Unloading Profiles Research Articles

On the adhesion of sinusoidal surfaces

In this work, we study the adhesive loading and unloading of a one-dimensional sinusoidal surface and use design of experiments to provide for response surface maps for the work of adhesion and the interaction length, which depend only on Johnson’s α parameter and the Maugis parameter μ. As showcased by some example, these can be used to replace the fine scale roughness by a cohesive zone model. Besides that, we provide ranges of α and μ in which the most common analytical solutions present accurate results. Finally, we characterize the presence of instabilities in the loading and unloading profiles.

Task sequencing in heterogeneous device for improved offloading decision using optimization technique

Edge Computing (EC) has made decisions regarding offloading tasks. Also, it might be a challenging task for a gadget of the multi-hop cause of competing network models due to the limited bandwidth available. The literature provides several studies on the issue of the multi-hop cloud environment. Moreover, partial offloading of multi-hop computing and dynamic network management leads to network problems. And inefficient performance measured in terms of task completion time has not been factored into current studies. To reduce the average finishing time of all jobs, this article proposed joint multi-task complete unloading and a network that supports the scheduling issue. Several variable decision factors such as the partial systematic ratio of offloading, Offloading remote devices, task start time, path of routing & dynamic network start time were optimized by the formulated problem. To manage tasks, we use the features inherent in multiple processors with various CPU frequencies. Under the restrictions of power & latency, we determine the appropriate quantity of task data to be handled immediately or distributed to the preferred nodes on the clouds remotely. Our objective is to solve the issue of optimization of task scheduling on a limited quasi-quadratic function. We offer an Improved Offloading and Heuristic Flow Optimization (IOHFO) solution effectively to solve these problems by using semi-definite relaxation. Finally, a simulator can be used to evaluate our proposed unloading system to reduce the (optimal) cost of unloading profiles for various parameters.

Optimization of volume-limited thermal energy storage in non-continuous processes

Due to the nature of non-continuous processes, heat recovery through direct heat integration is limited. Thermal energy storage (TES) is usually employed for indirect heat transfer, provided excess heat sources and sinks are available. Such processes may have brief peaks in energy demand, necessitating large TES. However, practical space constraints often limit maximal storage volumes, restricting the potential for heat recovery. This paper aims to develop a linear programming optimization model to determine the storage integration solutions which maximize heat recovery per batch for volume-limited sensible stratified storage. Indirect source and sink profiles are used to determine maximum process heat recovery and subsequently the initial TES capacity. The results produce a process-specific capacity limitation chart of batch-wise maximal heat recovery, allowing generation of optimal storage loading and unloading profiles. The optimization model was applied to two case studies. The resulting capacity limitation chart shows that a stratified storage, with a volume of total 96m3 is needed to achieve 100% of the trageted direct and indirect heat recovery. Approximately 60% heat recovery can already be achieved by using only a 4m3 storage. The model is extended to a fixed temperature variable mass storage with multiple VSUs.

Batch Process Integration: Management of Capacity-Limited Thermal Energy Storage by Optimization of Heat Recovery

Integration of batch processes is preferably accomplished by indirect heat recovery using thermal energy storage. Such processes may have brief peaks in energy demand, necessitating high storage capacity within short time periods. However, practical space constraints often limit maximal storage volumes, restricting the potential capacity to recover process heat. Consequently, the required utility costs of storage-limited integration solutions are increased, influencing their economic viability. Given increasing importance in the industry to utilize thermal energy efficiently, process operators may want to explore what is maximally possible energetically, within current space constraints, before contemplating expansion and further capital expenditure. Therefore, linear programming is utilized to determine storage integration solutions which maximize heat recovery per batch for volume-limited sensible stratified storage, specified by an insight-based approach from Pinch Analysis. The results produce a process-specific capacity limitation chart of batch-wise maximal heat recovery as a function of limited capacity, allowing generation of optimal storage loading and unloading profiles. Total batch costs (investment and operating cost per batch) are used to estimate the influence of limited capacity. The methodology is demonstrated in a case study. The resulting capacity limitation chart shows that for a stratified storage with four VSUs, which would require a volume of 97.4 m3 to achieve 100 % of the indirect heat recovery potential, approximately 60 % can be covered by an 8 m3 storage.

Development of a Robotic Unloader Brace for Investigation of Conservative Treatment of Medial Knee Osteoarthritis.

Knee osteoarthritis (KOA) is a painful and debilitating condition that is associated with mechanical loading of the knee joint. Numerous conservative treatment strategies have been developed to delay time to total joint replacement. Unloader braces are commonly prescribed for medial uni-compartmental KOA, however their evidence of efficacy is inconclusive and limited by user compliance. Typical commercial braces transfer load from the medial knee compartment to the lateral knee compartment by applying a continuous brace abduction moment (BAM). We propose that brace utilization and effectiveness could be improved with a robotic device that intelligently modulates BAM in real time over the course of a step, day, and year to better protect the knee joint, improve pain relief, and increase comfort. To this end, we developed a robotic unloader knee brace ABLE (active brace for laboratory exploration) to flexibly emulate and explore different active and passive brace behaviors that may be more efficacious than traditional braces. The system is capable of modulating BAM within each step per researcher defined unloading profiles. ABLE was realized as a lightweight orthosis driven by an off-board system containing a servo motor, drive, real-time controller, and host PC. Frequency response and intra-step trajectory tracking during level-ground walking were evaluated in a single healthy human subject test to verify system performance. The system tracked BAM vs percent gait cycle trajectories with a root mean square error of 0.18 to 0.58 Nm for conditions varying in walking speed, 85-115% nominal, and trajectory peak BAM, 2.7 to 8.1 Nm. Biomechanical and subjective outcomes will be evaluated next for KOA patients to investigate how novel robotic brace operation affects pain relief, comfort, and KOA progression.

Noninvasive Assessment of Hemodynamic Status in HeartWare Left Ventricular Assist Device Patients: Validation of an Echocardiographic Approach

ObjectivesThe aim of this prospective study was to validate an echocardiographic protocol derived from 5 HeartWare left ventricular assist device (HVAD) patients for the noninvasive evaluation of right atrial pressure (RAP) and left atrial pressure (LAP) in HVAD patients. BackgroundEchocardiography is an invaluable tool to optimize medical treatment and pump settings and also for troubleshooting residual heart failure. Little is known about the echocardiographic evaluation of hemodynamic status in HVAD patients. MethodsRight heart catheterization and Doppler echocardiography were performed in 35 HVAD patients. Echocardiography-estimated RAP (eRAP) was assessed using inferior vena cava diameter, hepatic venous flow analysis, and tricuspid E/e′ ratio. Echocardiography-estimated LAP was assessed using E/A ratio, mitral E/e′ ratio, and deceleration time. ResultseRAP and estimated LAP significantly correlated with invasive RAP and LAP (respectively, r = 0.839, p < 0.001, and r = 0.889, p < 0.001) and accurately detected high RAP and high LAP (respectively, area under the curve 0.94, p < 0.001, and area under the curve 0.91, p < 0.001). High eRAP was associated with high LAP (area under the curve 0.92, p < 0.001) and correlated with death or hospitalization at 180 days (odds ratio: 8.2; 95% confidence interval: 1.1 to 21.0; p = 0.04). According to estimated LAP and eRAP, patients were categorized into 4 hemodynamic profiles. Fifteen patients (43%) showed the optimal unloading profile (normal eRAP and normal wedge pressure). This profile showed a trend toward a lower risk for adverse cardiac events at follow-up (odds ratio: 0.2; 95% confidence interval: 0.1 to 1.0; p = 0.05) compared with other hemodynamic profiles. ConclusionsDoppler echocardiography accurately estimated hemodynamic status in HVAD patients. This algorithm reliably detected high RAP and LAP. Notably, high RAP was associated with high wedge pressure and adverse outcome. The benefit of noninvasive estimation of hemodynamic status in the clinical management of patients with left ventricular assist devices needs further evaluation.

Boundary conditions effects on the particle dynamic flow in a rotary drum with a single flight

This study presents an experimental and numerical investigation of the particle dynamic flow in a rotary drum with one flight, under different boundary conditions. The Euler-Euler approach with the kinetic theory of granular flow was used for all CFD simulations. The influence of different specularity coefficient values and no-slip boundary condition was assessed varying the particle-particle restitution coefficient and the rotational speeds. The particle-particle restitution coefficient of glass beads was experimentally measured and the effect of this parameter on the particle dynamics was also investigated. A high-speed video camera was used to measure the flight unloading profile and the bed height of particles in rolling regime at the drum bottom. Quantitative and qualitative analysis were performed in order to compare the simulated results with the experimental data, and then to determine the appropriate parameters to represent the real particle flow. It was observed that the specularity coefficient value of 0.5 and the restitution coefficient of 0.9 represented well the particle flow behavior in the flight at the rolling regime for the different rotational speeds analyzed.

Proteomics investigation identifies prominent changes in synapse-related proteins in a fragile X mouse model

Fragile X syndrome (FXS) is a single gene disorder that is the most common heritable cause of intellectual disability and the most frequent monogenic cause of autism spectrum disorders (ASD). FXS is caused by trinucleotide repeats in the promoter region of the fragile X mental retardation gene (fmr1). This leads to the downregulation of the fragile X mental retardation protein (FMRP), which regulates translation of a wide range of proteins. The extent of expression level alterations of synaptic proteins affected by FMRP loss and their consequences on synaptic dynamics in FXS has not been fully investigated. Here, we have investigated the molecular mechanisms underlying FXS by identifying the molecular signature and elucidating the function of FXS-associated proteins. The first part of the study consists of an exploratory molecular profiling study on brain tissue samples of a fmr1 KO mouse model using shotgun label-free liquid chromatography mass spectrometry (LC-MS). These studies indicate that most of the changed proteins are involved in synaptic functions. Thus, as a next step we investigated synaptosomes from the cerebellum and hippocampus using LC-MS and label-based selected reaction monitoring (SRM). Key findings relate to altered levels of proteins involved in GABA-signalling in the cerebellum. To explore these findings further, FM1-43 dye was used in cultured hippocampal neurons and cerebellar Purkinje cells to track vesicle recycling and unloading profiles. Furthermore, ultrastructural analysis of synaptic vesicles of the GABA-ergic Purkinje cells in the cerebellum was performed to investigate potential pre-synaptic effects. Taken together, these studies provide novel insights into the molecular changes associated with FXS.

Viscoelastic shock wave in ballistic gelatin behind soft body armor

Ballistic gelatins are widely used as a surrogate of biological tissue in blunt trauma tests. Non-penetration impact tests of handgun bullets on the 10wt% ballistic gelatin block behind soft armor were carried out in which a high-speed camera recorded the crater׳s movement and pressure sensors imbedded in the gelatin block recorded the pressure waves at different locations. The observed shock wave attenuation indicates the necessity of considering the gelatin׳s viscoelasticity. A three-element viscoelastic constitutive model was adopted, in which the relevant parameters were obtained via fitting the damping free oscillations at the beginning of the creep-mode of rheological measurement, and by examining the data of published split Hopkinson pressure bar (SHPB) experiments. The viscoelastic model is determined by a retardation time of 5.5×10−5s for high oscillation frequencies and a stress relaxation time of 2.0–4.5×10−7s for shock wave attenuation. Using the characteristic-line method and the spherical wave assumption, the propagation of impact pressure wave front and the subsequent unloading profile can be simulated using the experimental velocity boundary condition. The established viscoelastic model considerably improves the prediction of shock wave attenuation in the ballistic gelatin.

Development of a geometric flight unloading model for flighted rotary dryers

Flighted rotary dryers are used extensively in industrial applications for the drying of granular materials, and the understanding of the unloading characteristics of the flights within these units is critical to understanding their behaviour. This paper presents the development of a geometrical derived model for the unloading profile of a generic two-section flight. This model is then validated using experimental data from a flight unloading apparatus. The model is shown to be able to accurately reproduce the observed unloading profiles, however the results are shown to be highly sensitive to the material surface angle used in the model. High-speed photography is used to observe the surface of the granular material during unloading and measurements of key properties are made. Observation of these high-speed images shows that the unloading of the flight is discontinuous, and that there are significant fluctuations in the behaviour of the discharging solids.

Residual Stress in an Autofrettaged Tube Taking Bauschinger Effect as a Function of the Prior Plastic Strain

Autofrettage is a practical method for increasing the elastic carrying capacity and the fatigue life of thick-walled cylinders such as cannon and high-pressure tubular reactor. Many analytical and numerical solutions for determining the residual stress distribution in an autofrettaged tube have been reported. It is still difficult to model the Bauchinger effect, which is dependent on the prior plasticity in an analytical solution. The reduced Young’s modulus during unloading affects residual stress distribution. However, until now this effect has not been considered in any analytical model. In this paper, an autofrettage analytical solution considering Young’s modulus and the reverse yield stress dependent on the prior plasticity, based on the actual tensile-compressive curve of the material and the von Mises yield criterion, has been proposed. New model incorporates the Bauschinger effect factor and the unloading modulus variation as a function of prior plastic strain, and hence of the radius. Thereafter it assumes a fixed nonlinear unloading profile. The comparison of predicted residual stress distribution by the present solution with that of fixed unloading curve model, and test results shows that the present solution gives accurate prediction of residual stress distribution of an autofrettaged tube. This analytical procedure for the cylinder permits an excellent representation of various pressure vessel steels.

Laser driven quasi-isentropic compression experiments (ICE) for dynamically loading materials at high strain rates

We demonstrate the recently developed technique of laser driven isentropic compression (ICE) for dynamically compressing Al samples at high laoding rates close to the room temperature isentrope and up to peak stresses above 100GPa. Upon analysis of the unloading profiles from a multi-stepped Al/LiF target a continuous path through Stress-Density space may be calculated. For materials with phase transformations ramp compression techniques reveals the location of equilibrium phase boundaries and provide information on the kinetics of the lattice re-ordering.

Cyclic loading as an extended nanoindentation technique

Conventional depth sensing nanoindentation test which produces a load–depth curve for a monotonically increasing load can be used to determine many mechanical properties. Alternatively, if the specimen is loaded to a specific value, unloaded and immediately reloaded, a cyclic nanoindentation curve is produced. The unloading–reloading paths do not necessarily overlap in all materials. The reason for this is thought to be the different response of the dislocations generated under the indentation, in different materials. The dislocation behaviour will be controlled by the chemistry and microstructure of the material. Therefore, sensitive dislocation–microstructure interactions may be detectable in the unloading–reloading curves during cyclic indentation. This paper reports such cyclic nanoindentation investigation done in calcium-doped gold used in wire bonding. It is shown that calcium, even in ppm levels, can influence the cyclic load–depth curves to measurable extents. The loading and unloading profiles obtained are reported and the effect of increasing dopant level is evident in them. This is attributed to dislocation–solute interactions. The microstructure of the material consists of elongated (drawn) grains of diameter of about 200 nm and length of a few micrometers. It is concluded that cyclic nanoindentation could be used as an extended technique to extract sensitive material information that are not reflected in the conventional test.