Wave energy is one of the most abundant renewable clean energy sources, and has been widely studied because of its advantages of continuity and low seasonal variation. However, its low capture ...efficiency and narrow capture frequency bandwidth are still technical bottlenecks that restrict the commercial application of wave energy converters (WECs). In recent years, using a nonlinear stiffness mechanism (NSM) for passive control has provided a new way to solve these technical bottlenecks. This literature review focuses on the research performed on the use of nonlinear mechanisms in wave energy device utilization, including the conceptual design of a mechanism, hydrodynamic models, dynamic characteristics, response mechanisms, and some examples of experimental verification. Finally, future research directions are discussed and recommended.
•Litter peaks of tropical forests occurred at the dry spring or winter.•Litter peaks of evergreen forests occurred at various seasons.•Precipitation and radiation dominate the litterfall seasonality ...at tropical forests.•Radiation and temperature dominate the seasonality at temperate and boreal forests.•Ecosystem models need to consider litterfall seasonal patterns.
The seasonal litterfall plays an important role in the process of forest carbon and nutrient cycles. The current dynamic vegetation models use a simplified method to simulate seasonal patterns of litterfall, and assume that litterfall inputs distributed evenly through the year for deciduous trees or occur once during the start of year for evergreen trees. In this study, we collected more than 400 litterfall measurements for different forest ecosystems from existing literature and monographs, and analyzed the seasonal patterns of litterfall over the various forest types. The results showed that the total annual litterfall varied significantly by forest types in the range of 3–11Mgha−1y−1. The seasonal litterfall patterns had diverse forms and varied obviously among the forest types. For tropical forests, the litter peaks occurred mostly in spring or winter, corresponding to the drought season; for temperate broadleaved and needle-leaved evergreen forests, litter peaks could occur at various seasons; and for temperate deciduous broadleaved and boreal evergreen needle-leaved forests, litter peaks were observed in autumn. Global analyses showed that seasonal patterns of litterfall were determined by both the physiological mechanism and environmental variables.
Global fish production (capture and aquaculture) has increased quickly, which has altered global flows of phosphorus (P). Here we show that in 2016, Formula: see text Tg P yr
(mean and interquartile ...range) was applied in aquaculture to increase fish production; while Formula: see text Tg P yr
was removed from aquatic systems by fish harvesting. Between 1950 and 1986, P from fish production went from aquatic towards the land-human systems. This landward P peaked at 0.54 Tg P yr
, representing a large but overlooked P flux that might benefit land activities under P scarcity. After 1986, the landward P flux decreased significantly, and became negative around 2004, meaning that humans spend more P to produce fish than harvest P in fish capture. An idealized pathway to return to the balanced anthropogenic P flow would require the mean phosphorus use efficiency (the ratio of harvested to input P) of aquaculture to be increased from a current value of 20% to at least 48% by 2050 - a big challenge.
For any positive integer
n
, let
A
n
be a linearly oriented quiver of type
A
with
n
vertices. It is well-known that the quotient of an exact category by projective-injectives is an extriangulated ...category. We show that there exists an extriangulated equivalence between the extriangulated categories
ℳ
n
+
1
and
ℱ
n
, where
ℳ
n
+
1
and
ℱ
n
are the two extriangulated categories corresponding to the representation category of
A
n
+1
and the morphism category of projective representations of
A
n
, respectively. As a by-product, the Hall algebras of
ℳ
n
+
1
and
ℱ
n
are isomorphic. As an application, we use the Hall algebra of
ℳ
2
n
+
1
to relate with the quantum cluster algebras of type
A
2
n
.
Objective
To investigative the performance of intratumoral and peritumoral radiomics based on contrast-enhanced spectral mammography (CESM) to preoperatively predict the effect of the neoadjuvant ...chemotherapy (NAC) of breast cancers.
Materials and methods
A total of 118 patients with breast cancer who underwent preoperative CESM and NAC from July 2017 to June 2020 were retrospectively analyzed, and the patients were grouped into training (
n
= 81) and test sets (
n
= 37) according to the CESM examination time. NAC effect for each patient was assessed by pathology. Intratumoral and peritumoral radiomics features were extracted from CESM images, and feature selection was performed through the Mann–Whitney
U
test and least absolute shrinkage and selection operator regression (LASSO). Five radiomics signatures based on intratumoral regions, 5-mm peritumoral regions, 10-mm peritumoral regions, intratumoral regions + 5-mm peritumoral regions, and intratumoral regions + 10-mm peritumoral regions were calculated through a linear combination of selected features weighted by their respective coefficients. The prediction performance of radiomics signatures was assessed by the area under the receiver operator characteristic (ROC) curve, the precision-recall (P-R) curve, the calibration curve, and decision curve analysis (DCA).
Results
Ten radiomics features were selected to establish the radiomics signature of intratumoral regions + 5-mm peritumoral regions, which yielded a maximum AUC of 0.85 (95% CI, 0.72–0.98) in the test set. The calibration curves, P-R curves, and DCA showed favorable predictive performance of the five radiomics signatures.
Conclusion
The intratumoral and peritumoral radiomics based on CESM exhibited potential for predicting the NAC effect in breast cancer, which could guide treatment decisions.
Key Points
•
The intratumoral and peritumoral CESM-based radiomics signatures show good performance in predicting the NAC effect in breast cancer.
Let
C
be an extriangulated category and
τ
be any
n
-cluster tilting subcategory of
C
. We consider the index with respect to
τ
and introduce the index Grothendieck group of
τ
. Using the index, we ...prove that the index Grothendieck group of
τ
is isomorphic to the Grothendieck group of
C
, which implies that the index Grothendieck groups of any two
n
-cluster tilting subcategories are isomorphic. In particular, we show that the split Grothendieck groups of any two 2-cluster tilting subcategories are isomorphic. Then we develop a general framework for
c
-vectors of 2-Calabi-Yau extriangulated categories with respect to arbitrary 2-cluster tilting subcategories. We show that the
c
-vectors have the sign-coherence property and provide some formulas for calculating
c
-vectors.
Let
A
be a finitary hereditary abelian category. We give a Hall algebra presentation of Kashaev’s theorem on the relation between Drinfeld double and Heisenberg double. As applications, we obtain ...realizations of the Drinfeld double Hall algebra of
A
via its derived Hall algebra and Bridgeland’s Hall algebra of
m
-cyclic complexes.
Analyzing wave power is important for exploiting renewable energy in the South China Sea, particularly near reef islands. This study analyzes the distribution and evolution of wave power and its ...harnessing potential in the South China Sea based on 26 years of high-resolution hindcast data. A hindcast simulation of wave characteristics is conducted using the WAVEWATCH III model, which has a 3-hour temporal resolution and a high spatial resolution of 0.067°, and the results are used to evaluate the blocking effect of the island groups. The hindcast data are validated using altimeter data from nine satellites for the entire computing period. The mean values over 26 years, seasonal evolutions, and trends are evaluated to determine the wave power distribution, and variabilities in wave power near coastlines and offshore islands are studied at ten reference points. The results show that the South China Sea has considerable wave power and areas that are rich in power originate from the Luzon Strait. Wave energy near the offshore islands is more stable than that at locations near the Chinese mainland, which indicates that installing a wave farm near the islands would be an economically viable and environmentally friendly way to supply power.
•A 26-year high resolution wave hindcast data for the South China Sea is established and validated.•The mean, seasonal, and trend analysis are conducted for the distribution of wave power in the whole domain.•Wave power variability near coastlines and offshore islands are studied at 10 reference points at the depth of 100 m.•Wave energy near the offshore islands is found to be more stable than that in the locations near the mainland of China.
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