Basis material decomposition has been a common tool in spectral computed tomography (CT), which is used to acquire the material-specific information about human tissues. However, the performance of ...current methods for material decomposition is seriously affected by noise, especially when the X-ray radiation dose is reduced. To address this problem, a novel approach with modified U-net convolutional neural network is proposed and evaluated. First, the raw data (sinograms) collected from spectral CT detector are decomposed into different substances directly. Then a filtered back projection algorithm is used to generate the basis material maps. The modified U-net is trained with the raw data in the projection domain, and the input of the network are different energy sinograms while the decomposed sinograms of basis materials could be obtained from the output. In the experiment, water and iodine are selected as basis materials. Comparing with the traditional method, the PSNR of materials maps is improved about 7dB to 17dB of different slices, which shows that this proposed approach could make more accurate material maps in low-dose spectral CT.
This paper reports on the latest advances and challenges of a 2D Fourier Transform Computational Accelerator using GHz Ultrasonics. Firstly, the accelerator architecture is presented in four parts: ...(1) a brief overview of the system architecture and the principles of Fourier Transform using ultrasonic waves; (2) CMOS circuit architecture of the transmitter and receiver IC; (3) MEMS transducer pixel design and post-CMOS integration; and (4) GHz acoustic meta-lens design. The following section discusses the latest advances in the sonic DAC and front-end receiver CMOS circuit testing, CMOS-MEMS integration, fabrication of GHz flat acoustic meta-lens, and studies of a novel low-temperature heterogeneous integration process suitable for GHz acoustic transmission.
Compared with general polymers, polyureathane-urea( PUU) elastoner shows more superior properties such as toughness, tear strength, lexibility, elongation, hydrolytic stability and good low ...temperature noperty, so it is widely used in coating, foam, textile, elastomers, nedicine equipment, etc. However, these good mechanical properties !an not be retained for a long time at high temperature, for this reaon, its application at high temperature is restricted. To improve its hermal stability and mechanical properties, the adjacency crosslinked 'UU with HTBN as soft segment was prepared in this study.
This paper presents the upgrading of locally one-dimensional finite-difference time-domain (LOD-FDTD) method to efficient method with second-order accuracy. The fundamental ADI-FDTD and LOD-FDTD ...methods with source implementations are given to derive the upgraded LOD-FDTD method. Using proper initial input processing, second-order accurate field values can be obtained. The upgraded LOD-FDTD method can yield the results of both original and upgraded LOD-FDTD methods simultaneously. Numerical results are demonstrated to verify the upgraded (second-order) accuracy.
Apotyvirus isolated from perennial whitegrass ( Pennisetum centrasiaticum Tzvel.) in North China was characterized at the molecular level. The 3' terminal nucleotide (nt) sequence of 1669 nt of the ...viral RNA genome has been determined, which covered the coding region of the C-terminal part of the large nuclear inclusion protein (NIb, RNA polymerase), capsid protein (CP) gene and the 3' nontranslated region (NTR). The CP gene consisted of 909 nt (including the stop codon) encoding 302 amino acid residues, and the 3' NTR was 241 nt in length excluding the polyadenylated tract. Sequence comparison of the amino acids of CPs showed that this virus was most closely related to Sorghum mosaic virus and Maize dwarf mosaic virus with percent identities of 77% to 78% while that of the 3' NTRs suggested that it was most closely related to Zea mosaic virus with identity of 72%. This virus isolate was to some extent closely related to other members of the Sugarcane mosaic virus subgroup of potyviruses for the CP amino acid sequences. Phylogenetic analyses of the sequences indicated that this virus isolate represented a distinct potyvirus, and the name Pennisetum mosaic virus (PenMV) is proposed.
Illicit traffic monetization is a type of Internet fraud that hijacks users' web requests and reroutes them to a traffic network (e.g., advertising network), in order to unethically gain monetary ...rewards. Despite its popularity among Internet fraudsters, our understanding of the problem is still limited. Since the behavior is highly dynamic (can happen at any place including client-side, transport-layer and server-side) and selective (could target a regional network), prior approaches like active probing can only reveal a small piece of the entire ecosystem. So far, questions including how this fraud works at a global scale and what fraudsters' preferred methods are, still remain unanswered. To fill the missing pieces, we developed TraffickStop the first system that can detect this fraud passively. Our key contribution is a novel algorithm that works on large-scale DNS logs and efficiently discovers abnormal domain correlations. TraffickStop enables the first landscape study of this fraud, and we have some interesting findings. By analyzing over 231 billion DNS logs of two weeks, we discovered 1,457 fraud sites. Regarding its scale, the fraud sites receive more than 53 billion DNS requests within one year, and a company could lose up to 53K dollars per day due to fraud traffic. We also discovered two new strategies that are leveraged by fraudsters to evade inspection. Our work provides new insights into illicit traffic monetization, raises its public awareness, and contributes to a better understanding and ultimate elimination of this threat.
A mapping method of image mosaic algorithm based on Reconfigurable Processing Element Array (RPEA) is proposed. This method can effectively improve the utilization rate of parallel resources. In the ...image mosaic algorithm, Harris corner detection is used to extract the feature points. Normalized Cross Correlation (NCC) algorithm is used to match these feature points and Random sample consensus (RANSAC) algorithm is used to eliminate the mismatching. Critical parts of the algorithms described in C language are found out, which are dynamically mapped onto the RPEA to run concurrently. The execution time on RPEA is reported to compare with execution time on general single-core processor. This paper focuses on the mapping methods based on loop unrolling and software pipeline loop and proposes an optimized method. The test results show that the speedups of mapping the mosaic algorithm on the reconfigurable processor with the proposed method versus using Intel Atom 230 reach more than 2.
With ultrasonic wave assistant mixing way, a well intercalated mixture of polyol/organic montmorilonite (OMMT) was made. Exfoliated and intercalated OMMT/prepolymer was prepared by polymerization of ...polyol/OMMT mixture with toluene di-isocyanate. The resultant prepolymer reacted with chain extender, and then polyurethane-urea(PUU)/OMMT nanocomposites were prepared. The PUU/OMMT nanocomposites were characterized by wide angle X-ray diffraction and differential scanning cal-orimetry. The results showed that the intercalated structure and exfoliated structure coexisted at lower content of OMMT. The PUU/OMMT nanocomposites had better intercalated and exfoliated effect at ultrasonic medium temperature of 50 deg C and showed the better mechanical properties. When the mass fraction of OMMT was 4%, the balanced mechanical properties were the best. The PUU/OMMT nanocomposites showed good mechanical properties when post cure thermal treatment condition was 100 deg C x 12 h.
The rare earth ion doped upconversion nanoparticles (UCNPs) synthesized by hydrophobic organic ligands possess poor solubility and low fluorescence quantum yield in aqueous media. To conquer this ...issue, NaYF
:Yb
/Tm
UCNPs, synthesized by a hydrothermal method, were coated with F127 and then assembled with chitosan to fabricate the chitosan/NaYF
:Yb
/Tm
composite beads (CS/NaYF
:Yb
/Tm
CBs) by Pickering emulsion system. The characterization results revealed that the as-synthesized NaYF
:Yb
/Tm
UCNPs with an average size of 20nm exhibited spherical morphology, high crystallinity and characteristic emission upconversion fluorescence with an overall blue color output. The NaYF
:Yb
/Tm
UCNPs were successfully conjugated on the surface of chitosan beads by the gelling of emulsion droplets. The resultant CS/NaYF
:Yb
/Tm
CBs showed good upconversion luminescent property, drug-loading capacity, release performance and excellent biocompatibility, exhibiting great potentials in targeted drug delivery and tissue engineering with potential tracking capability and lasting release performance.
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