Earticle

부적응 학생들의 적응을 돕고, 문제 행동들을 치유하기 위한 목적으로 학생들의 고민이나 문제점을 극복하는데 도움을 주기 위하여 2008년 처음 시작된, 기존 상담실의 역할이 보다 진보된 상담실의 성격을 가진, ‘친한 친구 교실’인 ‘Wee 클래스’에 대하여 조사·분석하여 향후 학교의 상담실 및 Wee 클래스 시설계획에 활용할 수 있는 자료를 제안해 보고자 한다. 본 연구의 범위로는 Wee 클래스가 배치되어 있는 청주시내의 총 21개의 중학교 중 흥덕구, 상당구로 분류하여 흥덕구의 10곳의 중학교와 상당구의 6곳의 중학교를 선정·방문하고, 상담교사를 대상으로 한 설문조사 및 공간구성, 배치, 위치 및 규모, 필요한 공간 등의 유무를 조사·분석 하였다. 현재 Wee 클래스의 규모는 1.0실 규모가 일반적이며, 1.0실의 규모의 Wee 클래스의 내부 공간 구성 및 세부공간들은 상담 및 업무공간, 학생들을 위한 공간 및 휴게공간 등으로 구성되며 규모에 따른 적합한 공간 구성이 요구된다. 이상적으로는 1.5실 이상 2.0실 규모의 Wee 클래스가 합리적이라 판단된다. 2.0실 규모의 경우, 개인상담실 0.5실 + 집단상담실 0.5실 + 휴게공간 0.5실 + 상담교사공간(인포데스크) 0.5실로 구성하는 것이 바람직하다. 대규모일 경우 0.5실의 집단상담실을 별도로 확보하는 것이 바람직하며, 학생들을 위한 컴퓨터테이블, 휴식공간, 수납공간, 놀이공간등으로 역할 할 수 있는 0.5실 규모의 휴게공간도 바람직하다. 또한 Wee 클래스를 학교 내 보건실(이상적)과 연계하여 배치할 경우, Wee 클래스 2.0실 +보건실 공간(보건실 1.0실 +보건교육실 0.5실)로 구성하여 보건실과 이용효과 및 활용도를 극대화 시키는 배치를 고려해 볼 수 있다.

This study is intended to investigate and compare the existing consulting rooms against Wee class which is an advanced one characterized by a concept of “class of close friends” The Wee class was launched for the first time in 2008 in an effort to help maladjusted students get adapted to new circumstances, cure their problem behaviors and assist them in overcoming their worries and problems. Such research and analysis will provide data to be utilized for facilities planning of consulting rooms and Wee class of schools in the future. The scope of this study covers 10 middles schools located in Heungdeok-gu and 6 others in Sangdang-du among total of 21 middle schools in Cheongju City. Selected middles schools were visited and inquiries made against counselors into spatial arrangement, location, scale and required space etc., for purpose of investigation and research. Currently, ordinary scale of Wee class has 1.0 room. It’s interior spatial arrangement and detailed layout consists of spaces for consulting, works, students and rest, all of which will require appropriate allotment of space. Ideally, Wee class of ranging from 1.5 to 2.0 rooms would be reasonable. It would be desirable for 2.0 room scale to be comprised of 0.5 private consulting room + 0.5 group counseling room + counselor’s space (information desk). In case of larger facilities, it would be desirable to secure a group counseling space of 0.5 rooms and a rest area providing computer table, rest zone, storage space and play space. In case where Wee class is laid out in conjunction with an infirmary (ideal), an arrangement consisting of 2.0 rooms of Wee class + infirmary space (1.0 room of infirmary + 0.5 room of health education) can be considered thereby maximizing their effect of utilization.

The importance of the direction for health education in school is growing day by day as the society changes. The object of this study is to protect and improve the health of students and school personnel, and provide the data for construction needed to plan for a health room convenient for students by researching and analysing the cases of the health room in the elementary schools of Cheongju. In order study the data needed for the constructing of an elementary school health room, the researcher, who classified the schools into a large, a middle, and a small sized school, selected 27 schools out of 48 elementary schools with a health teacher in Cheongju, including three schools with 1,500 students or above, eleven schools with 1,000 students or above, and thirteen schools with 500 students or above. The research method was to visit all the 27 elementary school health room, surveying the health teachers, and analysed the spatial composition, the arrangement, the location and the scale, whether the necessary space is secured or not, and the students' using condition of each school health room. Based on the background and the research, when a waiting space of health room, a health room, and a health training room are separately secured, which is ideal, the site plan and the floor plan for them should desirably look as follows: a waiting room(or space) 0.5 + a health room 1.0 + a health training room 1.0. When a health room contains a health training room, it should look as follows: waiting room(or space) / health room 1.0 + a health training room 1.0. When it is impossible to secure a separate small-sized health training room, it should look as follows : a health room + a health training room 1.0. It is desirable that the expansion and improvement should take the given condition of each school into account.

There are students who feel uncomfortable with the regular class and show maladjustment, cause behavioral problems, and try to get away from school. However, if the school fails to lead them and leave them to be, our future generation will become unstable. Thus, a study and research has been done on Wee class, a consulting class that was founded in 2008 to help students who are maladjusted to the society and to help solve their problems. Out of 25 middles schools in Cheongju running Wee class, they were classified into 2 schools from Heungdeok province and 3 schools from Sangdang province. All 5 schools listed above have been visited and a survey regarding the environment, location, size, space has been done on the consulting teachers. Also, this study was carried out in order to find out the accessibility of Wee class to students having problems, whether academic or personal, and whether or not they receive and personal or group programs. In addition, finding out if the students felt comfortable with the Wee class spacing was necessary.

Temporal medical data is often collected during patient treatments that require personal analysis. Each observation recorded in the temporal medical data is associated with measurements and time treatments. A major problem in the analysis of temporal medical data are the missing values that are caused, for example, by patients dropping out of a study before completion. Therefore, the imputation of missing data is an important step during pre-processing and can provide useful information before the data is mined. For each patient and each variable, this imputation replaces the missing data with a value drawn from an estimated distribution of that variable. In this paper, we propose a new method, called Newton's finite divided difference polynomial interpolation with condition order degree, for dealing with missing values in temporal medical data related to obesity. We compared the new imputation method with three existing subspace estimation techniques, including the k-nearest neighbor, local least squares, and natural cubic spline approaches. The performance of each approach was then evaluated by using the normalized root mean square error and the statistically significant test results. The experimental results have demonstrated that the proposed method provides the best fit with the smallest error and is more accurate than the other methods.

Cutting by a high speed laser cutting machine is one of most effective technologies to improve productivity. This paper has presented the cutting characteristics and optimal cutting conditions in a high speed feeding type laser cutting machine by using Tacuchi method in the design of experiment. An L9(34) orthogonal array is adopted to study the effect of adjustment parameters. The adjustment parameters consist of cutting speed, laser power, laser output duty and assistant gas pressure. The surface roughness of sheet metal is regarded as a quality feature. Analysis of variance is performed in order to evaluate the effect of adjustment parameters on the quality feature of laser cutting process.

Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near- isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid propellant stored in space is proven with good measurement accuracy.

Porcine oviduct epithelial cells (POEC) are widely used in co-culture experiments to improve early embryonic development, in vitro fertilization in embryo transfer programs for domestic animals and in vitro maturation of immature germ cells. POEC were mechanically isolated and cultured in tissue culture medium 199. Cells grew continuously, and confluent monolayers were formed after 7 days. After forming confluent monolayer of epithelial cells, supernatant was collected as the condition medium for maturing round spermatids in vitro. Round spermatids were also separated mechanically and cultured in the POEC condition medium. In this study we observed that 20% of round spermatid cultured were matured into elongating spermatid after 24 h, and about 10% of round spermatid cultured showed complete elongation (elongated spermatid) within 24~48 h of in vitro culture. No further development was observed within 50~72 h and transformed cells lost their viability after 72 h. These preliminary findings suggest that the condition medium from POEC may be possible to overcome the round spermatid block by improving the milieu of culture system.

Methane is considered the second most important greenhouse gas in the atmosphere and has 21 times high global warming potential(GWP) of CO2. Methane emissions have increased by more than 150% since 1750, with agriculture being the major source for human living. In Korea, approximately 22% of domestic methane(CH4) emissions are emitted from rice cultivation. Study for reducing methane emission from paddy soil is needed. Biochar has the potential to mitigate CH4 emissions from flooded soils that has characteristic of wetlands and irrigated fields cropped to rice(paddy soils). In this study, biochar(BC) is pyrolyzed from diverse temperature and time condition. BC pyrolyzed from 200,300,400,500°C(BC-200, 300, 400, 500) and lasted for 1,3,5 hours are injected to rice paddy and monitored to evaluate which one has best potential for reducing methane. For BC-500 sample, methane generation rate(MGR) is high at week 4 while BC-300,400 sample has highest MGR at week 5. For blank and BC-200 sample has highest MGR at week 6. Further monitoring is needed to evaluate which BC has a high potential for mitigating CH4.

목적: 본 연구는 반응표면분석법(RSM)을 이용하여 당뇨 개선을 위한 동결건조 누에의 로스팅 최적 조건을 도출하였다. 방법: 독립 변수는 온도(X1), 시간(X2)으로 설정하였고, 예비실험을 거쳐 각 요인의 최소 및 최대 범위를 온도 140-180℃, 시간 20-40 min으 로 설정하였다. 종속변수는 total polyphenol 함량, total flavonoid 함량, DPPH radical 소거능, ABTS radical 소거능, α-glucosidase 저해 활성으로 설정하여 측정하였다. 결과: RSM을 통해 얻은 항산화 활성과 항당뇨 활성이 최대로 발현되는 동결건조 누에 열수 추출물의 최적 로스팅 조건은 180℃, 30 min이었다. 이때의 total polyphenol 함량은 466.61 mg TAE/g, total flavonoid 함량은 274.64 mg QE/g, DPPH radical 소거능은 69.43%, ABTS radical 소거능은 72.94%, α-glucosidase 저해 활성은 57.19%로 예측되 었다. 결론: 누에는 혈당 강하작용과 항산화 작용 등의 뛰어난 효능을 가지고 있지만 비릿한 맛과 역한 냄새로 인하여 누에 그대로 의 섭취가 쉽지 않은 결점이 있는 소재였다. 이 단점을 로스팅 처리하여 보완하기 위한 첫 번째 시도가 본 연구의 의의라 할 수 있겠 다. 차후 본 연구 결과가 식품산업계에서 혈당 개선용 제품의 소재로 다양하게 활용되길 기대해 본다

Purpose: This study was designed to optimize the conditions used for roasting freeze-dried silkworms for improving the quality using response surface methodology (RSM). Methods: Independent variables included temperature (X1; range 140°C–180°C) and time (X2; range 20–40 min) based on findings from preliminary experiments. Dependent variables included total polyphenol content, total flavonoid content, DPPH radical-scavenging activity, ABTS radical-scavenging activity and α-glucosidase inhibition activity. Results: We identified the optimal conditions for roasting freeze-dried silkworms that included temperature (X1) and time (X2) of 180°C and 30 min, respectively. With these optimized variables, the total polyphenol content was 468.20 mg TAE/g, total flavonoid content was 294.62 mg QE/g, DPPH radical-scavenging ability was 72.07%, ABTS radical-scavenging activity was 71.81%, and α-glucosidase inhibition was 67.31%. Conclusion: Our results suggest that the biochemical properties of freeze-dried silkworms were improved by the roasting process using specific timing and temperature as indicated. We anticipate further interest in the use of roasted freeze-dried silkworms by the food industry and as a means to improve blood glucose levels.

目的: 采用响应面法（RSM）对冻干蚕的烘烤条件进行优化，以提高冻干蚕的品质。方法: 根据初步实验结果， 自变量包括温度（X1；范围140 -180°C）和时间（X2；范围 20-40 min）。因变量包括总多酚含量、总黄酮 含量、DPPH自由基清除活性、ABTS自由基清除活性和α-葡萄糖苷酶抑制活性。结果: 确定了冻干桑蚕的最佳 烘烤条件为：温度（X1）180℃、时间（X2）30 min。优化后的总多酚含量为468.20 mg-TAE/g，总黄酮含量 为294.62 mg-QE/g，DPPH自由基清除率为72.07%，ABTS自由基清除率为71.81%，α-葡萄糖苷酶抑制率为 67.31%。结论: 采用特定的烘烤时间和温度，可以改善冻干蚕的生化特性。我们预计食品工业将进一步关注烤 冻干蚕的使用，并将其作为提高血糖水平的手段。

Electric doors have been applied in urban trains since 2007 and operated for a long time. Recently, the failure of mechanical devices in electric doors have been increasing. The door is a device that is directly related to the safety of passengers. The rivet breakage of a ball/nut assembly may occur to an accident during train operation. In this study, the operating voltage and acceleration data of the door were collected for rivet condition monitoring, and 4 features were extracted in the frequency domain using the acceleration data. The classification performance of the rivet condition according to the axial direction of the acceleration data and 4 kernel functions was evaluated using SVM algorithm. When the X-axis data and Gaussian kernel function were used, the highest classification performance was shown for the electric door’s rivet with 90% accuracy.

Wood boring insects are pests that burrow into the interior of trees, causing significant damage and posing serious threats to forest ecosystems and urban landscapes. Especially in Korea, the native species Aromia bungii causes severe damage to Prunus × yedoensis trees, posing significant problems. The damage caused by A.bungii can be identified externally through signs such as emergence and entrance holes on tree stems with sawdust like frass on grounds, but accurately assessing the extent of internal damage requires cutting down the tree. This study uses a non-invasive sonic tomography technique to analyze the correlation between external damage characteristics and internal damage in P.× yedoensis trees affected by A.bungii. The findings show significant difference in internal damage rates of infested trees compared to undamaged trees, although some undamaged trees exhibited injuries caused by abiotic factors and wood-decay fungi. The results demonstrate that sonic tomography is an effective tool for non-invasive assessment of internal damage caused by wood-boring insects, offering a practical alternative to more destructive methods.

CO2-EOR공법에서 혼화압력측정은 중요한 과정 중 하나로 CO2 주입의 최적설계를 위해서는 혼화압력인 MMP(최소혼화압력)와 FCMP(초기접촉혼화압력) 측정이 필수적이다. 계면장력소멸방법은 혼화압력을 측정하는 방법 중 하나로 적은 양의 오일을 이용하면서 비용효율적이고, 정확한 방법이다. 혼화압력측정 연구는 대부분 무용해 가스오일(Dead oil)을 이용하는 방식으로 이루어져 왔으나 본 연구에서는 저류층 조건을 정확히 모사하기 위해 용해 가스를 오일과 혼합하여 용해가스오일(Live oil)로 제조하여 진행하였으며, 용해가스의 양과 온도에 따른 MMP와 FCMP 값을 측정하였다. 용해가스오일은 CCE(동성분리팽창)실험을 통해 기포점 압력을 측정하여, 공인된 기관인 LEMIGAS의 검증된 자료와 비교함으로써 제조된 오일의 유사성을 확인하였다. 계면장력소멸실험에서는 메탄가스의 용해도가 증가함에 따라 MMP, FCMP 값이 증가하였으며, 온도가 증가하면 무용해가스오일 및 용해가스오일/CO2, 두 시스템 모두 MMP, FCMP 값이 큰 폭으로 증가함을 확인하였다.

Miscibility condition is an important parameter for CO2-EOR process. In order to optimize the CO2 injection process, miscibility should be tested in advance. VIT method is the one of the main methods for evaluating miscibility condition. It is cost effective, accurate and requires smaller amount of crude oil sample and time saving experiment. Many experiments have been implemented using dead oil and we determined miscibility condition using VIT method with CO2-live oil at reservoir condition. MMP and FCMP were estimated according to the methane solubility and various temperature changes. Pb was measured to verify the reliability of the synthetic live oil. Pb is compared to the data from authorized organization (LEMIGAS) and validated reliability of synthetic live oil. VIT experiment results show that the amount of solution gas increases both MMP and FCMP. When the temperature increases, MMP and FCMP increased rapidly for both dead oil and live oil experiment.

PURPOSES : In this study, algorithms were proposed for determining the crack condition of an asphalt pavement image using deep learning methods. METHODS : For the configuration of a deep learning network, the study used a Convolution Neural Network and You Only Look Once algorithms. To obtain input data for analysis, a camera was mounted on the bonnet of the vehicle to obtain images of asphalt pavement and to mark the ground-truth cracks in the asphalt pavement image. In addition, an algorithm suitable for the automatic determination function of Deep Learning was proposed in order to calculate the crack ratio and crack rating. RESULTS:The result of analysis showed that the recall rate of cracks in this system was higher from FPPW 5.0E-06 to 96.03%. Furthermore, the accuracy of the grading system was found to be 100%, enabling the determination of very accurate ratings. The rate of processing per image was 0.4448 seconds on average, and the real-time analysis of pavement images presented no problem because the assessment took place within a short time. CONCLUSIONS : Applying this system to the pavement management system is expected to reduce the time required in finishing work and to determine a quantitative crack rating.

자전거 이용 활성화를 위해 자전거도로 이용자의 안전성 및 승차감을 고려한 포장상태 평가 기준을 제시하고자 하였다. 자전거도로는 주행환경의 변화에 민감하게 반응하기 때문에 일반적인 도로에 적용하는 포장상태 평가기준을 도입하기에 무리가 있다. 본 연구에서는 자전거도로에 적합한 새로운 포장상태 평가기준을 제시하였다. 제시된 자전거도로 포장상태 평가기준은 자전거 조사장비(RMSI; Road Monitoring System using ICT)를 통해 측정된 충격가속도 값을 기준으로 5등급으로 구분하였으며, 자전거도로 이용자의 만족도조사를 통해 제시 기준의 타당성을 검토하였다. 제시된 기준의 등급은 포장상태가 매우 양호한 A 등급부터 즉각적인 보수가 필요한 E 등급으로 구분된다. 이용자 만족도조사 결과 A 등급의 경우 91%, E 등급은 95%의 상관성을 보여 만족도조사 결과와 제시된 기준의 상관성이 매우 높은 것으로 나타났다. 이를 통해 자전거도로 조사장비를 이용한 자전거도로 유지관리에 상당히 효과적이며 자전거도로 이용자의 안전성 및 주행성을 확보할 수 있을 것으로 기대된다.

The purpose of this paper is to establish an evaluation criteria for pavement condition in bicycle road. The suggested criteria would help in the activation policy of bicycle use. The conventional evaluation criteria is difficult to be applied for the bicycle road since the bicycle road is sensitive to changes in the driving environments such as obstacles and bumps. This study presents the evaluation criteria that is suitable for bicycle road. The criteria was suggested in 5 grades through the impact acceleration range of RMSI (Road Monitoring System using ICT). The grades of the criteria are divided into a range of grade A to E. The grade A is a very good condition, while the grade E is a state that requires immediate maintenance. This study were confirmed the validity through the survey of user's satisfaction. According to the results of survey, the grade A was shown correlation of 91%. The grade E requiring immediate repair was presented correlation of 94%. It showed that the results of surveying the bicycle road users are highly correlated with the suggested criteria for pavement condition. It showed that the criteria are highly correlated with the survey results. Suggested criteria using the RMSI is expected to be effective for maintenance of the bicycle road. In addition, it is expected to ensure the serviceability and safety for the bicycle users.

연성포장(延性鋪裝)의 포괄적인 검사는 매우 복잡하므로 그것의 상태평가는 피상적 판정에 근거하여 이루어지고 있다. 특히 포장의 질적(質的) 측정은 오해의 소지가 많은 구어적(口語的) 표현으로 이루어 져 왔다. 그리고 포장의 현 상태를 적절히 사정(査定)할 수 있는 기준도 마련되어 있지 못하다. 따라서 본 연구는 모호집합(模糊集合)의 개념을 이용하여 포장표층의 현재상태와 기대되는 상태를 평가하는 기법을 개발하기 위하여 착안, 수행 되었다. 그리고 이의 유용성을 입증하기 위하여 한 예제를 시범적으로 수행 하였다. 구어적(口語的)인 모호한 표현들을 모호집합의 수리적 계산을 통하여 양적(量的)으로 다루어서 구체적인 도해적(圖解的) 모델로 전환할 수 있으므로 예제를 통하여 보여주듯이 누구나 이해가 쉬운 결과를 얻을 수 있었다.

Since comprehensive examination of flexible pavement is complex, evaluation of its condition has been based on subjective judgements. Especially, qualitative measure of pavement has been based on linguistic expressions which often cause misinterpretation. There has been no such a criterion that can appropiately assess pavement status. Therefore, this study was devised to develop an approach, using fuzzy set concept, for evaluation of current and expected service conditions of flexibel pavement surface course. An example study was conducted to verify its usefulness. Since arithematic operation of fuzzy set can quantify the linguistic values and translate them into illustrative models, the results shown in the example was easy for anyone to understand.

우리나라는 지형적인 특성과 강우 발생 특성에 따라 댐이나 다기능보 등 수리구조물의 수문 운영이 하천의 적절한 관리를 위해 매우 중요하다. 이에 본 연구에서는 홍수도달시간에 대한 이론을 정립하고, 금강하류부의 금강하굿둑~백제보 구간을 대상으로 1차원과 2차원의 연계해석이 가능한 HEC-RAS 모형을 활용하여 홍수도달시간을 홍수파도달시간과 수위상승도달시간으로 구분하고 보의 방류조건에 따라 홍수도달시간을 분석 예측하고자 한다. 분석 결과, 방류량이 증가하는 시점에 하도를 범람하여 하천 폭의 급격한 증가로 인해 도달시간이 증가하는 형태가 나타났으며, 홍수파 도달시간이 수위상승 도달시간보다 약 2배정도 빠르게 나타나 실제 도달하는 유수의 양보다 수파가 빨리 진행됨을 알 수 있었다. 본 연구결과를 활용한다면, 하천 관리에 도움이 될 것으로 판단된다.

Gate operation of hydraulic structures is important for proper management in rivers. In this study, the characteristics of flood time were analyzed and predicted using the HEC-RAS model, which is capable of one-dimensional and two-dimensional connectivity analysis of the main points downstream of the Geum river. As a result, flood travel time was decreased once discharge increase and downstream water level rising. However, When the floodplain was overflowed, the arrival time increased due to the rapid increase of the river width. Also, the same condition, flood wave travel time at the major point was approximately twice as fast as water level rising travel time, indicating that waves progressed faster than actually water. Using the results of this study, it will be helpful in the river.

AGNPS model is applied in this study to analyze the changes of non-point source pollutant according to AMC condition using probable rainfall. Probable rainfall of H-dam area by Gumber's extreme value distribution is computed through frequency analysis for each return period. 35 coarse grids are subdivided into 134 find grids of finite differential network to analyze peak flow soil loss quantity and nutrients of study area and the modified CN estimation equation shows good result about rainfall events-peak flow relationship. And as the consequence of estimation of soil loss quantity for each rainfall event soil loss quantity shows 120%-170% of actual soil loss quantity Regression analysis for the observed and calculated values of flow T-P AMC has an important effect on nutrients concentration of outflow and it if found that the excessive fertilization under AMC III condition may cause eutrophication by nutrients because the range of increase of outflow concentration appears relatively high.

This paper investigated into the impact characteristics of the stainless sheet with thickness of 0.7 mm on the stretching boundary condition through three-dimensional finite element analysis. High speed tensile tests were carried out to obtain strain-stress relationships with the effects of the strain rate. The FE analysis was performed by the ABAQUS explicit code. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor were introduced. Through the comparison of the results of the FE analyses and those of the impact tests, a proper FE model was obtained. The results of the FE analyses showed that the absorption rate of energy maintains almost 82.5-83.5% irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, variations of stress, strain, dissipation energy, strain energy density, and local deformation characteristics in the stainless sheet during the collision and the rebound of the impact head were quantitatively examined. In addition, it was shown that the fracture of the specimen occurs when the plastic strain is 0.42 and the maximum value of the plastic dissipation energy of the specimen is nearly 1.83 J.

The present research works investigated into the low velocity impact characteristics of DP 780 high strength steel sheet with 1.7 mm in thickness subjected to free boundary condition using three-dimensional finite element analysis. Finite element analysis was carried out via ABAQUS explicit code. Hyper-elastic model and the damping factor were introduced to improve an accuracy of the FE analysis. An appropriate FE model was obtained via the comparison of the results of the FE analyses and those of the impact tests. The influence of the impact energy and nose diameter of the impact head on the force-deflection curves, impact time, absorption characteristics of the impact energy, deformation behaviours, and stress-strain distributions was quantitatively examined using the results of FE analysis. The results of the FE analysis showed that the absorption rate of impact energy lies in the range of the 70.7-77.5 %. In addition, it was noted that the absorption rate of impact energy decreases when the impact energy increases and the nose diameter of the impact head decreases. The local deformation of the impacted region was rapidly increased when the impact energy was larger than 76.2 J and the nose diameter was 20 mm. A critical impact energy, which occur the instability of the DP780, was estimated using the relationship between the plastic strain and the impact energy. Finally, characteristics of the plastic energy dissipation and the strain energy density were discussed.