scholarly journals Rapid Algorithm for Generating Entry Landing Footprints Satisfying the No-Fly Zone Constraint

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Shengnan Fu ◽  
Tianyu Lu ◽  
Jian Yin ◽  
Qunli Xia
Keyword(s):  
Estimation Algorithm ◽  
Hypersonic Vehicle ◽  
Energy Profile ◽  
Accurate Calculation ◽  
Bank Angle ◽  
Energy Profiles ◽  
Heading Angle ◽  
Constraint Model ◽  
Acceleration Tracking ◽  
Acceleration Guidance

An online estimation algorithm of landing footprints based on the drag acceleration-energy profile is proposed for an entry hypersonic vehicle. Firstly, based on the Evolved Acceleration Guidance Logic for Entry (EAGLE), drag acceleration-energy profiles are designed. To track the drag acceleration-energy profile obtained by the interpolation, a drag acceleration tracking law is designed. Secondly, based on the constraint model of the no-fly zone, flying around strategies are proposed for different conditions, and a reachable area algorithm is designed for no-fly zones. Additionally, by interpolating the minimum and maximum drag acceleration profiles, the terminal heading angle constraint is designed to realize the accurate calculation of the minimum and maximum downrange ranges by adjusting the sign of the bank angle. In this way, the distribution of landing footprints is more reasonable, and the boundary of a reachable area is more accurate. The simulation results under typical conditions indicate that the proposed method can calculate landing footprints for different situations rapidly and with the good adaptability.

Free energy profile analysis to identify factors activating the aggregation-induced emission of a cyanostilbene derivative

2021 ◽  
Author(s):  
Norifumi Yamamoto
Keyword(s):  
Free Energy ◽  
Profile Analysis ◽  
Energy Profile ◽  
Contributing Factors ◽  
Free Energy Profile ◽  
Aggregation Induced Emission ◽  
Energy Profiles ◽  
Free Energy Profiles

The contributing factors that cause the aggregation-induced emission (AIE) are determined by identifying characteristic differences in the free energy profiles of the AIE processes of the AIE-active E-form of CN-MBE and the inactive Z-form.

scholarly journals The jet energy profile: A BSM analysis tool

2017 ◽  
Vol 32 (36) ◽  
pp. 1747022 ◽  
Author(s):  
R. S. Chivukula ◽  
E. H. Simmons ◽  
N. Vignaroli
Keyword(s):  
Analysis Tool ◽  
Energy Profile ◽  
Energy Profiles ◽  
Systematic Uncertainties ◽  
Jet Energy

A new heavy di-jet resonance could be discovered at the 14 TeV LHC. In this talk we present a strategy to reveal the nature of such a particle; in particular to discern whether it is a quark–antiquark [Formula: see text], quark–gluon [Formula: see text], or gluon–gluon [Formula: see text] resonance. The strategy is based on the study of the energy profiles of the two leading jets in the di-jet channel. Including statistical uncertainties in the signal and the QCD backgrounds, we show that one can distinguish between [Formula: see text], [Formula: see text], and [Formula: see text] resonances; an evaluation of systematic uncertainties in the measurement of the jet energy profile will require a detailed detector study once sufficient 14 TeV di-jet data is in hand.

scholarly journals Accelerated Computation of Free Energy Profile at ab Initio Quantum Mechanical/Molecular Mechanics Accuracy via a Semi-Empirical Reference Potential. II. Recalibrating Semi-Empirical Parameters with Force Matching

2019 ◽  
Author(s):  
Xiaoliang Pan ◽  
Pengfei Li ◽  
Junming Ho ◽  
Jingzhi Pu ◽  
Ye Mei ◽  
...  
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Quantum Mechanical ◽  
Energy Profile ◽  
Free Energy Profile ◽  
Force Matching ◽  
Energy Profiles ◽  
Reference Potential ◽  
Semi Empirical ◽  
Free Energy Profiles

An efficient and accurate reference potential simulation protocol is proposed for producing ab initio quantum mechanical molecular mechanical (AI-QM/MM) quality free energy profiles for chemical<br>reactions in a solvent or macromolecular environment. This protocol involves three stages: (a) using force matching to recalibrate a semi-empirical quantum mechanical (SE-QM) Hamiltonian for the specific reaction under study; (b) employing the recalibrated SE-QM Hamiltonian (in combination with molecular mechanical force fields) as the reference potential to drive umbrella samplings along the reaction pathway; and (c) computing AI-QM/MM energy values for collected configurations from the sampling and performing weighted thermodynamic perturbation to acquire AI-QM/MM corrected reaction free energy profile. For three model reactions (identity SN2 reaction, Menshutkin reaction, and glycine proton transfer reaction) in aqueous solution and one enzyme reaction (Claisen arrangement in chorismate mutase), our simulations using recalibrated PM3 SE-QM Hamiltonians well reproduced AI-QM/MM free energy profiles (at the B3LYP/6-31G* level of theory) all within 1 kcal/mol with a 20 to 45 fold reduction in the computer time.

scholarly journals Accelerated computation of free energy profile at ab initio quantum mechanical/molecular mechanical accuracy via a semi-empirical reference potential. II. Recalibrating semi-empirical parameters with force matching

2019 ◽  
Vol 21 (37) ◽  
pp. 20595-20605 ◽  
Author(s):  
Xiaoliang Pan ◽  
Pengfei Li ◽  
Junming Ho ◽  
Jingzhi Pu ◽  
Ye Mei ◽  
...  
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Quantum Mechanical ◽  
Energy Profile ◽  
Force Matching ◽  
Energy Profiles ◽  
Reference Potential ◽  
Simulation Protocol ◽  
Semi Empirical ◽  
Free Energy Profiles

An efficient and accurate reference potential simulation protocol is proposed for producing ab initio quantum mechanical/molecular mechanical (AI-QM/MM) quality free energy profiles for chemical reactions in a solvent or macromolecular environment.

scholarly journals Extensions of the applicability of the MMX molecular modelling system to determination of barriers to rotation of π-bonded ligands

1995 ◽  
Vol 73 (7) ◽  
pp. 1078-1083 ◽  
Author(s):  
Joel Polowin ◽  
Robert Poe ◽  
Michael C. Baird
Keyword(s):  
Molecular Mechanics ◽  
Molecular Modelling ◽  
Conformational Energy ◽  
Energy Profile ◽  
Arene Ligands ◽  
Energy Profiles ◽  
Keywords Molecular Mechanics ◽  
Modelling System ◽  
The Way

The commercially available molecular mechanics package PCMODEL, which has been shown to be very useful for determining conformational energy profiles for rotation of σ-bonded ligands, cannot be utilized to determine barriers to rotation of π-bonded ligands because of limitations in the way the π-bonding interactions are defined. This paper describes a partially successful modification of the dihedral driver of PCMODEL that makes possible reasonable calculations of the conformational energy profiles for rotation of the π-bonded arene ligands in the compounds (η6-arene)Cr(CO)2(PPh3) (arene = C6H6, C6Me6) and of the π-bonded ethylene ligands in [PtCl3(η2-CH2=CH2)]− and [(η5-C5H5)Re(NO)(PPh3)(η2-CH2=CH2)]+. The steric barriers to ethylene rotation in the latter two complexes were found to be small relative to the electronic barriers to ligand rotation. Keywords: molecular mechanics, olefin rotation, conformational energy profile.

scholarly journals Chemical-state-dependent free energy profile from single-molecule trajectories of biomolecular motor: Application to processive chitinase

2019 ◽  
Author(s):  
Kei-ichi Okazaki ◽  
Akihiko Nakamura ◽  
Ryota Iino
Keyword(s):  
Free Energy ◽  
Single Molecule ◽  
Chemical State ◽  
Energy Profile ◽  
Free Energy Profile ◽  
Energy Profiles ◽  
Biomolecular Motors ◽  
State Dependent ◽  
Chitinase A ◽  
State Changes

ABSTRACTThe mechanism of biomolecular motors has been elucidated using single-molecule experiments for visualizing motor motion. However, it remains elusive that how changes in the chemical state during the catalytic cycle of motors lead to unidirectional motions. In this study, we use singlemolecule trajectories to estimate an underlying diffusion model with chemical-state-dependent free energy profile. To consider nonequilibrium trajectories driven by the chemical energy consumed by biomolecular motors, we develop a novel framework based on a hidden Markov model, wherein switching among multiple energy profiles occurs reflecting the chemical state changes in motors. The method is tested using simulation trajectories and applied to singlemolecule trajectories of processive chitinase, a linear motor that is driven by the hydrolysis energy of a single chitin chain. The chemical-state-dependent free energy profile underlying the burnt- bridge Brownian ratchet mechanism of processive chitinase is determined. The novel framework allows us to connect the chemical state changes to the unidirectional motion of biomolecular motors.

scholarly journals Autopilot Structured H∞ Synthesis for Satisfying Gain and Phase Margin Constraints

2019 ◽  
Vol 37 (2) ◽  
pp. 211-217
Author(s):  
Xiaochuan Ma ◽  
Jie Yan ◽  
Wenxing Fu ◽  
Kang Chen
Keyword(s):  
Present Method ◽  
Hypersonic Vehicle ◽  
Open Loop ◽  
Phase Margin ◽  
Gain Margin ◽  
Performance Specifications ◽  
Acceleration Tracking ◽  
Fixed Structure ◽  
Is Design ◽  
Nyquist Curve

Aiming at the static unstable Hypersonic vehicle, a method for designing H∞ autopilot to satisfy gain margin and phase margin is proposed. Structured H∞ synthesis is used to synthesize the autopilot under the fixed structure. The gain margin and phase margin were constrained by using H∞ norm of the complementary of the scaled plant. The requirement for the gain margin and phase margin is represented by the distance between the open loop Nyquist curve and the circle that represents the gain margin and phase margin in the complex plane. The distance is adjusted by tuning the parameter of performance specifications automatically to reduce the conservatism of the controller. The present method is applicable to both static stable vehicle and static unstable vehicle, and a three loops acceleration tracking autopilot is design. The numerical simulations have demonstrated that the autopilot satisfys the performance specifications, gain margin and phase margin simultaneously.

scholarly journals Algorithm of Reentry Guidance for Hypersonic Vehicle Based on Lateral Maneuverability Prediction

2020 ◽  
Vol 38 (3) ◽  
pp. 523-532
Author(s):  
Guoxiang Shi ◽  
Ke Zhang ◽  
Pei Wang ◽  
Zhiguo Han
Keyword(s):  
Mean Value ◽  
Hypersonic Vehicle ◽  
Parameters Estimation ◽  
Initial State ◽  
Bank Angle ◽  
Aerodynamic Parameters ◽  
Guidance Algorithm ◽  
Predictor Model ◽  
Process Disturbances ◽  
Predictor Corrector

Aiming at the problem that the traditional error corridor guidance method has poor adaptability in lateral guidance of predictor-corrector guidance, an algorithm of reentry guidance based on the vehicle lateral maneuverability prediction is proposed without increasing the calculation too much. The lateral component mean value of lift at reentry is calculated by using the bank angle magnitude function obtained from longitudinal guidance. According to the above-mentioned, a crossrange corridor with dynamic boundary constraint is designed to control bank angle reversal timing. Online parameters estimation is introduced to suppress the influence of the atmospheric density and aerodynamic parameters disturbance on the predictor model. The CAV-L, a kind of hypersonic vehicle, is used as an object to carry out reentry guidance simulation. The results show that the guidance algorithm can effectively guide vehicle to target for reentry missions of different range, the landing point error are small and the guidance effect is stable. The simulated results via Monte Carlo method verify that the guidance algorithm has a good adaptability and robustness to initial state deviations and process disturbances.

Entry guidance for high-L/D hypersonic vehicle based on drag-vs-energy profile

2018 ◽  
Vol 83 ◽  
pp. 176-188 ◽  
Author(s):  
Wanqing Zhang ◽  
Wanchun Chen ◽  
Wenbin Yu
Keyword(s):  
Hypersonic Vehicle ◽  
Energy Profile ◽  
Entry Guidance

scholarly journals Temperature Dependent Entropy Driven Water Uptake in Phase Separated Aerosol from Steered Molecular Dynamics and Intrinsic Surface Analysis

2021 ◽  
Author(s):  
Mária Lbadaoui-Darvas ◽  
Satoshi Takahama ◽  
Athanasios Nenes
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Water Uptake ◽  
Energy Profile ◽  
Temperature Dependent ◽  
Finite Velocity ◽  
Free Energy Profile ◽  
Energy Profiles ◽  
Accommodation Coefficients ◽  
Free Energy Profiles

&lt;p&gt;Dynamic water uptake by aerosol is a major driver of cloud droplet activation and growth. Interfacial mass transfer&amp;#8212; that governs water uptake if the mean free path of molecules in the vapour phase is comparable to particle size &amp;#8212; is represented in models by the mass accommodation coefficient. Although widely used, this approach neglects &lt;em&gt;i&lt;/em&gt;) other internal interfaces (e.g., liquid-liquid that may be important for water uptake), and, &lt;em&gt;ii&lt;/em&gt;) fluctuations of the liquid surface from capillary waves that modulate the surface and induce ambiguity in the estimation of mass accommodation coefficients. These issues can be addressed if the full path of the water molecule &amp;#8211; from vapour to the bulk aqueous phase - is considered.&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;We demonstrate, using steered molecular simulations, that a full treatment of the water uptake process reveals important details of the mechanism. The simulations are used to reconstruct the free energy profile of water transport across a vapour/hydroxy cis-pinonic acid/water double interface at 300 K and 200 K. In steered molecular dynamics the transferred molecule is pulled with a finite velocity along an aptly chosen reaction coordinate and the work exerted is used to reconstruct the free energy profile. Due to the finite velocity pulling, this method takes the effect of friction on the transport mechanism into account, which is important for phases of considerably different friction coefficients and is neglected by&lt;span&gt;&amp;#160; &lt;/span&gt;quasi equilibrium free energy methods. Free energy profiles are used to estimate surface and bulk uptake coefficients and are decomposed into entropic and enthalpic contributions.&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;Surface accommodation coefficients are unity at both temperatures, while bulk uptake at 300 K from the internal interface is strongly hindered (k&lt;sub&gt;b&lt;/sub&gt;=0.05) by the increased density and molecular order in the first layer of the aqueous phase, which results in decreased orientational entropy. The difference between bulk and surface uptake coefficients also implies that water accumulates in the organic shell, which cannot be predicted using a single uptake coefficient for the whole particle. The minimum of the free energy profile at the organic/water interface, rationalised by increased conformational entropy due to local mixing and the depleted system density, results in a concentration gradient which helps maintain low surface tension and phase separation. Low surface tensions may explain increased CCN activity. These entropic features of the free energy profiles diminish at low temperature, which invokes a completely different mechanism of water uptake. Our results point out the need to describe water uptake in aerosol growth models using a temperature dependent parametrisation.&lt;/p&gt;

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