• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.515-519
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• 2002

As the number of the company to acquire the certifications of ISO 9001/1400, OHSAS 18001(not official standard) is increasing, it is needed to construct a integrated business management system for the efficient application of the certifications. In this circumstances the integrated construction of the SHE & Q system so called, for Safety, Health, Environment and Qualify can take a part for the communication in the customer, the company convenience and the interested parties(the worker. the supplier and the provider). In case that each certification systems are integrated, the problems of the redundancy in the management processes and the conflicting demands are able to be solved and the efficiency of the restricted management resources fan be raised as the complexity of the redundancies in the certification management is simplified. This paper deals with the integrated strategies, its convenience and its expecting merit and demerit for the efficient application of the certification parties haying the various characters.

• Journal of Power Electronics
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• v.14 no.5
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• pp.852-858
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• 2014

A novel 12/10 axial field switched reluctance motor (AF-SRM) is proposed for cooling fan applications in this paper. Unlike from conventional structures, the proposed motor uses the axial field instead of the radio field, the rotor is constructed from a series of discrete segments, and the stator poles are constructed from two types of stator poles: exciting and auxiliary poles. This concept improves the torque capability of a previous design by reducing the copper volume, which leads to a higher efficiency. To verify the proposed structure, the finite element method (FEM) and Matlab-Simulink are employed to get characteristics of the proposed SRM. Finally, a prototype of the proposed motor was tested for characteristic comparisons.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.71-74
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• 2008

This paper aims at studying the key design elements for the optimal ventilation system design, developing the design models and suggesting the design guidelines. The key elements include the basic exhaust emission rate, wall friction coefficient, vehicle drag coefficient and slip streaming effect, jet fan operating efficiency, natural ventilation force and installation scheme for jet fans and ventilation monitors in tunnel. The design models developed in this study are one-dimensional ventilation simulator to analyze the air flow, pressure profile and pollutant dispersion inside and outside tunnel, expert model to choose the optimal ventilation method, and the ventilation characteristic chart to evaluate the preliminary ventilation system. The study results are reflected in the design guideline for road tunnel ventilation system.

• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.279-284
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• 2010

Tip clearance losses occur in every turbomachine. To estimate the losses in efficiency it is important to understand the mechanism of this secondary flow. Tip clearance losses are mainly caused by a spiral vortex formed on the suction side of the blade of a turbomachine, which induces a drag and also has an influence on the incident flow of the blades. In this paper a physical based scaling method is developed out of an analytical ansatz for the tip clearance losses. This scaling method is validated by measurements on an axial fan with five different tip clearances.

• International Journal of Fluid Machinery and Systems
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• v.6 no.4
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• pp.177-187
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• 2013

A scaling method valid for most turbomachines based on first principles is derived. It accounts for axial and centrifugal turbomachines with respect to relative gap width/tip clearance, relative roughness, Reynolds number and/or Mach number for design and off-design operation as well. The scaling method has been successfully validated by a variety of experimental data obtained at TU Darmstadt. The physically based, hence reliable and universal method is compared with previous, empirical scaling methods.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.136-140
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• 2007

In this paper, an adaptive minimum transmit power modulation scheme under constant data rate and fixed bit error rate (BER) for the multiple-input multiple-output (MIMO) system is proposed. It adjusts the modulation order and allocates the transmit power to each spatial sub-channel when meeting the user's requirements at the cost of minimum transmission power. Compared to the other algorithm, it can obtain good performance with lower computational complexity and can be applied to the wireless communication system. Computer simulation results present the efficiency of the proposed scheme. And its performance under different channel condition has been compared with the other algorithm.

• IE interfaces
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• v.13 no.4
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• pp.717-724
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• 2000

In this paper, an integrated system of optimal design, performance evaluation, and die design and manufacturing of axial fans for cooling tower is presented. The design and performance evaluation are developed based on three dimensional flow analysis so as to ensure low noise and high efficiency. The methodologies are implemented on computer as a GUI system including 3-D surface modeling and 2-D drawing file output modules. The CAD/CAM system is engaged to design the die and generate NC tool path, but the processes are also automated and integrated into the system by means of a part program coded from the design data. It is shown that the newly developed fans have superior performance and shortened lead-time compared to the existing dead-copied fans.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.3
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• pp.51-59
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• 2006

The air purity-sterilizer was developed and the CFD and experimental studies were carried out in order to investigate the performance of a air purity-sterilizer. Overhaul and exchange efficiency were increased by the modularization of the air purity-sterilizer. The good performance was validated by the hot-wire measurements and flow simulations in the room. Mean velocities at the exit of the air purity-sterilizer were 0.91, 1.62, 1.99, and 6.14 m/sec according to the fan mode. And the flow visualization of pured air was shown by using CFD flow simulation in the room of 24, 50 pyeong. The results show that the air purity-sterilizer has a high performance enough to produce air purity-sterilizer on a commercial scale.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.6
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• pp.299-311
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• 2008

The Radio Frequency IDentification (RFID) system is a contactless automatic identification system, which comprises readers and tags. In RFID systems, a reader collision occurs when there is interference in communication between one reader and the tags, due to the signals from other readers. The reader collision problem is considered as the fundamental problem affecting high density RFID reader installations. In this paper, we analyze the existing reader anti-collision algorithms. We also propose a pulse protocol-based reader anti-collision algorithm using slot occupied probability (SOP). The implementation of this improvement is simple, yet it effectively mitigates most reader collisions in dense reader mode, as shown in our simulation. That is, the proposed algorithm reduces the identification time, and increasesthe system throughput and system efficiency compared with the conventional reader anti-collision algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4025-4042
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• 2017

Session initiation protocol (SIP) is a kind of powerful and common protocols applied for the voice over internet protocol. The security and efficiency are two urgent requirements and admired properties of SIP. Recently, Hamed et al. proposed an efficient authentication and key agreement scheme for SIP. However, we demonstrate that Hamed et al.'s scheme is vulnerable to de-synchronization attack and cannot provide anonymity for users. Furthermore, we propose an improved and efficient authentication and key agreement scheme by using elliptic curve cryptosystem. Besides, we prove that the proposed scheme is provably secure by using secure formal proof based on Burrows-Abadi-Needham logic. The comparison with the relevant schemes shows that our proposed scheme has lower computation costs and can provide stronger security.