ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Artikel  (18.127)
  • Springer  (18.127)
  • 1990-1994  (18.127)
  • 1935-1939
  • 1990  (18.127)
  • Physik  (13.914)
  • Werkstoffwissenschaften, Fertigungsverfahren, Fertigung  (1.863)
  • Informatik  (1.509)
  • Geographie  (885)
  • Technik allgemein  (697)
Sammlung
  • Artikel  (18.127)
Erscheinungszeitraum
  • 1990-1994  (18.127)
  • 1935-1939
Jahr
Zeitschrift
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 131-138 
    ISSN: 1476-5535
    Schlagwort(e): Capsule ; Aggregation ; Disaggregation ; Polyglucan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Conditions of growth are described which lead to the formation of a dense capsule aboutCellulomonas flavigena and provide data which suggest that, although accumulated as an extracellular structure, it may function as an energy reserve. The capsule is formed when the bacteria are cultured in a minimal medium containing an excess of one of several carbohydrates. The bacterial cells which are encapsulated are also densely aggregated. The capsule is not formed and the cells are not aggregated when the bacteria are cultured in complex growth media. The transfer of aggregated cells to a medium devoid of carbon and energy source results in disappearance of the capsule and disaggregation of the cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 167-182 
    ISSN: 1476-5535
    Schlagwort(e): Bacteriophage ; Integration ; Deletions ; Cohesive ends ; Gentamicin ; Transfection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A temperate actinophage was isolated from soil using the gentamicin-producing microorganism,Micromonospora purpurea ATCC 15835 as host. The characterization of the phage represents the initial step in its development as a cloning vector. The phage isolated, MPphiWR-1, formed red- to purple-pigmented turbid plaques. Cells isolated from these plaques were resistant to superinfection with lytic mutants of MPphiWR-1. Southern blots of genomic DNA from a resistant culture showed that MPphiWR-1 integrated into the host genome. The phage was UV- or Mitomycin C-inducible. The integration, resistance to superinfection and inducibility indicated a lysogenic relationship with the host. Using MPphiE-RCPM, a lytic derivative, the phage host range was demonstrated to include members of three genera: one species each ofAmpullariella andCatellatospora, and 12 species ofMicromonospora. The phage belonged to Ackerman's B1 morphotype having an isometric head and a flexible noncontractile tail. The density of the phage was 1.525 g/cc. Restriction site mapping demonstrated that the phage DNA was 57.9 kb long and had cohesive ends. Using EDTA enrichment, viable mutants with deletions of at least 3.5 kb were isolated and mapped. Phage adsorption, sensitivities and plating efficiency were investigated. Non-liposome PEG-mediated transfection was demonstrated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 207-214 
    ISSN: 1476-5535
    Schlagwort(e): Yersinia enterocolitica ; Plasmid ; Outer membrane proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary In vitro synthesis of proteins directed byYersinia enterocolitica virulence plasmid DNA was studied using a cell-freeEscherichia coli coupled transcription-translation system. Out of a total of twenty-four polypeptides synthesized in vitro, ten were identified (based on virtually identical molecular masses) as outer membrane proteins synthesized in vivo when virulent plasmid-bearingY. enterocolitica cells were grown on four different solid media. Two high molecular weight outer membrane proteins synthesized in vivo by plasmid-bearing cells were not detected in the in vitro protein synthesizing system. Different plasmid-mediated outer membrane proteins were expressed in vivo inY. enterocolitica grown on different media.Y. enterocolitica grown on media with high calcium concentration (1·4–1·5 mM) expressed twice the number of lower molecular weight outer membrane proteins than the organism grown on low calcium (238–311 μM) media. This is the first report that a single serotype has been shown to synthesize all the reported virulence plasmid-encoded outer membrane proteins including three new polypeptides. The constituents in the medium as well as the level of calcium appeared to have a regulatory role in plasmid gene expression for lower molecular weight outer membrane proteins.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    ISSN: 1476-5535
    Schlagwort(e): Beta-lactam antibiotic biosynthesis ; Heterologous gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Streptomyces clavuligerus isopenicillin N synthase (IPNS) gene expression was achieved inEscherichia coli by the construction of two-cistron expression systems formed in the high copy number plasmid vector pUC119. These two-cistron constructions were composed of the IPNS gene and its flanking sequences which encoded an upstream open reading frame (ORF), the IPNS ribosome binding site and a putative transcription terminator. NoE. coli- likeStreptomyces promoter motif was present upstream of the IPNS gene therefore transcriptional regulation of the two-cistron system was provided by thelac promoter of pUC119. Enzymatically active IPNS was detected inE. coli cells harboring the recombinant plasmids thereby providing evidence for the activity of the IPNS ORF and for the feasibility of production ofS. clavuligerus IPNS inE. coli. These results indicate that simple two-cistron constructions involving foreign gene flanking sequences may be used to express foreign proteins inE. coli.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 183-189 
    ISSN: 1476-5535
    Schlagwort(e): Iron ore improvement ; Organic acids ; Phosphorus dissolution ; Liquid chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The value of iron ore is adversely affected by phosphorus in concentrations over 0.03% by weight. The present research concerns the use of metabolic products of aPenicillium-like fungus to leach insoluble phosphates (hydroxyapatite) from ores. Ion chromatography was used to measure metabolism of glucose into acidic fragments. The rate and products of glucose degradation depended on both the chemical composition of the growth medium (buffered or not) and incubation conditions (shaken or quiescent). The principal products were identified as oxalic acid and isomers of propylene dicarboxylic acid, mainly itaconic acid. Continued, slow metabolism of itaconic acid generates more oxalic acid. Aliphatic acids were not detected. Both iron ore phosphate and calcium phosphate were partially solubilized by either the spent broth or aqueous oxalic acid. Solubilization of ore phosphorus was greatly assisted by hydrochloric acid added to the spent broth in small increments. The data suggest biological alternatives to costly leaching procedures that use only mineral acids.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    ISSN: 1476-5535
    Schlagwort(e): IL-4 ; E. coli ; Expression ; Plasmid constructions ; Secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Human IL-4 (hIL-4) has been cloned from a human T cell line based on its homology to the murine IL-4 cDNA sequence [36]. We have compared cytoplasmic and extra-cytoplasmic expression of this basic protein inEscherichia coli using various combinations of promoters, replicons and host strains. Strains producing a cytoplasmic product were most successful at heterologous protein expression, producing up to 500 mg/l of an inactive aggregated form of the protein. The biological activity of the protein could be restored by refolding the protein with guanidine hydrochloride and glutathione giving a specific activity identical to that of IL-4 derived from CHO cell lines stably transformed with an hIL-4 expression plasmid. Strains designed to secrete human IL-4 into the periplasmic space produced far less protein (approximately 5 mg/l). However, a significant fraction of this protein was detected in the culture medium. This fraction appeared to be soluble after ultracentrifugation, and demonstrated high specific activity without refolding. Leakage of heterologous protein into the culture medium may be a viable way to recover biologically active products without relying on the denaturation and refolding in vitro that can, at times, yield incorrectly folded gene product.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 229-237 
    ISSN: 1476-5535
    Schlagwort(e): Chymosin ; Acid protease ; Diazoacetyl-norleucine methyl ester ; Microculture ; Aspergillus awamori ; Heterologous protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Through the course of five rounds of mutagenesis of a genetically-engineered strain ofAspergillus awamori, the yield of a heterologous protein (the acid protease, calf chymosin) increased four-fold. This was accomplished through the use of an agar plate screen incorporating the colony restrictor 2,6-dichloro-4-nitroaniline (dichloran) and the acid protease inhibitor diazoacetyl-norleucine methyl ester (DAN) to reduce high background concentrations of the native acid protease. A miniaturized liquid culture growth method using 24-well culture plates was an intermediate screen between agar plate and shake flask cultures. Analysis of broth samples for active calf chymosin was accomplished with a highly specific, 96-well microtiter plate turbidimetric assay.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 239-246 
    ISSN: 1476-5535
    Schlagwort(e): Streptomyces avidinii streptavidin ; Assay ; Production ; Media improvement ; Improved process
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The production of streptavidin byStreptomyces avidinii in several different media was examined at 24, 48 and 72 hours. Flask studies indicated that fermentation media containing either complex or multiple carbon sources resulted in higher yields of streptavidin than media with a single carbon source. Streptavidin could be detected in crude fermentation broths by use of a tritiated biotin binding assay. This assay appears to give useful estimates of streptavidin production. Depending upon the medium employed, streptavidin yields ranged from 0.5 mg/l to 53 mg/l. Production was successfully scaled up to ten liter fermentors. Streptavidin was purified in a one step process from centrifuged, concentrated fermentation broths by binding the protein to an iminobiotin column at pH 11 followed by elution at pH 4.0. Recovery percentages varied depending upon the solubility of the fermentation media ingredients.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 247-257 
    ISSN: 1476-5535
    Schlagwort(e): Methanogenesis ; Sulfate reduction ; Competitive inhibition ; Sulfide inhibition ; COD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The continuously operated suspended growth anaerobic contact system was utilized to estimate the effect of sulfate reduction on the thermophilic (55°C) methane fermentation process. Results indicated that reduction in methanogenesis in the presence of sulfate was due to two separate, but related, processes;i.e. competitive and sulfide inhibition. Although prevention of competitive inhibition would be difficult under normal fermenter operation, sulfide inhibition could be minimized by environmental selection of sulfide tolerant microbial populations through biomass recycle and pH control. Stable fermenter operation was achieved at soluble sulfide concentrations as high as 330 mg/l soluble sulfide. Using batch fermenters, a maximum thermophilic sulfate reduction rate of 3.7 mg SO4 2−−S/g volatile solids (VS)-day was estimated. The importance of reporting sulfate reduction rates on a biomass basis is demonstrated by a simple population adjustment kinetic model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 259-263 
    ISSN: 1476-5535
    Schlagwort(e): Marine microalgae ; Vitamins ; Nutritional requirements ; Vitamin supplements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Certain marine microalgae contain water-and lipid-soluble vitamins and can be used as food supplements or food ingredients. A number of vitamins are present in higher concentrations in the microalgae than in conventional foods traditionally considered rich in them. Ingestion of relatively small quantities of microalgae can cover the requirements for some vitamins in animal nutrition, including human nutrition, while supplementing others. Marine microalgae can thus be considered to represent a non-conventional source of vitamins or a vitamin supplement for animal or human nutrition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 265-266 
    ISSN: 1476-5535
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 267-267 
    ISSN: 1476-5535
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 1-18 
    ISSN: 1476-5535
    Schlagwort(e): Microbody ; Glyoxysome ; Peroxisome ; Catalase ; Hydrocarbon ; Enzyme ; Fungal microbody ; Fungus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Microbodies are ubiquitous organelles in fungal cells, occurring in both vegetative hyphae and spores. They are bounded by a single membrane and may contain a crystalloid inclusion with subunits spaced at regular intervals. Typically, they contain catalase which reacts with the cytochemical stain 3,3′-diaminobenzidine to yield an electron-opaque product, urate oxidase,l-α-hydroxy acid oxidase andd-amino acid oxidase. Their fragility and the necessity to disrupt the tough fungal cell wall before isolating them make them difficult to isolate. Analysis of enzymes in purified or partially purified microbodies from fungi indicates that they participate in fatty acid degradation, the glyoxylate cycle, purine metabolism, methanol oxidation, assimilation of nitrogenous compounds, amine metabolism and oxalate synthesis. In organisms where microbodies are known to contain enzymes of the glyoxylate cycle, they are known as glyoxysomes; where they are known to contain peroxidatic activity, they are known as peroxisomes. In some cases microbodies contain enzymes for only a portion of a pathway or cycle. Thus, they must be involved in metabolic cooperation with other organelles, particularly mitochondria. The number, size and shape of microbodies in cells, their buoyant density and their enzyme contents may vary with the composition of the medium; their proliferation in cells is regulated by the growth environment. The isolation from the same organism of microbodies with different buoyant densities and different enzymes suggests strongly that more than one type of microbody can be formed by fungi.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 43-48 
    ISSN: 1476-5535
    Schlagwort(e): Streptomyces ; Streptonigrin ; Nitrogen regulation ; Secondary metabolite ; Shikimic acid pathway
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A defined medium containing glucose and ammonium as the sole carbon and nitrogen sources was developed to support growth and streptonigrin production. In this defined medium, increased initial levels of ammonium resulted in increased growth suggesting that nitrogen is the growth limiting nutrient. In some cases, increased initial ammonium levels resulted in decreased specific streptonigrin productivity, suggesting that nitrogen regulatory mechanisms may adversely affect streptonigrin biosynthesis. This suggestion that nitrogen regulation adversely affects antibiotic biosynthesis is further supported by results from two studies in which the ammonium supply to the cells was controlled. In the first study, streptonigrin productivity and final titer were enhanced by the addition of an ammonium trapping agent. In the second experiment, when ammonium chloride was fed slowly throughout the course of cultivation, the production phase was lengthened and the maximum antibiotic concentration was enhanced compared to the batch controls containing either the same initial or the same total ammonium chloride levels. Although our results indicate streptonigrin production may be subject to nitrogen regulatory mechanisms, the effect of nitrogen on streptonigrin production cannot be strictly correlated to the extracellular ammonium concentration. In fact, we observed that when ammonium was depleted from the medium, streptonigrin production ceased.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 49-52 
    ISSN: 1476-5535
    Schlagwort(e): Leaching ; Metal recovery ; Strategic metal ; Cobalt ; Smelter waste ; Thiobacillus ferrooxidans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The bioleaching of cobalt from domestic, industrial smelter wastes was studied.Thiobacillus ferrooxidans solubilized Co from sulfidic dross furnace mattes. At pulp densities of 4% (w/v) up to 600 mg of Co per liter of leaching solution was released from nickel matte, corresponding to removal of about two-thirds of the original amount of Co in the matte. Bioleaching methods may be useful as a component of a process for solubilization and recovery of Co from sulfidic smelter mattes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. i 
    ISSN: 1476-5535
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 71-75 
    ISSN: 1476-5535
    Schlagwort(e): Bacterial identification ; Infrared spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A study motivated by the recent revival of interest in the use of IR spectroscopy to identify bacteria is reported. A library of FT-IR spectra of dried bacterial films was compled using 16 different strains. A test set was complied from spectra of the same strains grown several months later. The test set was quantitatively compared with the library on the basis of spectral similarity in the region 980–1190 cm−1. Six of the strains in the test set were not matched with the correct strain in the library despite efforts to reproduce the conditions under which cells were grown and prepared. The results suggest that reproducibility of the bacterial spectra is a potential difficulty that must be addressed by any attempts to develop FT-IR spectroscopy as a bacterial identification method.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    ISSN: 1476-5535
    Schlagwort(e): Nybomycin ; Deoxynybomycin ; Nybomycin acetate ; Thin layer chromatography ; High performance liquid chromatography ; Mass spectrometry ; Fermentation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and mass spectrometry (MS) methods have been developed for the analysis of the antibiotic nybomycin, its derivatives deoxynybomycin and nybomycin acetate, during the fermentation and isolation of nybomycin. Using a quantitative HPLC based assay, the time course of nybomycin production (nybomycin titers) in 1000 liter fermentations was determined. Desorption chemical ionization mass spectrometry (DCI/MS) of standard nybomycin samples, fermentation broth samples and purified fractions suggested the co-production of deoxynybomycin which was not reported previously from this organism. TLC and HPLC were used to confirm the presence of deoxynybomycin in the crude extracts of fermentation broths.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 77-84 
    ISSN: 1476-5535
    Schlagwort(e): Copper ; Cofactor ; Copper-resistance mechanisms ; Toxicity ; Microorganisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Copper is a required trace element for growth of microorganisms since it is a cofactor for numerous enzymes. Also, proteins containing copper are important electron transfer carriers. However, at elevated concentrations, copper can be highly toxic to microorganisms. This review examines copper toxicity and uptake in microorganisms, with an emphasis on copper-resistance mechanisms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 143-147 
    ISSN: 1476-5535
    Schlagwort(e): Congo red binding ; Plasmid ; Shigella flexneri ; Curing ; Virulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The effect of growth ofShigella flexneri on various selective media on retention of congo red (CR) binding ability was determined to evaluate the effectiveness of isolation techniques regarding maintenance of the virulence plasmid. WhenS. flexneri was surface-plated onto selective agars and the resulting colonies replica plated onto CR plates, no white colonies indicative of loss of virulence were found despite repeated trials. However, whenS. flexneri was grown in liquid media (agar was removed from agar-containing media by centrifugation), white colonies were found upon plating onto CR plates. Most common selective media for shigellae produced fewer than 5–10 white colonies/1000 red colonies. However, growth in broth prepared from violet red bile agar, desoxycholate citrate agar, and SS agar gave more than 100 white colonies/1000 red colonies. Loss of CR binding was demonstrated whenS. flexneri was grown in broth containing tergitol 7, sodium dodecyl sulfate, bile salts #3, crystal violet, eosin y or methylen blue. However, concentrations of selective agents that led to loss of CR binding were much higher than those used in selective media. Results indicate that under usual conditions of isolation ofS. flexneri from food and clinical specimens, CR binding appears to be a relatively stable character with most selective media; however, use of violet red bile agar, desoxycholate citrate agar, and SS agar may lead to substantial loss of congo red binding indicating that the isolates may not be virulent.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 21
    ISSN: 1476-5535
    Schlagwort(e): Fermentation ; Recombinant DNA ; Phage λp L promoter ; Expression vector ; α1-Antitrypsin ; Malaria vaccine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The major leftward early promoter of phage λp L, has frequently been used to drive expression of heterologous genes inEscherichia coli.p L is typically maintained fully repressed by the lambda cl protein. When induction of heterologous protein synthesis is desired, one of several potential mechanisms of destroying cl function is employed and the expression of the foreign gene commences. One method of derepressingp L involves exposing cells to nalidixic acid, which results in the “activation” of RecA protein and the subsequent RecA-mediated proteolytic cleavage of cl. Activated RecA also mediates the cleavage of theE. coli LexA protein, resulting in induction of the SOS regulon (at least 15E. coli genes, includingrec A). We have examined the effect of two chromosomal mutations on the productivity of nalidixic acid inductions. One of the tested mutations (recA o) increased the intracellular concentration of RecA prior to induction; the other (lexAind−) resulted in a mutated lexA protein insensitive to RecA-mediated cleavage. These mutations were introduced into a strain carrying acl+ defective lysogen. Synthesis of two heterologous proteins, human α1-antitrypsin and a fusion protein partially derived from thePlasmodium falciparum circumsporozooite surface antigen, was examined in the wild-type and mutant strains. The maximum α-1 antitrypsin concentration achieved was improved by 50% when therecA o strain was used rather than the wild type; however; only smaller changes (20% or less) in the maximum concentration of the malaria fusion protein wer observed. Use of thelexAind− strain resulted in a decrease in the maximum concentration attained for both heterologous products.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 95-101 
    ISSN: 1476-5535
    Schlagwort(e): Microbially enhanced oil recovery ; bioemulsifiers ; Anaerobic production
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The activity of the biosurfactant produced byBacillus licheniformis strain JF-2 was quantified using a unit defined as the amount of the acid-precipitated biosurfactant that lowered the surface tension by 10 mN/m. One unit was equivalent to 37 μg/ml of the acid-precipitated biosurfactant. Acid precipitation was very effective in the removal of the biosurfactant from the spent medium. Among the solvents tested methanol was the most efficient in extracting the surfactant activity from acid-precipitated material. Thin-layer chromatography of the acid-precipitated biosurfactant revealed four components, two of which contained a lipid moiety and one of which contained an amino group. The methanol-soluble fraction also contained these four components. Studies suggested that all four components were needed for full activity. The lowest interfacial tensions against octane were observed when NaCl concentrations were 50 g/l or greater. Calcium concentrations greater than 25 g/l significantly increased the interfacial tension
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 65-69 
    ISSN: 1476-5535
    Schlagwort(e): Acetonitrile utilizing bacteria ; Chromobacterium ; Pseudomonas aeruginosa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Bacteria utilizing high concentrations of acetonitrile as the sole carbon source were isolated and identified asChromobacterium sp. andPseudomonas aeruginosa. Maximum growth was attained after 96 h of incubation andP. aeruginosa grew slightly faster thanChromobacterium sp. The strains were able to grow and oxidize acetonitrile at concentrations as high as 600 mM. However, higher concentrations inhibited growth and oxygen uptake. Degradation studies with (14C)acetonitrile indicated 57% of acetonitrile was degraded byPseudomonas aeruginosa as compared to 43% byChromobacterium. The isolates utilized different nitrile compounds as carbon substrates.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 59-64 
    ISSN: 1476-5535
    Schlagwort(e): Cellulase ; Endoglucanase ; Cellulose ; Pseudomonas
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The recombinant plasmid, pPFC4, which carriesPseudomonas fluorescens subsp.cellulosa chromosomal DNA was previously isolated on the basis of its ability to direct the expression of endoglucanase inEscherichia coli. In the present study, some physical and chemical properties of this activity were characterized. The major portion (78.4%) of the endoglucanase activity is found in the periplasmic space ofE. coli. This plasmid-encoded endoglucanase has a pH optimum of approximately 6.0 and a temperature optimum of approximately 50°C. With carboxymethylcellulose-zymograms, after polyacrylamide gel electrophoresis, periplasmic extracts fromE. coli carrying pPFC4 show six distinct bands with endoglucanase activity. The molecular mass of the major endoglucanase band is approximately 29 kDa while the remaining bands with endoglucanase activity range from 48 to 100 kDa. Although the basis of this heterogeneity is not known, the DNA insert of pPFC4 that encodes endoglucanase activity is not large enough to contain six separate genes; hence, the observed array of endoglucanases may result from post-translational modification of one or two primary gene products.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 71-77 
    ISSN: 1476-5535
    Schlagwort(e): Brevibacterium R-312 ; Enzyme production ; Nitrile hydratase activity ; Amidase activity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary 3-cyanopyridine was hydrated to nicotinamide by whole cells ofBrevibacterium R-312 containing nitrile hydratase. Cells used for kinetic studies had an initial activity of 0.30 mg nicotinamide/mg cells(dry)-min and storage half-lives (pH 8) of approximately 100 days, 10 days, 5 days and less than 1 day at 4°C, 10°C, 25°C, and 30°C respectively. Temperature and pH maxima were 35°C and 8.0, respectively. Fermentations gave a maximum total hydratase activity of 1.25 mg nicotinamide/min, but at this maximum the amidase activity was unacceptably high (25% of the hydratase activity): nicotinamide was converted too rapidly to nicotinic acid. But systematic fermentation studies (7 1) showed that harvesting at mid-log phase (18–20 h) prior to the attainment of maximum total activity gave reasonably high levels of hydratase (0.3 mg nicotinamide/mg cells-min) and acceptable levels of amidase (0.03 mg nicotinic acid/mg cells-min).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 26
    ISSN: 1476-5535
    Schlagwort(e): Cyanobacteria ; Eukaryotic microalgae ; Macroalgae ; Natural products ; Screening ; Pharmaceuticals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary An algae screening program, including cultured macroalgae, cultured cyanobacteria and cultured eukaryotic microalgae has been undertaken. Methods for the isolation, purification, preservation and cultivation of axenic cyanobacteria and eukaryotic cultures have been developed. Screening of these groups for biologically active components has lead to the isolation of pachydictyol and caulerpenyne from cultured macroalgae, while a series of hapalindoles and an antifungal depsipeptide have been isolated from cyanobacteria.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 85-93 
    ISSN: 1476-5535
    Schlagwort(e): Fermentation ; RecombinantE. coli ; Beta-galactosidase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The productivity ofEscherichia coli biomass and recombinant beta-galactosidase was increased in Luria broth (LB) enriched with yeast extract. In flask culture under conditions of LB limitation, yeast extract suplementation gave the highest biomass (strain HB101/pRW756) stimulation per unit of component added compared with supplementation by various amounts of amino acids, vitamins, minerals, purines/pyrimidines, tryptone, casamino acids, casein peptone or gelatin peptone. The biomass production ofE. coli HB101/pRW756, XL-1 blue/puc118, XL-1 Blue FF/puc118 and TB-1/p1034 cells was stimulated in fermentor-scale experiments with additional yeast extract in LB. Total beta-galactosidase production from plasmid genes in fermentor-scale experiments was increased 105.4% in XL-1 blue/puc118 cells, 365.5% in XL-1 blue FF/puc118 cells and 421.4% in TB-1/p1034 cells by 0.5%, 1% and 1% weight per volume of additional yeast extract in LB, respectively. Depending on different strains, the increase of the enzyme production was obtained either by increased biomass, or the combination of enhanced gene expression and increased biomass. Neither the biomass nor beta-galactosidase production was stimulated in N4830/p1034 cells by the increase in yeast extract concentration in the medium.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 79-84 
    ISSN: 1476-5535
    Schlagwort(e): Bacteria ; Soil ; Conjugation ; Gene transfer ; Plasmids ; Survival
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Experiments conducted in microcosms containing loam soil samples inoculated with eitherE. coli orPseudomonas spp. donor and recipient cells showed that bacterial cells survived and conjugated over a 24-h incubation period.E. coli transconjugants were detected 6 h after donor and recipient strains were introduced into sterile soil samples. In non-sterile soil samples, transconjugants were detected between 8 and 24 h incubation.Pseudomonas transconjugants were recovered from sterile soil samples between 6 and 12 h after their introduction and as early as 2 h in non-sterile soil. The results show that genetic interactions occur in non-sterile soil in relatively short periods of time at relatively high transfer frequencies (10−3 to 10−4). Studies on genetic interactions in soil are becoming necessary in risk assessment/environmental impact studies prior to the release of genetically engineered or modified organisms into uncontained environments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 103-112 
    ISSN: 1476-5535
    Schlagwort(e): Filamentous fungi ; Ligninase production ; White-rot fungus ; Submerged culture ; Fungal pellets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Lignin peroxidases produced byPhanerochaete chrysosporium have several important potential industrial applications based on their ability to degrade lignin and lignin-like compounds. A stirred tank reactor system for the production of lignin peroxidases is described here. Included in this study is an examination of the mechanics of pellet biocatalyst formation and the optimization of an acetate buffered medium. Higher levels of lignin peroxidase were obtained with acetate buffer compared to the other buffer systems tested. Concentrations of 0.05% (w/v) Tween 80 and 0.4 mM veratryl alcohol gave optimal lignin peroxidase activity in acetate buffered medium. In shake flask cultures, mycelial fragments in the inoculum aggregated into pellets during the first eight hours of incubation and thereafter increased in size through the eighth day. The agitation rate in shake flask cultures affected pellet size, the number of pellets formed, and lignin peroxidase activity. Transfer of fungal pellets from shake flask culture to a continuously oxygenated baffled stirred tank reactor (STR) resulted in production of high lignin peroxidase titres comparable to those of shake flask cultures when the agitation rate, oxygen dispersion and foaming were closely controlled.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 125-129 
    ISSN: 1476-5535
    Schlagwort(e): Cellulomonas flavigena ; Morphology ; Intracellular inclusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A cellulolytic bacterium was isolated from leaf litter. Its nutritional characteristics and most of its morphological features closely resemble those of ATCC # 482, which is considered to be the type species ofCellulomonas flavigena (Stackebrandt and Keddie in Bergey's Manual of Systematic Bacteriology). However, when stationary phase cells from cultures using a minimal medium containing an excess carbon and energy source are compared, a very prominent morphological difference is manifest. Phase contrast microscopy and transmission electron microscopy indicate the presence of large swollen polar structures in the type species. The absence of such structures from the new isolate and the production of large amounts of an extracellular polysaccharide indicate that it is a new strain ofCellulomonas flavigena.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 193-193 
    ISSN: 1476-5535
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 191-192 
    ISSN: 1476-5535
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 289-293 
    ISSN: 1476-5535
    Schlagwort(e): Living cell reaction process ; l-Isoleucine production ; l-Valine production ; Brevibacterium flavum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A new process (Living Cell Reaction Process) forl-isoleucine production using viable, non-growing cells ofBrevibacterium flavum AB-07 was optimised using ethanol as the energy source and α-ketobutyric acid (α-KB) as precursor.l-valine also could be produced from glucose at high yield by this process. This process differs from the usual fermentation method in that non-growing cells are used, and the production ofl-isoleucine andl-valine were carried out under conditions of repressed cell division and growth. Minimal medium missing the essential growth factor, biotin was employed as the reaction mixture for the production ofl-isoleucine andl-valine. The productivity ofl-isoleucine andl-valine were 200 mmol·l−1 · day−1 (molecular yield to α-KB: 95%) and 300 mmol · l−1 · day−1 (molecular yield to glucose: 80%) respectively. The content ofl-isoleucine andl-valine in total amino acids produced in the each mixture were 97% and 96% respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 295-301 
    ISSN: 1476-5535
    Schlagwort(e): Alpha-amylase assay ; Turbidity ; Kinetic determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A simple, reliable and sensitive assay for alpha-amylase activity is reported, together with its theoretical derivation, that overcomes many of the problems encountered with other assays, especially when attempting to assay alpha-amylase activity in crude cell extracts or culture supernatants. The method relies on the reduction in turbidity that occurs upon digestion of a starch suspension with alpha-amylase. The initial rate of decrease in turbidity is shown to be proportional to a wide range of enzyme concentrations, permitting a rapid spectrophotometric and kinetic determination of alpha-amylase activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 323-327 
    ISSN: 1476-5535
    Schlagwort(e): Pyrimidine biosynthesis ; Fluorouracil resistance ; Efrotomycin ; Nocardia lactamdurans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Nocardia lactamdurans, which produces the antibiotics efrotomycin and cephamycin C, exhibits essentially unregulated pyrimidine synthesis. Neither the first nor the second step is subject to feedback regulation. In a series of strains, comprising the original soil isolate, a set of spontaneous fluorouracil-resistant (FUR) mutants and the first improved efrotomycin producer, three of the pyrimidine biosynthetic enzymes were found to be coordinately regulated over a tenfold range. This amplification of enzyme activity accounts for the pyrimidine-related properties but not, at present, for their improved efrotomycin capacity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 313-321 
    ISSN: 1476-5535
    Schlagwort(e): Nocardia lactamdurans ; Efrotomycin ; Fluorouracil ; UMP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Selection of spontaneous mutants ofNocardia lactamdurans MA2908 for resistance to 5-fluorouracil results in the simultaneous development of resistance to 5-fluorouridine. The resulting mutants fall into four distinct classes based on the amount of uracil accumulating in fermentation broths. An additional characteristic of these mutants is a reduction in the ability to incorporate exogenous uracil into nucleic acids even though transport and conversion to the nucleotide level appears normal. Finally, production of efrotomycin is increased in these mutants in both chemically defined and complex fermentation media to levels equivalent to those of MA4820, the first productivity mutant isolated in a conventional strain improvement program. Resistance development and uracil excretion are adequately explained by an elevation of the intracellular uridine nucleotide pool, in particular UMP. The role of the uridine necleotides in the efrotomycin fermentation is unknown.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 329-332 
    ISSN: 1476-5535
    Schlagwort(e): Actinophage ; Gentamicin ; Actinomycete
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A previously undescribed cryptic phage was found associated withMicromonospora purpurea ATCC 15835.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 207-210 
    ISSN: 1476-5535
    Schlagwort(e): Kluyveromyces fragilis ; Arthrobacter ; Yeast lytic enzyme complex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary An enzyme complex capable of lysing yeast cells was produced byArthrobacter sp. in a medium containing live cells ofKluyveromyces fragilis as the sole source of nutrients. The enzyme complex caused a 90% reduction in the optical density of viable yeast cells in 6 h at 25°C. This yeast cell hydrolysate can be used as a source of nitrogen, vitamins and minerals for subsequent growth of yeast cells (8.3 mg/ml) and further production of inulase (167 U/ml) representing 88 and 87% yield respectively, compared to cells grown on a standard yeast extract (1%) and sucrose (2%) medium.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 211-214 
    ISSN: 1476-5535
    Schlagwort(e): Food condiments ; Melon ; Bacillus ; Protein ; Fatty acids ; pH ; ‘In vitro’
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Biochemical and sensory changes of Nigerian melon seeds fermented with fourBacillus strains isolated from African locust beans were studied. In all fermentations, the reducing sugar content doubled from a starting value of 45 mg/g. The total free amino acid content decreased for the first 40 h and then increased. WithB. licheniformis, B. subtilis andB. pumilis, there was a subsequent large increase in free amino acid content. The extracted oils in the fermentation product increased in saponification number and free acid content but decreased in iodine number. The sensory properties of theB. licheniformis product was similar to that of ogiri and that ofB. subtiis to Iru.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 27-41 
    ISSN: 1436-3259
    Schlagwort(e): Groundwater monitoring networks ; Information reliability ; Information scales ; Kalman filtering in groundwater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 65-81 
    ISSN: 1436-3259
    Schlagwort(e): Lagoons ; Ponds ; Facultative ; First-order kinetics ; Complete mixing ; Probabilistic ; Uncertainty ; Environmental ; Stochastic differential equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract Two stochastic models are developed to describe the BOD output (i.e. effluent) variation of facultative aerated lagoons in series. One of the models uses the uncertainty analysis (UA) technique and the other is based on the moment equation solution methodology of stochastic differential equations (SDE's). The former considers a second-order approximation of the expectation (SOAE) and a first-order approximation of the variance (FOAV). The SDE model considers that output variability is accounted for by random variations in the rate coefficient. Comparisons are provided. Calibration and verification of the two models are aciieved by using field observations from two different lagoon systems in series. The predictive performances of the two models are compared with each other and with another SDE model, presented in a previous paper, that considers input randomness. The three methods show similar predictive performances and provide good predictions of the mean and standard deviation of the lagoon effluent BOD concentrations and thus are considered as appropriate methodologies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 89-103 
    ISSN: 1436-3259
    Schlagwort(e): maximum precipitation depths ; extreme-value distributions ; seasonal variation ; partial duration series ; model misspecification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract Quantile estimates of the annual maximum distribution can be obtained by fitting theoretical distributions to the maxima in separate seasons, e.g. to the monthly maxima. In this paper, asymptotic expressions for the bias and the variance of such estimates are derived for the case that the seasonal maxima follow a Gumbel distribution. Results from these expressions are presented for a situation with no seasonal variation and for maximum precipitation depths at Uccle/Ukkel (Belgium). It is shown that the bias is often negligible and that the variance reduction by using seasonal maxima instead of just the annual maxima strongly depends on the seasonal variation in the data. A comparison is made between the asymptotic standard error of quantile estimates from monthlymaxima with those from a partial duration series. Much attention is paid to the effect of model misspecification on the resulting quantile estimates of the annual maximum distribution. The use of seasonal maxima should be viewed with caution when the upper tail of this distribution is of interest.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 193-208 
    ISSN: 1436-3259
    Schlagwort(e): Stochastic tidal modeling ; parameter identification ; model calibration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract In this paper a parameter estimation algorithm is developed to estimate uncertain parameters in two dimensional shallow water flow models. Since in practice the open boundary conditions of these models are usually not known accurately, the uncertainty of these boundary conditions has to be taken into account to prevent that boundary errors are interpreted by the estimation procedure as parameter fluctuations. Therefore the open boundary conditions are embedded into a stochastic environment and a constant gain extended Kalman filter is employed to identify the state of the system. Defining a error functional that measures the differences between the filtered state of the system and the measurements, a quasi Newton method is employed to determine the minimum of this functional. To reduce the computational burden, the gradient of the criterium that is required using the quasi Newton method is determined by solving the adjoint system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 217-226 
    ISSN: 1436-3259
    Schlagwort(e): Exponential distribution ; bivariate exponential distribution ; distribution of flood volume ; partial duration series
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract A methodology based on the theory of stochastic processes is applied to the analysis of floods. The approach will be based on some results of the theory of extreme values over a threshold. In this paper, we focus on the estimation of the distribution of the flood volume in partial duration series analysis of flood phenomena, by using a bivariate exponential distribution of discharge exceedances and durations over a base level.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 254-254 
    ISSN: 1436-3259
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 277-294 
    ISSN: 1436-3259
    Schlagwort(e): Water distribution ; optimization ; nonlinear programming ; integer programming ; chance constraints ; rehabilation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract This paper presents the mathematical development of an integer — nonlinear programming chance — constrained optimization model for the minimum cost rehabilitation/replacement of water distribution system components. Particular attention is given to the handling of uncertainties in the roughness factors and the loading conditions including both the random demand and preassure head requirements. The advantages of the proposed model include the ability to: 1) handle the optimal timing of rehabilitation/replacement for water distribution system components; 2) link a mixed-integer linear program solver, a nonlinear program solver, and a hydraulic simulator into an optimization framework; 3) handle the uncertainties of some of the variables; 4) incorporate various kinds of cost functions; and 5) handle multiple loading conditions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 309-320 
    ISSN: 1436-3259
    Schlagwort(e): Entropy ; reliability ; redundancy ; water distribution networks ; nodal pair reliability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract Entropy based expressions for measurement of reliability and redundancy have recently been reported. These measures approach assessment of the reliability of the distribution network from the intrinsic redundancy of the network layout. The paper extends earlier work on entropy functions by including a more explicit statement of the alternate paths available in the network and by recognizing that under certain circumstances, e.g., failure of some part of the network work, an outflow link from a node under normal working condition may become an inflow link to the same node. The measures are assessed by comparison with parameters measuring Nodal Pair Reliability and percentage of flow supplied at adequate pressure for a range of networks and link failure conditions in this networks. The entropy measures are shown to reflect changes in the network reliability, as measured by these two comparative parameters, very well.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 1-26 
    ISSN: 1436-3259
    Schlagwort(e): Inverse ; calibration ; estimation ; groundwater flow
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract The development of stochastic methods for groundwater flow representation has undergone enormous expansion in recent years. The calibration of groundwater models, the inverse problem, has lately received comparable attention especially and almost exclusively from the stochastic perspective. In this review we trace the evolution of the methods to date with a specific view toward identifying the most important issues involved in the usefulness of the approaches. The methods are critiqued regarding practical usefulness, and future directions for requisite study are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 55-64 
    ISSN: 1436-3259
    Schlagwort(e): Predictive distribution ; Bayesian approximation ; parameter uncertainty ; non-informative prior ; method of moments ; Gumbel distribution ; maximum likelihood estimates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract In this paper Lindley's Bayesian approximation procedure is used to obtain the Bayes estimate of the probability of exceedence of a flood discharge. The Bayes estimates of the probability of exceedence has been shown by S.K. Sinha to be equivalent to the estimate of the probability of exceedence from the predictive or Bayesian disribution, of a future flood discharge. The evaluation of complex ratios of multiple integrals common in a Bayesian analysis is not necessary using Lindley's procedure. The Bayes estimates are compared to those obtained by the method of maximum likelihood and the method of moments. The results show that Bayes estimates of the probability of exceedence are larger as expected, but have smaller posterior standard deviations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 105-119 
    ISSN: 1436-3259
    Schlagwort(e): Kalman filtering ; Optimal smoothing ; Shallow water equations ; Wind stress ; On-line prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract Using the state space approach, an on-line filter procedure for combined wind stress identification and tidal flow forecasting is developed. The stochastic dynamic approach is based on the linear twodimensional shallow water equations. Using a finite difference scheme, a system representation of the model is obtained. To account for uncertainties, the system is embedded into a stochastic environment. By employing a Kalman filter, the on-line measurements of the water-level available can be used to identify and predict the shallow water flow. Because it takes a certain time before a fluctuation in the wind stress can be noticed in the water-level measurements, an optimal fixed-lag smoother is used to identify the stress.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 135-150 
    ISSN: 1436-3259
    Schlagwort(e): Radar ; rainfall prediction ; real-time prediction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract A computational method for the determination of rainfall distribution for applications in short term rainfall prediction is presented here. The method is strongly influenced by the experience gained from the observation and analysis of data gathered on a heavy rainfall event in 1986 that occurred during the Baiu Season in Japan. The method is based on the concept that rainfall occurs as an interaction between an instability field, appropriately modeled, and a field of water vapor under the influence of topography. The results from this computational method showed good agreement with the temporal variation in the rainband that moved across the observation field in 1986. Towards determination of the parameters in the computational model, another method for the determination of the rainfield is also developed. This second method determines the rainfall distribution from estimation of the conversion rate of water vapor to liquid water through use of data from a three dimensional scanning radar. The results are consistent with those obtained from the first method.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Stochastic environmental research and risk assessment 4 (1990), S. 151-160 
    ISSN: 1436-3259
    Schlagwort(e): Instantaneous Unit Hydrograph ; Conceptual models ; Stochastic differential equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract Recognizing that simple watershed conceptual models such as the Nash cascade ofn equal linear reservoirs continue to be reasonable means to approximate the Instantaneous Unit Hydrograph (IUH), it is natural to accept that random errors generated by climatological variability of data used in fitting an imprecise conceptual model will produce an IUH which is random itself. It is desirable to define the random properties of the IUH in a watershed in order to have a more realistic hydrologic application of this important function. Since in this case the IUH results from a series of differential equations where one or more of the uncertain parameters is treated in stochastic terms, then the statistical properties of the IUH are best described by the solution of the corresponding Stochastic Differential Equations (SDE's). This article attempts to present a methodology to derive the IUH in a small watershed by combining a classical conceptual model with the theory of SDE's. The procedure is illustrated with the application to the Middle Thames River, Ontario, Canada, and the model is verified by the comparison of the simulated statistical measures of the IUH with the corresponding observed ones with good agreement.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 163-187 
    ISSN: 1436-4646
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract A commonly studied relaxation of the travelling salesman problem is obtained by adding subtour elimination constraints to the constraints of a 2-factor problem and removing the integrality requirement. We investigate the problem of solving this relaxation for a special type of objective function. We also discuss some ways in which this relates to the concept of rank introduced by Chvátal.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 46 (1990), S. 1-29 
    ISSN: 1436-4646
    Schlagwort(e): Global optimization ; concurrent ; parallel ; stochastic ; network of computers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The global optimization problem, finding the lowest minimizer of a nonlinear function of several variables that has multiple local minimizers, appears well suited to concurrent computation. This paper presents a new parallel algorithm for the global optimization problem. The algorithm is a stochastic method related to the multi-level single-linkage methods of Rinnooy Kan and Timmer for sequential computers. Concurrency is achieved by partitioning the work of each of the three main parts of the algorithm, sampling, local minimization start point selection, and multiple local minimizations, among the processors. This parallelism is of a coarse grain type and is especially well suited to a local memory multiprocessing environment. The paper presents test results of a distributed implementation of this algorithm on a local area network of computer workstations. It also summarizes the theoretical properties of the algorithm.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 46 (1990), S. 105-122 
    ISSN: 1436-4646
    Schlagwort(e): Nondifferentiable minimization ; convex programming ; numerical methods ; descent methods
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Proximal bundle methods for minimizing a convex functionf generate a sequence {x k } by takingx k+1 to be the minimizer of $$\hat f^k (x) + u^k |x - x^k |^2 /2$$ , where $$\hat f^k $$ is a sufficiently accurate polyhedral approximation tof andu k 〉 0. The usual choice ofu k = 1 may yield very slow convergence. A technique is given for choosing {u k } adaptively that eliminates sensitivity to objective scaling. Some encouraging numerical experience is reported.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 46 (1990), S. 127-151 
    ISSN: 1436-4646
    Schlagwort(e): Dual descent ; monotropic program ; Tucker tableau ; elementary vector
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We propose a dual descent method for the problem of minimizing a convex, possibly nondifferentiable, separable cost subject to linear constraints. The method has properties reminiscent of the Gauss-Seidel method in numerical analysis and uses theε-complementary slackness mechanism introduced in Bertsekas, Hosein and Tseng (1987) to ensure finite convergence to near optimality. As special cases we obtain the methods in Bertsekas, Hosein and Tseng (1987) for network flow programs and the methods in Tseng and Bertsekas (1987) for linear programs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 46 (1990), S. 219-224 
    ISSN: 1436-4646
    Schlagwort(e): Algebraic optimization ; location theory ; ellipsoid algorithms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The Fermat-Weber location problem is to find a point in ℝ n that minimizes the sum of the (weighted) Euclidean distances fromm given points in ℝ n . In this work we discuss some relevant complexity and algorithmic issues. First, using Tarski's theory on solvability over real closed fields we argue that there is an infinite scheme to solve the problem, where the rate of convergence is equal to the rate of the best method to locate a real algebraic root of a one-dimensional polynomial. Secondly, we exhibit an explicit solution to the strong separation problem associated with the Fermat-Weber model. This separation result shows that anε-approximation solution can be constructed in polynomial time using the standard Ellipsoid Method.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 46 (1990), S. 255-256 
    ISSN: 1436-4646
    Schlagwort(e): Linear complementarity problem ; P-matrix
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We give a short proof of the finiteness of Murty's principal pivoting algorithm for solving the linear complementarity problemy = Mz + q, y T z = 0,y ≥ 0,z ≥ 0 withP-matrixM.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 47 (1990), S. 305-336 
    ISSN: 1436-4646
    Schlagwort(e): Trust region ; linear constraints ; convex constraints ; global convergence ; local convergence ; degeneracy ; rate of convergence ; identification of active constraints ; Newton's method ; sequential quadratic programming ; gradient projection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We develop a convergence theory for convex and linearly constrained trust region methods which only requires that the step between iterates produce a sufficient reduction in the trust region subproblem. Global convergence is established for general convex constraints while the local analysis is for linearly constrained problems. The main local result establishes that if the sequence converges to a nondegenerate stationary point then the active constraints at the solution are identified in a finite number of iterations. As a consequence of the identification properties, we develop rate of convergence results by assuming that the step is a truncated Newton method. Our development is mainly geometrical; this approach allows the development of a convergence theory without any linear independence assumptions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 47 (1990), S. 425-439 
    ISSN: 1436-4646
    Schlagwort(e): Isotonic regression ; active sets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract In this and subsequent papers we will show that several algorithms for the isotonic regression problem may be viewed as active set methods. The active set approach provides a unifying framework for studying algorithms for isotonic regression, simplifies the exposition of existing algorithms and leads to several new efficient algorithms. We also investigate the computational complexity of several algorithms. In this paper we consider the isotonic regression problem with respect to a complete order $$\begin{gathered} minimize\sum\limits_{i = 1}^n {w_i } (y_i - x_i )^2 \hfill \\ subject tox_1 \leqslant x_2 \leqslant \cdot \cdot \cdot \leqslant x_n \hfill \\ \end{gathered} $$ where eachw i is strictly positive and eachy i is an arbitrary real number. We show that the Pool Adjacent Violators algorithm (due to Ayer et al., 1955; Miles, 1959; Kruskal, 1964), is a dual feasible active set method and that the Minimum Lower Set algorithm (due to Brunk et al., 1957) is a primal feasible active set method of computational complexity O(n 2). We present a new O(n) primal feasible active set algorithm. Finally we discuss Van Eeden's method and show that it is of worst-case exponential time complexity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 47 (1990), S. 463-463 
    ISSN: 1436-4646
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 48 (1990), S. 1-17 
    ISSN: 1436-4646
    Schlagwort(e): Coercivity ; quadratic programming ; linear programming ; aggregation ; relaxation ; multigrid methods
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract This paper is concerned with multilevel iterative methods which combine a descent scheme with a hierarchy of auxiliary problems in lower dimensional subspaces. The construction of auxiliary problems as well as applications to elasto-plastic model and linear programming are described. The auxiliary problem for the dual of a perturbed linear program is interpreted as a dual of perturbed aggregated linear program. Coercivity of the objective function over the feasible set is sufficient for the boundedness of the iterates. Equivalents of this condition are presented in special cases.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 91-111 
    ISSN: 1436-4646
    Schlagwort(e): Sparse matrices ; linear programming ; bipartite matching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Many optimization algorithms involve repeated processing of a fixed set of linear constraints. If we pre-process the constraint matrixA to be sparser, then algebraic operations onA will become faster. We consider the problem of making a given matrix as sparse as possible, theSparsity Problem (SP). In a companion paper with S. Frank Chang, we developed some theoretical algorithms for SP under a non-degeneracy assumption (McCormick and Chang, 1988). Here we investigate what must be done to make those algorithms applicable in practice. We report encouraging computational results in making linear programming constraint matrices sparser. We also find that the Simplex Algorithm can solve the reduced LPs faster. Comparisons are made to a heuristic algorithm for SP of Adler et al. (1989).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 64
    ISSN: 1436-4646
    Schlagwort(e): Quasi-Newton methods ; collinear scalings ; conic approximations ; local and q-superlinear convergence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract This paper is concerned with collinear scaling algorithms for unconstrained minimization where the underlying local approximants are forced to interpolate the objective function value and gradient at only the two most recent iterates. By suitably modifying the procedure of Sorensen (1980) for deriving such algorithms, we show that two members of the algorithm class derived related to the DFP and BFGS methods respectively are locally and q-superlinearly convergent. This local analysis as well as the results they yield exhibit the same sort of “duality” exhibited by those of Broyden, Dennis and Moré (1973) and Dennis and Moré (1974) for the DFP and BFGS methods. The results in this paper also imply the local and q-superlinear convergence of collinear scaling algorithms of Sorensen (1982, pp. 154–156) related to the DFP and BFGS methods.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 139-141 
    ISSN: 1436-4646
    Schlagwort(e): Linear complementarity problem ; copositive ; strictly copositive ; Q-matrix
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Recently, Jeter and Pye gave an example to show that Pang's conjecture, thatL 1 ⋂Q $$ \subseteq R_0 $$ , is false. We show in this article that the above conjecture is true for symmetric matrices. Specifically, we show that a symmetric copositive matrix is inQ if and only if it is strictly copositive.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 145-162 
    ISSN: 1436-4646
    Schlagwort(e): Linear programming ; interior-point methods ; primal—dual algorithms ; feasibility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract A new method for obtaining an initial feasible interior-point solution to a linear program is presented. This method avoids the use of a “big-M”, and is shown to work well on a standard set of test problems. Conditions are developed for obtaining a near-optimal solution that is feasible for an associated problem, and details of the computational testing are presented. Other issues related to obtaining and maintaining accurate feasible solutions to linear programs with an interior-point method are discussed. These issues are important to consider when solving problems that have no primal or dual interior-point feasible solutions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 231-251 
    ISSN: 1436-4646
    Schlagwort(e): Nonsmooth optimization ; subgradient ; ε-subgradient ; exact penalty function ; successive quadratic programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract In this paper we present an algorithm for solving nonlinear programming problems where the objective function contains a possibly nonsmooth convex term. The algorithm successively solves direction finding subproblems which are quadratic programming problems constructed by exploiting the special feature of the objective function. An exact penalty function is used to determine a step-size, once a search direction thus obtained is judged to yield a sufficient reduction in the penalty function value. The penalty parameter is adjusted to a suitable value automatically. Under appropriate assumptions, the algorithm is shown to produce an approximate optimal solution to the problem with any desirable accuracy in a finite number of iterations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 325-340 
    ISSN: 1436-4646
    Schlagwort(e): Convex quadratic programming ; interior point method ; Karmarkar's method ; logarithmic barrier function method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We present a primal interior point method for convex quadratic programming which is based upon a logarithmic barrier function approach. This approach generates a sequence of problems, each of which is approximately solved by taking a single Newton step. It is shown that the method requires $$O(\sqrt n L)$$ iterations and O(n 3.5 L) arithmetic operations. By using modified Newton steps the number of arithmetic operations required by the algorithm can be reduced to O(n 3 L).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 371-379 
    ISSN: 1436-4646
    Schlagwort(e): Z-function ; strong solvability with nonnegativity ; strictly semimonotone function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract This paper focuses on the relationship between the ‘strong’ solvability of a certain system involving a Z-function, and the strict semimonotonicity of such a function. Our main result shows that, for a system defined by a continuous, superhomogeneous Z-function, the additional condition of strict semimonotonicity is both necessary and sufficient for strong solvability.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 49 (1990), S. 397-411 
    ISSN: 1436-4646
    Schlagwort(e): Concave functions ; knapsack problems ; strict minimizers ; NP-hard ; nonconvex ; local minimizers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We consider a version of the knapsack problem which gives rise to a separable concave minimization problem subject to bounds on the variables and one equality constraint. We characterize strict local miniimizers of concave minimization problems subject to linear constraints, and use this characterization to show that although the problem of determining a global minimizer of the concave knapsack problem is NP-hard, it is possible to determine a local minimizer of this problem with at most O(n logn) operations and 1+[logn] evaluations of the function. If the function is quadratic this algorithm requires at most O(n logn) operations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Computing 43 (1990), S. 199-207 
    ISSN: 1436-5057
    Schlagwort(e): 65C99 ; Particle methods ; linearized Boltzmann equation ; Gauss integration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In [3] ist eine Partikelmethode vorgestellt, die unendlich viele Partikel benötigt. Zu ihrer numerischen Implementierung muß der numerisch relevante Träger abgeschätzt werden. Um dies zu vermeiden, führen wir über die Gasß-Integration eine a priori endliche Form ein und stellen numerische Ergebnisse für verschiedene Testbereiche vor.
    Notizen: Abstract In [3] a particle method is proposed which acts on an infinite grid. Hence, for a numerical application an estimation of the numerically relevant support is necessary. To overcome this difficulty we suggest a finite grid based on Gaussian integration formulas and present numerical results of different test examples.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Computing 43 (1990), S. 255-266 
    ISSN: 1436-5057
    Schlagwort(e): 65L05 ; Initial value problem ; Rung-Kutta methods ; Interpolation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Neue Interpolanten für explizite Runge-Kutta-Verfahren für Anfangswertprobleme werden vorgeschlagen. Diese Interpolanten beruhen auf Werten der Lösung und ihrer Ableitung aus zwei aufeinanderfolgenden Integrationsschritten. Für Verfahren der Ordnung 5 (nämlich Runge-Kutta-Fehlberg 4(5), Dormand-Prince (5(4) und Verner 5(6)) haben wir Interpolanten mit einem lokalen FehlerO(h 6) hergeleitet, die keine zusätzlichen Funktionsauswertungen benötigen. Für die Lösung der Ordnung 6 des Verfahrens von Verner erhalten wir mit einer zusätzlichen Funktionsauswertung einen Interpolanten mitO(h 7)-Fehler. Es tritt dabei keine Aufblähung der Größenordnung der Fehlerkonstanten auf.
    Notizen: Abstract New interpolants of the explicit Runge-Kutta method for the initial value problem are proposed. These interpolants are based on values of the solution and its derivative from two successive integration steps. In this paper, three interpolants withO(h 6) local error (l.e.), for the fifth order solution, of the methods Fehlberg 4(5) (RKF 4(5)), Dormand and Prince 5(4) (RKDP 5(4)) and Verner 5(6) (RKV 5(6)) without extra cost are derived. An interpolant withO(h 7) (l.e.) for the sixth order solution of the Verner's method with only one extra function evaluation per integration step is also constructed. The above advantages are obtained without any cost in the magnitude of the error.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Computing 43 (1990), S. 309-323 
    ISSN: 1436-5057
    Schlagwort(e): 65 K 05 ; 90 C 30 ; nonlinear systems of equations ; Lipschitzian global optimization ; adaptive partition algorithms ; random test problems ; numerical results
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird ein allgemeiner Rahmen für die Lösung nichtlinearer Gleichungssysteme vorgeschlagen, der auf Prinzipien der globalen Optimierung beruht. Nach einer kurzen Darstellung der benötigten Grundlagen werden numerische Testergebnisse für zwei Klassen von leicht reproduzierbaren Pseudo-Random-Testproblemen vorgestellt.
    Notizen: Abstract A general framework is proposed for the solution of nonlinear equation systems, applying multiextremal (global) optimization methodology. Following a brief presentation of the background needed, numerical results are reported for two classes of easily reproducible pseudo-random test problems.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Computing 43 (1990), S. 391-400 
    ISSN: 1436-5057
    Schlagwort(e): 68C25 ; 68E99 ; Algorithms ; Data Base ; Estimation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Wir untersuchen das Verhältnis Speichergröße zu Genauigkeit eines adaptiven Abtast-Algorithmus von Wegman, der es ermöglicht die Anzahl der verschiedenen Elemente einer großen Datei die auf Magnetplatte abgespeichert ist, abzuschätzen.
    Notizen: Abstract We analyze the storage/accuracy trade-off of an adaptive sampling algorithm due to Wegman that makes it possible to evaluate probabilistically the number of distinct elements in a large file stored on disk.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 1-15 
    ISSN: 1436-5057
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Bisher haben sich Untersuchungen über Wachstumsschranken für Lösungen von Randwertproblemen entweder mit 2-Punkt-oder mit Mehrpunkt-Bedingungen beschäftigt. Wenn jedoch einige der 2-Punkt-Bedingungen unabhängig von den übrigen Bedingungen sind, dann konnte man nur ein gröberes Polychotomie-Resultat angeben. In dieser Note wird gezeigt, daß eine solche (entkoppelte) 2-Punkt-Bedingung tatsächlich einen dichotomen Unterraum induziert. Dazu werden die Begriffe Dichotomie und Polychotomie genauer untersucht und es werden geeignete Projektionen zur Beschreibung der Struktur des Lösungsraumes hergeleitet.
    Notizen: Abstract Previous analyses on bounds for the growth of solutions of BVP were dealing either with two point or multipoint conditions. For BVP where some of the two point boundary conditions are separated from the rest one could only give a cruder polychotomy result for a multipoint case as such. In this note we show that such a (decoupled) two point condition actually induces a dichotomic subspace. This is done by reconsidering the notions of dichotomy and polychotomy and deriving appropriate projection mappings which describe the solution space structure.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 93-93 
    ISSN: 1436-5057
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 365-368 
    ISSN: 1436-5057
    Schlagwort(e): 65D07 ; 41A15 ; Positive spline interpolation ; sufficient and necessary existence condition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird eine hinreichend und notwendige Bedingung für die Positivität von rational-kubischen Splines angegeben, welche sich leicht überprüfen läßt. Sie ist bei Interpolationsdaten mit positiven Ordinaten durch hinreichend große Rationalitätsparameter stets erfüllbar.
    Notizen: Abstract By means of a finite set of inequalities a sufficient and necessary condition for the positivity of rational cubic splines is given which holds true whenever the rationality parameters are sufficiently large.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 69-77 
    ISSN: 1436-5057
    Schlagwort(e): 65G10 ; Interval mathematics ; Hausdorff distances
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In der vorliegenden Arbeit werden für eine Klasse von Metriken in ℝ n , darunter die Hölder-Metriken, explizite Ausdrücke zur Berechnung der Werte der zugehörigen Hausdorff-Metriken entwickelt.
    Notizen: Abstract In the present paper for a class of metrices in ℝ n including the Hölder metrices explicit expressions will be developed for evaluating the values of the corresponding Hausdorff metrices.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 119-129 
    ISSN: 1436-5057
    Schlagwort(e): 65D07 ; 41A15 ; Bézier ; geometric continuity ; visual continuity ; conversion ; positivity ; convex hull ; variation diminishing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Gegeben wird eine Bézier-Darstellung visuell stetiger quartischer und quintischer Kurven. Es werden explizite Ausdrücke für die Konversion der Bézier in und vice versa eine Hermite Darstellung, definiert durch die Stetigkeitsbedingungen, angegeben. Es werden Positivitätsbedingungen, die Eigenschaften wie z.B. die Eigenschaften der konvexen Hülle und der Variationsreduktion sichern, gegeben.
    Notizen: Abstract We present a Bézier representation of visually continuous quartics and quintics. Explicit formulas are given for the conversion of the Bézier representation to and vice versa a Hermite-like representation, defined by the continuity conditions. Positivity conditions which insure properties like convex hull and variation diminishing properties are given.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 197-208 
    ISSN: 1436-5057
    Schlagwort(e): 65F35 ; 65L05 ; 65L07 ; Stiff differential equations ; logarithmic norms ; one-sided Lipschitz continuity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die meisten Konvergenzkonzepte für Diskretisierungen nichtlinearer steifer Anfangswertprobleme basieren auf dem Begriff der einseitigen Lipschitz-Stetigkeit. Folglich sind durch diese theoretischen Konzepte nur steife Probleme mit moderater einseitiger Lipschitzkonstante abgedeckt. In der vorliegenden Arbeit zeigen wir, daß die Annahme moderater einseitiger Lipschitzkonstanten für viele steife Probleme verletzt ist. Wir weisen auf einige Konvergenzresultate hin, die nicht auf einseitigen Lipschitzkonstanten basieren; die Konzepte der singulären Störungstheorie sind hier von wesentlicher Relevanz. Wir berichten über einige numerische Erfahrungen mit steifen Problemen, die durch keine existierende Konvergenztheorie abgedeckt sind.
    Notizen: Abstract Most convergence concepts for discretizations of nonlinear stiff initial value problems are based on one-sided Lipschitz continuity. Therefore only those stiff problems that admit moderately sized one-sided Lipschitz constants are covered in a satisfactory way by the respective theory. In the present note we show that the assumption of moderately sized one-sided Lipschitz constants is violated for many stiff problems. We recall some convergence results that are not based on one-sided Lipschitz constants; the concept of singular perturbations is one of the key issues. Numerical experience with stiff problems that are not covered by available convergence results is reported.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 273-278 
    ISSN: 1436-5057
    Schlagwort(e): 65G10 ; Interval arithmetic ; interval expressions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die reele Funktionf besitze über dem IntervallX eine Darstellung der Formf(x)=ϕ0+ℓ(x)·h(x),x∈X. Für den Durchmesser vonh(X) gelted(h(X))≤σd(X) und für den Absolutbetrag von ℓ(X) bestehe die Ungleichung ∇ℓ(X)∇≤τd(X)n. Dann geben wir einen Intervallausdruck an, der den Wertebereich vonf über dem IntervallX mit der Ordnungn+1 approximiert. Unser Resultat enthält als Spezialfall das Theorem aus [2] über zentrierte Formen höherer Ordnung und außerdem eine Reihe von Darstellungen vonf, für die diese Resultate bisher nicht bekannt waren.
    Notizen: Abstract If the real-valued mappingf has a representation of the formf(x)=ϕ0+ℓ(x)·h(x),x∈X where for the diameter ofh(X) the inequalityd(h(X))≤σd(X) holds and for the absolute value of ℓ(X) we have ∇ℓ(X)∇≤τd(X) n, then we introduce an interval expression forf which approximates the range of values off over the compact intervalX with ordern+1. Our result contains as a special case the theorem on higher order centered forms from [2] and a series of representations off not discussed before.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 331-356 
    ISSN: 1436-5057
    Schlagwort(e): 65L05 ; 65M20 ; Stiff systems ; method of lines ; error structures ; extrapolation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In dieser Arbeit wird, als Fortführung der Betrachtungen im [1] die Struktur des globalen Fehlers einiger Zeit-Diskretisierungsschemata bei Anwendung auf eine Klasse steifer Anfangswertprobleme studiert, wie sie typischerweise bei der Semi-Diskretisierung parabolischer Anfangs/Randwertprobleme auftreten (Linienmethode). Im Mittelpunkt der Betrachtungen stehen das implizite Eulerverfahren, die implizite Trapezregel und ein lokal eindimensionales Zwischenschritt-Schema, und es werden ‘gestörte’ asymptotische Entwicklungen hergeleitet, deren Gültigkeit unabhängig von der Steifheit (unabhängig von der Gitterfeinheit der Raum-Diskretisierung) besteht. Der entscheidende, Punkt in der Analyse besteht in einer sorgfältigen, quantitativen Beschreibung des Restgliedes einer solchen Entwicklung. Die Resultate sind im Kontext der Linienmethode anwendbar und erlauben eine Vorhersage über das Verhalten von Extrapolationsverfahren bei der betrachteten Problemklasse. Die theoretischen Betrachtungen werden durch numerische Beispiele illustriert.
    Notizen: Abstract In this paper, which carries on the considerations in [1], the structure of the global error is studied for some time discretization schemes, applied to a class of stiff initial value problems as they typically arise from the semi-discretization of parabolic initial/boundary value problems (method of lines). The implicit Euler and trapezoidal schemes and a locally one-dimensional splitting method are considered, and ‘perturbed’ asymptotic error expansions are derived which are valid independent of the stiffness (independent of the meshwidth in space). The key point within the analysis is a careful, quantitative description of the remainder term in such an expansion. The results are applicable in the method of lines setting and enable the prediction of the behavior of extrapolation algorithms for the class of problems under consideration. These theoretical considerations are illustrated by numerical examples.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 39-50 
    ISSN: 1436-5057
    Schlagwort(e): Iterative methods ; multiple complex zeros ; polynomial equations ; computational efficiency ; circular complex arithmetic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Durch Verwendung der in [14] eingeführten iterativen Newton-Typ-Methode in zirkulärer Arithmetik wird eine neue iterative Methode zum Auffinden mehrfacher komplexer Nullstellen eines Polynoms hergeleitet. Diese Methode kann als Version der klassischen Schröder-Methode angesehen werden. Anfangsbedingungen, die eine sichere Konvergenz der vorgeschlagenen Methode garantieren, werden eingegeben. Die Steigerung der Berechnungseffizienz wird durch Kombination der komplexen Approximationsmethode vom Schröder-Typ mit einigen Intervallmethoden erreicht. Der erreichte Algorithmus wird in Hinsicht auf seine Effizienz analysiert und numerisch am Beispiel einer Polynomgleichung illustriert.
    Notizen: Abstract Using the iterative method of Newton's type in circular arithmetic, introduced in [14], a new iterative method for finding a multiple complex zero of a polynomial is derived. This method can be regarded as a version of classical Schröder's method. Initial conditions which guarantee a safe convergence of the proposed method are stated. The increase of the computational efficiency is achieved by a combination of the complex approximation methods of Schröder's type with some interval methods. The presented algorithms are analysed in view of their efficiency and illustrated numerically in the example of a polynomial equation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 79-91 
    ISSN: 1436-5057
    Schlagwort(e): 65H05 ; 65H15 ; Determination of polynomial zeros ; simultaneous iterative methods ; multiple roots of equation ; Q-order of convergence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird eine Klasse adaptiver Iterationsverfahren höherer Ordnung zur Berechnung aller Nullstellen eines Polynoms konstruiert. Diese Verfahren erhalten die Ordnung der Konvergenz auch im Fall mehrfacher Nullstellen. Numerische Beispiele werden angegeben.
    Notizen: Abstract A class of adaptive iterative methods of higher order for the simultaneous determination of all zeros of a polynomial is constructed. These methods preserve their order of convergence also in the case of multiple roots. Numerical examples are included.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 51-68 
    ISSN: 1436-5057
    Schlagwort(e): 68U05 ; 90C25 ; Shortest polygonal paths ; shortest inpolygons ; funnel ; linear time algorithm ; constrained paths ; convex function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Ein klassisches Problem der Geometrie fragt nach einem einbeschriebenen Polygon kürzesten Umfanges eines gegebenen konvexen Polygons. Wir verallgemeinern dieses Problem auf beliebige Polygonzüge im Raum und untersuchen zwei Fälle: im “offenen” Fall kann der gesuchte Streckenzug kürzester Länge einen unterschiedlichen Anfangs- und Endpunkt haben, während im “geschlossenen” Fall diese beiden Punkte zusammenfallen müssen. Es wird gezeigt, daß solche kürzesten Polygonzüge durch kürzeste Streckenzüge in einem ebenen “Kanal” bestimmt werden, die in beiden Fällen durch einen Algorithmus mit linearer Laufzeit bestimmt werden können. Ferner wird der Fall behandelt, daß der gesuchte Polygonzug ohne Knick durch einen vorgegebenen Punkt gehen soll. Es wird gezeigt, daß die Länge des Polygonzuges dann eine streng konvexe Funktion eines bestimmten Winkels ist, wodurch es möglich wird, auch dieses Problem effizient zu lösen.
    Notizen: Abstract A classical problem of geometry is the following: given a convex polygon in the plane, find an inscribed polygon of shortest circumference. In this paper we generalize this problem to arbitrary polygonal paths in space and consider two cases: in the “open” case the wanted path of shortest length can have different start and end point, whereas in the “closed” case these two points must coincide. We show that finding such shortest paths can be reduced to finding a shortest path in a planar “channel”. The latter problem can be solved by an algorithm of linear-time complexity in the open as well in the closed case. Finally, we deal with constrained problems where the wanted path has to fulfill additional properties; in particular, if it has to pass straight through a further point, we show that the length of such a constrained polygonal path is a strictly convex function of some angle α, and we derive an algorithm for determining such constrained polygonal paths efficiently.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 145-155 
    ISSN: 1436-5057
    Schlagwort(e): 65D32 ; 41A55 ; 65H10 ; Cubature formula ; continuation ; triangulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Eine KubaturformelQ ist eine Approximation für einn-dimensionales IntegralI. Q ist exakt für den von den Polynomenf 1, ...f d aufgespannten Vektorraum, wenn $$Q[f_i ] = I[f_i ] i = 1,...,d.$$ Die Unbekannten sind die Knoten und Gewichte der Kubaturformel. Wir nehmen an, daß es soviele Unbekannte wie Gleichungen gibt. Zur Bestimmung von Lösungen dieses Systems konstruieren wir eine Familie von Systemen, die stetig von einem Parametert abhängt: $$Q[f_i (t)] = I[f_i (t)] i = 1,...,d,$$ die fürt=1 mit dem ersten System zusammenfällt und fürt=0 eine einfach zu bestimmende Lösungsmenge hat. Die Lösungszweige, die in jeder Lösung dieser Menge beginnen, werden numerisch verfolgt und können eine Lösung fürt=1 liefern.
    Notizen: Abstract A cubature formulaQ is an approximation of ann-dimensional integralI. Q is exact for the space spanned by the polynomialsf 1, ...,f d if it verifies the system of equations: $$Q[f_i ] = I[f_i ] i = 1,...,d.$$ The unknowns are knots and weights of the cubature formula. We suppose that there are as many unknowns as equations. For searching solutions to this system, we construct a family of systems depending continuously on a parametert: $$Q[f_i (t)] = I[f_i (t)] i = 1,...,d,$$ coinciding with the previous system fort=1 and whose solutions att=0 are easily computed. The solution curves originating from these solutions are followed numerically and may yield a solution fort=1.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 183-191 
    ISSN: 1436-5057
    Schlagwort(e): 65G10 ; 65F30 ; 41A21 ; Matrix exponential ; Pade approximations ; verified bounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Vorgeschlagen wird ein Verfahren zur gleichzeitigen Berechnung von verifizierten Schranken für die Matrixfunktionen exp (A) und ∫ 0 1 exp (As) ds, bei dem die Einschließung des Integrals während der Berechnung von verifizierten Schranken für exp (A) mit sehr geringem zusätzlichen Rechenaufwand erhalten wird. Eine hohe Ergebnisgenauigkeit wird durch die Anwendung einer besonderen Rechnerarithmetik und durch dynamische Genauigkeit mit der “staggered correction”-Darstellung erzielt.
    Notizen: Abstract We propose a method for simultaneous computation of verified bounds for the matrix functions exp (A) and ∫ 0 1 exp (As) ds where the inclusion of the integral is obtained during the computation of verified bounds for exp (A) at very little additional cost. Highly accurate results of our method are achieved by the use of advanced computer arithmetic and an implementation of dynamic precision by means of staggered correction representation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 235-249 
    ISSN: 1436-5057
    Schlagwort(e): Primary 65N99, 65P05 ; Secondary 35A40, 35K05, 35R35, 80A20 ; Stefan problem ; boundary integral methods ; front tracking of the free boundary ; numerical solution of free boundary problems
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Das klassische ein dimensionale Ein-Phasen Stefan Problem wird numerisch über wachsende RechteckeR j gelöst, die von der Stefan Bedingung geregelt werden. Dieses Verfahren beruht auf einer Methode, die von E. Di Benedetto und R. Spigler 1983 entwickelt wurde. Die praktische Implementierung beruht auf einer Darstellung mittelsthermischer Potentiale der Lösungu j (x, t) der Wärmegleichung inR j . Der Wertu x j (x j ,jΔt), der das (j+1)-ste Rechteck bestimmt, wird analytisch durch die explizite Lösung einer Integralgleichung berechnet. Die Lösung inR j+1 wird durch numerische Berechnung eines anderen Integralausdruckes bestimmt. Der Algorithmus wird an zwei Problemen getestet, deren Lösung explizit bekannt ist. Die Konvergenz, die Stabilität und die Konvergenzgeschwindgkeit für Δx→0, Δt→0 werden ebenfalls getestet und graphisch dargestellt.
    Notizen: Abstract The classical one-phase one-dimensional Stefan problem is numerically solved on rectangles,R j , of increasing size controlled by the Stefan condition. This approach is based on a scheme introduced by E. Di Benedetto and R. Spigler in 1983. The practical implementation rests on the representation viathermal potentials of the solutionu j (x, t) to the heat equation inR j . The quantityu x j (x j ,jΔt) which determines the (j+1)-th rectangle is evaluatedanalytically by solving explicitly an integral equation. The solution inR j+1 is then obtained bynumerically evaluating a further integral expression. The algorithm is tested by solving two problems whose solution is explicitly known. Convergence, stability and convergence rate as Δx→0, Δt→0 have been tested and plots are shown.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 311-319 
    ISSN: 1436-5057
    Schlagwort(e): 1980 Mathematics Subject Classification (1985 Revision) ; Primary 65N10 ; 65N30 ; Coupling strategy ; combined methods ; singularity problems ; interface problems ; elliptic equation ; error analysis ; stability analysis ; optimal rate of convergence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Zur Lösung elliptischer Randwert probleme mit Singularitäten haben wir kombinierte Methoden vorgeschlagen, die aus der Ritz-Galerkin-Methode mit singulären (oder analytischen) Basisfunktionen für einen TeilS 2 des LösungsraumesS, in dem es singuläre Punkte gibt, und aus der Finite-Elemente-Methode für den restlichen TeilS 1 vonS, wo die Lösung genügend glatt ist, bestehen. In dieser Arbeit werden allgemeine Ansätze, die zusätzliche Integrale verwenden, präsentiert, um verschiedene numerische Methoden längs ihres gemeinsamen Randes Г0 zu verbinden. Fehler und Stabilitätsuntersuchungen für eine solche allgemeine Kombinationsstrategie werden angegeben. Diese Untersuchungen sind wichtig, da sie eine theoretische Grundlage für eine Reihe von Kombinationen zwischen der Ritz-Galerkin-Methode und der Finite-Elemente-Methode bilden, die in [7] angegeben werden, und weil sie zu neuen Kombinationen von anderen analogen Methoden führen können. Außerdem können die Untersuchungen dieser Arbeit angewendet und erweitert werden, um allgemeine elliptische Randwert probleme mit Winkel-Singularitäten, Oberflächen-Singularitäten oder unbeschränkten Gebieten zu lösen.
    Notizen: Abstract For solving elliptic boundary value problems with singularities, we have proposed the combined methods consisting of the Ritz-Galerkin method using singular (or analytic) basic functions for one part,S 2, of the solution domainS, where there exist singular points, and the finite element method for the remaining partS 1 ofS, where the solution is smooth enough. In this paper, general approaches using additional integrals are presented to match different numerical methods along their common boundary Г0. Errors and stability analyses are provided for such a general coupling strategy. These analyses are important because they form a theoretical basis for a number of combinations between the Ritz-Galerkin and finite element methods addressed in [7], and because they can lead to new combinations of other methods, such as the combined methods of the Ritz-Galerkin and finite difference methods. Moreover, the analyses in this paper can be applied or extended to solve general elliptic boundary value problems with angular singularities, interface singularity or unbounded domain.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Computing 45 (1990), S. 369-375 
    ISSN: 1436-5057
    Schlagwort(e): 90 B 35 ; Job-Shop scheduling ; flexible manufacturing ; shortest path
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Folgende Verallgemeinerung des klassischen Job-Shop Scheduling Problems wird untersucht. Jeder Operation eines Jobs sei eine Menge von Maschinen zugeordnet. Wählt man für jede Operation genau eine Maschine aus dieser Menge aus, so erhält man ein klassisches Job-Shop Problem, dessen minimale Gesamtbearbeitungszeitf(μ) von dieser Zuordnung μ abhängt. Gesucht ist eine Zuordnung μ, dief(μ) minimiert. Für zwei Jobs wird ein polynomialer Algorithmus entwickelt, der dieses Problem löst.
    Notizen: Abstract Consider the following generalization of the classical job-shop scheduling problem in which a set of machines is associated with each operation of a job. The operation can be processed on any of the machines in this set. For each assignment μ of operations to machines letP(μ) be the corresponding job-shop problem andf(μ) be the minimum makespan ofP(μ). How to find an assignment which minimizesf(μ)? For problems with two jobs a polynomial algorithm is derived.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 167-194 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary Low-frequency modes of the monsoon are examined in the context of their radiation balance and diagnosed for the 13-month period between May 1979 and May 1980 using Earth radiation budget and cloud measurements taken by experiments carried on board the Nimbus-7 satellite. Simultaneous observations of the albedo, longwave radiation, absorbed shortwave radiation, and net radiation at the top of the atmosphere (TOA), and the total cloud fraction and cloud-top temperature are considered. The use of broad-band radiation budget measurements permits a description of the observed longwave, shortwave, and net radiative energy exchange by the low-frequency modes. When wavenumber one fields are considered, the entire morphology of the 1979 summer monsoon (pre-onset, onset, break, re-intensification, and withdrawal) can be fully explained in terms of an eastward propagating mode. Ridge passages occurred over the Arabian Sea and India in June prior to onset, during the July break, and during the retreat of the monsoon. Trough passages occurred prior to the onset during a period of increased tropical cyclone activity, at the time of the onset, and immediately following the break. These low-frequency waves can be unambiguously tracked around the world over extended time periods. The latitudinal structure of the waves indicated that a thermally direct Hadley Cell perturbation propagated eastward with the oscillation. These cells were evident from extratropical extensions of the oscillation, each about 180° of longitude out-of-phase with the tropical oscillation. Because the absorbed shortwave and emitted longwave radrative components are in phase and of nearly identical amplitudes, the net radiative effect of the low-frequency mode is small in general. However, in certain latitudinal belts, the passage of the waves induced perturbations in the net radiation. Because longwave cloud-radiative forcing acts in the same direction as latent heat release, it is able to contribute to the diabatic energetics maintaining the structure and propagation of the eastward propagating 30- to 60-day waves. Between trough and ridge, the TOA longwave flux varies in a coherent manner by on the order of 50 to 60 Wm−2.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 153-165 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary The interannual variability of the monthly mean upper layer thickness for the central Arabian Sea (5°N-15° N and 60° E-70° E) from a numerical model of the Indian Ocean during the period 1954–1976 is investigated in relation to Indian monsoon rainfall variability. The variability in the surface structure of the Somali Current in the western Arabian Sea is also briefly discussed. It is found that these fields show a great deal of interannual variability that is correlated with variability in Indian monsoon rainfall. Model upper layer thickness (H) is taken as a surrogate variable for thermocline depth, which is assumed to be correlated with sea surface temperature. In general, during the period 1967 to 1974, which is a period of lower than normal monsoon rainfall, the upper ocean warm water sphere is thicker (deeper thermocline which implies warmer surface water); in contrast, during the period 1954–1966, which is a period of higher than normal monsoon rainfall, the upper warm water sphere is thinner (shallower thermocline which implies cooler surface water). The filtered time series of uppper layer thickness indieates the presence of a quasi-biennial oscillation (QBO) during the wet monsoon period, but this QBO signal is conspicuously absent during the dry monsoon period. Since model H primarily responds to wind stress curl, the interannual variability of the stress curl is investigated by means of an empirical orthogonal function (EOF) analysis. The first three EOF modes represent more than 72% of the curl variance. The spatial patterns for these modes exhibit many elements of central Arabian Sea climatology. Features observed include the annual variation in the intensity of the summer monsoon ridge in the Arabian Sea and the annual zonal oscillation of the ridge during pre- and post-monsoon seasons. The time coefficients for the first EOF amplitude indicate the presence of a QBO during the wet monsoon period only, as seen in the ocean upper layer thickness. The variability in the model upper layer thickness is a passive response to variability in the wind field, or more specifically to variability in the Findlater Jet. When the winds are stronger, they drive stronger currents in the ocean and have stronger curl fields associated with them, driving stronger Ekman pumping. They transport more moisture from the southern hemisphere toward the Indian subcontinent, and they also drive a greater evaporative heat flux beneath the Findlater Jet in the Arabian Sea. It has been suggested that variability in the heat content of the Arabian Sea drives variability in Indian monsoon rainfall. The results of this study suggest that the opposite is true, that the northern Arabian Sea responds passively to variability in the monsoon system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 195-218 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary The role of organized tropical storms and typhoons within the West Pacific-Indian Ocean dipole of low frequency activity is examined with the aid of INSAT satellite observations. Two Asian summer monsoon seasons-1984 and 1987-are analyzed in conjunction with a satellite derived convective index. The former year was noted as an above average Indian monsoon; the latter year as an extreme Indian monsoon failure. The analysis demonstrates that the dipole region is actually an organized collection of seven smaller scale high amplitude, low frequency centers which blur together to form the semblance of a dipole which had been originally identified in 2.5° resolution outgoing Longwave Radiation (OLR) data derived from NOAA satellite measurements. The centers are basically situated over oceanic regions in the eastern and western sectors of the dipole, although, an isolated high amplitude center is also found over central Tibet. Of considerable interest is that the locations of the seven centers, whereas not equivalent, are very similar for both the 1984 and 1987 seasonsinar. The analysis indicates that there are coherent phase relationships between the eastern sector of the dipole and the western sector, but that it is not a simple dipole-like process. Rather, the four high amplitude centers, within the western sector, all fall within a longitudinal channel in which the well known, northward propagating behavior of Monsoon convection anomalies serves to modulate the east-west phase lag along the meridional channel. The result is that the western paelfic phase lags the equatorial Indian Ocean center whereas it generally phase leads the more northern centers within the Arabian Sea and Bay of Bengal. In the two years studied here, there is little evidence of east-west propagation of anomalies between he two centers. The contribution of organized tropical storms and cyclones to the amplitude and phase characteristics of the high amplitude centers is irregular but important, particularly in the eastern sector of the dipole, where up to 50% of the variance can be explained by organized storms. It is also shown that the influence of storms on the phase propagation characteristics of convective anomalies is irregular but significant.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 219-250 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary In this paper we have studied the low frequency variability of the sensible and latent heat flux over the Indian monsoon area. We have used an atmospheric energy budget (vertical integrated heat sources and moisture sinks), as well as the similarity theory in order to compute the surface fluxes on a darly basis. Mainly, the three following data sets were used: the First GARP Global Experiment analyzed data, the TIROS-N outgoing longwave radiation data and the Monsoon Experiment precipitation data. Our three main findings are the following. First, the variability of the temperature and the specific humidity at the surface is more important over the land than over the sea on the intraseasonal time scale (30% over land, but 20% over sea). For the wind an energy peak appears clearly around 30–40 days. The surface fluxes show an uneven variance percentage field (10% to 40%); the energy peaks stretch from 10 to 40 days. Second, the wind has a significant influence on the surface fluxes, except at some locations exclusively over the land areas. Of the temperature and the specific humidity, the temperature is the one which influences the fluxes the most. (This influence may be very strong over land.) The specific humidity may have a significant influence, over the land and sea, at the same time. Thus, one cannot neglect the influence of temperature and specific humidity over land on the intraseasonal time scale. Third, we have found a close relation between the propagation of low frequency waves and the propagation of surface flux patterns. This may suggest a feedback mechanism which relates surface processes to the northward propagation of these waves over India.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 265-279 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary Using a General Circulation Model developed at FSU (FSUGCM), the role of the diabatic heating on the 30–60-day oscillation is investigated. To concentrate on the radiation and the moist convection processes, an aqua planet model is employed in this paper. We have obtained a 40-day oscillation with relatively lower frequency than other GCMs without strong heating in the lower troposphere. Unlike some GCMs and simple models, the convective area does not move eastward along with the oscillation. Adiabatic cooling due to the upward motion is mostly compensated by diabatic heating. This implies that Kelvin CISK theory might not explain our 40-day oscillation. We have also examined the impact of radiative heating on the low frequency oscillation. When we reduce the radiative cooling rate, our 40-day mode does not appear and a Kelvin CISK mode appears with a faster phase speed. The impact of the different convection schemes is also investigated. With an enhanced convection scheme, zonal wave number two with a 40-day period is generated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 281-292 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary The present paper discusses the build-up, the air mass transformation and the propagation of the Siberian high as well as its relations to the development of cold surges in East Asia. It has been found that (1) the genesis and development of the Siberian high result from the combined effects of the mass convergence at middle and upper-level and the radiative cooling; (2) the apparent transformation of the Siberian high over land is observed in winter, which is caused by the upward sensible heat and latent heat flux from the underlying surface; (3) the Siberian high and its attendant cold air outbreaks usually undergo a marked low-frequency, southward propagation with the period of 10–20 days; (4) activity of cold surge over the East China Sea and the South China Sea is closely related to the intensity of the Siberian high. The active cold surge occurs when the Siberian high is usually strong.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 251-263 
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary The Indian summer monsoon, one of the earth's most vigorous and energetic seasonally occurring weather events, influences the global atmospheric circulation. Its onset, duration, and intensity are governed by large- and meso-scale geophysical processes, such as surface solar heating and air-sea interactions. In this paper, using innovative combinations of satellite sensor data, we investigate some of these fundamental processes which are closely tied to clouds and control the monsoon system's evolution. The study, which focuses on the monsoon period of June, 1979, examines the low-frequency variability of clouds and their effects on air-sea processes through an analysis of the complex influence clouds play on the surface heat and water budgets. First, the effects of clouds on both the solar and longwave components of the surface radiation budget are assessed using a cloud radiative forcing parameter. While the effects of clouds on the long-wave irradiance act in a manner opposite to their effects on the shortwave irradiance, only a partial compensation is found to take place and the net effect results in a maximum cloud forcing of 60 Wm−2 in the southwestern Arabian Sea. Second, employing satellite-derived precipitation and evaporation estimates, the paper analyzes the net surface fresh water budget variability around the monsoon onset. This budget is important in that fresh water affects the upper ocean density distribution and, consequently, the thermohaline circulation. Two regions are found to dominate the analysis: the western Arabian Sea, where evaporation is dominant by more than 10 mm day−1, and the eastern Arabian Sea, where precipitation is dominant by more than 10 mm day−1. Thus, a strong zonal gradient of fresh water at the surface is established during the monsoon. The last topic investigated is the intraseasonal variability of convection as analyzed using a cloud parameter indicative of deep convection. Cloud oscillations of 30–50 days, associated with the different phases of the monsoon, are found to propagate northward in the eastern Indian Ocean and eastward in the Bay of Bengal. Our analysis not only supports the hypothesis that the 30–50-day oscillation is driven by deep convection but also, and more importantly, suggests that the ocean thermal forcing is modulated by 30–50-day oscillations through cloud-induced surface radiative forcing. Although the results presented are limited in scope and preliminary because of the diffculty in quantifying the accuracy of the parameters examined, they do demonstrate: 1) the role of clouds in modulating the surface heat and water budgets, 2) the advantage of using combinations of multi-sensor and multi-platform satellite observations to quantify interrelated surface heat/water budget processes, and 3) the potential to examine the intraseasonal variability of air-sea interaction processes associated with the monsoon, even though these processes are not directly measurable from space.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 98
    Digitale Medien
    Digitale Medien
    Springer
    AI & society 4 (1990), S. 39-50 
    ISSN: 1435-5655
    Schlagwort(e): Cognition ; Cognitive science ; Concepts ; Connectionism ; Consciousness ; Content
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract Cognitive psychology and cognitive science are concerned with a domain of cognition that is much broader than the realm of judgement, belief, and inference. The idea of states with semantic content is extended far beyond the space of reasons and justification. Within this broad class of states we should, however, differentiate between the states distinctive of thinking persons — centrally, beliefs, desires, and intentions — and other states. The idea of consciousness does not furnish a principle of demarcation. But the distinction between states whose content is conceptualized by the person whose states they are and states for which this is not so is more promising. This principle of demarcation contains the seeds of a problem for distributed connectionism. The article ends with some more general reflections about cognitive science.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 99
    Digitale Medien
    Digitale Medien
    Springer
    AI & society 4 (1990), S. 91-91 
    ISSN: 1435-5655
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 100
    Digitale Medien
    Digitale Medien
    Springer
    AI & society 4 (1990), S. 93-95 
    ISSN: 1435-5655
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...