Source apportionment of heavy metals in soils around a coal gangue heap with the APCS-MLR and PMF receptor models in Chongqing,southwest China

This study studied the characteristics and source apportionment of heavy metal pollution in the agricultural soil surrounding a gangue coal heap in Chongqing,China by using absolute principal component scores-multiple linear regression(APCSMLR)model and positive matrix factorization(PMF)model.The applicability of the models was compared in the assessment of source apportionment.The results showed that the average contents of Cd,Hg,As,Pb,Cr,Cu,Ni,and Zn in the surface soil were 0.46,0.14,9.66,31.2,127,95.6,76.0,and 158 mg/kg,respectively.Combined with the spatial distribution and correlation analyses,the results of source apportionment were consistent for both the APCSMLR and PMF models.Cd,Hg,As,and Pb were mainly affected by the gangue heap accumulation,with respective contributions of 74.6%,79.4%,69.1%,and 67.2%based on the APCS-MLR model and respective contributions of 69.7%,60.7%,57.4%,and 41.9%based on the PMF model.Ni and Zn were mainly affected by industrial and agricultural activities,while Cr and Cu were mainly affected by natural factors.The results of the source apportionment were approximately consistent between the APCS-MLR and PMF models.The combined application of the two receptor models can make the results of source apportionment more comprehensive,accurate,and reliable.

Effect of ore size and heap porosity on capillary process inside leaching heap

The capillary process coexists with gravity flow within leaching heap due to the dual-porosity structure. Capillary rise is responsible for the mineral dissolution in fine particle zones and interior coarse rock. The effect of particle size and heap porosity on the capillary process was investigated through a series of column tests. Macropore of the ore heap was identified, and its capillary rise theory analysis was put forward. Two groups of ore particles, mono-size and non-uniform, were selected for the capillary rise test. The result shows that particle size has an inverse effect on the capillary ultimate height, and smaller particles exhibit higher capillary rise. Meanwhile, the poorly graded group exhibits small rise height and velocity, while the capillary rise in the well-graded particles is much greater. The relationship between porosity and fitting parameters of capillary rise was obtained. Low porosity and high surface tension lead to higher capillary height of the fine gradation. Moisture content increases with the capillary rise level going up, the relationship between capillary height and moisture content was obtained.

HeapAFL:基于堆操作行为引导的灰盒模糊测试

随着软件开发环境和业务逻辑的复杂度不断增加,大量的堆内存对象生命周期及其引用关系造成堆内存操作行为错综复杂,极易引发程序错误造成漏洞.模糊测试作为高效的软件代码错误检测技术,常用于漏洞挖掘.然而,目前最先进的模糊测试工具专注于代码全覆盖功能测试,忽略了执行时堆内存操作状态信息,从而错过堆内存漏洞发现机会.针对上述问题,提出了一种基于堆操作行为引导的灰盒模糊测试方法HeapAFL,在不依赖漏洞先验知识的情况下,其通过静态分析插桩基础堆操作函数及其参数监测执行时控制流和数据流变化,反馈堆操作行为信息,指导模糊测试中种子优先变异阶段,探索多样化堆操作行为从而更高概率触发堆内存错误类漏洞.在6个真实应用程序上验证方法效果,并与6个最先进的模糊测试工具进行比较,实验中的CPU总共测试了4032 h.实验结果表明,HeapAFL在漏洞挖掘效果和崩溃发现效率上优于对比工作.在漏洞挖掘数量上,HeapAFL相比于基准模糊测试方法AFL,AFLFast,PathAFL,TortoiseFuzz,Angora,Memlock分别提升了1.32倍,1.39倍,1.92倍,1.56倍,2.78倍,2.08倍.最终,HeapAFL在数据集上挖掘到了25个堆内存错误类漏洞,其中包括19个已知的漏洞(即1 day)和6个未知的漏洞(即0 day),并报告给CVE(common vulnerabilities and exposures)官方漏洞库后已经获得了2个CVE漏洞编号,其余漏洞正在等待审核.

开展HEAP,加强医院文化建设

随着医院改革创新工作实践的发展,医院文化对医院发展的作用越来越重要。医院员工援助计划(HEAP)是贯彻“以人为本”的思想,加强医院文化建设的有效途径。本文阐述了员工援助计划(EAP)的起源、发展、功能和医院文化的概念,指出开展HEAP是提高员工绩效、提高组织管理水平和加强医院文化建设的有效途径。

幂律思考系列文章4——论Heaps律与Zipf律等价的条件

在词频服从拟幂律分布并满足致密性的条件下,证明了Zipf律和Heaps律相互等价,并且讨论了词频序号为2时的临界行为。

Heaps定律鲁棒性在文本中统计验证与分析

Heaps定律无疑是揭示人类文献内在规律的有力武器。本文运用R语言和SPSS程序。通过对"20世纪百大英文小说"——读者票选名单中的16个文本进行统计分析以验证Heaps定律鲁棒性。

HEAP方案治疗急性成人非淋巴细胞白血病20例疗效分析

我院1993年1月至1997年6月,应用HEAP[高三尖杉酯碱,足叶乙甙(etoposide,Vp-16),阿糖胞苷,泼尼松]方案治疗急性成人非淋巴细胞白血病(ANLL)20例,取得了较好疗效。现总结报道如下。 1 病例和方法 1.1 病例 1993年1月至1997年6月住院的ANLL20例。男性12例,女性8例,年龄19～58岁,中位数年龄38岁。其中M_(?)3例,M 2a6例,M_(4a)4例,M_(4b)2例,M_(5a)4例,M_(5b)1例。初治者13例,复治者7例。复治者中在院外应用过HOAP(O为长春新碱,VCR)、HA及DA(柔红霉素,阿糖胞苷)等方案治疗未获缓解。

Sulfide mineral dissolution microbes: Community structure and function in industrial bioleaching heaps

Heap bioleaching is one of the most clean and economical processes for recovery of low-grade and complex ores, because the sulfide minerals are natural habitats for acidophiles capable of iron-and sulfur-oxidation. The most exciting advances in heap bioleaching are occurring in the field of microbiology, especially with the development of advanced molecular biology approaches. These chemolithotrophic microorganisms living in the acid mine environment fix N_2 and CO_2 and obtain energy for growth from soluble ferrous iron and reduced inorganic sulfur compounds during oxidation of sulfide minerals. The ferric iron as oxidant and sulfuric acid are a result of microbial activity and provide favorable conditions for the dissolution of sulfide minerals. Various microbial consortia were applied successfully in commercial bioleaching heaps around the world, and microbial community and activity were adapted related to the local climatic conditions, ore characteristics and engineering configuration. This review focuses on diversity of bioleaching microbes, their role in heap bioleaching processes, their community structure and function in industrial heaps and the relation to the ore characteristics and the engineering configuration, to give implications for optimizing leaching efficiency of heap bioleaching.

Evaluation of spontaneous combustion tendency of sulfide ore heap based on nonlinear parameters

To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variations of the measuring points of simulated ore heap were measured. Combined with wavelet transform and nonlinear parameters extraction, a new method for spontaneous combustion tendency of different areas in sulfide ore heap based on nonlinear parameters was proposed and its reliability was verified by field test. The results indicate that temperature field evolution of the simulated ore heap presents significant spatial difference during self-heating process. Area with the maximum increasing extent of temperature in sulfide ore heap changes notably with the proceeding of self-heating reaction. Self-heating of sulfide ore heap is a chaotic evolution process, which means that it is feasible to evaluate spontaneous combustion tendency of different areas by nonlinear analysis method. There is a relatively strong correlation between the maximum Lyapunov exponent and spontaneous combustion tendency with the correlation coefficient of 0.9792. Furthermore, the sort of the maximum Lyapunov exponent is consistent with that of spontaneous combustion tendency. Therefore, spontaneous combustion tendency of different areas in sulfide ore heap can be evaluated by means of the maximum Lyapunov exponent method.

Feasibility study on heap bioleaching of chalcopyrite

Bioleaching of chalcopyrite often encountered the formation of passivation layer, which inhibited the leaching process and resulted in a low leaching rate. This inhibitory effect can be eliminated by thermophilic biole- aching. The industrial test of BioCOP technology based on thermophiles was successfully completed, which confirmed the feasibility of chalcopyrite bioleaching. However, industrial leaching rate of chalcopyrite heap bioleaching is lower. This paper described the development status and industrial test of chalcopyrite heap bioleaching technology. The reasons for the lower efficiency of chalcopyrite heap bioleaching were analyzed. The strategies for successful chalcopyrite heap bioleaching were proposed.

Modeling heap biooxidation of arsenic-bearing gold ore

To design heap biooxidation process,it is necessary to understand its internal rules.The heap biooxidation of gold ore from Anhui province was researched in this study.The results showed that the main microorganisms in the heap were A.ferrooxidans,F.acidiphilum and L.ferrodiazotrophum.Under their combined action,gold leaching extent rose from 35.62%to 78.08%in 80 d.Boltzmann model matches the actual oxidation effect better and the model equations were obtained.The model predicted that the oxidation extents of arsenic and sulfur are 58.577%and 42.122%after one year,and the gold leaching extent was 80.40%.The arsenic and sulfur oxidation extents,and gold leaching extent were all linearly correlated.It is more reliable to predict gold leaching extent by sulfur oxidation extent.These results provided good guidance for practical application in the actual production.

Mathematical model for coupled reactive flow and solute transport during heap bioleaching of copper sulfide

Based on the momentum and mass conservation equations, a comprehensive model of heap bioleaching process is developed to investigate the interaction between chemical reactions, solution flow, gas flow, and solute transport within the leaching system. The governing equations are solved numerically using the COMSOL Multiphysics software for the coupled reactive flow and solute transport at micro-scale, meso-scale and macro-scale levels. At or near the surface of ore particle, the acid concentration is relatively higher than that in the central area, while the concentration gradient decreases after 72 d of leaching. The flow simulation between ore particles by combining X-ray CT technology shows that the highest velocity in narrow pore reaches 0.375 m/s. The air velocity within the dump shows that the velocity near the top and side surface is relatively high, which leads to the high oxygen concentration in that area. The coupled heat transfer and liquid flow process shows that the solution can act as an effective remover from the heap, dropping the highest temperature from 60 to 38 ℃. The reagent transfer coupled with solution flow is also analyzed. The results obtained allow us to obtain a better understanding of the fundamental physical phenomenon of the bioleaching process.

Simulation of pore scale fluid flow of granular ore media in heap leaching based on realistic model

Two-dimensional images of the granular ore media with different grain sizes were obtained from the X-ray computed tomography.Combined with the digital image processing and finite element techniques,the original grayscale images were transformed into the finite element models directly.By using these models,the simulations of pore scale fluid flow among particles were conducted with the COMSOL Multiphysics,and the distribution characteristics of fluid flow velocity and pressure were analyzed.The simulation results show that there exist obvious preferential flow and leaching blind zone in each granular medium.The flow velocity at pore throat is larger than that of pore body and the largest velocity reaches 0.22 m/s.The velocity decreases gradually from the center of pore throat and body to the surface of particles.The flow paths of granular media with larger grain size distribute equally,while the fluid flow velocities in most of areas of granular media with smaller grain size are lower,and some of them approach to zero,so the permeability is very low.There exist some pore clusters with different pressures,which is the basic reason for the uneven flow velocity distribution.

Simulation of coupled flowing-reaction-deformation with mass transfer in heap leaching processes

Governing equations for a fully coupled flowing-reaction-deformation behavior with mass transfer in heap leaching are developed. The model equations are solved using an explicit finite difference method under the conditions of invariable application rate and constant hydraulic head. The distribution of the degree of the saturation, as well as the distributions of the concentration of the reagent and the solute is given. A cubic relationship between the mineral recovery and the leaching duration is obtained based on the numerical results. The relationship can be used to predict the recovery percentage of the valuable metal.

Dynamic experiment and numerical simulation of solute transmission in heap leaching processing

Solute transmission in saturated ore heap was studied numerically and experimentally. The convection-diffusion equation (CDE) used to describe the mass transportation in porous media was solved by characteristic difference method to give the distribution of the concentration of ferrous ion in the ore column. To calibrate the computational model, a column test was performed using infiltration of sulfide ferrous solution (the initial concentration is c0=0.04 mol/L) on a 100 cm high column composed of ore particles smaller than 10 mm for 2.5 h. The numerical analysis shows that the results obtained from numerical modeling under the same operating conditions as used for column test are in good agreement with those from experimental procedure on the whole trend, which indicates that the model, the numerical method, and the parameters chosen can reflect the rule of ferrous ion transmission in ore heap.

Heap Spray攻击的防范

本文介绍了Heap spray攻击的原理、特点以及防范方法。

Responses of bacterial community to potential heap construction methods of fine-grained copper tailings in column bioleaching system

The column bioleaching of copper flotation tailings was comparatively investigated using layered heap construction method(LM),agglomerate heap construction method(AM),and pellets-sintering heap construction method(PM).The bacterial communities of free,attached,weakly-attached,and strongly-attached microbes in the later bioleaching stage were investigated.In AM group,the addition of lump sulphide ore resulted in the low leachate pH,high ferric iron concentration,and rapid microbial adsorption,which obtained the maximum copper extraction(60.1%)compared with LM(54.6%)and PM(43.9%)groups.The relative abundance of dominant genera and microbial communities of different microbiota underwent changes in three heap construction methods.The alpha-diversity indexes of attached,weakly-attached,and strongly-attached microbes were different,while no significant change was observed in free bacteria.The variation of whole bacterial community was significantly associated with solution pH,total iron,and ferric iron concentrations.Pearson correlation analysis and partial least square path model both indicated that attached bacteria made larger contribution to the copper extraction of tailings.

Membership Proof and Verification in Authenticated Skip Lists Based on Heap

How to keep cloud data intact and available to users is a problem to be solved. Authenticated skip list is an important data structure used in cloud data integrity verification. How to get the membership proof of the element in authenticated skip list efficiently is an important part of authentication. Kaouthar Blibech and Alban Gabillon proposed a head proof and a tail proof algorithms for the membership proof of elements in the authenticated skip list. However, the proposed algorithms are uncorrelated each other and need plateau function. We propose a new algorithm for computing the membership proof for elements in the authenticated skip list by using two stacks, one is for storing traversal chain of leaf node, the other is for storing authentication path for the leaf. The proposed algorithm is simple and effective without needing plateau function. It can also be applicable for other similar binary hash trees.

Bacterial oxidation activity in heap leaching

Bioleaching of sulfide minerals by bacteria, mainly Thiobacillus ferrooxidans(T.f.) and Thiobacillus thiooxidans, plays an important role in hydrometallurgy because of its economic and environmental attractions. The surveys of production process and the bacterial oxidation activity in the heap bioleaching were investigated. The results show that pH value is high, bacteria biomass and ferric concentration are low, generation time (above 7.13 h) is long in leachate, and less bacteria are adsorbed on the ores. The bacteria in the leachate exposing on the surface and connecting with mineral, have much faster oxidation rate of Fe(Ⅱ) and shorter generation time, compared with those which are in the reservoir for a long time. There is diversity for oxidation activity of Fe(Ⅱ), while there is no diversity for oxidation of sulfur. So it is advisable to add sulfuric acid to degrade pH value to 2.0, add nutrients and shorten recycling time of leachate, so as to enhance bacteria concentration of leachate and the leaching efficiency.

Field load testing of copper extraction aeration pipes under simulated high heap pile

Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from the mine was used in recreating the in situ conditions.Electric heaters were utilized to raise the temperature inside each pipe to simulate the essential element of the copper extraction process.The maximum vertical deflection reached by the test pipes was close to 20%,when the simulated heap pile height was 80 m.The plastic pipes and the overliner material were also tested in the laboratory.Based on the results,the maximum heap pile fll depth was recommended for the aeration system.The results indicated that the vertical deflection was the primary performance index for the aeration pipes installed in heap piles at mines.Lastly,the pipe made of polypropylene resin was super.