Like most cities in the world, population in Indonesia continues to grow every year. Problems that can arise from this are the increasing amount of municipal solid waste (MSW) production and the growing demand for electricity. To deal with the problems, Indonesian government runs 3R (Reduce, Reuse and Recycle) and WTE (Waste to Energy) Programs simultaneously. 3R program aims to reduce the number of waste, while WTE program aims to generate electricity as an alternative energy source. This study aims to find out the optimal proportion of MSW treated through the 3R and WTE programs. For the purpose, a goal programming model has been developed and solved using LINGO 11. The results showed that the optimal proportion of MSW through the 3R program is 49.90%, 12.37% through WTE program. This leaves 37.73% of waste untreated. The electricity generated from WTE program reached 1,229.695 GWh, total emissions that can be saved is 1,809,208.2 tons CO2 equivalent and total land-use for the programs is 4,036,239.1 m 2 . This study was enriched by performing some scenarios, i.e. adding budget allocation of WTE program, tightening the limit of total emission from waste management and reducing the limit of land-use for waste treatment. AbstractOptimasi Program 3R dan WTE untuk Sampah Perkotaan di Indonesia. Seperti umumnya kota-kota di dunia, penduduk kota-kota besar di Indonesia terus bertambah tiap tahun. Keadaan ini memunculkan dua permasalahan yaitu bertambahnya jumlah sampah kota (MSW) dan bertambahnya permintaan akan listrik. Untuk mengatasi permasalahan tersebut, pemerintah memunculkan program 3R (Reduce, Reuse, and Recycle) dan program WTE (Waste to Energy) secara bersamaan. Program 3R bertujuan mengurangi jumlah sampah yang dibuang sedangkan program WTE bertujuan memanfaatkan sampah sebagai alternative untuk menghasilkan listrik. Penelitian ini untuk menjawab berapa porsi sampah yang optimal untuk digunakan untuk membangkit listrik dan berapa untuk 3R. Untuk tujuan tersebut telah dibuat model goal programming dan dipecahkan dengan menggunakan software optimasi Lingo release 11. Hasil running dari model yang dibangun menunjukkan bahwa porsi MSW yang dapat dikelola lewat 3R adalah 49,90%, lewat WTE 12,37%. Sisanya 37,73% sampah tidak terkelola. Listrik yang dihasilkan dari program WTE ini mencapai 1.229,695 GWh. Emisi yang dapat dikurangi sebesar 1.809.208,2 tons CO2 equivalen dan total lahan yang digunakan adalah 4.036.239,1 m 2 . Dalam penelitian ini juga dilakukan beberapa skenario yaitu penambahan alokasi dana pada program WTE, pengetatan emisi dan berkurangnya luas lahan yang dapat digunakan.

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Most classical scheduling approaches deal with single products, single machines, and static manufacturing environments. In real-world manufacturing systems, however, scheduling can be assigned for multi-item production on multimachines in a dynamic environment in which unexpected new orders may be received. This paper focuses on scheduling problems in an assembly job shop with parallel machines that produce multi-item multi-level products. Models were developed for due date fulfillment and due date assignment in static and dynamic conditions, with the objectives of minimizing total actual flow time, while considering the defect rate at each stage of the process. The insertion technique was used in the scheduling process; insertion can be performed in batch operations at all available positions on all machines. A hypothetical case of job shop scheduling problems associated with multi-item, multi-level production on parallel machines was studied, and the computational results demonstrated the validity of the proposed algorithms.