66 research outputs found
An Iterative Bidirectional Gradient Boosting Algorithm for CVR Baseline Estimation
This paper presents a novel iterative, bidirectional, gradient boosting
(bidirectional-GB) algorithm for estimating the baseline of the Conservation
Voltage Reduction (CVR) program. We define the CVR baseline as the load profile
during the CVR period if the substation voltage is not lowered. The proposed
algorithm consists of two key steps: selection of similar days and iterative
bidirectional-GB training. In the first step, pre- and post-event temperature
profiles of the targeted CVR day are used to select similar days from
historical non-CVR days. In the second step, the pre-event and post-event
similar days are used to train two GBMs iteratively: a forward-GBM and a
backward-GBM. After each iteration, the two generated CVR baselines are
reconciled and only the first and the last points on the reconciled baseline
are kept. The iteration repeats until all CVR baseline points are generated. We
tested two gradient boosting methods (i.e., GBM and LighGBM) with two data
resolutions (i.e., 15- and 30-minute). The results demonstrate that both the
accuracy and performance of the algorithm are satisfactory.Comment: 5 pages, 8 figures, 2 table
MultiLoad-GAN: A GAN-Based Synthetic Load Group Generation Method Considering Spatial-Temporal Correlations
This paper presents a deep-learning framework, Multi-load Generative
Adversarial Network (MultiLoad-GAN), for generating a group of load profiles in
one shot. The main contribution of MultiLoad-GAN is the capture of
spatial-temporal correlations among a group of loads to enable the generation
of realistic synthetic load profiles in large quantity for meeting the emerging
need in distribution system planning. The novelty and uniqueness of the
MultiLoad-GAN framework are three-fold. First, it generates a group of load
profiles bearing realistic spatial-temporal correlations in one shot. Second,
two complementary metrics for evaluating realisticness of generated load
profiles are developed: statistics metrics based on domain knowledge and a
deep-learning classifier for comparing high-level features. Third, to tackle
data scarcity, a novel iterative data augmentation mechanism is developed to
generate training samples for enhancing the training of both the classifier and
the MultiLoad-GAN model. Simulation results show that MultiLoad-GAN outperforms
state-of-the-art approaches in realisticness, computational efficiency, and
robustness. With little finetuning, the MultiLoad-GAN approach can be readily
extended to generate a group of load or PV profiles for a feeder, a substation,
or a service area.Comment: Submitted to IEEE Transactions on Smart Gri
A Load Switching Group based Feeder-level Microgrid Energy Management Algorithm for Service Restoration in Power Distribution System
This paper presents a load switching group based energy management system
(LSG-EMS) for operating microgrids on a distribution feeder powered by one or
multiple grid-forming distributed energy resources. Loads on a distribution
feeder are divided into load switching groups that can be remotely switched on
and off. The LSG-EMS algorithm, formulated as a mixed-integer linear
programming (MILP) problem, has an objective function of maximizing the served
loads while minimizing the total number of switching actions. A new set of
topology constraints are developed for allowing multiple microgrids to be
formed on the feeder and selecting the optimal supply path. Customer comfort is
accounted for by maximizing the supply duration in the customer preferred
service period and enforcing a minimum service duration. The proposed method is
demonstrated on a modified IEEE 33-bus system using actual customer data.
Simulation results show that the LSG-EMS successfully coordinates multiple
grid-forming sources by selecting an optimal supply topology that maximizes the
supply period of both the critical and noncritical loads while minimizing
customer service interruptions in the service restoration process.Comment: 5 pages, 7 figures, submitted to 2021 IEEE PES General Meetin
A Novel Feeder-level Microgrid Unit Commitment Algorithm Considering Cold-load Pickup, Phase Balancing, and Reconfiguration
This paper presents a novel 2-stage microgrid unit commitment (Microgrid-UC)
algorithm considering cold-load pickup (CLPU) effects, three-phase load
balancing requirements, and feasible reconfiguration options. Microgrid-UC
schedules the operation of switches, generators, battery energy storage
systems, and demand response resources to supply 3-phase unbalanced loads in an
islanded microgrid for multiple days. A performance-based CLPU model is
developed to estimate additional energy needs of CLPU so that CLPU can be
formulated into the traditional 2-stage UC scheduling process. A per-phase
demand response budget term is added to the 1st stage UC objective function to
meet 3-phase load unbalance limits. To reduce computational complexity in the
1st stage UC, we replace the spanning tree method with a feasible
reconfiguration topology list method. The proposed algorithm is developed on a
modified IEEE 123-bus system and tested on the real-time simulation testbed
using actual load and PV data. Simulation results show that Microgrid-UC
successfully accounts for CLPU, phase imbalance, and feeder reconfiguration
requirements.Comment: 10 pages, submitted to IEEE Transactions on Smart Gri
Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Pseudomyxoma Peritonei of Appendiceal Origin - 801 Cases from a Single Institution in China
Aim: As more and more centers has published their treatment results ofpseudomyxoma peritonei (PMP) with cytoreductive surgery (CRS) andhyperthermic intraperitoneal chemotherapy (HIPEC), the data from Chinais missing. Myxoma Department of Aerospace Hospital is the biggestcenter treating PMP in China. The purpose of this study is to report theearly and long-term outcomes for PMP from this single center. Methods:801 appendix-derived PMP out of 1008 consecutive patients treated inMyxoma Department of Aerospace Hospital between 2008 and 2019 wereretrospectively analyzed. Results: Complete cytoreductive surgery (CCRS)was achieved in 240 (30%) patients with median PCI of 14(1~39), andthe rest had maximal tumor debulking (MTD), HIPEC was implementedin 96.3% of CCRS and 78.6% of MTD. The major morbidity (gradeIII/IV) was 11.4% and the 30-day operative mortality is 0.7%. The 5-and 10-year OS of CCRS was 76.9% and 64.1%, which is significantlyhigher than MTD (5-, 10-year OS as 36.1%, 27.1%; p20, MTD, high pathologic grade and without HIPECwere independent factors predicting poorer prognosis. Conclusions: CCRS+HIPEC can benefit PMP well with controllable risks. MTD+HIPEC maybenefit PMP as well when CCRS cannot be achieved after fully asscessmentby an experienced peritoneal maglignacy center, but the surgery should beperformed as limited as possible
Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic.
Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality.
Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States.
Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis.
Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection
Study of the Tensile Properties of CFRP Strengthened Steel Plates
This paper presents the experimental results of steel plates strengthened with carbon fiber reinforced polymer (CFRP) sheets under tensile load. The number of CFRP layers (ranging from one to four), strengthening schemes (single-sided and double-sided bonding), and temperatures (ranging from 25 to 120 °C) were investigated. Results showed that the number of CFRP layers and strengthening schemes had insignificant effects on failure modes of specimens. The failure modes were dominated by the degradation of resin matrix at temperatures lower than Tg + 10 or 20 °C, where Tg is the glass transition temperature, and were dominated by the volume decrease of resin matrix at temperatures above that. Through bonding CFRP sheets, the ultimate load and post-elastic stiffness of specimens were significantly increased. However, the increase in the number of CFRP layers also led to the decrease in strengthening and stiffening efficiency. The double-sided strengthened specimens showed more preferable mechanical properties than the single-sided strengthened specimens. As temperature increased, significant decreases in ultimate load and post-elastic stiffness were observed. Analytical modeling to predict the mechanical properties at ambient and elevated temperatures were conducted, respectively. The modeling results were verified by the test data
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