• Ocean and Polar Research
• /
• v.26 no.2
• /
• pp.361-365
• /
• 2004

Deep-sea Resources Research Center (DRRC) has been using a free-fall grab (FFG) for the resource evaluation of polymetallic nodules in the KODOS (Korea Deep Ocean Study) area, NE Pacific, since 1992. A FFG model (Model 4200, Benthos) adapting one glass buoy system (diameter 17 inch, net buoyance 25.4 kg) has been used until 1993. Since then, DRRC has carried out a study to increase the recovery rate of FFG and it was found that a revised system adapting an additional buoy (diameter 10 inch, net buoyance 4.5 kg) gives improved results. The nodule sampling tests were performed using two different models for the same study area and the resulting recovery rates were compared. The result shows no distinct difference in recovery time between two models, but average recovery rate of the revised model was increased to 99.44% from 96.06% of the original model.

• Textile Coloration and Finishing
• /
• v.27 no.2
• /
• pp.132-141
• /
• 2015

Fall-arrest systems(maximum arrest force and allowable free-fall) have been widely applied to provide a safe stop during fall incidents for various industrial activities. Fabric structure affects on the mechanical properties of shock energy absorber. The object of this study is to perform the basic research for the evaluation of the capacity of fall arrest energy absorber in relation to the different interlace yarn density. In this work, pack style energy absorber was prepared by weaving 10 types(Interlace yarn density used high tenacity PET 1000D : 60, 59, 58, 57, 56, 55, 54, 53, 52, 51). The paper presents the results of theoretical investigations of the performance of adjustable absorber during fall arrest. Dynamic load tests based on the EU fall protection equipment standard(CE : EN355:2002) were conducted. Results showed that the maximum arrest force by dynamic load test of energy absorber was satisfied with global standard(below 6,000N). Also, Maximum allowable free-fall of energy absorber showed below 1.75m.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.11
• /
• pp.33-38
• /
• 2012

An free-fall object is received only force of gravity. Movement that only accept gravity is free-fall movement, and a free-falling object is free falling body. In other words, free falling body is only freely falling objects under the influence of gravity, regardless of the initial state of objects movement. In this paper, we assume, ignoring the resistance of the air, and the free-fall acceleration by the height does not change within the range of the short distance in the vertical direction. Under these assumptions, we can know about time and maximum height to reach the peak point from jumping vertically upward direction, time and speed of the car return to the starting position, and time and speed when the car fall to the ground. It can be measured by jumping degree and risk of accident from car or motorcycle in telematics.

• Journal of Advanced Marine Engineering and Technology
• /
• v.31 no.2
• /
• pp.197-205
• /
• 2007

Lifeboats of vessels are necessary for protection of seafarer's safety. However, many accidents have been happened during free-fall type lifeboat drills on board a ship. The aim of this study describes IMO's efforts and some solutions against constructional problem of lifeboats regulated by the provisions of the SOLAS Convention for prevention of accidents with lifeboats and provides information for revising national laws in accordance with the revision of the International Conventions such as SOLAS and STCW.

• Journal of Navigation and Port Research
• /
• v.39 no.1
• /
• pp.77-82
• /
• 2015

Slamming means that the hull hits the waves and receives impact pressure. This slamming effect may cause harm to people and when you put the hull at risk. so it is very harmful for cargo safety. Therefor slamming impact pressure should be fully considered in ship designing. In this study the model of wedged type structure are produced aimed to simulate a free fall that the experiments were carried out on different weight and free fall height. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method and experiment was divided into water entry and water exit. The impact pressure of free fall structure by a pressure acquisition system apply to dewetron system. The angles between a model and the water surface are adapted $15^{\circ}$ respectively. The weight change of models was given as 1.5, 1.8 and 2.0kg. To study slamming phenomenon for free fall height the experiments were carried out by the free fall height of 100, 200 and 300mm. The experimental value of the impact pressure according to the changes in weight was increase impact pressure in proportion to the increase in weight and higher free falling height has also influenced the increase in impact pressures.

• Journal of The Korean Association For Science Education
• /
• v.21 no.3
• /
• pp.566-579
• /
• 2001

The purpose of this study was to investigate students' actual thinking processes during conceptual change about free fall. To do this, middle school students were made an interview designed based on a teaching model using thought experiment. From the study, it was found that strategy for generating cognitive conflict by suggesting opposite views was not effective. However, many students changed their prior conceptions when new explanatory hypothesis, which explained why heavy object and light object fall equally, was introduced. And finally, even though students realized that the changed idea did not accord with the real world, they could easily solve that problem by observing demonstration designed to show the effect of air resistance.

• Journal of The Korean Association For Science Education
• /
• v.19 no.3
• /
• pp.389-399
• /
• 1999

The purpose of this study was to identify children's mental models of the free-fall objects. This study examined children's prediction and observation about the free-fall of objects. The experimental procedure involved conducting interviews with first-, third-, fifth-, and seventh grade students. The interview had three phases: Prediction, explanation, and observation. During the prediction phase, the object pairs which varied on the dimensions of size, weight, shape, color were presented to students. The students were asked to predict what would happen if the objects were dropped simultaneously. During the explanation phase, the students were asked to explain how they arrived at their answers. During the observation phase, the students observed the free-fall of the object pairs and were asked to describe what they saw. The results showed as follows. (1) Fifth-and seventh grade students made more correct predictions than first- and third grade students. (2) The conflict problems, object pairs involving the dimensions of size and weight, were the most difficult for students to accurately predict. (3) With regard to observations, there was a non-significant effect of grade, indicating equivalence in the number of correct observations made by first-, third-, fifth-, and seventh graders. (4) The conflict problems were the most difficult for students to correctly observe. (5) First- and third grade students showed a significant difference between prediction and observation about the free-fall of objects. However. no difference was found in the fifth- and seventh grade students.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.4
• /
• pp.371-377
• /
• 2012

This paper presents an experimental investigation to figure out slamming impact pressure and flow characteristics of a rectangular Marine structure($800{\times}250{\times}50mm^3$) in free fall. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method, the impact pressure of the free fall model by a pressure acquisition system(Dewatron). The angles between a model and the free surface are adapted $10^{\circ}$ and $20^{\circ}$ respectively. Velocity field of water exit has higher better than water entry. The highest point, P2 of impact pressure under the bottom of the model has been appeared about 6 % higher values at 20 degrees than 10 degrees.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.5
• /
• pp.493-499
• /
• 2013

This paper presents are experimental investigation to figure out impact pressure and flow characteristics of a wedge type structure in free fall. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method, the impact pressure of free fall structure by a pressure acquisition system apply to Dewetron system. The angles between a model and the free surface are adapted $15^{\circ}$, $25^{\circ}$, $35^{\circ}$ and $45^{\circ}$ respectively. Velocity field of water exit has higher better than water entry. The impact pressure under the bottom of the model has been appeared higher values at $15^{\circ}$ than $45^{\circ}$, and also at P1.

• Journal of Trauma and Injury
• /
• v.22 no.1
• /
• pp.12-17
• /
• 2009

Purpose: In this study, the prognostic significance of the Injury Severity Score (ISS) and the height of fall in free-fall patients were investigated. Methods: The medical records of 179 victims of falls from a height who were brought alive to the Emergency Department of Gyeongsang National University Hospital between January 2003 and December 2007 were analyzed. The age, the sex of the patients, the rate of admission, the hospital stay, the site of injury, the severity of injury, the rate of surgery, the site of the fall and the presence of alcohol intoxication were evaluated by using a retrospective review of the medical records. Injury severity was measured by using the ISS. Patients were categorized into four subgroups according to the height from where they had fallen. The data were statistically analyzed with using SPSS ver. 10.0. Results: The admission rates for the subgroups with falls of less than 3 stories were significantly lower than those for the subgroups with higher heights of falls (70.7% vs. 100%, p<0.05). These two subgroups showed statistically significant differences in mean hospital stay ($17.11{\pm}24.88$ vs. $56.73{\pm}49.21$, p<0.05), rate of operation (30.6% vs. 53.8%, p<0.05), and mean ISS ($6.86{\pm}4.97$ vs. $13.96{\pm}9.14$, p<0.05). In the correlation analysis, the ISS and the mean hospital stay showed the highest correlation with correlation coefficient of 0.666. Conclusion: In this retrospective analysis of 179 free-fall patients, we evaluated the prognostic factors affecting the outcomes for the free-fall patients. The patients who had fallen from heights of 3 stories or higher showed statistically significant higher rates of admission, longer durations of hospital stay, higher ISSs, and higher operation rates. The most accurate factor in predicting the length of hospital stay was the ISS.