Preparation and promising optoelectronic applications of lead halide perovskite patterned structures:A review

Lead halide perovskites have received considerable attention from researchers over the past several years due to their superior optical and optoelectronic properties,because of which they can be a versatile platform for fundamental science research and applications.Patterned structures based on lead halide perovskites have much more novel properties compared with their more commonly seen bulk-,micro-,and nano-crystals,such as improvement in antireflection,light-scattering effects,and light absorption,as a result of their adjustability of spatial distributions.However,there are many challenges yet to be resolved in this field,such as insufficient patterned resolution,imperfect crystal quality,complicated preparation process,and so on.To pave the way to solve these problems,we provide a systematic presentation of current methods for fabricating lead halide perovskite patterned structures,including thermal imprint,use of etching films,two-step vapor-phase growth,template-confined solution growth,and seed-assisted growth.Furthermore,the advantages and disadvantages of these methods are elaborated in detail.In addition,thanks to the extraordinary properties of lead halide perovskite patterned structures,a variety of potential applications in optics and optoelectronics of these structures are described.Lastly,we put forward existing challenges and prospects in this exciting field.

Disc-Electrospun PCL Nanofiber Formed Micro-patterned Structure Scaffold

Disc-electrospinning using a disc as spinneret and a rotary drum as collector is a novel technology to prepare nanofiber which has been applied in tissue engineering scaffolds.In this study,nanofibrous mats with micro-patterned structure were fabricated via disc-electrospinning.Poly( #-caprolactone)( PCL) was dissolved in trifluoroethanol( TFE) at various concentrations( 2%-7%)( w / v)for electrospinning and the applied voltage ranged from 40 to 70 kV.Scanning electron microscopy( SEM) was employed to observe the morphology of the nanofibrous scaffolds.SEM images illustrated that the nanofibers with beads formed micro-patterned structure such as triangles and other polygons.The average diameter of nanofibers presented various size with the concentration increased from 2% to 7%.The beads on the nanofibers constructed the vertexes of the polygons,while nanofibers bridged between adjacent vertexes.The concentration of solution and applied voltage may be two dominant factors to influence the topological structure of the nanofibrous scaffolds.Cells cultured on the micro-patterned scaffold spread along the edges of the polygons.The scaffold with patterned structure may have a promising application in tissue engineering.

SIMULATION OF ELECTRICAL FIELD FOR THE FORMATION MECHANISM OF BIRD'S NEST PATTERNED STRUCTURES BY ELECTROSPINNING

In our previous work, it was found that large electrospun from chlorinated polypropylene solution doped Bird＇s Nest patterned nanofibrous membranes can be simply with an ionic liquid, and a plausible formation mechanism of Bird＇s Nest patterned architectures was proposed. Here, we use Ansoft Maxwell version 12 software （3D, electrostatic solver） to simulate the electrical field distribution of the electrospinning setup, and to clarify the rationality of proposed formation mechanism. Calculation results clearly show that the introduction of charged nanofibrous bundles would produce a similar patterned electrical field distribution, which definitely confirms the important role of surface residual charges. The proposed mechanism can be well extended to other polymer systems including polystyrene, poly（acrylonitrile-co-acrylic acid） and chitosan/poly（ethylene oxide）.

The ICM method with objective function transformed by variable discrete condition for continuum structure

ICM （Independent Continuous Mapping） method can solve topological optimization problems with the minimized weight as the objective and subjected to displacement constraints. To get a clearer topological configuration, by introducing the discrete condition of topological variables and integrating with the original objective, an optimal model with multi-objectives is formulated to make the topological variables approach 0 or 1 as near as possible, and the model reduces the effect of deleting rate on the result. The image-filtering method is employed to eliminate the checkerboard patterns and mesh dependence that occurred in the topology optimization of a continuum structure. The computational efficiency is enhanced through selecting quasi-active displacement constraints and a design region. Numerical examples indicate that this algorithm is robust and practicable, though the number of iterations is slightly increased with respect to the original algorithm.

Structure and regeneration dynamics of three forest types at different succession stages of spruce – fir mixed forest in Changbai Mountain, northeastern China

Analyzing and understanding the structure and growth dynamics of forests at different stages is helpful to promote forest succession, restoration and management. Three spots representing three succession stages of spruce-fir mixed forest(SF: polar-birch secondary forest, MF: spruce-fir mixed forest and PF: spruce-fir near primary forest) were established. Structure, growth dynamics during two growth seasons for dominant tree species, regeneration were examined, and a univariate O-ring function statistic was used to analyze the spatial patterns of main regeneration tree species. Results showed that,(1) composition of tree species, periodic annual increment(PAI) of the diameter at breast height(DBH), basal area for overstory trees and of ground diameter(DGH) for saplings, were significantly different with the succession;(2) the current species composition and regeneration dynamics of SF suggested a development towards spruce-fir mixed forests. Pioneer species like Betula platyphyllaa will gradually disappear while climax species, such as Abies nephrolepis, Pinus koraiensis, Picea koraiensis and Tilia amurensis will dominate forest stands;(3) Despite the highest volume occurring in PF, and saplings in it grew better than in the others, this forest type is unstable because of its unsustainable structure of DBH class and insufficient regeneration; and(4) MF had the most reasonable distribution of DBH class for adult trees(DBH > 5.0 cm) and DGH class for saplings(H ≥30 cm and DBH ≤5 cm), as well as an optimal volume increment. Limiting canopy opening size can lessen the physiological stress and promote the growth and competitive status of regeneration. Management implications for increasing the gaps and thus creating better growth conditions for understory saplings and facilitating forest succession were discussed.

The community structure and seasonal dynamics of plankton in Bange Lake, northern Tibet, China

The seasonal variations in biomass, abundance, and species composition of plankton in relation to hydrography were studied in the saline Bange Lake, northern Tibet, China. Sampling was carried out between one to three times per month from May 2001 to July 2002. Salinity ranged from 14 to 146. The air and water temperature exhibited a clear seasonal pattern, and mean annual temperatures were approximately 4.8℃ and 7.3℃, respectively. The lowest water temperature occurred in winter from December to March at-2℃ and the highest in June and July at 17.7℃. Forty-one phytoplankton taxa, 21 zooplankton, and 5 benthic or facultative zooplankton were identifi ed. The predominant phytoplankton species were Gloeothece linearis, Oscillatoria tenuis, Gloeocapsa punctata, Ctenocladus circinnatus, Dunaliella salina, and Spirulina major. The predominant zooplankton species included H olophrya actra, Brachionus plicatilis, Daphniopsis tibetana, Cletocamptus dertersi, and A rctodiaptomus salinus. The mean annual total phytoplankton density and biomass for the entire lake were 4.52×10^7 cells/L and 1.60 mg/L, respectively. The annual mean zooplankton abundance was 52, 162, 322, and 57, 144 ind./L, in the three sublakes. The annual mean total zooplankton biomass in Lakes 1–3 was 1.23, 9.98, and 2.13 mg/L, respectively. The annual mean tychoplankton abundances in Bg1, 2, and 3 were 47, 67, and 654 ind./L. The annual mean tychoplankton biomass was 2.36, 0.16, and 2.03 mg/L, respectively. The zooplankton biomass（including tychoplankton） in the lake was 9.11 mg/L. The total number of plankton species in the salt lake was signifi cantly negatively correlated with salinity.

Pattern Structure of Deterministic Displacement in Random Porous Media with Dispersion Effect

A new model — model of random porous media degradation via several fluid displacing, freezing, and thawing cycles is introduced and investigated in this paper. The fluid transport is based on the deterministic method with dispersion effect. The result shows that the topology and the geometry of the porous media have a strong effect on displacement processes. The cluster size of viscous fingering (VF) pattern in percolation cluster increases with the increase of iteration parameter n. When iteration parameter , VF pattern does not change with n. We find that the displacement fluid forms trapping regions in random porous media with dispersion effect. And the trapping regions will expand with the increasing of the iteration parameter n. When r (throat size) and , the peak value of the distribution increases as n increases, where is the normalized distribution of throat sizes after different displacement-damages but before freezing. The peak value of the distribution reaches a maximum when and , where is the normalized distribution of the size of invaded throat. This result is different from invasion percolation. It is found that the sweep efficiency E increases along with the increasing of iteration parameter n and decreases with the network size L, and E has a minimum as L increases to the maximum size of lattice. The VF pattern in percolation cluster has one frozen zone and one active zone.

TOPOLOGY AND VORTEX STRUCTURES OF A CURVING TURBINE CASCADE WITH TIP CLEARANCE (Ⅱ)- TOPOLOGICAL FLOW PATTERN AND VORTEX STRUCTURE IN THE TRANSVERSE SECTION OF A BLADE CASCADE

By means of ink trace visualization of the flows in conventional straight, positively curved and negatively curved cascades with tip clearance, and measurement of the aerodynamic parameters in transverse section, and by appling topology theory, the topological structures and vortex structure in the transverse section of a blade cascade were analyzed. Compared with conventional straight cascade, blade positive curving eliminates the separation line of the upper passage vortex, and leads the secondary vortex to change from close separation to open separation, while blade negative curving effects merely the positions of singular points and the intensities and scales of vortex.

Vertical structure and dominating factors of sand body during Late Triassic Chang 9 time of Yanchang Formation in Ordos Basin, NW China

Based on a synthetic geological study of drilling, well logging and core observations, two main genetic types of Chang 9sand body in Odors Basin were recognized, which included two effects, that is, delta environment and tractive current effects that lead to the development of mouth bar, distal bar, sheet sand and other sand bodies of subaerial and subaqueous distributary channel,natural levee, flood fan and delta front, and shore-shallow lake environment and lake flow transformation effects that result in the development of sandy beach bar, sheet sand and other sand bodies. Chang 9 sand body mainly developed five basic vertical structures, namely box shape, campaniform, infundibuliform, finger and dentoid. The vertical stacking patterns of multilayer sand body was complex, and the common shapes included box shape + box shape, campaniform + campaniform, campaniform + box shape, infundibuliform + infundibuliform, campaniform + infundibuliform, box shape + campaniform, box shape + infundibuliform,and finger + finger. Based on the analysis on major dominating factors of vertical structure of sand body, sedimentary environment,sedimentary facies and rise, fall and cycle of base level are identified as the major geological factors that control the vertical structure of single sand body as well as vertical stacking patterns and distribution of multistory sand bodies.

Structural patterns of land types and optimal allocation of land use in Qinling Mountains

The case study based on Qinling Mountains in Shaanxi Province of China, in virtue of the information from TM image, classifies the land types and analyzes their spatial and temporal differential law, and puts forward three structural patterns of land types in mountainous areas, namely, spatial, quantitative and qualitative structures of mountainous land types. Furthermore, it has been noticed that the analysis of structural patterns can disclose the heterogeneity and orderliness of combination of land types, which can lay the theoretic foundation for comprehensively recognizing ecological characteristics and succession law of structure and function of land types. After the all-around comparative analysis, an optimal allocation of land use in Qinling Mountains has been put forward according to the principle of sustainable development and landscape ecology, which can lay the scientific foundation in practice for the structural adjustment and distribution optimization from the macro level to micro level.

Pattern formation induced by cross-diffusion in a predator-prey system

This paper considers the Holling-Tanner model for predator-prey with self and cross-diffusion. From the Turing theory, it is believed that there is no Turing pattern formation for the equal self-diffusion coefficients. However, combined with cross-diffusion, it shows that the system will exhibit spotted pattern by both mathematical analysis and numerical simulations. Furthermore, asynchrony of the predator and the prey in the space. The obtained results show that cross-diffusion plays an important role on the pattern formation of the predator-prey system.

A local and global statistics pattern analysis method and its application to process fault identification

Traditional principal component analysis （PCA） is a second-order method and lacks the ability to provide higherorder representations for data variables. Recently, a statistics pattern analysis （SPA） framework has been incorporated into PCA model to make full use of various statistics of data variables effectively. However, these methods omit the local information, which is also important for process monitoring and fault diagnosis. In this paper, a local and global statistics pattern analysis （LGSPA） method, which integrates SPA framework and locality pre- serving projections within the PCK is proposed to utilize various statistics and preserve both local and global in- formation in the observed data. For the purpose of fault detection, two monitoring indices are constructed based on the LGSPA model. In order to identify fault variables, an improved reconstruction based contribution （IRBC） plot based on LGSPA model is proposed to locate fault variables. The RBC of various statistics of original process variables to the monitoring indices is calculated with the proposed RBC method. Based on the calculated RBC of process variables＇ statistics, a new contribution of process variables is built to locate fault variables. The simula- tion results on a simple six-variable system and a continuous stirred tank reactor system demonstrate that the proposed fault diagnosis method can effectively detect fault and distinguish the fault variables from normal variables.

Characteristics of Spatial Structural Patterns and Temporal Variability of Annual Precipitation in Ningxia

[Objective] The aim was to study the characteristics of the spatial structural patterns and temporal variability of annual precipitation in Ningxia.[Method] Using rotated empirical orthogonal function,the precipitation concentration index,wavelet analysis and Mann-Kendall rank statistic method,the characteristics of precipitation on the spatial-temporal variability and trend were analyzed by the monthly precipitation series in Ningxia during 1951-2008.[Result] In Ningxia,the spatial structural patterns of annual precipitation appeared 'North-south type' and 'North-center-south type'.It increased from north to south,the changes of interannual precipitation decreased from north to south.Precipitation changed significantly in month and distributed differently in the Yellow River irrigation area.But it was conversely steady in central arid zone and mountainous area of southern Ningxia.The probability of single abundant precipitation year was higher than single short precipitation year and the continuous short precipitation year was higher than continuous abundant precipitation year.The main cycles were 3a,6a and 10a approximately.In the mid arid zone and the mountainous area of southern Ningxia,the probability of precipitation reduction was about 75% and the Yellow river irrigation area,71.4%,respectively.The reduction in the entire area was about 73.3%.The annual precipitation in the middle arid area and irrigation area was increasing.The variability would change slowly for the intra-annual distribution of precipitation.Especially,the reduction tendency rate in the middle arid area reached 100.0%.[Conclusion] The study provided references for the effective utilization of the local precipitation,and the coordinated development of the regional social economy and ecological environment.

Modeling of Heat Transfer and Steam Condensation Inside a Horizontal Flattened Tube

This work investigates the steam condensation phenomena in an air-cooled condenser.The considered horizontal flattened tube has a 30 mm hydraulic diameter,and its length is a function of the steam quality with a limit value between 0.95 and 0.05.The mass flow rate ranges from 4 to 40 kg/m^(2).s with a saturated temperature spanning an interval from 40°C to 80°C.A special approach has been implemented using the Engineering Equation Solver(EES)to solve a series of equations for the two-phase flow pattern and the related heat transfer coefficients.A wavy-stratified structure of the two-phase flow has been found when the mass rate was between 4 and 24 kg/m^(2).s.In contrast,an initially annular flow is gradually converted into a wavy stratified flow(due to the condensation process taking place inside the flattened tube)when the considered range ranges from 32 to 40 kg/m^(2).s.

Influence of structural depth of laser-patterned steel surfaces on the solid lubricity of carbon nanoparticle coatings

Carbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern's recessions act as lubricant-retaining reservoirs.This study investigates the influence of the structural depth of line patterns coated with multi-walled carbon nanotubes(CNTs)and carbon onions(COs)on their respective potential to reduce friction and wear.Direct laser interference patterning(DLIP)with a pulse duration of 12 ps is used to create line patterns with three different structural depths at a periodicity of 3.5μm on AISI 304 steel platelets.Subsequently,electrophoretic deposition(EPD)is applied to form homogeneous carbon nanoparticle coatings on the patterned platelets.Tribological ball-on-disc experiments are conducted on the as-described surfaces with an alumina counter body at a load of 100 mN.The results show that the shallower the coated structure,the lower its coefficient of friction(COF),regardless of the particle type.Thereby,with a minimum of just below 0.20,CNTs reach lower COF values than COs over most of the testing period.The resulting wear tracks are characterized by scanning electron microscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy.During friction testing,the CNTs remain in contact,and the immediate proximity,whereas the CO coating is largely removed.Regardless of structural depth,no oxidation occurs on CNT-coated surfaces,whereas minor oxidation is detected on CO-coated wear tracks.

From Sequential Pattern Mining to Structured Pattern Mining： A Pattern-Growth Approach

Sequential pattern mining is an important data mining problem with broadapplications. However, it is also a challenging problem since the mining may have to generate orexamine a combinatorially explosive number of intermediate subsequences. Recent studies havedeveloped two major classes of sequential pattern mining methods: (1) a candidategeneration-and-test approach, represented by (ⅰ) GSP, a horizontal format-based sequential patternmining method, and (ⅱ) SPADE, a vertical format-based method; and (2) a pattern-growth method,represented by PrefixSpan and its further extensions, such as gSpan for mining structured patterns.In this study, we perform a systematic introduction and presentation of the pattern-growthmethodology and study its principles and extensions. We first introduce two interestingpattern-growth algorithms, FreeSpan and PrefixSpan, for efficient sequential pattern mining. Then weintroduce gSpan for mining structured patterns using the same methodology. Their relativeperformance in large databases is presented and analyzed. Several extensions of these methods arealso discussed in the paper, including mining multi-level, multi-dimensional patterns and miningconstraint-based patterns.

Laser direct writing pattern structures on AgInSbTe phase change thin film

Different pattern structures are obtained on the AglnSbTe （AIST） phase change film as induced by laser beam. Atomic force microscopy （AFM） was used to observe and analyze the different pattern structures. The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects, such as crystallization threshold, microbump threshold, melting threshold, and ablation threshold. The analysis indicates that the AIST material is very effective in the fabrication of pattern structures and can offer relevant guidance for application of the material in the future.

EFFECT OF LOCAL BASIC FLOW STRUCTURE PATTERN IN FORMATION OF BLOCKING HIGHS

The effect of local basic flow structure pattern(BFSP)on a blocking high formation is investigated within the framework of forced dissipation KDV dynamics.The zonal and meridional positions of the high's center excited by a heat source depend on the BFSP selected.

Structure prediction for error pattern and extension of Welch-Berlekamp theorem

As the Welch-Berlekamp (W-B) theorem accurately predicts structure of error locator polynomials of the error patterns, it results in the Welch-Berlekamp algorithm of decoding cyclic codes. However, it is only valid within the BCH bound. Now, a prediction formula for error locator determination is presented based on the study of theory of minimal homogeneous interpolation problem, which extends the Welch-Berlekamp theorem and expands the Welch-Berlekamp algorithm so that the constraint from the BCH

Chinese Semantic Parsing Based on Feature Structure with Recursive Directed Graph

It is difficult to analyze semantic relations automatically, especially the semantic relations of Chinese special sentence patterns. In this paper, we apply a novel model feature structure to represent Chinese semantic relations, which is formalized as ＂recursive directed graph＂. We focus on Chinese special sentence patterns, including the complex noun phrase, verb-complement structure, pivotal sentences, serial verb sentence and subject-predicate predicate sentence. Feature structure facilitates a richer Chinese semantic information extraction when compared with dependency structure. The results show that using recursive directed graph is more suitable for extracting Chinese complex semantic relations.