• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.164-168
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• 2017

This study experimentally determined the effect of calcium ion ($Ca^{2+}$) (0-0.55 mM) and intial pH (4.0-10.0) on phosphorus (P) removal in synthetic wastewater (2 mg P/L) using titanium tetrachloride ($TiCl_4$) (0.12-0.18 mM). At TiCl4 concentration ([$TiCl_4$]) = 0.12 mM, the P removal efficiency was the highest (95.1%) at pH 7 but the efficiency decreased to 51.4% at pH 8. The P removal efficiency was 55.6% at $Ca^{2+}$ concentration ([$Ca^{2+}$]) = 0 mM but the efficiency increased to 90.5% at [$Ca^{2+}$] = 0.045 mM at [$TiCl_4$] = 0.12 mM. On the other hand, the P removal efficiency difference was not large (96.5-99.5%) with [$Ca^{2+}$] at [$TiCl_4$] = 0.15-0.18 mM. Within the design boundaries of $0.00{\leq}[Ca^{2+}]{\leq}0.18mM$ and $7.0{\leq}initial$ $pH{\leq}9.0$ at [$TiCl_4$] = 0.12 mM, the 90% P removal efficiency could be achieved at $[Ca2+]{\geq}0.10mM$ with pH 8.0 and $[Ca2+]{\geq}0.12mM$ with pH 9.0.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.261-271
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• 2016

In the prediction of response of a pile in soil, numerical approaches such as a finite element method are generally applied due to complicate nonlinear behaviors of soils. However, the numerical methods based on the finite elements require heavy efforts in pile and soil modelling and also take long computing time. So their usage is limited especially in the early design stage in which principal dimensions and properties are not specified and tend to vary. On the contrary, theoretical approaches adopting linear approximations for soils are relatively simple and easy to model and take short computing time. Therefore, if they are validated to be reliable, they would be applicable in predicting responses of a pile in soil, particularly in early design stage. In case of wind turbines regarded in this study, it is required to assess their natural frequencies in early stages, and in this simulation the supporting pile inserted in soil could be replaced with a simplified elastic boundary condition at the bottom end of the wind turbine tower. To do this, analysis for a pile in soil is performed in this study to extract the spring constants at the top end of the pile. The pile in soil can be modelled as a beam on elastic spring by assuming that the soils deform within an elastic range. In this study, it is attempted to predict pile deformations and influence factors for lateral loads by means of the beam-on-spring model. As two example supporting structures for wind turbines, mono pile and suction pile models with different diameters are examined by evaluating their influence factors and validated by comparing them with those reported in literature. In addition, the deflection profiles along the depth and spring constants at the top end of the piles are compared to assess their supporting features.

• Horticultural Science & Technology
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• v.30 no.4
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• pp.385-391
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• 2012

The growth of terminal shoots of persimmon (Diospyros kaki) was analyzed during the first two months from the time of bud sprout to understand the dynamics of their early growth. Field-grown, mature 'Fuyu' and 'Nishimurawase' trees were used in a three-year study at two locations in Gyeongnam province. The growth of terminal shoots was most active from late April, about 10 days after foliation, to early May, followed by a gradual decline by late May. The increase in leaf area continued unabated throughout May. The weight of a flower bud increased slowly until early May and rapidly after flowering. Although its extension growth had been ceased by late May, dry weight (DW) of a terminal shoot continued to increase almost linearly throughout May due to shoot thickening and continued growth of leaves and fruits. In late May, the leaves and the stem accounted for more than 60% and less than 20% of total DW of a shoot respectively; fruit proportion increased to 7 to 17% by then. Relative growth rate (RGR) of the terminal shoot was higher than 213 $mg{\cdot}g^{-1}{\cdot}d^{-1}$ in late April, but declined to less than 63 $mg{\cdot}g^{-1}{\cdot}d^{-1}$ in late May. Like the pattern of seasonal changes in RGR, net assimilation rate (NAR) of the shoots decreased from 1.9 to 2 $mg{\cdot}cm^{-2}{\cdot}d^{-1}$ to 0.5 to 0.8 $mg{\cdot}cm^{-2}{\cdot}d^{-1}$. An early-season 'Nishimurawase' did not differ from a late-season 'Fuyu' in RGR and NAR during the first two months of growth. The early growth of the shoots was affected mainly by the reserves redistributed from permanent organs, however, environmental conditions at the time was also involved.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.561-568
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• 2005

The object of this paper is to determine appropriateness for use of high-strength tensile bar as a tension web member. The gap K-joint of tensile bar types were compared with gap K-joint of square hollow section (SHS) types. For the same width-to-thickness ratio ($2{\gamma}=33.3$ ), tests were performed on four specimens of the SHS type and eight specimens of the tensile bar type. The comparison of capacity with the experimental results showed a capacity of the SHS type joint to be higher than that of the tensile bartype joint for the same brace-to-chord width ratio. Moreover, the capacity of the SHS type joints increased proportionally to the width ratio ${\beta}$), while tensile bar type joints increased as the tension width ratio (${\beta}2$). In failure mode, SHS-type specimens showed local buckling of the compression brace and plastic failure was observed between the tension brace and chord face, and with the tensile bar type specimens there appeared punching shear failure of the chord face at the toe of the connection plate. It is, therefore, concluded that width-to-thickness ratio should be lower than that of the hollow-section type and the relation between tension and compression width ratio should be considered.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.769-780
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• 2004

This paper's objective is to evaluate the experimental behavior of gap N-joints made of cold-formed, square, hollow steel sections, with a connection plate as a tension member. The principal parameters for testing included the ratio of chord width to thickness, the ratio of brace width to chord width, eccentric ratio, the shape of the compression member, the branch angle, and the stiffening plate of the chord flange. The strength and failure mode were examined through the test for the gap N-joint, consisting of several parameters. Based on the results of the test, the gap N-joints were determined according to the capacity preceding the displacement of the tension, regardless of the width ratio, and the split failure mode-connected surface for a chord in joints. The strength of the gap N-joints increased proportionally as the $2\gamma$(B/T) ratio decreased, and as the width ratio(${\beta}$) of branch to chord increased. Particularly, $2\gamma$(B/T) decreased as the capacity of gap N-joint increased. The results of the test were summarized for the capacity, initial stiffness, ductility, and change of the failure mode of each gap N-joint.

• Journal of Korean Society of Steel Construction
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• v.21 no.2
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• pp.135-144
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• 2009

This study aims to suggest an appropriate flexural reinforcement technique by evaluating the reinforcement capacity of specimens that underwent flexural reinforcement according to the post-tension method with the anchoring position of an unbonded tension member on the conventional SC composite beam and the applied tension level as variables. For the experiment, up to a predetermined yield load was applied to each type of specimen and then, unbounded post-tensioning was additionally conducted to examine its reinforcement capacity. The analysis of the said experiment showed that the post-reinforced SC composite beam was characterized by significantly improved yield stress and initial stiffness, compared with the pre-reinforced one and the experimental measurements/theoretical values of maximum stress ranged from 0.95 to 1.13 following reinforcement. There was little or no change depending on the maximum stress and tension in the specimen (D160, Class 240) whose neutral axis and upper part had anchoring devices mounted prior to reinforcement. Rather, the ductility decreased with the increasing tension. On the contrary, in the case of the other specimen (Class D120) whose neutral axis had anchoring devices mounted after reinforcement, both the maximum stress and ductility increased with increasing tension, which indicates that the latter tension reinforcement was reasonably appropriate and effective for the neutral axis reinforcement.

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.475-482
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• 2009

The behavior of earth retention wall installed in cut slope is different from the behavior of retention wall applied in urban excavation. In order to establish the design method of anchored retention walls in cut slope, the behavior of anchored retention wall can be investigated and checked in detail. In this study, the behavior of anchored retention wall was investigated by instrumentation installed in cut slope for an apartment construction stabilized by a row of piles. The horizontal displacement of anchored retention wall was larger than the displacement of slope soil behind the wall at the early stage of excavation. As the excavation depth became deeper, the horizontal displacement of slope soil was larger than the displacement of anchored retention wall. It means that the horizontal displacement of anchored retention wall due to excavation is restrained by soldier pile stiffness and jacking force of anchor. Jacking force of anchor was mainly influenced in the horizontal displacement of anchored retention wall. The displacements of anchored retention wall and slope soil were affected mainly by an rainfall infiltrated from the ground surface. Meanwhile, the horizontal displacement of anchored retention wall with slope backside was about 2-6 times larger than the displacement of anchored retention wall with horizontal backside of excavation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.527-533
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• 2010

The feeling that is evoked when products are handled has become increasingly important in the design of products primarily used by humans. In the traditional product design process, prototypes are built several times in order to evaluate the feeling evoked during use. However, these design processes can be optimized by adopting a haptic simulator that can serve as a prototype. The design method based on the use of the haptic simulator is called haptics-aided design (HAD), which is the main subject of this paper. Here, a new HAD method that can be effectively used to design a custom-made chair is proposed. A haptic simulator, which is composed of a haptic chair and an intuitive graphical user interface, was developed. The simulator can adjust the impedance of the backrest and seat pan of a chair in real time. The haptic chair was used instead of real prototypes in order to evaluate the comfort of the initially designed seat pan and backrest on the basis of their stiffness and damping values. It was shown that the HAD method can be effectively used to design a custom-made chair and can be extended to other product design processes.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.35-45
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• 2013

The concrete-filled tube column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. It suggests that pipe should be produced by welding two sides together where two shapes are joined after a channel is pre-welded onto the three sides in order to form an internal diaphragm. The upper diaphragm of the connection used the horizontal plate and the lower diaphragm used the Vertical plate. This research performed 6 monotonic tension experiments describing the connection upside and downside in order to evaluate the structural capability of the offered connection. And the cyclic loading experiment was performed about 2 T-Type column to beam connections. As to the experimental result edge cutting geometry, there was no big effect. An increase in the number of holes of the plate ultimate strength was increased by 5% and The thickness of the plate increases, the maximum strength was increased by 4%. T-Type connections until it reaches the plastic moment showed a stable behavior.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.505-510
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• 2001

To improve germinability of carrot seeds of 'Inari', 'Mansan', 'Mussang', and 'Hongsim' cultivars, various levels of solid matrix priming (SMP) and the physiological changes of seeds associated with SMP were examined. As the ratio of water in a seed-Micro Cel E-water mix and priming duration increased, seed germinability enhanced. However, there was radicle protrusion during SMP in some cultivars, indicating the existence of cultivar different variations of the optimum conditions. The optimum ratio for a seed-Micro Cel E-water mix was 5 : 3 : 10.5. In this mix, the optimum durations for the treatment were 3 days for 'Mansan' and 5 days for other cultivars. SMP at $20^{\circ}C$ to $25^{\circ}C$ resulted in a higher germination percentage and a shorter $T_{50}$. Seeds absorbed water quickly within an hour and the percentage of moisture was stable at 43 to 49 after 24 hours of the treatment. Conductivity of the mix declined for the first 6 hours to $100{\mu}S{\cdot}cm^{-1}$ with little changes thereafter. On the other hand, the pH of the mixed increased slightly during the early phase, and then returned to the initial level as the treatment proceeded.