Single-mode Research Articles

Nonlinear simulations of GAEs in NSTX-U

A set of nonlinear simulations has been performed in order to study the nonlinear evolution of unstable global Alfvén eigenmodes in the National Spherical Torus Experiment-Upgrade (NSTX-U). Results of the single toroidal mode number, n, simulations are compared with a full nonlinear simulation (all toroidal harmonics included). In single-n simulations, the conservation of two integrals of motion of a particle in a cyclotron resonance with a monochromatic wave is demonstrated, resulting in a one-dimensional evolution of the particle distribution in (E,μ,pϕ) phase-space. Nonlinear simulations (both single-n and full nonlinear) show a significant redistribution of the resonant fast ions, especially in the pitch parameter. Thus, the changes in the resonant particle's parallel and perpendicular energies can be several times larger than the total particle energy change, with only a small fraction transferring into the excitation of the mode itself. This implies that even a relatively small amplitude mode can significantly modify the beam distribution in the resonant region. For the NSTX-U case considered, the single-n simulation results are close to full nonlinear simulation only for the most unstable mode, in which case the saturation amplitudes and changes in the fast ion distribution are comparable. In contrast, peak amplitudes of subdominant modes in all-n simulations are smaller by a factor of 3–10 compared to single-n runs due to the flattening of the beam ion distribution by the fastest growing mode.

Research on PV array reconstruction and Full-cycle maximum power point tracking technology of space solar power station

Space solar power station is an energy system that converts solar energy into electrical energy in the space environment and then transmits it to the space platform or ground using wireless power transmission technology. To improve the power generation and system efficiency of the space solar power station, an adaptive and reconfigurable photovoltaic array with multi-configuration is proposed, which can avoid large attenuation of the output power and efficiency of the photovoltaic array when the photovoltaic modules have a fault occurs or the receive different irradiation intensity. Then, according to the orbit area and light condition of the space solar power station, the operation mode are divided in detail. Furthermore, a novel full-cycle and multi-mode GMPPT (maximum power point tracking) strategy is proposed. Compared to the single mode MPPT, the control strategy has shorter response time, faster convergence and higher tracking accuracy. Through the above research, the output power and photoelectric conversion efficiency of space solar power station can be significantly improved.

The Fundamental of Fiber Bragg Grating (FBG) Sensor

An optical sensor known as an FBG is produced by laterally exposing a single mode fiber core to a strong UV laser light pattern on a regular basis. The exposure causes a sustained increase in the refractive index (ncore) of the fiber's core, resulting in fixed index modulation called grating (λ). The grating inside the fiber optic core must reflect a certain wavelength of incoming light while transmitting all other wavelengths. This wavelength is referred to as the Bragg wavelength or Bragg linked to grating period. FBG functions as intended when a Bragg reflector is built on an optical fiber by taking use of the regular fluctuations in the refractive index of the single mode fiber core. When light travels through the FBG, certain wavelengths will be transmitted and others will be reflected. When the strain or temperature around the grating varies, a shift in the wavelength of the light reflected is observed.

Identifying mode coupling wavelengths in doubly-clad optical fibers with deep learning

Understanding the transmission of light waves in optical fibers and accurately determining the locations of mode coupling are crucial for enhancing the efficiency of optical devices and advancing innovative technologies such as fiber optic sensors, lasers, and modulators. This study utilizes deep learning and image recognition techniques to identify the wavelengths at which mode coupling occurs in optical fibers. Our research findings show that using the ResNet-18 model allows for the rapid and accurate identification of the wavelengths at which mode coupling occurs in optical fibers, as well as the modes involved, achieving an accuracy close to 100 %. We experimented with sampling the dataset at 5 nm and 10 nm intervals to create smaller training and validation sets. Despite the reduced data volume, high accuracy rates were maintained, exceeding 99 % and 97 % respectively. This study provides new insights into the use of deep learning for precise localization of mode coupling points and tracking of transmission modes in optical fibers.

Topology optimization design of multi-modal resonators for metamaterial panels with maximized broadband vibroacoustic attenuation

Resonant metamaterial panels can achieve exceptional vibroacoustic attenuation by subwavelength local resonators attached to a host structure. While single-mode resonators provide improvements only in a narrow band, recent advancements propose multi-modal resonators for broadband attenuation. However, existing designs utilize only a limited number of modes, and effective methodologies are lacking to systematically design resonator layouts that achieve an appropriate amount of resonances across the target frequency range, with an adequate participating mass. In this study, we tackle this challenge by developing a dedicated topology optimization method for multi-modal resonator design in metamaterial panels. The method leverages effective thin plate modelling, i.e. a homogenized metamaterial representation through an effective mass density, which provides accurate and very efficient vibroacoustic predictions. The optimization objective is to maximize the broadband diffuse field sound transmission loss (STL) of the metamaterial panel while constraining mass. The optimization problem is solved by gradient-based mathematical programming, for which the necessary (adjoint) sensitivities of objective and constraints are derived. The efficacy of the proposed topology optimization approach is demonstrated by targeting the suppression of coincidence dips in orthotropic host plates. For narrowband coincidence dips, the optimized resonator exhibits maximized mass participation in one single mode of interest. For broadband coincidence dips, the method effectively generates multi-modal resonators with up to 6 resonances distributed across the target frequency range. It is finally demonstrated that the topology-optimized designs surpass the performance of simpler, parametrically optimized multi-modal resonator layouts, as well as of conventional treatments by a damping layer of rubber.

Resilience optimization of bus-metro double-layer network against extreme weather events

The resilience of bus and metro systems to extreme weather events is a critical concern in urban planning, given their growing complexity and interconnectivity. Traditional studies often simplify or overlook the interdependency between different transportation modes, focusing on recovery strategies for a single mode to enhance system resilience. This study proposes an integrated resilience assessment framework for bus and metro systems, conceptualized as a Bus-Metro Double-Layer Network (B-M DLN). The framework considers both network structure and system function to accurately evaluate the B-M DLN resilience. A resilience optimization model for B-M DLN based on Genetic Algorithm (GA) is established to suggest the optimal recovery sequence of damaged stations, emphasizing the importance of station repair time, node strength, and node degree in recovery prioritization. Through a case analysis of Xi’an City, China, the B-M DLN shows significantly enhanced resilience when applying the optimal recovery strategy, especially in large-scale failure scenarios.

Unseeded one-third harmonic generation in optical fibers

We propose a new concept to generate efficient one-third harmonic light from an unseeded third harmonic process in optical fibers. Our concept is based on the dynamic constant (Hamiltonian) of the nonlinear third harmonic generation in optical fibers and includes a periodic array of nonlinear fibers and phase compensation elements. We test our concept with a simulation of the nonlinear interaction between the fundamental and third harmonic modes of a realistic optical fiber, demonstrating high-efficiency one-third harmonic generation. Our work opens a new approach to achieving the so far elusive one-third harmonic generation in optical fibers.

Optimizing Response Rates to Examine Health IT Maturity and Nurse Practitioner Care Environments in US Nursing Homes: Mixed Mode Survey Recruitment Protocol.

Survey-driven research is a reliable method for large-scale data collection. Investigators incorporating mixed-mode survey designs report benefits for survey research including greater engagement, improved survey access, and higher response rate. Mix-mode survey designs combine 2 or more modes for data collection including web, phone, face-to-face, and mail. Types of mixed-mode survey designs include simultaneous (ie, concurrent), sequential, delayed concurrent, and adaptive. This paper describes a research protocol using mixed-mode survey designs to explore health IT (HIT) maturity and care environments reported by administrators and nurse practitioners (NPs), respectively, in US nursing homes (NHs). The aim of this study is to describe a research protocol using mixed-mode survey designs in research using 2 survey tools to explore HIT maturity and NP care environments in US NHs. We are conducting a national survey of 1400 NH administrators and NPs. Two data sets (ie, Care Compare and IQVIA) were used to identify eligible facilities at random. The protocol incorporates 2 surveys to explore how HIT maturity (survey 1 collected by administrators) impacts care environments where NPs work (survey 2 collected by NPs). Higher HIT maturity collected by administrators indicates greater IT capabilities, use, and integration in resident care, clinical support, and administrative activities. The NP care environment survey measures relationships, independent practice, resource availability, and visibility. The research team conducted 3 iterative focus groups, including 14 clinicians (NP and NH experts) and recruiters from 2 national survey teams experienced with these populations to achieve consensus on which mixed-mode designs to use. During focus groups we identified the pros and cons of using mixed-mode designs in these settings. We determined that 2 mixed-mode designs with regular follow-up calls (Delayed Concurrent Mode and Sequential Mode) is effective for recruiting NH administrators while a concurrent mixed-mode design is best to recruit NPs. Participant recruitment for the project began in June 2023. As of April 22, 2024, a total of 98 HIT maturity surveys and 81 NP surveys have been returned. Recruitment of NH administrators and NPs is anticipated through July 2025. About 71% of the HIT maturity surveys have been submitted using the electronic link and 23% were submitted after a QR code was sent to the administrator. Approximately 95% of the NP surveys were returned with electronic survey links. Pros of mixed-mode designs for NH research identified by the team were that delayed concurrent, concurrent, and sequential mixed-mode methods of delivering surveys to potential participants save on recruitment time compared to single mode delivery methods. One disadvantage of single-mode strategies is decreased versatility and adaptability to different organizational capabilities (eg, access to email and firewalls), which could reduce response rates. DERR1-10.2196/56170.

Programmable Photonic Quantum Circuits with Ultrafast Time-Bin Encoding.

We propose a quantum information processing platform that utilizes the ultrafast time-bin encoding of photons. This approach offers a pathway to scalability by leveraging the inherent phase stability of collinear temporal interferometric networks at the femtosecond-to-picosecond timescale. The proposed architecture encodes information in ultrafast temporal bins processed using optically induced nonlinearities and birefringent materials while keeping photons in a single spatial mode. We demonstrate the potential for scalable photonic quantum information processing through two independent experiments that showcase the platform's programmability and scalability, respectively. The scheme's programmability is demonstrated in the first experiment, where we successfully program 362 different unitary transformations in up to eight dimensions in a temporal circuit. In the second experiment, we show the scalability of ultrafast time-bin encoding by building a passive optical network, with increasing circuit depth, of up to 36 optical modes. In each experiment, fidelities exceed 97%, while the interferometric phase remains passively stable for several days.

TetraBall: A single-moderator neutron spectrometer for HL-LHC

This contribution presents a novel single-moderator neutron spectrometer, named “TetraBall”, developed at INFN and optimized for characterizing the neutron field in the CMS experimental cavern. The TetraBall condenses the functionality of several Bonner Spheres (BS) in a single moderator and it is equipped with 42 SiC radiation-hard detectors organized in a tetrahedral geometry designed to be insensitive to incident gammas and charged particles. Thanks to lead inserts, it can respond up to GeV energies. It works in single exposure mode, suitable for real-time monitoring. It is designed to be used as neutron monitor during the High-Luminosity LHC data taking.

Beyond the regional average: Drivers of geographical rainfall variability during East Africa's short rains

AbstractThe East African “short rains” from October–December (OND) are crucial for the region's cultural and agricultural landscape. Traditional climate studies have often treated these rains as a single mode, representing the average rainfall across the region. This approach, however, fails to capture the complex geographical variations in seasonal rainfall. In our study, we analyse 4200 reforecasts from a seasonal prediction system spanning 1981–2022, identifying distinct clusters that represent different geographical patterns of the short rains. We explore the influence of tropical sea‐surface temperature patterns, upper‐level tropospheric flow, and low‐level moisture fluxes on these clusters. A key revelation of our research is the limited predictability of certain geographical rainfall structures based on large‐scale climatic drivers. This finding highlights a gap in current forecasting methodologies, emphasising the necessity for further research to understand and predict these intricate patterns. Our study illuminates the complexities of regional rainfall variability in East Africa, underlining the importance of continued investigation to improve climate resilience strategies in the region.

Fabrication of Helical Carbon Fiber Skeleton Using Arc Glow Discharge Method.

An arc glow discharge device was used to prepare a helical carbon fiber skeleton with helical carbon fibers hooked to each other by spraying a hydrogen and ethanol mixture onto the iron wire substrate through the discharge area, using anhydrous ethanol as the carbon source. The samples were characterized by SEM, EDS, Raman and XPS. A growth mechanism of helical carbon fiber driven by C sp3 was proposed. The various growth modes of carbon fiber during the formation of carbon fiber skeleton were investigated. A ring appearance that indicated a change in the direction of carbon fiber growth was observed. And double helical carbon fiber was constructed from single helical carbon fiber in two ways. Super-large carbon fiber with a diameter of about 13 μm was observed, and it was speculated that this super-large carbon fiber is the backbone of the carbon fiber skeleton. The mechanical properties of the carbon fiber skeleton are isotropic.

Characterization of PM2.5 emissions from on-road vehicles in the tunnel of a major Middle Eastern city

Traffic emissions are an important source of air pollution worldwide, but in the Middle East, this problem is exacerbated by weak or no enforcement of emission regulations. Comprehensive measurements of fine PM emission factors (EFs) from road transport in the region have not yet been conducted, but such data are necessary for quantitative assessments of the health impact of transport emissions in the region. To address this need, PM2.5 samples collected inside the Salim Slam tunnel in Beirut, Lebanon were analyzed for carbonaceous matter (organic carbon (OC) and elemental carbon (EC)), water-soluble ions, elements, and selected organic compounds. The OC/EC ratio was 1.8 for the total fleet and 2.6 for light-duty vehicles (LDV), in agreement with the dominant proportion of gasoline LDV in the Lebanese fleet. A Cu/Sb ratio of 4.2 ± 0.1 was observed, offering a valuable metric for detecting brake wear emissions in subsequent studies conducted in the region. The EFs of carbonaceous matter, elements and ions generally varied by a factor 0.1 and 10 in comparison to literature values, while those for alkanes and polycyclic aromatic hydrocarbons were similar to the upper values previously reported. The average number size distribution was characterized by a single mode around 35 nm. The particles number EF (for diameters between 10 and 480 nm) was within the range of 1014-1015 particles per kg of fuel. The chemical mass balance model showed an average contribution to EF of 62% from non-exhaust sources. This study highlights the need for more enforceable stringent vehicular regulations because of the local practices (i.e., removal of catalyst) and some EF values are very high compared to other studies/countries.

Single or Multiplayer Mode? Examining the Effects of Exergames in Improving Physical Health and Well-Being Among Older Adults.

Objective: This study assesses the impact of single-player and multiplayer exergaming modes on improving exercise intentions, reduction of fear of falling, and emotional well-being among older adults, primarily from low socioeconomic status (SES) backgrounds-a group often underrepresented in exergame research. Method: We engaged 48 participants, primarily from low-SES communities in Singapore for a 4-week community-based exergaming intervention. Participants were divided into four groups as follows: (1) conventional exercise alone, (2) exergames alone, (3) exergames with a health coach, and (4) exergames with a peer. Using two-way repeated-measures ANOVA, we analyzed the effects of these interventions. Results: The findings revealed that all exergaming modes positively influenced exercise intentions, fear of falling, and emotional well-being to varying extents. Notably, exergaming with a health coach significantly improved participants' exercise intentions and emotional well-being, underscoring the value of expert guidance in motivating and supporting older adults in adopting healthier lifestyles. Exergaming with a peer was most effective in reducing fear of falling, highlighting the importance of social support and peer interaction in addressing physical health concerns among this population. Conclusion: This study emphasizes the potential of tailored exergame interventions incorporating various social interactions to improve health outcomes for older adults, contributing to more inclusive health promotion strategies.

Sub-picometer level all-solid-state narrow linewidth single-frequency Pr3+:LiYF4 laser in the near-infrared spectral region.

We report an all-solid-state near-infrared single-frequency (single longitudinal mode, SLM) Pr3+:LiYF4 (Pr:YLF) laser with the spectral linewidth at the sub-picometer level. The SLM lasers with center wavelengths of 868 and 907 nm are realized in Pr:YLF crystal for the first time to the best of our knowledge. The maximum output powers of SLM lasers at 868 and 907 nm are 102 and 213mW, corresponding to the narrowest spectral linewidths of 82 MHz (0.21 pm) and 94 MHz (0.26 pm), respectively. At the maximum output power, the beam quality factors in the x and y directions are measured as 1.25 and 1.16 at 868 nm and 1.21 and 1.13 at 907 nm, respectively. The output power stabilities of the 868 and 907 nm SLM lasers are calculated as 1.39% and 0.87%, respectively. The successful realization of 868 and 907 nm all-solid-state SLM lasers makes up for the gap that the Pr:YLF SLM lasers developed in the past are focused on the visible region, enriches the types of near-infrared (NIR) SLM lasers, and can provide practical applications in biomedicine, cold atom physics, and optical atom manipulation.

Elliptic curves in continuous-variable quantum systems

Elliptic curves are planar curves which can be used to define an abelian group. The computation of this group's addition operation, as well as related operations such as the discrete logarithm, could be performed on quantum computing devices, potentially leading to better performance. Currently, however, thousands of logical qubits are required for elliptic curve group addition, putting this application out of reach for near-term quantum hardware. Here we give an algorithm for computing elliptic curve group addition (over the real numbers) using a single continuous-variable mode, based on weak measurements of a system with a cubic potential energy. This result could lead to improvements in the efficiency of elliptic curve operations using a quantum device.

Scalable transfer printing approach to heterogeneous integration of InP lasers on silicon-on-insulator waveguide platform

InP-based edge-emitting O-band lasers are integrated onto silicon photonics circuit employing micro-transfer printing technology. Blocks of unpatterned InP gain material of typical size 1000 × 60 μ m2 are first transferred onto 400 nm thick silicon rib waveguides with the fabrication steps performed on the target wafer to realize the final lasers. As a result, the InP ridge waveguides are aligned with lithographic accuracy to the underlying Si waveguides resulting in an approach free from any misalignment stemming from the transfer printing process. The fabricated Distributed Bragg Reflector laser shows lasing around 100 mA current injection with minimum 1 mW of output power coupled to a single mode fiber. This integration method paves a reliable route toward scaling-up the integration of active devices such as lasers, modulators, and detectors on 300-mm diameter silicon wafers, which requires high-uniformity across the wafer.

Nonlinear, single-mode, two-dimensional Rayleigh-Taylor instability in ideal media.

A model for the single mode, two-dimensional Rayleigh-Taylor instability in ideal, incompressible, immiscible, and inviscid fluids is developed as an extension of a previous linear model based on the Newton's second law [A. R. Piriz et al., Am. J. Phys. 74, 1095 (2006)0002-950510.1119/1.2358158]. It describes the transition from linear to nonlinear regimes and takes into account the mass of fluids participating in the motion during the instability evolution, including the laterally displaced mass. This latter feature naturally leads to the bubble and spike velocity saturation without requiring the usual drag term necessary in the well-known buoyancy-drag model (BDM). In addition, it also provides an explanation to the latter phase of bubble reacceleration without appealing to the vorticity generation due to the Kelvin-Helmholtz instability. The model is in perfect agreement with the BDM buoyancy-drag model, but, apart from extending its range of application, it solves many of its issues of concern and provides a more consistent physical picture.

Preparation of a novel MR fluid for squeeze-shear mode by compositing micron-scale and nano-scale particles

The magnetorheological (MR) fluid under the squeeze-shear mode has an enhanced structure by reducing the distance between particles, significantly increasing the yield stress compared to the single shear mode. The existing research on preparing MR fluid is all based on single shear mode. This work mixes micron-scale carbonyl iron powders and micron-scale soft magnetic particles to prepare the specialized MR fluid for the devices working under squeeze-shear mode. Several kinds of micron-scale carbonyl iron powders and micron-scale soft magnetic particles are selected, of which the magnetic properties are tested to obtain the suitable soft magnetic particles for MR fluid. Then, the optimal combination of micron-scale carbonyl iron powders and micron-scale soft magnetic particles is obtained when the orthogonal test is used to compare the yield stress of different combinations. At the same time, the appropriate surfactants and base carrier fluid were selected, according to the previous work. On this basis, the novel MR fluid is prepared by the base fluid displacement method, and its performances are tested. The results show that the sedimentation rate is 0.8 % after standing for 20 days, which can keep the MR device in a stable state. The viscosity of the novel MR fluid is 8.0 Pa·s at room temperature, exhibiting good liquidity, which allows it to be injected into MR devices. The shear yield stress of the novel MR fluid is 60.28 kPa at the squeeze pressure of 600 kPa, which is 1.5 times higher than that under single shear mode, significantly enhancing the mechanical performance of MR fluid. The novel MR fluid with good sedimentation stability, appropriate viscosity, and better mechanical performance can be applied to more MR devices, especially the MR devices under squeeze-shear mode.

Single vector mode transmission in hollow-core photonic bandgap fiber based on surface mode coupling effect

Single vector mode transmission in hollow-core photonic bandgap fiber based on surface mode coupling effect