The Control of Diagenesis and Mineral Assemblages on Brittleness of Mudstones

The variation in mineral composition will affect the rock brittleness, thus the change of mineral assemblages during diagenesis has a potential control on the brittleness of mudstones. In this study, thin section, X-ray diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were used to investigate compositional and microscopic features of mudstones. With the enhancement of diagenesis, three mineral assemblages were divided due to the diagenetic evolution of minerals. Quartz, feldspar, dolomite, chlorite, and illite were regarded as brittle minerals and (quartz + feldspar + dolomite + illite + chlorite)/(detrital mineral + carbonate + clay mineral) was defined as the brittleness evaluation index The mudstone brittleness changed slightly during early diagenesis but increased gradually with enhancement of diagenesis in the late diagenesis stage. Quartz and feldspar were scattered above the clay matrix and the contact of grains was limited, therefore, the contribution of detrital minerals to the brittleness was affected by the properties of clay minerals. The diagenetic transformation of clay minerals resulted in the reduction of ductile components (smectite/I-Sm and kaolinite) and increase of brittle components (illite and chlorite), leading to the enhancement of integral rigidity of the mudstones. Meanwhile, the improved crystallization of carbonate in late diagenesis stage enlarged the carbonate grains which resulted in rigid contact between grains. These results highlighted the influence of diagenesis on mudstone brittleness. Therefore, for evaluation of mudstone brittleness, attention should be paid to the diagenesis process besides mineral composition.

Japan: Diagnosis and Management of Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis With Severe Ocular Complications

In 2005, the “Japanese Research Committee on Severe Cutaneous Adverse Reaction” (J-SCAR) presented the official “Diagnostic Criteria” for SJS/TEN, and the specific ocular findings are included in these very important criteria. In SJS/TEN cases involving ocular disorder, conjunctivitis often occurs prior to the onset of the high fever. In a Japanese survey, ocular involvement was observed in 77% of the cases, and the incidence of ocular sequelae increased depending on the score of the acute ocular severity findings. Pseudo-membrane formation and epithelial defects are considered to be high-risk signs of ocular sequelae. At the chronic stage, limbal stem cell deficiency, visual disturbance, and severe dryness of the ocular surface are the primary disease characteristics. In 2002, we started performing Cultivated Oral Mucosal Epithelial Transplantation (COMET) for the treatment of severe ocular disorders, including SJS/TEN. As an additional treatment method, we developed a new type of rigid contact lens (CL) that is 13 to 14.0-mm in diameter, known as the “Limbal Rigid Contact Lens (Limbal CL).” Our Limbal Rigid CL greatly enhances the postoperative outcome of COMET. The detection rate of ocular surface bacteria is high in SJS/TEN cases. Thus, appropriate use of topical antibiotics reduces the risk of ocular surface inflammation. Moreover, rebamipide is an ophthalmic solution for dry eye that was developed in Japan, and it also has the effect of suppressing ocular surface inflammation. From disease onset until the chronic stage, the control of inflammation and stem cell loss is key to successfully treating eyes afflicted with SJS/TEN.

WALKING MOTION OPTIMIZATION OF THE WALKING MACHINE WITH DYNAMIC STABILITY

The movement of machines with a walking legs is accompanied by dynamic vibrations of its body and a large energy consumption for the reciprocating movements of the legs. The greatest influence on the smoothness of the course is exerted by the alternating accelerations of the moving masses and the rigid contact of the leg with the ground surface. To reduce the negative factors affecting the smoothness of movement and energy consumption, are proposed to optimize the trajectory of movement of the legs. The optimized trajectory of the legs movement made it possible to reduce the consumption of electrical energy by 12 ... 18% per cycle of movement compared to the trajectory lying in the same geometric plane. In order to reduce shock loads, the time interval between the triggering of the shock sensor and the load sensor when lowering the support to the surface was experimentally determined, which was about 100 ms at a lowering speed of 20 mm/s. Reducing the speed of the leg at the moment of triggering the shock sensor after contact with the surface and its subsequent smooth loading made it possible to reduce shock loads and reduce body vibrations caused by sharp impacts of the feet on the surface. Support acceleration on impact decreased from 6g to 1.5g. The triggering of the shock sensor located on the support foot when it touches hard and soft surfaces requires adjusting the sensor's sensitivity while the machine is moving. Optimization of the algorithm for filtering false alarms and dynamic change in sensitivity did not give a satisfactory result, therefore, it is necessary to equip the design with additional load sensors that react to contact with the surface when lowering the support

SOUND PROPAGATION THROUGH STRUCTURAL COMPONENTS UNDER CONDITIONS OF NON-RIGID CONTACT AT THE BOUNDARIES BETWEEN THEM

The report considers the problem statement, derivation and solution of the dispersion equation for sound propagation in a layered inhomogeneous medium with oriented fracturing, simulated by the presence of boundary conditions in the "linear slip" approximation. Numerical solutions are obtained and analyzed for the frequency range and values of the parameters of contact breaking, which is relevant in the problems of ultrasonic measurements

Vibrations of Cylindrical Shell Structures Filled With Layered Viscoelastic Material

A thin-walled shell and a thick-walled mass (cylinder) in contact with it, made of a different material, are structural elements of many machines, apparatus, and structures. The paper considers forced steady-state vibrations of cylindrical shell structures filled with a layered viscoelastic material. The study aims to determine the damping properties of vibrations of a structurally inhomogeneous cylindrical mechanical system under the influence of harmonic loads. The dynamic stress-strain state of a three-layer cylindrical shell filled with a viscoelastic material under the action of internal time-harmonic pressure is investigated. The oscillatory processes of the filler and the bonded shell satisfy the Lamé equations. At the contact between the shell and the filler, the rigid contact conditions are satisfied. Dependences between stresses and strains for a linear viscoelastic material are presented in the form of the Boltzmann-Voltaire integral. The method of separation of variables, the method of the theory of potential functions (special functions), and the Gauss method are used to solve this problem. Based on the analysis of the numerical results, it was found that the dependence of the resonant amplitude of the shell displacements on the viscous properties of the filler is 12-15%. Analysis of the results obtained shows that the study of vibrations of shells containing fillers according to the rod theory will lead to rather large erroneous results (up to 20%).

Reactive Balance Control for Legged Robots under Visco-Elastic Contacts

Contacts between robots and environment are often assumed to be rigid for control purposes. This assumption can lead to poor performance when contacts are soft and/or underdamped. However, the problem of balancing on soft contacts has not received much attention in the literature. This paper presents two novel approaches to control a legged robot balancing on visco-elastic contacts, and compares them to other two state-of-the-art methods. Our simulation results show that performance heavily depends on the contact stiffness and the noises/uncertainties introduced in the simulation. Briefly, the two novel controllers performed best for soft/medium contacts, whereas “inverse-dynamics control under rigid-contact assumptions” was the best one for stiff contacts. Admittance control was instead the most robust, but suffered in terms of performance. These results shed light on this challenging problem, while pointing out interesting directions for future investigation.

Topology synthesis of a 3-kink contact-aided compliant switch

A topology synthesis approach to design 2D Contact-aided Compliant Mechanisms (CCMs) to trace output paths with three or more kinks is presented. Synthesis process uses three different types of external, rigid contact surfaces – circular, elliptical and rectangular – which in combination, offer intricate local curvatures that CCMs can benefit from, to deliver desired, complex output characteristics. A network of line elements is employed to generate topologies. A set of circular subregions is laid over this network, and external contact surfaces are generated within each subregion. Both, discrete and continuous design variables are employed – the former set controls the CCM topology, appearance and type of external contact surfaces, whereas the latter set governs shapes and sizes of the CCM constituents, and sizes of contact surfaces. All contact types are permitted with contact modeling made significantly easier through identification of outer and inner loops. Line topologies are fleshed out via a user-defined number of quadrilateral elements along lateral and longitudinal directions. Candidate CCM designs are carefully preprocessed before analysis via a commercial software and evolution using a stochastic search. The process is exemplified via a contact-aided, 3-kink mechanical switch which is thoroughly analysed in presence of friction and wear.