Decision Support System to Risk Stratification in the Acute Coronary Syndrome Using Fuzzy Logic

Acute coronary syndrome (ACS) is a set of symptoms and signs which define a range of conditions related with the unexpected reduced blood flow to the heart. In ACS, the heart muscles cannot function properly due to the decrease of blood flow. Myocardial infarction (MI) is a condition which comes under the umbrella of acute coronary syndrome. The aim of risk stratification (RS) in ACS is to recognize patients at high risk of ischemic events. Yet, no investigative study is available to identify the patients at high risk. Therefore, to facilitate this process, it would be ideal to have a reliable and trustworthy method by the help of which the doctors can make early and easy decisions for the patient and for detecting the related disease. This research used the features of GRACE Score to RS in the ACS and presented decision support system (DSS). The concept of probabilistic approach has been used as a tool to model the identified features for decision-making (DM). This technique can be further used for DM purposes to RS in the ACS in healthcare. Furthermore, the result of the proposed method has proved closer and more reliable DM of patient and then eventually can be used for advice of medicine and rest accordingly by the doctors

Characteristics of micro scale nonlinear filtration

Take the flow characteristics of fluid in micro tube as the object, the characteristics of nonlinear filtration in low permeability reservoirs were studied using micro scale method by simulating the micro pore throat of reservoir with the micro tube which has the similar scale pore throat of low permeability reservoirs. The flow characteristics of de-ionized water flowing through fused silica capillary tubes with radius of 10.0 μm, 7.5 μm, 5.0 μm and 2.5 μm were investigated in experiments. Relationship between average flow rate and pressure gradient, effect of pressure gradient on fluid boundary layer, and relationships between flow resistance coefficient and Reynolds number were analyzed respectively in these experiments with different micro tubes. The flow of fluid through micro tubes with low velocity has nonlinearity, and the extent of nonlinearity increases with the tube radius decreasing. Nonlinear flow experimental points can be matched by quadratic curve. In micro flow, the percentage of effective fluid boundary layer thickness to micro tube radius decreases with the pressure gradient increasing. Research results indicated that Reynolds number can be used as the criteria of nonlinear flow. Flows with Reynolds number less than 10−3 have nonlinear features. Key words: low permeability reservoir, micro scale, nonlinear flow, boundary fluid laye

Microscopic production characteristics of tight oil in the nanopores of different CO2-affected areas from molecular dynamics simulations

Understanding the mechanisms of CO2 extraction or flooding are vital for enhancing oil recovery (EOR) in tight reservoirs. In this study, the CO2 EOR mechanism in the displacement-affected area (DPAA) and diffusionaffected area (DFAA) of quartz nanopores were thoroughly investigated using molecular dynamics simulation techniques. First, the following two contents were mainly simulated, namely CO2 flooding oil in the single/ double nanopores of DPAA and CO2 extraction oil in dead-end nanopores of the DFAA with and without the water film. Then, tight oil potential energy, threshold capillary pressure, CO2 solubility, and oil swelling in nanopores were calculated to clarify the effects of CO2 on oil transport. Moreover, different CO2 injection/ flowback rates and different water film thicknesses on dead-end nanopores on oil recovery were discussed. In the DPAA, the CO2 solubility and the oil swelling factor gradually decreased with distance from the CO2-oil interface (Y = 0 nm), where the higher the injection rate, the more easily the CO2 dissolved in the oil. However, the injection rate of CO2 was inversely proportional to oil recovery. In addition, it took longer for the displacement efficiency in the 6 nm pore of double pores to reach the same displacement efficiency as in the single 6 nm pore. In the DFAA, the effect of flowback rate on the displacement efficiency of oil was relatively low. However, the thickness of the water film was a key factor that affected the oil displacement efficiency in the DFAA

Microscopic production characteristics of tight oil in the nanopores of different CO2-affected areas from molecular dynamics simulations

Understanding the mechanisms of CO2 extraction or flooding are vital for enhancing oil recovery (EOR) in tight reservoirs. In this study, the CO2 EOR mechanism in the displacement-affected area (DPAA) and diffusionaffected area (DFAA) of quartz nanopores were thoroughly investigated using molecular dynamics simulation techniques. First, the following two contents were mainly simulated, namely CO2 flooding oil in the single/ double nanopores of DPAA and CO2 extraction oil in dead-end nanopores of the DFAA with and without the water film. Then, tight oil potential energy, threshold capillary pressure, CO2 solubility, and oil swelling in nanopores were calculated to clarify the effects of CO2 on oil transport. Moreover, different CO2 injection/ flowback rates and different water film thicknesses on dead-end nanopores on oil recovery were discussed. In the DPAA, the CO2 solubility and the oil swelling factor gradually decreased with distance from the CO2-oil interface (Y = 0 nm), where the higher the injection rate, the more easily the CO2 dissolved in the oil. However, the injection rate of CO2 was inversely proportional to oil recovery. In addition, it took longer for the displacement efficiency in the 6 nm pore of double pores to reach the same displacement efficiency as in the single 6 nm pore. In the DFAA, the effect of flowback rate on the displacement efficiency of oil was relatively low. However, the thickness of the water film was a key factor that affected the oil displacement efficiency in the DFAA

Occurrence characteristics and influential factors of movable oil in nano-pores by molecular dynamics simulation

CO2-enhanced oil recovery (CO2-EOR) technology has shown great application potential in the development of tight reservoirs. Since the proportion of nano-pores in tight oil reservoirs exceeds 77%, it is necessary to further study the occurrence state of crude oil in nano-pores. In this paper, the molecular dynamics simulation was applied to study the adsorption and diffusion behaviors of multi-component crude oil in quartz (hydrophilic) nano-pores. Besides, the density discretization method was used to investigate the occurrence characteristics of crude oil, the proportion of movable fluid in nano-pores, and the effects of CO2 and polar molecules (C3H6O) on the adsorption characteristics of crude oil. The simulation results showed that the adsorption state of crude oil in the quartz nano-pores was in the form of 4 adsorption layers with a thickness of 0.45 nm each. In nano-pores, the oil molecules with longer molecular chains were more likely to aggregate and adsorb on the quartz surface. Among them, polar oil molecules have the strongest adsorption capacity on the quartz surface. Moreover, the crude oil potential energy and the self-diffusion coefficient gradually increased from the vicinity of the quartz wall and tended to be stable in the free layer. Meanwhile, the content of movable crude oil gradually augmented with the increasement of nanometer pore width and temperature. Furthermore, the pressure had little effect on the density distribution of crude oil in the pores. In contrast, the temperature had a more significant effect on the density distribution of the adsorption layer. At last, due to the more substantial adsorption capacity of CO2 on the rock surface, the crude oil adsorbed initially on the rock surface would be stripped off by CO2, converting from irreducible oil to moveable oil

Diffusion coefficient and the volume swelling of CO2/light oil systems: Insights from dynamic volume analysis and molecular dynamics simulation

The oil volume expansion and CO2 diffusion are one of the main mechanism of CO2-enhanced oil recovery (CO2- EOR). This paper established a series of experiments, numerical simulations, and molecular dynamics (MD) simulations to describe mass transfer behaviors between oil-gas phases. Expressly, the CO2 diffusion coefficient and light oil swelling factor are signification parameters to quantify and analyze these behaviors. In detail, the CO2 diffusion coefficient and the oil swelling factor were obtained from the traditional pressure decay method and the advanced MD simulation. Synthetically, the pressure decay method and MD simulation results were mutually verified. The results showed that the equilibrium pressure was proportional to the mole fraction of CO2 and inversely proportional to the mole fraction of light oil. The equilibrium time was proportional to the mole fraction of CO2 and light oil. At the temperature of 333.15 K and the initial pressure of 7.5 MPa, the CO2 diffusion coefficient in light oil was positively correlated with the relative molar proportion of CO2, while the light oil swelling factor was vice versa. In addition, the closer to the CO2-light oil interface, the greater the light oil's potential energy and self-diffusion coefficient, and the stronger the transport ability

An Optimized Prediction Intervals Approach for Short Term PV Power Forecasting

High quality photovoltaic (PV) power prediction intervals (PIs) are essential to power system operation and planning. To improve the reliability and sharpness of PIs, in this paper, a new method is proposed, which involves the model uncertainties and noise uncertainties, and PIs are constructed with a two-step formulation. In the first step, the variance of model uncertainties is obtained by using extreme learning machine to make deterministic forecasts of PV power. In the second stage, innovative PI-based cost function is developed to optimize the parameters of ELM and noise uncertainties are quantization in terms of variance. The performance of the proposed approach is examined by using the PV power and meteorological data measured from 1kW rooftop DC micro-grid system. The validity of the proposed method is verified by comparing the experimental analysis with other benchmarking methods, and the results exhibit a superior performance

Investigation effect of wettability and heterogeneity in water flooding and on microscopic residual oil distribution in tight sandstone cores with NMR technique

In order to explore the effect of wettability and pore throat heterogeneity on oil recovery efficiency in porous media, physical simulation experiment and nuclear magnetic resonance (NMR) measurements were conducted to investigate how crude oil residing in different sized pores are recovered by water flooding. Experimental results indicate that the recovery factor of water flooding is governed by spontaneous imbibition and also pore throat heterogeneity. It is found that intermediate wetting cores lead to the highest final recovery factor in comparison with water wet cores and weak oil wet cores, and the recovery oil difference in clay micro pore is mainly because of the wettability, the difference in medium pore and large pore is affected by pore throat heterogeneity. Water wet core has a lower recovery factor in medium and large pore due to its poor heterogeneity, in spite of the spontaneous imbibition effect is very satisfying. Intermediate wetting cores has significant result in different sized pore and throat, the difference in medium pore and large pore is affected by pore throat heterogeneity

Studies on the performance of distributed combined cooling, heat and power system under off-design conditions based on exergy analysis

This paper adopts the exergy analysis method of second law of thermodynamics to analyze the characteristics of off-design conditions of distributed combined cooling, heat and power system (CCHP). The research results show that off-design conditions are the primary cause of the performance decline of the system. Under the off-design conditions, although the system’s power generation and cooling capacities decline with the reduction of load, the cooling capacity declines more slowly than generating capacity. When the gas turbine load drops under 60%, the distributed combined cooling, heat and power system may not save energy. If the low grade residual heat in the system could be effectively used, it will obviously improve the system’s performance under off-design conditions. Combustor, high pressure producer, and turbine change significantly in grade differences during the change of load in gas turbine, which also means that these three parts are the areas with the highest potential for improvement of the system’s performance. The biggest loss of system exergy occurs in combustor and high-pressure producer