Optical properties of drying wood studied by time-resolved near-infrared spectroscopy

Abstract

We measured the optical properties of drying wood with the moisture contents ranging from 10% to 200%. By using time-resolved near-infrared spectroscopy, the reduced scattering coefficient μ_s' and absorption coefficient μ_a were determined independent of each other, providing information on the chemical and structural changes, respectively, of wood on the nanometer scale. Scattering from dry pores dominated, which allowed us to determine the drying process of large pores during the period of constant drying rate, and the drying process of smaller pores during the period of decreasing drying rate. The surface layer and interior of the wood exhibit different moisture states, which affect the scattering properties of the wood.

Exact bright and dark solitary wave solutions of the generalized higher-order nonlinear Schrödinger equation describing the propagation of ultra-short pulse in optical fiber

“…During the last few decades, nonlinear partial differential equations (NPDEs) have seriously draw the attention of the world scientific research. These NPDEs permit to model phenomena in several fields of sciences, notably in physics, such as fluid mechanics, electronics, plasma physics, condensate mater and optical fiber communication [1][2][3][4][5][6][7].…”

“…">IntroductionDuring the last few decades, nonlinear partial differential equations (NPDEs) have seriously draw the attention of the world scientific research. These NPDEs permit to model phenomena in several fields of sciences, notably in physics, such as fluid mechanics, electronics, plasma physics, condensate mater and optical fiber communication [1][2][3][4][5][6][7].The numerical or analytical studies of NPDEs are one of the very important and essential tasks in nonlinear sciences, but the construction of exact solutions plays a very important role, because they can provide much information for a best comprehension of a physical problem. That is why some mathematical methods have been developed to solve NPDEs.…”

“…Step 4: We assume that the solution of equation (7) can be expressed under the shape: where m, n, q and r are numbers to determine.…”

“…Inserting equation (8) into equation (7), and taking into account the transformations related to the BDKm [27], we get the equation of the form indicated below Step 5: If the functions F(a i , α, β, ω, k), H(a i , α, β, ω, k), G(a i , α, β, ω, k), T(a i , α, β, ω, k), V(a i , α, β, ω, k) can be null for some values of the coefficients a i , α, β, ω or k (nontrivial values), the ansatz given in equation (9) can be supported by equation (5) for any values of m, n, K, q, r and can be considered as solution of equation.…”

Effect of cellular structure on the optical properties of wood

“…The water retained in cell walls or cell lumens also significantly affects the optical properties of wood. 4 To construct a robust calibration of wood properties by NIR spectroscopy, we must independently evaluate the spectral contributions of light absorption (which results from harmonics or overtones of the fundamental absorptions of the molecular vibrations of cellulose, hemicellulose, lignin, extractives and water) and light scattering (caused mainly by the cellular structure).…”