刘公岛海洋牧场底层海水溶解氧浓度的变化特征     

李兆钦  李欣  孙利元  刘子洲  顾艳镇  翟方国  李培良 《海洋与湖沼》2019,50(1):86-99

由于缺乏长期观测资料,前人对山东半岛邻近海域海水溶解氧的时间变化和空间分布特征的研究较少。本文基于威海刘公岛海洋牧场于2016年7月20日至2017年3月14日期间,利用生态环境实时在线观测系统获得的底层海水的温度、盐度、水深、溶解氧数据,分析了该牧场海水溶解氧浓度的时间变化特征及其影响因素,并探讨了低氧灾害发生的可能性。结果表明在观测期间,该牧场海水溶解氧浓度以季节变化为主,冬季最大、夏季最小,其中2月份平均值最高,约为10.86mg/L,8月份平均值最低,约为5.91mg/L。同时海水溶解氧浓度也存在显著的小时变化和日变化,且变化幅度于8月份最大、3月份最小。影响海水溶解氧浓度变化的主要因素是海水温度,溶解氧浓度随着温度的季节性变化而变化。夏季,水体分层会使溶解氧浓度发生大幅度的降低,大风过程对于溶解氧浓度也有一定的影响,通过打破夏季的季节性温跃层使水体发生垂向混合从而为海底提供氧气,但大风过程之后的几天会出现溶解氧浓度降低的现象。本次研究发现刘公岛海洋牧场在观测期间不存在低氧现象。  相似文献   

安徽宿松志留系—泥盆系碎屑锆石物源分析及其大地构造意义^*     

罗立源  李双应 《古地理学报》2021,23(5):999-1009

安徽宿松志留系—泥盆系分布于下扬子地层区西部,大别造山带东南缘,郯庐断裂带南端东侧。为了获得宿松地区志留系—泥盆系的物源信息,对出露于宿松地区的坟头组、茅山组及五通组细砂岩及粉砂岩进行了碎屑锆石LA-ICP-MS U-Pb定年。结果显示,3个样品均获得了约970 Ma、820 Ma的主要峰值年龄和约450 Ma的次要峰值年龄。碎屑锆石主要来源于花岗质岩石。根据花岗岩中锆石的判别图,研究层段碎屑锆石大多属于I型和S型花岗岩锆石,而江南造山带内新元古代及华南地区加里东期的花岗质岩石大多为I型和S型。通过与华南碎屑锆石年龄谱的对比,认为研究地层物源主要来自华南板块内部。根据锆石结晶年龄与沉积年龄差异模式图,判别出安徽宿松志留系—泥盆系形成于碰撞背景。  相似文献   

Tsunami-like solitary waves impinging and overtopping an impermeable seawall: Experiment and RANS modeling   总被引：1，自引：0，他引：1  

Shih-Chun Hsiao  Ting-Chieh Lin 《Coastal Engineering》2010

This study investigates tsunami-like solitary waves impinging and overtopping an impermeable trapezoidal seawall on a 1:20 sloping beach. New laboratory experiments are performed for describing three typical cases: a turbulent bore rushes inland and subsequently impacts and overtops the seawall (Type 1); a wave directly collapses on the seawall and then generates overtopping flow (Type 2); and, a wave straightforwardly overtops the seawall crown and collapses behind the seawall (Type 3). A two-dimensional volume of fluid (VOF) type model called the COBRAS (COrnell BReaking And Structure) model, which is based on the Reynolds-Averaged Navier–Stokes (RANS) equations and the k–ε turbulence closure solver, is validated by experimental data and then applied to investigate wave dynamics for which laboratory data are unavailable. Additionally, a set of numerical experiments is conducted to examine the dynamic wave acting force due to waves impacting the seawall. Effects of wave nonlinearity and freeboard are elucidated. Special attention is given to a distinct vortex evolutionary behavior behind the seawall, in which the dynamic properties of entrapped air-bubbles are briefly addressed experimentally and numerically.  相似文献   

Bowen ratio/energy balance technique for estimating crop net CO2 assimilation,and comparison with a canopy chamber     

A. A. Held  P. Steduto  F. Orgaz  A. Matista  T. C. Hsiao 《Theoretical and Applied Climatology》1990,42(4):203-213

Summary This paper describes a Bowen ratio/energy balance (BREB) system which, in conjunction with an infra-red gas analyzer (IRGA), is referred to as BREB+ and is used to estimate evapotranspiration (ET) and net CO₂ flux (NCF) over crop canopies. The system is composed of a net radiometer, soil heat flux plates, two psychrometers based on platinum resistance thermometers (PRT), bridge circuits to measure resistances, an IRGA, air pumps and switching valves, and a data logger. The psychrometers are triple shielded and aspirated, and with aspiration also between the two inner shields. High resistance (1 000 ohm) PRT's are used for dry and wet bulbs to minimize errors due to wiring and connector resistances. A high (55 K ohm) fixed resistance serves as one arm of the resistance bridge to ensure linearity in output signals. To minimize gaps in data, to allow measurements at short (e.g., 5 min) intervals, and to simplify operation, the psychrometers were fixed at their upper and lower position over the crop and not alternated. Instead, the PRT's, connected to the bridge circuit and the data logger, were carefully calibrated together. Field tests using a common air source showed appartent effects of the local environment around each psychrometer on the temperatures measured. ET rates estimated with the BREB system were compared to those measured with large lysimeters. Daily totals agreed within 5%. There was a tendency, however, for the lysimeter measurements to lag behind the BREB measurements. Daily patterns ofNCF estimated with the BREB+ system are consistent with expectations from theories and data in the literature. Side-by-side comparisons with a stirred Mylar canopy chamber showed similarNCF patterns. On the other hand, discrepancies between the results of the two methods were quite marked in the morning or afternoon on certain dates. Part of the discrepancies may be attributed to inaccuracies in the psychrometric temperature measurements. Other possible causes include the highly artificial air turbulence in the canopy chamber and possible associated stomatal response. More work is necessary to identify conclusively the causes. In spite of these uncertainties, the BREB+ technique appears well suited for the automated and simultaneous tracking of photosynthetic performance and water economy of crops in their virtually undisturbed natural environment.To whom reprint requests should be sent.With 7 Figures  相似文献   

余辉等离子体中的谐振现象及其在空间研究中的可能应用          下载免费PDF全文

肖佐 《地球物理学报》1980,23(1):13-18

用谐振探针在余辉式等离子体中进行测量,观察到了谐振效应。与某些作者的结论不同的是:可证明这一谐振发生在等离子体频率ω_p处而没有强的阻尼。如果用这一方法进行等离子体浓度测量也不受探针污染的影响。进而指出这一技术在空间等离子体研究方面可能的应用。  相似文献   

Development of MSP430-based ultra-low power expandable underwater acoustic recorder     

Chau-Chang Wang  Yu-Hung Hsiao  Min-Chih Huang 《Ocean Engineering》2009,36(6-7):446-455

Reducing overall power consumption is core issue in low power, high sampling rate, large storage data loggers necessary for long-term underwater acoustics research and other applications. A low-power microprocessor MSP430 offers a solution for the development of long-term deployment remote systems. In this paper, we present a multi-MSP430, master-slave architecture to resolve the power limitation issue. The proposed design is scalable in nature. For every additional slave unit installed in the array, the data sampling and streaming rate can be increased proportionally. We demonstrate the advantages of this concept using a multi-channel underwater acoustic recorder with a 100 kHz sampling rate. The performance of the system is demonstrated by a field acoustic experiment in which the reflection coefficient of the seafloor is measured. The proposed architecture will be applicable to many underwater long-term deployment systems. With its flexibility in configuration and synchronization of multi-channel sampling, it also provides a simple architecture for the construction of hydrophone arrays.  相似文献   

A trophic model for the Danshuei River Estuary, a hypoxic estuary in northern Taiwan   总被引：1，自引：0，他引：1  

Lin HJ  Shao KT  Jan RQ  Hsieh HL  Chen CP  Hsieh LY  Hsiao YT 《Marine pollution bulletin》2007,54(11):1789-1800

The estuary of the Danshuei River, a hypoxic subtropical estuary, receives a high rate of untreated sewage effluent. The Ecopath with Ecosim software system was used to construct a mass-balanced trophic model for the estuary, and network analysis was used to characterize the structure and matter flow in the food web. The estuary model was comprised of 16 compartments, and the trophic levels varied from 1.0 for primary producers and detritus to 3.0 for carnivorous and piscivorous fishes. The large organic nutrient loading from the upper reaches has resulted in detritivory being more important than herbivory in the food web. The food-chain length of the estuary was relatively short when compared with other tropical/subtropical coastal systems. The shortness of food-chain length in the estuary could be attributed to the low biomass of the top predators. Consequently, the trophic efficiencies declined sharply for higher trophic levels due to low fractions of flows to the top predators and then high fractions to detritus. The low biomass of the top predators in the estuary was likely subject to over-exploitation and/or hypoxic water. Summation of individual rate measurements for primary production and respiration yielded an estimate of −1791 g WW m⁻² year⁻¹, or −95 g C m⁻² year⁻¹, suggesting a heterotrophic ecosystem, which implies that more organic matter was consumed than was produced in the estuary.  相似文献   

Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)   总被引：1，自引：0，他引：1  

Kwang Bae Kim  Yu-Shen Hsiao  Jeong Woo Kim  Bang Yong Lee  Yi Kyun Kwon  Chang Hwan Kim 《Marine Geophysical Researches》2010,31(4):285-298

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm³ between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.  相似文献   

Seismic design and testing of buckling‐restrained braces with a thin profile          下载免费PDF全文

Pao‐Chun Lin  Keh‐Chyuan Tsai  Chieh‐An Chang  Yu‐Yun Hsiao  An‐Chien Wu 《地震工程与结构动力学》2016,45(3):339-358

A thin‐profile buckling‐restrained brace (thin‐BRB) consists of a rectangular steel casing and a flat steel core that is parallel to a gusset plate. A thin configuration reduces the width of the restraining member and thus saves usable space in buildings. However, deformable debonding layers, which cover the steel core plate in order to mitigate the difference between the peak tensile and compressive axial forces, provide a space for the steel core to form high mode buckling waves when the thin‐BRB is under compression. The wave crests squeeze the debonding layers and produce outward forces on the inner surface of the restraining member. If the restraining member is too weak in sustaining the outward forces, local bulging failure occurs and the thin‐BRB loses its compression capacity immediately. In order to investigate local bulging behavior, a total of 22 thin‐BRB specimens with a ratio of steel core plate to restraining steel tube depth ranging from 0.3 to 0.7 and axial yield force capacities ranging from 421 kN to 3036 kN were tested by applying either cyclically increasing, decreasing, or constant axial strains. The restraining steel tube widths of all the specimens were smaller than 200 mm and were infilled with mortar with a compressive strength of 97 MPa or 55 MPa. Thirteen of the 22 thin‐BRB specimens' restraining members bulged out when the compressive core strains exceeded 0.03. A seismic design method of the thin‐BRB in preventing local bulging failure is proposed in this study. Test and finite element model (FEM) analysis results suggest that the outward forces can be estimated according to the BRB compressive strength, steel core high mode buckling wavelength, and the debonding layer thickness. In addition, the capacity of the restraining member in resisting the outward forces can be estimated by using the upper bound theory in plastic analysis. Both the FEM analysis and test results indicate that the proposed method is effective in predicting the possibility of local bulging failure. Test results indicate that the proposed design method is conservative for thin‐BRB specimens with a large steel core plate to restraining steel tube depth ratio. This paper concludes with design recommendations for thin‐BRBs for severe seismic services. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Probabilistic assessment of aggregate risk for bisphenol A by integrating the currently available environmental data     

I-Lun Hsiao  Charlene Wu  Yuh-Jeen Huang  Dalaijamts Chimeddulam  Kuen-Yuh Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):1851-1861

Bisphenol A (BPA) is an endocrine disruptor widely used in the production of polycarbonate plastics and epoxy resins. Exposures to BPA have been associated with reproductive, developmental, and cardiovascular effects. In this study, the CalTOX model was used to assess the aggregate health risks on BPA by integrating the currently available BPA data in various environmental media in Taiwan. Local parameters such as chemical properties, local landscape data, and exposure factors were used as model inputs under the continuous source mode. A reference dose (RfD) of 50 μg/kg-day was adopted in this assessment. Monte Carlo simulation was used to simulate great variability of the environmental data. Our results show that an upper limit of 95 % confidence interval of aggregate exposures for the adults (19–64 years old) was 1.05 μg/kg-day, corresponding to a hazard index (HI) of 0.021. The chemical properties (BPA half-life in surface water), intake rates (fruit, vegetable, and fluid intake), and landscape data (average depth of surface waters and leaf wet density) are critical parameters. Finally, HI value would approach to 1 as BPA concentrations in ambient air, surface water, and sediment was greater than 20 ng/m³, 100 μg/L, and 3.3 mg/kg. The quality of the risk assessment on BPA can be further improved by reduction of uncertainty of the abovementioned critical parameters as well as considering additional BPA exposures from canned and packaged goods.  相似文献