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Preparation and properties of chitosan-coated NPK compound
fertilizer with controlled-release and water-retention
Lan Wu
a,b
,Mingzhu Liu
a,*
a
Department of Chemistry and State Key Laboratory of Applied Organic Chemistry,Lanzhou University,Lanzhou 730000,PR China
b
College of Chemical Engineering,Northwest Minorities University,Lanzhou 730030,PR China
Received 22April 2007;received in revised form 5August 2007;accepted 8August 2007
Available online 6September 2007
Abstract
To improve the utilization of fertilizer and water resource at the same time,a new type chitosan-coated nitrogen,phosphorus and potassium compound fertilizer with controlled-release and water-retention (CFCW)was prepared,which possessed the three-layer struc-ture.Its core was water-soluble nitrogen,phosphorus and potassium (NPK)fertilizer granular,the inner coating was chitosan (CTS),and the outer coating was poly(acrylic acid-co-acrylamide)(P(AA-co-AM))superabsorbent polymer.Atomic absorption spectrophotometer and element analysis results showed that the product contained 7.98%potassium (shown by K 2O),8.14%phosphorus (shown by P 2O 5),and 8.06%nitrogen.The synthesis conditions of inversion suspension polymerization were studied systematically.The water absorbency of the product was 70times its own weight if it was allowed to swell in tap water at room temperature for 90min.The nutrients slow release behaviors of the CFCW in soil and water-retention capacity of the soil with CFCW were investigated.A possible slow release mechanism was proposed and the release rate factor K and the release exponent n of nutrients in CFCW was calculated.This product with good controlled-release and water-retention capacity,being degradable in soil and environment-friendly,could be especially useful in agricultural and horticultural applications.ó2008Published by Elsevier Ltd.
Keywords:Chitosan;P(AA-co-AM)superabsorbent;Controlled-release;Water-retention;NPK compound fertilizer
1.Introduction
The growth of plants and their quality are mainly a function of the quantity of fertilizer and water.So it is very important to improve the utilization of water resources and fertilizer nutrients.However,about 40–70%of nitrogen,80–90%of phosphorus,and 50–70%of potassium of the applied normal fertilizers is lost to the environment and cannot be absorbed by plants,which causes not only large economic and resource losses but also very serious environ-mental pollution.Recently,the use of slow release fertiliz-ers is a new trend to save fertilizer consumption and to minimize environmental pollution (Akelah,1996;Jar-osiewicz &Tomaszewska,2003).
Slow release fertilizers are made to release their nutrient contents gradually and to coincide with the nutrient requirement of a plant.These fertilizers can be physically prepared by coating granules of conventional fertilizers with various materials that reduce their dissolution rate.The release and dissolution rates of water-soluble fertilizers depend on the coating materials.At present,coating mate-rial’s degradability is an important focus of the research in this ?eld because of the renewed attention towards environ-mental protection issues (Ge et al.,2002;Shavit,Reiss,&Shaviv,2002).
Chitosan is a highly deacetylated derivative of chitin,one of the most abundant natural and biodegradable poly-mers.It has been widely applied in the biomedical,pharma-ceutical,and agricultural ?elds.In many of these applications chitosan is extremely attractive due to its bio-degradability,biocompatibility,and nontoxicity (Huacai,Wan,&Dengke,2006).Therefore,the soluble fertilizer
0144-8617/$-see front matter ó2008Published by Elsevier Ltd.*
Corresponding author.Tel.:+869318912387;fax:+869318912582.E-mail address:mzliu@https://www.wendangku.net/doc/279879920.html, (M.Liu).
https://www.wendangku.net/doc/279879920.html,/locate/carbpol
Available online at https://www.wendangku.net/doc/279879920.html,
Carbohydrate Polymers 72(2008)
240–247
coated by carbohydrate polymers,such as chitosan,would be an ideal slow release formulation.
Superabsorbents are loosely crosslinked hydrophilic polymers that can absorb and retain aqueous?uids up to thousands of times their own weight,and the absorbed water is hardly removable even under some pressure. Because of their excellent characteristics,superabsorbent polymers had been widely used in agriculture and horticul-ture(Zhang,Li,&Wang,2006).Recently,research on the use of superabsorbent polymers as water managing materi-als for the renewal of arid and desert environment has attracted great attention,and encouraging results have been observed as they can reduce irrigation water con-sumption,and lower the death rate of plants(Bajpai& Giri,2003;Lin,Wu,Yang,&Pu,2001).The optimized combination of slow release fertilizers and superabsorbent polymers may improve the nutrition of plants,mitigate the environmental impact from water-soluble fertilizers,reduce water evaporation losses,and lower the frequency of irrigation.
On the basis of the above background and our previous studies on superabsorbent polymers(Chen,Liu,&Ma, 2005;Qi,Liu,Chen,&Liang,2007)and slow release fertil-izers(Guo,Liu,Zhan,&Wu,2005;Liang&Liu,2006),we prepared in this study chitosan-coated NPK compound fertilizer with controlled-release and water-retention (CFCW),whose inner coating was chitosan(CTS),and the outer coating was poly(acrylic acid-co-acrylamide) (P(AA-co-AM))superabsorbent polymer.The product we prepared not only has controlled-release property but also could absorb water and preserve the soil moisture at the same time.These were signi?cant advantages over the nor-mal slow release fertilizers and superabsorbent polymers for agriculture,which general have only a controlled-release property or water-retention function.In addition, the chitosan in the?rst layer of the coating material was a biodegradable material and the copolymer of AA and AM of the outer coating material can also be degraded in soil,so the coating materials were not harmful to the soil. The aim of the present work is to reveal the synthesis con-ditions of inversion suspension polymerization,controlled-release,and water-retention properties of the CFCW.
2.Experimental
2.1.Materials
Chitosan(CTS,degree of deacetylation is0.9,average molecular weight is6.0·105)was kindly provided by Jinx-ing Biochemical Co(Zhejiang,China).Acrylic acid(AA, distilled under reduced pressure before use)was supplied by Beijing Eastern Chemical Works(Beijing,China). Acrylamide(AM),ammonium persulfate(APS,recrystal-lized from distilled water before use)and N,N0-methylene-bisacrylamide(NN MBA,used as received)were supplied by Shanghai Chemical Reagent Factory(Shanghai,China).2.2.Preparation of CFCW
NPK compound fertilizer granule,previously sieved to about2mm in diameter was placed into a rotary drum, and the CTS powder was stuck on the granules by means of epoxy dissolved in acetone.The adhesive was applied by spraying at regular time intervals.The process was?n-ished until compact and homogeneous coating formed on fertilizer granule.The coated granules were dried to a con-stant mass at room temperature for8h.Then the CTS-coated NPK compound fertilizer granules were obtained.
The CTS-coated NPK compound fertilizer granules (5g)were added into a?ask equipped with a mechanical stirrer,a condenser,and a drop funnel.A certain amount of carbon tetrachloride,polyethylene glycoloctyl phenyl ether(OP),and sorbite anhydride monostearic acid ester (Span-80)were added into the?ask.The temperature was raised to65°C using a water bath while the contents were constantly stirred.After that,a certain amount of mixed solution of partially neutralized acrylic acid(AA,by ammonia),acrylamide,N,N0-methylenebisacrylamide (NN MBA)solution,and ammonium persulfate(APS)solu-tion was slowly dropped into the?ask.The mixture was?l-tered to remove the carbon tetrachloride after being stirred for2h at65°C and then dried in a70°C oven to obtain the?nal product,chitosan-coated NPK compound fertil-izer with controlled-release and water-retention(CFCW).
https://www.wendangku.net/doc/279879920.html,ponent and structural analysis of CFCW
Contents of nitrogen,phosphorus,and potassium in the CFCW were determined by an element analysis instrument (Germany Elemental Vario EL Crop.,model1106)and atomic absorption spectrophotometer(American TJA Crop.,model1100-B).The structure of CFCW was also subjected to a scanning electron microscopy(SEM)study. They were split into two halves,and the fractions obtained were adhered to sample holders with carbon LIT-C glue. The sample was metal coated with a layer of gold and observed in a JSM-5600LV SEM manufactured in Japan.
2.4.Characterization of the outer coating material of CFCW by FTIR
The outer coating material of CFCW,P(AA-co-AM) was characterized by a Fourier Transform Infrared(FTIR) spectrophotometer(American Nicolet crop.,model170-SX).
2.5.Measurement of water absorbency of CFCW
A sample(1g)of the CFCW was immersed into a cer-tain amount of tap water and allowed to soak at room tem-perature for90min.The swollen CFCW was?ltrated through an80-mesh sieve to remove non-absorbed water and weighted.The water absorbency was calculated using
L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247241
WA?MàM0
M0
e1T
Here M and M0denote the weight of swollen CFCW and the weight of the dry CFCW,respectively,and WA is the water absorbency per gram of dried CFCW.
2.6.Slow release behavior of CFCW in soil
To study the slow release behavior of CFCW in soil,the following experiment was carried out:1g of CFCW was well mixed with200g of dry soil(below26-mesh)and kept in a200ml beaker properly covered and incubated for dif-ferent periods at room temperature.Throughout the exper-iment,the soil was maintained at30wt%water-holding capacity by weighing and adding distilled water if neces-sary,periodically.After1,3,5,10,15,20,25and30days incubation period,the remaining granular CFCW in the beakers were picked out and washed with distilled water, and then dried at room temperature overnight to estimate the contents of N,P and K.For eight measurements,eight beakers were prepared at the same time.The remaining amount of N,P and K was estimated by the Kjeldahl method of distillation(Abraham&Rajasekharan,1996) and atomic absorption spectrophotometer,respectively.
The release results were analyzed by using an empirical equation to estimate the value of n and K as follows(Al-Zahrani,1999;Peng,Zhang,&Kennedy,2006):
M t M ?Kt n or log
M t
M
?logeKTtn logetTe2T
where M t/M is the released fraction at time t,n is the re-lease exponent,and K is the release factor.From the slope and intercept of the plot of log(M t/M)versus log(t),kinetic parameters n and K were calculated.
https://www.wendangku.net/doc/279879920.html,rgest water-holding ratio of the soil
The sandy soil used in this study was representative of the area of Lanzhou,which lies in the northwest of China and is a dry and semi-desert region.A2g sample of CFCW was well mixed with200g of dry soil(below26-mesh)and placed in a PVC tube of4.5cm diameter;the bottom of the tube was sealed by nylon fabric(with an aperture of 0.076mm)and weighed(W1).The soil samples were slowly drenched by tap water from the top of the tube until the water seeped out from the bottom.After there was no seep-ing water at the bottom,the tube was weighed again(W2).
A control experiment,viz.,with no CFCW,was also car-ried out.The largest water-holding ratio(W%)of the soil was calculated using the following equation:
100?eW2àW1T2.8.Measurement of the water retention of CFCW in soil
Two grams of CFCW was well mixed with200g of dry sandy soil(below2mm in diameter)and kept in a beaker and then200g of tap water was slowly added into the bea-ker and weighed(W1).A controlled experiment,i.e.,with-out CFCW,was also carried out.The beakers were maintained at room temperature and were weighed every 4days(W i)over a period of28days.The water retention ratio(WR%)of soil was calculated using the following equation:
WR%?
W i
W1
e4T3.Results and discussion
3.1.The structure and characteristics of CFCW
The structure of CFCW fertilizer granule was the three-layer,which the core is NPK compound fertilizer (52.8wt%),the inner coating is CTS(12.3wt%)and the outer coating is P(AA-co-AM)superabsorbent polymer (34.9wt%),respectively(see Fig.1).Element analysis and atomic absorption spectrophotometer results showed that N,P,and K contents of CFCW were8.06,8.14% (shown by P2O5),and7.98%(shown by K2O)wt%.The average weight of the CFCW fertilizer granules was0.26 g.The average diameters of dry CFCW and swollen CFCW granules in tap water were 2.3and12.4mm, respectively.
3.2.FTIR analysis of P(AA-co-AM)(the outer coating material)
The infrared spectrum of P(AA-co-AM)shows in Fig.2. The observed peaks are at3439cmà1,corresponding to N–H stretching of acrylamide unit,2925cmà1,correspond-ing to the C–H stretching of acrylate unit,1701cmà1,cor-responding to the stretching of C@O in acrylate unit, 1635cmà1,corresponding to the carbonyl moiety of the acrylamide unit,1075cmà1,corresponding to the–CO–O–stretching of acrylate unit.These results proved that the outer coating was P(AA-co-AM)superabsorbent polymer.
3.3.In?uence of the parameters on water absorbency
The key properties of superabsorbent polymers are the water absorbency and the elastic modulus of the swollen crosslinked gel,both of which are related to the crosslink-ing density of the network.To improve the water absor-bency capacity of the CFCW,various reaction parameters are employed.The complete details of the in?u-ence of the reaction parameters on water absorbency in tap water,such as the content of AM,crosslinking agent,initi-
242L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247
3.3.1.E?ect of the amount of AM on water absorbency
Hydrophilic group plays an extremely important part in water absorbency.In the P(AA-co-AM)polymeric system, the ratio of di?erent hydrophilic groups can be adjusted by changing the proportion of AA–AM.The e?ect of the amount of AM on water absorbency of CFCW is shown in Fig.3.The water absorbency increases as the amount of AM rise from10to20wt%and decreases when the amount of AM is greater than20wt%.It is known that AM is a nonionic monomer.It almost does not ionize in solution,so the ions in solution have little in?uence on it, which would improve the salt-resistance ability of CFCW. Therefore,with the increase of the amount of AM,water absorbency would increase with that.On the other hand,–COOàgroup has better hydrophilic ability than –CONH2,so water absorbency would decrease with the further increase of the amount of AM.In other words, the maximum in the dependence of water absorbency on the amount of AM could be attributed to the cooperation e?ect between the salt-resistance property of the–CONH2 group and the high hydrophilic ability of the–COOàgroup.
3.3.2.E?ect of the amount of initiator on water absorbency
Fig.4shows the e?ect of the amount of initiator on water absorbency of CFCW.The water absorbency increases as the amount of initiator rise from0.45to
L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247243
0.91wt%and decreases when the amount of initiator is greater than0.91wt%.According to the theory of Flory (Flory,1953),the molecular weight in free radical polymer-ization will decrease with an increase of initiator concentra-tion.With the decrease of the molecular weight,the relative amount of polymer chain ends increases.As reported in a previous study(Kiatkamjornwong&Wongwatthaasatien, 2004),the polymer chain ends do not contribute to the water absorbency.Therefore,the increase of the amount of initiator is responsible for the decrease in water absor-bency.However,further decreases in the amount of initia-tor below the optimum values are accompanied by a decrease in water absorbency.This result may be attributed to a decrease in the number of radicals produced as the amount of initiator decreases.The network cannot form e?ciently with a small number of radicals in the free radi-cal polymerization that result in the decrease of the water absorbency.
3.3.3.E?ect of the amount of crosslinking agent on water absorbency
The crosslinking agent plays an important role in the formation of three-dimensional network structures perma-nently in the polymerization process.This is also a prom-ising factor directly a?ecting the water absorbency of CFCW.Fig.5shows the water absorbency in tap water as a function of the amount of crosslinking agent.It can be found that there exists a maximum,and the high-est water absorbency occurs at0.28wt%crosslinking agent.When the crosslinking agent is lower than0.28 wt%,the water absorbencies decrease because of the increase of soluble materials.On the other hand,higher crosslinking agent results in the generation of more cross-link points,which in turn cause the formation of an addi-tional network and decrease the space for holding water. These results are in conformity with the theory of Flory (Flory,1953).3.3.4.E?ect of neutralization degree of AA on water absorbency
The neutralization degree of AA dependence of water absorbency of CFCW is presented in Fig.6.Neutralization degree is de?ned as the molar percentage of carboxyls in AA neutralized by ammonia.It can be found that there exists a maximum and the highest water absorbency occurs at neutralization degree=70%.It was expected that the activity of acrylic acid is higher than acrylate,when the neutralization degree was lower than70%,the lower neu-tralization degree was faster than the rate of the polymeri-zation,the content of the oligomers would increase,and the content of acrylate would decrease,so the soluble part increased and the electrostatic repulsion between the attached carboxylate anions decreased,so that the stretch-ing extend of hydrogel network decreased,and this resulted in water absorbency increasing with the increase of neutral-ization degree.It was expected that the activity of acrylic acid is higher than acrylate so the lower the neutralization degree was,the faster the polymerization rate was,and the high polymerization rate would result the increase of the content of oligomers(the soluble part)in CFCW.At the same time,the charge density of the network would increase with the increase of neutralization degree,and this would result the increase of the stretching extend of the hydrogel network,so it is easy to understand the increase of water absorbency as the neutralization degree increased from0to70%.
3.4.Slow release behavior of CFCW
One of the most important characteristics of CFCW we prepared was its controlled-release property.Fig.7repre-sents the N,P and K slow release behaviors of CFCW in soil.It could be seen from Fig.7that the N,P,and K in CFCW released14.7,10.9and12.4%on the3rd days, 19.2,14.3and16.7%on the5th days,and79,62,and
244L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247
69%on the30th days,respectively.With the sum of nutri-ents release lower than15%on the3rd day and not above 75%on the30th day,this indicated that the slow release character of the CFCW we prepared agreed with the stan-dard of slow release fertilizers of the Committee of Euro-pean Normalization(CEN)(Trenkel,1997),and also indicated that the CFCW had an excellent controlled-release property.
The nutrient release mechanism of CFCW in soil can be
described by the following steps:(1)The outer P(AA-co-AM)layer is slowly swollen by the water in soil and trans-forms to hydrogel.A dynamic exchange between the free water in the hydrogel and the water in soil will develop (David&Mark,1994;Smyth,Francis,&Vincent,1998).
(2)When the free water in the P(AA-co-AM)layer migrates to the middle layer,i.e.CTS coating,the water will penetrate the inner coating slowly in the initial stage and the dissolved NPK compound fertilizer in the core. In this stage,di?usion would be the release rate-limiting step.(3)Under the e?ect of water,ions and microorgan-isms existing in the soil,the middle CTS layer will slowly degrade in the last stage and continue to dissolve NPK compound fertilizer.In this stage,degradation rate deter-mines the nutrients release rate.(4)The dissolved NPK compound fertilizer di?uses out the CTS layer and enters into the P(AA-co-AM)layer,and then releases into the soil through the dynamic exchange of free water.
The n value is an empirical parameter characterizing the release mechanism(Shaviv,2000).On the basis of the dif-fusion exponent,an n value of0.5indicates the nutrient release mechanism approaches to a Fickian di?usion con-trolled release,whereas n equal to1.0indicates the nutrient release mechanism approaches to zero-order release.The n value from0.5to1.0is a nutrient release mechanism for non-Fickian di?usion or chain relaxation control release. From the plot of log(M t/M)versus log(t)(Fig.8),the release exponent(n)and release factor(K)have been calcu-release from CFCW in soil.The n value is in the range from 0.52to0.57.Therefore,the nutrients release mechanism is non-Fickian di?usion,and is controlled by a combination of di?usion of fertilizer from coating material and degrada-tion rate of CTS layer.Additionally,due to the existing of many kinds of ions in soil solution,the swelling degree of P(AA-co-AM)is less in soil than that in distilled water, then the di?usion of soluble fertilizer in it would be di?-cult,which also contribute to slow release of nutrients from CFCW(Li&Wang,2005).
3.5.The largest water-holding ratio of the soil
Besides its controlled-release property,another one of the most important characters of the CFCW we prepared is its water-retention capacity or,in other words,its e?ec-tive utilization of water in arid and desert regions to trans-form them into‘‘green and fertile lands’’.It was reported (Bakass,Mokhlisse,&Lallemant,2002)that the use of superabsorbent polymer in the agricultural?eld could increase the largest water-holding capacity and water reten-tion capacity of soil.Therefore,the experiments to test the water-holding capacity and water retention behaviors of soil with CFCW were performed.The experiment results of the largest water-holding ratio of the soil indicated that the largest water-holding ratio of the soil without CFCW was30.17%,and that of the soil with CFCW was40.35%
Table1
The release factors(K),release exponents(n),and determination coe?-
cients(r2)following linear regression of release data of nutrients from
CFCW in soil
Nutrients n K r2
N0.527.480.9851
K0.54 6.190.9905
P0.57 5.200.9899 L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247245
than the former.This showed that the CFCW we prepared still had excellent water absorbency in soil,could obviously improve the water-holding capacity of the soil,and could e?ciently store rainwater or irrigation water resources. This was one of the signi?cant advantages over the normal slow release fertilizers.
3.6.Water retention behavior of CFCW in soil
The most important application of CFCW is for agricul-ture and horticulture,especially for saving water in dry and desert regions and for accelerating plant growth.So,it is necessary to investigate the water-retention ability of CFCW in soil.Fig.9shows the water-retention behaviors of the soil with(a)and without(b)CFCW.From Fig.9 we?nd that the addition of CFCW to soil could obviously increase the water-retention and decrease the water evapo-ration.The water retention ratio of soil without CFCW had only remained12.4and 2.6wt%on the10th and 20th days,respectively,while that of the soil with CFCW was24.7and15.5wt%,respectively.After30days,the soil without CFCW had already given o?all the water,while the soil with CFCW still had7.8wt%water-retention ratios.
From this study,it could be inferred that CFCW had good water-retention capacity in soil,and that with CFCW use water can be saved and managed so that they can be e?ectively used for the growth of plant.These were the signi?cant advantages over the normal slow release fertilizers,which always only had a controlled-release property.The reason was that the outer coating of CFCW could absorb and store a large quantity of the water in soil,and allow the water absorbed in it to be slowly released with the decrease of the soil moisture. Simultaneously,nutrition could also be released slowly with the water.Therefore,the swollen CFCW was just like an additional nutrient reservoir for the plant–soil sys-tem,and thus could increase the utilization e?ciency of water and fertilizer at the same time.Furthermore,as we known,the chitosan in the?rst layer of the coating material was a biodegradable material(Borzacchiello et al.,2001)and the copolymer of AA and AM of the outer coating material can also be degradable in soil (Ye,Zhao,&Zhang,2004),so the coating materials were not harmful to the soil.Thus there would be a good use potentiality in dry-prone regions.
3.7.Morphological analysis
From the SEM of the surface of the CFCW,it can be seen that the surface of CFCW is rugged,which structur-ally increased the surface area of the CFCW.Therefore, when CFCW is dipped in water,it can absorb water quickly to form a swollen hydrogel,which is responsible for the water-retention property of CFCW.The SEM of the cross-section of the CFCW shows the three-layers structure of CFCW.The outer layer is P(AA-co-AM) superabsorbent polymer,which could absorb a large amount of water.The middle layer is CTS,which serves as a physical barrier for mass transfer,and reduces the rate of water di?usion into the core and the nutrient di?usion outside the core,this provided the CFCW with a good con-trolled-release property.The inner core is a water-soluble NPK compound fertilizer granule.In summary,the outer P(AA-co-AM)layer enables the CFCW water-retention property,and the middle CTS layer enables the CFCW controlled-release property.
4.Conclusions
A chitosan-coated NPK compound fertilizer with con-trolled-release and water-retention(CFCW)was prepared, which possessed the three-layer structure.Its core was water-soluble NPK fertilizer granular,the inner coating was chitosan(CTS),and the outer coating was P(AA-co-AM)superabsorbent polymer.Element analysis and atomic absorption spectrophotometer results showed that the N,P and K contents were8.06,8.14(shown by P2O5) and7.98(shown by K2O)wt%,respectively.The product had good slow release property,the nutrients released did not exceed75%on the30th day.The analysis of release showed that nutrient might be released from CFCW in soil by non-Fickian di?usion mechanism.The addition of CFCW into soil could greatly improve the water holding ability and water retention property of the soil.Moreover, this new approach showed promising in utilizing natural resource such as chitosan in the production of coating material,which could signi?cantly reduce the production cost and make the technique quite environmental friendly. The results of the present work indicate that the CFCW was a good slow release fertilizer with excellent water-retention capability.Therefore,CFCW would?nd good application in agriculture and in the renewal of arid and
246L.Wu,M.Liu/Carbohydrate Polymers72(2008)240–247
Acknowledgement
This work was supported by Special Doctorial Program Funds of the Ministry of Education of China(Grant No. 20030730013).
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数字视音频技术
1)英文缩写的中文全称 BD(Blu-ray Disc蓝光光盘) HD(High Defination高解析度) DVD(Digital Video Disc数字视频光盘) CD (COMPACT DISC激光唱片) EVD(Enhanced Versatile Disk增强型多媒体盘片系统) DTS-HD(数字影院系统) HDMI(High Definition Multimedia Interface高清晰多媒体接口) 2) 欣赏音乐的主要内容 旋律,乐器,低中高频率成分,立体声空间感,乐器层次解析度,和声,情感抒发 3) 9C消费电子产品制造商:索尼,飞利浦,松下,日立,LG,先锋,三星,夏普,汤普森 4) 美国7大制片商 华纳,20世纪福克斯,迪斯尼,米高梅(索尼)华纳,环球,派拉蒙,梦工厂(东芝) 5) 消费类电子产品和影音制造业在国家经济发展中的地位和战略 消费类电子和影音制造的销售已经超过了家具,汽车等产品,成为国家经济增长的一个重要推动力.随着中国经济的快速发展，中国的经济发展进入了一个新的关键时期,而从扩大内需来看，家电产品，或者说消费电子产品，已经成为了其中的一个重要的方面,消费结构变化,消费品质提升.第一，我们继续支持和鼓励家电企业扩展消费类电子产品的销售，特别是要在农村市场销售方面的拓展；第二，通过商务部掌握的市场信息，向工商企业提供第一手的市场需求；第三，要鼓励中国的家电生产和销售企业走出去，走出国门，走向世界；第四，就是要维护公平竞争秩序，促进工商业共同发展。 6) CBHD标准的中文含义?那些技术专利属于中国公司? 中国蓝光高清光盘,物理格式中的调制编码部分;音视频压缩,导航系统以及版权保护系统方面的专利是中国公司和国外公司共有. 7) 多媒体系统包括哪六个基本形式? 感觉形式;机器表示;交互技术;存储技术;传输媒介;传输媒体的操作软件 8) 当今社会的3大基本资源?能源,材料,信息 9) 多媒体技术处理的6个对象?文本,图形,图像,动画,声音,视频 10) 商业上的高清和全高清的平板显示器的分辨率各为多少? 商业高清HD:1366x768标清数字节目商业全高清FullHD:1920x1080高清节目11) 高清(倍线)DVD播放机的主要功能是什么/ 二维分辨率升频，提升DVD视频讯号至高清息层次，还设有Dual PureCinemaProfressive Scan,对影像扫描率加倍，形成稳定清晰的影院式效果。 12) WiFi:802.11b标准, 载波频率为 2.4GHz 数码传输频率为11Mps带宽可高达 5.5Mbps通讯距离为76~122米 13) CMMB代表China Mobile Multimedia Broadcasting （中国移动多媒体广播） 其信号传输过程为利用大功率S波段卫星信号覆盖全国，利用地面增补转发器同频同时同内容转发卫星信号补点覆盖卫星信号盲区，利用无线移动通信网络构建回传通道，从而组成单向广播和双向交互相结合的移动多媒体广播网络。 14) 模拟声信号在采样量化中的量化精度决定了音响系统的什么特性?决定信噪比 15) 模拟声信号在采样量化中的采样频率过低会影响音响系统的什么特性？ 还原后的模拟声音将失去原声中的高频成分 16) DSD数字音响标准主要是哪些公司提出的？ Direct Stream Digital 索尼和飞利浦 17) PCM,MIDI,DSD,SACD的英文全称是什么？ PCM数字音频文件Pulse Code Modulation MIDI乐器数字接口Musical Instrument Digital Interface DSD 直接数据流Direct Stream Digital
旅游与文化 翻译
旅游与文化I Part I 1．charming autumn scenery in a most fresh air and clear weather 秋高气爽，秋色宜人 2．the 15th General Assembly Session of the World Tourism Organization 世界旅游组织第15届全体大会3．to travel ten thousand li and read ten thousand books 读万卷书，行万里路 4．enriching themselves mentally and physically 承天地之灵气，接山水之精华 5．tourist arrival 旅游人数 6．foreign currency receipts 外汇收入 7．outbound tourists 出境旅游人数 8．unique, rich and varied tourism resources 得天独厚的旅游资源 9．World Cultural and Natural Heritages sites 世界文化遗产地和世界自然遗产地 10．t o add radiance and charm to each other 交相辉映 11．a thriving modern metropolis 繁华的现代化大都市 12．a patchwork of cottages 村舍星罗棋布 13．t o exist side by side 鳞次栉比 14．I nternational Architecture Exhibition 万国建筑博览会 15．c lock towers and turrets , marble pillars 钟塔、角楼和大理石柱 16．e ach representing a distinctively individual appearance 风格迥异，各领风骚 17．t he rainy season 梅雨季节 18．t o linger longer 留连忘返 19．e xcellence, elegance and the best quality 卓越超群，富丽堂皇，一流质量 20．e mbroidery, inlaid lacquer 刺绣，金漆镶嵌 21．g old and silver jewelleries, water-color woodblock prints 金银首饰，木刻水印 22．c arvings in jade, ivory, bamboo and woven bamboo baskets 玉雕、牙雕，竹雕，竹编筐篮 23．b ird cages, lanterns 鸟笼灯笼 24．d ouble-sided embroidery and sandal wood fans from Suzhou 双面绣和苏州的檀香扇 25．t erracotta teapots from Yixing, and clay figures from Wuxi 宜兴的陶制茶壶和无锡的泥人 26．t he Peach Blossom Fair 桃花节 27．t he Daci Temple Fair 大慈寺庙会 28．t he Chengdu Tourism Festival 成都旅游节 29．a place blessed with favorite climate, fertile land, rich resources and outstanding talents 物华天宝，人杰地灵30．s uperb artistic style of aiming at catching the sprit of the landscape 写意山水 31．a rtistic gems 艺术瑰宝 32．U NESCO Heritage Committee 联合国教科文组织遗产委员会 33．t he list of World cultural heritage 世界文化遗产名录 34．b ronzeware 青铜器 35．b amboo, wood and lacquer ware 竹木漆器 36．i nscribed bones and tortoise shells 甲骨 37．s eals 玺印 38．a rchaeology 39．r estoration room 文物修复馆 旅游与文化II Part II景点描述常用语 Match work: 雄伟壮丽imposing 灯火辉煌glittering
数字音视频技术考核内容
数字音视频技术考核内容 1、声波基本要素：振幅、频率、频谱 2、彩色三要素：亮度、色调、饱和度 3、音视频输入有设备哪些？ 话筒、摄像机等 4、音视频模/数（A/D）数/模（D/A）转换的设备有哪些？ 非线性编辑卡、数字录像机等。 5、数字音视频节目存储介质： 磁带、光盘、磁盘等 6、模拟音频信号波形的振幅反映了是什么、频率反映了是什么？ 用信号的幅度值来模拟音量的高低，音量高，信号的幅度值就大。 用信号的频率模拟音调的高低，音调高，信号的频率就高。 模拟信号具有直观、形象的特点。 7、视频分量YUV的意义及数字化格式（比例）？ 用Y:U:V来表示YUV三分量的采样比例,则数字视频的采样格式分别 有4:2:0 ,4:1:1、4:2:2和4:4:4多种 8、音频信号的冗余度有哪些？ 1、 时域冗余:: (1)、幅度分布的非均匀性(2)、样值间的相关性 (3)、周期之间的相关性(4)、基音之间的相关性(5)、静止系数(6)、长时自相关函数 2、 频域冗余： (1)、长时功率谱密度的非均匀性。(2)、语音特有的短时功率谱密度。 3、 听觉冗余： ①人的听觉具有掩蔽效应。②人耳对不同频段的声音的敏感程度不同，通常对低频段较之高频段更敏感。③人耳对音频信号的相位变化不敏感 9、视频信号具有的特点： 、直观性：人眼视觉所获得的视频信息具有直观的特点，与语音信 1、直观性： 息相比，由于视频信息给人的印象更生动、更深刻、更具体、更直接，所以视频信息交流的效果也就更好。这是视频通信的魅力所在，例如电视、电影。 、确定性：“百闻不如一见”，即视频信息是确定无疑的，是什么 2、确定性： 就是什么，不易与其他内容相混淆，能保证信息传递的准确性。而语音则由于方言、多义等原因可能会导致不同的含义。 、高效性：由于人眼视觉是一个高度复杂的并行信息处理系统，它 3、高效性： 能并行快速地观察一幅幅图像的细节，因此，它获取视频信息的效率要
《论语十则》——《中国文化经典研读》(整理)
《论语十则》——《中国文化经典研读》（整理） 1 子曰:“君子食无求饱，居无求安，敏于事而慎于言，就(1)有道(2)而正(3)焉，可谓好学也已。” 【注释】 (1)就:靠近、看齐。 (2)有道:指有道德的人。 (3)正:匡正、端正。 【译文】 孔子说:“君子，饮食不求饱足，居住不要求舒适，对工作勤劳敏捷，说话却小心谨慎，到有道的人那里去匡正自己，这样可以说是好学了。” 2 2?4 子曰:“吾十有(1)五而志于学，三十而立(2)，四十而不惑(3)，五十而知天命(4)，六十而耳顺(5)，七十而从心所欲不逾矩(6)。” 【注释】 (1)有:同“又”。 (2)立:站得住的意思。 (3)不惑:掌握了知识，不被外界事物所迷惑。 (4)天命:指不能为人力所支配的事情。 (5)耳顺:对此有多种解释。一般而言，指对那些于己不利的意见也能正确对待。 (6)从心所欲不逾矩:从，遵从的意思;逾，越过;矩，规矩。 【译文】 孔子说:“我十五岁立志于学习;三十岁能够自立;四十岁能不被外界事物所迷惑;五十岁懂得了天命;六十岁能正确对待各种言论，不觉得不顺;七十岁能随心所
欲而不越出规矩。” 3 子曰:“由(1)，诲女(2)，知之乎,知之为知之，不知为不知，是知也。” 【注释】 (1)由:姓仲名由，字子路。生于公元前542年，孔子的学生，长期追随孔子。 (2)女:同汝，你。 【译文】 孔子说:“由，我教给你怎样做的话，你明白了吗,知道的就是知道，不知道就是不知道，这就是智慧啊～” 4.颜渊、季路侍(1)。子曰:“盍(2)各言尔志。”子路曰:“原车马，衣轻裘，与朋友共，敝之而无憾。”颜渊曰:“愿无伐(3)善，无施劳(4)。”子路曰:“愿闻子之志。”子曰:“老者安之，朋友信之，少者怀之(5)。” 【注释】 (1)侍:服侍，站在旁边陪着尊贵者叫侍。 (2)盍:何不。 (3)伐:夸耀。 (4)施劳:施，表白。劳，功劳。 (5)少者怀之:让少者得到关怀。 【译文】 颜渊、子路两人侍立在孔子身边。孔子说:“你们何不各自说说自己的志向,”子路说:“愿意拿出自己的车马、衣服、皮袍，同我的朋友共同使用，用坏了也不抱怨。”颜渊说:“我愿意不夸耀自己的长处，不表白自己的功劳。”子路向孔子说:“愿意听听您的志向。”孔子说:“(我的志向是)让年老的安心，让朋友们信任我，让年轻的子弟们得到关怀。” 5 子曰:“知之者不如好之者，好之者不如乐之者。” 【译文】
sdarticle11
Effect of shearing on crystallization behavior of poly(ethylene naphthalate) W.J.Yoon,H.S.Myung,B.C.Kim,S.S.Im * Department of Textile Engineering,Hanyang University,Haengdang,Seongdong,Seoul 133-791,South Korea Received 11August 1999;received in revised form 24September 1999;accepted 30September 1999 Abstract The effect of shear history on the isothermal crystallization behavior of poly(ethylene naphthalate)(PEN)was investigated by rheological and morphological measurements.Time sweep measurements of storage modulus (G H )and dynamic viscosity (h H )were carried out on the molten PEN by Advanced Rheometric Expansion System (ARES)in the parallel-plate geometry at several different temperatures and frequencies,followed by structural analysis by differential scanning calorimeter (DSC),X-ray diffractometer,and polarizing microscopy for the shear-induced crystallized PEN specimens in the ARES measurements.The rate of isothermal crystallization of PEN was notably affected by temperature,while the shear rate has an important effect on the structures of the resultant crystals.At a constant shear rate,the rate of crystallization by shear-induced structuring mechanism was increased with lowering temperature over the temperature range 230–250?C.The rate of crystallization was increased with increasing shear rate at a given temperature.An increase in shear rate increased both nucleation and number of crystallites.Further,it increased the content of the a -form crystal in the specimen.On the other hand,lower shear rate offered more favorable conditions for forming the b -form crystal.DSC analysis exhibited that the b -form crystal had higher melting temperature (T m )than the a -form crystal.The wide angle X-ray diffraction (WAXD)patterns also ascertained that higher content of the a -form crystal was produced in the PEN specimen crystallized at higher frequency.?2000Elsevier Science Ltd.All rights reserved. Keywords :Poly(ethylene naphthalate);Rheology;Shear-induced crystallization 1.Introduction Shear-induced structural changes in polymeric materials take an increasing interest in the ?eld of polymer proces-sing.In real polymer processing very complex deformation histories are involved,which can in?uence ultimate proper-ties of plastics.Recent advances in experimental techniques that allow in situ measurements of materials under deforma-tion have escalated research in this subject area.It has been known for a long time that ?ow stress have accelerating effect on the crystallization of semi-crystalline polymers [1–6].It is supposed that the application of a shear stress to a polymer melt should lead to formation of orientation and reduce the entropy of the melt,which results in a higher melting temperature and,hence,lead to an increased super-cooling [3,7].Several experiments have been described in the literature where attempts were made to quantify the shear stress-induced crystallization in molten semi-crystal-line polymers such as polypropylene [3,8,9],polyethylene oxide [10],polypropylene [11–13],and polybutene-1[3,14].Some investigators used rotational viscometers and measured either the volume change [15]or the number of nuclei formed during shearing [11,14].The polymers enum-erated above are apt to process because of low melting point and viscosity.On the other hand,PEN has good thermal and mechanical properties and is being used as engineering plastics.PEN is reported to have two different triclinic crystalline structures,a -form and b -form crystals.Of two crystal forms,the b -form crystal is known to be more stable than the a -form.The effect of crystallization temperature on the resultant crystal structure is well recognized;lower temperature favors formation of the a -form crystal.The critical temperature is reported about 230?C.However,the effect of shear history on the crystal structure of PEN has not been reported.In this study,the shear-induced crystallization behavior of PEN was investigated on the rheological basis.The effect of shear history on the crystalline structure was also discussed in terms of thermal and morphological properties.2.Experimental 2.1.Material The PEN tested was a commercially available grade Polymer 41(2000)4933–4942 0032-3861/00/$-see front matter ?2000Elsevier Science Ltd.All rights reserved.PII:S0032-3861(99)00703-X *Corresponding author.Tel.:?82-2-2292-0495;fax:?82-2-2297-5859.E-mail address:imss007@email.hanyang.ac.kr (S.S.Im).
sdarticle2
Computational note Electronic dipole polarizabilities of polychlorinated dibenzofurans and semiempirical PM6level performance Andrea Alparone,Vito Librando * Research Centre for Analysis,Monitoring and Minimization Methods of Environmental Risk,Department of Chemistry,University of Catania,viale A.Doria 8,Catania I-95125,Italy Polychlorinated dibenzofurans (PCDFs)are widespread and per-sistent environmental contaminants [1].Electronic dipole polariz-abilities (a )of PCDFs were previously computed at the B3LYP level with cc-pVDZ,6-31G ?and 6-31G ??basis sets in order to elucidate the effect of the substituent position on the congener speci?c tox-icity [2,3]and aqueous solubility [4].Recently,semiempirical PM6method [5]has been implemented in MOPAC 2007package [6],giving satisfactory estimates of molecular properties such as heats of formation [5]and electronic a values [7,8]. This work is principally concerned on the validation of the PM6method in the determination of a values,focusing attention on DF and the 135PCDF congeners (Fig.S1of the Supporting Material).Static a ij (i,j =x ,y ,z )components were calculated at the AM1,PM3and PM6levels.Additionally,we computed a ij values for DF and its octacloro substituted congener at the HF,MP2and PBE0levels with aug-cc-pVDZ basis set on the B3LYP/6-31G ??geometry.Present computations were performed with MOPAC 2007[6]and PC GAMESS [9,10]programs.Calculated average polarizability,h a i ?1=3ea xx ta yy ta zz T,and polarizability anisotropy,D a ? f 1?ea xx àa yy T2tea xx àa zz T2tea yy àa zz T2t6ea 2xy ta 2 xz ta 2yz T g 1=2,are given in Tables S1–S3of the Supporting Material.The results show that PM6is noticeably superior to both the commonly em-ployed semiempirical AM1and PM3methods,reproducing the PBE0/aug-cc-pVDZ (and also MP2/aug-cc-pVDZ)h a i values of DF and 1,2,3,4,5,6,7,8-OCDF within 5a.u.(2–3%)and D a data within 8–11a.u.(3–8%),geometrical effects (PM6vs.B3LYP/6-31G ??)being almost negligible.Note that the corresponding deviations for h a i obtained using the AM1,PM3and B3LYP/6-31G ??[3]data are substantially larger,being 36–94a.u.(25–34%),41–76a.u.(27–28%),24–47a.u.(16–17%),respectively,while those for D a are 22–25a.u.(9–20%),16–43a.u.(12–18%)and 11–14a.u.(4–11%),respectively.However,least-mean squared ?tting linear relationships between the semiempirical and B3LYP/6-31G ??h a i and D a data (See Figs.S2and S3of the Supporting Material)are satisfactory (r 2=0.97–1.00).As can be appreciated from Figs.S4and S5of the Supporting Material,on passing from PM6to AM1(PM3),h a i and D a values decrease and increase by 21–33%(26–28%)and 13–31%(19–23%),respectively.These discrepancies are principally originated from differences in the out of the plane polarizability component.Due to its relatively low computational cost and good accuracy,PM6is a promising method for the predic-tion of a of large p -conjugated systems and is particularly indi-cated for QSPR studies.Acknowledgement Work partially supported by MIUR,Rome.Appendix A.Supplementary data Supplementary data associated with this article can be found,in the online version,at doi:10.1016/j.theochem.2008.09.023.References [1]S.Safe,Crit.Rev.Toxicol.21(1990)51. [2]S.Hirokawa,T.Imasaka,T.Imasaka,Chem.Res.Toxicol.18(2005)232.[3]C.Gu,X.Jiang,X.Ju,G.Yu,Y.Bian,Chemosphere 67(2007)1325. [4]G.Yang,X.Zhang,Z.Wang,H.Liu,X.Ju,J.Mol.Struct.(Theochem)766(2006)25. [5]J.J.P.Stewart,J.Mol.Model.13(2007)1173. [6]J.J.P.Stewart,MOPAC 2007,Stewart Computational Chemistry,Colorado Springs,CO,USA,https://www.wendangku.net/doc/279879920.html, [7]T.Puzyn,N.Suzuki,M.Haranczyk,J.Rak,J.Chem.Inf.Model.48(2008)1174.[8]A.Alparone,V.Librando,Z.Minniti,Chem.Phys.Lett.460(2008)151. [9] M.W.Schmidt,K.K.Baldridge,J.A.Boatz,S.T.Elbert,M.S.Gordon,J.H.Jensen,S.Koseki,N.Matsunaga,K.A.Nguyen,S.J.Su,T.L.Windus,M.Dupuis,J.A.Montgomery,https://www.wendangku.net/doc/279879920.html,put.Chem.14(1993)1347. [10] A.A.Granovsky,PC GAMESS version 7.0,Available from:
《数字音视频处理技术》教学大纲
《数字音视频处理技术》教学大纲《数字音视频处理技术》教学大纲课程名称:数字音视频处理技术 学时:64 学分:3 课程性质:专业选修课 考核方式:考查 )专业学生开课对象:计算机科学与技术(师范 一. 教学目的与要求 《数字音视频处理技术》是计算机科学与技术(师范)专业的一门应用性较强的专业选修课程。 随着多媒体技术日益成熟，使用数字音视频处理技术来处理各种媒体在师范生以后的工作过程中显 得十分重要。 本课程的目的和要求是: 1. 使学生了解数字音视频技术的基本概念，掌握数字音视频技术的基本原理，具备一定的理论 知识; 2. 使学生掌握专业音视频软件的使用方法，能够进行音视频的采集与编辑操作，并能进行典型 的艺术特效处理。 4. 培养学生的审美能力、艺术创造能力和多媒体技术的实际应用能力。本课程总授课64学时，在第六学期开设，为考查课程，其中理论教学为32学时，实践教学为
32学时。 二. 课程内容及学时分配 章节内容学时 第一章数字音视频处理技术的产生与发展 2 第二章音频技术概述 2 第三章音频处理 8 第四章视频技术概述 2 第五章视频处理 12 第六章音视频处理技术综合应用 6 实验一音视频软件的安装与基本操作 2 实验二音频采集与编辑 4 实验三数字音频特效与合成 6 实验四视频采集与编辑 4 实验五数字视频特效 8 实验六音视频处理技术综合应用 8 合计 64 第一部分理论教学第一章数字音视频处理技术的产生与发展(2学时) 主要内容: 1. 数字音视频处理技术的基本概念; 2. 数字音视频处理技术的产生与发展过程; 3. 数字音视 频处理的主要研究内容;4. 数字音视频处理的软硬件环境。要求: 1. 了解数字音视频处理技术的基本概念、产生与发展过程; 2. 了解数字音视频处理的技术概况和主要研究内容; 3. 了解数字音视频处理的软硬件环境要求; 4. 了解常见的音视频处理软件及其功能特点。
翻译中国文化和历史
翻译（一）、中国文化和历史 1、狮舞（Lion Dance）是中国最广为流传的民间舞蹈之一。狮为百兽之首，在中国传统中，狮子被视为是能带来好运的吉祥物（mascot）。古人将狮子视作是勇敢和力量的化身，能驱赶邪恶、保护人类。据记载，狮舞已拥有了2,000多年的历史。在唐代（the Tang Dynasty），狮舞就已经被引入了皇室。因此，舞狮成为元宵节（the Lantern Festival）和其他节日的习俗，人们以此来祈祷好运、平安和幸福。 The Lion Dance is one of the most widespread folk dances in China.The lion is the king of animals. In Chinese tradition, the lion is regarded as a mascot, which can bring good luck.Ancient people regarded the lion as a symbol of braveness and strength, which could drive away evil and protect humans. The dance has a recorded history of more than 2,000 years. During the Tang Dynasty, the Lion Dance was already introduced into the royal family of the dynasty. Therefore, performing the lion dance at the Lantern Festival and other festive occasions became a custom where people could pray for good luck, safety and happiness. 2、端午节，又叫龙舟节，是为了纪念爱国诗人屈原。屈原是一位忠诚和受人敬仰的大臣（minister）,他给国家带来了和平和繁荣。但最后因为受到诽谤（vilify）而最终投河自尽。人们撑船到他自尽的地方，抛下粽子，希望鱼儿吃粽子，不要吃屈原的身躯。几千年来，端午节的特色在于吃粽子（glutinous dumplings）和赛龙舟，尤其是在一些河湖密布的南方省份。 ? The Duanwu Festival, also called the Dragon Boat Festival, is to commemorate the patriotic poet Qu Yuan. Qu Yuan was a loyal and highly esteemed minister, who brought peace and prosperity to the state but ended up drowning himself in a river as a result of being vilified. People got to the spot by boat and cast glutinous dumplings into the water, hoping that the fishes ate the dumplings instead of Qu Yuan’s body. For thousands of years, the festival has been marked by glutinous dumplings and dragon boat races, especially in the southern provinces where there are many rivers and lakes. 3、上海菜系是中国最年轻的地方菜系，通常被成为“本帮菜”，有着400多年的历史。同中国其他菜系一样，“本帮菜”具有“色，香，味”三大要素。//上海菜的特点是注重调料的使用，食物的质地和菜的原汁原味。其中最著名的有特色点心“南翔小笼”和特色菜“松鼠鲑鱼”。//“南翔小笼”是猪肉馅，个小味美，皮薄汁醇。“松鼠鲑鱼”色泽黄亮，形如松鼠，外皮脆而内肉嫩，汤汁酸甜适口。//在品尝过“松鼠鲑鱼”之后，我们常常惊讶于“松鼠”的形状，觉得在三大评价标准上在添加“形”这个标准才更合适。 Shanghai cuisine, usually called Benbang cuisine, is the youngest among themajor regional cuisines in China, with a history of more than 400 years. Like all other Chinese regional cuisines, Benbang cuisines takes “color, aroma and taste”as its essential quality elements.//Shanghai cuisine emphasizes in particular the expert use of seasonings,
Stand structure, woody species richness and composition of subtropical karst forests in Maolan
STAND STRUCTURE, WOODY SPECIES RICHNESS AND COMPOSITION OF SUBTROPICAL KARST FORESTS IN MAOLAN, SOUTH-WEST CHINA ZH Zhang1, G Hu1, JD Zhu2 & J Ni3, 4 1School of Chemistry and Life Science, Guangxi Teachers Education University, Nanning 530001, China 2State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China 3State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China; nijian@https://www.wendangku.net/doc/279879920.html, 4Department of Environmental Science, East China Normal University, Shanghai 200062, China Received September 2011 ZHANG ZH, HU G, ZHU JD & NI J.2012. Stand structure, woody species richness and composition of subtropical karst forests in Maolan, south-west China. Natural karst forests have long been degraded due to human disturbances in mountainous regions of south-west China. We analysed the woody species diversity, floristic composition and stand structure of subtropical karst forests in Maolan, Guizhou Province of south- western China. A census of all woody species with diameter at breast height ≥ 1 cm in two 1-ha plots was made. A total of 8138 individuals belonging to 278 species, 167 genera and 69 families were recorded in the two plots. The most ecologically significant families as determined by stem density were Lauraceae, Fagaceae and Juglandaceae. The tree species Platycarya longipes (Juglandaceae) was the most dominant species in Dongge plot and Castanopsis carlesii var. spinulosa (Fagaceae), in Gengzheng plot. Total basal area was 42.22 m2 in the two plots, ranging from 18.60 to 23.62 m2 per plot. Forest structure was characterised by a large number of saplings. Compared with subtropical non-karst forests in China and karst forests in the tropics, the Maolan karst forest had higher species diversity with different tree species compositions. This study improved our understanding of the species diversity, community structure and functions of karst forests in subtropical Asia. Keywords: Limestone forest, rocky desertification, vegetation restoration, size class, stem density ZHANG ZH, HU G, ZHU JD & NI J. 2012. Struktur dirian, kekayaan spesies berkayu dan komposisi hutan kars subtropika di Maolan, barat daya China. Hutan kars asli telah lama dinyah gred di kawasan bergunung- ganang di barat daya China akibat gangguan manusia. Kami menganalisis kepelbagaian spesies berkayu, komposisi flora dan struktur dirian hutan kars subtropika di Maolan, wilayah Guizhou di barat daya China. Banci dijalankan ke atas semua spesies berkayu yang mempunyai diameter aras dada > 1 cm di dua plot yang luasnya masing-masing 1 ha. Sebanyak 8138 individu daripada 278 spesies, 167 genus dan 69 famili dicerap di kedua-dua plot. Famili yang paling signifikan dari segi ekologi berdasarkan kepadatan batang ialah Lauraceae, Fagaceae dan Juglandaceae. Platycarya longipes (Juglandaceae) merupakan spesies yang paling dominan di plot Dongge manakala Castanopsis carlesic var. spinulosa (Fagaceae) di plot Gengzheng. Jumlah luas pangkal ialah 42.22 m2 di kedua-dua plot dengan julat antara 18.60 m2/plot hingga 23.62 m2/plot. Struktur hutan dicirikan oleh anak benih yang banyak. Hutan kars Maolan mempunyai kepelbagaian spesies yang lebih tinggi dengan komposisi spesies pokok yang berlainan berbanding dengan hutan bukan kars subtropika di China dan hutan kars tropika. Kajian ini menambah baik pemahaman kita tentang kepelbagaian spesies, struktur komuniti dan fungsi hutan kars di Asia subtropika. INTRODUCTION Karst is a distinctive topography created by rainfall and groundwater acting on carbonate bedrock such as limestone dolomite or marble (He et al. 2008). The karst landscape is distributed all over the world, occupying 22 million km2 and accounting for 15% of the world land area (Yuan 1991). China has the largest and widest karst area in the world, which is mainly distributed in mountainous regions of south-western (SW) China (Li et al. 2002). Among them, Guizhou Province has the largest and most unique karst terrain dominated by limestone substrata. Soils in karst terrain are typically shallow and experience strong seasonal drought and rapid drainage. They have high levels of calcium and magnesium, relatively high pH and organic