Rate Enhancement Research Articles

Real-Time EtherCAT-Based Control Architecture for Electro-Hydraulic Humanoid

Electro-hydraulic actuators have witnessed significant development over recent years due to their remarkable abilities to perform complex and dynamic movements. Integrating such an actuator in humanoids is highly beneficial, leading to a humanoid capable of performing complex tasks requiring high force. This highlights the importance of safety, especially since high power output and safe interaction seem to be contradictory; the greater the robot’s ability to generate high dynamic movements, the more difficult it is to achieve safety, as this requires managing a large amount of motor energy before, during, and after the collision. No matter what technology or algorithm is used to achieve safety, none can be implemented without a stable control system. Hence, one of the main parameters remains the quality and reliability of the robot’s control architecture through handling a huge amount of data without system failure. This paper addresses the development of a stable control architecture that ensures, in later stages, that the safety algorithm is implemented correctly. The optimum control architecture to utilize and ensure the maximum benefit of electro-hydraulic actuators in humanoid robots is one of the important subjects in this field. For a stable and safe functioning of the humanoid, the development of the control architecture and the communication between the different components should adhere to some requirements such as stability, robustness, speed, and reduced complexity, ensuring the easy addition of numerous components. This paper presents the developed control architecture for an underdeveloped electro-hydraulic actuated humanoid. The proposed solution has the advantage of being a distributed, real-time, open-source, modular, and adaptable control architecture, enabling simple integration of numerous sensors and actuators to emulate human actions and safely interact with them. The contribution of this paper is an enhancement of the updated rate compared to other humanoids by 20% and by 40 % in the latency of the master. The results demonstrate the potential of using EtherCAT fieldbus and open-source software to develop a stable robot control architecture capable of integrating safety and security algorithms in later stages.

Heating and storage of medium-deep borehole heat exchangers: Analysis of operational characteristics via an optimized analytical solution model

This study focuses on investigating the thermal storage potential of medium-deep borehole heat exchanger (MDBHE) to address the issues of temperature attenuation of thermal reservoir and heating capacity reduction during the one-way heat extraction process in the heating period. By establishing an MDBHE heating system that integrates an external thermal storage source, a comprehensive analysis of the heat transfer progress and operational characteristics of the MDBHE is conducted, including optimizing burial depth, thermal storage scenarios, and aquifer conditions. The calculated solution under the typical thermal storage conditions (S60–30) in this study reveals that the average heat supply capacity increasement of a 1200 m MDBHE is 37.2 % higher than that of a 2000 m MDBHE, and the power consumption of the circulating water pump also can be reduced by 40 % in heating period. Furthermore, the enhancement of storage temperature and flow rate both contribute to a noticeable improvement in the heating performance of the MDBHE during the heating period. The heat transfer power and energy efficiency of MDBHE both increase with the elevation of seepage velocity and aquifer thickness during the energy storage and heating period. The significance of this research lies in its contribution to the enhancement of thermal storage and heat transfer efficiency in MDBHE and offering novel insights for the multi-thermal energy storage systems.

Micro- and Mesoporous Structural Effects of Beta Zeolites for Volatile Organic Compound Sorption.

To fully exploit pore engineering in the design of more efficient zeolite adsorbents for volatile organic compound (VOC) treatment, the roles of meso- and micropores need to be clarified to provide the theoretical basis and feasible measures. In this work, the three VOC sorption properties of conventional and hierarchical porous beta zeolites were comparatively investigated to study the roles of meso- and micropores. There is a division of functions between micro- and mesopores, with micropores being the main VOC adsorption sites and mesopores greatly enhancing VOC diffusion and adsorbent reusability. On the one hand, micropores should be preserved as much as possible because obtaining mesopores by sacrificing micropores (i.e., alkali treatment) results in 28-60% decreases in adsorption capacities. On the other hand, mesopore introduction is highly desirable, which results in an enhancement of VOC intraparticle diffusion rates by 1.3-2.3 times (at the VOC concentration of 600 ppm) and chlorobenzene adsorption capacity on the 20th cycle increasing from 78% of the initial value to 89 and 93%. The findings may provide valuable information about zeolite-based adsorbents for adsorption removal or recovery of VOCs.

Bioceramic filled PLA based nanocomposites for biomedical application: An experimental investigation

Orthopedic implants require innovative biodegradable materials to eliminate the need for a second surgery post-healing and to counteract the stress shielding issues associated with conventional metallic implants. Polylactic acid (PLA) was chosen for its biocompatibility and biodegradability within the human body. Hydroxyapatite (HAP) and eggshell nanoparticles (ESNPs) were selected as bioceramics due to their similarity to the major constituents of human bone. In the present study, ESNPs were prepared through a ball mill. HAP and Mg particles coated with TiO2 (TiO2@Mg) were synthesized through chemical precipitation and the sol-gel technique, respectively. Subsequently, four samples were prepared: PLA/ESNP/Mg (PEM), PLA/HAP/Mg (PHM), PLA/ESNP/TiO2@Mg (PEMT), and PLA/HAP/TiO2@Mg (PHMT) using the solvent casting process. The addition of Mg demonstrated an enhancement of degradation rates, and TiO2@Mg served to eliminate hydrogen release from Mg. The confirmation of synthesized NPs and PLA nanocomposites was validated through Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Field-Emission Scanning Electron Microscopy (FE-SEM) analysis. The prepared PEMT and PHMT showed tensile strength (42.70 ± 7.55 MPa and 31.57 ± 3.84 MPa), tensile modulus (1624.49 ± 155.05 MPa and 1674.25 ± 87.04 MPa), and shore D hardness (79.41 ± 2.40 SHN and 77.81 ± 3.18 SHN), respectively. The findings showed that PEMT and PHMT composites exhibited enhanced surface roughness, hydrophilicity, degradation rate, and swelling behavior compared to PEM and PHM samples. Moreover, the viability of MG63 cells cultured in different diluted extracts of both samples reached approximately 80 %, indicating no observable cytotoxicity and a hemolysis rate of less than 1.4 %, indicating the potential for use in maxillofacial region implants.

Laminar convective heat transfer combining buoyancy and thermal radiation of Carreau fluid within a concentric and eccentric annulus

The present study concerns a steady-state laminar combined thermal radiation and buoyancy-driven conjugate magnetohydrodynamic (MHD) natural convective flow and heat transfer inside a fully porous medium eccentric circular annulus bounded by two infinite horizontal cylinders occupied by a Carreau fluid permeated by a uniform transverse magnetic field (B0 ) and inclined by an angle (α). The convective and thermal radiation are approximated by the Boussinesq and Roseland models, respectively. The numerical integration was performed using the implicit finite volume method. The convective terms in the momentum and energy equations were Discretized using the second-order upwind method. On the other hand, the diffusive terms were Discretized using the central difference scheme. The pressure-velocity coupling was solved using the SIMPLE approach. The findings suggest a clear trend of enhancement in the heat transfer rate when the aspect ratio and annulus eccentricity increase. This pattern is more pronounced in the negative vertical eccentricities. It is worth noting that the eccentric annulus, which has an annulus aspect ratio of 1.6 and a vertical eccentricity of −0.8, offers the best performance regarding the heat transfer mechanism inside the annulus gap. The heat transfer mechanism turns out to be strongly affected by thermal radiation, Hartmann number, and magnetic field inclination angle. The increased thermal radiation parameter and the decreased flow behavior index improve the heat transfer mechanism between the Carreau fluid and the inner cylinder in the annular gap. Furthermore, the average Nusselt number increases considerably as the induced magnetic field inclines.

Chitosan/Alginate-Based Nanoparticles for Antibacterial Agents Delivery.

Nanoparticle systems integrating alginate and chitosan emerge as a promising avenue to tackle challenges in leveraging the potency of pharmacological active agents. Owing to their intrinsic properties as polysaccharides, alginate and chitosan, exhibit remarkable biocompatibility, rendering them conducive to bodily integration. By downsizing drug particles to the nano-scale, the system enhances drug solubility in aqueous environments by augmenting surface area. Additionally, the system orchestrates extended drug release kinetics, aligning well with the exigencies of chronic drug release requisite for antibacterial therapeutics. A thorough scrutiny of existing literature underscores a wealth of evidence supporting the utilization of the alginate-chitosan nanoparticle system for antibacterial agent delivery. Literature reviews present abundant evidence of the utilization of nanoparticle systems based on a combination of alginate and chitosan for antibacterial agent delivery. Various experiments demonstrate enhanced antibacterial efficacy, including an increase in the inhibitory zone diameter, improvement in the minimum inhibitory concentration, and an enhancement in the bacterial reduction rate. This enhancement in efficacy occurs due to mechanisms involving increased solubility resulting from particle size reduction, prolonged release effects, and enhanced selectivity towards bacterial cell walls, stemming from ionic interactions between positively charged particles and teichoic acid on bacterial cell walls. However, clinical studies remain limited, and there are currently no marketed antibacterial drugs utilizing this system. Hence, expediting clinical efficacy validation is crucial to maximize its benefits promptly.

Development and Evaluation of Sulfobutylether-β-cyclodextrin Inclusion Complexes of Etoricoxib for Enhancing Dissolution

Introduction: Etoricoxib is a BCS class II drug with poor aqueous solubility and analgesic and anti-inflammatory properties. Complexation with cyclodextrins is one of the widely used methods, amongst others, for enhancing the solubility and bioavailability of drugs. In current research work, inclusion complexes of etoricoxib using modified forms of cyclodextrin, i.e., captisol were prepared using kneading, evaporation, and freeze-drying methods to improve the solubility and dissolution characteristics. Methods: Etoricoxib inclusion complexes (ratio 1:1) were formulated using kneading, evaporation, and freeze-drying methods. The formulated inclusion complexes were evaluated for phase solubility, equilibrium solubility studies, Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, differential scanning calorimetry studies, in vitro drug release, similarity factor and in vivo studies. Results: The freeze-drying method produced inclusion complexes with the highest equilibrium solubility (ten times that of the pure drug). Fourier transform infrared spectroscopy studies showed no drug-polymer interaction. Differential scanning calorimetry and scanning electron microscopy studies suggested the incorporation of the drug into inclusion complexes of cyclodextrin. In vitro dissolution studies of kneading, evaporation and freeze-drying method inclusion complexes showed 66.53%, 79.13% and 88% drug release, respectively, in 3h, whereas pure drug exhibited 61.77% drug release in 3 h. The f1 value obtained was less than 50, which is indicative of a significant difference in release characteristics of kneading, evaporation and freeze-drying methods with that of the marketed formulation. In vivo studies indicated that inclusion complexes formulated by the freeze-drying method showed better analgesic and anti-inflammatory effects in comparison to formulations prepared by kneading and evaporation methods. Conclusion: It is concluded that the formulation prepared by the freeze-drying method led to a significant enhancement of dissolution and solubility rate of etoricoxib in comparison to the formulation prepared by the kneading method and evaporation method.

Oxygen vacancy engineering and rare earth ion modification in Er-doped Bi0.5Na0.5TiO3–BaTiO3 for piezo-photocatalysis

The pursuit of high-performance piezo-photocatalysts through structural modifications has been a focal point of investigation within the realm of related scientific disciplines. In this study, we successfully designed Er-doped Bi0.5Na0.5TiO3–BaTiO3 combined with rare earth ion doping and solid solution modification, and the prepared particles exhibited homogeneous grain sizes and optimized concentrations of oxygen vacancies (OV). The synergistic incorporation of OV (accelerator for catalytic reaction) and Er3+ results in an impressive 12-fold enhancement of the piezo-photocatalytic rate when degrading the Rhodamine B dye. The optimal composition 0.96BNT-0.04BT-Er demonstrates outstanding electrochemical properties, including a superior photocurrent response and minimal impedance, highlighting its exceptional performance in piezo-photocatalysis. The fundamental enhancement in catalytic performance can be attributed to the reconfiguration of the band structure of 0.96BNT-0.04BT-Er, which has been meticulously calculated utilizing DRS and VB-XPS and the internal mechanism was explained in detail. This research serves as a source of inspiration for the investigation of solid solutions among piezo-photocatalysts and sheds light on the vital role of band structure in governing catalytic performance.

Close Major-merger Pairs at z = 0: Star-forming Galaxies with Pseudobulges

We present a study of star-forming galaxies (SFGs) with pseudobulges (bulges with Sérsic index n < 2) in a local close major-merger galaxy pair sample (H-KPAIR). With data from new aperture photometries in the optical and near-infrared bands (aperture size of 7 kpc) and from the literature, we find that the mean Age of central stellar populations in Spirals with pseudobulges is consistent with that of disky galaxies and is nearly constant against the bulge-to-total ratio (B/T). Paired Spirals have a slightly lower fraction of pure disk galaxies (B/T ≤ 0.1) than their counterparts in the control sample. Compared to SFGs with classical bulges, those with pseudobulges have a higher (>2σ) mean of specific star formation rate (sSFR) enhancement (sSFRenh = 0.33 ± 0.07 versus sSFRenh = 0.12 ± 0.06) and broader scatter (by ∼1 dex). The eight SFGs that have the highest sSFRenh in the sample all have pseudobulges. A majority (69%) of paired SFGs with strong enhancement (having sSFR more than 5 times the median of the control galaxies) have pseudobulges. The Spitzer data show that the pseudobulges in these galaxies are tightly linked to nuclear/circum-nuclear starbursts. Pseudobulge SFGs in S+S and in S+E pairs have significantly (>3σ) different sSFR enhancement, with the means of sSFRenh = 0.45 ± 0.08 and −0.04 ± 0.11, respectively. We find a decrease in the sSFR enhancements with the density of the environment for SFGs with pseudobulges. Since a high fraction (5/11) of pseudobulge SFGs in S+E pairs are in rich groups/clusters (local density N1Mpc ≥ 7), the dense environment might be the cause for their low sSFRenh.

Persons with Parkinson`s disease show the motor behavioral phenomenon repeated bout rate enhancement during cycling

Persons with Parkinson`s disease show the motor behavioral phenomenon repeated bout rate enhancement during cycling

Enhancement of deposition rate by accelerators employing D-Mannitol as complexing agent

Copper possesses better conductivity which makes it an ideal plating choice for the electronics and semiconductor industries. Copper electroless plating can be carried easily on non-conductors like plastics, ceramics, fabrics, glasses etc. One of the limitations of electroless plating is its very low plating rate, which is further reduced by the addition of stabilizers which is quite essential for the plating process. A stabilizer improves stability of bath and deposit qualities, but slows down the plating rate. The current study focuses on the enhancement of plating rate by the addition of accelerators in eco-friendly copper methane sulphonate bath. It is observed that accelerators like guanidine hydrochloride and 2,6-diaminopyridine improves the rate of deposition with good deposit quality. It was studied with weight gain method and analyzed with tafel polarization studies. The surface of the deposit was analyzed with X-ray diffraction (XRD) and scanning electrode microscope (SEM). KEY WORDS: Copper, Methane sulphonic acid, Accelerators, Guanidine hydrochloride, 2,6- Diaminopyridine Bull. Chem. Soc. Ethiop. 2024, 38(4), 901-908. DOI: https://dx.doi.org/10.4314/bcse.v38i4.7

Enhancing Performance of Power Allocation for VLC Networks by Non-Orthogonal Multiple Access-MIMO

Visible light communication, or VLC, networks emerged as a viable option for data access, particularly indoors. Their cost-effectiveness, protection to radio frequency (RF) intrusion, and extraordinarily high data speeds make them a desirable option for the upcoming generation of indoor networking technologies. In this paper, we propose the Exponential Gain Ratio Power Allocation (EGRPA), an effective and low-complex power splitting method, to increase the attainable sum amount in Multiple Input Multiple Output (MIMO) VLC downlink networks. Using numerical simulations, we assess the enactment of an indoor 2x2 MIMO VLC downlink model for several users. We also use Non-Orthogonal Multiple Access (NOMA) for enhancing spectrum efficacy. The usefulness and resilience of the suggested power splitting approach are established by the simulation outcomes, especially in scenarios with a high user count. In particular, the EGRPA power allocation algorithm shows a sum rate enhancement of more than 38.7%, 7.86%, and 7.04% for a system with three users when compared to the GRPA method, Normalized Gain Difference Power Allocation (NGDPA) method, and Logarithmic GRPA (NLGRPA) method, correspondingly.

Dynamic compressive behavior of steel fiber synergistically reinforced cellular concrete under high strain-rate loading

To better understand the reinforcement and toughness effects of steel fibers, a 75-mm split Hopkinson pressure bar (SHPB) device was used to test the uniaxial dynamic compression properties of steel fiber synergistically reinforced cellular concrete (SFSRCC) under high strain rates. The dynamic compression performance characteristics of the SFSRCC, including the stressstrain curve, dynamic strength, impact toughness and failure mode, were analyzed. The results showed that the dynamic strength, peak strain and impact toughness of SFSRCC increase with increasing strain rate. Compared with that of cellular concrete (SAP10S0), a higher steel fiber volume ratio corresponded to a greater enhancement in the dynamic performance characteristic indices of the SFRCC. The maximum increases were 138.4%, 180.0% and 280.0% for the DIF, peak strain, and impact toughness, respectively. The damage degree of the SFSRCC specimen decreased with increasing fiber content, and a larger area of residual "core retention" was observed, which indicated that the impact resistance of the SFSRCC with a high fiber content was improved. An empirical formula that can accurately characterize the dynamic strength increase factor (DIF) of SFSRCC with high strain rates was proposed, and the prediction results obtained by using the DIF of the SFSRCC were highly consistent with the test results, which confirmed its effectiveness. To further quantify the strain rate enhancement effect and fiber content for the reinforcement and toughening ability of SFSRCC, the relationships between the peak strength/peak strain/impact toughness and strain rate and between the DIF increment ratio/strain energy density increment ratio and fiber volume fraction were determined. In conclusion, the dynamic compression performance characteristics of SFSRCC can be enhanced by incorporating an appropriate quantity of steel fibers with a dynamic impact load.

A facile strategy for enhancement of heat storage rate in LHS units

LHS units suffer from long melting periods, resulting in overestimated amounts of PCMs for specific heat storage rate as well as larger surface areas for heat transfer. In this paper, we propose a facile strategy for the enhancement of heat storage rate in LHS units, with the contribution of natural convection by the addition of materials with low melting temperatures. Morphology analysis and preliminary experiments are conducted and the validity of the strategy proposed is verified. The principle of natural convection contribution is concluded from the observation of curved boundary of solid PCMs in morphology analysis, after the addition of materials with low melting temperature. The melting period is shortened by 44.8 % and the heat storage amount is augmented due to the existence of added materials. The effects of the novel strategy on heat storage enhancement are more obvious in the case of container with smaller size. As in the experiments of a prototype of LHS units, the heat storage rate is augmented by 31.09 %. The strategy proposed in this paper offers a facile method for the design of LHS units with fast melting and heat storage augment.

Parametric study on thermal performance augmentation of TiO2/water nanofluids flowing a tube contained with dual counter twisted-tapes

The study of compound heat transfer enhancement technique using dual counter twisted tapes (DCTs) together with TiO2/water nanofluids was carried out. The dual twisted tapes in form of counter-swirl tape arrangement were utilized at three twist ratios (y/w = 1.5, 2.0 and 2.5). TiO2/water nanofluids having three different volume concentrations (φ = 0.05, 0.10 and 0.15 %) were employed as the testing fluids. The results indicated that heat transfer rate, friction factor and thermal enhancement index rose with decreasing tape twisted ratio and elevating nanofluid concentration. The TiO2/water nanofluids applied in the present work offered higher Nu than pure water (the base fluid) by 7.3–10.0 %. The application of DCT with the smallest y/w of 1.5 and TiO2/water nanofluids with the largest φ of 0.15 vol% led to the highest thermal enhancement index (TEI) of 1.53, under the same pumping power criteria. Additionally, the k-nearest neighbor (k-NN) and artificial neural network (ANN) were developed to predict the thermal enhancement index (TEI). It was found that the k-NN and ANN models provided maximum R2 values of 0.919 and 0.992 f, respectively.

A numerical study on premixed laminar ammonia/air flames enriched with hydrogen: An analysis on flame–wall interaction

Ammonia (NH3) has been recognized as a potential carbon-free synthetic fuel of the near future. To enhance its low reactivity, one practical option is to blend it with hydrogen (H2). In this study, the transient head-on quenching of premixed laminar ammonia/air flames enriched with hydrogen is explored based on numerical simulations using detailed chemistry and the mixture-averaged transport model. In this respect, nine different test cases are studied for blending ratios (the molar ratio of hydrogen to the ammonia/hydrogen mixture) of 0.0, 0.2, and 0.4, equivalence ratios of 0.8, 1.0, and 1.2, wall temperatures of 300, 500, and 750 K, and pressures of 1, 2, and 5 atm. The results reveal that the quenching distance (maximum absolute wall heat flux) decreases (increases) with increasing the blending ratio, the equivalence ratio, the wall temperature, and the pressure. For all the test cases, the quenching Peclet number changes between 1 and 3.5. In addition, the local heat release rate enhancement and the role of radical recombination reactions are highlighted at the time of quenching in the vicinity of the wall. This effect is augmented as the blending ratio, the equivalence ratio, and the wall temperature increase. Furthermore, the results show that the N2 pathway is the dominant pathway in consumption of NO near the wall at the time of quenching, in which R76 (NH2+NO⇔N2+H2O) poses the rate controlling role. In addition, the leading role of R85 (NH+NO⇔N2O+H) in consuming NO and converting it to N2O is highlighted at the time of quenching near the wall. Moreover, the significant roles of molecular diffusion and reaction source terms over convection are discussed for both NO and N2O species transport in the vicinity of the wall.Novelty and significance statement: The significance of this work is that using ammonia and its blends with hydrogen as promising carbon-free fuels for the future has several technical issues/uncertainties, which needs to be addressed fundamentally. One of the relatively unexplored issues in the combustion devices for ammonia/hydrogen/air flames is the head-on quenching phenomenon, which is investigated in detail in this study. The novelty of this work is that, for the first time, (1) the head-on quenching of various ammonia/hydrogen blends is systematically studied numerically, employing detailed chemistry, (2) effect of wall on the heat release rate chemistry is discussed wherein the role of radical recombination reactions is highlighted, and (3) the formation pathways of pollutant emissions (NO and N2O) for such flames are thoroughly investigated in the freely propagating flame scenario and in the vicinity of the wall at the time of quenching.

Scalable polycondensation approach for efficient Al/S@g-C3N4 hydrogen production catalyst

This article investigates the development of an efficient Al/S@g-C3N4 catalyst for hydrogen production through sodium borohydride (NaBH4) methanolysis. The catalyst was prepared using a facile and scalable polycondensation technique. The prepared catalyst was characterized extensively by XRD, FTIR, SEM, and surface area analyses. XRD and FTIR analysis showed a reduction in the interlayer distance between the S@g-C3N4 sheets with increasing Al content. The SEM images showed a rough and uneven surface of the nanosheets. The obtained values of Eg are 2.6, 2.4 and 2.5 eV for the samples doped with 0.0, 1.0 and 2.0 wt% of Al. Increased surface area (up to 92 m2/g) and slightly smaller mesopores (1.56 nm) observed with increasing Al doping up to 2.0 wt%. Significant enhancement in hydrogen generation rate with a maximum of 10,112 mL/g.min was achieved for 2.0 wt% Al. Low activation energy of 27.08 kJ/mol for the 2.0 wt% Al-doped catalyst. The catalyst demonstrated good stability after undergoing multiple NaBH4 methanolysis cycles.

Effects of power broadening on NMOR of alkali atoms with partially resolved hyperfine structure

This study investigates the effects of power broadening on nonlinear magneto-optical rotation (NMOR) magnetometers. As the laser power increases, the interference between two partially resolved transitions of 87Rb induced by velocity-changing collisions can be exacerbated by power broadening, resulting in a reduction of the rotation rate, and the shift of the optimal laser frequency corresponding to the maximum rotation rate. The theoretical model of NMOR is established using a four-level double Λ scheme, which takes into account power broadening effects, and experimentally studied in a single-beam NMOR magnetometer with a buffer-gas filled cell. The results indicate that the significant enhancement in rotation rate can be achieved by tuning the laser frequency to the optimal detuning based on our model. This study holds considerable importance for the improvement of magnetic field sensitivity in NMOR magnetometers.

Modelization of extended axial field-of-view PET scanners to analyze the performance improvement

Positron Emission Tomography (PET) offers non-invasive insights into physiological processes. However, in clinical practice conventional PET scanners face limitations in comprehensive imaging due to their restricted axial field of view (FOV).This study explores the benefits and challenges of extending PET scanner AFOV using Monte Carlo simulation with GATE 9.1. The Biograph Vision Quadra scanner is a novel system based on the Digital Biograph Vision 600 scanner. Both devices use silicon photomultipliers and 3.2 x 3.2 × 20 mm Lutetium Oxyorthosilicate crystals (LSO). However, the 32 detector rings of the Quadra scanner enable a four-fold expansion in the Axial Field Of View (FOV) compared to Vision. As a result, higher sensitivity, and an enhancement of noise equivalent count rate and image quality are achieved. The purpose of this study is to analyze the effect of increasing the number of detector rings and the axial FOV on the scanner performance. To accomplish this, four different geometries are modeled using GATE (GEANT4 Application for Tomographic Emission). Based on the Biograph Vision 600 model, the length and the number of detector rings are gradually extended to reach the length of the Quadra scanner. Thus, four geometries with 8 (25.6 cm), 16 (51.2 cm), 24 (76.8 cm) and 32 (102.4 cm) detector rings are simulated, keeping the crystal configuration and the dimensions in the transaxial plane. The study evaluates sensitivity, Noise Equivalent Count Rate (NECR), and image quality parameters. Results indicate a significant increase in sensitivity and NECR with FOV extension, underscoring enhanced performance. However, artifact occurrence, particularly concentric circular patterns and background homogeneity changes, accentuates with extended AFOV. Normalization algorithms, particularly component-based normalization, mitigate these artifacts. This study contributes to the understanding of the advantages and limitations of extending PET scanner AFOV, offering insights into the effectiveness of component-based normalization for improving PET image quality.

Rapid hydrolysis of NO2 at High Ionic Strengths of Deliquesced Aerosol Particles.

Nitrogen dioxide (NO2) hydrolysis in deliquesced aerosol particles forms nitrous acid and nitrate and thus impacts air quality, climate, and the nitrogen cycle. Traditionally, it is considered to proceed far too slowly in the atmosphere. However, the significance of this process is highly uncertain because kinetic studies have only been made in dilute aqueous solutions but not under high ionic strength conditions of the aerosol particles. Here, we use laboratory experiments, air quality models, and field measurements to examine the effect of the ionic strength on the reaction kinetics of NO2 hydrolysis. We find that high ionic strengths (I) enhance the reaction rate constants (kI) by more than an order of magnitude compared to that at infinite dilution (kI=0), yielding log10(kI/kI=0) = 0.04I or rate enhancement factor = 100.04I. A state-of-the-art air quality model shows that the enhanced NO2 hydrolysis reduces the negative bias in the simulated concentrations of nitrous acid by 28% on average when compared to field observations over the North China Plain. Rapid NO2 hydrolysis also enhances the levels of nitrous acid in other polluted regions such as North India and further promotes atmospheric oxidation capacity. This study highlights the need to evaluate various reaction kinetics of atmospheric aerosols with high ionic strengths.