• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.396-408
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• 2019

The tubes which are applied in jacket platforms as the supporting structure might be collided by supply vessels. Such kind of impact will lead to plastic deformation on tube members. As a result, the ultimate strength of tubes will decrease compared to that of intact ones. In order to make a decision on whether to repair or replace the members, it is crucial to know the residual strength of the tubes. After being damaged by lateral impact, the simply supported tubes will definitely loss a certain extent of load carrying capacity under uniform axial compression. Therefore, in this paper, the relationship between the residual ultimate strength of the damaged circular tube by collision and the energy dissipation due to lateral impact is investigated. The influences of several parameters, such as the length, diameter and thickness of the tube and the impact energy, on the reduction of ultimate strength are investigated. A series of numerical simulations are performed using nonlinear FEA software LS-DYNA. Based on simulation results, a non-dimensional parameter is introduced to represent the degree of damage of various size of tubes after collision impact. By applying this non-dimensional parameter, a simplified formula has been derived to describe the relationship between axial compressive residual ultimate and lateral impact energy and tube parameters. Finally, by comparing with the allowable compressive stress proposed in API rules (RP2A-WSD A P I, 2000), the critical damage of tube due to collision impact to be repaired is proposed.

• International journal of steel structures
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• v.18 no.4
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• pp.1440-1463
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• 2018

The Wagner coefficient is a key parameter used to describe the inelastic lateral-torsional buckling (LTB) behaviour of the I-beam, since even for a doubly-symmetric I-section with residual stress, it becomes a monosymmetric I-section due to the characteristics of the non-symmetrical distribution of plastic regions. However, so far no theoretical derivation on the energy equation and Wagner's coefficient have been presented due to the limitation of Vlasov's buckling theory. In order to simplify the nonlinear analysis and calculation, this paper presents a simplified mechanical model and an analytical solution for doubly-symmetric I-beams under pure bending, in which residual stresses and yielding are taken into account. According to the plate-beam theory proposed by the lead author, the energy equation for the inelastic LTB of an I-beam is derived in detail, using only the Euler-Bernoulli beam model and the Kirchhoff-plate model. In this derivation, the concept of the instantaneous shear centre is used and its position can be determined naturally by the condition that the coefficient of the cross-term in the strain energy should be zero; formulae for both the critical moment and the corresponding critical beam length are proposed based upon the analytical buckling equation. An analytical formula of the Wagner coefficient is obtained and the validity of Wagner hypothesis is reconfirmed. Finally, the accuracy of the analytical solution is verified by a FEM solution based upon a bi-modulus model of I-beams. It is found that the critical moments given by the analytical solution almost is identical to those given by Trahair's formulae, and hence the analytical solution can be used as a benchmark to verify the results obtained by other numerical algorithms for inelastic LTB behaviour.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.1
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• pp.19-25
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• 2022

Physical experiments were conducted to establish an empirical formula that predicts the wave force on the upside of the pavement behind crown wall of rubble mound seawall due to wave overtopping as well as the uplift force on the downside of the pavement. The experiments were performed by different conditions of the parapet, water depth, relative freeboard, and thickness of the armour layer. Then, the wave force on the upside and downside of the pavement behind the crown wall was analyzed. The parameters that affect the wave overtopping force and the uplift force were identified and empirical formulae were suggested for evaluating the forces on the pavement.

• Journal of Powder Materials
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• v.29 no.5
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• pp.390-398
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• 2022

Recently, considerable attention has been given to nickel-based superalloys used in additive manufacturing. However, additive manufacturing is limited by a slow build rate in obtaining optimal densities. In this study, optimal volumetric energy density (VED) was calculated using optimal process parameters of IN718 provided by additive manufacturing of laser powder-bed fusion. The laser power and scan speed were controlled using the same ratio to maintain the optimal VED and achieve a fast build rate. Cube samples were manufactured using seven process parameters, including an optimal process parameter. Analysis was conducted based on changes in density and melt-pool morphology. At a low laser power and scan speed, the energy applied to the powder bed was proportional to ${\frac{P}{\sqrt{V}}}$ and not ${\frac{P}{V}}$. At a high laser power and scan speed, a curved track was formed due to Plateau-Rayleigh instability. However, a wide melt-pool shape and continuous track were formed, which did not significantly affect the density. We were able to verify the validity of the VED formula and succeeded in achieving a 75% higher build rate than that of the optimal parameter, with a slight decrease in density and hardness.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.6
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• pp.1100-1105
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• 2002

This thesis aims to provide an analytical basis for existing or new prescriptions based on the theory for properties and tastes of Korean oriental herbal medicines. To this end, prescriptions presented in 「the Various Changes in the Dominations of the Six Energies and their Relations with the Diseases」 of 『Plain Questions』 were analyzed based on the theory for properties and tastes of Korean oriental herbal medicines in 『Yellow Emperor's Canon Internal Medicine』. This thesis focused on symptoms and prescriptions based on the theory for properties and tastes of Korean oriental herbal medicines, which were described in 「the Various Changes in the Dominations of the Six Energies and their Relations with the Diseases」 of 『Plain Questions』 with regard to the year when Kweoleum is affecting the earth energy and the wind energy is partially over-abundant. Those symptoms and prescriptions originate from the theory of the five elements and six climates. The symptoms were analyzed from the perspective of physiology. The prescriptions were first analyzed based on the theory for properties and tastes of Korean oriental herbal medicines in 『Yellow Emperor's Canon Internal Medicine』. Then, a mix formula of oriental medicines pursuant to those prescriptions was studied. Lastly, proper prescriptions from 『Treatise of Cold-Induced Diseases』, which were in conformity with the above prescriptions, were selected. From the physiological point of view, symptoms with regard to the year when Kweoleum is affecting the earth energy and the wind energy is partially over-abundant can be, based on the theory of the five elements and six climates, diagnosed as the symptoms from impaired spleen and stomach due to excessive wind energy. Prescriptions from 『Treatise of Cold-Induced Diseases』pursuant to prescriptions based on the theory for properties and tastes of Korean oriental herbal medicines can be broken down into the following: pinellia decoction for reducing stomach-fire(Banhasasimtang); ginger decoction for reducing stomach-fire(Saenggangsasimtang); liquorice root decoction for reducing stomach-fire(Gamchosasimtang); and Chinese goldthread decoction(Hwangryentang). Therefore, symptoms of six kinds of weather presented in 「the Various Changes in the Dominations of the Six Energies and their Relations with the Diseases」 of 『Plain Questions』 can be analyzed from the physiological point of view. As a result, in addition to the methodology that analyzes existing prescriptions within the boundary of the theory for properties and tastes of Korean oriental herbal medicines in 『Yellow Emperor's Canon Internal Medicine』, it is expected that a theoretical basis for new prescriptions can be provided by analyzing prescriptions from 『Treatise of Cold-Induced Diseases』, based on prescriptions from the theory for properties and tastes of Korean oriental herbal medicines.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2196-2203
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• 2020

A dryout mechanism model for rectangular narrow channels at high pressure conditions is developed by assuming that the Kelvin-Helmholtz instability triggered the occurrence of dryout. This model combines the advantages of theoretical analysis and empirical correlation. The unknown coefficients in the theoretical derivation are supported by the experimental data. Meanwhile, the decisive restriction of the experimental conditions on the applicability of the empirical correlation is avoided. The expression of vapor phase velocity at the time of dryout is derived, and the empirical correlation of liquid film thickness is introduced. Since the CHF value obtained from the liquid film thickness should be the same as the value obtained from the Kelvin-Helmholtz critical stability under the same condition, the convergent CHF value is obtained by iteratively calculating. Comparing with the experimental data under the pressure of 6.89-13.79 MPa, the average error of the model is -15.4% with the 95% confidence interval [-20.5%, -10.4%]. And the pressure has a decisive influence on the prediction accuracy of this model. Compared with the existing dryout code, the calculation speed of this model is faster, and the calculation accuracy is improved. This model, with great portability, could be applied to different objects and working conditions by changing the expression of the vapor phase velocity when the dryout phenomenon is triggered and the calculation formula of the liquid film.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.269-275
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• 1981

The fishing hooks were tested for breaking and unbending due to plastic deformation of the material. Study of tensile test is not complicated, but has not even worked out fully enough, especially when the test specimen is subjected to plastic deformation. The fishing hook is subjected to unbending stress and the critical section is a Point which is furthest from the line of action of the forces. The dynamic force of fish during jerks depends on their speed of movement and body weight, the kinetic energy corresponding to it and also on the rlastic displacement of the rigging which absorb the energy. Six kinds of hook were tested by the dynamometer under tensile speed 290mm/min (subscript s) and 780mm/min (subscript f). According to their results, the breaking load(B: kg) can be induced with the formula $B={\alpha}wd^2+\beta$ where w(mm) is the distance between the barb base and the lower shank and d(mm) is diameter. The coefficients of the formula for the round hooks(R) and the angular hooks(A) are approximately as follows: $$R:\;\alpha_{s}=0.5,\;\beta_{s}=1.6,\;\alpha_{f}=0.4,\;\beta_{f}=1.4$$ $$A:\;\alpha_{s}=1.1,\;\beta_{s}=2.0,\;\alpha_{f}=1.0,\;\beta_{f}=0.9$$ The ratio of $B_{f}\;to\;B_{s}$ is corresponding to 0.8. The ratio of deformation(X) that is moved distance of barb base at break to the distance(H) between head base and barb base is about $50\%$. Further study should be carried out on the subject of impact and fatigue test under the same condition which is exerted force by the hooked fish.

• Steel and Composite Structures
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• v.49 no.1
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.

• Herbal Formula Science
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• v.16 no.1
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• pp.29-38
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• 2008

Background and Objectives : There are four kinds of formulas for invigorating the kidney to cure its asthenic syndrome based on the types of preparation formulas : Boshintang, Boshinhwan, Boshinsan, and Boshingaeng. There are 16 kinds of Boshintang, 28 kinds of Boshinhwan, 3 kinds of Boshinsan, and one kind of Boshingaeng. Combination of herbal medicines, carried out in formulas for invigorating the kidney, consists of various kinds depending on medical scientists' personal experience in medical treatment without any general principles, which makes it difficult to apply it to clinical use. The objectives of this study lie in theoretical establishment of Boshintang for curing the asthenic syndrome of kidney through analyzing the component medicines and combination principles of Hyeongok's Boshintang, and furthermore, maximizing the clinical use of Boshintang. Methods : This study analyzed the component medicines and combination principles of Hyeongok's Boshintang based on the theory for properties and tastes of herbal medicines from the ${\ulcorner}$Yellow Emperor's Canon of Internal Medicine${\lrcorner}$ , the theory for principal herbal medicine, assistant herbal medicine, adjuvant herbal medicine, dispatcher herbal medicine, and the five elements doctrine. Hyeongok's Boshintang is an even prescription, composed of 6 kinds of ingredients : No.1 Fructus Lycii (3don;11.25g), No.2 Radix Polygoni Multiflori (1don:3.75g), No.3 Sarcucarpium Corni (1don), No.4 Fructus Schisandrae (1don), No.5 Rhizoma Anemarrhenae (5poon: 1.875g), and No.6 Cortex Phellodendri (5poon) Results : There are three methods for curing the asthenic syndrome of kidney according to the five elements doctrine : invigorating the kidney, invigorating the lung and purging the spleen. First, if you suffer from the asthenic syndrome of the kidney, you need to invigorate your kidney. There are two available methods, including taste and property invigoration according to the theory for properties and tastes of herbal medicines. They each imply the bitter taste and the cold property invigorate the kidney. In the case of taste invigoration, two herbal medicines with bitter taste, Fructus Lycii and Radix Polygoni Multiflori, are combined into the principal and assistant herbal medicine, respectively. For property invigoration, two herbal medicines with the cold property, Rhizoma Anemarrhenae and Cortex Phellodendri, are combined into adjuvant herbal medicines. Secondly, if you suffer from the asthenic syndrome of the kidney, you need to invigorate your lung which is mother in the mother-child relationship in inter-promotion among the five elements. There are two methods to invigorate the lung, including taste and property invigoration according to the theory for properties and tastes of herbal medicines. They each mean the sour taste and the cool property invigorate the lung. Therefore, it is important to use sour herbal medicines for taste invigoration and cool ones for property invigoration. Both bitter and cool herbal medicines, Rhizoma Anemarrhenae and Cortex Phellodendri, are combined into adjuvant herbal medicines. Lastly, if you suffer from the asthenic syndrome of the kidney, you need to purge your spleen which is an element being surpassed in the relationship between the elements surpassed and ones not surpassed in inter-restraint among the five elements. There are two methods to purge the spleen, which include taste and property purgation according to the theory for properties and tastes of herbal medicines. Taste purgation means to purge the spleen with bitter taste and property purgation to purge the spleen with cool property. Therefore, it is important to use bitter herbal medicines for taste purgation and cool ones for property purgation. Both bitter and cool herbal medicines, Rhizome Anemarrhenae and Cortex Phellodendri. were combined to purge the spleen and invigorate the kidney. In addition, Rhizome Anemarrhenae and Cortex Phellodendri are combined as dispatcher herbal medicine, reinforcing the kidney energy. Conclusions : First, to cure the asthenic syndrome of the kidney, the methods of invigorating the kidney and the lung, and purging the spleen should be used according to the five elements doctrine. Secondly, herbal medicines appropriate for those treatment methods should be chosen according to the theory for properties and tastes of herbal medicine and thirdly, the combination of those herbal medicines should be carried out according to the theory for principal herbal medicine, assistant herbal medicine, adjuvant herbal medicine, dispatcher herbal medicine. As a good example, Hyeongok's Boshintang is combined according to the above theories. In conclusion, this formula was created by applying to the theory for properties and tastes of herbal medicines.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.281-287
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• 2011

We consider the uncertainty in the elastic buckling formula for a thin tube. We take into account the measurement uncertainty of Young's modulus and Poisson's ratio and the tolerance of the tube thickness and diameter. Elastic buckling must be prohibited for a thin tube such as a nuclear fuel rod that must satisfy a self-stand criterion. Since the predicted critical buckling pressure overestimated that found in the experiment, the determination of the minimum safety factor is crucial. The uncertainty in each parameter (i.e., Young's modulus, Poisson's ratio, thickness, and diameter) is mutually independent, so the safety factor is evaluated as the sum of the inverse of each uncertainty. We found that the thickness variation greatly affects the uncertainty. The minimum safety factor of a thin tube of Zirconium alloy is evaluated as 1.547 for a thickness of 0.87 mm and 3.487 for a thickness of 0.254 mm.