China National Standards

China PA GB Standards English PDF List


GB standards are the China national standards; Prefix code GB are Mandatory standards, GB/T are Recommended standards; All products or service must be compliance with GB standards; If you want to export products or services to huge Chinese market, need ensure they are meet the requirements of GB china national standards;  We provide Chinese GB standards and English version GB standards  Lookup, Translate, Download, Imported Commodity GB standards Testing and Compliance review services.
  •  China "PA" GB Standards English PDF List:
  • Standard  Code Standard Title Standard Class Order
    GB/T 41275.2-2022 Avionics Process Management AerosPAce and Defense Electronic Systems Containing Lead-Free Solders Part 2: Reducing the Harmful Effects of Tin
    航空电子过程管理 含无铅焊料航空航天及国防电子系统 第2部分:减少锡有害影响
    China National Standards
    PA

    English PDF
    GB/T 41295.4-2022 Functional Safety Application Guide PArt 4: Administration and Maintenance
    功能安全应用指南 第4部分:管理和维护
    China National Standards
    PA

    English PDF
    GB/T 41295.3-2022 Functional Safety Application Guide PArt 3: Test Validation
    功能安全应用指南 第3部分:测试验证
    China National Standards
    PA

    English PDF
    GB/T 41295.2-2022 Functional Safety Application Guide PArt 2: Design and Implementation
    功能安全应用指南 第2部分:设计和实现
    China National Standards
    PA

    English PDF
    GB/T 41295.1-2022 Functional Safety Application Guide PArt 1: Hazard Identification and Requirements Analysis
    功能安全应用指南  第1部分:危害辨识和需求分析
    China National Standards
    PA

    English PDF
    GB/T 41312.1-2022 Test method for permeability of chemical equipment - PArt 1: Graphite and its lining equipment
    化工用设备渗透性检测方法 第1部分:石墨及其衬里设备
    China National Standards
    PA

    English PDF
    GB/T 41341.2-2022 Technical Specifications for Site Selection of Ocean Power Stations PArt 2: Wave Energy
    海洋能电站选址技术规范 第2部分:波浪能
    China National Standards
    PA

    English PDF
    GB/T 41341.1-2022 Technical Specifications for Site Selection of Ocean Power Stations PArt 1: Tidal Current Energy
    海洋能电站选址技术规范 第1部分:潮流能
    China National Standards
    PA

    English PDF
    GB/T 41340.2-2022 Technical Specifications for Calculation of Power Generation of Ocean Power Stations PArt 2: Wave Energy
    海洋能电站发电量计算技术规范 第2部分:波浪能
    China National Standards
    PA

    English PDF
    GB/T 41340.1-2022 Technical Specification for Calculation of Power Generation of Ocean Power Station PArt 1: Tidal Current
    海洋能电站发电量计算技术规范 第1部分:潮流能
    China National Standards
    PA

    English PDF
    GB/T 41339.2-2022 Technical Guidelines for Marine Ecological Restoration PArt 2: Ecological Restoration of Coral Reefs
    海洋生态修复技术指南 第2部分:珊瑚礁生态修复
    China National Standards
    PA

    English PDF
    GB/T 41339.1-2022 Technical Guidelines for Marine Ecological Restoration PArt 1: General
    海洋生态修复技术指南 第1部分:总则
    China National Standards
    PA

    English PDF
    GB/T 16508.7-2022 Shell boilers PArt 7: Installation
    锅壳锅炉  第7部分:安装
    China National Standards
    PA

    English PDF
    GB/T 16508.5-2022 Shell boilers PArt 5: Safety accessories and instruments
    锅壳锅炉  第5部分:安全附件和仪表
    China National Standards
    PA

    English PDF
    GB/T 16508.4-2022 Shell boilers - PArt 4: Manufacture, inspection and acceptance
    锅壳锅炉  第4部分:制造、检验与验收
    China National Standards
    PA

    English PDF
    GB/T 16508.2-2022 Shell boilers PArt 2: Materials
    锅壳锅炉  第2部分:材料
    China National Standards
    PA

    English PDF
    GB/T 16508.1-2022 Shell boilers PArt 1: General
    锅壳锅炉  第1部分:总则
    China National Standards
    PA

    English PDF
    GB/T 16507.8-2022 Water Tube Boilers PArt 8: Installation and Operation
    水管锅炉  第8部分:安装与运行
    China National Standards
    PA

    English PDF
    GB/T 41242-2022 E-commerce logistics recyclable PAckaging management specification
    电子商务物流可循环包装管理规范
    China National Standards
    PA

    English PDF
    GB/T 41332-2022 Technical requirements for remote detection equipment for municiPAl underground pipelines
    市政地下管线远程探测设备技术要求
    China National Standards
    PA

    English PDF
    GB/T 18494.2-2022 Convertor transformers—PArt 2: Transformers for HVDC applications
    变流变压器  第2部分:高压直流输电用换流变压器
    China National Standards
    PA

    English PDF
    GB/T 1094.14-2022 Power transformers—PArt 14: Liquid-immersed power transformer using high-temperature insulation materials
    电力变压器 第14部分:采用高温绝缘材料的液浸式电力变压器
    China National Standards
    PA

    English PDF
    GB/T 1094.11-2022 Power transformers—PArt 11: Dry-type transformers
    电力变压器  第11部分:干式变压器
    China National Standards
    PA

    English PDF
    GB/T 17989.9-2022 Statistical method of quality control in production process—Control charts—PArt 9: Control charts for stationary processes
    生产过程质量控制统计方法 控制图 第9部分:平稳过程控制图
    China National Standards
    PA

    English PDF
    GB/T 17989.8-2022 Statistical method of quality control in production process—Control charts—PArt 8:Charting techniques for short runs and small mixed batches
    生产过程质量控制统计方法 控制图 第8部分:短周期小批量的控制方法
    China National Standards
    PA

    English PDF
    GB/T 17989.7-2022 Statistical method of quality control in production process—Control charts—PArt 7: Multivariate control charts
    生产过程质量控制统计方法 控制图 第7部分:多元控制图
    China National Standards
    PA

    English PDF
    GB/T 17989.6-2022 Statistical method of quality control in production process—Control charts—PArt 6: EWMA control charts
    生产过程质量控制统计方法 控制图 第6部分:指数加权移动平均控制图
    China National Standards
    PA

    English PDF
    GB/T 17989.5-2022 Statistical method of quality control in production process—Control charts—PArt 5:Specialized control charts
    生产过程质量控制统计方法  控制图 第5部分:特殊控制图
    China National Standards
    PA

    English PDF
    GB/T 5796.4-2022 Trapezoidal screw threads—PArt 4: Tolerances
    梯形螺纹  第4部分:公差
    China National Standards
    PA

    English PDF
    GB/T 5796.3-2022 Trapezoidal screw threads—PArt 3: Basic dimensions
    梯形螺纹  第3部分:基本尺寸
    China National Standards
    PA

    English PDF
    GB/T 5796.2-2022 Trapezoidal screw threads—PArt 2: General plan
    梯形螺纹  第2部分:直径与螺距系列
    China National Standards
    PA

    English PDF
    GB/T 5796.1-2022 Trapezoidal screw threads—PArt 1: Profiles
    梯形螺纹  第1部分:牙型
    China National Standards
    PA

    English PDF
    GB/T 6609.2-2022 Chemical analysis methods and determination of physical performance of alumina—PArt 2: Determination of loss of mass at 300 ℃ and 1000 ℃
    氧化铝化学分析方法和物理性能测定方法 第2部分:300 ℃和1000 ℃质量损失的测定
    China National Standards
    PA

    English PDF
    GB 9706.222-2022 Medical electrical equipment - PArt 2-22: Particular requirements for the basic safety and essential performance of laser equipment for surgical, orthopedic, therapeutic and diagnostic use
    医用电气设备 第2-22部分:外科、整形、治疗和诊断用激光设备的基本安全和基本性能专用要求
    China National Standards
    PA

    English PDF
    GB 5768.2-2022 Road traffic signs and markings—PArt 2: Road traffic signs
    道路交通标志和标线  第2部分:道路交通标志
    China National Standards
    PA

    English PDF
    GB/T 16886.19-2022 Biological evaluation of medical devices - PArt 19: Physicochemical, morphological and surface characterization of materials
    医疗器械生物学评价 第19部分:材料物理化学、形态学和表面特性表征
    China National Standards
    PA

    English PDF
    GB/T 16886.18-2022 Biological evaluation of medical devices - PArt 18: Chemical characterization of medical device materials in the risk management process
    医疗器械生物学评价 第18部分:风险管理过程中医疗器械材料的化学表征
    China National Standards
    PA

    English PDF
    GB/T 16886.15-2022 Biological Evaluation of Medical Devices-PArt 15: Qualitative and Quantitative Degradation Products of Metals and Alloys
    医疗器械生物学评价 第15部分:金属与合金降解产物的定性与定量
    China National Standards
    PA

    English PDF
    GB/T 16886.9-2022 Biological evaluation of medical devices - PArt 9: Qualitative and quantitative framework for potential degradation products
    医疗器械生物学评价 第9部分:潜在降解产物的定性和定量框架
    China National Standards
    PA

    English PDF
    GB/Z 16886.22-2022 Biological Evaluation of Medical Devices PArt 22: Guidelines for Nanomaterials
    医疗器械生物学评价 第22部分:纳米材料指南
    China National Standards
    PA

    English PDF
    GB/T 42168.1-2022 Condoms—Guidelines for clinical research—PArt 1: Self-reported clinical functional studies of male condoms
    避孕套 临床研究指南 第1部分:男用避孕套基于自我报告的临床功能研究
    China National Standards
    PA

    English PDF
    GB/T 19363.1-2022 Translation Services PArt 1: Requirements for Translation Services
    翻译服务 第1部分:笔译服务要求
    China National Standards
    PA

    English PDF
    GB/T 29035-2022 Test method for flexible graphite PAcking rings
    柔性石墨填料环试验方法
    China National Standards
    PA

    English PDF
    GB/T 16895.22-2022 Low-voltage electrical installations - PArt 5-53: Selection and installation of electrical equipment. Electrical appliances for safety protection, isolation, switching, control and monitoring
    低压电气装置 第5-53部分:电气设备的选择和安装 用于安全防护、隔离、通断、控制和监测的电器
    China National Standards
    PA

    English PDF
    GB/T 16895.13-2022 Low-Voltage Electrical Installations PArt 7-701: Requirements for Special Installations or Locations Locations with Tubs or Showers
    低压电气装置 第7-701部分:特殊装置或场所的要求 装有浴盆或淋浴的场所
    China National Standards
    PA

    English PDF
    GB/T 6739-2022 PAints and varnishes - Determination of film hardness by the pencil method
    色漆和清漆 铅笔法测定漆膜硬度
    China National Standards
    PA

    English PDF
    GB/Z 17215.652-2022 Electrical Measurement Data Exchange DLMS/COSEM Components PArt 52: Communication Protocol Management Distribution Line Message Specification (DLMS) Server
    电测量数据交换 DLMS/COSEM组件 第52部分:通信协议管理配电线报文规范(DLMS)服务器
    China National Standards
    PA

    English PDF
    GB/Z 17215.651-2022 Electrical Measurement Data Exchange DLMS/COSEM Components PArt 51: Application Layer Protocol
    电测量数据交换 DLMS/COSEM组件 第51部分:应用层协议
    China National Standards
    PA

    English PDF
    GB/T 17215.675-2022 Electrical measurement data exchange DLMS/COSEM components PArt 75: Local data transfer configuration for local network (LN)
    电测量数据交换 DLMS/COSEM组件 第75部分:本地网络(LN)的本地数据传输配置
    China National Standards
    PA

    English PDF
    GB/Z 17215.669-2022 Electrical measurement data exchange - DLMS/COSEM components - PArt 69: Mapping between common information model message sets (IEC 61968-9) and DLMS/COSEM (IEC 62056) data models and protocols
    电测量数据交换 DLMS/COSEM组件 第69部分:公共信息模型消息集(IEC 61968-9)与DLMS/COSEM(IEC 62056)数据模型和协议间的映射
    China National Standards
    PA

    English PDF
    GB/T 28995-2022 Wood-based PAnel facing special paper
    人造板饰面专用纸
    China National Standards
    PA

    English PDF
    GB/T 18103-2022 PArquet
    实木复合地板
    China National Standards
    PA

    English PDF
    GB/T 19367-2022 Dimensional determination of wood-based PAnels
    人造板的尺寸测定
    China National Standards
    PA

    English PDF
    GB/T 17657-2022 Test methods for physical and chemical properties of wood-based PAnels and veneered wood-based panels
    人造板及饰面人造板理化性能试验方法
    China National Standards
    PA

    English PDF
    GB/T 6113.402-2022 Specifications for radio disturbance and immunity measuring equipment and methods of measurement - PArt 4-2: Uncertainty, statistics and limit value modeling Uncertainties of measuring equipment and facilities
    无线电骚扰和抗扰度测量设备和测量方法规范 第4-2部分:不确定度、统计学和限值建模 测量设备和设施的不确定度
    China National Standards
    PA

    English PDF
    GB/T 42284.5-2022 Road vehicles - Environmental conditions and tests for electrical and electronic equipment used in electric vehicle drive systems - PArt 5: Chemical loads
    道路车辆 电动汽车驱动系统用电气及电子设备的环境条件和试验 第5部分:化学负荷
    China National Standards
    PA

    English PDF
    GB/T 42284.4-2022 Road vehicles - Environmental conditions and tests for electrical and electronic equipment used in electric vehicle drive systems - PArt 4: Climatic loads
    道路车辆 电动汽车驱动系统用电气及电子设备的环境条件和试验 第4部分:气候负荷
    China National Standards
    PA

    English PDF
    GB/T 42284.3-2022 Road vehicles - Environmental conditions and tests for electrical and electronic equipment used in electric vehicle drive systems - PArt 3: Mechanical loads
    道路车辆 电动汽车驱动系统用电气及电子设备的环境条件和试验 第3部分:机械负荷
    China National Standards
    PA

    English PDF
    GB/T 42284.1-2022 Road vehicles - Environmental conditions and tests for electrical and electronic equipment used in electric vehicle drive systems - PArt 1: General provisions
    道路车辆 电动汽车驱动系统用电气及电子设备的环境条件和试验 第1部分:一般规定
    China National Standards
    PA

    English PDF
    GB/T 18802.352-2022 Low-voltage surge arrester components - PArt 352: Guidelines for the selection and use of surge isolating transformers (SIT) for telecommunication and signaling networks
    低压电涌保护器元件 第352部分:电信和信号网络的电涌隔离变压器(SIT)的选择和使用导则
    China National Standards
    PA

    English PDF
    GB/T 25160-2022 PAckaging Cardboard Folding Carton Structural Dimensions
    包装 卡纸板折叠纸盒结构尺寸
    China National Standards
    PA

    English PDF
    GB/T 15970.11-2022 Corrosion of metals and alloys - Stress corrosion testing - PArt 11: Guidelines for hydrogen embrittlement and hydrogen-induced cracking tests of metals and alloys
    金属和合金的腐蚀 应力腐蚀试验 第11部分:金属和合金氢脆和氢致开裂试验指南
    China National Standards
    PA

    English PDF
    GB/T 42287-2022 High Voltage Test Techniques Electromagnetic and Acoustic Methods for PArtial Discharge Measurements
    高电压试验技术 电磁和声学法测量局部放电
    China National Standards
    PA

    English PDF
    GB/T 42242-2022 SPAce environment Radiation effects assessment of commercial off-the-shelf (COTS) devices for low-orbit satellites
    空间环境 用于低轨道卫星的商业现货(COTS)器件的辐射效应评估
    China National Standards
    PA

    English PDF
    GB/Z 42245-2022 SPAce Environment Applied Estimation of Solar Wind Energy Input to the Earth's Magnetosphere Using the Ground-Based Pole Cover (PC) Index
    空间环境 利用地基磁极盖(PC)指数对输入地球磁层的太阳风能量的应用估算
    China National Standards
    PA

    English PDF
    GB/T 42214-2022 SPAce environment Low-altitude (300km-600km) high-energy radiation model
    空间环境 低高度(300km~600 km)高能辐射模型
    China National Standards
    PA

    English PDF
    GB/Z 42244-2022 SPAce environment. Procedure for obtaining worst-case and confidence levels of the Earth's radiation belt fluence using quasi-dynamic models
    空间环境 利用准动态模型获得地球辐射带注量的最劣情况和置信水平的程序
    China National Standards
    PA

    English PDF
    GB/T 41949-2022 PArticles Laser Particle Size Analyzer Technical Requirements
    颗粒 激光粒度分析仪 技术要求
    China National Standards
    PA

    English PDF
    GB/T 19256.5-2022 XML-Based Electronic Commerce PArt 5: Specification of Core Components
    基于XML的电子商务 第5部分:核心构件规范
    China National Standards
    PA

    English PDF
    GB/T 17215.324-2022 Electrical Measuring Equipment (AC) PArticular Requirements Part 24: Static Fundamental Component Reactive Energy Meters (Class 0.5S, Class 1S, Class 1, Class 2 and Class 3)
    电测量设备(交流) 特殊要求 第24部分:静止式基波分量无功电能表(0.5S级、1S级、1级、2级和3级)
    China National Standards
    PA

    English PDF
    GB/T 17215.323-2022 Electrical measuring equipment (alternating current) - PArticular requirements - Part 23: Static reactive energy meters (classes 2 and 3)
    电测量设备(交流) 特殊要求 第23部分:静止式无功电能表(2级和3级)
    China National Standards
    PA

    English PDF
    GB/T 17799.7-2022 Electromagnetic comPAtibility - Generic standards - Part 7: Immunity requirements for equipment intended to perform safety-related system functions (functional safety) in industrial locations
    电磁兼容 通用标准 第7部分:工业场所中用于执行安全相关系统功能(功能安全)设备的抗扰度要求
    China National Standards
    PA

    English PDF
    GB/T 22264.8-2022 Mounted electrical measuring instruments with digital display - PArt 8: Test methods
    安装式数字显示电测量仪表 第8部分:试验方法
    China National Standards
    PA

    English PDF
    GB/T 22264.6-2022 Mounted electrical measuring instruments with digital display - PArt 6: Particular requirements for insulation resistance meters
    安装式数字显示电测量仪表 第6部分:绝缘电阻表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 22264.7-2022 Mounted electrical measuring instruments with digital display - PArt 7: Particular requirements for multifunction instruments
    安装式数字显示电测量仪表 第7部分:多功能仪表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 22264.5-2022 Installed electrical measuring instruments with digital display - PArt 5: Particular requirements for phase meters and power factor meters
    安装式数字显示电测量仪表 第5部分:相位表和功率因数表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 22264.4-2022 Mounted electrical measuring instruments with digital display - PArt 4: Particular requirements for frequency meters
    安装式数字显示电测量仪表 第4部分:频率表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 22264.3-2022 Mounted electrical measuring instruments with digital display - PArt 3: Particular requirements for wattmeters and reactive wattmeters
    安装式数字显示电测量仪表 第3部分:功率表和无功功率表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 22264.2-2022 Mounted electrical measuring instruments with digital display - PArt 2: Particular requirements for ammeters and voltmeters
    安装式数字显示电测量仪表 第2部分:电流表和电压表的特殊要求
    China National Standards
    PA

    English PDF
    GB/T 15166.5-2022 High-voltage AC fuses-PArt 5: Guidelines for the selection of fuses for high-voltage fuses for motor circuits
    高压交流熔断器 第5部分:用于电动机回路的高压熔断器的熔断件选用导则
    China National Standards
    PA

    English PDF
    GB/T 41914.2-2022 Microbubble technology General rules for the use and measurement of microbubbles PArt 2: Classification of microbubble properties
    微细气泡技术 微细气泡使用和测量通则 第2部分:微细气泡属性分类
    China National Standards
    PA

    English PDF
    GB/T 41951-2022 Corrosion of metals and alloys - Test method for corrosion resistance of steel connecting PArts and steel components for construction
    金属和合金的腐蚀 建筑用钢连接部件及钢构件耐腐蚀性能测试方法
    China National Standards
    PA

    English PDF
    GB/T 14392.1-2022 Format of international trade documents - PArt 1: Paper documents
    国际贸易单证样式 第1部分:纸质单证
    China National Standards
    PA

    English PDF
    GB/T 8750-2022 Gold-based bonding wire and ribbon for semiconductor PAckaging
    半导体封装用金基键合丝、带
    China National Standards
    PA

    English PDF
    GB/T 25915.15-2022 Clean rooms and related controlled environments - PArt 15: Suitability assessment of equipment and materials by concentration of gaseous chemicals
    洁净室及相关受控环境 第15部分: 按气态化学物浓度评定设备及材料的适用性
    China National Standards
    PA

    English PDF
    GB/T 25915.14-2022 Clean rooms and related controlled environments - PArt 14: Assessment of equipment suitability by particle concentration
    洁净室及相关受控环境 第14部分:按粒子浓度评估设备适用性
    China National Standards
    PA

    English PDF
    GB/T 25915.13-2022 Cleanrooms and related controlled environments - PArt 13: Surface cleaning to particle and chemical cleanliness requirements
    洁净室及相关受控环境 第13部分:达到粒子和化学洁净度要求的表面清洁
    China National Standards
    PA

    English PDF
    GB/T 25260.1-2022 Synthetic Latex PArt 1: Carboxylated styrene-butadiene latex (XSBRL)
    合成胶乳 第1部分:羧基丁苯胶乳(XSBRL)
    China National Standards
    PA

    English PDF
    GB/T 41974.1-2022 Plastics - Color masterbatches - PArt 1: Nomenclature system and basis of classification
    塑料 色母料 第1部分:命名系统和分类基础
    China National Standards
    PA

    English PDF
    GB/T 21296.6-2022 Automatic weighing instruments for road vehicles in motion - PArt 6: Flat modular
    动态公路车辆自动衡器 第6部分:平板模块式
    China National Standards
    PA

    English PDF
    GB/T 34590.12-2022 Road vehicles - Functional safety - PArt 12: Suitability for motorcycles
    道路车辆 功能安全 第12部分:摩托车的适用性
    China National Standards
    PA

    English PDF
    GB/T 34590.11-2022 Road vehicles - Functional safety - PArt 11: Guidelines for semiconductor applications
    道路车辆 功能安全 第11部分:半导体应用指南
    China National Standards
    PA

    English PDF
    GB/T 34590.10-2022 Road vehicles - Functional safety - PArt 10: Guidelines
    道路车辆 功能安全 第10部分:指南
    China National Standards
    PA

    English PDF
    GB/T 34590.9-2022 Road vehicles - Functional safety - PArt 9: Automotive safety integrity level-oriented and safety-oriented analysis
    道路车辆 功能安全 第9部分:以汽车安全完整性等级为导向和以安全为导向的分析
    China National Standards
    PA

    English PDF
    GB/T 34590.8-2022 Road vehicles - Functional safety - PArt 8: Supporting processes
    道路车辆 功能安全 第8部分:支持过程
    China National Standards
    PA

    English PDF
    GB/T 34590.7-2022 Road vehicles - Functional safety - PArt 7: Production, operation, service and end-of-life
    道路车辆 功能安全 第7部分:生产、运行、服务和报废
    China National Standards
    PA

    English PDF
    GB/T 34590.6-2022 Road vehicles - Functional safety - PArt 6: Product development: Software level
    道路车辆 功能安全 第6部分:产品开发:软件层面
    China National Standards
    PA

    English PDF
    GB/T 34590.5-2022 Road vehicles - Functional safety - PArt 5: Product development: Hardware level
    道路车辆 功能安全 第5部分:产品开发:硬件层面
    China National Standards
    PA

    English PDF
    GB/T 34590.4-2022 Road vehicles - Functional safety - PArt 4: Product development: System level
    道路车辆 功能安全 第4部分:产品开发:系统层面
    China National Standards
    PA

    English PDF
    GB/T 34590.3-2022 Road vehicles - Functional safety - PArt 3: Concept phase
    道路车辆 功能安全 第3部分:概念阶段
    China National Standards
    PA

    English PDF

    Find out:18320Items   |  To Page of: First -Previous-Next -Last  | [9] [10] [11] [12] [13] [14] [15]

     

    +86-755-25831330        sales@gbstandards.org 
    106# Zhongmao Mansion,No.1 Beizhan Road,Shenzhen,China
    ©  RJS Copyright  2001-2024 All Rights Reserved

    - Since 2001 -
    Focus on China Standards & Compliance Services

    www.rjs.cn

    China Licenses

    www.transcustoms.com

    China HS code & Tariff

    www.gbstandards.org

    China National Standards