Methods and Techniques of Electricity Thieving in Pakistan

The situation of electricity in Pakistan has been alarming from the last ten years. The deficiency in electricity has not only obstructed the business activities but also affected the domestic consumers, educational institutes and hospitals. Usually electrical power companies are liable for electricity shortfall and power interruption. However, electricity end consumers are also equally responsible behind strange shortfall and unusual power interruption. Frequently, the consumers use the heavy electrical equipment in their homes including heaters, geysers, irons and water motors which causes the more electricity consumption, load shedding and huge amount of bills. For escaping the huge amount of electricity bill, the consumers commit the illegal and unethical connections. The illegal usage of electrical power failed the power companies to plan schedule load shedding accordingly and the other side the damaged electricity wires or Pole Mount Transformer increased faults due to overburdening, which directly affected on extend power interruption. In addition that, responsible teams of electrical power companies cannot reach instantly to repair faults and prevent the theft. Electricity thieving is social crime committed by the consumers or meter readers which causes the electricity strange shortfall within country. This paper presents the practical demonstration about the common energy theft methods and techniques done by electricity consumers within their home and residential building. In Pakistan EPC (electrical power companies) deploy the traditional electromechanical meters for electricity consumption measurements, however, these meters do not have any real time communication. Therefore there are many easy ways to manipulate the meter reading as well as internal structural of metering system.

The Velocity Aberration Effect of the CSST Main Survey Camera

In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous work,our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale,with a more pronounced influence as the size of the focal plane increases.Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions.The apparent scale variation follows a sinusoidal distribution throughout one orbital period.Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude.At low ecliptic latitudes,the total aberration leads to about a 0.94 pixel offset(a 20 minute exposure)and a 0.26 pixel offset(a 300 s exposure)at the edge of the field of view.Appropriate processings for the geometric effect during the CSST pre-and post-observation phases are presented.

Digital Beamforming Demonstration of a Microstrip Antenna Phased Array Feeds(PAF)at 1.25 GHz

We introduce the structure of a radio astronomy phased array feeds(PAF)beamforming demonstrator.In a laboratory environment,we have demonstrated beamforming on a received 1.25 GHz sinusoidal signal and used digital weighting techniques to plot the 2D pattern of the PAF.The radio frequency part of the demonstrator includes a 4×4 linearly polarized microstrip antenna array,all of which is connected in series with a low-noise amplifier.The signals from the central 4×2 array elements are injected into a radio frequency system-on-chip digital board,which can receive eight inputs with a bandwidth of 512 MHz.Combining the principle of undersampling,the beamforming is completed at a frequency of 1.25 GHz for the offline data,and a 2D image of the beam is plotted using beam scanning technology.

Combination of terrestrial reference frames based on space geodetic techniques in SHAO:methodology and main issues

Based on years of input from the four geodetic techniques （SLR, GPS, VLBI and DORIS）, the strategies of the combination were studied in SHAO to generate a new global terrestrial reference frame as the material realization of the ITRS defined in IERS Conventions. The main input includes the time series of weekly solutions （or fortnightly for SLR 1983-1993） of observational data for satellite techniques and session-wise normal equations for VLBI. The set of estimated unknowns includes 3- dimensional Cartesian coordinates at the reference epoch 2005.0 of the stations distributed globally and their rates as well as the time series of consistent Earth Orientation Parameters （EOPs） at the same epochs as the input. Besides the final solution, namely SOL-2, generated by using all the inputs before 2015.0 obtained from short-term observation processing, another reference solution, namely SOL- 1, was also computed by using the input before 2009.0 based on the same combination of procedures for the purpose of comparison with ITRF2008 and DTRF2008 and for evaluating the effect of the latest six more years of data on the combined results. The estimated accuracy of the x-component and y-component of the SOL- 1 TRF-origin was better than 0.1 mm at epoch 2005.0 and better than 0.3 mm yr- 1 in time evolution, either compared with ITRF2008 or DTRF2008. However, the z-component of the translation parameters from SOL-1 to ITRF2008 and DTRF2008 were 3.4 mm and -1.0 ram, respectively. It seems that the z-component of the SOL-1 TRF-origin was much closer to the one in DTRF2008 than the one in ITRF2008. The translation parameters from SOL-2 to ITRF2014 were 2.2, -1.8 and 0.9 mm in the x-, y- and z-components respectively with rates smaller than 0.4 mmyr-1. Similarly, the scale factor transformed from SOL-1 to DTRF2008 was much smaller than that to ITRF2008. The scale parameter from SOL-2 to ITRF2014 was -0.31 ppb with a rate lower than 0.01 ppb yr-1. The external precision （WRMS） compared with IERS EOP 08 C04 of the combined EOP series was smaller than 0.06 mas for the polar motions, smaller than 0.01 ms for the UT1-UTC and smaller than 0.02 ms for the LODs. The precision of the EOPs in SOL-2 was slightly higher than that of SOL-1.

Noise reduction methods in the analysis of near infrared lunar occultation light curves for high angular resolution measurements

A lunar occultation （LO） technique in the near-infrared （NIR） provides angular resolution down to milliarcseconds for an occulted source, even with ground- based 1 m class telescopes. LO observations are limited to brighter objects because they require a high signal-to-noise ratio （S/N ~40） for proper extraction of angular diameter values. Hence, methods to improve the S/N ratio by reducing noise using Fourier and wavelet transforms have been explored in this study. A sample of 54 NIR LO light curves observed with the IR camera at Mt Abu Observatory has been used. It is seen that both Fourier and wavelet methods have shown an improvement in S/N compared to the original data. However, the application of wavelet transforms causes a slight smoothing of the fringes and results in a higher value for angular diameter. Fourier transforms which reduce discrete noise frequencies do not distort the fringe. The Fourier transform method seems to be effective in improving the S/N, as well as improving the model fit, particularly in the fainter regime of our sample. These methods also provide a better model fit for brighter sources in some cases, though there may not be a significant imorovement in S/N.

Narrowband EUV Sc/Si Multilayer for the Solar Upper Transition Region Imager at 46.5 nm

The transition region is the key region between the lower solar atmosphere and the corona, which has been limitedly understood by human beings. Therefore, the Solar Upper Transition Region Imager(SUTRI) was proposed by Chinese scientists and launched in 2022 July. Right now, the first imaging observation of the upper transition region around 46.5 nm has been carried out by SUTRI. To ensure the spectral and temporal resolution of the SUTRI telescope, we have developed a narrowband Sc/Si multilayer. Based on the extreme ultraviolet(EUV)reflectivity measurements, the multilayer structure has been modified for ensuring the peak position of reflectivity was at 46.5 nm. Finally, the narrowband Sc/Si multilayer was successfully deposited on the hyperboloid primary mirror and secondary mirrors. The deviation of multilayer thickness uniformity was below than 1%, and the average EUV reflectivity at 46.1 nm was 27.8% with a near-normal incident angle of 5°. The calculated bandwidth of the reflectivity curve after primary and secondary mirrors was 2.82 nm, which could ensure the requirements of spectral resolution and reflectivity of SUTRI telescope to achieve its scientific goals.

Direct Ion Beam Figuring Process and Rotational Measurement Method for Ultra-smooth Aspherical Surfaces of a 46.5 nm Telescope

This paper describes a fabrication process for the hyperboloidal concave mirror of a 46.5 nm telescope. The180 mm aperture hyperboloidal concave mirror and 70 mm aperture compensator are machined directly from chemical mechanical polishing of a spherical surface to a high-accuracy aspherical surface by ion beam figuring.The aspherical measurement method is the Dall null test. To minimize system errors in the measurement process,the rotational measurement method with six rotations is used in the null test. The results of the analysis for the ME(first solve the machined surface profile, then solve the system errors) and EM(first solve the system errors, then solve the machined surface profile) methods of calculation in the measurement are given. The ME method is a more accurate rotational test method, and the six rotations are appropriate for rotational measurements. After the figuring process, the hyperboloidal concave mirror surface profile reached 8.27 nm rms and the compensator surface profile is approximately 4 nm rms. The roughness of the hyperboloidal concave mirror is smooth to0.160 nm rms.

The Edge Sensor of Segmented Mirror Based on Fringes of Equal Thickness

Co-phase and co-focus detection is one of the key technologies for large-aperture segmented mirror telescopes.In this paper,a new edge sensor based on fringes of equal thickness is developed,which can detect each segment's relative piston,tilt,and tip errors from the interferograms.Based on the co-focus demand for many ground-based seeing limited segmented mirror telescopes,an edge sensor prototype based on such a principle is built and applied in the indoor segmented mirror experiment system in the lab.According to the co-focus requirement of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,many simulations and experiments are carried out for cofocus error detection of the segmented mirror system.Experiment results show that the co-focus accuracy is better than 002 rms,which can meet the co-focus requirements of most large or extremely large segmented mirror astronomical telescopes.

Distributed Control Software for the Active Surface System of Tian-ma Radio Telescope

The Tian-ma Radio Telescope(TMRT) applies an Active Surface System(ASFS), which corrects for large-scale deformations due to gravity and thermal on the primary reflector. The centralized and automated management of the ASFS using software has become a challenge, for which we have developed the TMRT Active Surface System Control Software(TASCS). This paper describes the design and implementation of TASCS for device control,status monitoring, human-computer interaction, and data management functionalities. TASCS adopts the opensource Tango Controls framework and distributes middleware technology to realize real-time automated adjustment of the primary reflector through remote centralized control of a large number of actuators. At present, it has been successfully deployed on the TMRT and has played an important role in Event Horizon Telescope observations.

The Chromatic Point-spread Function of Weak Lensing Measurement in the Chinese Space Station Survey Telescope

Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to correct the smearing effect of the Point-Spread Function(PSF)on the shape of the galaxies.The chromaticity of PSF for a broad-band observation can lead to new subtle effects.Since the PSF is wavelength-dependent and the spectrum energy distributions between stars and galaxies are different,the effective PSF measured from the star images will be different from those that smear the galaxies.Such a bias is called color bias.We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs,and show the dependence on the color and redshift of the galaxies.Moreover,due to the spatial variation of spectra over the galaxy image,another higher-order bias exists:color gradient bias.Our results show that both color bias and color gradient bias are generally below 0.1%in CSST.Only for small-size galaxies,one needs to be careful about the color gradient bias in the weak lensing analysis using CSST data.

Preface: Frontiers in Astrophysics(Ⅱ)——A special issue dedicated to the 20th anniversary of RAA(2001–2020)

On the arrival of the 20 th anniversary of the journal,Research in Astronomy and Astrophysics(RAA),we see rapid progress in the frontiers of astronomy and astrophysics.To celebrate the birth and growth of RAA,a special issue consisting of 11 invited reviews from more than 30 authors,mainly from China,has been organized.This is the second volume of the special issues entitled Frontiers in Astrophysics published in RAA.The publication aims at evaluating the current status and key progress in some frontier areas of astronomy and astrophysics with a spirit of guiding future studies.

Prognostics and health management of FAST cable-net structure based on digital twin technology

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)will be fully commissioned later in 2019.Once commissioned,operation and maintenance of FAST will be the most prominent task.The unique working mode of active shape-changing of FAST cable-net structure makes the traditional maintenance way,which combines routine inspection with preventive maintenances not only expensive,but also unable to effectively avoid potential risks in operations.Therefore,it is necessary to develop an economical and reliable operation/maintenance technology for FAST cable-net structure.In this paper,a Prognostics and Health Management(PHM)system is proposed based on the advanced Digital Twin(DT)technology.Through the finite element analysis of DT model,the current safety status of FAST cablenet is evaluated,and the fatigue life of components in the cable-net is predicted.Hence Condition-Based Maintenance(CBM)of FAST cable-net structure can be realized.The PHM system described in this paper can effectively guarantee the healthy and safe operation of the FAST cable-net structure,greatly improve the maintenance efficiency and reduce the cost for maintenance works.

Research on design of adaptive connecting mechanisms for the cable-net and panels of FAST

The reflector system of the Five-hundred-meter Aperture Spherical radio Telescope （FAST） is designed to incorporate 4450 rigid panels supported by a flexible cable-net structure. The shapechanging operation that occurs in the process of observation will lead to a relative displacement between adjacent nodes in the cable-net. In addition, three nodes on a rigid panel are fixed with respect to each other. Thus, adaptive connecting mechanisms between panels and the cable-net are certainly needed. The present work focuses on the following aspects. Firstly, the degrees of freedom of adaptive connecting mechanisms were designed so that we can not only adapt the panel to the deformation of the cable- net, but also restrict the panel to its right place. Secondly, finite element and theoretical analyses were applied to calculate the scope of motion in adaptive connecting mechanisms during the cable-net＇s shape-changing operation, thus providing input parameters for the design size of the adaptive connecting mechanisms. In addition, the gap size between the panels is also investigated to solve the trade-off between avoiding panel collisions and increasing the observation efficiency of FAST.

Sky subtraction for LAMOST

Sky subtraction is a key technique in data reduction of multi-fiber spectra. Knowledge of characteristics related to the instrument is necessary to determine the method adopted in sky subtraction. In this study, we describe the sky subtraction method designed for the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） survey. The method has been integrated into the LAMOST 2D Pipeline v2.6 and applied to data from LAMOST DR3 and later. For LAMOST, calibration using sky emission lines is used to alleviate the position-dependent （and thus time-dependent） ,-~ 4% fiber throughput uncertainty and small wavelength instability （0.1/~） during observation. Sky subtraction using principal component analysis （PCA） further reduces 25% of the sky line residual from OH fines in the red part of LAMOST spectra after the master sky spectrum, which is derived from a B-spline fit of 20 sky fibers in each spectrograph. Using this approach, values are adjusted by a sky emission line and subtracted from each fiber. Further analysis shows that our wavelength calibration accuracy is about 4.5 km s-1, and the averages of residuals after sky subtraction are about 3% for sky emission lines and 3% for the continuum region. The relative sky subtraction residuals vary with moonlight background brightness, and can reach as low as 1.5% for regions that have sky emission lines during a dark night. Tests on F stars with both similar sky emission line strength and similar object continuum intensity show that the sky emission line residual of LAMOST is smaller than that of the SDSS survey.

A Wideband Microwave Holography Methodology for Reflector Surface Measurement of Large Radio Telescopes

Most reflector surface holographic measurements of a large radio telescope utilize a geostationary satellite as the signal source. The shortcoming is that those measurements could only be done at a limited elevation angle due to the satellite’s relatively stationary state. This paper proposed a new wideband microwave holographic measurement method based on radio sources to achieve full-elevation-angle measurement with small size reference antenna. In theoretical derivation, the time delay and phase change due to path length and device difference between the antenna under test and reference antenna are compensated first. Then the correct method of wideband holography effect, which is because of antenna pattern differing under different wavelengths when receiving a wideband signal, is presented. To verify the proposed methodology, a wideband microwave holographic measurement system is established, the data processing procedure is illustrated, and the reflector surface measurement experiments on a 40 m radio telescope at different elevation angles are conducted. The result shows that the primary reflector surface root-mean-square at around elevation angles of 28°, 44°, 49°, and 75° are respectively 0.213 mm, 0.170 mm, 0.188 mm, and 0.199 mm. It is basically consistent with the real data, indicating that the proposed wideband microwave holography methodology is feasible.

The New Wuqing 70 m Radio Telescope and Measurements of Main Electronic Properties in the X-band

The new Wuqing 70 m radio telescope is first used for the downlink data reception in the first Mars exploration mission of China,and will be used for the other deep space communications and radio astronomical observations in the future.The main specifications and measurement results of some properties in the X-band are introduced in this paper,such as pointing calibration,gain and efficiency,system noise temperature,system equivalent flux density,and variations with elevation.The 23 parameters pointing calibration model considering the atmospheric refraction correction in real time is presented in the telescope,and the pointing accuracy reaches 570 in azimuth direction and 607 in elevation direction for different weather conditions.More than 62%efficiencies are achieved at full elevation range,and more than 70%in the mid-elevation.The system equivalent flux density of the X-band in the mid-elevation reaches 26 Jy.

Distortion mapping correction in the AIMS primary mirror testing by a computer-generated hologram

The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m and with a large off-axis amount of 1 m. Due to the surface figure of the primary mirror under the used state is directly related to image quality of the whole system, a computer-generated hologram(CGH) is carried out to test the primary mirror, and the test results are used to polish the mirror to a higher surface accuracy. However, the fact that the distortion exists in the testing results leads to the failure of a further guide to deterministic optical processing. In this paper, a distortion correction method is proposed, which uses an orthogonal set of vector polynomials to mapping the coordinates of the mirror and the pixels of fringes, and then an interpolation method is adopted to obtain the corrected results. The testing accuracy by using CGH is also verified by an auto-collimate test experiment. According to the distorted corrected results, the root-mean-square of the surface figure is about 1/50λ(λ=632.8 nm) after polishing.

Recognition of FAST reflector nodes based on Canny operator

The reflector system of Five-hundred-meter Aperture Spherical radio Telescope(FAST)is designed as 4450 rigid panels a flexible cable-net structure.We use 10 total stations to measure2225 nodes of the cable-net and then control the shape of the reflectors.Every time,it takes at least 35 minutes to finish the calibration of the whole cable-net once.It is indeed far too inefficient.Thus,we developed a set of highly efficient instrument CRRS(CCD Rotation Ranging System).It is based on photogrammetry and can finish the measurement in 1 minute.However,the target we used in CRRS is active target,and it has serious electromagnetic interference problems to affect the use of FAST.Take the above reasons into consideration,we plan to identify the nodes by taking the gap between the reflector panels as the feature condition.The new method can take the place of active targets to finish the measuring task.The present work focuses on the following aspects.First,combined with the characteristics of FAST reflector images,the representative algorithms of image edge detection are discussed.Second,the process of node extraction is introduced in detail so that we know that it works.In addition,experimental results are given to draw a conclusion so that Canny algorithm was used for continuous research of reflector edge detection.

Stochastic parallel gradient descent based adaptive optics used for a high contrast imaging coronagraph

An adaptive optics （AO） system based on a stochastic parallel gradient descent （SPGD） algorithm is proposed to reduce the speckle noises in the optical system of a stellar coronagraph in order to further improve the contrast. The principle of the SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of the SPGD algorithm is demonstrated by an experimental system featured with a 140-actuator deformable mirror and a Hartrnann-Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array （LCA） based coronagraph to improve the contrast. The LCA can modulate the incoming light to generate a pupil apodization mask of any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10^-3 to 10^-4.5 at an angular distance of 2A/D after being corrected by SPGD based AO.

Variable stars in M37

The CCD photometric observations of open star cluster M37(NGC 2099) were carried out up to a limiting magnitude of V ～ 20 in both B and V filters to search for variable stars using a 2k×4k CCD and the 1.3 m telescope at the Vainu Bapu Observatory, Kavalur.A total of 314 stars were in the first observing run, out of which 60 were identified as variables.Eight out of the identified 60 variables are classified as W UMa binary stars.For model fitting, we used PHOEBE based on the W-D code to estimate the physical parameters of these newly detected W UMa binaries that theoretically best match the observed light curves.