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oracle中coalesce函数用法

oracle中coalesce函数用法

oracle中coalesce函数用法Coalesce函数是Oracle数据库中的一个非常有用的函数,在处理数据时非常常用。

Coalesce函数的作用是从其参数列表中返回第一个非空的值。

换句话说,它会按顺序取参数值,直到找到一个不为NULL的值为止,然后返回这个值。

Coalesce函数的语法如下:```COALESCE(value1, value2, value3, ...)```其中,value1, value2, value3等为参数,可以是列名、常量、表达式等。

Coalesce函数的使用非常灵活,可以用于任何地方需要返回非空值的场景。

下面我们将详细讨论Coalesce函数的用法和实际应用场景。

1.替代NULL值Coalesce函数最常见的用途就是替代NULL值。

在实际开发中,经常会遇到需要在查询结果中将NULL值替换为其他特定的值或者默认值的情况。

这时,Coalesce函数就可以派上用场了。

假设有一个员工表,其中有一个字段为工资,但该字段中有些值为空。

现在我们想要查询员工工资,如果工资为空,则显示默认值为0。

可以使用Coalesce函数来实现这个需求:```SELECT employee_id, COALESCE(salary, 0) AS salaryFROM employees;```这样就可以将工资中的NULL值替换为0,使查询结果更加清晰和易读。

2.多列取值除了替代NULL值,Coalesce函数还可以用于从多列中取值。

在某些情况下,我们需要从多个列中选取一个非空的值进行显示。

这时,Coalesce函数同样可以帮助我们实现这个需求。

比如,有一个订单表,其中记录了订单的支付方式。

订单表中有多个支付字段,比如cash_payment、credit_card_payment和online_payment。

现在我们想要查询订单的支付方式,如果在线支付为空,则显示信用卡支付,如果信用卡支付也为空,则显示现金支付。

Oracle FLEXCUBE FX Accelerator Pack 14.5.0.0.0 产品说

Oracle FLEXCUBE FX Accelerator Pack 14.5.0.0.0 产品说

APACK 14.5.0.0.0 Foreign ExchangePart Number: F43223-01APACK 14.5.0.0.0 –FXContents▪Introduction▪Brief info on Functional / Operations features ▪Product▪Standard Advices▪Standard Reports▪MaintenanceAccelerator Pack –FXIntroductionAPACK 14.5.0.0.0 –FXIntroductionForeign Exchange module of FLEXCUBE is used for buying and selling of currencies.It supports all types of FX deals i.e.Cash,Tom,Spot and Forward.Accelerator Pack –FXFX ProductsAPACK 14.5.0.0.0 –FXList of FX Products▪FFB1-FX Forward Product-Discounted Straight Line Revaluation ▪FFB2-FX Forward Product-Net Present Value Revaluation▪FFC1-FX Forward Product-Rebate Revaluation▪FFR1-FX Forward Product-Straight Line Revaluation▪FRR1-FX Forward Product-Rollover▪FSB1-FX Bank Deals-Spot-Cash▪FSB2-FX Bank Deals-Spot-Tom▪FSB3-FX Bank Deals-SpotAPACK 14.5.0.0.0 –FXList of FX Products▪FSC1-FX Corporate Deals-Spot-Cash.▪FSC2-FX Corporate Deals-Spot-Tom.▪FSC3-FX Corporate Deals-Spot.▪FSR1-FX Retail Deals-Spot-Cash.▪FSR2-FX Retail Deals-Spot-Tom.▪FSR3-FX Retail Deals-Spot.▪FSW1-FX Swap Deals-Spot-Forward.▪FSW2-FX Swap Deals-Forward-Forward.▪FXFW-FX Forward Product-Discounted Straight Line Revaluation.APACK 14.5.1.0.0 –FXList of FX Products▪FXN1-FX Corporate Forward Product-NDF▪FXN2-FX Corporate Spot Product-NDF Fixing ▪FXNF-FX Forward Product-NDF▪FXNS-FX Spot Product-NDF Fixing▪INS1 -Internal Swap (FX Internal Swap Deal)Accelerator Pack –FXFunctional / Operations featuresAPACK 14.5.0.0.0 –FXFunctional/Operations features •Booking of Foreign Exchange contract •Cross currency contract booking •Capturing of brokerage details •Counterparty Confirmation •Contract Re-assign•Holiday period treatment •Capturing of UDE values•Auto/Manual Liquidation•Partial Liquidation/Cancellation •Cancellation of FX contract •SettlementsAPACK 14.5.0.0.0 –FXFunctional/Operations features •Amendment of FX contract•Rollover of FX contract•Limit Tracking•CLS Status change•CLS Alleged deal status change•CLS Net position check•CLS Status change alert•Split Value Date•Currency/Pair wise netting-Auto/Manual •Deal Revaluation•Option Date•Fixing and Unfixing of FX dealAccelerator Pack –FXFX EventsAPACK 14.5.0.0.0 –FXEventsEvents Covered TerminologyBOOK Contract Booking event triggers when Bank Initiate the Deal.CONF On Counterparty Confirmation this event will get triggered.REAS Reassign User event will get triggered on new User Assign.SGEN Settlement Message GenerationCANC Deal Cancellation event will get triggered on cancellation of the deal.LIQD Liquidation Event will get triggered on Manual/Auto Payment of the DealREVP Payment Reversal is processed under this eventREVR Contract Reversal is processed under this eventAccelerator Pack –FXFX AdvicesAPACK 14.5.0.0.0 –FXStandard AdviceAdvices DescriptionBANK_REVSWIFT Bank Transfer ReversalCOVER_REVSWIFT Cover Transfer ReversalCREDIT_ADVICE Credit AdviceCUST_COVER Customer CoverCUST_COVERL Customer Cover LCUST_REVSWIFT Customer Transfer ReversalCUST_RTGS_COV Customer RTGS CoverageDEBIT_ADVICE DEBIT AdviceFX_BROKERAGE Brokerage AdviceAccelerator Pack –FXFX Swift MessagesAPACK 14.5.0.0.0 –FXMessagesSWIFT Messages Contract Field MT300Confirmation,Amendment,ReverseMT304T-Copy SettlementMT103/MT202/MT205Payment MessageMT192/MT292Payment ReversalMT210Receive NoticeMT940/MT950Account StatementAccelerator Pack –FXFX ReportsAPACK 14.5.0.0.0 –FXStandard Reports▪FX Currency Analysis report▪FX Tenor-wise Currency Position report▪FX Contract Activity report▪FX Contract Overrides report▪FX Brokerage details report▪FX Daily Exception report -Automatic Processing ▪FX Discounting Rate Report▪Netting Agreement▪Fund Transfer to Foreign Exchange Netting Report ▪FX to FT Netting Report▪Process Exception Report▪FX Broker confirmation ReportAccelerator Pack –FXFX MaintenanceAPACK 14.5.0.0.0 –FXOther MaintenanceFollowing are the Maintenance Required in OBTR to use a product for FX:▪FX Branch Parameter▪Messaging Parameter▪Local Holidays▪FX Batch Maintenance▪Exchange Rate Maintenance▪Forward Rate Maintenance▪Discount Rate Maintenance▪Charge Class▪Tax Scheme Class。

风电词汇4

风电词汇4

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analysis元素分析ultimate analysis工业分析proximate analysis低位发热量low heating value(LHV)高位发热量high heating value(HHV)分析质as analysed basis有机质organic basis工作质as-fired basis干燥质dry basis可燃质combustible basis挥发份volatile matter固定碳fixed carbon固有水分inherent moisture表面水分surface moisture全水分total moisture可磨性系数grindability index灰变形温度ash deformation temperature(t)灰软化温度ash softening temperature(t)灰熔化温度ash fusion temperature, ash melting point(t)灰比电阻specific resistance of ash设计煤种design coal校核煤种check coal重油heavy oil轻油light oil柴油diesel oil燃料油fuel oil凝点pour point甲烷methane乙烷ethane丙烷propane煤气gas天然气natural gas机械制图mechanical drawing图纸drawing平面图plan, plan view轴测图axonometric drawing描图trace校对check审核review批准approve数量quantity重量weight材料material材料型号material type图号drawing number编号serial number符号symbol, sign代号code number比例proportion测量measurement量具measuring tools卡尺calipers, caliper rule塞尺clearance gauge, feeler gauge高度尺height gauge深度尺depth gauge卡钳calipers百分表dial indicator, micrometer, microcallipers 千分表micrometer, dial indicator尺寸size, dimension刀具cutting tools夹具clamping apparatus, fixture, jig顶针thimble, knock-out pin测绘survey and drawing分度graduation分度圆divided circle热处理heat treatment, thermal treatment调质hardening and tempering淬火quenching回火tempering退火annealing氮化nitridation渗碳carburization外圆磨床external grinder内圆磨床internal grinder键槽铣床key slot milling machine插床slotter刨床planer立车vertical lathe液压机hydraulic press机床lathe工艺technology铆riveting锻forging车lathing钳fitting锯sawing割cutting铣milling刨planning磨grinding镗boring插削slotting粗车rough lathing细车finish lathing绞削reaming钻孔drilling, boring绞孔reaming木模wooden model, wooden form铸造casting浇铸casting翻砂founding, foundry, moulding系数factor, coefficient直径diameter划线scribing互换性changeability中心距center distance加工余量finish allowance, machine allowance 时效aging精度precision, accuracy光洁度fineness, degree of finish表面surface粗糙度roughness斜度gradient, slope基准datum模数modual水平level倒角inverted angle检验test, check, examination圆锥度coning, conicity椭圆度ellipticity圆锥cone圆柱cylinder抛光polishing公差tolerance, allowance板牙screw plate丝锥screw tap中心孔center bore, center hole, center opening 装配assembly, installation配合coordination配制manufacture, parts manufacturing剖面section, cross-section修配repair, maintenance毛胚blank锻件forged piece零件parts, details, elements紧固件fastener花键spline键槽key slot销pin定位positioning, locating铆钉rivet螺旋screw螺纹screw thread螺距screw pitch螺母screw nut螺钉bolt轴颈journal滑动sliding下料material preparation端面end face合金alloy硬质合金hard alloy合金钢alloy steel不锈钢stainless steel碳钢carbon steel钨金(巴氏合金)babbit metal哈氏合金(铅-锡-锑)Haynes satellite青铜bronze黄铜brass电焊electric welding电焊条welding electrode焊丝welding wire焊把welding torch焊枪welding gun氩弧焊argon arc welding焊接welding电焊机welding machine直流电焊机DC welding machine自动电弧焊automatic electrical arc welding 密封焊接seal welding堆焊bead welding夹焊slag welding气孔blowhole咬边undercut熔深weld penetration焊道weld pass焊口裂纹weld seam crack焊跟weld root坡口加工edge preparation加强焊缝reinforced weld seam开焊open weld应力stress金属硬度metal hardness硬度试验机hardness tester探伤flaw detection, detect detection 超声波探伤机ultrasonic flaw detector磁力探伤机magnetic flaw detector涡流探伤机eddy current flaw detector渗透探伤penetration flaw detector放射性检查radiographic test金相显微镜metallurgical microscope金相光谱仪metallurgical spectrum analyzer 着色剂colorants, coloring agent超声波测厚仪ultrasonic thickness meter蠕变creep无损探伤non-destructive test断口试验fracture test表面检查surface inspection备品spare parts垫片gasket, pad, shim平垫plane pad齿形垫tooth type gasket铜垫copper gasket, copper cushion 缠绕垫wound gasket石棉垫asbestos pad, babbit cushion巴金垫babbit pad, babblt cushion磁力电站magnetic electric drill角向磨光机angular finishing grinder剪板机plate shears卷板机plate bending rolls面积area体积(容积)volume质量mass能量energy形状shape方形square圆形round三角形triangle半径radius周长circumference, perimeter参数parameter工况operating condition温度temperature压力pressure力矩moment of force时间常数time constant真空vacuum流量flow, flow capacity比热specific heat比容specific volume热流量heat flow吸热heat absorption, thermal absorption 吸热反应endothermic reaction放热heat liberation, heat release压缩compression膨胀expansion节流throttle起动start-up, starting空转idle running停机shutdown, outage, stoppage试验test检测detection, test并联parallel connection串联series connection过热overheat再热reheat回热regeneration饱和蒸汽saturated steam允许温度allowable temperature干度dryness水蒸汽steam, water vapor焓enthalpy熵entropy郎肯循环(兰金循环)rankine cycle卡诺循环carnot cycle气体gas液体liquid固体solid海拔altitude标高elevation规程rules, regulation运行规程operation rules(regulations)工艺规程process rules(regulations)检修规程maintenance rules(regulations)安全规程safety rules(regulations)反事故措施anti-accident measures防火措施fire-prevention measures防爆措施explosion prevention measure维护maintenance缺陷处理defect treatment铭牌nameplate合格证书passport, certificate国际单位international unit技术检验记录technical check record技术资料technical information, technical data 检修间repair shop, service shop检修记录repair record, maintenance检查性试验check-up test日常检查daily inspection, routine inspection 定期检查periodic repair解体检查repair with disassembly现场检修on-site repair临时检修temporary repair, running repair事故accident, emergency占地指标land allocation绿化面积area of greenery space绿化系数greenery factor, greening factor发电量power generation, generated energy 装机容量installed capacity额定转速rated speed线损率line loss rate热耗率(热耗)heat consumption rate耗煤率(煤耗)coal consumption rate供电标准耗煤率net standard coal consumption rate发电标准耗煤率gross standard coal consumption rate厂前区面积area of administrative zone建筑系数building coverage场地利用系数site utilization factor百万千瓦耗水指标water consumption per GW发电成本power generation cost单位千瓦造价cost per KW烟气排放标准flue gas emission standard污水排放标准sewage discharge standard职工定员personnel quota运行可用率operation availability运行可靠性operation reliability利用小时数number of utilization hours三材消耗率(钢/水泥/木材)consumption of steel, cement and timber生活福利区面积living and welfare facility zone area年耗煤量annual coal consumption小时耗煤量hourly coal consumption单元机组联合试运行integral trial operation of unit plant设备效率equipment efficiency设备利用率equipment capacity factor设备缺陷equipment defector热备用状态hot reserve冷备用状态cold reserve设备备用equipment in reserve紧急备用emergency reserve停止备用stop standby凝汽式电厂condensing power plant热电厂cogeneration power plant坑口电厂mine-mouth power plant路口电厂railway-side power plant港口电厂port power plant核电站nuclear power plant水电站hydropower plant(station)抽水蓄能电站pumped storage power station风力发电站wind power station太阳能发电站solar power station地热电站geothermal power station柴油发电厂diesel generating power station燃气蒸汽联合循环电厂steam and gas turbine combined-cycle power plant 燃气轮机电厂gas turbine power plant煤气化联合循环电厂integral gasified combined-cycle power plant自备电站captive power plant峰荷电站peak load power plant(station)基荷电站base load power plant新建电厂newly-built power plant扩建工程extension project技术改造工程technical renovation project初步可行性研究preliminary feasibility study概念设计conceptual design预设计predesign初步设计preliminary design施工图设计detail design施工组织设计construction organization design设计审查design review, design examination设计审批design examination and approval设计回访feedback on design quality计算书calculation sheet技术规范书technical specifications设计说明书design instructions总工程师chief designer设计总工程师project chief engineer主要设计人chief designer设计人designer校核人checker描图号tracer晒图blueprint复印copying装订binding出版publication工地代表site resident representative项目建议书project proposal可研批复comments on and approve of feasibility study report 中外合作设计sino-foreign cooperative design设计联络会design liaison meeting行业标准industrial standard国家标准national standard技术标准technical standard项目咨询project consultation设备选择equipment selection建议规模construction scale工程设想engineering projection电力系统地理接线图geographical system connection diagram负荷测试load forecast总平面布置图general layout竖向布置图vertical layout drawing厂区地下沟道图plant-area underground piping and culvertsdrawing交通运输communication and transportation煤源coal source水源water source接入系统connection to power system经济效益分析economic benefit analysis热力系统图thermodynamic system diagram主厂房布置图main machine building arrangement drawing燃烧系统图combustion system diagram供水系统图water supply system diagram除灰系统图ash handling system diagram工业水处理系统industrial water system diagram化学水处理系统图chemical water treatment system diagram锅炉点火系统图boiler ignition system diagram电气主接线图main wiring diagram, main electrical connection diagram 单元系统图unit system diagram二次系统secondary system diagram输电电压等级transmission voltage grade(class)回路数loop number纵向布置longitudinal arrangement横向布置transversal arrangement室内布置indoor arrangement露天布置outdoor arrangement, open-air arrangement半露天布置semi-outdoor arrangement, semi-open-air arrangement 环境影响评价报告environmental impact assessment report推荐方案recommended proposal优化方案optimum proposal工程地质engineering geology工程测量engineering survey水文气象hydrometeorology岩土工程rock and earth engineering水文地质hydrogeology物理勘探physical prospecting航测aerial survey地层结构stratum structure地震烈度seismic intensity, earthquake intensity地质断裂geologic fracture, geologic rift地耐力earth bearing capacity天然地基natural foundation人工地基artificial foundation, artificial base软土地基soft soil base地基处理base treatment, foundation treatment桩型选择pile type selection打桩piling, pile driving试桩trial piling预制桩precast pile钢板桩steel sheet pile钢管桩steel pipe pile夯实ramming ,tamping地下水ground water, underground water地表水surface water泉水spring, spring water储量reserve迳流量run-off volume勘测大纲survey outline初步勘测preliminary survey详细勘测detailed survey最终勘测final survey河势分析river potential analysis航道waterway主厂房main machine hall, main power building汽机房turbine hall, turbine house除氧间(除气间)deaerator bay煤仓间bunker bay锅炉房boiler hall, boiler house单管烟囱single-shaft chimney(stack)多管烟囱multi-shaft chimney(stack)脱硫装置desulphurization equipment铁路专用线plant service railway line, special service railway line 铁路专用线接轨点special service railway coupling point山谷灰场valley ash yard渣场slag yard灰坝ash dam事故灰场emergency ash yard近期near future, short-term远期future, long-term屋顶roof屋架roof truss屋架下弦标高roof truss lower chord elevation天窗skylight远转层operation floor底层ground floor皮带层belt conveyor floor地下室basement电缆沟cable trench电缆隧道cable tunnel集水坑water collection pit梁beam柱column, pillar楼板floor slab网格板grating plate平台platform扶梯stair地面ground牛腿bracket下水道sewer设备基础equipment foundation抗震架构shockproof structure, aseis-matic structure跨度span柱距column space钢结构steel structure钢筋混凝土结构reinforced concrete structure预制构件precast parts, prefabricated parts空心板hollow block压型钢板channeled steel plate沟盖板trench cover plate防浪堤revetment涵洞culvert防火距离fire proof distance装饰标准decoration standard环境保护environmental protection污水处理站sewage treatment station干法脱硫dry desulphurization湿法脱硫wet desulphurization综合利用comprehensive utilization环保检测站environmental monitoring制氢站hydrogen generation station制氧站oxygen generation station变压器检修间transformer maintenance room空压机间air compressor room输煤综合楼coal handling complex building网络控制楼grid control building, network control building 生产办公楼plant service building化学水处理间chemical water treatment room修配厂repair workshop油罐区oil tank zone重油罐heavy oil tank消防器材fire-fighting equipment泡沫消防foam fire extinguishing消防拴fire hyfrant翻车机室wagon tipper house推煤机库coal bulldozer house煤场coal yard混煤仓mixed coal silo输煤皮带栈桥coal belt conveyor gallery行政办公楼administrative building传达室reception room单身宿舍楼dormitory食堂dining room, canteen医院hospital俱乐部club礼堂auditorium, assembly hall商店shop, store码头wharf煤码头coal unloading wharf, coal jetty油码头oil unloading wharf大件运输码头heavy goods wharf水库reservoir库容reservoir capacity蓄水池water storage pond最高洪水位maximum flood level厂址标高site elevation冲沟rush channel渗漏leakage, seepage排洪渠(沟)flood discharge channel围墙enclosing wall, enclosure主导风向(东、南、西、北)prevailing wind direction(east,west, south, north)平均风速average wind speed最大风速maximum wind speed上风向upwind direction下风向downwind direction城市规划city planning采暖heating空调air conditioning照明lighting日光灯fluorescent lamp白炽灯incandescent lamp通风ventilation热交换器heat exchange机械排风mechanical ventilation, mechanical draft施工机械construction machine大型吊车heavy-duty crane塔吊tower crane坦克吊caterpillar crane门型吊gantry crane拆迁removal and rebuilding征地land acquisition租地land leasing工程承包project contracting工程监理project supervision交钥匙工程turn-key project大修overhaul小修routine maintenance, running maintenance, minor maintenance 中修periodic maintenance临修temporary maintenance, regular maintenance非计划检查unplanned maintenance丁烷butane丁烷气butagas单元制unit system母管制header system冷态起动cold start热态起动hot start快速起动quick start变压运行variable pressure operation滑参数起动starting at sliding parameters汽机快速冷却装置turbine quick cooling device安装erection, installation调试test and adjustment值班on-duty巡回检查patrol and inspection事故预想accident anticipation反事故演习anti-accident exercise技术问答technical interrogation and reply考问讲解oral examination and explanation保温heat insulation, thermal insulation油漆paint节能energy conservation, energy saving节水water saving节电power saving, power conservation节约用电economizing land in use灭火器fire extinguisher泡沫灭火器foam fire extinguisher土方开挖earth excavation回填土backfilled earth仿真机(模拟机)simulator检修maintenance, repair运行operation, running涉外谈判negotiation with foreigners独立自主maintaining independence and keeping the initiative in one 自力更生relying on one沿海地区coastal areas经济特区special economic zone出口贸易export trade商品commodity出口额export volume出口许可证export license法人legal person企业法人legal entity法人代表representative of legal entity, representative of legal person 业主owner超额累进税surtax比例税proportional tax承包工程contracting project出口关税export duty注册资本额registered capital amount多边支援multilateral assistance专利权patent, patent right商标权trademark right固定资产fixed assets工业产权industrial property资源开发resources development, resources exploitation子公司subsidiary company, branch company母公司holding company, parent company国际债券international bond生产线production line流动资金current capital, current fund托收collection银行信贷bank credit海运提单ocean bill of lading, ocean waybill签定合同contract signing备用信用证standby letter of credit条款terms and conditions询价inquiry顺汇favorable exchange逆汇reverse remittance相对免赔率franchise汇票draft共同海损general average离岸品质shipping quality到岸品质arrival quality国际投资银行international investment Bank国际金融公司international finance Corporation劳务贸易service trade银团贷款syndicated loan项目选定project identification项目准备project preparation项目评估project appraisal项目谈判project negotiation项目执行与监督project implementation and supervision 项目后评估project evaluation出口信贷export credit利息期interest period软贷款soft loan硬贷款hard loan合同contract混合贷款blend协议agreement意向书letter of intent项目经济评价project economic evaluation资金筹措fund raising比例分配proportional distribution股份share董事会board of directors董事长chairman of the board总经理president, general manager易货贸易barter trade, barter集资fund collection融资financing外汇偿还能力foreign exchange repaying ability设备费equipment价格price人工费labour cost征地价格land acquisition price进口范围import scope国产设备domestic manufactured equipment建设期贷款利率interest rate during construction流动资金贷款利率current fund loan interest rate工程投资估算project cost estimate工程投资概算project budgetary estinate工程投资决算final accounts of project cost调整概算budgetary estimate adjustment工程投资预算project budget设备验收equipment acceptance国家开发银行state development bank商业贷款commercial loan经济用语economic expressions投资回收年限investment recovery period总投资total investment注册资本registered capital信贷资本credit proceeds敏感性分析sensitive analysis电价electricity price, electricity tariff煤价coal price, coal tariff汇率exchange rate静态static status动态dynamic status金融finance资本capital离岸价格FOB price (free on board)到岸价格CIF price (cost, insurance, freight)运输费freight风险费risk premium保险金insurance premium签字仪式signing ceremony招商inviting businessmen to invest租赁lease证券securities税率taxation rate经营management盈利profiting亏损lossing效益benefit货币currency售电价格electricity selling price市场经济market economy市场竞争market competition计划经济planned economy独立核算independent accounting中外合资企业Sino-foreign joint venture enterprise 固定资产所有权ownership of fixed assets建议银行construction bank亚洲开发银行Asian development bank世界银行world bank招标inviting bids。

sqlite3 计算相邻行差 coalesce

sqlite3 计算相邻行差 coalesce

主题:SQLite3中使用coalesce函数计算相邻行差内容:1. 介绍SQLite3数据库SQLite3是一种轻量级的关系型数据库管理系统,它支持大部分SQL语句的标准,是许多嵌入式数据库的选择,由于其易用性和稳定性,被广泛应用于移动设备和小型应用的开发中。

2. coalesce函数的作用coalesce函数是SQLite3中的一个常用函数,其主要作用是返回参数列表中第一个非NULL值。

在处理相邻行之间的差值计算时,coalesce函数可以帮助我们简化SQL语句,使得计算相邻行差更加便捷。

3. 使用coalesce函数计算相邻行差在SQLite3中,我们可以通过使用coalesce函数结合自连接子查询来计算相邻行差。

以下是一个示例的SQL语句:```sqlSELECT t1.id,t1.value - coalesce(t2.value, 0) AS diffFROM your_table t1LEFT JOIN your_table t2 ON t1.id = t2.id + 1;```在这个SQL语句中,我们首先对表进行自连接,将表自身连接起来,然后通过使用coalesce函数将NULL值替换为0,最终得到相邻行之间的差值。

4. 常见应用场景在实际应用中,计算相邻行差是一个常见的需求。

在处理时间序列数据时,我们经常需要计算相邻时间点的差值,以便分析数据的趋势和变化情况。

通过使用coalesce函数,我们可以快速高效地完成这一计算任务。

5. 总结在SQLite3中,coalesce函数是一个非常有用的函数,可以简化SQL语句,提高计算效率。

对于需要计算相邻行差的场景,使用coalesce函数可以帮助我们更加方便地完成这一任务。

通过学习和掌握coalesce函数的使用方法,我们可以更好地利用SQLite3数据库的功能,从而更加高效地处理数据。

结尾:通过以上介绍,我们了解了在SQLite3中使用coalesce函数来计算相邻行差的方法和应用场景。

axum框架原理解析

axum框架原理解析

Axum框架原理解析一、引言Axum是一个用于构建并发、异步和分布式应用程序的框架,它基于Actor 模型和Erlang的编程范式,提供了强大的功能和灵活性。

Axum通过利用现代硬件的优势,提高了应用程序的性能和可扩展性。

本文将深入解析Axum框架的核心概念、主要组件和优势,探讨如何使用Axum,并总结其结论。

二、Axum核心概念1.并发和异步编程:Axum基于Actor模型,允许开发者使用简洁的语法和语义来编写并发和异步代码。

通过将应用程序分解为多个独立执行的Actor,Axum能够充分利用多核处理器和分布式系统的优势。

2.不可变性和函数式编程:Axum遵循函数式编程的原则,如不可变性、无副作用等。

这有助于提高代码的可靠性和可维护性,降低程序中的错误和缺陷。

3.消息传递:在Axum中,Actor之间通过消息进行通信。

消息是异步传递的,确保了系统的高吞吐量和低延迟。

4.分布式系统支持:Axum框架天生支持分布式系统,提供了构建可扩展、可靠和高效分布式应用程序的能力。

三、Axum的主要组件1.Actors:在Axum中,Actor是构成应用程序的基本单元。

每个Actor执行独立的操作,并通过消息传递进行通信。

开发者可以使用Axum提供的Actor API创建和管理Actor。

2.Mailboxes:每个Actor都有一个与之关联的邮箱,用于接收和存储发送给它的消息。

邮箱充当了消息队列的角色,确保消息按照发送顺序被处理。

3.Schedulers:调度器负责调度Actor的执行。

在多核处理器上,Axum可以同时运行多个Actor实例,从而提高性能和并发处理能力。

4.Fault-Tolerance:Axum提供了一组机制来处理错误和异常情况,确保应用程序的可靠性和稳定性。

例如,当某个Actor出现故障时,其他Actor可以继续执行操作,而不会影响整个系统的运行。

5.Distributed Capabilities:Axum框架天生支持分布式系统,提供了构建可扩展、可靠和高效分布式应用程序的能力。

coalesce算子

coalesce算子

Coalesce算子1. 简介Coalesce算子是一种用于数据处理的常见操作符,可以用来合并多个数据流或者将多个小文件合并成一个大文件。

它在大数据领域中被广泛应用,特别是在分布式计算框架中,如Spark、Hadoop等。

Coalesce算子的主要功能是将多个输入流合并成一个输出流,并且可以选择性地指定输出流的分区数。

这个操作可以提高数据处理的效率和性能,减少数据传输和网络开销。

2. 使用场景Coalesce算子适用于以下场景:•数据文件合并:当需要将多个小文件合并成一个大文件时,可以使用Coalesce算子来减少文件的数量,提高读写效率。

•数据分区调整:当需要重新调整数据的分区数时,可以使用Coalesce算子来减少或增加分区数。

•数据集合合并:当需要将多个数据集合合并成一个数据集时,可以使用Coalesce算子来实现。

3. 实现原理Coalesce算子的实现原理主要涉及两个方面:分区调整和数据复制。

分区调整在分布式计算框架中,数据通常被划分为多个分区进行处理。

每个分区包含一部分数据,并且可能存储在不同的节点上。

当需要调整数据的分区数时,Coalesce算子会根据指定的分区数来重新分配数据,将原有的数据重新划分到新的分区中。

数据复制当需要将多个输入流合并成一个输出流时,Coalesce算子会将输入流中的数据复制到输出流中。

这涉及到数据的拷贝和传输过程,需要考虑网络开销和数据传输效率。

为了提高性能和效率,Coalesce算子通常会选择合适的节点来执行合并操作。

它会根据节点之间的网络拓扑结构、节点负载情况等因素来选择执行节点,并尽量减少数据传输和复制操作。

4. 使用示例下面是一个使用Coalesce算子进行文件合并的示例:from pyspark import SparkContext# 创建SparkContext对象sc = SparkContext("local", "coalesce example")# 读取多个小文件rdd1 = sc.textFile("file1.txt")rdd2 = sc.textFile("file2.txt")rdd3 = sc.textFile("file3.txt")# 合并文件merged_rdd = rdd1.coalesce(1).union(rdd2.coalesce(1)).union(rdd3.coalesce(1))# 将结果保存到一个大文件中merged_rdd.saveAsTextFile("merged_file.txt")在上述示例中,我们首先创建了一个SparkContext对象,并读取了三个小文件。

煤表面分子氧化机理的数值实验

煤表面分子氧化机理的数值实验

论文题目:煤表面分子氧化机理的数值实验专业:安全技术及工程硕士生:杨迎(签名)______________ 指导教师:徐精彩(签名)______________摘要煤自燃涉及资源、环境、经济以及人口等问题,因此我国政府在“21世纪议程”已将煤自燃列为重大自然灾害之一。

为了更好的防止煤矿火灾的发生,加强对煤自燃基础机理的研究显得尤为重要。

近年来煤氧复合学说得到广泛认同,各国学者从不同的角度进行相应的研究,如研究煤的活化能、煤分子结构模型、煤与氧化学反应和表面反应热、红外光谱等等,但是其微观机理的研究与探讨还没有起步,有待进一步发展。

随着计算机技术和量子化学计算方法的飞速发展,利用计算机来模拟化学反应正被广泛应用于化学研究的各个领域,并都已取得到了较好的成果。

本文针对煤分子表面活性基团进行研究,在已有实验研究的基础上,利用简单芳香环(苯)代替稠环芳香烃与煤活性基团组合模拟煤表面的简单分子形态。

计算采用DFT-B3LYP,基组为6-31G。

由于氧分子的基态为三重态,故所有氧化反应过程的自旋均取三重态计算。

通过计算表明,在煤的自燃反应初期,芳香环数对煤活性基团性质的影响不大,可以用简单芳香环(简单的苯结构)与活性基团联结替代复杂的煤表面分子。

这一简化的煤分子模型,减小了计算工作量,是从理论上研究煤自燃反应的一个合理的出发点。

计算得到了各个模拟分子反应过程中的优化构型,找到了过渡态,并经内禀反应坐标(IRC)确认了反应通道,连通了反应路径。

通过对数据的分析和整理得到了各反应的反应热力学和动力学参数,从而对煤自燃反应初期各活性基团与氧的反应机理有了更进一步的认识。

通过活化能的计算和比较,首次从理论上获得了煤活性基团的活泼性次序,为煤自燃初期的反应机理提供了新的思路和研究方法。

关键词:煤自燃;活性基团;密度泛函;热力学数据研究类型:应用研究Subject : The Study On Mechanism of the Low Temperature Oxidation of Simulated Coal MoleculeSpecialty : Safety Technology and EngineeringName : Yang Ying (Signature) ______________ Instructor : Xu JingCai (Signature) ______________ABSTRACTCoal is an abundant natural resource in China, which accounted for more than 2/3 of the total energy in recent years. While spontaneous combustion of coal is one of the big disaster in the coal product. Every year the country put lots of money, financial to prevent the spontaneous combustion of coal seams. So to study the basic mechanism of the spontaneous combustion of coal is very important.Nowadays the oxidation of coal study is well recognized among the so many coal spontaneous combustion. Scholar study the mechanism from different point, such as study the activation energy, study the coal molecular structure model, study the surface reaction enthalpy, study infrared technique and detect spontaneous combustion in coal seams by isotope niton, etc. With the developing of computer technique, quantum chemistry expands faster. This makes it possible to study the reaction mechanism of coal molecular from microcosmic.This article simulates the oxidation of the coal molecule with benzene and some active groups on the surface at low temperature by using B3LYP/6-31G calculations. We use model complicated aromatic structures with a single phenyl to investigate the mechanism of coal oxidation at room temperature. It is proved that this method is available. The optimized geometries of reactants, transition state and products in the coal-oxygen reactions are found. Based on these optimized structures we obtain the reaction enthalpy, Gibbs free energy and the activation energy, etc., which should be helpful to understand the microcosmic mechanism of the low temperature oxidation of the nine simulated coal molecules.Key words:Spontaneous combustion Active group DFT Thermodynamic data Thesis : Application Research目录1 绪论 (1)1.1 问题的提出 (1)1.2 国内外的研究动态及发展趋势 (2)1.2.1 国内外煤自燃学说 (2)1.2.2 国内外煤自燃研究方法 (3)1.3 研究的目的与意义 (5)1.3.1 研究的目的 (5)1.3.2 研究意义 (5)1.4 主要研究内容 (5)1.5 本课题拟采取的研究方案 (6)2 数值模拟理论基础 (7)2.1 化学反应动力学理论 (7)2.1.1 势能面 (7)2.1.2 过渡态理论 (8)2.1.3 频率计算和热力学校正 (10)2.1.4 IRC理论 (13)2.1.5 化学反应速率常数的计算理论 (13)2.2 量子化学的计算方法 (18)2.2.1 分子轨道法在物理模型上的三个基本近似 (18)2.2.2 变分法和LCAO-MO近似 (22)2.2.3 Hartree-Fock能量的得到 (23)2.2.4 后Hartree-Fock计算 (24)2.2.5 密度泛函方法(DFT) (24)2.3 应用程序简介 (25)2.3.1 Gaussian03的主要功能与应用 (25)2.3.2 POLYRATE程序简介 (26)2.3.3 SIMPLEX程序简介 (27)2.3.4 MELD程序的主要功能与应用 (27)2.4 本章小结 (28)3 煤表面活性基团分析 (29)3.1 煤分子结构特点 (29)3.1.1 煤分子的结构组成 (29)3.2 自燃煤表面分子的活性基团 (30)3.2.1 类似有机结构的氧化特性 (31)3.2.2 自燃煤表面分子活性基团 (33)3.3 煤氧复合微观机理 (34)3.3.1 煤表面分子活性基团的氧化作用机理 (34)4 煤表面氧化反应机理的模拟 (38)4.1 构型的建立 (38)4.2 芳香环数对活性基团性质影响的分析 (38)4.2.1 芳香环数对-CH2-活性基团影响分析 (39)4.2.2 芳香环数对-CHO活性基团影响分析 (40)4.3 反应历程分析 (41)4.3.1 -CH2-活性基团模拟的简单煤表面分子反应历程 (42)4.3.2 -CH2O-活性基团模拟的简单煤表面分子反应历程 (45)4.3.3 -HCOH-活性基团模拟的简单煤表面分子反应历程 (47)4.3.4 -CHO活性基团模拟的简单煤表面分子反应历程 (50)4.3.5 -CH3活性基团模拟的简单煤表面分子反应历程 (53)4.3.6 -CHCH3-CH2-活性基团模拟的简单煤表面分子反应历程 (56)4.3.7 -HCOH-CH2-活性基团模拟的简单煤表面分子反应历程 (59)4.3.8 -HCOH-CH3活性基团模拟的简单煤表面分子反应历程 (61)4.3.9 -O-CH3活性基团模拟的简单煤表面分子反应历程 (64)4.4 本章小结 (70)5 结论 (71)致谢 (74)参考文献 (75)附录 (77)1 绪论1.1 问题的提出煤自燃是自然界存在一种客观现象,这种现象已经存在数百万年。

coalesce在hql中的用法

coalesce在hql中的用法

coalesce在hql中的用法## COALESCE Function in HQL.The COALESCE function in HQL is used to return thefirst non-null value in a list of expressions. It is similar to the ISNULL function in SQL, but COALESCE can accept multiple expressions while ISNULL can only accept two.The syntax of the COALESCE function is as follows:COALESCE(expr1, expr2, ..., exprN)。

where:expr1, expr2, ..., exprN are the expressions to be evaluated.The COALESCE function will return the first expression that is not null. If all of the expressions are null, thenthe COALESCE function will return null.### Examples.The following example shows how to use the COALESCE function to return the first non-null value in a list of three expressions:SELECT COALESCE(name, username, 'Unknown') FROM users;In this example, the COALESCE function will return the value of the name column if it is not null. If the name column is null, then the COALESCE function will return the value of the username column. If both the name and username columns are null, then the COALESCE function will return the value 'Unknown'.The following example shows how to use the COALESCE function to return a default value if all of the expressions are null:SELECT COALESCE(name, username, 'Unknown') AS user_nameFROM users;In this example, the COALESCE function will return the value of the name column if it is not null. If the name column is null, then the COALESCE function will return the value of the username column. If both the name and username columns are null, then the COALESCE function will return the value 'Unknown'. However, in this example, the result of the COALESCE function is aliased as user_name.### Performance Considerations.The COALESCE function can be expensive to use, especially if it is used in a WHERE clause. This is because the COALESCE function must evaluate all of the expressions in the list in order to determine which one is not null.If performance is a concern, then it is better to use the ISNULL function instead of the COALESCE function. The ISNULL function only evaluates two expressions, so it is more efficient than the COALESCE function.## COALESCE函数在HQL中的用法。

Vent-Rite Guardian Plus Condensate Pump 安装和维护指南说明书

Vent-Rite Guardian Plus Condensate Pump 安装和维护指南说明书

Revision 1 Form VSM3431GCondensate Pump, type Guardian PlusUnit Installation and Maintenance Instructions1875 Dewey Avenue Benton Harbor, MI 49022 Phone 269-925-2522 /Guardian Plus Condensate ReturnGuardian Plus Boiler FeedINTRODUCTIONThis form contains information necessary to install, operate and maintain Guardian Plus Condensate Units manufactured by Vent-Rite. The information is assembled in order, from receiving the product to its proper maintenance, to enable you to follow the product through the various steps necessary to implement. The Guardian Plus Condensate Units are complete assemblies for returning condensate to low pressure boilers from gravity heating systems, low pressure steam process. equipment, or from combinations of both. They are used where low return mains are located at elevations which do not permit gravity flow of condensate to the boiler.INSTALLATIONA.Receiving Inspection. When the unit is delivered, an immediate visual inspection of the unit and its accessories should be made in the presence of the carrier's representative. If there is any evidence of rough handling or damage, a notation should be made on the delivery receipt. Shipping damages are the responsibility of the carrier, and it is the customer's responsibility to file the claim.B. Uncrating. When uncrating the unit be sure that all temporary plugs remain in their tapping until you are ready to connect the pump to the system, and all instructional tags are attached. Locate the unit in a clean, dry, well ventilated and drained location. The top of the pump receiver should be below the lowest return to maintain dry return lines. If receiver is above the lowest return, the returns will be wet, and the system will not free itself of air.C. Rigging. Each unit has been carefully tested and inspected at the factory where every precaution was taken to ensure that it reaches its destination in perfect condition. It is very important that the installers, movers, and riggers use the same care in handling of the unit. Chains, cables, or other moving equipment should be placed to avoid damage to any part of the unit.D. Piping Connections. All piping should be tight and properly supported by hangers, not by connections. Connect returns to inlet of receiver with a Vent-Rite gate valve in each return and a union or flange joint next to the receiver. Connect discharge of pump to boiler using a union, swing check valve and gate valve, with the swing check valve as close to pump as possible. Piping must be of proper length and size to prevent any strain upon the unit. WARNING:Venting to same room may cause humidity which can lead to damaged equipment (pumps, control panels, etc.). Vent to exterior of building when possible.E. Wiring. The electrical connections between the motor, float switch and automatic starter (if furnished) are made at the factory. Connect the electric service to the float switch or automatic starter using conduit and wire sizes as required by state/local codes. Provide a fused main line switch in motor circuit. CAUTION: The motor is wired at the factory to operate at the voltage specified. If voltage is other than originally specified, consult motor manufacturer's instructions accompanying unit for proper wiring. Where a polyphase motor is furnished with only a float switch, IT WILL BE NECESSARY TO INSTALL A SUITABLE PHASE PROTECTOR SWITCH IN THE MOTOR CIRCUIT TO PREVENT MOTOR BURNOUTS SHOULD A SINGLE-PHASE CONDITION OCCUR.F. Fuses. Be sure fuses are installed which comply in size with NEC (National Electrical Code) recommendations. When a fuse blows out, it indicates that something is wrong either in the motor, pump, switch, fuse rating or electric service. Do not replace fuse until the cause has been determined. If a thermal cut-out is used, an element with a maximum tripping current rating 50% greater than motor nameplate Amperes may be selected. Condensate boiler feed pumps operate intermittently and are therefore permissible.OPERATIONBefore placing the unit in service, operate the system for atleast several days, wasting the condensate to the sewer through draw-off to remove dirt, grease, scale and other foreign matter. When discharging condensate to sewer, supply make-up water to boiler to maintain proper water line.On installations equipped with manually operated coal, oil or gas-fired boilers an automatic water feeder is recommended. A low water cut-out of fuel supply should be installed on all installations equipped with automatically operated stoker, oil or gas-fired boilers. For Trial Operation of Unit, Proceed as Follows:1. Shut power off to unit.2. Remove plug on rear of motor and with large-bladed screwdriver, rotate shaft to be sure pump isfree.3. Jog pump to ensure correct pump rotation(Clockwise when viewed from the top). Do notcontinuously operate pump without water inthe receiving tank as the pump is equipped with amechanical shaft seal. Continuously operating thepump dry may ruin seal.4. Fill the receiver tank with enough water to close thefloat switch.5. Open gate valve.6. The pump will discharge water from the receivingtank into the boiler, stopping automatically whenwater in receiving tank reaches a low level. OPERATING POINTS1. Check motor speed. If motor speed is low checkwiring connections to motor. If wired for higher voltcurrent than actual volt current, the motor will nevercome up to proper speed, and motor may burn out.2. Lack of capacity may indicate that passageways ofpump impeller have become clogged with foreignmatter. 3. If the pump fails to start, it may be due to the floatball having lost its buoyancy. This can be checked by operating the float head lever manually. If the float ball is not buoyant, replace with new float ball.4. If after long service, water flows from around themotor shaft out through the space between the pump head motor flange and the pump head case flange, it is an indication of a mechanical seal failure, and the complete mechanical shaft seal should be replaced. Motor(s) not provided with grease fittings have bearings greased for life by motor manufacturer.PARTS- When ordering parts, give type, size and serial number shown on the pump nameplate.MAINTENANCEINSPECTION.To ensure best operation of unit, make a systematic inspection at least once a week. CLEANLINESS. Keep the interior and exterior of motor and automatic switches free from moisture, oil and dirt. If necessary, use compressed air for blowing out dirt. FLOAT SWITCH(Simplex) or MECHANICAL ALTERNATOR (Duplex) Occasionally examine contacts of automatic switches and see that they make a full firm contact and break the circuit quickly. Be sure all terminal connections are tight and not corroded.MECHANICAL SHAFT SEAL.Occasionally examine water slinger on motor shaft and look for water leakage. Any leakage will also be visible on seal plate. Leakage indicates that the seal surfaces are worn and will need replacing. CAUTION: Never operate pump when receiver is empty, because the seal will be damaged if run dry. SHUT DOWN. At the end of the heating season, open main line switch, close valves in return line and discharge piping, - and drain receiver and pump. If necessary, cover electric motor and automatic switches to protect them against dirt, oil and moisture. CAUTION:Never operate pump when receiver is empty or expose it to freezing temperature when filled with water.TYPICAL SYSTEM CONNECTIONSFigure 1TROUBLESHOOTINGA troubleshooting chart is shown below to enable you to isolate any problems you may encounter when operating the Guardian Plus Condensate Unit.SYMPTOMPOSSIBLE CAUSEREMEDY1. No condensate discharge1a. Not enough condensate in tank to prime pump. 1b. Speed too low.1c. Discharge head too high.1d. Impeller loose on shaft, plugged or worn.1a. Check return lines from boiler. 1b. Check wiring connections to motor. 1c. Open discharge valve.1d. Inspect pump end and motor. Repair and/or replace.2. Insufficient condensate discharge2a. Air or water leak. 2b. Plugged pump vent line. 2c. Speed too low.2d. Impeller loose on shaft, plugged or worn.2a. Check bleeder line.2b. Disconnect vent line from Guardian Pump – Reconnect.2c. Check motor wiring.2d. Replace impeller. Check with manufacturer. 3. Pump does not start3a. Motor lead connections may be wired wrong. 3b. Blown fuses in disconnect switch. 3c. Loose connection.3d. Rotating assembly is bound.3a. Check wiring diagram, page 2. 3b. Check fuses. 3c. Check wiring.3d. Try turning motor shaft from top side of motor with screwdriver or open wrench. 4. Excessive power consumption4a. Speed too high. 4b. Loose wiring connection. 4c. Mechanical defects: (1) Motor shaft bent (2) Rotating element binds (3) Foreign elements between impeller andwearing ring.4a. Check voltage4b. Check wiring connections. 4c. (1) Replace motor.(2) Reassemble & tighten parts. (3) Disassemble & check condition.5. Pump is noisy5a. Bearings bad (sealed bearings in motor) 5b. Pump may be operating at a low enough head to be in cavitation range. Cavitation sounds like pebbles rattling in a pail.5c. Pump is operating too near shut-off head. 5d. Internal parts rubbing.5e. Motor has magnetic hum or high windage noises.5a. Check with motor manufacturer.5b. Throttle discharge valve to correct pressure and lock. (If cavitation noise disappears it may be wise to install a smaller diameter impeller, reduce speed, or install on orifice on discharge). 5c. Check discharge piping to lower the head. 5d. Disassemble and check internal parts. 5e. check with motor manufacturer.6. Loss of Suction following period of satisfactory operation6a. Air leak at mechanical shaft seal or pump gasket.6b. Pump vent line plugged.6c. Air gasses in condensate or condensate too hot.6a. Disassemble pump and motor unit. Replace mech. Shaft seal or gasket. Be sure all parts are clean. Do not scratch or mar seal component rings. Reassemble. Never run pump with receiver empty. Damage to seal may result. 6b. Flush.6c. Check mechanical shaft seal and gasket.Table 1Guardian®Boiler Feed Pumps (WITH MAKE-UP WATER VALVE)The Model GSB (simplex unit) or GSBD (duplex unit) Guardian Boiler Feed Pump is designed for those installations where it is important to maintain the boiler water line within narrow limits, and to automatically supply “make -up” water from an outside source. Precise boiler line control is accomplished by governing the pump operation with a Boiler Water Line Controller installed at the boiler water line.When the boiler requires water, the float operated switch in the Controller starts the pump motor(s) through magnetic starters that can be furnished as an optional extra. Water level is maintained in the pump receiver by an electric solenoid make-up valve activated by a reverse acting float switch. The construction of these pumps is similar to the GS model except that a water make-up circuit (solenoid valve and reverse acting float switch) is furnished.Figure 2SIDE MOUNT FLOAT SWITCH - MAINTENANCE INSTRUCTIONSTO AVOID SHOCK HAZARD, DISCONNECT ALL POWER BEFORE INSTALLING OR SERVICING DEVICE.Float Adjustment: Floats that are shipped with a Vent-Rite unit will be pre-set to the proper float travel; however, if a replacement float switch is to be installed on an existing unit or if adjustment is required, travel may be adjusted via the adjusting strips, held in place by bolts “A” and “B”. Track secured by bolt “A” determines upward limit of travel, with “B” determining the lower. Either may be adjusted by loosening their respective bolts and sliding the adjustment track to the desired angle.Note: If possible, filling the tank to desired high or low point will allow adjusting strip to be fastened in exact location, with no guesswork or calculation required.Removing the Float Switch: The side mount float switch can be mounted either with a 2-1/2” NPT bushing or a cast iron mounting flange. If a flange-mounted float must be removed from the tank, the nuts may be loosened on the flange and the float removed. Gaskets should be replaced i f damaged. For the bushing mounted float switch, loosen the locking nut “C”. This will allow the bushing to be rotated out of the tank and the float removed.Replacement Parts:For replacement parts, contact your local Vent-Rite representative. Float switch arm and tank mounting configuration can differ from tank to tank, so be sure to provide the tank dimensions and mounting configuration in the request. Vent-Rite will not replace sub-components on the float switch, such as the float arm or switching mechanism. Wiring Diagrams:Electrical Ratings:SIDE MOUNT MECHANICAL ALTERNATOR - MAINTENANCE INSTRUCTIONSTO AVOID SHOCK HAZARD, DISCONNECT ALL POWER BEFORE INSTALLING OR SERVICING DEVICE.Float Adjustment: Mechanical Alternators that are shipped with a Vent-Rite unit will be pre-set to the proper float travel; however, if a replacement float switch is to be installed on an existing unit or if adjustment is required, travel may be adjusted via the adjusting strips, held in place by bolts “A” and “B”. Track secured by bolt “A” determines upward limit of travel, with “B” determining the lower. Either may be adjusted by loosening their respective bolts and sliding the adjustment track to the desired angle.Note: If possible, filling the tank to desired high or low point will allow adjusting strip to be fastened in exact location, with no guesswork or calculation required.Pump 1 will activate at roughly 3/4 of the vertical float travel, and alternate to pump 2 at the low end of the travel. If Pump 1 is not sufficient to empty the tank, pump 2 will activate at the high point of the float travel.Removing the Mechanical Alternator: The side mount mechanical alternator can be mounted either with a 2-1/2” NPT bushing or a cast iron mounting flange. If a flange-mounted alternator must be removed from the tank, the nuts may be loosened on the flange and the float removed. Gaskets should be replaced if damaged. For the bushing mounted mechanical alternator, loosen the l ocking nut “C”. This will allow the bushing to be rotated out of the tank and the alternator removed.Replacement Parts: For replacement parts, contact your local Vent-Rite representative. Mechanical alternator arm and tank mounting configuration can differ from tank to tank, so be sure to provide the tank dimensions and mounting configuration in the request. Vent-Rite will not replace sub-components on the mechanical alternator, such as the float arm or switching mechanism.Wiring Diagrams:Electrical Ratings:TOP MOUNT FLOAT SWITCH - MAINTENANCE INSTRUCTIONSTO AVOID SHOCK HAZARD, DISCONNECT ALL POWER BEFORE INSTALLING OR SERVICING DEVICE.Float Adjustment: Floats that are shipped with a Vent-Rite unit will be pre-set to the proper float travel; however, if a replacement float switch is to be installed on an existing unit or if adjustment is required, travel may be adjusted via the adjusting nuts. These may b e accessed by loosening housing nut “A” and sliding the housing off. By turning adjusting nut “B” and “C” closer together, float travel will be reduced, likewise turning the nuts further apart will increase float travel. Do not tighten the bots together, a s this will bind the mechanism, always leave at least 1/16” of space between the bolts and the mechanism.Note: If possible, filling the tank to desired high or low point will allow respective adjusting nut to be fastened in exact location, with no guesswork or calculation required.Removing the Float Switch: The top mount float switch is mounted using an integrated flange. If the float must be removed from the tank, the nuts may be loosened on the flange and the float removed. Gaskets should be replaced if damaged.Replacement Parts: For replacement parts, contact your local Vent-Rite representative. Float switch arm can differ from tank to tank, so be sure to provide the tank dimensions in the request. Vent-Rite will not replace sub-components on the float switch, such as the float arm or switching mechanism.Wiring Diagrams:Electrical Ratings:TOP MOUNT MECHANICAL ALTERNATOR - MAINTENANCE INSTRUCTIONSTO AVOID SHOCK HAZARD, DISCONNECT ALL POWER BEFORE INSTALLING OR SERVICING DEVICE.Float Adjustment: Floats that are shipped with a Vent-Rite unit will be pre-set to the proper float travel; however, if a replacement mechanical alternator is to be installed on an existing unit or if adjustment is required, travel may be adjusted via the adjusting nuts. Th ese may be accessed by loosening housing nuts “A” and sliding the housing off. By turning adjusting nut “B” and “C” closer together, float travel will be reduced, likewise turning the nuts further apart will increaseC Afloat travel. “B” will adjust the high point, and “C” the low point. These adjustments are very sensitive, so adjust only when absolutely necessary.Note: If possible, filling the tank to desired high or low point will allow respective adjusting nut to be fastened in exact location, with no guesswork or calculation required.Removing the Float Switch: The top mount mechanical alternator is mounted using an integrated flange. If the alternator must be removed from the tank, the nuts may be loosened on the flange and the float removed. Gaskets should be replaced if damaged.Replacement Parts: For replacement parts, contact your local Vent-Rite representative. Mechanical alternator arm can differ from tank to tank, so be sure to provide the tank dimensions in the request. Vent-Rite will not replace sub-components on the mechanical alternator, such as the float arm or switching mechanism.Wiring Diagrams:Electrical Ratings:Guardian Condensate PumpREPAIR PARTS LISTFigure 3Figure 4Table 21875 Dewey Avenue Benton Harbor, Michigan 49022Phone 269.925.2522 Website: /MANUFACTURING AND DESIGN OF QUALITY HVAC SYSTEMS SINCE 1921The specifications contained in this bulletin were effective at the time of publishing. We reserve the right to discontinue products at any time or to change specifications or design without incurring any obligation. For most current information, contact your Vent-Rite® representative.。

.coalesce函数用法

.coalesce函数用法

.coalesce函数用法==========一、概述----在许多编程语言和数据结构中,`coalesce`函数是一个常见的函数,用于返回参数列表中的第一个非空值。

这个函数在处理可能为空的变量或值时非常有用。

本篇文章将介绍`coalesce`函数的用法,包括其定义、参数、返回值以及在各种编程语言中的实现。

二、基本定义------`coalesce`函数接受一个或多个参数,并返回参数列表中的第一个非空值。

如果所有参数都为空,则返回`null`。

这个函数在处理可能为空的变量或值时非常有用,可以避免因为变量为空而导致的错误或异常。

三、常见编程语言中的实现------------以下是在一些常见编程语言中`coalesce`函数的用法示例:### 1. Python在Python中,可以使用内置的`coalesce`函数来返回参数列表中的第一个非空值。

示例如下:```pythondef coalesce(*args):for arg in args:if arg:return argreturn None```### 2. JavaScript在JavaScript中,可以使用`Array.prototype.find`方法来找到第一个非空元素,并使用该元素作为`coalesce`函数的返回值。

示例如下:```javascriptfunction coalesce(...args) {for (let arg of args) {if (arg !== null && arg !== undefined) {return arg;}}return null;}```### 3. Java在Java中,可以使用`Optional`类来处理可能为空的变量或值。

示例如下:```javaimport java.util.Optional;public class CoalesceExample {public static void main(String[] args) {Optional<String> opt1 = Optional.ofNullable("Hello");Optional<String> opt2 = Optional.empty();String result = coalesce(opt1, opt2); // "Hello" 是第一个非空值,返回 "Hello"}}```四、使用方法及注意事项-----------在使用`coalesce`函数时,可以根据具体需求传递一个或多个参数。

coalesce sql标准

coalesce sql标准

coalesce sql标准Coalesce是一种在SQL中常用的函数,用于返回参数列表中第一个非NULL的表达式。

它的目的是为了简化在查询中处理NULL值的逻辑。

在本文中,我将介绍coalesce函数的定义、用法和一些例子,同时也会探讨一些与之相关的话题。

首先,让我们来看一下coalesce函数的定义。

在标准SQL中,coalesce函数的语法如下:```COALESCE(expression1, expression2, ..., expressionn)```上述语法中,expression1到expressionn是参数列表。

它们可以是任意类型的表达式,包括列、常量、函数等。

coalesce函数会从左到右逐个检查这些表达式,并返回第一个非NULL的表达式的值。

如果所有表达式都为NULL,那么coalesce函数会返回NULL。

Coalesce函数的使用非常灵活,可以用于各种查询场景。

以下是几种常见的用法示例:1.使用coalesce函数处理NULL值假设我们有一个包含学生成绩的表格,其中的某些值可能为NULL。

要计算每个学生的总分,我们可以使用coalesce函数来处理可能出现的NULL值,确保最终结果不会受到NULL的影响。

```sqlSELECT student_id, COALESCE(score1, 0) + COALESCE(score2, 0) + COALESCE(score3, 0) AS total_scoreFROM scores;```上述代码中,COALESCE(score1, 0)表示如果score1为NULL,则返回0,否则返回score1的值。

通过使用coalesce函数,我们可以在计算总分时处理NULL值,避免出现错误的计算结果。

2.使用coalesce函数设置默认值除了处理NULL值,coalesce函数还可以使用默认值来代替NULL。

这在需要为某个字段提供默认值的情况下非常有用。

coalesce() 函数

coalesce() 函数

coalesce() 函数一、coalesce() 函数简介coalesce() 函数是一个在编程中常用的处理null值的方法。

它的作用是将一个或多个可能的null值转换为非null值,返回第一个非null参数。

在Java、C#、Python等编程语言中都有类似的函数。

二、coalesce() 函数的语法与参数coalesce() 函数的语法如下:```coalesce(param1, param2, ..., paramN)```参数可以是任意类型,包括nullable类型和非null类型。

函数会依次检查每个参数,如果遇到非null值,就立即返回该值;如果遇到null值,则会继续检查下一个参数。

直到找到一个非null值为止。

三、coalesce() 函数的应用场景1.当需要从多个值中选择一个非null值时,可以使用coalesce() 函数。

2.在集合操作中,当需要处理可能包含null值的集合时,可以使用coalesce() 函数来确保结果集的非null属性。

3.在数据库查询中,当需要对可能为null的列进行处理时,可以使用coalesce() 函数来返回一个非null值。

四、coalesce() 函数的优缺点优点:1.简洁明了地处理了null值的问题。

2.易于理解和使用。

缺点:1.在某些情况下,可能需要对多个非null值进行处理,这时候coalesce() 函数就不太适用了。

2.如果输入参数全部为null,coalesce() 函数会抛出异常,需要处理异常情况。

五、示例代码以下是一个使用coalesce() 函数的示例:```javapublic class CoalesceDemo {public static void main(String[] args) {String str1 = "Hello";String str2 = null;String str3 = "World";String result = coalesce(str1, str2, str3);System.out.println(result); // 输出:Hello}}```在这个示例中,我们有两个可能为null的字符串变量str1和str2。

coalesce函数的实际用法

coalesce函数的实际用法

文章主题:coalesce函数的实际用法1. 简介在数据库管理系统中,coalesce函数是一种常用的函数,用于返回参数列表中第一个非NULL值。

它在处理数据库中的数据时非常实用,可以帮助我们处理各种情况下的空值和NULL值。

在本篇文章中,我将会详细介绍coalesce函数的实际用法,以及我对其个人观点和理解。

2. 基本用法coalesce函数的基本用法非常简单,它接受一个参数列表,并返回第一个非NULL值。

如果我们使用coalesce函数来处理一个包含NULL 值的字段,它会返回该字段的第一个非NULL值。

这在数据处理和分析中非常有用,可以帮助我们准确获取需要的数据。

3. 在实际项目中的应用在我的实际项目中,我经常会用到coalesce函数来处理数据库中的空值。

在一个电子商务系统中,商品的价格可能会存在空值或NULL值。

而在展示商品信息时,我们需要准确显示价格,这时就可以使用coalesce函数来获取第一个非NULL值,以保证展示的准确性和完整性。

4. 对coalesce函数的个人理解个人认为,coalesce函数是一种非常实用的数据处理函数。

它可以帮助我们轻松应对各种数据情况,避免因空值或NULL值而导致的错误或不完整的数据展示。

在实际项目中,我对其灵活性和实用性深有体会,它为我们提供了一种简单而有效的方式来处理数据的空值情况。

5. 总结在本篇文章中,我详细介绍了coalesce函数的实际用法和个人观点。

通过对其基本用法和在实际项目中的应用进行介绍,我希望读者能更深入地了解和掌握这一实用函数。

在数据处理和分析中,coalesce函数无疑是一种强大的工具,可以帮助我们提高数据处理的准确性和完整性。

6. 继续探索当然,除了在本文中介绍的基本用法之外,coalesce函数还有很多高级用法和应用场景。

读者可以继续学习和探索,发现更多关于coalesce函数的实际用法和技巧,以及在实际项目中的更多应用场景。

postgresql中的COALESCE()函数使用小技巧

postgresql中的COALESCE()函数使用小技巧

postgresql中的COALESCE()函数使⽤⼩技巧场景:存在⼀个⽤户⽩名单表,提供了此⽤户的⽤户名和地区信息,判断此⽤户是否在此⽩名单表中。

如:姓名⽩名单地区张三中国,美国则可使⽤如下语句:SELECTID,user,area_listFROMt_white_userWHEREuser = #{ user,jdbcType = VARCHAR }AND (COALESCE (area_list, '') LIKE CONCAT ('%' ,#{ country,jdbcType = VARCHAR }, '%')OR area_list IS NULL)LIMIT 1技巧点分析:1、coalesce函数说明:返回其参数中第⼀个⾮空表达式,这⾥使⽤即 area_list2、⽩名单地区为多个国家以逗号分隔,则使⽤like concat的⽅式,能查询出某个国家是否被包含其中。

补充:PostgreSQL - null和''的区别与判断以及COALESCE函数null和''的区别与判断null是⼀种类型,''是空字符串,打个⽐⽅,''是你参加了考试且得了零分,⽽null则是你压根就没有参加考试。

如果要在sql中对两者进⾏判断,是有区别的://null只能和is或is not搭配,不能使⽤=、!=或者<>select * from student where name is null;select * from student where name is not null;//''的判断可以使⽤=、!=或者<>select * from student where name = '';select * from student where name != '';select * from student where name <> '';使⽤COALESCE函数COALESCE函数是返回参数中的第⼀个⾮null的值,它要求参数中⾄少有⼀个是⾮null的,如果参数都是null会报错。

函数coalesce

函数coalesce

函数coalesce函数coalesce的介绍在数据库中,coalesce函数可以用来返回第一个非空值。

在编程中,我们也可以使用这个函数来处理一些变量为空的情况。

本文将详细介绍如何使用coalesce函数来编写一个实用的函数。

函数的定义本文所要实现的函数是一个自定义的coalesce函数,它接受多个参数,并返回第一个非空值。

以下是该函数的定义:```pythondef coalesce(*args):"""返回第一个非空值:param args: 多个参数:return: 第一个非空值"""```该函数使用了可变参数args,这意味着我们可以传入任意数量的参数。

接下来我们将逐步实现这个函数。

检查参数数量首先,我们需要检查传入的参数数量是否为零。

如果是零,则无法返回任何值,此时应该抛出异常。

以下是代码实现:```pythondef coalesce(*args):"""返回第一个非空值:param args: 多个参数:return: 第一个非空值"""if len(args) == 0:raise ValueError('至少需要传入一个参数')```检查每个参数是否为空接下来,我们需要遍历每个参数,并检查它们是否为空。

如果某个参数不为空,则直接返回它即可。

以下是代码实现:```pythondef coalesce(*args):"""返回第一个非空值:param args: 多个参数:return: 第一个非空值"""if len(args) == 0:raise ValueError('至少需要传入一个参数')for arg in args:if arg is not None:return arg```处理空字符串上面的代码可以处理None类型的参数,但是如果传入了空字符串,它会被视为非空值。

oracle中coalesce函数用法

oracle中coalesce函数用法

oracle中coalesce函数用法
在Oracle中,COALESCE函数用于返回参数列表中的第一个非空表达式的值。

它的语法如下:
COALESCE(expression1,expression2,expression3,...)
该函数将按照参数列表的顺序依次评估每个表达式,直到找到一
个非空值为止,然后返回该值。

如果所有表达式都为空,则返回空值。

下面是一些COALESCE函数的示例用法:
1.使用COALESCE函数来选择非空的列值:
SELECT COALESCE(first_name, last_name) AS name
FROM employees;
该查询用于从employees表中选择first_name列值,如果该列为空,则选择last_name列值,然后将选择的列值作为名字进行返回。

2.使用COALESCE函数来提供默认值:
SELECT COALESCE(salary,0) AS salary
FROM employees;
该查询将在从employees表中选择salary列值时,如果该列为空,则返回0作为默认值。

除了以上用法,COALESCE函数还可以用于其他一些场景,比如:
-在条件语句中使用COALESCE函数来提供替代值。

-在合并多个表中的数据时,使用COALESCE函数来选择非空值。

-在处理日期或时间数据时,使用COALESCE函数来选择非空日期
或时间。

总结来说,COALESCE函数是一个非常有用的函数,可以在需要选
择非空值或提供默认值的情况下使用。

它可以帮助简化SQL查询,并
增强数据的可靠性和一致性。

coalesce的用法

coalesce的用法

coalesce的用法一、什么是coalesce函数?1.1 引言在编程中,经常会遇到需要从多个选项中选择一个非空值的情况。

为了解决这个问题,我们可以使用coalesce函数。

1.2 coalesce函数的定义和作用coalesce函数是一种在许多不同编程语言中都存在的函数,它的作用是从一组表达式中选择第一个非空值。

换句话说,coalesce函数返回参数列表中第一个不为NULL的值。

二、使用coalesce函数的场景及示例2.1 场景一:处理数据库查询结果在数据库查询结果中,有时候需要处理一些可能为空的字段。

这时候,可以使用coalesce函数来处理空值并提供默认值。

示例代码:SELECT coalesce(name, 'No value') AS name FROM users;上述示例代码将会返回一个名字列,如果name列为NULL,则返回字符串'No value'。

2.2 场景二:合并多个列数据当我们需要将两个或多个列数据合并成一个新的列时,可以使用coalesce 函数。

示例代码:SELECT coalesce(first_name || ' ' || last_name, 'No Name') AS full_name FROM employees;这个示例代码将first_name和last_name列合并,并且如果两者都为空,则返回字符串'No Name'。

三、应用案例:使用coalesce函数优化数据检索假设我们有一个电商网站,用户可以通过搜索商品名称来查找物品。

当用户输入搜索关键词时,我们需要根据关键词在数据库中进行检索。

然而,由于用户输入的关键词可能是大小写不一致的,或者包含了部分信息,这就需要我们对关键词进行处理以便提供更准确的搜索结果。

在这种情况下,coalesce函数可以帮助我们处理这个问题。

coalesce() 函数

coalesce() 函数

coalesce() 函数摘要:一、coalesce() 函数的概述二、coalesce() 函数的使用方法三、coalesce() 函数在实际编程中的应用四、总结正文:coalesce() 函数是编程中常用的一种函数,主要用途是返回第一个非空参数。

该函数在不同的编程语言和框架中可能有不同的实现和名称,但其核心功能都是类似的。

首先,我们来看一下coalesce() 函数的使用方法。

在Python 中,coalesce() 函数可以直接使用,而在其他语言中,可能需要先导入相应的库或模块。

以下是一个Python 中使用coalesce() 函数的例子:```pythondef coalesce(*args):return next(arg for arg in args if arg is not None)```在这个例子中,coalesce() 函数接收任意数量的参数,并返回第一个非空参数。

如果所有参数都是空,那么coalesce() 函数将返回None。

在实际编程中,coalesce() 函数可以用于处理默认值、空值等问题。

例如,当从数据库中查询数据时,如果某个字段为空,可以使用coalesce() 函数返回一个默认值。

以下是一个使用coalesce() 函数处理数据库查询的例子:```pythonfrom sqlalchemy import func# 假设我们有一个User 模型,其中包含name 和age 两个字段user = session.query(User).filter_by(name=coalesce(name, "default_name")).first()```在这个例子中,我们使用coalesce() 函数来处理name 参数。

如果name 参数为空,那么将使用默认值"default_name"来查询数据库。

总结一下,coalesce() 函数是一个非常实用的函数,可以用于处理各种非空参数的问题。

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安装指南安装有自动振打收尘过滤器的Weigh hopper的维护与检查.Smpler 喂料器的操作要求Weigh hopper内部压力和大气压力一致.●保证在比重喂料时,少量空气的流入有助于减少物质的流量。

●保证在填充料时,空气可以从Weigh hopper中排出,为了防止煤粉随气体排到大气中,在Weigh hopper上部连接有脉冲过滤器,其作用如下所述:在①点时,如果喂料器锁定于容积,在②点处fill gate打开,在③点时供气如果填料系统安装有填料漏斗,漏斗的反吹气体启动填料系统(参照操作说明)。

●当料喂入Weigh hopper时,将会导致hopper内的压力上升。

④其压力可以计量并且fill gate在⑤作用时关闭,压力会暂时降低,过滤器袋子具有渗透性,在⑥时,喂料器重新锁定于比重计量状态,气体须达到⑦时可允许的压力±5mm WC与大气压力有关。

过滤器的清灰工作在⑧到⑨时启动,在向Weigh hopper中喂料的同时清除积累的粉尘。

在Weigh hopper内保持较低④的压力以提高收尘器的收尘效果。

以比重方式连续喂料时,在Weigh hopper内部具有稳定的气体压力。

注意:在比重喂科状态时应尽量避免压力的波动。

维护:●在喂料器运行过程中,确定收尘器的维护的周期。

●使用干焊的无伸的高压气体清扫收尘器。

●清洗滤布应按照生产商的说明进行。

●对于自动清扫装置,参照收尘器制造厂商的说明书。

检查:当收尘器冒灰时更换袋子1.3 smpler失重喂料器根据控制失重来计算设计的,重量的计算不是根据喂入粉底的多少而是通过供给他损的重量来计算的,以此来控制喂料速率Weigh Bar的重量是通过一个或几个重量感应器来测量的,它们的输出电压和实际作多的压力是成比例的,也就是填气料的重量,随着填料挡板的关闭,bar的料位变化与卸料挡板的喂料速率相一致,通过喂料速率计量器,A/D转换器把实际喂料获得的结果转换成电压,控制器随着电压的大小来改变控制信号,直到实际下料速度和设定相一致。

在重新填料时,由于风度流动性冲击的影响,不能得到实际喂料速度,在这种状态时,disdange wnit所反馈的流量保持稳定,根据控制流量的大小,应用成比例性设定元件,由限先进的控制器连续有效的输出。

是否重新填料和以空重测量形式喂料时间比以比重测量时的时间短,是否喂料器精确测量,在填充状态下,几乎不在考虑流量的变化,其对喂料的稳定性没有影响。

图1.3形卡simpler Feeder的使用说明:(A)喂料器开始喂料且bar料位下降到HMINI,缓冲器发出的响应信号重新填料命令发送到fill unit。

(B)响应时间之后,fill unit开始打开。

(C)在打开时间过后,fill unit全部打开。

(D)Bin的物料达到HMAX1时,fill unit开始关闭。

(E)fill unit切断时,流动物料对喂料机的冲击也随之消失。

(F)设定TBRUHE时间后,开始实际测量和控制,也就是说,以比重形式喂料。

(G)循环填料重要的说明原则就是可以进行参政设定和内部监料。

填料时的控制信号由重新填料时Bar重量来响应,Bar的重量由缓冲器和喂料量来划分成两部分,要求weigh bin内的缓冲器能持久耐用,以便于消除feed unit喂料时的不利带来的影响。

为了防止weigh bin中的粉料溢出成大块物料的堵塞,通过脉冲阀来控制fill unit,实现连续填料的循环,在重新填料时要控制和监测易阳窑的几个参极P06、P07、P13。

以下是填料控制过程的基本形式:〉首次喂料(bin level h〈HMIN2〉)〉循环喂料(HMIN2〈bin level h〈Hmax1)其它控制方式:附加另外的fill units(如K17、K18结构)辅助fill驱动(如K19结构)首次喂料只有在喂料器停止状态时才能启动。

如果首次自动喂料,由于联锁设定的相关条件(feeder off, fill weight〈Hmin2),循环喂料也同时启动,然而,首次filling的启动的信息“SCO1”“Bir leved〈 HMIN2”只有在送电或停电之后才可泻到。

如果自动控制切断,循环喂料方式在启动之前应先设定,需要附加安全措施,在限位达到HMIN1或者Hmax1时,循环喂料模式启动或停止。

循环填料方式可以:〉外部fill control完全控制。

〉首次填料或阻塞,可通过举自动控制MULTCONT控制。

〉单独由MULTCONT控制。

〉完全切断。

还可以通过设定切断指令,利用分配器的作用启动或中断循环填料,如果fill unit不是处于自动状态,那么重新填料将不被执行,而由手动控制来执行,对于控制信号在bin料位降低到HMIN1时仅有警告信号出现。

Smiplex Pulverized cool feeler的通风装置:1、在Smiplex失重控制喂料器中,空气从煤粉仓转移到计量仓内,然后经过过虑器排放到大气中。

过滤器安装在计量仓上面,是feeder的部分。

在过滤器中残留的灰尘对于计量的精确度没有影响。

为了保证清除灰尘时产生的脉冲压力不会影响喂养料的精确度,清灰工作应该在filling时进行。

清灰工作由喂料器的电子系统来控制在比重喂出料时,Weigh hopper通过过虑器通风。

2、气力输送系统中产生漏气的收尘从煤喂料器到燃烧器的物料通常具通气力输送系统输送的,气力输送系统中泄漏的气体须经过过滤器后再排入到大气中,过滤器的尺寸规格以及操作须确保从喂料器到输送系统的传送区域无正压或压力小于5mbar。

清灰工作应在气力输送系统运行时有规律的间隔进行,不受Simplex feeder的影响。

为了安全,以上两种粉尘排进各自的收尘器中,过滤器是根据目前Germand Standards和VDI rules设计中关于磨煤系统中10ber防爆压力设计的有关细节,请参照以下条款和建议,以及我们的报价或供给说明。

2.4气力输送系统中收集的气体成分比例:2.4.1确定在预期范围内逸出气体最大量(m3/min)逸出气体流量的数值受制造规格,系统的数据,每分0-9 m3气体流量波支范围的影响。

生产商所提供的气力输送系统的操作说明是可靠的。

2.4.2从气力输送系统到过滤器的输送管道的尺寸应使空气速度不超过3m/s,其直径应不小于150mm,以免造成管道系统堵塞。

2.4.3过滤器的规格应根据预期范围内逸出气体的最大量来计算,其实际的过滤面积不能超过其最小值0.8 m3/m2,这样可以保证过滤器中的压力不大于5mber,(如果还有其它细节被标注,过滤器的间隔使用须与生产商的说明相符)。

气力输送系统中的最佳运转的前提是过滤器的压力,或泵入口处的正压最大不超过5mbar。

2.4.4 Star feeder的性能和正压值一致,其容量根据系统的最大流量比率来计算的,Star feeder应具有存储功能,以免物料不影响喂料。

如果根据Example I设计,Star feeder安装在过滤器出口处仅作为一个锁风阀,当物料达到最大时,Star feeder关闭使物料不能进入过滤器。

作为设计原则,Star feeder在入口处或出口处的面积为200×200mm(DN200)在I或II类型和正类型Star feeder的入口处,防止从物料中的气体进入过滤器时吹入其它粉尘。

Exemple I的优点:—没有Star feeder/airlock,降低投资成本。

—磨损少,喂料速度慢。

—整体高度低,上部空调要求小。

3、泵的特殊要求(Examples I、II)当泄漏的气体从泵经过没有安装风机的过滤器逸出时,在泵的入口处将可能产生不大于5mbar的正压力(参看2.2.4至2.2.3)。

泵在较低的正压下可以正常运行。

如果泵的供应商要求泵的入口具有较小的正压或负压力,过滤器应安装风机。

当预先不能决定是否使用风机时,由于不同的泵要求的配量不同,选用的风机应经供应商许可。

泵的生产商必须保证说明的准确性(泵运行时逸出气体的最大流量/Vm3/min,泵入口处的许可压力)。

如有疑问,风机的安装和使用应根据实际需要有计划的进行。

4、气力输送系统的需要应符合ExampleII如果输送的长度较短且压力较低(小于100bar),starfeeder在气力输送系统的喂料区域将作为一个关闭装置。

从Star feeder处遗漏的空气被吹进过滤器中,一些Star feeder供应商提供一些特殊的Star feeder混合排气系统,它需要通过一个旁线路和过滤器连接。

Star feeder的密封件易于磨损,目的随着使用时间的延长,逸出气体的量将增加。

针对这个原因核对供应商提供的遗漏气体说明。

只有遗漏气体范围内,而且Star feeder被很好的维护时,过滤器才能确保正常运行。

这点说明仅仅是正常运行时的气体逸出量,而不能被认为是一成不变的。

5、防止结露的预防措施在喂料口的过滤器的外壳和使用方内部连接管道的隔热层原约70mm。

正常状态下不需加热,当周围环境的温度较低或者是输送空气的水分较高时,建议在安装隔热装置前安装电加热器,通过恒温器来控制,以防过滤吕或管道内结露。

The Supermounted fitter正常不需要加热或隔热,然而,当条件比较特殊时,比如环境温度较低或者煤压较温易引起结露的情况下,这时过滤器需要加热和隔热。

例如:加热垫的功率为300w/m2,隔离层原度为70mm。

其表面温度每小时增加10℃。

6、需方压缩空气的质量要求:—水分最大值为4g/m3时,在6ber压力下的结露点为28℃,而在正常大气压下的结露点为1.7℃;—压缩空气的最大含油量不超过3my/ m3;—粉尘颗粒拉柱径不超过0.075mm;7、综述:以上的描述和实例都是根据以前运行的经验设计的。

在说明中可能存在一定的编差,需要和Schenck公司协商。

以上描述仅是大概一致,实际操作的具体细节在报价和供给说明中都有提示。

其它设备和系统的备用件不直接提供给使用者,而只能从Schenckw公司订购。

为了确保Srmplex feeder的正常运行,应该遵循以上建议。

在订购设备时,我们应及时核查气体输送系统供应商所提供的有关设备的说明。

软连接的安装说明安装软连接*可以自由转动*使接头完全嵌入法兰槽中*准确的中心位置*确保各件*最小的shunt forces*具有防爆、防震装置,能够抵抗10bar的压力。

因而,进程表述如下:把8个金属环老在软连接上,而后牢固的固定往下接口。

① ②中心法兰,用树脂胶和在一起固定。

③在法兰位置用另外8个金属环固定软连接的上接口。

④在法兰两侧划线准确指出其位置。

⑤移动时要小心,软连接和法兰一起移动。

⑥具有保护管的软连接内的滑槽和上部密封。

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