ON THE GEOMETRY OF VECTOR BUNDLES WITH FLAT CONNECTIONS

Abbassi, Mohamed Tahar Kadaoui,Lakrini, Ibrahim Korean Mathematical Society 2019 대한수학회보 Vol.56 No.5

Let $E{\rightarrow}M$ be an arbitrary vector bundle of rank k over a Riemannian manifold M equipped with a fiber metric and a compatible connection $D^E$. R. Albuquerque constructed a general class of (two-weights) spherically symmetric metrics on E. In this paper, we give a characterization of locally symmetric spherically symmetric metrics on E in the case when $D^E$ is flat. We study also the Einstein property on E proving, among other results, that if $k{\geq}2$ and the base manifold is Einstein with positive constant scalar curvature, then there is a 1-parameter family of Einstein spherically symmetric metrics on E, which are not Ricci-flat.

Analysis of organochlorine pesticides residues in fish from Edko Lake (North of Egypt) using eco-friendly method and their health implications for humans

Abbassy Moustafa A.,Khalifa Moustafa A.,Nassar Atef M. K.,El-Deen Eman E. Nour,Salim Yehia M. 한국독성학회 2021 Toxicological Research Vol.37 No.4

Levels of organochlorine pesticides (OCPs) residues in tilapia fish and their health risk associated with the consumption of fish from Edko lake, Egypt were determined. The quick, easy, cheap, effective, rugged, and safe method (QuEChERS) was used for extraction and clean-up of 18 OCPs residues from fish followed by GC-ECD and GC-ITD analytical tools were employed for identification of OPs. Out of the 18 OCPs, only heptachlorepoxide, p,p-DDE, dieldrin, p,p-DDD, and endrin ketone were detected in muscles of fish with concentrations of 0.1144, 0.2119, 0.4352, 0.1196, and 0.1323 μg/Kg bw, respectively. Results of the risk assessment calculations showed that dieldrin had a health risk index of more than one. This means that there was a health risk to adults associated with the consumption of fish. On the other hand, heptachlorepoxide, p,p-DDE, p,p-DDD, and endrin ketone did not show any direct health risk. Contamination of fish, collected from Edko lake in Egypt, with residues of OCPs might pose health implications if fish were consumed fresh.

Design of T-shaped tube hydroforming using finite element and artificial neural network modeling

Fethi Abbassi,Furqan Ahmad,Sana Gulzar,Touhami Belhadj,Ali Karrech,Heung-Soap Choi 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

Tube hydroforming (THF) is a frequently used manufacturing method in the industry, especially on automotive and aircraft industries. Compared with other manufacturing processes, THF provides parts with better quality and lower production costs. This paper proposes a design approach to estimate the T-shaped THF parameters, such as counter force, axial feed, and internal pressure, through finite element (FE) and artificial neural network (ANN) modeling. A numerical database is built through Taguchi’s L27 orthogonal array of experiments to train the ANN. The micromechanical damage model of Gurson-Tvergaard-Needleman is used with an elastoplastic approach to describe the material behavior. This study aims to find the combinations of THF parameters that maximize the bulge ratio and minimize the thinning ratio and wrinkling. The numerical results obtained by the FE model show good correlation with the results predicted by the ANN.

A Sub-threshold based 747 nW Resistor-less Low-dropout Regulator for IoT Application

Fatemeh Abbassi,Sung Jin Kim,Abdolhamid Noori,Ji-Hyeon Cheon,Truong Van Cong Thuong,Truong Thi Kim Nga,Kang-Yoon Lee 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.3

This paper presents a curvature-compensated Band-Gap reference used as a reference voltage for a Low-Dropout Regulator. The circuit is totally implemented with only MOS transistors functional from 1.8 V to 3.6 V for Internet of Things (IoT) applications. In designed Ultra-Low Power (ULP) BGR, only one stage high slope proportional-to-absolute temperature (PTAT) voltage generator is employed to compensate complementary-to-absolute temperature (CTAT) voltage generated in the current reference. In addition, cascode tail current is utilized to improve Power Supply Rejection Ratio (PSRR). The proposed BGR-LDO uses only the MOSFETs in the subthreshold region to greatly reduce power consumption, in the other words, BJTs and resistors are removed. Therefore, not only consumed power decreases significantly, but also occupied chip area declines. The proposed BGR-LDO circuit fabricated in a 55 nm CMOS process. It consumes 747 nW power for input voltage of 3.3 V. The measurement results illustrate -55 dB power supply rejection ratio, a TC of 16 ppm/°C within a range of the -40°C to 80°C and line regulation of 4.4 mV/V for supply voltage variation from 1.8 V to 3.6 V. Load regulation is 0.8 mV/mA for load current variation form 0 A to 10 mA. The active area is 190 µm × 390 µm.

Using Machine Learning Technique for Analytical Customer Loyalty

Mohamed M. Abbassy International Journal of Computer ScienceNetwork S 2023 International journal of computer science and netw Vol.23 No.8

To enhance customer satisfaction for higher profits, an e-commerce sector can establish a continuous relationship and acquire new customers. Utilize machine-learning models to analyse their customer's behavioural evidence to produce their competitive advantage to the e-commerce platform by helping to improve overall satisfaction. These models will forecast customers who will churn and churn causes. Forecasts are used to build unique business strategies and services offers. This work is intended to develop a machine-learning model that can accurately forecast retainable customers of the entire e-commerce customer data. Developing predictive models classifying different imbalanced data effectively is a major challenge in collected data and machine learning algorithms. Build a machine learning model for solving class imbalance and forecast customers. The satisfaction accuracy is used for this research as evaluation metrics. This paper aims to enable to evaluate the use of different machine learning models utilized to forecast satisfaction. For this research paper are selected three analytical methods come from various classifications of learning. Classifier Selection, the efficiency of various classifiers like Random Forest, Logistic Regression, SVM, and Gradient Boosting Algorithm. Models have been used for a dataset of 8000 records of e-commerce websites and apps. Results indicate the best accuracy in determining satisfaction class with both gradient-boosting algorithm classifications. The results showed maximum accuracy compared to other algorithms, including Gradient Boosting Algorithm, Support Vector Machine Algorithm, Random Forest Algorithm, and logistic regression Algorithm. The best model developed for this paper to forecast satisfaction customers and accuracy achieve 88 %.

On the geometry of vector bundles with flat connections

Mohamed Tahar Kadaoui Abbassi,Ibrahim Lakrini 대한수학회 2019 대한수학회보 Vol.56 No.5

Let $E \rightarrow M$ be an arbitrary vector bundle of rank $k$ over a Riemannian manifold $M$ equipped with a fiber metric and a compatible connection $D^{E}$. R.~Albuquerque constructed a general class of (two-weights) spherically symmetric metrics on $E$. In this paper, we give a characterization of locally symmetric spherically symmetric metrics on $E$ in the case when $D^E$ is flat. We study also the Einstein property on $E$ proving, among other results, that if $k \geq 2$ and the base manifold is Einstein with positive constant scalar curvature, then there is a 1-parameter family of Einstein spherically symmetric metrics on $E$, which are not Ricci-flat.

Hygroscopic effects on the penetration-resistance behavior of a specially-orthotropic CFRP composite plates

Ahmad, F.,Abbassi, F.,Hong, J.W.,Chang, S.H.,Park, M.K. Applied Science Publishers ; Elsevier 2017 Composite structures Vol.176 No.-

This paper addresses the impact responses of dry and wet specially-orthotropic cross-ply CFRP composite plates under low-velocity impact loading. Experimental tests were performed for five different moisture content conditions using anti-symmetric cross-ply composite plates. To analyze the hygroscopic effects, all plates were immersed in hot water for water absorption and then impacted by constant weight via an impactor. Absorbed water cause matrix swelling and leads to disbanding between the matrix and fiber at the interface, as observed in SEM images. The results showed that plates with a higher level of moisture content showed more undulation in the time-force curve and a relatively small change in the peak force for all plates. Moisture content does not have a substantial effect on the penetration-resistance of the plates. The flexural rigidity or stiffness of the plates decreases due to moisture content and large damage sizes were observed for wet specimens in the C-scan pictures as compared to dry plate.

Effect of Commercial Compost on Yield and Nitrate Content of Chinese Cabbage

Gholamali Peyvast,Massoumeh Abbassi 한국원예학회 2006 Horticulture, Environment, and Biotechnology Vol.47 No.3

This study was conducted to assess the yield and nitrate content of Chinese cabbage (Brassica campestris ssp. pekinensis Rupr) grown in the field with four different levels of commercial compost; 0 (control), 37.5, 75.0, and 150 tㆍ㏊?¹ commercial compost. There was a tendency for the total yield to be highest when fertilized with compost and lowest when the compost was not supplied. The plants with the highest compost treatment (150.0 tㆍ㏊?¹) gave significantly highest yield at 46.87 tㆍ㏊?¹ which was statistically different from other treatments with the lower compost. The significant differences were also found on marketable yield with an exception at the lowest compost treatment. The highest head weight at 520.8 g was obtained in 150.0 tㆍ㏊?¹ compost treatment, which was statistically significant from other treatments with lower compost. The lowest nitrate content in the leaf was observed in 150 tㆍ㏊?¹ compost treatment followed by 37.5 and 75.0 tㆍ㏊?¹ compost treatments with 2,161 and 2,608 ㎎ㆍ㎏?¹, respectively. Nitrate contents in the petiole were shown the same results with those in the leaf. However, significant differences in nitrate contents were not found among the treatments.

Risk assessment of heavy metals in soil based on the geographic information system-Kriging technique in Anka, Nigeria

Onisoya Johnbull,Bassim Abbassi,Richard G. Zytner 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.1

Soil contaminated with heavy metals from artisanal gold mining in Anka Local Government Area in Northwestern Nigeria was investigated to evaluate the human health risk as a result of heavy metals. Measured concentration of heavy metals and exposure parameters were used to estimate human carcinogenic and non-carcinogenic risk. GIS-based Kriging method was utilized to create a prediction maps of human health risks and probability maps of heavy metals concentrations exceeding their threshold limits. Hazard index calculation showed that 21 out of 23 locations are posing non-cancer risk for children. Adults and children are at high cancer risk in all locations as the total cancer risk exceeded 1×10<SUP>-6</SUP> (the lower limit CTR value). Kriging model showed that only a very small area in Anka has a hazard index of less than unity and cumulative target risk of less than 1×10<SUP>-4</SUP>, indicating a significant carcinogenic and non-carcinogenic risks for children. The probability of heavy metals to exceed their threshold concentrations around the study area was also found to be high.

Emulsion flooding for enhanced oil recovery: Interactive optimization of phase behavior, microvisual and core-flood experiments

Mohammad Saber Karambeigi,Reza Abbassi,Emad Roayaei,Mohammad Ali Emadi 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.29 No.-

Emulsion flooding has been proved to be an effective chemical enhanced oil recovery (CEOR) method. The performance of this technique is strongly dependant on the formulation of the emulsion slug. Toachieve the best formulation, different approaches have been introduced in the literature. Nevertheless,a systematic workflow containing the method(s) of the design of experiments (DOEs) has not beenreported as yet. In this paper, we developed a workflow which is comprised mainly of three stages. In thefirst place, the phase behavior experiments of sodium dodecyl sulfate (SDS)/water/diesel (as an efficientand economic hydrocarbon phase)/salt system were carried out using response surface methodology(RSM) to model and optimize the emulsification process. The second stage was followed by thecharacterization of optimum formulation in terms of rheological behavior and particle size distribution. Finally, microvisual and core-flood displacement tests were performed to evaluate the efficacy ofemulsion flooding to recover the residual oil bypassed or trapped after water flooding. This paperpresents the results of experiments done in different stages of the proposed workflow. The resultsdemonstrate the high potential of emulsion formulated systematically by DOE approach to increase oilrecovery factor