Papers by Rachmawati Wangsaputra
Lecture notes in mechanical engineering, Dec 31, 2022
Quality Technology & Quantitative Management
Journal of Industrial Engineering and Management, Nov 28, 2022
Purpose: The role of speculators in distributing products across rural areas is increasing the po... more Purpose: The role of speculators in distributing products across rural areas is increasing the poverty rate in Indonesia. Therefore, this study aims to develop a conceptual framework of the rural logistics system model to influence the welfare and sustainability of farmers. Design/methodology/approach: Conceptual framework was used to evaluate logistics and supply chain networks. The method consists of developing stages based on four components, namely network structure, management, resources, and business processes. Furthermore, it also proposed the management function of the rural logistics system models. Findings: The model of a rural logistics system obtained in this study consists of 1) a trade related to the network of business, 2) a freight, related to the flow of goods, and 3) management functions related to crucial activities in rural logistics management. Research limitations/implications: This model is conceptual, therefore future studies must accommodate optimizing models to predict the performance of rural logistics systems when they are applied in Indonesia. Practical implications: This study promotes the actors in intermediaries of the rural logistics system to synergize the distribution of goods effectively and efficiently. It also reduces the role of speculators in product distribution in form of availability and price in rural areas. Social implications: This model is a strategy to achieve the Rural Sustainable Development Goals (Rural-SDGs) agenda and complements the Blueprint of The National Logistics System. Originality/value: There are fewer studies in rural logistics compared to other fields such as agricultural logistics, food logistics, disaster logistics, etc. Therefore, this study organizes the actors in the rural logistics network and plans management functions for the efficient distribution of products across Indonesia. It also raises the awareness of logistics management to improve the welfare of rural communities.
A report submitted by Rachmawati Wangsaputra to the Research and Creative Productions Committee i... more A report submitted by Rachmawati Wangsaputra to the Research and Creative Productions Committee in 2005 on generating tool paths for machining sculptured surfaces
2022 6th International Conference on Robotics, Control and Automation (ICRCA)
Lecture Notes in Mechanical Engineering, 2019
This paper is a second paper on the use of Exponential distribution in competing risk problems. T... more This paper is a second paper on the use of Exponential distribution in competing risk problems. The difference is this model is developed using Gamma distribution as its prior distribution. For the cases where the failure data together with their causes of failure are simply quantitatively inadequate, time consuming and expensive to perform the life tests, especially in engineering areas, Bayesian analysis approach is used. This model is limited for independent causes of failure. In this paper our effort is to introduce the basic notions that constitute an exponential competing risks model in reliability using Bayesian analysis approach and presenting their analytic methods. Once the model has been developed through the system likelihood function and individual posterior distributions then the parameter of estimates are derived. The results are the estimations of the failure rate of individual risk, the MTTF of individual and system risks, and the reliability estimations of the individual and of the system of the model.
IOP Conference Series: Materials Science and Engineering, 2018
A hybrid assembly differentiation flow shop is a three-stage flow shop consisting of Machining, A... more A hybrid assembly differentiation flow shop is a three-stage flow shop consisting of Machining, Assembly and Differentiation Stages and producing different types of products. In the machining stage, parts are processed in batches on different (unrelated) machines. In the assembly stage, each part of the different parts is assembled into an assembly product. Finally, the assembled products will further be processed into different types of final products in the differentiation stage. In this paper, we develop a batch scheduling model for a hybrid assembly differentiation flow shop to minimize the total actual flow time defined as the total times part spent in the shop floor from the arrival times until its due date. We also proposed a heuristic algorithm for solving the problems. The proposed algorithm is tested using a set of hypothetic data. The solution shows that the algorithm can solve the problems effectively.
2018 IEEE International Conference on Industrial Engineering and Engineering Management (IEEM), 2018
A lease contract (LC) model for a fleet of dump truck with availability target is developed in th... more A lease contract (LC) model for a fleet of dump truck with availability target is developed in this paper. Under this LC, the Iessor provides a maintenance service including preventive maintenance (PM) and corrective maintenance (CM) within the contract period, and offers a price discount if the Iessee leases for more than one equipment. To sustain high performance of the fleet, we proposed an availability target as performance of the LC. In addition, the Iessor gives some incentive in term of a price discount if the Iessee leases more dump trucks. The study is done from the Iessor’s viewed point and hence the decision problems of interest are to determine the tresshold between total cost and the price which is dependent on the fleet size. The optimal decisions are obtained to minimize the total cost. To illustrate the theory and optimal decisions, we provide numerical examples in the last section.
Lecture Notes in Mechanical Engineering, 2019
In this paper we present a mathematical model of technology transfer. The model takes form in a s... more In this paper we present a mathematical model of technology transfer. The model takes form in a system of differential equations. We assume that there are two competing followers. We also assume a logistic growth function of technological development for all parties involved. Most papers of similar model assume a crisp initial condition for each of the followers. Here we use the assumption that the fuzziness of the input in the process propagates to the output. Some numerical examples are presented to illustrate properties of the model. We found that in some circumstances fuzzy initial condition might result in a crisp long-term solution.
Lecture Notes in Mechanical Engineering, 2019
A heavy-duty equipment, such as a dump truck operated in a mining industry experiences degradatio... more A heavy-duty equipment, such as a dump truck operated in a mining industry experiences degradation caused by usage and operational condition. There are operational conditions influencing dump truck failure rate, such as load weight, road inclination and environmental conditions. In this research, dump truck failure is modeled using proportional hazard model (PHM) considering operational condition, age, and usage factors. Maintenance action is needed to control continuing failure to maintain the equipment always in good operation condition. A dump truck will need both preventive and corrective maintenance actions in order to be readily available for operation in mining industry. Considering that dump trucks are very complex and expensive, maintenance will be economical if it is conducted by an agent. In this research maintenance contract involved 2 parties, the owner and the agent. The agent offers 3 (three) options of maintenance contracts: (i) in house preventive maintenance conducting by the owner and corrective maintenance conducted by the agent (ii) both preventive and corrective maintenance conducted by the agent, (iii) preventive maintenance by the agent and in-house corrective maintenance by the owner, and determination of the optimal contract price for each option. Next the owner will choose the best option based on several options offered by the agent. The model used for decision is formulated by Nash game theory.
Journal of Industrial Engineering and Management, 2021
Virgin Coconut Oil BUMDes Bumi Lestari has supply chain and demand chain activities. There was an... more Virgin Coconut Oil BUMDes Bumi Lestari has supply chain and demand chain activities. There was an imbalance in oil production which reached 1,000 liters per month with a relatively low sales volume. The aim of this research is to apply demand chain management performance assessment on a Virgin Coconut Oil BUMDes Bumi Lestari, Desa Selemadeg, Kec. Selemadeg, Kab. Tabanan. The method used in this research is performance appraisal with the demand chain operation reference model approach, AHP weighting, OMAX, traffic light system, and SWOT analysis. The results showed that the demand chain management performance in the BUMDes Bumi Lestari Virgin Coconut Oil business was 6,388 which was in the range of 3.01 ≤ 6,388 ≤ 8.00 (quite good). The results of the SWOT analysis recommend improvements in performance such as maintaining cooperation with suppliers, maintaining cooperation with farmer groups, maintaining the quality of Virgin Coconut Oil, improving customer service, adding workers to...
Lecture Notes in Mechanical Engineering, 2019
Connector clamp is an essential component which effects transformer 150/20 kV performance in an e... more Connector clamp is an essential component which effects transformer 150/20 kV performance in an electricity substation. Previous research developed a Statistical Process Control (SPC) chart combine with a Back Propagation Neural Network (BPNN) for determining the condition of connection clamp. Connector clamp condition assessment is designed using clamp and conductor’s temperature as parameters at certain load values to shape limit-1 (3σ) and limit-6 (1.645σ). Its condition is necessary to be controlled effectively and efficiently. This paper improves the level of neural network. This research develops an Adaptive Resonance Theory-2 Neural Network with advantages that can renew the knowledge by adding new data for learning.
Sebuah model manajemen performa dibutuhkan oleh institusi pengelola klaster industri sebagai pand... more Sebuah model manajemen performa dibutuhkan oleh institusi pengelola klaster industri sebagai panduan penyelenggaraan layanan. Perubahan jenis layanan akan menyebabkan perlunya penyesuaian model manajemen performa. Penelitian ini mengembangkan instrumen asesmen model manajemen performa & perubahan Carpinetti & Lima untuk penyelenggaraan layanan kolaborasi antar perusahaan dalam rantai pasok (layanan joint action Cluster Supply Chain (CSC)). Pengembangan instrumen diawali dengan pengembangan penggunaan model Carpinetti & Lima. Kerangka kerja CSC dianalisis dan dijalankan sesuai dengan model Carpinetti & Lima. Hasil akhirnya adalah variabel-variabel dalam model Carpinetti & Lima yang didefinisikan ulang menurut konsep CSC. Variabel yang didefinisikan kembali ini akan mempengaruhi keluaran pertanyaan atau pernyataan yang akan digunakan sebagai instrumen asesmen. Setelah instrumen asesmen didapatkan, dilakukan ujicoba penggunaan instrumen di lingkungan industri kecil dan technopark, anal...
Heliyon, 2021
Many firms prefer to lease rather than to buy a product as leasing does not require a large inves... more Many firms prefer to lease rather than to buy a product as leasing does not require a large investment cost. Leased products can be brand new products or remanufactured products (henceforth referred to as reman products). The market of reman products has grown in the last two decades due to the increasing concern of sustainability issues. This in turn brings a positive impact on the demand of leased reman products. In general, the reliability of the reman product is closed to the reliability level of a new product. To guarantee a high performance of a leased reman product, a more effective maintenance strategy is required. In this paper, we investigate a condition-based maintenance (CBM) policy to be used for maintaining a lease reman product. With the CBM policy, the condition of the reman product is monitored and controlled periodically, and hence it can avoid failure before it occurs and reduce unnecessary maintenance actions. This in turn improves the performance of the leased reman product and provides more value to the lessee. The lessor will incur a penalty cost if the performance is below a predefined threshold value. We obtain the optimal inspection interval minimizing the expected total cost and provide the numerical example for illustrating the optimal solution.
International Journal of Technology, 2020
This paper addresses a batch scheduling problem for a three-stage hybrid flowshop consisting of a... more This paper addresses a batch scheduling problem for a three-stage hybrid flowshop consisting of a machining stage processing common and unique components on unrelated parallel machines, an assembly stage combining the components into assembled products with complex assembly structures, and a differentiation stage processing the assembled products on dedicated machines to produce different product types. The common components are the same for all products and are processed in batches, while the unique components are dedicated to respective given product types and are processed individually (one-by-one component). The goal is to schedule all the products with different assembly structures to minimize total actual flow time (TAFT) defined as total time interval of components to be processed from their arrival times to their common due date. A non-linear programming model is proposed, where small size problems can be solved optimally using the LINGO software, and large size problems is to be solved using a heuristic algorithm. The proposed algorithm consists of two sub-algorithms. The first one is constructed using a shortest processing time (SPT) based heuristic to get a job sequence as an initial solution and the second one is to improve the initial solution using the variable neighbourhood descent (VND) method with neighbourhood insert and swap move operators. In solving the problem with the algorithm, two scenarios arise, e.g., the same and the different sequences for all stages. A set of hypothetical data is generated for different hierarchical assembly structures to test the model and the algorithm, and the results show that the different sequences for all stages obtain solutions with better performances than the same ones.
IOP Conference Series: Materials Science and Engineering, Mar 1, 2018
This study aims to develop a combined economical lot size model between supplier and manufacturer... more This study aims to develop a combined economical lot size model between supplier and manufacturer for imperfect production processes with probabilistic demand patterns and constant lead times. The supplier side produces the product within a certain time interval then sent to the manufacturer with a certain amount of lot size. Imperfect supplier production systems are characterized by the probability of defective product (γ). The model decision variables are the lot size of the manufacturer's ordering, supplier lot size, and the reorder point of the manufacturer. The optimal decision variables are obtained by minimizing the total expected cost of the combined costs between the suppliers and the manufacturers borne by both parties. The model is built compared to the transactional partnership model, in which the supplier does not participate in the efficiency of its inventory system. A numerical example is given as an illustration of the JELS model and the transactional partnership model. Sensitivity analysis of the model is done by changing the parameters aimed at analyzing the behavior of the developed model.
IOP Conference Series: Materials Science and Engineering, 2019
The hybrid assembly differentiation flow shop is a three-stage flow shop system with machining, a... more The hybrid assembly differentiation flow shop is a three-stage flow shop system with machining, assembly and differentiation stages. The machining stage produces k parts in independently unrelated dedicated machines. After k parts of a job completed, they are assembled at the assembly stage and assigned to dedicated machines for a final process. At the end, several types of finished products are resulted. The finished products should be delivered at their respective different due dates. The problem is to find a schedule considering multi due dates, and the criterion of minimizing total actual flow time. This paper proposes a model for job scheduling in a hybrid assembly differentiation flow shops and its algorithm for solving the problems. The initial solution is defined using SPT-based heuristic and it is optimized using variable neighbourhood descend method. The proposed model is tested using a set of hypothetic data. The solution shows that the algorithm can solve the problems ef...
Journal of Advanced Manufacturing Systems, 2019
This paper discusses production scheduling problems on CNC-machines having a set of cutting tools... more This paper discusses production scheduling problems on CNC-machines having a set of cutting tools in a Flexible Manufacturing System (FMS) to maximize the cutting tools utilization. This objective has been selected because it is frequently found that cutting tools are under-utilized as they are used far below their respective lifetime limits. We will consider the situation where several identical CNC-machines are operated in an FMS; each of which is equipped with the same cutting tool configuration. The jobs to be scheduled are machining parts, and each of the parts requires one to two stages of processes, and each of the stages consists of several sequential operations, where a specific operation requires a certain type of cutting tool. Whenever a certain cutting tool is being used, the time consumption will be accumulated to calculate its remaining lifetime. The assignment of an operation to a particular CNC-machine will be based on the sufficiency of the cutting tool remaining li...
IOP Conference Series: Materials Science and Engineering, 2016
A mining company needs high availability of dump trucks used to haul mining materials. As a resul... more A mining company needs high availability of dump trucks used to haul mining materials. As a result, an effective maintenance action is required to keep the dump trucks in a good condition and hence reducing failure and downtime of the dump trucks. To carry out maintenance in-house requires a high intensive maintenance facility and high skilled maintenance specialists. Often, outsourcing maintenance is an economic option for the company. An external agent takes a proactive action with offering some maintenance contract options to the owner. The decision problem for the owner is to decide the best option and for the agent is to determine the optimal price for each option offered. A non-cooperative game-theory is used to formulate the decision problems for the owner and the agent. We consider that failure pattern of each truck follows a non-homogeneous Poisson process (NHPP) and a queueing theory with multiple servers is used to estimate the downtime. As it involves high complexity to model downtime using a queueing theory, then in this paper we use a simulation method. Furthermore, we conduct experiment to seek for the best number of maintenance facilities (servers) which minimises maintenance and penalty costs incurred to the agent.
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Papers by Rachmawati Wangsaputra