On oscillatory motion in the problem of three bodies     

Donald G. Saari 《Celestial Mechanics and Dynamical Astronomy》1970,1(3-4):343-346

In the case of oscillatory motion in the problem of three bodies it is shown that ast the mutual distances between particles cannot separate faster thanCt ^2/3 whereC is some positive constant. As bounding functions of time exist for the other classifications of motion in the three body problem, it follows in general that the mutual distances between particles is 0(t) ast.  相似文献   

Recordings and occurrence of geomagnetically induced currents in the Finnish natural gas pipeline network     

Antti Pulkkinen  Ari Viljanen  Kari Pajunp  Risto Pirjola 《Journal of Applied Geophysics》2001,48(4)

A project implemented to study the effects of space weather on the Finnish natural gas pipeline was started in August 1998. The aims of the project were (1) to derive a model for calculating geomagnetically induced currents (GIC) and pipe-to-soil (P/S) voltages in the Finnish natural gas pipeline, (2) to perform measurements of GIC and P/S voltages in the pipeline and (3) to derive statistical predictions for the occurrences of GIC and P/S voltages at different locations in the pipeline network.GIC and P/S voltage were recorded at a compressor station. The GIC measurement was made with two magnetometers, one right above the pipe, and another at the Nurmijärvi Geophysical Observatory about 30 km southwest. The largest GIC since November 1998 has been 30 A. The P/S voltage recording was stopped in May 1999, but GIC is still measured.GIC statistics were derived based on the recordings of the geomagnetic field at Nurmijärvi. The geoelectric field was calculated by using the plane wave model. This field was input to the general pipeline model resulting in the distribution of currents and P/S voltages at selected points in the pipeline. As could be expected, the largest P/S voltage variations occur at the ends of the pipeline network, while the largest GIC flow in the middle parts.  相似文献   

Geochemistry and mineralogy of platinum-group elements at Hartley Platinum Mine,Zimbabwe     

Thomas?OberthürEmail author  Thorolf?W.?Weiser  Lothar?Gast  Kari?Kojonen 《Mineralium Deposita》2003,38(3):327-343

The behaviour of platinum-group elements (PGE) in the exogenic cycle was examined in profiles of oxidized Main Sulfide Zone (MSZ) ores, in which the general metal distribution patterns of the pristine MSZ are grossly preserved. However, at similar Pt grades, significant proportions of Pd have been lost from the system. This indicates that Pd is more mobile than Pt and is dispersed in the supergene environment. Sperrylite and cooperite/braggite are stable in the oxidized MSZ. In contrast, the (Pt,Pd)-bismuthotellurides, common in pristine MSZ ores, have disintegrated, and ill-defined (Pt,Pd)-oxides or (Pt,Pd)-hydroxides have formed. The assemblage of detrital PGM present in the Makwiro River close to the Hartley Platinum Mine indicates further mineralogical changes. Sperrylite largely remains stable whereas most cooperite/braggite grains have been partly altered or completely destroyed. Grains of Pt-Fe alloy are ubiquitous in the alluvial sediments. Most likely, these grains are neo-formations that formed either from pre-existing, unstable PGM or via a solution stage under low-temperature conditions.  相似文献   

The investigations of aerosol particle formation in urban background area of Helsinki     

Kaarle Hmeri  Markku Kulmala  Pasi Aalto  Kirsti Leszczynski  Reijo Visuri  Kari Hmekoski 《Atmospheric Research》1996,41(3-4)

In this study the possible conditions for new aerosol particle formation in a background area of Helsinki have been analysed. The measurements of aerosol particle size distribution, main gaseous pollutant compounds, UV spectra and meteorological parameters were performed during April–May 1993. The main interest was concentrated on the investigations of photochemical OH radical formation, the oxidation of gas phase SO₂ to H₂SO₄ and the formation of H₂SO₄---H₂O aerosol particles. The measurements were analysed using a model for OH radical formation and aerosol dynamics. The analysis of aerosol size distributions was carried out using positive matrix factorization. The main conclusion is that based on our model analysis no evidence of new particle formation in the vicinity of the measurement station was found. However, the high concentrations of aerosol particles in the ultrafine size range indicate that some other particle formation pathways are to be considered.  相似文献   

Microearthquakes and seismotectonic analysis for a nuclear plant area in southeastern Finland     

Jouni Saari 《Engineering Geology》1991,31(3-4):231-247

Microearthquake observations are used to study the local seismicity and seismotectonics in the Precambrian Rapakivi Granite, in the Loviisa area, SE Fi around the nuclear power plant in Loviisa, is limited to a radius of 100 km.

The results from a local microearthquake network in the Loviisa area showed that, during 6 years of measuring there were 29 micro- and ultra-microearth 0.1–1.2) in the area. The events identify active faults in the area.

The estimated value of the peak slip is an important parameter connecting microearthquakes to geodynamical processes. The peak slip gives an approximat and aseismic movement on a certain fault and thus an indication of ongoing tectonic processes. The movements on the active fault may continue for thous

Source parameters were computed for a simple circular source model, giving peak slips less than 0.25 mm, stress drop values less than 2 × 10⁵N/m² and source radii generally less than 50 m. The earthquakes occurred at depths of less than 5 km.  相似文献   

The tilt effect for Saturn's rings     

Larry W. Esposito  Kari Lumme 《Icarus》1977,31(1):157-167

Multiple-scattering computations are carried out to explain the variation of the observed brightness of the A and B rings of Saturn with declination of the Earth and Sun. These computations are performed by a doubling scheme for a homogeneous plane-parallel scattering medium. We test a range of choices for the phase function, albedo for single scattering, and optical depth of both the rings. Isotropic scattering and several other simple phase functions are ruled out, and we find that the phase function must be moderately peaked in both the forward and backward directions. The tilt effect can be explained by multiple scattering in a homogeneous layer, but, for ring B, this requires a single-scattering albedo in excess of 0.8. The brightest part of ring B must have an optical depth greater than 0.9. We find that the tilt effect for ring A can be reproduced by particles having the same properties as those in ring B with the optical depth for the A ring in the range 0.4 to 0.6.  相似文献   

Particle Size Distribution and Gas-Particle Partition of Polycyclic Aromatic Hydrocarbons in Helsinki Urban Area     

Masahiko Shimmo  Karri Saarnio  Pasi Aalto  Kari Hartonen  Tuulia Hyötyläinen  Markku Kulmala  Marja-Liisa Riekkola 《Journal of Atmospheric Chemistry》2004,47(3):223-241

Ambient concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in Helsinki (Finland). Particle mass size distributions were obtained with a cascade impactor (12 stages) with glass fibre filters as substrates. Simultaneously with the impactor measurements, particulate and gaseous PAHs were collected on a quartz filter and XAD-2 adsorbent, respectively, for evaluation of gas-partition coefficients. Samples were analysed for PAHs by on-line coupled supercritical fluid extraction — liquid chromatography — gas chromatography — mass spectrometry. The impactor results showed that most of the PAHs in Helsinki urban area were concentrated in fine particles (<2.5 μm diameter) with unimode peak at about 1 μm. The results were comparable with the number distribution measured with a differential mobility particle sizer. Total amounts of PAHs (gas + particle) varied from 15 (acenaphthylene) to 1990 (fluorene) pg/m³. The PAHs lighter than 202 amu (pyrene and fluoranthene) were exclusively in gas phase, whereas those heavier than 202 amu were mostly associated with particles. A plot of the partition coefficients (logKp) versus the temperature dependent sub-cooled vapour pressures (logp _L ⁰ ) showed a gradient of −0.66, which deviated from equilibrium state (gradient = −1).  相似文献   

Structure of the crust and uppermost mantle beneath southern Finland revealed by analysis of local events registered by the SVEKALAPKO seismic array     

SVEKALAPKO Seismic Tomography Working Group  Jukka Yliniemi  Elena Kozlovskaya  Sven-Erik Hjelt  Kari Komminaho  Anton Ushakov 《Tectonophysics》2004,394(1-2):41-67

In 1998–1999, a large-scale seismic array was deployed in Finland as a part of the EUROPROBE/SVEKALAPKO subproject, involving 14 European universities and research institutes. The objective of the project was to map the deep lithosphere structure and thickness beneath the Fennoscandian Shield by means of teleseismic events. In addition, about 580 local seismic events were registered during the data acquisition period. Among them, only eight local earthquakes were recorded, the rest being quarry blasts from mining sites in Russia, Finland, Estonia and Sweden. In this study, we present the analysis of the seismic wave field from the strongest local events registered by the majority of the stations of the SVEcofennian–KArelian–LAPland–KOla Transect (SVEKALAPKO) array with the aim of mapping the structure of the upper mantle beneath the array. For this purpose, we selected the events corresponding to a single source type and compared these recordings with those from wide-angle reflection and refraction experiments in the area to identify the regional phases. The record sections of selected events demonstrate strong reflections (PmP) from the Moho boundary. The refracted Pn phases can be seen as first arrivals at distances of about 200–400 km from the source. At offsets of about 400–800 km, phases reflected from inhomogeneities in the uppermost mantle (P1) and double reflections from the Moho boundary (PmPPmP) were recorded.Results from 2D forward ray trace modeling of reflected and refracted P-waves along four profile swathes from SVEKALAPKO stations demonstrate that the mantle reflections originate from two different groups of boundaries beneath the array: one group of phases arrive from subhorizontal and gently dipping reflectors below the Moho boundary at a depth of 70–90 km, while the other group are phases originating from a depth of 100 to 130 km. Based on the irregular character of the first group of reflections, their different spatial orientation and correlation with the Moho offsets, we interpret the boundaries of this group as relicts of ancient subduction and collision processes. The second group of reflections can be explained by a transition from mechanically strong to mechanically weak lithosphere.  相似文献   

Holocene floristic diversity and richness in northeast Norway revealed by sedimentary ancient DNA (sedaDNA) and pollen     

Charlotte L. Clarke  Mary E. Edwards  Antony G. Brown  Ludovic Gielly  Youri Lammers  Peter D. Heintzman  Francisco Javier Ancin‐Murguzur  Kari‐Anne Brthen  Tomasz Goslar  Inger G. Alsos 《Boreas: An International Journal of Quaternary Research》2019,48(2):299-316

We present a Holocene record of floristic diversity and environmental change for the central Varanger Peninsula, Finnmark, based on ancient DNA extracted from the sediments of a small lake (sedaDNA). The record covers the period c. 10 700 to 3300 cal. a BP and is complemented by pollen data. Measures of species richness, sample evenness and beta diversity were calculated based on sedaDNA sampling intervals and 1000‐year time windows. We identified 101 vascular plant and 17 bryophyte taxa, a high proportion (86%) of which are still growing within the region today. The high species richness (>60 taxa) observed in the Early Holocene, including representatives from all important plant functional groups, shows that modern shrub‐tundra communities, and much of their species complement, were in place as early as c. 10 700 cal. a BP. We infer that postglacial colonization of the area occurred prior to the full Holocene, during the Pleistocene‐Holocene transition, Younger Dryas stadial or earlier. Abundant DNA of the extra‐limital aquatic plant Callitriche hermaphroditica suggests it expanded its range northward between c. 10 200 and 9600 cal. a BP, when summers were warmer than present. High values of Pinus DNA occur throughout the record, but we cannot say with certainty if they represent prior local presence; however, pollen influx values >500 grains cm^?2 a^?1 between c. 8000 and 7300 cal. a BP strongly suggest the presence of pine woodland during this period. As the site lies beyond the modern tree limit of pine, it is likely that this expansion also reflects a response to warmer Early Holocene summers.  相似文献   

Kimberlite emplacement and mantle sampling through time at A154N kimberlite volcano,Diavik Diamond Mine: lessons from the deep     

Moss  Stephen W.  Kobussen  Alan  Powell  William  Pollock  Kari 《Mineralogy and Petrology》2018,112(2):397-410

The Diavik Diamond Mine in the NWT of Canada has produced in excess of 100 million carats from 3 kimberlite pipes since mining commenced in 2002. Here, we present new findings from deep (>400 m below surface) mining, sampling and drilling work in the A154N kimberlite volcano that require a revision of previous geological and emplacement models and provide a window into how the sub-continental lithospheric mantle (SCLM) below Diavik was sampled by kimberlite magmas through time. Updated internal geological models feature two volcanic packages interpreted to represent two successive cycles of explosive eruption followed by active and passive sedimentation from a presumed crater-rim, both preceded and followed by intrusions of coherent kimberlite. Contact relationships apparent among the geological units allow for a sequential organization of as many as five temporally-discrete emplacement events. Representative populations of mantle minerals extracted from geological units corresponding to four of the emplacement events at A154N are analyzed for major and trace elements, and provide insights into the whether or not kimberlites randomly sample from the mantle. Two independent geothermometers using clinopyroxene and garnet data indicate similar source depths for clinopyroxenes and G9 garnets (130–160 km), and suggest deeper sampling with time for both clinopyroxene and garnets. Harzburgite is limited to 110–160 km, and appears more prevalent in early, low-volume events. Variable ratios of garnet parageneses from the same depth horizons suggest random sampling by passing magmas, but deeper garnet sampling through time suggests early preferential sampling of shallow/depleted SCLM. Evaluations of Ti, Zr, Y and Ga over the range of estimated depths support models of the SCLM underlying the central Slave terrane.

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