An Anti-multipath Frequency Hopped Communication Technique in Shallow-water Acoustic Channels

This paper introduces a frequency-hopped (FH) communication system to anti-intersymbol interferences (ISI) caused by the multipath propagation in shallow-water acoustic channels, and uses high-speed digital signal processor (DSP) and serial ADC (MAX121) chip to demodulate received signal efficiently based Fast Fourier Transform (FFT) algorithm. The field experimental results show: a data rate of 1Kbit/s with the bit error rates on the order of 10 -4 is demonstrated at 2000 m in the shallow-water acoustic channel of Xiamen harbor, and the key techniques of the system is analyzed in the paper.

Selection of Environmental Conditions for Nearshore Structure Design

Different from the traditional one dimensional extreme value statistical method, practical design criteria for nearshore structure design are presented based on joint probability theory in this paper. The proposed procedure considers the combined effect of tide level, huge waves and wind affecting coastal structures. The Importance Sampling Procedure (ISP) is utilized to solve the joint distribution of non Gaussian correlated multivariate distributions. The calculation results show that the ISP is a simulating technique with the advantages of efficiency and high convergency. Finally the environmental conditions are given using this technique for near shore structure design in the Qingdao area.

Nonlinear Fitting Method of Long-Term Distributions for Statistical Analysis of Extreme Negative Surge Elevations

Hydrologic frequency analysis plays an important role in coastal and ocean engineering for structural design and disaster prevention in coastal areas. This paper proposes a Nonlinear Least Squares Method (NLSM), which estimates the three unknown parameters of the Weibull distribution simultaneously by an iteration method. Statistical test shows that the NLSM fits each data sample well. The effects of different parameter-fitting methods, distribution models, and threshold values are also discussed in the statistical analysis of storm set-down elevation. The best-fitting probability distribution is given and the corresponding return values are estimated for engineering design.

Experimental Study on the Effectiveness of TLDs under Wave Loading

The objective of this study is to experimentally investigate the effectiveness of Tuned Liquid Dampers (TLDs) for suppressing the dynamic response of a platform structure subjected to wave loading and to explore the applicability of TLDs for suppressing the structural vibration of fixed offshore platforms. The experimental model is scaled according to a full size platform by matching its dynamic properties. Rectangular and circular TLDs of various sizes and water depths are examined. The experiments were performed in a 2-D wave flume. The effectiveness of TLDs is evaluated based on their response reduction. By observing the performance and the behavior of TLDs through laboratory experiments, the effects of a number of parameters including container shape, container size, number of dampers, frequency ratio, mass ratio, and incident wave characteristics are investigated.

顺势牵引微创治疗在下肢骨折中的应用

目的介绍顺势牵引微创治疗在下肢骨折中的应用,分析其复位技巧和闭合复位的成功率。方法回顾性分析2015年10月到2017年5月山东大学齐鲁医院青岛院区创伤骨科应用双反牵引微创治疗的58例下肢骨折患者。所有患者均采用张氏牵引复位器闭合复位治疗骨折,闭合复位成功后选择接骨板经皮置入或髓内钉内固定。采集闭合复位成功率、术后感染率、神经血管并发症、骨折愈合、功能恢复情况。结果 53例患者获得随访,随访时间为7～24个月,平均(11±4)个月。在顺势双反牵引辅助下,所有骨干骨折闭合复位均获得成功,36例胫骨平台骨折有21例闭合复位成功,15例有关节面塌陷的骨折结合阶梯钻和顶棒复位成功。1例切口出现浅表感染,经换药后愈合,没有血管神经并发症发生,所有患者骨折获得愈合,无内植物松动断裂、复位丢失等并发症。53例患者功能恢复良好,52例患者恢复到伤前生活或工作状态,1例工伤患者未回到工作岗位。结论在下肢骨折的治疗中,顺势微创技术是一种简单迅速、创伤小、恢复快的治疗方式,值得临床推广。