定价： 1047元 / 折扣价： 890 元

5.1 This test method can be applied to measure sound absorption coefficients of absorptive materials at normal incidence, that is, 0°. It also can be used to determine specific impedance and admittance ratios. The properties measured with this test method are useful in basic research and product development of sound absorptive materials.5.2 Normal incidence sound absorption coefficients can be quite useful in certain situations where the material is placed within a small acoustical cavity close to a sound source, for example a closely-fitted machine enclosure.5.3 This test method allows one to compare relative values of sound absorption when it is impractical to procure large samples for accurate random-incidence measurements in a reverberation room. Estimates of the random incidence absorption coefficients can be obtained from normal impedance data for locally-reacting materials (2).NOTE 2: The classification, “locally-reacting” includes fibrous materials having high internal losses. Formulas have been developed for converting sound absorption properties from normal incidence to random incidence, for both locally-reacting and bulk-reacing materials (3).5.4 Measurements described in this test method can be made with high precision, but these measurements may be misleading. Uncertainties of greater magnitude than those from the measurements may occur from other sources. Care should be exercised to sample nonuniform materials adequately (see 11.1).1.1 This test method covers the use of an impedance tube, two microphone locations, and a digital frequency analysis system for the determination of normal incidence sound absorption coefficients and normal specific acoustic impedance ratios of materials.1.2 Laboratory Accreditation—A procedure for accrediting a laboratory for performing this test method is given in Annex A1.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 646元 / 折扣价： 550 元 加购物车

定价： 1183元 / 折扣价： 1006 元

定价： 728元 / 折扣价： 619 元

1 Scope This part of ISO/IEC 14443 specifies the characteristics of the fields to be provided for power and bi-directional communication between proximity coupling devices (PCDs) and proximity cards (PICCs). This part of ISO/IEC 14443 is intended to

定价： 592元 / 折扣价： 504 元

Identification cards - Contactless integrated circuit(s) cards - Proximity cards - Part 2: Radio frequency power and signal interface AMENDMENT 1: Bit rates of fc/64, fc/32 and fc/16

定价： 182元 / 折扣价： 155 元

5.1 This test method describes a test procedure for evaluating the ∆T associated with RF power deposition during an MR procedure, involving a specific frequency of RF irradiation of a passive implant. The method allows characterization of the heating propensity of an implant rather than the prediction of heating during a specific MR procedure in a patient. The results may be used as an input to a computational model for estimating ∆T due to the presence of that implant in a patient. The combination of the test results and the computational model results may then be used to help assess the safety of a patient with the implant during an MR examination.1.1 This test method covers measurement of radio frequency (RF)-induced heating on or near a passive medical implant within a phantom during magnetic resonance imaging (MRI). The test method does not specify levels of heating considered to be safe to the patient and relies on users to define their own acceptance criteria.1.2 This test method does not address other possible safety issues which include, but are not limited to: issues of magnetically-induced displacement, magnetically-induced torque, image artifact, acoustic noise, tissue heating, interaction among devices, and the functionality of the device and the MR system.1.3 The amount of RF-induced temperature rise (∆T) for a given incident electric field will depend on the RF frequency, which is dependent on the static magnetic field strength of the MR system. While the focus in this test method is on 1.5 tesla (T) or 3 T MR systems, the ∆T for an implant in MR systems of other static magnetic field strengths or magnet designs can be evaluated by suitable modification of the method described herein.1.4 This test method assumes that testing is done on devices that will be entirely inside the body. Testing for devices with other implantation conditions (e.g., external fixation devices, percutaneous needles, catheters or tethered devices such as ablation probes) is beyond the scope of this standard; for such devices, modifications of this test method may be necessary.NOTE 1: RF-heating induced by any electrically conductive implanted device may be impacted by the presence of other metallic or otherwise electrically conductive devices present nearby.1.5 This test method is written for several possible RF exposure systems, including Volume RF transmit coils. The exposure system needs to be properly characterized, within the stated uncertainties, in term of local background RF exposure for the implants which are tested.1.6 The values stated in SI units are to be regarded as standard.1.7 A device with deployed dimensions of less than 2 cm in all directions may not need to be tested with respect to RF-induced heating, as it is expected to generate ∆T of less than 2°C over 1 h of exposure at 1.5 T/64-MHz or 3 T/128-MHz frequencies (1, 2)2 and ANSI/AAMI/ISO 14708-3:2017). This condition is not valid when multiple replicas of the device (e.g., multiple anchors) are implanted within 3 cm of the device.NOTE 2: The above values were derived from existing data and literature. The 3 cm distance is recommended to avoid any RF coupling with other neighboring devices.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 646元 / 折扣价： 550 元 加购物车

This specification covers a standard basis for uniform testing and frequency to determine physical and electrical compliance for aluminum and copper conductors. Diameter, tensile, resistivity and all other material properties shall be tested per specific level and acceptable quality level (AQL) and must meet the corresponding requirements. Any lot of drawing stock/wire that has been sampled and from which the number of specimens failing to comply with the requirements does not equal or exceed the appropriate reject number of the sampling used, shall be considered as complying with requirements of ASTM. Rejected lots may be screened to remove nonconforming production units by testing one specimen form each production unit in the lot for the failing characteristic. Identify and classify product, process, and service characteristics for which statistical techniques will be used as basis for the assurance and control of quality and acceptance or rejection of lots. The process performance index (CPK) shall meet the requirements of the applicable ASTM standard.1.1 This specification covers a standard basis for uniform testing and frequency to determine physical and electrical compliance for aluminum and copper drawing stock, and aluminum and copper conductors.1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.2.1 Exception—Resistivity is measured in SI units.1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车