University of Denver
  • Denver, CO, United States
Recent publications
Microgrids are facing several operational and control issues while integrating with the grid. To deal with it, STATCOM, as one of the emerging power converter circuits, is connected with such microgrids. STATCOM with microgrid introduces current harmonic, inherent resonance, and active power losses related to high switching frequency. Filter design can help attenuate these effects and maintain the predefined standards as in IEEE 519-1992 and IEEE P1547.2-2003. There are also some more points of concern about filter design. Inappropriate filter types and parameters may cause worse filtering, reactive power surplus production, and low power factor. Therefore, this paper suggests that the reactive power compensation capability, as a local area problem, must be attended through the proper designing of LCL filtered grid-tied STATCOM. The parameters are estimated through transient analysis, power quality, and power balance studies for proposed Micro-grid and the results obtained are compared using nature-inspired algorithms such as GA, PSO, and FA over conventional mathematical formulation. The main contributions of this work are; (i) study of system with the inclusion of voltage and frequency-dependent load, (ii) modified STATCOM model clubbing reactive power control feedback and LCL filter with damping resistance, (iii) real and reactive power tracking system using dynamic compensator capabilities, and (iv) suppression of total harmonic distortions along with real and reactive power tracking using advanced tuning for filter parameters with GA, PSO, and FA based algorithms.
Inter-unit collaboration in transnational multinational corporations (MNCs) is central to unlocking MNCs' competitive advantage. We find that managing multilevel interaction of macro-level (social structures within and outside the MNC) and micro-level (individual interpretations and behaviors) factors ensures the implementation of strategic goals regarding inter-unit collaboration. In a case study of Finnish, Russian, and Indian unit collaboration in one European-origin transnational MNC, we observe that individual ascriptions of social identity to Indian colleagues (micro-level factor) affect the MNC's strategy implementation (SI) process and outcomes (macro-level factors). Building on the latter observations, critical realist theory of identity, and the idiosyncratic Indian context, we develop the currently inadequate multilevel theorization on the SI process in the MNC and expand perspectives on social identity in International Business literature. For MNC managers from Western countries, the paper offers insights into factors that should be considered to succeed in strategic and operational inter-unit collaboration with India.
The current study investigates whether prepregnancy maternal posttraumatic stress disorder (PTSD) symptoms, depressive symptoms, and stress predict children's cortisol diurnal slopes and cortisol awakening responses (CARs) adjusting for relevant variables. Mothers were enrolled after delivering a baby and followed through their subsequent pregnancy with 5 years of longitudinal data on their subsequent child. This prospective design allowed assessment of PTSD symptoms, depressive symptoms, and perceived stress prior to pregnancy. Children provided three saliva samples per day on three consecutive days at two timepoints in early childhood (M age = 3.7 years, SD = 0.38; M age = 5.04 years, SD = 0.43). Mothers’ PTSD symptoms prior to pregnancy were significantly associated with flatter child diurnal cortisol slopes at 4 and 5 years, but not with child CAR. Findings at the age of 4 years, but not 5 years, remained statistically significant after adjustment for maternal socioeconomic status, race/ethnicity, child age, and other covariates. In contrast, maternal prepregnancy depressive symptoms and perceived stress did not significantly predict cortisol slopes or CAR. Results suggest that maternal prepregnancy PTSD symptoms may contribute to variation in early childhood physiology. This study extends earlier work demonstrating risk of adverse outcomes among children whose mothers experienced trauma but associations cannot be disentangled from effects of prenatal mental health of mothers on children's early childhood.
Trialities of W-algebras are isomorphisms between the affine cosets of three different W-(super)algebras, and were first conjectured in the physics literature by Gaiotto and Rapčák. In this paper we prove trialities among eight families of W-(super)algebras of types B, C, and D. The key idea is to identify the affine cosets of these algebras with one-parameter quotients of the universal two-parameter even spin W∞-algebra which was recently constructed by Kanade and the second author. Our result is a vast generalization of both Feigin-Frenkel duality in types B, C, and D, and the coset realization of principal W-algebras of type D due to Arakawa and us. It also provides a new coset realization of principal W-algebras of types B and C. As an application, we prove the rationality of the affine vertex superalgebra Lk(osp1|2n), the minimal W-algebra Wk−1/2(sp2n+2,fmin), and the coset Com(Lk(sp2m),Lk(sp2n)), for all integers k,n,m≥1 with m<n. We also prove the rationality of some families of principal W-superalgebras of osp1|2n and osp2|2n, and subregular W-algebras of so2n+1.
The promotion of Social emotional learning (SEL) in elementary schools has increased; however, little is known about early childhood teachers’ perceptions about the effectiveness of their elementary school’s approach to SEL. The present study used mixed methods methodology to explore the perceptions of 1154 preschool through second grade teachers working in elementary schools regarding the effectiveness of their school’s SEL approach. Study findings revealed that early childhood teachers overall viewed their classroom and school SEL approaches as effective. Eight themes emerged regarding key elements of effective SEL approaches. Participating teachers expressed specific concerns about SEL implementation when their unique early childhood classroom context was not considered or included in their school’s SEL approach. Findings are interpreted in the context of relevant literature and implications for practice are discussed.
With the increasing penetration rate of electric vehicles, the fast charging demands of electric vehicles will have a significant influence on the operation of coupled power-transportation networks. To promote the interests of the coupled system, fast charging stations, and electric vehicle users, in this paper, a multi-objective system-level fast charging station recommendation method is proposed to dynamically allocate electric vehicles to suitable stations. The recommendation problem is formulated as a sequential decision-making problem and a deep reinforcement learning method is adopted. To deal with the network-structure coupled system states, graph attention networks are introduced. Considering the heterogeneity between entities, we propose a physical connection-based graph formulation method with feature projection to integrate multi-dimensional information from charging stations, traffic nodes, and power grid buses into a graph. The graph convolution of coupled system states can then be realized to promote environment perception. Besides, to address the long time-delay action execution in recommendation problem, a double-prioritized DQN(λ) training mechanism is developed to update the guidance strategy, where an attention-prioritized cache construction method is proposed to improve the training efficiency cooperated with prioritized experience replay. The proposed graph reinforcement learning method is trained and evaluated in a joint power-transportation simulation platform. Simulation results show that the proposed strategy can promote the interest of multiple facets in coupled power-transportation networks by handling the requests in a real-time manner. Its feasibility and robustness in the urban transportation systems are also demonstrated.
Background Periprosthetic joint infection may result from pathogen to patient transmission within the environment. The purpose of this study is to evaluate the contamination level of selected high-touch surfaces in the operating room (OR) using a blacklight fluorescent marking system after a manual terminal clean. Methods Prior to the manual terminal clean, 16 high-touch surfaces were marked using a blacklight fluorescent gel. The marked areas were assessed the next morning for thoroughness of cleaning. Surfaces were categorized based on the average percent of the marks removed as “clean” (>75%), “partially clean” (26%-74%), or poorly cleaned (<25%). This process was repeated randomly 12 times. Terminal cleaning was done in the standard fashion, and the perioperative team was unaware of the initiation of this study. Results A total of 936 marks were analyzed. There was a significant difference in the number of marks completely clean (29.1%, 272/936) vs marks that were not touched (40.8%, 382/936), P < .001. Only the OR back table (75%) had a rating of clean. Partially clean areas included Mayfield table (72%), overhead lights (70.1%), infusion pump (61.1%), clock reset button (58.3%), table remote control (50%), tourniquet machine (50%), and the OR table (33.3%). Poorly cleaned surfaces included anesthesia medication cart (21.8%), door handles (20.8%), phone (16.7%), electrocautery unit (16.7%), foot pedal (16.7%), anesthesia cart (16.2%), nurses’ station (14.1%), and supply cabinet doors (6%). Conclusions Effectiveness of manual terminal cleaning varied greatly across surfaces. In general, surfaces further from the operative field were less likely to have markings removed.
Our paper adds to the aging mobilities literature by addressing the need for more empirical studies in the Global South and utilizing the 2017 Household Origin-Destination Survey (HODS 2017) to broadly understand the mobility of older adults in Mexico City. We use descriptive statistics to reveal travel behavior patterns and construct a multinomial logit model to understand variations in mode choice of older adults in Mexico City. Our analysis does provide an emphasis on differences by income class, gender, and neighborhood level access to public transportation. Results uncovered transport-related inequalities as poorer older adults travel for longer periods of time compared to their wealthier peers. In terms of travel behaviors, we found that 40.5% of older adults reported using public and paid transit, 32% walked, 26.5% drove, and only 1.2% biked. Also, we learned that when older adults have access to good public transit infrastructure, they use it, regardless of car ownership status. Also, mobilities resulting from gender differences among older adults showed that older females are less likely to use structured public transit, walking, and biking in comparison to older males. Lastly we outline research limitations and recommendations for future transport policies.
Background Legalization of cannabis, along with concern over prescription opiate use, has garnered interest in cannabis for adjuvant pain control. This study examines the relationship between cannabis and opioid consumption after total hip (THA) or knee (TKA) arthroplasty. Methods Patients undergoing primary THA or TKA with minimum 6-month follow-up who self-reported cannabis use were retrospectively reviewed. A total of 210 patients (128 TKAs and 82 THAs) were matched by age; gender; type of arthroplasty; Charlson Comorbidity Index; and use of nicotine, antidepressants, or benzodiazepines to patients who did not self-report cannabis use. Patients receiving an opioid prescription after 90 days postoperatively were classified as persistent opioid users (POUs). Duration of opioid use (DOU) was calculated for non-POU patients as the time between surgery and their last opioid prescription. Differences in inpatient morphine milligram equivalents (MMEs), outpatient MMEs, POU, and DOU were analyzed. Results Cannabis users required equivalent inpatient and outpatient MMEs. There was no difference in DOU. There was a significant difference in POU between cannabis users and matched controls (1.4% [n = 3] vs 9.5% [n = 20], P < .001, respectively). Grouping patients by TKA or THA, there remained a difference in POU for TKA (1.5% [n = 2] vs 10.9% [n = 14], P = .002) and THA (1.2% [n = 1] vs 7.3% [n = 6], P = .04). There was no difference in inpatient or outpatient MMEs or DOU for THA and TKA patients. Conclusions There is a reduced rate of POU in patients who self-report perioperative cannabis use. Prospective studies are needed to clarify the role of cannabis as an adjunct to perioperative pain control.
Purpose: This study investigates the effects of normobaric hypoxia on repeated sprint exercise (RSE) with different balance between oxidative (phosphocreatine and oxidative pathway) and glycolytic contributions. Therefore, performance and psycho-physiological responses were compared during RSE to exhaustion with the same exercise-to-rest ratio (1:2) but different sprint durations (5, 10 or 20s) either in normoxic (RSN) or hypoxic (RSH; FiO2 = 0.13) conditions. Methods: On separate visits, 10 active participants completed in random order three cycling RSN (5:10; 10:20 and 20:40) and three similar RSH sessions to exhaustion. Vastus lateralis muscle oxygenation was recorded by near infrared spectroscopy. Blood lactate concentration, limb and breathing discomfort, and ratings of perceived exertion (RPE) were measured. Results: Total sprint number was smaller in hypoxia than in normoxia for 5:10 (20.8 ± 8.6 vs 14.7 ± 3.4; p = 0.014) and 10:20 (13.7 ± 6.3 vs 8.8 ± 2.5; p = 0.018) but not 20:40 (5.6 ± 1.9 vs 5.6 ± 2.5). The fatigue index was larger in hypoxia only for 5:10 (-43.5%, p < 0.001). Irrespective of condition, blood lactate concentration increased with the sprint duration with higher values for 20:40 than 5:10 (13.1 ± 2.7 vs 11.5 ± 2.2 mmol.l-1; p = 0.027). Limb and breathing discomfort and RPE did not differ in all RSE. Muscle oxygenation was mainly impacted by sprint duration (i.e., main effect of sprint duration on [HHb] min, [tHb] max, Δ[HHb] and Δ[tHb]) but not by hypoxia. The normoxia-to-hypoxia percentage decrease for total sprint number for 5:10 was correlated with the highest power output over 5 s (R2 = 0.55; p = 0.013) and 10s (R2 = 0.53; p = 0.016). Conclusions: Hypoxia impairs repeated sprint ability when the oxidative but not the glycolytic contribution is substantial. The oxidative-glycolytic balance, influenced partly by sprint duration, is key during repeated sprint in hypoxia.
Accurate models of generation systems are critical for maintaining reliable and secure grid operations. In this paper, a novel and systematic approach is proposed to identify and calibrate the generator system problematic parameters using continuous wavelet transform (CWT) and advanced deep-learning technology. At the beginning, the phasor measurement unit (PMU) data are used through “event playback” to check the consistency between simulated and measured real and reactive power of the generation system. Once the results indicate a model parameter validation is required, a group of suspicious parameters will be identified as the primary problematic parameter candidates (PPCs). These primary PPCs are randomly perturbed to generate the event playback simulation data, which are used by the CWT and convolutional neural networks (CNNs) to further narrow down the primary PPCs into a smaller set of candidates. Then, the identified candidates are perturbed again to generate massive event playback simulation data for training a parameter calibration neural network. We designed a multi-output neural network structure to find the mappings between the perturbed parameters and the simulation data using both CNN and long short-term memory (LSTM) models. Finally, the well-trained and tested CNN-LSTM model is used to estimate the accurate value of the suspicious parameters with actual PMU measurements. The proposed CNN-LSTM network can accurately and reliably estimate the generation-system problematic parameters, and has better performance when compared to other machine-learning methods, such as the multilayer perceptron network and the conditional variational autoencoder method. The accuracy and effectiveness of the proposed approach have been validated through simulation and real-world data.
In the early Drosophila embryo, the elongation of the anterior-posterior body axis is driven by cell intercalation in the germband epithelium. Neighboring cells intercalate through the contraction of AP interfaces (between anterior-posterior neighbors) into higher-order vertices, which then resolve through the extension of new DV interfaces (between dorsal-ventral neighbors). Although interface contraction has been extensively studied, less is known about how new interfaces are established. Here, we show that DV interface elongation behaviors initiate at the same time as AP contractions, and that DV interfaces which are newly created from resolution of higher-order vertices do not appear to possess a unique ‘identity’; instead, all horizontal interfaces undergo lengthening, elongating through ratchet-like sliding behaviors analogous to those found in AP interfaces. Cortical F-actin networks are essential for high area oscillation amplitudes required for effective ratcheting. Our results suggest that, contrary to canonical models, the elongation of new DV interfaces is not produced by a mechanistically separate process. Instead, medial Myosin populations drive oscillating radial forces in the cells to generate transient force asymmetries at all tricellular vertices, which - combined with planar polarized stabilization - produce directional ratcheted sliding to generate both AP interface contraction and DV interface elongation. [Media: see text] [Media: see text] [Media: see text] [Media: see text]
Using psychotropic medications to treat and prevent self-injurious thoughts and behaviors (SITBs) has become increasingly popular, but conclusive evidence supporting the efficacy this approach remains elusive. To empirically examine whether psychotropic medications are efficacious treatments for SITBs, the present meta-analysis comprehensively summarizes all published randomized controlled trials (RCTs) that have reported the causal effects of psychotropic medications on suicide and self-injury. A total of 251 papers from 718 unique RCTs were included. A frequentist pairwise approach was adopted for meta-analyses. Potential effect modifiers were examined via met regressions and potential biases were evaluated through sensitivity analyses. On average, medications yielded an 8% reduction in SITB frequency and a reduction of 0.2 standard deviations in symptoms and severity. Findings were largely consistent across potential effect modifiers, and significant evidence of publication bias was not detected. Only one medication class (i.e., antipsychotics) and two specific medications (i.e., citalopram, ketamine) produced larger-than-average treatment effects. Psychostimulants and typical antipsychotics may produce iatrogenic effects. Less than 4% of included studies required individuals to exhibit SITBs, and nearly half of analyzed effects were drawn from studies that excluded individuals on the basis of SITB risk. Taken together, findings suggest that psychotropic medications produce small treatment effects on SITBs; however, these findings should be considered in light of the methodological constraints of the existing literature, including the lack of studies intentionally including individuals with SITBs. It is critical for future RCTs to prioritize including individuals with existing SITBs to further clarify treatment effects in self-injurious and suicidal populations. Additional research is needed to better understand the treatment mechanisms of psychotropic medications and identify the causal processes underlying SITBs.
Retaining staff remains a challenge for public and private child welfare organizations, and current research does not explain the underrepresentation of workers of Color in leadership and supervisory positions. This study used data from a multi-site survey of child welfare staff to compare factors associated with intention to remain employed between caseworkers of Color and White caseworkers using path analysis. Factors associated with job satisfaction, the strongest predictor of intention to remain employed for both groups in our path analysis, differed slightly between workers of Color and White workers. Age and job stress were significantly more influential for workers of Color, while work related burnout was more more influential for White workers. For workers of Color, perception of leadership was significantly more influential on workers’ of Color intention to remain employed, compared to White workers, and having an MSW was a significant predictor of intent to remain employed for White workers, but not for workers of Color. Implications for agency practice and policy, including suggested strategies to address retention of workers at the caseworker level, are discussed.
The 2020 health pandemic and high-profile police murders of Black people inspired national conversations about racism and police brutality. This study examined how Intermediary Public Policy Organizations (IPPOs) discursively engaged with the racialized nature of the pandemic and the police murder of George Floyd, which have increased awareness of systemic racism in society. Our discursive analysis of IPPO statements published during these events revealed a pattern of humanizing higher education institutions, race evasive policy proposals, and a lack of policy action addressing systemic racism. IPPO evasion of race is consequential because it has the potential to limit the ability of public policy to dismantle systems of oppression and highlights the need for race-conscious policies to support Black, Indigenous, and people of color students and communities.
Large social media platforms are generally designed for scalability—the ambition to increase in size without a fundamental change in form. This means that to address harm among users, they favor automated moderation wherever possible and typically apply a uniform set of rules. This article contrasts scalability with restorative and transformative justice approaches to harm, which are usually context-sensitive, relational, and individualized. We argue that subsidiarity—the principle that local social units should have meaningful autonomy within larger systems—might foster the balance between context and scale that is needed for improving responses to harm.
Organizational autonomy is a fundamental organizational design choice that holds a central position in management theories and practice. To date, this construct has suffered from definitional vagueness and conceptual fragmentation in its academic study across different management subfields. Drawing from a review of 87 articles appearing in top academic management journals, we had four objectives. We sought to establish clarity and consensus on the construct of organizational autonomy, to review the fragmented fields of studies on its determinants and outcomes, to identify unresolved or neglected debates, and to provide an organizing template for guiding future research. In a first section, we discuss the development of the organizational autonomy construct and review its diverse definitions, primary determinants, and outcomes. In a second section, we provide a set of recommendations spanning methodological directions and conceptual opportunities on the overlooked dynamics of organizational autonomy. Overall, our review provides a unified framework and direction for enhancing the understanding of one of the management field’s fundamental concepts.
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5,130 members
J. Donald Hughes
  • Department of History
Walter LaMendola
  • Graduate School of Social Work
Toshiya Ueta
  • Department of Physics and Astronomy
Shannon M. Murphy
  • Department of Biological Sciences
Elysia Poggi Davis
  • Department of Psychology
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