scholarly journals A Method for Predicting Efficiency of Perforated Muzzle Brakes

2021 ◽  
Vol 12 (4) ◽  
pp. 29-42
Author(s):  
Marta CZYŻEWSKA ◽  
Radosław TRĘBIŃSKI
Keyword(s):  
Partition Coefficient ◽  
Efficiency Coefficient ◽  
Flow Parameters ◽  
A Value ◽  
Mass Fluxes ◽  
Time Period ◽  
Long Time ◽  
Gasdynamic Flow ◽  
Time Changes ◽  
The Moment

This paper presents a method for predicting a value of a gasdynamic efficiency coefficient for perforated muzzle brakes. The method is based on the interior ballistics modelling for determining gasdynamic flow parameters at the brake inlet and 2D modelling the processes inside the brake with treating vents as circumferential slots. The modelling provides information about the mass flux time changes at the inlet and at the outlet of the brake. Using this information, the mass partition coefficient values and the gasdynamic efficiency coefficient values are calculated. It has been shown that the mass partition coefficient establishes very quickly and it is determined only by the geometry of the brake. The gasdynamic efficiency coefficient establishes after a relatively long time, what demands carrying out calculations for a relatively long time period. However, it has been shown that this problem can be solved by making use of the established ratio of mass fluxes at the outlet and the inlet. So, flow parameters’ values at the inlet are sufficient for determining the gasdynamic efficiency coefficient to the moment of attaining the final value. It has been shown that this value depends on the ballistics and on the vents inclination angle.

scholarly journals Lagrangian structures in time-periodic vortical flows

2006 ◽  
Vol 13 (6) ◽  
pp. 621-628 ◽  
Author(s):  
S. V. Kostrykin ◽  
A. A. Khapaev ◽  
V. M. Ponomarev ◽  
I. G. Yakushkin
Keyword(s):  
Velocity Field ◽  
Temporal Change ◽  
Regular Structures ◽  
Flow Parameters ◽  
Qualitative Interpretation ◽  
Time Period ◽  
Long Time ◽  
Adiabatic Chaos ◽  
Short Time ◽  
Time Periodic

Abstract. The Lagrangian trajectories of fluid particles are experimentally studied in an oscillating four-vortex velocity field. The oscillations occur due to a loss of stability of a steady flow and result in a regular reclosure of streamlines between the vortices of the same sign. The Eulerian velocity field is visualized by tracer displacements over a short time period. The obtained data on tracer motions during a number of oscillation periods show that the Lagrangian trajectories form quasi-regular structures. The destruction of these structures is determined by two characteristic time scales: the tracers are redistributed sufficiently fast between the vortices of the same sign and much more slowly transported into the vortices of opposite sign. The observed behavior of the Lagrangian trajectories is quantitatively reproduced in a new numerical experiment with two-dimensional model of the velocity field with a small number of spatial harmonics. A qualitative interpretation of phenomena observed on the basis of the theory of adiabatic chaos in the Hamiltonian systems is given. The Lagrangian trajectories are numerically simulated under varying flow parameters. It is shown that the spatial-temporal characteristics of the Lagrangian structures depend on the properties of temporal change in the streamlines topology and on the adiabatic parameter corresponding to the flow. The condition for the occurrence of traps (the regions where the Lagrangian particles reside for a long time) is obtained.

scholarly journals Global diagnostics of the ionospheric perturbations related to the seismic activity using the VLF radio signals collected on the DEMETER satellite

2006 ◽  
Vol 6 (5) ◽  
pp. 745-753 ◽  
Author(s):  
O. Molchanov ◽  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Akentieva ◽  
J. J. Berthelier ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Satellite Orbits ◽  
Acoustic Gravity Waves ◽  
Time Period ◽  
Demeter Satellite ◽  
The World ◽  
Long Time ◽  
Radio Signals ◽  
The Moment ◽  
Large Earthquakes

Abstract. The analysis of the VLF signals radiated by ground transmitters and received on board of the French DEMETER satellite, reveals a drop of the signals (scattering spot) connected with the occurrence of large earthquakes. The extension of the "scattering spots" zone is large enough (1000–5000 km) and, probably, it increases with the magnitude of the "relative" earthquake. A possible model to explain the phenomenology, based on the acoustic gravity waves and the ionosphere turbulence, is proposed. The method of diagnostics applied to this study has the advantage to be a global one due to the world wide location of the powerful VLF transmitters and of the satellite reception. However, a specific disadvantage exists because the method requires rather a long time period of analysis due to the large longitudinal displacements among the successive satellite orbits. At the moment, at least, one month seems to be necessary.

'A town built on migration?' Calculating the human capital value of migration to Reading, 1851-1871

2019 ◽  
pp. 26-54
Author(s):  
Daniel James Gooch
Keyword(s):  
Human Capital ◽  
Economic Value ◽  
Infrastructure Projects ◽  
Economic Output ◽  
Net Migration ◽  
A Value ◽  
Time Period ◽  
The Town ◽  
Age And Sex ◽  
Capital Value

This article provides an estimate of the human capital value of migration to Reading in the period 1851-1871 to the town's economy. This is determined by estimating total net migration to the town across this period by age and sex and assigning all migrants a value for expected lifetime economic output less expected lifetime consumption costs. The final figures are contextualised by comparison with the value of social overhead capital used to fund significant local infrastructure projects in the same time period and show that, from a human capital perspective, the value of migration to Reading was very significant. This article thus addresses significant historiographical gaps in the study of Victorian labour migration to southern provincial towns and provides an original perspective to studies of the economic value of migration and its role in the growth of such communities.

THE USE OF HISTORICAL DATA IN ACCOUNTING RESEARCH: THE CASE OF THE AMERICAN SUGAR REFINING COMPANY

1997 ◽  
Vol 24 (2) ◽  
pp. 1-24 ◽  
Author(s):  
Robert Bricker ◽  
Kevin Brown
Keyword(s):  
Capital Market ◽  
Historical Data ◽  
Abnormal Returns ◽  
Deep Understanding ◽  
Historical Record ◽  
Historical Period ◽  
Financial Condition ◽  
A Value ◽  
Time Period ◽  
And Performance

In 1908, the American Sugar Refining Company (ASR) reversed its long-held policy of secrecy as to its financial condition and performance. Prior work, applying contemporary capital market methods to ASR security price data of that period, has suggested a value to ASR shareholders of this policy reversal. This paper examines the historical record of that time and presents additional evidence on this matter, particularly in terms of identifying potentially confounding events occurring during the period under study. The results of this analysis suggest a difficulty in attributing observed abnormal returns to ASR's secrecy policy reversal on the basis of the results obtained from applying capital markets methods. This analysis is useful for scholars interested in applying modern capital market methods to historical data. It highlights the significance of the possible effects of contemporaneous historical events, focuses attention on the importance of a deep understanding of the historical period studied, and suggests a value in combining historical and empirical-markets methods to gain a richer understanding of the events and conditions in the time period under study.

scholarly journals Internet page content analysis of north European Sea ports

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Olli-Pekka Hilmola ◽  
Andres Tolli ◽  
Ain Kiisler
Keyword(s):  
Content Analysis ◽  
Environmental Issues ◽  
Basic Design ◽  
Time Period ◽  
Long Time ◽  
Sea Ports ◽  
Selection Of

Abstract This study analyses 98 Internet pages of sea ports located in Sweden, Finland and Estonia during years 2017–2019. Aim of the study is to find, how website basic design is completed (colours and languages), how slogans, environmental issues, statistics and hinterland transports are reported. Based on the analysis, it appears as rather common that sea ports follow conservative selection of colours in their websites, where blue and white are clearly most popular. Typically, English and Swedish are as the most common used language, followed by Finnish, Russian and Estonian. In some rare cases, websites are offered in Chinese or German. Larger sea ports do have clear “slogans”, where smaller ones are just having lengthy justification for their existence. Environmental issues are increasing concern among sea ports, and these are mostly mentioned in details within Swedish actors. Providing statistics varies among companies, and in some sea ports these are provided from very long time period, where in others from just previous years or then only from last year (or even at all). It is common for companies to report that they have sustainable hinterland access, railway available.

Gonad morphology and gametogenesis in the deep-sea jellyfish Atolla wyvillei and Periphylla periphylla (Scyphozoa: Coronatae) collected from Cape Hatteras and the Gulf of Mexico

2009 ◽  
Vol 90 (6) ◽  
pp. 1095-1104 ◽  
Author(s):  
Cathy H. Lucas ◽  
Adam J. Reed
Keyword(s):  
Gulf Of Mexico ◽  
Gonad Development ◽  
Bell Diameter ◽  
Western Atlantic ◽  
Gonad Morphology ◽  
Time Period ◽  
Cape Hatteras ◽  
Literature Evidence ◽  
Long Time ◽  
North Western

Observations on gonad morphology and the structure of ovaries and testes of the coronate scyphozoans Atolla wyvillei and Periphylla periphylla are described based on samples collected from the Gulf of Mexico and Cape Hatteras (north-western Atlantic). In A. wyvillei, gonads of distinguishable sex were observed in medusae as small as 17 mm bell diameter (BD). Spermatogenesis occurred within follicles (average 366 × 254 μm) that were evenly distributed throughout the gonad. Oocytes in different stages of development were observed in all the females with gonads. Oocytes arise from the gastrodermis and migrate into the mesoglea to develop from early-mid to late vitellogenic oocytes characterized by a large nucleus and granular (organic-rich) cytoplasm. The largest oocytes measured were 543 μm and 263 μm from the Gulf of Mexico and Cape Hatteras respectively. Possible reasons for this difference are discussed. In P. periphylla gonads were also initially observed in medusae 17 mm BD, although not all larger medusae had obvious gonads. Unlike A. wyvillei sperm follicles were arranged in long convoluted rows normally only one follicle thick. The organization of ooytes in female P. periphylla was very similar to A. wyvillei, although the gonads were small and the number of oocytes present in each gonad very low (<22). The largest oocyte measured was 777 μm in a 53 mm BD medusa. Although medusae were collected from one time period only (September) in this study, our findings appear to be in agreement with literature evidence indicating that coronate jellyfish produce few eggs continuously over a long time period. Aspects of gonad development and gametogenesis are discussed with respect to potential differences in site productivity and species identification.

scholarly journals Development of COVID-19 vaccines utilizing gene therapy technology

2021 ◽  
Author(s):  
Hironori Nakagami
Keyword(s):  
Viral Vectors ◽  
High Efficiency ◽  
Genetic Disorders ◽  
Rapid Development ◽  
Adenovirus Vector ◽  
Phase 3 ◽  
Double Blind ◽  
Time Period ◽  
Short Period ◽  
Long Time

Abstract There is currently an outbreak of respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Coronavirus disease 2019 (COVID-19) is caused by infection with SARS-CoV-2. Individuals with COVID-19 have symptoms that are usually asymptomatic or mild in most initial cases. However, in some cases, moderate and severe symptoms have been observed with pneumonia. Many companies are developing COVID-19 vaccine candidates using different technologies that are classified into four groups (intact target viruses, proteins, viral vectors and nucleic acids). For rapid development, RNA vaccines and adenovirus vector vaccines have been urgently approved, and their injection has already started across the world. These types of vaccine technologies have been developed over more than 20 years using translational research for use against cancer or diseases caused by genetic disorders but the COVID-19 vaccines are the first licensed drugs to prevent infectious diseases using RNA vaccine technology. Although these vaccines are highly effective in preventing COVID-19 for a short period, safety and efficiency evaluations should be continuously monitored over a long time period. As the time of writing, more than 10 projects are now in phase 3 to evaluate the prevention of infection in double-blind studies. Hopefully, several projects may be approved to ensure high-efficiency and safe vaccines.

Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

2002 ◽  
Author(s):  
Masahiro Ishibashi
Keyword(s):  
Fine Structure ◽  
Steady State ◽  
Discharge Coefficient ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Time Intervals ◽  
Critical Flow Rate ◽  
A Value ◽  
Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

scholarly journals Comparison of the spatial patterns of schistosomiasis in Zimbabwe at two points in time, spaced twenty-nine years apart: is climate variability of importance?

2017 ◽  
Vol 12 (1) ◽  
Author(s):  
Ulrik B. Pedersen ◽  
Dimitrios-Alexios Karagiannis-Voules ◽  
Nicholas Midzi ◽  
Tkafira Mduluza ◽  
Samson Mukaratirwa ◽  
...  
Keyword(s):  
Climate Change ◽  
Geographical Distribution ◽  
Predictive Accuracy ◽  
Weather Data ◽  
Geostatistical Model ◽  
Prevalence Data ◽  
Time Period ◽  
Long Time ◽  
Potential Risk Factors ◽  
The Impact

Temperature, precipitation and humidity are known to be important factors for the development of schistosome parasites as well as their intermediate snail hosts. Climate therefore plays an important role in determining the geographical distribution of schistosomiasis and it is expected that climate change will alter distribution and transmission patterns. Reliable predictions of distribution changes and likely transmission scenarios are key to efficient schistosomiasis intervention-planning. However, it is often difficult to assess the direction and magnitude of the impact on schistosomiasis induced by climate change, as well as the temporal transferability and predictive accuracy of the models, as prevalence data is often only available from one point in time. We evaluated potential climate-induced changes on the geographical distribution of schistosomiasis in Zimbabwe using prevalence data from two points in time, 29 years apart; to our knowledge, this is the first study investigating this over such a long time period. We applied historical weather data and matched prevalence data of two schistosome species (<em>Schistosoma haematobium</em> and <em>S. mansoni</em>). For each time period studied, a Bayesian geostatistical model was fitted to a range of climatic, environmental and other potential risk factors to identify significant predictors that could help us to obtain spatially explicit schistosomiasis risk estimates for Zimbabwe. The observed general downward trend in schistosomiasis prevalence for Zimbabwe from 1981 and the period preceding a survey and control campaign in 2010 parallels a shift towards a drier and warmer climate. However, a statistically significant relationship between climate change and the change in prevalence could not be established.

scholarly journals Local Differential Privacy for Evolving Data

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Matthew Joseph ◽  
Aaron Roth ◽  
Jonathan Ullman ◽  
Bo Waggoner
Keyword(s):  
Large Scale ◽  
Differential Privacy ◽  
Statistical Information ◽  
Underlying Distribution ◽  
Specific Distribution ◽  
Time Period ◽  
Long Time ◽  
Heavy Hitter ◽  
Single Use ◽  
A New Technique

There are now several large scale deployments of differential privacy used to collect statistical information about users. However, these deployments periodically recollect the data and recompute the statistics using algorithms designed for a single use. As a result, these systems do not provide meaningful privacy guarantees over long time scales. Moreover, existing techniques to mitigate this effect do not apply in the “local model” of differential privacy that these systems use. In this paper, we introduce a new technique for local differential privacy that makes it possible to maintain up-to-date statistics over time, with privacy guarantees that degrade only in the number of changes in the underlying distribution rather than the number of collection periods. We use our technique for tracking a changing statistic in the setting where users are partitioned into an unknown collection of groups, and at every time period each user draws a single bit from a common (but changing) group-specific distribution. We also provide an application to frequency and heavy-hitter estimation.

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