Adaptive Simulated Annealing Technique Research Articles

Optimising laser pulses for selective vibrational excitations and photo-dissociation of the C–H bond in methane

This paper presents a study on the optimisation of laser pulse parameters using an optimal control theory based adaptive simulated annealing technique. The objective of this study is to obtain a cost-effective laser pulse that can selectively excite the vibrational state and cause photo-dissociation of the C–H bond in a methane molecule. We have optimised both sinusoidal and linear ramped pulses using the proposed technique, and incorporated a linear chirping in the field as well. The results demonstrate the effectiveness of the proposed approach in designing laser pulses for targeted molecular excitation and dissociation.

Design of laser pulse to enhance the photo-dissociation of a tri-atomic molecular system using optimal control theory based adaptive simulated annealing technique

In this communication, we design and optimize laser pulses to enhance the dissociation of a tri-atomic molecule using optimal control theory based adaptive simulated annealing technique. ClCN is chosen as tri-atomic molecular system as molecules containing fluorine and chlorine atoms are involved in the depletion of ozone layer and also dissociative electron attachment is possible. Fourier Grid Hamiltonian based 2D mean field methodology has been used for numerical calculations. We find an effective laser pulse by combining polychromatic Gaussian pulses and polychromatic linear pulses with different frequencies and different field intensities.

Laser pulse design using optimal control theory-based adaptive simulated annealing technique: vibrational transitions and photo-dissociation

We have designed and optimised a combined laser pulse using optimal control theory-based adaptive simulated annealing technique for selective vibrational excitations and photo-dissociation. Since proper choice of pulses for specific excitation and dissociation phenomena is very difficult, we have designed a linearly combined pulse for such processes and optimised the different parameters involved in those pulses so that we can get an efficient combined pulse. The technique makes us free from choosing any arbitrary type of pulses and makes a ground to check their suitability. We have also emphasised on how we can improve the performance of simulated annealing technique by introducing an adaptive step length of the different variables during the optimisation processes. We have also pointed out on how we can choose the initial temperature for the optimisation process by introducing heating/cooling step to reduce the annealing steps so that the method becomes cost effective.

Optimal control theory in adaptive simulated annealing technique: optimisation of laser pulse for selective vibrational excitations and photo-dissociation of HBr+

An optimisation method using optimal control theory based adaptive simulated annealing technique has been explored to get optimised laser pulses for selective vibrational excitations and photo-dissociation of the HBr+ in its ground electronic state. Potential energy curve of the system has been obtained by coupled cluster singles and doubles (CCSD) level calculation, using aug-cc-pVTZ as basis set. To have a simple pulse, a limited number of parameters is chosen as variables and the technique so developed works well. The study is extended with chirping field frequency to explore the effect of chirping in dynamics.

Experimental and numerical investigation of an adaptive simulated annealing technique in optimization of warm tube hydroforming

Simulated annealing technique – which has attracted significant attention as being suitable for combinatorial optimization problems – has been used in many engineering applications. In current research, this method is used in optimization of a complicated forming process. Warm tube hydroforming is a new technology in the forming of lightweight aluminum and magnesium alloys in automotive, electronics and leisure industries. Owing to the complex nature of this process at high temperatures, and difficulty of obtaining the optimized forming conditions, this process has not received the credit it deserves yet. A new method for optimization of the warm tube hydroforming process is developed by using the simulated annealing algorithm with a novel adaptive annealing schedule. The optimal pressure loading paths are obtained for AA6061 aluminum alloy tubes with different wall thicknesses and corner fillets. The results obtained by simulated annealing technique are verified numerically and experimentally.

Best Probability Density Function for Random Sampled Data

The maximum entropy method is a theoretically sound approach to construct an analytical form for the probability density function (pdf) given a sample of random events. In practice, numerical methods employed to determine the appropriate Lagrange multipliers associated with a set of moments are generally unstable in the presence of noise due to limited sampling. A robust method is presented that always returns the best pdf, where tradeoff in smoothing a highly varying function due to noise can be controlled. An unconventional adaptive simulated annealing technique, called funnel diffusion, determines expansion coefficients for Chebyshev polynomials in the exponential function.

Dynamic delivery of IMRT using an independent collimator: a model study

This study aims to develop intensity-modulated beam delivery using an independent collimator in dynamic mode (dIC). A model was built to solve the problem of optimizing the dIC jaw trajectories for a desired beam intensity map with the adaptive simulated annealing technique. Like a leaf trajectory for a dynamic multileaf collimator (dMLC), a dIC jaw trajectory is composed of a series of control points. When delivering a beam in dynamic mode, all four jaws move continuously and independently while the beam is on. The performance of the proposed model is evaluated by comparing the delivery time of dIC with that of dMLC for 56 intensity maps of eight prostate cases and 72 maps of eight nasopharynx cases. The premises for the comparison are that (1) all MLC leaves have a width of 1 cm; (2) MLC leaf trajectories are generated with the algorithm of Spirou and Chui (1994 Generation of arbitrary intensity profiles by dynamic jaws or multileaf collimators Med. Phys. 21 1031), and (3) dIC delivers the desired intensity maps with equivalent or better accuracy as that of dMLC. We found that the dIC delivery time was 2.00 ± 0.83 times that of dMLC delivery for 56 intensity maps of prostate cases, and 2.90 ± 1.39 times that of dMLC delivery for 72 intensity maps of nasopharynx cases. The estimated mean treatment delivery time is 5.8 min for prostate cases, and 12.2 min for nasopharynx cases. Considering the advantages of dIC such as two-dimensional continuous spatial resolution, sharp penumbra, minimal leakage and no tongue-and-groove effects, dIC has the potential for high-resolution IMRT treatments of certain lesions.

SU-GG-T-99: Dynamic Delivery of IMRT Using Independent Jaws

Purpose: This study aims to evaluate a jaw-trajectory algorithm for delivering intensity-modulated beams using independent jaws in dynamic mode. Method and Materials: The algorithm builds up an optimization model for the problem of generating jaw trajectories for a desired beam intensity map and solves the problem with adaptive simulated annealing technique. Like leaf trajectory for MLC, a jaw trajectory is composed of a series of control points. When delivering a beam in dynamic mode, all four conventional jaws move continuously and independently. The performance of the proposed algorithm was evaluated through comparing the delivery time of dynamic jaws (DJaw) with that of dynamic MLC (DMLC) for 74 intensity maps of prostate cases and 45 maps of nasopharynx cases. The preconditions for the comparison were that MLC leaves had a width of 1 cm; MLC Leaf trajectories were generated with the algorithm proposed by Spirou et al (Med. Phys, 1994); DJaw delivered desired intensity maps as accurately as or even more accurately than DMLC. Results: DJaw delivery time was 1.8±0.76 and 2.6±1.6 times of DMLC's for 74 intensity maps of prostate cases and 45 large-size intensity maps of nasopharynx cases respectively. For 8 prostate maps, DJaw delivery time actually was shorter than DMLC's, because those maps were small and had minor intensity modulations. Conclusion: Although the delivery time of DJaw usually is longer than that of DMLC, and the difference increases with the size and the complexity of intensity map, the absolute delivery time of DJaw is expected to be 20mins or less. Plus its advantages (i.e., continuous spatial resolution, sharper penumbra, no interleaf leakage or tongue and groove effect, low cost and easy maintenance) over DMLC, DJaw has the potential to become the choice of some (small) institutes for their IMRT practice.

Adaptive simulated annealing algorithm for the fiber Bragg grating distributed strain sensing

Adaptive simulated annealing algorithm used for determining the strain profile along a fiber Bragg grating (FBG) from its reflection spectrum has been demonstrated. By combining the matrix method for calculating the reflection spectrum of a FBG and the adaptive simulated annealing technique, we obtain a new method for the distributed sensing. The numerical simulations show good agreements between the original and the reconstructed strain profiles.

USE OF A CROP MODEL TO EVALUATE SOIL IMPEDANCE AND ROOT CLUMPING EFFECTS ON SOIL WATER EXTRACTION IN THREE ARGENTINE SOILS

Argentina is the third largest producer of grain soybean in the world and the largest producer of soybean meal and soybean oil exports. Soybean is grown mostly in the Pampas of central–eastern Argentina. Argillic soils (typic and vertic argiudolls) and typic pelluderts are present in approximately 50% of the soils used for soybean production. Those soils have swelling and cracking behavior that may result in root clumping, and thus the root system’s ability to extract water may be restricted due to limited proliferation into the surrounding soil. The CROPGRO–Soybean model’s root growth and root water uptake routines were modified to improve its ability to simulate root growth and water uptake in soils where root penetration is restricted or roots are clumped together. Two empirical soil parameters, referred to as a soil impedance factor and a root clumping factor, were incorporated into this “revised” model. Data sets from a vertic argiudoll (Oliveros, Santa Fe), a typic argiudoll (Balcarce, Buenos Aires), and an enthic hapludoll (Manfredi, Cordoba) were used to evaluate the ability of the model to predict soil water extraction by soybean crops. An adaptive simulated annealing technique was used to estimate the soil impedance and root clumping factors. The revised CROPGRO–Soybean model was able to predict soil water extraction for three Argentine soils with different soil textures. The effectiveness of the model was expressed by low percent errors of estimation, ranging from 3.5% to 7.0% among different sites. The incorporation of soil impedance and root clumping factors allowed us to assess the effects of the argillic horizons in restricting root depth growth and root proliferation and thus in decreasing the potential root water uptake rates. The argillic horizons had more significant effects on root clumping than on restrictions of root depth growth. The clumping of roots caused by the presence of cracking horizons also reduced the rate of water uptake below those layers. Critical clay content thresholds as predictors of soil impedance and root clumping were found, providing a method for predicting soil impedance and root clumping factors for argillic soils.