• International conference on construction engineering and project management
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• 2007.03a
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• pp.96-105
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• 2007

This paper presents a study on the impact of variation of construction material prices on the feasibility of building projects in Vietnam. The paper makes use of Monte-Carlo simulation for financial risk analysis of net present Value (NPV) and internal rate of return (IRR). To well illustrate the influencing, a case study is presented. The research results show that there is a strong correlation between steel prices, gold prices, and $US exchange rate. Outputs of statistics also reveal that the concurrent variation of prices of cement, steel, sand, brick, formwork and stone has strongly negative impact on NPV and IRR of building projects. The results also indicate that the proportion of steel cost to total construction cost is 17.95% which is the cause of risks for the feasibility of building project in Vietnam. The paper stresses that feasibility study of building project must integrate the impact of construction materials prices in order to mitigate risks in developing countries as Vietnam.

• Ocean Systems Engineering
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• v.9 no.4
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• pp.349-368
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• 2019

Triceratops is one of the new generations of offshore compliant platforms suitable for ultra-deepwater applications. Apart from environmental loads, the offshore structures are also susceptible to accidental loads. Due to the increase in the risk of collision between ships and offshore platforms, the accurate prediction of structural response under impact loads becomes necessary. This paper presents the numerical investigations of the impact response of the buoyant leg of triceratops usually designed as an orthogonally stiffened cylindrical shell with stringers and ring frames. The impact analysis of buoyant leg with a rectangularly shaped indenter is carried out using ANSYS explicit analysis solver under different impact load cases. The results show that the shell deformation increases with the increase in impact load, and the ring stiffeners hinder the shell damage from spreading in the longitudinal direction. The response of triceratops is then obtained through hydrodynamic response analysis carried out using ANSYS AQWA. From the results, it is observed that the impact load on single buoyant leg causes periodic vibration in the deck in the surge and pitch degrees of freedom. Since the impact response of the structure is highly affected by the geometric and material properties, numerical studies are also carried out by varying the strain rate, and the location of the indenter and the results are discussed.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.151-159
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• 2012

The characteristics of an impact load and pressure were experimentally investigated. Drop tests were carried out using a modified Wigley with CB = 0.56. The vertical force, pressures, and vertical accelerations were measured. A 6-component load cell was used to measure the forces, piezo-electric sensors were used to capture the impact pressure, and strain-gauge type accelerometers were used to measure the vertical accelerations. A 50-kHz sampling rate was applied to capture the peak values. The repeatability of the measured data was confirmed and the basic characteristics of the impact load and pressure such as the linearity to the falling height were observed for all of the measurements. A simple formula was derived to extract the physical impact load from the measured force based on a simple mass-sensor-mass diagram, which was validated by comparing impact forces with existing data using the mathematical model of Faltinsen and Chezhian (2005). The effects of the elasticity of the model and change in acceleration during the water entry were investigated. It is interesting to observe that the impact loads occurred and reached peak values at the same time duration after water entry for all drop heights.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.95-101
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• 2018

The low rate of penetration and short lifetime of drilling bit served as the most common problems encountered in hard formation drilling, thus leading to severe restriction of drilling efficiency in oil and gas reservoir. This study developed a new local impact drilling method to enhance hard formation drilling efficiency. The limitation length formulas of radial/lateral cracks under static indentation and dynamic impact are derived based on the experimental research of Marshall D.B considering the mud column pressure and confining pressure. The local impact rock breaking simulation model is conducted to investigate its ROP raising effect. The results demonstrate that the length of radial/lateral cracks will increase as the decrease of mud pressure and confining pressure, and the local impact can result in a damage zone round the impact crater which helps the rock cutting, thus leading to the ROP increase. The numerical results also demonstrate the advantages of local impact method for raising ROP and the vibration reduction of bit in hard formation drilling. This study has shown that the local impact method can help raising the ROP and vibration reduction of bit, and it may be applied in drilling engineering.

• Smart Media Journal
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• v.11 no.7
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• pp.9-18
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• 2022

With the outbreak of COVID-19, the world is in unexpected chaos. In particular, the Korean economy, which has a large number of self-employed people, is experiencing enormous damage from COVID-19. The purpose of this study is to analyze the causal impact of start-ups and closures by industry due to the COVID-19 outbreak. For the causal impact analysis, we collected and analyzed 8,312,224 cases of start-up and closure of 190 businesses that occurred on the local administrative license data public site for 11 years from 2010 to 2020. As a result of the analysis of the causal impact of COVID-19, there were 29 industries in which start-ups increased(increase rate 313.14% ~ 6.39%), 23 industries in which start-ups decreased(decrease rate 70.62% ~ 11.27%), 21 industries in which closures increased(increase rate 157.55% ~ 13.57%), and 18 industries in which business closures decreased(reduction rate 49.45% ~ 12.91%). The industries in which start-ups increased and closures decreased due to the COVID-19 outbreak were disinfection, food transportation, and general sales of health functional food. The industries in where start-ups decreased and closures increased due to the COVID-19 outbreak were youth game providing industry, danran pub business, and general game providing industry. It is expected that the results of this study will help practitioners who manage various infectious diseases to understand the causal impact of infectious disease outbreaks and to prepare countermeasures.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.197-201
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• 2001

The influence of argon, oxygen, and nitrogen admixtures on the dissociation of $Cl_2$ molecules in a glow discharge low-temperature plasma under the constant pressure conditions was investigated. For $Cl_2/Ar$ and $Cl_2/O_2$mixtures, the concentration of chlorine atoms was observed to be a practically constant at argon or oxygen concentrations up to 50%. This invariability is a most pro bably explained by relative increase in rate of $Cl_2$ direct electron impact dissociation due to the changes in electrophysical parameters of plasma such as EEDF, electron drift rate and mean energy. For all the considered mixtures, the contribution of stepwise dissociation involving active species from gas additives (metastable atoms and molecules, vibrationally excited molecules) was found to be negligible.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.419-424
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• 2012

This paper presents a tubular reciprocating translational motion permanent magnet synchronous motor for percussive drilling applications for offshore oil & gas industry. The motor model and rock model are built up by doing force analysis of the motor and analyzing the physical procesof impact. The optimization of input voltage waveforms to maximize the rate of penetration is done by simulations. The simulation results show that the motor can be utilized in percussive drilling applications and achieve a very large impact force. Simulation results for optimization also show that second harmonic input voltage produces a higher rate of penetration than the sine wave and fourth harmonic input voltages.

• Journal of Preventive Medicine and Public Health
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• v.22 no.2 s.26
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• pp.189-196
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• 1989

In January 1988, district medical insurance plan was executed on a national scale in Korea. We conducted an evaluation of the impact of execution of district medical insurance plan on number of hospital patients: number of outpatients; and occupancy rate. This study was carried out by Box-Jenkins time series analysis. We tested the statistical significance with intervention component added to ARIMA model. Results of our time series analysis showed that district medical insurance plan had a significant effect on the number of outpatients and occupancy rate. Due to this plan the number of outpatients had increased by 925 patients every month which is equivalent to 8.3 percents of average monthly insurance outpatients in 1987, and occupancy rate had also increased by 0.12 which is equivalent to 16 percents of that in 1987.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2115-2122
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• 2000

The understanding of impact-induced delamination is important in safety and reliability of composite structure. In this study, a model for arrest toughness is proposed in consideration of fracture behavior of composite materials. Also, the probabilistic model is proposed to describe the variability of arrest toughness due to the nonhomogeneity of material. For these models, experiments were conducted on the Carbon/Epoxy composite plates with various thickness using the impact hammer. The elastic work factor used in J-Integral is applicable to the evaluation of energy release rate. The fracture behavior can be described by crack arrest concept and the arrest toughness is independent of the delamination size. Additionally, a probabilistic characteristics of arrest toughness is well described by the Weibull distribution function. A variation of arrest toughness increases with specimen thickness.

• Journal of Distribution Science
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• v.16 no.12
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• pp.13-21
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• 2018

Purpose - Because it is not possible to assess the quality of service products before experiencing them, one feature of a service product is quality uncertainty; hence consumers may react sensitively to pricing. It is necessary to investigate how different pricing strategies affect consumer purchase intention depending on the level of service quality uncertainty. Research design, data, and methodology - The authors have investigated the potential impact of the level of service quality uncertainty, price discount rate and presentation method on consumer purchase intention. A play was selected as an experimental stimulus, and Vietnamese consumers were surveyed to verify the hypotheses. Results - When uncertainty regarding service quality is low, consumer purchase intention is higher when the price discount rate is high or when the price is low. When uncertainty regarding service quality is high, if the normal price, discount rate, and discounted price are presented simultaneously, consumer purchase intention is higher when the price discount rate is low, but when only the discounted price is presented, purchase intention is higher when the price discount rate is high. Conclusions - The results of this study can provide valuable practical implications for pricing for service products with quality uncertainty.