Oblique Path Research Articles

UAV-BIM-BEM: An automatic unmanned aerial vehicles-based building energy model generation platform

Many existing and aging buildings were in urgent need of upgrades and renovations, but lack accurate geometric and energy consumption information. This study introduced an unmanned aerial vehicles-based (UAV-based) automated platform for building information modellings (BIM) to generate builidng energy modellings (BEM), which was called the UAV-BIM-BEM platform. The platform enabled the creation of energy models for existing buildings to estimate energy consumption and perform retrofit analysis. A four-story office building in Hong Kong, with dimensions of 52.3 m in length, 14.3 m in width, and 16.5 m in height, was selected as the case study building. Firstly, using UAV oblique photography techniques and path planning algorithms, the building images were transformed into a detailed 3D point cloud model. The point cloud model was provided to Revit to generate the BIM model in IFC format. The IFC file containing the geometric information of the building was then supplied to the AutoBPS-BIM tool, resulting in the generation of the BEM model in EnergyPlus to simulate detailed end-use energy consumption. The annual electricity use intensity (EUI) of the building was estimated to be 145.05 kWh/m2. Lastly, the generated energy model was used to evaluate the energy-saving potential of three different measures. The results showed that the electrical energy savings from cooling equipment, lighting systems, and window replacement are 17.22 %, 6.91 %, and 6.61 %, respectively. This research demonstrated that the UAV-BIM-BEM platform has great potential in BEM modeling for existing buildings and building energy retrofitting.

The allocentric nature of ground-surface representation: A study of depth and location perception

When observers perceive 3D relations, they represent depth and spatial locations with the ground as a reference. This frame of reference could be egocentric, that is, moving with the observer, or allocentric, that is, remaining stationary and independent of the moving observer. We tested whether the representation of relative depth and of spatial location took an egocentric or allocentric frame of reference in three experiments, using a blind walking task. In Experiments 1 and 2, participants either observed a target in depth, and then straightaway blind walked for the previously seen distance between the target and the self; or walked to the side or along an oblique path for 3 m and then started blind walking for the previously seen distance. The difference between the conditions was whether blind walking started from the observation point. Results showed that blind walking distance varied with the starting locations. Thus, the represented distance did not seem to go through spatial updating with the moving observer and the frame of reference was likely allocentric. In Experiment 3, participants observed a target in space, then immediately blind walked to the target, or blind walked to another starting point and then blind walked to the target. Results showed that the end location of blind walking was different for different starting points, which suggested the representation of spatial location is likely to take an allocentric frame of reference. Taken together, these experiments convergingly suggested that observers used an allocentric frame of reference to construct their mental space representation.

A triangle decomposition method for the mobility control of mecanum wheel-based robots

Mobile robots are used in a variety of applications including research, education, healthcare, customer service, security and so on. Based upon the application, the robots employ different locomotion systems for their mobility. When it comes to rolling locomotion, the wheels used to provide mobility to robots can be categorized as: tracks, omnidirectional wheels, and unidirectional wheels with a steering system. The ability of omnidirectional wheels to drive machines in small spaces makes them interesting to use. Among the types of omnidirectional wheels, mecanum wheels are widely used due to their inherent benefits. With the right control strategy, robots equipped with mecanum wheels can move freely, in all possible directions. In this study, a triangle decomposition approach is employed for controlling omnidirectional mecanum wheel-based robots. The method consists of breaking down any path into a set of linear motions that can be horizontal, vertical, or oblique. Furthermore, the oblique paths are divided into smaller segments that can be resolved into a horizontal and vertical component in a right-angle triangle. The suggested control method is tested and proved on a simple scenario using Webots simulation software.

Interface debonding by growth of interface defect ahead of main crack approaching with oblique paths in layered systems

Interface debonding by growth of interface defect ahead of main crack approaching with oblique paths in layered systems

Trabecular bone structure of the proximal capitate in extant hominids and fossil hominins with implications for midcarpal joint loading and the dart-thrower's motion.

This research examines whether the distribution of trabecular bone in the proximal capitates of extant hominids, as well as several fossil hominin taxa, is associated with the oblique path of the midcarpal joint known as the dart-thrower's motion (DTM). We analyzed proximal capitates from extant (Pongo n = 12; Gorilla n = 11; Pan n = 10; fossil and recent Homo sapiens n = 29) and extinct (Australopithecus sediba n = 2; Homo naledi n = 1; Homo floresiensis n = 2; Neandertals n = 3) hominids using a new canonical holistic morphometric analysis, which quantifies and visualizes the distribution of trabecular bone using relative bone volume as a fraction of total volume (rBV/TV). Homo sapiens and Neandertals had a continuous band of high rBV/TV that extended across the scaphoid, lunate, and hamate subarticular regions, but other fossil hominins and extant great apes did not. A. sediba expressed a distinct combination of human-like and Pan-like rBV/TV distribution. Both H. floresiensis and H. naledi had high rBV/TV on the ulnar-side of the capitate but low rBV/TV on the radial-side. The proximal capitates of H. sapiens and Neandertals share a distinctive distribution of trabecular bone that suggests that these two species of Homo regularly load(ed) their midcarpal joints along the full extent of the oblique path of the DTM. The observed pattern in A. sediba suggests that human-like stress at the capito-scaphoid articular surface was combined with Pan-like wrist postures, whereas the patterns in H. floresiensis and H. naledi suggest their midcarpal joints were loaded differently from that of H. sapiens and Neandertals.

A new inclining flight mode and oblique takeoff technique for a tiltrotor aircraft

A new tiltrotor inclining flight mode is presented in the study. Based on this mode, an optimized tiltrotor oblique takeoff technique is designed to improve the flight performance and efficiency in tiltrotor's takeoff operation. First, the proposed inclining flight mode is built through the dynamics analysis of the tiltrotor and related maneuver design and that makes the tiltrotor able to fly along an oblique path with its body line parallel to the flying direction. Then, with this new mode, a tiltrotor oblique takeoff technique and related control program are devised. Third, the shape of takeoff path in the oblique takeoff operation is studied, and an optimized oblique curved path is introduced to further improve the tiltrotor flight performance and efficiency. Simulations are conducted to investigate the effectiveness of the designed inclining flight mode and implemented oblique takeoff procedure in a set of different takeoff paths. It is found that the tiltrotor's flight performance and efficiency are significantly improved in terms of both required takeoff time and energy consumption. Finally, flight tests corresponding to the simulation work are conducted, that prove the effectiveness of the newly designed inclining flight mode and oblique takeoff technique.

On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid

We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The particles are oblate spheroids of aspect ratio $1.5$ and density ratio $1.5$ . Two Galileo numbers are considered, namely $111$ and $152$ , for which a single oblate spheroid follows a steady vertical and a steady oblique path, respectively. In both cases, a strongly inhomogeneous spatial distribution of the disperse phase in the form of columnar clusters is observed, with a significantly enhanced average settling velocity as a consequence. Thus, in contrast to previous results for spheres, the qualitative difference in the single-particle regime does not result in a qualitatively different behaviour of the many-particle cases. In addition, we have carried out an analysis of pairwise interactions of particles in the well-known drafting–kissing–tumbling set-up, for oblate spheroids of aspect ratio $1.5$ and for spheres. We have varied systematically the relative initial position between the particle pair and we have considered free-to-rotate particles and rotationally locked ones. We have found that the region of attraction for both particle shapes, with and without rotation, is very similar. However, significant differences occur during the drafting and tumbling phases. In particular, free-to-rotate spheres present longer drafting phases and separate quickly after the collision. Spheroids remain close to each other for longer times after the collision, and free-to-rotate ones experience two or more collision events. Therefore, we have observed a shape-induced increase in the interaction time which might explain the increased tendency to cluster of the many-particle cases.

Effects of the super-powerful tropospheric western Pacific phenomenon of September–October 2018 on the ionosphere over China: results from oblique sounding

Abstract. Doppler measurements at oblique propagation paths from the city of Harbin, the People's Republic of China (PRC), to 10 high-frequency (HF) radio broadcast stations in the PRC, Japan, Mongolia, and the Republic of Korea captured the response in the ionosphere to the activity of the super typhoon, Typhoon Kong-rey, from 30 September to 6 October 2018. The Harbin Engineering University coherent software-defined radio system generates the database containing the complex amplitudes of the radio signals that have been acquired along 14 propagation paths since 2018. The complex amplitudes are used for calculating the temporal dependences of the Doppler spectra and signal amplitudes, and the Doppler spectra are used to plot the Doppler shift as a function of time, fD(t), for all rays. The scientific objectives of this study are to reveal the possible perturbations caused by the activity of Typhoon Kong-rey and to estimate the magnitudes of wave parameters of the ionospheric plasma and radio signals. The amplitudes, fDa, of the Doppler shift variations were observed to noticeably increase (factor of ∼2–3) on 1–2 and 5–6 October 2018, while the 20–120 min periods, T, of the Doppler shift variations suggest that the wavelike disturbances in the ionosphere are caused by atmospheric gravity waves. The periods and amplitudes of quasi-sinusoidal variations in the Doppler shift, which have been determined for all propagation paths, may be used to estimate the amplitudes, δNa, of quasi-sinusoidal variations in the electron density. Thus, T≈20 min and fDa≈0.1 Hz yield δNa≈0.4 %, whereas T≈30 min and fDa≈0.2 Hz give δNa≈1.2 %. If T≈60 min and fDa≈0.5 Hz, then δNa≈6 %. The periods T are found to change within the 15–120 min limits, and the Doppler shift amplitudes, fDa, show variability within the 0.05–0.4 Hz limits.

Crowdsourced Doppler measurements of time standard stations demonstrating ionospheric variability

Abstract. Ionospheric variability produces measurable effects in Doppler shift of HF (high-frequency, 3–30 MHz) skywave signals. These effects are straightforward to measure with low-cost equipment and are conducive to citizen science campaigns. The low-cost Personal Space Weather Station (PSWS) network is a modular network of community-maintained, open-source receivers, which measure Doppler shift in the precise carrier signals of time standard stations. The primary goal of this paper is to explain the types of measurements this instrument can make and some of its use cases, demonstrating its role as the building block for a large-scale ionospheric and HF propagation measurement network which complements existing professional networks. Here, data from the PSWS network are presented for a period of time spanning late 2019 to early 2022. Software tools for the visualization and analysis of this living dataset are also discussed and provided. These tools are robust to data interruptions and to the addition, removal or modification of stations, allowing both short- and long-term visualization at higher density and faster cadence than other methods. These data may be used to supplement observations made with other geospace instruments in event-based analyses, e.g., traveling ionospheric disturbances and solar flares, and to assess the accuracy of the bottomside estimates of ionospheric models by comparing the oblique paths obtained by ionospheric ray tracers with those obtained by these receivers. The data are archived at https://doi.org/10.5281/zenodo.6622111 (Collins, 2022).

Tunable Multiple Fano Resonance Plasmonic Nanosensor with an Oblique Path in a Pentagonal-Ring-Shaped Resonator

Tunable Multiple Fano Resonance Plasmonic Nanosensor with an Oblique Path in a Pentagonal-Ring-Shaped Resonator

Permeability sets the linear path instability of buoyancy-driven disks

The prediction of trajectories of buoyancy-driven objects immersed in a viscous fluid is a key problem in fluid dynamics. Simple-shaped objects, such as disks, present a great variety of trajectories, ranging from zig-zag to tumbling and chaotic motions. Yet, similar studies are lacking when the object is permeable. We perform a linear stability analysis of the steady vertical path of a thin permeable disk, whose flow through the microstructure is modelled via a stress-jump model based on homogenization theory. The relative velocity of the flow associated with the vertical steady path presents a recirculation region detached from the body, which shrinks and eventually disappears as the disk becomes more permeable. In analogy with the solid disk, one non-oscillatory and several oscillatory modes are identified and found to destabilize the fluid–solid coupled system away from its straight trajectory. Permeability progressively filters out the wake dynamics in the instability of the steady vertical path. Modes dominated by wake oscillations are first stabilized, followed by those characterized by weaker, or absent, wake oscillations, in which the wake is typically a tilting induced by the disk inclined trajectory. For sufficiently large permeabilities, the disk first undergoes a non-oscillatory divergence instability, which is expected to lead to a steady oblique path with a constant disk inclination, in the nonlinear regime. A further permeability increase reduces the unstable range of all modes until quenching of all linear instabilities.

Optimisation of path planning for minimally invasive interventions on prostate using MR-robot: Application to on-live pets

The robot-assisted biopsy system under Magnetic Resonance Imaging (MRI) guidance is a promising candidate for prostate cancer diagnosis in terms of improving the reliability and accuracy of reaching micro-lesions of perineum organ tissues. This has been explored for the last decade. A pre-requisite for effective interventional diagnosis is an accurate intervention planning that is difficult to achieve manually. This is due to multiple factors mainly, the fact that the insertion needles trajectories should avoid organs at risk and limited manoeuvrability, under clinician control. Thus, Biopsy-robot is a feasible solution to improve targeting accuracy. However, the planned trajectories should be consistent with the needle-driven robot's kinematics capabilities. To eliminate these problems, we present an integrated concept composed of MRI-robot and Brachytherapy (BT) path planning algorithm, allowing to minimise the number of entry points of BT needles, from a physical grid to reach all the treatable volume of the prostate gland. This means minimising the number of inserted needles from the perineum, compared to a conventional straight insertion of multiple needles. Indeed, the proposed method is able to set-up safe percutaneous routes defined by a set of oblique straight-line paths linking a minimum number of feasible entry points and desired finite target points, defined within the prostate volume. By adopting such a procedure, the aim is to contribute in minimising tissue damage and patient trauma, and risk of infection, and shortening recovery time. A combinatorial approach is proposed for the minimisation of the insertion point. The development, implementation, and experimental evaluation of the needle path planning method for the 5 Degree of Freedom (DoF) robot guide is presented and performed within a 1.5 Tesla MRI to evaluate how the proposed approach is efficient and reliable on-live pets.

Repetitively burst-spiking neurons in reeler mice show conserved but also highly variable morphological features of layer Vb-fated "thick-tufted" pyramidal cells.

Reelin is a large extracellular glycoprotein that is secreted by Cajal-Retzius cells during embryonic development to regulate neuronal migration and cell proliferation but it also seems to regulate ion channel distribution and synaptic vesicle release properties of excitatory neurons well into adulthood. Mouse mutants with a compromised reelin signaling cascade show a highly disorganized neocortex but the basic connectional features of the displaced excitatory principal cells seem to be relatively intact. Very little is known, however, about the intrinsic electrophysiological and morphological properties of individual cells in the reeler cortex. Repetitive burst-spiking (RB) is a unique property of large, thick-tufted pyramidal cells of wild-type layer Vb exclusively, which project to several subcortical targets. In addition, they are known to possess sparse but far-reaching intracortical recurrent collaterals. Here, we compared the electrophysiological properties and morphological features of neurons in the reeler primary somatosensory cortex with those of wild-type controls. Whereas in wild-type mice, RB pyramidal cells were only detected in layer Vb, and the vast majority of reeler RB pyramidal cells were found in the superficial third of the cortical depth. There were no obvious differences in the intrinsic electrophysiological properties and basic morphological features (such as soma size or the number of dendrites) were also well preserved. However, the spatial orientation of the entire dendritic tree was highly variable in the reeler neocortex, whereas it was completely stereotyped in wild-type mice. It seems that basic quantitative features of layer Vb-fated RB pyramidal cells are well conserved in the highly disorganized mutant neocortex, whereas qualitative morphological features vary, possibly to properly orient toward the appropriate input pathways, which are known to show an atypical oblique path through the reeler cortex. The oblique dendritic orientation thus presumably reflects a re-orientation of dendritic input domains toward spatially highly disorganized afferent projections.

Montaigne: A Very Short Introduction

This compact new study by William Hamlin, professor of English at Washington State and specialist on the English reception of Montaigne, was written for the Oxford series of Very Short Introductions, which claims over 650 titles, very few of which are devoted to French authors. They’ve done Voltaire and Descartes but not (yet) Molière or Proust. Even more scandalously, there’s no volume on Erasmus, but we won’t blame Hamlin for that. His work is organized in nine chapters that cover the main topics and contexts of Montaigne’s Essays, and for each chapter Hamlin has included bibliographical references and suggestions for further reading. A general bibliography and an index round out the volume.The book is obviously aimed at English-language readers with no previous knowledge of Montaigne, but I found it to be an agreeable and profitable use of my time. The whole thing is written in a congenial and unpretentious style that makes it quite readable and even worthy of Montaigne himself, which is no small praise. Hamlin knows the Essays from cover to cover, and he is a reliable and unobtrusive guide to an endlessly fascinating topic. I especially recommend chapter 5 on “sociable solitude,” which is an oxymoron quite suited to the Essays and captures one of the characteristic intricacies of Montaigne’s thought.Very short introductions of this sort are certainly not meant to be polemical (Erasmus would never have written one, but he still deserves his own volume), and it may seem petty to find fault, but I will allow myself one criticism (just to honor the convention of the one-criticism review). Hamlin tends to emphasize what he calls “Montaigne’s devotional identity” (84) as a limit to his skepticism, and he goes to what may seem unseemly lengths to verify the genuineness of Montaigne’s religious faith, which results in a more pious essayist than may suit some of us. Yet it’s hard to argue with a book that so thoroughly assimilates the spirit of Montaigne in its undogmatic exposition of the oblique path the reader must follow to know Montaigne. All students and teachers of Montaigne should be grateful to William Hamlin for the thorough justice he does to one of the greatest achievements of our literary tradition.

On the use of high-frequency surface wave oceanographic research radars as bistatic single-frequency oblique ionospheric sounders

Abstract. We demonstrate that bistatic reception of high-frequency oceanographic radars can be used as single-frequency oblique ionospheric sounders. We develop methods that are agnostic of the software-defined radio system to estimate the group range from the bistatic observations. The group range observations are used to estimate the virtual height and equivalent vertical frequency at the midpoint of the oblique propagation path. Uncertainty estimates of the virtual height and equivalent vertical frequency are presented. We apply this analysis to observations collected from two experiments run at two locations in different years, but utilizing similar software-defined radio data collection systems. In the first experiment, 10 d of data were collected in March 2016 at a site located in Maryland, USA, while the second experiment collected 20 d of data in October 2020 at a site located in South Carolina, USA. In both experiments, three Coastal Oceanographic Dynamics and Applications Radars (CODARs) located along the Virginia and North Carolina coast of the US were bistatically observed at 4.53718 MHz. The virtual height and equivalent virtual frequency were estimated in both experiments and compared with contemporaneous observations from a vertical incident digisonde–ionosonde at Wallops Island, VA, USA. We find good agreement between the oblique CODAR-derived and WP937 digisonde virtual heights. Variations in the virtual height from the CODAR observations and the digisonde are found to be nearly in phase with each other. We conclude from this investigation that observations of oceanographic radar can be used as single-frequency oblique incidence sounders. We discuss applications with respect to investigations of traveling ionospheric disturbances, studies of day-to-day ionospheric variability, and using these observations in data assimilation.

Investigation of Two Prediction Models of Maximum Usable Frequency for HF Communication Based on Oblique- and Vertical-Incidence Sounding Data

As one of the key technologies of HF communication, the maximum usable frequency (MUF) prediction method has been widely discussed. To experimentally confirm the reliability of commonly used MUFs prediction models for high-frequency communication, we have compared maximum observed frequencies (MOFs) and predicted MUFs to assess the accuracy of two typical prediction models. The root-mean-square error (RMSE) and relative RMSE (RRMSE) between oblique sounding MOFs and the predicted MUFs were used to assess the model’s accuracy. The oblique sounding path was from Changchun to Jinyang, and the vertical-sounding ionosonde was located in Beijing, which was approximately the midpoint of the oblique sounding circuit. The statistical analysis results show that: (a) the trend of prediction results from the Lockwood and the Istituto Nazionale di Geofisica e Vulcanologia (INGV) model are in good agreement with the observations: the mean RMSE and RRMSE of the INGV model are less than those of the Lockwood model; (b) in the four different periods (sunrise, daytime, sunset, and nighttime) of the whole day, the maximum difference of RMSE between the Lockwood and INGV model is 0.14 MHz (the INGV performs better than the LWM), with the corresponding differences of RRMSE being 0.31% at sunrise and 0.68% at daytime; (c) in the four seasons of spring, summer, autumn, and winter, the minimum RMSE values of the Lockwood and INGV models are 1.51 MHz and 1.37 MHz, respectively, which are obtained in winter, and the corresponding RRMSEs are 11.47% and 11.79%, respectively; (d) in the high and low solar activity epochs, the mean RMSEs of the Lockwood and INGV models are 1.63 MHz, and 1.54 MHz, with corresponding mean RRMSE values of 11.47% and 11.55%. In conclusion, the INGV model is more suitable for MUF prediction over Beijing and its adjacent mid-latitude regions from the RMSE comparison of the two models.

Path instabilities of a freely rising or falling sphere

Path instabilities of a sphere rising or falling in a quiescent Newtonian fluid have been studied experimentally. The rich palette of possible instabilities is dependent upon two dimensionless quantities, namely the Galileo number (Ga) and the particle/fluid mass density ratio (ρ¯). In recent literature, several (Ga,ρ¯) regime maps have been proposed to characterize path instabilities, based on both numerical and experimental studies, with substantial disagreements among them. The present study attempts to shed light on path instabilities for which previous studies disagree. A detailed experimental investigation has been conducted for 219 different combinations of Ga and ρ¯, grouped around four values of ρ¯ (∼ 0.87, 1.12, 3.19 and 3.9) and Ga in the range of ∼ 100 to 700. Our results agree well with literature for the low Ga range in which a particle takes a steady vertical or steady oblique path and for which all previous studies agree with each other. For the higher and more controversial Ga range, we discuss consensus and disagreements with previous studies. Some regimes, which were only recently observed in numerical simulations, have been observed experimentally for the first time. Also, intriguing bi-stable regimes (i.e., coexistence of two stable asymptotic states) have been observed. For all four investigated density ratios, an update of the regime map is proposed. Finally, for both the rising and falling spheres, the drag coefficient as function of terminal settling Reynolds number has been determined, which for the investigated density ratios does not differ significantly from that of flow past a fixed sphere.

Design of a high-resolution fluorescence imaging system with oblique right angle optical path and ring-shaped beams

We theoretically demonstrate a high-resolution fluorescence imaging scheme with configurations of oblique right angle optical path and ring-shaped excitation and fluorescent beams. The oblique right angle optical path configuration with two orthogonally aligned objective lenses over the specimen. It has strong abilities to eliminate the imaging stacking process in depth direction, to enhance the fluorescent collection efficiency, to improve the resolution, and to simplify the architecture of the fast fluorescent imaging system. Based on the Fourier domain model simulation, it is verified that the ring-shaped beams can further improve the imaging depth and resolution. The axial resolution can be optimized to 472 nm, the lateral resolution can be improved to 275 nm; meanwhile, the system can have an imaging depth of 398 μm.

MITIGATOR: GNSS-Based System for Remote Sensing of Ionospheric Absolute Total Electron Content

Monitoring the Earth’s ionosphere is an important, fundamental and applied problem. Global Navigation Satellite Systems (GNSS) provide a way of measuring the ionospheric total electron content (TEC), but real-time single-station absolute TEC measurements are still a problem. This study describes a single-station system to measure the absolute TEC, based on the GNSS–MITIGATOR (MonITorInG the Absolute TOtal electRon content) system. The latter enables real-time measurements for the absolute TEC and its derivatives in time and in space to be obtained. The system is implemented by using JAVAD receivers. The convergence time and the run-mode retention time is ~8 h. We provide potential methods for using the system to estimate the critical frequency of the ionosphere, foF2, at oblique paths in the Siberian region. The developed tool could be useful for supporting real-time multi-instrumental ionosphere monitoring or for compensating for the ionospheric errors of radio equipment.

Error Correction of Water Vapor Radiometers for VLBI Observations in Deep-Space Networks

In this paper, we present the design and implementation tests of a water vapor radiometer (WVR) suitable for very long baseline interferometry (VLBI) observation. We describe the calibration method with an analysis of the sources of measurement errors. The experimental results show that the long-term measurement accuracy of the brightness temperature of the water vapor radiometer can reach 0.2 K under arbitrary ambient conditions by absolute calibration, receiver gain error calibration, and antenna feeder system temperature noise error calibration. Furthermore, we present a method for measurements of the calibration error of the oblique path measurement. This results in an oblique path wet delay measurement accuracy of the water vapor radiometer reaching 20 mm (within one month).