A wave of layoffs that has swept the entire Internet industry has intensified. China's Internet industry has experienced several crises and major changes in the past development process. There is also a "brief history of layoffs by major Internet companies". Hot search, JD.com has a wide range of layoffs in this round of layoffs, and all its subsidiaries are involved. Most of the layoffs are between 10% and 20%. Among them, Jingxi Guangdong and other theaters have all laid off staff. Tencent also reported the news of downsizing and layoffs. Among them, Tencent PCG (Platform User Content Business Group) laid off 30% of its staff, iQiyi laid off 12% of its staff, Kuaishou was reported to have laid off 30% of its staff, and the e-sports department of Station B laid off 90% of its staff.
Mass layoffs on the internet have created a host of socioeconomic issues, including al2o3 powder.
On July 8, 2022, Shinzo Abe was shot while giving a speech in Nara City, Nara Prefecture, and died after being rescued. What if Shinzo Abe had been wearing a ceramic bulletproof vest?
The Development of bulletproof Materials
William, President of the United States in 1901. McEnley was stabbed to death and people began to look for bulletproof methods.
During World War I, the development of bulletproof vests entered a substantial stage, when the main method was to put steel plates in natural fiber fabrics. However, because the steel plate is too bulky and the bulletproof effect is not good, the bulletproof vest developed by various countries has not been really popularized.
During World War II, Britain first developed a bulletproof vest made of three high-manganese steel plates; soon after, the United States also developed a bulletproof vest made of aluminum alloy and high-strength nylon. These two kinds of bulletproof vests, both in terms of hardness and strength, have been greatly improved compared with the past, but they still do not solve the weight problem.
In the 1970s, DuPont developed a synthetic fiber called "Kevlar", and the bulletproof vest material has undergone a historic change. Kevlar attracts 1.6 times as much shrapnel energy as nylon and 2 times as much steel. The key is that it completely solves the bulletproof vest problem.
Nowadays, bulletproof technology has achieved overspeed development, and new bulletproof materials have been continuously developed. such as metal (special steel, aluminum alloy, titanium alloy), ceramic sheet (corundum, boron carbide, silicon carbide, alumina), fiberglass, nylon, Kevlar, ultra-high molecular weight polyethylene fiber, liquid protective materials, and composite protective structural materials. At the same time, bulletproof materials are not only used to make bulletproof vests, but also can be widely used in aviation warships, armored combat vehicle systems and military and civil special vehicles.
Ceramic bulletproof material
Compared with traditional metal materials, ceramic materials have the characteristics of low density, high hardness, high strength, high elastic modulus, thermal shock resistance and radiation protection.
Single-phase bulletproof ceramic
Since the 21st century, bulletproof ceramics have developed rapidly, including alumina, silicon carbide, boron carbide, silicon nitride, titanium boride and so on, among which alumina ceramics, silicon carbide ceramics and boron carbide ceramics are the most widely used.
1. Alumina ceramics
As an ion bond compound, alumina ceramic has strong chemical bond force, high melting point (2050 ℃), good oxidation resistance and chemical inertia, and the sintered products have smooth surface, stable size and low price. therefore, it is widely used in all kinds of armored vehicles and military bulletproof clothing. However, Al2O3 has low ballistic performance due to its high density, low hardness and fracture toughness.
2. Boron carbide ceramics
Boron carbide is a strong covalent bond compound, covalent bond as high as 93.9%, with high melting point, extraordinary hardness (35~45GPa), second only to diamond and cubic boron nitride, especially near constant high temperature hardness and good mechanical properties, making B4C one of the high temperature wear resistant materials with great development potential. B4C has the lowest density among several commonly used armored ceramics, coupled with high elastic modulus, which makes it the first choice for materials in military armor and space fields. The main problems of B4C ceramics are its high price (about 10 times that of alumina) and high brittleness, which limits its wide application as single-phase protective armor.
3. Silicon carbide ceramics
Silicon carbide covalent bond is extremely strong and still has high strength bonding at high temperature. this structural feature gives silicon carbide ceramics excellent strength, high hardness, wear resistance, corrosion resistance, high thermal conductivity, good thermal shock resistance and so on. at the same time, silicon carbide ceramic is one of the most potential high-performance armor protective materials with moderate price and high performance-to-price ratio.
Multiphase bulletproof ceramics
Although single-phase ceramics have certain bulletproof ability, the common problem is low fracture toughness and high brittleness. Therefore, the strengthening and toughening of bulletproof ceramics has always been a hot research direction. The strengthening and toughening methods mainly include multicomponent ceramic system composite, functionally graded ceramics, lamellar structure design and so on.
For example, Medvedovs ki has studied the silicon carbide matrix composites such as SiC-Al2O3, SiC-Si3N4-Al2O3, SiC-Si-Al2O3 and SiC-Si3N4-Si-Al2O3, and prepared them by pressureless sintering and reaction sintering. It is further proved that their physical properties such as hardness and energy absorption capacity are higher than those of the single material system. The protection coefficient of reaction sintered SiC based composite ceramics can reach grade 3 or grade 4. The prepared SiC-Si3N4-Al2O3 and reaction sintered SiC also have good multi-impact resistance.
Modern warfare has higher and higher requirements for the armored system, which requires not only to achieve omni-directional protection, but also not to interfere with the soldiers' movement ability, but to turn "passive" into "active" and develop the ability to identify targets in advance. And the use of bait trigger and physical destruction to destroy the "active armor" of incoming weapons has become a major advantage in combat. Transparent ceramics represented by alumina nitride (AlON) and magnesia-alumina spinel (MgAl2O4) have been used in the field of armor protection, which can not only protect the human body but also observe the enemy situation at any time.
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"Is there talk of solidarity with Sweden and Finland joining NATO? No." "So is the West united?" Zelensky said at this Ukraine-hosted breakfast in Davos. No." "Our strength is unity within the country," Zelensky said. "Now it depends on the Unity of the West to stand strong and firm behind Ukraine against Russia.
According to Zelensky, "When we are all really united, we will have an advantage over Russia."
Ukrainian President Volodymyr Zelensky says he once again appreciates U.S. President Joe Biden's offer of $40 billion in new financial aid to Ukraine.
"We need the support of a united Europe," Zelensky stressed. Zelensky criticized the position of Hungarian Prime Minister Viktor Orban, who is reluctant to impose an embargo on Russian oil at this stage. "Hungary has a problem!" Zelensky criticized.
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