Browse

You are looking at 1 - 10 of 1,728 items for :

  • Atmospheric Science and Climatology x
Clear All
Open access

Ahmed Salem

Abstract

According to an official study conducted by the IMO Correspondence Group on Casualty Analysis concerning the fire incidents that occurred on the vehicle-decks of RoPax ships, covering the period from 1994 to 2011, it has been shown that a very serious incident has occurred every other year since 2002, resulting in six constructive total losses. The results of this review shed the light on the need to investigate the application of fire models to simulate fire scenarios that may occur on the vehicle-decks aboard RoPax ships. This will be very useful for the RoPax designers who are willing to introduce new technologies or deviate from the current prescriptive regulations of fire safety design in order to reduce the risk of such catastrophic accidents. The aim of this paper is to present the results of a comparison between the predictions of three different fire models and the experimental results of a model-scale fire test that represents a fire scenario on a vehicle-deck aboard a RoPax ship. A statistical analysis technique was used to illustrate the ability of each fire model to predict five outputs of concern. The main conclusion of this comparison is that there is always an optimal fire model that can predict one or more of the five outputs of concern with results in good agreement with the measured values.

Open access

Giurma-Handley Catrinel-Raluca, Telișcă Marius and Paerele Cosmin-Marian

Abstract

The concept of sustainable development resulted from the conciliation of three aspirations: economic and social development, protection of the state of environment and increasing the importance of environmental policies. In order to protect the water quality, the catchments are arranged by organizational, agricultural and technical measures and works that need to be applied both on the slopes and in the drainage network. The paper presents new concepts of authors to limit the liquid and solid runoff that could affect water quality as an indispensable factor for life.

Open access

Donny Harisuseno, Dian Noorvy Khaeruddin and Riyanto Haribowo

Abstract

Time of concentration, Tc, is defined as time elapsed from the beginning of rainfall infiltrated into soil layer until it reaches a constant infiltration rate (fc) which is indicated an equilibrium subsurface flow rate. In hydrological view, time of concentration plays a significant role in elaboration of transformation of rainfall into runoff in a watershed. The aims of this research are to define influence of soil density and soil water content in determining time of concentration using infiltration concept based on water balance theory, and to find out the effect of land slope this time. Watershed laboratory experiment using rainfall simulator was employed to examine time of concentration associated with infiltration process under different slope, soil density and soil water content based on water balance concept. The steady rainfall intensity was simulated using sprinklers which produced 2 dm3∙min−1. Rainfall, runoff and infiltration analysis were carried out at laboratory experiment on soil media with varied of soil density (d) and soil water content (w), where variation of land slopes (s) were designed in three land slopes 2, 3 and 4%. The results show that relationship between soil density and land slope to time of concentration showed a quadratic positive relationship where the higher the soil density address to the longer time of concentration. Moreover, time of concentration had an inverse relationship with soil water content and land slope that means time of concentration decreased when the soil water content increased.

Open access

Krzysztof Woloszyk and Yordan Garbatov

Abstract

This work deals with the reliability assessment of a tanker ship hull structure subjected to a vertical bending moment and corrosion degradation. The progressive collapse and ultimate load carrying capacity are estimated based on experimentally tested scaled box-shaped-specimens. The translation of the strength estimate of the scaled specimen to the real tanker ship hull structure is performed based on the dimensional theory developing a step-wise linear stress-strain relationship. The load-carrying capacity is considered as a stochastic variable, and the uncertainties resulted from the scaled-specimen to the real-structure strength translation, and the subjected load of the real ship are also accounted for. A sensitivity analysis concerning the stochastic variables, included in the ultimate limit state function is performed. The partial safety factors, in the case of a scaled specimen and real structure, are also identified, and conclusions are derived.

Open access

Monica Dumitrașcu, Mihaela Lungu, Sorin Liviu Ștefănescu, Victoria Mocanu, Gabi Mirela Matei and Rodica Lazăr

Abstract

As low-input environmentally friendly agricultural practices are currently associated with the delivery of a wide range of public goods and socioeconomic benefits, the strategy of European Union in mitigating climate change effects, protecting environment and ensuring public health has, among others, focused around preserving the High Natural Value (HNV) areas. About a quarter of the land in Romania is potentially covered by HNV farming and eligible for associated support payments, mostly along the chain of the Carpathian Mountains. Since soil systematic data on HNV area are scarce, recent research developments currently undertake to build up a first national HNV soil data base.

Soil fertility state in a HNV payment eligible area of south-eastern Transylvania was studied in seven in-depth dug profiles and seven additional shallow dug profiles. Soil samples were taken by genetic horizons as well as agrochemical samples from the upper soil layers (0-20 cm). Physical, chemical, and microbiological analyses revealed that the studied soils have a medium clayey loamy texture, good fertility and are subject to an adequate HNV management in the area, as the analytical values mostly range in favorable intervals for plant growth and nutrition. Thus, soil reaction is moderately acid up to slightly alkaline in the presence of carbonates, the soil organic matter, generally well mineralized, reaches fair levels and the high and very high cation exchange capacity ensure good conditions for plants growth and nutrition whilst nitrogen and potassium supply is adequate. Phosphorus is the only element in short supply – a situation often encountered in Romania unfertilized soils. Soil bulk density and total porosity are also favorable for root growth and spreading and plant nutrition. Microorganisms’ activity is diverse and is also adequate for plant nutrition.

Open access

Agnieszka Barszczewska, Ewa Piątkowska and Wojciech Litwin

Abstract

This paper presents typical methods for conducting experimental tests on main shaft slide bearings. There are described their possible testing capabilities, advantages, drawbacks and limitations. Various testing methods were analyzed to find a solution able of providing a wide range of possible investigations at possibly acceptable limitations.

Open access

Gheorghe Romanescu

Abstract

Deposit salt in Romania has extremely important reserves, considered even inexhaustible at the current exploitation level. The biggest salt resources are found in the intra-Carpathian arch, represented by Transylvania and Maramures. Most sources of salt outcrops are disseminated on the edge of the Transylvania Depression, in the diapir folds formed following salt migration. The salt mines – Turda, Praid, Ocna Mures, Ocna Dej, Ocna Sibiu, Cojocna, Ocna Sugatag – represented an important source of incomes, reason for which important human settlements formed around them. All these localities have turned nowadays into balneal and climacteric resorts that fully use the beneficial effect of the atmosphere within galleries (Praid, Turda). The most important incomes from tourism are represented by the galleries of the mines of Turda (one of the 10 wonders of the modern world) and Praid. The balneal and climacteric resorts also developed around the salt lakes installed in the areas of collapsed mines: Sovata, Ocna Sibiu, Ocna Dej, Cojocna. The most well known human settlements and the most important balneal and climacteric resorts, implicitly, are disseminated on the external branch of the Transylvania Depression (Sovata, Praid, Ocna Mures, Baile Figa, Cojocna thermae, Ocna Dej, Ocna Sibiu) and of the Maramures Depression (Ocna Sugata, Costiui, Vad). The oldest mining exploitation is situated at Figa (county of Bistrita-Nasaud) was founded around the year AD 3000. From this point of view, it is one of the oldest mining exploitations on Earth. The existence of the world-important archaeological site can invigorate the development of the surrounding localities, but mostly of the city of Beclean.

Open access

Anna M. Baryła

Abstract

Green roofs play a significant role in sustainable drainage systems. They form absorbent surfaces for rainwater, which they retain with the aid of profile and plants. Such roofs therefore take an active part in improving the climatic conditions of a city and, more broadly, the water balance of urbanized areas. One of the factors influencing the hydrological efficiency of green roofs is the drainage layer. In the article, column studies were carried out under field conditions involving the comparison of the retention abilities of two aggregates serving as the drainage layer of green roofs, i.e. Leca® and quartzite grit. The average retention of the substrate was 48%; for a 5 cm drainage layer of Leca® retention was 57%, for a 10 cm layer of Leca average retention was 61%. For a 5 cm layer of quartzite grit average retention was 50%, for 10 cm layer of quartzite grit 53%. The highest retention was obtained for the column with the substrate and 10-centimeter layer of Leca®. At the same time, it was shown that Leca® is a better retention material than quartzite grit. The initial state of substrate moisture content from a green roof appears to be a significant factor in reducing rainfall runoff from a green roof; the obtained values of initial moisture content made for a higher correlation than the antecedent dry weather period.

Open access

Hossein Nejatbakhsh Esfahani

Abstract

This paper proposes an improved Model Predictive Control (MPC) approach including a fuzzy compensator in order to track desired trajectories of autonomous Underwater Vehicle Manipulator Systems (UVMS). The tracking performance can be affected by robot dynamical model uncertainties and applied external disturbances. Nevertheless, the MPC as a known proficient nonlinear control approach should be improved by the uncertainty estimator and disturbance compensator particularly in high nonlinear circumstances such as underwater environment in which operation of the UVMS is extremely impressed by added nonlinear terms to its model. In this research, a new methodology is proposed to promote robustness virtue of MPC that is done by designing a fuzzy compensator based on the uncertainty and disturbance estimation in order to reduce or even omit undesired effects of these perturbations. The proposed control design is compared with conventional MPC control approach to confirm the superiority of the proposed approach in terms of robustness against uncertainties, guaranteed stability and precision.

Open access

Ion Constantin, Baltag Emanuel Ştefan, Ursu Adrian, Sfîcă Lucian, Ignat Alina Elena and Stoleriu Cristian Constantin

Abstract

The avian habitats in Eastern Europe are poorly managed in last decades. It is of highly noteworthy influence importance to obtain more information regarding the link between birds’ presence and environmental features in wetlands to improve this poorly managed system. In our study we investigated the effects of the various habitat, landscape fragmentation and weather variables on the bird assemblages in Eastern Romania, described by diversity, species richness and abundance of non-passerine birds in wetlands. Poisson regression modelling revealed wetland area, wetland heterogeneity, proportion of open-water, density of patches and habitats, landscape shape and temperature conditions have a noteworthy influence on the bird assemblages (p<0,05). Our results suggest that the link between environmental features and birds’ assemblage, in our study areas could be dependent on the presence of the emergent vegetation (shelter / reproduction zones), the balance between open-water area (feeding / nesting zones) and also other variables, as the temperature, the presence of the human living facilities and/or intensive fish nurseries in the neighboring zones. Waterbird distribution and abundance in eastern part of Romania are driven by similar factors to other part of the world and this study could be one of the first published on the topic in a region where It is a lack of information on waterbirds ecology. Such studies would bring valuable information about the ecologic factors influencing the lives of the birds, in the areas that were not stueid before, resulting in better conservation efforts and wetland protection, in estern part of Europe.