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There is a constant need to regularly calibrate He–Ne laser sources to ensure their precision in various applications. However, such calibration systems are currently not available in Indonesia. For this reason, developing a decent calibration system capable of maintaining He–Ne laser traceability is essential. This paper studies the realization of substitution methods to calibrate stabilized He–Ne lasers. The wavelength of the stabilized He–Ne laser to be calibrated (DUC) and the reference He–Ne laser (Agilent 5519B) were measured by a wavelength meter, Advantest (Q8326), that has sufficient short-time stability. The calculated ratio between both wavelengths was used as a reference value in determining the wavelength of the DUC laser. A calibration of laser head Polytec OPV-503 at 632.8 nm with instability 1.5 × 10⁻⁵, was performed to validate the method. It was found that the DUC has a wavelength of (632.9907 ± 0.0001) nm. The result shows that the calibration system can be used to establish traceability to the SI unit of the metre, particularly for the He–Ne laser with stability greater than 0.0001 nm that we expect to be sufficient for laser displacement interferometer applications, e.g., as the primary standard in vibration calibration.

The present study examined the long–term characteristics and relationship of atmospheric ammonia (NH₃) with other trace gases (NO, NO₂, SO₂ and CO) at highly polluted urban agglomeration of Delhi, India. Measurements of ambient trace gases (NH₃, NO, NO₂, SO₂, and CO) and meteorology were recorded at the observational site of Delhi from 2011–2022. Overall mean mixing ratios of ambient NH₃, NO, NO₂, SO₂ and CO were 18.9 ± 5.0 ppb, 19.9 ± 4.8 ppb, 19.1 ± 5.3 ppb, 2.15 ± 0.38 ppb, and 1.47 ± 0.42 ppm, respectively during 2011—2022. During study, a significant diurnal and seasonal variation in mixing ratios of NH₃, NO, NO₂, and CO were observed except SO₂ mixing ratio. During all the seasons, the mixing ratios of trace gases were observed higher during nighttime and lower during daytime. Correlation analysis reveals that the higher loading of NO, NO₂ and CO influenced the mixing ratio of NH₃ at the study site of Delhi.

Accurate dimensional characterization of automotive components is extremely critical, as assorted components are assembled to develop the final product with structural complexities. This article demonstrates the significance of equitable dimensional measurements in the automotive sector; a considerable economic and industrial force for the socio-economic growth of a country. It emphasizes the requirement of precise dimensional measurements for optimal quality assurance in automotive industries, leading toward extensive customer satisfaction, elevated productivity, and immense employment opportunities. This article elaborates on the momentousness of dimensional metrology in the automotive sector through substantial case studies and explicates the importance of intercomparisons in metrology. The present manuscript deliberates the evolution of industrial dimensional metrology for in-line/near-line measurements and fast automation in the automotive segment and delineates the role of CSIR-National Physical Laboratory India (CSIR-NPLI); The National Measurement Institute of India, in catering to the ever-augmenting dimensional metrology demands of the automotive sector.

The hydrocarbon species (CxHy) released by the material have a significant impact on the performance and life of precision instruments. The quadrupole mass spectrometer (QMS) is one of the most established and widely used partial outgassing rate measurement instruments. However, a potential issue with QMS is the high-mass discrimination effect, wherein ions with lower m/z values are transmitted more efficiently than those with higher m/z values. It also leads to a reduction in the sensitivity of QMS when measuring CxHy with higher m/z values. To address this problem, this paper proposes a method using dodecane to correct the high-mass discrimination effect of QMS. To ensure stable injection of dodecane gas and maintain the pressure within the working conditions of QMS, a dedicated sampling device for dodecane gas is designed. Furthermore, to verify the effectiveness of the proposed method, the high-mass discrimination effect of two quadrupole mass spectrometers of the model QMG250 M2 was corrected, and the CxHy outgassing rate of polytetrafluoroethylene (PTFE) was measured by continuous expansion method. The results demonstrate that the method proposed in this paper can effectively reduce the impact of the high-mass discrimination effect on the measurement of CxHy with higher m/z values, while significantly increasing the outgassing rate of CxHy from PTFE.

This investigation aimed to evaluate the severity of heavy metal concentrations in suspended sediments along a 225 km section of the Ganges River in the eastern part of Uttar Pradesh, India. Metal concentrations were measured via Atomic Absorption Spectrometry, with averages recorded as Fe (50230 µg/g), Mn (1283 µg/g), Cr (201 µg/g), Zn (183 µg/g), Pb (55.1 µg/g), Ni (50.9 µg/g), Cu (42.8 µg/g), and Cd (1.01 µg/g). Zn, Fe, Cr and Pb showed anthropogenic contribution at all selected locations, while anthropogenic inputs of Mn and Ni were also observed at few locations. Risk evaluation was conducted using various pollution indicators. The Contamination Factor (CF) revealed moderate contamination (CF between 1 and 3) by Cr. The Geoaccumulation Index (GI) indicated a stage of uncontaminated to moderate contamination (GI between 0 and 1) for Cr at upstream locations. The values of Enrichment Ratios (ER) indicated minor enrichment (ER between 1 and 3) of Cr at all locations. The Pollution Load Index values ranged from 0.72 to 0.86, suggesting that the selected section is overall uncontaminated. The study highlights significant but localized anthropogenic impacts on heavy metal concentrations, particularly for chromium. While the overall assessment suggests that the suspended sediment in the studied stretch are not heavily contaminated, the elevated concentrations of iron, manganese, chromium, and nickel pose significant ecological risks. The study underscores the need for targeted pollution control measures, especially for metals with high anthropogenic contributions, to ensure the long-term health and safety of this vital water resource.

In pursuit of newer lightweight components, clad sheets emerge as a solution to meet the demand for automotive and aerospace applications. The present work focuses on the effect of warm forming temperature on the tensile properties, microstructural characteristics, formability, and residual stress of a two-ply clad sheet composed of SS430 and AA1050 layers. Tensile properties of the clad sheet and individual components are determined through testing of laser cut specimens as per standard at ambient and elevated temperatures (220 °C). These tensile properties are used in the material model for prediction of failure in Erichsen cupping experiments through simulations. At 220 °C, the yield and ultimate tensile strengths of clad sheets are found to decrease by approximately 10% and 18%, respectively, but ductility is observed to increase by almost 5%. Electron backscatter diffraction analysis is done to measure and evaluate the microstructural characteristics of the clad material after the tensile deformation at both temperatures. The kernel average misorientations measured from electron backscatter diffraction show that the transition layer retained its integrity during the plastic deformation, whereas the number fraction at peak misorientation values has risen substantially on either side of the transition layer, i.e., on the steel and aluminium layers. The pole figure maps indicate a weak texture of the AA1050 layer, but a stronger texture of the SS430 layer after warm forming than after forming at ambient temperature. The cupping experiments are performed to assess the formability of the clad and individual layers, at two different temperatures. To study the effect of each layer during forming, two possible cases of sheet placements are investigated; i.e., in the first case, the SS430 is on the outer side, and AA1050 is in contact with the punch, whereas in the second case, it is the opposite. The clad sheet shows better formability when the steel layer is on the outer side of the dome. The formability of the clad sheet is observed to increase by 15% at the warm forming temperature. The predicted simulation results are in good agreement with the experimental results. In order to investigate the effect of temperature on the residual stress, the variation of stresses was also determined and mapped on the tested samples across the dome after forming at ambient and warm temperatures. The residual stress across the dome of the tested samples after the warm forming is significantly reduced compared to that of the samples tested at room temperature. The favourable tensile properties, microstructural characteristics, and reduced residual stress at elevated temperature indicate better formability of the clad sheet with good bond integrity at warm forming temperature.

As a common sensor widely used in near-surface wind speed measurement, the three-cup anemometer may gradually fail to measure the start-up threshold of wind speed value (0.3 m/s ~ 1.0 m/s) in environmental observation. If the indicates value is abnormal, additional outdoor calibration should be performed. The aim of this paper is to provide a numerical analysis of the key factors for field calibrator models. The resource of measurement error and the calculation of start-up thresholds for three-cup anemometers are investigated. In addition, four types of calibrator models are built. Based on the realizable k-epsilon model, the streamline and flow deviation angle of different calibrator models are analyzed. One fan set and nine fan sets are available in the model with airflow perpendicular to the specified plane. As a calibration component in the actual field calibration, the installation of a honeycomb screen at the inlet can dramatically change the airflow direction of one fan model. The honeycomb screen can also change the airflow deviation angle of a nine-fan group model to an acceptable range. In order to meet the requirements of the wind speed calibration regulation, a model with nine-fan group and a honeycomb screen best meet the field conditions. Each start-up threshold of the three-cup anemometer has a corresponding fan pressure jump at reasonable intervals.

Characterizing the variation dynamics of amplitude scintillation within the lowest layers of the troposphere is important for many communication system applications. It provides fast fade statistics used to determine the non-rain-induced fade margin needed for implementing effective fade mitigation techniques on both terrestrial and satellite radio channels. This study employed three-year in-situ data of primary radio-climatic factors (temperature and relative humidity) and radio channel parameters (frequency, elevation angle, and antenna diameter) for estimating tropospheric amplitude scintillation and evaluating its vertical profile over Akure, Nigeria, using the Karasawa scintillation model. The radio-climatic parameters were measured at five altitudinal layers from the surface to a height of 200 m at 50 m interval on a 220 m-tall mast using a Davis Vantage Pro2 automatic weather station at 30 min interval. The extracted data spanned January 2008 to December 2010 (3 years). Radio link parameters frequency, elevation angle, and antenna diameter, with values of 12.5 GHz, 53°, and 0.9 m, respectively, were employed for the computation of scintillation amplitude (χ) and intensity (σ) along with the weather variables. From the results, the histogram of annual scintillation intensity at all levels was well approximated by the stable probability density function (pdf) distribution model. The magnitude of scintillation intensity was found to be much higher during the rainy season than during the dry season. Minimal differences, between 2 and 8% in magnitude, were observed in the annual averaged amplitude across the levels, but the rainy-dry season dichotomy was conspicuous following monthly analysis. An allowance of 0.5 dB and 0.38 dB is required to counteract the effects of scintillation amplitude fade and enhancement, respectively, at this location.

The Stirling cryocoolers are widely used in the military and aerospace fields due to advantages such as high efficiency and compact structure. The pistons of these coolers with very small clearances operate at high speed and without lubrication. Piston failure in the coolers has often affected the operational life of the cooler. The objective of the study was to find a solution to piston failure by providing a surface coat to the pistons, carrying out their tribological evaluation, and analyse cooler thermal performance to identify the better of two coatings for field applications. In the present experimental study, a Stirling cooler developed with a cooling capacity of 0.5 W @80 K with Helium as the working fluid was integrated with surface-coated pistons and tested for its mechanical and thermal performance. On testing, DLC coating exhibits better wear resistance than TiN coating and therefore is a more suitable coating for cryocooler pistons. The present study clearly shows that DLC-coated pistons reduce power consumption and increase the number of operational hours of miniature Stirling cryocoolers.