A novel scheme to suppress both stimulated Brillouin scattering(SBS) and stimulated Raman scattering(SRS) by combining an alternating frequency(AF) laser and a transverse magnetic field is proposed. The AF laser allow...A novel scheme to suppress both stimulated Brillouin scattering(SBS) and stimulated Raman scattering(SRS) by combining an alternating frequency(AF) laser and a transverse magnetic field is proposed. The AF laser allows the laser frequency to change discretely and alternately over time. The suppression of SBS is significant as long as the AF difference is greater than the linear growth rate of SBS or the alternating time of the laser frequency is shorter than the linear growth time of SBS. However, the AF laser proves ineffective in suppressing SRS, which usually has a much higher linear growth rate than SBS. To remedy that, a transverse magnetic field is included to suppress the SRS instability. The electrons trapped in the electron plasma waves(EPWs) of SRS can be accelerated by the surfatron mechanism in a transverse magnetic field and eventually detrapped. While continuously extracting energy from EPWs, the EPWs are dissipated and the kinetic inflation of SRS is suppressed. The one-dimensional particle-in-cell simulation results show that both SBS and SRS can be effectively suppressed by combining the AF laser with a transverse magnetic field with tens of Tesla. The total reflectivity can be dramatically reduced by more than one order of magnitude. These results provide a potential reference for controlling SBS and SRS under the related parameters of inertial confinement fusion.展开更多
Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in undergroun...Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.展开更多
Objective:Clinical education plays a key role in preparing students for patient care.Laparoscopy is one of the most important minimally invasive surgeries(MISs)wherein surgical technologists are responsible for camera...Objective:Clinical education plays a key role in preparing students for patient care.Laparoscopy is one of the most important minimally invasive surgeries(MISs)wherein surgical technologists are responsible for camera navigation and assistant surgeons are responsible for peg transfer.Therefore,it is necessary to improve the attitude of the operating room students toward these skills during their study period.The present study was conducted to determine the effect of simulating training in the fundamentals of laparoscopic surgery(FLS)on the attitude of the operating room students.Methods:This interventional study was conducted on 28 operating room students of Iran University of Medical Sciences in 2019.The census sampling method was used.The data-collection tool included the“Intrinsic motivation inventory(IMI)questionnaire.”The educational intervention was carried out in theoretical(booklet design)and practical(simulation)sections.Data analysis was carried out using descriptive and inferential analyses including the paired t-test,Mann–Whitney U test,and independent t-test.The collected data were analyzed using R and SPSS software.P-value<0.05 was considered as the significant level.Results:The mean±SD of the participants'age was 22.93±2.14 years,and the majority of them were women(67.9%).There was a significant difference in the mean scores of students'attitudes toward the FLS before and after the educational intervention(P<0.001)in all dimensions(interest,perceived competence,perceived choice,and tension).There was also a significant correlation between gender and interest dimension(P=0.005).Conclusions:The results of the present study showed that simulating the training FLS curriculum positively affects students'attitudes.Therefore,the researchers suggest that for creating a positive attitude,increasing students'interest in laparoscopic surgery,and ensuring a more effective presence in the operating room,this training should be considered in the operating room curriculum.展开更多
The ultimate goal of foreign language teaching is to enable the students to use the foreign language in work of life when necessary.Thus we should teach language in the way that is used in the real world.But the basic...The ultimate goal of foreign language teaching is to enable the students to use the foreign language in work of life when necessary.Thus we should teach language in the way that is used in the real world.But the basic precondition is that learner must be interested in foreign language.In my opinion,during the English learning process,"interest is the best teacher".But many students don’t like to learn English,the reason is that they are not interested in English.Therefore,a successful language teacher must know how to raise students’interest in learning English,make them enjoy learning English.In addition,the language teaching method is very important,it must renew continuously,teachers should use the vivid and diverse teaching method to organize students to participate in extensive language practice activities,so as to improve students’study enthusiasm.展开更多
Motivation to language learning is a complex set of variables including effort, desire to achieve goals, as well as attitudes toward the learning of the language. Individuals' motivation to second-language learnin...Motivation to language learning is a complex set of variables including effort, desire to achieve goals, as well as attitudes toward the learning of the language. Individuals' motivation to second-language learning also includes their motivation orientations, interest in the second language, attitudes toward the second-language group, attitudes toward the second-language learning situations and second-language anxiety. Based on the basic theories and approaches, teaching activities are part of motivation in English classes. The teacher of language should have a good influence on students and develop students' keen interest in study in order to strengthen their intrinsic motivation, and set up some new goals for students to pursue and give the feedback to reinforce their inner drive and confidence. Thus, students will become major conductors, make full use of their potentials and enhance their study results.展开更多
The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under th...The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under the loading of rocks.An electrical and mechanics test system was established in this paper to explore the impacts of loading rates on PSCs.The results indicated that PSC curves of different rocks had different change laws under low/high loading rates.When the loading rate was relatively low,PSC curves firstly changed gently and then increased exponentially.Under high loading rates,PSC curves experienced the rapid increase stage,gentle increase stage and sudden change stage.The compressive strength could greatly affect the peak PSC in case of rock failure.The loading rate was a key factor in average PSC.Under low loading rates,the variations of PSCs conformed to the damage charge model of fracture mechanics,while they did not at the fracture moment.Under high loading rates,the PSCs at low stress didn’t fit the model due to the stress impact effects.The experimental results could provide theoretical basis for the influence of loading rates on PSCs.展开更多
In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or ...In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or temperature sensors.The high cost limits the spatial resolution,which ultimately affects the measuring accuracy of the ISW amplitude.In this paper,we developed an experimental measurement system for detecting ISWs based on the stimulated Raman scattering in distributed optical fibers.This system has the advantages of high precision,low cost,and easy operation.The experimental results show that the system is consistent with CTDs in the measurement of vertical ocean temperature variation.The spatial resolution of the system can reach 1.0 m and the measuring accuracy of temperature is 0.2℃.We successfully detected 3 ISWs by the system in the South China Sea and two optical remote sensing images collected on May 18,2021,the same day of two detected ISWs,verify the occurrence of the measured ISWs.We used the image pairs method to calculate the phase velocity of ISW and the result is 1.71 ms^(-1).By extracting the distances between wave packets,it can be found that the semi-diurnal tide generates the detected ISWs.The impact of the tidal current velocity on the ISW in amplitude is undeniable.Undoubtedly,the system has a great application prospect for detecting ISWs and other dynamic phenomena in the ocean.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11975059 and 12005021)。
文摘A novel scheme to suppress both stimulated Brillouin scattering(SBS) and stimulated Raman scattering(SRS) by combining an alternating frequency(AF) laser and a transverse magnetic field is proposed. The AF laser allows the laser frequency to change discretely and alternately over time. The suppression of SBS is significant as long as the AF difference is greater than the linear growth rate of SBS or the alternating time of the laser frequency is shorter than the linear growth time of SBS. However, the AF laser proves ineffective in suppressing SRS, which usually has a much higher linear growth rate than SBS. To remedy that, a transverse magnetic field is included to suppress the SRS instability. The electrons trapped in the electron plasma waves(EPWs) of SRS can be accelerated by the surfatron mechanism in a transverse magnetic field and eventually detrapped. While continuously extracting energy from EPWs, the EPWs are dissipated and the kinetic inflation of SRS is suppressed. The one-dimensional particle-in-cell simulation results show that both SBS and SRS can be effectively suppressed by combining the AF laser with a transverse magnetic field with tens of Tesla. The total reflectivity can be dramatically reduced by more than one order of magnitude. These results provide a potential reference for controlling SBS and SRS under the related parameters of inertial confinement fusion.
基金supported by National Key R&D Program of China(No.2022YFC3004705)the National Natural Science Foundation of China(Nos.52074280,52227901 and 52204249)National Natural Science Foundation of China Youth Fund(No.52104230).
文摘Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.
基金supported by the Iran University of Medical Science。
文摘Objective:Clinical education plays a key role in preparing students for patient care.Laparoscopy is one of the most important minimally invasive surgeries(MISs)wherein surgical technologists are responsible for camera navigation and assistant surgeons are responsible for peg transfer.Therefore,it is necessary to improve the attitude of the operating room students toward these skills during their study period.The present study was conducted to determine the effect of simulating training in the fundamentals of laparoscopic surgery(FLS)on the attitude of the operating room students.Methods:This interventional study was conducted on 28 operating room students of Iran University of Medical Sciences in 2019.The census sampling method was used.The data-collection tool included the“Intrinsic motivation inventory(IMI)questionnaire.”The educational intervention was carried out in theoretical(booklet design)and practical(simulation)sections.Data analysis was carried out using descriptive and inferential analyses including the paired t-test,Mann–Whitney U test,and independent t-test.The collected data were analyzed using R and SPSS software.P-value<0.05 was considered as the significant level.Results:The mean±SD of the participants'age was 22.93±2.14 years,and the majority of them were women(67.9%).There was a significant difference in the mean scores of students'attitudes toward the FLS before and after the educational intervention(P<0.001)in all dimensions(interest,perceived competence,perceived choice,and tension).There was also a significant correlation between gender and interest dimension(P=0.005).Conclusions:The results of the present study showed that simulating the training FLS curriculum positively affects students'attitudes.Therefore,the researchers suggest that for creating a positive attitude,increasing students'interest in laparoscopic surgery,and ensuring a more effective presence in the operating room,this training should be considered in the operating room curriculum.
文摘The ultimate goal of foreign language teaching is to enable the students to use the foreign language in work of life when necessary.Thus we should teach language in the way that is used in the real world.But the basic precondition is that learner must be interested in foreign language.In my opinion,during the English learning process,"interest is the best teacher".But many students don’t like to learn English,the reason is that they are not interested in English.Therefore,a successful language teacher must know how to raise students’interest in learning English,make them enjoy learning English.In addition,the language teaching method is very important,it must renew continuously,teachers should use the vivid and diverse teaching method to organize students to participate in extensive language practice activities,so as to improve students’study enthusiasm.
文摘Motivation to language learning is a complex set of variables including effort, desire to achieve goals, as well as attitudes toward the learning of the language. Individuals' motivation to second-language learning also includes their motivation orientations, interest in the second language, attitudes toward the second-language group, attitudes toward the second-language learning situations and second-language anxiety. Based on the basic theories and approaches, teaching activities are part of motivation in English classes. The teacher of language should have a good influence on students and develop students' keen interest in study in order to strengthen their intrinsic motivation, and set up some new goals for students to pursue and give the feedback to reinforce their inner drive and confidence. Thus, students will become major conductors, make full use of their potentials and enhance their study results.
基金the State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology(No.SKLCRSM22KF011)the National Natural Science Foundation of China(Nos.52130411,52104191,51974120,and 51904103)+1 种基金the Natural Science Foundation of Hunan Province(No.2021JJ40204)the Science and Technology Innovation Program of Hunan Province(No.2020RC3047).
文摘The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under the loading of rocks.An electrical and mechanics test system was established in this paper to explore the impacts of loading rates on PSCs.The results indicated that PSC curves of different rocks had different change laws under low/high loading rates.When the loading rate was relatively low,PSC curves firstly changed gently and then increased exponentially.Under high loading rates,PSC curves experienced the rapid increase stage,gentle increase stage and sudden change stage.The compressive strength could greatly affect the peak PSC in case of rock failure.The loading rate was a key factor in average PSC.Under low loading rates,the variations of PSCs conformed to the damage charge model of fracture mechanics,while they did not at the fracture moment.Under high loading rates,the PSCs at low stress didn’t fit the model due to the stress impact effects.The experimental results could provide theoretical basis for the influence of loading rates on PSCs.
基金National Natural Science Foundation of China(Nos.61871353,62031005)。
文摘In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or temperature sensors.The high cost limits the spatial resolution,which ultimately affects the measuring accuracy of the ISW amplitude.In this paper,we developed an experimental measurement system for detecting ISWs based on the stimulated Raman scattering in distributed optical fibers.This system has the advantages of high precision,low cost,and easy operation.The experimental results show that the system is consistent with CTDs in the measurement of vertical ocean temperature variation.The spatial resolution of the system can reach 1.0 m and the measuring accuracy of temperature is 0.2℃.We successfully detected 3 ISWs by the system in the South China Sea and two optical remote sensing images collected on May 18,2021,the same day of two detected ISWs,verify the occurrence of the measured ISWs.We used the image pairs method to calculate the phase velocity of ISW and the result is 1.71 ms^(-1).By extracting the distances between wave packets,it can be found that the semi-diurnal tide generates the detected ISWs.The impact of the tidal current velocity on the ISW in amplitude is undeniable.Undoubtedly,the system has a great application prospect for detecting ISWs and other dynamic phenomena in the ocean.
