• Environmental Engineering Research
• /
• v.15 no.2
• /
• pp.93-98
• /
• 2010

This study aims to determine the chemical composition and seasonal variation of atmospheric acid deposition in order to identify possible sources contributing to precipitation. Sampling and analysis of 132 wet deposition samples were carried out from January to December 2008 at Mae Hia Research Center, Chiang Mai University, Chiang Mai Province. Total precipitation was 1,286.7 mm. Mean electro-conductivity and pH values were 0.94 mS/m and 6.27, respectively. Major cations ($Na^+$, ${NH_4}^+$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$) and major anions ($HCOO^-$, $CH_3COO^-$, $Cl^-$, ${NO_3}^-$, and ${SO_4}^{2-}$) were determined by Ion Chromatography. The relative volume weight mean concentrations of anions, in descending order, were ${SO_4}^{2-}$ > ${NO_3}^-$ > $Cl^-$ > $CH_3COO^-$ > $HCOO^-$ and those of cations were $NH_4^+$ > $Ca^{2+}$ > $Mg^{2+}$ > $K^{+}$ > $Na^+$. Results of a principle component analysis highlighted the influence of various possible sources of ions such as agricultural activity, fuel combustion, marine sources, soil resuspension, and biomass burning.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.5
• /
• pp.762-768
• /
• 1987

The capacitive transducers, which are used of the principle of capacitance changes by means of the variation of distance between electrodes, are usually utilized for measurement of small displacements. But the measurement ranges of this method are limited. In this study, the measurement ranges are extended by using the variation method of the surface area of electrodes. Thus the capacitive transducer and signal conditioner, which are having the capability of measurement range of 25mm and resolution of 0.1\ulcorner, have developed, and its environmental characteristics are also tested.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.12 no.2
• /
• pp.42-50
• /
• 1987

This objective of this paper is to develop an efficient method with small memory requirement for a feed-mixing problem on a micro computer. First this method uses the decomposition principle to reduce the memory requirement. Next, the decomposition principle is modified to fit the problem. Further four different variations in solving subproblems are designed in order to improve efficiency of the principle. According to the test with respect to the processing time, the best variation is such that the dual simplex method is used, and the optimal basis of a previous subproblem is used as an initial basis, and the master problem is (M +1) dimensional. In general, the convergence of solution becomes slower near the optimal value. This paper introduces a termination criterion for a sufficiently good solution. According to the test, 5%-tolerence is acceptable with respect to the relation between the processing time and optimal value.

• Journal of applied mathematics & informatics
• /
• v.12 no.1_2
• /
• pp.429-436
• /
• 2003

We study the asymptotic equivalence between the nonlinear differential system $\chi$'(t) = f(t, $\chi$(t)) and its variational system ν'(t) = f$\chi$(t, 0)ν(t) by using the comparison principle and notion of strong stability.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.370-373
• /
• 2005

We have developed Hybrid algorithm for yellow sand detection. Hybrid algorithm is composed of three methods using infrared bands. The first method used the differential absorption in brightness temperature difference between $11\mu m\;and\;12\mu m$ (BID _1), through which help distinguish the yellow sand from various meteorological clouds. The second method uses the brightness temperature difference between $3.7\mu m\;and\;11\mu m$ (BID_2). The technique would be most sensitive to dust loading during the day when the BID _2 is enhanced by reflection of $3.7\mu m$ solar radiation. The third one is a newly developed algorithm from our research, the so-called surface temperature variation method (STY). We have applied the three methods to MODIS for derivation of the yellow sand dust and in conjunction with the Principle Component Analysis (PCA), a form of eigenvector statistical analysis. PCI shows better results for yellow sand detection in comparison with the results from individual method. The comparison between PCI and MODIS aerosols optical depth (AOD) shows remarkable good correlations during daytime and relatively good correlations over the land.

• Coupled systems mechanics
• /
• v.13 no.4
• /
• pp.359-373
• /
• 2024

The present study aims to investigate the free vibration of bi-directional functionally graded (BDFG) beams using a refined shear deformation (RSD) theory. Power law variation of material composition was considered along thickness and longitudinal directions. The beams are considered simply supported. The methodology adopted is the Hamilton principle and the governing equation was solved using Navier's method for simply supported boundary conditions. A metal-ceramic combination of materials was used to provide gradation as per power law variation. The equivalent elasticity modulus and density of BDFG were computed using the rule of mixture. The results of the study were related to published works and found to be a good match. The effect of grading parameters in the thickness and longitudinal direction was studied to investigate its impact on the natural frequency.

• Earthquakes and Structures
• /
• v.1 no.1
• /
• pp.1-19
• /
• 2010

It has been known that one-dimensional rod theory is very effective as a simplified analytical approach to large scale or complicated structures such as high-rise buildings, in preliminary design stages. It replaces an original structure by a one-dimensional rod which has an equivalent stiffness in terms of global properties. If the structure is composed of distinct constituents of different stiffness such as coupled walls with opening, structural behavior is significantly governed by the local variation of stiffness. This paper proposes an extended version of the rod theory which accounts for the two-dimensional local variation of structural stiffness; viz, variation in the transverse direction as well as longitudinal stiffness distribution. The governing equation for the two-dimensional rod theory is formulated from Hamilton's principle by making use of a displacement function which satisfies continuity conditions across the boundary between the distinct structural components in the transverse direction. Validity of the proposed theory is confirmed by comparison with numerical results of computational tools in the cases of static, free vibration and forced vibration problems for various structures.

• Journal of the Optical Society of Korea
• /
• v.4 no.1
• /
• pp.14-18
• /
• 2000

We have investigated gain flattening of EDFA systems with or without a gain equalizer for WDM long-haul transmission using a re-circulating EDFA loop. Without a gain equalizer, gain variation as small as 2.9 dB was achieved over the 10-nm band of a 100 cascaded EDFA system by the inversion principle. With a gain equalizer based on all-fiber acousto-optic tunable filters, two different config-urations of EDFAs were tested. For a single-stage EDFA scheme, the 21-nm band has shown 3.8 dB of gain variation at 17.4 ∼ 20.3 dB of OSNRs after the 100the stage of EDFAs. For a dual-stage EDFA scheme, a wider bandwidth of 34 nm has shown 3.6-dB variation after 40 cascaded EDFAs.

• Advances in nano research
• /
• v.14 no.5
• /
• pp.421-433
• /
• 2023

In the present paper, the influences of the variation of exponent of volume fraction of carbon nanotubes (CNTs) on the natural frequencies (NFs) of the carbon nanotube-reinforced composite (CNTRC) beams under four different boundary conditions (BCs) are investigated. The single-walled carbon nanotubes (SWCNTs) are assumed to be aligned and dispersed in a polymeric matrix with various reinforcing patterns, according to the variation of exponent of volume fraction of CNTs for functionally graded (FG) reinforcements. Besides, uniform distribution (UD) of reinforcement is also considered to analyze the influence of the non-linear (NL) variation of the reinforcement of CNTs. Using Hamilton's principle and third-order shear deformation theory (TSDT), the equations of motion of the CNTRC beam are derived. Under four different BCs, the resulting equations are solved analytically. To verify the present formulation, comparison investigations are conducted. To examine the impacts of several factors on the NFs of the CNTRC beams, numerical examples and some benchmark results are presented.

• Structural Engineering and Mechanics
• /
• v.74 no.4
• /
• pp.533-545
• /
• 2020

An optimal design method for a spoke double-layer cable-net structure (SDLC) is proposed in this study. Simplified calculation models of the SDLC are put forward to reveal the static responses under vertical loads and wind loads. Next, based on an energy principle, the relationship among the initial prestress level, cross-sectional areas of the components, rise height, sag height, overall displacement, and relative deformation is proposed. Moreover, a calculation model of the Foshan Center SDLC is built and optimized. Given the limited loading cases, material properties of the components, and variation ranges of the rise height and sag height, the self-weight and initial prestress level of the entire structure can be obtained. Because the self-weight of the cables decreases with increasing of the rise height and sag height, while the self-weight of the inner strut increases, the total weight of the entire structure successively exhibits a sharp reduction, a gradual decrease, a slow increase, and a sharp increase during the optimization process. For the simplified model, the optimal design corresponds to the combination of rise height and sag height that results in an appropriate prestress level of the entire structure with the minimum total weight.