66 research outputs found
What Could Tourism Do to a Small Fishing Village: A Case Study of the City of Weihai, China
Weihai City, located on the east end of Shandong Peninsula in Northeastern China was once a small and remote fishing village. In recent years Weihai City has become one of the most popular tourism destinations in China. The tremendous development of tourism has had a significant impact on Weihai’s economy, physical environment, and culture. Weihai is now famous for the beautiful coastal scenery, high quality leisure living, and a strong Korean and increasingly Russian influence. This study examines the perception of Weihai residents on the position of Weihai as a tourist destination and also their vision of Weihai’s future tourism development. Based on the resident surveys and available secondary data, tourism impacts in Weihai can be said to be largely positive. Place attachment and a sense of pride about belonging to the place are noticeable among the locals. Economic data suggests overall prosperity, too. However, available evidence also highlights some strained relationships among the various stakeholder groups
Analytical Frequency Nadir Prediction Considering Inverter-Based Fast Frequency Response
This letter develops an analytical frequency nadir prediction method that
allows for the consideration of three potential forms of fast frequency
response (FFR) provided by inverter-based resources. The proposed method
provides fast and accurate frequency nadir estimation after N-1 generation
tripping contingencies. Our method is grounded on the closed-form solution for
the frequency nadir, which is solved from the second-order system frequency
response model considering the governor dynamics and three types of FFR. The
simulation results in the IEEE 39-bus system with different types of FFR
demonstrate that the proposed method provides accurate and fast prediction for
the frequency nadir under various disturbances
Large-Signal Stability Criteria in DC Power Grids with Distributed-Controlled Converters and Constant Power Loads
The increasing adoption of power electronic devices may lead to large
disturbance and destabilization of future power systems. However, stability
criteria are still an unsolved puzzle, since traditional small-signal stability
analysis is not applicable to power electronics-enabled power systems when a
large disturbance occurs, such as a fault, a pulse power load, or load
switching. To address this issue, this paper presents for the first time the
rigorous derivation of the sufficient criteria for large-signal stability in DC
microgrids with distributed-controlled DC-DC power converters. A novel type of
closed-loop converter controllers is designed and considered. Moreover, this
paper is the first to prove that the well-known and frequently cited
Brayton-Moser mixed potential theory (published in 1964) is incomplete. Case
studies are carried out to illustrate the defects of Brayton-Moser mixed
potential theory and verify the effectiveness of the proposed novel stability
criteria
Optimizing Partial Power Processing for Second-Use Battery Energy Storage Systems
Repurposing automotive batteries to second-use battery energy storage systems
(2-BESS) may have environmental and economic benefits. The challenge with
second-use batteries is the uncertainty and diversity of the expected packs in
terms of their chemistry, capacity and remaining useful life. This paper
introduces a new strategy to optimize 2-BESS performance despite the diversity
or heterogeneity of individual batteries while reducing the cost of power
conversion. In this paper, the statistical distribution of the power
heterogeneity in the supply of batteries is considered when optimizing the
choice of power converters and designing the power flow within the battery
energy storage system (BESS) to maximize battery utilization. By leveraging a
new lite-sparse hierarchical partial power processing (LS-HiPPP) approach, we
show a hierarchy in partial power processing (PPP) partitions power converters
to a) significantly reduce converter ratings, b) process less power to achieve
high system efficiency with lower cost (lower efficiency) converters, and c)
take advantage of economies of scale by requiring only a minimal number of sets
of identical converters. The results demonstrate that LS-HiPPP architectures
offer the best tradeoff between battery utilization and converter cost and had
higher system efficiency than conventional partial power processing (C-PPP) in
all cases
Challenges and Opportunities for Second-life Batteries: A Review of Key Technologies and Economy
Due to the increasing volume of Electric Vehicles in automotive markets and
the limited lifetime of onboard lithium-ion batteries (LIBs), the large-scale
retirement of LIBs is imminent. The battery packs retired from Electric
Vehicles still own 70%-80% of the initial capacity, thus having the potential
to be utilized in scenarios with lower energy and power requirements to
maximize the value of LIBs. However, spent batteries are commonly less reliable
than fresh batteries due to their degraded performance, thereby necessitating a
comprehensive assessment from safety and economic perspectives before further
utilization. To this end, this paper reviews the key technological and economic
aspects of second-life batteries (SLBs). Firstly, we introduce various
degradation models for first-life batteries and identify an opportunity to
combine physics-based theories with data-driven methods to establish
explainable models with physical laws that can be generalized. However,
degradation models specifically tailored to SLBs are currently absent.
Therefore, we analyze the applicability of existing battery degradation models
developed for first-life batteries in SLB applications. Secondly, we
investigate fast screening and regrouping techniques and discuss the regrouping
standards for the first time to guide the classification procedure and enhance
the performance and safety of SLBs. Thirdly, we scrutinize the economic
analysis of SLBs and summarize the potentially profitable applications.
Finally, we comprehensively examine and compare power electronics technologies
that can substantially improve the performance of SLBs, including
high-efficiency energy transformation technologies, active equalization
technologies, and technologies to improve reliability and safety
The genetic architecture of membranous nephropathy and its potential to improve non-invasive diagnosis
Membranous Nephropathy (MN) is a rare autoimmune cause of kidney failure. Here we report a genome-wide association study (GWAS) for primary MN in 3,782 cases and 9,038 controls of East Asian and European ancestries. We discover two previously unreported loci, NFKB1 (rs230540, OR = 1.25, P = 3.4 × 10−12) and IRF4 (rs9405192, OR = 1.29, P = 1.4 × 10−14), fine-map the PLA2R1 locus (rs17831251, OR = 2.25, P = 4.7 × 10−103) and report ancestry-specific effects of three classical HLA alleles: DRB1*1501 in East Asians (OR = 3.81, P = 2.0 × 10−49), DQA1*0501 in Europeans (OR = 2.88, P = 5.7 × 10−93), and DRB1*0301 in both ethnicities (OR = 3.50, P = 9.2 × 10−23 and OR = 3.39, P = 5.2 × 10−82, respectively). GWAS loci explain 32% of disease risk in East Asians and 25% in Europeans, and correctly re-classify 20–37% of the cases in validation cohorts that are antibody-negative by the serum anti-PLA2R ELISA diagnostic test. Our findings highlight an unusual genetic architecture of MN, with four loci and their interactions accounting for nearly one-third of the disease risk
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