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排序方式: 共有1100条查询结果,搜索用时 15 毫秒
991.
Thibaud Bucquet Timo Hoja Steffen Waldeck Sören Sander Udo Fritsching 《International Journal of Material Forming》2018,11(1):1-10
The metal working industry is continuously seeking for process chain improvements, involving, for instance, forging techniques, principally aiming at reducing the process costs, and improving the mechanical properties of the automotive parts. Promising new forging materials (e.g., high-strength ductile bainite ‘HDB’ steel alloy) offer new fields for process combinations, such as cold and warm forging, machining, and controlled in-process quenching. In the present paper, the design, implementation, and validation of a controlled gas and spray-quenching unit within an automated forging unit is described. A two-fluid, flat-spray nozzle is characterized for spray-quenching purposes (droplet size, mass flux, and heat-transfer distributions). Experiments are utilized to validate transient heat transfer simulations in order to extend the numerical model for quenching scenarios of complex specimen geometries (a stepped shaft and a common rail), involving various steel grades from the forging heat. The scenarios are validated using the automated forging/quenching unit, through hardness and microscopy tests. The high potential of the combination of forging and heat treatment (gas and spray-quenching) into a single manufacturing unit to ensure the homogeneous bainitizing of forged components is demonstrated in the present paper. 相似文献
992.
Steven D. Lacey Dylan J. Kirsch Yiju Li Joseph T. Morgenstern Brady C. Zarket Yonggang Yao Jiaqi Dai Laurence Q. Garcia Boyang Liu Tingting Gao Shaomao Xu Srinivasa R. Raghavan John W. Connell Yi Lin Liangbing Hu 《Advanced materials (Deerfield Beach, Fla.)》2018,30(12)
A highly porous 2D nanomaterial, holey graphene oxide (hGO), is synthesized directly from holey graphene powder and employed to create an aqueous 3D printable ink without the use of additives or binders. Stable dispersions of hydrophilic hGO sheets in water (≈100 mg mL?1) can be readily achieved. The shear‐thinning behavior of the aqueous hGO ink enables extrusion‐based printing of fine filaments into complex 3D architectures, such as stacked mesh structures, on arbitrary substrates. The freestanding 3D printed hGO meshes exhibit trimodal porosity: nanoscale (4–25 nm through‐holes on hGO sheets), microscale (tens of micrometer‐sized pores introduced by lyophilization), and macroscale (<500 µm square pores of the mesh design), which are advantageous for high‐performance energy storage devices that rely on interfacial reactions to promote full active‐site utilization. To elucidate the benefit of (nano)porosity and structurally conscious designs, the additive‐free architectures are demonstrated as the first 3D printed lithium–oxygen (Li–O2) cathodes and characterized alongside 3D printed GO‐based materials without nanoporosity as well as nanoporous 2D vacuum filtrated films. The results indicate the synergistic effect between 2D nanomaterials, hierarchical porosity, and overall structural design, as well as the promise of a freeform generation of high‐energy‐density battery systems. 相似文献
993.
Hartmut Luttermann Prof. Dr. Bernd Freisleben Prof. Dr. Manfred Grauer Prof. Dr. Udo Kelter Dr. Thomas Kamphusmann Dr. Udo Merten Guido Rößling Thomas Unger Jürgen Waldhans 《WIRTSCHAFTSINFORMATIK》2002,44(1):41-51
This paper presents Mediana, a computer-based, integrated workbench for the management and analysis of media data supporting media researchers. Its main components are the recording and management of multimedia data (i.e. image, video and text data) in a database system, semi-automatical analysis tools for images and videos, and a graphical user interface (GUI) integrating all tools and components applied in media research. 相似文献
994.
There are well known mechanistic similarities in human physiology between adaptations for endurance performance and hypoxia tolerance. By using background principles arising from recent studies of the evolution of the diving response in marine mammals, here we analyze human responses to hypobaric hypoxia based on studies with several different low and high altitude human lineages. As in the evolution of the diving response in pinnipeds, we found "conservative" and "adaptable" physiological characters involved in human responses to hypoxia. Because the analysis concerns traits within a single species, conservative characters dominate the picture (they define basic human physiology and largely are independent of environmental parameters). Most notably, we also found evidence for adaptable characters forming the foundations for a fairly unique physiological phenotype-a low capacity version favored under hypobaric hypoxia and a high capacity one favored for endurance performance. Because current evidence implies that the human species arose under conditions that were getting colder, drier, and higher (situations in which these traits would have been advantageous), we hypothesize that this physiology is our "ancestral" condition. 相似文献
995.
Fatemeh Azadi Seyed Hassan Jafari Hossein Ali Khonakdar Mohammad Arjmand Udo Wagenknecht Volker Altstädt 《大分子材料与工程》2021,306(2):2000576
In this study, shape memory is thermally induced in a series of graphene oxide (GO) filled poly(lactic acid)/thermoplastic polyurethane (PLA/TPU) blends, prepared via melt mixing process, and their shape recovery and shape fixity are measured, and the results are correlated with morphology, dynamic mechanical properties, crystallinity and creep recovery behavior. Morphological analysis by scanning and transmission electron microscopy reveals that the blends are immiscible, and GO platelets are mainly localized in the TPU phase of the blends, which lead to smaller and more elongated TPU droplets with improved interfacial adhesion being responsible for the improved shape recovery performance compared to the unfilled blend. A systematic enhancement found in storage and Young's modulus, tensile strength, creep resistance and creep recovery, and cold crystallinity as a result of GO inclusion are in agreement with the improved shape recovery, shape fixity and overall shape memory performance of the filled systems. The developed PLA/TPU/GO nanocomposites with highly improved mechanical properties can be utilized as a new class of environmentally friendly shape memory materials for a broad range of applications. 相似文献
996.
Affordances in design can be understood as the action possibilities of a user interacting with a designed object. In this paper, we develop the notion of ??representational affordances?? to denote affordances provided by design representations to the designer as the ??user?? of these representations. A major characteristic of representational affordances is that they do not have to rely on existing representations but can drive the construction of new representations that may then afford different design actions. We describe representational affordances ontologically, proposing three affordance types: reflexive, reactive and reflective. We illustrate them with examples of analogy making and optimization. 相似文献
997.
998.
Ein Naturstoff macht Karriere 总被引:1,自引:1,他引:0
Dr. Udo Kienle 《Journal für Verbraucherschutz und Lebensmittelsicherheit》2010,5(2):199-203
999.
1000.
Ulrike Breiner Udo Krappe Thomas Jakob Volker Abetz Reimund Stadler 《Polymer Bulletin》1998,40(2-3):219-226
A novel morphology for linear ABC-triblock copolymers is presented, where A forms spherical microdomains, covered by small
B-spheres and C forming the matrix. This morphology is characterized by transmission electron microscopy and small angle X-ray
scattering. The morphology forms both in solution cast and melt extruded samples. Qualitative arguments to understand the
thermodynamic stability of this morphology are given.
Received: 2 December 1997/Accepted: 3 December 1997 相似文献