Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 17
items per page: 25 50 75
Sort by:

Abstract

The main current system occurring at Admiralty Bay is a two-phase flow system typical for fiords. Tidal waters are a decisive factor in determining the movements of water, whereas surface circulation is determined by winds, when the wind speed is higher than 4 m/s. The maximum values and directions of the surface drift current depend exclusively upon the actually prevailing wind field. The current speeds may reach the order of magnitude up to 100 cm/s. This flow lies above the two-phase system of currents generated by tides. The value of the currents produced by tides may reach up to ~50 cm/s. The direction of the current flow is not always in line with the corresponding of the tide. This is due probably to the irregularity and asymmetry of the tide and great inertis of the water masses.
Go to article

Abstract

Despite many years of research, we have yet to discover all the myriad ways various components of the climate interact. For instance, it looks likely that the circulation of oceanic waters has a much broader impact than previously thought.
Go to article

Abstract

The article presents the biometeorological impact of thermal and humidity conditions on the human body in the Hornsund area in the southern Spitsbergen, Svalbard. This was determined based on diurnal air temperature range, the day-to-day variation in average diurnal air temperature and the average diurnal relative humidity. The temporal variability of thermal and humidity biometeorological stimuli in Hornsund was examined for the period 01.11.1978–31.12.2017. A lessening of biometeorological impact was found in the southern Spitsbergen region, including a statistically significant negative trend in strongly- and severely-felt stimuli (according to diurnal air temperature range), and in significant and severe stimuli (according to day-to-day variation in average diurnal air temperature). A non-significant positive trend was observed in the number of days of relative humidity with humid and very humid air. To analyse the spatial variability of the stimuli around the Hornsund fjord, data were used from seven year-round measuring stations for the period 01.07.2014–31.06.2015. The most unfavourable conditions were found on the Hans Glacier, on the summit of Fugleberget and inside the fjord. The paper presents the role of atmospheric circulation on thermal and humidity stimuli. In the Hornsund region, the highest probability of unfavourable sensible temperatures for humans occurring during the year was mostly in winter and early spring. This was related to the advection of air masses from the north-east sector, regardless of baric regime type. It was found that very humid air (> 85%) flowed over Hornsund for practically the entire year from the S–SW as part of both cyclonic and anti-cyclonic systems.
Go to article

Abstract

Meteorological and biometeorological conditions during the warm seasons (June– September) of 1979–2008 are described for the Hornsund area, Spitsbergen. The measure− ments were taken at four sites: at Hornsund, at the Hans Glacier (at its equilibrium line and in the firn section) and at the summit of Fugleberget. The variation of meteorological and biometeorological conditions was analysed in relation to altitude, distance from the sea and the ground type. In warm seasons, the air temperature at Hornsund was 2.2°C higher on aver− age than at the Hans Glacier (central section) and by 2.8°C than at the Hans Glacier (firn sec− tion) and at Fugleberget. The average wind speed recorded at Hornsund was higher (0.6ms−1) than at the Hans Glacier and lower (0.9ms−1) than at Fugleberget. Four biometeorological in− dices were used: wind chill index (WCI), predicted insulation of clothing (Iclp), cooling power (H) and subjective temperature index (STI). The strongest thermal stimuli were ob− served on the Hans Glacier and in the upper mountain areas. The study has found a consider− able degree of spatial variation between the meteorological elements investigated and the biometeorological indices in the Hornsund area. The impact of atmospheric circulation on meteorological elements and biometeorological indices is also presented. The mildest bio− meteorological conditions of the warm season found at Hornsund were associated with air masses arriving from the southwest and west.
Go to article

Abstract

Certain chemical parameters such pH, specific electric conductivity (SpC) and concentrations of chloride ions (Cl-) have been analysed in samples of precipitation collected close to the Polish Polar Station at Hornsund (PPS), SW Spitsbergen. On the basis of seasonal data from years 1993-1994 and 1998-1999, some differences are apparent from the two sets. There is also a marked difference in the seasonal results, especially with respects to pH values; summer precipitation (pH of which can be as low as 3.78) is much more acidic than winter. This was particularly notable in respect of the summer of 1993, and was presumably the result of a relatively unusual atmospheric circulation and a high influx of airborne contaminants from Europe. The wide variation in specific electrical conductivity measurements is considered to be related to variations in wind direction and speed. That precipitation the highest total dissolved salts, of 11.7 mm w.e. (water equivalent), (November 1993), provided 10.7 g of salt per square metre of tundra near the Polish Polar Station. The proximity of the sea, consequently the development of marine aerosols, largely determines the chemical nature of the precipitation. Thus, variations in the chloride ion concentrations during the study periods more or less reflect the variations in the marine aerosol influences on the nature of the polluted precipitation. An analysis of the atmospheric circulation reveals that the most acid precipitation occurs most frequently in the C-8 type of circulation (cyclonic S + SW) and also, less so, for type C-3 (anticyclonic S + SW).
Go to article

Abstract

In this study, weather conditions causing warm waves in north−western Spits − bergen, exemplified by Ny− Å lesund station, were analyzed. Between 1981 and 2010, 536 days with the maximum temperature exceeding 8.3 ° C (the value of 95 percentile) were selected. 37 warm waves, which altogether lasted 268 days, were identified. A typical feature of pressure pattern causing warm waves was the appearance of positive anomalies of both the sea level pressure and the height of isobaric surface 500 hPa in the Euro−Atlantic sector of the Arctic. This indicates a presence of high−pressure systems in this region. Extremely warm days appeared more often with the circulation from the eastern than the western sector. Longer and warmer heat waves occurring in the last decade of the analyzed period may be considered as a sign of climate warming, which has a significant impact on environment, i.e. reduction in area and thickness of glaciers, reduction of permafrost and snow cover, changes in biodiversity, etc . The increase in the air temperature and more frequent occurrence of heat waves may encourage development of tourism in polar areas, potentially causing further changes in the environment.
Go to article

Abstract

This paper presents the spatial distribution of changes in the value of the predicted insulation index of clothing (Iclp) in the Norwegian Arctic for the period 1971-2000. For this study, data from six meteorological stations were used: Ny-Alesund, Svalbard Airport, Hornsund, Hopen, Bjřrnřya and Jan Mayen. The impact on the atmospheric circulation to the course of the Iclp index was analyzed using the catalogue of circulation types by Niedźwiedź (1993, 2002), the circulation index according to Murray and Lewis (1966) modified by Niedźwiedź (2001), the North Atlantic Oscillation Index according to Luterbacher et al. (1999, 2002), and the Arctic Oscillation Index (Thompson and Wallace 1998).
Go to article

Abstract

This article aims to analyse the influence of weather types on meteorological conditions in Petuniabukta (Svalbard) during July and August of 2016. The paper analyses the daily courses of air temperature and humidity at four measurement points located on the west bank of Petuniabukta near Adam Mickiewicz University Polar Station during two different types of weather conditions: (i) cloudy and windy, (ii) calm and clear. These weather types, distinguished on the basis of wind speed and cloudiness, allowed for the creation of composite maps of the synoptic situation (SLP and geopotential height of 500 hPa distribution) and its anomalies. In the study area, the air temperature range in windy and cloudy weather conditions was larger (-10°C to 15°C) than that in sunny and calm weather (0°C to 15°C), which contrasts the range of humidity values. The diurnal cycle of meteorological elements in sunny and calm days is strongly related to the sun elevation angle. In the above-mentioned weather types, the air temperature was higher by several degrees (median 5°C to 8°C) than on windy and cloudy days (median about 0°C to 6°C) at each measurement point. On days with sunny and calm weather, a smaller vertical temperature gradient of air is observed (for sunny and calm days 0.63°C and for windy weather 0.8°C).
Go to article

Abstract

In this study, atlases of wave characteristics and wave energy for the Barents Sea have been generated for the years from 1996 to 2015 based on ERA-Interim datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF). The wave power resources in the Barents Sea can be exploited with sea ice extent declining in recent years. The entire Barents Sea has been divided into multi-year sea ice zones, seasonal sea ice zones and open water zones according to the 20-year averaged sea ice concentration. In the entire domain, the spatial distributions of the annual averaged and mean monthly significant wave heights and wave energy flux are presented. For the open water zones, 15 points have been selected at different locations so as to derive and study the wave energy roses and the inter-annual wave power variation. Moreover, the correlations between the wave energy period and the significant wave height are shown in the energy and scatter diagrams. The maximum wave power occurs in the winter in the western parts of the Barents Sea with more than 60kW/m. The wave energy can therefore be exploited in the open water zones.
Go to article

Abstract

This paper provides an overview of the results of research on changes in ground temperature down to 50 cm depth, on the Kaffiøyra Plain, Spitsbergen in the summer seasons. To achieve this, measurement data were analysed from three different ecotopes (CALM Site P2A, P2B and P2C) – a beach, a moraine and tundra – collected during 22 polar expeditions between 1975 and 2014. To ensure comparability, data sets for the common period from 21 July to 31 August (referred to as the “summer season” further in the text) were analysed. The greatest influence on temperature across the investigated ground layers comes from air temperature (correlation coefficients ranging from 0.61 to 0.84). For the purpose of the analysis of the changes in ground temperature in the years 1975–2014, missing data for certain summer seasons were reconstructed on the basis of similar data from a meteorological station at Ny-Ålesund. The ground temperature at the Beach site demonstrated a statistically−significant growing trend: at depths from 1 to 10 cm the temperature increased by 0.27–0.28 ° C per decade, and from 20 to 50 cm by as much as 0.30 ° C per decade. On the Kaffiøyra Plain, the North Atlantic Oscillation (NAO) has a greater influence on the ground an d air temperature than the Arctic Oscillation (AO).
Go to article

Abstract

The coreless winters ( i.e. not having a cold core) were distinguished in four stations within the European sector of the Arctic. Anomalies of the frequency of the Niedźwiedź’s (2011) circulation types were calculated separately for the mid−winter warm months and for cold months preceding and following the warm−spells. Furthermore, composite and anomaly maps of the sea level pressure as s well as anomaly maps of the air temperature at 850 gpm (geopotential meters) were constructed separately for the mid−winter warm events and for the cold months before and after warming. Different pressure patterns were recognized among the days of mid−winter warm spells, using the clustering method. The occurrence of coreless winters in the study area seems to be highly controlled by the position, extension and intensity of large scale atmospheric systems, mainly the Icelandic Low. When the Low spreads to the east and its centre locates over the Barents Sea the inflow of air masses from the northern quadrant is observed over the North Atlantic. This brings cold air of Arctic origin to the islands and causes an essential drop in the air temperature. Such situation takes place during the cold months preceding and following the warm mid−winter events. During the warm spells the Icelandic Low gets deeper−than−usual and it is pushed to the northeast, which contributes to the air inflow from the southern quadrant.
Go to article

Abstract

We describe the development of a new type of heat exchanger. This heat exchanger operates using reverse thermosiphon action and consists of a self-acting and self-controlled liquid circulation loop with heat transfer in a downward direction, opposite to the direction of natural convection. This process moves a heat-carrying hot liquid downwards with the help of local heat transferred through the loop. This flow loop is partly filled with liquid and the upper part of the loop contains vapour from the liquid heat-carrier. The pressure difference in the saturated vapour is used to move the heated liquid downwards. The principles of action and the possibility of developing such a device using laboratory experimental methods are presented.
Go to article

Abstract

αB-crystallin is a member of a small family of thermal shock proteins that protects cells from stress. Because of lack of its expression in peripheral blood leukocytes, it was proposed as a molecular marker of circulating tumor cells in canine mammary gland tumors. The aim of the present study was to determine if αB-crystallin shows stability of expression, what is the requirement for this type of marker. It was also assessed whether there is co-expression of αB-crystallin with the basal marker, cytokeratin 17. For this purpose, samples of various types of canine mammary gland tumors of epithelial origin, were selected. Using RT-qPCR, we have found αB-crystallin and cytokeratin 17 co-expression in benign and malignant canine mammary gland tumors. It has been demonstrated that the expression of αB-crystallin in tested neoplastic samples is not stable in comparison to the control group. Furthermore αB-crystallin overor down- expression was associated witch the same cytokeratin 17 pattern. αB-crystallin can be a marker of circulating tumor cells in the bloodstream, but for cancers in which basal marker expression occurs and thus not universal for all cancers originating from the mammary gland tissue.
Go to article

Abstract

The influence of external factors, temperature and flow velocity on the corrosion processes St3 in model solutions petrochemical plant recycled water with high salinity and hardness without open systems and in the presence of the inhibiting composition. It was found that an increase in temperature leads to a linear increase in corrosion rates, and the change in circulating water flow rate leads to the extreme nature of corrosion processes; optimal conditions are determined. Recommended use of cathodic inhibitors or mixed type inhibitor, in particular, the composition "SVOD-BI" (means for controlling the biological corrosion), which can significantly reduce the effect of temperature and flow on the corrosion rate St3, promotes the growth and strengthening of the oxide film in the presence of oxygen, increases the degree of protection of steel and preventing the formation of at its surface carbonate-calcium deposits.
Go to article

Abstract

Nowadays, the most popular production method for manufacturing high quality casts of aluminium alloys is the hot and cold chamber die casting. Die casts made of hypereutectoid silumin Silafont 36 AlSi9Mg are used for construction elements in the automotive industry. The influence of the metal input and circulating scrap proportion on porosity and mechanical properties of the cast has been examined and the results have been shown in this article. A little porosity in samples has not influenced the details strength and the addition of the circulating scrap has contributed to the growth of the maximum tensile force. Introducing 80% of the circulating scrap has caused great porosity which led to reduce the strength of the detail. The proportion of 40% of the metal input and 60% of the circulating scrap is a configuration safe for the details quality in terms of porosity and mechanical strength.
Go to article

Abstract

In order to solve the problem of traditional carrier phase-shift modulation with multiple ratios or PI controllers and cumbersome tuning parameters, this paper uses improved carrier phase-shift modulation. The total turn-on number of sub-modules each bridge arm is determined by comparing the sinusoidal modulated wave with the triangular carrier, and then the control signal is generated according to the capacitance voltage sorting result and the bridge armcurrent polarity. However, this modulation method uses a sorting method that causes the insulated gate bipolar transistor (IGBT) have an excessively high switching frequency. Therefore, a sorting trigger condition that can effectively reduce the switching frequency is used. The method determines whether to reorder based on the error between the voltage average and the actual value. For the circulation problem, the double-frequency negative sequence component is extracted by rotating coordinate transformation, and it is suppressed by PI control. A 21-level MMC model was built in MATLAB/simulink to analyze the sub-module capacitor voltage fluctuation, output current, voltage distortion rate and bridge arm circulation. It is verified that the modulation method can combine the sorting algorithm and circulation suppression method at the same time, and has better voltage equalization and circulation suppression effects.
Go to article

This page uses 'cookies'. Learn more