Long-term changes in stochastic structure of hydrolagic time series

Hidrološki proces moguće je analizirati kao stohastički proces na osnovu koga se donosi zaključak o njegovoj unutrašnjoj stohastičkoj strukturi. Struktura hidrološkog procesa predstavlja bitnu osobinu na osnovu koje se dobijaju informacije o njegovoj vremenskoj zakonomernosti. Dugoročne promene u strukturi hidrološkog procesa predstavljaju značajno pitanje savremene nauke. Isto tako, važna istraživačka pitanja predstavljaju i matematičko opisivanje hidroloških procesa, opisivanje njihove uzročno-posledične veze sa meteorološkim parametrima, kao i predviđanje dugoročnih promena hidroloških procesa. Osnovni cilj ovog rada je razvoj metodologije kojom se analiziraju dugogodišnje promene u hidrološkim serijama. U doktorskoj disertaciji su predložene metodologije za formiranje stohastičkih modela za kratkoročne i dugoročne projekcije godišnjih i mesečnih protoka. Metodologija za kratkoročne projekcije godišnjih i sezonskih protoka se zasniva na dekompoziciji vremenskih serija na trend, periodičnost, stohastičku i slučajnu komponentu, po uzoru na metodu TIPS koju je predložio Jevđević (1984). Predložena metodologija je nazvana modifikovana TIPS metoda. Vremenska serija se deli na deterministički deo koga čine linearni trend i višegodišnja periodičnost. Drugi deo predstavlja stohastička komponenta koja se modelira autoregresionim modelima višeg reda. Modifikacija TIPS metode se sastoji u identifikaciji makroperiodične komponente na uglačanim godišnjim i sezonskim serijama proticaja tehnikom LOESS. Na ovaj način se uklanjaju oscilacije visoke frekvencije i olakšava identifikacija makroperiodične komponente koja je od prevashodnog značaja za razmatranje dugoročnih promena u hidrološkim nizovima. Ovako uspostavljen model se koristi za kratkoročne projekcije godišnjih proticaja tako što se determinističke komponente ekstrapoluju, vrši se prognoza stohastičke komponente i određuje interval poverenja prognoziranih proticaja. Za razliku od kratkoročnih projekcija koje se dobijaju pomoću modela zasnovanog na unutrašnjoj strukturi serija protoka, za dugoročne projekcije mesečnih proticaja predložen je model koji koristi zavisnost proticaja od padavina i temperatura. Cilj modela jeste da se omogući njegova primena za dugoročne projekcije proticaja na osnovu klimatskih scenarija. Primenom analize osetljivosti protoka na glavne meteorološke faktore, utvrđeno je da na mesečne proticaje najviše utiču mesečne padavine. Takođe, dugoročne promene u proticajima su posledica postojanja istih promena u padavinama. Drugi uticajni faktor je temperatura, zbog čega je odlučeno da se model za dugoročne projekcije zasniva na zavisnosti protoka od padavina i temperatura. Za dugoročne projekcije protoka predložen je model SDTS, kojim se mesečni proticaji dele na deterministički deo sastavljen iz kompozitnog nelinearnog trenda, makroperiodične i sezonske komponente. Drugi deo je stohastički baziran na transfer funkcijama sa dvostrukim ulazom (padavinama i temperaturama) na mesečnoj vremenskoj skali. Ostatak serije čini potpuno slučajna komponenta. Prve dve determinističke komponente u predloženom modelu SDTS (nelinearni trend i makroperiodična komponenta) se modeliraju na godišnjem nivou, dok se preostale komponente modeliraju na mesečnom nivou. Pored modela SDTS, kao pomoćni model, razvijen je inicijalni model godišnjih proticaja zasnovan na transfer funkcijama sa godišnjim padavinama i temperaturama kao ulaznim vremenskim serijama. Ovaj model omogućava dugoročnu prognozu trenda i makroperiodične komponente na godišnjem nivou. Primena modela SDTS sa dugoročnim projekcijama padavina i temperatura iz klimatskih modela je moguća ukoliko se obezbedi ekstrapolacija svih komponenti modela u budućnost. U predloženom modelu komponente su ekstrapolovane na različite načine: (1) Nelinearni trend i makroperiodična komponenta za budućnost su dobijene na osnovu simuliranih godišnjih proticaja inicijalnim modelom sa padavinama i temperaturama iz klimatskih scenarija na godišnjem nivou; (2) Sezonska komponenta u budućnosti je formirana na osnovu pretpostavke da će se unutargodišnji ciklus proticaja u budućnosti menjati u skladu sa promenom unutargodišnjeg ciklusa padavina; (3) Stohastička komponenta za budućnost je rezultat primene modela transfer funkcija na mesečnom nivou sa mesečnim padavinama i temperaturama iz klimatskih scenarija.Hydrological time series is analysed as a stochastic process that is utilized to make an inference according to the internal stochastic structure. The stochastic structure of a hydrological process presents the main characteristic that is used to obtain information about its realization pattern through the time. The long-term change in the structure of hydrological process presents essential issue of contemporary science. Also, the important research questions are mathematical modeling of hydrological process, its cause-consequence relation with meteorological variables and prediction of a long-term change of hydrological process. The aim of this research is to develop the methodology used to analyse the long-term projections in hydrological time series. In the doctoral dissertation the methodologies for constituting stochastic models for the short-term and long-term projection of annual and monthly flows are proposed. The methodology for short-term projection of annual and seasonal flows is based on decomposition of time series on trend, periodical component, stochastic and random component inspired by TIPS method proposed by Yevjevich (1984). The proposed methodology is called the modified TIPS method. The time series is divided into two parts: the deterministic part which is constituted of linear trend and long-term periodicity and the stochastic component is modeled by autoregression models of higher orders. The modification of the TIPS method consists of identification of macroperiodical component of annual and seasonal flows by using the LOESS technique. In this manner, the high-frequency oscillations are removed. This fact is facilitated identification of long-term periodical component which is of fundamental significance for consideration of long-term changes in hydrological time series. The established model is used for the short-term projection of annual flows by extrapolation of deterministic component, the projection of stochastic component and determining the confidence interval of projected flows. In contrary to the short-term projections determined by using the model based on internal structure of flow series, the model based on relations among flows, precipitations and temperatures is proposed for a long-term projection of annual flows. The aim of the model is to provide the application of long-term projection of flows in accordance with climatic scenarios. The Application of sensitivity analysis of flow using the main meteorological factors is determined by the precipitations as the major influental parameter on flows pattern. Moreover, the long-term changes of flow time series are the consequence of the same multi-decadal changes in precipitations. The second influential parameter is temperature. Due to this fact, the model for long-term projection is considered to be constituted by using the relation among the flows, precipitations and temperatures. For the long-term projection the proposed SDTD model is used for decomposition of the monthly flow series into the deterministic part composed of composite non-linear trend, macroperiodical component and seasonal component. The second part is stochastic component modeled by the Transfer Functions with multiple inputs (precipitation and temperature) on monthly time scale. The first two deterministic components of the proposed SDTS model (non-linear trend and macroperiodical component) are modeled at the annual level, while the rest of the components are modeled by using a monthly time scale. In addition to the SDTS model, the Initial model of annual flows is developed as an auxiliary model based on Transfer Functions with annual precipitations and temperatures as input time series. This model provides the long-term projection of trends and macroperiodical component at annual level. The application of the SDTD model with long-tem projections of precipitations and temperatures from climatic models is possible under conditions provided by extrapolation of all model’s components in the future. In the proposed model the components are extrapolated by employing different manners: (1) Non-linear trend and macroperiodical component in the future are determined by using the simulated annual flows which are modeled with precipitations and temperatures from climatic model at annual time scale, (2) Seasonal component in the future is formed on the assumption that the interannual flows will be changed according to the interannual changes of precipitations, (3) Stochastic component in the future is result of the Transfer Function model on monthly time scales with monthly precipitations and temperatures from the climatic scenarios

Current state and perspective of water management policy in terms of climate change: Case study of the Velika Morava River

The purpose of this paper is to set out the policy guidelines and recommendations to harmonise the Serbian water legislation with European Union standards in the area of water system management as impacted by climate change. The EU Water Framework Directive is analysed in the context of implementation of the integrated water management policy presented in the Serbian Water Law (2010), as well as the National Water Management Strategy (2016). It has been found that the water management legislation that deals with the impact of climate change on water resources is incomplete. Although there are numerous challenges related to research of climate change and water systems, water policy and legal aspects cannot be neglected. The so-called soft law instruments represented in a form of strategy documents could be a valuable response in terms of an adaptive and integrated water policy approach. The research is applied to a case study of the Velika Morava River Basin, at Ljubicevski Most hydrological station. Long-term projections suggest a decrease in annual precipitation levels and annual flows up to the year 2100 for climatic scenarios A1B and A2, accompanied by a rapid increase in air temperatures. This study proposes a water management policy and provides recommendations for the Velika Morava River Basin as impacted by climate change, according to the European Union legislation

Variability of dry substance accumulation and utilization parameters of Winter wheat plant

Some dry substance accumulation and utilization parameters of wheat plant and their influence on grain yield have been studied through a field trial with 20 winter wheat cultivars. The studied parameters value (biological yield dry substance reutilization, number of grains per spike, 1000 grain mass plant height, etc) varried depending of genotypic specificity and environmental conditions. Grain yield was influenced not only by the total dry substance accumulation in plant (i.e. biological yield), but also by this accumulation amount before and after flowering. Yield forming was affected by many parameters, and cultivar range was different for various parameters. The best grain yield was observed in cultivars having elevated values of more than few parameters. The highest mean grain yield was observed in cultivar Tina, and also high grain yield values were found in cultivars Gruža Nevesinjka, and Toplica

DETECTION AND HANDLING EXCEPTIONS IN BUSINESS PROCESS MANAGEMENT SYSTEMS USING ACTIVE SEMANTIC MODEL

Although business process management systems (BPM) have been used over the years, their performance in unpredicted situations has not been adequately solved. In these cases, it is common to request user assistance or invoke predefined procedures. In this paper, we propose using the Active Semantic Model (ASM) to detect and handle exceptions. This is a specifically developed semantic network model for modeling of semantic features of the business processes. ASM is capable of classifying new situations based on their similarities with existing ones. Within BPM systems this is then used to classify new situations as exceptions and to handle the exceptions by changing the process based on ASM’s previous experience. This enables automatic detection and handling of exceptions which significantly improves the performance of bpm systems

THE INFLUENCE OF VARIOUS MICROENVIRONMENTAL FACTORS ON BIOMECHANICAL FEATURES OF DIFFERENT SUTURE MATERIALS USED IN HEPATO-PANCREATO-BILIARY SURGERY

The key features of any suture material, such as its tensile strength, knot security, resorbability, handling characteristics and biological behavior must be taken into account during the selection process. These biomechanical features may be variable in different microenvironmental conditions in the human body in which the sutures are placed due to the influence of numerous local biohumoral factors. We have reviewed the data on the impact of pancreatic juice and bile, various pH conditions, chemotherapy and heat on different suture materials behavior. It is suggested that in pancreatic and biliary surgery polydioxanone sutures should be used. The review has also demonstrated that absorbable suture materials were more sensitive to pH than non-absorbable sutures. In addition, polyglyconate sutures were the strongest of all absorbable synthetic sutures when exposed to heat and cytotoxic drugs. This review provides a better basis for the selection of suture materials for specific applications

USER DEFINED GEOMETRIC FEATURE FOR THE CREATION OF THE FEMORAL NECK ENVELOPING SURFACE

There is a growing demand for application of personalized bone implants (endoprostheses or macro-scaffolds, and fixators) which conform the anatomy of patient. Hence the need for a CAD procedure that enables fast and sufficiently accurate digital reconstruction of the traumatized bone geometry. Research presented in this paper addresses digital reconstruction of the femoral neck fracture. The results point out that User-Defined (geometric) Feature (UDF) concept is the most convenient to use in digital reconstruction of numerous variants of the same topology, such as in this kind of bone region. UDF, named FemoNeck, is developed to demonstrate capability of the chosen concept. Its geometry, controlled by a dozen of parameters, can be easily shaped according to anatomy of femoral neck region of the specific patient. That kind of CAD procedure should use minimally required set of geometric (anatomical) parameters, which can be easily captured from X-ray or Computed Tomography (CT) images. For the statistical analysis of geometry and UDF development we used CT scans of proximal femur of 24 Caucasian female and male adults. The validation of the proposed method was done by applying it for remodeling four femoral necks of four different proximal femurs and by comparing the geometrical congruency between the raw polygonal models gained directly from CT scan and reconstructed models

REVIEW OF BONE SCAFFOLD DESIGN CONCEPTS AND DESIGN METHODS

The paper brings out a review of existing, state-of-the-art approaches to designing the geometry of the scaffolds that are used for tissue engineering with a special emphasis on the macro scaffolds aimed for bone tissue recovery. Similar concepts of different authors are organized into groups. The focus of the paper is on determining the existing concepts as well as their advantages and disadvantages. Besides the review of scaffolds' geometry solutions, the analysis of the existing designs points to some serious misconceptions regarding the scaffold role within the (bone) tissue recovery. In the last section of the paper, the main requirements regarding geometry, that is, architecture and corresponding mechanical properties and permeability are reconsidered

Productivity of some winter wheat genotypes

Yields given by different genotypes are affected by many factors, but mostly by genotype, climatic conditions and applied growing practice. Therefore, the aim of this study was to establish productivity of many winter wheat genotypes in southern Serbia, through macro-trials. The results showed the difference of grain yield mean between the investigated seasons, and that difference amounted about 1300 kg/ha. The average yield was the highest in cultivars Toplica, Stamena, Evropa, NS-rana 5, and Renesansa. The lowest grain yield was given by cultivars Tina, Sara, Sreća, and Mina

Dugoročne promene godišnjih i sezonskih proticaja - primer reke Save

This paper investigates the long-term changes in the hydrological time series. For this purpose, we use the trend analysis. The trend analysis is performed by using the standard Mann-Kendall trend test and by using the multi-temporal approach. The analysis is applied to the standardized and averaged time series of seasonal and annual flow of the river Sava at the stations Zagreb and Sremska Mitrovica for period from 1926 to 2005. It is concluded that the trend of seasonal and annual flow series of the Sava River are downward. The trends of annual flows in the region (Danube, Velika Morava, Lim) confirm this general pattern according to which the trends of annual flows in south-eastern Europe are downward. The multi-temporal analysis shows that the trend direction and intensity in the sub-series change with the long-term periodicity. The changes in trend direction and intensity depend on the length of the sub-series and the position of the sub-series within the whole time series.U ovom radu analizirane su dugoročne promene u vremenskim serijama oticaja. Razmatrano je prisustvo trenda i višegodišnjih vodnih i sušnih ciklusa. Analiza trenda vršena je standardnim Mann-Kendall testom, a pored toga trend je analiziran korišćenjem tzv. multi-vremenskog pristupa u kojoj se trendovi računaju za podserije različitih početaka i dužina. Analiza je sprovedena na standardizovanim i osrednjenim serijama sezonskih i godišnjih proticaja na reci Savi na stanicama Zagreb i Sremska Mitrovica za period 1926-2005. Kada se posmatra ceo period, zaključuje se da je trend sezonskih i godišnjih proticaja na reci Savi opadajući. Trendovi godišnjih proticaja u širem području (Dunav, Velika Morava, Lim) su u skladu sa ovim rezultatima, dok reka Tisa poseduje rastuće trendove godišnjih proticaja. Multivremenskom analizom pokazano je da se trend razlikuje za različite podserije. Na smer i nagib trenda vremenskih serija utiče dužina serije kao i položaj podserije unutar cele serije. Promena smera i nagiba trenda ima ciklični karakter što odgovara smenama višegodišnjih vodnih i sušnih perioda

Stochastic structure of annual discharges of large European rivers

Water resource has become a guarantee for sustainable development on both local and global scales. Exploiting water resources involves development of hydrological models for water management planning. In this paper we present a new stochastic model for generation of mean annul flows. The model is based on historical characteristics of time series of annual flows and consists of the trend component, long-term periodic component and stochastic component. The rest of specified components are model errors which are represented as a random time series. The random time series is generated by the single bootstrap model (SBM). Stochastic ensemble of error terms at the single hydrological station is formed using the SBM method. The ultimate stochastic model gives solutions of annual flows and presents a useful tool for integrated river basin planning and water management studies. The model is applied for ten large European rivers with long observed period. Validation of model results suggests that the stochastic flows simulated by the model can be used for hydrological simulations in river basins