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

Understanding Material Properties and Types

Material Classification by Origin

• Raw Materials: Substances used for crafting objects or other materials.
• Natural Materials: Found in nature.
• Manufactured Materials: Obtained after an industrial process.
• Recycled Materials: Can be reused after initial use.

Material Families: A Technological Perspective

From a technological point of view, materials are categorized into five main families:

• Wood: Includes all types of wood, paper, and cardboard.
• Metals:
  • Natural: Such as iron (Fe), tin (Sn), aluminum (Al), copper (Cu), gold (Au), silver (Ag), platinum (Pt), lead (Pb), and zinc (Zn).
  • Artificial (Alloys): Like steel (Fe+C), bronze (Cu+Sn), or brass (Cu+Zn).
• Plastics: Mostly artificial, with exceptions like natural

Basic SQL Statements: DDL and DML Commands

Data Definition Language (DDL) Commands

DDL commands are used to define or modify the structure of database objects. All DDL commands are auto-committed, meaning they save all changes permanently in the database immediately after execution.

The primary DDL commands are:

• CREATE
• ALTER
• TRUNCATE
• DROP
• RENAME

CREATE Command

The CREATE command is used to define a new table structure. It uniquely defines each column, specifying its name and data type. Each column definition is separated by a comma, and the SQL statement is terminated with a semicolon.

Syntax:

CREATE TABLE table_name (
    column_name1 datatype1,
    column_name2 datatype2,
    ...
    column_namen datatypen
);

Example:

CREATE TABLE Student (
    reg_no

Electrical Resistivity of Materials

Materials are classified as conductors, semiconductors, and insulators depending on their resistivities, in an increasing order of their values.

• Conductors (e.g., Metals): Have low resistivities, typically in the range of 10^–8 Ωm to 10^–6 Ωm.
• Insulators (e.g., Ceramic, Rubber, Plastics): Have resistivities 10¹⁸ times greater than metals or more.
• Semiconductors: Fall in between conductors and insulators. Their resistivities characteristically decrease with a rise in temperature. The presence of small amounts of impurities also affects their resistivities. This last feature is exploited in the use of semiconductors for electronic devices.

Kirchhoff's Rules for Electric Circuit Analysis

Electric circuits generally... Continue reading "Electrical Properties of Materials and Circuit Analysis" »

Timber as a Construction Material

1. Types of Construction Timber

Hardwoods (e.g., Mvuli, Meru Oak, Mahogany, Eucalyptus)

• Difficult to work because of hardness; may require pre-drilled holes for jointing with nails.
• Useful for severe environmental exposure conditions, offering better resistance to wear, insect, and fungal attack than softwoods.
• Valued for aesthetic appeal.

Softwoods (e.g., Cedar, Podo, Pine, Cypress, Grevillea Robusta)

• Some types are commonly available in stockyards and are generally cheaper than hardwoods.
• Preferred in construction because they are easier to work and joint with nails.
• Have straighter grains than hardwoods.
• More liable to insect and fungal attack than hardwoods and require intensive preservation treatment.

Available Sizes:

What is Computer-Aided Engineering (CAE)?

CAE formalizes ideas through computer modeling and then fabricates the models into real-world objects through CAD and CAM.

What is Computer-Aided Reverse Engineering (CARE)?

CARE works in the opposite direction. CARE creates a computer model of an object through measurements of the object as it exists in the real world. CARE is the reversal of CAE.

What is a Coordinate Measuring Machine (CMM)?

• Coordinate Measuring Machines (CMMs) are a practical means for characterizing and inspecting free-form surfaces.
• Coordinate Measuring Machines (CMMs) first appeared in the early 1960s.
• A CMM consists of a probe supported on three mutually perpendicular (x, y, and z) axes, and each axis has a built-in reference standard.

Traffic Light with Arduino

This code simulates a traffic light using an Arduino.

int led_rojo = 3;
int led_verde = 4;
int led_amarillo = 5;

void setup() {
  pinMode(led_rojo, OUTPUT);  // PIN 3 as output
  pinMode(led_verde, OUTPUT); // PIN 4 as output
  pinMode(led_amarillo, OUTPUT); // PIN 5 as output
}

void loop() {
  digitalWrite(led_verde, HIGH); // Turn on green LED
  delay(2000);
  digitalWrite(led_verde, LOW);  // Turn off green LED
  delay(500);
  digitalWrite(led_amarillo, HIGH); // Turn on yellow LED
  delay(2000);
  digitalWrite(led_amarillo, LOW);  // Turn off yellow LED
  delay(500);
  digitalWrite(led_rojo, HIGH);   // Turn on red LED
  delay(2000);
  digitalWrite(led_rojo, LOW);    // Turn off red LED
  delay(500);
}

Button

Malware

Malicious software, is a type of software that has been particularly designed to gain access to or damage a computer, mostly without the knowledge of the owner. There are a lot of types of malware, including computer worm, computer viruses, Trojan horse, adware and spyware.

Computer Crime

Defined as a crime in which a computer is the object of the crime (hacking, phishing, spamming) or is used as a tool to commit an offense (child pornography, hate crimes). Cybercriminals may use computer technology to access personal information, business secrets or use the internet for malicious purposes.

Trojan Horse

A type of malware that is often disguised as legitimate software. Trojans can be employed by cyber-thieves and hackers that offer useful... Continue reading "Understanding Malware and Cybercrime: A Comprehensive Guide" »

The Project Approach in Technology

Technology addresses societal challenges by utilizing a structured project approach. This methodology consists of the following stages:

• Problem
• Investigation
• Possible solution
• Chosen solution
• Design
• Planning
• Building
• Check
• Presentation and assessment

Project Report Requirements

Every report must include:

• Description of the prototype
• List of modifications made
• Final drawing of the solution
• Total cost and hours spent
• Environmental impact assessment

Team Roles and Responsibilities

• Coordinator: Coordinates the workflow.
• Secretary: Manages project documentation and tracks daily task completion.
• Tools Manager: Oversees tool maintenance and usage.
• Materials Manager: Organizes necessary resources.
• Cleaning Manager: Ensures the workspace

Brakes

Disc Brakes

A disc is connected to an axle. Brake pads apply pressure to the disc via friction.

Band Brakes

A drum is connected to an axle. A flexible band applies pressure to the outside of the drum.

Drum Brakes

A drum is connected to the axle. A pair of brake shoes apply pressure to the inside of the drum via friction.

Energy Absorption and Dissipation

Springs

Springs are devices that, thanks to the elasticity of their materials and their shape, can absorb energy when force is applied. This energy can then be dissipated in a controlled way. Depending on the type of external force applied, springs work in different ways:

• Compression: Pushing on the spring makes it shorter (e.g., a sofa).
• Traction: Pulling on the spring makes it longer (e.g., a