Effective Area Research Articles

Scalable wet-spinning approach to fabricate polydimethylsiloxane composite fibers for tunable photomechanical actuators

Photomechanical actuator with large deformation and rapid response is highly desirable for smart textiles and soft robots. However, the conventional polydimethylsiloxane (PDMS) elastomer-based actuators with multilayered or blocky configuration suffer from interlayer instability, low effective utilization area, and manual assembly process, which limit their practical application. Herein, a series of PDMS composite fibers were fabricated through a scalable wet-spinning approach. To investigate the effects of light-responsive material dimension on the photomechanical performance of PDMS composite fibers, pseudo-1D gold nanorod (AuNR), 1D carbon nanotube (CNT), and 2D reduced graphene oxide (RGO) were used as photoresponsivity materials. To obtain a superior photomechanical property of these fibers, the effects of the light intensity, pre-train, fiber diameter, filler concentration and chemical structure were discussed, and their light-induced actuation mechanisms were presented. Among them, the RGO/PDMS fiber actuator showed the highest actuation stress (72.1 kPa at 40 % pre-stain), while the AuNR/PDMS fiber actuator exhibited the fastest response times of 12.6 s at 40 % pre-strain. This study provides valuable insights for the design and development of fiber actuators with outstanding photomechanical performance.

Numerical analysis of microstructured optical fibers based on flint glass for ultra-high nonlinearity, low loss, and broadband dispersion compensation across telecom bands

This research investigates the potential of flint glass as a foundational material for photonic crystal configurations designed to achieve high nonlinear coefficients across various communication wavelengths. We explore dispersion management within telecom bands using flint glass-based micro-structured optical fibers, employing numerical analysis via the finite element method to assess optical properties. In this study, three different basic MOF structures (hexagonal, square, and octagonal) were created using flint glass background material rather of the commonly utilized fused silica material, and the numerically was assessed in contrast to prior studies and designs. Among the configurations studied, the octagonal arrangement (FGO-MOF) excels in dispersion compensation, achieving −136.6 ps/(nm.km) at 1.55 µm. Conversely, the hexagonal air hole ring cladding design (FGH-MOF) displays higher nonlinearity (770.5 W−1.km−1), a smaller effective area (1.115 µm2), and a high numerical aperture (0.6378). In contrast, the square air hole ring cladding optical fiber (FGS-MOF) exhibits low confinement loss (6.309 × 10−7 dB/cm) at 1.55 µm but with comparatively less favorable optical properties. Our study demonstrates that the hexagonal microstructured optical fiber with flint glass (FGH-MOF) offers superior performance in dispersion compensation, nonlinearity, and low loss within telecom bands. This finding suggests promising applications in high-bit-rate communication systems, biomedical sensing, and supercontinuum generation, presenting exciting avenues for further research and practical implementation.

Effect of hydrogen permeation and operating parameters on thermochemical performance of solar-driven steam methane reforming membrane reactor

When the steam methane reforming membrane reactor is coupled with trough solar collector to achieve solar thermochemical energy storage, the dimension of the membrane reactor is enlarged and the catalyst filling amount increases dramatically. As a results, the hydrogen permeation property should be well addressed to match the permeation and the reaction characteristics for a better energy storage performance. In the present paper, the effect of hydrogen permeation, including the effective permeation area and the membrane permeance was investigated by numerical simulations. Results show that the sensitivity factors of the membrane surface area on CH4 conversion, H2 yield and H2 recovery are 0.379, 0.325 and 2.196 respectively while that of membrane permeance are 0.007, 0.009 and 0.488 respectively. This indicates that influence of membrane surface area is more remarkable and H2 recovery is the most sensitive to the hydrogen permeation. The reactor with a membrane tube diameter of 50 mm and a permeance of 1.07 × 10−2 mol/(m2·s·Pa0.62) can achieve best reaction performance. Besides the reaction performance, a solar thermochemical system is proposed and a solar-to-fuel efficiency is defined to evaluate the thermochemical performance. Again the aforementioned reactor has the highest solar-to-fuel efficiency which can exceed 70 %. Furthermore, for a better thermochemical performance, lower inlet mass flow rate and higher inlet temperature are recommended, but too small or too high values should be avoided to maintain the operating temperature of the membrane. A suitable combination of pressures in the reaction side and the permeating side is also suggested. The results of the present paper reveal the role of hydrogen permeation and helps the reactor design.

Enhancing the performance of triboelectric nanogenerator via chitosan films surface modification

The triboelectric nanogenerator (TENG) has enormous application prospects and research value in energy collection due to its small size, simple structure, and ability to convert mechanical energy into electrical energy output. The microstructure of TENG’s friction layer has a significant impact on its output performance. We, herein, propose a surface modification method by replicating the surface morphology of sandpaper to construct microstructure on the surface of chitosan film or by constructing porous structure using electrospinning technology. Thanks to the significant increase in the effective contact area between the two friction materials, the output performance of the vertical contact-separation TENG with chitosan (Fluorinated ethylene propylene) film being used as a friction positive (negative) material is greatly enhanced. This TENG also exhibits its sensitivity in perceiving human movements and has good power supply capabilities. Our results indicate that surface modification of the friction materials is a facile strategy to boost the performance of TENG.

Architecture engineering enables high-stability 2D/multi-2D heterostructured MXene/TiO2 for boosting solar-driven CO2 reduction

Photocatalytic CO2 reduction to produce value-added products is considered a promising solution to solve the global energy crisis and the greenhouse effect. In this study, 2D/multi-2D heterostructures were successfully synthesized through electrostatic self-assembly between Ti3C2 and TiO2 nanosheets. The optimal sample (15TC/TiO2) shows yields of 209.98 and 28.09 μmol·g−1·h−1 for CO and CH4, respectively. According to the characterization and simulation study, the enhanced performance is mostly attributable to the 2D/multi-2D heterostructures, which are formed from two phases with huge differences in morphology and size, enabling the development of multiple tiny contact surfaces to increase the effective contact area. In addition, the TiO2 nanosheets utilized in the construction have up to 80 % exposure to the (001) facets, which offer catalytically active sites. This work provides a feasible method for constructing 2D/multi-2D heterostructure catalyst materials.

Assessing parabolic trough collectors and linear Fresnel reflectors direct steam generation solar power plants in Northwest México

Concentrating solar power (CSP) systems offer promising solutions for harnessing solar energy. Parabolic trough collectors (PTC) are prevalent in CSP, but direct steam generation (DSG) in solar fields is an innovative alternative that eliminates the need for thermal oils. This study compares EuroTrough PTC and optimized linear Fresnel reflector (LFR) geometries for DSG for Mexican operating conditions. Two 10 MW Rankine cycles with two and three steam extractions are considered. The study evaluates 16 solar field configurations capable of delivering 400 °C superheated steam at 100 bar. Assessment parameters include effective concentration area, nominal loop inlet pressure, energy and exergy efficiency, and hypothetical thermal storage size. The findings strongly favor PTC solar fields with 14 loops, exhibiting superior performance. However, three-loop LFR configurations are suggested where pressure reduction prevails. Three-loop LFR arrays minimize land utilization for spatially constrained installations, while larger five-loop configurations optimize efficiency. Employing 14 PTC loops prioritizes thermal energy storage. In contrast, 8 PTC loops maximize storage capacity. The study underscores the advantages of Fresnel reflectors over parabolic troughs in specific scenarios, presenting avenues for future exploration. This analysis lays the groundwork for assessing these technologies in the distinctive context of Mexican operations, offering valuable insights into sustainable energy applications.

The level of preparedness of military personnel for hand-to-hand combat

Abstract. In modern conditions, the military profession does not exclude activities related to the forcible detention of a criminal or aggressor. A serviceman who is proficient in hand-to-hand combat often achieves superiority over a physically stronger enemy who outnumbers him. In this case, the defenders use motor actions that, if properly directed and applied by internal and external forces, provide either a gain in strength or a gain in time. Naturally, in the process of special physical training (SPT) the issue of effective training of hand-to-hand combat techniques plays an important role in achieving a positive result in the performance of the task.
 The existing practice of special physical training in higher military educational institutions of the Ministry of Defense of Ukraine shows that today, in the process of cadets' SPT, the rich material accumulated by specialists in the theory and methods of physical education and sports training is not yet fully used.
 The introduction of the latest technologies based on the use of hand-to-hand combat requires specialists to search for and apply innovative teaching methods and technologies, identify the most effective areas of the educational process that contribute to the achievement of a high professional level of students.

Impact of thermal lensing on the TMI threshold powers in rod-type Yb-doped fiber amplifiers

The impact of thermal lensing (TL) on the transverse mode instability (TMI) threshold power in rod-type fiber amplifiers is investigated. Simulations are conducted with a 3D coupled mode analysis on a set of five scaled large pitch fiber (LPF) amplifiers. The LPF fibers are represented by surrogate step-index fibers (SIFs) with scaled cladding diameters, core diameters, and numerical apertures for a fixed normalized frequency V equal to 3.0 and scaled modal field overlap integrals with the core and cladding. It is found that thermal lensing decreases the TMI threshold powers due to increases in the TMI nonlinear gain. This gain increase is attributed to an increase in the nonlinear gain overlap integrals that occurs with the reduction in the fundamental mode effective area. Estimates for the TMI threshold power are in good agreement with measurements; however, the simulations overestimate the mode shrinkage factor. This discrepancy is tentatively attributed to the representation of the LPF by an effective SIF. These results may offer opportunities for fiber designs that increase the TMI threshold powers.

Confinement-based design and behaviour of concrete-filled stiffened steel tubular square slender columns

This paper presents the details, analysis and results of an investigation into the compressive behaviour of concrete-filled stiffened steel tubular (CFSST) slender columns. These are members comprising an outer steel section with longitudinal stiffeners welded to the interior surface. A finite element (FE) model was developed and validated. An improvement in ultimate strength compared to conventional concrete-filled steel tubular column has been found due to the presence of stiffeners that reduce the width-to-thickness ratio of the steel tube, which in turn increases the effective cross-sectional area of the steel tube. Moreover, it was found that stiffeners increase the lateral confining pressure on the concrete. FE modelling was then employed to conduct a thorough parametric study to investigate the influence of a wide range of parameters. These included the slenderness ratio, concrete compressive strength, as well as the geometry and details of the stiffeners. Both medium-length and long CFSST columns, classified on the basis of slenderness ratio, were carefully studied and discussed, as well as their inherent differences. The strengths predicted from the FE simulations were compared with the design strengths obtained from various international design codes, and it was shown that the design expressions provide very conservative capacity predictions. Accordingly, a new three-stage confinement-based design model was proposed, which takes into account different confining mechanisms of columns based on their slenderness ratio. It is illustrated that this model provides a very accurate prediction of the square CFSST slender columns, and captures the key behavioural characteristics.

Whale shark abundance, spatial distribution and effective tourism areas in the northern Mexican Caribbean

ABSTRACT Every year, from June to September, the whale shark (Rhincodon typus) is present in the Mexican Caribbean and has become a highly attractive tourist resource. In this study, we assess the spatial and temporal distribution of whale sharks and estimate the size of the effective tourism area from data collected between 2016 and 2021. The main whale shark aggregation site in the Mexican Caribbean is called ‘El Azul’, it has an average size of 400 km2. Using aerial survey data, we found 37 whale shark aggregations where we counted 1–170 individuals and 16–150 tourist boats. The average size of the area covered by these groups was 2.9 km2. The highest density of whale sharks was recorded in 2020 (48 whale sharks per km2) and the lowest in 2021 (5 whale sharks per km2). Estimating the effective tourism area (where whale shark tourism takes place) within the entire aggregation area is important to refine tourism carrying capacity calculations and to avoid miscalculations that could lead to over-exploitation of whale shark tourism activities with negative consequences for the species. The information from this study is directly applicable to adaptive ecotourism management, improving the sustainability of whale shark tourism, and biological monitoring.

Mapping the intracluster medium in the era of high-resolution X-ray spectroscopy

ABSTRACT High-resolution spectroscopy in soft X-rays will open a new window to map multiphase gas in galaxy clusters and probe physics of the intracluster medium (ICM), including chemical enrichment histories, circulation of matter and energy during large-scale structure evolution, stellar and black hole feedback, halo virialization, and gas mixing processes. An eV-level spectral resolution, large field of view, and effective area are essential to separate cluster emissions from the Galactic foreground and efficiently map the cluster outskirts. Several mission concepts that meet these criteria have been proposed recently, e.g. LEM, HUBS, and Super DIOS. This theoretical study explores what information on ICM physics could be recovered with such missions and the associated challenges. We emphasize the need for a comprehensive comparison between simulations and observations to interpret the high-resolution spectroscopic observations correctly. Using Line Emission Mapper (LEM) characteristics as an example, we demonstrate that it enables the use of soft X-ray emission lines (e.g. O vii/viii and Fe-L complex) from the cluster outskirts to measure the thermodynamic, chemical, and kinematic properties of the gas up to r200 and beyond. By generating mock observations with full backgrounds, analysing their images/spectra with observational approaches, and comparing the recovered characteristics with true ones from simulations, we develop six key science drivers for future missions, including the exploration of multiphase gas in galaxy clusters (e.g. temperature fluctuations, phase-space distributions), metallicity, ICM gas bulk motions and turbulence power spectra, ICM-cosmic filament interactions, and advances for cluster cosmology.

Transcatheter or Surgical Aortic Valve Replacement in Women With Small Annuli at Low or Intermediate Surgical Risk

There are limited data from randomized controlled trials assessing the impact of transcatheter aortic valve replacement (TAVR) or surgery in women with aortic stenosis and small aortic annuli. We evaluated 2-year clinical and hemodynamic outcomes after aortic valve replacement to understand acute valve performance and early and midterm clinical outcomes. This post hoc analysis pooled women enrolled in the randomized, prospective, multicenter Evolut Low Risk and Surgical Replacement and Transcatheter Aortic Valve Implantation (SURTAVI) intermediate risk trials. Women with severe aortic stenosis at low or intermediate surgical risk who had a computed tomography-measured annular perimeter of ≤72.3 mm were included and underwent self-expanding, supra-annular TAVR or surgery. The primary end point was 2-year all-cause mortality or disabling stroke rate. The study included 620 women (323 TAVR, 297 surgery) with a mean age of 78 years. At 2 years, the all-cause mortality or disabling stroke was 6.5% for TAVR and 8.0% for surgery, p = 0.47. Pacemaker rates were 20.0% for TAVR and 8.3% for surgery, p <0.001. The mean effective orifice area at 2 years was 1.9 ± 0.5 cm2 for TAVR and 1.6 ± 0.5 cm2 for surgery and the mean gradient was 8.0 ± 4.1 versus 12.7 ± 6.0 mm Hg, respectively (both p <0.001). Moderate or severe patient-prothesis mismatch at discharge occurred in 10.9% of patients who underwent TAVR and 33.2% of patients who underwent surgery, p <0.001. In conclusion, in women with small annuli, the clinical outcomes to 2 years were similar between self-expanding, supra-annular TAVR and surgery, with better hemodynamics in the TAVR group and fewer pacemakers in the surgical group.

Clinical Observation of 10-mm Endoscopic Minimally Invasive Interlaminar Decompression in the Treatment of Ossified Lumbar Spinal Stenosis

This study aims to observe the safety and effectiveness of 10-mm endoscopic minimally invasive interlaminar decompression in the treatment of ossified lumbar spinal stenosis. The clinical data of 50 consecutive patients with ossified lumbar spinal stenosis were retrospectively analyzed. All patients underwent minimally invasive interlaminar decompression with 10-mm endoscope. Patient demographics, perioperative data, and clinical outcomes were recorded. Visual analog scale scores, Oswestry disability index scores, and modified Macnab criteria were used to assess clinical outcomes. The lateral recess angle, real spinal canal area, and effective intervertebral foramen area were used to assess the effect of decompression. The mean age of all patients was 59.0±12.3years. The mean operative time and intraoperative blood loss were 43.7±8.7minutes and <20ml, respectively. Two years after surgery, the leg pain Visual analog scale score decreased from 7.4±1.0 to 1.6±0.6 (P<0.05) and the Oswestry disability index score decreased from 63.8±7.6 to 21.7±3.4 (P<0.05). The lateral recess angle, real spinal canal area and effective intervertebral foramen area were significantly larger than before surgery (P<0.05). The overall excellent and good rate at the last follow-up was 92.0% according to the modified Macnab criteria. The 10-mm endoscopic minimally invasive interlaminar decompression can safely and effectively remove the ossification in the spinal canal and achieve adequate decompression in patients with ossified lumbar spinal stenosis.

Ultra-thin ventilated metasurface pipeline coating for broadband noise reduction✰

This paper proposes a method of designing a metasurface muffling coating for pipeline ventilation and noise reduction, which realises low-frequency broadband noise reduction by laying ultra-thin labyrinth-channel acoustic absorbing metasurface structures on the inner wall surface of the pipeline. With the advantage of relatively loose size constraints in the length direction of the fluid conveying pipeline, the thickness dimensions required for low-frequency broadband sound absorption are transferred to the length direction, which significantly increases the effective ventilation area, and the ventilatable area is as high as 55.5 % of the overall structural section area. Since sound waves can be gradually attenuated in the pipeline as the fluid medium flows along the length of the pipeline rather than needing to be attenuated at the same time as in a flat plate acoustic structure, the performance requirements of the acoustic structure are substantially reduced, enabling a significant increase in the operating bandwidth. We have tried the arrangement method of coating layers with gradient thickness, which shows that the combination of different thicknesses of metasurface coating layers can broaden the muffling frequency band and improve the transmission loss of the muffling structure. The design is equally suitable for the noise reduction of liquid-filled piping systems, and the peak transmission loss can be as high as 54.6 dB, which represents a pleasing combination of low-frequency muffling and lightweight design, as well as excellent ventilation capability, and embraces a promising future for application.

Urban public transport system accessibility for different groups of residents: Case of Bratislava city

The main goal of the article is to characterize the functioning of the Urban Public Transport System (UPTS) in the capital city of the Slovak Republic (Bratislava) during different time periods (morning rush, evening, night, average working day, and weekend − Sunday) and express its accessibility for various groups of city residents (low-income households, unemployed individuals, seniors (age 60+), children (age 0–14), women (for comparison, men as well). To achieve this goal, we combined datasets of UPTS in Bratislava with the pedestrian communication network and identified an effective service area for which we subsequently determined the sizes of the respective population groups of residents. Finally, we verified the functionality of the entire UPTS model by measuring the accessibility of the selected destination, Ružinov Hospital. Our results could be summarized as follows: The functioning of UPTS is very similar during the morning rush, evening, average working day (Monday to Friday), and weekend − Sunday. During these time periods, approximately the same main lines operate, and there is a higher utilization of the same transfer points. The difference lies mainly in the frequency of departures of specific lines. During the night, the system operates based on different lines compared to the daytime, with transfers possible only at one central point/corridor. This fact also affects the usability and accessibility of UPTS, reflected in the accessibility of Ružinov Hospital, which is very limited during the night-time period. However, the accessibility of the hospital by UPTS is higher for the unemployed residents, low-income individuals, and children than the overall residents average, which is also reflected in the distribution of women. A negative aspect is that UPTS is less accessible for seniors. It must be said that this fact varies significantly in the heterogeneous spatial layout of the city. This was confirmed in our measurement of the accessibility to Ružinov Hospital, where seniors have roughly the same level of accessibility as the overall residents average.

Two-dimensional imaging of elastic properties of rock core samples from measurements of angle-dependent ultrasonic reflection coefficients

Laboratory and field measurements often fail to identify small-scale variations in rock elastic properties. Due to limited spatial resolution, conventional laboratory methods cannot properly describe rock formations exhibiting a high degree of heterogeneity, thereby masking differences between stiff and compliant layers. Continuous sample measurements can mitigate this problem but are not widely used by the industry. We build upon our previous work and apply laboratory angle-dependent ultrasonic reflection coefficient (ADURC) measurements to achieve detailed two-dimensional descriptions of the elastic properties of complex rock samples. This method successfully yields high-resolution information on P- and S-wave velocities, as well as bulk density, across the surface of rock samples. Elastic properties are estimated using a nonlinear inversion algorithm that matches laboratory measurements with numerical simulations. ADURC data acquired at various sample locations enable detailed rock descriptions, where the effective measurement area is determined by the size of the receiver, measurement frequency, and incidence angle. Consequently, the sampling area is smaller compared with triaxial loading and acoustic transmission tests, for which the resolution is controlled by sample size. Measurements conducted on samples exhibiting different levels of spatial complexity validate the capability of the ADURC method to identify small-scale heterogeneities. For the reported experiments, variations in angle-dependent reflectivity give rise to corresponding variations in the estimated P- and S-wave velocities and density, which can exceed 60%. These small-scale variations across heterogeneous rock samples often are overlooked by conventional laboratory methods.

Optimizing electrocoagulation for poultry slaughterhouse wastewater treatment: a fuzzy axiomatic design approach

White meat consumption is increasing day by day, and accordingly, there is an increase in the amount of wastewater resulting from the processes. Today, the reuse of wastewater has become a goal within the scope of the Green Deal. For this reason, wastewater treatment with high pollution and volume has gained importance. In this study, the fuzzy axiomatic design (FAD) method, one of the multi-criteria decision-making methods, has been used. With this method, coagulation, electrocoagulation (EC), dissolved air flotation (DAF), and anaerobic treatment alternatives preferred in poultry slaughterhouse wastewater (PSW) treatment were compared with each other and their information contents were calculated. The information content from the smallest to the largest is EC, DAF, coagulation, and anaerobic treatment, respectively. This treatment method was chosen because the smallest information content is in electrocoagulation. EC was applied to bloody PSW containing 1% blood by volume. The effectiveness of Fe and Al electrodes for PSW treatment in the batch EC reactor has been compared. The effective surface areas of 2 anodes and 2 cathodes connected bipolarly in the processes are 288 cm2. The electrolyte, pH, time, and current density effects on energy consumption were also investigated. The optimum conditions for Al and Fe electrodes were found to be 0.5 g·L−1 NaCl concentration, pH 5, 0.639 mA·cm−2 current density, and 5 min time. Under optimum conditions for the Fe electrode, COD, TOC, TN, and oil-grease removal efficiencies were determined as 76.3%, 71.8%, 70%, and 74%, respectively. Moreover, the highest COD, TOC, TN, and oil-grease removal efficiencies were achieved with an Al electrode (82.2%, 82.3%, 82.7%, and 78.9%, respectively). The experimental data were fit to a variety of isotherms and kinetic models to determine the characteristics of the EC. The results indicated that the pseudo-second-order equation provided the best fit for COD removal. Under optimum conditions, the operating cost was calculated as $3.39 and $3.09 for Al and Fe electrodes, respectively. In this study, the fuzzy axiomatic design method was used for the first time to select the most appropriate treatment method for PSW. In addition, blood, a major problem for the poultry slaughterhouse industry, was mixed with PSW at a ratio of 1% (v/v) and treated with EC for the first time with high removal efficiency. By treating PSW, which has a high pollution load, with electrocoagulation, the pollution load of the water to be given to secondary treatment has been greatly reduced.

A combination of polypeptide and magnetic molecular imprinted electrochemical sensor based on BSA-AuNPs/Fe3O4@ZIF-8 for the detection of norfloxacin

Norfloxacin (NOR) is now extensively used for the treatment of human and animal diseases. Unfortunately, large accumulations of NOR will pose a significant threat to the human body. Thus, it is urgent to develop a rapid and sensitive detection technique for the trace determination of NOR. In this study, an electrochemical molecular imprinting sensor with great properties was fabricated for the determination of NOR in milk and environmental water. The incorporation of bovine serum proteins produced a hybrid recognition interface consisting of molecularly imprinted polymers and peptides that provided good recognition properties for norfloxacin. The Fe3O4@ZIF-8 was distributed orderly on the electrode after the embedding of the magnets inside the electrode, then the BSA was coated on the electrode with the electrodeposited AuNPs through Au-S bonding. The sensor constructed in this study achieved ultra-sensitive detection of norfloxacin with an effective area of 0.08433 cm2, a limit of detection (LOD) of 0.108 pmol·L−1, and a wide linear range (1 ∼ 100, 100 ∼ 1000 and 1000 ∼ 8000 pmol·L−1). The prepared sensors exhibited satisfactory performance in the detection of milk and environmental water, with acceptable recoveries ranging from 96.24 % to 104.88 %, and the relative standard deviation (RSD) was no more than 4.84 %.

Theoretical and experimental investigation of vibration-assisted scratching silicon

Interaction between tip and workpiece plays a crucial role in determining the scratching depth in Vibration-assisted Tip Based Nanofabrication (VTBN), which is more complicated than that of conventional scratching (without vibration-assisted). To establish the relationship between the scratching depth and machining parameters, a cubecorner indenter is employed to conduct VTBN procedure. The indenter is simplified as a cone to calculate the contact model in both 1D groove and 2D surface machining processes. An instantaneous normal load model is established based on the developed tip-workpiece contact model. Due to the variation of instantaneous contact area, effective contact area is put forward for the first time to predict the normal load. Effects of vibration frequency and amplitude on the normal load and surface quality are analyzed based on the proposed model. Experimental results show that higher frequency and larger amplitude will reduce the effective contact area. Vibration can increase the scratching depth and width without enlarging the cutting force. Furthermore, the inconsistency caused by scratching directions in conventional scratching is also overcome during VTBN.

Matching area selection for arctic gravity matching navigation based on adaptive all‐field extended extremum algorithm

AbstractSuitable and effective matching area selection is crucial for gravity matching‐aided navigation. In this paper, an all‐field extended extremum algorithm based on an adaptive threshold (AT‐AEE) is proposed for matching area selection in the Arctic Sea. The gradient data is obtained by using the convolution of gravity reference graph data and all‐field extended extremum parameters. Then, the adaptive threshold method was employed to determine the optimal gradient threshold based on gravity anomaly data across various test areas. Data points with gradients exceeding the specified threshold are identified as local candidate points for matching areas. The test areas containing a certain proportion of local candidate points are designated as the suitable matching areas. Nine test areas in the Arctic Sea with different gravity change characteristics were chosen for simulation experiments to verify the performance of the proposed algorithm. Simulation experiments showed that superior navigation positioning results could be obtained in the matching areas selected by the AT‐AEE algorithm. Compared to traditional algorithm, the matching areas derived from the AT‐AEE algorithm performed with a better consistency in the gravity matching navigation results. In suitable matching areas with the proportion of local candidate points reaching 70%, the average positioning errors could be reduced to less than 1.5 n miles.