Climate-dependent enhancement of radiative cooling with mirror structures

Radiative cooling exploits the imbalance between the thermal emission from the radiative cooling surface and the downward atmospheric emission. Since the atmospheric emission power is polar angle-dependent, a mirror structure can be used to increase this imbalance and to amplify the net cooling power. The degree of amplification is determined by various parameters such as the sky emissivity, the geometry of the mirror structure and the degree of thermal insulation. A parametric study of the aperture mirror-enhanced radiative cooling is presented using a model atmosphere, characterized by an average sky window emissivity and the ambient temperature. A counterintuitive finding is obtained, namely that the aperture mirror structure is more effective in the tropics than in the desert, both in terms of the cooling power and the temperature reduction. The power enhancement obtainable from a relatively simple mirror structure can be significant. For example, in the tropics, the cooling power can be enhanced by more than 40%. The aperture mirror structure holds potential to be a practical augmentation to improve the stagnant temperature and the response time of radiative cooling devices.Comment: arXiv admin note: text overlap with arXiv:2310.0930

Interferometry of a Single Nanoparticle Using the Gouy Phase of a Focused Laser Beam

We provide a quantitative explanation of the mechanism of the far-field intensity modulation induced by a nanoparticle in a focused Gaussian laser beam, as was demonstrated in several recent direct detection studies. Most approaches take advantage of interference between the incident light and the scattered light from a nanoparticle to facilitate a linear dependence of the signal on the nanoparticle volume. The phase relation between the incoming field and the scattered field by the nanoparticle is elucidated by the concept of Gouy phase. This phase relation is used to analyze the far-field signal-to-noise ratio as a function of exact nanoparticle position with respect to the beam focus. The calculation suggests that a purely dispersive nanoparticle should be displaced from the Gaussian beam focus to generate a far-field intensity change

Multi-level anomalous Hall resistance in a single Hall cross for the applications of neuromorphic device

We demonstrate the process of obtaining memristive multi-states Hall resistance (RH) change in a single Hall cross (SHC) structure. Otherwise, the working mechanism successfully mimics the behavior of biological neural systems. The motion of domain wall (DW) in the SHC was used to control the ascend (or descend) of the RH amplitude. The primary synaptic functions such as long-term potentiation (LTP), long-term depression (LTD), and spike-time-dependent plasticity (STDP) could then be emulated by regulating RH. Applied programmable magnetic field pulses are in varying conditions such as intensity and duration to adjust RH. These results show that analog readings of DW movement can be closely resembled with the change of synaptic weight and have great potentials for bioinspired neuromorphic computing. © 2020, The Author(s).1

Bidirectional propagation of tilting domain walls in perpendicularly magnetized T shaped structure with the interfacial Dzyaloshinskii-Moriya interaction

Abstract Understanding of domain wall (DW) propagation in a complex structure is an essential first step toward the development of any magnetic-domain based devices including spin-based logic or magnetic memristors. Interfacial Dzyaloshinskii-Moriya interaction (iDMI) in the structure with broken inversion symmetry induces an asymmetrical DW configuration with respect to the direction of in-plane field. Dynamic behaviors of field-driven DW within the film with perpendicular magnetic anisotropy is influenced by DW tilt from the iDMI effect and the corners in the T-shaped structure of the DW path. Images from Kerr microscopy reveal that the iDMI effective field contributes to a tilted structure of DW configuration and evolution along its propagation. With the combination of iDMI and T-shaped structure, we observed two distinguished bidirectional DW propagations in two output branches and distinct arriving times at the destination pads with a uniform external field. Micromagnetic simulation results is compared with the observed dynamics of a DW configuration in the structure providing an additional confirmation of the interpreted results

Energy-Efficient High-Voltage Pulsers for Ultrasound Transducers

This brief reviews high-voltage pulsers for ultrasound imaging systems with a focus on energy efficiency. Most ultrasound imaging systems have been developed with the aim of achieving a high signal-to-noise ratio for good image quality. As miniaturization and portability of the systems are pursued recently, high energy efficiency is of great need. In the ultrasonic imaging systems, the most power-hungry block is typically the pulser that drives the ultrasound transducer at a high voltage. To better understand the pulser's operation and power consumption, an equivalent circuit model of the transducer is introduced. Based on the model, we investigate the fundamentals of pulser driving methods and review the conventional class-D pulser as well as state-of-the-art pulsers with dynamic power loss reduction techniques. Their operation principles, strengths, and limitations are analyzed and discussed in depth. © 2004-2012 IEEE.1

Memristive behavior of field-driven domain-wall motion in a width-modulated structure with multiple Hall crosses

The remarkable property of a memristor is that it provides multiple resistance states by remembering the current or voltage history associated with the magnetic flux and charge in the device. We investigate the domain wall (DW) motion in a multiple Hall crosses (MHCs) structure to realize the memristive DW device. We fabricated perpendicular magnetic anisotropy (PMA) micro-wires for a [Co/Pt]4 multilayer stack, and they contain MHCs with various widths. When an external field is applied, a DW alternately passes through each Hall cross, thereby creating a hysteresis loop with various magnitudes of Hall resistance states depending on the DW position. Because the measured Hall signal relies on the DW position, which is a function of the history of the field, the basic requirements of a memristor are satisfied. In addition to the anomalous Hall signal, the movement of the DW in the PMA system by field pulses has been recorded using a Kerr microscope to confirm the DW position. The results reveal that the DW motion in the width-modulated MHCs system can be used as a promising test bed and/or application of the memristive DW-motion device. © 2018 Author(s).1

A Wide-Bandwidth Ultrasound Receiver and On-Chip Ultrasound Transmitter for Ultrasound Capsule Endoscopy

This article presents an ultrasound (US) transceiver IC including a highly power-efficient US receiver (RX) and a high-voltage (HV) US transmitter (TX) for US capsule endoscopy (USCE) systems for the first time. The proposed USCE system employs the developed IC, a single-element piezoelectric transducer (PZT), and a mechanically rotating reflector to obtain 360 transmural scans while traveling through the gastrointestinal (GI) tract. Since the USCE system operates with a tiny battery, power efficiency is greatly important. To reduce power consumption by decreasing the required operating speed of the analog-to-digital converter (ADC), we propose a new RX structure employing synchronized analog envelope detection. It is unlike conventional US RX ICs that necessitate power-hungry high-speed ADCs to acquire the US signal residing at a high center frequency with wide bandwidth. Instead, the proposed work employs an analog envelope detector based on a quadrature demodulation method. As a result, it uses only a single circuit path rather than two (I and Q) paths by using a demodulation carrier whose phase is synchronized with the incoming US signal. A ping-pong noise-shaping (NS) SAR ADC is adopted to improve resolution while maintaining low power consumption. Besides, the TX IC, including an on-chip charge pump, is designed to generate HV pulses to drive the PZT. The prototype IC is fabricated in a 0.18 m bipolar-CMOS-DMOS (BCD) process. The RX consumes 2.3 mW, and the ADC achieves a 53.71 dB SNDR and a 66.45 dB SFDR. The TX generates 25 V pulses with 25 ns pulsewidth. US B-mode images of a water tank and a custom phantom are successfully obtained by using the prototype capsule endoscopy system employing the fabricated IC chip. IEEEFALS

34.4 An Energy-Replenishing Ultrasound Pulser with 0.25CV2f Dynamic Power Consumption

A battery-powered miniature ultrasound (US) imaging system implemented in the form of an endoscopy capsule is a promising diagnostic device [1]. IC technology enables such extreme miniaturization of the US imaging system, and high energy efficiency is one of the most critical features for form-factor reduction and image quality (e.g., frame rate) improvement. Typically, a pulser driving a US transducer is the most power-hungry block in US imaging systems due to the massive parasitic capacitance [2] of the transducer (Fig. 34.4.1). © 2021 IEEE

A novel smart navigation system for intramedullary nailing in orthopedic surgery

<div><p>This paper proposes a novel smart surgical navigation system for intramedullary nailing in orthopedic surgery. Using a handle-integrated laser guidance module, the system can target a drill insertion point onto skin, indicating an accurate target position to perpendicularly access an invisible distal hole. The proposed handle-integration-based fixation of the laser guidance module precisely defines the relative position of the module with respect to the distal hole. Consequently, unlike conventional systems, the proposed system can indicate the target insertion point without any help from bulky and costly external position-tracking equipment that is usually required for compensating disturbances generated by external impacts. After insertion, a correct drilling direction toward the distal hole is guided by real-time drilling angle measurement modules–one integrated with the nail handle and the other with the drill body. Each module contains a 9-axis inertial sensor and a Bluetooth communication device. These two modules work together to provide real-time drilling angle data, allowing calculation of the directional error toward the center of the distal hole in real time. The proposed system removes the need for fluoroscopy and provides a compact and cost-effective solution compared with conventional systems.</p></div