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Push-On Push-Off: A Compliant Bistable Gripper with Mechanical Sensing and Actuation
Get PDFGrasping is an essential task in robotic applications and is an open challenge due to the complexity and uncertainty of contact interactions. In order to achieve robust grasping, systems typically rely on precise actuators and reliable sensing in order to control the contact state. We propose an alternative design paradigm that leverages contact and a compliant bistable mechanism in order to achieve sensing and actuation purely mechanically. To grasp an object, the manipulator holding our end effector presses the bistable mechanism into the object until snap-through causes the gripper to enclose it. To release the object, the tips of the gripper are pushed against the ground, until rotation of the linkages causes snap-through in the other direction. This push-on push-off scheme reduces the complexity of the grasping task by allowing the manipulator to automatically achieve the correct grasping behavior as long as it can get the end effector to the correct location and apply sufficient force. We present our dynamic model for the bistable gripping mechanism, propose an optimized result, and demonstrate the functionality of the concept on a fabricated prototype. We discuss our stiffness tuning strategy for the 3D printed springs, and verify the snap-through behavior of the system using compression tests on an MTS machine.
Acknowledgements
Support for this project has been provided in part by NSF Grant No. 1138847 and DGE-1845298. We also thank Terry Kientz, Jeremy Wang, Peter Szczesniak, and Joe Valdez for their assistance with the fabrication, and Neal Tinaikar for assistance with initial prototypes. We are grateful
Interactive Journaling as a Positive Intervention: Examining an Established Practice Through the Lens of Positive Psychology
Get PDFInteractive Journaling is a structured writing process that motivates and guides individuals toward positive change and greater well-being in target life areas. This paper maps the properties of Interactive Journaling to core properties and criteria of positive interventions – activities within the field of positive psychology that are empirically validated and strive to promote well-being. These properties include underpinnings in the evidence-based paradigm of expressive writing, an emphasis on participant agency and person-activity fit, and other evidence-based norms within the practice of Interactive Journaling. Based on this alignment, Interactive Journaling can be considered a positive intervention. Existing positive interventions may also be enhanced when integrated into the Interactive Journaling framework. Researchers are invited to examine Interactive Journaling more closely using validated well-being measures and new populations
Module 4: Civil Liberties After 9/11 (2004)
Get PDFhttps://repository.upenn.edu/teachingbeyondsept11-domestic-policy/1001/thumbnail.jp
Periapical Healing following Endodontic Microsurgery with Collagen Based Bone Filling Material: A Randomized Controlled Clinical Trial
Get PDFImaging Glutamate In The Human Brain At Ultra-High Magnetic Field: Advances And Applications
Get PDFGlutamate is one of the primary neurotransmitters in the human brain, and many unanswered questions in neuroscience, psychiatry and medicine revolve around this molecule: its production, transport, conversion or degradation, regulation and effects. Yet, to date, methods for actually measuring glutamate within the human body are extremely limited. Amongst the few options in the medical imaging toolbox are magnetic resonance spectroscopy (MRS) and a recently introduced specialized form of magnetic resonance imaging (MRI) known as glutamate-weighted chemical exchange saturation transfer imaging, or gluCEST. MRS, while providing good specificity at high field strengths, lacks spatial or temporal resolution. GluCEST has the potential to provide excellent spatial resolution, but has generally been limited to single-slice acquisitions with sub-optimal B1 correction, precluding its wider application to volumetric measurements of brain structures. In this thesis, we present a novel way to correct gluCEST for B1 inhomogeneity, yielding higher quality images. We then demonstrate expansion of single-slice gluCEST imaging to volumetric ‘slab’ imaging, greatly expanding our ability to capture specific structures within the brain. We apply gluCEST in both two and three dimensions to investigate healthy brain physiology as well as the response of healthy subjects to transcranial magnetic stimulation (TMS). We were able to detect elevated gluCEST in the dentate gyrus in the brains of healthy subjects, the first non invasive measurement of its kind pertaining to this small but vital structure. We also detected, for the first time, a change in glutamate concentration in the brains of subjects who have received TMS. Finally, we present work in the area of spectroscopy, presenting a technique in which –in sharp contrast to existing methodologies requiring non-standard hardware-- metabolic dynamics of glutamate can be detected using only proton-based chemical shift imaging (CSI) in conjunction with oral ingestion of deuterium labeled glucose. While itself limited in spatial resolution, this ability to detect and visualize the dynamic neural metabolism of glucose to glutamate provides a deeply complimentary source of information to gluCEST. In the future, qCSI and gluCEST could be used in tandem to provide next-generation precision diagnostics for patients suffering from neurological maladies of metabolic origin
Some Results On Two-Dimensional Lattice Random Field Models
Get PDFThis dissertation deals with two different stochastic processes defined on the two-dimensional integer lattice. These are the random field Ising model with Gaussian disorder and the Gaussian free field. In each case the questions we study are different but throughout the goal is to understand the large-scale (macroscopic) behavior of the process. Likewise, the techniques used to analyze each model will be different, but throughout there will be an emphasis on geometric thinking and the properties of Gaussian processes. The results can be roughly summarized as follows\begin{itemize} \item The correlation length of the random field Ising model scales as as the disorder strength goes to 0. \item For a metric Gaussian free field defined on a square of size and a macroscopic annulus inside that box, the length of the shortest crossing of the annulus by a path where the field is positive is at most . \item When defined on a rectangle, the metric graph and discrete Gaussian free fields exhibit different crossing probabilities. That is, the probability that there exists a path connecting the left and right sides of the box on which the field is positive differs between the two models. \end{itemize
Trailblazing Motivation And Marginalized Group Members: Defying Expectations To Pave The Way For Others
No full textResearch on employees from marginalized groups finds that when they feel like tokens, they can experience lower well-being and lower levels of job-satisfaction, which can lead them to disengage from their work over time. How might marginalized group members overcome these negative effects, given that it is often challenging for them to remove or completely avoid the causes of feeling like a token? To help answer this, I focus specifically on one antecedent of tokenism – low expectations based on group membership. Research on stereotype reactance indicates that marginalized group members may sometimes rebuff low expectations and strive to prove them wrong, but this response is not fully understood. Importantly, this research takes for granted that people who seek to prove expectations wrong are driven by self-related motives, despite passing reference to concerns for the stereotyped group and anecdotal examples to the contrary. To address this discrepancy, I introduce trailblazing motivation, which captures the desire to set new precedents that open doors for others. I argue that for marginalized group members, trailblazing motivation is activated to the extent that people perceive low expectations and feel a greater sense of belonging with their broad marginalized group. I further hypothesize that trailblazing motivation will attenuate the negative effects of feelings of tokenism on persistence. I test and find robust support for these hypotheses across a time-lagged survey study and two experiments
Study Of Metal Catalysts Supported On Thin Films Of Perovskites Prepared By Atomic Layer Deposition (ald)
Get PDFSintering is a severe problem for supported-metal catalysts in high-temperature applications, such as in automotive-emissions control, because it leads to a loss of catalytically active surface area. To stabilize the metal particles, in 2001, the Daihatsu group proposed using perovskite-supported metals, which they referred to as “intelligent” catalysts. The original goal was to regenerate sintered metals by driving the metal into the oxide lattice by high-temperature oxidation and releasing the metal as small particles by reduction. Unfortunately, the concept has not been entirely successful, partially because of the large crystallite size and low surface areas of typical perovskites. To achieve higher surface areas and reduce the length scale for any ingress-egress of metal particles, Atomic Layer Deposition (ALD) was used in this thesis to prepare thin films of perovskites on high-surface-area supports. These ALD films were shown to be uniform and thermally stable under high-temperature operating conditions. Metal catalysts, Pt, Ni, Pd, and Rh, were deposited onto the perovskite thin films, LaCoO3 and LaFeO3, using ALD. The catalysts exhibited several key properties similar to bulk “intelligent” catalysts. First, the metal particles could be stabilized by the perovskite films under high-temperature conditions. Second, the ALD platinum-group metal catalysts showed self-regenerative activity in CO oxidation upon oxidation and reduction at high temperatures. Third, like the Ni ex-solved from bulk perovskite materials, Ni supported by ALD perovskite films showed superior coking resistance towards methane. The metal particles in this thesis were likely very different from bulk intelligent catalysts because the film thickness was much smaller than the metal particle size. To understand their behaviors, this thesis focused on studying metal-perovskite interactions in the ALD samples of metals supported on LaFeO3 films. It was found that metal-perovskite interactions could dramatically affect the preferential alignment of metal particles with the substrate, the metal dispersions, and catalytic activity. In the presence of the perovskite films, the equilibrium oxidation of the metals could also shift several order-of-magnitudes towards lower PO2. The changes in the thermodynamic properties would further cause different catalytic behaviors. Systems of different metals supported on LaFeO3 films were studied and compared; it was found that the metal-perovskite interaction is specific for each system
Insights Into Inherited Thrombocytopenia Resulting From Mutations In Etv6 Or Runx1 Using A Human Pluripotent Stem Cell Model
Get PDFInherited thrombocytopenia results in low platelet counts and increased bleeding. Subsets of these patients have monoallelic germline mutations in either ETV6 or RUNX1 and thus a heightened risk of developing hematologic malignancies. Patients with mutations in either of these transcription factors display the same phenotype of small megakaryocytes that give rise to fewer, less-functional platelets. Utilizing CRISPR/Cas9 technology, we compared and contrasted the in vitro phenotype of hematopoietic progenitor cells and megakaryocytes derived from induced pluripotent stem cell (iPSC) lines harboring mutations in either ETV6 or RUNX1. Both mutant lines display phenotypes consistent with a platelet-related bleeding disorder. Surprisingly, these cellular phenotypes were distinct, suggesting that the mechanisms driving the thrombocytopenia are different. The iPSCs harboring a mutation in ETV6 yield significantly more hematopoietic progenitor cells and megakaryocytes, but the megakaryocytes are immature and less responsive to agonist stimulation. On the contrary, iPSCs with a heterozygous mutation in RUNX1 yield significantly fewer hematopoietic progenitor cells and megakaryocytes, but the megakaryocytes are more responsive to agonist stimulation, though both mutant-MK populations have deficient proplatelet formation. Our work highlights that while patients harboring germline ETV6 or RUNX1 mutations have similar clinical phenotypes, the mechanisms by which these occurs are distinct. This work emphasizes the importance of defining the exact nature of a mutation in patients with a phenotypically similar disorder, as the disease pathology and therapeutic interventions may be different
On Optimizing The Radio Side-Channel For Application Modeling
Get PDFThis dissertation introduces techniques for passively determining the instructions executed by embeddedmicrocontroller devices. Microcontroller applications are increasingly important for programmed mechanical control, analog sensor input, human interface operations and other roles, and when connected form an Internet of Things (IoT). Their simplicity, programmability, robust I/O, small size, low energy, low cost and widespread uses in vehicles, medical devices, wearables, thermostats, toasters, and myriad ”smart” systems have led to estimates of many tens of billions deployed in the near future. Their ubiquity and importance make them attractive targets for malicious actors. Today’s malware often evades detection. This thesis introduces novel techniques to exploit electromagnetic (EM) side-channels to overcome this threat.
First, we rely on the observation of the EM field. CMOS microcontroller chips create complex currentfluctuations on the ground and power wiring as circuits open and close. The wiring acts as an antenna, emanating in the RF spectrum. We record emissions from a running system with a software defined radio and use a principled analysis of the EM field to yield far more information than reported in prior work.
Second, we develop a robust theory relating application operation and produced radiation and use novelinformation recovery and feature extraction methods to recover a full understanding of the applications with zero prior knowledge of the code. This allows anomalies in a device under test to be detected by comparison against a reference model from a known, reliable device. This is a major advantage in the common case of proprietary application code.
Finally, these claims are validated with measurements across a diverse set of complex applications using arealized system incorporating the novel signal capture, analysis, and application modeling schemes. The principled design and robust theoretical foundations have resulted in an implementation on inexpensive commodity hardware that outperforms published prior work. Particulars of the design enable other capabilities beyond malware in microcontrollers, including the detection of hardware failures, software operation debugging, and reverse engineering, to detect faults or suspicious activities that originate early in the device supply-chain