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排序方式: 共有950条查询结果,搜索用时 15 毫秒
31.
Won-Ik ChoSuck-Joo Na Claus ThomyFrank Vollertsen 《Journal of Materials Processing Technology》2012,212(1):262-275
A single-phase problem is solved rather than a multiphase problem for numerical simplicity: and the solution is based on the assumption that the region of gas or plasma can be treated as a void because solid or liquid steel has a greater density level than gas or plasma. The volume-of-fluid method, which can calculate the free surface shape of the keyhole, is used in conjunction with a ray-tracing algorithm to estimate the multiple reflections. Fresnel's reflection model is simplified by the Hagen-Rubens relation for handling a laser beam interaction with materials. Factors considered in the simulations include buoyancy force, Marangoni force and recoil pressure; furthermore, pore generation is simulated by means of an adiabatic bubble model, which can also lead to the phenomenon of a keyhole collapse. Models of the shear stress on the keyhole surface and of the heat transfer to the molten pool via a plasma plume are introduced in simulations of the weld pool dynamics. Analysis of the temperature profile characteristics of the weld bead and molten pool flow in the molten pool is based on the results of the numerical simulations. The simulation results are used to estimate the weld fusion zone shape; and the results of the simulated fusion zone formation are compared with the results of the experimental fusion zone formation and found to be in good agreement. The effects of laser beam profile (Gaussian vs. measured), vapor shear stress, vapor heat source and sulfur content on the molten pool behavior and fusion zone shape are analyzed. 相似文献
32.
Claus Knapheide 《International journal of human-computer interaction》2013,29(3-4):415-430
The quality of a software product is determined by its usability; the quality of technical documentation is determined by its comprehensibility. Usability conceptualizes the person using a software product to perform a task; comprehensibility deals with the reader of operating instructions-although they are generally one and the same person. However, only rarely are the software and technical documentation part of an integrated design. This is all the more surprising in that, on the technical level, the boundary between software and user information is becoming increasingly blurred; one need only think of the hypertext links between software and help systems, or of electronic versions of operating instructions. We make the case for considering user, software, and operating instructions as a single system oriented toward performing a task; the operating instructions therefore are regarded as a subsidiary subsystem of a structure to be described. This is done from a linguistic perspective, with reference to the central category of knowledge available to the user or contained in the software and in the operating instructions and that we approach via an empirical analysis of authentic material (operating instructions as primary data, statements of end users concerning operating instructions). Taking the example of creating software and operating instructions for a computer tomograph, we show how the relevant knowledge elements contribute to the accomplishment of an operating task and discuss the resultant requirements concerning the contents of software and operating instructions, particularly for handling fault and problem situations. 相似文献
33.
Claus Schreiner Sabine Scharf Volkmar Stenzel Albert Rössler 《Journal of Coatings Technology and Research》2017,14(4):809-816
The use of microcapsules containing healing agents, which can serve as source of self-healing for coatings, was investigated. The appropriate self-repairing coatings are designed to be used for heavy-duty corrosion protection or for the protection of moisture-sensitive substrates like wood. Microcapsules based on thermoset resins (urea–formaldehyde and melamine–formaldehyde) which contained components of different chemical natures (resins or inhibitors) were fabricated using emulsion techniques. The subsequent characterization included optical, fluorescence, and electron microscopy as well as adapted microindentation techniques to determine capsule break forces. Different model coatings were formulated making use of varying amounts of healing agent-charged microcapsules. The coated samples were then injured under controlled conditions (by Erichsen cupping in the case of steel, by simulated hail in the case of wood) and then subjected to salt spray testing (natural and accelerated), weathering, or even real-life exposure, always in comparison with a blank. The results obtained demonstrate the superiority of microcapsule-based self-healing coatings compared to classical protection formulations, and appropriate coating systems have in the meantime been successfully brought to the market. 相似文献
34.
Claus Bech-Danielsen 《The Journal of Architecture》2013,18(3):321-336
For many years, the environmental effort in Scandinavian residential building has taken the form of construction-related improvements and technical renewal. For example, the standard in insulation has been improved and, to an increasing extent, the supply of energy is being covered by alternative energy sources. However, 'green' accounts reveal that the building and its environmental standards are not the most important factors in the residence's consumption of resources. The most crucial factors are the residents and their behaviour. Resource consumption in the residence is thus entirely dependent on the residents' habits, on their behaviour and life style. In the final analysis, it is our culture that becomes the topic for debate, as a direct consequence of environmental problems. Question marks are being placed alongside the consumption society and concomitantly alongside the entire occidental culture. The upshot of this is that, sooner or later, environmental problems will eventually come to influence the architectonic design, which reflects the culture and the societal values from which such modelling originates. The environmentally oriented work can, in this way, be discussed in an architectonic context. This is the aim of the present paper: to describe urban ecological endeavours in a wide cultural perspective. This ought to make it possible to look at this work in conjunction with current tendencies in contemporary design. In order to understand the present day, however, it is necessary to start at some distance from it - with the Renaissance. 相似文献
35.
36.
Behavior of internal stakeholders in project portfolio management and its impact on success 总被引:1,自引:0,他引:1
Stakeholder behavior and stakeholder management are key success factors within project portfolio management (PPM). This empirical study of 197 project portfolios investigates the effect of the intensity of engagement (IoE) of portfolio-internal stakeholders on project portfolio success. We show that the effect of stakeholders is phase-specific and that role clarity as a measure of PPM maturity affects the nature of the relationship between the IoE of stakeholders and portfolio success. The effects of the IoE of senior managers on success are not clearly positive with regard to strategic portfolio structuring and are even negative in operative portfolio steering in established PPM systems. In immature PPM systems, line managers tend to take advantage of their position in resource management. Surprisingly, the influence of portfolio managers in portfolio steering is insignificant. Altogether, this paper shows the diverse effect of the IoE of stakeholders on portfolio success. This study enriches project research by applying stakeholder theory to the project portfolio context and offers practical guidance for further professionalizing PPM. 相似文献
37.
After hydrothermal pretreatment and enzymatic hydrolysis of wheat straw, a slurry rich in lignin but with a high content of inorganic substances, especially silica, and residual carbohydrates is produced. This slurry was used to develop an ethanol organosolv separation method to produce silica-free lignin fractions. The addition of para toluene sulphonic acid (PTSA) and the use of two alternative long-chain alcohols, oleyl alcohol or nonylphenol, were tested. In every reaction, two lignin fractions were produced and their molecular size and elemental composition were characterized. The yield of each fraction and the change in MWD were studied as a function of temperature and solid to liquid ratio. At 100, 150, and 200°C and with the use of PTSA, high-purity lignin fractions were obtained. After lignin fractionation with nonylphenol, a liquid silica-free product with high lignin content was obtained in yields between 17 and 72%. 相似文献
38.
Claas Spille Anastasios Lyberis Maria Isabelle Maiwald Dirk Herzog Marko Hoffmann Claus Emmelmann Michael Schlüter 《化学工程与技术》2020,43(10):2053-2061
In chemical process engineering, fast gas-liquid reactions often suffer from an inefficient distribution of gas and therefore mixing and mass transfer performance. This study deals with the possibility of influencing the local gas holdup and bubble size distribution in a gas-liquid process using additively manufactured lattice structures (AMLS). The used measuring technique to study bubble size, velocity, and the local gas holdup is a photo-optical needle probe. By using AMLS, a significant radial homogenization of the local gas holdup and the mean bubble size is achieved. Furthermore, it can be demonstrated that the bubble size can be tailored by the geometry of the inserted structure. It is illustrated that the mean bubble velocities are lowered within the lattice resulting in a higher residence time of the dispersed phase with an impact on the mass transfer performance within the AMLS. 相似文献
39.
Anja Wessely Theresa Steeb Ulrike Leiter Claus Garbe Carola Berking Markus Vincent Heppt 《International journal of molecular sciences》2020,21(23)
Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer that predominantly arises in chronically sun-damaged skin. Immunosuppression, genetic disorders such as xeroderma pigmentosum (XP), exposure to certain drugs and environmental noxae have been identified as major risk factors. Surgical removal of cSCC is the therapy of choice and mostly curative in early stages. However, a minority of patients develop locally advanced tumors or distant metastases that are still challenging to treat. Immune checkpoint blockade (ICB) targeting CTLA-4, PD-L1 and PD-1 has tremendously changed the field of oncological therapy and especially the treatment of skin cancers as tumors with a high mutational burden. In this review, we focus on the differences between cSCC and cutaneous melanoma (CM) and their implications on therapy, summarize the current evidence on ICB for the treatment of advanced cSCC and discuss the chances and pitfalls of this therapy option for this cancer entity. Furthermore, we focus on special subgroups of interest such as organ transplant recipients, patients with hematologic malignancies, XP and field cancerization. 相似文献
40.
Metabolic profile biomarkers of metal contamination in a sentinel terrestrial species are applicable across multiple sites 总被引:3,自引:0,他引:3
Bundy JG Keun HC Sidhu JK Spurgeon DJ Svendsen C Kille P Morgan AJ 《Environmental science & technology》2007,41(12):4458-4464
In this study, we addressed the question of whether an omic approach could genuinely be useful for biomarker profile analysis across different field sites with different physicochemical characteristics. We collected earthworms (Lumbricus rubellus) from seven sites with very different levels of metal contamination and prevailing soil type and analyzed tissue extracts by 1H nuclear magnetic resonance spectroscopy. Pattern recognition analysis of the data showed that both site- and contaminant-specific effects on the metabolic profiles could be discerned. Zinc was identified as the probable major contaminant causing a metabolic change in the earthworms. Individual sites could be resolved on the basis of NMR spectral profiles by principal component analysis; these site differences may also have been caused by additional abiotic factors such as soil pH. Despite an inevitable degree of confounding between site and contaminant concentrations, it was possible to identify metabolites which were correlated with zinc across all different sites. This study therefore acts as a proof of principle for the use of NMR-based metabolic profiling as a diagnostic tool for ecotoxicological research in polluted field soils. 相似文献