243,559 research outputs found
New approaches to casting hypereutectic Al-Si alloys to achieve simultaneous refinement of primary silicon and modification of eutectic silicon
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityHypereutectic Al-Si alloys are of increasing interest for applications that require a combination of light weight and high wear resistance, such as pistons, liner-less engine blocks and pumps. The wear resistance of this class of alloys is due to the presence of hard primary Si particles formed during casting. The objective of this work was to develop one or more methods of refining primary silicon in cast hypereutectic Al-Si alloys to compete with the conventional process of adding phosphorous and to achieve the simultaneous modification of silicon in the Al-Si eutectic. A robust sampling/casting technique was developed to minimise macro-segregation of primary silicon during solidification of hypereutectic Al-Si alloys by using water cooled steel mould with cooling rate in excess of 15 K/s. The morphology of silicon phases was found to change with increasing melt temperature and cooling rate. The high cooling rate and superheat temperature produces a good distribution of polyhedral primary silicon particles in a refined lamellar eutectic matrix in solidification of commercial purity Al-Si alloys. Removing Ca by fluxing with K2SiF6 prior to casting can improve the refinement and modification effect of Mg and Sb respectively. Effects of various inoculants were studied. Microstructural analysis showed that Mg and ZnS refined primary Si whereas MgO, CaO and Na2S coarsened the primary Si together with a modification effect on the eutectic Si. Adding Zn had no effect on morphology of Si phases. Refinement of both primary and eutectic silicon phases was observed for the Al-15Si alloy with Mg content ≤ 0.3 wt%.
P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities.
A new solid-liquid duplex casting process was devised to achieve simultaneous refinement and modification of Si phases in hypereutectic Al-Si alloys with improvement in mechanical properties. The static mechanical properties of Al-Si produced by the solid-liquid duplex casting process are significantly better than conventionally cast untreated Al-Si and slightly better than conventionally cast Al-Si treated with P and/or Sr. A novel Al-ZnS master alloy was developed by in situ reaction of Zn and Na2S in the Al melt. The results from this study leave little doubt that this novel Al-ZnS master alloy is a promising refiner in solidification of hypereutectic Al-Si alloys. It refines primary silicon to the same extent as that achieved by adding P via Cu-P following the same refinement mechanism.EPSRC,U
Lyman break galaxies and the star formation rate of the Universe at z ~ 6
No full textWe determine the space density of UV-luminous starburst galaxies at z≈ 6 using deep HST ACS SDSS-i′ (F775W) and SDSS-z′ (F850LP) and VLT ISAAC J and Ks band imaging of the Chandra Deep Field South. We find eight galaxies and one star with (i′−z′) > 1.5 to a depth of z′AB= 25.6 (an 8σ detection in each of the 3 available ACS epochs). This corresponds to an unobscured star formation rate of ≈15 h−270 M⊙ yr−1 at z= 5.9, equivalent to L* for the Lyman-break population at z= 3–4 (ΩΛ= 0.7, ΩM= 0.3). We are sensitive to star-forming galaxies at 5.6 ≲z≲ 7.0 with an effective comoving volume of ≈1.8 × 105h−370 Mpc3 after accounting for incompleteness at the higher redshifts due to luminosity bias. This volume should encompass the primeval subgalactic-scale fragments of the progenitors of about a thousand L* galaxies at the current epoch. We determine a volume-averaged global star formation rate of (6.7 ± 2.7) × 10−4h70 M⊙ yr−1 Mpc−3 at z∼ 6 from rest-frame UV selected starbursts at the bright end of the luminosity function: this is a lower limit because of dust obscuration and galaxies below our sensitivity limit. This measurement shows that at z∼ 6 the star formation density at the bright end is a factor of ∼6 times less than that determined by Steidel et al. for a comparable sample of UV-selected galaxies at z= 3–4, and so extends our knowledge of the star formation history of the Universe to earlier times than previous work and into the epoch where reionization may have occurred
Analisis Pengaruh Penggunaan Kata Anjay terhadap Kondisi Psikis Generasi-Z
No full textAbstract – The word "anjay" is a multi-situation term, it can be used in a happy atmosphere to anger. The purpose of this study is to find out how Anjay's effect on the psychic condition of Z-generations. The study is a kind of quantitative study using a correlation approach survey method. Z-generations is a research population that is derived from south sulawesi, southeast sulawesi and Java. As many as 100 respondents followed the instruments in charge of questionnaires on Google form to measure whether or not there was an impact between Anjay and his psychic condition. . Based on the value of R2 = 0.019, it was found that the influence of anjay’s word on the psychological condition of the Z-generation was 1.9%, the rest of the psychological condition was influenced by other causes. Based on the t-test where tcount < ttable which is 1.359 < 1.98447 and F-test where Fcount < Ftable which is 1.847 < 3.94 with a significance value of 0.177 > 0.05 indicates that anjay has no significant effect on psychic conditions. It can be argued that anjay's word was less influential in the psychic condition of Z-generations.Keywords - Anjay, psychological condition, z- generation
The Urgency of Reading in the Character Formation of Generation Z Youth from an Al-Qur'an Perspective (Examination of Maudhu'i Tafsir)
No full textThis research discusses the urgency of reading from generation Z of the perspective of the Koran and the implications of the character formed in it. Along with rapid technological development, generation Z faces major challenges in the form of literacy crises and moral decline. The phenomenon of low interest in reading among young people is associated with the negative influence of modernity and digital technology. In the context of the literacy crisis faced by young people in the digital era, this research raises the importance of reading as a fundamental character that can help generation Z to strengthen character and faith in facing the challenges of modern times. Using a maudhu'I interpretation approach, several verses of the Koran that will be analyzed include QS. Al-Alaq verses 1 and 3, QS. Al-Isra’ verse 14, QS. Al-Haqqah verse 19 which emphasizes the command to read and QS. Taha verse 114, QS. Yusuf verse 30, QS. Al-Kahf verses 13, 60, 62 and QS. Al-Anbiya’ verse 60 which shows the character of an ideal young man. This research aims to explore communication between the two classification verses. In order to provide solutions and understanding of how reading can form a strong and positive mentality both from a spiritual and social perspective in Generazi Z which is in line with the teachings of the Al-Qur’an
Kitāb Riḥlat Banī-Hilāl ilā bilād al-ġarb wa-ḥurūbihim maʿa 'z-Zanātī ...
No full textErsch.-Jahr 1302 h.In arab. Schrift, arab
Kitāb Riḥlat Banī-Hilāl ilā bilād al-ġarb wa-ḥurūbihim maʿa 'z-Zanātī ...
No full textErsch.-Jahr 1303 h
Kitāb Riḥlat Banī-Hilāl ilā bilād al-ġarb wa-ḥurūbihim maʿa 'z-Zanātī ...
No full textErsch.-Jahr 1298 h
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