Acoustic emission frequency discrimination

In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered

Adaptive interference techniques for mobile antennas

The results of a study performed to investigate effective, low cost adaptive signal processing techniques for suppressing mutual satellite interference that can arise in a mobile satellite (MSAT) communication system are discussed. The study focused on the use of adaptive sidelobe cancelling as a method to overcome undesired interference caused by a multiplicity of satellite transmissions within the field of view of the ground station. Results are presented which show that the conventional sidelobe canceller produces undesired reduction of the useful signal. This effect is due to the presence of the useful component in the reference antenna element. An alternative structure, the generalized sidelobe canceller (GSC), has been proposed to overcome this difficulty. A preliminary investigation of possible implementations of the GSC was conducted. It was found that at most 8 bits would be required to implement the GSC processor under conditions in which the desired signal-to-interference ratio is 25 dB

Rental rates for farm machines

Caption title.Digitized 2006 AES MoU

Adapting horse-drawn mowers to tractor power

Caption title.Digitized 2006 AES MoU

Girls Count: A Global Investment & Action Agenda

Explains how girls' welfare affects overall economic and social outcomes. Outlines steps to disaggregate health, education, and other data by age and gender; invest strategically in girls' programs; and ensure equitable benefits for girls in all sectors

Fruit volatile analysis using an electronic nose.

Numerous and diverse physiological changes occur during fruit ripening, including the development of a specific volatile blend that characterizes fruit aroma. Maturity at harvest is one of the key factors influencing the flavor quality of fruits and vegetables. The validation of robust methods that rapidly assess fruit maturity and aroma quality would allow improved management of advanced breeding programs, production practices and postharvest handling. Over the last three decades, much research has been conducted to develop so-called electronic noses, which are devices able to rapidly detect odors and flavors. Currently there are several commercially available electronic noses able to perform volatile analysis, based on different technologies. The electronic nose used in our work (zNose, EST, Newbury Park, CA, USA), consists of ultra-fast gas chromatography coupled with a surface acoustic wave sensor (UFGC-SAW). This technology has already been tested for its ability to monitor quality of various commodities, including detection of deterioration in apple; ripeness and rot evaluation in mango; aroma profiling of thymus species; C(6) volatile compounds in grape berries; characterization of vegetable oil and detection of adulterants in virgin coconut oil. This system can perform the three major steps of aroma analysis: headspace sampling, separation of volatile compounds, and detection. In about one minute, the output, a chromatogram, is produced and, after a purging cycle, the instrument is ready for further analysis. The results obtained with the zNose can be compared to those of other gas-chromatographic systems by calculation of Kovats Indices (KI). Once the instrument has been tuned with an alkane standard solution, the retention times are automatically converted into KIs. However, slight changes in temperature and flow rate are expected to occur over time, causing retention times to drift. Also, depending on the polarity of the column stationary phase, the reproducibility of KI calculations can vary by several index units. A series of programs and graphical interfaces were therefore developed to compare calculated KIs among samples in a semi-automated fashion. These programs reduce the time required for chromatogram analysis of large data sets and minimize the potential for misinterpretation of the data when chromatograms are not perfectly aligned. We present a method for rapid volatile compound analysis in fruit. Sample preparation, data acquisition and handling procedures are also discussed

Kinematic Analysis of Hip and Knee Joints between Barefoot and Shod Treadmill Running

Running shoes have recently been designed to mimic barefoot walking or running, and they are marketed with promises that runners will benefit from the effects of barefoot running. Studying gait analysis with particular running shoes is extremely important because the ankle and foot serve as the foundation of structural balance, support, and propulsion. In this study, the knee and hip joint motions will be addressed while wearing Vibram FiveFinger and Nike Free Run shoes, which are designed to imitate barefoot running while providing protection from the elements. The purpose of this current study was to investigate the movement kinematics in the hip and knee joint while running on the treadmill at 0%, 4%, and 8% inclines in the barefoot condition as well as in Nike Free Run and Vibram FiveFinger shoes. Five experienced distance runners with a heel strike landing style in the traditional cushioned shoe were selected to participate in the study. During the testing each participant ran at 3.0 m/s on a slope of 0%, 4% and 8% in all three types of footwear. A two-way repeated measures ANOVA test was conducted at α = 0.05 followed by a t-test with a Bonferroni adjustment if a significant difference was found. The results of the study showed a significant difference in slope was observed between the 0% incline and the 8% incline during the heel strike phase in the hip joint and the mid support phase of the knee joint, and a significant difference in footwear was found between the barefoot and Nike shoe during the mid support phase of gait in the hip joint. Also during the mid support phase of gait, a significant difference was found between the barefoot and Nike shoe as well as the Vibram and Nike shoe in the knee joint. No significant differences were found when comparing shoe or slope in regards to angular velocity in both hip and knee joints. The findings of this study show that when looking at the phases of the gait cycle, the mid support phase of gait is the most crucial phase of gait. The toe off phase was found to be the least important phase of gait to be examined. Running slope is important because the slope can affect the running kinematics when the gradient is substantial (0% to 8%). It is critical that when developing new footwear that the mid support phase should be the most important phase of gait to be examined, particularly in respect to the knee joint

Distribution of Spectral Characteristics and the Cosmological Evolution of GRBs

We investigate the cosmological evolution of GRBs, using the total gamma ray fluence as a measure of the burst strength. This involves an understanding of the distributions of the spectral parameters of GRBs as well as the total fluence distribution - both of which are subject to detector selection effects. We present new non-parametric statistical techniques to account for these effects, and use these methods to estimate the true distribution of the peak of the nu F_nu spectrum, E_p, from the raw distribution. The distributions are obtained from four channel data and therefore are rough estimates. Here, we emphasize the methods and present qualitative results. Given its spectral parameters, we then calculate the total fluence for each burst, and compute its cumulative and differential distributions. We use these distributions to estimate the cosmological rate evolution of GRBs, for three cosmological models. Our two main conclusions are the following: 1) Given our estimates of the spectral parameters, we find that there may exist a significant population of high E_p bursts that are not detected by BATSE, 2) We find a GRB co-moving rate density quite different from that of other extragalactic objects; in particular, it is different from the recently determined star formation rate.Comment: 20 pages, including 10 postscript figures. Submitted to Ap