Low High Ratio Research Articles

Regulation of the electron concentration distribution in TiO2/BaTiO3 photodetector

TiO2 film ultraviolet photodetectors (UVPDs) always suffered from high dark current and low on-off ratio, which have been studied by many works. To improve the performance of the UVPDs based on TiO2, we fabricated a UVPD based on TiO2 with self-polarized BaTiO3 (SPBTO) through a spin-coating method. Compared with the dark current (1.12 nA) and on-off ratio (1.15 × 103) of the single TiO2 film UVPD, that of TiO2-SPBTO film UVPD are 1.27 × 10−1 nA and 1.17 × 104, respectively. The result shows that TiO2-SPBTO has better photoelectric detection capabilities, which may be due to the modulating the electronic distribution of TiO2 films by SPBTO film. To explore the mechanism of the device, we analyzed the carrier distribution within the heterojunction by finite element analysis, which demonstrated that the SPBTO film modulates the electron concentration distribution of TiO2 film, resulting in a lower dark current and a higher on-off ratio. This work provides a potential candidate for high-performance UVPDs.

The Role of Performance to Continue the Business for Nascent Entrepreneurs: The Effect of Entrepreneurial Self-Efficacy

High mortality rates and low entrepreneur ratios are problems in developing sustainable small businesses. Previous research has shown that entrepreneurial self-efficacy (ESE) is an important factor for increasing entrepreneurial intentions, but how ESE explains the continuity of business for nascent entrepreneurs is less researched. This study aims to investigate the role of business performance in explaining the relationship of ESE and career switching for nascent entrepreneur. Data were collected from nascent entrepreneur using questionnaires and analyzed by Partial Least Square-Structural Equation Modelling (PLS-SEM). The results of this study shown that ESE positively influence business performance. ESE and business performance negatively influence career switching intention for nascent entrepreneur. In summary, ESE can reinforce nascent entrepreneurs to continue and survive their business. Some theoreticals on entrepreneurship and practicals implication on entrepreneurship development are suggested in the rest of this paper.

Premixed combustion and emission characteristics of methane diluted with ammonia under F-class gas turbine relevant operating condition

Ammonia has been used on a small scale in other industrial equipment, such as gas turbines, as a carbon-free fuel. However, ammonia fuel suffers disadvantages such as high ignition temperature, low flame velocity and high NOx emissions. Doping with ammonia using a more reactive fuel, such as methane, can solve the above problems. Therefore, under the relevant operating conditions of the gas turbine (T = 723 K, p = 16.5 atm), the effect of ammonia content on the combustion and emission characteristics of laminar premixed methane flames was numerically investigated. This research uses the PREMIX code from ANSYS CHEMKIN-PRO 2020 and Okafor chemical kinetic mechanisms and provides a reference for our subsequent analysis of gas turbine operating conditions. Firstly, the emission data of major pollutants under different ammonia content (XNH3 = 0–1.0) and equivalent ratio (Φ = .6–1.4) were calculated. Then, the laminar premixed flame structure is analyzed under the lean fuel conditions associated with gas turbines (Φ = .6, .8). Finally, the effect of ammonia addition on the chemical reaction path of NO and CO emission was studied. The results show that ammonia/methane mixture fuel is more suitable for combustion at .6 < Φ < .8 under high temperature and pressure. High ammonia content (XNH3 > .6) and low equivalent ratio can reduce NO and CO emissions. The molar fractions of H, O, and OH radicals and flame temperature decreased with the increase in ammonia content. In addition, high temperature and high pressure conditions and ammonia content greatly influence the reaction path of NO and CO production. The increase in pressure resulted in a change in the primary reaction that produced NO. In conclusion, this study guides reducing the emission of NO and CO from lean side of gas turbine plants.

Rural system sustainability evaluation based on emergy analysis: An empirical study of 321 villages in China

The deterioration of the rural ecosystem, the poverty of population, and the low well-being of farmers have brought great challenges to the realization of the Sustainable Development Goals (SDGs). Assessing the current situation of rural sustainable development and identifying limiting factors are critical to sustainable development of rural areas. This study evaluates rural sustainability of 321 villages in China based on emergy analysis. Then, random forest has been employed to determine the limiting factors of villages with different sustainable development levels. The results show that the current level of sustainable development in Chinese rural areas is relatively low (from 0.0040 to 9.5468), showing the trend of gradual increase in rural sustainability from the east to the west. There is a trade-off relationship between social-economic development and the ecological environment, resulting from only 32% of villages are high Emergy Yield Rate and low Environmental Loading Ratio. High-sustainability villages are rich in natural resources and higher metabolic efficiency but poor in people's living, indicating that the natural capital needs to be excavated to improve economic levels and social well-being in the future. Low-sustainability villages have better human well-being due to faster economic development, but unbalanced external inputs and outputs result in low metabolic efficiency and high environmental pressure. Precipitation, agricultural materials input, and people living consumption are the main driving factors for rural sustainability. It is suggested to introduce effective policies to increase economic measures and human well-being for high-sustainability villages, and appropriately decrease external purchasing such as fertilizer and pesticides for low-sustainability villages to make progress in rural sustainable development and Chinese Rural Revitalization.

Empirical investigation of dynamic relations among foreign direct investment, economic growth and poverty prevalence using African data

This study examined dynamic relations among foreign direct investment (FDI), economic growth and poverty headcount ratio using a sample of 24 African Countries. To achieve this goal, historical data of the variables regarding cross section of countries were collected over 14-year period. The stratified random sampling technique was employed in selecting the sample. Following pre-regression diagnostics, we specified Vector-Auto-Regression model for computation of coefficients of the variables in dynamic relations. These were complimented with computation of relative impulse response function and forecast-error-variance decomposition of regression estimates. We found that FDI did not granger-cause economic growth among African economies, just as growth was found not sustainable and inclusive enough as to achieve substantial poverty reduction. More-so, evidence appeared to support earlier isolated findings that FDI has been largely exploitative and attracted to economies with high growth rates and low poverty ratios. The study reinforces earlier isolated findings that it is not necessarily ‘growth’ that results in decline in poverty prevalence but ‘sustained economic growth’. Hence most developing nations that depend on annual fiscal plans for poverty reduction may consistently miss development targets. Again, contrary to widely held view that foreign direct development leads to economic growth, the study established exceptional case for Africa.

Separationless method of determination of volume fractions of gas, condensate and water in products extracted from gas condensate wells

The problem of the lack of instruments for the operational measurement of the components of the production of gas condensate wells – multiphase flow meters – is considered. Actual problems solved with the use of multiphase flowmeters are described, and the main requirement for these devices is the measurement of the components of a gas condensate flow without separating it into gas and liquid phases using a separator. A method is proposed for determining the volumetric contents of the components of the products of gas condensate and oil and gas condensate wells using a non-separation technique for registering components. The probing of a gas-liquid flow by decimeter radio waves at the moment of flow passing through a microwave resonator is described, and a variant of the design of a non-separation analyzer of volume fractions of gas, condensate and water in the production products of gas condensate wells is proposed. The volume fractions of gas, water, and condensate were determined from the results of measurements of the frequency shift and the quality factor of the resonator. At the same time, an acceptable accuracy (less than 5 %) of determining the amount of condensate is provided only at high condensategas ratios (300–1000 cm3/ m3) and low water-gas ratios (30–100 cm3/m3). With an increase in the proportion of water or a decrease in the proportion of condensate, the error in determining the gas-condensate factor becomes unacceptably high (more than 10 %). It is proposed to reduce this error by introducing a bypass line into the flow meter containing a filter for separating the liquid phase and a reference resonator. The reference resonator registers the frequency shift due to the gas phase. The filter is probed with an eight-millimeter radio beam, which reacts to the content of only the water component. The data obtained from the resonator and filter significantly expand the range of recorded condensate-gas and water-gas factors. Possibilities of using the proposed technique: determination of volume fractions in the production products of gas condensate wells; application in multiphase flow meters for gas condensate fields; quality control of separators that separate liquid before further gas supply (when equipment is installed both before the separator and after it). Large bore resonators could be used to control gas-liquid flow through pipelines of large diameters, such as collector pipelines.

Identification of stage I/II melanoma patients at high risk for recurrence using a model combining clinicopathologic factors with gene expression profiling (CP-GEP)

PurposePatients with cutaneous melanoma stage I/IIA disease are currently not eligible for adjuvant therapy, despite their risk for relapses and death. This study validates the ability of a model combining clinicopathologic factors with gene expression profiling (CP-GEP) to identify patients at high risk for disease recurrence in stage I/II and subgroup stage I/IIA. Patients and methods543 patients with stage I/II primary cutaneous melanoma from the University of Tuebingen diagnosed between 2000 and 2017 were analysed. All patients received sentinel lymph node biopsy (SLNB). Analysis was conducted for a separate group of 80 patients who did not undergo SLNB. ResultsCP-GEP stratified 424 stage I/IIA patients (78% of the cohort) according to their risk for recurrence, with five-year relapse-free survival (RFS) rates of 77.8% and 93% for CP-GEP high risk (195 patients) and low risk (229 patients), respectively, and hazard ratio of 3.53 (p-value <0.001). In patients who did not receive SLNB biopsy, CP-GEP captured 6 out of 7 relapses. ConclusionCP-GEP can be used to identify primary cutaneous melanoma patients with a high risk for disease recurrence – especially for stage I/IIA, who are considered low risk by AJCC 8th. These patients may benefit from adjuvant therapy. Also, in the future, when SLNB may become irrelevant, CP-GEP may serve as a risk stratification tool.

The Effect of Rectangular Confinement Aspect Ratio on the Flame Transfer Function of a Turbulent Swirling Flame

Abstract The flame transfer function (FTF) has been experimentally investigated for a premixed, turbulent and highly swirled flame in rectangular enclosures with varying aspect ratio. A range of equivalence ratios and inlet bulk velocities are considered to vary the length of the flame. Increasing confinement is also shown to increase flame length. More confined flames become increasingly asymmetric, with significant changes to the mean flame shape. Characteristic peaks and dips are observed in the FTF gain for several configurations, caused by constructive and destructive interference between different sources of flow perturbations. Changes in the geometrical confinement distinctly affects these interactions, with FTFs in the most confined chamber containing more pronounced peaks and dips. Analysis of the phase-averaged dynamics has been conducted for two limiting operational conditions in the least and most confined enclosures: a short flame at a low bulk velocity and high equivalence ratio condition; and a long flame at a high velocity and low equivalence ratio condition. The analysis of the short flames shows similar behavior in both enclosures, both in terms of the global response and the local structure of the heat release rate oscillations. Small differences in local response symmetry in the flame due to the close confinement do not affect the global flame response. By comparison, close confinement significantly affects the symmetry of the flame dynamics in the long flame. However, the changes in symmetry do not significantly modify the response, and more important is the change in flame length, which significantly alters the cutoff frequency, reducing the gain at high frequencies.

Ultrasmall Fe3O4 and Gd2O3 hybrid nanoparticles for T1-weighted MR imaging of cancer

AbstractGadolinium-based contrast agents (GdCAs) have been the most frequently used T1-weighted magnetic resonance imaging (MRI) contrast agents for decades. However, they have serious disadvantages such as low longitudinal relaxivity value (r1) and high dose associated-nephrotoxicity that restrict their wide applications. These emphasize the need for an ideal stable and biocompatible T1-weighted CA with high contrast enhancement performance. Here, we propose a wet-chemical synthesis technique to form a nanocomposite consisting of ultrasmall iron oxide nanoparticles (US-IO) and Gd2O3 hybrid nanoparticles stabilized with dextran (FG-HNPs) for T1-weighted MR imaging. Relaxometry study showed that FG-HNPs have a high r1 value (42.28 mM−1S−1) and low relaxivity ratio (r2/r1: 1.416) at 3.0T. In vivo MRI contrast enhancement factor (ΔSNR) for FG-HNPs (257.025 ± 17.4%) was found to be 1.99-fold higher than US-IO (129.102 ± 15%) and 3.35-fold higher than Dotarem (76.71 ± 14.2%) as routinely used T1-weighted CA. The cytotoxicity assay and histological examination confirmed the biocompatibility of FG-HNPs. The biodistribution study, transmission electron microscopy (TEM) and Prussian blue (PB) staining of tumor tissue proved the effective tumor localization of FG-HNPs. Therefore, FG-HNPs can be suggested as a promising CA for T1-weighted MRI of tumors by virtue of their remarkable relaxivities and high biocompatibility.

A Torque-Controlled Actuator With High Rigidity and Low Aspect Ratio

To ensure safe and accurate environment-robot interaction, a torque sensor is usually mounted at the output of an actuator to detect and control the output torque. Deformation-based sensors at the actuator output would significantly increase the actuator size and complexity while decreasing the output rigidity in off-axis directions. To reduce the extra complexity, space, and output compliance required for torque sensing, this article proposes a torque-controlled actuator that does not rely on deformation-based sensing at the actuator output. Instead, a torsion spring is mounted at the input of the harmonic drive. Encoders are used to sense the spring deformation to control the output torque with low sensing noise. Hence, the size of the actuator can be minimized while the output rigidity can be maintained. Using the torsion spring can also significantly reduce the reflected output inertia of the actuator. Experiments are provided to demonstrate torque control accuracy and bandwidth. Position control results also show a comparable response to actuators that do not have torque sensors. This new torque-controlled actuator can provide a more competitive solution for collaborative robots to interact with humans or the environment.

Numerical investigation of a two-bladed vertical-axis turbine operating in a confined channel

The energy harvesting performance of a hydrokinetic turbine in a confined channel has been investigated through numerical simulations. It consists of a two-bladed vertical-axis turbine with a NACA0015 profile. Fluid dynamics are reproduced by a 2D numerical model solving the unsteady RANS equations through a finite volume approach in OpenFOAM-v6 . Following a numerical sensitivity analysis, the baseline model has been validated with respect to reference data for an unconfined turbine with similar design. The model has then been employed for assessing the influence of the main design parameters – namely blade-channel gap ε 0 , solidity σ and tip-speed ratio λ – on the performance of the turbine. First, a parametric study on the plane λ × σ revealed that best performance is obtained at high solidity and low tip-speed ratios. In a range of solidities from 0.06 up to 0.48 , the optimal value of tip-speed ratio – which is considerably higher when compared with unconfined turbines – is precisely identified. Finally, the effects of the blade-channel gap ε 0 on the performance of the turbine has been investigated as well. It has been found that ε 0 should be set as small as possible in order to maximise energy harvesting. Moreover, numerical results allowed for estimating a limit value of ε 0 > 9 over which the performance of a turbine operating in a confined channel should match that of an unconfined turbine.

Characterization of three naturally occurring lignans, sesamol, sesamolin, and sesamin, as potent inhibitors of human cytochrome P450 46A1: Implications for treating excitatory neurotoxicity.

CYP46A1 is a brain-specific enzyme responsible for cholesterol homeostasis. Inhibition of CYP46A1 activity serves as a therapeutic target for excitatory neurotoxicity. Sesame is a common medicine and food resource; its component lignans possess various pharmacological activities. In this study, the inhibitory effects of sesame lignans on CYP46A1 activity were investigated. Inhibition kinetics analyses revealed that sesamin and sesamolin produce mixed partial competitive inhibition of CYP46A1, while sesamol produces non-competitive inhibition. Notably, molecular simulations revealed that the sesame lignans have excellent orientations within the active cavity of CYP46A1. Importantly, the sesame lignans had high permeability coefficients and low efflux ratios. Furthermore, sesamin significantly reduced the levels of 24S-hydroxycholesterol in rat plasma and brain tissues, and down-regulated the protein expressions of CYP46A1, NMDAR2A, NMDAR2B, and HMGCR. Collectively, sesame lignans exhibit significant inhibitory effects on CYP46A1 activity, highlighting their potential therapeutic role in treating excitatory neurotoxicity.

The FLT3-ITD Allelic Ratio and NPM1 Mutation Do Not Impact Outcomes in AML Patients with FLT3-ITD after Allo-HSCT: A Retrospective Propensity-Score Matching Study

Introduction: FLT3-ITD occurred in about 25% of adult patients with acute myeloid leukemia (AML), which has been correlated with poor outcomes mainly in cytogenetically normal AML, thus being one of the most frequently affected genes in AML. Whether allogeneic hematopoietic stem cell transplantation (allo-HSCT) can eliminate the detrimental effects of FLT3-ITD mutation in AML patients remain debatable. Studies from our group and others showed that allo-HSCT may overcome the adverse effect of FLT3-ITD on survival outcomes, comparable outcomes were not confirmed in other studies. Additionally, high allelic ratio was correlated with inferior outcomes while NPM1 mutation was associated with favorable outcomes in several studies, but their association with prognosis was not observed in other studies. Previous study from our group showed comparable outcomes between FLT3-ITDmut and FLT3-ITDwt patients, however, the influence of NPM1 mutation and allelic ratio on FLT3-ITDmut patients remains unclear in our database. Hence, we designed a retrospective matched-pair study to compare the survival outcomes between FLT3-ITDmut and FLT3-ITDwt patients who underwent allo-HSCT and further analyzed the impact of NPM1 and allelic ratio on outcomes. Methods: 118 FLT3-ITDmut patients and 497 FLT3-ITDwt patients undergoing allo-HSCT were observed. Each FLT3-ITDmut patients was matched with three FLT3-ITDwt patients using the nearest neighbor-matching method with a caliper size of 0.2. Age and sex of patients, disease status, cytogenetics, pre-MRD, and follow-up days were included in the propensity score model. Results: 116 FLT3-ITDmut patients and 314 FLT3-ITDwt patients were included with a median (range) age of 35 years (1-64). FLT3-ITDmut patients showed higher WBC counts at diagnosis (P<0.001) and NPM1 mutation rate (P<0.001). CIR and LFS of FLT3-ITDmut patients were similar to FLT3-ITDwt patients (CIR:16.9% vs 14.2%, P= 0.266; LFS: 75.1% vs 77.7%, P= 0.399). 32 patients and 41 patients showed NPM1 mutation in FLT3-ITDmut and FLT3-ITDwt patients, respectively. We divided them into four groups based on the status of FLT3-ITD and NPM1 status, no significant difference in CIR and LFS was observed between FLT3-ITDwt NPM1wt, FLT3-ITDwt NPM1mut, FLT3-ITDmut NPM1wt and FLT3-ITDmut NPM1mut patients (FLT3-ITDwt NPM1wt vs FLT3-ITDwt NPM1mut vs FLT3-ITDmut NPM1wt vs FLT3-ITDmut NPM1mut: CIR: 14.8% vs 9.4% vs 16.4% vs 17.8%, P= 0.570; LFS: 76.9% vs 84.4% vs 79.5% vs 67.1%, P= 0.176). 49 patients with available allelic ratio were divided into low allelic ratio (n=25) and high allelic ratio groups (n=24) according to a cut-off 0.50. High allelic ratio was not correlated with inferior outcomes in this study (high allelic ratio vs low allelic ratio: CIR: 21.1% vs 18.1%, P= 0.617; LFS: 70.6% vs 73.7%, P= 0.563). To further analyze the differences between different donor type, we compared the outcomes of 318 haploidentical transplantation and 98 sibling-matched transplantation patients, respectively. FLT3-ITDmut patients had higher CIR and lower LFS than FLT3-ITDwt patients among sibling-matched transplantation (CIR:24.7% vs 12.0%, P= 0.064; LFS:68.2% vs 83.5%, P= 0.0502), but no difference was observed in haploidentical transplantation (CIR: 13.7% vs 15.0%, P= 0.996; LFS:77.8% vs 75.9%, P= 0.885). FLT3-ITD mutation didn't become a prognostic factor in survival outcomes when all patients received transplantation. Prognostic factors with P< 0.1 in univariate analysis were included in multivariate analysis. Apart from pre-MRD, and disease status influencing OS and CIR, another factor affecting OS was the gender of patients. Age played a prognostic role in NRM while pre-MRD and disease status also became the significant factors influencing LFS. Conclusion: Our results showed that allo-HSCT, especially haploidentical HSCT, may overcome the adverse effect of FLT3-ITD mutation, regardless of the NPM1 status or allelic ratio. Allo-HSCT could be an ideal option for AML patients with FLT3-ITD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Economic policy uncertainty and firm performance: Evidence from the energy-intensive industry in China

As a result of high energy consumption and pollution from energy-intensive industries, the Chinese government has implemented a series of policies. A comprehensive assessment of these policies is necessary to guide the green transformation and upgrading of the industry, however, little research has been conducted on this issue. This article takes China's economic policy uncertainty (EPU) Index as a comprehensive and continuous policy shock and investigates the impact of EPU on the financial performance of energy-intensive firms. Based on 289 listed energy-intensive companies from 2003 to 2018, we find that EPU negatively affects the financial performance of firms, and the negative effect is robust after replacing the dependent variable and endogenous discussion. Further, the negative impacts are more pronounced for midwestern, non-SOE firms, as well as ferrous metal and chemical product manufacturers. Moreover, our results indicate that the negative impact of EPU on performance is mitigated for firms with high cash holdings and low debt ratios.

Fabrication of robust ceramic supported polymeric composite nanofiltration membrane for heavy metal contaminated wastewater treatment

Nanofiltration (NF) membranes with positive charge are essential for efficient removal of heavy metals and salts from waste water. In this work surface modified positively charged novel ‘ceramic-supported-polymeric’ (CSP) composite NF membranes were fabricated with the copper ions embedded crosslinked polyethyleneimine polymer matrix over tubular ceramic substrate using facile dipcoating method. EDX, ATR-FTIR, XPS, FESEM, AFM and contact angle analyses were performed to characterize the chemical structures and morphologies of the prepared membranes. The composite NF membrane exhibited satisfactory pure water permeability (PWP) of 8.1 L.m−2.h−1.bar−1 and promising salt (87.19 % and 74.41 % for Mg2+ and Ca2+, respectively) and heavy metal ion rejections (91.73 %, 83.15 % and 75.50 % for Zn2+, Ni2+ and Cd2+, respectively). Activation energy and overall size-exclusion-dehydration phenomena along with steric hindrance and Donnan electrostatic exclusion plays an important role for heavy metals and salts rejection. In addition, the membrane showed excellent antifouling properties (>99 % humic acid removal) with high flux recovery ratio (77.6 %) and low flux decline ratio (33 %) for 5 h operations (3rd cycle) together with outstanding antibiofouling ability towards Brevibacillusagri and Leclerciaadecarboxylata. Furthermore, excellent chemical stability of the membrane suggests its potential application for waste water treatment under critical conditions.

Structural design for wearable self-powered thermoelectric modules with efficient temperature difference utilization and high normalized maximum power density

Flexible thermoelectric generators (FTEGs) show great potential as energy harvesters for wearable electronics by directly converting body heat into electricity. However, the limited temperature difference due to the high fill factor and low TE leg aspect ratio, which determines the open-circuit voltage and follow-up thermoelectric output, hinders application of FTEGs in self-powered wearable electronics. Herein, to realize efficient temperature difference utilization and high normalized maximum power density simultaneously, we designed a flexible device with a nonplanar zigzag π-type structure based on rigid Bi2Te3-based alloys with a much lower fill factor and a higher TE leg aspect ratio than those of commercial TE modules, which exhibits efficient body heat collection performance. Meanwhile, passive radiative cooling and wavy radiator fins were applied as a substitute for traditional metal bulky heat sinks, thereby enhancing the heat dissipation. These structural design strategies endow the generator with a thermoelectric voltage of 22.6 mV and a maximum output power of 75.76 μW from human body heat at 23 °C. Besides, with further optimization, the thermoelectric modules can generate an output power density of 12.36 μW/cm2 and a voltage density of 4.04 mV/cm2 at 23 °C, sufficient to drive some microwatt or sub-microwatt wearable electronics. The ultrahigh temperature difference utilization efficiency and the decent normalized power density suggest that these structural design strategies can be used to efficiently harvest energy in contexts in which there are limited temperature differences, such as human body heat.

Migration Rule of Crude Oil in Microscopic Pore Throat of the Low-Permeability Conglomerate Reservoir in Mahu Sag, Junggar Basin

The low-permeability conglomerate reservoir in the Mahu Sag has great resource potential, but its strong heterogeneity and complex microscopic pore structure lead to a high oil-gas decline ratio and low recovery ratio. Clarifying the migration rule of crude oil in microscopic pore throat of different scales is the premise of efficient reservoir development. The low-permeability conglomerate reservoir of the Baikouquan Formation in the Mahu Sag is selected as the research object, and two NMR experimental methods of centrifugal displacement and imbibition replacement are designed to reveal the differences in the migration rule of crude oil in different pore throats. According to the lithology and physical properties, the reservoirs in the study area can be divided into four categories: sandy grain-supported conglomerates, gravelly coarse sandstones, sandy-gravelly matrix-supported conglomerates and argillaceous-supported conglomerates. From type I to type IV, the shale content of the reservoir increases, and the physical property parameters worsen. Centrifugal displacement mainly produces crude oil in large pore throats, while imbibition replacement mainly produces crude oil in small pores. In the process of centrifugal displacement, for type I reservoirs, the crude oil in the pore throats with radii greater than 0.5 μm is mainly displaced, and for the other three types, it is greater than 0.1 μm. The crude oil in the pore throats with radii of 0.02–0.1 μm, which is the main storage space for the remaining oil, is difficult to effectively displace. The crude oil in the pore throats with radii less than 0.02 μm cannot be displaced. The two experimental methods of centrifugation and imbibition correspond to the two development methods of displacement and soaking in field development, respectively. The combination of displacement and soaking can effectively use crude oil in the full-scale pore throat space to greatly improve the recovery of low-permeability conglomerate reservoirs.

Dynamic regional splitting planning of remote sensing satellite swarm using parallel genetic PSO algorithm

The strips from region splitting method are critical premise of meta-task generation and task planning for satellite swarm. To achieve the regional observation with high coverage and low overlap ratio and satellites usage, a novel region splitting algorithm is designed based on Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) algorithm. In the hybrid algorithm of GA and PSO, these two algorithms are executed paralleled, and then exchange the best genes and individuals periodically, to overcome the disadvantage of GA's poor local searching ability and PSO's low convergence speed. The encoding method and parallel iterative optimal method are given in detail. Finally, a simulation scenario is designed and executed to verify proposed algorithm, and the effects of algorithm parameters are analyzed by simulation results.

Innovative design of modular pantograph tensegrity deployable cylindrical reflectors

To solve the problems of high areal density and low packaging ratio in available deployable cylindrical reflector antennas, an innovative design concept named the modular pantograph tensegrity deployable cylindrical reflector is proposed. The innovative design mainly consists of a pantograph tensegrity deployable truss, flexible cable nets, and reflective wire mesh surface. Based on the modular design concept, the pantograph tensegrity deployable truss can realize synchronous deployment in both parabolic and cylindrical directions. Compared with two typical deployable cylindrical reflectors, the proposed design has the advantages of lower areal density and higher packaging ratio. Simulations of performance analysis demonstrate the benefits of the innovative design.

Effect of bubble cutting on spray characteristics and dust control performance in the effervescent atomization

Effervescent atomization performance depends on the bubble size inside the mixing chamber, consequently influencing the spray dust control performance. This paper proposes an optimization of atomization quality and dust control performance by incorporating a bubble cutter in the atomizer mixing chamber. The effects of the bubble cutter aperture on spray characteristics and flow characteristics were experimentally investigated under different operating conditions. Experimental results showed that Sauter means diameter (SMD) decreases with increasing injection pressure and gas-liquid mass flow ratio (GLR). Furthermore, SMD initially increased and then decreased by reducing the aperture of the bubble cutter from 500 µm to 80 µm. In particular, high injection pressure (Pi =0.6 MPa) and low gas-liquid mass flow ratio (GLR=0.09) strengthened the effects of the bubble cutter aperture on SMD. Moreover, bubble cutter causes a contiguous concentrated droplet size distribution, but it has little effect on droplet velocity. Ultimately, the optimal bubble cutter aperture on the efficiency of respirable dust control efficiencies was theoretically calculated. The dust control efficiency is a maximum at the bubble cutter with an aperture of 230 µm for the effervescent atomizer in this paper. Spray dust control efficiency reaches 93.15 %, which effectively solves the problem of high dust concentration pollution in the mechanized working environment.