Методи визначення оптимальних виробничих програм за фінансовими критеріями розвитку підприємства

Запропоновано методи визначення оптимальних обсягів виробництва за критеріями максимізації чистого прибутку і рентабельності продукції підприємства. За результатами розрахунків, проведених за допомогою розроблених моделей для промислових підприємств Львівської області, доведена методологічна різниця між абсолютним і відносним критеріями ефективності

Sorting out sand and gravel : sediment transport and deposition in sand-gravel bed rivers

The general aim of this PhD-project was to gain better understanding of the sediment transport and depositional processes of sand-gravel mixtures in rivers with subaqueous dunes. The understanding of the fundamental processes of sediment transport and deposition in channel beds is crucial for morphological models. Sand-gravel bed rivers have a mixture of sand and gravel in their beds, and have dunes while the coarsest sediment is near incipient motion. In this thesis, the sediment transport, sorting and deposition processes are studied with field measurements and laboratory experiments. Existing bedform stability diagrams were shown to be valid for bedforms observed in sand- gravel bed rivers and experiments, but new bedform types were identified as well: sand ribbons, barchans and bedload sheets. When the bed surface is armoured, barchans and sand ribbons are dependend on the sediment supply from upstream. This supply is often not predictable from the local hydraulics and sediment characteristics. A predictor for bedload transport of sediment mixtures was developed by extending existing deterministic bedload transport predictors to non-uniform sediment, based on flume experiments reported herein. The near-bed turbulence is modelled stochastically to obtain realistic bedload transport rates at incipient motion. The difference in mobility of small and large grains is represented by hiding-exposure functions. The transport predictor was tested on data from the river Rhine, the Netherlands during a discharge wave in 1998. For the measurements, a new measurement strategy was developed during a discharge wave in 1997, leading to an uncertainty in transport rates of less than 20%. Strong time-lag effects were observed in the field that could not be hindcast by the predictor. Part of the observed hysteresis can be explained by vertical sorting of bedload sediment by the dunes, combined with the time lag between dune height development and the changing flow. A record of vertically sorted sediment is left in the channel bed after a discharge wave, which is the antecedent sorting for the next discharge wave, often called history effect'. The entrainment and deposition depth of the sediment depends on the dune trough level below the average bed level and therefore on the dune height. The vertical sorting is in general fining upward by two processes: by grain flows at the lee side of the dunes, and by grain size-selective entrainment and deposition in the dune troughs (gravel lag deposit). Both processes are studied in detail in additional experiments in both equilibrium and non-equilibrium conditions (discharge events). The implications of these results for modelling are discussed

“Вибране” Миколи Воробйова

Braided rivers have complicated and dynamic bar patterns, which are challenging tofully understand and to predict both qualitatively and quantitatively. Linear theoryignores nonlinear processes that dominate fully developed bars, whereas natural riverpatterns are determined by the combined effects of boundary conditions, initial conditionssuch as planimetric forcing by fixed banks and the physical processes. Here we determinethe capability of a state-of-the-art physics-based morphological model to r eproducemorphology and dynamics characteristic of braided rivers and determine the modelsensitivity to generally used constitutive relations for flow and sediment transport. We usethe 2-D depth-averaged morphodynamic model Delft3D, which includes the necessaryspiral flow and bed slope effects on morphology. We present idealized scenarios with thesmallest possible number of enforced details in the planform and boundary conditions inorder to allow free development of bars driven by the physical processes in the model.We analyze bar and channel shapes and dynamics quantified by a number ofcomplementary metrics and compare these with imagery, field data captured in empiricalrelations, flume experiments, and predictions by linear analyses. The results show that thechosen set of boundary conditions and physics in the numerical model is sufficient toproduce many morphological characteristics and dynamics of a braided river butinsufficient for long-term modeling. Initially, braiding intensity with low-amplitude barsis high in agreement with linear analysis. In a second stage when bars merge, split, andincrease amplitude up to the water surface, the shape, size, and dynamics of individualbars compare well to those in natural rivers. However, long-term modeling results in areduction of bar and channel dynamics and formation of exaggerated bar height andlength. This suggests that additional processes, such as physics-based bank erosion, orenforced fluctuations in boundary conditions, such as spatial-temporal dischargevariation, are necessary for the simulation of a dynamic equilibrium river. The mostimportant outcome is that the modeled pattern of bars and channels is highly sensitive tothe constitutive relation for bed slope effects that is used in many morphological models.Regardless of this sensitivity and present model limitations of many models, this studyshows that physics-based modeling of sand-bed braided improves our understanding andprediction of morphological patterns and dynamics in sand-bed braided rivers

Local late Amazonian boulder breakdown and denudation rate on Mars

Inactive fan surfaces become smoother and develop desert pavement over time by weathering and erosion. We use this mechanism to estimate late Amazonian boulder breakdown and surface denudation rates on a young (1.25 Ma) (Schon et al., 2009) fan on Mars. This is done by comparing boulder size and surface relief between lobes of different ages. The boulder breakdown rate is 3.5 m/Myr, surface smoothing (denudation) rate is approximated as 0.89 m/Myr. These rates exceed previous estimates for the Amazonian by orders of magnitude. We attribute this to locality, high initial smoothing rates after morphological activity and obliquity and eccentricity-driven variation in the availability of (metastable) liquid water, which acts as a catalyst for weathering during these periods. The results have major implications for process interpretation of Martian landforms, as they imply that typical small-scale morphology may be subdued within <1 Myr

Огляд матеріалів всеукраїнської науково-теоретичної конференції «Ірраціональне підгрунтя раціональності»

Конференція відбулася 14 квітня 2009 року в приміщенні ПДПУ імені В.Г.Короленка. Організаторами конференції були кафедра філософії Полтавського державного педагогічного університету імені В.Г.Короленка, відділ філософської антропології інституту філософії імені Г.С.Сковороди НАН України, кафедра філософії Київського національного педагогічного університету імені М.П.Драгоманова

Bifurcation instability and chute cutoff development in meandering gravel-bed rivers

Chute cutoffs reduce sinuosity of meandering rivers and potentially cause a transition from a single to a multiple channel river. The channel bifurcation of the main channel and the mouth of the incipient chute channel controls sediment and flow partitioning and development of the chute. Recent channel bifurcation models suggest that upstream bend radius, gradient advantage, inlet step, and upstream sediment supply at the bifurcation are important factors in the evolution of bifurcations. Our objective is to unravel the relative importance of these factors for chute cutoff success and development. We compare results from a morphodynamic three-dimensional (3D) model and a one-dimensional (1D) model with nodal-point relation with field observations of chute cutoffs in a meandering gravel-bed river. The balance between increased gradient advantage and flow curvature upstream of the chute channel bifurcation was systematically investigated with the 1D model. The 3D model runs and the field observations show the development of two types of chute cutoffs: a scroll-slough cutoff and a bend cutoff. The morphodynamic 3D model demonstrates that chutes are initiated when flow depth exceeds the floodplain elevation. Overbank flow and a significant gradient advantage result in a bend cutoff. The outcome of the 1D model shows that channel curvature at the bifurcation determines the success or failure of the chute cutoff when the chute channel is located at the inner bend, as in the case of scroll-slough cutoffs. We conclude that chute initiation depends on floodplain characteristics, i.e., floodplain elevation, sediment composition, and the presence of vegetation. Chute cutoff success or failure is determined by the dynamics just upstream of the channel bifurcation and location of the chute channel in the bend, which determines channel curvature and gradient advantage. These findings have ramifications for the prediction of chute cutoff in a wide range of rivers under natural and managed conditions and for the understanding of stratigraphy and architecture of deposits

Bank pull or bar push: what drives scroll-bar formation in meandering river?

One of the most striking features of meandering rivers are quasi-regular ridges of the point bar, evidence of a pulsed lateral migration of meander bends. Scroll bars formed on the inner bend are preserved on the point-bar surface as a series of ridges as meanders migrate, and in the subsurface of the point bar as inclined heterolithic stratification with lateral accretion surfaces. It is necessary to understand the formation and sedimentary architecture of these point bars, which are fundamental geomorphic building blocks of meandering rivers and potential reservoirs for water, oil, and gas. However, it remains unresolved whether the scroll-bar pattern forms in response to outer bend bank erosion during floods (i.e., bank pull), or is forced by bank progradation (i.e., bar push). Here we use experimentally formed meandering rivers with a set of static and migrating bends to isolate the effects of sediment supply to the point bar, bank protection, and forced bank retreat. We find that channel widening caused by bank retreat near the bend apex causes deposition of new scroll ridges along the inner bend point bar, whereas scroll bars cannot be forced by sediment pulses. Thus channel width variations along meander bends cause bank pull, which is necessary for scroll-bar formation. Furthermore, we find that each newly attached scroll bar overlies a nonpermeable layer of finer-grained sediment caused by the temporary flow expansion, which explains the fining-upward tendency of point bars

Origin of circular collapsed features in the Chryse region of Mars

The quasi-circular collapsed features occurring in the Chryse region of Mars share similar morphological charac- teristics, such as deeply collapsed quasi-circular areas with intensively fractured floor characterized by polygonal tilted blocks of highly variable size. We analyze statistical relations between diameter, maximum and minimum depth, and amount of collapse of several of these features. Based on their morphometric characteristics, we find that these features have a common origin. Different scenarios have been proposed to explain quasi-circular collapsed features. We find that the maximum depth and minimum amount of collapse are strongly correlated to diameter. Impact craters show the same relations, strongly suggesting that collapsed features originated as impact craters. Furthermore, the morphometric characteristics of the infill agree with melting and subsequent collapse of an ice layer below a sediment layer. This interpretation agrees with a buried sub-ice lake scenario. After the formation of an impact crater the increase in temperature resulting from the release of impact energy would induce melting of the surrounding cryosphere. The generated groundwater flows towards the crater, which represents a topograph- ically depressed area with low hydraulic head and produces a crater-lake. The volume of molten cryosphere and the amount of water flow is strictly related to the size of the impact crater: larger craters result in more melting and deeper lake. Due to low surface temperatures, the water lake freezes and sediments can be depositated at the top of the ice layer. The buried ice unit melts as result of the thermal insulation by the overburden in combination with the planetary heat loss, creating a subsurface lake. The system is no longer stable and the overburden collapses, resulting in massive expulsion of liquid water to the surface. Taking into account a uniformly distributed heat loss, the amount of melting is strictly affected by the crater size. This is a non-climatic mechanism for producing and storing abundant liquid water under martian conditions

Earth-like aqueous debris-flow activity on Mars at high orbital obliquity in the last million years

Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. This is testified by the widespread occurrence of mid-latitude gullies: small catchment-fan systems. However, there are no direct estimates of the amount and frequency of liquid water generation during these periods. Here we determine debris-flow size, frequency and associated water volumes in Istok crater, and show that debris flows occurred at Earth-like frequencies during high-obliquity periods in the last million years on Mars. Results further imply that local accumulations of snow/ice within gullies were much more voluminous than currently predicted; melting must have yielded centimetres of liquid water in catchments; and recent aqueous activity in some mid-latitude craters was much more frequent than previously anticipated

Asynchronous formation of Hesperian and Amazonian-aged deltas on Mars and implications for climate

Most fluvial and lacustrine landforms on Mars are thought to be old and have formed more than ~3.8 Gyr ago, in the Noachian period. After a major climatic transition, surface liquid water became less abundant and finally disappeared almost completely. Recent work has shown that observational evidence for Hesperian and Amazonian aqueous processes is more common than previously recognized, but their nature is poorly understood. Moreover, it is not clear how the paleoclimate of Mars can be constrained by this activity. Here we report our investigation of a population of deltas around the ancient impact basin Chryse Planitia. To test whether the results are globally applicable, we also studied selected deltas with similar morphologies in the eastern hemisphere and found that the results are consistent. We compared the morphology of deltas, feeder channels, and receiving lakes, dated deltas by crater counting and searched for alteration minerals in hyperspectral images. The valleys and associated late-stage deltas were formed by short-lived aqueous processes, as suggested by their morphology and the general lack of associated aqueous alteration minerals. The likely source of water was neither widespread precipitation nor a regionally connected groundwater aquifer, but water mobilized locally from the cryosphere. Delta formation in our study areas occurred from the Early Hesperian to the Late Amazonian and did not require sustained periods of global climatic conditions favoring widespread precipitation. Liquid surface water has been locally present on Mars even after the Noachian, although only episodically, for transient intervals, and widely separated in space