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排序方式: 共有89条查询结果,搜索用时 15 毫秒
1.
Elena Crespi Antonio Capolongo Davide Fissore Antonello A. Barresi 《Drying Technology》2008,26(3):349-356
The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed. 相似文献
2.
An important problem in the control of locomotion of robots with multiple degrees of freedom (e.g., biomimetic robots) is to adapt the locomotor patterns to the properties of the environment. This article addresses this problem for the locomotion of an amphibious snake robot, and aims at identifying fast swimming and crawling gaits for a variety of environments. Our approach uses a locomotion controller based on the biological concept of central pattern generators (CPGs) together with a gradient-free optimization method, Powell's method. A key aspect of our approach is that the gaits are optimized online, i.e., while moving, rather than as an off-line optimization process. We present various experiments with the real robot and in simulation: swimming, crawling on horizontal ground, and crawling on slopes. For each of these different situations, the optimized gaits are compared with the results of systematic explorations of the parameter space. The main outcomes of the experiments are: 1) optimal gaits are significantly different from one medium to the other; 2) the optimums are usually peaked, i.e., speed rapidly becomes suboptimal when the parameters are moved away from the optimal values; 3) our approach finds optimal gaits in much fewer iterations than the systematic search; and 4) the CPG has no problem dealing with the abrupt parameter changes during the optimization process. The relevance for robotic locomotion control is discussed. 相似文献
3.
Traditionally, two alternative design approaches have been available to engineers: top-down and bottom-up. In the top-down
approach, the design process starts with specifying the global system state and assuming that each component has global knowledge
of the system, as in a centralized approach. The solution is then decentralized by replacing global knowledge with communication.
In the bottom-up approach, on the other hand, the design starts with specifying requirements and capabilities of individual
components, and the global behavior is said to emerge out of interactions among constituent components and between components
and the environment. In this paper we present a comparative study of both approaches with particular emphasis on applications
to multi-agent system engineering and robotics. We outline the generic characteristics of both approaches from the MAS perspective,
and identify three elements that we believe should serve as criteria for how and when to apply either of the approaches. We
demonstrate our analysis on a specific example of load balancing problem in robotics. We also show that under certain assumptions
on the communication and the external environment, both bottom-up and top-down methodologies produce very similar solutions.
相似文献
Valentino CrespiEmail: |
4.
DA Kokodoko C Pasquino AM Barra L Santoro MG Crespi M Bertoni G Giorgetti L Ballardini C Cargnelutti L Spinazzola M Gallì 《Canadian Metallurgical Quarterly》1996,18(4-6):129-134
With the intent of estimating the proprioceptive sensitivity of the cervical rachis, the Authors subjected 17 healthy volunteers and 20 patients suffering from various cervical disorders to a clinical head positioning test, which was previously experimented upon by several french Authors was modified under certain aspects by our equipe. The test, consists in flexion and extension of the head after maximal rotations to the left and right, then repositioning the head at the starting point "0" which corresponds to the crossing point of two orthogonal axis of a target. The positions are marked on the target by a laser beam situated on the helmet worn by the subject undergoing testing. The results obtained corresponding to the errors committed regarding point "0", permit us to confirm the reliability of the test and significant definitions between the control group and the patients suffering from cervical disorders. 相似文献
5.
Comments on the article by Sanchez and Turner (see record 2003-03405-005) examining the implications for practice and training in psychology in the era of managed care. The current author states that Sanchez and Turner should be commended. Their article amplifies and clarifies critical issues psychologists must consider while practicing within an era increasingly shaped by health insurance policies and practices. Nevertheless, the author feels that several intriguing facets of managed care were not highlighted. Discussion focuses on the impact that reimbursement and managed care is having on school (and clinical) psychologists. The author points out that it is unknown to what extent managed care may (and has) altered psychological services delivered by school psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Stefano Crespi Reghizzi Dino Mandrioli 《Journal of Computer and System Sciences》2012,78(6):1837-1867
Floyd?s operator precedence grammars and languages (FG, FL) are a classical subclass of deterministic context-free (DCF) grammars and languages. We prove that several recently introduced language families motivated by the needs of model checking and of specifying XML-like languages are proper subsets of FL. The main cases considered include visibly pushdown languages (VPL) and balanced languages (BALAN), which are characterized by restricted precedence relations. FL have all the closure properties available for regular languages and generally viewed as necessary for application to model checking: reversal, prefixing and suffixing, concatenation, Kleene star, and boolean operations. All but the last results are new, and some require complex proofs, due to the necessary changes of syntax structure. Thus FL are the largest known subfamily of DCF having the same closure properties as VPL. FG, unlike VPL grammars, which are intended for abstract syntax modelling, are structurally adequate to specify real programming languages. 相似文献
7.
Colour removal from textile wastewater containing reactive dyes can be achieved by using a small commercial electrochemical cell which was not specifically designed for this use. In this study, the decolorisation and electrical consumption are modelled. The results show that the electrolyte employed in the dyeing process is the main factor influencing the decolorisation of the wastewater. The flow and potential difference are also important factors controlling the electrochemical process. There are other variables such as pH and temperature that, within the intervals studied, do not have any effect on the results. 相似文献
8.
Piero Malcovati Luca Picolli Lorenzo Crespi Faouzi Chaahoub Andrea Baschirotto 《Analog Integrated Circuits and Signal Processing》2010,64(2):159-172
In this paper a dual operating mode 8-bit, 1.1-V pipeline ADC for Gigabit Ethernet applications is presented. In the two operating
modes, the ADC features different sampling frequency (125 and 250 MHz) and power consumption (9.4 and 22.8 mW). Considering
a signal bandwidth of 60 MHz in both operating modes, as required by the Gigabit Ethernet standard, the ADC achieves a SNDR always larger than 39.4 dB at 125 MHz and 38.7 dB at 250 MHz (6.25-bit and 6.13-bit ENOB, respectively), with a FoM of 0.84 pJ/conv at 125 MHz and 2.2 pJ/conv at 250 MHz. The ENOB achieved is mainly limited by clock jitter. The ADC is fabricated with a 90-nm CMOS technology, with an active area of 1.25
× 0.65 mm2. 相似文献
9.
EL Code CL Crespi BW Penman FJ Gonzalez TK Chang DJ Waxman 《Canadian Metallurgical Quarterly》1997,25(8):985-993
In situ hybridization was combined with serotonin (5-hydroxytryptamine, 5-HT) or tyrosine hydroxylase immunocytochemistry and with Fluoro-Gold retrograde labeling of bulbo-spinal pathways in order to investigate the expression of GAP-43 mRNA in monoamine cell groups of the adult rat brain stem. Consistent with previous reports, GAP-43 mRNA was observed in serotonin and dopamine cell groups in the pons. In addition, GAP-43 expressing cells were observed in all the major monoamine cell groups in the medulla. Thus the B1, B2 and B3 serotonin cell groups all showed high GAP-43 expression in all contained many GAP-43 expressing serotonin cells with spinal cord projections. The A1, A2, A5 and A6 noradrenaline cell groups also showed high GAP-43 expression, although cells with spinal cord projections were largely restricted to the A5 group and A6 subcoeruleus region. In all areas, GAP-43 expressing cells with spinal cord projections were also observed which were not serotonergic or noradrenergic. 相似文献
10.
Whereas psychological assessment remains a critical skill, it can demand considerable time and effort. In fact, it can often feel tedious and even laborious. As a partial outgrowth, short forms in psychological testing are intrinsically appealing. Unfortunately, many concerns can be raised regarding this practice. This article represents a response to A. P. Thompson, S. G. LoBello, L. Atkinson, V. Chisholm, and J. J. Ryan (see record 2004-95164-011) and is intended to strengthen the discussion on this practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献