Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

On-line voltammetric monitoring of dissolved Cu and Ni in the Gulf of Cadiz, south-west Spain

Geochemical processes in estuarine and coastal waters often occur on temporally and spatially small scales, resulting in variability of metal speciation and dissolved concentrations. Thus, surveys, which are aimed to improve our understanding of metal behaviour in such systems, benefit from high-resolution, interactive sampling campaigns. The present paper discusses a high-resolution approach to coastal monitoring, with the application of an automated voltammetric metal analyser for on-line measurements of dissolved trace metals in the Gulf of Cadiz, south-west Spain. This coastal sea receives metal-rich inputs from a metalliferous mining area, mainly via the Huelva estuary. On-line measurements of dissolved Cu, Zn, Ni and Co were carried out on-board ship during an eight-day sampling campaign in the study area in June 1997. A pumping system operated continuously underway and provided sampled water from a depth of ca. 4 m. Total dissolved metal concentrations measured on-line in the Gulf of Cadiz ranged between <5 nM Cu (<3 nM Ni) ca. 50 km off-shore and 60–90 nM Cu (5–13 nM Ni) in the vicinity of the Huelva estuary. The survey revealed steep gradients and strong tidal variability in the dissolved metal plume extending from the Huelva estuary into the Gulf of Cadiz. Further on-line measurements were carried out with the automatic metal monitor from the bank of the Odiel estuary over a full tidal cycle, at dissolved metal concentrations in the μM range. The application confirmed the suitability of the automated metal monitor for coastal sampling, and demonstrated its adaptability to a wide range of environmental conditions in the dynamic waters of estuaries and coastal seas. The near-real time acquisition of dissolved metal concentrations at high resolution enabled an interactive sampling campaign and therefore the close investigation of tidal variability in the development of the Huelva estuary metal plume.

Combined Effects of Hot Curing Conditions and Reaction Heat on Rubber Vulcanization Efficiency and Vulcanizate Uniformity

A mathematical model of the chemical kinetics of silicone rubber Vulcanization is developed, with the thermal effects being computed using the increment method, and the hot Vulcanization process estimated with the finite element method. The results show that the reaction heat of rubber vulcanization is important for energy saving, and that a proper curing medium temperature is important when considering both vulcanization efficiency and vulcanizate uniformity. The results also indicate that increases in the forced convective heat transfer coefficient have no significant effect above a certain level. The validity of the numerical model is indirectly proven by comparison with existing data.

Chain propagation kinetics on melt grafting reaction

Graft copolymerization in the molten state is of fundamental importance as a probe of chemical modification and reactive compatibilization. However, few grafting kinetic studies on reactive extrusion have been carried out because of the inherent difficulties, as expected. In this work, we have studied chain propagation kinetics on melt grafting using pre-irradiated linear low density polyethylene (LLDPE) and three monomers, acrylic acid (AA), methacrylic acid (MAA), and methyl methacrylate (MMA), as the model system. We measured the apparent chain propagation rate coefficients of grafting (k(p,g)) and homopolymerization (k(p,h)) at an initial stage for the melt grafting by FT-IR spectroscopy and electron spin resonance spectroscopy. It was observed that the convective mixing affected the rate coefficients. The magnitude of k(p,h) and k(p,g) were in the same order, but k(p,h) was slightly larger than k(p,g) The k(p,g) of the three grafting systems increased in the order: LLDPE/MMA < LLDPE/MAA < LLDPE/AA. These results are explained in terms of phase separation, solubility, and inherent reactivity of the monomer.

珠江口冲淡水扩展变化及机制研究

本文利用1978~1984年南海北部的逐月调查资料，分析珠江口冲淡水的扩展特征及其扩展变化。资料分析显示，在风及入海径流量等因素的影响下，珠江口冲淡水的扩展具有季节变化和年际变化。夏季珠江口冲淡水在河口外的扩展形态可划分出四种扩展形态，包括向海扩展型、粤东扩展型、粤西扩展型及似对称扩展型。同时根据珠江入海月平均流量与冲淡水扩展面积的相关分析可知，珠江口入海流量的大小决定了河口冲淡水在口外的扩展大小，流量的季节变化决定了冲淡水扩展大小的季节变化，而流量的年变化影响着冲淡水扩展的年变化。根据海域风场与冲淡水扩展形态的对比分析表明，风的季节变化和日变化影响着冲淡水扩展方向的变化，风场影响控制了珠江口冲淡水不同的扩展形态。夏季在E~SE向风的作用下，珠江口冲淡水扩展表现为粤西扩展型；而珠江口冲淡水扩展为粤东扩展型时，南海北部的月平均风场为SSW~SW向风。冲淡水扩展倾向于向海扩展型时，海域吹S风为主，且风速较小。 在资料分析的基础上，本文利用ECOM模式对冲淡水扩展的动力机制进行进一步探讨。模式试验结果表明，理想情况下，珠江河口冲淡水向外海突出，冲淡水扩展形态为向海扩展型；珠江入海流量的大小决定冲淡水扩展范围的大小，入海流量大，冲淡水扩展的范围大。不同方向的盛行风是珠江河口冲淡水扩展形态和动力的决定因子。在东北风、东风和东南风的作用下，河口冲淡水形态为粤西扩展型，风持续时间长，冲淡水扩展形态表现为极端粤西扩展型。在西南季风的影响下，河口冲淡水的扩展方向明显相反，冲淡水扩展形态表现为典型的粤东向离岸扩展型。S、SSE风约束了河口冲淡水向口外的扩展，冲淡水扩展形态表现为轻微的粤东向扩展。在偏E风与偏S风交替作用下，表层冲淡水在一定时刻会出现似对称形态。 在对南海北部潮汐潮流研究的基础上，本文进一步模拟了潮汐潮流对珠江口冲淡水扩展的影响。模型试验结果显示，珠江口周期性的潮流运动所造成的低盐水的净水平输运很小，其主要作用更多体现在对冲淡水与周围高盐水体的混合上，在很大程度上限制了低盐水向海或向两侧方向的扩展。 在模型试验的基础上，本文进一步模拟了在多种动力因子作用下夏季珠江口冲淡水的扩展演化规律。模式计算表明，珠江口冲淡水扩展形态的演变受多种因素影响，而风是其中影响冲淡水扩展演化最重要的因子。 将考虑斜压效应和不考虑斜压效应的模式计算结果进行比较，结果显示珠江口冲淡水扩展对粤东、粤西沿岸流的形成和发育影响明显。夏季珠江口冲淡水的扩展可促进粤东沿岸流的进一步发育，粤东沿岸流强化。而影响粤西沿岸流的主要因子是风应力和珠江口冲淡水的西向扩展，无风或弱风时，粤西西向流主要是由于冲淡水与周围水体的压力差所产生的密度流经过地转调整作用形成的；否则是SE~NE风与珠江口冲淡水的西向扩展同时影响粤西沿岸流的西向流动。

Tectonics in the northwestern West Philippine basin

The West Philippine basin (WPB) is a currently inactive marginal basin belonging to Philippine Sea plate, which has a complex formation history and various crust structures. Based on gravity, magnetic and seismic data, the tectonics in West Philippine basin is characterized by amagma spreading stage and strike slip fractures. NNE trending Okinawa-Luzon fracture zone is a large fracture zone with apparent geomorphology and shows a right-handed movement. The results of joint gravity-magnetic-seismic inversion suggest that the Okinawa-Luzon fracture zone has intensive deformation and is a transform fault. Western existence of the NW trending fractures under Ryukyu Islands Arc is the main cause of the differences between south and north Okinawa Trough. The Urdaneta plateau is not a remained arc, but remnant of mantle plume although its lava chemistry is similar to oceanic island basalt (OIB).

Major element, trace element, and Sr, Nd and Pb isotope studies of Cenozoic basalts from the South China Sea

The whole rock K-Ar ages of basalts from the South China Sea basin vary from 3.8 to 7.9 Ma, which suggest that intra-plate volcanism after the cessation of spreading of the South China Sea (SCS) is comparable to that in adjacent regions around the SCS, i.e., Leiqiong Peninsula, northern margin of the SCS, Indochina block, and so on. Based on detailed petrographic studies, we selected many fresh basaltic rocks and measured their major element, trace element, and Sr-Nd-Pb isotope compositions. Geochemical characteristics of major element and trace element show that these basaltic rocks belong to alkali basalt magma series, and are similar to OIB-type basalt. The extent of partial melting of mantle rock in source region is very low, and magma may experience crystallization differentiation and cumulation during the ascent to or storing in the high-level magma chamber. Sr-Nd-Pb isotopic data of these basaltic rocks imply an inhomogeneous mantle below the South China Sea. The nature of magma origin has a two end-member mixing model, one is EM2 (Enriched Mantle 2) which may be originated from mantle plume, the other is DMM (Depleted MORB Mantle). Pb isotopic characteristics show the Dupal anomaly in the South China Sea, and combined with newly found Dupal anomaly at Gakkel ridge in Arctic Ocean, this implies that Dupal anomaly is not only limited to South Hemisphere. In variation diagrams among Sr, Nd and Pb, the origin nature of mantle below the SCS is similar to those below Leiqiong peninsula, northern margin of the SCS and Indochina peninsula, and is different from those below north and northeast China. This study provides geochemical constraints on Hainan mantle plume.

Formation of Fe-oxyhydroxides from the East Pacific Rise near latitude 13 degrees N: Evidence from mineralogical and geochemical data

The mineralogical and geochemical characteristics of Fe-oxyhydroxide samples from one dredge station (long. 103 degrees 54.48'W, lat. 12 degrees 42.30'N, water depth 2655 m) on the East Pacific Rise near lat 13 degrees N were analyzed by XRD, ICP-AES, and ICP-MS. Most Fe-oxyhydroxides are amorphous, with a few sphalerite microlites. In comparison with Fe-oxyhydroxides from other fields, the variable ranges in the chemical composition of Fe-oxyhydroxide samples are very narrow; their Fe, Si, and Mn contents were 39.90%, 8.92%, and 1.59%, respectively; they have high Cu (0.88%-1.85%) and Co (65x10(-6)-704x10(-6)) contents, and contain Co+Cu+Zn+Ni > 1.01%. The trace-element (As, Co, Ni, Cu, Zn, Ba, Sr) and major-element (Fe, Ca, Al, Mg) contents of these samples are in the range of hydrothermal sulfide from the East Pacific Rise near 13 degrees N, reflecting that this type of Fe-oxyhydroxide constitutes a secondary oxidation product of hydrothermal sulfide. The Fe-oxyhydroxide samples from one dredge station on the East Pacific Rise near 13 degrees N are lower in Sigma REE (5.44x10(-6)-17.01x10(-6)), with a distinct negative Ce anomaly (0.12-0.28). The Fe-oxyhydroxide samples have similar chondrite-normalized rare-earth-element (REE) patterns to that of seawater, and they are very different from the REE composition characteristics of hydrothermal plume particles and hydrothermal fluids, showing that the REEs of Fe-oxyhydroxide are a major constituent of seawater and that the Fe-oxyhydroxides can become a sink of REE from seawater. The quick settling of hydrothermal plume particles resulted in the lower REE content and higher Mn content of these Fe-oxyhydroxides, which are captured in part of the V and P from seawater by adsorption. The Fe-oxyhydroxides from one dredge station on the East Pacific Rise near 13 degrees N were formed by secondary oxidation in a low temperature, oxygenated environment. In comparison with the elemental (Zn, Cd, Pb, Fe, Co, Cu) average content of hydrothermal sulfide samples from the East Pacific Rise near 13 degrees N, the Zn, Cd, and Pb contents of the Fe-oxyhydroxides are lower, and their Fe, Co, and Cu contents are higher.

Mineral chemistry and its genetic significance of olivine in Cenozoic basalts from the South China Sea

We dredged lots of Cenozoic basalts from areas covered from the northern sub-slope to the southern sub- slope of the South China Sea. Based on the study on mineral chemistry of clinopyroxenes in these Cenozoic hasalts, this paper indicates that pyroxenes are mostly enstatite and a few of augite, sahlite and Ca-rich pyroxene. Pyroxene microlite has higher content in, Ca, Ti and Fe than pyroxene phenocryst, it may reflect that the evolution trend of host magma of pyroxene is coincidence with that of alkali rock series. The depth of magma chambers which calculated from equilibrium temperatures and pressures between clinopyroxene and melt are as follows, that of magma of tephrite is about 49km, that of magma of trachybasalt is about 25km, and that of magma of basalt is about 15km. Correspondingly, Equilibrium temperatures( K) of three types rocks mentioned above gradually decrease from 1535 1498 to 1429 to 1369. By using discriminant plot which developed from pyroxene and alkali discriminant diagram of host rock, Cenozoic basalt from the South China Sea belongs to intraplate alkali basalt. The results suggest that alkali basalt series in the study area may be the products of continuous evolution of mantle plume, which result from some physical and chemistry process including partial melting and fractional crystallization of mantle plume during the course of its ascent to the surface.

Cross-shelf circulation in the Yellow and East China Seas indicated by MODIS satellite observations

Ocean color and sea surface temperature data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite are used to study the cross-shelf circulation and transport of suspended sediments in the Yellow and the East China Seas. The ocean color images show a significant turbid water plume extending in the southeast direction from the Subei coasts of China to the shelf edge south of Cheju during fall-winter, suggesting significant cross-shelf currents in the Yellow Sea/East China Sea in winter. The currents transport suspended sediments from the area of the old Huanghe mouth into the Okinawa Trough. Part of the turbid plume joins the Yellow Sea Warm Current to enter the Yellow Sea trough in winter. The satellite images suggest that the time scales of cross-shelf transport and surface-to-subsurface descending of the suspended sediments are a few weeks. The turbid plume grows in fall, reaches its maximum expansion and intensity in winter-spring, and subsides in late spring. In summer, the plume becomes coastally trapped. Substantial interannual variations of the intensity and coverage of the turbid plume are indicated by the observations. In comparison, the Changjiang Diluted Water in summer only transports a small amount of the Changjiang suspended sediment to the outer shelf south of Cheju, which does not enter the Yellow Sea owing to the weak intrusion of the Yellow Sea Warm Current in summer. The dynamics of the cross-shelf circulation in the Yellow Sea in winter are hypothesized to be associated with (1) the convergence of the Yellow Sea Coastal Current and the Taiwan Warm Current off the Changjiang mouth and (2) the time-dependent forcing of the northerly wind bursts that drives the intrusion of the Yellow Sea Warm Current. (C) 2007 Elsevier B.V. All rights reserved.

Evolution of freshwater plumes and salinity fronts in the northern Bay of Bengal

[1] The evolution of freshwater plumes and the associated salinity fronts in the northern Bay of Bengal ( henceforth the bay) is studied using rotated empirical orthogonal function (REOF) analysis and extended associate pattern analysis (EAPA). The results show that sea surface salinity distribution is featured by eastern-bay and western-bay plumes in the northern bay during different seasons. The western-bay plume begins in early July, peaks in late August, and then turns into a bay-shaped plume with the two plumes in either side of the bay, which peaks in late October. The southward extension of the western-bay plume can be explained by the southwestward geostrophic flow associated with the cyclonic gyre in the northern bay, which counters the northeastward Ekman drift driven by wind stress. The offshore expansion of the western-bay plume is induced by the offshore Ekman drift which also produces a salinity front near the east coast of India. The bay-shaped plume appears when the cyclonic gyre shifts westward and a weak anticyclonic gyre occupies the northeastern bay. As the season advances, the western part of the bay-shaped plume decays while the eastern part persists until the following June, which is believed to be associated with the anticyclonic gyre in the northern bay. The evolution of the plumes except the eastern part of the bay-shaped plume in fall can be partly explained by the seasonal variation of mass transport associated with the Sverdrup balance. The fact that the western-bay (eastern-bay) plume appears when surface freshwater flux in the northeastern bay increases ( decreases) dramatically suggests that the plumes are not produced directly by surface freshwater flux. River discharge seems to be the freshwater source for the plumes and has little to do with the evolution of the plumes.

东太平洋海隆13°N附近含金属沉积物中的有机碳氮研究

本文根据热液活动对海底沉积环境影响的程度，将海底沉积环境划分为三个部分：热液直接作用区（硫化物分布区），热液间接作用区（含金属沉积物区），正常沉积区。东太平洋海隆13°N附近所取得的三个沉积物柱状样(E271、E272、E53)属于含金属沉积物区，以它们为研究对象（E271和E272是重点研究对象），进行了粒度、粘土矿物、有机碳氮和无机碳分析，并结合已有的测年数据和金属元素含量数据，对含金属沉积物中的有机碳氮进行了系统的讨论。 沉积物无机组分的物源分析表明，沉积物中富含铁锰的组分主要是非晶质或结晶程度较差的铁锰氧化物和氢氧化物。来自于火山灰蚀变的富铁蒙脱石也有一定的贡献，但是含量太少。铁锰氧化物或氧氧化物倾向于集中在细粒的物质中。铁锰含量自下而上的递增趋势反映了热液活动程度增强的趋势。 三个站位沉积物中有机碳的含量都很高，E271、E272 有机碳含量在0.9%-1.5%之间，而E53含量则相对更高，最高可达4.6%。E271、E272自下而上有递增的趋势，它与铁锰的含量有一定的相关性，可能有机质与铁锰之间存在某种联系。有机碳的沉积通量很低，E271上层为4.06mg/ka•cm2 ，下层仅为0.84mg/ ka•cm2。因此沉积物中高有机碳含量显示的高生产力是一种假像，并不能代表古海水表层生产力很高。 C/N值在三个站位的变化情况各有不同。按照常规的把有机质来源分为海洋表层生物与陆源有机碳来源，那么E271和E53站位总体上水生有机碳在总有机碳中居主要成分。E272上层是海洋生物来源占优，下层是陆源生物占优。但是根据热液plume存在细菌和TEP的特性，应该考虑沉积物中有机质是表层生物源和热液影响的生物源。经过假设计算，认为热液影响的生物有机碳源受到热液柱扩散形态的影响，且与热液活动的稳定性有关。因此两相比较，认为该研究区，有机质来源应该选择表生有机碳与受热液影响生物有机碳为两个端元组分。受热液生物影响的程度为E272>E271>E53。 在E272站位沉积物中发现的一些细菌种类与热液喷口区的嗜热细菌相似程度很高，它们可能是随着Plume飘移而迁移，并沉降到沉积物中。它们的存在对有机碳的含量和组成将会产生影响。这是一个热液生物影响沉积物有机碳的直观的证据。 通过Fe、Mn、Al 含量随深度变化的趋势，推断出碳酸钙自下而上减小不是因为热液组份的加入对其含量稀释而成的，应该是沉积环境的改变，导致其溶解度增加所致。 在研究过程中，还对沉积物中有机碳的测定方法进行了探讨，鉴于不同方法之间带来的有机碳数据上的误差，建议建立一种标准的测试方法，便于有机碳数据的比较。计算沉积速率和沉积通量时，对E271用含水量进行了去压实校正。根据计算，当含水量变化很大时，去压实作用是有必要的。

Close coupling between phytoplankton growth and microzooplankton grazing in the western South China Sea

We conducted 28 dilution experiments during August-September 2007 to investigate the coupling of growth and microzooplankton grazing rates among ultraphytoplankton populations and the phytoplankton community and their responses to habitat variability (open-ocean oligotrophy, eddy-induced upwelling, and the Mekong River plume) in the western South China Sea. At the community level, standing stocks, growth, and grazing rates were strongly and positively correlated, and were related to the higher abundance of larger phytoplankton cells (diatoms) at stations with elevated chlorophyll concentration. Phytoplankton growth rates were highest (> 2 d(-1)) within an eastward offshore jet at 13 degrees N and at a station influenced by the river plume. Among ultraphytoplankton populations, Prochlorococcus dominated the more oceanic and oligotrophic stations characterized by generally lower biomass and phytoplankton community growth, whereas Synechococcus became more important in mesotrophic areas (eddies, offshore jet, and river plume). The shift to Synechococcus dominance reflected, in part, its higher growth rates (0.87 +/- 0.45 d(-1)) compared to Prochlorococcus (0.65 +/- 0.29 d(-1)) or picophytoeukaryotes (0.54 +/- 0.50 d(-1)). However, close coupling of microbial mortality rates via common predators is seen to play a major role in driving the dominance transition as a replacement of Prochlorococcus, rather than an overprinting of its steady-state standing stock.

Phytoplankton biomass size structure and its regulation in the Southern Yellow Sea (China): Seasonal variability

Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters. as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006-2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 142 and 1.27 mg m(-3), respectively. Conversely, in the winter and spring. the average Chl a levels were only 098 and 0.99 mg m(-3) Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the Surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients. temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions. hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton. (C) 2009 Elsevier Ltd. All rights reserved.