high-quality reconstructions of complex global illumination effects like caustics with an order of magnitude fewer photons compared with previous photon mapping methods. Besides, our denoising network can reduce most multi-scale noises on both low-frequency and high-frequency areas while preserving more illumination details, especially caustics, compared with other state-of-the-art learning-based denoising methods.
Two degree-of-freedom robotic eye: design, modeling, and learning-based control in foveation and smooth pursuit
Authors: Rajendran Sunil Kumar , Wei Qi , Zhang Feitian 
Published: May 2021

Abstract
With increasing ocular motility disorders affecting human eye movement, the need to understand the biomechanics of the human eye rises constantly. A robotic eye system that physically mimics the human eye can serve as a useful tool for biomedical researchers to obtain an intuitive understanding of the functions and defects of the extraocular muscles and the eye. This paper presents the design, modeling, and control of a two degree-of-freedom (2-DOF) robotic eye, driven by artificial muscles, in particular, made of super-coiled polymers (SCPs). Considering the highly nonlinear dynamics of the robotic eye system, this paper applies deep deterministic policy gradient (DDPG), a machine learning algorithm to solve the control design problem in foveation and smooth pursuit of the robotic eye. To the best of our knowledge, this paper presents the first modeling effort to establish the dynamics of a robotic eye driven by SCP actuators, as well as the first control design effort for robotic eyes using a DDPG-based control strategy. A linear quadratic regulator-type reward function is proposed to achieve a balance between system performances (convergence speed and tracking accuracy) and control efforts. Simulation results are presented to demonstrate the effectiveness of the proposed control strategy for the 2-DOF robotic eye.
Grassland-to-cropland conversion increased soil, nutrient, and carbon losses in the US Midwest between 2008 and 2016
Authors: Zhang Xuesong , Lark Tyler J , Clark Christopher M , Yuan Yongping , LeDuc Stephen D 
Published: May 2021

Abstract
After decades of declining cropland area, the United States (US) experienced a reversal in land use/land cover change in recent years, with substantial grassland conversion to cropland in the US Midwest. Although previous studies estimated soil carbon (C) loss due to cropland expansion, other important environmental indicators, such as soil erosion and nutrient loss, remain largely unquantified. Here, we simulated the environmental impacts from the conversion of grassland to corn and soybeans for 12 US Midwestern states using the EPIC (Environmental Policy Integrated Climate) model. Between 2008 and 2016, over 2 Mha of grassland were converted to crop production in these states, with much less cropland concomitantly abandoned or retired from production. The net grassland-cropland conversion increased annual soil erosion by 7.9%, nitrogen (N) loss by 3.7%, and soil organic carbon loss by 5.6% relative to that of existing cropland, despite an associated increase in cropland area of only 2.5%. Notably, the above estimates represent the scenario of converting unmanaged grassland to tilled corn and soybeans, and impacts varied depending upon crop type and tillage regime. Corn and soybeans are dominant biofuel feedstocks, yet the grassland conversion and subsequent environmental impacts simulated in this study are likely not attributable solely to biofuel-driven land use change since other factors also contribute to corn and soybean prices and land use decisions. Nevertheless, our results suggest grassland conversion in the Upper Midwest has resulted in substantial degradation of soil quality, with implications for air and water quality as well. Additional conservation measures are likely necessary to counterbalance the impacts, particularly in areas with high rates of grassland conversion (e.g. the Dakotas, southern Iowa).
Effect of Powder Composition on the Preparation of SiCfoam/Al Co-continuous Phase Composites by In-situ Reactive Pressureless Infiltration
Authors: Xiao Qing , Jiang Guojian 
Published: May 2021

AbstractThe SiCfoam/Al co-continuous phase composite was prepared by in-situ reaction pressureless infiltration (ISRPI). The influence of powder ratio on the impregnation effect and the mechanical properties of the material was studied. The relationship between the mechanical properties and the interfacial reaction was discussed. The results show that the addition of Mg powder of 8% mass fraction increases the impregnation effect, and the formed magnesium spinel strengthens the bonding interface, which makes the compacting of the composite improve. At the same time, adding 2% mass fraction of Si in the infiltrated powder can inhibit the production of brittle material Al4C3and improve the mechanical properties of the composites. The compressive strength of SiCfoam/Al co-continuous phase composites with good interfacial bonding reaches 832MPa.
Prediction of ultimate burst pressure and comparison of failure criteria for thermoplastic composite pipes
Authors: Ge P , Xia H , Liu Q , Shi C , Xiao W , Jia X , Xu Y 
Published: May 2021

Abstract
Thermoplastic composite pipes (TCPs) are becoming the ideal substitute for traditional steel pipe due to its superiorities including light weight and corrosive resistance. The cross-section of TCPs consists of an inner liner, a laminate layer, and an outer jacket. The laminate layer is made of multi-plies of helically wound continuous fibre reinforced unidirectional tape. In the present study, a three-dimensional (3D) theoretical model and a 3D finite element model were developed to analyse the stress state of a TCP under internal pressure. With a selected failure criterion for composite laminate, the ultimate burst pressure of a TCP can be predicted. By comparing the predicted burst pressure with the experimental results, several commonly used failure criteria were compared in terms of their accuracy.
Quantitative Changes in the Hepatopancreas Cells of the Bivalve Mollusk Batissa Violaceae Exposed to Anthropogenic Activities in Catubig River, Northern Samar, Philippines
Authors: Salinas RI 
Published: May 2021

Abstract
This study aims to determine the quantitative changes in the hepatopancreas cells of bivalve mollusk as a bioindicator of pollution on aquatic species. Clams Batissa violaceae inhabiting in Catubig River, Northern Samar was used as the bioindicator of pollution. Clams were collected during high flow and low flow periods at two different sites along the Catubig River. Pooled hepatopancreas were used for quantitative analyses; from chronically exposed group, depurated laboratory control group and those clams that were brought back to the river and immersed for 72 hrs. Histological sections of hepatopancreas were examined by Ken-a-vision microprojector microscope. Results have shown that acute exposures in the number of digestive tubules were significantly different from chronically exposed group of clams. The hepatopancreas epithelium heights also showed significant differences during high and low flow regimes. Overall, quantitative changes found in the hepatopancreas cells after acute and chronic exposures, could serve as a biomarker of exposure to pollutants.
Analysis of Horizontal to Vertical Spectral Ratio (HVSR) Curve Results from Processing using Interpolated Finite Impulse Response (IFIR) Filter
Authors: Olivia M A , Rochman J P G N , Warnana D D 
Published: May 2021

Abstract
Microtremor is recorded with a device that is very sensitive to subsurface soil vibrations, that unwanted noise frequency waves are often also included. For this reason, processing needs to be done using filters that can attenuate the noise. In the previous research, signal decomposition was performed using the Interpolated Finite Impulse Response (IFIR) filter and resulted attenuation at the desired frequency value. Using the MATLAB program, microtremor data are processed with IFIR filtering, smoothing, calculation of: Horizontal to Vertical Spectral Ratio (H / V) curve, natural frequency (f0) and standard deviation (σ). The same process was carried out using Butterworth, Gaussian, and Cosine filters as a comparison with the Geopsy program. As a result, the amplitude characteristics obtained can provide a value of f 0 < 2.5 Hz. The value of f0 obtained using IFIR filter is also stable, proven by the standard deviation ranging from σ = 0.009 - 0.83 Hz, with an average of σ = 0.132 Hz. In conclusion, the IFIR filter can provide a well-attenuated H/V curve according to the specified cutoff frequency, which was 2 Hz. The IFIR filter is also considered capable of being applied to the HVSR method Microtremor data. Lowpass IFIR filter can attenuate high-frequency noise in microtremor data.
Current status and prospect of research on combine harvester header for rape
Authors: Wang Hanhao , Li Yaoming , Qing Yiren 
Published: May 2021

Abstract
Rapeseed is one of the most important oil-bearing crops in China. Because of its poor efficiency, the planting area is in a trend of declining year by year. In order to change the status quo of low efficiency and stimulate farmers’ enthusiasm for planting oilseed rape, it is of great significance to vigorously promote the mechanized harvest in the process of rapeseed production. The rape header is an important part of the rape combine harvester. It is different from the header structure of common rice and wheat combine harvesters, and the header depth is larger. At the same time, in order to solve the problem of dense branches and cross-linking of rapeseed, in addition to the main cutter, reel and screw conveyor, the rape header also needs to be equipped with a vertical splitting cutter on the side. In this way, the entangled branches are cut and the loss of shattering can be reduced. Head loss accounts for a considerable proportion of the total loss during the rape harvest. By reasonably configuring the structure of the rape header and optimizing the working parameters, the vibration of the header and the power consumption of the header can be reduced, and the work efficiency can be improved. It is of great significance to reduce the mechanical harvest loss of rape and increase the efficiency of rape planting. This article introduces the current status and progress of the research on the working structure of the rape header at home and abroad. Point out the existing problems and put forward suggestions for the development of rape header in the future.
Transcriptomic analyze of the less branches of Brassica napus L. suitable for mechanized harvesting
Authors: Qing Yiren , Li Yaoming , Ma Zheng 
Published: May 2021

Abstract
Rapeseed (Brassica napus L.) is one of the main oil crops in the world. Its multi branching characteristics cause great difficulties and losses to mechanical harvesting. Less branched plant type is a favorable feature for promoting mechanical harvesting. In this paper, a natural mutant rape of less branches with NY12 (Ningyou 12) as background was obtained, which was named sfz (shao fen zhi, meaning less branches in Chinese). The mutant showed a significant decrease in branching and a significant increase in the lowest branch height, which are beneficial to harvest. Transcriptomic analysis of shoot tip tissue showed that the expression of gens related to strigolactone is up-regulated, which promotes its inhibitory effect on plant branching, and the expression of genes related to cell division cycle and cytoplasmic division were all down regulated. It is speculated that the decrease of cell division may also result in the decrease of branching. The research provides a basis for the formation of branching and promoted the development of mechanized harvesting.
Using CiteSpace Knowledge Information Visualization Software in the Visual Analysis of the Law Research: Set Juvenile Sexual Assault as an Example
Authors: Zhu Ai’nan , Yang Xue , Cui Daiyao 
Published: May 2021

Abstract
The crime of sexual assault is of one essential aspect of law research in China nowadays. At present, the number of domestic research literature on the crime of sexual assault on minors is rising. In this paper, CiteSpace knowledge information visualization software, SPSS, excel analysis software are used to analyze all the sexually assaulting juvenile literatures collected in CNKI in the past 10 years, and show the current situation and structural characteristics of the research on sexual assault juvenile crime in the form of knowledge network atlas, so as to grasp the current situation of the research on juvenile sexual assault crime in China from a macro perspective. This paper aims to provide a valuable reference for the research on the attack and prevention of juvenile sexual assault.
Cause Analysis and Management Countermeasures for Unsafe Drinking Water Quality in Rural Guangxi China
Authors: Ding Haoqing 
Published: May 2021

Abstract
In recent years, as China has been vigorously promoting the construction of drinking water safety project in rural areas, rural drinking water safety is guaranteed to some extent, but the safety of water quality is still not up to standard in some areas. In view of the situation of drinking water safety in rural Guangxi China, according to the authoritative judgment method of safe drinking water, this thesis analyzes the present situation of rural drinking water safety in Guangxi, and decides that the major causes of unsafe drinking water quality in rural Guangxi include the exceedance of content standard of hazardous substances in drinking water sources, pollution in transportation and treatment process of drinking water, lack of water quality monitoring ability and imperfect management mechanism after the completion of water supply project. Furthermore, the thesis proposes management strategies to improve the safety of water supply quality in rural Guangxi, such as the construction of consolidation and promotion project of rural drinking water safety, the implementation of contiguous water supply project, the establishment and perfection of engineering operating mechanism, the strengthening of quality supervision on rural drinking water safety projects, the use of Internet of Things and big data technique for real-time monitoring, the strengthening of the management on drinking water conservation districts, the improvement of water treatment technique and timely check and solving of the defects. The aim is to enable more rural people to drink safe water with the above management strategies.
Recovery behaviors of acid-modified cement hydration material on phosphorous
Authors: Jiang Bo 
Published: May 2021

Abstract
Silicate cement hydration product is a promising phosphorus adsorption material. In view of the strong alkali characteristics of early hardening cement paste, this study adopted acid leaching method to modify and then investigated its phosphorus recovery performance. The results showed that acid modification could weaken the strong alkali property, nevertheless, it also lowered phosphorus removal efficiency. The decline of phosphorus recovery was closely related to the depletion of calcium source. By the fit calculation, it can be determined that the adsorption kinetics of modified material on phosphorus met the pseudo-second-order model. This was consistent with the behavior of unmodified material. Additionally, XRD analysis demonstrated that the phosphorus species enriched on the surface of modified material mainly consisted of hydroxyapatite and variscite, which was different from the brushite of unmodified material. Acid modification would provide much more aluminum sites on the adsorption of phosphorous.