Power transfer efficiency in an air-breathing radio frequency ion thruster

Due to a series of challenges such as low-orbit maintenance of satellites, the air-breathing electric propulsion has got widespread attention. Commonly, the radio frequency ion thruster is favored by low-orbit missions due to its high specific impulse and efficiency. In this paper, the power transfer efficiency of the radio frequency ion thruster with different gas compositions is studied experimentally, which is obtained by measuring the radio frequency power and current of the antenna coil with and without discharge operation. The results show that increasing the turns of antenna coils can effectively improve the radio frequency power transfer efficiency, which is due to the improvement of Q factor. In pure N_2 discharge,with the increase of radio frequency power, the radio frequency power transfer efficiency first rises rapidly and then exhibits a less steep increasing trend. The radio frequency power transfer efficiency increases with the increase of gas pressure at relatively high power, while declines rapidly at relatively low power. In N_(2)/O_(2) discharge, increasing the N_(2) content at high power can improve the radio frequency power transfer efficiency, but the opposite was observed at low power. In order to give a better understanding of these trends, an analytic solution in limit cases is utilized, and a Langmuir probe was employed to measure the electron density. It is found that the evolution of radio frequency power transfer efficiency can be well explained by the variation of plasma resistance, which is related to the electron density and the effective electron collision frequency.

Schedule optimization to improve trunk-local bus transfer efficiency in small conurbations: A case study of New York's capital region

Fostering the use of transit has been broadly accepted as an effective way to improve social equity and reduce the externalities caused by transportation. In the great body of transit literature, many have focused on the improvement of transfer efficiency. However, investigation on transit transfer efficiency is still lacking for medium sized cities or suburban areas that have sprawled from city centers. The special features associated with such an urban form lead to unique travel patterns and bus operations. This work develops a process to improve bus transfer efficiency for small conurbations considering their special characteristics. A case study of New York's Capital District is used to illustrate the proposed method. Results show that the transfer waiting time can be remarkably shortened. The proposed method can be widely adapted to other transit systems in small conurbations.

Charge transfer efficiency improvement of a 4-T pixel by the optimization of electrical potential distribution under the transfer gate

The charge transfer efficiency improvement method is introduced by optimizing the electrical potential distribution under the transfer gate along the charge transfer path. A non-uniform doped transfer transistor chan- nel is introduced to provide an ascending electrical potential gradient in the transfer transistor channel. With the adjustments to the overlap length between the R1 region and the transfer gate, the doping dose of the R1 region, and the overlap length between the anti-punch-through （APT） implantations and transfer gate, the potential barrier and potential pocket in the connecting region of transfer transistor channel and the pinned photodiode （PPD） are reduced to improve the electrical potential connection. The simulation results show that the percentage of residual charges to total charges drops from 1/10^4 to 1/10^7, and the transfer time is reduced from 500 to 110 ns. This means the charge transfer efficiency is improved.

Novel CMOS image sensor pixel to improve charge transfer speed and efficiency by overlapping gate and temporary storage diffusing node

A novel CMOS image sensor(CIS) pinned photodiode(PPD) pixel, named as O-T pixel, is proposed and investigated by TCAD simulations. Compared with the conventional PPD pixel, the proposed pixel features the overlapping gate(OG)and the temporary storage diffusing(TSD) region, based on which the several-nanosecond-level charge transfer could be achieved and the complete charge transfer from the PPD to the floating node(FD) could be realized. And systematic analyses of the influence of the doping conditions of the proposed processes, the OG length, and the photodiode length on the transfer performances of the proposed pixel are conducted. Optimized simulation results show that the total charge transfer time could reach about 5.862 ns from the photodiode to the sensed node and the corresponding charge transfer efficiency could reach as high as 99.995% in the proposed pixel with 10 μm long photodiode and 2.22 μm long OG. These results demonstrate a great potential of the proposed pixel in high-speed applications.

An analysis and preliminary experiment of the discharge characteristics of RF ion source with electromagnetic shielding

Combined with two-dimensional(2D)and three-dimensional(3D)finite element analysis and preliminary experimental tests,the effects of size and placement of the electromagnetic shield of the radio-frequency(RF)ion source with two drivers on plasma parameters and RF power transfer efficiency are analyzed.It is found that the same input direction of the current is better for the RF ion source with multiple drivers.The electromagnetic shield(EMS)should be placed symmetrically around the drivers,which is beneficial for the plasma to distribute uniformly and symmetrically in both drivers.Furthermore,the bigger the EMS shield radius is the better generating a higher electron density.These results will be of guiding significance to the design of electromagnetic shielding for RF ion sources with a multi-driver.

Estimation of Turbulent Fluxes Using the Flux-Variance Method over an Alpine Meadow Surface in the Eastern Tibetan Plateau

The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles （active or passive） of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones.

A Novel SiC Foam Valve Tray for Distillation Columns

The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surfacearea. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmos-pheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquidheight. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Comparedwith the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70%lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, theoverall performance of the novel SiC foam valve tray was better than that of F1 float valve tray.

Study on extraction phenol from coal tar with high flux centrifugal extractor

Solvent extraction phenol from coal tar were carried out with novel composite YH-3 as extraction agent, and the high flux centrifugal extractor was used as extraction device. Under the premise of high phenol extraction rate, composite YH-3 extraction agent reduces n-n interaction between phenolic compounds and aromatic hydrocarbons, thus decreasing the entrainment of neutral oil. The optimization of operation conditions, such as the diameter of heavy phase weir HWD, the flow ratio, the total flow rate and the rotation speed, are necessary. For single stage extraction experiment, the mass transfer efficiency was up to 84% while the rate of extraction agent loss was lower than 0.28% with the operation conditions of 29 mm of the heavy phase weir diameter （HWD）, 1：1-1.4：1 of the flow ratio range, 160-200 mL/min of the total flow rate and the rotation speed varied from 2200 to 2600 r/min. For three stage counter-current test, the mass transfer efficiency reached up to 92.6% with the optimum operation condition of 29 mm of the HWD, 1：1 of the flow ratio, 200 rnL/min of the total flow rate and 2400 r/rain of the rotation speed. The results indicated that phenol could be extracted effectively from coal tar in the process of multistage continuous count current centrifugal extraction.

Air flow patterns and noise analysis inside high speed angular contact ball bearings

The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.

Electron transfer dynamics in Schottky junction photocatalyst during electron donor-assisted hydrogen production

Electron donors(EDs)are widely used to improve the H 2 production performance of Schottky junction photocatalysts,but the functions of EDs are still unknown from the perspective of electron transfer dy-namics.Herein,Pt nanocluster-decorated CdS nanorod is successfully prepared to construct a typical CdS/Pt Schottky junction.Pt nanoclusters with a diameter of∼2 nm are deposited on the surface of CdS nanorods by in situ photoreduction at sub-zero temperature.The CdS/Pt photocatalyst using lactic acid shows a higher H_(2)production rate of 4762μmol g^(-1)h^(-1)compared to that using methanol,tri-ethanolamine,and glycerol.To understand the cause,the dynamics of photogenerated carriers in CdS/Pt photocatalysts during ED-assisted H_(2)production are revealed by femtosecond transient absorption spec-troscopy.Among the four organic EDs,lactic acid enables the fastest electron transfer rate of 1.8×10^(9)s^(-1)and the highest electron transfer efficiency of 76%at the CdS/Pt interface due to the most efficient hole consumption.This work sheds light on the importance of efficient interfacial electron transfer for im-proving the photocatalytic performance of Schottky junction photocatalysts.

Power Balance Consideration in the Design of Indirectly Driven Targets

A preliminary design for a heavy ion driver inertial fusion（HIDIF） target is presented. The effect of target material and dimensions on transfer efficiency and symmetrical irradiation in the hohlraum are investigated.The analysis led to the evaluation of optimal target materials and dimensions to achieve a positive power balance of an ICF power plant.The results show that the best choice is a high Z material for cavity wall materials and a low Z material for the capsule ablator.It is concluded that for achieving the highest transfer efficiency and best symmetrization we need an area ratio between 5≤A2/A1≤9.

Study on Jet Coflow Packing Tray

Experimental study on hydrodynamics and mass transfer efficiencyof jet coflow packing tray (JCPT) was conducted in a φ285 mm columnand φ200 mm column, respectively. Compared with new vertical sievetray which has been applied in the petrochemical industry since 1968,the JCPT has lower pressure drop, higher capacity and higher masstransfer efficiency, and seems promising in commercial application.

Effects of carrier-attached biofilm on oxygen transfer efficiency in a moving bed biofilm reactor

Three laboratory-scale moving bed biofilm reactors （MBBR） with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In this study, we evaluated the performance of three MBBRs in degrading chemical oxygen demand and ammonia. The three reactors removed more than 95% of NH4^＋ -N at an air flow-rate of 60L·h^-1. The standard oxygen transfer efficiency （αSOTE） of the three reactors was also investigated at air flow-rates ranging from 60 to 100L·h^-1. These results were compared to αSOTE of wastewater with a clean carrier （no biofilm attached）. Results showed that under. these process conditions, αSOTE decreased by approximately 70% as compared to αSOTE of wastewater at a different carrier-filling ratio. This indicated that the biofilm attached to the cartier had a negative effect on αSOTE. Mechanism analysis showed that the main inhibiting effects were related to biofilm flocculants and soluble microbial product （SMP）. Biofilm flocs could decrease otSOTE by about 20%, and SMP could decrease aαSOTE by 30%--50%.

Grain carbon emission transfer and its spatiotemporal shifts based on the increasing supply-demand separation in China over the past three decades

The food system is one of the major sources of anthropogenic greenhouse gas(GHG)emissions.The impact of emission transfer due to the separation between food production and consumption within the context of carbon neutrality remains unclear.In this study,we constructed an emission inventory for three types of grains at the production stage of their life cycle and then analysed the spatiotemporal evolution characteristics of the grain supply and demand.With the use of a spatial equilibrium model,we simulated the spatial distribution flow of the different types of grains from 1990 to 2018 and calculated the resulting GHG emission transfer efficiency.The main results include the following:(1)The imbalance between the grain supply and demand intensified,which was mainly reflected in the distance between the geographic centre of the grain supply and consumption increasing 3.2 times,and thus,the self-sufficiency decreased.(2)The total emission transfer TET of rice and wheat decreased because of the increase in the intra-regional supply,while that of maize gradually increased due to the increase in the inter-regional supply.(3)Overall,grain trade improved the carbon efficiency of grain production in China.The trade efficiency of crops varied,with wheat and maize leading to overall effective carbon reductions,while the carbon transfer efficiency of rice from trade was relatively low.(4)The carbon footprint of grain production in China's provinces exhibited a downward trend,but due to the intensified separation between the grain supply and demand,certain major grain-producing areas achieved inefficient carbon increases.Therefore,we suggest further optimization of the spatial structure of planting and breeding,strengthening of the grain supply in the region,and enhancement in the optimization of the low-carbon production structure and adjustment of cultivated land use combined with regional governance strategies.The application of these measures could contribute to achieving dual-carbon goals.

Review on heterophase/homophase junctions for efficient photocatalysis: The case of phase transition construction

Semiconductor photocatalysts are extensively applied in environmental treatment and energy conversion.However,one of their major disadvantages is their relatively low photocatalytic performance owing to the recombination of generated electron-hole pairs.The presence of the phase junction is an effective way to promote the photocatalytic activity by increasing the separation efficiency of the electron-hole pairs.Accordingly,extensive research has been conducted on the design of phase junctions of photocatalysts to improve their charge transfer properties and efficiencies.Therefore,for the design of an appropriate phase junction and the understanding of the mechanism of electron-hole separation,the development of the photocatalytic phase junction,including the preparation methods of the heterogeneous materials,is tremendously important and helpful.Herein,the commonly used,externally induced phase transformation fabrication techniques and the primary components of the semiconductors are reviewed.Future directions will still focus on the design and optimization of the phase junction of photocatalytic materials according to the phase transition with higher efficiencies for broadband responses and solar energy utilization.Additionally,the most popular phase transformation fabrication techniques of phase junctions are briefly reviewed from the application viewpoint.

Overexpression of Stella improves the efficiency of nuclear transfer reprogramming

In mammalians, the state of a somatic cell can be reversed from the terminal state to the totipotent state by means of somatic cell nuclear transfer （SCNT） （Gurdon, 1962） or induced pluripotent stem cells （iPSCs） （Takahashi and Yamanaka, 2006）. The DNA methylation and transcriptome profiles of embryonic stern cells （ESCs） derived from SCNT embryos （NT-ESCs） correspond closely to those of ESCs derived from in vitro fertilization embryos （IVF- ESCs）. In contrast, iPSCs differ from both NT-ESCs and IVF-ESCs in that they retain the residual DNA methylation patterns of their parental somatic cells. As SCNT can be used to faithfully reprogram human somatic cells to pluripotency, it is ideal for cell replacement therapies （Ma et al., 2014）. Following the successful production of the first human NT-ESCs （Tachibana et al., 2013） and the later gen- eration of human NT-ESCs based on cells from elderly adults or pa- tient cells （Chung et al., 2014; Yamada et al., 2014）, a version of the SCNT technique for human therapeutics comes closer to reality. However, no matter what animal species or donor cell types are used in the cloned process, the cloning efficiency remains undesir- able. Besides, there are many phenotypic abnormalities in cloned animals, containing frequent embryonic and perinatal death and placentomegaly, and the underlying mechanisms remain unclear （Yang et al, 2007）.

Evaluation of light extraction efficiency for the light-emitting diodes based on the transfer matrix formalism and ray-tracing method

The internal quantum efficiency（IQE） of the light-emitting diodes can be calculated by the ratio of the external quantum efficiency（EQE） and the light extraction efficiency（LEE）.The EQE can be measured experimentally,but the LEE is difficult to calculate due to the complicated LED structures.In this work,a model was established to calculate the LEE by combining the transfer matrix formalism and an in-plane ray tracing method.With the calculated LEE,the IQE was determined and made a good agreement with that obtained by the ABC model and temperature-dependent photoluminescence method.The proposed method makes the determination of the IQE more practical and conventional.

Design and analysis of an underwater inductive coupling power transfer system for autonomous underwater vehicle docking applications

We develop a new kind of underwater inductive coupling power transfer(ICPT)system to evaluate wireless power transfer in autonomous underwater vehicle(AUV)docking applications.Parameters that determine the performance of the system are systematically analyzed through mathematical methods.A circuit simulation model and a finite element analysis(FEA)simulation model are developed to study the power losses of the system,including copper loss in coils,semiconductor loss in circuits,and eddy current loss in transmission media.The characteristics of the power losses can provide guidelines to improve the efficiency of ICPT systems.Calculation results and simulation results are validated by relevant experiments of the prototype system.The output power of the prototype system is up to 45 W and the efficiency is up to 0.84.The preliminary results indicate that the efficiency will increase as the transmission power is raised by increasing the input voltage.When the output power reaches 500 W,the efficiency is expected to exceed 0.94.The efficiency can be further improved by choosing proper semiconductors and coils.The analysis methods prove effective in predicting the performance of similar ICPT systems and should be useful in designing new systems.

Optimizing Cr^(3+) concentration and evaluating energy transfer from Cr^(3+) to Nd^(3+) in Cr,Nd:GGG nanocrystals prepared by sol-gel method

Nanopowder of Cr：GGG and nanopowder of Cr,Nd：GGG with different concentrations of Cr3＋ ranging from 0.1 at.% to 1.5 at.% were synthesized by the sol-gel method using acetic acid and ethylene glycol. Thermal gravimetric analysis and differential scanning calorimetry （TGA-DSC）, X-ray diffraction （XRD） and photoluminescence spectroscopy were used to characterize the powder. The crystallite size was about 58 nm when treated at 1000 oC for 2 h. Cr3＋ photoluminescence spectrum in GGG showed a broad band emission around 730 nm. The intensity of this band decreased when co-doped with Nd, indicating an efficient energy transfer from Cr3＋ to Nd3＋. Photoluminescence intensity of Nd in Cr,Nd：GGG at 1.06μm showed that the optimum concentration of Cr3＋ was about 1 at.% （more or less） for 1 at.% Nd3＋. This result was also confirmed by chromium fluorescence decay rate analysis. Energy transfer efficiency was found to be about 84% for 1 at.% concentration of each chromium and neodymium.

Energy Transfer in the Light-Harvesting Complexes of Purple Bacteria

In this paper, we use a nonlinear decohering quantum model to study the initial step of photosynthesis which is an ultrafast transfer process of absorption the sunlight by light-harvesting complexes and electronic excitation transfer to the reaction center(RC). In this decohering model, the Hamiltonian of the system commutes with the systemenvironment interaction. We take B850 ring of light-harvesting complex II(LH-II) in purple bacteria as an example to calculate the efficiency of the energy transfer as a function of time. We find that the environmental noise can make the LH-II have stable energy transfer efficiency over a long time. This is to say that the environmental noise which is the decohering source has advantage of the energy transfer in the process of photosynthesis.