Pedestrian Traffic: on the Quickest Path

When a large group of pedestrians moves around a corner, most pedestrians do not follow the shortest path, which is to stay as close as possible to the inner wall, but try to minimize the travel time. For this they accept to move on a longer path with some distance to the corner, to avoid large densities and by this succeed in maintaining a comparatively high speed. In many models of pedestrian dynamics the basic rule of motion is often either "move as far as possible toward the destination" or - reformulated - "of all coordinates accessible in this time step move to the one with the smallest distance to the destination". Atop of this rule modifications are placed to make the motion more realistic. These modifications usually focus on local behavior and neglect long-ranged effects. Compared to real pedestrians this leads to agents in a simulation valuing the shortest path a lot better than the quickest. So, in a situation as the movement of a large crowd around a corner, one needs an additional element in a model of pedestrian dynamics that makes the agents deviate from the rule of the shortest path. In this work it is shown, how this can be achieved by using a flood fill dynamic potential field method, where during the filling process the value of a field cell is not increased by 1, but by a larger value, if it is occupied by an agent. This idea may be an obvious one, however, the tricky part - and therefore in a strict sense the contribution of this work - is a) to minimize unrealistic artifacts, as naive flood fill metrics deviate considerably from the Euclidean metric and in this respect yield large errors, b) do this with limited computational effort, and c) keep agents' movement at very low densities unaltered

The Scaling of Speeds and Distances in Galileo’s Two New Sciences: A reply to Palmerino and Laird

In this reply, we respond to the comments of Palmerino and Laird on our article, "Galileo's Refutation of the Speed Distance Law of Fall Rehabilitated," published in the same issue of Centaurus

KERENTANAN PANGAN MASYARAKAT (STUDI KASUS TENTANG PERUBAHAN SISTEM MATA PENCAHARIAN DARI BERTANI MENJADI PENGUMPUL KERIKIL BATUBARA DI SUNGAI PADA MASYARAKAT DESA TANJUNG RAMAN KECAMATAN TABA PENANJUNG KABUPATEN BENGKULU TENGAH)

Penelitian bertujuan untuk memberikan gambaran dan penjelasan mengenai kaitan antara perubahan sistem mata pencaharian dari bertani menjadi pengumpul kerikil batubara di sungai dengan kerentanan pangan pada masyarakat Desa Tanjung Raman. Metode yang digunakan dalam penelitian ialah metode deskriptif kualitatif. Informan kunci dalam penelitiannya berjumlah 5 orang, yaitu: AJ, Rn, Dn, AM, dan Bn. Hasil penelitian menunjukkan bahwa masyarakat Desa Tanjung Raman tidak mengolah lagi lahan pertanian, mereka sekarang lebih tertarik nangguk baro di sungai karena pendapatannya lebih banyak, pendapatannya bersifat cepat tanpa menunggu musim panen dan kerja lebih ringan. Dapat dikatakan penghasilan masyarakat semenjak nangguk baro meningkat. Ketahahan pangan masyarakat Desa Tanjung Raman menjadi rentan. Ini ditandai dengan ketergantungan akan bahan pangan pada pihak lain, semenjak tahun 2007 hingga sekarang hampir semua bahan pokok atau bahan pangan hanya dapat dibeli. Kapasitas produksi yang tidak dapat memenuhi peningkatan permintaan kebutuhan pangan membawa konsekuensi stabilitas ketersediaan pangan menjadi rentan. Secara tak terduga seperti naiknya harga bahkan kelangkaan bahan pangan akan membuat masyarakat mengalami goncangan sehingga menyebabkan hilangnya rasa aman. Kesimpulan, penelitian ini memperlihatkan adanya kaitan antara perubahan sistem mata pencaharian dengan kerentanan pangan masyarakat