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排序方式: 共有416条查询结果,搜索用时 15 毫秒
1.
This study aimed to better understand the impact of business trips on the traveler, the family, and the organization; to learn about maximizing the positive aspects of business travel; and to suggest measures to prevent and manage travel stress. Thirty-five business travelers (American, Israeli, and Swedish) were interviewed about the costs and benefits of their traveling, with a focus on gaining insight into coping strategies. Content analysis of the interviews showed that trips consist of 4 phases--(a) pretrip, (b) journey, (c) stay, and (d) posttrip--and that each phase is characterized by different coping strategies. Business travelers reported using proactive individual and organizational coping strategies in the pretrip phase and a combination of proactive and reactive coping strategies in the other phases. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Lennart J. Lundqvist 《Housing Studies》1998,13(2):217-231
Starting from the Conservative assertion that home ownership fosters politically active and virtuous citizens, this paper examines two lines of argument in housing theory; (a) Jim Kemeny's thesis that owner occupation is closely linked to increasing privatism, i.e. a growth in lifestyles centred around the home and privacy rather than the workplace or the public affairs in a society, and (b) Peter Saunders' thesis that home owners will organise and mobilise politically in defence of their property interests if and when various government agencies threaten to remove their tax subsidies. To test these propositions empirically, data on the effects of the rapid and comprehensive dismantling of tax privileges to Swedish home owners in the 1980s and early 1990s are confronted with data on political interest, participation and knowledge as well as civic trust and responsibility from the Swedish election surveys of 1979, 1985 and 1991. Contrary to Conservative beliefs, home owners do not stand out as 'democratic examples'; with the exception of political knowledge and party membership, they are no more 'civil' or 'democratic' than other citizens. There is also not much to support Kemeny's 'privatism' or Saunders' 'reaction-to-threat' theses. Although home owners in Sweden saw their tax privileges diminishing rapidly during the 1980s and early 1990s, they do not show the distinctive patterns of change in democratic orientation and spirit predicted by these two housing theorists. To allow for an even more conclusive test of Kemeny's 'privatism' thesis, however, one must overcome the mismatch of income definitions in housing statistics and election survey data. 相似文献
3.
Lennart Ljung Pierre Priouret 《International Journal of Adaptive Control and Signal Processing》1991,5(6):395-403
The purpose of this paper is to extend recent results of Ljung and Priouret to a more general class of regressors. 相似文献
4.
Lennart Sjberg 《Displays》1987,8(4):210-212
A discussion of the factors involved in the subjective perception of television picture quality is presented. Much of the work in this field is cited, and it is concluded that future work needs to consider a broader range of variables than has been looked at so far. 相似文献
5.
Lei Guo Lennart Ljung 《Automatic Control, IEEE Transactions on》1995,40(8):1388-1402
A general family of tracking algorithms for linear regression models is studied. It includes the familiar least mean square gradient approach, recursive least squares, and Kalman filter based estimators. The exact expressions for the quality of the obtained estimates are complicated. Approximate, and easy-to-use, expressions for the covariance matrix of the parameter tracking error are developed. These are applicable over the whole time interval, including the transient, and the approximation error can be explicitly calculated 相似文献
6.
Jonas Sjberg Qinghua Zhang Lennart Ljung Albert Benveniste Bernard Delyon Pierre-Yves Glorennec Hkan Hjalmarsson Anatoli Juditsky 《Automatica》1995,31(12):1691-1724
A nonlinear black-box structure for a dynamical system is a model structure that is prepared to describe virtually any nonlinear dynamics. There has been considerable recent interest in this area, with structures based on neural networks, radial basis networks, wavelet networks and hinging hyperplanes, as well as wavelet-transform-based methods and models based on fuzzy sets and fuzzy rules. This paper describes all these approaches in a common framework, from a user's perspective. It focuses on what are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques. It is pointed out that the nonlinear structures can be seen as a concatenation of a mapping form observed data to a regression vector and a nonlinear mapping from the regressor space to the output space. These mappings are discussed separately. The latter mapping is usually formed as a basis function expansion. The basis functions are typically formed from one simple scalar function, which is modified in terms of scale and location. The expansion from the scalar argument to the regressor space is achieved by a radial- or a ridge-type approach. Basic techniques for estimating the parameters in the structures are criterion minimization, as well as two-step procedures, where first the relevant basis functions are determined, using data, and then a linear least-squares step to determine the coordinates of the function approximation. A particular problem is to deal with the large number of potentially necessary parameters. This is handled by making the number of ‘used’ parameters considerably less than the number of ‘offered’ parameters, by regularization, shrinking, pruning or regressor selection. 相似文献
7.
F Hammarqvist B Westman CE Leijonmarck K Andersson J Wernerman 《Canadian Metallurgical Quarterly》1996,119(4):417-423
A number of studies have localized CGRP to nerves in the cornea and iris, and it is thought that CGRP, along with other neuropeptides, is involved in pain sensation. It is also possible that CGRP could mediate trophic influences between nerve endings and corneal epithelium. This investigation utilized an in vitro rabbit corneal whole mount preparation to study the effect of topical 2.5 microM CGRP application on epithelial wound healing rates of 5 mm diameter epithelial wounds. CGRP (2.5 microM) was applied topically to 5 mm epithelial wounds at 0, 4, 16, 20, 24, 28, 40, 44, 48, 52, 56, 64, 68, and 72 hours after wounding and healing was visualized with fluorescein. CGRP was found to increase the epithelial wound healing rate by 25%, from 51 +/- 3 microns/hr for the control corneas, to 64 +/- 2 microns/hr for CGRP-treated corneas (mean +/- standard error, n = 10). Histological examination of the corneas following healing showed that the epithelium of the CGRP-treated corneas healed in a similar manner as in the control corneas. These findings may have clinical utility for the understanding and treatment of corneal and other epithelial wounds. 相似文献
8.
Smokeless tobacco use is a significant health risk for carcinoma of the oropharynx, and has a high prevalence in the southern United States. To evaluate the potential demand for a smokeless tobacco cessation program, we surveyed patients attending the General Medicine Clinic of a Veterans Affairs Medical Center. The prevalence of smokeless tobacco use was 5.8%, which did not justify creation of a clinic-based cessation program. Since we observed adults using smokeless tobacco as a means to reduce or stop their smoking, smoking cessation programs should include counseling against smokeless tobacco use. 相似文献
9.
Lei Guo Lennart Ljung Pierre Priouret 《International Journal of Adaptive Control and Signal Processing》1993,7(6):525-537
An analysis is given of the performance of the standard forgetting factor recursive least squares (RLS) algorithm when used for tracking time-varying linear regression models. Three basic results are obtained: (1) the ‘P-matrix’ in the algorithm remains bounded if and only if the (time-varying) covariance matrix of the regressors is uniformly non-singular; (2) if so, the parameter tracking error covariance matrix is of the order O(μ + γ2/μ), where μ = 1 - λ, λ is the forgetting factor and γ is a quantity reflecting the speed of the parameter variations; (3) this covariance matrix can be arbitrarily well approximated (for small enough μ) by an expression that is easy to compute. 相似文献
10.
Lennart P.J. Teunissen Li-Chu Wang Shih-Nung Chou Chin-hsien Huang Gwo-Tsuen Jou Hein A.M. Daanen 《Applied ergonomics》2014
Firemen often suffer from heat strain. This study investigated two chest cooling systems for use under a firefighting suit. In nine male subjects, a vest with water soaked cooling pads and a vest with water perfused tubes were compared to a control condition. Subjects performed 30 min walking and 10 min recovery in hot conditions, while physiological and perceptual parameters were measured. No differences were observed in heart rate and rectal temperature, but scapular skin temperature and fluid loss were lower using the perfused vest. Thermal sensation was cooler for the perfused vest than for the other conditions, while the cool pad vest felt initially cooler than control. However, comfort and RPE scores were similar. We conclude that the cooling effect of both tested systems, mainly providing a (temporally) cooler thermal sensation, was limited and did not meet the expectations. 相似文献