Floc meal as potential substitute for soybean meal in tilapia diets under biofloc system conditions     

Mabroke  Rania S.  El-Husseiny  Osama M.  Zidan  Abd El-Naem F. A.  Tahoun  Al-Azab  Suloma  Ashraf 《中国海洋湖沼学报》2019,37(1):313-320

This study was conducted to evaluate the effect of replacing soybean meal (SBM) by low protein floc meal (LPFM; 24% CP) in tilapia diets on growth performance, feed utilization and fish chemical composition. Three isonitrogenous and isocaloric diets were formulated; control diet (C; without LPFM), FM ₂₅ (25% of SBM protein was substituted by LPFM) and FM ₅₀ (50% of SBM protein was substituted by LPFM). Nine 55l circular plastic tanks were stocked by 12 fish to form three experimental groups. No differences in tilapia performance were observed between the control and the FM ₂₅ diet. Chemical composition of fish did not differ significantly among treatments except for protein and selenium contents where the highest values were recorded in the control treatment. The highest mineral content was recorded in floc collected from the control tanks, while calcium content showed its highest value in floc collected from FM ₅₀ effluent. These data indicate that replacing soybean meal with LPFM up to 25%, had no negative effect on growth performance and potentially may improve the system sustainability. Meanwhile, the adverse effect of more inclusion of LPFM in tilapia diet may be attributed to the higher content of ash. In other word, minerals seem to cause more energy utilization in fish fed floc meal since it is needed to maintain osmotic homeostasis.

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Markov stochastic technique to determine galactic cosmic ray sources distribution     

Ashraf Farahat 《Journal of Astrophysics and Astronomy》2010,31(2):81-88

A new numerical model of particle propagation in the Galaxy has been developed, which allows the study of cosmic-ray production and propagation in 2D. The model has been used to solve cosmic ray diffusive transport equation with a complete network of nuclear interactions using the time backward Markov stochastic process by tracing the particles’ trajectories starting from the Solar System back to their sources in the Galaxy. This paper describes a further development of the model to calculate the contribution of various galactic locations to the production of certain cosmic ray nuclei observed at the Solar System.  相似文献   

Radially accelerated optimal feedback orbits in central gravity field with linear drag     

Ashraf Owis  Francesco Topputo  Franco Bernelli-Zazzera 《Celestial Mechanics and Dynamical Astronomy》2009,103(1):1-16

The solution of a feedback optimal control problem arising in orbital mechanics is addressed in this paper. The dynamics is that of a massless body moving in a central gravitational force field subject also to a drag and a radial modulated force. The drag is linearly proportional to the velocity and inversely proportional to the square of the distance from the center of attraction. The problem is tackled by exploiting the properties of a suitably devised linearizing map that transforms the nonlinear dynamics into an inhomogeneous linear system of differential equations supplemented by a quadratic objective function. The generating function method is then applied to this new system, and the solution is back transformed in the old variables. The proposed technique, in contrast to the classical optimal control problem, allows us to derive analytic closed-loop solutions without solving any two-point boundary value problem. Applications are discussed.  相似文献   

Stochastic analysis of free surface flow through earth dams   总被引：1，自引：0，他引：1  

Ashraf A. Ahmed   《Computers and Geotechnics》2009,36(7):1186-1190

This research investigated the unconfined flow through dams. The hydraulic conductivity was modeled as spatially random field following lognormal distribution. Results showed that the seepage flow produced from the stochastic solution was smaller than its deterministic value. In addition, the free surface was observed to exit at a point lower than that obtained from the deterministic solution. When the hydraulic conductivity was strongly correlated in the horizontal direction than the vertical direction, the flow through the dam has markedly increased. It is suggested that it may not be necessary to construct a core in dams made from soils that exhibit high degree of variability.  相似文献   

Image data fusion for the remote sensing of freshwater environments   总被引：2，自引：0，他引：2  

Salman Ashraf  Lars BrabynBrendan J. Hicks 《Applied geography (Sevenoaks, England)》2012,32(2):619-628

Remote sensing based mapping of diverse and heterogeneous freshwater environments requires high-resolution images. Data fusion is a useful technique for producing a high-resolution multispectral image from the merging of a high-resolution panchromatic image with a low-resolution multispectral image. Given the increasing availability of images from different satellite sensors that have different spectral and spatial resolutions, data fusion techniques that combine the strengths of different images will be increasingly important to Geography for land-cover mapping. Different data fusion methods however, add spectral and spatial distortions to the resultant data depending on the geographical context; therefore a careful selection of the fusion method is required. This paper compares a technique called subtractive resolution merge, which has not previously been formally tested, with conventional techniques such as Brovey transformation, principal component substitution, local mean and variance matching, and optimised high pass filter addition. Data fusion techniques are grouped into spectral and spatial centric methods. Subtractive resolution merge belongs to a new class of data fusion techniques that uses a mix of both spatial and spectral centric approaches. The different data fusion techniques were applied to a QuickBird image of a semi-aquatic freshwater environment in New Zealand. The results were compared both qualitatively and quantitatively using spectral and spatial error metrics. This research concludes that subtractive resolution merge performed better than all the other techniques and will be a valuable technique for enhancing images for freshwater land-cover mapping.  相似文献   

基于图像相减和随机森林的AST3巡天暂现源及变源搜寻方法     

黄天君  孙天瑞  胡镭  宁宗军  吴雪峰  王力帆  王晓峰  朱镇熹  UDDIN Ashraf Sye  ASHLEY Charles Brewster Michael 《天文学报》2019,60(5):98-114

AST3-2 (Antarctic Survey Telescopes)光学巡天望远镜位于南极大陆最高点冰穹A,其产生的大量观测数据对数据处理的效率提出了较高要求.同时南极通信不便,数据回传有诸多困难,有必要在南极本地实现自动处理AST3-2观测数据,进行变源和暂现源观测的数据处理,但是受到低功耗计算机的限制,数据的快速自动处理的实现存在诸多困难.将已有的图像相减方案同机器学习算法相结合,并利用AST3-2 2016年观测数据作为测试样本,发展一套的暂现源及变源的筛选方法成为可行的选择.该筛选方法使用图像相减法初步筛选出可能的变源,再用主成分分析法抽取候选源的特征,并选择随机森林作为机器学习分类器,在测试中对正样本的召回率达到了97%,验证了这种方法的可行性,并最终在2016年观测数据中探测出一批变星候选体.  相似文献   

Design of hydraulic structures considering different sheetpile configurations and flow through canal banks     

Ashraf A Ahmed 《Computers and Geotechnics》2011

This research investigated seepage under hydraulic structures considering flow through the banks of the canal. A computer model, utilizing the finite element method, was used. Different configurations of sheetpile driven under the floor of the structure were studied. Results showed that the transverse extension of sheetpile, driven at the middle of the floor, into the banks of the canal had very little effect on seepage losses, uplift force, and on the exit gradient at the downstream end of the floor. Likewise, confining the downstream floor with sheetpile from three sides was not found effective. When the downstream floor was confined with sheetpile from all sides, this has significantly reduced the exit gradient. Furthermore, all the different configurations of the sheetpile had insignificant effect on seepage losses. The most effective configuration of the sheetpile was the case when two rows of sheetpiles were driven at the middle and at the downstream end of the floor, with the latter sheetpile extended few meters into the banks of the canal. This case has significantly reduced the exit gradient and caused only slight increase in the uplift force when compared to other sheetpile configurations. The present study suggests that two-dimensional analysis of seepage problems underestimates the exit gradient and uplift force on hydraulic structures.  相似文献   

Geochemical and isotopic evolution of groundwater in the Wadi Watir watershed,Sinai Peninsula,Egypt     

Mustafa A. Eissa  James M. Thomas  Ronald L. Hershey  Maher I. Dawoud  Greg Pohll  Kamal A. Dahab  Mohamed A. Gomaa  Ashraf R. Shabana 《Environmental Earth Sciences》2014,71(4):1855-1869

The Wadi Watir delta in the Wadi Watir watershed is a tourist area in the arid southeastern part of the Sinai Peninsula, Egypt, where development and growth of the community on the delta are constrained by the amount of groundwater that can be withdrawn sustainably. To effectively manage groundwater resources in the Wadi Watir delta, the origin of groundwater recharge, groundwater age, and changes in groundwater chemistry in the watershed needs to be understood. Mineral identification, rock chemistry, water chemistry, and the isotopes of hydrogen, oxygen, and carbon in groundwater were used to identify the sources, mixing, and ages of groundwater in the watershed and the chemical evolution of groundwater as it flows from the upland areas in the watershed to the developed areas at the Wadi Watir delta. Groundwater in the Wadi Watir watershed is primarily from recent recharge while groundwater salinity is controlled by mixing of chemically different waters and dissolution of minerals and salts in the aquifers. The El Shiekh Attia and Wadi El Ain areas in the upper Wadi Watir watershed have different recharge sources, either from recharge from other areas or from different storm events. The downgradient Main Channel area receives groundwater flow primarily from the El Shiekh Attia area. Groundwater in the Main Channel area is the primary source of groundwater supplying the aquifers of the Wadi Watir delta.  相似文献   

Ionic liquid as a medium to remove iron and other metal ions: a case study of the North Kelantan Aquifer,Malaysia   总被引：1，自引：1，他引：0  

Nur Hayati Hussin  Ismail Yusoff  Yatimah Alias  Sharifah Mohamad  Nurul Yani Rahim  Muhammad Aqeel Ashraf 《Environmental Earth Sciences》2014,71(5):2105-2113

An alternative iron removal treatment method using liquid-liquid extraction with the room-temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, as a solvent medium was studied. The chelating agent 1,10-phenanthroline was used as the extractant. The extraction of Fe(III) and Fe(II) was influenced significantly by the pH of the aqueous phase. The successful removal of iron was achieved; more than 95 % of the initial iron concentration was removed from the groundwater samples. However, detailed research is needed before the ionic liquid method can replace the conventional groundwater treatment protocol because the recovery rate was very low upon reuse (approximately 25–60 %). This low recovery was due to the ion exchange process; the appearance of anions from ionic liquids was also detected in groundwater samples.  相似文献   

¹³C/¹²C ratio double cyclicity in a Miocene browncoal: isotopic signals and orbital forcing     

Timothy P. Jones  Steven M. Fortier  Volker Mosbrugger  Jochen Roessler  Thorsen Utescher  & Abdul R. Ashraf 《地学学报》1997,9(1):19-23

A detailed stable carbon isotopic profile of a late Miocene browncoal seam from the Lower Rhine Embayment, Germany, reveals two clear separate cycles of different frequency: this is the first instance of this type of isotopic signature being recognized within coals. The ratio of the two frequencies suggests this isotopic signal possibly resulted from climatic or vegetational responses to orbital forcing. The cyclicity has been enhanced by the application of conventional filtering methods on the data set. An analysis of the seam's palynology indicates a correlation between heavier isotopic compositions and the presence of Sequoiapollenites polyformosus , whose parent plant is believed to have favoured moist climates and higher groundwater tables.  相似文献