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All Journal International Journal of Science and Engineering (IJSE) Waste Technology Journal of Engineering and Technological Sciences Proceeding of the Electrical Engineering Computer Science and Informatics International Journal of Supply Chain Management PRISMATIKA: Jurnal Pendidikan dan Riset Matematika Indonesian Journal of Electrical Engineering and Computer Science Jurnal Sains dan Edukasi Sains Journal of Fundamental Mathematics and Applications (JFMA)

Widowati, Widowati

Department Of Mathematics, Faculty Of Sciences And Mathematics, Diponegoro University, Semarang

Author-ID : 3969069

Computer Science & IT Decision Sciences, Operations Research & Management Education Electrical & Electronics Engineering Engineering Environmental Science Industrial & Manufacturing Engineering Materials Science & Nanotechnology Mathematics Physics Transportation Other

Published : 12 Documents Claim Missing Document

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ANALISIS PENGARUH ANGKA HARAPAN LAMA SEKOLAH, RATA-RATA LAMA SEKOLAH, DAN PENGELUARAN PER KAPITA TERHADAP INDEKS PEMBANGUNAN MANUSIA A. Jauhar Mahya; Widowati Widowati
Prismatika: Jurnal Pendidikan dan Riset Matematika Vol 3 No 2 (2021): Prismatika: Jurnal Pendidikan dan Riset Matematika
Publisher : Program Studi Pendidikan Matematika

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33503/prismatika.v3i2.1180

The Human Development Index (HDI) is one of the data and information used by local governments to measure the achievement of human development. HDI is formed by three basic dimensions, namely a long and healthy life, knowledge, and a decent standard of living. This study explain whether there is an influence and to obtain the magnitude of the influence of the expected number of years of schooling, the average length of schooling, and the per capita expenditure together on the Human Development Index in Central Java Province. This study was completed using multiple linear regression analysis with the help of SPSS 1.6 (Statistical Package for Social Sciences) software. The results of this study indicate that the expected length of schooling, average length of schooling, and per capita expenditure have a significant effect on the human development index, which is 97.8% and only 2.2% is influenced by other factors.

Linear Parameter-Varying Versus Linear Time-Invariant Reduced-Order Controller Design for Turboprop Aircraft Dynamics Widowati Widowati; Bambang Riyanto; Hari Muhammad
Journal of Engineering and Technological Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.eng.sci.2012.44.2.5

The applicability of parameter-varying reduced-order controllers to aircraft models is proposed. A generalization of the balanced singular perturbation method of the linear time-invariant (LTI) system was used to reduce the order of the linear parameter-varying (LPV) system. Based on the reducedorder model, a low-order LPV controller was designed using the Hâˆž synthesis technique. The performance of the reduced-order controller was examined by applying it to the lateral-directional control of a 20th-order aircraft model. Furthermore, the time responses of the closed-loop system with several reducedorder LPV controllers and a reduced-order LTI controller were compared. The simulation results show that an , 8th -order LPV controller can maintain stability and provide the same level of closed-loop system performance as a full-order LPV controller. This was not the case with the reduced-order LTI controller, which cannot maintain stability and performance for all allowable parameter trajectories.

The Application of Integrated Multi Trophic Aquaculture (IMTA) Using Stratified Double Net Rounded Cage (SDFNC) for Aquaculture Sustainability Sapto P. Putro; Widowati Widowati; Suhartana Suhartana; Fuad Muhammad
International Journal of Science and Engineering Vol 9, No 2 (2015)
Publisher : Chemical Engineering Diponegoro University

The increase of fishery production nationally and internationally may impact on the potential emergence of a variety of environmental problems. The application of sustainable aquaculture is urgently needed by breeding fish for commercial purposes in a manner such that it has a minimum impact on the environment, contributing to the development of local communities and generating economic benefits. The design of the cage and farming practice in aquaculture activities are the important steps to ensure that farming activity is still observed in order to anticipate the risk of organic enrichment caused by the activities. The application of Integrated Multi-Trophic Aquaculture (IMTA) on the Stratified Double Floating Net Cage (SDFNC) integrated with biomonitoring are an appropriate solution to the ongoing productive farming practices. IMTA is an aquaculture practice using more than one species of biotas which have ecologically mutual relationship as a part of the food chain in the area at the same time. The application of IMTA allows farmers to get several aquaculture products in the same area without increasing the horizontal area of the farms. At first, the SDFNC has been applied for farming Cyprinus carpio and Tilapia niloticus as polyculture system in freshwater ecosystem of Rawapening Lake, Central Java. Its operation has been able to increase the production capacity of at least 75% of conventional cages. The application of SDFNC-IMTA using milkfish (Chanos Chanos), seaweed (Kappaphycus alvarezii), and white shrimp (Litopenaeus vannamei) has been able to minimize the impact and maintain the water ecosystem in the Gulf Awerange, South Sulawesi.

Analysis of Crout, Lu, Cholesky Decomposition, and QR Factorization: A Case Study On The Relationship Between Abiotic (Carbon and Nitrogen) and Biotic (Macrobenthos Diversity) Factors Widowati Widowati
Waste Technology Vol 2, No 2 (2014)
Publisher : Diponegoro University

Many real world problems can be represented by a system of linear equations, such as in the field of ecology, i.e, the relationship of carbon and nitrogen with macrobenthos diversity. There are many methods to solve linear equations system, then it is necessary to do an analysis of which method is the best so that the user can choose the most efficient method. The methods that will be analyzed are LU, Crout, Cholesky decomposition, and QR factorization. From the calculation of arithmetic operations obtained Cholesky decomposition method is the most efficient method because it has the fewest arithmetic operations. Further, to verify the proposed method we demonstrated simulation with a case study of the relationship between carbon and nitrogen with the macrobenthos diversity based on data from the area of polyculture system and PT. Kayu Lapis Indonesia coastal, Mororejo village subdistrict Kaliwungu district Kendal. From the simulation resultsis obtained that computing time the smallest is the Cholesky decomposition is equal to 1.4664 seconds, which means that the Cholesky decomposition is the most efficient method than the method of LU, Crout decomposition and QR factorization. Keywords— LU Decomposition, Crout decomposition, QR factorization, Cholesky decomposition, Carbon, Nitrogen, Macrobenthos

Probabilistic Programming with Piecewise Objective Function for Solving Supplier Selection Problem with Price Discount and Probabilistic Demand Sutrisno Sutrisno; Sunarsih Sunarsih; Widowati Widowati
Proceeding of the Electrical Engineering Computer Science and Informatics Vol 7, No 2: EECSI 2020
Publisher : IAES Indonesia Section

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/eecsi.v7.2038

In this article, a supplier selection problem with price discount and probabilistic demand was solved by formulating a new probabilistic programming model with a piecewise objective function. The proposed model was able to be used by the decision-maker to calculate the optimal decision involving the appropriate raw material quantity to be ordered from each supplier to have minimal total procurement cost. A numerical experiment was conducted with some randomly generated data and the results showed the supplier selection problem was solved by the proposed model and the optimal decision value is achieved.

Implementasi Microsoft Power BI Dalam Memantau Kehadiran dan Transportasi Pegawai Shabrina Zata Yumni; Widowati Widowati
Jurnal Sains dan Edukasi Sains Vol. 4 No. 1 (2021): Jurnal Sains dan Edukasi Sains
Publisher : Faculty of Science and Mathematics, Universitas Kristen Satya Wacana, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24246/juses.v4i1p1-8

Absensi karyawan merupakan suatu hal yang penting dalam operasional kantor. Absensi secara tidak langsung dapat menggambarkan pola kerja dari karyawan yang terdapat di suatu perusahaan. Absensi juga dapat memengaruhi hal-hal lain, salah satunya adalah keproduktivitasan karyawan. Jika tingkat produktivitas karyawan dalam suatu perusahaan relatif tinggi, maka karyawan mampu memenuhi target yang telah ditentukan oleh perusahaan. Dengan informasi dari data-data tersebut akan diperoleh data yang besar dan belum di proses. Agar data tersebut dapat diolah menjadi informasi yang bernilai, dibutuhkan sebuah bisnis intelligence (BI) software yang dapat memvisualisasikan data-data tersebut sehingga dapat menampilkan informasi mengenai data kehadiran dan data transportasi. Penelitian ini bertujuan untuk mendapatkan dashboard yang menggambarkan mengenai data kehadiran sehingga perusahaan mengetahui trend dari kehadiran mengenai jam kehadiran hingga status kehadiran karyawan dan data transportasi dari pengeluaran tiap jenis kendaraan hingga tiap kode perjalanan yang nantinya akan mempermudah perusahaan dalam memantau. Penelitian ini dilakukan menggunakan BI software, yaitu Microsoft Power BI untuk dapat memvisualisasikan mengenai data yang didapat dan Microsoft SQL Server Management Studio untuk membuat gudang data. Hasil dari penelitian ini adalah dashboard daily attendance dengan grafik Clock In memperlihatkan presensi terbanyak pada pukul 10.00 dan grafik Clock Out memperlihatkan presensi terbanyak pada pukul 18.00. Lalu, dashboard trip dengan informasi total tarif terbesar berdasarkan kode perjalanan adalah “19AC0113” dengan total melebihi Rp. 9.000.000,00 dari karyawan PT. ATG dan dashboard trip information memperlihatkan penggunaan transportasi terjadi pada tiga kota, yaitu Jakarta, Bandung, dan Surabaya dengan total tarif terbesar terdapat di Jakarta sebesar Rp. 99.552.000.

Fuzzy Expected Value Approach to Solve Integrated Supplier Selection and Inventory Control Problem in Fuzzy Environment Sutrisno Sutrisno; Widowati Widowati; R. Heru Tjahjana
International Journal of Supply Chain Management Vol 7, No 3 (2018): International Journal of Supply Chain Management (IJSCM)
Publisher : International Journal of Supply Chain Management

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (13.161 KB)

In a production and inventory planning management, the future parameters like future demand, future product buying cost, future transport cost and future holding cost are obviously unknown/uncertain. To determine the optimal strategy in uncertain condition, a method that can handle the uncertainty of parameters is needed. If the historical data of the uncertain parameters are known then they can be approached by using probability distribution, but if there is no historical data then it cannot be used. In this paper, we propose a new mathematical optimization model with fuzzy parameters to solve an integrated supplier selection problem and inventory control problem in fuzzy environment where fuzzy variables are used to approach the uncertain parameters. To solve the corresponding optimization problem, we use fuzzy expected value based integer quadratic programming where the fuzzy variables are approximated by fuzzy expected value. From the numerical experiment results, the optimal strategy i.e. the optimal supplier and the optimal stored product volume were obtained and the actual inventory level followed the desired level with minimal total expected cost.

Joint Decision on Integrated Supplier Selection and Stock Control of Inventory System Considering Purchase Discount Widowati Widowati; Sutrisno Sutrisno; R. Heru Tjahjana
International Journal of Supply Chain Management Vol 6, No 4 (2017): International Journal of Supply Chain Management (IJSCM)
Publisher : International Journal of Supply Chain Management

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (13.161 KB)

Stock control and supplier selection are two vital parts on supply chain and management. Integrating these parts by solving them simultaneously is a good idea for cost reducing. Furthermore, if some suppliers give a purchase discount for their product, how to determine the optimal strategy is interesting. In this paper, we propose a mathematical model in a mixed integer quadratic programming with piecewise objective function to determine the optimal strategy for integrated supplier selection and stock control of multiproduct inventory system considering purchase discount. This stock control refers to bring the stock level of each product to a reference level given by decision maker. We formulate the model in two environments which are deterministic where all parameters are known and stochastic where the demand is random. Two numerical experiments are performed to evaluate the model. From the results, the optimal strategy was generated i.e. the optimal product volume purchased from each supplier and the stock level of each product follows the reference level.

Control of inventory system with random demand and product damage during delivery using the linear quadratic gaussian method Sutrisno Sutrisno; Widowati Widowati; R. Heru Tjahjana
Indonesian Journal of Electrical Engineering and Computer Science Vol 22, No 3: June 2021
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijeecs.v22.i3.pp1748-1753

This study formulates a dynamical system for the control of a single product inventory system in accordance with the random value of demand and the percentage of damaged product during the delivery process. The formulated model has the form of a linear state-space system comprising of two disturbances, which represents the random value of demand and the percentage of the damaged product during delivery. The optimal value of the product amount ordered to the supplier is properly calculated by using the linear quadratic gaussian (LQG) method. The controller is used by the manager to make inventory level decisions under the uncertainty of demand and damaged items during the product delivery process. The result showed that the optimal product order for each review time was achieved, and the inventory level was used to obtain the right set point properly. Moreover, based on comparison with other research results, the proposed model was well performed.

LOGISTIC MODEL DEVELOPMENT OF COVID-19 SPREAD WITH PHYSICAL DISTANCING INTERVENTION Okky Widya Arditya; Widowati Widowati; Sutimin Sutimin; R. Heru Tjahjana; Priyo Sidik Sasongko
Journal of Fundamental Mathematics and Applications (JFMA) Vol 4, No 1 (2021)
Publisher : Diponegoro University

In early 2020, covid-19 spread fast in the worldwide and cause the high death. The disease started from the Asian region which resulted in a viral pandemic in 2020. In order to anticipate the increasing of the cases, a strategy is needed to inhibit its transmission. The mathematical model approach is important tool for predicting of covid-19 spread in populations. In this paper we propose and analyze the dynamical behaviour of a developed logistic model by considering the effect of the contact patterns in reducing the covid-19 spread process. To verify the developed logistic model, numerical simulation was given with case study of covid-19 spread for patients under supervision in Central Java Province, Indonesia. Based on simulation results, it was found that physical distancing can reduce the growth of the covid-19 spread for patient under supervision. It can be seen from the number of covid-19 spread for patients under supervision with physical distancing intervention smaller compared to without physical distancing intervention.

Co-Authors A. Jauhar Mahya Aulia, Lathifatul Bambang Riyanto Dinar Mutiara Kusumo Nugraheni Fuad Muhammad Hari Muhammad Okky Widya Arditya Priyo Sidik Sasongko Redemtus Heru Tjahjana Rina Fiati Sapto P. Putro Shabrina Zata Yumni Suhartana Suhartana Sunarsih Sunarsih Sutimin Sutimin Sutrisno Sutrisno Sutrisno, Sutrisno

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