Numerical analysis of the compressive and shear failure behavior of rock containing multi-intermittent joints

The failure behavior of intermittent jointed rocks is dependent on joint configurations. Joint inclination angle and continuity factor determined the joint arrangement in a rectangular numerical sample that was established by using the particle flow code approach. To identify the differences in the failure processes of identical intermittent jointed samples, uniaxial compressive and shear loads were applied on each sample. The crack growth path presented the four typical crack coalescence patterns identified via compressive and shear numerical tests. The crack coalescence pattern was associated with joint slant angle and continuity factor. The observed crack coalescence patterns of every sample with the same inclination angle and continuity factor were partially identical under compressive and shear loading. The differences in the crack patterns of the compressive and shear failure processes were described and compared. Typical compressive and shear failure processes were illustrated. Four compressive and three shear failure modes were identified. The cracking location and number of cracks in each failure mode were different. Additionally, the contact force evolution among particles during shear and compressive loading was different and likely accounted for the differences in cracking patterns. Under compressive or shear loading, the contact force concentration in each sample underwent the following stages: uniform distribution before loading, concentrated distribution, and scattered distribution after failure.     

Synthesis of nanocrystalline CdS thin film by SILAR and their characterization

Cadmium sulphide (CdS) thin film was prepared by successive ion layer adsorption and reaction (SILAR) technique using ammonium sulphide as anionic precursor. Characterization techniques of XRD, SEM, TEM, FTIR and EDX were utilized to study the microstructure of the films. Structural characterization by x-ray diffraction reveals the polycrystalline nature of the films. Cubic structure is revealed from X-ray diffraction and selected area diffraction (SAD) patterns. The particle size estimated using X-ray line broadening method is approximately 7 nm. Instrumental broadening was taken into account while particle size estimation. TEM shows CdS nanoparticles in the range 5–15 nm. Elemental mapping using EFTEM reveals good stoichiometric composition of CdS. Characteristic stretching vibration mode of CdS was observed in the absorption band of FTIR spectrum. Optical absorption study exhibits a distinct blue shift in band gap energy value of about 2.56 eV which confirms the size quantization.     

具有选择性胶凝能力的小分子胶凝剂研究进展

不相溶混合溶剂的选择性胶凝对于溶剂纯化和分离,特别是溢油处理和水体净化具有十分重要的意义。 具有选择性胶凝能力的胶凝剂可以是高分子、微纳米颗粒和小分子胶凝剂。 然而,相对于高分子和微纳米颗粒材料,以小分子化合物为胶凝剂的凝胶往往具有凝胶 溶胶相变可逆性,这种可逆性无疑会对凝胶体系的实际应用带来额外的好处。 基于这些考虑,本文按照胶凝剂分子的结构,分类介绍此类小分子胶凝剂研究进展,并展望了相关研究的前景和可能应用。     

单细胞凝胶电泳其及光学图像分析

采用单细胞凝胶电泳检测DNA损伤度,运用光学图像处理软件对彗星试验得到的参数进行图像分析,结果表明:该方法快捷,灵敏度高,能够较好地应用于DNA损伤度的修复、细胞遗传、环境检测等方面.     

Vacancy diffusion in Cu∑ = 5[0 0 1] twist grain boundary

Both the formation energies and the diffusive activation energy of a single vacancy migrating intra- and inter-layer in the first four atomic planes near Cu∑ = 5[0 0 1] twist GB have been investigated by means of MD in conjunction with MAEAM. The effects of the GB on the vacancy formation and migration are only to the third layer. The vacancy is favorable to be formed on the un-coincident site in the first, second and third layers near the GB plane and this case is enhanced successively following the third, second and first layers. A single vacancy either on un-coincident site or on coincident site in the forth, third and second layers is favorable to migrate to un-coincident site (its first-nearest-neighbor) in its adjacent layer near the GB. But for the first layer, the favorable migration path of the vacancy on the un-coincident site is between un-coincident sites of the first layer or to its nearest-neighbor of the first layer in the rotating grain, which is not the case for the vacancy on the coincident site ‘1’ that is migrated difficultly. So, there are collective tendency of the vacancy in the GB.     

Diffusion of single adatom Cu on Cu (0 0 1) and (1 1 0) surfaces

With static relaxation, the surface diffusion activation energies of a single Cu adatom migrated by both atomic exchange and hopping mechanisms and the forces acted on the diffusing adatom from other atoms of Cu (0 0 1) or (1 1 0) surface are calculated by using the MAEAM. When adatom migrated on Cu (0 0 1) or (1 1 0) surface, the increment curves of the system energy by hopping mechanism are symmetrical and the saddle points are in the midpoints of the migration path, but the ones by the exchange mechanism are dissymmetrical and the saddle points are always close to the initial hole positions of the adatom and away from the initial equilibrium positions of the exchanged atom. From minimization of both the diffusion activation energy and the force acted on the diffusing adatom from other atoms, we found that, on Cu (0 0 1) surface the favorable diffusion mechanism is hopping mechanism, however, on Cu (1 1 0) surface, hopping via long bridge is easier than the exchange mechanism but the hopping via short bridge is more difficult than the exchange mechanism.     

成都市主城区“两抢一盗”犯罪的多尺度时空格局研究

以四川省成都市三环内城区为例,使用标准化犯罪强度指数和核密度估计方法,对成都市“两抢一盗”犯罪者行为的时空规律进行研究。结果发现,成都市中部和中北部存在2个稳定的犯罪热点;在年内月尺度上,“两抢一盗”犯罪案件集中在商贸区、住宅区和火车站,月内日尺度上,犯罪热点存在“波动式”空间偏移,月内周尺度上犯罪热点以原热点为基础,呈现明显的外延式空间偏移,日内时尺度上,犯罪热点沿主要道路转移。犯罪成因分析和影像图片分析表明,成都市“两抢一盗”犯罪以流窜作案为主,犯案者与复杂的环境因素在时空上的交互作用导致了作案地域的演变。整体来看,基于案件汇总数据的“两抢一盗”犯罪多尺度时空分析,可以在一定程度上解释区域内犯罪者的犯罪行为规律。     

Hypervalent Iodine(III)‐Mediated Benzannulation of Enamines with Alkynes: an Efficient Synthesis of Substituted Aminonaphthoic Acid Derivatives

An intermolecular two C? C bond formation procedure for the synthesis of carbocycles mediated by hypervalent iodine(III) reagents was developed. This metal free protocol provided a new approach for the synthesis of useful substituted 1‐amino‐2‐naphthoic acid derivatives via benzannulation reactions. Various N‐unsubstituted and N‐alkyl substituted aromatic enamines with terminal alkynes and non‐terminal alkynes can be converted into corresponding 1‐amino‐2‐naphthoic acid derivatives under mild reaction conditions. When meta‐substituted phenyl enamines were employed in the reaction, two cyclization paths were detected in the reaction and ortho‐cyclization products were the only or major products. Good functional group tolerance, readily available material and high atom utilization efficiency make this method a potential procedure which may find broad application in organic synthesis.     

聚酯废料乙二醇解聚反应的研究

在选定的条件下,使聚酯废料乙二醇解聚,反应产物中BHET含量高,易精制,对乙二醇醚化反应也有所抑制。BHET缩聚后得到的聚酯的各顷指标达到了纺丝要求,可纺性能良好。     

基于一种柔性双咪唑和不同双羧基配体构筑的两例镉(Ⅱ)的配位聚合物

在水热条件下合成了2个新颖的镉(Ⅱ)配位聚合物:[Cd₂(μ2-H₂O)(1,5-Bip)(Tpa)₂]_n(1)和[Cd(1,5-Bip)(Oba)]_n(2)(H₂Oba=4,4''-二羧酸二苯甲醚,H₂Tpa=对苯二甲酸,1,5-Bip=1,5-二(咪唑基)戊烷)。并通过X射线单晶衍射,粉末XRD、红外光谱、元素分析以及热重分析对其结构进行表征。单晶解析结果表明:配位聚合物1是一个单节点5连接(4⁶.6⁴)拓扑三维空间网络结构,配位聚合物2是一个二维的(4,4)网格层状结构。另外,研究了2个配位聚合物在室温下的热稳定和荧光性能。