Showing papers by "Drexel University published in 2022"

Fault Current Bypass-Based LVDC Solid-State Circuit Breakers

Abstract: This letter presents a new low-voltage direct-current fault current bypass-based solid-state circuit breaker (SSCB) using silicon-carbide mosfet s. The proposed SSCB provides the possibility to select the clamping voltage of metal–oxide varistors (MOVs) close to the nominal voltage of the dc system. This reduces voltage overshoots across the main switch and snubber components and extends the maximum allowable dc bus voltage on the SSCB. The MOVs are removed from the power line, and their leakage currents are completely eliminated. The clamping voltage of the MOV and its surge energy rating is considered to optimize the MOV. The dv/dt across the main switchis controlled by an auxiliary capacitor, where a design procedure is presented to optimize its value. Also, the stored inductive energy of the line inductor in dc systems is bypassed using an auxiliary branch and prevented from flowing through the faulty section to enhance the safety. LTspice simulations are presented to show the significance of the proposed SSCB. The experiments of 375 V/170 A/2.4 μs and 600 V/163 A/2.4 μs verify the effectiveness of the proposed design in practice.

Room-temperature high-precision printing of flexible wireless electronics based on MXene inks

Abstract: Abstract Wireless technologies-supported printed flexible electronics are crucial for the Internet of Things (IoTs), human-machine interaction, wearable and biomedical applications. However, the challenges to existing printing approaches remain, such as low printing precision, difficulty in conformal printing, complex ink formulations and processes. Here we present a room-temperature direct printing strategy for flexible wireless electronics, where distinct high-performance functional modules (e.g., antennas, micro-supercapacitors, and sensors) can be fabricated with high resolution and further integrated on various flat/curved substrates. The additive-free titanium carbide (Ti 3 C 2 T x ) MXene aqueous inks are regulated with large single-layer ratio (>90%) and narrow flake size distribution, offering metallic conductivity (~6, 900 S cm −1 ) in the ultrafine-printed tracks (3 μm line gap and 0.43% spatial uniformity) without annealing. In particular, we build an all-MXene-printed integrated system capable of wireless communication, energy harvesting, and smart sensing. This work opens a door for high-precision additive manufacturing of printed wireless electronics at room temperature.

Endurance-Aware Mapping of Spiking Neural Networks to Neuromorphic Hardware

Abstract: Neuromorphic computing systems are embracing memristors to implement high density and low power synaptic storage as crossbar arrays in hardware. These systems are energy efficient in executing Spiking Neural Networks (SNNs). We observe that long bitlines and wordlines in a memristive crossbar are a major source of parasitic voltage drops, which create current asymmetry. Through circuit simulations, we show the significant endurance variation that results from this asymmetry. Therefore, if the critical memristors (ones with lower endurance) are overutilized, they may lead to a reduction of the crossbar’s lifetime. We propose eSpine, a novel technique to improve lifetime by incorporating the endurance variation within each crossbar in mapping machine learning workloads, ensuring that synapses with higher activation are always implemented on memristors with higher endurance, and vice versa. eSpine works in two steps. First, it uses the Kernighan-Lin Graph Partitioning algorithm to partition a workload into clusters of neurons and synapses, where each cluster can fit in a crossbar. Second, it uses an instance of Particle Swarm Optimization (PSO) to map clusters to tiles, where the placement of synapses of a cluster to memristors of a crossbar is performed by analyzing their activation within the workload. We evaluate eSpine for a state-of-the-art neuromorphic hardware model with phase-change memory (PCM)-based memristors. Using 10 SNN workloads, we demonstrate a significant improvement in the effective lifetime.

An aqueous 2.1 V pseudocapacitor with MXene and V-MnO2 electrodes

Abstract: MXenes have shown record-breaking redox capacitance in aqueous electrolytes, but in a limited voltage window due to oxidation under anodic potential and hydrogen evolution under high cathodic potential. Coupling Ti3C2Tx MXene negative electrode with RuO2 or carbon-based positive electrodes expanded the voltage window in sulfuric acid electrolyte to about 1.5 V. Here, we present an asymmetric pseudocapacitor using abundant and eco-friendly vanadium doped MnO2 as the positive and Ti3C2Tx MXene as the negative electrode in a neutral 1 M Li2SO4 electrolyte. This all-pseudocapacitive asymmetric device not only uses a safer electrolyte and is a much less expensive counter-electrode than RuO2, but also can operate within a 2.1 V voltage window, leading to a maximum energy density of 46 Wh/kg. This study also demonstrates the possibility of using MXene electrodes to expand the working voltage window of traditional redox-capable materials.

High-Efficiency Bilateral S–SP Compensated Multiload IPT System With Constant-Voltage Outputs

Abstract: In this article, we propose a bilaterally transmitted domino-type multiload inductive power transfer (IPT) system for constant-voltage (CV) outputs, low voltage attenuation, and high efficiency. There are three major contributions. First, the series–series/parallel (S–SP) topology is developed to design the multiload IPT system, which can realize the load-independent CV outputs without using compensation inductors, enabling a compact IPT system. Second, a bilateral IPT structure is proposed with two parallel power transfer routes to mitigate the practical output voltage attenuation issue, resulting in a better CV property. Third, system efficiency is improved by the proposed bilateral IPT structure. With the bilateral S–SP compensated multiload IPT design, the output voltage attenuation analysis and system efficiency are investigated considering parasitic resistances. A 70 W six-load bilateral IPT prototype is implemented and compared with the unilateral counterpart. With k = 0.26 and Q = 300, the proposed bilateral IPT system validates an improved CV output with a small attenuation rate of 10.22%, which is much lower than the unilateral one. The maximum efficiency achieves 90.39%, showing 5.17% higher than the unilateral IPT system in the identical load condition.

Development and validation of the workplace hazing scale

Abstract: What is workplace hazing and how does it affect newcomers? Although most people associate hazing behaviors with university life, sports teams, or military organizations, hazing has been reported in...

Development of dynamic energy storage hub concept: A comprehensive literature review of multi storage systems

Abstract: Utilizing the Multi Energy Carrier System (MECS) or energy hub method is a practical tool to increase efficiency and reduce the cost of any energy conversion infrastructure. Reversible Energy Sources (RES) with variable availability and also the uncertain demand side energy needs are considered in these systems. In this regard, various chemical, mechanical and electrochemical energy storage technologies have been examined in literature to increase the energy hub performance. However, investigation of previous proposed models reveals lack of a comprehensive review study to develop a dynamic multi storage model in energy hubs. In the present study, achievements for development of single- and multi-energy storage systems in energy hubs are reviewed and classified. Accordingly, different comparison tables are proposed for energy storage systems in energy hubs based on type of stored energy carriers. Also, techno-economic characteristics of recent energy storage models in literature are studied. Considering the energy storage facilities applicability, the present review research will add valuable data to the body of review investigations in this field. The results of this study revealed that there are some technical deficiencies for multi energy storage phenomena in hybrid energy systems. These include the technical advantages of interconnected storage, multi discharging capability and modeling real operational constraints of facilities. Accordingly, conceptual development of a novel Dynamic Energy Storage Hub (DESH) is proposed and basic relations are discussed. The findings of current research could be used as a basis for related planning and operating optimization model developments in energy hub context.

Creative Arts Therapies for the Mental Health of Emerging Adults: A Systematic Review

Abstract: Emerging adults face significant risk of experiencing mental health problems, especially since most lifetime mental problems have first onset by age 24. Despite the pervasiveness of these issues, emerging adults face barriers in receiving help including stigma surrounding help-seeking behavior and negative attitudes about perceived usefulness of therapy. Creative and expressive art therapies (CATs) can address these needs by providing potentially destigmatized, non-invasive approaches to mental health care. To examine how this population can benefit from CAT, we conducted a systematic review of the literature to understand the types of CAT interventions that have been empirically tested among emerging adults. From a total of 7,276 articles published between 1985 and 2020, we filtered down to 11 studies, both qualitative and quantitative, meeting our inclusion and exclusion criteria. Results showed art therapy and poetry therapy were the most frequently studied CATs for the emerging adult population; and art therapy studies comprised the largest proportion of studies reporting statistical significance on its efficacy among all CATs reviewed. We highlight the need for more studies using replicable, generalizable methods in evaluating CAT. We then discuss implications for counselors, practitioners, and clinician-researchers interested in using CAT to improve mental health care among emerging adults.

Computational study of the mechanical influence of lacunae and perilacunar zones in cortical bone microcracking

Abstract: The mechanical behavior of cortical bone is influenced by microstructural components such as osteons, Haversian canals, and osteocyte lacunae that arise from biological remodeling processes. This study takes a computational approach to investigate the role of the perilacunar zones formed by the local remodeling processes of lacunar-dwelling osteocytes by utilizing phase-field finite element models based on histological imaging of human bone. The models simulated the microdamage accumulation that occurs in cortical bone under transverse compression in bone without lacunae, with lacunae, and with a perilacunar zone surrounding lacunae in order to investigate the role of these features. The results of the simulations found that while lacunae create stress concentration which initiate further damage, perilacunar regions can delay or prevent the emergence and growth of microcracks.

Rate-Dependent Fracture Behavior of Aerospace Epoxies: PR-520 and 3502

Abstract: To understand the response of polymeric materials used in fiber-reinforced composite structures, it is necessary to examine their brittle failure mechanisms under various loading scenarios....

Cost-effectiveness of dehydrated human amnion/chorion membrane allografts in lower extremity diabetic ulcer treatment

Abstract: To evaluate the cost-effectiveness and budget impact of using standard care (no advanced treatment, NAT) compared with an advanced treatment (AT), dehydrated human amnion/chorion membrane (DHACM), when following parameters for use (FPFU) in treating lower extremity diabetic ulcers (LEDUs).We analysed a retrospective cohort of Medicare patients (2015-2019) to generate four propensity-matched cohorts of LEDU episodes. Outcomes for DHACM and NAT, such as amputations, and healthcare utilisation were tracked from claims codes, analysed and used to build a hybrid economic model, combining a one-year decision tree and a four-year Markov model. The budget impact was evaluated in the difference in per member per month spending following completion of the decision tree. Likewise, the cost-effectiveness was analysed before and after the Markov model at a willingness to pay (WTP) threshold of $100,000 per quality adjusted life year (QALY). The analysis was conducted from the healthcare sector perspective.There were 10,900,127 patients with a diagnosis of diabetes, of whom 1,213,614 had an LEDU. Propensity-matched Group 1 was generated from the 19,910 episodes that received AT. Only 9.2% of episodes were FPFU and DHACM was identified as the most widely used AT product among Medicare episodes. Propensity-matched Group 4 was limited by the 590 episodes that used DHACM FPFU. Episodes treated with DHACM FPFU had statistically fewer amputations and healthcare utilisation. In year one, DHACM FPFU provided an additional 0.013 QALYs, while saving $3,670 per patient. At a WTP of $100,000 per QALY, the five-year net monetary benefit was $5003.The findings of this study showed that DHACM FPFU reduced costs and improved clinical benefits compared with NAT for LEDU Medicare patients. DHACM FPFU provided better clinical outcomes than NAT by reducing major amputations, ED visits, inpatient admissions and readmissions. These clinical gains were achieved at a lower cost, in years 1-5, and were likely to be cost-effective at any WTP threshold. Adoption of best practices identified in this retrospective analysis is expected to generate clinically significant decreases in amputations and hospital utilisation while saving money.

Long COVID and the Autonomic Nervous System: The Journey from Dysautonomia to Therapeutic Neuro-Modulation through the Retrospective Analysis of 152 Patients

Abstract: Introduction. The severity and prevalence of Post-Acute COVID-19 Sequela (PACS) or long-COVID syndrome (long COVID) should not be a surprise. Long-COVID symptoms may be explained by oxidative stress and parasympathetic and sympathetic (P&S) dysfunction. This is a retrospective, hypothesis generating, outcomes study. Methods. From two suburban practices in northeastern United States, 152 long COVID patients were exposed to the following practices: (1) first, they were P&S tested (P&S Monitor 4.0; Physio PS, Inc., Atlanta, GA, USA) prior to being infected with COVID-19 due to other causes of autonomic dysfunction; (2) received a pre-COVID-19 follow-up P&S test after autonomic therapy; (3) then, they were infected with COVID-19; (4) P&S tested within three months of surviving the COVID-19 infection with long-COVID symptoms; and, finally, (5) post-COVID-19, follow-up P&S tested, again, after autonomic therapy. All the patients completed autonomic questionnaires with each test. This cohort included 88 females (57.8%), with an average age of 47.0 years (ranging from 14 to 79 years), and an average BMI of 26.9 #/in2. Results. More pre-COVID-19 patients presented with sympathetic withdrawal than parasympathetic excess. Post-COVID-19, these patients presented with this ratio reversed and, on average, 49.9% more autonomic symptoms than they did pre-COVID-19. Discussion. Both parasympathetic excess and sympathetic withdrawal are separate and treatable autonomic dysfunctions and autonomic treatment significantly reduces the prevalence of autonomic symptoms. Conclusion. SARS-CoV-2, via its oxidative stress, can lead to P&S dysfunction, which, in turn, affects the control and coordination of all systems throughout the whole body and may explain all of the symptoms of long-COVID syndrome. Autonomic therapy leads to positive outcomes and patient quality of life may be restored.

Fairness and Ethics in Artificial Intelligence-Based Medical Imagining

Abstract: Artificial intelligence has a huge array of current and potential applications in healthcare and medicine. Ethical issues arising due to algorithmic biases are one of the greatest challenges faced in the generalizability of AI models today. The authors address safety and regulatory barriers that impede data sharing in medicine as well as potential changes to existing techniques and frameworks that might allow ethical data sharing for machine learning. With these developments in view, they also present different algorithmic models that are being used to develop machine learning-based medical systems that will potentially evolve to be free of the sample, annotator, and temporal bias. These AI-based medical imaging models will then be completely implemented in healthcare facilities and institutions all around the world, even in the remotest areas, making diagnosis and patient care both cheaper and freely accessible.

A thermodynamics-guided framework to design lightweight aggregate from waste coal combustion fly ash

Abstract: A systematic thermodynamics-based framework was applied to recycle waste low and high-calcium coal combustion Fly Ash (FA) into synthetic lightweight aggregates (LWA) through sintering. The process to successfully manufacture synthetic LWA was investigated, which requires a delicate balance among three phenomena: (i) sufficient liquid phase formation during sintering, (ii) appropriate viscosity for the liquid-solid phase, and (iii) sufficient amount of gas emission to form pores in the LWA. Thermodynamics modeling was used to quantify the formation of the liquid phase during sintering while the fluxing agent and the temperature change. The Urbain- Kalmanovitch, Browning, and Krieger-Dougherty models were used to quantify the viscosity of the liquid and liquid-solid phase, respectively. A lower bound of 100 Pa•s for the viscosity was found to ensure spherical shape of the LWA. Using thermogravimetric analysis, it was shown that the LWA had a notable gas release potential, owing to the presence of anhydrite and hematite, which could create gas-filled pores in the LWA macro-microstructure. X-ray computed tomography (X-CT) observation revealed the formation of a porous structure for the produced LWA where high calcium FA LWA generally had larger pores compared with low calcium FA LWA. By correlating the X-CT and scanning electron microscopy (SEM) observations and thermodynamic modeling results, it was found that a minimum of 40% liquid phase content (% by mass) is necessary for the formation of gas-filled pores in FA-LWA.