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991.
Database views are traditionally described as unmaterialized queries, which may be coincidentally updatable according to some fixed criteria. One of the problems in updating through views lies in determining whether a given view modification can be correctly translated by the system. To define an updatable view, a view designer must be aware of how an update request in the view will be mapped into updates of the underlying relations. Furthermore, because of side effects, the view designer must also be made aware of the effects of isolated updates back into the view. To address this problem, we present a general algorithm that predicts the effects of arbitrary mapping policies. Given an update policy, this algorithm indicates whether a desired update will, in fact, occur in the view and describes all possible side effects it may have, documenting the conditions under which they occur. The algorithm subsumes the results obtained by other view design tools, and generalizes their use to encompass a larger class of views. 相似文献
992.
Grau James W.; Salinas Juan A.; Illich Paul A.; Meagher Mary W. 《Canadian Metallurgical Quarterly》1990,104(3):489
Prior research suggests that associative and memorial processes can modulate the activation of the endogenous antinociceptive systems. It has been generally assumed that forebrain systems play an essential role in mediating the impact of these processes. The present experiments explored whether the behavioral effects indicative of associative and memorial processes can be obtained in spinalized rats. Experiment 1 demonstrated that a conditioned nonopioid antinociception can be established after rats have experienced a spinal transection at the level of the 2nd thoracic vertebrae. Experiment 2 showed that a postshock distractor can speed the decay of shock-induced antinociception in the spinalized rat. These findings suggest that the circuitry needed to obtain associative and memorylike effects is present within the spinal cord. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Rothstein Hannah R.; Schmidt Frank L.; Erwin Frank W.; Owens William A.; Sparks C. Paul 《Canadian Metallurgical Quarterly》1990,75(2):175
The hypothesis was examined that organizational specificity of biodata validity results from the methods typically used to select and key items. In this study, items were initially screened for job relevance, keying was based on large samples from multiple organizations, and items were retained only if they showed validity across organizations. Cross-validation was performed on approximately 11,000 first-line supervisors in 79 organizations. The resulting validities were meta-analyzed across organizations, age levels, sex, and levels of education, supervisory experience, and company tenure. In all cases, validities were generalizable. Validities were also stable across time and did not appear to stem from measurement of knowledge, skills, or abilities acquired through job experience. Finally, these results provide additional evidence against the hypothesis of situational specificity of validities, the first large-sample evidence in a noncognitive domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Frank D. Conforti Jocelyn A. Totty 《International Journal of Food Science & Technology》2007,42(9):1101-1106
The shelf life quality of freshly harvested Golden Delicious apples coated with three individually developed lipid/hydrocolloid coatings was assessed throughout refrigerated storage. The apples were monitored for 8 weeks. The coatings resulted in low internal O2 and the least loss of fruit firmness when compared with the non‐coated apple group. The coated apples had very little starch breakdown, minimum flesh colour development, or loss of titratable acidity content. Soluble solids and fresh weight loss remained unchanged for both the non‐coated and coated groups. Sensory analysis confirmed that the coated apples maintained consistent quality in firmness, crispness and juiciness throughout the storage period. 相似文献
995.
A plating for electrical contact surfaces should be selected on the bases of acceptable electrical characteristics (in conjunction with common contact surfaces) and of adequate corrosion resistance in the anticipated environments. One of the problem electrical interfaces which must be considered is between the selected plating and nonplated aluminum contact surfaces. 相似文献
996.
997.
The nano- and macro-wear characteristics of calcium titanate, single crystal ferrite and polycrystalline ferrite were investigated using nano-scratch testing and wear bar testing. Nano- and micro-indentations were made to determine nano- and micro-hardness, and nano-scratch testing was used to evaluate relative wear rates on the nano-scale. The macro-wear characteristics of the various head materials against metal particle tapes was investigated as a function of tape speed using wear bars mounted in a DLT tape drive. The micro-indentation method was used to investigate wear of the head/tape interface in a linear tape drive. The results from nano- and macro-wear tests were analysed and correlated with the microstructure of the materials. 相似文献
998.
Frank van Steenbergen Abraham Mehari Haile Taye Alemehayu Tena Alamirew Yohannes Geleta 《Water Resources Management》2011,25(7):1899-1913
This article discusses spate irrigation in Ethiopia and aims to take stock of the current status of spate irrigation development.
It summarizes experiences so far and formulates a number of recommendations on the development of this upcoming resource management
system. It argues that raised weirs are useful mainly in areas where a large head for spate flow diversion is required, but
that traditional earthen structures with conical stone/gabion reinforcements are cost-effective and technically adequate for
floodwater distribution and management. It contends that the practical successes of sediment settling ponds (gravel traps)
are at best mixed. Even where a small basin is justified, it can only ever trap a small proportion of the incoming sediment
load. It is better to allow large floods with excessive sediment load (>100,000 ppm) to by-pass upstream intakes to be diverted
lower down the system, and provide additional livelihood opportunities in downstream areas in the form of rangeland and agro-forestry
development. This is particularly useful in the lowlands of Ethiopia with large pastoral community where spate irrigation
is yet to make in-roads. The article further explains that water rights in spate are different from the sharing and allocation
of perennial flows—they are dynamic and respond to a situation that differs from year to year as well as within a year and
that a certain degree of inequity among users is inevitable. Keeping the command area compact can ensure two or more irrigation
turns and this can highly increase productivity as crops are no longer in the ‘stress zone’. To transform spate irrigation
in Ethiopia from subsistence to a business-oriented production system, the article proposes the promotion of cash crops including
pulses and oil seeds as well as encouraging investors to go for bio-fuel development and agro-forestry in the lowland areas
where huge potential exist. To avoid vehement conflicts that may arise among the settled agricultural and pastoral communities
due to the implementation of the business-oriented production system, the traditional rights of the pastoral communities must
be respected and their rangeland and water resources be safeguarded. For maximum yield, soil moisture conservation measures
such as pre-irrigation land preparation, deep ploughing and mulching are essential as is the conjunctive use of spate flow
and groundwater. Last, but most important, the article emphasizes that farmers need to be placed at the heart of any spate
irrigation development programme as primary beneficiaries, managers and operators as well as part of the decision making institution. 相似文献
999.
Thoits Peggy A.; Hohmann Ann A.; Harvey Mary R.; Fletcher Bill 《Canadian Metallurgical Quarterly》2000,19(3):264
This field experiment examined effects of a support intervention on the physical and mental health of coronary artery bypass graft (CABG) surgery patients. Control participants (N?=?90) received usual hospital care; experimental participants (N?=?100) also received visits from a "similar other" while in the hospital. Similar others were Veterans Administration veterans who had CABG surgery previously and were trained in simple supportive techniques. Outcomes were assessed prior to surgery and at 1, 6, and 12 months afterwards. Unexpectedly, the intervention generally had no effects on participants' well-being. Further analysis showed that participants who talked often with fellow cardiac patients in the hospital ("de facto similar others") experienced improvements in their physical and emotional well-being over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.