Hexbyte Glen Cove China allows couples third child amid demographic crisis thumbnail

Hexbyte Glen Cove China allows couples third child amid demographic crisis

Hexbyte Glen Cove

Adults and children ride pedal cycles at a public park in Beijing, Saturday, Aug. 21, 2021. China will now allow couples to have a third child as the country seeks to hold off a demographic crisis that threatens its hopes of increased prosperity and global influence. Credit: AP Photo/Mark Schiefelbein

China will now allow couples to legally have a third child as it seeks to hold off a demographic crisis that could threaten its hopes of increased prosperity and global influence.

The ceremonial legislature on Friday amended the Population and Family Planning Law as part of a decades-long effort by the ruling Communist Party to dictate the size of families in keeping with political directives. It comes just six years after the last change.

From the 1980s, China strictly limited most couples to one child, a policy enforced with threats of fines or loss of jobs, leading to abuses including forced abortions. A preference for sons led parents to kill baby girls, leading to a massive imbalance in the sex ratio.

The rules were eased for the first time in 2015 to allow two children as officials acknowledged the looming consequences of the plummeting birthrate. The overwhelming fear is that China will grow old before it becomes wealthy.

China long touted its one-child policy as a success in preventing 400 million additional births in the world’s most populous country, thus saving resources and helping drive economic growth.

However, China’s birth rate, paralleling trends in South Korea, Thailand and other Asian economies, already was falling before the one-child rule. The average number of children per mother tumbled from above six in the 1960s to below three by 1980, according to the World Bank.

Children hold Chinese flags as they pose for a photo at Tiananmen Square in Beijing, on June 22, 2021. China will now allow couples to have a third child as the country seeks to hold-off a demographic crisis that threatens its hopes of increased prosperity and global influence. Credit: AP Photo/Mark Schiefelbein

Meanwhile, the number of working-age people in China has fallen over the past decade and the population has barely grown, adding to strains in an aging society. A once-a-decade government census found the population rose to 1.411 billion people last year, up 72 million from 2010.

Statistics show 12 million babies were born last year, which would be down 18% from 2019’s 14.6 million.

Chinese over 60, who number 264 million, accounted for 18.7% of the country’s total population in 2020, 5.44 percentage points higher than in 2010. At the same time, the working-age population fell to 63.3% of the total from 70.1% a decade ago.

The shift to the two-child rule led to a temporary bump in the numbers of births but its effects soon wore off and total births continued to fall because many women continued to decide against starting families.

Japan, Germany and some other wealthy countries face the same challenge of having fewer workers to support aging populations. However, they can draw on investments in factories, technology and foreign assets, while China is a middle-income country with labor-intensive farming and manufacturing.

At its session Friday, the Standing Committee of the National People’s Congress canceled the leveling of fines for breaking the earlier restrictions and called for additional parental leave and childcare resources. New measures in finance, taxation, schooling, housing and employment should be introduced to “to ease the burden on families,” the amendment said.

It also seeks to address longstanding discrimination against pregnant women and new mothers in the workplace that is considered one of the chief disincentives to having additional children, along with high costs and cramped housing.

While female representation in the labor force is high, women, especially those with children, are severely underrepresented at the higher levels, holding just 8.4% of leadership positions at the central and provincial levels. Among the young party leaders who will take the reins in the coming decades, only 11% are women



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China allows couples third child amid demographic crisis (2021, August 21)
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Hexbyte Glen Cove New type of metasurface allows unprecedented laser control thumbnail

Hexbyte Glen Cove New type of metasurface allows unprecedented laser control

Hexbyte Glen Cove

The shape of the laser beam can be fully controlled to project a complex hologram, such as the one above. Credit: Christina Spägele/Harvard SEAS

The ability to precisely control the various properties of laser light is critical to much of the technology that we use today, from commercial virtual reality (VR) headsets to microscopic imaging for biomedical research. Many of today’s laser systems rely on separate, rotating components to control the wavelength, shape and power of a laser beam, making these devices bulky and difficult to maintain.

Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have developed a single that can effectively tune the different properties of light, including wavelength, without the need of additional optical components. The metasurface can split light into multiple beams and control their shape and intensity in an independent, precise and power-efficient way.

The research opens the door for lightweight and efficient optical systems for a range of applications, from quantum sensing to VR/AR headsets.

“Our approach paves the way to new methods to engineer the emission of optical sources and control multiple functions, such as focusing, holograms, polarization, and beam shaping, in parallel in a single metasurface,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper.

The research was published recently in Nature Communications.

The tunable laser has just two components—a and a reflective metasurface. Unlike previous metasurfaces, which relied on a network of individual pillars to control light, this surface uses so-called supercells, groups of pillars which work together to control different aspects of light.

The incident light can be split into three independent beams, each with different properties — a conventional beam (right), a beam known as a Bessel beam (center) and an optical vortex (left). Credit: Christina Spägele/Harvard SEAS

When light from the diode hits the supercells on the metasurface, part of the light is reflected back, creating a laser cavity between the diode and the metasurface. The other part of the light is reflected into a second beam that is independent from the first.

“When light hits the metasurface, different colors are deflected in different directions,” said Christina Spägele, a graduate student at SEAS and first author of the paper. “We managed to harness this effect and design it so that only the wavelength that we selected has the correct direction to enter back in the diode, enabling the laser to operate only at that specific wavelength.”

To change the wavelength, the researchers simply move the metasurface with respect to the laser diode.

“The design is more compact and simpler than existing wavelength-tunable lasers, since it does not require any rotating component,” said Michele Tamagnone, former postdoctoral fellow at SEAS and co-author of the paper.

The researchers also showed that the shape of the laser beam can be fully controlled to project a complex hologram—in this case the complex, century-old Harvard shield. The team also demonstrated the ability to split the incident into three independent beams, each with different properties—a conventional beam, an optical vortex and a beam known as a Bessel , which looks like a bullseye and is used in many applications including optical tweezing.

“In addition to controlling any type of laser, this ability to generate multiple beams in parallel and directed at arbitrary angles, each implementing a different function, will enable many applications from scientific instrumentation to augmented or virtual reality and holography,” said Capasso.



More information:
Christina Spägele et al, Multifunctional wide-angle optics and lasing based on supercell metasurfaces, Nature Communications (2021). DOI: 10.1038/s41467-021-24071-2

Citation:
New type of metasurface allows unprecedented laser control (2021, June 29)
retrieved 29 June 2021
from https://phys.org/news/2021-06-metasurface-unprecedented-laser.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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