An Efficient Construction of Self-Dual Codes. (arXiv:1201.5689v1 [cs.IT])

from cs.IT updates on arXiv.org http://arxiv.org/abs/1201.5689

We complete the building-up construction for self-dual codes by resolving the
open cases over $GF(q)$ with $q \equiv 3 \pmod 4$, and over $\Z_{p^m}$ and
Galois rings $\GR(p^m,r)$ with an odd prime $p$ satisfying $p \equiv 3 \pmod 4$
with $r$ odd. We also extend the building-up construction for self-dual codes
to finite chain rings. Our building-up construction produces many new
interesting self-dual codes. In particular, we construct 945 new extremal
self-dual ternary $[32,16,9]$ codes, each of which has a trivial automorphism
group. We also obtain many new self-dual codes over $\mathbb Z_9$ of lengths
$12, 16, 20$ all with minimum Hamming weight 6, which is the best possible
minimum Hamming weight that free self-dual codes over $\Z_9$ of these lengths
can attain. From the constructed codes over $\mathbb Z_9$, we reconstruct
optimal Type I lattices of dimensions $12, 16, 20,$ and 24 using Construction
$A$; this shows that our building-up construction can make a good contribution
for finding optimal Type I lattices as well as self-dual codes. We also find
new optimal self-dual $[16,8,7]$ codes over GF(7) and new self-dual codes over
GF(7) with the best known parameters $[24,12,9]$.

Advertisements

二.5.快乐陷阱：甜蜜泛滥的世界

http://www.psywww.com/intropsych/ch08_animals/08supernormal.gif

• 有一名性伴侣的人最幸福，太多、太少都会降低幸福；
• 嫖过妓的人要比其他人不幸福得多；
• 有婚外性行为的人要比其他人不幸福得多。

• 电子游戏让我们在虚拟世界里攻城略地、杀人越货，一个晚上就能登基宇宙之王，可以满足我们的成就感，却没有多少现实意义；
• 互联网上那无穷无尽的链接，可以满足我们的好奇心，但铺天盖地而来的信息却反倒可能损害我们的判断力；
• 成人图片、成人电影，可以满足男性对色情场面的需求，却不可能带来真正的子孙；
• 电视剧可以满足人类打探别人生活的本能，但却不能带来什么有用的信息；
• 化妆品，可以满足女性爱美的天性，但美貌本是健康的衡量，把钱和时间花在化妆上，而不是去锻炼身体，是本末倒置；
• 减肥，可以减少女性的腰臀比，而腰臀比是生殖能力的指标，可过度减肥，反倒会降低生殖能力；
• 某些意识形态和宗教组织，利用人追寻人生意义的天性，许诺简单易行的天堂路径，最终害人害己；
• 成功学，利用人追求成功的天性，但当人太执着于成功时，幸福感会降低。

———-小练习———–

1.  容易获得；

2.  难以抗拒，或者容易上瘾；

3.  带来的快乐难以持久，很快你就心痒痒地想再来一次；

4.  除了当时的愉悦外，不会带来其他好处；

5.  事后回顾时，常觉得后悔或者毫无意义。

———————

[1]哈佛大学心理学家丹尼尔·吉尔伯特（Daniel Gilbert）曾经半开玩笑地说：“进化应该得‘微软奖’，因为它为我们安装软件时，从来不先征得我们的同意。”参见Gilbert, D., (2006). Stumbling on Happiness. New York: Kopf。

[2]说是“基本”正确，是因为自然界也有例外，比如这个本能可以被杜鹃利用，把大的杜鹃蛋下在其他鸟的巢内，引诱她们孵它的蛋。

[3]Barrett, D., (2010). Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose. New York: W. W. Norton & Company, Inc.

[4]人类学家发现，有些原始部落一直都不知道性交与生殖的关系，但丝毫也没妨碍他们的男人好色。

[5]参见Blanchflower, D. G., Oswald, A. J. (2004). Money, sex and happiness: An empirical study. Scandavian Journal of Economics, 106(3), 393–415.。

[6]“得逞”这个词和说基因“自私”一样，只是比喻。虽然很多超常刺激是商家有意识的发明，但也有相当一部分超常刺激只是文化基因竞争、进化的自然结果。

教你识破“神秘”巧合：林肯与肯尼迪的故事

from 科学松鼠会 http://songshuhui.net/archives/64004

关键词一：编造

“刺杀林肯的凶手布思（John Wilkes Booth）生于1839年，刺杀肯尼迪的凶手奥司华德（Lee Harvey Oswald）生于1939年”也是一条被硬拉上去的巧合。事实上，布思出生在1838年，而不是1839年。

“刺杀林肯的凶手从一间戏院跑出，在一间仓库被抓获”并不准确，事实上，凶手先在戏院里刺杀了林肯，然后几天后在一片烟地里被抓获。

关键词二：概率其实不小

“杀害两人的凶手都是南方人”“他们的继任者也都是南方人”发生的概率也很大，何况南方的定义也很模糊。而根据记载，杀害肯尼迪的凶手Oswald只是出生在南方的一个州，后来辗转多处居住，并不是完全的南方人。

……

【最近】《论当前形势下学习扶乩请神技术之现实意义》

from 【枪·东东枪的枪】 http://thisisdongdongqiang.com/archives/2304

【最近】《论当前形势下学习扶乩请神技术之现实意义》

“不妄言”这种事，似乎是只合自省，不该对人的。毕竟任何人也没有资格判定他人是否有发表意见的权利，更无法由谁设定标准以控制发言权。但还是总希望不假思索、不做探究、无知而妄言的景况能少一些，所以只能劝大家从自己做起。我看作家蒋方舟老师新年之初在微博上写给自己的几点期冀里有一条就是“戒在自己不擅长的领域发言”，应该也就是这个意思。

创新与自由（刘荻）

2012-01-24

（文章只代表特约评论员个人的立场和观点）

时间估计的难题

from Free Mind http://blog.pluskid.org/?p=830

Holy Shmoly: SSH Socks Proxy for Android Phones

from Planet Linode http://ocaoimh.ie/?p=89496836

Android has had VPN support for donkey’s years but I could never get it working. I tried pptpd and xl2tpd but pptpd didn’t work (and has security holes) or the configuration is daunting and lengthy when all I want is a simple proxy.

There’s also HTTP proxy support built into Android. It’s exposed in Samsung and other ROMs at Settings->Wireless and Network->Wi-Fi Settings, Advanced. Apparently this app sets things up correctly too. I’m not sure if it’ll do authentication however unless you add the username:password in the hostname. I also don’t want to install Squid on my public internet server!

So, the holy grail of proxying would be doing so through ssh. Nothing else to install on my server and I get an encrypted tunnel through the internet and out of Ireland which might be a good thing to protect my privacy from the prying eyes of the Irish Government. A far more mundane reason is the security of my data from others on a public wifi network. (Aside, on what will the record companies blame the falling numbers of CDs sold when the Irish version of SOPA is passed?)

The good news is that you can now create an ssh tunnel from your Android device. The bad news is that it has to be rooted to make the most of it. Go grab the SSH Tunnel app and you’ll be sending data through your remote host in no time. There’s also a beta version that uses an OpenSSH native binary rather than a Java implementation. I haven’t tried that yet, the stable version worked fine for me.

You can stream Netflix through it, and browse the net, post to your blog or whatever else takes your fancy. All through a secure tunnel to a remote server.

In case you’re interested, it’s simplicity itself to do the same thing on Linux or Mac computers using the installed ssh client. On Windows just use Putty!

Related Posts