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Wyświetlanie 1-15 z 53
Tytuł:
Influence of organisational culture on total quality management implementation and firm performance: evidence from the Vietnamese construction industry
Autorzy:
Panuwatwanich, K.
Nguyen, T. T.
Powiązania:
https://bibliotekanauki.pl/articles/406983.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Total Quality Management
Competing Value Framework
Construction
Culture
Vietnam
Opis:
The main purpose of this study is to examine the relationship between organisational culture (OC) and Total Quality Management (TQM), and the influence of TQM implementation on organisational performance improvement within the context of the Vietnamese construction industry. A survey was conducted with 104 respondents from Vietnamese construction firms, using validated survey instruments developed in past research. Analysis techniques include cluster analysis and Structural Equation Modelling. Findings showed that Vietnamese construction firms are dominated by clan and hierarchy cultures rather than adhocracy and market cultures according to Competing Value Framework (CVF) of OC classification. urthermore, it was found that organisations dominated by either clan or adhocracy cultures could provide a favourable environment for successful TQM implementation, whereas this is not the case for those dominated by both market and hierarchy cultures. This study also confirmed the significant and positive relationship between TQM implementation and organisational performance improvement.
Źródło:
Management and Production Engineering Review; 2017, 8, 1; 5-15
2080-8208
2082-1344
Pojawia się w:
Management and Production Engineering Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solution to Reduce Air Environmental Pollution from Ships
Autorzy:
Pham, H.T.
Nguyen, T.M.
Powiązania:
https://bibliotekanauki.pl/articles/116944.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
Pollution at Sea
Environment Protection
Ecology, MARPOL
Air Environmental Pollution
Gas Emissions
Exhaust Gas Emissions
Exhaust Gas
Opis:
Exhaust gas emissions from ships are increasingly polluting the air environment seriously. Therefore, the MARPOL 73/78 Annex VI is applied for all ships from 2017, Annex VI provided that the concentrations of NOx,SOx CO contained in ship’s exhaust gases must be less than 6.4 g/kWh, 0.6 g/kWh, and 5.5g/kWh respectively. Today, there are many solutions to reduce pollution emissions from exhaust gas of ships, such as improving combustion, using oil emulsion, using biofuel,…However, these solutions also have a handful of disadventages such as being unable to thoroughly resoulve problems, high cost, and very difficult to improve the quality of ship exhaust gas emissions for old ships. Exhaust gas treatment method uses a centralized treatment system where exhaust gas from the thermal engines is taken in a centralized treatment system before discharging into the air. After centralized treatment system, in comparision with raw exhaust gas, soot can be reduced by 98%, NOx can be reduced by 75%, SOx can be reduced by 80%. This method of treatment is not only low cost, good quality but also make marine heat-engines still use traditional fuels as well as need not improve its structure.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2015, 9, 2; 257-261
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Indifference pricing with counterparty risk
Autorzy:
Ngo, M.
Nguyen, T.
Duong, T.
Powiązania:
https://bibliotekanauki.pl/articles/200331.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
indifference pricing
counterparty risk
minimal entropy
BSDE
ryzyko kontrahenta
entropia minimalna
Opis:
We present counterparty risk by a jump in the underlying price and a structural change of the price process after the default of the counterparty. The default time is modeled by a default-density approach. Then we study an exponential utility-indifference price of an European option whose underlying asset is exposed to this counterparty risk. Utility-indifference pricing method normally consists in solving two optimization problems. However, by using the minimal entropy martingale measure, we reduce to solving just one optimal control problem. In addition, to overcome the incompleteness obstacle generated by the possible jump and the change in structure of the price process, we employ the BSDE-decomposition approach in order to decompose the problem into a global-before-default optimal control problem and an after-default one. Each problem works in its own complete framework. We demonstrate the result by numerical simulation of an European option price under the impact of jump’s size, intensity of the default, absolute risk aversion and change in the underlying volatility.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 5; 695-702
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ecological risk, seasonal and depth variations of toxic elements in a closed landfill in Vietnamese Mekong Delta province
Autorzy:
Giao, Nguyen T.
Nhien, Huynh T.H.
Powiązania:
https://bibliotekanauki.pl/articles/27312657.pdf
Data publikacji:
2023
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
environmental risk
heavy metals
landfill
soil properties
Opis:
The study was carried out to assess ecological risks at the closed landfill in Cai Dau town, Chau Phu district, An Giang province. Soil samples were collected at six locations (S1-S6) at depths of 0-20 cm and 60-80 cm in the rainy season (November 2020) and dry season (March 2021). The soil quality was evaluated using eight heavy metals (Mn, Fe, Cu, Zn, Ni, Pb, Cr and As). The results showed that most monitoring sites had heavy metal contents within the allowable limits for agricultural land of QCVN 03-MT:2015/BTNMT. Some heavy metals have been found to migrate to the soil layer of 60-80 cm. The heavy metals accumulation (Igeo) in the two soil layers did not differ; Ni, Cr, Pb and As accumulated at non-polluting levels - moderate to high in the rainy season, while Cr and As only accumulated in the dry season. The composite pollution index (PLI) indicated that the locations around the landfill were polluted; however, the ecological risk ranged from low to moderate (potential ecological risk index (PERI) = 102-195) in the rainy season. Only about 50% of study sites during the dry season were contaminated and the risk was low (PERI = 44-68). However, the area around the landfill always poses potential risks due to the presence of heavy metals, including Ni, Cr, As and Pb. Monitoring the heavy metals in the surrounding landfill for the potential risks to human health and environment is needed.
Źródło:
Journal of Water and Land Development; 2023, 57; 188--196
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Możliwości i opłacalność wykorzystania ścieków szarych do nawadniania roślin
Feasibility and economic efficiency of greywater reuse for plant irrigation
Autorzy:
Nguyen, T. H.
Błażejewski, R.
Spychała, M.
Powiązania:
https://bibliotekanauki.pl/articles/401811.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
wykorzystanie ścieków
nawadnianie
woda wodociągowa
ścieki szare
życica trwała
greywater reuse
irrigation
tap water
greywater
perennial ryegrass
Opis:
Celem badań była ocena wpływu użycia ścieków szarych (surowych i oczyszczonych) do nawadniania trawy (życica trwała, Lolium perenne), wyhodowanej na drobnym piasku, na przyrost biomasy w okresie 4 miesięcy. Zastosowano trzy rodzaje cieczy do nawadniania (woda wodociągowa, surowe ścieki szare i oczyszczone ścieki szare) w na dwóch poziomach dawek częściowych: niskim i wysokim (5 i 15 mm na tydzień), w dawkach całkowitych o wysokości 15, 25, 35 i 45 mm na tydzień. Ścieki surowe z pralki, kąpieli w wannie i mycia rąk charakteryzowały się następującymi wskaźnikami: ChZT - 247 ± 33 mg O2·dm-3, BZT5 - 81 ± 12 mg O2·dm-3, azot całkowity - 7,2 ± 0,9 mg N·dm-3 i fosfor całkowity - 4,7 ± 0,7 mg P·dm-3, zaś ścieki oczyszczone odpowiednio: 81 ± 12 mg O2·dm-3, 23 ± 6 mg O2·dm-3, 4,8 ± 0.9 mg N·dm-3, 2 ± 0,2 mg P·dm-3. Wyniki badań wykazały, że wzrost nadziemnej biomasy jest zależny od całkowitej dawki cieczy w zakresie 15 do 45 mm na tydzień. Średni przyrost biomasy trawy podlewanej wodą wodociągową, ściekami oczyszczonymi i ściekami surowymi dla dawki częściowej 5 mm na tydzień (w ramach dawek całkowitych 15-45 mm na tydzień) wyniósł 40,5 ± 7,5, 39,1 ± 7,3, 42,8 ± 6,0 mg s.m., odpowiednio, a dla dawki częściowej 15 mm na tydzień: 52,6 ± 7,8, 54,0 ± 7,5, 50,3 ± 9,2 mg s.m., odpowiednio. Różnica przyrostu suchej biomasy nawadnianej oczyszczonymi ściekami szarymi dawką częściową 5 mm na tydzień i dawką częściową 15 mm na tydzień (na korzyść tej wyższej) była większa niż dla pozostałych rodzajów cieczy; była też istotna statystycznie (p > 6%). Badania wykazały, że surowe i oczyszczone ścieki szare, mogą stanowić alternatywę dla wody wodociągowej w kontekście nawadniania trawnika, nie wywierając negatywnego wpływu na przyrost biomasy.
The study was conducted on grass (Lolium perenne) grown on fine sand in pots to evaluate the effect of greywater reuse on total dry biomass of grass during 4 months. The experiment has been designed as full factorial with total water load: 15, 25, 35 and 45 mm·week-1. Three categories of irrigation water (tap water, treated greywater, raw greywater) were tested in conditional combination with two levels for each category that is the low and high level at 5 and 15 mm·week-1, respectively. The COD, BOD5, total nitrogen, total phosphorus is 247 ± 33 mg·dm-3, 81 ± 12 mg·dm-3, 7.2 ± 0.9 mg·dm-3, 4.7 ± 0.7 mg·dm-3 of raw greywater and 81 ± 12 mg·dm-3, 23 ± 6 mg·dm-3, 4.8 ± 0.9 mg·dm-3, 2 ± 0.2 mg·dm-3 of treated greywater, respectively. The results showed that the dry biomass yields increase when increasing total irrigation water dose from 15 to 45 mm·week-1. The dry biomass yields at 5 mm·week-1 share of tap water, treated greywater, or raw greywater in total irrigation water doses 15-45 mm·week-1 were equal to 40,5 ± 7,5, 39,1 ± 7,3, 42,8 ± 6,0 mg d.m. and at 15 mm·week-1 partial dose: 52,6 ± 7,8, 54,0 ± 7,5, 50,3 ± 9,2 mg d.m. per pot, respectively. The increase in dry biomass yield of grass irrigated with treated greywater (partial dose from 5 to 15 mm·week-1) was higher and more significant (p = 0.13, 0.06, 0.37) than in the two other cases. The study concludes that treated greywater, raw greywater can be a partial or complete replacement for tap water without compromising ryegrass biomass yield.
Źródło:
Inżynieria Ekologiczna; 2018, 19, 6; 80-86
2081-139X
2392-0629
Pojawia się w:
Inżynieria Ekologiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Recovery of HCL from chloride leach solution of spent HDS catalyst by solvent extraction
Autorzy:
Banda, R.
Nguyen, T.H.
Lee, M.S.
Powiązania:
https://bibliotekanauki.pl/articles/185588.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
HCl
extraction
stripping
recovery
TEHA
wydobycie
Opis:
In the present work, amine based extractant and its mixture with cationic and solvating extractants were tested for the extraction of HCl from chloride solution containing Al(III). The chloride feed solution resulted from the leaching of spent HDS (hydro-desulfurization) catalysts. For this purpose, amine extractants, such as TOA (trioctyl amine), Alamine 336 (a mixture of tri-octyl/decyl amine), Alamine 308 (tri-isooctyl amine), and TEHA (tri 2-ethylhexyl amine) were used and the extraction and stripping behavior of HCl was compared. The extracted HCl was easily stripped from loaded TEHA phase, when compared with the other tested tertiary amine system. Solvent extraction reaction of HCl by TEHA was determined from the extraction data. Unlike TOA and Alamine 336, adding cationic extractant to TEHA had negligible effect on the extraction and stripping of HCl. In our experimental ranges, no Al was extracted by amines and pure HCl was recovered. MaCabe-Thiele diagrams for the extraction and stripping of HCl by TEHA were constructed.
Źródło:
Chemical and Process Engineering; 2013, 34, 1; 153-163
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ekonomiczne kryterium wyboru sposobu wzbogacania miałów węgla koksowego
Economic criterion of choosing the way of coking coal fines beneficiation
Autorzy:
Blaschke, W.
Nguyen, T. T. L.
Czarny, G.
Powiązania:
https://bibliotekanauki.pl/articles/283715.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN
Tematy:
węgiel koksowy
wzbogacanie
efekty ekonomiczne
coking coal
beneficiation
economic effects
Opis:
Miały węgla koksowego wzbogacane są w osadzarkach miałowych lub w cyklonach cieczy ciężkiej. Wybór urządzeń wzbogacających zależy od inwestora lub od projektantów zakładu przeróbczego.W Polsce preferowane są osadzarki, w innych krajach (np. w Australii, USA, RPA) stosowane są głównie cyklony cieczy ciężkiej. W artykule przeprowadzono analizę wzbogacania dwóch przykładowych węgli w urządzeniach o różnej dokładności rozdziału ocenianej wskaźnikami imperfekcji. Pokazano różnice w efektach ekonomicznych wynikające z dokładności wzbogacania. Zwrócono uwagę na wpływ charakterystyk technologicznych węgli (krzywe wzbogacania) na uzyskiwane rezultaty wzbogacania przy założonych parametrach jakościowych koncentratów węgli koksowych. Stwierdzono, że wybór sposobu wzbogacania (osadzarki czy cyklony c.c.) powinien być oparty na analizie uzyskiwanych, dla konkretnych węgli, efektów ekonomicznych wzbogacania.
Coking coal fines are beneficiated in jigs or in dense media cyclones. The choice beneficiation equipment depends on investor or preparation plant design engineer. In Poland jigs are preferred while in other countries (like Australia, United States, South Africa) mainly dense media cyclones are used. Beneficiation of two exemplary coals in equipment of different accuracy of separation, measured by imperfection factors, has been analysed in the paper. Different economic effects resulting from beneficiation accuracy has been shown. Attention has been put on the impact of coal technological characteristics (washability curves) on beneficiation effects achieved at assumed quality parameters of coking coal concentrates. It has been stated that the choice of beneficiation method (jigs or dense media cyclones) should be based on economic effects for specific (given) coals.
Źródło:
Polityka Energetyczna; 2009, T. 12, z. 2/2; 29-41
1429-6675
Pojawia się w:
Polityka Energetyczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Development of Solution for Safe Ship Considering Seakeeping PERformance
Autorzy:
Yoon, H.K.
Nguyen, V.M.
Nguyen, T.T.
Powiązania:
https://bibliotekanauki.pl/articles/116617.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
seakeeping
seakeeping performance
safe ship
safe ship considering
optimal weather routing
container ship
Dynamic Programming (DP)
Changwon National University (CWNU)
Opis:
In recent years, safety of a ships has become one important issues needed to solved as soon as possible in ship navigation. Optimal weather routing is one of best solution for ensuring safe operation of a ship with a with short passage time or minimum energy to avoid a certain excessive motion. This paper introduced the development of solution for safety and optimal weather routing a ship considering seakeeping performance based on model test result. This study introduced how to apply A* algorithm based on result of the seakeeping model test for determining the optimal ship routes. Seakeeping model test of 8600 TEU container ship was carried out in Changwon National University's seakeeping basin and its RAOs at various frequencies were used to predict the RMS motion values in irregular waves. The specially modelled path-cost function and the safety constraints were proposed for finding the optimal path of the ship. The comparison of ship performances estimated by great circle’s path and estimated optimal route during the voyage of the ship was investigated.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2018, 12, 3; 517-525
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A syntactic component for Vietnamese language processing
Autorzy:
Le-Hong, P.
Roussanaly, A.
Nguyen, T. M. H.
Powiązania:
https://bibliotekanauki.pl/articles/103931.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Podstaw Informatyki PAN
Tematy:
language
parsing
segmentation
syntactic component
tagging
tree-adjoining grammar
Vietnamese
Opis:
This paper presents the development of a grammar and a syntactic parser for the Vietnamese language. We first discuss the construction of a lexicalized tree-adjoining grammar using an automatic extraction approach. We then present the construction and evaluation of a deep syntactic parser based on the extracted grammar. This is a complete system that produces syntactic structures for Vietnamese sentences. A dependency annotation scheme for Vietnamese and an algorithm for extracting dependency structures from derivation trees are also proposed. This is the first Vietnamese parsing system capable of producing both constituency and dependency analyses. It offers encouraging performance: accuracy of 69.33% and 73.21% for constituency and dependency analysis, respectively.
Źródło:
Journal of Language Modelling; 2015, 3, 1; 145-184
2299-856X
2299-8470
Pojawia się w:
Journal of Language Modelling
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simple method to improve the TCXDVN 306:2004 indoor climate standard for closed office workplaces in Vietnam
Autorzy:
Ha, Pham T. H.
Hoa, Nguyen T.
Binh, Pham T.
Powiązania:
https://bibliotekanauki.pl/articles/35521811.pdf
Data publikacji:
2021
Wydawca:
Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
Tematy:
thermal comfort
artificial indoor environment
standard indoor climatic parameters
office workplace
energy efficient building
Vietnam
Opis:
Thermal comfort is an important parameter of indoor climate, which affects office worker health and productivity, and also aids planning for energy efficient building design and operation. To provide satisfactory thermal comfort in office workplaces under hot and humid outdoor conditions, most contemporary office buildings in Vietnam are fitted with ducted air-conditioning systems. The current Vietnamese standard TCXDVN 306:2004 for indoor climate was derived from thermal comfort research conducted between the 1960s and 1980s. This standard is limited by various drawbacks, including no distinction between natural or artificial environments. In response, this 2018 research provides physical measurements and opinion surveys of current indoor climatic conditions in representative office workplaces in three regions of Vietnam: North, Central and South. The measurement results have been transformed into ET, PMV and PPD indicators, which value demonstrate the shortcomings of the TCXDVN 306:2004 standard, while providing a baseline input for updating this standard to meet the thermal comfort needs of air-conditioned office workplaces, based on the concept of probability comfort, which are integral with the ISO and the ASHRAE standard.
Źródło:
Scientific Review Engineering and Environmental Sciences; 2021, 30, 1; 117-133
1732-9353
Pojawia się w:
Scientific Review Engineering and Environmental Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concrete grade change in the layers of three-layer steel fibre reinforced concrete beams
Autorzy:
Lam, T. Q. K.
Do, T. M. D.
Ngo, V. T.
Nguyen, T. T. N.
Pham, D. Q.
Powiązania:
https://bibliotekanauki.pl/articles/1818828.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
steel fibre concrete
stress-strain
crack
material nonlinear
multi-layer beams
concrete grade
beton
włókno stalowe
naprężenie-odkształcenie
pęknięcie
materiał nieliniowy
belki wielowarstwowe
klasa betonu
Opis:
Purpose: Determine the state of stress-strain, formation and development cracks, three-layer beam diagrams of load-compression stress, load-tension stress, load-vertical displacement relationships with a change in concrete grade. Design/methodology/approach: This paper presents the results of an ANSYS numerical simulation analysis involving stress-strain state and cracking of the steel fiber concrete layers of three-layer reinforced concrete beams with the upper and lower layers. With a cross-section of 150x300 mm, a total span of 2200 mm and an effective length of 2000 mm, the middle is a normal concrete layer. Under two-point loads, all the beam samples were tested. The research simulated three-layer concrete beams in different layers of beams with a change in concrete grade, and compared with and without the use of steel fibers in layers of concrete beams, including the nonlinearity of the material considered. Findings: A diagram of the formation and development of cracks in three-layer concrete beams has been constructed by the study results, determining the load at which the concrete beams begin to crack, the load at which the concrete beams are damaged. In the middle of three-layer steel fiber reinforced concrete beams, load-compression stress, loadtension stress, load-vertical displacement relationships are established. Study results show that these three-layer concrete beams appear to crack earlier than in other cases in cases 2 and 3, but the beam bearing capacity is damaged at 67 kN, the earliest in case 3. And case 6 at 116 kN is the latest. The effects of case 1 and case 3 are small compared with and without the use of steel fibers in cases, while the effects of case 5 and case 6 are very high. Research limitations/implications: The research focuses only on the change of concrete grade in the layers, but the input parameters affecting three-layer steel fiber concrete beams have not been researched, such as the number of tensile steel bars, tensile steel bar diameter, steel fiber content in concrete, thickness variation in three-layer concrete beam layers, etc. Practical implications: Provides a result of experimental study and ANSYS numerical simulation in multi-layer steel fiber concrete beams. Originality/value: The analysis of multi-layered steel fiber concrete beams using experimental and simulation methods shows that other parameters influencing the beams will continue to analysis the working stages of three-layer beams.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2020, 102, 1; 16--29
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
CardS4: modal theorem proving on Java smart cards
Autorzy:
Gore, R.P.
Nguyen, P.T.
Powiązania:
https://bibliotekanauki.pl/articles/309413.pdf
Data publikacji:
2002
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
bezpieczeństwo
kod
kryptografia
security of mobile code
modal deduction
Opis:
We describe a successful implementation of a theorem prover for modal logic S4 that runs on a Java smart card with only 512 KBytes of RAM and 32 KBytes of EEPROM. Since proof search in S4 can lead to infinite branches, this is "proof of principle" that non-trivial modal deduction is feasible even on current Java cards. We hope to use this prover as the basis of an on-board security manager for restricting the flow of "secrets" between multiple applets residing on the same card, although much work needs to be done to design the appropriate modal logics of "permission" and "obligations". Such security concerns are the major impediments to the commercial deployment of multi-application smart cards.
Źródło:
Journal of Telecommunications and Information Technology; 2002, 4; 68-80
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of hydraulic sweeps in horizontal wells
Badanie możliwości oczyszczania hydraulicznego w otworach poziomych
Autorzy:
Nguyen, T. N.
Miska, S. Z.
Yu, M.
Takach, N. E.
Ahmed, R.
Powiązania:
https://bibliotekanauki.pl/articles/300465.pdf
Data publikacji:
2010
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
otwory poziome
oczyszczanie hydrauliczne
horizontal wells
hydraulic sweeps
Opis:
Drilling fluid sweeps are commonly run in the field to help clean the borehole of cuttings that have not been removed with normal drilling fluid circulation, especially in high angle or extended reach wells where efficient hole cleaning is more difficult to maintain. This study focuses on the use of "conventional" and "enhanced" sweeps in horizontal well bores. Not much information pertaining to the use of drilling fluid sweeps is available in the literature. Furthermore, there has been a lack of agreement as to which types of sweep fluids are most effective. Conventional sweeps most often include high viscosity fluids, high density fluids or a combination of both. In addition to conventional sweep fluids, an attempt was made to use enhanced sweep fluids, in which surfactants are used to attach cuttings to oil droplets that are intentionally introduced to the drilling fluid system. Because of their low density, oil droplets can have the ability to keep cuttings particles in suspension. The use of oil droplets is a new concept in cleaning horizontal and deviated wellbores. This work focuses on experimental analysis of sweep fluids with the goal of quantifying the sweep "efficiency". A small-scale sweep loop (SSL) was mainly used to conduct sweep experiments. Moreover, some experiments were carried out in a field-scale flow loop that operates at low-pressure ambient temperature (LPAT) conditions. Results show that pipe rotation plays a very important role in improving hole cleaning. Particularly, the improvement is substantial with high-viscosity fluids. The rotation of pipe has agitation effect that forces the cuttings particles into the main flow and facilitates the removal process. As anticipated, increasing the flow rate enhances the sweep efficiency or cuttings removal regardless of the drillpipe rotation. Furthermore, the study suggests that with a more rigorous evaluation of sweep efficiency, one can objectively determine the type and frequency of drilling sweep. The results of this study are useful for selection of the optimal sweep fluid.
Płuczki czyszczące są powszechnie stosowane do oczyszczania otworów z pozostałości zwiercin, których nie udało się wynieść na powierzchnię za pomocą tradycyjnych płynów płuczkowych, głównie w przypadku otworów kierunkowych i rozgałęzionych, gdzie możliwość oczyszczenia jest ograniczona. Badania skoncentrowały się na wykorzystaniu konwencjonalnych i ulepszonych systemów czyszczących w otworach kierunkowych. W literaturze niezbyt wiele można znaleźć informacji na ten temat. Co więcej, brak jest zgody co do tego, która płuczka czyszcząca jest najskuteczniejsza. Tradycyjne płuczki czyszczące często zawierają płyny o wysokiej lepkości i/lub gęstości. Ponadto podjęto próbę stworzenia ulepszonych płuczek czyszczących, w których zastosowane surfaktanty mają powodować przyklejanie się zwiercin do drobin oleju, który celowo wprowadzono do systemu płuczkowego. Ze względu na niską gęstość, krople oleju utrzymują zwierciny w zawieszeniu. Zastosowanie kropli oleju to nowa koncepcja oczyszczania otworów horyzontalnych. W artykule skoncentrowano się na przeanalizowaniu płuczek czyszczących mających na celu zwiększenie skuteczności oczyszczania. Do badań z reguły stosowano mały obieg czyszczący SSL (small-scale sweep loop). Niektóre eksperymenty prowadzono na złożu w warunkach niskiego ciśnienia i temperatury otoczenia. Wyniki pokazują, że ruch rur odgrywa istotną rolę w zwiększeniu skuteczności oczyszczania otworu. Służy temu również zastosowanie wysoko lepkich płuczek. Rotacja rur podrywa zwierciny doprowadzając je do głównego strumienia, wspomagając proces oczyszczania. Jak przewidywano, ruch w otworze wzmaga wydajność oczyszczania lub wynoszenia zwiercin, niezależnie od rotacji rur. Z badań wynika, że szacując bardziej rygorystycznie zdolności czyszczące, można obiektywnie określić rodzaj i częstotliwość oczyszczania. Wyniki badań pozwalają na stosowny wybór optymalnego środka czyszczącego.
Źródło:
Wiertnictwo, Nafta, Gaz; 2010, 27, 1--2; 307-331
1507-0042
Pojawia się w:
Wiertnictwo, Nafta, Gaz
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method for learning scenario determination and modification in intelligent tutoring systems
Autorzy:
Kozierkiewicz-Hetmańska, A.
Nguyen, N. T.
Powiązania:
https://bibliotekanauki.pl/articles/907820.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
system e-learningowy
nauczanie zdalne
inteligentny system uczący
e-learning system
intelligent tutoring system
learning scenario
personalization
Opis:
Computers have been employed in education for years. They help to provide educational aids using multimedia forms such as films, pictures, interactive tasks in the learning process, automated testing, etc. In this paper, a concept of an intelligent e-learning system will be proposed. The main purpose of this system is to teach effectively by providing an optimal learning path in each step of the educational process. The determination of a suitable learning path depends on the student's preferences, learning styles, personal features, interests and knowledge state. Therefore, the system has to collect information about the student, which is done during the registration process. A user is classified into a group of students who are similar to him/her. Using information about final successful scenarios of students who belong to the same class as the new student, the system determines an opening learning scenario. The opening learning scenario is the first learning scenario proposed to a student after registering in an intelligent e-learning system. After each lesson, the system tries to evaluate the student's knowledge. If the student has a problem with achieving an assumed score in a test, this means that the opening learning scenario is not adequate for this user. In our concept, for this case an intelligent e-learning system offers a modification of the opening learning scenario using data gathered during the functioning of the system and based on a Bayesian network. In this paper, an algorithm of scenario determination (named ADOLS) and a procedure for modifying the learning scenario AMLS with auxiliary definitions are presented. Preliminary results of an experiment conducted in a prototype of the described system are also described.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2011, 21, 1; 69-82
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cultural characteristics and cordycepin production of some Cordyceps militaris strains under artificial cultivation conditions
Autorzy:
Nguyen, L.T.
Le, V.V.
Nguyen, B.T.T.
Ngo, N.X.
Nguyen, H.T.T.
Nguyen, Q.D.
Mulla, S.
Powiązania:
https://bibliotekanauki.pl/articles/2096987.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Cordyceps militaris
mycelial
fruiting body
cordycepin
Opis:
Cordyceps militaris, a precious medical mushroom, has attracted wide attention in industrial fields. Currently, the degeneration phenomenon of C. militaris commercial strains is amongst the major challenges for cultivation at the industrial scale. The screening for superior strains with high yield and medicinal value is considered a realistic approach to overcome degeneration problems. In the present study, the mycelial growth, primordia formation, yield performance, and cordycepin content of five strains (DT1, DT2, DT3, DT4, and DT5) under artificial cultivation conditions were investigated. All strains showed mycelial growth on SDAY and liquid medium. The strains were successfully cultivated in brown rice medium and required 18 (strain DT3) to 25 days (strain DT5) to form primordia. Additionally, morphological characteristics of fruiting bodies varied among the strains. Strains DT4 and DT3 exhibited the highest fruiting body length with 74.23 ± 5.13 mm and 72.63 ± 2.62 mm, respectively whereas the highest diameter was recorded for strains DT1 (4.05 ± 0.18 mm) and DT2 (3.63 ± 0.12 mm). Of note, among the investigated strains, strain DT3 exhibited the highest biological efficiency (8.95 ± 0.07%) and cordycepin content (1.68 mg/g). Therefore, strain DT3 could be selected as a potential strain for commercial cultivation.
Źródło:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology; 2020, 101, 2; 135-145
0860-7796
Pojawia się w:
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 53

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