• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4146-4158
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• 2022

Ultra-high performance concrete (UHPC) has been widely utilized in military and civil protective structures to resist intensive loadings attributed to its excellent properties, e.g., high tensile/compressive strength, high dynamic toughness and impact resistance. At present, aiming to improve the defects of the traditional vertical concrete cask (VCC), i.e., the external storage facility of spent fuel, with normal strength concrete (NSC) shield, e.g., heavy weight and difficult to fabricate/transform, the feasibility of UHPC applied in the shield of VCC is numerically examined considering its high radiation and corrosion resistance. Firstly, the finite element (FE) analyses approach and material model parameters of NSC and UHPC are verified based on the 1/3 scaled VCC tip-over test and drop hammer test on UHPC members, respectively. Then, the refined FE model of prototypical VCC is established and utilized to examine its dynamic behaviors and damage distribution in accidental tip-over and end-drop events, in which the various influential factors, e.g., UHPC shield thickness, concrete ground thickness, and sealing methods of steel container are considered. In conclusion, by quantitatively evaluating the safety of VCC in terms of the shield damage and vibrations, it is found that adopting the 300 mm-thick UHPC shield instead of the conventional 650 mm-thick NSC shield can reduce about 1/3 of the total weight of VCC, i.e., about 50 t, and 37% floor space, as well as guarantee the structural integrity of VCC during the accidental drop simultaneously. Besides, based on the parametric analyses, the thickness of concrete ground in the VCC storage site is recommended as less than 500 mm, and the welded connection is recommended for the sealing method of steel containers.

• Journal of the Korean Society of Tobacco Science
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• v.26 no.2 s.52
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• pp.117-125
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• 2004

In this study, we have investigated the natural and puffing combustibility of cigarette brands and the compulsory ash-drop, and analysed factors related to the materials. Cigarette combustibility was greatly affected by the tobacco weight in cigarettes rod. Combustion rate of 4AOR cigarette made by flue-cured tobacco was 5.02 $^{mm}/_{min}\;and\;10\%$ faster than 1BO cigarette. Combustion pattern has interrelation with sugars, chlorine and ash contents among tobacco components. Combustion rate of 4DL, flue-cured tobacco was 55 seconds faster than 1CL tobacco extremely much in sugars contents, and ash drop was maintained at $21\%$ longer. Combustion time and burning rate were fast in cigarette made by expanded tobacco slice and tobacco stem and the formation of ash was poor. The length of puffed ash drop of expanded tobacco slice and tobacco stem were 18.6 mm and 25.2 mm and these forced ash drop length were 3.8 mm and 4.9 mm respectively. Puffed burning rate of general cigarette was $14.3\%$ faster than static burning rate and super slim type cigarettes was $21.3\%$ faster. Combustion rate and ash drop of domestic and foreign cigarette brands were quite different depending on tar level and cigarette types. The lower tar level, the faster combustion rate and the shorter ash drop.

• Journal of Environmental Science International
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• v.16 no.8
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• pp.873-879
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• 2007

For the purpose of development of an environmentally friendly aqueous cleanser, some experimental researches on emulsification of D-limonene were performed. OA series surfactants with different molecular weight were adapted as an emulsifier for preparation of O/W emulsion. Cleaning power of aqueous cleanser was measured by a dipping method adapting abietic acid(AA) as a solubilizate. Besides, drop size and drop size distribution, contact angle and storage stability of the aqueous cleansers were also measured and relationships among them were examined. Decrease in molecular weight of surfactant induced small drop size and contact angie, resulting in high cleaning power of aqueous cleanser. Aqueous cleanser consisted of 3wt.% OA300 and 30wt.% D-limonene showed the highest cleaning power, but displayed unfortunately with low storage stability. The storage stability of the aqueous cleanser with OA300 was significantly enhanced by addition of 0.5wt.% OA600 at the expanse of decrease in cleaning power.

• Journal of the Korean Society of Tobacco Science
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• v.27 no.2
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• pp.201-206
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• 2005

In this work, we studied the effects of the moisture contents of cut tobacco on loose end of cigarettes. The loose end of the cigarette groups decreased with the increase of moisture contents of the cut tobacco and especially the loose end of A and C groups decreased to $31\%\;and\;52\%$ with the increase of $1\%$ moisture contents. $A-13.5\%\;and\;B-14.0\%\;and\; C-14.0\%$ moisture samples showed the increase of the weight ratio of cut tobacco over 1.4mm cut length but the decrease under 1.4mm cut length. We concluded that the main reasons were regarded to reduction of small fragment tobaccos caused by increase of moisture contents and exception of air-suction transport of tobaccos to cigarette making machine. In spite of the moisture increase of cut tobaccos under fixed EPD(encapsulated pressure drop), the hardness of Band C sample groups were maintained constantly except A group. This result means that under fixed EPD, the weight of cut tobacco in cigarette rods increases to compensate the reduction of pressure drop by moisture increase of cut tobaccos.

• The Korean Journal of Pain
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• v.32 no.1
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• pp.12-21
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• 2019

Spinal cord contusion injury is one of the most serious nervous system disorders, characterized by high morbidity and disability. To mimic spinal cord contusion in humans, various animal models of spinal contusion injury have been developed. These models have been developed in rats, mice, and monkeys. However, most of these models are developed using rats. Two types of animal models, i.e. bilateral contusion injury and unilateral contusion injury models, are developed using either a weight drop method or impactor method. In the weight drop method, a specific weight or a rod, having a specific weight and diameter, is dropped from a specific height on to the exposed spinal cord. Low intensity injury is produced by dropping a 5 g weight from a height of 8 cm, moderate injury by dropping 10 g weight from a height of 12.5-25 mm, and high intensity injury by dropping a 25 g weight from a height of 50 mm. In the impactor method, injury is produced through an impactor by delivering a specific force to the exposed spinal cord area. Mild injury is produced by delivering $100{\pm}5kdyn$ of force, moderate injury by delivering $200{\pm}10kdyn$ of force, and severe injury by delivering $300{\pm}10kdyn$ of force. The contusion injury produces a significant development of locomotor dysfunction, which is generally evident from the $0-14^{th}$ day of surgery and is at its peak after the $28-56^{th}$ day. The present review discusses different animal models of spinal contusion injury.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2129-2134
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• 2004

The present study has been conducted to develop a heat pump system using river water of temperature energy which not only belongs to unutilized energy but is a kind of good heat source due to maintain its temperature in a certain degree regardless of seasonal variation. The system did not meet the proposed performance after setup. In this paper, the system performance affected by refrigerant Oil, by pressure drop, or by other factors has been discussed. The followings were obtained : (1) Refrigerant Oil mixture rate was 2.5 in weight percentage, (2) Pressure drop through evaporator was 29.1kPa($3.1^{\circ}C$ in saturated tempearture) (3) Pressure drop from the end of evaporator to compressor inlet was 39.8kPa($4.0^{\circ}C$ in saturated tempearture). (4) The system performance can to be improved by modifying a part of pipe line to compressor, and reducing pressure drop through heat exchangers.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.67-73
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• 2010

The purpose of this study was to compare the differences in kinematic and kinetic parameters of the ankle and knee joint according to three landing direction(central, left, right). Fifteen collegiate male athletes(age: $22.7{\pm}3.5$ years, height: $174.9{\pm}7.1\;cm$, weight: $69.4{\pm}6.7\;kg$) with the right leg as dominant were chosen. The subjects performed series of drop landings in three directions. In terms of the three different landing directions, plantar flexion was the greatest during the central drop landings. For each initial contact of the landing direction, plantar flexion of the ankle was greatest at the central drop landing, inversion of the ankle was greatest at the right landing and valgus of the knee was greatest at the left drop landing. Regarding the peak force, the greatest was at the 1st peak force during the central drop landing. For the time-span of the 2nd peak force and the 2-1 peak force, both right sides resulted as the greatest. Therefore, with the appropriate training in landing techniques and developing neuromuscular training for proprioception by taking the injury mechanisms on ankle and knee during drop landings into account, it will assist in preventing such injuries.

• Korean Journal of Applied Biomechanics
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• v.22 no.4
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• pp.379-386
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• 2012

The aim of this study was to investigate and identify the differences in lower extremity energy dissipation strategies between drop-landing and countermovement-jump maneuvers. Fourteen recreational athletes(Age : $23.3{\pm}2.1years$, Height : $172.3{\pm}4.0cm$, Weight : $69.2{\pm}4.7kg$) were recruited and instructed to perform drop-landing from 45 cm height and countermovement-jump from 45 cm to 20 cm height. The landing phase was taken as the time between initial contact and peak knee flexion. A motion-capture system consisting of eight infra-red cameras was employed to collect kinematics data at a sampling rate of 200 Hz and a force-plate was used to collect GRF data at a sampling rate of 2000 Hz. Paired t-test was performed to determine the difference in kinematics and kinetics variables between each task. During the countermovement-jump task, all of lower extremity joint ROM and the hip joint eccentric moment were decreased and the ankle joint plantarflexion moment was increased than drop-landing task. In the eccentric work during countermovement-jump task, the ankle joint displayed greater while knee and hip joint showed lesser than drop-landing. Therefore, the knee joint acted as the key energy dissipater during drop-landing while the ankle joint contributed the most energy dissipation during countermovement-jump. Our findings collectively indicated that different energy dissipation strategies were adopted for drop-landing and countermovement-jump.

• Physical Therapy Korea
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• v.29 no.4
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• pp.249-254
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• 2022

Background: The lateral step down (LSD) is a form of stair negotiation used by the elderly because it requires less movement of the lower extremity. Although it is necessary to study the amount of pelvic drop and the strength of a hip abductor during LSD for intervention, limited studies have investigated the relationship between the amount of pelvic drop and strength of a hip abductor during LSD in elderly people. Objects: This study aimed to determine the relationship between the amount of pelvic drop on an unsupported leg and the strength of the hip abductor during LSD in the elderly. Methods: Thirty elderly people (male: 17, female: 13) were recruited. Subjects performed the LSD task, and the evaluator measured and the amount of pelvic drop on an unsupported side. Also, the isometric strength of the hip abductor was measured in a supine position. Results: We found significant relationships between the strength of the hip abductor and the amount of pelvic drop (r = -0.386). The average hip abductor strength normalized by body weight was 1.06 N/kg (max: 1.99, min: 0.52) and the average contralateral pelvic drop (CPD) angle was 4.16° (max: 15.3, min: 0). Conclusion: Our results indicated that the strength of the hip abductor had a moderate correlation with the CPD during a LSD in the elderly. Hip abductor weakness could translate into altered movement of the pelvis.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.111-114
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• 2003

Thermosets are highly cross-linked polymers with a three-dimensional molecular structure. The network structure gives rise to mechanical properties, however, one major drawback of thermosets, which also results from their network structure, is their poor resistance to impact and to crack initiation. In this study, to solve this problem, the reactive thermoplastics such as amine terminated polyetherimide (ATPEI), ATPEI-CTBN-ATPEI(ABA) triblock copolymer, CTBN-ATPEI(AB) diblock copolymer, and carboxyl group modified ATPEI was synthesized, after that blended with epoxy resin, and the carbon fiber reinforced composites were fabricated. The impact load, energy, and delamination were investigated by using drop weight impact test and C-scan test. As a results, the ABA/epoxy blend system showed good impact properties.