Gravity theory in SAP-geometry

The aim of the present paper is to construct a field theory in the context of absolute parallelism (Teleparallel) geometry under the assumption that the canonical connection is semi-symmetric. The field equations are formulated using a suitable Lagrangian first proposed by Mikhail and Wanas. The mathematical and physical consequences arising from the obtained field equations are investigated.Comment: 14 pages, References added and a reference updated, minor correction

Estimating the Number of Patents in the World Using Count Panel Data Models

In this paper, we review some estimators of count regression (Poisson and negative binomial) models in panel data modeling. These estimators based on the type of the panel data model (the model with fixed or random effects). Moreover, we study and compare the performance of these estimators based on a real dataset application. In our application, we study the effect of some economic variables on the number of patents for seventeen high-income countries in the world over the period from 2005 to 2016. The results indicate that the negative binomial model with fixed effects is the better and suitable for data, and the important (statistically significant) variables that effect on the number of patents in high-income countries are research and development (R&D) expenditures and gross domestic product (GDP) per capita

Thermodynamical Properties of Hall Systems

We study quantum Hall effect within the framework of a newly proposed approach, which captures the principal results of some proposals. This can be established by considering a system of particles living on the non-commutative plane in the presence of an electromagnetic field and quantum statistical mechanically investigate its basic features. Solving the eigenvalue equation, we analytically derive the energy levels and the corresponding wavefunctions. These will be used, at low temperature and weak electric field, to determine the thermodynamical potential \Omega^{nc} and related physical quantities. Varying \Omega^{nc} with respect to the non-commutativity parameter \theta, we define a new function that can be interpreted as a \Omega^{nc} density. Evaluating the particle number, we show that the Hall conductivity of the system is \theta-dependent. This allows us to make contact with quantum Hall effect by offering different interpretations. We study the high temperature regime and discuss the magnetism of the system. We finally show that at \theta=2l_B^2, the system is sharing some common features with the Laughlin theory.Comment: 20 pages, misprints correcte

NOVEL DESIGN OF MULTIPHASE REACTORS FOR BIOMASS-TO-LIQUID SYNTHESIS

Generation of liquid fuels from renewable sources such as biomass has been practiced since early 1900’s. In view of the skyrocketing oil prices and the depleting reserves of natural gas, it has gained further interest. The Fischer-Tropsch synthesis is one of the main processes considered. It involves the reaction of syngas in presence of a catalyst to produce liquid fuels. Syngas sources are numerous ranging from waste gasification, anaerobic digestion to clean coal. The reactor of choice for gas to liquid conversion is a slurry bubble column. Although, these multiphase reactors offer several advantages including good heat and mass transfer, ease of construction and operation, the absence of moving parts, one of their main disadvantages is the difficulties associated with the scale-up. The latter is due to complex phases’ interactions and significant backmixing of phases. In general, the scaling rules are derived from mass and momentum balances resulting in dimensionless hydrodynamic numbers. For a proper scaling these numbers should be kept constant, together with dimensionless geometric numbers in order to ensure both dynamic and geometrical similarity. With the complex nature of the flow in these systems, this becomes very hard to achieve since it may result in the need for matching a large numbers of dimensionless quantities. Hence, different routes to provide a firm scale-up methodology are needed. Controlling the effect of scale using heat exchanging internals by means of reactor compartmentalization is proposed in this study. The details of this methodology can be summarized as follows: a) The large reactor diameter is subdivided into similar, vertical compartments by means of the cooling tubes; b)The compartments are to have a diameter similar to that of a small scale column on which investigations can be (have been) performed; and c) The various hydrodynamic parameters within each compartment are to be compared with those measured in a bubble column of the same diameter. Preliminary results show that radial gas holdup profiles inside the compartments exhibited similar behavior as inside a solid wall column, with a close agreement between resulting gas holdup profile inside the single tube bundle compartment and data obtained in 6 inches steel bubble column

Stability of Rock Slopes along Raidah Escarpment Road, Asir Area, Kingdom of Saudi Arabia

The Raidah Escarpment road is located north west of Abha city, Asir region, Kingdom of Saudi Arabia. This escarpment road represents an important corridor in the area which connects different villages and tourist resorts with each other. The total length of this road section is about 9 km which passes through a highly mountainous area. The road also passes through areas of different geological hazards (rock, debris flow, soil, and weathered zones). The different environmental factors (e.g. intensive rainy summer), variable geological and structural elements (weak rocks, slide debris weak soils, shear zones, and faults) difficult road characteristics (narrow roads with tight horizontal andvertical curvature) and various human activities in the area make the road susceptible to frequent slope failures (rockfalls, rock sliding, debris flow, soil slides, and raveling) from time to time. This paper deals with the evaluation of the stability of the rock cuts along the Raidah escarpment road using two methods including a structural controlled method and a raveling type method. Raidah escarpment rock cuts have been classified into sixty nine stations which were investigated and subsequently rated. Results of this study indicated that: (1) Based on the structiural control mode of failures, it was found that 12 stations are potentially unstable due to planar, wedge, and toppling failures, and out of them five stations have a major impact on the road in the event of failure, including stations 11, 17, 20, 31, and 40. (2) According to the Modified Colorado Rockfall hazard rating system, it was found that 13, 12, 13, 17, and 49 stations are of high, high to moderate, moderate, moderate to low, and low hazard. On the other hand, it was found that 13, 11, 11, and 69 stations have a high, high to moderate, moderate, and low impact on the road in the case of failure. (3) According to the field simulation tests it was found that 6 stations potentially show highly problems from rolling and bouncing rocks. However, out of these sites it was found that only 4 stations have a high impact on the road due to rolling and bouncing. (4) the areas that are impacted by the debris flows have been mapped and determined. Finally, different recommendations and remediation methods have been discussed to minimise the impact of problimatic sites

Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers

We report temperature dependencies of material properties such as dielectric anisotropy, birefringence, splay (K₁₁), twist (K₂₂), and bend (K₃₃) elastic constants of the uniaxial nematic (N) phase formed by flexible dimers of DTC5C9 and compare their behavior to that of a corresponding monomer MCT5. DTC5C9 forms a twist-bend nematic (Ntb) at temperatures below the N phase. Anisotropic properties of MCT5 are typical of the rod-like mesogens. In particular, birefringence increases as the temperature is reduced, following the classic behavior, described by Haller. The elastic constants also follow the standard behavior, with their ratios being practically temperature-independent. In contrast, DTC5C9 shows a dramatic departure from the standard case. Birefringence changes non-monotonously with temperature, decreasing on approaching the N-Ntb phase transition. K₃₃ decreases strongly to 0.4 pN near the N - Ntb transition, although remains finite. The ratios of the elastic constants in DTC5C9 show a strong temperature dependence that can be associated with the bend-induced changes in the orientational distribution function. The measured elastic properties are consistent with the tendency of the dimeric molecules to adopt bent configurations that give rise to the Ntb phase

Experimental and Numerical Studies on Flexural Behavior of GGBS-Based Geopolymer Ferrocement Beams

The ferrocement structural concept has been shown to offer exceptional mechanical properties in terms of toughness, fracture control, and impact resistance, which are achieved by tight spacing and homogeneous reinforcement dispersion within the matrix. The flexure behavior of geopolymer ferrocement beams under axial flexural stress is being explored experimentally and computationally in this present work. Under flexural loads, nine samples of geopolymer ferrocement beams 150 mm thick, 75 mm wide, and 1700 mm long were tested to failure. The reinforcing steel bars and wire meshes, as well as the quantity of wire mesh layers, were the key factors studied. The initial crack load, ultimate failure load, and mid-span deflection with various loading phases, cracking patterns, energy absorption, and ductility index were all studied in relation to the behavior. In terms of carrying capacity, absorbing energy, and ductility, welded steel wire mesh beams fared better than other materials. Using ANSYS-19 software, nonlinear finite element analysis (NLFEA) was carried out to demonstrate the behavior of composite ferrocement geopolymer beams. The ensuing experimental and numerical data demonstrated that the degree of experimental value estimation supplied by the FE simulations was sufficient. It is crucial to demonstrate that, in comparison to control specimens, the increase in strength of specimens reinforced with tensar meshes was reduced by around 15%. Doi: 10.28991/CEJ-2023-09-03-010 Full Text: PD

A Comparative Study for Estimation Parameters in Panel Data Model

This paper examines the panel data models when the regression coefficients are fixed, random, and mixed, and proposed the different estimators for this model. We used the Mote Carlo simulation for making comparisons between the behavior of several estimation methods, such as Random Coefficient Regression (RCR), Classical Pooling (CP), and Mean Group (MG) estimators, in the three cases for regression coefficients. The Monte Carlo simulation results suggest that the RCR estimators perform well in small samples if the coefficients are random. While CP estimators perform well in the case of fixed model only. But the MG estimators perform well if the coefficients are random or fixed

Heterotopic pregnancy after a spontaneous conception a case report with a review of clinical, laboratory and imaging findings

Heterotopic pregnancy (HP) describes the simultaneous presence of two pregnancies at different implantation sites. Usually, one pregnancy is intrauterine and the other one is ectopic. The incidence of HP after assisted reproductive technologies reaches 1:3900, but is very rare after a spontaneous pregnancy, with a reported incidence of 1 to 30,000 pregnancies. Due to its rarity, complex clinical picture, and laboratory findings, it is challenging to diagnose HP. We present a case of spontaneous HP diagnosed in the first trimester by ultrasound (US) and magnetic resonance imaging (MRI) and subsequently managed successfully. We present an analysis of the clinical and laboratory findings as well as imaging, including MRI that we used to diagnose the condition. Additionally, we performed a literature review. HP is a very rare condition frequently faced in obstetrics, gynecology, and emergency departments that requires a high index of clinical suspicion. US remains the imaging modality of choice in diagnosing a HP, however, in some cases, an MRI with a reported safety in the first trimester, can be used to provide additional information over US.Qatar National Library (QNL) funded open access

Impact Factors on Subcontractor's Cash Flow Management

Objective: This study aims to define how to maintain and protect the subcontractor firms' cash flow from economic fluctuation through legally sustainable solutions. Methods/Analysis: We conducted a case study in the Eastern Delta Region of Egypt. A questionnaire containing a list of 22 impact factors on subcontractors' cash flow was distributed across multiple subcontractor firms with an 82% response rate. It was designed to explore the factors causing cash flow instability and analyze them using SPSS statistics. Findings: The study finds that inflation, late payments, non-compensation for late payments, poor subcontractor cash flow management, subcontractor firms' inclination to avoid disputes, material price fluctuation, and non-compensation terms, as well as suppliers rejection of payment delays, are the most critical factors of subcontractor cash flow problems. Novelty/Improvement:The study suggests adding three sub-articles to Article 57 in "Tender Law" as legally sustainable solutions to protect and maintain the firm's growth rate from inflation, late payment, and the inclination to avoid disputes. Also, the study recommends that the owner ensure that cash is available before procuring the general contractors, as stated in Egyptian Law 182 of 2018. This study will contribute to establishing a sustainable win-win relationship between subcontractors and general contractors. Doi: 10.28991/CEJ-SP2023-09-08 Full Text: PD