Thermally unstable maghaemite and its palaeoclimatic significance in Chinese loess

Magnetite and maghaemite are the two main contributors to magnetic susceptibility in the Chinese loess/palaeosol sequence. Due to the close similarity in physical properties, early investigators treated them together as "magnetite". Utilising the property of thermally instability of maghaemite, we have been able to separate it from magnetite in loess and palaeosol samples from the upper parts of the Xifeng and Luochuan sections on the central Chinese Loess Plateau and compare its variation with depth and horizon. Our results indicate that thermally unstable maghaemite is relatively enriched in both 1) weakly weathered loess units and 2) towards the west, the direction of dust supply, suggesting that maghaemite is at least partially (coarse grains) of detrital aeolian origin while some pedogenic maghaemite (extra fine grains) occurs in the palaeosols. The physical meaning of magnetic susceptibility, therefore, needs to be reconsidered as a synthetic indicator reflecting the palaeoenvironment for both source area and deposition area. Thermally unstable goethite is a minor magnetic component of palaeosol samples, but it may play a significant role in determining characteristic magnetic remanence of weakly weathered loess samples, especially when one applies alternating-field cleaning.     

黄土震陷试验与评价

通过对兰州中川民用机场扩建工程场地黄土的震陷试验,研究探讨了该场地黄土的震陷特性,并对震陷进行了评价和分区预测。     

Banach空间中混合型非线性积分──微分方程的最大解和最小解

在弱序列完备的Ｂａｎａｃｈ空间中，利用推理论和单调迭代方法，研究了混合型非线性积分－微分方程初值问题最大解和最小解的存在性。其结果改进和推广了许多已知的结果。     

收敛复数列空间上的Taylor猜想

本文证明,取值于收敛复数列Banach空间c的随机元列Vn,不能同时满足EV_n=0,||V_n||≡1及||∑_(i=1)~nV_1/n||≡1.c为收敛实数列空间时,这是Taylor在Stochastic Convergence of Weighted sums of Random Elementsin Linear Spaces,Springer,107面中提出的一个猜想,已被作者解决,并在1986年世界数学家会议上宣读,当时有人问,c能否是收敛复数列空间?本文回答了这个问题.     

运营公路路基压实黄土的湿陷性研究

通过对临潼～渭南高速公路和312国道甘肃段不同交通量的路基黄土做比较研究,总结出黄土湿陷系数的变化规律。     

m序列法测量室内脉冲响应的非线性失真分析

m序列法测量室内脉冲响应已经被广泛接受，鉴于实际系统中的噪声和非线性会降低脉冲响应测量的精确性，对m序列法测量过程中室内系统微弱非线性所引起的失真进行了分析．叠加有微弱非线性的室内系统在时域可以等效为一个线性子系统和非线性无记忆环节的级联模型．根据该模型，推导了单一非线性作用下运用m序列法测量的室内脉冲响应误差，并且分析了该方法对各阶非线性的抑制能力．仿真实验验证了推论的正确性．     

黄土公路隧道衬砌开裂分析

衬砌开裂是黄土公路隧道普遍存在的病害。为了预防和处治衬砌开裂,保证黄土隧道结构的长期稳定性,针对甘肃省榆中县新庄岭黄土公路隧道衬砌开裂的病害特征,运用数值仿真、实测等手段分析了病害产生的机理和原因。结果表明,黄土浸水导致土体强度降低、变形增大,从而增大了围岩塑性区范围和变形压力,恶化了衬砌结构受力状况,使衬砌结构拱顶内侧及拱脚外侧被拉裂,进而使拱脚内侧被压裂。根据隧道病害状况,提出了采用环氧树脂嵌补及凿槽嵌入钢拱架法处治衬砌开裂的建议,为分析和处治黄土公路隧道衬砌开裂提供了依据。     

Test of magnetic susceptibility and grain-size age models of loess

Ages of the stratigraphic boundary MIS1/2 and MIS3/4 of the Yuanbu loess section in Linxia are used as the basis of the nodal control age. The age of MIS1/2 and MIS3/4 are obtained from the latest international research result—the climatic events recorded in the stalagmite in the Hulu Cave in Nanjing, that MIS1/2 is 11.5 kaB.P. and MIS3/4 is 59.8 kaB.P.. The ages of the two climatic events contain three nodal age control models (Model 1: 0 kaB.P.—59.8 kaB.P.; Model 2: 0 kaB.P.—11.5 kaB.P. and 11.5 kaB.P.—59.8 kaB.P.; Model 3: 11.5 kaB.P.—59.8 kaB.P.), which are used as the nodal control age separately. The deposition times of various stratigraphic horizons are calculated by using the magnetic susceptibility age model and grain-size age model, and then compared with each other. In addition, the AMS14C age, OSL age and the ages of YD and H events are compared with the ages of the corresponding horizons calculated by the three models of nodal control ages. From the analyses of lithologic characters and climatic stages it has been found that both the magnetic susceptibility age model and the grain-size age model have some defects. Because the accurate control ages are selected as the nodal points of the glacial period or interglacial period, the stratigraphic deposition times determined by the high resolution of magnetic susceptibility age model and grain-size age model approximate to the actual ages. As for the relative accuracy of the two age models, the magnetic susceptibility age model is more accurate than the grain-size age model.     

Multi-objective carrier chaotic evolutionary algorithm for DNA sequences design

DNA computing is a new vista of computation, which is of biochemical type. Since each piece of information is encoded in biological sequences, their design is crucial for successful DNA computation. DNA sequence design is involved with a number of design criteria, which is difficult to be solved by the traditional optimization methods. In this paper, the multi-objective carrier chaotic evolution algorithm (MCCEA) is introduced to solve the DNA sequence design problem. By merging the chaotic search base on power function carrier, a set of good DNA sequences are generated. Furthermore, the simulation results show the efficiency of our method.     

二重序列空间｜pq的对偶空间（0〈p，q〈1）

研究了当0〈P〈1，0〈q〈1时二重序列空间｜pq的对偶空间以及当p为区间（0，1）中的序列且q〉1时的赋准范二重序列空间的对偶空间，证明了在0〈p，q〈1时lpq韵对偶空间是l∞，∞。而在第二种情况下它的对偶空间是l∞u，其中，u〉1，1/q＋q/u=1。