scholarly journals Optical Technique Using Nano-Spark Lightsource for Macro and Microscale Image Acquisition to Study Diesel Spray Atomization

2015 ◽  
Vol 773-774 ◽  
pp. 545-549
Author(s):  
Azwan Sapit ◽  
Mohd Azahari Razali ◽  
M. Jaat ◽  
Akmal Nizam Mohammad ◽  
Amir Khalid ◽  
...  
Keyword(s):  
Diesel Engine ◽  
High Resolution ◽  
Diesel Spray ◽  
Time Interval ◽  
Short Time Interval ◽  
Optical Technique ◽  
Dynamic Behaviors ◽  
Critical Data ◽  
Optical Arrangement ◽  
Air Mixing

Atomization and fuel-air mixing is an important process in diesel combustion. It directly affects the combustion and emission of diesel engine. Optical technique has the advantage of being unobtrusive in nature when compared to other technique. nanospark unit that has spark duration of 30ns was used as a lightsource to capture high resolution spray image using still film camera. The very short duration of the spark freeze the fast movement of the spray droplet, and sharp image of fuel droplet to be successfully captured by the camera, and then analyzed for sizing and spatial distribution. In addition, by using a more elaborate optical setup, dual image of the same spray can be captured, with a very short time interval between each of them. This provides the means to study dynamic behaviors of the diesel spray and also the droplets, as the progression of the spray and trajectory and velocity of the droplet can be analyze from these images. With the proposed optical technique and optical arrangement, microscopic detail of the diesel engine spray can be captured. Critical data such as droplet sizing can be extracted from this high resolution image. Furthermore, by introducing a more sophisticated optical arrangement coined dual-nano spark photography method, the droplet dynamic behaviors such as flying angle and velocity can be study.

Assessment of the S-5P tropospheric NO2 product based on coincident airborne APEX observations over polluted regions

2020 ◽  
Author(s):  
Frederik Tack ◽  
Alexis Merlaud ◽  
Marian-Daniel Iordache ◽  
Gaia Pinardi ◽  
Ermioni Dimitropoulou ◽  
...  
Keyword(s):  
High Resolution ◽  
A Priori ◽  
Horizontal Distribution ◽  
Time Interval ◽  
Short Time Interval ◽  
Vertical Column ◽  
Urban Regions ◽  
Accuracy Requirement ◽  
Spatio Temporal ◽  
The Impact

<p>Sentinel-5 Precursor (S-5P), launched in October 2017, is the first mission of the Copernicus Programme dedicated to the monitoring of air quality and climate. Its characteristics, such as the fine spatial resolution, introduce many new opportunities and challenges, requiring to carefully assess the quality and validity of the generated data products by comparison with independent reference observations.</p><p>In the presented study, the S-5P/TROPOMI tropospheric nitrogen dioxide (NO<sub>2</sub>) L2 product (3.5 x 7 km<sup>2 </sup>at nadir observations) has been validated over strongly polluted urban regions based on comparison with coincident high-resolution airborne remote sensing observations (~100 m<sup>2</sup>). Airborne imagers are able to map the horizontal distribution of tropospheric NO<sub>2</sub>, as well as its strong spatio-temporal variability, at high resolution and with high accuracy. Satellite products can be optimally assessed based on airborne observations as a large amount of satellite pixels can be fully mapped in a relatively short time interval, reducing the impact of spatiotemporal mismatches. Additionally, such data sets allow to study the TROPOMI subpixel variability and impact of signal smoothing due to its finite satellite pixel size, typically coarser than fine-scale gradients in the urban NO<sub>2</sub> field.</p><p>In the framework of the S5PVAL-BE campaign, the Airborne Prism EXperiment (APEX) imaging spectrometer has been deployed during four mapping flights (26-29 June 2019) over the two largest urban regions in Belgium, i.e. Brussels and Antwerp, in order to map the horizontal distribution of tropospheric NO<sub>2</sub>. Per flight, 15 to 20 TROPOMI pixels were fully covered by approximately 5000 APEX measurements for each TROPOMI pixel. Mapping flights and ancillary ground-based measurements (car-mobile DOAS, MAX-DOAS, CIMEL, ceilometer, etc.) were conducted in coincidence with the overpass of TROPOMI (typically between noon and 2 PM UTC). The TROPOMI and APEX NO<sub>2</sub> vertical column density (VCD) retrieval schemes are similar in concept. Retrieved NO<sub>2 </sub>VCDs were georeferenced, gridded and intercompared. As strongly polluted areas typically exhibit strong NO<sub>2 </sub>vertical gradients (besides the strong horizontal gradients), a custom TROPOMI tropospheric NO<sub>2 </sub>product was computed and compared as well with APEX by replacing the coarse 1° x 1° a priori NO<sub>2 </sub>vertical profiles from TM5-MP by NO<sub>2</sub> profile shapes from the CAMS regional CTM ensemble at 0.1° x 0.1°.</p><p>Overall for the ensemble of the four flights, the standard TROPOMI NO<sub>2</sub> VCD product is well correlated (R= 0.94) but biased low (slope = 0.73) with respect to APEX NO<sub>2</sub> retrievals. When replacing the TM5-MP a priori NO<sub>2</sub> profiles by CAMS-based profiles, the slope increases to 0.88. When calculating the NO<sub>2</sub> VCD differences, the bias is on average -1.3 ± 1.2 x 10<sup>15</sup> molec cm<sup>-2</sup> or -16% ± 11% for the difference between APEX NO<sub>2</sub> VCDs and the standard TROPOMI NO<sub>2</sub> VCD product. The bias is substantially reduced when replacing the coarse TM5-MP a priori NO<sub>2</sub> profiles by CAMS-based profiles, being -0.1 ± 1.1  x 10<sup>15</sup> molec cm<sup>-2</sup> or -0.1% ± 11%. Both sets of retrievals are well within the accuracy requirement of a maximum bias of 25-50% for the TROPOMI tropospheric NO<sub>2</sub> product for all individual compared pixels.</p>

scholarly journals Fermi surface tomography

2021 ◽  
Author(s):  
Sergey Borisenko ◽  
Alexander Fedorov ◽  
Kuibarov Andrii ◽  
Marco Bianchi ◽  
Volodymyr Bezguba ◽  
...  
Keyword(s):  
High Resolution ◽  
Fermi Surface ◽  
Monochromatic Light ◽  
Three Dimensional ◽  
Detailed Comparison ◽  
Time Interval ◽  
Short Time Interval ◽  
Light Sources ◽  
Surface Mapping ◽  
Fermi Surfaces

Abstract Fermi surfaces, three-dimensional (3D) abstract interfaces that define the occupied energies of electrons in a solid, are important for characterizing and predicting the thermal, electrical, magnetic, and optical properties of crystalline metals and semiconductors [1]. Angle-resolved photoemission spectroscopy (ARPES) is the only technique directly probing the Fermi surface by measuring the Fermi momenta ( kF ) from energy- and angular distribution of photoelectrons dislodged by monochromatic light [2]. Existing electron analyzers are able to determine a number of kF -vectors simultaneously, but current technical limitations prohibit a direct high-resolution 3D Fermi surface mapping. As a result, no such datasets exist, strongly limiting our knowledge about the Fermi surfaces and restricting a detailed comparison with the widely available nowadays calculated 3D Fermi surfaces. Here we show that using a simpler instrumentation, based on the Fourier electron optics combined with a retardation field of the detector, it is possible to perform 3D-mapping within a very short time interval and with very high resolution. We present the first detailed experimental 3D Fermi surface recorded in the full Brillouin zone along the kz-direction as well as other experimental results featuring multiple advantages of our technique. In combination with various light sources, including synchrotron radiation, our methodology and instrumentation offer new opportunities for high-resolution ARPES in the physical and life sciences.

On Multiple Access of a Large Number of Machine-Type Devices in Cellular Networks

2018 ◽  
pp. 105-114
Author(s):  
O. S. Galinina ◽  
S. D. Andreev ◽  
A. M. Tyurlikov
Keyword(s):  
Success Probability ◽  
Random Access ◽  
Time Interval ◽  
Short Time Interval ◽  
Control Mechanisms ◽  
Network Access ◽  
Smart Meters ◽  
Machine To Machine ◽  
Machine To Machine Communication ◽  
Machine Communication

Introduction: Machine-to-machine communication assumes data transmission from various wireless devices and attracts attention of cellular operators. In this regard, it is crucial to recognize and control overload situations when a large number of such devices access the network over a short time interval.Purpose:Analysis of the radio network overload at the initial network entry stage in a machine-to-machine communication system.Results: A system is considered that features multiple smart meters, which may report alarms and autonomously collect energy consumption information. An analytical approach is proposed to study the operation of a large number of devices in such a system as well as model the settings of the random-access protocol in a cellular network and overload control mechanisms with respect to the access success probability, network access latency, and device power consumption. A comparison between the obtained analytical results and simulation data is also offered. 

scholarly journals Improving the Stochastic Model of Ionospheric Delays for BDS Long-Range Real-Time Kinematic Positioning

2021 ◽  
Vol 13 (14) ◽  
pp. 2739
Author(s):  
Huizhong Zhu ◽  
Jun Li ◽  
Longjiang Tang ◽  
Maorong Ge ◽  
Aigong Xu
Keyword(s):  
Real Time ◽  
Long Range ◽  
Ionospheric Delay ◽  
Time Interval ◽  
Short Time Interval ◽  
Dual Frequency ◽  
Triple Frequency ◽  
Ambiguity Fixing ◽  
Power Spectral ◽  
Observation Noise

Although ionosphere-free (IF) combination is usually employed in long-range precise positioning, in order to employ the knowledge of the spatiotemporal ionospheric delays variations and avoid the difficulty in choosing the IF combinations in case of triple-frequency data processing, using uncombined observations with proper ionospheric constraints is more beneficial. Yet, determining the appropriate power spectral density (PSD) of ionospheric delays is one of the most important issues in the uncombined processing, as the empirical methods cannot consider the actual ionosphere activities. The ionospheric delays derived from actual dual-frequency phase observations contain not only the real-time ionospheric delays variations, but also the observation noise which could be much larger than ionospheric delays changes over a very short time interval, so that the statistics of the ionospheric delays cannot be retrieved properly. Fortunately, the ionospheric delays variations and the observation noise behave in different ways, i.e., can be represented by random-walk and white noise process, respectively, so that they can be separated statistically. In this paper, we proposed an approach to determine the PSD of ionospheric delays for each satellite in real-time by denoising the ionospheric delay observations. Based on the relationship between the PSD, observation noise and the ionospheric observations, several aspects impacting the PSD calculation are investigated numerically and the optimal values are suggested. The proposed approach with the suggested optimal parameters is applied to the processing of three long-range baselines of 103 km, 175 km and 200 km with triple-frequency BDS data in both static and kinematic mode. The improvement in the first ambiguity fixing time (FAFT), the positioning accuracy and the estimated ionospheric delays are analysed and compared with that using empirical PSD. The results show that the FAFT can be shortened by at least 8% compared with using a unique empirical PSD for all satellites although it is even fine-tuned according to the actual observations and improved by 34% compared with that using PSD derived from ionospheric delay observations without denoising. Finally, the positioning performance of BDS three-frequency observations shows that the averaged FAFT is 226 s and 270 s, and the positioning accuracies after ambiguity fixing are 1 cm, 1 cm and 3 cm in the East, North and Up directions for static and 3 cm, 3 cm and 6 cm for kinematic mode, respectively.

scholarly journals Evaluation and Validation of a Joint Stress Test to Induce Activity-Related Knee Joint Discomfort — a Prospective Case-Control Study

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Christiane Schön ◽  
Claudia Reule ◽  
Katharina Knaub ◽  
Antje Micka ◽  
Manfred Wilhelm ◽  
...  
Keyword(s):  
Knee Joint ◽  
Healthy Subjects ◽  
Stress Test ◽  
Osteoarthritis Of The Knee ◽  
Time Interval ◽  
Short Time Interval ◽  
Joint Stress ◽  
Joint Health ◽  
The Impact ◽  
Health Function

Abstract Background The assessment of improvement or maintenance of joint health in healthy subjects is a great challenge. The aim of the study was the evaluation of a joint stress test to assess joint discomfort in subjects with activity-related knee joint discomfort (ArJD). Results Forty-five subjects were recruited to perform the single-leg-step-down (SLSD) test (15 subjects per group). Subjects with ArJD of the knee (age 22–62 years) were compared to healthy subjects (age 24–59 years) with no knee joint discomfort during daily life sporting activity and to subjects with mild-to-moderate osteoarthritis of the knee joint (OA, Kellgren score 2–3, age 42–64 years). The subjects performed the SLSD test with two different protocols: (I) standardization for knee joint discomfort; (II) standardization for load on the knee joint. In addition, range of motion (ROM), reach test, acute pain at rest and after a single-leg squat and knee injury, and osteoarthritis outcome score (KOOS) were assessed. In OA and ArJD subjects, knee joint discomfort could be reproducibly induced in a short time interval of less than 10 min (200 steps). In healthy subjects, no pain was recorded. A clear differentiation between study groups was observed with the SLSD test (maximal step number) as well as KOOS questionnaire, ROM, and reach test. In addition, a moderate to good intra-class correlation was shown for the investigated outcomes. Conclusions These results suggest the SLSD test is a reliable tool for the assessment of knee joint health function in ArJD and OA subjects to study the improvements in their activities. Further, this model can be used as a stress model in intervention studies to study the impact of stress on knee joint health function.

Model Verification of the Evaporating Diesel Spray Distribution in the Combustion Chamber of a D.I. Diesel Engine

1996 ◽  
Author(s):  
Takuo Yoshizaki ◽  
Keiichiro Yuzaki ◽  
Hiroyuki Hiroyasu ◽  
Hideo Yamashita ◽  
Kazufumi Kaneda ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Model Verification ◽  
Diesel Spray ◽  
Spray Distribution

Estimation of Time-Dependent Turning Fractions at Signalized Intersections

1998 ◽  
Vol 1644 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Gang-Len Chang ◽  
Xianding Tao
Keyword(s):  
Signalized Intersections ◽  
Efficient Estimation ◽  
Estimation Accuracy ◽  
Time Interval ◽  
Short Time Interval ◽  
Simulation Experiments ◽  
Proposed Model ◽  
Short Time ◽  
Estimation Of Time ◽  
Additional Constraints

An effective method for estimating time-varying turning fractions at signalized intersections is described. With the inclusion of approximate intersection delay, the proposed model can account for the impacts of signal setting on the dynamic distribution of intersection flows. To improve the estimation accuracy, the use of preestimated turning fractions from a relatively longer time interval has been proposed to serve as additional constraints for the same estimation but over a short time interval. The results of extensive simulation experiments indicated that the proposed method can yield sufficiently accurate as well as efficient estimation of dynamic turning fractions for signalized intersections.

Micro-Expression Recognition using 3D - CNN

2020 ◽  
pp. 5-13
Author(s):  
Vishal Dubey ◽  
◽  
◽  
◽  
Bhavya Takkar ◽  
...  
Keyword(s):  
Emotional Response ◽  
High Speed ◽  
Actual State ◽  
Time Interval ◽  
Short Time Interval ◽  
Expression Recognition ◽  
Specific Emotion ◽  
3D Cnn ◽  
Short Time ◽  
Micro Expression

Micro-expression comes under nonverbal communication, and for a matter of fact, it appears for minute fractions of a second. One cannot control micro-expression as it tells about our actual state emotionally, even if we try to hide or conceal our genuine emotions. As we know that micro-expressions are very rapid due to which it becomes challenging for any human being to detect it with bare eyes. This subtle-expression is spontaneous, and involuntary gives the emotional response. It happens when a person wants to conceal the specific emotion, but the brain is reacting appropriately to what that person is feeling then. Due to which the person displays their true feelings very briefly and later tries to make a false emotional response. Human emotions tend to last about 0.5 - 4.0 seconds, whereas micro-expression can last less than 1/2 of a second. On comparing micro-expression with regular facial expressions, it is found that for micro-expression, it is complicated to hide responses of a particular situation. Micro-expressions cannot be controlled because of the short time interval, but with a high-speed camera, we can capture one's expressions and replay them at a slow speed. Over the last ten years, researchers from all over the globe are researching automatic micro-expression recognition in the fields of computer science, security, psychology, and many more. The objective of this paper is to provide insight regarding micro-expression analysis using 3D CNN. A lot of datasets of micro-expression have been released in the last decade, we have performed this experiment on SMIC micro-expression dataset and compared the results after applying two different activation functions.

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