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161.
Sodium paranitrophenolate dihydrate (NPNa·2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mmx6 mmx3 mm are obtained by isothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa·2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa·2H2O was revealed in this paper. 相似文献
162.
163.
In broadcast disks systems, information is broadcasted in a shared medium. When a client needs an item from the disk, it waits until that item is broadcasted. Broadcast disks systems are particularly attractive in settings where the potential customers have a highly-asymmetric communication capabilities, i.e., receiving is significantly cheaper than transmitting. This is the case with satellite networks, mobile hosts in wireless networks, and Teletext system.The fundamental algorithmic problem for such systems is to determine the broadcast schedule based on the demand probability of items, and the cost incurred to the system by clients waiting. The goal is to minimize the mean access cost of a random client. Typically, it was assumed that the access cost is proportional to the waiting time. In this paper, we ask what are the best broadcast schedules for access costs which are arbitrary polynomials in the waiting time. These may serve as reasonable representations of reality in many cases, where the patience of a client is not necessarily proportional to its waiting time.We present an asymptotically optimal algorithm for a fractional model, where the bandwidth may be divided to allow for fractional concurrent broadcasting. This algorithm, besides being justified in its own right, also serves as a lower bound against which we test known discrete algorithms. We show that the Greedy algorithm has the best performance in most cases. Then we show that the performance of other algorithms deteriorate exponentially with the degree of the cost polynomial and approaches the fractional solution for sub-linear cost. Finally, we study the quality of approximating the greedy schedule by a finite schedule. 相似文献
164.
The study aims were to assess the independent contribution of motor ability to the incidence of school injuries. The study included 2057 pupils in grades 3-6 of primary schools in a city in the north of Israel. A surveillance system gathered information about injuries that occurred on school premises or during school related activities and required medical treatment or caused limitation of usual activities. Children provided information on sensation seeking, self-appraisal of health, academic performance, physical activity, and dominant hand; anthropometric measurements and motor ability tests were performed.The incidence of injury events was 4% (95% CI=3.2-5.0). Injuries increased with increased balance and agility, but there were no differences according to reaction time. No other study variables were associated with the incidence of injuries. Our findings of an increase in the incidence of injuries with better motor ability may express differences in exposure to risk situations between children with better and poorer motor abilities. 相似文献
165.
Boaz Ronen Ph.D. 《Computers & Industrial Engineering》1987,13(1-4):71-72
Inventory management is being discussed recently as one of the key elements for survival and success in the production industry today. Little efforts were made to solve inventory problems in the Hi R&D environment.
In this paper, a prototype of a Microcomputer Based Decision Support is introduced to support decisions for managing Hi R&D inventories. The decisions involve timing and scheduling of purchased components, as well as classification of those items. 相似文献
166.
R. W. Gibbs (see record 1992-42479-001) argued that metaphoric expressions may reflect preexisting conventional metaphoric mappings in long-term memory. The class-inclusion model, in contrast, focuses on conceptual structures that are constructed and accessible in working memory during metaphor comprehension. The authors agree that prestored metaphoric mappings may be available, but they may not be accessible and hence not used in any given context. The authors point out problems in identifying those metaphorical mappings that may be relevant to a given metaphoric expression and suggest that conceptual metaphors may not be identifiable until after a metaphor has been interpreted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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168.
The nature of the search of primary memory by persons with a presumptive diagnosis of mild Alzheimer's disease (dementia of the Alzheimer type [DAT]) was compared with that of normal elderly and young persons using the S. Sternberg (1966) paradigm. DAT Ss evidenced a substantial deficit in the speed of scanning in primary memory and a deficit in at least one other stage of processing. These findings are consistent with the hypothesis that the decline in memory performance evidenced by persons with DAT may be attributable to an increase in the time requirements of mnemonic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
169.
The composition of groundwater reclaimed from tertiary soil aquifer treatment systems reflects the dynamic processes taking place in the subsurface, between the infiltration basin and the production wells. At the end of year 2000, following more than a decade of operation, high Mn concentrations (2 micromol L(-1) < or = Mn < or = 40 micromol L(-1)) appeared in the reclaimed effluents of the Dan Region Sewage Reclamation Project (Shafdan), Israel. A mass balance indicates that the high Mn excess originated from the aquifer rocks, most likely following reduction of sedimentary Mn-oxides under suboxic conditions. The subsequent adsorption of the Mn2+ results in a slow Mn2+ front that advances in the direction of groundwater flow only when all the Mn2+ exchangeable sites are saturated. A retardation factor obtained from two independent estimates based on a simple reduction-adsorption-advection model yields a value of about 10. This explains the delayed appearance of the high Mn concentrations at a distance of only -500 m from the infiltration basin. 相似文献
170.
R. Kiyengo M. Majaliwa R. Twinomuhangi H. Waswa 《The International journal of environmental studies》2020,77(3):480-491
ABSTRACT This study was conducted to establish the spatio-temporal distribution of flash floods and to learn why people prefer to settle in flood-prone areas of Lubiji micro-catchment in Kampala City. Rainfall data were analysed to ascertain Peak Runoff expected for the given flood event based on Soil Conservation Service Curve Numbers. The micro-catchment was delineated in the Arc GIS 10.0 programme, from the Digital Elevation Model. Feature classes were created to obtain the reach extents and river banks. HEC-RAS model was then used to create flood inundation maps in Arc GIS 10.0 between 1983 and 2014. High magnitude flash floods occurred almost after every three years and the spatial extent varied from 4.4 to 6.8 km2. The choice of settlement location in flood-prone areas was influenced by socio-economic ties. The flood hazard maps produced will aid land-use planning, resettlement of the people and setting up a flood forecasting system. 相似文献