1,754 research outputs found
Kinematic functions for the 7 DOF robotics research arm
The Robotics Research Model K-1207 manipulator is a redundant 7R serial link arm with offsets at all joints. To uniquely determine joint angles for a given end-effector configuration, the redundancy is parameterized by a scalar variable which corresponds to the angle between the manipulator elbow plane and the vertical plane. The forward kinematic mappings from joint-space to end-effector configuration and elbow angle, and the augmented Jacobian matrix which gives end-effector and elbow angle rates as a function of joint rates, are also derived
VELOX – A Demonstration Facilility for Lunar Oxygen Extraction in a Laboratory Environment
The ultimate goal of a permanent human presence on the Moon is discussed intensively within the global lunar community. Obviously, such an effort poses stringent demands not only on the technology but also on logistics, especially considering the important aspects of masses and volume for materials and replenishments of consumables. On-site propellant production (i.e. liquid oxygen) is one of the main needs and would lead to more efficient return-to-Earth or further exploration missions. Additionally, the supply of breathable air and water for the survival of the crew on the lunar surface is also a major aspect. Thus, large effort is put into the development and research of technologies for in-situ resources utilization (ISRU) to drastically reduce the required supply from Earth and to increase the level of autonomy of a lunar outpost. The major resource on the Moon for such a purpose is regolith, which covers the first meters of the lunar surface and contains about 45% of mineralogically bounded Oxygen in terms of mass. By using adequate processing methods of this material, one could be able to extract valuable minerals and volatiles for further utilization. At DLR Bremen a compact and flexible lab experimenting facility has been developed, built and tested, which shall demonstrate the feasibility of the process by extracting oxygen out of lunar regolith, respectively soil simulants and certain minerals in the laboratory case. For this purpose, important boundary conditions have been investigated such as temperatures during the process, chemical reaction characteristics and material properties for the buildup of the facility, which shall be analyzed within this paper. Since it is one of the most elaborated chemical processes regarding ISRU and has comparably low temperature and energy constraints it has been primarily concentrated on the Hydrogen-reduction process which reduces the iron oxide component of Ilmenite (FeTiO3) within the lunar regolith. Based on the obtained results, a first line-out of a planned superior test set-up and infrastructure with pre- and post-processing units such as feeding and extraction is also presented, as well as an analysis of reaction products with common methods. This paper will present the first results of DLR efforts regarding these topics. Finally, important aspects of the future development of the processes and technologies are discussed with special consideration of lunar applicability and with respect to environmental conditions as well as mass and energy constraints
ANCHOR: logically-centralized security for Software-Defined Networks
While the centralization of SDN brought advantages such as a faster pace of
innovation, it also disrupted some of the natural defenses of traditional
architectures against different threats. The literature on SDN has mostly been
concerned with the functional side, despite some specific works concerning
non-functional properties like 'security' or 'dependability'. Though addressing
the latter in an ad-hoc, piecemeal way, may work, it will most likely lead to
efficiency and effectiveness problems. We claim that the enforcement of
non-functional properties as a pillar of SDN robustness calls for a systemic
approach. As a general concept, we propose ANCHOR, a subsystem architecture
that promotes the logical centralization of non-functional properties. To show
the effectiveness of the concept, we focus on 'security' in this paper: we
identify the current security gaps in SDNs and we populate the architecture
middleware with the appropriate security mechanisms, in a global and consistent
manner. Essential security mechanisms provided by anchor include reliable
entropy and resilient pseudo-random generators, and protocols for secure
registration and association of SDN devices. We claim and justify in the paper
that centralizing such mechanisms is key for their effectiveness, by allowing
us to: define and enforce global policies for those properties; reduce the
complexity of controllers and forwarding devices; ensure higher levels of
robustness for critical services; foster interoperability of the non-functional
property enforcement mechanisms; and promote the security and resilience of the
architecture itself. We discuss design and implementation aspects, and we prove
and evaluate our algorithms and mechanisms, including the formalisation of the
main protocols and the verification of their core security properties using the
Tamarin prover.Comment: 42 pages, 4 figures, 3 tables, 5 algorithms, 139 reference
Моделирование кинетики синтеза Фишера- Тропша на ультрадисперсном катализаторе
Large area pulsed laser deposition of alumina on stainless steel with Ar or Ar/O2 mixtures as processing gas in investigated using excimer laser radiation. The high area coveraging was achieved by a simultaneous movement of target and substrate in combination with the use of a certain power density distribution achieving a special angular distribution of the vapour/plasma plume. The chemical properties of the films were studied by X-ray photoelectron spectroscopy, and the morphology and uniformness by optical microscopy and ellipsometry
Constraining recent lead pollution sources in the North Pacific using ice core stable lead isotopes
Trends and sources of lead (Pb) aerosol pollution in the North Pacific rim of North America from 1850 to 2001 are investigated using a high-resolution (subannual to annual) ice core record recovered from Eclipse Icefield (3017 masl; St. Elias Mountains, Canada). Beginning in the early 1940s, increasing Pb concentration at Eclipse Icefield occurs coevally with anthropogenic Pb deposition in central Greenland, suggesting that North American Pb pollution may have been in part or wholly responsible in both regions. Isotopic ratios (208Pb/207Pb and 206Pb/207Pb) from 1970 to 2001 confirm that a portion of the Pb deposited at Eclipse Icefield is anthropogenic, and that it represents a variable mixture of East Asian (Chinese and Japanese) emissions transported eastward across the Pacific Ocean and a North American component resulting from transient meridional atmospheric flow. Based on comparison with source material Pb isotope ratios, Chinese and North American coal combustion have likely been the primary sources of Eclipse Icefield Pb over the 1970–2001 time period. The Eclipse Icefield Pb isotope composition also implies that the North Pacific mid-troposphere is not directly impacted by transpolar atmospheric flow from Europe. Annually averaged Pb concentrations in the Eclipse Icefield ice core record show no long-term trend during 1970–2001; however, increasing 208Pb/207Pb and decreasing 206Pb/207Pb ratios reflect the progressive East Asian industrialization and increase in Asian pollutant outflow. The post-1970 decrease in North American Pb emissions is likely necessary to explain the Eclipse Icefield Pb concentration time series. When compared with low (lichen) and high (Mt. Logan ice core) elevation Pb data, the Eclipse ice core record suggests a gradual increase in pollutant deposition and stronger trans-Pacific Asian contribution with rising elevation in the mountains of the North Pacific rim
Synthesis and physicochemical properties of spherical catalysts based on TiO2-SiO2/MxOy, where M - Co, Cr
Catalysts TiO2-SiO2 composition in the form of hollow spheres modified cobalt and chromium was obtained. Spatial structure of spherical samples after heat treatment was study by method of 3D microtomography. Status cations of transition elements and titanium was characterized by UV-Vis DRS. The catalysts were tested in the oxidation reaction of heptane
Characterization of the monocyte-specific esterase (MSE) gene
Carboxylic esterases are widely distributed in hematopoietic cells. Monocytes express the esterase isoenzyme (termed 'monocyte-specific esterase', MSE) that can be inhibited by NaF in the alpha-naphthyl acetate cytochemical staining. We examined the expression of MSE in normal cells and primary and cultured leukemia-lymphoma cells. The MSE protein was demonstrated by isoelectric focusing (IEF); MSE mRNA expression was investigated by Northern blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). The following samples were positive for MSE protein and Northern mRNA expression: 20/24 monocytic, 4/32 myeloid, and 1/20 erythroid-megakaryocytic leukemia cell lines, but none of the 112 lymphoid leukemia or lymphoma cell lines; of the normal purified cell populations only the monocytes were positive whereas, T, B cells, and granulocytes were negative; of primary acute (myelo) monocytic leukemia cells (CD14-positive, FAB M4/M5 morphology) 14/20 were Northern mRNA and 11/14 IEF protein positive. RT-PCR revealed MSE expression in 29/49 Northern-negative lymphoid leukemia-lymphoma cell lines. The RT-PCR signals in monocytic cell lines were on average 50-fold stronger than the mostly weak trace expression in lymphoid specimens. On treatment with various biomodulators, only all-trans retinoic acid significantly upregulated MSE message and protein levels but could not induce new MSE expression in several leukemia cell lines; lipopolysaccharide and interferon-gamma increased MSE expression in normal monocytes. Analysis of DNA methylation with sensitive restriction enzymes showed no apparent regulation of gene expression by differential methylation; the MSE gene is evolutionarily conserved among mammalian species; the half-life of the human MSE transcripts was about 5-6 h. The extent of MSE expression varied greatly among different monocytic leukemia samples. However, the MSE overexpression in a significant number of specimens was not associated with gene amplification, gross structural rearrangements or point mutations within the cDNA region. Taken together, the results suggest that MSE expression is not absolutely specific for, but strongly associated with cells of the monocytic lineage; MSE is either not expressed at all or expressed at much lower levels in cells from other lineages. The biological significance, if any, of rare MSE messages in lymphoid cells detectable only by the hypersensitive RT-PCR remains unclear. Further studies on the regulation of this gene and on the physiological function of the enzyme will no doubt be informative with respect to its striking overexpression in some malignant cells and to a possible role in the pathobiology of monocytic leukemias
Complete nucleotide sequence and structural organization of pPB1, a small Lactobacillus plantarum cryptic plasmid that originated by modular exchange
A small cryptic plasmid designated pPB1 was isolated from Lactobacillus plantarum BIFI-38 and its complete 2899 bp
nucleotide sequence was determined. Sequence analysis revealed four putative open reading frames. Based on sequence
analysis two modules could be identified. First, the replication module consisted of a sequence coding for a replication
protein (RepB) and its corresponding target site, and two putative repressor proteins (RepA and RepC). Sequence analysis
indicated the possible synthesis of an antisense RNA that might regulate RepB production. A putative laggingstrand
initiation site was also found, suggesting that pPB1 replicates via a rolling circle mechanism. The second module
of pPB1 consisted of a sequence coding for a putative mobilization protein and its corresponding oriT site. Since the
nucleotide sequence of the replication module showed 94.5% identity to the similar region on the Leuconostoc lactis plasmid
pCI411, and the nucleotide sequence of the mobilization module had 97.5% identity to L. plantarum plasmid pLB4,
it is concluded that pPB1 originated by modular exchange between two such plasmids by homologous recombination.
Putative recombination sites where crossover might have taken place were also identifiedThis work was supported by Grant 07G/0035/2003 from the Comunidad de Madrid and
RM03-002 from the Instituto Nacional de Investigación y Tecnologı´a Agraria y Alimentaria
(INIA). We thank R. Gonza´lez and A.V. Carrascosa for their advice and critical reading of the
manuscript. B. de las Rivas was a recipient of a postdoctoral fellowship and A. Marcobal of a predoctoral fellowship both from the Comunidad de Madrid.Peer reviewe
Моделирование реакционно-ректификационной колонны синтеза этил-трет-бутилового эфира (ЭТБЭ)
Die vorliegende fünfteilige Artikelserie beschreibt Konzepte und Anwendungen der Lasertechnik in der Fertigung. Aufbauend auf einer Erhebung des Anwendungspotentials werden Aspekte der Anlagen- und Prozessplanung sowie zugeschnittene Fertigungskonzepte diskutiert. Hieraus wird eine integrierte Vorgehensweise zur Einbindung in Systeme für die Qualitätssicherung und der Arbeitssicherheit abgeleitet
Masked hypertension in type 2 diabetes: never take normotension for granted and always assess out-of-office blood pressure.
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