The Effect of Nb and S Segregation on the Solidification Cracking of Alloy 52M Weld Overlay on CF8 Stainless Steel

The weld overlay of Alloy 52M (a nickel-based filler metal) on a cast 304 (CF8) stainless steel (SS) was made to simulate overlay welding of the safe end of reactor pressure vessels in nuclear power plants. The deteriorated effect of sulfur on solidification cracking of the Alloy 52M overlay was highlighted by using a CF8 substrate with 0.14 wt.% S. Severe solidification cracking was observed when Alloy 52M was directly overlaid on the CF8 substrate. To lower the cracking susceptibility, ER 308L was deposited on the CF8 SS as a buffer layer before the subsequent deposition of Alloy 52M. Under such circumstances, the region near the weld interface between the SS buffer layer and Alloy 52M overlay was susceptible to solidification cracking. The formation of γ-NbC(N), γ-Laves, and γ-(Fe-Ni-S) eutectic-type constituents at the solidification boundaries was responsible for cracking near the weld interface. Nevertheless, depositing two layers of 308L prior to applying Alloy 52M could effectively reduce the cracking susceptibility of the overlay.     

Peptide coated quantum dots for biological applications

Quantum dots (QDOTs) have been widely recognized by the scientific community and the biotechnology industry, as witnessed by the exponential growth of this field in the past several years. We describe the synthesis and characterization of visible and near infrared QDots-a critical step for engineering organic molecules like proteins and peptides for building nanocomposite materials with multifunctional properties suitable for biological applications     

A Structural‐Factor Approach to Modeling High‐Dimensional Time Series and Space‐Time Data

This article considers a structural‐factor approach to modeling high‐dimensional time series and space‐time data by decomposing individual series into trend, seasonal, and irregular components. For ease in analyzing many time series, we employ a time polynomial for the trend, a linear combination of trigonometric series for the seasonal component, and a new factor model for the irregular components. The new factor model simplifies the modeling process and achieves parsimony in parameterization. We propose a Bayesian information criterion to consistently select the order of the polynomial trend and the number of trigonometric functions, and use a test statistic to determine the number of common factors. The convergence rates for the estimators of the trend and seasonal components and the limiting distribution of the test statistic are established under the setting that the number of time series tends to infinity with the sample size, but at a slower rate. We study the finite‐sample performance of the proposed analysis via simulation, and analyze two real examples. The first example considers modeling weekly PM_2.5 data of 15 monitoring stations in the southern region of Taiwan and the second example consists of monthly value‐weighted returns of 12 industrial portfolios.     

NON-LINEAR TIME SERIES ANALYSIS OF BLOWFLY POPULATION

Abstract. In recent years there has been a growing interest in studying non-linear time series and various non-linear models have been proposed in the literature. In this paper, I consider non-linear time series modelling via a case study. Several important issues concerning non-linear time series models and data analysis emerge from the study.     

Modal recovery methods for solution of fluid-structure problems with rigid wall loads

A method is presented which enables the acoustic modes of a fluid to be recovered in an analysis based on rigid wall loads of a structure or portion of a structure. It is shown that the method leads to a structural solution which is identical to the coupled fluid-structure solution provided that the fluid is discretized sufficiently to retain the requisite spectral fidelity. An application of this method to the waterhammer response of a pipe segment is given, which in addition to validating the method, shows that the coupled response differs significantly from the structural behavior predicted by added mass, or incompressible, representations of the fluid. When the method is used to recapture fluid-structure interaction in a subsystem, silent boundaries are needed for the fluid domain. The method is also applicable to many other fluid-structure problems, and is particularly useful when the fluid loads are determined experimentally or by complex computational methods that are not readily coupled with structural models.     

Numerical simulation of ground water mounding and its verification by Hele–Shaw model

Ground water mounding is the rise of the water table above its regional level in a local area of an aquifer in order to provide sufficient head to distribute the water supplied by a localized source to that area. The shape and height of the mound depend on many factors including recharge rate and distribution, geology, hydraulic conductivity, flow/head control locations, saturated thickness and regional flow in the aquifer in that area. In this work, an accurate and efficient numerical model for calculating ground water mounding was developed. Numerical calculations were done on a uniform rectangular grid, obtained by a transformation of the physical domain. Grid for computation were generated by a grid generation code, EagleView, which is developed by the Mississippi State University. Model predictions were verified with tests in a Hele–Shaw model for situations with and without a regional flow, with and without heterogeneity, and for two recharge rates. SAE#50 oil was used as the fluid in the Hele–Shaw. A peristaltic pump was used to supply the constant (and adjustable) recharge rate from the reservoir below the Hele–Shaw model. The results of experiments of estimating mounds and the numerical mounding model are in good agreement. However, mound height of the region below recharge of Hele–Shaw model can not be observed because the flow of this region combines vertical flow from recharge and the rising of the free surface (horizontal flow). Hence, an emulated perched aquifer was used so that mound height of the recharge region can be observed.     

Design and implementation of a Chinese terminal controller

In a Chinese data processing system, a vast amount of memory and CPU time are required to perform the I/O operation of Chinese characters. If the operation is done fully by a minicomputer, it will degrade the capability of the minicomputer and decrease the number of terminals which can be connected to the minicomputer. In order to avoid these drawbacks, we built a microcomputer-based Chinese terminal controller. It stands between a host computer (e.g. a PDP-11 minicomputer) and 16 Chinese terminals (each terminal consists of a Chinese keyboard and a TV monitor) and takes all the responsibilities of doing the I/O operation of Chinese characters. The important characteristics of the controller are: (1) the controller can control up to 16 Chinese terminals simultaneously; (2) not only can PDP-11 be a host computer but also other computers; (3) all the well-developed system programs (such as EDIT, BASIC, FORTRAN, etc.) of the host computer can be used to do the data processing of English and or Chinese data. Due to these elegant characteristics, the processing capability for Chinese characters can be added to the original capability of any computer as soon as the controller is connected to it. The design and implementation of such a controller are described.     

An efficient cluster and decomposition algorithm for mining association rules

Conventional algorithms for mining association rules operate in a combination of smaller large itemsets. This paper presents a new efficient which combines both the cluster concept and decomposition of larger candidate itemsets, while proceeds from mining the maximal large itemsets down to large 1-itemsets, named cluster-decomposition association rule (CDAR). First, the CDAR method creates some clusters by reading the database only once, and then clustering the transaction records to the kth cluster, where the length of a record is k. Then, the large k-itemsets are generated by contrasts with the kth cluster only, unlike the combination concept that contrasts with the entire database. Experiments with real-life databases show that CDAR outperforms Apriori, a well-known and widely used association rule.     

A unified approach to deadbeat systems design

This paper is concerned with the design of a discrete-time regulator by using an observer in conjunction with a state feedback law. Previous techniques have been examined, modified, and simplified to a unified procedure. For example, in the initial step, Krylov's transformation is used which has never been applied explicitly. In the second step, an alternate use of Krylov's transformation is demonstrated to design feedback laws that achieve eigenvalue placement. In the final stage of the controller design, the combination of the observer and the state feedback law is clearly seen. Two new matrix identities are derived and applied in the transfer function manipulation.     

Geometrical-optics solution to light scattering by droxtal ice crystals

We investigate the phase matrices of droxtals at wavelengths of 0.66 and 11 microm by using an improved geometrical-optics method. An efficient method is developed to specify the incident rays and the corresponding impinging points on the particle surface necessary to initialize the ray-tracing computations. At the 0.66-microm wavelength, the optical properties of droxtals are different from those of hexagonal ice crystals. At the 11-microm wavelength, the phase functions for droxtals are essentially featureless because of strong absorption within the particles, except for ripple structures that are caused by the phase interference of the diffracted wave.