A new approach to determine tensile stress-strain evolution in semi-solid state at near-solidus temperature of aluminum alloys

Accurate determination of the materials’ strength and ductility in the semi-solid state at near-solidus temperatures is essential, but it remains a challenging task. This study aimed to develop a new method to determine the stress-strain evolution in the semi-solid state of aluminum alloys within the Gleeble 3800 unit. Stress evolution was determined by the newly developed “L-gauge” method, which converted the displacement of the “restrained” jaw, measured using an L-gauge, into the force. This method gives the possibility to determine the flow stress more accurately, especially for the very low stress rang (1–10 MPa) in the semi-solid state at near-solidus temperatures. The digital image correlation technique implemented in the Gleeble unit allowed effective measurement of the heterogeneous strain fields evolving within the specimen under tensile loading. Therefore, the stress-strain curves measured in the semi-solid state help to better understand the alloy’s susceptibility to hot tearing. The results of an AA6111 alloy under different liquid fractions (2.8% at 535 °C and 5.8% at 571 °C) were demonstrated. The reliable stress-strain data and heterogenous strain distribution are beneficial to develop the thermomechanical models and hot-tearing criteria

Gestational diabetes prevalence and risk factors among pregnant women — Jazan Region, Saudi Arabia

Background. The gestational diabetes (GDM) is considered as a global public health problem that affects pregnant women. GDM can become chronic type II and usually it is associated with many risk factors that may lead to many serious complications for the mother and the fetus. The main objective of this study was to estimate the prevalence of GDM among pregnant women in Jazan region and to determine the possible associated factors of the GDM. Material and methods. The study involved pregnant women attending department of Obstetrics and Gynecology at government hospitals of Jazan region. A sample of 440 pregnant women were randomly selected. Interviews were conducted using a questionnaire prepared to measure the GDM prevalence, risk factors, awareness and adherence to the advice of the doctor and medications. Results. The prevalence of gestational diabetes among pregnant women in Jazan is estimated at 8.2%. The GDM prevalence was significantly higher among obese women (20.2%; 95% CI 13.2–29.2) compared with women with normal weight (7.1%; 95% CI 1.7–7.6). The analysis showed that GDM was significantly associated with child weight more than 3.5 kg (OR 4.315; p = 0.004), mother’s BMI more than 30 kg/m2 (OR 4.703; p = 0.001), and family history of GDM (OR 2.606; p = 0.046). Conclusion. In conclusion, the GDM prevalence obtained in this study is more than global prevalence and less than other studies in KSA. The BMI of mothers and having neonates that weight more than 3.5 kg are the main risk factors for GDM. Suitable interventions programs are highly required for control and risk factor modifications

Częstość występowania cukrzycy ciążowej i jej czynników ryzyka u ciężarnych kobiet w prowincji Dżazan w Arabii Saudyjskiej

Wstęp. Cukrzycę ciążową (GDM) uważa się za globalny problem zdrowotny dotyczący ciężarnych kobiet. Może ona przejść w cukrzycę typu 2 i zwykle wiąże się z wieloma czynnikami ryzyka, które mogą prowadzić do poważnych powikłań u matki i płodu. Głównym celem badania było oszacowanie częstości GDM u kobiet w ciąży mieszkających w prowincji Dżazan oraz określenie czynników, które mogą wiązać się z GDM. Materiał i metody. Badanie obejmowało kobiety w ciąży będące pod opieką oddziałów położniczo-ginekologicznych szpitali państwowych w prowincji Dżazan. Wybrano losowo próbę liczącą 440 ciężarnych kobiet. Przeprowadzając wywiady z uczestniczkami badania, korzystano z kwestionariusza opracowanego w celu oceny częstości występowania GDM, czynników ryzyka, wiedzy kobiet na temat GDM i przestrzegania zaleceń lekarskich oraz przyjmowania leków. Wyniki. Częstość GDM wśród ciężarnych kobiet w prowincji Dżazan wynosiła 8,2%. Była ona istotnie wyższa u kobiet otyłych [20,2%; 95-procentowy przedział ufności (CI) 13,2–29,2) niż u osób z prawidłową masą ciała (7,1%; 95% CI 1,7–7,6). Analiza wykazała, że GDM wiązała się istotnie z urodzeniem dziecka o masie ciała wynoszącej ponad 3,5 kg [iloraz szans (OR) 4,315; p = 0,004), wskaźnikiem masy ciała (BMI) matki wynoszącym ponad 30 kg/m2 (OR 4,703; p = 0,001) oraz dodatnim wywiadem rodzinnym dotyczącym GDM (OR 2,606; p = 0,046). Wnioski. Podsumowując, częstość GDM stwierdzona w badaniu była większa niż globalna częstość występowania GDM, lecz mniejsza niż obserwowana w innych badaniach w populacji saudyjskiej. Wskaźnik BMI matki i urodzenie dziecka o masie ciała powyżej 3,5 kg to główne czynniki ryzyka GDM. Potrzebne są odpowiednie programy interwencyjne w celu kontroli i modyfikacji czynników ryzyka

Ultrasonic Characterization, Tensile Testing And Thermal Properties Of Y Irradiated Low Density Polyethylene, Fb 5005

Ultrasonic pulse-echo technique, tensile testing and thermal gravimetric analysis have been utilised to characterise and monitor the effect of y irradiation on the physicomechanical properties of low density polyethylene LDPE, grade FB 5005. The sonic modulus, elastic modulus, rupture stress and decomposition temperature exhibit a minimum value at 2 Mrad irradiated samples, whereas, toughness and rupture strain exhibit a maximum at the same irradiation dose. The changes in mechanical properties (rupture stress and toughness) correlate well with decomposition temperature and the change in the sonic modulus correlates as well with elastic modulus for the tested material. The results are discussed in terms of cross-linking. Below 2 Mrad the loss of crystallinity overrides the effect of cross-linking, whereas above 2 Mrad the cross-linking dominates

التنبؤ بالأداء المهاري في كرة اليد من خلال التفاؤل

هدف البحث إلى التعرف على مستوى كل من الأداء المهاري والتفاؤل لدى لاعبي كرة اليد في أندية الدرجة الاولى والدرجة الممتازة للرجال والنساء في اقليم كوردستان العراق، ودلالة الفروق في كل من الأداء المهاري والتفاؤل تبعاً للمتغيرات الديمغرافية، ونسبة مساهمة كل من والتفاؤل في الأداء المهاري. لتحقيق أهداف البحث استخدم المنهج الوصفي المسحي في الدراسة الحالية. وتكون مجتمع البحث من لاعبي كرة اليد والبالغ عددهم (252) لاعباً ولاعبة موزعون على (21) نادياً رياضياً بواقع (15) نادي للرجال و(6) اندية للنساء، وتألفت العينة من (120) لاعباً ولاعبة لكرة اليد تم اختيارهم بواقع (12) لاعباً ولاعبة بطريقة عشوائية من (10) أندية رياضية من الدرجة الأولى والممتازة وبواقع (7) أندية للرجال و(3) أندية للنساء، وتمثل نسبة (48%) من مجتمع البحث. واعتمدت الدراسة في جمع البيانات على مقياس التفاؤل. وتم معالجة البيانات إحصائياً باستخدام الوسط الحسابي والانحراف المعياري، ومعامل ارتباط بيرسون، ومعادلة سبيرمان براون، والتحليل العاملي والاختبار التائي لعينة واحدة ولعينتين مستقلتين، وتحليل التباين الأحادي واختبار L.S.D والانحدار المتعدد وباستعمال برنامج (SPSS). وبعد عرض النتائج وتحليلها ومناقشتها توصل الباحثان إلى جملة استنتاجات وأهمها مستوى التفاؤل لدى لاعبين كرة اليد كان عاليا ومستوى الأداء المهاري لدى نفس افراد عينة البحث كانت متوسطا

Combined exercises for balance and their impact on learning the skill of peaceful shooting in basketball for the education team of Misan Governor

Scientific development and training methods are considered a goal that the countries of the world seek to present their knowledge, curricula and concepts in a simplified manner to their teachers with the aim of preparing and developing sports. As for the problem, this may be related to teachers not using this balance ability or perhaps on these abilities and the presence of a weakness in the harmonious abilities of students and the goal of identifying complex exercises for my ability Balance ability and its impact on learning the skill of peaceful shooting in basketball for the Misan educational team, and the imposition of the research there are statistically significant differences between the results of the post tests for the experimental and control groups and in favor of the experimental group. As for the research method, the researchers used the experimental method due to its relevance to the nature of the problem. And the research sample was done by the intentional method, and they are a group of (20) players in the Misan Governorate education team

Learning Styles Preference of Student Teachers: A Cross Cultural Perspective. Volume 1.

Abstract All students learn, but not all learn in the same way

Effect of chemical composition on the semisolid tensile properties and hot tearing susceptibility of AA6111 DC cast alloys

The semisolid tensile properties of two AA6111 direct-chill cast alloys (A and B) have been studied. The Cu, Mn, and Si contents of alloy A are higher than those of alloy B. The microstructures of the alloys were analyzed before tensile testing and after tensile fracture. Isothermal holding was performed in the temperatures of 510, 520, 535, 552, 564 and 580 °C for 1 h to study porosity/void formation in both alloys. Tensile tests were conducted near the solidus temperature in the temperature range of 450–580 °C at a strain rate of 10–4 s−1. The strain during tensile testing was measured using the digital image correlation method to obtain reliable stress–strain curves. The results revealed that the tensile strengths of the alloys gradually decreased to zero with increasing temperature to arrive at the zero-stress temperature, whereas the strains at the failure decreased sharply with increasing temperature until zero-ductility temperature (ZDT) was reached. Moreover, the failure strain of alloy B at any given testing temperature was higher than that of alloy A. Non-mechanical and mechanical hot-tearing criteria were used to study the hot-tearing susceptibilities (HTSs) of the alloys. Considering the mechanical criterion, the ZDT and brittle temperature range of alloy A were lower and larger than those of alloy B, respectively, indicating that the HTS index of alloy A was higher than that of alloy B

Temperature dependence of elastic properties of Al-Mg-Si direct-Chill-cast AA6111 alloy at near-solidus temperatures

The elastic properties of the Al-Mg-Si direct-chill-cast AA6111 alloy were determined during the unloading stage of the cyclic tensile test over a wide range of temperatures (25-550 °C), and particular attention was paid to high temperatures near the solidus. Young’s modulus was calculated based on macroscopic and localized strains, which were measured using an extensometer and the digital image correlation (DIC) method. Poisson's ratio was determined based on the localized axial and lateral strains measured using DIC method. Over the entire temperature range, the DIC method demonstrated a higher stability in its accuracy with increasing temperature than that using the extensometer. A sharp change in the slope of Young's modulus as a function of the temperature, starting from the solidus temperature, was detected using the DIC method. Correlations between Young's modulus and temperature in both the solid and semi-solid states were established. Poisson’s ratio as a function of the temperature exhibited a dramatic change near the solidus temperature because of the presence of liquid pockets. The onset brittle temperature of AA6111 alloy in the semi-solid state was estimated to be 550 °C based on the critical values of Poisson’s ratio and the shear modulus to bulk modulus ratio