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111.
Human participants earned money by responding on a progressive-ratio (PR) schedule (initial value $50) or received money without responding on a fixed-time (FT) schedule. During the session, participants could terminate the PR schedule and initiate an FT 200-s schedule. In Experiment 1, increases in monetary value produced increased number of responses, time spent, and money earned in the PR component. In Experiment 2, marijuana smoking produced potency-related reductions in the number of responses, time spent, and money earned in the PR component, effects that can be interpreted as amotivational. Increasing the monetary value of the reinforcer diminished the acute marijuana effects on PR responding, suggesting that marijuana exerted an effect primarily on reinforcers of a smaller magnitude. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
112.
The mammillothalamic tracts, which connect the mammillary bodies of the brain stem with the anterior thalamic nuclei of the forebrain, are an integral segment of Papez's circuit and have long been considered to be involved in mediation of emotional aspects of behavior. The present study, with 33 male Long-Evans rats, showed that a complete transection of these tracts substantially impaired Ss' ability to perform discriminations that depended on representational memory but not those that depended on dispositional memory. Partial lesions of the tract had no effect, and the lesion-induced changes in response time were too small to account for the decrease in accuracy of discriminations that depended on memory. No marked alterations in emotional behavior were observed. Recovery of functional representational memory appeared to be experience- rather than time-dependent. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
114.
Preparation and characterization of biodegradable polymer blends from poly(3‐hydroxybutyrate)/poly(vinyl acetate)‐modified corn starch
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Biodegradable polymer blends prepared by blending poly(3‐hydroxybutyrate) (PHB) and corn starch do not form intact films due to their incompatibility and brittle behavior. For improving their compatibility and flexibility, poly(vinyl acetate) (PVAc) was grafted from the corn starch to prepare the PVAc‐modified corn starch (CSV). The resulting CSV consisted of 47.2 wt% starch‐g‐PVAc copolymer and 52.8 wt% PVAc homopolymer and its structure was verified by FT‐IR analysis. In comparison with 35°C of the neat PVAc, the glass transition temperature (Tg) of the grafted PVAc chains on starch‐g‐PVAc was higher at 44°C because of the hindered molecular mobility imposed from starch on the grafted PVAc. After blending PHB with the CSV, structure and thermal properties of the blends were investigated. Only a single Tg was found for all the PHB/CSV blends and increased with increasing the CSV content. The Tg‐composition dependence of the PHB/CSV blends was well‐fitted with the Gordon‐Taylor equation, indicating that the CSV was compatible with the PHB. In addition, the presence of the CSV could raise the thermal stability of the PHB component. It was also found that the presence of the PHB and PVAc components would not hinder the enzymatic degradation of the corn starch by α‐amylase. POLYM. ENG. SCI., 55:1321–1329, 2015. © 2015 Society of Plastics Engineers 相似文献
115.
Claudio Modena Giovanni Tecchio Francesca da Porto Marco Donà Paolo Zampieri 《Structure and Infrastructure Engineering》2015,11(4):415-442
In recent years, appraisal of the condition and rehabilitation of existing bridges has become an ongoing problem for bridge owners and administrators in all developed countries. Reliable methodologies are therefore needed in the assessment and retrofit design phases, to identify the vulnerability of each bridge class. The specific problems of common arch bridge types are discussed herein, for both reinforced concrete and masonry structures, proper interventions for their static and seismic retrofitting are illustrated and several examples of applications are provided. Retrofitting is usually coupled with functional refurbishment, according to a methodological approach that takes into account bridge characteristics, state of maintenance and functional requirements, and environmental aspects connected with repair and strengthening systems. 相似文献
116.
Xiaofeng Lu Fletcher D. Wicker Don Towsley Zhang Xiong Pietro Lio’ 《Wireless Personal Communications》2010,55(1):51-63
This paper studies the problem of detection of directional antennas and omni-directional antennas by hostile detection systems.
We present a model for calculating the probability of detecting a transmitter at arbitrary location around the transmitter.
Our study shows that, if a directional antenna employs the same transmit power as an omni-directional antenna, the directional
antenna can not decrease the probability of being detected. In some scenarios, a directional antenna is more likely to be
detected than an omni-directional antenna. However, if a directional antenna provides the same Effective Isotropic Radiated
Power in the direction of the receiver as an omni-directional antenna, the transmit power needed by a directional antenna
to send data is much less than that of an omni-directional antenna. In this scenario, the probability of detecting a directional
antenna is reduced by over 90%. This reveals that directional antennas can be used to build a secure path to send data at
low probability of being detected by adversaries. 相似文献
117.
Hybrid processes in manufacturing 总被引:2,自引:0,他引:2
Bert Lauwers Fritz Klocke Andreas Klink A. Erman Tekkaya Reimund Neugebauer Don Mcintosh 《CIRP Annals》2014,63(2):561-583
118.
Performance of Tube and Plate Fiberglass Composite Bridge Deck 总被引:1,自引:0,他引:1
Michael D. Hayes Don Ohanehi John J. Lesko Thomas E. Cousins Dan Witcher 《Canadian Metallurgical Quarterly》2000,4(2):48-55
A composite bridge deck system assembled from glass∕polyester pultruded components has been developed. This system utilizes square tubes running transverse to the traffic direction, mechanically fastened and bonded together, and flat cover plates bonded to the tubes with an epoxy adhesive and through-anchored to the deck support structure using mechanical connectors. A 4.27 × 1.22 m section of the deck system integrally connected to the superstructure at a 1.2 m girder spacing was tested to failure under a single patch loading. The results indicate a factor of safety of 4 on strength and a deflection-to-span ratio of about L∕300. Another section of the deck was fatigued to 3,000,000 cycles under service loading at a load ratio of R = 0.1 and a nominal frequency of 3 Hz. Results from these tests indicate no loss in stiffness up to 3,000,000 cycles. Following the fatigue testing, this section was also tested to failure; no loss in strength was observed. In addition, a finite-element model of the laboratory tests was developed. The results from the model showed good correlation to deflections and longitudinal strains measured during the tests. 相似文献
119.
The highly active process stabilizer bis(2,4‐dicumylphenyl)pentaerythritol diphosphite (P1) was compared in a series of polyolefin formulations with tris(2,4‐di‐t‐butylphenyl) phosphite (P2). Because of its high activity, there was less polymer degradation during processing with P1 as compared to P2. As a result, improvements in color and other physical properties were observed for the polymers, not only during processing, but also after treatment with gamma radiation. 相似文献
120.
Bosco Leung Guang Gong Don Mcleish Stewart Robson 《Analog Integrated Circuits and Signal Processing》2014,78(3):853-863
In a ring oscillator, the behaviour in which the output voltage ramp (up/down) of its individual delay cell crosses the threshold, which triggers the next stage delay cell, is crucial in determining the timing jitter, and hence phase noise. Specifically, as the slew rate of the ramp decreases and/or the amount of noise contribution from the transistors in the delay cell increases, the voltage ramp (up or down) has a higher probability of crossing the threshold multiple times, before finally passing it at a time denoted as last passage time, which is more accurate than the conventional first passage time model. This multiple crossing results in a higher jitter. In the past, investigation in last passage time jitter model results in jitter expression that can only be calculated numerically and thus no design guidelines/insights are apparent. In this paper, a novel model is presented with a simple closed form formula, which shows the extra jitter, due to multiple crossing, adds a term that increases as a function of the fourth power of the noise strength/slew rate ratio. The formula is applied to a real life practical low slow rate/high noise ring oscillator which finds application, for example, in random number generator implementation. Corresponding transistor level simulation results agree reasonably well with the model. Furthermore, it is shown that, on example designs, the last passage time approach in this paper can lead to time jitter that is 100 % larger than that due to conventional first passage time model. 相似文献