Influential parameters on working performance of the oscillatory transporting platforms for sieving moist materials

Kod postojećih mašina i uređaja za transportovanje čvrste mase pomoću oscilatornih platformi, osnovni zahtevi koje treba ispuniti u toku rada jesu: maksimalan transport, maksimalno razbijanje (usitnjavanje) i maksimalna separacija (izdvajanje) pojedinih komponenetnih sastojaka iz čvrste mase. Poznata je činjenica da je vlažnost zemljišne mase w iskazana u % jedan od najuticajnijih faktora od koga zavise njen transport, separacija i proseja-vanje kroz rešetku (sito) oscilatorne platforme. Najbolji radni efekti postižu se pri radu sa suvom i mekom zemljom bez prisustva čvrstih grudvi. Takva zemljana masa korišćena je u toku eksperimentalne faze istraživanja, koju je autor disertacije realizovao na prototipu oscilatorne platforme na Tehničkom fakultetu u Čačku i na Institutu za krompir u Guči, za vreme izrade svog magistarskog rada 1995. godine [1]. Pod takvim okolnostima platforma je uvek besprekorno obavljala predviđenu radnu funkciju. Međutim, iskustvo iz eksploatacije stečeno u protekle dve decenije pokazalo je da problemi u radu oscilatorne platforme nastupaju nakon obilnih kiša, tj. onda kada se vlažnost zemlje w jako poveća. Tada je efekat transporta i separacije najslabiji, zbog lepljenja vlažne zemlje za raonik koji je u tom slučaju veoma teško podkopava. U pojedinim ekstremnim slučajevima, dolazilo je i do potpunog onemogućavanja rada platforme. Od početka šezdesetih godina prošlog veka, veći broj autora u svetu bavio se konkretnom problematikom povećanja radne sposobnosti platformi, mahom namenjenih za sitnozrnaste i suve materijale. Teorijske osnove rada ovakvih platformi mogu se naći u odgovarajućoj literaturi [2, 3, 4]. Njihovi fizički modeli imali su svoj razvojni - dijalektički put i to počev od najjed-nostavnijih sa jednom ili dve mase međusobno povezane elastičnim vezama [5, 6], pa do najsloženijih modela kod kojih je izvršena optimizacija najuticajnijih radnih parametara [7, 8, 9, 10]. Međutim, svi navedeni modeli odnose se uglavnom na transportovanje suve, najčešće zemljane mase i isti mogu biti dobra polazna osnova za formiranje modela oscilatornih platformi za transport vlažnih materijala. Stoga je autor disertacije došao na ideju da obavi jedno novo teorijsko i praktično istraživanje spomenute problematike, kojim bi se ustanovilo kakav bi bio rad oscilatorne platforme u ekstremno teškim radnim uslovima i to kod maksimalno vlažne i plastične zemlje (tzv. "teške ilovače"). Istraživanjem je trebalo prihvatiti ili odbaciti postavljene hipo-teze, imajući u vidu sve relevantne faktore tj. parametre koji utiču na rad oscilatornih platformi. Nakon realizacije celokupnog istraživanja koje je sprovedeno u dve faze- teorijskoj i eksperimentalnoj, pristupilo se elaboraciji i analizi dobijenih rezultata. Potom su usledili tabeliranje i prezentacija dobijenih rezultata, kako bi isti bili dostupni što širem krugu potencijalnih korisnika. Rezultati i zaključci dobijeni jednim ovakvim kompleksnim istraživa-njem sigurno bi mogli korisno poslužiti za modifikaciju već postojećih, a takođe i za izradu potpuno novih mašina i uređaja koje u svom radu koriste oscilatorne platforme za separaciju i prosejavanje vlažne zemljišne mase. Stoga su na kraju ove disertacije i izneti konkretni predlozi i preporuke za neka nova, buduća istraživanja spomenute problematike.For existing machines and devices for transporting solid mass using oscillatory platforms, the basic requirements that must be met during operation are: maximal transportation, maximal breaking (fragmentation) and maximal separation (segregation) of each component from the solid mass. It is known a fact that the humidity of the land mass w expressed in % is one of the most influential factors from which depends its transportation, separation and sieving through the grille (sieve) of oscillatory platform. The best working effects are achieved when working with dry and soft earth without the presence of solid pieces. Such land mass was used during the experimental phase of the research, which the author of the dissertation realized on the prototype of oscillatory platform at the Technical Faculty in Čačak and at the Institute of potato in Guča, during the drafting his MA thesis in 1995. [1]. Under such circumstances, the platform was always perfectly performed anticipated operating function. However, the experience acquired from the exploitation in the past two decades has shown that problems in the work of oscillatory platforms appear after heavy rains, i.e. when the soil moisture w is greatly increased. Then the effect of transportation and separation is the weakest, due to sticking moist earth for ploughshare, because the ploughshare in this case a very hard to undermines moist eart. In some extreme cases, occurred a complete disabling work of the platform. Since the beginning of the sixties the last century, great number of authors in the world dealt with the specific problems of increasing the working abilities of platforms, mainly intended for fine-grained and dry materials. Theoretical basis of operation of these platforms can be found in the relevant literature [2, 3, 4]. Their physical models had their developmental-dialectical trend starting from the simplest with one or two masses interconnected by elastic connections [5, 6], to the most complex models which have been subjected to optimization of the most influential operating parameters [7, 8, 9, 10]. However, all mentioned models relate mainly to the transport of dry, mostly earthen mass and they may be a good starting point for creation of models the oscillatory platforms for transportation of moist material. Therefore, the author of the dissertation got the idea to do a new theoretical and practical research the mentioned problems, by which it can be established what would be the work of oscillatory platform in extremely difficult working conditions, primarily in the case of maximal wet and plastic land mass (so called "heavy loam"). By using investigations, it was to be accept or reject the proposed hypotheses, having in mind all relevant factors, i.e. parameters which affect the work of oscillatory platform. After realization of whole research, which was conducted in two phases - theoretical and experimental, next step was elaboration and analysis the obtained results. Then followed the tabulation and presentation the obtained results, with the aim that they be available to a wider range of potential users. The results and conclusions obtained by means one such complex research can surely serve useful for modification already existing, and also for the development of a completely new machines and devices which in their work using oscillatory platforms for separation and sieving of wet land mass. Therefore, some particular proposals and recommendations are listed at the end of this dissertation for a new, future research the aforementioned problems

Surgical treatment of intradiploic epidermoid cyst treated as depression

Introduction. Extradural intradiploic epidermoid cysts are rare, representing less than 0.25% of all primary intracranial tumors. They can be neurologically silent and can only present psychiatric symptoms like depression, cognitive or personality changes. Case Outline. A 68-year-old male with two year long history of depressive mood, lack of motivation, helplessness, hopelessness and poor response to antidepressive drug therapy was described. CT scan showed a well-defined mass in the parietal scalp with destruction of the scull. He underwent intracranial tumor resection. Surgical resection and cranioplasty were performed. Pathology confirmed intradiploic epidermoid cyst. Conclusion. Total removal of these cysts and repeated washing of the cavity with 0.9 % saline may prevent recurrence and aseptic meningitis and may improve mental state of the patient. We also emphasize the need for neuroimaging studies in a patient with atypical changes in mental status, even without neurological signs or symptoms

Contribution to the study of climate change in Serbia using continentality, oceanity, and aridity indices

The aim of the study is to present some specific climatic conditions on the territory of the Republic of Serbia based on the analysis of four climate indices, which can help in understanding contemporary climate changes. Temperature and precipitation data from 31 meteorological stations for the period 1951–2010 were used. The relative homogeneity of the data series was done using the MASH v3.02 method. The indices used are: Johansson Continentality Index, Kerner Oceanity Index, De Martonne Aridity Index, and Pinna Combinative Index. Geospatial analysis of the distribution of the values of the four mentioned indices was done using the QGIS package 2.8.1. The results of the research show that the continentality effect is present in most of Serbia, while oceanity is observed locally, mainly in the western and southwestern parts of the country. The further analysis showed that there is no dry and semi–dry Mediterranean climate in Serbia. Considering that it is dry in the warmest part of the year (July–September), when the need for water is increased, which is clearly shown by the Walter climate diagram, as well as the fact that an increase in temperature and a decrease in precipitation during the vegetation period were observed in the second 30–year period (1981–2010), it can be concluded that in Serbia there is a tendency towards arid climate. The results presented in this paper can help decision makers to plan certain climate change adaptation measures

COMPARISON OF THREE FUZZY MCDM METHODS FOR SOLVING THE SUPPLIER SELECTION PROBLEM

The evaluation and selection of an optimal, efficient and reliable supplier is becoming more and more important for companies in today’s logistics and supply chain management. Decision-making in the supplier selection domain, as an essential component of the supply chain management, is a complex process since a wide range of diverse criteria, stakeholders and possible solutions are embedded into this process. This paper shows a fuzzy approach in multi – criteria decision-making (MCDM) process. Criteria weights have been determined by fuzzy SWARA (Step-wise Weight Assessment Ratio Analysis) method. Chosen methods, fuzzy TOPSIS (Technique for the Order Preference by Similarity to Ideal Solution), fuzzy WASPAS (Weighted Aggregated Sum Product Assessment) and fuzzy ARAS (Additive Ratio Assessment) have been used for evaluation and selection of suppliers in the case of procurement of THK Linear motion guide components by the group of specialists in the “Lagerton” company in Serbia. Finally, results obtained using different MCDM approaches were compared in order to help managers to identify appropriate method for supplier selection problem solving

Forensic Science and Fractal Nature Analysis

The forensic photography, also referred to as crime scene photography, is an activity that records the initial appearance of the crime scene and physical evidence, in order to provide a permanent record for the court. Now a day, we can imagine the crime scene investigation without photography evidence. Crime or accident scene photographs can often be re-analysed in cold cases or when the images need to be enlarged to show critical details. Fractals are rough or fragmented geometric shape that can be subdivided in parts, each of which is a reduced copy of the whole Fractal dimension (FD) is an important fractal geometry feature. There are many applications in various fields including image processing, image analysis, texture segmentation, shape classification and identifying the image features such as roughness and smoothness of an image. The damage image can be reviewed, analyzed and reconstructed by fractals

Influence of inorganic consistuents on photocatalytic degradation of ibuprofen

Non-steroidal anti-inflammatory pollutants such as ibuprofen are continuously introduced in water media through various environmental routes. Due to their variability in physico-chemical properties, characteristics of sludge used in secondary treatment and other features, pharmaceutical residues are partially removed in conventional wastewater treatment plants. The effect of inorganic constituent (nitrates) present in real aquatic matrices was examined to assess the overall efficacy of the photocatalytic removal of ibuprofen by nanostructured mixture ZnO/SnO2

Primena hidrostatičkog klipnog uređaja za proveru sile pritezanja i dilatacije zavrtnja pri ostvarivanju zavrtanjske veze

For the most responsible screw connections (especially those with large prestressing) it is very important to precisely define the required tightening force Fp which must not be less than the minimum necessary force Fpmin, nor greater than the maximum permissible force Fpmax . If Fp Fmax plastic deformations may occur and consequently permanent damage of some elements of screw connection.Therefore, the tightening force should be defined as precisely as possible, and then in practice it needs to be adequately measured and controlled in a screw connection. The paper presents an original laboratoryexperimental method for measuring the forces and dilatations of the screw during tightening based on the application of a special hydrostatic piston device as well as a brief description and operating principle of the device. The device was designed at the Higher Technical School of Mechanical Engineering in Trstenik and it can be used for laboratory exercises in technical schools and faculties, as well as in the industry for checking the mechanical properties of the screws before being mounted, and also for various experiments in research laboratories and institutes.Publishe

Research on parameters influencing performance of vibrating platforms during transporting the dry earth mass

Jedan od osnovnih zahtjeva pri korištenju vibracijskih transportnih platformi ogleda se u ostvarenju maksimalnog učinka tijekom njihovog rada, uz istovremeno usitnjavanje mase i odvajanje pojedinih sastojaka iz same mase. U radu je primjenom response surface methodology (RSM), koja je bazirana na design of experiments (DoE), formiran matematički model za istraživanje utjecajnih geometrijskih i kinematskih parametara na optimalni radni učinak vibracijske platforme. Provedenim eksperimentom, korištenjem višefaktornog ortogonalnog plana tipa 2k formirane su krive hiperboličkog tipa i utvrđeno je da se one uvijek nalaze između krivih koje su formirane na temelju rezultata teorijskog modela, čime su potvrđeni i verificirani istraživački rezultati.One of the main requirements related to application of vibrating platforms is to achieve the maximum productivity during their operation and, at the same time, to break mass and separate some components from the mass itself. Application of response surface methodology (RSM), which is based on design of experiments (DoE), resulted in mathematical model for exploring geometrical and kinematic parameters influencing the optimum operating performance of vibrating platform. The experiment was conducted by means of multifactor orthogonal plan type 2k and hyperbolic curves were formed. It was also determined that these curves are always between the curves formed on the basis of results of theoretical model, which verifies the research results