W-Band GaAs HEMT MMIC Subharmonically Pumped Diode Mixers with 20 GHz IF Bandwidth

Two subharmonically pumped (SHP) diode mixers are designed for wideband W-band RF frequencies, fixed LO frequency operation. These mixers are fabricated on a 4-mil substrate using 0.1- µµµµm GaAs MMIC process. Both simulation and test results show that the mixers are with 12.25 and 11.75 dB average conversion losses, respectively. Both mixers have IF bandwidth wider than 20 GHz. The conversion loss flatness of the symmetric circuit is within ±1.25 dB. To our knowledge, these are the state-of-the-art result on low-conversion-loss wideband MMIC SHP diode mixers

Dancing on the edge: International students' transformative journeys in the United States of America.

This study explored international students' experiences of studying in the United States, including the motives that brought them to the United States, the challenges they confronted, and the learning and development opportunities that arose. The theoretical framework of the study was embedded in theories of adult learning and development, chaos and complexity, and transformative learning. The qualitative methodology aimed to gain an understanding of the lived experiences of these international students, and to capture and represent their meaning making and their learning journeys. Data were collected primarily from two in-depth interviews with eighteen participants, and analyzed qualitatively following the guidelines of interpretivism.The findings revealed that the journeys of these participants studying in the United States comprised a process of cultural crossing, in which four major themes were identified that, in turn, addressed the research questions. These included seizing opportunities to determine their destinies, confronting difficulties and disequilibrium, navigating between home and host cultures, and being and becoming authentic. The major elements that contributed to these participants' adjustment and success were their personal capacities, relationships with others including their new living environments, and their capabilities to engage in transformative learning. Out of the research findings, a conceptual schema of being and becoming was introduced to capture these participants' change and growth during the process of cultural crossing.Implications and recommendations arising from this study include the need for: (1) American universities to undertake further research, conduct needs assessments, and provide cultural learning training programs; (2) staff, faculty members, and classmates to perform active listening and share their know-how with international students; (3) international students to befriend others, form learning communities, and open themselves to learning. Finally, researching the corresponding impacts, challenges, and difficulties that American counterparts may experience while interacting with international students may further contribute to both domestic and international students' change and growth. Confronting challenges and difficulties leads these participants to dance on the edge of disequilibrium and re-equilibrium in a foreign land; however, their lives and the lives of those around them will never be the same

A Framework of Risk-Based Decision Making by Characterizing Variability and Uncertainty Probabilistically: Using Arsenic in Dinking Water as an Example

Risk-based regulatory decisions generally apply a margin of safety meant to guard against underestimation of risk in the face of inter-subject variability and uncertainty. Since these two components often are unknown or only vaguely characterized, the decisions involved usually employ conservative default assumptions concerning the margin of safety, resulting in regulatory limits that may be more (or less) health protective than necessary if variability and uncertainty could be characterized probabilistically. As a result, it remains impossible in most cases to determine the degree of protectiveness inherent in a standard. The debate about maximum contaminant levels (MCLs) of arsenic is an example. At present, we can only get a vague idea that lowering MCLs results in larger margins of safety, but at the expense of greater compliance costs. If the magnitude of this margin of safety is not taken into account, it is possible that an MCL may be established based on a significantly larger margin of safety than is necessary, reasonable or consistent with that applied to other contaminants. Thus an unnecessarily expensive treatment policy may be selected. In this study, a new framework of probabilistic risk-based decision making was developed. A meta-analysis was conducted for arsenic in drinking water by combining several epidemiological studies from various regions (such as Taiwan, US, Argentina, Chile and Finland). Then the results of the meta-analysis were incorporated into the framework to characterize the margin of safety through variability and uncertainty analyses. The final product of this study is a method of probabilistic risk assessment that better deals with variability and uncertainty issues. This risk assessment methodology can help decision-makers make optimal determinations on regulatory limits for a contaminant that adequately protect human health with an ample margin of safety at a more reasonable cost than currently is the case

Estimation of a Linear Regression Model When the Variance Is a Linear Function of Unknown Parameters

Statistic

The Artificial Neural Networks Applied to Servo Control Systems

This chapter utilizes the direct neural control (DNC) based on back propagation neural networks (BPN) with specialized learning architecture applied to the speed control of DC servo motor. The proposed neural controller can be treated as a speed regulator to keep the motor in constant speed, and be applied to DC servo motor speed control. The proposed neural control applied to position control for hydraulic servo system is also studied for some modern robotic applications. A tangent hyperbolic function is used as the activation function, and the back propagation error is approximated by a linear combination of error and error!s differential. The simulation and experiment results reveal that the proposed neural controller is available to DC servo control system and hydraulic servo system with high convergent speed, and enhances the adaptability of the control system

Effect of non-lattice oxygen on ZrO2-based resistive switching memory

ZrO2-based resistive switching memory has attracted much attention according to its possible application in the next-generation nonvolatile memory. The Al/ZrO2/Pt resistive switching memory with bipolar resistive switching behavior is revealed in this work. The thickness of the ZrO2 film is only 20 nm. The device yield improved by the non-lattice oxygen existing in the ZrO2 film deposited at room temperature is firstly proposed. The stable resistive switching behavior and the long retention time with a large current ratio are also observed. Furthermore, it is demonstrated that the resistive switching mechanism agrees with the formation and rupture of a conductive filament in the ZrO2 film. In addition, the Al/ZrO2/Pt resistive switching memory is also possible for application in flexible electronic equipment because it can be fully fabricated at room temperature

Dating Breaks for Global Crude Oil Prices and Their Volatility: A Possible Price Band for Global Crude Prices

[[abstract]]This paper applies the structural change testing method of Bai and Perron (1998, 2003) to the problem of locating and identifying significant changes in the global oil market. We use this method to investigate daily WTI spot prices from January 2, 1986 to December 30, 2004 as collected by the DOE. Our empirical results indicate that a significant structural change took place on November 12, 1999. The average WTI price was U$19.02 per barrel before the structural change and U$30 .90 per barrel after the change. This higher price may well reveal clues for revising the current price band as claimed by OPEC. Moreover, the issue of volatility is also examined by following the same method. We find two structural breaks for the price volatility, and price is rather stable in the middle period. This interesting result is valuable in evaluating the current argument regarding the more volatile world crud e oil prices.[[booktype]]紙