bluuebunny/crossref_metadata_2025 huggingface dataset:
Local atomic decompositions for multidimensional Hardy spaces
Authors: Kania-Strojec Edyta , Plewa Paweł , Preisner Marcin
Published: March 2020

We consider a nonnegative self-adjoint operator L on $$L^2(X)$$

L
2

(
X
)

, where $$X\subseteq {{\mathbb {R}}}^d$$

X
⊆

R

d

. Under certain assumptions, we prove atomic characterizations of the Hardy space $$\begin{aligned} H^1(L) = \left\{ f\in L^1(X) \ : \ \left\| \sup _{t>0} \left| \exp (-tL)f \right| \right\| _{L^1(X)}<\infty \right\} . \end{aligned}$$

H
1

(
L
)

=

f
∈

L
1

(
X
)

:

sup

t
>
0

exp
(
-
t
L
)
f

L
1

(
X
)

<
∞

.

We state simple conditions, such that $$H^1(L)$$

H
1

(
L
)

is characterized by atoms being either the classical atoms on $$X\subseteq {\mathbb {R}^d}$$

X
⊆

R

d

or local atoms of the form $$|Q|^{-1}\chi _Q$$

|
Q
|

-
1

χ
Q

, where $$Q\subseteq X$$

Q
⊆
X

is a cube (or cuboid). One of our main motivation is to study multidimensional operators related to orthogonal expansions. We prove that if two operators $$L_1, L_2$$

L
1

,

L
2

satisfy the assumptions of our theorem, then the sum $$L_1 + L_2$$

L
1

+

L
2

also does. As a consequence, we give atomic characterizations for multidimensional Bessel, Laguerre, and Schrödinger operators. As a by-product, under the same assumptions, we characterize $$H^1(L)$$

H
1

(
L
)

also by the maximal operator related to the subordinate semigroup $$\exp (-tL^\nu )$$

exp
(
-
t

L
ν

)

, where $$\nu \in (0,1)$$

ν
∈
(
0
,
1
)

.
Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals
Authors: Thomas Maximilian , Vollert Florian , Weidemann Jens , Gibmeier Jens , Kromm Arne , Kannengießer Thomas
Published: March 2020

The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNi- and CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern high-performance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account.
Effect of coal mine organic aerosol on the methane/air lower explosive limit
Authors: Valiulin S. V. , Onischuk A. A. , Baklanov A. M. , Bazhina A. A. , Paleev D. Yu. , Zamashchikov V. V. , Korzhavin A. A. , Dubtsov S. N.
Published: March 2020

Organic aerosol is formed in coal mines due to heat release and evaporation of organics from coal during the longwall operation. This frictional heating occurs when a metallic cutting bit strikes a rock. Thus formed organic aerosol can contribute significantly to the explosivity of methane/air atmosphere in coal mines. In this paper, the flammable limits for the methane–air mixtures with organic aerosol are determined. For this purpose, organic aerosol is synthesizes from the coal-tar pitch in a laboratory evaporation–nucleation flow chamber. Aerosol particles synthesized under laboratory conditions are aggregates consisting of small primary particles with the fractal-like dimension Df = 2.0 ± 0.1, which is close to Df = 2.1 ± 0.1 of coal mine aerosol. It is shown that the flammability of organic aerosol/methane mixture in air is in good agreement with the Le Chatelier additive principle. The lower ignition limit for the pure organic aerosol in air is 44 g/m3.
Heterojunction Incorporating Perovskite and Microporous Metal–Organic Framework Nanocrystals for Efficient and Stable Solar Cells
Authors: Zhou Xuesong , Qiu Lele , Fan Ruiqing , Zhang Jian , Hao Sue , Yang Yulin
Published: March 2020

In this paper, we present a facile approach to enhance the efficiency and stability of perovskite solar cells (PSCs) by incorporating perovskite with microporous indium-based metal–organic framework [In12O(OH)16(H2O)5(btc)6]n (In-BTC) nanocrystals and forming heterojunction light-harvesting layer. The interconnected micropores and terminal oxygen sites of In-BTC allow the preferential crystallization of perovskite inside the regular cavities, endowing the derived films with improved morphology/crystallinity and reduced grain boundaries/defects. Consequently, the In-BTC-modified PSC yields enhanced fill factor of 0.79 and power conversion efficiency (PCE) of 20.87%, surpassing the pristine device (0.76 and 19.52%, respectively). More importantly, over 80% of the original PCE is retained after 12 days of exposure to ambient environment (25 °C and relative humidity of ~ 65%) without encapsulation, while only about 35% is left to the pristine device.
Structure, Performance, and Application of BiFeO3 Nanomaterials
Authors: Wang Nan , Luo Xudong , Han Lu , Zhang Zhiqiang , Zhang Renyun , Olin Håkan , Yang Ya
Published: March 2020

Multiferroic nanomaterials have attracted great interest due to simultaneous two or more properties such as ferroelectricity, ferromagnetism, and ferroelasticity, which can promise a broad application in multifunctional, low-power consumption, environmentally friendly devices. Bismuth ferrite (BiFeO3, BFO) exhibits both (anti)ferromagnetic and ferroelectric properties at room temperature. Thus, it has played an increasingly important role in multiferroic system. In this review, we systematically discussed the developments of BFO nanomaterials including morphology, structures, properties, and potential applications in multiferroic devices with novel functions. Even the opportunities and challenges were all analyzed and summarized. We hope this review can act as an updating and encourage more researchers to push on the development of BFO nanomaterials in the future.
Stationary solutions to a nonlocal fourth-order elliptic obstacle problem
Authors: Laurençot Philippe , Walker Christoph
Published: March 2020

Existence of stationary solutions to a nonlocal fourth-order elliptic obstacle problem arising from the modelling of microelectromechanical systems with heterogeneous dielectric properties is shown. The underlying variational structure of the model is exploited to construct these solutions as minimizers of a suitably regularized energy, which allows us to weaken considerably the assumptions on the model used in a previous article.
Minding the gap between cortisol levels measured with second-generation assays and current diagnostic thresholds for the diagnosis of adrenal insufficiency: a single-center experience
Authors: Grassi G. , Morelli V. , Ceriotti F. , Polledri E. , Fustinoni S. , D’Agostino S. , Mantovani G. , Chiodini I. , Arosio M.
Published: March 2020

Purpose

The current cut-offs for the diagnosis of adrenal insufficiency (AI) have been established using outdated immunoassays. We compared the cortisol concentrations measured with Roche Cortisol I (R1), the newly available Roche Cortisol II (R2), and liquid chromatography tandem mass spectrometry (LC-MS/MS), the gold standard procedure to measure steroids in patients undergoing the corticotropin (ACTH) test.

Methods

We enrolled 30 patients (age 47 ± 21 years) referred to undergo the ACTH test (1 or 250 μg). Cortisol was measured at 0, 30, and 60 min after stimulation with R1, R2, and LC-MS/MS. AI was diagnosed for R1-stimulated peak cortisol concentrations < 500 nmol/L.

Results

Mean cortisol concentrations measured with R2 and LC-MS/MS were comparable, while mean cortisol concentrations measured by R1 were higher than those of both R2 and LC-MS/MS (respectively, basal 411 ± 177, 287 ± 119, and 295 ± 119 nmol/L; at 30 min, 704 ± 204, 480 ± 132, and 500 ± 132 nmol/L; at 60 min, 737 ± 301, 502 ± 196, and 519 ± 201 nmol/L, p ≤ 0.01 for R1 vs. both R2 and LC-MS/MS at each point). Considering the 500 nmol/L cortisol peak cut-off, AI was diagnosed in 5/30 patients using R1 and in 12/30 using R2 (+ 140%). Based on the correlation between R1 and R2, the threshold of 500 nmol/L became 351 nmol/L (12.7 μg/dL) when cortisol was measured with R2, and 368 nmol/L (13.3 μg/dL) with LC-MS/MS.

Conclusions

The use of more specific cortisol assays results in lower cortisol concentrations. This could lead to misdiagnosis and overtreatment when assessing AI with the ACTH test if a different cut-off for cortisol peak is not adopted.
Model of Load Distribution Between Web Proxy Servers Using Network Traffic Analysis
Authors: Renuka B. S. , Prafulla Shashikiran G. T.
Published: March 2020

Proxy servers are installed to give information access services to requested client nodes or units individually. As of now, in the present framework intermediaries are confronting the performance bottleneck that is when numerous clients get to the Internet all the while since such servers have a constrained limit. Web servers often experience and face overload situations due to the extremely bursty nature of traffic caused on the Internet. Our concentration in the work is to propose successful load control instruments for web servers. A significant angle in the load control is to limit the work spent by the proxy server to distribute the load and pass on to the main servers. This research work proposes a technique for load balancing on proxy servers by investigating the load on the network between servers and proxy servers. The research investigation is based on calculating the bits per second movements of packet and sockets with respect to the ports such as HTTP/HTTPS and TCP. This proposed method increases the performance by reducing the load on the proxy servers.
Profiles of narcissism and self‐esteem associated with comprehensive mental health in adolescents
Authors: Xu Xiaofeng , Huebner E. Scott , Tian Lili
Published: March 2020

Introduction

This study firstly aimed to identify different profiles of narcissism and self‐esteem in adolescents using latent profile analysis (LPA). A secondary aim was to examine associations between the identified profiles and subsequent measures of comprehensive mental health.

Methods

Chinese adolescents (N = 1009, 50.8%girls, Mage = 12.99, SD = 0.66) completed a packet of measures on two occasions at 6‐month intervals. Narcissism and self‐esteem were assessed at Time 1. Positive and negative indicators of mental health were assessed at Time 2.

Results

Latent profile analysis of narcissism and self‐esteem identified six profiles: (1) high narcissism and high self‐esteem; (2) high‐moderate self‐regard; (3) moderate self‐regard; (4) low‐moderate self‐regard; (5) high narcissism but low self‐esteem; (6) low self‐regard. Adolescents in the high narcissism and high self‐esteem and high‐moderate self‐regard profiles displayed positive mental health outcomes whereas adolescents in the high narcissism but low self‐esteem and low self‐regard profiles reported problematic mental health outcomes.

Conclusion

Differing profiles of narcissism and self‐esteem in adolescents were identified; these profiles provide new insight into the structure of self‐concept for adolescents. Further, the identified profiles of narcissism and self‐esteem were differentially related to subsequent comprehensive mental health outcomes.
Overriding Plate Velocity Control on Surface Topography in 2‐D Models of Subduction Zones
Authors: Cerpa Nestor G. , Arcay Diane
Published: March 2020

We study the dynamically induced flexural topography in subduction numerical mechanical models. We focus on the topographic changes at the overriding plate (OP) surface induced by variations in OP kinematics, particularly when the subducting plate (SP) has a stationary motion after having reached the rigid base of the upper mantle. Our models consist of two viscoelastic plates with free surfaces and an isoviscous mantle. Friction is imposed along the planar subduction interface. We first characterize the main topographic features at a constant OP velocity, using spatial definitions based on geometrical estimations of the volcanic arc position. The models exhibit the formation of a bulge in the forearc area followed landwards by a depression and a smaller second bulge, both bracketing the arc region. The steady‐state distance to the trench of these features increases with OP velocity. Their amplitude is affected by the far‐field OP tectonic regime that depends on kinematics, and plates and subduction interface strength. We next test the effect of sudden changes in OP velocity. An OP acceleration yields a transient topographic tilt, during which the outer forearc quickly subsides whereas the arc region uplifts, and that is followed by reverse slower motions. An OP slowdown induces opposite motions. The rates of elevation change during the tilt are approximately proportional to velocity variations and mainly sensitive to the SP strength. The rates are higher than 0.1 mm/yr for velocity changes higher than 1 cm/yr. We suggest that topographic accommodations of OP velocity changes should be considered when quantifying nonisostatic topography.
Tide‐Induced Periodic Sea Surface Temperature Drops in the Coral Reef Area of Nanwan Bay, Southern Taiwan
Authors: Hsu Po‐Chun , Lee Hung‐Jen , Zheng Quanan , Lai Jian‐Wu , Su Feng‐Chun , Ho Chung‐Ru
Published: March 2020

Tidal current‐induced cyclonic eddies cause cold‐water upwelling and periodic sea surface temperature (SST) drops around the coral reef area in Nanwan Bay, which is located at the southern tip of Taiwan. This study used Himawari‐8 satellite data and tide gauge and coastal ocean dynamics application radar (CODAR) data to analyze the characteristics of the SST drops and cyclonic eddy propagation and used an oceanic general circulation model (OGCM) to simulate the tidal current flowing process. According to the CODAR data analysis, the mixed primary semidiurnal tide had an average current velocity of 0.3–0.4 m s−1 throughout the bay, and the average life cycle of a cyclonic eddy is 6.6 hr, with a propagation speed of 0.35 m s−1. The SST drop during the spring tide period was greater than that during the neap tide period, and the SST dropped in both summer and winter. The average daily SST drop in the summer reached 2 °C with a maximum observed value of 4.7 °C, and the SST drop rate was 0.3–0.5 °C hr−1. The annual mean chlorophyll‐a concentration was 0.25 mg m−3. This study explored the special properties of the Nanwan Bay coral reef area from the perspective of ocean physics to allow ecologists to facilitate the implementation of long‐term conservation and monitoring programs.
Dominguez, Murphy, Noone, Sorooshian, and Volkamer Receive 2019 Atmospheric Sciences Ascent Awards
Authors:   AGU
Published: March 2020

Francina Dominguez, Jennifer Murphy, David Noone, Armin Sorooshian, and Rainer M. Volkamer received the 2019 Atmospheric Sciences Ascent Award at AGU’s Fall Meeting 2019, held 9–13 December in San Francisco, Calif. The award recognizes “research contributions by exceptional mid-career scientists in the fields of atmospheric and climate sciences.”
Jeevanjee Receives 2019 James R. Holton Award
Authors:   AGU
Published: March 2020

Nadir Jeevanjee received the 2019 James R. Holton Award at AGU’s Fall Meeting 2019, held 9–13 December in San Francisco, Calif. The award recognizes “outstanding scientific research and accomplishments of early-career scientists” who are no more than 3 years past receiving the Ph.D. degree.
Barnes Receives 2019 Sulzman Award for Excellence in Education and Mentoring
Authors:   AGU
Published: March 2020

Rebecca Barnes received the 2019 Sulzman Award for Excellence in Education and Mentoring at AGU’s Fall Meeting 2019, held 9–13 December in San Francisco, Calif. The award is given to “one mid-career female scientist…for significant contributions as a role model and mentor for the next generation of biogeoscientists.”
Modeling Under Pressure
Authors: Betancourt Mark
Published: March 2020

At a critical moment in the effort to end one of the world’s worst oil spills, one scientist holed up in his office and pulled an all-nighter to calculate the well’s aquifer support.
Taro Takahashi (1930–2019)
Authors: Bassett William
Published: March 2020

This giant in geochemistry also pioneered early high-pressure, high-temperature studies that launched the field of mineral physics.
Mapping Lightning Strikes from Space
Authors: Sima Richard
Published: March 2020

A new technique spatially tracks lightning in real time and has been adapted by the National Weather Service.
High Water: Prolonged Flooding on the Deltaic Mississippi River
Authors: Gasparini Nicole , Yuill Brendan
Published: March 2020

Changing climate and land use practices are bringing extended periods of high water to the lower Mississippi River. New management practices are needed to protect people, industry, and the land.
A Shared Resource for Studying Extreme Polar Environments
Authors: Sweet Justin , Winberry J. , Huerta Audrey , Anderson Kent , Beaudoin Bruce , Bilek Susan , Carpenter Paul , Nikolaus Kevin , Roth Aurora , Arnell Kirsten , Lingutla Narendra , Woodward Bob
Published: March 2020

A new community pool of seismic instrumentation will facilitate and advance geologic and cryospheric research in Earth’s ice-covered environments.
Early Sprouting of Leaves Enhances Northern Hemisphere Warming
Authors: Hornyak Tim
Published: March 2020

As leaf out has been advancing 4–5 days per decade, scientists say the effect of vegetation on climate remains poorly understood.
Climate Change Will Reduce Spanish Olive Oil Production
Authors: Barbuzano Javier
Published: March 2020

Increased droughts will reduce southern Spain’s olive oil output by 30% before the end of the century.
Geodetic Data Pinpoint Earthquake-Prone Regions of the Himalayas
Authors: Kornei Katherine
Published: March 2020

GPS measurements of the Indian and Eurasian plates reveal four locked segments most likely to produce large earthquakes.
This Week: From Online Ed to the Battle of the Ologies
Authors:   AGU
Published: March 2020

What Earth and space science stories are we recommending this week?
AGU’s Online Learning Exchange Shares Education Resources
Authors:   AGU
Published: March 2020

As teachers worldwide transition to virtual learning, expert educators offer a new place to find and share the best ways to keep your students on track.
Sustainable Agriculture Reflected in Cuba’s Water Quality
Authors: Kornei Katherine
Published: March 2020

Water samples from 25 rivers in central Cuba are dominated by signs of rock weathering rather than fertilizer runoff, researchers working at Cuban and American institutions show.
Larger Role for Shallow Intermediate Waters in Ocean Circulation
Authors: Pratt Sara
Published: March 2020

Water masses formed off southeastern Greenland may contribute more than previously thought to the variability of the Atlantic Meridional Overturning Circulation, which strongly influences global climate.
Evaluating Cloud Cover Predictions in Climate Models
Authors: Stanley Sarah
Published: March 2020

A new analysis highlights progress in predictions of cloud cover from models that are part of the Coupled Model Intercomparison Project.
Mapping Martian Dunes from Orbit
Authors: Shultz David
Published: March 2020

New research shows how fast the sands shift on the Red Planet and how useful imagery from different orbiting cameras can be in studies of Mars’s dunes.
Lost in the Everglades
Authors: Morton Mary
Published: March 2020

Living in Geologic Time: An unintentional adventure in the River of Grass shows how Florida has changed dramatically over 15,000 years of human habitation.
Podcast: Et Tu, Etna?
Authors: Lester Liza
Published: March 2020

Global environmental calamity followed the death of Caesar. The source may have been a volcano in Sicily.
Mapping Nutrient Inputs in the Great Lakes Basin
Authors: Sidder Aaron
Published: March 2020

A new tool links nitrogen and phosphorus applications to land use classifications to better understand where and how much of the nutrients enter watersheds in the U.S. Great Lakes Basin.
Reindeer Could Trample Permafrost Thaw
Authors: Cartier Kimberly
Published: March 2020

Thick, fluffy snow traps summer’s heat in the top layers of Arctic permafrost even as winter chills the air above. Grazing animals stomp that snow flat.
Why Is Climate More Sensitive in the Latest Earth System Models?
Authors: Shultz David
Published: March 2020

Compared with previous generations, current Earth system models predict that Earth’s climate is more sensitive to carbon dioxide. Where does the increased sensitivity come from?
Space-Based Data Expand Understanding of Crustal Deformation
Authors: Wheeling Kate
Published: March 2020

Researchers used the largest GPS data set yet to examine deformation of the crust across continental China and its implications for tectonic activity.
Leveraging Satellite Sensors for Oil Spill Detection
Authors: Derouin Sarah
Published: March 2020

By using multiple remote sensors, scientists can quickly estimate the nature and thickness of oil spills—important factors for containment efforts.
Shallow Seismicity and the Classification of Structures in the Lau Back‐Arc Basin
Authors: Baxter A. T. , Hannington M. D. , Stewart M. S. , Emberley J. M. , Breker K. , Krätschell A. , Petersen S. , Brandl P. A. , Klischies M. , Mensing R. , Anderson M. O.
Published: March 2020

Back‐arc basins open in response to subduction processes, which cause extension in the upper plate, usually along trench‐parallel spreading axes. However, global seismic databases reveal that the majority of seismic events in the Lau Basin occur along transcurrent (strike‐slip) rather than extensional faults. To better characterize active deformation in this region, we compared centroid moment tensors (CMTs), calculated for large (Mw > 5), shallow (<30 km) seismic events, to the orientations of seafloor lineaments mapped throughout the Lau Basin. Ship‐based multibeam and satellite altimetry were combined with vertical gravity gradient data to create the lineament map. By comparing the possible focal planes of the CMTs to the orientations of the lineaments, the most likely fault plane solutions were selected, thus classifying the faults and establishing the nature of the highly variable stress regimes in the basin. We resolved the strike, dip, and dip direction of 308 faults and classified 258 additional structures by fault type. The analysis highlights a stress regime that is dominated by a combination of left‐lateral and right‐lateral strike‐slip faults, large‐scale transcurrent motion along rigid crustal‐scale fault zones, and nonrigid diffuse deformation along preexisting seafloor structures, with extension mainly limited to the tips of propagating rifts and spreading centers. By resolving many of the uncertain motions on the mapped lineaments of the Lau Basin, the CMT analysis addresses a number of questions concerning basin‐scale stress regimes and microplate development, complementing GPS measurements, and providing a more complete picture of the complexities of back‐arc basin development.
Comparison of platinum photodeposition processes on two types of titanium dioxide photocatalysts
Authors: Yamamoto Muneaki , Minoura Yasuhiro , Akatsuka Masato , Ogawa Satoshi , Yagi Shinya , Yamamoto Akira , Yoshida Hisao , Yoshida Tomoko
Published: March 2020

The photodeposition method is useful for the preparation of metal-loaded photocatalysts, by which the metal precursors are adsorbed on the photocatalyst surface and reduced by photoexcited electrons to typically form metallic nanoparticles.
Enzymes in a golden cage
Authors: Baruch-Shpigler Yael , Avnir David
Published: March 2020

We describe a general method for the entrapment of enzymes within bulk metallic gold.
A highly active Rh1/CeO2 single-atom catalyst for low-temperature CO oxidation
Authors: Han Bing , Li Tianbo , Zhang Junying , Zeng Chaobin , Matsumoto Hiroaki , Su Yang , Qiao Botao , Zhang Tao
Published: March 2020

Rh1/CeO2 SAC is highly active for CO oxidation, which exhibits a high TOF of 0.41 s−1via the Mars–van Krevelen mechanism.
Crystal structure, thermodynamics, and crystallization of bio-based polyamide 56 salt
Authors: Yang Pengpeng , Peng Xiaoqiang , Wang Sen , Li Dong , Li Ming , Jiao Pengfei , Zhuang Wei , Wu Jinglan , Wen Qingshi , Ying Hanjie
Published: March 2020

Polyamide 56 is regarded as one of the most promising materials for the textile industry. This report gives the crystallization route of high-quality polyamide 56 monomers, and its crystal structure, transformation behaviors, and solubility.
Novel energetic metal–organic frameworks assembled from the energetic combination of furazan and tetrazole
Authors: Hao Wenjia , Jin Bo , Zhang Jinhao , Li Xiaoyi , Huang Tao , Shen Juan , Peng Rufang
Published: March 2020

Two energetic MOFs based on the combination of furazan and tetrazole, exhibit enhanced energetic properties and reduced sensitivity, due to outstanding oxygen balance and the presence of hydrogen bonds.
A facile one-step synthesis of super-hydrophilic (NH4)0.33WO3/WS2 composites: a highly efficient adsorbent for methylene blue
Authors: Zhang Shuai , Yang Ying , Xu Lishuang , Yu Hui , Li Dan , Wang Xinlu , Dong Xiangting
Published: March 2020

Super-hydrophilic ATBDs-3 composites synthesized using a hydrothermal method only needed less than 2 min to attain more than 80% of the MAC (80.45 mg g−1).
Highly efficient CO2 capture and conversion of a microporous acylamide functionalized rht-type metal–organic framework
Authors: Liao Junxiong , Zeng Wenjiang , Zheng Baishu , Cao Xiyang , Wang Zhaoxu , Wang Guanyu , Yang Qingyuan
Published: March 2020

A microporous acylamide functionalized rht-type MOF (HNUST-9) with Lewis acidic open copper sites and CO2-philic acylamide groups exhibits high performance for CO2 capture, separation and chemical conversion.
The electronic properties tuned by the synergy of polaron and d-orbital in a Co–Sn co-intercalated α-MoO3 system
Authors: Xu Xin , Lai Haojie , Xia Yufan , Luo Tian , Chen Yuxuan , Wang Siyuan , Chen Ke , Wang Xin , Shi Tingting , Xie Weiguang , Liu Pengyi
Published: March 2020

Internal mechanism of the Sn–Co co-intercalated α-MoO3 system with excellent electrical conductivity: synergistic effects of polaron and d orbitals.
Strategic wind power investment in competitive electricity markets considering the possibility of participation in intraday market
Authors: Mousavi Seyed Milad , Barforoushi Taghi
Published: March 2020

Wind power application in producing electrical energy is an integral part of the increased eco‐friendly generation. Accordingly, wind power producers may have a dominant position in some electricity markets. This study mainly concerns a strategic wind power investor who owns a number of units and seeks to optimise its expansion plans on sizes and sites of new generation capacities in a horizon year. Here, the investor is a price‐maker in both day‐ahead (DA) and intraday (ID) markets, while acts as a deviator in the balancing market. A stochastic bi‐level model is proposed wherein the upper‐level, the investor maximises the expected profit. Both DA and ID market clearings are considered in the lower‐level (LL). The model is formulated as a mathematical program with equilibrium constraints (MPEC) by replacing the LL problem with its Karush–Kuhn–Tucker (KKT) conditions. The MPEC model is then converted to a mixed‐integer linear programming model. A three‐bus illustrative example and IEEE 24‐bus reliability test system are used to demonstrate the effectiveness of the proposed model. The results confirm that the presence of the ID market in the investment model has increased the expected profits of the investor and also increases invested wind capacity.
Novelty method for the utility harmonic impedance estimation based on Gaussian mixed model
Authors: Tang Zhirong , Shu Qin , Xu Fangwei , Jiang Yue
Published: March 2020

The accurate estimation of harmonic impedance on the utility side of a point of common coupling (PCC) is much important to harmonic control, harmonic emission level, and harmonic responsibility analysis. In this study, a novel estimation method for the utility harmonic impedance is proposed, which employs the Gaussian mixed model (GMM) to fit the measured data at a PCC, because the authors find that the statistical distribution of the measured data at a PCC is close to the Gaussian distribution. Also, in theory, GMM can approach the probability distribution of any data. In this method, the Norton equivalent circuit model at a PCC is first expressed as a GMM, and the utility harmonic impedance in the GMM is estimated by expectation maximisation iterative method. Compared to the existing estimation methods, an outstanding advantage of this method is that it is less affected by background harmonics; therefore, higher accuracy can be acquired in this method. The effectiveness and accuracy of this method are verified by simulation experiments and field data.
Incorporation of generator maintenance scheduling with long‐term power sector forecasting and planning studies
Authors: İlseven Engin , Göl Murat
Published: March 2020

The objective of this study is to propose a dynamic generator maintenance scheduling (GMS) algorithm for long‐term power sector forecasting and planning studies in which electricity price and the resulting supply composition are determined with merit‐order dispatch. Compatible with the GMS algorithm, a reasonable strategy for the utilisation of storage hydropower plants along with clear definitions for each stage including must‐run renewable electricity generation modelling, calculation of reserve capacity, derivation of scenarios for storage hydropower plants and problem formulation is presented. Generation from storage hydropower plants are modelled such as must‐run and price‐dependent parts, to better approximate reality. The proposed structure is tested with real data of the Turkish system, with a demand and capacity projection in the long term. The results are compared with the actual maintenance plan of the base year and the general profile is evaluated as satisfactory. The results show that the GMS plan and profile may significantly change based on hydro and renewable generation expectation, future capacity evolution, and storage hydropower plant utilisation. Therefore, the proposed GMS algorithm can be utilised especially in long‐term price forecasting and supply modelling studies, instead of using a fixed factor to represent the maintenance effect on available generation capacity.
Heterogeneous‐decomposition‐based coordinated optimisation for integrated transmission and distribution networks considering communication conditions
Authors: Tang Kunjie , Dong Shufeng , Ma Xiang , Fei Yongpan , Song Yonghua
Published: March 2020

An asynchronous heterogeneous decomposition (async‐HGD) algorithm for integrated transmission and distribution networks coordinated optimisation considering communication conditions is proposed. Compared with traditional synchronous HGD (sync‐HGD), a partial synchronisation mechanism is introduced instead of the full synchronisation to alleviate the influence of communication delays. Under this mechanism, the transmission system operator does not need to wait for the slowest distribution system operator to complete its subproblem and update boundary parameters before the next iteration can proceed. Also, a bounded delay is introduced under this mechanism to ensure sufficient freshness of all the updates. Further, the previous value strategy (PVS) and linear regression strategy (LVS) are applied to handle non‐instantaneous interruptions in the communication networks as an improvement of the async‐HGD. Numerical experiments show that considering communication delays in the actual operation; the async‐HGD takes less time to converge compared with the sync‐HGD under appropriate settings. In addition, PVS and LVS can both enhance the robustness of the overall algorithm by achieving approximate solutions, and the LVS can achieve more accurate results compared with the PVS.
Use of EV hosting capacity for management of low‐voltage distribution systems
Authors: Barbosa Tiago , Andrade José , Torquato Ricardo , Freitas Walmir , Trindade Fernanda C.L.
Published: March 2020

With the increasing penetration of plug‐in electric vehicles (EVs), it has become important for utilities to identify how EV charging will affect their low‐voltage (LV) systems. In this context, EV hosting capacity can be useful to assist utility engineers. However, the appropriate strategy to estimate this index and determine its practical application for utilities is still unclear. In response, this study provides a framework to obtain and apply the hosting capacity information for EVs. Results of analyses are obtained considering the whole universe of a utility. Firstly, a method is developed for estimating this index based only on information readily available to utility engineers. The method is then used in a wide‐scale assessment of EV hosting capacity on 75,550 real LV systems. Quantitative results of this study provide insights into how to manage a system with high EV penetration. It is seen, e.g. that EV charging location is the most important variable to consider when stochastically assessing EV impacts, reducing difficulties to apply this type of solution for practical cases. Practical applications that employ EV hosting capacity statistics are also presented and discussed. Results are shown to be useful not only for utilities but also for regulatory agencies.
Reducing the risk of cascading failure in active distribution networks using adaptive critic design
Authors: Dutta Oindrilla , Mohamed Ahmed
Published: March 2020

In this study, a technique for developing a distribution management system (DMS), which possesses the flexibility to take both preventive and corrective actions against thermal overloading of branches in active distribution networks (ADNs), has been demonstrated. An ADN comprises microgrids that consist of photovoltaic and battery energy storage systems (BESSs). The DMS primarily minimizes the hourly cumulative cost incurred by loads due to energy pricing of utility, by effectively dispatching the BESSs. Besides, the DMS regulates BESS state of charge and bus voltages within their limits. It also controls loading of branches by taking corrective measures during overloading or preventive measures during critical loading conditions. This DMS has been designed using a reinforcement learning based technique, namely, adaptive critic design (ACD). This study elaborates the formulation of ACD algorithm so that an effective performance of the controller can be achieved. As case study, a modified IEEE 5‐bus system along with a microgrid and its controllers have been modelled in detail and simulated in real‐time by developing a simulation‐in‐the‐loop testbed using OPAL‐RT and DSpace. This testbed facilitates simulation of the detailed model along with its power electronic components, such that both transient and steady‐state performance of the system can be observed.
Experimental and computational study on epoxy resin reinforced with micro‐sized OPEFB using rectangular waveguide and finite element method
Authors: Khamis Ahmad Mamoun , Abbas Zulkifly , Ahmad Ahmad F. , Syahidah Azis Raba'ah , Abdalhadi Daw M. , Mensah Ebenezer Ekow
Published: March 2020

Epoxy resin (ER) composites reinforced with micro‐sized oil palm empty fruit bunch (OPEFB) were fabricated to improve the biodegradability of electromagnetic interference connector gasket. The dielectric properties, transmission coefficient |S21|, reflection coefficient |S11|, reflection loss, power loss and shielding effectiveness were studied at a frequency range of 8–12 GHz. OPEFB–ER composites were prepared by varying the percentages of OPEFB (0, 5, 10, 15, 20, 25, 30 and 40%) at room temperature (25°C ±2). Dielectric constant (ɛ′), loss factor (ɛ″), reflection and transmission coefficients of the composites were measured using rectangular waveguide connected to vector network analyser. In addition, ɛ′ and ɛ″ were used in finite element method technique to obtain |S11| and |S21|. The results showed that the dielectric properties increased but |S11| and |S21| decreased with increasing OPEFB percentage in the composites. The shielding effectiveness, power loss and reflection loss increased with increasing OPEFB percentage in the composites. The simulated and measured results of |S11| and |S21| were in good agreement.
Broadband and high gain dielectric‐rod end‐fire antenna fed by a tapered ridge waveguide for K/Ka bands applications
Authors: Zhang Yuwei , Lin Shu , Zhu Baoqi , Cui Jingxuan , Mao Yu , Jiao Jianlin , Denisov Alexander
Published: March 2020

In this study, a broadband and high gain dielectric‐rod end‐fire antenna are proposed for applications on both the K and Ka bands. By employing the double‐ridged waveguide (DRW) feeding structure which is composed of a coaxial line to tapered DRW transition, a parabolic tapered DRW, and a parabolic‐tapered flared parallel waveguide section, the impedance bandwidth of this proposed antenna is broadened to 84.5%. The dielectric‐rod with the double circular truncated cone structure acted as the main radiator of the proposed antenna is adopted to achieve higher gains and lower side‐lobe levels as compared to the traditional circular cone dielectric‐rod, while the four‐wedges structure inserted in the waveguide is developed as the matching section of the dielectric‐rod to further improve the impedance matching. The measured results show that this antenna can be operated in 17.9–44.1 GHz, and the measured gain changes from 9.9 to 15.5 dBi. Moreover, the radiation patterns are demonstrated with observed end‐fire characteristic in the overall operating band.
Compact dual‐band filtering power divider with independently controllable bandwidths using shorted patch resonators
Authors: Dong Gaoya , Wang Weimin , Wu Yongle , Liu Yuanan , Fang Yunnan , Tentzeris Manos M.
Published: March 2020

This study presents a novel dual‐band filtering power divider (DB‐FPD) structure with independently controllable bandwidths for dual‐band application. The proposed DB‐FPD structure is constructed by shorted G‐ and T‐shaped patch resonators, and meandered slot lines are etched on shorted patch resonators to generate resonance in the upper band. The 3 dB fractional bandwidth (FBW) of designed DB‐FPD structure in a lower band (upper band) can be adjusted from 5.2 to 24.2% (3.1 to 26.9%), respectively, using a substrate of 31 mil thick TLY‐5. The even‐/odd‐mode method is adopted to demonstrate the power splitting and isolation performances. The lumped‐element equivalent circuit is extracted to explain the power splitting transmission performance. Also, the coupling matrix analysis is applied to present the detailed design procedures for practical DB‐FPD, with specific passband bandwidths and centre frequencies of dual passbands. Finally, the isolation performances are analysed with different isolation resistor values and loading positions. For verification, two DB‐FPDs with equal absolute bandwidths (ABW) and equal FBWs are simulated, fabricated and measured for dual‐band WLAN application. The measured results agree well with the simulated ones, exhibiting a favourable frequency selectivity and controllable passband bandwidths.
Load frequency control of smart isolated power grids with high wind farm penetrations
Authors: Kazemi Golkhandan Reza , Torkaman Hossein , Aghaebrahimi Mohammad Reza , Keyhani Ali
Published: March 2020

The increasing contribution of wind turbine generators (WTGs) in power grids requires the control of wind generators and their impacts on the load frequency control (LFC). In this study, a detailed strategy for the control of WTGs in a smart power grid for LFC is presented. The WTGs are controlled by applying fuzzy logic controller with three inputs from wind velocity, frequency deviations, and wind velocity changes per second. The control takes into account for each WTG, an improved pitch angle controller to assist in fast damping of frequency deviations due to sudden high wind. Also, a feedback signal from frequency deviations, with the participation factor determined by a smart learning‐based intelligent controller (BELBIC) is used to determine rotor speed deviations. The controller facilitates frequency stability, and lower variations in the output power of conventional units. Simulation results, performed on a test system with three interconnected zones, validate the effectiveness of the proposed control strategy.
Modified leaky LMS‐based control strategy for reliable operation of single‐stage three‐phase grid‐tied PV system
Authors: Parida Abhisek , Subudhi Bidyadhar
Published: March 2020

This study presents development of a modified leaky least mean square (MLLMS)‐based control strategy for a single‐stage three‐phase grid‐tied photovoltaic (PV) system. In the proposed MLLMS‐based control scheme, the authors employ an incremental conductance maximum power point tracking algorithm for maximum power extraction, MLLMS algorithm for extraction of fundamental active and reactive components of the load current, delivering PV power to the grid, balancing the grid current and compensating harmonics of the connected loads at the point of common coupling. By virtue of a leakage factor and selection of sum of the exponential of the adaptation error in the cost function, the MLLMS algorithm overcomes the problems of drifting, low convergence and oscillations in weights encountered by some popular adaptive algorithms, e.g. least mean square (LMS) and least mean fourth (LMF) algorithms. The proposed control scheme is simulated in MATLAB/Simulink environment under different load and environmental conditions. Subsequently, the proposed control scheme is realised on a prototype grid‐tied PV system developed in the laboratory. From both the simulation and experimental results, it is observed that the proposed MLLMS algorithm outperforms LMS and LMF algorithms in terms of mean square error, oscillation in weights and total harmonic distortions of the grid currents.
Does renewable energy really decarbonise a power system? – An investigation
Authors: Kathiravan Renganathan , Kumudini Devi Raguru Pandu
Published: March 2020

Minimising emissions and operational costs are essential during energy production. To address this, a rational emission conversion factor‐based optimal economic emission dispatch model is proposed to allocate generators in a dispatch fleet optimally. Additionally, the role of renewable energy (RE) generators in enhancing the decarbonised operation of power systems is investigated. A multi‐objective function – consisting of fuel cost, RE forecasting deviation cost, and emission cost – is solved using the flower pollination algorithm, and the proposed scheme is successfully tested on the IEEE 30‐bus and Indian utility 30‐bus systems. The need for exact quantification of emissions and minimising the RE forecasting error, which offsets the benefits of RE, is demonstrated through various case studies.
Improving the transient performance of DFIG wind turbine using pitch angle controller low pass filter timing and network side connected damper circuitry
Authors: Okedu Kenneth E.
Published: March 2020

In wind turbine systems, pitch angle controllers are employed to reduce the aerodynamic power gained during high wind speeds. On the other hand, passive filters are usually used to mitigate disturbances in grid‐connected voltage source converters (VSCs). To avoid the risk of instability in the grid‐connected VSC, as a result of resonance in the capacitive and inductive components, it is necessary to consider damping. In this study, the low pass filter timing constant of the pitch angle controller of the doubly‐fed induction generator (DFIG) wind turbine was varied considering different time constants. The best timing response of the low pass filter was further used to analyse different filter topologies, in addition to a new control strategy that uses two trap passive filters with shunt resistor–capacitor as an active damper, in augmenting the DFIG wind turbine during grid fault. Simulation studies in PSCAD/EMTDC were carried out to compare the performance of the proposed scheme with some other conventional filter solutions for the DFIG wind generator, during a severe bolted three‐phase to ground fault. The simulation results demonstrate the improved performance and faster recovery of the wind generator variables after the fault considering the proposed filter scheme.
Path planning of autonomous agricultural machineries in complex rural road
Authors: Cui Jinbo , Zhang Xianfeng , Fan Xinmiao , Feng Wei , Li Ping , Wu Yu
Published: March 2020

This study mainly investigates the path planning and collision avoidance problem of autonomous agricultural machineries in the complex rural road. First, the grid model is used to build the global map of machineries and the particle swarm optimisation algorithm is used to search the global path. A non‐linear dynamic inertia weight is introduced to avoid the local lock‐up problem of traditional particle swarm optimisation. Then the artificial potential energy method for addressing the local collision problem is used, which is the sum of the attraction of the target point and the repulsion of the obstacles and the road boundary force. To solve the problem of the slip and roll of autonomous machinery caused by complex roads, a machinery dynamic model considering road curvature and topographic inclination is established, and the model predictive control algorithm is used to track the planned path. The simulation results show that proposed method can make the autonomous agricultural machinery driving safely and smoothly.
Optimisation of dynamic quantisation and control for quantised state feedback control system
Authors: Soe Than Zaw , Zanma Tadanao , Tokunaga Atsuki , Koiwa Kenta , Liu Kang Zhi
Published: March 2020

Networked control systems (NCSs) are control systems closed through communication network and applied to remote control of robots, tele‐surgery and numerous industrial applications. In NCS, data have to coarsely quantised when the communication network is restricted due to the traffic limit. Under the traffic limitation, the design of an appropriate quantiser is highly important in realising a desired control performance. Further, the coordination of quantisation and control input also plays a decisive role. Towards an optimal balance between the traffic capacity of network and the control performance, this study proposes an MPC based approach for quantised state feedback control systems with dynamic quantisers. In the proposed approach, the control input and the quantisation interval of the quantiser are optimised online. The proposed method can explicitly treat input/state constraints, the parameter of quantiser and other physical restriction. The effectiveness of the proposed method is demonstrated by simulations and experiments.