• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.405-413
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• 2013

During the land operations, the enemy's gunnery is the primary threat. For the military vehicle, the bulletproof effect is the one of the important issues regarding the safety of soldiers on duty. Recently, the advanced military vehicles have planned to install armor plates. However, due to the budget problem, it is difficult to equip the protection systems. Hence, the optimum approach to increase bulletproof capability is essential. In this paper, the optimum thickness and component of the armor of military vehicles were evaluated by using finite element analysis for bullet impact effects. To achieve this aim, 7.62mm NATO bullet, 1.6mm steel and Kevlar-29 composite have been modeled and the simulations were conducted with various thickness cases by using MSC Nastran sol 700. Consequently, it was revealed that Kevlar-29 45 Layer is appropriate thickness for 7.62 bulletproof. Furthermore, Kevlar-29 in front of steel was effective by comparison with the back of steel for bulletproof.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.142-151
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• 2004

A method for the determination of concrete armor unit weights with hydraulic stability and structural stability may be formulated in this paper. The hydraulic stability is analyzed by using Hudson's formula, the structural stability is also studied by evaluation of maximum flexural tensile stresses in armor unit induced by the impact loads and by comparison of those with the tensile resistance strength directly. The applicable criteria for concrete armor units can be represented as a function of design wave heights with return period, armor weights, and tensile strengths for the practical uses. In addition, reliability analyses for two failure modes are carried out to take into account some uncertainties. Finally, a series system for two-failure mode analysis can be made up straightforwardly, by which the optimal weights of armor units can be estimated with the various relative breakages, given the specific target probability of failure under the concepts of reliability-based design method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.478-484
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• 2019

The submarine cable for Yongsu wave power plant was cut in 2014 winter. This study investigated the probability of high-wave occurrence exceeding the 50-year return period and the underestimation of armor unit weight used to protect the cable. The observation data from KMA buoy and the hindcast wave data were reviewed to determine the return period of wave height during the winter. In order to investigate the armor unit weight of cable-protection, we calculated the required weight of armor unit using not only Design Standard for Harbor and Fishery Port, but also the previous researches for the wave with large incident angle. As a result, it appeared that the high wave exceeding the 50-year return period did not occur during the winter of 2014 and the armor unit weight of the cable protection was not sufficient to sustain the obliquely incident wave, which induced the cable protection failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1007-1015
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• 2013

A stochastic probability model based on the non-homogeneous Poisson process is represented that can correctly analyze the time-dependent linear and nonlinear behaviors of total damage over the occurrence process of loads. Introducing several types of damage intensity functions, the probability of failure and the total damage with respect to mean time to failure has been investigated in detail. Taking particularly the limit state to be the random variables followed with a distribution function, the uncertainty of that would be taken into consideration in this paper. In addition, the stochastic probability model has been straightforwardly applied to the rubble-mound breakwaters with the definition of damage level about the erosion of armor units. The probability of failure and the nonlinear total damage with respect to mean time to failure has been analyzed with the damage intensity functions for armor units estimated by fitting the expected total damage to the experimental datum. Based on the present results from the stochastic probability model, the preventive management for the armor units of the rubble-mound breakwaters would be suggested to make a decision on the repairing time and the minimum amounts repaired quantitatively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.21-32
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• 2003

In this study, the reliability design method developed by Hanzawa et al. in 1996 for calculation of the expected damage to armor blocks of a horizontally composite breakwater is extended to take into account the variability in wave direction such as directional spreading of waves, obliquity of the design principal wave direction from the shore-normal direction, and its variation about the design value. To calculate the transformation of random directional waves. the model developed by Kweon et al. in 1997 is used instead of Goda's model, which was developed in 1975 for unidirectional random waves normally incident to a straight coast with parallel depth contours and has been used by Hanzawa et al. It was found that the variability in wave direction had great influence on the computed expected damage to armor blocks. The previous design, which disregarded wave directionality, could either overestimate or underestimate the expected damage by a factor of two depending on water depth and seabed slope, if the assumption of the present study that the stability formula for breakwater armor blocks proposed for normal incidence can be used for obliquely incident waves is valid.

• Korean Journal of Heritage: History & Science
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• v.54 no.2
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• pp.78-97
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• 2021

Seojangdaeyajodo is a drawing of military night training on February 12th (lunar leap month), 1795. Focusing on the Seojangdaeyajodo, the characteristics and of the costumes worn by various types of officials were examined. There were 34 officials located near King Jeongjo in and around Seojangdae, with 27 Dangsanggwan and 7 Danghagwan. They wore three types of costumes, including armor, yungbok, and military uniforms. All of the twelve armor wearers and the five officials wearing yungbok were dangsanggwan, and the military uniform wearers included eleven dangsanggwan and six danghagwan. For the shape of the armor, the armor relics of General Yeoban, suitable for riding horses, and the armor painting of Muyedobotongji were referenced, and the composition of the armor was based on practicality. The armor consists of a helmet, a suit of armor, a neck guard, armpit guards, arm guards, and a crotch guard. The color of the armor was red and green, which are the most frequently used colors in Seojangdaeyajodo. The composition of yungbok was jurip, navy cheollik, red gwangdahoe, socks made of leather, and suhwaja. The composition of the military uniform was a lined jeolrip, dongdari, jeonbok, yodae, jeondae, and suhwaja. There were differences in the fabrics used in dangsanggwan and danghagwan military uniforms. Dangsanggwan used fabric with depictions of clouds and jewels, and danghagwan used unpatterned fabric. Moreover, jade, gold, and silver were used for detailed ornamental materials in dangsanggwan. The weapons included bows and a bow case, a sword, a rattan stick, wrist straps, and a ggakji. In the records of the King Jeongjo period, various colored heopsu were mentioned; the colors of the dongdari and jeonbok of dangsanggwan and danghagwan were referenced in various colors. It was presented as an illustration of costumes that could be used to produce objects accurately reflecting the above historical results. The basic principle of the illustration was to present the modeling standards for 3D content production. Samples of form, color, and material of the corresponding times and statuses were presented. The front, the side, and the back of each costume and its accessories were presented, and the colors were presented in RGB and CMYK.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.2
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• pp.23-32
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• 2023

Probabilistic and deterministic analyses are implemented for the armor units of rubble foundation mound of composite breakwaters which is needed to protect the upright section against the scour of foundation mounds. By a little modification and incorporation of the previous empirical formulas that has commonly been applied to design the armor units of foundation mound, a new type formula of stability number has been suggested which is capable of taking into account slopes of foundation mounds, damage ratios of armor units, and incident wave numbers. The new proposed formula becomes mathematically identical with the previous empirical formula under the same conditions used in the developing process. Deterministic design have first been carried out to evaluate the minimum weights of armor units for several conditions associated with a typical section of composite breakwater. When the slopes of foundation mound become steepening and the incident wave numbers are increasing, the bigger armor units more than those from the previous empirical formula should be required. The opposite trends however are shown if the damage ratios is much more allowed. Meanwhile, the reliability analysis, which is one of probabilistic models, has been performed in order to quantitatively verify how the armor unit resulted from the deterministic design is stable. It has been confirmed that 1.2% of annual encounter probability of failure has been evaluated under the condition of 1% damage ratio of armor units for the design wave of 50 years return period. By additionally calculating the influence factors of the related random variables on the failure probability due to those uncertainties, it has been found that Hudson's stability coefficient, significant wave height, and water depth above foundation mound have sequentially been given the impacts on failure regardless of the incident wave angles. Finally, sensitivity analysis has been interpreted with respect to the variations of random variables which are implicitly involved in the formula of stability number for armor units of foundation mound. Then, the probability of failure have been rapidly decreased as the water depth above foundation mound are deepening. However, it has been shown that the probability of failure have been increased according as the berm width of foundation mound are widening and wave periods become shortening.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.4
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• pp.249-258
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• 2003

In this study, the stability of armor blocks of rubble-mound breakwaters is investigated based on the 2-dimensional hydraulic model test with irregular waves. Amor blocks were used the three types; rock, cube and tetrapod. And Hudson formula and van der Meer formula which are used for calculating the weight of armor blocks are considered. Hudson formula was developed from regular wave tests, while van der Meer formula was developed from irregular wave tests. The purpose of this paper is to compare and test two selected stability formulas using the experimental data.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.70-76
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• 2006

A Probabilistic neural network (PNN) technique for predicting the stability number for the armor blocks of breakwaters is presented. A PNN is prepared using the experimental data of van der Meer and is then compared with the empirical formula and previous artificial neural network (ANN) model. This comparison shows that a PNN can effectively predict the stability numbers in spite of data complexity, incompleteness, and incoherence, and can be an effective tool for the designers of rubble mound breakwaters to support their decision process and to improve design efficiency.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.270-277
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• 1999

The ballistic capability of an alumina-rich oxide armor ceramic against a shaped jet was characterized as a function of penetration depth in a layered target structure. The penetration resistance of the ceramic, based upon the determination of penetration velocity, was not equally realized throughout the depth of penetration. It was abnormally low at an early stage of penetration, followed by a sudden increase to reach ~16GPa thereafter. There was no apparent change in such a profile with respect to the lateral size of the specimen. Based upon 2-D flash x-ray radiography and 3-D Hull code simulation, the feasibility of forming a pressure-induced predamnaged zone in front of the jet tip was speculated to foster an increased penetration velocity in the initial stage penetration, resulting in the diminished penetration resistance. The disappearance of such a predamaged zone with penetration was interpreted to restore the resistance of the ceramic in the later penetration stage.