Population dynamics of the solitary ascidian <Emphasis Type="Italic">Herdmania momus</Emphasis> (Savignyi, 1816) in Jeju Island,Korea

In 2007–2008, a population outbreak of the solitary ascidian Herdmania momus was observed along the coasts of Jeju Island and the ascidians became the top dominant species in macrobenthic communities. We conducted field experiments on population dynamics and demographic parameters including seasonal density fluctuation, vertical distribution, recruitment patterns, mortality, and growth rate. Recruitment continued year-round except in April following the lowest water temperature season in February. Population density was highest in August-October, concomitantly with the peak in recruitment, related to the highest water temperature. The lowest density was observed in February-April when the water temperature was lowest. In April all individuals disappeared from all permanent plots, resulting in a maximum life span of 10–12 months. Individuals of newly recruited H. momus grew to have an adult size of 4–6 cm in only 3–4 months. Higher densities were observed in the shallower areas (5 m) compared to the deeper zones. More recruitment occurred on vertical slopes than horizontal substrates, but substrate pre-occupancy caused no difference in recruitment. This is the first report on H. momus population-level investigation in Korea, which provides valuable baseline information on the current status of population demography and their potential community-level influence on Jeju coasts.     

Factors controlling carbon isotope ratios of dissolved inorganic carbon in two major tributaries of the Han River,Korea

Understanding the carbon cycle of the Han River system in Korea is of prime interest in managing and preserving this valuable water resource for more than 20 million residents in the area. As a part of a comprehensive carbon cycling study for the Han River system, this report focuses on the carbon isotope compositions of dissolved inorganic carbon (DIC) in its two major tributaries, the North and the South Han Rivers. The major difference in carbonate chemistry of the tributaries originates primarily from the lithology of the catchment areas. The South Han River, draining a carbonate‐dominant terrain, has much higher alkalinities and DIC concentrations, whereas the lower concentrations in the North Han River indicate little influence of carbonate weathering. Likewise, δ¹³C_DIC values in the South Han River indicate that the DIC input from the carbonate rocks is important in controlling carbon isotope ratios of DIC. For the North Han River, the oxidation of organic material influences the amount of riverine DIC and δ¹³C_DIC values to a greater extent. Overall, remarkable seasonal and spatial variations of river chemistry and carbon isotope compositions of DIC reflect the variability in geo‐hydrologic characteristics, in the water regime, and in metabolic activities in the river water and/or the drainage areas. Copyright © 2006 John Wiley & Sons, Ltd.     

The energy exchange within a vegetation layer

Summary The concept of vegetation as a multi-layered heat exchange system is discussed with reference to measurements in a barley field. These measurements included the monitoring of net radiation at various levels inside the crop and the conducted heat flux in the soil for typical clear and overcast days. The diurnal variations of the components of the heat balance throughout the crop are discussed, computing the combined flux of sensible and latent heat as a remainder term. The results show a complete reversal of the flux of sensible and latent heat from the top of the crop to the soil surface: during the night the surface loses heat by eddy diffusion as well as radiation and during the day it gains heat through both these processes. The total heat exchange between the crop and the atmosphere gives the usual heat gains by eddy diffusion during the night and losses during the day. The radiation absorbed by a layer of vegetation is converted into sensible and latent heat and 80% of the total energy exchange takes place in the upper half of the crop. The magnitude of the exchange process falls off rapidly with depth in the crop.

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Zusammenfassung Die Vegetation wird als mehrschichtiges System im Hinblick auf den Wärmeaustausch betrachtet, wobei Messungen in einem Gerstenfeld verwendet werden. Die Messungen umfaßten die Registrieuung der Wärmebilanz in verschiedenen Höhen im Getreidestand und des Wärmeflusses im Boden an typischen klaren und bedeckten Tagen. Der Tagesgang der Komponenten der Wärmebilanz durch die Vegetationsschicht wird untersucht, dabei wird die Summe des Fluesses von fühlbarer und von latenter Wärme als Restglied berechnet. Die Resultate zeigen eine vollkommene Umkehr des Flusses von fühlbarer und latenter Wärme von der Obergrenze des Getreidestandes zum Boden: während der Nacht verliert die Erdoberfläche Wärme sowohl durch turbulenten Austausch wie durch Strahlung, während des Tages nimmt sie durch beide Prozesse Wärme auf. Der gesamte Wärmeastausch zwischen dem Getreidefeld und der Atmosphäre ergibt die gewöhnlichen Wärmegewinne durch turbulenten Austausch bei Nacht und die Wärmeverluste bei Tag. Die von der Vegetationsschicht absorbierte Strahlung wird in fühlbare und latente Wärme umgesetzt, wobei 80% des gesamten Wärmeaustausches in der oberen Hälfte der Vegetationsschicht erfolgen. Die Größe des Austauschprozesses vermindert sich rasch mit der Tiefe in der Vegetationsschicht.

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Résumé On considère ici la végétation comme un système à plusieurs strates vis à vis des échanges de chaleur. Pour cela on se sert de mesures effectuées dans un champ d'orge. Ces mesures comprenaient l'enregistrement du bilan de chaleur à différentes hauteurs dans le dit champ ainsi que du flux de chaleur dans le sol à des jours typiques: couverts ou clairs. On étudie l'évolution diurne des composantes du bilan de chaleur au travers de la couche végétale. Pour ce faire, on clacule la somme du flux des chaleurs sensible et latente comme terme final de l'équation. Les résultats montrent une inversion complète du flux de ces deux chaleurs de la surface supérieure du champ jusqu'au sol. Pendant la nuit, la surface du sol perd de la chaleur aussi bien par des échanges turbulents que par rayonnement. Pendant le jour, le sol reçoit de la chaleur par ces deux processus. L'échange total de chaleur entre le champ d'orge et l'atmosphère présente les gains de chaleur ordinaire par turbulence de nuit et les pertes de jour. Le rayonnement absorbé par la couche végétale est transformé en chaleur latente et sensible. 80% de la totalité des échanges de chaleur se passent dans la moitié supérieure de la couche végétale. L'importance des processus d'échange diminue rapidement avec la profondeur de la couche végétale.

     

柴达木盆地低频地震探测结晶基底的工作方法

根据地质资料,柴达木盆地的基岩（结晶基底）埋藏深度,可达十公里以上.勘探这样深的基岩,利用反射和一般折射方法是不容易得到良好的效果.1958年6月,在柴达木盆地开始试验低频地震的方法,来接收基岩面的折射波.所用检波器的谐振频率为13周/秒,放大器最低谐振频率为8周/秒.最大接收距离为100公里左右.     

Spectral Analysis based on Wavelet Transform Maxima: Identification of Multi-order Stratigraphic Boundaries and Cycles

In sedimentology, stratigraphic sequences and cycles are ordered by time spans and physical scales, such as thickness, and bounded by discontinuities, including unconformities or flooding surfaces. Spectral analysis based on wavelet transform (WT) maxima is proposed and used as a quantitative tool to identify multi-order stratigraphic boundaries and cycles in well log data. The proposed spectral analysis is based on quantitative analysis on the center frequencies and resolutions of Gaussian wavelets in time and frequency, and uses a combination of the WT maxima based on both the first order Gaussian wavelet having a high time resolution and the seventh order Gaussian wavelet having a high frequency resolution. WT maxima spectra, which can characterize the evolution of WT maxima across scales and periods along WT maxima lines concerned with sequence boundaries, are used to detect dominant spectral peaks corresponding to the time-period domain WT maxima and to determine WT maxima spectral slopes. The WT maxima spectral slopes are helpful for discriminating sequence boundaries from intrasequence cyclic variations in well log data, and the time-period domain WT maxima are used to relate the detected boundaries to relevant cycles. The interval WT maxima spectra and the stationary index, related to the WT maxima spectra, are introduced as indicators that can be used for the hierarchical ordering of the boundaries and cycles. Application of the proposed method to well log data shows that the suggested method is efficient in identifying multi-order sequences that relate well to the Milankovitch cycles.

     

Using major nutrient concentrations to derive vertical movement of water masses in the coastal region of eastern Taiwan

Significant variations of phosphate and silicate concentrations have been observed in seawater from selected industrial pipelines at intake depths between 400 and 710 m off the Hualien coast, eastern Taiwan, revealing a strong vertical movement of water mass in this intermediate layer. An intensive monitoring experiment was carried out, in which pipeline seawater from three land-based pumping stations and seawater collected by a research vessel were obtained and analyzed in parallel during a 2-day observation period. The results showed clearly that the changes of nutrient concentrations in both pipeline and shipboard samples followed a semidiurnal cycle. The maximum vertical displacement occurred in the 300–800 m layer with a scale as surprisingly large as 100 m, when compared with that observed in other areas. The tidal cycles for different layers may not synchronize with surface tide or each other. Empirical equations have been implemented between nutrient concentrations and temperature for the Hualien off-shore area. The equation can be used to check temperature variation of the intermediate water by measuring either phosphate or silicate in pipeline seawater.     

Performance evaluation of a physically based model for shallow landslide prediction

Evaluating the performance of a physically based model for landslide prediction was conducted in this study. The model was developed based on the basis of the infinite slope instability analysis and TOPMODEL for saturated water level estimation, which enabled to predict the location and time of occurrence of shallow landslides. Field data from 2008 to 2013 in two areas vulnerable to landslide in Taiwan were collected to test the applicability of the model for landslide prediction. Three indexes including the probability of detection (POD), false alarm ratio (FAR), and threat score (TS) were adopted to assess the advantages and disadvantages of the model. The results indicated that the POD for the landslide prediction by using the proposed model was 1.00, the FAR was lower than 0.25, and the overall TS value was higher than 0.75. It is promising to apply the proposed model for landslide early warnings to reduce the loss of life and property.     

Study of shear stress in laminar pipe flow using entropy concept

In fluid mechanics, the shear stress is calculated from the frictional force caused by viscosity and fluctuating velocity. Shear stress equations are used widely because of their simplicity. On the other hand, they have a critical limitation of requiring an energy gradient, which is generally difficult to estimate in practice. In particular, measuring the shear stress and velocity gradient on the boundary layer is difficult. The point velocity throughout the entire cross section is needed to calculate the velocity gradient. This study proposes the shear stress distribution equations for laminar flow based on entropy theory using the mean velocity and entropy coefficient. The proposed equations were compared with the measured shear stress distribution using Nikuradse’s data. The results revealed a correlation coefficient of approximately 0.99, indicating that the proposed method fits the Nikuradse’s data. Therefore, the shear stress distribution can be estimated easily and accurately using the proposed equations, which can be used in future for the management and design of a water pipeline.     

Spatial distribution,mineralogy, and weathering of heavy metals in soils along zinc-concentrate ground transportation routes: implication for assessing heavy metal sources

We investigated the source of heavy metals in soils at a site in South Korea, where a ground transportation of zinc-concentrates (ZnS, sphalerite) occurs daily. Seventy soil samples were collected at the site and analyzed for residual concentrations of heavy metals, as well as their chemical and mineralogical properties. Enrichment factor was calculated based on local geochemical background level of metals in soils and confirmed the contamination of soils in the area by an anthropogenic source. The concentration data were also subjected to a Pearson correlation analysis to determine the possible influences of anthropogenic sources and identify the primary source. A slight negative correlation between heavy metals and Al, and a weak correlation between heavy metals and Fe implied that the heavy metals originated from anthropogenic inputs rather than a geogenic source. A strong positive linear correlation between Zn and other heavy metals (i.e., As, Cd, Cu, Pb, r ≥ 0.96, p ≤ 0.001) suggested the influence of a single anthropogenic source of zinc-concentrates containing all of these heavy metals. Zinc-concentrate oxidation and leaching experiments, which mimicked physical and chemical weathering in the environment, indicated that zinc-concentrate could be transformed to zinc oxides and release Cd and Pb upon precipitation. The findings in this study provide an insight into the fate of the Zn that the original form of zinc-concentrate would not remain in the soil after long-term weathering, which should be considered when source of heavy metals is identified.