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1.
A decade of research into electroactive polymer actuators is leading to the exploration of applications. These technologies are not ready to compete with the internal combustion engine and electric motors in high power propulsion systems but are suitable for intermittent or aperiodic applications with moderate cycle life requirements, providing an alternative to solenoids and direct drive electric motors. Polypyrrole, an emerging actuator material, is applied to drive hydrodynamic control surfaces and in particular to change the camber of a foil. The foil is intended for use in the propeller blade of an autonomous underwater vehicle. A scaled prototype is constructed which employs polypyrrole actuators imbedded within the blade itself to vary camber. The kinematics required to generate camber change are demonstrated, with >30/spl deg/ deflections of the trailing edge being observed from both bending bilayer and linear actuator designs. Forces developed in still conditions are five times lower than the 3.5 N estimated to be required to implement variable camber. The observed 70 kJ/m/sup 3/ polypyrrole work density however is more than sufficient to produce the desired actuation from within the limited blade volume, enabling an application that is not feasible using direct drive electric motors. A key challenge with the polypyrrole actuators is to increase force without sacrificing speed of actuation.  相似文献   

2.
Pneumatic muscles have been used for a number of years as actuators in robotic systems, usually for those that mimic human actions. They are most commonly used in systems designed to aid physically handicapped people. This feasibility study reports mechanical testing and modeling results for the Shadow™ artificial muscle pneumatic actuator working in both air and underwater. The static and dynamic tension-contraction measurements were recorded through both the force and contraction relationship test and the dynamic response and time relationship test. A model of the properties of the muscle working in water was derived from the measurements of the tests that can be considered for its feasibility for use in undersea robotics.   相似文献   

3.
Cross-flow ultrafiltration (CFF) is often used to obtain separation and concentration of colloids from bulk natural water samples. Application of the ultrafiltration permeation model allows the quantitative determination of the low molecular weight material (LMW, < 1 kDa) and colloids in bulk dissolved organic matter (DOM) from measurements of time series permeate samples obtained from CFF. Detailed analysis of a Yukon River water sample shows that DOM absorption coefficient and fluorescence follow the permeation model and that the complex spectral optical properties of LMW DOM can be reconstructed from CFF data. A combination of measured and modeled data indicates that the LMW contribution to bulk DOM optical properties obtained from CFF can be grossly underestimated by the use of a low concentration factor (CF, the ratio of initial sample volume to retentate volume). Even at a relatively high CF of 19, optical properties of LMW DOM calculated from measurements of the retentate or integrated permeate would underestimate true values by 5–36%. In the Yukon River sample, LMW dissolved organic carbon represented 26% of the bulk concentration, but only 3–14% of the colored DOM was in the LMW fraction while 31–33% of bulk DOM florescence was due to LMW DOM. The contrasting optical properties of LMW and colloidal DOM support the concept that analysis of bulk DOM absorption and fluorescence properties reveals information about DOM molecular weight.  相似文献   

4.
Fiber reinforced polymer composite deck panels are effectively used in the construction of offshore structures such as pontoons, floating docks, oil drilling platforms, ocean thermal energy conversion (OTEC) systems and harbor structures due to their excellent corrosion and fatigue resistance, high strength to weight ratio and stiffness to weight ratio and less maintenance cost. The main objective of this investigation is to study the load–deflection behavior of glass fiber reinforced polymer (GFRP) composite deck panels under static loading. Three prototype GFRP composite deck panels each with a size of 3000 mm×1000 mm×300 mm were fabricated using hand lay-up process and tested under a factored load of AASHTO HS20/IRC Class A wheeled vehicle. The deck panels were analyzed using the standard FE software, ANSYS. Maximum deflection and strain at factored load, and flexural and shear rigidities were calculated in the FE analysis and compared with the experimental data, and also with the specifications given by the Ohio Department of Transportation (ODOT), USA. From this study, it is concluded that the fabricated GFRP deck panels satisfied the performance criteria specified by ODOT and can be used in berthing structures, bridges in coastal regions, offshore oil platforms, OTEC systems and also in seismic prone areas.  相似文献   

5.
This work has investigated the possible formation of humic and fulvic acids, particularly high molecular weight moieties, in degrading diatom debris. The diatom debris was collected, freshly sedimented, from a well characterized natural field diatom population and allowed to degrade under conditions similar to those found at the sediment-water interface of many marine, organic-rich sediments.Samples of the detritus and overlying water were taken regularly over a period of 4 months and analysed for the presence of humic compounds. In the case of the detrital material, a sequential series of extractions were used. Molecular weight fractionation of the extracted humic material was carried out using Diaflow Ultrafiltration Membranes and two different fractionation methods have been compared. It appears that the choice of method may have an important effect on the determined distribution of the humic material, particularly when humic acid concentrations are low.High molecular weight (> 300 000- > 100 000) humic and fulvic acids were found in all the detrital samples, the content increasing with the period of decomposition. No evidence of any humic material was found in extracts of the living diatoms, the conclusion being that this material had been formed in situ during the degradation of the diatom debris. Most (65–90%) of the humic material was extracted from the detritus using a mild 0·05 m NaOH extraction at room temperature. Fulvic acids comprised approximately 90% of the total 0·05 m NaOH extraction, being composed mainly of either low molecular weight compounds (40–50% < 10000) or high molecular weight compounds (38–48% > 100000). Levels of humic acids were much lower and included a wide range of molecular weight fractions.The relevance of these findings to the possible origin of humic material in certain marine sediments is discussed.  相似文献   

6.
采用动态剪切实验研究了两种有机凝胶类调剖剂强度的剪切恢复性能,通过测定不同条件下凝胶体系的储能模量／耗能模量和相位角的变化,分析了在聚交比一定的条件下,聚合物浓度、温度以及交联剂类型对凝胶剪切后强度恢复性能的影响。结果表明：在一定的应力下,随着聚合物浓度的增加,凝胶的成交点频率向低频移动;相同聚合物浓度和放置时间下,有机金属交联型调剖剂的强度大于有机酚醛交联型调剖剂;同种凝胶体系,在聚交比一定的条件下,浓度高时体系强度的剪切恢复性能好;对于两种凝胶体系来说,温度升高使得体系的剪切恢复性能下降;有机金属交联的凝胶体系剪切恢复能力高于有机树脂交联的凝胶体系。  相似文献   

7.
The presence and nature of high molecular weight organic matter in seawater was critically reviewed and its biogeochemical cycle was discussed.Organic matter that passes through a filter of 0.5–1 μm pore size is called dissolved and that which does not pass through such a filter is defined as particulate. The size of colloidal particles ranges from 0.001 to 1 μm, and therefore, they are included in the dissolved fraction having high molecular weight.High molecular weight organic matter greater than 100,000 molecular weight was found in the seawater of Tokyo Bay. The values ranged from 0.1 to 1.5 mgC/l, and accounted for 8–45% of the total dissolved organic matter.Decomposition experiments on dissolved organic matter showed that macromolecular organic matter is refractory to bacterial attack. However, macromolecular organic materials tend to aggregate or adsorb on small particles to a sufficient size for precipitation. Organic aggregates thus formed sink to the bottom of the sea and bioelements included in them are removed from water column. High molecular weight organic materials are, therefore, considered to play an important role in transportation and distribution of matter in seawater.In order to elucidate the chemical and biological properties of macromolecular organic matter, concentration and isolation of this material are important, using methods such as adsorption on organic adsorbents or ultrafiltration.  相似文献   

8.
Abstract

The coastal area of Fujian Province in China is rich in both sea sand and sea mud. However, sea sand and sea mud are both unsuitable as direct filler materials for seawalls due to their poor geotechnical properties. To turn waste into a useful product, a mixture composed of sea sand and sea mud is proposed as a filler material for seawalls. The strength, compressibility, moisture sensitivity, and permeability of the mixture are investigated experimentally. The results show that when the mass ratio of sea sand to limed sea mud is 1:2, the mixture exhibits good engineering properties and can serve as a filler material for general engineering purposes in dry environments. To apply the mixture under saturated conditions, both cement and lime are used to improve the engineering properties of the mixture. The improvements in the properties increase with both the binding agent content and the curing time, and the improvement with the addition of cement to the mixture is better than that with the addition of lime. The engineering requirements of seawalls can be satisfied by adding cement, and the cement content can be chosen according to considerations of the construction period and engineering costs.  相似文献   

9.
In this work, the influence of a small-molecule material, tris(8-hydroxyquinoline) aluminum (Alq3), on bulk heterojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). By doping Alq3 into MEH-PPV:PCBM solution, the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq3 to MEH-PPV, which probably induces the increase of photocurrent generated by excitons dissociation. However, the low carrier mobility of Alq3 is detrimental to the efficient charge transport, thereby blocking the charge collection by the respective electrodes. The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs. For the case of 5 wt.% Alq3 doping, the device performance is deteriorated rather than improved as compared with that of the undoped device. On the other hand, we adopt Alq3 as a buffer layer instead of commonly used LiF. All the photovoltaic parameters are improved, yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer. Even for the 5 wt.% Alq3 doped device, the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq3. The performance deterioration of Alq3-doped devices can be explained by the low solubility of Alq3, which probably deteriorates the bicontinuous D-A network morphology; while the performance improvement of the devices with Alq_3 as a buffer layer is attributed to the increased light harvesting, as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq3 compared with that of MEH-PPV.  相似文献   

10.
利用高效凝胶渗透色谱法(HPGPC)和明胶比浊法研究了海洋硫酸多糖916在溶菌酶和胰蛋白酶作用下的稳定性，分别考察了酶作用下916的重均分子量、分子量分布系数和游离硫酸根含量的变化。结果表明：在所选定的实验条件下，916的重均分子量、分子量分布系数和游离硫酸根含量均未发生显著变化，表明在所选择的实验条件下916对溶菌酶和胰蛋白酶是稳定的。  相似文献   

11.
Seismic reflection profiling demonstrates the importance of mass movement in the north-central California Borderland. Bulk properties of surficial hemipelagic sediments in the Santa Barbara, Santa Cruz, and San Nicolas basins show that different types of mass-transported sediments have different properties, although their general sedimentologic characteristics are very similar. Slump deposits have moderate water contents (48% wet weight basis), high plasticity indices (46%), and moderate activities (1.6). For debris flows these values are low: 28%, 5%, and 0.3, respectively, and for other types (liquefied flow, mudflows, and turbidities) the values are high: 54 to 63%, 49 to 58%, and 1.2 to 1.5, respectively.  相似文献   

12.
A numerical solution was derived to determine wave field in a converging channel bounded by rubble-mound jetties. The solution was achieved by applying boundary element method. The model was applied to analyze the effect of channel convergence, the cross-section of the jetties and their physical and damping properties on wave field in the channel. The study reveals numerous non-intuitive results specific for jetted and convergent channels. The analysis shows that wave reflection is usually low and is of secondary practical importance. Wave transmission strongly depends on the channel geometry and transmitted waves may be higher than incident waves, despite reflection and damping processes. Moreover, wave transmission depends on physical and damping properties of rubble jetties and the results show that wave transmission may increase with the increasing damping properties of jetties, which is a non-intuitive feature of wave fields in jetted channels. The analysis reveals several novel results of practical importance. It is shown that the rubble-mound jetties should be constructed from the material of high porosity, which ensures low transmission. More attention should be devoted to hydraulic properties of porous materials. It is recommended to use the material of moderate damping properties. The material of high damping properties often increases the wave transmission. It is possible, by a selection of rubble-mound material, to obtain lower transmission level for steep waves than for waves of moderate steepness. A series of laboratory experiments were conducted in the wave flume to verify the theoretical results. The comparisons show that theoretical results are in fairly good agreement with experimental data.  相似文献   

13.
An engineering geological study was undertaken to determine the engineering properties, and mineralogy of ultrasoft soils (USS) obtained from a nearshore mine tailings sedimentation pond. The USS is a high plasticity clay of high water content and low shear strength. Marine bathymetric and seismic reflection surveys were undertaken in the sedimentation pond located in the foreshore of the Eastern part of the Republic of Singapore. Specimens collected from the bore holes were tested to determine the engineering and mineralogy properties of the USS. Field vane shear tests were undertaken just adjacent to the sampling bore holes to determine the shear strength properties of the USS. The mineralogical properties of the USS were determined using X-ray diffraction and scanning electron microscope techniques. The USS is under consolidated soil where higher density and lower water content were found at deeper depth. The USS had three different compression indices under three log cycles of effective stress between 1–10, 10–100, and 100–1,000 kPa. This is the main characteristic of USS, which diverts from reconstituted soil. The outcome of this research is fundamental for understanding the compression behavior and subsequently the development of a constitutive model for USS, typical found in sedimentary pond.  相似文献   

14.
浙闽近岸与南黄海中部沉积物物理力学性质的差异性分析   总被引：1，自引：0，他引：1  
本文对浙闽近岸和南黄海中部泥质区沉积物的物理力学性质,分别从基本物理性质、水理性质及力学性质进行对比分析,发现两个区域沉积物均以淤泥为主,含水率与密度、压缩系数与压缩模量均呈良好的幂函数负相关性,液限与塑限呈良好的幂函数正相关性,含水率与孔隙比呈较好的线性正相关,十字板剪切强度与微型贯入阻力呈较好的多项式函数关系。总体来说,南黄海中部泥质区沉积物相对于浙闽近岸泥质区沉积物具有含水率高、孔隙比大、密度小、塑性高,压缩性大,抗剪强度低等特征。从地形特征、物质来源、水动力条件、沉积速率和物质组成等方面进行两个区域沉积物物理力学性质差异性的成因分析。结果显示,与浙闽近岸相比,南黄海中部离陆较远、地势低洼、水动力条件较弱,能够扩散至此的物质较少并以极细的粘粒物质为主,沉积物中的蒙脱石和有机质含量高。这些因素使得南黄海中部沉积物的含水率高,塑性大,密度低,强度低。  相似文献   

15.
针对从中国南海北部海域某深水区采集的表层沉积物柱状样,进行了沉积物微观结构的扫描电镜测试、矿物成分的X射线衍射试验以及物理和力学性质的统计学分析。结果表明,该深水区海底表层沉积物通常为有机质软黏土,具有高含水率、低密度、高孔隙比、高液限、高可塑性、低强度等典型特征。统计分析和假设检验表明,沉积物的物理和力学指标均呈现变异性,且后者普遍高于前者。相对密度、含水率、液塑限和塑性指数服从正态分布;容重、碳酸盐含量、不排水抗剪强度、灵敏度接近假设检验结果,近似服从正态分布。研究结果可为深水海底工程结构设计的海床土性参数取值提供参考。  相似文献   

16.
大庆油田萨北开发区二类油层二元复合驱技术研究   总被引：1，自引：0，他引：1  
大庆油田萨北开发区二类油层具有渗透率低和非均质严重等特点,水驱开采效果差。对4种不同表面活性剂二元复合体系黏度、界面张力及其稳定性进行了评价,优选出性能好的“炼化石油磺酸盐／聚合物”二元复合体系。还对该体系的驱油效果、注入参数、黏度和段塞组合等进行了实验研究,结果表明“炼化石油磺酸盐／聚合物”二元复合体系具有较好增油效果。“整体”段塞和段塞黏度排序“低中高”注入方式的增油效果较好,调剖愈早,增油效果愈好。推荐矿场采用的注入方式为：先注入0．05～0．08PV的Cr^3＋聚合物凝胶段塞,再转注0．33～0．49PV二元复合体系（CP=1200mg／L,CS=0．2％）。在上述配方组成和段塞组合条件下,比水驱提高采收率15％以上。  相似文献   

17.
The unique material properties of volcanic soils may cause stability problems within the soil. However, few studies have examined the composition and engineering characteristics of volcanic soils below sea level. The objective of this study is to investigate the engineering properties of volcanic soils sampled from Ulleung Island. For the volcanic soils, the index properties, particle geometry, and mineralogy are analyzed in the laboratory. An oedometer cell incorporated with bender elements is used to measure the small-strain stiffness and compressibility of the volcanic soils. To obtain the large strain strength parameter and hydraulic conductivity of the volcanic soils, direct shear tests, and constant head permeability tests are performed. The experimental results show that the basic index properties of volcanic soils sampled from Ulleung Island are very similar to the values of previously published reference data: poorly graded with a median grain size, very low fine fraction, and slightly high specific gravity. In addition, the particle surface texture features and elementary analysis indicates a dark grain color, small pits or holes in the grain, and relatively low SiO2 and high Fe2O3 contents. The friction angle of the volcanic soils depends on the relative density, and the hydraulic conductivity varies according to e3/(1 + e) and D102. The characterization of the electrical properties in Ulleung Island needs to be conducted with caution due to the high Fe2O3 content in the volcanic soils.  相似文献   

18.
玻纤增强柔性管作为一种新型海底油气输送管道,具有比强度高、柔度大和抗腐蚀性强等特点,因此在深海油气开发中具有非常广阔的应用前景。玻纤增强柔性管主要由内衬层、增强层和外保护层组成,其中增强层的等效模拟是玻纤增强柔性管设计成功与否的关键。根据玻纤增强柔性管的结构特征和材料特性,选取了四种不同的等效简化模型,对比研究了玻纤增强柔性管在轴向拉压荷载、弯曲荷载以及内压荷载作用下的力学性能。将不同简化模型的计算结果与相应的试验数据进行对比,进行等效模型的优选。研究结果表明,在内压载荷和弯曲载荷作用下,基于Halpin-Tsai模型数值结果与试验结果最为接近。在轴向载荷作用下,采用分离式模型或回形模型计算精度更高,若材料达到屈服状态时,则建议采用分离式模型进行模拟。  相似文献   

19.
Unbonded flexible pipe is one of the important pieces of equipment in floating production systems for transport of oil and gas between floaters and subsea wells located in deep water. To assure safety over a long-term service period, analysis of fatigue behavior under alternative bending is a key requirement. An analytical model for prediction of bending behavior is essential for understanding the mechanism of the local stress distribution in the helical wires of the tension armor layers under alternative curvatures and rapid estimation of the service life of flexible pipes for designers in engineering practice. In this paper, seven analytical models available in the literature are selected and summarized. Although the experimental results reported in the literature are limited, a three-dimensional finite element model is developed for investigation of the seven models, and the validity and limitations of these models for different structural parameters of helical wire are discussed, i.e., the width-thickness ratio of the wire section and helical angle. The analytical model based on spring theory resulted in a satisfactory estimation of bending stress for most cases and is recommended as a tool for the basic design of the helical armor wire structures in flexible pipes.  相似文献   

20.
Matched-field methods concern estimation of source locations and/or ocean environmental parameters by exploiting full wave modeling of acoustic waveguide propagation. Typical estimation performance demonstrates two fundamental limitations. First, sidelobe ambiguities dominate the estimation at low signal-to-noise ratio (SNR), leading to a threshold performance behavior. Second, most matched-field algorithms show a strong sensitivity to environmental/system mismatch, introducing biased estimates at high SNR. In this paper, some theoretical developments on matched-field performance analysis are summarized, including Bayesian performance bounds and probabilistic ambiguity analysis, both incorporating environmental/system uncertainty/mismatch. Performance analysis is then implemented for source localization in a typical shallow water environment chosen from the Shallow Water Evaluation Cell Experiments (SWellEX). The performance predictions describe the simulations of the maximum-likelihood estimator (MLE) well, including the mean-square error (MSE) in all SNR regions as well as the bias at high SNR. The threshold SNR and bias predictions are also validated through SWellEX experimental data processing. The results suggest the current environmental, acoustic, and statistical modeling has developed to such a level that the optimum theoretical matched-field performance can be achieved in a well-controlled experiment.  相似文献   

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