Solar energy in electric utility planning: A linear programming approach

This paper considers a multi-year capacity expansion plan for an electric utility with the option of investing in solar generation units. It is demonstrated how issues such as randomness on both the demand and supply side of the problem, as well as the varying availability of solar energy may be conveniently modelled under some plausible assumptions, to yield a large-scale linear programming problem. A brief discussion is provided relating to the evaluation of the capacity credit attributable to the solar generation units. Computational considerations, some possible simplifications, and an illustrative example are also presented.     

Procedures for preventing juvenile violence in Switzerland: the Zurich model

The Swiss legal system places strong emphasis on risk assessment and treatment of potentially violent offenders. Especially after the 2001 Zug massacre, there is close cooperation between the judicial and mental health systems to prevent violence through early detection and intervention. A case study of a risk management program for a dangerous seventeen-year-old delinquent youth illustrates this approach.     

Perceptions of charisma from thin slices of behavior predict leadership prototypicality judgments

Signaling theory suggests that people use cues transmitted by leaders to form impressions of charisma but the validity of these impressions remains unexplored. Here, we examined whether perceptions of charisma from thin slices of nonverbal behavior relate to inferences based on more information. We tested whether ratings of charisma from 5-, 15-, and 30-s clips (with no audio) of speakers delivering a message predicted evaluations of vision articulation and leadership prototypicality made from 60-s multimedia clips (with audio). The results indicated that thin-slice charisma judgments predicted the criterion scores for leadership prototypicality but not vision articulation from all of the 5-, 15-, and 30-s silent clips. The current data therefore suggest that thin slices of charisma can be valid indicators of leadership.     

Approximating the equilibrium quantity traded and welfare in large markets

We consider the efficient outcome of a canonical economic market model involving buyers and sellers with independent and identically distributed random valuations and costs, respectively. When the number of buyers and sellers is large, we show that the joint distribution of the equilibrium quantity traded and welfare is asymptotically normal. Moreover, we bound the approximation rate. The proof proceeds by constructing, on a common probability space, a representation consisting of two independent empirical quantile processes, which in large markets can be approximated by independent Brownian bridges. The distribution of interest can then be approximated by that of a functional of a Gaussian process. This methodology applies to a variety of mechanism design problems.     

The complexity of VLSI power-delay optimization by?interconnect resizing

The lithography used for 32 nanometers and smaller VLSI process technologies restricts the interconnect widths and spaces to a very small set of admissible values. Until recently the sizes of interconnects were allowed to change continuously and the implied power-delay optimal tradeoff could be formulated as a convex programming problem, for which classical search algorithms are applicable. Once the admissible geometries become discrete, continuous search techniques are inappropriate and new combinatorial optimization solutions are in order. A first step towards such solutions is to study the complexity of the problem, which this paper is aiming at. Though dynamic programming has been shown lately to solve the problem, we show that it is NP-complete. Two typical VLSI design scenarios are considered. The first trades off power and sum of delays (L ₁), and is shown to be NP-complete by reduction of PARTITION. The second considers power and max delays (L _∞), and is shown to be NP-complete by reduction of SUBSET_SUM.     

Statistical Inference for High‐Dimensional Global Minimum Variance Portfolios

Many studies demonstrate that inference for the parameters arising in portfolio optimization often fails. The recent literature shows that this phenomenon is mainly due to a high‐dimensional asset universe. Typically, such a universe refers to the asymptotics that the sample size n + 1 and the sample dimension d both go to infinity while d ∕ n → c ∈ (0,1). In this paper, we analyze the estimators for the excess returns’ mean and variance, the weights and the Sharpe ratio of the global minimum variance portfolio under these asymptotics concerning consistency and asymptotic distribution. Problems for stating hypotheses in high dimension are also discussed. The applicability of the results is demonstrated by an empirical study. Copyright © 2014 John Wiley & Sons, Ltd.     

The Limits of Monetizing and Paying for Volunteering in Eldercare: A Behavioral-Economic Approach

The monetary value of informal eldercare in the family and voluntary sector has drawn much attention as it concerns a resource of welfare governments and nonprofit organizations try to activate via cash benefits. Studies addressing the issue in order to assess the economic impact of non-market activities and the willingness to accept financial rewards have largely ignored differences in the utility function of caregivers. Applying a behavioral-economic approach, we report a profound and formerly unobserved distinction between care in the household and non-household care for a family member or in a voluntary framework: whereas caregivers within the household perceive care as a burden and a positive shadow price arises, in the non-household context—and particularly in the volunteering case–care extends well-being and leads to negative shadow prices. The results show that non-market activities can only be measured in monetary terms to a limited extent and contribute to explaining the boundaries of monetary incentive policies.     

Review and Assessment of Poliovirus Immunity and Transmission: Synthesis of Knowledge Gaps and Identification of Research Needs

With the intensifying global efforts to eradicate wild polioviruses, policymakers face complex decisions related to achieving eradication and managing posteradication risks. These decisions and the expanding use of inactivated poliovirus vaccine (IPV) trigger renewed interest in poliovirus immunity, particularly the role of mucosal immunity in the transmission of polioviruses. Sustained high population immunity to poliovirus transmission represents a key prerequisite to eradication, but poliovirus immunity and transmission remain poorly understood despite decades of studies. In April 2010, the U.S. Centers for Disease Control and Prevention convened an international group of experts on poliovirus immunology and virology to review the literature relevant for modeling poliovirus transmission, develop a consensus about related uncertainties, and identify research needs. This article synthesizes the quantitative assessments and research needs identified during the process. Limitations in the evidence from oral poliovirus vaccine (OPV) challenge studies and other relevant data led to differences in expert assessments, indicating the need for additional data, particularly in several priority areas for research: (1) the ability of IPV‐induced immunity to prevent or reduce excretion and affect transmission, (2) the impact of waning immunity on the probability and extent of poliovirus excretion, (3) the relationship between the concentration of poliovirus excreted and infectiousness to others in different settings, and (4) the relative role of fecal‐oral versus oropharyngeal transmission. This assessment of current knowledge supports the immediate conduct of additional studies to address the gaps.     

Forecasting time series of economic processes by model averaging across data frames of various lengths

This paper presents an extension of mean-squared forecast error (MSFE) model averaging for integrating linear regression models computed on data frames of various lengths. Proposed method is considered to be a preferable alternative to best model selection by various efficiency criteria such as Bayesian information criterion (BIC), Akaike information criterion (AIC), F-statistics and mean-squared error (MSE) as well as to Bayesian model averaging (BMA) and naïve simple forecast average. The method is developed to deal with possibly non-nested models having different number of observations and selects forecast weights by minimizing the unbiased estimator of MSFE. Proposed method also yields forecast confidence intervals with a given significance level what is not possible when applying other model averaging methods. In addition, out-of-sample simulation and empirical testing proves efficiency of such kind of averaging when forecasting economic processes.     

Exploring user experience and technology acceptance for a fall prevention system: results from a randomized clinical trial and a living lab

Background

Falls are common in older adults and can result in serious injuries. Due to demographic changes, falls and related healthcare costs are likely to increase over the next years. Participation and motivation of older adults in fall prevention measures remain a challenge. The iStoppFalls project developed an information and communication technology (ICT)-based system for older adults to use at home in order to reduce common fall risk factors such as impaired balance and muscle weakness. The system aims at increasing older adults’ motivation to participate in ICT-based fall prevention measures. This article reports on usability, user-experience and user-acceptance aspects affecting the use of the iStoppFalls system by older adults.

Methods

In the course of a 16-week international multicenter study, 153 community-dwelling older adults aged 65+ participated in the iStoppFalls randomized controlled trial, of which half used the system in their home to exercise and assess their risk of falling. During the study, 60 participants completed questionnaires regarding the usability, user experience and user acceptance of the iStoppFalls system. Usability was measured with the System Usability Scale (SUS). For user experience the Physical Activity Enjoyment Scale (PACES) was applied. User acceptance was assessed with the Dynamic Acceptance Model for the Re-evaluation of Technologies (DART). To collect more detailed data on usability, user experience and user acceptance, additional qualitative interviews and observations were conducted with participants.

Results

Participants evaluated the usability of the system with an overall score of 62 (Standard Deviation, SD 15.58) out of 100, which suggests good usability. Most users enjoyed the iStoppFalls games and assessments, as shown by the overall PACES score of 31 (SD 8.03). With a score of 0.87 (SD 0.26), user acceptance results showed that participants accepted the iStoppFalls system for use in their own home. Interview data suggested that certain factors such as motivation, complexity or graphical design were different for gender and age.

Conclusions

The results suggest that the iStoppFalls system has good usability, user experience and user acceptance. It will be important to take these along with factors such as motivation, gender and age into consideration when designing and further developing ICT-based fall prevention systems.