Solar collectors for the Beirut climate

The performance of solar collector systems is optimized for the Beirut climate with respect to the following parameters: angle of tilt and orientation, plate emissivity and number of glass covers. The Beirut hourly ambient temperature, wind speed, wind direction and the monthly averaged hourly and daily global, beam and diffuse radiation are used in the calculation of the useful harnessed energy, collector's efficiency, storage-tank temperature and other relevant parameters.

The optimal thermal performance of the solar collector in Beirut is obtained for a south-facing collector all the year with a slope angle equal to latitude +15° in winter and latitude −15° in the summer. The use of a selective surface of low emissivity in the collector gives a higher useful energy gain of about 25% in summer and 10% in winter as compared with a nonselective plate surface. The collector's daily efficiency, under optimal conditions, varies from 55 to 65% depending upon the month of the year.     

Speech enhancement with an adaptive Wiener filter

This paper proposes an adaptive Wiener filtering method for speech enhancement. This method depends on the adaptation of the filter transfer function from sample to sample based on the speech signal statistics; the local mean and the local variance. It is implemented in the time domain rather than in the frequency domain to accommodate for the time-varying nature of the speech signals. The proposed method is compared to the traditional frequency-domain Wiener filtering, spectral subtraction and wavelet denoising methods using different speech quality metrics. The simulation results reveal the superiority of the proposed Wiener filtering method in the case of Additive White Gaussian Noise (AWGN) as well as colored noise.     

Using I2P (Invisible Internet Protocol) Encrypted Virtual Tunnels for a Secure and Anonymous Communication in VANets: I2P Vehicular Protocol (IVP)

Wireless Personal Communications - The Invisible Internet Project (I2P) as a secure protocol uses robust mechanisms and strong algorithms to reinforce the security and the anonymity of the...     

Fingerprint recognition using mel-frequency cepstral coefficients

This paper presents a new fingerprint recognition method based on mel-frequency cepstral coefficients (MFCCs). In this method, cepstral features are extracted from a group of fingerprint images, which are transformed first to 1-D signals by lexicographic ordering. MFCCs and polynomial shape coefficients are extracted from these 1-D signals or their transforms to generate a database of features, which can be used to train a neural network. The fingerprint recognition can be performed by extracting features from any new fingerprint image with the same method used in the training phase. These features are tested with the neural network. The different domains are tested and compared for efficient feature extraction from the lexicographically ordered 1-D signals. Experimental results show the success of the proposed cepstral method for fingerprint recognition at low as well as high signal to noise ratios (SNRs). Results also show that the discrete cosine transform (DCT) is the most appropriate domain for feature extraction.     

Anodic dissolution of nickel in acidic chloride solutions

The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 ± 10 mV · decade⁻¹ was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol⁻¹. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.     

A computer-aided teaching package for microprocessor systemseducation

A computer-aided teaching (CAT) package for use in a microprocessor systems course is described. It uses the Z80 CPU as the basis for describing how an eight-bit CPU functions internally and as the master of a microcomputer system. The package, which consists of an assembler and a graphics simulator, aids as a powerful teaching tool that enables the student to learn about the internal architecture of a microprocessor as applied to the Z80 CPU and its instruction set with a step-by-step graphics animation of the instruction execution and timing. The package allows the user to execute a program step by step and to test the operation of the internal registers, buses, and memory contents at every clock edge. It also simulates read/write cycles from/to memory and input-output devices. Finally, it allows the user to write and debug problems at the assembly language or machine code level. The package is menu driven, interactive, flexible, and user-friendly     

10-Gb/s Transmission on Single-Wavelength Multichannel SCM-Based FDDI-Grade MMF Links at Lengths Over 300 m: A Statistical Investigation

We propose and comprehensively investigate a subcarrier-multiplexing (SCM) system based on 62.5-mum-core-diameter multimode fiber (MMF) using a single wavelength to achieve 10-Gb/s transmission over link lengths beyond 300 m, using 1.3-mum-wavelength lasers with radial offset launch into MMF links. The system utilizes multichannel SCM transmission using quadrature-phase-shift-keyed modulation in combining baseband transmission with three passband SCM channels at the carrier frequencies of 3.75, 6.25, and 8.75 GHz while incorporating a maximum laser modulation bandwidth of 10 GHz to ensure system compliance with the limits of current uncooled laser devices. A statistical investigation of the system highlights its capability to achieve an acceptable yield over worst-case MMF links of length 600 m. We also investigate the improvement in system performance granted by allowing a controlled overlap of frequency spectra of the passband SCM channels. In addition, we test the accuracy of the previously proposed usable average slope criterion of less than 4 dB/GHz, which is needed to achieve low-penalty transmission with eye-closure penalties <3 dB.     

RETRACTED: Reproducibility study of (TLD-100) dosimeters using an automated and manual TLD reader for radiotherapy applications

The precision of the response of Harshow thermoluminescent dosimeters (TLD-100) is investigated for two Harshow TLD readers. The mean reproducibility for chips pre-readout annealed at 100 °C for 15 min, evaluated with the manual planchet reader 4500, is 0.61% (1 standard deviation) using pre-readout method. When chips are evaluated with the automated hot-gas reader 4500, reproducibility values are undoubtedly worse, mean reproducibility for numerically stabilized dosimeters being equal to 2.12%(1 standard deviation) using pre-readout method also. The pre-readout method was used for elimination of lower temperature peaks in order to obtain more stability. These results indicate that the automated hot-gas 4500 reader, or, at least, the instrument used for the present measurements, is not adequate for chips evaluation, if precise and accurate dosimetry is required. The difference in precision for manual planchet reader is apparently due to geometry inconsistencies in the orientation of the planchet to imperfect chips faces during readout, requiring careful and manual reproducible arrangement of the selected chips faces in contact with the manual reader planchet. In order to elucidate this point, the planchet support face of all chips dosimeters was identified with a small point made by pencil, reducing in this way geometrical variations.     

Closure versus non-closure of peritoneum at cesarean section--evaluation of pain. A randomized study

OBJECTIVE: To evaluate the effects of leaving the parietal peritoneum open at lower segment cesarean section (LSCS) measured by postoperative pain. DESIGN: A randomized, prospective and double-blind study. SETTING: Department of Obstetrics and Gynecology, Aarhus University Hospital, Denmark. POPULATION: Forty women referred for an elective cesarean section were assigned to one of two groups: peritoneum open (n=21) or peritoneum closed (n=19). METHODS: Pain was evaluated twice a day from the first to the fifth postoperative day by Visual Analog Scales. MAIN OUTCOME MEASURES: Postoperative pain. Other outcomes include usage of analgesics, bowel function, postoperative complications, and hospital stay. RESULTS: We found no overall difference in postoperative pain. A tendency to less pain was found in the non-closure group from the third postoperative day to the fifth postoperative day. No differences were found either in the incidence of postoperative complications, or the time to return of bowel function. Concerning opiate analgesics the non-closure group had a significantly higher use in the second postoperative 24-hour period, but in the remains of the registration period it was significantly lower. For oral analgesics no difference was found in the first 24-hour period, but in the remains of the period the non-closure group had a significantly lower use. CONCLUSIONS: The VAS-scales showed no difference in postoperative pain comparing closure to non-closure of the parietal peritoneum. However, the use of analgesics is lower in the non-closure group. We suggest leaving the parietal peritoneum open when performing LSCS.