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

Enviropreneurial marketing in greening corporate activities: Evidence from four Chinese green firms

Purpose: The purpose of this study is to explore the enviropreneurial marketing approach used by firms in China and its impact on the success of green marketing actions, with the aim of drawing useful lessons from the literature and successful green firms. Design/methodology/approach: This study follows the inductive case study approach, and the qualitative data come from a study of four firms engaging in enviropreneurial marketing activities. Interview data were triangulated with qualitative data from other sources. Findings: The evidence from this study indicates that enviropreneurial marketing plays a central role in developing innovative product or services, adopting an innovative and pragmatic green marketing mix that differentiates and creates changes within industry and markets. Research limitations/implications: The main limitation of this study is that data samples are from successful firms labelled as “green” by the Chinese authorities, based on winning “official” awards. These do not necessarily represent the opinions of a cross section of firms within China with respect to enviropreneurial marketing. Future studies should include a mixed population of firms. Practical implications: Policy makers and marketing practitioners need to consider drivers to ensure that Chinese firms integrate enviropreneurial marketing activities, which need to complement the delivery of functional value. Social implications: Green initiatives/changes within the firm seem to be partly driven by the environmental orientation of these firms’ founders, thus, developing an environmental orientation in managers may be important to drive enviropreneurial marketing activities. Originality/value: This study contributes by confirming the current literature on green marketing and examining the positive impact of enviropreneurial marketing on firms’ performance in the context of marketing in emerging markets

Descriptions and prices of one hundred select hardy perennial plants of the Rocky Mountains /

1903-1904 RareSeed

Descriptions and prices of one hundred select hardy perennial plants of the Rocky Mountains /

1902 Spring Wholesale Catalogu

Descriptions and prices of one hundred select hardy perennial plants of the Rocky Mountains /

1899 Hardy Perennials from See