Two hundred and eighty nine years ago, “Arts of conjecturing”, the posthumous work of the great mathematician James Bernoulli, was finally produced in the eager wait of mathematicians. Ian Hacking, a famous historia...Two hundred and eighty nine years ago, “Arts of conjecturing”, the posthumous work of the great mathematician James Bernoulli, was finally produced in the eager wait of mathematicians. Ian Hacking, a famous historian of statistics, commented that the publication of the book signaled the beginning of the mathematical theory of probability and terminated man’s long process in the forming of the probability concept By introducing James Bernoulli and his “Arts of conjecturing”, this paper aims at providing the reader with the 18 th century story of Bernoulli’s work, and at making the reader know that even today Bernoulli’s idea is very helpful and instructive in the research of modern statistics.展开更多
A new type of impulsive microthruster and its measurement system were designed for the aim of testing the performance of a basic prototype of solid propellant impulsive microthruster. Two sets of tests were conducted....A new type of impulsive microthruster and its measurement system were designed for the aim of testing the performance of a basic prototype of solid propellant impulsive microthruster. Two sets of tests were conducted. The tests show that the ignitor and the main charge of the microthruster match well, the dynamic and static capability of the test and measurement meets the test requirement and the result is creditable. The measured technical characteristics of the microthruster are that the ignition delay time is shorter than 0 3?ms, the total impulse is over 3?N·s, the operational time is shorter than 16?ms and the mass ratio of the thruster is 0 216.展开更多
The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previousl...The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previously been made either directly by mounting thrusters to the m easurement system or indirectly by mounting a target in the direct path of the e jected propellant.Several typical direct and indirect thrust-stands are presen ted and discussed in detail to illustrate the principles.Typical calibration me thods are also expounded.Finally,the resolution,uncertainty and thrust range of each thrust-stand are given,which may be helpful for the future thrust stan d design and micro-thrusters research.展开更多
文摘Two hundred and eighty nine years ago, “Arts of conjecturing”, the posthumous work of the great mathematician James Bernoulli, was finally produced in the eager wait of mathematicians. Ian Hacking, a famous historian of statistics, commented that the publication of the book signaled the beginning of the mathematical theory of probability and terminated man’s long process in the forming of the probability concept By introducing James Bernoulli and his “Arts of conjecturing”, this paper aims at providing the reader with the 18 th century story of Bernoulli’s work, and at making the reader know that even today Bernoulli’s idea is very helpful and instructive in the research of modern statistics.
文摘A new type of impulsive microthruster and its measurement system were designed for the aim of testing the performance of a basic prototype of solid propellant impulsive microthruster. Two sets of tests were conducted. The tests show that the ignitor and the main charge of the microthruster match well, the dynamic and static capability of the test and measurement meets the test requirement and the result is creditable. The measured technical characteristics of the microthruster are that the ignition delay time is shorter than 0 3?ms, the total impulse is over 3?N·s, the operational time is shorter than 16?ms and the mass ratio of the thruster is 0 216.
基金National Natural Science Foundation of China (No.91216201, No.51205403)
文摘The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previously been made either directly by mounting thrusters to the m easurement system or indirectly by mounting a target in the direct path of the e jected propellant.Several typical direct and indirect thrust-stands are presen ted and discussed in detail to illustrate the principles.Typical calibration me thods are also expounded.Finally,the resolution,uncertainty and thrust range of each thrust-stand are given,which may be helpful for the future thrust stan d design and micro-thrusters research.
