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Influence of liquid layers on energy absorption during particle impact

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Particuology 2009年第4期7卷 245-259页

作者： Sergiy Antonyuk Stefan Heinrich niels Deen Hans Kuipers Hamburg University of Technology Institute of Solids Process Engineering and Particle Technology Denickestr. 15 21071 Hamburg Germany University of Twente Fundamentals of Chemical Reaction Engineering Faculty of Science and Technology PO Box 217 Enschede 7500 AE The Netherlands

The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic-plastic γ- Al2O3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity （1-300 mPa s）, In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained, A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.

关键词： Granule impact Restitution coefficient Energy dissipation Liquid layer Liquid bridge

A Review of Self-healing Metals: Fundamentals, Design Principles and Performance

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Acta Metallurgica Sinica(English Letters) 2020年第9期33卷 1167-1179页

作者： Shasha Zhang niels van Dijk Sybrand van der Zwaag College of Materials and Technology Nanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Materials Preparation and Protection for Harsh Environment(Nanjing University of Aeronautics and Astronautics) Ministry of Industry and Information TechnologyNanjing 211106China Fundamental Aspects of Materials and Energy Group Faculty of Applied SciencesDelft University of TechnologyMekelweg 152629 JB DelftThe Netherlands Novel Aerospace Materials Group Faculty of Aerospace EngineeringDelft University of TechnologyKluyverweg 12629 HS DelftThe Netherlands School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China

Self-healing metals possess the capability to autonomously repair structural damage during service. While self-healing concepts remain challenging to be realized in metals and metallic systems due to the small atomic volume of the mobile atoms, the slow diffusion unless at high temperatures and the strong isotropic metallic bonds, the scientific interest has increased sharply and promising progress is obtained. This article provides a comprehensive and updated review on the developments and limitations associated with the various modes of potentially healable damage induced in metals and alloys, i.e., stressinduced damage, irradiation-induced damage in bulk materials and contact damage in corrosion protective coatings. The spontaneous intrinsic healing mechanisms not requiring external assistance other than the material operating at the right temperature and an assisted healing mechanism with external intervention are reviewed. Promising strategies to achieve self-healing in metals are identified. Finally, we give some prospects for future research directions in self-healing metals.

关键词： Metal Self-healing Creep behavior Fatigue damage Irradiation Coating

Assimilation of Feng-Yun-3B Satellite Microwave Humidity Sounder Data over Land

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Advances in Atmospheric Sciences 2018年第3期35卷 268-275页

作者： Keyi CHEN niels BORMANN Stephen ENGLISH Jiang ZHU School of Atmospheric Sciences Chengdu University of Information & Technology Chengdu Sichuan 610225 China International Centre for Climate and Environment Sciences Institute of Atmospheric Physics China Beijing 100029 China European Centre for Medium-Range Weather Forecasts Reading RG2 9AX UK

The ECMWF has been assimilating Feng-Yun-3B （FY-3B） satellite microwave humidity sounder （MWHS） data over ocean in an operational forecasting system since 24 September 2014, It is more difficult, however, to assimilate microwave observations over land and sea ice than over the open ocean due to higher uncertainties in land surface temperature, surface emissivity and less effective cloud screening. We compare approaches in which the emissivity is retrieved dynamically from MWHS channel l [150 GHz （vertical polarization）] with the use of an evolving emissivity atlas from 89 GHz observations from the MWHS onboard NOAA and EUMETSAT satellites. The assimilation of the additional data over land improves the fit of short-range forecasts to other observations, notably ATMS （Advanced Technology Microwave Sounder） humidity channels, and the forecast impacts are mainly neutral to slightly positive over the first five days. The forecast impacts are better in boreal summer and the Southern Hemisphere. These results suggest that the techniques tested allow for effective assimilation of MWHS/FY-3B data over land.

关键词： data assimilation over land Chinese satellite FY-3B Microwave Humidity Sounder

Axially variable-length solid element of absolute nodal coordinate formulation

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Acta Mechanica Sinica 2019年第3期35卷 653-663页

作者： Jialiang Sun Qiang Tian Haiyan Hu niels L.Pedersen State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China MOE Key Laboratory of Dynamics and Control of Flight Vehicle School of Aerospace EngineeringBeijing Institute of TechnologyBeijing 100081China Department of Mechanical Engineering Solid MechanicsTechnical University of Denmark2800 Kongens LyngbyDenmark

An axially variable-length solid element with eight nodes is proposed by integrating the arbitrary Lagrangian-Eulerian (ALE) formulation and the absolute nodal coordinate formulation (ANCF). In addition to the nodal positions and slopes of eight nodes, two material coordinates in the axial direction are used as the generalized coordinates. As a consequence, the nodes in the ALE-ANCF are not associated with any specific material points and the axial length of the solid element can be varied over time. These two material coordinates give rise to a variable mass matrix and an additional inertial force vector. Computationally efficient formulae of the additional inertial forces and elastic forces, as well as their Jacobians, are also derived. The dynamic equation of a flexible multibody system (FMBS) with variable-length bodies is presented. The maximum and minimum lengths of the boundary elements of an FMBS have to be appropriately defined to ensure accuracy and non-singularity when solving the dynamic equation. Three numerical examples of static and dynamic problems are given to validate the variable-length solid elements of ALE-ANCF and show their capability.

关键词： Flexible multibody dynamics Arbitrary Lagrangian-Eulerian formulation Absolute nodal coordinate formulation Variable-length solid element

TLR3-independent activation of mast cells by cytomegalovirus contributes to control of pulmonary infection

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Cellular & Molecular Immunology 2017年第6期14卷 479-481页

作者： niels AW Lemmermann Matthias J Reddehase Institute for Virology and Research Center forImmunotherapy (FZI) University Medical Centerof the Johannes Gutenberg University MainzGermany.

Interstitial pneumonia is a life-threatening clinical manifestation of human cytomegalovirus （hCMV） infection. In particular, it can be deadly in patients with hematopoietic malignancies who undergo hematopoietic cell transplantation （HCT） in whom a ＇window of risk＇, which is defined by transient immunodeficiency, occurs between hematoablative therapeutic treatment and immunological reconsfi- tution.

关键词： activation cytomegalovirus pulmonary

Testicular biopsy： clinical practice and interpretation

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Asian Journal of Andrology 2012年第1期14卷 88-93,177页

作者： Gert R Dohle Saad Elzanaty niels J van Casteren Department of Urology Erasmus MC 3000 CA Rotterdam The Netherlands Department of General Surgery U rology Section Kristianstad Central Hospital Kristianstad SE 291 85 Sweden

Testicular biopsy was considered the cornerstone of male infertility diagnosis for many years in men with unexplained infertility and azoospermia. Recent guidelines for male infertility have limited the indications for a diagnostic testicular biopsy to the confirmation of obstructive azoospermia in men with normal size testes and normal reproductive hormones. Nowadays, testicular biopsies are mainly performed for sperm harvesting in men with non-obstructive azoospermia, to be used for intracytoplasmic sperm injection. Testicular biopsy is also performed in men with risk factors for testicular malignancy. In a subgroup of infertile men, there is an increased risk for carcinoma in situ of the testis, especially in men with a history of cryptorchidism and testicular malignancy and in men with testicular atrophy. Ultrasonographic abnormalities, such as testicular microlithiasis, inhomogeneous parenchyma and lesions of the testes, further increase the risk of carcinoma in situ （CIS） in these men. For an accurate histological classification, proper tissue handling, fixation, preparation of the specimen and evaluation are needed. A standardized approach to testicular biopsy is recommended. In addition, approaches to the detection of CIS of the testis testicular immunohistochemistry are mandatory. In this mini-review, we describe the current indications for testicular biopsies in the diagnosis and management of male infertility.

关键词： carcinoma in situ of the testis diagnosis male infertility testicular sperm extraction testicular biopsy testicular germ cell malignancies

Reduced energy consumption by using streamlined gating systems

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China Foundry 2008年第4期5卷 272-279页

作者： Sфren Skov-Hansen niels Skat Tiedje DISA Industries A/S Technical University of Denmark

In foundries a lot of effort is done to minimize energy consumption in the production to reduce costs and hence increase the competitiveness. At the same time the foundries must live up to the increased demands for high quality castings. Traditional gating systems are known for a straight tapered down runner, a well base and 90° bends in the runner system. Previous work has shown that the traditional way of designing gating systems creates high inconsistency in flow patterns during filling. In the streamlined gating systems there are no sharp changes in direction and a large effort is done to confine and control the flow of the molten metal during mould filling. The main objective in the work presented here is to use the principles of the streamlined gating systems to reduce the weight of the gating system relative to the traditional layouts. By reducing the weight of gating system and thereby improving yield, the amount of molten iron needed is also reduced, hence reducing the energy consumption for melting. Experiments in real production lines have proven that it is possible to achieve a reduction in the poured weight by using the streamlined gating systems. In a layout for casting of three valve housings in a vertically parted mould the weight of the gating system was reduced by 1.1 kg changing from the traditional layouts to the streamlined gating systems. This weight reduction corresponds in this case to a 20% weight reduction for the gating system. Using streamlined gating systems with fan gates to give a beneficial heat distribution in the castings may be an efficient tool to eliminate the need for heat treatment. In the experiments the change in gating system from the traditional layout to the streamlined layout removed the need for heat treatment. This obviously means a huge energy saving in the foundry. The energy consumption for heat treatment of iron has been found to be 0.489 kWh/ kg. The valve housing in the experiments weighs 3 kg so when the need

关键词： streamlined gating systems energy consumption mould filling weight layout

Interferometric measurement of injection nozzles using ultra-small fiber-optical probes

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Chinese Optics Letters 2011年第7期9卷 37-40页

作者： Tilo Pfeifer Robert Schmitt niels Knig Guilherme Francisco Mallmann Fraunhofer Institute for Production Technology Steinbachstr. 17 52074 Aachen Germany Laboratory for Machine Tools and Production Engineering of RWTH Aachen University

The measurement of boreholes with diameters smaller than 500 μm is a demanding task that cannot be performed using state-of-the-art production metrology. In this letter, a miniaturized fiber probe with a diameter of 80μm is presented. A probe is used for low-coherence interferometry to conduct highly precise measurements of form deviations of small boreholes. Measurements conducted in nozzles are also presented. The results prove the potential of the fiber-optical sensor for quality inspection of high-precision parts, such as injection nozzles, for common-rail diesel engines.

关键词： Charge coupled devices Fizeau interferometry Low coherence interferometry Metrology Michelson interferometers Optical fibers

The neurobiology of sensing respiratory gases for the control of animal behavior

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Frontiers in Biology 2012年第3期7卷 246-253页

作者： Dengke K. MA niels RINGSTAD Department of Biology McGovern Institute for Brain Research MIT Cambridge MA 02139 USA. Department of Cell Biology and the Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Slarball Institute of Biomolecular Medicine New York University Langone Medical Center New York NY 10016 USA

Aerobic metabolism is fundamental for almost all animal life. Cellular consumption of oxygen （O2） and production of carbon dioxide （CO2） signal metabolic states and physiologic stresses. These respiratory gases are also detected as environmental cues that can signal external food quality and the presence of prey, predators and mates. In both contexts, animal nervous systems are endowed with mechanisms for sensing O2/CO2 to trigger appropriate behaviors and maintain homeostasis of internal O2/CO2. Although different animal species show different behavioral responses to O2/CO2, some underlying molecular mechanisms and pathways that function in the detection of respiratory gases are fundamentally similar and evolutionarily conserved. Studies of Caenorhabditis elegans and Drosophila melanogaster have identified roles for cyclic nucleotide signaling and the hypoxia inducible factor （HIF） transcriptional pathway in mediating behavioral responses to respiratory gases. Understanding how simple invertebrate nervous systems detect respiratory gases to control behavior might reveal general principles common to nematodes, insects and vertebrates that function in the molecular sensing of respiratory gases and the neural control of animal behaviors.

关键词： oxygen carbon dioxide C. elegans Drosophila respiratory gases animal behaviors