Daniel Dodzi Yao Setsoafia¹, Kiran Sreedhar Ram¹, Hooman Mehdizadeh-Rad^1,2, David Ompong^1,2, Vinuthaa Murthy^1,2, Jai Singh^1,2,*

Journal of Renewable Materials, Vol.10, No.10, pp. 2553-2567, 2022, DOI:10.32604/jrm.2022.020967

Abstract DFT and TD-DFT calculations of HOMO and LUMO energies and photovoltaic properties are carried out on four selected pentathiophene donor and one IDIC-4F acceptor molecules using B3LYP and PBE0 functionals for the ground state energy calculations and CAM-B3LYP functional for the excited state calculations. The discrepancy between the calculated and experimental energies is reduced by correlating them with a linear fit. The fitted energies of HOMO and LUMO are used to calculate the V_oc of an OSC based on these donors and acceptor blend and compared with experimental values. Using the Scharber model the calculated PCE of the donor-acceptor molecules… More >

JUAN CARLOS STOCKERT^1,2,*, ALFONSO BLÁZQUEZ-CASTRO³

BIOCELL, Vol.46, No.6, pp. 1391-1415, 2022, DOI:10.32604/biocell.2022.019493

Abstract

Melanins represent one of the most ancient and important group of natural macromolecular pigments. They have multiple biological roles in almost all organisms across the Phyla, examples being photoprotection, anti-oxidative action, radical scavenger activity, and heavy metal removal. From the biomedical point of view, melanocytes are involved in the origin of melanoma tumors, and the main therapeutic advances for their treatment have been revised in Part 1 of this review. The chemical structure of eumelanin is a biological concern of great importance, and therefore, exploring theoretical molecular models and synthesis mechanisms will be here described, as well as molecular orbital… More >

Lihua Zhu^1,*, Yu Wang¹, Zhiqiang Wu¹, Cheire Cheng²

Intelligent Automation & Soft Computing, Vol.33, No.1, pp. 291-303, 2022, DOI:10.32604/iasc.2022.024252

Abstract The rapid developments of artificial intelligence in the last decade are influencing aerospace engineering to a great extent and research in this context is proliferating. In this paper, the trajectory optimization of a three-stage launch vehicle in the powering phase subject to the sun-synchronous orbit is considered. To solve the optimal control problem, the Gauss pseudo-spectral method (GPM) is used to transform the optimization model to a nonlinear programming (NLP) problem and sequential quadratic programming is applied to find the optimal solution. However, the sensitivity of the initial guess may cost the solver significant time to do the Newton iteration… More >

Danhe Chen^1,*, A. A. Baranov², Chuangge Wang¹, M. O. Karatunov³, N. Yu. Makarov³

CMES-Computer Modeling in Engineering & Sciences, Vol.127, No.3, pp. 977-991, 2021, DOI:10.32604/cmes.2021.014662

Abstract As the number of space objects (SO) increases, collision avoidance problem in the rendezvous tasks or re-constellation of satellites with SO has been paid more attention, and the dangerous area of a possible collision should be derived. In this paper, a maneuvering method is proposed for avoiding collision with a space debris object in the phasing orbit of the initial optimal solution. Accordingly, based on the plane of eccentricity vector components, relevant dangerous area which is bounded by two parallel lines is formulated. The axises of eccentricity vector system pass through the end of eccentricity vector of phasing orbit in… More >

Jian Ma^1,2, Changxuan Wen³, Chen Zhang^2,*

CMES-Computer Modeling in Engineering & Sciences, Vol.126, No.2, pp. 617-644, 2021, DOI:10.32604/cmes.2021.014474

Abstract High-specific-impulse electric propulsion technology is promising for future space robotic debris removal in sun-synchronous orbits. Such a prospect involves solving a class of challenging problems of low-thrust orbital rendezvous between an active spacecraft and a free-flying debris. This study focuses on computing optimal low-thrust minimum-time many-revolution trajectories, considering the effects of the Earth oblateness perturbations and null thrust in Earth shadow. Firstly, a set of mean-element orbital dynamic equations of a chaser (spacecraft) and a target (debris) are derived by using the orbital averaging technique, and specifically a slow-changing state of the mean longitude difference is proposed to accommodate to… More >

Gen Xu, Danhe Chen, Xiang Zhang, Wenhe Liao^*

CMES-Computer Modeling in Engineering & Sciences, Vol.125, No.2, pp. 865-878, 2020, DOI:10.32604/cmes.2020.012844

Abstract For the on-orbit flight missions, the model of orbit prediction is critical for the tasks with high accuracy requirement and limited computing resources of spacecraft. The precession-nutation model, as the main part of extended orbit prediction, affects the efficiency and accuracy of on-board operation. In this paper, the previous research about the conversion between the Geocentric Celestial Reference System and International Terrestrial Reference System is briefly summarized, and a practical concise precession-nutation model is proposed for coordinate transformation computation based on Celestial Intermediate Pole (CIP). The idea that simplifying the CIP-based model with interpolation method is driven by characteristics of… More >

Meng Wang¹, Hong Lai^{1, *}, Lei Pan²

CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 369-387, 2020, DOI:10.32604/cmc.2020.07342

Abstract On the one hand, existing measurement device independent quantum key distribution (MDI-QKD) protocols have usually adopted single photon source (SPS) and weak coherent photon (WCP), however, these protocols have suffered from multi-photon problem brought from photon splitter number attacks. On the other hand, the orbital angular momentum (OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame, solving the dependency of the base in the MDI-QKD protocol. Given that, we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent (SPACS) and heralded single-photon sources (HSPS). Due to the stability of OAM and the… More >

Baichun Gong¹, Shuang Li^{1, *}, Lili Zheng², Jinglang Feng³

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.1, pp. 221-234, 2020, DOI:10.32604/cmes.2020.07769

Abstract A closed-form solution to the angles-only initial relative orbit determination (IROD) problem for space rendezvous with non-cooperated target is developed, where a method of hybrid dynamics with the concept of virtual formation is introduced to analytically solve the problem. Emphasis is placed on developing the solution based on hybrid dynamics (i.e., Clohessy-Wiltshire equations and two-body dynamics), obtaining formation geometries that produce relative orbit state observability, and deriving the approximate analytic error covariance for the IROD solution. A standard Monte Carlo simulation system based on two-body dynamics is used to verify the feasibility and evaluate the performance proposed algorithms. The sensitivity… More >

Renyong Zhang¹, Caisheng Wei^{2, *}, Zeyang Yin^{3, *}

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.1, pp. 89-107, 2020, DOI:10.32604/cmes.2020.07985

Abstract This paper investigates a novel quasi fixed-time orbit tracking control method for spacecraft around an asteroid in the presence of uncertain dynamics and unknown uncertainties. To quantitatively characterize the transient and steady-state responses of orbit tracking error system, a continuous performance function is devised via using a quartic polynomial. Then, integrating backstepping control technique and barrier Lyapunov function leads to a quasi fixed-time convergent orbit tracking controller without using any fractional state information and symbolic functions. Finally, two groups of illustrative examples are employed to test the effectiveness of the proposed orbit control method. More >

Xin Wang^{1, 2, *}, Xiaokui Yue^{1, 2}, Haowei Wen^{1, 2}, Jianping Yuan^{1, 2}

CMES-Computer Modeling in Engineering & Sciences, Vol.122, No.1, pp. 61-87, 2020, DOI:10.32604/cmes.2020.06871

Abstract In this paper, a hybrid passive/active vibration (HPAV) controller of a loosely connected spacecraft consisting of a servicing satellite, a target and an X-shape structure isolator is first proposed to suppress vibrations of the system when subjected to the impulsive external excitations during the on-orbit missions. The passive dynamic response of the combined system can be adjusted appropriately to achieve the desired vibration isolation performance by tuning the structural parameters of the bio-inspired X-shape structure. Moreover, the adaptive control design through dynamic scaling technique is selected as the active component to maintain high vibration isolation performance in the presence of… More >