A
bstract
We first revisit impact-parameter dependent collisions of ultra-relativistic particles in quantum field theory. Two conditions sufficient for defining an impact-parameter dependent cross ...section are given, which could be violated in proton-proton collisions. By imposing these conditions, a general formula for the impact-parameter dependent cross section is derived. Then, using soft-collinear effective theory, we derive a factorization formula for the impact-parameter dependent cross section for inclusive hard processes with only colorless final-state products in hadron and nuclear collisions. It entails defining thickness beam functions, which are Fourier transforms of transverse phase-space parton distribution functions. By modelling non-perturbative modes in thickness beam functions of large nuclei in heavy-ion collisions, the factorization formula confirms the cross section in the Glauber model for hard processes. Besides, the factorization formula is verified up to one loop in perturbative QCD for the inclusive Drell-Yan process in quark-antiquark collisions at a finite impact parameter.
This paper proposes a novel balancing approach for an electric vehicle bipolar dc charging station at the megawatt level, enabled by a grid-tied neutral-point-clamped converter. The study uses the ...presence of an energy storage stage with access to both of the dc buses to perform the complementary balance. It proposes a generic balancing structure that can achieve balance regardless the kind of energy storage system (ESS) employed. This is aiming to reduce the hardware requirements of the system and maximize the usage of the ESS, whose main function is to perform the energy management related tasks. To meet this purpose, a three-level dc-dc interface is employed, allowing to compensate the dc currents with a single ESS. Furthermore, in order to prevent the appearance of even-order harmonics in the input current during asymmetrical operation, an alternative switching sequence for the central converter is proposed. Results indicate that, without altering dramatically the charging process of the ESS, it is possible to cover the whole load scenario without the need of a balancing circuit. This allows the use of off-the-shelf products both for the rectifier and the fast chargers. In this paper, simulation and experimental results are presented to validate the proposed balancing strategy.
In this paper, a new medium voltage power converter topology using a diode rectifier, three-level boost (TLB) converter, and neutral-point-clamped (NPC) inverter is proposed for a high-power ...permanent magnet synchronous generator-based wind energy conversion system. The generator-side TLB converter performs the maximum power point tracking and balancing of dc-link capacitor voltages, while the grid-side NPC inverter regulates the net dc-bus voltage and reactive power to the grid. A significant improvement in the grid power quality is accomplished as the NPC inverter no longer controls the dc-link neutral point voltage. A model predictive strategy is proposed to control the complete system where the discrete-time models of the proposed power electronic converters are used to predict the future behavior of control variables. These predictions are evaluated using two independent cost functions, and the switching states which minimize these cost functions are selected and applied to the generator- and grid-side converters directly. In order to comply with the high-power application, the switching frequencies of the TLB converter and NPC inverter are minimized and maintained below 1.5 and 1 kHz, respectively. The proposed topology and control strategy are verified through MATLAB simulations on a 3-MW/3000-V/577-A system and dSPACE DS1103-based experiments on 3.6-kW/208-V/10-A prototype.
Conventional liquid electrolytes for lithium batteries usually suffer from irreversible decomposition and safety concerns. Solid state electrolytes (SSEs) have been considered as the key for advanced ...lithium batteries with improved energy density and safety, whereas challenges remain for polymer and inorganic SSEs. Recently, hybrid solid‐state electrolytes (HSSEs) that integrate the merits of different electrolyte systems have been under intensive study. Herein, we summarize the recent progress of HSSEs with different compositions and structures. The design principle of each type of HSSEs are discussed, as well as their ionic conducting mechanism, electrochemical performance and effects of compositional/structural control. Finally, challenges and perspectives are provided for the future development of HSSEs and solid‐state lithium batteries.
Hybrid solid‐state electrolytes (HSSEs) are keys to the development of lithium batteries with enhanced energy density and safety. This Minireview summarizes the recent development of HSSEs and discusses their design principles, performance and ionic conducting mechanism.
At present, the understanding of the sedimentary paleoenvironment and organic matter enrichment law of black shale in the Wufeng-Longmaxi Formation is still insufficient. This time, we investigated ...the total organic carbon (TOC) content, X-ray diffraction mineralogical composition, and the major and trace element abundances of the newly recovered cores of three shale gas exploration wells in Changning, Qianjiang, and Xiushan areas which were, respectively, selected to discuss and compare the varying paleoenvironmental conditions and the factors that control organic matter accumulation, such as terrigenous input, redox conditions, primary productivity, and the degree of water retention in the basin. The results show that black siliceous shale lithofacies, gray-black shale lithofacies, gray-black silty shale lithofacies, gray argillaceous siltstone lithofacies, and gray shell marl lithofacies are mainly deposited in the Wufeng-Longmaxi Formation in the southeastern Sichuan Basin. Organic-rich black shale is mainly concentrated in the lower part of the Wufeng Formation and Longmaxi Formation. The continuous thickness of organic carbon content greater than 2% in the Changning area is 32 m, the continuous thickness in the Qianjiang area is 22 m, and the continuous thickness in the Xiushan area is 11 m. The hydrocarbon generation potential gradually weakens from west to east. The identification of the geochemical behavior characteristics of major and trace elements shows that enrichment of the organic matter black shale section in the Changning-Qianjiang-Xiushan areas is mainly formation in the anoxic-moderate water mass restriction environment with high primary productivity and less terrigenous detritus input under the low hydrodynamic conditions. However, the correlations of terrigenous detrital proxies Ti/Al, redox proxies V/Cr, Ni/Co, and paleoproductivity proxies Babio with the TOC contents show that the Changning area is a favorable area for the formation of organic-rich black shale and the Qianjiang area is affected by the Wuling underwater uplift; the thickness of the black shale deposits becomes thinner; the Xiushan area is adjacent to the Xuefeng uplift, and the deposition conditions of the accumulation of organic matter black shale deteriorate, which is unfavorable for shale gas exploration.
Abstract
Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to ...characterize small defects and correlate their structures with properties. Here, we show that tip-enhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS
2
, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edge-induced Raman peak (396 cm
−1
) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm
−1
. The power of TERS demonstrated in MoS
2
can also be extended to other 2D materials, which may guide the defect engineering for desired properties.
Objectives
To assess the efficacy of dynamic computer‐aided surgery (dCAS) in replacing a single missing posterior tooth, we compare outcomes when using registration‐and‐fixation devices positioned ...anterior or posterior to the surgical site. Registration is performed on either the anterior or opposite posterior teeth.
Methods
Forty individuals needing posterior single‐tooth implant placement were randomly assigned to anterior or posterior registration. Nine parameters were analyzed to detect the deviations between planned and actual implant placement, using Mann–Whitney and t‐tests for nonnormally and normally distributed data, respectively.
Results
The overall average angular deviation for this study was 2.08 ± 1.12°, with the respective average 3D platform and apex deviations of 0.77 ± 0.32 mm and 0.88 ± 0.32 mm. Angular deviation values for individuals in the anterior and posterior registration groups were 1.58°(IQR: 0.98°–2.38°) and 2.25°(IQR: 1.46°–3.43°), respectively (p = .165), with 3D platform deviations of 0.81 ± 0.29 mm and 0.74 ± 0.36 mm (p = .464), as well as 3D apex deviations of 0.89 ± 0.32 mm and 0.88 ± 0.33 mm (p = .986). No significant variations in absolute buccolingual (platform, p = .659; apex, p = .063), apicocoronal (platform, p = .671; apex, p = .649), or mesiodistal (platform, p = .134; apex, p = .355) deviations were observed at either analyzed levels.
Conclusions
Both anterior and posterior registration approaches facilitate accurate dCAS‐mediated implant placement for single missing posterior teeth. The device's placement (posterior‐to or anterior‐to the surgical site) did not affect the clinician's ability to achieve the planned implant location.
The Exocyst at a Glance Wu, Bin; Guo, Wei
Journal of cell science,
08/2015, Letnik:
128, Številka:
16
Journal Article
Recenzirano
Odprti dostop
The exocyst is an octameric protein complex that is implicated in the tethering of secretory vesicles to the plasma membrane prior to SNARE-mediated fusion. Spatial and temporal control of exocytosis ...through the exocyst has a crucial role in a number of physiological processes, such as morphogenesis, cell cycle progression, primary ciliogenesis, cell migration and tumor invasion. In this Cell Science at a Glance poster article, we summarize recent works on the molecular organization, function and regulation of the exocyst complex, as they provide rationales to the involvement of this complex in such a diverse array of cellular processes.
Designing highly active and robust electrocatalysts for oxygen evolution reaction (OER) is crucial for many renewable energy storage and conversion devices. Here, self‐supported monolithic hybrid ...electrodes that are composed of bimetallic cobalt–molybdenum nitride nanosheets vertically aligned on 3D and bicontinuous nanoporous gold (NP Au/CoMoNx) are reported as highly efficient electrocatalysts to boost the sluggish reaction kinetics of water oxidation in alkaline media. By virtue of the constituent CoMoNx nanosheets having large accessible CoMoOx surface with remarkably enhanced electrocatalytic activity and the nanoporous Au skeleton facilitating electron transfer and mass transport, the NP Au/CoMoNx electrode exhibits superior OER electrocatalysis in 1 m KOH, with low onset overpotential (166 mV) and Tafel slope (46 mV dec−1). It only takes a low overpotential of 370 mV to reach ultrahigh current density of 1156 mA cm−2, ≈140‐fold higher than free CoMoNx nanosheets. The electrocatalytic performance makes it an attractive candidate as the OER catalyst in the water electrolysis.
A flexible Co–Mo–N/Au electrode, which is composed of bimetallic cobalt–molybdenum nitride nanosheets vertically aligned on nanoporous gold, is successfully developed as a robust oxygen evolution reaction (OER) electrocatalyst in alkaline media. This electrode exhibits enhanced OER activity and durability by virtue of the CoMoNx nanosheets having large accessible CoMoOx surface and the nanoporous Au facilitating electron transfer and mass transport.
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