Judul: Mapping of Mangrove Distribution and Density in Mojo Village, Pemalang Regency
Abstrak: Hutan mangrove merupakan sebuah ekosistem yang memiliki banyak kegunaan seperti pelindung garis pantai, habitat berbagai biota, dan sumber ekonomi nelayan. Pemanfaatan teknologi penginderaan jauh seperti citra satelit untuk memantau kondisi mangrove menjadi alternatif di tengah berkembangnya teknologi saat ini. Penelitian ini bertujuan untuk mengetahui sebaran dan kerapatan mangrove serta tingkat keakuratan Citra Sentinel-2A dalam memetakan hutan mangrove di Desa Mojo, Kabupaten Pemalang. Metode yang digunakan dalam penelitian ini yaitu menduga tingkat kerapatan mangrove dengan algoritma Normalized Difference Vegetation Index (NDVI) dan survei lapang dengan hemispherical photography. Komposit band yang digunakan guna mendapatkan reflektan vegetasi mangrove dengan maksimal yaitu gabungan band 8-11-4 dari Citra Sentinel-2A. Penelitian ini menghasilkan beberapa kelas objek seperti pemukiman, vegetasi mangrove, dan vegetasi lain menggunakan klasifikasi supervised metode maximum likelihood. Penelitian ini juga menghasilkan tiga kelas kerapatan mangrove yaitu kelas rapat, sedang, dan jarang dengan luas masing-masing sebesar 54,86 Ha, 16,78 Ha, dan 84,68 Ha. Total luas hutan mangrove di Desa Mojo yaitu 168,68 Ha yang tersebar di wilayah utara desa. Dalam penelitian ini, nilai akurasi Citra Sentinel-2A yaitu 80% menggunakan metode confussion matrix., Mangrove forests are an ecosystem that has many uses, such protecting coastlines, habitat for various biota, and an economic source for fishermen. The use of remote sensing technology such as satellite imagery to monitor mangrove conditions is an alternative amidst current technological developments. This research aims to determine the distribution and density of mangroves as well as the level of accuracy of Sentinel-2A imagery in mapping mangrove forests in Mojo Village, Pemalang Regency. The method used in this research was estimating the level of mangrove density using the Normalized Difference Vegetation Index (NDVI) algorithm and field surveys using hemispherical photography. The composite band used to obtain maximum reflectance of mangrove vegetation was a combination of bands 8-11-4 from Sentinel-2A imagery. This research produced several classes of objects such as settlements, mangrove vegetation and other vegetation using the supervised classification method of maximum likelihood. This research also produced three classes of mangrove density, namely dense, medium and sparse classes with areas of 54.86 Ha, 16.78 Ha and 84.68 Ha respectively. The total area of mangrove forests in Mojo Village is 168.68 Ha spread across the northern area of the village. In this research, the accuracy value of the Sentinel-2A imagery was 80% using the confusion matrix method.
Keyword: Mangrove, NDVI, Sentinel-2A, Hemispherical Photography, Desa Mojo

Judul: Mangrove Vegetation Mapping Using Sentinel-2A Satellite Data Utilizing MVI and NDVI Algorithms on Cirebon Coast
Abstrak: Kondisi ekosistem mangrove yang telah menurun di Desa Mundupesisir, Kecamatan Mundu, Kabupaten Cirebon, Jawa Barat akibat dari kegiatan antropologis. Hal tersebut memunculkan urgensi pemantauan ekosistem mangrove agar kerusakan tidak memburuk. Penelitian ini bertujuan untuk memetakan sebaran, kerapatan, dan luasan mangrove di Desa Mundupesisir menggunakan citra Sentinel-2A. Terdapat 2 algoritma yang digunakan, yaitu algoritma Mangrove Vegetation Index (MVI) dan Normalized Difference Vegetation Index (NDVI). Algoritma MVI digunakan untuk membedakan vegetasi mangrove dan bukan mangrove dengan nilai ambang batas 2.374–19.409. Algoritma NDVI digunakan untuk memetakan sebaran kerapatan mangrove. Klasifikasi menggunakan metode maximum likelihood menghasilkan 3 kelas kerapatan mangrove dengan total luas 23.07 hektar. Kelas kerapatan tersebut terdiri dari kelas rapat (21.31 ha), sedang (0.67 ha), dan jarang (1.07 ha). Uji akurasi menggunakan metode confusion matrix terhadap kerapatan mangrove yang menghasilkan nilai akurasi keseluruhan sebesar 94.52% dengan nilai koefisien kappa sebesar 0.97. Uji korelasi statistik dari persentase tutupan kanopi mangrove antara nilai NDVI dan data lapang menghasilkan nilai koefisien korelasi (r) yaitu 0.882 serta nilai koefisien determinasi (R2) yaitu 0.778., The condition of the mangrove ecosystem had declined in Mundupesisir Village, Mundu District, Cirebon Regency, West Java due to anthropological activities. This raised the urgency of monitoring the mangrove ecosystem so that damage did not worsen. This research aimed to map the distribution, density, and extent of mangroves in Mundupesisir Village using Sentinel-2A imagery. There were 2 algorithms used, namely the Mangrove Vegetation Index (MVI) algorithm and the Normalized Difference Vegetation Index (NDVI). The MVI algorithm was used to differentiate mangrove and non-mangrove vegetation with a threshold value of 2.374–19.409. The NDVI algorithm was used to map the distribution of mangrove density. Classification using the maximum likelihood method produced 3 classes of mangrove density with a total area of 23.07 hectares. These density classes consisted of dense (21.31 ha), medium (0.67 ha), and sparse (1.07 ha). The accuracy test using the confusion matrix method for mangrove density resulted in an overall accuracy value of 94.52% with a kappa coefficient value of 0.97. The statistical correlation test of the percentage of mangrove canopy cover between NDVI values and field data produced a correlation coefficient (r) value of 0.882 and a coefficient of determination (R2) value of 0.778.
Keyword: NDVI, MVI, Threshold, Cirebon Coast, Sentinel-2A

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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