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Impact of Inverter-Based Resources on Grid Dynamics
Get PDFThe increasing integration of renewable energy resources such as wind and solar into the electric power grid through power electronic inverters has changed grid dynamics and posed challenges to grid planning, operation, and protection. The growing penetration of renewable energy resources may drive the grid towards weak power grid conditions, under which grid stability issues may affect the operation of inverter-based renewable generators. To more accurately identify the weak grid conditions for guiding grid planning to prevent potential weak grid issues, a method for grid strength assessment is proposed by considering not only the impact the of interaction between interconnected renewable resources, but also the impact of the interactions between shunt capacitors interconnected through the power network. On this basis, we use a real-time digital simulator to explore inverter dynamics under different grid conditions including weak grid conditions. One of the major findings is that there are undesired transient events during the grid restoration process, and the undesired transient events become more significant when increasing the number of solar PV inverters or under weak grid operating conditions. This finding motivates us to study the impact of inverter dynamics on grid protection during the grid restoration period by using a real-time digital simulator. It is found that inverters can act as negative-sequence sources to inject negative-sequence currents into the grid during the grid restoration period and thus can adversely impact the performance of protection schemes based on negative sequence components and potentially cause relay maloperations during the grid restoration period, thus making system protection less secure and reliable
Appraising Anterior Cruciate Ligament Injury Risk: Single-Legged Jump-Landing Dynamic Postural Stability
Get PDFAppraising anterior cruciate ligament (ACL) injury risk is of great interest to the orthopedic and sports medicine professional. Due to the high prevalence of non-contact ACL injuries, professionals have sought to identify intrinsic and modifiable neuromuscular and biomechanical risk factors to aid in the design of injury risk screens that have the discriminatory capacity to stratify ACL injury risk and the efficiency to be implemented at-scale. Prospective studies have revealed that poor dynamic postural stability (DPS), quantified as time to stabilization (TTS), following a backwards single-legged jump-landing (BSLJL) and poor hip external rotation and abduction strength relative to body weight, quantified using a handheld dynamometer, are two risk factors for ACL injury. The purposes of this study were to assess the effects of repeated BSLJL on within-session motor learning as quantified by DPS, evaluate the reliability of DPS, and determine the relation between DPS, hip strength, and fatigue. Twenty-seven recreationally active college-aged adults (24.0 ? 2.8 y, 1.73 ? 0.08 m, 75. ? 14.0 kg) were enrolled in this semi-randomized, cross-over study. During visit one, subjects completed 10 BSLJL trials per leg without familiarization and had their hip external rotation and abduction strength measured. During visits two through four, subjects complete two fatigue sessions and one control session in a randomized order. During these sessions, subjects completed two sets of three BSLJL trials per leg separate by either a seated rest in a chair (control) or a short-term functional fatigue protocol (fatigue). DPS was quantified as TTS and the dynamic postural stability index (DPSI). To appropriately familiarize a subject to the BSLJL, results suggest that a minimum of six familiarization trials per leg are required to sufficiently reduce the motor learning effect. Results also indicate that TTS reliability is poor after 10 trials per leg whereas DPSI reliability is good after just two trials per leg and excellent after just six trials per leg. Finally, results indicate that following completion of a fatigue protocol, there are decrements in TTS, but not in DPSI. Further, greater hip abduction strength is associated with better DPSI when rested and fatigued, but not TTS
Dynamic 3D In Vitro Bone Metastatic Testbeds for Prostate and Breast Cancer
Get PDFMetastatic prostate cancer spreads preferentially to the bone, causing skeletal complications associated with significant morbidity and a poor prognosis, despite current therapeutic approaches. Increasing evidence suggests the synergistic role of biochemical and biophysical cues in cancer progression at metastases. However, the mechanism underlying the crosstalk between interstitial flow-induced mechanical stimuli and prostate cancer progression in the bone microenvironment remains poorly understood. To this end, we have developed 3D in vitro dynamic models of prostate cancer bone metastasis using perfusion bioreactor and horizontal flow bioreactor to delineate the role of flow-induced shear stress on prostate cancer progression and migration, respectively at metastases. Using a perfusion bioreactor, we observed changes in the expressions of MET biomarkers and the tumoroid morphologies of prostate cancer cells under dynamic culture. Evaluation of cell adhesion proteins indicated that the altered cancer cell morphologies resulted from the constant force pulling due to increased E-cadherin and FAK proteins under shear stress.
Using a horizontal flow bioreactor, we demonstrated that the percent cell migration rate of prostate cancer cells was increased in the presence of bone under dynamic conditions. The results showed that interstitial fluid flow did not alter the CXCR4 level, but bone upregulated CXCR4 levels, leading to increased MMP-9 levels. In addition, both ?v?3 integrins and MMP-9 levels were upregulated by fluid flow conditions, contributing to an increased migration rate under dynamic conditions.
Breast cancer cells also tend to preferentially disseminate to bone and colonize within the remodeling bone site to cause bone metastases. We have previously developed a 3D in vitro breast cancer bone metastasis model using hMSCs and commercial breast cancer cells (MCF-7 and MDAMB231), recapitulating late-stage breast cancer metastasis to bone. In the present study, we have validated our model using patient-derived breast cancer cell lines- NT013 and NT023, exhibiting hormone-positive and triple-negative characteristics, respectively that showed MET and formed tumors in the presence of bone. In addition, the results showed ET-1 (NT013) and DKK-1 (NT023) mediated stimulation and abrogation of the osteogenesis via Wnt/? catenin pathway, in line with our previous results with MCF-7 and MDAMB231 cell lines
A Study of Conformal Metasurfaces on Passive Beam Steering for Arrays
Get PDFBeam-steering has drawn significant interest due to the expansion of network capacity. However, a traditional beam steering system involves active phase shifters and controlling networks which can be complex. This work proposes a passive conformal metasurface design on beam steering. The phase shifting is achieved by changing the curvature of a conformal metasurface. In addition, three conformal prototypes were fabricated and tested using different techniques such as 3D printing. The simulations and test results indicate up to 20? of beam shifting. This study can be extended to higher frequency bands for lower power consumption beam steering systems
Exploration of Mutli-Threshold Ferro-Electric FET Based Designs
Get PDFThe surge in data intensive applications has given rise to demand for high density storage devices and their efficient implementations. Consequently, Multi-level-cell(MLC) memories are getting explored for their promising aspects of higher storage density and lower unit storage cost. However, the multi-bit data stored in these memories need to be converted to processor compatible forms (typically binary) for processing. In this work, we have proposed an adaptable multi-level voltage to binary converter using Ferro-electric Field Effect Transistors(FeFET) capable of translating input voltage to bits. The use of FeFETs as voltage comparators simplifies the circuit and offers adaptable voltage quantization, flexible output bit-width(1/2 bits) and security feature. The circuit also employs incremental output encoding, which limits error margin to the least significant bits(LSB). The proposed 4-level to 2-bit converter circuit is demonstrated in simulation to have an input voltage range of [0 ? 3.75V] / [0 ? 2.7V] for FeFETs with 20/2000-domains respectively
Microwave Measurement of Grain and Biomass
Get PDFMicrowave measurement is a powerful method for mass prediction and grain detection. Existing systems are well adapted for small volume grain measurements, but cannot accommodate materials other than grain (e.g. biomass), which are larger in size or dimensional ratios. Therefore, an enlarged measuring system with unique design is needed. This new system?s large size improves measurement repeatability by capturing an average response for randomly aligned bulk samples. The system supports homogenous samples up to 0.5 m thick and 1 m square, and it has been validated from 1-50 GHz. By increasing the measurement system?s physical size relative to existing systems, it is now possible to measure the plants associated with these grains and seeds in a similar manner. Preliminary results for mixtures of grain and biomass are reported.
Having been validated for grain measurements, the One Meter Fixture is next used to collect phase shift and attenuation data for a variety of grain and oil seed samples (soybean, canola and corn). Using multiple variable linear regression analysis, a comprehensive clean grain mass estimation model was developed based on the dielectric properties of the grain samples derived from the S-Parameters at 13 GHz. Dielectric (?') constant / properties and phase shift were introduced into the regression models and generated a grain mass estimation result with R2 values of 0.976, 0.977 and 0.989 for soybean, canola and corn samples, respectively. The results indicate that RF sensing technology has the potential to provide more accurate non-contact sensing methods for estimating grain mass in multiple precision agricultural applications
In the Pursuit of Poultry: ?-Phenylethylamine and Ethyl Acetoacetate as Antimicrobials on Chicken
Get PDFThis research examines the effect of ?-phenylethylamine (PEA), a natural trace amine commonly found in food, and ethyl acetoacetate (EAA), an FDA approved flavoring agent and food additive, as novel antimicrobials on store-bought chicken thighs in a 5-minute immersion. In the first part of this experiment, 5%, 7.5%, and 10% treatments of ?-phenylethylamine and ethyl acetoacetate were compared to control H2O treatments utilized on chicken thighs. 10% treatments of PEA and EAA had significant reductions in counts of total aerobic bacteria and Pseudomonas spp. grown at 20?C by >1 log10 CFU/g of chicken meat. In the next experiments regarded 10% EAA as an antimicrobial on potential pathogens on chicken meat. The treatments of 10% EAA only succeeded in partial efficacy in the reduction of inoculated Salmonella spp. and Campylobacter spp. on chicken thighs
Automated Approaches for the Early-Stage Distinguishing of Palmer Amaranth from Waterhemp
Get PDFPalmer amaranth is an invasive pigweed species, possessing rapid growth, posing a threat to the economy of crops including corn. Its early detection and mitigation are of utmost importance; however, it is visually similar to waterhemp in the early growth stages. In this study, automated approaches are employed to distinguish palmer amaranth from waterhemp, within two weeks after emergence, from their RGB images. Morphological characteristics of these weeds are estimated and fed to several Machine Learning (ML) models. To improve classification accuracy, RGB images are augmented, and a Convolutional neural network is trained on 16000 images. Validated on images embedded with gaussian noise, it produced a better accuracy compared to ML approaches. Finally, YOLOv5, an object detection algorithm based on transfer learning, is successfully prepared. Tested on synthetic images consisting of both weeds, YOLOv5 successfully detected a significantly high number of palmer amaranth objects while also distinguishing it from waterhemp
Evaluating Financial, Social, and Waterbird Implications of Farming Within Wetlands Imbedded in Agricultural Fields
Get PDFWetlands of the Prairie Pothole Region (PPR) provide many ecosystem services to the region such as floodwater attenuation, maintenance of water quality, carbon sequestration, and wildlife habitat. The biophysical process characteristics of the region that have made it beneficial for wildlife have also made the region conducive to cultivation; consequently, many wetlands (>49%) in the PPR have been drained and converted to cropland. Although wetlands are often noted for their natural ecosystem services, their contributions to agriculture are often overlooked. Understanding aspects of PPR wetlands, such as value for migrating waterbirds, how wetlands fit into farming operations, and how farmers perceive the fit of those wetlands in their operations will help to find mutually beneficial solutions to wetland management for farmers and conservation efforts.
I evaluated occurrence and densities of various species of waterfowl and shorebirds within agricultural wetlands receiving different manipulations. Most manipulations reduced vegetation heights and proportions of vegetation coverage of the inundated areas of wetlands. Manipulation technique was only important for four species and varied in its effect on density and occurrence probabilities. Most species of waterfowl occurred at higher densities in the low to mid ranges of vegetation coverage.
Based on data collected from farmers, I estimated about half of the area of temporary wetlands and nearly one third of the area of seasonal wetlands are planted on average. Soybean yield and profitability from cultivated portions of temporary wetlands were similar to uplands at average precipitation but were significantly lower in seasonal wetlands. Corn profitability was significantly lower for cultivated portions of temporary and seasonal wetlands for average precipitation conditions. The differences were more pronounced under wetter conditions and especially when considering the entirety of wetland area, not just the cultivated portions of wetlands.
I examined farmers? perceptions through a questionnaire regarding how they view agricultural wetlands and how wetlands fit into the respondents? farming operations. Despite a low response rate, some informative responses may provide a foundation for further exploration of these data. The results of this dissertation may provide an opportunity for farmers and conservationists to find mutually beneficial management practices for agricultural wetlands
How Female Fans Make Sense of Gender, Power, and Gendered Violence in HBO?S Game of Thrones
Get PDFViolence and abuse towards women are common themes in media today. HBO?s television series, Game of Thrones, is filled with scenes of women being tortured, raped, and abused. Yet, Game of Thrones was one of the most watched shows of the 2010s (Hibberd, 2014). In this study, I explore how women view the relationship between power and gender in Game of Thrones and how they make sense of justify gendered violence. Interviews were conducted with 20 women who had seen more than one season of the series. The goal of this research is to gain insight into these perceptions in order to dispel internalized sexist ideals and create more understanding of internal biases. Results suggest female fans demonstrate feminist ideas in their critiques of the series? portrayal of women but assess characters and plotlines in a way that values masculine qualities and masculine forms of power