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2009年3月2日星期一

Landsat 5 25岁了

Landsat 5
Image via Wikipedia


>[ScienceDaily](http://www.sciencedaily.com/releases/2009/03/090302112924.htm#) (2009-03-02) -- Like a trusty watch counting up the minutes, the Landsat 5 satellite keeps on ticking, orbit after orbit around Earth. Still observing the Earth after 25 years -- 22 beyond its three-year primary mission lifetime -- Landsat 5 collects valuable scientific data daily. Some attribute the satellite's longevity to over-engineering. Others say it's a long run of good luck. Whatever the reason, no one who attended the satellite's March 1984 launch could have expected it would still be working today.

Landsat 5 于1984年3月1日发射升空,是 NASA 和 NOAA 的地球观测项目 Landsat 卫星系列中的第5颗,原本设计使用寿命仅3年的它已工作了25年,收集了超过70万帧图像[1. The Landsat Program - News]。考虑到 Landsat 6 的发射失败,以及 Landsat 7 在1999年才发射,如果 Landsat 5 不是这么长寿,Landsat 图像将有最长达12年的断档。来自同一颗卫星的图像序列对基于遥感技术的研究有特别重要的意义,因为它意味着研究者不需要考虑对不同传感器和轨道参数带来的图像变化进行校正,而只需要弥补传感器老化带来的偏差。

Landsat 5 在轨的这25年并非一帆风顺,它出过大大小小22次故障,目前只有基本的TM传感器还在继续观测,被形容成太空中“满身绷带的木乃伊”。但是 NASA 计划的 Landsat 后续任务 [LDCM](http://ldcm.gsfc.nasa.gov/about.html) 还要等到2011年(一说2012年)才会发射新的卫星替代 Landsat 5 和 Landsat 7。在那之前,我们只能期待 Landsat 7 和 Landsat 5 都能继续坚持工作。在 NASA 网站上有一个 Landsat 5 图像[画廊](http://www.nasa.gov/topics/earth/features/landsat25/index.html),讲述了 Landsat 5 是怎样记录25年来的历史(很遗憾,主要是美国历史)。










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2009年2月27日星期五

links for 2009-02-27

2009年2月26日星期四

Can Fairtrade be more fair?

a T-Shirt made from Fairtrade certified cotton
Image via Wikipedia
First, I need to point out that this is a really quick post, I haven't done much research as it is late in the night and I don't have much time on this one. So if there is anything you think is unfairly biased or plainly wrong please do point it out in comments, I would really appreciate that.

This article begins as a quick thought during one of the tutorial group discussions of which I am in charge. We were discussing about the globalisation of production and the topic shifted to Fairtrade and their practices in developing economies. I asked one of my tutees that why Fairtrade does not set up factories in the area where they grow coffee and bananas etc., to better help local farmers? Her guess was that this may introduce unwanted environmental impact and damage to local culture as well. I was not totally content with this answer although I think this is a brilliant enough answer for a first year student. Environmental impacts can be assessed and controlled; cultural invasion and mingling is happening anyway; but local people have the rights to have better life and more opportunities in international competitions. This calls for better institutions and infrastructure, which does not happen merely by sending in more money like Fairtrade does, as proved by Chinese experience in our poverty reduction campaigns.

The current world production pattern of extracting raw materials from developing economies, produce them in countries with cheap labour, under the command of offices from developed countries, and sold worldwide is determined to a quite large extent by colonism history and capitalism world economy. Comparing developing economies in Asia and Africa or South America, especially between countries like South Korea, Singapore and countries like Bolivia and Ghana. They were all exploited in 19th and early 20th century, and reached independence at about the same time, why the Asian countries are walking into modernization with established legal and political institutions and greatly improved livelihood while their African and Latin American counterparts are stilled bogged by corruption, lack of education and low industry output? One of my tutees brilliantly suggest that these continents are being exploited in different manners. In Asia, for some reason the labour resources are what the colonizers seek about, while in Africa it is largely natural resources. Thus Asia enjoys establishment of manufacture industries while only resource extraction industry was available in Africa and South America when they reach independence. On such different base, the different paths of development and continued being exploited were determined.

Although not sounding political correct, I think this is an interesting theory, I don't know if scholars mentioned it in their works already. In the following discussion we identified more factors contributing to different development levels: skill of workers, education, social institutions, technology, and transportation. The role of the last is pronounced in the difference between North Africa and central African countries, thanks to the former's developed transportation system and advantage of Mediterranean Sea. In a word, these things are one thing all development workers seek to build: capacity to develop further. Pay more to coffee-picking farmers is good, but without another forces to build capacity, the farmers would have no place good to invest their income, and further change won't take place.

Yes, I believe by setting up local factories by Fairtrade and export to Europe chocolate bars instead of fermented chocolate seeds will help local people better. Technology can be spread to these economies, and local people won't have to buy from, say, Nescafe, and be exploited for a second time (the first when Nescafe buys from local warehouses). Why this did not happen? Again I think it is the almighty economy at play here. One reason I can think of is that the chocolate has to be exported to areas with sufficient purchase power, say Europe, yet the strict standard used to protect its people from bad food would make the cost of setting a factory in the Fairtrade partner country so prohibitive that it is simply not feasible economically.

How to deal with this problem? Again quick but surely far from perfect answer: as part of the international or multinational firms' social responsibility, they need to invest a portion of their sales income in helping the country of source and Fairtrade develop infrastructure and education of workers. When the condition is met a local factory should be established, meeting environmental requirements and managed by local staff. Firms like Nescafe do [set factories](http://www.nescafe.com/NR/rdonlyres/CA26CACB-CE8A-4F5A-BCFF-8C908DF55B77/67164/whatcanbedone1.pdf) in ``developing countries'', however to what extent this has helped knowledge and skill transfer is absent from their report.

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英国城市垃圾回收的问题与经验

今天《卫报》发表文章,题为[《垃圾回收的真相》](http://www.guardian.co.uk/environment/2009/feb/26/recycling-waste-environment)(The truth about recycling),讨论了生活垃圾的大量产生,“可回收垃圾”的复杂定义,以及具体实施过程中在搜集、处理和再利用环节当中的问题。虽然讨论的范围局限在英国,但垃圾分类处理和回收利用在中国这样一个无论是[填埋](http://news.xinhuanet.com/environment/2009-02/06/content_10772832.htm)还是[焚烧](http://www.sei.gov.cn/ShowArticle2008.asp?ArticleID=167998)都受到诸多限制的国家应该是一个可能性最大的发展趋势,因此这篇文章中谈到的问题对中国以及处于类似阶段的国家都有引以为鉴的意义。

英国目前使用的“双桶”系统建立在原有的以户为单位的垃圾收集制度基础上,除了原有的黑色盖子的垃圾桶,英国不少城市的居民现在都可以把常见的可回收垃圾如纸张、金属等投入绿色盖子的垃圾桶。市政部门一周收集黑色盖子的垃圾桶,下一周收集绿色盖子的垃圾桶,如此循环。市政部门专门印制了宣传材料通过邮政部门发放到各家各户,告诉居民哪些垃圾可以被回收,以及在什么日期派人收集可回收和不可回收垃圾。在网站上也有类似的信息,例如我所在的区的政府[网站](http://www.broxtowe.gov.uk/index.aspx?articleid=1352)。我猜测,由于对可回收和不可回收垃圾的回收周期都由过去的一周变成了两周,而生活垃圾的产生总量和垃圾桶的总容积短时间内不变,居民就自然而然地产生了将垃圾分类处理的动机——否则一个垃圾桶放不下,而把不可回收垃圾放入可回收垃圾桶是会被市政部门拒收的。从我对住处附近垃圾处理设施的观察看,这套系统的效果还是不错的。

但是《卫报》的文章暴露了这套系统的问题,并向读者展示了ta们看不到的层面。对我来说,有切身感受的就是这套系统由于某种原因被复杂化了。比如,玻璃瓶是可回收的,但如果我将其放入绿色盖子的垃圾桶,也会导致被拒收。我们必须将其放入一个专用的绿色大袋子等待专人来收取,或者自己把瓶子带到超市停车场的玻璃回收箱。同样是塑料袋,超市购物使用的聚乙烯塑料袋也不鼓励放进绿色垃圾桶,只能通过超市渠道回收。仍然是我的猜测,玻璃分开处理大概是为了分拣工人的安全和健康考虑,怕玻璃碴子划伤工人,但这无法解释为什么不把聚乙烯塑料袋也纳入同一个回收体系。这套系统对于熟悉它的人尚且很混乱,对于初来乍到的人就更难搞清楚了。

不难想象,这种混乱会带来效率的降低和成本的提高。而更严重的问题,据《卫报》说,是垃圾被回收后的去向问题。英国自身对这部分垃圾的利用程度有限,虽然在造纸和塑料行业有成功的例子,但据说不少垃圾实际上在本国由于企业缺乏经济动机而没有市场,都被来自中国这样对资源需求较大的国家的买主以相对低廉的价格收购。但也有人声称,并不是所有可回收垃圾都被回收利用了,有些可回收垃圾可能最终还是在尼日利亚等国家的填埋场埋掉了。这些问题使得有人提出应该用焚烧替代回收,因为它成本更低,更简单,也许更环保。

但我的担心是如果“双桶”系统被焚烧取代,很可能会导致垃圾产生量的增加。再没有什么比想到所有的垃圾都只会化作一缕青烟和可以用来发电的热能更能让人放心地产生垃圾的想法了。现有的回收系统虽然问题不少,但它至少有效地控制了垃圾的源头产生量。垃圾税系统也可能成为有效的控制源头的手段,但它其实并没有给居民提供一个有效的替代选择。在现有的生活方式和商业行为没有改变的情况下,很可能住户该扔多少垃圾还是会扔多少垃圾。

如果中国要推行垃圾分类回收制度的话,可以从英国经验学到什么呢?“双桶”模式对于单元楼为主的大部分中国社区不好复制,但也许可以通过收集渠道的多元化和结合回收补贴与垃圾费(读作:胡萝卜加大棒)的方式促进回收率的提高。最值得学习的正面经验应该是英国市政部门系统化的投入和对居民有效的信息支持。而对于回收垃圾的消化,可能需要一个比现在更好的经济气候,还需要一个更透明的定价系统和适当的政策激励。将回收垃圾转移到国外似乎并不可行,考虑到英国在有这条渠道的情况下仍然面临着垃圾无处可去的困境,当中国也开始进行垃圾回收后这条渠道的容量就更小了。无论在中国还是英国,源头的控制都是垃圾问题根本的解决之道,但中国的现代化进程和促进消费的政策无疑都会给这种控制带来挑战。

2009年2月17日星期二

links for 2009-02-17