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Direct thrust measurements are performed on a circular waveguide electron cyclotron resonance (ECR) thruster working at 5.8 GHz using a pendulum thrust balance with mechanically amplified displacement. Thrust levels between 1 and 3.5 mN are found for power levels in the range of 60–350 W and xenon flow rate between 2 and 8 SCCM. A maximum thrust efficiency of 3.5% is reached at 2 SCCM and 60 W. Plasma plume diagnostics are used to estimate the thruster partial efficiencies to understand the main losses, and to perform a comparative analysis between directly and indirectly measured thrust. Results suggest that the low energy conversion efficiency and propellant utilization efficiency (< 6.4 % and < 53%, respectively) are the key factors spoiling the ECR thruster performance. Finally, retarding potential analyzer measurements show the presence of energetic electrons with energy tail up to about 300 eV. [ABSTRACT FROM AUTHOR]

The behavior of four algebraic closure models for anomalous electron transport is investigated using a fluid Hall thruster code. The models, which were selected because they have been previously described in the literature, are calibrated against a baseline experimental condition of a 9-kW-class magnetically shielded Hall thruster operating at 300 V and 15 A on xenon propellant. The extensibility of the models is then assessed by using this calibrated model to simulate three additional operating conditions—300 V and 30 A, 600 V and 15 A, and 300 V and 15 A operating on krypton propellant. The quality of the model prediction is quantified by comparing the model outputs to experimental measurements of discharge current, thrust, and ion velocity. It is found that while none of the models can predict the ion acceleration characteristics accurately, some compare favorably in terms of the scaling of thrust and discharge current across operating conditions. The limitations of the models are attributed to the coupling between the functional scaling of the closure models with respect to the local plasma properties and the fluid model. The role of the electron energy balance in this coupling is also highlighted. These results are discussed in the context of motivating improved closure models of the anomalous electron transport in Hall thrusters. [ABSTRACT FROM AUTHOR]

During drilling CFRP composite plates, the direction pointing to the hole wall along the length can be considered the forward direction of the carbon fiber. The angle between the forward direction of the cutting speed and the forward direction of the carbon fiber is regarded as the main cutting angle of the major cutting edge. If the main cutting angle is an acute angle, the cutting is called as forward cutting. If the main cutting angle is an obtuse angle, the cutting is called reverse cutting. From the above concepts, the forward cutting zone and the reverse cutting zone can be defined. Based on viscoelastic mechanics and foundation beam theory, the carbon fiber among CFRP composite plate is regarded as an infinite or semi-infinite foundation beam with equal section on elastic foundation. The calculation model of equivalent stiffness modulus is derived, and the thrust force model of the major cutting edge is established. The research shows that when the drill bit turns for a revolution, the forward cutting and reverse cutting alternately change twice, and the main cutting angle and thrust force of the major cutting edge change 2 cycles. The cutting mode of the major cutting edge is the fundamental reason which brings about the periodic change of the thrust force and the defects of the entrance or exit. The reliability of the thrust force model of the major cutting edge is proved by drilling experiments. This study can provide theoretical support for improving the drilling process of CFRP composite plates. [ABSTRACT FROM AUTHOR]

The Kashmir "seismic gap" in NW Himalaya is marked by hinterland‐to‐foreland reduction in GPS‐geodetic arc‐normal convergence‐velocity and increase in horizontal strain‐rate, associated with occurrence of moderate‐to‐small earthquakes. We analyze continuous waveforms from Jammu and Kashmir seismological network (2015–2017) to detect and preliminarily locate 1064 events, followed by probabilistic non‐linear relocation of 360 well‐located local earthquakes, with magnitudes 0.6–4.7 and hypocentral depths 0–60 km. Hypocenters shallower than 20 km lie on or above the Main Himalayan Thrust (MHT), clustered beneath the Kishtwar Higher‐Himalaya. Hinterlandward dipping seismicity‐clusters coincide with a MHT mid‐crustal frontal ramp, marking a ∼ ${\sim} $50 km wide locked‐to‐creep transition. The frictionally‐locked up‐dip MHT segment is ∼ ${\sim} $100 km wide, capable of hosting a Mw∼ ${M}_{w}\sim $ 8.4 earthquake, if ruptured completely. Clustered seismicity SW of the Kishtwar Window and to its east illuminate MHT lateral‐ramps, which may limit the rupture width and/or modulate the rupture propagation. Entirely seismogenic underthrust Indian‐crust poses additional hazard from large earthquakes within it. Plain Language Summary: In the NW Himalaya, the region between the 1905 Kangra and 2005 Kashmir earthquake rupture zones is known as the Kashmir 'seismic gap'. The last major earthquake in this "gap" was the 1555 magnitude ∼ ${\sim} $8 event. From the measured convergence rate across the NW Himalaya it is estimated that this region has accumulated sufficient strain‐energy to cause a major‐to‐great earthquake. We established the Jammu and Kashmir seismological network in 2013 to study the seismicity in this "gap." Continuous ground‐motion data from 2015 to 2017 has been used to detect and locate 1064 events. After visual assessment and accurate P‐ and S‐wave arrival‐time picks, we relocated earthquakes using a probabilistic non‐linear location method. These 360 well‐located local earthquakes have magnitudes of 0.6–4.7 and source depths of 0–60 km. Depth distribution of these earthquakes indicate that the entire crust deforms brittlely. The majority of these earthquakes are shallower than 20 km and are clustered beneath the Jammu‐Kishtwar Higher‐Himalaya. They originated on or above the Main Himalayan Thrust (MHT), a fault zone which separates the underthrusting Indian crust from the overriding Himalaya. The distribution of the clustered seismicity illuminates structural heterogeneities on the MHT, which could influence rupture initiation and propagation of future large earthquakes. Key Points: We detect and (re)locate earthquakes with magnitudes 0.6–4.7, hypocentral depths 0–60 km, within the Kashmir "seismic gap," NW HimalayaShallow hypocenters (<20 km) cluster beneath Kishtwar Higher Himalaya, illuminating the Main Himalayan Thrust (MHT) frontal and lateral rampsThe clustered seismicity marks a ∼50 km wide locked‐to‐creep transition on the MHT, with a ∼100 km wide frictionally locked up‐dip segment [ABSTRACT FROM AUTHOR]

This paper presents a Neural Networks (NNs) based approach to generate the fuel-optimal powered descent guidance for lunar pinpoint landing. According to Pontryagin's Minimum Principle, the optimality conditions are first derived. To generate the dataset of optimal trajectories for training NNs, we formulate a parameterized system, which allows for generating each optimal trajectory by a simple propagation without using any optimization method. Then, a dataset containing the optimal state-thrust vector pairs can be readily collected. Since it is challenging for NNs to approximate a bang-bang (or discontinuous) type of optimal thrust magnitude, we introduce a regularisation function to the switching function so that the regularized switching function approximated by a simple NN can be used to represent the optimal thrust magnitude. Meanwhile, another two well-trained NNs are used to predict the thrust steering angle and the time of flight given a flight state. Finally, numerical simulations show that the proposed method is capable of generating the optimal guidance that steers the lunar lander to the desired landing site with acceptable landing errors. [ABSTRACT FROM AUTHOR]

The Russian invasion of Ukraine has thrust the issue of European Union and NATO enlargement back into the political spotlight. However, it remains uncertain whether established theoretical frameworks are still applicable in today’s rapidly changing world. In response to this uncertainty, this debate section brings together five short reflection pieces, with a response from Frank Schimmelfennig, to assess the relevance of the theory of ‘rhetorical action’ in light of recent developments in European and international politics. How effectively does rhetorical action explain current EU and NATO enlargement processes, as well as broader forms of international cooperation? The authors find strong overall support for the theory’s continued validity. However, they caution that the increasing politicisation of issues, the rising competition from populist, non-liberal forces, and the broader crisis of the Liberal International Order require more careful reflection and specification of the scope conditions that define the theory’s limits. [ABSTRACT FROM AUTHOR]

We conduct an experimental investigation on the implementation of cat-ear-shaped film cooling holes for thermal protection in a hydrogen-air rotating detonation engine (RDE). The rotating detonation combustor adopts a cylindrical configuration with 390 cat-ear-shaped film cooling holes densely distributed over its outer wall. We successfully achieve ignition and self-sustained propagation of the rotating detonation wave (RDW) under film cooling conditions, resulting in the RDE producing a supersonic outflow via a Laval nozzle installed at the exit. During operation of the film-cooled RDE, the introduction of cooling air through the film cooling holes leads to an increase in the static pressure of the combustor, and potentially causes up to a 15% variation in RDW propagation velocity, depending on the main flow-based equivalence ratio and the mass flow rate of cooling air. The effect of film cooling on the thrust performance of the RDE is analyzed, and additional cooling air is found to result in an increase in thrust. Periodic blockage of film cooling holes occurs due to RDW propagation, causing an elevation in static pressure within the cooling air chamber. Additionally, as the RDW sweeps across the film cooling holes at a high frequency along the tangential direction, cooling air jets deflect, resulting in distinctive burned traces in areas relative to their proximity to the film cooling holes. • Experimental study on cat-ear-shaped film cooling holes for thermal protection of RDE. • 390 cat-ear-shaped cooling holes densely distributed on a cylindrical RDE's outer wall. • Successful ignition and self-sustained RDW achieved under film cooling conditions. • High-frequency RDW causes periodic blockage and deflection of cooling air jets. [ABSTRACT FROM AUTHOR]

Real service requirements of the assembly performance and joining properties of design components are critical for composite usage in the aerospace industry. This experimental study offers a novel and comprehensive analysis of dry drilling optimization for glass-reinforced, high-performance epoxy matrix composites used in aerospace structures, focusing on thrust force and delamination. The study presents a first-time investigation into the combined effects of spindle speed (1000, 2250, 4000 and 5750 rpm), feed rate (0.2, 0.4, 0.6 and 0.8 mm/rev) and tool diameter (3 and 5 mm) using a custom-designed drill tool specifically developed for this application, filling a gap in the current literature. By employing the Taguchi design of experiments, the study identified that medium spindle speeds (2250–4000 rpm), lower feed rates (0.2 mm/rev) and smaller tool diameters (3 mm) provided optimal conditions for minimizing thrust force and delamination. These results present actionable insights into improving the structural integrity and performance of drilled aerospace-grade composite components, offering innovative advancements in both the aerospace and defense industries. [ABSTRACT FROM AUTHOR]

The transformative nature and accelerating pace of development of Artificial Intelligence (AI) technologies have generated frenzied political debate and urgent calls for regulation. The European Union's (EU) AI Act is one of the earliest, most ambitious, legally binding efforts to regulate high-risk AI systems. This article argues that the thrust of the EU's focus on 'ethical and secure' AI and its first-mover regulatory status have helped to foster transatlantic cooperation on AI governance. To probe this assertion, the article analyzes the ethical underpinnings and key provisions of the AI Act and compares them to policy developments in the United States. The analysis provides preliminary evidence of policy similarities across the Atlantic from an alignment of ethical concerns to a shared understanding of the risks and associated need for common guidelines and standards in the AI sector. Tracing agreements within the EU-US Trade and Technology Council (TTC) suggests further cooperation and relative congruence in the EU and US approaches to AI. [ABSTRACT FROM AUTHOR]

Flow field organization significantly influences the performance criterion of a scramjet combustor. Recently, DLR scramjet combustor with strut injector has been mostly used to alter the flow field. Researchers have used innovative strut injectors to enhance the performance of the DLR scramjet combustor. However, the effect of utilizing a strut with both parallel and normal injections of air and fuel in the DLR scramjet combustor has not been investigated till date. Hence, in this study, the DLR combustor is numerically investigated using a modified strut injector with both parallel and normal injections of air and fuel. The 2D numerical solver is validated with the experimental results having a maximum deviation of 7.3%. The analysis shows that the combustors with modified strut injectors produce better turbulence mixing compared to the DLR combustor, resulting in higher combustion performance. The modified strut combustors, i.e., CMSI-1, CMSI-2, and CMSI-3 produced a combustion efficiency of 76%, 79%, and 81%. In contrast, the maximum combustion efficiency produced by the DLR combustor is 50%. This improvement in the combustion performance of the combustors with modified strut injectors resulted in higher thrust force than the DLR combustor. The thrust force produced by CMSI-1, CMSI-2 and CMSI-3 are 3160 Pa.m2, 3200 Pa.m2 and 3216 Pa.m2, respectively. Finally, it has been found that the CMSI-3 has produced the maximum combustion efficiency and better thrust force among all the scramjet combustor models considered in the study. [ABSTRACT FROM AUTHOR]

In this paper, we design two trajectory tracking control schemes based on generalized Rodrigues parameters (GRPs) for underactuated vertical take-off and landing (VTOL) unmanned aerial vehicle (UAV). In the attitude loop, we use rotation matrix to describe the attitude to ensure the global motion of the attitude, and use Rodrigues parameters (RPs) to describe the attitude error to make the attitude error have almost global convergence and avoid unwinding. At the same time, we design the GRP to extend the generalization ability of the attitude error description scheme and improve the control accuracy. Unlike the existing attitude constraint schemes, GRP only needs a constraint boundary to constrain the error angle of PR. The thrust error caused by underactuated characteristics is compensated in the attitude controller by position–attitude cascade decomposition. The controller based on backstepping is designed to exponentially stabilize the zero equilibrium of the error system. In order to simplify the controller structure and reduce the difficulty of engineering application, a control scheme with saturation property is proposed. Finally, numerical simulation is carried out to verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of guiding a rocket-powered vehicle to land using aerodynamic and thrust controls. The vehicle initially glides towards the landing site, flying at an unprecedentedly high angle-of-attack to decelerate, thereby reducing the propellant needed for a later retro-thrust landing. The high angle-of-attack pure aerodynamic flight leads to highly nonlinear dynamics that have not been addressed by existing powered descent guidance methods. In particular, real-time optimization of the vehicle's landing trajectory has been very challenging. In this paper, a closed-loop guidance method is proposed that optimizes a restricted 6-degrees-of-freedom (6-DoF) trajectory in real-time. To remedy the difficulty caused by the highly nonlinear dynamics, the general propellant-optimal problem is regularized with two modifications. The first is to augment the angular velocity to the performance index, removing possible singularity arcs that cause numerical difficulties. The second is to parameterize the thrust magnitude with a piecewise-constant form, reducing the number of control variables to be optimized. The regularized problem is then solved with successive convexification to update the restricted 6-DoF landing trajectory in each guidance cycle. Monte Carlo experiments with aerodynamic and thrust dispersions are conducted to examine the proposed guidance method. • A new guidance method is proposed that uses both aerodynamic and thrust controls. • The guided vehicle can fly at unprecedentedly high angle-of-attack to decelerate. • The guidance method optimizes a restricted 6-degree-of-freedom trajectory in real-time. • The guidance problem is regularized twice to address the highly nonlinear dynamics. [ABSTRACT FROM AUTHOR]

Bone drilling mechanism study is the basis for the optimization of cortical bone drilling process and drill geometry. In this paper, a drilling force model for modified drills with thinned chisel edge is established considering the heterogeneous structure of cortical bone. The bone mineral density is embedded into the established model, the model can predict the axial thrust force change along the drilling depth direction, and the model is verified through cortical bone drilling experiments. The thrust force and torque predicted by the model are in good agreement with the drilling experimental results of cortical bone drilling. Then, the drilling performance of the modified drill and the common drill is compared through cortical bone drilling experiments. Compared with common drill bits, the maximum reduction in average thrust force of the modified drill bit during stable drilling is 21.21 % (n = 2500 rpm, V f =60 mm/min). The maximum reduction in average roughness of the hole wall is 21.87 % (n = 500 rpm, V f =10 mm/min). The drill chisel edge thinning design reduces the negative impact of the negative normal rake angle on the cutting lip of common drill on drilling force and stability. Therefore, the drill bit chisel edge thinning design can effectively improve the drilling performance. • Considering the heterogeneous structure of cortical bone, a drilling force model is established.. • The model can predict the variation of axial thrust force and torque along the drilling depth. • Thinning the chisel edge of the drill can effectively improve the drilling performance. [ABSTRACT FROM AUTHOR]

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Most towing tank model tests conducted on planing hulls are not performed under self-propulsion conditions, and it is often not feasible to directly apply towing force at the corresponding point of action and along the thrust of the full-scale vessel. Therefore, it is essential to establish a well-defined method for accurately applying the thrust line in bare hull model tests using alternative loading solutions, such as CG shift, and understand how any deviation affects the model's running attitude and performance. This article presents an analysis of the dynamic equilibrium equations of motion for the model, considering various variables that can be used to adjust the thrust line in towing tank tests. The proposed formalism can aid in determining the external loading requirements in resistance tests. Finally, the article discusses the challenges and provides an error estimation for a simplified method of applying a constant thrust angle in the accelerated tests. [ABSTRACT FROM AUTHOR]

Highlights Carbon fiber reinforced polyetherketoneketone (CF/PEKK) possess excellent mechanical properties and also meet low‐carbon environmental standards, leading to their increasingly widespread application in recent years. To ensure the strength of mechanical connections, it is crucial to minimize drilling damage. This paper utilizes Ultrasonic Vibration‐Assisted Drilling (UVAD) to enhance hole‐making quality, comparing multiple drilling performance indicators with Conventional Drilling (CD), including thrust force, drilling temperature, delamination factor, and burr factor. The results demonstrate that UVAD significantly reduces thrust force and drilling temperature, decreases delamination and burring damage, and effectively improves hole quality. To further optimize processing parameters, the Non‐dominated Sorting Genetic Algorithm II (NSGA‐II) was used, targeting thrust force, Material removal rate (MRR), and delamination factor as optimization goals. The reliability of the model was verified through experimentations. This paper provides an effective technical approach for high‐quality drilling in CF/PEKK materials, offering significant practical application value for material processing in aerospace and other fields. The quality of CF/PEKK processed by CD and UVAD was compared. UVAD can effectively improve the quality of drilling. The drilling parameters were optimized by NSGA‐II. The reliability of the prediction model was verified by experiments. [ABSTRACT FROM AUTHOR]

With the advancement of imaging technology, the performance of optical focusing modules becomes crucial for determining imaging quality. Conventional focusing modules frequently face challenges of excessive bulk and weight, complicating the integrated design and limiting application fields. Herein, this study presents a piezo‐actuated optical focusing module (POFM) and the construction strategy to alleviate these issues. A novel radial‐bending resonant‐type piezoelectric actuator (RB‐RPA) is developed to directly drive the POFM. The RB‐RPA, which features a hollow structure (27 × 27 × 7 mm3), utilizes both radial and bending vibration modes of a thin metal plate. It achieves a speed of 122.93 mm s−1, a thrust force of 0.14 N, and a displacement resolution of 0.52 µm. Employing the proposed construction strategy, RB‐RPA is integrated with imaging components to fabricate a POFM prototype. Furthermore, the micrometer‐level displacement resolution of POFM facilitates optical focusing on imaging targets, allowing the acquisition of sharp images within 70 ms. It achieves an image resolution of 119.57 lp mm−1 within a 42 mm segment of the captured image. Finally, a QT‐based interface for the POFM, enables real‐time image capture and sharpness evaluation, thereby enhancing imaging efficiency and integration. This work provides a potential candidate for next‐generation imaging devices. [ABSTRACT FROM AUTHOR]

In the uneven publishing landscape between Africa and the global north publishing industry, almost all editorial rejections or requests for revision are initially narcissistically injurious. They compel one to pause, to revisit their views, and perhaps they make writers second guess themselves. In this paper, I focus on review feedback as a productive pause. I think with the affects and potentialities that follow the initial injury. I posit that if we look past the wounding, most revisions can be transformed into practices of care. I contemplate what it means for one’s work to be attended to by others and the generative possibilities that different lenses might enable. This thrust to focus on the positive is not to dismiss the epistemic violences that being revised and corrected might enact. Instead, I suggest that as writers committed to our craft and ideas, we might mine the review process for glimmers of care even if this entails rummaging through the dregs of callous feedback. Focusing on two writing projects, I think about iterative review as involving a wide network of readers that include formal reviewers and informal readers that are part of a reading community of practice. I suggest that conceived of broadly, reviewers might mediate the writing process in ways that nurse underdeveloped ideas, push us beyond parochial reading practices, and widen the resonance of our work beyond our initial imaginaries. To read the review and publication process through body politics and geopolitics as potentially inhibiting and enabling, propels us beyond binaries and broadens the scope of review to consider the roles of our informal readers. Conceived of this way, review is an important part of the practice of writing. It enhances our craft, ideas and political commitments. [ABSTRACT FROM AUTHOR]

ABSTRACT The southern margin of the Junggar Basin (SMJB) represents the typical intra‐continental basin–orogen coupling structure of the Central Asian Orogenic Belt and is a key area to study the deformation mechanisms and the geodynamic evolution processes of the North Tianshan Orogen. Herein, we compiled data from boreholes, gravity and magnetism, seismicity‐ and magnetotellurics‐derived geological profiles and field data to recover the sedimentary history of the SMJB and discuss the intra‐continental deformation driven by the basin–orogen coupling mechanism. The results show that the sedimentary and tectonic evolution of the SMJB were both profoundly controlled by the intra‐continental orogeny of the North Tianshan Orogen and its coupling with the Junggar Basin during the Meso‐Cenozoic period. Consequently, the SMJB is dominated by thick‐skinned thrust nappes accompanied with strike‐slip faulting and thrusting. The foreland thrust belt of the SMJB is characterised by three structural belts, from south to north, including the basement‐involved thrust belt, the cover‐detached foreland thrust‐fold belt and the thrusted foreland basement uplifts, respectively. Meanwhile, as indicated by the geometry of the basement thrusts, the thickness of décollements and the structure of the foreland basement, the stress field in the SMJB is obviously stronger in the west and weaker in the east. The sedimentation and deformation migrated northwards into the basin area in a stepwise process, that corresponded to the pace of the overthrusting of the North Tianshan Orogen onto the Junggar Block. Intense regional compression induced the rapid uplifting of the North Tianshan and the significant crustal shortening of the Junggar Block, driving the three structural belts to form accordingly during the Late Jurassic to the Neogene. There are at least one or two décollements within the SMJB, representing one of the main features of basin–orogen coupling structure in most cases. The décollement of some layers represents the decoupling of the sedimentary cover with the basement, which helps to accommodate the lateral crustal shortening of the SMJB by a translation into vertical uplift. As a result, the detached foreland thrust‐fold belts in the shallow level of the upper crust overthrusted upon the basement‐involved nappes of the mountain's side, forming the opposite thrust system. Coevally, the basement of the basin, in the deep level of the upper crust keeps underthrusting beneath the North Tianshan Orogen, forming a typical crocodile mouth‐like structure. In general, both the shallow and deep deformation in the SMJB have been formed by the intense intra‐continental compression during the Meso‐Cenozoic, which were driven by the basin–orogen coupling mechanism. [ABSTRACT FROM AUTHOR]

Tectonic tremors occur around the subducting seamount of the Kyushu Palau Ridge (KPR) in Hyuga-nada, Japan. We investigate the relationship between tremor activity and structural and physical characteristics using high-resolution reflection seismic imaging of the KR0114-8 line, encompassing areas with both high and low occurrences of tremors. The reflection data are reprocessed using broadband processing, reflection tomography and Kirchhoff pre-stack depth migration. The resulting image delineates complex deformation and lithological boundaries, such as the accretionary prism, underthrust sediments, décollement, and top of the seamount. The observed splay faults and seafloor uplift to the west of the KPR, coupled with frequent tremors, confirm the compressional stress regime on the leading side of the subducting seamount. A stress shadow over the seamount effectively suppresses tremors. Numerous faults indicate significant deformation of the overburden when positioned on the leading side of the seamount. The trailing side exhibits a compressional stress regime, rather than an extensional one, as evidenced by the development of in-sequence thrusts and frequent tremors. Local physical, mechanical, and structural factors critically influence the tremor activity. The increased frequency of tremors is correlated with the thickness of the underthrust sediments and presence of in-sequence thrusts, whereas it is inversely correlated with the reflectivity of the décollement. Several potential mechanisms for this phenomenon include elevated pore pressure above the décollement and/or within the underthrust sediments, as well as structural effects. High-resolution velocity imaging, scientific drilling, and precise tremor-depth estimation are essential for advancing our understanding of these mechanisms. [ABSTRACT FROM AUTHOR]

Ion wind propulsion systems have potential applications in the field of unmanned aerial vehicle due to their compactness, quiet operation, and simple design. Previous studies have focused on the influences of power source, electrode arrangement, size, and shape on the output thrust characteristics. However, few studies have been performed on the environmental conditions, which can be beneficial for the practical applications of ion wind aircraft in various climatic conditions. In this work, a measurement platform of the output characteristics of ion wind propulsion system under various environmental conditions has been established. The experimental pressure range was 1–0.7 atm, and the relative humidity (RH) range was 30%–92%. The effects of air pressure and humidity, and voltage level on the thrust, thrust-to-power radio (TPR) corona current have been investigated. The results showed that the corona current and thrust of the wire-wing electrode array decreased with RH within the range of 30%– to 80%. Under higher humidity, the corona current and thrust tend to increase at most voltage levels. Moreover, the thrust and current both decreased with reduced pressure when keeping the voltage-to-pressure ratio (U/P) unchanged. It was also found that the thrust was roughly proportional to the square of the pressure. Finally, the possible explanations of the coupled influences on the output characteristics were discussed. [ABSTRACT FROM AUTHOR]

The goal of this paper is to establish a motion control system for unmanned surface vehicles (USVs) that enables point-to-point tracking and dynamic positioning. This includes the heading control and path following control of USVs. A hardware and software platform for USVs using microcontrollers is designed. This paper presents the construction of a kinematics and dynamics model for an unmanned catamaran. The motion process is divided into two segments. In the target point tracking segment, the heading coordinate system and the ship coordinate system are established. Based on these, a control method using differential steering to track the desired yaw angle is designed to improve the tracking efficiency. And the accuracy of heading keeping and path following is improved by combining the cascade PID controller. In the dynamic positioning segment, a self-adjusting mechanism is designed, thereby enhancing the flexibility of thrust distribution and improving the accuracy of the USV's positioning retention in wind and wave environments. Finally, experimental validation is carried out to verify the effectiveness of the design proposed in this paper by issuing control commands and saving the return data through the upper computer, and then analyzing the return data with MATLAB (R2022b, MathWorks, Natick, MA, USA). [ABSTRACT FROM AUTHOR]

As a propulsor with a good application prospect, the flapping foil has been a hot research topic in the past decade. Although the research results of flapping foils have been very abundant, the performance-influencing mechanism of flapping foils is still not perfect, and the research considering three-dimensional (3D) effects for engineering applications is still very limited. Based on the above considerations, a systematic and parametric analysis of a small aspect ratio flapping foil is conducted to correlate the influencing factors including angle of attack (AoA) characteristics and wake vortex on the propulsive efficiency. Three-dimensional numerical analyses of full-active and semi-active flapping foils are carried out in this paper, in which the former focuses on different heave amplitudes and pitch amplitudes, and the latter concentrates on different spring stiffnesses. The analysis covers the full range of advance coefficient, which starts around 0 and ends at a thrust drop of 0. Firstly, the influence of the maximum AoA (αmax) on the efficiency and thrust coefficient of these two kinds of flapping foils is analyzed. The results show that for the small aspect ratio flapping foil in this paper, regardless of the full-active or semi-active form, the peak efficiency as high as 75% for both generally appears around αmax = 0.2 rad, while the peak thrust coefficient of 0.5 occurs near αmax = 0.3 rad. Then, by analyzing the wake flow field, it is found that the lower efficiency of larger αmax working points is mainly due to the larger vortex dissipation loss, while the lower efficiency of smaller αmax working points is mainly due to the larger friction loss of the foil surface. Furthermore, the plumpness of different AoA curves is compared and analyzed. It was found that, unlike the results of full-active flapping foils, the shape of the AoA curve of semi-active flapping foils with different spring stiffnesses is similar, and the relationship with efficiency is not strictly corresponding. This study is expected to provide guidance on both academics and industries in relevant fields. [ABSTRACT FROM AUTHOR]

Drawing upon presence theory, this study seeks to unravel the critical determinants converting engagement into value cocreation in travel livestreaming. To configure an optimal path for real-time interaction, live room setting, and product attributes in livestreaming via viewers' sense of presence, we performed a scenario-based quasi-experiment with four alternative models. Model 1 elucidated the direct influence mechanism how real-time interaction, authenticity, and remuneration evoke value cocreation, while Model 2 reflected the moderation impact of the objective attributes between communication behaviours and value cocreation. Model 3 and Model 4 incorporated viewers' physical and social presence into assessments as mediators. The results reveal that communication behaviours psychologically drive viewers' sense of presence, thereby leading to value cocreation, while objective attributes moderate the subjective consciousness of presence. The research positions insightful theoretical implications to thrust value co-creation of tourism academia spotlight and practically contributes to promoting sales performance in the nascent tourism market. [ABSTRACT FROM AUTHOR]

The seismic attenuation relationship between ground motion parameters (such as peak acceleration and response spectra value) and seismic parameters (such as magnitude and epicentral distance) is an important foundation for seismic hazard analysis and the core of determining seismic input parameters for seismic resistance engineering. The acceleration envelope parameters, which describe the relationship between ground motion intensity and time variation, are primarily used for artificially synthesizing seismic motion. At present, little research has been performed on the attenuation relationship of acceleration envelope parameters in the Longmenshan fault zone on the eastern side of the Tibetan Plateau in China. Therefore, this study selected the Mw4-6 aftershock records of the 2008 Wenchuan earthquake that occurred on the Longmenshan fault zone and established a commonly used three segment envelope model parameter attenuation relationship. We classified aftershock records based on their source mechanisms and obtained attenuation relationship models for thrust slip aftershocks, thrust and strike slip aftershocks, and strike slip aftershocks. The results are as follows: (1) The thrust slip aftershock records had the longest rising stage which is the time difference from the arrival of P-waves to the beginning of the stable sustained stage of seismic motion. Thrust and strike slip aftershocks records had the longest stable sustained stage period and the slowest attenuation at the tail of the record. (2) The attenuation relationship of the acceleration envelope parameters commonly used in Chinese engineering for artificially synthesizing seismic motion is based on the strong earthquake records in the western United States. But, compared to the attenuation characteristics of the acceleration envelope function in the western United States, the Mw4-6 earthquake records on the Longmenshan fault zone had a slower attenuation rate at the tail of the record. So, accurately artificially synthesizing seismic motion through envelope parameter attenuation model requires the use of attenuation model established by earthquake records in this region. [ABSTRACT FROM AUTHOR]

Background Objective Method Results Conclusion Sexual position is one of the several aspects that affects ejaculation control, which is essential for sexual pleasure. Still little is known, nevertheless, about the connection between sexual positions and ejaculation duration.To investigate the impact of various sexual positions on the duration of ejaculation and gain a deeper understanding of the elements that influence the ability to control ejaculation.An online survey was carried out on a sample of 1904 heterosexual men between the ages of 18–65 years. Premature ejaculation (PE) diagnostic tool was used to define PE. Demographic, behavioral, and physiological traits that are linked to PE and non‐PE groups were collected. The participants listed their preferred sexual positions and the ones they changed to during ejaculating. Also, analyses were performed between male/female active or deep/shallow thrust positions and PE status.Although there were no appreciable variations in age or circumcision between PE and non‐PE groups, the age of first sexual experience was associated with PE status. Groups also varied in the number of weekly ejaculations, the duration of the favored ejaculations, and the characteristics of the erection. The most preferred sexual posture was the doggy style regardless of the group. When the non‐PE group felt to ejaculate, they preferred to change the position significantly more than the PE group (74% vs 67.2%; p < 0.05). However, when participants felt ejaculate, non‐PE participants tended to switch to shallow thrusting positions significantly more than PE participants, who preferred deeper positions (27.1% vs. 18%; p < 0.05).This study underlines the relevance of considering sexual positions in controlling PE. Modifying positions during sexual intercourse may offer a non‐pharmacological therapeutic alternative for improving ejaculation control. Future studies in this field might help to create tailored PE treatment strategies. [ABSTRACT FROM AUTHOR]

We report three U–Pb sulfate ages from the recently identified Intra-PQ Thrust within the Phyllite–Quartzite (PQ) Nappe of the Ionian high-pressure belt of the external Hellenides in the eastern Mediterranean. Crosscutting relations show that a distinct pressure-solution laminae/microlithon fabric is the oldest deformation structure. Two analyses of sulfate minerals that are part of this structure yielded indistinguishable dates, with a weighted average of 20.03 ± 5.96 Ma. The crosscutting fabric with alteration halos of the sulfate provided a date of 9.37 ± 4.64 Ma. The initial 207Pb/206Pb ratios are ~ 0.40 and thus distinctively lower than the terrestrial model lead isotope ratio of 0.84 for the calculated ages. This can only be explained if the dated sulfate precipitated from a fluid enriched in radiogenic 206Pb, probably sourced by the surrounding country rock through (partial) dissolution of older U-rich minerals. The dates of ~ 20 Ma agree with recently reported fault-gouge ages of 26–21 Ma from the Intra-PQ Thrust. The study demonstrates, for the first time, the possibility of dating sulfate minerals in metamorphosed rocks applying the U–Pb system. [ABSTRACT FROM AUTHOR]

Oblique detonation engines (ODE) have significant potential for hypersonic propulsion, yet there is a paucity of research investigating internal injection ODEs. In this study, a numerical simulation of the internal flow field of a Mach 10 internal injection kerosene-fueled ODE is conducted. The fuel mixing, pre-combustion, and combustor wave structure in the flow field are analyzed in a situation closer to the real flow field conditions. Further studies have demonstrated that alterations to the upper wall initiation position of nozzle can influence the separation zone, flow field stability and the engine performance. An upper wall initiation position that is too far forward will increase the separation zone area and reduce the engine thrust. Conversely, an upper wall initiation position that is too far back will lead to flow field destabilization and eventually thermal choking. Finally, the effects of increasing the equivalent ratio on the flow field structure and engine performance for a certain configuration are analyzed. The results demonstrate that when the equivalent ratio is elevated, an increase in either the bottom or top incoming flow equivalent ratio results in a transformation of the wave structure within the combustor due to the presence of the incoming boundary layer and the subsonic zone. A large-scale separation zone will form at the bottom of the combustor, resulting in a reduction in nozzle thrust. However, the wedge drag is reduced more, thereby increasing the engine's specific impulse. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of the rotor hovering on the air–water free-surface, which is significant for cross-medium unmanned aerial vehicles, is merely studied. In this study, a compressible two-phase flow model is used to compare the aerodynamic performance in the free-surface effect (FSE) and the ground effect (GE) with various dimensionless distances, γ , between the rotor and the ground (or free-surface). According to the results, the vortex core in FSE moves further in both vertical and radial directions than in GE for the early stages. Additionally, the blade surface is separated into three parts. In zone I, the aerodynamic performance is mostly determined by proximity effects. For both FSE and GE, the downward induced velocity at the rotor disk rises with increasing γ , leading to a decrease in the sectional thrust coefficient C T , S . By the way, C T , S is larger in FSE. In zone III, the aerodynamic performance is mostly governed by the blade tip vortex. The trend of aerodynamic performance with γ is reversed compared with zone I. The above-mentioned two opposing tendencies result in a smaller rotor thrust in FSE than in GE within the range of 0.60 ≤ γ ≤ 3.00 , but a higher rotor thrust in FSE within the range of γ ≤ 0.60. [ABSTRACT FROM AUTHOR]

This study employs the improved delayed detached-eddy simulation method for detailed numerical simulations to investigate the impact of barnacle attachment on the hydrodynamic performance of propellers. The simulations were conducted on an unstructured grid comprising 50.7 × 106 cells, ensuring high fidelity in capturing complex flow phenomena. The study examines the near-field evolution of the propeller wake, focusing on the changes in vortex structures and flow characteristics caused by barnacle attachment. The results indicate that barnacles not only reduce the propeller's propulsion efficiency but also significantly alter the topology of tip vortices, leading to increased turbulence intensity. The simulations also reveal the mechanism by which barnacles affect the hydrodynamic performance of the propeller, notably by significantly altering the flow direction around the blades, exacerbating flow separation and the generation of localized vortices. In addition to affecting normal thrust generation, the interaction between small-scale vortices and tip vortices further destabilizes the tip vortices. These findings provide insight into the complex flow interactions in marine environments and their impact on propeller efficiency and durability. [ABSTRACT FROM AUTHOR]

The single stiffness makes the micro-air vehicles (MAVs) only to show excellent flight performance in a specific flow field environment. The MAVs should have the ability to actively deform to adapt to different application scenarios. This study investigates the effects of spanwise active deformation amplitude ( ψ max ), phase difference ( φ P ), and Strouhal number (St) on the aerodynamic loads and vortex of a wing through numerical simulations. Under the condition of Re = 1000, numerical simulations were conducted on a rectangular wing with an aspect ratio of 4 during the flapping process. The study reveals that moderate spanwise deformation can increase the thrust of the wing and improve propulsion efficiency ( η P ). Within the study's scope, the thrust coefficient increases monotonically and linearly with the deformation, but the propulsion efficiency improves only within a limited parameter range. By observing the vortex under different spanwise deformations and monitoring the forces at different positions of the wing, it was found that active deformation can enhance the strength of the leading-edge vortex (LEV) and the wingtip vortex (TV), thereby enhancing the generation of thrust. The results also indicate that the enhancement of LEV is achieved through the coupling between LEV and secondary vortex. At different Strouhal numbers, improvements in η P can only be achieved through the combined effects of increased vortex strength and optimal vortex residence time. Additionally, it was observed that at lower St, TV can switch from contributing thrust to causing drag. [ABSTRACT FROM AUTHOR]

Studies have shown that fish can enhance propulsion performance by utilizing the interaction between median fins (dorsal, anal, and caudal fins), compared to fish with only caudal fin. However, most of the current studies are based on the fish oscillating in-place, and the analysis of median fins interaction to improve swimming propulsion performance is still insufficient, and the mechanism needs further study. This study applied three-dimensional numerical simulation methods to solve the process of grass carp accelerating from a stationary state to cruising state under different body and median fins combination, as well as different motion parameter models. A comparative quantitative analysis of different models was conducted to assess the impact of median fins interactions on enhancing swimming performance, with a detailed analysis of the hydrodynamic mechanisms and their relationship with vortex dynamics. The results indicated that interactions between median fins could generate significant hydrodynamic benefits, with the fish's average swimming speed increasing up to 4.6 times, thrust up to 33.47%, and swimming efficiency up to 25.48%. This study found that the enhancement of propulsion performance was due to the formation of high-intensity and persistent posterior body vortices by the movements of the dorsal and anal fins, which were captured by the leading-edge of the caudal fin, greatly enhancing the strength of the leading-edge vortex. This study elucidates the hydrodynamic mechanisms of the interaction between median fins and could provide new insights into the efficient swimming mechanism of fish in nature. [ABSTRACT FROM AUTHOR]

This study explores the hydrodynamic performance of a National Advisory Committee for Aeronautics 0012 foil using computational fluid dynamics with the unsteady Reynolds-averaged Navier–Stokes (URANS) method and shear stress transport k-ω model to assess the impact of asymmetric motion parameters in manta-like swimming. The angles of attack during the mid-upstroke (αmu), mid-downstroke (αmd), and stroke duration (S) are varied to understand their effect. At low Strouhal numbers (StA = 0.2–0.35), a smaller αmd compensates for thrust loss at the start of the upstroke due to a greater αmu. At high Strouhal numbers (StA = 0.5), a greater αmd reduces negative thrust and compensates for the smaller thrust generated by a small αmu during the upstroke. Shorter stroke durations increase asymmetry, leading to more significant positive thrust peaks during the downstroke. If both the angle of attack and S are large, the slower downward speed extends negative thrust, reducing thrust peaks and lowering average thrust. A smaller stroke duration combined with a large angle of attack enhances efficiency due to a greater thrust-to-power ratio, highlighting the interplay between these parameters. A smaller S and greater αmd and StA maximize thrust and efficiency, suggesting aquatic organisms increase thrust while ensuring propulsion efficiency by using a large angle of attack and an asymmetric stroke duration. This study demonstrates how asymmetric parameters interact, providing insights into designing biomimetic underwater vehicles. The findings suggest that asymmetric dynamics enhance propulsion efficiency. [ABSTRACT FROM AUTHOR]

This study investigates the thrust generation mechanism and performance of a plunging airfoil undergoing double-peak periodic motion, specifically utilizing superposition of the regular sinusoidal waveform with another less-weighted faster one. It is revealed that the proposed waveform produces 200% more thrust when compared to sinusoidal plunging with a small efficiency difference. Also, it produces two vortex pairs (2P) per cycle all over the plunging frequency-amplitude space, instead of the reverse von Karman vortices. Using this proposed waveform, the 2P wake is generated through interaction of three types of vortices shed during plunging, opposing the regular 2P pattern found in the literature. [ABSTRACT FROM AUTHOR]

The stochastic EXtended finite‐fault ground‐motion SIMulation algorithm (EXSIM) has been widely applied in simulating and predicting broadband strong ground‐motion. However, an increasingly number of researchers have found that EXSIM may overestimate ground‐motions at low frequencies for some large‐magnitude earthquakes and/or thrust earthquakes, for which the far‐field source model has been explained by a double‐corner‐frequency model. Despite controversy, the double‐corner‐frequency model is now being accepted as one of the main categories of the far‐field source model. This study demonstrated the limited applicability of EXSIM to earthquakes explained by the double‐corner‐frequency source model, by presenting the equivalence between motions generated by EXSIM and those generated by EXSIM's point‐source version, SMSIM, which adopts the ω‐square single‐corner‐frequency model. Furthermore, two improvements to EXSIM have been proposed: (a) the incorporation of the asperity‐distributed stress‐drop compound faults model and (b) the hybrid application of EXSIM with the proposed model. The effects of the two improvements have been verified by comparing EXSIM‐generating motions with recorded ground‐motions for the 2013 Mw 6.7 Lushan thrust earthquake. Significantly, consistent simulation accuracy has been achieved across high‐ and low‐frequency bands as well as in far‐ and near‐fields. The consistent accuracy of the improved EXSIM in simulating high‐ and low‐frequency ground motions enables its direct and independent application to broadband ground motion simulations. Moreover, the first validation of this consistent accuracy in both near‐ and far‐field scenarios further enhances its application in earthquake engineering practices. Key Points: EXtended finite‐fault ground‐motion SIMulation algorithm (EXSIM) could overestimate the low‐frequency ground motions of earthquakes with double‐corner‐frequency source model characteristicsTwo improvements to EXSIM were proposed: the asperity‐distributed stress‐drop compound faults model and the hybrid application of EXSIMThe improvements have been validated by comparing EXSIM‐generating motions with records for Mw 6.7 Lushan thrust earthquake [ABSTRACT FROM AUTHOR]

Indicating the tectonic features of the Hanshan–Wuwei basin can reconstruct the framework of the basins formed in Mesozoic and further understand the Mesozoic tectonic evolution of the South China Block. Studies on surface structure, regional stress field and deep geophysical characteristics of the Mesozoic Hanshan–Wuwei basin in Lower Yangtze region were carried out. NE–NNE trending folds and faults developed in the northern margin of the basins. The reconstruction of tectonic stress fields indicates four stress stages dominating the basins' evolution including NW–SE compression, N–S compression, NW–SE extension and NWW–SEE compression. 2D seismic profiles reveal coexistence of thrust, strike‐slip and normal faults in the basin. Combined with regional geological studies, the geodynamic processes for the formation of the Hanshan–Wuwei basin can be divided into five stages: 1) During the Late Triassic, EW trending foreland basin was formed by N–S compression; 2) From Mid‐Jurassic to Late Jurassic, continuous compression strengthened the foreland deformation and formed thrust nappes. In this stage, the integrated foreland basin was compartmentalized or fragmented, and transferred to the broken foreland basin; 3) NE‐trending sinistral strike‐slip movement at the beginning of the Early Cretaceous; 4) Regional extension resulted in normal faults and rift basins developing in the Late Cretaceous; 5) The NWW–SEE compression at the end of the Late Cretaceous caused NW sinistral strike‐slip faults to form, which partly transformed the rift basin. [ABSTRACT FROM AUTHOR]

The Enriquillo-Plantain Garden fault (EPGF), the southern branch of the northern Caribbean left-lateral transpressional plate boundary, has ruptured in two devastating earthquakes along the Haiti southern peninsula: the Mw 7.0, 2010 Haiti and the Mw 7.2, 2021 Nippes earthquakes. In Jamaica, the 1692 Port Royal and 1907 Great Kingston earthquakes caused widespread damage and loss of life. No large earthquakes are known from the 200-km-long Jamaica Passage segment of this plate boundary. To address these hazards, a National Science Foundation Rapid Response survey was conducted to map the EPGF in the Jamaica Passage south of Kingston, Jamaica, and east of the island of Jamaica. From the R/V Pelican we collected >50 high-resolution seismic profiles and 47 gravity cores. Event deposits (EDs) were identified from lithology, physical properties, and geochemistry and were dated in 13 cores. A robust 14C chronology was obtained for the Holocene. A Bayesian age model using OxCal 4.4 calibration was applied. Out of 58 EDs that were recognized, 50 have ages that overlap within their 95% confidence ranges. This allowed for their grouping in multiple basins located as much as 150 km apart. The significant age overlap suggests that EDs along the Enriquillo-Plantain Garden plate boundary resulted from large and potentially dangerous earthquakes. Most of these earthquakes may derive from the EPGF but also from thrust faulting at this strain-partitioned transpressional boundary. The recent increase in Coulomb stress on the EPGF from the Mw 7.2 Nippes earthquake in southwestern Haiti and the discoveries reported here enhance the significance for hazard in the Jamaica Passage. [ABSTRACT FROM AUTHOR]

In order to achieve better synchronization performance for H-type platform servo systems during motion, an adaptive nonlinear second-order sliding mode synchronous control method with zero error constraint is proposed in this paper. The reason and mechanism of unsynchronized movement of H-type platform are analyzed. A synchronous thrust allocation algorithm based on dynamics is designed by using the thrust balance equation under zero error constraint to suppress the rotation movement of the crossbeam theoretically. To minimize the impact of external disturbances on the system, the system employs a robust adaptive nonlinear second-order sliding mode control method. In this method, the nonlinear sliding mode function is constructed to enhance the dynamic performance of the system, the second-order sliding mode surface is designed to achieve chatter-free control input. To address the issue of limitations in sliding mode control caused by upper limits of external disturbances, an adaptive control technique is employed to estimate and compensate for uncertainties such as external disturbances. Experimental results demonstrate that the proposed synchronous control strategy can effectively adjust the operating conditions of the two motors, improve the synchronous control performance and enhance the anti-interference ability of the system. [ABSTRACT FROM AUTHOR]

This paper presents an allocator design that considers the power consumption of rotors in the attitude and altitude control system of a hexarotor drone. Based on the power consumption model, the proposed method computes the thrust force that minimizes the total power consumption of the rotor while satisfying the control force constraints required by the controller. To obtain the rotor power consumption model, we conducted experiments on the rotor characteristics using the motors and electronic speed controllers used in the drones. Finally, numerical simulations were performed using the obtained power consumption models to compare the rotor power consumption of the proposed method with that of the conventional method, quantitatively evaluating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a force-sensing wing, Senswing, to enhance the intelligence of flapping-wing aerial vehicles (FWAVs). Force perception is a crucial capability for robots to interact safely and effectively in unknown environments. However, FWAVs perform flapping motions with significant acceleration and deceleration, which can cause the flexure element inside force sensors to deteriorate due to repeated loading or even fail due to impulsive forces. To address this, we constructed a force measurement system by attaching 16 strain gauges directly to the wing root while maintaining high rigidity. We confirmed that the external force measurement capability closely matched the values obtained by a six-axis force sensor, with almost no error. Additionally, when measuring aerodynamic forces during wing flapping, the sensor could detect differences in wind speed even during flapping. With this sensor, FWAVs can achieve in-flight measurement of thrust and lift through a force-sensing system. [ABSTRACT FROM AUTHOR]

There has been significant interest in the field of bio-inspired robotics, particularly in the development of flapping-wing robots from micro to bird size. Most flapping robots use lever-crank mechanisms or servomotors as wing flapping mechanisms. Servomotor-based flapping has the advantage of being able to generate various flapping patterns according to amplitude, offset, frequency, waveform, and other factors. However, it is not clear how these factors affect thrust generation. Therefore, this study focuses on the force generation and power consumption in different flapping patterns as well as the wing deformation during the flapping motion to provide some insights into the performance improvement. The results showed that the response characteristics of the actuators caused the thrust to saturate at high frequencies, and that sinusoidal pattern could generally achieve good performance and efficiency. [ABSTRACT FROM AUTHOR]

W* is the category of the title. For G ∈ W*, we have the canonical compact space YG, and Yosida representation G ≤ C(YG), thus, for g ∈ G, one has the cozero-set coz(g) in YG. The ideals at issue in G include the principal ideals and polars, G(g) and g⊥⊥, respectively, and the W*-kernels of W*-morphisms from G. The "coincidences of types" include these properties of G: (M) Each G(g) = g⊥⊥; (Y) Each G(g) is a W*-kernel; (CR) Each g⊥⊥ is a W*-kernel (iff each coz(g) is regular open). For each of these, we give numerous "rephrasings" and examples, and note that (M) = (Y) ∩ (CR). This paper is a companion to a paper in preparation by the present authors, which includes the present thrust in contexts less restrictive and more algebraic. Here, the focus on W* brings topology to bear, and sharpens the view. [ABSTRACT FROM AUTHOR]

The geological condition monitoring and identification based on TBM-equipped sensors is of great significance for efficient and safe tunnel construction. Full-scale rotary cutting experiments are carried out using tunnel-boring machine disc cutters. Thrust, torque and vibration sensors are equipped on the rotary cutting machine (RCM). A stacking ensemble-learning model for real-time prediction of rock mass classification using features of mathematical statistics is proposed. Three signals, thrust, torque and a novel vibration spectrogram-based local amplification feature, are fed into the model and trained separately. The results show that the stacked ensemble-learning model has better accuracy and stability than any single model, showing a good application prospect in the rock mass classification. [ABSTRACT FROM AUTHOR]

This attempt covers an investigation of cutting temperature at interfaces of Fiber Metal Laminates (FMLs) made of glass fiber-reinforced polymer (GFRP) stacked with an Al2020 alloy. GFRP/Al/GFRP and Al/GFRP/Al composite stacks are both investigated to highlight the effect of stacking arrangement on thermal behavior within the interfaces. In a first test series, temperature history is recorded within the metal/composite stack interfaces using preinstalled thermocouples. In a second test series, a wireless telemetry system connected to K-type thermocouples implanted adjacent to the cutting edge of the solid carbide drill is used to record temperature evolution at the tool tip. Focus is put on the effects of cutting speed and stacking arrangement on the thrust force, drilling temperature, and delamination. From findings, the temperature histories show high sensitivity to the cutting speed. When cutting Al/GFRP/Al, the peak temperature is found to be much higher than that recorded in GFRP/Al/GFRP and exceeds the glass transition point of the GFRP matrix under critical cutting speeds. However, thrust force obtained at constitutive phases exhibits close magnitude when the stacking arrangement varies, regardless of cutting speed. Damage analysis is also discussed through the delamination factor at different stages of FML thickness. [ABSTRACT FROM AUTHOR]

Combustion through detonation marks an important leap in efficiency over standard deflagration methods. This research introduces a Pulsed Detonation Combustor (PDC) model that uses Hydrogen as fuel and Oxygen as an oxidizer, specifically targeting carbon-free combustion efforts. The PDC aerodynamic features boost operating cycle frequency and facilitate Deflagration-to-Detonation Transition (DDT) within distances less than 200 mm by means of Hartmann–Sprenger resonators and cross-flow fuel/oxidizer injection. The achievement of quality mixing in a short-time filling process represents not only higher cycle operation but also enhanced performances. The scope of this paper is to assess the impact of different fuel injectors with different opening areas on the performances of the PDC. This assessment, expressed as a function of the Equivalence Ratio (ER), is conducted using two primary methods. Instantaneous static pressures are recorded and processed to extract the maximum and average cycle pressure and characterize the pressure augmentation. Thrust measurements obtained using a load cell are averaged over the detonation cycle to calculate the time-averaged thrust. The specific impulse is subsequently determined based on these thrust measurements and the corresponding mass flow data. [ABSTRACT FROM AUTHOR]

We present significant findings of the Kausani Granite Gneiss within the Inner Lesser Himalayan Sedimentary Zone (iLHSZ) just north of the North Almora Thrust (NAT). The Kausani Granite Gneiss body lies within the quartzite of the Someshwar Formation and has a tectonized contact and a discordant relationship on the north side. Detailed seismic profiling across the body also confirms a similar result. Cathodoluminescence images of zircon from the Kausani body show no inheritance of older cores. The U–Pb ages from the zircon populations separated from the Kausani body give a crystallization age of 1866 ± 3 Ma. Along with the Upalda granite gneiss and Toneta granite gneiss near the Alakhnanda Thrust in the Garhwal Himalaya and the Dungeshwari granite gneiss near the Dailekh Thrust in Nepal, the Kausani Granite Gneiss north of NAT Kumaun Himalaya forms a major terrain boundary. These gneissic bodies mark the southernmost extent of felsic magmatism at NAT, rather than the Main Central Thrust. An about 1.8 billion years‐old magmatic event in the LHSZ suggests that it is a currently active continental margin inside the 'Greater India' region, now situated in the Himalayan domain. However, the Pb‐loss modelling of the U–Pb zircon data reveals thermal events during the Himalayan Orogeny (~45 Ma). [ABSTRACT FROM AUTHOR]

• The infeasibility of the fuel-optimal powered landing problem is analyzed. • A maximum-thrust regulation strategy is proposed to reduce infeasibility. • A trajectory-tracking method with a disturbance compensator is proposed. • The disturbance compensator requires only the current state information. Convex optimization has great potential for onboard trajectory generation which can eliminate large state deviations and improve landing precision. In practical applications, the convex optimization problem is often infeasible under disturbances. In this paper, we analyze the reason for the infeasibility of the fuel-optimal trajectory optimization problem. The analysis result shows that the thrust saturation degrade the anti-disturbance performance and then lead to infeasibility. Based on this analysis, we improved the anti-disturbance performance of convex optimization-based guidance from two aspects: (1) a maximum-thrust regulation strategy is embedded into the original fuel-optimal problem to avoid thrust saturation; (2) a trajectory tracking method with a disturbance compensator is performed to attenuate disturbance effects and to make the initial state of each optimization cycle close to the existing feasible trajectory. Numerical simulations demonstrate that the proposed method can improve the infeasibility and can realize the high-precision landing under disturbances. [ABSTRACT FROM AUTHOR]

Flying cars, or vertical takeoff and landing (VTOL) aircraft, are revolutionary devices that can address traffic congestion and help build a three-dimensional transportation system in the future. Flight safety could deteriorate in actual flight because ducted fans may suffer from significant thrust fluctuations induced by crosswinds. In this article, we propose a variable-speed control method to reduce thrust fluctuations by applying a speed waveform opposite to the fluctuation waveform. We choose a typical condition of a 5 m/s crosswind for validation. The results of unsteady Reynolds averaged Navier‒Stokes (URANS) calculations show that crosswinds lead to fluctuations in all thrusts with the frequency of the blade passing frequency. The total thrust fluctuation amplitude accounts for 6.2% of the total thrust. By applying the variable-speed control where the frequency is identical to the thrust fluctuation frequency, the phase difference is 180 degrees, and the amplitude is approximately the square root of the fluctuation amplitude, the standard deviation of the thrust fluctuation is reduced by 92% without affecting the mean total thrust. Fluctuations in other performance parameters, such as lateral force and pitching moment, are improved as well. This active control method can achieve accurate control without any auxiliary equipment and has good application prospects. It provides a promising idea for solving the problem of performance fluctuations in turbomachinery. [ABSTRACT FROM AUTHOR]