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Karen Brown addressing attendees at the grand opening of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown (Acting NIST Director) accepting Certificate of Congratulations at NIST 2001 Centennial History and Reunion Day
No full textNIST held a number of events to mark its centennial celebration in March 2001. The NIST History and Centennial Symposium-Reunion Day for NIST staff and alumni was held on March 5 AT NIST Boulder and NIST Gaithersburg, pictured here. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection consists of images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
Karen Brown shaking hands with Gail Porter at the grand opening of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards
The development of fluorescence intensity standards
No full textThe use of fluorescence as an analytical technique has been growing over the last 20 years. A major factor in inhibiting more rapid growth has been the inability to make comparable fluorescence intensity measurements across laboratories. NIST recognizes the need to develop and provide primary fluorescence intensity standard (FIS) reference materials to the scientific and technical communities involved in these assays. The critical component of the effort will be the cooperation between the Federal laboratories, the manufacturers, and the technical personnel who will use the fluorescence intensity standards. We realize that the development and use of FIS will have to overcome many difficulties. However, as we outline in this article, the development of FIS is feasible
Video transmission for third generation wireless communication systems
No full textThis paper presents a twin-class unequal protected video transmission system over wireless channels. Video partitioning based on a separation of the Variable Length Coded (VLC) Discrete Cosine Transform (DCT) coefficients within each block is considered for constant bitrate transmission (CBR). In the splitting process the fraction of bits assigned to each of the two partitions is adjusted according to the requirements of the unequal error protection scheme employed. Subsequently, partitioning is applied to the ITU-T H.263 coding standard. As a transport vehicle, we have considered one of the leading third generation cellular radio standards known as WCDMA. A dual-priority transmission system is then invoked on the WCDMA system where the video data, after being broken into two streams, is unequally protected. We use a very simple error correction coding scheme for illustration and then propose more sophisticated forms of unequal protection of the digitized video signals. We show that this strategy results in a significantly higher quality of the reconstructed video data when it is transmitted over time-varying multipath fading channels
Treasure of the Past VIII: Molecular basis of flame inhibition
No full textThe role played by inorganic chemical additives in fire retardancy and flame inhibition is considered. Particular attention is given to the molecular level aspects of commercially important systems containing compounds of antimony, halogens, and phosphorus. The flame inhibiting function of metal containing additives is also discussed
Hysteresis in transport critical-current measurements of oxide superconductors
No full textWe have investigated magnetic hysteresis in transport critical-current (I-c) measurements of Ag-matrix (Bi,Pb)(2)Sr2Ca2Cu3O10-x(Bi-2223) and AgMg-matrix Bi2SrxCaCu2O8+x (Bi-2212) tapes. The effect of magnetic hysteresis on the measured critical current of high temperature superconductors is a very important consideration for every measurement procedure that involves more than one sweep of magnetic field, changes in field angle, or changes in temperature at a given field. The existence of this hysteresis is well known; however, the implications for a measurement standard or interlaboratory comparisons are often ignored and the measurements are often made in the most expedient way. A key finding is that I-c at a given angle, determined by sweeping the angles in a given magnetic field, can be 17% different from the I-c determined after the angle was fixed in zero field and the magnet then ramped to the given field. Which value is correct is addressed in the context that the proper sequence of measurement conditions reflects the application conditions. The hysteresis in angle-sweep and temperature-sweep data is related to the hysteresis observed when the field is swept up and down at constant angle and temperature. The necessity of heating a specimen to near its transition temperature to reset it to an initial state between measurements at different angles and temperatures is discussed
Sources of error in UV radiation measurements
No full textIncreasing commercial, scientific, and technical applications involving ultraviolet (UV) radiation have led to the demand for improved understanding of the performance of instrumentation used to measure this radiation. There has been an effort by manufacturers of UV measuring devices (meters) to produce simple, optically filtered sensor systems to accomplish the varied measurement needs. We address common sources of measurement errors using these meters. The uncertainty in the calibration of the instrument depends on the response of the UV meter to the spectrum of the sources used and its similarity to the spectrum of the quantity to be measured. In addition, large errors can occur due to out-of-band, non-linear, and non-ideal geometric or spatial response of the UV meters. Finally, in many applications, how well the response of the UV meter approximates the presumed action spectrum needs to be understood for optimal use of the meters
Compressing spin-polarized 3He with a modified diaphragm pump
No full textNuclear spin-polarized He-3 gas at pressures on the order of 100 kPa (1 bar) are required for several applications, such as neutron spin filters and magnetic resonance imaging. The metastability-exchange optical pumping (MEOP) method for polarizing He-3 gas can rapidly produce highly polarized gas, but the best results are obtained at much lower pressure (similar to0.1 kPa). We describe a compact compression apparatus for polarized gas that is based on a modified commercial diaphragm pump. The gas is polarized by MEOP at a typical pressure of 0.25 kPa (2.5 mbar), and compressed into a storage cell at a typical pressure of 100 kPa. In the storage cell, we have obtained 20% to 35% He-3 polarization using pure He-3 gas and 35% to 50% He-3 polarization Using He-3-He-4 mixtures. By maintaining the storage cell at liquid nitrogen temperature during compression, the density has been increased by a factor of four
Karen Brown addressing attendees at the grand opening of the Lobby and Information Center during the NIST 2001 Centennial
No full textNIST celebrated the grand opening of its Lobby and Information Center during its March 2001 Centennial Celebration. Attendees at the opening included Acting NIST Director Karen Brown, NIST staff, alumni, and guests. This image is part of the NIST 2001 Centennial collection. The NIST 2001 Centennial collection includes images of various celebrations of the 100th anniversary of the National Institute of Standards and Technology (NIST), previously known as the National Bureau of Standards