Coupling Of States Research Articles

Quasi-bound state in the continuum enhancing background limited infrared detectivity

Quasi-bound states in the continuum (quasi-BIC) have tunable high Q factors and thus have many potential applications in optoelectronics. Here, we propose to construct a quasi-BIC with a perturbated elliptical-cylinder photonic crystal slab, and then develop a new way based on the quasi-BIC to address the background noise problem of infrared detectors. By integrating the photonic crystal slab with a quantum well infrared photodetector (QWIP), and by pushing the quasi-BIC system with absorption to the critical coupling state, an ultra-narrow photoresponse band (Q factor equal to 1150) with a high peak quantum efficiency (over 60%) is achieved in the long-wavelength infrared range. The critical coupling state is realized by matching the radiation Q factor, which is mainly controlled by the quasi-BIC, to the absorption Q factor, which is mainly controlled by the doping of the quantum wells (QWs). This device rejects most background radiation and thus significantly suppresses the background noise, resulting in a background limited specific detectivity (DBLIP∗) 11.85 times that of a conventional ideal photoconductor. A detailed formula is employed for calculation of DBLIP∗, incorporating the wavelength and incident angle dependence of the quantum efficiency. The ultra-narrow photoresponse band with a high peak responsivity can be tuned over the photosensitive wavelength range of the QWs by simply modifying the in-plane structural parameters. This work opens a new avenue to greatly enhance the specific detectivity for infrared detectors based on the joint effect of quasi-BIC and critical coupling.

Optimal Control of a Domestic Frost-Free Refrigerator Inlet Freezer from the Perspective of Reducing Energy Consumption

This study is dedicated to the development of a mathematical model based on shape optimal control of the inlet domestic frost-free refrigerator in the context of energy consumption reduction. A three-dimensional thermofluid model is established for the numerical studies. As the physical system (with shelves and fruits) can be seen as a porous medium, the coupled state equations of the transport mechanism (for velocity and temperature fields) are governed by Navier–Stokes–Forchheimer/Fourier equations. Then, based on the finite element method, the numerical scheme computation is made with FreeFem++ software (Version 4.6). Numerical results are shown for three different cases: empty without shelves, empty with shelves, and loaded with foods. For each case, the velocity and temperature fields’ results are discussed for the optimal configurations. The characterization of these physical parameters would help engineers in domestic frost-free refrigerator design.

Exchange coupling states of cobalt complexes to control proton-coupled electron transfer

The electrochemical proton reactivity of transition metal complexes receives significant attentions. A thorough understanding of proton-coupled electron transfer (PCET) pathways is essential for elucidating the mechanism behind a proton reduction reaction, and controlling the pathway is a key focus in the field of the catalyst development. Spin interactions within complexes, which arise during electron transfer, can affect significantly the PCET pathway. Herein, we explore the phenomenon of spin rearrangement during the electrochemical reorganization of high-spin cobalt complexes. Our findings reveal that opposing spin interactions, induced by different coordination environments, can alter the PCET pathway. Finally, detailed analysis of the PCET pathway allows us to propose mechanisms for proton reduction in high-spin cobalt complexes.

Research on numerical prediction of hydrodynamic interference under coupling of pod propeller and hull

Abstract Taking the cable-laying ship and the pod propeller as the research objects, based on the Reynolds time-averaged RANS equation and sliding moving grid technology, the self-propulsion numerical calculation of the coupling of the pod propeller and the hull was completed. By comparing the resistance of the bare hull and the thrust of the pod propeller, the hydrodynamic interference under the coupling state of the pod propeller and the hull is analyzed. The results show that when Fr=0.295, the total resistance of the ship increases by 21.6%, the pressure difference resistance increases by 30.5%, the wake fraction is 0.011, and the thrust derating is 0.178. The research results provide theoretical and technical guidance on the interference problem between the hull and the pod propeller.

Accounting for carbon emissions in social water cycle system in nine provinces along the yellow river and analysis of influencing factors.

Water resources is an essential factor to ensure the sustainable development of the society, but along with the utilization and treatment of water resources, a large amount of carbon emissions will be generated. The study of carbon emissions in social water cycle system is of great significance in promoting the achievement of carbon peaking and carbon neutrality. This study calculated the carbon emissions generated in social water cycle system in nine provinces along the Yellow River, used the Tapio decoupling model to analyze the decoupling relationship between water and carbon emissions, and constructed the STIRPAT expanded model to analyze the main influencing factors of carbon emissions. (1) The total carbon emissions of the nine provinces showed an increasing trend over time, with a growth rate of 25.13%. (2) The carbon emission intensity of water use (1.60kg/m3) and drainage (1.45kg/m3) system is higher, the carbon emission intensity of water supply (0.30kg/m3) and water withdrawal (0.56kg/m3) system is lower. (3) The relationship between water resources utilization and carbon emissions along the Yellow River is generally in a state of negative decoupling and coupling. (4) Energy structure and population growth are the main factors affecting carbon emissions in social water cycle system, while water supply quantity and water use system are secondary factors. Water use system is the main body of carbon emissions in social water cycle system, and as the water consumption increases, the carbon emissions will continue to increase. In order to reduce carbon emissions and mitigate climate change, carbon emission factors should be incorporated into water resources management.

The Crust-Mantle Interaction of the Qiangtang Terrane: New evidence from the Effective Elastic Thickness of the Lithosphere

The crust-mantle interaction in the Qiangtang terrane is significant to study continental rheology and evolution. Its mechanism remains a subject of considerable debate for the reason of lack of sufficient geophysical evidence. The effective elastic thickness (Te) of the lithosphere can provide important constraints on this issue because it is sensitive to the state of mechanical coupling between the crust and the lithospheric mantle. We present new high-resolution Te of the Qiangtang terrane by using the multitaper admittance method with fusion of different window, based on satellite gravity and topographical data. Thus, a detailed study of the lithosphere is conducted, for the first time to utilize the spatial variations of Te and associated parameters, including thermal structures of the lithosphere, uppermost mantle seismic Pn-velocity, and crustal deformation. The results indicate that crust-mantle interaction in the Qiangtang terrane primarily occurs in the middle Qiangtang terrane (87°E ∼ 95°E, 32°N ∼ 34°N), where Te values are lower. In the eastern and western Qiangtang terrane, Te values are higher, implying weaker late-stage modification. Due to Rayleigh-Taylor instability, lithospheric delamination occurred beneath the south Qiangtang terrane. Based on the extent of these low Te values (Te < 50 km), we conclude that the delaminated lithospheric slab sinking into the mantle is ∼400 km in length and elongated in shape. The delamination induces the upwelling of mantle material, upward stress, volcanic activity, extensional faults, and hot springs in the Qiangtang terrane.

Research on sensing characteristics of high Q-factor all-dielectric metasurfaces based on geometric breaking

The bound states in the continuum (BIC) are widely used in designing metamaterials with high quality factor (Q-factor) resonances due to their perfect localization in the continuous spectral range coexisting with expanding waves. In this study, a T-shaped nanohole all-dielectric metasurface structure is proposed based on the unique electromagnetic properties of all-dielectric metasurfaces, and the fundamental reason of its coupled state and the theoretical basis of BIC excitation are deeply investigated based on the theory of group theory, and the geometric symmetry is broken from multiple angles, and the coupling relationship between discrete eigenmodes and the external continuum is specifically analyzed during the change of symmetry, its spectral response and near-field distribution are numerically calculated. In addition, based on the modulation mechanism of the incident light polarization angle, the three-channel resonance tuning with two resonances of the same frequency and one of a different frequency is realized under the condition that the resonance position and the Q-factor are not affected. This study not only provides a theoretical basis for the excitation conditions and evolution regularity of symmetry-protected BIC, but also solves the problem in the traditional analysis of resonance phenomena without taking the high Q-factor and stability into account, which can provide new designing methods for optical metasurface devices with multi-channel resonance.

Fast and accurate extraction of ultrahigh quality factors from cavity ringdown measurement.

Cavity ringdown spectroscopy is an essential test to measure ultrahigh quality factor (UHQ) optical cavities, which is, however, frequently misinterpreted due to lack of a specified analysis guideline. Here we clarify the basic property of cavity ringdown and present a step-by-step method that enables extraction of the overall quality factor, as well as the intrinsic loss and coupling state of UHQ cavities with better fidelity and simplicity than prior schemes. Our work can facilitate an accurate design and characterization of UHQ cavities for ultra-low noise lasers, high finesse reference cavities, and ultra-narrow optical filters.

Research on the coupling of ecological environment and socio-economic development in resource-based cities: Based on scenario simulation method

Resource-based cities (RBCs) encounter numerous challenges in terms of ecological environment (EE) protection and socio-economy (SE) upgrading. This exerts pressure on the advancement of sustainable development. A benign relationship between EE and SE is a crucial factor in promoting RBCs to realize sustainable development. Using Sichuan RBCs as a case study, this study determined the EE and SE resilience levels, examined the degree of coupling coordination between the two levels of resilience, and investigated the specific pathways in which RBCs might reach a high coupling state. The level of resilience in Sichuan RBCs is dropping for EE, stable for SE, and steadily increasing overall. The degree of coupling coordination is suboptimal, as shown by a D-value of 0.260. However, there is an overall trend towards improved coordination. There 8 cities with a moderate state of dysfunction. In the high state development scenario, the coupling coordination degree of the cities rises significantly. Guang'an, Luzhou, Nanchong, and Zigong should prioritize addressing the issue of EE pollution emission and work to strengthen the regulation and treatment of industrial pollutants. Moreover, to enhance the influx of talent and population, the cities of Dazhou, Guangyuan, Panzhihua, and Ya'an should implement human-centered urban design and layout.

Surface Rupture and Fault Characteristics Associated With the 2020 Magnitude (MW) 6.6 Masbate Earthquake, Masbate Island, Philippines

AbstractOn 18 August 2020, Masbate Island was struck by a magnitude (MW) 6.6 earthquake. This seismic event represents the second occurrence of a strong earthquake (M &gt; 6) in 17 years, emphasizing the necessity for further investigation into the characteristics of this event. In this study, we employ Interferometric Synthetic Aperture Radar, seismicity analysis, and field investigations to comprehensively characterize the coseismic and postseismic slip associated with the event. Our findings reveal a 50‐km‐long fault rupture along the Masbate segment of the Philippine Fault, with ∼23 km surface rupture mapped onshore, despite the occurrence of interseismic creep. The slip distribution demonstrates decreasing displacements northwestward toward the creeping section, with a maximum left‐lateral displacement of 0.97 m near the epicenter. Toward the southeast offshore, the rupture terminates at a left stepover of a fault. While the surface rupture appears relatively straight and narrowly concentrated, the secondary ruptures and mapped offshore faults reveal a more complex transtensional fault structure in the southeastern part of Masbate Island. This fault complexity represents an asperity that facilitates high‐stress accumulation and rupture initiation. Postseismic slip persists for several months along the onshore creeping segment. Based on comprehensive measurements of both cumulative and coseismic slip along the Masbate fault segment, we calculate a slip rate ranging between 2.8 and 3.8 cm/year and a recurrence interval of 16–41 years for earthquakes similar to the 2020 earthquake. Our study highlights how heterogeneity in fault properties, including geometry and coupling state, influences the distribution of slip and magnitude of earthquakes. The 2020 Masbate earthquake provides valuable insights into the rupture dynamics and fault behavior of the Philippine Fault in the Masbate region.

Different neural correlates of deception: Crafting high and low creative scams

Deception is a complex social behavior that manifests in various forms, including scams. To successfully deceive victims, liars have to continually devise novel scams. This ability to create novel scams represents one kind of malevolent creativity, referred to as lying. This study aimed to explore different neural substrates involved in the generation of high and low creative scams. A total of 40 participants were required to design several creative scams, and their cortical activity was recorded by functional near-infrared spectroscopy. The results revealed that the right frontopolar cortex (FPC) was significantly active in scam generation. This region associated with theory of mind may be a key region for creating novel and complex scams. Moreover, creativity-related regions were positively involved in creative scams, while morality-related areas showed negative involvement. This suggests that individuals might attempt to use malevolent creativity while simultaneously minimizing the influence of moral considerations. The right FPC exhibited increased coupling with the right precentral gyrus during the design of high-harmfulness scams, suggesting a diminished control over immoral thoughts in the generation of harmful scams. Additionally, the perception of the victim’s emotions (related to right pre-motor cortex) might diminish the quality of highly original scams. Furthermore, an efficient and cohesive neural coupling state appears to be a key factor in generating high-creativity scams. These findings suggest that the right FPC was crucial in scam creation, highlighting a neural basis for balancing malevolent creativity against moral considerations in high-creativity deception.

Coupled topological edge and corner states in two-dimensional phononic heterostructures with nonsymmorphic symmetries

The exciting discovery of topological phononic states has aroused great interest in the field of acoustic wave control. However, conventional topological edge states and corner states localized at the interface and corner of the two-phase domain wall structures are limited by single channel transmission characteristics, which decreases the flexibility of designing multi-channel acoustic wave devices. Here, we propose a two-dimensional (2D) topological phononic heterostructure with nonsymmorphic symmetries to realize the multiple interface topological multimode interference effect based on the coupling of topological edge and corner states. Topological phase transitions are achieved by altering the rotation angle of the split-ring scatterers in a square lattice. The coupled edge states are generated by the coupling between the edge states of ordinary-topological-ordinary (OTO) interfaces. Moreover, the higher-order topology of the square phononic crystals (PCs) is characterized by nontrivial bulk polarization, the topological and coupled corner states splitting into two pairs appear in the square OTO bend structure owing to the nonsymmorphic PC lack of mirror symmetries. Finally, the topological robustness of the multimode interference effect of coupled edge and corner states against defects is demonstrated. Our results pave the way for guiding and trapping acoustic waves in topological nonsymmorphic heterostructures, whose multi-channel transmission capability can be employed for designing topological phononic filters, couplers and multiplexers.

Lower magnetic field measurement limit of the coupled dark state magnetometer

Abstract The Coupled Dark State Magnetometer (CDSM) is an optically pumped magnetometer. For the Jupiter Icy Moons Explorer (JUICE) mission, the CDSM and two fluxgate magnetometers are combined in the J-MAG instrument to measure the static and low frequency magnetic field in the Jupiter system. During certain calibration manoeuvres, the CDSM has to be able to measure magnetic field strengths down to 100 nT with an accuracy of 0.2 nT (1 σ). At such low magnetic fields, the CDSM’s operational parameters must be carefully selected to obtain narrow resonance structures. Otherwise, the coupled dark state resonances, used for the magnetic field detection in different instrument modes, overlap and result in a systematic error. In this paper we demonstrate that with the found instrument settings the CDSM is able to measure magnetic field strengths below 100 nT with a systematic error less than 0.2 nT resulting from the overlap of the resonances.

Isomeric Effects of Au28(S-c-C6H11)20 Nanoclusters on Photoluminescence: Roles of Electron-Vibration Coupling and Higher Triplet State.

The exploration of near-infrared photoluminescence (PL) from atomically precise nanoclusters is currently a prominent area of interest owing to its importance in both fundamental research and diverse applications. In this work, we investigate the near-infrared (NIR) photoluminescence mechanisms of two structural isomers of atomically precise gold nanoclusters of 28 atoms protected by cyclohexanethiolate (CHT) ligands, i.e., Au28i(CHT)20 and Au28ii(CHT)20. Based on their structures, analysis of 3O2 (triplet oxygen) quenching of the nanocluster triplet states, temperature-dependent photophysical studies, and theoretical calculations, we have elucidated the intricate processes governing the photoluminescence of these isomeric nanoclusters. For Au28i(CHT)20, its emission characteristics are identified as phosphorescence plus thermally activated delayed fluorescence (TADF) with a PL quantum yield (PLQY) of 0.3% in dichloromethane under ambient conditions. In contrast, the Au28ii(CHT)20 isomer exhibits exclusive phosphorescence with a PLQY of 3.7% in dichloromethane under ambient conditions. Theoretical simulations reveal a larger singlet (S1)-triplet (T1) gap in Au28ii than that in Au28i, and the higher T2 state plays a critical role in both isomers' photophysical processes. The insights derived from this investigation not only contribute to a more profound comprehension of the fundamental principles underlying the photoluminescence of atomically precise gold nanoclusters but also provide avenues for tailoring their optical properties for diverse applications.

Light elements adsorption modulates the electronic structure of h-BC2N/g-C6N6 nanoribbons

The electronic properties of h-BC2N/g-C6N6 nanoribbons were calculated using the first principles method. Three states of ferromagnetic, antiferromagnetic, and paramagnetic coupling were set. The energy of the ferromagnetic coupling state was found to be the lowest, indicating that the final stable state was the ferromagnetic coupling state. The thermodynamic stability was also verified in the ferromagnetic coupling state. The h-BC2N/g-C6N6 nanoribbons itself is magnetic with a magnetic moment of 2 μB and is a direct narrow band gap semiconductor material. In order to change the electronic properties, six different atoms (B, C, N, Al, Si, P) were adsorbed in the h-BC2N/g-C6N6 nanoribbon, and their band structure and charge density were studied. The results show that the adsorption of different atoms in h-BC2N/g-C6N6 nanoribbons will produce different results. Among them, the adsorption of N and P atoms changes its properties from a semiconductor to a half-metal, which can generate a 100% polarized current in the Fermi surface. This provides more development directions for spintronics devices.

Battery asynchronous fractional-order thermoelectric coupling modeling and state of charge estimation based on frequency characteristic separation at low temperatures

Due to the widespread application of lithium-ion batteries in new energy vehicles and energy storage fields, fractional-order theory and coupling modeling methods have developed rapidly in battery modeling. This paper proposes an asynchronous fractional-order hot zone coupling modeling method based on frequency domain separation to adapt to battery characteristics. Specifically, in the electrochemical impedance spectroscopy test, the behavior of the battery exhibits different frequency characteristics. Furthermore, a model parameter identification strategy based on frequency domain separation is constructed, and asynchronous parameter updates are achieved through mutually coupled sub-algorithms with different time scales. Additionally, the robustness of the asynchronous fractional-order thermal-electric coupling model (AFO-TCM) was validated under low ambient temperatures, along with its superiority in state of charge (SOC) estimation. Compared to models that do not consider frequency characteristics, the proposed model achieved a reduction in the root mean square error (RMSE) of SOC estimation results by 57 %, 52 %, and 45 % at 0 °C, −10 °C, and −20 °C environments, respectively, under the US06 Supplemental Federal Test Procedure Cycle (US06) driving cycle. This method provides a novel approach to addressing the interdependence between the order of fractional models and temperature.

Spectroscopic and computational characterization of lanthanide-mediated bond activation of ethylamine

Ln (Ln = La and Ce) atom reactions with ethylamine are conducted in a pulsed laser vaporization supersonic molecular beam source. Dehydrogenation and association metal-containing species are observed with time-of-flight mass spectrometry, and the dehydrogenated Ln ethylimido species in the formula Ln(NC2H5) are characterized by single-photon mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and a scalar relativity correction, electron correlation, and spin-orbit coupling through multiconfiguration quasi-degenerate second-order perturbation theory for the Ce species. The MATI spectrum of lanthanum ethylimido La(NCH2CH3) has a single vibronic band system from the ionization of the doublet ground state with the La 6s1 configuration, whereas that of the cerium ethylimido Ce(NCH2CH3) displays two vibronic band system from the ionization of the two lowest-energy spin-orbit coupling states with the Ce 4f16s1 configuration. Both Ln ethylimido complexes are formed by the thermodynamically and kinetically favorable concerted dehydrogenation of the amino group. Two additional isomers of Ln(NC2H5) include a four-membered metallacycle Ln(NHCH2CH2) from the dehydrogenation of the amino and methyl groups and a three-membered cycle Ln(NHCHCH3) from the dehydrogenation of the amino and methylene groups. The cyclic isomers are not observed experimentally as they are not populated under the experimental conditions.

Layer-Dependent Quantum Anomalous Hall and Quantum Spin Hall Effects in Two-Dimensional LiFeTe.

The emergence of an intrinsic quantum anomalous Hall (QAH) insulator with long-range magnetic order triggers unprecedented prosperity for combining topology and magnetism in low dimensions. Here, based on stacked two-dimensional LiFeTe, we confirm that magnetic coupling and topological electronic states can be simultaneously manipulated by just changing the layer numbers. Monolayer LiFeTe shows intralayer ferrimagnetic coupling, behaving as a QAH insulator with Chern number C = 2. Beyond the monolayer, the odd and even layers of LiFeTe correspond to uncompensated and compensated interlayer antiferromagnets, resulting in unexpected QAH and quantum spin Hall (QSH) states, respectively. Moreover, the spin Chern number is proportional to the stacking layer numbers in even-layer LiFeTe, proving that the spin Hall conductivity can be continuously enhanced by increasing layer numbers. Therefore, the odd-even-layer-dependent QAH and QSH effects found in LiFeTe topological insulators offer new insight into regulating quantum states in two-dimensional topological materials.

Research on the Spatiotemporal Coupling Characteristics between Urban Population and Land in China Based on the Improved Coupling Model of Polar Coordinates

Scientific quantitative measurement of the coupling relationship between urban population (UP) and urban land (UL) is conducive to promoting intensive land use, coordinated human–land development, and new urbanization development. This research proposed an improved coupling model of polar coordinates to study the spatiotemporal coupling characteristics between UP and UL at the prefecture-level city scale in China from 2010 to 2020. The study results include the following: (1) The growth rate of UL in China’s prefecture-level cities was higher than that of UP. The per capita urban land (PUL) was always within the ideal range, and the dynamic human–land coupling state remained reasonable. (2) The UP, UL, and dynamic human–land coupling rationality in China showed characteristics that were high in the east and low in the west. The PUL showed characteristics that were high in the northwest and low in the southeast. (3) This study divided China’s prefecture-level cities into four regions according to the coupling characteristics and formulated regionally differentiated optimization strategies. In summary, this study carried out a more scientific and reasonable quantitative measurement of the coupling relationship between UP and UL in China, resulting in a more reliable and targeted formulation of optimization strategies.

Factors influencing the relationship between perceptions of ecosystem services and well-being of farmers in the ore-agriculture zone, China

Understanding the coupling relationship between ecosystem service perceptions (ESP) and farmers’ well-being (FWB) in the ore-agriculture zone plays an important strategic role in maintaining regional ecological security and improving the well-being of regional farmers. Based on field research, questionnaire surveys and other methods, this study took farmers around the coal mining development zone as research subjects and used a comprehensive multi-index assessment method to evaluate the level of ESP and the FWB in the research area. A coupling coordination degree model was used to analyze the coupling relationship between ESP and FWB, and the random forest model was used to explore the influencing factors of the coupling relationship between the two. The results showed: (1) The FWB index was moderate and the ESP index was low. Farmers’ perceptions of the different ecosystem services varied, with provisioning services being perceived most strongly and supporting services least strongly. Satisfaction with basic material needs was highest on the well-being assessment. (2) The overall state of ESP and FWB coupling was good, with most of them in the state of coordination improvement. From the perspective of dimensional differentiation, the coupling of the dimensions of ESP and FWB was poorly coordinated, and all of them were in the state of dysfunction regression. (3) The coupling relationship between ESP and FWB was influenced by both environmental and household characteristics, with the former having a stronger effect. The results of this study can serve as a reference for promoting the coordination of ESP and FWB in the ore-agriculture zone, and ultimately realize the sustainable development of ecology and human in the ore-agriculture zone.