Judul: Multi-Product Vehicle  Routing Problem dengan Time Windows dan Penerapannya pada Penentuan Rute  Distribusi Buku
Abstrak: Vehicle routing problem (VRP) merupakan suatu permasalahan penentuan rute kendaraan yang bertujuan meminimumkan jarak tempuh atau biaya distribusi. Dalam penerapannya, permasalahan VRP ditemukan pada berbagai perusahaan dengan berbagai kendala, seperti kapasitas kendaraan, jenis dan ukuran barang yang berbeda-beda, serta pelayanan tiap pelanggan sesuai dengan time windows (selang waktu). Dalam penelitian ini akan dibahas masalah penentuan rute distribusi buku pada Percetakan Gema Insani yang terletak di wilayah Jabodetabek. Kendala yang dimiliki perusahaan terkait dengan jenis dan ukuran buku untuk permasalahan time windows pada setiap pelanggan. Permasalahan ini dapat dimodelkan sebagai Multi-Product Vehicle Routing Problem with Time Windows (MPVRPTW). Ukuran masalah yang ada membutuhkan waktu komputasi yang lama. Oleh karenanya, solusi optimal tidak dapat diperoleh. Kondisi ini dapat diatasi dengan menyelesaikan masalah ini melalui dua tahap. Tahap pertama dilakukan pengelompokan node pelanggan ke dalam empat klaster. Klaster dibentuk berdasarkan jarak antar node pelanggan menggunakan metode k-Means dengan bantuan perangkat lunak RStudio 2022. Tahap kedua ditentukan rute distribusi pada masing-masing klaster dengan model MPVRPTW menggunakan bantuan perangkat lunak LINGO 19.0., The vehicle routing problem (VRP) is the problem of determining the vehicle route in order to minimize the distance traveled or distribution costs. In its application, VRP problems are found in various companies with various constraints, such as vehicle capacity, different types and sizes of goods, and service for each customer according to time windows. In this study, we will discuss the problem of determining vehicle routes to distribute books at Gema Insani Printing in the Jabodetabek area. The company's constraints include the types and sizes of books for each customer’s time windows. This problem can be modeled as the Multi Product Vehicle Routing Problem with Time Windows (MPVRPTW). The size of the problem requires a long computation time. Because of that, the optimal solution cannot be obtained. This situation can be overcome by solving this problem in two stages. The first stage is grouping customer points into four clusters. The clusters are formed based on the distance between customer points using the k-Means method with RStudio 2022 software. The second stage is determining the distribution route for each cluster using the MPVRPTW model with LINGO 19.0 software.
Keyword: klaster, cluster, multi product, vehicle routing problem, time windows

Judul: Vehicle Routing Problem pada Distribusi Sayuran Organik
Abstrak: Pengendalian permasalahan yang terjadi pada distribusi sayuran organik dapat diselesaikan dengan Multiple Trip Vehicle Routing Problem for Multiple Product and Compartments with Time Windows (MTVRPMPCTW) dan diselesaikan dengan salah satu metode eksak, yaitu Integer Linear Programming. Aplikasi model dilakukan terhadap tiga kasus berbeda, pelayanan 5 lokasi dengan rute tunggal, pelayanan 10 lokasi dengan rute majemuk, dan pelayanan 15 lokasi dengan rute majemuk serta adanya time windows yang harus terpenuhi. Pada kasus 10 lokasi dan 15 lokasi, kendaraan yang telah selesai mengantarkan sayuran organik harus kembali ke depot dan dapat melakukan lebih dari satu kali proses distribusi apabila masih terdapat lokasi yang belum dilayani. Setiap lokasi pada seluruh kasus dapat memesan lebih dari satu jenis sayuran organik. Produk yang dikirim akan ditempatkan di kompartemen yang spesifik agar produk tidak saling bercampur. Solusi yang diperoleh berupa rute pendistribusian sayuran organik yang meminimumkan total biaya distribusi, serta semakin bertambahnya lokasi maka semakin bertambah pula waktu komputasi yang diperlukan., The distribution problem of organic vegetables can be solved by the Multiple Trip Vehicle Routing Problem for Multiple Products and Compartments with Time Windows (MTVRPMPCTW) and solved by one exact method, namely Integer Linear Programming. The application of the model is carried out on three different cases, service for 5 locations with a single trip, service for 10 locations with multiple trip, and service for 15 locations with multiple trip and there are time windows that must be met. In the case of 10 locations and 15 locations, vehicles that have finished delivering organic vegetables must return to the depot and can carry out more than one distribution process if there are still locations that have not been served. Each location in all cases can order more than one type of organic vegetable. Products sent will be placed in a specific compartment so that the products do not mix with each other. The solution obtained is in the form of an organic vegetable distribution route that minimizes the total distribution cost, and the more locations, the more computational time required.
Keyword: distribution route, exact method, MTVRPMPCTW, organic vegetables

Judul: Hydroxyapatite-Chitosan Composite Coating on Stainless Steel 316 to Improve Corrosion Resistance
Abstrak: Metals that were used in bone implantation should have good corrosion resistance that were not easily corroded when implanted into the body. Metal corrosion resistance of stainless steel 316 can be enhanced through the metal coating by hydroxyapatite-chitosan composite with composition ratio of hydroxyapatite (gram) and chitosan 3% (mL) 0.2:0, 0.2:0.1, 0.2:0.5, 0.2:1.0, and 0.2:1.5. Besides improving the corrosion resistance of metal, the presence of chitosan also maintain the position of hydroxyapatite on metal surfaces. Corrosion resistance increases with increasing amount of chitosan added and the best composition of hydroxyapatite-chitosan composite was 0.2:1.0.
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