A Scaling Law for SPAD Pixel Miniaturization

The growing demands on compact and high-definition single-photon avalanche diode (SPAD) arrays have motivated researchers to explore pixel miniaturization techniques to achieve sub-10 m pixels. The scaling of the SPAD pixel size has an impact on key performance metrics, and it is, thereby, critical to conduct a systematic analysis of the underlying tradeoffs in miniaturized SPADs. On the basis of the general assumptions and constraints for layout geometry, we performed an analytical formulation of the scaling laws for the key metrics, such as the fill factor (FF), photon detection probability (PDP), dark count rate (DCR), correlated noise, and power consumption. Numerical calculations for various parameter sets indicated that some of the metrics, such as the DCR and power consumption, were improved by pixel miniaturization, whereas other metrics, such as the FF and PDP, were degraded. Comparison of the theoretically estimated scaling trends with previously published experimental results suggests that the scaling law analysis is in good agreement with practical SPAD devices. Our scaling law analysis could provide a useful tool to conduct a detailed performance comparison between various process, device, and layout configurations, which is essential for pushing the limit of SPAD pixel miniaturization toward sub-2 m-pitch SPADs.

The Effect of Modifying Double Continuous Flow Intersections Layout Geometric Features on their Operation

Introduction: Continuous flow interventions were first introduced as an alternative to improve traffic operations in the intersections with severe congestion caused by heavy left-turn movements. Objective: This study quantified the effect of modifying the intersection angles of Double Continuous Flow Intersections (DCFI) on their operational characteristics. Mainly, the effects of changing the intersection angle between the different approaches of the main intersection and the angle of the minor cross-over intersections were investigated. Methods: VISSIM software simulation models were used for modifying several design features related to the DCFI and the operational performance was compared between the different simulation scenarios. Results and Discussion: Changes to the cross-over intersection angle increase the safety levels by providing better channelization of traffic movements on the minor intersections of the DCFI and reduce the intersection footprint to be used at high-density urban locations. Increasing the cross-over intersection angle and changing the layout geometry have adverse effects on the capacity of the conventional DCFI. This is mainly because of the added curvature in the intersection approaches which reduces the vehicle speeds, therefore reducing the overall capacity of the modified intersection when compared to the conventional DCFI. However, the total footprint for the intersection is reduced for the modified layout geometry, which improves the capacity of the DCFI. Conclusion: The study has explored the effects of modifying the DCFI intersection angles to fit the limited space in major urban areas on the capacity and performance of the intersection. It showed that DCFI designs could be applied in areas with limited space availability and skewed intersection angles.

Layout symmetry facilitates spatial learning in the house cricket, Acheta domesticus, in the absence of visual cues

There is heavy debate about the mechanisms of spatial navigation by insects. Researchers tend to focus mainly on vision-based models, neglecting non-visual modalities. The capacity to navigate by layout symmetry has been reported in vertebrates. Nevertheless, there has been no direct evidence for such an ability in insects, especially regarding center finding. To provide novel insight into the ongoing debate, we developed a non-visual paradigm for testing navigation by layout geometry. We tested the house crickets to find a cool spot positioned centrally in heated arenas of different shapes. We found that the symmetry of the arena significantly facilitates how crickets learn to find the center of the arena, both in terms of time spent on the cool spot and the latency of locating it. Because there were no visual cues, this observation challenges visiocentric models. As alternatives, we discuss the possibility of non-visual space representation, or non-spatial search strategy.

Rooms Without Walls: Young Children Draw Objects But Not Layouts

Drawing is an epitome of uniquely human expression, with few known limits beyond those of our perceptual and motor systems and the cultures in and for which we draw. The present study evaluates whether the drawings of young children nevertheless reveal an early emerging bias in the depiction of two different foundational spatial categories: layouts and objects. Across two experiments following preregistered designs and analysis plans, 4-year-old children either sat in a colorful “fort” or looked at a small “toy” version of the fort and were asked to draw exactly what they saw. Children’s drawings often omitted the walls composing the fort’s layout but included the corresponding object parts of the toy. Symbolic representations of space in young children’s drawings thus privilege small-scale objects over large and fixed layout geometry. A distinction between the intuitive geometries of layouts and objects leads to their differential treatment in both humans and other animals during everyday navigation. This distinction may also underlie the differential treatment of layouts and objects in children’s drawings.

ПОНЯТИЕ КОЭФФИЦИЕНТА ЭЛЛИПТИЧНОСТИ ТРАПЕЦИЕВИДНОГО КРЫЛА И МЕТОД ЕГО ОЦЕНКИ

When developing modifications of the transport category aircraft to increase their transport efficiency and economy in many cases, there is a need for profound changes in wing parameters. When such changes are implemented, the problem of the wing layout geometry, and the whole lift system “wing + tail unit assemblies”, inevitably arises. The most important step in the selection of parameters of lifting surfaces is to ensure, during their design, the law of change in circulation spanwise, the maximum approximate distribution of circulation in an elliptical wing, which leads to a minimum value of its inductive resistance for a given lift value.The ratio of the circulation values of the velocity of the elliptical (Ge) and tapered (Gt) wings, the values of which are usually estimated using the known coefficients of the wing shapes, was taken as the elliptic coefficient of the tapered wing:– Ktsh and Kesh – the factors of the tapered wing shape and elliptical wing in plan view, equivalent in lift force, as well as in the span and aspect ratio;– Ksh(hi) – the shape factor of the tapered wing, depending on its taper ratio (hi);– Kesh – the optimal value of the shape factor of a simple tapered wing if the taper ratio is h = 2.857 (according to Karafoli), and Сxi min.The analysis of such dependences showed that the increase in the elliptic coefficient Кe is realized by increasing the number of trapezoids (n), forming the plan of the composite wing, and the geometric twist of their local chords.When using such design solutions, it is possible to increase the value Ken, e, and the numerical evaluation models depend, among other things, on: n – the number of trapeziums that form the wing half-sizes; zn i- the coordinates of the wing kinks in its span; ηn – total narrowing of the wing, formed by n trapeziums. e - the relative angles of the geometric twist of the local chords of the trapezoids forming the plan of the modified wing.The developed models are the scientific basis for the re-assembly of not only an isolated wing, but also the entire lift system “wing + tail unit assemblies” that provide minimal inductive resistance, and should also be used as the basis for constructing longitudinal static stability limits and reducing the trim loss of the modification.

Identification of Determinants of the Speed-Reducing Effect of Pedestrian Refuges in Villages Located on a Chosen Regional Road

Traffic calming, as a traffic engineering discipline, is becoming an increasingly important aspect of the road engineering process. One of the traffic calming treatments are pedestrian refuges—raised islands located on or at the road centreline. This paper presents factors relevant to the performance of this kind of traffic calming devices retrofitted on the stretches of regional roads in village areas. To this end, speed surveys were carried out before and after the islands in each direction on purposefully chosen test sections. In order to identify the determinants, each test section was characterised by features including the symmetry of the road layout geometry, surrounding features and the existing traffic signs and, last but not least, visibility of the road ahead. The survey data were used by the authors to perform analyses in order to group the speeds at the pedestrian refuges and relate them to specific factors and, finally, identify the determinants of speed reduction. In this way, the authors arrived at a conclusion that the performance of pedestrian refuges depends on a number of factors rather than solely on their geometric parameters. The analyses showed that the pedestrian refuge geometric parameters, features located in its proximity that influence the driver’s perception and placement of appropriate marking, can, in combination, result in achieving the desired speed reduction and ensure safety of non-motorised users. These hypotheses were tested on a stretch of a regional road in village area at three points of the process: before upgrading, after installation of pedestrian refuges, and after retrofitting of enhancements.

Simulation Studies on the Effect of Material Characteristics and Runners Layout Geometry on the Filling Imbalance in Geometrically Balanced Injection Molds

Simulation studies were performed on filling imbalance in geometrically balanced injection molds. A special simulation procedure was applied to simulate properly the phenomenon, including inertia effects and 3D tetrahedron meshing as well as meshing of the nozzle. The phenomenon was investigated by simulation using several different runner systems at various thermo-rheological material parameters and process operating conditions. It has been observed that the Cross-WLF parameters, index flow, critical shear stress (relaxation time), and zero viscosity, as well as thermal diffusivity and heat transfer coefficient strongly affect the filling imbalance. The effect is substantially dependent on the runners’ layout geometry, as well as on the operating conditions, flow rate, and shear rate. The standard layout geometry and the corrected layout with circled element induce positive imbalance which means that inner cavities fills out faster, and it is opposite for the corrected layouts with one/two overturn elements which cause negative imbalance. Generally, for the standard layout geometry and the corrected layout with circled element, an effect of the zero shear rate viscosity η0 is positive (imbalance increases with an increase of viscosity), and an effect of the power law index n and the relaxation time λ is negative (imbalance decreases with an increase of index n and relaxation time λ). An effect of the thermal diffusivity α and heat transfer coefficient h is negative while an effect of the shear rate is positive. For the corrected layouts with one/two overturn elements, the results of simulations indicate opposite relationships. A novel optimization approach solving the filling imbalance problem and a novel concept of global modeling of injection molding process are also discussed.

Rooms without walls: Young children draw objects but not layouts

Drawing is an epitome of uniquely human expression, with few limits beyond those of our perceptual and motor systems and the cultures in and for which we draw. The present study suggests a previously unrecognized yet early emerging cognitive constraint on human drawing rooted in the basic processes of navigation that humans share with other animals and evidenced in the untutored drawings of young children. Following a preregistered design and analysis, 64 4-year-old children either sat in a colorful “fort” or looked at a small “toy” version of the fort and were asked to draw exactly what they saw. Children’s drawings often omitted the walls composing the fort’s layout but included the corresponding object-part information for the toy. Symbolic representations of space in children’s untutored drawings may thus privilege small-scale objects, which elicit explicit attention, over large and fixed layout geometry, which is used automatically for navigation.

Application of a New Geophone and Geometry in Tunnel Seismic Detection

Seismic imaging is the most effective geophysical method and has been extensively implemented to detect potential geological hazards in tunnels during construction. The coupling of geophones and the design of geometry in tunnels are the two major challenges. To ensure successful coupling, a high-sensitivity semi-automatic coupling geophone with a broadband was designed. In practice, this geophone is attached with a wheel and two springs. Once inserted into the borehole, an automatic coupling action occurs. This semi-automatic coupling design within the geophone not only guarantees good coupling, but reduces the time and costs usually required to install a traditional geophone. In the use of geophones for tunnel seismic detection, we propose two new two-dimensional (2D) seismic geometries based on the two commonly used geometries. A test to assess the effectiveness of the qualities of imaging from four geometries was completed by comparing the results of the forward modeling of sandwich models. The conclusion is that the larger the horizontal offset of the layout geometry, the higher the resolution of the imaging; the larger the vertical offset, the weaker the mirror image. The vertical offset is limited due to the narrow tunnel condition. Therefore, the mirror effect cannot be entirely eliminated; however, it can be further suppressed by constructing 2D geometry. The two newly proposed 2D geometries caused the imaging arc of the inter-layer, but suppressed the mirror image. The mirror image added a significant number of errors to the data, which could misguide tunnel construction; therefore the new 2D geometries are more reasonable than the two most commonly used. We applied one of the two new 2D geometries that was more practical to an actual project, the Chongqing Jinyunshan Tunnel in China, and acquired high-quality seismic data using two semi-automatic coupling geophones. The detection results were essentially consistent with the excavation conclusions.

Flow Velocity Distribution Towards Flowmeter Accuracy: CFD, UDV, and Field Tests

Inconsistences regarding flow measurements in real hydraulic circuits have been detected. Intensive studies stated that these errors are mostly associated to flowmeters, and the low accuracy is connected to the perturbations induced by the system layout. In order to verify the source of this problem, and assess the hypotheses drawn by operator experts, a computational fluid dynamics (CFD) model, COMSOL Multiphysics 4.3.b, was used. To validate the results provided by the numerical model, intensive experimental campaigns were developed using ultrasonic Doppler velocimetry (UDV) as calibration, and a pumping station was simulated using as boundary conditions the values measured in situ. After calibrated and validated, a new layout/geometry was proposed in order to mitigate the observed perturbations.