In 1966, Marie Van Brittan Brown, a Black nurse from Queens, New York, made history when she invented the world’s first home security system with TV surveillance. Living in a neighborhood where police response was slow, she wanted a way to feel safer at home. Her design included a camera that could move between peepholes in the front door, a monitor inside the house, and even a microphone to speak with visitors. She also built in an emergency button to alert authorities. Brown received a patent for her invention in 1969, and her groundbreaking work became the foundation for modern home security systems used across the world today. A true pioneer, she not only protected her own family but also changed the way we all think about safety in our homes.

This infographic explains how to calculate the exact amounts of cement, sand, and gravel needed for M20 grade concrete. The process starts with the standard M20 mix proportion of 1:1.5:3 (1 part cement, 1.5 parts sand, and 3 parts gravel). A crucial step often overlooked is accounting for the shrinkage that occurs when wet concrete hardens. To compensate for this volume loss, civil engineers apply a safety factor (typically 1.54 to 1.57) to the desired wet volume to determine the required dry volume of materials. Following the calculations in the image to get 1 cubic meter of finished concrete, you would need: Cement: 0.28 m³, or approximately 8 bags. Sand: 0.42 m³, or about 16 cubic feet. Aggregate (Gravel): 0.85 m³, or about 21 cubic feet. This is a fantastic reference for getting your mix proportions right every time! #CivilEngineering #Construction #ConcreteMix #BuildingTips #DIYProjects #Engineering #M20Concrete #ConstructionMath #BuildingMaterials

🔥⛺ How to Build a Campfire That Lasts Through the Night 🌲✨ This guide shows a pyramid-style campfire, perfect for keeping you warm and safe all night long. Here’s the breakdown: --- 🔥 Step-by-Step Instructions: 1. Stack Wood in a Pyramid Shape Start with the biggest logs at the bottom. Place each layer perpendicular to the last (like building blocks). Use smaller and lighter pieces as you go up. 2. Place Tinder on Top Use dry leaves, twigs, or paper as tinder. Light it just like a regular fire; the flames will work their way down through the layers. 3. Position Wood with Minimal Spacing Keep wood close together to maintain a steady burn. Leave just enough room for air circulation. 4. Place a Circle of Rocks Around the Fire Acts as a fire barrier for safety. Helps reflect heat inward and keep the fire contained. --- 🌟 Pro Tips: Always build your fire on bare soil or sand, never on dry grass. Keep a bucket of water or sand nearby for emergencies. Never leave the fire unattended, even with rock barriers. --- #CampfireTips #OutdoorSkills #Bushcraft #CampingLife #SurvivalTips #WildernessLiving #FireMaking #AdventureReady #BackpackingSkills #CampSmart

Step-by-step explanation of how reinforced and prestressed concrete beams work under heavy loads. Concrete alone is strong in compression but weak in tension, which is why reinforcement is crucial for structural safety and durability. 1️⃣ Concrete Beam Under Load: A plain concrete beam bends when a heavy load (like a truck) is applied, showing its natural weakness under tension. 2️⃣ Cracking at the Base: The base of the beam begins to crack because concrete is being pulled apart due to tensile stress. 3️⃣ Reinforced with Steel Rods: By placing a steel rod inside the beam, the reinforcement holds the concrete together, preventing cracks and providing tensile strength. 4️⃣ Prestressed Concrete: When the steel rod is stretched before pouring concrete and then released, it compresses the beam. This pre-compression counters the tensile forces when loads are applied, making the beam significantly stronger and more durable. 👉 This is why modern construction uses reinforced and prestressed concrete beams in bridges, buildings, and highways, ensuring safety and longevity under massive loads. 🚛🏗️ #EngineeringExplained #CivilEngineering #ConcreteStructures #StructuralEngineering #ReinforcedConcrete #PrestressedConcrete #ConstructionTech