pumping_nylon第一章：该做的和不该做的

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《吉他教程》pumping_nylon_第二章：左手

“失败的准备就是在准备失败。

”左手手指按弦的位置和精确度让手指让成一种强而有力的“站姿”，并且将手指放在恰当的位置使它拥有最大的控制范围和灵活性是十分必要的。

从下面的插图你可以看出，左手手指并不总是用指尖正中按弦，而应该采用下列的更有效的位置：1食指用指尖左边按弦2中指用指尖正中稍微偏左部分按弦3无名指用指尖正中稍微偏右部分按弦4小指用指尖右边按弦这样按弦可以使手左右两边更多的肌肉参与进来，不仅仅是为了四根手指更有力（尽管这也是它的好处之一），同时也使整只手更平衡，更有力，更牢固。

他也可以使手指更灵巧。

注意看每只手的第二关节，它们并不相互接触！不仅不要接触，还要留出一定的空间。

这样可使手得到扩张，并在必要时可以快速移动。

保持第二关节不接触，这比单纯的撑开手指有更大的锻炼肌肉的效果，本书的关键词是“节约”：节约影响，节约能量，节约动作。

大拇指应该在中指的下方，这有助于平衡拇指和其它手指的压力，得到类似老虎钳的效果。

压弦﹑放松；压弦﹑放松为了使你的左手熟悉上述的按弦姿势，尤其是你初次接触这个姿势的话，做下面的练习。

压弦/放松练习把左手按照上一页所说的放好（注意不要忽略拇指）。

四根手指分别按在随便某根弦的一到四品（我建议从第三根弦开始）。

按下四个品，然后放开（释放压力），但手指保持放在弦上。

通过这种“弦上放松”确保手指位置固定，继续按下四个品，然后放松。

按弦﹑放松，按弦﹑放松，一直这样保持手指不离弦地做一定次数。

这个练习的重点是记住手指按弦（提供压力），还有放松（完全释放压力）时的感觉。

四根手指必须同时按弦，同时放松。

感觉一下前面说的老虎钳一般的效果。

感受一下压力是怎样平均分配到四根手指和拇指的。

当你重复这个练习很多遍并且掌握到诀窍后，尝试四根指头逐根按下。

同样从前面说的那个位置开始——四指触到弦但不压下去。

手指变换虽然看上去很简单，但我们刚刚接触到了拥有一只灵活的左手的关键开端：控制手指的按弦和放松。

古典吉他完全自学的书

古典吉他完全自学的书以下是一些古典吉他完全自学的书籍推荐：1. "Solo Guitar Playing Book 1" by Frederick Noad - 适合初学者，介绍了基本的技巧和指法，并提供了一系列的练习和曲目。

2. "The Christopher Parkening Guitar Method - Volume 1" by Christopher Parkening and David Brandon - Christopher Parkening 是一位著名的古典吉他演奏家，他的教学方法很清晰易懂。

这本书适合初级和中级学生，并包括了一些经典曲目的乐谱。

3. "Pumping Nylon: The Classical Guitarist's Technique Handbook" by Scott Tennant - 这是一本关于古典吉他技巧的经典手册。

书中包含了大量的练习和建议，适合不同水平的学习者。

4. "Grade by Grade - Classical Guitar: Grade 1" by Janet Dowsett and David Burden - 这本书是《ABRSM 古典吉他等级考试》的指定教材之一。

书中包含了不同难度的曲目和技巧练习。

5. "The Art of Classical Guitar Playing" by Charles Duncan - 这是一本经典的古典吉他教材，适合初学者和中级学生。

书中介绍了各种技巧和乐谱。

这些书籍提供了各种不同级别的教学材料和练习，适合自学古典吉他。

同时，建议结合在线视频教程或找一位古典吉他老师进行指导，以获得更好的学习效果。

林菲尔·拜肯斯朗电动液

SAM400 & 650 PERKINS DIESEL ENGINE DRIVENIM568 April, 1997Mar ‘95Mar ‘95Mar.‘93for selecting a QUALITY product by Lincoln Electric.We want you to take pride in operating this Lincoln Electric Company product •••as much pride as we have in bringing this product to you!Read this Operators Manual completely before attempting to use this equipment.Save this manual and keep it handy for quick reference.Pay particular attention to the safety instructions we have provided for your protection.The level of seriousness to be applied to each is explained below:vv(1)Consult applicable federal, state and local laws regardingspecific requirements for use on public highways.SPEED CONTROL LEVERManually allows the engine to run at its high idle speed controlled by the governor or at the factory set low idle speed.When welding or using auxiliary power the speed control lever must be in the “RUN”position.T o reduce the engine to low idle speed when not welding or not using auxiliary power place the speed control lever in the “IDLE”position notch.ENGINE TEMPERATURE GAUGEDisplays the coolant temperature in the engine block. OIL PRESSURE GAUGEDisplays the oil pressure to the engine.When the engine starts running, watch for the oil pressure to build up.If no pressure shows within 30 seconds, stop the engine and consult the engine instruction manual. BATTERY CHARGING AMMETERDisplays the current going from the charging alternator into the batteries.It is normal for charging current to be high (above 15 amps) after starting or when the batter-ies are ‘low’on charge.ENGINE HOUR METER(Factory Installed Optional Feature)The optional engine hour meter records the total run-ning time on the engine in hours.It can be used to keep a record of maintenance on the engine and or welder. ENGINE PROTECTION SYSTEMThe engine protection system shuts down the engine under high coolant temperature or low oil pressure conditions by allowing the fuel solenoid valve to close.place.3.Remove the two screws on the top end of the wirefeeder nameplate.4.Position the “Portable Field Control”mounting slotsover these holes and replace the screws.5.Route the leads with the LN-5 or LN-6 control cableback to the power source.MOUNTING ON LN-71.Remove the top screws on the side of the LN-7 con-trol box cover.(This is the left side when facing the nameplate).2.Position the “Portable Field Control”on the side ofthe control box with the mounting slots over these holes and replace the screws.3.Route the leads with the LN-7 control cable back tothe power source.OUTPUT STUDSWith the Engine OFF connect the work cable to the “T o Work”stud.A.For Stick Electrode Welding1.Connect the electrode cable to the “Stick”studand the work cable to the “T o Work”stud.Connect the “T AP”lead in the SAM650 to theappropriate stud to adjust current and the arccharacteristics as described under “Currentand Voltage Controls.”2.Install the “Portable Field Control”.B.Automatic or Semiautomatic WeldingFor all automatic welding processes, connect the welding power cable from the wire feeder to the “Connect to Auto.Equipment”stud.Connect the “T AP”lead in the SAM650 to the appropriate stud to adjust current and the arc characteristics as described under “Current and Voltage Controls.”1.LN-7, LN-8, LN-9, NA-3, NA-5, LT-7 and LT-56 Wire Feeders.a.Make the connections exactly as speci-fied on the connection wiring diagramincluded in the wire feeder InstructionManual.b.Install the “Portable Field Control”whenusing an LN-7.CURRENT AND VOLTAGE CONTROLS Constant Voltage WeldingThe SAM-400 “Current Control”is NOT in the circuit when the ‘Electrode Polarity’switch is set for constant voltage welding.Set the open circuit voltage (OCV) needed for the par-ticular application with the “Constant Voltage Control”located to the left of the nameplate.Adjust the final welding voltage with either the wire feeder voltage con-trol or the “Portable Field Control”.Set the welding cur-rent with “Amps”or “Wire Feed Speed”control on the wire feeder.Low Range Feature (SAM400 K1279-1 only) --Extends the output voltage range of the SAM400 welder down to 12 volts for constant voltage welding. The maximum output current is not to exceed the rat-ing of the machine.The Low Range Feature provides a two-position manual switch which allows the operator to set his machine for normal welding or for low voltage welding.Factory installed only.On the SAM650 connect the “T ap”lead inside the machine to the appropriate “Innershield”stud for”Min. (Flat) Slope.”“Med.Slope”or “Max.Slope”.Low voltage (below 20 volts) low current welding often requires “Max.Slope”to adjust the weld metal droplet size for minimum spatter and to control puddle fluidity and bead shape.Innershield and other spray transfer type processes generally operate with “Med.Slope”.A Hot Start circuit on all models operates automatical-ly whenever the toggle switch is set on “Constant Voltage.”It increases the open circuit voltage by sev-eral volts until the arc is established -- then the voltage automatically drops to normal welding voltage.When the wire feeder is started before the arc is started, the voltmeter indicates a voltage several volts higher than welding voltage.T o read actual welding voltage, the arc must be established.Constant Voltage Welding With Variable Inductance Control:SAM-400 Only.Variable inductance or slope control is usually desir-able for low voltage (below 20 volts) applications and is sometimes useful in other constant voltage jobs.To introduce this control into the circuit, set the “Electrode Polarity”switch to “Variable Voltage”and the toggle switch to “Constant Voltage”.Then the “Current Control”acts as the variable inductance control. Normally this control must be kept within the 8 to 1 o’clock range.To Set The Controls -- Stick Weldinga.Make the coarse setting of welding heat with theSAM400 “Current Control”or the SAM650“T ap’”lead.b.Adjust for the desired arc characteristics with the“Variable Voltage Control”.For a soft arc desired for most welding keep this control between 7 and High.For a more digging arc, set it lower.c.If remote control is NOT desired leave the“Portable Field Control”on “High”.For remote con-trol, leave the “Variable Voltage Control”near “High”and make the adjustments described in paragraph “b”above with the “Portable Field Control”.Remember, increasing either the “Variable Voltage Control”or “Portable Field Control”setting also increases the current.To Set The Controls -- Submerged Arca.The open circuit voltage (OCV) is generally notcritical in submerged arc welding.Therefore, the “Variable Voltage Control”can usually be left between 7 and “High”-- no future adjustments are needed.b.Set SAM400 “Current Control”so the calibrationon the higher scale is a little above the current desired.Set the SAM650 “T ap”lead to the stud with the lowest current range that still provides the desired current.c.Make the final current adjustment with either thewire feeder current control or the “Portable Field Control”.Set the arc voltage with the wire feeder control.Consult the following illustrations for examples of how to set the machine.STARTING WELDERS WITH DEAD BATTERIES Array DO NOT attempt to start a SAM engine driven welder by driving the welding generator as a starter motor using the output of another welder.In addition to the possibility of damaging the machines, starting a SAM engine welder without using its starting circuit elimi-nates the operation of the flashing circuit.This can cause the generator to fail to produce any output. AUXILIARY POWERAn alternator generates 2 KVA of 120/240 volt 60 Hertz AC power.It is available either from #31 and #32 on the terminal strip or from the receptacles on the Control Panel.Be careful not to overload this circuit. The auxiliary power receptacle should only be used with three wire grounded type plugs or approved dou-ble insulated tools with two wire plugs.The alternator is protected by thermostats and fuses. DUTY CYCLEDuty cycle is based on a ten minute period and opera-tion in an ambient temperature of 104°F(40°C).The SAM400 is NEMA rated at 60% duty cycle.The SAM650 is NEMA rated at 80% duty cycle.Duty cycle is based on a ten minute period.Therefore, a 60% duty cycle welder can be operated at nameplate rated out-put for 6 minutes (8 minutes for 80% duty cycle) out of every 10 minute period without overheating.The auxiliary power can be used continuously (100% duty cycle) within its rated current capacities.STARTING INSTRUCTIONSBe sure all Pre-Operation Maintenance has been per-formed.(See Installation Section of this manual.)T o start the engine, set the speed control lever in the “RUN”position.Place ignition toggle switch in the “ON”position.Push in the engine protection system reset button (if so equipped).Engage the starter button. When the engine starts running, observe the oil pres-sure.If no pressure shows within 30 seconds, stop the engine and consult the engine operating manual.T o stop the engine, place the ignition toggle switch in the “OFF”position.When an engine is started for the first time, some of the oil will be needed to fill the passages of the lubricatingsystem.Therefore, on initial starting, run the engine forK799 Hi-Freq™-Provides high frequency plus a gas valve for TIG welding.A water valve is available as an option.Requires 115 volt AC input.Cannot be used with optional meters connected, or in constant voltage mode.(Limited to 250A - 60% Duty Cycle).K802-D Power Plug Kit -For SAM welders with stan-dard 2KVA of AC auxiliary power.Kit includes male plugs for each auxiliary receptacle.K805-1 Ether Start Kit -Injects ether for starting aid. Recommended only when engines are frequently started at temperatures under 10°F (-12°C).Ether cylinder is not included.K767-1 Undercarriage -A 4-wheel steerable under-carriage for in-plant and yard towing1with E78-14 load range (B) tubeless tires.Mounts directly to welder base.1For highway use, consult applicable federal, state and local laws regarding possible requirements for brakes, lights, fenders, etc.Linc-Thaw™- Includes meter and fuse to protect the welder when thawing frozen water pipes.(L2964-[ ] Specify SAM400 or SAM650)K704(SAM400 only) Standard Accessory Kit -Includes electrode and work cables, headshield, work clamp and electrode holder.K865(SAM400 only) Engine Hour Meter Kit -(Standard on K1279-1).Keeps track of how long engine has been eful for following recom-mended maintenance schedules on machine.SAM400 only:Inspect the oil bath air filter daily - more often in dusty conditions.When necessary clean and fill the oil bath. The filter should never be removed while the engine is running.PERIODIC MAINTENANCE1.Blow out the welder and controls with an air hose atleast once every two months.In particularly dirty locations, this cleaning may be necessary once a e low pressure air to avoid driving dirt into the insulation.2.The SAM400 current control reactor brushes areself-lubricating and should not be greased.Keep the contacts clean.This control should be moved from maximum to minimum daily to prevent the controls from sticking.3.See the engine Instruction Manual for periodicengine maintenance information.Change the crankcase oil at regular intervals using the proper grade of oil as recommended in the engine operat-ing manual.Change the oil filter in accordance with the instructions in the engine operating manual.When the filter is changed add one quart of oil to the crankcase to replace the oil held in the filter dur-ing operation.4.Belts tend to loosen after the first 30 or 40 hours ofoperation.Check the cooling fan belt and tighten if necessary.DO NOT OVER TIGHTEN.BEARING MAINTENANCEThis welder is equipped with a double-shielded ball bearing having sufficient grease to last indefinitely under normal service.Where the welder is used con-stantly or in excessively dirty locations, it may be nec-essary to add one-half ounce of grease per year.A pad of grease one inch wide, one inch long and one inch high weighs approximately one-half ounce.Over greasing is far worse than insufficient greasing. When greasing the bearings, keep all dirt out of the area.Wipe the fittings completely clean and use clean equipment.More bearing failures are caused by dirt introduced during greasing than from insufficient grease.Arcing or excessive exciter brush wear indicates a pos-sible misaligned shaft.Have an authorized Field Service Shop check and realign the shaft. COOLING SYSTEMThe SAM welders are equipped with a pressure radia-tor.Keep the radiator cap tight to prevent loss of coolant.Clean and flush the cooling system periodi-cally to prevent clogging the passage and overheating the engine.When antifreeze is needed, always use the permanent type.CONTACTOR MAINTENANCEWhere the output contactor is operated frequently when tacking or making short welds, turn the engine off and inspect the contactor every three months:1.be sure the mating surfaces of silver contacts arenot worn and all make contact at approximately the same time.2.Make sure the springs and holders are not brokenor out of adjustment.Approximate spring com-pression after making contact is 1/8”.Less than 1/16”compression indicates worn contacts that should be replaced.3.Make sure the moving contact or other movingparts are not binding.4.Check interlock contacts and springs.Be suremounting screws are tight.NOTE A:If at any time either of the Control (PC) boards is replaced, follow the calibration procedure outlined later in this sec-tion under “Control P.C.Board Calibration Procedure”.The open circuit voltage will be out of range if trimmers are not properly set.If both trimmers are set at minimum, the machine might lose excitation.NOTE B:When making continuity checks, use the 1K (X1000) or next higher range.NOTE C:Do not replace PC boards without following outlined procedure for indicated trouble -- damage may result due to other defective parts.DC on SAM400 machines or 45±1 volts forSAM650 machines.Recheck to make surereadings fall within limits.T rimmer #4 set-ting is dependent on T rimmer #3.B.Constant Voltage1.Place toggle switch in constant voltageposition.2.T urn constant voltage rheostat and portablefield control to high.3.Set T rimmer #1 so that OCV is 60±1 voltsDC on SAM400 machines or 68±1 volts forSAM650 machines.4.T urn constant voltage rheostat and portablefield control to low.5.Set T rimmer #2 so that OCV is 21±0.5 voltsDC on SAM400 machines or 22±0.5 voltsfor SAM650 machines.Recheck to makesure readings fall within limits.T rimmer #2setting is dependent on T rimmer #1.N O T E :T h i s d i a g r a m i s f o r r e f e r e n c e o n l y .I t m a y n o t b e a c c u r a t e f o r a l l m a c h i n e s c o v e r e d b y t h i s m a n u a l.T h e s p e c i f i c d i a g r a m f o r a p a r t i c u l a r c o d e i s p a s t e d i n s i d e t h e m a c h i n e o n o n e o f t h e e n c l o s u r e p a n e l s .Now Available...12th EditionThe Procedure Handbook of Arc WeldingWith over 500,000 copies of previous editions published since 1933, the Procedure Handbook is considered by many to be the “Bible”of the arc welding industry.This printing will go fast so don’t delay.Place your order now using the coupon below.The hardbound book contains over 750 pages of welding infor-mation, techniques and procedures.Much of this material has never been included in any other book.A must for all welders, supervisors, engineers and designers.Many welding instructors will want to use the book as a reference for all students by taking advantage of the low quan-tity discount prices which include shipping by 4th class parcel post.$15.00postage paid U.S.A.MainlandHow To Read Shop DrawingsThe book contains the latest information and application data on the American Welding Society Standard Welding Symbols.Detailed discussion tells how engineers and drafts-men use the “short-cut”language of symbols to pass on assembly and welding information to shop personnel.Practical exercises and examples develop the reader’s ability to visualize mechanically drawn objects as they will appear in their assembled form.187 pages with more than 100 illustrations.Size 8-1/2”x 11”Durable, cloth-covered board binding.$4.50postage paid U.S.A.MainlandNew Lessons in Arc WeldingLessons, simply written, cover manipulatory techniques;machine and electrode characteristics;related subjects, such as distortion;and supplemental information on arc welding applications, speeds and costs.Practice materials, exercises,questions and answers are suggested for each lesson.528 pages, well illustrated, 6”x 9”size, bound in simulated,gold embossed leather.$5.00postage paid U.S.A.MainlandNeed Welding Training?The Lincoln Electric Company operates the oldest and most respected Arc Welding School in the United States at its corporate headquarters in Cleveland, Ohio.Over 100,000students have graduated.Tuition is low and the training is “hands on”For details write:Lincoln Welding School 22801 St.Clair Ave.Cleveland, Ohio 44117-1199.and ask for bulletin ED-80 or call 216-383-2259 and ask for the Welding School Registrar.Lincoln Welding SchoolBASIC COURSE $700.005 weeks of fundamentalsThere is a 10%discount on all orders of $50.00 or more for shipment at one time to one location.Orders of $50 or less before discount or orders outside of North America must be prepaid with charge, check or money order in U.S. Funds Only.Prices include shipment by 4th 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Mainland Only.Please allow up to 4 weeks for delivery.UPS Shipping for North America Only.All prepaid orders that request UPS shipment please add:$5.00For order value up to $49.99$10.00For order value between $50.00 & $99.99$15.00For order value between $100.00 & $149.00For North America invoiced orders over $50.00 & credit card orders, if UPS is requested, it will be invoiced or charged to you at cost.Outside U.S.A. Mainland order must be prepaid in U.S. Funds.Please add $2.00 per book for surface mail or $15.00 per book for air parcel post shipment.METHOD OF PAYMENT:(Sorry, No C.O.D.Orders)CHECK ONE:Name:_______________________________________________Address:_______________________________________________Ohio 44117-1199216-361-5901.JapaneseChineseKoreanArabicREAD AND UNDERSTAND THE MANUFACTURER’S INSTRUCTION FOR THIS EQUIPMENT AND THE CONSUMABLES TO BE USED AND FOLLOW YOUR EMPLOYER’S SAFETY PRACTICES.SE RECOMIENDA LEER Y ENTENDER LAS INSTRUCCIONES DEL FABRICANTE PARA EL USO DE ESTE EQUIPO Y LOS CONSUMIBLES QUE VA A UTILIZAR, SIGA LAS MEDIDAS DE SEGURIDAD DE SU SUPERVISOR.LISEZ ET COMPRENEZ LES INSTRUCTIONS DU FABRICANT EN CE QUI REGARDE CET EQUIPMENT ET LES PRODUITS A ETRE EMPLOYES ET SUIVEZ LES PROCEDURES DE SECURITE DE VOTRE EMPLOYEUR.LESEN SIE UND BEFOLGEN SIE DIE BETRIEBSANLEITUNG DER ANLAGE UND DEN ELEKTRODENEINSATZ DES HER-STELLERS. DIE UNFALLVERHÜTUNGSVORSCHRIFTEN DES ARBEITGEBERS SIND EBENFALLS ZU BEACHTEN.JapaneseChineseKoreanArabicLEIA E COMPREENDA AS INSTRUÇÕES DO FABRICANTE PARA ESTE EQUIPAMENTO E AS PARTES DE USO, E SIGA AS PRÁTICAS DE SEGURANÇA DO EMPREGADOR.。

曼昆微观经济学经济学十大原理英文版

课程简介
教材（英文版）：Principles of Economics, 7ed.
written by N. Gregory Mankiw
中文版：《经济学原理（微观经济学分册）》，梁小明、
梁砾译，北京大学出版社
参考书：《经济学原理学习指南》，大卫· 哈克斯著，梁小
民译，北京大学出版社；《曼昆<经济学原理（微观经济学分册）>笔记和课后习题（含考研真题）详解》，圣才考研网主编，中国石化出版社
万美元时，高中篮球明星科比.布赖恩特（Kobe Bryant ）决定不读大学而直接进入职业篮球联盟（ NBA ）。
TEN PRINCIPLES OF ECONOMICS
11
Examples:
Choice A B C D E Revenue 200$ 150$ 180$ 201$ 200$ opportunity cost 201$ 201$ 201$ 200$ 201$
1
CHAPTER
1
Ten Principles of Economics （经济学十大原理）
Economics
PRINCIPLES OF
N. Gregory Mankiw
© 2015 CUFE
In this chapter, look for the answers to these questions:
society gets the most from its scarce resources
Equality:经济成果在社会成员中公平分配的特性 when
prosperity is distributed uniformly among society’s members.
Tradeoff: To achieve greater equality, income could be

1-2007_-_Y_F_Han_-_PreparationofnanosizedMn3O4SBA15catalystforcomplet[retrieved-2016-11-15]

Preparation of nanosized Mn 3O 4/SBA-15catalyst for complete oxidation of low concentration EtOH in aqueous solution with H 2O 2Yi-Fan Han *,Fengxi Chen,Kanaparthi Ramesh,Ziyi Zhong,Effendi Widjaja,Luwei ChenInstitute of Chemical and Engineering Sciences,1Pesek Road,Jurong Island 627833,Singapore Received 11May 2006;received in revised form 18December 2006;accepted 29May 2007Available online 2June 2007AbstractA new heterogeneous Fenton-like system consisting of nano-composite Mn 3O 4/SBA-15catalyst has been developed for the complete oxidation of low concentration ethanol (100ppm)by H 2O 2in aqueous solution.A novel preparation method has been developed to synthesize nanoparticles of Mn 3O 4by thermolysis of manganese (II)acetylacetonate on SBA-15.Mn 3O 4/SBA-15was characterized by various techniques like TEM,XRD,Raman spectroscopy and N 2adsorption isotherms.TEM images demonstrate that Mn 3O 4nanocrystals located mainly inside the SBA-15pores.The reaction rate for ethanol oxidation can be strongly affected by several factors,including reaction temperature,pH value,catalyst/solution ratio and concentration of ethanol.A plausible reaction mechanism has been proposed in order to explain the kinetic data.The rate for the reaction is supposed to associate with the concentration of intermediates (radicals: OH,O 2Àand HO 2)that are derived from the decomposition of H 2O 2during reaction.The complete oxidation of ethanol can be remarkably improved only under the circumstances:(i)the intermediates are stabilized,such as stronger acidic conditions and high temperature or (ii)scavenging those radicals is reduced,such as less amount of catalyst and high concentration of reactant.Nevertheless,the reactivity of the presented catalytic system is still lower comparing to the conventional homogenous Fenton process,Fe 2+/H 2O 2.A possible reason is that the concentration of intermediates in the latter is relatively high.#2007Elsevier B.V .All rights reserved.Keywords:Hydrogen peroxide;Fenton catalyst;Complete oxidation of ethanol;Mn 3O 4/SBA-151.IntroductionRemediation of wastewater containing organic constitutes is of great importance because organic substances,such as benzene,phenol and other alcohols may impose toxic effects on human and animal anic efﬂuents from pharmaceu-tical,chemical and petrochemical industry usually contaminate water system by dissolving into groundwater.Up to date,several processes have been developed for treating wastewater that contains toxic organic compounds,such as wet oxidation with or without solid catalysts [1–4],biological oxidation,supercritical oxidation and adsorption [5,6],etc.Among them,catalytic oxidation is a promising alternative,since it avoids the problem of the adsorbent regeneration in the adsorption process,decreases signiﬁcantly the temperature and pressure in non-catalytic oxidation techniques [7].Generally,the disposalof wastewater containing low concentration organic pollutants (e.g.<100ppm)can be more costly through all aforementioned processes.Thus,catalytic oxidation found to be the most economical way for this purpose with considering its low cost and high efﬁciency.Currently,a Fenton reagent that consists of homogenous iron ions (Fe 2+)and hydrogen peroxide (H 2O 2)is an effective oxidant and widely applied for treating industrial efﬂuents,especially at low concentrations in the range of 10À2to 10À3M organic compounds [8].However,several problems raised by the homogenous Fenton system are still unsolved,e.g.disposing the iron-containing waste sludge,limiting the pH range (2.0–5.0)of the aqueous solution,and importantly irreversible loss of activity of the reagent.To overcome these drawbacks raised from the homogenous Fenton system,since 1995,a heterogeneous Fenton reagent using metal ions exchanged zeolites,i.e.Fe/ZSM-5has proved to be an interesting alternative catalytic system for treating wastewater,and showed a comparable activity with the homogenous Fenton system [9].However,most reported heterogeneous Fenton reagents still need UV radiation during/locate/apcatbApplied Catalysis B:Environmental 76(2007)227–234*Corresponding author.Tel.:+6567963806.E-mail address:han_yi_fan@.sg (Y .-F.Han).0926-3373/$–see front matter #2007Elsevier B.V .All rights reserved.doi:10.1016/j.apcatb.2007.05.031oxidation of organic compounds.This might limit the application of homogeneous Fenton system.Exploring other heterogeneous catalytic system considering the above disadvantages,is still desirable for this purpose.Here,we present an alternative catalytic system for the complete oxidation of organic com-pounds in aqueous solution using supported manganese oxide as catalyst under mild conditions,which has rarely been addressed.Mn-containing oxide catalysts have been found to be very active for the catalytic wet oxidation of organic efﬂuents (CWO)[10–14],which is operated at high air pressures(1–22MPa)and at high temperatures(423–643K)[15].On the other hand,manganese oxide,e.g.MnO2[16],is well known to be active for the decomposition of H2O2in aqueous solution to produce hydroxyl radical( OH),which is considered to be the most robust oxidant so far.The organic constitutes can be deeply oxidized by those radicals rapidly[17].The only by-product is H2O from decomposing H2O2.Therefore,H2O2is a suitable oxidant for treating the wastewater containing organic compounds.Due to the recent progress in the synthesis of H2O2 directly from H2and O2[18,19],H2O2is believed to be produced through more economical process in the coming future.So,the heterogeneous Fenton system is economically acceptable.In this study,nano-crystalline Mn3O4highly dispersed inside the mesoporous silica,SBA-15,has been prepared by thermolysis of organic manganese(II)acetylacetonate in air. We expect the unique mesoporous structure may provide add-itional function(conﬁnement effect)to the catalytic reaction, i.e.occluding/entrapping large organic molecules inside pores. The catalyst as prepared has been examined for the complete oxidation of ethanol in aqueous solution with H2O2,or to say, wet peroxide oxidation.Ethanol was selected as a model organic compound because(i)it is one of the simplest organic compounds and can be easily analyzed,(ii)it has high solu-bility in water due to its strong hydrogen bond with water molecule and(iii)the structure of ethanol is quite stable and only changed through catalytic reaction.Presently,for theﬁrst time by using the Mn3O4/SBA-15catalyst,we investigated the peroxide ethanol oxidation affected by factors such as temperature,pH value,ratio of catalyst(g)and volume of solution(L),and concentration of ethanol in aqueous solution. In addition,plausible reaction mechanisms are established to explain the peroxidation of ethanol determined by the H2O2 decomposition.2.Experimental2.1.Preparation and characterization of Mn3O4/SBA-15 catalystSynthesis of SBA-15is similar to the previous reported method[20]by using Pluronic P123(BASF)surfactant as template and tetraethyl orthosilicate(TEOS,98%)as silica source.Manganese(II)acetylacetonate([CH3COCH C(O)CH3]2Mn,Aldrich)by a ratio of2.5mmol/gram(SBA-15)wereﬁrst dissolved in acetone(C.P.)at room temperature, corresponding to ca.13wt.%of Mn3O4with respect to SBA-15.The preparation method in detail can be seen in our recent publications[21,22].X-ray diffraction proﬁles were obtained with a Bruker D8 diffractometer using Cu K a radiation(l=1.540589A˚).The diffraction pattern was taken in the Bragg angle(2u)range at low angles from0.68to58and at high angles from308to608at room temperature.The XRD patterns were obtained by scanning overnight with a step size:0.028per step,8s per step.The dispersive Raman microscope employed in this study was a JY Horiba LabRAM HR equipped with three laser sources(UV,visible and NIR),a confocal microscope,and a liquid nitrogen cooled charge-coupled device(CCD)multi-channel detector(256pixelsÂ1024pixels).The visible 514.5nm argon ion laser was selected to excite the Raman scattering.The laser power from the source is around20MW, but when it reached the samples,the laser output was reduced to around6–7MW after passing throughﬁltering optics and microscope objective.A100Âobjective lens was used and the acquisition time for each Raman spectrum was approximately 60–120s depending on the sample.The Raman shift range acquired was in the range of50–1200cmÀ1with spectral resolution1.7–2cmÀ1.Adsorption and desorption isotherms were collected on Autosorb-6at77K.Prior to the measurement,all samples were degassed at573K until a stable vacuum of ca.5m Torr was reached.The pore size distribution curves were calculated from the adsorption branch using Barrett–Joyner–Halenda(BJH) method.The speciﬁc surface area was assessed using the BET method from adsorption data in a relative pressure range from 0.06to0.10.The total pore volume,V t,was assessed from the adsorbed amount of nitrogen at a relative pressure of0.99by converting it to the corresponding volume of liquid adsorbate. The conversion factor between the volume of gas and liquid adsorbate is0.0,015,468for N2at77K when they are expressed in cm3/g and cm3STP/g,respectively.The measurements of transmission electron microscopy (TEM)were performed at Tecnai TF20S-twin with Lorentz Lens.The samples were ultrasonically dispersed in ethanol solvent,and then dried over a carbon grid.2.2.Kinetic measurement and analysisThe experiment for the wet peroxide oxidation of ethanol was carried out in a glass batch reactor connected to a condenser with continuous stirring(400rpm).Typically,20ml of aqueous ethanol solution(initial concentration of ethanol: 100ppm)wasﬁrst taken in the round bottomﬂask(reactor) together with5mg of catalyst,corresponding to ca.1(g Mn)/30 (L)ratio of catalyst/solution.Then,1ml of30%H2O2solution was introduced into the reactor at different time intervals (0.5ml at$0min,0.25ml at32min and0.25ml at62min). The total molar ratio of H2O2/ethanol is about400/1. Hydrochloric acid(HCl,0.01M)was used to acidify the solution if necessary.NH4OH(0.1M)solution was used to adjust pH to9.0when investigating the effect of pH.The pH for the deionized water is ca.7.0(Oakton pH meter)and decreased to 6.7after adding ethanol.All the measurements wereY.-F.Han et al./Applied Catalysis B:Environmental76(2007)227–234 228performed under the similar conditions described above if without any special mention.For comparison,the reaction was also carried out with a typical homogenous Fenton reagent[17], FeSO4(5ppm)–H2O2,under the similar reaction conditions.The conversion of ethanol during reaction was detected using gas chromatography(GC:Agilent Technologies,6890N), equipped with HP-5capillary column connecting to a thermal conductive detector(TCD).There is no other species but ethanol determined in the reaction system as evidenced by the GC–MS. Ethanol is supposed to be completely oxidized into CO2and H2O.The variation of H2O2concentration during reaction was analyzed colorimetrically using a UV–vis spectrophotometer (Epp2000,StellarNet Inc.)after complexation with a TiOSO4/ H2SO4reagent[18].Note that there was almost no measurable leaching of Mn ion during reaction analyzed by ICP(Vista-Mpx, Varian).3.Results and discussion3.1.Characterization of Mn3O4/SBA-15catalystThe structure of as-synthesized Mn3O4inside SBA-15has beenﬁrst investigated with powder XRD(PXRD),and the proﬁles are shown in Fig.1.The proﬁle at low angles(Fig.1a) suggests that SBA-15still has a high degree of hexagonal mesoscopic organization even after forming Mn3O4nanocrys-tals[23].Several peaks at high angles of XRD(Fig.1b)indicate the formation of a well-crystallized Mn3O4.All the major diffraction peaks can be assigned to hausmannite Mn3O4 structure(JCPDS80-0382).By N2adsorption measurements shown in Fig.2,the pore volume and speciﬁc surface areas(S BET)decrease from 1.27cm3/g and937m2/g for bare SBA-15to0.49cm3/g and 299m2/g for the Mn3O4/SBA-15,respectively.About7.7nm of mesoporous diameter for SBA-15decreases to ca.6.3nm for Mn3O4/SBA-15.The decrease of the mesopore dimension suggests the uniform coating of Mn3O4on the inner walls of SBA-15.This nano-composite was further characterized by TEM. Obviously,the SBA-15employed has typical p6mm hex-agonal morphology with the well-ordered1D array(Fig.3a). The average pore size of SBA-15is ca.8.0nm,which is very close to the value(ca.7.7nm)determined by N2adsorption. Along[001]orientation,Fig.3b shows that the some pores areﬁlled with Mn3O4nanocrystals.From the pore A to D marked in Fig.3b correspond to the pores from empty to partially and fullyﬁlled;while the features for the SBA-15 nanostructure remains even after forming Mn3O4nanocrys-tals.Nevertheless,further evidences for the location of Mn3O4inside the SBA-15channels are still undergoing in our group.Raman spectra obtained for Mn3O4/SBA-15is presented in Fig.4a.For comparison the Raman spectrum was also recorded for the bulk Mn3O4(97.0%,Aldrich)under the similar conditions(Fig.4b).For the bulk Mn3O4,the bands at310,365, 472and655cmÀ1correspond to the bending modes of Mn3O4, asymmetric stretch of Mn–O–Mn,symmetric stretch of Mn3O4Fig.1.XRD patterns of the bare SBA-15and the Mn3O4/SBA-15nano-composite catalyst.(a)At low angles:(A)Mn3O4/SBA-15,(B)SBA-15;and (b)at high angles of Mn3O4/SBA-15.Fig.2.N2adsorption–desorption isotherms:(!)SBA-15,(~)Mn3O4/SBA-15.Y.-F.Han et al./Applied Catalysis B:Environmental76(2007)227–234229groups,respectively [24–26].However,a downward shift ($D n 7cm À1)of the peaks accompanying with a broadening of the bands was observed for Mn 3O 4/SBA-15.For instance,the distinct feature at 655cm À1for the bulk Mn 3O 4shifted to 648cm À1for the nanocrystals.The Raman bands broadened and shifted were observed for the nanocrystals due to the effect of phonon conﬁnement as suggested previously in the literature [27,28].Furthermore,a weak band at 940cm À1,which should associate with the stretch of terminal Mn O,is an indicative of the existence of the isolated Mn 3O 4group [26].The assignment of this unique band has been discussed in our previous publication [22].3.2.Kinetic study3.2.1.Blank testsUnder a typical reaction conditions,that is,20ml of 100ppm ethanol aqueous solution (pH 6.7)mixed with 1ml of 30%H 2O 2,at 343K,there is no conversion of ethanol was observed after running for 120min in the absence of catalyst or in the presence of bare SBA-15(5mg).Also,under the similar conditions in H 2O 2-free solution,ethanol was not converted for all blank tests even with Mn 3O 4/SBA-15catalyst (5mg)in the reactor.It suggests that a trace amount of oxygen dissolved in water or potential dissociation of adsorbed ethanol does not have any contribution to the conversion of ethanol under reaction conditions.To study the effect of low temperature evaporation of ethanol during reaction,we further examined the concentration of ethanol (100ppm)versus time at different temperatures in the absence of catalyst and H 2O 2.Loss of ca.5%ethanol was observed only at 363K after running for 120min.Hence,to avoid the loss of ethanol through evaporation at high temperatures,which may lead to a higher conversion of ethanol than the real value,the kinetic experiments in this study were performed at or below 343K.The results from blank tests conﬁrm clearly that ethanol can be transformed only by catalytic oxidation during reaction.3.2.2.Effect of amount of catalystThe effect of amount of catalyst on ethanol oxidation is presented in Fig.5.Different amounts of catalyst ranging from 2to 10mg were taken for the same concentration of ethanol (100ppm)in aqueous solution under the standard conditions.It can be observed that the conversion of ethanol increases monotonically within 120min,reaching 15,20and 12%for 2,5and 10mg catalysts,respectively.On the other hand,Fig.5shows that the relative reaction rates (30min)decreased from 0.7to ca 0.1mmol/g Mn min with the rise of catalyst amount from 2to 10mg.Apparently,more catalyst in the system may decrease the rate for ethanol peroxidation,and a proper ratio of catalyst (g)/solution (L)is required for acquiring a balance between the overall conversion of ethanol and reaction rate.In order to investigate the effects from other factors,5mg (catalyst)/20ml (solution),corresponding to 1(g Mn )/30(L)ratio of catalyst/solution,has been selected for the followedexperiments.Fig.4.Raman spectroscopy of the Mn 3O 4/SBA-15(a)and bulk Mn 3O 4(b).Fig.3.TEM images recorded along the [001]of SBA-15(a),Mn 3O 4/SBA-15(b):pore A unﬁlled with hexagonal structure,pores B and C partially ﬁlled and pore D completely ﬁlled.Y.-F .Han et al./Applied Catalysis B:Environmental 76(2007)227–2342303.2.3.Effect of temperatureAs shown in Fig.6,the reaction rate increases with increasing the reaction temperature.After 120min,the conversion of ethanol increases from 12.5to 20%when varying the temp-erature from 298to 343K.Further increasing the temperature was not performed in order to avoid the loss of ethanol by evaporation.Interestingly,the relative reaction rate increased with time within initial 60min at 298and 313K,but upward tendency was observed above 333K.3.2.4.Effect of pHIn the pH range from 2.0to 9.0,as illustrated in Fig.7,the reaction rate drops down with the rise of pH.It indicates that acidic environment,or to say,proton concentration ([H +])in the solution is essential for this reaction.With considering our target for this study:purifying water,pH approaching to 7.0in the reaction system is preferred.Because acidifying the solution with organic/inorganic acids may potentially causea second time pollution and result in surplus cost.Actually,there is almost no effect on ethanol conversion with changing pH from 5.5to 6.7in this system.It is really a merit comparing with the conventional homogenous Fenton system,by which the catalyst works only in the pH range of 2.0–5.0.3.2.5.Effect of ethanol concentrationThe investigation of the effect of ethanol concentration on the reaction rate was carried out in the ethanol ranging from 50to 500ppm.The results in Fig.8show that the relative reaction rate increased from 0.07to 2.37mmol/g Mn min after 120min with increasing the concentration of ethanol from 50to 500ppm.It is worth to note that the pH value of the solution slightly decreased from 6.7to 6.5when raising the ethanol concentration from 100to 500ppm.paring to a typical homogenous Fenton reagent For comparison,under the similar reaction conditions ethanol oxidation was performed using aconventionalFig.5.The ethanol oxidation as a function of time with different amount of catalyst.Conversion of ethanol vs.time (solid line)on 2mg (&),5mg (*)and 10mg (~)Mn 3O 4/SBA-15catalyst,the relative reaction rate vs.time (dash line)on 2mg (&),5mg (*)and 10mg (~)Mn 3O 4/SBA-15catalyst.Rest conditions:20ml of ethanol (100ppm),1ml of 30%H 2O 2,708C and pH of6.7.Fig.6.The ethanol oxidation as a function of temperature.Conversion of ethanol vs.time (solid line)at 258C (&),408C (*),608C (~)and 708C (!),the relative reaction rate vs.time (dash line)at 258C (&),408C (*),608C (~)and 708C (5).Rest conditions:20ml of ethanol (100ppm),1ml of 30%H 2O 2,pH of 6.7,5mg ofcatalyst.Fig.7.The ethanol oxidation as a function of pH value.Conversion of ethanol vs.time (solid line)at pH value of 2.0(&),3.5(*),4.5(~),5.5(!),6.7(^)and 9.0("),the relative reaction rate vs.time (dash line)at pH value of 2.0(&),3.5(*),4.5(~),5.5(5),6.7(^)and 9.0(").Rest conditions:20ml of ethanol (100ppm),1ml of 30%H 2O 2,708C,5mg ofcatalyst.Fig.8.The ethanol oxidation as a function of ethanol concentration.Conver-sion of ethanol vs.time (solid line)for ethanol concentration (ppm)of 50(&),100(*),300(~),500(!),the relative reaction rate vs.time (dash line)for ethanol concentration (ppm)of 50(&),100(*),300(~),500(5).Condi-tions:20ml of ethanol,pH of 6.7,1ml of 30%H 2O 2,708C,5mg of catalyst.Y.-F .Han et al./Applied Catalysis B:Environmental 76(2007)227–234231homogenous reagent,Fe 2+(5ppm)–H 2O 2(1ml)at pH of 5.0.It has been reported to be an optimum condition for this system [17].As shown in Fig.9,the reaction in both catalytic systems exhibits a similar behavior,that is,the conversion of ethanol increases with extending the reaction time.Varying reaction temperature from 298to 343K seems not to impact the conversion of ethanol when using the homogenous Fenton reagent.Furthermore,the conversion of ethanol (deﬁning at 120min)in the system of Mn 3O 4/SBA-15–H 2O 2is about 60%of that obtained from the conventional Fenton reagent.There are no other organic compounds observed in the reaction mixture other than ethanol suggesting that ethanol directly decomposing to CO 2and H 2O.3.2.7.Decomposition of H 2O 2In the aqueous solution,the capability of metal ions such as Fe 2+and Mn 2+has long been evidenced to be effective on the decomposition of H 2O 2to produce the hydroxyl radical ( OH),which is oxidant for the complete oxidation/degrading of organic compounds [9,17].Therefore,ethanol oxidation is supposed to be associated with H 2O 2decomposition.The investigation of H 2O 2decomposition has been performed under the reaction conditions (in an ethanol-free solution)with different amounts of catalyst.H 2O 2was introduced into the reaction system by three steps,initially 0.5ml followed by twice 0.25ml at 32and 62min,the pH of 6.7is set for all experiments except pH of 5.0for Fe 2+.As shown in Fig.10,H 2O 2was not converted in the absence of catalyst or presence of bare SBA-15(5mg);in contrast,by using the Mn 3O 4/SBA-15catalyst we observed that ca.Ninety percent of total H 2O 2was decomposed in the whole experiment.It can be concluded that that dissociation of H 2O 2is mainly caused by Mn 3O paratively,the rate of H 2O 2decomposition is relatively low with the homogenous Fenton reagent,total conversion of H 2O 2,was ca.50%after runningfor 120min.Considering the fact that H 2O 2decomposition can be signiﬁcantly enhanced with the rise of Fe 2+concentration,however,it seems not to have the inﬂuence on the reaction rate for ethanol oxidation simultaneously.The similar behavior of H 2O 2decomposition was also observed during ethanol oxidation.The rate for ethanol oxidation is lower for Mn 3O 4/SBA-15comparing to the conventional Fenton reagent.The possible reasons will be discussed in the proceeding section.3.3.Plausible reaction mechanism for ethanol oxidation with H 2O 2In general,the wet peroxide oxidation of organic constitutes has been suggested to proceed via four steps [15]:activation of H 2O 2to produce OH,oxidation of organic compounds withOH,recombination of OH to form O 2and wet oxidation of organic compounds with O 2.It can be further described by Eqs.(1)–(4):H 2O 2À!Catalyst =temperture 2OH(1)OH þorganic compoundsÀ!Temperatureproduct(2)2 OHÀ!Temperature 12O 2þH 2O(3)O 2þorganic compoundsÀ!Temperature =pressureproduct(4)The reactive intermediates produced from step 1(Eq.(1))participate in the oxidation through step 2(Eq.(2)).In fact,several kinds of radical including OH,perhydroxyl radicals ( HO 2)and superoxide anions (O 2À)may be created during reaction.Previous studies [29–33]suggested that the process for producing radicals could be expressed by Eqs.(5)–(7)when H 2O 2was catalytically decomposed by metal ions,such asFeparison of ethanol oxidation in systems of typical homogenous Fenton catalyst (5ppm of Fe 2+,20ml of ethanol (100ppm),1ml of 30%H 2O 2,pH of 5.0acidiﬁed with HCl)at room temperature (~)and 708C (!),and Mn 3O 4/SBA-15catalyst (&)under conditions of 20ml of ethanol (100ppm),pH of 6.7,1ml of 30%H 2O 2,708C,5mg ofcatalyst.Fig.10.An investigation of H 2O 2decomposition under different conditions.One milliliter of 30%H 2O 2was dropped into the 20ml deionized water by three intervals,initial 0.5ml followed by twice 0.25ml at 32and 62min.H 2O 2concentration vs.time:by calculation (&),without catalyst (*),SBA-15(~),5ppm of Fe 2+(!)and Mn 3O 4/SBA-15(^).Rest conditions:5mg of solid catalyst,pH of 7.0(5.0for Fe 2+),708C.Y.-F .Han et al./Applied Catalysis B:Environmental 76(2007)227–234232and Mn,S þH 2O 2!S þþOH Àþ OH (5)S þþH 2O 2!S þ HO 2þH þ(6)H 2O $H þþO 2À(7)where S and S +represent reduced and oxidized metal ions,both the HO 2and O 2Àare not stable and react further with H 2O 2to form OH through Eqs.(8)and (9):HO 2þH 2O 2! OH þH 2O þO 2(8)O 2ÀþH 2O 2! OH þOH ÀþO 2(9)Presently, OH radical has been suggested to be the main intermediate responsible for oxidation/degradation of organic compounds.Therefore,the rate for ethanol oxidation in the studied system is supposed to be dependent on the concentra-tion of OH.Note that the oxidation may proceed via step four (Eq.(4))in the presence of high pressure O 2,which is so-called ‘‘wet oxidation’’and usually occurs at air pressures (1–22MPa)and at high temperatures (423–643K)[15].However,it is unlikely to happen in the present reaction conditions.According to Wolfenden’s study [34],we envisaged that the complete oxidation of ethanol may proceed through a route like Eq.(10):C 2H 5OH þ OH À!ÀH 2OC 2H 4O À! OHCO 2þH 2O(10)Whereby,it is believed that organic radicals containing hydroxy-groups a and b to carbon radicals centre can eliminate water to form oxidizing species.With the degrading of organic intermediates step by step as the way described in Eq.(10),the ﬁnal products should be CO 2and H 2O.However,no other species but ethanol was detected by GC and GC–MS in the present study possibly due to the rapid of the reaction that leads to unstable intermediate.Fig.5indicates that a proper ratio of catalyst/solution is a necessary factor to attain the high conversion of ethanol.It can be understood that over exposure of H 2O 2to catalyst will increase the rate of H 2O 2decomposition;but on the other hand,more OH radical produced may be scavenged by catalyst with increasing the amount of catalyst and transformed into O 2and H 2O as expressed in Eq.(3),instead of participating the oxidation reaction.In terms of Eq.(10),stoichiometric ethanol/H 2O 2should be 1/6for the complete oxidation of ethanol;however,in the present system the total molar ratio is 1/400.In other words,most intermediates were extinguished through scavenging during reaction.This may explain well that the decrease of reaction rate with the rise of ratio of catalyst/solution in the system.The same reason may also explain the decrease of reaction rate with prolonging the time.Actually,H 2O 2decomposition (ca.90%)may be completed within a few minutes over the Mn 3O 4/SBA-15catalyst as illustrated in Fig.10,irrespective of amount of catalyst (not shown for the sake of brevity);in contrast,the rate for H 2O 2decomposition became dawdling for Fe 2+catalyst.As a result,presumably,the homogenous system has relatively high concentration ofradicals.It may explain the superior reactivity of the conventional Fenton reagent to the presented system as depicted in Fig.9.Therefore,how to reduce scavenging,especially in the heterogeneous Fenton system [29],is crucial for enhancing the reaction rate.C 2H 5OH þ6H 2O 2!2CO 2þ9H 2O(11)On the other hand,as illustrated by Eqs.(1)–(4),all steps in the oxidation process are affected by the reaction temperature.Fig.6demonstrates that increasing temperature remarkably boosts the reactivity of ethanol oxidation in the system of Mn 3O 4/SBA-15–H 2O 2possibly,due to the improvement of the reactions in Eqs.(2)and (4)at elevated temperatures.In terms of Eqs.(6)and (7),acidic conditions may delay the H 2O 2decomposition but enhance the formation of OH (Eqs.(5),(8)and (9)).This ‘‘delay’’is supposed to reduce the chance of the scavenging of radicals and improve the efﬁciency of H 2O 2in the reaction.The protons are believed to have capability for stabilizing H 2O 2,which has been elucidated well previously [18,19].Consequently,it is understandable that the reaction is favored in the strong acidic environment.Fig.7shows a maximum reactivity at pH of 2.0and the lowest at pH of 9.0.As depicted in Fig.8,the reaction rate for ethanol oxidation is proportional to the concentration of ethanol in the range of 50–500ppm.It suggests that at low concentration of ethanol (100ppm)most of the radicals might not take part in the reaction before scavenged by catalyst.With increasing the ethanol concentration,the possibility of the collision between ethanol and radicals can be increased signiﬁcantly.As a result,the rate of scavenging radicals is reduced relatively.Thus,it is reasonable for the faster rate observed at higher concentration of ethanol.Finally,it is noteworthy that as compared to the bulk Mn 3O 4(Aldrich,98.0%of purity),the reactivity of the nano-crystalline Mn 3O 4on SBA-15is increased by factor of 20under the same typical reaction conditions.Obviously,Mn 3O 4nanocrystal is an effective alternative for this catalytic system.The present study has evidenced that the unique structure of SBA-15can act as a special ‘‘nanoreactor’’for synthesizing Mn 3O 4nanocrystals.Interestingly,a latest study has revealed that iron oxide nanoparticles could be immobilized on alumina coated SBA-15,which also showed excellent performance as a Fenton catalyst [35].However,the role of the pore structure of SBA-15in this reaction is still unclear.We do expect that during reaction SBA-15may have additional function to trap larger organic molecules by adsorption.Thus,it may broaden its application in this ﬁeld.So,relevant study on the structure of nano-composites of various MnO x and its role in the Fenton-like reaction for remediation of organic compounds in aqueous solution is undergoing in our group.4.ConclusionsIn the present study,we have addressed a new catalytic system suitable for remediation of trivial organic compound from contaminated water through a Fenton-like reaction withY.-F .Han et al./Applied Catalysis B:Environmental 76(2007)227–234233。

Pumping and Storing Breast Milk

Pumping and Storing Breast Milk You may need to express or pump breast milk to relieve engorgement, to increase your milk supply or to feed your baby breast milk with a bottle.Why and When to Pump• To soften your breasts if your baby is having trouble latching on.Pump for a few minutes and try your baby at your breast again. • To have a milk supply when your baby is unable to breastfeed or tostore breast milk.Pump every 2 to 4 hours through the day and one time at night. • To increase your milk supply.Pump every 2 to 3 hours if you are not breastfeeding, orPump between feedings as often as you can.Pump on the second breast if your baby only nurses on one side. • To prepare to return to work or school.Pump one time each day, between feedings to store extra milk.Morning is a good time to pump.Pump extra milk and store it at least 2 weeks before your return date.Pump at least every 4 hours when away.用吸奶器吸出乳汁和储存乳汁为了缓解涨奶、促进乳汁分泌或用奶瓶喂宝宝乳汁，可能需要挤出乳汁或用吸奶器吸出乳汁。

PUMPINGNYLON(跳动的尼龙)字幕(用记事本打开后,另存为SRT格式就能用了)

指甲的修剪
81
00:15:59,999-->00:16:07,000
指甲的修剪十分重要
82
00:16:08,000-->00:16:23,000
把指甲修剪成良好的形状，可以使演奏的音色饱满，
使手指拨弦的动作非常轻松
Hale Waihona Puke 83 00:16:26,000-->00:16:33,000
牢记：修剪的原则是，
96
00:21:58,000-->00:22:08,000
它有两面，共四种不同的粗细度
97
00:22:30,000-->00:22:50,000
这是一张非常细的砂纸，500#号的
不同国家可能标准不同（总之用很细的砂纸）
98
00:23:03,000-->00:23:06,000
撕下一小块
46
00:08:36,000-->00:08:39,000
是不是觉得很难受？很不自然？
47
00:08:42,000-->00:08:59,000
将手臂转向正面，左右运动手腕并握拳
这样感觉也很轻松，我们可以做很多次
48
00:09:02,000-->00:09:15,000
当我们演奏时，实际上就好比是在做握拳和松开的动作，
这两种都是可取的方法，充分的利用了指甲的边缘
87
00:18:54,000-->00:18:59,000
再强调一遍：尽可能多的使用指甲边缘
88
00:19:25,000-->00:19:40,000
从指甲左侧开始触弦，到右侧结束，

MASSAGING BREAST PUMP AND FUNNEL THEREFOR

申请人：JOHANSEN, Jean, Louise,MEYERS, Brenda, Jean,MENSCH, Alice, A.,MCCORMICK, Patrick, A.,SLAVEN, Mark, P.
地址：US,CH,US,,US,US 代理机构：LIPHARDT, Bernd 更多信息请下载全文后查看
专利内容由知识产权出版社提供
专利名称：MASSAGING BREAST PUMP AND FUNNEL T H EREFOR
发明人：JOHANSEN, Jean, Louise,MEYERS, Brenda, Jean,MENSCH, Alice, A.,MCCORMICK, Patrick, A.,SLAVEN, Mark, P.
申请号：EP2001011178 申请日：20010926 公开号：WO02/026290P1 公开日：200204 04
摘要：A breast pump funnel is disclosed. The funnel is shaped and dimensioned to fit a woman's breast, and has a neck to receive the nipple, a cup to fit over an inner part of the breast and a plurality of fingers extending outwardly from the cup to contact an outer part of the breast. The pump section of the brest pump is connected to the neck of the funnel to apply a varying suction to draw milk from the breast and to deliver the milk into a receiving vessel. The tips of the fingers of the funnel serve to massage the breast and stimulate the release of milk from the breast during pumping.

PUMP-ACTION SHOTGUN INSTRUCTION MANUAL

12. Do not shoot at a hard surface or at water. Bullet and shot can ricochet or bounce off and travel in unoredictable directions with great velocity.
Your TriStar is manually operated. Once a shell has been fired, the locking lug in the bolt moves down, unlocking the gun. The forend can then be moved to the rear and forward again, ejecting and loading a new shell.
B- To engage the safety, push the button so that it protrudes from the right side of the gun and the RED BAND MARKING CAN NOT BE SEEN. The safety should always be in the ‘‘on’’ or ‘‘safe’’ position until you intend to fire the gun. (Photo 1)
10. Wear protective shooting glasses and adequate ear protection when shooting.
11. Never climb or jump over anything, such as a tree, fence, or ditch, with a loaded gun. Open the barrel, remove the shells and hand the gun to someone else or place it on the ground on the other side of the obstacle before crossing it yourself. Do not lean a gun against a tree or other object; it could fall and possibly discharge.

托班活动教案：我的幼儿园

托班活动教案：我的幼儿园活动总目标：1、通过活动，让幼儿认识幼儿园，了解幼儿园的各个环境设施，熟悉幼儿园的生活场所及日常活动。

2通过活动培养幼儿敢于表达的能力，提高幼儿积极参与活动的意识。

3、激发幼儿喜欢上幼儿园的情感，懂得自己长大了，要高高兴兴地来幼儿园。

活动（一）：语言活动名称：高高兴兴上幼儿园活动目标：1、通过活动让幼儿知道幼儿园里有许多有趣的事物和小伙伴。

2、教育幼儿挨上幼儿园，高高兴兴上幼儿园。

3、发展幼儿的口语讲述力、表达能力，西汉参加集体活动的情感。

活动准备：投影仪、图片等活动过程：1、出示图片，教师引导幼儿观察图片，了解图片的内容。

2、谈话：请幼儿说说愿意上幼儿园吗？在幼儿园里都干些什么？心情怎样？3、讲故事：高高兴兴上幼儿园提问：故事叫什么名字？里面都有谁？小动物们都是怎样来幼儿园的？你是怎样上幼儿园的？（教育孩子要高高兴兴地来幼儿园）活动（二）：常识活动名称：我的幼儿园活动目标：1、通过活动让幼儿认识幼儿园里的各活动场所，熟悉幼儿园的环境设施，知道其功用。

2、了解工作人员的工作，体会其劳动辛苦，懂得珍惜他人劳动成果。

活动准备：课前联系幼儿园各工作人员，以便让幼儿很好的了解、体会工作人员的工作。

活动过程：1、引起幼儿参与活动的兴趣：你知道幼儿园里都有哪些场所吗？都有哪些工作人员吗？他们都干些什么？想看看吗？2、带幼儿参观幼儿园1）|出门前提醒幼儿注意安静、不讲话、跟着老师走、不掉队）2）、引导幼儿注意看工作人员的工作情况：如伙房，看炊事员阿姨的衣着、如何为小朋友做饭。

3）、介绍各活动场所，了解其功用：教学楼：传达室：：办公室：：更衣室：：多功能厅：：舞蹈教室：：会议室：：保健室：：各教学班。

活动场地：院子：：大型器械：：器械屋。

3、自由谈话教师引导幼儿将自己看到的幼儿园的各个活动场所及工作人员的工作进行讲述，体会工作人员的辛苦。

2017北京高考物理试卷及答案

2017北京高考物理试卷及答案D理科综合能力测试（北京卷）第 2 页（共22 页）理科综合能力测试（北京卷）第 3 页（共22 页）的是A．t =1s时，振子的速度为零，加速度为负的最大值B．t =2s时，振子的速度为负，加速度为正的最大值C．t =3s时，振子的速度为负的最大值，加速度为零D．t =4s时，振子的速度为正，加速度为负的最大值16．如图所示，理想变压器的原线圈接在=（）的交流电源上，副u t2202sin100πV线圈接有55R=Ω的负载电阻，原、副线圈匝数之比为2∶1，电流表、电压表均为理想电表。

下列说法正确的是理科综合能力测试（北京卷）第 4 页（共22 页）A．原线圈的输入功率为2202B．电流表的读数为1 AC．电压表的读数为1102VD．副线圈输出交流电的周期为50s17．利用引力常量G和下列某一组数据，不能．．计算出地球质量的是A．地球的半径及重力加速度（不考虑地球自转）B．人造卫星在地面附近绕地球做圆周运动的速度及周期C．月球绕地球做圆周运动的周期及月球与地球间的距离D．地球绕太阳做圆周运动的周期及地球与太阳间的距离2017年北京高考理综物理试卷2017.6理科综合能力测试（北京卷）第 5 页（共22 页）18．2017年年初，我国研制的“大连光源”——极紫外自由电子激光装置，发出了波长在100 nm（1nm=10-9 m）附近连续可调的世界上最强的极紫外激光脉冲。

大连光源因其光子的能量大、密度高，可在能源利用、光刻技术、雾霾治理等领域的研究中发挥重要作用。

一个处于极紫外波段的光子所具有的能量可以电离一个分子，但又不会把分子打碎。

据此判断，能够电离一个分子的能量约为（取普朗克常量h=6.6⨯10-34 J∙s，真空光速c=3⨯108 m/s）A．10-21 J B．10-18 J C．10-15 JD．10-12 J19．图1和图2是教材中演示自感现象的两个电理科综合能力测试（北京卷）第 6 页（共22 页）路图，L1和L2为电感线圈。

2021年承德市七年级数学下期末模拟试题带答案

一、选择题1．甲、乙两人分别从相距40km 的两地同时出发，若同向而行，则5h 后，快者追上慢者；若相向而行，则2h 后，两人相遇，那么快者速度和慢者速度(单位：km/h)分别是（）A ．14和6B ．24和16C ．28和12D ．30和12．若关于x ，y 的二元一次方程组432x y k x y k+=⎧⎨-=⎩的解也是二元一次方程2310x y +=的解，则x y -的值为（）A ．2B ．10C ．2-D ．43．已知 xyz≠0，且4520430x y z x y z -+=⎧⎨+-=⎩，则 x ：y ：z 等于（） A ．3：2：1 B ．1：2：3 C ．4：5：3 D ．3：4：5 4．如果a b >，可知下面哪个不等式一定成立（）A ．a b ->-B ．11a b <C ．2a b b +>D ．2a ab >5．不等式组10,{360x x -≤-<的解集在数轴上表示正确的是（） A ． B ．C ．D ．6．若|65|56x x -=-，则x 的取值范围是（）A ．56x >B ．56x <C ．56x ≥D ．56x ≤ 7．下列方程是二元一次方程的是（）．A ．32x y -=B ．1xy =C ．2+3=x xD ．153x y -= 8．平面直角坐标系中，线段CD 是由线段AB 平移得到的，点A(-1，4)的对应点C(4，7)，点B(-4，-1)的对应点D 的坐标为（）A ．(-1，-4)B ．(1，-4)C ．(1，2)D ．(-1，2) 9．在平面直角坐标系中，点()25,1N a -+一定在（）A ．第一象限B ．第二象限C ．第三象限D ．第四象限 10．已知：m 、n 为两个连续的整数，且5m n <，以下判断正确的是（）A ．5的整数部分与小数部分的差是45-B ．3m =C ．5的小数部分是0.236D ．9m n += 11．已知//DE FG ，三角尺ABC 按如图所示摆放，90C ∠=︒，若137∠=︒，则2∠的度数为（）A ．57°B ．53°C ．51°D ．37°12．已知实数x ，y ，且2<2x y ++，则下列不等式一定成立的是（）A ．x y >B ．44x y ->-C ．33x y ->-D ．22x y > 二、填空题13．已知关于x 的不等式24132m x mx +-≤的解集是34x ≥，那么m 的值是________． 14．已知关于x 、y 的方程组2326324x y k x y k +=+⎧⎨+=+⎩的解满足2x y +=，则k 的值为__． 15．如图，用大小、形状完全相同的长方形纸片在平面直角坐标系中摆成如图所示的图案，已知(2,6)A -，则点B 的坐标为_________．16．如图，动点P 在平面直角坐标系中按图中箭头所示方向运动，第1次从原点运动到点(1，1)，第2次运动到点(2，0)，第3次运动到点(3，-1)，…，按照这样的运动规律，点P 第17次运动到的点的坐标为__________．17．如图，在平面直角坐标系中，()()()()1,1,1,1,1,2,1,2A B C D ----，把一条长为2021个单位长度且没有弹性的细线（线的粗细忽略不计）的一端固定在点A 处，并按 A B C D A ----⋯的规律绕在四边形ABCD 的边上，则细线另一端所在位置的点的坐标是 ____．18．（1）求x 的值：2490x -=；（2）计算：()2325227+--19．如图，AD 平分,34BDF ∠∠=∠，若150,2130∠=︒∠=︒，则CBD ∠=________︒．20．不等式组210360x x ->⎧⎨-<⎩的解集为_______．三、解答题21．某商场销售A 、B 两种型号的计算器，两种计算器的进货价格分别为每台15元，20元．商场销售5台A 型号和1台B 型号计算器，可获利润38元；销售6台A 型号和3台型号计算器，可获利润6元．（1）求商场销售A 、B 两种型号计算器的销售价格分别是多少元？（2）商场准备用不多于1250元的资金购进A 、B 两种型号计算器共70台，且全部售出后至少获利460元．问：最少需要购进A 型号的计算器多少台？最多可购进A 型号的计算器多少台？22．解不等式（组），并将解集表示在数轴上：（1）6194x x ->-（2）13215232(3)4x x x x -+⎧-≥⎪⎨⎪-->⎩23．解方程组：（1）35,24;x y x y +=⎧⎨-=⎩（2）3(1)1,5(1)2 1.x y y x --=⎧⎨-=+⎩24．如图，在平面直角坐标系中，点A ，B ，C 的坐标分别为()6,6-，()3,0-，()0,3．（1）画出三角形ABC ，并求它的面积．（2）在三角形ABC 中，点C 经过平移后的对应点为()5,4C '，将三角形ABC 做同样的平移得到三角形A B C '''，画出平移后的三角形A B C '''，并写出点A '，B '的坐标． 25．阅读下面的文字，解答问题：无理数是无限不循环小数，因此无理数的小数部分我们不可能全部地写出来，比如π、2等，而常用“……”或者“≈”212的小数部分，你同意小刚的表示方法吗？事实上，小刚的表示方法是有道理的，因为2的整数部分是1，将这个数减去其整数部分，差就是小数部分．又例如：因为459<<，即253<<，所以，5的整数部分为2，小数部分为52-也就是说，任何一个无理数，都可以夹在两个相邻的整数之间．根据上述信息，请回答下列问题：（1）13的整数部分是______，小数部分是_______；（2）107+也是夹在两个整数之间的，可以表示为107a b <+<，则a b +=_____；（3）若404x y -=+，其中x 是整数，且01y <<．求：x y -的相反数． 26．如图，已知BE 平分ABC ∠，点D 在射线BA 上，且ABE BED ∠=∠．判断BC 与DE 的位置关系，并说明理由．【参考答案】***试卷处理标记，请不要删除一、选择题1．A解析：A【分析】设快者的速度是/xkm h ，慢者的速度是/ykm h ，根据追及问题和相遇问题的求解方法列二元一次方程组求解．【详解】解：设快者的速度是/xkm h ，慢者的速度是/ykm h ，列式()()540240x y x y ⎧-=⎪⎨+=⎪⎩，解得146x y =⎧⎨=⎩．故选：A ．【点睛】本题考查二元一次方程组的应用，解题的关键是根据题意列出二元一次方程组． 2．D【分析】把k 看做已知数求出x 与y ，代入已知方程计算即可求出k 的值，从而求得x y -的值．【详解】432x y k x y k +=⎧⎨-=⎩①②， ①-②得：5k y =，把5k y =代入②得：115k x =，把115k x =，5k y =代入2310x y +=，得：11231055k k ⨯+⨯= 解得：2k =， ∴225x =，25y =， ∴222455x y -=-=．【点睛】本题考查了二元一次方程组的解，以及二元一次方程的解，方程组的解即为能使方程组中两方程都成立的未知数的值．3．B解析：B【分析】由4520430x y z x y z -+⎧⎨+-⎩＝①＝②，①×3+②×2，得出x 与y 的关系式，①×4+②×5，得出x 与z 的关系式，从而算出xyz 的比值即可．【详解】∵4520430x y z x y z -+⎧⎨+-⎩＝①＝②， ∴①×3+②×2，得2x=y ，①×4+②×5，得3x=z ，∴x ：y ：z=x ：2x ：3x=1：2：3，故选B ．【点睛】本题考查了三元一次方程组的解法，用含有x 的代数式表示y 与z 是解此题的关键． 4．C解析：C【分析】由基本不等式a ＞b ，根据不等式的性质，逐一判断．解：A 、∵a ＞b ，∴-a ＜-b ，故本选项不符合题意；B 、∵a ＞b ，∴当a 与b 同号时有11a b <，当a 与b 异号时，有11a b＞，故本选项不符合题意；C 、∵a ＞b ，∴a+b ＞2b ，故本选项符合题意；D 、∵a ＞b ，且a ＞0时，∴a 2＞ab ，故本选项不符合题意；故选：C ．【点睛】本题考查了不等式的性质．不等式的基本性质：（1）不等式两边加（或减）同一个数（或式子），不等号的方向不变．（2）不等式两边乘（或除以）同一个正数，不等号的方向不变．（3）不等式两边乘（或除以）同一个负数，不等号的方向改变．5．D解析：D【解析】试题分析：10{360x x -≤-<①②，由①得：x≥1，由②得：x ＜2，在数轴上表示不等式的解集是：，故选D ．考点：1．在数轴上表示不等式的解集；2．解一元一次不等式组．6．D解析：D【分析】先根据绝对值的性质判断出65x -的符号，再求出x 的取值范围即可．【详解】∵6556x x -=-，∴650x -≤，∴56x ≤．故选：D ．本题考查了绝对值的性质以及解一元一次不等式，解答此题的关键是熟知绝对值的性质：一个正数的绝对值是它本身，一个负数的绝对值是它的相反数，0的绝对值是0． 7．A解析：A【分析】根据二元一次方程的定义，对各个选项逐个分析，即可得到答案．【详解】32x y -=是二元一次方程，故选项A 正确；1xy =，含未知数的项的次数是2，故选项B 错误；2+3=x x 是一元一次方程，故选项C 错误；153x y-=，不是整式方程，故选项D 错误；故选：A ．【点睛】本题考查了二元一次方程的知识；解题的关键是熟练掌握二元一次方程的定义，从而完成求解．8．C解析：C【分析】由于线段CD 是由线段AB 平移得到的，而点A （-1，4）的对应点为C （4，7），比较它们的坐标发现横坐标增加5，纵坐标增加3，利用此规律即可求出点B （-4，-1）的对应点D 的坐标．【详解】∵线段CD 是由线段AB 平移得到的，而点A （-1，4）的对应点为C （4，7），∴由A 平移到C 点的横坐标增加5，纵坐标增加3，则点B （-4，-1）的对应点D 的坐标为（-4+5，-1+3），即（1，2）．故选：C ．【点睛】本题考查了坐标与图形变化－平移规律，在平面直角坐标系中，图形的平移与图形上某点的平移相同．平移中点的变化规律是：横坐标右移加，左移减；纵坐标上移加，下移减． 9．B解析：B【分析】根据点的坐标特征求解即可．【详解】横坐标是50-<，纵坐标是210a +>，∴点N （5-，21a +）一定在第二象限，故选：B ．【点睛】本题考查了各象限内点的坐标的符号特征，记住各象限内点的坐标的符号是解决的关键，四个象限的符号特点分别是：第一象限（+，+），第二象限（-，+），第三象限（-，-），第四象限（+，-）．10．A解析：A【分析】根据无理数的估算、实数的运算即可得．【详解】459<<， 459∴<<，即253<<，5∴的整数部分为2，小数部分为52-，则选项C 错误；∴5的整数部分与小数部分的差是()25245--=-，则选项A 正确；又m 、n 为两个连续的整数，且5m n <<，2,3m n ==∴，则选项B 错误；235m n ∴+=+=，则选项D 错误；故选：A ．【点睛】本题考查了无理数的估算、实数的运算，熟练掌握无理数的估算方法是解题关键． 11．B解析：B【分析】作GH ∥FG ，推出GH ∥FG ∥DE ，得到∠1=∠3，∠2=∠4，由90C ∠=︒， 137∠=︒，即可求解．【详解】作GH ∥FG ，∵DE ∥FG ，∴GH ∥FG ∥DE ，∴∠1=∠3，∠2=∠4，∵90C ∠=︒， 137∠=︒，∴∠3+∠4=90︒，即37︒+∠2=90︒，∴∠2=53︒，故选：B ．【点睛】本题考查了平行线的性质，根据题意作出辅助线，构造出平行线是解答此题的关键． 12．B解析：B【分析】根据不等式的性质逐项排除即可．【详解】解：∵2<2x y ++∴x ＜y ，故选项A 不符合题意；∴44x y ->-，故B 选项符合题意；33x y --＜,故选项C 不符合题意；22x y ＜，故D 选项不符合题意．故答案为B ．【点睛】本题主要考查了不等式的性质，给不等式左右两边乘以（除以）一个大于0的代数式（数），不等式符号不变，反之改变．二、填空题13．【分析】先移项合并然后根据不等式的解集得形式可得出关于m 的方程解出即可得出答案【详解】解：由题意得：∵不等式的解为∴解得：故答案为：【点睛】本题考查解一元一次不等式的知识有一定的难度注意先表示出不等解析：910．【分析】先移项合并，然后根据不等式的解集得形式可得出关于m 的方程，解出即可得出答案．【详解】解：由题意得：112(2)323m x m -≥+， ∵不等式的解为34x ≥，∴123231423m m +=-，解得：910m =．故答案为：910．【点睛】本题考查解一元一次不等式的知识，有一定的难度，注意先表示出不等式的解得形式，然后运用方程思想解答． 14．0【分析】根据x+y=2求出5x+5y=10方程组的两方程的两边分别相加得出5x+5y=3k+10得出方程3k+10=10求出方程的解即可【详解】解：①②得：故答案为：0【点睛】本题考查了二元一次方解析：0【分析】根据x+y=2求出5x+5y=10，方程组的两方程的两边分别相加得出5x+5y=3k+10，得出方程3k+10=10，求出方程的解即可．【详解】解：2326324x y k x y k +=+⎧⎨+=+⎩①②， ①+②得：55310x y k +=+，2x y +=，5510x y ∴+=，31010k ∴+=，0k ∴=，故答案为：0．【点睛】本题考查了二元一次方程组的解，解一元一次方程和解二元一次方程组等知识点，能得出关于k 的一元一次方程是解此题的关键．15．（）【分析】设长方形的长为x 宽为y 根据点A 的坐标列出关于xy 的二元一次方程组然后解方程组进而可求得点B 的坐标【详解】解：设长方形的长为x 宽为y ∵A(﹣26)∴解得：∴2x=x+y=+=∵点B 在第二象解析：（203-，143）【分析】设长方形的长为x ，宽为y ，根据点A 的坐标列出关于x 、y 的二元一次方程组，然后解方程组，进而可求得点B 的坐标【详解】解：设长方形的长为x ，宽为y ，∵A(﹣2，6)，∴262x y x y +=⎧⎨-=⎩，解得：10343x y ⎧=⎪⎪⎨⎪=⎪⎩， ∴2x=203， x+y= 103+ 43= 143， ∵点B 在第二象限， ∴点B 的坐标为（203-，143），故答案为：（203-，143）．【点睛】本题考查二元一次方程组的应用、坐标与图形，根据点A 坐标，结合图形，列出方程组是解答的关键． 16．【分析】令P 点第n 次运动到的点为Pn 点(n 为自然数)列出部分Pn 点的坐标根据点的坐标变化找出规律P4n(4n0)P4n+1(4n+11)P4n+2(4n+20)P4n+3(4n+3-1)根据该规律即解析：()17,1【分析】令P 点第n 次运动到的点为P n 点(n 为自然数)．列出部分P n 点的坐标，根据点的坐标变化找出规律“P 4n (4n ，0)，P 4n+1(4n+1，1)，P 4n+2(4n+2，0)，P 4n+3(4n+3，-1) ”，根据该规律即可得出结论．【详解】令P 点第n 次运动到的点为P n 点(n 为自然数)．观察，发现规律：P 0(0，0)，P 1(1，1)，P 2(2，0)，P 3(3，-1)，P 4(4，0)，P 5(5，1)，…， ∴P 4n (4n ，0)，P 4n+1(4n+1，1)，P 4n+2(4n+2，0)，P 4n+3(4n+3，-1)．∵17=4×4+1，∴P 第17次运动到点(17，1)．故答案为：(17，1)．【点睛】本题考查了规律型中的点的坐标，解决该题型题目时，根据点的变化罗列出部分点的坐标，根据坐标的变化找出变化规律是关键．17．【分析】先根据点的坐标求出四边形ABCD 的周长然后求出另一端是绕第几圈后的第几个单位长度从而确定答案【详解】解：∵A （11）B （﹣11）C （﹣1﹣2）D （1﹣2）∴AB ＝1﹣（﹣1）＝2BC ＝1﹣（解析：()0,1【分析】先根据点的坐标求出四边形ABCD 的周长，然后求出另一端是绕第几圈后的第几个单位长度，从而确定答案．【详解】解：∵A （1，1），B （﹣1，1），C （﹣1，﹣2），D （1，﹣2），∴AB ＝1﹣（﹣1）＝2，BC ＝1﹣（﹣2）＝3，CD ＝1﹣（﹣1）＝2，DA ＝1﹣（﹣2）＝3，∴绕四边形ABCD 一周的细线长度为2+3+2+3＝10，2021÷10＝202…1，∴细线另一端在绕四边形第203圈的第1个单位长度的位置，即细线另一端所在位置的点的坐标是（0，1）．故答案为：（0，1）．【点睛】本题考查了点的坐标规律探求，根据点的坐标求出四边形ABCD 一周的长度，从而确定2021个单位长度的细线的另一端落在第几圈第几个单位长度的位置是解题的关键． 18．（1）或；（2）4【分析】（1）利用开方要根的概念求出x 的值即可；（2）根据实数混合运算的法则进行计算即可【详解】解：（1）或(2)原式＝5+2﹣3＝4【点睛】本题考查的是实数的运算熟知实数混合运算解析：（1）32x =或32x =-；（2）4 【分析】（1）利用开方要根的概念求出x 的值即可；（2）根据实数混合运算的法则进行计算即可．【详解】解：（1）294x = 32x =或3-2x = (2)原式＝5+2﹣3＝4．【点睛】本题考查的是实数的运算，熟知实数混合运算的法则是解答此题的关键．19．65【分析】利用平行线的判定定理和性质定理等量代换可得∠CBD=∠EBC可得结果【详解】∵∠1=50°∴∠DBE=180°-∠1=180°-50°=130°∵∠2=130°∴∠DBE=∠2∴AE ∥C解析：65【分析】利用平行线的判定定理和性质定理，等量代换可得∠CBD=∠EBC ，可得结果．【详解】∵∠1=50°，∴∠DBE=180°-∠1=180°-50°=130°，∵∠2=130°，∴∠DBE=∠2，∴AE ∥CF ，∴∠4=∠ADF ，∵∠3=∠4，∴∠EBC=∠4，∴AD ∥BC ，∵AD 平分∠BDF ，∴∠ADB=∠ADF ，∵AD ∥BC ，∴∠ADB=∠CBD ，∴∠4=∠CBD ，∴∠CBD=∠EBC=12∠DBE=12×130°=65°．故答案为：65．【点睛】本题主要考查了平行线的判定定理和性质定理，角平分线的定义等，熟练掌握定理是解答此题的关键． 20．【分析】先求出两个不等式的解再找出它们的公共部分即为不等式组的解集【详解】解不等式①得：解不等式②得：则不等式组的解集为故答案为：【点睛】本题考查了解一元一次不等式组熟练掌握不等式组的解法是解题关键解析：122x << 【分析】先求出两个不等式的解，再找出它们的公共部分即为不等式组的解集．【详解】210360x x ->⎧⎨-<⎩①②，解不等式①得：12x >，解不等式②得：2x <，则不等式组的解集为122x <<，故答案为：122x <<．【点睛】本题考查了解一元一次不等式组，熟练掌握不等式组的解法是解题关键．三、解答题21．（1）A 、B 两种型号计算器的销售价格分别为21元、28元；（2）最少需要购进A 型号的计算器30台，最多可购进A 型号的计算器50台【分析】（1）设A 种型号计算器的销售价格是x 元，B 种型号计算器的销售价格是y 元，根据题意可等量关系：①5台A 型号和1台B 型号计算器，可获利润38元；②销售6台A 型号和3台B 型号计算器，可获利润6元，由①②等量关系列出方程组，解方程即可；（2）根据题意表示出所用成本，进而得出不等式组求出即可．【详解】（1）设A 种型号计算器的销售价格是x 元，B 种型号计算器的销售价格是y 元，由题意得：551520386361532060x y x y +-⨯-=⎧⎨+-⨯-⨯=⎩，解得：2128x y =⎧⎨=⎩ 答：A 、B 两种型号计算器的销售价格分别为21元、28元；（2）设购进A 型号的计算器z 台，则B 种计算器为（70-z ）台，依题意得：1520(70)1250(2115)(2820)(70)460z z z z +-≤⎧⎨-+--≥⎩，解得：3050z ≤≤，∴最少需要购进A 型号的计算器30台，最多可购进A 型号的计算器50台．答：最少需要购进A 型号的计算器30台，最多可购进A 型号的计算器50台．【点睛】考查了二元一次方程组和一元一次不等式组的应用，解题关键是读懂题意，设出未知数，找出合适的等量关系和不等关系，列方程组和不等式组求解．22．（1）x ＜1，数轴见解析；（2）﹣5≤x ＜ 2，数轴见解析【分析】（1）先解一元一次不等式，再在数轴上表示出不等式的解集；（2）先解一元一次不等式组，再在数轴上表示出不等式组的解集；【详解】解：（1）6194x x ->-6941x x ->-+33x ->-解得：x ＜1,在数轴上表示如下：（2）13215232(3)4x x x x -+⎧-≥⎪⎨⎪-->⎩①②解不等式①得：x≥﹣5解不等式②得：x ＜ 2∴不等式组的解集为﹣5≤x ＜ 2 ；在数轴上表示如下：.【点睛】本题主要考查求一元一次不等式和一元一次不等式组的解集和数轴，解题的关键是熟练掌握解一元一次不等式和一元一次不等式组的方法.23．（1）21x y =⎧⎨=-⎩；（2）22x y =⎧⎨=⎩．【分析】（1）利用加减消元法求解即可；（2）原方程整理后利用加减消元法求解即可．【详解】解：（1）3524x y x y +=⎧⎨-=⎩①② ①×2得：6210x y +=③，②+③得：714x =，解得2x =，代入①得：65y +=，解得1y =-，所以，该方程组的解为21x y =⎧⎨=-⎩；（2）原方程组整理得：34256x y x y -=⎧⎨-+=⎩①②， ①×5得：15520x y -=③，②+③得：1326x =，解得2x =，代入①得：64y -=，解得2y =，所以，该方程组的解为22 xy=⎧⎨=⎩．【点睛】本题考查解二元一次方程组．解二元一次方程组主要有两种方法，加减消元法和代入消元法，掌握“消元”思想是解题关键．24．（1）画△ABC见解析，△ABC的面积为272；（2）平移后的△A′B′C′见解析，A′（-1，7），B′（2，1）【分析】（1）直接利用△ABC所在矩形面积减去周围三角形面积进而得出答案；（2）直接利用平移的性质得出各对应点位置，进而得出答案．【详解】（1）△ABC如图所示：△ABC的面积为：ABC11127 666333362222S=⨯-⨯⨯-⨯⨯-⨯⨯=；（2）如图所示：△A′B′C′即为所求，A′（-1，7），B′（2，1）；故答案为：A′（-1，7），B′（2，1）．【点睛】本题考查了作图-平移变换，熟知图形平移不变性的性质以及正确得出对应点位置是解答此题的关键．25．（1）3 133；（2）25；（3）()2108x y --=．【分析】（1）由3134可得答案；（2）由27＜3知12＜7＜13，可求出a ，b 的值，据此求解可得；（3）得出24043<-<，即可得出x ，y ，从而得出结论．【详解】解：（1）∵9＜13＜16∴3134， ∴13313；故答案为：313．（2）∵4＜7＜9，∴27＜3∴12＜7＜13∴a=12，b=13∴a+b=12+13=25，故答案为：25；（3364049<<6407<< 所以6440474-<<- 即24043<-<4的整数部分为2，即2x =，426y =-=()26x y x y --=-+=-+=8=【点睛】本题考查了估算无理数的大小，解决本题的关键是熟记估算无理数的大小．26．BC ∥DE ；理由见解析【分析】根据角平分线的定义和已知条件可得∠CBE =∠BED ，再根据平行线的判定即得结论．【详解】解：BC ∥DE ；理由如下：因为BE 平分ABC ∠，所以∠ABE =∠CBE ，因为ABE BED ∠=∠，所以∠CBE =∠BED ，所以BC ∥DE ．【点睛】本题考查了角平分线的定义和平行线的判定，属于基础题目，熟练掌握基本知识是解题的关键．。

2021年教科版三年级科学下册第一次月考考试卷及答案【必考题】

2021年教科版三年级科学下册第一次月考考试卷及答案【必考题】班级：姓名：题序一二三四五六总分得分一、填空题。

（共20分）1、帆船远去时，先是看不见_____，最后才看不见______。

2、在水温和食盐颗粒大小相同的情况下，我们可以通过________加快食盐在水中的溶解速度。

3、太阳和月球的大小，看上去____________。

但是，太阳和地球之间的距离比月球和地球之间的距离要_________得多。

4、在同一条轨道上，要比较不同小球运动的快慢，可以用___________测量不同小球运动相同距离所花的___________，并记录下来。

至少测量__________次。

5、在模拟实验中，一开始就观察到了整个船模，说明了他是在______移动。

6、渗水性最强的土壤是___________。

7、如果我们不停地给杯子里的水加热，水会被烧开，这叫水_________了，这时水的温度是_________℃，水面上出现的“白汽”是_________凝结形成的。

8、两位同学沿直线行走，但是出发时间和出发地点都不相同，这样比较快慢就用来_______来比较，也就是________。

9、过山车轨道的长度可以用_______和_______来测量。

10、_____是古代测量时间的仪器。

二、选择题。

（共20分）1、生活中我们常见的白酒和白醋，其实它们的颜色是（）。

A．白色的B．无色的C．淡蓝色的2、在游泳比赛中，运动员穿着模仿鱼皮肤的泳衣主要是因为（）。

A．穿着舒服B．穿泳衣漂亮C．能减少水的阻力D．增大摩擦力3、依靠昆虫传粉的花叫（）。

A．虫媒花 B．风媒花 C．人工辅助授粉 D．双性花4、下列不是利用水的浮力的事件的是（）。

A．曹冲称象B．捞铁牛C．气球飘在半空中5、可乐属于液体，它（）。

A．有确定形状B．有确定质量C．没有确定体积6、下列不属于发酵食品的是（）。

A．豆腐乳B．食用醋C．牛奶7、救生圈可以帮助不会游泳的人浮在水面上，是因为（）。