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Moisture,Water Holding,Drying and Wetting in Forest Soils

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Open Journal of Soil Science 2014年第5期4卷 174-184页

作者： pavel blazka Zofia Fischer Faculty of Science University of South BohemiaCeske BudejoviceCzech Present Address:Ulrychova 23 162 00 Praha 6Czech Department of Applied Ecology John Paul ⅡCatholic University of LublinLublinPoland

Relationship of soil and water is generally considered as important in soil science. To specify it further we studied two different soils in 2012-2013, three additional soils once and made several series of experiments with drying and wetting of the soils. Principal parameters studied were the gravimetric water content (GWC), water holding capacity (WHC), soil organic matter (SOM), their correlations and rates of change in drying or wetting. The three parameters are significantly inter-correlated. Distribution of GWC in the replicates of soils dried both in nature and in experiments was narrower than that in wet soils, while WHC changed less in drying. The correlations (GWC- WHC) became steeper (the slope coefficient higher) and the coefficient of determination (R2) lower. Attempts to increase WHC in wet soils with a high WHC even further were not successful. Drying may be fast or slow;rates of increase of WHC in wetting were all low, both in field and in the experiments, less than 0.1 g (H2O) g-1 (soil)·day-1. None of the three parameters can be considered as fixed characteristics of forest soils.

关键词： Soil-Water Relationships Climate Change Water Holding Capacity

Respiration Rates of Organic Soil Depending on Changes of Moisture and Aeration

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Open Journal of Soil Science 2017年第6期7卷 101-110页

作者： Zofia Fischer pavel blazka Lidya Dubis Faculty of Mathematics Informatics and Landscape ArchitectureJohn Paul ⅡCatholic University of LublinLublinPoland Department of Science University of South BohemiaCeske BudejoviceCzech

This paper aims at analyzing changes in soil respiration depending on the levels of soil moisture and aeration. Organic forest soil was used in the experiments. Watering of the soil was applied starting from two initial moisture contents: 1) GWC > 0.1, desiccated soil, respiration equals to zero;2) GWC between 0.46 - 0.78, moisture of the soil approximately the same as at the time of sample collection. Watering of the soil was applied once or continuously during the experiment. The experiments were conducted under both: unrestricted air-supply and anoxic conditions. Measurements of: oxygen consumption, carbon dioxide emission, and RQ were determined with a volumetric respirometer. Soil desiccation, which occurs under good access of the air, and leads to the increase of respiration rate (the “Birch effect”), is predominantly related to aerobic respiration following the change in soil aeration. If respiration of non-desiccated soil is assumed as 100%, the oxygen consumption of desiccated soil equaled to 209.90% of such value in the non-desiccated soil at the lowest moisture level, and only to 51% at the highest. Carbon dioxide emission equaled to 191.92% and 111% at the lowest and the highest moisture levels, respectively. Desiccation did not increase the respiration rate under anoxic conditions. It either decreased or remained statistically unchanged. However, obtained values of RQ index suggest that under anoxic conditions desiccation affects fermentation processes in the soil. The value of RQ index at the moisture level lower than GWC 1 was very low attaining merely 0.3 - 0.4, which suggests active fermentation processes. At higher moisture content yet, RQ value exceeded 2.

关键词： Birch Effect Anoxia RQ Watering

Interaction of water droplets with pyrolyzing coal particles and tablets

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Defence Technology（防务技术） 2023年第12期30卷 1-12页

作者： Anastasia Islamova pavel Tkachenko pavel Strizhak National Research Tomsk Polytechnic University Heat and Mass Transfer Laboratory30 Lenin AvenueTomsk634050Russia

The paper presents the experimental research findings for the patterns of collisions of water droplets with pressed tableted samples used as substrates and with small particles of a pyrolyzing solid *** coal samples were ***-substrate interactions were studied when varying the droplet diameter in the range from 1 to 4 mm and velocity from 0.5 to 4 m/*** corresponded to the Weber number range of *** coal tablet surface temperature was varied from 20 to 700℃.In the interactions of water droplets(0.7-1.5 mm in diameter,pre-collision velocity from 1 to 3 m/s)with coal particles(with a size of 0.2-1 mm,pre-collision velocity 0.7-2 m/s),the temperature of the latter was varied in the range of 330-480℃.The following regimes of the interaction of droplets with solid particles during chemical reactions and phase transformations were distinguished:spreading/agglomeration and break-up/*** in the characteristics of the interaction of water droplets with coal particles at varying temperatures were ***-particle interaction regime maps for B(We),We(Oh)and We(Ca)were *** collision regime boundaries were described using fitted curves that can be utilized to develop the existing mathematical models of droplet-particle collisions in *** was established that the gaseous volatile production in coal pyrolysis has a modest effect on the regimes and characteristics of the droplet destruction in the temperature range under consideration(20-700℃).

关键词： Droplet Particle Solid substrate Collision Agglomeration Separation

Influence of stress path change on the resistance to plastic deformation of cold rolled sheets

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Journal of University of Science and Technology Beijing 2005年第6期12卷 521-526页

作者： pavel Huml Metal Forming Department of Materials Science and Engineering The Royal Institute of Technology 10044 Stockholm Sweden

Flat workpieces have been tested in order to investigate the influence of stress path change （loading mode） while keeping strain path unchanged. These investigations are pertinent to the testing of cold rolled strips and to subsequent forming. The workpieces which first compressed by plane strain compression in thickness direction were then tested in perpendicular direction in order to measure the influence of strain and stress path. The tension workpieces came from flat die compression test at different deformation histories. Two different materials were investigated： 18/8 Ti stainless steel and AW-1050 aluminium. The results show that the plastic flow by tension in lengthwise direction after pre-strain by compression in thickness direction will begin at an appreciably lower stress than that of the workpieces unloaded after pre-compression. Comparing with two materials, it can be seen that both 18/8 Ti stainless steel and AW-1050 aluminium behave similarly. The drop in yield stress is lower for AW-1050 aluminium than that for 18/8 Ti stainless steel. However, reloading in different directions than in the precious step results in significantly higher strain hardening.

关键词： cold working plastic deformation strain path stress path loading mode flow stress yield stress strain hardening

Evaluation of the seismic hazard for 20 cities in Romania using Monte Carlo based simulations

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Earthquake Engineering and Engineering Vibration 2017年第3期16卷 513-523页

作者： Florin pavel Radu Vacareanu Seismic Risk Assessment Research Center Technical University of Civil Engineering Bucharest Romania

This work focuses on the evaluation of the seismic hazard for Romania using earthquake catalogues generated by a Monte Carlo approach. The seismicity of Romania can be attributed to the Vrancea intermediate-depth seismic source and to 13 other crustal seismic sources. The recurrence times of large magnitude seismic events（both crustal and subcrustal）, as well as the moment release rates are computed using simulated earthquake catalogues. The results show that the largest contribution to the overall moment release for the crustal seismic sources is from the seismic regions in Bulgaria, while the seismic regions in Romania contribute less than 5% of the overall moment release. In addition, the computations show that the moment release rate for the Vrancea subcrustal seismic source is about ten times larger than that of all the crustal seismic sources. Finally, the Monte Carlo approach is used to evaluate the seismic hazard for 20 cities in Romania with populations larger than 100,000 inhabitants. The results show some differences between the seismic hazard values obtained through Monte-Carlo simulation and those in the Romanian seismic design code P100-1/2013, notably for cities situated in the western part of Romania that are influenced by local crustal seismic sources.

关键词： seismic sources uncertainty seismic moment GMPE percentile

Prognosis of residual coal gas capacity made by the ‘Express' method

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International Journal of Minerals,Metallurgy and Materials 2011年第2期18卷 127-131页

作者： pavel Prokop pavel Zapletal Ivo Pěgímek Technical University of Ostrava

An easy, reliable, and inexpensive method, called ＇Express＇ method, was described to determine the residual gas capacity of deep mines using results from an air and gas balance. Air and gas balances are common elements of mine management and must be performed periodically. Using the process described here to obtain balance results, it is straightforward to obtain the residual gas capacity, which is an important parameter for decision-making in current mine operations. After a mine is closed, the residual gas capacity becomes a dominant factor used to select methods to protect against gas emissions from the closed underground area or perhaps to provide information for the use of gas reserves. The proposed ＇Express＇ method is a much simpler method to obtain the residual gas capacity than other procedures used for this purpose to date.

关键词： coal mines gas storage methane ventilation degassing

Time-headway distribution for random-sequential-update TASEP with periodic and open boundaries

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第1期7卷 30-41页

作者： pavel Hrabák Faculty of Information Technology Czech Technical University in PraguePrague 16000Czechia

The temporal-headway distribution for Totally Asymmetric Simple Exclusion Process(TASEP) with random-sequential update is *** the stationary/steady state of the process,exact formula for the step-headway distribution is derived for conditions when the stationary measure is Bernoulli,Le.,for periodic boundaries and for open boundaries with entering boundary rate α and leaving boundary rate 0 satisfying α+β=*** step-headway formula for general values of boundary rates is calculated numerically by means of the matrix product *** formula is applicable mainly for the model defined on finite small lattice representing short segment of complex *** this case the dependency of the motion of individual particles is noticeable and cannot be *** finite lattice results are compared to continuous time distribution obtained by mans of the large L limit It can be observed that the scaled distribution converges quite fast to continuous time ***,in the case of rather small lattice the distribution significantly differs from the limiting ***,in the case of Bernoulli stationary measure,the distribution is not dependent on the position of the reference site on the *** general values of boundary parameters,the shape of the distribution is influenced by the density profile of the process near *** influence vanishes with increasing lattice size.

关键词： Transportation TASEP Time-headway distribution Random-sequential update Periodic and open boundaries

Transonic Instability in Entrance Part of Mixing Chamber of High-Speed Ejector

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Journal of Thermal Science 2005年第3期14卷 258-263,271页

作者： Vaclav Dvorak pavel Safarik Technical University of Liberec Faculty of Mechanical Engineering Division of Power Engineering Halkova 6 461 17 Liberec Czech Republic Ph.DCzech Technical University in Prague Faculty of Mechanical Engineering 207- Institute of Fluid Dynamics and Power Engineering Division of Fluid Dynamics and Thermodynamics. Technicka 4 166 07 Praha 6 Czech Republic

The paper deals with experimental and numerical study of flow structure in two-dimensional model of supersonic ejector. Schlieren pictures of flow structure were taken, static pressure distributions on side wall were measured and Fluent software to calculate the flow structure in supersonic ejector was used. For certain region of back pressure ratio pb/p02 and stagnation pressure ratio of both streams p01/p02 the terminal shock wave is close to the trailing edge of the primary flow nozzle and a transonic instability occurs. The instability causes the movement of position of boundary layer separation, the structure of shock waves changes and all flow structure oscillates. The movie of these regimes during schlieren experiments was taken and relevant numerical modelling was performed.

关键词： transonic instability ejector shock waves

Comparison of three methods for natural gas dehydration

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Journal of Natural Gas Chemistry 2011年第5期20卷 471-476页

作者： Michal Netusil pavel Ditl Department of Process Engineering Czech Technical University

This paper compares three methods for natural gas dehydration that are widely applied in industry：（1） absorption by triethylene glycol, （2） adsorption on solid desiccants and （3） condensation. A comparison is made according to their energy demand and suitability for use. The energy calculations are performed on a model where 105 Nm3/h water saturated natural gas is processed at 30 °C. The pressure of the gas varies from 7 to 20 MPa. The required outlet concentration of water in natural gas is equivalent to the dew point temperature of -10 °C at gas pressure of 4 MPa.

关键词： gas reservoir underground gas storage natural gas gas dehydration