Clemson University
  • Clemson, SC, United States
Recent publications
Residential demand response (DR) programs are designed to reduce peak load from residential homes. It is essential for utilities to identify how much peak load could be potentially reduced from DR to optimally plan and operate the power system. However, it is extremely challenging to identify such a maximum load reduction, i.e., demand flexibility, offered by DR for a large group of residential homes due to the difficulties in modeling the willingness of customers to participate in DR programs and diverse loads in households. The willingness is also related to the incentives; a higher incentive can obviously attract more customers to participate. Targeting these problems, this paper provides an electricity cost minimization model for residential homes. DR incentives and customer willingness to respond to incentives are modeled to identify the realistic maximum demand flexibility. A case study using actual data from 98 homes at the Pecan Street microgrid database shows 9.7% of the controllable peak load (43 kW) can be reduced when the DR incentive is half of the peak electricity tariff. This demand flexibility increases to 66 kW, accounting for 14.9% of the controllable peak loads, when the incentive increases to twice of the peak tariff.
A serious of novel and stable BiFeO3/α-Fe2O3 type-Ⅱ heterojunction photocatalysts with different weight contents of α-Fe2O3 were prepared just by a facile one step grinding method. XRD, TEM, SEM, XPS, UV–vis, and photoluminescence spectra, etc. were used to analyze the structure, surface state, optical properties, and interfacial interactions of the as-prepared catalysts. The results showed that type-Ⅱ heterojunction were successfully formed by this one step grinding method at the interface between BiFeO3 and α-Fe2O3, and thus the transformation of the photogenerated electrons, separation of the photogenerated electron-hole pairs and visible-light absorption were enhanced. Among them, BiFeO3/α-Fe2O3-30% composite exhibits the optimal activity, there is 85.87% of phenol degraded under simulated solar irradiation after 2 h, which is 1.97 times of single α-Fe2O3 and 4.23 times of single BiFeO3, respectively. Besides, the BiFeO3/α-Fe2O3-30% heterojunction composite also keeps an excellent catalytic performance after 3 cycles.
This study was guided by the notion of tourist attractiveness to understand residents' perception of tourists in establishing a reciprocal resident-tourist relationship. To explore the concept of reciprocity and how it is associated with tourist attractiveness, this study adopted an exploratory sequential mixed-method approach in the context of Chinese tourists visiting Jeju Island, South Korea. Findings from semi-structured interviews indicate that residents' perception of reciprocity can be conceptualized and measured through the constructs of resident satisfaction and resident commitment. Further, structural equation modeling found that residents are more satisfied and likely to be committed to the relationship with tourists when these visitors are perceived as attractive partners. The results demonstrate a mechanism for explaining how the residents’ perceptions of tourists influence their satisfaction with tourists and intention to host, market, or attract them again in the future.
Introduction Opioids are commonly prescribed beyond what is necessary to adequately manage postoperative pain, increasing the likelihood of chronic opioid use, pill diversion, and misuse. We sought to assess opioid utilization and patient-reported outcomes (PROs) in patients undergoing ventral hernia repair (VHR) following the implementation of a patient-tailored opioid prescribing guideline. Methods A patient-tailored opioid prescribing guideline was implemented in March of 2018 for patients undergoing inpatient VHR in a large regional healthcare system. We retrospectively assessed opioid utilization and patient-reported outcomes among patients who did (n = 42) and did not receive guideline-based care (n = 121) between March 2018 and December 2019. PROs, operative details, and patient characteristics were extracted from the Abdominal Core Health Quality Collaborative (ACHQC) registry data, and length-of-stay and prescription information were extracted from the electronic health record system at the healthcare institution. Results The milligram morphine equivalents (MME) prescribed at discharge was lower for patients receiving guideline-based care (Median = 65, interquartile range [IQR] = 50-75) than patients receiving standard care (Median = 100, IQR = 60-150). After adjusting for patient characteristics, the odds of receiving an opioid refill after discharge did not significantly differ between patient groups (P = 0.43). Patient Reported Outcomes Measurement Information System (PROMIS) pain scores and hernia-specific quality-of-life (HerQLes) scores at follow-up also did not differ between patients receiving guideline-based care (Mean PROMIS = 57.3; Mean HerQLes = 53.1) versus those that did not (Mean PROMIS = 56.7; Mean HerQLes = 46.6). Conclusions Patients who received tailored, guideline-based opioid prescriptions were discharged with lower opioid dosages and did not require more opioid refills than patients receiving standard opioid prescriptions. Additionally, we found no differences in pain or quality-of-life scores after discharge, indicating the opioids prescribed under the guideline were sufficient for patients.
Affective states can influence a range of cognitive outcomes, such as decision-making. However, the effect of valence and arousal state inductions on effort-based decision-making is unclear. This study employed a mixed design in which all participants viewed low and high-arousal images, and participants were randomized to either a neutral, positive, or negative valence image manipulation. Participants repeatedly viewed a valenced-image and then completed a trial of the Effort Expenditure for Rewards Task (EFfRT). Results of Experiment 1 (N = 197) demonstrated that a valence induction manipulation influenced effort-based decision-making. Individuals in the negative valence condition chose fewer high-effort, difficult options than those in the neutral and positive valence conditions. Experiment 2 (N = 226) sought to explore the interplay between affective states and motivation on effort-based decision-making. Results of Experiment 2 replicated the finding that negative affective states impair willingness to engage in effortful tasks and showed that negative affect moderated the relationship between intrinsic motivation and willingness to exert effort. Self-reported arousal ratings, but not valence ratings, were also predictive of effort-based decisions. This work demonstrates that affective states may alter the cost of effort expenditure for potential rewards. Negative valence weakens one's volition to exert physical effort to obtain a monetary reward.
Understanding natural landscape preferences is essential to creating attractive green spaces that promote the benefits people may receive from nature. Previous research on landscape preference has primarily relied on quantitative, theory-driven approaches that may neglect complex and detailed human feelings and thoughts, as well as still images, which may not represent moving immersive stimuli representative of real-world experiences. The current study sought to reveal the key reasons for landscape preferences using virtual reality (VR) and open-ended questions. Ninety-five university students in the U.S. watched six 360 • videos of natural environments from Costa Rica and the U.S. We found that tropical beaches and rainforests were the favorite and the least favored landscapes in our sample, respectively. Preference rankings were explained by natural elements, emotional responses, and to a lesser degree, the creation of the 360 • videos. Sounds, water, coastal elements, and feeling relaxed were the most frequent reasons for "favoriting" a video; greenery and feeling bored were the most frequent reasons for "least favoring" a video. Low arousal emotions (i.e., relaxing, boring) and multiple scene transitions played important roles in explaining preferences. The results demonstrated the relevance of landscape preference theories while suggesting a greater emphasis on open views, sounds, and rhythmic features of the coast for landscape planning and design.
The failure of suspended ceiling system (SCS) has been one of the most widely reported seismic damage to non-structural components in buildings in recent years. In China, there are several types of SCSs applied in practice, among which the double-layer SCS with mineral wool boards is widely used in public buildings. It was found from the past earthquakes that the ceiling perimeter is one of the most vulnerable parts of SCS due to lack of reliable connection at the boundary. In this study a new semi-free boundary condition is proposed to improve the seismic performance of SCS. The full-scale shaking table tests on this type of SCS installed on a steel platform are conducted. The working mechanism, failure patterns, damage evolution, and earthquake responses including acceleration, displacement, and strain responses are studied. Experimental results verify that the proposed boundary condition is able to protect the ceiling perimeter from damage. The failure of SCS is mainly caused by the high vulnerability of grid connections. The pounding at the perimeter of SCS affects the seismic performance of the SCS harmfully. Effective seismic measures should be developed to reduce the impact between the ceiling and surroundings. A simplified numerical model for SCS with semi-free boundary condition is developed using OpenSEES. The calculated acceleration and displacement responses agree well with the test results. Moreover, seismic design recommendations for the type of SCS are provided.
Both the sharp interface and diffuse interface Poisson-Boltzmann (PB) models have been developed in the literature for studying electrostatic interaction between a solute molecule and its surrounding solvent environment. In the mathematical analysis and numerical computation for these PB models, a significant challenge is due to singular charge sources in terms of Dirac delta distributions. Recently, based on various regularization schemes for the sharp interface PB equation, the first regularization method for the diffuse interface PB model has been developed in [S. Wang, E. Alexov, and S. Zhao, Mathematical Biosciences and Engineering, 18, 1370–1405, (2021)] for analytically treating the singular charges. This work concerns with the convergence of a diffuse interface PB model to the sharp interface PB model, as the diffused Gaussian-convolution surface (GCS) approaches to the sharp solvent accessible surface (SAS). Due to the limitation in numerical algorithm and mesh resolution, such a convergence is impossible to be verified numerically. Through analyzing the weak solution for the regularized PB equations, the convergences for both the reaction-field potential and electrostatic free energy are rigorously proved in this work. Moreover, this study provides a unified regularization for both sharp interface and diffuse interface PB models, and clarifies the connection between this unified formulation and the existing regularizations. This lays a theoretical foundation to develop regularization for more complicated PB models.
Continuous supercritical extraction (SCE) was investigated for its ability to control the oligomeric composition of a pyrene pitch generated by the catalytic polymerization of pyrene in the presence of AlCl3. Key objectives of this work were the nearly complete removal of the starting monomer, generation of a well-defined pitch with a high char yield, and isolation of a fraction consisting exclusively of intermediate-sized oligomers. Following the design and construction of an SCE unit for processing up to 500 g/h of feed pyrene pitch with supercritical toluene (Tc = 319 °C, Pc = 41.1 bar), a 2-column setup was used to isolate ∼350 g of a fraction consisting of greater than 90 % isotropic dimer plus mesogenic trimer combined. Although the char yield of this oligomeric mixture was only moderate (i.e., 47.1 %), it still significantly exceeded the weighted average char yield (i.e., 30 %) of the individual monomers present, suggesting a synergistic interplay between the different species during charring. With the above results indicating that pyrene oligomers larger than trimer (i.e., X-mers) are needed to attain higher char yields, the focus of our next continuous SCE run was simply on removing as much unreacted monomer as possible, to the exclusion of all other oligomers. Using a one-column SCE setup, a ∼350 g fraction containing almost 90 % dimer and higher oligomers was isolated, and a respectable char yield of 65.2 % was obtained with this “monomer-depleted” pitch. Furthermore, the softening point was a relatively low 185 °C, quite respectable in terms of processability. In summary, these initial results indicate the potential of continuous SCE as a tool for controlling the properties of oligomeric pyrene pitches for selected applications.
We report the efficient electrocatalytic oxidation of glycerol (Gly) and ethylene glycol (EG) using a thin film of gold-curcumin (Au-CM) nanocomposite deposited on a glassy carbon electrode. The nanocomposite was synthesized using a galvanostatic technique in a two-electrode system with a very low current of 0.5 mA. Extensive characterization confirmed that the deposit consists of gold nanoparticles in a porous curcumin envelope. The Au-CM/GCE showed excellent catalytic activity for the electrocatalytic oxidation of Gly and EG with a low activation energy of 20.7 and 49.7 kJ mol⁻¹ and a low onset potential of −0.17 V and −0.14 V, respectively.
Prestressed steel-concrete composite beams with concreted and corrugated webs are a novel system that have been attracting attention lately. Unfortunately, there has been little research with regard to the fire performance of such beams. To overcome this knowledge gap and in the hope of exploring attractive solutions to improve the fire resistance of these beams, a testing campaign was conducted to examine the potential of reinforcing the webs of such beams via concrete. In this pursuit, three different prestressed steel-concrete composite beams (PCBCWs) were examined under fire conditions. The first beam was conventional PCBCW, the second PCBCW was unilaterally concreted between flanges and the third PCBCW was bilaterally concreted between flanges. These PCBCWs were exposed to the standard ISO834 fire and mechanical loading. The results of the fire tests revealed that PCBCWs without encased concrete suffer from the buckling of the web, but beams reinforced with concreted webs did not. Moreover, the vertical deformations were significantly influenced by the concreting of webs or the absence of such reinforcement. PCBCW with one-sided concrete between the flanges also underwent horizontal deflection during the test. To complement the conducted fire tests, finite element models (FEM) were developed to further explore the fire response of PCBCWs. The FE simulations show that, for PCBCW with one-sided encased concrete between flanges, there is horizontal deflection due to asymmetrical tension of the cable strands, horizontal temperature gradient, and torque around the longitudinal axis of the beam. Further, the shear center of PCBCW with one-sided encased concrete moves towards the coldest side with temperature rise. Finally, the FE analysis indicates signs of rupture of the cable strands inside the encased concrete triggers the failure and corresponding horizontal deflection of PCBCW with one-sided encased concrete between the flanges at high temperatures.
The food industry has recently invested in research to develop new processes that are more respectful to the environment, without sacrificing the quality and safety standards of the final products. The introduction of supercritical fluids (SCFs) in food processing and production has revolutionized different areas of food technology, providing solutions or improvements in extraction, transformation, preservation, and drying processes, among others. Throughout this chapter, new developments in the field of SCFs applied to food are presented. The advantages and importance of their use for sustainability in food production are discussed, forecasting the future scenario toward which this technology is heading.
In this paper we consider the maximum value of the independent domination number of outerplanar graphs. If one considers all outerplanar graphs or restricts to all maximal outerplanar graphs, this maximum is easy to find and known. So we focus on some subfamilies. Our main contribution is that, if one restricts to 2-connected outerplanar graphs of order n, then the maximum is (2n+1)/5, and there exists an infinite family of graphs that achieve this bound whenever 2n+1 is a multiple of 5.
Research-Practice Partnerships (RPP) bridge the gap between schools and universities. However, few have embraced the co-design process through a communities of practice lens and investigated how knowledge is co-constructed and negotiated. This mixed-method study explored how elementary school teachers co-construct knowledge with researchers to understand better how a community of practice can be cultivated during a co-design RPP. Findings from a survey, journal entries, observational field notes, and focus groups suggest teachers co-constructed knowledge while acknowledging and mitigating conflicts. Based on these findings, we offer ways to seed and cultivate communities of practice among teachers and researchers for co-designing educational innovations.
Climate change is becoming an increasing concern for many communities, particularly coastal communities subject to tidal and sea-level flooding. As a result, shoreline municipalities walk a fine line between protecting their communities and allowing more development. A prime example of this dilemma is the port city of Charleston, South Carolina, USA. Despite being ground zero for sea-level flooding, the city has seen rapid real estate development growth. This paper analyzes a survey conducted with Urban Land Institute (ULI) members in the Charleston region to understand how the real estate community is coping with and combating flooding impacts. Results show that while residential real estate developers are rethinking their development patterns, commercial developers are slow to recognize the threat of climate change impacts. The paper concludes with suggestions for policies and practices to address these threats, strengthen Charleston’s commercial real estate, and better prepare the city for a safe, prosperous future.
Artisanal and small-scale gold mining (ASGM) is the largest anthropogenic source of mercury emissions globally. Concern over mercury pollution increases due to its long-term impacts on human health and aquatic and terrestrial ecosystems. Using a participatory research methodology, we gathered social and behavioral information regarding daily practices and water usage by an ASGM community in Suárez, Colombia. Based on this information, we identified 18 sampling sites of water sources commonly used by the community. The samples were analyzed for total mercury, total coliforms, pH, electrical conductivity, and total dissolved oxygen. Physicochemical and microbiological parameters from the water assessment were compared with the drinking water thresholds set by the Colombian regulatory agencies, the EPA, and the WHO. Our results showed that the majority of the samples do not meet one or more quality and safety standards. On average, the sampling sites showed total mercury levels below the regulatory limits; however, the data had considerable variability, and in many cases, individual observations fell above the maximum concentration limit for drinking water. We discuss these results within the larger framework of the regulatory gaps for human and environmental protection in ASGM contexts. The total lack of water, sanitation, and hygiene infrastructure, combined with the long-term consumption of sublethal doses of mercury and other water contaminants, constitutes a significant threat to the well-being of communities and territories that necessitates further research and intervention by institutional authorities.
Background Granivore-mediated seed dispersal is susceptible to changes in seed availability and silvicultural management, which alters synzoochorous interactions in the antagonism-mutualism continuum and affects the seed dispersal effectiveness (SDE), and eventually, the plant recruitment. We conducted a whole-year study of seed addition to quantify the granivores-Korean pine ( Pinus koraiensis ) synzoochorous interactions and the SDE in the same secondary forests with two treatments. Both treatments had seed source limitations: one was caused by the disappearance of Korean pine due to the historical disturbance, the other by pinecone harvesting in Korean pine plantations adjacent to the secondary forests. Thinning with different intensities (control, 25%, and 50%) were also performed to further explore the synzoochorous interactions and SDE in response to silvicultural management in the second type of forests. Results Source limitation increased the proportion of pre- and post-dispersal seed predation, and made the granivores-Korean pine interaction shift more towards antagonism, with the estimated SDE of 2.31 and 3.60, respectively, for the secondary forests without and with Korean pine. Thinning with different intensities did not alleviate the reactions towards antagonism but altered SDE; granivores occurrence decreased, but the proportion of pre- and post-dispersal seed predation increased, resulting in a fivefold decreased seedling recruitment in 25% thinning (the lowest SDE of 0.26). Conclusion The source limitation coupling thinning biased the synzoochorous interactions more towards antagonism and significantly lowered granivore-mediated SDE, which limited the successful recruitment of Korean pine in secondary forests. Forest managers should control pinecone harvesting, protect the synzoochorous interaction, and take into account masting event for Korean pine regeneration in the future.
Nonlinear oscillations in micro- and nanoelectromechanical systems have emerged as an exciting research area in recent years due to their promise in realizing low-power, scalable, and reconfigurable mechanical memory and logic devices. Here, we report ultralow-power mechanical memory operations utilizing the nonlinear oscillation regime of GaN microcantilevers with embedded piezotransistive AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers. Switching between the high and low oscillatory states of the nonlinear oscillation regime was demonstrated using a novel phase-controlled opto-mechanical excitation setup, utilizing a piezo actuator and a pulsed laser as the primary and secondary excitation sources, respectively. Laser-based photoacoustic excitation was amplified through plasmonic absorption in Au nanoparticles deposited on a transistor. Thus, the minimum switching energy required for reliable memory operations was reduced to less than a picojoule (pJ), which translates to one of the lowest ever reported, when normalized for mass.
Lossless compressors have very low compression ratios that do not meet the needs of today’s large-scale scientific applications that produce vast volumes of data. Error-bounded lossy compression (EBLC) is considered a critical technique for the success of scientific research. Although EBLC allows users to set an error bound for the compression, users have been unable to specify the requirements on the compression quality, limiting practical use. Our contributions are: (1) We formulate the problem of configuring EBLC to preserve a user-defined metric as an optimization problem. This allows many classes of new metrics to be preserved, which improves over current practices. (2) We present a framework, OptZConfig, that can adapt to improvements in the search algorithm, compressor, and metrics with minimal changes, enabling future advancements in this area. (3) We demonstrate the advantages of our approach against the leading methods to configure compressors to preserve specific metrics. Our approach improves compression ratios against a specialized compressor by up to $3\times$ , has a 56× speedup over FRaZ, 1000× speedup over MGARD-QOI post tuning, and 110× speedup over systematic approaches which had not been bounded by compressors before.
Preparation strategies of cellulose nanopaper were elaborated.Functionalization of cellulose nanopaper and its advanced applications were summarized.Prospects and challenges of cellulose nanopaper were discussed. Preparation strategies of cellulose nanopaper were elaborated. Functionalization of cellulose nanopaper and its advanced applications were summarized. Prospects and challenges of cellulose nanopaper were discussed. Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices, food packaging, biomedical application, and so forth, owing to their various advantages such as good flexibility, tunable light transmittance, high thermal stability, low thermal expansion coefficient, and superior mechanical properties. Herein, recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies. We begin with a brief introduction of the three types of nanocellulose: cellulose nanocrystals, cellulose nanofibrils and bacterial cellulose, recapitulating their differences in preparation and properties. Then, the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared. Furthermore, the advanced applications of cellulose nanopaper including energy storage, electronic devices, water treatment, and high-performance packaging materials were highlighted. Finally, the prospects and ongoing challenges of cellulose nanopaper were summarized.
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9,500 members
Anthony Guiseppi-Elie
  • Center for Bioelectronics, Biosensors and Biochips (C3B)
Pierluigi Pisu
  • Department of Automotive Engineering
Rodrigo Martinez-Duarte
  • Department of Mechanical Engineering
U. J. Gibson
  • Center for Optical Materials Science and Engineering Technologies
Naren Vyavahare
  • Department of Bioengineering
81 Duke Innovation Center, 29625, Clemson, SC, United States
Head of institution
James P. Clements, Ph.D.