533,131 research outputs found
G-jitter effects on half floating-zone convection in intermediate-frequency range
No full textThe g-jitter influence on thermocapillary convection and critical Marangoni number in a liquid bridge of half-floating rone was discussed in the low frequency range of 0.4 to 1.5 Hz in a previous paper. This paper extended the experiments to the intermediate frequency range of 2 to 18 Hz, which htrs often been recorded as vibration environment of spacecrafts. The experiment was completed on the deck of a vibration machine, which gave a periodical applied acceleration to simulate the effects of g-jitter. The experimental results in the intermediate frequency range are different from that in the low frequency range. The velocity field and the shape of the free surface have periodical fluctuations in response to g-jitter. The amplitude of the periodical varying part of the temperature response decreases obviously with increasing frequency of g-jitter and vanishes almost when the frequency of g-jitter is high enough. The critical Marangoni number is defined to describe the transition from a periodical convection in response to g-jitter to an oscillatory convection due to internal instability, and will increase with increasing g-jitter frequency. According to the spectral analysis, it can be found that the oscillatory part of temperature is a superposition of two harmonic waves if the Marangoni number is larger than a critical value
A power-saving modulation technique for time-of-flight range imaging sensors
No full textTime-of-flight range imaging cameras measure distance and intensity simultaneously for every pixel in an image. With the continued advancement of the technology, a wide variety of new depth sensing applications are emerging; however a number of these potential applications have stringent electrical power constraints that are difficult to meet with the current state-of-the-art systems. Sensor gain modulation contributes a significant proportion of the total image sensor power consumption, and as higher spatial resolution range image sensors operating at higher modulation frequencies (to achieve better measurement precision) are developed, this proportion is likely to increase. The authors have developed a new sensor modulation technique using resonant circuit concepts that is more power efficient than the standard mode of operation. With a proof of principle system, a 93–96% reduction in modulation drive power was demonstrated across a range of modulation frequencies from 1–11 MHz. Finally, an evaluation of the range imaging performance revealed an improvement in measurement linearity in the resonant configuration due primarily to the more sinusoidal shape of the resonant electrical waveforms, while the average precision values were comparable between the standard and resonant operating modes
Major General Horace G. Davisson, Commanding General, White Sands Missile Range.
No full textMajor General Horace G. Davidson, Commanding General, Whute Sands Missile Range, New Mexico
Maximizing precision over extended unambiguous range for TOF range imaging systems
No full textThe maximum unambiguous range for time-of-flight range imaging systems is inversely proportional to the chosen modulation frequency. However, increasing the unambiguous range by decreasing the modulation frequency will generally also degrade the range measurement precision. We describe a technique that significantly extends the range of a time-of-flight imaging system without compromising range precision. This is achieved by employing two modulation frequencies simultaneously. The chosen frequencies can be a combination of high and low frequency, or two similarly high frequencies. In this paper we present experimental results comparing single frequency; dual high and low frequency; and dual high frequency operation and demonstrate that range precision need not be appreciably compromised to achieve an extended unambiguous range
Characterization for high dynamic range imaging
No full textIn this paper we present a new practical camera characterization technique to improve color accuracy in high dynamic range (HDR) imaging. Camera characterization refers to the process of mapping device-dependent signals, such as digital camera RAW images, into a well-defined color space. This is a well-understood process for low dynamic range (LDR) imaging and is part of most digital cameras — usually mapping from the raw camera signal to the sRGB or Adobe RGB color space. This paper presents an efficient and accurate characterization method for high dynamic range imaging that extends previous methods originally designed for LDR imaging. We demonstrate that our characterization method is very accurate even in unknown illumination conditions, effectively turning a digital camera into a measurement device that measures physically accurate radiance values — both in terms of luminance and color — rivaling more expensive measurement instruments
Variation and association in Lathyrus species based on seed biochemical constituents
No full textGülümser, Erdem (Bilecik, Author)
Mut, Hanife (Bilecik, Author)The seeds of twelve Lathyrus species were analyzed for crude protein, ODAP, ash, mineral contents and thousand seed weight. CP content varied from 20.78% in L. cicera to 30.92% in L. ochrus. ODAP content was the most variable trait (CV= 97.81%), being highest (10.31 mg g(-1)) in L. clymenum (cultivar) and lowest (0.65 mg g(-1)) in L. laxiflorus (wild). This was followed by thousand seed weight (TSW) being highest in L. sativus (114.54 g) and lowest in L. nissolia (3.45 g). These species also exhibited a reasonable variation regarding mineral contents, especially for Ca (CV= 40.29%) and Mn (CV= 40.96%). Correlation analysis, based on interspecies means indicated that ODAP was highly correlated with TSW (r = 0.762), Zinc (r= 0.732) and B (r=- 0.507), while there was no significant correlation of ODAP with CP and ash contents
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The History of Telemetry at White Sands Missile Range, NM
No full textInternational Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper presents a history of telemetry at White Sands Missile Range, New Mexico. White Sands Missile Range is located in the Tularosa Basin between the San Andres and the Organ Mountains on the west and the Sacramento Mountains on the east. Designation of more than one million acres of New Mexico range land as a testing areas established White Sands Proving Ground on July 9, 1945 as the Birthplace of Americas Missile and Space activity. On July 16, 1945 the first Atomic Bomb was exploded at Trinity Site. Project Hermes began in November of 1944 with a contract to General Electric by the Ordnance Department to develop a long range guided missile for the Army. Missile testing began in September of 1945 with the firing of Tiny Tim missiles. The capture of German V2 rockets led to testing and firing V2s concurrently with the Hermes. The first two-stage rocket consisted of a WAC Corporal mounted on the nose of a V2. Bumper # 5 set flight records of 5,150 miles an hour and an altitude of 244 miles on February 24, 1949. The paper includes: *Chronological highlights of telemetering events. *Discussion of telemetry systems and events that occurred at WSPG/WSMR from 1944 through 1990. *Telemetry systems and events from 1990 to the present. *Planned future telemetry systems and probable future systems.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection
Development and characterisation of an easily configurable range imaging system
No full textRange imaging is becoming a popular tool for many applications, with several commercial variants now available. These systems find numerous real world applications such as interactive gaming and the automotive industry. This paper describes the development of a range imaging system employing the PMD-19 k sensor from PMD technologies. One specific advantage of our system is that it is extremely customisable in terms of modulation patterns to act as a platform for further research into time-of-flight range imaging. Experimental results are presented giving an indication of the precision and accuracy of the system, and how modifying certain operating parameters can improve system performance
Aspect-ratio dependence of the transition to the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the ultimate-state transition in turbulent Rayleigh-B\'enard convection obtained in a large facility known as the ``Uboot of G\"ottingen" and using pressurized sulfur hexafluoride as the convecting fluid. We found that the transition occurs over a range of which becomes more narrow as increases, ranging from which is at most weakly dependent on and close to to which varies from about for to about for
G. P. Range Reseeding
No full textPhotograph of a close up shot of an UNIDENTIFED man looking at young seedlings on the G. P. Range. These seedlings were planted with a furrow type drill in the spring of 1960 as part of the G. P. range reseeding project. The back of the photograph proclaims, "Close-up of range reseeding made with furrow type drill in spring of 1960. Note the young seedlings showing up in furrows where competitive grasses have been eliminated with this type drill.
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