Efficient bit-parallel multipliers over finite fields GF(2)

Hardware implementation of multiplication in finite field GF(2^m) based on sparse polynomials is found to be advantageous in terms of space-complexity as well as the time-complexity. In this paper, we present a new permutation method to construct the irreducible like-trinomials of the form (x + 1)^m + (x + 1)ⁿ + 1 for the implementation of efficient bit-parallel multipliers. For implementing the multiplications based on such polynomials, we have defined a like-polynomial basis (LPB) as an alternative to the original polynomial basis of GF(2^m). We have shown further that the modular arithmetic for the binary field based on like-trinomials is equivalent to the arithmetic for the field based on trinomials. In order to design multipliers for composite fields, we have found another permutation polynomial to convert irreducible polynomials into like-trinomials of the forms (x² + x + 1)^m + (x² + x + 1)ⁿ + 1, (x² + x)^m + (x² + x)ⁿ + 1 and (x⁴ + x + 1)^m + (x⁴ + x + 1)ⁿ + 1. The proposed bit-parallel multiplier over GF(2^4m) is found to offer a saving of about 33% multiplications and 42.8% additions over the corresponding existing architectures.     

低渗透气藏非达西渗流三项式产能方程的建立

低渗透气藏由于存在启动压力梯度,气体的渗流不再符合达西定律。考虑启动压力梯度影响,从气体多孔介质渗流力学理论出发,基于低渗透气藏非达西低速稳定渗流微分方程,建立了考虑启动压力梯度影响的低渗透气藏三项式产能方程,并提出了求解方法。通过某气藏的实际资料计算结果表明提出的方法切实可行,计算结果可靠。     

实物期权在矿业最佳投资时机中的应用

矿产项目的投资被看成是一份延期的看涨期权。针对传统DCF法的缺陷,以钼矿为例,通过改进三叉树期权定价模型,构建了最佳投资时机下确立栏杆价格的理论方法,并以实际数据进行了期权定价模拟,表明了方法的可靠性。同时依据金属矿山的特点,将价格波动对于边界品位、矿石储量、服务年限等因素的影响予以量化,提升了期权理论对于矿业项目投资决策的准确度。     

Binomial and trinomial models in quantitative biostratigraphy

The theory of binomial and trinomial models is reviewed briefly. It is shown that a modified version of Glenn and David's trinomial model can be used to estimate probabilities of coeval events in biostratigraphy. However, a modified binomial model is preferred for the purpose of ranking and scaling of stratigraphic events.