• Korean Journal of Clinical Laboratory Science
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• v.45 no.3
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• pp.96-101
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• 2013

Increased waist circumference has shown to be more strongly associated with cardiovascular disease risk factors. The purpose of this study is to investigate the association between exercise capacity and cardiovascular risk factors among obese types in adult men. The subjects of this study were a total fifty-four obese persons and obesity criteria is body mass index $(BMI){\geq}25kg/m^2$. Diagnostic criteria for obesity was defined as a waist circumference of ${\geq}90cm$. The BMI in the obese subjects, as judged by the presence or absence of abdominal obesity, were classified into two groups (non-AO: without abdominal obesity group, AO: with abdominal obesity group). AO presented lower total exercise time, metabolic equivalents (METs) than Non-AO. AO showed slow HRR (heart rate recovery) response. HRR was negative correlated with BMI, body fat mass, waist circumference. AO had a high heart rate and a low cardiac output in submaximal exercise stage 1~2. In conclusion, AO's (with abdominal obesity groups) total exercise time, METs and HRR are lower than Non-AO. HRR is related with BMI, body fat mass and waist circumference.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.35-41
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• 2013

In this study, flame retardancy of polyurethane foam and phenolic foam were investigated by addition of phosphorous flame retardants. The thermal degradation behavior of polyurethane foam and phenolic foam in the presence of flame retardants has been studied by thermogravimetric analysis(TGA). Heat release rate(HRR), mean HRR, mass loss rate(MLR), total smoke released(TSR) and limited oxygen index(LOI) were tested by cone calorimeter. From the test results, Phenolic foam showed low HRR, MLR and TSR than polyurethane foam.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.908-913
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• 2000

In the process of integrity evaluation for nuclear power plant components, a series of fracture mechanics evaluation on surface cracks in reactor pressure vessel(RPV) must be conducted. These fracture mechanics evaluations are based on stress intensity factor, K. However, under pressurized thermal shock(PTS) conditions, the combination of thermal and mechanical stress by steep temperature gradient and internal pressure causes considerably high tensile stress at the inside of RPV wall. Besides, the internal pressure during the normal operation produces high tensile stress at the RPV wall. As a result cracks on inner surface of RPVs may experience elastic-plastic behavior which can be explained with J-integral. In such a case, however, J-integral may possibly lose its validity due to constraint effect. In this paper, in order to verify the suitability of J-integral, two dimensional finite element analyses were applied for various surface crack. Total of 18 crack geometries were analyzed, and Q stresses were obtained by comparing resulting HRR stress distribution with corresponding actual stress distributions. In conclusion, HRR stress fields were found to overestimate the actual crack-tin stress field due to constraint effect.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.141-147
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• 2015

Objective : This study aimed to understand how increased heart rates at the time of drop landing during a step test would affect biomechanical variables of the lower extremity limbs. Background : Ballet performers do more than 200 landings in a daily training. This training raises the heart rate and the fatigability of the lower extremity limbs. Ballet performance high heart rate can trigger lower extremity limb injury. Method : We instructed eight female ballet dancers with no instability in their ankle joints(mean ${\pm}$ SD: age, $20.7{\pm}0.7yr$; body mass index, $19.5{\pm}1.2kg/m^2$, career duration, $8.7{\pm}2.0yr$) to perform the drop landing under the following conditions: rest, 60% heart rate reserve (HRR) and 80% HRR. Results : First, the study confirmed that the increased heart rates of the female ballet dancers did not affect the working ranges of the knee joints during drop landing but only increased angular speeds, which was considered a negative shock-absorption strategy. Second, 80% HRR, which was increased through the step tests, led to severe fatigue among the female ballet dancers, which made them unable to perform a lower extremity limb-neutral position. Hence, their drop landing was unstable, with increased introversion and extroversion moments. Third, we observed that the increasing 80% HRR failed to help the dancers effectively control ground reaction forces but improved the muscular activities of the rectus femoris and vastus medialis oblique muscles. Fourth, the increasing heart rates were positively related to the muscular activities of the vastus medialis oblique and rectus femoris muscles, and the extroversion and introversion moments. Conclusion/Application : Our results prove that increased HRR during a step test negatively affects the biomechanical variables of the lower extremity limbs at the time of drop landing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.486-495
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• 2002

In this paper, we propose a delay reduction method for frame-based packet transmit scheduling algorithm. A high-speed network such as ATM network has to provide some performance guarantees such as bandwidth and delay bound. Framing strategy naturally guarantees bandwidth and enables simple rate-control while having the inherently bad delay characteristics. The proposed delay reduction method uses the same hierarchical frame structure as HRR (Hierarchical Round-Robin) but does not use the static priority scheme such as round-robin. Instead, we use a dynamic priority change scheme so that the delay unfairness between wide bandwidth connection and narrow bandwidth connection can be eliminated. That is, we use FIFO (First-In First-Out) concept to effectively reduce the occurrence of worst-case delay and to enhance delay distribution. We compare the performance for the proposed algorithm with that of HRR. The analytic and simulation results show that HFIFO inherits almost all merits of HRR with fairly better delay characteristics.

• Fire Science and Engineering
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• v.28 no.5
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• pp.1-7
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• 2014

The present study has been conducted to analyse the effects of various pool diameters on the measurement of heat release rate (HRR) of heptane fire using large scale cone calorimeter (LSC). The burning rate which is the major parameter for HRR compared with the previous model suggested by A. Hamins. The combustion efficiency for heptane by oxygen consumption method is about 91%, which is almost same with the previous results of 92% suggested by J. Gore. The convective HRR by enthalpy consumption method was 54% lower than HRR by oxygen consumption method. This results are practical use for establishing the reliability of heat release rate for fire experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1358-1361
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• 2012

This paper presents a study on the analysis for activation time and threshold value of heat detection sensor using HRR(Heat Release Rate). And it is represented to quantity of heat to activate heat detection sensor. The experiment is conducted to measure activation time and HRR of fire detection sensor burning alcohol and n-heptane. In order to burn the alcohol and n-heptane using $43.5cm(L){\times}43.5cm(W){\times}5cm(D)$ and $33cm(L){\times}33cm(L){\times}5cm(D)$ steel pan and the quantity of alcohol and n-heptane are 2.5 L and 650 g, respectively. The results show that peak HRR are in case of alcohol 66.13 kW and in case of n-heptane 151.64 kW, respectively. Total heat releases of heat detection sensor are in case of alcohol approximately 20.7 MJ and in case of n-heptane approximately 18 MJ, respectively.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1157-1166
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• 2021

In this study, a numerical sensitivity analysis was performed to determine the fire suppression time for a large number of water mist nozzles in a large fire compartment. Fire simulations were performed using FDS (Fire dynamics simulator) 6.5.2 under the same condition as the test scenario 5 of the International Maritime Organization (IMO) 1165 test protocol. The sensitivities of input parameters including cell size, extinguishing coefficient (EC), droplets per second (DPS), and peak heat release rate (HRR) of fuel were investigated in terms of the normalized HRR and temperature distribution in the compartment. A new method of determining the fire suppression time using FDS simulation was developed, based on the concept of the cut-off time by cut-off value (COV) of the heat release rate per unit volume (HRRPUV) and the cooling time by the HRR cooling time criteria value (CTCV). In addition, a method was developed to determine the average EC value for the simulation input, using the cooling time and cut-off time.

• Journal of Life Science
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• v.18 no.9
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• pp.1263-1270
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• 2008

The purpose of this study is to investigate the effect of exercise mode and anti-hypertensive drug responding status on the cardiovascular response and perceived exertion in acute coronary syndrome (ACS) patients. Seventy-five patients who participated in six-week exercise rehabilitation therapy performed a treadmill running and a cycle ergometer exercise at intensities of 60%HRR and 85%HRR respectively. Systolic and diastolic blood pressure, mean arterial blood pressure (MAP), rate pressure production (RPP), and ratings of perceived exertion (RPE) were measured. The results of cardiovascular response by the different exercise modes with moderate and intensive intensity of anti-hypertensive drug responder and nonresponder ACS patients were following: First cycle ergometer exercise induced significantly higher SBP, DBP, MAP, RPP and MAP than treadmill running exercise at the intensities of 60%HRR and 85%HRR in both anti-hypertensive responder and nonresponder ACS patients (p<0.05). Secondly anti-hypertensive nonresponder ACS patients had significantly higher DBP and MAP that anti-hypertensive responder ACS patients at all the exercise modes (p<0.05). Finally there was no difference of RPP between anti-hypertensive responder and nomresponder ACS patients, although anti-hypertensive nonresponder ACS patients showed higher blood pressure and RPP than anti-hypertensive responder ACS patients. In conclusion, cycle ergometer induced increased cardiovascular response at same intensities of treadmill running exercise and anti-hypertensive nonresponder ACS patients had even more increased cardiovascular response than anti-hypertensive responder ACS patients with no difference in perceived exertion during exercise. These results suggested that cycle ergometer exercise should be greatly careful with the risk of higher blood pressure, especially for those who are patients with hypertensive blood pressure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.140-148
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• 2017

The purpose of this study was to examine the effects of acute aerobic exercise at different intensities on the blood pressure, blood lipids and fibrinolytic markers in pre-hypertension college-aged males. Six subjects performed an acute running exercise at three different intensities(low intensity(LI): 50-60% heart rate reserve(HRR), moderate intensity(MI): 60-70%HRR, and high intensity(HI): 70-80%HRR). The blood pressure(systolic(SBP) and diastolic blood pressure(DBP), blood lipids(total cholesterol(TC) and high-density lipoprotein cholesterol(HDL-C)) and fibrinolytic markers(tissue plasminogen activator(tPA) and plasminogen activator inhibitor-1(PAI-1)) were determined before(PRE), immediately after(POST) and 60minutes after the exercise(60 POST). Results: the SBP in the LI group was significantly increased at POST(p=0.013). The ES levels for the SBP in the MI and HI groups were reduced (-1.33 and -1.23, respectively), though the differences were not significant. The HDL in the MI(p=0.003) and HI(p=0.002) groups were significantly increased at 60 POST. Also, the tPA in the MI(p=0.021) and HI(p=0.042) groups were significantly increased at POST.