Static Mode Research Articles

Dynamics of a hot flexible cantilever plate under natural convection heat transfer in a square cavity

This study investigates the fluid-structure interactions of a flapping plate within a square cavity under four distinct boundary conditions, where two opposing walls are heated isothermally, and the others are adiabatic. These configurations are defined as case 1 (cooled side walls), case 2 (cooled top and bottom walls), case 3 (heated bottom and cooled top wall), and case 4 (heated top wall and cooled bottom wall). The effects of non-dimensional parameters, including Rayleigh number (Ra), Cauchy number (Ca), and mass ratio (β) on plate dynamics and convective heat transfer are analyzed. Numerical investigations are executed utilizing the SU2 open-source multi-physics computational fluid dynamics solver, with a fixed Prandtl number (Pr) set at 0.71 and dimensionless temperature difference (ϵ) established at 0.6. The results show that in cases 1 and 4, the plate exhibits no observable unsteadiness, while cases 2 and 3 reveal different oscillatory behavior within certain parameter ranges, including static mode, periodic flapping mode, quasi-periodic flapping mode, and chaotic flapping mode. In particular, the configuration in case 3 possesses higher inherent instability than case 2, causing the earlier onset of Hopf bifurcation. These findings provide valuable insights into the influence of boundary conditions on the behavior of flexible structures in fluid environments, highlighting the critical role of flow instabilities and boundary conditions in determining the dynamic response of the system.

Unlocking Molecular Interactions of Biredox Eutectic Electrolyte for Non‐Aqueous Symmetrical Organic Redox Flow Batteries

AbstractBiredox deep‐eutectic solvents (DESs)‐based electrolytes have shown unique features in non‐aqueous asymmetrical redox flow batteries (RFBs) that can potentially mitigate the crossover issue. However, strong intermolecular interactions among the electrolyte constituents in DESs bring in practical challenges such as limited mass transfer rates, slow redox kinetics, and degraded cyclability. Here, by using a novel biredox‐type DES based on 4‐methoxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (4‐MeO‐TEMPO) and 3,3′‐dimethylazobenzene (3,3′‐Azo) as a model electrolyte system, the intermolecular interaction involving in the biredox DESs is unlocked by first‐principles calculations, and their influence on the electrochemical performance of biredox DESs couples is systematically investigated in comprehensive consideration of the solvents and the supporting salts. It demonstrates that employing tetrabutylammonium bis‐trifluoromethane sulfonimidate‐acetonitrile as the supporting electrolyte synergistically weakens the intermolecular interactions within the DESs, thereby significantly promoting the redox kinetics and electrochemical reversibility in non‐aqueous symmetrical RBFs. With such an optimized electrolyte, a prototype symmetrical cell under static mode is capable of delivering a high output voltage of ∼2.15 V, a decent cyclability, and the exceptional rate capability with a current density of 25 mA cm−2. This study provides a simple yet effective way to develop advanced RFBs with dependable electrolyte regulation.

Conservation of the Charge in Signal from Drift Tube Ion Mobility Spectrometers.

Quantitative information obtained from drift tube detectors used in ion mobility spectrometry is contained in the area of peaks forming the drift time spectrum. The area of all peaks corresponds to the total charge of ions entering the drift section of the spectrometer. It was found that this charge is not conserved when the ion composition changes. This work is devoted to studying the causes of this phenomenon. Experimental research consisted of recording drift time spectra for 2-pentanone and n-heptanone, at various analyte concentrations and different opening times of the shutter grid. Measurements of the total ion current were also performed in static mode with an open grid. The research results indicated that the reasons for the lack of ion charge conservation in the drift time spectrum are ion recombination, mutual repulsion, and mobility-dependent transmission of ions through the shutter grid. The explanation of the relationships obtained experimentally was based on a simple theoretical model, which considered the phenomenon of ion transport along the reaction section and the penetration of ions through the shutter. The developed model provides a good description of the measurement results and allows the estimation of ion currents and ion concentrations in the reaction section upstream of the grid. This information is important for proper quantitative analysis as well as when the ion mobility spectrometer is used in quantitative studies of chemical ionization processes.

Mechanical analysis of modified femoral neck system in the treatment of osteoporotic femoral neck fractures

BackgroundDespite the explicit biomechanical advantages associated with FNS, it is currently inconclusive, based on the existing literature, whether Femoral Neck System (FNS) outperforms Cannulated cancellous screws (CSS) in all aspects. Due to variances in bone morphology and bone density between the elderly and young cohorts, additional research is warranted to ascertain whether the benefits of FNS remain applicable to elderly osteoporosis patients. This study aimed to investigate the biomechanical properties of FNS in osteoporotic femoral neck fractures and propose optimization strategies including additional anti-rotation screw.MethodsThe Pauwels type III femoral neck fracture models were reconstructed using finite element numerical techniques. The CSS, FNS, and modified FNS (M-FNS) models were created based on features and parameterization. The various internal fixations were individually assembled with the assigned normal and osteoporotic models. In the static analysis mode, uniform stress loads were imposed on all models. The deformation and stress variations of the femur and internal fixation models were recorded. Simultaneously, descriptions of shear stress and strain energy were also incorporated into the figures.ResultsFollowing bone mass reduction, deformations in CSS, FNS, and M-FNS increased by 47%, 52%, and 40%, respectively. The equivalent stress increments for CSS, FNS, and M-FNS were 3%, 43%, 17%, respectively. Meanwhile, variations in strain energy and shear stress were observed. The strain energy increments for CSS, FNS, and M-FNS were 4%, 76%, and 5%, respectively. The shear stress increments for CSS, FNS, and M-FNS were 4%, 65% and 44%, respectively. Within the osteoporotic model, M-FNS demonstrated the lowest total displacement, shear stress, and strain energy.ConclusionModified FNS showed better stability in the osteoporotic model (OM). Using FNS alone may not exhibit immediate shear resistance advantages in OM. Concurrently, the addition of one anti-rotation screw can be regarded as a potential optimization choice, ensuring a harmonious alignment with the structural characteristics of FNS.

Impaired brain ability of older adults to transit and persist to latent states with well-organized structures at wakeful rest.

The intrinsic brain functional network organization continuously changes with aging. By integrating spatial and temporal information, the process of how brain networks temporally reconfigure and remain well-organized spatial structure largely reflects the brain function, thereby holds the potential to capture its age-related declines. In this study, we examined the spatiotemporal brain dynamics from resting-state functional Magnetic Resonance Imaging (fMRI) data of healthy young and older adults using a Hidden Markov Model (HMM). Six brain states were generated by HMM, with the young group showing higher fractional occupancy and mean dwell time in states 1, 3, and 4 (SY1, SY2 and SY3), and the older group in states 2, 5, and 6 (SO1, SO2 and SO3). Importantly, comparisons of transition probabilities revealed that the older group showed a reduced brain ability to transition into states dominated by the younger group, as well as a diminished capacity to persist in them. Moreover, graph analysis revealed that these young-specific states exhibited higher modularity and k-coreness. Collectively, these findings suggested that the older group showed impaired brain ability of both transition into and sustain well spatially organized states. This emphasized that the temporal changes in brain state organization, rather than its static mode, could be a key biomarker for detecting age-related functional decline. These insights may pave the way for targeted interventions aimed at mitigating cognitive decline in the aging population.

Cohesion Model and Scenario Simulation for Risk Prevention of “Blockchain + Agriculture Crowdfunding” from the Synergistic Perspective

Aiming at the problems such as scattered subjects, static mode and single function, this paper explores a dynamic synergistic risk prevention mode of agricultural crowdfunding that adapts to the age of data intelligence. Based on multiple prevention subjects, the blockchain technology and cohesion principle are introduced into agricultural crowdfunding prevention, and then a risk prevention dynamic model of “blockchain + agricultural crowdfunding” is constructed from the synergistic perspective. Fuzzy cognitive map model and its reasoning mechanism are used to simulate four scenarios of 1-subject, 2-subjects, 3-subjects, and 4-subjects respectively in the dynamic model and the static model. The results show that: as the number of risk prevention subjects increases, so does the cohesion, and the cohesion of multi-subjects reaches a higher state in less time and the steady-state faster, even though the fluctuation range reduces. The risk value for the multi-agent reduces rapidly and reaches a lower risk value in a shorter period of time. Overall, cohesion increases while risk reduces. In the same scenario, dynamic mode cohesion is stronger than static mode cohesion, and it takes less time to attain the steady-state value. Under various scenarios, the dynamic model’s cohesiveness steady-state value increases with the number of subjects, which is stronger than the static model’s. This study not only enriches and develops the theory of risk management of agricultural crowdfunding, but also provides a decision-making basis for the enterprises and the government, etc., to formulate, adjust, and implement risk prevention measures.

Gold nanoparticles decorated crystalline carbon nitride nano-walls as a SERS chip for rapid and sensitive detection of benzidine

Risk level of benzidine residue to the environment and food safety urges surface enhanced Raman scattering (SERS) substrates to develop with high sensitivity and rapid enrichment. Herein, a hybrid of Au NPs decorated crystalline carbon nitride nano-walls (Au/CCN NWs) is fabricated on Al sheet and employed as a SERS substrate for the first time. An electro-enhanced adsorption strategy is employed to endow as-prepared Au/CCN NWs/Al chip with rapid assay capability. Crystalline phase transition and nano-wall morphology respectively bestows high charge transfer efficiency and favorable enrichment activity upon Au/CCN NWs/Al chip, and the hybrid substrate owns a considerable enhancement factor of 1.76×106 under static adsorption mode. Moreover, Au/CCN NWs/Al substrate can achieve the saturation enrichment of benzidine in 120 s with the help of electro-enhanced adsorption, and gains a significantly enhanced signal response compared to static adsorption. Likewise, the highly sensitive response (1 μg L-1), superior reproducibility (RSD=9.11 %, n=100) and reliable accuracy (recovery rate of 95.55%-109.46%) jointly demonstrate that Au/CCN NWs/Al substrate may be applicable for detecting benzidine residue in actual application. This work offers an integrated solution to both enhance charge transfer efficiency and enrichment activity based on collaborative crystalline phase transition and electro-enhanced adsorption, and may inspire the design of novel noble metal/semiconductor hybrid SERS substrates.

Design and experiment of Beidou satellite navigation railway tunnel coverage enhancement system

Abstract In areas of satellite navigation signals being obstructed, coveraging the interior of the tunnel with Satellite navigation signals based on navigation signals real-time regeneration technology is an important way to achieve the applications of satellite navigation in railway mobile equipment positioning and auxiliary protection for operators. We analyzed the application requirements on navigation positioning and time synchronization, and technical requirements on universality and electromagnetic compatibility, etc. The article designed the composition and logical architecture of the Beidou satellite navigation railway tunnel coverage enhancement system, proposed the design of system functions and performance parameters, and verified the system’s functionality and performance through static mode testing and dynamic mode testing. The design and implementation of the Beidou satellite navigation railway tunnel coverage enhancement system have important practical value for the application in mobile equipment positioning and auxiliary protection for operators in railway tunnel.

ENHANCING BIODECOLORIZATION OF MALACHITE GREEN BY FLAVOBACTERIUM sp. THROUGH MONOTHETIC ANALYSIS

Malachite Green (MG) is a prevalent dye in the textile industry, known for its harmful environmental impacts. Addressing the urgent need for environmentally friendly and cost-effective methods to remove MG from wastewater, this study investigated the efficacy of Flavobacterium sp., isolated from Malaysian batik wastewater, in decolorizing MG. Under shaking conditions at 160 rpm, Flavobacterium sp. exhibited a notable decolorization efficiency, with 91% removal of MG after a 3-day incubation time, surpassing the static mode efficiency of 39%. Further optimization using a one-factor-at-a-time (OFAT) methodology at 37°C, pH 10, 6% (v/v) inoculum, banana peel as the carbon source and 250 mg/L MG resulted in a remarkable enhancement, achieving 95% decolorization within a reduced incubation time of 12 hours. Moreover, repeated addition of 250 mg/L MG showed consistent and complete decolorization after 6 hours by Flavobacterium sp. for four successive cycles, suggesting its economic viability for treating actual Malaysian batik wastewater. Ultraviolet-visible (UV) analysis confirmed the biodegradation of MG, evidenced by the disappearance of characteristic peaks at 618 nm and the appearance of new peaks, indicating the formation of metabolites. Flavobacterium sp. reduced pH, temperature, color, TDS, TSS, BOD and COD in batik wastewater, showing 99% color removal efficiency. This research highlights its potential as an eco-friendly, cost-effective treatment for batik wastewater. The capacity of Flavobacterium sp. to decolorize MG in an immobilized state will be the subject of future research endeavors, aimed at elucidating the adaptability and usefulness of the biocatalyst.

Natural convection characteristics of novel immersion liquid applied to battery thermal management in static mode

Battery thermal management (BTM) based on immersion liquid is a novel and promising technology due to its excellent thermal performance. However, the natural convection characteristics of immersion liquid are crucial yet often neglected for the design of immersion-based BTM. In this study, a typical BTM unit and module are designed utilizing a multi-component oil as the immersion liquid. To characterize the effect of natural convection, a rigorously validated model coupled with heat transfer and natural convection is developed. For the BTM unit, the impact of varying space occupied by immersion liquid is investigated. The increase in the thickness of the immersion liquid progressively enhances the natural convection effect. The Grashof number in the vertical interlayer of finite space helps assess the strength of natural convection of the BTM unit. Furthermore, a comparison of the BTM module with and without natural convection is performed. The results show that the natural convection effect enhances heat dissipation but reduces thermal uniformity in static mode. When the thickness of immersion liquid is 10 mm, the natural convection effect results in a decrease of 1.4 °C in the average battery temperature. Meanwhile, the battery temperature difference increases from 1.27 °C to 3.14 °C, and the average temperature of the terminals and busbars increases by >1 °C. This study can provide a foundation and reference for the BTM design based on immersion liquid.

Estimating observable-specific phase biases of GEO satellites from regional CORS to analyze its contribution in PPP ambiguity resolution

Achieving high-precision positioning and fast convergence has been the objective of Precision Point Positioning (PPP), which is restricted by the integer ambiguity resolution (AR). Recently, the emergence of observable specific code/phase bias (OSB) has gratefully alleviated this phenomenon. However, for the BeiDou Satellite Navigation System (BDS), only MEO/IGSO satellites are applied in BDS PPP-AR, while GEO satellites are generally ignored. It will largely limit the utilization in China or Asia-Pacific region, influencing both the convergence time and the positioning accuracy. To investigate the feasibility of applying GEO satellites for AR, the phase OSB of GEO satellites is estimated through the raw observations in this research. Based on the observations data from regional network in China region, the characteristics of BDS mixed-constellation OSBs are analyzed, and PPP-AR with different processing strategies in both static and kinematic mode are performed. The results indicate that the phase OSBs were relatively stable and the percentage of the estimated residuals for B1I/B3I signals within ±0.15/0.25 cycles were over 95/99% and 92/97% for IGSO and MEO satellites, while GEO satellites were slightly poor, with 89 and 96%, respectively. The average positioning accuracy of static PPP-AR containing GEO satellites was 0.55, 0.56 and 1.43 cm in the east, north and up directions, with improvements of 14.06, 3.44 and 9.48% respect to fixed solutions without GEO satellites. For kinematic mode, when the ambiguity of GEO satellites was solved, the convergence time and the average time to first fix were considerably reduced to 25.51 and 27.12 min, exhibiting the improvement of 26.16 and 14.80% compared to fixed solutions without GEO satellites, respectively. This further demonstrated the considerable applications potential of GEO satellites to regional users.

Biomechanics on Ultra-Sensitivity of Venus Flytrap's Micronewton Trigger Hairs.

Numerous plants evolve ingeniously microcantilever-based hairs to ultra-sensitively detect out-of-plane quasi-static tactile loads, providing a natural blueprint for upgrading the industrial static mode microcantilever sensors, but how do the biological sensory hairs work mechanically? Here, the action potential-producing trigger hairs of carnivorous Venus flytraps (Dionaea muscipula) are investigated in detail from biomechanical perspective. Under tiny mechanical stimulation, the deformable trigger hair, composed of distal stiff lever and proximal flexible podium, will lead to rapid trap closure and prey capture. The multiple features determining the sensitivity such as conical morphology, multi-scale functional structures, kidney-shaped sensory cells, and combined deformation under tiny mechanical stimulation are comprehensively researched. Based on materials mechanics, finite element simulation, and bio-inspired original artificial sensors, it is verified that the omnidirectional ultra-sensitivity of trigger hair is attributed to the stiff-flexible coupling of material, the double stress concentration, the circular distribution of sensory cells, and the positive local buckling. Also, the balance strategy of slender hair between sensitivity and structural stability (i.e., avoiding disastrous collapse) is detailed revealed. The unique basic biomechanical mechanism underlying trigger hairs is essential for significantly enhancing the performance of the traditional industrial static mode microcantilever sensors, and ensure the stability of arbitrary load perception.

Physical and chemical treatments in obtaining and purifying Kombucha SCOBY Cellulose

SCOBY cellulose (CS) is a biopolymer with exceptional physical properties, serving as a source of fiber, water retention capacity, crystallinity, and purity. Its potential as a byproduct of kombucha production and a source of bacterial cellulose (BC) has been a subject of exploration. This study aims to gather information from experimental studies in the scientific literature on various methods of CS extraction, processing, and purification, and their impact on microscopic, macroscopic structure, and functional characteristics. The purification treatments for CS, as described in the literature, include immersion in deionized, distilled, or sterile water, sodium hydroxide, hydrogen peroxide, and sodium hypochlorite under agitation or static mode at different temperatures (23ºC, 30ºC, 50ºC, 80ºC, 90ºC, 110ºC) and under variable contact times with the substance chosen for treatment (1, 2, 20, 24 hours to 3 days). Alkaline treatments on SCOBY cellulose enhance extensibility, viscoelasticity, absorptivity, tensile strength, heat stability, and remove microorganisms, sugars, and other components of the culture medium adhered to the cellulose. With CS being obtained at a low cost and low complexity in the fermentation process, and the potential for less polluting treatments, it presents a sustainable process and source of CB that can be applied in a variety of industries, particularly in the exciting field of food.

DNA/BSA Binding and Antimicrobial Properties of Biguanide-Cu(II) Complexes.

The biguanide Cu(II) complexes [Cu(L1-4)2](ClO4)2 were synthesized and spectroscopic/analytical techniques were used to clarify their structures. Single crystals of complex [Cu(L4)2](ClO4)2 was obtained and its definite structure was determined by single crystal X-ray diffraction study. The complexes [Cu(L1-4)2](ClO4)2 were screened for their FSds-DNA interactions by using UV-Vis absorption and fluorescence spectroscopies. The complexes [Cu(L2)2](ClO4)2 and [Cu(L3)2](ClO4)2 were shown to exhibit higher affinity for binding DNA. Examining the EB-DNA interaction, it is believed that the complexes interact with DNA through a groove binding mechanism. The interaction of complexes with BSA were observed through the quenching of the fluorescence emission. Complexes [Cu(L2)2](ClO4)2 and [Cu(L3)2](ClO4)2 show moderate binding affinity to BSA through a static mode. Additionally, the Cu(II) complexes were screened for their antibacterial activities against various bacterial strains. Complexes showed potential antimicrobial activity against Salmonella typhimurium, Bacillus cereus, Salmonella typhimurium and S. aureus.

Effects on tissue oxygenation in the gluteal region with a smart pressure redistribution wheelchair cushion compared to a pressure relief manoeuvre

Objective The study examines the effects of the air-bladder offloading mode of a smart pressure redistribution wheelchair cushion on tissue oxygenation in the gluteal tissue of non-disabled participants. The hypothesis is that the cushion’s offloading mode, which involves sequentially deflating its five air-bladders one at a time for a specific duration, would improve tissue oxygenation during sitting. Methods Two procedures were conducted. The first compared the cushion’s offloads to a loaded control (LC) with the cushion on static mode, and the second compared the cushion’s offloading mode to a standard manual offload performed by the participant. Three trials of each procedure were performed in randomized order. Tissue oxygenation was continuously monitored with three oxygenation parameters analysed: oxygen saturation (SO2), oxygenated haemoglobin (OxyHb), and deoxygenated haemoglobin (DeoxyHb). Data recordings were segmented in each step of the offloading sequence for analysis. A paired t-test was performed for comparisons with significance considered at α = 0.05. Ten healthy adults participated in the study. Impact Results showed that as the air bladders deflated over time, the three evaluated parameters changed, affecting oxygenation even when other tissue areas were offloaded. The results indicated that the cushion’s sacral offload had the greatest impact on improving tissue oxygenation among the five air-bladders in all ten subjects (p < 0.05). Furthermore, SO2 during the cushion’s offload in the sacral region was similar to a manual offload. The study results suggest that the cushion could benefit tissue oxygenation, especially for individuals unable to change positions independently. Further research is needed to determine its effectiveness for wheelchair users.

Static Output Feedback Sliding Mode Control With Structured Sliding Surface Matrices

Static Output Feedback Sliding Mode Control With Structured Sliding Surface Matrices

A light-fueled self-rolling unicycle with a liquid crystal elastomer rod engine

Active materials hold substantial potential for self-sustaining motion, however, the dependency on movable light or extensive area illumination in current structures often restricts the design and practical deployment of such active machines. In this study, we report a novel zero-energy-mode, self-rolling unicycle equipped with a liquid crystal elastomer rod engine, which fueled by a fixed, small-area light source. By employing an elaborate dynamic model for liquid crystal elastomer, we derive the lateral curvature of the liquid crystal elastomer rod and the driving moment necessary for the unicycle's self-rolling. The study results demonstrate that the self-rolling of the unicycle is driven by a moment induced by the shift in the center of gravity of the curved liquid crystal elastomer rod. Our numerical simulations indicate the presence of a supercritical Hopf bifurcation point delineating the transition between the self-rolling mode and the static mode within the unicycle system. Additionally, the rolling velocity of the unicycle relies on a handful of key system parameters, notably including light intensity, light penetration depth, length of the liquid crystal elastomer rod, rolling friction coefficient, total mass of the unicycle, and wheel radius of the unicycle. The experimental validation of a self-rolling unicycle with zero-energy-mode has been conducted. The self-rolling unicycle constructed in this paper has excellent characteristics of simple structure, zero-energy-mode, horizontal constant light source, and small area light source, providing valuable insights for the utilization of photoresponsive liquid crystal elastomer rods in soft robotics, medical devices, energy harvesting systems, and actuators.

Node and edge centrality based failures in multi-layer complex networks

Multi-layer complex networks (MLCN) appears in various domains, such as, transportation, supply chains, etc. Failures in MLCN can lead to major disruptions in systems. Several research have focussed on different kinds of failures, such as, cascades, their reasons and ways to avoid them. This paper considers failures in a specific type of MLCN where the lower layer provides services to the higher layer without cross layer interaction, typical of a computer network. A three layer MLCN is constructed with the same set of nodes where each layer has different characteristics, the bottom most layer is Erdos–Renyi (ER) random graph with shortest path hop count among the nodes as gaussian, the middle layer is ER graph with higher number of edges from the previous, and the top most layer is preferential attachment graph with even higher number of edges. Both edge and node failures are considered. Failures happen with decreasing order of centralities of edges and nodes in static batch mode and when the centralities change dynamically with progressive failures. Emergent pattern of three key parameters, namely, average shortest path length (ASPL), total shortest path count (TSPC) and total number of edges (TNE) for all the three layers after node or edge failures are studied. Extensive simulations show that all but one parameters show definite degrading patterns. Surprising, ASPL for the middle layer starts showing a chaotic behaviour beyond a certain point for all types of failures.

Bacterial nanocellulose by static, static intermittent fed-batch and rotary disc bioreactor-based fermentation routes using economical black tea broth medium: A comparative account

Bacterial nanocellulose was produced here using static, static intermittent-fed batch (SIFB) and rotary disc bioreactor (RDB) mode. Economical black tea broth media with symbiotic consortia of bacteria and yeast (SCOBY) was used towards feasible BNC production (instead of commercial NCIM 2526 strain and conventional HS media). The physicochemical characterization of BNC produced in all three modes via FE-SEM, ATR-FTIR, XRD and TGA results showed a highly porous morphology, mostly Iα form, good crystallinity and thermal stability, respectively. BNC crystallinity lies in the range of 68 % (RDB) to 79.4 % (static and SIFB). Water retention value (86 to 93 %) and moisture content (85 to 93 %) are high for BNC produced in all three modes. Commendable difference in the BNC yield, sugar consumption, conversion yield and residual sugar was observed using different methods. Highest BNC yield 29.4 ± 0.66 gL−1 was obtained under SIFB method as compared to static mode (13.6 ± 0.32 g L−1). Under RDB, a negligible amount of BNC i.e., 1.0 ± 0.2 g L−1 was produced. SCOBY with BTB medium was found unsuitable for BNC production under RDB and needs further investigation. Thus, this comparative study offers a way to produce a commendable amount of low-priced BNC for various techno-industrial usage.

BDS-3 full-frequency precise point positioning: models and performance comparison

With the BDS-3 six-frequency integration, there are more choices to implement the precise point positioning (PPP) technology. To take full advantage of the multi-frequency combination, six typical BDS-3 six-frequency PPP models using uncombined observation (UC), five dual-frequency ionospheric-free (IF) combinations (IF2), four triple-frequency IF combinations (IF3), three four-frequency IF combinations (IF4), two five-frequency IF combinations (IF5), and a single six-frequency IF combination (IF6) were constructed and compared. The results indicate that the positioning accuracies of the six models are similar. The static positioning accuracies reach 4, 3–5, and 12–14 mm in the east, north, and up directions, respectively, while the kinematic positioning accuracies are 24–26, 16–17, and 42–43 mm, respectively. Regarding the convergence times, the UC model is slightly worse than the five IF combined models, except for some cases in the up direction. In the static mode, benefiting from the smallest noise amplification factor, the average convergence times of the IF6 model are the shortest, reaching 12.1, 5.5, and 13.4 min in the three directions, respectively, and are 7%, 15%, and 6% shorter than those of the UC model. In the kinematic mode, with the combination of more signals into a single IF combination, the noise level of the IF combined observables gradually decreases, but the convergence times gradually increase. The kinematic average convergence times of the IF2 model are 15.3, 3.6, and 18.0 min in the three directions, which are 6%, 22%, and 10% and 1%, 16%, and 20% shorter than those of the UC and IF6 models, respectively. In addition, the observation residuals, and the estimates of inter-frequency bias, tropospheric zenith wet delay, and receiver clock offsets from different models were compared and analyzed. The specific selection of the model should be based on actual situations.