scholarly journals Hydrogen Maser Clocks and Deep Space Systems Involving Clocks: Ultra-Long Baseline Interferometry Definition of an Inertial Frame, Searches for Pulsed Gravitational Radiation

1988 ◽  
Vol 129 ◽  
pp. 507-507
Author(s):  
R.F.C. Vessot
Keyword(s):  
Gravitational Radiation ◽  
Time Correlation ◽  
Deep Space ◽  
Hydrogen Maser ◽  
Deep Space Network ◽  
University Of British Columbia ◽  
Long Baseline ◽  
The Stability ◽  
Definition Of

The present status of research and development in atomic hydrogen maser clocks gives stability of 3×10−16 in Δf/f for intervals of several hours. Long-term drift rates are in the order of 1×10−15/day and uninterrupted operating lifetimes of more than 4 years are fairly common with SAO's VLG-series masers. Experiments with improved techniques for separating atoms in the desired state confirm that stability can be achieved with existing technology at levels below 1×10−16. A four-fold improvement beyond this level appears feasible with more smoothly applied storage volume coatings of fluorinated materials. A recent breakthrough in technology has been made by SAO/Harvard, M.I.T. and, University of British Columbia, by operating hydrogen masers at 0.4K using storage coatings of superfluid liquid helium. This promises stability better than 1 × 10−17 in Δf/f for intervals longer than 30 seconds. Features of a hydrogen maser operating at room temperature, developed at SAO for long-term (∼7 years) unattended operation in space, are described. Possible applications of such masers with stability ∼1×10−16 for intervals 104–105 seconds in a deep space network of 4 (or more) radio astronomy antennas interconnected by time correlated one-way and two-way Doppler systems are discussed. By comparing the phase of signals propagated in both senses around the four (or more) closed triangular paths, changes in the magnitude and direction of the baselines can be determined with reference to inertial space defined by the constancy and isotropy of the velocity of light. The system is also sensitive to pulsed gravitational radiation at wavelengths less than the inter-terminal distances. Sensitivity is limited by the stability of the clocks and the fluctuations of ionization in the paths between stations. Multiple station time correlation of Doppler fluctuation in the signals between the six (or more) inter-terminal paths can be used to determine the direction and polarization of the pulsed gravitational radiation.

scholarly journals Determination of UT1 and Polar Motion by the Deep Space Network Using Very Long Baseline Interferometry

1979 ◽  
Vol 82 ◽  
pp. 199-209 ◽  
Author(s):  
J. L. Fanselow ◽  
J. B. Thomas ◽  
E. J. Cohen ◽  
P. F. MacDoran ◽  
W. G. Melbourne ◽  
...  
Keyword(s):  
Polar Motion ◽  
Very Long Baseline Interferometry ◽  
Deep Space ◽  
Deep Space Network ◽  
Accuracy Requirement ◽  
Space Network ◽  
Long Baseline ◽  
Navigation Accuracy ◽  
Better Than

The Deep Space Network (DSN) [operated by JPL under contract to the National Aeronautics and Space Administration] is implementing a Very Long Baseline Interferometry (VLBI) capability at DSS 63 (Spain), DSS 14 (California, USA), and DSS 43 (Australia) to support the navigation requirements of planetary space missions. The early development work for this system has already demonstrated the capability of measuring UT1 with a formal accuracy as low as 0.6 msec with only 6 hours of data. Further, a radio astrometric catalog of approximately 45 sources whose positions are known to better than has been constructed. In addition to these measurements, this paper describes the characteristics and anticipated performance of the complete VLBI system being implemented within the DSN for operational use in mid-1979. In particular, one of the capabilities of this system will be the measurement of UT1 and polar motion at weekly intervals. Although the navigation accuracy requirement is only 50 cm for the Voyager mission, this system should be capable of delivering UT1 and polar motion determinations with decimeter accuracy if it is operated at maximum performance. An additional requirement of this operational system is that it have the capability of providing these results within 24 hours of the actual observations.

Determination of UT1 and Polar Motion by the Deep Space Network using very Long Baseline Interferometry

1979 ◽  
pp. 199-209 ◽  
Author(s):  
J. L. Fanselow ◽  
J. B. Thomas ◽  
E. J. Cohen ◽  
P. F. MacDoran ◽  
W. G. Melbourne ◽  
...  
Keyword(s):  
Polar Motion ◽  
Very Long Baseline Interferometry ◽  
Deep Space ◽  
Deep Space Network ◽  
Space Network ◽  
Long Baseline

scholarly journals A Clock Stabilization System for CHIME/FRB Outriggers

2022 ◽  
Vol 163 (2) ◽  
pp. 48
Author(s):  
J. Mena-Parra ◽  
C. Leung ◽  
S. Cary ◽  
K. W. Masui ◽  
J. F. Kaczmarek ◽  
...  
Keyword(s):  
Stabilization System ◽  
Hydrogen Maser ◽  
Crystal Oscillator ◽  
Term Stability ◽  
Long Term Stability ◽  
Intensity Mapping ◽  
Long Baseline ◽  
Cygnus A ◽  
The Stability ◽  
Reference Clock

Abstract The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the prime telescope for detecting fast radio bursts (FRBs). CHIME/FRB Outriggers will be a dedicated very-long-baseline interferometry (VLBI) instrument consisting of outrigger telescopes at continental baselines working with CHIME and its specialized real-time transient-search backend (CHIME/FRB) to detect and localize FRBs with 50 mas precision. In this paper, we present a minimally invasive clock stabilization system that effectively transfers the CHIME digital backend reference clock from its original GPS-disciplined ovenized crystal oscillator to a passive hydrogen maser. This enables us to combine the long-term stability and absolute time tagging of the GPS clock with the short- and intermediate-term stability of the maser to reduce the clock timing errors between VLBI calibration observations. We validate the system with VLBI-style observations of Cygnus A over a 400 m baseline between CHIME and the CHIME Pathfinder, demonstrating agreement between sky-based and maser-based timing measurements at the 30 ps rms level on timescales ranging from one minute to up to nine days, and meeting the stability requirements for CHIME/FRB Outriggers. In addition, we present an alternate reference clock solution for outrigger stations that lack the infrastructure to support a passive hydrogen maser.

scholarly journals The Bolsheviks in Eastern Ukraine and their Competing State Projects (1917-1918): The Case of the Donets-Krivoi Rog Soviet Republic

2021 ◽  
Vol 7 ◽  
Author(s):  
Hanna Perekhoda
Keyword(s):  
Russian Revolution ◽  
Peace Treaty ◽  
Eastern Region ◽  
Political Strategy ◽  
The Russian Empire ◽  
The Stability ◽  
Definition Of ◽  
State Projects ◽  
The Military

After the Russian Revolution of February 1917, the definition of the Ukrainian territory became an important issue. One of the major controversies concerned the territorial affiliation of the eastern part of the country, a highly industrialised region located halfway between the Russian core and the Ukrainian periphery of the empire. This article focuses on the split within the Bolshevik Party between supporters of Donbass belonging to Ukraine and defenders of a Donets-Krivoi Rog republic attached to Russia. We show that this was not so much an ideological conflict between the "pro-Russians" and the "pro-Ukrainians" as it was a difference of views on the military and political strategy to be implemented in order to preserve the gains of the revolution and make its expansion possible. Moscow's decision to support the project of a Soviet Ukraine, thereby ruling out any possibility of separation of its eastern region, can be explained both by the desire to solve immediate problems (circumventing the provisions of a peace treaty, strengthening control over local Soviet institutions) and by the search for long-term solutions (advancing the world revolution, guaranteeing the stability of a multiethnic state that emerged from the disintegration of the Russian Empire).

The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

1979 ◽  
Vol 42 (04) ◽  
pp. 1135-1140 ◽  
Author(s):  
G I C Ingram
Keyword(s):  
Human Brain ◽  
Collaborative Study ◽  
Calibration Constant ◽  
Long Term Stability ◽  
Freeze Dried ◽  
Show Evidence ◽  
Human Material ◽  
Reference Preparation ◽  
The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

Central Otago - Built on gold, growing on grass.

2014 ◽  
Vol 76 ◽  
pp. 15-23
Author(s):  
Barrie J. Wills
Keyword(s):  
Economic Growth ◽  
Land Use ◽  
National Economy ◽  
Local Community ◽  
Central Government ◽  
Future Generations ◽  
Economic Potential ◽  
District Council ◽  
Definition Of

A warm welcome to our "World of Difference" to all delegates attending this conference - we hope your stay is enjoyable and that you will leave Central Otago with an enhanced appreciation of the diversity of land use and the resilient and growing economic potential that this region has to offer. Without regional wellbeing the national economy will struggle to grow, something Central Government finally seems to be realising, and the Central Otago District Council Long Term Plan 2012-2022 (LTP) signals the importance of establishing a productive economy for the local community which will aid in the economic growth of the district and seeks to create a thriving economy that will be attractive to business and residents alike. Two key principles that underpin the LTP are sustainability and affordability, with the definition of sustainability being "… development that meets the needs of the present without compromising the ability of future generations to meet their own needs."

Postmodern More

Moreana ◽  
2003 ◽  
Vol 40 (Number 153- (1-2) ◽  
pp. 219-239
Author(s):  
Anne Lake Prescott
Keyword(s):  
Human Language ◽  
Thomas More ◽  
The Stability ◽  
Definition Of ◽  
Recent Critic

Thomas More is often called a “humanist,” and rightly so if the word has its usual meaning in scholarship on the Renaissance. “Humanist” has by now acquired so many different and contradictory meanings, however, that it needs to be applied carefully to the likes of More. Many postmodernists tend to use the word, pejoratively, to mean someone who believes in an autonomous self, the stability of words, reason, and the possibility of determinable meanings. Without quite arguing that More was a postmodernist avant la lettre, this essay suggests that he was not a “humanist” who stalks the pages of much recent postmodernist theory and that in fact even while remaining a devout Catholic and sensible lawyer he was quite as aware as any recent critic of the slipperiness of human selves and human language. It is time that literary critics tightened up their definition of “humanist,” especially when writing about the Renaissance.

Application of the method of mathematical modeling for forecasting channel deformations at the underwater crossing of the main pipeline

2020 ◽  
Vol 10 (6) ◽  
pp. 599-609
Author(s):  
Valery А. Gruzdev ◽  
◽  
Georgy V. Mosolov ◽  
Ekaterina A. Sabayda ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Roughness Coefficient ◽  
Computational Domain ◽  
Channel Deformations ◽  
Geological Surveys ◽  
Kuban River ◽  
The Stability ◽  
Protective Structures

In order to determine the possibility of using the method of mathematical modeling for making long-term forecasts of channel deformations of trunk line underwater crossing (TLUC) through water obstacles, a methodology for performing and analyzing the results of mathematical modeling of channel deformations in the TLUC zone across the Kuban River is considered. Within the framework of the work, the following tasks were solved: 1) the format and composition of the initial data necessary for mathematical modeling were determined; 2) the procedure for assigning the boundaries of the computational domain of the model was considered, the computational domain was broken down into the computational grid, the zoning of the computational domain was performed by the value of the roughness coefficient; 3) the analysis of the results of modeling the water flow was carried out without taking the bottom deformations into account, as well as modeling the bottom deformations, the specifics of the verification and calibration calculations were determined to build a reliable mathematical model; 4) considered the possibility of using the method of mathematical modeling to check the stability of the bottom in the area of TLUC in the presence of man-made dumping or protective structure. It has been established that modeling the flow hydraulics and structure of currents, making short-term forecasts of local high-altitude reshaping of the bottom, determining the tendencies of erosion and accumulation of sediments upstream and downstream of protective structures are applicable for predicting channel deformations in the zone of the TLUC. In all these cases, it is mandatory to have materials from engineering-hydro-meteorological and engineering-geological surveys in an amount sufficient to compile a reliable mathematical model.

Influence of internal and external risks on sustainability of financial system of Аltai krai

2018 ◽  
Vol 35 (4) ◽  
pp. 133-136
Author(s):  
R. N. Ibragimov
Keyword(s):  
Sustainable Development ◽  
Financial Stability ◽  
Management Strategy ◽  
Financial System ◽  
Risk Management Strategy ◽  
The Sustainable Development ◽  
The Stability ◽  
The Impact

The article examines the impact of internal and external risks on the stability of the financial system of the Altai Territory. Classification of internal and external risks of decline, affecting the sustainable development of the financial system, is presented. A risk management strategy is proposed that will allow monitoring of risks, thereby these measures will help reduce the loss of financial stability and ensure the long-term development of the economy of the region.

Rate Constants, Reactive Flux

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Correlation Function ◽  
Rate Constant ◽  
Cross Sections ◽  
Time Correlation ◽  
Time Correlation Function ◽  
Exact Expression ◽  
Reaction Cross ◽  
Dividing Surface ◽  
Definition Of ◽  
Reactive Flux

This chapter discusses a direct approach to the calculation of the rate constant k(T) that bypasses the detailed state-to-state reaction cross-sections. The method is based on the calculation of the reactive flux across a dividing surface on the potential energy surface. Versions based on classical as well as quantum mechanics are described. The classical version and its relation to Wigner’s variational theorem and recrossings of the dividing surface is discussed. Neglecting recrossings, an approximate result based on the calculation of the classical one-way flux from reactants to products is considered. Recrossings can subsequently be included via a transmission coefficient. An alternative exact expression is formulated based on a canonical average of the flux time-correlation function. It concludes with the quantum mechanical definition of the flux operator and the derivation of a relation between the rate constant and a flux correlation function.

Sign in / Sign up

Export Citation Format

Share Document