Physicochemical and Thermal Properties of Some Key Tropical Sawdust Woods for Energy Production

In South Saharan countries, 85% of the population uses biomass as a primary energy source. Cameroon presents one of the highest biomass energy and sawmills produce important sawdust resources which are not used and are burnt in piles leading to significant air toxic emissions. Therefore, we have to valorize industrially these available sawdusts. This study focuses on the physicochemical and thermochemical analysis of Ayous, Sapelli and Tali sawdust. The proximate and ultimate analysis, particle size, structural composition, as well as heavy metal content and calorific value were determined. In addition, the thermogravimetric mass losses were also estimated. The results showed that high water contents (24% - 41%) were recorded in the raw sawdust, and the thermal treatment reduced these contents from 78% to values in the range of 4% - 9%. The values for ash and volatile matter content were respectively between 0.25% - 0.74% and 68% - 76%. The LHV is higher in Ayous (17.5 MJ/kg) and Sapelli (16.8 MJ/kg) than that of Tali (15.7 MJ/kg). The concentration of heavy metals is very low in each species. Extractives are more present in Tali (16.06%) than in the other sawdusts. Pyrolysis of sawdust shows the typical decomposition of hemicellulose (270˚C - 325˚C), cellulose (325˚C - 400˚C) and lignin (200˚C - 550˚C) with a maximum loss of 75% at 370˚C and the melting point is 320˚C. The results of the sawdust parameters determined in the paper can be valorized to reduce pollutants emissions by developing the efficiency and effectiveness of biomass energy processes and promoting the use of biomass as a sustainable alternative to traditional fossil fuels.

A Review of the Advances Made in Improving the Durability of Welded Wood against Water in Light of the Results of African Tropical Woods Welding

Wood plays a major role in the production of furniture and wooden structures.Nevertheless,in this process,the massive use of adhesives and plural connectors remains a definite problem for health and the environment.Therefore,wood welding is a breakthrough in this respect.This paper reviews the applications of wood welding in furniture and construction and then examines advances in improving the durability of welded wood against water.Our contribution also highlights the need to join African tropical woods using the rotational friction welding technique.According to our results,these woods present interesting chemical singularities,which could provide solutions to the water vulnerability of the welded wood.Moreover,the use of such a joining method would first free the Cameroonian furniture industry from the chemical industry,secondly position it at the forefront of new eco-design trends and thirdly make it competitive with other countries in the Central African sub-region.These works enrich the long and rich bibliography on the technique of wood welding,which has long been conspicuous by its absence of tropical woods.

Woods定理的正确性

本文重新给出 Woods定理的证明 ,证明了 Woods定理是成立的 ,因此认为该定理不成立的论断是不正确的 .此外 ,还给出了投入产出模型中投入系数矩阵 A各元素有变化时各部门完全需要系数 (即 L eontief逆矩阵 B各列 )增长率相同或按指定速率增长的充分必要条件 ,以及 A中仅一行 (列 )变化时各部门产出乘数(总产出 )按指定速率增长的充分必要条件 .

Wolf Nature,Dog Nature and Human Nature——An Interpretation of the Theme of Sherwood Anderson's Death in the Woods

This thesis,by analyzing the wolf nature,the dog nature and the human nature,and their relations,expounds the author's personal interpretation of the theme of Sherwood Anderson's short story Death in the Woods.The author maintains that Anderson reveals to readers the ugliness of life and the strange beauty of life,condemns the loss of love and the dehumanization of human life in the modern world and implies Anderson's deep concern on the human alienation,an important theme in the 20th century modern literature.

A Stylistic Analysis of “Stopping by Woods on a Snowy Evening”

This paper gives a stylistic analysis of the poem "Stopping by Woods on a Snowy Evening" by American poet Robert Frost, and then probes how the author achieves his expected goal through attracting readers' attention and leaving them much space to create their own imagination.

Analysis on the Theme of Death in the Woods by Means of Symbols

Sherwood Anderson is an American famous short story writer.The most enduring work of his is the short story sequence Winesburg,Ohio.He is good at capturing the real sound of everyday speech in his writing and creating it in new forms and styles.And Death in the Woods is considered as one of his most distinctive stories.It depicts a miserable old woman who feeds others all her life by using symbols to enrich the simple story.This paper intends to reveal the author's deep reflection of American's indifferent and apathetic attitudes in the whole society by means of the symbols of the person,color and dog.

独立林雪夜——Stopping by Woods on a Snowy Evening一诗的翻译和欣赏

分析了《StoppingbyWoodsOnaSnowyEvening》一诗的原义 ,并用适当的汉语和诗歌形式将原义表达出来。说明了此诗所描写的一种典型环境对揭示诗中人物性格所起的作用。

Simple phenols in tropical woods determined by UHPLC-PDA and their antioxidant capacities: an experimental design for Randall extraction using environmentally friendly solvents

A comprehensive experimental design was developed to determine suitable conditions(volume, percentage of solvent, extraction temperature) for the ethanol extraction of phenolic compounds from ten tropical woody plants. Wenge, angelim vermelho, zebrano, merbau,tigerwood, angelim pedra, jatoba, angelim amargoso,massaranduba, and doussie woods were used in experiments. The effects of three independent variables and their interactions on the yields of cinnamic and benzoic acid derivates were analyzed using UHPLC-PDA. The most significant parameters were found to be solvent percentage,extraction volume, and extraction temperature. Optimal conditions for the extraction of phenolic compound contents were an 80℃ extraction temperature, a 30 mL extraction volume, and the use of pure water as the extraction solvent. The tested species of woods contained mainly cinnamic acid derivates. Water extracts after hydrolysis contained greater amounts of cinnamic acid derivates than those extracts from non-hydrolyzed material.The total phenolics content was highest in water extracts of tigerwood, wenge and merbau;however, the extract of merbau wood was a stronger radical scavenger in ABTS?áassays: 34.11 ± 0.02 mM Trolox equivalents per g of dry extract. The main compounds possessing antioxidant activity in the extracts of vermelho wood assessed by UHPLC analysis were hydroxycinnamic acids.

Formalistic Study on Death in the Woods

Sherwood Anderson is famous American short story writer.Death in the woods is considered as one of his most famous and best short stories.In order to have a deeper understanding of this short story,in this paper,the formalistic approach will be used to analyze the whole text from the perspective of symbol and style.

Analysis on Quality of Coptis chinensis Grown under Different Woods

[Objectives] To analyze the quality of Coptis chinensis grown under woods of Magnolia officinalis Rehd. et Wils.,Platycladus orientalis( Linn.) Franco.,and Cunninghamia lanceolata( Lamb.). [Methods] The content of five kinds of alkaloids in C. chinensis grown under three different woods was determined by high-performance liquid chromatography( HPLC). Detection conditions: 0. 03 mol/L methanol and potassium dihydrogen phosphate solution( volume ratio of 65∶ 35) as the mobile phase,flow rate of 1. 0 mL/min,detection wavelength of 350 nm,and column temperature of 35℃. [Results] In these three woods,the quality of C. chinensis grown under P. orientalis woods was the highest. [Conclusions] This study is expected to provide certain references for cultivation and planting of C. chinensis under woods.

ONE MAN BAND!——专访科多巴尼龙弦吉他巡演之另类弗拉明戈吉他大师Ben Woods

11月12日起,为了让更多吉他爱好者了解尼龙弦吉他的魅力,魔方乐器公司携手各地经销商推出"Cordoba爱在尼龙弦"演奏会系列巡演!北京站的演出于12日晚在吉他发烧堂展厅蛊大上演。本次演出,"魔方"特邀了两位箱琴演奏艺术家,一位是来自美国的新派Flamenco巨匠Ben Woods大师,他的演奏风格以弗拉明戈为根基,再混合各类音乐,使现场气氛火爆异常!另一位则是古典吉他背景出身的赖康康老师,他是当今我国的尼龙箱琴指弹开创者,曲风悠扬,适合初次接触吉他音乐的爱好者,他本人的另种身份是著名的古典吉他演奏家和教育家。本刊记者也于第一时间专访了这两位不同风格的吉他艺术家。首先,请跟随本刊一同领略异域风情的弗拉明戈吉他大师Ben的风采吧。

Stopping by Woods on a Snowy Evening两个中译本对比赏析

罗伯特·弗罗斯特是20世纪美国最受欢迎的诗人之一,曾四度获得普利策奖。其代表作之一＂Stopping by Woods on a Snowy Evening＂已被译成多种版本来供中国的广大读者阅读与欣赏。本文通过文学文体学理论,从词汇表达、句法结构、修辞特征、衔接与语境四个方面对比与欣赏余光中和顾子欣对该诗的译本,揭示文学文体学理论对评价诗歌文体翻译的指导意义。

An Interpretation of the Theme of Death in the Woods

Death in the Woods is one of Sherwood Anderson’s masterpieces.This paper intends to explore the theme of Death in the Woods.The author reveals to readers the ugliness of life and the strange beauty of life in this short story.It condemns the loss of love and dehumanization of human life in the modern world and implies Anderson's deep concern for human alienation.It is an important theme of modern literature in the 20th century.

The Big Sleep in the Woods

Now it's the time of the bigsleep for the bees and the bears.Even the buds of the plantswhose leaves fall off share in it.But the intensity of this wintersleep, or hibernation, dependson who's doing it.The big sleepof the bears, for instance, wouldprobably be thought of as amighty bad case of inability

Damage Evaluation of Two Equatorial Hardwoods under Uniaxial Compression: Case of <i>Entandrophragma cylindricum</i>(Sapelli) and <i>Chlorophora exelcia</i>(Iroko)

This work aims at characterizing the evolution of the damage of two tropical hardwoods. Two species from Cameroon, the Entandrophragma Cylindricum and the Chlorora Exelcia were used for the purpose. Repeated compressive loading has been made on specimens strictly selected along with longitudinal and radial directions of each species. Each cycle was made of one phase of monotonic loading and a phase of elastic release. From data obtained, we determined the variation of Young modulus and plastic deformation during each cycle of loading, and we had deduced the damage of the material. Results show that the damage appears only after a certain threshold of the plastic deformation;that damage then grows exponentially to reach a threshold after which the failure of the material occurs. As well, we noticed that the growth of damage is accompanied by the progressive decrease of the Young modulus;this confirms the deteriorating effect of the damage on the mechanical properties. Elsewhere, the damage failure threshold is less than the theoretical value, and differs from one direction to another. Finally, we noticed that the damage failure threshold of sapelli is greater than that of iroko that allows concluding that iroko gets damaged and fails more rapidly than sapelli.

Demarcation of juvenile and mature woods of planted Chinese fir and its wood quality prediction

According to the dara of trashed length, micro fiber angle, air density, ring width and late wood percentage, with the analysis of optimum method of classification, the boundary line of juvenile wood and maturewood of planted Chinese fir (Cunninghamia lanceolata) was determined as the 14th year. Based on the variationpattern of these parameters, the prediction equations were established. Wood quality prediction can be realizedby these equations. By error analysis between the values of measured data and the values of prediction data, it isfound that the results of wood prediction of planted Chinese fire are satisfactory.

SYSTEMATIC STUDY OF PHYSICAL AND MECHANICAL PROPERTIES OF IMPORTANT CHINESE WOODS

In this paper,the physical and mechanical properties of important Chinese woodswere studied by using the methods of variable analysis, regression analysis,correlation analysis,principle component analysis and so on systematically.The results showed synthetical characteristicof the physical and mechanical properties of Chinese woods.Some opinions of former authors wererevised and some new laws were discovered.That is helpful to study of the physical and mechanicalproperties of woods.

GREUNEISEN FORM OF STATE EQUATION OF WOODS

In this paper the wood was regarded as the thermodynamie system. Using solid theory of crystalline state and thermodynamic theory, based on the expression of wood thermal capacity theory, the basic thermodynamic function of wood was derived. This paper emphasized the state equation of wood, brought it into Greuneisen form and comparcd the thcorctical value with the experimental value. And the relative error was in about 5%. This indicatcd that the results of the theoretical studies were right, explored a new way on the quantitative study of the physical characters of wood.

Preparation of epoxy resin/rare earth doped aluminate nanocomposite toward photoluminescent and superhydrophobic transparent woods

A translucent wooden substrate with long-lasting phosphorescence,high photostability and durability,tough surface,ultraviolet protection,high optical transmittance,and superhydrophobicity was developed.This long-lasting phosphorescent wooden substrate is able to continue emitting light for extended time periods.Lignin-modified wood(LMW)was immobilized with a solution of epoxy resin(ER)and rare-earth doped aluminate(REDA)phosphor nanoparticles(NPs).For an improved dispersion of pigment,REDA was synthesized in a nanoscale particle size,and characterized by transmission electron microscopy(TEM)to indicate a particle size of 8-14 nm.The crystal structure of REDA nanoparticles was also proved by X-ray diffraction(XRD).For an improved production of long-persistent phosphorescent colo rless woods,REDA must be well-dispersed in MAA without aggregation.Absorption and emissio n,as well as decay and lifetime spectra were explored.The morphologies of the wooden substrates with different ratios of REDA were investigated by scanning electron microscopy(SEM),X-ray fluorescence(XRF)analysis,Fourier transform infrared spectra(FT-IR),elemental mapping,and energy-dispersion Xray(EDXA).The phosphorescent woods show changes in color from colorless to green under ultraviolet(UV)irradiation,and to yellowish-green in the dark,as proved by the colorimetric parameters of the CIE Lab system.The afterglow wood samples display an absorbance band at 365 nm and two phosphorescent bands at 431 and 520 nm.Improved UV shielding,photostability,and hydrophobicity were explored.With increasing REDA ratio,both static contact and slide angles are found to improve in the ranges of147.6°-163.6°and 9°-14°,respectively.The long-lasting photoluminescence is optimized at a REDA ratio of 8%.The present strategy shows a large-scale production approach of multiple functional woods for many potential applications,such as smart glow in the dark windows and safety signs.

关于投入产出模型的比较静态分析——谦评Woods定理之误

在一个由n个部门组成的经济系统中,投入产出模型的基本模型是产量模型,即其中:x_i>0是总产出列向量X中的第i个元素,即部门i的总产出,b_(ij)≥0是列昂惕夫逆矩阵B=(I-A)^(-1)=(b_(ij))n×n中的第i行第j列元素,即部门j对部门i的完全需要系数,I是单位矩阵,A=(a_(ij))n×n。是非负的投入系数矩阵,y_j≥0是最终需求列向量Y中的第j个元素,即部门j的最终需求。与产量模型相对偶的是价格模型。