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

#useradd nombredeusuario :: para crear usuarios

#passwd :: nombredelusuario

#groupadd :: nombredelgrupo :: (forma normal)

#groupadd -g 600 nombredelgrupo :: (guid sobre 650)

#userdel nombredelusuario :: para deletear usuarios

#groupdelnombredelgrupo :: borrar el grupo

#usermod -G nombredelgrupo nombredeusuario :: para asignar usuario a grupo.

opcion 2: editar archivo /etc/group -> grupo:x:600:usuarioqueseagregara

#nano /etc/shadow :: para poder ver los usuarios y poder bloquearlos

#passwd -l nombredeusuario :: para bloquear usuario

#passwd -u nombredeusuario :: para desbloquear usuario

#sudo passwd :: para cambiar la contraseña de root

# tail /etc/passwd :: paraver informacion de usuarios

#su nombredelotrousuario :: para iniciar sesion como el usuario...

1. Refer to the exhibit. The network administrator needs to setup Switch1 for remote access from HostA. Theshow ip interface brief is issued on Router1 and the show interfaces trunk command is issued on theSwitch1 to verify the current status. The administrator applies the additional configuration shown in theexhibit to Switch1. However, the telnet from HostA fails. What additional commands need to be appliedto the switch?
Switch(config)# interface vlan 10
Switch(config-if)# ip address 10.1.1.250 255.255.255.0
Switch(config-if)# no shutdown
Switch(config-if)# ip default-gateway 10.1.10.254

2. Refer to the exhibit. On the basis of the configuration shown, how will an Ethernet frame on port GigabitEthernet0/1 be modified?
802.1Q encapsulation inserts

...

ELECTRICAL INSTALLATIONS:
The electricity used to meet our energy needs (housing, buildings and industries) But there are serious dangers such as fires and electrocucions if facilities do not meet the appropriate security.
Low Voltage Electrotechnical Regulations (REBT) technical conditions and guarantees must be met by electrical installations connected to a low voltage supply in order to:
-Preserve the safety of persons and property.
-Ensure the normal operation of these facilities and prevent disruptions that could cause other facilities and prevent disruptions that could cause other facilities and services.
-Contribute to the technical reliability and efficiency of economic facilities.
Complementary technical instructions (ITC - BT)...

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...

Ten Engineering Achievements:

• Telephone
• Computers
• AC and refrigeration
• Electronics
• Airplane
• Automobile
• Highways
• Spacecraft
• Internet
• Household appliances
• Imaging
• Radio and TV

Ten of Fourteen Challenges:

• Provide clean access to water
• Enhance VR
• Prevent nuclear terror
• Improve urban infrastructure
• Make solar energy economical
• Secure cyberspace
• Producing energy from fusion
• Manage the nitrogen cycle
• Engineer better medicine
• Advance health informatics

12 Steps:

1. Recognition of need
2. Problem identification and specification
3. Information gathering
4. Incubation and ideation
5. Development of concepts
6. Synthesis
7. Analysis
8. Prototyping and testing
9. Manufacturing
10. Marketing
11. Maintenance
12. Afterlife

Fundamental Differences Between Engine Lathe and Vertical Mill:

Lathe - the workpiece rotates but remains stationary,...

Shipboard Equipment and Parts

Anchors

Anchor: An iron instrument, heavy and strong, shaped like a harpoon or hook. Doubled and attached to a rope, chain, or cable, it's thrown into the water to hold a vessel.

1. Plow anchor (Figure 1-37)
2. Danforth anchor (Figure 1-35)

Windlass

Windlass: A horizontal axis machine used to weigh chains. It has an iron mechanism called a chainstopper to bite and stop the chain. Often incorporates drums (Cabirol or warping ends).

Gypsy

Gypsy: A drum-shaped part of the windlass with notches or molds where the chain's mating link engages as the anchor is raised or lowered. The gypsy is in gear when turning the reel to raise the anchor, or it decouples and engages the brake to stop the shaft's rotation.

Escobar

Escobar: The location...

Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT)

Activity Duration and Delays

If an activity's slack (MTIJ) equals zero, any delay in this activity will delay subsequent activities. However, activities can not delay the project if MTIJ is greater than zero.

Critical Path

The critical path is the longest path, which represents the minimum time necessary to complete the project. Activities on the critical path are called critical activities.

Activities with Uncertain Duration

When the duration of activities is not known with certainty, three estimates are used: optimistic (a_ij), realistic (m_ij), and pessimistic (b_ij). It is assumed that the duration of activities follows a beta distribution. Assuming t_ij are independent...

Introduction to Computer Graphics

Computer Graphics (CG) is the art and science of communicating information or ideas through digital images. It involves the generation, representation, manipulation, and display of pictorial data using computers. From simple 2D line drawings to hyper-realistic 3D animations, computer graphics has transformed how we interact with technology.

History of Computer Graphics

The evolution of computer graphics spans several decades, moving from massive, specialized military systems to ubiquitous, high-powered mobile chips.

1. The Early Beginnings (1950s)

• MIT’s Whirlwind (1951): One of the first computers to use a CRT (Cathode Ray Tube) display to output real-time data, paving the way for visual computing.
• SAGE System

...

Memory Hierarchy: Faster, Smaller, Costlier

The computer memory hierarchy organizes storage based on speed, size, and cost, moving from the fastest (CPU internal) to the slowest (external storage):

• Registers: CPU internal (Fastest, Smallest)
• Cache: L1, L2, L3 (Fast)
• Main Memory: RAM (DRAM)
• Secondary Storage: HDD, SSD
• Tertiary Storage: Optical, Tape (Slowest, Largest)

What Is Cache Memory?

Cache memory is a small, high-speed memory located close to the CPU. It stores frequently accessed data and instructions so the processor doesn’t have to fetch them repeatedly from slower main memory (RAM).

Cache significantly reduces memory access time, thereby improving overall system performance.

Why Cache Outperforms Main Memory (RAM)

Cache memory achieves superior...

Chains

Drawbacks of Chains

A drawback of chains is the production of vibrations during operation.

Chain Rollers

Chains consist of inner and outer plates. Pins connect these plates. The outer plates are thicker than the inner plates, with larger holes. Rollers rotate freely on the pins, minimizing friction between the chain and the sprockets.

Chain Cassettes

Cassettes are similar to rollers but without the rolling action. They are more economical and suitable for short chains with light loads.

Chain Blocks

Block chains are designed for heavy loads. They consist of outer plates, pins, and solid blocks between consecutive links.

Chain Links

Links are angled plates that serve as both outer and inner plates. The advantage is the adjustability of chain length...