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Chouping Luo Marek Klisinski 《International journal for numerical methods in engineering》2004,61(2):159-188
The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
3.
Marek Markowski Ireneusz Bialobrzewski Janusz Bowszys Stanislaw Suchecki 《Drying Technology》2007,25(9):1527-1536
A neural-deterministic simulation model applied for calculating distributions of temperatures and moisture content in a bed of wheat stored in a steel silo without aeration is presented in the article. The model consists of differential equations of heat and moisture transfer, initial and boundary conditions, and three artificial neural networks used during simulated ambient air conditions. Experiments and computer simulations were carried out in order to determine temperature fields in wheat grain stored in a steel silo for two months. The computer simulations were carried using MATLAB and FEMLAB software. The difference between measured and simulated temperature in grain near the silo wall at a height of 2.5 m from the bottom was less than 3.0°C. On the basis of the analysis performed it was concluded that the temperature distributions obtained with the model were consistent with the measured results obtained for grain stored in a steel silo without aeration. 相似文献
4.
Marek Gondzio 《Software》1987,17(3):215-226
Every microprocessor-based system needs powerful debugging tools. Debugging power strongly depends on a mechanism of control exchange between the debugger and an application program. Several implementation methods of such a mechanism are briefly described and compared in this paper. It is shown that conditional breakpoints facilitate a semantics-oriented approach to program debugging. Some debugging techniques derived from elementary control-exchange mechanisms are proposed. Most of the techniques discussed are implemented in the MD-86 debugger designed for the Intel 8086 microprocessor. The debugger itself is also briefly described. 相似文献
5.
Marek Pronobis 《Fuel》2006,85(4):474-480
The paper presents an attempt to evaluate the influence of biomass co-combustion on the fouling of boiler convection surfaces. In order to show the influence of co-firing biomass with bituminous coal on boiler efficiency, the calculations of pulverized fuel (PF) OP 140 steam generator have been carried out. Typical Upper Silesian coal with medium fouling inclination has been chosen as a basic fuel. Three kinds of biomass have been taken into consideration: straw, wood and dried sewage sludge. The results confirm that the properties of additional fuels cause deterioration of the boiler efficiency as well as the changes in boilers operational parameters (amount of water injected in attemperators, ash stream, hot air temperature). The biomass during cofiring in fact replaces the coal, but always the additional fuel consumption is higher than that of the substituted coal. Therefore, the actual decrease of coal consumption is smaller than the thermal fraction of the biomass. 相似文献
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In new institutional economics, the variance in institutions explains differences in cross-country output per capita. Institutions may also explain how the supply of oil is affected within oil-producing countries. For example in the early 1970s, as nominal oil prices increased from $3 per barrel to $11 per barrel, a number of OPEC oil producers changed the institutional environment by nationalizing their oil production and putting under government control all petroleum-related capital and infrastructure. This affected oil supplies. Similar institutional changes may be happening again now that oil prices are rising. In particular, the newly democratic Russia may be following the same path. The Russian government has already effectively taken over control of much of the oil production capacity in the country and is still heavily involved in natural gas production. In this paper, we will look at the Russian upstream oil industry as it changed from central planning to a market-oriented sector and is now swaying toward re-nationalization. Some of the laws and institutional transitions will be detailed in order to elucidate what has taken place. 相似文献
9.
Marek Zaionc 《Journal of Automated Reasoning》1988,4(2):173-190
In this paper is presented an algorithm for constructing natural deduction proofs in the propositional intuitionistic and classical logics according to the analogy relating intuitionistic propositional formulas and natural deduction proofs, respectively, to types and terms of simple type theory. Proofs are constructed as closed terms in the simple typed calculus. The soundness and completeness of this method are proved. 相似文献
10.
Barbora Peltanova Marketa Liskova Jaromir Gumulec Martina Raudenska Hana Holcova Polanska Tomas Vaculovic David Kalfert Marek Grega Jan Plzak Jan Betka Michal Masarik 《International journal of molecular sciences》2021,22(4)
Cancer-associated fibroblasts (CAFs) are one of the most abundant and critical components of the tumor stroma. CAFs can impact many important steps of cancerogenesis and may also influence treatment resistance. Some of these effects need the direct contact of CAFs and cancer cells, while some involve paracrine signals. In this study, we investigated the ability of head and neck squamous cell carcinomas (HNSCC) patient-derived CAFs to promote or inhibit the colony-forming ability of HNSCC cells. The effect of cisplatin on this promoting or inhibiting influence was also studied. The subsequent analysis focused on changes in the expression of genes associated with cancer progression. We found that cisplatin response in model HNSCC cancer cells was modified by coculture with CAFs, was CAF-specific, and different patient-derived CAFs had a different “sensitizing ratio”. Increased expression of VEGFA, PGE2S, COX2, EGFR, and NANOG in cancer cells was characteristic for the increase of resistance. On the other hand, CCL2 expression was associated with sensitizing effect. Significantly higher amounts of cisplatin were found in CAFs derived from patients who subsequently experienced a recurrence. In conclusion, our results showed that CAFs could promote and/or inhibit colony-forming capability and cisplatin resistance in HNSCC cells via paracrine effects and subsequent changes in gene expression of cancer-associated genes in cancer cells. 相似文献