数码相机颜色复制性能的研究

实验选取了2款具有代表性的数码相机,采集了各设备在制作特性化文件前后的特性化数据,接着通过数据拟合和进一步分析,得出了数码相机之间的性能差异,最后通过建立六大评判标准进行主观评价,对实验结果进行验证。实验结果表明,进行色彩管理图像的色差要小于未进行色彩管理图像的色差,由制作特性化文件前后图像效果的差别,可知制作数码相机的特性文件是很有必要的。最后给出了不同相机不同拍摄条件下对不同原稿的再现结果,为相关工作者和使用者提出一项可行的评价方案。

基于纸张类型的静电数字印刷复制性能研究

参照胶印印品质量标准,对静电数字印刷复制性能进行分析。实验选取6类常用于印刷生产的纸张作为承印材料输出测试样张,对实地密度、网点扩大、相对反差、阶调响应、网点微观形态、油墨的显色性能及色域等质量评价指标进行测量与分析。发现同一设备在不同纸张上的印刷复制性能存在差异,但仍在合理的范围内。输出样张的大部分质量指标与胶印相近,但静电印刷的网点扩大及相对反差相对更大。静电数字印刷复制性能与传统胶印一样可以规定统一的印品质量要求及相关标准,同时建议将油墨的显色性能考虑到数字印刷质量的检测与评价指标中去,对制定静电数字印刷的印品质量标准具有一定的参考作用。

宣纸数码复制适性的分析

宣纸作为承印材料,是影响国画艺术品复制质量的主要因素之一。通过测量生宣和熟宣纸的断裂长、湿强度和挺度,对比墨滴扩散渗透情况,测量耐久性和耐水性,综合分析了生宣和熟宣纸的运行性能、复制性能和保存性,得出熟宣纸在运行性能、复制性能和耐水性上较生宣纸更适合喷墨复制,能够得到质量较好的复制艺术品。

更优的高性能解决方案——文件系统级数据复制

绝大多数高性能解决方案都采用共享存储器簇结构，在这种结构中，多个服务器都连到外部的RAID子系统上。然而，这种结构存在许多不足，例如不能有效防范数据丢失，也不能提供高性能方案。而这种在两个完全独立系统之间通过TCP／IP协议实现磁盘数据复制的高性能系统，就不会出现以上问题。这种解决方案与共享存储器簇相比能够降低系统成本，提供高性能服务。但这种方案至今仍末得到广泛使用。

带窗口的净增量数据库复制优化算法

数据库复制是保持数据一致性、提高灾难应对能力和数据可访问性的途径。目前常用的复制工具大多采用异步方式,需要处理增量的问题。本文在Daffodil Replicator的基础上,针对数据库净增量复制技术做一些探讨和研究,提出利用窗口算法来平衡产生、传输和解析净增量数据的资源压力和时间代价,对该算法的时间复杂度做出估计,使用采样的方法来拟合时间函数曲线,确定最优情况。

利用SQL SERVER复制技术实现数据的多服务器存储

复制是将数据存储到其它数据库或服务器中的一种方法。文章介绍了SQLSERVER复制技术的基本原理,并提出了增强复制性能的一些方法。

APPLICATION OF HYBRID AERO-ENGINE MODEL FOR INTEGRATED FLIGHT/PROPULSION OPTIMAL CONTROL

The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.

Performance analysis of ammonia-water absorption/compression combined refrigeration cycle

In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.

Stem cell pluripotency and transcription factor Oct4

Mammalian cell totipotency is a subject that has fascinated scientists for generations. A long lasting question whether some of the somatic cells retains totipotency was answered by the cloning of Dolly at the end of the 20th century. The dawn of the 21st has brought forward great expectations in harnessing the power of totipotentcy in medicine. Through stem cell biology, it is possible to generate any parts of the human body by stem cell engineering. Considerable resources will be devoted to harness the untapped potentials of stem cells in the foreseeable future which may transform medicine as we know today. At the molecular level, totipotency has been linked to a singular transcription factor and its expression appears to define whether a cell should be totipotent. Named Oct4, it can activate or repress the expression of various genes. Curiously, very little is known about Oct4 beyond its ability to regulate gene expression. The mechanism by which Oct4 specifies totipotency remains entirely unresolved. In this review, we summarize the structure and function of Oct4 and address issues related to Oct4 function in maintaining totipotency or pluripotency of embryonic stem cells.

Facile synthesis of Sb@Sb2O3/reduced graphene oxide composite with superior lithium-storage performance

Sb-based materials have been considered one of the most promising anode electrode materials for lithium-ion batteries,whereas they were commonly synthesized through time-consuming and costly processes.Here,Sb@Sb2O3/reduced graphene oxide(Sb@Sb2O3/rGO)composite was successfully synthesized by a facile one-pot chemical method at ambient temperature.Based on the XRD and TGA analysis,the mass fractions of Sb and Sb2O3 in the Sb@Sb2O3/rGO composite are ca.34.05%and 26.6%,respectively.When used as an alternative electrode for lithium ion batteries,a high reversible capacity of 790.9 mA·h/g could be delivered after 200 cycles with the capacity retention of 93.8%at a current density of 200 mA/g.And a capacity of 260 mA·h/g could be maintained even at 2000 mA/g.These excellent electrochemical properties can be attributed to its well-constructed nanostructure.The Sb and Sb2O3 particles with size of 10 nm were tightly anchored on rGO sheets through electronic coupling,which could not only alleviate the stress induced by the volume expansion,suppress the aggregation of Sb and Sb2O3 particles,but also improve the electron transfer ability during cycling.

Microstructure and mechanical properties of Al-TiB_2/TiC in situ composites improved via hot rolling

A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the particles and mechanical properties of the composites,subsequent hot rolling with increasing reduction was carried out.The microstructure evolution of the composites was characterized using field emission scanning electron microscopy(FESEM)and the mechanical properties were studied through tensile tests and microhardness measurement.It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction.The ultimate tensile strength and microhardness of the composites with90%rolling reduction reach185.9MPa and HV59.8,respectively,140%and35%higher than those of as-cast ones.Furthermore,the strengthening mechanism of the composite was analyzed based on the fracture morphologies.

Effects of Mg content on microstructure and mechanical properties of SiC_p/Al-Mg composites fabricated by semi-solid stirring technique

10%(volume fraction) SiCp/Al-Mg composites with different Mg contents were successfully fabricated by semi-solid mechanical stirring technique under optimum processing conditions.Effects of Mg content on microstructure and mechanical properties were studied by scanning electron microscopy(SEM),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).The results indicate that SiC particles disperse homogeneously in Al-Mg matrix and interfacial reaction between Al matrix and SiC particles is effectively controlled.Distribution of SiCp reinforcement and interfacial bonding are improved by adding Mg.Additionally,the mechanical properties of composites are remarkably improved with the Mg content increasing.

Microstructure evolution,mechanical properties and tailoring of coefficient of thermal expansion for Cu/Mo/Cu clad sheets fabricated by hot rolling

The law of microstructure evolution and mechanical properties of hot roll bonded Cu/Mo/Cu clad sheets were systematically investigated and the theoretical prediction model of the coefficient of thermal expansion(CTE)of Cu/Mo/Cu clad sheets was established successfully.The results show that the deformation of Cu and Mo layers was gradually coherent with an increase in rolling reduction and temperature and excellent interface bonding was achieved under the condition of a large rolling reduction.The development of the microstructure and texture through the thickness of Cu and Mo layers was inhomogeneous.This phenomenon can be attributed to the friction between the roller and sheet surface and the uncoordinated deformation between Cu and Mo.The tensile strength of the clad sheets increased with increasing rolling reduction and the elongation was gradually decreased.The CTE of Cu/Mo/Cu clad sheets was related to the volume fraction of Mo.The finite element method can simulate the deformation and stress distribution during the thermal expansion process.The simulation result indicates that the terminal face of the clad sheets was sunken inward.

Microstructures and compressive properties of AZ91D/fly-ash cenospheres composites

Novel AZ91D Mg alloy/fly-ash cenospheres(AZ91D/FACs)composites were fabricated by melt stir technique.Fly-ash cenosphere particles with 4%,6%,8%,10%in mass fraction and 100μm in size were used.Hardness and compressive strength of the composites were measured.The effects of mass fraction of cenospheres on the microstructure and compressive properties were characterized.The results show that the cenospheres are uniformly distributed in the matrix and there is no sign of cenosphere cluster or residual pore.The densities of the composites are 1.85-1.92 g/cm 3 .By comparing with matrix,the compressive yield strength of the composites is improved,and the cenospheres is filled with Mg matrix alloy.SEM,XRD and EDX results of the composites show clear evidence of reaction product at cenosphere/matrix interface.On the basis of XRD and EDX,composition, structure and thermodynamic analysis,the main interfacial phase between the cenosphere and AZ91D Mg alloy was identified to be MgAl2O4.

In-situ Synthesis and Catalytic Properties of ZSM-5/Rectorite Composites as Propylene Boosting Additive in Fluid Catalytic Cracking Process

Using rectorite extrudates from calcined rectorite powder as the starting material, a series of ZSM-5/rectorite composites were prepared via the in-situ crystallization method. The physicochemical properties and propylene boosting performance of the resulting samples were characterized by using X-ray diffraction, scan- ning electronic microscopy/energy dispersive spectrometer, N2 adsorption-desorption, and Fourier transformed in/tared spectroscopy of pyndine adsorption, respectively, and assessed by using Daqing atmospheric residue as Iced- stock. The results showed that the ZSM-5/rectorite composites in which the ZSM-5 phase grows inositu as a 2-3 p,m thick layer on rectorite particles have a trimodal microporous-mesoporous-macroporous structure and thus exhibit outstanding propylene boosting performance. Compared with a commercial ZSM-5 incorporated fluid catalytic cracking catalyst, the ZSM-5/rectorite composite incorporated catalyst increased the yield and selectivity of propylene by 2.44% and 5.35%, respectively.

Preparation and Properties of a New Type of Poly(butylene-terephthalate)with Layered Silicate Nanocomposites

In this paper, poly(butylene-terephthalate)-layered silicate of clay nanocomposites (NPBT) are reported. Their thermal properties, heat distortion temperature (HDT) and crystallization nucleation are investigated. NPBT samples have apparent viscosity over 0.85, HDT of 30℃ to 50℃ higher than that of poly (butylene-terephthalate) (PBT) for clay load from 1.0% to 10.0% (by mass), and higher capability to accommodate clay than other polymers. The nonisothermal crystallization experiments indicate that the better thermal degradation behavior and crystallization rate of NPBT are 50% higher than PBT, and its injection mould processing temperature is lowered from 110℃ to 55℃. NPBT samples are characterized by several techniques. X-ray shows an original clay interlayer distance enlarged from 1.0 nm to 2.5 nm, while both TBM and AFM indicate an average size from 30nm to lOOnm of exfoliated clay layers, and 3%(by mass) of particle agglomeration being phase separated from PBT matrix, which are factors on some mechanical properties decrease of NPBT. The disappearance of spherulitic morphology in NPBT resulted from layers nucleation is detected. Improving NPBT properties by treating clay with long chain organic reagent and controlling the way to load it is suggested.

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al2O3 filler （Cr（a-Al2O3）/geopolymer composites） were fabricated, and the effects of heat treatment temperatures up to 1 200 ℃ on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature （25 ℃ ） to 1000 ℃. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000℃, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 ℃ as the hydration water of geopolymer matrix is lost. The addition of α-Al2O3 particle filler into the composites clearly increases the onset crystalline temperature of leucite （KAlSi2O6） from the amorphous geopolymer matrix. In addition, the addition of α-Al2O3 particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.

Microstructures and wear properties of graphite and Al_2O_3 reinforced AZ91D-Cex composites

The magnesium matrix composites reinforced by graphite particles and Al2O3 short fibers were fabricated by squeeze-infiltration technique.The additions dispersed uniformly and no agglomeration and casting defect were observed.The microstructures and wear properties of the composites with different Ce contents of 0,0.4%,0.8%and 1.0%,respectively,were investigated.Especially,the effect of Ce on the properties was discussed.The results reveal that Ce enriches around the boundaries of graphite particles and forms Al3Ce phase with Al.The addition of Ce refines the microstructures of the composites.With the increase of Ce content,the grain size becomes smaller and the wear resistance of the composite is improved.At low load,the composites have similar worn surface.At high load,the composite with 1.0%Ce has the best wear resistance due to the existence of Al3Ce phase.The Al3Ce phase improves the thermal stability of the matrix so the graphite particles can keep intact,which can still work as lubricant. At low load,the wear mechanism is abrasive wear and oxidation wear.At high load,the wear mechanism changes to delamination wear for all the composites.

Research on the Relationship between Molecular Activity of Additives and Lubricating Performance of Aluminum Rolling Oil

In this paper,an ab initio,local density functional(LDF)method was used to explore the relationship between the molecular properties of additives and the lubricating performance of aluminum rolling oil.The structural properties of butyl stearate,dodecanol,docosanol,and methyl dodecanoate were studied according to the density functional theory.The calculated data showed that the atoms in or around the functional groups might be likely the reacting sites.Because of the different functional groups and structure of ester and alcohol,two types of complex additives,dodecanol and butyl stearate,methyl dodecanoate and butyl stearate,respectively,were chosen for studying their tribological properties and performing aluminum cold rolling experiments.The test results agreed with the calculated results very well.The complex ester,viz.methyl dodecanoate and butyl stearate,had the best lubricating performance with a friction coefficient of 0.084 1 and a permissive-rolling thickness of 0.040 mm as compared with that of dodecanol-butyl stearate-base oil formulation.