• Journal of the Korean Electrochemical Society
• /
• v.10 no.3
• /
• pp.213-218
• /
• 2007

In order to find out proper PVdF gel polymer electrolyte for Li/S battery, we investigated PVdF gel polymer electrolytes with various glyme type plasticizer such as polyglyme, tetraglyme, triglyme. The organic solvents as triglyme, tetraglyme, polyglyme (Mn = 250, 500) has different chain length of ethylene oxide(EO) in solvent of glyme system. ionic conductivity decreased as increasing chain length of EO in plasticizers. Ionic conductivity of PVdF gel electrolyte with tetraglyme, triglyme, polyglyme (Mn = 250, 500) at room temperature was $5{\times}10^{-4},\;3{\times}10^{-4},\;6{\times}10^{-5},\;3{\times}10^{-5}\;S/cm$, respectively. Li/S cell with PVdF gel polymer electrolyte using tetraglyme plasticizer had low interfacial resistance and the highest initial discharge capacity of 1232 mAh/g of active sulfur, which was about 70% utilization of theoretical value.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.5
• /
• pp.155-161
• /
• 2009

This paper proposes a high capacity data hiding method using modulus function of pixel-value differencing (PVD) and least significant bit (LSB) replacement method. Many novel data hiding methods based on LSB and PVD methods were presented to enlarge hiding capacity and provide an imperceptible quality. A small difference value for two consecutive pixels is belonged to a smooth area and a large difference one is located on an edge area. In our proposed method, the secret data are hidden on the smooth area by the LSB substitution method and PVD method on the edge area. From the experimental results, the proposed method sustains a higher capacity and still a good quality compared with other LSB and modified PVD methods.

• Membrane Journal
• /
• v.17 no.3
• /
• pp.233-243
• /
• 2007

In this study, a separate. which is a microporous membrane based on poly(vinylidene fluoride)(PVdF) was prepared by phase inversion method. Being prepared by dissolving the PVdF in the N,N'-dimethylformamide(DMF) with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Pore size and porosity of the membranes were controlled by changing preparation condition. The highest porosity of the membrane was 78.6%. The mechanical property of the membrane was determined by using an universal testing machine(UTM). The morphology of the membrane was investigated by scanning electron microscopy(SEM). The cross-section of the membrane shows sponge-like small micro-pores.

• Applied Chemistry for Engineering
• /
• v.21 no.5
• /
• pp.527-531
• /
• 2010

The optimized sheet for EMI shielding was prepared by metal power with Fe series. Then various metal powders were deposited on the sheet by PVD method. Moreover, the PVdF nanofiber membrane was used to compare the characteristic of EMI shielding efficiency of various metal powders. The electrical property was measured by the 4-point probe method. The result from EDS confirmed that the metal powder existed on the sheet. EMI shielding efficiency was analysed by EMI shielding measurement apparatus. The lowest electrical resistance, $641.95{\Omega}{wcdot}cm$, was obtained with $1000\;{\AA}$ deposition of Cu on the sheet. It was revealed that the EMI shielding efficiency increased with increase of the metal deposition thickness. The sheet deposited by Cu with $1000\;{\AA}$ showed the highest EMI shielding efficiency, 32.5 dB.

• Membrane Journal
• /
• v.17 no.4
• /
• pp.359-368
• /
• 2007

The copolymer membranes, poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by phase inversion method using as an additive with N,N-dimethylformamid as a solvent. The pores are generated during the solvent and non-solvent exchange process in the coagulation bath filled with non-solvent (distilled water). The highest porosity of the membrane was 60%. The surface and cross-section of the membranes was observed with a scanning electron microscopy (SEM). The mechanical property of the membrane was determined by using an universal testing machine (UTM). Tensile strength of measured membranes is presented the maximum 6.57 MPa at 30 wt% of PVdF-HFP.

• Polymer(Korea)
• /
• v.33 no.6
• /
• pp.544-550
• /
• 2009

In this study, we have designed [Epoxy/PEG] polymer gel electrolyte systems by thermal curing the mixtures of epoxy, PEG, imidazole catalyst, and a plasticizer of 1:1 ethylene carbonate and propylene carbonate in the presence of $LiPF_6$ salt. In order to enhance the poor mechanical property of the Corresponding [Epoxy/PEG] gel electrolyte PVdF-HFP was incorporated into the system. The ionic conductivities of the polymer gel electrolytes were related to the amount of PVdF-HFP in blends as well as the amount of liquid electrolyte. The optimized gel system showed room-temperature conductivities of $2.56\times10^{-3}S/cm$.

• 한국전기화학회:학술대회논문집
• /
• 1999.10a
• /
• pp.71-71
• /
• 1999

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.6
• /
• pp.133-146
• /
• 2021

Providing weather information on roads today means that the road weather conditions near weather observation points are presented to road managers and road users. These weather observation points are managed by the Korea Meteorological Administration. However, it is difficult to provide accurate weather information due to physical limitations such as the presence of precipitation collection points, distance to weather information provision roads, and the presence of mountains. Therefore, this study intends to perform a comparative analysis by time zone and administrative dong provided by the Meteorological Administration using the wiper information among the information contained in the PVD(Probe Vehicle Data) collected from the highway C-ITS project. As a result of the analysis it was possible to detect rainfall even in the event of local rainfall and rainfall over a long period of time and the higher the cumulative precipitation per hour, the higher the probability of coincidence. This study is meaningful because it used PVD to solve the limitations of the existing road weather information provision method and suggested utilization plan for PVD.

• Journal of the Korean Geosynthetics Society
• /
• v.7 no.2
• /
• pp.15-21
• /
• 2008

The advantages of prefabricated vertical drains over conventional sand drains include their relatively low costs, less disturbance to the soil mass, the easinees of installation, and their flexibility which ensures the integrity of the drains during installation. This study tested the change of discharge capacities with respect to the hydraulic gradients for each lateral pressure. From the test results, as increases the overburden pressure, the clay soil is being consolidated, and also lateral pressure to the PVD specimen is increased. Therefore, the discharge capacity is decreased. The size of opening space in the core of PVDs is proportionally related to the discharge capacity. The numerical analysis was performed with utilizing computer simulation with considering field conditions. The results of numerical analysis are compared well with the field measurements.

• Geomechanics and Engineering
• /
• v.7 no.5
• /
• pp.525-537
• /
• 2014

The typical design of ground improvement with prefabricated vertical drains (PVD) and surcharge preloading involves a series of deterministic analyses using averaged or mean soil properties for the various combination of the PVD spacing and surcharge preloading height that would meet the criteria for minimum consolidation time and required degree of consolidation. The optimum design combination is then selected in which the total cost of ground improvement is a minimum. Considering the variability and uncertainties of the soil consolidation parameters, as well as considering the effects of soil disturbance (smear zone) and drain resistance in the analysis, this study presents a stochastic cost optimization of ground improvement with PVD and surcharge preloading. Direct Monte Carlo (MC) simulation and importance sampling (IS) technique is used in the stochastic analysis by limiting the sampled random soil parameters within the range from a minimum to maximum value while considering their statistical distribution. The method has been verified in a case study of PVD improved ground with preloading, in which average results of the stochastic analysis showed a good agreement with field monitoring data.