• Geomechanics and Engineering
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• v.28 no.4
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• pp.375-384
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• 2022

The glacial tills and shales in Midwestern states of the USA often show strength degradation after construction. They are often in need of applying soil modification techniques to remediate their strength degradation with weathering process. This study investigated the weathering durability of these natural soils and biopolymer treated soils by comparing direct shear test results for wet-dry and wet-freeze-thaw-dry cycled specimens. The tests showed that untreated glacial tills maintained only 62% and 50% initial shear strength after eight wet-dry cycles and eight wet-freeze-thaw-dry cycles, respectively. These untreated soils could not withstand by themselves after 16 weathering cycles. The same soils treated with 1.5% (by dry weight) food-grade Xanthan gum maintained 140% and 88% initial shear strength of untreated soils after 16 weathering cycles for wet-dry cycles and wet-freeze-thaw-dry cycles, respectively. The same soils treated with 1.5% (by dry weight) Gellan gum maintained 82% and 60% initial shear strength of untreated ones after 16 weathering cycles, respectively. Similar results were obtained for crushed shales, manifesting that the biopolymerization method may be adopted as a new eco-friendly method to enhance the weathering durability of these problematic soils of glacial tills and shales.

• Physical Therapy Korea
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• v.21 no.1
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• pp.37-46
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• 2014

Asymmetric sitting posture may cause asymmetric buttock pressure and unilateral low back pain (LBP). The purpose of this study was to compare the differences of buttock pressure between both sides, and pelvic angle (sagittal and coronal planes) during typing in a sitting position on a pressure mat (Baltube) in individuals with and without unilateral LBP. Ten subjects with unilateral LBP and ten subjects without unilateral LBP were recruited for this study. Buttock pressure was measured using a pressure mat and pelvic angles were measured using a palpation meter. The subjects performed typing in a sitting posture for 30 minutes. Pressure data were collected and averaged at initial term (from start to first minutes) and final term (last minutes of 30 minutes). Angles of pelvic tilting were measured after 30 minutes typing. Pressure asymmetry values (difference in pressure between both sides) were calculated at the initial and final terms. A two-way analysis of variance was used to compare the differences between the initial and final pressure asymmetry values in subjects with and without unilateral LBP. An independent t-test was applied to compare the pelvic tilt angles between the two groups. To compare the change of pressure from the initial term to the final term between the symptomatic and asymptomatic sides in the unilateral LBP group, a paired t-test was applied. In the unilateral LBP group, the pressure asymmetric value at the final term was significantly greater than that of the initial term (p<.05). The angle of pelvic tilting in coronal plane was significantly greater in the unilateral back pain group compared to the without unilateral LBP group (p<.05), however, there was no significant difference in the angle of pelvic tilting in the sagittal plane between the two groups (p>.05). In the unilateral LBP group, the change of pressure from the initial term to the final term was significantly less in the symptomatic side (-6.90 mmHg) than the asymptomatic side (5.10 mmHg). This asymmetric sitting posture may contribute to unilateral LBP in the sitting position. Further studies are needed to determine if asymmetric weight bearing in sitting causes unilateral LBP or if unilateral back pain causes asymmetric weight bearing, and if the correction of asymmetric weight bearing in sitting can reduce unilateral LBP.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.313-318
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• 2004

We studied a storage of waste-brown seaweed at room temperature and degradation of alginate in seaweed by microorganism DS-02. The seaweeds, mixed with 5.0 wt% DS-02 and sealed in vinyl package without any other treatment, could be stored longer than 1 year without spoilage at room temperature. During the storage process, the alginate of seaweed was decomposed by enzyme of DS-02 and the molecular weight of alginate decreased to about 1/10 of initial quantity. DS-02 growed as fast as it had maximum weight after 24 hour culture and it's enzyme had a maximum activity of alginate degradation at $40^{\circ}C.$ The seaweed sample became particles in DS-02 culture solution and the M. W of alginate decreased to about 1/10 of initial value after 24 hour decomposition. The effect of alginate degradation with DS-02 was similar to that of degradation with 3.0 M HCI solution for 24 hour.

• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.412-415
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• 1998

The accumulation process of $Pb^{2＋}$ in an industrial strain of Saccharomyces cerevisiae proved to be temperature-dependent, and was quite similar to chemical adsorption at the initial stage of $Pb^{2＋}$accumulation. The initial $Pb^{2＋}$ accumulation rate increased from 11.4 to 46.2 mg $Pb^{2＋}$/g cell dry weight/day, in response to the increased temperature from $20^{\circ}C\;to\;50^{\circ}C$ while the maximal $Pb^{2＋}$ accumulation amount (175.8 mg $Pb^{2＋}$/g cell dry weight) was achieved at $30^{\circ}C$. The maximal $Pb^{2＋}$/ accumulation amount with temperature was independent of ion exchange with $K^＋\;and\;Mg^{2+}$.

• Structural Engineering and Mechanics
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• v.59 no.6
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• pp.951-972
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• 2016

The purpose of this study is to illustrate the propagation of the shear waves (SH-waves) in a prestressed hetrogeneous orthotropic media overlying a pre-stressed anisotropic porous half-space with self weight. It is considered that the compressive initial stress, mass density and moduli of rigidity of the upper layer are space dependent. The proposed model is solved to obtain the different dispersion relations for the SH-wave in the elastic-porous medium of different properties. The effects of compressive and tensile stresses along with the heterogeneity, porosity, Biot's gravity parameter on the dispersion of SH-wave are shown numerically. The wave analysis further indicates that the technical parameters of upper and lower half-space affect the wave velocity significantly. The results may be useful to understand the nature of seismic wave propagation in geophysical applications and in the field of earthquake and material science engineering.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1517-1520
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• 2003

In this paper, we design a wedge type rail-clamp which can protect container crane from wind with constant clamping force regardless of the operating period. When we design wedge type rail clamp, it is important to determine the weight for locker to descent smoothly with an initial clamping force of rail and pad. Therefor, this paper suggest a process to decide a wright within proper range which could be obtained using FEA of wedge type rail clamp.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.208-211
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• 2003

Characteristics of biosorption of lead by marine algae, Laminaria japonica, were examined. The biosorption capacity of lead by L. japonica was achieved up to 30％ of its own weight and proportional to the initial lead concentration. However, the opposite result was shown in different initial weight of biomass. Ion exchange reaction between lead ions and calcium ions was observed on lead biosorption with Ca-Ioaded biomass. Stoichiometric coefficient, which can represent the exchange ratio between metal ions and protons during elution process, was determined as 1.39. Therefore, it was concluded that the reaction between lead ions already attached in biomass and protons in bulk solution was not fully stoichiometric ion exchange relation at elution process.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.74-84
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• 2004

In this paper, a theoretical method was derived to redesign carbody members by substituting light-weight materials, and to estimate their structural characteristics. Some performance indices to estimate structural behaviors were derived in order to obtain equivalent designs in case of material substitutions under important design constraints of rolling stock, such as bending stiffness, natural frequency, bending and buckling strength. Validity of the theoretical method was evaluated by comparing its results with finite element results in some examples where the aluminium alloy was substituted for the structural steel. The numerical results of the examples show that the proposed method gives reasonable initial guesses for the material substitution designs.

• Journal of Applied Reliability
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• v.17 no.2
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• pp.143-149
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• 2017

Purpose: In recent years, weight reduction for improving fuel efficiency of the vehicle and cost reduction have been developed. The structure of suspension link is widely used as a single plate press structure which can reduce process and weight compared to existing pipe welding method. However, it was found that the lifetime of a single plate press structure is determined by initial defects that occurred during initial manufacturing rather than fatigue damage caused by driving. Methods: I research the mechanism of failure phenomenon of the single plate press assist arm of rear wheel. In addition, I investigate durability effect parameters to determine the link lifetime in inserting bush into single plate press process through durability test. Conclusion: I discover significant durability effect parameter in inserting bush into single plate press process. It is expected that the durability can be improved by suggesting a bush inserting process inspection guide for similar suspension link like single plate press structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.149-156
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• 1999

Numerical studies were carried out to investigate the mechanical properties of competent hysteric isolators for seismic design of bridge. For dynamic analysis, bridges with isolator were simplified to a model with single degree of freedom. The initial stiffness and the yielding forces of hysteric isolators were varied. Seismic responses obtained by time history analysis show that about 4% of the weight acting as the inertia force is appropriate for the yielding force of isolator. And also better results could be achieved with the values about two times the weight per unit displacement for the initial stiffness of isolator.