Teaching Magneto-Thermal Coupling Using Thomson\u27s Levitating Ring Experiment

The levitating ring experiment is presented as a method for teaching magneto-thermal interactions. The complete electromagnetic model of a problem is given, together with the insight in thermal analysis. The factors for determining the vertical displacements are explained, and an elegant method for indirect measurement of induced current in the ring is introduced. The whole apparatus is explained in detail so an accurate computer model can be made. Several simulation approaches are given, and all prove the applicability in teaching coupled problems using laboratory experiments and computer modeling

PREBAČAJ KUNJKE Arca noae Linnaeus, 1758 IZ PRIRODNIH UVJETA U RAZLIČITE UVJETE EKSPERIMENTALNOG UZGOJA

Noah’s ark shell Arca noae Linnaeus, 1758 is one of commercially important species in Croatia harvested from the wild. Its length/sex relationship, sex ratio and survival after transfer from natural habitat to different experimental farming conditions were examined. Statistically smaller lengths were detected for males (x=52.6±8.7 mm) than for females (x=60.2±9.5 mm). The overall sex ratio was 1.8 : 1.0 in favour of males. Survival after 17 months was only 20.5%. This study demonstrated that A. noae specimens can be transferred from the wild onto field experimental conditions, but high post transfer mortalities occurred. Gathered data about post transfer mortalities and relationship between the sexes and lengths could be useful when planning aquaculture/hatchery operations for this bivalve species. Furthermore, they will be of great help for the further development of farming technology of this species.Kunjka Arca noae Linnaeus, 1758 je jedna od komercijalno važnih vrsta školjkaša u Hrvatskoj koja se izlovljava iz prirodnih staništa. Istražili smo odnos dužina prema spolu, udio spolova i preživljavanje nakon prebačaja iz prirodnog staništa u eksperimentalne uzgojne uvjete. Statistički značajno manje dužine uočene su kod mužjaka (x=52,6±8,7 mm) u odnosu na ženke (x=60,2±9,5 mm). Ukupni udio spolova bio je 1,8 : 1,0 u korist mužjaka. Preživljavanje nakon 17 mjeseci iznosilo je 20,5%. Istraživanje ukazuje na mogućnost prebačaja kunjke iz prirodnih staništa u nove uzgojne uvjete, ali uz posljedično visoku smrtnost. Dobiveni podatci o mortalitetu nakon prebačaja i odnosa između spola i dužine mogu biti korisni prilikom planiranja akvakulture/mrijesta za ovu vrstu. Nadalje, podatci će biti korisni za daljnji razvoj tehnologije uzgoja kunjke

Integral Approach for Overvoltage Management Based on Field Data and Modelling

The requirements for the power network to be flexible and to be able to transmit more power are becoming more important as a consequence of high share of the renewables. Therefore, to maintain the level of reliability of the power network, it is necessary to monitor more and more data as well as to better understand the phenomena that might exist in the power system, such as transients. One of the points that are of interest are interaction between power transformer and the other components in the network. A failure of such component may lead to power network unavailability and high economic cost. According to the CIGRE WG A2.37, high portion of the transformer failure may have been caused by the overvoltage. Therefore, it is important to handle overvoltage in the power network with high care. In this paper, an integral approach for power transformer overvoltages management based on field measurements and advanced electromagnetic transients (EMT) modelling is presented. It consists of simulating overvoltages using detailed power network models, including the high frequency transformer models and continuous monitoring of overvoltage events at the places of interest in the power network. This work gives a framework for dealing with overvoltages in the power network that could be implemented by power utilities

Crecimiento e índice de condición – dos importantes factores en la crianza de los mejillones

Proizvodnja dagnje zastupljena je u većini mediteranskih zemalja, a najveći proizvođači su Španjolska i Grčka. Hrvatska proizvodnja je u odnosu na ukupnu količinu vrlo mala i već desetljećima konstantno iznosi oko 3.000 tona godišnje. Tehnologija uzgoja dagnji je relativno jednostavna, a cijeli sektor karakterizira neorganiziranost tržišta i nepovezanost proizvođača. Prirast i indeks kondicije dagnji važni su čimbenici u proizvodnji dagnji, zbog što bržeg postizanja tržišne veličine te količine mesa u ljušturi. Poznavanjem hidrodinamičkih i trofičkih karakteristika uzgojnog područja te bioloških karakteristika dagnje, uz pravilne zootehničke zahvate, može se djelomično utjecati i na vrijednosti prirasta i indeksa kondicije. Cilj ovog rada je opisati osnovne faktore koji utječu na brzinu rasta i kondicije dagnje. Svrha rada je opis osnovnih tehnoloških postupaka u proizvodnji, čime se mogu maksimalno iskoristiti prirodni potencijali određene lokacije za uzgoj, te direktno povećati korist (dobit) uzgajivača.Production of mussels is present in most of the Mediterranean countries, with Spain and Greece as the largest producers. Compared to the total production, Croatian mussel production is continuously small – only around 3.000 tones of mussels a year are placed on the market. Farming technology is relatively simple, while the whole sector is characterized with unorganized market and unconsolidated small producers. Growth and condition index are important factors for mussel farming in terms of reaching the market sized length and good meat yield. By knowing the hydrodynamics and trophic features of the production area and the biological characteristics of mussels, along with the right zoo technical procedures, we can partially influence growth and condition index of cultured mussels. The aim of this paper is to describe main ecological impacts on these two factors under aquaculture. The purpose is to summarize important farming procedures, which can reflect with utilization of the natural potentials on the production site and with increased profitability for the producer.Die Pfahlmuschelzucht ist in den meisten Mediteranländern vertreten. Die größten Hersteller sind Spanien und Griechenland. Die kroatische Herstellung ist in Bezug auf die Gesamtmenge sehr klein. Sie beträgt seit Jahrzehnten ständig um 3.000 Tonnen jährlich. Die Technologie der Pfahlmuschelzucht ist verhältnismäßig einfach. Der ganze Sektor ist durch das Nicht-Organisiertsein des Marktes und die Nicht-Verbundenheit der Hersteller charakterisiert. Zuwachs und Konditionsindex sind wichtige Faktoren in der Pfalmuschelzucht, dies zwecks Erreichens der Marktgröße und der Fleischmenge in der Muschel. Durch hydrodynamische und tropische Charakteristiken des Zuchtgebietes sowie durch biologische Charakteristiken der Pfahlmuscheln und auch durch richtige zootechnische Eingriffe kann man teilweise auf den Zuwachs- und Konditionsindexwert einen Einflus ausüben. Das Ziel dieser Arbeit ist die Grundfaktoren zu beschreiben, die die Schnelligkeit des Zuwachses und die Kondition von Pfahlmuscheln haben. Der Zweck der Arbeit ist, die technologischen Grundprozesse in der Herstellung zu beschreiben, womit Naturpotentiale der bestimmten Zuchtlokalität maximal ausgenützt werden können. Somit wird der Gewinn des Herstellers direkt vergrößert.La mitilicoltura è presente nella maggior parte dei paesi del Mediterraneo, tra i quali primeggiano la Spagna e la Grecia. La produzione croata, in rapporto alla quantità complessiva, è molto piccola ed è ormai da decenni costantemente assestata attorno alle 3.000 tonnellate l’anno. La tecnologia di produzione dei mitili è relativamente semplice, mentre l’intero settore è caratterizzato dalla disorganizzazione del mercato e dalla mancanza di collegamento tra produttori. La crescita e l’indice di condizione dei mitili sono fattori importanti nella loro produzione. È importante, infatti, che raggiungano quanto prima la taglia commerciale e la maggior quantità di polpa tra le valve. Grazie alla conoscenza delle caratteristiche idrodinamiche e trofiche dell’area di produzione e delle caratteristiche biologiche dei mitili, con interventi zootecnici adeguati è possibile influire parzialmente anche sui valori della crescita e dell’indice di condizione. Obiettivo di questo lavoro è descrivere i fattori base che incidono sulla velocità della crescita e sull’indice di condizione dei mitili. Scopo del lavoro è descrivere le procedure tecnologiche di base nella produzione, in modo tale da sfruttare appieno le potenzialità naturali di una determinata area d’allevamento e determinare, così, anche un incremento diretto degli utili degli allevatori.La producción de los mejillónes está presente en la mayoría de los países mediterráneos y los productores mayores son España y Grecia. La producción de Croacia es pequeña en vista de la cantidad total y es alrededor de 3.000 toneladas por año. La tecnología de la crianza de mejillónes es relativamente simple y el sector entero está caracterizado por la falta de organización del mercado y la desconexión de los productores. El crecimiento y el índice de condición son los factores importantes en la producción de mejillones. Se trata de obtener la masa mercantil optimal y la carne en la concha lo más pronto posible. Es posible influir parcialmente en los valores del crecimiento y el índice de condición conociendo las características hidrodinámicas y tróficas del territorio, tanto como las características biológicas de los mejillones. El objetivo de este artículo fue describir los factores que influyen sobre la rapidez del crecimiento y la condición de mejillón. La finalidad del artículo es la descripción de los tratamientos tecnológicos básicos de la producción, lo que permite la eficacia maximal de los potenciales naturales de cualquier lugar para la crianza y así incrementar directamente el provecho (beneficio) de los productores

Shellfish as biological indicators of environmental pollution in costal ecosystems

Shellfish are filter feeders, able to accumulate different contaminants present in seawater (microorganisms, metals, pesticides, etc.) within its tissue. Consequently, they act as bio indicators of the environmental status of coastal ecosystems. On the other hand, the collection of wild populations and farming of shellfish in coastal areas and theirs consumption, (whether cooked or raw), are widely distributed around the globe. During 2015 and 2016, we monitored the presence and amount of aerobic mesophilic bacteria and the Enterococcus spp., Listeria monocytogenes, Salmonella spp. and Escherichia coli bacteria on three commercial shellfish farms and at one finfish farm in the Middle Adriatic. The results revealed that mussels cultured at all sites are completely safe for human consumption according to the Croatian national legislation of food standards. During 2016, we determined the geochemical and isotopic characteristics of noble pen shell Pinna nobilis tissues (Linne, 1758) collected at different locations of Kornati National Park. The obtained results showed differences in the amounts of PTE (Potentially Toxic Elements), REE (Rare Earth Elements), PGE (Platinum Group Elements), δ13CORG and δ15N between zones with different protection and management regimes. Coastal ecosystems are considered to be the most productive areas on earth but are also the most exposed to anthropogenic influences. Monitoring of the microbiological status of shellfish from these areas, as well as the levels of different metals in their tissues, is important from the perspective of monitoring environmental pollution but also from the perspective of food safety