Abstract

The effects of annealing temperature and holding time on recrystallization and grain growth in Nb-stabilized AISI 347H austenitic stainless steel containing 0.55 wt.% Nb were investigated under isothermal conditions. Specimens were annealed at 1000°C and 1200°C for 5, 10, and 30 min. Recrystallization at 1000°C was characterized by scanning electron microscopy–electron backscatter diffraction (SEM–EBSD), while grain size was quantified by optical metallography using ImageJ software. At 1000°C, the material was approximately 65% recrystallized after 5 min and approximately 95% recrystallized after 10 min; after 30 min, the microstructure was fully recrystallized and exhibited substantial grain growth. At 1200°C, rapid transition from precipitate-controlled boundary pinning to rapid grain growth where fully recrystallized structure was obtained within the first 5 min, followed by pronounced grain coarsening with increasing holding time. The measured mean grain sizes at 1200°C were 57, 85, and 235 μm after 5, 10, and 30 min, respectively. The accelerated grain growth at 1200°C is consistent with increased grain-boundary mobility and reduced effectiveness of Nb containing precipitates as boundary-pinning agents. A power-law grain-growth model was applied to the 1200°C data, giving a growth exponent of 1.597 and predicting a grain size of approximately 162 μm after 20 min. The results demonstrate the strong influence of annealing temperature and time on recrystallization and subsequent grain-boundary migration in AISI 347H. 

ABSTRACT

The fatigue behavior of 2024 aluminum alloy is strongly influenced by heat treatment conditions, particularly T6 and retrogression and re-ageing (RRA) processes. In this study, specimens obtained from 2024 alloy plates were solution heat-treated at 520°C /2 h and subsequently aged to the T4 condition at 120°C/24 h. All samples were then subjected to a natural ageing (shelf life) period of 15 days before undergoing retrogression at approximately 220°C/3 min, followed by re-ageing at 165°C for 2h. The heat-treated samples were evaluated using tensile testing, electrical conductivity in %IACS and high cycle fatigue testing after all proposed heat treatment cycles. The samples were further tested under high-cycle fatigue conditions. The results indicate that both tensile properties and electrical conductivity were adversely affected after the 15-day shelf life. Distinct differences in fatigue behavior were observed between the retrogression and T6 (re-ageing) treated alloys. The retrogression treatment for a short time for the samples after 15 days, exhibited an improvement of mechanical strength and electrical conductivity. However, re-aging of these samples for 165/2hr shows beak strength with decrease in electrical conductivity. Although, T6 condition provides superior strength, the Retrogression treatment offers high fatigue performance by improving crack growth resistance, making it a more suitable choice for applications requiring enhanced fatigue durability. Keywords: Retrogression and re-aging, Fatigue, Electrical conductivity, crack growth, Strength 

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This paper presents a comparative performance 

analysis of Wavelength Division Multiplexing (WDM) optical fiber and Free Space Optics (FSO) communication systems. A simulation-based optical communication system was designed, incorporating transmitters and receivers to achieve efficient data transmission among several locations, including Tripoli central post office, Gharyan post office, and Gharyan University linked to its affiliated faculties. The study involved collecting fundamental system parameters, developing a theoretical model, and implementing it using OptiSystem 7.0. Using the same operational parameters, network performance was assessed based on key indicators such as signal quality, bit error rate (BER) and Q-factor. In addition, the FSO system was evaluated under two different environmental scenarios: Ideal weather conditions and Atmospheric turbulence conditions, reflecting the typical climatic characteristics of Gharyan city, 

where the city is frequently experiences windy atmospheric conditions. Simulation results demonstrate that the proposed systems are capable of efficient data transmission, enhancing the effectiveness of optical communications in the region. Both Optical Fiber and FSO networks achieved satisfactory performance; however, FSO showed superior performance in some metrics under ideal weather conditions. Some faculties had short links (≤ 2 km) that did not require precise point-to-point alignment, while others required accurate point-to-point links. In contrast, the findings indicate that FSO can serve as an effective and competitive alternative to optical fiber in environments with suitable climatic conditions, particularly when reducing deployment cost and installation time is a priority, while providing a scalable and sustainable solution to meet future communication requirements. 

This paper analyzes a power system of three regions, each independently responsible for meeting its daily load demands. The regions are interconnected via transmission tie lines, allowing maximum power capacity (MW) transfer in both directions. This study investigates the operation of the power system under different load conditions and examines the possible effects of power transfer limits on the reliability and efficiency of electricity supply across the regions. The research evaluates the optimal operation of generation units within each region while considering the constraints imposed by the transmission tie lines. It indicates that increasing the capacity of transmission tie lines would greatly improve power transfer between regions. Our findings discover that strategic coordination between the regions significantly enhances the system efficiency, reduces generation costs, and minimizes the risk of load shedding during periods of high demand. Additionally, the paper analyzes the effects of different load demands and transmission capacities on system performance, highlighting the advantages of regional interconnections in enhancing energy resilience. The research also investigates the optimal unit commitment for the total load for the same daily load curve by using the quad program. Quadratic Programming allows a full quadratic cost function for each variable together with linear equality and inequality constraints, as well as lower and upper bound limits on the variables.

Abstract:

Occupational Health and Safety (OHS) is a major concern in vital sectors such as the energy sector, especially in countries where law enforcement and safety practices are still developing. This study aims to evaluate the effectiveness of the Occupational Health and Safety Management System (OHSMS) implemented at the General Electricity Company of Libya (GECOL), in light of international standards and global best practices. The research adopted a quantitative and qualitative analytical methodology by analyzing secondary data related to injuries and accidents during the period (2012-2014), in addition to analyzing a field questionnaire that included a sample of workers. The results showed a significant weakness in the application of occupational health and safety management systems, as the percentage of injuries resulting from safety instruction violations reached 36% in 2012, 20% in 2013, and 27% in 2014. The study also revealed the absence of effective supervision, lack of training, and insufficient personal protective equipment. The study concludes with the necessity of adopting an Integrated Occupational Health and Safety Strategy that includes planning, implementation, review, and continuous improvement, emphasizing the importance of training, awareness, and the presence of effective supervisory systems such as ISO 45001. It is important for the company to implement a specific occupational health and safety system, which may be designed by the company or based on international systems.

Keywords: Occupational Health and Safety (OHS), General Electricity Company of Libya, Work Injuries, Integrated Safety Management. 

This paper presents a comprehensive analysis of load expansion planning through the integration of photovoltaic systems at the Bir Alganame 220/30 kV substation. An electrical planning system serves as a crucial tool for designing electrical systems that effectively meet evolving energy demands. The study investigates the impact of load expansion on hybrid photovoltaic system design, focusing on system reliability and total project cost as primary design objectives. The research methodology encompasses a detailed load flow study conducted in 2024, coupled with load forecasting for 5 and 10-year horizons at an 8% load increase rate. The investigation includes analyzing the optimal parameters of the PV system integration with the existing grid to ensure proper functionality. Additionally, the study addresses the probabilistic scenario set of load demand and natural characteristics of renewable energy, which is crucial for power system planning studies. The research emphasizes the importance of proper transmission system network development to reliably and securely evacuate the generated power to meet future domestic load demand. Through simulation and analysis, this study demonstrates an integrated approach to improving power system performance while considering geographical and environmental factors affecting PV output. The findings provide valuable insights into optimal electrical network planning procedures, incorporating both long and short-term perspectives through PV system integration.

Abstract:

This study assesses the implementation level of the Occupational Health and Safety Management System (OHSMS) based on ISO 45001:2018 at Brega Oil Marketing Company (BOMC), Libya. A quantitative descriptive methodology was employed using a structured questionnaire derived from ISO 45001 clauses. Data were collected from 60 employees across four operational sites and analyzed using descriptive statistics in IBM SPSS. The results indicate partial compliance with ISO 45001 requirements (mean ≈ 3.82). Strong performance was observed in safety awareness and employee satisfaction, whereas weaknesses were identified in planning, hazard identification, and performance evaluation processes. The study recommends strengthening risk-based planning and internal auditing mechanisms to improve system effectiveness and ensure continual improvement.

Keywords: Occupational Health and Safety, ISO 45001, Gap Analysis, Oil and Gas Industry, Brega Oil Marketing Company. 

This paper presents the design and implementation of a smart robotic vacuum cleaner based on Internet of Things (IoT) technologies, named IO-VAC, specifically developed for smart home environments. The paper covers both the mechanical and electronic aspects of the robot’s development. A 2D layout was created using ArchiCAD to define the positioning of components and sensor angles when designing the robot, followed by a 3D model to visualize the final design. The robot chassis was fabricated using reinforced plastic to ensure durability and lightweight structure. The IO-VAC is controlled using an Arduino Mega board programmed in C/C++. Where, the system includes three ultrasonic sensors for obstacle avoidance, along with an infrared (IR) sensor for edge detection to prevent falls. The embedded system of IO-VAC integrates an ESP8266 Wi-Fi module, allowing for remote control via the Blynk IoT platform to enable users to control the robot’s movement (forward, backward, left, right), adjust suction power, select the desired cleaning algorithm, and monitor the battery level in real-time. In this paper three movement algorithms were developed: random, spiral and zigzag, and their performance was tested on two types of surfaces smooth and rough to ensure reliability and efficiency in various cleaning conditions after testing the validation of IO-VAC. Based on the test results of robot performance, the zigzag algorithm proved to be the most effective in terms of covered area, cleaning mission time, power consumption and minimizing redundancy. This work demonstrates an effective integration of embedded systems with IoT technologies, offering a smart and cost-efficient solution for automating household cleaning tasks.