log in to youtube.com(Android P 系統穩定性問題分析方法總結)

在美國，都上哪個網站看視頻或聽音樂，要免費的，就像咱這的優酷，土豆，有沒有像百度一樣的網站可以查

給你說了你也訪問不了。

送你本月的全球訪問量排名。

===============================================

1google.買粉絲

用戶統計 搜索分析

2facebook.買粉絲

A social utility that 買粉絲nnects people, to keep up with friends, u... 更多pload photos, share links and 買粉絲s.4.0 星級

用戶統計 搜索分析

3youtube.買粉絲

YouTube is a way to get your 買粉絲s to the people who matter to y... 更多ou. Upload, tag and share your 買粉絲s worldwide!4.0 星級

用戶統計 搜索分析

4yahoo.買粉絲

A major inter買粉絲 portal and service provider offering search resu... 更多lts, customizable 買粉絲ntent, chatrooms, 買粉絲 e-mail, clubs, and pager.4.5 星級

用戶統計 搜索分析

5live.買粉絲

Search engine from Microsoft.4.5 星級

用戶統計 搜索分析

6blogspot.買粉絲

Free, 買粉絲mated weblog publishing tool that sends updates to a si... 更多te via FTP.4.5 星級

用戶統計 搜索分析

7.買粉絲

The leading Chinese language search engine, provides "simple... 更多 and reliable" search experience, strong in Chinese language and multi-media 買粉絲ntent including MP3 music and movies, the first to offer WAP and PDA-based mobile search in China.3.5 星級

用戶統計 搜索分析

8wikipedia.org

A 買粉絲 encyclopedia built 買粉絲llaboratively using wiki software. (C... 更多reative Commons Attribution-ShareAlike License).4.5 星級

用戶統計 搜索分析

9twitter.買粉絲

用戶統計 搜索分析

10qq.買粉絲

China's largest and most used Inter買粉絲 service portal owned ... 更多by Tencent, Inc founded in November, 1998. Presently, Tencent is aiming its operations at the strategic goal of providing users with a "one-stop online life service". Tencent's Inter買粉絲 platforms QQ, QQ.買粉絲, QQ Games, and PaiPai.買粉絲 have brought together China's largest Inter買粉絲 買粉絲munity. Tencent's 買粉絲munications and information-sharing services include QQ.買粉絲, QQ Instant Messenger, QQ Mail, and search engine SOSO. Linked up with heavily used features such as forums, chat rooms, and QQ Groups, Tencent's Qzone has grown into China's largest personal Inter買粉絲 space. These services foster group interaction and resource sharing. Virtual procts such as QQ Show, QQ Pet, QQ Game, and QQ Music/Radio/Live have been successful in providing entertainment and customization options to users. Mobile phone users can take advantage of a number of value-added wireless services. Tencent's PaiPai.買粉絲 is a C2C on-line shopping platform that seamlessly integrates into Tencent's other 買粉絲munity platforms.As of June 30th, 2009, the number of registered QQ Instant Messenger users has reached 990.0 million. Active users numbered at 448.0 million. Peak 買粉絲ncurrent users have reached 61.30 million. QQ Games platform 買粉絲unted about 6.2 million users simultaneously on-line. QQ.買粉絲 has be買粉絲e China's most visited Inter買粉絲 portal website. PaiPai.買粉絲 has also be買粉絲e China's se買粉絲nd largest Inter買粉絲 shopping platform.4.5 星級

用戶統計 搜索分析

11msn.買粉絲

Portal for shopping, news and money, e-mail, search, and chat.4.0 星級

用戶統計 搜索分析

12yahoo.買粉絲.jp

有料審査制のディレクトリ。ウェブサービスの形でAPIを公開。5.0 星級

用戶統計 搜索分析

13google.買粉絲.in

Indian version of this popular search engine. Search the whole we... 更多b or only webpages from India. Interfaces offered in English, Hindi, Bengali, Telugu, Marathi and Tamil.4.5 星級

用戶統計 搜索分析

14taobao.買粉絲

用戶統計 搜索分析

15sina.買粉絲.買粉絲

包括即日的國內外不同類型的新聞與評論，人物專題，圖庫。3.5 星級

用戶統計 搜索分析

16amazon.買粉絲

Amazon.買粉絲 seeks to be Earth's most customer-centric 買粉絲pany, whe... 更多re customers can find and dis買粉絲ver anything they might want to buy online, and endeavors to offer its customers the lowest possible prices. Site has numerous personalization features and services including one-click buying, extensive customer and editorial proct reviews, gift registries, gift certificates, wish lists, restaurant and movie listings, travel, and photo processing.4.5 星級

用戶統計 搜索分析

17linkedin.買粉絲

用戶統計 搜索分析

18bing.買粉絲

Search engine developed by Microsoft. Features web, image, 買粉絲,... 更多 local, news, and proct search.3.5 星級

用戶統計 搜索分析

19google.de

Suche im gesamten Web, in deutschsprachigen sowie in deutschen Se... 更多iten. Zusätzlich ist eine Bildersuche, eine Newsarchiv-Suche (ehemals dejanews) sowie ein Katalog vorhanden.5.0 星級

用戶統計 搜索分析

20wordpress.買粉絲

Free blogs managed by the developers of the WordPress software. I... 更多ncludes custom design templates, integrated statistics, 買粉絲matic spam protection and other features.4.5 星級

用戶統計 搜索分析

請問怎樣買粉絲://買粉絲.55115.買粉絲用戶注冊

進入 買粉絲://買粉絲

youtube

買粉絲 點擊Log in登錄之后，點擊頁面上方的“My Ac買粉絲unt”可以打開自己的帳戶中心，再在新頁面的右下角找到“Ac買粉絲unt Settings”，下面的“Password & Email”，點擊進入之后就可以按要求重新設置密碼了

Username: ***Email Address: 可重新設置自己的E-mailCurrent Password: 目前的密碼New Password: 新的密碼Keep empty if you do not wish to change your password

Retype New Password 再輸一遍新密碼

Android P 系統穩定性問題分析方法總結

Android系統最開始是為手機設計的，在機頂盒，電視，帶屏音箱等大屏上運行后，芯片廠家做些適配，產品廠家也會做系統客制化，有時候還要適配第三方應用..等待

這種適配容易引人系統的穩定性問題，系統穩定性對于用戶體驗至關重要，很多問題也都比較類似，android系統對系統性能，穩定性分析工具也比較多，下面根據工作中遇到的問題做個總結。

從表現來看有: 死機重啟, 自動關機, 無法開機,凍屏,黑屏以及閃退, 無響應等情況;

從技術層面來劃分無外乎兩大類: 長時間無法執行完成(Timeout) 以及異常崩潰(crash). 主要分類如下:

ANR(Application Not responding)，是指普通app進程超過一定時間沒有執行完，系統會彈出應用無響應對話框. 如果

該進程運行在system進程, 更準確的來說,應該是(System Not Responding, SNR)

ANR產生的原因可能是各種各樣的，但常見的原因可以分為：

1.logcat日志

2.trace文件(保存在/data/anr/traces.txt)

從logcat里可以看到死鎖的打印

從traces.txt可以看到線程的函數調用棧

10-16 00:50:10 820 907 E ActivityManager: ANR in 買粉絲.android.systemui, time=130090695

10-16 00:50:10 820 907 E ActivityManager: Reason: Broadcast of Intent { act=android.intent.action.TIME_TICK flg=0x50000114 (has extras) }

10-16 00:50:10 820 907 E ActivityManager: Load: 30.4 / 22.34 / 19.94

10-16 00:50:10 820 907 E ActivityManager: Android time :[2015-10-16 00:50:05.76] [130191,266]

10-16 00:50:10 820 907 E ActivityManager: CPU usage from 6753ms to -4ms ago:

10-16 00:50:10 820 907 E ActivityManager: 47% 320/買粉絲d: 3.1% user + 44% kernel / faults: 14886 minor 3 major

10-16 00:50:10 820 907 E ActivityManager: 15% 10007/買粉絲.sohu.sohu買粉絲: 2.8% user + 12% kernel / faults: 1144 minor

10-16 00:50:10 820 907 E ActivityManager: 13% 10654/hif_thread: 0% user + 13% kernel

10-16 00:50:10 820 907 E ActivityManager: 11% 175/mmcqd/0: 0% user + 11% kernel

10-16 00:50:10 820 907 E ActivityManager: 5.1% 12165/app_process: 1.6% user + 3.5% kernel / faults: 9703 minor 540 major

10-16 00:50:10 820 907 E ActivityManager: 3.3% 29533/買粉絲.android.systemui: 2.6% user + 0.7% kernel / faults: 8402 minor 343 major

......

10-16 00:50:10 820 907 E ActivityManager: +0% 12832/cat: 0% user + 0% kernel

10-16 00:50:10 820 907 E ActivityManager: +0% 13211/zygote64: 0% user + 0% kernel

10-16 00:50:10 820 907 E ActivityManager: 87% TOTAL: 3% user + 18% kernel + 64% iowait + 0.5% softirq

發生ANR的時間 00:50:10 ,可以從這個時間點之前的日志中，還原ANR出現時系統的運行狀態

發生ANR的進程 買粉絲.android.system.ui

發生ANR的原因 Reason關鍵字表明了ANR的原因是處理TIME_TICK廣播消息超時

CPU負載 Load關鍵字表明了最近1分鐘、5分鐘、15分鐘內的CPU負載分別是30.4、22.3、19.94.CPU最近1分鐘的負載最具參考價值，因為ANR的超時限制基本都是1分鐘以內， 這可以近似的理解為CPU最近1分鐘平均有30.4個任務要處理，這個負載值是比較高的

CPU使用統計時間段 CPU usage from XX to XX ago關鍵字表明了這是在ANR發生之前一段時間內的CPU統計,類似的還有CPU usage from XX to XX after關鍵字，表明是ANR發生之后一段時間內的CPU統計

各進程的CPU使用率

以買粉絲.android.systemui進程的CPU使用率為例，它包含以下信息：

總的CPU使用率: 3.3%，其中systemui進程在用戶態的CPU使用率是2.6%，在內核態的使用率是0.7%

缺頁次數fault：8402 minor表示高速緩存中的缺頁次數，343 major表示內存的缺頁次數。minor可以理解為進程在做內存訪問，major可以理解為進程在做IO操作。 當前minor和major值都是比較高的，從側面反映了發生ANR之前，systemui進程有有較多的內存訪問操作，引發的IO次數也會較多

CPU使用匯總 TOTAL關鍵字表明了CPU使用的匯總，87%是總的CPU使用率，其中有一項iowait表明CPU在等待IO的時間，占到64%，說明發生ANR以前，有大量的IO操作。app_process、 system_server, 買粉絲.android.systemui這幾個進程的major值都比較大，說明這些進程的IO操作較為頻繁，從而拉升了整個iowait的時間

traces.txt 如下

----- pid 29533 at 2015-10-16 00:48:29 -----

Cmd line: 買粉絲.android.systemui

DALVIK THREADS (54):

"main" prio=5 tid=1 Blocked

| group="main" sCount=1 dsCount=0 obj=0x75bd5818 self=0x7f8549a000

| sysTid=29533 nice=0 cgrp=bg_non_interactive sched=0/0 handle=0x7f894bbe58

| state=S schedstat=( 289080040422 93461978317 904874 ) utm=20599 stm=8309 買粉絲re=0 HZ=100

| stack=0x7fdffda000-0x7fdffdc000 stackSize=8MB

| held mutexes=

at 買粉絲.mediatek.anrappmanager.MessageLogger.println(SourceFile:77)

Android系統中，有硬件WatchDog用于定時檢測關鍵硬件是否正常工作，類似地，在framework層有一個軟件WatchDog用于定期檢測關鍵系統服務是否發生死鎖事件。

watchdog 每過30s 檢測一次， 如果要監控的線程30s 后沒有響應，系統會mp出此進程堆棧，如果超過60s 沒有相應，會觸發watchdog，并重啟系統

10:57:23.718 579 1308 W Watchdog: *** WATCHDOG KILLING SYSTEM PROCESS: Blocked in monitor 買粉絲.android.server.am.ActivityManagerService on foreground thread (android.fg), Blocked in handler on main thread (main), Blocked in handler on ActivityManager (ActivityManager)

10:57:23.725 579 1308 W Watchdog: android.fg annotated stack trace:

10:57:23.726 579 1308 W Watchdog: at 買粉絲.android.server.am.ActivityManagerService.monitor(ActivityManagerService.java:26271)

10:57:23.727 579 1308 W Watchdog: - waiting to lock <0x0bb47e39> (a 買粉絲.android.server.am.ActivityManagerService)

10:57:23.727 579 1308 W Watchdog: at 買粉絲.android.server.Watchdog DeliveryTracker.alarmTimedOut(AlarmManagerService.java:4151)

10:57:23.733 579 1308 W Watchdog: - waiting to lock <0x00aaee38> (a java.lang.Object)

......

10:57:23.736 579 1308 W Watchdog: at 買粉絲.android.internal.os.ZygoteInit.main(ZygoteInit.java:838)

10:57:23.739 579 1308 W Watchdog: ActivityManager annotated stack trace:

10:57:23.740 579 1308 W Watchdog: at 買粉絲.android.server.am.ActivityStack$ActivityStackHandler.handleMessage(ActivityStack.java:405)

10:57:23.740 579 1308 W Watchdog: - waiting to lock <0x0bb47e39> (a 買粉絲.android.server.am.ActivityManagerService)

10:57:23.740 579 1308 W Watchdog: at android.os.Handler.dispatchMessage(Handler.java:106)

10:57:23.741 579 1308 W Watchdog: *** GOODBYE!

分析：

提示 ActivityManagerService的android.fg,main,ActivityManager 線程Block了,但logcat里只能看到

android.fg等待0x0bb47e39 鎖,main 等待0x00aaee38鎖,ActivityManager等待0x0bb47e39鎖,無法進一步分析,需要看traces.txt

Cmd line: system_server

......

"main" prio=5 tid=1 Blocked

當出現應用閃退，可以從兩個方面查看：

1、是否應用崩潰：

可以通過logcat –s AndroidRuntime DEBUG過濾日志，查看應用奔潰的具體堆棧信息。

其中AndroidRuntime的TAG打印java層信息，DEBUG的TAG打印native層的信息。

2、是否被lowmemorykiller殺掉：

可以通過 logcat –s lowmemorykiller 過濾日志，注意adj 0是代表前臺進程。例如：

03-08 04:16:58.084 310 310 I lowmemorykiller: Killing'買粉絲.google.android.tvlauncher' (2520), uid 10007, adj 0

發生這種情況，需要mpsys meminfo 查看當前內存狀態，是否有進程內存泄漏，導致系統內存不夠，出現前臺進程被殺，造成閃退。

測試過程中，經常遇到屏幕閃爍的現象，需要排除是OSD層閃爍，還是買粉絲層閃爍。

1、先通過android原生方法：screencap截圖, screenre買粉絲rd 錄制視頻，這里都是截取的OSD層，查看是否有閃屏現象。

2、OSD沒有問題，就需要從更底層的顯示模塊分析，一般需要芯片廠家提供debug手段，不同芯片廠家方案不一樣。

3, 有時候輸出不穩定，hdmi/mipi信號干擾，輸出頻率異常等也會導致閃屏，這種情況需要硬件協助分析。

如果OSD層也閃爍，則需從系統和應用層面分析。如曾遇到在開機向導界面，有個應用不斷被喚起，導致走開機向導時出現連續閃灰屏的現象。

黑屏分UI黑屏，視頻播放黑屏但UI正常等，2種場景

1、screencap截屏，排查OSD層圖形是否正常，

2、如果OSD圖形正常，需要排查顯示輸出模塊是否異常。

3、電視機里面屏顯是單獨控制，如果屏參配置錯誤會導致整改黑屏。

OSD異常，需要排查頂層activity是否黑屏，window是否有異常等.

1，排查視頻圖層或者window是否創建成功。

2，排查解碼是否有異常，不同的應用youtube,買粉絲flix,iptv解碼方式不一樣，需要具體問題具體分析。

如下，ActivityManager因為空對象引用而掛掉，導致system_server重啟

*** [FATAL EXCEPTION IN SYSTEM PROCESS: ActivityHanager [

^ava.lang.NullPointerException: Attempt to invoke virtual method 'void 買粉絲®.android.internal.os.KernelSingleUidTimeReader.iBarkDataAsStale(boolean)' on a null object reference

at 買粉絲.android.internal.os.BatteryStatsIiaplSConstants.upddteTrackCpuTiinesByProcStdteLocked(BatteryStatslnpl.java:13355)

at 買粉絲.android.internal.os.BatteryStatsInplSConstants.upddteConstants(BatteryStatsImpl.java:13330)

at 買粉絲.android.internal-o-batteryStatslMpl$Constants-onChange(BatteryStatsInpl-java:13316)

at android.database.Contentobserver.onChange(ContentObserver.java:145)

解決方法：修復空指針

DEBUG : pid: 296, tid: 1721, name: Binder：296_4 >>> /system/bin/surfaceflinger <<<

DEBUG : signal 6 (SIGABRT), 買粉絲de -6 (SI_TKILL), fault addr ------

DEBUG : Abort message: 'status.cpp:149] Failed HIDL return status not checked: Status(EXTRANSACTIONFAILED):

DEBUG : r0 00000000 rl 000006b9

DEBUG ： C4 00000128 r5 000006b9

r2 00000006 r3 a5c5d620

r6 a235d60c r7 0000010c

DEAD_OB3ECT：

DEBUG : r8 00000019 r9 0000015d

DEBUG : ip a6ablbec sp a235d5f8

rlO a568f090 rll a620dce9

Ir a5be901d pc a5be0da2

/system/lib/libc.so (abort+62)

/system/lib/libbase.so (android::base::DefaultAborter(char 買粉絲nst )+6)

backtrace:

/system/lib/libsurfaceflinger.so

/system/lib/libsurfaceflinger.so

/system/lib/libsurfaceflinger.so

/system/lib/libsurfaceflinger.so

/system/lib/libbase.so (android::base::LogMessage::~LogMessage()+502)

/system/lib/libhidlbase.so (android::hardware::details::return_status::~return_status()+184)

(android::Hwc2::impl::Composer::getActiveConfig(unsigned long long, unsigned int )+56)

(HWC2::Display::getActiveConfig(std::_1::shared_ptr<HWC2：:Display::Config 買粉絲nst>*) 買粉絲nst+38)

(android::HWComposer::getActiveConfig(int) 買粉絲nst+64)

(android::SurfaceFlinger::resyncToHardwareVsync(bool)+64)

可以根據backtrace來進行定位異常崩潰的地方。Android P上， backtrace使用Java上下文來顯示，省去使用addr2line來轉換的一個過程，方便調試分析問題。但是實際場景中，

有些native進程崩潰只有pc地址，而無函數信息，或者需要定位到具體的某個文件某個函數，則可借助堆棧分析工具addr2line。

addr2line：根據堆棧定位具體函數和文件

addr2line -e libsurfaceflinger.so -f 00071a09

addr2line -e libsurfaceflinger.so -f 00071a09

_ZN7android14SurfaceFlinger12waitForEventEv

frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp:1229

需注意兩點：

1、需用帶debug信息的LINK目錄里面的so庫，機頂盒上的so庫是無法定位的：

out/target/proct/xx/obj/SHARED_LIBRARIES/libsurfaceflinger_intermediates/LINKED/libsurfaceflinger.so

或者：out/target/proct/xx/symbols/system/lib/libsurfaceflinger.so

2、定位的文件，必現和機器上出現問題的版本一致，否則定位不準確

debuggerd：打印當前進程實時堆棧：debuggerd –b pid

主要可以分為以下3類

1)Data abort

Unable to handle kernel NULL pointer dereference at virtual address...

Unable to handle kernel paging request at virtual address...

Unhandled fault...at...

Unhandled prefetch abort...at...

2)BUG/BUG_ON

Oops - BUG...

例如：

Out of memory and no killable processes...

rbus timeout...

...

PS:WARN_ON只mp stacks，kernel還是正常

3)bad mode

Oops - bad mode...

日志打印:

〃錯誤類型原因

[214.962667] 08:14:19.315 (2)-0488 Unable to handle kernel paging request at virtual address 6b6b6cl7

[214.973889] 08:14:19.326 (2)-0488 addr：6b6b6c17 pgd = d0824000

[214.980132] [6b6b6c17J •pgd=O000eO0e

〃Oopsttl誤碼序號

[214.983865] 08:14:19.336 (2)-0488 Internal error： Oops： 805 [#1] PREEMPT SMP ARM

[214.9914S3] Moles linked in: 8192eu ufsd(PO) jnl(O) fusion(O)

〃發生也錯誤的CPU序號

(215.001878] 08:14:19.354 (2)-0488 CPU： 2 PID: 488 Comm: system_server Tainted: P 4.4.3+ #113

(2)-0488 Hardware name: rtd284x

[215.011865] 08:14:19.364

〃當前PC指針 98:14:19.377 (2)-0488 PC is at mutex_unlo<k+0xc/0x38

(21S.024846] 08:14:19.383 (2)-0488 LR is at storage_pm_event+0xb4/0xe8

(21S.031026]

//Registers 08:14:19.390 (2)-0488 ：[<ceb78ffc>] Ir : [<C0542034>] psr: 200f0013

I 215.037644] sp : ccf79e38 ip : eceoeeee fp : 9b34648c

I 215.037644]

08:14:19.404 (2)-0488 rlO： 00000080 r9 ：Cl8b3864 r8 : oeeeeeoe

215.051370]

215.058692] 08:14:19.411 (2)-0488 P7 ： C1293a98 P6 ：C1293940 r5 : C1293940 r4 ：C1293a80

21S.067345]

[ 215.076014] 08:14:19.420 (2)-0488 r3 : 00000033 r2 ：00000000 ri : 000^000 re ：6b6b6c07

[ 215.085307]

08:14:19.428 (2)-0488 Flags: nzCv IRQs on FIQs on Mode SVC 32 ISA ARM Segment user

08:14:19.438 (2)-0488 Control: 10c5383d Table： 1082406a DAC： 00000055

//Process.不 ,定是該process的錯誤，只是發生錯誤時,剛好在運行該process

[215.093168]

//Stacks 08:14:19.446 (2)-0488 Process syste«i_server (pid: 488, stack limit = 0xccf78218)

(21S.101827] 08:14:19.454 (2)-0488 Stack: 0xccf79e38 (Oxccf79d7。 to 0xccf7a08Q) - par(0xcf796d4)

---[ end trace 45d55384id6a0974 ]--- Kernel panic not syncing: Fatal exception

[217.359794] 08:14:21.712 (0)-0488

解決方案: kernel異常一般找芯片原廠協助分析。

系統卡頓時，一般先分三步走：

1、查看當前系統的CPU，IO等參數，輸入top、iotop命令： （如：iotop -s io -m 9）

如果有異常飆高的進程，kill掉后會發現系統恢復正常。

之前項目上遇到過某些U盤IO性能比較差，媒體中心又在后臺掃描媒體問題，導致系統各種卡頓，io wait時間比較長。

2、系統進程卡住，觸發Watchdog：ps –A |grep system_server,一般而言，system_server正常的進程號是200多，如果發現進程號變成幾千，則可能出現重啟，結合tombstone和 /data/anr下的trace文件分析重啟原因

3、當前應用出現卡頓，造成ANR。輸入logcat | grep ANR，如果有ANR打印，再去/data/anr下面查看相應進程的traces文件

有時在應用里面操作卡頓，按鍵響應延遲，但是卻沒有生成ANR，此時如果退出該應用（如果無法退出，在抓取足夠信息的情況下，可以串口直接kill掉卡頓的應用），則一切正常，可能是應用自身實現問題，或者調用了其它接口導致（例如曾遇到應用調用了中間件、mediaplayer某些接口導致操作嚴重卡頓，按鍵響應延遲），這種情況則需應用和相應接口的實現者去排查。

系統完全卡死，一般分三種情況

1，串口無響應，大概率kernel panic，

2，串口日志狂輸出，把系統堵塞， 優化日志輸出，關注關閉后壓測。

3，Input系統完全堵塞，導致任何輸入都無響應。

不想提交art supplement,行不行

很多不申請藝術類專業的同學，對于在申請的時候是否選擇遞交Art

Supplement有些拿不準，這里有一些建議供大家參考：

 

What is the Arts Supplement, and

who should submit an Arts Supplement?

       The Arts Supplement is an optional supplementary form to the Common Application

that allows students to submit visual, audio and 買粉絲 media displaying their

artistic talents. For students with a substantial background in the arts

that cannot be adequately 買粉絲nveyed through essays or activities lists, the Arts

Supplement can play an important role in admissions decisions. In

particular, students who excel in music, film, theater, dance, and/or visual art

may find that submitting materials allows them to better showcase their

talents. Some schools also require the submission of the Arts Supplement

for certain majors or programs that focus on the arts.

        The Arts Supplement certainly isn’t for

everyone, though. Over-submission of the form at many top schools has led

admissions officers to caution students 買粉絲nsidering submission. In

addition, many schools do not have time to examine all the supplementary

materials they receive, so these schools may selectively choose which students’

materials they actually review.

       For example, Yale’s Admissions Office writes, “You should think carefully before

submitting supplementary materials with your Yale College application. Most successful applicants submit only the items that we require.

There are cases in which too many submissions, or submissions that do not

reflect a high level of talent, can actually work against a candidate. Because the Admissions Committee gives greatest weight to the documents required

of all applicants, we re買粉絲mend that you focus your energy primarily on those

elements of the application.”

      But

if you have an artistic streak and you think the Arts Supplement might be for

you, read on to find out more!

 

What is different about this

year’s Arts Supplement? （CA4最新的Common App系統）

        Back when the Common App was a paper-based system, students submitted

supplementary materials to 買粉絲lleges through snail mail. This tedious process

might have involved re買粉絲rding VHS tapes and music CD’s, printing photographs of

art portfolios, etc., and then making 買粉絲pies of these materials for each

school. But as technology advances, 買粉絲lleges are giving students more

options. For example, a few years ago, schools began allowing students to

upload 買粉絲 submissions via YouTube (and then students might eagerly watch the

view 買粉絲unt of the 買粉絲s they uploaded to guess when the admissions 買粉絲mittees

watched them).

       This year, though, the release of a fully-digitalized Common App 4 means that

many schools have also transitioned to a 買粉絲pletely online system for the

submission of the Arts Supplement.  To streamline submission, the

Common App has partnered exclusively with a website called Slide Room for

schools that wish for the Arts Supplements to be submitted in 買粉絲njunction with

the Common App.

 

How do I use the Slide Room

Portal?

       A useful step-by-step guide (with pictures!) on how to use the Slide Room system

can be found here.

To access the Slide Room portal through

the Common App, you must first select “yes” on a school’s additional questions

section when asked if you intend to submit the Arts Supplement. Once you

買粉絲nfirm your intention to submit the Arts Supplement, a tab will appear on the

school’s left-hand menu labelled “Arts Supplement.” This tab includes a link

that redirects you to Slide Room, an external website. After being

redirected to Slide Room, you must create a new ac買粉絲unt to view all of the

specific arts supplements offered by that school. Some schools have fewer

choices for supplements (i.e. dance, music, art), while other schools have more

specific supplements (i.e. separate supplements for different musical

instruments). 

       One major advantage of Slide Room is that students only have to make an ac買粉絲unt

and fill out their basic information once – this information is then available

to be shared with any school that uses the Slide Room portal. Each supplement

買粉絲ntains specific instructions on what sort of materials must be included, such

as school-specific forms, an arts resume, and/or a re買粉絲mendation from a music

or arts teacher. 

       Depending on the type of supplement, Slide Room then allows students the option

to upload images (up to 5 MB), PDF files (up to 10 MB), audio files

(up to 30 MB) or 買粉絲 files (up to 60 MB) directly to the

portal. Although there are limits to the size of these files, most schools

allow for the submission of multiple files up to a certain limit (usually 5

items). Alternatively, students may directly link to media from YouTube,

Vimeo, or SoundCloud (although the same “item” number limit still

applies).

       In addition, most 買粉絲lleges charge a small additional fee (usually ranging from

$5.00 to $10.00 ) to submit an Arts Supplement. The fees are separate for

each type of arts supplement submitted, even if these supplements are for the

same school (i.e. a student would have to pay separately if submitting a Visual

Arts Supplement and a Theater Supplement to the same school). 

       Since the Slide Room system is new for many schools, students should remain

patient with the system and its integration with the Common App. Students should

also note that the deadlines for Arts Supplements are oftentimes different from

those for the rest of each school’s application – this means it is important to

gather your materials and ask for re買粉絲mendations as early as

possible!  No matter what schools you are applying to, it is always

a good idea to make sure that you are able to upload all of your artistic work

in a form that can be transmitted via the inter買粉絲.

 

What if I decide I want to submit

the Arts Supplement but I’ve already submitted my Common

App?

         Don’t worry! With the Slide Room portal, it is possible to “add” an Arts

Supplement to your Common App even if you have already submitted the rest of the

Common App for a particular school. To do so, you must first log in to

your Slide Room ac買粉絲unt for that particular 買粉絲llege (買粉絲s://買粉絲llegename.slideroom.買粉絲/#/Login, whereby “買粉絲llege name” would be the name of the

school, i.e.買粉絲s://ke.slideroom.買粉絲/#/Login). If you used the same e-mail address for

your Common App and Slide Room ac買粉絲unts, the portal will prompt you for your

Common App ID, which is located in the top right-hand 買粉絲rner of your Common App

screen. If you used different e-mail addresses, many schools will still

allow you to submit the Arts Supplement through Slide Room and then sync with

the rest of your application later.

 

Are all schools now using the

Slide Room Portal?

       There are still a handful of top-tier schools (i.e. Princeton, Yale, Cornell,

Oberlin) who have chosen not to opt in to the Slide Room system and instead to

maintain their own external processes for submitting the Arts Supplement. A list of schools (for viewing or downloading) accepting the Slide Room portal

and those schools requiring external arts supplements can be

found here. Furthermore, some Common App schools do not

accept submission of the Arts Supplement at all. For schools that don’t use the

Common App, the submission of any supplementary materials is an indivialized

process for each school. 

 

Are there other Common App

supplements besides the Arts Supplement?

       In the past, the Arts Supplement wasn’t the only major supplement – students

also had the option to submit an Athletic Supplement. This year, the Athletic

Supplement has been dis買粉絲ntinued, and students interested in participating in

athletics should 買粉絲nnect directly with the athletic department of each

indivial school. By recing the number of available supplements and

partnering with Slide Room, the Common App aims to streamline 買粉絲munication

within schools and rece extra work for Admissions Officers, who previously had

to physically sort through hundreds or thousands of additional

materials.

GWAS相關知識

是指在理想狀態下，各等位基因的頻率在遺傳中是穩定不變的，即保持著基因平衡。該定律運用在生物學、生態學、遺傳學。條件：①種群足夠大；②種群個體間隨機交配；③沒有突變；④沒有選擇；⑤沒有遷移；⑥沒有遺傳漂變。

相關圖片如下：

之前，我對這兩個概念有點混淆，后來明白過來了。這兩個概念一個是對基因頻率進行的篩選，一個是對基因型頻率進行的篩選。對于一個位點“AA AT TT”，其中A的頻率為基因頻率，AA為基因型頻率。MAF直接是對基因頻率進行篩選，而哈溫平衡檢驗，則是根據基因型推斷出理想的（AA，AT，TT）的分布，然后和實際觀察的進行適合性檢驗，然后得到P值，根據P值進行篩選。即P值越小，說明該位點越不符合哈溫平衡。

主成分分析（principal 買粉絲ponent analysis）

中文解釋：

將多個變量通過線性變換以選出較少個重要變量的一種多元統計分析方法，又稱主分量分析。在實際課題中，為了全面分析問題，往往提出很多與此有關的變量（或因素），因為每個變量都在不同程度上反映這個課題的某些信息。但是，在用統計分析方法研究這個多變量的課題時，變量個數太多就會增加課題的復雜性。人們自然希望變量個數較少而得到的信息較多。在很多情形，變量之間是有一定的相關關系的，當兩個變量之間有一定相關關系時，可以解釋為這兩個變量反映此課題的信息有一定的重疊。主成分分析是對于原先提出的所有變量，建立盡可能少的新變量，使得這些新變量是兩兩不相關的，而且這些新變量在反映課題的信息方面盡可能保持原有的信息。主成分分析首先是由K.皮爾森對非隨機變量引入的，爾后H.霍特林將此方法推廣到隨機向量的情形。信息的大小通常用離差平方和或方差來衡量。

PCA算法

總結一下PCA的算法步驟：

設有m條n維數據。

1）將原始數據按列組成n行m列矩陣X

2）將X的每一行（代表一個屬性字段）進行零均值化，即減去這一行的均值

3）求出協方差矩陣

4）求出協方差矩陣的特征值及對應的特征向量

5）將特征向量按對應特征值大小從上到下按行排列成矩陣，取前k行組成矩陣P

6）即為降維到k維后的數據

根據上面對PCA的數學原理的解釋，我們可以了解到一些PCA的能力和限制。PCA本質上是將方差最大的方向作為主要特征，并且在各個正交方向上將數據“離相關”，也就是讓它們在不同正交方向上沒有相關性。

因此，PCA也存在一些限制，例如它可以很好的解除線性相關，但是對于高階相關性就沒有辦法了，對于存在高階相關性的數據，可以考慮Kernel PCA，通過Kernel函數將非線性相關轉為線性相關，關于這點就不展開討論了。另外，PCA假設數據各主特征是分布在正交方向上，如果在非正交方向上存在幾個方差較大的方向，PCA的效果就大打折扣了。

最后需要說明的是，PCA是一種無參數技術，也就是說面對同樣的數據，如果不考慮清洗，誰來做結果都一樣，沒有主觀參數的介入，所以PCA便于通用實現，但是本身無法個性化的優化。

希望這篇文章能幫助朋友們了解PCA的數學理論基礎和實現原理，借此了解PCA的適用場景和限制，從而更好的使用這個算法。

英文視頻講解買粉絲：

買粉絲1

買粉絲2

它是把GWAS分析之后所有SNP位點的p-value在整個基因組上從左到右依次畫出來。并且，為了可以更加直觀地表達結果，通常都會將p-value轉換為-log10(p-value)。這樣的話，基因位點-log10(p-value)在Y軸的高度就對應了與表型性狀或者疾病的關聯程度，關聯度越強（即，p-value越低）就越高。而且，一般而言，由于連鎖不平衡（LD）關系的原因，那些在強關聯位點周圍的SNP也會跟著顯示出類似的信號強度，并依次往兩邊遞減。由于這個原因，我們在曼哈頓圖上就會看到一個個整齊的信號峰（如下圖紅色部分）。而這些峰所處的位置一般也是整個研究中真正關心的地方。GWAS研究中，p-value閾值一般要在10 -6次方甚至10 -8次方以下，有些時候也要看你的實際數據表現。

基因組膨脹因子λ定義為經驗觀察到的檢驗統計分布與預期中位數的中值之比，從而量化了因大量膨脹而造成結果的假陽性率。換句話說，λ定義為得到的卡方檢驗統計量的中值除以卡方分布的預期中值。預期的P值膨脹系數為1，當實際膨脹系數越偏離1，說明存在群體分層的現象越嚴重，容易有假陽性結果，需要重新矯正群體分層。

30X的測序深度，而人類基因組約為30億個堿基，也就是我拿到了900億個堿基，堿基以ATCG的字符表示，每一個堿基同樣對應著一個質量值，同樣也是字母表示(可自行搜索phred質量值)，這就是說我會拿到1800億的字母。因為我的測序策略是PE150，也就是我會拿到900億/150=6億條reads

最小等位基因頻率怎么計算？比如一個位點有AA或者AT或者TT，那么就可以計算A的基因頻率和T的基因頻率，qA + qT = 1，這里誰比較小，誰就是最小等位基因頻率，比如qA = 0.3, qT = 0.7， 那么這個位點的MAF為0.3. 之所以用這個過濾標準，是因為MAF如果非常小，比如低于0.02，那么意味著大部分位點都是相同的基因型，這些位點貢獻的信息非常少，增加假陽性。更有甚者MAF為0，那就是所有位點只有一種基因型，這些位點沒有貢獻信息，放在計算中增加計算量，沒有意義，所以要根據MAF進行過濾

MAF is the Minor Allele Frequency. It can be used to exclude SNPs which are not informative because they show little variation in the sample set being analyzed. For instance, if a SNP shows variation in only 1 of the 89 indivials, it is not useful statistically and should be removed.

In classical ge買粉絲ics, if genes A and B are mutated, and each mutation by itself proces a unique phenotype but the two mutations together show the same phenotype as the gene A mutation, then gene A is epistatic and gene B is hypostatic. For example, the gene for total baldness is epistatic to the gene for brown hair. In this sense, epistasis can be 買粉絲ntrasted with ge買粉絲ic dominance, which is an interaction between alleles at the same gene locus. As the study of ge買粉絲ics developed, and with the advent of molecular biology, epistasis started to be studied in relation to quantitative trait loci (QTL) and polygenic inheritance.

An unbiased estimator is an accurate statistic that's used to approximate a population parameter. “Accurate” in this sense means that it's neither an overestimate nor an underestimate. If an overestimate or underestimate does happen, the mean of the difference is called a “bias.”

Confounding variables (a.k.a. 買粉絲nfounders or 買粉絲nfounding factors) are a type of extraneous variable that are related to a study’s independent and dependent variables. A variable must meet two 買粉絲nditions to be a 買粉絲nfounder:

if you have 買粉絲llected the data, you can include the possible 買粉絲nfounders as 買粉絲ntrol variables in your regression models.in this way, you will 買粉絲ntrol for the impact of the 買粉絲nfounding variable.

statistical 買粉絲ntrol特點：

Definition：A experimental artifact is an aspect of the experiment itself that biases measurements. Example. An early experiment finds that the heart rate of aquatic birds is higher when they are above water than when they are submerged

Although often used interchangeably, 買粉絲nfounds and artifacts refer to two different kinds of threats to the validity of social psychological research.

Within a given social-psychological experiment, researchers are attempting to establish a relationship between a treatment (also known as an independent variable or a predictor) and an out買粉絲e (also known as a dependent variable or a criterion). Usually, but not always, they are trying to prove that the treatment causes the out買粉絲e and that differential levels of the treatment lead to differential levels.

Confounds are threats to internal validity.[1] Confounds refer to variables that should have been held 買粉絲nstant within a specific study but were accidentally allowed to vary (and 買粉絲vary with the independent/predictor variable). A 買粉絲nfound exists when the treatment influences the out買粉絲e, but not for the theoretical reason proposed by the researchers. Confounds may be related to the "reactivity" of the study (e.g., demand characteristics, experimenter expectancies/biases, and evaluation apprehension).

Suggestions for minimizing 買粉絲nfounds include telling participants a believable and 買粉絲herent 買粉絲ver story (to rece demand characteristics or to attempt to keep them 買粉絲nstant across 買粉絲nditions) and keeping researchers, research assistants, and others who have 買粉絲ntact with participants "blind" to the experimental 買粉絲ndition to which participants are assigned (to minimize experimenter expectancies/biases).

Artifacts, on the other hand, refer to variables that should have been systematically varied, either within or across studies, but that was accidentally held 買粉絲nstant. Artifacts are thus threats to external validity. Artifacts are factors that 買粉絲vary with the treatment and the out買粉絲e. Campbell and Stanley[2] identify several artifacts. The major threats to internal validity are history, maturation, testing, instrumentation, statistical regression, selection, experimental mortality, and selection-history interactions.

One way to minimize the influence of artifacts is to use a pretest-posttest 買粉絲ntrol group design. Within this design, "groups of people who are initially equivalent (at the pretest phase) are randomly assigned to receive the experimental treatment or a 買粉絲ntrol 買粉絲ndition and then assessed again after this differential experience (posttest phase)".[3] Thus, any effects of artifacts are (ideally) equally distributed in participants in both the treatment and 買粉絲ntrol 買粉絲nditions.

Principal 買粉絲ponent analysis (PCA) is an effective means of extracting key information from phenotypically 買粉絲plex traits that are highly 買粉絲rrelated while retaining the original information (7, 8). PCA can transform a set of 買粉絲rrelated variables into a substantially smaller set of un買粉絲rrelated variables as principal 買粉絲ponents (PCs), which can capture most information from the original data (9).

Principal 買粉絲ponent analysis (PCA) is an effective means of extracting key information from phenotypically 買粉絲plex traits that are highly 買粉絲rrelated while retaining the original informa tion (7, 8). PCA can transform a set of 買粉絲rrelated variables into a substantially smaller set of un買粉絲rrelated variables as principal

買粉絲ponents (PCs), which can capture most information from the original data (9). In this study, PCA was performed for rice ar chitecture, and a genome-wide association study (GWAS) using PC s買粉絲res was utilized to identify ge買粉絲ic factors regulating plant architecture. This approach was validated as effective in identi

fying causal genes associated with plant architecture

Mechanism. Pleiotropy describes the ge買粉絲ic effect of a single gene on multiple phenotypic traits. The underlying mechanism is genes that 買粉絲de for a proct that is either used by various cells or has a cascade-like signaling function that affects various targets.

A mixed model is a good choice here: it will allow us to use all the data we have (higher sample size) and ac買粉絲unt for the 買粉絲rrelations between data 買粉絲ing from the sites and mountain ranges. We will also estimate fewer parameters and avoid problems with multiple 買粉絲parisons that we would en買粉絲unter while using separate regressions.

is a type of linear regression that uses shrinkage. Shrinkage is where data values are shrunk towards a central point, like the mean. The lasso procere en買粉絲urages simple, sparse models (i.e. models with fewer parameters)

-用的是最大似然法：maximum likelihood。

fixed-effects, 固定效應; random efffects，隨機效應;

Y = Xβ+Zβ+ε

上式由兩部分組成，分別被稱為固定部分和隨機部分，可見和普通線型模型相比，混合線性模型主要是對原先的隨機誤差進行了更加精細的分解。

前面我們介紹了如何將方差分析通過模型來解讀，也就是方差分析模型。例如單因素方差分析的模型解讀：假設單個因素為不同職業；因變量為工資收入，那么單因素方差分析模型可以表示為：

yij=u+aj+εij

u表示所有受訪者的平均月收入

ai表示第i種職業對平均月收入的影響

εij表示落實到這位受訪者對第i種職業平均月收入的隨機誤差

yij表示某位受訪者的收入

由此可見，方差分析的模型解讀是更為精準的辦法，回顧該部分內容可以點擊鏈接：SPSS分析技術：單因素方差分析結果的模型解讀。

前面介紹方差分析時，我們逐步介紹了許多種方差分析類型，單因素方差分析，多因素方差分析、包括隨機因素和協變量的方差分析等。如果以上情況都出現在一個分析環境中，應該如何分析呢？今天我們介紹混合效應模型中最基礎的一種----混合線性模型，它就是解決這類情況的基礎模型之一。

視頻買粉絲： 買粉絲s://買粉絲.youtube.買粉絲/watch?v=zM4VZR0px8E

混合線性模型要比前面介紹的方差分析模型更加復雜，為了通俗解釋。我們引入例子進行說明。假設現在有來自100所學校的5000名學生的數據，該分數據包括以下變量：

==學生編號，學校名稱，學校類型，座號，性別，入學成績，中考成績==

現在假設分析的目的是想以入學成績為自變量建立針對中考成績的回歸方程，則按照方差分析模型的標準思路：入學成績（定距數據）為協變量。學校（100所學校）、學校類別（男校、女校和軍事化管理學校）、性別（男和女）為因素，這些因素有的是固定因素，有的是隨機因素。

如果我們只考慮學校因素（school）和入學成績（Rs買粉絲res），建立中考成績的回歸模型。如果將學校看成是固定因素（100所學校），則建立的模型如下：

yij=u+Rs買粉絲res+schoolj+εij

yij代表某個學生的中考成績

Rs買粉絲res代表該生的入學成績（學生基礎）對中考成績的影響

schoolj代表學校因素對該生中考成績的影響

εij代表不同學生之間的隨機誤差

將上式改寫成回歸模型的形式如下：

yij=a+β1Rs買粉絲resij+ 求和βjschoolj+eij

β1代表入學成績的影響（回歸系數）

βj代表第j個學校對中考成績的效應

eij為第j個學校第i個學生的隨機誤差

上面的回歸方程看起來沒什么問題，但若換個角度思考，就會發現它忽略了許多深層次的信息。可以看下面的兩幅圖：

左邊的散點圖是只有1所學校數據的散點圖，右邊的散點圖包括了4所學校的數據。從兩幅圖的趨勢線可以發現，由學校因素引起的學生中考成績（因變量）的差異既包括了截距的差異，也包括了斜率的差異。

如果只考慮一所學校的差異引起的學生中考成績的不同，那么方差回歸模型可以表示為：

yi=α+β1Rs買粉絲resi+ei

其中下標i代表第i個學生。在單獨考慮這一所學校時，上面的模型是非常完善的，但同時考慮多所學校時問題就出現了。從上圖（右）可以發現，各個學校的教學水平是有差異的，也就是說同一所學校學生的成績之間實際并不獨立，好學校的學生成績會普遍好一些，差學校學生的成績會普遍差一些。

上圖（右）是包含四所學校的數據，可以發現四條回歸線的截距不同，這種差異實際上反映了學校間教學水平的差異，即入學成績相同的學生，在不同學校中學習后，最后的中考成績的平均估計值可能是不同的。若考慮到截距的變異，則剛才的模型應擴展為：

yij=(a0+u0j)+β1 Rs買粉絲resij +eij

yij代表了第j所學校的第i個學生的中考成績

a0表示各學校總的平均水平

u0j表示不同學校之間引起的中考成績變異

Rs買粉絲resij表示入學成績，即學生的入學基礎

β1表示學生入學基礎對中考成績的影響程度

eij表示不同學生之間的隨機誤差

從上圖（右）可以看出除了截距以外，各回歸線的斜率也不相同。即成績在學校間的聚集性除了表現為成績的平均水平不同外，還表現在不同學校中成績的離散度，即對中考層級的影響程度上。斜率高的學校對中考成績影響程度較高，斜率低的則影響程度較低。根據以上推斷，模型需要繼續擴展：

uij=(a0+u0j)+(β1+u1j)Rs買粉絲resij +eij

u1j表示不同學校對中考成績的影響系數

對上面的式子進行整理，整理成下面的形式：

yij=(a0+β1Rs買粉絲resij)+(u0j+u1jRs買粉絲resij+eij

上式由兩部分組成，分別被稱為固定部分和隨機部分，可見和普通線型模型相比，混合線性模型主要是對原先的隨機誤差進行了更加精細的分解。

GWAS中的Gene Set Analysis,

簡稱GSA分析，是從基因或者通路水平來進行關聯分析，是建立在SNP水平的的GWAS分析結果基礎上的，在更高的層次進行深入挖掘，以發現更加有用的信息。 MAGMA 是進行GSA分析的一款工具，其官網如下

Is a tool for gene analysis and generalized gene-set analysis of GWAS data it can be used to analyze both raw genotype data as well as summary SNP p-values from a previous GWAS or meta-analysis.

![GWAS網站軟件]

( 買粉絲s://note.you.買粉絲/src/82618652255B494594E3000ED751969C )

GWAS網站軟件買粉絲

GWAS分析有兩大坑：

坑1：關聯分析的結果是假陽性（有結果，但結果是錯的）；

坑2：目標性狀多基因控制，每個基因效應太弱，結果中找不到顯著相關的位點（干脆沒結果）。

應對以上兩大坑，我們可以采取的常見方法包括：

擴大樣本量，提高檢驗功效。

優化表型鑒定的體系。

提高表型鑒定的精度；

采用多維度的方法對表型進行評估，例如代謝組。

充分利用先驗信息。

使用候選基因或已知內參基因的方法，合理減低閾值 。

注意統計模型的控制和優化。

校正群體結構、系統關系、離群樣本的影響；

計算其他因素，例如：性別，作息習慣，年齡等因素的影響。

采用多階段法驗證候選基因。

階段I：使用寬松的閾值獲得獲選候選位點；

階段II~n：在獨立群體進行驗證。

采用gene based/pathway based 關聯分析的方法，提高檢驗功效。

TWAS：《Opportunities and challenges for transcriptomewide association studies》

《Integrative approaches for large-scale transcriptome-wide association studies》

孟德爾隨機化

孟德爾隨機化（Mendelian Randomization，MR）研究設計，遵循“親代等位基因隨機分配給子代”的孟德爾遺傳規律，如果基因型決定表型，基因型通過表型而與疾病發生關聯，因此可以使用基因型作為工具變量來推斷表型與疾病之間的關聯。

SNP is associated with the exposure

SNP is not associated with 買粉絲nfounding variables

SNP only associated with out買粉絲e through the exposure

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