• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.133-138
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• 2002

The developments of the solar and the wind power energy are necessary since the future alternative energies that have no pollution and no limitation are restricted. Currently power generation system of MW scale has been developed, but it still has a few faults with the weather condition. In order to solve these existing problems, combined generation system of photovoltaic(400W) and wind power generation system(400W) was suggested. It combines wind power and solar energy to have the supporting effect from each other. However, since even combined generation system cannot always generate stable output with ever-changing weather condition, power compensation device that uses elastic energy of spiral spring to combined generation system was also added for the present study. In an experiment, when output of system gets lower than 12V(charging voltage), power was continuously supplied to load through the inverter by charging energy obtained from generating rotary energy of spiral spring operates in small scale generator.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.1
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• pp.35-41
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• 2016

Internet of Things (IoT) services are widely used in appliances of daily life and industries. IoT services also provide various conveniences to users and are expected to affect value added of all industries and national competitiveness. However, a variety of security threats are increased in IoT environments and lowers reliability of IoT devices and services that make some obstacles for commercialization. The attacks arising in IoT environments are making industrial and normal life accidents unlike existing information leak and monetary damages, and can expand damage scale of leakage of personal information and privacy more than existing them. To solve these problems, we design a session key based access control scheme for secure communications in IoT environments. The proposed scheme reinforces message security by generating session key between device and access control network system. We analyzed the stability of the proposed access scheme in terms of data forgery and corruption, unauthorized access, information disclosure, privacy violations, and denial of service attacks. And we also evaluated the proposed scheme in terms of permission settings, privacy indemnity, data confidentiality and integrity, authentication, and access control.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.3
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• pp.95-102
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• 2013

It is indispensable to modern society metal processing since the industrialized rapidly, but it is a metalworking cutting fluid immediately. In addition, this means selecting a emulsion on the basis of quality criteria processing method, the material of the material, cutting depth, cutting speed, Djourou fence Liang, and surface roughness, cutting oil, the shape of the device based on the emulsion, I will be the structure of the tank, filtration equipment also changes. In particular, acting bacteria is now breeding in response to the passage of time due to metal ion degradation due to heat generated hydraulic fluid leakage, humidity tung, during processing, seep from processing material at the time of processing the water-soluble cutting oil for generating the malodor by dropping significantly the performance of the cutting oil to corruption from, sometimes by introducing various additives to suppress spoilage in advance. In this study, we expect the effect of the cost reduction in the extension of fluid replacement cycle through the application of the management apparatus and deep understanding in the management of cutting fluid, the working environment through the understanding and interest of workers in the production site more than anything I try to become useful for the improvement.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.117-120
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• 2008

If the management through the center server is unnecessary and JXTA is connected to a network, a communication with any kind of devices or some device is possible. And features that a communication with heterogeneous P2P systems is possible have. The important module of the designed Data exchange system an interworking between the P2P system which it is made we used API and the each other different protocol the possible data for replacement Data exchange system were designed this kind of a feature was to the utmost utilized may account for the XML Parser Component(XPC) which we use it parses the or about a request and the generated request, and the structure of the XML Making Component(XMC) which we use in generating the inappropriate a request and response.

• Macromolecular Research
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• v.11 no.4
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• pp.283-290
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• 2003

Organic drugs including aspirin, omeprazole, and naproxen with three different levels of octanol/water partition coefficient were examined for their release behavior from the amphiphilic PCL-b-PEO-b-PCL (PCEC) matrix. Scanning electron micrograph (SEM) of PCEC illustrated a well defined two-phase morphology consisted of dispersed poly(ethylene oxide) (PEO) domain and continuous polycaprolactone (PCL) phase. Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) experiments veri tied that three model drugs are dissolved as a molecular dispersion in PCEC matrix. The release of hydrophilic aspirin closely followed the water absorption profile of the matrix indicating that its major fraction is present in PEO domain. However, substantial amount of aspirin present in less hydrophilic region displayed discontinuous biphasic release pattern. In the case of omeprazole with intermediate hydrophobicity consistent release behavior was observed for a period of 24 hrs after the rapid liberation of ca. 10% of the drug presumably partitioned in PEO phase. It was ascribed to the fact that the progressive hydration of PCEC matrix gradually increased the chance of drug/water exposure to compensate the exhaustion of device. Naproxen with the highest octanol/water distribution coefficient among three model drugs exhibited a limited release of 35% for 24 hrs. Finally, hydroxypropyl methylcellulose phthalate (HPMCP)/PCEC blend matrix demonstrated an accelerated and quantitative release of hydrophobic naproxen by generating high porosity and thereby expanding polymer/water interface.

• ETRI Journal
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• v.31 no.6
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• pp.688-694
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• 2009

In this paper, we present the results of a preliminary study on the piezoelectric energy harvesting performance of a Zr-doped $PbMg_{1/3}Nb_{2/3}O_3-PbTiO_3$ (PMN-PZT) single crystal beam. A novel piezoelectric beam cantilever structure is used to demonstrate the feasibility of generating AC voltage during a state of vibration. The energy-harvesting capability of a PMN-PZT beam is calculated and tested. The frequency response of the cantilever device shows that the first mode resonance frequency of the excitation model exists in the neighborhood of several hundreds of hertz, which is similar to the calculated value. These tests show that several significantly open AC voltages and sub-mW power are achieved. To test the possibility of a small scale power source for a ubiquitous sensor network service, energy conversion and the testing of storage experiment are also carried out.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.156-163
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• 2010

A nonequilibrium molecular dynamics(NEMD) simulation method is developed and applied to study shock waves propagating through argon gas. In this simulation method, shock waves are generated by pushing a piston at a constant speed from one side of a simulation box filled with argon molecules. A linear relationship between piston speeds and shock speeds is observed. Thermodynamic properties including density, temperature, and pressure before and after the shock front are obtained from the simulations and compared with the well-known Rankine-Hugoniot equations based on ideal gases. The comparison shows an excellent agreement, indicating that this NEMD simulation method can be employed to investigate various physical properties of shock waves further.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.6
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• pp.34-40
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• 2009

The present study describes the methods and standards for the combustion stability assessment of a thrust chamber and a gas generator as parts of a liquid rocket engine. The first method uses a statistical approach through typical static combustion tests and the second one a dynamic assessment identifying decaying characteristics of pressure fluctuations excited by a pulse generating device. Based on accumulated test results, it is concluded that the maximal values for combustion stability are 3% of a chamber static pressure with a Root-Mean-Square value of pressure fluctuations, and 10 msec with a decay time.

• Journal of IKEEE
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• v.21 no.3
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• pp.276-279
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• 2017

In this paper, SIMT structure based GPGPU (General Purpose Computing on Graphics Processing Units) is used for accelerating the Rasterizer which constitutes the screen of the display device in pixel unit. The GPU has a large number of ALUs, and the processing is very fast because of parallel processing. Therefore, in this paper, we implemented a rasterizer that generates a 3D graphics model using a CPU that performs operations sequentially and a GPU that performs operations in parallel. We confirmed that proposed rasterizer in this paper is 1.45 times better than rasterizer using Intel CPU when generating one frame.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.86-93
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• 2007

The PEM (polymer electrolyte membrane) fuel cell is one of the promising fuel cell systems as a new small power generating device for automobiles and buildings. The optimal design of cooling plates installed between MEA (membrane electrode assembly) is very important to achieve high performance and reliability of the PEMFC because it is very sensitive to temperature variations. In this study, six types of cooling plate models for the PEMFC including basic serpentine and parallel shapes were designed and their cooling performances were analyzed by using three-dimensional fluid dynamics with commercial software. The model 3 designed by revising the basic serpentine model represented the best cooling performance among them in the aspect of uniformity of temperature distribution and thermal reliability, The serpentine models showed higher pressure drop than the parallel models due to a higher flow rate.