【文章內(nèi)容簡(jiǎn)介】 ow, I don?t think I need to draw the echoes, your reading assignment for the next class。 it has diagram shows this very clearly. So, anyway, as I were saying, by analyzing this echo, the bat can determine, say, if there is wall in a cave that needs to avoid, and how far away it is. Another thing uses the ultrasound to detect is the size and the shape of objects. For example, one echo they quickly identified is one way associated with moth, which is mon prey for a bat, particularly a moth meeting its wings. However, moth happened to have major advantage over most other insects. They can detect ultrasound。 this means that when the bat approaches, the moth can detect the bat?s presence. So, it has time to escape to safety, or else they can just remain motionless. Since, when they stop meeting their wings, they will be much hard for the bat to distinguish from, oh… a leave or some other object. Now, we have tended to underestimate just how sophisticated the ability that animals that use ultrasound are. In fact, we kinds of assume that they were filtering a lot out. The ways are sophisticated radar on our system can ignore the echo from the stationary object on the ground. Radar are does this to remove ground clutter , information about the hills or buildings that they doesn?t need. But bats, we thought they were filtering out kinds of information, because they simply couldn?t analyze it. But, it looks as we are wrong. Recent there was the experiment with trees and specific species of bat. A bat called: the laser spear nosed bat. Now, a tree should be huge and acoustic challenge for bat, right? I mean it got all kinds of surfaces with different shapes and angles. So, well, the echoes from trees are going to be massive and chaotic acoustic reflection, right, not like the echo from the moth. So, we thought for a long time that the bat stop their evaluation as simply that is tree. Yet, it turns out that is or at least particular species, cannot only tell that is trees, but can also distinguish between a pine tree, and a deciduous tree, like a maple or oak tree, just by their leaves. And when I say, leaves, I mean pine needles too. Any idea on how we would know that? Stu: Well, like with the moth, could be their shape? Pro: You are on the right trackit actually the echo of all the leaves as whole the matters. Now, think, a pine trees with little densely packed needles. Those produced a large number of fain reflection in which what?s we called as: a smooth of echo. The wave forms were very even, but an oak which has fewer but bigger leaves with stronger reflections, produces a gigots wave form, or what we called: a rough echo. And these bats can distinguish between a two, and not just was trees, but with any echo e in smooth and rough shape. Conversation Stu: Hi, I am a new here and I couldn39。t e to our student orientation and I39。m wondering if you can give me a few quick points just about library. I?d really appreciate it. Pro: Sure. I will be glad to. What39。s your major area of study? Stu: Latin American Literature. Pro: OK. Well, over here39。s the section where we have language, literature and arts. And if you go down stairs you will find history section. Generally, the students who concentrated in Latin American literature find themselves research in history section a lot. Stu: Hum, you are right. I am a transfer student and I39。ve already done a year in another university so I know how the research can go that spent a lot of time on history section. So how long can I borrow books for? Pro: Our loan period is a month. Oh I should also mention that we have an interlibrary loan service. If you need to get to hold a book that not in our library, there is a truck that runs between our library and a few public and university libraries in this area. It es around three times a week. Stu: It39。s great! At my last school, it takes really a long time to get the materials I needed. So when I had a project, I had to make a plan away in advance. This sounds much faster. Another thing I was wondering is: is there a place where I can bring my puter and hook it up? Pro: Sure. There is a whole area here on the main floor where you can bring a laptop and plug it in for power but on top of that we also have a connection for the inter that every seat. Stu: Nice, so I can do the all research I need to do right here in the library. All I have the resources, all the books and the information I need right here in one