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Number of results: 155
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Abstract

On the basis of 35 one-hour series of the measurement of the wind velocity, read out every two minutes, the wind structure at the Arctowski Station, situated on Admiralty Bay, King George Island, was analysed. Very strong turbulence was found with air flow directions from over the area of the Island (S, SW. W and NW) and laminarity with directions from SE, E, NE and partly N, i.e. when the air flows from Admiralty Bay or from over the open waters of Bransfield Strait. The qustiness coefficient, the relationship between the maximum and mean velocities and the intensity of turbulence were determined for the two flow types. Two extremely different cases, in terms of flow character, were considered, by determining for them the distributions of instantaneous velocities and those of oscillations.
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Abstract

Helical coil heat exchangers are widely used in a variety of industry applications such as refrigeration systems, process plants and heat recovery. In this study, the effect of Reynolds number and the operating temperature on heat transfer coefficients and pressure drop for laminar flow conditions was investigated. Experiments were carried out in a shell and tube heat exchanger with a copper coiled pipe (4 mm ID, length of 1.7 m and coil pitch of 7.5 mm) in the temperature range from 243 to 273 K. Air – propan-2-ol vapor mixture and coolant (methylsilicone oil) flowed inside and around the coil, respectively. The fluid flow in the shell-side was kept constant, while in the coil it was varied from 6.6 to 26.6 m/s (the Reynolds number below the critical value of 7600). Results showed that the helical pipe provided higher heat transfer performance than a straight pipe with the same dimensions. The convective coefficients were determined using theWilson method. The values for the coiled pipe were in the range of 3–40 W/m2 ·K. They increased with increasing the gas flow rate and decreasing the coolant temperature.
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Abstract

Over the South American sector of the Antarctic Ocean intensive cyclonal activity occurred in turn with meridional circulation, which was a more common feature of winter 1986 than it usually is. At the Arctowski Station strong temperature oscillations were observed during the austral winter from May to October. In the end of July the lowest temperature of this winter, — 32.3°C, was recorded. In the first half of the winter an easterly air flow prevailed and in the second part — the westerly one. Winds were strong and gusty. The highest speed reached 74 ms-1 . Snowfalls were abundant; depth of snow exceeded 100 cm.
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Abstract

An algorithm of determination of mechanical stresses and deformations of the magnetic circuit shape, caused by forces of magnetic origin, is presented in this paper. The mechanical stresses cause changes of magnetizing characteristics of the magnetic circuit. The mutual coupling of magnetic and mechanical fields was taken into account in the algorithm worked out. A computational experiment showed that it was possible to include the interaction of both fields into one numerical model. The elaborated algorithm, taking into account the impact of mechanical stresses on magnetic parameters of construction materials, can be used in both the 2D and the 3D type field-model.
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Abstract

This paper presents a complex study of anhydrite interbeds influence on the cavern stability in the Mechelinki salt deposit. The impact of interbeds on the cavern shape and the stress concentrations were also considered. The stability analysis was based on the 3D numerical modelling. Numerical simulations were performed with use of the Finite Difference Method (FDM) and the FLAC3D v. 6.00 software. The numerical model in a cuboidal shape and the following dimensions: length 1400, width 1400, height 1400 m, comprised the part of the Mechelinki salt deposit. Three (K-6, K-8, K-9) caverns were projected inside this model. The mesh of the numerical model contained about 15 million tetrahedral elements. The occurrence of anhydrite interbeds within the rock salt beds had contributed to the reduction in a diameter and irregular shape of the analysed caverns. The results of the 3D numerical modelling had indicated that the contact area between the rock salt beds and the anhydrite interbeds is likely to the occurrence of displacements. Irregularities in a shape of the analysed caverns are prone to the stress concentration. However, the stability of the analysed caverns are not expected to be affected in the assumed operation conditions and time period (9.5 years).
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Abstract

Paper discusses an issue of old-time gentry estates landscape formation based on po-lish agricultural textbooks. Theoretical proposals as well as real-life structures of gentry estates on polish lands in pre-parti-tion and post-partition times are analyzed. Article presents both rules of shaping mo-dest gardens of decorative and utilitarian functions alike in the vicinity of mansions, and other components of estate’s land-scape. Partial concurrence between theore-tical postulates and real land use is proven.
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Abstract

Article 51 of the UN Charter, in affi rming the inherent right of self-defence of each UN Member State “against which an armed attack has occurred”, clearly indicates that the concept of armed attack plays a key role in delineating the right of self-defence. The concept in question was not, however, defi ned in the UN Charter, and no universally acceptable defi nition has yet emerged either in practice or in doctrine. One of the fundamental questions to be addressed in this context is who must engage in armed activity for it to qualify as an armed attack. This question is of particular relevance today because of the threat of international terrorism and the expansion of the concept of armed attack through the inclusion of an act of terrorism. The article discusses in some detail the emerging legal framework for attribution of actions undertaken by non-state actors to states.
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Abstract

This article is referenced to the thirtieth anniversary of the ICJ’s Nicaragua judgement on the merits of 1986. It acknowledges the significance of this much-debated judgement for the modern international law on the use of force (jus ad bellum). However the text focuses on one aspect of the judgment only, i.e. the definition of the notion of “armed attack” as the most grave form of the use of force. The impact of the judgement in this respect is critically analysed. It is argued that the introduction to the UN Charter text of undefined notions of the use of force, aggression, and armed attack may be labelled as the “original sin” of contemporary jus ad bellum, as it results in conceptual obscurity. It is also claimed that the ICJ reaffirmed this original sin in its Nicaragua judgment because it explicitly argued for the notion of “armed attack” as the most grave form of the use of armed force and, in consequence, distinguished it from the other, lesser forms of the use of force, while failing to introduce any sort of clarity in the conceptual ambiguity of jus ad bellum. The article also offers some remarks de lege ferenda and suggests abandoning the gravity criterion, which would require abandoning the well-established judicial and doctrinal interpretation approaches to jus ad bellum.
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Abstract

The aim of this article is to present a modern method of convective drying intensification caused by the external action of ultrasound. The purpose of this study is to discover the mechanism of ultrasonic interaction between the solid skeleton and the moisture in pores. This knowledge may help to explain the enhancement of drying mechanism affected by ultrasound, particularly with respect to biological products like fruits and vegetables. The experimental kinetics tests were conducted in a hybrid dryer equipped with a new ultrasonic generator. The drying kinetics curves determined on the basis of drying model developed by the author were validated with those by the ones obtained from experimental tests. The intensification of heat and mass transfer processes due to ultrasound induced heating effect and vibration effect are analysed. The obtained results allow to state that ultrasound makes drying processes more effective and enhance the drying efficiency of biological products without significant elevation of their temperature.
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