Carbon Aerogel Composites as Promising Electrode Materials for High-Performance Supercapacitors
DOI:10.1021/la903947c 2209
Langmuir 2010,26(4),2209–2213Published on Web
01/12/https://www.sodocs.net/doc/225144439.html,/Langmuir ?2010American Chemical Society
Mesoporous MnO 2/Carbon Aerogel Composites as Promising Electrode
Materials for High-Performance Supercapacitors
Gao-Ren Li,*Zhan-Ping Feng,Yan-Nan Ou,Dingcai Wu,Ruowen Fu,and Ye-Xiang Tong*
MOE Laboratory of Bioinorganic and Synthetic Chemistry,School of Chemistry and Chemical Engineering,Institute of Optoelectronic and Functional Composite Materials,Sun Yat-Sen University,Guangzhou 510275,China
Received October 18,2009.Revised Manuscript Received December 18,2009
MnO 2as one of the most promising candidates for electrochemical supercapacitors has attracted much attention because of its superior electrochemical performance,low cost,and environmentally benign nature.In this Letter,we explored a novel route to prepare mesoporous MnO 2/carbon aerogel composites by electrochemical deposition assisted by gas bubbles.The products were characterized by energy-dispersive spectrometry (EDS),X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS),scanning electron microscopy (SEM),and transmission electron microscopy (TEM).The MnO 2deposits are found to have high purity and have a mesoporous structure that will optimize the electronic and ionic conductivity to minimize the total resistance of the system and thereby maximize the performance characteristics of this material for use in supercapacitor electrodes.The results of nitrogen adsorption -desorption experiments and electrochemical measurements showed that these obtained mesoporous MnO 2/carbon aerogel composites had a large specific surface area (120m 2/g),uniform pore-size distribution (around 5nm),high specific capacitance (515.5F/g),and good stability over 1000cycles,which give these composites potential application as high-performance supercapacitor electrode materials.
1.Introduction
In recent years,electrochemical supercapacitors as a kind of attractive energy-storage/conversion device are attracting wide interest owing to their higher power density and longer life cycle compared with batteries and higher energy density than conven-tional dielectric capacitors,which show potential applications in electric vehicles,power sources,portable electronics,and other devices.1Various materials were investigated for electrochemical supercapacitors including (i)carboneous materials,(ii)conduct-ing polymers,and (iii)transition-metal oxides.2Among transi-tion-metal oxides,amorphous hydrated ruthenium oxide exhibits remarkably high specific capacitance and excellent reversibility because of the ideal solid-state pseudofaradaic reaction.3How-ever,the high cost,low porosity,and toxic nature of RuO 2limit its practical application.Therefore,some cheap and environmentally friendly metal oxides have received more and more attention.MnO 2as a promising material for electrochemical supercapa-citors has attracted much attention because of its high specific capacitance,ability to charge -discharge rapidly,good cycle stability,low cost,and environmentally benign nature.4Further-more,MnO 2can be used in neutral aqueous electrolytes,unlike
RuO 23x H 2O and NiOOH,which can only be used in strong acidic or alkaline electrolytes,thus causing environmental pro-blems.It has been especially emphasized that the electro-chemical characteristics of MnO 2materials strongly depend on their structural parameters such as polymorphs,morphology,particle size,and bulk density.5Up to now,various nanostruc-tures of MnO 2,such as nanoparticles,6nanorods,7nanowires,8nanofibers,9nanobelts,10nanotubes,11nanosheets,12branched
*To whom correspondence should be addressed.
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Letter Li et al.
nanostructures,13and other nanostructures,14have been synthe-sized by different https://www.sodocs.net/doc/225144439.html,pared with hydrous RuO2 with high specific capacitance(SC)values ranging from720to 1000F/g,MnO2exhibits a lower electrochemical SC values that are usually about150-300F/g and are far from its theoretical value of ca.1400F/g.5,15-18Therefore,it is significant and necessary to further improve the capacitive performance of MnO2.
Recently,some efforts focused on mesoporous MnO2with pore sizes of2-50nm because confining d-electrons to the thin walls between pores can endow such materials with unusual electrical,magnetic,and optical properties.19With the character-istics of mesoporous materials,it will also be possible to optimize the electronic and ionic conductivity of MnO2to minimize the total resistance of the system and thereby maximize the perfor-mance characteristics of this material for use in supercapacitor applications.20The present work focuses on the facile creation of open and mesoporous morphologies of MnO2/carbon aerogel composites for use as high-performance supercapacitor electrode materials.At present,the preparation of mesoporous silicas, alumino-silicates,alumino-phosphates,and related materials has been already well established.However,it has proved difficult to synthesize transition metal oxides including MnO2in the form of mesoporous materials,although the challenge has seen important advances in recent years.21The synthesis of mesoporous materials usually involves the use of a hard template(e.g., mesoporous silica)within the pores of which the mesoporous solid is formed,followed by template dissolution,or a soft template(e.g.,alkyl amine)around which the mesoporous solid is assembled.However,sometimes the above routes may have some shortcomings.For example,if the temperature range within which the target phase forms does not coincide with the stability range of the template,the desired phase may not be obtained. Here,we investigated a novel and facile route for the preparation of mesoporous MnO2on carbon aerogels via electrochemical deposition assisted by gas bubbles.It is well-known that the mesoporous carbon materials including carbon aerogels,worm-holelike mesoporous carbons,and ordered mesoporous carbons used as substrates can obviously increase the active sites,enhance the electric conductivity,improve the homogeneity of electro-chemical reaction,and reduce the ionic resistance of the metal oxide and,consequently,further increase both the power and energy densities of the electrode.22In this study,mesoporous MnO2with a high density of pores has been successfully synthe-sized on the substrate of carbon aerogels accompanying hydrogen evolution,which can be deliberately suppressed in typical electro-deposition processes to produce dense crystalline walls of pores. The growth rates of deposits can easily be well controlled by deposition potentials,current densities,or salt concentrations. The results of nitrogen adsorption-desorption experiments and electrochemical measurements showed that the obtained products had a large specific surface area,uniform pore-size distribution, and good capacitance performance,which give the composites potential application as high-performance supercapacitor elec-trode materials.
2.Experimental Section
The detailed preparation procedure of carbon aerogels can be obtained in ref23.According to the predetermined formulations, all reactants,including formaldehyde,resorcinol,deionized water,and cetyltrimethylammonium bromide,were mixed with a magnetic stirrer and then were transferred into a glass vial (20mL).The vial was sealed and then was put into a water bath (85°C)to cure for5days.After curing,at first the gels were directly dried in air at room temperature for2days,then further dried under an infrared lamp with an irradiation temperature of about50°C for1day,and finally dried in an oven at110°C at ambient pressure for3h.Subsequently,the resultant resorcinol-formaldehyde aerogels were pyrolyzed at300-900°C for3h in flowing N2.
The electrodeposition of mesoporous MnO2was carried out in a simple three-electrode electrochemical cell with the carbon aerogels/Cu as the working electrode(WE,1.0cm2),a graphite electrode as the counter electrode(CE,2.5cm2),and a saturated calomel electrode(SCE)as the reference electrode(RE)that was connected to the cell with a double salt bridge system(ShangHai Yueci).The electrolyte was an aqueous solution of0.1M Mn-(NO3)2.The electrodeposition was performed by potentiostatic electrolysis with a potential of-1.30V versus SCE at room temperature for120min.The electrolysis plot of the current versus time is shown in Supporting Information Figure S1.
The surface morphologies of the obtained mesoporous MnO2 deposits were observed by field emission scanning electron micro-scopy(FE-SEM,JSM-6330F)and transmission electron micro-scopy(TEM,JEM-2010HR).The as-deposited products were also characterized by X-ray diffraction(XRD,PIGAKU, D/MAX2200VPC)to determine the deposit structures.Chemical-state analysis of deposits was carried out by X-ray photoelectron spectroscopy(XPS)using an ESCALAB250X-ray photoelectron spectrometer.All XPS spectra were corrected using the C1s line at 284.6eV.Curve fitting and background subtraction were accom-plished.The samples were also characterized by Brunauer, Emmett,and Teller(BET)nitrogen sorption surface area mea-surements(Micromeritics ASAP2010).Specific surface areas of the prepared deposits were calculated by the BET method,and pore sizes were calculated using the Barrett,Joyner,and Halenda (BJH)method(for large pores)or density functional theory
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(DFT)method (for small pores)on the basis of the adsorption branch of the nitrogen sorption isotherms.
A Chi750
B electrochemical workstation was used for the elec-trochemical measurements.The mesoporous MnO 2/carbon aero-gel composites as electrodes were studied for redox supercapacitor applications in 1.0M Na 2SO 4electrolyte.The graphite sheet was used as a counter electrode,and the SCE was used as the reference electrode.The cyclic voltammetry experiments were performed between 0and 0.9V versus SCE at a scan rate of 2-40mV/s.
3.Results and Discussion
Under electrodeposition with a constant potential of -1.30V (vs SCE),Mn 2t(0.1M Mn(NO 3)2)can be successfully converted to MnO 2via eqs 1and 2.Simultaneously,the water in the deposition solution could be also electroreduced with H 2gas release according to eq 3.Very interestingly,this electrodeposition gives rise to the formation of mesoporous MnO 2.This can be attributed to no deposit growth toward the gas bubbles because of no metal ions being available there,which finally leads to the electrodeposition only happening between gas bubbles and,accordingly,the forma-tion of mesoporous structures.The growth of mesoporous MnO 2is illustrated in Scheme 1.Supporting Information Figure S2shows the SEM image of mesoporous MnO 2deposited in a solution of 0.1M Mn(NO 3)2at -1.30V.The porosity corresponds to the interstitial pores formed between nanoparticles.Figure 1shows the TEM images of mesoporous MnO 2with different magnification.From Figure 1b,the sizes of pores can be estimated as about 10-15nm.
NO 3-tH 2O t2e f NO 2-t2OH -e1T2Mn 2tt4OH -tO 2f 2MnO 2t2H 2O
e2T2H 2O t2e f H 2v t2OH -e3T
A typical energy-dispersive spectrometry (EDS)spectrum of MnO 2products is shown in Supporting Information Figure S3,
which shows that the obtained deposits are pure MnO 2.Support-ing Information Figure S4shows the XRD pattern of the synthesized MnO 2products.All the diffraction peaks can be readily indexed to a pure tetragonal symmetry of R -MnO 2with a space group of I 4/m (87)(JCPDS 44-0141).No characteristic peaks for other manganese oxides were detected,indicating the high purity of the as-prepared products.In addition,the powder pattern shows a large background that starts at 20°,and it arises from the carbon aerogel.The XPS spectra of the R -MnO 2deposits are shown in Supporting Information Figure S5.The detected peak at the bonding energy of 642eV,which corresponds to Mn 2p 3/2,indicates that the element Mn of the as-prepared samples is present in the chemical state of Mn 4t.The peak appearing at the binding energy of 654eV,which can be assigned to Mn 2p 1/2,further confirms the sole existence of Mn 4t.There-fore,on the basis of the results of EDS,XRD,and XPS,no unoxidized Mn,suboxide MnO,Mn 2O 3,and Mn 3O 4phases were found in MnO 2products,and the high purity MnO 2was successfully obtained.In addition,quantitative XPS analysis demonstrates that the atomic ratio of Mn to O is approximately 1:2,which is in good agreement with the XRD results.The atomic concentration of O in oxide is determined on the basis of decon-voluted peak areas in order to separate it from the contributions of hydroxide and H 2O.
As the obtained MnO 2deposits have a mesoporous structure,a high surface area is expected.In order to examine the surface properties of the synthesized mesoporous structures,the porosity was characterized by nitrogen sorption analysis using standard BET techniques.The adsorption -desorption isotherm is shown in Figure 2a,indicating a hysteresis loop characteristic to meso-porous materials.The hysteresis loop in the low relative pressure (P /P 0)range of 0.45-0.90might be ascribed to the presence of a mesoporous structure,and the hysteresis loop at P /P 0=0.90-1.0might result from the interplates space.4c According to the BET method,the resulting MnO 2mesoporous structures have a specific surface area of about 120m 2/g.The pore-size
distribution
Figure 1.TEM images of mesoporous MnO 2deposited on carbon aerogels with different magnetification.
Scheme 1.General Schematic Representation of the Electrochemical Synthesis of Porous MnO 2Nanostructures Assisted by Gas
Bubbles
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of deposits is shown in Figure 2b,which shows a pore-size distribution of around 5nm calculated from the adsorption branch of the isotherm using the BJH model.The high BET surface area and mesoporous structure of the MnO 2deposit provide the possibility of efficient transport of electrons and ions,which can lead to the high electrochemical capacity of these materials.
The electrochemical performances of the prepared mesoporous MnO 2/carbon aerogel composites were investigated by cyclic voltammetry experiments.The potential window was chosen in the range of 0-0.9V versus SCE.The representative cyclic voltammograms (CVs)of mesoporous MnO 2/carbon aerogel composites and bare carbon aerogel electrodes in 1.0M Na 2SO 4at 20mV/s are presented in Figure 3a and b,respectively.The nearly symmetrical rectangular shapes are clearly exhibited in the CVs,which show the symmetric current -potential characteristics of electrochemical double layer capacitor of mesoporous MnO 2.This indicates a good capacitor with relatively low solution resistance.CVs of mesoporous MnO 2/carbon aerogel composites in 1.0mol/L Na 2SO 4aqueous solution at various scan rates are shown in Supporting Information Figure S6.The CV curve at the faster scan rate has a bigger area than the lower scan rate one,but it should be noted that this does not indicate it has more charge at the higher scan rate.It is well-known that the specific capacitance is an important parameter to evaluate the performance of electrochemical supercapacitors.The mean specific capacitance of the mesoporous MnO 2electrode can be estimated by the equation C =Q/ΔVw ,where Q is the charge amount correspond-ing to the area within the rectangular voltammogram curve,ΔV is the value of potential window,and w is the mass of the material.The mean specific capacitances of mesoporous MnO 2electrodes in 1.0mol/L Na 2SO 4were calculated as 515.5,456.0,447.6,426.2,and 332.4F/g at sweep rates of 2,5,10,20,and 40mV/s,https://www.sodocs.net/doc/225144439.html,pared with the specific capacitance of bare carbon aerogel (182F/g)and bulk MnO 2/carbon aerogel (327F/g)at 2mV/s,the specific capacitance enhancement for the mesoporous MnO 2/carbon aerogel composite electrodes may
be attributed to electrochemical activity of the mesoporous MnO 2phase.The crystalline phase in mesoporous MnO 2is a critically favorable parameter for electron/ion insertion reactions involving large hydrated cations.The whole charging/discharging pro-cess may mainly involve (i)cation transport in the electrolyte;(ii)adsorption/desorption of cations at the surface sites of electrodes,which may be dependent on the ion size and the dehydration/hydration rate;and (iii)cation extraction/insertion into solid MnO 2matrix.Therefore,the relative high capacity of MnO 2may be attributed to the mesoporous structure with high specific surface area.
The decrease of capacitance with the sweep rate increase can be explained as follows.For crystalline samples of MnO 2,the following mechanism was usually proposed for charge storage in MnO 2.This mechanism involves intercalation/extraction of protons (H 3O t)or alkali cations such as Li t,Na t,K t,and so forth into the bulk of oxide particles with concomitant reduction/oxidation of the Mn ion.24
MnO 2tM tte -T MnOOM eM t?Li t,Na t,K t,or H 3O tT
e4T
When the scan rate is slower,the diffusion of ions from the electrolyte can gain access to almost all available pores of the electrode,which will lead to a complete insertion/extraction reaction and accordingly enhance the reduction/oxidation pro-cess.However,the effective interaction between the ions and the electrode will be greatly reduced when the scan rate is increased,and accordingly the voltammetric charge will be reduced,which can be attributed to some hindered exchange of charged compo-nents between the solution and electroactive sites in less accessible parts of the film surface.25In this study,the diffusion of Na tions into the pores of mesoporous MnO 2/carbon aerogel composite electrodes will evidently decrease with increasing scan rate,and will finally only be limited to the outer surface of the MnO 2electrode when the scan rate is higher.The effective utilization for the redox reaction will decrease with increasing scan rate.There-fore,the main reason for such a behavior is that the higher scan rate prevents the accessibility of Na tions to all the pores of the electrode.
The electrochemical stability of mesoporous MnO 2was exam-ined by subjecting a mesoporous MnO 2/carbon aerogel
composite
Figure 2.(a)Adsorption -desorption isotherms and (b)pore-size
distributions of mesoporous MnO 2deposited on carbon aerogels in solution of 0.1M Mn(NO 3)2at -1.30
V.
Figure 3.CVs of (a)mesoporous MnO 2/carbon aerogel compo-
sites and (b)bare carbon aerogels in 1mol/L Na 2SO 4aqueous solution at 20mV/s.
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Li et al.Letter
electrode for CVs for a long number of cycles.The cycling process was performed at a scan rate of20mV/s for1000cycles.Supporting Information Figure S7shows the variation of specific capacitance as a function of cycle number.As revealed from this data,a little decrease of specific capacitance is observed during1000cycles,and it is still about97%of the first cycle after1000cycles.The system can withstand over1000cycles without any significant decrease in the specific capacitance.Therefore,this demonstrates that,within the voltage window0-0.9V,the charge and discharge processes do not seem to induce significant structural or microstructural changes in the mesoporous MnO2as expected for pseudocapacitance reactions.The long-term stability implies that the mesoporous MnO2/carbon aerogel composites are good candidates as a material for supercapacitor electrodes.This kind of material may have future application for supercapacitors.
4.Conclusions
In summary,herein we developed a simple and facile electro-chemical deposition method for the preparation of mesoporous structures with a high density of pores.Novel mesoporous MnO2/ carbon aerogel composites have been successfully synthesized in aqueous electrolytes by electrochemical deposition accompanying hydrogen evolution,which is crucial for the growth of mesopor-ous structures.The high BET surface area and mesoporous structure of the products provide the possibility of efficient trans-port of electrons and ions.The prepared mesoporous MnO2/ carbon aerogel composites have been successfully employed as supercapacitor electrodes and give a highest specific capacitance (515.5F/g).The high specific capacitance and good cycle ability coupled with the low cost and environmentally benign nature of the MnO2/carbon aerogel composite may make this material attractive for large applications.Furthermore,the unique syn-thetic mechanism of mesoporous structures is expected to be applicable for other metal oxides of technological importance. Acknowledgment.This work was supported by NSFC (20603048,20873184,90923008,and J0730420),Guangdong Province(2008B010600040and9251027501000002),and Sun Yat-Sen University(09lgpy17).
Supporting Information Available:Electrolysis plot of current versus time;SEM image of mesoporous MnO2 deposited on carbon aerogels;EDS pattern of mesoporous MnO2deposited on carbon aerogels;XRD pattern of meso-porous MnO2deposited on carbon aerogels;XPS spectra of mesoporous MnO2deposited on carbon aerogels;CVs of mesoporous MnO2/carbon aerogel composites;plot of spe-cific capacitance versus cycle number of mesoporous MnO2/ carbon aerogel electrode;TEM images of mesoporous MnO2on Ti sheet;SEM images of bare carbon aerogel and MnO2deposited on carbon aerogel;adsorption-desorption isotherms and pore-size distributions of aerogel before deposition of MnO2.This material is available free of charge via the Internet at https://www.sodocs.net/doc/225144439.html,.
DOI:10.1021/la903947c2213
Langmuir2010,26(4),2209–2213
同方系统还原卡(BIOS)MAX版说明书
目录 1同方系统还原卡MAX版安装流程图 (2) 2 同方系统还原卡MAX版及操作系统的安装 (3) 2.1安装前的准备 (3) 2.2安装发送端 (4) 2.3网络拷贝 (15) 2.4硬盘复制 (20) 3 自动维护 (22) 4 系统设定 (25) 4.1密码设定 (25) 4.2参数设定 (26) 4.3分区信息 (28) 4.4工具 (28) 4.5重新分区 (29) 4.6更版 (29) 4.7移除 (29) 4.8版本信息 (29) 5 同方易教使用方法 (30) 5.1.系统安装要求 (30) 5.2.软件安装 (31) 5.3.同方易教控制端说明 (32) 5.4.软件分发功能 (39) 6 自动分配IP操作流程 (47)
附录一热键提示 (50) 附录二硬盘大传小功能 (51) 附录三LINUX系统安装说明 (51) 附录四网域登录使用方式 (56) 附录五常见问题解答 (59)
1同方系统还原卡MAX版安装流程图
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[用户须知] 本手册同时可适用于小哨兵网吧专用卡，详情请见附录部分。 本手册适用于7.0及以上版本。
目录 第一章产品简介........................................ 错误！未定义书签。第二章主要功能特点................................ 错误！未定义书签。第三章系统需求…………………………………………………第四章安装指南…………………………………………. 4.1安装前的准备工作.......................................................................... 4.2驱动程序的安装.............................................................................. 4.3还原卡的安装.................................................................................. 第五章使用指南............................................................................ 5.1数据恢复.......................................................................................... 5.2参数设置.......................................................................................... 5.3设置管理员口令 ............................................................................. 5.4备份CMOS数据………………………………………………… 5.5更新硬盘数据…………………………………………………… 5.6软盘升级………………………………………………………….
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1、从学生用机中选择一台计算机，开机,出现"第一次安装"界面。? 2、将随机的还原卡光盘放进光驱。? 3、选择“本机安装”,有三个选项：?a＼简易安装：请确保原分区的工具为FDＩSＫ。使用此种安装方式将会保留硬盘所有原有的分区及分区内所有的资料数据。完成简易安装后计算机将会重新启动，启动后会停留在开机菜单上，此时该项方式安装完成。（这种方式不会破坏硬盘的任何数据) b\自订安装:此中安装方式是用于安装多个操作系统或变更原硬盘分区状况时最常用的一种安装方式。完成自订安装后计算机将会重新启动。(这种方式会破坏硬盘的所有数据,适用于全新安装)?c\网络安装:自动将该台计算机设置成接收端,等待发射端的数据传送。（这种方式不使用光盘安装)?(六)、自订安装”,设置分区的各种参数?"属性"说明:?立即复原型引导盘(Ａ）?用于引导、安装操作系统,，可瞬间复原分区数据。?备份复原型引导盘（B) 用于引导、安装操作系统，需占用与该分区同样大小的硬盘空间备份该分区数据，以供复原时使用，并且复原时间较长。 一般引导盘(C)?用于引导、安装操作系统，此种引导盘不具备复原功能。?共用资料盘(S) 资料盘，该分区可被分区格式兼容的引导盘共享。?专属资料盘（P)?资料盘，该分区只能被与其名称相同且分区格式相兼容的引导盘识别使用。例如：如果引导盘的名称叫做＂Win２K"，那么它的专属资料盘的名称也必须叫做"Wiｎ2K";如果引导盘的名称叫
关于去北京的英语作文
关于去北京的英语作文 北京是中国的首都，是经济、政治、文化的中心，也是一座历史悠久的现代化城市。下面小编为大家搜集整理有关北京的英语作文，仅供阅读! 北京Beijing Id like to go to a beautiful place. I think it would be Beijing. Beijing is not only our capital city, but also a famous city with long history and wonderful culture. Beijing is also Chinas political and cultural center. Therere many old places of great interest, such as the Great Wall, the Summer Palace, the Forbidden City, the Temple of Heaven, and Tiananmen Square. Once you see Tiananmen Square, you will think of Beijing. It has been the symbol of Beijing since 1949. 我想去一个美丽的地方。我觉得那应该是北京。北京不仅仅是我们的首都，也是有着悠久的历史和精彩地文化的著名城市。北京也是中国的政治和文化中心。有很多古迹，比如，长城，颐和园，紫禁城，天坛，天安门广场。只要你看到天安门广场，你就会想起北京。自从1949年起它就是北京的象征了。 北京之旅Journey to Beijing This summer holiday, I visited toBeijingwith my aunt. We visited to many famous places, such as TiananMen Square, theImperialPalace,
联想电脑带还原卡系统安装开局
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快速安装主要是已经设置好分区并安装好操作系统后对已做数据做保留处理时使用。 2、选择安装 选择安装可以重新划分硬盘，所以会删除硬盘上所有的原有数据，新安装机器与多系统安装都建议使用选择安装，先使用还原卡自带的硬盘分割工具划分硬盘后再安装操作系统。 3、网络安装 网络安装是通过网络安装的客户端程序，使用网络安装后本次将进入网络接收模式，网络安装有可能删除原有硬盘的所有数据。 本文主要介绍选择安装方法。 三、硬盘分割 进入选择安装后，出现分割硬盘界面，如图2，此时列出目前机器上使用的硬盘情况，以及可能正在使用的分区情况，如需重新划分硬盘请选择“重新分区”进入下一步，此时原硬盘上所有数据删除，此时出现分割硬盘的分区情况界面，如图3，此界面可以对硬盘分区做相应配置。 图2
初中英语作文：关于北京(About Beijing)
初中英语作文：关于北京(About Beijing) 2017-12-02虽然言语很简单，却在字里行间透露出自己的情感，不错的初中英语作文。 (天添资源网收集整理)初中英语作文：关于北京(aboutbeijing)(收集:https://www.sodocs.net/doc/225144439.html,)beijinghasahistoryofover3,000yearswithapopula tionofnearly13millionandalotofplacesofinterestaroundit.inrecentyears,thec ityofbeijinghasbeenadvancingveryquickly.youcanseemoremuseums,parksa nshoppingcentershereandthere.moreandmorehighwaysandoverheadwalk wayshavebeenbuiltup.what'smore,alotmorebuseswhichburncleanerfuel,su chascngorlpg,areputintouse,topreventairfrombeingpolluted.waterintherive rsiscleanagain.whereveryougo,youcanseegreentrees,grassandbeautifulflow ers.allthesemakelifeinbeijingmoreconvenient,pleasantandcolorful.beijingis stilladvancingtothebrightfuture.关于北京北京有3000多年的历史，近1300万人口和许多名胜古迹。 近年来，北京发展得很快。 你能看到更多的博物馆、公园和购物中心，比比皆是。 北京已建成越来越多的高速公路和过街天桥。 还有，更多的公共汽车投入使用，它们都使用环保燃料，以防空气受到污染。 河水又变得清澈了。 无论你走到哪里，你都能看到绿树、青草和美丽的花朵。
小哨兵还原卡说明书
目录 1.系统需求 (2) 2.功能特点 (2) 3.安装流程 (4) 4.安装 (7) 5.使用 (12) 6.预置多重引导 (14) 7.注意事项 (15) 8.疑难解答 (18) 9.其他功能 (26)
一、系统需求 CPU ： 386 及以上PC兼容机 内存： 640 KB 以上 显示： VGA 彩显 硬盘： 30 MB至100 GB 总线槽：至少1个ISA或PCI空插槽 二、功能特点 ·全中文界面，“即插即用”无需重做硬盘，不占硬盘空间。非专业人员10秒 钟安装完成。 ·支持DOS、Win3.1、Windows95/98、Win dows NT、Windows 2000、UNIX、LINUX、 OS/2等操作系统。 ·集成32位Windows驱动程序,不须安装软盘，安装简单方便。 ·纯32位内核及VXD驱动程序，Windows 中设备管理器的硬盘控制器上无黄色惊 叹号，运行Windows快速、稳定。 ·提供自动复原、手工复原、定时复原、
继续保持、完全开放等多种还原方式， 灵活方便。 ·同时支持多重引导、多盘保护，在一个硬盘上可同时安装多个可独立引导的操 作系统，同时保护多个分区。 ·支持高达100G以上的大硬盘。 ·支持硬盘复制，方便批量安装。 ·提供管理员软件安装模式，随时为系统增加新的软件。 ·提供数据更新功能，随时为系统添加新的需保护的软件，不必担心无意中资料 丢失。 ·提供CMOS自动侦测和恢复功能，杜绝误判现象。 ·支持FAT12、FAT16、BIGDOS、FAT32、 NTFS、HPFS等文件系统格式，支持文件系统之间的动态转换。 ·支持IDE、SCSI等各种形式的硬盘。·可有效防止FDISK、DEL、FORMAT等命令造成系统的意外破坏。
介绍北京的英语作文介绍北京的高中英语作文
介绍北京的英语作文介绍北京的高 中英语作文 作为中国的首都,北京已成为中国最受 欢迎的城市,所以越来越多的人想参观北京。你对北京的了解有多少呢?下面，X帮你整理了介绍北京的高中英语作文，希望你喜欢! 介绍北京的高中英语作文篇 1 As the captain of China，Beijing has been the most popular city of china。So more and more people want to visit Beijing. I think the best time to visit Beijing is spring ,for the weather of that time is very fine ,neither too hot nor too cold . The warm wind will make you fell people visit Beijing for it's beautiful sence and cultural inheritance . If you want to have a enjoyable journey ,I suggest you to pay a visit to
the Great Wall,the Summer Palace ,the Olympic Park and many other you feel tired after one day's journey ,you can taste the "Zha Jiang Mian",a kind of traditional food in Beijing. There are many other things you can do in Beijing,as shopping in the big shopping mall,visit the different kinds park ,visit the"Si He Yuan"and so on. I hope you can have a happy time in Beijing. 介绍北京的高中英语作文篇 2 Beijing is a metropolis in northern China and the capital of the People's Republic of China. It is one of the four municipalities of the PRC, which are equivalent to provinces in China's administrative structure. Beijing is one of the Four Great Ancient Capitals of China. The municipality of Beijing borders Hebei Province to the north, west, south,
联想自带教育软件功能
4-6级政教行业售前支持技术与方案月刊 第六期（2011年8月） 主题：教育应用升级版：7.5 目录 一、方案介绍 (1) 1.1应用概述 (1) 1.2系统特色 (1) 1.3功能概述 (2) 二、竞品对比 (4) 三、常见问题 (5) 四、标底举例 (6) 五、接口人查询 (8)
一、方案介绍 1.1 应用概述 联想教育应用方案是专门为电子教室等公共机房环境设计开发的，适用于教育行业机房、电子教室及其它行业类似环境 在教育应用7.5增强了电子教室功能。 教育应用7.5包含四大功能：硬盘保护、网络同传、网络控制、电子教室； 1）四大功能模块全面解决从部署、维护、管理到教学的各种问题 2）支持多种机型及配置，适合从小学到高校的不同层次用户 1.2 系统特色 1）多点还原、智能排序、断电续传、资产监控、电子教室等功能及规格处于行业领先地位 2）先进的技术架构支持千兆网卡、EFI主板、Liniux等高端规格平台 3）嵌入式解决方案，具有良好的兼容性、稳定性
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北京的英文介绍
北京英文介绍： Beijing is an ancient city with a long history. Back in 3000 years ago in Zhou dynasty, Beijing, which was called Ji at the moment, had been named capital of Yan. Thereafter, Liao, Jin, Yuan, Ming and Qing dynasty all made Beijing their capital. Therefore, Beijing was famous for "Capital of a thousand years". The long history leaves Beijing precious cultural treasure. Winding for several kilometers in Beijing area, the Great Wall is the only man-made structure that could been seen in the space. The Summer Palace is a classic composition of ancient royal gardens, and the Forbidden City is the largest royal palaces in the world. Tiantan is where the emperor used to fete their ancestors, and also the soul of Chinese ancient constructions. The four sites above has been confirmed world cultural heritage by UNESCO. However, the best representatives for Beijing are the vanishing Hutongs and square courtyards. Through hundreds of years, they have become symbol of Beijing's life. Tian'anmen square being still brilliant today with cloverleaf junctions and skyscrapers everywhere, the old-timey scene and modern culture are combined to present a brand new visage of Beijing. As Beijing has been confirmed home city of Olympics 2008, the spirit of "green Olympics, scientific Olympics and humanized Olympic" will surely bring more and more changes to Beijing, promote the development of sports and Olympics in China as well as in the world, and strengthen the friendly communications between Chinese and foreign people. The Temple of Heaven was initially built in Yongle year 18 of the Ming Dynasty (in 1420). Situated in the southern part of the city, it covers the total area of 273 hectares. With the additions and rebuild during the Ming, Qing and other Dynasties, this grand set of structures look magnificent and glorious, the dignified environment appears solemn and respectful, it is the place for both Ming and Qing Dynasty's Emperors to worship Heaven and pray for good harvest. The northern part of the Temple is circular while the southern part is square, implies "sky is round and earth is square" to better symbolize heaven and earth. The whole compound is enclosed by two walls, dividing the whole Temple into inner and outer areas, with the main structures enclosed in the inner area. The most important constructions are the Hall of Prayer for Good Harvest, the Circular Mound Altar, Imperial Heaven, The Imperial Vault of Heaven, Heaven Kitchen, Long Corridor and so on, as well as the Echo Wall, the Triple-Sound Stone, the