136879 research outputs found
Sort by
Exploration of New Passive and Active Attacks and Defense Methods for the KLJN and the VMG-KLJN Secure Key Exchangers
No full textThe Kirchhoff-Law-Johnson-Noise (KLJN) scheme is an unconditionally secure (information-theoretic) key exchanger based on the laws of classical statistical physics. The unconditional security of the KLJN scheme is provided by the Second Law of Thermodynamics, which requires thermal equilibrium (homogeneous temperature) for the system with zero flow. The KLJN scheme's foundational security principle was challenged by Vadai, Mingesz, and Gingl (VMG) through their VMG-KLJN system, which operates under inhomogeneous temperature and nonzero power flow conditions, while claiming equivalent security. Through our research, by applying various passive and active attacks against both schemes, we prove ideal KLJN scheme offers superior security over the VMG-KLJN scheme and reaffirm that thermal equilibrium remains the foundation of security. However, the VMG-KLJN method can, with appropriate countermeasures, be sufficiently secure for practical situations.
Our first study reveals that under practical conditions with nonzero cable capacitance and inductance, the VMG-KLJN scheme is vulnerable to certain passive attacks (crossover frequency attack and noise temperature attack), while the original KLJN scheme remains resistant against such attacks. In other words, the VMG-KLJN system is less secure than the original KLJN system. We also show that some of these vulnerabilities can be fixed by yet another new protocol that we introduce here. However at least one of these vulnerabilities will always remain. Thus, the information leak is never mathematically zero.
In our second study, the vulnerability of the VMG-KLJN key exchanger against two active attacks (current injection and voltage insertion attacks) is exposed. The security vulnerability arises from the fact that the effective driving impedances are different between the HL and LH cases for the VMG-KLJN scheme, whereas for the ideal KLJN scheme, they are the same. Two defense schemes are demonstrated, each effective against only one type of attack, but not against the two attacks simultaneously. The theoretical results are confirmed by computer simulations.
In the latter part of the dissertation, we demonstrate the security vulnerability of the ideal KLJN key exchanger and the VMG-KLJN key exchanger, respectively, against transient attacks. Transients start when Alice and Bob (two communicating parties) connect the wire to their chosen resistor at the beginning of each clock cycle. A transient attack occurs during a short duration of time, before the transients reflected from the ends of Alice and Bob mix together. The information leak arises from the fact that Eve (eavesdropper) monitors the cable and analyzes the transients during this time period. We demonstrate such a transient attack, and, then we introduce a defense protocol to protect against the attack. Computer simulations demonstrate that after applying the defense method the information leak becomes negligible
Influence of Saccharomyces cerevisiae CNCM I-1077 on the Intestinal Environment, Gut Permeability, and Markers of Systemic Inflammation in Horses Fed a High-Starch Diet
No full textThirty mature Quarter Horse geldings were used in a completely randomized 32-d study to test the hypotheses that supplemental live Saccharomyces cerevisiae CNCM I-1077 improves apparent digestion, stabilizes the intestinal environment, reduces gut permeability, and decreases inflammation in horses fed a high-starch diet. Horses were stratified by BW, age, and body condition score (BCS) to one of two treatments (n=15/treatment): concentrate formulated with 2g starch ��� kg BW^-1 ��� meal^-1 (CON) or the same concentrate top-dressed with 25 g/d Saccharomyces cerevisiae (SC; 20 billion CFU). Horses were fed individually in stalls every 12h. Between meals, horses were housed in dry-lots with ad libitum access to Coastal bermudagrass hay. On d 0 and 32, BW and BCS were recorded, and blood was collected prior to feeding at 2, 8, 16, and 24h post meal. Samples were analyzed for serum D-lactate, chemokine (CCL2) and cytokine (TNF��) concentrations. Whole blood 16s rRNA sequencing was performed. Fecal samples were obtained on d 0, 16, and 32 prior to feeding and at 8, 16, and 24h post meal; fecal pH and fecal starch were measured. Beginning d 28, intake and total fecal production were recorded over 4-d. There was an effect of treatment on ���BW (P=0.03), with no change in BCS (P=0.97). D-lactate peaked at h 8 on d 0, and CON was greater than SC (P���0.01). On d 32, D-lactate tended to be higher in SC at 16h compared to CON (P<0.10). LogCCL2 and TNF�� declined (P���0.02) across treatments to d 32. Fold change of percent reads from d 0 in bacterial 16s rRNA was not different between treatment groups. On d 0, fecal pH declined to h 16 (P���0.01) in both groups but returned to baseline by 24h. At h 0, CON had lower fecal pH on d 32 than d 0 (P���0.01). Fecal starch was undetectable indicating nearly complete dietary starch digestion. There was no effect of treatment for any measure of intake (P���0.25) or digestibility (P���0.77). High-starch diet reduced fecal pH and increased BW but after 32-d, there was no difference in digestibility, intestinal inflammation, or gut permeability, regardless of SC supplementation
Structural Composite Electrode for Space Applications
No full textStructural batteries offer a solution for more range-efficient vehicles with its multifunctional ability to hold mechanical load and store energy. The earth���s atmosphere and space environment require vehicles and satellites to have structures which are sturdy against potential environmental debris collisions and able to withstand low temperature. This thesis focuses on the material processing and electrochemical performance of a multifunctional structural composite electrode which consists of carbon fibers for structural reinforcement and a structural biphasic bicontinuous electrolyte (SBBE) for the composite matrix. The SBBE-coated carbon fiber versus lithium half-cell is studied in coin cell configuration. The solid biphasic bicontinuous electrolyte is made from lithium bis(trifluoromethanesulfonyl)imide salt, diglyme, and fluoroethylene carbonate for the liquid electrolyte ionic-conducting phase and resin for high modulus phase.
The effect of the pre-cured volume of SBBE (i.e., volume of SBBE pipetted on top of carbon fiber fabric prior to curing) on the electrochemical performance of the carbon fiber versus lithium foil half-cell in coin cell configuration was studied. After the solid biphasic electrolyte is cured as a layer on the carbon fiber fabric composite electrode, electrochemical characterizations were performed on structural composite electrode half cells with pre-cured SBBE volumes ranging from 25 to 100 ��������. Results indicated that the optimal structural battery volume is 50 �������� because it has the highest electrochemical charge and discharge capacity for the structural composite electrode versus lithium metal foil half-cell at 180 mAh/g for the first cycle, the lowest charge transfer resistance from the electrochemical impedance spectra, and relatively the highest anodic peak when comparing 5th cycle cyclic voltammograms of structural composite electrode with pre-cured SBBE volumes ranging from 25 to 100 ��������. Future work includes testing samples with biphasic electrolyte coated on desized carbon fiber tows on an in-situ electrochemo-mechanical coupling machine
Management Decisions for U.S. Ranches
No full textRanchers face many challenging decisions impacting operational longevity. This dissertation examines rancher decisions regarding 1) generational transfer of a family-operated ranch and 2) cow herd rebuilding strategies after drought. Chapter 1 provides an analysis of survey responses from U.S. ranchers regarding plans to transition their ranch to the next generation. Less than 40% of survey participants have a transition plan in place. Participants shared the details of their ranch transition plans or the roadblocks preventing them from developing a plan. Transition plan scenarios were developed based on producer responses to the survey.
In Chapter 2, transition plan scenarios from Chapter 1 were imposed on representative ranches, and financial performance was evaluated under each scenario. Ranch transition scenarios considered the use of business entities vs. sole proprietorships; willingness of parents to relinquish management or ownership to heirs; gifting vs. selling assets to heirs; buyouts between siblings; and asset balancing between on-farm and off-farm heirs.
For Chapter 3, different scenarios for cow herd rebuilding after drought were imposed on the representative ranches. The most common drought management response was partial liquidation of the cow herd. In this analysis, each representative ranch liquidated 20% of their mature cows during the drought. Post-drought herd rebuilding scenarios included slow-rebuild versus quick-rebuild strategies and strategies to rebuild with ranch-raised replacements versus rebuilding by purchasing females. Ranch financial performance was evaluated under each scenario, and results showed the optimal scenarios included retained replacement heifers during drought. For scenarios that did not include retained replacements during drought, quick-rebuild scenarios with purchased females were considered optimal; ranches under these scenarios were able to capitalize more on high cattle prices in the early post-drought years
Contrast-Independent Partially Explicit Time Discretization for Multiscale Problems and Its Application
No full textPartial differential equations are widely used in modeling and simulations. In many applications, there are high contrast changes in media properties. The implicit methods are typically used for temporal discretization and are unconditionally stable such that the time step size can be large during the computation. However, the implicit methods are more complicated to solve, especially for nonlinear problems. In contrast, the explicit methods are relatively easier to compute, while they require a much smaller time step size. This work focus on developing a contrast-independent partially explicit time discretization scheme for multiscale problems, specifically, nonlinear problems and also its application. The proposed method divides the spatial space into two components: contrast dependent (fast) and contrast independent (slow) spaces defined via multiscale space decomposition. Following this decomposition, temporal splitting is proposed that treats fast components implicitly and slow components explicitly. As a result, the scheme contains two equations, one implicit and the other explicit. The space decomposition and temporal splitting are chosen such that it guarantees a stability and formulate a condition for the time stepping. With the appropriate construction of spaces and stability analysis, we find that the required time step in our proposed scheme scales as the coarse mesh size, which creates a significant computational saving.
We first apply this approach on the parabolic diffusion reaction equations. We present numerical results and show that the proposed methods provide accuracy similar to implicit methods and the required time step size is independent of the contrast.
Nonlinear time fractional partial differential equations has wide application in physics and engineering. For the case of time fractional diffusion equations, the constraints on time steps are more severe and we extend our partially explicit methods to help alleviate this problem.
In our scheme, the implicit solution part can still be expensive, especially for nonlinear problems. Therefore, we introduce a modified partial machine learning algorithm to replace the implicit solution part of the original algorithm. Then we compute the explicit part of the solution using our splitting strategy. In addition, we use Proper Orthogonal Decomposition based model reduction to further improve our algorithms.
We extend the proposed scheme to solve multi-physics problems. We propose a partially explicit scheme with physics-based splitting. We take the convection diffusion equation as an example. In this scheme, we do a physics-based splitting, i.e. the convection equation is solved using the exact solution, and then we solve the diffusion equation via the partially explicit scheme
Development of a Finite Element Analysis (FEA) Model for Predicting Elbow Torque of the Apollo A7LB Extravehicular Activity (EVA) Spacesuit Pressurized Sleeve
No full textEVA spacesuits are critical to human survivability in the hostile environment of space, which consists of low atmospheric pressures (e.g., vacuum in LEO and on the lunar surface) and temperature extremes (e.g., ���65��C to 125��C in LEO). While spacesuits must protect humans against these conditions, maintaining an astronaut���s mobility is also crucial to achieve mission objectives such as in a return to the Moon as defined by the Artemis architectures. Spacesuit mobility is largely driven by the design of joints such as in the knees, shoulders, ankles, waist, and elbows. In the Apollo A7L/A7LB spacesuits, full circumferential rubber-dipped nylon convolutes were utilized in these joint locations. Understanding the Apollo elbow joint design���s mobility, in comparison to the Extravehicular Mobility Unit���s (EMU) flat pattern gore design, could provide new insights for the development of future spacesuits. In this research, an Abaqus FEA model was developed to predict elbow joint torques during pressurized bends using the A7L/A7LB pressure garment assembly arm configuration. The model was scripted to allow for simple adjustment of numerous design variables, such as the number and size of the convolutes. Through DOE studies, it was found that sleeve radius had the largest proportional effect on joint torque, while sleeve thickness and fabric bias direction Young���s modulus had smaller effects. Increasing number of convolutes reduced joint torque, but this effect diminished at larger numbers. Increasing operating pressure significantly increased joint torque, especially at high bend angles (such as 120 degrees). The results showed that lowest torque designs from these DOE studies required less joint torque than an Aerospace Human Systems Laboratory (AHSL) EMU FEA elbow model up to 55-60 degrees, and after 105 degrees. The model was also adjusted to available Apollo sleeve dimensions, and the material properties were approximated to yield joint torque data closely aligned with an A7LB empirical measurement in literature. Results showed this Apollo sleeve required less joint torque than the AHSL EMU model from 0-40 degrees. Lastly, the model was adjusted to an alternative convolute joint used in empirical joint testing, and joint torque results were the same order of magnitude as reported data
Hydro-Mechanical Study of Two Shrink-Swell Soils Under Hydrating and Shearing
No full textShrink-swell soils are a type of soil that expands and contracts in response to changes in moisture content. The soil is widely spread across the world and has become a prevalent geotechnical practice problem. The uneven shrink and swell behavior of shrink-swell soil causes damage to infrastructure and cost millions to repair. Most mechanical tests on shrink-swell soils have been conducted under oedometer conditions which restrict lateral movement. A limitation of such approach is that lateral soil strains are possible in practical problems. Triaxial tests, under controlled shear and confinement conditions, can represent better actual soil conditions. Very limited research has been conducted involving soil shearing and soaking behaviors under triaxial conditions, and they were related to low to intermediate expansive soils. Our research is pioneering in this area, exploring this feature of soil behavior of high to very high expansive clays under triaxial conditions. This study focuses on examining the behavior of unsaturated shrink-swell soils during shearing and soaking, aiming to offer reference soil data for civil structures like foundations and retaining walls built on these soils. It specifically investigates two types of shrink-swell soils, Texas natural soil and MX-80 bentonite, using an updated triaxial test protocol in the laboratory. The triaxial test results for Texas natural soil are utilized to validate the Barcelona Basic Model (BBM) in numerical modeling. Additionally, this dissertation includes a numerical study exploring the effect of horizontal swelling pressure on retaining wall structures in shrink-swell soil environments. The goal is to apply theoretical understanding of shrink-swell soils to address real-world geotechnical challenges. The behaviors of two shrink-swell soils under shearing and soaking are discussed and compared. The effects of stress level (particular deviatoric stress) on unsaturated shrink-swell soil volume change and final shear strength when subjected to soaking are investigated. The study also concludes how varying swelling properties of soils affect their behavior under shearing and soaking in different triaxial test conditions. BBM successfully replicates the behavior of Texas natural soil in terms of deviator stress and volume change under triaxial conditions. These insights contribute to setting benchmarks for shearing and soaking shear strength of shrink-swell soils in triaxial conditions and expanding the database available for the Texas region, aiding in foundation design. Moreover, the BBM helps to understand the distribution of horizontal swelling pressure on retaining walls, leading to simplified methods for inclusion in retaining wall design standards
Testing the Benefits of Using Silicon Photomultipliers on Organic Scintillator Portal Monitors
No full textRapid and accurate detection of radiation at checkpoints is of vital importance to national security. One proposed method for improving radiation detection capabilities is using Silicon Photomultipliers (SiPMs) on the organic scintillation panels used at checkpoints to detect radiation. Research on SiPMs has been relegated to small detectors with volumes in the cubic millimeter range, but large portal monitors are often used at ports of entry and traffic control points to monitor radiation. This research examined the efficacy of SiPMs placed on larger plastic scintillators with volumes orders of magnitude larger than previous tests have analyzed. For this research two arrays of SiPMs were determined to be the most advantageous due to superior intrinsic efficiency and were tested on plastic scintillators using three different gamma emitting isotopes. Experiments testing a single SiPM to a PMT when placed in geometrically similar configurations gave an average SiPM to PMT total count ratio of 0.0963 �� 0.0006 for the highest-energy gammas, which was within 5% of the expected value based on the ratio of the active areas of the single SiPM and PMT. However, when two arrays of SiPMs were selected based on numerical simulations and tested, the best ratio of SiPM to PMT total count ratio for a single array observing a source was 0.394 �� 0.001, which was within 5% of the active area ratio. SiPM arrays and PMTs were also compared by the ratio of source counts to background counts observed for each isotope, with the best SiPM array observing a ratio of 1.391 �� 0.003 while the PMT���s ratio was 1.584 �� 0.003 for the same isotope. Ultimately, the results of the study do not suggest that SiPMs are an optimal substitute for PMTs on large-volume plastic scintillators, but this result is not concluded decisively by the experiment���s results
Culturally Responsive Coaching for African American Parents of Children with Autism: A Single-Case Analysis, Qualitative Systematic, and Practitioner Paper
No full textAfrican American children and their families face a heightened susceptibility to disparities associated with autism (Dababnah et al., 2018). While advancements have been made in mitigating racial inequities in the identification of autism, Constantino et al. (2020) still report the existence of diagnostic delays for autism in Black children. This study suggests a gap of approximately three years between the period when parents initially express concerns about their child's developmental milestones and the eventual diagnosis of autism. The purpose of these three studies were (1) to identify how culturally responsive parent coaching for African American families of children with autism can increase parent implementation of naturalistic intervention strategies by conducting a multiple-probe single case experimental design across participants; (2) to conduct a qualitative systematic review on the experience and quality of studies on African American families of children with autism; 3) To provide a practitioner guideline of culturally responsive parent coaching, for educators and service providers working with African American families of children with autism.
The findings of the study indicated that culturally responsive parent coaching is effective in improving communication for African American parents and their children with autism. The findings from the second study reports the different experiences of African American families ranging from lack of source of support, cultural differences, cost of health care services, and parents lack of prior knowledge of autism. The third study provides a guideline for practitioners who serve culturally diverse families like African American parents.
The findings of these three studies presents several implications for practice and research. Service providers and healthcare professionals need to be trained to become more culturally responsive to better serve African American families. There is also a need for more research on the implementation of culturally responsive practice with African American families of children with autism
Disparities of Flood Risk in Urban Areas and Historically Marginalized Populations in Sarasota County, FL
No full textDisaster vulnerability and risk assessments typically focus on socioeconomic characteristics and physical hazards, often omitting factors such as risk perception. Assessing disaster risk using physical and standardized demographic data (i.e., census data) can limit risk assessment accuracy, as the results do not fully encapsulate the complexity of disaster vulnerability, risk, and resilience contexts. Risk perception is essential when planning for disasters because it directly affects how people and communities prepare for, respond to, and recover from disasters. Examining how a community perceives and reacts to a hazard can help planners develop more accurate risk assessments and help decision-makers more equitably allocate disaster resources and develop/implement community-relevant mitigation strategies. Flooding is the most common natural hazard and the leading cause of natural hazard fatalities in the US. For these reasons, it is crucial to develop a more accurate baseline of flood risk identification in addition to analyzing the geosocial relationships to vulnerability by analyzing risk perception, socioeconomic demographics, and urban growth. Finally, the capacity to recover from disasters is often directly correlated to socioeconomic inequality, historic marginalization, and the current structure of the political system. Communities with higher percentages of black, indigenous, and people of color (BIPOC) or low income per capita are often the last to see disaster recovery or risk reduction resources and, even then, are often underfunded and underserved. Historically marginalized demographics are also more likely than their white, affluent counterparts to live with higher exposure and vulnerability to flood hazard. Findings within this study have identified discrepancies within FEMA DFIRMs within smaller urban communities, and a reclassified floodplain better represented underestimated areas within Sarasota County. This reclassified floodplain allowed a further analysis into a geocoded risk perception survey to observe disparities of vulnerability based on sociodemographic variables and exposure to flood. This analysis showed significant positive correlation between perceived vulnerability to damage from flood and women exposed to flood. Additionally, while statistical significance was lacking for multiple relationships, regression models succeeded in showing relationship trends between marginalized groups and how their vulnerability to flood is affected by exposure to flood