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41.
High-speed digital signal processing and control   总被引:13,自引:0,他引:13  
An attempt is made to organize and survey recent work, and to present it in a unified and accessible form. The need for a new approach suitable for high-speed processing is discussed in the context of several applications in control and communications, and a historical perspective of the use of difference operators in numerical analysis is presented. The general systems calculus, based on divided-different operators is introduced to unify the continuous-time and discrete-time systems theories. This calculus is then used as a framework to treat the three problems of system state estimation; system identification and time-series modeling; and control system design. Realization aspects of algorithms based on the difference operator representation, including such issues as coefficient rounding and implementation with standard hardware, are also discussed  相似文献   
42.
Capacity enhancement and volume reduction benefits of step-feeding fully aerobic bioreactors has been well documented. Application of step-feed technology to biological nutrient removal (BNR) systems, particularly those removing nitrogen alone or both nitrogen and phosphorus, is relatively new to the industry. In recent years, a number of full-scale step-feed facilities have been brought into service. This paper reviews nine full-scale step-feed biological nutrient removal systems--both nitrogen removal alone, and nitrogen and phosphorus removal. The objective is to compare the theoretical benefits of such systems with their actual operation. The predicted benefits of reduced bioreactor volume or increased process capacity, reduced energy usage, more robust nitrification performance, and the flexibility to tune (or de-tune) nitrification efficiency were verified in full-scale systems. Equations are also presented that may be used in the prediction of step-feed benefits. There are two primary drivers for considering a step-feed biological reactor system: 1. Reduced bioreactor volume for a defined capacity or performance or increased process capacity given a fixed bioreactor volume. 2. More robust nitrification performance. Full-scale operation of these step-feed nutrient removal systems provides a real world basis for the claimed benefits of step-feed operation. These systems have uniformly shown additional capacity. A number of them have also exhibited more robust performance, especially during storms. Where possible, side-by-side comparisons of full-scale step-feed systems with non-step-feed systems have exhibited greater process reliability and flexibility.  相似文献   
43.
We have used comparative sequence analysis to identify an intein-like sequence (protein splicing element) present in Cryptococcus neoformans, a fungal pathogen of humans. The sequence encoding this element is present in the C. neoformans PRP8 gene, as an in-frame insertion relative to the PRP8 genes of other organisms. It contains sequences similar to those of the protein-splicing domains of two previously described yeast inteins (in Saccharomyces cerevisiae and Candida tropicalis), although it lacks any recognizable internal endonuclease domain. The Cryptococcus neoformans intein (Cne PRP8) is only the second to be found in a eukaryote nuclear genome; the previously described yeast inteins occur at the same site in the VMA gene homologues of S. cerevisiae and C. tropicalis. The host gene of the Cryptococcus intein, PRP8, encodes a highly conserved mRNA splicing protein found as part of the spliceosome. The Cne PRP8 intein may be a useful drug target in addressing the cryptococcal infections so prevalent in AIDS patients.  相似文献   
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The genetic diversity of 88 Streptococcus suis serotype 2 isolates which were recovered from various countries was examined by randomly amplified polymorphic DNA (RAPD) analysis with three primers. This bacterial collection included 80 isolates of porcine origin and 8 of human origin. This investigation allowed the identification of 23 RAPD types containing 1 to 30 isolates originating from one to six countries. Common RAPD patterns were found between human and pig isolates. The isolates were also tested for the production of virulent factors such as hemolysin, muramidase-released protein (MRP), and extracellular factor (EF). All isolates exhibiting the virulent phenotype hemolysin+ MRP+ EF+ clearly clustered on the basis of fingerprinting by RAPD analysis. In a similar way, most of isolates with the hemolysin- MRP- EF- phenotype were assigned to one RAPD cluster. Therefore, RAPD clusters are more related to the phenotype defined with hemolysin, MRP, and EF than to the geographic origin of the isolates. These data indicate that RAPD analysis used in conjunction with phenotypic methods provides a reliable method for the assessment of the clonal relationship between S. suis isolates responsible for infections in pigs or humans, especially for those exhibiting the classic "virulent" phenotype hemolysin+ MRP+ EF+.  相似文献   
47.
A 1*8 element III-V photodetector/silicon bipolar circuit receiver array has been fabricated using a selfaligning, low parasitic, flipchip solder bond hybridisation process. Receiver elements operate at data rates up to 1 Gbit/s with an input sensitivity of -23 dBm at 1.3 mu m wavelength, and with negligible interchannel crosstalk. An overall delay of 1.5 ns was measured between optical input and digital output.<>  相似文献   
48.
The present investigation examined the effects of placebo (P), low dose (LD), and high dose (HD) ethanol on auditory event-related potential (AEP) recovery functions in a group of males at high risk to develop alcoholism (HR; n = 23, mean = 22.3 years) and a low risk (LR; n = 27, mean = 23.0 years) control group. Condition order was randomized, with one condition (P, LD, or HD) per day and a minimum 1-day interval between conditions. For each subject, both blood alcohol levels (BALs) measured via breathalyzer, and event-related potentials recorded with the entire 10/20 International System, were assessed prior to and at mean intervals of 20, 60, 90, and 130 min after P, LD, or HD administration. A series of binaural auditory stimuli with randomly interposed interstimulus intervals of 0.5, 1.0, and 10.0 sec were used to elicit the N100 and P200 components of the AEP. Between-groups comparisons indicated that ethanol elicited risk group differences in recovery functions not present at baseline. The differences were manifested in the HR group as larger decrements in P200 amplitude during the ascending blood alcohol curve (acute sensitivity) and more rapid returns of both N100 and P200 to baseline levels during the descending blood alcohol curve (acute tolerance). These findings support Newlin and Thomson's (1990) Differentiator Model, suggesting that LR and HR individuals are differentially sensitive to the effects of ethanol.  相似文献   
49.
National leprosy control programmes currently face a number of changes to the environment within which they operate. This paper examines the issues arising from these. It focuses, in particular, on those arising from changes in the structure of the health sector as a result of policies of health sector reform which are being considered or adopted in many developing countries. These include decentralization, financing strategies, greater role for the private and NGO sectors and the integration of vertical programmes. The paper is structured around a number of key steps in the development of a strategy for sustainability of appropriate leprosy services. These are the assessment of the epidemiological, social and health services context, development of programme objectives, planning of human and financial resources, development of the strategy, mapping the roles of potential actors, development of regulatory and incentive mechanism, action planning and managing change and, finally, re-evaluation of the programme objectives and service delivery organization. The paper stresses the importance of process in developing ownership of a strategy. It concludes with a set of key questions which it suggests need to be addressed by leprosy programme managers in the development of a proactive response to the changes.  相似文献   
50.
Parents play a crucial role in the life of a child suffering from an anorectal malformation (ARM), since their guidance contributes to the degree to which the child learns to cope with his or her disability. We investigated whether they experience stress in parenting such a child and also attempted to identify somatic or behavioral characteristics in the child that influence the stress of parenting. The parents of 109 children (69 males, 40 females; median age 5.9 years, range 1-18 years) with an ARM (58 low, 10 intermediate, 41 high) were studied. The Nijmegen Questionnaire on Child-rearing Situations (NQCS) was used to investigate the existing parenting situation. Behavioral characteristics of the children were studied by means of the Child Behaviour Checklist (CBCL) and the Teacher Report Form (TRF). In a semi-structured interview, we investigated how parents experienced the implications of the disability in everyday life with their child. Our study showed that as far as the perception of parenting stress is concerned, parents of children with an ARM do not differ from those with healthy primary-school children. Within the group of parents with ARM-afflicted children, the parents of older, incontinent children experienced relatively more stress, especially when the child concerned was male. With regard to the children's behavior, the parents and teachers under investigation did not report a higher than normal incidence of deviant behavior. However, when individual parents observed difficult behavior in their child, they found it harder to deal with than the incontinence for feces. Regarding the implications of the disorder for their everyday lives, parents were concerned and indicated a need for specific counselling. We conclude that having a child with a somatic affliction, in this case an ARM, does not automatically imply that the parents experience child-rearing problems. However, certain groups of parents are more at risk, i.e., parents with older, incontinent sons and parents with children exhibiting behavioral problems. In addition, our study shows that parents do have difficulties in coping with the implications of the disorder and express a need for support. We feel that patient care can be improved if aid is tailored to these specific problems.  相似文献   
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