NEWS NOTES     

Marvin Saines 《Ground water》1970,8(5):35-35

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Benefits of Software GPS Receivers for Enhanced Signal Processing   总被引：8，自引：0，他引：8  

Alison Brown  Marvin May  Barry Tanju 《GPS Solutions》2000,4(1):56-66

In this article, the architecture of a software Global Positioning System (GPS) receiver is described and an analysis is included of the performance of a software GPS receiver when tracking the GPS signals in challenging environments. Results are included that demonstrate the advantage of the software GPS receiver in tracking the GPS signals in low signal-to-noise or jamming scenarios. Various current and previous applications of the software GPS receiver are also described. ? 2000 John Wiley & Sons, Inc.  相似文献   

Memorial for Edward L. Fireman     

Raymond Davis  Ursula B. Marvin  John A. Wood 《Meteoritics & planetary science》1991,26(2):171-171

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NEWS NOTES     

Marvin Saines 《Ground water》1971,9(1):51-51

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Petrology and geochemistry of the Northwest Africa 3368 eucrite     

Kathryn G. GARDNER‐VANDY  Dolores H. HILL  Dante S. LAURETTA  Yulia S. GOREVA  Kenneth J. DOMANIK  Richard C. GREENWOOD  Ian A. FRANCHI  Marvin KILLGORE 《Meteoritics & planetary science》2011,46(7):1052-1070

Abstract– Analysis of the mineralogy, isotopic, and bulk compositions of the eucrite meteorites is imperative for understanding their origin on the asteroid 4 Vesta, the proposed parent body of the HED meteorites. We present here the petrology, mineral compositions, and bulk chemistry of several lithic components of the new brecciated basaltic eucrite Northwest Africa (NWA) 3368 to determine if all the lithologies reflect formation from one rock type or many rock types. The meteorite has three main lithologies: coarse‐ and fine‐grained clasts surrounded by a fine‐grained recrystallized silicate matrix. Silicate compositions are homogeneous, and the average rare earth element pattern for NWA 3368 is approximately 10× CI chondrites with a slight negative Eu anomaly. Major and trace element data place NWA 3368 with the Main Group‐Nuevo Laredo trend. High‐Ti chromites with ilmenite exsolution lamellae provide evidence of NWA 3368’s history of intense metamorphism. We suggest that this meteorite underwent several episodes of brecciation and metamorphism, similar to that proposed by Metzler et al. (1995) . We conclude that NWA 3368 is a monomict basaltic eucrite breccia related to known eucrites in texture and in mineral, bulk, and oxygen isotopic composition.  相似文献   

Portales Valley: Petrology of a metallic‐melt meteorite breccia     

Alex Ruzicka  Marvin Killgore  David W. Mittlefehldt  Marc D. Fries 《Meteoritics & planetary science》2005,40(2):261-295

Abstract— Portales Valley (PV) is an unusual metal‐veined meteorite that has been classified as an H6 chondrite. It has been regarded either as an annealed impact melt breccia, as a primitive achondrite, or as a meteorite with affinities to silicated iron meteorites. We studied the petrology of PV using a variety of geochemical‐mineralogical techniques. Our results suggest that PV is the first well‐documented metallic‐melt meteorite breccia. Mineral‐chemical and other data suggest that the protolith to PV was an H chondrite. The composition of FeNi metal in PV is somewhat fractionated compared to H chondrites and varies between coarse vein and silicate‐rich portions. It is best modeled as having formed by partial melting at temperatures of ?940–1150 °C, with incomplete separation of solid from liquid metal. Solid metal concentrated in the coarse vein areas and S‐bearing liquid metal concentrated in the silicate‐rich areas, possibly as a result of a surface energy effect. Both carbon and phosphorus must have been scavenged from large volumes and concentrated in metallic liquid. Graphite nodules formed by crystallization from this liquid, whereas phosphate formed by reaction between P‐bearing metal and clinopyroxene components, depleting clinopyroxene throughout much of the meteorite and growing coarse phosphate at metal‐silicate interfaces. Some phosphate probably crystallized from P‐bearing liquids, but most probably formed by solid‐state reaction at ?975‐725 °C. Phosphate‐forming and FeO‐reduction reactions were widespread in PV and entailed a change in the mineralogy of the stony portion on a large scale. Portales Valley experienced protracted annealing from supersolidus to subsolidus temperatures, probably by cooling at depth within its parent body, but the main differences between PV and H chondrites arose because maximum temperatures were higher in PV. A combination of a relatively weak shock event and elevated pre‐shock temperatures probably produced the vein‐and‐breccia texture, with endogenic heating being the main heat source for melting, and with stress waves from an impact event being an essential trigger for mobilizing metal. Portales Valley is best classified as an H7 metallic‐melt breccia of shock stage S1. The meteorite is transitional between more primitive (chondritic) and evolved (achondrite, iron) meteorite types and offers clues as to how differentiation could have occurred in some asteroidal bodies.  相似文献   

NEW BOOKS     

Marvin Saines 《Ground water》1976,14(5):344-344

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A DUNITE-NORITE LUNAR MICROBRECCIA     

G. Jeffrey Taylor  Ursula B. Marvin 《Meteoritics & planetary science》1971,6(3):173-180

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OBC signal fidelity     

Michael W. Norris  Marvin L. Johnson  Mat Walsh 《Geophysical Prospecting》2006,54(6):793-815

A suite of three tests was performed to characterize the signal fidelity of OBC 4C acquisition systems. The test methodology was to evaluate individual sensor stations by acquiring source lines that were parallel to the in‐line and cross‐line horizontal sensors and source lines that were at 45° to the in‐line and cross‐line sensors. This technique provides constant azimuth gathers with a uniform offset range and removes issues associated with source array directivity. Characterization of the test data identified the frequency content of the geophone signals and the correlation between the vertical and cross‐line geophones as the most sensitive indicators of signal infidelity. In the former case, stations with questionable signal fidelity exhibited a very reverberatory signal. This signal was most evident on the cross‐line sensor. In the latter case, when normalized cross‐correlation coefficients are computed in a moving window, the cross‐line sensor and the vertical sensor are highly correlated, beginning several hundred milliseconds after the first arrivals. These characteristics can be exploited to allow stations with questionable signal fidelity to be programmatically identified. One means of identifying questionable stations is to compute the histogram of the instantaneous frequency. The frequency distributions from questionable stations are unambiguously distinguishable from stations that exhibit better signal fidelity. It was noted that signal fidelity appeared as a range, between acceptable and poor. To characterize the signal fidelity of an acquisition system adequately, the number of test samples must be statistically significant.  相似文献   

THE SIXTEEN-MILLION-HOUR QUESTION     

Marvin W. Mikesell 《The Professional geographer》1980,32(3):263-268

Promotion of nonacademic geography is a logical response to curtailment of opportunity for new teaching careers. Yet this necessary redirection of effort must be accompanied by renewed dedication to education and especially to nonprofessional undergraduate education. The case for geography in the liberal arts curriculum may well be a strong one, but questions about what we can offer need to be raised more frequently among ourselves if we are to respond effectively when such questions are asked by outsiders.  相似文献