• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.371-377
• /
• 2009

The propulsion system of turboprop has been rarely used in the large aircraft due to the limitation of the maximum velocity of the propeller, the power limitation by the reduction gear, etc. Recently, the demand on turboprop aircraft continues to increase because of economical efficiency and environmental factors. In this paper, turboprop propulsion system which is composed of a Pratt & Whitney 127F turboprop engine and a Hamilton Standard 568F propeller was modeled by using the Gasturb11 software. The result of the performance analysis on this propulsion system model showed that the propulsion system model was evaluated to have been successfully builded.

• Proceedings of the KIEE Conference
• /
• 2004.07d
• /
• pp.2367-2369
• /
• 2004

It is well known that an indirect methanol based fuel cell system imposes a performance limitation on the fuel cell electric vehicle (FCEV) due to the reformer lag. An optional battery system can be used together with fuel cell to improve this performance limitation and it is called a fuel cell hybrid electric vehicle (FCHEV) this paper first describes the configuration of FCHEV with explanation of the energy flow between subsystems. Mathematical modeling of each subsystem such as a fuel cell system, a battery system, a driving motor with the transmission are formulated and coded using Matlab/simulink software. It is illustrated by simulation results that fuel cell modeling yields appropriate stack voltage in order to get the required current quantity with varying hydrogen flow.

• Journal of the military operations research society of Korea
• /
• v.24 no.1
• /
• pp.41-57
• /
• 1998

Since the aircraft has a property of moving in the three-dimensional space, it may cause personally and financially critical damage in the case of an accident. Among the causes of aircraft accident, human factor has occupied about 70% of all accidents. Specially, fatigue among human's problems has been studied earlier than any other factor. Fatigue has been the cause of 75% of accidents that are related to human factor. So many studies have been conducted. But the direction of these studies mainly attach importance to the sleep loss and circadian rhythm. Limitation for flight time of ICAO is 8 hours per day, civil airlines in domestic line also adopt the limitation. But this rule is not based on human's performance but compromise between labor and management. The long-haul flight brings about a mental block to pilot. This mental block decreases performance of pilot and loses a lot of important information. So this may cause many accidents. This paper is to offer optimal flight time according to the amount of fatigue due to increasing flight time. The optimal flight time is searched through the field experiment. The experiment has adopted two methods. One is to examine pilot's objective fatigue accumulation rate through the critical fusion frequency, and another is to investigate pilot's subjective fatigue feeling through the fatigue subjective symptoms investigation table.

• Solar Energy
• /
• v.12 no.2
• /
• pp.9-17
• /
• 1992

This is an experimental work concerning about an application of a heat pipe to an evacuated-glass-tube solar collector system. A methanol heat pipe with length of 0.7 m and diameter of 8 mm was manufactured and tested to compare its performance with that of freon thermosyphon which was originally used in a solar collector system fabricated at Thermomax Co.. Then this methanol heat pipe was utilized to be one component, i.e. heat transfer element, of the present experimental model of a solar collector. This model was performed the operation test as its absorber plate was irradiated by infrared lamps. The following results were obtained. (1) The methanol heat pipe was showed a stable operation when the variation of axial heat transport was $0{\sim}40$ watts and that of inclination angle was $30{\sim}90^{\circ}$. (2) The heat transport capability of the heat pipe was proved to be higher than that of the thermosyphon, because the heat transport limitation of the latter was occured at about 30 watt. (3) The heat pipe in a solar collector was also showed good performance as it transmitted absorbed energy.

• International Journal of Internet, Broadcasting and Communication
• /
• v.16 no.2
• /
• pp.1-9
• /
• 2024

As the Internet of Things (IoT) continues to permeate every facet of modern life, the imperative to secure this vast and dynamic frontier becomes increasingly paramount. This presents a comprehensive exploration of the challenges and opportunities inherent in safeguarding the interconnected web of IoT devices. The research critically examines the limitations of current cybersecurity measures through an extensive review of diverse topics, including IoT network performance, smart grid security, and the escalating cyber threats against critical infrastructures. A meticulous analysis of research findings underscores the need for enhanced infrastructure and ongoing research to fortify the cybersecurity mechanisms surrounding IoT objects. We underline the imperative of relentless research efforts to parry the advancing threats and leverage the promise of nascent technologies. Our findings affirm the pivotal influence of robust cybersecurity measures in crafting a resiliently connected ecosystem. The paper underscores the importance of ongoing research to address evolving threats and harness the potential of emerging technologies, reaffirming the central role of cybersecurity in shaping a secure interconnected world. In conclusion, the study emphasizes the dynamic and ever-evolving nature of cybersecurity on the IoT frontier. It unveils a complex landscape of challenges, ranging from network performance intricacies to the security concerns of critical infrastructures.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.7 no.4
• /
• pp.225-230
• /
• 2002

Experiments on deactivation kinetics of immobilized lipase enzyme from Candida cyl-indracea were performed in stirred bath reactor using rice bran oil as the substrate and temperature as the deactivation parameter. The data were fitted In first order deactivation model. The effect of temperature on deactivation rate was represented by Arrhenius equation. Theoretical equations were developed based on pseudo-steady state approximation and Michaelis -Menten rate expression to predict the time course of conversion due to enzyme deactivation and apparent half-life of the immobilized enzyme activity in PFR and CSTH under constant feed rate polity for no diffusion limitation and diffusion limitation of first order. Stability of enzyme in these continuous reactors was predicted and factors affecting the stability were analyzed.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.178-180
• /
• 2002

Limitation countermeasure on harmonics occurred by power conversion installation, motor speed control equipment, and so on of power system is very important problem, and first of all, accuracy harmonics analysis in system is required for appropriate limitation counterplan. Analysis and judgement on power system harmonic by measurement are needed because analysis by mathematical model generally used for these harmonic analysis, if nonlinear ingredient is included in system, is not relatively correct. So, in this paper, system to measure and analyze harmonic by installing it in a power system, using DSP(Digital Signal Processor), is designed and developed. Also, it's performance is verified by installing it in the system that harmonics occurred.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.5
• /
• pp.8-14
• /
• 2015

Heat treatment for car body molds is mainly a manual process performed by a worker. The performance of this process is affected by workers' skill level, and has limitation in maintaining uniform product quality. In this study, we developed a diode laser heat treatment robot system that implements an OLP type simulator to overcome the limitation of manual process, and to improve and stabilize the quality level. In addition, we verified the efficiency of the robot system and mechanism stability from the early stage through design verification and simulated analysis in the development stage. In addition, we carried out a field test to study the way to establish optimized D/B for diode laser heat treatment criteria for car body molds, such as heat treatment speed, interval, etc. via site experiment.

• IEIE Transactions on Smart Processing and Computing
• /
• v.5 no.5
• /
• pp.337-345
• /
• 2016

Recently, as the number of cores in computer systems has increased, the need for larger memory capacity has also increased. Unfortunately, dynamic random access memory (DRAM), popularly used as main memory for decades, now faces a scalability limitation. Phase change memory (PCM) is considered one of the strong alternatives to DRAM due to its advantages, such as high scalability, non-volatility, low idle power, and so on. However, since PCM suffers from short write endurance, direct use of PCM in main memory incurs a significant problem due to its short lifetime. To solve the lifetime limitation, many studies have focused on reducing the number of bit flips per write request. In this paper, we describe the PCM operating principles in detail and explore various bit flip reduction schemes. Also, we compare their performance in terms of bit reduction rate and lifetime improvement.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.2
• /
• pp.104-111
• /
• 2003

Micro force measurement is required more frequently for a precision manufacturing and investment in fields of precision industries such as semiconductor, chemistry and biology, and so forth. Null balance method has been introduced as an alternative of a loadcell. Loadcells have advantages in aspects of low cost and easy manufacturing, but have also the limitation in resolution and sensitivity to environment variations. In this paper, null balance method is explained and the dominant parameters related to system performances are mentioned. Null position sensor, electromagnetic system and controller are investigated. Also, the characteristic experiment is carried out in order to estimate the resolution and the measurement range. In order to overcome the limitation by the drift of position sensor and the performance of controller, double electromagnetic force compensation method is proposed and experimented. After controlling and filtering, the resolution under $\pm$ 1mg and measurement range over 300g could be obtained.