• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.151-157
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• 1996

Postural tremor of the upper arm in a static posture was measured to provide guidelines of hand tool weight. Three types of camera recording postures were selected. Postural tremor was measured on five levels of tool weights; no weight, 400g, 800, 1200g, and 1600g. For each conditions, upper arm postural tremor was measured together with EMG of biceps, deltoid, and pectoralis major, and Borg's CR-20 scale ratings of perceived exertion. Results of the experiment are as follows; Frequency analysis of tremor revealed that increased amplitude of frequency band of 2-4Hz and 10-14Hz was observed. Postural tremor of the upper arm maintained the initial level until fatigue developed. After the development of fatigue, the rate of the change of postural tremor was significantly increased. Different tool weights and hand postures showed different rate of tremor increase. And time to fatigue and the corresponding endurance time was positively correlated with Borg's RPF scores.

• 대한기계학회논문집B
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• 제24권4호
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• pp.512-518
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• 2000

A wall fuel-film flow model is developed to predict the effect of a wall-fuel-film on air-fuel ratio in an SI engine in transient conditions. Fuel redistribution in the intake port resulting from charge backflow and a simple liquid fuel behavior in the cylinder are included in this model. Liquid fuel film flow is calculated of every crank angle degree using the instantaneous air flow rate. The model is validated by comparing the calculated results and corresponding engine experiment results of a commercial 4 cylinder DOHC engine. The predicted results match well with the experimental results. To maintain the constant air-fuel ratio during transient operation. the fuel injection rate control can be obtained from the simulation result.

• 대한화학회지
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• 제15권6호
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• pp.330-347
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• 1971

Catalytic effects of metallic salts on the combustion of diesel fuel oil have been studied. In the case of organometallic salt, the active species are the metallic oxides resulted from combustion of the salts. The oxides act only on the residual solid carbon produced from the fuel oil combustion. The catalytic activity can be explained with the semiconductor theory just as in the case of the gas phase reaction. The chemical rate constant of the combustion of carbon, the soot from diesel fuel oil, is found to be $k_c=1.1{\times}10^4\;exp$ (-16,600/T) below $800^{\circ}K$. By addition of metallic oxides, the rate constant increases remarkably. This work has substantiated the belief that the effect of the metallic salts on the fuel oil combustion can conveniently be studied by checking directly the effect of the corresponding metallic oxide on the soot carbon.

• 한국가시화정보학회지
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• 제13권3호
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• pp.20-23
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• 2015

In this experiment, a heterogeneous droplet consisted of de-ionized water and olive oil was made through two 31G injection needles. The injection flow rate was $50{\mu}{\ell}/min$ and the droplet size was 2 mm. The droplet was impinged onto a sapphire plate which was heated up to $300^{\circ}C$ by a heater. Two high speed cameras were used for visualization, and the frame rate was 20,000 fps. A 150W metal halite lamp was used for illumination. The dropping height was fixed to 20 mm and the corresponding Weber number was 10.6 based on water. Due to different boiling points of two liquids, partial boiling features of heterogeneous droplet was observed. At the Leidenfrost condition, micro explosion phenomenon has occurred.

• Asian-Australasian Journal of Animal Sciences
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• 제14권8호
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• pp.1062-1066
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• 2001

Studies were carried out on forty young bulls of the Hariana breed (around 18 months of age) selected on the basis of their dam's milk yield at the animal farm of CCS HAU, Hisar during the period 1993-1999. Since animals showed variation in capacity to work over prolonged periods, they were subjected to regimes of carting without load and with 8 qtls. of load for three hours. The study revealed that maximum change took place in the pulse rate, followed by respiration rate and rectal temperature. The mean fatigue score for pulling an empty cart ranged between 1.66 to 2.20 after two hours work, and 2.36 to 2.73 after three hours work. For a cart loaded with 8 qtls., the corresponding ranges were 2.90 to 3.36 and 3.40 to 4.10, respectively. These results indicated that the animals under experiment had the capacity to pull moderate load (8 qtls.) for about two hours without showing any serious effect on the ability to recover and soon to work again.

• Macromolecular Research
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• 제14권6호
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• pp.596-602
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• 2006

The effect of high-temperature spinning and poly(vinyl pyrrolidone) (PVP) additive on poly(vinylidene fluoride) (PVDF) hollow fiber membranes was investigated using differential scanning calorimetry, X-ray diffraction measurement, and scanning electron microscopy, together with the corresponding microfiltration performances such as water flux, rejection rate, and elongational strength. Using high-temperature spinning, porous hollow fiber membranes with particulate morphology were prepared through PVDF crystallization. The particulate structure of the membranes was further modified by the addition of miscible PVP with PVDF. Due to these effects, the rejection rate and strength of the fibers were increased at the expense of reduced water flux and mean pore size, which indicates that high-temperature spinning and PVP addition are vary effective to control the morphology of PVDF hollow fiber membranes for microfiltration.

• 한국건축시공학회지
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• 제8권4호
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• pp.87-93
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• 2008

With an increased use of alternative aggregate due to exhaustion of quality aggregate resources, the amount of used crushed aggregates have been increased and as a result, development of admixture materials has also been improved and its amount of use is increasing from day to day in order to secure quality in concrete. Accordingly, the purpose of this study is to make concrete of good quality by using chemical admixture developed in this study by replacement rate of fine aggregate. At first, susceptibility, compressive strength ratio and length change ratio in both fresh and hardened concrete were evaluated according to corresponding regulation. As for high performance related regulation, APC NO.3 and PC series were going to rule, and as for AE agent regulation, replacement ratio of fine aggregate of high performance chemical admixture was 10:0 and other chemical admixture met quality regulation for AE agent.

• Journal of Communications and Networks
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• 제17권4호
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• pp.346-350
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• 2015

It is known that the progressive edge-growth (PEG) algorithm can be used to construct low-density parity-check (LDPC) codes at finite code lengths with large girths through the establishment of edges between variable and check nodes in an edge-by-edge manner. In [1], the authors derived a class of LDPC codes for relay communication systems by extending the full-diversity root-LDPC code. However, the submatrices of the parity-check matrix H corresponding to this code were constructed separately; thus, the girth of H was not optimized. To solve this problem, this paper proposes a modified PEG algorithm for use in the design of large girth and full-diversity LDPC codes. Simulation results indicated that the LDPC codes constructed using the modified PEG algorithm exhibited a more favorable frame error rate performance than did codes proposed in [1] over block-fading channels.

• International Journal of Aeronautical and Space Sciences
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• 제2권1호
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• pp.1-11
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• 2001

The time implicit point SGS scheme is applied to compute hypersonic viscous flows in thermochemical nonequilibrium. The performance of the point SGS scheme is then compared with those of the line SGS and the LU-SGS schemes. Comparison of convergence histories with the effect of multiple forward and backward sweeps are made for the flow over a 2D cylinder experimentally studied by Hornung and the flow over a hemisphere at conditions corresponding to the peak heating condition during the reentry flight of an SSTO vehicle. Results indicate that the point SGS scheme with multiple sweeps is as robust and efficient as the line SGS scheme. For the point SGS and the LU-SGS scheme, the rate of improvement in convergence is largest with two sweep cycles. However, for the line SGS scheme, it is found that more than one sweep cycle deteriorates the convergence rate.

• Journal of Astronomy and Space Sciences
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• 제14권2호
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• pp.355-366
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• 1997

This paper presents a comprehensive analytical approach for determining key maneuver parameters associated with the acquisition and maintenance of the ground track for a low-earth orbit. A livearized model relating changes in the drift rate of the ground track directly to changes in the orbital semi-major axis is also developed. The effect of terrestrial atmospheric drag on the semi-major axis is also explored, being quantified through an analytical expression for the decay rate as a function of density. The non-singular Lagrange planetary equations, further simplified for nearly circular orbits, provide the desired relationships between the corrective in-plane impulsive velocity increments and the corresponding effects on the orbit elements. The resulting solution strategy offers excellent insight into the dynamics affecting the timing, magnitude, and frequency of these maneuvers. Simulations are executed for the ground track acquisition and maintenance maneuver as a pre-flight planning and analysis.