Dasar-Dasar Mekanika Retakan

Buku ini berguna juga bagi masyarakat industri yang dalam kesehariannya bekerja dalam lingkungan industri yang berhubungan dengan persoalan kekuatan dan keretakan material khususnya pada bagian inspeksi.Dalam Bab 1 membahas secara umum mengapa struktur gagal karena patah dan juga penjelasan singkat tentang pendekatan Mekanika Retakan dalam Desain dan juga pengaruh sifat material pada perpatahan. Bab 2 menjelaskan tentang Mekanika Retakan Elastis Linier yang merupakan pengetahuan dasar dalam Mekanika Retakan. Untuk memahami persamaan matematis yang sering digunakan dalam analisa tegangan sekitar ujung retak,maka materi tentang matematika yang terkait dengan analisa tegangan juga di sajikan dalam Bab 3.Lebih lanjut aplikasi mekanika retakan dalam menentukan besaran parameter retakan yaitu ketangguhan retak material (fracture toughness) dibahas dalam Bab 4. Untuk lebih memperluas wawasan mahasiswa tentang kasus-kasus keretakan dan perpatahan pada elemen dan komponen mesin, maka dalam Bab 5 dijelaskan materi tentang aplikasi mekanika retakan pada komponen mesin dengan menyajikan contoh studi kasus pada elemen mesin yang mengalami perpatahan.Studi perpatahan dan retakan yang dibahas dalam Bab 5 yaitu Studi Kasus Pada Perpatahan Poros, dan Studi Kasus Pada Perpatahan Roda Gigi.</jats:p

Making a synthetic zeolite from a residue of bauxite washing

A zeolite synthetic of NaA type is generally prepared by mixing the alumina and silicate-containing materials (alkali alumino hydro-silicates). The used raw materials include the amorphous solids such as metakaolin, siliceous earth, coal ash, kimberlite waste, alumina trihydrate [Al(OH)3], bauxite, and aluminum metal. Residue of bauxite washing retains a fine texture and contains significant alumina and silica content, namely 30-36% Al2O3 and 10-15% SiO2. Both components are required for making the zeolite NaA . In this research, the zeolite NaA was made by extracting the alumina from residue of bauxite washing with caustic soda, and followed by reacting it with a water glass after through the flushing and washing process. The composition of zeolite NaA is as follows: 33.87% SiO2, 27.63% Al2O3, 16.31% Na2O, and 22.18% H2O with Na96Al96Si96O384.216H2O or Na12(AlO2)12(SiO2)12.27H2O as its mineral composition.</jats:p

(بحث إجرائي بجامعة التربية شمس الضحى أتشيه شمالية) قدرة الطلبة على التعبير بالجمل العربية

تم إجراء هذا البحث على الطلبةبجامعة التربية شمس الضحى أتشيه الشمالية بهدف معرفة كيفية تكوين الجمل العربية عند الطلبة وقدرتهم على التحدث باللغة العربية. لذلك كان هذ البحث بحثاإجرائيًّا. وكانت النتائج التي حصل عليهاالطلبة هي أن الطلبةبهذه الجامعة قاموا بتأليف جمل عربية من خلال الانتباه إلى قواعد اللغة العربية، وكانت قدرتهم على التعبير العربي جيدة. وذلك دل على أن الطلبة يفهمون اللغة العربية ويقدرون على التعبيرات العربية.</jats:p

Effect of Anisaldehyde as Corrosion Inhibitor for Aluminium in Sulphuric Acid Solution

The inhibition effect of anisaldehyde on the corrosion of aluminium in sulphuric acid was investigated by weight loss method and characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) analyses. The effect of different inhibitor concentrations was studied at varying temperature (308, 313 and 318 K). It was found that the percentage of inhibition efficiency (% I.E.) increases with increase of inhibitor concentration and decreases with increase in temperature. The values of activation energy and half-life were found to be higher in inhibited acid solution compared to uninhibited acid solution, while that for the rate constant reduced from uninhibited to inhibited acid solution. The negative values of Gibbs free energy of adsorption confirmed the spontaneity of the process. Other thermodynamic parameters such as enthalpy and entropy were also evaluated and discussed. The investigation of adsorption isotherm model indicates that the inhibitor fitted to Langmuir isotherm model. Result of SEM analysis shows how the inhibitor reduced the acid attack on the aluminium surface, and FTIR analysis result of the corrosion product proves the formation of thin layer of inhibitor molecules on aluminium surface.</jats:p

Analysis Managerial Ownership, Free Cash Flow And Debt On Dividends For Transportation And Infrastructure Companies In Indonesia

This study examines the effect of managerial ownership, free cash flow and debt on dividends in transportation and infrastructure companies in Indonesia. Sampling method use purposive and gotten 27 companies from 2015-2020. The data analysis method uses the Panel Data Regression analysis. The results of this study find that managerial ownership has a positive and significant effect, FCF has a negative and significant effect, while leverage proxy by DER has no significant effect on dividends. The results of this study indicate the occurrence of type I agency conflict in transportation and infrastructure companies in Indonesia.</jats:p