A New Multidimensional Repulsive Potential Field to Avoid Obstacles by Nonholonomic UAVs in Dynamic Environments

The ability of autonomous flight with obstacle avoidance should be a fundamental feature of all modern unmanned aerial vehicles (UAVs). The complexity and difficulty of such a task, however, significantly increase in cases combining moving obstacles and nonholonomic UAVs. Additionally, since they assume the symmetrical distribution of repulsive forces around obstacles, traditional repulsive potential fields are not well suited for nonholonomic vehicles. The limited maneuverability of these types of UAVs, including fixed-wing aircraft, requires consideration not only of their relative position, but also their speed as well as the direction in which the obstacles are moving. To address this issue, the following work presents a novel multidimensional repulsive potential field dedicated to nonholonomic UAVs. This field generates forces that repulse the UAV not from the obstacle’s geometrical center, but from areas immediately behind and in front of it located along a line defined by the obstacle’s velocity vector. The strength of the repulsive force depends on the UAV’s distance to the line representing the obstacle’s movement direction, distance to the obstacle along that line, and the relative speed between the UAV and the obstacle projected to the line, making the proposed repulsive potential field multidimensional. Numerical simulations presented within the paper prove the effectiveness of the proposed novel repulsive potential field in controlling the flight of nonholonomic UAVs.

Experimental investigation of combinational fans influencing on the effective ventilation in an undersea metro interval tunnel

Based on the metro undersea interval from Wawuzhuang Station to Guizhou Road Station of Qingdao Metro Line 1, a physical model system is built for the sake to further study the Ventilation and Smoke Exhaust System (VSES) of this interval tunnel. In the VSES experimental system, it gains data of variable frequencies inputting to fans, consumed-power values of fans, velocities in carriageways and SEDs (Smoke Exhaust Ducts), static pressure in carriageways under the conditions of the TP (Two Pressing-in) and TP+OE (Two Pressing-in + One Extracted-out) combinations of fans. The experimental data are shown that the static pressure field in horizontal carriageways has a symmetrical distribution, whose symmetry axis is as the plane of a smoke ceiling, whether TP or TP+OE. Under the TP+OE, the velocities in SEDs and carriageways are influenced dominantly by an extracted-out fan; two pressing-in fans of the TP combination influence mainly those velocities. A velocity is capable to dilute and coerce a smog flue. The pushing force of the smog flue is supplied by a pressing-in fan with consumed-power values, and another pressing-in fan with the lower values prevents this flue from another carriageway; furthermore, the pulling force of this flue is supplied by an extracted-out fan with the largest consumed-power values. The ratio of the total values of fans to the discharged volume flow rates in both SEDs is proposed as a new criterion, which can quantify VSES performance and is equivalent to airflow pressure; it is shown that the VSES performance of the TP+OE combination promotes gradually and becomes superior to one of the TP. Finally, it is advisory that the TP+OE should be a preferential combination of fans in designs and engineering situ management of extra length and large section tunnel ventilation.

A case report of generalised eruptive syringoma: a rare variant of syringoma

<p class="abstract">Syringomas are benign adnexal neoplasm of eccrine sweat duct usually affecting adult women. They present as firm, skin coloured to yellowish papules in a symmetrical distribution over periorbital region. Eruptive syringomas are infrequent and usually appear at uncommon sites. Herein, we report a case of a 21-year old girl with eruptive syringomas with an extensive involvement.</p>

Dynamic Gait Parameters in Patients with Nonunion of the Tibia Following Treatment with the Ilizarov Method

INTRODUCTION: The purpose of this study was a comprehensive assessment of the dynamic parameters of gait in patients who underwent Ilizarov treatment for nonunion of the tibia. MATERIALS AND METHODS: The experimental group consisted of24 individuals treated with the Ilizarov method for nonunion of the tibia.The control group comprised31healthy individuals,matched for BMI,sex,and age.The dynamic gait parameters in patients and in the control group were measured with a Zebris pedobarographic platform. RESULTS: The treatment group and the control group showed statistically significant differences in terms of the following gait parameters:Maximum force 1NOL(non-operated-limb),Time maximum force1OL(operated-limb),Time maximum force 1 NOL,Maximum force 2NOL,Time maximum force 2OL,and Maximum force forefoot OL.Most of the evaluated gait parameters were bilaterally similar in patients group.The only significant differences between the operated and non-operated limb were seen in terms of Time maximum force 2and Maximum force forefoot. CONCLUSIONS: The most pronounced abnormalities in dynamic gait parameters were observed in the forefoot.The patients treated with the Ilizarov method did not achieve a complete normalization of dynamic gait parameters,as their gait parameters did not equal those measured in the control group.The Ilizarov method for the treatment of tibial nonunion helps restore a symmetrical distribution of gait parameter values between the affected limb and the healthy limb.Patients with tibial nonunion treated with the Ilizarov method continue to show some abnormalities in their dynamic gait parameters after treatment.

Half-leaf width symmetric distribution reveals buffering strategy of Cunninghamia lanceolata

Background Leaf length and width could be a functioning relationship naturally as plant designs. Single-vein leaves have the simplest symmetrical distribution and structural design, which means that fast-growing single-vein species could interpret the scheme more efficiently. The distribution of leaf length and width can be modulated for better adaptation, providing an informative perspective on the various operational strategies in an emergency, while this mechanism is less clear. Here we selected six age groups of Cunninghamia lanceolata pure forests, including saplings, juveniles, mature, and old-growth trees. We pioneered a tapering model to describe half-leaf symmetric distribution with mathematical approximation based on every measured leaf along developmental sequence, and evaluated the ratio of leaf basal part length to total length (called tipping leaf length ratio). Results The tipping leaf length ratio varied among different tree ages. That means the changes of tipping leaf length ratio and leaf shape are a significant but less-noticed reflection of trees tradeoff strategies at different growth stages. For instance, there exhibited relatively low ratio during sapling and juvenile, then increased with increasing age, showing the highest value in their maturity, and finally decreased on mature to old-growth transition. The tipping leaf length ratio serves as a cost-benefit ratio, thus the subtle changes in the leaf symmetrical distribution within individuals reveal buffering strategy, indicating the selection for efficient design of growth and hydraulic in their developmental sequences. Conclusions Our model provides a physical explanation of varied signatures for tree operations in hydraulic buffering through growth stages, and the buffering strategy revealed from leaf distribution morphologically provides evidence on the regulation mechanism of leaf biomechanics, hydraulics and physiologies. Our insight contributes greatly to plant trait modeling, policy and management, and will be of interest to some scientists and policy makers who are involved in climate change, ecology and environment protection, as well as forest ecology and management.

Hotspot Detection and Spatiotemporal Evolution of Catering Service Grade in Mountainous Cities from the Perspective of Geo-Information Tupu

Catering services are an essential part of urban life. The spatial structure and evolution of catering services can reflect the characteristics of an urban structure to a certain extent. In this study, we selected the main urban area of Chongqing, a typical mountainous city, as the research area. According to data sources for 200,000 catering POI data points in 2015 and 2020, we extracted the hotspots according to catering service grade based on kernel density. We quantitatively analyzed the spatiotemporal structure of catering services in the mountainous city. In addition, we used digital field hierarchical structure Tupu and generalized symmetric structure Tupu to identify the spatial morphology and evolution characteristics to enhance the understanding of geoscience trends. The results showed that (1) the distribution of catering services was statically consistent with the “multi-center group” distribution of the mountainous city and dynamically similar to the “sprawling leap” development of the mountainous city where it developed from independent points to cross mountains and rivers. Moreover, we found that there was a tendency of adhering development between groups. (2) From the perspective of symmetrical distribution, the symmetrical distribution of the catering industry reflected a certain generalized symmetrical structure with mountains and rivers in the mountainous city. Furthermore, the city tended to develop symmetrically along the topography, thus forming the symmetry of economic geography.

Gianotti-Crosti syndrome: a challenging exanthema

Gianotti-Crosti syndrome (GCS) is a self-limited condition, mainly affecting children younger than 6 years, less common in adolescents and adults. It consists of a viral exanthema with papular lesions with a flat top and symmetrical distribution, affecting predominantly extremities, gluteal region and extensor surfaces. It is often associated with viral infections but can also be related to bacterial infections, vaccination or be idiopathic. In this report, we present a case of GCS in a 13-year-old healthy female adolescent who presented with fever, odynophagia, prostration and diffuse maculopapular rash. The diagnosis of infectious mononucleosis due to infection by the Epstein-Barr virus was established. On the second week of the disease, a clinical recrudescence occurred, with worsening of the fever and modification of the exanthema characteristics. GCS is often an underdiagnosed entity. The differential diagnosis of viral exanthema can prove to be challenging and clinical suspicion is essential to achieve the diagnosis.

Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

We have demonstrated that adsorption of silica nanoparticles at the interface of a solubilizing oil droplet in surfactant solution can significantly accelerate the droplets’ self-propulsion speed. Using fluorescent particle visualization, we correlated the degree of particle surface coverage on bromodecane droplets to the droplet speed in TX surfactant. Slowest speeds were found at the lowest and highest surface coverages and the fastest speeds were achieved at intermediate surface coverages of about 40%. The particle-assisted propulsion acceleration was further demonstrated in nonionic, anionic, and cationic surfactants and a range of oils with varying solubilization rates. We propose that particles at the droplet interface hinder solubilization by displacing oil-water interfacial area, providing asymmetry in the distribution of oil-filled micelles along the droplet surface and accelerating Marangoni flow. We describe a fluid-mechanical model to rationalize the effect of the particles by considering the effect of a non-symmetrical distribution of solubilized oil at the droplet surface. Approaches by which to modulate the distribution of solubilization across droplet interfaces may provide a facile route to tuning active colloid speeds and dynamics. <br>

Transmembrane phospholipid translocation mediated by Atg9 is involved in autophagosome formation

The mechanism of isolation membrane formation in autophagy is receiving intensive study. We recently found that Atg9 translocates phospholipids across liposomal membranes and proposed that this functionality plays an essential role in the expansion of isolation membranes. The distribution of phosphatidylinositol 3-phosphate in both leaflets of yeast autophagosomal membranes supports this proposal, but if Atg9-mediated lipid transport is crucial, symmetrical distribution in autophagosomes should be found broadly for other phospholipids. To test this idea, we analyzed the distributions of phosphatidylcholine, phosphatidylserine, and phosphatidylinositol 4-phosphate by freeze-fracture electron microscopy. We found that all these phospholipids are distributed with comparable densities in the two leaflets of autophagosomes and autophagic bodies. Moreover, de novo–synthesized phosphatidylcholine is incorporated into autophagosomes preferentially and shows symmetrical distribution in autophagosomes within 30 min after synthesis, whereas this symmetrical distribution is compromised in yeast expressing an Atg9 mutant. These results indicate that transbilayer phospholipid movement that is mediated by Atg9 is involved in the biogenesis of autophagosomes.