• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1757-1761
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• 2001

"Drifting cups on a meandering stream" is a same originating from the ancient China. It takes advantage of the stopover of the cup at the different positions on a meandering stream to choose a person sitting on the bank to participate the game. In this paper, a model is devised to make the cups move around or stop at some place on the stream as required by the game. A typical flow field Is abstracted and studied using the PIV technique and the topological analysis. Some motions of the cup on the stream have been explained in the mechanics theory.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.23-36
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• 2005

The main obstacle hindering the wide deployment of identity-based cryptosystem is that the entity responsible for creating the private key has too much power. As a result, private keys are no longer private. One obvious solution to this problem is to apply the threshold technique. However, this increases the authentication computation, and communication cost during the key issuing phase. In this paper, we propose a new effi ient model for issuing multiple private keys in identity-based encryption schemes based on the Weil pairing that also alleviates the key escrow problem. In our system, the private key of a user is divided into two components, KGK (Key Description Key) and KUD(Key Usage Desscriptor), which are issued separately by different parties. The KGK is issued in a threshold manner by KIC (Key Issuing Center), whereas the KW is issued by a single authority called KUM (Key Usage Manager). Changing KW results in a different private key. As a result, a user can efficiently obtain a new private key by interacting with KUM. We can also adapt Gentry's time-slot based private key revocation approach to our scheme more efficiently than others. We also show the security of the system and its efficiency by analyzing the existing systems.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 1998.03a
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• pp.15-19
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• 1998

The arthroscopic treatment may prove to be the desirable method, but this arthroscopic technique cannot be appliable to all surgeons and all patients, It should be determined on the base of type of lesion, effectiveness of arthroscopic procedure, and the surgeon's skill. The Key to an excellent result in arthroscopic treatment of rotator cuff lesion is doing a proper diagnosis, well-established arthroscopic technique and following through a well-designed rehabilitation program.

• ETRI Journal
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• v.34 no.1
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• pp.142-145
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• 2012

The main challenge at present in constructing hierarchical identity-based encryption (HIBE) is to solve the trade-off between private-key size and ciphertext size. At least one private-key size or ciphertext size in the existing schemes must rely on the hierarchy depth. In this letter, a new hierarchical computing technique is introduced to HIBE. Unlike others, the proposed scheme, which consists of only two group elements, achieves constant-size private keys. In addition, the ciphertext consists of just three group elements, regardless of the hierarchy depth. To the best of our knowledge, it is the first efficient scheme where both ciphertexts and private keys achieve O(1)-size, which is the best trade-off between private-key size and ciphertext size at present. We also give the security proof in the selective-identity model.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.329-337
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• 2019

This paper presents an experimental investigation about visualization of bulging development of geosynthetic-encased stone column (GESC) based on the digital image correlation (DIC) technique and transparent soil. Visual model tests on GESC and ordinary stone column (OSC) were carried out. In order to delete the warping effect resulting from transparent soil and experiment setup, a modification for experiment results was performed. The bulging development process of the GESC and the displacement field of the surrounding soil were measured. By comparing with the existing experimental and theoretical results, it demonstrates that the model test system developed for studying the continuous bulging development of GESC is suitable. The current test results show that the bulging depth of GESC ranges from 1.05 to 1.40 times the diameter of GESC. The influence depth of GESC bulging on surrounding soil displacement is 0~3 the times diameter of GESC.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.68-77
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• 2005

A transient liquid crystal technique has become one of the most effective ways in measuring the local heat transfer coefficients on the entire surface. The key Point of this technique is to convert the inlet flow temperature into an exponential temperature profile using a mesh heater. In order to verify the validity of this technique. the heat transfer characteristics on the wall surface by a pair of longitudinal vortices is investigated experimently and numerically. A standard ${\kappa}-{\varepsilon}$ is used for the numerical analysis of turbulent flow field. It is found from experiment and numerical analysis that two peak values exist over the whole domain. as the longitudinal vortices move to the farther downstream. these peak values decrease and the dimensionless averaged Nusselt number with the lapse of time is maintained nearly at constant values. The experiment results obtained from the present experiment in terms of the transient liquid crystal technique are in good agreement with the numerical results. Therefore, the transient liquid crystal technique developed for the measurement of heat transfer coefficient is proved to be a valid method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.491-498
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• 2001

IN this Paper we propose an encryption algorithm for security in data communication. this algorithm acts encryption operation after the compression of data in order to reduce the transmission time and storage an encryption key is generated by using a parameter. as soon as key value is generated the parameter is transmitted and key is recreated every 26 times of parameter changing. the random number which is a constituent unit of encryption key is stored in a table the table is reorganized when the key is generated 40 times in order to intensity the security of encryption key. the encryption of data is made through the operation process of the generated key and sour data and the decryption performs the revers operation of encryption after getting decryption key by searching the transmitted parameter. as this algorithm is performed lastly it is possible to be used in practice.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1324-1335
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• 2016

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1639-1645
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• 2011

A technique to allocate responsibilities among the interested parties in electric power system with harmonic voltage distortion at the point of common coupling (PCC) has been presented. The recursive least-squares technique has been used to estimate the parameters of the Thevenin equivalent load model. The validity of the technique has been verified using a simulation which considered the voltage waveform distortion at the PCC between the utility and two industrial consumers. With the estimated data from the measured voltage and current waveform at the PCC, the individual contributions to the distortion of voltage waveform at an interested harmonic frequency have been calculated and could provide a flexible solution to identify the source of harmonic pollution in distribution systems.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.169-176
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• 2009

This paper introduces 60 apply method at a railroad vehicle including basic technique of the 60. Basically rolling stock maintenance cost is high and life cycle is long. Therefore, the maintenance efficiency is the most important. Usually the length of the rolling stock life cycle is over 20years, the method of maintenance technique must be reformed periodically. So the key point of a inspection efficiency is to update the maintenance method regularly. The early days 60 method began from the thing to reduce a productions era. But after the year 2000, it took the place to the management reform technique of all business field. Finally optimal rolling stock maintenance method is introduced through the example.