Pulse Injection Research Articles

Trace elements and textures of scheelite in porphyry-skarn Cu-Au systems: The example of Dongguashan deposit, eastern China

Porphyry-skarn deposits are the major sources of Cu and Au in eastern China, and W is a common byproduct of these mines. Scheelite is the W-bearing mineral in these deposits, and is widespread in both porphyry and skarn ore, however, systematic variations in the textures and geochemistry of the scheelite are not well constrained. Here, multiple generations of scheelite in Dongguashan deposit provide an opportunity for systematic study of the evolution of scheelite textures and chemistry, and their implications for ore-forming processes in a porphyry-skarn Cu-Au system. Scheelite is widespread in the porphyry and skarn zones at Dongguashan, and five types of scheelite are identified. Type1 scheelite occurs in quartz-sulfide veins from the porphyry potassic alteration stage; it displays oscillatory zoning and patchy cathodoluminescent (CL) zones. Type2 and 3 scheelite show relatively homogeneous CL image and occur interstitial to garnet and pyroxene. Type4 scheelite from the skarn ore has patchy CL zones; type5 scheelite shows patchy (core-rim) CL texture and occurs in quartz-sulfide veins that cut massive skarn or skarn sulfide ore. We conclude that the oscillatory banding of type1 scheelite was controlled by crystal kinetics, whereas the patchy, chaotic and sector CL textures in other types were mainly produced by extrinsic fluids of variable composition. The trace elements Mo, Na, Nb, V and REE strongly affect the CL intensity of scheelite at Dongguashan, and trace elements Na, Nb, V and ∑REE decrease in the order type1 and 5 → type4 → type2 and 3. All scheelite types show Y/Ho ratios (12.5–30) similar to igneous rocks (20–27.5), indicating the tungsten mineralization is genetically related to the associated quartz monzodiorite. High Mo, Nb, V and the negative Eu anomaly in type1 scheelite indicate that the fluid related to the porphyry ore was oxidized and F-rich. The homogeneous compositions of type2, 3 and 4 scheelite, together with their weakly negative Eu anomalies show that they formed in a stable high T oxidized environment. The hydrothermal vein features with enrichment of REE (1 wt%) in the late type5 scheelite indicate it formed by injection of a late magmatic-hydrothermal pulse, and the variations in Eu anomalies in type5 suggest the fO2 gradually decreased in late fluids. Our study highlights that scheelite CL textures and geochemistry are effective for tracing multiple ore-forming processes in porphyry-skarn Cu-Au systems.

Removal of nitrate and pesticides from groundwater by nano zero-valent iron injection pulses under biostimulation and bioaugmentation scenarios in continuous-flow packed soil columns

This study evaluates the NO3− removal from groundwater through Heterotrophic Denitrification (HDN) (promoted by the addition of acetate and/or an inoculum rich in denitrifiers) and Abiotic Chemical Nitrate Reduction (ACNR) (promoted by pulse injection of zerovalent iron nanoparticles (nZVI)). HDN and ACNR were applied, separately or combined, in packed soil column experiments to complement the scarce research on pulse-injected nZVI in continuous-flow systems mimicking a Well-based Denitrification Barrier. Together with NO3−, the removal of two common pesticides (dieldrin and lindane) was evaluated. Results showed that total NO3− removal (>97%) could be achieved by either bioestimulation with acetate (converting NO3− to N2(g) via HDN) or by injecting nZVI (removing NO3− via ACNR). In the presence of nZVI, NO3− was partially converted to N2(g) and to a lower extent NO2−, with unreacted NO3− being likely adsorbed onto Fe-(oxy)hydroxides. Combination of both HDN and ACNR resulted in even a higher NO3− removal (>99%). Interestingly, nZVI did not seem to pose any toxic effect on denitrifiers. These results showed that both processes can be alterned or combined to take advantage of the benefits of each individual process while overcoming their disadvantages if applied alone. With regard to the target pesticides, the removal was high for dieldrin (>93%) and moderate for lindane (38%), and it was not due to biodegradation but to adsorption onto soil. When nZVI was applied, the removal increased (generally >91%) due to chemical degradation by nZVI and/or adsorption onto formed Fe-(oxy)hydroxides.

Mode-locking threshold decrease in a fiber laser by heterochromic optical pulse injection

A Yb-doped fiber laser mode locked by a nonlinear amplifying loop mirror (NALM) with a figure-9 configuration is experimentally realized. By coupling heterochromic 1580-nm optical pulses into the circular part of the Yb-doped laser oscillator, a new injection-induced Q-switched mode-locking (Q-ML) like transition state is found for the first time to the best of our knowledge. We have investigated the envelope interval and duration of this Q-switched envelope by changing the pump power, injection power, and cavity length detuning. Experimental results have shown the injected pulses serve as a complementary source for establishing mode-locking (ML). As a result, the self-starting ML threshold of the Yb-doped fiber laser is significantly reduced from 355 to 171 mW, which is only half that in the non-injection case. This optical pulse injection assisted ML process is observed with a real-time oscilloscope, revealing stable and consistent buildup dynamics. Our finding may provide a new approach for understanding the buildup dynamics and building mode-locked fiber lasers with low threshold and high consistency.

Numerical Study of Growth Rate and Purge Time in the AlN Pulsed MOCVD Process

The relationship between the purge time and the overall growth rate in pulsed injection metal–organic chemical vapor deposition with different V/III ratios is studied by numerical analysis. The transport behavior of TMAl and TMAlNH3 during the process is studied to understand the effect of the adductive reaction. The results show that, as the V/III ratio increases, there is a significant reduction in the average growth rate per cycle, without the addition of a purging H2 pulse between the III and V pulses, due to stronger adductive reaction. The adductive reaction can be reduced by inserting a purging pulse of pure H2 between the III and V pulses, but there is a decrease in the overall growth rate due to the longer cycle time. At smaller V/III ratios, the growth rate decreases with increasing purge times, since the gain in reducing the adductive reaction is offset by the detrimental effect of extending the cycle time. The degree of reduction in the adductive reaction is higher for larger V/III ratios. When the benefit of reducing the adductive reaction overcomes the deficiency of the extending cycle time, a remarkable enhancement of the growth rate can be obtained at high V/III ratios by inserting a pure H2 purge pulse between the III and V pulses. A higher overall growth rate can be achieved at higher V/III ratios by choosing an appropriate purge time.

Carrier Transition Techniques for Parallel Connected VSCs Using Cross-Coupled Inductors

Parallel inverters can be connected using cross-coupled inductors (CIs) to produce high-quality line voltages in three-phase ac systems. Since no fundamental flux is present in the inductor cores, their size can be made considerably smaller than alternative inductor configurations. Interleaved switching and phase-shifted carriers (PS-PWM) can be used to produce multilevel three-phase line voltages. A modified approach (MPS-PWM) improves the quality of the line voltages by changing the phase of the carriers, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">carrier swapping</i> , based upon the magnitude of the modulating signals. Since carrier swapping in MPS-PWM can cause the inductor circulating currents and flux patterns to jump and have dc offsets, two carrier transition techniques are presented to eliminate these jumps: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">carrier manipulation</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pulse injection</i> . These techniques represent open-loop PWM control, dependent only on the carrier phase change being used, and can easily be applied to an arbitrary number of parallel-connected inverters. The circulating currents and inductor flux patterns follow predictable patterns, allowing the CIs to be designed more precisely. The relative merits of using MPS-PWM over PS-PWM are assessed using measurements of the load current total harmonic distortion and the line voltage harmonic volt–seconds. The feasibility of the parallel inverter system described is verified using simulations and results from an experimental laboratory prototype.

Spray–wall impingement in a multi-hole GDI injector for split injection at elevated wall temperature and ambient conditions

Post wall-impingement characteristics of pulsatile and split injection sprays in multi-hole Gasoline Direct Injection (GDI) are investigated. A combined experimental and numerical approach is adopted, to examine the influence of wall temperature as well as gas temperature and pressure on spray evolution. For fuel injection condition, split proportion and wall stand-off distance are not varied. The single injection case is also studied for comparison. The experiments were conducted under atmospheric conditions but for different wall temperatures, and the fuel spray was visualized using high-speed shadowgraph technique. The three-dimensional Eulerian–Lagrangian spray simulations were validated against the measured post-impingement plume width and height. Simulations were carried out to analyse spray–wall interaction process under elevated ambient temperature and pressure conditions also. Considerably smaller radial and vertical spread of the spray plume is obtained for split injection, highlighting its benefits over the single injection case. Both plume and wall film characteristics are strongly influenced by the ambient gas density and temperature rather than the wall temperature. However, time evolutions of the mass, thickness and temperature of the film are similar for both single and split cases at different operating conditions, exhibiting some interesting trends. For split injection, the vapour plumes from the two injection pulses interact. At high ambient temperatures, the peak equivalence ratio values are lower for split injection due to lower injected mass per pulse, in comparison to the single injection strategy. • GDI spray–wall interaction is investigated experimentally and computationally. • The measured post-impingement plume height/width corroborate well with the predictions. • The plume characteristics are primarily dependent on gas phase density. • The wall film thickness reduces considerably for split-injection compared to single injection. • For split-injection and elevated ambient temperature, the initial wall film vaporizes prior to 2nd injection.

Comparison between Pulsed Radio-Frequency Plus Steroid Injection and Thermal Radio-Frequency in Treatment of Trigeminal Neuralgia

Comparison between Pulsed Radio-Frequency Plus Steroid Injection and Thermal Radio-Frequency in Treatment of Trigeminal Neuralgia

Comparison between Pulsed Radio-Frequency Plus Steroid Injection and Thermal Radio-Frequency in Treatment of Trigeminal Neuralgia

Comparison between Pulsed Radio-Frequency Plus Steroid Injection and Thermal Radio-Frequency in Treatment of Trigeminal Neuralgia

Green edge emitting lasers with porous GaN cladding.

GaN lasers with green emission wavelength at λ = 510 nm have been fabricated using novel nano-porous GaN cladding under pulsed electrical injection. The low slope efficiency of 0.13 W/A and high threshold current density of 14 kA/cm2 are related to a combination of poor injection efficiency and high loss, analyzed by the independent characterization methods of variable stripe length and segmented contacts. Continuous wave operation showed narrowed spectra and augmented spontaneous emission.

Study on Dynamic Injection Prediction Model of High-Pressure Common Rail Injector under Thermal Effect

This study investigates a prediction model for the cycle injection quantity in a high-pressure common rail injector under a transient thermal boundary. The results show that the transient temperature increase curve calculated by the mathematical model of the common rail injector under adiabatic flow is significantly different from the experimental data. A non-isothermal model of the injector coupled with heat transfer is established, which considers the actual heat transfer phenomenon. The excellent agreement between the new calculation results and the experimental data confirms that the fuel injection process of a common rail injector comprises the coupled phenomena of fuel heating and heat transfer. Based on the established simulation model, it is found that in the continuous injection process of the injector, owing to the thermal effect of injection, the cycle injection quantity decreases gradually with an increase in the injector working time and then stabilizes. Under the condition of an injection pulse width of 1.2 ms and frequency of 100 Hz, when the injection pressure increases from 140 MPa to 300 MPa, the reduction in the cycle injection quantity increases from 3.9% to 7.8%, because the higher injection pressure results in higher transient heat at the nozzle holes. In the work of common rail injector assemblies, to achieve more accurate control of the cycle injection quantity, it is necessary to include the correction of a decreasing cycle injection quantity caused by transient heat in the electronic control system.

Design and Analysis: Servo-Tube-Powered Liquid Jet Injector for Drug Delivery Applications

The current state of commercially available needle-free liquid jet injectors for drug delivery offers no way of controlling the output pressure of the device in real time, as the driving mechanism for these injectors provides a fixed delivery pressure profile. In order to improve the delivery efficiency as well as the precision of the targeted tissue depth, it is necessary to develop a power source that can accurately control the plunger velocity. The duration of a liquid jet injection can vary from 10 to 100 ms, and it generate acceleration greater than 2 g (where g is the gravity); thus, a platform for real-time control must exhibit a response time greater than 1 kHz and good accuracy. Improving the pioneering work by Taberner and others whereby a Lorentz force actuator based upon a voice coil is designed, this study presents a prototype injector system with greater controllability based on the use of a fully closed-loop control system and a classical three-phase linear motor consisting of three fixed coils and multiple permanent magnets. Apart from being capable of generating jets with a required stagnation pressure of 15–16 MPa for skin penetration and liquid injection, as well as reproducing typical injection dynamics using commercially available injectors, the novelty of this proposed platform is that it is proven to be capable of shaping the real-time jet injection pressure profile, including pulsed injection, so that it can later be tailored for more efficient drug delivery.

Investigation of cross-stream spray injection and wall impingement in a circular channel for SCR application

A parametric study of cross-stream pulsed spray injection and wall impingement characteristics in a circular channel has been carried out with an objective to investigate performance improvement in selective catalytic reduction (SCR) systems for exhaust gas after-treatment in diesel engines. The spray computations are performed based on a combined Eulerian and Lagrangian based modeling approach for the continuous and the discrete phases respectively. The simulation results are validated using the in-house experimental data for water injection in both open atmospheric and channel flow conditions. The spray structure, penetration, and droplet size are compared and good agreement between the experiments and simulations is demonstrated. Though the focus of the present work is on studying the influence of liquid preheating on post-impingement spray and wall-film characteristics as well as evolution of species mass fraction, the effect of air mass flow rates, and temperature, and the choice of the working liquid (water or Urea Water Solution (UWS)) are also investigated. While the mass flow rate of air and the selection of the above liquids for spray injection are found to have marginal influence on the results, the liquid preheating is shown to strongly affect the droplet evaporation and thus, the spray impact process. Especially, the liquid injection temperature that leads to flash evaporation results in reduced wall filming, higher ammonia generation rate and spatial uniformity of NH 3 across the channel. This paper demonstrates preheating as a promising approach for the improvement of SCR performance. • Spray injection and wall impingement in a duct air flow relevant to SCR systems is numerically investigated. • The predicted post-impingement droplet size and spatial distribution compared well against the in-house experiments. • Marginal influence of air mass flow rate and choice of the liquid (water or UWS) is observed. • Preheating the injected liquid is a viable alternate for performance optimization of the SCR systems. • Especially, the flash evaporation condition ensures reduced wall filming and, higher rate of NH 3 and its spatial uniformity.

Purgeless atomic layer etching of SiO2

Atomic layer etching (ALE) typically proceeds through four sequential steps of surface modification, purging, removal of the modified surface, and a second purging. This serial process is repeated to achieve atomic-scale precision etching by removing material layer by layer. However, it is is challenging for ALE to play a bigger role in semiconductor fabrication due to its low productivity. Among various obstacles, the time-consuming purging steps between the surface modification and removal steps of the ALE cycle have been a major hurdle hindering the ALE process. In this work, we experimentally demonstrate a purgeless SiO2 ALE methodology in which the surface modification and removal steps are controlled solely by pulsed C4F8 injection into continuous Ar plasma. The working principle of this simple approach is based on the conventional fluorocarbon (FC) plasma SiO2 etching mechanism, where the SiO2 etch rate decreases to zero when the thickness of an FC film on the SiO2 is above a certain level. Here, a thick FC film is considered to act as a protective layer against residual FC radicals in the surface removal step, allowing the purging step between the surface modification and removal steps to be omitted. The proposed approach is expected to facilitate the improvement of ALE equipment costs and potentially lead to wider employment of ALE technology in semiconductor manufacturing.

Predictive-Pulse-Injection-Based Dual-Inverter Complementary Sensorless Drive for 12/10 DC Vernier Reluctance Machine

A dc-excited Vernier reluctance machine (DC-VRM) using a 12-slot/10-pole-pair design exhibits the advantages of small torque ripple and a robust structure, which has good potential to be applied as an aerospace integrated starter/generator. By eliminating vulnerable position sensors, system reliability can be further improved by sensorless startup. However, driven by the traditional three-phase inverter, the phase inductance of the 12/10 DC-VRM becomes constant due to its complementary characteristic, which means the saliency effect in DC-VRM is obliterated, and thereby a sensorless operation using self-inductance detection cannot be applied. To release the machine saliency effect and further improve sensorless drive performance, a dual-inverter sensorless drive structure is introduced to reconstruct the machine saliency by using separated dual three-phase inverters. The released series inductance model with mutual inductance coupling is established through a piecewise function, and an accurate position estimation method without finite-element analysis or complex measurements is introduced. Moreover, by further analyzing the linearity of series inductance, the full-cycle inductance high-linearity range is composed of dual-inverter complementary features, and thus position estimation accuracy can be guaranteed. Through this feature, a predictive-position-based pulse injection sensorless drive method is proposed to improve acceleration performance with detection time reduction. Based on the predictive position, the detection pulses are only injected into one inverter whose corresponding phases are located at the inductance high-linearity range, thus decreasing the detection time and improving acceleration performance.

Sensorless Control of a Switched Reluctance Machine Based on Switching Frequency Evaluation

This article illustrates a method for sensorless control of a switched reluctance motor. The detection of the time instants for switching between the working phases is determined based on the evaluation of the switching frequency of the hysteresis current controllers for appropriately selected sensing phases. This enables a simple and cost efficient implementation. The method is compared with a pulse injection method in terms of efficiency and resolution.

High voltage pulser for ion shutters in ion mobility spectrometry based on an optocoupler.

A novel high voltage pulser for an ion shutter used in drift-tube ion-mobility spectrometers is described. The simple design suitable for the in-house construction of these spectrometers relies on a special optocoupler to isolate the triggering circuitry from the high voltage at the ion shutter. The device was tested with an electrospray-ionization ion-mobility device with a 10cm drift tube operated at 4kV into which a standard test mixture of four tetraalkylamines was injected with a negative going gating pulse of about 50V on top of 4kV. A fall time of 15.7 µs and a rise time of 2.0 µs were determined for the pulse, which was adequate for the required injection pulse width of 450 µs. Resolving powers between 61 and 81 were determined for the four quaternary amines, which were found to be comparable to the performance obtained with a previously reported pulser circuitry of a different design used as a reference.

Experimental implementation of spike-based neuromorphic XOR operation based on polarization-mode competition in a single VCSOA.

We experimentally and numerically propose an approach for implementing spike-based neuromorphic exclusive OR (XOR) operation using a single vertical-cavity semiconductor optical amplifier (VCSOA). XOR operation is realized based on the neuron-like inhibitory dynamics of the VCSOA subject to dual-polarized pulsed optical injections. The inhibitory dynamics based on the polarization-mode competition effect are analyzed, and the inhibitory response can be obtained in a suitable range of wavelength detuning. Here, all input and output bits are represented by spikes that are compatible with the photonic spiking neural network. The experimental and numerical results show that XOR operation can be realized in two polarization modes by adjusting the time offset in the inhibitory window and setting defined reference thresholds. In addition, the influences of delay time and input intensity ratio on XOR operation are studied experimentally. This scheme is energy efficient because VCSOA neuromorphic photonics computing and information processing.

Almost perfect sequence modulated multiplexing ion mobility spectrometry.

Multiplexing ion mobility spectrometry with multiple ion injection pulses was used to achieve a high duty cycle and thus improve the signal-to-noise (S/N) ratio while maintaining high resolving power compared with the traditional single-pulse signal averaging method. Historically, an ion mobility spectrum was reconstructed by various multiplexing methods including Fourier transform ion mobility spectrometry (FT-IMS), Hadamard transform ion mobility spectrometry (HT-IMS), and linear frequency modulation correlation ion mobility spectrometry (LFM-CIMS) sequence or Barker code. To achieve an artifact-free multiplexing ion mobility spectrum, an almost perfect sequence (APS) with correlation technique was proposed to modulate the Bradbury-Nielson ion gate and was compared with FT-IMS, HT-IMS, LFM-IMS, and the traditional single-pulse signal averaging method. Experimental results showed that there are no artifact peaks in the APS-IMS spectra except an inverted mirror peak, and the S/N ratio was improved 5-8 times with a repetition time of 40-60 ms, corresponding to the improvement in the duty cycle. With the same duty cycle and similar acquisition time, APS-IMS showed a higher S/N ratio than HT-IMS for its unique autocorrelation response. The APS-IMS technique offered a higher duty cycle and relatively shorter modulation period compared with reported multiplexing methods and is suitable to track rapidly changing signals without losing information and adding extra transformation artifact peaks.

Continuous low pH viral inactivation: Operation and scaling strategy informs viral clearance study.

A continuous viral inactivation (CVI) tubular reactor was designed for low pH viral inactivation within a continuous downstream system across multiple scales of operation. The reactors were designed to provide a minimum residence time of >60 min. The efficacy of this tubular reactor was tested with xenotropic murine leukemia virus (X-MuLV)through pulse injection experiments. It was determined that the minimum residence time of the small-scale reactor design, when operated at the target process flow rate, occurred between 63 and 67 min. Inactivation kinetics were compared between continuous operation and standard batch practices using three monoclonal antibodies. The quantification of the virus log reduction values (LRV) wassimilar between the two modes of operation and most of the acid-treated samples had virus concentrations below the limit of detection. However, residual infectivity was still present in the endpoint batch samples of two experiments while the continuous samples always remained below the limit of detection. This provides the foundation for leveraging a standard batch-based model to quantify the LRV for a CVI unit operation.

Fluid pressure monitoring during hydraulic testing in faulted Opalinus Clay using seismic velocity observations

Carbon capture and storage in geologic reservoirs is essential to mitigate carbon dioxide emissions, but it is only effective if long-term storage is ensured and no leakage occurs, for example, through unknown faults in the caprock that seals the reservoir. To test how the integrity of a caprock can be monitored noninvasively, the authors conducted an injection experiment directly into a faulted caprock analog at the Mont Terri Rock Laboratory. The authors monitored the experiment using active seismic techniques, along with strain, fluid pressure, and microseismicity measurements. Pulse injection with pressures of up to 4.8 MPa caused a perturbation of effective stress, which we observed through a reduction of seismic P-wave velocities by approximately 1%. This perturbation was not sensed by means of microseismicity, even though a sudden pressure drop indicated that the injection caused the opening of some fractures within the fault zone. Substantial rock deformation also was only detected at the injection borehole but not in surrounding monitoring boreholes. Thus, with seismic velocity monitoring, processes can be detected within a faulted caprock for which other methods may be blind. This demonstrates the value of seismic velocity monitoring as a tool to complement a monitoring system.