DESIGN OF MODULATION AND COMPRESSION CODING IN UNDERWATER ACOUSTIC IMAGE TRANSMISSION     

程恩  余丽敏  林耿超 《中国海洋湖沼学报》2002,20(3):202-207

This paper describes the design of modulation, compression coding and transmission control in underwater acoustic color image transmission system. This design adapts a special system of modulation and transmission control based on a DSP(Digital Signal Processing) chip, to cope with the complex underwater acoustic channel. The hardware block diagram and software flow chart are presented.  相似文献   

细基江篱喷霧裁培试验     

刘思俭  曾淑芳  揭振英  刘莉 《广东海洋大学学报》1989,(Z1)

本文探讨了用噴雾栽培细基江篱的新方法。试验表明:此法能有效地避开自然海区对细江篱的生物敌害,促进藻体生长,比自然海区可增产,而且藻体清洁干净,收获方便。  相似文献   

南昌地区风沙化土地风沙地貌发育规模和风沙活动预测   总被引：3，自引：0，他引：3  

邹学勇 《地理研究》1991,10(3):51-58

本文通过对南昌地区风沙化土地扩展方式,沙源量及人为因素在风沙地貌发育中的作用等方面的分析,初步认为本风沙地貌发育规模不会很大,且目前已接近其顶锋状态。在建立GM(1,1)和方差分析(ANOVA)联合预测模型的基础上,对厚田地区三个月的干旱程度和冬季风沙活动强度进行预测,结果令人满意。  相似文献   

模糊综合评判在土地适宜性评价中应用研究   总被引：5，自引：0，他引：5  

刘耀林  刘艳芳  夏早发 《武汉大学学报(信息科学版)》1995,(1)

在十堰市土地利用现状调查的基础上，针对现有坡荒地，通过对制约土地的自然因素和社会经济条件的综合分析，依照土地质量满足对预定用途要求的程度，采用模糊数学的方法，在计算机上完成了坡荒地的宜农、宜林、宜牧、宜园４个适宜类的评价；同时对宜农地进行了更进一步的讨论。  相似文献   

中国江蓠的商品生产及其与对虾混养(英文)   总被引：1，自引：0，他引：1  

刘思俭  揭振英  曾淑芳 《广东海洋大学学报》1997,(2)

以江湾和对虾混养预防虾病。试验和生产实践表明，江蒿和对虾混养能明显地改善虾池水质，防止对虾细菌性病害，除江南有一定产量外，可使对虾产量比单养增加60％以上。并论述了中国江蓠人工栽培的种类、生长条件和主要生产方式。  相似文献   

三峡库区稻田复养河蟹的农田生态系统能量特征与经济效益   总被引：1，自引：0，他引：1  

陈铭达  刘兆普  刘文斌  王景艳  叶志娟 《山地学报》2005,23(4):469-475

在2002年四川南充稻田养蟹田间探索性试验的基础上,2003年在位于三峡库区淹没带边缘非淹区的重庆市开县竹溪镇进行稻田复养河蟹的田间试验,对种、养结合模式农田生态系统的能流与物流进行了初步探索,并进行了经济效益分析.结果表明：稻蟹复养田的光能利用率高于单作水稻田的15.7%;水稻生长期间的防病治虫用药、运作管理用工、无机肥用量、机械耗材的投入成本明显减少,总的投入比单作水稻田少4.3%,总能、无机能、有机能的产投比分别少35.1%、51.0%和31.6%;土壤全氮、氨态氮分别高于单作水稻田的21.4%和55.2%,稻田水中的氨态氮高达61.3%,这些无机态氮是培育水生生物、高等植物的营养源,又是供应河蟹生长的饵料,而硝态氮则要低得多;河蟹的甲壳质及其排泄物经分解矿化后,是提高土壤有效养分,供应水稻生长的主要肥源.稻田养蟹后,虽然稻谷产量比单作水稻低10.1%,投入成本且低于20.0%,而利润比单作水稻增加77.8%;河蟹的产投比1.54：1,获利润6 381.49元/hm^2;稻田复养河蟹的净利润为7104.19元/hm^2,是单作水稻的44.3倍.  相似文献   

Vegetation diversity and its application in sandy desert revegetation on Tibetan Plateau   总被引：4，自引：0，他引：4  

H. Yang  Q. Lu  B. Wu  H. Yang  J. Zhang  Y. Lin 《Journal of Arid Environments》2006,65(4):619-631

The dry and cold Tibetan Plateau is, by its nature, sensitive to desertification, and now human impacts and overexploitation makes things worse. One of the most important things involved in combating desertification is to stabilize mobile sandy land and facilitate revegetation. A study was conducted on shifting sand dunes of Tibetan Plateau to investigate the relationships among sand control, vegetation restoration and diversity dynamics of seed plant species. It was found that a positive correlation lay between sand stabilizing shrubs (Caragana korshinskii and Artemisia ordosica) and Leymus secalinus, a species of dominant and perennial grass in well-restored vegetation, but a negative correlation occurred between those shrubs and Agriophyllum arenarium indicator of shifting dunes. Secondly, sand stabilization facilitated revegetation, and total cover and cover of L. secalinus rose continuously from the beginning of restoration, but diversity indices showed a complex tendency. Based on these results, it was reasoned that on alpine shifting dunes of desertified regions, continual sand drifting caused by gales was the limiting factor for plant to survival. If sand barriers were established, sand drifting would be effectively controlled, then many native plant species could colonize shifting dunes gradually, so the process of revegetation was facilitated.  相似文献   

Interrill erosion in the sloping lands of northern Laos subjected to shifting cultivation     

V. Chaplot  X. Khampaseuth  C. Valentin  Y. Le Bissonnais 《地球表面变化过程与地形》2007,32(3):415-428

In this study our main objective was to quantify water interrill erosion in the sloping lands of Southeast Asia, one of the most bio‐geochemically active regions of the world. Investigations were performed on a typical hillslope of Northern Laos subjected to slash and burn agriculture practiced as shifting cultivation. Situations with different periods of the shifting cultivation cycle (secondary forest, upland rice cultivation following a four‐year fallow period and three‐year continuous upland rice cultivation) and soil orders (Ultisols, Alfisols, Inceptisols) were selected. One metre square micro‐plots were installed to quantify the soil material removed by either detachment of entire soil aggregate or aggregate destruction, and the detached material transported by thin sheet flow, the main mechanisms of interrill erosion. In addition, laboratory tests were carried out to quantify the aggregate destruction in the process of water erosion by slaking, dispersion and mechanical breakdown. The average runoff coefficient (R) evaluated throughout the 2002 rainy season was 30·1 per cent and the interrill erosion was 1413 g m^?2 yr^?1 for sediments and 68 g C m^?2 yr^?1 for soil organic carbon, which was relatively high. Among the mechanisms of interrill water erosion, aggregate destruction was low and mostly caused by mechanical breakdown due to raindrops, thus leading to the conclusion that detachment and further transport by the shallow runoff of macro‐aggregates predominates. R ranged from 23·1 to 35·8 per cent. It decreased with the proportion of mosses on the soil surface and soil surface coverage, and increased with increasing proportion of structural crust, thus confirming previous results. Water erosion varied from 621 to 2433 g m^?2 yr^?1 for sediments and from 31 to 146 g C m^?2 yr^?1 for soil organic carbon, and significantly increased with increasing clay content of the surface horizon, probably due to the formation of easily detachable and transportable sand‐size aggregates, and proportion of macro‐aggregates not embedded in the soil matrix and prone to transport. In addition, water erosion decreased with increasing proportion of structural crusts, probably due to their higher hardness, and when cultivation follows a fallow period rather than after a long period of cultivation due to the greater occurrence of algae on the soil surface, which affords physical protection and greater aggregate stability through binding and gluing. This study based on simultaneous field and laboratory investigations allowed successful identification and quantification of the main erosion mechanisms and controlling factors of interrill erosion, which will give arguments to further set up optimal strategies for sustainable use of the sloping lands of Southeast Asia. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

兼养对雨生红球藻细胞生长的促进作用及藻株差异性   总被引：1，自引：0，他引：1  

龙元薷  刘建国  张立涛 《海洋科学》2014,38(12):1-7

结合叶绿素荧光技术,对比研究了不同雨生红球藻藻株在兼养(光照+乙酸钠)培养过程中细胞生长和光合作用的共性与差异性反应。结果表明:兼养明显提高红球藻细胞密度和比生长速率;乙酸钠不仅为红球藻提供异养的有机碳源,而且还明显导致藻细胞光自养的光合综合性能指数发生改变,兼养对细胞生长促进作用的贡献在前期主要来自于其中的异养部分,而在后期却明显来自于自养部分;兼养对细胞生长的促进作用在藻株之间存在一定差异,不同藻株对乙酸钠的适应能力和最适质量浓度也存在明显差异,藻株H0可适应的乙酸钠质量浓度较高,而藻株H6对乙酸钠需求和适应性相对较低。上述结果意味着规模化培养红球藻过程中,针对不同藻株采用适宜乙酸钠兼养方式可有效缩短培养周期,提高生产效率。  相似文献   

不同适温海洋富油微藻在富碳培养条件下的油脂积累特性研究   总被引：1，自引：0，他引：1  

王帅  郑立  韩笑天  李林  杨佰娟  刘晨光 《海洋学报》2014,36(12):41-52

本实验分别针对3株低温藻株:微拟球藻Nannochloropsis sp.ZL-12、四爿藻Tetraselmis chui ZL-33和小球藻Chlorellasp.ZL-45,3株中温藻株:球等鞭金藻Isochrysis galbana CCMM5001、等鞭金藻Isochrysis sp.CCMM5002和微拟球藻Nannochloropsis sp.CCMM7001,3株高温藻株:微拟球藻Nannochloropsis sp.JN1、绿色巴夫藻Pavlova viridis JN2和海洋小球藻Chlorellasp.JN3,研究了在通入0.03%(空气)、5%、10%3个CO2浓度梯度条件下的生长特性,同时考察了其总酯及中性脂的累积情况。结果显示,富碳培养有利于不同温度条件下9株藻株的生长,除微拟球藻Nannochloropsis sp.CCMM7001最适生长的CO2浓度为5%外,其余8株藻株最适生长的CO2浓度均为10%。在低温和高温条件下,6株海洋富油微藻在通入10%CO2时具有最大生物量产率,在中温条件下球等鞭金藻和等鞭金藻在通入10%CO2时获得最大生物量产率,而微拟球藻在通入5%时获得最大生物量产率,随着CO2浓度的增加,9株藻株的总脂含量和中性脂含量有明显提高。低温和中温藻株的总脂含量高于高温藻株的总脂含量,从中性脂的累积规律来看,9株藻株均在平台期的累积达到最大值,GC-MS分析结果表明,9株微藻适合制备生物柴油的C14~C18系脂肪酸相对含量在不同CO2条件下基本保持不变,维持在90%左右。实验结果显示,所研究的藻株作为富油高固碳优良藻株,具备用于海洋生物质能耦合CO2减排开发的潜力。  相似文献