Notes, summaries, assignments, exams, and problems

SCR Construction

A thyristor, or SCR, consists of four P-N-P-N layers and has three PN junctions (J1, J2, J3) in series. It has three terminals: Anode, Cathode, and Gate. The Gate terminal is attached to the P-type layer near the Cathode terminal. The two-transistor model shows that an SCR is a combination of one PNP transistor and one NPN transistor.

The emitter of the PNP transistor is taken as the Anode terminal, the emitter of the NPN transistor is taken as the Cathode, and the base of the PNP is taken as the Gate terminal. The base of the PNP is connected to the collector of the NPN, and the collector of the PNP is connected to the base of the NPN transistor.

Advantages of SCRs:

• Easy to turn ON
• Can handle large voltage, current, and power
• Possible

Modal Verbs Exercises

Exercise 1: Rewrite the sentences using modal verbs.

1. It's forbidden to drive without fastening your seatbelt. You mustn't drive without fastening your seatbelt.
2. Perhaps they told John about the party. They might have told John about the party.
3. It isn't necessary for us to book a table. We needn't book a table.
4. It isn't necessary for her to phone me back. She needn't phone me back.
5. It was a mistake to sell the house. I wish I hadn't. I shouldn't have sold the house.
6. I'm sure he didn't lock the door. He couldn't have locked the door.
7. Perhaps John knew about the trip. He could have known about the trip.
8. You cannot smoke in the underground. You mustn't smoke in the underground.
9. I'm sure Ann didn't send that letter. Ann couldn't have

Robot Kinematics

Euler’s Rotation Theorem

Any rigid body motion that leaves one point fixed can be represented by a single rotation about an axis through the fixed point.

Chasles’ Theorem

Any rigid body motion is the translation of a designated point & a rotation of the whole body about that point.

Kinematic Parameters

These parameters are associated with the kinematic configuration of each link and joint of the robot arm. There are four main kinematic parameters:

Joint Parameters

The relative position and orientation of two successive links can be specified by two joint parameters:

• Joint Angle (θk): The amount of rotation about zk-1 so that Xk-1 is parallel to Xk.
• Joint Distance (dk): The amount of translation along the Zk-1 needed to make

Internet Fundamentals: A Network of Networks

The Internet is often described as a "network of networks," comprising interconnected Internet Service Providers (ISPs).

Key Components of the Internet

• Hosts: End Systems for Applications

  Hosts are the end systems (clients & servers) that run applications. They connect at the edge of the Internet.

• Packet Switches: Forwarding Data

  Packet switches forward data in chunks called packets. These include:

  • Routers: Forward data between different networks.
  • Switches: Operate within the core of the Internet, not at the edge.

• Communication Links: The Data Pathways

  Communication links connect routers and can be made of:

  • Fiber optic cables
  • Copper wires
  • Radio waves
  • Satellite connections

  The transmission rate of a link is

Hedging with S&P 500 Index Futures

SIF hedging: NF = V_F(antiguo) = F_o x Z. NF (Number of contracts) = V_p (portfolio value) / (V_F x B_p) (Beta). With this hedge, risk is removed. If the index goes up, the profit in the portfolio will be offset by losses in SIFs contracts and vice versa.

Example: S&P 500 falls 5%:

• In the portfolio: R_p = B_p x (-5%) = -10% of a portfolio of $10M, resulting in $9M (Final Value).
• In the SIFS contracts: S_i = 980 (S&P 500 value given) x 0.95 (100% - 5%) = 931. F_i = 931 x (1 + 0.04 x 5/12 (next month timeframe)) = 946.52. V_F = NF x (F_i - F_o) x Z (250).
• Gain on futures: V_F(New) / Equity portfolio value.
• Outcome stock portfolio: 2 x (-5%) = -10%.
• Final Value portfolio: $10M - $1M + V_F(New).

Margin Payments

Margin payments... Continue reading "Hedging and Speculation with Futures and Options" »

The Enlightenment: The Age of Reason

The Enlightenment (also known as the Age of Reason or the Century of the Lights) is understood as an intellectual movement based on a set of philosophical ideas that emphasize trust in reason to solve many of the ills of mankind.

Metaphysics: The Nature of Being

Metaphysics is a traditional branch of philosophy concerned with explaining the fundamental nature of being and the world that encompasses it. It answers two basic questions: "What is ultimately there?" and "What is it like?" It seeks to understand:

• Existence
• Objects
• Properties

Key Enlightenment Philosophers

Prominent thinkers of this era include:

• Francis Bacon
• René Descartes
• John Locke
• Baruch Spinoza
• Pierre Bayle
• Voltaire
• David Hume
• Cesare Beccaria
• Immanuel Kant
• Sir

Key Concepts in Microbial Pathogenicity

• Pathogenicity: The ability of a microorganism to cause disease.
• Virulence: The extent or degree of pathogenicity.
• Normal Microbiota: Resident microbes, often referred to as commensals.
• Infection: The invasion of normally sterile tissues by microorganisms.
• Pathogen: An infectious agent capable of causing disease.
• Infectious Disease: A disease caused by infection by a pathogen.
• Colonization: The process of establishing a population of organisms in a host.
• Resident Colonizer: An organism that establishes a long-term presence in the host.
• Transient Presence: A short-term presence of an organism in the host.

Major Factors in the Development of an Infection

1. Adherence: Initial Attachment to Host Cells

   Adherence is crucial

T-Cell Coreceptor Specificity

• Helper T-cells require antigen and Class II markers.
• Co-presentation requirements stem from different coreceptors on Killer and Helper T cells:
  • Killer T-cell coreceptor CD8 interacts only with Class I markers.
  • Helper T-cell coreceptor CD4 interacts only with Class II markers.

Interactions: Antigen-Presenting Cells & Lymphocytes

Active Immunity

Primary and Secondary Immune Responses

1. On first exposure to a pathogen, there is a latency of 5-10 days before specific antibodies are made, known as the primary response.
   • Antibody levels plateau after a few days and decline after a few weeks.
2. Subsequent exposure to the same antigen causes a secondary response.
   • Antibody production is much more rapid and sustained.

Clonal Selection

Theme II: The Development of the Global Economy

5. Japan's Post-War Economic Growth

I. Role of Government

• Growth-driven policies and focused leadership
  • The Liberal Democratic Party (LDP) mostly ruled after 1955.
  • A cohesive unity of bureaucrats and politicians made up competent policymakers focused on achieving economic development and self-reliance.
  • Tight policy coordination was known as the "Iron Triangle."
  • The Yoshida Doctrine was implemented in the early 1950s.
  • Ikeda's Income Doubling Plan was introduced in the early 1960s.
  • Sato's Three Non-Nuclear Principles were established in the early 1970s.
• Heavy government involvement in the free market
  • The Ministry of International Trade and Industry (MITI) decided, charted, and planned Japan's industrial and

E-commerce: Buying and Selling Online

Like many people, I regularly buy things online, mostly books, music, and airline tickets. Many online retailers offer good rates or discounts. Occasionally, I also buy things on internet auction sites such as eBay, where people sell items to the highest bidder.

The Four Main Steps to Buying Online

There are four main steps to buying online:

1. First, you enter a site dedicated to e-commerce and browse their products.
2. Then, you put the items you want to buy into a virtual shopping cart, a program that lets you select the products and purchase with a credit card.
3. Third, you enter your personal data – you may have to log in with a username and a password if you have an account with the site.
4. Finally, you confirm