Injection Phase Research Articles

Design of Experiment Centered Multivariate Optimization Strategy for RP-HPLC Method to Quantitate Retapamulin in Topical Cream and Microemulsion

Background: Retapamulin is the first pleuromutilin antibacterial approved for the treatment of impetigo. The objective of the current research was to utilize the design of experiments approach for development and optimization of robust RP-HPLC method for the quantitation of Retapamulin in marketed cream and in-house developed microemulsion based formulations with an oily matrix. Methods: The impact of various chromatographic conditions (independent variables) was assessed using Plackett–Burman design on critical analytical attributes (response) to screen initial experimental conditions. The Box-Behnken design was employed to optimize the selected chromatographic factors on the responses. Further, validation of optimized RP-HPLC was carried out as per the ICHQ2(R1) guideline. Results: Pareto ranking analysis showed that % organic phase, flow rate, and volume of injection were found statistically significant (p < 0.05) variables influencing the retention time, number of plates, and tailing of the Retapamulin peak. The optimized RP-HPLC method with the stationary phase, C18 (250 mm × 4.6 mm, 5 μm) column, and mobile phase as a mixture of methanol and potassium dihydrogen orthophosphate buffer (50 mM, pH 7.0, 90:10 % v/v, isocratic), the flow rate of 1.0 mL/min, 10 μL injection volume, 25°C column oven temperature, 247 nm as detection wavelength, was successfully validated based on ICHQ2(R1) guideline. Conclusion: RP-HPLC method was successfully used to separate (retention time 4.34 ± 0.2 min)and assay Retapamulin in microemulsion and marketed cream. The outcomes of the investigation exhibited the effective application of a multivariant approach in the optimization of the RP-HPLCfor routine analysis of Retapamulin.

Use of a Holistic Design and Manufacturing Approach to Implement Optimized Additively Manufactured Mould Inserts for the Production of Injection-Moulded Thermoplastics

Injection moulding is one the most familiar processes for manufacturing of plastic parts by injecting molten thermoplastic polymers into a metallic mould. The cycle time of this process consists of the phases of injection, packing, cooling, and ejection of the final product. Shortening of cycle time is a key consideration to increase productivity. Therefore, in this manuscript the adoption of additively manufactured mould inserts with conformal cooling channels by means of selective laser melting (SLM) with the aim to reduce process cycles is presented. The design and manufacture of a mould insert with conformal cooling channels for producing pressure fitting thermoplastic parts is described. Numerical analysis of the injection process and simulation of shape distortions after SLM were conducted providing useful results for the design and manufacture of the mould insert. The results of the numerical analyses are compared with experimental 3D geometrical data of the additively manufactured mould insert. Temperature measurements during the real injection moulding process demonstrating promising findings. The adoption of the introduced method for the series production of injection moulded thermoplastics proves a shortening of cycle times of up to 32% and a final product shape quality improvement of up to 77% when using mould inserts with conformal cooling channels over the conventional mould inserts.

Effects of flow-interruption on the bacteria transport behavior in porous media

Attachment is an important strategy for microorganisms to survive, grow, and perform biogeochemical functions in soil and groundwater systems. This study investigated the effect of flow-interruption (FI) that is common in subsurface environments on bacterial attachment/detachment using a metal-reducing bacterium Shewanella oneidensis strain (MR1) as an example. Column experiments and one dimensional bacterial transport models were performed by varying flow interruption duration, fluid ionic strength, and solid grain surface electrostatic properties with a goal to understand the effect of FI on bacterial attachment/detachment. The results indicated that MR1 generally behaved as colloidal particles in transport and attachment/detachment under continuous flow conditions. However, the FI events induced a significant release of MR1 in both injection and elution phases, showing a peak MR1 concentration, which was higher than that in the injecting solution, immediately after the FI events. The peak MR1 concentrations were higher in systems with lower adhesive forces between bacteria and solid grains, a lower attachment site capacity in porous media, and a longer FI duration. The diffusive release of the previously attached bacteria during the FI events and the momentum force when flow re-started immediately after the FI events were likely the mechanisms leading to bursting release of bacteria with the release concentrations higher than that in the influent solutions. The results have important implication for understanding bacterial migration and attachment, and their subsequent functions, especially in dynamic hydraulic environments such as in hyporheic zones or in soils subject to dynamic changes in infiltration rates under for example extreme precipitation and drought conditions.

Analysis of the particle longitudinal motion during the injection process into the disk loaded traveling wave accelerating structure

We study longitudinal beam motion of the beam with a nonrelativistic energy during the injection into the disk loaded accelerating structure with traveling wave. Analysis of the particle dynamics is carried out with the help of the Hamiltonian formalism. Condition of the particle capture into the acceleration is derived. Trajectories of the particles in the longitudinal phase space are shown. We also discuss the optimal injection phase for the maximum particle energy gain together with beam bunching during the injection.

Effects of a ketone mutual solvent on the dynamic and equilibrium behaviors of crude oil swelling in enhanced oil recovery process by carbonated seawater flooding

Carbon dioxide (CO2) dissolved in water can be used as an additive in enhanced oil recovery (EOR) process. Mechanisms of carbonated water injection into oil reservoirs are highly dependent on the water solubility of CO2. Combining carbonated water injection method with other methods is a common EOR method. Using mutual and lighter than water solvents such as ketones and alcohols to increase the water solubility of CO2 and enrich carbonated water is a new formulation of injectable water. Crude oil swelling is one of basic mechanisms of EOR. This mechanism is more important in methods such as carbonated water and mutual solvent injection due to the transfer of the additives masses between injection and oil phases. In this study, the dynamic and equilibrium oil swelling in interaction with injected fluid containing dissolved CO2 and acetone as a mutual solvent was investigated. The experiments were performed at 75 °C and different pressures. The effects of time, injection fluid salinity and mutual solvent ratio on crude oil swelling behavior and equilibrium oil swelling and equilibrium time were investigated. The results of these studies briefly show that oil swelling constantly increases over time to reach a near-constant value at equilibrium time. The swelling of crude oil in interaction with carbonated water containing different volumetric ratios of acetone at a constant temperature, dependents on pressure, acetone volumetric ratio and salinity of the base fluid. The equilibrium oil swelling has a direct relationship with pressure, acetone volumetric ratio and salinity. The presence of acetone can increase oil swelling by 13.64%, taking into account its ratio. Time is an influential parameter in crude oil swelling. Crude oil swelling in the early times in the presence of acetone is lower than the oil swelling in the presence of acetone-free carbonated water. However, in meso-equilibrium and equilibrium times, the final rate is greater than the swelling of oil in the presence of acetone-free carbonated water. At 10.342 MPa, the equilibrium time of oil swelling for the salinity of the seawater and the acetone volumetric ratios of 0, 5, 10 and 15% were 11.5, 13.5, 15.5 and 20.5 min, respectively. These values were equal to 15.5, 17.5, 22.0 and 27.5 min, respectively, for the salinity of the base fluid equal to 16500 ppm and were equal to 22.5, 24.5, 26.0 and 32.5 min, respectively, for the salinity of 11000 ppm.

Improvement of instantaneous turbine efficiency through late intake valve phase (LIVP) in a turbocharged-gasoline direct injection (T-GDI) engine

The effects of a late intake valve phase (LIVP) strategy on crank-angle resolved real-time turbocharger efficiency were analyzed. The research is composed of experiments and simulations. In the experiments, an engine test was conducted with a downsized 2.0 L 4-cylinder turbocharged-gasoline direct injection (T-GDI) engine. In order to evaluate the effects of LIVP on the instantaneous turbocharger efficiency, the intake valve phase was retarded from its reference phase to 30 crank angle degrees (CADs) by steps of 10 CADs, while maintaining the fixed position of the other engine control parameters. Pressure in the intake and exhaust systems and turbocharger rotational speed were also measured in the experiments. In the simulation, a 1-D simulation model was built to simulate the same conditions as in the experiments. Instantaneous turbine mass flow rate as well as, temperature upstream and downstream of the turbine were extracted from the model in the units of CAD. This was done because it is inherently impossible to measure these data in the units of CAD with the existing real-world mass flow meter and thermocouples. The instantaneous blade speed ratio (BSR), turbine efficiency, and mass flow parameter were calculated by combining the results of the experiment and the 1-D simulation. In the results, the instantaneous turbine efficiency was divided into two phases and analyzed. First, in the filling phase, the effects of exhaust blow-down pulse arrival on the instantaneous turbine efficiency were analyzed. Second, in the emptying phase, the effects of exhaust gas scavenged from the cylinder on the instantaneous turbine efficiency were analyzed. The instantaneous turbine efficiency showed strong unsteady characteristics and deviated from the quasi-steady performance line. This was due to large fluctuations in the turbine inlet conditions. With the application of the LIVP strategy, the instantaneous turbine efficiency was increased. This was because of a decrease in the amount the waste-gate opened while meeting the same engine load lead to more exhaust gas energy entering the turbine, and the turbine’s operating conditions were changed to more efficient conditions. Finally, correlation of the engine thermal efficiency rising according to the instantaneous turbine efficiency rising was confirmed.

Exact frequency and phase control of a terahertz laser

The accuracy of high-resolution spectroscopy depends critically on the stability, frequency control, and traceability available from laser sources. In this work, we report exact tunable frequency synthesis and phase control of a terahertz laser. The terahertz laser is locked by a terahertz injection phase lock loop for the first time, with the terahertz signal generated by heterodyning selected lines from an all-fiber infrared frequency comb generator in an ultrafast photodetector. The comb line frequency separation is exactly determined by a Global Positioning System-locked microwave frequency synthesizer, providing traceability of the terahertz laser frequency to primary standards. The locking technique reduced the heterodyne linewidth of the terahertz laser to a measurement instrument-limited linewidth of < 1 H z , robust against short- and long-term environmental fluctuations. The terahertz laser frequency can be tuned in increments determined only by the microwave synthesizer resolution, and the phase of the laser, relative to the reference, is independently and precisely controlled within a range ± 0.3 π . These findings are expected to enable applications in phase-resolved high-precision terahertz gas spectroscopy and radiometry.

Oral Spirulina Platensis Attenuates Hyperglycemia and Exhibits Antinociceptive Effect in Streptozotocin-Induced Diabetic Neuropathy Rat Model.

IntroductionDiabetic neuropathy is a common consequence of diabetes. Hyperalgesia is one of the main symptoms of diabetic neuropathy. In response to noxious stimuli, streptozotocin (STZ)-induced diabetic rats show exaggerated hyperalgesic behavior, while Spirulina platensis has anti-inflammatory, antioxidant, and insulin-like effects. To assess the antinociceptive effect of oral Spirulina platensis (SP) powder on formalin-induced nociceptive responses in STZ-induced diabetic rats.MethodsSixty mature male albino rats were randomly allocated into six equal groups (10 in each group). Group 1 (control non-diabetic group) received 0.9% saline; group 2 was given oral pure SP powder-treated as a non-diabetic control group, group 3 was sodium salicylate-treated rats and used as a positive non-diabetic control group, group 4 managed as vehicle-treated diabetic rats, group 5 considered as SP-treated-diabetic group, and sodium salicylate-treated-diabetic rats used as a diabetic positive control group (group 6). STZ-diabetic rats were orally given SP in a dose of 500 mg kg/day for 1 month. The formalin test was implemented in two phases: the early phase in the first 10-min post-formalin injection, and the late phase was considered in the 15–60 min post-formalin injection time interval.ResultsPain scores were increased in the diabetic groups during both phases of the experiment. Blood glucose was significantly reduced in diabetic rats that received oral SP, P < 0.01. Besides, SP-treated rats had lower pain scores during both phases of the experiment than untreated diabetic ones. However, in the sodium salicylate group, the pain score was reduced only during the second phase. An exaggerated nociceptive response occurred in diabetic rats after the formalin test. A significant antinociceptive effect appeared in SP-treated control and diabetic rats.DiscussionThe findings suggest that oral Spirulina platensis could have a potential therapeutic role for managing induced painful diabetic neuropathy in rats.

FUEL INJECTION PROCESS AT SPEED CHARACTERISTICS OF MEDIUM-SPEED DIESEL ENGINE AT VARIABLE MODES

The results of an experimental study of the features of the fuel injection process on the speed response of a medium-speed marine diesel engine under variable conditions are presented. The study of hydrodynamic processes for these characteristics expands the possibilities for improving the operation of a diesel engine, and also allows to clarify the methods for calculating the processes associated with fuel injection. Experimental studies have been performed on an engineless test bench under various initial conditions with the refinement of the measuring complex. The first option - before starting the high-pressure fuel system was unloaded. The second option - the engineless test bench was started after a short stop. At the same time, the residual pressure remains in the system after the first start option. The generalized results of the experimental study allowed to evaluate the process of fuel supply development during the whole experiment. At the same time, in the first option, the essential feature is the absence of a noticeable increase in pressure in the nozzles during the first three injection cycles in the acceleration process, despite the rather high rotational speed of the camshaft. Only in the fourth cycle, a pressure increase of up to 40 bar was obtained, which is not enough to lift the nozzle needle. The first injection conditions are formed in the fifth cycle (stepwise injection phase). In the second option, with an initial pressure in the fuel system of 27 bar, during acceleration already on the first revolution with a relatively low rotational speed, the pressure value corresponds to the injection conditions and reaches 166 bar. Thus, the initial pressure in the fuel system during acceleration has a significant impact on the development of the injection characteristics, which is a specific feature of the diesel engine operation in variable modes. The peculiarity of the formation of injection parameters during coasting in both options does not depend on the initial conditions in the fuel system. Consideration of the injection process features at a continuously varying rotation speed will improve the reliability of marine diesel engines during maneuvering and will ensure the improvement of diesel engine working processes at variable modes.

Investigation of mode activity in NBI-heated experiments of Wendelstein 7-X

The 2018 operation phase (OP 1.2b) of the stellarator Wendelstein 7-X (W7-X) included, for the first time, neutral beam injection (NBI) to heat the plasma. Since the injection geometry at W7-X is not parallel, this generates both passing and trapped fast particles. During longer phases of NBI injection, with the primary purpose to study the heating efficiency of this system, Alfvén eigenmodes (AEs) were observed by a number of diagnostics, including the phase contrast imaging (PCI) system, the magnetic pick-up coils (Mirnov coils), and the soft x-ray multi-camera tomography system (XMCTS).Alfvén eigenmodes are of great interest for future fusion reactors as it has been shown that the resonant interaction of fast ions with self-excited AEs can lead to enhanced transport of fast ions and potentially to energy losses. This is especially true for so-called gap-modes, Alfvén eigenmodes with frequencies in gaps of the continuous spectrum, since they lack continuum damping. These modes are commonly known to be excited by fast ions, but other destabilizing mechanisms, e.g. the electron-pressure gradient are also possible.In this article we present a first analysis of the experimentally observed frequencies from the theoretical side. The calculation of shear Alfvén wave continua for selected cases and the assignment of observed frequencies to the gaps of the continuous spectra are presented. Using the ideal-MHD code CKA (Könies A. 2007 10th IAEA TM on Energetic Particles in Magnetic Confinement System), we find gap modes that match the experimental measurements in terms of the observed frequencies. We emphasize the crucial roles played by the coupling of sound and Alfvén waves as well as of the Doppler shift arising as a consequence of the radial electric field in W7-X.We employ the perturbative gyrokinetic code CKA-EUTERPE (Feh´er 2013 Simulation of the interaction between Alfv´en waves and fast particles), using a slowing-down distribution function for the fast ions as calculated by the Monte-Carlo particle following code ASCOT (Hirvijoki et al 2014 Comput. Phys. Commun. 185 1310–21) to assess the fast-ion drive. We find that the fast-ion drive is insufficient to overcome the background-plasma damping. The fact that unstable modes were observed experimentally may point to problems with the modelling or indicate the existence of other destabilizing mechanisms, e.g. associated with the electron-pressure gradient (Windisch et al 2017 Plasma Phys. Control. Fusion 59 105002) that sensitively depend on the profiles of the background plasma.

Rock Deformation and Strain-Rate Characterization during Hydraulic Fracturing Treatments: Insights for Interpretation of Low-Frequency Distributed Acoustic-Sensing Signals

SummaryLow-frequency distributed acoustic-sensing (LF-DAS) data are promising attributes for detecting fracture hits and fracture characterization. However, measured signals from different wells exhibiting various characteristics and mechanisms attributing to the difference are not well understood, which makes the interpretation of field LF-DAS data most challenging. In this study, our in-house hydraulic fracturing simulator is used to simulate fracture propagation. The induced rock deformation and corresponding strain-rate variations along offset monitor wells are analyzed and related to specific fracture features. The mechanisms for LF-DAS signals are investigated through five synthetic case studies with single fracture propagation. A typical strain-rate waterfall plot of LF-DAS measurements during the fluid injection phase of a fracturing treatment can be divided into two distinct regions. A heart-shaped extending region forms as the fracture approaches to the monitor well, indicating that the magnitude of extension keeps increasing as the fracture tip gets closer to the monitor well. After the fracture hits the monitor well, the extending region shrinks to a line (the field-measured data may be a wide band, depending on the spatial resolution of the measurement), and a two-wing compressing zone is observed, illustrating large compressional strain variations on both sides of the fracture. As the fracture continues propagating, the strain rate tends to be stable, the characteristics of which depend on specific fracture geometry and propagation conditions. The size and shape of observable signatures on LF-DAS data are directly influenced by fracture width, height, and height growth. Larger fracture width results in larger sizes of heart-shaped extending region and two-wing compressing region in the strain-rate waterfall plot. Larger fracture height also induces a larger heart-shaped extending region before the fracture hits. However, a fracture with larger height could lead to larger extension along the fiber near the fracture, which results in less overall compression and a zone of decreasing compression in the vicinity of the fracture as the fracture propagates away from the fiber after the fracture hit. This signature is more pronounced when the fracture height growth is considered.The interpretation of a field example with four clusters based on our forward physical modeling results indicates that, although the distinct signatures of field data are not as obvious as the simulation results because of low measurement resolution and unavoidable noise, they do convey valuable information on fracture characteristics. There is a shrinkage of the extending zone from a heart shape to a band at the fracture-hit time. During simultaneous multifracture propagation, fracture-hit time of each fracture, which determines the fracture propagation speed and perforation efficiency, can be identified. The discontinuous extending band after fracture hit could be attributed to the intermittent stop and restart of fracture propagation and relative fracture opening/closing. The results of this study help to better interpret the real-time LF-DAS data and provide critical insights into hydraulic fracture characterization using LF-DAS data.

New model of reactive transport in a single-well push–pull test with aquitard effect and wellbore storage

Abstract. The model of single-well push–pull (SWPP) test has been widely used to investigate reactive radial dispersion in remediation or parameter estimation of in situ aquifers. Previous analytical solutions only focused on a completely isolated aquifer for the SWPP test, excluding any influence of aquitards bounding the tested aquifer, and ignored the wellbore storage of the chaser and rest phases in the SWPP test. Such simplification might be questionable in field applications when test durations are relatively long because solute transport in or out of the bounding aquitards is inevitable due to molecular diffusion and cross-formational advective transport. Here, a new SWPP model is developed in an aquifer–aquitard system with wellbore storage, and the analytical solution in the Laplace domain is derived. Four phases of the test are included: the injection phase, the chaser phase, the rest phase and the extraction phase. As the permeability of the aquitard is much smaller than the permeability of the aquifer, the flow is assumed to be perpendicular to the aquitard; thus only vertical dispersive and advective transports are considered for the aquitard. The validity of this treatment is tested against results grounded in numerical simulations. The global sensitivity analysis indicates that the results of the SWPP test are largely sensitive (i.e., influenced by) to the parameters of porosity and radial dispersion of the aquifer, whereas the influence of the aquitard on results could not be ignored. In the injection phase, the larger radial dispersivity of the aquifer could result in the smaller values of breakthrough curves (BTCs), while there are greater BTC values in the chaser and rest phases. In the extraction phase, it could lead to the smaller peak values of BTCs. The new model of this study is a generalization of several previous studies, and it performs better than previous studies ignoring the aquitard effect and wellbore storage for interpreting data of the field SWPP test reported by Yang et al. (2014).

Novel hybrid Fast Marching Method-based simulation workflow for rapid history matching and completion design optimization of hydraulically fractured shale wells

This paper introduces a novel hybrid Fast Marching Method-based simulation (FMM-Sim) workflow for rapid history matching and completion design optimization of hydraulically fractured shale wells in unconventional reservoirs. The workflow incorporates fracture propagation to model the injection phase using a 3D finite difference (FD) simulation and seamlessly transitions to FMM-Sim for the subsequent production phase modeling. A simplified physical model for pressure-dependent fracture dilation/compaction was proposed and parameterized to emulate fracture propagation. The model was validated with ABAQUS, a fully coupled fluid flow and geomechanics simulator. In the workflow, the fracture parameters such as fracture geometry and permeability are obtained as a result of the injection phase modeling. Next, they are transferred into the subsequent production phase modeling with FMM-Sim which transforms 3D reservoir simulation model into 1D simulation model leading to orders of magnitude faster computation. The workflow was successfully applied to a field case in the Delaware Basin. The injection and production well data was first history-matched using a genetic algorithm. The calibrated models provide a range of estimated ultimate recovery (EUR) and net present value (NPV) of the history-matched well. After the history matching, the calibrated fracture dilation/compaction curves were used to investigate the optimum completion design for the well. The workflow has been proposed in practical and efficient way in the sense that the entire workflow, from the fracture propagation to the subsequent production, can be performed in any 3D FD simulator. This substantially saves computation resources and manpower compared to common industry workflows. The proposed workflow which connects completion design and hydrocarbon production with efficient computation would be beneficial for field development planning and economic decision making in unconventional reservoirs.

New Simplified Models of Single‐Well Push‐Pull Tests With Mixing Effect

AbstractWhen using single‐well push‐pull (SWPP) tests to characterize in situ aquifer related to reactive transport, approximate analytical solutions were preferred to determine the aquifer dispersivity and other parameters, due to its computational efficiency. Simplified models were proposed in this study to estimate the retardation factor for a SWPP test with a reactive tracer, where the dispersivity had to be determined firstly using a SWPP test with a conservative tracer. Here, we find that previous models associated with SWPP tests contain an untested assumption when dealing with solute transport in the wellbore, probably causing great errors when interpreting the test data. This assumption states that the wellbore mixing effect is negligible in both injection and extraction phases, where the mixing effect refers to the mixing process between the native wellbore water and solute introduced into the wellbore. In this study, new approximate analytical solutions of the SWPP test are proposed for a fully penetrating well and a point‐source well by specifically considering the wellbore mixing effect. The new models of this study are tested by semianalytical solutions in Laplace domain and finite difference solutions. Results indicate that the new models perform substantially better than previous models of ignoring the wellbore mixing effect, which should not be overlooked when interpreting SWPP test data.

A new solution to transient single-well push-pull test with low-permeability non-Darcian leakage effects

An accurate solute transport model is critical to the interpretation of single-well push-pull (SWPP) test. Previous studies of SWPP test generally consider solitary aquifer that is confined by impermeable layers. Also, existing solutions for solute transport in aquifer-aquitard systems only consider the injection phase and over-simplify the flow field by assuming uniformly distributed velocity in the aquitard. In this study, we developed a numerical model with Dirichlet boundary condition for SWPP test affected by leakage described by a low-permeability non-Darcian expression involving a threshold pressure gradient (I0). Our SWPP test model considered transient flow in multi-phases, which include injection, chase, rest and extraction phases. Finite-difference scheme was adopted to solve the models of flow and solute transport. The results indicate that an increasing hydraulic diffusivity leads to a greater peak value of breakthrough curve (BTC) while a medium with larger grain size results in less estimation error when using steady-state flow model to interpret the transient SWPP test. Additionally, A greater I0 makes the solute stored in aquitard more difficult to be extracted out due to dispersion dominance, which results in higher BTC values. For the purpose of application, a lumped dimensionless index called the non-Darcian index (NDI) was proposed to quantify the overestimation degree by neglecting leakage, and the underestimation degree by accounting for Darcian leakage, when interpreting the SWPP test with low-permeability non-Darcian leakage. The long-term slope of breakthrough curve coupled with the NDI can be employed to determine the cases in which the low-permeability non-Darcian leakage should be considered.

Quantitative characterisation of gas loss and numerical simulations of underground gas storage based on gas displacement experiments performed with systems of small-core devices connected in series

In this study, an experimental system in which small core devices with different configurations are connected in series was designed, and high-intensity gas injection and production experiments (3 groups, 28 times) were conducted to quantify the per-cycle gas loss (difference between the amounts of injected and produced gas). These experiments reveal that the lost gas fraction is positively correlated with the porosity and permeability of sandstone but negatively related to the number of injection-production cycles. Based on the experimental results, a three-dimensional gas–water two-phase numerical simulation model for high-intensity injection and production of underground gas was established, and a numerical simulation study (10 injection-production cycles) was performed to clarify the macroscopic migration law of gas and water during injection-production. The simulation results show that the gas could cross the gas–water contact (GWC) into the lower water area at approximately 350 m in the injection phase, while the water intrudes into the gas area at approximately 150 m along the high-permeability channel in the production process. Owing to the complex interaction between the gas and water, a large amount of the lost gas that cannot be produced accumulates in the transition zone generated by the reciprocating motion of the gas and water. A certain amount of the lost gas is produced in every cycle; however, the lost gas fraction will decrease with an increasing number of injection and production cycles (a single cycle yields a reduction of more than 10%) and eventually stabilise at approximately 5%. Finally, based on our results, some suggestions were provided for avoiding gas loss while building underground gas storage systems.

Lightweight Learning-Based Automatic Segmentation of Subretinal Blebs on Microscope-Integrated Optical Coherence Tomography Images

Subretinal injections of therapeutics are commonly used to treat ocular diseases. Accurate dosing of therapeutics at target locations is crucial but difficult to achieve using subretinal injections due to leakage, and there is no method available to measure the volume of therapeutics successfully administered to the subretinal location during surgery. Here, we introduce the first automatic method for quantifying the volume of subretinal blebs, using porcine eyes injected with Ringer's lactate solution as samples. Ex vivo animal study. Microscope-integrated optical coherence tomography was used to obtain 3D visualization of subretinal blebs in porcine eyes at Duke Eye Center. Two different injection phases were imaged and analyzed in 15 eyes (30 volumes), selected from a total of 37 eyes. The inclusion/exclusion criteria were set independently from the algorithm-development and testing team. A novel lightweight, deep learning-based algorithm was designed to segment subretinal bleb boundaries. A cross-validation method was used to avoid selection bias. An ensemble-classifier strategy was applied to generate final results for the test dataset. The algorithm performs notably better than 4 other state-of-the-art deep learning-based segmentation methods, achieving an F1 score of 93.86 ± 1.17% and 96.90 ± 0.59% on the independent test data for entry and full blebs, respectively. The proposed algorithm accurately segmented the volumetric boundaries of Ringer's lactate solution delivered into the subretinal space of porcine eyes with robust performance and real-time speed. This is the first step for future applications in computer-guided delivery of therapeutics into the subretinal space in human subjects.

Observations and analyses of the first two hydraulic stimulations in the Pohang geothermal development site, South Korea

We present key observations and analyses of the first and second stimulations conducted at the Pohang enhanced geothermal system (EGS) site in Korea in 2016. The first hydraulic stimulation was conducted in the PX-2 well of 4.3 km depth, with the maximum wellhead pressure of 89.2 MPa, the maximum injection rate of 46.8 L/s, and a total injected volume of 1970 m3. The first stimulation showed non-linear and reversible fracture-opening behavior with injection pressure increase. The stimulation mechanism of PX-2 is interpreted as a combination of tensile fracture extension and hydraulic jacking. The second hydraulic stimulation was conducted in the PX-1 well of 4.2 km depth, with the maximum wellhead pressure of 27.7 MPa, the maximum injection rate of 18.0 L/s, and a total injected volume of 3907 m3. The fracture-opening pressure of PX-1 was evaluated from the clear pressure peaks and the pressure at differential injectivity increase, and was drastically lower than that of PX-2. The transmissivity of PX-1 permanently increased by 6.4 times during the second stimulation. The wellhead injectivity of PX-1 was 3.6 times as high as that of PX-2 at the same injection rate. The stimulation mechanism in PX-1 is interpreted as a combination of hydraulic shearing and hydraulic jacking of unmated or shear-dilated fracture. Both stimulations in the two wells showed consistently greater seismicity rate and magnitude during the shut-in phases than during the preceding injection phases. A close correlation between the injected fluid volume and seismic magnitude was observed in both wells, and the seismic events induced by the two stimulations were in general below the maximum magnitude envelopes expected by the previous studies. Despite the close distance of approximately 600 m in the same rock formation, the two wells showed distinctly different behavior in terms of the overall pressure ranges, pressure peaks, pressure for injectivity increases, transmissivity changes, and the stimulation mechanisms due possibly to the heavy mud and lost circulation material used during the drilling and completion of PX-2. The contrasting hydromechanical responses observed in the same reservoir at the two nearby wells emphasize the importance of proper drilling and completion with close consideration of stimulation strategy.

Analytical energy spectra and wake effects for relativistic dielectric laser accelerators

Dielectric laser acceleration (DLA) is one of the advanced concepts for more compact accelerators. DLA gratings have apertures and period lengths within the range of optical wavelengths. Phase stability and wakefield effects are thus crucial for upcoming experiments with highly relativistic electrons. For this, we present a method to analytically calculate energy spectra for comparison with measurements in order to reconstruct the phase of injection into the DLA grating structure. Knowing the injection phase is important for both alignment and interpretation of measured data. Furthermore, we estimate the effects of wakefields on bunches which are coherently accelerated in a DLA. We are calculating the energy spectrum affected by the longitudinal wake by evaluating the analytical description numerically and give estimates for the transverse kicks of an off-centered injected electron bunch.

Extended Operation Range of Photovoltaic Inverters by Current Waveform Shaping

The grid connection of photovoltaic voltage source inverters depends on the dc-link voltage level that can be supplied by the maximum power tracking of the photovoltaic system. The inverter disconnects from the grid, if the minimum required dc-link voltage level is violated, which leads to unwanted energy curtailments implying losses to the system owner. This article proposes to apply current waveform shaping to the inverter current in order to reduce the peak value of the voltage waveform at the point of common coupling by which the minimum required dc-link voltage level for power injection is reduced. This extended operation range of photovoltaic inverters is achieved through third harmonic current injection and can be applied to single-phase and three-phase, four-wire inverters without additional converter stages. A control structure for harmonic current injection and harmonic phase determination is presented and validated by simulations and the analysis is verified by experiments.