Natural gas hydrate(NGH)has been widely considered as an alternative form of energy with huge potential,due to its tremendous reserves,cleanness and high energy density.Several countries involving Japan,Canada,India a...Natural gas hydrate(NGH)has been widely considered as an alternative form of energy with huge potential,due to its tremendous reserves,cleanness and high energy density.Several countries involving Japan,Canada,India and China have launched national projects on the exploration and exploitation of gas hydrate resources.At the beginning of this century,an early trial production of hydrate resources was carried out in Mallik permafrost region,Canada.Japan has conducted the first field test from marine hydrates in 2013,followed by another trial in 2017.China also made its first trial production from marine hydrate sediments in 2017.Yet the low production efficiency,ice/hydrate regeneration,and sand problems are still commonly encountered;the worldwide progress is far before commercialization.Up to now,many gas production techniques have been proposed,and a few of them have been adopted in the field production tests.Nevertheless,hardly any method appears really promising;each of them shows limitations at certain conditions.Therefore,further efforts should be made on the economic efficiency as well as sustainability and environmental impacts.In this paper,the investigations on NGH exploitation techniques are comprehensively reviewed,involving depressurization,thermal stimulation,chemical inhibitor injection,CO2–CH4 exchange,their combinations,and some novel techniques.The behavior of each method and its further potential in the field test are discussed.The advantages and limitations of laboratory studies are also analyzed.The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs.展开更多
Objective:The transanal approach to specimen collection,combined with the prolapsing technique,is a wellestablished and minimally invasive surgery for treating rectal cancer.However,reports on outcomes for this approa...Objective:The transanal approach to specimen collection,combined with the prolapsing technique,is a wellestablished and minimally invasive surgery for treating rectal cancer.However,reports on outcomes for this approach are sparse.We compared short-and long-term outcomes of conventional laparoscopic surgery(CLS)vs.transanal natural orifice specimen extraction(NOSE)using the prolapsing technique for patients with middle-to low-rectal cancer.Methods:From January 2013 to December 2017,we enrolled consecutive patients with middle-to low-rectal cancer undergoing laparoscopic anterior resection.Totally,50 patients who underwent transanal NOSE using the prolapsing technique were matched with 50 patients who received CLS.Clinical parameters and survival outcomes between the two groups were compared.Results:Estimated blood loss(29.70±29.28 vs.52.80±45.09 mL,P=0.003),time to first flatus(2.50±0.79 vs.2.86±0.76,P=0.022),time to liquid diet(3.62±0.64 vs.4.20±0.76 d,P<0.001),and the need for analgesics(22%vs.48%,P=0.006)were significantly lower for the NOSE group compared to the CLS group.The incidences of overall complications and fecal incontinence were comparable in both groups.After a median follow-up of 44.52 months,the overall local recurrence rate(6%vs.5%,P=0.670),3-year disease-free survival(86.7%vs.88.0%,P=0.945)and 3-year overall survival(95.6%vs.96.0%,P=0.708),were not significantly different.Conclusions:For total laparoscopic rectal resection,transanal NOSE using the prolapsing technique is effective and safe,and associated with less trauma and pain,a faster recovery,and similar survival outcomes compared to CLS.展开更多
To measure the radiation properties of relativistic diffraction generator(RDG) in Ka-band,a TM0n modal excitation model is established,which consists of an overmoded circular waveguide and a coaxial line feeding probe...To measure the radiation properties of relativistic diffraction generator(RDG) in Ka-band,a TM0n modal excitation model is established,which consists of an overmoded circular waveguide and a coaxial line feeding probe.Using the transverse E-field mode matching and the conservation of complex power technique(CCPT),we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions.Then using the overall cascaded junction scattering matrix,the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented.The numerical results are in agreement with HFSS simulation results and experimental results.The analysis shows that by choosing the appropriate position of coaxial line probe,the power proportion of the device operating mode excited in circular waveguide could be the largest.展开更多
Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governin...Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.展开更多
文章分别采用常规环境激励法与IBIS-FS(Image by Interferometric Survey-Frequency Structures)微波干涉技术两种方法对装配整体式混凝土结构进行动力特性检测,同时按照与现浇结构混凝土相同的方法进行结构理论计算分析。结果表明:实...文章分别采用常规环境激励法与IBIS-FS(Image by Interferometric Survey-Frequency Structures)微波干涉技术两种方法对装配整体式混凝土结构进行动力特性检测,同时按照与现浇结构混凝土相同的方法进行结构理论计算分析。结果表明:实测动力特性结果与计算结果基本符合,常规环境激励法与IBIS-FS微波干涉技术可以在不需要任何激振设备的情况下检测出装配整体式混凝土结构的固有频率、振型、阻尼比;可以根据结构动力特性的测试结果对结构性能进行分析和判断。展开更多
基金Supported by the National Natural Science Foundation of China(51622603,51806027 and 51890911)the Major Program of National Natural Science Foundation of China(51436003)the National Key R&D Program of China(2017YFC0307300,2016YFC0304001)
文摘Natural gas hydrate(NGH)has been widely considered as an alternative form of energy with huge potential,due to its tremendous reserves,cleanness and high energy density.Several countries involving Japan,Canada,India and China have launched national projects on the exploration and exploitation of gas hydrate resources.At the beginning of this century,an early trial production of hydrate resources was carried out in Mallik permafrost region,Canada.Japan has conducted the first field test from marine hydrates in 2013,followed by another trial in 2017.China also made its first trial production from marine hydrate sediments in 2017.Yet the low production efficiency,ice/hydrate regeneration,and sand problems are still commonly encountered;the worldwide progress is far before commercialization.Up to now,many gas production techniques have been proposed,and a few of them have been adopted in the field production tests.Nevertheless,hardly any method appears really promising;each of them shows limitations at certain conditions.Therefore,further efforts should be made on the economic efficiency as well as sustainability and environmental impacts.In this paper,the investigations on NGH exploitation techniques are comprehensively reviewed,involving depressurization,thermal stimulation,chemical inhibitor injection,CO2–CH4 exchange,their combinations,and some novel techniques.The behavior of each method and its further potential in the field test are discussed.The advantages and limitations of laboratory studies are also analyzed.The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs.
基金supported by National Key R&D Program of China(No.2017YFC0908203)Chinese Academy of Medical Sciences Initiative for Innovative Medicine(No.2017-I2M-2-003 and 2016-I2M-1-001)+2 种基金Science and Technology Project of Chaoyang District,Beijing(No.CYSF-1931)Beijing Science and Technology Program(No.D17110002617004)Beijing Gold-Bridge Funds(No.ZZ19055)。
文摘Objective:The transanal approach to specimen collection,combined with the prolapsing technique,is a wellestablished and minimally invasive surgery for treating rectal cancer.However,reports on outcomes for this approach are sparse.We compared short-and long-term outcomes of conventional laparoscopic surgery(CLS)vs.transanal natural orifice specimen extraction(NOSE)using the prolapsing technique for patients with middle-to low-rectal cancer.Methods:From January 2013 to December 2017,we enrolled consecutive patients with middle-to low-rectal cancer undergoing laparoscopic anterior resection.Totally,50 patients who underwent transanal NOSE using the prolapsing technique were matched with 50 patients who received CLS.Clinical parameters and survival outcomes between the two groups were compared.Results:Estimated blood loss(29.70±29.28 vs.52.80±45.09 mL,P=0.003),time to first flatus(2.50±0.79 vs.2.86±0.76,P=0.022),time to liquid diet(3.62±0.64 vs.4.20±0.76 d,P<0.001),and the need for analgesics(22%vs.48%,P=0.006)were significantly lower for the NOSE group compared to the CLS group.The incidences of overall complications and fecal incontinence were comparable in both groups.After a median follow-up of 44.52 months,the overall local recurrence rate(6%vs.5%,P=0.670),3-year disease-free survival(86.7%vs.88.0%,P=0.945)and 3-year overall survival(95.6%vs.96.0%,P=0.708),were not significantly different.Conclusions:For total laparoscopic rectal resection,transanal NOSE using the prolapsing technique is effective and safe,and associated with less trauma and pain,a faster recovery,and similar survival outcomes compared to CLS.
基金supported by the National Natural Science Foundation of Chinaunder Grant No.60571020
文摘To measure the radiation properties of relativistic diffraction generator(RDG) in Ka-band,a TM0n modal excitation model is established,which consists of an overmoded circular waveguide and a coaxial line feeding probe.Using the transverse E-field mode matching and the conservation of complex power technique(CCPT),we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions.Then using the overall cascaded junction scattering matrix,the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented.The numerical results are in agreement with HFSS simulation results and experimental results.The analysis shows that by choosing the appropriate position of coaxial line probe,the power proportion of the device operating mode excited in circular waveguide could be the largest.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52171288,51890914)the Key Research and Development Program of Shandong Province(Major Innovation Project)(Grant No.2022CXGC020405)+1 种基金the National Ministry of Industry and Information Technology Innovation Special Project-Engineering Demonstration Application of Subsea Oil and Gas Production SystemSubject 4:Research on Subsea Christmas Tree and Wellhead Offshore Testing Technology(Grant No.MC-201901-S01-04)CNPq,CAPES and FAPERJ of Brazil。
文摘Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.
文摘文章分别采用常规环境激励法与IBIS-FS(Image by Interferometric Survey-Frequency Structures)微波干涉技术两种方法对装配整体式混凝土结构进行动力特性检测,同时按照与现浇结构混凝土相同的方法进行结构理论计算分析。结果表明:实测动力特性结果与计算结果基本符合,常规环境激励法与IBIS-FS微波干涉技术可以在不需要任何激振设备的情况下检测出装配整体式混凝土结构的固有频率、振型、阻尼比;可以根据结构动力特性的测试结果对结构性能进行分析和判断。
