Dynamic Analysis and Parametric Optimization of Telescopic Tubular Mast Applied on Solar Sail

Large-scale solar sails can provide power to spacecraft for deep space exploration.A new type of telescopic tubular mast(TTM)driven by a bistable carbon fiber-reinforced polymer tube was designed in this study to solve the problem of contact between the sail membrane and the spacecraft under light pressure.Compared with the traditional TTM,it has a small size,light weight,high extension ratio,and simple structure.The anti-blossoming and self-unlocking structure of the proposed TTM was described.We aimed to simplify the TTM with a complex structure into a beam model with equal linear mass density,and the simulation results showed good consistency.The dynamic equation was derived based on the equivalent model,and the effects of different factors on the vibration characteristics of the TTM were analyzed.The performance parameters were optimized based on a multiobjective genetic algorithm,and prototype production and load experiments were conducted.The results show that the advantages of the new TTM can complete the deployment of large-scale solar sails,which is valuable for future deep space exploration.

Model Design and Development of a Telescopic Palm Fruit Harvester

This research paper presents a comprehensive conceptual design approach for the development of a telescopic machine system, which is portable and will provide a safe method of harvesting palm fruits. For this machine system development, the material for each component of the machine system was first selected, the boom length, maximum boom angle, force and stroke length of each hydraulic cylinder, the hydraulic pump pressure, base weight, permissible weight of the cutting system and power required were then calculated in the design analysis. Furthermore, from the calculated parameters, the model of the system was created using SolidWorks engineering software, the model was developed and tested. The result shows that the cutting time of the system for one bunch of palm fruit was longer when compared to conventional systems. It was concluded that though the machine is maintenance friendly and portable, further improvements in its design are necessary so as to develop a system that will give desirable economic output at a shorter time.

Influence of Section Size of Telescopic Boom on Stability

The telescopic boom is the main bearing force component of the crane.The rationality of the design will directly affect the performance of the machine and safety.The telescopic boom is a typical thin-walled plate and shell structure.Its main form of damage is the occurrence of buckling,resulting in decreased carrying capacity,or even a security incident.In order to meet the lifting weight and height,to ensure the stability of the telescopic boom has become a major problem of the designer.There are many factors that affect the critical load of the telescopic boom,including support method,inertia moment,length and material.When the support mode,material and length are determined,the maximum factor affecting the buckling critical load is the inertia moment.In this paper,the influence of the section size on the buckling critical load of the telescopic boom is analyzed by using the inertia moment of section method ande finite element method.And the sensitivity analysis is carried out on this basis.The results of the analysis can provide designers with design reference basis.Then a reasonable cross-sectional size can be used to improve the buckling resistance capacity of the telescopic boom.

Anus-preserving rectectomy via telescopic colorectal mucosal anastomosis for low rectal cancer: Experience from a Chinese cohort

AIM: To investigate the safety and efficacy of anus-preserving rectectomy via telescopic colorectal mucosal anastomosis (TCMA) for low rectal cancer. METHODS: From August 1993 to October 2012, 420 patients including 253 males and 167 females with low rectal cancer underwent transabdominal and transanal anterior resection, followed by TCMA. The distance be-tween the anus and inferior margin of the tumor ranged from 5 to 7 cm, and was 5 cm in 6 patients, 6 cm in 127, and 7 cm in 287 patients. Tumor-node-metastasis staging showed that 136 patients had stage Ⅰ, 252 had stage Ⅱ and 32 had stage Ⅲ. Fifty-six patients with T3 or over received preoperative neoadjuvant chemoradio-therapy. RESULTS: The postoperative follow-up rate was 91.9% (386/420) with a median time of 6.4 years. All 420 pa-tients underwent radical resection. No postoperativedeath occurred. Postoperative complications included anastomotic leakage in 13 (3.1%) patients and anas-tomotic stenosis in 7 (1.6%). The local recurrence rate after surgery was 6.2%, the hepatic metastasis rate was 13.2% and the pulmonary metastasis rate was 2.3%. The 5-year survival rate was 74.0% and the disease-free survival rate was 71.0%. Kirwan classification showed that continence was good in 94.4% of patients with stage I when scored 12 mo after resection. CONCLUSION: TCMA for patients with low rectal cancer leads to better quality of life and satisfactory defecation function, and lowers anastomotic leakage occurrence, and might be one of the safe operative procedures in anus-preserving rectectomy.

Laparoscopic resection of lower rectal cancer with telescopic anastomosis without abdominal incisions

AIM:To assess laparoscopic radical resection of lower rectal cancer with telescopic anastomosis through transanal resection without abdominal incisions.METHODS:From March 2010 to June 2014, 30 patients(14 men and 16 women, aged 36-78 years, mean age 59.8 years) underwent laparoscopic radical resection of lower rectal cancer with telescopic anastomosis through anus-preserving transanal resection.The tumors were 5-7 cm away from the anal margin in 24 cases, and 4 cm in six cases.In preoperative assessment, there were 21 cases of T1N0M0 and nine of T2N0M0.Through the middle approach, the sigmoid mesentery was freed at the root with an ultrasonic scalpel and the roots of the inferior mesenteric artery and vein were dissected, clamped and cut.Following the total mesorectal excision principle, the rectum was separated until the anorectal ring reached 3-5 cm from the distal end of the tumor.For perineal surgery, a ring incision was made 2 cm above the dentate line, and sharp dissection was performed submucosally towards the superior direction, until the plane of the levator ani muscle, to transect the rectum.The rectum and distal sigmoid colon were removed together from the anus, followed by a telescopic anastomosis between the full thickness of the proximal colon and the mucosa and submucosal tissue of the rectum.RESULTS:For the present cohort of 30 cases,the mean operative time was 178 min,with an average of 13 positive lymph nodes detected.One case of postoperative anastomotic leak was observed,requiring temporary colostomy,which was closed and recovered3 mo later.The postoperative pathology showed T1-T2N0M0 in 19 cases and T2N1M0 in 11 cases.Twelve months after surgery,94.4%patients achieved anal function Kirwan grade 1,indicating that their analfunction returned to normal.The patients were followed up for 1-36 mo,with an average of 23 mo.There was no local recurrence,and 17 patients survived for>3years(with a survival rate of 100%).CONCLUSION:Laparoscopic radical resection of lower rectal cancer with telescopic anastomosis through transanal resection without abdominal incisions is safe and feasible.

Development of flexible telescopic boom model using ANCF sliding joint constraints with LuGre friction

In this investigation, a modeling procedure of a telescopic boom of cranes is developed using the absolute nodal coordinate formulation together with the sliding joint constraints. Since telescopic booms are extracted and retracted under various operating conditions, the overall length of the boom changes dynamically, leading to the time-variant vibration characteristics. For modeling the telescopic structure of booms, a special care needs to be exercised since the location of the sliding contact point moves Mong the deformable axis of the flexible boom and the solution to a moving boundary problem is required. This issue indeed makes the modeling of the telescopic boom difficult, despite the significant needs for the analysis. It is, therefore, the objective of this investigation to develop a modeling procedure for the flexible telescopic boom by considering the sliding contact condition with the dynamic frictional effect. To this end, the sliding joint constraint developed for the absolute nodal coordinate formulation is employed for describing relative sliding motion between flexible booms, while flexible booms are modeled using the beam element of the absolute nodal coordinate formulation, which allows for modeling the large rotation and deformation of the structure.

A Novel Conceptual Telescopic Positioning Pile for VLFS Deployed in Shallow Water:Structure Design

A conceptual design of using novel telescopic piles to position a multi-modular very large floating structure(VLFS),which is supposed to be severed as a movable floating airport,is proposed.The telescopic piles can automatically plug in the soil to resist the environmental loads and pull out from the soil to evacuate or move on to the next operational sea.The feasibility demonstration of the conceptual design includes two parts:function verification and structure design.In the latter part of the conceptual design,a time-domain structural analysis is firstly conducted by using Abaqus software.The simulation results suggest that the preliminary structure scheme is not optimum due to the insufficient structure utilization,although both structure safety of the piles and positioning accuracy are guaranteed.To realize a cost reduction of construction and installation,a Genetic Algorithm-Finite Element Analysis(GA-FEA)method is employed to perform structural optimization.After optimization,31 percent of the weight of each pile is reduced and higher structure utilization is maintained.The difference of the self-weight and allowable buoyancy of a single module(SMOD)of a semisubmersible-type VLFS is much larger than the weight of the piles.Combined with the function verification in our previous work,the conceptual design of using the novel telescopic pile to position VLFS is demonstrated to be feasible.

Aplanatic and Telescopic Lens with a Radial Gradient of Refraction Index

It is shown that aplanatic lens with a radial gradient of refraction index is simultaneously a telescopic lens, notably not only for an axial beam, but also for an off axis parallel beam. Consideration is carried out by an algebraic way on the basis of regularities of ray paths. It is also shown that aplanatic and telescopic properties of the lens are independent of the refracting surface shapes. Various versions of lens performance are shown below.

Modified Multi-Resolution Telescopic Search Algorithm for Block-Matching Motion Estimation

This paper presents a modified multi-resolution telescopic search algorithm (MRTlcSA) for the block-matching motion estimation. A novel inverse telescopic search is substituted for the conventional telescopic search, that reduces the on-chip memory size and memory bandwidth for VLSI implementation. In addition, strategies of motion track and adaptive search window are applied to reduce the computational complexity of motion estimation. Simulation results show that, compared with the MRTleSA, the proposed algorithm reduces the computational load to only 30% while preserving almost the same image quality. Comparisons on hardware cost and power consumption of the VLSI implementations using the two algorithms are also presented in the paper.

Basic Survey Scheduling for the Wide Field Survey Telescope(WFST)

Aiming at improving the survey efficiency of the Wide Field Survey Telescope, we have developed a basic scheduling strategy that takes into account the telescope characteristics, observing conditions, and weather conditions at the Lenghu site. The sky area is divided into rectangular regions, referred to as “tiles,” with a size of2°. 577 × 2°. 634 slightly smaller than the focal area of the mosaic CCDs. These tiles are continuously filled in annulars parallel to the equator. The brightness of the sky background, which varies with the moon phase and distance from the moon, plays a significant role in determining the accessible survey fields. Approximately 50connected tiles are grouped into one block for observation. To optimize the survey schedule, we perform simulations by taking into account the length of exposures, data readout, telescope slewing, and all relevant observing conditions. We utilize the Greedy Algorithm for scheduling optimization. Additionally, we propose a dedicated dithering pattern to cover the gaps between CCDs and the four corners of the mosaic CCD array, which are located outside of the 3° field of view. This dithering pattern helps to achieve relatively uniform exposure maps for the final survey outputs.

Quantitative Analysis of Seeing with Height and Time at Muztagh-Ata Site Based on ERA5 Database

Seeing is an important index to evaluate the quality of an astronomical site.To estimate seeing at the Muztagh-Ata site with height and time quantitatively,the European Centre for Medium-Range Weather Forecasts reanalysis database(ERA5)is used.Seeing calculated from ERA5 is compared consistently with the Differential Image Motion Monitor seeing at the height of 12 m.Results show that seeing decays exponentially with height at the Muztagh-Ata site.Seeing decays the fastest in fall in 2021 and most slowly with height in summer.The seeing condition is better in fall than in summer.The median value of seeing at 12 m is 0.89 arcsec,the maximum value is1.21 arcsec in August and the minimum is 0.66 arcsec in October.The median value of seeing at 12 m is 0.72arcsec in the nighttime and 1.08 arcsec in the daytime.Seeing is a combination of annual and about biannual variations with the same phase as temperature and wind speed indicating that seeing variation with time is influenced by temperature and wind speed.The Richardson number Ri is used to analyze the atmospheric stability and the variations of seeing are consistent with Ri between layers.These quantitative results can provide an important reference for a telescopic observation strategy.

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

The thermal gradient is an important factor that causes degradation to the image quality of telescopes. In order to ensure the accurate alignment of the primary focus unit and the primary mirror, the hexapod platform(as a corrector) is investigated in this paper. First, a ground-based telescope with 2.5 m aperture and 3.5 deg field of view is described. The telescope is under construction, and it is expected to be finished in 2023. Second, the hexapod platform with flexure hinges utilized to adjust the primary focus unit is proposed, which is applied as a corrector.Then, the inverse kinematics of the platform is established and an open-loop control system is built based on it.Finally, the cryogenic performance test for the hexapod platform is performed. The experimental results show that the resolution and repeatability of the translation for the hexapod platform can be achieved at the micrometer level.The resolution and repeatability of the rotation can be achieved at the arc-second level. Therefore, the cryogenic performance of the hexapod platform can meet the optical imaging requirements of the wide-field ground-based telescope. The kinematic analysis and cryogenic performance tests in the paper provide a technical reference for the precise alignment of the primary focus unit and the primary mirror, which can improve the imaging quality of the telescope.

Disturbance Observer-based Pointing Control of Leighton Chajnantor Telescope

Leighton Chajnantor Telescope(LCT), i.e., the former Caltech Submillimeter Observatory telescope, will be refurbished at the new site in Chajnantor Plateau, Chile in 2023. The environment of LCT will change significantly after its relocation, and the telescope will be exposed to large wind disturbances directly because its enclosure will be completely open during observation. The wind disturbance is expected to be a challenge for LCT's pointing control since the existing control method cannot reject this disturbance very well. Therefore, it is very necessary to develop a new pointing control method with good capability of disturbance rejection. In this research, a disturbance observer—based composite position controller(DOB-CPC) is designed, in which an H∞feedback controller is employed to compress the disturbance, and a feedforward linear quadratic regulator is employed to compensate the disturbance precisely based on the estimated disturbance signal. Moreover, a controller switching policy is adopted, which applies the proportional controller to the transient process to achieve a quick response and applies the DOB-CPC to the steady state to achieve a small position error. Numerical experiments are conducted to verify the good performance of the proposed pointing controller(i.e., DOB-CPC) for rejecting the disturbance acting on LCT.

Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.

Simulation of RFI Cancellation Using Subspace Projection Algorithm for PAF Receiver

The simulation of radio frequency interference(RFI) cancellation by applying a spatial filtering technique for phased array feed(PAF) is presented. In order to better reflect the characteristics of PAF, a new signal model is to add the coupling coefficient among elements of PAF to the conventional array signal model. Then the subspace projection(SP) algorithm is used to cancel RFI from the correlation matrix of the signal, and finally, the 2D power image is drawn. The power variation of signal-of-interest direction and RFI direction before and after using the SP algorithm is analyzed. The new signal model and simulation strategy can be used to test and verify the beamformer.

Prospects of the Multi-channel Photometric Survey Telescope in the Cosmological Application of Type Ia Supernovae

The Multi-channel Photometric Survey Telescope(Mephisto)is a real-time,three-color photometric system designed to capture the color evolution of stars and transients accurately.This telescope system can be crucial in cosmological distance measurements of low-redshift(low-z,z■0.1)Type Ia supernovae(SNe Ia).To optimize the capabilities of this instrument,we perform a comprehensive simulation study before its official operation is scheduled to start.By considering the impact of atmospheric extinction,weather conditions,and the lunar phase at the observing site involving the instrumental features,we simulate light curves of SNe Ia obtained by Mephisto.The best strategy in the case of SN Ia cosmology is to take the image at an exposure time of 130 s with a cadence of 3 days.In this condition,Mephisto can obtain hundreds of high-quality SNe Ia to achieve a distance measurement better than 4.5%.Given the on-time spectral classification and monitoring of the Lijiang 2.4 m Telescope at the same observatory,Mephisto,in the whole operation,can significantly enrich the well-calibrated sample of supernovae at low-z and improve the calibration accuracy of high-z SNe Ia.

The FAST Core Array

The Five-hundred-meter Aperture Spherical Radio Telescope(FAST)Core Array is a proposed extension of FAST,integrating 24 secondary 40-m antennas implanted within 5 km of the FAST site.This original array design will combine the unprecedented sensitivity of FAST with a high angular resolution(4.3"at a frequency of 1.4 GHz),thereby exceeding the capabilities at similar frequencies of next-generation arrays such as the Square Kilometre Array Phase 1 or the next-generation Very Large Array.This article presents the technical specifications of the FAST Core Array,evaluates its potential relatively to existing radio telescope arrays,and describes its expected scientific prospects.The proposed array will be equipped with technologically advanced backend devices,such as real-time signal processing systems.A phased array feed receiver will be mounted on FAST to improve the survey efficiency of the FAST Core Array,whose broad frequency coverage and large field of view(FOV)will be essential to study transient cosmic phenomena such as fast radio bursts and gravitational wave events,to conduct surveys and resolve structures in neutral hydrogen galaxies,to monitor or detect pulsars,and to investigate exoplanetary systems.Finally,the FAST Core Array can strengthen China's major role in the global radio astronomy community,owing to a wide range of potential scientific applications from cosmology to exoplanet science.

Solar image reconstruction method under atmospheric turbulence at Fuxian Lake Solar Observatory

Strong atmospheric turbulence reduces astronomical seeing,causing speckle images acquired by ground-based solar telescopes to become blurred and distorted.Severe distortion in speckle images impedes image phase deviation in the speckle masking reconstruction method,leading to the appearance of spurious imaging artifacts.Relying only on linear image degradation principles to reconstruct solar images is insufficient.To solve this problem,we propose the multiframe blind deconvolution combined with non-rigid alignment(MFBD-CNRA)method for solar image reconstruction.We consider image distortion caused by atmospheric turbulence and use non-rigid alignment to correct pixel-level distortion,thereby achieving nonlinear constraints to complement image intensity changes.After creating the corrected speckle image,we use the linear method to solve the wavefront phase,obtaining the target image.We verify the effectiveness of our method results,compared with others,using solar observation data from the 1 m new vacuum solar telescope(NVST).This new method successfully reconstructs high-resolution images of solar observations with a Fried parameter r0 of approximately 10 cm,and enhances images at high frequency.When r0 is approximately 5 cm,the new method is even more effective.It reconstructs the edges of solar graining and sunspots,and is greatly enhanced at mid and high frequency compared with other methods.Comparisons confirm the effectiveness of this method,with respect to both nonlinear and linear constraints in solar image reconstruction.This provides a suitable solution for image reconstruction in ground-based solar observations under strong atmospheric turbulence.

The Jiao Tong University Spectroscopic Telescope Project

The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.

A design constraint for a double-acting telescopic hydraulic cylinder in a hydraulic erecting system

Hydraulic erecting systems are widely used in missile and rocket launchers because of their high power density.The double-acting telescopic hydraulic cylinder(DATHC)plays a decisive role in the safe and proper operation of such systems.In particular,improper design of effective areas of a DATHC could potentially lead to an overspeed descent with severe damage for the erecting system.Unfortunately,there is no design constraint for DATHC to prevent this.Therefore,in this paper,a simplified and practical design constraint is proposed.Based on a developed mathematical model of a typical erecting system,we simulated and analyzed not only six cases meeting and not meeting the design constraint,but also the effectiveness of the design constraint under different loads.Experiments were then carried out under four cases.Simulation and experimental results validate the simplified design constraint,a constraint inequation guiding the design of diameters of effective areas for a DATHC.