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1.
Landron O. Feuerstein M.J. Rappaport T.S. 《Antennas and Propagation, IEEE Transactions on》1996,44(3):341-351
This paper presents microwave reflection coefficient measurements at 1.9 GHz and 4.0 GHz for a variety of typical smooth and rough exterior building surfaces. The measured test surfaces include walls composed of limestone blocks, glass, and brick. Reflection coefficients were measured by resolving individual reflected signal components temporally and spatially, using a spread-spectrum sliding correlation system with directional antennas. Measured reflection coefficients are compared to theoretical Fresnel reflection coefficients, applying Gaussian rough surface scattering corrections where applicable. Comparisons of theoretical calculations and measured test cases reveal that Fresnel reflection coefficients adequately predict the reflective properties of the glass and brick wall surfaces. The rough limestone block wall reflection measurements are shown to be bounded by the predictions using the Fresnel reflection coefficients for a smooth surface and the modified reflection coefficients using the Gaussian rough surface correction factors. A simple, but effective, reflection model for rough surfaces is proposed, which is in good agreement with propagation measurements at 1.9 GHz and 4 GHz for both vertical and horizontal antenna polarizations. These reflection coefficient models can be directly applied to the estimation of multipath signal strength in ray tracing algorithms for propagation prediction 相似文献
2.
The next generation of video tapes will use evaporated thin films with their superior properties such as recording density, output level, frequency characteristics and signal-to-noise ratio. This paper describes the metal layer formation by a simple model for the growth of microcolumns at oblique incidence deposition. The most relevant process parameters are discussed. The layout of a production coater is described. 相似文献
3.
RM Summers J Andrasko-Bourgeois IM Feuerstein SC Hill EC Jones MK Busse B Wise KE Bove BA Rishforth E Tucker TL Spray JM Hoeg 《Canadian Metallurgical Quarterly》1998,98(6):509-518
Hepatitis C chronically infects approximately 1.5% of Americans and is the most common clinical problem facing hepatologists. Since the virus was initially described in 1989, development of an effective therapy has been challenging. Although several different therapeutic agents have been used, no therapy has been shown to reliably eradicate the virus. Interferon-alpha, a cytokine with immunostimulatory and anti-viral properties, has become the therapy of choice for patients with chronic hepatitis C infection. Trials assessing the efficacy of interferon-alpha have characterized host and viral factors predictive of responses to treatment. A thorough understanding of these predictive factors is requisite to providing cost-effective therapeutic decisions for the patient with chronic hepatitis C infection. 相似文献
4.
Abstract. In this paper we introduce a generalization of Paging to the case where there are many threads of requests. This models situations
in which the requests come from more than one independent source. Hence, apart from deciding how to serve a request, at each stage it is necessary to decide which request to serve among several possibilities.
Four different on-line problems arise depending on whether we consider fairness restrictions or not, with finite or infinite
input sequences. We study all of them, proving lower and upper bounds for the competitiveness of on-line algorithms.
The main competitiveness results presented in this paper state that when no fairness restrictions are imposed it is possible
to obtain competitive algorithms for finite and infinite inputs. On the other hand, for the fair case in general there exist
no competitive algorithms.
In addition, we consider three definitions of competitiveness for infinite inputs. One of them forces algorithms to behave
efficiently at every finite stage, while the other two aim at comparing the algorithms' steady-state performances. A priori,
the three definitions seem different. We study them and find, however, that they are essentially equivalent. This suggests
that the competitiveness results that we obtain reflect the intrinsic difficulty of the problem and are not a consequence
of a too strict definition of competitiveness. 相似文献
5.
We built and tested one of the key components of a free-space holographically interconnected stored-program optoelectronic computer: a counter. The counter is constructed with 1-ns-latency optoelectronic NOR gates and is interconnected with holographic optical elements. Two synchronization methods were also demonstrated: the gate-and-strobe method and the time-of-flight method. These counters represent prototypical optoelectronic finite-state controllers. They were developed to demonstrate the feasibility of providing optoelectronic controllers for optoelectronic processors. 相似文献
6.
Feuerstein Günter Kollek Regine Schmedders Mechtild van Aken Jan 《Ethik in der Medizin》2003,15(2):77-86
Ethik in der Medizin - Die prospektive Analyse der ethischen Implikationen medizinisch-technischer Innovationen läuft immer auch Gefahr, sich in den Wunschbildern von Marketingexperten zu... 相似文献
7.
M Feuerstein LM Burrell VI Miller A Lincoln GD Huang R Berger 《Canadian Metallurgical Quarterly》1999,35(3):232-245
Carpal tunnel syndrome (CTS) is a disorder frequently encountered by occupational health care specialists. The health care management of this disorder has involved a diverse set of clinical procedures. The present article is a review of the literature related to CTS with an emphasis on occupational-related CTS. MEDLINE, Cumulative Index to Nursing and Allied Health Literature, PsycLIT, and NIOSHTIC databases from 1985-1997 were searched for treatment outcome studies related to CTS. Treatments of interest included surgery, physical therapy, drug therapy, chiropractic treatment, biobehavioral interventions, and occupational rehabilitation. A systematic review of the effects of these interventions on symptoms, medical status, function, return to work, psychological well-being, and patient satisfaction was completed. Compared to other treatments, the majority of studies assessed the effects of surgical interventions. Endoscopic release was associated with higher levels of physical functioning and fewer days to return to work when compared to open release. Limited evidence indicated: 1) steroid injections and oral use of B6 were associated with pain reduction; 2) in comparison to splinting, range of motion exercises appeared to be associated with less pain and fewer days to return to work; 3) cognitive behavior therapy yielded reductions in pain, anxiety, and depression; and, 4) multidisciplinary occupational rehabilitation was associated with a higher percentage of chronic cases returning to work than usual care. Workers' compensation status was associated with increased time to return to work following surgery. Conclusions are preliminary due to the small number of well-controlled studies, variability in duration of symptoms and disability, and the broad range of reported outcome measures. While there are several opinions regarding effective treatment, there is very little scientific support for the range of options currently used in practice. Despite the emerging evidence of the multivariate nature of CTS, the majority of outcome studies have focused on single interventions directed at individual etiological factors or symptoms and functional limitations secondary to CTS. 相似文献
8.
High vacuum evaporation of ferromagnetic materials -- A new production technology for magnetic tapes
The vacuum deposition of ferromagnetic material at oblique incidence will become a major production technology for magnetic tapes for longitudinal recording applications in the future. In this paper the general formation mechanism of magnetic thin films, the field of relevant parameters and the dependance of magnetic properties on the essential parameters is discussed and demonstrated by a few examples of hysteresis loops: The resulting layout of laboratory and pilot production equipment developed so far for this application is demonstrated. For typical application examples, the material efficiency of the systems has been calculated as a function of the used incidence angle range. Also the differential increase in layer thickness as a function of incidence angle has been calculated in order to get a simple model for the formation of microcolumns. 相似文献
9.
D.K. Cartwright G. Manent P. Chenebault R. Sesuy E. De Nontaignac W.R. Diggle F.A. Johnson J.R. Findlay W. Glauner S. Jacobi H. Feuerstein M. Relic 《Nuclear Engineering and Design》1980,59(2):287-300
During the course of the ‘SCARABEE’ experimental programme, the primary objective of which was to study the fuel and thermohydraulic behaviour, fission-product concentration were measured by a number of techniques. These included delayed neutron monitoring, total gamma, gamma spectrometry, sodium sampling and analysis and gas sampling and analysis. This paper describes the methods used to evaluate the data from these measurements and discusses the results.The theoretical models for fission-product generation and release are described and compared with the experimental data, and a critical examination of the techniques and results leads to recommendations for improvements in methods for future experiments. Conclusions are drawn relating to fission-product behaviour in LMFBRs. It is recognized that the experiments do not model closely the power reactor situation, but it is argued that the results obtained, particularly from delayed-neutron measurements, do provide a useful pointer to the value of fission-product monitoring in limiting fuel damage from local fuel overheating faults. 相似文献
10.
In this paper the problem of efficiently serving a sequence of requests presented in an on-line fashion located at points
of a metric space is considered. We call this problem the On-Line Travelling Salesman Problem (OLTSP). It has a variety of
relevant applications in logistics and robotics.
We consider two versions of the problem. In the first one the server is not required to return to the departure point after
all presented requests have been served. For this problem we derive a lower bound on the competitive ratio of 2 on the real line. Besides, a 2.5 -competitive algorithm for a wide class of metric spaces, and a 7/3 -competitive algorithm for the real line are provided.
For the other version of the problem, in which returning to the departure point is required, we present an optimal 2 -competitive algorithm for the above-mentioned general class of metric spaces. If in this case the metric space is the real
line we present a 1.75 -competitive algorithm that compares with a \approx 1.64 lower bound.
Received November 12, 1997; revised June 8, 1998. 相似文献