Horizontal Speed Research Articles

Developmental eye movement test results of Hebrew-speaking children with cross-linguistic comparisons.

The developmental eye movement (DEM) test is designed to assess saccadic eye movements and visual-verbal automaticity in children. This study aimed to assess whether there is a need for independent DEM Hebrew norms and to compare DEM results for Hebrew-speaking children with eight other language norms. The DEM test was administered to 224 Hebrew-speaking children aged 6-13 years who met the inclusion criteria and read the numbers in Hebrew. Test C of the DEM was performed twice, once from right (R) to left (L) and once from L to R, in random order. Age group and language comparisons, including vertical and horizontal reading speeds, errors and horizontal/vertical (H/V) ratios in both directions were analysed. The participants were almost evenly distributed between the sexes (46.8% female). Statistically significant differences were found between age groups (6-9 and 10-13 years) for vertical and horizontal reading speeds and H/V ratios in both directions (p < 0.001). Older children, as compared to younger children, exhibited faster vertical and horizontal times, with fewer errors, as well as lower ratios (p < 0.001). No significant difference was noted between reading directions for horizontal time and H/V ratio within both age groups (6-9 year olds: p = 0.27 and p = 0.06; 10-13 year olds: p = 0.89 and p = 0.49, respectively). Comparison of DEM norms across languages showed significant differences, with post-hoc analysis revealing specific language-related variations. DEM results for Hebrew-speaking children had similar outcomes to both original English and French values. This study compared DEM results of Hebrew-speaking children and scores across nine languages. DEM test values for Hebrew-speaking children aligned with norms from other languages, particularly the French and original English norms, with consistent ratio scores. It is recommended for practitioners who test Hebrew-speaking children to continue using the original English norms and to enable the children to read using their preferred reading direction.

Design and experiments of an integrated device for shrimp orientation and decapitation

To realize the automatic orientation and decapitation of shrimp, an integrated device for shrimp orientation and decapitation was designed based on the shape and size characteristics of shrimp, which was mainly composed of oriented rollers, shrimp pushing boards, adaptive clamping claw and knife for the decapitation of shrimp. Three kinds of shrimp of small, medium, and large size were selected. Taking the speed of the shrimp pushing boards, the horizontal speed of the adaptive clamping claw, the rotational speed of oriented rollers and the radius of the oriented rollers as the test factors, and the success rate of the shrimp decapitation as the index, the single factor test and the orthogonal test were carried out to study the effect of each factor on the shrimp decapitation, and then the main parameters of the device were optimized. The results showed that the optimal parameter combinations of the three sizes of shrimp were the speed of shrimp pushing plates of 60mm/s, the horizontal speed of adaptive clamping claw of 70mm/s, the rotational speed of oriented rollers of 60r/min, and the radius of oriented rollers of 20mm. Under the optimal combination of parameters, the device has the highest decapitation success rate and the success rate of shrimp decapitation was 91.5% for small shrimp, 94.6% for medium shrimp, and 92.8% for large shrimp, the decapitation speed was 36pcs/min for small shrimp, 38 pcs/min for medium shrimp, and 37 pcs/min for large shrimp. Therefore, the feasibility of the device design is verified.

Novel additive lamination manufacturing system for rapid fabrication of large-scale reinforced structural members

Purpose Additive lamination manufacturing (ALM), as a novel additive manufacturing technology, builds up the geometry via the lamination of fiber-reinforced polymer (FRP) fabric laterally, rendering it suitable for fabricating large-scale Stay-in-Place concrete formwork. This paper aims to investigate the control parameters and structure performance of ALM and assess its application for the fabrication of large-scale concrete formwork. Design/methodology/approach Based on previous feasibility studies, this research systematically investigates the control and material parameters that influence horizontal and vertical extrusion speeds, as well as the overall quality of ALM. Once the system parameters are established, a series of prototypes are fabricated and tested to validate the tensile strength of the formwork and its reinforcement capabilities. In addition, this study assesses the potential geometric freedom and implementation constraints of ALM. Findings This research identifies the essential control parameters for path planning in ALM and examines their impact on fabrication. In addition, this paper evaluates ALM’s strengths and limitations in producing concrete formwork for large-scale concrete structures, comparing these to industry benchmarks. Originality/value A critical challenge in additive manufacturing lies in its scalability and compatibility with existing construction processes. In comparison to concrete, FRP offers advantages such as being lighter, easier to handle and providing surface protection and reinforcement. These qualities make FRP superior for formwork and compatible with existing building standards. Despite its advantages and potential, the current path planning and control model in 3D printing do not apply to ALM due to its novel build-up process. Also, the performance of fabricated parts as part of integrated large-scale structures is yet to be studied.

Design of a bipedal robot for water running based on a six-linkage mechanism inspired by basilisk lizards

Legged robots have received widespread attention in academia and engineering owing to their excellent terrain adaptability. However, most legged robots can only adapt to high-hardness environments instead of flexible environments. Expanding the motion range of legged robots to water is a promising but challenging work. Inspired by basilisk lizards which can run on water surfaces by feet, this paper proposes a bipedal robot for water running by hydrodynamics instead of buoyancy. According to the motion parameters of the basilisk lizard during water running, a single-degree of freedom bipedal mechanism is proposed to reproduce the motion trajectory of the feet of the basilisk lizard. Scale optimization is conducted by a particle swarm optimization algorithm to determine the geometrical parameters of the mechanism. The effects of motion frequency and foot area on mechanism performance are studied and the optimal solutions are determined by the maximum single-cycle lift impulse through numerical calculations. A bipedal water running robot prototype was fabricated, and the experimental results show that the prototype can generate enough support for the robot running on the water by providing a maximum lift of 2.4 times its weight (160 g) and reaching a horizontal forward speed range of 0.3-0.8 m s-1, compared with the basilisk lizard weighs 2-200 g, generates a lift impulse that is 111%-225% of its body weight, and moves at a speed of 1.3 ± 0.1 m s-1.

Turkey vultures tune their airspeed to changing air density.

Animals must tune their physical performance to changing environmental conditions, and the breadth of environmental tolerance may contribute to delineating the geographic range of a species. A common environmental challenge that flying animals face is the reduction of air density at high elevation and the reduction in the effectiveness of lift production that accompanies it. As a species, turkey vultures (Cathartes aura) inhabit a >3000 m elevation range, and fly considerably higher, necessitating that they accommodate for a 27% change in air density (0.890 to 1.227 kg m-3) through behavior, physiology or biomechanics. We predicted that birds flying at high elevation would maintain aerodynamic lift performance behaviorally via higher flight speeds, rather than increases in power output or local phenotypic adaptation. We used three-dimensional videography to track turkey vultures flying at three elevations, and data supported the hypothesized negative relationship between median airspeed and air density. Additionally, neither the ratio of horizontal speed to sinking speed nor flapping behavior varied with air density.

Transition from bouncing to rolling on a horizontal surface

If a ball is incident obliquely on a horizontal surface and is allowed to bounce more than once, then it is likely to bounce many times before it starts rolling along the surface. The number of bounces before rolling commences depends on the initial vertical speed and the normal coefficient of restitution. The transition from bouncing to rolling is examined using a simple theoretical model and is compared with experimental data obtained by filming the process with a video camera. We find that the final rolling speed is proportional to the initial horizontal speed of the ball and depends on the initial ball spin, but is independent of the tangential coefficient of restitution. Representative videos for different balls are included as supplementary material, including a superball thrown with a backspin that creates a back and forth motion. Instructors could use the experiment and/or analysis for an advanced undergraduate lab or use a simplified observational exercise for non-majors.

Effects of buoyancy on the spherical flame and explosion pressure of a CH4 mixture under dilution conditions

To determine the effects of buoyancy on the spherical flame and explosion pressure under dilution conditions, a series of explosion experiments were conducted in a 20-L spherical container. The schlieren technique was used to record CH4 flames to assess the buoyancy effect. The change in the explosion pressure was recorded and correlated with the flame shape to analyze the explosion characteristics. The methane explosion occurred in two stages: initial ignition and flame development. During initial ignition, the addition of CO2 caused the flame buoyancy to increase considerably. Flames with different buoyancies had different shapes, such as spherical, ellipsoidal, and “ω” shapes. The radius of the flame at 12 mm may serve as the threshold for the onset of buoyancy effects; once the radius exceeds this value, the flame could deform due to buoyancy effects. Increasing the added CO2 concentration caused the buoyancy effect to be enhanced and appear at a very low radius of the flame. The combined effects of buoyancy and dilution reduced the flame expansion speed. The difference between the horizontal and upward expansion speeds linearly increased with the CO2 concentration. At a high CO2 concentration, the flame stagnated at speeds below 0.5 m/s. During flame development, CO2 addition made the flame surface smoother. Suppressing the cellular flame structure delayed the maximum explosion pressure rise rate and reduced the pressure peak. A coupled analysis of the flame shape and the maximum explosion pressure rise rate showed a dense cellular structure for a high explosion pressure rise rate and a smooth flame surface for a low maximum explosion pressure rise rate. The size and number of cellular structures for different mixtures were similar at a fixed maximum explosion pressure rise rate.

Early detection of Tonga volcanic-eruption from internal gravity wave effects on ionosphere, using satellite geodetic techniques

The occurrence of some natural hazards in the troposphere may lead to creation of Internal Gravity Waves (IGWs). These waves transfer energy from the lower troposphere to upper layers, and to the ionosphere. When these IGWs reach the ionosphere, they create significant variations in the ionospheric parameters. Therefore, they have considerable effects on performance of Global Navigation Satellite Systems (GNSS) receivers. In this study, we used double-frequency measurements of GNSS ground-based stations from GEONET network in New Zealand to detect the IGWs created by the tsunami induced from the 2022 Tonga volcanic eruption. In addition to GNSS measurements, FORMOSAT-7/COSMIC-2 (F7/C2) data, and SWARM data were also used to study these IGWs. It is known that many of the IGWs have horizontal phase speeds faster than that of the tsunami. As the volcanic-originated IGWs spread in cone-shape pattern, it is possible to detect these fast IGWs in the ionosphere earlier than the tsunami waves, reaching the tide gauges or DART buoys. In our study, we could detect the first IGWs at the New Zealand GNSS stations, 2 h earlier than the first registration of the tsunami waves at tide gauges and DART buoys near the New Zealand peninsula, which is located approximately 1.600 km from the Tonga Volcano. It can be concluded that IGWs can be used to warn tsunamis faster than the current early-warning systems, which make use of tide gauges and DART buoys. Furthermore, the spatial variations in ionospheric electron density (IED) were investigated using F7/C2 RO data. The results show that the volcanic-originated IGWs cause reduction in the IED peak value and altitude. The results of IED derived from F7/C2 and SWARM were in good agreement.

Worm-Inspired, Untethered, Soft Crawling Robots for Pipe Inspections.

The increasing demand for inspection, upkeep, and repair of pipeline and tunnel infrastructures has catalyzed research into the creation of robots with superior flexibility, adaptability, and load-bearing capacities. This study introduces an autonomous soft robot designed for navigating both straight and curved pipelines of 90 mm diameter. The soft robot is enabled by an elongation pneumatic actuator (EPA) as its body and multiple radial expansion pneumatic actuators (REPAs) as its feet to provide adhesion and support on the pipe walls. It achieves a horizontal movement speed of 1.27 mm/s and ascends vertically at 0.39 mm/s. An integrated control mechanism, merging both pneumatic and electrical systems is employed to facilitate unrestrained movement. A novel control tactic has been formulated to ensure synchronized coordination between the robot's body deformation and leg anchoring, ensuring stable movement. This soft robot demonstrates remarkable mobility metrics, boasting an anchoring strength of over 100 N, a propelling force of 43.8 N when moving vertically, and a pulling strength of 31.4 N during navigation in curved pipelines. It can carry a camera to capture the internal view of the pipe and remove obstacles autonomously. The unconstrained and autonomous movement of the untethered soft robot presents new opportunities for various applications at different scales.

Observation of meteors from space with the Mini-EUSO detector on board the International Space Station

Context. Observations of meteors in the Earth’s atmosphere offer a unique tool for determining the flux of meteoroids that are too small to be detected by direct telescopic observations. Although these objects are routinely observed from ground-based facilities, such as meteor and fireball networks, space-based instruments come with notable advantages and have the potential to achieve a broad and uniform exposure. Aims. In this paper, we describe the first observations of meteor events with Mini-EUSO, a very wide field-of-view telescope launched in August 2019 from the Baikonur cosmodrome and installed on board the Russian Zvezda module of the International Space Station. Mini-EUSO can map the night-time Earth in the near-UV range (290-130 nm) with a field of view equal to 44° × 44° and a spatial resolution of about 4.7 km at an altitude of 100 km from the ground. The detector saves triggered transient phenomena with a sampling frequency of 2.5 µs and 320 µs, as well as a continuous acquisition at 40.96 ms scale that is suitable for meteor observations. Methods. We designed two dedicated and complementary trigger methods, together with an analysis pipeline able to estimate the main physical parameters of the observed population of meteors, such as the duration, horizontal speed, azimuth, and absolute magnitude. To compute the absolute flux of meteors from Mini-EUSO observations, we implemented a simulation framework able to estimate the detection efficiency as a function of the meteor magnitude and the background illumination conditions. Results. The instrument detected 24 thousand meteors within the first 40 data-taking sessions from November 2019 to August 2021, for a total observation time of approximately 6 days with a limiting absolute magnitude of +6. Our estimation of the absolute flux density of meteoroids in the range of mass between 10−5 kg to 10−1 kg was found to be comparable to other results available in the literature. Conclusions. The results of this work prove the potential for space-based observations to increase the statistics of meteor observations achievable with instruments operating on the ground. The slope of the mass distribution of meteoroids sampled with Mini-EUSO suggests a mass index of either s = 2.09 ± 0.02 or s = 2.31 ± 0.03, according to two different methodologies for the computation of the pre-atmospheric mass starting from the luminosity of each event.

How interchange spacing effects drivers’ visual performance in high-density interchange groups − a naturalistic driving study

The aim of this study was to evaluate the effects of interchange spacing on the visual characteristics and visual load of drivers in the exit zone of the urban expressway. A naturalistic driving experiment was conducted in a high-density interchange group on the North Ring Expressway in Chongqing, China. Eye-movement data from 47 participants were collected to assess the pattern of visual performance, seven indicators were selected to characterize drivers’ visual characteristics, and the entropy weighting method was used to assess the drivers’ visual loads under different interchange spacing and driving zones. The results show that insufficient spacing of the interchange affects drivers’ visual behavior and increases their visual load level. The fixation duration for drivers is significantly affected by interchange spacing, with longer fixation duration in the diversion and ramp zones of small-spacing interchanging(SSI). The mean horizontal visual angle of drivers was mainly distributed in the middle of the field of view, and there was a tendency for the overall left side to be shifted under the conditions of SSI, and the mean vertical visual angle was mainly distributed in the nearer part in front of the lanes. In the ramp zone of SSI, the driver’s attention to the vehicle dashboard had a significant increase. In normal-spacing interchange(NSI), drivers’ horizontal saccade amplitude and speed were higher than those in SSI, and the difference was most significant in the diversion zone. Vertical saccade amplitude and speed of the driver were found to be significantly affected by interchange spacing only in the ramp zone. Drivers’ visual load had the highest correlation with pupil variation, and the visual load scores of drivers at SSI were 39.65% and 17.7% higher than at NSI in the diversion and ramp zones, respectively. This study provides valuable insights into the effects of the high-density interchange group on the visual performance of drivers on urban expressways, and the results provide a theoretical basis for the spacing control of interchanges.

Glacial lakes control ice flow: new insights from satellite SAR PO-SBAS observations in Duiya Glacier, southern Tibetan Plateau

ABSTRACT This study investigates the effects of glacial lakes on the flow velocities of Duiya Glacier, southern Tibetan Plateau, by employing satellite Synthetic Aperture Radar (SAR) Pixel-Offset-Tracking Small-Baseline-Subset (PO-SBAS) technology. Duiya Glacier, which terminates in a lake, exhibits approximately 10 m/yr higher horizontal speed and a higher melting rate with a vertical Non-Surface-Parallel-Flow (nSPF) velocity of – 7 m/yr than those of its land-terminating counterpart – West Duosangpu Glacier. Notably, Duiya Glacier experiences significant seasonal velocity fluctuations with accelerated flow between May and October. By integrating glacier geometry, changes in glacier boundaries and the extent of proglacial lakes, the distribution of supraglacial lakes, and climatic variables, we reveal that proglacial and supraglacial lakes play a crucial role in increasing the flow velocities of Duiya Glacier. Duiya Glacier flows faster because of increased subglacial water pressure resulting from water influx from these lakes. This phenomenon becomes conspicuously evident during May – October, when increased meltwater due to increased temperatures and precipitation further elevates the subglacial water pressure. Our method highlights the potential for understanding the impact of glacial lakes on glacier movements at a large scale, leveraging the capabilities of satellite SAR PO-SBAS technology for continuous, wide-scale, high temporal resolution, and 3D velocity monitoring.

Factors affecting evacuation in intellectually disabled children: An experimental study

Children with intellectual disabilities are considered a vulnerable group in evacuations during emergencies, yet their evacuation needs have not received sufficient attention. To bridge this gap, this study provides one of the very few experimental analyses of the evacuation of intellectually disabled children. Therefore, this study aimed to gather unique evacuation data for intellectually disabled children and identify factors influencing their evacuation process. Two evacuation experiments were conducted on 49 intellectually disabled children aged 7 to 16 from a special education school. Data collected through video recordings include recognition time, response time, pre-movement time, indoor travel speed, horizontal travel speed, and vertical travel speed. This study explored whether and how several key factors (e.g., drill announcement status, sex, age, floor level, and students' dependency behavior) affect the evacuation of intellectually disabled children. Results indicate that drill announcement status significantly affected the recognition time and pre-movement time in intellectually disabled children but did not impact their response time or travel speed. The floor level on which children were located significantly influenced their evacuation process, with children on higher floors showing longer response and pre-movement time and slower indoor travel speed and horizontal travel speed compared to those on the first floor. Additionally, the dependency behavior of these children on teachers significantly influenced their recognition time. Moreover, this dependency behavior tended to be prevalent among intellectually disabled children during emergency evacuations. These findings provide valuable insights for the design of educational buildings tailored to the needs of special populations, evacuation simulation modeling, and the development of building regulations.

Soft Electrohydraulic Bending Actuators for Untethered Underwater Robots

Traditional underwater rigid robots have some shortcomings that limit their applications in the ocean. In contrast, because of their inherent flexibility, soft robots, which have gained popularity recently, offer greater adaptability, efficiency, and safety than rigid robots. Among them, the soft actuator is the core component to power the soft robot. Here, we propose a class of soft electrohydraulic bending actuators suitable for underwater robots, which realize the bending motion of the actuator by squeezing the working liquid with an electric field. The actuator consists of a silicone rubber film, polydimethylsiloxane (PDMS) films, soft electrodes, silicone oils, an acrylic frame, and a soft flipper. When a square wave voltage is applied, the actuator can generate continuous flapping motions. By mimicking Haliclystus auricula, we designed an underwater robot based on six soft electrohydraulic bending actuators and constructed a mechanical model of the robot. Additionally, a high-voltage square wave circuit board was created to achieve the robot’s untethered motions and remote control using a smart phone via WiFi. The test results show that 1 Hz was the robot’s ideal driving frequency, and the maximum horizontal swimming speed of the robot was 7.3 mm/s.

Performance Optimization and Experimental Study of Small-Scale Potato-Grading Device

Traditional potato grading in China relies mostly on manual sorting, which is labor-intensive, time-consuming, costly, and inefficient. To enhance the operational performance of potato-grading devices, this paper focuses on optimizing the slide rail structure, which is the key component of a self-developed first-generation potato-grading device. A five-factor, three-level orthogonal experiment was designed, with the experimental factors being the height of the horizontal slide rail, angle of the first-stage inclined slide, angle of the second-stage inclined rail, chain horizontal movement speed, and conveyor belt speed. The indoor experiments were conducted using grading accuracy and grading efficiency as the experimental indicators. On the basis of the analysis of the orthogonal experiment results, two relatively optimal solutions were obtained, and validation experiments were conducted. The validation results show that when the height of the horizontal slide rail was 185 mm, the angle of the first-stage inclined rail was 4°, the angle of the second-stage inclined rail was 2.5°, the horizontal movement speed of the chain was 700 mm/s, and the movement speed of the conveyor belt was 275.60 mm/s, the performance of the movable rotating plate (MRP)-type grading device for potatoes reached its optimum. At this point, the grading accuracy was 94.88%, and the grading efficiency was 13.9477 t/h. Compared with the first-generation grading device, the optimized grading device achieved an improvement of 3.84% in grading accuracy and 12.94% in grading efficiency. The research methodology provided in this paper serves as a reference for the performance optimization of potato-grading devices.

Chip breakage in silk microfibre production using elliptical vibration turning

To overcome the precision limitation and environmental impact of current chemical-based production methods for manufacturing silk microfibres used for targeted drug delivery, this paper presents a high-precision, scalable, eco-friendly mechanical machining approach to produce such microfibres in the form of discontinuous chips obtained through elliptical vibration turning of silk fibroin film using a diamond tool. The length and waist width of fabricated microfibres can be precisely controlled. As each vibration cycle will produce one silk microfibre, complete and deterministic chip breakage becomes an essential and challenging task in this approach due to its unique two-phase structure. Thus, the hybrid FE-SPH numerical simulations and machining experiments were conducted to gain a pioneering and in-depth exploration of the chip-breaking mechanism in this process. It was found that applying a low depth ratio (ratio of the nominal depth of cut to the tool path vertical amplitude) and a high horizontal speed ratio (the nominal cutting speed versus the critical workpiece velocity) could effectively reduce the average tool velocity angle (the angle from the deepest cut to the tool exit point along the cutting direction). A smaller angle would enhance the diamond tool's shearing action and led to the reduction of hydrostatic pressure in the cutting zone and a consequent decrease in the ductility of silk fibroin due to its unique structure dominated by beta-sheet crystallites. The above adjustments collectively facilitated chip breakage. This paper, therefore, established a governing rule for the controlled and repeatable formation of microfibres based on the average tool velocity angle for the first time and revealed that the cutting chips would undergo complete and deterministic breakages once the angle approached below 22.6°. On this basis, the high-precision and scalable manufacturing of silk microfibres with precisely controllable length and waist width was ultimately achieved.

Older Adult Stair and Walking Speeds from Controlled Trials as Inputs into Simulations of Retirement Home Evacuation

This work aims to add to the current database of human movement data, specifically, 3-stair descent speeds from controlled trials of typically aging older adults (n=212, aged 60-99) with and without mobility impairments. Additionally, to explore the impacts of model input parameters, stair and walking speeds obtained from controlled trials are used to simulate first-iteration Canadian retirement home egress scenarios with Pathfinder. Analysis of descending stair speeds reveal interesting trends and key inter-population variations. Moreover, when the stair and horizontal walking speeds determined from these controlled trials are used as inputs into the illustrative egress simulations, a difference in predicted egress outcomes are seen compared to when model defaults are used. Together, the findings indicate important egress considerations for a vulnerable population.

Optimasi Setting Mesin Cutting roll Menggunakan Design off Experiment (Studi Kasus: CV. Surya Gemilang)

The economic growth of the manufacturing sector in Indonesia is increasing rapidly every year. One that contributes to this economic growth is the textile industry. Along with the growth that occurs, textile companies strive to achieve a more effective and efficient production process, namely by reducing defective products or defects from the production carried out. CV. Surya Gemilang is a company that faces similar problems. CV. Surya Gemilang is a company engaged in the manufacturing industry sector, one of whose products is textile products, namely list webbing. list webbing is a superior product from CV. Surya Gemilang which has collaborated with 4 companies with requests for up to 15 rolls per month per company, where each 1 roll contains approximately 60 list webbing. In the production process list webbing still has a defect value produced after a fairly large production process. One of the factors that cause defective products to occur is the machine used, the machine used for the production of list webbing is a cutting roll machine. For this reason, it is necessary to conduct research using the Design of Experiment method using a Full Factorial Design approach with 2 replications. The factors used are roll rotational speed (rpm), feeding speed (rpm), and horizontal moving blade speed (rpm). This study aims to find factors that have a significant effect and find the optimal cutting roll machine settings to reduce the defects produced. From the results of this study, the factors that have a significant effect are the factor of feeding speed, horizontal speed, and the interaction between the factors of rotating speed and feeding speed and the optimal cutting roll machine settings are rotating speed with a level of 50 rpm, feeding speed with a level of 125 rpm and horizontal speed with a level of 50 rpm

A Linear Theory for Periodic Convectively Forced Gravity Waves near a Coastline

Abstract This study presents a simple 2D linear analytical model aimed at investigating gravity waves forced by temporally periodic convection near a coastline. This investigation encompasses two distinct convective heating scenarios: deep convective heating and stratiform heating/cooling. Our model explores the intricate behavior of gravity waves in proximity to a time-dependent convective source and examines their propagation characteristics across diverse atmospheric conditions. Close to the convective source, gravity waves demonstrate nearly horizontal propagation with vertically aligned phase lines. The velocity of their propagation primarily depends on the vertical scale of the convective heating. The presence of a tropopause further extends their horizontal reach through partial wave ducting between the surface and the tropopause. However, the horizontal scale of the convective heating also plays a crucial role in determining the horizontal wavelength, and consequently, affecting the horizontal propagation speed of the gravity waves. If the heating horizontal scale is small compared to the horizontal scale of free waves at the forcing frequency, the heating vertical scale determines the vertical wavelength and thus the horizontal wavelength. However, if the heating horizontal scale is large, the horizontal wavelength determined by the heating vertical scale has little energy, so that the horizontal wavelength is mainly determined by the heating horizontal scale. Moreover, longer periods of convective heating and stronger background winds contribute to an increased downstream propagation distance of the gravity waves away from the source. Additionally, inertia-gravity waves generated by diurnal convection can propagate horizontally over greater distances at a higher latitude but become confined or trapped at latitudes exceeding 30°.

An Underwater Biomimetic Robot that can Swim, Bipedal Walk and Grasp

In developing and exploring extreme and harsh underwater environments, underwater robots can effectively replace humans to complete tasks. To meet the requirements of underwater flexible motion and comprehensive subsea operation, a novel octopus-inspired robot with eight soft limbs was designed and developed. This robot possesses the capabilities of underwater bipedal walking, multi-arm swimming, and grasping objects. To closely interact with the underwater seabed environment and minimize disturbance, the robot employs a cable-driven flexible arm for its walking in underwater floor through a bipedal walking mode. The multi-arm swimming offers a means of three-dimensional spatial movement, allowing the robot to swiftly explore and navigate over large areas, thereby enhancing its flexibility. Furthermore, the robot’s walking arm enables it to grasp and transport objects underwater, thereby enhancing its practicality in underwater environments. A simplified motion models and gait generation strategies were proposed for two modes of robot locomotion: swimming and walking, inspired by the movement characteristics of octopus-inspired multi-arm swimming and bipedal walking. Through experimental verification, the robot’s average speed of underwater bipedal walking reaches 7.26 cm/s, while the horizontal movement speed for multi-arm swimming is 8.6 cm/s.