• Tuberculosis and Respiratory Diseases
• /
• v.70 no.6
• /
• pp.498-503
• /
• 2011

Background: The causes of exertional desaturation in patients with COPD can be multifactorial. We aimed to investigate factors predict exertional desaturation in patients with moderate to severe COPD. Methods: We tested 51 consecutive patients with stable COPD (FEV1/FVC, $40{\pm}13%$ predicted). Patients performed a six minute walk test (6MWT). Pulse oxymetric saturation (SpO2) and pulse rate were recorded. Results: Oxygen desaturation was found in 15 subjects after 6MWT, while 36 subjects were not desaturated. Lung diffusing capacity was significantly lower in desaturation (DS) group ($62{\pm}18%$ predicted) compared with not desaturated (ND) group ($84{\pm}20$, p<0.01). However there was no statistical difference of FEV1/FVC ratio or residual volume between two groups. The pulse rate change was significantly higher in the desaturated compared with the not desaturated group. Six minute walking distance, subjective dyspnea scale, airflow obstruction, and residual volume did not predict exertional oxygen desaturation. Independent factors assessed by multiple logistic regression revealed that a pulse rate increment (odd ratio [OR], 1.19; 95% confidence interval [CI], 1.01~1.40; p=0.02), a decrease in baseline PaO2 (OR, 1.105; 95% CI, 1.003~1.218; p=0.04) and a decrease in lung diffusing capacity (OR, 1.10; 95% CI, 1.01~1.19; p=0.01) were significantly associated with oxygen desaturation. Receiver operator characteristic (ROC) analysis showed that an absolute increment in pulse rate of 16/min gave optimal discrimination between desaturated and not desaturated patients after 6MWT. Conclusion: Pulse rate increment and diffusion capacity can predict exertional oxygen desaturation in stable COPD patients with moderate to severe airflow obstruction.

• Asian Journal of Turfgrass Science
• /
• v.3 no.1
• /
• pp.5-12
• /
• 1989

Tiller numbers per Unit area were increased as plant density heightened followed by little difference in tiller number in 110 days after transplanting(ll0DAT), this being caused by the immediate increment of tiller since' 90DAT During the growth period, the greatest number of green leaves per unit area was attained in 90DAT of both 160-density and 200-density plots, and in l00DAT of 40-, 80-, and I 20-density plots. Thus, the period to reach the maximum green leaf number with the high plant density was earlier than with the' low plant density. The increment of plant density increased the DM weight of ahoveground part and, with 40-densitytreatment. DNI weight was increased 6.1 times as much up to 110DAT as up to 7ODAT but 2 to 2.9 times with other ehe'nsity treatments. The' rate of increase in stolon length was greatest at the period between 80 and 90DAT when DM weight of stolon showed a large increment. Meanwhile, the average number of stolon was 1.7 at 70DAT but was increased up to 10 at 110DAT probably due to accelerative appeance of Ist stolon branch since 8.0DAT. DM weight of stolon was found to exceeded that of root after 90DAT Thus it was concluded that, when turfs is estahlished from sprig. it may be desirable for first mowing practice to be made at least within l00 days after planting.

• International Journal of Highway Engineering
• /
• v.15 no.4
• /
• pp.85-94
• /
• 2013

PURPOSES: The performance of tack coat, commonly used for layer interface bonding, is affected by application rate and curing time. In this study, bonding strength tests were performed according to the application rate and curing time of asphalt emulsion. Based on finding from this study, optimum application rates and curing times are proposed. METHODS: In order to investigate bonding characteristic of asphalt emulsion, tests were performed on both asphalt concrete pavement and portland concrete pavement. Also, asphalt emulsions were tested at the application rate of 0, 0.2, 0.4, 0.6, and $0.8{\ell}/m^2$ and at the curing time of 0, 0.5, 1, 2, and 24 hours. Pull-off test and shear bonding strength test, which commonly used for bonding strength measurement of asphalt emulsion, were adopted for this study. To assess field performance under different testing condition, asphalt emulsions were applied to in-service pavement. Throughout coefficient of determination analysis between material index properties from asphalt emulsion and mechanical response from bonding strength tests, performance correlativity was analyzed. RESULTS: Test results show that optimum application rate for asphalt overlay on asphalt concrete pavement (AOA) and asphalt overlay on concrete pavement (AOC) was $0.4{\sim}0.5{\ell}/m^2$ and $0.3{\sim}0.5{\ell}/m^2$, respectively. According to the curing time increment, tensile strength and shear strength of AOC were increased to 22~44% and 20~39%, respectively. AOA case also show strength increment in tensile strength (42%) and shear strength (9%). We tested the applicability of tack coat materials at the field sites, and our findings demonstrated that the bonding (for D and E) and rapid curing (for B, C, and D, E) performances were superior than others. Among material index properties, there was a high correlation between penetration ratio and bonding strength test result. CONCLUSIONS : Result show that interlayer bonding strength was affected by asphalt emulsion type, application rate and curing time. AOC required slightly higher application ($0.1{\ell}/m^2$) than AOA. Both AOA and AOC cases show higher strength at longer curing time. Up to 2hours of curing, rapid strength increments were observed, but strength increment ratio was decreased after 2hours of curing. From the observed correlation between penetration ratio and bonding strength, it is expected that penetration ratio can be used as one of important factors affecting bonding strength analysis.

• Journal of the Korean Solar Energy Society
• /
• v.35 no.3
• /
• pp.73-79
• /
• 2015

In this study, a thermal storage performance and characteristics of daily operation were investigated when the air and the liquid were heated simultaneously by a hybrid solar air-water heater that can make hot water as well as heated air. The hybrid solar air-water heater is kind of a flat plate solar collector that can make hot water and heated air by installing air channel beneath absorber plate of traditional flat plate solar collector for hot water. As a result of daily operation, maximum water temperature reached in a thermal storage was shown $44^{\circ}C$ on 73kg/h of air mass flow rate and about $40^{\circ}C$ on 176kg/h of air mass flow rate. Thus, the necessity of heating water in thermal storage by operating only liquid side was confirmed when the temperature of liquid in thermal storage is lower than we need. In case of efficiency investigated on daily operation, the thermal efficiency of the liquid side was decreased with increment of the inlet liquid temperature and decrement of the solar radiation, but efficiency of the air side was increased with increment of inlet liquid temperature difference as the traditional solar air heater. Total thermal efficiency of the collector was shown from 65.85% to 78.23% and it was decreased with increment of the inlet liquid temperature and decrement of solar radiation same as the traditional system.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.314-321
• /
• 1987

Post weld heat treatment (PWHT) of weldment of the low alloy Cr-Mo steel, in general, is carried out not only to remove residual stress and hydrogen existing in weldment but to improve fracture toughness of weld heat affected zone (HAZ). There occur some problems such as toughness decrement and stress relief cracking (SRC) in the coarse grained region of weld HAZ when PWHT is practiced. Especially, embrittlement of structure directly relates to the mode of fracture and is appeared as the difference of fracture surface such as grain boundary failure. Therefore, in this paper, the effect of heating rate on PWHT embrittlement under the various kinds of stresses simulated residual stress in weld HAZ was evaluated by COD fracture toughness test and observation of fracture surface. Fracture toughness of weld HAZ decreased with increment of heating rate under no stress, but it was improved to increment of heating rate under the stress. Grain boundary failure didn't almost appear at the heating rate of 600.deg.C/hr but it appeared from being the applied stress of 294 MPa at 220.deg.C/hr and 196 MPa at 60.deg.C/hr.

• Journal of Korean Society for Quality Management
• /
• v.14 no.2
• /
• pp.28-32
• /
• 1986

This paper studies a new replacement policy in case that average repair cost rate increases linearly in proportion to time t. At the moment when the repair cost rate reaches or exceeds a fixed level, the component is replaced. This policy is compared with the economic lifetime policy. Advantages of this model according to the increment of replacement cost is shown in numerical example.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.7
• /
• pp.110-116
• /
• 1994

In this paper a Duty Effective Overlap Scanning method (DEOS) for the improvement of driving efficiency of LC displays which have the RMS voltage responding characteristics is proposed and new processing method of data signals for optimum application of this method is also proposed. Proposed method has a few advantages such as the increment of duty ratio the increment of driving power loaded on LC cell and the decrement of RMS voltage error rate caused by signal attenuation on electrodes composing of display when compared with the conventional method which is called as optimum voltage amplitude selection method. And also by adopting new data signal processing method which has 3 kinds of voltage levels additional advantage much improving crosstalk phenomenon which is the most serious problems of simple matrix structured display is obtained. For the characteristic estimation new mathematical representation for new overlap scanning method and data signal processing method are induced and defined. And by the defined formula and simulation the characteristics of the proposed method and the conventional method are compared and analyzed. As a result of estimation this new method being able to optimize the overlap rate of scan signal and using 3 levels of data signals has the characteristic which can improve the driving efficiency of LC displays.

• Journal of Korean Society of Water and Wastewater
• /
• v.10 no.4
• /
• pp.111-118
• /
• 1996

Effects of $CO_2$ partial pressure($pCO_2$) on the characteristics of methane production rate and organic matter degradation in anaerobic digestion were investigated by using anaerobic chemostat type reactors at $35{\pm}1^{\circ}C$, at the HRT of 7days. The $pCO_2$ of the reactors was controlled in the range from 0.1 to 0.8 atm. Since the $pCO_2$ in an uncontrolled condition was about 0.4atm, $N_2$ was added for the reactors controlled of $pCO_2$ of between 0.1 and 0.4atm. At $pCO_2$ of 0.5 atm, the methane production rate was approximately 20% more that in an uncontrolled condition of $pCO_2$. Based on the carbon mass balance, it was concluded that methane production was related to the increment of removal organic carbon and consumption of $CO_2$. At $pCO_2$ of 0.5atm, the methane production by the increment of removal substrates increased 13.6%, on the orther hand, hand, the methane production by the conversion of $CO_2$ to methane increased 6.4%.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.11
• /
• pp.477-482
• /
• 2005

We have investigated volume resistivity and thermal properties showed by changing the content of carbon black which is the component parts of semiconducting shield in underground power transmission cable. Specimens were made of sheet form with the nine of specimens for measurement. Volume resistivity of specimens was measured by volume resistivity meter after 10 minutes in the preheated oven of both 25$\pm$1[$^{\circ}C$] and 90$\pm$1[$^{\circ}C$]. And specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The measurement temperature ranges of specific heat using the BSC was from 20[$^{\circ}C$] to 60[$^{\circ}C$], and the heating rate was 1[$^{\circ}C$/min]. And the measurement temperatures of thermal conductivity using Nano Flash Diffusivity were both 25[$^{\circ}C$] and 55[$^{\circ}C$]. Volume resistivity was high according to an increment of the content of carbon black from these experimental results. And specific heat was decreased, while thermal conductivity was increased by an increment of the content of carbon black. And both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature.

• The Korean Journal of Physiology
• /
• v.28 no.1
• /
• pp.79-90
• /
• 1994

The objective of the present study is to assess the contribution of bulk flow to the regulatory mechanism of amniotic fluid volume and its ionic concentration in the membranes surrounding the amniotic fluid. For quantitative assessment, we prepared 4 kinds of artificial amniotic fIuids (isotonic isovolumetric, hypotonic isovolumetric, isotonic hypervolumetric and hypotonic hypervolumetric ones) by replacing 70% of amniotic fluid of pregnant rabbits with water or normal Tyrode solutions. Isoosmotic saline of 0.5 ml volume containing 0.05% Censored and 15 mM/l LiCl was administered initially into amniotic sacs of all subject animals. Samples of amniotic fluid were collected in after 30 and 90 minute intervals; the concentrations of Censored, $Na^+\;and\;Li^+$ were determined and compared. Followings are the results obtained. 1. from isovolumetric and increased Congcord group, we couldn't find significant change in $Li^+\;and\;Na^+$ concentration in isotonic amniotic fluid. However, $Na^+$ concentration increased significantly as well as a striking increase in Censored concentration in hypotonic amniotic fluid. 2. In isovoIumetric and decreased Censored group, the rate of $[Li^+]$ decrement and the rate of $[Na^+]$ increment were much higher in hypotonic amniotic fluid than in isotonic. 3. In hypervolumetric and increased Censored group, the rate of $Na^+$ efflux increased proportionately with the increment of Censored concentration up to 0.98, which was higher than the rate of $Li^+$ efflux in isotonic amniotic fluid. However, the increment of $Na^+$ concentration was rather related with the initial $Na^+$ concentration in hypotonic amniotic fluid, showing inverse relationship. $Li^+$ concentration increased only when there was a marked increase in Censored concentration and approached near a maximum value or 1. 4. For hypervolumetric and decreased Censored group, the observations were identical to isovolumetric and decreased Censored group. From these results the following conclusions could be made: 1) There is no net movement of water or monovalent cations across the membranes surrounding amniotic fIuid in isotonic isovolumetric condition. In contrast, there is a net efflux of amniotic fluid by osmotic bulk flow, resulting in elevation of $Na^+$ concentration in hypotonic isovolumetric condition. 2) In hypervolumetric conditions, there is a massive efflux of amniotic fluid or solvent drag through the surrounding membranes by fiItrative bulk flow, where the rate of $Na^+$ efflux has a linear relationship with that of water efflux. This is assumed to be carried out through enlarged and newly opened intercellular spaces resulting from increased intraamniotic pressure. 3) Once increasing intraamniotic pressure reaches a point allowing $Li^+$ to pass through during osmotic bulk flow in hypotonic amniotic fIuid, $Na^+$ influx seems to occur by diffusion simultaneously or immediately thereafter, too.