Sweep Range Research Articles

PCA-Kriging-Based Oscillating Jet Actuator Optimization and Wing Separation Flow Control

In order to improve the separation control effect of an oscillating jet, the external flow field of the actuators and the wing wake are obtained via hot-wire measurements to optimize the actuator and achieve wing separation flow control. The optimization objectives are to improve the sweeping uniformity and range of the jet. In the present study, the PCA method is used for the modal decomposition of the velocity distribution. The modal-based actuator evaluation parameters are proposed, and the kriging surrogate models of the modal coefficients (principal components) on the actuator parameters are established. The multi-objective genetic algorithm was utilized to complete the optimization of the actuator, and the effect of flow separation control on the wing was verified. The results show that three patterns exist in the time-averaged velocity distribution of the external flow field: unimodal, broad and bimodal, from unimodal to bimodal, the degree of the jet sweeping uniformity gradually decreases, and the sweeping range gradually increases. The pattern of the velocity distribution modals affects the degree of jet sweeping uniformity, while the distance of the modal peaks affects the jet sweeping range. The two evaluation parameters are negatively correlated: insufficient sweeping range or poor sweeping uniformity of the jet are not conducive to wing separation flow control, and the two must be coordinated to achieve the optimal control effect.

Enhanced Stability of N‐Type Organic Electrochemical Transistors Via Small‐Molecule Passivation

AbstractOrganic electrochemical transistors (OECTs) are of great interest owing to their potential applications in bioelectronics and neuromorphic systems. However, n‐type OECTs suffer from poor stability and facile degradation, mainly due to the oxygen reduction reactions in organic mixed ionic‐electronic conductors during device operation. In this study, a small‐molecule passivation strategy is introduced to greatly improve the stability of poly(benzobisimidazobenzophenanthroline) (BBL)‐based n‐type OECTs. 6,6‐Phenyl‐C61‐butyric acid methyl ester (PCBM) is spin‐coated onto the BBL layer to form a smooth and hydrophobic passivation layer, which effectively inhibits the oxygen reduction reactions while enabling ion permeation in aqueous electrolytes. Consequently, the OECTs employing the PCBM/BBL bilayers with an optimized PCBM thickness exhibit significantly improved operational stability at various electrolyte conditions (0.1 m NaCl or NaOH) and over a wide gate‐voltage sweep range (from −0.7 to 0.7 V). Owing to the high electron mobility of PCBM, the carrier mobility and switching speed of the PCBM/BBL OECTs are also improved compared with those of the pristine BBL OECTs. This study demonstrates the beneficial effects of simple surface passivation in organic mixed ionic‐electronic conductors and provides valuable insights for the design of high‐performance and stable OECTs for more specialized and advanced applications.

New insight into synergistic interaction between the backbone or side chain of xanthan gum and the backbone of Gleditsia sinensis polysaccharide

In this study, the synergistic effect and weak gel mechanism of XG and Gleditsia sinensis polysaccharide (GSP) in different ratios were studied through the rheological properties, microstructure and molecular simulation based on density functional theory (DFT). The results of rheological properties showed that the mixtures formed a weak gel at the concentration of 0.5 % (w/v), with the synergistic impact peaking at a XG/GSP ratio of 3:7. Weak gels produced by XG and GSP had the intersection of G' and G" within the temperature sweep range, and the largest change in the G' slope at a XG/GSP ratio of 3:7. By calculating the interaction energy, it was found that the backbone of XG was more likely to interact with the backbone of GSP. Furthermore, the XG mainchain intersected with the backbone of GSP in a cross shape (“X” shape). As a result, this paper proposed a possible mechanism for the formation of the XG/GSP weak gel, with XG as the main chain and GSP as the grid point, and the main interaction type being hydrogen bonding, with the van der Waals force also involved. The results provide new insight for designing and producing physical gels with specific interactions in food industry.

Towards an EPR on a Chip Spectrometer for Monitoring Radiation Damage During X-ray Absorption Spectroscopy

AbstractElectron paramagnetic resonance (EPR) spectroscopy is an essential tool to investigate the effects of ionizing radiation, which is routinely administered for reducing contaminations and waste in food products and cosmetics as well as for sterilization in industry and medicine. In materials research, EPR methods are not only employed as a spectroscopic method of structural investigations, but also have been employed for detection of changes in electronic structure due to radiation damage from high energy X-rays, for example, to monitor radical formation inside biomolecules caused by X-ray irradiation at carbon, nitrogen, and oxygen K-edges at synchrotron facilities. Here a compact EPR spectrometer, based on EPR-on-a-chip (EPRoC) sensor and a portable electromagnet, has been developed as a solution for monitoring radiation damage of samples during their investigation by X-ray absorption spectroscopy (XAS) at synchrotron facilities. A portable electromagnet with a soft iron core and forced air temperature stabilization was constructed as the source of the external magnetic field. The sweep range of magnetic field inside the most homogeneous region of the portable electromagnet is 12–290 mT. The compact spectrometer performance was evaluated by placing the EPRoC sensor inside either a commercial electromagnet or the portable electromagnet to record the EPR spectrum of tempol, irradiated alanine, and dilithium phthalocyanine (Li2Pc). The potential performance of the portable spectrometer for the detection of radiation damage in organic compounds and transition metal-containing catalysts during XAS measurements in both fluorescence and transmission modes was calculated with promising implications for measurements after implementation in a synchrotron-based XAS spectrometer.

Study on Nonlinear Parameter Inversion and Numerical Simulation in Condensate Reservoirs

The B6 metamorphic buried hill condensate gas reservoir exhibits a highly compact matrix, leading to a rapid decline in bottom-hole pressure during initial production. The minimal difference between formation and saturation pressures results in severe retrograde condensation, with multiphase flow further increasing resistance. Conventional numerical simulations often overestimate reservoir energy supply due to their failure to account for this additional resistance, leading to inaccuracies in bottom-hole pressure predictions and gas–oil ratio during history matching. To address these challenges, this study conducted research on nonlinear numerical simulation for buried hill condensate gas reservoirs and established a method for calculating a multiphase pressure sweep range based on the well testing theory. By correcting and fitting the pressure propagation boundaries with numerical simulation, the nonlinear flow parameters applicable to the B6 gas field were inversed. This study revealed that conventional Darcy flow is inadequate for predicting pressure propagation boundaries and that it is possible to reasonably characterize the pressure sweep range through nonlinear flow. This approach resulted in an improvement in the accuracy of historical matching for bottom-hole pressure and gas–oil ratio, which improve the historical fitting accuracy to 85%, providing valuable insights for the development of similar reservoirs.

Analysis of asynchronous/inter-fracture injection-production mechanism under the condition of five-spot vertical and horizontal well combination in low permeability oil reservoirs

At present, low permeability resources are the focus of the development of petroleum industry. In this paper, firstly, the oil displacement mechanism under the condition of vertical and horizontal well combination is clarified. Secondly, the difference of the mechanism of enhancing oil recovery between asynchronous and inter-fracture injection and production is revealed. Thirdly, the difference of energy supplement mechanism between huff and puff and displacement is compared and analyzed. Results show that: (a) with asynchronous injection-production development, the oil saturation drop around the water injection well is greater than that of periodic injection-production and synchronous injection-production. (b) Under the dual effects of water injection pressure difference and capillary force, part of the injected water enters the reservoir with relatively small pore channels, expanding the swept volume. (c) In the soak stage of asynchronous injection-production development, capillary force is the main control factor of oil-water permeability, and its size determines the permeability level. (d) The injected water first flows through the large channel and then flows into small channel to complete the imbibition and replacement. (e) The flow field of asynchronous injection-production has a large sweep range, which is conducive to improving oil recovery.

On-axis full-field swept-source optical coherence tomography for murine retinal imaging

A full-field swept-source optical coherence tomography (FF-SS-OCT) for in vivo murine retinal imaging is demonstrated. The on-axis FF-SS-OCT system was built in a Mach–Zehnder interferometer configuration employing a tunable laser source with an adjustable sweep rate and sweep range in conjunction with a fast 2D-CMOS camera. A large field retinal (coherent) illumination was accomplished using an imaging interface comprised of a short-focal length imaging lens and a contact lens. The magnification between the camera and retina (spatial sampling) was appropriately chosen to record the microscopic structural features of the retina in the image. A pupil stop was employed in the detection path to reject unwanted backscattering from the mouse eye and other sources and limit aberrations distorting the retinal images. In vivo mouse retinal imaging was performed at a sweep rate of 150 Hz to acquire volumes unaffected by the system vibrations, which predominated at lower frequencies. Operating the FF-SS-OCT at this speed yielded an effective axial scan rate of 20 million A-scans/s and a field of view of 820 × 410 µm (24.12° × 12.06°). High-quality retinal B-scans and enface images of the retina were obtained with the SS-FF-OCT, revealing all major retinal layers and vascular plexuses.

Synthesis and investigation of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid copolymer-modified graphene oxide nanomaterials with intensive viscosification capacity: An experimental and molecular dynamics study

The polymer-modified nanomaterials with spontaneously generated cross-linked network greatly improve the dispersion viscosity, which is crucial for extending the sweep range and enhancing oil recovery. Recently, graphene oxide (GO) nanosheets have attracted extensive attention due to their high chemical reactivity and specific surface. In this paper, the AA molecule, synthesized by acrylamide (AM) and 2-acrylamido-2-methypropanesulfonic acid (AMPS) copolymerization, modified GO nanosheets (GAA) material is firstly synthesized and characterized. With the same content of AMPS segments, GAAn systems consistently exhibit better dispersion stability than AAn systems, along with higher absolute zeta potential values. The comprehensive investigation on the rheological property of GAA system reveals that GAA15 with the highest AMPS content exhibits the largest zero-shear viscosity (409.27 mPa·s) and the longest relaxation time. Based on the molecular dynamic simulation approaches, the aggregation morphology and stability of AA and GAA molecules are evaluated via the configuration analysis and the statistics of hydrogen bond numbers. The abundant binding sites from GO segments of GAA promote additional hydrogen bonds between GAA molecules and water, resulting in a more stable configuration. Molecular surface potential analysis and the independent gradient model based on Hirshfeld partition (IGMH) methods are further used to visualize the non-bonded interaction existed in cross-linked networks, which also predict and validate non-bonding interaction sites among molecular segments. The simulation results indicate higher viscosity in the GAA system should be ascribed to the formation of dispersion-strengthened cross-linked structures (AM-GO plane and GO-GO stacking segments). In summary, the microscopic viscosity-increasing mechanism of novel GAA system is proposed from the perspective of intermolecular interactions, which lays a preliminary theoretical foundation for the application of GAA material in the oil industry.

Gas channeling control with CO2-responsive gel system in fractured low-permeability reservoirs: Enhancing oil recovery during CO2 flooding

During the CO2 flooding process in fractured low-permeability oil reservoirs, the injected CO2 is prone to channeling along fractures due to severe reservoir heterogeneity, resulting in poor development effect. The CO2-responsive gel system shows dual advantages in achieving CO2 capture and plugging gas channeling to enhance oil recovery. This paper constructed a system with good CO2 sensitivity based on long-chain alkyl amide propyl dimethyl tertiary amine first. Subsequently, the properties of the system before and after the response were evaluated through rheological test, and its microstructure was characterized by Cryo-TEM. The system exhibited good CO2 responsiveness, transitioning from low-viscosity solution system to high-viscosity CO2-responsive gel system upon contact with CO2, with its viscosity increasing by nearly five orders of magnitude. The CO2-responsive gel demonstrated excellent shear resistance, viscoelasticity and shear self-repairing ability. The change of microstructure further verified the mechanism of molecules self-assembly in the system under the action of CO2. Then, a series of core physical simulation experiments were carried out to comprehensively evaluate the effects of different factors on the injection capacity, plugging characteristics, dynamic filtration damage performance and EOR effect of CO2-responsive gel. The gel maintained injectability while achieving an exceptional deep plugging effect, and the plugging rate reached 98.77%. It showed good characteristics of low filtration and permeability damage in low permeability reservoirs, effectively ensuring the fracture plugging effect. After the fracture was plugged by gel, the sweep range of CO2 to the matrix significantly expanded, and the gas flooding recovery increased by 18.19–21.7%. Finally, the matrix-fracture dual-media chip model was used to conduct microfluidic experiment, the oil displacement characteristics in different displacement stages were visually clarified, and the synergistic plugging and oil displacement mechanism between the CO2-responsive gel and CO2 was summarized. The research results can provide important insights for the green and efficient application of CO2-responsive gel in fractured low-permeability reservoirs.

High-Magnification Object Tracking with Ultra-Fast View Adjustment and Continuous Autofocus Based on Dynamic-Range Focal Sweep.

Active vision systems (AVSs) have been widely used to obtain high-resolution images of objects of interest. However, tracking small objects in high-magnification scenes is challenging due to shallow depth of field (DoF) and narrow field of view (FoV). To address this, we introduce a novel high-speed AVS with a continuous autofocus (C-AF) approach based on dynamic-range focal sweep and a high-frame-rate (HFR) frame-by-frame tracking pipeline. Our AVS leverages an ultra-fast pan-tilt mechanism based on a Galvano mirror, enabling high-frequency view direction adjustment. Specifically, the proposed C-AF approach uses a 500 fps high-speed camera and a focus-tunable liquid lens operating at a sine wave, providing a 50 Hz focal sweep around the object's optimal focus. During each focal sweep, 10 images with varying focuses are captured, and the one with the highest focus value is selected, resulting in a stable output of well-focused images at 50 fps. Simultaneously, the object's depth is measured using the depth-from-focus (DFF) technique, allowing dynamic adjustment of the focal sweep range. Importantly, because the remaining images are only slightly less focused, all 500 fps images can be utilized for object tracking. The proposed tracking pipeline combines deep-learning-based object detection, K-means color clustering, and HFR tracking based on color filtering, achieving 500 fps frame-by-frame tracking. Experimental results demonstrate the effectiveness of the proposed C-AF approach and the advanced capabilities of the high-speed AVS for magnified object tracking.

Simulation Analysis of Mode Hopping Impacts on OFDR Sensing Performance

This article examines the impacts of mode hopping on the sensing performance of optical frequency domain reflectometry (OFDR) and explores the potential for developing economical OFDR interrogators employing low-cost distributed feedback (DFB) lasers. By conducting numerical simulations, this study reveals that mode hopping has minimal effects on distance sensing measurements in free space due to the limited duration of beat interference signal at the incorrect frequency within the coherence length. Additionally, the simulations indicate that mode hopping only slightly affects the distributed strain sensing of OFDR, resulting in an error range of less than ±1µε when 100µε is applied to the sensing fiber. These findings highlight the potential of using low-cost DFB lasers with a 1-nm wavelength sweep range and a 1-MHz linewidth as tunable laser sources in OFDR while maintaining reliable and accurate sensing performance.

Unmodified α-LiFe5O8 as potential anode material of lithium ion battery and the revelation of conversion mechanism

Spinel structured α-LiFe5O8 were prepared via ball milling combined with a straightforward solid-phase method, using Fe2O3 and Li2CO3 as the raw materials. The material maintained a stable capacity of 440 mAh g−1 after 200 cycles at 900 mA g−1 with Coulomb efficiency more than 95 % and also showed facile lithium ion diffusion dynamics. The calculated diffusion coefficient of α-LiFe5O8 ranged around 10−10-10−12 cm2 s−1. Diffusion controlled contribution was dominant over capacitive contribution in the sweeping range 0.1–1.5 mV s−1. A new intercalation-decomposition-conversion mechanism was proposed on the basis that there existed a small pit at the initial stage of the discharge plateau and a significantly low initial discharge plateau voltage was observed compared with the followed discharge cycles. Based on the DFT calculations and the phase diagram of the Li–Fe–O system, we supposed that for the initial discharge of the material, after 1 mol of lithium ion intercalation per unit formula, α-LiFe5O8 decomposed to LiFeO2 and Fe3O4. The followed discharge was the conversion of both LiFeO2 and Fe3O4 to metal Fe and Li2O. Thereafter, the system cycled between Fe2O3 at the fully charged state and metal Fe and Li2O at the fully discharged state.

Effects of the VGS sweep range on the short channel effect in negative capacitance FinFETs

Effects of the VGS sweep range on the short channel effect in negative capacitance FinFETs

An Enhanced Synaptic Plasticity of Electrolyte-Gated Transistors through the Tungsten Doping of an Oxide Semiconductor

Oxide electrolyte-gated transistors have shown the ability to emulate various synaptic functions, but they still require a high gate voltage to form long-term plasticity. Here, we studied electrolyte-gated transistors based on InOx with tungsten doping (W-InOx). When the tungsten-to-indium ratio increased from 0% to 7.6%, the memory window of the transfer curve increased from 0.2 V to 2 V over a small sweep range of −2 V to 2.5 V. Under 50 pulses with a duty cycle of 2%, the conductance of the transistor increased from 40-fold to 30,000-fold. Furthermore, the W-InOx transistor exhibited improved paired pulse facilitation and successfully passed the Pavlovian test after training. The formation of WO3 within InOx and its ion intercalation into the channel may account for the enhanced synaptic plasticity.

Application of Flue Gas Foam-Assisted Steam Flooding in Complex and Difficult-to-Produce Heavy Oil Reservoirs.

In order to study the mechanism of improving recovery efficiency of complex difficult-to-recover heavy oil reservoirs and explain the interaction and migration law of flue gas, foam, and steam, this paper designed the experiment of flue gas influence on heavy oil flow and the experiment of flue gas foam displacement in complex difficult-to-recover heavy oil model. The results show that the flue gas has expansion and an energy enhancement effect. Moreover, the interfacial tension of heavy oil can be reduced, and the higher the CO2 content in flue gas, the more beneficial it is to reduce the interfacial tension. When there is an interlayer in the reservoir, the gas can form a "puncture" in the interlayer, which provides a channel for the subsequent upward expansion of steam, so that the upper part of the interlayer can be used to expand the steam sweep range. The main mechanism of improving heavy oil recovery with flue gas foam is that the foam regulates fluid mobility and improves the thermal sweep efficiency of steam. In addition, the injected foam can emulsify with heavy oil, reduce the viscosity of heavy oil, and improve the fluidity of heavy oil. Finally, the maximum oil production rate increased from 1.809 to 2.455 g/min, and the recovery rate increased from 44.3 to 68.8%.

Design of Mutiple Signal Generators based on DDS

The hardware circuit of the signal generator mainly includes the main control module, DDS module, Voltage-Controlled Gain Amplifier (VCGA) module, keypad module, and LCD display module. The main control module is based on the STM32F103C8T6 as the core controller, and the signal processing section employs the low-power, programmable AD9834 DDS device. The VCGA module utilizes the AD8367 module, providing a controllable 32dB gain range to offer a 20mV/dB output. The waveform voltage amplitude can be adjusted by manipulating the potentiometer on the module and fed back to the oscilloscope. Experimental results demonstrate that the signal generator can produce square waves, triangular waves, sine waves, and sweep frequency waves with stable output waveforms and high resolution. Specifically, the sine wave and triangular wave can be generated within the frequency range of 1kHz to 200KHz, the square wave within the range of 75kHz to 200kHz, and the sweep frequency wave with a sweeping range from 1kHz to 100kHz.

Pore-scale simulation of miscible displacement in an inclined porous medium

Introduction: This study investigates the displacement of two miscible fluids within an inclined porous medium at the pore scale, highlighting how the pore-scale microstructure, inclination angle, and viscosity ratio affect the interfacial instability between two fluids during displacement processes.Methods: The lattice Boltzmann Method (LBM) is employed to solve the governing equations. Two distribution functions are used to simulate the velocity field and the concentration field, respectively.Results and discussion: An increase in inclination angle exacerbates the interfacial instability between fluids and the viscous fingering phenomenon. This viscous fingering expands the sweep range of displacing fluids, which improves the displacement efficiency. When θ > 50°, further increase in inclination angle will not cause significant changes in displacement efficiency. In addition, the viscosity ratio is a key factor affecting displacement efficiency. The larger the viscosity ratio, the greater the displacement efficiency. Furthermore, the critical viscosity ratio has been found, and any increase in the viscosity ratio above the critical value will not affect the displacement efficiency.

Simulation and solution of a proppant migration and sedimentation model for hydraulically fractured inhomogeneously wide fractures

The distribution of proppant during hydraulic fracturing may directly contribute to the flow conductivity of the proppant fracture, so research on the migration and sedimentation of proppant in the fracture and the final distribution pattern is of great relevance. The mass conservation equations of proppant solids and fracturing fluid were adopted to describe the distribution of proppant migration and sedimentation in the fracture, improving the additional gravity coefficient by utilizing the density difference between proppant and fracturing fluid and the concentration of proppant, together with the proppant sedimentation velocity at different Reynolds numbers in this study. The flow coefficients were obtained by discretizing the system of equations through the finite volume method combined with the harmonic mean method and the upstream weight method. The concentration additional pressure gradient term was computed by using the Superbee format innovatively to improve the solution convergence of the model. Numerical simulations with identical parameters were compared with indoor test results, which fully verified the correctness of the model and the accuracy of the discrete solution based on the finite volume method. The effects of flow rate of fracturing fluid, ratio of injected sand, viscosity of fracturing fluid, grain size of proppant and density of proppant on proppant migration and sedimentation based on three elliptical fracture morphologies: even-wide, top-wide and bottom-narrow as well as top-narrow and bottom-wide were investigated and analyzed through comparing the rate of proppant front movement, the level of sweeping range and the degree of inhomogeneity in the range under different conditions. Findings of this study suggest that: (1) top-wide and bottom-narrow fractures are more preferable for homogenous sanding in the early stage of proppant injection, and top-narrow and bottom-wide fractures are best for sanding in the later stage; (2) the viscosity of fracturing fluid is the most influential factor on proppant migration and sedimentation, which increases in the range of 100 mPa.s to enhance the sweeping range and homogeneity of proppant sanding and therefore achieve a better fracturing effect.

Resistive Memory-Switching Behavior in Solution-Processed Trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) Benzene-PVA-Composite-Based Aryl Acrylate on ITO-Coated PET.

Resistive switching memories are among the emerging next-generation technologies that are possible candidates for in-memory and neuromorphic computing. In this report, resistive memory-switching behavior in solution-processed trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate on an ITO-coated PET device was studied. A sandwich configuration was selected, with silver (Ag) serving as a top contact and trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate and ITO-PET serving as a bottom contact. The current-voltage (I-V) characteristics showed hysteresis behavior and non-zero crossing owing to voltages sweeping from positive to negative and vice versa. The results showed non-zero crossing in the devices' current-voltage (I-V) characteristics due to the nanobattery effect or resistance, capacitive, and inductive effects. The device also displayed a negative differential resistance (NDR) effect. Non-volatile storage was feasible with non-zero crossing due to the exhibition of resistive switching behavior. The sweeping range was -10 V to +10 V. These devices had two distinct states: 'ON' and 'OFF'. The ON/OFF ratios of the devices were 14 and 100 under stable operating conditions. The open-circuit voltages (Voc) and short-circuit currents (Isc) corresponding to memristor operation were explained. The DC endurance was stable. Ohmic conduction and direct tunneling mechanisms with traps explained the charge transport model governing the resistive switching behavior. This work gives insight into data storage in terms of a new conception of electronic devices based on facile and low-temperature processed material composites for emerging computational devices.

The mechanisms of thermal solidification agent promoting steam diversion in heavy oil reservoirs

At high cycles of steam huff & puff, oil distribution in reservoirs becomes stronger heterogeneity due to steam channeling. Thermal solidification agent can be used to solve this problem. Its solution is a low-viscosity liquid at normal temperature, but it can be solidified above 80 °C. The plugging degree is up to 99% at 250 °C. The sweep efficiency reaches 59.2%, which is 7.3% higher than pure steam injection. In addition, simultaneous injection of viscosity reducer and/or nitrogen foams can further enhance oil recovery. The mechanism of this technology depends on its strong plugging ability, which changes the flowing pattern of steam to effectively mobilize remaining oil. Viscosity reducer and nitrogen foams further expand the sweep range and extends the effective period. Therefore, thermal solidification agent can plug steam channeling paths and adjust steam flowing direction to significantly enhance oil recovery at high cycles of steam huff & puff.