Моделирование оптоакустических сигналов в системе с упругим рассеянием и поглощением света

We propose a method for simulating optoacoustic signals initiated by a laser pulse in an absorbing medium with elastic radiation scattering and carry out corresponding calculations. It is shown that the use of the method of spherical harmonics allows obtaining an analytical expression for the optoacoustic signal. The deviation of the absorption profile from the Bouguer type near the sample surface leads to a strong influence of the medium parameters on the position of the signal maximum. The growth of the albedo of onefold scattering leads to a decrease in the effective signal growth constant and its amplitude.

Securing Communication via Transmission of Artificial Noise by Both Sides: Bipolar-Beamforming Optimization

The paper considers the secure transmission in a wireless environment in which both the transmitter (Alice) and the legitimate receiver (Bob) send artificial noise (AN) to interfere with the eavesdropper (Eve). Optimal design is analyzed in detail for this AN-by-both-side model to deal with Eve’s stochastic channel condition and random spatial distribution. Bipolar-beamforming is first proposed to jointly design Alice and Bob’s transmitting signals. By optimally assigning the transmitting antenna for Bob and allocating the power ratio between Alice’s information and the AN signal, maximum secrecy capacity can be achieved. Simulation is done to illustrate the process of bipolar-beamforming optimization. Results show that the AN-by-both-side model has good secrecy performance on both average and extreme conditions as Eve approaches Alice or Bob.

A rapid and accurate spectrofluorometric method for quantification and screening of urinary porphyrins.

We describe a fluorescence method for screening and quantifying urinary porphyrins. New and effective approaches are used to oxidize prophyrinogens, correct the baseline, and ensure that uroporphyrin (uro) and coproporphyrin (copro) are equally detected, mole for mole. No preliminary purification is required. A 45-microL aliquot of urine is oxidized with 3 mmol/L iodine in 3 mol/L HCl to convert porphyrinogens to porphyrins, and then decolorized with 5 mL of 0.45 mmol/L sodium thiosulfate. An excitation scan is done from 350 nm to 440 nm, monitoring emission at 650 nm. Total porphyrin content is determined at the isosbestic point for uro and copro, and the mole fractions of uro and copro are estimated from the wavelength of the signal maximum. There is no interference from protein, glucose, bilirubin, or hemoglobin in high concentration. The limit of detection is less than 30 nmol/L and linearity is maintained up to 3200 nmol/L. Recoveries and precision are excellent. This is a rapid, sensitive screen for porphyrinuria as well as an accurate and precise quantitative method. We compared the method with existing methods and discuss some shortcomings common to many of them.

Attenuation Problems Associated with a 5 cm Radar

The reflectivity pattern from a 5 cm Doppler radar is compared to that from a colocated 10 cm Doppler radar to determine the relative attenuation of the 5 cm signal. Maximum attenuation occurred on 10 April 1979 during the alignment of two severe thunderstorms on the same radar azimuth. During alignment, the near-range storm caused total attenuation of the 5 cm signal from the far-range storm. Maximum attenuation in the far-range storm was much in excess of 23 dB. was on the order of 30dB. Characteristics of the two storms are presented, along with the rainfall rate (maximum of 6.4 in h−1, of the Maximum attenuation in the back side of the near-range storm was on the order of 30 dB. Characteristics of the two storms are presented, along with the rainfall rate (maximum of 6.4 in h−1) of the near-range storm, a reflectivity contour analysis for each radar, and difference fields showing the attenuation of the 5 cm signal in both storms. Some operational problems associated with a 5 cm radar in an attenuating environment include degradation of peak values and distortion of severe weather indicators, as well as the possibility of the loss of the capability to detect severe storms.