Abstract In celestial conformal field theory (CCFT), the 4d massless scalars are represented by 2d conformal operators with conformal dimensions h = h ¯ $$ \overline{h} $$ = (1 + iλ)/2. The Mellin ...transform of 4d massless scalar amplitudes gives the conformal correlators of CCFT. We study the conformal block decomposition of these celestial correlators in CCFT and obtain the explicit blocks. This conformal block decomposition is highly nontrivial, even for the simplest 4d massless scalar amplitude. We use the analytic continuation of the Appell hypergeometric function F 1 and the method of monodromy projection of conformal blocks, to achieve this block decomposition. This procedure is consistent with the crossing symmetry, in both the correlator-level and each explicit block-level. We also investigate its behavior in the conformal soft limit and find that the Appell hypergeometric function F 1 does not reduce to the Gauss hypergeometric function. This is different from the block decomposition of celestial gluons we studied before, where the Appell hypergeometric function F 1 reduces to the Gauss hypergeometric function. This difference comes from the shift of conformal dimensions and is the reason why we adopt the new method here for the block decomposition of celestial massless scalars.
Sparse code multiple access (SCMA) is one of the most promising methods among all the non-orthogonal multiple access techniques in the future 5G communication. Compared with some other non-orthogonal ...multiple access techniques, such as low density signature, SCMA can achieve better performance due to the shaping gain of the SCMA code words. However, despite the sparsity of the code words, the decoding complexity of the current message passing algorithm utilized by SCMA is still prohibitively high. In this paper, by exploring the lattice structure of SCMA code words, we propose a low-complexity decoding algorithm based on list sphere decoding (LSD). The LSD avoids the exhaustive search for all possible hypotheses and only considers signal within a hypersphere. As LSD can be viewed a depth-first tree search algorithm, we further propose several methods to prune the redundancy-visited nodes in order to reduce the size of the search tree. Simulation results show that the proposed algorithm can reduce the decoding complexity substantially while the performance loss compared with the existing algorithm is negligible.
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•The working mechanism of ZABs is introduced, especially oxygen electrochemistry.•Neutral and near-neutral electrolytes were reviewed for ZABs.•Oxygen catalysts were summarized within ...or beyond neutral ZABs.•A brief outlook was proposed for electrolytes and catalysts in neutral ZABs.
Rechargeable Zn-air batteries (R-ZABs) are promising electrochemical energy storage devices with the advantages of high theoretical energy density, low cost of Zn metal and environment-friendliness. ZABs with neutral electrolytes can avoid or mitigate many side reactions harassing alkaline ZABs because neutral electrolyte is mild and green, which is conducive to battery life. However, the development of neutral ZABs is still in an initial stage. In this review, we would like to summarize the recent progress of neutral electrolytes and electrocatalysts, which are applied in or beyond ZABs. The working mechanism of ZABs is first introduced, especially oxygen electrochemistry on cathode. After elucidating the disadvantages of alkaline electrolytes, several neutral and near-neutral electrolytes are then summarized on developments as well as challenges, such as inorganic/organic salt solutions, high concentration electrolytes and quasi-solid electrolytes. Next, different cathode structures and their impacts on catalysts are presented. The latest progress of different catalysts in neutral electrolytes are classified and summarized, including metal oxides, metal phosphides/sulfides, metal phosphates, single-atom catalysts, etc. Finally, we conclude with a summary and propose a brief outlook for the future developments of electrolytes and oxygen catalysts applied in neutral ZABs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, hydroxyl-modified/Na-intercalated g-C3N4 was used as an effective material for the removal of gaseous formaldehyde (HCHO) through adsorption and photocatalytic oxidation. In a simple ...reflux reaction using different NaOH concentrations, the surface-grafted hydroxyl (‒OH) groups of g-C3N4 formed internal hydrogen bonds with gaseous HCHO, while the Na atoms intercalated into the layered structure of g-C3N4 to create an electron transfer path (layer‒Na‒layer) to improve charge separation for photocatalytic oxidation. The hydroxylation as well as Na intercalation of g-C3N4 significantly increased its HCHO removal efficiency compared with that of bare g-C3N4. The HCHO removal capacity of the modified g-C3N4 reached approximately 0.12 ppm g−1 min−1, which was twice that of bare g-C3N4 (<0.06 ppm g−1 min−1). Moreover, the modified g-C3N4 was reused at least thrice without any decline in activity. This work provides a facile, simple, and fast approach to the modification of g-C3N4 via hydroxylation and Na intercalation to enhance HCHO adsorption as well as electron transfer, rendering it a promising material for indoor HCHO removal.
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•Hydroxyl-modified and Na-intercalated g-C3N4 was prepared via treatment with NaOH.•Hydroxylation of g-C3N4 significantly improved HCHO adsorption.•Na intercalation in g-C3N4 created an electron transfer path for charge migration.•Hydroxyl-modified and Na-intercalated g-C3N4 exhibited high HCHO removal performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The single-valued projection (sv) is a relation between scattering amplitudes of gauge bosons in heterotic and open superstring theories. Recently we have studied sv from the aspect of nonlinear ...sigma models 1, where the gauge physics of open string sigma model is under the Wilson loop representation but the gauge physics of heterotic string sigma model is under the fermionic representation since the Wilson loop representation is absent in the heterotic case. There we showed that the sv comes from a sum of six radial orderings of heterotic vertices on the complex plane. In this paper, we propose a Wilson loop representation for the heterotic case and using the Wilson loop representation to show that sv comes from a sum of two opposite-directed contours of the heterotic sigma model. We firstly prove that the Wilson loop is the exact propagator of the fermion field that carry the gauge physics of the heterotic string in the fermionic representation. Then we construct the action of the heterotic string sigma model in terms of the Wilson loop, by exploring the geometry of the Wilson loop and by generalizing the nonabelian Stokes's theorem 2–4 to the fermionic case. After that, we compute some three loop and four loop diagrams as an example, to show how the sv for ζ2 and ζ3 arises from a sum of the contours of the Wilson loop. Finally we conjecture that this sum of contours of the Wilson loop is the mechanism behind the sv for general cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A comprehensive review on modal parameter-based damage identification methods for beam- or plate-type structures is presented, and the damage identification algorithms in terms of signal processing ...are particularly emphasized. Based on the vibration features, the damage identification methods are classified into four major categories: natural frequency-based methods, mode shape-based methods, curvature mode shape-based methods, and methods using both mode shapes and frequencies, and their merits and drawbacks are discussed. It is observed that most mode shape-based and curvature mode shape-based methods only focus on damage localization. In order to precisely locate the damage, the mode shape-based methods have to rely on optimization algorithms or signal processing techniques; while the curvature mode shape-based methods are in general a very effective type of damage localization algorithms. As an implementation, a comparative study of five extensively-used damage detection algorithms for beam-type structures is conducted to evaluate and demonstrate the validity and effectiveness of the signal processing algorithms. This brief review aims to help the readers in identifying starting points for research in vibration-based damage identification and structural health monitoring and guides researchers and practitioners in better implementing available damage identification algorithms and signal processing methods for beam- or plate-type structures.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Connected and autonomous vehicle (CAV) technologies are expected to change driving/vehicle behavior on freeways. This study investigates the impact of CAVs on freeway capacity using a microsimulation ...tool. A four-lane basic freeway segment is selected as the case study through the Caltrans Performance Measurement System (PeMS). To obtain valid results, various driving behavior parameters are calibrated to the real traffic conditions for human-driven vehicles. In particular, the calibration is conducted using genetic algorithm. A revised Intelligent Driver Model (IDM) is developed and used as the car-following model for CAVs. The simulation is conducted on the basic freeway segment under different penetration rates of CAVs and different freeway speed limits. The results show that with an increase in the market penetration rate, freeway capacity increases, and will increase significantly as the speed limit increases.
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BFBNIB, NUK, PILJ, SAZU, UL, UM, UPUK
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bstract
We study tree-level celestial amplitudes in Yang-Mills theory — Mellin transforms of multi-gluon scattering amplitudes that convert them into the correlators of conformal primary fields on ...two-dimensional celestial sphere. By using purely field-theoretical methods, we show that the soft conformal limit of celestial amplitudes, in which one of the primary field operators associated to gauge bosons becomes a dimension one current, is dominated by the contributions of low-energy soft particles. This result confirms conclusions reached by using Yang-Mills theory formulated in curvilinear coordinates, as pioneered by Strominger. By using well-known collinear limits of Yang-Mills amplitudes, we derive the OPE rules for the primary fields and the holomorphic currents arising in the conformally soft limit. The Ward identities following from OPE have the same form as the identities derived by using soft theorems.
Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here we provide an up-to-date review ...on the spatial distributions of ticks and tick-borne pathogens in China. We map at the county level 124 tick species, 103 tick-borne agents, and human cases infected with 29 species (subspecies) of tick-borne pathogens that were reported in China during 1950-2018. Haemaphysalis longicornis is found to harbor the highest variety of tick-borne agents, followed by Ixodes persulcatus, Dermacentor nutalli and Rhipicephalus microplus. Using a machine learning algorithm, we assess ecoclimatic and socioenvironmental drivers for the distributions of 19 predominant vector ticks and two tick-borne pathogens associated with the highest disease burden. The model-predicted suitable habitats for the 19 tick species are 14‒476% larger in size than the geographic areas where these species were detected, indicating severe under-detection. Tick species harboring pathogens of imminent threats to public health should be prioritized for more active field surveillance.
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