基于遗传算法的岩体参数辨识研究

目前,对于岩体流固耦合分析研究已经很多,而耦合分析常常受困于计算参数的取值,因此对两场耦合模型中的计算参数反演分析是非常必要的.根据实测的水头、位移资料,利用遗传算法,建立了等效连续岩体渗流场与应力场耦合计算参数辨识模型.并对某算例在库水位下降情况下,以渗流场与应力场耦合正分析计算结果作为"实测值",进行两场耦合参数辨识分析.从参数辨识的结果来看,验证了所提出的思路、方法以及程序的正确性和可行性.两场耦合计算参数进行反演分.析,对于两场耦合模型的建立和计算结果的可靠性是非常有意义的.     

Animal urine as painting materials in African rock art revealed by cluster ToF‐SIMS mass spectrometry imaging

The rock art site at the village of Songo in Mali is a very important Dogon ritual place where, since the end of the nineteenth century until today, takes place the ceremony of circumcision. During these ceremonies, paintings are performed on the walls of the shelter with mainly three colors: red, black and white. Ethnological literature mentions the use of animal urine of different species such as birds, lizards or snakes as a white pigment. Urine of these animals is mainly composed of uric acid or urate salts. In this article, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is used to compare uric acid, snake urine and a sample of a white pigment of a Dogon painting coming from the rock art site of Songo. ToF‐SIMS measurements in both positive and negative ion modes on reference compounds and snake urine proved useful for the study of uric acid and urate salts. This method enables to identify unambiguously these compounds owing to the detection in negative ion mode of the ion corresponding to the deprotonated molecule ([M ? H]^? at m/z 167.01) and its fragment ions. Moreover, the mass spectra obtained in positive ion mode permit to differentiate uric acid and urate salts on the basis of specific ions. Applying this method to the Dogon white pigments sample, we show that the sample is entirely composed of uric acid. This proves for the first time, that animal urine was used as a pigment by the Dogon. The presence of uric acid instead of urate salts as normally expected in animal urine could be explained by the preparation of the pigment for its application on the stone. Copyright © 2010 John Wiley & Sons, Ltd.     

四川得荣地区徐麦超基性岩体地球化学特征及成矿潜力

对四川得荣地区徐麦超基性岩体的主量元素进行了分析。结果表明,该岩体中S iO2含量为35.27%~42.25%,MgO含量34.85%~38.16%,ALK为0.019 3%~0.031 9%,m/f比值为7.06~12.78;微量元素分析成果显示其富相容元素Cr、Co、N i,几乎亏损所有的不相容元素;稀土元素球粒陨石标准化曲线显示轻稀土富集而重稀土亏损;δEu值介于0.82~12.61之间,具明显正铕异常特征。结合该岩体的地质特征,认为徐麦超基性岩体属于镁质超基性岩,含矿性较好,其成矿远景意义相对较大。     

军队安全管理中的脆性风险分析及其评估方法

安全管理作为部队日常管理的重要职能,对维持部队安全稳定具有重要作用.为全面分析其可能面临的风险威胁,促进军队安全管理模式转型,在分析军队安全事故的基础上,提出了基于脆性风险熵的安全管理脆性风险分析及评估方法.结合脆性传递原理,提出了安全管理对象间基于不同脆性关系和风险事件相关性的脆性概率计算方法;按照安全事故的分类原则,量化确定了军队管理对象的风险等级,并结合直觉模糊集的基本原理提出了相应的脆性风险量化方法.最后以某部某次危险品输送任务为例进行说明,梳理任务各执行阶段中的脆性传递关系及触发过程,并通过分析各管理对象的脆性风险熵及其脆性风险值变化验证脆性变化的基本规律,结果表明,其变化趋势满足安全管理对风险触发过程的认知.     

钢中脆硬粒子裂纹形成机理

钢中的脆硬粒子对钢的解理脆断有直接的影响，解理断裂源大都发生在脆硬粒子上.根据微裂纹形成的热力学模型，利用钢中脆硬粒子开裂时所释放的弹性应变能、位错塞积弹性能，所产生的表面能，对脆硬粒子裂纹形成机理进行分析.模型计算表明，正应力和位错塞积力都是脆硬粒子开裂的必要条件，这与实验事实相符；同时给出脆硬粒子开裂的临界条件计算方法，计算发现，脆硬粒子临界开裂应力不仅取决于脆硬粒子尺寸及表面能，而且与晶粒直径有一定的相关关系，当晶粒直径较小时，这种关系与实验测定的材料解理断裂应力与晶粒尺寸的关系一致，说明整体失稳解 关键词： 解理断裂 裂纹形核 脆硬粒子     

脆性基体复合材料层板弯曲破坏的数值模拟

讨论了复合材料层板的弯曲破坏问题,纤维层是正交异性弹性体,而基体为脆性损伤材料。提出了一种脆性损伤模型,虽是各向同性连续损伤模型,但利用等效损伤应变的定义,可以区分拉、压和剪切对损伤的不同响应。用有限元法数值模拟了如下现象,一旦基体出现临界损伤,弯曲载荷则从最大值急速下降,同时基体的临界损伤区很快扩展,并且发生局部纤维断裂,从而使复合材料层板几乎失去了承弯能力,整体呈脆性特性。为便于了解破坏过程,给出了若干状态时板内的应力等值线分布图。     

BRITTLE-DAMAGE ANALYSIS OF CRACKS UNDER CONDITIONS OF PLANE-STRAIN TENSILE LOADING

An abrupt damage model, taking full account of finite geometrychanges, is used to study both the shapes of damage zones and the stress strain fieldsfor a plane-strain tensile crack under the small-scale yielding condition. Two typicalcrack-tip damage profiles are simulated by the element vanish technique. The fracturetoughness increment due to damage dissipation is evaluated in terms of the energyrelease rate.     

冲击压缩下非均质脆性固体的弛豫破坏研究

通过平板冲击实验研究了富含微缺陷的非均质脆性固体的冲击压缩响应特性.选取“强角闪石化橄榄二辉岩”作为样品材料，利用激光速度干涉仪测量样品后自由面的速度历史，在冲击加载应力远低于样品材料Hugoniot弹性极限的条件下，观测到了表征破坏波出现的再加载信号，并且该破坏波的速度远大于玻璃中破坏波的速度，以接近于冲击波的速度在样品内向前传播，其形成机理与玻璃样品中的破坏机理不同，称之为“就位扩展机理”.采用同一冲击加载应力(～3.9GPa)作用于不同厚度的样品,获得了破坏波穿过样品的运动过程，确定出样品中破坏波的轨迹线近似为一条不过原点的直线，相应的产生此破坏波的弛豫时间约为0.5 μs.     

Hardness and Elastic Modulus Profiles of Hybrid Coatings

Instrumented-indentation testing (IIT) provided with a continuous stiffness measurement (CSM) technique was employed to measure hardness and elastic modulus profiles of thin organic/inorganic hybrid coatings on glass surfaces. Hybrids were synthesized by the hydrolytic condensation of (3-methacryloxypropyl) trimethoxysilane (MPMS) or vinyltrimethoxysilane (VMS), with 5–30 wt% tetraethoxysilane (TEOS), in the presence of formic acid. Coatings of 600–800 nm on glass substrates were obtained by dip-coating solutions of these hybrids with benzoyl peroxide (BPO) addition, and curing in an oven following a thermal cycle up to 120C. Both hardness and elastic modulus showed a maximum value close to the surface, followed by a plateau and a significant increase at higher penetrations. Hybrids based on MPMS and 20–30 wt% TEOS exhibited a good combination of intrinsic values of hardness (0.50 GPa) and brittle index (0.06–0.07), that makes them suitable for coatings of plastic substrates.     

Rapid on-line sample dissolution assisted by focused microwave radiation for silicate analysis employing flame atomic absorption spectrometry: iron determination

An on-line automated flow injection system with microwave-assisted sample digestion was used to perform silicate rock dissolution in acid medium for iron determination. For this purpose, a continuous flow system was built up by using an automatic flow injection analysis (FIA) system coupled to a flame atomic absorption spectrometer (FAAS), including a focused microwave oven unit. Inside the microwave cavity was inserted a polytetrafluoroethylene (PTFE) reactor coil (300 cm length and 0.8 mm i.d.) where the dissolution takes place. Chemical and flow variables as well as iron determination parameters were studied. In the flow system, a slurry of the rock sample (50 mg in 200 ml of acid mixture HF+HCl+HNO₃) is pumped through the reaction coil and the microwaves are turned on. After elapsed the time required to complete the sample dissolution, the mixture is pumped again in order to fill the sampling loop (500 μl). Then, by changing the valve position, a water carrier stream pushes the sample solution through the flame atomic absorption spectrometer nebulizer. To achieve an accurate determination of the rock certified materials, the slurry sample was irradiated during 210 s at 90 W power. Working in that condition, a detection limit of 0.80 μg ml⁻¹ (which corresponds to an Fe₂O₃ content of 0.46%) and an analytical throughput of 10 h⁻¹ were achieved. The relative standard deviation (R.S.D.) of the method varied between 1 and 11% when applied to the rock certified materials.