In the over 150 years of hydrocarbon history, the year 2017 will be one of the many similar. However, it will be a breakthrough year for liquefied natural gas. In Asia, China grew to become the leader of import growth, becoming the second world importer, overtaking even South Korea and chasing Japan. The Panama Canal for LNG trade and the “Northern Passage” was opened, so that Russian LNG supplies appeared in Europe. The year 2017 was marked by a dramatic shortening of the length of long-term concluded contracts, their shorter tenure and reduction of volumes – that is, it was another period of market commoditization of this energy resource. The article describes the current state of LNG production and trade till 2018. It focuses on natural gas production in the United States, Qatar, Australia, Russia as countries that can produce and supply LNG to the European Union. The issue of prices and the contracts terms in 2017 was analyzed in detail. The authors stress that the market is currently characterized by an oversupply and will last at least until mid–2020. Novatek, Total – Yamal-LNG project leaders have put the condensing facility at 5.5 million tons into operation. The Christophe de Margerie oil tanker was the first commercial unit to cross the route to Norway and then further to the UK without icebreakers and set a new record on the North Sea Road. In 2017, the Russian company increased its share in the European gas market from 33.1 to 34.7%. In 2017, Russia and Norway exported record volumes of „tubular” – classic natural gas to Europe (and Turkey), 194 and 122 billion m3 respectively, which is 15 and 9 billion m3 more natural gas than in 2016. The thesis was put forward that Russia would not easily give up its sphere of influence and would do everything and use various mechanisms, not only on the market, that it would simply be more expensive and economically unprofitable than natural gas. It was also emphasized that the pressure of the technically possible and economically viable redirection to European terminals of methane carriers landed in the American LNG, results in Gazprom not having a choice but to adjust its prices. The Americans, but also any other supplier (Australia?) can simply do the same and this awareness alone is enough for Russian gas to be present in Europe at a good price.

In spite of technological, logistic and economic difficulties, interest in renewable energy sources in the world is consistently increasing. This trend is also observed in Poland, mainly due to the urgent need to tackle the problem of climate change, which is caused by the increasing concentration of gaseous pollutants in the atmosphere. The paper presents a short script of the issue of estimating renewable energy resources in Poland in the context of creating local low carbon economy plans at the level of municipalities/counties where RES sources should be taken into account. The author proposed an individual approach to estimate the potential of RES, taking the local conditions and the short characteristics of the small and medium companies sector in Poland into account. These companies have a great application potential to increase the share of renewable energies and to improve energy efficiency in their business. The actions, which are taken by the Ministry of Energy in the field of civil energy development, enhancing local energy security and the sustainable development of renewable energy resources support the development of energy clusters covering one district or five municipalities. In the article, the author presents data on the number of companies possessing a concession for generating electricity in RES installations in the power range from 40 kW to 200 kW. These companies can largely be the nucleus for creating a local cluster in which microgrids will be a key element.

The national total expenditure of a country is precipitated on several factors of which revenue generated could be one and very significant. This paper therefore examines the contribution of some selected sources of Nigerian government revenue to total national expenditure. Statistical and econometric techniques used for the data analysis are unit root test, cointegration test, combined estimators’ analysis, the error correction model (ECM) and the feasible generalized linear (FGLS) estimators. Results showed that the variables are non stationary but are stationary at first difference. The long-run relationship of total expenditure on oil revenue, non-oil revenue, federation account and federal retained revenue revealed that the variables are co-integrated and required the use of combined estimators. The effect of non-oil revenue and federal retained revenue is very significant. Investigations on the short-run modeling necessitated the use of FGLS estimators. The effect of ECM and federal retained revenue is very significant. Consequently, other sources of revenue apart from federal retained revenue need to be enhanced and tailored towards improving economic growth and development through national expenditure.

This study examined whether differences in reverberation time (RT) between typical sound field test rooms used in audiology clinics have an effect on speech recognition in multi-talker environments. Separate groups of participants listened to target speech sentences presented simultaneously with 0-to-3 competing sentences through four spatially-separated loudspeakers in two sound field test rooms having RT = 0:6 sec (Site 1: N = 16) and RT = 0:4 sec (Site 2: N = 12). Speech recognition scores (SRSs) for the Synchronized Sentence Set (S3) test and subjective estimates of perceived task difficulty were recorded. Obtained results indicate that the change in room RT from 0.4 to 0.6 sec did not significantly influence SRSs in quiet or in the presence of one competing sentence. However, this small change in RT affected SRSs when 2 and 3 competing sentences were present, resulting in mean SRSs that were about 8-10% better in the room with RT = 0:4 sec. Perceived task difficulty ratings increased as the complexity of the task increased, with average ratings similar across test sites for each level of sentence competition. These results suggest that site-specific normative data must be collected for sound field rooms if clinicians would like to use two or more directional speech maskers during routine sound field testing.

In the paper the idea of rational polynomial windows optimised towards low level of Fourier spectrum's sidelobes is presented. A relevant advantage of the polynomial windows family and their modifications is their ability to easily change their properties changing only the values of the polynomial coefficients. The obtained frequency characteristics demonstrate better properties of proposed rational Windows than their standard polynomial equivalents requiring only the additional division operation. Such approach does not increase the computational complexity in significant way and the great advantage of polynomial windows which is their low computational complexity is preserved.

With increasing technology development, an increasing emphasis is placed on the precision of products, but cannot be guaranteed without a stable production process. To ensure the stability of the production process, it is necessary to monitor it in detail, find its critical locations and eliminate or at least control it. With such a precise manufacturing method as investment casting, such a process is a must. This paper therefore deals with monitoring the production process of wax models of large turbine blades using infrared thermography. The aim was to evaluate the critical locations of this production and to propose recommendations for their elimination or, at the very least, significant mitigation of their impact on the final quality of the large turbine blade casting.

The goal of this article is non-destructive ultrasonic testing of internal castings defects. Our task was to cast several samples with defects like porosity and cavities (where belongs mostly shrinkages) and then pass these samples under ultrasonic testing. The characteristics of ultrasonic control of castings are presented in the theoretical part of this article. Ultrasonic control is a volume non-destructive method that can detect internal defects in controlled materials without damaging the construction. It is one of the most widely used methods of volume non-destructive testing. For experimental control were made several cylindrical samples from ferritic grey and ductile cast iron. Because of the form and dispersion of graphite of grey cast iron it was not possible to make ultrasonic records on this casting with probe we used, so we worked only with ductile cast iron. Ultrasonic records of casting control are shown and described in the experimental part. The evaluation of the measurement results and the reliability of the ultrasonic method in castings control is listed at the end of this article.

This paper describes a new and efficient method for quantifying and detection of the source of distortion caused by a single customer in a case when many other customers exist in a power grid. It is based on measuring distortion power, a component of apparent power that only exists with a nonlinear load. Different definitions for distortion power calculation are investigated. All these definitions show without doubt that the proposed method is feasible. Moreover, this method allows to develop fair and reliable billing schemes for controlling harmonic pollution. Measurement and simulation results confirm the effectiveness and applicability of the method. The proposed solution is suitable for software/hardware upgrade of existing electronic power-meters.