Finite Element Analysis of Precursors to Macroscopic Stick–Slip Motion in Elastic Materials: Analysis of Friction Test as a Boundary Value Problem

In this study, we apply the finite element method to investigate precursor to frictional sliding phenomena arising immediately prior to macroscopic stick–slip transitions in elastic bodies within the framework of a continuum theory. Using a numerical model that mimics an actual experimental system, we study the behavior of contact surface nodes to assess the influence of stiffness, driving velocity, initial conditions, and discretization conditions on the propagation characteristics of microscopic slips. In particular, we show that the initial distribution of frictional stress arising due to the Poisson effect has a significant effect on the propagation characteristics in slip regions. Next, based on the results of a finite element analysis of precursor phenomena that accounts for the influence of bulk compliance, we consider the determination of parameters in rate-dependent friction models. With regard to the behavior of sliding friction, we show that the relationship between friction tests and friction models is fundamentally different from the relationship between material tests and constitutive models for material deformation. We conclude that a proper understanding and classification of friction tests, friction models, and the relationship between these tests and boundary value problems are crucial ingredients in the application of computer-aided engineering techniques to sliding-friction phenomena; indeed, friction tests must ultimately be treated as boundary value problems.     

Self-Irradiation Damage of a Curium-Doped Titanate Ceramic Containing Sodium-Rich High-Level Nuclear Waste

The polyphase titanate ceramic containing sodium-rich simulated high-level nuclear waste was doped with 0.69 wt% of ²⁴⁴Cm to accelerate long-term self-irradiation due to α decays. α autoradiography showed that α emissions were almost uniformaly distributed throughout the curium-doped samples on a >20-μm scale although micropore surfaces and titanium oxide agglomerates were free of α-emitting nuclides. The phase assemblage of the curium-doped titanate ceramic included freudenbergite and loveringite in addition to the more abundant oxide phases: hollandite, perovskite, and zirconolite. Accumulation of α decays was accompanied by a gradual decrease in density. The increment of density was – 1% after an equivalent age of 5000 yr. Leach tests showed a slight trend toward higher total release of curium with equivalent age. The release of soluble nonradioactive elements (e.g., Na, Cs, Sr, and Ca) in the oldest specimens (equivalent age, 2000 yr) varied from specimen to specimen but, on average, were higher than specimens that had suffered a lower radiation dose.     

Acoustical parameters of polyethylene glycol/water mixtures

Ultrasonic velocity (v) and density (d) have been measured for polyethylene glycol/water mixtures at 30°C. The adiabatic compressibility (β _ad), molar compressibility (β), specific acoustic impendance (Z), Rao number (R) and van der Waals constant (b) have been computed. The variations ofv, d, β _ad,β, Z, R andb with mole ratio of water/ether group oxygen have been studied. The association between the components and the formation of tetrahydrate have been reported.     

Fabrication of Bi2Sr2CaCu2Ox films on metal substrates by the chemical process using metal alkoxides

The formation behaviour of Bi₂Sr₂CaCu₂O_x from compounds prepared by hydrolysis of metal alkoxides was studied and Bi₂Sr₂CaCu₂O_x films on metal substrates were fabricated using a metal alkoxide solution. Bi₂Sr₂CaCu₂O_x was formed through intermediate phases such as Bi₂Sr₂Cu₁O_x, Bi₂CuO₄, SrCO₃, CaCO₃ and CuO. Bi₂CuO₄ was initially formed with SrCO₃, CaCO₃ and CuO, and then reacted with SrCO₃ to form Bi₂Sr₂Cu₁O_x. Bi₂Sr₂Cu₁O_x reacted with CaCO₃ and CuO to give Bi₂Sr₂CaCu₂O_x. Bi₂Sr₂CaCu₂O_x films were successfully fabricated on nickel substrates using the metal alkoxide solution at the nominal composition of BiSrCaCu=2223. Bi₂Sr₂CaCu₂O_x was precipitated on Ni substrates at firing temperature of 770 °C or above, and a sharp T _c was obtained at the firing temperature of 800 °C.     

13.3‐inch 8k4k 664‐ppi foldable OLED display using crystalline oxide semiconductor FETs

A prototype 13.3‐inch 8k4k 664‐ppi high‐resolution foldable organic light emitting diode display is constructed. C‐axis aligned a‐b‐plane‐anchored crystal In–Ga–Zn oxide field effect transistors designed using a 1.5‐µm rule process are used in the backplane. Each pixel circuit has three transistors and one capacitor, and an external circuit is used to correct pixel current.     

Viewer,converter and preprocessor for smart machining process using an industrial robot

In this paper, viewer and converter softwares are presented for smart machining process using an industrial robot. The viewers for NC, CLS, DXF and STL files illustrate their surface representation with normal direction vectors. For example, the DXF is a data format developed by Autodesk to realize data interoperability among different makers’ CAD systems. The STL means Stereolithography which is a file format proposed by 3D Systems and recently is supported by many design tools and CAD/CAM softwares. In addition, the converters for DXF and STL files generate the corresponding CLS files with normal direction vectors for machining. Further, the proposed preprocessor allows the developed machining robot to work based on information included in STL files. The convenience and user-friendliness of the proposed integrated system are confirmed through experiments of viewing, converting and machining.     

Experimental study on mechanism of autogenous shrinkage of concrete

It was proved that autogenous shrinkage of high-strength concrete could be almost the same as drying shrinkage. For cement paste with low water-cement ratio, shrinkage was observed even in water. Existing composite low evaluated well the restraining effect of aggregate on autogenous shrinkage. Moisture movement caused by capillary condensation was thought to be the cause of flexural strength reduction for sealed specimens.     

Resource Name-Based Routing in the Network Layer

New network architectures and routing technologies are being proposed to reflect the changes in the current trend of Internet communication that are becoming more and more resource-centric; the demand for the hierarchically structured resource in the network is emphasized, not the location of the resource. Therefore, routing by the resource rather than routing by the conventional Internet protocol address is more suitable for the future Internet with some attractive advantages such as reducing the burden of resolving identifier to location and achieving higher scalability by using a provider-independent addressing structure. In this paper, we propose resource name-based routing within the routers in the network layer since te ardware architecture should also be able to support the paradigm shift from host-centric to resource-centric communication. Through evaluating the required network architecture and memory size in routers, we show the feasibility of resource name-based routing by using fully qualified domain names (FQDN) as an example of describing structured information. Using approximately 700 million existing FQDNs, the evaluation result shows that resource name-based routing is feasible even when considering the limitations of ternary content addressable memory size in routers.     

Isotopic assessment of CO<Subscript>2</Subscript> production through soil organic matter decomposition in the tropics

Values of ¹³C and ¹⁵N of soil organic matter (SOM) under different land cover in Pasir Mayang, Jambi Province, Sumatra Island, Indonesia were examined to apply them as indicators of SOM dynamics and related CO₂ production. The ¹³C and ¹⁵N values of SOM increased with depth in the 0–30 cm layer in the preserved forest, reflecting ¹³C and ¹⁵N richment in SOM through mineralization and immobilization. The degree of vertical enrichment, difference between 0–5 cm and 10–15 cm SOM, was more pronounced in ¹⁵N than in ¹³C at all sites in Pasir Mayang. The ¹³C -SOM profiles fluctuated through clear-cutting the forest and subsequent burning, which was due to input of biomass with higher C/N molar ratio and lower ¹³C value than the original SOM. However, the ¹⁵N-SOM profiles before and after such a drastic event did not change appreciably. The ¹⁵N-SOM became higher as the C/N ratio decreased and as soil sugar content decreased. These observations suggest that ¹⁵N-SOM is a variable that changes with the amount of easily decomposable organic matter (EDOM) in soil. Soil incubation experiments demonstrated a correlation between CO₂ production rate and degree of vertical ¹⁵N-enrichment in SOM, which was applied to field data to estimate CO₂ production through SOM decomposition. A similar analysis was performed with the soils collected at 27 locations in other districts in Jambi Province than Pasir Mayang. In five locations covered by oil palm plantation, CO₂ production through SOM decomposition controlled 70 of variation in CO₂ emission among the locations. In the remaining 22 locations, however, the CO₂ emission was neither related to CO₂ production from SOM nor to ground litter amount. This observation indicated that mechanisms other than dead organic matter decomposition such as root respiration were dominant sources for CO₂ emission in these sites.     

Development and motion control of a biped walking robot based on passive walking theory

This research aims to develop the biped walking robot that can walk on the horizontal ground and improve walking efficiency by utilizing the theory of the passive walking robot, namely the pendulum principle. For that, two motors were installed on the hip of the robot to generate the control torques to perform a walking motion. The computer simulations with dynamic model were carried out to investigate the walking capability of the system. Experimental robot was developed considering the calculated results. The proportional control law was used in walking experiment. The robot can walk on the horizontal ground with the proposed method.