Effect of the addition of YAG(Y3Al5O12) nanopowder on the mechanical properties of lanthanum zirconate

La2Zr2O7 (LZ) is a promising thermal barrier coating material for the high-temperature applications, which could be significantly toughened by the YAG nanopowder incorporated into the matrix. The composites of xYAG/(1-x)LZ (Y=10, 15, 20 vol. %, LZ-x-YAG) were densified by means of high-pressure sintering (HPS) under a pressure of 4.5 GPa at 1650 degrees C for 5 min, by which a high-relative density above 93% could be obtained. The morphologies of the fractured surfaces were investigated by the scanning electron microscope, and the fracture toughness and Vicker's-hardness of the composites were evaluated by the microindentation. The grain size of the LZ matrix drops significantly with the addition of YAG nanoparticles and the fracture type changes from the intergranular to a mixture type of the transgranular and intergranular in the nanocomposites. The LZ-20-YAG nanocomposite has a fracture toughness of 1.93 MPa m(1/2), which is obviously higher than that of the pure LZ (1.57 MPa m(1/2)), and the toughening mechanism is discussed in this paper.

Shape-gradient composite surfaces: Water droplets move uphill

The approach of water droplets self-running horizontally and uphill without any other forces was proposed by patterning the shape-gradient hydrophilic material (i.e., mica) to the hydrophobic matrix (i.e., wax or low-density polyethylene (LDPE)). The shape-gradient composite surface is the best one to drive water droplet self-running both at the high velocity and the maximal distance among four different geometrical mica/wax composite surfaces. The driving force for the water droplets self-running includes: (1) the great difference in wettability of surface materials, (2) the low contact angle hysteresis of surface materials, and (3) the space limitation of the shape-gradient transportation area. Furthermore, the average velocity and the maximal distance of the self-running were mainly determined by the gradient angle (alpha), the droplet volume, and the difference of the contact angle hysteresis. Theoretical analysis is in agreement with the experimental results.

Atomic force microscope investigation of large-circle DNA molecules

A circular bacterial artificial chromosome of 148.9 kbp on human chromosome 3 has been extended and fixed on bare mica substrates using a developed fluid capillary flow method in evaporating liquid drops. Extended circular DNA molecules were imaged with an atomic force microscope (AFM) under ambient conditions. The measured total lengths of the whole DNA molecules were in agreement with sequencing analysis data with an error range of +/-3.6%. This work is important groundwork for probing single nucleotide polymorphisms in the human genome, mapping genomic DNA, manipulating biomolecular nanotechnology, and studying the interaction of DNA-protein complexes investigated by AFM.

Electrochemiluminescence of the Ru(bpy)(3)(2+)/S(2)O(8)(2-)system in purely aqueous solution at carbon paste electrode

The electrochemiluminescence (ECL) of the Ru(bgy)(3)(2-)/S2O82- system in purely aqueous solution at a carbon paste electrode can be clearly seen with the naked eye for Ru(bpy)(3)(2+) concentrations higher than 1 mmol L-1. The log-log plot of the emmitted light intensity vs. Ru(bpy)(3)(2+) concentration is linear over the region 10(-3)-10(-7) mol L-1 with a correlation coefficient of 0.997. The ECL intensity increases linearly with the S2O82- concentration from 10(-6) mol L-1 up to 0.3 mmol L-1 and drops off sharply at concentrations higher than 1 mmol L-1. In addition, a weak ECL signal was obtained when the potential was biased more negative than -0.6 V even in the absence of S2O82-.

STUDIES ON THE PEROVSKITE-TYPE MIXED CATALYSTS OF TITANIUM SYSTEM FOR OXIDATIVE COUPLING OF METHANE - THE INFLUENCE OF CALCINATION TEMPERATURE

The correlations of the calcination temperature, structure and catalytic activity for the oxidative coupling of methane on the LiLa0.5Ti0.5O2+lambda catalysts whose main phase and major active phase is Perovskite-type ternary complex oxide LaTi1-yLiyO3-lambda have been studied. The surface and bulk structures of the catalysts were characterized by means of XRD, XPS, IR, BET and so on, The results cleary indicated that the effect of calcination temperature on the activity for the oxidative coupling of methane is twofold. On one hand, it is favorable for Li+ substitution for Ti3+ to enter into the lattice of LaTiO3 and produce more oxygen vacancies in which active oxygens are formed; however, excessively high calcination temperature make the amount of Li+ substitution for Ti3+ lower, due to a little change of structure or phases for the catalyst. On the other hand, the conversion of CH4 drops because of the decrease of surface area, when the calcination temperature is raised.

Responses of vegetative gametophytes of Undaria pinnatifida to high irradiance in the process of gametogenesis

The population of Undaria pinnatifida in its ecologic niche sustains itself in high temperature summer in the form of vegetative gametophytes, the haploid stage in its heteromorphic life cycle. Gametogenesis initiates when seawater temperature drops below the threshold levels in autumn in the northern hemisphere. Given that the temperature may fall into the appropriate range for gametogenesis, the level of irradiance determines the final destiny of a gametophytic cell, either undergoing vegetative cell division or initiating gametogenesis. In elucidating how vegetatively propagated gametophytes cope with changes of irradiance in gametogenesis, we carried out a series of culture experiments and found that a direct exposure to irradiance as high as 270 mu mol photons m(-2) s(-1) was lethal to dim-light (7-10 mu mol photons m(-2) s(-1)) adapted male and female gametophytes. This lethal effect was linearly corelated with the exposure time. However, dim-light adapted vegetative gametophytes were shown to be able tolerate as high as 420 mu mol photons m(-2) s(-1) if the irradiance was steadily increased from dim light levels (7-10 mu mol photons m(-2) s(-1)) to 90, 180 and finally 420 mu mol photons m(-2) s(-1), respectively, at a minimum of 1-3 h intervals. Percentage of female gametophytic cells that turned into oogonia and were eventually fertilized was significantly higher if cultured at higher but not lethal irradiances. Findings of this investigation help to understand the dynamic changes of population size of sporophytic plants under different light climates at different site-specific ecologic niches. It may help to establish specific technical details of manipulation of light during mass production of seedlings by use of vegetatively propagated gametophytes.

A Holocene paleotemperature record based on radiolaria from the northern Okinawa Trough (East China Sea)

Using a radiolarian-based transfer function, mean annual sea surface temperature (SST) and seasonal temperature range are reconstructed through the last 10,500yrs in the northern Okinawa Trough. Down-core SST estimates reveal that throughout the Holocene the changes of mean annual SST display a three-step trend: (i) an early Holocene continuous warming between 10,500 and 8500yr BP which ends up with a abrupt cooling at about 8200yr BP; (ii) a relatively stable middle Holocene with high SST that lasted until 3200yr BP; and (iii) a late-Holocene distinct SST decline between 3200 and 500yr BP. This pattern is in agreement with the ice core and terrestrial paleoclimatic records in the Chinese continent and other regions of the world. Five cooling events with abrupt mean annual SST drops, which occur at similar to 300-600, 1400, 3100, 4600-5100 and 8200yr BP, are recognized during the last 10,500yrs. Comparison of our results with records of GISP2 ice core and marine sediment in North Atlantic region suggests these cooling events are strongly coupled, which implies a possible significant climatic correlation between high- and low-latitude areas. (C) 2007 Elsevier Ltd and INQUA. All rights reserved.

高温实验中重金属钼在硅酸盐熔体中的含量研究

This dissertation discusses current status of high temperature and high pressure and focuses on analyzing systematically the solubility of heavy metals in the silicate magma in HTHP experiments. The high temperature study on the content of heavy metal molybdenum in the silicate melts in this dissertation, which is granted, based on the geology mineralization model and the theory of HTHP experiments and combined with mineralization grade and geochemical nature of Mo, discusses the difference of mineralization between mantle plume and aqueous fluids and comes to the conclusions, which are as follows: (1) The content of Mo in the silicate melts is much greater than Mo mineralization grade. The molybdenum ore has the exploitation value when the industrial grade is higher than 0.06%. Mo content in different silicate melts varies because of the concentration of SiO2, that is, Mo content in the granodiorite is greater. (2) The content of Mo, which varies with reaction time, arises first and drops down in the alkali basalt melts, while variation is not too obvious in the granodiorite melts on the whole. (3) According to the picture of sample, the conclusion is not reached very well on some issues, such as the volatility and characteristic of molybdenum oxide and dependence on the geology environment.

渤海湾地区末次冰期古环境

The loess-paleosol sequence in China is one of the best archives for studying paleoenvironmental and paleoclimatic processes. The loess deposits in the coast of the Bohai Sea are suitable for the study of aridification in the northern China during glacial periods (fig.2-1). In this paper, stratigraphy was correlated by using magnetic susceptibility, grain size, and thermoluminence (TL) and accelerater mass spectrometer (AMS) ~(14)C ages. Based on the loess records, an interpretation has been made for paleoenvironmental changes on the coast of the Bohai Sea during the last glacials. The results of magnetic susceptibility, grain size, biostratigraphy, TL and ~(14)C dating, suggest that the loess-paleosol sequence in the coast of the Bohai Sea is discontinuous. The loess deposits correlated with the marine δ~(18)O stage 2 are usually absent in some profiles. Also, the thickness of the loess deposits in the same period varied significantly in different sections. In the coast of the Bohai Sea, the higher magnetic susceptibility corresponds to the finer grain size, consistent with the results of the Loess Plateau. It is indicated that the changes in magnetic susceptibility and grain size may record the paleoclimatic fluctuations of the last glacial. Although the loess deposits during the last glacial have been slightly altered by slope runoff, they have still remained main characters as the representative loess deposits of the Loess Plateau. During the last glacial, the less accumulation rate in the coast of the Bohai Sea is similar to that of the desert-loess transition zone in the northwestern Loess Plateau, and the all section contain high concentrations of sand (>60μm), indicate that the aridification in the Bohai Sea occurred during the glacial. But the changes in sand content of loess deposits along a north-south transect of the Bohai Sea and the changes of magnetic susceptibility implicate that desertification might not occur in the shelf of the Bohai Sea during the last glacial. The frequent fluctuations of summer monsoon during the marine δ~(18)O stage 4 are demonstrated by magnetic susceptibility, frequency-dependent susceptibility and the abundance of foraminifera. 46 genera, 71 species of foraminifera were identified from 138 loess samples. Almost all of the foraminifera are present in the last glacial loess, but the distribution patterns of foraminifera show significant temporal changes. The results of magnetic susceptibility, grain size and XRD indicate that not only sea-level changes had influences on foraminifera abundance, but also variations in sediment flux by rivers when sea-level drops might control the abundance of foraminifera. In addition, the diversity and exquitability of the foraminifera suggest that the frequent fluctuations of foraminifera fossil abundance during the marine δ~(18)O stages could be partly attributed to leaching. In summary, the changes in foraminifera of abundance related to the paleoclimatic variations, and the aridification extends to the coast of the eastern China during the last glacial.

利用重力与地形数据探讨我国大陆若干地区岩石圈有效弹性厚度

The lithosphere behaves as an elastic thin plate overlying a weak fluid. When loaded by topography, it deflects to compensate the topography and isostasy is achieved. The response of the plate is often characterized by the flexural rigidity, or equivalently, by the effective elastic thickness(EET). The relationships between gravity and topography have commonly been employed to investigate quantitively the isostatic compensation of the lithosphere. Cross-spectral techniques have been developed to estimate the admittance and coherence between gravity and topography. The observed admittance and coherence functions, when compared with theoretical admittance and coherence computed for various models and parameters, can provide an estimate of the effective elastic thickness. As for coherence, the wavelength at which the coherence drops from approaching unity at long wavelengths to value approaching zero at short wavelengths is a measure of the rigidity of the lithosphere. This research takes advantage of the high-resolution gravity and topography data in Erdos. Using the coherence technique, we have estimated the effective elastic thickness of this region. Subsurface loads are also considered in our calculation. When the admittance between topography and gravity is obtained, we can filter the topography to give an estimate of gravity anomaly. This would be very important when the gravity data is scarce. Several other regions of China have been selected to investigate the effective elastic thickness of lithosphere. We compare those result with lithosphere thickness obtained through seismological technique and heat flow of the region. We find the effective elastic thickness is always smaller than the seismogenic thickness. This is due to what the effective elastic thickness reflects is only the up elastic part of the lithosphere. And we also find there is some degree of correlation between effective elastic thickness and heat flow. This suggests EET is probably controlled by the thermal state of the lithosphere and correlates with their tectonic age. Thus the estimations of the effective elastic thickness of lithosphere can help to investigate geophysical features of active tectonics of continental lithosphere.

Heterogeneous asymmetric hydrogenation of ethyl pyruvate on chirally modified Pt/Al2O3 catalyst with fixed-bed reactor

The enantioselective hydrogenation of ethyl pyruvate on the cinchonidine modified Pt/Al2O3 catalyst was investigated using a high-pressure reaction system with a fixed-bed reactor for the purpose to produce the,chiral product without separating the catalyst from the reaction system. The reaction was also investigated in a batch reactor for comparison. About 60% e. e. and 90% e. e. were obtained with the fixed-bed reactor and the batch reactor respectively, demonstrating the possibility for the heterogeneous asymmetric hydrogenation in the fixed-bed reactor. Some adsorbed chiral modifier, cinchonidine, can be slowly removed from the surface of Pt/Al2O3 under the continuous flow reaction, as a result, the e, e, values drops with the reaction time in the fixed-bed reactor. The enantio-selectivity is higher in the fixed-bed reactor, but lower in the batch reactor when ethanol was used as solvent than that when acetic acid as solvent. CO was used as molecular probe to characterize the adsorption of cinchonidine an the catalyst surface by IR spectroscopy, A red shift observed in IR spectra of coadsorbed CO with cinchonidine suggests that the cinchonidine adsorption is mainly through the pi -interaction with platinum surface and donating electron to the platinum surface.

Electrochemical performance of mixed ionic-electronic conducting oxides as anodes for solid oxide fuel cell

Mixed ionic-electronic conducting (MIEC) oxides, SrFeCo0.5Ox, SrCo0.8Fe0.2O3-delta and La0.6Sr0.4Fe0.8Co0.2O3-delta have been synthesized and prepared on yttria-stabilized zirconia as anodes for solid oxide fuel cells. Power output measurements show that the anodes composed of such kinds of oxides exhibit modest electrochemical activities to both H-2 and CH4 fuels, giving maximum power densities of around 0.1 W/cm(2) at 950 degrees C. Polarization and AC impedance measurements found that large activation overpotentials and ohmic resistance drops were the main causes for the relative inferior performance to the Ni-YSZ anode. While interlayered with an Ni-YSZ anode, a significant improvement in the electrochemical performance was observed. in particular, for the SrFeCo0.5Ox oxide interlayered Ni-YSZ anode, the maximum power output reaches 0.25 W/cm2 on CH,, exceeding those of both SrFeCo0.5Ox and the Ni-YSZ, as anodes alone. A synergetic effect of SrFeCo0.5Ox and the Ni-YSZ has been observed. Future work is needed to examine the long-term stability of MIEC oxide electrodes under a very reducing environment. (C) 1999 Elsevier Science B.V. All rights reserved.

影响汉语阅读能力发展的相关认知因素及其作用的发展变化

The present cross-sectional study paid attention to Chinese reading acquisition of 391 children from preschool to grade 3 in two elementary schools, and investigated the relationship between orthographic processing skills, morphological awareness, phonological awareness, naming, phonological memory, visual processing skill and reading skills, after controlling the variance of age, nonverbal intelligence and pinyin knowledge. The main results are as follows: Firstly, there are many different language skills as the predictors of Chinese reading success. Orthographic processing skills, morphological awareness, phonological awareness and naming are important in single-character recognition and comprehension. Beside them, the effect of visual processing skill and phonological memory for comprehension are also significant. Among them, the role of orthographic processing skills is the most important, whatever in single-character recognition or in comprehension. Secondly, orthographic processing skills are the most important factors in reading acquisition at low grade and its effect drops obviously after grade 2. Thirdly, morphological awareness is also the factor that cannot be ignored whatever for single-character recognition or for comprehension. Its influence appears in preschool and becomes the only significant predictor of character recognition in grade 3. Furthermore, morphological awareness is more relevant with the development of comprehension. Fourthly, phonological awareness plays the secondary role in Chinese reading acquisition except in grade 2 when its contribution is most of all. And compare with morphological awareness, the effect of phonological awareness is relative low. Fifthly, naming is important through preschool to grade 2. The contribution of phonological memory increases from preschool to grade 3 in comprehension.

Summer Sprite for Orchestra

Summer Sprite for Orchestra was completed in December, 2004. The piece originated from a singular encounter with little angels at Chang-Kyung Palace, which is the oldest and the most beautiful palace in Korea, and where the kings of the Chosun Dynasty (1393-1897) lived. This encounter was in the summer of 2002. I certainly could not prove that those angels I met were real. Possibly they were the reflection of drops of water after a sudden shower on that summer day. However, I definitely remember that short, unforgettable, and mysterious moment and the angels' beautiful dance-like celebration. Summer Sprite is based on these special memories and the encounter with the little angels that summer. Summer Sprite consists of 3 movements: "Greeting," "Encounter," and "Celebration." These follow the course of my encounter with the little angels. In Summer Sprite, I wished to describe the image of the angels as well as the progression of greeting, encounter, and celebration with them. The moods that follow in Summer Sprite are by turns lyrical, poetic, fantastic, mysterious, and dream-like. In each movement, I describe the meeting of angels and composer through the use of the soloists -- violin (sometimes viola) and cello. As suggested by the subtitle of the first movement, "Greeting" portrays the moment when a surprised I met the angels. It begins with tam-tam, marimba, harp, and piano and sets a mysterious and dark mood. The second movement, "Encounter," is shorter than the first movement. This movement provides a more tranquil mood as well as more unique timbres resulting from the use of mutes and special instruments (English horn, harp, crotales, suspended cymbal, and celesta). The delicate expression of the percussion is particularly important in establishing the static mood of this movement . The last movement, °?Celebration,°± is bright and energetic. It is also the longest. Here, I require the most delicate changes of dynamics and tempo, the most vigorous harmonies, and the fastest rhythmic figures, as well as the most independent, lyrical, and poetic melodies. For bright orchestral tone color, I used various kinds of percussion such as timpani, xylophone, marimba, vibraphone, cymbals, side drum, tambourine, triangle, and bass drum. This last movement is divided rondo-like into five sections: The first (mm.1-3), second (mm.4 - rehearsal number 1), third (rehearsal numbers 2-4), fourth (rehearsal numbers 5-7), and fifth, (rehearsal numbers 8 -18). To sum up, Summer Sprite describes an unforgettable and mysterious moment in a my life. My intention was to portray this through a concerto-like framework. A model for this would be Brahms°Ø °?Double Concerto°± in A minor, op.102, in which the solo cello stands for my angel and the solo violin (sometimes solo viola) for me.

Design Optimization and Security For Communication Networks

In this work we introduce a new mathematical tool for optimization of routes, topology design, and energy efficiency in wireless sensor networks. We introduce a vector field formulation that models communication in the network, and routing is performed in the direction of this vector field at every location of the network. The magnitude of the vector field at every location represents the density of amount of data that is being transited through that location. We define the total communication cost in the network as the integral of a quadratic form of the vector field over the network area. With the above formulation, we introduce a mathematical machinery based on partial differential equations very similar to the Maxwell's equations in electrostatic theory. We show that in order to minimize the cost, the routes should be found based on the solution of these partial differential equations. In our formulation, the sensors are sources of information, and they are similar to the positive charges in electrostatics, the destinations are sinks of information and they are similar to negative charges, and the network is similar to a non-homogeneous dielectric media with variable dielectric constant (or permittivity coefficient). In one of the applications of our mathematical model based on the vector fields, we offer a scheme for energy efficient routing. Our routing scheme is based on changing the permittivity coefficient to a higher value in the places of the network where nodes have high residual energy, and setting it to a low value in the places of the network where the nodes do not have much energy left. Our simulations show that our method gives a significant increase in the network life compared to the shortest path and weighted shortest path schemes. Our initial focus is on the case where there is only one destination in the network, and later we extend our approach to the case where there are multiple destinations in the network. In the case of having multiple destinations, we need to partition the network into several areas known as regions of attraction of the destinations. Each destination is responsible for collecting all messages being generated in its region of attraction. The complexity of the optimization problem in this case is how to define regions of attraction for the destinations and how much communication load to assign to each destination to optimize the performance of the network. We use our vector field model to solve the optimization problem for this case. We define a vector field, which is conservative, and hence it can be written as the gradient of a scalar field (also known as a potential field). Then we show that in the optimal assignment of the communication load of the network to the destinations, the value of that potential field should be equal at the locations of all the destinations. Another application of our vector field model is to find the optimal locations of the destinations in the network. We show that the vector field gives the gradient of the cost function with respect to the locations of the destinations. Based on this fact, we suggest an algorithm to be applied during the design phase of a network to relocate the destinations for reducing the communication cost function. The performance of our proposed schemes is confirmed by several examples and simulation experiments. In another part of this work we focus on the notions of responsiveness and conformance of TCP traffic in communication networks. We introduce the notion of responsiveness for TCP aggregates and define it as the degree to which a TCP aggregate reduces its sending rate to the network as a response to packet drops. We define metrics that describe the responsiveness of TCP aggregates, and suggest two methods for determining the values of these quantities. The first method is based on a test in which we drop a few packets from the aggregate intentionally and measure the resulting rate decrease of that aggregate. This kind of test is not robust to multiple simultaneous tests performed at different routers. We make the test robust to multiple simultaneous tests by using ideas from the CDMA approach to multiple access channels in communication theory. Based on this approach, we introduce tests of responsiveness for aggregates, and call it CDMA based Aggregate Perturbation Method (CAPM). We use CAPM to perform congestion control. A distinguishing feature of our congestion control scheme is that it maintains a degree of fairness among different aggregates. In the next step we modify CAPM to offer methods for estimating the proportion of an aggregate of TCP traffic that does not conform to protocol specifications, and hence may belong to a DDoS attack. Our methods work by intentionally perturbing the aggregate by dropping a very small number of packets from it and observing the response of the aggregate. We offer two methods for conformance testing. In the first method, we apply the perturbation tests to SYN packets being sent at the start of the TCP 3-way handshake, and we use the fact that the rate of ACK packets being exchanged in the handshake should follow the rate of perturbations. In the second method, we apply the perturbation tests to the TCP data packets and use the fact that the rate of retransmitted data packets should follow the rate of perturbations. In both methods, we use signature based perturbations, which means packet drops are performed with a rate given by a function of time. We use analogy of our problem with multiple access communication to find signatures. Specifically, we assign orthogonal CDMA based signatures to different routers in a distributed implementation of our methods. As a result of orthogonality, the performance does not degrade because of cross interference made by simultaneously testing routers. We have shown efficacy of our methods through mathematical analysis and extensive simulation experiments.