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An evaluation of WSR-88D severe hail algorithms along the northeastern Gulf Coast

WEATHER AND FORECASTING 1998年第4期13卷 1029-1044页

作者： Lenning, E Fuelberg, HE Watson, WI Florida State Univ Tallahassee FL 32306 USA NOAA Natl Weather Serv Tallahassee FL USA

Software build 9.0 for the Weather Surveillance Radar-1988 Doppler (WSR-88D) contains several new or improved algorithms for detecting severe thunderstorms. The WSR-88D Operational Support Facility supports testing and optimization of these algorithms by local National Weather Service offices. This paper presents a new methodology for using Storm Data in these local evaluations. The methodology defines specific conditions a storm cell must meet to be included in the evaluation. These conditions include cell intensity and duration, population density along the cell track, and any previous severe reports in the county where the storm is located. These requirements avoid including storm cells that may have produced severe weather where reports would be very unlikely. The technique provides a more accurate picture of algorithm performance than if Storm Data is used with no special considerations. This study utilizes the new methodology with data currently available for the Tallahassee, Florida, county warning area (TLH CWA). It describes the performance of two algorithms used for detecting severe hail. The first is the Probability of Severe Hail (POSH), a component of the build 9.0 Hail Detection algorithm. The second is the algorithm that calculates vertically integrated liquid (VIL). Early results show that the recommended POSH threshold of 50% appears appropriate for the TLH CWA. This suggests that the height of the freezing level provides a reasonably good estimate of the best severe hail index (SHI). However, early results also indicate that the average wet-bulb temperature from 1000 to 700 mb (low-level wet-bulb temperature) might produce an even better indication of the SHI threshold. Similarly, the threshold for VIL is highly correlated to the low-level wet-bulb temperature. Finally, the VIL algorithm is found to perform as well as the POSH parameter if the best VIL threshold can be determined in advance. Since the database used in these evaluations was relative

关键词： .intensity Weather Service VIL severe weather Severe Hail Tallahassee Florida new methodology Storm Data local evaluations storm cell population density algorithm performance TLH CWA POSH Hail Detection Early results

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DYNAMIC MEMORY ALLOCATION IN COMPUTER-SIMULATION

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COMMUNICATIONS OF THE ACM 1977年第11期20卷 864-873页

作者： NIELSEN, NR STANFORD RES INST INFORMAT SYST GRPMENLO PKCA 94025

This paper investigates the performance of 35 dynamic memory allocation algorithms when used to service simulation programs as represented by 18 test cases. algorithm performance was measured in terms of processing time, memory usage, and external memory fragmentation. algorithms maintaining separate free space lists for each size of memory block used tended to perform quite well compared with other algorithms. Simple algorithms operating on memory ordered lists (without any free list) performed surprisingly well. algorithms employing power-of-two block sizes had favorable processing requirements hut generally unfavorable memory usage. algorithms employing LIFO, FIFO, or memory ordered free lists generally performed poorly compared with others. [ABSTRACT FROM AUTHOR]

关键词： algorithm performance dynamic memory allocation dynamic memory management dynamic storage allocation garbage collection list processing memory allocation memory management programming techniques simulation simulation memory management simulation techniques space allocation storage allocation

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Choosing Classification algorithms and Its Optimum Parameters based on Data Set Characteristics

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电脑学刊 2017年第5期28卷 26-38页

作者： Yang Zhongguo Li Hongqi Sikandar Ali Ao Yile

Choosing a correct classification algorithm for a given data set is an important task considering the existing multiple classifiers. A method of recommending a suitable algorithm and its optimum parameters for a given data set is proposed. Firstly, six different types of measures are computed for each data set to be representation of its characteristics. Then, the performance and optimum parameters for a given algorithm are computed by using grid search method. Afterwards, a model was built to predict the variance of classifiers for a given data set and another model was built to predict the best suitable algorithm. The proposed method tries to predict the optimum parameter for a certain algorithm based on knowledge learning from history data sets. To evaluate the performance of the proposed method, some extensive experiments for four different types of algorithms are conducted upon the UCI data sets. The results indicate that the proposed method is effective.

关键词： algorithm automatic recommendation algorithm performance data set characteristics optimum parameters

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Segmentace 2D Point-cloudu pro proložení křivkami

Segmentace 2D Point-cloudu pro proložení křivkami

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作者： Šooš, Marek Brno University of Technology

Predložená diplomová práca sa zaoberá rozdeľovaním súradnicových bodov do homogénnych skupín. Práca poskytuje široký prehľad súčasného stavu v danej t&#... 详细信息

Predložená diplomová práca sa zaoberá rozdeľovaním súradnicových bodov do homogénnych skupín. Práca poskytuje široký prehľad súčasného stavu v danej téme vo forme analýzy článkov ako aj stručné vysvetlenie princípov hlavných segmentačných metód. Z analýzy článkov je vybraná pätica algoritmov, ktorá je naprogramovaná. V práci sú opísané princípy vybraných algoritmov a vysvetlené ich matematické modely. Pre každý algoritmus je uvedený aj popis návrhu ich kódového spracovania. Diplomová práca taktiež obsahuje vzájomné porovnania schopností segmentácie jednotlivých algoritmov na vytvorených ako aj nameraných dátach. Výsledky porovnávania preloženia jednotlivých kriviek sú medzi sebou porovnané grafickou aj číselnou formou. Na konci práce sa nachádza porovnávací graf časovej závislosti výpočtového času od počtu bodov point cloudu a súčasne tabuľka zahŕňajúca vzájomné porovnania algoritmov v jednotlivých oblastiach.

关键词： point cloud segmentácia preloženie kriviek Lidar rýchlosť algoritmu point cloud segmentation curve extrapolation Lidar algorithm performance Text

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Ant-Based Automated Mission Planning for Data Relay Space Missions

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2019年第7期16卷 249-262页

作者： Ntagiou, Evridiki, V Armellin, Roberto Iacopino, Claudio Policella, Nicola Donati, Alessandro Univ Surrey Surrey Space Ctr Guildford GU2 7XH Surrey England Surrey Satellite Technol Ltd Ground Software Team Guildford GU2 7YE Surrey England ESA Adv Mission Concepts & Technol European Space Operat Ctr Robert Bosch Str 5 D-64293 Darmstadt Germany ESA Adv Mission Concepts & Technol Robert Bosch Str 5 D-64293 Darmstadt Germany

The Earth observation (EO) market is rapidly growing due to technology miniaturization, cheaper launch opportunities, and a wider spectrum of EO applications. Along with an exponential growth of the ground-based users that can access low-Earth-orbit (LEO) spacecraft data, this growing community represents an important demand for data relay missions. LEO spacecraft have short visibility windows to the ground stations (GSs), which limits their throughput. Data relay missions comprise spacecraft at higher-altitude orbits (geostationary orbits) acting as relays of data among LEO spacecraft and GSs. Those missions are then able to offer more frequent data downlink opportunities to the LEO spacecraft, thus increasing the volume of the data reaching the ground and improving the responsiveness between users' requests and downlink operations. Ground-based mission planning systems (MPSs) are commonly managing such complex missions, representing a large operational cost. In this paper, the application of a swarm intelligence algorithm to the design of an automated MPS for data relay missions is proposed. Automated MPSs have the potential to save operational costs while leaving the high-level decisions to human operators. This paper represents the first time that an ant colony optimization (ACO) algorithm is applied to this type of scheduling problem. This family of algorithms is generally found to offer a good level of efficiency and scalability. In this work, an ACO approach is compared against an algorithm that is popular in the literature, called Squeaky Wheel Optimization, outperforming it.

关键词： Space Operations Earth Ground Station Central Processing Unit Greedy algorithm Ant Colony Optimization algorithms Constellations Satellites Air Force Satellite Control Network algorithm performance

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Vertical distribution analysis and total mass estimation of nitrogen and phosphorus in large shallow lakes

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JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023年第1期344卷 118465页

作者： Xiong, Junfeng Xue, Kun Li, Jing Hu, Minqi Li, Jiaxin Wang, Xiaoyang Lin, Chen Ma, Ronghua Chen, Lei Chinese Acad Sci Nanjing Inst Geog & Limnol Key Lab Watershed Geog Sci Nanjing 210008 Peoples R China Nanjing Hydraul Res Inst Hydrol & Water Resources Dept Nanjing 210029 Peoples R China Xian Univ Sci & Technol Coll Geometr Xian 710054 Peoples R China Beijing Normal Univ Sch Environm State Key Lab Water Qual Simulat Beijing 100875 Peoples R China

Analysing the vertical distribution of nutrient salts and estimating the total mass of lake nutrients is helpful for the management of lake nutrient status and the formulation of drainage standards in basins. However, studies on nitrogen (N) and phosphorus (P) in lakes have focused on obtaining measures of N and P concentrations, but no understanding exists on the vertical distribution of N and P in the entire water column. The present study proposes algorithms for estimating the total masses of N/P per unit water column (ALGO-TNmass/ALGO-TPmass) for shallow eutrophic lakes. Using Lake Taihu as an example, the total masses of nutrients in Lake Taihu in the historical period were obtained, and the algorithm performance was discussed. The results showed that the vertical distribution of nutrients decreased with increasing depth and exhibited a quadratic distribution. Surface nutrients and chlorophyll-a concentrations play important roles in the vertical distribution of nutrients. Based on conventional surface water quality indicators, algorithms for the vertical nutrient concentration in Lake Taihu were proposed. Both algorithms had good accuracy (ALGO-TNmass R2 > 0.75, RMSE <0.57;ALGO-TPmass R2 > 0.80, RMSE & LE;0.50), the ALGO-TPmass had better applicability than the ALGO-TNmass, and had good accuracy in other shallow lakes. Therefore, deducing the TPmass using conventional water quality indicators in surface water, which not only simplifies the sampling process but also provides an opportunity for remote sensing technology to monitor the total masses of nutrients, is feasible. The long-term average total mass of N was 11,727 t, showing a gradual downward trend before 2010, after which it stabilised. The maximum and minimum intra-annual total N masses were observed in May and November, respectively. The long-term average total mass of P was 512 t, showing a gradual downward trend before 2010, and a slow upward trend thereafter. The maximum and minimum intra-annual t

关键词： Water total masses of N and P Vertical distribution Shallow eutrophic lake algorithm performance

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Experimental Investigation of On-Ground Flightworthiness Determination for Modular Vertical Lift Vehicles

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JOURNAL OF AIRCRAFT 2019年第3期56卷 1135-1148页

作者： Warner, Jonathan Rogers, Jonathan Georgia Inst Technol Woodruff Sch Mech Engn Atlanta GA 30332 USA Georgia Inst Technol Guggenheim Sch Aerosp Engn Atlanta GA 30332 USA

Cooperative transportation of payloads by multiple unmanned air vehicles has received increasing interest due to unique operational advantages. These include the portability of the individual vehicles and the scalability of the lifting strategy in the presence of differing payloads. By rigidly attaching a set of unmanned air vehicles to a payload, the control effort required to transport the payload is divided across the vehicles. In the presence of uncertainty about a payload's mass and inertial characteristics, there is no inherent flightworthiness guarantee for a specific connected unmanned air vehicle configuration. This Paper describes a method for determining on-ground flightworthiness of the unmanned air vehicle-payload system while making minimal assumptions about inertial properties of the payload or the attachment configuration of the unmanned air vehicles. The probabilistic model itself is initialized and updated (built) by the algorithm. Within the model, the vehicles are positioned. Building upon prior theoretical developments, this Paper explores the differing sources of error in the estimates and experimentally validates the algorithm through a series of tests using prototype modular vehicles. Overall, simulation and test results highlight the dominant performance factors and demonstrate the feasibility of the approach for a range of payload geometries.

关键词： Composite Aircraft Payload System Thrust to Weight Ratio IMU Machine Learning Quadrotor algorithm performance Static Analysis Pitching Moment Ground Station

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A New Multiobjective Simulated Annealing algorithm-MOSA-GR: Application to the Optimal Design of Water Distribution Networks

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WATER RESOURCES RESEARCH 2020年第3期56卷 e2019WR025852-e2019WR025852页

作者： Cunha, M. Marques, J. Univ Coimbra Dept Civil Engn INESC Coimbra Inst Syst Engn & Comp Coimbra Coimbra Portugal

This paper presents a simulated annealing multiobjective algorithm developed to include novel features for promoting the convergence toward the best Pareto front that shows diversity and uniformity in the distribution of solutions. The new algorithm, MultiObjective Simulated Annealing with new Generation and Reannealing procedures (MOSA-GR), is a trajectory-based algorithm, where, in a first phase, diversified generation strategies are used to define candidate solutions at different stages of the search procedure. In a second phase a reannealing process starting at low temperature is implemented to intensify the search based on the last solutions of the first phase. An extensive comparison with solutions obtained by various multiobjective evolutionary algorithms (MOEAs) described in the literature is provided. Using a limited budget for the number of function evaluations, the results show that MOSA-GR has a very good performance and gives rise to better fronts, even compared with those obtained by merging the results from different MOEAs implemented in similar conditions.

关键词： optimization multiobjective simulated annealing water distribution networks algorithm performance Pareto solutions

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NEW MODIFIED HYBRID algorithm FOR PSEUDO-CONTRACTIVE MAPPINGS IN HILBERT SPACES

JOURNAL OF NONLINEAR FUNCTIONAL ANALYSIS

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JOURNAL OF NONLINEAR FUNCTIONAL ANALYSIS 2022年 2022卷

作者： Khomphurngson, Kannika Kamyun, Nilobol Nammanee, Kamonrat Univ Phayao Sch Sci Dept Math Phayao Thailand

In this study, we construct a modified hybrid algorithm and prove a convergence theorem for pseudo-contractive mappings in Hilbert spaces. Our results improve and generalize some recent related results in the literature.

关键词： algorithm performance Fixed point Hybrid algorithm Pseudo-contractive mapping Strong convergence

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Key Concepts, Weakness and Benchmark on Hash Table Data Structures

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algorithmS 2022年第3期15卷 100页

作者： Tapia-Fernandez, Santiago Garcia-Garcia, Daniel Garcia-Hernandez, Pablo Univ Politecn Madrid UPM Escuela Tecn Super Ingn Informat Calle Ramiro de Maeztu Madrid 28040 Spain

Most computer programs or applications need fast data structures. The performance of a data structure is necessarily influenced by the complexity of its common operations;thus, any data-structure that exhibits a theoretical complexity of amortized constant time in several of its main operations should draw a lot of attention. Such is the case of a family of data structures that is called hash tables. However, what is the real efficiency of these hash tables? That is an interesting question with no simple answer and there are some issues to be considered. Of course, there is not a unique hash table;in fact, there are several sub-groups of hash tables, and, even more, not all programming languages use the same variety of hash tables in their default hash table implementation, neither they have the same interface. Nevertheless, all hash tables do have a common issue: they have to solve hash collisions;that is a potential weakness and it also induces a classification of hash tables according to the strategy to solve collisions. In this paper, some key concepts about hash tables are exposed and some definitions about those key concepts are reviewed and clarified, especially in order to study the characteristics of the main strategies to implement hash tables and how they deal with hash collisions. Then, some benchmark cases are designed and presented to assess the performance of hash tables. The cases have been designed to be randomized, to be self-tested, to be representative of a real user cases, and to expose and analyze the impact of different factors over the performance across different hash tables and programming languages. Then, all cases have been programmed using C++, Java and Python and analyzed in terms of interfaces and efficiency (time and memory). The benchmark yields important results about the performance of these structures and its (lack of) relationship with complexity analysis.

关键词： data structures hash table hash tree algorithm performance complexity analysis

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