Recent Advances in Metrology

Carbonaceous aerosol (CAs) pollution is a significant cause of the deterioration of the susceptible Himalayan region, which profoundly affects climate change. In this study, we examined the winter-time pollution load of carbonaceous species [Organic Carbon (OC), Elemental Carbon (EC), Water-Soluble Organic Carbon (WSOC), Water-Soluble Ionic Species (WSIS), Primary Organic Carbon (POC), Secondary Organic Carbon (SOC), and Total Carbonaceous Aerosols (TCAs)] of PM₁₀ over a semi-urban high-altitude site of Darjeeling (27.041° N, 88.266° E, 2200 m above mean sea level (AMSL); an eastern Himalayan region), India, from January to February 2019. During winter, the PM₁₀ concentration (µg m⁻³) was found to be 52 ± 18, which comprises 24% of CAs, 30% of WSIS, and 8% of sea salts. The secondary aerosols contribute about 79% to WSIS and 24% to PM₁₀. The average concentration of WSIS was observed in the order of SO₄²⁻ > NH₄⁺  > NO₃⁻ > Na⁺  > K⁺  = Ca⁺² > Cl⁻ > Mg⁺² > F⁻, respectively. Lower ECR (Effective Carbon Ratio) suggests a reduction in the number of scatterings CAs and possibly an increase in the absorbing CAs. The mean OC/EC ratio (2.04 ± 0.37), K⁺/OC (0.11 ± 0.04), and their good correlations of 0.77 and 0.74, respectively, suggested fuel combustion (biomass burning and fossil fuels) as the major contributing source in Eastern Himalayas. In addition, a high WSOC/OC ratio (0.74 ± 0.22) implied the formation of secondary aerosols and the presence of aged aerosols. The trajectory analysis showed that the air masses mainly originated from the IGP region, Nepal, and the local region of the sampling site.

The paper discusses about the Sound Impedance Tube facility for evaluation of sound absorption characteristics of acoustical materials at CSIR-National Physical Laboratory, New Delhi, the National Metrology Institute (NMI) of India. The facility has been recently revived and brought under the Quality Management System as per ISO 17025:2017 and traceable to the national standards to the Sound Pressure Level. The paper reports methodology and measurement uncertainty in the evaluation of the sound absorption characteristics of acoustical materials as per ISO 10534-2: 1998. The revived facility traceable to the national standards of sound pressure level is instrumental in design and development of building acoustic materials for noise management and control.

With the advent of time sensitive innovative applications under the Internet of Things and Industry 4.0 landscape, timing accuracy requirements have become crucial. Many current areas, like telecommunications, smart grids, the stock market, intelligent sensors ecosystems, etc., require timing accuracies in milliseconds to microseconds. The upcoming applications will require even more precise timing synchronization. For time synchronization, industrial applications are considering various approaches based on satellite or network-oriented techniques. These techniques are unique in terms of their functioning and pose unique challenges regarding their applicability. For example, Global Navigation Satellite System (GNSS) based time synchronization can provide nanosecond-level accuracy; however, the accessibility of satellite signals in indoor and other scenarios is a challenge. Distributed systems, like sensor networks, vehicular ad-hoc networks, distributed clouds, and many smart technologies under the umbrella of Industry 4.0, pose their unique challenges for time synchronization. The paper presents timing accuracy requirements for different application scenarios and discusses the suitability of available timing technologies to support them. It discusses the applicability and constraints of different technological solutions and explores new research directions in the area.

Non-invasive glucose monitoring is the need of the hour due to steep rise in diabetic patients worldwide. Monitoring of glucose level at regular interval is important for preventing the diabetes related complications. Several non-invasive methods Raman, MIR, NIR, photo acoustic, bio impedance and fluorescence spectroscopy, polarimetry, microwave assisted monitoring etc. have been explored for this purpose. However, none of the techniques have achieved accuracies that are suitable for clinical use. NIR spectroscopy is a popular technique which is being extensively employed for the development of a non-invasive glucose measurement device. However, the NIR spectra is prone to variations due to changes in temperature, machine drift, time drift, water content etc. and seem dominant because of extremely low level of absorption variation in glucose. In the present study, the variations in the glucose absorbance at 960 nm as a result of consecutive measurements are demonstrated. The study reveals that there is a decrease in the glucose absorbance because consecutive measurements cause long exposure of sample to NIR and hence the heating of the solutions which results in a rise in temperature. The absorbance at a wavelength of 960 nm is affected by temperature because it corresponds to OH stretching vibrations and the OH groups of sugars are sensitive to temperature. The results also reveal that even at 1 °C variation in the temperature of a 100 mg/dl glucose solution leads to a decrease in the glucose absorbance from 0.00301 to 0.00150 (δ_abs = 1.52 × 10^–3). Even this small variation in the absorbance can cause large errors in the prediction of glucose concentrations. Therefore, for device fabrication using NIR spectroscopy temperature variations must be taken into consideration to improve the accuracy of glucose predictions.

Accuracy and Precision measurement of an object in a complex environment for mobile robot applications is an important task. In a complex environment it is difficult to identify similar objects, such as chairs, tables, furniture and other objects available. Different methods are available to identify such objects, but high accuracy and precision are not easily achievable. This paper presents MobileNet with Vision Transformer for identification of objects in complex environments. Several experiments have been conducted for indoor environments where 94.3% accuracy is achieved for indoor environment with the implementation of MobileNet with Vision Transformer model.

The requirement of metrological controls and performance tests stems from either the intended or potential use of measuring instruments in activities where the quality of measurement is of public concern. Such uses may be identified as the measurement of quantities related to specified classes of objects, commodities, phenomena, materials, or conditions. Performances of Liquefied Natural Gas Dispensers are critical because of their potential use in commerce, especially where custody transfer is involved. At an auto LNG dispensing station, LNG is stored and dispensed as automotive fuel to motor vehicles. Billing is done based on the quantity measured by the dispenser. Any potential error in measurement will lead to losses to the public. Tests were conducted as per general guidelines of OIML R117 (OIML R 117-1:2019 (E), Dynamic measuring systems for liquids other than water, 2019), Dynamic measuring systems for liquids other than water. This paper focuses on the model approval studies, metrological controls and performance tests on a LNG dispenser along with discussions and interpretations of results (OIML R 117-1:2019 (E), Dynamic measuring systems for liquids other than water, 2019; ISO/IEC 17,025, General requirements for the competence of testing and calibration laboratories, 2017; ISO/TS 21,748, Guide to the use of repeatability, reproducibility, and trueness estimates in measurement uncertainty estimation; Certificate number FCRI/WFL/T/2021/75 issued by Fluid Control Research Institute).

According to the definition, calibration refers to the procedures with which comparison is carried out between the results of a measuring instrument or a measuring system and the corresponding values in the measurement standard. It includes evaluation of measurement uncertainty and providing measurement traceability to SI units. Calibration is carried out in a periodic time cycle referred as a calibration interval, which is expected to ensure the reliability of the equipment performance. In order to confirm the equipment performance and maintain confidence in the measurement carried out, intermediate checks in between calibrations shall be performed as per documented procedure. Intermediate checks are the best monitoring system in between the calibration interval for identifying any drift or change in the performance of the equipment. The ISO/IEC 17,025:2017 (1) standard requirement is that ‘when intermediate checks are necessary to maintain confidence in the performance of the equipment these checks shall be carried out’ and ‘when’ mentioned in the requirement is the selection of periodicity for performing intermediate checks based on the significance of applications. Discovering an equipment which is out of calibration (beyond tolerance limits) has a high potential value which would result in reducing the risks like financial risk, consumer risk etc. The sooner the equipment is identified as out of tolerance, the lesser the risks associated with the measurements. The purpose of this paper is to provide the details about the importance of the intermediate checks, plan and perform intermediate checks, analyze the results and maintain the records. It is hoped that the intermediate checks on measuring and test equipment will be given more importance and carried out for the equipment which requires calibration to minimize the risks involved in performing measurements.

The most prevalent malignancy nowadays in women is breast cancer. Breast cancer risk factors include changes in lifestyle, hormonal changes, genetic mutations, radiation therapy, and alcohol consumption. Ultrasound is the predominantly used mode of examination due to its portability, low cost, and lack of ionising radiation. Despite these benefits, the quality of ultrasound images can be lowered by the presence of speckle noise and low contrast. With the advancement of computer technology, medical image processing techniques, and artificial intelligence-based algorithms, numerous opportunities for the research community to investigate the potential of computer-aided diagnosis (CAD) for the classification of breast abnormalities using ultrasound images have arisen. Tissue-specific features must be computed during medical image characterisation; e.g., when analysing breast abnormalities, the texture, as well as the shape of the tumour region, are considered important for diagnostic purposes. As a result, the current study compared the performance of texture, shape, and combined feature vectors on a total of 110 breast ultrasound images collected from a scan centre in Patiala. The results of the experiments show that the PCA-SVM classifier achieves an overall accuracy of 93.9% using feature vectors containing texture features (computed using 2D Gabor wavelet transform) combined with shape features. Radiologists can use the proposed CAD system to verify their diagnosis in the course of their regular medical procedures.

Due to rapid industrialization and urbanization, noise pollution emerges as one of the serious threats to human beings. Noise is countered by sound-absorbing materials in the buildings and other places. In this study sound absorption properties of pinewood-based high-density fiberboard (HDF) perforated ceiling panels have been investigated. Perforated panels have been selected because they can counter the noise in specific low frequency ranges. The panels of different specific drilled hole sizes and perforation ratios have been studied to see the influence of these parameters on sound absorption characteristics. Further, an attempt has been done to enhance the sound absorption bandwidth by inserting a porous material behind the perforated panels. The experiments for the measurement of sound absorption coefficients (alpha) have been done by the Reverberation Chamber method as per ISO 8285-1987. The main aim of this study is to optimize different parameters and design a structure for the ceiling panel that can provide an efficient, economical noise reduction solution for confidential speech privacy by reducing echoes and long reverberation inside rooms.

The paper reports the parametric sensitivity of the factors affecting the sound absorption characteristics of the acoustical materials tested in the reverberation chambers. The various factors affecting the sound absorption characteristics such as air-gap, thickness, bulk density, porosity, tortuosity and air flow resistivity have been discussed based on the previous studies. The study also reports some of the recently developed acoustical sound absorbing materials having higher sound absorption characteristics for noise control applications.

Precise transfer of time and frequency signals is an indispensable activity in the field of time and frequency metrology. Accurate time is a critical requirement for various fields, e.g., navigation, telecommunication and finance sectors along with many technological applications and advanced scientific research. Satellite based time transfer methods fulfil the requirements of accurate time for most of these applications but vulnerability to jamming and spoofing of satellite signals are big concerns for many of the critical applications. Optical fibre-based time transfer techniques provide excellent options for transferring precise and secure time over a distance of several hundreds of kilometers. The present work describes the establishment of an optical fibre link at CSIR-National Physical Laboratory, India utilising White Rabbit Precision Time Protocol (WR-PTP) for precise and accurate transfer of time and frequency signals from a reference atomic clock. White Rabbit (WR) technique includes several advanced features, e.g., synchronous ethernet, precision time protocol, digital dual mixer time difference etc. for measuring as well as compensating link delays very accurately and provides time synchronisation within sub-nanosecond uncertainty. In order to enhance the accuracy and stability of the optical fibre link, a feedback loop has been utilised for estimating as well as compensating dynamic phase variation, which arises due to ambient temperature variation around the link.

During the Diwali festival in the Delhi region, the Atmospheric Boundary Layer (ABL) height is examined in relation to pollution (caused by firecrackers) and climatic conditions. Air quality, ABL height, and Ventilation Coefficient (VC) have all been studied over the past four years as a result of firecracker use. By employing a forward selection technique, we have determined the most important factors that influence the ABL's height. The primary goal of this study is to discover the air pollution parameter that has the greatest impact on the ABL height. SOund Detection And Ranging (SODAR) has become a key tool for the continuous monitoring of ABL height. On Diwali in 2014–2017, the daily average ABL height was 300, 660, 308, and 263 m, respectively. These year's heights were about 25, 15, and 6% lower than the comparable Pre-Diwali days in 2014, 2016, and 2017, respectively; nevertheless, they were 15% higher in 2015. Mean comparisons and correlations show that the burning of firecrackers on Diwali contributes significantly to the amount of particulate matter and gaseous pollutants in the atmosphere. Using a forward selection strategy to choose the most influential parameters, the strongest correlations between meteorological variables and pollution concentrations were found. Temperature, relative humidity, wind speed, NO₂, and SO₂ input variables were selected based on their importance in 2014–2017 using a forward selection technique.

Weak signals are available from various applications like, geological explorations, biomedical sciences, military, aerospace and other fields. Detection of such signals is important for further studies. However, these signals are often mixed with high-frequency noises. These noises have very high-frequency, zero expectation value and zero average value. Various fields of control theory like, convolution time domain, frequency domain, and time domain analysis are required along with different nonlinear theoretical tools, like, chaos, stochastic resonance etc. These theoretical algorithms are used to develop an instrument called a lock-in amplifier which has a strong detection ability and high reliability of many weak signals. Before actually developing the amplifier, a simulation model is required to be developed. In this paper, the authors have developed a simulated model for the separation of weak input signals from white noises. For this process, Google Colab notebook and Python software have been used. The main advantage of this work is that the authors have used Python-based software which is open source software and takes very less computer space.

Volatile organic compounds (VOCs) are the precursor of secondary aerosols and surface ozone in the atmosphere. The present study has been carried out to understand the ozone formation potential (OFP) of different VOCs at an urban site of Delhi in November 2021. Ambient air samples were collected for VOC analysis using GC-FID. The total concentration of VOCs was (80.47 ± 38.77) ppbv. Out of 22 species of VOCs, n-butane has the highest monthly average concentration (14.47 ± 8.78) ppbv. Alkanes were the most abundant (63.80%) followed by alkenes (19.66%), aromatic hydrocarbons (11.25%), and, acetylene (5.29%) respectively. 1 hexene has the highest OFP value (56.11 ppbv) and n-nonane has the lowest OFP (0.54 ppbv) as well as the lowest concentration (0.69 ± 0.15) ppbv. Alkenes have the maximum percentage contribution (56.09%) to total OFP followed by alkanes (24.03%), aromatics (17.73%), and Alkyne (2.15%).

The series combination of standards resistor and capacitors is used as dissipation factor standard to calibrate precision LCR meter and capacitance bridge. The dissipation factor is measured in the range of 0.1 to 0.0001 with uncertainties in the range of 0.1% to 11%. The precision capacitance bridge and LCR meter are calibrated for dissipation factor at 1 kHz. The calibration results are compared and discussed in the presented work. It is observed that the accuracy of the dissipation factor measured with the GR1615 precision capacitance bridge is in good agreement with theoretical values.

In order to comprehend the elemental annual contributions to PM_2.5 over Delhi’s urban region from January 2021 to December 2021, this study was carried out. Elemental analysis (Na, Mg, Ca, Cr, Al, P, S, K, Fe, Cu, Zn, Cl, and Mo) of PM_2.5 was performed using a non-destructive method (Wavelength Dispersive X-Ray Fluorescence Spectrometry). During the sampling period, the observed annual average concentration of PM_2.5 was 105 ± 44 μg m⁻³, which exceeds the National Ambient Air Quality Standards (NAAQS) limit (40 μg m⁻³) by approximately 2.5 times. Among elements, majorly Cl (22%), S (21%), and K (19%), Fe (11%), Zn (6%), Ca (5%), Al (4%), Cr (3%) contributed to PM_2.5. Whereas Cu, Ga, Mo, Zr, Mg, Na, B, P, Mn, Pd, As, Br, Ni and Ti contributed ≤1%. The diagnostic ratios of Al/Fe, Al/Ca, and Al/Mg indicates their common source of these elements. According to enrichment factor estimation, Fe, Ca, Mg and Na contribute to crustal/ soil dust, while Mo, Cr, Zn, and Cu are likely to be emitted due to industrial activities. The health risk assessment (HRA) evaluated the non-carcinogenic risk of Cr and Pb along with the carcinogenic risk of Cr. The burning of fossil fuels and biomass, industrial pollutants, automobile emissions, and crustal or mineral dust are among the likely sources of the PM_2.5 anticipated at Delhi's urban site.

It’s imperative to ascertain and specify the roundness of mechanical components, otherwise, they could fail in the real world. In this paper, an attempt is made to analyze the roundness of a flick standard with Least Squares Reference Circle method using different filtration techniques. This analysis will help us understand the effect of these filters during measurements and the results thus obtained will be compared against each other to optimize the filters for roundness measurements.

The paper presents the effects of seasonal variations on environmental noise levels and also discusses the correlation of different meteorological factors with the ambient noise levels. The present study is conducted for two major cities of India–Delhi and Mumbai. The day and night equivalent levels of different seasons for ten sites of each of the two cities were analysed. No specific trend was observed for the seasonal variation of the noise levels for different seasons. It was observed that day, night, and 24 h equivalent levels show the highest values in the summer season.

In an attempt to realize the total spectral radiant flux (TSRF) scale from spectral irradiance and total luminous flux, a study has been carried out to determine the suitability of the spectroradiometric configurations for sphere spectroradiometric measurements. Three spectroradiometric configurations have been studied and spectral irradiance measured from all the configurations was used to derive the TSRF scale, which has been used for the calibration of sphere-spectroradiometer system. Total luminous flux of a set of test lamps was measured under all three calibrations. Ananalysis of the measured total luminous flux has been done to ascertain the suitability of all the configurations for deriving TSRF from the spectral irradiance.

Measurement of pressure with required accuracy is important in many industries such as process, chemical manufacturing, automobile etc. The accurate pressure measurement is important not only due to quality considerations but also for safety purposes. A large number of instruments and sensors are available to measure gauge, differential, and absolute pressures. The primary standards measure the pressure using the fundamental units. The Secondary or transfer pressure standards measure pressure in terms of some other quantity like resistance, capacitances etc. Since the discovery of ferroelectricity in single crystal materials (Rochelle salts) in 1921 and its subsequent extension towards the poly-crystalline material (barium titanate, BT) during the 1940s, there has been a continued discovery of new material and technological development leading to the use of ferroelectric relaxor in a significant number of applications like multilayer capacitor, actuators, energy storage etc. The present study describes the investigation of pressure and temperature dependent dielectric properties of Lead Magnesium Niobate-Lead Titanatebinary (PMN-PT) Binary relaxor specimens. In this study, the investigator optimized the specimen's preparation method by changing PT concentration to improve the specimen's pressure sensing properties. This study adds another pressure sensing application of relaxor materials amongst many other applications.

CSIR-National Physical Laboratory (NPL), India, has recently initiated the activity of development and production of CRMs in various sectors (including Water & Chemicals, Cement and Building Materials, Petroleum Products, Precious Metals, Hardness Blocks, Ores & Minerals, Organic Substances, etc.) in collaboration with recognized RMPs under the “Make-In-India” initiative of the Government of India (GoI). The aim of this joint development activity is to harmonize the Quality Infrastructure and also to boost the production and availability of indigenous CRMs in the country. The developed CRMs are available with the trade name ‘BND®’. The procedure of the development and production of BNDs jointly by CSIR-NPL and concerned RMPs is controlled by the Quality Management System (QMS) of CSIR-NPL that is based on IS/ISO 17034: 2016 and IS/ISO/IEC 17,025: 2017. The ‘BND Outreach’ and ‘BND Management’ Sub-Divisions falling under the ‘BND Division’ at CSIR-NPL actively coordinate with numerous recognized RMPs for the joint development and production of BNDs. The ‘QMS’ system being followed by CSIR-NPL and concerned RMPs is being discussed in this article.