| 1. |
- Chen, Hui, et al.
(författare)
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A CORDIC-Based Architecture with Adjustable Precision and Flexible Scalability to Implement Sigmoid and Tanh Functions
- 2020
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Ingår i: IEEE International Symposium on Circuits and Systems, ISCAS 2020. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- In the artificial neural networks, tanh (hyperbolic tangent) and sigmoid functions are widely used as activation functions. Past methods to compute them may have shortcomings such as low precision or inflexible architecture that is difficult to expand, so we propose a CORDIC-based architecture to implement sigmoid and tanh functions, which has adjustable precision and flexible scalability. It just needs shift-add-or-subtract operations to compute high-accuracy results and is easy to expand the input range through scaling the negative iterations of CORDIC without changing the original architecture. We adopt the control variable method to explore the accuracy distribution through software simulation. A specific case (ARCH:(1, 15, 18), RMSE: 10(-6)) is designed and synthesized under the TSMC 40nm CMOS technology, the report shows that it has the area of 36512.78 mu m(2) and power of 12.35mW at the frequency of 1GHz. The maximum work frequency can reach 1.5GHz, which is better than the state-of-the-art methods.
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| 2. |
- Chen, Hui, et al.
(författare)
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An Efficient Hardware Architecture with Adjustable Precision and Extensible Range to Implement Sigmoid and Tanh Functions
- 2020
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Ingår i: Electronics. - : MDPI. - 2079-9292. ; 9:10
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Tidskriftsartikel (refereegranskat)abstract
- The efficient and precise hardware implementations of tanh and sigmoid functions play an important role in various neural network algorithms. Different applications have different requirements for accuracy. However, it is difficult for traditional methods to achieve adjustable precision. Therefore, we propose an efficient-hardware, adjustable-precision and high-speed architecture to implement them for the first time. Firstly, we present two methods to implement sigmoid and tanh functions. One is based on the rotation mode of hyperbolic CORDIC and the vector mode of linear CORDIC (called RHC-VLC), another is based on the carry-save method and the vector mode of linear CORDIC (called CSM-VLC). We validate the two methods by MATLAB and RTL implementations. Synthesized under the TSMC 40 nm CMOS technology, we find that a special case AR divide VR(3,0), based on RHC-VLC method, has the area of 4290.98 mu m2 and the power of 1.69 mW at the frequency of 1.5 GHz. However, under the same frequency, AR divide VC(3) (a special case based on CSM-VLC method) costs 3196.36 mu m2 area and 1.38 mW power. They are both superior to existing methods for implementing such an architecture with adjustable precision.
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| 3. |
- Daneshjou, Roxana, et al.
(författare)
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Working toward precision medicine : Predicting phenotypes from exomes in the Critical Assessment of Genome Interpretation (CAGI) challenges
- 2017
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 38:9, s. 1182-1192
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Tidskriftsartikel (refereegranskat)abstract
- Precision medicine aims to predict a patient's disease risk and best therapeutic options by using that individual's genetic sequencing data. The Critical Assessment of Genome Interpretation (CAGI) is a community experiment consisting of genotype-phenotype prediction challenges; participants build models, undergo assessment, and share key findings. For CAGI 4, three challenges involved using exome-sequencing data: Crohn's disease, bipolar disorder, and warfarin dosing. Previous CAGI challenges included prior versions of the Crohn's disease challenge. Here, we discuss the range of techniques used for phenotype prediction as well as the methods used for assessing predictive models. Additionally, we outline some of the difficulties associated with making predictions and evaluating them. The lessons learned from the exome challenges can be applied to both research and clinical efforts to improve phenotype prediction from genotype. In addition, these challenges serve as a vehicle for sharing clinical and research exome data in a secure manner with scientists who have a broad range of expertise, contributing to a collaborative effort to advance our understanding of genotype-phenotype relationships.
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| 4. |
- Kang, Chengjun, et al.
(författare)
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Growing single crystals of two-dimensional covalent organic frameworks enabled by intermediate tracing study
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Resolving single-crystal structures of two-dimensional covalent organic frameworks (2D COFs) is a great challenge, hindered in part by limited strategies for growing high-quality crystals. A better understanding of the growth mechanism facilitates development of methods to grow high-quality 2D COF single crystals. Here, we take a different perspective to explore the 2D COF growth process by tracing growth intermediates. We discover two different growth mechanisms, nucleation and self-healing, in which self-assembly and pre-arrangement of monomers and oligomers are important factors for obtaining highly crystalline 2D COFs. These findings enable us to grow micron-sized 2D single crystalline COF Py-1P. The crystal structure of Py-1P is successfully characterized by three-dimensional electron diffraction (3DED), which confirms that Py-1P does, in part, adopt the widely predicted AA stacking structure. In addition, we find the majority of Py-1P crystals (>90%) have a previously unknown structure, containing 6 stacking layers within one unit cell.
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| 5. |
- Yin, Yongguang, et al.
(författare)
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Possible alkylation of inorganic Hg(II) by photochemical processes in the environment
- 2012
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 88:1, s. 8-16
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Tidskriftsartikel (refereegranskat)abstract
- The methylation of inorganic Hg by anaerobic bacteria in aquatic environments is considered to be the major pathway for methylmercury (MeHg) production. However, recent research has suggested that abiotic or chemical methylation by humic substances and other low-molecular-weight organic compounds in natural environments is also possible. Here, the aqueous photo-transformation of Hg(2+) to organomercurials was investigated in the presence of ketones, aldehydes and low molecular weight organic acids under UV irradiation. MeHg and/or ethylmercury (EtHg) were identified as the main organomercurial products by multiple analytical techniques, including chromatography-atomic spectrometry and molecular mass spectrometry and further confirmed by stable isotope tracer experiments. The yield of organomercurials was markedly influenced by pH, NaCl concentration, alkylation donor concentration and the presence of chelating ligands in the aqueous solution. Electron paramagnetic resonance spectrometry demonstrated that the radical reaction was not the predominating alkylation pathway, although methyl radicals were detected in the photo-alkylation procedure. A mechanism based on intra-molecular alkyl transfer in the Hg(2+)-low-molecular-weight organic compound complex is proposed. The present work helps us better understand of MeHg and EtHg photo-generation in natural environments.
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