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"Time Measurement."
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Time zones
Explains the origin of standard time and the international system of time zones, and discusses Greenwich Mean Time and Coordinated Universal Time, time zones in the United States, daylight savings time, and the cases of India and Australia.
Book
Applications of Online UV-Vis Spectrophotometer for Drinking Water Quality Monitoring and Process Control: A Review
Water quality monitoring is an essential component of water quality management for water utilities for managing the drinking water supply. Online UV-Vis spectrophotometers are becoming popular choices for online water quality monitoring and process control, as they are reagent free, do not require sample pre-treatments and can provide continuous measurements. The advantages of the online UV-Vis sensors are that they can capture events and allow quicker responses to water quality changes compared to conventional water quality monitoring. This review summarizes the applications of online UV-Vis spectrophotometers for drinking water quality management in the last two decades. Water quality measurements can be performed directly using the built-in generic algorithms of the online UV-Vis instruments, including absorbance at 254 nm (UV254), colour, dissolved organic carbon (DOC), total organic carbon (TOC), turbidity and nitrate. To enhance the usability of this technique by providing a higher level of operations intelligence, the UV-Vis spectra combined with chemometrics approach offers simplicity, flexibility and applicability. The use of anomaly detection and an early warning was also discussed for drinking water quality monitoring at the source or in the distribution system. As most of the online UV-Vis instruments studies in the drinking water field were conducted at the laboratory- and pilot-scale, future work is needed for industrial-scale evaluation with ab appropriate validation methodology. Issues and potential solutions associated with online instruments for water quality monitoring have been provided. Current technique development outcomes indicate that future research and development work is needed for the integration of early warnings and real-time water treatment process control systems using the online UV-Vis spectrophotometers as part of the water quality management system.
Journal Article
Structural and optical properties of zirconium oxide (ZrO2) nanoparticles: effect of calcination temperature
In this article, we report the structural and optical properties of zirconium oxide (ZrO2) nanoparticles synthesized via chemical co-precipitation method. The effect of calcination temperature on structural and optical properties of ZrO2 nanoparticles is investigated through XRD, FESEM, EDX, FTIR, UV-Vis absorption, fluorescence emission and life time measurements. XRD spectrum reveals the tetragonal phase at calcination temperature 600 °C and crystallinity of samples increases with calcination temperature. At 800 °C the phase transition from tetragonal to tetragonal-monoclinic mixed phase is noticed. The FESEM images show the particles are of irregular shape and highly agglomerated. FTIR spectra also confirm the formation of ZrO2 in crystalline phase. From UV-vis absorption spectra it is found a strong quantization and varying band gap with calcination temperature. The change in emission wavelength and intensity with phase change is observed form fluorescence emission spectra. At higher calcination temperature emission intensity is decreased which may be due to the phase change and the formation of surface defects. The life time measurements also reveal the different trap states and life time with calcination temperature.
Journal Article
WiFi FTM, UWB and Cellular-Based Radio Fusion for Indoor Positioning
High-precision indoor localisation is becoming a necessity with novel location-based services that are emerging around 5G. The deployment of high-precision indoor location technologies is usually costly due to the high density of reference points. In this work, we propose the opportunistic fusion of several different technologies, such as ultra-wide band (UWB) and WiFi fine-time measurement (FTM), in order to improve the performance of location. We also propose the use of fusion with cellular networks, such as LTE, to complement these technologies where the number of reference points is under-determined, increasing the availability of the location service. Maximum likelihood estimation (MLE) is presented to weight the different reference points to eliminate outliers, and several searching methods are presented and evaluated for the localisation algorithm. An experimental setup is used to validate the presented system, using UWB and WiFi FTM due to their incorporation in the latest flagship smartphones. It is shown that the use of multi-technology fusion in trilateration algorithm remarkably optimises the precise coverage area. In addition, it reduces the positioning error by over-determining the positioning problem. This technique reduces the costs of any network deployment oriented to location services, since a reduced number of reference points from each technology is required.
Journal Article
Small-Angle Particle Counting Coupled Photometry for Real-Time Detection of Respirable Particle Size Segmentation Mass Concentration
Respirable particulate matter air pollution is positively associated with SARS-CoV-2 mortality. Real-time and accurate monitoring of particle concentration changes is the first step to prevent and control air pollution from inhalable particles. In this research, a new light scattering instrument has been developed to detect the mass concentration of inhalable particles. This instrument couples the forward small-angle single particle counting method with the lateral group particle photometry method in a single device. The mass concentration of four sizes of inhalable particles in the environment can be detected simultaneously in a large area in real-time without using a particle impactor. Different from the traditional light scattering instrument, this new optical instrument can detect darker particles with strong light absorption, and the measurement results mainly depend on the particle size and ignore the properties of the particles. Comparative experiments have shown that the instrument can detect particles with different properties by simply calibrating the environmental density parameters, and the measurement results have good stability and accuracy.
Journal Article
Characterization of pre-diapause phase in the northern Drosophila species D. ezoana
Drosophila ezoana is a virilis group Drosophila species inhabiting northern latitudes. The flies enter adult reproductive diapause to survive winter upon exposure to short photoperiod conditions (short-day) over several consecutive days. Insect pre-diapause phase – the duration between the beginning of exposure to short days and expression of diapause is thought to be comprised of two distinct phases - (a) photoperiodic time measurement that detects short-days, followed by (b) physiological events leading to the expression of diapause phenotype. A short-day dependent segment of the pre-diapause phase thus approximates the process of photoperiodic time measurement. Continuous darkness has been found to be a neutral condition with respect to diapause regulation in many insect species. The effect of variable number of short-days followed by continuous darkness on diapause incidence thus allows identification of short-day dependent segment of pre-diapause phase thereby mapping the process of photo-periodic time measurement. Although, few weeks of exposure to short-days in adult stage is known to be sufficient for the expression of diapause in D. ezoana, the number of short days required for the completion of photo-periodic time measurement has never been systematically analysed. Our experiments show that continuous darkness is a neutral condition for diapause regulation also in D. ezoana. We utilized the neutral nature of continuous darkness to map the process of photoperiodic time measurement in the D. ezoana strain 124OJ8 which showed that integration of short-day photic cues over the first 10 days of pre-diapause phase is essential for diapause induction.
Journal Article
Rapid Manufacturing Approach of an Ultrathin Moisture Sensor for Health Monitoring
This study developed a rapid manufacturing approach for a moisture sensor based on contactless jet printing technology. A compact measurement system with ultrathin and flexure sensor electrodes was fabricated. The proposed sensor system focuses on continuous urine measurement, which can provide timely information on subjects to ensure efficient diagnosis and treatment. The obtained results verify that the proposed sensor system can exhibit a typical responsivity of up to −7.76 mV/%RH in the high-sensitivity range of 50–80 %RH. A preliminary field experiment was conducted on a hairless rat, and the effectiveness of the proposed ultrathin moisture sensor was verified. This ultrathin sensor electrode can be fabricated in the micrometer range, and its application does not affect the comfort of the user. The ultrathin electrode sensors can be printed directly on the diaper or undergarment of the user for in situ urine health monitoring, particularly of infants and the elderly.
Journal Article
Wi-Fi Fine Time Measurement: Data Analysis and Processing for Indoor Localisation
Indoor positioning systems have received increasing attention for supporting location-based services in indoor environments. Wi-Fi based indoor localisation has become attractive due to its extensive distribution and low cost properties. IEEE 802.11-2016 now includes a Wi-Fi Fine Time Measurement (FTM) protocol which can be used for Wi-Fi ranging between intelligent terminal and Wi-Fi access point. This paper introduces a framework of Wi-Fi FTM data acquisition and processing that can be used for indoor localisation. We analyse the main factors that affect the accuracy of Wi-Fi ranging and propose a calibration, filtering and modelling algorithm that can effectively reduce the ranging error caused by clock deviation, non-line-of-sight (NLOS) and multipath propagation. Experimental results show that the proposed calibration and filtering method is able to achieve metre-level ranging accuracy in case of line-of-sight by using large bandwidth. Estimation results also show that the proposed Wi-Fi ranging model provides an accurate ranging performance in NLOS and multipath contained indoor environment; the final positioning error is less than 2·2 m with a stable output frequency of 3 Hz.
Journal Article
A dimension and positioning measurement approach for hot forgings based on image segmentation by edgings of grayscale surface continuity
Machine vision measurement is an ideal method for real-time non-contact measurement of hot forgings, where image segmentation is the most important issue in extracting contours and effective areas. However, existing image segmentation methods have limitations of poor performance or complex algorithms with high computational costs, thus are not suitable for real-time processing of hot forging images in industrial processing. This paper proposes an efficient and robust passive visual image segmentation approach by extracting edges of forging images based on discrete grayscale surface continuity, by which experiments on forging positioning and dimension measurement are conducted to prove the performance and feasibility of the image segmentation approach. In this paper, three types of edges by the geometric continuity of the equivalent grayscale surface for forging images are proposed, so that segmentation can be realized by extracting feature edges directly, or combined with the Snakes model. Continuity edges directly related to the geometric characteristics of grayscale surface for forging images, the extracted primary and secondary edges, subsequently the edge-based segmentation approach, can be identified as suitable and stable for forgings with different thermal radiations and dimensions. The experimental results show that the proposed image segmentation approach based on continuity edges works well for segmenting forging images of different temperatures and dimensions, which provides good results in real-time dimension and positioning measurement experiments for hot forging.
Journal Article
A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture
Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si3N4 membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk.
Journal Article