Magnetorheological Variable Stiffness Robot Legs for Improved Locomotion Performance

In an increasingly automated world, interest in the field of robotics is surging, with an exciting branch of this area being legged robotics. These biologically inspired robots have leg-like limbs which enable locomotion, suited to challenging terrains which wheels struggle to conquer. While it has been quite some time since the idea of a legged machine was first made a reality, this technology has been modernised with compliant legs to improve locomotion performance. Recently, developments in biological science have uncovered that humans and animals alike control their leg stiffness, adapting to different locomotion conditions. Furthermore, as these studies highlighted potential to improve upon the existing compliant-legged robots, modern robot designs have seen implementation of variable stiffness into their legs. As this is quite a new concept, few works have been published which document such designs, and hence much potential exists for research in this area. As a promising technology which can achieve variable stiffness, magnetorheological (MR) smart materials may be ideal for use in robot legs. In particular, recent advances have enabled the use of MR fluid (MRF) to facilitate variable stiffness in a robust manner, in contrast to MR elastomer (MRE). Developed in this thesis is what was at the time the first rotary MR damper variable stiffness mechanism. This is proposed by the author for use within a robot leg to enable rapid stiffness control during locomotion. Based its mechanics and actuation, the leg is termed the magnetorheological variable stiffness actuator leg mark-I (MRVSAL-I). The leg, with a C-shaped morphology suited to torque actuation is first characterised through linear compression testing, demonstrating a wide range of stiffness variation. This variation is in response to an increase in electric current supplied to the internal electromagnetic coils of the MR damper. A limited degrees-of-freedom (DOF) bipedal locomotion platform is designed and manufactured to study the locomotion performance resulting from the variable stiffness leg. It is established that optimal stiffness tuning of the leg could achieve reduced mechanical cost of transport (MCOT), thereby improving locomotion performance. Despite the advancements to locomotion demonstrated, some design issues with the leg required further optimisation and a new leg morphology

Magnetic resonance imaging of myocardial strain after acute ST-segment-elevation myocardial infarction: a systematic review

The purpose of this systematic review is to provide a clinically relevant, disease-based perspective on myocardial strain imaging in patients with acute myocardial infarction or stable ischemic heart disease. Cardiac magnetic resonance imaging uniquely integrates myocardial function with pathology. Therefore, this review focuses on strain imaging with cardiac magnetic resonance. We have specifically considered the relationships between left ventricular (LV) strain, infarct pathologies, and their associations with prognosis. A comprehensive literature review was conducted in accordance with the PRISMA guidelines. Publications were identified that (1) described the relationship between strain and infarct pathologies, (2) assessed the relationship between strain and subsequent LV outcomes, and (3) assessed the relationship between strain and health outcomes. In patients with acute myocardial infarction, circumferential strain predicts the recovery of LV systolic function in the longer term. The prognostic value of longitudinal strain is less certain. Strain differentiates between infarcted versus noninfarcted myocardium, even in patients with stable ischemic heart disease with preserved LV ejection fraction. Strain recovery is impaired in infarcted segments with intramyocardial hemorrhage or microvascular obstruction. There are practical limitations to measuring strain with cardiac magnetic resonance in the acute setting, and knowledge gaps, including the lack of data showing incremental value in clinical practice. Critically, studies of cardiac magnetic resonance strain imaging in patients with ischemic heart disease have been limited by sample size and design. Strain imaging has potential as a tool to assess for early or subclinical changes in LV function, and strain is now being included as a surrogate measure of outcome in therapeutic trials

International Climate Efforts Beyond 2012: A Survey of Approaches

Provides an overview of key issues in the design and negotiation of future international climate efforts and describes how various proposals seek to address them. Outlines criteria for assessing different options from a policy and a political perspective

Site-resolved imaging of a fermionic Mott insulator

The complexity of quantum many-body systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantum-mechanical degrees of freedom. Probing these systems on a microscopic level with single-site resolution offers important insights. Here we report site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators using ultracold atoms in a square lattice. For strong repulsive interactions we observe two-dimensional Mott insulators containing over 400 atoms. For intermediate interactions, we observe a coexistence of phases. From comparison to theory we find trap-averaged entropies per particle of $1.0\,k_{\mathrm{B}}$. In the band-insulator we find local entropies as low as $0.5\,k_{\mathrm{B}}$. Access to local observables will aid the understanding of fermionic many-body systems in regimes inaccessible by modern theoretical methods.Comment: 6+7 page

Parton theory of magnetic polarons: Mesonic resonances and signatures in dynamics

When a mobile hole is moving in an anti-ferromagnet it distorts the surrounding Neel order and forms a magnetic polaron. Such interplay between hole motion and anti-ferromagnetism is believed to be at the heart of high-Tc superconductivity in cuprates. We study a single hole described by the t-Jz model with Ising interactions between the spins in 2D. This situation can be experimentally realized in quantum gas microscopes. When the hole hopping is much larger than couplings between the spins, we find strong evidence that magnetic polarons can be understood as bound states of two partons, a spinon and a holon carrying spin and charge quantum numbers respectively. We introduce a microscopic parton description which is benchmarked by comparison with results from advanced numerical simulations. Using this parton theory, we predict a series of excited states that are invisible in the spectral function and correspond to rotational excitations of the spinon-holon pair. This is reminiscent of mesonic resonances observed in high-energy physics, which can be understood as rotating quark antiquark pairs. We also apply the strong coupling parton theory to study far-from equilibrium dynamics of magnetic polarons observable in current experiments with ultracold atoms. Our work supports earlier ideas that partons in a confining phase of matter represent a useful paradigm in condensed-matter physics and in the context of high-Tc superconductivity. While direct observations of spinons and holons in real space are impossible in traditional solid-state experiments, quantum gas microscopes provide a new experimental toolbox. We show that, using this platform, direct observations of partons in and out-of equilibrium are possible. Extensions of our approach to the t-J model are also discussed. Our predictions in this case are relevant to current experiments with quantum gas microscopes for ultracold atoms.Comment: 30 pages, 4 appendices, 26 figure

PENGARUH DISIPLIN KERJA DAN MOTIVASI KERJA TERHADAP KINERJA KARYAWAN PADA HOTEL GRAND TJOKRO KLATEN

Penelitian ini bertujuan untuk mengetahui: (1) tingkat disiplin kerja, motivasi kerja, dan kinerja karyawan pada karyawan Hotel Grand Tjokro Klaten, (2) pengaruh disiplin kerja terhadap kinerja karyawan pada karyawan Hotel Grand Tjokro Klaten, (3) pengaruh motivasi kerja terhadap kinerja karyawan pada karyawan Hotel Grand Tjokro Klaten, dan (4) pengaruh disiplin kerja dan motivasi kerja terhadap kinerja karyawan pada karyawan Hotel Grand Tjokro Klaten. Penelitian ini termasuk penelitian asosiatif kausal dengan pendekatan kuantitatif. Populasi dari penelitian ini adalah seluruh karyawan Hotel Grand Tjokro Klaten berjumlah 90 orang. Data dikumpulkan dengan kuesioner yang telah diuji validitas dan reliabilitasnya. Teknik analisis data yang digunakan adalah regresi berganda. Hasil penelitian menunjukkan bahwa: (1) disiplin kerja karyawan Hotel Grand Tjokro Klaten dalam kategori sedang (60,0%), motivasi kerja karyawan Hotel Grand Tjokro Klaten dalam kategori sedang (52,2%), dan kinerja karyawan Hotel Grand Tjokro Klaten dalam kategori sedang (68,9%), (2) disiplin kerja berpengaruh positif terhadap kinerja karyawan Hotel Grand Tjokro Klaten. Hal ini dibuktikan dengan koefisien beta sebesar (β) sebesar 0,218 dan p=0,001. Kontribusi pengaruh disiplin kerja terhadap kinerja karyawan sebesar (ΔR2) 0,033 atau 3,3%; (3) motivasi kerja berpengaruh positif terhadap kinerja karyawan Hotel Grand Tjokro Klaten. Hal ini dibuktikan dengan koefisien beta sebesar (β) 0,276 dan p=0,000. Kontribusi pengaruh motivasi kerja terhadap kinerja karyawan sebesar (ΔR2) 0,056 atau 5,6%; dan (4) disiplin kerja dan motivasi kerja mempunyai pengaruh positif terhadap kinerja karyawan Hotel Grand Tjokro Klaten. Hal ini dibuktikan dengan koefisien beta (β) pada variabel disiplin kerja sebesar 0,144 dan p=0,027; dan koefisien beta (β) pada variabel motivasi kerja sebesar 0,232 dan p=0,000. Kontribusi pengaruh disiplin kerja dan motivasi kerja terhadap kinerja karyawan sebesar (ΔR2) 0,068 atau 6,8%

Inappropriate electrolyte repletion for patients undergoing endoscopic procedures

At Thomas Jefferson University Hospital (TJUH), there has been a perceived necessity among housestaff and fellows to routinely check and replete serum potassium and magnesium for inpatients prior to endoscopic procedures In addition, there was an unwritten policy that these electrolytes needed to be aggressively repleted, with a goal potassium above 4.0 and magnesium above 2.0 Contributing factors include absence of clear policy, fear of adverse outcomes during procedures, and fear of delay of procedures leading to increased hospital stay This practice has led to unwarranted lab draws, costs of lab tests and electrolyte riders, and possible delayed procedures Goals Clarify policies regarding electrolyte repletion Determine frequency of inappropriate electrolyte checking and repletion Determine monetary cost of this action Decrease frequency of inappropriate electrolyte lab check and repletionhttps://jdc.jefferson.edu/patientsafetyposters/1023/thumbnail.jp

String patterns in the doped Hubbard model

Understanding strongly correlated quantum many-body states is one of the most difficult challenges in modern physics. For example, there remain fundamental open questions on the phase diagram of the Hubbard model, which describes strongly correlated electrons in solids. In this work we realize the Hubbard Hamiltonian and search for specific patterns within the individual images of many realizations of strongly correlated ultracold fermions in an optical lattice. Upon doping a cold-atom antiferromagnet we find consistency with geometric strings, entities that may explain the relationship between hole motion and spin order, in both pattern-based and conventional observables. Our results demonstrate the potential for pattern recognition to provide key insights into cold-atom quantum many-body systems.Comment: 8+28 pages, 5+10 figure