News on China's scientific and technological development.

"a metamaterial design paradigm using gears with encoded stiffness gradients as the constituent elements and organizing gear clusters for versatile functionalities."

"continuously tunable elastic properties while preserving stability and robust manoeuvrability, even under a heavy load."

"shape morphing between ultrasoft and solid states, and fast response."

IMO this is epic level invention. Imagine the robots and exoskeletons made from this metamaterial.

The Chinese scientists also got their inspiration from the .

Programmable gear-based mechanical metamaterials​

Abstract​

Elastic properties of classical bulk materials can hardly be changed or adjusted in operando, while such tunable elasticity is highly desired for robots and smart machinery. Although possible in reconfigurable metamaterials, continuous tunability in existing designs is plagued by issues such as structural instability, weak robustness, plastic failure and slow response. Here we report a metamaterial design paradigm using gears with encoded stiffness gradients as the constituent elements and organizing gear clusters for versatile functionalities. The design enables continuously tunable elastic properties while preserving stability and robust manoeuvrability, even under a heavy load. Such gear-based metamaterials enable excellent properties such as continuous modulation of Young’s modulus by two orders of magnitude, shape morphing between ultrasoft and solid states, and fast response. This allows for metamaterial customization and brings fully programmable materials and adaptive robots within reach.

Click to expand...

记者9月12日从国防科技大学获悉，该校的研究者们提出一种原创性的智能超材料设计方法，实现了金属基材料刚度和形状的大范围、连续、快速调节，具有重要的科学意义和工程应用价值。

相关研究作为8月封面文章近日发表于《自然—材料》，并被《自然》评为今年6月全球重要科技进展（全球共4项）。

齿轮簇实现机械性能调节

近年来，智能材料广受关注，它是智能装备与结构设计的基础。材料弹性的调节对于智能机器、机器人、飞机和其他系统非常必要。然而，常规材料一旦制备，特性就几乎不能改变，部分材料在高温相变时才能呈现一定的调节性，但不具备工程实际可操作性。

“机械/力学超材料是具有超出常规材料力学性能的结构功能材料，为高性能装备设计提供了前沿技术支撑，但传统超材料设计方法依然无法实现稳定连续的参数控制，需要颠覆性设计思维才能突破该瓶颈。”该校智能科学学院振动与噪声控制研究团队带头人、论文共同通讯作者温激鸿表示。

“限制力学超材料实现智能化调节的根本原因在于传统超材料的设计都遵循同一种模式，即将梁、杆、板等单功能的承载基元用固定或屈曲结点连接构成确定性拓扑结构，这种模式下，当受到应力、热或电磁场的刺激时，超材料会因为屈曲或旋转铰链而发生重构，从而改变刚度，同时会造成塑性变形且变化不连续，调节过程十分困难。”论文第一作者兼共同通讯作者、研究团队副研究员方鑫说。

为解决这个难题，研究团队提出了基于多功能动态基元和易变—牢固耦合模式的智能可编程机械/力学超材料设计范式，设计了系列基于齿轮的智能超材料，突破了宏观与微观、金属基和复合材料基超材料的集成一体化制造和集成驱动技术，实现了金属基材料的大范围、连续、快速调节。

通俗地说，该团队设计了一个由齿轮制成的智能材料，它可以根据不同的“命令”，在齿轮旋转时，使坚固的材料变得更坚硬/更柔软或变形。

“这是一种前所未有的设计方法。”方鑫表示，可调性能够通过组装具有内置刚度梯度的元件实现。要实现机械性能可调但坚固的固体，需要确保在大作用力下的可调性和强耦合（可靠连接），同时避免在调整时发生塑性变形。“我们发现，这种可变而又强的耦合可以通过齿轮簇实现。”

方鑫透露，除了尝试以齿轮作为基元外，团队还尝试过很多其他构型，比如广泛关注的折纸构型、各类弹性屈曲构型、双稳态/多稳态构型，但都无法实现他们想要的这种调控特性。

为什么是齿轮簇？“可靠的齿轮啮合可以平稳地传递旋转和沉重的压缩载荷。”方鑫说，刚度梯度可以内置到单独的齿轮体中，也可以通过分层齿轮组件实现。齿轮组可以组装成单元组，而单元做恰当排列就可形成超材料。

从太极图中获取内部结构设计灵感

既然齿轮是可被利用的元件，那它的内部结构该如何设计？

超材料的可调性取决于其内置中空部分的形状。“想要实现可调但坚固的材料，需要确保在大作用力下的可调性和鲁棒可控性，同时避免调谐中塑性变形。”方鑫表示，在众多设计方案中，团队从太极图中获取灵感，最终设计了形似太极图的齿轮，其形状以螺旋方向为特征，可以提供平滑的变化和极性。

“太极图的灵感是从中国传统文化中获得的。当时我在用笔构思各种简单大气又有用的形状，脑子里突然闪现《易经》中‘两仪生四象，四象生八卦’这句话，随之就想起了太极图。因为太极的核心思想就是‘变化’，而我们想要的材料特性也是‘变’。”方鑫说，“引入太极理念后，我们设计的构型具有正极性和负极性，提供了一个很好的设计维度。”

在此基础上，该团队使用紧密耦合的周期齿轮和两个格子框架（前和后）将齿轮排列成简单的图案，外部形成两个弹性臂，其径向厚度随旋转角度θ平滑变化。在压缩载荷作用下，臂部的变形以弯曲为主。

“任何两个啮合齿轮的自转方向都是相反的。正面和背面太极图案的螺旋方向是相反的。因此，一对齿轮的啮合模式有两极。当图案的螺旋方向相反时，极性为正，反之则具有负极性。”方鑫说。

为了验证这一构想，团队采用投影显微立体光刻3D打印技术制作了5行6列的太极齿轮组成的集成微型超材料。太极齿轮的直径和齿厚分别为3.6毫米和235微米，最粗的臂为75微米。样品由杨氏模量为3.5GPa的光敏树脂制成。

“这种微型试件的等效模量Ey（θ）可以平滑地调整35倍（从8.3MPa到295MPa）。用金属材料制备的样品调节范围则可达到75倍。”方鑫说，这意味着即使是在微尺度上，基于齿轮的集成超材料也可以通过三维打印直接制造。这种集成制造的主要挑战是确保啮合齿不会融合在一起，但仍能有效地参与啮合。

旋转变速器行星齿轮即可“变身”

该团队设计的第一种超材料仅在压缩载荷下可调。“我们期望找到一种设计方法，使其压缩模量和拉伸模量均可调，同时保持结构完整性。”方鑫介绍，团队探索发现，这可以通过将行星齿轮系统组织为元胞来实现。团队使用行星齿轮簇创建了一个层次分明的超材料，其可调性来自元胞内齿轮的相对旋转。

“我们设计的行星齿轮超材料的变刚度来自每个行星齿轮内部。齿轮环产生弹性弯曲变形，其内部的行星齿轮是齿环变形的支点，通过旋转行星齿轮改变齿轮环的位置就可以改变它的变形刚度，从而对超材料参数进行调节。”方鑫说，对于组装的超材料，所有的太阳齿轮通过轴连接到传递转动的齿轮上，这些传动齿轮紧凑地耦合在一起。因此，只需要旋转其中的几个传动齿轮就可以实现对所有元素的重新配置和调节。

“有趣的是，我们设计的超材料可在很大的压缩力下保持稳定，并在剪切时显示出较大的刚度。支撑稳定性的因素之一是一种齿轮组的自锁机制，另一因素则是轮齿的咬合力。”方鑫表示。

该团队提出了几个可展示齿轮基超材料广泛应用潜力的场景。“对于机器人，可调刚度腿/执行器能够提供高刚度以在行走时稳定支撑重物，低刚度则在跳跃或跑步时提供减震保护。航空发动机挂架系统中需要类似的可调刚度隔离器，以在不同飞行阶段保持最佳性能和效率。”温激鸿表示。

“人们还可以通过使用锥齿轮、将平面齿轮组装成分层结构或合成不同类型的齿轮来设想3D超材料，利用集成制造将这些可调特性连接起来，以生产坚固的多用途设备。以微型超材料为例，高分辨率和大规模的3D打印，使基于齿轮的超材料进一步小型化和延伸成为可能。” 方鑫说。

《自然》审稿编辑认为，这种基于齿轮的力学超材料是使机器部件实现刚度可调的同时保持结构强稳定的可行途径，比如通过使机器人的结构变软或变硬来更好地适应跳跃和抓取物品等动作。

One of the impressive results of more than 10 years of hard work by Chinese scientists: fatigue life (of a certain bearing steel) is greatly improved by only parts-per-million-level RE addition, with 40 fold improvement for the tension-compression fatigue life and 40% enhancement of the rolling contact fatigue life.

Low-oxygen rare earth steels​

Abstract​

Rare earth (RE) addition to steels to produce RE steels has been widely applied when aiming to improve steel properties. However, RE steels have exhibited extremely variable mechanical performances, which has become a bottleneck in the past few decades for their production, utilization and related study. Here in this work, we discovered that the property variation of RE steels stems from the presence of oxygen-based inclusions. We proposed a dual low-oxygen technology, and keeping low levels of oxygen content in steel melts and particularly in the raw RE materials, which have long been ignored, to achieve impressively stable and favourable RE effects. The fatigue life is greatly improved by only parts-per-million-level RE addition, with a 40-fold improvement for the tension–compression fatigue life and a 40% enhancement of the rolling contact fatigue life. We find that RE appears to act by lowering the carbon diffusion rate and by retarding ferrite nucleation at the austenite grain boundaries. Our study reveals that only under very low-oxygen conditions can RE perform a vital role in purifying, modifying and micro-alloying steels, to improve the performance of RE steels.

Click to expand...

我国低氧稀土钢研究取得重要进展​

稀土元素电子结构独特，具有优异的磁、光、电等物理和化学特性，在多种材料中发挥着重要作用。自20世纪20年代稀土在钢中加入以来，国内外大量研究表明，微量稀土添加显著提高了钢的韧塑性、耐磨、耐热、耐蚀性能等。

通过长达十余年的机理研究和工业实验，近期，中国科学院金属研究所沈阳材料科学国家研究中心研究团队受前期氧致偏析新机制的启发，发现稀土钢性能波动、浇口堵塞问题的根源在于氧含量。他们通过降低钢液和稀土金属中的氧含量，结合实验、计算和表征揭示了稀土在钢中的关键作用机制，控制夹杂物和稀土固溶，制备出性能优越、稳定的低氧稀土钢。相关研究结果日前在《自然》杂志子刊《自然材料》上发表。

研究发现，不仅钢液中的氧含量影响稀土钢的性能，更为重要的是，长期被学界和产业界忽视的稀土金属中的氧含量，对稀土钢的性能具有十分重要的影响。因为稀土金属极为活泼，在稀土金属电解制备时容易形成大尺寸稀土氧化物，这些稀土氧化物随稀土金属加入钢液中，带入的大尺寸稀土夹杂物难以上浮去除，从而导致稀土钢性能波动并与耐火材料反应堵塞浇口。

基于上述发现，研究人员进一步开发了“双低氧稀土钢”技术，即钢液低氧和稀土金属低氧的控制技术，从而有效解决了稀土钢工业应用中的瓶颈问题。在高纯净的GCr15轴承钢中应用后，与不加稀土的轴承钢相比，稀土轴承钢±800MPa拉压疲劳寿命提升了40倍，4.2GPa接触应力下滚动疲劳寿命提升了40%。

研究揭示了稀土钢性能波动的根源，发现只有在低氧条件下稀土才能在钢中稳定发挥深度净化钢液、细化改变夹杂物和强烈微合金化的作用。该研究工作表明，吨钢只需添加百余克的镧铈轻稀土，在成本基本不增加、工艺流程基本不改变的条件下即可显著提升钢的性能，这对于发挥我国稀土资源优势，平衡稀土资源利用，提升优特钢的品质具有重要意义。

Can anyone please explain what is going on here?

China’s top weapons scientist says nuclear fusion power is 6 years away​

• Peng Xianjue unveils plans for combined fusion-fission reactor that could make China world’s first to achieve the elusive viable energy source
• No country has so far managed to build a facility that generates more power than it uses in the fission process

Topic |





The Chinese government has approved construction of the world’s largest pulsed-power plant with plans to generate energy by 2028, according to the top nuclear weapons scientist leading the project.
“Fusion ignition is the jewel in the crown of science and technology in today’s world,” said Peng Xianjue, a professor with the Chinese Academy of Engineering Physics, in an online meeting organised by Beijing-based think tank Techxcope on September 9.
“Being the world’s first to achieve energy-scale fusion energy release will lay the most important milestone in the road to fusion energy for human beings.”
Peng, 81, has developed some of China’s most advanced small nuclear warheads and served as a top adviser to the country’s nuclear weapons programme, according to openly available information.
The Z-pinch machine – which replicates the fusion reactions of a thermonuclear bomb through magnetic pressure created by an extremely strong electric pulse – is expected to be completed around 2025 in Chengdu, Sichuan province in southwest China.
The machine will produce 50 million amperes of electricity – about twice as much as the record-holding Z pulsed power facility, a similar device at the Sandia National Laboratory in the US, Peng said.
Nuclear powers like the US, Russia and China have built a number of Z-pinch machines over the past few decades – some of which have never been officially disclosed – to simulate the extreme conditions needed to develop atomic weapons.These facilities can store a huge amount of electricity and release it in just a few nanoseconds. The electric pulse can create extreme pressure and enough radiation for two lightweight atoms to “fuse” into a heavier one, and give up some mass in the form of energy.
But building a machine that can produce more fusion power output than input is extremely difficult and so far, no country has been successful.
According to Peng’s presentation, the Chinese researchers will try to create a nuclear fusion reaction by using the strong electric charge to ignite a small number of hydrogen isotopes deuterium and tritium.
By carefully controlling the process, they hope to be able to cap the pulse energy released to a few hundred million joules – about as powerful as a 20kg (44lbs) bag of TNT.
And in a departure from previous designs, the fusion energy produced by the Chinese facility will not go to the power grid, but drive a swamp of superfast particles to hit uranium – the fuel which will power the facility’s fission component.
In his conference presentation, Peng said this inclusion of fusion and fission reactors is responsible for the Chinese design’s designation as Z-FFR.
The intention is for the walls of the fusion ignition chamber to be filled with uranium which will absorb the flying neurons produced by the explosion, causing it to split into two lighter elements – the same process used in existing nuclear power facilities.
The uranium fission will increase the facility’s total heat output by 10 to 20 times, significantly accelerating the application of fusion energy and making it ready for commercial power production by 2035, according to an estimate by Peng’s team.
If China’s machine is to succeed, it will need many high-performance capacitors to store the electricity and laser-powered switches that can operate instantly without causing a shortage.
Other challenges include special wires able to transmit the strongest electric currents on Earth, and a peanut-sized target device to efficiently convert electricity to ignition charge.
Peng said many of these problems had been solved, thanks to new scientific discoveries and technical breakthroughs by Chinese nuclear scientists in recent years. And some of their approaches are fundamentally different from what has been tried in the West.
In its fusion experiments, the Sandia lab tried to start ignition from the centre of the target device. But the Chinese researchers say they have found ignition could more easily be achieved by first creating a thin line of fusion reactions that runs through the target’s centre.
This linear approach reduces the complex, three-dimensional problem of squeezing the entire target – at equal pressure from many directions simultaneously – to a one-dimensional issue, Peng said.
The Chinese approach significantly simplifies the physical models for computer analysis while relaxing the demand for energy input, he said. “This is a big innovation.”
The researchers said the future power plant could use natural uranium ore, the nuclear waste produced by today’s reactors, or thorium, which could meet energy demand for thousands – or even tens of thousands – of years while producing little radioactive waste.
And because the fusion explosion will happen only once every 10 seconds, it will be incapable of generating enough energy to start a chain reaction and cause a meltdown, making the design safe and suitable for most places on Earth, they said.
The Z machine is just one of a range of methods – including powerful lasers and hot plasma caged in a magnetic field – being tried and tested by China and other countries in the race to achieve fusion ignition.
A number of giant facilities are in development around the world, with most aiming for commercial power production by the middle of this century.
A Beijing-based nuclear physicist, who asked not to be named because of the issue’s sensitivity, said that while the Z machine has some unique advantages, it also presents some difficult problems that may affect its mass application.
The electric power source, for instance, will need to generate and release charges at a high frequency every few seconds, putting an enormous strain on the capacitors and other components, the physicist said.
In addition, the target device will need to be replaced after each explosion, while the reactor chamber will need to withstand thousands of explosive shocks per day.
But whether ignition can be achieved, one thing is certain, according to the physicist: the facility will be a “mega lab” for cutting edge research on everything from Big Bang physics to new weapons.

Nuclear fusion is the holy grail of energy. this is hugeeeeeeee breakthrough.

China’s top weapons scientist says nuclear fusion power is 6 years away​

• Peng Xianjue unveils plans for combined fusion-fission reactor that could make China world’s first to achieve the elusive viable energy source
• No country has so far managed to build a facility that generates more power than it uses in the fission process

The Chinese government has approved construction of the world’s largest pulsed-power plant with plans to generate nuclear fusion energy by 2028, according to the top nuclear weapons scientist leading the project.

“Fusion ignition is the jewel in the crown of science and technology in today’s world,” said Peng Xianjue, a professor with the Chinese Academy of Engineering Physics, in an online meeting organised by Beijing-based think tank Techxcope on September 9.

“Being the world’s first to achieve energy-scale fusion energy release will lay the most important milestone in the road to fusion energy for human beings.”

Peng, 81, has developed some of China’s most advanced small nuclear warheads and served as a top adviser to the country’s nuclear weapons programme, according to openly available information.
The Z-pinch machine – which replicates the fusion reactions of a thermonuclear bomb through magnetic pressure created by an extremely strong electric pulse – is expected to be completed around 2025 in Chengdu the capital of the southwestern province of Sichuan.

The machine will produce 50 million amperes of electricity – about twice as much as the record-holding Z pulsed power facility, a similar device at the Sandia National Laboratory in the US, Peng said.

Nuclear powers like the US, Russia and China have built a number of Z-pinch machines over the past few decades – some of which have never been officially disclosed – to simulate the extreme conditions needed to develop atomic weapons.

These facilities can store a huge amount of electricity and release it in just a few nanoseconds. The electric pulse can create extreme pressure and enough radiation for two lightweight atoms to “fuse” into a heavier one, and give up some mass in the form of energy.
But building a machine that can produce more fusion power output than input is extremely difficult and so far, no country has been successful.

According to Peng’s presentation, the Chinese researchers will try to create a nuclear fusion reaction by using the strong electric charge to ignite a small number of the hydrogen isotopes deuterium and tritium.

By carefully controlling the process, they hope to be able to cap the pulse energy released to a few hundred million joules – about as powerful as a 20kg (44lbs) bag of TNT.

And in a departure from previous designs, the fusion energy produced by the Chinese facility will not go to the power grid, but drive a swamp of superfast particles to hit uranium – the fuel which will power the facility’s fission component.

In his conference presentation, Peng said this inclusion of fusion and fission reactors is responsible for the Chinese design’s designation as Z-FFR.
The intention is for the walls of the fusion ignition chamber to be filled with uranium which will absorb the flying neurons produced by the explosion, causing it to split into two lighter elements – the same process used in existing nuclear power facilities.

The uranium fission will increase the facility’s total heat output by 10 to 20 times, significantly accelerating the application of fusion energy and making it ready for commercial power production by 2035, according to an estimate by Peng’s team.

If China’s machine is to succeed, it will need many high-performance capacitors to store the electricity and laser-powered switches that can operate instantly without causing a shortage.

Other challenges include special wires able to transmit the strongest electric currents on Earth, and a peanut-sized target device to efficiently convert electricity to an ignition charge.

Peng said many of these problems had been solved, thanks to new scientific discoveries and technical breakthroughs by Chinese nuclear scientists in recent years. And some of their approaches are fundamentally different from what has been tried in the West.
In its fusion experiments, the Sandia lab tried to start ignition from the centre of the target device. But the Chinese researchers say they have found ignition could more easily be achieved by first creating a thin line of fusion reactions that runs through the target’s centre.
This linear approach reduces the complex, three-dimensional problem of squeezing the entire target – at equal pressure from many directions simultaneously – to a one-dimensional issue, Peng said.

The Chinese approach significantly simplifies the physical models for computer analysis while relaxing the demand for energy input, he said. “This is a big innovation.”

The researchers said the future power plant could use natural uranium ore, the nuclear waste produced by today’s reactors, or thorium, which could meet energy demand for thousands – or even tens of thousands – of years while producing little radioactive waste.
And because the fusion explosion will happen only once every 10 seconds, it will be incapable of generating enough energy to start a chain reaction and cause a meltdown, making the design safe and suitable for most places on Earth, they said.

The Z machine is just one of a range of methods – including powerful lasers and hot plasma caged in a magnetic field – being tried and tested by China and other countries in the race to achieve fusion ignition.

A number of giant facilities are in development around the world, with most aiming for commercial power production by the middle of this century.

A Beijing-based nuclear physicist, who asked not to be named because of the issue’s sensitivity, said that while the Z machine has some unique advantages, it also presents some difficult problems that may affect its mass application.

The electric power source, for instance, will need to generate and release charges at a high frequency every few seconds, putting an enormous strain on the capacitors and other components, the physicist said.

In addition, the target device will need to be replaced after each explosion, while the reactor chamber will need to withstand thousands of explosive shocks per day.

But whether ignition can be achieved, one thing is certain, according to the physicist: the facility will be a “mega lab” for cutting edge research on everything from Big Bang physics to new weapons.

A diagram of the overall structure of China’s planned Z Fusion Fission Reactor

ChongqingHotPot92 said:

Can anyone please explain what is going on here?

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China’s top weapons scientist says nuclear fusion power is 6 years away​

• Peng Xianjue unveils plans for combined fusion-fission reactor that could make China world’s first to achieve the elusive viable energy source
• No country has so far managed to build a facility that generates more power than it uses in the fission process

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The Chinese government has approved construction of the world’s largest pulsed-power plant with plans to generate

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energy by 2028, according to the top nuclear weapons scientist leading the project.
“Fusion ignition is the jewel in the crown of science and technology in today’s world,” said Peng Xianjue, a professor with the Chinese Academy of Engineering Physics, in an online meeting organised by Beijing-based think tank Techxcope on September 9.
“Being the world’s first to achieve energy-scale fusion energy release will lay the most important milestone in the road to fusion energy for human beings.”
Peng, 81, has developed some of China’s most advanced small nuclear warheads and served as a top adviser to the country’s nuclear weapons programme, according to openly available information.
The Z-pinch machine – which replicates the fusion reactions of a thermonuclear bomb through magnetic pressure created by an extremely strong electric pulse – is expected to be completed around 2025 in Chengdu, Sichuan province in southwest China.
The machine will produce 50 million amperes of electricity – about twice as much as the record-holding Z pulsed power facility, a similar device at the Sandia National Laboratory in the US, Peng said.
Nuclear powers like the US, Russia and China have built a number of Z-pinch machines over the past few decades – some of which have never been officially disclosed – to simulate the extreme conditions needed to develop atomic weapons.These facilities can store a huge amount of electricity and release it in just a few nanoseconds. The electric pulse can create extreme pressure and enough radiation for two lightweight atoms to “fuse” into a heavier one, and give up some mass in the form of energy.
But building a machine that can produce more fusion power output than input is extremely difficult and so far, no country has been successful.
According to Peng’s presentation, the Chinese researchers will try to create a nuclear fusion reaction by using the strong electric charge to ignite a small number of hydrogen isotopes deuterium and tritium.
By carefully controlling the process, they hope to be able to cap the pulse energy released to a few hundred million joules – about as powerful as a 20kg (44lbs) bag of TNT.
And in a departure from previous designs, the fusion energy produced by the Chinese facility will not go to the power grid, but drive a swamp of superfast particles to hit uranium – the fuel which will power the facility’s fission component.
In his conference presentation, Peng said this inclusion of fusion and fission reactors is responsible for the Chinese design’s designation as Z-FFR.
The intention is for the walls of the fusion ignition chamber to be filled with uranium which will absorb the flying neurons produced by the explosion, causing it to split into two lighter elements – the same process used in existing nuclear power facilities.
The uranium fission will increase the facility’s total heat output by 10 to 20 times, significantly accelerating the application of fusion energy and making it ready for commercial power production by 2035, according to an estimate by Peng’s team.
If China’s machine is to succeed, it will need many high-performance capacitors to store the electricity and laser-powered switches that can operate instantly without causing a shortage.
Other challenges include special wires able to transmit the strongest electric currents on Earth, and a peanut-sized target device to efficiently convert electricity to ignition charge.
Peng said many of these problems had been solved, thanks to new scientific discoveries and technical breakthroughs by Chinese nuclear scientists in recent years. And some of their approaches are fundamentally different from what has been tried in the West.
In its fusion experiments, the Sandia lab tried to start ignition from the centre of the target device. But the Chinese researchers say they have found ignition could more easily be achieved by first creating a thin line of fusion reactions that runs through the target’s centre.
This linear approach reduces the complex, three-dimensional problem of squeezing the entire target – at equal pressure from many directions simultaneously – to a one-dimensional issue, Peng said.
The Chinese approach significantly simplifies the physical models for computer analysis while relaxing the demand for energy input, he said. “This is a big innovation.”
The researchers said the future power plant could use natural uranium ore, the nuclear waste produced by today’s reactors, or thorium, which could meet energy demand for thousands – or even tens of thousands – of years while producing little radioactive waste.
And because the fusion explosion will happen only once every 10 seconds, it will be incapable of generating enough energy to start a chain reaction and cause a meltdown, making the design safe and suitable for most places on Earth, they said.
The Z machine is just one of a range of methods – including powerful lasers and hot plasma caged in a magnetic field – being tried and tested by China and other countries in the race to achieve fusion ignition.
A number of giant facilities are in development around the world, with most aiming for commercial power production by the middle of this century.
A Beijing-based nuclear physicist, who asked not to be named because of the issue’s sensitivity, said that while the Z machine has some unique advantages, it also presents some difficult problems that may affect its mass application.
The electric power source, for instance, will need to generate and release charges at a high frequency every few seconds, putting an enormous strain on the capacitors and other components, the physicist said.
In addition, the target device will need to be replaced after each explosion, while the reactor chamber will need to withstand thousands of explosive shocks per day.
But whether ignition can be achieved, one thing is certain, according to the physicist: the facility will be a “mega lab” for cutting edge research on everything from Big Bang physics to new weapons.

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Stephen is scarcely better than Minnie Chan. He probably took things out of context to get clicks.

tphuang said:

I mean China definitely has to work a lot harder in this area. If they are using any Western systems with possible backdoors and trojan horses, they need to get those removed.

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As I wrote over three years ago, China must replace Windows with a local operating system. Microsoft's long relationship with the US's spies is well known.

Paper published in English:

Optical amplification enables a huge sensitivity improvement to laser heterodyne radiometers for high-resolution measurements of atmospheric gases​

Abstract​

A novel, to the best of our knowledge, performance-enhanced laser heterodyne radiometer has been developed by utilizing a semiconductor optical amplifier to amplify the collected weak solar radiation in an optical fiber. High-spectral-resolution measurements of atmospheric carbon dioxide column absorption are used to validate the technique and performance of the developed instrument. The implementation of optical amplification led to a 9-times improvement in sensitivity according to the Allan variance analysis for noise fluctuations, and resulted in a 7.7-times enhancement in measurement precision for atmospheric carbon dioxide. The promising results showed the great potential of employing this type of compact fiber-optics-based spectral radiometer for applications such as atmospheric greenhouse gas sensing.


News report in Chinese:

近期，中国科学院合肥物质科学研究院安徽光学精密机械研究所副研究员许振宇团队在激光外差光谱技术研究中获进展。相关研究成果发表在《光学通信》（Optics Letters）上。

激光外差光谱仪因具有高光谱分辨率、体积小、易集成等优点，已经逐渐发展成为与地基傅里叶变换光谱仪互补的温室气体柱浓度与廓线测量工具。激光外差光谱技术因受限于光学天线理论，无法通过增加光学接收口径的方法提高外差信号信噪比，这导致高分辨率激光外差探测中气体廓线测量精度受限。

对此，研究人员提出基于半导体光放大技术的微弱太阳光放大方法，解决了高分辨率激光外差探测中光学天线理论限制的外差信号信噪比提高问题。研究结果表明，相比于传统的高分辨率激光外差光谱仪，所研发的基于半导体光放大的高分辨率激光外差光谱仪的弱光信号探测和气体浓度测量精度得到大幅提升。

该研究有助于提高高分辨率激光外差光谱仪的性能，在大气温室气体传感等方面具有巨大应用潜力。相关研究工作获得国家自然科学基金、国家重点研发计划等项目的资助。

Paper published in English:

Lattice distortion inducing exciton splitting and coherent quantum beating in CsPbI3 perovskite quantum dots​

Abstract​

Anisotropic exchange splitting in semiconductor quantum dots results in bright-exciton fine-structure splitting important for quantum information processing. Direct measurement of fine-structure splitting usually requires single/few quantum dots at liquid-helium temperature because of its sensitivity to quantum dot size and shape, whereas measuring and controlling fine-structure splitting at an ensemble level seem to be impossible unless all the dots are made to be nearly identical. Here we report strong bright-exciton fine-structure splitting up to 1.6 meV in solution-processed CsPbI3 perovskite quantum dots, manifested as quantum beats in ensemble-level transient absorption at liquid-nitrogen to room temperature. The splitting is robust to quantum dot size and shape heterogeneity, and increases with decreasing temperature, pointing towards a mechanism associated with orthorhombic distortion of the perovskite lattice. Effective-mass-approximation calculations reveal an intrinsic ‘fine-structure gap’ that agrees well with the observed fine-structure splitting. This gap stems from an avoided crossing of bright excitons confined in orthorhombically distorted quantum dots that are bounded by the pseudocubic {100} family of planes.

News report in Chinese:

我所揭示量子点激子精细能级裂分及量子拍频新机制​

近日，我所光电材料动力学研究组 (1121组) 吴凯丰研究员团队等在胶体量子点超快光物理研究中取得新进展，观测到CsPbI3钙钛矿量子点中激子精细结构裂分导致的系综量子拍频，并提出了一种通过温度诱导晶格畸变进而调控裂分能的新机制。

在半导体量子点中，形貌或晶格对称破缺导致的电子—空穴各向异性交换作用使激子能级发生精细结构裂分（FSS）。FSS亮激子态可用于量子态相干操控或偏振纠缠光子对发射。观测和调控FSS对这些应用至关重要。由于FSS能量对量子点的尺寸、形貌非常敏感，通常需要在液氦温度下测定单个或少数量子点的发射谱来测定FSS。因此，在系综水平观测FSS极具挑战，尤其是定量调控FSS尚未有报道。

吴凯丰团队一直致力于胶体量子点的超快光物理与光化学研究。本工作中，研究团队利用圆偏振飞秒瞬态吸收光谱（即瞬态圆二色谱），在液氮到室温区间测定了溶液合成、成本低廉的CsPbI3钙钛矿量子点系综的亮激子FSS。研究发现，FSS能量可通过量子点尺寸进行调控，在液氮温度下最高可达1.6meV。更有趣的是，同一样品的FSS能量展现出强烈的温度依赖性，温度越低，裂分越大，这在以往的外延生长或胶体量子点体系都未有观测到。

通过变温的晶格结构表征，结合美国能源部能源前沿研究中心Peter Sercel博士的有效质量模型理论计算，研究团队发现这种温度依赖的FSS源于CsPbI3钙钛矿高度动态的晶格结构：降温能加剧Pb-I八面体扭曲，降低晶格对称性，进而增大FSS。此外，这些晶格扭曲的正交相量子点却仍然拥有准立方相晶面，该特性使亮激子之间产生避免交叉的精细结构能量间隙。实验上观测到的系综层面量子拍频正是对应于该能量间隙。

该工作精准测定了胶体量子点系综的亮激子精细结构裂分，提出了通过温度诱导CsPbI3量子点晶格畸变进而调控亮激子裂分能的新原理，展示了其在量子信息科学领域的重要应用潜力。

相关文章以“Lattice distortion inducing exciton splitting and coherent quantum beating in CsPbI3 perovskite quantum dots”为题，于近日发表在《自然—材料》（Nature Materials）上。该工作的第一作者是我所1121组毕业生韩瑶瑶博士。上述工作得到中科院稳定支持基础研究领域青年团队计划、国家重点研发计划、我所创新基金等项目的支持。

Currently transparent electrode in organic optoelectronic devices are mostly made from ITO (Indium Tin Oxide). Indium is a rare metal thus makes the organic optoelectronic devices expensive.

Chinese scientists developed a method to replace ITO with ZnO in transparent electrodes.

Paper in English:

A Transparent Electrode Based on Solution-Processed ZnO for Organic Optoelectronic Devices​

Abstract​

Achieving high-efficiency indium tin oxide (ITO)-free organic optoelectronic devices requires the development of high-conductivity and high-transparency materials for being used as the front electrode. Herein, sol-gel-grown zinc oxide (ZnO) films with high conductivity (460 S cm−1) and low optical absorption losses in both visible and near-infrared (NIR) spectral regions are realized utilizing the persistent photoinduced doping effect. The origin of the increased conductivity after photo-doping is ascribed to selective trapping of photogenerated holes by oxygen vacancies at the surface of the ZnO film. Then, the conductivity of the sol-gel-grown ZnO is further increased by stacking the ZnO using a newly developed sequential deposition strategy. Finally, the stacked ZnO is used as the cathode to construct ITO-free organic solar cells, photodetectors, and light emitting diodes: The devices based on ZnO outperform those based on ITO, owing to the reduced surface recombination losses at the cathode/active layer interface, and the reduced parasitic absorption losses in the electrodes of the ZnO based devices.


News report in Chinese:

新型透明电极材料助推有机光伏技术走向市场​

近日，东华大学先进低维材料中心特聘研究员唐正课题组展示了一种全新溶液法制备的透明导电薄膜材料，明确了薄膜的导电机制，并使用该薄膜材料作有机光伏器件的阴极，实现了器件的“免氧化铟锡(ITO) ”发展，为促进有机光伏技术的市场化发展提供了新思路。相关研究成果已发表于《自然—通讯》。

有机光伏器件的透明电极材料主要是ITO，而铟元素是稀有元素，因此，ITO的使用会大幅提高有机光伏器件的制造成本，阻碍其市场化发展。目前常见的ITO替代材料有导电聚合物、金属纳米线、掺杂金属氧化物等。然而，这些材料通常在近红外波段具有较高的吸收系数，限制了其在有机光伏器件中的应用。因此，开发性能更为优异的，可替代ITO的透明导电材料对有机光伏器件市场化发展极为重要。

为此，唐正课题组与苏黎世应用科技大学教授Wolfgang Tress合作，通过多次沉积法及紫外光掺杂效应，大幅提高了溶胶凝胶法制备的ZnO（氧化锌）薄膜的导电率（高至460西门子），并成功将其用于构建器件，实现了免ITO有机光伏器件性能的突破。

研究人员通过电镜和光谱学表征手段，明确了溶胶凝胶法制备的ZnO薄膜在紫外光掺杂作用下导电率的提升，源自ZnO晶体中的氧空位对光生空穴的捕获作用。随后，作者推断氧空位的形成局限于ZnO晶体的表界面处，因此，通过设计多次沉积工艺，制备多层薄膜，提升了ZnO薄膜中的氧空位浓度，在维持了高光学透过率的前提下，提高了其导电率。

研究人员最终将多层ZnO薄膜用作透明电极构建了有机光伏器件。测试结果显示，得益于多层ZnO电极的高导电率以及高光学透过性，基于ZnO的有机光伏器件展现出了优异的，可媲美基于ITO电极的光电转换性能。

“这项研究基于溶液加工ZnO，开发出具有高导电率和高光学透过率的透明导电薄膜材料，基于这一材料构建的有机光电器件表现出优异的性能，相信会对有机光伏技术的市场化发展起到很好的促进作用。”唐正说。