• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.417-425
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• 2016

Desalination is a key technology to overcome water shortage problem in a near future. High energy consumption is an Achilles' heel in desalination technology. Osmotically driven membrane processes like forward osmosis(FO) was introduced to address this energy issue. Characterizing membrane properties such as water permeability(A), salt permeability(B), and the resistance to salt diffusion within the support layer($K_{ICP}$) are very important to predict the performance of scaled-up FO processes. Currently, most of researches reported that the water permeability of FO membrane was measured by reverse osmosis(RO) type test. Permeating direction of RO and FO are different and RO test needs hydraulic pressure so that several problems can be occurred(i.e. membrane deformation, compaction and effect of concentration polarization). This study focuses on measuring water permeability of FO membrane by FO type test results in various experimental conditions. A statistical approach was developed to evaluate the three FO membrane properties(A, B, and $K_{ICP}$) and it predicted test result by the internal and external concentration polarization model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.721-727
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• 2009

Wireless Sensor Networks(WSN) make use of low cost and energy constrained sensor nodes. Thus, reaching the successful execution of its tasks with low energy consumption is one of the most important issues. The limitation of existing hierarchical algorithms is that many times the data are transmitted to the opposite direction to the sink. In this paper, DDACM (Data Direction Aware Clustering Method) is proposed. In this method, the nearest node to the sink is elected as cluster head, and when its energy level reaches a threshold value, the cluster head is reelected. We also make a comparison with LEACH showing how this method can reduce the energy consumption minimizing the reverse direction data transmission.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.6
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• pp.38-48
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• 1993

A recessed n-p Juction diode with the self-aligned sturcture is proposed and fabricated by using the polysilicon as an n$^{+}$ diffusion source. The diode structure can be applicable to the emitter-base formation of high performance bipolar divice and the n$^{+}$ polysilicone mitter has an important effect on the device characteristics. The considered parameters for the polysilicon formation are the deposition condition. As$^{+}$ dose for the doping of the polysilicon and the annealing condition using RTP system. The vertical depth profiles of the fabricated diode are obtained by SIMS and the electrical characteristics are analyzed in terms of the ideality factor of diode (n), contact resistance and reverse leakage current. In addition, n$^{+}$-p junction diodes are formed by using the amorphous silicon (of combination of amorphous and polysiliocn) instead of polysilicon and their characteristics are compared with those of the standard sample. The As$^{+}$ dose for the formation of good junction is about 1~2${\times}10^{16}cm^{2}$ at given RTA conditions (1100.deg. C, 10sec).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.105-109
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• 1992

ITO film, 1500${\AA}$ of thickness, onto glass and p-InP wafer was prepared by e-beam evaporator. The bet ITO film had the resistivity 5.3${\times}$10$\^$-3/ $\Omega$-cm, the concentration 6.5${\times}$10$\^$20/cm$\^$-3/, the transmittance above 80%, and the optical energy gap about 3.5eV. The higher pressure of injected oxygen, the less reverse bias saturation current and the more open circuit voltage. Under the optimum evaporation conditions, the efficiency was 7.19% and the series resistance, and the shunt resistance were respectively 8.5%, 3${\alpha}$, and 26K$\Omega$. The interdependence between activation energy and pre-exponential factor was found. We found he surface of the p-InP became n-type and consquently supposed that the buried homojunction formation, that is, n+-ITO/n-InP/p-InP was caused by Sn diffusion or loss of phosphorus in the interface layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.152-153
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• 1994

A recessed $n^{+}$-p junction diode with the serf-aligned structure is proposed and fabricated by using the polysilicon as an $n^{+}$ diffusion source. The diode structure can be applicable to the emitter-base formation of high performance bipolar device and the $n^{+}$ polysilicon emitter has an important effect on the device characteristics. The considered parameters for the polysilicon formation are the deposition condition $As^{+}$ dose for the doping of the polysilicon, and the annealing using RTP system. The vertical depth profiles of the fabricated diode are obtained by SIMS. The eleotrical characteristics are analyzed in trims of the ideality factor of diode (n), contact resistance arid reverse leakage current. The $As_{+}$ dose for the formation of good junction is current. The $As^{+}$ dose for the formation of goodjunctions is about 1∼2${\times}$$10^{16}$$cm^{-2}$ at given RTA condition ($1100^{\circ}C$, 10 sec). The $n^{+}$-p structure is successfully applied to the self-aligned bipolar device adopting a single polysilicon technology.

• Journal of applied mathematics & informatics
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• v.42 no.3
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• pp.607-623
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• 2024

This article studies the effects of heat generation/absorption and thermal radiation on the unsteady magnetohydrodynamic (MHD) Casson fluid flow past a vertical plate through rotating porous medium with constant temperature and mass diffusion. It is assumed that the plate temperature and concentration level are raised uniformly. For finding the exact solution, a set of non-dimensional partial differential equations is solved analytically using the Laplace transform technique. The influence of various non-dimensional parameters on the velocity are discussed, including the effects of the magnetic parameter M, heat generation/absorption Q, thermal radiation parameter R, Prandtl number Pr, Schmidt number Sc, permeability of porous medium parameter, Casson fluid parameter γ, on velocity, temperature, and concentration profiles, which are discussed through several figures. It is found that velocity, temperature, and concentration profiles in the case of heat generation parameter Q, Casson fluid parameter γ, thermal Grashof number Gr, mass Grashof number Gc, Permeability Porous medium parameter K, and time t have retarding effects. It is also seen that the magnetic field M, Thermal Radiation parameter R, Prandtl field Pr, Schmidt number Sc have reverse effects on it.

• Membrane Journal
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• v.28 no.1
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• pp.75-82
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• 2018

Forward osmosis (FO) desalination system has been highlighted to improve the energy efficiency and drive down the carbon footprint of current reverse osmosis (RO) desalination technology. To improve the trade-off between water flux and salt rejection of thin film composite (TFC) desalination membrane, thin film nanocomposite membranes (TFN), in which nanomaterials as a filler are embeded within a polymeric matrix, are being explored to tailor the separation performance and add new functionality to membranes for water purification applications. The objective of this article is to develop a graphene nanocomposite membrane with high performance of water selective permeability (high water flux, high salt rejection, and low reverse solute diffusion) as a next-generation FO desalination membrane. For advances in fabrication of graphene oxide (GO) membranes, layer-by-layer (LBL) technique was used to control the desirable structure, alignment, and chemical functionality that can lead to ultrahigh-permeability membranes due to highly selective transport of water molecules. In this study, the GO nanocomposite membrane fabricated by LBL dip coating method showed high water flux ($J_w/{\Delta}{\pi}=2.51LMH/bar$), water selectivity ($J_w/J_s=8.3L/g$), and salt rejection (99.5%) as well as high stability in aqueous solution and under FO operation condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1448-1452
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• 2004

In this paper, a photodiode capable of obtaining a sufficient photo/ dark current ratio at both a forward bias state and a reverse bias state is proposed. The photodiode includes a glass substrate, an Cr thin film formed as a lower electrode over the glass substrate, Cr silicide thin film(∼l00$\AA$) ) formed as a schottky barrier over the Cr thin film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the Cr silicide thin film. Transparent conduction film ITO (thickness 100nm) formed as an upper electrode over the hydro-generated amorphous silicon film is then deposited in pure argon at room temperature for the Schottky contact and light window. The high quality Cr silicide thin film using annealing of Cr and a-Si:H is formed and analyzed by experiment. We have obtained the film with a superior characteristics. The dark current of the ITO/a-Si:H Schottky at a reverse bias of -5V is ∼3$\times$IO-12 A/un2, and one of the lowest reported, hitherto. AES(Auger Electron Spectroscophy) measurements indicate that this notable improvement in device characteristics stems from reduced diffusion of oxygen, rather than indium, from the ITO into the a-Si:H layer, thus, preserving the integrity of the Schottky interface. The spectral response of the photodiode for wavelengths in the range from 400nm to 800nm shows the expected behavior whereby the photocurrent is governed by the absorption characteristics of a-Si:H.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.185-191
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• 2014

The width of depletion region in a varactor diode can be modulated by varying a reverse bias voltage. Thus, the preferred characteristics of depletion capacitance can obtained by the change in the width of depletion region so that it can select only the desirable frequencies. In this paper, the TV tuner varactor diode fabricated by hyper-abrupt profile control technique is presented. This diode can be operated within 3.3 V of driving voltage with capability of UHF band tuning. To form the hyperabrupt profile, firstly, p+ high concentration shallow junction with $0.2{\mu}m$ of junction depth and $1E+20ions/cm^3$ of surface concentration was formed using $BF_2$ implantation source. Simulation results optimized important factors such as epitaxial thickness and dose quality, diffusion time of n+ layer. To form steep hyper-abrupt profile, Formed n+ profile implanted the $PH_3$ source at Si(100) n-type epitaxial layer that has resistivity of $1.4{\Omega}cm$ and thickness of $2.4{\mu}m$ using p+ high concentration Shallow junction. Aluminum containing to 1% of Si was used as a electrode metal. Area of electrode was $30,200{\mu}m^2$. The C-V and Q-V electric characteristics were investigated by using impedance Analyzer (HP4291B). By controlling of concentration profile by n+ dosage at p+ high concentration shallow junction, the device with maximum $L_F$ at -1.5 V and 21.5~3.47 pF at 0.3~3.3 V was fabricated. We got the appropriate device in driving voltage 3.3 V having hyper-abrupt junction that profile order (m factor) is about -3/2. The deviation of capacitance by hyper-abrupt junction with C0.3 V of initial capacitance is due to the deviation of thermal process, ion implantation and diffusion. The deviation of initial capacitance at 0.3 V can be reduced by control of thermal process tolerance using RTP on wafer.

• Archives of Plastic Surgery
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• v.37 no.3
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• pp.207-212
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• 2010

Purpose: The object of this study is to develop a novel BMP-2 delivery system for continuous osteogenic differentiation and to induce osteogenesis of stem cells using a bi-phase alginate carrier in vitro. Methods: Alginate nanoparticle loaded BMP-2 was prepared by the reverse emulsification-diffusion technique. Physical properties and release profiles of alginate carriers were measured by Instron and ELISA kit, respectively. Cell viability and alkaline phosphate activity of hBMSCs differentiation was also evaluated by MTS and Metra BAP assays, respectively. Results: Optimal concentration for bi-phase alginate carrier was determined as 2 wt% by evaluating mechanical and biological properties, and differentiation of BMSCs for bone regeneration. The 2% bi-phase alginate carrier had the lowest initial and final release ratio. In addition, the 2% bi-phase alginate carrier had a little higher ALP activity than the homogeneous carrier. An improved controlled release profile was obtained by combining alginate hydrogel with lyophilized particles. Conclusion: Bi-phase alginate carrier has many advantages such as biocompatibility and controlled release capability. It is expected to be effective as a scaffold and carrier in bone tissue engineering.