High-response hydraulic linear drive with integrated motion sensor and digital valve control

Main purpose of the paper is to present high-response hydraulic linear drive, which is controlled with new digital piezo valve and where the new position transducer is integrated as a part of hydraulic cylinder. Hydraulic digital piezo valve with main static and dynamic characteristics as well as its functionality is presented in detail. The main static and dynamic characteristics of dygital piezo valve which influence directly on the linear drive performance are high resolution of the volume flow rate and high resposne of the valve. Beside valve characteristics the new integrated position transducer, the digital controller and control method, presented in the paper, have major impact on linear drive preformance. At the end of the paper the step response and position resolution of the hydraulic linear drive controlled with the new digital valve is compared with the results of reference hydraulic drive controlled with high response proportional valve

Analysis of the implementation of geodetic engineering works in geodetic companies

Geodetic engineering tasks represent the most demanding tasks in geodetic profession. It is important that geodesist complete those tasks accurately and professionally. We used online survey to investigate what kind of geodetic engineering tasks are performed by slovenian geodetic companies. Survey questions were asking about the method and the type of approacch of solving problems of engineering geodesy. This thesis presents results of the survey and its graphical presentation. Questions, that were set, are described theoretically and there is a commentary added to the results.\u

CFD simulation of flow force reduction in hydraulic valves

Ovaj članak opisuje neke moguće metode za smanjenje statičnih sila protok ulja u hidrauličkom ventilu sa uzdužnim klipom i malim "on/off" sjedežnim ventilom. Sa porastom strujnog toka i razlike tlakova dolazi do povećanja aksijalnih statičnih sila što prouzročava upotrebu viših potisni sila odnosno veću potrošnju energije pri upravljanu ventila. Spomenjeno rezultira obaveznom upotrebom aktuatora veće snage za direktno upravljanje hidrauličkog ventila. Sa stajališta potrošnje energije pri upravljanju ventilom ova tema je veoma važna. Da bi omogućili upotrebu aktuatora niže snage za direktno upravljane ventila s visokim protokom ulja, potrebno je smanjiti aksijale sile koje djeluju na klip u ventilu.Ovaj istraživački rad predstavlja jedno od mogućih rješenja s takvim dizajnom kućišta hidrauličkog ventila i klipa da strujni tok ulja kroz ventil uzrokuje minimalne statične aksijalne sile. Glavni parametri geometrije ventila sa uzdužnim klipom i malim "on/off" ventila su definirani i detaljno analizirani pomoću CFD (Computational Fluid Dynamics) simulacijskoj alata Ansys CFX. Poslije toga provedena je eksperimentalna analiza za validaciju numeričkog modela ventila. Rezultati istraživanja su vrlo obećavajući i dokazuju da aksijalna komponenta sile protoka, a stoga i snaga potrebna za aktiviranje, može se značajno smanjiti samo promjenom geometrije kućišta ventila i klipa. Tako je potrošnja energije za pogon smanjena na minimum, a dinamične karakteristike ventila su poboljšane u isto vrijeme.This paper describes some possible methods for the reduction of the axial static flow forces in hydraulic sliding-spool and small on/off seat valves. These forces increase with the increase in the volume flow and the pressure difference and thus determine higher actuation forces for the control of the valve unit. This results in the necessary use of more powerful actuators for the direct control of hydraulic valves. The topic is therefore very relevant from the energy consumption point of view regarding the actuation of hydraulic valves. To make the use of low-power actuators for the control of directly actuated valves possible also for higher hydraulic power the flow forces acting on the valve piston in the axial direction must be reduced. This paper presents one of the possible solutions with such a design of the hydraulic valve housing and the spool that the flow stream of the fluid through the valve causes minimal axial static forces. The main influential geometry parameters of the sliding-spool and seat valve are defined and analysed in detail using the CFD (Computational Fluid Dynamics) simulation tool Ansys CFX and experimental analysis for the validation of the numerical fluid model of the valve. The results of the research are very promising and prove that the axial component of the flow forces and therefore the necessary actuation force can be reduced significantly just by modifying the geometry of the valve housing and spool. Thus the power consumption of the actuator is minimised and the valve dynamic characteristics are improved at the same time

RESULTS OF RESEARCH INTO THE INFLUENCE OF AN INFORMATION SYSTEM FOR MANAGING CITY UNDERGROUND INFRASTRUCTURE

The paper describes an information system for transforming an "old-fashioned" city infrastructure management system into an interactive system for the future. The paper presents first results from ongoing research into cost analyses and other characteristics of comparisons between traditional and trenchless (Cured-In-Place, CIPP [l]) construction methods for the rehabilitation of sewer pipes at 3 locations (projects) in Zagreb, Croatia. The management of city underground pipe infrastructure has in the last decade experienced large changes in construction techniques, authority policies, and public opinion. The consideration of social costs in reconstruction and installation of underground public utilities is becoming commonplace in most cities. There remain, however, some public utility companies in some countries, including in central Europe, where decision makers have not made significant steps away from traditional methods of construction and continue to work according to old maintenance programs and without proper information systems. The results of this are ailing city infrastructure systems and nowhere near the amount of necessary money available in order to reconstruct all that needs to be improved. The authors are proposing an information system that combines modern trenchless construction technologies with a restructured maintenance, construction and repair program as an optimal means for improving underground infrastructure conditions in cities at a minimum cost. The presented research results are strong indicators of the potential gains a city can achieve by implementing such an information system

EFFECTS OF DIFFERENT VARIANTS OF STERILE AND FERTILE PLANTS ON MAIZE HYBRID YIELDS

Maize is a very important field crop according to both, its distribution and sown areas. The possibility of different utilisation of maize for food, feed and industrial processing is greatly contribute to high economic significance of this crop. The aim of conducted studies was to determine the effect of various proportions of fertile and sterile plants on the yield by performing trials in a certain location. The three-replication trial was set up according to the randomised complete block design in the location of Zemun Polje under conditions dry land farming. A mixture of different variants of sterile and fertile plants of the commercial hybrid ZPSC 341 was made. Statistical data processing included the analysis of variance according to the randomised complete block design, regression and correlation analyses of grain yield and the percentage of fertile plants in the hybrid ZPSC 341, in order to determine the changes in grain yields in relation to the percentage ratio of sterile to fertile plants. Obtained results indicate that the highest (15.472 t ha-1), i.e. lowest (14.046 t ha-1) average yield was recorded in the hybrid with 80%, i.e. 5% fertility, respectively. The coefficient of correlation points to a weak dependence of the yield and the fertility percentage (rxy=0.101). Based on the coefficient of determination, the percentage dependence between the yield and the percentage of fertile plants was low (R²=0.010)

UTJECAJ VREMENA SKLADIŠTENJA NA KAKVOĆU SJEMENA LUCERNE

Alfalfa (Medicago sativa L.) is a crop characterised by presence of hard (dormant) seed that are viable but do not germinate in seed quality testing. In Republic of Croatia seed are frequently stored for three to four years due to low needs for seed of alfalfa and considerable import. The share of hard seed is decreased by storage time, temperature and air moisture changes and therefore directly keeps the level of seed germination in a longer period of storage.Lucerna (Medicago sativa L.) je kultura za koju je karakteristična prisutnost tvrdog (dormantnog) sjemena, koje je živo ali ne klija pri ispitivanju kvalitete sjemena. Zbog malih potreba za sjemenom lucerne i velikog uvoza u Republiku Hrvatsku, nerijetko se događa da sjeme stoji u skladištu tri do četiri godine. Udio tvrdog sjemena sa starenjem, promjenom temperature i vlage zraka se smanjuje, te s tim neposredno utječe na zadržavanje razine klijavih zrna kroz duže vrijeme skladištenja

Nutritionally Enhanced Staple Food Crops

Crop biofortification is a sustainable and cost-effective strategy to address malnutrition in developing countries. This review synthesizes the progress toward developing seed micronutrient-dense cereals and legumes cultivars by exploiting natural genetic variation using conventional breeding and/or transgenic technology, and discusses the associated issues to strengthen crop biofortification research and development. Some major QTL for seed iron and zinc, seed phosphorus, and seed phytate in common bean, rice,J;md wheat have been mapped. An iron reductase QTL associated with seed-iron ~QTL is found in common bean where the genes coding for candidate enzymes involved in phytic acid synthesis have also been mapped. Candidate genes for Ipa co segregate with mutant phenotypes identified in rice and soybean. The Gpe-B1 locus in wild emmer wheat accelerates senescence and increases nutrient remobilization from leaves to developing seeds, and another gene named TtNAM-B1 affecting these traits has been cloned. Seed iron-dense common bean and rice in Latin America; seed iron-dense common bean in eastern and southern Africa;....

Vibration identification using digital image correlation

V zaključni nalogi so predstavljene metode identifikacije kinematike na podlagi korelacije digitalnih slik. V programskem okolju Python smo razvili aplikacijo za namene določanja nihanja in njegovih lastnosti s hitro kamero, na podlagi metode Lucas-Kanade. Opisana sta preizkusa aplikacije s sintetičnim posnetkom in posnetkom iz realnega primera, na katerem smo preverili vpliv nekaterih parametrov na izračun pomikov.In this final thesis methods of kinematics identification based on digital image correlation are presented. An application with the purpose of identifying vibrations and its characteristics using high-speed camera, based on Lucas-Kanade method was developed in the Python ecosystem. Experiments with syntetic and real recordings on which the effect of analysis parameters were tested are also presented