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• 1
Article
2015
ISSN: 10944087
In: Optics Express, 14 September 2015, Vol.23(19), pp.24910-24922
Description: Non-intrusive fast 3d measurements of volumetric velocity fields are necessary for understanding complex flows. Using high-speed cameras and spectroscopic measurement principles, where the Doppler frequency of scattered light is evaluated within the illuminated plane, each pixel allows one measurement and, thus, planar measurements with high data rates are possible. While scanning is one standard technique to add the third dimension, the volumetric data is not acquired simultaneously. In order to overcome this drawback, a high-speed light field camera is proposed for obtaining volumetric data with each single frame. The high-speed light field camera approach is applied to a Doppler global velocimeter with sinusoidal laser frequency modulation. As a result, a frequency multiplexing technique is required in addition to the plenoptic refocusing for eliminating the crosstalk between the measurement planes. However, the plenoptic refocusing is still necessary in order to achieve a large refocusing...
ISSN: 10944087
E-ISSN: 10944087
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• 2
Article
2011
ISSN: 19352727
Language: English
In: PLoS Neglected Tropical Diseases, 2011, Vol.5(9), p.e1336
Description: Control of tsetse flies using insecticide-treated targets is often hampered by vegetation re-growth and encroachment which obscures a target and renders it less effective. Potentially this is of particular concern for the newly developed small targets (0.25 high × 0.5 m wide) which show promise for cost-efficient control of Palpalis group tsetse flies. Consequently the performance of a small target was investigated for Glossina fuscipes fuscipes in Kenya, when the target was obscured following the placement of vegetation to simulate various degrees of natural bush encroachment. Catches decreased significantly only when the target was obscured by more than 80%. Even if a small target is underneath a very low overhanging bush (0.5 m above ground), the numbers of G. f. fuscipes decreased by only about 30% compared to a target in the open. We show that the efficiency of the small targets, even in small (1 m diameter) clearings, is largely uncompromised by vegetation re-growth because G. f. fuscipes readily enter between and under vegetation. The essential characteristic is that there should be some openings between vegetation. ; This implies that for this important vector of HAT, and possibly other Palpalis group flies, a smaller initial clearance zone around targets can be made and longer interval between site maintenance visits is possible both of which will result in cost savings for large scale operations. We also investigated and discuss other site features e.g. large solid objects and position in relation to the water's edge in terms of the efficacy of the small targets. ; Sleeping Sickness (Human African Trypanosomiasis) is a serious threat to health and development in sub-Saharan Africa. Due to lack of vaccines and prophylactic drugs, vector control is the only method of disease prevention. Small (0.25×0.5 m) insecticide-treated targets have been shown to be cost-efficient for several Palpalis group tsetse flies, but there are concerns that they may become obscured by vegetation with a subsequent reduction in efficiency. We showed that the efficiency of the small targets was largely uncompromised by vegetation encroachment because readily enter between and under vegetation to locate a small target, e.g. into small (1 m diameter) site clearings and underneath a very low (0.5 m) canopy. This implies that the dense vegetation, typical of the riverine habitats of Palpalis group tsetse, will not compromise the performance of tiny targets, as long as there are adequate openings of 〉30 cm between vegetation. Moreover, the maintanence of cleared areas around targets seems less important for the control of with consequent savings in costs for control operations.
Subject(s): Research Article ; Medicine ; Infectious Diseases
ISSN: 19352727
E-ISSN: 1935-2735
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• 3
Article
2015
ISSN: 07234864
In: Experiments in Fluids, 1 September 2015, Vol.56(9), pp.1-11
Description: In order to reduce the fuel consumption and exhaust emissions of modern Diesel engines, the high-pressure fuel injections have to be optimized. This requires continuous, time-resolved measurements of the fuel velocity distribution during multiple complete injection cycles, which can provide a deeper understanding of the injection process. However, fuel velocity measurements at high-pressure injection nozzles are a challenging task due to the high velocities of up to 300 m/s, the short injection durations in the $$\upmu\text{s}$$ μ s range and the high fuel droplet density especially near the nozzle exit. In order to solve these challenges, a fast imaging Doppler global velocimeter with laser frequency modulation (2D-FM-DGV) incorporating a high-speed camera is presented. As a result, continuous planar velocity field measurements are performed with a measurement rate of 200 kHz in the near-nozzle region of a high-pressure Diesel injection. The injection system is operated under atmospheric surrounding conditions with injection pressures up to 1400 bar thereby reaching fuel velocities up to 380 m/s. The measurements over multiple entire injection cycles resolved the spatio-temporal fluctuations of the fuel velocity, which occur especially for low injection pressures. Furthermore, a sudden setback of the velocity at the beginning of the injection is identified for various injection pressures. In conclusion, the fast measurement system enables the investigation of the complete temporal behavior of single injection cycles or a series of it. Since this eliminates the necessity of phase-locked measurements, the proposed measurement approach provides new insights for the analysis of high-pressure injections regarding unsteady phenomena.
Subject(s): Engineering ; Engineering Fluid Dynamics ; Fluid- and Aerodynamics ; Engineering Thermodynamics, Heat and Mass Transfer ; Engineering ; Applied Sciences;
ISSN: 07234864
E-ISSN: 14321114
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• 4
Article
2016
ISSN: 2194-8771
Language: English
In: Journal of sensors and sensor systems, 01 April 2016, Vol.5(1), pp.125-136
Description: The interaction of sound and flow enables an efficient noise damping. Inevitable for understanding of this aeroacoustic damping phenomenon is the simultaneous measurement of flow and sound fields. Optical sensor systems have the advantage of non-contact measurements. The necessary simultaneous determination of sound levels and flow velocities with high dynamic range has major hurdles. We present an approach based on frequency-modulated Doppler global velocimetry, where a high-speed CMOS camera with data rates over 160 MSamples s−1 of velocity samples is employed. Using the proposed system, two-component flow velocity measurements are performed in a three-dimensional region of interest with a spatial resolution of 224 µm, based on single-pixel evaluation, and a measurement rate of 10 kHz. The sensor system can simultaneously capture sound and turbulent flow velocity oscillations down to a minimal power density of 40.5 (mm s−1)2 Hz−1 in a frequency range up to 5 kHz. The presented...
Subject(s): Engineering
ISSN: 2194-8771
E-ISSN: 2194-878X
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• 5
Article
2018
ISSN: 2194-8771
Language: English
In: Journal of sensors and sensor systems, 01 March 2018, Vol.7, pp.113-122
Description: The analysis of aeroacoustic phenomena is crucial for a deeper understanding of the damping mechanisms of a sound-absorbing bias flow liner (BFL). For this purpose, simultaneous measurements of the sound field and the flow field in a BFL are required. The fluid velocity can serve as the measurand, where both the acoustic particle velocity and the aerodynamic flow velocity contribute and, thus, can be acquired simultaneously. However, there is a need to separate these two quantities to distinguish between them. This is challenging because they generally coincide with each other in the time domain. Due to the interaction of sound and flow in a BFL, both velocities also overlap in the temporal frequency domain, having a coherent oscillation at the acoustic frequency. For this reason, the recently developed natural Helmholtz–Hodge decomposition (NHHD) is applied to separate both quantities from the measured oscillation velocity field in the spatial domain. The evaluation of synthetic...
Subject(s): Engineering
ISSN: 2194-8771
E-ISSN: 2194-878X
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• 6
Article
2015
ISSN: 1076-2752
In: Journal of Occupational and Environmental Medicine, 2015, Vol.57(3), pp.321-328
Description: OBJECTIVE:: This study aims to examine the relationship of lifestyle behaviors (physical activity, work and non-work sitting time, sleep quality, and sleep duration) with presenteeism while controlling for sociodemographics, work- and health-related variables. METHODS:: Data were collected from 710 workers (aged 20 to 76 years; 47.9% women) from randomly selected Australian adults who completed an online survey. Linear regression was used to examine the relationship between lifestyle behaviors and presenteeism. RESULTS:: Poorer sleep quality (standardized regression coefficients [B] = 0.112; P 〈 0.05), suboptimal duration (B = 0.081; P 〈 0.05), and lower work sitting time (B = −0.086; P 〈 0.05) were significantly associated with higher presenteeism when controlling for all lifestyle behaviors. Engaging in three risky lifestyle behaviors was associated with higher presenteeism (B = 0.150; P 〈 0.01) compared with engaging in none or one. CONCLUSIONS:: The results of this study highlight the importance of sleep behaviors for presenteeism and call for behavioral interventions that simultaneously address sleep in conjunction with other activity-related behaviors.
Subject(s): Objectives ; Sleep ; Women ; Surveys ; Work ; Adults ; Exercise ; Sitting ; Lifestyle ; Physical Activity ; Risk Taking ; Intervention ; Standards ; Australia ; Occupational Safety and Health ; Medical and Environmental Health ; Exercise, Health & Physical Fitness;
ISSN: 1076-2752
E-ISSN: 15365948
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• 7
Lexicon Article
2004
ISSN: 0018-974X
In: ifo Schnelldienst, 2004, Vol.57, p.49-53
Subject(s): Dienstleistung
ISSN: 0018-974X
Source: wiso Wirtschaftswissenschaften (GBI-Genios Deutsche Wirtschaftsdatenbank GmbH) 〈img src="http://exlibris-pub.s3.amazonaws.com/wiso_logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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• 8
Article
1986
ISSN: 0004-640X
Language: English
In: Astrophysics and Space Science, 1986, Vol.128(1), pp.163-177
Description: In this paper we investigate the properties of dust in circumstellar shells around very young massive compact IR sources (Becklin-Neugebauer objects). We found no correlation between the optical depth in the centre of the 10-μm band and the 3.1-μm ice band. An inverse correlation between the strength of the silicate feature and the colour temperature for the 8–13 μm interval was detected. Our sample of BN objects extends this kind of relation already known for Mira stars and OH/IR stars to higher optical depths. We present a radiative transfer model for BN objects and discuss its main properties. Using this model, the interpretation of the observations led to the conclusion that the type of silicates present in the dust shells of very young stellar objects is different from that type around oxygen-rich giants and supergiants. These different silicates may be tentatively identified with pyroxenes and olivines, respectively. We studied the influence of the adopted dust model in deriving source parameters of BN objects. The object W3-IRS5 was discussed in some detail.
Subject(s): Cosmic Dust ; Early Stars ; Infrared Sources (Astronomy) ; Infrared Stars ; Stellar Envelopes ; Optical Properties ; Radiative Transfer ; Silicates ; Supermassive Stars ; Astrophysics (Ah);
ISSN: 0004-640X
E-ISSN: 1572-946X
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• 9
Article
1986
ISSN: 0004-640X
Language: English
In: Astrophysics and Space Science, 1986, Vol.128(1), pp.199-216
Description: The Becklin-Neugebauer objects are identified by means of a wide range of observable features as a separate class of very young and massive stars surrounded by optically thick dust shells. We show that they evolutionarily connect real protostars to compact Hii regions. We give criteria which should be appropriate to segregate the BN objects from compact Hii regions. Finally, we describe the structure of a typical BN object.
Subject(s): Infrared Stars ; Protostars ; Stellar Envelopes ; Stellar Evolution ; Supermassive Stars ; Absorption Spectra ; H II Regions ; Stellar Spectra ; Stellar Structure ; Stellar Winds ; Astrophysics (Ah);
ISSN: 0004-640X
E-ISSN: 1572-946X
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• 10
Article
1972
ISSN: 00032700
Language: English
In: Analytical Chemistry, 1 February 1972, Vol.44(2), pp.277-279
Subject(s): Engineering ; Chemistry;
ISSN: 00032700
E-ISSN: 15206882
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