scholarly journals Optimal Search Parameters for A Random Pulsed-Point Source with the Required Accuracy

2019 ◽  
Vol 9 (1) ◽  
pp. 2540-2554
Keyword(s):  
High Speed ◽  
Point Sources ◽  
Multidimensional Case ◽  
Optimal Search ◽  
Localization Accuracy ◽  
Optimal Procedure ◽  
Statistical Sense ◽  
The Moment ◽  
Random Times ◽  
Localization Time

The questions of creating high-speed algorithms for detecting and localizing point sources having a random distribution and manifesting themselves by generating instantaneous delta pulses at random times are described. The search is carried out by a system including one or more receiving devices, and is performed taking into account the requirements for localization accuracy. It is assumed that all receivers have freely tunable viewing windows. The optimal procedure is one that minimizes (in a statistical sense) the average localization time. It is established that even with relatively low requirements for localization accuracy, the optimal procedure consists of several stages (each such stage ends at the moment of the next pulse registration). In this case, it is possible receiving system to miss some pulses generated by the source during the optimal search. In the work, the optimal search parameters are calculated depending on the number of receiving devices and the required localization accuracy. The possibility of using the results in a multidimensional case is shown.

scholarly journals Time-optimal algorithms focused on the search for random pulsed-point sources

2019 ◽  
Vol 43 (4) ◽  
pp. 605-610 ◽  
Author(s):  
A.L. Reznik ◽  
A.V. Tuzikov ◽  
A.A. Soloviev ◽  
A.V. Torgov ◽  
V.A. Kovalev
Keyword(s):  
Optimal Strategies ◽  
Pulse Generation ◽  
Point Sources ◽  
Optimal Search ◽  
Localization Accuracy ◽  
Time Optimal ◽  
One Step ◽  
The Moment ◽  
Random Times ◽  
Localization Time

The article describes methods and algorithms related to the analysis of dynamically changing discrete random fields. Time-optimal strategies for the localization of pulsed-point sources having a random spatial distribution and indicating themselves by generating instant delta pulses at random times are proposed. An optimal strategy is a procedure that has a minimum (statistically) average localization time. The search is performed in accordance with the requirements for localization accuracy and is carried out by a system with one or several receiving devices. Along with the predetermined accuracy of localization of a random pulsed-point source, a significant complicating factor of the formulated problem is that the choice of the optimal search procedure is not limited to one-step algorithms that end at the moment of first pulse generation. Moreover, the article shows that even with relatively low requirements for localization accuracy, the time-optimal procedure consists of several steps, and the transition from one step to another occurs at the time of registration of the next pulse by the receiving system. In this case, the situation is acceptable when during the process of optimal search some of the generated pulses are not fixed by the receiving system. The parameters of the optimal search depending on the number of receiving devices and the required accuracy of localization are calculated and described in the paper.

Search time optimization for random pulse sources with given accuracy

2020 ◽  
Author(s):  
А.Л. Резник ◽  
А.В. Тузиков ◽  
А.А. Соловьев ◽  
А.В. Торгов ◽  
В.А. Ковалев
Keyword(s):  
A Priori ◽  
Search Algorithms ◽  
Point Sources ◽  
Random Point ◽  
Technical Diagnostics ◽  
Optimal Search ◽  
Localization Accuracy ◽  
Random Pulse ◽  
Time Optimal ◽  
Equivalent Problems

Исследуются вопросы построения быстродействующих алгоритмов обнаружения и локализации точечных источников, имеющих случайное распределение и обнаруживающих себя в случайные моменты времени генерацией мгновенных дельта-импульсов. Поиск осуществляется системой, включающей одно либо несколько приемных устройств, и выполняется с соблюдением требований по точности локализации. Предполагается, что все приемные устройства имеют произвольно перестраиваемые во времени окна обзора. Оптимальной считается процедура, которая в статистическом плане (т.е. по ансамблю реализаций) минимизирует среднее время локализации. Показано, что даже при сравнительно невысоких требованиях к точности локализации оптимальная процедура состоит из нескольких этапов, каждый из которых заканчивается в момент регистрации очередного импульса. Вполне допускается ситуация, когда в процессе оптимального поиска часть генерируемых источником импульсов может быть пропущена приемной системой. В работе рассчитаны и систематизированы параметры оптимального поиска в зависимости от количества приемных устройств и требуемой точности локализации. Для случая предельно высоких требований к точности локализации рассчитаны параметры асимптотически оптимальных поисковых алгоритмов. Показана возможность использования полученных результатов в многомерном случае. Purpose. The main goal of the research is to develop time-optimal algorithms for the localization of point sources that have a random spatial distribution and indicate themselves by generating instantaneous delta pulses at random time points. Methods. In many practically important problems requiring the highest reduction in the average time of localization of signal objects, the complexity of constructing optimal search algorithms forces researchers to resort to various kinds of simplifications or to the use of methods of numerical and simulation modelling. The mathematical apparatus used in the article belongs to probabilistic-statistical and non-linear programming methods. In a number of sections of the study (in particular, when constructing optimal control algorithms for multi-receiving search engines), traditional methods of discrete analysis and applied programming were used. Results. The solution of the variational problem is found, which minimizes the average localization time in the class of one-stage search algorithms with a known distribution density and the simultaneous absence of a priori information about the intensity of a random pulse source. For random point sources with a priori known intensity of the instantaneous generation of pulses, physically realizable multistage search algorithms have been constructed that have a significant gain in speed over single-stage algorithms, especially with increased requirements for localization accuracy. For a uniform distribution of a random source, an optimal strategy of multi-stage search was calculated, depending on the required localization accuracy and the number of receivers used. Findings. A distinctive feature of the studies is their universality, since in mathematical terms, the discussed problems and algorithms for the time-optimal search of random point-pulse objects arise in many scientific and technical applications. In particular, such studies are needed when developing methods for intermittent failures troubleshooting in the theory of reliability, in mathematical communication theory and in problems of technical diagnostics. Scientifically equivalent problems appear in the problems of detection, localization and tracking of radiation targets for eliminating malfunctions that manifest themselves in the form of intermittent failures. Scientifically equivalent problems arise in the problems of detecting, localizing and tracking radiation source targets.

Gliding Flight of the White-Backed Vulture Gyps Africanus

1971 ◽  
Vol 55 (1) ◽  
pp. 13-38 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
High Speed ◽  
Lift Coefficient ◽  
The Body ◽  
East African ◽  
Induced Drag ◽  
Gliding Flight ◽  
Vertical Speed ◽  
Statistical Sense ◽  
Pass Through ◽  
Comparison Measurements

1. Glide-comparison measurements were made on ten species of East African soaring birds using a Schleicher ASK-14 powered sailplane. Horizontal and vertical speed differences between bird and glider were measured by a photographic method, and used to estimate the bird's horizontal and vertical speeds relative to the air. The analysis refers to the white-backed vulture, since by far the largest number of measurements was obtained on this species. 2. A regression analysis using a two-term approximation to the glide polar yielded an implausibly high estimate of induced drag, which was attributed to a lack of observations at lift coefficients above 0.72. An amended glide polar was constructed assuming elliptical lift distribution and a maximum lift coefficient of 1.6 to define the low-speed end, while the high-speed end was made to pass through the mean horizontal and sinking speeds of all the experimental points. This curve gave a minimum sinking speed of 0.76 m/s at a forward speed of 10 m/s, and a best glide ratio of 15.3:1 at 13 m/s. It did not differ significantly (in the statistical sense) from the original regression curve. 3. In comparing the estimated circling performance, based on the amended glide polar, with that of the ASK-14, it was concluded that the rates of sink of both should be comparable, but that the glider would require thermals with radii about 4.3 times as great as those needed to sustain the birds. The conclusions are consistent with experience of soaring in company with birds. 4. In an attempt to assess the adaptive significance of the low-aspect-ratio wings of birds specializing in thermal soaring, the white-backed vulture's circling performance was compared with that of an ‘albatross-shaped vulture’, an imaginary creature having the same mass as a white-backed vulture, combined with the body proportions of a wandering albatross. It appears that the real white-back would be at an advantage when trying to remain airborne in thermals with radii between 14 and 17 m, but that the albatross-shaped vulture would climb faster in all wider thermals; on account of its much better maximum glide ratio, it should also achieve higher cross-country speeds. It is concluded that the wing shape seen in vultures and storks is not an adaptation to thermal soaring as such, but is more probably a compromise dictated by take-off and landing requirements. 5. The doubts recently expressed by Tucker & Parrott (1970) about the results and conclusions of Raspet (1950a, b; 1960) are re-inforced by the present experience.

scholarly journals THORACIC AND LUMBAR HEMIVERTEBRA EXCISION IN PEDIATRIC PATIENTS: HOW DOES THE OPERATION TECHNIQUE INFLUENCE ON OUTCOMES? (СOHORT ANALYSIS AND LITERATURE REVIEW)

2018 ◽  
Vol 24 (3) ◽  
pp. 83-90 ◽  
Author(s):  
A. Yu. Mushkin ◽  
D. G. Naumov ◽  
E. Yu. Umenushkina
Keyword(s):  
Blood Loss ◽  
Surgical Approach ◽  
High Speed ◽  
Operation Technique ◽  
Posterior Fixation ◽  
Surgical Trauma ◽  
Dorsal Approach ◽  
Total Blood ◽  
High Speed Burr ◽  
The Moment

Purpose of the study— to study impact of hemi-vertebrae extirpation technique in mono-segmental reconstructionon the surgical trauma.Material and Methods.34 patients underwent 36 mono-segmental extirpations of hemi-vertebrae followed by aposterior fixation during a single center four years cohort study. Mean age of children at the moment of procedure was 4 years and 3 months (min — 1 year, max — 14 years). The authors studied impact of pathology level, surgical approach, type of bony structures removal technique and age of the patients on the time of procedure and volume of blood loss. Results.Extirpation of thoracic hemi-vertebrae was characterized by a lengthier procedure and greater blood lossin contrast to lumbar hemi-vertebrae. Patients were divided into three groups depending on extirpation technique: 1)  extirpation from two approaches using a high-speed burr; 2) from a single dorsal approach using the same extirpation technique; 3) from dorsal approach using ultrasonic bone scalpel. Surgery time was 208±72 min in the first group, 187±54 min in the second group, and 170±30 min in the third group; blood loss volume was 181±39, 181±53, 132±73 ml respectively in the groups, or 11.5±4.3%, 9.4±2.8% and 9.6±5.2% of total blood volume, respectively.Conclusion.Surgical approach and hemi-vertebrae extirpation technique in children have a varying impact onsurgery time and intraoperative blood loss, and the least values were reported for posterior approach using ultrasonic bone scalpel.

scholarly journals Enriching particles on a bubble through drainage: Measuring and modeling the concentration of microbial particles in a bubble film at rupture

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Peter L. L. Walls ◽  
James C. Bird
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
High Speed ◽  
Ocean Surface ◽  
Sea Surface ◽  
Bulk Liquid ◽  
Surface Microlayer ◽  
Exchange Processes ◽  
Sea Surface Microlayer ◽  
The Moment

The concentration of microbes and other particulates is frequently enriched in the droplets produced by bursting bubbles. As a bubble rises to the ocean surface, particulates in the bulk liquid can be transported to the sea surface microlayer by attaching to the bubble’s interface. When the bubble eventually ruptures, a fraction of these particulates is often ejected into the surroundings in film droplets with a particulate concentration that is higher than in the liquid from which they formed. The precise mechanisms responsible for this enrichment are unclear, yet such enrichment at the ocean surface influences important exchange processes with the atmosphere. Here we provide evidence that drainage, coupled with scavenging, is responsible for the enrichment. By simultaneously recording the drainage and rupture effects with high-speed and standard photography, we directly measured the particulate concentrations in the thin film of a bubble cap at the moment before it ruptures. We observed that the enrichment factor strongly depends on the film thickness at rupture, and developed a physical model, based on scavenging and drainage, that is consistent with our observations. We have also demonstrated that this model is quantitatively consistent with prior observations of film drop enrichment, indicating its potential for a broader range of applications in the study of the sea surface microlayer and related phenomena.

Vibrations of Elastic Connecting Rod of a High-Speed Slider-Crank Mechanism

1971 ◽  
Vol 93 (2) ◽  
pp. 636-644 ◽  
Author(s):  
Peter W. Jasinski ◽  
Ho Chong Lee ◽  
George N. Sandor
Keyword(s):  
Small Parameter ◽  
High Speed ◽  
Elastic Stability ◽  
Method Of Averaging ◽  
Connecting Rod ◽  
Transverse Vibrations ◽  
Elastic Bar ◽  
The Moment ◽  
Steady State Solutions ◽  
Crank Mechanism

The research involved in this paper falls into the area of analytical vibrations applied to planar mechanical linkages. Specifically, a study of the vibrations, associated with an elastic connecting-bar for a high-speed slider-crank mechanism, is made. To simplify the mathematical analysis, the vibrations of an externally viscously damped uniform elastic connecting bar is taken to be hinged at each end (i.e., the moment and displacement are assumed to vanish at each end). The equations governing the vibrations of the elastic bar are derived, a small parameter is found, and the solution is developed as an asymptotic expansion in terms of this small parameter with the aid of the Krylov-Bogoliubov method of averaging. The elastic stability is studied and the steady-state solutions for both the longitudinal and transverse vibrations are found.

In vivo cinematographic analysis of behavior of the aortic valve

1981 ◽  
Vol 240 (2) ◽  
pp. H286-H292 ◽  
Author(s):  
A. A. Van Steenhoven ◽  
C. W. Verlaan ◽  
P. C. Veenstra ◽  
R. S. Reneman
Keyword(s):  
Aortic Valve ◽  
Left Atrium ◽  
High Speed ◽  
Aortic Flow ◽  
Fluid Viscosity ◽  
Valve Closure ◽  
Flow Deceleration ◽  
Transparent Liquid ◽  
The Moment

In open-chest dogs direct-cinematographic high-speed recordings of aortic valve movement were made using a thin flexible fiberscope. Simultaneously ECG, ascending aortic flow (electromagnetically), and the pressures in the aorta, left ventricle, and left atrium were recorded. Replacement of blood by a transparent liquid (Tyrode solution) was done with two roller pumps, one connected to the left atrium and the other to the femoral artery. Free outflow occurred through a cannula in the pulmonary artery. Comparison of the film frames with the aortic flow signals revealed that 1) the valve was completely open at the moment that aortic flow had reached about 75% of its maximum value; 2) the opening time was 32 ms; 3) valve closure started before the onset of aortic flow deceleration; 4) at least 80% of the closure was completed before aortic flow becomes zero; 5) complete valve closing coincided with the moment of maximum backflow in the valve; 6) the shape of the valvular orifice at complete opening was almost circular; and 7) fluid viscosity had no significant effect on valve closure.

Design, Simulation and Testing of Overpack Encapsulation Vessels

2012 ◽  
Author(s):  
A. Towse ◽  
J. Dodds
Keyword(s):  
Pressure Vessel ◽  
High Speed ◽  
Failure Modes ◽  
Inner Product ◽  
Central Position ◽  
Video Footage ◽  
Rule Approach ◽  
The Moment ◽  
Explicit Dynamic ◽  
The Impact

The paper presents an overpack designed to contain nuclear product cans which may become pressurised or contaminated. The overpack provides a protective barrier to an inner product can, and due to the possibility of leakage of gas from the contents, the overpack must also function as a pressure vessel. Furthermore, the overpack is required to provide physical protection to the inner can and proof of containment was therefore necessary under a number of different impact scenarios, both pre-pressurised and also with the simulation of pressurisation at the moment of impact. Additionally, the inner product can was to be maintained in a central position during the deceleration at impact. This paper focuses on the analytical design and substantiation of the impact of the system which was performed using an explicit dynamic solver for a number of impact orientations. The design of the overpack to satisfy the relevant pressure vessel Code are not discussed in detail. The potential failure modes of the overpack during impact were assessed and design improvements made over a number of iterations. Following completion of the design and simulation phase, prototypes were built and tested to verify the engineering design and analysis. The testing showed that simulation driven design in conjunction with a pressure vessel design by rule approach was successful in creating a solution for the product can encapsulation. A comparison between the analytical simulation and high-speed video footage of the testing was also made.

Numerical Modeling of Fragmentation Characteristics of Explosive Fragmentation Munitions

2002 ◽  
Author(s):  
Vladimir M. Gold
Keyword(s):  
High Speed ◽  
Average Length ◽  
Three Dimensional ◽  
Fragmentation Model ◽  
Computational Technique ◽  
Entire Body ◽  
Detonation Products ◽  
Explosive Fragmentation ◽  
Break Up ◽  
The Moment

Numerical simulations of explosive fragmentation munitions presented in this work integrate three-dimensional axisymmetric hydrocode analyses with analytical fragmentation modeling. The developed analytical fragmentation model is based on the Mott’s theory of break-up of cylindrical “ring-bombs” (Mott, 1947), in which the average length of fragments is a function of the radius and velocity of the ring at the moment of break-up, and the mechanical properties of the metal. The fundamental assumption of the model is that the fragmentation occurs instantly throughout the entire body of the shell. Adopting Mott’s critical fracture strain concept (Mott, 1947), the moment of the shell break-up is identified in terms of the high explosive detonation products volume expansions, V/V0. The assumed fragmentation time determined from the high-speed photographic data of Pearson (1990) had been approximately three volume expansions, the fragmentation being defined as the instant at which the detonation products first appear as they emanate from the fractures in the shell. The newly developed computational technique is applied to both the natural and preformed explosive fragmentation munitions problems. Considering relative simplicity of the model, the accuracy of the prediction of fragment spray experimental data is rather remarkable.

Improved Techniques for Measuring the Indentation and Thickness of Articular Cartilage

1989 ◽  
Vol 203 (3) ◽  
pp. 143-150 ◽  
Author(s):  
A C Swann ◽  
B B Seedhom
Keyword(s):  
Articular Cartilage ◽  
High Speed ◽  
Articular Surface ◽  
Indentation Test ◽  
Displacement Transducer ◽  
Data Logging ◽  
Large Numbers ◽  
Indentation Tests ◽  
The Moment ◽  
Measurement Repeatability

A review of the techniques previously employed in the indentation and measurement of the thickness of articular cartilage has led to new and improved techniques for performing both measurements. By utilizing high-speed, microcomputer-controlled data logging techniques, simultaneous monitoring of signals from a dynamic load cell and a displacement transducer could be made throughout an indentation test. The position of the indenter as it touched the articular surface could thus be determined automatically by identifying the moment at which a positive change in the load signal occurred. Less accurate and more time consuming techniques previously required for determining the position of the cartilage surface were hence avoided. The apparatus also included a critically damped dashpot which prevented any transient loads being applied to the cartilage. Depths of indentation could be measured to an accuracy of 0.005 mm with a measurement repeatability of 2.14 per cent. By replacing the indenter with a sharp needle, the apparatus was also capable of measuring the undeformed thickness of cartilage. An accuracy of ±0.012 mm could be achieved with a measurement repeatability of 1.2 per cent. The apparatus is particularly suited to survey work where large numbers of indentation tests are to be performed.

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