In this research the effect of cooling rate and mold type on mechanical properties of the eutectic
and hypoeutectic (Al-Si) alloys has been studied. The alloys used in this research work were (Al- 12.6%Si
alloy) and (Al- 7%Si alloy).The two alloys have been melted and poured in two types of molds with
different cooling rates. One of them was a sand mold and the other was metal mold. Mechanical tests
(hardness, tensile test and impact test) were carried out on the specimens. Also the metallographic
examination was performed.
It has been found that the values of hardness for the alloys(Al-12.6%Si and Al-7%Si) which poured in
metal mold is greater than the values of hardness for the same alloy when it poured in a heated metal
mold at different temperatures or in sand mold. The strength and impact resistance for the alloys (Al-
12.6%Si and Al-7%Si) are greater when these were poured in a metal molds than that when it poured in a
sand mold.
Furthermore, the higher cooling rates enhance the strength, hardness and impact resistance for the
two alloys, while the low cooling rates reduces these mechanical properties.
The percentage of elongation and the amounts of formed porosity decreased when the cooling rates
increased
Indicative supervision represents the comparison between direct intervention (acquisition, nationalism) and participation through rules.
The last financial crisis reflected our needs for different approaches of supervision consist with our goals, but the crisis reveals also number of sounds requested and pressured toward direct control (Intervention via forces) through government acquisition and nationalization.
This study attempts to deal with crisis lessons, in the field of choice between indicative and direct supervision which government authorities used to reduce the bad effect on the monetary firms.
Iraqi banks suffered from high levels of direct co
... Show MoreA study of some mite species of alfalfa. wheat, and barley was conducted in central Iraq.
The mites were extracted using a tullgren funnel method. Twelve species were recorded. 10 of
them belong to suborder Trombidiformes and 2 belong to suborder Sarcoptiforms. Three
mites, Irnpar(pes hystricinus, Scutacarus longitarsus, and Rhizoglyphus echin opus are new
records for Iraqi mite fauna, and 11 are new host records in alfalfa soil.
A simple all optical fiber sensor based on multimode interference (MMI) for chemical liquids sensing was designed and fabricated. A segment of coreless fiber (CF) was spliced between two single mode fibers to buildup single mode-coreless-single mode (SCS) structure. Broadband source and optical signal analyzer were connected to the ends of SCS structure. De-ionized water, acetone, and n-hexane were used to test the performance of the sensor. Two influence factors on the sensitivity namely the length and the diameter of the CF were investigated. The obtained maximum sensitivity was at n-hexane at 340.89 nm/RIU (at a wavelength resolution of the optical spectrum analyzer of 0.02 nm) when the diameter of the CF reduced from 125 μm to 60 μ
... Show MoreIn the spreading of the Internet, mobile smart devices, and interactive websites such as YouTube, the educational video becomes more widespread and deliberative among users. The reasons for its spread are the prevalence of technologies, cheap cost, and easy to use. However, these products often lack to the distinction in video production. By following videos of an educational channel on YouTube, some comments found to discuss the lack of the content presented to motivate the learners, which lead to reduce the viewers of the videos. Therefore, there is an important decision to find general standards for the design and production of educational videos. A list of standards has been drawn up to help those interested in producing educational
... Show MoreThe searching process using a binary codebook of combined Block Truncation Coding (BTC) method and Vector Quantization (VQ), i.e. a full codebook search for each input image vector to find the best matched code word in the codebook, requires a long time. Therefore, in this paper, after designing a small binary codebook, we adopted a new method by rotating each binary code word in this codebook into 900 to 2700 step 900 directions. Then, we systematized each code word depending on its angle to involve four types of binary code books (i.e. Pour when , Flat when , Vertical when, or Zigzag). The proposed scheme was used for decreasing the time of the coding procedure, with very small distortion per block, by designing s
... Show MoreSelf-repairing technology based on micro-capsules is an efficient solution for repairing cracked cementitious composites. Self-repairing based on microcapsules begins with the occurrence of cracks and develops by releasing self-repairing factors in the cracks located in concrete. Based on previous comprehensive studies, this paper provides an overview of various repairing factors and investigative methodologies. There has recently been a lack of consensus on the most efficient criteria for assessing self-repairing based on microcapsules and the smart solutions for improving capsule survival ratios during mixing. The most commonly utilized self-repairing efficiency assessment indicators are mechanical resistance and durab
... Show Moreيعد هذا النص أحد النصوص المسمارية المصادرة التي بحوزة المتحف العراقي، ويحمل الرقم المتحفي (235869)، قياساته )12،7x 6x 2،5سم). يتضمن مدخولات كميات من الشعير،أرخ النص الى عصر أور الثالثة (2012-2004 ق.م) و يعود الى السنة الثالثة من حكم الملك أبي-سين (2028-2004 ق.م)،أن الشخصية الرئيسة في هذا النص هو)با-اَ-كا مسمن الماشية( من مدينة أري-ساكرك، ومقارنته مع النصوص المسمارية المنشورة التي تعود الى أرشيفه يبلغ عددها (196) نصاً تضمنت نشاطاته م
... Show MoreAbstract
Black paint laser peening (bPLP) technique is currently applied for many engineering materials , especially for aluminum alloys due to high improvement in fatigue life and strength . Constant and variable bending fatigue tests have been performed at RT and stress ratio R= -1 . The results of the present work observed that the significance of the surface work hardening which generated high negative residual stresses in bPLP specimens .The fatigue life improvement factor (FLIF) for bPLP constant fatigue behavior was from 2.543 to 3.3 compared to untreated fatigue and the increase in fatigue strength at 107 cycle was 21% . The bPLP cumulative fatigue life behav
... Show MoreThe Old World Screwworm Fly Chrysomya bezziana is a new insect pest on cattles and other domestic recor¬ded for the first from Iraq. It was first observed in cow's vagina in September of 1996 in Shaikh Hammed (Tarmiya), near Baghdad city. Chrysomya bezziana Villeneuve is well known as one of the most important insect pests of livestock. Its larvae infest living tissues by causing myiasis. In a wide range of worm-blooded host species (Spradbery and Vanningham, 1980; Spradbery and Kirk. 1992). It is widely dist¬ributed species over an extensive area of tropical and subtropical Africa, the Arabian Gulf countries, Iran. Indian subcontinent. South-East Asia. Indonesia, and as far east as Papua New Guinea (Zurapt, 1965; Djalayer et al. 1978;
... Show More