Approximating Euclidean circles by neighbourhood sequences in a hexagonal grid

In this paper the nodes of the hexagonal grid are used as points. There are three types of neighbours on this grid, therefore neighbourhood sequences contain values 1, 2, 3. The grid is coordinatized by three coordinates in a symmetric way. Digital circles are classified based on digital distances using neighbourhood sequences. They can be triangle, hexagon, enneagon and dodecagon. Their corners and side-lengths are computed, such as their perimeters and areas. The radius of a digital disk is usually not well-defined, i.e., the same disk can have various radii according to the neighbourhood sequence used. Therefore the non-compactness ratio is used to measure the quality of approximation of the Euclidean circles. The best approximating neighbourhood sequence is presented. It is shown that the approximation can be improved using two neighbourhood sequences in parallel. Comparisons to other approximations are also shown.     

蒙古文整词计算机生成理论研究

采用面向对象方法,模拟传统蒙古文整词各种形式构成机理,提出了几种蒙古语整词计算机生成数据模型。文章主要依据整词计算机生成三种模型,探讨了传统蒙古文整词计算机最优化生成理论所涉及的精确度、时间复杂度、空间复杂度三项基本要素以及最优化生成必须考虑的整词复杂特征载荷与一体化合一计算知识表示方法和计算结构,证明了“B - J - T= W”数据模型是传统蒙古文整词计算与生成最优化对象模型。     

存储器替换机制及其实现

提出一种解决PACT01一种结合动态可编程逻辑阵列(DPGA)的处理器的新型体系结制中cache的一致性与同步性问题的算法,并且解决多线程支持的快速上下文切换及快速用户级操作问题。存储器替换机制是解决cache的一致性问题及当cache未命中时从局部或远程存储器到cacbe存储器的数据替换问题的一种硬件实现方法,产生冲突的原因是由于多线程并行的写入／读取的位置相同和读或写的位置相同。文中选择的是相联映射策略,同时也选择了最少最近使用LRU算法,即在cache未命中时替换最少最近使用的参考块,为实现LRU算法设置了与每块相对应的计数器。     

蚁群算法参数对物流配送路径问题求解的影响

描述了蚁群系统算法求解物流配送路径问题的过程;通过仿真实验分析了蚁群系统算法中各参数对物流配送路径问题求解的影响.     

Accommodation of impurities in α-Al2O3, α-Cr2O3 and α-Fe2O3

Atomic scale computer simulation was used to predict the mechanisms and energies associated with the accommodation of aliovalent and isovalent dopants in three host oxides with the corundum structure. Here we consider a much more extensive range of dopant ions than has previously been the case. This enables a rigorous comparison of calculated mechanism energetics. From this we predict that divalent ions are charge compensated by oxygen vacancies and tetravalent ions by cation vacancies over the full range of dopant radii. When defect associations are included in the model these conclusions remain valid. At equilibrium, defects resulting from extrinsic dopant solution dominate intrinsic processes, except for the largest dopant cations. Solution reaction energies increase markedly with increasing dopant radius. The behaviour of cluster binding energies is more complex.     

A calibration protocol of a one-dimensional moving bed bioreactor (MBBR) dynamic model for nitrogen removal

This work suggests a procedure to correctly calibrate the parameters of a one-dimensional MBBR dynamic model in nitrification treatment. The study deals with the MBBR configuration with two reactors in series, one for carbon treatment and the other for nitrogen treatment. Because of the influence of the first reactor on the second one, the approach needs a specific calibration strategy. Firstly, a comparison between measured values and simulated ones obtained with default parameters has been carried out. Simulated values of filtered COD, NH(4)-N and dissolved oxygen are underestimated and nitrates are overestimated compared with observed data. Thus, nitrifying rate and oxygen transfer into the biofilm are overvalued. Secondly, a sensitivity analysis was carried out for parameters and for COD fractionation. It revealed three classes of sensitive parameters: physical, diffusional and kinetic. Then a calibration protocol of the MBBR dynamic model was proposed. It was successfully tested on data recorded at a pilot-scale plant and a calibrated set of values was obtained for four parameters: the maximum biofilm thickness, the detachment rate, the maximum autotrophic growth rate and the oxygen transfer rate.     

Impact of pulmonary vascular stiffness and vasodilator treatment in pediatric pulmonary hypertension: 21 patient-specific fluid-structure interaction studies

Recent clinical studies of pulmonary arterial hypertension (PAH) have found correlations between increased pulmonary vascular stiffness (PVS) and poorer disease outcomes. However, mechanistic questions remain about the relationships amongst PVS, RV power, and vascular hemodynamics in the setting of progressive PAH that are difficult or impossible to answer using direct measurements. Clinically validated patient-specific computational modeling may allow exploration of these issues through perturbation-based predictive testing. Here we use a simple patient-specific model to answer four questions: how do hemodynamics change as PAH worsens? How does increasing PVS impact hemodynamics and RV power? For a patient with moderate PAH, what are the consequences if the pressures increase modestly yet sufficiently to engage collagen in those vessels? What impact does pressure-reducing vasodilator treatment have on hemodynamics? Twenty-one sets of model-predicted impedance and mean PA pressure (mPAP) show good agreement with clinical measurements, thereby validating the model. Worsening was modeled using data from three PAH outcomes groups; these show not only the expected increase in mPAP, but also an increase in pressure pulsatility. Interestingly, chronically increasing mPAP decreased WSS, suggesting that increased PA cross-sectional area affected WSS greater than increased PVS. For a patient with moderately high PVR (12.7 WU) with elastin-based upstream vascular remodeling, moving from elastin-dominant vessel behavior to collagen-dominant behavior caused substantial increases in mPAP, pressure and WSS pulsatility. For the same patient, reducing PVR through a simulated vasodilator to a value equivalent to mild PAH did not decrease pressure pulsatility and dramatically increased WSS pulsatility. Overall, these results suggest a close association between PVS and hemodynamics and that hemodynamics may play an important role in progressing PAH. These support the hypothesis that treatments should target decreasing or reversing upstream vascular remodeling in addition to decreasing mean pressures.     

不同含盐量及离子含量对土的界限含水率的影响规律研究

土中含盐量影响土的物理力学性能,研究细粒土中总盐含量及不同离子含量(硫酸盐和氯盐)对认识土的界限含水率的影响规律有重要意义。人工配制不同含盐量、不同离子含量的土样,测定土的界限含水率,并运用投影寻踪回归分析方法研究含盐量对土的界限含水率的影响。研究结果表明:加氯化钠时,随着含盐量的增加,土的液、塑限均有下降;加硫酸钠时,随着含盐量的增加,土的液、塑限均有上升,体积发生变化,出现膨胀现象;各加一半时,随着含盐量的增加,土的液限明显下降,塑限变化不大。     

塔里木河流域中游绿洲地下水资源评价——以沙雅县为例

地下水资源是我国西部地区水资源的主要组成部分,对地下水资源全面科学的调查和评价,是解决水资源问题的基础性工作。本文尝试采用水均衡方法的同时进行数值模拟的方法对塔里木河流域中游绿洲沙雅县地下水水资源进行评价。结果表明:通过地下水资源均衡计算,绿洲地下水处于正均衡状态,通过数值模拟法计算,绿洲地下水处于负均衡状态。水均衡方法对较大区域地下水资源评价方便易行,但是局部地区精细化计算能力不足,由于多数补给项采用补给系数法计算,结果误差偏大;数值模拟方法对各种尺度研究区均可以进行模拟计算,但是对已有基础资料要求较高,模拟过程充分考虑实际水文地质条件及地下水位动态拟合精度,各源汇项计算精度优于水均衡评价方法结果。两种方法结合应用可更好地用于地下水资源评价。对沙雅县的地下水资源进行评价和分析,目的是科学合理开发利用地下水,保持水土平衡,促进沙雅县经济可持续发展。     

复掺掺和料对混凝土抗冻性的影响试验

通过试验分析了粉煤灰和矿渣微粉掺和料复掺对混凝土抗冻性能的影响。结果表明:复掺掺和料后混凝土强度比基准混凝土增加,混凝土冻融循环后的质量损失率和动弹性模量损失率低于基准混凝土;当掺和物掺量达50%时,混凝土快速冻融循环500次未被破坏,说明混凝土具有良好的抗冻性和抗渗性,符合混凝土高性能、高耐久性要求。