# I’m Zigang Xiao (Ivan), a PhD candidate in University of Illinois.

I write about technical stuff in the field of computer science, my hobbies, including guitar playing and ballroom dancing, and my study abroad experience in US. And yes, some of my posts are in Chinese ;)

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# Popular Watches Under $150 - - posted in I’ve been looking around entry-level watches for some time. Recently, I answered a question in Zhihu (Chinese Quora), and I feel like to transcribe this collection in my blog. # Watch Review: Rodina R005GB - - posted in So NOMOS has this awesome looking Bauhaus style watch: Tangente. Apparently everyone wants one, but not everyone wants to break their bank ($2330 USD).

Luckily, we have an alternative here: Rodina series watches (or with Date).

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# Notes on Maximum Likelihood, Maximum a Posteriori and Naive Bayes

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Let $$\data$$ be a set of data generated from some distribution parameterized by $$\theta$$. We want to estimate the unknown parameter $$\theta$$. What we can do?

Essentially, we want to find a most likely value of $$\theta$$ given $$\data$$, that is $$\arg \max P(\theta | \data)$$. According to Bayes Rule, we have

$P(\theta \given \data) = \frac{P(\data \given \theta)P(\theta)}{P(\data)}$

and the terms have the following meanings:

• $$P(\theta \given \data)$$: Posterior
• $$P(\data \given \theta)$$: Likelihood
• $$P(\theta)$$: Prior
• $$P(\data)$$: Evidence

# Fix Mid 2009 MBP RAM Not Recognized Issue

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A few days ago, I encountered an issue which seems to be common among mid-2009 MBPs: one of the RAM (in slot 1) is not recognized anymore. Or, sometimes it is recognized, but after sleep and wake up, the computer freezes and impossible to recover but force power off.

# Replacing SATA Cable in Mid 2009 MBP

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Recently, my mid 2009 MBP (Model A1278) fails to recognize the hard drive. My first bet was another disk failure on me, but it was not the case. I took down the hard drive and put it to a mobile hard drive case and it can be read smoothly.

# My Octopress Blogging Flow

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After blogging with Octopress for a while, I have already gained some insights on it, and my publishing flow has been smoother. I think it is right time to share my flow as a reference.

# Sparse Image Reconstruction via L1-minimization

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 Original Minimum Energy Reconstruction Sparse Reconstruction

## Introduction

This is a follow up of the L1-minimization series. The previous two posts are: