Faster, Smaller, Cheaper: An Hedonic Price Analysis of PDAs

We compute quality-adjusted price indexes for Personal Digital Assistants (PDAs) for the period 1999-2004, using data on prices and characteristics of 203 models sold by 12 manufacturers. The PDA market is growing in size, it is technologically dynamic with very substantial changes in measured characteristics over time, and it has experienced rapid rates of product introduction. Hedonic regressions consistently show prices to be positively related to processor performance, RAM memory, permanent storage capacity, and battery life, as well as several measures of screen size and quality. Features such as networking, biometric identification, camera, and cellphone capability are also positively associated with price. Hedonic price indexes implied by these regressions decline at an AAGR of 21.1% to 25.6% per year during this period. A matched model price index computed from a subset of observations declines at 18.75% per year. Though these PDA rates of price decline are lower than have been estimated for desktop and laptop PCs, consumers in this "ultra-portable" segment of the computer market appear to have enjoyed substantial welfare gains over the past five years.

Cold sintering of YBa₂Cu₃O₇-δ

Cold sintering is a sintering technique which enables ceramic powders to be densified at greatly reduced temperatures compared to traditional solid state techniques, which often require temperatures in excess of 1000 °C. These temperatures often preclude the exploitation of size or orientational effects in ceramics as these are lost during heating. One such effect is the orientation of the crystallographic c axis in YBa2Cu3O7−δ (YBCO) which can be controlled through applied pressure. This effect is of interest for increasing critical current density which is highly dependent on the orientation of the a–b (CuO2) planes within the ceramic. Using cold sintering, we demonstrate that dense YBCO can be created at 180 °C (vs. 1000 °C using solid state) and demonstrate that the likely sintering mechanism is mediated by the cracking which occurs in YBCO when exposed to water. In addition, the ceramics produced show and retain the orientational effect, representing a unique opportunity to study the effect on critical current density. We show that the intergranular critical current when the a–b planes are parallel to the applied field is around 15% higher than when perpendicular

Historical roots of Agile methods: where did “Agile thinking” come from?

The appearance of Agile methods has been the most noticeable change to software process thinking in the last fifteen years [16], but in fact many of the “Agile ideas” have been around since 70’s or even before. Many studies and reviews have been conducted about Agile methods which ascribe their emergence as a reaction against traditional methods. In this paper, we argue that although Agile methods are new as a whole, they have strong roots in the history of software engineering. In addition to the iterative and incremental approaches that have been in use since 1957 [21], people who criticised the traditional methods suggested alternative approaches which were actually Agile ideas such as the response to change, customer involvement, and working software over documentation. The authors of this paper believe that education about the history of Agile thinking will help to develop better understanding as well as promoting the use of Agile methods. We therefore present and discuss the reasons behind the development and introduction of Agile methods, as a reaction to traditional methods, as a result of people's experience, and in particular focusing on reusing ideas from histor

Price indexes for clinical trial research: a feasibility study

Research support from the National Science Foundation, Collaborative Research: “An Experimental Producer Price Index for Clinical Trials” to the National Bureau of Economic Research, Award Number 0915674, and Boston University, Award Number 0915677, is gratefully acknowledged. We thank Medidata Solutions Worldwide, Inc. (“Medidata”) for supplying database extracts, Ed Seguine (formerly at Fast Track Solutions, Inc. and Medidata) for helpful discussions, Rafael Campo and other individuals at Medidata for helpful comments and data support, and Marshall Reinsdorf from the Bureau of Economic Analysis for constructive discussant’s comments at the Annual Meetings of the American Economic Association in San Diego, CA, January 6, 2013. Rania Gihleb provided able research assistance. The opinions expressed herein are those of the authors, and do not necessarily reflect those of the National Science Foundation, Medidata, or the institutions with whom the authors are affiliated. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Researc

Examining perceptions of agility in software development practice

This is the post-print version of the final published article that is available from the link below. Copyright @ 2010 ACM.Organizations undertaking software development are often reminded that successful practice depends on a number of non-technical issues that are managerial, cultural and organizational in nature. These issues cover aspects from appropriate corporate structure, through software process development and standardization to effective collaborative practice. Since the articulation of the 'software crisis' in the late-1960s, significant effort has been put into addressing problems related to the cost, time and quality of software development via the application of systematic processes and management practices for software engineering. Early efforts resulted in prescriptive structured methods, which have evolved and expanded over time to embrace consortia/ company-led initiatives such as the Unified Modeling Language and the Unified Process alongside formal process improvement frameworks such as the International Standards Organization's 9000 series, the Capability Maturity Model and SPICE. More recently, the philosophy behind traditional plan-based initiatives has been questioned by the agile movement, which seeks to emphasize the human and craft aspects of software development over and above the engineering aspects. Agile practice is strongly collaborative in its outlook, favoring individuals and interactions over processes and tools, working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a plan (see Sidebar 1). Early experience reports on the use of agile practice suggest some success in dealing with the problems of the software crisis, and suggest that plan-based and agile practice are not mutually exclusive. Indeed, flexibility may arise from this unlikely marriage in an aim to strike a balance between the rigor of traditional plan-based approaches and the need for adaptation of those to suit particular development situations. With this in mind, this article surveys the current practice in software engineering alongside perceptions of senior development managers in relation to agile practice in order to understand the principles of agility that may be practiced implicitly and their effects on plan-based approach

Tutorial on Hybridizable Discontinous Galerkin (HDG) for second-order elliptic problems

The HDG is a new class of discontinuous Galerkin (DG) methods that shares favorable properties with classical mixed methods such as the well known Raviart-Thomas methods. In particular, HDG provides optimal convergence of both the primal and the dual variables of the mixed formulation. This property enables the construction of superconvergent solutions, contrary to other popular DG methods. In addition, its reduced computational cost, compared to other DG methods, has made HDG an attractive alternative for solving problems governed by partial differential equations. A tutorial on HDG for the numerical solution of second-order elliptic problems is presented. Particular emphasis is placed on providing all the necessary details for the implementation of HDG methods.Peer ReviewedPreprin

Gender, war and militarism: making and questioning the links

The gender dynamics of militarism have traditionally been seen as straightforward, given the cultural mythologies of warfare and the disciplining of ‘masculinity’ that occurs in the training and use of men's capacity for violence in the armed services. However, women's relation to both war and peace has been varied and complex. It is women who have often been most prominent in working for peace, although there are no necessary links between women and opposition to militarism. In addition, more women than ever are serving in many of today's armies, with feminists rather uncertain on how to relate to this phenomenon. In this article, I explore some of the complexities of applying gender analyses to militarism and peace work in sites of conflict today, looking most closely at the Israeli feminist group, New Profile, and their insistence upon the costs of the militarized nature of Israeli society. They expose the very permeable boundaries between the military and civil society, as violence seeps into the fears and practices of everyday life in Israel. I place their work in the context of broader feminist analysis offered by researchers such as Cynthia Enloe and Cynthia Cockburn, who have for decades been writing about the ‘masculinist’ postures and practices of warfare, as well as the situation of women caught up in them. Finally, I suggest that rethinking the gendered nature of warfare must also encompass the costs of war to men, whose fundamental vulnerability to psychological abuse and physical injury is often downplayed, whether in mainstream accounts of warfare or in more specific gender analysis. Feminists need to pay careful attention to masculinity and its fragmentations in addressing the topic of gender, war and militarism

Quantitative study of quasi-one-dimensional Bose gas experiments via the stochastic Gross-Pitaevskii equation

The stochastic Gross-Pitaevskii equation is shown to be an excellent model for quasi-one-dimensional Bose gas experiments, accurately reproducing the in situ density profiles recently obtained in the experiments of Trebbia et al. [Phys. Rev. Lett. 97, 250403 (2006)] and van Amerongen et al. [Phys. Rev. Lett. 100, 090402 (2008)], and the density fluctuation data reported by Armijo et al. [Phys. Rev. Lett. 105, 230402 (2010)]. To facilitate such agreement, we propose and implement a quasi-one-dimensional stochastic equation for the low-energy, axial modes, while atoms in excited transverse modes are treated as independent ideal Bose gases.Comment: 10 pages, 5 figures; updated figures with experimental dat