Location and routing are the main critical problems investigated in a logistic. Location-Routing Problem (LRP) involves determining the location of facilities and vehicle routes to supply customer's demands. Determination of depots as distribution centers is one of the problems in LRP.  In LRP, carbon emissions need to be considered because these problems cause global warming and climate change. In this paper, a new mathematical model for LRP considering CO2 emissions minimization is proposed. This study developed a new  Mixed Integer Linear Programming (MILP)  model for LRP with time windows and considered the environmental impacts.  Finally, a case study was conducted in the province of Central Java, Indonesia. In this case study, there are three depot candidates. The study results indicated that using this method in existing conditions and constraints provides a more optimal solution than the company's actual route. A sensitivity analysis was also carried out in this case study.

Sawmill industry is an industry that processes logs into sawn timber products through several processes to maximize profits and meet customer demand. The process involves important operations that has to be coordinated to get the desired product with the available resources optimally. Efficient operations can be achieved through optimal production planning by considering some factors to optimize the number of sawn timber product combinations. Optimal production planning is expected to have an impact, such as:  reduction of the use of raw materials that can affect inventory and procurement. In this research, the author has developed a mathematical model for production planning to determine the optimal number of sawn timber product combinations. Problems were solved using mixed-integer linear programming methods with mathematical modeling that aimed for maximizing profit. Production costs, raw material costs, and purchasing costs were critically considered in this mathematical modeling. The result showed that the use of the developed model could integrate the factors above, fulfil the demand, and increase company income.

Taxi services involve the number of taxi and demand. A balance is needed for operated taxi and demand, so that the number of canceled order decreases. This system involves taxi and consumers as agents with various behaviors from their agents, then solved using modeling methods. Agent-based modeling is a feasible method used in this study because it can accommodate the properties and attributes of each agent. From the scenario that has been done, the average number of good fleets to operate is 103 fleets, with the canceled order rate is 1.2% and this model proves that the number of operated taxi is sensitive to the number of requests that exist. Keywords. taxi; demand; agen based modelingAbstrak. Sistem layanan transportasi melibatkan jumlah taksi dan jumlah permintaan yang ada. Hal ini dibutuhkan keseimbangan agar tidak terlalu banyak taksi yang beroperasi dan kekurangan taksi yang mengakibatkan jumlah pembatalan pesanan meningkat. Maka masalah tersebut mengisyaratkan diperlukannya suatu alat analisis berupa model simulasi untuk mengevaluasi jumlah taksi yang beroperasi untuk memenuhi jumlah permintaan yang ada. Sistem tersebut sulit untuk dimodelkan dengan model matematik karena keragaman perilaku yang dapat terjadi, maka perangkat lunak simulasi merupakan salah satu solusi yang digunakan untuk permasalahan ini. Agen Based Modeling merupakan metode pemodelan yang digunakan karena dapat mengakomodasi sifat dan atribut pada setiap agennya.Hasil yang didapatkan adalah jumlah armada optimal yang beroperasi sejumlah 103 armada dengan jumlah pembatalah order 1,2 % dan model ini membuktikan bahwa jumlah armada yang beroperasi sensitif terhadap jumlah permintaan yang ada. Kata kunci. taksi, permintaan, agen based modeling.