44 resultados para Bezier patches
Resumo:
Porphyra katadae Miura var. hemiphylla Tseng et T. J. Chang, a species distributed around the Liaodong and Shandong Peninsulas of China, produces gametophytes from late winter to early spring. These are monoecious with male and female reproductive tissues in distinct halves or sectors. Vegetative tissues from sectors expected to differentiate into sexual tissue were cultured in the laboratory. Male and female reproductive organs, as well as conchocelis and blades, were differentiated from these tissues. The male and female reproductive tissues were in patches and mixed on the cultured tissue pieces. This was quite different from the wild-type sectored individuals. The F-1 conchospore germlings also produced monospores, carposporangia, spermatangia and conchocelis. These carposporangia and spermatangia were in patches and were mixed on the F-1 fronds. The results imply that P. katadae var. hemiphylla is possibly sex-differentiated rather than sex-determined. This is the first report of such a dimorphic life history in the genus Porphyra.
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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.
Resumo:
The bottom sediment types in the Bohai Sea, Yellow Sea and East China Sea (BYECS) are diversified, and their distribution pattern is very complicated. However, the bottom sediment types can be simplified to be sandy sediment, clayey sediment and mixed sediment, which comprise the complicated distribution pattern of bottom sediment in the BYECS. The continental shelves of the BYECS are broad, with shallow water depths and tidal currents which are permanent and dominate the marine dynamics in the BYECS. Based on numerical simulation of tidal elevations and currents in the BYECS, the rates of suspended load transport and bed load transport during a single tidal cycle for sediments of eight different grain size ranges are calculated. The results show that any sediment, whose threshold velocity is less than that of tidal current, has the same transport trend. Suspended load transport rare, bed load transport rate, and the ratio of the former to the latter decrease with grain size becoming coarser and coarser. The erosion/accretion patterns of sediments with different grain sizes are determined by the sediment transport rate divergences, and the results show that the patterns are the same for sediments with different grain sizes. Three main bottom sediment types, i.e. sandy sediment mainly composed of fine sand, clayey sediment mainly composed of silty clay, and mixed sediment mainly composed of fine sand, silt, and clay, are obtained by computation. The three bottom sediment types and their distribution pattern are consistent not only with sediment transport field and the sea bed erosion/accretion pattern obtained by simulation, but also with field data of bottom sediment types and divisions. In the BYECS, sand ridges form mainly in the areas with strong rectilinear tidal currents, sand sheets form mainly in the areas dominated by strong rotatory tidal currents, and clayey sediments, i.e. mud patches, form mainly in the areas with weak tidal currents. Hence, not only the sandy sediments but also the clayey sediments in the BYECS are formed under the control of the whole tidal current field of the BYECS. The three main bottom sediment types are not isolated respectively-in fact, they constitute a whole tidal depositional system. Under the condition with no cyclonic cold eddy, the clayey sediments in the BYECS can form in weak tidal current environments. Therefore, a cold eddy is not necessary for the deposition of clayey sediments in the BYECS. (C) 2000 Academic Press.
Resumo:
A three-dimensional (3-D) coupled physical and biological model was used to investigate the physical processes and their influence on the ecosystem dynamics of the Bohai Sea of China. The physical processes include M-2 tide, time - varying wind forcing and river discharge. Wind records from I to 31 May in 1993 were selected to force the model. The biological model is based on a simple, nitrate and phosphate limited, lower trophic food web system. The simulated results showed that variation of residual currents forced by M, tide, river discharge and time-varying wind had great impact on the distribution of phytoplankton biomass in the Laizhou Bay. High phytoplankton biomass appeared in the upwelling region. Numerical experiments based on the barotropic model and baroclinic model with no wind and water discharge were also conducted. Differences in the results by the baroclinic model and the barotropic model were significant: more patches appeared in the baroclinic model comparing with the barotropic model. And in the baroclinic model, the subsurface maximum phytoplankton biomass patches formed in the stratified water.
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A new species of Spionidae, Scolelepis (Scolelepis) daphoinos sp. nov., is described and illustrated from northern China seas. The species was frequently encountered and highly abundant on sand beaches, but rarely found in subtidal areas. It was formerly misidentified as S. (S.) squamata (Muller, 1806) in China but differed from the latter species in several details in morphology, including the presence of obvious reddish pigmentation patches and the absence of unidentate hooded hooks. Another two Scolelepis species, S. (S.) lingulata Imajima, 1992 and S. (S.) variegata Imajima, 1992, are reported for the first time from Chinese waters. Two species of Scolelepis, S. (S.) globosa Wu & Chen, 1964 and S. (S.) lefebvrei (Gravier, 1905), were reported previously; therefore, five species in this genus are known from China in total. A key to all Scolelepis species from Chinese waters is provided.
Resumo:
Paraprionospio pinnata (Ehlers, 1901), a poorly known and potentially cosmopolitan polychaete, was examined from museum specimens and from collections in Jiaozhou Bay, the Yellow Sea. New observations indicate that previous Chinese records of P. pinnata are doubtful, and that Chinese waters contain at least three valid species of Paraprionospio, two are known and one is new. Paraprionospio inaequibranchia (Caullery, 1914) and Paraprionospio coora Wilson, 1990, previously misidentified as P. pinnata, are reported from Chinese waters for the first time. Paraprionospio crist'ata. new species, is characterized by having brown pigment patches on the prostomium, ventral crests on chaetigers 9 and 10, dorsal crests on the middle part of the body (from chaetigers 21-23, not beyond chaetiger 29). thin filaments on chaetiger 3, and bifoliate branchial lamellae.
Resumo:
This research was conducted on alpine meadow site at Menyuan county, Qinghai Province, People's Republic of China to determine the effects of native, subterranean rodent of Qinghai-Tibet grasslands, the plateau zokors (Myospalax baileyi), on seasonal above-and below-ground plant biomass, plant species diversity and productivity. Both total peaks of above-and below-ground biomass were the greatest (413.600 g/m~2 and 2297.502 g/m~2) in the patch no any plateau zokors colonized by plateau zokors over 10 years in August and October, respectively. Both above-and below-ground biomass were significantly increased in the patches where plateau zokors were removed or the burrow systems were abandoned for five years compared to the patches plateau zokors colonized over 10 years. However, both above-and below-ground biomass in abandoned patches were significantly lower than that in uncolonized patches. Monocotyledonous biomass was reduced greatly, but the non-palatable dicots were significantly increased in colonized patches. The palatable biomass of monocots and dicots were increased in abandoned patches. Total plant species diversity was the greatest in uncolonized patchesand least in abandoned patch. The total net primary production in colonized patches was reduced by 68.98% compared with uncolonized patches. Although the patches were without any plateau zokors disturbance for fives years, the total net primary production just reached 58.69% of the uncolonized patches. The above-ground net primary production in abandoned patches increased 28.74% and the below-ground increased 54.91% compared with the colonized patches. We suggest that plateau zokor-induced changes in plant above- and below-ground biomass and species diversity may lead to further alterations of nutrient cycling and trophic dynamics in this alpine meadow ecosystem.
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The disjunct distribution of forests in the Qinghai-Tibetan Plateau (QTP) and adjacent Helan Shan and Daqing Shan highlands provides an excellent model to examine vegetation shifts, glacial refugia and gene flow of key species in this complex landscape region in response to past climatic oscillations and human disturbance. In this study, we examined maternally inherited mitochondrial DNA (nad1 intron b/c and nad5 intron 1) and paternally inherited chloroplast DNA (trnC-trnD) sequence variation within a dominant forest species, Picea crassifolia Kom. We recovered nine mitotypes and two chlorotypes in a survey of 442 individuals from 32 populations sampled throughout the species' range. Significant mitochondrial DNA population subdivision was detected (G(ST) = 0.512; N-ST = 0.679), suggesting low levels of recurrent gene flow through seeds among populations and significant phylogeographical structure (N-ST > GST, P < 0.05). Plateau haplotypes differed in sequence from those in the adjacent highlands, suggesting a long period of allopatric fragmentation between the species in the two regions and the presence of independent refugia in each region during Quaternary glaciations. On the QTP platform, all but one of the disjunct populations surveyed were fixed for the same mitotype, while most populations at the plateau edge contained more than one haplotype with the mitotype that was fixed in plateau platform populations always present at high frequency. This distribution pattern suggests that present-day disjunct populations on the QTP platform experienced a common recolonization history. The same phylogeographical pattern, however, was not detected for paternally inherited chloroplast DNA haplotypes. Two chlorotypes were distributed throughout the range of the species with little geographical population differentiation (G(ST) = N-ST = 0.093). This provides evidence for highly efficient pollen-mediated gene flow among isolated forest patches, both within and between the QTP and adjacent highland populations. A lack of isolation to pollen-mediated gene flow between forests on the QTP and adjacent highlands is surprising given that the Tengger Desert has been a geographical barrier between these two regions for approximately the last 1.8 million years.
Resumo:
Grazing animal excrement plays an important role in nutrient cycling and redistribution in grazing ecosystems, due to grazing in large areas and return in small areas. To elucidate the changes to the soil and pasture caused by sheep urine, fresh dung, and compost patches, a short- term field experiment using artificially placed pats was set up in the autumn of 2003 in the Inner Mongolian steppe. Urine application significantly increased soil pH during the first 32 days in soil layers at depths of both 0 - 5 cm and 5 - 15 cm. Rapid hydrolysis of urea gave large amounts of urine- nitrogen ( N) as ammonium ( NH4+) in soil extracts and was followed by apparent nitrification from day 2. Higher inorganic N content in the urine- treated soil was found throughout the experiment compared with the control. No significant effects of sheep excrement on soil microbial carbon ( C) and soil microbial N was found, but microbial activities significantly increased compared with the control after application of sheep excrement. Forty- six percent of dung- N and 27% of compost- N were transferred into vegetation after the experiment. The results from this study suggest that large amounts of nutrients have been lost from the returned excrement patches in the degraded grassland of Inner Mongolia, especially from sheep urine- N.
Resumo:
Excrement patches of grazing animals play an important role in greenhouse gas (GHG) fluxes due to the high nitrogen (N) and available carbon (C) deposited in small areas, but little information is available for the effect of excrement in the Inner Mongolian grassland (43 26 degrees N, 116 degrees 40'E). To elucidate the effect of grazing sheep urine, fresh dung and compost on fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O), a short-term field study (65 days) was carried out in the typical grassland of Inner Mongolia with the optimised closed chamber/GC technique. Compared with the control, cumulative net CH4 consumption decreased 36, 31, and 18% from urine, fresh dung, and compost plots, respectively; net CO2-C output increased by 6.5, 1.5, and 1.2% from urine, fresh dung, and compost treated soil, respectively; about three times as much N2O-N was emitted from urine and the fresh dung treatments during 65 days. Nitrous oxide emission was positively correlated with CO, emission (R = 0.691, P < 0.01) and water-filled pore space (R = 0.698, P < 0.01). The percentages of N2O-N loss of applied-N were 0.44 and 1.05% for urine and fresh dung, respectively. Our results suggest that in autumn in the degraded grassland of Inner Mongolia, the effect of sheep excrement may be ignored when evaluating the total GHG emissions.
Resumo:
本文通过对卷曲类工件IGES文件的分析,本文提出了一种新的基于IGES文件的测量路径规划策略。根据张量积曲面的性质,提出了一种曲面组合算法,运用了张量积曲面的性质,将曲面操作转化为多次曲线操作,将IGES文件中存储的多片曲面片组合为一整片曲面,从而为自由曲面测量路径的提取提供了数学模型。运用二次逼近原理,提出了一种B样条曲线上的等距采样算法。通过在实际系统进行实验,上述策略及算法得到了验证,并在自主开发的智能测量建模加工一体化装备中得到了应用。
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Describing visually space-time properties of geological phenomena consists of one of the most important parts in geology research. Such visual images are of usually helpful for analyzing geological phenomena and for discovering the regulations behind geological phenomena. This report studies mainly three application problems of scientific visualization in geology: (Dvisualizing geological body A new geometric modeling technique with trimmed surface patches has been eveloped to visualize geological body. Constructional surfaces are represented as trimmed surfaces and a constructional solid is represented by the upper and lower surface composed of trimmed surface patches from constructional surfaces. The technique can completely and definitely represent the structure of geological body. It has been applied in visualization for the coal deposit in Huolinhe, the aquifer thermal energy storage in Tianjin and the structure of meteorite impact in Cangshan et al. (2)visualizing geological space field Efficient visualization methods have been discussed. Marching-Cube algorithm used has been improved and is used to extract iso~surface from 3D data set, iso-line from 2D data set and iso-point from ID data set. The improved method has been used to visualize distribution and evolution of the abnormal pressures in Zhungaer Basin. (3)visualizing porous space a novel way was proposed to define distance from any point to a convex set. Thus a convex set skeleton-based implicit surface modeling technique is developed and used to construct a simplified porous space model. A Buoyancy Percolation numerical simulation platform has been developed to simulate the process of migration of oil in the porous media saturated with water.
Resumo:
The seismic survey is the most effective prospecting geophysical method during exploration and development of oil/gas. The structure and the lithology of the geological body become increasingly complex now. So it must assure that the seismic section own upper resolution if we need accurately describe the targets. High signal/noise ratio is the precondition of high-resolution. For the sake of improving signal/noise ratio, we put forward four methods for eliminating random noise on the basis of detailed analysis of the technique for noise elimination using prediction filtering in f-x-y domain. The four methods are put forward for settling different problems, which are in the technique for noise elimination using prediction filtering in f-x-y domain. For weak noise and large filters, the response of the noise to the filter is little. For strong noise and short filters, the response of the noise to the filter is important. For the response of the noise, the predicting operators are inaccurate. The inaccurate operators result in incorrect results. So we put forward the method using prediction filtering by inversion in f-x-y domain. The method makes the assumption that the seismic signal comprises predictable proportion and unpredictable proportion. The transcendental information about predicting operator is introduced in the function. The method eliminates the response of the noise to filtering operator, and assures that the filtering operators are accurate. The filtering results are effectively improved by the method. When the dip of the stratum is very complex, we generally divide the data into rectangular patches in order to obtain the predicting operators using prediction filtering in f-x-y domain. These patches usually need to have significant overlap in order to get a good result. The overlap causes that the data is repeatedly used. It effectively increases the size of the data. The computational cost increases with the size of the data. The computational efficiency is depressed. The predicting operators, which are obtained by general prediction filtering in f-x-y domain, can not describe the change of the dip when the dip of the stratum is very complex. It causes that the filtering results are aliased. And each patch is an independent problem. In order to settle these problems, we put forward the method for eliminating noise using space varying prediction filtering in f-x-y domain. The predicting operators accordingly change with space varying in this method. Therefore it eliminates the false event in the result. The transcendental information about predicting operator is introduced into the function. To obtain the predicting operators of each patch is no longer independent problem, but related problem. Thus it avoids that the data is repeatedly used, and improves computational efficiency. The random noise that is eliminated by prediction filtering in f-x-y domain is Gaussian noise. The general method can't effectively eliminate non-Gaussian noise. The prediction filtering method using lp norm (especially p=l) can effectively eliminate non-Gaussian noise in f-x-y domain. The method is described in this paper. Considering the dip of stratum can be accurately obtained, we put forward the method for eliminating noise using prediction filtering under the restriction of the dip in f-x-y domain. The method can effectively increase computational efficiency and improve the result. Through calculating in the theoretic model and applying it to the field data, it is proved that the four methods in this paper can effectively solve these different problems in the general method. Their practicability is very better. And the effect is very obvious.
Resumo:
According to the influential dual-route model of reading (Coltheart, Rastle et al. 2001), there are two routes to access the meaning of visual words: one directly by orthography (orthography-semantic) and the other indirectly via the phonology (phonology-semantic). Because of the dramatic difference between written Chinese and alphabetical languages, it is still on debate whether Chinese readers have the same semantic activation processes as readers of alphabetical languages. In this study, the semantic activation processes in alphabetical German and logographic Chinese were compared. Since the N450 for incongruent color words in the Stroop tasks was induced by the semantic conflict between the meaning of the incongruent color words and color naming, this component could be taken as an index for semantic activation of incongruent color words in Stroop tasks. Two cross-script Stroop experiments were adopted to investigate the semantic activation processes in Chinese and German. The first experiment focused on the the role of phonology, while the second one focused on the realative importance of orthography. Cultural differences in cognitive processing between individuals in western and eastern countries have been found (Nisbett & Miyamoto, 2005). In order to exclude potential differences in basic cognitive processes like visual discrimination capabilities during reading, a visual Oddball experiment with non-lexical materials was conducted with all participants. However, as indicated by the P300 elicited by deviant stimuli in both groups, no group difference was observed. In the first Stroop experiments, color words (e.g., “green”), color-word associates (e.g., “grass”), and homophones of color words were used. These words were embedded into color patches with either congruent color (e.g. word “green” in green color patch) or incongruent colors (e.g. word “green” in either red or yellow or blue color patch). The key point is to observe whether homophones in both languages could induce similar behavioral and ERP Stroop effects to that induced by color words. It was also interesting to observe to which extent the N450 was related to the semantic conflicts. Nineteen Chinese adult readers and twenty German adult readers were asked to respond to the back color of these words in the Stroop experiment in their native languages by pressing the corresponding keys. In the behavioral data, incongruent conditions (incongruent color words, incongruent color-word associates, incongruent homophones) had significantly longer reaction times as compared to corresponding congruent conditions. All incongruent conditions in the Geman group elicited an N450 in the 400 to 500 ms time window. In the Chinese group, the N450 in the same time window was also observed for the incongruent color words and incongruent color-word associates. These results indicated that the N450 was very sensitive to semantic conflict-even words with semantic association to colors (e.g. “grass”) could elicite similar N450. However, the N450 was absent for incongruent homophones of color words in the Chinese group. Instead, in a later time window (600-800 ms), incongruent homophones elicited a positivity over left posterior regions as compared to congruent homophones. Similar positivity was also observed for color words in the 700 to 1000 ms time window in the Chinese group and 600 to 1000 ms time window for incongruent color words and homophones in the Geman group. These results indicate that phonology plays an important role in Geman semantic activation processes, but not in Chinese. In the second Stroop experiment, color words and pseudowords which had similiar visual shape to color words in both languages were used as materials. Another group of eighteen Chinese and twenty Germans were involved in the Stroop experiment in their native languages.The ERPs were recorded during their performance. In the behavioral data, strong and comparable Stroop effects (as counted by substract the reaction times in the congruent conditions from reaction times in the incongruent conditions) were observed. In the ERP data, both incongruent color words and incongruent pseudowords elicited an N450 over the whole brain scalp in both groups. These results indicated that orthography played an equally important role in semantic activation processes in both languages. The results of the two Stroop experiments support the view that the semantic activation process in Chiense readers differs significantly from that in German readers. The former rely mainly on the direct route (orthography-semantic), while the latter use both direct route and incirect route (phonology-semantic). These findings also indicate that the characteritics of different languages shape the semantic activation processes.