.

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 

• English plays an important role in university study, academic communication, access to information, technology, and future employment. For many first-year students, however, the transition from school English to the language demands of university study can be challenging. This volume develops the core grammatical foundations required for first-year university English. The sequence begins with basic sentence structure and the verb to be, then develops through the present simple, questions and negatives, there is/there are, countable and uncountable nouns, and the past simple in affirmative, negative, and question forms. Each lecture is organised around explicit learning outcomes and combines explanation, examples, guided practice, vocabulary, reading, speaking, writing, review, and homework. The aim is not only to teach grammatical forms but also to help students use those forms to communicate about their studies, routines, experiences, plans, and academic life. Teachers may use the book as a core classroom text or adapt individual lectures to suit student level, contact hours, and local curriculum requirements. Students are encouraged to complete the exercises actively, speak and write whenever possible, review recurring errors, and build confidence through regular practice. 

ABSTRACT

Background: Incisional hernia is a common complication following abdominal surgery, and mesh reinforcement has become

the standard of care. This study aimed to compare the clinical outcomes of sublay versus onlay mesh repair in patients with

incisional her

nia.

Methods: This prospective randomized controlled clinical trial was conducted at the General Surgery Department, Faculty

of Medicine, ..... Hospitals. A total of 60 patients diagnosed with incisional hernia and scheduled for elective surgical repai

r

were recr

uited from general surgery outpatient clinics and the emergency department. Patients were randomly assigned into

two equal groups: Group A (Onlay Group, n=30) underwent onlay mesh repair, and Group B (Sublay Group, n=30)

underwent sublay (retrorectus) mesh

repair. Baseline demographic, clinical, laboratory, and radiological characteristics were

recorded. Operative parameters, postoperative pain scores (Visual Analogue Scale), hospital stay, return to normal activity,

postoperative complications (seroma, hem

atoma, surgical site infection), and hernia recurrence at 12 months were compared

between the two groups.

Results: Operative time was significantly shorter in the onlay group (88.93 ± 7.93 minutes) compared to the sublay group

(99.67 ± 7.74 minutes) (p < 0.001). Postoperative pain scores were significantly lower in the sublay group at day 1 (4.70 ±

0.76 vs. 6.

10 ± 0.79), 1 week (2.39 ± 0.75 vs. 3.99 ± 0.82), 1 month (0.85 ± 0.74 vs. 2.41 ± 0.88), 3 months (0.30 ± 0.49 vs.

1.41 ± 0.86), 6 months (0.16 ± 0.36 vs. 1.02 ± 0.82), and 12 months (0.14 ± 0.48 vs. 0.82 ± 0.86) (p < 0.001 for all). Hospit

al

stay was sign

ificantly shorter in the sublay group (3.47 ± 1.11 days vs. 4.40 ± 0.93 days, p < 0.001), and return to normal

activity was significantly earlier (21.53 ± 3.41 days vs. 26.07 ± 4.73 days, p < 0.001). No significant difference was found

in drain removal day

(p = 0.257). Postoperative complications including seroma (10.0% vs. 23.3%, p = 0.299), hematoma

(3.3% vs. 6.7%, p = 1.000), and surgical site infection (6.7% vs. 16.7%, p = 0.424) were directionally lower in the sublay

group but did not reach statistical

significance. Hernia recurrence at 12 months was 3.3% in the sublay group versus 10.0%

in the onlay group (p = 0.612). All patients completed the 12

-

month follow

-

up.

Conclusion: Sublay (retrorectus) mesh repair offers significant clinical advantages over onlay mesh repair for incisional

hernia, including superior postoperative pain control, shorter hospital stay, and earlier return to normal activity. Postoper

ative

com

plications and recurrence showed consistent trends favoring sublay repair. These findings support sublay mesh repair as

the preferred technique for elective incisional hernia repair in appropriately selected patients.

.

Keywords

: Incisional hernia, mesh repair, sublay, retrorectus, onlay, postoperative pain, randomized controlled trial.