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This paper conducts an in-depth study of a wireless, hierarchical structure-based active balancing system for power batteries, aimed at addressing the rapid advancements in battery technology within the electric vehicle industry. The system is designed to enhance energy density and the reliability of the battery system, developing a balancing system capable of managing cells with significant disparities in characteristics, which is crucial for extending the lifespan of lithium-ion battery packs. The proposed system integrates wireless self-networking technology into the battery management system and adopts a more efficient active balancing approach, replacing traditional passive energy-consuming methods. In its design, inter-group balancing at the upper layer is achieved through a soft-switching LLC resonant converter, while intra-group balancing among individual cells at the lower layer is managed by an active balancing control IC and a bidirectional buck–boost converter. This configuration not only ensures precise control but also significantly enhances the speed and efficiency of balancing, effectively addressing the heat issues caused by energy dissipation. Key technologies involved include lithium-ion batteries, battery management systems, battery balancing systems, LLC resonant converters, and wireless self-networking technology. Tests have shown that this system not only reduces energy consumption but also significantly improves energy transfer efficiency and the overall balance of the battery pack, thereby extending battery life and optimizing vehicle performance, ensuring a safer and more reliable operation of electric vehicle battery systems. [ABSTRACT FROM AUTHOR]

Behavior models of electronic components are critical in many metrological and measurement areas, e.g., time-domain simulations for analog-integrated circuit design and predistortion of the amplifier to reduce the distortion. This paper describes the use of pulse-driven ac Josephson voltage standard (ACJVS) to synthesize quantum accurate waveforms with ultralow distortion and noise floor to model the amplifier nonlinearity, which is a promising way to increase the modeling accuracy. Four Volterra series models including the memory polynomial model and three submodels of the dynamic deviation reduction model are analyzed and compared in detail. Normalized mean square error is calculated to evaluate the modeling accuracy. The difference of the measured and predicted outputs of the amplifier are compared in both time and frequency domains. The result shows that high-performance models can be achieved, which demonstrates the feasibility of modeling nonlinear amplifier behavior with the ACJVS. [ABSTRACT FROM AUTHOR]

In the pulse-driven ac Josephson voltage standard, the low frequency (LF) component of a drive signal increases the system complexity and induces unwanted voltages through on-chip inductances. A novel zero compensation (ZC) method for pulse-driven ac waveform synthesis is presented in this paper. A pulse train is obtained through a two-level \Delta-\Sigma modulation and then reconstructed by replacing each pulse with three pulses of a negative–positive–negative pattern. The amplitudes of the reconstructed pulse train are carefully adjusted so that the positive pulses drive the Josephson junctions to the first quantum state, whereas the negative pulses keep the junctions on the zero quantum state and cancel the contribution of the positive pulses to the LF inductive voltage component. This new method eliminates the need for LF signal reinjection required by the conventional bias method and eliminates the need for a direct-current bias required by the recently proposed ZC method. An 8-kHz sinusoidal waveform with an amplitude of 1 mV rms is synthesized to demonstrate the feasibility of the approach. We also demonstrate that the inductive voltage error is significantly reduced for waveforms synthesized with the new method. [ABSTRACT FROM PUBLISHER]

A new quantum-voltage-calibrated Johnson noise thermometer was developed at the National Institute of Metrology to demonstrate the electrical approach that determines Boltzmann's constant k, by comparing electrical and thermal noise power. A measurement with an integration period of 19 h and a bandwidth of 638 kHz results in a relative offset of 1 \times 10^-6, from the current Committee on Data for Science and Technology value of k, and a type A relative standard uncertainty of 17 \times 10^-6. Closely matched noise powers and transmission-line impedances were achieved, and consequently, the quadratic fitting parameters of the ratio spectrum show flat frequency responses with respect to the measurement bandwidth. This flat response produces a dramatically reduced systematic error compared to that of the National Institute of Standards and Technology measurement of k, in which the relative combined uncertainty was dominated by this error. [ABSTRACT FROM PUBLISHER]

The National Institute of Standards and Technology has developed a quantum-voltage-noise-source-calibrated Johnson noise thermometer (JNT) to provide a new electronic measurement technique for determining the Boltzmann constant. Improvements in electronics and synthesized noise waveforms have led to reduced uncertainty in the measurement. Recent investigations have shown that some of the distortion in the present electronics arises in the differential stage of both the preamplifier and the analog-to-digital converter (ADC). The distortion can be reduced by compensating the direct current offset of the signal at the inputs to the differential stage. A four-channel cross correlation JNT with optimized preamplifiers and new ADCs is being assembled. The improvements are on track to reach the goal of an electronic measurement of the Boltzmann constant at a relative uncertainty of 6 \times 10^-6. [ABSTRACT FROM AUTHOR]

This paper reports an all-optical vector magnetometer enhanced by a machine learning model. Using a dual probing beam setup, spin projections in both probe directions are simultaneously detected. Vector information is directly obtained from the measured phases of spin projection signals. To enhance the measurement accuracy and mitigate the dead zone effect, we introduce an artificial neural network (ANN) to link the phase signals to the field direction. With the addition of amplitude information to the ANN input, the average angle error is reduced to less than 0.3 ° within a hemisphere. Furthermore, this configuration demonstrates a field angle sensitivity of better than 30 μ rad / Hz 1 / 2 . [ABSTRACT FROM AUTHOR]

We describe a microwave (MW) magnetic-field detection technique based on the Rabi resonance of a Cs-buffer gas vapor cell. Inside the vapor cell, alkali atoms interact with MWs radiated from an antenna through an open-ended rectangular waveguide. We obtained the Rabi resonance line shape, which determines precisely the Rabi frequency of the MW magnetic field with a phase modulation frequency. For various vapor cells, a detailed characterization of several experimental parameters and a theoretical analysis were performed. The optimal laser intensity and the cell temperature that maximize the Rabi resonance amplitude are obtained. Moreover, the cell-temperature-based frequency shift of the Rabi resonance was investigated. These experimental results are important in developing future International System of Units-traceable MW magnetic field sensors and an MW power standard. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative differential sampling technique for calibrating AC waveforms, leveraging a commercially available 16-bit digital-to-analog converter (DAC) as the reference standard. The novelty of this approach lies in its enhanced stability over traditional direct sampling methods, especially as the frequency of the AC waveform increases. Notably, this technique provides a cost-effective sampler alternative to the differential sampling methods that rely on a programmable Josephson voltage standard (PJVS). A critical aspect of this methodology is the precise measurement of the DAC's output voltage, for which a static measurement strategy is adopted to utilize the exceptional linearity and transfer accuracy of the Keysight 3458A (Santa Rosa, CA, USA) in its standard DCV mode. The differential sampling method has demonstrated good accuracy, achieving a near 1 µV/V agreement with a pulse-driven AC Josephson voltage standard (ACJVS) across a 40 Hz to 200 Hz frequency range. The method attained an expanded uncertainty (k = 2) of 1 part in 106 while measuring a 0.707107 VRMS sine wave at 50 Hz, showcasing its efficacy in precise AC waveform calibration. [ABSTRACT FROM AUTHOR]

Abstract The heat transfer oil dibenzyltoluene (DBT) offered an intriguing approach for the scattered storage of renewable excess energy as a novel Liquid Organic Hydrogen Carrier (LOHC). The integration of hydrogenation and dehydrogenation in H0-DBT/H18-DBT pairs demonstrated that the feasibility of hydrogenation and dehydrogenation reaction conducted in one reactor with the same catalyst, which would be proposed to simplify the hydrogen storage process. The optimal reaction temperature based on the inhibition of ring opening and cracking was investigated combined with the 1H NMR analysis. Meanwhile, the ideal catalyst 3 wt% Pt/Al 2 O 3 for high hydrogen storage efficiency was screened out. Cycle tests of hydrogenation and dehydrogenation integration reaction had shown that the hydrogen storage efficiency was 84.6% after five cycle tests. The integration of hydrogenation and dehydrogenation reaction based on DBT exhibited the ideal thermal stability, which demonstrated its potential as a reversible H 2 carrier. Highlights • The integration of hydrogenation and dehydrogenation is conducted. • The hydrogen storage process of liquid organic hydrogen carrier is simplified. • The integration reaction is catalyzed by supported Pt catalyst. • The dibenzyltoluene hydrogen carrier has ideal thermal stability. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate the direct measurement of a microwave (MW) magnetic field through the detection of atomic Rabi resonances with Cs vapor cells in a free-space low-Q cavity. The line shape (amplitude and linewidth) of detected Rabi resonances is investigated versus several experimental parameters such as the laser intensity, cell buffer gas pressure, and cell length. The specially designed low-Q cavity creates a suitable MW environment allowing easy testing of different vapor cells with distinct properties. Obtained results are analyzed to optimize the performances of a MW magnetic field sensor based on the present atom-based detection technique. [ABSTRACT FROM AUTHOR]

Highly sensitive and quantitative detection of tumor markers is critically important for the early diagnosis and treatment of cancers. In this study, we propose a novel magnetic/photothermal dual-sensing capillary immunochromatographic assay (CICA) strategy for the sensitive detection of carcinoembryonic antigen (CEA). To achieve this, we developed a rambutan-like Fe 3 O 4 @Cu 2− x S@PDA-Au core-shell heterostructure with a high photothermal conversion efficiency of 59.1 % and stable magnetic characteristics through a shell-by-shell method. Under optimal conditions, the dual-mode CICA platform exhibited good linearity within the ranges of 0.5–10 ng mL−1 and 0.005–2.5 ng mL−1 for photothermal and magnetic modes, respectively. Notably, leveraging the biosensing system based on the atomic spin-exchange relaxation-free (SERF) effect, the magnetic mode achieved an enhanced sensitivity with a limit of detection as low as 0.0021 ng mL−1, two orders of magnitude higher than that of the photothermal mode. The complementary detection of dual signals effectively overcomes the limitations of the single-signal mode. These findings provide new insights into the sensitive and quantitative detection of low-abundance CEA analytes, exhibiting enormous potential for the detection of other biomarkers. [Display omitted] • A magnetic/photothermal capillary immunoassay for CEA detection with a LOD of 0.0021 ng mL−1. • Fe 3 O 4 @Cu 2− x S@PDA-Au has an excellent photothermal performance (η = 59.1 %). • Fe 3 O 4 @Cu 2− x S@PDA-Au has a stable magnetic characteristic. • Self-developed atomic magnetometer biosensing platform is based on atomic spin SERF effect. • The magnetic detection of CEA with a response linear range of 0.005–2.5 ng mL−1. [ABSTRACT FROM AUTHOR]

Abstract: Currently, the CODATA value of the Boltzmann constant is dominated by a single gas-based thermometry measurement with a relative standard uncertainty of [P.J. Mohr, B.N. Taylor, D.B. Newell, CODATA recommended values of the fundamental physical constants: 2006, Rev. Mod. Phys. 80 (2008) 633–730]. This article describes an electronic approach to measuring the Boltzmann constant that compares Johnson noise from a resistor at the water triple point with a pseudo-random noise generated using quantized ac-voltage synthesis. Measurement of the ratio of the two power spectral densities links Boltzmann''s constant to Planck''s constant. Recent experiments and detailed uncertainty analysis indicate that Boltzmann''s constant can presently be determined using Johnson noise with a relative standard uncertainty below , which would support both historic and new determinations. To cite this article: S. Benz et al., C. R. Physique 10 (2009). [Copyright &y& Elsevier]

As an important tool in microwave detection, quantum sensing techniques have been studied in a broad range of fields such as microwave electrometry and microwave magnetic field detection. In this work, we measure the relaxation rate of Rb atoms in vapor cells using a Rabi-resonance-based quantum sensing technique. The characterizations of the Rabi resonance line shape with different experimental parameters are investigated. The relaxation rate of the vapor cell can be obtained with the Rabi resonance line shape. [ABSTRACT FROM AUTHOR]

We experimentally investigated continuously frequency-tunable microwave (MW) magnetic field detection based on Rabi resonance with a single cesium-rubidium hybrid vapor cell. The multispecies atomic systems, with their tunable abilities in transition frequencies, enabled this atomic sensing head to cover a broader detectable MW field scope compared to the use of a single alkali atom. Here, we demonstrated the simultaneous observation of atomic Rabi resonance signals with 85Rb, 87Rb, and 133Cs in the same vapor cell. Using an experimentally feasible static magnetic field (DC field) below 500 G, we realized a MW magnetic field strength detection with a bandwidth of 4.8 GHz around 8.1 GHz. The use of a hybrid cell system cell also enabled the detection of an identical MW field for different atomic species with the help of the DC field, allowing us to perform a perfect comparison for different applications that require the same electromagnetic environment. The results may be useful for the realization and application of many atomic detectors based on different physical principles. [ABSTRACT FROM AUTHOR]

Magneto-optical traps based on grating chips can simplify cold atom physical package architectures significantly. Here we report the design and fabrication of a high-diffraction-efficiency grating magneto-optical trap (GMOT). The numerical simulation is performed with an optimized profile and measured refractive index of the gold film. In the design, the fabrication tolerance is also considered. The fabricated grating chip achieved a diffraction efficiency of up to 40%. Up to 2.8 × 107 are trapped with the chip, and the characterization of the GMOT is performed. High absorption contrast CPT resonance signal was also obtained. The proposed atom chip can be leveraged to realize compact cold atom clocks and other cold atom-based quantum sensors. [ABSTRACT FROM AUTHOR]

Long integration periods are necessary to reach low uncertainty when measuring temperature through Johnson noise thermometry (JNT). The main goal of the National Institute of Standards and Technology JNT program is to achieve a combined relative uncertainty of 6 \times 10^-6 in the measurement of the water triple point temperature, which, in turn, allows determination of Boltzmann's constant at the same uncertainty. To this end, a four-channel JNT system, which will reduce the measurement period twofold, is being developed with new components, including a switchboard, analog-to-digital converters (ADCs), and a programmable recharging power supply system. A significant source of systematic error that was discovered while implementing the new ADCs is described. New measurements are presented using a doubled ADC sampling rate, which show the potential for higher measurement bandwidth. [ABSTRACT FROM AUTHOR]

Highly excited Rydberg atoms in a room-temperature vapor cell are promising for developing a radio-frequency (RF) electric field (E-field) sensor and relevant measurement standards with high accuracy and sensitivity. The all-optical sensing approach is based on electromagnetically-induced transparency and Autler-Townes splitting induced by the RF E-field. Systematic investigation of measurement uncertainty is of great importance for developing a national measurement standard. The presence of a dielectric vapor cell containing alkali atoms changes the magnitude, polarization, and spatial distribution of the incident RF field. In this paper, the field distortion of rubidium vapor cells is investigated, in terms of both field strength distortion and depolarization. Full-wave numerical simulation and analysis are employed to determine general optimization solutions for minimizing such distortion and validated by measuring the E-field vector distribution inside different vapor cells. This work can improve the accuracy of atom-based RF E-field measurements and contributes to the development of related RF quantum sensors. [ABSTRACT FROM AUTHOR]