计算时间

It provides a way to find optimal lower dimensional approximations of the given data, and It enormously reduce the storage of the data which is needed when the physical processes is recurred. The physical process can be described in series expansion function that only is related to the time and space. It is optimal approximation of the given data in a certain least squares optimal sense. The most obvious advantage of the method is that it reduces the computation cost and computation time markedly.

它提供了一种描绘物理过程的有效方法，该物理过程可以写成一个只与时间相关的函数和一个只与空间相关的函数的展开式序列，且它们在均方意义上是最优的，在展开式中只需要少量的项数就可较准确地描述该物理过程，因此降低计算维数、减少计算量和节省计算时间是这个方法最明显的优点。

For the requirement of instantaneity, an implicit real-time discretisation is used, and the equations are integrated in a fictitiously pseudo time. This approach allows the real-time step to have two-order accuracy and accelerates the speed of convergence. Based on the theory of Mr. John K. Dukowicz and the algorithm of Mr.

在非定常计算中，本文同时采用当地和虚拟时间步，即双时间推进，在每个真实时间步上采用虚拟时间进行定常迭代，从而不但使时间迭代具有二阶精度，并使计算时间大大缩短，这样程序与定常程序在算法思想上一脉相承。

In the integral formula of Fourier transforms of option pricing formula,by using residues theorem two integrations were simplified into a single numerical integration which has a faster rate of decay.

在期权定价公式的傅立叶变换积分公式中，运用留数定理将公式中的两个积分式子化简成一个被积函数衰减较快的积分函数式，从理论上提高了计算效率，缩短了计算时间，为投资者快速计算期权价值节约了时间。

In order to reduce the computing time, a method to divide the load curve into sections and to form the related computation loads and ...

为减少计算时间，还提出了一种将负荷曲线分段并形成相应的计算负荷和持续时间的方法，该方法可明显地减少计算时间，而其所带来的误差不影响重构的最终结果

Comparison with the classical fourth-order LWC scheme shows that the NAD-type methods have many advantages. They can generate clearer snapshots of wave fields without any visible dispersion. To obtain the results without any numerical dispersion, the time cost by the LWC schemes is about 559, 1222 and 1955 times of that taken by ONADM, RNADM and SNADM, receptively. Besides, the storage space of ONADM is roughly about 3.3% of that needed for the fourth-order LWC scheme, while of RNADM and SNADM is about 5.8‰.

和经典的4阶LWC格式相比：NAD类算法在粗网格下可以有效的压制数值频散，得到清楚的波场快照；在达到消除数值频散要求时，4阶LWC格式的计算时间是ONADM计算时间的559倍，是RNADM方法计算时间的1222倍，是SNADM方法计算时间的1955倍；而此时ONADM方法存储量只有4阶LWC存储量的3.3%，RNADM方法和SNADM方法的存储量只有4阶LWC格式存储量的5.8‰。

High precision format, unstructured dynamic mesh with a large displacement and multi-species gas flows were computationally expensive, the problem of resourceless and inefficient of single computer appeared. Parallel arithmetic based on PC-Cluster system for the oblique detonation wave flow and the muzzle flow include high speed projectile were discussed. The results proved that the rationality of parallel arithmetic provided a new method to simulate the complex chemical reaction flows. The present code represents a validated, efficient and versatile tool developed for the simulation of hypersonic multi-species chemical non-equilibrium flows.

高精度计算格式、化学反应源项的刚性和大位移的运动边界处理都给计算和存储带来了沉重的负担，单机资源不足和计算时间长的问题凸现，利用PC机和局域网资源建立分布存储式并行计算系统，并基于非结构动网格和分区算法开发了复杂化学反应流场数值模拟的并行计算程序，对高速飞行实验弹丸诱导的斜爆轰波流场和含有大位移动边界的膛口燃气射流场进行了并行模拟，有效地缩短了计算时间，扩展了计算规模，为复杂化学反应流数值模拟研究提供了新的手段。

The model has the following features: 1 The security information provided by the assessment result is more dependable because of the consideration of some main uncertain factors; 2 The improved analytic method of power system DSR and the dynamic equivalent technologies are applied to reduce the computing time and to make the model more practical; 3 Step-up assessment strategy is adopted in order to balance the precision and computing time requirements; 4 Decompounding of system insecurity indexes to each system component, or to each generator and consumer, and the visualization of assessment results, will help the operators to understand the security status of the power system more clearly; 5 The assessment results can be beneficial to the preventive control in traditional power systems and the security pricing in power market environments.

模型具有如下特点： 1由于综合考虑了一些不确定因素对系统安全性的影响，使得评估结果更加可靠； 2采用求解电力系统动态安全域的改进解析法，结合动态降维技术，大大减少了动态安全域的计算时间，使得模型比较实用； 3采取逐步递进的评估策略，以适应计算精度和计算时间要求； 4可定量分解出各元件或各发电与用户对系统不安全的贡献，配以形象直观的评估结果显示，使操作人员清楚了解系统的安全状况； 5评估结果在传统电力系统可帮助制定预防控制措施，在电力市场可用于安全性定价。

Finally, the temperature field variations of two kinds of frame structures with the height and the time are calculated, in which the time step, the frill calculation time, the fire growth coefficient t and the fire decay coefficient t are selected respectively as 1s, 50min, l50s and 600s, and the fire experiences all the fire period including the growth, the flashover, the full development and the decay stages.

随后，取时间步长为1s，计算时间为50min，分别计算了两种围护结构内部温度场随时间和位置的变化规律。计算时，火灾增长时间t为150s，衰减时间t为600s，所选取的火灾为经历了生长阶段、轰然阶段、充分发展阶段和衰减阶段的全过程燃烧。

It is the first time to calculate the near noise field with ray method, and replace the inhomogenous SSP in the vertical direction with constant SSP, while other models usually use Fast Field Program such as SARFRI to calculate the near noise field. This model increases the calculation speed about 100 times without decreasing much precision. It can meet the need of engineering.

首次采用射线模型计算噪声近场的贡献，并进一步用等声速代替有垂直分布的声速剖面，而其他模型通常采用诸如SARFRI等快速场程序计算近场的贡献；本模型的计算时间比其他模型的计算时间缩短了2个数量级，精度并未有明显损失，适合工程需要。

A novel numerical boundary condition is presented in the paper, which is compared with the method of measured equation of invariance on computational time and memory requirement. It is demonstrated that the new boundary condition is of benefit both on the time and memory, therefore is an efficient method for computation of electrically large dimension objects.

本文给出了一种新的吸收边界条件，并与不变性测试方程法、矩量法在计算时间、存贮空间方面进行比较，结果表明运用这个条件在计算时间和存贮空间上都具有优点，是计算电大尺寸媒质柱体电磁散射特性的一种有效手段。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。