In this study, an integrated inventory model was developed among one vendor, multi buyers, and multi products. The total inventory cost to be minimized in this model is a combination of the vendor's and the buyers' total inventory costs. The total vendor inventory costs consist of setup costs and holding costs and the total inventory cost of the buyer consists of ordering costs, holding costs, stockout costs, and crashing lead time costs where the crashing lead time cost is approximated with an exponential function. Three decision variables will be calculated: the number of buyer orders, the lead time of each buyer, and the frequency of vendor shipments to all buyers in one production cycle. In this study, the optimal solution of each decision variable has been developed and applied to a case to show the use of models for finding optimal solutions. The sensitivity has also been performed to show the effects of some factors on the decision variables.
COVID-19 is a new disease that is affecting almost all of the world. Until now there has not been a single drug (vaccine) that can be used to cure it. Many attempts were made to prevent the spread of this disease but COVID-19 patients are increasing every day, although at the same time some are recovering. This study will calculate the probability of additional patients occurring over a long period of time, referred as a steady state state condition, using the Markov chain method. Nine states have been formed to represent the daily increase ranges of COVID-19 patients number. The calculation results show that the possibility of additional patient number between 1 to 91, 92 to 182, 182 to 272, 273 to 363, 364 to 454, 455 to 545, 546 to 636, 637 to 727, or greater than 728 people a day are 0.21197, 0.05644, 0.08408, 0.16337, 0.13999, 0.14512, 0.07189, 0.07695, and 0.05014, respectively.
Continuing study to higher education is an important thing for most of high school students, but there are still obstacles related to the information availability of higher education for high school students. These constraints can be divided into 3 categories, namely limited university information, limited department information, and limited registration information. Currently, there are university information apps, however those applications have not been able to overcome the three categories of obstacles faced. Thus, an design for application that can handle these problems. In this research, a design for application for information about higher education providers was conducted. The application design consists of 4 stages, started by determining needs using the focus group discussion method which involved 9 respondents and produced 23 needs. The second stage, determining design alternatives using the participatory design workshop method involving 8 respondents and producing 4 design alternatives, and selecting an alternative design involving 19 respondents. The third stage is making a high-fidelity prototype with the help of Adobe XD software. In the last stage, evaluation and improvement are carried out by considering the factors of usefulness, effectiveness, efficiency, learnability, and satisfaction. The result of this research is a design of application that provide information about university that meets aspects of functionality and usability. Those aspects including the usefulness factor 81.79%, the effectiveness factor 82.14%, the efficiency factor 82.14%, the learnability factor 71.43%, and the satisfaction factor 79.64%. Based on these results, this application able to use and meets user needs.
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