[A Method to Measure the Velocity of Fragments of Large Equivalence Explosion Field Based on Explosion Flame Spectral Analysis].

The deflagration fire lasting for a long time and covering a large area in the process of large equivalent explosion makes it difficult to obtain velocity parameters of fragments in the near-field. In order to solve the problem, it is proposed in this paper a photoelectric transceiver integrated method which utilize laser screen as the sensing area. The analysis of three different types of warhead explosion flame spectral distribution of radiation shows that 0.3 to 1.0 µm within the band is at relatively low intensity. On the basis of this, the optical system applies the principle of determining the fixed distance by measuring the time and the reflector technology, which consists of single longitudinal mode laser, cylindrical Fresnel lens, narrow-band filters and high-speed optical sensors, etc. The system has its advantage, such as transceiver, compact structure and combination of narrowband filter and single longitudinal mode laser, which can stop the spectrum of fire from suppressing the interference of background light effectively. Large amounts of experiments in different models and equivalent have been conducted to measure the velocity of difference kinds of warheads, obtaining higher signal-to-noise ratio of the waveform signal after a series of signal de-noising and recognition through NI company data acquisition and recording system. The experimental results show that this method can complete the accurately test velocity of fragments around center of the explosion. Specifically, the minimum size of fragments can be measured is 4 mm while the speed can be obtained is up to 1 200 m x s(-1) and the capture rate is better than 95% comparing with test results of target plate. At the same time, the system adopts Fresnel lenses-transparent to form a rectangular screen, which makes the distribution of rectangular light uniform in vertical direction, and the light intensity uniformity in horizontal direction is more than 80%. Consequently, the system can distinguish preliminarily the correspondence between the velocity and the sizes of prefabricated fragments.

[Monitoring of Curing Temperature of Pouring Explosive Based on Fiber Bragg Grating].

For the first time, we real time measured released reaction heat between the binder and the curing agent in the curing process of cast explosive using fiber Bragg grating. In order to obtain the temperature in the process of pouring explosive casting real time and accurately, we designed the temperature monitoring system based on fiber Bragg grating. Given the risk of explosive component, long curing time and the requirements of constant temperature, a suitable measurement method for direct real-time monitoring has not been found. In recent years, due to its superior characteristics, fiber Bragg grating is widely used in the field of communication and sensing. We will make the collected reflection wavelength to convert real-time temperature displaying, utilizing linear relationship between fiber Bragg grating and temperature. Through WDM technology, seven grating points are written in two optical fibers to measure at the same time, and distribution trend of explosives internal temperature can be displayed in real time by multi-point distributed measurement. The curved design of the sensor not only improves the connection between sensor and jumper, but also benefits to place in oven. The txt data is made to draw a graph using origin software, and the changes in temperature in the curing process are displayed intuitively. The results show that this method is simple and high-precision, and meets the testing requirements of curing temperature of explosives.

[Frequency correction in terahertz absorption spectroscopy].

Measurement errors in frequency domain always appear when testing samples' terahertz (THz) absorption spectrum using terahertz time-domain spectroscopy (THz-TDS) system, which is supposed to be attributed to the sampling accuracy of the high speed electro-optic sampling system In order to make the measurement have a high accuracy, the method of error correction was studied in the present article. Carbon monoxide in gas phase was employed as our standard sample, and its absorption spectrum at the pressure of 2.0 x 10(5) Pa was measured experimentally. Comparing the obtained absorption frequencies with the corresponding standard data in JPL database, we got the error values, and their distribution law shows that the values have a linear correlation with the standard absorption frequency. Based on this, the error correction model was built. Using the model to correct the experimental data, the result shows the maximum error after correction is reduced to 3.36 GHz, which is two orders of magnitude lower than the error before correction. This states that the model can be used to correct the error of the THz spectrum caused by high speed electro-optic sampling system. At last, the authors draw a conclusion that the THz-TDS system is supposed to be corrected by the terahertz spectrum of carbon monoxide before measurement, in this way, the terahertz spectrum of sample can have a high accuracy. The study contributes to the material identification and the construction of molecular spectroscopy database in THz region.