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1.
以成分为Nd28.5Fe余B1.0Ga0.3Nb0.3 (%)的钕铁硼合金锭作为原料,采用 HDDR 工艺制备各向异性钕铁硼磁粉。重点研究了HDDR工艺过程中钙添加量对磁粉氧含量和磁性能的影响。结果表明,在不改变原有HDDR工艺参数的基础上,添加少量金属钙即可显著降低磁粉的氧化程度,大幅提高磁粉的磁性能。钙添加量小于0.1%时,由于磁粉的氧含量仍然较高而导致内禀矫顽力Hcj和最大磁能积(BH)max低劣;钙添加量大于0.3%时,由于磁粉中残留的非磁性相过多以及颗粒团聚加重会导致磁性能指标全面下降;钙添加量为0.1 ~ 0.3%是适宜的,在钙添加量为0.2%时,磁粉的综合磁性能最佳,其Br为1.37 T、Hcj为1 296 kA/m、(BH)max为340 kJ/m3。  相似文献   
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This paper reports a deep‐ultraviolet LED (deep‐UV‐LED) package based on silicon MEMS process technology (Si‐PKG). The package consists of a cavity formed by silicon crystalline anisotropic etching, through‐silicon vias (TSVs) filled with electroplated Cu, bonding metals made of electroplated Ni/AuSn and a quartz lid for hermetic sealing. A deep‐UV LED die is directly mounted in the Si‐PKG by AuSn eutectic bonding without a submount. It has advantages in terms of size, heat dissipation, light utilization efficiency, productivity and cost over conventional AlN ceramic packages. We confirmed a light output of 30 mW and effective reflection on Si (111) cavity slopes in the Si‐PKG. Based on simulation, further improvement of the optical output is expected by optimizing DUV‐LED die mount condition.  相似文献   
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In the digestion of amino acids, carbohydrates, and lipids, as well as protein synthesis from the consumed food, the liver has many diverse responsibilities and functions that are to be performed. Liver disease may impact the hormonal and nutritional balance in the human body. The earlier diagnosis of such critical conditions may help to treat the patient effectively. A computationally efficient AW-HARIS algorithm is used in this paper to perform automated segmentation of CT scan images to identify abnormalities in the human liver. The proposed approach can recognize the abnormalities with better accuracy without training, unlike in supervisory procedures requiring considerable computational efforts for training. In the earlier stages, the CT images are pre-processed through an Adaptive Multiscale Data Condensation Kernel to normalize the underlying noise and enhance the image’s contrast for better segmentation. Then, the preliminary phase’s outcome is being fed as the input for the Anisotropic Weighted–-Heuristic Algorithm for Real-time Image Segmentation algorithm that uses texture-related information, which has resulted in precise outcome with acceptable computational latency when compared to that of its counterparts. It is observed that the proposed approach has outperformed in the majority of the cases with an accuracy of 78%. The smart diagnosis approach would help the medical staff accurately predict the abnormality and disease progression in earlier ailment stages.  相似文献   
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由于普通土体本构模型不能反应土体初始应力状态及开挖应力路径,在进行有限元计算时得到的特征点位移也会与工程实际有偏差。选用可以对开挖前边坡土体的初始K0应力状态以及开挖应力路径进行合理描述的修正关口太田模型,对开挖边坡进行有限元计算。根据位移突变判据,采用单因素敏感性分析,对54例简单边坡进行有限元计算,得出与边坡位移量呈正、负关联的基本参量。利用灰色关联分析方法,首次同时考虑了土坡几何参数、物理参数、本构模型等基本参数,将边坡的变形量进行归一化处理,构建以变形量为基础的归一化失稳判据Fu及警戒位移值U′1,从而可以通过实时监控边坡位移及时给出滑坡体的安全性评价。  相似文献   
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Cellulose nanofibrils are attractive as building blocks for advanced photonic, optoelectronic, microfluidic, and bio‐based devices ranging from transistors and solar cells to fluidic and biocompatible injectable devices. For the first time, an ultrastrong and ultratough cellulose film, which is composed of densely packed bacterial cellulose (BC) nanofibrils with hierarchical fibril alignments, is successfully demonstrated. The molecular level alignment stems from the intrinsic parallel orientation of crystalline cellulose molecules produced by Acetobacter xylinum. These aligned long‐chain cellulose molecules form subfibrils with a diameter of 2–4 nm, which are further aligned to form nanofibril bundles. The BC film yields a record‐high tensile strength (≈1.0 GPa) and toughness (≈25 MJ m?3). Being ultrastrong and ultratough, yet the BC film is also highly flexible and can be folded into desirable shapes. The BC film exhibits a controllable manner of alignment and is highly transparent with modulated optical properties, paving the way to enabling new functionalities in mechanical, electrical, fluidic, photonics, and biocompatible applications.  相似文献   
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The high-performance unidirectional manipulation of microdroplets is crucial for many vital applications including water collection and bioanalysis. Among several actuation methods (e.g., electric, magnetic, light, and thermal actuation), mechanical vibration is pollution-free and biocompatible. However, it suffers from limited droplet movement mode, small volume range (VMax/VMin < 3), and low transport velocity (≤11.5 mm s−1) because the droplet motion is a sliding state caused by the vertical vibration on the asymmetric hydrophobic microstructures. Here, an alternative strategy is proposed—horizontal vibration for multimode (rolling, bouncing/reverse bouncing, converging/diffusing, climbing, 90o turning, and sequential transport), large-volume-range (VMax/VMin ≈ 100), and high-speed (≈22.86 mm s−1) unidirectional microdroplet manipulation, which is ascribed to the rolling state on superhydrophobic slant microwall arrays (SMWAs) fabricated by the one-step femtosecond laser oblique ablation. The unidirectional transport mechanism relies on the variance of viscous resistance induced by the difference of contact area between the microdroplet and the slant microwalls. Furthermore, a circular, curved, and “L”-shaped SMWA is designed and fabricated for droplet motion with particular paths. Finally, sequential transport of large-volume-range droplets and chemical mixing microreaction of water-based droplets are demonstrated on the SMWA, which demonstrates the great potential in the field of microdroplet manipulation.  相似文献   
9.
Anisotropic diffusion is important to many different types of common materials and media. Based on structured Cartesian meshes, we develop a three-dimensional (3D) nonhomogeneous immersed finite-element (IFE) method for the interface problem of anisotropic diffusion, which is characterized by an anisotropic elliptic equation with discontinuous tensor coefficient and nonhomogeneous flux jump. We first construct the 3D linear IFE space for the anisotropic nonhomogeneous jump conditions. Then we present the IFE Galerkin method for the anisotropic elliptic equation. Since this method can efficiently solve interface problems on structured Cartesian meshes, it provides a promising tool to solve the physical models with complex geometries of different materials, hence can serve as an efficient field solver in a simulation on Cartesian meshes for related problems, such as the particle-in-cell simulation. Numerical examples are provided to demonstrate the features of the proposed method.  相似文献   
10.
Red sweet peppers held in cold storage were periodically sampled at 1-week intervals over a 3-weeks period using three-point bending, puncture, cutting, and Volodkevich (coupled with acoustic emission) tests, confocal laser scanning microscopy (CLSM) and other physicochemical measurements. At each sampling, tissue specimens were soaked in mannitol solutions (0.0–0.9M) and puncture test, dimension changes and CLSM were used to identify degrees of turgidity present in osmotically manipulated pepper tissue. Pepper texture became crumbly with increased storage time due to softening and wilting processes. The Young's modulus, derived from the bending test using the single-edge notched bend geometry without notches decreased progressively during cold storage and resulted as the best mechanical parameter for measuring the loss of whole-tissue stiffness by both decreased cell wall stiffness and turgor pressure. Osmotic adjustment indicated that the pepper structure is extremely anisotropic, with the specimen's “average” relative thickness (RT) being the dimension change more affected. Incipient plasmolysis was evident in the highest mannitol concentration (0.9M), therefore, the turgor pressure of nonsoaked tissue could not be inferred. However, significant correlations were found between RT and puncture parameters such as initial slope, initial and final distances, and the number of flesh and skin force peaks, which depended on the dilation or shrinkage caused by the osmotic adjustment. During storage, soaked tissues had lower crunchy texture than nonsoaked, reflecting that cell wall stiffness plays a more significant role in determining pepper crunchiness than cell turgor pressure.  相似文献   
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