ARTICLE | doi:10.20944/preprints202107.0452.v1
Online: 20 July 2021 (14:44:23 CEST)
Recent advances in differential topology single out four-dimensions as being special, allowing for vast varieties of exotic smoothness (differential) structures, distinguished by their handlebody decompositions, even as the coarser algebraic topology is fixed. Should the spacetime we reside in takes up one of the more exotic choices, and there is no obvious reason why it shouldn't, apparent pathologies would inevitably plague calculus-based physical theories assuming the standard vanilla structure, due to the non-existence of a diffeomorphism and the consequent lack of a suitable portal through which to transfer the complete information regarding the exotic physical dynamics into the vanilla theories. An obvious plausible consequence of this deficiency would be the uncertainty permeating our attempted description of the microscopic world. We tentatively argue here, that a re-inspection of the key ingredients of the phenomenological particle models, from the perspective of exotica, could possibly yield interesting insights. Our short and rudimentary discussion is qualitative and speculative, because the necessary mathematical tools have only just began to be developed.
ARTICLE | doi:10.20944/preprints201812.0147.v2
Subject: Physical Sciences, Astronomy And Astrophysics Keywords: Dark matter; galaxies; gravitation; rotation curves; galaxy rotation period
Online: 29 January 2019 (09:24:48 CET)
It is well known but under-appreciated in astrophysical applications, that it is possible for gravity to take on a life of its own in the form of Weyl-curvature-only metrics (note we are referring to the Weyl-only solutions of ordinary General Relativity, we are not considering Weyl conformal gravity or any other modified gravity theories), as numerous examples demonstrate the existence of gravitational fields not being sourced by any matter. In the weak field limit, such autonomous gravitational contents of our universe manifest as solutions to the homogeneous Poisson's equation. In this note, we tentatively explore the possibility that they may perhaps account for some phenomenologies commonly attributed to dark matter. Specifically, we show that a very simple solution of this kind exists that can be utilized to describe the rising tails seen in many galaxy rotation curves, which had been difficult to reconcile within the cold dark matter or modified Newtonian dynamics frameworks. This solution may also help explain the universal $\sim 1$Gyr rotation periods of galaxies in the local universe.
ARTICLE | doi:10.20944/preprints201912.0346.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: water quality; machine learning; Recurrent Neural Network; PCA
Online: 25 December 2019 (10:37:27 CET)
Water quality forecasting is increasingly significant for agricultural management and environmental protection. Enormous amounts of water quality data are increasingly being collected by advanced sensors, which leads to an interest in using data-driven models for predicting trends in water quality. However, the unpredictable background noises introduced during water quality monitoring seriously degrade the performance of those models. Meanwhile, artificial neural networks (ANN) with feed-forward architecture lack the capability of maintaining and utilizing the accumulated temporal information, which leads to biased predictions in processing time series data. Hence, we propose a water quality predictive model based on a combination of Kernal Principal Component Analysis (kPCA) and Recurrent Neural Network (RNN) to forecast the trend of dissolved oxygen. Water quality variables are reconstructed based on kPCA method, which aims to reduce the noise from the raw sensory data and preserve actionable information. With the RNN's recurrent connections, our model can make use of the previous information in predicting the trend in the future. Data collected from Burnett River, Australia was applied to evaluate our kPCA-RNN model. The kPCA-RNN model achieved R2 scores up to 0.908, 0.823 and 0.671 for predicting the concentration of dissolved oxygen in the upcoming 1, 2 and 3 hours, respectively. Compared to current data-driven methods like ANN and SVR, the predictive accuracy of the kPCA-RNN model was at least 8 %, 17 % and 21 % better than the comparative models in these 3 cases. The study demonstrates the effectiveness of the kPAC-RNN modeling technique in predicting water quality variables with noisy sensory data.
ARTICLE | doi:10.20944/preprints202304.0297.v1
Subject: Chemistry And Materials Science, Ceramics And Composites Keywords: mechanical properties; microstructure; toughness; crack propagation
Online: 13 April 2023 (05:20:40 CEST)
ZrO2-YO1.5-TaO2.5(ZYTO) composite ceramic is considered to be the candidate of next generation of thermal barrier coatings as its excellent thermal stability and low thermal conductivity in high temperature, however, the mechanical properties and fracture tougheness of ZYTO system may be the shortcomings compared with the 8YSZ. In this study, ZYTO composite ceramics were successfully prepared by chemical coprecipitation reaction, the microsture of resulting composites were studied as a function of doping of M-YTaO4. Mechanical properties, including the density, porosity, hardness and Young's modulus, are determinate; the toughening mechanism were verified by the crack growth behavior of Vickers indentation test Results suggested that M-YTaO4 refines the fluorite phase grain and strengthens the grain interface in the composite ceramic. The thermal mismatch between the second phase and matrix produces residual stress in the bulk and affects the crack propagation behavior. With the increase of M-YTaO4 doping, the grain coarsening and ferroelastic domains are observed in the experiments. The ferroelastic domains with orthogonal polarization directions near crack tip evidences the ferroelastic toughening mechanism. The competition among these crack behaviors, such as cracks deflection, bridging and bifurcation, dominates the actual fracture toughness of the composite. The best toughening formula is determinate in the two-phase region and the highest fracture toughness is about to 3.1MPa·m1/2. Above all, mechanical properties of ZYTO composite ceramics look potential for thermal barrier coatings materials.
ARTICLE | doi:10.20944/preprints202105.0244.v1
Subject: Business, Economics And Management, Accounting And Taxation Keywords: Cost containment; Performance Evaluation; Multi-level System; Diagnosis-related Group (DRG); Health system sustainability
Online: 11 May 2021 (11:29:16 CEST)
This study aims to develop a performance evaluation system that can facilitate performance evaluation at region, hospital, and department levels to enable better cost management for sustainable development. A multi-level system of performance evaluation informs a hierarchical assessment of cost management from regions to hospitals to departments using diagnosis-related group (DRGs). Various metrics are developed employing the variances between targets and actuals where targets are determined from two perspectives: benchmarking using external regional prices and change management using internal data. Targets for the latter are statistically based and specifically incorporate variability. The model is applied to two hospitals, twenty departments, nine DRGs and 1071 inpatients. The analyses indicate that the approach can provide a practical evaluation tool that allows for particular characteristics at multiple levels. The system provides macro-micro and external-internal perspectives in performance, enabling high-level variances to be decomposed thereby identifying sources of performance variability and financial impact.
ARTICLE | doi:10.20944/preprints201702.0060.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: microgrid; multi-microgrid; measured admittance; protection scheme
Online: 16 February 2017 (09:17:26 CET)
Multi-microgrid has many new characteristics, such as bi-directional power flows, flexible operation modes and variable fault currents with different control strategy of inverter interfaced distributed generations (IIDGs). All these featuring aspects pose challenges to multi-microgrid protection. In this paper, current and voltage characteristics of different feeders are analyzed when fault occurs in different positions of multi-microgrid. Based on the voltage and current distribution characteristics of the line parameters, a new protection scheme for the internal fault of multi-microgrid is proposed, which takes the change of phase difference and amplitude of measured bus admittance as the criterion. This scheme with high sensitivity and reliability, has a simple principle and is easy to be adjusted. PSCAD/EMTDC is used in simulation analysis, and simulation results have verified the correctness and effectiveness of the protection scheme.