Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Subject "compression"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Bear Hug: The Design and Development of an Active Deep Touch Pressure Garment for Sensory Processing Disorder
    (2017-08) Duvall, Julia
    Many medical conditions, including sensory processing disorder (SPD), employ compression therapy as a form of treatment. SPD patients often wear weighted or elastic vests to produce compression, deep touch pressure (DTP), on the body, which have been shown to have a calming effect on the wearer. Unfortunately, current products (weighted vests and blankets, pneumatic garments, and negative ease stretch garments) are unable to meet their wearers’ needs, in that they are unable to both provide the dynamic compression required, while also meeting the user’s comfort needs by being unobtrusive. Recent advances in compression garment technology incorporate active materials to produce dynamic, low bulk compression garments that can be remotely controlled. The purpose of this thesis is twofold, first, to identify requirements for a DTP therapy garment, and second, to a build a dynamic garment for DTP therapy. A literature review, a qualitative investigation with experts and occupational therapists, and a quantitative study of current DTP garments were used to build a problem variable framework for a more optimal DTP therapy garment. The variables that were identified fell into two major categories; system variables, which encompass the basic important features needed in order to provide DTP on the body, and usability variables, which are the other important features required for an effective and efficient system. Following this investigation, an active compression vest using shape memory alloy (SMA) spring actuators was developed in order to better meet these requirements than existing DTP products. The vest prototype incorporates 16 SMA spring actuators (1.25 mm diameter, spring index = 3) that constrict when heated, producing large forces and displacements that can be controlled via an applied current. When power is applied (up to 43.8 W), the prototype vest generates increasing magnitudes of pressure (up to 37.6 mmHg, spatially averaged across the front of the torso) on a representative child-sized form. Average pressure generated was measured up to 71.6% of the modeled pressure, and spatial pressure non-uniformities were observed that can be traced to specific garment architectural features. Although there are no consistent standards in magnitude of applied force in compression therapy garments, it is clear from comparative benchmarks that the compression produced by this garment exceeds the demands of the target application. Additionally, the garment can produce a dynamic and controllable pressure durations and magnitudes within a low and unobtrusive form factor, which are identified as important requirements for DTP therapy. There are several variables that require further investigation, including thermal comfort of the garment. This study demonstrates the viability of SMA-based compression garments as an enabling technology for individualized and enhanced SPD (and other compression-based) treatment. Additionally, the technology can be used as a tool to determine and standardize optimal treatment parameters.
  • Thumbnail Image
    Item
    Data supporting 'Subdiffusion of loci and cytoplasmic particles are different in compressed E. coli cells'
    (2018-05-15) Yu, Shi; Sheats, Julian; Cicuta, Pietro; Sclavi, Bianca; Cosentino Lagomarsino, Marco; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D
    The complex physical nature of the bacterial intracellular environment remains largely unknown, and has relevance for key biochemical and biological processes of the cell. While recent work has addressed the role of non-equilibrium drives and crowding, the consequences of mechanical perturbations are relatively less explored.We have used a microfabricated valve system to track both fluorescently labeled chromosomal loci and cytoplasmic particles in E.~coli cells shortly after the application of a compressive force on time scales that are too sudden to allow for biochemical response from the cell. While cytoplasmic diffusion is slowed down significantly under compression, the mobility of DNA loci is much less affected. These results suggest that the dynamics of the bacterial chromosome are decoupled from the viscoelastic environment of the cytoplasm under such short time scales, and that DNA elasticity and nucleoid organization play a more important role in loci subdiffusion than cytoplasmic viscoelasticity.
  • Thumbnail Image
    Item
    debreach: Selective Dictionary Compression to Prevent BREACH and CRIME
    (2017-07) Paulsen, Brandon
    Compression side-channel attacks like CRIME and BREACH have made compression a liability even though it is a powerful tool for improving efficiency. We present debreach, a step towards a general and robust mitigation for these attacks. A modified DEFLATE compressor with output that is fully backwards-compatible with existing decompressors, debreach has the ability to mitigate compression side-channels by excluding from compression sensitive data (e.g., security tokens, emails) identified either by explicit byte ranges or through string matching. In terms of usability, security, and efficiency, we find that string matching is well-suited to the task of protecting security tokens, but we also find that existing approaches to token security work equally as well. On the other hand, we find explicit byte ranges are well-suited to protect arbitrary content, whereas existing approaches lack in either efficiency or generality. When compared to the widely-used and insecure zlib in realistic scenarios, explicit byte ranges reduce throughput in networked connections by 16-24% on popular website's data, though this still results in a 106-269% improvement over not compressing depending on the available bandwidth. While the reduction is significant, we show that debreach can still improve throughput on connections between 112-208 Mb/s. We end with a discussion of practical use cases for debreach along with suggestions for their implementation and potential improvements to the algorithm.
  • Thumbnail Image
    Item
    Discovery, characterization, and pharmaceutical applications of two loratadine- oxalic acid cocrystals
    (2020-08) Liang, Zhengxuan
    Crystallization of multi-component crystals is widely used in pharmaceutical science to enhance the physiochemical properties, such as stability, mechanical properties and solubility. Loratadine (Lor) is a BCS II antihistamine drug commonly used to relieve the symptoms of allergy. It has high permeability but low solubility at physiological pHs. To overcome the problem of low solubility, we synthesized and fully characterized two Loratadine multi-component crystalline phases with oxalic acid (Oxa), i.e., a 1:1 Lor-Oxa conjugate acid-base cocrystal (Lor-Oxa CAB) and a 2:1 Lor-Oxa cocrystal monohydrate (Lor-Oxa hydrate). Both cocrystals exhibited adequate physical stability, enhanced solubility and, higher intrinsic dissolution rate than Lor. The intrinsic dissolution rate of Lor-Oxa CAB is 90 times that of Lor, which makes it a promising candidate for tablet formulation development.
  • Thumbnail Image
    Item
    Dynamic Compression for Novel Haptic Interactions
    (2020-12) Foo, Esther
    The sense of touch is an integral part of our everyday experiences. This research examines one of the ubiquitous touch sensations—compression, as a novel interface and mode of interaction. Specifically, it seeks to answer questions related to how people experience compression stimulus given varying compression inputs, applications and contexts. This work first investigates user perception of on-body compression, broadly, from an experience standpoint, including the consideration of parameters (varying compression intensity, duration, pattern, location) and confounds that influence user experience. In order to understand, evaluate, and deploy garment-based compression, however, advancements in wearable technology were required. Therefore, a portion of this work was also dedicated to the design and development of novel compression garment technologies. Taking a human-centered and iterative design approach, soft, garment-based compression technologies driven by shape memory alloy (SMA) actuation—a type of soft robotic actuator—were developed. The second half of this research builds upon the initial findings and examines application-specific cases of such compression technologies, with particular focus on its use in communicating and modulating emotions. The first application on the communication of emotions was motivated by the close relationship between social touch and emotions. Through two online surveys, this research characterized user expectations in selecting strategies of various intensities and patterns on different body locations for emotional communication through warm, compressive actuation (as afforded by the SMA garment), while delimiting/categorizing the range of mental models used during the process. The second application area involves the use of compression for affect modulation. Through a mindful meditation study augmented with compressive haptics delivered through the SMA-based garment, the potential of using compression to promote focused attention and facilitate an overall, positive meditation experience for novice practitioners was demonstrated. Ultimately, the results of this research give rise to new opportunities in a variety of applications and provide a roadmap for interface/interaction design in those context, including enabling new modes of interaction between users separated by distance (e.g., tele-rehabilitation, social mediated touch) as well as new haptic sensations in the area of immersive experiences (e.g., media augmentation, virtual reality).
  • Thumbnail Image
    Item
    Modeling Outputs of Efficient Compressibility Estimators
    (2018-06) Asamoah Owusu, Dennis
    There are times when it is helpful to know whether data is compressible before expending computational resources to compress it. The standard deviation of the byte distribution of data is an example of a measure of compressibility that does not involve actually compressing the data. This work considered five such measures of compressibility: byte standard deviation, shannon entropy, “average meaning entropy”, “byte counting” and “heuristic method”. We developed models that relate the output of these measures to the compression ratios of gzip, lz4 and xz using data retrieved from browsing Facebook, Wikipedia and YouTube. The models for byte standard deviation, shannon entropy and “average meaning entropy” were linear in both the parameters and the variables. The model for “byte counting” was non-linear in the predictor variable but linear in the parameters. The “heuristic method” was a classification model. In general, there was a strong relationship between the measures and the compressibility of a given data. Also, in many cases the models developed using one set of data from a source (like Youtube) was able to estimate the compressibility of another data set from the same source to a useful extent. This suggests the potential for developing a model per ECE for a source that can predict, to a useful degree, the compressibility of data from that source. At the same time, the differences in accuracy when models were evaluated on the data they were developed from versus when evaluated on new data from the same source indicate that there are important differences in the nature of the data coming from even the same source.
  • Thumbnail Image
    Item
    Supporting Data for Circular Dichroism of Distorted Double Gyroid Thin Film Metamaterials
    (2024-11-04) McGuinness, Emily; Magruder, Benjamin; Dorfman, Kevin; Ellison, Chris; Ferry, Vivian; veferry@umn.edu; Ferry, Vivian; Department of Chemical Engineering and Materials Science, University of Minnesota
    Strong circular dichroism (CD) has been reported in triply periodic, co-continuous gyroid thin films for certain orientations and surface terminations. However, processing of gyroid thin films introduces distortions experimentally, creating a mismatch between the structures created practically and those explored computationally. This work explores the impact of compression normal to the substrate (z-compression) with conserved volume in (110)-oriented plasmonic silver double gyroid thin films on CD using finite-difference time-domain (FDTD) simulations. As compression reaches fifteen percent and above, new features emerge including termination-dependent opposite-handed CD responses and, at larger compressions, shorter wavelength responses that span many surface terminations. The longest wavelength responses of the system red-shift with increasing compression. The top surface structure contributes strongly to the emerging opposite-handed features and red-shifting of wavelengths. However, the less surface termination dependent features arise from a mixture of contributions from the top surface and interior of the films. Interplay of these leads to CD-switching phenomena as a function of compression for certain terminations and wavelengths. When alternative methods are utilized to compress the system, such as compression with a Poisson’s ratio of 0.33 (comparable to polystyrene) or the generation of compressed equilibrium structures with non-affine strut changes via self-consistent field theory, similar optical responses persist. Overall, this study highlights the significant impact experimentally relevant distortions (especially compression and some non-affine structural shifts) can have on the CD response of block copolymer templated plasmonic double gyroid thin films, and provides mechanistic insight into the film interior versus surface contributions to the CD response during compression.