• Safety and Health at Work
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• v.9 no.4
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• pp.468-472
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• 2018

Background: Firefighters are required to use self-contained breathing apparatus (SCBA), which impairs ventilatory mechanics. We hypothesized that firefighters have elevated arterial $CO_2$ when using SCBA. Methods: Firefighters and controls performed a maximal exercise test on a cycle ergometer and two graded exercise tests (GXTs) at 25%, 50%, and 70% of their maximal aerobic power, once with a SCBA facemask and once with protective clothing and full SCBA. Results: Respiratory rate increased more in controls than firefighters. Heart rate increased as a function of oxygen consumption ($V_{O_2}$) more in controls than firefighters. End-tidal $CO_2$ ($ETCO_2$) during the GXTs was not affected by work rate in either group for either condition but was higher in firefighters at all work rates in both GXTs. SCBA increased $ETCO_2$ in controls but not firefighters. Conclusions: The present study showed that when compared to controls, firefighters' hypoventilate during a maximal test and GXT. The hypoventilation resulted in increased $ETCO_2$, and presumably increased arterial $CO_2$, during exertion. It is proposed that firefighters have altered $CO_2$ sensitivity due to voluntary hypoventilation during training and work. Confirmation of low $CO_2$ sensitivity and the consequence of this on performance and long-term health remain to be determined.

• Communications of the Korean Mathematical Society
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• v.24 no.2
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• pp.215-226
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• 2009

For a class of Holling type II food chain systems with biological and chemical controls, we give conditions of the local stability of prey-free periodic solutions and of the permanence of the system. Further, we show the system is uniformly bounded.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.6-12
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• 2005

This paper presents Z-source inverters, their controls,, and their systems for motor drives. System configurations, analysis, controls, and unique features of the new Z-source motor drive systems will be summarized and given. Simulation and experimental results demonstrate advantageous features over the traditional voltage- and current-source inverter systems.

• Communications of the Korean Mathematical Society
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• v.35 no.4
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• pp.1329-1352
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• 2020

In this paper we consider a class of nonlinear evolution equations on infinite dimensional Banach spaces driven by vector measures. We prove existence and uniqueness of solutions and continuous dependence of solutions on the control measures. Using these results we prove existence of optimal controls for Bolza problems. Based on this result we present necessary conditions of optimality.

• Fire Science and Engineering
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• v.10 no.2
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• pp.20-27
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• 1996

This paper discussed the limit of existing safety controls where the use of land around hazardous industry. There is a gap between engineering evaluation of acceptable criteria for loss reduction and risk exposure to the areas of high risk outside plants from the aspects of risk perception. The paper performed how land use safety could be designed between the density of uses with the duration of risk exposure by type of land use. It concluded the needs of multi-dimensional presentation for an appropriate risk controls on existing and future land use safety.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1998.10a
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• pp.385-391
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• 1998

As the increase in the use of computers and rapid development of information technology exacerbate auditors' judgmental process, achieving objectives(effectiveness) of control and auditing with limited resources requires auditors to identify relative importance and priority of controls. Consequently, auditors' review and evaluation of internal control is been highlighted in modrn auditing process. Especially, as more organizations adopted LAN(Local Area Network) systems. LAN environment is facing with problems arising from characteristics of theLAN and the evaluation of LAN controls. The modern in this study is LAN control evaluation model with information system auditing objectives. This study concludes that auditors' proper evalution of the importance of LAN controls contributes to the effective achievement of IS auditing objectives.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.212-218
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• 2000

Osteoporosis is a bone disease associated with reduced bone mineral density resulting in debilitating bone fractures. The present study was carried out to determine the influence of ovariectomy(OVX) on serum level of sex steroid and bone metabolism, as well as bone mechanical property, in OVX subjects in comparison with controls. Body weight and food intake was significantly increased in OVX subjects than in controls. The serum level of estradiol(E2) was significantly lower in OVX subjects than in controls. The serum level of calcium and alkalin phosphatae were significantly increased in OVX subjects than in controls. The bone strength, based on the three point bending test, was not significantly different. Seven weeks after ovariectomy, the cavities in the bone reached 223% of the normal. In conclusion, seven weeks after ovariectomy osteoporo sis was evidently appeared.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.881-888
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• 2015

Financial Authorities have added security controls to the Electronic Financial Transaction Act and the Supervisory Regulation according to the recent frequent personal credit information leakages. Accordingly, the security level has been upgraded. But it is necessary to study more security controls to add. This paper deduces 19 security controls over the mean value to be added to the financial area receiving 15 security consultant's help.

• Journal of KSNVE
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• v.6 no.5
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• pp.595-605
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• 1996

If the control force designed on the basis of the mathematical model with parameter errors is applied to control the actual system, the closed-loop performance of the actual system will be degraded depending on the degree of the errors, In this study, the effect of parameter errors on the robustness of several natural controls has been analyzed and compared. Every asymptoic stability condition for the natural controls has been derived using Lyapunov approach, and the characteristics of the stability conditions has also been compared. The extent of deviation of the closed-loop performance from the designed one for the natural controls is derived using operator techniques, and evaluated by numerical method. It has been found that the optimal control, acceleration feedback control, and acceleration-position feedback control among the considered natural controls would be robust one with respect to the parameter errors.

• Bulletin of the Korean Mathematical Society
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• v.25 no.2
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• pp.185-194
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• 1988

In [2], we have shown that the optimal boundary controls for hyperbolic systems in L$^{2}$-spaces can be attained in a feedback form via Riccati operators. A number of authors [1, 5, 7 and 10] have investigated approximations of Riccati operators arising in distributed parameter systems. They assumed bounded controls for parabolic systems. However, we in this paper study Galerkin approximations of Riccati operators and feedback controls for hyperbolic systems with unbounded control actions. Let us briefly introduce some results of [2]. Let .ohm. be an open bounded region in R$^{n}$ with smooth boundary .GAMMA. where n is a fixed positive integer. We consider a strictly hyperbolic differential operator H(x) of order 1 on .ohm. with noncharacteristic boundary on .GAMMA.