Very Fast Simulated Reannealing Research Articles

Choice of regularization weight in basis pursuit reflectivity inversion

Seismic inverse problem of estimating P- and S-wave reflectivity from seismic traces has recently been revisited using a basis pursuit denoising inversion (BPI) approach. The BPI uses a wedge dictionary to define model constraints, which has been successful in resolving thin beds. Here we address two fundamental problems associated with BPI, namely, the uniqueness of the estimate and the choice of regularization weight λ to be used in the model norm. We investigated these using very fast simulated re-annealing (VFSR) and gradient projection sparse reconstruction (GPSR) approaches. For a synthetic model with two reflectors separated by one time sample, we are able to demonstrate convergence of VFSR to the true model with different random starting models. Two numerical approaches to estimating the regularization weight were investigated. One uses λ as a hyper-parameter and the other uses this as a temperature-like annealing parameter. In both cases, we were able to obtain λ fairly rapidly. Finally, an analytic formula for λ that is iteration adaptive was also implemented. Successful applications of our approach to synthetic and field data demonstrate validity and robustness.

캐비테이션 터널 시험용 청음기배열 최적 설계기법

본 논문에서는 캐비테이션 터널에서의 소음계측용 청음기 배열 설계를 위한 최적화 기법을 제안하였다. 제안된 최적설계 기법은 배열 설계인자 및 목적함수 정의 그리고 최적화 알고리즘 적용 등의 내용으로 구성되어 있다. 설계인자 정의는 원형배열, 나선배열, 다중나선배열을 대상으로 하였다. 목적함수는 주엽의 빔폭과 최대 부엽 크기를 동시에 고려할 수 있도록 정의하였다. 최적화 알고리즘으로는 광역 최적화 기법의 일종인 VFSR 기법을 적용하였다. 최적 설계기법을 각 배열에 적용 후 도출된 최적 배열을 대상으로 최대 부엽크기 및 주엽의 빔폭을 분석하였다. 끝으로 캐비테이션 터널 내부의 다중반사를 고려한 빔형성 결과 평가를 통해 본 기법의 유용성을 확인하였다. This paper proposes a hydrophone array design optimization technique for cavitation tunnel noise measurements. The optimization technique comprises of design parameters, an objective function and an optimization algorithm. The design parameters are defined for circular, spiral and multi-spiral arrays. The objective function is defined so as to consider the mainlobe beamwidth and the maximum sidelobe level simultaneously. A global optimization scheme is applied to the array design using very fast simulated reannealing (VFSR). After applying the optimization technique to arrays respectively, the peak sidelobe level and the mainlobe beamwidth of optimum arrays are analyzed. Finally the array patterns considering multiple reflections in the cavitation tunnel are evaluated to validate the proposed method.

Time-domain Geoacoustic Inversion of Short-range Acoustic Data with Fluctuating Arrivals

2006년 여름 New Jersey 대륙붕 근해에서 일련의 해상실험(Shallow Water 2006, SW06)이 수행되었다. 이 때 수직선배열에서 계측된 근거리 chirp 신호(1100~2900 Hz)에서 직접도달파와 해수면 반사파의 강한 시변동이 관찰되었다. 본 논문은 시변동성이 있는 근거리 음향신호의 지음향학적 역산기법과 실험 데이터에 대한 역산결과를 제시한다. 불규칙한 해수면 반사파가 역산에 미치는 영향을 최소화하기 위해 수직선배열에서 음원의 위치로 직접도달 경로와 해저면 반사경로를 통해 역전파된 신호의 에너지로써 목적함수를 정의하였다. 또한 VFSR(Very Fast Simulated Reannealing) 최적화기법을 활용한 다단계 역산기법을 실험데이터에 적용하였다. 역산 결과 음원은 주기적인 수직운동을 한 것으로 파악되었고 그 주기는 수면파의 주기와 일치하였다. 해저면의 음속은 1645 m/s로 추정되었고 이는 동일 해역의 다른 연구결과와 유사한 것으로 파악되었다. A set of experiments (Shallow Water 2006, SW06) was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in direct and surface reflected arrivals were observed from the chirp data (1100~2900 Hz) measured on a vertical line array. This paper presents a geoacoustic inverssion technique for short-range acoustic data with fluctuating arrivals and inversion results of experimental data. In order to reduce effects of random sea surface on the inversion, the acoustic energy back-propagated from the array to the source through direct and bottom-reflected paths is defined as the objective function. A multi-step inversion scheme is applied to the data using VFSR (Very Fast Simulated Reannealing) optimization technique. The inversion results show a source depth oscillation period equal to the measured ocean surface wave period. The inverted bottom sound speed is 1645 m/s and is similar to that estimated by other work at the same site.

Geoacoustic Inversion Using Backpropagation

This paper presents inversion results of the 2006 Shallow Water Experiment (SW06) data measured on a vertical line array. A low-frequency (100-900 Hz) chirp source was towed along two tracks (circle, straight line) at 30-m depth. For the inversions, a three-step optimization scheme is applied to the data using very fast simulated reannealing (VFSR). The objective function is defined by the energy of the backpropagated signal from the array to the source. At each step, water-column sound-speed profile (SSP), experimental geometry, and geoacoustic parameters are inverted successively. An environmental model is employed consisting of a linear segmented SSP in the water column, a sediment layer, and a half-space. The geometric parameter inversion results show good agreement with in situ measurements. Finally, the estimated geoacoustic parameters show that the experimental site near the vertical line array (VLA) is fairly homogeneous in bottom properties consisting of a 21-m-thick sediment layer with sound speed of around 1600 m/s over a hard basement whose sound speed is approximately 1750 m/s.

A very fast simulated re-annealing algorithm for the leather nesting problem

This article presents a novel approach for effectively optimizing the nesting problem in the leather manufacturing. A very fast simulated re-annealing (VFSRA) algorithm is developed for the placement of two-dimensional irregular sheets and stencils. Theoretically, this algorithm is exponentially faster than Cauchy and Bolzmann annealing approaches. Irregular profiles are represented by approximate polygons using geometrical processing of Weiler tuple. The search configuration space is considerably reduced by using a module slide technique. Compact nesting density is fulfilled by severe penalties of escaping and overlapping areas and the normal penalty of unoccupied area defined in the cost function. The designed stencil motion strategy and annealing schedule are suitable. Comparison of the experimental results show that the VFSRA is effective for the leather nesting problem. In addition, it can be applied in other similar fields.

A very fast simulated re-annealing (VFSA) approach for land data assimilation

We develop a new data assimilation algorithm by employing a heuristic optimization approach named very fast simulated re-annealing (VFSA), which is capable of minimizing the cost function without using the adjoint model. The method is independent on model operator and observation operator, and has advantages in dealing with strong nonlinearities and discontinuities. Based on the VFSA algorithm, we design a land data assimilation scheme which can assimilate both the in situ measurement of soil moisture, and the passive microwave remote sensing observations into a land surface model. The scheme is tested with GAME-Tibet observations and TMI brightness temperature. Results show that it works successfully with strongly nonlinear land surface model, SiB2 and the radiative transfer model of moist soil. The cost value calculated from optimized initial state is much smaller and the bias from observations are also significantly reduced.

Comparison of simulated annealing algorithms for conformal therapy treatment planning

The efficiency of four fast simulated annealing algorithms for optimizing conformal radiation therapy treatment plans was studied and the resulting plans were compared with each other and to optimized conventional plans. Four algorithms were selected on the basis of their reported successes in solving other minimization problems: fast simulated annealing with a Cauchy generating function, fast simulated annealing with a Lorentzian generating function, variable step size generalized simulated annealing (VSGSA), and very fast simulated reannealing (VFSR). They were tested on six clinical cases using a multiple beam coplanar conformal treatment technique. Relative beam weights were computed that maximized the minimum tumor dose subject to dose-volume constraints on normal organ doses. Following some initial tuning of the annealing parameters, each algorithm was applied identically to each test case. Optimization tests were run using different random number sequences and different numbers of iterations. The VSGSA algorithm consistently produced the best results. Using long run times, it generated plans with the highest minimum tumor dose in five of the six cases. For the short run times, the VSGSA solutions averaged larger minimum tumor doses than those of the other algorithms for all six patients, with increases ranging from 0.4 to 5.9 Gy. For three of the patients, the conformal plan gave a clinically significant increase in the minimum tumor dose over the conventional plan, ranging from 8.2 to 13.0 Gy. In two other cases, there was little difference between the two treatment approaches. For one case, the optimized conventional plan was much better than the conformal plan because the conventional beam arrangement included wedges, which offset the multiple beam advantage of the conformal plans. For equal computing times of both long and short duration, the VSGSA algorithm consistently produced conformal plans that were superior to those produced by the other algorithms. The simple conformal technique used in this study showed a significant potential advantage in the treatment of abdominal tumors. In three of the cases, the conformal plans showed clinically important increases in tumor dose over optimized conventional plans.

Design optimisation of coilguns

Many current filament coilgun models have been interfaced to optimisation routines. This has provided a valuable insight into the operation of coilguns, and has generally yielded kinetic energies superior to those obtained purely by analytical methods. Due to concern over the presence of local optima, the use of a global optimisation scheme, simulated annealing, has been investigated. In its basic form, simulated annealing requires a vast number of simulation runs, and is therefore impractical for coilgun optimisation. However, a variation on the algorithm, very fast simulated reannealing (VFSR) converges much faster and has produced good results. >

Registering multiview range data to create 3D computer objects

Concerns the problem of range image registration for the purpose of building surface models of 3D objects. The registration task involves finding the translation and rotation parameters which properly align overlapping views of the object so as to reconstruct from these partial surfaces, an integrated surface representation of the object. The registration task is expressed as an optimization problem. We define a function which measures the quality of the alignment between the partial surfaces contained in two range images as produced by a set of motion parameters. This function computes a sum of Euclidean distances from control points on one surfaces to corresponding points on the other. The strength of this approach is in the method used to determine point correspondences. It reverses the rangefinder calibration process, resulting in equations which can be used to directly compute the location of a point in a range image corresponding to an arbitrary point in 3D space. A stochastic optimization technique, very fast simulated reannealing (VFSR), is used to minimize the cost function. Dual-view registration experiments yielded excellent results in very reasonable time. A multiview registration experiment took a long time. A complete surface model was then constructed from the integration of multiple partial views. The effectiveness with which registration of range images can be accomplished makes this method attractive for many practical applications where surface models of 3D objects must be constructed. >

Genetic Algorithms and Very Fast Simulated Reannealing: A comparison

We compare Genetic Algorithms (GA) with a functional search method, Very Fast Simulated Reannealing (VFSR), that not only is efficient in its search strategy, but also is statistically guaranteed to find the function optima. GA previously has been demonstrated to be competitive with other standard Boltzmann-type simulated annealing techniques. Presenting a suite of six standard test functions to GA and VFSR codes from previous studies, without any additional fine tuning, strongly suggests that VFSR can be expected to be orders of magnitude more efficient than GA.

Statistical mechanics of combat with human factors

This highly interdisciplinary project extends previous work in combat modeling and in control-theoretic descriptions of decision-making human factors in complex activities. A previous paper has established the first theory of the statistical mechanics of combat (SMC), developed using modern methods of statistical mechanics, baselined to empirical data gleaned from the National Training Center (NTC). This previous project has also established a JANUS(T)-NTC computer simulation/wargame of NTC, providing a statistical “what-if” capability for NTC scenarios. This mathematical formulation is ripe for control-theoretic extension to include human factors, a methodology previously developed in the context of teleoperated vehicles. Similar NTC scenarios differing at crucial decision points will be used for data to model the influence of decision making on combat. The results may then be used to improve present human factors and C 2 algorithms in computer simulations/wargames. Our approach is to “subordinate” the SMC nonlinear stochastic equations, fitted to NTC scenarios, to establish the 0 th order description of that combat. In practice, an equivalent mathematical-physics representation is used, more suitable for numerical and formal work, i.e., a Lagrangian representation. Theoretically, these equations are nested within a larger set of nonlinear stochastic operator-equations which include C 3 human factors, e.g., supervisory decisions. In this study, we propose to perturb this operator theory about the SMC 0 th order set of equations. Then, subsets of scenarios fit to 0 th order, originally considered to be similarly degenerate, can be further split perturbatively to distinguish C 3 decision-making influences. New methods of Very Fast Simulated Re-Annealing (VFSR), developed in the previous project, will be used for fitting these models to empirical data.