Split Rate Research Articles

Split Bond Ratings: Evidence From Local Rating Agencies in Japan

Split Bond Ratings: Evidence From Local Rating Agencies in Japan

Optimum design of inline gas-liquid cyclone separator for wide range of inlet gas volume fractions

ABSTRACT The inline gas-liquid cyclone separator has been gradually used in oil & gas industry due to its high separation efficiency and less footprint. However, under the inlet flow conditions with large range of gas volume fractions, the research on structure design and separation performance are seriously insufficient. The preliminary structural design of the inline gas-liquid separator was carried out according to the particle separation theory, and the key structural parameters were optimized by using the Response Surface Method (RSM) together with Computational Fluid Dynamics (CFD). The structure optimization has improved the degassing efficiency by 17.44% and dehydration efficiency by 7.59%. With air and water as working medium, the separation performance of the inline gas-liquid cyclone separator was experimentally investigated in laboratory under a large range of gas volume fractions. The results show that the separation efficiency for both degassing and dehydration can exceed 80% with the inlet gas volume fraction ranges from 0.2 to 0.8. The optimum normalized flow split and liquid volume flow rate are 0.9 –1.2 and 8 m3/h, respectively.

The Effect of Property Assessment Reductions on Homeownership: A Quasi-Dynamic Economic Analysis

This article evaluates the impacts of reductions in residential effective tax rates on homeownership in Detroit, Michigan. The decline in effective tax rates was driven by a citywide reassessment that significantly reduced effective tax rates. These estimates are used to infer the potential impacts of moving from a traditional property tax to a split-rate tax in which the tax rate applied to land is higher than the tax rate applied to structures. Using Detroit parcel-level data over the years 2012–2019, we find that tax reductions resulting from property reassessment generated a very small net decrease in homeownership. Our evaluation suggests that moving to a split rate tax would likely result in a minimal change in the homeownership rate in Detroit.

Efficient Anion-Exchange Membranes with Anti-Scaling Properties Obtained by Surface Modification of Commercial Membranes Using a Polyquaternium-22.

Anion-exchange membranes modified with a polyquaternium-22 (PQ-22) polymer were studied for their use in electrodialysis. The use of PQ-22 for modification makes it possible to "replace" weakly basic amino groups on the membrane surface with quaternary amino groups. It was found that the content of quaternary amino groups in PQ-22 is higher than the content of carboxyl groups, which is the reason for the effectiveness of this polymer even when modifying Ralex AHM-PES membranes that initially contain only quaternary amino groups. In the case of membranes containing weakly basic amino groups, the PQ-22 polymer modification efficiency is even higher. The surface charge of the modified MA-41P membrane increased, while the limiting current density on the current-voltage curves increased by more than 1.5 times and the plateau length decreased by 2.5 times. These and other characteristics indicate that the rate of water splitting decreased and the electroconvective mixing at the membrane surface intensified, which was confirmed by direct visualization of vortex structures. Increasing the surface charge of the commercial MA-41P anion-exchange membrane, reducing the rate of water splitting, and enhancing electroconvection leads to mitigated scaling on its surface during electrodialysis.

TEA of a Unique Two-Pathways Process for Post-Combustion CO<sub>2</sub> Capture

A unique two-Pathways process using aqueous sodium glycinate for CO<sub>2</sub> capture from a split flue gas stream emitted from 600 MWe post-combustion coal power plant was developed in Aspen Plus v.10. The split gas flow rate used was 44.75 ton/h and contained 0.0023 mol% SO<sub>2</sub> and 13.33 mol% CO<sub>2</sub>. The process includes a washing unit, a CO<sub>2</sub> absorption unit, a reverse osmosis unit, and a solvent regeneration unit or an ultrafiltration unit. The washing unit uses deionized water to completely remove SO<sub>2</sub> and the CO<sub>2</sub> absorption unit uses SGS to capture at least 90 mol% of the CO<sub>2</sub> in the split flue gas stream. Upon CO<sub>2</sub> and SGS reactions, the resulting liquid products exhibit phase-separation into CO<sub>2</sub>-lean phase and CO<sub>2</sub>-rich phase, allow two distinct pathways. Pathway (i) is to regenerate mostly the CO<sub>2</sub>-rich phase, collect the released CO<sub>2</sub>, and compress it for sequestration purposes. Pathway (ii) is to send the liquid stream from the CO<sub>2</sub> absorption unit to the ultrafiltration unit to separate the solid nanomaterials. The hydraulics and mass transfer characteristics in the washing and CO<sub>2</sub> absorption units were obtained; and techno-economic analysis (TEA) for Pathways (i) and (ii), including Capital Expenditure (CAPEX), Operating Expenditure (OPEX), and Levelized Cost of CO<sub>2</sub> Captured (LCOC), were calculated and compared. The simulation results revealed that the CAPEX, OPEX, and LCOC for Pathway (i) were ($12,039,251), (261 $/h), and (54.01 $/ton-CO<sub>2</sub> captured), respectively, and those for Pathway (ii) were ($5,908,000), (237.2 $/h), and (39.90 $/ton-CO<sub>2</sub> captured), respectively. Moreover, in Pathway (ii), 8.19 ton/h of CO<sub>2</sub> were captured to produce 15.62 ton/h NaHCO<sub>3</sub> nanomaterials, which were sold to offset the overall process cost. The LCOC values indicate that Pathway (ii) is more cost-effective than Pathway (i) because LCOC values for Pathway (ii) are much lower than those for Pathway (i).

Hydrogen production performance of active Ce/N co-doped SrTiO3 for photocatalytic water splitting

An efficient visible light responsive photocatalyst Ce/N co-doped SrTiO3 was prepared via a hydrothermal method for hydrogen production. The phase structure, morphology, contents and valence states of the dopant elements, specific surface area, optical properties, and photocatalytic activity of the samples were characterized. The transient photocurrent response and electrochemical impedance spectra under visible light illumination indicated that Ce/N co-doped SrTiO3 possessed a more intense photo-current response and lower surface resistance than N–SrTiO3 and Ce–SrTiO3. The water splitting rate of Ce/N-co-doped SrTiO3 is 4.28 mmol/g/h, which is 84.49 times higher than that of pure SrTiO3. The enhanced photocatalytic performance is due to the narrowing of the band gap of SrTiO3 by Ce ion and N ion impurities.

Computational Screening of New Dopants for Nife-Based Layered Double Hydroxide Catalysts for Seawater Splitting

Water electrolysis is a key technology to convert and store sustainable energy into high-energy-dense hydrogen. However, slow kinetics of oxygen evolution reaction (OER) at the anode hinders overall reaction rate of water splitting and delays realization of hydrogen energy society. OER consists of four electron steps and an ideal catalyst has 1.23 V potential barrier for each step, but a real catalyst has a step which requires higher potential than 1.23 V, i.e., overpotential. Therefore, exploring OER catalyst with minimized OER overpotential is an important challenge in increasing water electrolysis efficiency. On the other side, the direct use of abundant seawater as a splitting reactant has advantage in terms of resources and cost. It can also help commercialization of water electrolysis. Since seawater contains chloride which causes undesirable side reactions and accelerated corrosion of the anode material, appropriate OER catalyst is necessary to avoid these problems.Conventional trial-and-error method in catalyst design usually requires many years of R&D and high cost. Computational screening can preemptively narrow down the candidate group of high-efficient catalyst to reduce time and economic cost. NiFe-based layered double hydroxide (NiFe-LDH) is a promising OER catalyst due to the comparable activity to commercial IrO2catalyst and can provide easily tunable metal composition during synthesis process. Its unique layered structure and reversible oxidation state change in redox condition also have arisen interest of many researchers. In this study, starting from the mechanism study of OER, chloride evolution reaction (ClER), and chloride-induced corrosion on this material, we performed DFT calculations to predict which transition metal dopants can enhance the OER activity of NiFe-LDH without accelerating selectivity and corrosion problems in seawater.NiFe-LDH is known to experience its transition to NiFeOOH phase under OER condition. [001] and [110] facets were set as edge and terrace sides of NiFeOOH, respectively, after their surface energies were investigated. Surface Pourbaix diagram showed that the [001] facet has clean termination without any adsorbate while [110] facet has dissociated-H2O covered termination under alkaline OER condition. OER energetic profile showed that the Fe site on the [110] surface is an OER active site with a theoretical overpotential of 280 mV, and seawater conditions do not significantly affect the OER activity itself. ClER mechanism study revealed that it occurs via *ClOH intermediates on [110] metal sites or *Cl intermediates on deprotonated [001] oxygen sites. Energy calculation of surface chlorination and metal dissolution steps showed that gradual chlorination accelerates metal dissolution and [110] facet is more vulnerable to chloride-induced corrosion than [001] facet.As the third metal candidate of NiFe-LDH, 3d to 5d transition metals excluding heavy metals were screened. Gibbs free energy correction terms such as vibrational entropy, zero-point energy and solvation parameter were calculated only for NiFeOOH case, and applied them to other candidates to simplify the screening process. NiFeOOH [001] surface could not be better than NiFeOOH [110] surface due to the inherent low activity of the [001] facet, but interestingly seven dopants could reduce the overpotential of NiFeOOH [110] surface by affecting the Fe active site or being active sites themselves. Since these dopants increased the oxidation ability of the active site, all of them also lowered chloride oxidation potential. However, fortunately, none of their ClER operating potential was lower than their OER operating condition, which means that there still exist potential windows where 100% OER selectivity can be achieved. In the last screening step, dissolution energies of fully chlorinated metal sites were calculated for the seven candidates, and two cases of them showed negative dissolution energy, which indicates very unstable doping state. As a result, five candidates passed through all three screening criteria: OER activity, OER vs. ClER selectivity, and durability against corrosion. Further, the experimental validation has performed on three promising candidates considering the raw material price, and it revealed that their activity is higher activity than NiFe-LDH. In addition, for the two abandoned cases in the third screening step (about metal dissolution), the experimental data showed that they were not seem to be actually doped into NiFe-LDH, indicating that the computational screening of seawater compatibility really worked. This study supports the utility of theoretical screening in electrochemical catalyst design and presents computational approach method to consider seawater compatibility.

Imperative Seasoning Characteristics of Yushania alpina (Highland Bamboo) Culms Grown in Dire-Inchini, Ethiopia

Bamboo is the world's fastest-growing plant and the finest conceivable substitute for future wood. It has a wide range of applications, from traditional use to industrial manufacture in many countries. Bamboo has been traditionally used in Ethiopia for the construction of huts and fencing, furniture, containers, beehives, and other small-scale objects. Lack of proper processing practices such as seasoning among the reasons for its low use. When bamboo culms are not properly seasoned, they have a high split and shrinkage rate that led to biological and physical degradations. 3–5year-old samples of Yushania alpinia culms were gathered from Dire-Inchni (Oromia Region). After harvesting culms, were cut into three portions (bottom, middle and top) to investigate the imperative characteristics of the material during the drying process. Kiln and air-drying procedures were used to dry the culms. Regression analysis was used to describe the functional relationship between moisture loss in the kiln and air drying. They had an average initial MC 103.67%, final MC 12.33%, and basic density 0.69 g/cm3. Bamboo culms dried in the kiln took 7.7 days to attain about 12 % final MC, while air-seasoned culms took 97 days. proper stacking, drying, and handling is critical for improving the quality, productivity, and service life of bamboo culms-based constructions and goods in the future.

회계 보수성이 신용등급 불일치에 미치는 영향

[Purpose] This study conducted an analysis of the effect of corporate accounting conservatism on split bond rating. Accounting conservatism directly or indirectly plays a role in reduction of information uncertainty and asymmetry and thus it can affect bond rating to be differently given by credit-rating agencies.
 [Methodology] A multivariate logit analysis was performed on 1,732 firm-year samples with corporate bond ratings from multiple credit rating agencies in the KOSPI market from 2012 to 2021.
 [Findings] The empirical result shows that accounting conservatism had a negative relationship with the split bond rating. This means that the higher the accounting conservatism, the less information uncertainty and asymmetry, resulting in a decrease in split bond rating. In order to make it more clear the cause and effect relationship between accounting conservatism and split bond rating, an additional analysis was conducted in which the degree of split bond rating was set as a dependent variable. As a result of additional analysis, it was found that the degree of split bond rating decreased as the accounting conservatism increased.
 [Implications] This study makes a kind of distinguishment by verifying that accounting conservatism is a component of the cause of split bond rating and reversely by suggesting that information uncertainty and asymmetry arising from the accounting conservatism can affect split bond rating. It also implies that the accounting conservatism should be considered in the process of interpreting credit ratings from an investor's point of view. Also, this research is valuable by giving an insight to management who plan to raise debt capital and to regulatory agencies that design disclosure systems.

Versatile Bifunctional and Supported IrNi Oxide Catalyst for Photoelectrochemical Water Splitting

Designing a high-performance electrocatalyst that operates with photon-level energy is of the utmost importance in order to address the world’s urgent energy concerns. Herein, we report IrNi nanoparticles uniformly distributed on cost-effective activated carbon support with a low mass loading of 3% by weight to drive the overall water splitting reaction under light illumination over a wide pH range. The prepared IrNi nanomaterials were extensively characterized by SEM/EDX, TEM, XRD, Raman, and UV-visible absorption spectroscopy. The experimental results demonstrate that when the Ir:Ni ratio is 4:1, the water splitting rate is high at 32 and 25 mA cm−2 for hydrogen (at −1.16 V) and oxygen evolution reactions (at 1.8 V) in alkaline electrolyte, respectively, upon the light irradiation (100 mW cm−2). The physical and electrochemical characterization of metal and alloy combinations show that the cumulative effect of relatively high crystallinity (among the materials used in this study), reduced charge recombination rate, and improved oxygen vacancies observed with the 4Ir1Ni@AC electrode is the reason for the superior activity obtained. A high level of durability for hydrogen and oxygen evolution under light illumination is seen in the chronoamperometric study over 15 h of operation. Overall water splitting examined in 0.1 M of NaOH medium at a 50 mV s−1 scan rate showed a cell voltage of 1.94 V at a 10 mA cm−2 current density.

Implementation strategy for complete pathogen reduction technology treated apheresis platelet inventory.

Bacterial contamination in platelets remain a major public health concern, which prompted the US Food and Drug Administration guidance for bacterial contamination mitigation. Pathogen reduction technology (PRT) is one mitigation strategy that has shown success in Europe over the last decade. Therefore, our center sought to transition from a dual system of bacterial culturing (BacT) and PRT to full PRT. A 1 month pilot study was conducted to simulate 100% PRT conditions. Our center also collected baseline data on key platelet production metrics in the 4 months prior to 100% PRT and compared it to the 4 months post-implementation. The pilot study showed no statistical differences in split rate, proportion of low-yield products, or proportion of single, double, and triple collections. The only observed difference was an 11 min increase in the average duration of double collections. Our baseline versus post-implementation monitoring showed no difference in split rate, discard rate, percentage of low-yield units, and average yield of low yield units. Statistical differences were detected in the proportion of single, double, and triple collections, as well as the average yield of full dose products. Roughly 20% of our inventory consisted of low-yield products. With suitable mitigation strategies, transitioning to a full PRT inventory may result in higher net margins while not adversely affecting overall platelet production. A pilot study is a good way to project potential effects of switching from a dual BacT and PRT inventory to full PRT, and can be adopted by other centers aiming to make the transition.

Debate: Are We Limiting the Potential of Oocytes by Not Using ICSI for All? - ICSI Should be Used for Most IVF Cycles

Background: Following earlier studies introducing an IVF-ICSI Split model on couples with unexplained infertility to avoid the scenario of unexplained failed or poor fertilization, PIVET has adopted a high ICSI rate approaching 90%, whereas the general rate among Australian facilities is around 60%. Aim: To compare the embryology and clinical outcomes in an IVF program where ICSI is applied beyond male-factor reasons and applies an IVF-ICSI Split protocol for IVF-naïve women with unexplained infertility. Method: This observational study with retrospective data analysis reports on autologous IVF± ICSI procedures conducted over the period 2011 to 2019 with follow-up of ensuing pregnancies through 2020. Results: Using autologous oocytes, 2343 women had 3434 IVF± ICSI cycles with 84.5% of women had 88.9% of initiated treatment cycles using ICSI and only 5.3% of women had 4.0% of cycles by IVF. The remaining 10.1% of women utilised the IVF-ICSI Split model for the remaining 7.2% of cycles. It was shown that oocyte fertilisation rates were significantly higher for ICSI (p<0.0001), but not significant for women >40 years. The utilisation rates of the ensuing embryos were [Formula: see text]45% across all ages with no significant differences across the ages, except for those small numbers of women [Formula: see text] 45 years who had a higher rate from IVF-generated embryos (p<0.0002). Pregnancy outcomes were higher from ICSI-generated embryos across the age groups, being especially marked among the younger women <40 years (p<0.0001). Miscarriage rates were lowest for the IVF-generated pregnancies (overall 6.7% vs 22.8%, p<0.0001) but nevertheless the final live birth productivity rates per initiated treatment cycle remained higher from the ICSI-generated pregnancies (56.5% vs 46.3%; p<0.0001). Conclusion: Although this study does not meet the highest standards for EBM, it emanates from a pioneer facility with >40 years of published activity and which practices 90% blastocyst transfers in >90% SET cycles. The study supports a high ICSI rate of 90% and an IVF-ICSI Split rate of 10%.

Baseline for Split DC Link Design in Three-Phase Three-Level Converters Operating with Unity Power Factor Based on Low-Frequency Partial Voltage Oscillations

The study sets a baseline for split DC link capacitance values and voltage set points in three-phase three-level AC/DC (or DC/AC) converters operating with unity power factor. In order to equalize the average values of partial DC link voltages, the controller generates a zero-sequence containing DC components only while employing neither dedicated DC link capacitance balancing hardware nor high-order zero-sequence component injection. Such a baseline is required in order to evaluate the effectiveness of different DC link capacitance reduction methods proposed in the literature. Unlike most previous works, utilizing neutral point current based on cumbersome analytical expressions to determine neutral point potential oscillations, the instantaneous power balance-based approach is employed in this paper, resulting in greatly simplified and more intuitive expressions. It is demonstrated that while the total DC link voltage is low-frequency ripple-free under unity power factor balanced AC-side operation, split DC link capacitors absorb triple-fundamental frequency power components with one-sixth load power magnitude. This yields significant opposite phase partial voltage ripples. In such a case, selection of DC link capacitances and voltage set points must take into account the expected values of AC-side phase voltage magnitude and split DC link capacitor voltage and current ratings. Simulation and experimental results validate the proposed methodology by application to a 10 kVA T-type converter prototype.

Effect of conical air distributors on drying of peppercorns in a fluidized bed dryer: Prediction using an artificial neural network

The effect of conical air distributors on the drying of peppercorns in a fluidized bed dryer was experimentally studied. A flat perforated sheet was installed in the column at the base of the bed. Conical air distributors consisted of two parts. The first was a solid cone located below an air duct, while the second part was a perforated metal cone placed on the flat perforated sheet. Experiments were carried out using perforated metal cones with three different height to base diameter ratios, ( h/H ) values of 0.5, 1.0, and 1.5 and three different air velocities, 1.2 U mf , 1.6 U mf , and 2.0 U mf . An air distributor, consisting of a solid cone and a perforated metal cone with h/H = 1.0 and an air velocity of 2.0 U mf , showed the best drying performance. It was also discovered that increasing the air velocity accelerated the drying process. A neural network was created to predict the moisture content of peppercorns during the drying process. The split, sample type, spilt ratio, momentum, and learning rate, as well as the numbers of hidden layers, hidden nodes, and training cycles all had an impact. A maximum coefficient of determination of 0.996 was found for the best model.

Bad splits in bilateral sagittal split osteotomy: A retrospective comparative analysis of the use of different tools

This study aims to analyse the relationship between the incidence of bad splits and the surgical tools adopteded to perform bilateral sagittal split ramus osteotomy (BSSRO).BSSROs performed by the same experienced surgeon period were reviewed, retrospectively. The patients were divided into three groups according to the surgical instrument used to perform the osteotomy: a Lindemann burr, reciprocating saw or piezosurgery. Among the 1120 BSSROs performed, 5 bad fractures were detected during the observation period: 3 among patients operated with the Lindemann burr (0.8%) and 2 among those operated with a reciprocating saw (0.5%). There was no significant correlation between the bad split rate and age and gender of the patients, the type of malocclusion or the type of instrument used to perform the osteotomy.Within the limitations of the study it seems that the the choice of the osteotomy tool for BSSRO does not influence the rate of bad fractures and, therefore, the selection of the osteotmy tool should be left to the discretion of the surgeon.

Use of CT-based renal volumetry for the measurement of split renal function: a split glomerular filtration rate prediction model based on unilateral renal volume parameters

To develop a split glomerular filtration rate (sGFR) prediction model based on unilateral renal volume parameters using three-dimensional (3D) computed tomography (CT) volumetry. Clinical data (age, sex, height, weight, serum creatinine level [sCr], and sGFR measured by 99mTc-diethylene triamine pentaacetic acid nuclear renal scintigraphy with the double plasma sample method) of 67 healthy renal donors and 111 patients with hydronephrosis admitted from April 2016 to September 2021 were analysed. The split renal parenchymal volume (sRPV) and split renal calyces and pelvis volume (sRCPV) of 67 unilateral donor left kidneys and 111 hydronephrotic kidneys were measured. Statistical analysis of these parameters was performed to develop and validate the sGFR prediction model. sRPV (p<0.001), sRCPV (p=0.012), age (p=0.015), serum creatinine level (p=0.004), and weight (p=0.006) were significantly associated with the measured sGFR and were included in the sGFR prediction formula, which was constructed as: 68.710+0.093×sRPV-0.041×sRCPV-0.228×W-0.219×A-14.432×sCr (r2=0.416; where A is age, W is weight). The paired difference of internal validation between the measured sGFR (42.34±13.71 ml/min/1.73 m2) and the sGFR estimated by the prediction model (41.46±8.99 ml/min/1.73 m2) was 0.879±11.475 ml/min/1.73 m2 (p=0.492) with a 95% confidence interval of the mean difference of ±2.54 ml/min/1.73 m2. The proposed model based on sRPV and sRCPV parameters could be used for estimating split renal function of healthy renal donors and patients with hydronephrosis to some extent. Further studies are required to evaluate and rectify the model.

Energy levels and magnetic dipole transition parameters for the nitrogen isoelectronic sequence

Theoretical calculations of the energy levels and magnetic dipole transition parameters for the 1s22s22p3 and 1s22p5 configurations of nitrogen isoelectronic sequence with Z = 21–30 are performed using multi-congfiguration Dirac–Fock (MCDF) method. Based on the relativistic computational code GRASP2k compiled within the framework of MCDF method, the electron correlations, Breit interaction and QED effects are well treated in detail. The energy levels, line strengths and transition rates of magnetic dipole transition are obtained and compared with the experimental data available. For most cases, good agreements are achieved and the relative differences of them are less than 0.114%, 8.43% and 9.80%, respectively. The scaling laws of the fine structure splitting and transition rate are obtained on the isoelectronic sequence and the corresponding physical mechanisms are discussed. The data sets for tables are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00022.

Scaling-resistant anion-exchange membrane prepared by in situ modification with a bifunctional polymer containing quaternary amino groups

Membrane scaling and subsequent cleaning efficiency are major factors limiting commercial applications of electrodialysis. The generation of OH− ions during water splitting at the membrane interface promotes scaling formation. We report a modification of a commercial anion-exchange membrane, which improves its scaling resistance by reducing the water splitting rate. This is achieved by replacing the weakly basic amino groups on the surface of membrane with quaternary ones that do not have catalytic activity with respect to water splitting. We have carried out a comprehensive study of membranes modified by ex situ, and new membranes, for the first time modified in situ, directly inside the electrodialyzer. The in situ modified membranes were found to exhibit better properties in decreasing the water splitting rate, which, in turn, significantly reduces the scale formation on the surface facing the concentration chamber.

Computation-Aided Discovery and Synthesis of 2D PrOBr Photocatalyst

Developing photocatalysts is essential for converting solar energy into chemical fuels. Herein, we report the discovery and synthesis of praseodymium oxyhide (PrOBr), a two-dimensional (2D) rare-earth material, as an efficient photocatalyst. By performing high-throughput screening over popular computational 2D materials databases, we have identified 2D PrOBr as a promising photocatalyst with potentially good stability and activity. 2D PrOBr was successfully synthesized via the exfoliation of bulk PrOBr powders. The intrinsic photocatalytic activities of this 2D material were further validated. The measured hydrogen evolution rate of water splitting and the methane production rate of carbon dioxide reduction are 60.28 μmol·h–1·g–1 and 0.862 μmol·h–1·g–1, which are about 3–6 times and 7 times higher than that of the typical 2D photocatalysts (e.g., 2D C3N4 and BiOCl), respectively.

Mitigating Vortex Splitting by Controlling the Wavefront Isophase Line Curvature of Vector Autofocusing Airy Vortex Beams in Free Space

The match between the orbital angular momentum (OAM) transmission and receipt is a prerequisite for vortex beams as a carrier of the wireless optical communication system in free space. However, the vortex splitting induced by atmospheric turbulence results in an offset in the average OAM measured after propagating over the free space optical communication link. Therefore, how to reduce the vortex splitting effect to improve the stability of orbital angular momentum propagation is studied in this paper. First, a new parameter (m) is introduced to modulate the radial distribution of the polarization state of the autofocusing Airy vortex beams (AAVBs). Second, to control the optical field distribution in focal plane, the wavefront isophase line curvature of the AAVBs is reconstructed by using the Pancharatnam-Berry phase generated in the polarization conversion process. Finally, by comparing the vortex splitting rates of the AAVBs with different wavefrontisophase line curvatures under different turbulence environments, it can be found that the vortex splitting in free space can be effectively mitigated by choosing an appropriate wavefront isophase line curvature. In addition, the mitigation effect is more obvious in the atmosphere with stronger turbulence. This study provides a new feasible method to control the phase structure of vortex beams and promises potential applications in the OAM-based free space optical communication system.