News on China's scientific and technological development.

B

B.I.B.

Captain
JayBird said:
So.. you are saying the Chinese are natural born capitalist even more so than the Jewish?:p
Click to expand...
The Jewish made their reputation through banking/finance and lent to the capitalist IMO Because Chinese and Americans have the same level of intensity for capatalism, they should be the bestest of buddies.
 
Last edited:
Equation

Equation

Lieutenant General
delft said:
I doubt if all the bridges needed in Houston are enough for such a machine. These are a waste of effort to design and make unless you need such viaduct on a really large scale.
Click to expand...

Trust me the city of Houston is growing and expanding rapidly (about 5,000 new residents coming into the city every month). Our roads are getting more congested and we have very little light rail train system for the public. If you want to get around town or go anywhere in Houston you need a car...period.
 
AssassinsMace

AssassinsMace

Lieutenant General
Please, Log in or Register to view URLs content!


Ultra-thin, tunable, broadband microwave absorber may advance radar cloaking | American Institute of Physics

Chinese scientists have developed an ultra-thin, tunable microwave absorber that can operate over a broad range of frequencies, demonstrating its potential in improving aircraft cloaking, warship stealth and broadband antenna


From the Journal:

Please, Log in or Register to view URLs content!

By Zhengzheng Zhang

Washington, D.C., Nov. 10, 2015 – Microwave absorbers are a kind of material that can effectively absorb incident microwave energy to make objects invisible to radar; therefore they are commonly used in aircraft cloaking and warship stealth. Recently, as radar detection devices have been improved to detect the near-meter microwave length regime, scientists are working on high-performance absorbers that can cloak objects in the equivalent ultra-high frequency regime (from 300 megahertz to two gigahertz). However, conventional absorbers for the ultra-high regime are usually thick, heavy or have narrow absorption bandwidth, making them unsuitable for stealth missions.

To solve this problem, a team of researchers from Huazhong University of Science and Technology in China has developed an ultra-thin, tunable broadband microwave absorber for ultra-high frequency applications. This ultra-thin absorbing surface, called an active frequency-selective surface absorber, consists of arrays of patterned conductors loaded with two common types of circuit elements known as resistors and varactors. The unit patterned cell absorbs microwaves and can also be actively controlled by stretching to expand the tunable bandwidth. In a paper published this week in theJournal of Applied Physics, from AIP Publishing, the researchers presented this work.

“Our proposed absorber was fabricated with a stretching transformation pattern, which is both thin and can absorb a wide range of frequencies for near-meter microwave application,” said Wenhua Xu, the primary researcher in the team led by Jianjun Jiang, a professor of School of Optical and Electronic Information at the Huazhong University of Science and Technology, China. “Its absorption range covers a broad band from 0.7 to 1.9 gigahertz below -10 decibel, and the total thickness of the absorber is only 7.8 millimeters, which is one of the thinnest microwave absorbers reported.”

“Usually the thickness of conventional radar absorbers is a quarter the wavelength of the incident microwave. In the high frequency regime, take one gigahertz as an example, the thickness of the absorber would be around 7.5 centimeters, which is too thick and heavy to be used in aircrafts or warships. Our proposed absorber is almost ten times thinner than conventional ones,” Xu said.

Other alternative absorbers, such as metamaterial absorbers made from a resonant metallic structure printed on a dielectric substrate, though significantly thinner than the wavelengths absorbed, have a narrow working bandwidth.

To develop a novel absorber that is both thin and with broadband performance, Jiang’s team employed a type of thin, light periodic structure called a frequency-selective surface, which consists of an assembly of patterned conductors arranged in a two-dimensional array, usually backed by a thin dielectric, to reflect incident microwaves according to their frequency.

In the experiment, Jiang’s team fabricated a broadband active frequency-selective surface with a stretching transformation pattern on a printed circuit board, and soldered the resistors and varactors between each of the two unit patterned cells. The fact that the surface could be stretched meant that the parameters of the unit patterned cell can be actively controlled by stretching.

By modeling the absorber using a transmission line, the researchers found that the varactor provides a variable capacitance at varying bias voltage, which produces the device’s tunability, while the lumped resistor with constant resistance reliably produces strong absorption at the resonance frequency. Besides the lumped impedances of the loaded elements, the researchers discovered that the parameters of the unit patterned cells contribute to the device’s absorption performance as well.

“We applied various stretching transformation coefficients to the unit cell pattern to obtain the available parameters to expand the tunable bandwidth,” Xu said. “Our results suggest that a cell pattern with a smaller stretching transformation coefficients ratio (i.e. width to length ratio of the unit cell) leads to higher resonance frequency absorption and produces a wider tunable bandwidth as well.”

Xu noted that it is the first time that stretching transformation pattern is used in the active frequency-selective surface absorber to expand the bandwidth, which turns out to be an effective technique for producing broadband tunability.

“At frequencies below two gigahertz, conventional microwaves absorbers are limited in application by their thickness and narrow absorption bandwidth. Our proposed absorber has achieved broadband tunability and ultra-thin film simultaneously,” Xu said. “The total thickness of 7.8 millimeters is around one twenty-ninth wavelength of the central frequency of incident microwaves, and the ultra-thin absorber with broad bandwidth may be widely used in warship stealth, airplane cloaking and tunable, broadband antennae.”

The researchers’ next step is to study the polarization and the oblique incidence performance for the proposed active frequency-selective surface absorber.
Click to expand...

I found this originally from another article which taunted that how this discovery served the Chinese no more since they gave it away by publishing the paper. Now everyone knows how to do it according to them. A lot of this is happening lately since there's steadily increasing number of Chinese advancements where they have to knock it some way to comfort their insecurity.
 
GreenestGDP

GreenestGDP

Junior Member
... taunted that how this discovery served the Chinese no more since they gave it away by publishing the paper to the American military scientists ...
Click to expand...


Yes, many, many Chinese scientists are so insecure when they compare themselves with the American scientists.

Thus, in order to show off their scientific prowess to the American audiences, they revealed too much.

This inferiority complex towards the American scientists, and their bending over-backward, in order to be likeable by the American audiences are so widespread.

Just look at the Huawei CEO * Ren Zheng Fei continuous brown nosing behaviors,
and CRH Sifang Qingdao brown nosing US in an attempt to build high speed train network in US.
Plus countless other Chinese companies who invest in US just for the sake of getting American recognitions.

It seems if they can not to sell their products in US,
then it is the end of the world for them.
And, it means their products are inferior and their products are NOT legitimate.

Just look at how much resources these Chinese idiots are investing in US soil.

Imagine if these Chinese corporations wise up, and invest their resources in
IRAN, CENTRAL ASIA, BRAZIL, CUBA, VENEZUELA,
and any other nations who dislike US.

It would be so much more productive, and win--win instead of win--lose.

This psychological Black--Hole is very troublesome.
When will Chinese scientists & entrepreneurs see the light ?


Many Chinese Psychological Black--Hole
blackhole--1.jpg
 
Last edited:
C

counterprime

New Member
Registered Member
You nailed it. I blame the stupid CPC for not educating and debunking western "soft-power". I won't say much more except that when the American military labs and silicon valley are disproportionately staffed by Chinese scientists, they ought to rethink the western trope of "uncreative Asians".
 
D

delft

Brigadier
Equation said:
Trust me the city of Houston is growing and expanding rapidly (about 5,000 new residents coming into the city every month). Our roads are getting more congested and we have very little light rail train system for the public. If you want to get around town or go anywhere in Houston you need a car...period.
Click to expand...
But do you need to build viaducts on a scale as is necessary to make the use of the Chinese viaduct building engines viable?
 
You must log in or register to reply here.
Top