Sulfur Strontium Carbon and Oxygen Isotopes of Calcium Sulfate Deposits in Late Carboniferous Rocks of the Loei-Wang Saphung (LWS) Area Loei Province Thailand

journal articl

Micromechanical testing of two-dimensional aggregated suspensions of colloidal particles

Includes bibliographical references (pages 119-123)

Compressive Aggregates of Two-Dimensional Mono-Disperse to Assess Flaw Dissemination

Polystyrene particles of 4 μm in diameter are aggregated as the monolayer clusters rearranged themselves when the compressive forces are applied to the clusters. Oriented structures of the clusters are then examined and characterized the failure mechanisms of two-dimensional (2D) aggregation. Failure mechanisms cause rearrangement of particles within the aggregates. Their flaw locations of each applying force change due to the particle bonding-rebonding themselves. Particles can move either relatively to each other or the small aggregates. Even though, these orientations occur in the small scale and barely significant, disturbed particles gradually accumulate stress. Small aggregates or particles inside the bulk perhaps cannot immediately change the cluster shape, but regularly oriented until reaching to yield. Compression to 2D aggregates can make an existing dislocation and fractures of this aggregated structure. Crack propagation of the dense is possible to proceed dynamically. The clusters collapse until reaching to yield. Two-dimensional structures of compressive aggregated polystyrene are always mechanical instable that increases in propagating rupture. Therefore, the quake will reasonably occur.</jats:p

Dynamics of Suspended Sediments Related to Fine Particles in Lower Mekong River

Analytical results are considered the factors of suspended sediment concentration, fall velocity, dimensionless shear stress, transportation rate and stream discharge. As a result of suspended sediments of Loei, Huang and Mekong River, fine particles account for the applicability in sediment deposits. Floating suspended sediments explicit more clay minerals than suspended sediments. Suspended sediment concentration (SSC) in the estuarine of Loei River and Huang River are moderately less than Mekong River. Flow directions of the interconnected rivers to the mainstream-Mekong River lead to the quantity of SSC. Sediment concentrations attain to the dynamic response. Dimensionless shear stress relates to shear velocity, geometry and grain size of particles, and difference of flow velocity. This shear stress is directly comparative to flow velocity and clay mineral concentrations. The transport rate involves in the flow velocity, SSC and depth of the river. Moreover, stream discharge can be presumed by the geometry of the river and topography of sampling locations.</jats:p

Mechanisms of Microstructural Rearrangement on Two-Dimensional Aggregates under Compressive Stress

Two-dimensional (2D) colloidal aggregates of polystyrene microspheres 4 μm were experimentally modeled to study the rearranged mechanisms and compression behaviors at the air-liquid interface. The aggregated models occurred due to the interaction forces between particles. The combination of mechanical testing technique and the digital video microscopy had been developed to quantitatively analyze the compressive deformation of 2D aggregates. When the compressive forces were applied to the cluster, these forces were transmitted trough the aggregated network during compression. Solid-like mechanical properties of 2D aggregated cluster were examined. Deformation mechanisms occurred within the aggregated network which presented the particle rearrangements during yield. Elastic deformation had undergone the compressive elastic stress of the elastic loading. Rearrangement mechanisms found generally were rolling-hinge, sliding mechanisms and tensile failure for a small-scale deformation. Shear failure and stick-slip mechanisms caused a large-scale plastic deformation. However, across the yield point, the tensile failures were dominated. Rearrangement mechanisms of particles affected both elastic and plastic deformations.</jats:p

Tensile Strength of PHBV/Natural Rubber Latex Mixtures

A polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is mingled with natural rubber latex (R) to develop its mechanical property of the blend. Normally, substantial effects of the PHBV are hard, fragile, and inelastic, whereas the natural rubber is represented itself as very high elastic matter. The mixtures between the PHBV and natural rubber latex (R) are considered in different proportions. The PHBV solutions (w/v) are defined suitability at 1% (P1), 2% (P2), and 3% (P3). Their liquid mixtures of the PHBV to natural rubber latex (P:R) are fabricated the blended films in three different ratios of 2:3, 1:1 and 3:2, respectively. The PHBV blended films are characterized the crystallinity form by x-ray diffractometry (XRD), which are appeared their identity crystals at 13.30 and 16.68 degree (2θ). Mechanical characterizations of the blends are examined by a universal testing machine (UTM). The average elastic moduli of P1, P2, and P3 mixtures are indicated as 773, 955, and 1,007 kPa, respectively. Their tensile strengths, similarly to elastic moduli, enhance with the PHBV concentrations. The effects of mechanical behaviors and crystallinity reveal that the PHBV blends can be improved their properties by more flexible with natural rubber latex

Interactive Force of Two-Dimensional Compressive Deformation by Discrete Element Method (DEM)

Discrete Element Method (DEM) computer simulation is used to examine the influence of contact force between two-dimensional aggregates of polystyrene microsphere formed on the air-liquid interface. Colloidal aggregates have been treated as the granular material or discontinuum materials. The interaction force models are related to experiment which had done by digital video microscopy. The interaction mechanisms of the contact forces between particles in the colloidal system can be considered as a combination of spring and dashpot force and van der Waals force. According to the DEM, the interaction forces are evaluated to introduce relations between particles and the result comparison between the computer simulation and the experimental work. This study indicates that the behavior of the colloidal aggregates depends on the long-ranged (spring and dashpot) and the short-ranged interaction force (van der Waals). Besides, the behaviors shown in both computer simulation and the experiment are in good agreement. Thus, this computer simulation method can mimic the behavior of colloidal aggregates forming as a monolayer at the air-liquid interface.</jats:p