堆浸工艺中流动-反应-变形-传质耦合过程数值模拟及应用

基于堆浸过程中的孔隙变形,发展了一孔隙发育模型,并建立了堆浸工艺中流动-反应-变形-传质全耦合模型控制方程组,在喷淋强度不变和常水头的的情况下,给出了方程的数值解.数值结果描述了浸出过程矿堆中溶浸液饱和度的分布、溶浸剂浓度和浸出矿石浓度的分布,拟合结果表明:有用矿物浸出百分比与浸出时间之间呈3次关系,这一关系可用来预测堆浸中的有用金属的浸出回收率.     

乙烯氧氯化催化剂动力学特征及其机理研究

本文得到氧氯化催化剂的转化率-空速关系曲线.由高空速到低空速和由低空速到高空速所测得的曲线差异较大,在高空速下催化剂活性衰减比低空速下快得多;其根源是催化剂的成份、结构和活性随反应气氛而变化.文中建议用络合-还原氧化机理来解释有关现象.此催化剂在一定温度和原料配比下有一“最宜空速”,在此空速下HCl转化率最高,低于此空速HCl转化率不但不增高反而降低,原因是生成的二氯乙烷再裂解生成HCl.副反应由乙烯氧化生成的CO和CO₂是并联反应,它是CuCl₂催化氧化的结果.     

遗煤层自燃影响因素重要性分析北大核心

为了预测采空区遗煤自燃,对遗煤自燃的重要表征氧气消耗速率的影响因素进行重要性分析.根据现场经验和相关参考文献确定水分u1、固定碳u2、氧浓度u3、挥发分u4、温度u5为影响遗煤自燃氧气消耗速率的因素.但这些因素的相关数据存在着随机性、模糊性和离散性,且这些因素之间并不是独立的,所以提出一种云化ANP算法来适应该因素重要性分析过程.以专家评判作为基础,应用该方法对这5个因素进行了重要性排序,其结果为：氧浓度u3〉温度u5〉挥发分u4〉固定碳u2〉水分u1,最后与已有类似算法进行了比较,说明了算法的可应用性.     

静水中正方形孔口的有障碍浮射流(Ⅰ)——数学模型及计算方法的验证

对静水中正方形孔口之上放置一正方形阻力盘的浮射流进行了试验,测量了不同工况下盘后自相似区域轴线上浓度的分布,并建立了其相应的三维数学模型,对不同工况进行了数值模拟计算,数值模拟结果与试验结果吻合较好．将结果与静水中圆孔有阻力浮射流的经验公式进行了比较,发现正方形孔口上放置一正方形阻力盘与圆孔上放置一圆盘在盘后自相似区轴线上浓度分布规律基本一致．对盘后不同高度位置处横截面上的温度等值线分布进行了分析,发现离正方形盘较近的一段高度内温度等值线呈现独特的星形分布,随着离盘距离的增加则变为与圆孔浮射流类似的同心圆形状．     

喷雾碰壁燃烧数值模拟研究北大核心CSCD

燃油喷雾碰壁是小型高压直喷式柴油机中普遍存在的现象.燃油碰壁会影响缸内燃烧过程,进而显著地影响柴油机的动力学、经济性和排放性.为了更好地认识燃油喷雾碰壁燃烧现象,该研究采用数值模拟的方法对该过程进行计算,探究其特殊的燃烧特性.研究结果表明:在碰壁喷雾的两阶段燃烧过程中,喷雾碰壁促进喷雾径向发展半径和卷吸高度的增加,促进近壁面油气混合,在近壁面形成有利于低温点火的条件.低温燃烧反应在混合气较为稀薄的近壁面区域开始,随后向碰壁喷雾中心浓混合气区域发展.随着低温氧化燃烧持续放热,碰壁喷雾雾束中心区域温度逐渐升高,同时积累大量甲醛.由于喷雾碰壁会导致碰壁雾束中心形成较浓混合气,并且低温燃烧放热量较少,导致部分碳氧化物无法完全燃烧,增加了碳烟的生成量.另外随着高温燃烧的进行,温度持续升高,碰壁喷雾卷吸更多环境气体,进而产生大量氮氧化物.     

An air sparging CFD model for heap bioleaching of chalcocite

A computational fluid dynamics (CFD) solver CFX4.4 is used to implement a steady state model of heap bioleaching of chalcocite, which includes air sparging (forced aeration) based on a previous model entirely under natural convection. The model assumes the oxygen supply limits the reaction rate. A parameter analysis is performed which shows that the factors important to copper leaching are liquid and air flow rates, permeability and fraction of pyrite to chalcocite leached (FPY). The ability to control which parts of the bed received the highest extraction as a function of the liquid and air flow rates was established. Sparging is found to increase the oxygen concentration throughout the heap compared to the circumstance with no sparging (natural convection), and consequently improves the copper extraction significantly. The results show that sparging does not provide any better copper extraction for very high heap permeabilities. The arrangement and spacing of air sparging inlets is analysed in regard to the existence of oxygen starved regions between the inlets.     

堆浸工艺中浸润面的牛顿迭代计算方法

为了研究堆浸工艺的机理,用牛顿迭代公式寻求浸润面的非线性方程的数值解,经过14次迭代的误差达到了10^-6,说明此算法收敛有效。     

Recognition of logically related regions based heap abstraction

This paper presents a novel set of algorithms for heap abstraction, identifying logically related regions of the heap. The targeted regions include objects that are part of the same component structure (recursive data structure). The result of the technique outlined in this paper has the form of a compact normal form (an abstract model) that boosts the efficiency of the static analysis via speeding its convergence. The result of heap abstraction, together with some properties of data structures, can be used to enable program optimizations like static deallocation, pool allocation, region-based garbage collection, and object co-location.More precisely, this paper proposes algorithms for abstracting heap components with the layout of a singly linked list, a binary tree, a cycle, and a directed acyclic graph. The termination and correctness of these algorithms are studied in the paper. Towards presenting the algorithms the paper also presents concrete and abstract models for heap representations.     

煤矸石堆积问题的电费计算

本文设计了一种矸石堆的成堆方法 :在堆积若干年之后 ,后移一定距离重新堆积并将之前的矸石堆覆盖 ,这一方法在文 [1 ]的基础上使电费的值继续减少 ,并计算了两次成堆情况下不同出矸率对应的电费值 .     

Bounds for min-max heaps

Very recently a new data structure, called a min-max heap, was presented for implementing the double-ended priority queue. A min-max heap onn keys is constructed inO(n) time; the minimum and maximum keys are found in constant time, and the operations of deleting the minimum, deleting the maximum and inserting a new key into the heap are performed inO(logn) time. In addition, the data structure can be stored implicitly, i.e. in an array ofn elements without using any additional pointers.In this paper, we present lower bound results on the number of comparisons required, in the worst case, for the operations i) to construct a min-max heap on a given set of keys; ii) to convert a min-max heap into a max-min heap; and iii) to merge two min-max heaps into one min-max heap. New upper bounds for the convert and merge operations are also derived. It is found that the main difference between traditional heaps and min-max heaps lies in the time needed to perform the merge operation. While traditional heaps can be merged efficiently, it is shown that min-max heaps are not sublinearly mergeable. Even the seemingly simple task of converting a min-max heap into a max-min heap cannot be performed in less than linear time.This research was supported by the Natural Science and Engineering Council of Canada under Grant No. A0392. (A preliminary version of this paper was presented at the 24th Annual Allerton Conference on Communication, Control and Computing.)     

On-line construction of position heaps

We propose a simple linear-time on-line algorithm for constructing a position heap for a string (Ehrenfeucht et al., 2011 [8]). Our definition of position heap differs slightly from the one proposed in Ehrenfeucht et al. (2011) [8] in that it considers the suffixes ordered in the descending order of length. Our construction is based on classic suffix pointers and resembles Ukkonenʼs algorithm for suffix trees (Ukkonen, 1995 [17]). Using suffix pointers, the position heap can be extended into the augmented position heap that allows for a linear-time string matching algorithm (Ehrenfeucht et al., 2011 [8]).     

A finite element model of localized deformation in frictional materials taking a strong discontinuity approach

A finite element model of localized deformation in frictional materials taking a strong discontinuity approach is presented. A rate-independent, non-associated, strain-softening Drucker–Prager plasticity model is formulated in the context of strong discontinuities and implemented along with an enhanced quadrilateral element within the framework of an assumed enhanced strain finite element method. For simple model problems such as uniform compression, the strong discontinuity approach has been shown to lead to mesh-independent finite element solutions when localized deformation is present. In this paper, a finite element analysis of localized deformation occurring in a more complex model problem of slope stability is conducted in a nearly mesh-independent manner. The effect of dilatancy on the orientation of slip lines is demonstrated for the slope stability problem.     

Controlled rolling of a disc along a plane curve

The plane-parallel rolling of a disc along a fairly smooth curve under the action of perturbing and controlling forces and moments of forces is investigated. Models of the controlled motion corresponding to an explicit or implicit coordinate specification of the curve are constructed. The requirements imposed on the values of the sliding friction force and the normal pressure force, which ensure that the disc rolls without slipping and without loss of contact are determined. The problem of bringing the disc into the required state of motion in a time-optimal way by the action of the force of gravity and a limited axial moment of forces are considered. The situation when the reference curve contains a linear component (inclined upwards or downwards) and a periodic (wavy) component is investigated. Problems of optimal synthesis for a relatively large and relatively small controlling moment are considered.Investigations of the rolling of bodies of different geometrical shape on surfaces, both flat and curved (see 1, 2, 3, 4, etc.), are important for applications in modern machine construction, transport, mobile robot systems,5, 6, 7 etc. However, there are no results of systematic investigations of the problems of the dynamics and control of rolling of bodies on curved surfaces, including comparatively simple bodies (cylinders, discs and spheres). From the applied point of view, the problem of controlled rolling of a disc under gravitational forces on a curve containing a linear incline and periodic smooth changes in the slope is of interest as a model of the motion of a wheel along a path with a curvilinear profile. The solution of problems of the control of the motion of a disc along a closed curve, for example, inside or outside a circle, surmounting obstacles or “rolling out” from hollows of different shapes etc. is of fundamental importance.     

Improving worst-case behavior of heaps

It is possible to improve the worst-case behavior of operations on heaps, when counting number of comparisons between elements in the heap, by modifying the traditional binary heap. The improvement suggested is the use of a heap with scattered leaves. This method can be combined with the use of a ternary heap for even greater improvement.Some other improvements of worst-case behavior compared to standard algorithms are discussed at the end of the paper, where the gain of at least (N-2) comparisons when sortingN elements with HEAPSORT is of great interest in implementations. An algorithm for inserting a new element in a heap inO(log logn) comparisons between elements is mentioned.