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Showing papers by "Yi Chen published in 1992"


Journal ArticleDOI
TL;DR: In this paper, the authors present the design and operation of a scanning probe microscope which simultaneously provides the attractive mode force and near-field optical images of objects, which is used to track the topography, thus allowing the optical signal primarily to show variations in transmissivity.
Abstract: We present the design and describe the operation of a scanning probe microscope which simultaneously provides the attractive mode force and near‐field optical images of objects. In this technique, the force signal is used to track the topography, thus allowing the optical signal primarily to show variations in transmissivity. A number of results are presented on the application of the technique to imaging different samples.

490 citations


Journal ArticleDOI
TL;DR: The addition of metformin to sulfonylurea-treated patients with NIDDM not in good glycemic control significantly lowered fasting and postprandial plasma glucose concentrations, presumably due to the combination of enhanced glucose uptake and decreased hepatic glucose production.
Abstract: The effect of metformin treatment was studied in 13 patients with noninsulin-dependent diabetes mellitus (NIDDM), whose fasting plasma glucose concentration was greater than 10 mmol/L with maximal sulfonylurea doses. Patients were studied before and 3 months after receiving 2.5 g/day metformin. The fasting plasma glucose concentration (12.4 +/- 0.8 vs. 8.8 +/- 0.7 mmol/L), mean hourly postprandial plasma glucose concentration from 0800-1600 h (14.0 +/- 1 vs. 9.4 +/- 0.9 mmol/L), and glycosylated hemoglobin level (12.3 +/- 0.6% vs. 9.0 +/- 0.6%) were all significantly (P less than 0.005-0.001) lower after the administration of metformin. The improvement in glycemic control was associated with a 24% increase (P less than 0.05) in insulin-stimulated glucose uptake during glucose clamp studies and a 16% decrease in basal hepatic glucose production (P less than 0.05). Mean hourly concentrations of plasma insulin (411 +/- 73 vs. 364 +/- 73 pmol/L) and FFA concentrations (440 +/- 31 vs. 390 +/- 40 mumol/L) were ...

105 citations


Journal ArticleDOI
TL;DR: An optimization procedure based upon the individual pattern spectra of the signal and noise, where if the image and noise grains are disjoint, then the pattern-spectra parametric estimation procedure yields exactly the optimal value of the parameter.

29 citations


Journal ArticleDOI
TL;DR: In this article, the effect of Na2WO4 loading and reaction conditions on the catalytic behavior was investigated, and the results were correlated with catalytic activity and selectivity.
Abstract: Methane oxidative coupling (MOC) was studied over Na2WO4/SiO2. The effect of Na2WO4 loading and reaction conditions on the catalytic behaviour was investigated. XRD, SEM, LRS and XPS have been used to study the catalyst morphology, Na2WO4 dispersity and surface oxygen species. These results were correlated with the catalytic activity and selectivity.

16 citations


Proceedings ArticleDOI
01 Nov 1992
TL;DR: In this article, the authors extend the local classification technique to gray-scale textures by using forty-two granulometric features, half generated by opening granulometries and a dual half generating by closing them.
Abstract: Binary morphological granulometric size distributions were conceived by Matheron as a way of describing image granularity (or texture). Since each normalized size distribution is a probability density, feature vectors of granulometric moments result. Recent application has focused on taking local size distributions around individual pixels so that the latter can be classified by surrounding texture. The present paper investigates the extension of the local- classification technique to gray-scale textures. It does so by using forty-two granulometric features, half generated by opening granulometries and a dual half generated by closing granulometries. After training and classification of both dependent and independent data, feature extraction (compression) is accomplished by means of the Karhunen-Loeve transform. The effect of randomly placed Gaussian noise is investigated.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

15 citations



Proceedings ArticleDOI
26 Jun 1992
TL;DR: A gray-scale version of the methodology to detect osteoporosis in magnetic resonance (MR) images of the wrist is applied, using maximum-likelihood classification to apply the local-pattern-spectra moment information.
Abstract: Local morphological granulometries are generated by opening an image successively by an increasing family of structuring elements and, at each pixel, keeping an image area count in a fixed-size window about the pixel. After normalization there is at each pixel a probability density, called a `local pattern spectrum,' and the moments of this density are used to classify the pixel according to surrounding texture. The method having been developed for binary images, the present paper applies a gray-scale version of the methodology to detect osteoporosis in magnetic resonance (MR) images of the wrist. Maximum-likelihood classification is used to apply the local-pattern-spectra moment information. Owing to the presence of a continuous intertwined network of bone fibers called trabeculae, when imaged by an MR imaging system a normal region of bone tissue possesses a coarse, grainy texture resulting in characteristic granulometric features. Osteoporosis is a metabolic bone disease typified by a gradual loss of trabecular bone, and this loss is revealed by significant changes in the granulometric features, thereby leading to detection.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

10 citations


Journal ArticleDOI
TL;DR: In this article, the structure relaxation and crystallisation of the amorphous sample were studied by Mossbauer spectroscopy after the sample had been annealed at various temperatures, showing that the sample started to crystallize at 573 K; it crystallized completely through the formation of the alpha -Fe and Fe3(P0.6B0.4) phases when the annealing temperature was raised to 673 or 773 K.
Abstract: Fe82P11B7 ultrafine amorphous particles have been prepared by the reaction of Fe(111) chloride, sodium hypophosphite and potassium borohydride in aqueous solution. X-ray diffraction and electron diffraction indicated the amorphous nature of the sample and scanning electron microscopy showed that the sample consists of nearly spherical particles with diameters from 150 to 350 nm. X-ray photoelectron spectroscopy revealed that iron, phosphorus and boron existed mainly in their elemental states. The structure relaxation and crystallisation of the amorphous sample were studied by Mossbauer spectroscopy after the sample had been annealed at various temperatures. The Mossbauer spectra suggested that the sample started to crystallize at 573 K; it crystallized completely through the formation of the alpha -Fe and Fe3(P0.6B0.4) phases when the annealing temperature was raised to 673 or 773 K. When the annealing temperature is low (below 573 K), no crystalline phases can be detected but, as evidenced by the dependence of hyperfine field distribution P(H) on annealing temperature, the heat treatment did cause a significant change in the microstructure of the amorphous sample.

6 citations


Journal ArticleDOI
TL;DR: A single polarization parameter is defined to describe the ordering of the spin-S exchange interaction model of ferromagnetism and thermal variation of the polarization q(T) is determined for various spins.
Abstract: The spin-S exchange interaction model of ferromagnetism is studied by the mean-field approximation. This model has 4S(S+1) order parameters, and has infinitely many ground-state configurations. We define a single polarization parameter to describe the ordering of the system. Thermal variation of the polarization q(T) is determined for various spins. The phase transition is first order (except for S=1/2) with phase transition temperature ${\mathit{kT}}_{\mathit{c}}$/Jz=(2S-1)/(4S ln2S), where z is the coordination number, and the discontinuity of q at ${\mathit{T}}_{\mathit{c}}$ is ${\mathit{q}}_{\mathit{c}}$=(2S-1)/2S.

3 citations


Journal ArticleDOI
Zheng Hu1, Jianyi Shen1, Lifeng Zhang1, Yi Chen1, Yuanfu Hsia1 
TL;DR: In this paper, the crystallization process of a−Fe35Ni15B26 ultrafine alloy particles prepared by chemical reduction with borohydride was investigated mainly by Mossbauer spectroscopy.
Abstract: The crystallization process of a−Fe35Ni15B26 ultrafine alloy particles prepared by chemical reduction with borohydride was investigated mainly by Mossbauer spectroscopy. The experimental results exhibit some new characteristics which were attributed to the microstructure of the sample.

3 citations


Journal ArticleDOI
Zheng Hu1, Jianyi Shen1, Yi Chen1, Yuanfu Hsia1, Hongru Zhai1 
TL;DR: In this article, a new chemical method for preparing uniform spherical a-Ni 85 P 15 ultrafine particles is reported, and the particles were characterized and investigated by several means, including several means.