Muhammad Ahsan Ullah

Digital image watermarking based on DWT-DCT: Evaluate for a new embedding algorithm

The authenticity of content or matter is crucial factors for solving the problem of copying, modifying, and distributing the intellectual properties in an illegal way. Watermarking can resolve the stealing problem of intellectual properties. This paper considers a robust image watermarking technique based on discrete wavelet transform (WDT) and discrete cosine transform (DCT) called hybrid watermarking. The hybrid watermarking is performed by two level, three level, and four level DWT followed by respective DCT on the host image. A new embedding algorithm (NEA) of digital watermarking is proposed in this paper. The simulation results are compared with Coxs additive embedding algorithm and the NEA for additive white Gaussian noise (AWGN) attack and without attack. Both algorithms use the hybrid watermarking. The NEA gives 3.04dB and 9.33dB better pick signal to noise ratio (PSNR) compared to Coxs additive algorithm for the 4 level DWT for AWGN attack and without attack, respectively. Moreover, the NEA extracts the marked image 46 times better of Coxs additive algorithm in 2 level DWT with AWGN attack. That means, the NEA can embed larger marks and high quality marks extract from the embedded watermarking even attacking condition. Though the NEA is evaluated in this paper by comparing performances with Coxs algorithm, the performances of NEA will compare among other algorithms like Gaussian sequence, image fusion, nonlinear quantization embedding with various attacking conditions in near future.

A comparative study on window functions for designing efficient FIR filter

The finite impulse response (FIR) filter designed using window method is a very popular, simpler and well working for various applications. This paper presents various window functions for designing FIR low pass filters and their comparative performance is given. Performance of windows are analyzed in both time and frequency domains. In term of main lobe-width, the Kaiser window is the most supercilious among other windows. On the other hand, the Dolph-Chebyshev shows better response in stop-band attenuation. Hamming window achieves the response in between Kaiser and Dolph-Chebyshev windows. In terms of frequency selectivity Hanning plays better role than the others.

Harvesting electrical power from waste heat using stirling engine

Different processes that use energy and machines that do work do not have perfect efficiency. So energy is wasted from these processes in the form of heat. Power generating stations, industrial processes, rice mills, brick fields and other human activities are major sources of waste heat. Mud stoves used in rural areas for cooking purpose produce above 85% of waste heat. This wasted heat can be used to generate electrical power using Stirling engine (SE). Stirling engine is a heat engine that is operated at different temperature levels by cyclic operation of compression and expansion of working gas. A DC generator is coupled with the SE to generate electrical energy. In this research amount of waste heat from significant sources has been presented and theoretical analysis has been made to harvest electrical power using a displacer type SE. Utilizing helium as working fluid and a DC generator having 90% efficiency a SE with displacer swept volume of 7.37 ×10-4 m3 can generate 80 watt of electrical power at 115 rpm engine frequency. In this mathematical approach the phase angle is 90o and the temperature difference is about 150 0K. The setup discussed is working as a personal power plant for each rural household.

An efficient approach for designing FIR low-pass filter and its application

In this paper, an adjustable window function, based on combination of tangent hyperbolic function and a weighted cosine series, is proposed to design an FIR filter. The proposed window has only one adjustable parameter “r”. By varying this parameter, it is possible to change the spectral characteristics of the filter. The performance of the proposed window is compared with Gaussian and Kaiser windows. The proposed window has slightly larger main-lobe width compare to the commonly used Gaussian and Kaiser windows, while featuring 19.71 dB and 8.29 dB smaller ripple ratios respectively. Moreover the side-lobe roll-off ratio of the proposed window is almost 115.03 dB and 14.95 dB better than the Gaussian and Kaiser windows respectively. Simulation results show that the filter designed by the proposed window yields 34.39 dB smaller ripple ratio than Kaiser window. Further, the low-pass filter, designed by the proposed method results 7.3766 times and 3.65 times better side-lobe roll-off ratios than those of Gaussian and Kaiser windows respectively. This paper also highlights an application of the proposed method in the area of eliminating noise from corrupted Audio signal.

Performance evaluation of Variable Threshold decoding on self-orthogonal convolutional codes

In communication theory, researchers are always trying to find fast and least complex decoding technique. Threshold decoding (TD) is such an easily implementable decoding technique to any modern communication system. Variable Threshold MTD (VT-MTD) is an improved version of conventional MTD system. The performance of hard decision and soft decision variable threshold decoding has been presented in this paper. Here, self-orthogonal convolutional codes are used for simulation. The proposed variable threshold hard decision decoding (VT-HMTD) produces 0.40dB coding gain at BER of 10-5 compared to HMTD system. Also, variable threshold soft decision decoding (VT-SMTD) gives 0.80dB coding gain at BER of 10-5 compared to soft decision technique. Both of these proposed algorithms give 4.5dB coding gain compared to the uncoded system.

An adjustable novel window function with its application to FIR filter design

A new class of adjustable window function, based on combination of tangent hyperbolic function and a weighted cosine series, is proposed. The proposed window is adjustable in the sense that by changing its controlling parameter, one can change not only its shape but also its spectral characteristics. The spectral characteristic of the proposed window is studied and its performance is compared with Dolph-Chebyshev, Gaussian and Kaiser Windows. Simulation results show that the proposed window yields better ripple ratio and side-lobe roll-off ratio than the above named windows. Moreover, the paper represents the application of the proposed window in finite impulse response (FIR) filter design. The results confirm that the filter designed by the proposed window provides better spectral characteristics than Kaiser window. This paper also highlights an application of the proposed Filtering method in the area of eliminating noise from corrupted ECG signal.

Analysis of membrane potential and ion concentration of axon cell

This paper provides a study of axon cell in terms of membrane potential and ion concentration using Nernst/Goldman Simulator and MATLAB. Conventional cancer detection only provides sufficient information about growth of cancer on human body, but there is little information about the growth of cancer in axon in terms of membrane potential and ion concentration. In a healthy cell the membrane potential preserves within range of -60 mV to -100 mV where negative sign of the membrane potential indicates that the inside surface of the cell membrane is relatively more negative than the immediate exterior surface. The ratio of ion concentration of major electrolytes, such as Potassium (K) and Sodium (Na) ions (K+, Na+) remains constant inside and outside of the cell membrane. Ratio of Potassium (K+) ions outside to inside a healthy cell is 20 : 400 expressed by [Ko] : [Ki] = 20 : 400. The ratio of Sodium (Na+) ions outside to inside a healthy cell is 440 : 50 expressed by [Nao] : [Nai] = 440 : 50. But whenever these cells become cancerous, the value of membrane potential becomes around -15 mV because of water flowing into the cells and Potassium, Magnesium and Calcium being lost from the cell interior and the ratio of electrolytes are no longer sustained within desired values of healthy cell. This paper provides ascending iteration process using Nernst/Goldman Simulator and MATLAB to achieve the desired ion ratios at -15 mV membrane potential in cancerous cell.

Design of a stirling engine to generate green energy in rural areas of Bangladesh

In Bangladesh the peak demand of power is greater than the amount of power generated. 30% of the villages of Bangladesh are deprived of electrical power. Again a great deal of energy is wasted in the form of heat in the mud stoves used for cooking purpose in rural areas. The temperature difference between the stoves and the environment can be used to produce green power with the help of Stirling engine. Stirling engine is a heat engine that is operated at various temperature levels by cyclic operation of expansion and compression of working gas. It converts heat energy to mechanical energy. It works on Stirling cycle. A DC generator is used to convert the mechanical energy to electrical energy. In this paper a displacer type Stirling engine has been designed and using the design parameters a prototype has been simulated that can be implemented on the mud stoves. Using helium as working fluid this prototype can generate 52 W of mechanical power at 100 rpm engine frequency, 4.216×10-4 m3 displacer swept volume, 90° phase angle and about 150 °K of temperature difference. This research concentrates on the design and implementation of Stirling engine in rural areas to generate green energy and lessen energy crisis of Bangladesh.

PB/MC-CDMA : A nobel modulation technique and multiple access scheme for broadband wireless communication

In the presence of frequency-selective multi path fading channels, Multi Carrier Code Division Multiple Access (MC-CDMA) suffers from multi-user interference (MUI) and inter-symbol interference (ISI). In this paper, the Partial Block MC-CDMA system was proposed and Performance of the system was analyzed. In the conventional MC-CDMA system, users are affected by MUI (multi-user experience) because all users use whole bandwidth. By the MUI, performance is degraded as the number of user increases. Furthermore, number of maximum user is limited to the length of spreading code. However, proposed system can increase the system performance by limiting MUI through assigning the users to the block-unit sub-carrier. And user capacity of the proposed system is much better than conventional system because spreading code can be reused in each block. And the proposed system can get frequency diversity gain so that performance becomes better. Performance is analyzed, and simulations are carried out to illustrate the merits of PB/MC-CDMA relative to existing alternatives given in this document.

Turbo like multi-stage threshold decoding for self-orthogonal convolutional codes

This paper presents a new dimension of soft decoding turbo-like multi-stage threshold decoding (TLMTD) for self-orthogonal convolutional codes (SOCCs). The TLMTD uses comparatively shorter constraint length conventional code of multi-stage threshold decoding (MTD) system. The bit error performance is considered for several types of soft decoding algorithms on the additive white Gaussian noise (AWGN) channel. When threshold value used as a priori threshold value for other decoding stage, TLMTD realizes better performance in waterfall and error floor regions. Moreover, the TLMTD gives 0.20 dB more coding gain compared to MTD for equivalent SOCCs at the bit error rate less than 104.