Optimal operation conditions for bio-hydrogen production from duckweed

Hydrogen gas is an ideal alternative fuel and produces no greenhouse gases. The dark fermentation is considered the most attractive for production of biohydrogen gas. Duckweed is an aquatic plant that has treatment properties and can be used as biomass for the fermentation to produce eventually bio-hydrogen production. This study investigated the impact of different temperature, pH, and substrate concentration on bio-hydrogen production by fermentation. Experimental tests were run flask studies in serum bottles by aim of determing the optimal operating conditions to maximize bio-hydrogen production. According to the results, concentration loading in the range 30–40 g DW/L was determined as suitable for efficient bio-hydrogen production. Different temperatures on bio-hydrogen production were compared, and 35°C was observed to be more effective than others. Moreover, pH 5.5 was determined as the optimal pH value.     

Utilization of waste marble dust as an additive in cement production

In this experimental study, the usability of waste marble dust (WMD) as an additive material in blended cement has been investigated. For this purpose, waste marble dust added cements (WMDCs) have been obtained by intergrinding WMD with Portland cement clinker at different blend ratios: 2.5%, 5.0%, 7.5% and 10% by weight. 40 × 40 × 160 mm mortar prisms have been produced with the obtained cements. Strength tests have been carried out on mortar specimen at 7, 28, and 90 days. WMDCs have been compared to each other as well as to control cements of CEM I and CEM II with respect to their physical, chemical and mechanical properties. Obtained results showed that WMDCs conform to EN 197-1 standard and thus 10% WMD can be used as an additive material in cement manufacturing.     

The Case of Baku-Tbilisi-Ceyhan Oil Pipeline System: A Review

Baku-Tbilisi-Ceyhan (BTC) Main Export Oil Pipeline Project (MEP) is one of the very good demonstrations of how governments could come together for the same purpose and could promote the realization of the specific project. The BTC project, being the first leg of the East-West Energy Corridor and once treated as a “dream project” by some group of experts, has now almost turned in to a physical entity. Until now, detailed project studies confirmed the project is well within its previously estimated budget of 1.427 billion USD for the Turkish section of the pipeline. The next phase will be the Land Acquisition and Construction Phase, which will take 32 months onwards. BTC-MEP has a maximum capacity of 50 million tons/year (1 million barrels/year) and a total length of 1,743 km.     

Capacitive micromachined ultrasonic transducers: next-generation arrays for acoustic imaging?

Piezoelectric materials have dominated the ultrasonic transducer technology. Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative technology offering advantages such as wide bandwidth, ease of fabricating large arrays, and potential for integration with electronics. The aim of this paper is to demonstrate the viability of CMUTs for ultrasound imaging. We present the first pulse-echo phased array B-scan sector images using a 128-element, one-dimensional (1-D) linear CMUT array. We fabricated 64- and 128-element 1-D CMUT arrays with 100% yield and uniform element response across the arrays. These arrays have been operated in immersion with no failure or degradation in performance over the time. For imaging experiments, we built a resolution test phantom roughly mimicking the attenuation properties of soft tissue. We used a PC-based experimental system, including custom-designed electronic circuits to acquire the complete set of 128 x 128 RF A-scans from all transmit-receive element combinations. We obtained the pulse-echo frequency response by analyzing the echo signals from wire targets. These echo signals presented an 80% fractional bandwidth around 3 MHz, including the effect of attenuation in the propagating medium. We reconstructed the B-scan images with a sector angle of 90 degrees and an image depth of 210 mm through offline processing by using RF beamforming and synthetic phased array approaches. The measured 6-dB lateral and axial resolutions at 135 mm depth were 0.0144 radians and 0.3 mm, respectively. The electronic noise floor of the image was more than 50 dB below the maximum mainlobe magnitude. We also performed preliminary investigations on the effects of crosstalk among array elements on the image quality. In the near field, some artifacts were observable extending out from the array to a depth of 2 cm. A tail also was observed in the point spread function (PSF) in the axial direction, indicating the existence of crosstalk. The relative amplitude of this tail with respect to the mainlobe was less than -20 dB.     

Lime-Soda Softening Process Modifications for Enhanced NOM Removal

In this research, a number of process modifications to the lime-soda softening process were examined, including utilization of high Mg-content lime, addition of MgCl2, and the recycling of softening sludge, in order to improve the removal of natural organic matter (NOM) and reduce the formation of disinfection byproducts (DBPs). Jar test results showed that dissolved organic carbon (DOC) removal increased and trihalomethane (THM) formation was reduced as the magnesium in hydrated lime increased, and was directly correlated with the amount of magnesium removed from the system. However, a dolomitic quick lime hydrated under atmospheric conditions resulted in less effective DOC removal due to a lack of available Mg, and subsequently, less co-precipitation of Mg(OH)2-NOM complexes. The addition of MgCl2 to the raw water also increased DOC removal and reduced THM formation in both the presence and absence of softening sludge, with DOC removal increasing as softening sludge and magnesium dosages increased. As high as 43% removal of DOC was achieved at the stoichoimetric lime-soda ash dose in the presence of 457 mg/L sludge and 7.5 mg/L MgCl2, as compared to only 13% removal in the absence of sludge and MgCl2. The recycling of softening sludge had little or no effect on the hardness and the level of inorganic elements in treated water. The results presented here provide new approaches for improving DBP precursor removal during lime-soda softening without significantly increasing lime and soda ash dosage or the generation of waste sludge.     

Improved design procedure for double‐ridged waveguides

This article presents a novel methodology for designing double‐ridged waveguides by numerically optimizing their geometric shape such that they sustain the two prescribed lowest order modes. The field solution to the problem is obtained by using the finite element method. The performance of the microgenetic algorithm and the quasi‐Newton methods is studied for carrying out geometry optimization. This generalized formulation is capable of handling inhomogeneous material fillings in the guide, and computational results are presented to demonstrate the versatility of the proposed technique. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 530–539, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10053     

Computer: A teaching aid for structural engineering seniors at the University of Riyadh

To cope with modern structural analysis and design using computers seen in the Kingdom of Saudi Arabia, the civil engineering seniors of University of Riyadh have started to select computer oriented-structural final year projects. Nonetheless, seniors have remained reluctant to select such projects, simply because a typical civil engineering student takes as a sophomore a FORTRAN course and can easily complete the B.Sc. in C.E. graduation requirements without going near the computer again. The author, while working in Saudi Arabia, has adopted the computer as a teaching aid for seniors in advanced elective structural course using the Finite Element Method. The selected textbook, and assignments are geared to computer applications on structures. The purpose of the elective course is to reinforce and exploit the material covered in the FORTRAN course, in order to enable the students to accomplish computer oriented-structural final year projects. The paper evaluates the course's achievement and the impact of the course on the performance of seniors in their computer oriented-structural final year projects supervised by the author. The author believes that the time has come for the computer to be adopted as a teaching aid in a series of electives and final year projects in the field of structural engineering at our universities. The paper concludes with the result that such a step is necessary and quite feasible.     

Transmutation of minor actinides discharged from LMFBR spent fuel in a high power density fusion reactor

Significant amounts of nuclear wastes consisting of plutonium, minor actinides and long lived fission products are produced during the operation of commercial nuclear power plants. Therefore, the destruction of these wastes is very important with respect to public health, environment and also the future of nuclear energy. In this study, transmutation of minor actinides (MAs) discharged from LMFBR spent fuel in a high power density fusion reactor has been investigated under a neutron wall load of 10 MW/m² for an operation period of 10 years. Also, the effect of MA percentage on the transmutation has been examined. The fuel zone, containing MAs as spheres cladded with W-5Re, has been located behind the first wall to utilize the high neutron flux for transmutation effectively. Helium at 40 atm has been used as an energy carrier. At the end of the operation period, the total burning and transmutation are greater than the total buildups in all investigated cases, and very high burnups (420–470 GWd/tHM) are reached, depending on the MA content. The total transmutation rate values are 906 and 979 kg/GW_th year at startup and decrease to 140 and 178 kg/GW_th year at the end of the operation for fuel with 10% and 20% MA, respectively. Over an operation period of 10 years, the effective half lives decrease from 2.38, 2.21 and 3.08 years to 1.95, 1.80 and 2.59 years for ²³⁷Np, ²⁴¹Am and ²⁴³Am, respectively. Total atomic densities decrease exponentially during the operation period. The reductions in the total atomic densities with respect to the initial ones are 79%, 81%, 82%, 83%, 85% and 86% for 10%, 12%, 14%, 16%, 18% and 20% MAs, respectively.