[1] An array of 24 stations, each with 24 crossed dipoles, has been built at the Haystack Observatory in Westford, Massachusetts. This array has been designed to make a sensitive search for the 327 MHz spectral line of deuterium. Since the deuterium line is expected to be about 50 dB weaker than the 1420 MHz hydrogen line, the amelioration of radio frequency interference (RFI) is a major challenge for the performance of the deuterium array. Locally generated RFI from the array and from nearby sites has been reduced by extensive shielding and in some cases by the removal of consumer electronics, like certain digital answering machines that emit strong signals in the 327.3-327.5 MHz band, which is of prime importance for the search. Since almost all the RFI comes from the horizon, the station array has parasitic directors added to the dipoles to reduce the response at the horizon. An RFI monitor with 12 active Yagi antennas pointed every 30°in azimuth provides a way of determining the direction of the RFI and yields information on frequencies and time spans that need to be excised from the array data. We describe the RFI excision techniques and the levels of spectral and continuum RFI measured at the observatory.Citation: Rogers, A. E. E., P. Pratap, J. C. Carter, and M. A. Diaz (2005), Radio frequency interference shielding and mitigation techniques for a sensitive search for the 327 MHz line of deuterium, Radio Sci., 40, RS5S17,
The term "period effect" is used here to describe a phenomenon of considerable importance to the design of reactor control systems. A reactor control system which is stable when the reactor is at steady power may be unstable when the reactor is on a period shorter than about 30 sec. The effect is considered to be due to changes in the reactor transfer function which occur when the reactor is in a dynamic condition. It has been described independently by five author s, all using the same analytical approach. An alternative approach is presented with attempts to demonstrate that insight may be gained from a consideration that the basic cause of the effect may be due to reactivity rather than to period as the previous authors have assumed. Methods for compensating for this effect are discussed. It is believed that for many systems the effect may be adequately corrected for by automatic adjustment of control loop gain proportional to the quantity []3-kgx(l-/3)]. The well-known zero-power transfer function is shown to be a special case of the general reactor transfer function which applies under any static, quasistatic, or dynamic condition whether subcritical, supercritical, or superpronapt critical.
by Roosevelt and generous American belief greatly impressed the Russian masses, and these impressions may even be expected to survive the repetitive effect of present-day official anti-American propaganda.In going over the rich data assembled by Prof. Barghoom, one is tempted to speculate on the effectiveness of the entire Soviet system of domestic indoctrination. There is litde evidence that the manipulators of public opinion in the Soviet Union are in possession of anything better than a crude theory of motivation, consisting largely of intimidation, displacement of aggression toward the outside world, and precarious rewards for conformism. In educating their subjects they act as if they were unaware of the self-defeating character of the endless reiteration of the same ideological paradigms. Resistance to official propaganda on the part of the Soviet masses should not, however, give the illusion that they could not be mobilized for service to the state.Prof. Barghoorn's book is written in the sober and lucid style of good political history, but without any trace of contemporary "content-analytical" or psycho-analytical frame of reference. A student of the dynamics underlying the emergence of intercultural and international imagery may find this disappointing.
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