On the stability of power systems containing doubly fed induction generator-based generation

This article is concerned with the impact of large-scale wind farms utilising doubly fed induction generators on the stability of a general power system. Inspection of the eigenstructure of the power system provides a foundation for assessing the impact, which is then quantified by means of detailed numerical simulations.     

Executive control in set switching: Residual switch cost and task-set inhibition.

Executive processes necessary for flexible switching between different tasks were studied using a set switching paradigm that requires Ss to rapidly switch between different tasks across consecutive trials. Switch cost reflects poorer performance for task-switch trials than for consecutive same-task trials. 34 Ss (aged 18–48 yrs) participated in the study. Significant switch cost was observed even with considerable preparation time before a task-switch, an effect known as residual switch cost. The study tested the hypothesis that one process underlying residual switch cost is inhibition of the previous task-set. The authors used semantic categorization tasks to compare switch cost between alternating task series (ABA) and nonalternating series (ABC) in order to test the generality of a task-set inhibition effect previously observed with perceptual judgment tasks. The results yielded significant switch cost only for alternating tasks, in both response times and errors resulting from performance of the wrong task. Thus, resolving inhibition associated with previously abandoned task-sets may be the main process underlying residual switch costs, suggesting that task-set inhibition is an important executive control process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Special Section on Theoretical Models and Conceptual Analyses: Second Installment.

The Journal of Applied Psychology's call for theoretical models and conceptual analyses brought a terrific response. The first set of articles accepted in response to the call appeared in the December 2004 issue. This installment contains the second set of articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maximizing versus satisficing: Happiness is a matter of choice.

Can people feel worse off as the options they face increase? The present studies suggest that some people--maximizers--can. Study 1 reported a Maximization Scale, which measures individual differences in desire to maximize. Seven samples revealed negative correlations between maximization and happiness, optimism, self-esteem, and life satisfaction, and positive correlations between maximization and depression, perfectionism, and regret. Study 2 found maximizers less satisfied than nonmaximizers (satisficers) with consumer decisions, and more likely to engage in social comparison. Study 3 found maximizers more adversely affected by upward social comparison. Study 4 found maximizers more sensitive to regret and less satisfied in an ultimatum bargaining game. The interaction between maximizing and choice is discussed in terms of regret, adaptation, and self-blame. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simplified gravimetric determination of total fat in food composites after chloroform-methanol extraction

A modification of Association of Official Analytical Chemists (AOAC) method 983.23 for the quantitative determination of total lipid in food composites was evaluated for the measurement of total fat. The procedure is based on the Bligh and Dyer chloroform/methanol total lipid extraction. Relative to AOAC 983.23, the proposed method is less labor-intensive and is applicable to batch analysis of a larger number of samples, thus reducing the cost of analysis and increasing sample throughput. Total lipid values from the proposed method are comparable to those from AOAC 983.23 and slightly higher than total fat determined by acid hydrolysis (AOAC 954.02, 945.44, or 922.06). Recoveries of standard additions of different food-grade oils from a mixed food composite were essentially quantitative, ranging from 96 to 101%. Total lipid measured in Total Diet Standard Reference Material 1548 (SRM 1548, National Institute of Standards and Technology) was 101% of the certified mean total fat content and within the certified range. The method is to be suitable for analysis of food composites with between 0.15 and 1.5 g total fat (3 to 30% by weight). More than 600 samples of a variety of total diet composites were collected and assayed as diet quality control samples for two National Heart, Lung and Blood Institute-sponsored multicenter clinical feeding trials: DELTA (Dietary Effects on Lipoproteins and Thrombogenic Activity) and DASH (Dietary Approaches to Stop Hypertension). The mean coefficient of variation was 1.2% for duplicate assays of these samples over the course of two years and multiple analysts. In addition, total lipid values for more than 200 samples of a diet composite quality control material, used in this laboratory over a two-year period, had a 3.99% coefficient of variation. Although the accuracy of all gravimetric total fat methods with respect to the U.S. Food and Drug Administration’s Nutritional Labeling and Education Act (NLEA) definition of total fat as the sum of triglycerides remains to be determined, the reported modification of AOAC 983.23 yields a total fat content of acceptable accuracy relative to other gravimetric methods, and with proper quality control the method has excellent precision.     

How do people really seek information about others?: Information seeking across Internet and traditional communication channels

The present research describes the manner in which individuals use various media in the interpersonal information seeking process. Stephens' (2007) information and communication technology (ICT) succession theory was applied to an interpersonal information seeking context, and hypotheses and research questions about the channels people use to seek information about others of various relationship to the seeker were offered. Two hundred and twenty-five participants responded to a survey about this topic, and they reported a greater likelihood to seek information about less-known targets using channels where they would be unidentifiable. However, participants reported a greater likelihood to seek information about more-known targets using channels where they would be identifiable. Channels such as social networking websites were frequently reported to be useful regardless of whether the target was well known or less known. Properties of these channels and their implications for interpersonal information seeking as well as theoretical implications of these findings are discussed and directions for future research are examined.     

Predicting change in depression following renal transplantation: Effect of patient coping preferences.

Improvement in patient quality of life is a central goal of renal transplantation. This study examined the hypothesis that change in depression following transplantation would vary as a function of patient coping preferences. Sixty patients were assessed with the Krantz Health Opinion Survey and the Beck Depression Inventory while on the waiting list for a cadaveric renal transplant. Patients were reassessed approximately 12 months later. Among the 33 patients receiving a transplant during the follow-up period, those with a high preference for health-related information exhibited a substantial reduction in depression. In contrast, patients low in preference for information showed a slight increase in depression. Among the 27 patients who were not transplanted during the follow-up period, preference for information had no effect on depression. Patient differences in preference for behavioral involvement did not exert a significant effect on depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Components of line-drawing interpretation: A developmental study.

In 2 experiments, with school-age children and adults, age changes in a line-drawing classification task were explored. Pairs of drawings were presented in Experiment 1. In 1 task, observers indicated whether the drawings were the same or different; in the second, they indicated whether the drawings could be interpreted as parts of the same object. Age differences in response time and accuracy were larger in the second task, pointing to the importance of the interpretation component. In Experiment 2, observers were instructed in 1 of 2 strategies, and the presentation of the 2 drawings was separated by 0–4 s. Instructions to engage in active hypothesis testing improved the performance of younger children more than older children, relative to instructions to simply form clear images of the drawings. Increases in the time interval between drawings made the task more difficult for younger children in both instruction conditions. This implies that younger children were less active in the interval between successive drawings, independent of the specific instructions they were given. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Employee stock ownership and employee attitudes: A test of three models.

Results of a test of three alternative models of the conditions necessary for employee ownership to positively influence employee attitudes are reported. Based on a study of 37 employee stock ownership plan (ESOP) companies (N of individuals?=?2,804), results support hypotheses for the extrinsic and instrumental satisfaction models. Average company ESOP satisfaction and organizational commitment are high and average company turnover intention is low when the ESOP provides substantial financial benefits to employees, when management is highly committed to employee ownership, and when the company maintains an extensive ESOP communications program. In contrast, the results provide no support for the intrinsic satisfaction model of ESOP effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)