• Steel and Composite Structures
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• v.25 no.5
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• pp.603-615
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• 2017

This experimental research presents the seismic performance of steel reinforced high-strength concrete (SRHC) short columns. Eleven SRHC column specimens were tested under simulated earthquake loading conditions, including six short column specimens and five normal column specimens. The parameters studied included the axial load level, stirrup details and shear span ratio. The failure modes, critical region length, energy dissipation capacity and deformation capacity, stiffness and strength degradation and shear displacement of SRHC short columns were analyzed in detail. The effects of the parameters on seismic performance were discussed. The test results showed that SRHC short columns exhibited shear-flexure failure characteristics. The critical region length of SRHC short columns could be taken as the whole column height, regardless of axial load level. In comparison to SRHC normal columns, SRHC short columns had weaker energy dissipation capacity and deformation capacity, and experienced faster stiffness degradation and strength degradation. The decrease in energy dissipation and deformation capacity due to the decreasing shear span ratio was more serious when the axial load level was higher. However, SRHC short columns confined by multiple stirrups might possess good seismic behavior with enough deformation capacity (ultimate drift ratio ${\geq}2.5%$), even though a relative large axial load ratio (= 0.38) and relative small structural steel ratio (= 3.58%) were used, and were suitable to be used in tall buildings in earthquake regions.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.1
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• pp.47-54
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• 2008

As the demands of environment protection increases, the pulp mold container is developed to substitute for EPS (expanded polystyrene) as a shock absorbing packaging material. The water-absorbing ratio and mechanical properties such as tensile strength and compressive strength of pulp mold are important factors to evaluate its shock absorbing characteristics. Influences of mixing ratios of ONP (old newspaper) and OCC (old corrugated container) on physical properties of pulp mold were investigated at various conditions of temperature and relative humidity. The optimum mixing ratio of ONP and OCC was also searched based on physical properties. The results showed that when relative humidity was increased from 60% to 90%, the water absorption ratio of pulp mold increased significantly, tensile strength decreased 20$\sim$30%, and compressive strength decreased 10$\sim$20%. In addition, the optimum mixing ratio of ONP and OCC was found to be 50%:50%.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2121-2126
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• 2003

Supersonic free jets discharging from an orifice or a nozzle have long been research subject with a number of engineering applications and have mainly been investigated using dry air or other gas without any condensation effects. The major characteristics of those supersonic jets are now well known in terms of jet pressure ratio and ratio of specific heats of gas. Recently, the supersonic jets of superheated steam or moist air are being used in many industrial applications, in which case is expected that the condensation effects might alter the fundamental structure of the dry air jet. The present study aims to investigate the supersonic moist air jet and to clarify the condensation effects on the jet structure. An experiment is carried out using an indraft wind tunnel facility. The relative humidity of moist air is controlled at the nozzle supply, and the jet pressure ratio is varied to obtain the moderately under expanded flows at the exit of the nozzle. It is found that the relative humidity of moist air can change the diameter and location of Mach Disk.

• Journal of Biosystems Engineering
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• v.29 no.6 s.107
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• pp.495-500
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• 2004

This study was performed to develop thin layer drying equations for low temperature. Thin layer drying tests of short grain rough rice were conducted at three low temperature levels of 15, 25, $35^{\circ}C$ and two relative humidity levels of 30, $50\%$, respectively. The measured moisture ratios were fitted to the selected four drying models (Page, Thompson, Simplified diffusion and Lewis model) using stepwise multiple regression analysis. The overall drying rate increased as the drying air temperature was increased and as relative humidity was decreased, but the effect of temperature increase was dominant. Half response time (Moisture ratio=0.5) of drying was affected by both drying temperature and relative humidity at drying temperature of below $25^{\circ}C$, but at $35^{\circ}C$ was mainly affected by drying temperature. The results of comparing coefficients of determination and root mean square error of moisture ratio for low drying models showed that Page model was found to fit adequately to all drying test data.

• Geomechanics and Engineering
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• v.11 no.5
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• pp.639-655
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• 2016

The effect of particle breakage and intermediate principal stress ratio on the behaviour of crushable granular assemblies under true triaxial stress conditions is studied using the discrete element method. Numerical results show that the increase of intermediate principal stress ratio $b(b=({\sigma}_2-{\sigma}_3)/({\sigma}_1-{\sigma}_3))$ results in the increase of dilatancy at low confining pressures but the decrease of dilatancy at high confining pressures, which stems from the distinct increasing compaction caused by breakage with b. The influence of b on the evolution of the peak apparent friction angle is also weakened by particle breakage. For low relative breakage, the relationship between the peak apparent friction angle and b is close to the Lade-Duncan failure model, whereas it conforms to the Matsuoka-Nakai failure model for high relative breakage. In addition, the increasing tendency of relative breakage, calculated based on a fractal particle size distribution with the fractal dimension being 2.5, declines with the increasing confining pressure and axial strain, which implies the existence of an ultimate graduation. Finally, the relationship between particle breakage and plastic work is found to conform to a unique hyperbolic correlation regardless of the test conditions.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.67-78
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• 1996

Gas sensing element, $\gamma-Fe_2O_3$was synthesized by dehydration, reduction, and oxidation of $$${\gamma}$-FeOOH, which was synthesized with $FeSO_4\;{\cdot}\;7H_2O$ and NaOH. They were produced as a bulk-type, a thick film-type. Then, their responses and mechanisms of response to the gas of liquefied-petroleum were studied. The qualities of gas sensing elements are decided by the structure and the relative surface area. In the process of $\alpha-FeOOH $synthesis, the effects of reaction conditions as the equivalent ratio, on the structure and the relative surface area of gas sensing element were observed. The changes of the structure were measured with XRD, SEM, TG-DTA and BET. The resistance changes of the synthesized gas sensor in the air were measured. The response ratio were also measured for the changes of working temperature and gas concentration. As a result of analysis with XRD, it was confirmed that the the best conditions for the synthesis of $\alpha -FeOOH$ were equivalent ratio 0.65. The thick film-type element of $\gamma-Fe_2O_3$responded more quickly than the bulk-type did. The structure and the relative surface area of the $\alpha-FeOOH $were confirmed as the important factors deciding gas response charcteristics.

• Journal of Biosystems Engineering
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• v.19 no.4
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• pp.358-368
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• 1994

Major factors in reducing the stacking strength of corrugated fiberboard boxes in cold storage or transport conditions are high relative humidity, causing elevated moisture absorption by the boxes. The bottom boxes in a stack will deform to the critical deflection causing agricultural products damage there, and eventually additional deflection will cause box collapse and finally toppling of the stack. The study was conducted to determine the water absorption characteristics and the compressive strength of the corrugated fiberboard boxes being widely used in packaging agricultural products in Korea. The sample boxes for the study were selected from the regular slotted containers (RSC) types, and one was the box used in apple packaging (Box A), another one was the box used in pear packaging (Box B). The corrugated shipping containers were made from a large portion of recycled fibers in Korea, and comparing with Box B, Box A was fabricated from fiberboard which contained more percentage of old corrugated containers (OCC) imported from foreign countries than domestic waste paper. The results obtained from the study were summarized as follows ; 1. Equilibrium moisture content (EMC) of the sample boxes was established after about 20 hours, and the EMC by absorption was lower than that by desorption. The EMC increased with the increasing of relative humidity and with the decreasing of temperature, and the rate of increasing was much higher above the relative humidity of 50%. 2. The maximum compressive strength of Box A was about 100 kgf greater than that of Box B on the same enviromental conditions. The strength of the sample boxes decreased rapidly with the increasing of relative humidity. The effect of relative humidity on the strength was a little higher than that of temperature. 3. As the applied load was progressively increased and a level was reached, the vertical side panels ($L{\times}D$) deflected laterally inwards or outwards. The panels deflected laterally inwards at higher relative humidity. 4. The maximum compressive deflection ratio and the critical deflection ratio of the sample boxes were increased linearly with the increasing of relative hunidity, but trends for its ratios showed inconsistant response to temperature.

• Communications of the Korean Mathematical Society
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• v.30 no.4
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• pp.481-491
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• 2015

We calculate volume ratio of a hypersurface orthogonal to a timelike geodesic relative to that of a hypersurface in the FLRW space-time.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.853-856
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• 2005

A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

• Bulletin of the Korean Mathematical Society
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• v.52 no.5
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• pp.1559-1568
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• 2015

The relative class number $H_d(f)$ of a real quadratic field $K=\mathbb{Q}(\sqrt{m})$ of discriminant d is the ratio of class numbers of $O_f$ and $O_K$, where $O_K$ denotes the ring of integers of K and $O_f$ is the order of conductor f given by $\mathbb{Z}+fO_K$. In a recent paper of A. Furness and E. A. Parker the relative class number of $\mathbb{Q}(\sqrt{m})$ has been investigated using continued fraction in the special case when $(\sqrt{m})$ has a diagonal form. Here, we extend their result and show that there exists a conductor f of relative class number 1 when the continued fraction of $(\sqrt{m})$ is non-diagonal of period 4 or 5. We also show that there exist infinitely many real quadratic fields with any power of 2 as relative class number if there are infinitely many Mersenne primes.