Adaptive Power Control Method Considering Reactive Power Reserve for Wave-Offshore Hybrid Power Generator System

AbstractThe combined generator system with the wind and wave power can share the off-shore platform and therefore have the advantage of constructing the transmission system as well as the power conversion system. The established wind power generator systems do output determination by following the transmission system operator's directions and control the turbine by focusing at PCC, but when connected with the wave-power generator; it is needed to do the complex control. Especially, since the method and impact of active power control are different, it is required to distribute demanding power and responsibility to each turbine by considering the grid condition. In this paper, the control system is formed to do output determination of the combined generator system by paying attention to reactive power reserve of utility grid with the analysis of the controllable elements of the wind and wave power generator. And the comparison with the existing system is carried out based on the real system information. Through using the PSCAD/EMTDC simulation, the suitability of the new control technique of the combined system is estimated by proposing the active power control according to the reference signal of TSO and the reactive power capability followed by it

Meteorological and chemical factors controlling ozone formation in Seoul during MAPS-Seoul 2015

To understand the chemical mechanisms of controlling factors in ozone (O3) formation in early summer in Seoul, a comprehensive study encompassing measurement and modeling was conducted under the Megacity Air Pollution Study-Seoul (MAPS-Seoul) campaign. From May 18 to June 12, 2015, O3 and peroxyacetyl nitrate (PAN) were measured, along with their precursors, including NOx and volatile organic compounds (VOCs), at the Korea Institute of Science and Technology, located in northeast Seoul. VOCs were sampled in a canister twice a day (at 09:30 and 15:00) and analyzed via gas chromatography. The meteorological conditions and chemical regimes of the air masses were clearly distinguished during the study period. In May, NOx concentrations were higher with more pronounced diurnal cycles of precursors and O3 under constant westerly winds. By contrast, stagnant conditions developed in June, which reduced the inflow of primary emissions from the downtown area but increased the influence from the neighboring forest under high temperatures. As a result, the ratio of O3 to odd oxygen was higher in June, indicating a less efficient removal of O3 by NOx. In the same context, the air mass was chemically more aged with a higher NO2/NOx ratio and enhanced OH reactivity of oxygenated and biogenic VOCs in June. The overall measurement results suggest that O3 formation is slightly more sensitive to VOCs than to NOx in Seoul during this season, when O3 concentrations are the highest of the year

Cloning and high-level production of a chitinase from Chromobacterium sp. and the role of conserved or nonconserved residues on its catalytic activity

A gene encoding an alkaline (pI of 8.67) chitinase was cloned and sequenced from Chromobacterium sp. strain C-61. The gene was composed of 1,611 nucleotides and encoded a signal sequence of 26N-terminal amino acids and a mature protein of 510 amino acids. Two chitinases of 54 and 52kDa from both recombinant Escherichia coli and C-61 were detected on SDS-PAGE. Maximum chitinase activity was obtained in the culture supernatant of recombinant E. coli when cultivated in TB medium for 6days at 37°C and was about fourfold higher than that from C-61. Chi54 from the culture supernatants could be purified by a single step based on isoelectric point. The purified Chi54 had about twofold higher binding affinity to chitin than to cellulose. The chi54 encoded a protein that included a type 3 chitin-binding domain belonging to group A and a family 18 catalytic domain belonging to subfamily A. In the catalytic domain, mutation of perfectly conserved residues and highly conserved residues resulted in loss of nearly all activity, while mutation of nonconserved residues resulted in enzymes that retained activity. In this process, a mutant (T218S) was obtained that had about 133% of the activity of the wild type, based on comparison of K cat value

Effective Vortex Mass from Microscopic Theory

We calculate the effective mass of a single quantized vortex in the BCS superconductor at finite temperature. Based on effective action approach, we arrive at the effective mass of a vortex as integral of the spectral function $J(\omega)$ divided by $\omega^3$ over frequency. The spectral function is given in terms of the quantum-mechanical transition elements of the gradient of the Hamiltonian between two Bogoliubov-deGennes (BdG) eigenstates. Based on self-consistent numerical diagonalization of the BdG equation we find that the effective mass per unit length of vortex at zero temperature is of order $m (k_f \xi_0)^2$ ($k_f$=Fermi momentum, $\xi_0$=coherence length), essentially equaling the electron mass displaced within the coherence length from the vortex core. Transitions between the core states are responsible for most of the mass. The mass reaches a maximum value at $T\approx 0.5 T_c$ and decreases continuously to zero at $T_c$.Comment: Supercedes prior version, cond-mat/990312

Chemical Variation In Lodgepole Pine With Sapwood/Heartwood, Stem Height, and Variety

The chemical variation in lodgepole pine over its geographical range with sapwood/heartwood, stem height, and variety was investigated. In both varieties, latifolia and murrayana, the heartwood was significantly higher in extractives than the sapwood, whereas the sapwood was significantly higher in holocellulose and alpha-cellulose than the heartwood. The sapwood and heartwood did not differ in pH and lignin content.Ash, lignin, and holocellulose content were positively correlated with stem height in latifolia and murrayana. Extractive and alpha-cellulose content were negatively correlated with stem height. The stem height variations appeared to be related to the heartwood/sapwood ratio, proportion of mature and juvenile wood, and the specific gravity.The variation between latifolia and murrayana in ash, extractive, and lignin content and pH was small. In contrast, the holocellulose and alpha-cellulose content was 2% higher in murrayana than in latifolia. The polysaccharide variation may be influenced by climate and site conditions as well as genetic differences