Saurav R. Tuladhar

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Provincetown visit

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Provincetown harbor from the High Pole Hill

After living in the Bay State for the last eight years, I finally visited the famed Provincetown during the Memorial day weekend. Provincetown (also locally called the P-town) is located at the tip of the Cape Cod region in Massachusetts. One can get to the P-town either by driving via US Route 6 which goes all the way to the town. But during a busy weekend, you are highly likely to get stuck in heavy traffic before you can even enter the Cape Cod region. So in order to avoid the ‘cape traffic’, we decided to take a ferry ride from Boston to Provincetown.

The Boston Harbor Cruises ferry ride was $88/person (roundtrip) and took about 90 minutes each way.  The ferry leaves from Long Wharf in Boston. If you are planning to do a weekend one day trip to the P-town (as we did) and looking for a parking, I strongly recommend the Post Office Square parking garage. It is only about 10-15 minutes walk from the garage to Long Wharf and the weekend fare is only $9, which is significantly cheaper compared to other parking lots nearby. Our morning ferry was at 9 AM, so we arrived at the parking garage around 7:30 AM and had plenty of parking spots.

Provincetown engraving

The ferry left the Long Wharf sharp at 9 AM and arrived at the Macmillan Wharf in Provincetown at litter after 10:30 AM. A warning, during the first 30 minutes of the ferry ride out of Boston, the sea was rough enough to cause sea-sickness to several passengers including us. The ferry crew were giving out paper bags incase somebody threw up.

From the Macmillan Wharf, it is a short walk to the Commercial Street which is the main thoroughfare of the town. There are lots of shops along the street and tourists like us walking about. I was surprised by how narrow the street was, but it makes sense give the time when the town was established. We arrived early enough that there weren’t too many people on the street (yet!), so walking around Commercial St was fun enough.

As you get of the ferry and walk towards the town, it is hard to miss the Pilgrim Monument  tower, which is the tallest structure in the town. We decided to visit the monument/museum where the entrance fee was $12/person. You can climb up the tower on foot. The climb is a combination of stairs and inclined flights. It must have taken us about 20 minutes to get to the top. But the views of the harbor and the town from the top are well worth the climb.

I also learnt that the monument was erected to mark the arrival of the Pilgrims, the early European settlers, in the Provincetown in 1620. The common belief around is that the Pilgrims first make landfall in Plymouth, Massachusetts. But it turns out that the Pilgrims actually landed in Provincetown and docked their ship, the Mayflower, in the harbor for a week before departing for Plymouth.

Pilgrims Monument

By the time we returned from the monument, and  wen to the Commercial St for lunch, the street was full of people. So after grabbing lunch, we ventured out of the town towards the shores. Crowd filled Commercial St can feel a bit suffocating, but as you move away from downtown and approach the shores the cape surrenders its most intimate natural beauty to its visitors. The Cape Code region has a distinct outlook due to it geography. I have noticed this ‘capey feeling’ every I visited the this region. The Provincetown shores were no different. Its rustic mixed with the constant sound of waves hitting the shores. All this is very relaxing.

Quintessential cape

Quintessential cape

We reached the Herring Cove beach, which is about 1.5 miles west of downtown. The beach crowd was not there and the water was still freezing cold. But still the Sun was warm enough to enjoy the late afternoon basking. After spending about and hour in the Sun and walking along the shoreline we headed back to the hustle and bustle of the Commercial St.

Herring Cove Beach

Our return ferry was scheduled for 8:30 PM and this time of the year the days are long and the Sun sets around that time. Just before our ferry departed, P-town treated us with this glorious sunset view leaving a lasting memory of the trip.

Pilgrims Monument

Written by Saurav

June 3, 2017 at 10:14 AM

Resources on Kalman filters for tracking applications

For the last couple of months, I have been working with Kalman filter and its variations for aircraft tracking applications. I have found following resources helpful in the course of learning about Kalman filters.

Estimation with Applications to Tracking and Navigation: Theory Algorithms and Software , Y. Bar-Shalom; T. Kirubarajan; X. Li

Prof. Y. Bar-Shalom is well known in the area of tracking applications. This book by Bar-Shalom and co-authors is the standard text book for anyone interested in learning about applying Kalman filters. The authors aim to “make things simple, but not too simple; clear but not too clear“. The book not only presents theoretical derivation of filters, but also discusses implementation details. I have found the discussion on practical issues extremely helpful in the course of implementing the filters myself.

Kalman and Bayesian Filters in Python

This is a book by Roger Labbe. This book covers a wide range of topics related to Kalman filters and its applications with focus on practical applications. What I liked about this book is that the entire book is composed as a Jupyter notebook. As a result, Roger not only presents the mathematical background but also presents code implementation of the filters. FilterPy is the accompanying python package which provides implementation of all the filters discussed in the book. If you are interested, it is straight forward to change the sample code in the chapter notebooks and see changes for yourself. This book is a fine example of literate programming.

 

Written by Saurav

August 14, 2016 at 7:35 PM

Posted in Uncategorized

Traceroute to Nepal

traceroute is a wonderful tool to analyse network structure. According to its man page,

traceroute tracks the route packets taken from an IP network on their way to a given host. It utilizes the IP protocol’s time to live (TTL) field and attempts to elicit an ICMP TIME_EXCEEDED response from each gateway along the path to the host.

From time to time, I like to run my traceroute to explore how I connect to different websites via my ISP’s network. It is specially interesting for me to to traceroute tests from US to servers hosted in Nepal, as I have some idea about how internet traffic flows in/out of Nepal. Today I’ll present results on traceroute test to Nepal Telecom’s (NT) website. Since NT had optical fiber links through to India and beyond, it will be interesting to see which links are utilized for a packet to reach from US to NT.

Traceroute result

Traceroute output for Nepal Telecom website.

Analysis:

  • Hops 1 – 9 , the packets are still in US
  • The trace starts from my router and goes into Comcast network and  to BOS (Boston) in hop 4 and comes down to NYC ( New York City ) in hop 7 via routers at Woburn and Needham MA in hos 5 and 6 respectively
  • At NYC, the packet drops off from Comcast network to L3’s  10 Gigabit ethernet links. Since NYC is the main landing site for Trans-Atlantic optical fiber cables coming ashore east coast in US,  it is expected that the packet going out to Nepal would also follow the same path.
  • From NYC , the next hop(9) is  to Airtel in India via L3’s 10Gigabit link
  •  Among several telecom operators in India, NT has bought the largest bandwidth with Airtel, so it makes sense that the route via Airtel’s network is most viable one.
  • At hop 11, the packet reached India. This is evident from the jump in round trip delay to ~400ms which translates to ~ 11,000 km. The fiber landing site is most likely Mumbai, India.
  • From there on, the packet enters Nepal at hop 12.  The router IP 202.70.x.x belongs to NT. The router at hope 12 is a Border Gateway router, most probably at Bhairahawa  where most of NT connection goes through to India.
  • The the packet goes through Butwal to Pokhara (pkr.btw) in hope 13
  • From Pokhara, the packet reaches NT’s Intn’l Exchange Bldg at Patan on hop 14. From there on the packet finally reaches the webserver at NT’s central office at Bhadrakali.

This was a traceroute analysis through Comcast network. Next I’ll do the same kind of analysis for trace through Verizon DSL network.

Written by Saurav

May 3, 2012 at 11:58 PM

Posted in Uncategorized

RMTool for Polynomial Method : The Bottleneck?

I have been reading The Polynomial Method for Random Matrices by N. Raj. Rao and A. Eldeman as a part of literature review for my PhD research. In this paper, the authors present a method to determine the limiting eigen distribution of  a particular subset of random matrices called algebraic random matrices.  In the proposed method, the Stieltjes transform of the limiting eigen distribution is encoded as a root of a bivariate polynomial. A defined set of transformations ( deterministic and stochastic )   on the matrix is mapped to an operation on the bivariate polynomial. The limiting eigen distribution of the resulting matrix can be determined from the new bivariate polynomial.

This method heavily relies on the symbolic computation methodology.  In parallel with the development of the mathematical framework for the polynomial method, the authors have developed a Matlab toolbox called the RMTool which leverages the symbolic computation capability of Matlab. However the RMTool uses the Maple Symbolic Toolbox for Matlab which Mathworks no longer supports (Above version 2009a). The original RMTool might even have been written in Maple itself and later forked to a Matlab toolbox. This has made RMTool extremely platform dependent tool preventing it from being used by other researchers. The method was proposed sometime in 2005 but I can hardly find an alternative reference on this topic or its application. It seems  me that the rigidity of the RMTool may be limiting its potential as a powerful tool in random matrix analysis and application to engineering problems.

I have been looking at possibilities of porting the RMTool to the new Matlab Symbolic Toolbox which is based on MUPad. I am also planning on developing a new package ( from scratch :o) on a more robust and compatible platform ( Python with Sage ). But these ideas are still in early phase and need a thorough understanding of the polynomial. method.

 

 

Written by Saurav

November 9, 2011 at 5:23 PM

Posted in Uncategorized

Fall 2011 at UMassD

The Fall 2011 semester officially commenced from 7th September. In the beginning of the summer I had already registered for a course on Discrete Mathematics ( MTH 550) and also planned to audit the CIS course on Algorithms and Data Structures.. I am also registered for Abstract Algebra (MTH 441) as suggested by my advisor. In addition to all that I am also attending the course on Random Signals and Systems being taught by my advisor.

 

Written by Saurav

September 22, 2011 at 10:24 AM

Posted in Uncategorized

Welcome

I have started this blog as a place where I can put forward my ideas and thoughts on my research/studies. This blog was inspired by my friend Abhishek Dutta who also maintains a blog about his research.

Written by Saurav

September 3, 2011 at 6:33 PM

Posted in Uncategorized