http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/89 Mon, 18 May 2026 09:47:56 GMT 2026-05-18T09:47:56Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/475 Development of a spectrometry system using lock-in amplification technique Nguyen, The Binh; Nguyen, Huy Binh; Nguyen, Anh Tuan Raman spectroscopy and optical second-harmonic (SH) spectroscopy has a very important role in studies of optical properties of materials. Our goal is to build a spectrometry system to measure weak optical signals such as Raman scattering and surface SH signals. We studied to improve an old Double Grating Spectrograph GDM-1000 (Carl Zeiss, Jena, Germany) for wider range of wavelengths and transformed it successfully into a spectrometry system coupling with computer using Lock-in amplification technique. By this spectrometry system we can now obtain weak optical signals, for example, Raman Spectra of Vietnam petrol extracts excited by not only an 2W Argon laser but also by a 30mW He-Ne laser. VNU. JOURNAL OF SCIENCE, Mathematics - Physics, Vol. 21, No. 2, 2005 Sat, 01 Jan 2005 00:00:00 GMT http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/475 2005-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/474 Singularity of Fractal Measure Associated with The $(0, 1, 7)$ - Problem Truong, Thi Thuy Duong; Vu, Hong Thanh Let μ be the probability measure induced by S = 􀀟 ∞n =1 3−nXn, where X1,X2, ... is a sequence of independent, identically distributed (i.i.d) random variables each taking values 0, 1, a with equal probability 1/3. Let α(s) (resp.α(s), α(s)) denote the local dimension (resp. lower, upper local dimension) of s ∈ supp μ, and let α = sup{α(s) : s ∈ supp μ}; α = inf{α(s) : s ∈ supp μ}; E = {α : α(s) = α for some s ∈ supp μ} . In the case a = 3k +1 for k = 1, E = [1 − log(1+√5)−log 2 log 3 , 1], see [10]. It is conjectured that in the general case, for a = 3k + 1 ( k ∈ N), the local dimension is of the form as the case k = 1, i.e., E = [1 − log a b log 3 , 1] for a, b depends on k. In fact, our result shows that for k = 2 (a = 7), we have α = 1, α = 1− log(1+√3) 3 log 3 and E = [1 − log(1+√3) 3 log 3 , 1]. VNU. JOURNAL OF SCIENCE, Mathematics - Physics. Vol. 21,No. 2 - 2005 Sat, 01 Jan 2005 00:00:00 GMT http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/474 2005-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/470 Fabrication of high-aspect-ratio micro structures using uv-liga technology Nguyen, Thi Minh Hang; Chien-Hung, Ho; Vu, Ngoc Hung; Nguyen, Phu Thuy Thanks to almost transparent property of SU8 for wavelength of 365- 400nm, UV-LIGA technology using this photoresist has been applied to fabricate high-aspect-ratio (HAR) microstructures. This allows transferring patterns with vertical sidewall from masks to the photoresist. This paper introduces UV-LIGA and its application in fabricating comb drive structure for an angular rate sensor of linewidth and thickness of 50μm and 120μm, respectively. VNU. JOURNAL OF SCIENCE, Mathematics - Physics, Vol. 21 , No. 2, 2005 Sat, 01 Jan 2005 00:00:00 GMT http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/470 2005-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/467 Correlation Effects in Atomic Thermal Vibration of fcc Crystals Nguyen, Van Hung Analytical expression for the Displacement-displacement Correlation Function (DCF) CR has been derived based on the derived Mean Square Relative Displacement (MSRD) σ2 and the Mean Square Displacement (MSD) u2 for fcc crystals. The effective interaction potential of the system has been considered by taking into account the influences of nearest atomic neighbors, and it contains the Morse potential characterizing the interaction of each pair of atoms. Numerical calculations have been carried out for u2 , σ2 and CR functions of Cu and Ni. The ratio CR /u2 is 40% and CR / σ2 25% at high temperatures. They are found to be in good agreement with experiment and with those calculated by the Debye model. VNU. JOURNAL OF SCIENCE, Mathematics - Physics, Vol. 21, No. 2, 2005 Sat, 01 Jan 2005 00:00:00 GMT http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/467 2005-01-01T00:00:00Z