scholarly journals Determination of Firebrand Characteristics Using Thermal Videos

Fire ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 68
Author(s):  
Sergey Prohanov ◽  
Alexander Filkov ◽  
Denis Kasymov ◽  
Mikhail Agafontsev ◽  
Vladimir Reyno
Keyword(s):  
Thermal Characteristics ◽  
Infrared Camera ◽  
Detection Algorithm ◽  
Current Approach ◽  
Prescribed Fires ◽  
Wood Pellets ◽  
Difference Of Gaussians ◽  
Detection And Tracking ◽  
Alternative Approach ◽  
The Difference

Burning firebrands generated by wildland or prescribed fires may lead to the initiation of spot fires and fire escapes. At the present time, there are no methods that provide information on the thermal characteristics and number of such firebrands with high spatial and temporal resolution. A number of algorithms have been developed to detect and track firebrands in field conditions in our previous study; however, each holds particular disadvantages. This work is devoted to the development of new algorithms and their testing and, as such, several laboratory experiments were conducted. Wood pellets, bark, and twigs of pine were used to generate firebrands. An infrared camera (JADE J530SB) was used to obtain the necessary thermal video files. The thermograms were then processed to create an annotated IR video database that was used to test both the detector and the tracker. Following these studies, the analysis showed that the Difference of Gaussians detection algorithm and the Hungarian tracking algorithm upheld the highest level of accuracy and were the easiest to implement. The study also indicated that further development of detection and tracking algorithms using the current approach will not significantly improve their accuracy. As such, convolutional neural networks hold high potential to be used as an alternative approach.

scholarly journals OPTIONS WRITTEN ON STOCKS WITH KNOWN DIVIDENDS

2004 ◽  
Vol 07 (07) ◽  
pp. 901-907
Author(s):  
ERIK EKSTRÖM ◽  
JOHAN TYSK
Keyword(s):  
Stock Price ◽  
Option Price ◽  
Option Prices ◽  
Strike Price ◽  
Call Options ◽  
Alternative Approach ◽  
Black Scholes ◽  
Market Practice ◽  
The Difference ◽  
Risk Free Rate

There are two common methods for pricing European call options on a stock with known dividends. The market practice is to use the Black–Scholes formula with the stock price reduced by the present value of the dividends. An alternative approach is to increase the strike price with the dividends compounded to expiry at the risk-free rate. These methods correspond to different stock price models and thus in general give different option prices. In the present paper we generalize these methods to time- and level-dependent volatilities and to arbitrary contract functions. We show, for convex contract functions and under very general conditions on the volatility, that the method which is market practice gives the lower option price. For call options and some other common contracts we find bounds for the difference between the two prices in the case of constant volatility.

scholarly journals Improving Lidar Windshear Detection Efficiency by Removal of “Gentle Ramps”

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1539
Author(s):  
Kai Kwong Hon ◽  
Pak Wai Chan
Keyword(s):  
Detection Efficiency ◽  
State Of The Art ◽  
Detection Algorithm ◽  
Doppler Lidar ◽  
Hit Rate ◽  
Glide Path ◽  
The World ◽  
Alerting System ◽  
The Difference ◽  
Hong Kong International Airport

The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world.

Detection and Tracking Cows by Computer Vision and Image Classification Methods

2021 ◽  
Vol 13 (1) ◽  
pp. 1-45
Author(s):  
Terry Gao
Keyword(s):  
Feature Fusion ◽  
Binary Classification ◽  
Classification Problem ◽  
Detection Algorithm ◽  
Video Sequences ◽  
Image Block ◽  
Body Contour ◽  
Adaboost Algorithm ◽  
Target Model ◽  
Detection And Tracking

In this paper, the cow recognition and traction in video sequences is studied. In the recognition phase, this paper does some discussion and analysis which aim at different classification algorithms and feature extraction algorithms, and cow's detection is transformed into a binary classification problem. The detection method extracts cow's features using a method of multiple feature fusion. These features include edge characters which reflects the cow body contour, grey value, and spatial position relationship. In addition, the algorithm detects the cow body through the classifier which is trained by Gentle Adaboost algorithm. Experiments show that the method has good detection performance when the target has deformation or the contrast between target and background is low. Compared with the general target detection algorithm, this method reduces the miss rate and the detection precision is improved. Detection rate can reach 97.3%. In traction phase, the popular compressive tracking (CT) algorithm is proposed. The learning rate is changed through adaptively calculating the pap distance of image block. Moreover, the update for target model is stopped to avoid introducing error and noise when the classification response values are negative. The experiment results show that the improved tracking algorithm can effectively solve the target model update by mistaken when there are large covers or the attitude is changed frequently. For the detection and tracking of cow body, a detection and tracking framework for the image of cow is built and the detector is combined with the tracking framework. The algorithm test for some video sequences under the complex environment indicates the detection algorithm based on improved compressed perception shows good tracking effect in the changing and complicated background.

scholarly journals Modal-based vibrothermography using feature extraction with application to composite materials

2019 ◽  
Vol 19 (4) ◽  
pp. 967-986 ◽  
Author(s):  
Xintian Chi ◽  
Dario Di Maio ◽  
Nicholas AJ Lieven
Keyword(s):  
Feature Extraction ◽  
Composite Materials ◽  
Damage Detection ◽  
Infrared Camera ◽  
Experimental Tests ◽  
Detection Algorithm ◽  
Modal Testing ◽  
Theoretical Development ◽  
Operational Environment ◽  
Practical Applications

This research focuses on the development of a damage detection algorithm based on modal testing, vibrothermography, and feature extraction. The theoretical development of mathematical models is presented to illustrate the principles supporting the associated algorithms, through which the importance of the three components contributing to this approach is demonstrated. Experimental tests and analytical simulations have been performed in laboratory conditions to show that the proposed damage detection algorithm is able to detect, locate, and extract the features generated due to the presence of sub-surface damage in aerospace grade composite materials captured by an infrared camera. Through tests and analyses, the reliability and repeatability of this damage detection algorithm are verified. In the concluding observations of this article, suggestions are proposed for this algorithm’s practical applications in an operational environment.

scholarly journals Visualization and analysis of SCImago Journal & Country Rank structure via journal clustering

2016 ◽  
Vol 68 (5) ◽  
pp. 607-627 ◽  
Author(s):  
Antonio J. Gómez-Núñez ◽  
Benjamin Vargas-Quesada ◽  
Zaida Chinchilla-Rodríguez ◽  
Vladimir Batagelj ◽  
Félix Moya-Anegón
Keyword(s):  
Clustering Algorithm ◽  
Citation Network ◽  
Detection Algorithm ◽  
Bibliographic Coupling ◽  
Content Type ◽  
Alternative Approach ◽  
Level Of Aggregation ◽  
Direct Citation ◽  
Community Detection Algorithm ◽  
Visualization Techniques

Purpose The purpose of this paper is to visualize the structure of SCImago Journal & Country Rank (SJR) coverage of the extensive citation network of Scopus journals, examining this bibliometric portal through an alternative approach, applying clustering and visualization techniques to a combination of citation-based links. Design/methodology/approach Three SJR journal-journal networks containing direct citation, co-citation and bibliographic coupling links are built. The three networks were then combined into a new one by summing up their values, which were later normalized through geo-normalization measure. Finally, the VOS clustering algorithm was executed and the journal clusters obtained were labeled using original SJR category tags and significant words from journal titles. Findings The resultant scientogram displays the SJR structure through a set of communities equivalent to SJR categories that represent the subject contents of the journals they cover. A higher level of aggregation by areas provides a broad view of the SJR structure, facilitating its analysis and visualization at the same time. Originality/value This is the first study using Persson’s combination of most popular citation-based links (direct citation, co-citation and bibliographic coupling) in order to develop a scientogram based on Scopus journals from SJR. The integration of the three measures along with performance of the VOS community detection algorithm gave a balanced set of clusters. The resulting scientogram is useful for assessing and validating previous classifications as well as for information retrieval and domain analysis.

Surface Temperature Field Statistics at an Air/Water Interface for Grid-Generated Sub-Surface Turbulence

2002 ◽  
Author(s):  
Karen A. Flack ◽  
Geoffrey B. Smith
Keyword(s):  
Surface Temperature ◽  
Infrared Camera ◽  
Temperature Fields ◽  
Interface Temperature ◽  
Water Interface ◽  
Bulk Fluid ◽  
Air Water Interface ◽  
Evaporative Convection ◽  
The Difference ◽  
Oscillation Frequencies

Surface temperature fields and statistics are presented for the case of sub-surface grid-generated turbulence impacting an air/water interface. Temperature measurements are obtained with an infrared camera, sensitive in the 3–5 micron wavelength range. Results indicate that increased grid oscillation frequencies, and shallower grid depths, lead to increased surface mixing, yielding lower values of RMS temperature. Non-dimensionalization of the RMS temperatures using the difference in the average surface and the bulk fluid temperatures, collapses the data obtained for different grid depths and oscillation frequencies. This scaling is related to the thermal boundary layer thickness. The results are compared to the baseline case of turbulence due to evaporative convection without an oscillating grid.

scholarly journals Thermal Characteristics of Positive Leaders under Different Electrode Terminals in a Long Air Gap

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4024 ◽  
Author(s):  
Du ◽  
Tang ◽  
Li ◽  
Zou ◽  
Ma ◽  
...  
Keyword(s):  
High Speed ◽  
Thermal Characteristics ◽  
Video Camera ◽  
Air Gap ◽  
Radius Of Curvature ◽  
Gas Temperature ◽  
Gas Density ◽  
Interference Fringes ◽  
High Speed Video Camera ◽  
The Difference

The thermal characteristics of the positive leader discharges occurring under the different electrode terminals in a 1 m rod-plate air gap were studied quantitatively using Mach–Zehnder interferometry and a high-speed video camera. When disturbed by the discharge channel, the interference fringes are distorted because of the change in the refractive index of air, which is related to the gas density. Therefore, the gas temperature and gas density distribution in the leader channel can be retrieved from the offset of the interference fringes. Based on these results, the thermal characteristics of the leader channel were studied under different electrode terminals with a radius of curvature of 2.5 mm and 5 mm for cone electrodes and a diameter of 40 mm for a spherical electrode. The results show that the gas temperature in the leader channel increased while the gas density decreased as the radius of curvature of the electrode terminal decreased. Additionally, a smaller radius of curvature leads to a larger thermal diameter, but the difference in the thermal diameter is not obvious; for the terminals used in this paper, the difference is within 2 mm.

scholarly journals 3D Measurement of Human Chest and Abdomen Surface Based on 3D Fourier Transform and Time Phase Unwrapping

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1091 ◽  
Author(s):  
Haibin Wu ◽  
Shuang Yu ◽  
Xiaoyang Yu
Keyword(s):  
Fourier Transform ◽  
Phase Error ◽  
Three Dimensional ◽  
Image Sequences ◽  
Current Approach ◽  
Individual Characteristics ◽  
Phase Unwrapping ◽  
3D Measurement ◽  
Human Experiments ◽  
The Difference

Monitoring respiratory movements is an effective way to improve radiotherapy treatments of thoracic and abdominal tumors, but the current approach is limited to measuring specific points in the chest and abdomen. In this paper, a dynamic three-dimensional (3D) measurement approach of the human chest and abdomen surface is proposed, which can infer tumor movement more accurately, so the radiotherapy damage to the human body can be reduced. Firstly, color stripe patterns in the RGB color model are projected, then after color correction, the collected stripe image sequences are separated into the three RGB primary color stripe image sequences. Secondly, a fringe projection approach is used to extract the folded phase combined 3D Fourier transform with 3D Gaussian filtering. By the relationship between adjacent fringe images in the time sequence, Gaussian filter parameters with individual characteristics are designed and optimized to improve the accuracy of wrapped phase extraction. In addition, based on the difference between the fractional parts of the folded phase error, one remainder equation can be determined, which is used for time-phase unwrapping. The simulation model and human experiments show that the proposed approach can obtain the 3D image sequences of the chest and abdomen surface in respiratory motion effectively and accurately with strong anti-interference ability.

Surrogate modeling of a 3D scramjet-powered hypersonic vehicle based on screening method IFFD

2016 ◽  
Vol 231 (2) ◽  
pp. 265-278 ◽  
Author(s):  
Chen Boyi ◽  
Liu Yanbin ◽  
Shen Haidong ◽  
Lu Yuping
Keyword(s):  
Vehicle Dynamics ◽  
Screening Method ◽  
Kriging Model ◽  
Surrogate Models ◽  
Hypersonic Vehicle ◽  
Fractional Factorial ◽  
Gap Metric ◽  
Alternative Approach ◽  
Pitch Moment ◽  
The Difference

The emphasis of this paper lies in the development of an efficient approach to reproduce the behaviors of the scramjet-powered hypersonic system with high fidelity. The modeling of the dual-mode scramjet powered hypersonic vehicle dynamics with shock interaction, Ram-to-Scram transition, and finite rate chemistry reaction is firstly introduced. The structure of surrogate model is identified with the implement of iterative fractional factorial design (IFFD). In order to declare the reliability of the surrogate models, ν-gap metric is applied to distinguish the difference among these surrogate models in terms of closed-loop performance. The results show that the influence of Mach number on the aerodynamics should not be overlooked, and the effect of propulsion system to the aerodynamic pitch moment is dramatic. Further, the partial Kriging model appears to have the closest plants throughout the flight envelope compared with the full Kriging model and polynomials model. Nevertheless, considering the briefness of analytical expression, the polynomials model may be an alternative approach for design-oriented modeling.

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