Trên một nửa diện tích khu vực này có độ sâu trên mét ( ft). Độ mặn trung bình của đại dương là khoảng 35 phần ngàn (ppt) (3,5%) và gần như mọi loại nước biển có độ mặn dao động trong khoảng từ 30 (ở vùng cận cực) tới 38 ppt (vùng nhiệt đới/cận nhiệt đới). | 6 2 Motivation In mathematics Eq. is termed a fi st-order ordinary differential equation and as it requires an initial value for C it is also referred to as an initial-value problem. Example Grandma used to keep a 10-litre carton of red wine in a storage room. I could not resist and crept every night to this room to get myself 1 litre of wine. To avoid grandma noticing the fast disappearance of the wine each night I topped up the carton with tab water. However I was caught soon or do you really think that grandma would not notice changes in the wine s taste and color owing to dilution with water Anyway the reader can easily work out how the concentration of wine changed with every day of my early-year drinking habit. All that needs to be done is to take away 10 of the wine concentration on a daily basis. The following table shows the result of this. Day Wine content l Wine concentration 0 10 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Figure shows a graph of the outcome of this f rst numerical prediction model only using a piece of paper and a pen. As expected there is a decrease of wine content as the days go past. In fact this decrease is approximately exponential. The Decay Problem 7 Fig. Evolution of wine content How to Produce a Simple Graph with SciLab This exercise explains how to use SciLab to produce Fig. . Stepl Open a suitable text editor and insert and save the three rows of the above table without header in a f le called for instance . Step 2 Fire up SciLab and change to the folder containing this file Step 3 Enter the following commands each followed by return x read -1 3 plot x 1 x 2 xtitle Time days Wine content litres The read command imports data from the file .