A New 3D Shaping Method for Low-Thrust Trajectories between Non-Intersect Orbits

This paper proposes a new shape-based method in spherical coordinates to solve three-dimensional rendezvous problems. Compared with the existing shape-based methods, the proposed method does not need parameter optimization. Moreover, it improves the flexibility of orbit fitting, greatly reduces the velocity increment and maximum thrust acceleration, and ensures the orbit safety to a certain extent. The shaping function can provide the initial estimate for numerical trajectory optimization and improve the convergence rate in a certain range when combined with the normalization method. The superiority of the proposed method over the existing methods is demonstrated by two numerical examples. Its effectiveness at initial estimation generation in the indirect optimization of a low-thrust trajectory is demonstrated by the third example.

Image Denoising Using Nonlocal Means with Shape-Adaptive Patches and New Weights

Digital images captured from CMOS/CCD image sensors are prone to noise due to inherent electronic fluctuations and low photon count. To efficiently reduce the noise in the image, a novel image denoising strategy is proposed, which exploits both nonlocal self-similarity and local shape adaptation. With wavelet thresholding, the residual image in method noise, derived from the initial estimate using nonlocal means (NLM), is exploited further. By incorporating the role of both the initial estimate and the residual image, spatially adaptive patch shapes are defined, and new weights are calculated, which thus results in better denoising performance for NLM. Experimental results demonstrate that our proposed method significantly outperforms original NLM and achieves competitive denoising performance compared with state-of-the-art denoising methods.

The MULTIPLISITAS NEWTON DAN TITIK TETAP ATRAKTIF DALAM MENENTUKAN KEKONVERGENAN

Newton's method is one of the numerical methods used in finding polynomial roots. This method will be very effective to use, if the initial estimate of the roots for the Newton iteration function satisfies sufficient Newtonian convergence, [11]. In this article we will analyze the efficacy of this method by looking at the relationship between the fixed point method and Newton's iteration function. When the iteration of the function converges to the root, the velocity of convergence can also be determined. In terms of the speed of convergence, it turns out to be very dependent on the multiplicity of Newton's method itself.

Association of Number of Bidders and Minimum Bid Ratio (AEr) with Effect of E-bidding of Different Project

The purpose of this research is to analyze the relation between the number of bidders versus the minimum bid ratio (AEr)/percentage below the initial engineer’s estimate to type and size of project within Road Divisions Butwal and Shivapur. Bidding data of four consecutive fiscal years starting from 072/73 of two Road Divisions which are already completed its procurement stage were analyzed. The percentage below/contract awarded cost is directly proportional or a significant correlation was found with the number of the participated bidder in any project s of both divisions during the data study period. Bidders have to bid below 20% of the initial estimate that was found to get a project in hand by contractors and they are willing to bid low for the utilization of resources, types of equipment, manpower, and also to get experiences. This research revealed correlation coefficients between the number of bidders and percentage below engineers' estimates are 0.61 for the Butwal division and 0.67 for the Shivapur division. Correlation coefficients 0.82 and 0.83 was found in Nepalgunj and Mahendranagar. Percentage below engineers' estimate depends on 67 and 69% on the number of bidders in Nepalgunj and Mahendranagar respectively. E-bidding helped to promote competition along with low bidding. As there is 17% below with only hardcopy bidding but with e-bid the below percentages rises to 28% with more number of bidder per project. Improvement in existing offer granting framework with additional capability rules ought to be engaged by doling out the weight in the monitory term, soliciting a technique from the proclamation, upgraded e-offering framework, and affirmation for venture exhibitions of the undertaking before execution. This research would be useful for those who are involving in policy making and governing agencies like Public Procurement Monitoring Office and for making necessary amendments in existing rules.

A variational model for computing the effective reproduction number of SARS-CoV-2

We propose a variational model for computing the temporal effective reproduction number, R(t), of SARS-CoV-2 from the daily count of incident cases and the serial interval. The R(t) estimate is made through the minimization of a functional that enforces: (i) the ability to reproduce the incidence curve from R(t) through a renewal equation, (ii) the regularity of R(t) and (iii) the adjustment of the initial value to an initial estimate of R0 obtained from the initial exponential growth of the epidemic. The model does not assume any statistical distribution for R(t) and does not require truncating the serial interval when its distribution contains negative days. A comparative study of the solution is carried out with the standard EpiEstim method. For a particular choice of the parameters of the variational model, a good agreement is found between the estimate provided by the variational model and an estimate obtained by EpiEstim shiftef backward more than 8 days. This backward shift suggests that our model finds values for R(t) that are more than 8 days closer to present. We also examine how to extrapolate R(t) and the form of the incidence curve i(t) in the short term. An implementation and comparison of both methods, applied every day on each country, is available at www.ipol.im/ern.

Environmental Impact of Phosphogypsum-Derived Building Materials

The aim of the present work was to characterize the products obtained from the treatment of phosphogypsum residue by means of two recovery routes, and also to evaluate the concentrations of heavy metals and radionuclides in the materials obtained and their leachates. In this way, it is possible to determine how the most hazardous components of phosphogypsum behave during procedures until their stabilization through CO2 fixation. This study provides an initial estimate of the possibilities of reusing the resulting products from a health and safety risk standpoint and their potential polluting capacity. The phases resulting from the transformations were controlled, and the behaviour of standard mortars manufactured from the resulting paste lime was studied. In all cases, an additional control of the leachate products was performed.

Adaptive Sensor Array Error Calibration Based Impact Localization on Composite Structure

Gains and phases delay induced by sensor position error would significantly degrade the performance of high-resolution two-dimensional multiple signal classification (2D-MUSIC) algorithm, which resulting in low positioning estimation accuracy and poor imaging. In this study, adaptive piezoelectric sensor array calibration based method is proposed for impact localization on composite structure. First, observed signal vector from the sensor array is represented by error calibration matrix with unknown gains and phases, and then it used to construct the cost function including sensor array parameters. Second, a 2D-MUSIC algorithm based on linear attenuation calibration is applied for estimating the initial estimate of impact location. Finally, substituting the initial estimate, the cost function is minimized by adaptive iterative to calculate the sensor array error parameters and the exact location of the impact source. Both finite element method (FEM) simulation and experimental results on carbon-fiber composite panel demonstrate the validity and effectiveness of the proposed method.