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All Journal VALENSI E-Jurnal Matematika Matematika: Jurnal Teori dan Terapan IJEBD (International Journal Of Entrepreneurship And Business Development) International Journal of Supply Chain Management International Journal of Research in Community Services International Journal of Global Operations Research Jurnal Matematika Integratif
Julita Nahar, Julita
Departemen Matematika, Fakultas MIPA, Universitas Padjadjaran
Chemistry Computer Science & IT Control & Systems Engineering Decision Sciences, Operations Research & Management Economics, Econometrics & Finance Education Electrical & Electronics Engineering Energy Engineering Environmental Science Industrial & Manufacturing Engineering Mathematics Mechanical Engineering Social Sciences Transportation Other

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Implementation of Jackson Queueing Network in General Polyclinic and Dental Polyclinic Patient Services at Jelekong Health Center Rasyid, Thariq Ahmad; Supian, Sudradjat; Nahar, Julita
International Journal of Global Operations Research Vol. 4 No. 4 (2023): International Journal of Global Operations Research (IJGOR), Nopember 2023
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v4i4.229

Abstract

The buildup in the service system is generally caused because service facilities cannot meet service needs, so service users need time to use the facilities. Health Center is one of the facilities that provide services in the health sector. However, the number of doctors needed in health centers in Indonesia has yet to be met, and the number of patients who are never empty every day causes a buildup in the service system. The application of the service network system using the open Jackson queueing network can model the optimal service system and analyze its performance. The observation method was used to observe patients' arrival and departure times at the Jelekong Health Center, especially in the registration section, general polyclinic, dental polyclinic, and pharmacy, for three days. There was an increase in patient waiting time before being served and time in the system at the general polyclinic after implementation, so one additional service facility was added. Meanwhile, the dental polyclinic experienced decreased patient waiting time before being served and time in the system, so there was no need to add service facilities.
Inventory Control for Eyeglass Supply Using the P Model Based on Sales Products Sales Forecasting (Case Study: Merry Optic Bandung) Suripto, Adi; Nahar, Julita; Napitupulu, Herlina
International Journal of Global Operations Research Vol. 4 No. 4 (2023): International Journal of Global Operations Research (IJGOR), Nopember 2023
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v4i4.255

Abstract

Inventory is a resource owned by the company to be used in the production process to meet consumer demand. Companies must be able to control inventory appropriately in order to avoid excess or shortage of inventory by using inventory control. Inventory control is a necessary part of a company that requires an appropriate inventory policy to meet uncertain needs. Based on this background, this study discusses the single item inventory model in the form of photochromic glasses at Merry Optik to find the optimal total inventory cost. In meeting the uncertain needs of the company, the Additive Decomposition forecasting method is used in order to find out the forecast sales data pattern in the future. Uncertain demand causes the inventory system to be probabilistic, so it is necessary to carry out probabilistic inventory control. The P model of the case of back orders was chosen because the range of ordering periods is fixed and the company can buy inventory when it runs out before the time the inventory order is made so that buyers can wait until the inventory arrives. By using Model P for the case of back orders, the company can obtain the period between orders, the total cost of inventory, and the optimal level of service. Based on the results of this study, a pattern of sales forecast data is obtained which repeats every 12 months. Companies must order glasses within a period of 32 days between orders so that it is optimal and able to provide a reduction in the total inventory cost of IDR 21,828,771 with a service level of 95%. Companies can save on inventory costs if they use shorter periods between orders. The total cost of inventory can be more optimal if the company reduces the cost of storing inventory in the warehouse.
Supply Control Of Oil Filter Spareparts Using EOQ And Min-Max Methods Based On Sales Forecast (Case Study: PT Astra International Tbk Soekarno Hatta) Arfemitha, Nurlia Asih; Supian, Sudradjat; Nahar, Julita
International Journal of Global Operations Research Vol. 5 No. 1 (2024): International Journal of Global Operations Research (IJGOR), February 2024
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v5i1.284

Abstract

Planning and controlling product inventory is very important for a company to ensure demand is met and maximize profits from sales effectively and efficiently. In addition, inventory planning and control are carried out to prevent excess or shortage of inventory. This study aims to predict sales and calculate inventory control to overcome excess stock and increased inventory costs on oil filter spare parts. The forecasting method used is Holt's Double Exponential Smoothing method to determine the number of sales of the four types of oil filter spare parts in the future and overcome the problem of oil filter spare parts inventory using the EOQ and Min-Max methods. Based on the research results, the resulting forecasting is accurate and the EOQ method results in a lower total inventory cost than the Min-Max method.
Multi-objective Optimization Model for Medical Waste Supply Chain Management Without Landfill Tax During COVID-19 In Indonesia Vionanda, Aurellya; Chaerani, Diah; Nahar, Julita
Jurnal Matematika Integratif Vol 20, No 1: April 2024
Publisher : Department of Matematics, Universitas Padjadjaran

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24198/jmi.v20.n1.55261.117-133

Abstract

The COVID-19 pandemic has brought various problems into our daily life, and one of them is an increase in the volume of medical waste, which poses a risk to the environment and health.An evaluation of how optimal the supply chain management of medical waste as a whole can assist in the development of medical waste management and policy making.  In this paper, the  study on observing and reformulating the existing medical waste supply chain optimization model using Mixed Integer Linear Programming (MILP) is discussed. This study is done by modifying the objective function and the constraints with considering elimination of the landfill tax variable. The resulted model is also a multi-objective optimization problem. To this end, the Lexicographic Method is employed to obtained the optimal solution. In this model, the most prioritizes that is considered in the environmental condition to the medical waste supply chain. A numerical experiment is done in this paper which it results suggests two things, first, the cost of medical waste processing is much greater than its revenue, and second, the waste processing through incineration is not favorable. Thus, it can be concluded that this study provides a modified medical waste optimization model and decisions in determining the combination of the amount and method for each subtype of medical waste to be processed by maximizing profit and the amount of waste sent to the landfill.
Linear Integer Optimization Model for Two-Stage Guillotine Cutting Stock Problem Using Branch and Bound Method in the Garment Industry Lesmana, Eman; Nahar, Julita; D. P, Annisa
International Journal of Global Operations Research Vol. 1 No. 1 (2020): International Journal of Global Operations Research (IJGOR), February 2020
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v1i1.17

Abstract

This paper discusses the Two-Stage Guillotine Cutting Stock Problem (2GCSP) in the garment industry, namely how to determine the two-stage guillotine pattern that is used to cut fabric stocks into several certain size t-shirt materials that are produced based on the demand for each size of the shirt. 2GCSP is modeled in the form of Linear Integer Optimization and finding solutions using the Branch and Bound method. In this paper also presented a Graphical User Interface with Maple software as an interactive tool to find the best fabric stock cutting patterns. The results show that the optimal solution can be determined by solving numerically using the Branch and Bound method and Maple optimization packages. The solution is shown with an illustration of the pattern and the amount of fabric cut based on the pattern.
Performance Analysis of Service System in the Pediatric Clinic Department at Rumah Sakit Umum Daerah (RSUD) Sumedang Annisa, Diana; Supian, Sudradjat; Nahar, Julita
International Journal of Global Operations Research Vol. 4 No. 3 (2023): International Journal of Global Operations Research (IJGOR), August 2023
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v4i3.233

Abstract

A service is considered good if it can provide fast service so that customers are not left waiting for too long. If a service has a long queue, then causing customers to wait for a long time, their satisfaction and trust levels may decrease. Rumah Sakit Umum Daerah (RSUD) Sumedang offers various outpatient services, including a pediatric clinic. Almost every day, a significant number of patients come to the pediatric clinic, resulting in considerable waiting time for patients. The service discipline used is First Come First Serve, and the service system falls under the multi-phase category, where each patient has to go through several stages to receive optimal service. This research will focus on the service system in the pediatric clinic at each stage, starting from registration, examination by the doctor, to medication collection at the pharmacy. The research findings indicate that the workload at the pharmacy counter is very high, while it is significantly low at the registration counter, resulting in suboptimal performance of the service system at these two stages. The performance of the service system can be improved by reducing service facilities at the registration counter and adding resources at the pharmacy counter. 
Analysis of Transportation Mode Selection at Padjadjaran University Campus Jatinangor Using Fuzzy Analytic Hierarchy Process (FAHP) Method Bhagawanta, Hanif Ibnu; Hertini, Elis; Nahar, Julita
International Journal of Global Operations Research Vol. 4 No. 3 (2023): International Journal of Global Operations Research (IJGOR), August 2023
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v4i3.239

Abstract

Transportation has become a very attached part of human daily life as a means of mobility in activities. Each transportation user has their own goals in transportation, so the mode of transportation travel takes effect in making it easier for users to reach their goals. At Padjadjaran University, Campus Jatinangor, there are several alternative modes of transportation, namely Odong-Odong, Easy Bike, conventional motorcycle taxis, and online motorcycle taxis. Each alternative mode of transportation has varying characteristics and user needs, so it is necessary to make the right decision. This study uses the Fuzzy Analytic Hierarchy Process (FAHP) method to determine priority criteria and alternative modes of transportation suitable for use on campus. The criteria used in this study include tariff, time, comfort, safety, and environmental responsibility. The results in this study obtained the order of priority criteria, is safety, comfort, time, tariff, and environmental responsibility. Moreover, the alternative priority orders are Odong-Odong, online motorcycle taxis, Easy Bike, and conventional motorcycle taxis. That can be interpreted as the safety criteria are the most considered, and Odong-Odong is the most appropriate alternative to be used at Padjadjaran University, Campus Jatinangor.
Implementation of Open Jackson Queueing Network on Customer Service and Ticket Service at Pasar Senen Train Station Jakarta Anisa Kisti, Vuji; Supian, Sudradjat; Nahar, Julita
International Journal of Global Operations Research Vol. 6 No. 1 (2025): International Journal of Global Operations Research (IJGOR)
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v6i1.344

Abstract

The increase in the number of users of train services causes a buildup in various service facilities, which affects the quality and efficiency of services. This study aims to optimize the service system at Pasar Senen Station by applying the open Jackson queueing network model using the First Come First Serve discipline. The data used includes external arrival times, service times, and cost components at three main facilities: customer service locket, ticket counter locket, and ticket vending machine locket. The results showed that optimal performance was achieved at the ticket counter (M/M/3) and ticket vending machine (M/M/2) with a busy level of 82.14% and 62.66% respectively. Simulation of reducing the number of servers in customer service to two (M/M/2) results in a busy level of 77.95% and lower total costs.
Application of Queue Theory in Campus Transportation at Padjadjaran Jatinangor University Using a Multiserver Queue System Model Aufhar, Ihkam Amalul; Sudradjat; Nahar, Julita
International Journal of Global Operations Research Vol. 6 No. 3 (2025): International Journal of Global Operations Research (IJGOR), August 2025
Publisher : iora

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.47194/ijgor.v6i3.386

Abstract

Trasnportation system on campus is an important aspect that supports the mobility of the Academic Community and the relations or partners of Padjadjaran University. Currently, Padjadjaran Jatinangor University provides several public transportation facilities that can be used around campus area, namely conventional motorcycle taxis, Beam electric bicycles, and campus transportation in the form of buses. Based on the results of a survey conducted by the author, campus transportation is a facility of public transportation that is more often used and in demand by the Academic Community compared to the other two facilities of public transportation. This study aims to analyze the performance of the passenger queuing system on that campus transportation using a multiserver queue system model. Data in the arrival rate of bus passenger ( ) and the rate of bus service ( ) were collected through direct observation. The results of the study showed that during the operating hours at 07:00-08:00, routes A, B, and C are optimal with number of buses as many as 5, 5, and 6 respectively. Then, during operating hours at 09:45-10:45, routes B and C are optimal with number of buses each as many as 3 buses. As for route A, it is necessary to reduce the number of buses by 1 piece. Then during operating hours at 13:00-14:00, all routes need to be reduced to 1 bus each.
Co-Authors Adi Suripto, Adi Anisa Kisti, Vuji Anita Triska Annisa, Diana Apriliza, Poppy Arfemitha, Nurlia Asih Aufhar, Ihkam Amalul Bhagawanta, Hanif Ibnu D. P, Annisa Diah Chaerani Elis Hertini Elis Hertini Eman Lesmana Farid H. Badruzzaman Felix Daniel Budiman Hapiz Jasman Herlina Napitupulu Iin Irianingsih Muhammad Deni Johansyah Nazihah, Nazihah Nurlelasari Nurlelasari PUTRI NUR PRASETIA Rasyid, Thariq Ahmad Ruby Larasati Ruby Larasati, Ruby Sri Purwani Sudradjat Supian, Sudradjat Tri Mayanti Vionanda, Aurellya Zulfikar Zulfikar