Modelling of the spring-in phenomenon in curved parts made of a thermosetting composite

In this study, a simple two step finite element model is developed to predict the spring-in of C-sections parts made of AS4/8552 composite. The development of resin properties throughout the MRCC were derived using Group Interaction Modelling and the mechanical properties of the composite predicted by using micromechanical models. Important mechanisms during manufacturing that are effective in the formation of residual stresses and shape distortions are defined. The finite element method implemented is composed of two steps before and after the vitrification of the resin. Vitrification is treated as a point at which the material suddenly changes from the rubbery to glassy state with constant properties in each state. The spring-in angles predicted by the finite element analysis are compared to the angles measured on C-section specimens of various lay-ups and thicknesses. The correlation is good showing the validity of the assumptions adopted.     

Drilling detritus and the operating parameters of thermally stable PDC core bits

A single rock type was drilled using two types of thermally stable polycrystalline diamond compact (PDC) and an impregnated diamond core bit using a fully instrumented laboratory drilling rig at a fixed rotational speed, and over a range of weights on bit (WOB). Operating parameters of the bits such as WOB, rate of penetration (ROP), rotational speed (RPM), torque and drilling specific energy (SE) were continuously monitored during the drilling trials. The effects of these parameters on the performance of the bits were examined. Relations between the drilling variables are also described. At each set WOB for each bit, the drilling detritus were collected. The detritus sizes between 1180 and 53 microns were analysed using wet sieving and sub 53 micron was analysed using a Malvern particle size machine. Both data were combined to obtain a particle size distribution at set WOBs for each bit. The relations between the particle size of the drilling detritus and operating parameters, cutter size and wear of the PDC and impregnated diamond core bits, and original rock grain size were established. An increase in WOB, ROP, wear rates, pins or diamond size increased the drilling detritus size for the bits. No relation was found between the drilling detritus and the rock grain size due to the regrinding effect and the high proportion (> 30%) of matrix material in the rock.     

Geostatistical Analysis of Spatial Distribution of Salt Bed Thickness

The data on salt bed thickness distribution are processed using the semi-variogram analysis. Two- and three-dimensional maps of bed thickness distribution, as well as the error maps are presented.     

Wake-up receivers for wireless sensor networks: benefits and challenges - [Accepted from open call]

For successful data delivery, the destination nodes should be listening to the medium to receive data when the sender node starts data communication. To achieve this synchronization, there are different rendezvous schemes, among which the most energy-efficient is utilizing wakeup receivers. Current hardware technologies of wake-up receivers enable us to evaluate them as a promising solution for wireless sensor networks. In this article the benefits achieved with wake-up receivers are investigated along with the challenges observed. In addition, an overview of state-of-the-art hardware and networking protocol proposals is presented. As wake-up receivers offer new opportunities, new potential application areas are also presented and discussed.     

Evaluation of destruction specific energy of fly ash and slag admixed concrete interlocking paving blocks (CIPB)

Concrete interlocking paving blocks (CIPB) are widely used in flooring and covering applications such as city roads, pedestrian foots, gardening architecture and many surface coverings. The focus of this study is to evaluate destruction specific energy (SE_des) of CIPB containing fly ash and blast-furnace slag at different curing conditions. The SE_des is estimated from the area (integral) under stress–strain envelope for an unconfined compression test. This method provides a better understanding between performance and the main mechanical character of CIPB. Compressive strength, splitting tensile and flexural tensile strengths, rebound hardness and abrasion resistance tests at 3, 7, 28, 90 and 180 days were carried out. The test results showed that fly ash (FA) and blast-furnace slag (BFS) can replace the cement by amounts of 10–20%, 30–40% of mass, respectively. This helps to produce CIPB with lower cost and better engineering properties. The relationship between SE_des, strength, hardness and abrasion are defined for CIPB.     

A dynamic theory for polarizable and magnetizable magneto-electro thermoviscoelastic,electrically and thermally conductive anisotropic solids having magnetic symmetry

A unified dynamic theory for polarizable and magnetizable magneto-electro thermoviscoelastic. electrically and thermally conducting anisotropic solids possessing magnetic symmetry is developed for time-dependent electromagnetic fields. Considering the Chu formulation of the Maxwell equations, the balance equations of nonrelativistic continuum mechanics and the boundary conditions together with the constitutive equations for anisotropic materials are given. It is shown that the entropy, polarization. magnetization and the nondissipative part of stress are derivable from a potential while the dissipative part of stress, electric current and heat flux vectors satisfy a residual inequality. The theory developed for a general anisotropy and interaction is applied to special cases.     

Periodic flow of a second-grade fluid induced by non-torsional oscillations of eccentric rotating disks

This paper deals with the periodic flow of a second-grade fluid caused by non-torsional oscillations of two disks rotating about non-coincident axes. While the two parallel disks are initially rotating with the same angular velocity about distinct axes, they start to execute non-torsional oscillations in their own planes and in the opposite directions. An exact solution is obtained for the components of the horizontal force per unit area exerted by the top and bottom disks on the fluid in the periodic state. The results are graphically displayed and the influence of the second-grade fluid parameter, the ratio of the frequency of oscillation to the angular velocity of the disks, the Reynolds number and the dimensionless velocity amplitudes of oscillation is discussed. It is observed that the change in the \( x \)-component of the mentioned force gets larger when the second-grade fluid parameter increases. However, an opposite effect is seen for the change in the \( y \)-component.     

Reflex sympathetic dystrophy syndrome due to arteriovenous fistula

A patient with end-stage renal disease presented with reflex sympathetic dystrophy syndrome (RSDS) on her left hand 1 month after arteriovenous fistula (AVF) surgery. Magnetic resonance angiography revealed steal syndrome at the AVF level. Bone scintigraphy revealed early-stage RSDS. We considered that arterial insufficiency because of steal phenomenon following AVF surgery and underlying occlusive arterial disease triggered RSDS development.