scholarly journals The effect of combustion chamber geometry layout on combustion and emission

2008 ◽  
Vol 12 (1) ◽  
pp. 7-24 ◽  
Author(s):  
Zoran Jovanovic ◽  
Stojan Petrovic ◽  
Miroljub Tomic
Keyword(s):  
Combustion Chamber ◽  
Flame Front ◽  
Moving Objects ◽  
Valve Lift ◽  
Data Set ◽  
Source Codes ◽  
Aspect Ratios ◽  
Front Shape ◽  
Computer Codes ◽  
Different Levels

In this paper some results concerning the combined effect of the tumble flow and combustion chamber geometry layout variations on flame front shape and its propagation through homogenous mixture of isooctane and air are presented. Spatial distributions of NO in different combustion chamber geometries are presented as well. The basic combustion chamber geometry layout considered consists of the flat head with two vertical valves and a cylindrical bowl subjected to variations of depth and squish area. All results presented were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry with moving objects and boundaries with modified KIVA3 and KIVA3V source codes. Two additional computer codes were applied to generate boundary conditions for KIVA3V calculations with moving valves. The AVL TYCON code was used for the calculation of valve lift profiles, and AVL BOOST code was used for the calculation of relevant data set in the valve regions. Different combustion chamber geometry layouts generate different levels of squish, and the combustion effects in essence depend on the interaction of that flow with tumble. It was found that for particular combustion chamber shapes with different diameter/depth aspect ratios entirely different flame front shapes and propagation velocities were encountered primarily due to variations of fluid flow patterns in the vicinity of top dead center.

scholarly journals Constraint-Based Hierarchical Cluster Selection in Automotive Radar Data

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3410
Author(s):  
Claudia Malzer ◽  
Marcus Baum
Keyword(s):  
Moving Objects ◽  
Hierarchical Cluster ◽  
Autonomous Driving ◽  
Radar Data ◽  
Background Information ◽  
Automotive Radar ◽  
Data Set ◽  
Radar Sensors ◽  
Small Clusters ◽  
Cluster Level

High-resolution automotive radar sensors play an increasing role in detection, classification and tracking of moving objects in traffic scenes. Clustering is frequently used to group detection points in this context. However, this is a particularly challenging task due to variations in number and density of available data points across different scans. Modified versions of the density-based clustering method DBSCAN have mostly been used so far, while hierarchical approaches are rarely considered. In this article, we explore the applicability of HDBSCAN, a hierarchical DBSCAN variant, for clustering radar measurements. To improve results achieved by its unsupervised version, we propose the use of cluster-level constraints based on aggregated background information from cluster candidates. Further, we propose the application of a distance threshold to avoid selection of small clusters at low hierarchy levels. Based on exemplary traffic scenes from nuScenes, a publicly available autonomous driving data set, we test our constraint-based approach along with other methods, including label-based semi-supervised HDBSCAN. Our experiments demonstrate that cluster-level constraints help to adjust HDBSCAN to the given application context and can therefore achieve considerably better results than the unsupervised method. However, the approach requires carefully selected constraint criteria that can be difficult to choose in constantly changing environments.

scholarly journals Analysis of creation and combustion process of hydrogen-air mixtures by optical method in isochoric chamber

2017 ◽  
Vol 170 (3) ◽  
pp. 121-125
Author(s):  
Marek BRZEŻAŃSKI ◽  
Tadeusz PAPUGA ◽  
Łukasz RODAK
Keyword(s):  
Combustion Chamber ◽  
Flame Front ◽  
Dose Distribution ◽  
Optical Method ◽  
Direct Injection ◽  
Combustion Process ◽  
Variable Composition ◽  
Mixture Formation ◽  
Before And After

The article considers the analysis of combustion process of hydrogen-air mixture of variable composition. Direct injection of hydrogen into the isochoric combustion chamber was applied and the mixture formation took place during the combustion process. The influence of the dose distribution of the fuel supplied before and after ignition on the formation of the flame front and the course of the pressure in the isochoric combustion chamber was discussed. The filming process and registration of pressure in the isochoric chamber during research of combustion process was applied.

scholarly journals A Real Time Image Processing Bird Repellent System Using Raspberry Pi

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Oluwole Arowolo ◽  
Adefemi A Adekunle ◽  
Joshua A Ade-Omowaye
Keyword(s):  
Image Processing ◽  
Real Time ◽  
Moving Objects ◽  
Detection System ◽  
Local Binary Patterns ◽  
Raspberry Pi ◽  
Feature Identification ◽  
Data Set ◽  
Haar Features ◽  
Haar Feature

Rice is one of the most consumed foods in Nigeria, therefore it’s production should be on the high as to meet the demand for it. Unfortunately, the quantity of rice produced is being affected by pests such as birds on fields and sometimes in storage. Due to the activities of birds, an effective repellent system is required on rice fields. The proposed effective repellent system is made up of hardware components which are the raspberry pi for image processing, the servo motors for rotation of camera for better field of view controlled by Arduino connected to the raspberry pi, a speaker for generating predator sounds to scare birds away and software component consisting of python and Open Cv library for bird feature identification. The model was trained separately using haar features, HOG (Histogram of Oriented Gradients) and LBP (Local Binary Patterns).Haar features resulted in the highest accuracy of 76% while HOG and LBP were, 27% and 72% respectively. Haar trained model was tested with two recorded real time videos with birds, the false positives were fairly low, about 41%. This haar feature trained model can distinguish between birds and other moving objects unlike a motion detection system which detects all moving objects. This proposed system can be improved to have a higher accuracy with a larger data set of positive and negative images. Keywords—Electronic pest repeller Haar cascade classifier, ultrasonic

scholarly journals Eye-hand coordination during flexible manual interception of an abruptly appearing, moving target

2018 ◽  
Vol 119 (1) ◽  
pp. 221-234 ◽  
Author(s):  
Yuhui Li ◽  
Yong Wang ◽  
He Cui
Keyword(s):  
Eye Movements ◽  
Moving Objects ◽  
Reaction Times ◽  
Hand Movements ◽  
Moving Target ◽  
Target Displacement ◽  
Transmission Delays ◽  
Sensory Transmission ◽  
Hand Coordination ◽  
Different Levels

As a vital skill in an evolving world, interception of moving objects relies on accurate prediction of target motion. In natural circumstances, active gaze shifts often accompany hand movements when exploring targets of interest, but how eye and hand movements are coordinated during manual interception and their dependence on visual prediction remain unclear. Here, we trained gaze-unrestrained monkeys to manually intercept targets appearing at random locations and circularly moving with random speeds. We found that well-trained animals were able to intercept the targets with adequate compensation for both sensory transmission and motor delays. Before interception, the animals' gaze followed the targets with adequate compensation for the sensory delay, but not for extra target displacement during the eye movements. Both hand and eye movements were modulated by target kinematics, and their reaction times were correlated. Moreover, retinal errors and reaching errors were correlated across different stages of reach execution. Our results reveal eye-hand coordination during manual interception, yet the eye and hand movements may show different levels of prediction based on the task context. NEW & NOTEWORTHY Here we studied the eye-hand coordination of monkeys during flexible manual interception of a moving target. Eye movements were untrained and not explicitly associated with reward. We found that the initial saccades toward the moving target adequately compensated for sensory transmission delays, but not for extra target displacement, whereas the reaching arm movements fully compensated for sensorimotor delays, suggesting that the mode of eye-hand coordination strongly depends on behavioral context.

Numerical Investigation of Heat Transfer in Rectangular Microchannels Under H2 Boundary Condition During Developing and Fully Developed Laminar Flow

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
V. V. Dharaiya ◽  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Fluid Flow ◽  
Microfluidic Devices ◽  
Transport Processes ◽  
Uniform Heat Flux ◽  
Data Set ◽  
Nusselt Numbers ◽  
Aspect Ratios

Study of fluid flow characteristics at microscale is gaining importance with shrinking device sizes. Better understanding of fluid flow and heat transfer in microchannels will have important implications in electronic chip cooling, heat exchangers, MEMS, and microfluidic devices. Due to short lengths employed in microchannels, entrance header effects can be significant and need to be investigated. In this work, three dimensional model of microchannels, with aspect ratios (α = a/b) ranging from 0.1 to 10, are numerically simulated using CFD software tool fluent. Heat transfer effects in the entrance region of microchannel are presented by plotting average Nusselt number as a function of nondimensional axial length x*. The numerical simulations with both circumferential and axial uniform heat flux (H2) boundary conditions are validated for existing data set for four wall heat flux case. Large numerical data sets are generated in this work for rectangular cross-sectional microchannels with heating on three walls, two opposing walls, one wall, and two adjacent walls under H2 boundary condition. This information can provide better understanding and insight into the transport processes in the microchannels. Although the results are seen as relevant in microscale applications, they are applicable to any sized channels. Based on the numerical results obtained for the whole range, generalized correlations for Nusselt numbers as a function of channel aspect ratio are presented for all the cases. The predicted correlations for Nusselt numbers can be very useful resource for the design and optimization of microchannel heat sinks and other microfluidic devices.

scholarly journals How Do Travel Costs Shape Collaboration?

2020 ◽  
Vol 66 (8) ◽  
pp. 3340-3360 ◽  
Author(s):  
Christian Catalini ◽  
Christian Fons-Rosen ◽  
Patrick Gaulé
Keyword(s):  
Collaborative Research ◽  
Low Cost ◽  
Scientific Publications ◽  
Data Set ◽  
Knowledge And Skills ◽  
Travel Costs ◽  
Local Environments ◽  
Development Teams ◽  
Specialized Equipment ◽  
Different Levels

We develop a simple theoretical framework for thinking about how geographic frictions, and in particular travel costs, shape scientists’ collaboration decisions and the types of projects that are developed locally versus over distance. We then take advantage of a quasi-experiment—the introduction of new routes by a low-cost airline—to test the predictions of the theory. Results show that travel costs constitute an important friction to collaboration: after a low-cost airline enters, the number of collaborations increases between 0.3 and 1.1 times, a result that is robust to multiple falsification tests and causal in nature. The reduction in geographic frictions is particularly beneficial for high-quality scientists that are otherwise embedded in worse local environments. Consistent with the theory, lower travel costs also endogenously change the types of projects scientists engage in at different levels of distance. After the shock, we observe an increase in higher-quality and novel projects, as well as projects that take advantage of complementary knowledge and skills between subfields, and that rely on specialized equipment. We test the generalizability of our findings from chemistry to a broader data set of scientific publications and to a different field where specialized equipment is less likely to be relevant, mathematics. Last, we discuss implications for the formation of collaborative research and development teams over distance. This paper was accepted by Toby Stuart, entrepreneurship and innovation.

scholarly journals A dynamic zone estimation method using cumulative voxels for autonomous driving

2017 ◽  
Vol 14 (1) ◽  
pp. 172988141668713 ◽  
Author(s):  
Seongjo Lee ◽  
Seoungjae Cho ◽  
Sungdae Sim ◽  
Kiho Kwak ◽  
Yong Woon Park ◽  
...  
Keyword(s):  
High Speed ◽  
Moving Objects ◽  
Three Dimensional ◽  
Estimation Method ◽  
Autonomous Driving ◽  
Significant Feature ◽  
Data Set ◽  
Ground Truth Data ◽  
Unmanned Vehicle ◽  
Space Data

Obstacle avoidance and available road identification technologies have been investigated for autonomous driving of an unmanned vehicle. In order to apply research results to autonomous driving in real environments, it is necessary to consider moving objects. This article proposes a preprocessing method to identify the dynamic zones where moving objects exist around an unmanned vehicle. This method accumulates three-dimensional points from a light detection and ranging sensor mounted on an unmanned vehicle in voxel space. Next, features are identified from the cumulative data at high speed, and zones with significant feature changes are estimated as zones where dynamic objects exist. The approach proposed in this article can identify dynamic zones even for a moving vehicle and processes data quickly using several features based on the geometry, height map and distribution of three-dimensional space data. The experiment for evaluating the performance of proposed approach was conducted using ground truth data on simulation and real environment data set.

Recirculation within a fluid sphere at moderate Reynolds numbers

2002 ◽  
Vol 465 ◽  
pp. 293-300 ◽  
Author(s):  
D. A. BARRY ◽  
J.-Y. PARLANGE
Keyword(s):  
Experimental Data ◽  
Vertical Velocity ◽  
Laboratory Data ◽  
Major Axis ◽  
Reynolds Numbers ◽  
Fluid Sphere ◽  
Stagnation Region ◽  
Data Set ◽  
Different Levels

Motion of a single fluid sphere is described by two theories, each characterized by different levels of Hill's vortex circulation within the sphere. An existing experimental data set giving measurements of vertical velocity along the major axis of the sphere is re-examined. Contrary to published discussions of that experiment, we find that the theory of Parlange agrees better with the laboratory data than that of Harper & Moore. This agreement supports the key difference between the two theories, i.e. that the fluid within the sphere is unlikely to have a singular (infinite) velocity as it moves upwards towards the stagnation region at the top of the sphere.

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