Notes, summaries, assignments, exams, and problems for Technology

What are Monomers and Polymers?

Plastics are formed by the combination of low molecular weight molecules called monomers. Polymers are formed by joining monomers.

• The union of monomers results in large molecules called polymers.

What is Polymerization?

Polymerization is a chemical reaction that joins monomers into large chains to build macromolecules called polymers.

Artificial vs. Synthetic Plastics

Artificial plastics are created by transforming natural materials. Synthetic plastics are created from materials such as oil and gas.

Thermoplastics vs. Thermosetting Plastics

Thermoplastics can be heated and molded multiple times. Thermosets can only be heated and molded once.

Plastic Applications

Thermoset Applications

• Phenol formaldehyde (PF) combined

Material Science Timeline

• 1769: Discovery of the steam engine (Watt)
• 1831: Discovery of the dynamo (Faraday)
• 1913: Popularization of stainless steel
• 1950: Discovery of silicones and first use in aircraft
• 1960: Perfection of silicon crystals (almost perfect purity)
• 1962: Discovery of the nickel and titanium alloy
• 1971: Presentation of soft contact lenses (Bausch & Lomb)
• 1983: First mobile phone
• 1991: First Web page

Second Industrial Revolution Key Points

• New production systems improve accelerated production.
• Amendment to the way we produce at all levels.
• Minimization of production costs.

Plastics: An Overview

Plastics are characterized by their plasticity, a property that allows them to be easily molded into the most convenient shapes. Their history began... Continue reading "Material Science Timeline and Innovations" »

Network Link Utilization Analysis

Suppose you want to convey 100,000,000 bits via a dedicated link at a speed of 10 Megabits/sec. The distance between the transmitter and receiver is 20,000 meters, and the signal propagation speed is 200,000 km/sec. Information is sent in blocks of 100,000 bits.

a) Stop-and-Wait ARQ Utilization

Calculate the exact link utilization, given that every time the computer receives a complete block, it takes 5 milliseconds to check for errors and save the block to disk before sending the ACK response. Utilization is defined as the total time taken to transmit useful information divided by the total time for transmission, error control, and flow set for that link. The number of bits in the ACK is negligible. Assume Stop-... Continue reading "Calculating Network Link Utilization and Efficiency" »

Mechanisms

Mechanisms are devices that transmit motion to perform a job. They are used to transmit motion in two primary ways:

Linear Motion Transmission

1. Fixed Pulleys

   A fixed pulley is a wheel with a grooved edge that rotates around a central axis. A rope or belt passes through the groove. The force applied at one end of the rope equals the resistance at the other (F = R). The advantage of a fixed pulley is the change in the direction of motion.

2. Movable Pulleys

   In a movable pulley, one end of the rope is fixed, and the resistance hangs from the pulley's axle. The force required is half the resistance (F = R/2).

3. Pulley Systems (Hoists)

   A hoist combines fixed and movable pulleys. The force required is calculated as F = R/(2n), where 'n' is the number

Filesystem Area Roles

NTFS Filesystem Areas

This section lists and discusses the role of areas of the NTFS file system:

1. Partition Boot Sector: Occupies several sectors. It contains the provision for the volume and file system structure, the location of the MFT and MFT2, and the boot code.
2. MFT (Master File Table): Contains information on files, directories, and available space.
3. MTT (Master File Table Mirror): A list of all the contents of the NTFS volume, organized as a set of rows in a structured relational database.
4. Archiving System: Contains MFT2, which is a mirror copy of the first three rows of the MFT to ensure access to the MFT in case of a sector failure. It also contains the bitmap (represented by the volume) showing which blocks are in use

Different Properties of Materials

The ability of a resistance material to resist forces without distorting excessively or breaking is a crucial property.

• Toughness

  Toughness is the property that some materials have to withstand forces repeatedly without breaking.

• Resilience

  Resilience is the property of a material to recover its original shape after being deformed by an effort.

• Ductility

  Ductility is the property of certain materials to deform permanently into a thin wire without breaking.

• Malleability

  Malleability is the property of certain materials to deform permanently in the form of a thin sheet without breaking.

• Hardness

  Hardness is the property that indicates the opposition a material offers to being penetrated or scratched.

Different Types of Stresses

• Traction

  Traction

Electrical Protection Devices

Protection devices safeguard electrical installations and connected components from potential overloads. They also protect people from electric shock, preventing current leakage to the ground and the consequent economic damage to the user.

Fuses

A fuse is connected in series with the circuit so that all the current flows through it. It consists of a base with two fixed contacts, a plug-piece cartridge or blade, and fusible material surrounded by a medium that acts as a means of extinction.

• Overload: Occurs when the current value in an electrical installation exceeds the fuse's rating.
• Short circuit: Occurs when a fault in an installation element or an accident causes a sudden surge in current, causing the fuse to blow.

DVD Data Storage

The DVD data zone consists of a highly reflective layer called the land. Projections known as pits rise from this land. These pits represent recorded data. The data track is recorded helically from the inside to the outside of the disc.

Pixelated Images and Freezing

If a DVD player displays pixelated images and freezes with different discs, the first step is to clean the lens.

DVD Photodetector Composition and Function

(Information needed)

DVD Servo Systems

DVD players have five servo systems:

1. Focus Control
2. Track Monitoring
3. Coil Monitoring (Tracking)
4. Sled Servo
5. Disc Speed Control

Symptoms of a Dirty Lens and Cleaning Procedure

A dirty lens can cause various playback issues. Here's how to clean it:

1. Moisten one end of a cotton swab with isopropyl

Fundamentals of Mechanical Systems

A machine is a set of interacting elements designed to perform work or apply force. The individual elements that make up a machine are called mechanisms.

The Lever: A Simple Machine

A lever is a simple machine that multiplies strength. It consists of a rigid bar and a fulcrum (support point). Using a lever, heavy weights can be lifted with minimal force.

Law of the Lever: Force multiplied by the force arm equals resistance multiplied by the resistance arm (F × Bf = R × Br), where Br is the distance from the fulcrum to the point of resistance.

Classes of Levers

• First-Class Lever: The fulcrum is located between the force and the resistance.
• Second-Class Lever: The resistance is located between the fulcrum and the