Libyan Journal for Engineering Research

Effect of Roughness, Compliance and Adhesion on Perception of Softness

2021-11-13T04:57:33+00:00

This paper concerns the perceived softness of objects, which is an important aspect of haptic perception. To design tactile displays, there are many unanswered questions about human touch perception and its relationship with material properties. This paper explores how the interaction of material properties affects perception of softness through the use of two psychophysical experiments. The first experiment used a set of nine stimuli representing three materials of different compliance, embossed with three different patterns to vary their surface roughness. The second used three materials of different compliance with three different coatings to vary their stickiness. Magnitude estimation was used to assess the perceived softness for the stimuli in both experiments under two conditions: pressing into the stimulus with the finger, and sliding the finger across the stimulus. The results indicated that compliance affected perception of softness when pressing the finger, but not when sliding; and that compliance, friction and thermal conductivity all influenced the perception of softness. This work is an essential step to understand interactions between compliance and other material properties. The new knowledge can be applied to the design of tactile displays for laparoscopic surgery.

Experimental Assessment of The 100 mV Polarization Shift Criterion for Cathodic Protection Systems of the Prestressed Concrete Cylinder pipes

2021-11-13T05:19:05+00:00

In this work, an experimental study was carried out to evaluate the 100 mV polarization shift criterion for confirming the effectiveness of applied cathodic protection viz via zinc sacrificial anodes to arrest progress of corrosion in uncorroded or partially corroded high tensile grade prestressing steel wires of the same grade as the one used to manufacture the prestressed concrete cylinder pipes (PCCP).

Total number of 14 wire samples were placed under constant tension approximately 55% of their ultimate tensile strength by the use of specially designed and fabricated holding metal frames. All samples were individually immersed in glass vessels filled with alkaline solutions of pH around 12 and variable chloride ions concentration ranging from 500 to 3000 ppm. With the exception of one wire sample left unprotected; the remaining samples were cathodically protectedby systems of zinc sacrificial anodes such that an average measured polarization shift near 100 mV with variable chloride content in solution was maintained for 9 samples and near 75, 50, and 25 mV with constant chloride content of 3000 ppm.

Evaluation of mechanical properties of wire samples suggested that 100 mV criterionand more than sufficient to confirm the adequacy and effectiveness of zinc sacrificial anodes cathodic protection system to arrest progress of corrosion of partially corroded and uncorroded prestressing steel wires in alkaline passivating environment contaminated with chloride ions up to 3000 ppm in solution and for shifts in polarization as low as 25 mV.

It was also evident that corrosion progress in the prestressing steel wires can not be arrested in the 3000 ppm chloride environment without the application of cathodic protection.

Thermal Efficiency Evaluation of Souk Elkhamis Cement Rotary Kiln

2021-11-13T05:28:24+00:00

Due to the fact that the cement industry is one of the discouraging energy-intensive industries, especially the thermal ones, study areas and aspects of the use of such a large amount of energy is one of the most important priorities in this area. This paper aims to highlight the merits and methods of use of this energy and calculate the output distribution of the energy produced from the burning of fuel to determine the amounts of wasted and used from them by conducting the thermal balance of the process in the kiln. It created that only about 47% of the energy is exploited in the completion of processes and chemical reactions, and the remaining approximately 53% is considered wasted. Part of this thermal energy lost is instrumental in some other purposes necessary in this industry as processes of drying and calcining of raw material nutrients before they entering the kiln, and stimulate the burning process of fuel in the kiln, etc., and the other, which is estimated at about 8.6% lose through the outer surface of the kiln to the surrounding. It was found that the total thermal energy entering the kiln to produce one kilogram of clinker equivalent 3658.53 kJ\kg when the kiln worked in about 89% of its production capacity, at the time that the amount of specific thermal energy used and registered when the initial tests carried out at the beginning of operating, which was equal to 3367.64 kJ\kg when the kiln worked with a capacity above 100%. This refers to the increase of approximately 9% of the energy.

This paper recommends research into the causes of this increase of amount of heat consumption. It also recommends focusing on the study of the possibility to recovering this wasted energy, which found equal to 313.27 kJ\kg which is not an insignificant amount that can be neglected or ignored.

Using Hazard-Based Duration Models to investigate the Impacts of RUC on Libyan Drivers Travel Patterns

2021-11-13T05:37:40+00:00

This paper studies the perceived impacts of road user charging (RUC) on drivers daily activity travel patterns in urban areas by using one of the large Libyan cities (Benghazi) as the case study. The analysis uses full parametric hazard models and data from a field-based RUC experiment that was conducted in Benghazi. The database consists of activity-based travel durations. This paper focuses on the analysis of the durations of drivers travel-to-work trips and addresses the changes on the patterns of driver’s trips over the study period to investigate the differences attributable to origin (home-based), time, gender and age as a result of the RUC impacts. The results indicate that RUC can have a positive impact in reducing traffic congestion with reduction of driver’s trips crossing restricted areas during peak period by around 35.5%. The paper concludes that RUC could serve as a good instrument in reducing traffic congestion and in improving the environment in city centre of Benghazi. The results could be of benefit to transport policy makers.

An Implementation of Fuzzy Logic Technique to Predict the Material Removal Rate in Abrasive Water Jet Machining Process

2021-11-13T05:43:40+00:00

In this study, the material removal rate values, obtained using machining abrasive water jet (AWJM), were modelled using fuzzy logic. The input variables considered are pressure, abrasive flow rate, orifice diameter, focusing tube diameter and standoff distance while the output variable was material removal rate (MRR). Fuzzy logic was developed using Matlab 2013.The mean absolute percentage errors (MAPE) of the predicted values was employed to compare the results with the previously published results obtained using response surface method technique. . The results showed that the predictive model using fuzzy logic model has reduced the errors by 0.28%, which means, using fuzzy logic model to predict material removal rate is sufficiently accurate.

Dynamic Performance of a Sensorless Speed Control for Induction Motor Drives based on Model Reference Adaptive System

2021-11-13T05:52:43+00:00

Sensorless vector control is greatly used and applied in induction machine drives instead of vector and scalar control for their reliability and robustness, and very low maintenance cost. The estimation of the rotor speed in MRAS-based technique obtained by comparing the output of the adjustable and adaptive models instead of using costly speed sensor gives the sensorless vector control great fortune. MRAS-based techniques are one of the best methods to estimate the rotor position and speed for its performance and stability. In this paper, MRAS-based technique used to estimate rotor speed based on rotor flux estimation, the estimated speed in MRAS used as a feedback for the vector control system. Modeling and simulation of the induction machine and the vector control drives implemented in MATLAB/SIMULINK. Simulation results of the proposed MRAS rotor speed technique are presented. The results show stability and accuracy for the proposed techniqu.

Modelling and Simulation of Multistage Flash Desalination Plants

2021-11-13T06:12:41+00:00

This study describes the mathematical model developed for evaluating the performance of multistage flash (MSF) desalination plants at steady state operation. The governing equations are linearized and are arranged in a tridiagonal matrix form. The solution of these equations are obtained by a computer code written in visual basic language with friendly user format developed for this purpose. This code can predict the plant productivity with profiles of temperatures and flow rates for all stages in the unit. The present results were compared with some previous results presented in literature, and with the design data of MSF plant existed in Benghazi city. The comparisons show good agreement with these available data.

Economic Evaluation of Mixed C4’sUpgrading Processes. (Raslanuf Ethylene Plant as a Case Study)

2021-11-13T06:18:27+00:00

Reducing the operating cost (opex) is a method implemented by Ethylene producers to keep ethylene prices from expensive feedstock more competitive in comparison with cheaper feed stocks like ethane. Alternatively economics maybe improved by upgrading the mixed C4 stream which is produced from ethylene plant and contains valuable unsaturated C4s such as butadiene, isobutylene, butene-1, and butene-2. There are different processing options available to recover these components or turn them into final products. These processing options or routes are combination of different chemical processes such as Total hydrogenation, Butadiene extraction, MTBE production form butylenes, Butane-1 recovery and other processes. Several upgrading options have been proposed and evaluated for Raslanuf ethylene plant c4 feed of about 130000 tonne/y. Internal rate of return IRR , payback time or period PBP, and the net present value NPV, all have been estimated for options which can be implemented at the site; butadiene extraction and metathesis.
Because base case results were not definitive, sensitivity analysis was performed. The parameters investigated are sales prices; feed cost, construction time and total investment. .The results suggest butadiene extraction is the best processing option for processing Raslanuf mixed C4 stream.

A comparative study for the effects of synthetic diesel fuels on the performance and emissions of a single cylinder DI diesel engine

2021-11-13T06:53:35+00:00

The high cost of crude oil, the volatility of the international energy market, the nation energy supply security and the negative environmental impacts have been significantly stimulating the use of alternative fuel in engine applications. The production process of waste cooking oil and waste plastic to diesel-range paraffinic compositions was appropriately proposed according to the conditions of the socioeconomic situations. Two alternative synthetic diesel fuels from waste cooking oil and from waste plastic were successfully manufactured by Biomass R&D Centre of Chulalongkorn University, Saraburi, and had been used in this study. Pyrolysis (thermal cracking) process was implemented to break the long chain hydrocarbons, which is the main composition of waste plastics and waste cooking oil, to diesel range hydrocarbons. The main target of this research is to evaluate the influence of using two synthetic diesels and palm cooking oil biodiesel (palm methyl ester) on the performance, and emissions of a direct-injection single cylinder diesel engine comparing with conventional diesel fuel (CD) as base line. Test bench experiments (constant speed steady state) were conducted with a single cylinder DI CI engine at 1400, 1700 and 2100 rpm, along selected part load. The acquired data was a comparative analysis dealt with: brake specific fuel consumption, brake specific energy consumption, brake thermal efficiency, and exhaust emissions. The knowledge of these comparative results on engine performance obtained in this research can be used to develop high performance green fuels in a near future. The results provided a realistic experimental investigation in terms of using such alternative diesel fuels on diesel engines in Southeast Asian countries.

Totally Volume Integral of Fluxes for Discontinuous Galerkin Method (TVI-DG) II-One Dimensional System of Equations

2021-11-13T07:10:13+00:00

This is the second paper in a series in which we construct the totally volume integrals of Riemann flux mimicking Godunov flux for discontinuous Galerkin method. In this work the boundaries integrals of the Riemann fluxes are transformed into volume integral. The new family of DG method is accomplished by applying the divergence theorem to the boundaries integrals of the Riemann fluxes. Therefore, the discontinuous Galerkin (DG) method is independent on the boundaries integrals of fluxes at the cell (element) boundaries as in the classical discontinuous Galerkin (DG) methods. The modified streamline upwind Petrov-Galerkin method is used to capture the oscillation of unphysical flow for shocked flow problems. The numerical results of applying totally volume integral discontinuous Galerkin method (TVI-DG) are presented for Euler's equations in one-dimensional cases. The numerical finding of this scheme is very accurate as compared to exact solutions.

ظاهرة الفراغات العمرانية في بنغازي – التحدي وفرص التطوير

2021-11-14T05:03:22+00:00

كنتيجة مباشرة للازمة السكنية الحالية بمدينة بنغازي، الناتجة عن العجز التراكمي بالرصيد السكني والظروف الأمنية الطارئة، اتسع سوق البناء العشوائي ليشمل إلي جانب التوسعات العشوائية خارج حدود المدينة أنواع أخري من البناء الغير قانوني بالفراغات ضمن المنطقة الحضرية القائمة.
هذه الورقة، إذ تؤكد على الأثر السلبي لمثل هذه الأعمال العشوائية والتعدي على الأملاك العامة، فهي كذلك تحاول إبراز الجانب الايجابي لاستغلال الأراضي الفضاء ضمن المنطقة الحضرية إذا ما تمذلك بالشكل السليم. إن الرفع من كثافة المناطق الحضرية من خلال عملية تكثيف عمراني مدروسة هو إجراء متبع بكثير من المدن وموصي به بتقرير السياسة المكانية الوطنية (2006-2030) باعتباره أداة للتنمية المستدامة.
تتطرق هذه الورقة لموضوع التنمية المشتتةUrban Sprawl وتأثيرها علي جودة المنطقة الحضرية بمدينة بنغازي. يلي ذلك تناول عدد من الأمثلة لأنواع الأراضي الفضاء بالمدينة واهم الأسباب المرتبطة بهذه الظاهرة، إلي جانب كونها نتيجة لأدوات التخطيط العمراني. ختاما،توصي هذه الدراسة بأهمية مراجعة معايير ولوائح التخطيط العمراني واتخاذ الإجراءات اللازمة للمضي بعملية التكثيف العمراني Urban Intensificationكونها أداة للرفع من جودة البيئة الحضرية وقدرتها على استيعاب جزء من الطلب على السكن، خصوصا بالفترة الحالية المرتبطة بالأزمة الأمنية بالمدينة وضعف التمويل العام.