• International Journal of Aeronautical and Space Sciences
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• 제16권2호
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• pp.123-136
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• 2015

The present study numerically investigates the effect of shield on the flow characteristics of Hartmann whistle. The flow characteristics of un-shielded Hartmann whistle are compared with whistles of different shield heights 15 mm, 17 mm, 20 mm, 25 mm and 30 mm. The comparison of Mach number contours and transient velocity vectors of shielded Hartmann whistles with un-shielded ones for the same conditions reveal that the presence of shield causes the exiting jet to stick to the wall of the shield without causing spill-over around the cavity inlet, thus sustaining the shock oscillation as seen in the unshielded Hartmann whistle, which has intense flow/shock oscillation and spill-over around the cavity mouth. The velocity vectors indicate jet regurgitance in shielded whistles showing inflow and outflow phases like un-shielded ones with different regurgitant phases. The sinusoidal variation of mass flow rate at the cavity inlet in un-shielded Hartmann whistle indicates jet regurgitance as the primary operating mode with large flow diversion around the cavity mouth whereas the non-sinusoidal behavior in shielded ones represent that the jet regurgitance is not the dominant operating mode. Thus, this paper sufficiently demonstrates the effect of shield in modifying the flow/shock oscillations in the vicinity of the cavity mouth.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1633-1642
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• 2000

Like many other mechanical dynamic systems, flexible manipulator systems experience stiction or sticking friction, which may cause input-dependent instabilities. Manipulator performance can be enha nced by identifying friction but it is hard and expensive to measure friction by direct and precise sensing of contact displacements and forces. This study addresses the problem of identifying flexible manipulator joint friction. A dynamic model of a two-link flexible manipulator based upon finite element and Lagrange's method is constructed. The dynamic model includes the effects of joint compliances and actuator dynamics. Friction is also incorporated in the dynamic model to account for stick-slip at the joints. Next, the friction parameters are to be determined. The identification problem is posed as an optimization problem to be solved using nonlinear programming methods. A genetic algorithm is used to increase the convergence rate and the chances of finding the global optimum. The identified friction parameters are experimentally verified and it is expected that the identification technique is applicable to a system parameter identification problem associated with a wide class of nonlinear systems.

• Journal of Biosystems Engineering
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• 제28권5호
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• pp.429-438
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• 2003

This study exploits the robot system which is necessary in gene study and bio-technology industry. As well, a DNA chip, which of use has been increased recently, can be manufactured with this system. The robot consists of a device spotting DNA on the silylated slide, a well plate, a bed for fixing well plates, devices of washing and drying the pin in DNA spotting .device, a distillation-water vessel, and a discharge vessel of wash water. We made the period of sticking DNA to the pin on the well plate to be 15 seconds. The spot size of DNA was set to be 0.28 mm on the average by bringing the slide into contact with pin during 1 second. If DNA is spotted in minimum space possible about 0.32mm, this system can stick about 8,100 DNA spots on the well plate with this rate. Analyzing the procedure: Movement starts, Pin washes, dries, and smears DNA on the well plate. Spotting DNA onto 12 chips took 2 minutes and 50 seconds.

• Clinical and Experimental Pediatrics
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• 제53권8호
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• pp.790-794
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• 2010

Purpose: The purpose of this study was to test the efficacy of treating the pain among newborn infants associated with a medical procedure with sucrose with regard to overall physiological and behavioral stability. Methods: 103 newborn infants were enrolled in this study. The control group (n=63) did not receive any treatment. The experimental group (n=40) received 2 mL of 24% sucrose solution two minutes before a routine heel stick. The pain was assessed by measurements of physiological changes [e.g. pulse rate, oxygen saturation, salivary cortisol (hydrocortisone)] and behavioral changes [e.g. crying time, and the neonatal infant pain scale (NIPS) for neonates]. Results: There were no differences among the groups with respect to physiological changes associated with the pain from the procedure. However, there were significant group differences in behavioral changes to the pain. In the control group, the median crying time was 13 seconds, while in the experimental group, the median crying time was 3.5 seconds ($P$=.000). In the control group the median NIPS score was 4, while in the experimental group the median NIPS score was 2 ($P$=.000). Conclusions: These findings suggest that sucrose can be an effective method for the management of stress responses in infants with regard to behavior. However, this treatment had no significant physiological effects.

• Journal of Trauma and Injury
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• 제20권2호
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• pp.65-71
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• 2007

Purpose: In the Korean armed forces, vaccination against tetanus is done when personnel join the military service, but we do not know how many military personnel are vaccinated and how many soldiers have protection against tetanus. We performed a qualitative analysis of the tetanus antibody in Korean military personnel by using the TQS (Tetanus Quick Stick) Methods: This study used a prospective collection method for military personnel visiting to the emergency department of a tertiary armed forces hospital from July 2005 to January 2007. We performed an analysis by using the TQS and asked whether the personnel had been inoculated during military service. Results: The number of enrolled military personnel was 474. Among them, 412 had been vaccinated against tetanus after entering the military service. The positive rate of TQS was 91.3% (373 patients) after vaccination for tetanus. Conclusion: Many military personnel were inoculated with tetanus toxoid during military service and have protective antibodies for tetanus. According as TQS should be used for military personnel who visit the emergency department of an armed forces hospital. Also, anti-tetanus immunoglobulin should not normally be used a positive TQS for tetanus prophylaxis.

• Tribology and Lubricants
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• 제11권4호
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• pp.28-34
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• 1995

PTFE has good mechanical and chemical stability at wide temperature range, and more over, shows a low value of friction coefficient. On the other hand, it shows cold flow and high wear rate. However, these short comings can be overcome by adding various fillers. In this experiment, PTFE and polyimide powder were mixed into composite and its tribological characteristics was investigated. 100% polyimide was also tested for comparison. The countefface material was a stainless steel (SUS304). Friction and wear tester of ring-on-block type was used at room temperature and under atmosphere. After the wear test, the worn surfaces were examined by optical microscope. The test results show that PTFE-polyimide composite generates. the wear transfer film on both sides of the friction surfaces, and, the friction coefficient and the wear rates are relatively low. 100% polyimide generated little wear transfer films, showed high friction and wear rates, and also showed some problems of vibration and noise. It even damaged the stainless steel countefface. It was concluded that 100% polyimide does not generate transfer film well because its shear resistanbe is high and it stickslips, thus, friction coefficients and wear rates are high. In case of PTFE-polyimide composite, on the other hand, transfer film containing sufficient PTFE adheres and remains on both wear surfaces well enough because PTFE has low shear resistance. Polyimide particles in the composite were proved to be able to bear normal load and does not show stick-slip because they are covered with transfer film containing much PTFE.

• Mycobiology
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• 제47권1호
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• pp.97-104
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• 2019

Mushroom cultivation has gained increased attention in recent years. Currently, only four types of spawn, including sawdust spawn, grain spawn, liquid spawn, and stick spawn, are commonly available for mushroom cultivation. This limited spawn diversity has led to difficulty in selecting suitable inoculum materials in some cultivation. In this study, three small blocks of lignocellulosic agro-wastes and one block of a synthetic matrix were prepared as support for growing Pleurotus ostreatus in liquid medium. Mycelium-adsorbed blocks were then evaluated for their potential as block spawn for fructification. Our results indicated that the edible fungus was adsorbed and abundantly grew internally and externally on loofah sponge and synthetic polyurethane foam (PUF) supports and also has the ability to attach and grow on the surface of sugarcane bagasse and corncob supports. The mycelia of P. ostreatus adhered on corncob exhibited the highest metabolic activity, while those on the PUF showed the least activity. Mycelial extension rates of block spawns made of agro-waste materials were comparable to that of sawdust spawn, but the block spawn of PUF showed a significantly lower rate. No significant differences in cropping time and yield were observed among cultivations between experimental block spawns and sawdust spawns. Moreover, the corncob block spawn maintained its fruiting potential during an examined period of 6-month storage. The developed block spawn could be practically applied in mushroom cultivation.

• 한국치위생학회지
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• 제1권2호
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• pp.181-192
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• 2001

The purpose of this was to evaluate the level of knowledge about Hepatitis B and AIDS among dental hygiene students at six dental hygiene educational programs in nationwide, compare the findings to those of Song's study. 1703 dental hygiene students surveyed by mail and answered a questionnaire, using the questionnaire used developed by DiClemente el al., on Hepatitis B vaccination, antibody production, experience of unintentional needle stick injuries, experience of surgical operation and blood transfusion, personal risk factors for HBV and HIV, management of HBV and HIV postexposure management et al. The data indicated that dental hygiene students (79.0%) in this study had more HIV vaccination than dental hygiene(74.3%) in Song's study. As for recognition of antibody production after Hepatitis B vaccination, only 34.6% of respondents answered they knew having antibody production and 95% of respondents knew not having antibody production. Over one-half of the respondents (55%) answered they didn't even recognize having antibody production. 52.3 percent of dental hygiene students experienced unintentional needle stick injuries. The findings on the knowledge about Hepatitis B and AIDS were that dental hygienists (76.5 points) received higher mean score than those of dental hygiene students (71.0 points) and that the distribution of right answer rate also showed wider range in dental hygiene students (27.7~97.5%) than those of dental hygienist (41.2~99.5%). There were no statistical differences among dental hygiene education programs. Finding of this study support that the curriculum of dental hygiene program should include instruction on sources and methods of transmission of infectious diseases, risk of virus transmission in the workplace and principles of infection control. Furthermore, infection-control practices should be utilized routinely and their application to dental personnel, management of HBV and HIV postexposure management. Furthermore, for preventing the further spread of infectious diseases (HBV, HIV and AIDS${\cdots}$) caused by bloodborne viruses, imposing an obligation rather than recommendation on Hepatitis B vaccination to all dental personnel and routinely utilizing infection-control guidelines for all dental patients in dental practices (include dental educational programs) should be accomplished by coordination the government agency.

• Journal of Biosystems Engineering
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• 제37권3호
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• pp.192-200
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• 2012

Purpose: Aerial application of chemicals with an agricultural helicopter allows for precise and timely spraying and reduces working labor and pollution. An attitude controller for an agricultural helicopter would be helpful to aerial application operator. The objectives of this paper are to determine the transfer function models and to estimate the handling qualities of a bare-airframe model helicopter. Methods: Transfer functions of a model unmanned helicopter were estimated by using NAVFIT and DERIVID modules of the $CIFER^{(R)}$ program to the time history data of frequency sweep flight tests. Control inputs of the transfer functions were elevator, aileron, rudder and collective pitch stick positions and the outputs were resulting on-axis movements of the fuselage. Results: Minimum realization of the transfer functions for pitch rate output to elevator control input and roll rate output to aileron control input produced second order transfer functions with undamped natural frequencies around 3.0 Hz and damping ratios of 0.139 and 0.530, respectively. The equivalent time delays of the transfer functions ranged from 0.16 to 0.44 second. Sensitivity analysis of the proposed parameters allowed derivation of minimal realization of the transfer functions. Conclusions: Handling quality of the model helicopter was addressed based on the eigenvalues of the transfer functions, corresponding undamped natural frequencies with damping ratios. The equivalent time delays of the lateral-directional motion ranged from 0.16 to 0.44 second, longer than the 0.1 to 0.15 second requirement for well-controlled typical manned aerial vehicles.

• Safety and Health at Work
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• 제10권4호
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• pp.445-451
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• 2019

Objective: The objective of this study was to evaluate the prevalence and incidence of accidents with biological material, the level of knowledge, and compliance to standard precautions (SPs) among dentists, physicians, nurses, and dental and medical students. Methods: A closed cohort study with a prospective and retrospective component was conducted between August 2014 and September 2015. The participants were contacted in two moments during the follow-up period, during which a structured questionnaire divided into six sections was used; the interviews were conducted during the follow-up period (Month 6) and at the end of the observation period (Month 12). Results: The global prevalence of accidents in the previous 12 months was 10.2%, with a difference between professionals and students (13.0% vs. 5.1%, respectively; p < 0.003). The incidence rate was 6.49 per 100 person/year, with difference between the groups (6.09 per 100 person/year in professionals and 7.26 per 100 person/year in students), type of specialization (hazard ratio, 3.27), and hours worked per week (hazard ratio, 2.27). The mean of compliance to SP was 31.99 (±3.85) points, with a median of 33 (30, 35) points against the expected 27.75 points. Adherence to SP was associated with the accident report (p < 0.020). Conclusion: We conclude that the proportion/incidence rate of accidents with biological material was high in relation to that in the literature, being higher in professionals and especially among physicians. The levels of knowledge and adherence to SP were good, with the best found in dentists and dental students.