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91.
92.
Jarle Aarstad Stig-Erik Jakobsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(5):290-300
ABSTRACTThe purpose of the article is to assess whether an entrepreneurial causation or effectuation logic is a function of geographical location in densely populated economic regions versus sparsely populated economic regions. A causation logic implies that the entrepreneur primarily focuses on a predefined goal and further aims to identify the means to reach that goal. By contrast, an effectuation logic implies that the entrepreneur to a larger extent focuses on the means at hand, which she or he aims at materialising into one or more goals that are not necessarily predefined. The empirical data for the study are based on an investigation and evaluation of Norwegian entrepreneurs in business incubation that are located in many different economic regions of the country. Multilevel regression analyses showed that geographical location in sparsely populated economic regions is associated with a causation logic, whereas a location in densely populated economic regions is associated with an effectuation logic. An implication of the article is that entrepreneurial stakeholders, such as policymakers, incubator managers, public and private partners, and entrepreneurs themselves should be aware of differences in causation and effectuation logics between entrepreneurs located in densely versus sparsely populated economic regions. 相似文献
93.
94.
Web-based Geographical Information Systems (GIS) are excellent tools within interdisciplinary and multi-national geoscience
projects to exchange and visualize project data. The web-based GIS presented in this paper was designed for the paleolimnological
project ‘High-resolution CONTINENTal paleoclimate record in Lake Baikal’ (CONTINENT) (Lake Baikal, Siberia, Russia) to allow
the interactive handling of spatial data. The GIS database combines project data (core positions, sample positions, thematic
maps) with auxiliary spatial data sets that were downloaded from freely available data sources on the world wide web. The
reliability of the external data was evaluated and suitable new spatial datasets were processed according to the scientific
questions of the project. GIS analysis of the data was used to assist studies on sediment provenance in Lake Baikal, or to
help answer questions such as whether the visualization of present-day vegetation distribution and pollen distribution supports
the conclusions derived from palynological analyses. The refined geodata are returned back to the scientific community by
using online data publication portals. Data were made citeable by assigning persistent identifiers (DOI) and were published
through the German National Library for Science and Technology (TIB Hannover, Hannover, Germany). 相似文献
95.
Werner Singer Ralph Latteck Luis Federico Millan Nick J. Mitchell Jens Fiedler 《Earth, Moon, and Planets》2008,102(1-4):403-409
Many meteoroids burn up between about 120 km and 70 km, deposit metals and dust and form ionized trails which are detected
by radars. Model studies about the influence of neutral or positively charged background dust on the ambipolar diffusion indicate
that significant smaller decay times should be observed for weak meteor echoes compared to strong meteor echoes which can
affect the estimation of temperatures. The variation of meteor decay times in dependence on echo strength, height, and season
was studied using radar observations at 69° N, 22° S, and 67° S. Significantly reduced decay times were found for weak echoes
below about 88 km at low latitudes throughout the year, and at high latitudes with the exception of summer. In summer at high
latitudes, decreasing decay times of weak and strong meteors are observed at altitudes below about 85 km during the appearance
of noctilucent clouds. The impact of reduced decay times on the estimation of neutral temperatures from decay times is discussed. 相似文献
96.
Erika?Kaufmann Günter?Kargl Norbert?I.?K?mleEmail author Manfred?Steller Johann?Hasiba Florian?Tatschl Stefan?Ulamec Jens?Biele Marc?Engelhardt Jens?Romstedt 《Earth, Moon, and Planets》2009,105(1):11-29
One possibility to explore the subsurface layers of icy bodies is to use a probe with a “hot tip", which is able to penetrate
ice layers by melting. Such probes have been built and used in the past for the exploration of terrestrial polar ice sheets
and may also become useful tools to explore other icy layers in the Solar System. Examples for such layers are the polar areas
of Mars or the icy crust of Jupiter’s moon Europa. However, while on Earth a heated probe launched into an ice sheet always
causes melting with subsequent refreezing, the behaviour of such a probe in a low pressure environment is quite different.
We report on the results of some experiments with a simple “melting probe" prototype with two different kinds of hot tips
in a vacuum environment. For one of the tips the probe moved into two types of ice samples: (i) compact water ice and (ii)
porous water ice with a snow (firn) like texture. It was also found that the penetration behaviour was basically different
for the two sample types even when the same kind of tip was used. While in the porous sample the ice was only subliming, the
phase changes occurring during the interaction of the tip with the compact ice are much more complex. Here alternating phases
of melting and sublimation occur. The absence of the liquid phase has severe consequences on the performance of a “melting
probe" under vacuum conditions: In this environment we find a high thermal resistance between the probe surface and the underlying
ice. Therefore, only a low percentage of the heat that is generated in the tip is used to melt or sublime the ice, the bulk
of the power is transferred towards the rear end of the probe. This is particularly a problem in the initial phases of an
ice penetration experiment, when the probe has not yet penetrated the ice over its whole length. In the compact ice sample,
phases could be observed, where a high enough gas pressure had built up locally underneath the probe, so that melting becomes
possible. Only during these melting periods the thermal contact between the probe and the ice is good and in consequence the
melting probe works effectively. 相似文献
97.
T-matrix approach to shale acoustics 总被引:2,自引:0,他引:2
Morten Jakobsen John A. Hudson Tor Arne Johansen 《Geophysical Journal International》2003,154(2):533-558
98.
Wind-induced drift of objects at sea: The leeway field method 总被引:3,自引:0,他引:3
Øyvind Breivik Arthur A. AllenChristophe Maisondieu Jens Christian Roth 《Applied Ocean Research》2011,33(2):100-109
A method for conducting leeway field experiments to establish the drift properties of small objects (0.1-25 m) is described. The objective is to define a standardized and unambiguous procedure for condensing the drift properties down to a set of coefficients that may be incorporated into existing stochastic trajectory forecast models for drifting objects of concern to search and rescue operations and other activities involving vessels lost at sea such as containers with hazardous material.An operational definition of the slip or wind and wave-induced motion of a drifting object relative to the ambient current is proposed. This definition taken together with a strict adherence to a 10 m wind speed allows us to refer unambiguously to the leeway of a drifting object. We recommend that all objects if possible be studied using what we term the direct method, where the object’s leeway is studied directly using an attached current meter.We establish a minimum set of parameters that should be estimated for a drifting object for it to be included in the operational forecast models used for prediction of search areas for drifting objects.We divide drifting objects into four categories, depending on their size. For the smaller objects (less than 0.5 m), an indirect method of measuring the object’s motion relative to the ambient current must be used. For larger objects, direct measurement of the motion through the near-surface water masses is strongly recommended. Larger objects are categorized according to the ability to attach current meters and wind monitoring systems to them.The leeway field method proposed here is illustrated with results from field work where three objects were studied in their distress configuration; a 1:3.3 sized model of a 40-foot Shipping container, a World War II mine and a 220 l (55-gallon) oil drum. 相似文献
99.
Louise Schlüter Peter HenriksenTorkel Gissel Nielsen Hans H. Jakobsen 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(5):546-556
Phytoplankton composition and biomass was investigated across the southern Indian Ocean. Phytoplankton composition was determined from pigment analysis with subsequent calculations of group contributions to total chlorophyll a (Chl a) using CHEMTAX and, in addition, by examination in the microscope. The different plankton communities detected reflected the different water masses along a transect from Cape Town, South Africa, to Broome, Australia. The first station was influenced by the Agulhas Current with a very deep mixed surface layer. Based on pigment analysis this station was dominated by haptophytes, pelagophytes, cyanobacteria, and prasinophytes. Sub-Antarctic waters of the Southern Ocean were encountered at the next station, where new nutrients were intruded to the surface layer and the total Chl a concentration reached high concentrations of 1.7 ??g Chl a L−1 with increased proportions of diatoms and dinoflagellates. The third station was also influenced by Southern Ocean waters, but located in a transition area on the boundary to subtropical water. Prochlorophytes appeared in the samples and Chl a was low, i.e., 0.3 ??g L−1 in the surface with prevalence of haptophytes, pelagophytes, and cyanobacteria. The next two stations were located in the subtropical gyre with little mixing and general oligotrophic conditions where prochlorophytes, haptophytes and pelagophytes dominated. The last two stations were located in tropical waters influenced by down-welling of the Leeuwin Current and particularly prochlorophytes dominated at these two stations, but also pelagophytes, haptophytes and cyanobacteria were abundant. Haptophytes Type 6 (sensuZapata et al., 2004), most likely Emiliania huxleyi, and pelagophytes were the dominating eucaryotes in the southern Indian Ocean. Prochlorophytes dominated in the subtrophic and oligotrophic eastern Indian Ocean where Chl a was low, i.e., 0.043-0.086 ??g total Chl a L−1 in the surface, and up to 0.4 ??g Chl a L−1 at deep Chl a maximum. From the pigment analyses it was found that the dinoflagellates of unknown trophy enumerated in the microscope at the oligotrophic stations were possibly heterotrophic or mixotrophic. Presence of zeaxanthin containing heterotrophic bacteria may have increased the abundance of cyanobacteria determined by CHEMTAX. 相似文献
100.
Lars Chresten Lund-Hansen Morten Pejrup Jens Valeur Anders Jensen 《Estuarine, Coastal and Shelf Science》1994,38(6)
Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m-2 day-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m-2 day-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (Ks), based on the measured GSR is given. The expression has been used for modelling of Ks at the different trap levels above the bed. High values (≈42 cm2 s-1) of Ks were obtained at the upper traps, whereas low values (≈2 cm2 s-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m Ks was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (Km) derived from the wind energy transfer to the water, giving an average β of 0·5 for Ks =βKm. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of Ks and Km . 相似文献