DivergenceDivergence is an operation on a vector field that tells us how the field behaves toward or away from a point. Locally, the divergence of a vector field $\vec{F}$ in $\mathbb{R}^2$ or $\mathbb{R}^3$ at a particular point $P$ is a measure of the “outflowing-ness” of the vector field at $P$.If $\vec{F}$ represents the velocity of a fluid, then the divergence of $\vec{F}$ at $P$ measures the net rate of change with respect to time of the amount of fluid flowing away from $P$ (the tendency of the fluid to flow “out of” P). In particular, if the amount of fluid flowing into $P$ is the same as the amount flowing out, then the divergence at $P$ is zero.
Antenna 📡
Antennas are widely used in the field of telecommunications and we know many applications for them. Antennas receive an electromagnetic wave and convert it to an electric signal, or receive an electric signal and radiate it as an electromagnetic wave.
Electromagnetic Radiation ☣️
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
Colored Pencils 🖍️
There’s a lot to like about drawing with colored pencils. They’re utterly convenient—a handful of colored pencils and a pad of paper are all you really need to start creating. Prep time and cleanup are practically non-issues, the materials are light and portable, and you don’t need messy or toxic solvents. At the same time, colored pencil drawing lends itself to highly refined and exquisite works of art that rival those created with any other medium.
Inception 💤
A thief who steals corporate secrets through the use of dream-sharing technology is given the inverse task of planting an idea into the mind of a C.E.O.
Nunchaku 🤸
The Handcrafted Nunchaku or nunchucks (Japanese: ヌンチャク nunchaku, often “nunchuks“, “chainsticks“, “chuka sticks” or “karate sticks” in English) is a traditional Okinawan martial arts weapon consisting of two sticks connected at one end by a short chain or rope. The two sections of the weapon are commonly made out of wood, while the link is a cord or a metal chain.
Pencil Sketch ✍️
A pencil is an implement for writing or drawing, constructed of a narrow, solid pigment core in a protective casing that prevents the core from being broken or marking the user’s hand. Pencils create marks by physical abrasion, leaving a trail of solid core material that adheres to a sheet of paper or other surface. They are distinct from pens, which dispense liquid or gel ink onto the marked surface.
Oil Painting 🎨
Oil painting is the process of painting with pigments with a medium of drying oil as the binder. Commonly used drying oils include linseed oil, poppy seed oil, walnut oil, and safflower oil. The choice of oil imparts a range of properties to the oil paint, such as the amount of yellowing or drying time.
Fast Fourier Transform 🎯
The fast fourier transform or FFT is without exaggeration one of the most important algorithms created in the last century. So much of the modern technology that we have today such as wireless communication, GPS and in fact anything related to the vast field of signal processing relies on the insights of the FFT.
But it’s also one of the most beautiful albums you’ll ever see. The depth and sheer number of brilliant ideas that went into it is just astounding it’s easy to miss the beauty aspect of the FFT since it’s often introduced in fairly complex settings that require a lot of prerequisite knowledge such as the discrete fourier transform time domain to frequency domain conversions and much more.
Baduk (1) 🧇
简介围棋的棋具
棋盘：棋盘由纵横各十九条等距离、垂直交叉的平行线构成。形成361个交叉点，在围棋中简称为“点”。棋盘整体形状以及每个格子纵、横向相比，横向稍短，通常为每格2.4厘米×2.3厘米。在棋盘上标有九个小圆点，称作“星”。中央的圆点又称“天元”。
棋子：棋子分黑白两色，形状为扁圆形体。棋子的数量应能保证顺利终局。正式比赛以黑白各180子为宜。