964 research outputs found
The New Biodegradable Surfactant Drilling Fluid for Offshore Drilling Environment
In oil and gas industry, there are many challenges faced before
reservoir fluid produced out of reservoir rock. In drilling progress, the
reservoir rock may be invaded by drilling fluid and cause several damage to
the wall formation. This is called as formation damaged. Formation damage is
defined as any type of a process which results in a reduction of the flow
capacity of an oil, water or gas bearing formation.
In oil and gas reservoirs, formation damage has known as a source of
serious productivity reductions as it could lead to water injectivity problems in
many waterflood projects. The injectivity problem has reduces the
effectiveness of recovery mechanism, mainly on third recovery mechanism.
Besides, formation damaged has negative affect to oil and gas production as it
could reduces the production due to its mechanism
Antiphospholipid Syndrome — controversies
Antiphospholipid Syndrome which was defined for the first time in 1985 is more and more frequently diagnosed and better treated. During the 30-year period of observation numerous new questions have appeared regarding the nature of this diseases. In particular: how to diagnose the disease in patients with non-classification criteria; how to prevent thrombosis and pregnancy complications, why does thrombosis appear despite the proper anticoagulation, is it possible to diagnose seronegative antiphospholipid syndrome? The current knowledge regarding diagnosis and treatment of APS has been presented in this paper
Comparison of tractor slip at three different driving wheels on grass
ArticleThe paper deals with a possibility of tractor slip reduction on a grass and evaluates an
use of two versions of special wheels. Both prototypes were developed at the Department of
Transport and Handling of the Slovak University of Agriculture in Nitra. The first system was
designed in 2010 year as blades wheels. The second system (spikes device) consists of spikes
which are mounted onto standard tractor tyres with special cuts, was designed in 2014 year. The
spikes are settled in these cuts while moving on road surface. The second one is placed near the
drive wheels and uses the blades. The spikes and blades are ejected to reduce wheels slip when
tractor operates on grass or soil. The base position allows tractor transport on road with standard
tyres. The goal of experiments realized on grass surface was to compare mutually slip behaviour
achieved. The measurements were realized with standard tyres without any modification, too. A
tractor with three types of drive wheels were loaded by heavier tractor. Drawbar pull and wheel
rotation speed for slip calculation were measured in tests. The results show a fact that a loss of
energy due to the wheels slip increases, while a penetrometric resistance in the surface layers of
a soil decreases, at soil humidity 33.2%. An application of both prototypes is very advantageous
because they reduce the wheels slip, increase tractor operation efficiency and so protect the soil
Volatile combustible release in biofuels
ArticlePlant biomass consists of varied materials. Biomass is used for different purposes, but it is most frequently burnt in modern combustion devices for heat production. The quality of solid biofuels depends on the total content of combustibles while the volatile combustible content affects the combustion process. The aim of the paper is to determine the exact content of the biofuel components by the means of the gravimetric method – namely volatile combustible, ash and moisture content – and to evaluate the process of volatile combustible release as a function of temperature during the experiment. The device Nabertherm L9/11/SW/P330 type with accessory was used to carry out the experiments. Various biofuel samples were examined, namely wood (9 kinds), wood cuttings and wood chips (2 kinds), pellets (4 kinds), sawdust (1 kind), compared to less traditional fuels (DDGS and RME – 2 kinds) and wood coal (1 kind). The tables and graphs present the experimental results, which allow evaluation of the components content in different biofuels and provide characteristics of the process of volatile combustible release in analysed fuels. Spruce wood without bark showed the highest content of combustible (99.89%). Sawdust of fruit trees contains the highest proportion of volatile combustible (93.978%) and releases the combustible at the highest rate (15.25 mg h-1)
Abū Al-Ḥasan Al-Masʻūdī on pre-Islamic Arab religions and belief
This study aims to shed light on one aspect of the contributions
of an early Muslim historian of religion, Abū al-Ḥasan al-Masʻūdī. It focuses
on al-Masʻūdī’s work on pre-Islamic Arab religions and beliefs. The study is
based on textual analysis of al-Masʻūdī’s treatment of the issue in his Murūj
(The Meadows), and comparisons are made with al-Masʻūdī’s treatments of the
non-Arab religions.
Kajian ini bertujuan untuk memberikan penerangan tentang satu
aspek dalam sumbangan seorang sejarawan Islam awal iaitu Abū al-Ḥasan alMasʻūdī,
dengan memfokuskan karya-karya beliau terhadap agama masyarakat
Arab pra-Islam. Kajian ini berasaskan analisis teks tentang pengendalian
al-Masʻūdī, terhadap isu tersebut dalam karyanya Murūj. Seterusnya ia
dibandingkan dengan pengendalian beliau terhadap agama masyarakat bukan
Arab
Special tractor driving wheels with two modification of spikes inclination angle
ArticleThe paper presents a research on an improvement of tractor drawbar properties using
special driving wheels. Two modifications of the special driving wheels were designed and tested
under field conditions. The results were compared with standard tyres. The special driving wheels
consists of the tyres with a modified tyre-tread pattern and equips with the spike segments. The
special driving wheels allow to activate or deactivate the spike segments to improve a drawbar
pull at worse adhesive conditions of the ground or transport on roads with standard tyres. The
first modification activates all 8 spike segments at spike inclination angle 90° and the second one
4 at angle 90°and 4 at 30°. The measurements were realised in October 2017 in an area of the
Slovak Agricultural Museum in Nitra. The drawbar properties of the special driving wheels were
evaluated based on drawbar pull of the test tractor Mini 070 type connected with a load tractor
MT8-065 type. Using the test tractor in 1st and 2nd gear, the measurements were realized at 100%
wheels slip and repeated 4 times. The results show the statistically significant differences in the
drawbar pull of the test tractor with different driving wheels on a grass plot. The highest increase
in drawbar pull reached the value 25.56% (2nd gear) and 19.98% (1st gear) in case of the special
driving wheels with 4 spike segments at 90° and 4 at 30°. In case of the special driving wheels
with 8 spike segments at 90°, increase in the drawbar pull reached the value 10.09% (1st gear)
and 15.21% (2nd gear) in comparation with the standard tyres
Comparison of consumption of tractor at three different driving wheels on grass surface
ArticleThe paper deals with possibility of reduction of tractor fuel consumption when working
on grass surface, and compares use of two
versions of spike devices embedded to the original tyre
body. The device was designed at Department Transport and Handling (Slovak University of
Agriculture in Nitra). Older as well as newer system proposed in 2017 comprises spikes and it is
assembled to
common tractor tyre tread pattern with auxiliary grooves cut in. Same device can
be set to two positions, allowing to work as 8
-
spikes and 16
-
spikes system. The spikes are tilted
in grooves when moving on paved road. The spikes are ejected out to reduce wh
eels slip when
operated in field. Remaining eight spikes are tilted in case of 8
-
spikes system. Measurements
were realised on grass surface. Tractor Mini 070 type was loaded with heavier tractor MT8
-
065
type in tests with 3 different driving wheels, balanc
ing the actual weight in all cases. Drawbar
pull and fuel consumption were measured in tests, allowing to compute specific drawbar
consumption and fuel consumption per hour for three different loads. The results pointed out a
fact the tyre slip loss and en
ergy consumption of tractor movement increase at the soil humidity
19.45%. It follows from results achieved that use of both 8
-
and 16
-
spikes wheel device versions
reduced fuel consumption when cultivating higher humidity soil, preferable for tillage. Eigh
t
spikes system with semi
-
tilted remaining spikes is the most efficient method
Contamination of transmission and hydraulic oils in agricultural tractors and proposal of by-pass filtration system
ArticleTractors use various types of lubricating oils in transmission and hydraulic system.
Oils are contaminated by different ways depending on the work of the lubricated system. There
are general requirements on the cleanliness level of the oil in the tractor transmission and
hydraulic system according to the standard DIN 51524. According to all that, this paper presents
research conducted by two tractors. The tractor John Deere 8100 used only its own implements
(ploughs, trailers etc.) and it was operated in compliance with user manual. In this tractor, the oil
cleanliness level met the standard DIN 51524 because reached the stage 7 (NAS 1638). The
tractor Zetor Forterra 124 41 contained extremely contaminated oil, it reached stage > 12
(NAS 1638), due to the non-standard operation which was opposite to the user manual. Both ways
of tractor operation are typical for farmers activity in the Slovak Republic, depending on the
tractor type and style of agricultural production at most. The second part of this paper is aimed at
the proposal of by-pass filtration system to eliminate the oil contamination. The by-pass filtration
system is the second stage of the oil filtration in the tractor, whereas the first one means standard
tractor filter. Function of the system was tested according to the decrease of chemical elements
concentration characterising the oil contamination and visual method based on filter and its
change after operating of tested tractor. There was evaluated the decrease of concentration of Fe
(41.6%), Cu (28.7%) and Si (20.5%) after by-pass filtration system was running under operational
conditions. It can be concluded that the by-pass filtration system was proposed correctly and it is
suitable for tractors operation
Implementation of selected database operations in parallel environment
Název práce: Implementace vybranĂ˝ch databázovĂ˝ch operacĂ v paralelnĂm pro- stĹ™edĂ Autor: Bc. Ján Majdan Katedra: Katedra softwarovĂ©ho inĹľenĂ˝rstvĂ VedoucĂ diplomovĂ© práce: RNDr. David Bednárek, Ph.D. Abstrakt: PĹ™edloĹľená diplomová práce se zabĂ˝vá moĹľnostmi implementace da- tabázovĂ˝ch operacĂ v paralelnĂm prostĹ™edĂ Bobox. Popisuje potĹ™ebnĂ© teore- tickĂ© znalosti z oblasti databázĂ, a tĂ©Ĺľ algoritmy potĹ™ebnĂ© pro implementaci da- tabázovĂ˝ch operacĂ v hlavnĂ pamÄ›ti poÄŤĂtaÄŤe. V textu jsou popsanĂ© moĹľnosti pa- ralelnĂ realizace databázovĂ˝ch operacĂ pomocĂ hašovacĂch tabulek. PĹ™edstavenĂ© jsou principy zaloĹľenĂ© na sdĂlenĂ hašovacĂ tabulky, a taky pĹ™edzpracovánĂ dat (lokálnĂ hašovacĂ tabulka). SoučástĂ diplomovĂ© práce je i paralelnĂ implementace vybranĂ˝ch operacĂ, která je zaloĹľená na postupech pĹ™edstavenĂ˝ch v textu práce. Realizace zahrnuje taky měřenĂ vĂ˝konnosti implementace pĹ™i rĹŻznĂ˝ch stupnĂch paralelizace. NaměřenĂ© vĂ˝sledky jsou pĹ™ehlednÄ› prezentovanĂ© a analyzovanĂ© z po- hledu škálovatelnosti paralelizace v prostĹ™edĂ Bobox. KlĂÄŤová slova: databázovĂ© operace, Bobox, paralelizace, hašovánĂ, pĹ™edspracovánĂ dat 1Title: Implementation of selected database operations in parallel environment Author: Bc. Ján Majdan Department: Department of Software Engineering Supervisor: RNDr. David Bednárek, Ph.D. Abstract: This thesis describes several design possibilities of database operations in a parallel environment called Bobox. First, the thesis covers theory of da- tabases as well as algorithms needed to implement database operations in main memory. Next part discusses the usage of hash tables to implement parallel data- base operations. The key principles discussed contain hashing approaches based on a shared hash table, as well as principles of data preprocessing (local hash Table). The thesis then describes practical usage of selected database operations, which were implemented based on the principles described in the first theory sec- tions. The implementation also involves performance measurement at different levels of parallelism. Finally, acquired results are analyzed and discussed in terms of scalability of parallelism and performance in the Bobox environment. Keywords: database operations, Bobox, parallelism, hashing, data preprocessing 1Department of Software EngineeringKatedra softwarovĂ©ho inĹľenĂ˝rstvĂFaculty of Mathematics and PhysicsMatematicko-fyzikálnĂ fakult
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