Resolution Capability Research Articles

In Situ Transmission Electron Microscopy Methods for Lithium-Ion Batteries.

In situ Transmission Electron Microscopy (TEM) stands as an invaluable instrument for the real-time examination of the structural changes in materials. It features ultrahigh spatial resolution and powerful analytical capability, making it significantly versatile across diverse fields. Particularly in the realm of Lithium-Ion Batteries (LIBs), in situ TEM is extensively utilized for real-time analysis of phase transitions, degradation mechanisms, and the lithiation process during charging and discharging. This review aims to provide an overview of the latest advancements in in situ TEM applications for LIBs. Additionally, it compares the suitability and effectiveness of two techniques: the open cell technique and the liquid cell technique. The technical aspects of both the open cell and liquid cell techniques are introduced, followed by a comparison of their applications in cathodes, anodes, solid electrolyte interphase (SEI) formation, and lithium dendrite growth in LIBs. Lastly, the review concludes by stimulating discussions on possible future research trajectories that hold potential to expedite the progression of battery technology.

Harnessing the Radio Frequency Power Level of Cellular Terminals for Weather Parameter Sensing

In light of recent extreme weather events, it is imperative to explore innovative methodologies for promptly and accurately measuring various meteorological parameters. The high spatial and temporal variability in precipitation often surpasses the resolution capabilities of traditional rain gauge measurements and satellite estimation algorithms. Therefore, exploring alternative methods to capture this variability is crucial. Research on the correlation between signal attenuation and precipitation could offer valuable insights into these alternative approaches. This study investigates (a) the feasibility of the classification of precipitation rate using signal power measurements in cellular terminals and (b) the impact of atmospheric humidity as well as other meteorological parameters on the signal. Specifically, signal power data were collected remotely through a specialized Android application designed for this research. During the time of analysis, the power data were processed alongside meteorological parameters obtained from the meteorological station of the Physics Department at the University of Ioannina gathered over one semester. Having in mind the radio refractivity of the air as a fascinating concept affecting the way radio waves travel through the atmosphere, the processed results revealed a correlation with signal attenuation, while a correlation between the latter and absolute humidity was also observed. Moreover, a precipitation rate classification was attained with an overall accuracy exceeding 88%.

Equivalent-time-active-cavitation-imaging enables vascular-resolution blood-brain-barrier-opening-therapy planning

Objective. Linking cavitation and anatomy was found to be important for predictable outcomes in focused-ultrasound blood-brain-barrier-opening and requires high resolution cavitation mapping. However, cavitation mapping techniques for planning and monitoring of therapeutic procedures either (1) do not leverage the full resolution capabilities of ultrasound imaging or (2) place constraints on the length of the therapeutic pulse. This study aimed to develop a high-resolution technique that could resolve vascular anatomy in the cavitation map. Approach. Herein, we develop BandPass-sampled-equivalent-time-active-cavitation-imaging (BP-ETACI), derived from bandpass sampling and dual-frequency contrast imaging at 12.5 MHz to produce cavitation maps prior and during blood–brain barrier opening with long therapeutic bursts using a 1.5 MHz focused transducer in the brain of C57BL/6 mice. Main results. The BP-ETACI cavitation maps were found to correlate with the vascular anatomy in ultrasound localization microscopy vascular maps and in histological sections. Cavitation maps produced from non-blood-brain-barrier disrupting doses showed the same cavitation-bearing vasculature as maps produced over entire blood-brain-barrier opening procedures, allowing use for (1) monitoring focused-ultrasound blood-brain-barrier-opening (FUS-BBBO), but also for (2) therapy planning and target verification. Significance. BP-ETACI is versatile, created high resolution cavitation maps in the mouse brain and is easily translatable to existing FUS-BBBO experiments. As such, it provides a means to further study cavitation phenomena in FUS-BBBO.

Multiresolution soil moisture products based on a spatially adaptive estimation model and CYGNSS data

ABSTRACT The estimation of soil moisture (SM) utilizing the data from the Cyclone Global Navigation Satellite System (CYGNSS) has attracted significant interest in recent times. However, CYGNSS’ inherent capability of variable resolution has not been fully exploited, often resulting in a loss of detailed spatial information in the raw data. In this paper, a novel downscaling scheme tailored for CYGNSS data is introduced to yield a “self-adjusting adaptive resolution” SM product, which dynamically varies the resolution of SM estimates based on the available CYGNSS data resolution at different geographic locations. Initially, a direct quantitative relationship is established between the key CYGNSS parameters reflecting SM variations and the reference SM from the Soil Moisture Active Passive (SMAP) mission with a coarse resolution of 36 km. This model is then applied to CYGNSS observations with resolutions down to 3 km to generate high-resolution, self-adjusting SM estimates that better conserve the fine-scale information linked to the original CYGNSS data. Extensive experimental results with error ratio diagrams show that the advanced geographically weighted regression (GWR)-based SM estimation method outperforms other competing estimation models and better retains localized spatial relationships and patterns. This study underscores the potential of CYGNSS as a novel and robust independent data source capable of delivering fine-resolution SM estimations by harnessing its unique multiresolution observational capability.

Improving the Resolution of Flexible Large-Area Tactile Sensors through Machine-Learning Perception.

Industrial robots are the main piece of equipment of intelligent manufacturing, and array-type tactile sensors are considered to be the core devices for their active sensing and understanding of the production environment. A great challenge for existing array-type tactile sensors is the wiring of sensing units in a limited area, the contradiction between a small number of sensing units and high resolution, and the deviation of the overall output pattern due to the difference in the performance of each sensing unit itself. Inspired by the human somatosensory processing hierarchy, we combine tactile sensors with artificial intelligence algorithms to simplify the sensor architecture while achieving tactile resolution capabilities far greater than the number of signal channels. The prepared 8-electrode carbon-based conductive network achieves high-precision identification of 32 regions with 97% classification accuracy assisted by a quadratic discriminant analysis algorithm. Notably, the output of the sensor remains unchanged after 13,000 cycles at 60 kPa, indicating its excellent durability performance. Moreover, the large-area skin-like continuous conductive network is simple to fabricate, cost-effective, and can be easily scaled up/down depending on the application. This work may address the increasing need for simple fabrication, rapid integration, and adaptable geometry tactile sensors for use in industrial robots.

Validation and assessment of multi-GNSS phase bias products from IGS analysis centers

Phase bias plays a crucial role in precision point positioning (PPP) with ambiguity resolution. Currently, an increasing number of analysis centers are being of releasing multi- Global Navigation Satellite System (GNSS) phase bias products. However, it remains uncertain how different phase bias products, receiver types, and GNSS systems combinations might impact user-side positioning performance and ambiguity resolution capabilities. In view of this, this contribution systematically investigates the effects on PPP with ambiguity resolution. Four types of receivers, including SEPTENTRIO POLARX5, LEICA GR50, JAVAD TRE_3 DELTA, and TRIMBLE ALLOY, are selected, and six types of GNSS system combinations, namely, GPS, Galileo, BDS3, GPS/Galileo, GPS/BDS3, GPS/Galileo/BDS3, are used, and the phase bias products from OSB (Observable-specific Bias)-CODE (Center for Orbit Determination in Europe), OSB-CNES/CLS (Centre National d’Etudes Spatiales Geodesy Team), OSB-GFZ (German Research Centre for Geosciences/Germany), OSB-WHU (Wuhan University), OSB-CNES/NAV (Centre National d’Etudes Spatiales Navigation Team), IRC (Integer Recovery Clock)-CNES/CLS, IRC-GFZ are adopted for the numerical experiment. Compared with the float-solution, the results show that the accuracy of PPP fixed-solution with single-system can be improved 1 cm–3 cm, and the convergence time is reduced 2 min–15 min. The positioning performance using the seven phase bias products for any single-system satisfies the following order from the best to the worst: OSB_WHU > OSB_CODE > OSB_CNES/CLS ≈ OSB_CNES/NAV > OSB_GFZ > IRC_CNES/CLS ≈ IRC_GFZ, but the performance of ambiguity resolution do not present certain characteristics. Meanwhile, the ambiguity-fix success-rate and Time to First Fix can keep at 80%–96% and 20 min–40 min with single-system, respectively. In the case of multi-system, although the difference in the positioning performance among the phase bias products is not significant, the multi-system outperforms the single-systemin terms of both positioning performance and ambiguity resolution. However, the difference between the dual-system and the triple-system is smaller. In addition, the positioning performance corresponding to different receiver types also shows distinction, while there is no significant difference in the ambiguity resolution performance between different receiver types.

Compressed sensing with deep learning reconstruction: Improving capability of gadolinium-EOB-enhanced 3D T1WI

PurposeThe purpose of this study was to determine the utility of compressed sensing (CS) with deep learning reconstruction (DLR) for improving spatial resolution, image quality and focal liver lesion detection on high-resolution contrast-enhanced T1-weighted imaging (HR-CE-T1WI) obtained by CS with DLR as compared with conventional CE-T1WI with parallel imaging (PI). MethodsSeventy-seven participants with focal liver lesions underwent conventional CE-T1WI with PI and HR-CE-T1WI, surgical resection, transarterial chemoembolization, and radiofrequency ablation, followed by histopathological or >2-year follow-up examinations in our hospital. Signal-to-noise ratios (SNRs) of liver, spleen and kidney were calculated for each patient, after which each SNR was compared by means of paired t-test. To compare focal lesion detection capabilities of the two methods, a 5-point visual scoring system was adopted for a per lesion basis analysis. Jackknife free-response receiver operating characteristic (JAFROC) analysis was then performed, while sensitivity and false positive rates (/data set) for consensus assessment of the two methods were also compared by using McNemar's test or the signed rank test. ResultsEach SNR of HR-CE-T1WI was significantly higher than that of conventional CE-T1WI with PI (p < 0.05). Sensitivities for consensus assessment showed that HR-CE-MRI had significantly higher sensitivity than conventional CE-T1WI with PI (p = 0.004). Moreover, there were significantly fewer FP/cases for HR-CE-T1WI than for conventional CE-T1WI with PI (p = 0.04). ConclusionCS with DLR are useful for improving spatial resolution, image quality and focal liver lesion detection capability of Gd-EOB-DTPA enhanced 3D T1WI without any need for longer breath-holding time.

TGFs, Gamma‐Ray Glows, and Direct Lightning Strike Radiation Observed During a Single Flight of a Balloon‐Borne Gamma‐Ray Spectrometer

AbstractTerrestrial gamma‐ray flashes (TGFs) and other high‐energy radiation phenomena related to thunderstorms remain incompletely understood since their discovery nearly 30 years ago. Space and ground‐based platforms have provided insights, but limitations exist in temporal resolution, signal‐to‐noise ratios, and proximity to events. This study presents findings from a balloon‐borne gamma‐ray spectrometer flown into a thunderstorm over northern Mississippi on 19 June 2023. The instrument detected three distinct millisecond‐duration TGF events correlated with lightning strikes. Sustained gamma‐ray glows lasting up to 2 minutes were measured and tied to thunderstorm electrostatic fields. Notably, radiation was observed during a direct lightning strike to the payload. This complex 800‐millisecond event reveals insights into radiation from leader propagation and return strokes. These findings from a single balloon flight demonstrate the prevalence of energetic processes within thunderstorms. Finally, the balloon platform offered an exceptional combination of temporal resolution and validation capabilities to advance the understanding of thunderstorm radiation motivating future follow‐up studies.

Development of a Triple-GEM detector with strip readout and GEMINI chip for X rays and neutron imaging

Thermal neutron imaging can be a useful tool in the study of the internal structure of an object. The different attenuation properties of the materials with respect to X rays give rise to different interactions and the result is a complementary non-destructive analysis, which can provide important additional information. This technique has been successfully employed in different areas of work, especially in material science and cultural heritage studies. This paper describes the development of a new detection system and its characterization performed with X ray emissions. The system features the use of a gaseous detector, based on the Gas Electron Multiplier technology, and a fully digital electronic readout, with a combination of custom-made ASICs (called GEMINI) and FPGA boards, enabling fast single photon counting. The detector can be thus used directly for X ray imaging, while the addition of a suitable converter in its active volume will allow for detection of neutrons and for reconstruction of their tracks. The readout system is based on a x-y strip structure and features the reconstruction of single events through the center of mass methodology, allowing for accurate tomography, with sub-mm spatial resolution, in combination with sub-ms time resolution and high rate capabilities (up to MHz/mm2).

Two-photon excitation fluorescence microspectroscopy protocols for examining fluorophores in fossil plants

Fluorescence emission is common in plants. While fluorescence microscopy has been widely used to study living plants, its application in quantifying the fluorescence of fossil plants has been limited. Fossil plant fluorescence, from original fluorophores or formed during fossilization, can offer valuable insights into fluorescence in ancient plants and fossilization processes. In this work, we utilize two-photon fluorescence microspectroscopy to spatially and spectrally resolve the fluorescence emitted by amber-embedded plants, leaf compressions, and silicified wood. The advanced micro-spectroscope utilized, with its pixel-level spectral resolution and line-scan excitation capabilities, allows us to collect comprehensive excitation and emission spectra with high sensitivity and minimal laser damage to the specimens. By applying linear spectral unmixing to the spectrally resolved fluorescence images, we can differentiate between (a) the matrix and (b) the materials that comprise the fossil. Our analysis suggests that the latter correspond to durable tissues such as lignin and cellulose. Additionally, we observe potential signals from chlorophyll derivatives/tannins, although minerals may have contributed to this. This research opens doors to exploring ancient ecosystems and understanding the ecological roles of fluorescence in plants throughout time. Furthermore, the protocols developed herein can also be applied to analyze non-plant fossils and biological specimens.

Review of Gold Nanoparticles in Surface Plasmon-Coupled Emission Technology: Effect of Shape, Hollow Nanostructures, Nano-Assembly, Metal-Dielectric and Heterometallic Nanohybrids.

Point-of-care (POC) diagnostic platforms are globally employed in modern smart technologies to detect events or changes in the analyte concentration and provide qualitative and quantitative information in biosensing. Surface plasmon-coupled emission (SPCE) technology has emerged as an effective POC diagnostic tool for developing robust biosensing frameworks. The simplicity, robustness and relevance of the technology has attracted researchers in physical, chemical and biological milieu on account of its unique attributes such as high specificity, sensitivity, low background noise, highly polarized, sharply directional, excellent spectral resolution capabilities. In the past decade, numerous nano-fabrication methods have been developed for augmenting the performance of the conventional SPCE technology. Among them the utility of plasmonic gold nanoparticles (AuNPs) has enabled the demonstration of plethora of reliable biosensing platforms. Here, we review the nano-engineering and biosensing applications of AuNPs based on the shape, hollow morphology, metal-dielectric, nano-assembly and heterometallic nanohybrids under optical as well as biosensing competencies. The current review emphasizes the recent past and evaluates the latest advancements in the field to comprehend the futuristic scope and perspectives of exploiting Au nano-antennas for plasmonic hotspot generation in SPCE technology.

Research on multi-dimensional micro-motion feature extraction of moving targets

The micro-Doppler effect is a physical phenomenon generated by the micro-motion of objects and their components, which have a significant influence on improving radar detection and resolution capability and also enhancing the radar imaging and target recognition performance. The extraction of micro-Doppler frequency, as a commonly used time-frequency analysis tool, is of great significance in extracting and reconstructing the signal with micro-motion targets. The micro-motion characteristics for moving targets can be verified by using simulation through combining the theory of micro-Doppler effect with the frequency domain model of electromagnetic waves. The simulation research on the micro-motion characteristics of a three-dimensional target is conducted by using the finite element method. The influences of environmental conditions such as relative humidity, visibility, and the presence or absence of turbulence on echo intensity and time-frequency relationship are investigated theoretically. The simulation results indicate that parameters such as relative humidity and visibility, which affect the atmospheric attenuation coefficient, can reduce echo intensity and the period of time-frequency curve. By triggering off beam drift in the transmission path, turbulence can lead to “frequency shift deformation” of the time-frequency curve, degrading the extraction of target motion attitude. A motion attitude classification method is proposed in order to study the micro-Doppler effect better. According to whether the frequency shift changes with time, the motion attitude can be divided into frequency shift time-invariant motion and time-variant motion. Frequency shift time-variant motion includes translation, rolling and vibration. Vibration and rolling are motions that periodically change with time, requiring the comparison of instantaneous frequency shifts at any three times within a cycle. Translation is a time-variant motion with irregular frequency shifts over time, which involves studying instantaneous frequency shifts at any three times. Transient frequency shifts should be analyzed and compared at different times for these motions. The frequency shift time-invariant motion is mainly rotation obtained experimental results indicate that the amplitude, plus-minus, and spectral width of frequency shift at different positions are aimed at inverting the target shape, attitude, direction and velocity. Demodulating one-dimensional data obtained from the FFTshift function can obtain the time-frequency-intensity relationship. This multi-parameter analysis method is a multi-dimensional processing method widely used in the fields of radar, sonar, and communication. The above research is conductive to the measurement of target macroscopic shape properties and the extraction of microscopic motion information, which lays the foundation for radar detection and recognition.

Metallofullerenes as potential candidates for the explanation of astrophysical phenomena.

Detection of complex organic species in space has been one of the biggest challenges of the astrophysical community since the beginning of space exploration, with C60-fullerene representing one of the largest molecules so far detected. The presence of small metal-containing organic molecules, like MgNC or CaCN, in space, promoted the idea that C60 may also interact with metals and form metallofullerenes based on the fact that in certain circumstellar and interstellar environments, the ingredients for the formation of metallofullerenes, i.e., metal and fullerenes, are abundant. In this perspective, we summarized the current effort to explore the presence of metallofullerenes in space, which started soon after the discovery of fullerenes about 40 years ago. Several implications of astrophysical phenomena were briefly discussed and shown to be addressable as the possible consequence of metallofullerenes' presence. We highlighted the spectral fingerprints that might be followed to achieve the future detection of cosmic metallofullerenes from a combined effort of laboratory and quantum chemical calculations. These results are expected to gain great importance with the James Webb Space Telescope (JWST), whose capability of unprecedented high sensitivity and high spectral resolution in the far- to mid-infrared range could aid the unequivocal detection of metallofullerenes in space.

Nanoimprint lithography guiding templates for advanced magnetic media fabrication

Nanoimprint lithography presents unique opportunities for advanced magnetic storage media with ordered bit arrangements such as bit patterned media or heated dot magnetic recording. Providing sub-10 nm resolution and full disk imprinting capability, UV-nanoimprint lithography based on rigid quartz templates bears the entitlement for patterned recording media manufacturing with high throughput at low cost. However, a key challenge is the fabrication of the high-resolution template that can transfer the desired pattern onto the disk with high fidelity and low line edge roughness. In this article, we present fabrication routes and overcome challenges to the fabrication of quartz templates suitable for self-alignment and guiding purposes to be used for template replication toward full disk imprints. Guiding patterns down to 40 nm pitch are prepared using a rotary electron beam lithography tool. We compare three different process approaches to fabricate an etching mask for patterning the quartz. Two methods target chromium patterning, one with traditional lift-off and another by dry etching, both using an e-beam resist mask. The third approach is based on the development of a carbon-based Tri-layer hard mask. The template pattern profile is optimized for imprint-suitable sidewall angles using dry etching in a CF4/O2 chemistry. The templates were characterized using scanning electron microscopy and atomic force microscopy to evaluate the quality of the transferred pattern as well as line edge roughness. Our results show that the Tri-layer process using carbon resulted in the lowest line edge roughness of ≈0.65 nm at the imprinted disk level. In addition, we show that Tri-layer masking allowed for the use of conventional ZEP e-beam resist and fast writing speeds, while gaining high selectivity during quartz patterning.

Muon spectrometers on China Spallation Neutron Source and its application prospects

&lt;sec&gt;The China Spallation Neutron Source Phase-II Project (CSNS-II) includes the construction of a muon source, namely “Muon station for sciEnce technoLOgy and inDustrY” (MELODY). A muon target station and a surface muon beam line will be completed as scheduled in 2029, making MELODY the first Chinese muon facility. This beam line mainly focuses on the application of muon spin relaxation/rotation/resonance (μSR) spectroscopy. The MELODY also reserves the tunnels for building a negative muon beam line and a decay muon beam line in the future, thereby further expanding the research field to muon-induced X-ray emission (MIXE) elemental analysis and μSR measurements in thick cells, respectively. The two types of material characterization technologies keep their uniqueness in multi-disciplinary researches, and also provide complementary insights for other techniques, such as neutron scattering, nuclear magnetic resonance, and X-ray fluorescence analysis.&lt;/sec&gt;&lt;sec&gt;The μSR spectroscopy is a mature technology for injecting highly spin polarized muon beams into various types of materials. The subsequent precession and relaxation of muon spin in its surrounding atomic environment reflect the static and dynamical properties of the material of interest, which are then measured by detecting the asymmetric emission of positrons from the decay of those muons, with an average lifetime of approximately 2.2 μs. This enables μSR to develop into a powerful quantum magnetic probe for investigating materials related to magnetism, superconductivity, and molecular dynamics. The combination of a positive muon and an electron is known as muonium, which is a unique and sensitive probe in studying semiconductors, new energy materials, free radical chemistry, etc. As the production of muon beams strongly relies on proton accelerator, only five muon facilities in the world are available for μSR experiments. This limits the large-scale application of muon related sciences. Especially, Chinese researchers face fierce competition and can only apply for precious and limited muon beam time from international muon sources to characterize the key properties of their materials.&lt;/sec&gt;&lt;sec&gt;The construction of the MELODY muon facility at CSNS-II aims to provide intense and pulsed muon beams for Chinese and international users to conduct their μSR measurements with high quality data in a low repetition rate operation mode. To achieve this goal, as shown in &lt;xref ref-type="fig" rid="Figure1"&gt;Fig. 1&lt;/xref&gt;, the μSR spectrometer is designed with 1) over 3000 detector units to obtain a sufficient counting rate of 80 Million/h to significantly suppress statistical fluctuations in a short measuring time, 2) a high asymmetry of 0.3 to greatly amplify μSR signals so as to further reduce statistical fluctuations, and 3) extendable low temperature devices to cover most μSR applications and also fulfill experiments with extreme condition requirements.&lt;/sec&gt;&lt;sec&gt;The MIXE elemental analysis is a type of particle induced X-ray emission (PIXE) technology. Due to the heavier mass of negative muon, the energy of muonic X-ray is around 207 higher than that of X-ray or electron induced fluorescence X-ray. Thus, the MIXE technology is more sensitive to materials with low atomic numbers, and thick samples can be effectively studied without scratching their surfaces. Due to these advantages, the MIXE has been successfully applied to the elemental analysis of cultural heritages, meteorites, Li-ion batteries, etc. MELODY reserves tunnels for negative muon extractions and transport to a MIXE terminal. The MELODY research team is developing a new detection technology with high energy resolution and high counting capability to shorten the measuring time to an acceptable amount based on the 1-Hz repetition rate of muon pulses.&lt;/sec&gt;&lt;sec&gt;The μSR spectroscopy and MIXE are the two most important application fields of accelerator muon beams. The MELODY muon facility aims to develop and promote these technologies in China by constructing dedicated muon beam lines in CSNS-II and in the future. In this overview, we introduce the principles and advantages of the μSR and MIXE technologies, as well as the physical design and application prospects of the μSR and MIXE spectrometers based on the CSNS-II muon source. Finally, discussions and expectations are made regarding the future upgrade of the CSNS-II muon source’s muon beamline and its broader applications.&lt;/sec&gt;

Future Prospects for Constraining Black Hole Spacetime: Horizon-scale Variability of Astrophysical Jets

The Event Horizon Telescope (EHT) Collaboration has recently published the first horizon-scale images of the supermassive black holes M87* and Sgr A* and provided some first information on the physical conditions in their vicinity. The comparison between the observations and the three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations has enabled the EHT to set initial constraints on the properties of these black hole spacetimes. However, accurately distinguishing the properties of the accretion flow from those of the spacetime, most notably, the black hole mass and spin, remains challenging because of the degeneracies the emitted radiation suffers when varying the properties of the plasma and those of the spacetime. The next-generation EHT (ngEHT) observations are expected to remove some of these degeneracies by exploring the complex interplay between the disk–jet dynamics, which represents one of the most promising tools for extracting information on the black hole spin. By using GRMHD simulations of magnetically arrested disks and general relativistic radiative transfer (GRRT) calculations of the emitted radiation, we have studied the properties of the jet and the accretion disk dynamics on spatial scales that are comparable with the horizon. In this way, we are able to highlight that the radial and azimuthal dynamics of the jet are well correlated with the black hole spin. Based on the resolution and image reconstruction capabilities of the ngEHT observations of M87*, we can assess the detectability and associated uncertainty of this correlation. Overall, our results serve to assess the prospects for constraining the black hole spin with future EHT observations.

FRACTAL GEOMETRY-BASED RESOURCE ALLOCATION FOR MIMO RADAR

The netted Collocated Multiple-Input Multiple-Output (C-MIMO) radar systems have attracted widespread attention due to their high resolution and excellent target detection capabilities. The self-similarity and spatial filling properties of fractal geometry enable antenna layouts to function effectively across multiple scales and frequency bands, which helps improve the overall performance and resource utilization of systems. In this paper, a radar array element model based on the Fudgeflake fractal is used to establish a target localization performance model directly related to power bandwidth allocation. Based on the model, a three-step solving strategy was designed with the Sequence Quadratic Program (SQP) algorithm as the foundation to achieve optimized allocation of power and bandwidth while maximizing overall performance. Experimental results demonstrate that under this algorithm, the use of power bandwidth resources is optimized through fractal geometry-based design.

Layer-dependent ultrafast carrier dynamics of PdSe2 investigated by photoemission electron microscopy.

For atomically thin two-dimensional materials, variations in layer thickness can result in significant changes in the electronic energy band structure and physicochemical properties, thereby influencing the carrier dynamics and device performance. In this work, we employ time- and energy-resolved photoemission electron microscopy to reveal the ultrafast carrier dynamics of PdSe2 with different layer thicknesses. We find that for few-layer PdSe2 with a semiconductor phase, an ultrafast hot carrier cooling on a timescale of approximately 0.3 ps and an ultrafast defect trapping on a timescale of approximately 1.3 ps are unveiled, followed by a slower decay of approximately tens of picoseconds. However, for bulk PdSe2 with a semimetal phase, only an ultrafast hot carrier cooling and a slower decay of approximately tens of picoseconds are observed, while the contribution of defect trapping is suppressed with the increase of layer number. Theoretical calculations of the electronic energy band structure further confirm the transition from a semiconductor to a semimetal. Our work demonstrates that TR- and ER-PEEM with ultrahigh spatiotemporal resolution and wide-field imaging capability has great advantages in revealing the intricate details of ultrafast carrier dynamics of nanomaterials.

Analysis of Optimal Spatial Resolution Capability of Pulse-Dilation Framing Camera

Analysis of Optimal Spatial Resolution Capability of Pulse-Dilation Framing Camera

A wall-modeled hybrid RANS/LES model for flow around circular cylinder with coherent structures in subcritical Reynolds number regions

In the present paper, a hybrid RANS/LES model with the wall-modelled LES capability (called WM-HRL model) is developed to perform the high-fidelity CFD simulation investigation for complex flow phenomena around a bluff body with coherent structure in subcritical Reynolds number region. The proposed method can achieve a fast and seamless transition from RANS to LES through a filter parameter &lt;i&gt;r&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt; which is only related to the space resolution capability of the local grid system for various turbulent scales. Furthermore, the boundary positions of the transition region from RANS to LES, as well as the resolving capabilities for the turbulent kinetic energy in the three regions, i.e. RANS, LES and transition region, can be preset by two guide index parameters &lt;i&gt;nr&lt;/i&gt;&lt;sub&gt;k1-Q&lt;/sub&gt; and &lt;i&gt;nr&lt;/i&gt;&lt;sub&gt;k2-Q&lt;/sub&gt;. Through a series of numerical simulations of the flow around a circular cylinder at Reynolds number &lt;i&gt;Re&lt;/i&gt; = 3900, the combination conditions are obtained for such two guide index parameters &lt;i&gt;nr&lt;/i&gt;&lt;sub&gt;k1-Q&lt;/sub&gt; and &lt;i&gt;nr&lt;/i&gt;&lt;sub&gt;k2-Q&lt;/sub&gt; that have the capability of high-fidelity resolving and capturing temporally- and spatially-developing coherent structures for such complex three-dimensional flows around such a circular cylinder. The results demonstrate that the new WM-HRL model is capable of accurately resolving and capturing the fine spectral structures of the small-scale Kelvin-Helmholtz instability in the shear layer for flow around such a circular cylinder. Furthermore, under a consistent grid system, through different combinations of these two guide index parameters &lt;i&gt;r&lt;/i&gt;&lt;sub&gt;k1&lt;/sub&gt; and &lt;i&gt;r&lt;/i&gt;&lt;sub&gt;k2&lt;/sub&gt;, the fine structuresof the recirculation zones with two different lengths and the U-shaped and V-shaped distribution of the average stream-wise velocity in the cylinder near the wake can also be obtained.