Study of the release in water of chemicals used for wood preservation. Effect of wood dimensions

Summary Various chemicals are used for protecting wood samples against fungi, and some of them are released in water, leading to pollution of the water. The kinetics of pentachlorophenol release in water has here been studied by considering the diffusion through the wood along the three principal axes of diffusion. The experiments and the modelling of the process is successfully coupled. The numerical model takes into account the three principal diffusivities, the partition factor, the volumes of wood and water. The effect of wood sample length along the longitudinal axis of diffusion is studied especially, as longitudinal diffusivity is much higher than the other two principal diffusivities. The effects of the relative volumes of wood and water are also of considerable interest not only for the concentration of the chemical in water but also for the rate of release.Symbols C concentration of liquid (g/cm³)_ - C _c ,C _eq concentration of liquid on the surface, at equilibrium with the surrounding, respectively - C _i,j,k concentration of liquid in the wood at positioni, j, k - D diffusivity (cm²/s) - h coefficient of mass transfer on the surface (cm/s) - K partition factor - i, j, k integers characterizing the position in the wood - M _L ,M _R ,M _T dimensionless numbers - M _t ,M amount of chemical released after time t, after infinite time, respectively - t increment of time - L, R, T thickness of the slices taken in the wood for calculation - N _L ,N _R ,N _T number of slices taken in the wood - x, y, z coordinates - V _water volume of the surrounding water     

On the activation energy of diffusion of water in wood

Summary The diffusion equation for water in wood is expanded in terms of temperature and moisture gradient on the assumption that the driving force for the diffusion of water in wood is the partial pressure of water vapour. An analytic expression is then developed for the activation energy of diffusion in terms of enthalpy and entropy changes associated with the sorption process. The expression is compared with another published curve and some similarity was observed.Symbols C water concentration, kg/m³ - D diffusion coefficient for water vapour in wood with vapour pressure as the driving potential, kg/ms Pa - D_c diffusion coefficient for water vapour in wood with water concentration as the driving potential, m²/s - D_c a constant value of D_c, m²/s - E activation energy of diffusion, J/kg - F flow density, kg/m² s - f h/l - h specific enthalpy, J/kg - L l/R T - l latent heat of vapourization of free water, J/kg - l_s latent heat of vapourization of sorbed water, J/kg - p partial pressure of water vapour, Pa - p_s pressure of water vapour at saturation, Pa - R specifc gas constant for water, J/kg K - r relative humidity - s specific entropy, J/kg K - w dry basis moisture content - x length coordinate, m - a constant temperature equal to 6,800 K - -/ln r - _w density of wood (dry mass/moisture volume) at a given moisture content, kg/m³ - s/R - L style as 2 lines above - free water relative to sorbed water The author is grateful to the Editorial Board in relation to the use of (4)     

Process of absorption and desorption of water in a wood board,with 3-dimensional transport beyond the FSP

Summary The process of absorption of water in a piece of solid wood, as well as the following stage of desorption is studied, when the water content is beyond the fiber saturation point. A model based on a numerical method with finite differences is built and successfully tested. This model takes into account a 3-dimensional transport of water controlled by diffusion, with three principal axes of diffusion and three various principal diffusivities. The model is able to predict the kinetics of absorption or desorption when the three principal diffusivities are known, as well as the operational conditions.Symbols C (i, j, k) Concentration at the position of the coordinates i, j, k and at the time t - CN (i, j, k) Concentration at the same position, at the time t + t - C_s Moisture content at the surface - D_L Longitudinal diffusivity - D_T Tangential diffusivity - D_R Radial diffusivity - L Increment of space along the longitudinal axis - T Increment of space along the tangential axis - R Increment of space along the radial axis - t Increment of time - EMC or C_eq Moisture concentration at equilibrium - K Factor of evaporation (cm/s) - L, T, R Dimensions of the board along the longitudinal, tangential, radial directions, respectively - M_L Dimensionless number for the longitudinal axis - M_T Dimensionless number for the tangential axis - M_R Dimensionless number for the radial axis - Th Thickness of a sheet (in Eq. 15)     

The distinction between average enthalpy and the isosteric heat of water sorbed on wood; and the spatial distribution of the specific enthalpy of the sorbed water

Summary It is commonly assumed that specific enthalpy is uniform throughout water sorbed on wood. It is suggested here that this is not the case and that as a result the isosteric heat and the differential heat of wetting are two distinct functions. An analysis is developed which enables the distribution of specific enthalpy within the adsorbed water to be approximated. The results are presented with reference to klinki pine.Symbols a parameter, Eq. (14) - h specific enthalpy of sorbed water, J/kg - h average specific enthalpy of sorbed water, J/kg - h isosteric heat, J/kg - h₁ integral heat of wetting, J/kg - k a constant - l latent heat of vaporization of free water, J/kg - P_s pressure of water vapour at saturation, Pa - q differential heat of wetting, J/kg - R specific gas constant for water, J/kg K - r relative humidity - T temperature, K - enthalpy function defined in Eq. (10), J/kg - moisture content - _p prevailing moisture content The author is grateful to Dr. A. N. Stokes for a substantial simplification of the original derivation of Eq. (13)     

Non-steady state water adsorption of wood

Summary The validity of the following equation of water adsorption into wood substance which was derived in the previous report, is examined: d(W)/dt = k₀(1 – exp(-k₁/t))W(l – W), which can approximately be written as: d(W)/d(logt) = rW(l – W), where W is moisture content; t is time (t > 0); k₀, k₁ and r are constants. After measuring dimensional change with change in time under various relative humidities, the change of moisture content was indirectly calculated from the proportional relationship between dimensional change and moisture content. It was found that the theoretical equation satisfactorily agreed with the experimental results. These results lead to the conclusion that the equation was valid. Furthermore, the properties of the equation, whose constants are determined from experimental results, is discussed. The rate of water adsorption of wood shows interesting and systematical properties, especially near relative humidities corresponding to the fiber-saturation point.     

Osmotic stress in wood — part II: on the computation of drying stresses in wood

Summary Plastic stress arising in wood during drying is calculated according to the theoretical model developed earlier. The mechanism of stress reversal and the type of resudual stress corresponding to different values of material constants are shown. The results are in qualitative agreement with experimental evidence.List of symbols A coefficient of swelling below the fibre saturation point - C concentration of moisture in wood; weight of moisture per weight of dry wood - C ₀ uniform concentration of moisture in wood at the beginning of drying - C ₁ equilibrium concentration of moisture at the boundary during drying - C =C-C ₁ - non-dimensional concentration - D diffusivity - D ₀ first term in the expansion of diffusivity as function of concentration: D=D ₀(1+D ₁ C+...) - D ₁ secondterm in the expansion (see D ₀) - E Young's modulus - e _ij deviator of tensor of strain: - e _ij ^P deviator of plastic strain: - e _ij ^E deviator of elastic strain - F fibre saturation point (concentration at which the function (c) changes slope) - F =F-C ₁ - g(x,t) function which assumes the value 1 in the elastic zone and 0 in the plastic zone - k von Mises' yield stress - L half width of the sample - M total moisture content - P plastic power - S _ij deviator of stress - S _kk =S ₁₁+S ₂₂+S ₃₃ - S _ij ^E =2 e _ij - T _ij tensor of stress - T _kk =T ₁₁+T ₂₂+T ₃₃ - T non-zero component of stress in a beam or plate - non-dimensional stress - actual stress rate in an elastic zone, fictitious stress rate in a plastic zone - t time - t increment of time - x y z spatial coordinates - X increment of spatial coordinate - Y - Y ₀, Y ₁ terms in the expansion of Y(C): Y(C)=Y ₀(1+Y ₁ C+...) - non-dimensional Y - , (c) coefficient of osmotic expansion (dependent on concentration) - _ij tensor of strain - _kk =₁₁+₂₂+₃₃ - =_yy=_zz non-zero component of strain in the case of a plate or beam - modified strain - elastic constants of an isotropic body - non-dimensional spatial coordinate - Poisson's ratio - non-dimensional time     

Effects of quenching on relaxation properties of wet wood

A new relaxation property is discussed on the basis of creep behavior of wet wood specimens pretreated with heating at various temperatures followed by quenching. The treated samples showed more marked relaxation than that of an untreated sample. The relationship between relaxation time and heating history was represented by an equation ln() = –( _f – k ₁)T + [ln( _g) + k ₂], where ln() is the logarithmic relaxation time of wet samples after quenching, T is the difference between the heating temperature and the glass transition temperature (T _g), ln( _g) is the logarithmic relaxation time at T _g, is a constant, _f is the coefficient of thermal bulk expansion, and k ₁ and k ₂ are constants. It was concluded from the analysis of experimental results that the change in the relaxation property caused by heating and the following quenching is due to the temporary free volume created by freezing of molecular chain motion of wood components, most probably lignin, during quenching.This work was presented at the 52nd Annual Meeting of Japan Wood Research Society, Gifu, April 2002     

Dimensional instability of cement bonded particleboard: Modelling CBPB as a composite of two materials

Previous papers have quantitatively indicated that the total movement of cement bonded particleboard (CBPB) is equal to the sum of the movement of its components. This paper examined the efficacy of the law of mixtures when applied to the movement of a wood-cement composite under internal swelling or shrinkage stresses. Abundant data generated in companion papers were first manipulated to develop the universal formulae for predicting the movement of components. In conjunction with previous numerical results from image analysis of the structure of CBPB, and the orientated elasticity and stress algorithms, the models for theoretically predicting mass and dimensional changes of CBPB were derived. Validation studies were conducted and these demonstrated an excellent agreement of the theoretical predictions with experimental data for both mass and dimensional changes of CBPB due to internal swelling or shrinkage stresses during adsorption and desorption. The success also implied that CBPB can be treated as a composite and its properties can be well derived by the law of mixtures even though CBPB is an unusual type of composite having a very high volume fraction of wood chips, but a very high mass fraction of cement paste.Notation E_RT Mean transverse modulus of elasticity of wood - E_L Longitudinal modulus of elasticity of wood - E_p Modulus of elasticity of cement paste - E_wa Modulus of elasticity of embedded wood chips at angle - E Modulus of elasticity of wood chips at direction - E Modulus of elasticity of wood chips at direction - G_LRT Mean transverse shear modulus of wood - L(T)_cp Length/width (thickness) change of CBPB at angle - L(T)_p Length (thickness) change of cement paste - m_pf Mass fraction of cement paste in unit mass of CBPB - m_wf Mass fraction of wood chips in unit mass of CBPB - M_cpj Mass change of CBPB at the various conditions tested - M_pj Mass change of cement paste at corresponding conditions - M_wj Mass change of wood chips at corresponding conditions - M(L; T)_w/P Mass, length or thickness changes of wood chips or cement paste at various conditions - t Duration of exposure - _LRT Mean transverse Poissons ratio of wood - V_pf Volume fraction of cement paste in unit mass of CBPB - V_wf Volume fraction of wood chip in unit mass of CBPB - _cp Density of CBPB - _k Density of wood chip or cement paste - _cp Overall stresses of CBPB at angle - _L Stress in the longitudinal direction of wood - _RT Mean stress in the transverse direction of wood - _p Stress of cement paste - _w Stress of the wood chips at angle - Stress of the wood chips at direction - Stress of the chip at direction - _cp Strain in CBPB - _p Strain of cement paste - _WL Strain in the length of wood chips - _WT Strain in the thickness of wood chips - _w Strain in wood chips - Angle between the longitudinal direction of wood chips and surfaces or edges of CBPB - Angle between wood chips and edges (length direction) of CBPB - Angle between wood chip and vertical coordinate - A, B, C Coefficients related to the feature of materials and exposure conditions The senior author wishes to thank Professor W.B. Banks of University of Wales, Bangor for his constructive discussions and assistance and the British Council for partly financial support.     

Exact analysis of shear strain in wood

Summary An analysis is given which enables the shear strain in a piece of timber to be specified in terms of the difference between tangential and radial strain, herein termed the angular strain. The angular strain is then evaluated in terms of the orientation of two lines at right angles prior to deformation. The equations involved are simple and facilitate the evaluation of strain parameters which would otherwise require numerical computation.Symbols a, b, c length parameters, Fig. 2 - C half chord length - k constant of proportionality - r radial coordinate (distance from pith) - x length coordinate (board) - , angle parameters, Fig. 1 - shear strain - width of segment - angular strain - #x025B; tangential strain - _r radial strain - ₁, ₂ components of shear strain, Fig. 1 - angle parameter, Fig. 2 - angle parameter, Fig. 3 - angle parameter, Fig. 2 The author wishes to thank Mr. J. W. Sutherland for his assistance with the presentation of this paper.     

The thermodynamics of sorption with reference to klinki pine

Summary An investigation into the bonding energy relationships for water in wood indicates that as the temperature increases at constant total moisture content, water moves from within the chemical structure to the adsorption surface. The analysis is evaluated for the wood Araucaria klinkii Lauterb and it is indicated that at 25 °C, less water is held in the chemical structure during adsorption than during desorption.Symbols A amplitude of liquid surface profile - A₀ amplitude of solid surface profile - a mean radius of curvature of liquid surface (bubble radius), Å - a₀ mean radius of curvature of solid surface, Å - a_c a constant value of a, Å - F a function of temperature - f capisorption energy fraction - G a function of - g specific Gibbs free energy of saturated water vapour relative to unsaturated water vapour at the same temperature, J/kg - g_c specific Gibbs free energy associated with capisorption, J/kg - g_p specific Gibbs free energy associated with physisorption, J/kg - h change in specific enthalpy of liquid water as it is desorbed, J/kg - l latent heat of vaporisation of free water, J/kg - m wave number/m - p_s pressure of water vapour at saturation, Pa - R specific gas constant for water vapour, J/kg K - r relative humidity - s change in specific entropy of liquid water as it is desorbed, J/kg K - T temperature, K - w dry basis moisture content - x ln p_s/p_s25 - y In r - z length coordinate, m - , , constant coefficients - change in mean height of liquid surface, Å - ₀ a constant length, Å - constant - distance from solid to liquid vapour interface measured normal to solid surface, Å - ₀ a constant value of , Å     

An irreversible thermodynamics model for unsteady-state nonisothermal moisture diffusion in wood

Summary A model that predicts heat and moisture transfer through wood in the hygroscopic range and which is based on the principles of irreversible thermodynamics, was evaluated with unsteady-state nonisothermal moisture desorption experimental data. The model predicted the phenomenon of thermal diffusion during the initial stages of desorption and results in a very good simulation of the desorption curve and the center's temperature change with time.Symbols C_p specific heat of air (= 0.24 cal/g K @ 70 °C) - C_T specific heat of wood, cal/g K - D transverse diffusion coefficient, cm²/s - E_b activation energy, cal/mol - E_o heat of vaporization, cal/mol - E_L differential heat of sorption, cal/mol - G specific gravity of wood - H relative humidity, % - h_T convective heat transfer coefficient, cal/cm² s K - h_c convective mass transfer coefficient based on the concentration of moisture in wood, cm/s - h_v convective mass transfer coefficient based on the concentration of moisture in the air in equilibrium with the wood surface, cm/s - K_M coefficient for diffusion due to moisture gradient, g/cm s % - K_T transverse thermal conductivity coefficient, cal/cm K s - M moisture content, % - P_o saturated vapor pressure, atm - R universal gas constant, cal/mol K (= 82.056 cm³ atm/mol K) - t time, s - T temperature, K - x distance, cm Greek Letters evaporation or condensation criterion - wood density, g/cm³ - _W water density (=1), g/cm³ - _a air density, g/cm³ Department of Wood Science and Forest Products Virginia Polytechnic Institute and State University Blackburg, Virginia 24061-0503     

Isolation of a β-1,3-glucan (laricinan) from compression wood of Larix laricina

Summary A -d-(13)-linked glucan has been isolated from compression wood of tamarack [Larix laricina (Du Roi) K. Koch]. The polysaccharide, which had []_D + 17.6°, consumed 0.17 mole of periodate per glucose residue and gave a methyl derivative which consisted of 115 2,4,6-tri- and 2,3,4,6-tetra-O-methyl-d-glucose residues in a ratio of 17.8:1. Partial acid hydrolysis yielded a series of -d-(13)-linked oligosaccharides, while enzymic hydrolysis with a -1,3-glucanase afforded glucose, laminaribiose, and laminaritriose. The glucan occurred in amounts varying from 2 to 4% in compression wood of this and other conifer species and was present in the wall of both tracheids and ray cells. It is proposed that this structural polysaccharide be designated as laricinan to distinguish it from callose and the various -1,3-glucans in lower plants.     

Applications of the capillary isotherm

The effect of temperature on the capillary isotherm is accounted for in a modified derivation. Some new equilibrium moisture content data for E. regnans are presented and fitted by the capillary isotherm. Some earlier data for Klinki pine are also fitted. It is shown precisely how reductions in the shear modulus of the cell wall material with increasing temperature give rise to reductions in equilibrium moisture content for a given relative humidity.Symbols A G₀/R, K - a₁ external radius of annulus, m - a₂ internal radius of annulus, m - a_f a₂ at fibre saturation, m - a a constant length, m - B a constant of integration - b₁, b₂ temperature parameters, K^1- - G rigidity of wood substance, Pa - G₀ G for dry wood, Pa - G_f G at fibre saturation, Pa - h isosteric heat, J/kg - latent heat, J/kg - p capillary pressure, Pa - P_s pressure of water vapour at saturation, Pa - R specific gas constant for water, J/kg K - r relative humidity - r_i inflection intercept - r_t tangent intercept - T temperature, K - t temperature, °C - X see equation (18) - x see equation (28) - , , ₁, ₁ coefficients, equations (27), (37) - y₁, y₂ see equations (25), (26), K - parameter, equation (9) - parameter, equation (33) - density of water, kg/m³ - _W density of wood substance, kg/m³ - equilibrium moisture content - _0.2 at r = 0.2 - _0.5 at r = 0.5 - _0.9 at r = 0.9 - _f at fibre saturation     

Stress-strain state of wood at kiln drying

Summary A model has been suggested which allows the calculation of stresses arising in kiln drying and humidification of wood, as well as the total residual strain, i.e. set strain _s, consisting of purely residual strain _r and the so-called frozen strain _f. Frozen strains arise under the operating influence of loading when the stiffness is increased because of a decrease in moisture content (or temperature) of the wood. The process of formation of set strains _s has been shown to depend on the history of loading, variations of the moisture content of the wood, as well as cooling of the section before the measurement of _s. The possibility of using set strain as a parameter of the state of stress of wood in kiln drying has been noted.Presented at the VIII. International Symposium on Fundamental Research of Wood. Warsaw, Poland, October 1990     

Phenomenological kinetics of wood delignification: application of a time-dependent rate constant and a generalized severity parameter to pulping and correlation of pulp properties

Summary Kraft delignification kinetics has been modelled on the basis of a first order decay process with a time-dependent rate constant. A generalized severity parameter derived from this kinetic model, R_oh, has been applied to describe the lignin solubilization during alkaline (soda and Kraft) and bisulphite pulping of different wood species. The model has been succesfuly applied to data sets available from the literature. Our approach has combined the main process variables (temperature, time and chemical load) into a single parameter, R_oh, which is then used as a reaction ordinate to map the changes in chemical composition and physical properties. An extension of the initial formulation of the R_oh parameter has been made to cover the situations where the catalytic system is composed by two active chemical species, as in the Kraft process.Symbols C Lignin concentration - C₀ Lignin concentration at t = 0. - _a Average activation energy (kJ/mol) - f_i Conversion of the reacting substrate (lignin) - F[ ] A function of the conversion - g(E) Distribution of activation energies function - k(t) Time-dependent rate constant - K Severity model constant - R_oh The generalized severity parameter, or reaction ordinate - S _i ⁰ Initial concentration of the reactive substrate (lignin) - t Reaction time (min) - T(t) Reaction temperature (°C),which may vary as a function of time in non isothermal conditions - T_ref Reference temperature (°C), normally choosen in the middle of the experimental conditions used - X(t) Chemical load (g chemical/g o.d. wood), for the first active specie - X_ref Reference chemical load (g chemical/g o.d. wood). - Y(t) Chemical load (g chemical/g o.d. wood), for the second active specie - Y_ref Reference chemical load (g chemical/g o.d. wood) Greek Letters Constant in k(t) (min^-) - Parameter defining the shape of the Kohlrausch function which describes the distribution of activation energies - () Euler's gamma function - Parameter expressing the strength of the first active chemical in the specific reaction considered - Parameter expressing the strength of the second active chemical in the specific reaction considered - ₀ Effective lifetime (min). - /- Average lifetime (min). - Parameter expressing the importance of temperature in the specific reaction considered. For instance a value of 14.75 will indicate that the rate of reaction has doubled ten degrees above the reference temperature, all the other variables remaining constant. Authors are indebted to CICYT (Science and Technology Inter Ministerial Commission, Spanish Government) and Generalitat de Catalunya (Catalan Regional Government) for financial support, project number QFN92-4317 and grant number AIRE 92/I-22. Contributions of the National Science and Engineering Research Council of Canada (NSERC) and Fonds des Chercheurs et Actions de Recherche (FCAR) are gratefully acknowledged.     

Chemical treatment of wood for musical instruments. Part I: acoustically important properties of wood for the Ranad (Thai traditional xylophone)

The purpose of this study is to determine the important acoustic properties of wood for making Ranad bars and the resonator box. The woods used in this study were separated into two groups. The first group is the type of wood that has been used to make Ranad for centuries: Ching-Chan (Dalbergia oliveri Gamble) and Ma-Had (Artocarpus lakoocha Roxb.) for making the bars, and Ka-Nun (Artocarpus neterophylla Lamk.) out of which the resonator box is made. The second group comprises woods that are abundant in Thailand and are genetically related to the first group. The physical and mechanical properties of the woods in both groups were measured including the specific dynamic Youngs modulus (E/), density (), hardness (H), acoustic conversion efficiency (ACE), and sound refraction coefficients (||). The results revealed that high and consistent || were crucial factors of the Ranad bar properties in addition to E/, , and H. The results from measurements made on the resonator box wood revealed that high E/, ACE, and high and consistent || were its crucial properties.     

Influence of rotatory inertia,shear deformation and support condition on natural frequencies of wooden beams

Summary The degree of influence of rotatory inertia and shear deformation on natural frequency determinations is discussed. It is found that for material such as wood, which has a relatively high ratio of bending modulus to shear modulus, these effects need to be taken into account even for supposedly slender beams. The discussion covers the four most common types of support condition, namely simply supported, free-free, clamped-free and clamped-clamped ends. As a perfectly rigid clamped condition can never be achieved in practice, especially for relatively soft material like wood, consideration is extended to also include partially-clamped beams.Symbols A cross sectional area - E modulus of elasticity in bending - E_c modulus of elasticity in compression perpendicular to the grain - G shear modulus - I second moment of area - K shear shape factor - K_H, K_HO, K_HL translational spring stiffness - K_T, K_TO, K_TL rotational spring stiffness - L span - b breadth - d depth - s clamp length - m mass per unit length - t time - v transverse displacement - x distance along the length of a beam - y transverse displacement with time - total rotation - angular natural frequency - f_T natural frequency of a Timoshenko beam - f_E natural frequency of an Euler beam This work was undertaken with financial support from Canadian Natural Sciences and Engineering Research Council under Special Support for Forestry Grant No. FRP0030800 and Operating Grant No. OGP0004417     

Neuere Beobachtungen und Untersuchungen zur Kartierung von Pflanzenschädlingen

Summary In the introduction a historical survey is given about the development of the registration service of pests. It can be seen that originally informations of the appearance of pests was mostly given by agricultural and horticultural experts in special journals of agriculture and horticulture.It is well known that a registration service was set up when a Plant Protection Organisation was foundet. Its efficiency has never ceased since its beginnings. These efforts are foundet intensionally to register the existence of pests as completely as possible.The registration service starting first of all from the damage caused by the pests maybe well understood.Our research work being a continuous contribution to the systematic registration of pests generally shows in a number of examples the heterogeneous character of the problem which must be studied concerning the individual pests and difficulties which arise. This is shown with regard to someElaterides and also because of experiments withLaspeyresia funebrana Tr. during several years.In accordance withKirchner and F. P.Müller, Rostock, we propose to register systematically a number of pests on index cards according to uniform principles in the whole of Europe, to register the vertical and horizontal appearance of pests with the same measure, in the same periods of classification and in the same way (seeAuersch 1 to 3).We are encouraged to do so by a number of appreciated views of specialists from Germany and foreign countries however it is, not enaugh to see the great importance of the card index (card-register) and to acknowledge its practicability, but it can only prove its efficiency if it is generally introduced.The systematic registration of pests will enable us to gather in the course of time empirical data, the reliability and evidence of which will steadily increase.

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Résumé On commence par livrer un aperçu historique sur le développement du système de rendre compte relativement aux plantes nuisibles. En lisant ces comptes rendus on peut reconnaître que les rapports donnés au début sur l'apparition des plantes nuisibles furent livrés en substance par la pratique agricole et jardinière par des revues spéciales de l' agriculture et de l'horticulture.Il est connu qu'avec l'établissement du service pour la protection des plantes on a établi un service de comptes rendus, au perfectionnement duquel on a travaillé dès son existance.Ces efforts furent influencés et activés par l'idée de saisir l'apparition des plantes nuisibles aussi complétement que possible. Le service des comptes rendus s'est orienté d'abord en première ligne aux dommages produits, ce qui est aisé à comprendre.Puisque notre traité doit être en général une contribution ultérieure à la connaissance systématique de l' apparition des plantes nuisibles, on explique au moyen de plusieurs exemples, comment sont différentes les questions se rapportant aux plantes nuisibles individuelles, questions qu'il faut ainsi prendre en considération et quelles difficultés en résultent. Cela est démontré pour quelques élatérides de même que sur la base d'examinations exécutées pendant plusieurs années avecLaspeyresia funebrana Tr.En concordance avecKirchner et F. P.Müller, Rostock, nous proposons de saisir systématiquement en classeurs à fiches une série de plantes nuisibles selon des points de vue uniformes, cela veut dire d'enregistrer dans les fiches proposées l'apparition verticale et horizontale des plantes nuisibles avec des mesures égales, dans les mêmes périodes d'examen et appréciation des qualités productives du sol et dans la même manière (voireAuersch 1 à 3).Nous sommes encouragés à faire ces propositions avant tout par des assentiments à notre disposition, qui nous ont été envoyés de la part des cercles compétents de notre pays et de l'é tranger. Il ne suffit pas cependant de reconnaître le fichier dans sa signification variée et d'apprécier son utilisation; le fichier peut faire ses preuves plutôt seulement, s'il est introduit en général. Au cours du temps il sera possible d'obtenir des valeurs expérimentelles par le fichement systématique des plantes nuisibles, dont la sûreté et faculté de déposition augmente constammant avec la durée de leur existence.

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õ . : . . . . õ . . , . Elateriden uLaspeyresia funebrana Tr. . . . , , , . . ( 1 3.) . . , . . .

     

Changes in the physical and chemical properties of six Japanese softwoods caused by lengthy smoke-heating treatment

The effects of prolonged smoke-heating treatments on wood quality were investigated. Six Japanese softwoods were smoke-heated for 100 and 200h at a temperature of 75° ± 5°C, which was recorded inside the log. After smoke heating, wood quality, including moisture content, amounts of chemical components, relative degree of crystallinity (RDC) of cellulose, and sapwood color were examined. Moisture content decreased as a result of smoke heating, especially in sapwood, leading to a uniform distribution of moisture content within a log. Almost no difference was found in the amounts of chemical components between the control woods and the woods that were smoke-heated for 100h. However, in the wood that was smoke-heated for 200h, the amounts of holocellulose decreased, suggesting that thermal deterioration and/or degradation of hemicelluloses had occurred. We assume that the increase in RDC was caused by smoke heating with the crystallization of cellulose and/or thermal degradation of hemicelluloses. Almost no differences were found in sapwood color between the control woods and the woods that were smoke-heated for 100h. In the wood that was smoke-heated for 200h, however, L*decreased, whereas a* and b* increased. As a result, E*ab, showing the total color change, increased, resulting in a deeper color. These results suggest that thermal degradation of hemicelluloses was caused by smoke heating for over 100h. Therefore, smoke heating of softwood logs using a commercial-scale kiln should not exceed 100h.     

New splitting method for wood fracture characterization

Summary A testing procedure with a new and simple specimen shape is presented which is appropriate to characterize fracturing of inhomogeneous and complex materials like wood. With this, the fracture energy of spruce wood is determined in the TL and RL direction. The size effect, i.e. influences of specimen dimensions on K_IC and G_f (specific fracture energy) are investigated. Stress and deformation distribution in the newly developed specimens are analysed with FE methods. The measured load-displacement curves are approximated by bilinear softening diagrams and FE analysis. Based on these results, it is tried to interpret typical deviations from LEFM's behaviour by mechanisms like microcracking, crack branching or crack tip bridging.The authors thank Dr. A. Teischinger for supplying the testing material and Dipl. Ing M. Elser for preparation of the diagrams. Financial support of the Fonds zur Förderung der wissenschaftlichen Forschung, Wien is gratefully acknowledged.