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

Machines and Heat Engines

Machines transform thermal-mechanical energy into thermal energy or vice versa.
Heat engines are machines that transform drive energy into heat or thermal-mechanical work.

External and Internal Combustion Engines

External combustion: Combustion occurs outside the machine. The external combustion burns and uses the machine's heat to vaporize water; the resulting gases drive a device to perform work.
Internal combustion: Fuel burns inside the engine, and the gaseous products are responsible for producing the driving work.

Reciprocating and Rotary Machines

Reciprocating (alternative) machines: Incorporate a plunger or piston that has an alternating rectilinear movement. A crank mechanism transforms rotary motion into reciprocating... Continue reading "Heat Engines, Fuel Types & Emission Reduction Techniques" »

The Digital Revolution and the Internet

The digital revolution, including the Internet and ARPANET, is built upon three foundational technological breakthroughs:

• Microprocessors
• Data transmission at the speed of light
• Compression and coding systems that allow information to be represented and sent as binary values.

The Origins of the Internet

The origins of the Internet date back to 1968 during the Cold War. The U.S. Department of Defense created a research agency with a mandate to develop a system capable of preserving information in the event of a nuclear attack. This led to the creation of ARPANET, which digitized information for transmission via telephone cables.

Initially intended for the military, the system was later made available to the scientific... Continue reading "The Evolution and Core Characteristics of the Internet" »

CAV Rotary Injection Pump Fundamentals

In CAV rotary injection pumps, fuel is sent from the transfer pump to the hydraulic head at a pressure regulated by a valve. The metering valve precisely controls the fuel flow, which is governed by the throttle position and the speed regulator assembly. The distributor then raises the fuel pressure from the transfer level to the injection pressure, distributing it to the various nozzles.

Fuel Pressure Transfer Mechanism

Under normal operating conditions, the generated pressure causes the control piston to move to the right, against the action of its spring. This pressure is applied to the valve through a conduit from the transfer pump. When the pressure exceeds the limits set by the adjusting screw, regulation

Pressure Vessels: Shapes, Design and Standards

Vessel shapes (forms)
Cylindrical: most cases, easy to manufacture and transport, better use of material, tapered cylindrical transition between two bodies.
Spherical: in theory the best option, less thickness and less weight. However, it is expensive, difficult to manufacture and transport, and occupies more space. Only used for large dimensions.
Toroidal

Accessories: droplet eliminators, skirt, openings, inspection manhole

Thickness of Heads and Tubesheets

The greater of the following two values:
- Calculated for internal pressure: thickness + corrosion allowance
- Structural thickness to withstand own weight, assembly and collapse due to external loads
Recommended minimum structural thickness (minimum... Continue reading "Pressure Vessel Design: Shapes, Materials, Standards and Inspection" »

Picture Tubes in Black and White

This device is responsible for converting luminance information, carried as an electrical signal, into a two-dimensional image on the screen.

Basic Components of a Picture Tube

The blocks that make up a picture tube include:

• Electron gun: continuously emits a thin beam of electrons that varies according to the scanned image.
• Deflection coils: permanently deflect the electron beam horizontally and vertically.
• Luminescent screen: produces light when struck by the electron beam.

Deflection System

To ensure the emitted electrons strike the correct point on the screen, the beam must be moved over the screen surface. There are two ways this process is implemented: electrostatic deflection and magnetic deflection.

Electrostatic... Continue reading "Picture Tube Technology: Black-and-White and Color CRTs" »

Electronics and Electricity

Electronics is the science and technology concerned with the study of electrons and their applications in information processing and transmission.

Direct Current (DC)

Direct current (DC) is the flow of electrons in a single, constant direction with consistent voltage and current over time.

Alternating Current (AC)

Alternating current (AC) is a variable current where voltage and current continuously change direction. The most common type of AC used in homes is sinusoidal, meaning it's a periodic electrical signal that repeats at regular intervals.

Transformers

Transformers are used to increase voltage for electricity transmission from power plants and then decrease it for safe household consumption.

Key AC Parameters

• Cycle:

Issue 31: Fuel Injection Power Systems

Food for Fuel Injection

This system supplies power to the combustion engine, replacing the carburetor with a system that injects gasoline directly into the air intake. Advantages of fuel injection systems:

• High performance
• Less fuel consumption
• Fast adaptation
• Reduced pollutants

Injection can be direct or indirect. Direct injection sprays fuel directly into the cylinder, maximizing engine power but requiring higher pressure. Indirect injection sprays gasoline into the intake manifold, with a simpler installation due to lower pressure requirements. Injection can also be continuous or discontinuous.

Mechanical Fuel Injection

Mechanical injection systems are powered by the internal combustion engine or lack an actuator.... Continue reading "Fuel Injection Power Systems: Operation and Types" »

Essential Steps for ATX Power Supply Repair

1 .- If the fuse is blown, replace it before you start measuring other diodes or the bridge rectifier. The diodes conduct current in one direction only. If reversing the ohmmeter leads shows continuity in both directions, they are shorted and should be replaced. Never solder a wire instead of a fuse; this will cause the power supply to deteriorate further.

Testing Switching Line Transistors

2 .- Continue by desoldering and measuring the transistor switching line input. Most of them are NPN; remember that when measuring base-collector or base-emitter junctions, they should conduct in one direction only. If they show very low resistance, they should be replaced. In the majority of power supplies, including... Continue reading "ATX Power Supply Repair and Troubleshooting Procedures" »

Practical Work No. 7

Topic: Media Guided - Part 2

1. What are the physical media used in telecommunications networks that are mentioned in the text?
2. In reference to copper wires, what are the main variants that exist?
3. What are some of the major disadvantages of bare wire lines?
4. How are UTP cables used? Features of these cables provide each one of their technical characteristics.
5. What are underground multipair cables? What is their utility, and how is their isolation?
6. What are aerial multipair cables and what is their use?
7. What is Coaxial Cable? Depict it graphically.
8. What is referred to as the characteristic impedance of coaxial cables? What are the normal values of the characteristic impedance?
9. What is referred to as attenuation and what is its unit?
10. How

Axles

Axles are intended to support rotating bodies without turning the shaft itself. They are primarily subject to bending loads.

Shafts

Shafts are machine parts that always rotate with the components they support. They transmit power or torque and are subject to both torsion and bending loads. Shafts can be solid or hollow. When a keyway is present, consideration must be given to the shaft diameter due to stress concentration.

Bearings and Supports

Both axles and shafts require support points to bear their weight, facilitate rotation, and prevent displacement. Bearings are the components that provide these supports for shafts and axles.

Bearing Types

Friction Bearings

In friction bearings, the shaft or axle slides within the bearing surface. The... Continue reading "Axles, Shafts, Bearings, and Couplings" »