Long-Pulse Single-Frequency All-Fiber Amplifier

In this paper, we report a high power long-pulse single-frequency all-fiber amplifier at 1064 nm with near-diffraction-limited beam quality based on a polarization-maintaining tapered Yb-doped fiber (T-YDF). By applying square wave pulse modulation to the diodes, with a frequency of 50 Hz and a pulse width of 668 μs, the peak power of the output laser reached 257 W with an average power of 8.65 W, linewidth of 10.6 kHz and M2 < 1.5. .

Long-pulse gastric electrical stimulation protects interstitial cells of Cajal in diabetic rats via IGF-1 signaling pathway

AIM: To investigate the effects of different parameters of gastric electrical stimulation(GES) on interstitial cells of Cajal(ICCs) and changes in the insulin-like growth factor 1(IGF-1) signal pathway in streptozotocininduced diabetic rats.METHODS: Male rats were randomized into control, diabetic(DM), diabetic with sham GES(DM + SGES), diabetic with GES1(5.5 cpm, 100 ms, 4 m A)(DM + GES1), diabetic with GES2(5.5 cpm, 300 ms, 4 m A)(DM + GES2) and diabetic with GES3(5.5 cpm, 550 ms, 2 m A)(DM + GES3) groups. The expression levels of c-kit, M-SCF and IGF-1 receptors were evaluated in the gastric antrum using Western blot analysis. The distribution of ICCs was observed using immunolabeling for c-kit, while smooth muscle cells and IGF-1 receptors were identified using α-SMA and IGF-1R antibodies. Serum level of IGF-1 was tested using enzyme-linked immunosorbent assay. RESULTS: Gastric emptying was delayed in the DM group but improved in all GES groups, especially in the GES2 group. The expression levels of c-kit, M-SCF and IGF-1R were decreased in the DM group but increased in all GES groups. More ICCs(c-kit+) and smooth muscle cells(α-SMA+/IGF-1R+) were observed in all GES groups than in the DM group. The average level of IGF-1 in the DM group was markedly decreased, but it was up-regulated in all GES groups, especially in the GES2 group. CONCLUSION: The results suggest that long-pulse GES promotes the regeneration of ICCs. The IGF-1 signaling pathway might be involved in the mechanism underlying this process, which results in improved gastric emptying.

Air-breathing mode laser propulsion with a long-pulse TE CO_2 laser

Air-breathing mode laser propulsion experiment with a long-pulse transversely excited （TE） CO2 laser is carried out, and its ignition problem is solved with the ignition needle of lightcraft. Owing to the ignition needle, an order of magnitude reduction in the ignition threshold is demonstrated. The result is compared with previous study. The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy （6 14 J） and pulse width （20, 32, and 40 μs） is discussed.

Research progresses on Cherenkov and transit-time high-power microwave sources at NUDT

Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed.The compact coaxial relativistic backward-wave oscillators(RBWOs)at low bands are developed.The power efficiency in M-Type HPM tubes without guiding magnetic field increased.The power capacities and power efficiencies in the triaxial klystron amplifier(TKA)and relativistic transit-time oscillator(TTO)at higher frequencies increased.In experiments,some exciting results were obtained.The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode.Both L-and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%.There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions.A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%.A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB.A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.

THE ANALYTICAL STUDY ON THE LASER INDUCED REVERSE－PLUGGING EFFECT BY USING THE CLASSICAL ELASTIC PLATE THEORY（II）──REVERSE－BULGE MOTION

Tile reverse-bulge motion (RBW) in the metallic foils. which is induced by spatially cylindrical long pulse laser. is examined in order to analyse the newly-discovered reverse-plugging effect (RPE). An uncoupled, thin plate theory is Used to determine the induced. flexural vibrations. The solution is obtained as the superposition of two displacement .fields, representing the quasi-static and the dynamic behaviors.Meanwhile. the equivalent thermal loading and the dimensionless analysis of thin plate motion are presented. Numerical results presented may partially explain the RBM of thin plate at the early stage of laser irradiation.

Intrapulse coherence degradation suppressing method of echo signal in coherent lidar

Aiming at coherence degradation during target detection,a suppressing method based on frequency-modulated continuous wave coherent lidar is proposed.Combined with a random iteration algorithm,a long-pulse echo signal with coherent degradation is matched with random phase noise of a certain frequency and achieves coherence restoration.Simulation and field experiment results show that this proposed method can recover the intrapulse coherence in long-pulse echo signals.In addition,for the real target echo signal at 4.2 and 19.8 km,the peak signal-to-noise ratio processed by this method is increased by 0.35 times and 4 times after pulse compression,respectively.