Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effectiv...Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effective treatment and avoid over-high temperature. Proposed in this paper is a method to modulate the temperature distribution in the focal region. It superimposes two signals which focus on two preset different targets with a certain distance. Then the temperature distribution is modulated by changing triggering time delay and amplitudes of the two signals. The simulation model is established based on an 82-element transducer and computed tomography （CT） data of a volunteer＇s head. A finite- difference time-domain （FDTD） method is used to calculate the temperature distributions. The results show that when the distances between the two targets respectively are 7.5-12.5 mm on the acoustic axis and 2.0-3.0 mm in the direction perpendicular to the acoustic axis, a focal region with a uniform temperature distribution （64-65 ℃） can be created. Moreover, the volume of the focal region formed by one irradiation can be adjusted （26.8-266.7 mm3） along with the uniform temperature distribution. This method may ensure the safety and efficacy of HIFU brain tumor therapy.展开更多
The electronic excitation temperature in a direct current positive streamer discharge based on ultra-thin sheet electrodes was measured by optical emission spectrometry in order to deposit materials for potential futu...The electronic excitation temperature in a direct current positive streamer discharge based on ultra-thin sheet electrodes was measured by optical emission spectrometry in order to deposit materials for potential future applications. It was remarkable that the electronic excitation temperature （Text） did not vary monotonically with the discharge current, but demonstrated a peak at a certain position. In a mixture of oxygen and argon （80% oxygen）, the maximum Texc reached about 6300 K at an average current of 600 pA. Both the positive ions accumulation in the discharge region and the increase of the local temperature around the streamer channel caused by Joule heating are considered to be the main reasons for the variations of Texc.展开更多
In the report,the recently developed relativistic multichannel theory(RMCT)is a full relativistic non-perturbative method and can be applied to the high-Z atomic ions which have given rise to some recent interests bec...In the report,the recently developed relativistic multichannel theory(RMCT)is a full relativistic non-perturbative method and can be applied to the high-Z atomic ions which have given rise to some recent interests because of researches of inertial confinement fusion and x-ray laser.Based on the RMCT,the positions and widths of doubly excited sp2n^(+),sp2n^(-),and 2pnd ^(1)P_(1) resonances are calculated,which are in agreement with the recent experimental measurements.It sets up a sound foundation on which the RMCT should be applicable to high Z atomic ions.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.81272495)the Natural Science Foundation of Tianjin,China(Grant No.16JC2DJC32200)
文摘Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effective treatment and avoid over-high temperature. Proposed in this paper is a method to modulate the temperature distribution in the focal region. It superimposes two signals which focus on two preset different targets with a certain distance. Then the temperature distribution is modulated by changing triggering time delay and amplitudes of the two signals. The simulation model is established based on an 82-element transducer and computed tomography （CT） data of a volunteer＇s head. A finite- difference time-domain （FDTD） method is used to calculate the temperature distributions. The results show that when the distances between the two targets respectively are 7.5-12.5 mm on the acoustic axis and 2.0-3.0 mm in the direction perpendicular to the acoustic axis, a focal region with a uniform temperature distribution （64-65 ℃） can be created. Moreover, the volume of the focal region formed by one irradiation can be adjusted （26.8-266.7 mm3） along with the uniform temperature distribution. This method may ensure the safety and efficacy of HIFU brain tumor therapy.
文摘The electronic excitation temperature in a direct current positive streamer discharge based on ultra-thin sheet electrodes was measured by optical emission spectrometry in order to deposit materials for potential future applications. It was remarkable that the electronic excitation temperature （Text） did not vary monotonically with the discharge current, but demonstrated a peak at a certain position. In a mixture of oxygen and argon （80% oxygen）, the maximum Texc reached about 6300 K at an average current of 600 pA. Both the positive ions accumulation in the discharge region and the increase of the local temperature around the streamer channel caused by Joule heating are considered to be the main reasons for the variations of Texc.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19474009Chinese National High-Tech ICF CommitteeChinese Commission of Science and Technology。
文摘In the report,the recently developed relativistic multichannel theory(RMCT)is a full relativistic non-perturbative method and can be applied to the high-Z atomic ions which have given rise to some recent interests because of researches of inertial confinement fusion and x-ray laser.Based on the RMCT,the positions and widths of doubly excited sp2n^(+),sp2n^(-),and 2pnd ^(1)P_(1) resonances are calculated,which are in agreement with the recent experimental measurements.It sets up a sound foundation on which the RMCT should be applicable to high Z atomic ions.
