Relationship between the Undrained Shear Strength, Water Content, and Mineralogical Properties of Fine-Grained Soils

The relationship between the undrained shear strength of fine-grained soils and the water content can be described with a nonlinear function in which the type of soil is determined by two parameters. It is well known that these parameters depend mainly on the mineral compositions of soils; these relationships, however, have not yet been investigated. The findings described in this paper define those mineralogical properties of soils which determine the values of both parameters. Experimentally obtained results suggest that the parameters primarily depend on the size of the clay minerals, their quantity in soil composition, and the interlayer water quantity in the expanding clay minerals. As this dependence is well defined, the parameters, and thus the undrained shear strength at different water content, can be defined from knowledge of these mineralogical soil properties.     

Tailoring the adhesion of optical films on polymethyl-methacrylate by plasma-induced surface stabilization

Adhesion of plasma-deposited optical and protective coatings, such as amorphous hydrogenated silicon nitride, SiN_1.3, on polymethyl-methacrylate (PMMA) substrates has been found to be limited by a cohesive failure inside the PMMA bulk. Using direct exposure to a low pressure plasma in helium or to vacuum ultraviolet (VUV) radiation generated from plasma, the adhesion of SiN_1.3 at high humidity and elevated temperature has been substantially increased. Using a multitechnique analytical approach, the enhanced adhesion was attributed to the initial etching of the weak boundary layer followed by formation of a crosslinked, graded, mechanically stabilized layer in the interfacial region (interphase), which possesses a physical thickness of 50 to 100 nm and a microhardness of about 2 GPa.     

Kinetic study of the depolymerization of Bruceton coal

The depolymerization of coals using phenol and p-toluenesulphonic acid, was studied.In this reaction the acid ‘catalyst’ is destroyed, its rate of destruction being different for different coals. A kinetic study of the depolymerization of Bruceton coal under conditions of gradually declining acid concentration has been carried out. Parameters which were monitored include the weight increase of the products, the solubility of the products in benzene-ethanol, the extractability of the products into pyridine, the amount of colloidal material present in the pyridine-extractables, and the molecular weight distribution of the pyridine-soluble products. Under the conditions used, the reaction produces primarily polymeric products from coal. The molecular weight distribution of the pyridine-soluble material seems to undergo no major changes with reaction time.     

Mechanical characteristics of optical coatings prepared by various techniques: a comparative study

Good performance of optical coatings depends on the appropriate combination of optical and mechanical properties. Therefore, successful applications require good understanding of the relationship between optical microstructural and mechanical characteristics and film stability. In addition, there is a lack of standard mechanical tests that allow one to compare film properties measured in different laboratories. We give an overview of the methodology of mechanical measurements suitable for optical coatings; this includes depth-sensing indentation, scratch resistance, friction, abrasion and wear testing, and stress and adhesion evaluation. We used the techniques mentioned above in the same laboratory to systematically compare the mechanical behavior of frequently used high- and low-index materials, namely, TiO2, Ta2O5, and SiO2, prepared by different complementary techniques. They include ion-beam-assisted deposition by electron-beam evaporation, magnetron sputtering, dual-ion-beam sputtering, plasma-enhanced chemical-vapor deposition, and filtered cathodic arc deposition. The mechanical properties are correlated with the film microstructure that is inherently related to energetic conditions during film growth.     

Single-material inhomogeneous optical filters based on microstructural gradients in plasma-deposited silicon nitride

Transparent hydrogenated amorphous silicon nitride (SiNx:H) coatings were prepared by dual-mode microwave-radio-frequency plasma-enhanced chemical vapor deposition. By controlling the effects of plasma density and ion energy on the film growth, it was possible to modify the microstructure of the coatings and hence the refractive index n. Using this method, we were able to vary n from 1.6 to 2.0, at 550 nm, by adjusting the power levels of the radio-frequency and microwave components while keeping the gas composition (SiH4, N2) and pressure constant. An inhomogeneous bandpass filter with a controlled refractive-index depth profile was fabricated, and its optical performance was compared with that of its multilayer counterpart. Besides the attractive optical features of such single-material rugate filters, we found that the mechanical resistance of inhomogeneous films is superior to that of multilayer systems.     

Digital connectedness: An algebraic approach

Let E be the incidence matrix of a graph G having m nodes; then the number of connected components of G is equal to m ? r, where r is the rank of E. In particular, if G represents an adjacency relation between points in a digital picture (or higher-dimensional array), this shows that the connected components of points can be counted by computing the rank of E. Two proofs of this result are given, one based on results from algebraic topology and the other based on a self-contained graph-theoretic argument. The former proof can be generalized to yield a method of counting holes.     

Some results on fuzzy (digital) convexity

The definition of fuzzy convexity is reviewed and some results on projections of convex and fuzzy convex sets are established. Digital fuzzy convexity is defined and relationships among alternative definitions are investigated.     

Comparison of noise parameters of diffused and ion-implanted microwave transistors

Two types of implanted microwave transistor structures are outlined, and their behaviour is compared with a totally diffused device. Minimum noise figures for the implanted transistors have been obtained in the range 3.6?4.5 dB at a frequency of 4 GHz.     

Mechanical and optical characteristics of superhard nanocomposite TiN/a-Si<Subscript>3</Subscript>N<Subscript>4</Subscript> and TiCN/a-SiCN coatings produced by PECVD

There is a continuous need for new hard and superhard (H > 40 GPa) materials for applications ranging from protective coatings for cutting tools and aerospace to automobile industries, MEMS and others. In this work nanocomposite hard coatings fabricated by plasma-enhanced chemical vapor deposition from TiCl₄/SiH₄/CH₄/N₂/H₂/Ar gas mixtures were found to possess unique properties such as superhardness, high toughness, and interesting optical properties and colors. The mechanical characteristics such as hardness and Young’s modulus were determined by depth-sensitive indentation. Film microstructure was studied by XRD, SEM, TEM, ERD-TOF, XPS, and AFM. Optical properties like color, refractive index and extinction coefficient were evaluated using combined spectrophotometry and spectroscopic ellipsometry. This multitechnique approach allowed us to determine the structure-property relationships. We have shown that nc-TiN/a-Si₃N₄ exhibits a hardness of 45 GPa, while the novel nc-TiCN/a-SiCN provides a hardness of 57 GPa in addition to a very high resistance to plastic deformation (1.8 GPa).