Long-term variations of water quality and phosphorus loading in Lake Andong, Korea

Tropic state parameters were measured in a reservoir (Lake Andong, Korea) from 1993 to 2000. Phosphorus loading from the watershed was estimated by measuring total phosphorus concentration in the main inflowing stream (the Nakdong River). Phosphrus discharge of the pen-type fish farms was estimated from the amount of fish feed supplied annually and the rate of phosphrus excretion per feed weight. Minimum transparency in summer was only about 2.0m in 1993 and 1994, but it decreased to about 1.2m in 1997 and 1998, and recovered to about 2.3m in 1999 and 2000. TP increased from 11～30 mgP/m³ in 1993 to 18～42 mgP/m³ in 1998, but recovered to 8～13mgP/m³ in 2000, whereas TN decreased slightly from1.81～2.96mgN/L in 1993 to 1.17～1.80mgN/L in 2000. TN/TP ratio decreased from 82～281 in 1993 to 21～143 in 1998, but again increased to 101～209 in 2000 due to the decrease of TP. The average chlorophyll a concentration in growing season was in the range of 4.8-16.2mg/m³ from 1993 to 1997, but it decreased to 3.7-5.2 mg/m³ after 1998. The major cause of the trophic state recovery is thought to be the removal of fish farms in April 1998.Article信州大学山地水環境教育研究センター研究報告 2: 131-134(2004)departmental bulletin pape

The limnological survey of a coastal lagoon in Korea: Lake Hwajinpo

Physicochemical parameters, plankton biomass, and sediment were surveyed from 1998 to 2000 on two months interval in a eutrophic costal lagoon (Lake Hwajinpo, Korea) segregated from the sea by a sand dune. Littoral zone is well developed and floating-leaved aquatic plants also thrive, A shallow sill divides the lake into two basins. It has permeation of seawater and chemoclines formed by salinity were observed at 1m demth all the year around. DO was often very low(＜1mgO₂/L) at hypolimnion. Temperature inversions were observed in November. Transparency was 0.2～1.7m. Nitrate and ammonium concentrations were very low (＜0.1mgN/L), even though TN was usually 2.0～3.5mgN/L. TN/TP was generally lower than the Redfield ratio. TSI was 63～74, COD, TP, and TN of sediment were 3.1～40.3mgO₂/g, 0.9～1.39mg/m³. Two basins showed different phytoplankton communities with Oscillatoria sp., Trachelomonas sp., Schiaochlarnys gekatinosa, and Anabaena spiroides dominant in South basin, and with Trachelomonas sp., Schroederia sp., Schizochlamys felatinosa, and Trachelomonas sp. dominant in the North basin. The seasonal succession of phytoplankton was very fast, possibly due to sudden changes in physical characteristics such as wind, turbidity, salinity and light, etc.Article信州大学山地水環境教育研究センター研究報告 2: 127-130(2004)departmental bulletin pape

Cache-Conscious Concurrency Control of Main-Memory Indexes on Shared-Memory Multiprocessor Systems

Recent research addressed the importance of optimizing L2 cache utilization in the design of main memory indexes and proposed the so-called cache-conscious indexes such as the CSB+-tree. However, none of these indexes took account of concurrency control, which is crucial for running the real-world main memory database applications involving index updates and taking advantage of the off-the-shelf multiprocessor systems for scaling up the performance of such applications. Observing that latching index nodes for concurrency control (CC) incurs the so-called coherence cache misses on shared-memory multiprocessors thus limiting the scalability of the index performance, this paper presents an optimistic, latch-free index traversal (OLFIT) CC scheme based on a pair of consistent node read and update primitives. An experiment with various index CC implementations for the B+- tree and CSB+-tree shows that the proposed scheme shows the superior scalability on the multiprocessor system as well as the performance comparable to that of the sequential execution without CC on the uniprocessor system. 1

An Improved Estimation Method of Mutual Inductance Angle for a Two-Dimensional Wireless Power Transfer System

The improvement of power transmission efficiency (PTE) is an important issue in the design of a wireless power transfer (WPT) system. The WPT system with multiple transmitting (Tx) or receiving (Rx) coils is a way to improve the PTE. This paper deals with the estimation of the mutual inductance angle for a two-dimensional (2D) WPT system with two Tx coils and one Rx coil. The mutual inductance angle is one of the most important parameters to determine the PTE in the 2D WPT system. The condition for the maximum PTE is investigated and the mutual inductance angle is defined for the 2D WPT system. An improved estimation method of the mutual inductance angle is proposed based on the phase-locked loop (PLL) technique using the voltages and currents of the Tx coils. The simulation and experimental results are provided to validate the effectiveness of the proposed method

Enhanced Electron Transfer Mediated by Conjugated Polyelectrolyte and Its Application to Washing-Free DNA Detection

Direct electron transfer between a redox label and an electrode requires a short working distance (<1–2 nm), and in general an affinity biosensor based on direct electron transfer requires a finely smoothed Au electrode to support efficient target binding. Here we report that direct electron transfer over a longer working distance is possible between (i) an anionic π-conjugated polyelectrolyte (CPE) label having many redox-active sites and (ii) a readily prepared, thin polymeric monolayer-modified indium–tin oxide electrode. In addition, the long CPE label (∼18 nm for 10 kDa) can approach the electrode within the working distance after sandwich-type target-specific binding, and fast CPE-mediated oxidation of ammonia borane along the entire CPE backbone affords high signal amplification