A Sweep-Line Algorithm and Its Application to Spiral Pocketing

EL-Midany, Tawfik T.,Elkeran, Ahmed,Tawfik, Hamdy Society for Computational Design and Engineering 2002 International Journal of CAD/CAM Vol.2 No.1

This paper presents an efficient line-offset algorithm for general polygonal shapes with islands. A developed sweep-line algorithm (SL) is introduced to find all self-intersection points accurately and quickly. The previous work is limited to handle polygons that having no line-segments in parallel to sweep-line directions. The proposed algorithm has been implemented in Visual C++ and applied to offset point sequence curves, which contain several islands.

An Efficient No-Core Cut Pocketing CAM System for Wire-EDM

EL-Midany, Tawfik T.,Kohail, Ahmed M.,Tawfik, Hamdy Society for Computational Design and Engineering 2006 International Journal of CAD/CAM Vol.6 No.1

Recently, wire-EDM became a necessity for many engineering applications, particularly in the dies making. No-Core cut process is helpful for operations in which falling slug can jam the machine or wire. In this paper a proposed CAM system (called NCPP) is introduced, to overcome the limitations of the existing CAM systems in the machining of No-Core cut. The proposed CAM system (NCPP) provides pocketing of No-core cut and optimal selection of the position of starting hole (wire threading point), to minimize toolpath length. It was written for data exchange between CAD-CAM-CNC machines. This data model will become part of the ISO (Data model for Computerized Numerical Controllers) international standard. The NCPP system has been implemented in Visual C++. Many examples are used to illustrate NCPP system. The results show that, NCPP saves the machining time by significant value. This value depends on the shape and complexity of the workpiece that is being cut.

Role of expanded clay aggregate, metakaolin and silica fume on the of modified lightweight concrete properties

Tawfik Taher A.,AlSaffar Doha M.,Tayeh Bassam A.,Metwally Khaled Ali,ElKattan Ibrahim M. 한국자원공학회 2021 Geosystem engineering Vol.24 No.3

This investigation aimed to assess the effect of micro-cementitious materials on the mechanical properties and sulphate resistance of modified eco-efficient lightweight concrete (MDLWC). A modified lightweight concrete (MDLWC) was produced by mixing Light-expanded clay aggregate (LECA) with normal coarse aggregate (dolomite cushed rock). The impact of using different percentage of micro-cementitious materials which was micro silica fume (5–20%) and metakaolin(10–35%) on the mechanical properties (compressive strength, splitting tensile and flexural strength), waves transmission velocity of the ultrasonic pulses and sulphate resistivity of MDLWC was studied. The overall results illustrated that the use of micro-cementitious materials in MDLWC caused an enhancement on MDLWC properties. However, the MDLWC specimens containing micro silica fume showed better results than metakaolin. The best results were observed while using samples containing 10% micro silica fume and 30 % metakaolin individually or combined. In addition, the usage of combined mixture of 10% micro silica fume and 30% metakaolin MDLWC mix showed the best improvement rate in compressive, splitting tensile and flexural strengths by 25, 53.3 and 66.6%, respectively, compared to control MDLWC specimens. On the other hand, the direct empirical equations were proposed on the basis of strong and nonlinear regression analysis using the test data to predict the mechanical properties of MDLWC relationships, rationally. Experimental tests were conducted on ultrasonic pulses velocity, which showed good correlation equation strength of MDLWC. Scanning electron microscopy illustrated that the pores of concrete is smaller for SF and MK individually or combined with MDLWC compared to the control concrete, demonstrating an enhancement within the interfacial microstructure with the pozzolanas incorporation. The previous difference could be explained due to the concrete strength and sulphate penetrability to an extent.

Molecularly Imprinted Cellulose Sensor Strips for Selective Determination of Phenols in Aqueous Environment

Tawfik A. Khattab,Meram S. Abdelrahman,Hanan B. Ahmed,Hossam E. Emam 한국섬유공학회 2020 Fibers and polymers Vol.21 No.10

The surrounding environment is largely contaminated with phenols, and consequently qualitative and quantitativedetermination of phenols in water is of interest. In the current report, a low cost, naked-eye, portable and disposable cellulosicstrips-based sensor was fabricated to detect phenols in aqueous media. The cellulosic filter paper was molecularly imprintedwith Fe(III) to prepare strips sensor of Fe(III)-imprinted filter paper. The prepared strips were characterized by X-raydiffraction, scanning electron microscopy, energy-dispersive X-ray analysis and Fourier-transform infrared spectroscopy. Thesensitivity performance of Fe(III)-imprinted filter paper strips was monitored for a series of phenolic compounds. Thecolorimetric detection of gallic acid was selectively studied herein due to its greatest sensibility. The chromogenic Fe(III)-imprinted filter paper strips provided an instant color shift from yellow to purple upon binding to Gallic acid in an aqueousenvironment, as visually noted and instrumentally detected by absorption spectral and coloration measurements. The changein color of strips attributing to sensing of Gallic acid was readout at quite low limit (0.1 ppb). This sensor performance wasrationalized on formation of coordination complex between phenol and Fe+3. The facile fabricated molecularly imprintedfilter paper strips could be easily used as sensor in rapid potential for colorimetric detection of phenols.

Metal-organic framework films functionalized with nonionic conjugated polythiophenes for visual detection of PAHs

Tawfik, Salah M.,Lee, Yong-Ill Techno-Press 2021 Advances in nano research Vol.11 No.5

Natural and anthropogenic activities lead to the generation of polycyclic aromatic hydrocarbons (PAHs), persistent contaminants that adversely affect the environment and public health. However, highly sensitive, fast, and portable techniques for the detection of PAHs remain a technological challenge. The rapid analysis of urinary levels of 1-hydroxypyrene (1-HP) would enable PAH carcinogens to be measured using biomonitoring techniques. Here, we demonstrate biocompatible, easy-to-use, and portable sensors based on novel π-conjugated metal-organic frameworks (MOFs) for the detection of 1-HP. These sensors were developed by incorporating nonionic conjugated polythiophenes with a PLQY as high as 65% into lanthanide-MOFs (CP1-Eu-MOF and CP2-Eu-MOF) using an in-situ synthesis strategy. The emission of the sensors can be effectively quenched by 1-HP via hydrophobic, π-π stacking, and hydrogen bonding interactions. Significantly, the unique structure of CP2-Eu-MOF sensor displays superior performance with enhanced sensitivity (LOD ~1.02 pM) that is 1.63 times higher than that of CP1-Eu-MOF (LOD ~1.66 pM). More importantly, we successfully demonstrated the possibility of employing wax-printed paper in combination with a fast and cost-effective smartphone for rapid 1-HP detection. Moreover, portable sensory films were fabricated by incorporating CP2-Eu-MOF into a poly(vinylidene difluoride) (PVDF) matrix to produce CP2-Eu-MOF/PVDF films for the visual detection of 1-HP levels as low as 25 pM. Finally, the feasibility of successfully analyzing the levels of 1-HP in urine was verified by testing real urine samples with satisfactory recoveries of 94.1-103.5%. This method provides new pathways for the biomonitoring of polyaromatic environmental pollutants.

Electroreflectance spectroscopy of compressively strained InGaN/GaN multi-quantum well structures

Tawfik, W.Z.,Ryu, H.Y.,Lee, J.K. Elsevier 2014 CURRENT APPLIED PHYSICS Vol.14 No.11

The built-in piezoelectric field induced by compressive stress in InGaN/GaN multi-quantum well (MQW) light-emitting diodes (LEDs) was investigated using the electric field dependent electroreflectance (ER) spectroscopic method. InGaN/GaN MQW structures were prepared on sapphire substrates of different thicknesses. Thinning the sapphire substrate enables control of the compressive stress by changing the curvature of the wafer bowing. The wafer bowing-induced mechanical stress alters the piezoelectric field in the InGaN/GaN MQW. The flat band voltage, estimated by measuring the applied reverse bias voltage that induces a 180<SUP>o</SUP> phase shift in the ER spectra, was decreased from -11.21 V to -10.51 V by thinning the sapphire substrate thickness from 200 to 60 μm. To calculate the piezoelectric field (F<SUB>pz</SUB>) from the compensation voltage, the depletion width was obtained from the capacitance-voltage measurement. The F<SUB>pz</SUB> estimated from the energy shift in ER peak in a bias range from 0 to -12 V was changed by 110 kV/cm.

Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

Tawfik, Wael Z.,Hyeon, Gil Yong,Lee, June Key American Institute of Physics 2014 JOURNAL OF APPLIED PHYSICS - Vol.116 No.16

Influence of thiourea synthesis with silica fume on the corrosion rate of reinforcement concrete

Tawfik Taher A.,El-Yamani Magdy A.,Serag Faried A.,Mohammed Shimaa M.,AbdEl-Hafez Gh.M. 한국자원공학회 2020 Geosystem engineering Vol.23 No.3

The examination of corrosion rate for steel reinforcement existent in concrete was carried out in the presence of silica fume and thiourea. The ordinary Portland cement (OPC) replacement was conducted with silica fume material at 5 and 10% by cement weight for concrete production, in addition to that using various percentage of thiourea (1, 2, 3 4 and 5%) added to concrete. Monitoring and estimating the corrosion rate for reinforcing steel existent in concrete with and without silica fume and thiourea was held with the usage of corrosion test cell. Besides, compressive and splitting tensile strength submerged in fresh and salty water of hardened concrete with and without silica fume and thiourea that were considered in the study. The immersion for all the samples of steel reinforcement with salty water (tap water with 1.5% of calcium sulphate and 3% of sodium chloride) for about 90 days of exposure were studied. The best results for the lowest corrosion rate were obtained when a mixture of silica fume with thiourea is used with concentrations of 10 and 3%, respectively compared with the ordinary concrete.

The Effect of Sustainable Dimensions on the Financial Performance of Commercial Banks: A Comparative Study in Emerging Markets

TAWFIK, Omar Ikbal,KAMAR, Saifaldin Hashim,BILAL, Zaroug Osman Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.3

The paper examines the impacts of the various sustainability dimensions on the financial performance of commercial banks in three Arab countries. Three dimensions have been considered as constitutive of the term sustainable development (social, economic, and environmental). The relationship between the sustainability dimensions of companies and accounting indicators was analyzed. The main hypothesis posits that the dimensions of sustainability do not have a significant and positive effect on the financial performance of the commercial banks. The study population consisted of commercial banks operating in three Arab countries (Oman, United Arab Emirates, and Jordan); the period of the study is from 2007 to 2018. The data were collected from the financial reports and sustainability reports of each bank through the Internet. The overall results of the study showed a moderately positive relationship between all sustainability dimensions and the banks' financial performance. The main contribution of the research is to study the dimensions of sustainability reports as contained in the Global Reporting Initiative (GRI-G4) and their impacts on the financial performance of commercial banks. Thus, this research will contribute to increasing the interest of the banks in sustainable development in a context where this research in Arab countries is scarce.

Weight reduction and strengthening of marine hatch covers by using composite materials

Tawfik, Basem E.,Leheta, Heba,Elhewy, Ahmed,Elsayed, Tarek The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.2

The application of composites as an alternative material for marine steel hatch covers is the subject of this study. Two separate approaches are considered; weight reduction approach and strengthening approach. For both approaches Finite Element Analysis (FEA) was performed using ANSYS software. Critical design parameters of the composite hatch cover and FEA are discussed in details. Regarding the weight reduction approach; steel hatch covers of a bulk carrier were replaced by composite covers and a weight reduction of 44.32% was achieved leading to many benefits including fuel saving, Deadweight Increment and lower center of gravity of the vessel. For the strengthening approach; the foremost hatch cover was strengthened to withstand 150% of the load required by IACS for safer navigation while no change in weight was made between the steel and composite covers. Results show that both approaches are feasible and advantageous.