Into the Unknown
TCP/IP Protocol Suite is to build a network of networks (Internet) that can operate over multiple, coexisting, and heterogeneous network technologies. It provides ubiquitous connectivity through the IP packet transfer. Besides the two well-known protocols, TCP (Transmission Control Protocol) and IP (Internet Protocol), there are other protocols: The Protocol Data Units (PDUs) of a given…
International Transaction in 19th Century Suppose we have a surplus country which is selling goods and receiving bills of exchange (the promise to pay in 90 days from a deficit country) as payments. On the other side of the trade, the deficit country buys the goods and issuing the bill of exchange. However, the bill…
The purpose of fitting models to data is to help answer research questions. We specify models based on theory or subject matter knowledge and then we fit these models to the data that we’ve collected, assuming that the variables in our dataset follow distributions or have certain relationships. The models that we fit to the…
We have been thinking the hierarchy of money, with reserves (or currency which is the liability of the central bank) being the best money. Some where below that in the hierarchy, there are Fed funds, which are promises to pay reserves by banks. Further below that is the Eurodollars, which are international dollars promising to…
Operations Research (3): Theory National Taiwan University What a long journey, but totally worth it! The theory taught in this course is critical, beautiful, powerful. Whatever fields or industry you are in, statistics, machine learning, economics, logistics, etc. This course definitely will help you consolidate the foundation for all skills you need to be professional….
The theory of Operations Research has been used to develop models in many fields like statistics and machine learning. Linear Regression We try to find 伪 and 尾 such that a line g = 伪 + 尾 x to minimize the sum of squared errors for all the data points: Despite the word linear in…
In the case of unconstrained non-linear programs, we may determine whether the objective function is convex and then use the first order condition (FOC) to find all local minima. However in practice, most of the time, nonlinear programs are constrained. We can not simply ignore those constraints treating the program as an unconstrained, and then…
Compared with linear programs, non-linear programs (NLPs) are much more difficult to solve. In an NLP, a local minimum is not always a global minimum. A greedy search method like gradient decent may be trapped at a local minimum. Also even the NLP has optimal solutions, these optimal solutions may exist on a boundary, but…
Packet Switching Networks and Algorithms University of Colorado System Since the emergence of cloud computing the late 1990s, the landscape of networking technology has changed a lot. Nowadays networks are more and more invisible and software-defined. This is the third course of the specialization which focus on the packet networks and switching. What taught are…
A packet switch network provides communication services among multiple nodes/routers. There are usually multiple route/path from one node/router to another. Which route this the best? The optimality depends on the objective function that the network tries to optimize, for example, minimal delay, minimal number of hops, maximum bandwidth, and the minimum cost. Routing Tables To…
Federal Taxation II: Property Transactions of Business Owners and Shareholders University of Illinois at Urbana-Champaign As individual or a business owner, have you ever googled questions like “Why are taxes so complicated?” There are quite many articles explaining the reason why. From the internet, I found this answer quite impressive: Our tax system could be…
Recall there are a few key items when evaluating a property transaction: Also recall the holding period of a property technically begins on the day after the property is acquired and includes the day of properties disposition. Short-term holding period is where an asset is held for one year or less. Long-term holding period is…
Network flow models are one specific format of mathematical programs. These are used to study operations that are related to network transportation. A unified model, called Minimum Cost Network Flow (MCNF) covers many network operations. MCNF is a special form of linear program or integer program. Even better, MCNF has a very nice property: once…
In the last post, we looked at two major non-taxable exchanges: like-kind exchanges and involuntary conversions. In those transactions, any realized gain or loss is generally not recognized at the time of the transaction. Instead, realized gain or loss is deferred until some future point, usually when newly acquired property is ultimately disposed off. This…
There are several ways of interconnecting networks, at different layers, there are different types of devices: Layers Devices If LANs are interconnected Application Application gateway Transport Transport gateways Network Router Inter-routingAll traffic stays in its own LAN Data Link Bridge or switch MAC address filteringLocal traffic stays in its own LAN Physical Repeater or hubHub…