Tight Space Research Articles

A Mixed Fast-RRT*-A* To Solve the Problem of Generating Nodes near Obstacles for Optimal Paths

In the robot environment with static obstacles, robots designed to avoid obstacles and move from the initial position to the destination position, the consumption of the minimum value and the search for the shortest path as the current research, most of the studies are based on obstacle detection to search for more than one path planning. The path using path planning has two sampling methods based on which by working according to random nodes while searching based on using heuristics to find the path. Fast-RRT*-A* were to optimize a path with fast time intensity. From Fast-RRT* developed with improvement-RRT with optimal fast, namely fast optimal in an unreachable space from random trees introduced for speed and algorithm stability; (2) Random steering is used in expansion to solve performance problems in tight spaces; (3) Path fusion path adjustments are obtained quickly. The results of this study are in the form of a profit map comparing the three PRC algorithms* with a time of 48.6474, A* with a time of 38.7527, and FastRRT*-A* with a time of 10.1411, So these three steps make Fast- RRT*-A*.

PBL in the space-time continuum for engineering education

ABSTRACT This article presents how Problem- and Project-Based Learning (PBL) in engineering education can exploit the theoretical framework of the Space–Time (ST)-Continuum, according to which educational contexts can be classified in terms of the tightness vs. looseness of the relevant conceptual space S and available time T. By crossing these two dimensions, four quadrants are obtained in the ST-Continuum: tight space and tight time, loose space and tight time, tight space and loose time, loose space and loose time. Different pedagogies are adaptive to different quadrants. We show how PBL can be mapped onto the ST-Continuum depending on the context characteristics or the chosen problem or project. Further, this article discusses how the intelligence and creativity constructs can be developed through diverse educational scenarios, giving examples of PBL interventions that can be located in different quadrants. Moreover, the analysis shows how through suitable planning, it is possible to have educational activities that consider all the quadrants of the ST-Continuum, even in traditional education curricula or teacher-centered approaches. Finally, the article discusses how teaching practices can promote intelligence and creativity in the curricula at different PBL organisational levels depending on their relationship with the ST-Continuum.

Design and adaptive control of a kinematically redundant robot with enhanced trajectory tracking for climbing in tight spaces

This work investigates the design and adaptive control of a miniature robot with multi-modal locomotion which has the ability to climb inside train bogies for inspection purposes. We propose and analyse a kinematically redundant mechanism with six 2-DOF couple joints. The robot can squeeze through narrow spaces and also climb on surfaces with transitions, irregularities and discontinuities. The unique design allows desirable self-motion close to obstacles but imposes strict requirements in motion control and precise path following. This paper applies such redundancy and self-motion by constructing an adaptive controller with time-varying safety constraints for all twelve joints of the mechanism. The control strategy relies on the time-varying Barrier Lyapunov Function to bound the trajectory error. It also deploys an adaptive radial basis function neural network to estimate the system parameters of the robot. Various simulation experiments show that the proposed controller satisfies all safety and physical joint constraints. It also minimises trajectory tracking error irrespective of initial conditions, disturbances, and unmodelled dynamic effects. Finally, we compare the tracking results with those obtained by a Feedback Linearisation controller and a Quadratic Lyapunov Function-based controller. Results demonstrate enhanced locomotion and trajectory tracking for collision-free manoeuvring in tight spaces. • A novel miniature wall-climbing robot for inspection in the rolling stock industry. • The proposed robot is bipedal with multi-modal locomotion. • The couple joints have been utilised to reach a compact and tiny design. • Intelligent time-varying-barrier-Lyapunov-based controller for wall-climbing robot. • A safe and collision motion planning in the tight space.

Countable tightness and the Grothendieck property in Cp-theory

The Grothendieck property has become important in research on the definability of pathological Banach spaces [4], [9], and especially [10]. We here answer a question of Arhangel'skiĭ by proving it undecidable whether countably tight spaces with Lindelöf finite powers are Grothendieck. We answer another of his questions by proving that PFA implies Lindelöf countably tight spaces are Grothendieck. We also prove that various other consequences of MAω1 and PFA considered by Arhangel'skiĭ, Okunev, and Reznichenko are not theorems of ZFC.

S2841 Ileo-Rectal Anastomotic Defect Treated Twice With Endoscopic Tack Suture System and Stenting

Introduction: The endoscopic tack suture system is a novel technique that includes a through the scope (TTS) suture-based device that was recently designed for the closure of large and irregular defects in the gastrointestinal tract. Choice of closure device depends on the location, size, and working space around the defect. Over-the-scope clips (OTSC) and endoscopic suturing devices require withdrawal of the scope to load and are harder to maneuver through smaller spaces such as strictures. The TTS tack suturing system prevents the need to withdraw the scope and can be deployed in very small spaces. We present a case of a recurrent post-surgical leak leading to wound dehiscence and enterocutaneous fistula of an ileorectal anastomosis associated with a stenosis requiring the tack suture device and stenting for closure. Case Description/Methods: A 60-year-old woman was admitted after a recent subtotal colectomy with ileo-colonic anastomosis for a large adenoma that was unable to be resected endoscopically. She developed a pelvic abscess and wound dehiscence. She underwent exploratory laparoscopy with resection of the anastomosis with end-ileostomy creation. She later underwent open ileostomy reversal with ileo-rectal anastomosis and drain placement. Output continued from both the drain and the midline incision. Colonoscopy showed a large defect in the ileo-rectal anastomosis that was 40% circumferential with significant stenosis. The tack suturing system was employed after argon plasma coagulation (APC) and a fully covered esophageal stent was deployed across the defect (Figure A). During repeat colonoscopy, the initial tack and suturing device was found to be in place on the ileal mucosa, but two tacks had dislodged from the colonic mucosa. An improved small, well defined, round defect was found at the anastomosis (Figure B). The defect was again treated with APC, tack suturing, and stent placement with subsequent resolution of symptoms (Figure C). Discussion: This case highlights the novel tack suturing system which ultimately prevented this patient from undergoing further operations and requiring a colostomy. The tack suture system is an ideal tool for defect closure in tight spaces where OTSC or endoscopic suturing are too bulky. Mahmoud et al. conducted the first and only multi-center study describing the feasibility and safety of the endoscopic tack suturing device in the clinical setting and found successful closure of defects in approximately 90% of cases.Figure 1.: (A) Tack placement following APC at anastomotic defect. (B) Initial tack suture with 2 tacks dislodged from colonic mucosa and small improved defect in anastomosis. (C) Tack placement for closure of persistent defect.

Design and Motion Planning for a Reconfigurable Robotic Base

A robotic platform for mobile manipulation needs to satisfy two contradicting requirements for many real-world applications: A compact base is required to navigate through cluttered indoor environments, while the support needs to be large enough to prevent tumbling or tip over, especially during fast manipulation operations with heavy payloads or forceful interaction with the environment. This paper proposes a novel robot design that fulfills both requirements through a versatile footprint. It can reconfigure its footprint to a narrow configuration when navigating through tight spaces and to a wide stance when manipulating heavy objects. Furthermore, its triangular configuration allows for high-precision tasks on uneven ground by preventing support switches. A model predictive control strategy is presented that unifies planning and control for simultaneous navigation, reconfiguration, and manipulation. It converts task-space goals into whole-body motion plans for the new robot. The proposed design has been tested extensively with a hardware prototype. The footprint reconfiguration allows to almost completely remove manipulation-induced vibrations. The control strategy proves effective in both lab experiment and during a real-world construction task.

Locomotion via Active Suction in a Sea Star-Inspired Soft Robot

Some marine animals, such as sea stars, have developed versatile adhesive appendages that can be used for a variety of behaviors including sticking to surfaces, manipulating objects, and locomoting. These appendages couple reversible adhesion capabilities with muscular structures that can do work on the world while still being soft enough to conform to various surfaces and to squeeze through tight spaces. We took inspiration from the hydraulic tube feet of sea star to create modules consisting of soft active suction discs and soft pneumatic linear actuators. Tube feet convert fluid motion into linear actuation using soft tubes that are constrained radially. In this work, we study the tradeoff between the stiffness of such radial constraints, and the ability of the linear actuators to apply axial forces. The adhesive force of the suction disc is dependent on both the pressure differential between the suction cavity and the environment and the deformation within the body of the disc while it is being loaded. We show that the tube foot modules are capable of creating locomotion over flat surfaces, up small steps, and in a confined space due to the redundancy caused by an array of actuators. We also show that active suction not only enables the use of softer tube foot actuators, but that sensing this active suction line provides feedback to increase the efficiency of locomotion over obstacles.

On the existence of supporting broken book decompositions for contact forms in dimension 3

We prove that in dimension 3 every nondegenerate contact form is carried by a broken book decomposition. As an application we obtain that on a closed 3-manifold, every nondegenerate Reeb vector field has either two or infinitely many periodic orbits, and two periodic orbits are possible only on the tight sphere or on a tight lens space. Moreover we get that if M is a closed oriented 3-manifold that is not a graph manifold, for example a hyperbolic manifold, then every nondegenerate Reeb vector field on M has positive topological entropy.

Wideband Dual-Polarized Hollow-Waveguide Slot Array Antenna

A wideband dual-polarized slot array antenna based on hollow waveguide (HW) is presented in this article. Its wide bandwidth and high performance are enabled by two separate feeding networks, from the side and the bottom, using square coaxial line and ridge waveguide structures, respectively. The full-corporate-feed networks excite the radiation slots in a one-to-one fashion without using backed cavities. Tight element spacing is made possible, suppressing the grating lobe and maintaining high cross-polarization discrimination (XPD) across the wideband. This resolves a usual tradeoff between bandwidth and grating lobe. A double-ridge rectangular waveguide cavity is devised as an orthogonal mode splitter for isolation enhancement. Several design features are used to minimize the signal path length and facilitate routing. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> element prototype in K-band is designed, fabricated, and measured. Experimental results show that the antenna has a wide bandwidth of 23.4% (from 17 to 21.5 GHz) free from grating lobes. More than 25.5 dBi peak gain higher than 51.2 dB isolation and over 43.6 dB XPD are also obtained for the dual polarizations.

Miniatured Fabry-Perot strain probe based on anti-resonant hollow core fiber

A novel miniature Fabry-Perot strain probe based on anti-resonant hollow core fiber (ARHCF) is proposed and experimentally demonstrated, which is fabricated by sandwiching a ARHCF between a single-mode fiber (SMF) and a multi-mode fiber (MMF). Two fusion points of the three optical fibers have been worked as mirrors to form a Fabry-Perot interferometer (FPI). The experimental results agree well with the simulation results. The ARHCF differs from the previous hollow core fiber (HCF) by obtaining high-resolution reflection spectra even when the air hole collapses during fiber fusion. By taking advantage of the insensitivity of ARCHF to temperature and refractive index (RI), the FPI is made small enough to work in tight spaces with high temperature (up to 1000 ℃) and humidity, which is unmatched by some previous transmissive strain sensors that are subject to multiparameter cross-sensitivity. This sensor provides new strategies and ideas for the development of strain sensors.

Nucleus size and its effect on nucleosome stability in living cells

DNA architectural proteins play a major role in organization of chromosomal DNA in living cells by packaging it into chromatin, whose spatial conformation is determined by an intricate interplay between the DNA-binding properties of architectural proteins and physical constraints applied to the DNA by a tight nuclear space. Yet, the exact effects of the nucleus size on DNA-protein interactions and chromatin structure currently remain obscure. Furthermore, there is even no clear understanding of molecular mechanisms responsible for the nucleus size regulation in living cells. To find answers to these questions, we developed a general theoretical framework based on a combination of polymer field theory and transfer-matrix calculations, which showed that the nucleus size is mainly determined by the difference between the surface tensions of the nuclear envelope and the endoplasmic reticulum membrane as well as the osmotic pressure exerted by cytosolic macromolecules on the nucleus. In addition, the model demonstrated that the cell nucleus functions as a piezoelectric element, changing its electrostatic potential in a size-dependent manner. This effect has been found to have a profound impact on stability of nucleosomes, revealing a previously unknown link between the nucleus size and chromatin structure. Overall, our study provides new insights into the molecular mechanisms responsible for regulation of the nucleus size, as well as the potential role of nuclear organization in shaping the cell response to environmental cues.

Low Tree Vigor, Free Palmette Training Form, and High Planting Density Increase Olive and Oil Yield Efficiency in Dry, Sloping Areas of Mediterranean Regions

Exploiting biodiversity must be considered today an effective strategy to improve the sustainability of olive production systems. The evaluation of local cultivars, based on their vegetative and fruiting traits, along with an analysis of product quality, may contribute significantly to the development and diffusion of new olive-growing systems. The aim of this study was to evaluate growth, productivity, and olive oil quality of three Sicilian cultivars with different vigor/growth habit grown in four different combinations of training form and planting density. ‘Abunara’, ‘Calatina’, and ‘Nocellara del Belice’ olive trees were planted in four different intensive planting systems: 2 × 5 m trained to central leader (CLx2), 3 × 5 m trained to free palmette (FPx3), 4 × 5 m trained to small globe vase (GVx4), and 5 × 5 m trained to poly-conic vase (PVx5) and evaluated for seven years. Planting systems with low-density showed faster growth (trunk cross section area and canopy volume) than high-density systems. High-density systems had higher yield per hectare but lower yield per tree than low-density systems. ‘Calatina’ was the least vigorous but most productive cultivar. ‘Abunara’ and ‘Nocellara’ were relatively vigorous and suffered the tight spacings of high-density systems. Yield efficiency was generally high in ‘Calatina’, and it showed an increase with time in ‘Abunara’ and ‘Nocellara’ grown under the GVx4 and PVx5 systems. Fruit yield per hectare was highest in ‘Calatina’ grown under high-density systems. Oil yield was lower in ‘Nocellara’ than in ‘Abunara’ and ‘Calatina’. In terms of oil quality, ‘Calatina’ and ‘Abunara’ produced oils with higher oleic acid content than ‘Nocellara’. Generally, ‘Calatina’ has production characteristics of considerable interest, which, combined with low canopy volume and vigor, make it suitable for intensive pedestrian olive orchards with high levels of harvest and pruning mechanization and using different strategies and machines. Overall, for their management flexibility, these planting systems can contribute to improve sustainability of the olive industry even in sloping, dry areas of the Mediterranean.

Improving Performance and Access to Difficult-to-Reach Anatomy with a Powered Articulating Stapler.

BackgroundModern surgical staplers should provide precise placement and transection, especially in tight spaces and on thick tissue. Ideally, a stapler would move to accommodate variations in the tissue and anatomy instead of having to move the tissue around to fit the stapler. This study was undertaken to evaluate the performance characteristics of the new Echelon 3000 Stapler (ECH3). Use of the ECH3 was compared to another marketed stapler, including tests for access, seal strength, staple formation in thick tissue, and end effector stability.MethodsPelvic anatomy measurements were used to construct a virtual model of a Low Anterior Resection (LAR). Monte Carlo simulations were performed on the staplers to compare the probability of completing a transection with one or two firings. Using water infusion of stapled porcine ileum, pressure at first leak and percentage of leaks at critical pressures were measured. Rate of malformed staples was measured in thick tissue. End effector stability while firing and under moderate pressure were compared between staplers. After use, surgeons were surveyed on the functionality of the device.ResultsECH3 had a markedly higher probability of completing an LAR transection in one or two firings than the comparator stapler. Median initial leak pressure of stapled ileum was significantly higher, and rate of leaks was lower at 40 and 50 mmHg. ECH3 had fewer malformed staples for both 3.3- and 4.0-mm thick tissue. The end effector exhibited less angular movement during firing, and less deflection under a moderate load. Surgeons agreed the ECH3 provided precise placement and easy one-handed operation.ConclusionThe Echelon 3000 Stapler demonstrated improved access capability, tighter seals, fewer malformed staples, and greater end effector stability. These advantages were recognized by surgeons who evaluated the use of the device preclinically.

Design, Manufacture and Measurement of Three Permanent Magnet Dipoles for FASER Experiment

FASER, the ForwArd Search ExpeRiment, is designed to search for new, yet undiscovered, light and weakly-interacting particles and study the interactions of high-energy neutrinos. Three dipoles, one 1.5 m-long and the other two 1.0 m-long each, installed upstream of the ATLAS experiment at CERN, are required to achieve sufficient separation of pairs of oppositely charged, high-energy Standard Model particles originating from decays of new physics particles. The dipoles have an aperture of 200 mm in diameter and a required magnetic field at the centre ≥ 0.55 T. Due to tight space constraints, a design based on permanent magnet technology was proposed. This paper describes the design, manufacturing, assembly and magnetic measurement of these large Halbach array dipoles.

Safe Technical Innovation: Development and Implementation of a Robotic Breast Operation Program.

Safe Technical Innovation: Development and Implementation of a Robotic Breast Operation Program.

Inverse transfer function identification for high-frequency pressure probes using M-sequence pressure generators

Accurate unsteady pressure measurement is important for the development and improvement of turbomachinery. The miniature pressure probe can adapt to the accurate measurement of pressure in a tight space under harsh working conditions, but the presence of the pressure transmission line makes the probe frequency response characteristics poor, and even causes the pressure signal to be distorted. In this paper, a novel Maximum-length sequence (M-sequence) pressure generator was developed, which generated pulsating pressure signals with wide frequency range and large amplitude pressure fluctuations at a fixed speed, and a time-domain parametric probe inverse transfer function identification method based on finite impulse response (FIR) adaptive filter using the generator was proposed. Four probes with different geometric parameters were fabricated. The probe inverse transfer function obtained by the FIR adaptive filter was compared with that obtained by the traditional non-parametric method to verify the accuracy of the identification method. The pressure at the pressure tap of the probes were reconstructed from the pressure measured by the probe and the inverse transfer function, which was in good agreement with the pressure measured by the reference sensor.

Study on Micro-Nano Pore Characteristics and Classification of Tight Sandstone Reservoir Based on Q-Cluster

To realize the quantitative classification and comprehensive evaluation of the tight oil reservoir in the 4th of Quantou Formation in Songliao Basin, the pore structure of tight oil reservoir was quantitatively analyzed. In this study, experiments based on the constant-speed mercury injection, nuclear magnetic resonance, and micron CT are based on the observation of cast thin sections, and scanning electron microscope is conducted. The result shows that a tight oil reservoir space is mainly composed of the intergranular dissolved pore, residual intergranular pore, and intragranular dissolve pore. There are few intercrystalline pore and fracture at the same time. The average pore radius is 1.28~4.58 μm, and the average throat radius is 0.52~1.27 μm. Hence, there is a typical micro-nano throat combination with micropores. The pore throat composition and pore structure of reservoirs differ in reservoir with different physical properties. The reservoir quality depends on pore structure especially the throat radius. And the microthroat is a critical factor for permeability. Based on Q-cluster analysis, tight oil reservoirs are classified into three types. The analysis was based on the data such as max throat radius, average throat radius, displacement pressure, median pressure, and permeability. Finally, the reservoirs in the study area are mainly II and I types.

Energy-Efficient Path Planning of Reconfigurable Robots in Complex Environments

Planning the energy-efficient and collision-free paths for reconfigurable robots in complex environments is more challenging than conventional fixed-shaped robots due to their flexible degrees of freedom while navigating through tight spaces. This article presents a novel algorithm, energy-efficient batch informed trees* (BIT*) for reconfigurable robots, which incorporates BIT*, an informed, anytime sampling-based planner, with the energy-based objectives that consider the energy cost for robot’s each reconfigurable action. Moreover, it proposes to improve the direct sampling technique of informed RRT* by defining an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L^2$</tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">greedy informed set</i> that shrinks as a function of the state with the maximum admissible estimated cost instead of shrinking as a function of the current solution, thereby improving the convergence rate of the algorithm. Experiments were conducted on a tetromino hinged-based reconfigurable robot as a case study to validate our proposed path planning technique. The outcome of our trials shows that the proposed approach produces energy-efficient solution paths, and outperforms existing techniques on simulated and real-world experiments.

Integration and evaluation of magnetic stimulation in physiology setups.

A large number of behavioral experiments have demonstrated the existence of a magnetic sense in many animal species. Further, studies with immediate gene expression markers have identified putative brain regions involved in magnetic information processing. In contrast, very little is known about the physiology of the magnetic sense and how the magnetic field is neuronally encoded. In vivo electrophysiological studies reporting neuronal correlates of the magnetic sense either have turned out to be irreproducible for lack of appropriate artifact controls or still await independent replication. Thus far, the research field of magnetoreception has little exploited the power of ex vivo physiological studies, which hold great promise for enabling stringent controls. However, tight space constraints in a recording setup and the presence of magnetizable materials in setup components and microscope objectives make it demanding to generate well-defined magnetic stimuli at the location of the biological specimen. Here, we present a solution based on a miniature vector magnetometer, a coil driver, and a calibration routine for the coil system to compensate for magnetic distortions in the setup. The magnetometer fits in common physiology recording chambers and has a sufficiently small spatial integration area to allow for probing spatial inhomogeneities. The coil-driver allows for the generation of defined non-stationary fast changing magnetic stimuli. Our ex vivo multielectrode array recordings from avian retinal ganglion cells show that artifacts induced by rapid magnetic stimulus changes can mimic the waveform of biological spikes on single electrodes. However, induction artifacts can be separated clearly from biological responses if the spatio-temporal characteristics of the artifact on multiple electrodes is taken into account. We provide the complete hardware design data and software resources for the integrated magnetic stimulation system.

Structure-Based Demystification of Radical Catalysis by a Coenzyme B12 Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.

Catalysis by radical enzymes dependent on coenzyme B12 (AdoCbl) relies on the reactive primary 5'-deoxy-5'adenosyl radical, which originates from reversible Co-C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 1012-fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic. As revealed here, a displaced firm adenosine binding cavity in substrate-loaded glutamate mutase (GM) causes a structural misfit for intact AdoCbl that is relieved by the homolytic Co-C bond cleavage. Strategically interacting adjacent adenosine- and substrate-binding protein cavities provide a tight caged radical reaction space, controlling the entire radical path. The GM active site is perfectly structured for promoting radical catalysis, including "negative catalysis", a paradigm for AdoCbl-dependent mutases.