Hello. In this video, I am going to show you how to activate and to use the applet i-Cremona which is a program that we are going to use throughout this course to have interactions dealing with graphical statics. i-Cremona is a Java applet, that is to say a small program which executes inside an Internet browser. Most the usual browsers like Firefox, Safari, Chrome, Internet Explorer, Opera and so forth, support the use of the Java applets. Although we are going to see later that it is necessary to activate them. However, and it is a bad news, most of the mobile platforms, whether it be cellphones or tablets working under IOS as well as under Androïd, do not support the use of Java applets. To use these applets, and it is a significant part of the course's exercises, you will have to have access to a classic computer like a PC, a Mac, or a Linux workstation to be able to use a complete version of these browsers which can host a compatible Java virtual machine. I am going to show you soon how to proceed. Once we will have activated the applet, I will show you how we can use the main commands to save the documents, to add forces and divers other elements inside, in relation to a structure. Generally, in the Art of Structures course, you will access an applet through a link which will be given to you for example in an exercise or in a lecture. When you follow this link, you arrive on a page where normally the applet should appear. If you arrive on a such page with this typical pink rectangle, it means that on the computer that you use, either Java is not installed, either it is not activated. In this case, you can follow the link which is proposed to you. Normally, here, on the right, in the window, you should have a yellow window. If it is pink again, it means that there is no installed Java virtual machine at all. You then have to go on the website of Oracle to install a virtual machine which corresponds to your platform whether it be Windows, Mac OS or the diverse versions of Linux. Once again, it will not be possible for a tablet or a cellphone, or at the least for the models which are common in 2013 when I record this video. When I have activated Java in my browser, I can now, directly clicking on the link, start the applet. Note that I receive here a security warning telling me that I am going to execute an applet. Why this ? Because there have been quite important security problems linked to Java the last few years and since then, the browsers give different kinds of warnings, here we can see the one of Internet Explorer on a PC, but there are different kinds of warnings which encourage us not to use the Java applets. In the present case, we want to do it, we can trust the Java applet i-Cremona, but it's a question of accepting the risk. We can also, without any troubles, accept not to see anymore this warning thereafter, since we will quite often start this applet. Once we have done this, the Java applet appears with its work zone which is here framed in gray with a series of buttons, here on the top, which we are going to look at later. A work zone on the middle and an input zone which we are going to use very soon. On the top-left corner, you can find a button to open a file. Actually, we are not going to use this very often since generally we will open a file following a link from an exercise. The save button is however very important because it will enable us to keep the work we have done. I am going to give you a very quick example. Here, using the button "force", we can introduce two forces here and we are going to push the "save" button. Let's say that we have thereafter to stop our work on the exercise. No problem, we can close the applet and when we will open it again, we will find again in the environment both arrows that we had introduced. Well, I want to quickly delete them so I click on the arrow and I click on the x to take it off and I am going to explain you a little bit more how to introduce a force. OK, I click on this button which stays down and black, and then, on the bottom, a text area appears with on the left, one hundred, on the middle, less than and on the right, minus ninety. What does it mean ? Well, the "one hundred" is the amplitude of the force which we are going to introduce, the "less than", symbolizes an angle and the "minus ninety", indicates that we are going to get a force which will point in the orientation minus ninety degrees when counterclockwise. Then, when we use the counterclockwise orientation, horizontally to the right it is zero, vertically upwards it is ninety degrees, vertically downwards it is minus ninety. If I want now to introduce a force of only 10 Newtons then I edit this field and I can directly introduce this force. If I put the cursor on the force, it shows indeed with its amplitude of ten and its orientation ninety. Note that it has exactly the same size than the force of one hundred I had introduced before. Why? Because the applet will automatically scale the first force that you introduce to have this size on the screen. If I introduce a second force which has an amplitude of twenty Newtons, it is clearly going to be longer and if I introduce a third force with only five Newtons, it will be smaller. If I want to move one of these forces, I can grasp it anywhere or particularly by the little ball which is at the lower end of the arrow and I can move it. Let's say that I am going to place these three arrows on top of each other. The three forces. Notice that when I move it, I can see the line of action of the force, which enable me to work with quite great precision. If I want to change the amplitude of a force, I can go at the other end of the force and choose, to change its amplitude, there we go. That is what I have done here. If I click again on this force, I can see that now it has an amplitude of 35.5 and that it points at minus 119 degrees. If I want to delete a force as you have seen before, I simply click, once it is selected, and we see it in pink, I click on the "delete" button. If I want to select several forces, I can do it. For that, I click on the button "control", do it rather with the keyboard but here I do it with this button on the mouse, and afterwards I can move them simultaneously or for example modify them making them turn like here. If I stop pressing "control", I can also make change the amplitude of the forces, delete them at the same time. Here we have a button "support" which we will use to represent the supports when we will arrive there in the structures course. We can introduce at most two supports and like for forces, if we select them, we can delete them. There is also a tool which enable us to draw a free-body. Then, I draw my free-body here in a quite simple way. Once the free-body is created, we can move it for it to correspond exactly to what we want. And then if we are patient, we can move and activate when we are individual points of the free-body, which we make appear as intermediary points. They are used for the drawing of the free-body and you can see that with this, we can improve the shape, that we have given to our free-body, if we want to get something more accurate. Please do not hesitate to delete your free-body and draw it again more accurately because it is maybe easier to draw it again in the good way the second time. A button which is also very important withing the framework of the applet is the button which is always above the applet, with the label "reset". When we click on "reset", we exactly get back where we started from at the beginning of the exercise. It is something which is very recommended, why ? Because the activities that you will do within the applet are generally very short. A couple of minutes at most and once you have understood what you have to do, maybe there will be something that does not work well but you have understood thus it is often easier to reset the applet and to do over everything we asked you to do. So, here you have on the right a button to replace the control key, to replace the shift key and to replace the alt key of the keyboard. When you hold them down, do not forget to inactivate them afterwards because otherwise, there will be secondary effects a little bit everywhere. These two buttons here allow you to introduce either red lines, or blue lines. These lines are really, completely free. They look like a free-body, and work a little bit in the same manner, that is to say that if you want to edit it you go to the end of this line, there will be a little ball which is going to form and then we will be able to edit and create drawings which combine blue elements and red elements. For some operations, we will ask you to create this kind of drawing to indicate where there is tension and where there is compression in a given structure. Finally, here this button of help activates the online help. It is essential to allow the website i-structure to display pop-ups for this to work. The first time, it is not going to work. We are going to make reappear the applet and then, it is necessary to have saved your work, otherwise we would have problems, but the second time, the online help is going to appear and for example, here we can go to the online help which explains how to create a free-body, how to modify it, how to delete it, and the all of the functions of the applet are described in the online help. The last button that I want to show you here is the background image. The background image is what you see in the applet. You will sometimes have a photo, you will have a little drawing, a sketch, etc. We can make it disappear by clicking on this button. If you have been worried, "But, I do not see anything anymore !", click on this button and generally, the background image will reappear. Another reason for which the drawing can disappear is because you will have zoomed too much. Here, I click on "zoom" and I zoom around the point where I am. If I want to unzoom, I have to click in the same time on "shift" and then now, I am dezooming. If I click on "control", I can pan the zoom. Most of you, at the least if you have a computer will prefer to use the scroll function of the middle wheel and to point, by clicking on the middle button. This enables to do that much more easily than what I do with the applet. However, sometimes there are secondary effects regarding the environment which can be a little bit complicated. Do not forget to click again on the zoom button to deactivate this mode at the end. To conclude, I want to summarize the buttons that we have see in the applet and their main functions. This first button here, it is open a file, it is relatively classic. But actually, it is rarely used. As I said it, generally you will open a file through a link. This button, however, it is used to save and it is very important. This button enables to activate or to deactivate the background image. It is also an important function, especially if you lose the background image. This button enables you to zoom or unzoom using the shift key or to move using the control key. This button enables to introduce a support. We will see later what a support is. This button enables you to introduce a force. We have seen that we can specify the amplitude and the orientation of the force or that we can change it interactively at a later time. This button enables you to draw a free-body. These two buttons, here, enable you to introduce red lines, respectively blue lines which represent lines in tension and in compression. This button, here, enables to delete a force or a support or a free-body. And then finally, here, these buttons here are buttons equivalent to keyboards button which reproduce the functions of the control, shift an alt keys. Finally, here, very important, this button enables you to have access to the online help, which I recommend you to use to get more information about the applet. During this lecture, we have seen the principle of activation of the Java applet i-Cremona which is used within the framework of this course of structure. We have seen how to open and save an applet's file with data inside. We have seen how to introduce forces and supports We have also seen how to introduce a free-body and how to use the online help.
