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"Paduan aluminium AC4B merupakan salah satu bahan baku pengecoran komponen cylinder head pada kendaran bermotor. Komponen ini dihasilkan dengan metode pengecoran Low Pressure Die Casting (LPDC). Namun, masalah yang sering muncul dalam proses pengecoran ini adalah banyaknya kegagalan yang disebabkan oleh adanya cacat seperti bocor, penyusutan, dan misrun. Proses rekayasa material berupa modifikasi dan penghalusan butir sering diaplikasikan pada pengecoran aluminium karena mampu meningkatkan kualitas dan menurunkan tingkat kegagalan. Penelitian ini mempelajari pengaruh kombinasi penambahan Ti dan Sr terhadap karakteristik paduan aluminium AC4B. Proses pengecoran dilakukan dengan menggunakan metode LPDC pada 0.1 wt. % Ti dengan variabel penambahan Sr yaitu 0.003, 0.018, dan 0.025 wt. % Sr untuk menghasilkan komponen cylinder head sebagai sampel uji kekerasan, pengamatan struktur mikro dan SEM. Sampel diambil pada bagian tebal dan tipis untuk mengetahui pengaruh dari kecepatan pembekuan. Pengujian tarik dilakukan dengan metode JIS 2201, pengujian kekerasan dengan Rockwell B, pengujian fluiditas dengan metode spiral dan pengujian porositas dengan metode vakum. Pengamatan struktur mikro menggunakan mikroskop optik dan Scanning Electron Microscopy(SEM)/Energy Dispersive X-Ray Analysis (EDAX) untuk identifikasi fasa. Hasil penelitian ini menunjukan bahwa penambahan Ti dan Sr meningkatkan kekerasan dan kekuatan tarik, nilai fluiditas, menurunkan nilai DAS serta meningkatkan derajat modifikasi. Secara keseluruhan nilai tersebut optimum pada 0.1 wt. % Ti dan 0.0018 wt. % Sr yaitu dengan nilai kekerasan 52.48 HRB pada bagian tipis dan 51.30 HRB pada bagian tebal. Nilai kekuatan tarik optimum pada 251.11 MPa, nilai fluiditas pada 63.4 cm dan DAS pada 13.4 ?m di bagian tipis dan 27.2 di bagian tebal. Tingkat modifikasi optimum pada kelas E dengan struktur fibrous. Jumlah porositas meningkat linier seiring peningkatan komposisi Sr. Selanjutnya terjadi penurunan sifat mekanis pada 0.025 wt. % Sr karena over modifikasi. Tidak ditemukannya interaksi antara Ti dan Sr dalam penelitian ini.

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AC4B aluminum alloy is a commonly used material for cylinder head of motorcycle. This component is produced by low pressure die casting (LPDC) method. However, problems that arise in this casting process are defects such as leaking, shrinkage, and misrun. Modification process and grain refining are often applied in aluminum casting because they can improve its quality and reduce the failure rate.

This research studied the combination effects of Ti and Sr additions on the characteristics of AC4B aluminum alloy. Low pressure die casting method was conducted to produced cylinder head with 0.1 wt. % Ti and the variables of Sr of 0.003, 0.018, and 0.025 wt. %.Samples were taken for hardness test, microstructure observation and SEM, from the thick and thin sections of the cylinder head to determine the effect of solidification rate. Tensile test was carried out in accordance with JIS 2201 method, while hardness test was performed by Rockwell B method. Fluidity test was conducted by spiral method and vacuum test was used to measure porosity content. Microstructure was observed by optical microscope and Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray Analysis (EDAX) for phase identification.

The results show that the addition of Ti and Sr increased hardness, tensile strength and fluidity, while reduced DAS (dendrite of spacing). Degree of modification was found increased by addition of Ti and Sr. The optimum properties was obtained at 0.1 wt. % Ti and 0.0018 wt. % Sr, of which hardness at thin and thick sections are 52.48 and 51.30 HRB, respectively. Optimum properties were tensile strength of 251.11 MPa, fluidity of 63.4 cm, DAS of 13.4 ?m of thick section and 27.2 ?m of thin section, with the level of modification fell in class E with fibrous structure. Number of porosity linearly raised with increasing Sr composition. However, the mechanical properties decrease at the content of 0.025 wt. % Sr because of over modification. There is no interaction between Ti and Sr was found."

"[ABSTRAKTesis ini membahas mengenai pengukuran kontribusi risiko sistemik danhubungannya dengan karakteristik individu bank pada perbankan Indonesiadengan periode pengamatan dari 2003 s.d 2013.Metode yang digunakan untukmengukur kontribusi risiko sistemik adalah CoVaR (Girardi dan Ergun, 2013) danMES (Acharya, 2010). CoVaR digunakan untuk melihat kontribusi risiko sistemikmasing-masing bank terhadap sistem keuangan apabila bank mengalami distresssedangkan MES digunakan untuk melihat bagaimana kontribusi risiko sistemikmasing-masing bank apabila sistem keuangan mengalami distress. Dari hasilpengukuran ditemukan bank yang memiliki nilai Delta CoVaR terbesar adalahBMRI, BBRI, BBCA dan BBNI.Ke 4 (empat) bank tersebut merupakan bankterbesar di Indonesia.Hal ini menunjukan bahwa bank yang akan memberikant kontribusi risikokepada sistem sebesar nilai Delta CoVaR nya saat bank mengalami distress.Sebaliknya dari hasil pengukuran MES diketahui bahwa bank yang akanmemberikan kontribusi risiko sistemik terbesar saat sistem mengalami distressadalah BBRI. Hasil penelitian menunjukan bahwa karakteristik individu bankseperti ukuran bank dan VaR memiliki pengaruh yang signifikan terhadap besarkontribusi risiko sistemik bank di Indonesia. Kondisi makroekonomi seperti inflasisecara signifikan mempengaruhi nilai kontribusi risiko sistemik dari masingmasingbank di Indonesia.

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ABSTRACTThis thesis discusses the contribution of systemic risk and its relationshipwith the individual characteristics of banks in the Indonesian banking with theobservation period from 2003 until 2013. The method used to measure systemicrisk contribution is CoVaR (Girardi and Ergun, 2013) and MES (Acharya, 2010).CoVaR looks ay the returns of the financial system when an institution is infinancial distress while MES looks at the returns of an institution when thefinancial system is in distress. From the results of measurements we found that thebank has the largest value of Delta CoVaR areBMRI , BBRI , BBCA and BBNI .All of the bank are the largest bank in Indonesia.This shows that the bank will contribute to the system at its current value ofDelta CoVaR bankswhile experiencing distress. On the other hand, the resultmeasurement of the MES is that BBRI will provide the largest contribution tosystemic risk when the system it experiencing distress.The results showed thatindividual characteristics such as bank size and VaR has a significant effect on thebank contribution to systemic risk in Indonesia. Macroeconomic conditions suchas inflation significantly affect the value of systemic risk contribution of each bankin Indonesia.;This thesis discusses the contribution of systemic risk and its relationshipwith the individual characteristics of banks in the Indonesian banking with theobservation period from 2003 until 2013. The method used to measure systemicrisk contribution is CoVaR (Girardi and Ergun, 2013) and MES (Acharya, 2010).CoVaR looks ay the returns of the financial system when an institution is infinancial distress while MES looks at the returns of an institution when thefinancial system is in distress. From the results of measurements we found that thebank has the largest value of Delta CoVaR areBMRI , BBRI , BBCA and BBNI .All of the bank are the largest bank in Indonesia.This shows that the bank will contribute to the system at its current value ofDelta CoVaR bankswhile experiencing distress. On the other hand, the resultmeasurement of the MES is that BBRI will provide the largest contribution tosystemic risk when the system it experiencing distress.The results showed thatindividual characteristics such as bank size and VaR has a significant effect on thebank contribution to systemic risk in Indonesia. Macroeconomic conditions suchas inflation significantly affect the value of systemic risk contribution of each bankin Indonesia., This thesis discusses the contribution of systemic risk and its relationshipwith the individual characteristics of banks in the Indonesian banking with theobservation period from 2003 until 2013. The method used to measure systemicrisk contribution is CoVaR (Girardi and Ergun, 2013) and MES (Acharya, 2010).CoVaR looks ay the returns of the financial system when an institution is infinancial distress while MES looks at the returns of an institution when thefinancial system is in distress. From the results of measurements we found that thebank has the largest value of Delta CoVaR areBMRI , BBRI , BBCA and BBNI .All of the bank are the largest bank in Indonesia.This shows that the bank will contribute to the system at its current value ofDelta CoVaR bankswhile experiencing distress. On the other hand, the resultmeasurement of the MES is that BBRI will provide the largest contribution tosystemic risk when the system it experiencing distress.The results showed thatindividual characteristics such as bank size and VaR has a significant effect on thebank contribution to systemic risk in Indonesia. Macroeconomic conditions suchas inflation significantly affect the value of systemic risk contribution of each bankin Indonesia.]"