CAJ | 학술논문

针对因参数精度不足，影响相关土壤水分运动建模、仿真结果等问题，引入萤火虫算法，并将固定随机步长改进为随萤火虫间距离变化的可变步长，旨在解决土壤水分特征曲线Van Genuchten模型参数优化的非线性拟合问题。结果表明：对不同深度的黑土和黏土的脱湿过程进行模拟，得到优化后的相关参数及体积含水率计算值。通过与粒子群算法、遗传算法对比，表明萤火虫算法模拟结果精度高，曲线吻合性好，最大相对误差仅在2%左右，是一种高精度的优化算法，且改进之后收敛效率提高。利用萤火虫算法解决这类非线性优化问题是可行的，尤其在对精度、准确性要求较高及需为后续研究确定其他土壤水分运动参数提供准确依据的情况下，适用性更强。
침대인삼수정도불족，영향상관토양수분운동건모、방진결과등문제，인입형화충산법，병장고정수궤보장개진위수형화충간거리변화적가변보장，지재해결토양수분특정곡선Van Genuchten모형삼수우화적비선성의합문제。결과표명：대불동심도적흑토화점토적탈습과정진행모의，득도우화후적상관삼수급체적함수솔계산치。통과여입자군산법、유전산법대비，표명형화충산법모의결과정도고，곡선문합성호，최대상대오차부재2%좌우，시일충고정도적우화산법，차개진지후수렴효솔제고。이용형화충산법해결저류비선성우화문제시가행적，우기재대정도、준학성요구교고급수위후속연구학정기타토양수분운동삼수제공준학의거적정황하，괄용성경강。
Inacurate estimation of parameters of soil water characteristic curves can cause simulation results of soil moisture models. This paper introduced firefly algorithm to solve the nonlinear fitting problem of soil water characteristic curve model (Van Genuchten) parameters. In the algorithm principle, the force of attraction and light are based on the distance between different individuals, based on which the whole population is divided into a number of subgroups at the beginning, and every sub-population gathered around local optimal value. All sub-population can optimize at the same time, improving the efficiency, and the global optimal solution is found between all these local optimal values. Compared with the particle swarm algorithm, the firefly algorithm does not use perception such as individual best position, the global optimal position to control calculation, which avoids the potential defects such as premature convergence. In addition, the algorithm dose not set speed for fireflies, which avoids the problem that the speed exceeds a threshold. But, when firefly individuals approach the optimal value, it is likely to move longer than the distance between the individual and the optimal value, therefore resulting in the jump-over of the optimal value and reaching the other side. If this situation appears repeatedly, it will affect the convergence speed and accuracy of algorithm. So in this paper we turned the fixed step length into a variant step length that changed according to the between-firefly distance, and thus the firefly algorithm had a better global optimization ability at the beginning and rapidly found the position adjacent to the optimal value region, in the end it had a good local search ability and was able to find the overall optimal value. The test samples came from test field of College of Water Conservancy and Architecture in Northeast Agricultural University(126°45'32″E、45°44'41″N), China. Black soil in Harbin area can represent the southern area of Heilongjiang. The samples were taken from four adjacent areas with a size of 10m×10m. Sampling depth was 0-20,>20-40,>40-60,>60-100,>100-140, and>140-180 cm, respectively. The relation of the soil suction and the soil moisture content was measured by a hypothermia supercentrifuge. The standard particle swarm algorithm, the standard genetic algorithm, the improved algorithm and the standard firefly algorithm were used in this paper to simulate the process of black soil and clay moisture desorption at different depths, and the relevant parameters and volumetric water content were obtained from calculation. The simulation results showed that simulation results from standard firefly algorithm and improved firefly algorithm were of high precision, in good agreement with the experimental results (the average error was less than 1%, the maximum relative error was only about 2%)by comparing calculating soil moisture characteristic curve with the experimental one. Firefly algorithm accuracy was higher than that of particle swarm algorithm and genetic algorithm, the improved firefly algorithm began to converge after about 23 iterations, the improved firefly algorithm was obviously better than the traditional ones. It was viable to use the firefly algorithm to solve this kind of nonlinear optimization problem, especially for high precision, accuracy or provide accurate basis for follow-up studies. For the surface black soil (0-20 cm) and clay in the lower layer (>20-40 cm), when the parameter range were [0.0251, 0.0496] and [0.0021, 0.0110], the maximum deviation of volumetric water content simulation results was less than 5%, indicating that the simulation precision was high. Fitting results can accurately reflect the characteristics of black soil in Harbin area, and the result of the reciprocal of air-entering value conformed to the actual situation, reflecting the characteristics of less clay and light texture in the surface layer, more clay and heavy texture in parent material horizon.