43 research outputs found
A Signal Processing Algorithm Based on 2D Matched Filtering for SSAR
This study discusses a smart radar antenna scanning mode that combines features of both the sector-scan mode used for conventional radar and the line-scan mode used for synthetic aperture radar (SAR) and achieves an application of the synthetic aperture technique in the conventional sector-scan (mechanically scanned) radar, and we refer to this mode as sector-scan synthetic aperture radar (SSAR). The mathematical model is presented based on the principle of SSAR, and a signal processing algorithm is proposed based on the idea of two-dimensional (2D) matched filtering. The influences of the line-scan range and speed on the SSAR system are analyzed, and the solution to the problem that the target velocity is very high is given. The performance of the proposed algorithm is evaluated through computer simulations. The simulation results indicate that the proposed signal processing algorithm of SSAR can gather the signal energy of targets, thereby improving the ability to detect dim targets
Towards Understanding Third-party Library Dependency in C/C++ Ecosystem
Third-party libraries (TPLs) are frequently reused in software to reduce
development cost and the time to market. However, external library dependencies
may introduce vulnerabilities into host applications. The issue of library
dependency has received considerable critical attention. Many package managers,
such as Maven, Pip, and NPM, are proposed to manage TPLs. Moreover, a
significant amount of effort has been put into studying dependencies in
language ecosystems like Java, Python, and JavaScript except C/C++. Due to the
lack of a unified package manager for C/C++, existing research has only few
understanding of TPL dependencies in the C/C++ ecosystem, especially at large
scale.
Towards understanding TPL dependencies in the C/C++ecosystem, we collect
existing TPL databases, package management tools, and dependency detection
tools, summarize the dependency patterns of C/C++ projects, and construct a
comprehensive and precise C/C++ dependency detector. Using our detector, we
extract dependencies from a large-scale database containing 24K C/C++
repositories from GitHub. Based on the extracted dependencies, we provide the
results and findings of an empirical study, which aims at understanding the
characteristics of the TPL dependencies. We further discuss the implications to
manage dependency for C/C++ and the future research directions for software
engineering researchers and developers in fields of library development,
software composition analysis, and C/C++package manager.Comment: ASE 202
Will ocean acidification affect the digestive physiology and gut microbiota of whelk *Brunneifusus ternatanus*?
To understand the physiological responses of the Brunneifusus ternatanus to future ocean acidification (OA), histology, enzyme activity and gut bacterial composition at different pH levels (Control : C group, pH 8.1; Exposure period : EP group, pH 7.3) for 28 days were studied under laboratory conditions. Microbiota composition was analyzed using 16S rRNA gene amplicon sequencing. Enzyme activities of trypsin (TRY), lipase (LPS), amylase (AMS), and lysozyme (LZM) were used as biochemical indicators, as well as weight gain rate (WGR), specific growth rate (SGR) as growth indicators. The stress caused by OA resulted in alterations to the intestine, including partially swollen and degranulated enterocytes and rough endoplasmic reticulum (RER). The relative abundance of the core phylum in the acidified group changed significantly, showing an increase in Tenericutes and a decrease in Proteobacteria. Firmicutes/Bacteroides ratio declined from 4.38 in the control group to 1.25 in the EP group. We found that the enzymes TRY, LPS, and AMS activities were inhibited at reduced pH, which was positively correlated with the dominant genera Mycoplasma and Bacteroides; while LZM activities showed a significant increment, but showing a strong negative correlation. Furthermore, both WG and SRG values showed a depression at low pH lever. These results suggest that if anthropogenic CO2 emissions continue to accelerate, OA could lead to a negative impact on the whelk health, also compromising their growth performance and even survival. These findings will benefit the future risk assessments of OA or other related emerging environmental issue
Highly efficient room-temperature nonvolatile magnetic switching by current in Fe3GaTe2 thin flakes
Effectively tuning magnetic state by using current is essential for novel
spintronic devices. Magnetic van der Waals (vdW) materials have shown superior
properties for the applications of magnetic information storage based on the
efficient spin torque effect. However, for most of known vdW ferromagnets, the
ferromagnetic transition temperatures lower than room temperature strongly
impede their applications and the room-temperature vdW spintronic device with
low energy consumption is still a long-sought goal. Here, we realize the highly
efficient room-temperature nonvolatile magnetic switching by current in a
single-material device based on vdW ferromagnet Fe3GaTe2. Moreover, the
switching current density and power dissipation are about 300 and 60000 times
smaller than conventional spin-orbit-torque devices of magnet/heavymetal
heterostructures. These findings make an important progress on the applications
of magnetic vdW materials in the fields of spintronics and magnetic information
storage.Comment: 18 page2, 4 figure
A Fast Visible-Infrared Imaging Radiometer Suite Simulator for Cloudy Atmopheres
A fast instrument simulator is developed to simulate the observations made in cloudy atmospheres by the Visible Infrared Imaging Radiometer Suite (VIIRS). The correlated k-distribution (CKD) technique is used to compute the transmissivity of absorbing atmospheric gases. The bulk scattering properties of ice clouds used in this study are based on the ice model used for the MODIS Collection 6 ice cloud products. Two fast radiative transfer models based on pre-computed ice cloud look-up-tables are used for the VIIRS solar and infrared channels. The accuracy and efficiency of the fast simulator are quantify in comparison with a combination of the rigorous line-by-line (LBLRTM) and discrete ordinate radiative transfer (DISORT) models. Relative errors are less than 2 for simulated TOA reflectances for the solar channels and the brightness temperature differences for the infrared channels are less than 0.2 K. The simulator is over three orders of magnitude faster than the benchmark LBLRTM+DISORT model. Furthermore, the cloudy atmosphere reflectances and brightness temperatures from the fast VIIRS simulator compare favorably with those from VIIRS observations
Scaling of Berry-curvature monopole dominated large linear positive magnetoresistance
The linear positive magnetoresistance (LPMR) is a widely observed phenomenon
in topological materials, which is promising for potential applications on
topological spintronics. However, its mechanism remains ambiguous yet and the
effect is thus uncontrollable. Here, we report a quantitative scaling model
that correlates the LPMR with the Berry curvature, based on a ferromagnetic
Weyl semimetal CoS2 that bears the largest LPMR of over 500% at 2 Kelvin and 9
Tesla, among known magnetic topological semimetals. In this system, masses of
Weyl nodes existing near the Fermi level, revealed by theoretical calculations,
serve as Berry-curvature monopoles and low-effective-mass carriers. Based on
the Weyl picture, we propose a relation , with B being the applied magnetic field and the average Berry curvature near the Fermi surface, and further
introduce temperature factor to both MR/B slope (MR per unit field) and
anomalous Hall conductivity, which establishes the connection between the model
and experimental measurements. A clear picture of the linearly slowing down of
carriers, i.e., the LPMR effect, is demonstrated under the cooperation of the
k-space Berry curvature and real-space magnetic field. Our study not only
provides an experimental evidence of Berry curvature induced LPMR for the first
time, but also promotes the common understanding and functional designing of
the large Berry-curvature MR in topological Dirac/Weyl systems for magnetic
sensing or information storage
Nearly-room-temperature ferromagnetism and tunable anomalous Hall effect in atomically thin Fe4CoGeTe2
Itinerant ferromagnetism at room temperature is a key ingredient for spin
transport and manipulation. Here, we report the realization of
nearly-room-temperature itinerant ferromagnetism in Co doped Fe5GeTe2 thin
flakes. The ferromagnetic transition temperature TC (323 K - 337 K) is almost
unchanged when thickness is down to 12 nm and is still about 284 K at 2 nm
(bilayer thickness). Theoretical calculations further indicate that the
ferromagnetism persists in monolayer Fe4CoGeTe2. In addition to the robust
ferromagnetism down to the ultrathin limit, Fe4CoGeTe2 exhibits an unusual
temperature- and thickness-dependent intrinsic anomalous Hall effect. We
propose that it could be ascribed to the dependence of band structure on
thickness that changes the Berry curvature near the Fermi energy level subtly.
The nearly-room-temperature ferromagnetism and tunable anomalous Hall effect in
atomically thin Fe4CoGeTe2 provide opportunities to understand the exotic
transport properties of two-dimensional van der Waals magnetic materials and
explore their potential applications in spintronics.Comment: 28 pages, 4 figures, 1 tabl
Investigation of Pectenotoxin Profiles in the Yellow Sea (China) Using a Passive Sampling Technique
Pectenotoxins (PTXs) are a group of lipophilic algal toxins. These toxins have been found in algae and shellfish from Japan, New Zealand, Ireland, Norway and Portugal. PTX profiles vary with geographic location of collection site. The aim of the present study was to investigate PTX profiles from the Yellow Sea, China. The sampling location was within an aquatic farm (N36°12.428′, E120°17.826′) near the coast of Qingdao, China, in the Yellow Sea from 28 July to 29 August 2006. PTXs in seawater were determined using a solid phase adsorption toxin tracking (SPATT) method. PTXs were analyzed by HPLC-MSMS. PTX-2, PTX-2 sec acid (PTX-2 SA) and 7-epi-PTX-2 SA were found in seawater samples. The highest levels of PTXs (107 ng/g of resin PTX-2, 50 ng/g of resin PTX-2 SA plus 7-epi-PTX-2 SA) in seawater were found on 1 August, 2006. From 1 August to 29 August, the levels of PTX-2 and PTX-2 SA decreased. In the same area, the marine algae, Dinophysis acuminata was found in the seawater in the summer months of 2006. This indicated that Dinophysis acuumuta might be the original source of PTXs. PTX-11 and PTX-12a/b were not found in seawater