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排序方式: 共有106条查询结果,搜索用时 31 毫秒
1.
Four oil families are identified in the southern Gulf of Suez, through high-resolution geochemical studies including gas chromatography, gas chromatography-mass spectrometry, and carbon isotope analyses. Biological features characterize oils in family 1a, suggesting tertiary carbonate source rocks for these oils, rich in type II organic matter and deposited under anoxic depositional environment. Family 1b oil shows minor variations in the source of organic matter and the depositional environment, as it was derived from carbonate source rock with more algal and bacterial contribution and minor input of terrestrial organic sources, deposited under less saline condition compared to family 1a oil. Family 2 oil, although genetically related to family 1a oil, has some distinctive features, such as diasterane to sterane and pristane to phytane ratios, which suggest clay-rich source rocks and a more oxic depositional environment. Also, the lack of oleanane indicates pre-tertiary source rocks for this oil. In contrast, family 3 oil is of mixed sources (marine and non-marine), generated from low sulfur and clay-rich source rock of tertiary and/or younger age. Family 4 oil seems to be mixed from family 1b and family 3 oils, sourced mainly from carbonate source rocks rich in clay minerals with algal and bacterial contributions. Family 4 oil is highly mature, family 1b oil lies within equilibrium values (peak oil generation stage), while the other families are more or less near equilibrium.  相似文献   
2.
A noise analysis of bipolar harmonic mixers (BHM) used for direct-conversion receivers is presented in this paper. Analytical and simulated results for the transfer function of the mixer are presented. Simple analytical expressions describing noise contribution from all sources are derived. Estimation of flicker noise quite agrees with harmonic-balance simulation results. Based on the derived expressions, total time average noise power spectral density (PSD) at the output is compared with simulation results. For the recommended regions of operation, error is less than 20%. The overall BHM noise figure (NF) is calculated and optimized based on a simple extracted formula. Errors introduced by analysis remain within a 1.5-dB margin with respect to simulation results. The validity of analysis for high frequencies is justified. The effect of flicker noise coefficient on the overall mixer NF is compared for different available processes.  相似文献   
3.
S Gabr  A Sharaf  S el-Saadany 《Die Nahrung》1985,29(3):219-228
The field experiment was conducted to study the effect of various levels of chlormequat (CCC) and alar on the biochemical changes in tomato plants and fruits at different stages of growth. This experiment included spraying with chlormequat and alar separately in two equal doses (250, 500 and 1000 ppm CCC or alar 25 and 40 days after transplanting). The different levels of chlormequat decreased the accumulation of dry matter in tomato plants, but alar increased it. Chlorophyll a, b, total chlorophyll and carotenoids content of tomato plants increased by the application of CCC or alar. The highest increase of concentration of chlorophyll a, b and carotenoids in tomato plants were found by spraying with 500 ppm alar or CCC. The application of CCC and alar declined the percentage of carbohydrates and the highest decrease resulted by adding of 1000 ppm alar or CCC. Alar caused an increase in the percentage of total nitrogen at the different stages of growth. The concentration of P, K, Ca and Mg increased by the foliar spray of all treatments. Alar application at all used levels significantly increased the yield and also the weight of fruits. Highest plant productivity was obtained by using alar and CCC at 250 ppm, followed by 500 ppm. However, the highest concentration (1000 ppm) depressed the plant productivity. The concentration of juice, total soluble solids and vitamin C in tomato fruits increased at most of the levels added. But the percentage of total sugars and total acidity seemed to exert another trend. The highest concentration of N, P, K, Ca and Mg in fruits was obtained by foliar application of 500 ppm CCC or alar.  相似文献   
4.
Interactive data exploration platforms in Web, business and scientific domains are becoming increasingly popular. Typically, users without prior knowledge of data interact with these platforms in an exploratory manner hoping they might retrieve the results they are looking for. One way to explore large-volume data is by posing aggregate queries which group values of multiple rows by an aggregate operator to form a single value: an aggregated value. Though, when a query fails, i.e., returns undesired aggregated value, users will have to undertake a frustrating trial-and-error process to refine their queries, until a desired result is attained. This data exploration process, however, is growing rather difficult as the underlying data is typically of large-volume and high-dimensionality. While heuristic-based techniques are fairly successful in generating refined queries that meet specified requirements on the aggregated values, they are rather oblivious to the (dis)similarity between the input query and its corresponding refined version. Meanwhile, enforcing a similarity-aware query refinement is rather a non-trivial challenge, as it requires a careful examination of the query space while maintaining a low processing cost. To address this challenge, we propose an innovative scheme for efficient Similarity-Aware Refinement of Aggregation Queries called (EAGER) which aims to balance the tradeoff between satisfying the aggregate and similarity constraints imposed on the refined query to maximize its overall benefit to the user. To achieve that goal, EAGER implements efficient strategies to minimize the costs incurred in exploring the available search space by utilizing similarity-based and monotonic-based pruning techniques to bound the search space and quickly find a refined query that meets users’ expectations. Our extensive experiments show the scalability exhibited by EAGER under various workload settings, and the significant benefits it provides.  相似文献   
5.
A series of poly(acrylic acid-co-methylvinylketone–graft–sulfamethoxazole)(AVMDS) species was synthesized for drug carrier applications. The synthesis involved two steps: copolymerization of acrylic acid(AA) with methyl vinyl ketone(MVK) through the free radical route and subsequent grafting of the sulfamethoxazole (SMX) onto the copolymer via the Schiff base reaction of the primary amine of SMX with the carbonyl groups of the MVK units. The structures and properties of the materials were characterized by nuclear magnetic resonance(NMR), X-ray diffraction(XRD), differential scanning calorimetry(DSC), and scanning electronic microscopy (SEM). An in-vitro cytotoxicity test of the drug-carrier systems via MTT assay revealed no significant cytotoxic effect at concentrations up to 100?µg?·?ml?1. The dynamic release of SMX from these systems through a retro-imidation reaction (inverse Schiff base reaction) was investigated in depth, where the diffusion through the polymer matrix, the enhancement of the water solubility of SMX, the influence of the initial drug concentration, the pH of the medium, and the effect of the degree of swelling of the polymer matrix on the release dynamics were evaluated. The AVMGS4 and AVMGS1 drug carrier systems containing 3.58 and 1.18?wt% of SMX were the best performing systems.  相似文献   
6.
Adsorption of Co2+ and Ni2+ from aqueous solutions onto titanate nanotubes (TNTs) synthesized by hydrothermal method in single and binary systems was investigated. The prepared TNTs were completely characterized showing very high surface area compared to previous studies (320 m2/g). The high surface area showed very good optimum removal conditions compared with previous studies (60 min contact time, 0.1 g TNTs dose at pH 5 and room temperature) with high adsorption capacity compared with previous studies as well as conventional adsorbent. Langmuir and Freundlich isothermal models were fitted during this study and Dubinin–Kaganer–Radushkevich isotherms showed physisorption with exclusion of ion exchange mechanism. Pseudo first and second-order kinetics were studied showing more fitting to pseudo second-order equation. Binary system and calculation of separation coefficient showed high ability for Co2+ adsorption by TNTs than Ni+2 in binary system.  相似文献   
7.
The deterioration of surface water quality occurs due to the presence of various types of pollutants generated from human, agricultural, and industrial activities. Thus, mapping concentrations of different surface water quality parameters (SWQPs), such as turbidity, total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and dissolved oxygen (DO), is indeed critical for providing the appropriate treatment to the affected waterbodies. Traditionally, concentrations of SWQPs have been measured through intensive field work. Additionally, quite a lot of studies have attempted to retrieve concentrations of SWQPs from satellite images using regression-based methods. However, the relationship between SWQPs and satellite data is complex to be modelled accurately by using regression-based methods. Therefore, our study attempts to develop an artificial intelligence modelling method for mapping concentrations of both optical and non-optical SWQPs. In this context, a remote-sensing framework based on the back-propagation neural network (BPNN) is developed for the first time to quantify concentrations of different SWQPs from the Landsat8 satellite imagery. Compared to other methods, such as Support Vector Machine, significant coefficients of determination (R2) between the Landsat8 surface reflectance and concentrations of SWQPs were obtained using the developed Landsat8-based-BPNN models. The resulting R2 values were 0.991, 0.933, 0.937, 0.930, and 0.934 for turbidity, TSS, COD, BOD, and DO, respectively. Indeed, these findings indicate that the developed Landsat8-based-BPNN framework is capable of developing highly accurate models for retrieving concentrations of different SWQPs from the Landsat8 imagery.  相似文献   
8.
In this study, flow cytometry was used for assessing and comparing the genome size (GS) and the whole genome base composition (AT/GC ratio) of the saw-toothed grain beetle Oryzaephilus surinamensis (L.). In addition, the presence and frequency of endosymbiotic Wolbachia bacteria was studied. The haploid GS was estimated to lie within the range of 151.5-154 Mbp in O. surinamensis, making it the smallest value of haploid GS known among beetles. Furthermore, it was found that in eight silo pest populations GS was significantly smaller than in eight feral (native) populations obtained from fallen oak acorns. The ability of O. surinamensis to colonize different habitats globally could be connected with an unusually AT-rich (for an invertebrate) genome (AT-base content ranging from 68 to 76%). Native (feral) populations of O. surinamensis appear to have genetically diverged from the storage-pest populations tested. Larvae of pest origin survived better than larvae of native (feral) origin under laboratory conditions, which resembled silo conditions more than natural habitats.  相似文献   
9.
Milk of high conjugated linoleic acid (CLA) level (1.25 g per 100 g milk fat) was produced by inclusion of fish oil and rousted soy bean in the ration of Holstein cows as compared to 0.55 g per 100 g milk fat in the milk of animals receiving control diet. Milk of normal (control) and high CLA content (treatment) was spray‐dried. Labneh was made from 20 g L?1 reconstituted milk using 3 mL per 100 mL yoghurt starter and 2 mL per 100 mL of probiotic cultures of Lactobacillus casei or Lactobacillus acidophilus. The control (C) and high CLA (T) labneh were analysed chemically and microbiologically, and their viscosities were determined during cold storage for 15 days. The fat content of labneh of high CLA was less than that of the control, but the total solids (TS) were unaffected by the CLA level. Labneh made with Lb. acidophilus had lower TS and higher acidity, exopolysaccharides and acetaldehyde contents and viscosity than that made with the use of Lb. casei. Labneh from the different treatments retained high counts of the added probiotic (>108 cfu g?1) throughout the storage period. The storage period had significant effects on all parameters determined.  相似文献   
10.
The structure and optical properties of Cu0.1Tl2Se3 alloy was studied. X-ray analysis showed that the polycrystalline powder consists of a mixture of two phases Cu3TlSe2 (monoclinic) and TlSe (tetragonal). Chalcopyrite phase CuTlSe2 can be obtained by annealing the powder at 250 ℃ for 1 h. Thin film with a monoclinic phase of Cu3TlSe2 was obtained for the thick film (0.7 mum). The optical parameters alpha, n, k, epsilon' and epsilon " and the energy gap were calculated. The thermoelectric power measurements showed that S has a positive polarity over the whole range of temperature.  相似文献   
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