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

Variable Brake Limiters for Cargo Vehicles

For certain types of cargo vehicles, the effectiveness of rear axle braking is a dominant factor. These vehicles often bear very little weight when empty, yet carry more than 50% of their total weight when loaded. In such cases, it is essential to use a variable brake limiter capable of adjusting the braking pressure to the rear wheels based on the weight resting on them.

The antagonistic spring force within the limiter varies according to the load. This mechanism, where an antagonistic tension spring applies a cut-off to the valve, adjusts the braking pressure based on the weight supported by the rear axle. For greater loads, higher tension is exerted on the spring, leading to a higher braking pressure... Continue reading "Essential Components of Vehicle Braking Systems" »

**Plastic Materials: Properties, Types, and Manufacturing**

**Properties of Plastics**

Definition: Plastics are materials of organic origin, solid at room temperature, and easily molded by applying heat. They have a high molecular weight.

Most used: Polypropylene (PP)

Qualities:

• Weight reduction
• Noise damping
• Impact absorption
• Chemical resistance
• Corrosion resistance
• Thermal and acoustic insulation

Disadvantages:

• Low mechanical resistance
• Cannot withstand high temperatures
• Easily scratched
• Can easily capture moisture
• Sensitivity to sunlight
• Sensitivity to environmental conditions

**Chemical Processes**

Plastics are of organic origin and are chemical compounds formed by the union of several units. They can be formed by polymerization, polycondensation, or polyaddition.... Continue reading "Plastic Materials: Properties, Types, and Manufacturing Processes" »

Autoclave: Moist Heat Sterilization

Autoclave sterilization utilizes moist heat to effectively destroy spores, fungi, bacteria, and viruses. This process requires temperatures above 120°C. The autoclave chamber features a thick, stainless steel wall and a sealing lid. It includes a pressure gauge to monitor temperature and pressure, and a safety valve that activates when pressure reaches a dangerous level. A key controls the steam vent, enabling cooling. The tank contains water up to a specific level and a grid for placing objects. Heating can be electric or gas-powered.

Sterilization Phases in the Autoclave Process

Conditioning

Objects are placed on the grid, the lid is closed, and the vent key is opened.

Exposure to Vapor

The vent key is closed,... Continue reading "Autoclave and Ethylene Oxide Sterilization Methods" »

LDR (Light Dependent Resistor): These are resistors whose resistance value changes when illuminated by light (visible or invisible, such as ultraviolet or infrared).

LDR Features:

1. Its resistance value depends on the amount of light that strikes it.
2. Ohm's Law does not apply directly.
3. Typically made from cadmium sulfide. This material, when kept in the dark, has very few free electrons, resulting in high resistance. However, when illuminated, it releases electrons, decreasing the resistance. This makes it a photoconductor.
4. Manufacturers provide values such as resistance in total darkness (R), resistance under illumination (e.g., 1000 lux), permissible maximum stress, and maximum power.
5. Can be used in lighting systems as detectors.

NTC (Negative Temperature

Dynamics of Suspension

Balance, Center of Gravity, and Roll Axis

The roll center is an imaginary point on an axle where lateral forces are transmitted to the wheels. The imaginary line connecting the front and rear roll centers is called the roll axis. The center of gravity is an imaginary point where the vehicle's entire mass is concentrated.

Charge Transfer and Axes of Rotation

A vehicle pivots around three axes of rotation:

• Longitudinal Axis (Roll): Rotation that occurs when cornering.
• Transverse Axis (Pitch): Rotation that occurs during acceleration or braking.
• Vertical Axis (Yaw): Rotation when the vehicle is subjected to various turning loads.

Sprung and Unsprung Mass

• Sprung Mass: The part of the vehicle that is supported by the suspension system

Gas Installation Principles

An installation consists of containers (portable or stationary), pipe networks, connections, and control and safety devices. These components are essential for safely delivering gas from containers to consumption appliances.

Natural Gas Defined

Natural gas is a chemical compound that may contain impurities. These impurities, which can have value for purposes other than fuel, are typically removed before the gas is piped to consumers. Natural gas is also known as dry or sweet gas. It is obtained from underground deposits of gas, oil, or gas condensate, and can be found either alone or associated with petroleum. The typical working pressure for domestic appliances is 28 gr/cm².

Manufactured Gas

Manufactured gas is primarily... Continue reading "Safe Gas Installation Practices and Types" »

Railway Track Crossings: Name, Schema Usage, and Design

Crossings are essential devices that ensure the continuity of connections via different paths and can provide maximum security. They consist of combinations of two devices:

• Bypass: Allows the separation of a railroad into two or more tracks.
• Journey: Allows the intersection of two roads.

Components of Diversions and Crossings

Diversions and crossings are formed from three elements:

• Change: The contra-needle assembly. The needle is the mobile part, and the immobile part is the contra-needle. The end of the needle tip, which is not machined, connects to the union rails and is called the heel. The contra-needle is a normal lane. The needle has to transition from one lane to become normal to an

Common PC Power Problems

Some of the most common power problems and their descriptions:

• High Voltage Fluctuations: Unexpected spikes in voltage.
• Power Outages: A total loss of electrical power.
• Overvoltage: An increase in voltage beyond the normal level. This can occur when a high-energy device is suddenly switched off.
• Voltage Drop: The opposite of overvoltage; a gradual decrease in voltage, potentially leading to a power outage.

Symptoms of Power Supply Issues

Some symptoms that may indicate a power supply problem include:

• Unexpected Freezing: The PC freezes for no apparent reason.
• Data Errors: Write errors or errors accessing files occur.
• Component Failures: Internal components fail, their intensity varies, or the PC behaves strangely when connecting

Basic Electrical Concepts

Voltage (Tension)

Voltage (also known as Tension or electromotive force) is the energy with which a generator is able to push electrons through a circuit.

Electric Current (Intensity)

Electric Current (or Intensity) is the number of electrical charges flowing through a circuit per unit time. It is measured in amperes (A).

Resistance

Resistance is the opposition a material offers to the flow of electric current. Materials with high resistance make it difficult for electricity to pass through. Resistance is measured in ohms (Ω).

Electric Power

Electric Power indicates the rate at which a device performs its function. The power consumed by a receiver is directly related to the voltage and current that feed the circuit. Power... Continue reading "Fundamentals of Electricity and Circuit Principles" »

Questions and Answers About Materials

1. What Kinds of Natural Fiber Fabrics Are There?

• a) Plant and animal fibers, including those of seaweeds.
• b) Plant and animal fibers.
• c) Plant, animal, and mineral fibers.
• d) Animal and seaweed fibers.

2. What Fibers Are Manufactured Without the Use of Any Natural Product?

• a) All use natural products.
• b) Synthetic.
• c) Artificial.
• d) Both b and c.

3. What Characteristic Should a Fabric Have If It Will Be in Contact With Skin for Many Hours?

• a) Tensile strength.
• b) Hygroscopy.
• c) Resistance to chemicals.
• d) Soft to the touch.

4. The Origin of Plastic Can Be:

• a) Natural and artificial.
• b) Natural, artificial, and synthetic.
• c) Elementary, artificial, and natural.
• d) Natural and recycled.

5. The Degree of Polymerization Is:

• a)