• The Korean Journal of Pain
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• v.34 no.4
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• pp.479-486
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• 2021

Background: Prior studies have reported that 40%-90% of the patients with celiac plexus-mediated visceral pain benefit from the neurolytic celiac plexus block (NCPB), but the predictive factors of response to NCPB have not been evaluated extensively. This study aimed to identify the factors associated with the immediate analgesic effectiveness of NCPB in patients with intractable upper abdominal cancer-related pain. Methods: A retrospective review was performed of 513 patients who underwent NCPB for upper abdominal cancer-related pain. Response to the procedure was defined as (1) a decrease of ≥ 50% or ≥ 4 points on the numerical rating scale (NRS) in pain intensity from the baseline without an increase in opioid requirement, or (2) a decrease of ≥ 30% or ≥ 2 points on the NRS from the baseline with simultaneously reduced opioid consumption after NCPB. Logistic regression analysis was performed to determine the factors associated with successful responses to NCPB. Results: Among the 513 patients included in the analysis, 255 (49.8%) and 258 (50.2%) patients were in the non-responder and responder group after NCPB, respectively. Multivariable logistic regression analysis showed that diabetes (odds ratio [OR] = 0.644, P = 0.035), history of upper abdominal surgery (OR = 0.691, P = 0.040), and celiac metastasis (OR = 1.496, P = 0.039) were the independent factors associated with response to NCPB. Conclusions: Celiac plexus metastases, absence of diabetes, and absence of prior upper abdominal surgery may be independently associated with better response to NCPB for upper abdominal cancer-related pain.

• Advances in Computational Design
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• v.4 no.3
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• pp.273-294
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• 2019

In this paper is presented the minimum cost (optimal design) for reinforced concrete circular isolated footings based on an analytic model. This model considers a load and two moments in directions of the X and Y axes, and the pressure has a variation linear, these are the effects that act on the footing. The minimum cost (optimal design) and the Maple program are shown in Flowcharts. Two numerical experiments are shown to obtain the minimum cost design of the two materials that are used for a circular footing supporting an axial load and moments in two directions in accordance to the code of the ACI (American Concrete Institute), and it is compared against the current design (uniform pressure). Also, the same examples are developed through the normal procedure to verify the minimum cost (optimal design) presented in this document, i.e., the equations of moment, bending shear and punching shear are used to check the thickness, and after, the steel areas of the footing are obtained, and it is compared against the current design (uniform pressure). Results section show that the optimal design is more accurate and more economical than to any other model. Therefore, it is concluded that the optimized design model presented in this paper should be used to obtain the minimum cost design for the circular isolated footings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.1
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• pp.97-102
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• 2019

Disaster accidents at industrial sites have been increasing every year. In shipyards there are countless enclosed spaces causing issues like harmful-toxic gases stuck in those sealed areas. And due to such special and complicated structures of the working places with many layers of walls separating each other, there exist more issues of communication with workers trapped inside when accidents happen. Under this circumstance there must be a huge difficulty to evacuate or rescue the workers in case of any disaster. Therefore, in this paper, We would like to introduce the "integrated safety system" to more effectively deal with the problems and prevent such disasters in tough working environments. The suggested integrated safety system can prevent accidents in advance because it can control the data on the location of the workers in real time and the numerical values such as gas, oxygen, and carbon dioxide generated in the workplace in real time.

• Advances in nano research
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• v.7 no.4
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• pp.249-263
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• 2019

In the current paper, an exact solution method is carried out for analyzing the thermo-mechanical vibration of curved FG nano-beams subjected to uniform thermal environmental conditions, by considering porosity distribution via nonlocal strain gradient beam theory for the first time. Nonlocal strain gradient elasticity theory is adopted to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field is considered. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Material properties of curved porous FG nanobeam are assumed to be temperature-dependent and are supposed to vary through the thickness direction of beam which modeled via modified power-law rule. Since variation of pores along the thickness direction influences the mechanical and physical properties, porosity play a key role in the mechanical response of curved FG nano-structures. The governing equations and related boundary condition of curved porous FG nanobeam under temperature field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved nanobeam supposed to thermal loading. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, porosity volume fractions, thermal effect, gradient index, opening angle and aspect ratio on the natural frequency of curved FG porous nanobeam are successfully discussed. It is concluded that these parameters play key roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Structural Engineering and Mechanics
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• v.71 no.6
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• pp.603-625
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• 2019

Main cable configurations under final dead load and in the unloaded state and critical construction parameters (e.g. unstrained cable length, unstrained hanger lengths, and pre-offsets for tower saddles and splay saddles) are the core considerations in the design and construction control of a suspension bridge. For the purpose of accurate calculations, it is necessary to take into account the effects of cable strands over the anchor spans, arc-shaped saddle top, and tower top pre-uplift. In this paper, a method for calculating the cable configuration under final dead load over a main span, two side spans, and two anchor spans, coordinates of tangent points, and unstrained cable length are firstly developed using conditions for mechanical equilibrium and geometric relationships. Hanger tensile forces and unstrained hanger lengths are calculated by iteratively solving the equations governing hanger tensile forces and the cable configuration, which gives careful consideration to the effect of hanger weight. Next, equations for calculating the cable configuration in the unloaded state and pre-offsets of saddles are derived from the cable configuration under final dead load and the conditions for unstrained cable length to be conserved. The equations for the main span, two side spans and two anchor spans are then solved simultaneously. In the proposed methods, coupled nonlinear equations are solved by turning them into an unconstrained optimization problem, making the procedure simplified. The feasibility and validity of the proposed methods are demonstrated through a numerical example.

• Earthquakes and Structures
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• v.17 no.2
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• pp.163-173
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• 2019

For Special Concentrically Braced Frame (SCBF), it is common that the damage concentrates at a certain story instead of spreading over all stories. Once the damage occurs, the soft-story mechanism is likely to take place and possibly to result in the failure of the whole system with more damage accumulation. In this study, we use a strongback column which is an additional structural component extending along the height of the building, to redistribute the excessive deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three specimens, namely S73, S42 and S0, which represent different combinations of stiffness and strength factors ${\alpha}$ and ${\beta}$ for the strongback columns, were designed based on results of numerical simulations. Specimens S73 and S42 were the specimens with the strongback columns, and S0 is the specimen without the strongback column. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), we can observe 29% and 11% improvement in Specimen S73 and S42, respectively. This improvement increases the nonlinear demand of the third-story braces and reduces that of the first-story braces where the demand used to be excessive, and, therefore, postpones the rupture of the first-story braces and enhances the ductility and energy dissipation capacity of the whole SCBF system.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.169-178
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• 2019

The replacement of damaged components is an important task for long-span bridges. Conventional strategy for component replacement is to close the bridge to traffic, so that the influence of the surrounding environment is reduced to a minimum extent. However, complete traffic interruption would bring substantial economic losses and negative social influence nowadays. This paper investigates traffic control technologies without interruption for component replacement of long-span bridges. A numerical procedure of traffic control technologies is proposed incorporating traffic microsimulation and site-specific data, which is then implemented through a case study of cable replacement of a long-span cable-stayed bridge. Results indicate traffic load effects on the bridge are lower than the design values under current low daily traffic volume, and therefore cable replacement could be conducted without traffic control. However, considering a possible medium or high level of daily traffic volume, traffic load effects of girder bending moment and cable force nearest to the replaced cable become larger than the design level. This indicates a potential risk of failure, and traffic control should be implemented. Parametric studies show that speed control does not decrease but increase the load effects, and flow control using lane closure is not effectual. However, weight control and gap control are very effective to mitigate traffic load effects, and it is recommended to employ a weight control with gross vehicle weight no more than 65 t or/and a gap control with minimum vehicle gap no less than 40 m for the cable replacement of the case bridge.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.485-496
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• 2021

So far analytical methods on collapse assessment of three-dimensional (3-D) steel frames have mainly focused on a single-column-removal scenario. However, the collapse of the Federal Building in the US due to car bomb explosion indicated that the loss of multiple columns may occur in the real structures, wherein the structures are more vulnerable to collapse. Meanwhile, the General Services Administration (GSA) in the US suggested that the removal of side columns of the structure has a great possibility to cause collapse. Therefore, this paper analytically deals with the robustness of 3-D steel frames in a two-side-column-removal (TSCR) scenario. Analytical method is first proposed to determine the collapse resistance of the frame during this column-removal procedure. The reliability of the analytical method is verified by the finite element results. Moreover, a design-based methodology is proposed to quickly assess the robustness of the frame due to a TSCR scenario. It is found the analytical method can reasonably predict the resistance-displacement relationship of the frame in the TSCR scenario, with an error generally less than 10%. The parametric numerical analyses suggest that the slab thickness mainly affects the plastic bearing capacity of the frame. The rebar diameter mainly affects the capacity of the frame at large displacement. However, the steel beam section height affects both the plastic and ultimate bearing capacity of the frame. A case study on a six-storey steel frame shows that the design-based methodology provides a conservative prediction on the robustness of the frame.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.401-409
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• 2020

Seismic fragility assessments include a procedure to combine the random variables of response and capacity to produce the relationship between failure probability and seismic intensity. The evaluation of the failure probability of simultaneous multiple failures of two or more components assumes that the failure probability of each component is independent of those of the others. However, a correlation is expected to exist because several random factors have the same cause. The multiple-failure probability can differ depending on this correlation and may be unconservative without considering the seismic correlation. Therefore, a practical methodology for fragility assessment should be evaluated using the seismic correlation and correlation coefficient for each random variable. In this study, several random variables were selected for numerical evaluation of the correlation coefficient. The correlation coefficient was then compared with each variable and the combined variables. The correlation coefficient using simplified and complex models were also compared to determine and analyze the differences between each of the approaches.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.93-100
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• 2021

Forward osmosis (FO) process is a chemical potential driven process, where highly concentrated draw solution (DS) is used to take water through semi-permeable membrane from feed solution (FS) with lower concentration. Recently, commercial FO membrane modules have been developed so that full-scale FO process can be applied to seawater desalination or water reuse. In order to design a real-scale FO plant, the performance prediction of FO membrane modules installed in the plant is essential. Especially, the flux prediction is the most important task because the amount of diluted draw solution and concentrate solution flowing out of FO modules can be expected from the flux. Through a previous study, a theoretical based FO module model to predict flux was developed. However it needs an intensive numerical calculation work and a fitting process to reflect a complex module geometry. The idea of this work is to introduce deep learning to predict flux of FO membrane modules using 116 experimental data set, which include six input variables (flow rate, pressure, and ion concentration of DS and FS) and one output variable (flux). The procedure of optimizing a deep learning model to minimize prediction error and overfitting problem was developed and tested. The optimized deep learning model (error of 3.87%) was found to predict flux better than the theoretical based FO module model (error of 10.13%) in the data set which were not used in machine learning.