I. Gede Agus Widyadana

Inventory models for stock-dependent demand have been developed continuously in recent years. In this paper, we develop inventory dependent model for multi-items by considering stock-dependent demand and stock-dependent holding rate for a rack that has a specific capacity. Two models are developed. The first model is an individual order quantity for each item and the second model is a joint replenishment model. The non-linear model with constraint is solved using an evolutionary algorithm. A numerical example and sensitivity analysis are conducted to show how the models work and to get some management insights. The sensitivity analysis shows that there is no dominant model. However, the joint replenishment order outperforms the individual order when the rack capacity is tight and there is a high ordering cost

The accuracy of production planning is crucial that must be achieved by manufacturing companies. Production planning is sensitive to sales patterns and the availability of raw materials. Production planning must be in line with raw material planning. To ensure that the raw materials are available, production planning has to be deed in advance. In the waiting period for these raw materials, sales patterns may change so that the forecast and actual value deviations differ significantly. A dynamic mechanism of calculating the value of safety stock is carried out and carrying out the correction function of forecasting value by rolling forecast for overcoming it. Rolling forecasts allow forecasts of updated forecasting due to changes in sales patterns detected from actual sales value renewal. Using a rolling forecast as an alternative tool in forecast correction can reduce excess inventory by up to fifty-seven percent.

Penelitian ini dilakukan untuk mengetahui pengaruh dari variabel gaya kepemimpinan transformasional dan gaya kepemimpinan transaksional terhadap motivasi kerja karyawan di perusahaan konstruksi kota Ambon. Sampel yang digunakan adalah karyawan dari perusahaan yang terdaftar sebagai anggota ASPEKINDO kota Ambon tahun 2022. Teknik analisis data yang digunakan adalah analisis deskriptif dan multivariat dengan PLS-SEM. Hasil penelitian pada perusahan konstruksi di kota Ambon, gaya kepemimpinan transformasional berpengaruh positif dan signifikan terhadap motivasi kerja karyawan. Sedangkan gaya kepemimpinan transaksional berpengaruh negatif dan signifikan terhadap motivasi kerja karyawan. Pada gaya kepemimpinan transformasional, ketika semakin tinggi persepsi terhadap gaya kepemimpinan atasan maka semakin tinggi motivasi kerja dari karyawan. Sedangkan untuk gaya kepemimpinan transaksional, mendapatkan kesimpulan berbeda yaitu ketika semakin tinggi persepsi gaya kepemimpinan transaksional maka semakin rendah motivasi kerja dari karyawan.

Inventory routing problems (IRP) are among important tools to be used for implementing vendor manage inventory. Many researchers try to develop methods for solving inventory routing problem, however, only a few developed methods for inventory routing problems for spoilage items. In reality, many items are deteriorated and spoiled during transportation and storage period. In this paper, we developed a model and methods to solve the inventory routing problem for deteriorating items with dynamic demand and spoilage rate, i.e., demand varies and items spoil during planning periods. Those cases are more realistic since many commodities such as fruits and vegetables have dynamic demand and spoilage rate. A Genetic Algorithm and Particle Swarm Optimization are developed to solve the problem with various demands in a specific planning period since the problem is Np-hard. A numerical example and sensitivity analysis are conducted to verify the model, and to get management insight it. The result is interesting and support general hypothesis that dynamic demands result in higher inventory cost than the static demands, and the increasing demand results in increasing inventory cost. Also, the results show that increasing demand and deteriorating rates significantly affect the total cost, therefore, the developed model is important and significantly useful to be used for solving IRP with dynamic demand and spoilage items

Today many retailers face high competition, therefore they have to operate in an efficient way. One aspect of efficiency is inventory. Many research on inventory is conducted intensively to get more realistic inventory model. In this paper, an inventory model was developed by considering pricing. Many retailers try to increase their profit by setting the best price for a single item, especially for some items that have high price-dependent demand. The customer demand depends on the price such household items. In the other side, some retailers face supply problems. Supplier often cannot supply products when the products needed on time. There is delay time between customer demand and products arrive at retailer warehouse. The retailer should determine the optimal price and replenishment time. There are some assumptions are used for the model. The first assumption, the demand is known and has constant elasticity. Second, there is stochastic replenishment period and demand that are not filled are lost sales. The model is developed mathematically and a numerical example is conducted to show how the model works. A sensitivity analysis is accomplished to get some management insight and some interesting result are derived. Keywords: deteriorating inventory model; genetic algorithm; stochastic time

Warehouse space allocation is a critical issue to be addressed in many firms, especially firms that have various types of products. Further, most of the owned warehouse has a limited capacity which leads to the usage of outsourcing policy for warehouse storage. In this case, a rented warehouse that has more flexibility in terms of capacity is used to store the products. Therefore, an optimal decision of warehouse configuration is required. The previous study proposed a two-stage stochastic optimization model for warehouse configuration and inventory policy for deteriorating items. Unfortunately, direct implementation of their proposed method in real case problems will incur high cost and takes up a lot of time. In this research, a simulation model is developed to monitor the real condition in the company as well as to ensure that the warehouse configuration is suitable to be implemented. A textile and apparel company is used as the study case. The result shows that simulation model can be used to monitor the real condition as well as to obtain the net profit when facing different demand possibility. Keywords: inventory control; real-time monitoring; system simulation; warehouse configuration; warehouse space allocation

Optimization models are increasingly developed for planning and scheduling in manufacturing of natural resources. However, the uncertainty of material from natural resources makes it more difficult to develop a model. In this paper, we concern about the cost of dry timber preparation for finishing process in a wood-board manufacturer. Based on characteristics of the material and wood-board production process, we develop two models to minimize transportation and drying cost of wood supply. The models consider the capacity of facilities, distances among facilities, and timber specification-based drying periods. The model is solved using linear programming, result in drying allocation of kiln dry’s chambers that gives the minimum cost of the process. A sensitivity analysis is conducted to demonstrate the effect of variation of internal capacity and external capacity to the objective function value. The results show that the total cost is more sensitive to the variation of the external capacity of kiln dry than the variation of the internal capacity.

A single container loading problem is a problem to effectively load boxes in a three-dimensional container. There are many researchers in this problem try to find the best solution to solve the problem with feasible computation time and to develop some models to solve real case problem. Heuristics are the most method used to solve this problem since the problem is an NP-hard. In this paper, we introduce a hybrid greedy algorithm and simulate annealing algorithm to solve a real container loading problem in one flexible packaging company in Indonesia. Validation is used to show that the method can be applied practically. We use seven real cases to check the validity and performance of the model. The proposed method outperformed the solution developed by the company in all seven cases with feasible computational time.