This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on-off and/or high power-low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.

This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on-off and/or high power-low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.

This volume examines the major cultural, religious, political, and urban changes that took place in the Iranian world of Inner and Central Asia in the transition from the pre-Islamic to the Islamic periods. One of the major civilizations of the first millennium was that of the Iranian linguistic and cultural world, which stretched from today's Iraq to what is now the Xinjiang Autonomous Region of China. No other region of the world underwent such radical transformation, which fundamentally altered the course of world history, as this area did during the centuries of transition from the pre-Islamic to the Islamic period. This transformation included the religious victory of Islam over Buddhism, Nestorian Christianity, and the other religions of the area; the military and political wresting of Inner Asia from the Chinese to the Islamic sphere of primary cultural influence; and the shifting of Central Asia from a culturally and demographically Iranian civilization to a Turkic one. This book contains essays by many of the preeminent scholars working in the fields of archeology, history, linguistics, and literature of both the pre-Islamic and the Islamic-era Iranian world, shedding light on some of the most significant aspects of the major changes that this important portion of the Asian continent underwent during this tumultuous era in its history. This collection of cutting-edge research will be read by scholars of Middle Eastern, Central Asian, Iranian, and Islamic studies and archaeology. Contributors: D. G. Tor, Frantz Grenet, Nicholas Sims-Williams, Etsuko Kageyama, Yutaka Yoshida, Michael Shenkar, Minoru Inaba, Rocco Rante, Arezou Azad, Soeren Stark, Louise Marlow, Gabrielle van den Berg, and Dilnoza Duturaeva.