Pregled znanstvenih napredaka u učinskoj elektronici usmjerenih ka osiguravanju efikasnog rada i dužeg životnog vijeka PEMgorivih ćelija

This article focuses on the main issues that affect the lifetime and performance of proton-exchange membrane fuel cells. The short lifespans of these fuel cells represent a barrier to their massive commercialization and usage in mobile and stationary applications. As fuel cell is a very complex system, a lot of knowledge of different areas is required, such as chemistry, electricity and mechanics, in order to completely understand its operation and all the problems that can occur during it. It is for this reason that an interdisciplinary approach needs to be taken when designing fuel-cell energy systems. This paper focuses on identifying and solving those issues that negatively affect the lifetime and performance of fuel cells. It is hoped that this article would be a valuable aid for power electronics’ researchers and engineers for better understanding the presented issues and a useful guide for solving them with the use of proper power electronic-devices. Initially, the basic operation and structure of a proton-exchange membrane fuel cell is explained. Three main issues that can occur during operation of a mobile or stationary fuel cell energy system are pointed out and discussed in details, on the basis of the state-of-the-art on fuel cell technology. These issues are poor water management, reactant gas starvation and fuel cell current ripple. This article provides answers as to why they occur, how they affect the fuel cell, how they can be mitigated, and what are the future trends within this research field.Članak se osvrće na ključna pitanja koja utječu na vrijeme rada i performanse gorivih ćelija s polimernom membranom kao elektrolitom. Kratak životni vijek gorivih ćelija takve vrste prepreka je njihovoj komercijalizaciji i masovnoj upotrebi u mobilnim i stacionarnim stanicama. Budući da su gorive ćelije komplicirani sustavi potrebno je znanje iz raznih područja kemije, elektrotehnike i mehanike da bi se u potpunosti mogao razumjeti njihov način rada i problemi koji se događaju. Upravo je zbog toga multidisciplinarni pristup nužnost pri razvoju sustava koji koriste gorive ćelije. Ovaj je članak usmjeren prema identifikaciji i rješavanju onih problema koji negativno utječu na životni vijek i performanse gorivih ćelija. Autori se nadaju da će se članak pokazati kao korisna pomoć i vodič istraživačima i inženjerima u domeni učinske elektronike pri susretu s navedenim problemima. Objašnjen je način rada i struktura gorive ćelije s polimernom membranom kao elektrolitom. Izložena su, i diskutirana do u detalje, tri glavna problema sa stajališta trenutačnih spoznaja u području učinske elektronike. Ti problemi su: loše upravljanje vodom, nestanak reaktantnog plina i strujni trzaji u gorivim ćelijama. Objašnjeno je zašto se ovi problemi događaju, kako utječu na gorivu ćeliju, kako ih se može spriječiti i koje su buduće perspektive istraživanja

Infoscience technology: the impact of internet accessible melanoid data on health issues

In this paper the development of a new internet information system for analyzing and classifying melanocytic dat, is briefly described. This system also has some teaching functions, improves the analysis of datasets based on calculating the values of the TDS (Total Dermatoscopy Score) (Braun-Falco, Stolz, Bilek, Merkle, & Landthaler, 1990; Hippe, Bajcar, Blajdo, Grzymala-Busse, Grzymala-Busse, & Knap, et al., 2003) parameter. Calculations are based on two methods: the classical ABCD formula (Braun-Falco et al., 1990) and the optimized ABCD formula (Alvarez, Bajcar, Brown, Grzymala-Busse, & Hippe, 2003). A third method of classification is devoted to quasi-optimal decision trees (Quinlan, 1993). The developed internet-based tool enables users to make an early, non-invasive diagnosis of melanocytic lesions. This is possible using a built-in set of instructions that animates the diagnosis of the four basic lesions types: benign nevus, blue nevus, suspicious nevus and melanoma malignant. This system is available on the Internet website: http://www.wsiz.rzeszow.pl/ksesi

Temperature Dependence of Magnetisation Reversal and GMR in Spin Valve Structures

Temperature measurements of magnetisation reversal, resistance and magnetoresistance of Co/Cu/Co/FeMn spin valve structures deposited in different conditions were performed. The influence of exchange anisotropy energy, interlayer coupling energy, and electron transport properties were taken into consideration in explaining differences in giant magnetoresistance effect of investigated samples

2018 IEEE 9th Power, Instrumentation and Measurement Meeting, EPIM 2018

875649

Diagnosing skin melanoma: current versus future directions

A new database containing 410 cases of nevi pigmentosi, in four categories: benign nevus, blue nevus, suspicious nevus and melanoma malignant, carefully verified by histopathology, is described. The database is entirely different from the base presented previously, and can be readily used for research based on the so-called constructive induction in machine learning. To achieve this, the database features a different set of thirteen descriptive attributes, with a fourteenth additional attribute computed by applying values of the remaining thirteen attributes. In addition, a new program environment for the validation of computer-assisted diagnosis of melanoma, is briefly discussed. Finally, results are presented on determining optimal coefficients for the well-known ABCD formula, useful for melanoma diagnosis

Absence of magnetic order in Yb₃Ga₅O₁₂: Relation between phase transition and entropy in geometrically frustrated materials

From muon spin relaxation spectroscopy experiments, we show that the sharp peak (lambda type anomaly) detected by specific heat measurements at 54 mK for the ytterbium gallium garnet compound, Yb3Ga5O12, does not correspond to the onset of a magnetic phase transition, but to a pronounced building up of dynamical magnetic pair-correlations. Beside the lambda anomaly, a broad hump is observed at higher temperature in the specific heat of this garnet and other geometrically frustrated compounds. Comparing with other frustrated magnetic systems we infer that a ground state with long-range order is reached only when at least 1/4-1/3 of the magnetic entropy is released at the lambda transition.Comment: 5 pages, 2 figure