ABSTRACT
Directional energy weapons such as high-power microwaves and high-energy lasers pose a huge threat to optoelectronic detection systems. With that in mind, we designed an infrared optical window that has a nonlinear optical response to high-energy lasers and electromagnetic shielding to microwaves. By constructing a periodic metal circular hole array structure at the subwavelength scale, surface plasmons resonance is excited and its local field enhanced characteristics are utilized to form information transmission compatibility in the infrared band. At the same time, after laser etching off the subwavelength structure, the remaining metal forms a continuous conductive structure, forming an ultra-wideband shielding layer to achieve ultra-high and wide protection in the microwave band. Moreover, a layer of Ge2Sb2Te5 thin film was deposited between the transparent substrate and the metal film. Utilizing its nonlinear optical properties of high-temperature phase transition to reduce damage of directed energy weapons to the photoelectric detection system and equipment. Thus, when the photoelectric detection system or device is damaged or interfered by signals of different frequency bands or energies, the filtering window can achieve multi-mode shielding function.
ABSTRACT
In this paper, a new probe is proposed for the dielectric measurement of anisotropic tissue in radio frequency band, which could accomplish the dielectric measurement in perpendicular directions by one operation. The simulative studies are performed in the frequency range from 1-1 000 MHz in order to investigate the influence of probe dimension on the energy coupling and sensitivity of measurement. The suitable probe is designed and validated for the actual measurement in this frequency band. According to the simulation results, the energy coupling of the probe could be kept below -12 dB in the frequency range from 200-400 MHz with high sensitivity of measurement for the dielectric properties of anisotropic tissue. That indicates the new type of probe has the potential to achieve the dielectric measurement of anisotropic tissue in radio frequency band and could avoid the measurement error by multi-operations in the conventional method. This new type of probe could provide a new method for the dielectric measurement of anisotropic tissue in radio frequency band.
ABSTRACT
Objective To explore the value of iDose4 iterative reconstruction for coronary CT angiography (CCTA).Methods Totally 124 coronary heart disease patients underwent iDose4 iterative reconstruction and filtered back projection (FBP) reconstruction,of whom,56 ones with BMI not less than 20 kg/m2 were put into No.1 iteration group using 135 kV tube voltage and 68 ones with BMI less than 20 kg/m2 were into No.2 iteration group using 110 kV tube voltage.FBP reconstruction was executed with 110 kV tube voltage.Comparison analyses were carried out on signal noise ratio (SNR),contrast to noise ratio (CNR) and image quality.Results There were significant differences between the values of SNR,radiation dose and image quality in No.1 iteration group and FBP group (P＜0.05).Statistical differences were also found between the values of CNR and radiation dose in No.2 iteration group and FBP group,while there were no obvious differences between the values of SNR and image quality in the above two groups (P＜0.05).Conclusion Low-voltage iDose reconstruction gains advantages in radiation dose and image quality during 64-slice CCTA,and thus is worthy promoting clinically.
ABSTRACT
Magnetic induction method aims at the noninvasive detection of liver iron overload by measuring the hepatic magnetic susceptibility. To solve the difficulty that eddy current effects interfere with the measurement of magnetic susceptibility, we proposed an improved coil system based on the static field magnetization principle in this study. We used a direct current excitation to eliminate the eddy current effect, and a rotary receiver coil to get the induced voltage. The magnetic field for a cylindrical object due to the magnetization effect was calculated and the relative change of maximum induced voltage was derived. The correlation between magnetic susceptibility of object and maximum magnetic flux, maximum induced voltage and relative change of maximum induced voltage of the receiver coil were obtained by simulation experiments, and the results were compared with those of the theory calculation. The contrast shows that the simulation results fit the theory results well, which proves our method can eliminate the eddy current effect effectively.