18 research outputs found
AutoDiffusion: Training-Free Optimization of Time Steps and Architectures for Automated Diffusion Model Acceleration
Diffusion models are emerging expressive generative models, in which a large
number of time steps (inference steps) are required for a single image
generation. To accelerate such tedious process, reducing steps uniformly is
considered as an undisputed principle of diffusion models. We consider that
such a uniform assumption is not the optimal solution in practice; i.e., we can
find different optimal time steps for different models. Therefore, we propose
to search the optimal time steps sequence and compressed model architecture in
a unified framework to achieve effective image generation for diffusion models
without any further training. Specifically, we first design a unified search
space that consists of all possible time steps and various architectures. Then,
a two stage evolutionary algorithm is introduced to find the optimal solution
in the designed search space. To further accelerate the search process, we
employ FID score between generated and real samples to estimate the performance
of the sampled examples. As a result, the proposed method is (i).training-free,
obtaining the optimal time steps and model architecture without any training
process; (ii). orthogonal to most advanced diffusion samplers and can be
integrated to gain better sample quality. (iii). generalized, where the
searched time steps and architectures can be directly applied on different
diffusion models with the same guidance scale. Experimental results show that
our method achieves excellent performance by using only a few time steps, e.g.
17.86 FID score on ImageNet 64 64 with only four steps, compared to
138.66 with DDIM. The code is available at
https://github.com/lilijiangg/AutoDiffusion
Superconductivity in the cobalt-doped V3Si A15 intermetallic compound
The A15 structure of superconductors is a prototypical type-II superconductor
that has generated considerable interest since the early history of
superconducting materials. This paper discusses the superconducting properties
of previously unreported V3-xCoxSi alloys. It is found that the lattice
parameter decreases with increasing cobalt-doped content and leads to an
increased residual resistivity ratio (RRR) value of the V3-xCoxSi system.
Meanwhile, the superconducting transition temperature (Tc) cobalt-doped
content. Furthermore, the fitted data show that the increase of cobalt-doped
content also reduces the lower/upper critical fields of the V3-xCoxSi system.
Type-II superconductivity is demonstrated on all V3-xCoxSi samples. With higher
Co-doped content, V3-xCoxSi alloys may have superconducting and structural
phase transitions at low-temperature regions. As the electron/atom (e/a) ratio
increases, the Tc variation trend of V3Si is as pronounced as in crystalline
alloys and monotonically follows the trend observed for amorphous
superconductors.Comment: 20 pages, 7 figure
Superconductivity in the high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx with possible nontrivial band topology
Topological superconductors have drawn significant interest from the
scientific community due to the accompanying Majorana fermions. Here, we report
the discovery of electronic structure and superconductivity in high-entropy
ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx (x = 1 and 0.8) combined with experiments
and first-principles calculations. The Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx high-entropy
ceramics show bulk type-II superconductivity with Tc about 4.00 K (x = 1) and
2.65 K (x = 0.8), respectively. The specific heat jump is equal to 1.45 (x = 1)
and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS
superconductor in the weak coupling limit. The high-pressure resistance
measurements show that a robust superconductivity against high physical
pressure in Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, with a slight Tc variation of 0.3 K
within 82.5 GPa. Furthermore, the first-principles calculations indicate that
the Dirac-like point exists in the electronic band structures of
Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, which is potentially a topological superconductor.
The Dirac-like point is mainly contributed by the d orbitals of transition
metals M and the p orbitals of C. The high-entropy ceramics provide an
excellent platform for the fabrication of novel quantum devices, and our study
may spark significant future physics investigations in this intriguing
material.Comment: 28 pages, 7 figures,The manuscript with the same title will be
published by Advanced Scienc
Constraints on the Genesis of the Shuangwang Gold Deposit in Qinling Orogen, Central China: Evidence from In Situ Trace Element and Sulfur Isotope
The Shuangwang gold deposit, with more than 70 tons of Au, is located in the Fengxian-Taibai ore concentration area in the Qinling Orogen of central China, hosted in a Northwest-trending breccia belt. Fragments of the breccia body are cemented by ankerite, albite, quartz, calcite, and pyrite. Four metallogenic stages are identified in mineral paragenesis: quartz-albite, ankerite-pyrite-albite, pyrite-quartz-calcite, and fluorite-anhydrite. Pyrite, as the main gold-bearing mineral, was formed in the syn-ore and post-ore stages, which are analyzed for trace elements. The experimental results show that Au (0.02 to 11.68 ppm), As (198.45 to 5502.86 ppm), Ag (0.00 to 1.56 ppm), Co (0.02 to 1002.75 ppm), Ni (0.15 to 646.30 ppm), Cu (0.00 to 64.76 ppm), Sb (0.00 to 4.67 ppm), Zn (0.23 to 260.59 ppm), Pb (0.00 to 10.42 ppm), Se (0.00 to 386.24 ppm), and Bi (0.00 to 47.72 ppm) are enriched in syn-ore pyrite much more than in post-ore pyrite, especially arsenic. The high arsenic content and rapid crystallization of pyrite may be the main reasons for precipitation of gold. δ34SV-CDT values of pyrite formed in stage II (PyII) vary from 11.1 to 15.2‰ (mean = 12.9‰), while those for pyrite formed in stage III (PyIII) vary from 11.1 to 13.5‰ (mean = 12.0‰). In situ sulfur isotope analysis indicates that sulfur of the Shuangwang deposit comes from the wallrock, mixed with sulfur from magma
Study on fluid inclusions and stable isotopics of W–Mo ore deposits in the Ningshan–Zhen’an area, South Qinling, China
Abstract The study of the fluid inclusions of W–Mo deposits in the mineralization area of Ningshan–Zhen’an , Shaanxi Province, China shows that the gas–liquid two-phase inclusions are mainly present in W–Mo deposits, and the ore-forming fluid can be divided into four types: high-temperature type, middle–high-temperature type, middle-temperature type and low-temperature type. The formation depths of the W–Mo mineralization range from 4.2 to 8.4 km. The boiling and mixing of fluid may have been important mechanisms for the formation of W–Mo mineralization. The skarn-type mineralization is dominated by magmatic water, the quartz-vein-type mineralization includes both magmatic water and meteoric water, and the meteoric water is more involved in the quartz-fluorite-vein-type, beryl-quartz-vein-type and pegmatite-type mineralization. Magma is the main source of sulfur; that is, magma is the main source of mineralization. Combined with the metallogenic setting and geological characteristics of typical ore deposits, in the process of structural system transformation in South Qinling, the ore-forming magma fluid in the Late Indosinian–Yanshanian period was uplifted and emplaced along the NW–WNW direction and NE–NNE direction, and eventually, NW–WNW fault-controlled skarn-type W–Mo mineralization and quartz-vein-type W–Mo deposits accompanied by greisenization, albitization and potash feldspathization formed
Constraints on the Genesis of the Shuangwang Gold Deposit in Qinling Orogen, Central China: Evidence from In Situ Trace Element and Sulfur Isotope
The Shuangwang gold deposit, with more than 70 tons of Au, is located in the Fengxian-Taibai ore concentration area in the Qinling Orogen of central China, hosted in a Northwest-trending breccia belt. Fragments of the breccia body are cemented by ankerite, albite, quartz, calcite, and pyrite. Four metallogenic stages are identified in mineral paragenesis: quartz-albite, ankerite-pyrite-albite, pyrite-quartz-calcite, and fluorite-anhydrite. Pyrite, as the main gold-bearing mineral, was formed in the syn-ore and post-ore stages, which are analyzed for trace elements. The experimental results show that Au (0.02 to 11.68 ppm), As (198.45 to 5502.86 ppm), Ag (0.00 to 1.56 ppm), Co (0.02 to 1002.75 ppm), Ni (0.15 to 646.30 ppm), Cu (0.00 to 64.76 ppm), Sb (0.00 to 4.67 ppm), Zn (0.23 to 260.59 ppm), Pb (0.00 to 10.42 ppm), Se (0.00 to 386.24 ppm), and Bi (0.00 to 47.72 ppm) are enriched in syn-ore pyrite much more than in post-ore pyrite, especially arsenic. The high arsenic content and rapid crystallization of pyrite may be the main reasons for precipitation of gold. δ34SV-CDT values of pyrite formed in stage II (PyII) vary from 11.1 to 15.2‰ (mean = 12.9‰), while those for pyrite formed in stage III (PyIII) vary from 11.1 to 13.5‰ (mean = 12.0‰). In situ sulfur isotope analysis indicates that sulfur of the Shuangwang deposit comes from the wallrock, mixed with sulfur from magma