Application of a fuzzy inference system for the prediction of longshore sediment transport

A fuzzy inference system (FIS) and a hybrid adaptive network-based fuzzy inference system (ANFIS), which combines a fuzzy inference system and a neural network, are used to predict and model longshore sediment transport (LST). The measurement data (field and experimental data) obtained from Kamphuis [1] and Smith et al. [2] were used to develop the model. The FIS and ANFIS models employ five inputs (breaking wave height, breaking wave angle, slope at the breaking point, peak wave period and median grain size) and one output (longshore sediment transport rate). The criteria used to measure the performances of the models include the bias, the root mean square error, the scatter index and the coefficients of determination and correlation. The results indicate that the ANFIS model is superior to the FIS model for predicting LST rates. To verify the ANFIS model, the model was applied to the Karaburun coastal region, which is located along the southwestern coast of the Black Sea. The LST rates obtained from the ANFIS model were compared with the field measurements, the CERC [3] formula, the Kamphuis [1] formula and the numerical model (LITPACK). The percentages of error between the measured rates and the calculated LST rates based on the ANFIS method, the CERC formula (K_sig = 0.39), the calibrated CERC formula (K_sig = 0.08), the Kamphuis [1] formula and the numerical model (LITPACK) are 6.5%, 413.9%, 6.9%, 15.3% and 18.1%, respectively. The comparison of the results suggests that the ANFIS model is superior to the FIS model for predicting LST rates and performs significantly better than the tested empirical formulas and the numerical model.     

GOCE卫星径向重力梯度一阶、二阶径向偏导数标准差的近似解析公式

基于Kaula准则,推导卫星重力梯度径向分量Tzz一阶、二阶径向偏导数T.zz、Tzz标准差的近似解析表达式,给出GOCE卫星.Tzz、Tzz标准差的近似估计值,由此分析Tzz延拓处理中可忽略的延拓误差最大高度。解析公式表明：T.zz、Tzz标准差的计算公式可近似表示成若干伽玛函数线性组合的开方,GOCE卫星.Tzz、Tzz标准差近似解析估值分别为1.269×10^-15s^-2m^-1和1.109×10^-20s^-2m^-2,由此若得到满足1 mE的精度要求,可忽略的延拓误差最大高度对于T.zz应小于0.8km,而对于Tzz应小于13.4km,延拓中重力场模型阶次应不低于200。最后基于模拟的GOCE卫星轨道,利用严格公式计算出的T.zz、Tzz标准差,验证近似解析表达式估算结果的正确性,解析结果与严格公式计算结果的相对误差小于2%。     

对利用跨断层基线和水准测量资料推算断层活动参数公式的改进

分析了利用两条跨断层基线和水准测量资料推算断层三维活动参数传统公式存在的问题,指出传统的计算公式实际是一个要求两侧点位处于同一水平面时的近似公式。本文对这一公式重新进行了严格的数学推导,得到了适用于一般情况的改进后的计算公式,并以实际算例指出传统公式对计算结果可能造成的误差量级。     

An explicit method for numerical simulation of wave equations: 3D wave motion

In this paper, an explicit method is generalized from 1D and 2D models to a 3D model for numerical simulation of wave motion, and the corresponding recursion formulas are developed for 3D irregular grids. For uniform cubic grids, the approach used to establish stable formulas with 2M-order accuracy is discussed in detail, with M being a positive integer, and is illustrated by establishing second order (M=1) recursion formulas. The theoretical results presented in this paper are demonstrated through numerical testing.     

某水电站库区滑坡滑速涌浪计算

对雅砻江流域某拟建电站库区边坡失稳后的滑速和涌浪高度进行计算。计算滑速采用潘家铮条分法,涌浪高度计算同时采用水科院经验公式法和潘家铮法两种方法。综合两种方法的计算结果获得库坝处滑坡产生的涌浪高度为0.41~0.88m,对拟建工程影响较小。此计算分析方法对类似工程具有借鉴意义。     

A new predictive formula for inception of regular wave breaking

Efforts are made to enhance the predictive formula for the inception of wave breaking. To achieve success, the existing formulas are extensively reviewed. They are categorized into four types, i.e., the McCowan type, the Miche type, the Goda type and the Munk type. The inherent relations among the different types are then exploited. The differences among each formula within a group are also discussed. Four representative formulas from the different types are chosen to compare with the measured data for a total number of 1193 cases reported in literatures. It is shown that Goda's and Ostendorf and Madsen's formulas are advantageous in general among the selected ones. Goda's formula, however, is found to be inaccurate as the beach slope becomes steeper than 1/10. Ostendorf and Madsen's formula is fairly good even for cases of very steep slopes, but its accuracy for the cases of ordinary slopes is not as good as Goda's. A new predictive formula for the inception of wave breaking is proposed. The unique index, defined by ψ′_b = (1.21 − 3.30λ_b)(1.48 − 0.54γ_b)ψ_b, where ψ_b = gH_b/C_b², H_b is the breaking wave height, C_b is the breaking wave celerity, λ_b is the breaking wave steepness, γ_b is the relative breaking wave height, and g is the gravity acceleration, is introduced. The incipient condition of wave breaking is then given by ψ′_b = 0.69. This formula is a significant improvement to the existing ones in terms of the accuracy. In addition, it is a local relation. Further verification shows that the proposed formula performs similarly well when applied to the field and to the waves over permeable bed.     

不适定方程正则化算法的谱分解式

从观测方程系数矩阵的谱分解着手探讨不适宜方程的正则化算法。利用谱分解式阐明了正则化的主要作用是平滑对参数估值比较敏感的观测误差的高频分量，完整给出了最小二乘平差、秩亏平差和病态方程正则化解的谱分解公式，证明了正则化解参数估值偏离真值的二次范数的期望值与均方误差是等价的。     

缔合勒让德函数的标准向前按列递推公式

针对推导扇谐项（次等于阶的项）和准扇谐项（次等于阶减1的项）存在不严谨性的问题,给出基于fnALFs的2个导数定积分按列递推公式,结果与已有的研究结论完全一致,但推导过程更简明,且该定积分公式可从第2阶开始递推。另外,本文还给出另外2个fnALFs定积分计算公式。     

地铁隧道爆破施工影响的邻近居民楼质点峰值振速研究

地铁隧道爆破施工时严重威胁邻近居民楼的结构安全,因此研究邻近居民楼爆破峰值振速是非常必要的。文章基于群孔荷载简化模型、柱面波理论及传统的应力波衰减理论,在考虑高程效应影响下推导质点峰值振速公式。依托乌鲁木齐地铁一号线工程,对一邻近六层居民楼的爆破施工响应进行监测,并将实测质点峰值振速、提出的修正公式预测振速和传统萨道夫公式预测的振速进行对比分析。研究结果表明:采用修正公式预测的质点峰值振速与现场实测值的分布规律一致,呈现出随着高程增大而逐渐增大的趋势;而且现场实测值与修正公式预测值相对误差较小,表明考虑高程因子的修正公式是可行的。