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Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phyllostachys praecox shoots were frozen using liquid nitrogen at –60, –90 or –120 ℃ to an internal temperature of –18 ℃, or frozen at –90 ℃ to an internal temperature of –6, –12 or –18 ℃, vacuum-packed and stored in a freezer at –18 ℃ for 24 weeks. In order to analyze the effect of liquid nitrogen freezing on physiological and biochemical characteristics of P. praecox shoots during frozen storage, L-phenylalanine ammonialyase (PAL) and peroxidase (POD) activities, total phenolic content, relative electrical conductivity, and water state were measured and ice crystal structure and cell morphology were observed. The results showed that with increasing freezing time, the PAL and POD activities, total phenolic content, and peak area of free water in all six groups decreased significantly (P 0.05). The PAL and POD activities and relative conductivity of P. praecox shoots frozen at –6 ℃ were higher than those frozen at –12 and –18 ℃, and the size of ice crystals was smaller and the degree of cell damage was greater in P. praecox shoots frozen at –6 ℃ than at –12 and –18 ℃. The difference between P. praecox shoots frozen at –12 and –18 ℃ was not significant (P > 0.05). Collectively, these findings indicated that the most suitable liquid nitrogen freezing conditions of P. praecox shoots are –90 and –12 ℃ for freezing and internal temperature, respectively.

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, BPSE was used as ducks semen diluent to explore the effect of thin tube freezing, preserving, and thawing technology on duck semen vitality, survival rate, and fertilization rate after cryopreservation and thawing. The effects of different volume fraction of 3 cryoprotectants including glycerol(GL), dimethyl sulfoxide(DMSO), and dimethyl acetamide (DMA) cryoprotectants at 4 ℃ for different equilibrium times on duck semen vitality were compared, and the effects of different thawing condtions and storage time on semen vitality and survival rate were compared. The fertilization rate and hatching rate of frozen duck semen and fresh duck semen(CK) were evaluated. The results showed that the vitality of the duck semen after thawing was better when balanced for 45 min in 6% DMA and 30 min in 8% DMA, with values of 0.416 and 0.415, respectively, and there was no significant difference between the two group. The semen survival rate after thawing at 37 ℃ for 30 s was 57.18%, significantly higher than that(45.28%) after thawing at 4 ℃ for 3 min. There was no significant difference in semen vitality and survival rate after thawing in liquid nitrogen for 1, 30, 365 d; the fertilization rate of thawed frozen semen was 37%, which was significantly lower than that(93.24%) of the control group. The hatching rate of thawed frozen semen was 84.79%, which was significantly lower than that(92.19%) of the control group. The thin tube method established in the study balanced for 30 min in 8% DMA could be used for cryopreservation of duck semen, and thawing for 30 s at 37 ℃ could be used for duck semen thawing. [ABSTRACT FROM AUTHOR]

[Objective] As an ultra-low-temperature medium, liquid nitrogen offers the advantages of low cost, fast freezing, and high freezing strength, which contribute to its wide use in urban underground engineering, tunnel construction, water plugging, mine construction, and production. In addition, liquid nitrogen freeze-thaw can promote the development of coal rock fractures and further increase the permeability of gas-bearing coal rock reservoirs. Therefore, it is highly important for freezing-applied construction and coalbed methane extraction engineering in cold regions to study the evolution of the mechanical properties of coal rock mass under liquid nitrogen freezing and freeze-thaw conditions. [Methods] In this study, experiments were conducted on the mechanical properties of coal under liquid nitrogen freezing and freeze-thaw conditions using a liquid nitrogen freezing coal rock experimental device. Using liquid nitrogen freezing time and liquid nitrogen freeze-thaw frequency as single-factor variables, the stress-strain curve was used to quantitatively analyze the changes in the mechanical parameters, including the compressive strength and elastic modulus of coal. The mechanisms of enhancing the mechanical strength of frozen coal and deteriorating the mechanical strength of the freeze-thaw coal were discussed based on the micropore and crack angles. [Results] The experimental results on the mechanical properties of coal under liquid nitrogen freezing and freeze-thaw conditions showed the following: 1) liquid nitrogen freezing has a positive effect on the mechanical strength of coal. The elastic modulus of the coal sample after 80 minutes of liquid nitrogen freezing is 3.67 GPa, while the elastic modulus of the original coal sample is 1.40 GPa, with an increase of 165.69%. Liquid nitrogen freeze-thaw deteriorates the mechanical strength of coal. After 15 cycles of liquid nitrogen freeze-thaw, the elastic modulus of the coal sample is 0.52 GPa, while the original coal sample has an elastic modulus of 1.50 GPa, i.e., a decrease of 65.33%. 2) The formation of porous ice has three positive effects on enhancing the mechanical strength of coal. Porous ice has a certain mechanical strength, and the mechanical properties of ice continue to increase with the decrease in temperature. The volume expansion effect of the ice-water phase transition increases the contact area between ice and coal matrix particles, revealing the cementing role of pore ice formation. After the formation of pore ice, the length of pore cracks decreases, further decreasing the stress concentration at the crack tip, which hinders the development of the pore structure of the loaded coal. 3) The damage and deterioration of the coal body caused by liquid nitrogen freeze-thaw primarily contain three aspects. In liquid nitrogen freezing and thawing, the shrinkage expansion cycle of the middling coal matrix will eventually increase the porosity of the coal sample, damaging the interior of the coal. The volume expansion caused by the phase change of pore water and the formation of pore ice will promote the expansion and connectivity of primary fractures, and thermal stress will facilitate the formation of new pores inside the coal body, further damaging and destroying the coal structure. Freezing coal samples can reduce the stress concentration due to short cracks, while freeze-thaw coal samples can increase the stress concentration due to the increased length of internal cracks in the coal. [Conclusions] This experiment uses a combination of macro and microanalysis methods, with comparative and in-depth mechanism analysis as the research tools, to cultivate students' flexible and innovative thinking to adapt to the changes in scientific research and disciplinary development. In terms of experimental organization, allowing students to participate directly in experiments requiring hands-on practice, data processing, and result analysis can greatly stimulate their learning enthusiasm and improve their subjective initiative and innovative thinking ability. [ABSTRACT FROM AUTHOR]

The blooms caused by eutrophication have a serious impact on the water environment. The method of removing algae from eutrophication by microorganisms has a broad prospect. In this study, a strain of algaeclytic bacteria Serratia sp., isolated in the laboratory, was added into the algal fluids of cyanobacteria (Aphanizomenon flosaquae) and green algal (Scenedesmus quadricauda) commonly found in eutrophic water respectively. The changes of algal biomass, Chl-a, pH, total nitrogen and total phosphorus in the algal fluids were monitored, and the algaeclytic products were analyzed by spectroscopic technology. The results showed that the algaeclytic bacteria Serratia sp. had better algaeclytic effect on both species, and the higher the concentration, the better the algae-soluble effect. The removal rates of Chl-a in the experimental group with the addition of protobacterial solution were 64.3% and 85.1% respectively, and the algal cell density decreased by 71.4% and 83.9% respectively. The total nitrogen in algal liquid decreased by 17.84 mg/L and 10.82 mg/L, and the total phosphorus decreased by 7.75 mg/L and 5.68 mg/L, respectively. The total nitrogen removal effect was better. It was preliminatively concluded that the algaeclytic products contained N-H, O=N-O- (-NO2), C-H, C-N, C-O, CH2 and other bonds. Combined with the three-dimensional fluorescence scanning results, it was preliminatively concluded that the algaeclytic products were tryptophan-like substances and fumeric-acid like substances. [ABSTRACT FROM AUTHOR]

Objective In order to reduce the equipment investment and energy loss of extracting helium from natural gas by using a single low-temperature method, a new natural gas helium extraction combined with LNG production process is provided. Methods Based on the data of low helium feed gas from a domestic gas field, the characteristics and adaptability of this new process have been simulated and analyzed, and the refrigeration cycle of the mixed refrigerant has been optimized by genetic algorithm. Results（1） Characteristic analysis shows that the lower the temperature before throttling and the higher the throttling pressure, the better the concentration effect of the flash tank on helium gas. At the same time, nitrogen products with a purity of 99.9 mol% can be produced, and liquid nitrogen products can be produced by itself;（2） The new process has strong adaptability to changes in nitrogen and helium content in the feed gas, as well as the pressure of the feed gas. The higher the feed gas pressure and the lower the nitrogen and helium content, the lower the compressor shaft power;（3） Through analysis of characteristics and adaptability, as well as optimization of mixed refrigerant refrigeration process parameters, it can be obtained that the temperature before throttling in the flash tank is-150 ℃, the throttling pressure is 350 kPa, the pressure of the helium extraction tower is 3 200 kPa, the number of plates in both the denitrification and helium extraction towers is 12,the optimal boost pressures for the first and second stages of the mixed refrigerant compressor are 1 341 kPa and 2 767 kPa, respectively, and the circulation rate of the mixed refrigerant is 1 722.67 kmol/h, the total compressor shaft power is 3 765 kW, the cooling water consumption is 6 474 t/d, the comprehensive energy consumption and unit energy consumption are 1 097 216.00 MJ/d and 3.66 MJ/m~3, respectively. Conclusions The helium recovery rate is more than 98%, and the crude helium purity is higher than 70 mol% for the new process. It can produce refrigerants by itself and obtain high-purity nitrogen and liquid nitrogen products, and has good adaptability to the gas quality conditions of the feed gas [ABSTRACT FROM AUTHOR]

Copyright of Modern Food Science & Technology is the property of Editorial Office of Modern Food Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the influence of liquid nitrogen cracking time on mechanical properties and permeability of coal samples, the independently developed WYS-800 triaxial gas seepage test device and acoustic emission detection system were used to conduct triaxial mechanical seepage tests on four groups of coal samples treated with different cracking time and collect acoustic emission signals. The mechanical properties and permeability of coal samples in triaxial mechanical seepage experiment were analyzed, and the characteristics of acoustic emission signals were described. Based on boiling heat transfer theory, one-dimensional cylinder heat conduction theory and thermal stress theory, the cracking mechanism was analyzed, and the thermal stress under different cracking time was calculated. The relationship between average temperature drop, average thermal stress, initial permeability and cracking time was revealed by data fitting. The results show that: ① Liquid nitrogen fracturing time have different influence on the mechanical properties of coal samples, the compressive strength and elastic modulus with the increase of the crack time shows the tendency of increase with the decrease of the first, the poisson's ratio are increased after the first decreases, coal sample triaxial loading when the axial stress and axial strain curve of the periodic evolution has obvious difference, associated with the change of mechanical parameters. ② The permeability of coal samples with different cracking time changes in u-shape during the triaxial loading process. The initial permeability, minimum permeability and maximum permeability increase with the increase of cracking time, and the increase rate is 119.05%, 437.5% and 146.49% when the cracking time is 30min. Acoustic emission signals are not active in compaction and elastic stages, and are mainly generated in yield and failure stages. The peak value of acoustic emission ringing count of coal samples after cracking is generated near the failure point, which is more than 20000 times. ③ The film boiling heat transfer coefficient between the coal sample and liquid nitrogen is 570.4 W/(m2·K). The average temperature drop of the coal sample is related to the cracking time, and the average thermal stress and initial permeability play a leading role. The average temperature drop of the coal sample can reach 213.63 K and the average thermal stress can reach 5.85 MPa after 30 min of cracking. ④ There is a linear relationship between initial permeability and average temperature drop, and a negative exponential relationship between initial permeability and cracking time of coal samples after liquid nitrogen treatment. Changing the parameter value can be extended to other similar coal samples or actual production evaluation.

With prepared from tobacco waste as material, natural drying (NAD), hot air drying (HAD), vacuum freeze drying ( VFD), -20 °C pre-freeze-vacuum freeze drying ( VFD-20), - 80 °C pre-freeze-vacuum freeze drying (VFD-80) and liquid nitrogen pre-freeze-vacuum freeze drying (VFD-FLN) were adopted to dry BC pellicles. The physical properties of dried BC pellicles were analyzed by colorimeter, FESEM and thermogravimetry. Then the aroma components of BC were analyzed by simultaneous distillation-extraction and GC-MS. The results showed that VFD-FLN could keep the fiber length on the basis of the original three-dimensional reticular structure of BC. VFD, VFD-20 and VFD-80 kept the three-dimensional spatial structure of BC better, but the fiber length became shorter. NAD and HAD destroyed the spatial structure, resulting in the lowest rehydration rate and swelling rate. The color retention of BC treated by NAD was the best, and the volatile aroma components of BC were mainly acidic substances, the relative content of which was 97. 93%. The content of aroma components after VFD was only second to NAD. The aroma components mainly included carotenoid degradation products, terpene degradation products and phenylalanine degradation products. The drying speed of HAD was the fastest, but the content of aroma components was the least. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chinese Institute of Food Science & Technology / Zhongguo Shipin Xuebao is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The thermal fracture of rock under cryogenic impact is caused by the instantaneous huge thermal stress caused by rapid temperature change. The law of heat transfer inside rock determines the magnitude and action form of thermal stress. In order to study the heat transfer law of rocks under cryogenic impact, the internal temperature fields of granite, sandstone, and limestone under cryogenic impact in liquid nitrogen environment at different times were measured, and the influence effect of rock characteristics on heat transfer law was discussed. The results show that: 1) The temperature change process of rock during cryogenic impact can be divided into three stages: slow cooling, rapid cooling, and temperature flattening; 2) The evolution law of temperature and temperature gradient of different types of rock is roughly the same, but its distribution is different owing to different rock characteristics; 3) The heat transfer and deformation of rock under cryogenic impact are affected by the mineral composition and structural characteristics of the rock itself, and they together determine the final degree of rock fracture.

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

【Objective】 Hybrid snakehead is an important special aquatic fish in China. In order to find out the infection status of hybrid snakehead rhabdovirus (HSHRV), the rhabdovirus disease of hybrid snakehead cultured in the Pearl River Delta was investigated from March 2021 to February 2022.【Method】The parents, fry and water samples of hybrid snakehead were randomly sampled in breeding stage, and these were randomly sampled at fixed time in culture stage and sampled when the outbreak of the virus. A total of 333 samples were collected during the whole monitoring period. Mixed samples of mung bean-sized liver, spleen and kidney were stored in liquid nitrogen for RNA extraction. And reverse-transcribed cDNA was used as template to detect rhabdovirus by real-time fluorescence quantitative PCR (qPCR).【Result】 The main clinical symptoms of rhabdovirus-infected fish were that the fish swam irregularly and spin. Although there was no obvious symptom on the body surface, the liver, spleen, kidney, intestine and swim bladder became red or swollen. The qPCR results revealed that the average positive rate of HSHRV was 13.21%, which was mainly detected from April to November. Among them, the positive rate of samples detected in August was as high as 23.91%. The average positive rate of HSHRV in the culture stage (17.01%) was significantly higher than that in the breeding stage (3.26%). In terms of fish body size, 32.20% of the fry were most susceptible to HSHRV infection within 10 cm, mainly detected from March to September, while 9.52% of the fish of more than 20 cm were least susceptible to HSHRV infection. 【Conclusion】 The positive rates of HSHRV in hybrid snakehead in breeding stage and cultivating stage as well as in different size are determined, which provide references for further understanding the epidemic regularity of hybrid snakehead rhabdovirus disease, with a view to providing data support for the prevention and control of hybrid snakehead rhabdovirus disease. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to explore the changes and distributions of the temperature of PDMS sample being impacted and cooled by the liquid nitrogen jet during the cryogenic micro-abrasive air jet machining the PDMS microchannels, this paper proposed a systematic research method of temperature that composed of temperature measurement experiments, Beck's inverse estimation method fitting and APDL temperature field simulation. The errors between the final simulation results and the temperature measurement ones are only 1.735%. The simulations find that it will take 5.747 s for the surfaces to reach the obvious embrittlement temperature -147 °C. PDMS may not reach a machinable embrittlement state at the moment of contact with liquid nitrogen, so it is necessary to pay attention to the pre-cooling time before machining. The simulation data was used to fit the cooling rate of PDMS to -147 °C, and the cooling rate was used as a reference to predict the pre-cooling time required in the actual machining. By comparing the cooling rate, it is found that the cooling rate in the depth range of 0~100 µm from the surface of the PDMS specimen is 22.054% faster than that in the depth range of 0~1500 µm, and the cooling rate of the aluminum alloy workbench is about 22.311% higher than that of the adiabatic workbench. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To compare the freezing effect and safety of heat-sealed cryovials and screw-cap cryovials in sperm freezing. Methods: Ten semen samples were involved in this study. After liquefaction, 1mL per semen was aspirated and added to a screw-cap cryovial and a heat-sealed cryovial. The two cryovials were tested at 1 hour, 2 hours, 3 hours and 4 hours, respectively. The progressive sperm ratio (PR) in the spermatozoa and the toxicity of the two cryotubes to fresh sperm were used to compared; 60 spermatozoa that met the freezing quality standard were selected and treated with the same cryoprotective solution and freezing procedure in two cryotubes referred above. The cryovials were transferred to a liquid nitrogen tank for storage, and the frozen specimens were recovered 24 hours later. The sperm concentration and PR after freezing were calculated to assess the freezing effect between the heat-sealed cryovials and screw-cap cryovials. The leakage of liquid nitrogen and the explosion of the cryotube during resuscitation were also used to evaluate the safety of the heat-sealed cryovials and screw-cap cryovials. Results: There was no significant difference in the toxicity test of fresh sperm, sperm concentration after freezing and PR between the two cryovials (P>0.05). When the specimens and cryopreserved tubes were taken out from the liquid nitrogen tank, it was found that there were 45 specimens with liquid nitrogen leakage, accounting for 75% of the total. 60 tubes of specimens frozen in heat-sealed cryovials without leakage of liquid nitrogen. During resuscitation, 3 of the 60 screw-cap cryotubes exploded, accounting for 5% of the total, and the heat-sealing cryotubes did not explode. Conclusion: Both types of cryovials can be used for sperm freezing in sperm banks. Although heating-sealing cryotubes are more complicated in operation than screw-cap cryotubes, they are better in prevent cross-contamination and explosion of cryovials between sperm samples due to liquid nitrogen. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The TC4 dual-phase titanium alloy was cryogenically treated for different times at -196 ℃ by liquid nitrogen direct cooling, and the grain size was characterized by metallurgical microscope; the volume fraction of α and β phases was measured by scanning electron microscope(SEM); Vickers hardness tester and electronic universal testing machine were applied to characterize hardness and tensile properties respectively. Through the change of grain size and the structure of α phase and β phase, the changes of material hardness and tensile properties were carefully explained. The experimental results show that with the extension of the cryogenic time, the grain size gradually decreases, and the volume fraction of the β phase gradually decreases by transforming into the α phase. After 12 h cryogenic treatment, the crystal grains are obviously refined, and the majority of β phase is transformed to the α phase. The samples shows superior comprehensive mechanical performance. When the cryogenic time exceeds 12 h, the volume fraction of the α phase and β phase have no obvious change. After taken out to room temperature, the recovery effect of the samples cryogenic treated over 12 h was more obvious, and the mean grain size was not significantly refined compared with that of the samples treated for 12 h. Consequently, the strength and hardness of the sample treated over 12 h were slightly lower than those of the sample treated at 12 h. In conclusion, the superior comprehensive mechanical properties can be obtained after cryogenic treated for 12 h in liquid nitrogen. [ABSTRACT FROM AUTHOR]

Objective In order to meet the demand of crude helium purification process that is needed to produce liquid helium products, an innovative process of helium purification by medium pressure and low temperature condensation closing by medium pressure and pressure swing adsorption (PSA) at room temperature on the basis of investigation of helium purification technology at home and abroad is proposed in this paper. Methods Using HYSYS simulation method, the characteristics and adaptability of the three processes are compared and analyzed. The influences of condensation temperature, condensation pressure, the change of main component yield of PSA and the change of feed gas composition on the process performance are also analyzed. Results Compared with traditional crude helium purification technology, the combination technology not only improved the yield of helium, but also obviously decreased the energy consumption and the liquid nitrogen consumption of the unit. It has characteristics of high automation, continuous technological process, strong operability, etc. and is suitable for liquid helium production. Conclusions This process can provide a guidance and data support for the process selection and application of domestic natural gas helium extraction unit construction. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spray cooling characteristics of TG6.5 solid cone nozzle are studied by building a liquid nitrogen spray cooling experimental bench. The relationships between the superheat and the heat flux as well as the superheat and the heat transfer coefficient near the critical point are analyzed. Then the influence of the spray area and the spray flow rate on the heat transfer effect is discussed. Results show that, in the process of heat transfer, with the increase of the heat flux, the change of superheat can be divided into three stages: a slow increase, an obvious increase and a sharp increase. Under the influence of bubbles in nucleate boiling, the superheat at the maximum heat transfer coefficient is less than that at the critical heat flux. Increasing the spray flow can significantly improve the heat transfer effect. Increasing the heat sink area will reduce the impact frequency and intensity of droplet particles in the unit area, so that the heat transfer effect will decrease. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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[ Objective] A good suspension cell culture system of Thesium chinese Turcz. is established, so as to lay a foundation for the subsequent use of genetic engineering to transform the metabolic pathway of Thesium chinese Turcz., obtain new varieties of high-order metabolites, and realize the substitution of wild resources. [ Method] On the basis of exploring the law of growth and nutrient consumption of Thesium chinese Turcz. suspension cells, the initial input of liquid nitrogen and phosphorus and the ratio of ammonium nitrogen to nitrate nitrogen (NH+4/ NO-3 ) were optimized. [Result] In the 30 days culture process, the growth curve of suspension cells showed an obvious delay period ( 0 - 6 days), logarithmic growth period ( 7 - 15 days) ), stable growth period ( 16 - 24 days) and decay period ( after 24 days) . The results showed that the dry matter mass of suspension cells reached the maximum when the initial total nitrogen concentration was 70 mmol/L and the phosphate concentration was 1. 3 mmol/L for 28 days, and it was unhealthy for the growth of cells when the nitrogen concentration and phosphate were higher and lower. On this basis, the demand of suspension cultured cells for nitrate nitrogen and ammonium nitrogen were explored. The results showed that the suspension cells during the culture process consumed more nitrate nitrogen than ammonium nitrogen, while the utilization and consumption of ammonium nitrogen precedes that of nitrate nitrogen and too high concentration of ammonium nitrogen would inhibit cell growth. It was most suitable for cell growth when NH+4 / NO+3- was 20/50. [ Conclusion] The growth curve of Thesium chinese Turcz. suspension cells shows ' S ' as taking MS as the basic medium, the concentration of nitrogen is 70 mmol/L, the concentration of phosphate is 1. 3 mmol/L, and the concentration of NH+4/NO-3 is 20/50, which is more conducive to the suspension culture of Thesium chinese cells. Under these conditions, the consumption of total sugar, sucrose, reducing sugar, nitrate nitrogen and inorganic phosphorus are faster in the logarithmic growth period, and the consumption of ammonium nitrogen is faster than nitrate nitrogen in the early growth period. [ABSTRACT FROM AUTHOR]

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In order to investigate the effect of liquid nitrogen on the physical and mechanical properties of high-temperature rocks, a series of laboratory tests were carried out on granite, gneiss and sandstone specimens cooled with liquid nitrogen at different temperatures (25 ～350℃). The damage mechanisms of the three types of rocks were analyzed in combination with microscopic observations. The results show that the increase in temperature exacerbates the damage to the internal structure of the rock induced by liquid nitrogen. With the increase of temperature, the porosity and peak strain of the rock gradually increase, while the P-wave velocity, compressive strength and elastic modulus of the rock decrease. Thermal stresses generated by heating and liquid nitrogen cooling lead to the initiation and propagation of microcracks mainly along quartz mineral boundaries within the rock. The sensitivity of the three types of rocks to heating and liquid nitrogen cooling differs, depending on the lithogenesis, mineral composition, type of cementation, and pore structure of rocks. [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to establish and optimize the cryopreservation technology system of embryogenic of Dioscorea bulbifera L by droplet-vitrification. [Method] The effects of different conditions on cryopreservation of embryogenic suspension cells of Dioscorea bulbifera L by droplet-vitrification were studied by single factor test, and the genetic stability of regenerated plantlets after freezing was detected by RAPD molecular markers. [Result] The best cryopreservation technology system of embryogenic suspension cells of Dioscorea bulbifera L by droplet-vitrification was as follows: Embryogenic suspension cells of Dioscorea bulbifera L was pre cultured in MS + 2 mg!L KT + 0. 5 mg/L NAA + 0. 5 mg/L 2, 4-D + 0. 8 mol/L sucrose at(25 ± 1) "C for 4 days, loaded in the loading solution (MS + 2 mol/Lglycerol + 0. 4 mol/L sucrose, pH 5. 8) at (25 ± 1) "C, dehydrated in PVS2 (300 g/L glycerol + 150 g/Lglycol + 150 g/LDMSO + 0. 4 moVLsucrose, pH 5. 8) at 0 "C, thawed by the aluminum foil being immersed in the culture solution (MS + KT 2 mg/ L + NAA 0. 5 mg/L + 2, 4-D 0. 5 mg/L + 1. 2 mol/L sucrose, pH 5. 8) preheated at 37 "C after freezing, washed with washing solution (MS +KT 2 mg/L + NAA 0. 5 mg/ L + 2, 4 -D 0. 5 mg/L + 1. 2 moVL sucrose, pH 5. 8) for three times (each washing time was 10 min) at (25 ± 1) "C, cultured in darkness for five days and then cultured in light cycle after washing. The relative survival rate of embryogenic suspension cells of Dioscorea bulbifera L by droplet-vitrification cryopreservation was 90. 5 % ± 4. 4 %. There was no significant effect of liquid nitrogen storage time on the survival rate of embryo suspension cells of Dioscorea bulbifera L after cryopreservation by dropletvitrification. The detection result of RAPD showed that there was no variation in the plantlets regenerated from embryogenic suspension cells of Dioscorea bulbifera L. after cryopreservation by droplet-vitrification, which could ensure the genetic stability. [Conclusion] The cryopreservation procedure of embryogenic suspension cells of Dioscorea bulbifera L by droplet-vitrification established in the study is reliable and can provide technical reference for the long-term preservation of xanthocellular suspension cells. [ABSTRACT FROM AUTHOR]