Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem ...Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem from the fact that there are no extra moving parts introduced into the system.The rotary valve is a key component in GM-PTCs that transfers the output exergy from the compressor to the cold head.Because a low Carnot efficiency of 1.58%is achieved at liquid helium temperatures,optimizing the rotary valve is crucial for improving the efficiency of GM-PTCs.In this regard,an exergy-loss analysis method is proposed in this paper to quantitatively obtain the leakage loss and viscosity loss of a rotary valve by experimental measurements.The results show that viscosity loss accounts for more than 97.5%of the total exergy loss in the rotary valve,and that it is possible to improve the structure of the rotary valve by expanding the flow area by 1.5 times.To verify the method,the cooling temperature and power of a remote two-stage GM-PTC were monitored,with original or optimized rotary valves installed.The experimental results show that compared to the original rotary valve,the optimized rotary valve can improve the cooling efficiency of a GM-PTC by 16.4%,with a cooling power of 0.78 W at 4.2 K.展开更多
It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and in...It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.展开更多
Importance of the main place of coal in Chinese energy structure&national economic development discussed;main achievement in clean&highefficient utilization of coal in recent ten years introduced;for following...Importance of the main place of coal in Chinese energy structure&national economic development discussed;main achievement in clean&highefficient utilization of coal in recent ten years introduced;for following our national green&lowcarbon development,proposal given that transformative development of coal be accelerated,high efficient conversion of coal be further promoted.展开更多
Based on the Kim-like's proxy multi-signature scheme, an improved proxymulti-signature scheme is proposed. The new scheme overcomes the two problems in the Kim-like'sproxy multi-signature scheme: (1) Security ...Based on the Kim-like's proxy multi-signature scheme, an improved proxymulti-signature scheme is proposed. The new scheme overcomes the two problems in the Kim-like'sproxy multi-signature scheme: (1) Security issue ( every original signer can forge a valid proxymulti-signature for any message); (2) Efficiency issue ( both the size of the proxy multi-signatureand the efficiency of signature checking are dependent on the number of the original signers).展开更多
A staff member adjusts the vol.ume of Fertilizers for vegetabLes in a greenhouse through an all-in-one machine for watering,power suppty and Fertilizing in Haimen,east China's Jiangsu Province,on December 4.Eco-fi...A staff member adjusts the vol.ume of Fertilizers for vegetabLes in a greenhouse through an all-in-one machine for watering,power suppty and Fertilizing in Haimen,east China's Jiangsu Province,on December 4.Eco-fiendly,highefficiency agricutture has become a new engine for the tocal growth.展开更多
基金supported by the National Key Research&Development Program of China(No.2023YFF0721304)the Key Research&Development Program of Jiangsu Province(No.2021015-4),China。
文摘Gifford-McMahon-type pulse-tube cryocoolers(GM-PTCs)working at liquid helium temperatures are promising in quantum technology and cryogenic physics for their high reliability and minimal vibration.These features stem from the fact that there are no extra moving parts introduced into the system.The rotary valve is a key component in GM-PTCs that transfers the output exergy from the compressor to the cold head.Because a low Carnot efficiency of 1.58%is achieved at liquid helium temperatures,optimizing the rotary valve is crucial for improving the efficiency of GM-PTCs.In this regard,an exergy-loss analysis method is proposed in this paper to quantitatively obtain the leakage loss and viscosity loss of a rotary valve by experimental measurements.The results show that viscosity loss accounts for more than 97.5%of the total exergy loss in the rotary valve,and that it is possible to improve the structure of the rotary valve by expanding the flow area by 1.5 times.To verify the method,the cooling temperature and power of a remote two-stage GM-PTC were monitored,with original or optimized rotary valves installed.The experimental results show that compared to the original rotary valve,the optimized rotary valve can improve the cooling efficiency of a GM-PTC by 16.4%,with a cooling power of 0.78 W at 4.2 K.
文摘It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.
文摘Importance of the main place of coal in Chinese energy structure&national economic development discussed;main achievement in clean&highefficient utilization of coal in recent ten years introduced;for following our national green&lowcarbon development,proposal given that transformative development of coal be accelerated,high efficient conversion of coal be further promoted.
基金This work is supported by the Natural Science Foundation of China (No.60372094No.90204017) and"973"project of China (No.G1999035804).
文摘Based on the Kim-like's proxy multi-signature scheme, an improved proxymulti-signature scheme is proposed. The new scheme overcomes the two problems in the Kim-like'sproxy multi-signature scheme: (1) Security issue ( every original signer can forge a valid proxymulti-signature for any message); (2) Efficiency issue ( both the size of the proxy multi-signatureand the efficiency of signature checking are dependent on the number of the original signers).
文摘A staff member adjusts the vol.ume of Fertilizers for vegetabLes in a greenhouse through an all-in-one machine for watering,power suppty and Fertilizing in Haimen,east China's Jiangsu Province,on December 4.Eco-fiendly,highefficiency agricutture has become a new engine for the tocal growth.
