In Europe and the Americas, there are great differences in the selection of standards for integrated cabling fireproof cables. The focus is whether to use halogen-containing fireproof materials or halogen-free "environmentally friendly" fireproof materials. In order to ensure the integrity of the data in the fire field, what conditions must our fire-resistant cables meet? Why can some fire-resistant cables be called "fire-resistant cables" instead of so-called "heat-resistant cables"? Industry trends have been elaborated and introduced one by one.
1 Introduction
The most valuable thing in network transmission is information rather than network equipment. There is such a news, a fire broke out in a citizen ’s house, she just took a drawer and escaped from the fire. They asked her what it was! So precious? She said it was a picture of me from childhood to other things They are all valuable, and the photos are priceless, and they will never be burnt out. It can be seen that the information is non-renewable, and once it is lost, it will never be lost. Therefore, people do everything possible to back up the data by various means, transmit the data through a stable network, and place them in a safe place. People gradually turn the integrated wiring system to resist external intrusion and avoid external hazards. Therefore, cable fire prevention has become the top priority.
It is often said that water and fire are ruthless. Since the discovery of fire, fire has not only accelerated the development of human civilization, but also brought destruction to human civilization. How many ancient civilizations were destroyed by fire. Similarly, a fire can also burn down the integrated wiring system and interrupt the network transmission. At the same time, if the cable produces a large amount of toxic gas and smoke during the combustion process, it will have a great impact on the escape of personnel and even become a hidden safety hazard. Therefore, engineers from various countries are stepping up research on fireproof cables that are safer for data backup and personnel.
2 Fire cable type
At present, the widely used fire-resistant cables mainly include UL series flame-retardant cables and flame-retardant low-smoke halogen-free cables. The imported products mainly come from the Americas and Europe. Due to the incompatibility between the fireproof cable standards in the Americas and Europe, the fire protection ideas are very different. Therefore, both Party A and the Design Institute are in a passive state when choosing products, each with their own The truth is that the choice is often based on the actual situation of the funds.
UL flame retardant standards mainly have the following grades: CMP, CMR, CM, CMG, CMX.
1) Supercharged level-CMP level (supply air combustion test / Steiner sodium duct test PlenumFlameTest / SteinerTunnelTest)
This is the most demanding cable (PlenumCable) in the UL fire protection standard. The applicable safety standard is UL910. The experiment stipulates that multiple samples are laid on the horizontal air duct of the device and burned with 87.9KW gas Bunsen burner (300,000 BTU / Hr) minute. The acceptance criterion is that the flame cannot extend beyond 5 feet from the front of the gas Bunsen burner flame. The peak value of the optical density is 0.5 at the maximum, and the average density value is 0.15 at the maximum.
This CMP cable is usually installed in the air return pressurization system used in ventilation ducts or air treatment equipment, and is approved by Canada and the United States. FEP / PLENUM materials that meet UL910 standards have better flame retardancy than low-smoke halogen-free materials that comply with IEC60332-1 and IEC60332-3 standards, and the concentration of smoke when burned is low.
2) Trunk level-CMR level (Riser Flame Test)
This is a commercial cable (RiserCable) in the UL standard, and the applicable safety standard is UL1666. The experiment stipulates that multiple samples are laid on the simulated vertical shaft, and the specified 154.5KW gas Bunsen burner (527, 500BTU / Hr) is used for 30 minutes. The eligibility criterion is that the flame cannot spread to the upper part of the 12-foot-high room. Trunk-level cables have no smoke density specifications and are generally used for vertical and horizontal wiring on floors.
3) Commercial grade-CM grade (VerTIalTrayFlameTest)
This is a commercial grade cable (GeneralPurposeCable) in the UL standard, and the applicable safety standard is UL1581. The experiment stipulates that multiple specimens are laid on a vertical 8-foot high bracket, and burned (70,000 BTU / Hr) for 20 minutes with a prescribed 20KW band torch. The acceptance criterion is that the flame cannot spread to the upper end of the cable and extinguish itself. UL1581 is similar to IEC60332-3C, except that the number of cables laid is different. Commercial grade cables do not have smoke density specifications and are generally only used for horizontal wiring on the same floor, not for vertical wiring on floors.
4) General grade-CMG grade (VerTIalTrayFlameTest)
This is the General Standard Cable (GeneralPurposeCable) in the UL standard, and the applicable safety standard is UL1581. The test conditions for commercial grade and general grade are similar, and they are both approved for use in Canada and the United States. General-grade cables do not have smoke density specifications, and are generally only used for horizontal wiring on the same floor, not for vertical wiring on floors.
Application-Specific Integrated Circuit refers to an integrated circuit specifically designed to perform a specific computing task. It is very common to use ASIC for mining in the field of blockchain. This article will analyze the principle of ASIC mining and why it should be anti-ASIC.
For Bitcoin, mining has gone through four stages: CPU, GPU, FPGA and ASIC. GPU is naturally suitable for parallel simple operations, so the execution of SHA256 is much higher than the CPU. FPGA is a programmable hardware, because it has a certain degree of universality, so the unit price will be relatively expensive. ASIC has a large initial design investment, but the unit price will be cheaper after mass production. Therefore, if you can determine that the market size is relatively large, the use of ASIC technology will be the most cost-effective.
This is the basic principle of ASIC.
In a nutshell, mining is running complicated calculations in the search for a specific number. Whether it`s an ASIC miner or a GPU mining rig, mining hardware must run through many calculations before finding that number. In proof of work systems like Bitcoin, the first one to find that number gets a reward - at the time of writing, 12.5 Bitcoins worth around $96,850. That reward will fall to 6.25 Bitcoins in May 2020.
There are so many people and powerful computing systems trying to mine Bitcoin that miner groups form to find that number and share the profit. Even more, the faster your hardware, the more you earn. That`s why people who can afford it opt for ASIC miners because it gives them the greatest chance of earning cryptocurrency in exchange for their investment.
Each cryptocurrency has its own cryptographic hash algorithm, and ASIC miners are designed to mine using that specific algorithm. Bitcoin ASIC miners are actually designed to calculate the SHA-256 hash algorithm. In the case of Litecoin, it uses Scrypt. That means technically they could mine any other coin that`s based on the same algorithm, though typically, people who buy ASIC hardware designed for Bitcoin mine that specific digital currency.
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