The Experts below are selected from a list of 10176 Experts worldwide ranked by ideXlab platform

Subhash C Mullick - One of the best experts on this subject based on the ideXlab platform.

  • glass cover temperature and top heat loss coefficient of a single glazed flat plate collector with nearly vertical configuration
    Ain Shams Engineering Journal, 2012
    Co-Authors: Suresh Kumar, Subhash C Mullick
    Abstract:

    Abstract An empirical relation for glass cover temperature of a single glazed flat plate collector for angle of tilt 60–90° is proposed. Values of glass cover temperature obtained from empirical relation have been used for computation of top heat loss coefficient of collector. Analytical equation has been employed for estimation of top heat loss coefficient, U t . The range of variables covered in the present analysis is 20 °C to 150 °C for absorber plate temperature, 0.1–0.95 for absorber coating emittance, 20–50 mm for air gap spacing, 60–90° for collector tilt, 5–30 W/m 2  K for wind heat transfer coefficient and −10 °C to 40 °C for ambient temperature. The Maximum Absolute Error in values of U t is within two percent, in comparison to values obtained by numerical solution of heat balance equations, over the entire range of variables.

  • computation of glass cover temperatures and top heat loss coefficient of flat plate solar collectors with double glazing
    Energy, 2007
    Co-Authors: Naiem Akhtar, Subhash C Mullick
    Abstract:

    A set of correlations for computing the glass-cover temperatures of flat-plate solar collectors with double glazing is developed. A semi-analytical correlation for the factor f2—the ratio of outer to inner thermal resistance of a double-glazed collector—as a function of collector parameters and atmospheric variables is obtained by regression analysis. This relation readily provides the temperature of the second (outer) glass cover (T2). For estimating the temperature of first (inner) glass cover (T1), another relation for the factor f1—the ratio of thermal resistance between the two glass covers to the thermal resistance between the absorber plate and first glass cover—is developed. A wide range of variables is covered in the present analysis. The results are compared with those obtained by numerical solutions of heat-balance equations. Using the proposed relations of glass-cover temperatures, the values of top heat loss coefficient (Ut) can be computed and are found to be very close to those obtained by numerical solutions of heat-balance equations. The Maximum Absolute Error in the calculation of Ut by the proposed method is only 1.0%, so numerical solutions of heat-balance equations for the computation of Ut are not required.

Andre Kaup - One of the best experts on this subject based on the ideXlab platform.

  • improving the rate distortion model of hevc intra by integrating the Maximum Absolute Error
    International Conference on Acoustics Speech and Signal Processing, 2019
    Co-Authors: Karina Jaskolka, Andre Kaup
    Abstract:

    Normally, the mean squared Error in conjunction with the rate is used to optimize the compression in hybrid video coding. However, in some areas, such as medical image coding, not only the average Error but also the Maximum Error should be considered. Recently, it has been shown that incorporating the Maximum Absolute Error into the calculation of the rate-distortion optimization (RDO) of the HEVC encoder can improve image quality, while preserving the average Error and the rate. In this paper, we optimize the inclusion of the Maximum Absolute Error in the RDO by considering the whole quantization parameter range as well as the different prediction unit sizes. Compared to the existing extended RDO, up to 1.5 % bitrate can be saved for the same Maximum Absolute Error reduction.

  • joint optimization of rate distortion and Maximum Absolute Error for compression of medical volumes using hevc intra
    Picture Coding Symposium, 2018
    Co-Authors: Karina Jaskolka, Andre Kaup
    Abstract:

    Many visual quality metrics are used to measure the quality of lossy compressed images and videos, and are integrated in the rate-distortion optimization of hybrid video codecs. However, most of the metrics focus on the average objective quality in a picture. In certain applications, like medical image processing, the Maximum Absolute Error should be more weighted. In this paper, the rate-distortion optimization of HEVC is extended by integrating this Error metric. Thus, rate, average Error, and Maximum Absolute Error are jointly optimized. Furthermore, a weighting factor α is included into the calculation of the optimization for balancing the ratio between average and Maximum Absolute Error. For HEVC intra with $\alpha =0.25$ an average Maximum Absolute Error reduction of −25.63 can be achieved, while the bitrate increases slightly by 0.59%. Furthermore, the visual quality of the medical volumes improves and the data fidelity increases, i.e. less block artifacts appear and less structure disappear.

E. George Walters - One of the best experts on this subject based on the ideXlab platform.

  • Optimized Linear, Quadratic and Cubic Interpolators for Elementary Function Hardware Implementations
    Electronics, 2016
    Co-Authors: Masoud Sadeghian, James E Stine, E. George Walters
    Abstract:

    This paper presents a method for designing linear, quadratic and cubic interpolators that compute elementary functions using truncated multipliers, squarers and cubers. Initial coefficient values are obtained using a Chebyshev series approximation. A direct search algorithm is then used to optimize the quantized coefficient values to meet a user-specified Error constraint. The algorithm minimizes coefficient lengths to reduce lookup table requirements, maximizes the number of truncated columns to reduce the area, delay and power of the arithmetic units, and minimizes the Maximum Absolute Error of the interpolator output. The method can be used to design interpolators to approximate any function to a user-specified accuracy, up to and beyond 53-bits of precision (e.g., IEEE double precision significand). Linear, quadratic and cubic interpolator designs that approximate reciprocal, square root, reciprocal square root and sine are presented and analyzed. Area, delay and power estimates are given for 16, 24 and 32-bit interpolators that compute the reciprocal function, targeting a 65 nm CMOS technology from IBM. Results indicate the proposed method uses smaller arithmetic units and has reduced lookup table sizes compared to previously proposed methods. The method can be used to optimize coefficients in other systems while accounting for coefficient quantization as well as truncation and rounding effects of multiple arithmetic units.

Sinchong Park - One of the best experts on this subject based on the ideXlab platform.

  • arctangent processor design for the frequency offset estimation of ieee 802 16d wirelessman ofdm system
    Signal Processing Systems, 2007
    Co-Authors: Taekyu Kim, Sinchong Park
    Abstract:

    This paper presents a hardware design of an arctangent processor for the IEEE 802.16d WirelessMAN-OFDM system. The arctangent processor is required in most OFDM-based communication system to estimate the frequency offset. We proposed an arctangent processor which can perform arctangent evaluation with efficiency of hardware size considering the operating speed. The proposed arctangent processor does not require the division value of imaginary/real for the input argument, and uses these two values, respectively, to look up the tangent ROM table which has only the arctangent values for octant phase, i.e. zero to ?/4 rad. The contribution of this design is the suggestion about the trade-off between the accuracy and complexity for arctangent evaluation considering the requirement allowed in WirelessMAN-OFDM standard. Consequently, the designed arctangent process for WirelessMAN-OFDM system takes six clocks to evaluate an arctangent value and has the resolution of 2?/256 rad. The Maximum Absolute Error of this arctangent hardware is 1.225e-2 rad (0.7°) comparing to mathematical result.

  • arctangent processor design for the frequency offset estimation of ieee 802 16d wirelessman ofdm system
    ITC-CSCC :International Technical Conference on Circuits Systems Computers and Communications, 2007
    Co-Authors: Taekyu Kim, Sinchong Park
    Abstract:

    This paper presents a hardware design of an arctangent processor for the IEEE 802.16d WirelessMANOFDM system. The proposed arctangent processor does not require the division value of imaginary/real for the input argument, and uses these two values, respectively, to look up the tangent ROM table. We reduce the tangent look-up table size to one eighth of 2π rad using the imaginary and real component exchange method for memory size and operation speed. Consequently, the designed arctangent process for WirelessMAN-OFDM system takes six clocks to evaluate an arctangent value and has the resolution of 2π/256 rad. The Maximum Absolute Error of this arctangent hardware is 1.225e-2 rad (0.7°) comparing to mathematical result.

Karina Jaskolka - One of the best experts on this subject based on the ideXlab platform.

  • improving the rate distortion model of hevc intra by integrating the Maximum Absolute Error
    International Conference on Acoustics Speech and Signal Processing, 2019
    Co-Authors: Karina Jaskolka, Andre Kaup
    Abstract:

    Normally, the mean squared Error in conjunction with the rate is used to optimize the compression in hybrid video coding. However, in some areas, such as medical image coding, not only the average Error but also the Maximum Error should be considered. Recently, it has been shown that incorporating the Maximum Absolute Error into the calculation of the rate-distortion optimization (RDO) of the HEVC encoder can improve image quality, while preserving the average Error and the rate. In this paper, we optimize the inclusion of the Maximum Absolute Error in the RDO by considering the whole quantization parameter range as well as the different prediction unit sizes. Compared to the existing extended RDO, up to 1.5 % bitrate can be saved for the same Maximum Absolute Error reduction.

  • joint optimization of rate distortion and Maximum Absolute Error for compression of medical volumes using hevc intra
    Picture Coding Symposium, 2018
    Co-Authors: Karina Jaskolka, Andre Kaup
    Abstract:

    Many visual quality metrics are used to measure the quality of lossy compressed images and videos, and are integrated in the rate-distortion optimization of hybrid video codecs. However, most of the metrics focus on the average objective quality in a picture. In certain applications, like medical image processing, the Maximum Absolute Error should be more weighted. In this paper, the rate-distortion optimization of HEVC is extended by integrating this Error metric. Thus, rate, average Error, and Maximum Absolute Error are jointly optimized. Furthermore, a weighting factor α is included into the calculation of the optimization for balancing the ratio between average and Maximum Absolute Error. For HEVC intra with $\alpha =0.25$ an average Maximum Absolute Error reduction of −25.63 can be achieved, while the bitrate increases slightly by 0.59%. Furthermore, the visual quality of the medical volumes improves and the data fidelity increases, i.e. less block artifacts appear and less structure disappear.