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.

Methods and Techniques for Teaching English to Children(10)

The place of grammar in the primaryschool classroomTask 1Read the following statements and decidewhether they are true or false according to

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 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.

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.

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.

Modeling and Measuring Friction of the Leighton 10m Telescope

Estimating and identifying friction are important aspects of simulating a mechanical drive system. Accurate friction modeling helps to improve a telescope's performance. However, the friction conditions inside are complex and hard to measure. We did simulations with mathematical transfer functions for the Leighton 10 m Telescope and employed a polyline model to identify sources of friction. We made a two-stage model for the Leighton 10 m Telescope. Based on measurements of the motor's currents and speeds, we constructed a curve containing the friction information of the transmission elements. We simulated the system using a step function input under many combinations of friction parameters. By comparing simulation results with the measured ones, we determined the various friction components. This model accurately reproduced the telescope performance including the nonlinearities.

Investigating the efficiency of the Beijing Faint Object Spectrograph and Camera(BFOSC)of the Xinglong 2.16-m reflector

The Beijing Faint Object Spectrograph and Camera （BFOSC） is one of the most important instruments operating in conjunction with the 2.16-m telescope at Xinglong Observatory. Every year there are - 20 SCI-papers published based on observational data acquired with this telescope. In this work, we have systemically measured the total efficiency of the BFOSC that operates as part of the 2.16-m reflector, based on observations of two ESO flux standard stars. We have obtained the total efficiencies of the BFOSC instrument of different grisms with various slit widths in almost all ranges, and analyzed factors which effect the efficiency of this telescope and spectrograph. For astronomical observers, the result will be useful for them to select a suitable slit width, depending on their scientific goals and weather conditions during observations. For technicians, the result will help them to systemically identify the real efficiency of the telescope and spectrograph, and to further improve the total efficiency and observing capacity of the telescope technically.

An experimental indoor phasing system based on active optics using dispersed Hartmann sensing technology in the visible waveband

A telescope with a larger primary mirror can collect much more light and resolve objects much better than one with a smaller mirror, and so the larger version is always pursued by astronomers and astronomical technicians. Instead of using a monolithic primary mirror, more and more large telescopes, which are currently being planned or in construction, have adopted a segmented primary mirror design. Therefore, how to sense and phase such a primary mirror is a key issue for the future of extremely large optical/infrared telescopes. The Dispersed Fringe Sensor （DFS）, or Dispersed Hartmann Sensor （DHS）, is a non-contact method using broadband point light sources and it can estimate the piston by the two-directional spectrum formed by the transmissive grating＇s dispersion and lenslet array. Thus it can implement the combination of co-focusing by Shack-Hartmann technology and phasing by dispersed fringe sensing technologies such as the template-mapping method and the Hartmann method. We introduce the successful design, construction and alignment of our dis- persed Hartmann sensor together with its design principles and simulations. We also conduct many successful real phasing tests and phasing corrections in the visible waveband using our existing indoor segmented mirror optics platform. Finally, some conclusions are reached based on the test and correction of experimental results.

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 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.

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.

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.

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.

The design of China Reconfigurable ANalog-digital backEnd for FAST

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)was launched on 2016 September 25.From early 2017,we began to use the FAST wideband receiver,which was designed,constructed and installed on the FAST in Guizhou,China.The front end of the receiver is composed an uncooled Quad Ridge Flared Horn feed(QRFH)with the frequency range of 270 to 1620 MHz,and a cryostat operating at 10 K.We have cooperated with the Institute of Automation of the Chinese Academy of Sciences to develop the China Reconfigurable ANalog-digital backEnd(CRANE).The system covers the 3 GHz operating band of FAST.The hardware part of the backend includes an Analog Front-end Board,a wideband high precision Analog Digital Converter,and a FAST Digital Back-end.Analog circuit boards,field programmable gate arrays,and control computers form a set of hardware,software,and firmware platforms to achieve flexible bandwidth requirements through parameter changes.It is also suitable for the versatility of different astronomical observations,and can meet specific requirements.This paper briefly introduces the hardware and software of CRANE,as well as some observations of the system.