• Journal of Forest and Environmental Science
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• v.29 no.2
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• pp.116-124
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• 2013

Differences in rates and patterns of nitrogen cycling have been correlated with nitrogen stable isotope measurements in forest ecosystems of tropical and temperate regions, but limited similar work has been conducted in sub-tropical forests. This study investigated patterns in stable N isotopic composition in a subtropical forest in Taiwan by sampling three soil profiles and overstory and understory foliage. Soil ${\delta}^{15}N$ in the forest floor ranged from -1.8 to -1.8‰. Mineral soils had higher ${\delta}^{15}N$ (4.1 to 6.0‰). Foliage ${\delta}^{15}N$ in overstory trees ranged from -6.6 to -2.0‰, and understory foliage ${\delta}^{15}N$ ranged from -5.0 to -1.2‰. There was a weak correlation between foliar % N and ${\delta}^{15}N$ ($r^2=0.214$). Compared to results from similar surveys in tropical and temperate forests, foliar ${\delta}^{15}N$ values were generally lower. These results help highlight the need for improved knowledge regarding the relationships between patterns in N stable isotopes and processes affecting rates of N cycling, especially as related to wider scale patterns in forest ecosystems within the east-Asia region.

• Structural Engineering and Mechanics
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• v.41 no.2
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• pp.263-284
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• 2012

This paper aims to propose a computational technique for estimating the region of attraction (RoA) for autonomous nonlinear systems. To achieve this, the collocation method is applied to approximate the Lyapunov function by satisfying the modified Zubov's partial differential equation around asymptotically stable equilibrium points. This method is formulated for n-scalar differential equations with two classes of basis functions. In order to show the efficiency of the suggested approach, some numerical examples are solved. Moreover, the estimated regions of attraction are compared with two similar methods. In most cases, the proposed scheme can estimate the region of attraction more efficient than the other techniques.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.103-109
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• 1998

A new flux-weakening scheme for an Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.569-578
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• 2003

In the present steady the flow characteristics of turbulent steady flows were experimentally investigated in the exit region of join stream. The experimental was carry out to measure the velocity profiles of air in a square duct. For the measurement of velocity profiles, a hot-wire anemometer was used. The experimental results shows that the velocity profiles do not change behind the fully developed flow region , which is defined as dimensionless axial direction x/Dh=50. In addition, the gradient of shear stress distribution became stable as the flow reached progress downstream.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.503-508
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• 1997

The change of the structure of homogeneous turbulence subject to irrotational strains has been studied in an anti-Morel type diffuser (center matched cubic contour) using the hot wire anemometry. It was observed that the profiles of mean velocities and turbulence velocities along the center line were stable at the entrance region but rapidly changed near the matching point. The wall induced turbulence at the entrance region grows fast and was diffused toward the center at downstream. It was also observed that the axial turbulence grows faster than the radial one in the middle region of the diffusing flow and that the diffusing process has the vortex compression mechanism due to the conservation of angular momentum. These phenomena are frequently observed at the initial flow region of the free jet.

• Environmental and Resource Economics Review
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• v.13 no.3
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• pp.367-385
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• 2004

This study offers the possibility of water allocation between upstream and downstream regions by side payment. In the case of river water, water use of an upstream region affect a downstream region's water use but not vise versa. In this case, the downstream region wants to secure stable water by suggesting side payment to the upper region. We examine the maximum compensation of the downstream region for acquiring additional water. Also we compare each region's total benefits between the cases with and without cooperation. The result of empirical study show that there was a Pareto improvement when two region cooperate in the water use. Also the amount of side payment depend on the degree of shortage of water and both regions are satisfied with the water allocation result by voluntary negotiation.

• Korean Institute of Interior Design Journal
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• no.32
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• pp.72-81
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• 2002

Southeast Asian region cruise market is expected to be stable or grow in the near future depending on the region's economy. Star Cruises company, which has entirely dominated the regional market since 1998, has attempted to expand beyond traditional cruise routes in Southeast Asian region and develop new markets in Thailand and Dubai. Such a situation urges Korean shipyards to study on Southeast Asian region based cruise ships. This study is to suggest directions for planning of interior spaces of Southeast Asian region based cruise ships. In order to accomplish this purpose the market situation is analyzed and the adequate ship's tonnage(70,000grt class) is decided. According to mission-based design process the sizes of standard staterooms are set up first and then the sizes of the important structural parts of ship are calculated. Through analyzing the 26 cruise ships of 70,000grt class the kinds, locations and sizes of public rooms are grasped. And we inspect 4 cruise ships of Star Cruises, which are now being operated in Southeast Asian region to understand design characteristics of interior spaces.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1086-1090
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• 2001

In this paper, a method deciding the permissible gains of the P and PT controllers for a retarded process under stable condition is proposed. For analysis, the controlled process is assumed to be first-order system with time delay. At first, the adjustable parameter sets causing stability limit are obtained based on the frequency domain condition which makes the roots of the characteristic equation locate on the imaginary axis. And the cut-in frequency ${\omega}_p$ to bring the parameter set to P control from PI control is derived is derived in terms of L and $T_m$ then ${\omega}_p$ is used to compute the maximum gain with stable condition. The results indicate that the permissible controller gains can be described by a unique if parameters L and $T_m$ are know.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.9-10
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• 2010

The lighting control power circuits should be designed in stable region according to the environment. A stable circuit is analyzed using ac equivalent circuits. The flyback converter with wide input voltage ranges is suitable for lighting control system. It is designed optimally for stability. The specifications are that the input voltage is 90V-230V, the output power is 12V/2.5A. The stability analysis is established using PSM(Phase Sensitive Multimeter) in experiment. As a result, it is confirmed that the gain margin and the phase margin are in stable area. The validity of the experimental measurement is verified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.321-327
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• 1996

Experiments were performed on the laminar premixed flame stabilized in a porous medium to know whether the flame downstream of the combustor exists or not. In previous theoretical studies, a stable flame has been predicted in the downstream region of the combustor, but it has never been observed in experiments. In this study, a stable downstream flame could be obtained for the lower burning velocity through circumferential heating by a blue flame positioned outside the periphery of the specially devised combustor. The existence of the stable downstream flame was confirmed by a direct photography of soot line, and temperature measurements. The effect of combustor diameter to flame stability was also considered. As the diameter of the combustor increases, the lean flammability limit was extended.