• Microbiology and Biotechnology Letters
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• v.17 no.1
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• pp.19-23
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• 1989

A sequential system composed of hydroxylapatite chromatography and gel permeation chromatography was developed to purify the IgM type monoclonal antibody against the colon cancer cell SC-1 from the ascitic fluid of mice injected with the murine hybridoma CH07E02. In the hydroxylapatite chromatographic step the band dilution could be reduced by controlling the gradient and flow rate of the eluent, the sodium phospate buffer, the optimum values for these variables being 5.82$\times$10$^{-3}$M/cm and 0.2$m\ell/\textrm{cm}^2$/min, respectively. A degree of purity better than 99.99% as judged from silverstaining of the SDS-PAGE bands, was obtained by adding the gel permeation chromatographic step in tandem.

• Current Photovoltaic Research
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• v.8 no.1
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• pp.6-11
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• 2020

The power conversion efficiency (PCE) of a two-terminal tandem solar cell depends upon the tunnel-recombination junction (TRJ) between the top and bottom sub-cells. An optimized TRJ in a tandem cell helps improve its open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), and efficiency (PCE). One of the parameters that affect the TRJ is the buffer layer thickness. Therefore, we investigated various TRJs by varying the thickness of the buffer or intermediate layer (TRJ-buffer) in between the highly doped p-type and n-type layers of the TRJ. The TRJ-buffer layer was p-type nc-Si:H, with a doping of 0.06%, an activation energy (E_a) of 43 meV, an optical gap (E_g) of 2.04 eV, and its thickness was varied from 0 nm to 125 nm. The tandem solar cells we investigated were a combination of a heterojunction with intrinsic thin layer (HIT) bottom sub-cell and an a-Si:H (amorphous silicon) top sub-cell. The initial cell efficiency without the TRJ buffer was 7.65% while with an optimized buffer layer, its efficiency improved to 11.74%, i.e., an improvement in efficiency by a factor of 1.53.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.216-219
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• 1997

We are developing a portable multipurpose gamma counting and imaging probe that will be useful for many applications in nuclear medicine including radioimmunoguided surgery in the detection and treatment of malignant tumors. Any diagnostic information provided by CT, MRI, PET, SPECT or gamma camera imaging prior to surgery obviously is very important, but current techniques are limited in many instances. To overcome some of these limitations, the portable multipurpose gamma probe is being developed. The gamma probe consists of NaI(Tl) crystal with 1" dia $\times$ 0.5" thick and singlechannel photomultiplier tube (SC-PMT) for counting, and 3" dia $\times$ 0.375" and multichannel photomultiplier tube (MC-PMT) for imaging, nuclear instrument module (NIM), position circuits, interface, and PC. The energy resolution using Tc-99m was measured as 14% and the spatial resolution using 3mm dia green LED was measured as 2.9mm. These priliminary results indicate that the currently developing probe is very promising and could be very useful for many applications in nuclear medicine.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.116-117
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• 2006

We investigated selective emitter effect of Porous Silicon (PSI) as antireflection coatings (ARC). The thin PSi layer, less than 100nm, was electrochemically formed by electrochemical method in about $3{\mu}m$ thick $n^+$ emitter on single crystalline silicon wafer (sc-Si). The appropriate PSi formations for selective emitter effect were carried out a two steps. A first set of samples allowed to be etched after metal-contact processing and a second one to evaporate Ag front-side metallization on PSi layer, by evaluating the I-V features The PSi has reflectance less than 20% in wavelength for 450-1000nm and porosity is about 60%. The cell made after front-contact has improved cell efficiency of about in comparison with the one made after PSi. The observed increase of efficiency for samples with PSi coating could be explained not only by the reduction of the reflection loss and surface recombination but also by the increased short-circuit current (Isc) within selective emitter. The assumption was confirmed by numerical modeling. The obtained results point out that it would be possible to prepare a solar cell over 15% efficiency by the proposed simple technology.

• Honam Mathematical Journal
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• v.36 no.3
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• pp.695-706
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• 2014

Various properties of digital covering spaces have been substantially used in studying digital homotopic properties of digital images. In particular, these are so related to the study of a digital fundamental group, a classification of digital images, an automorphism group of a digital covering space and so forth. The goal of the present paper, as a survey article, to speak out utility of digital covering theory. Besides, the present paper recalls that the papers [1, 4, 30] took their own approaches into the study of a digital fundamental group. For instance, they consider the digital fundamental group of the special digital image (X, 4), where X := $SC^{2,8}_4$ which is a simple closed 4-curve with eight elements in $Z^2$, as a group which is isomorphic to an infinite cyclic group such as (Z, +). In spite of this approach, they could not propose any digital topological tools to get the result. Namely, the papers [4, 30] consider a simple closed 4 or 8-curve to be a kind of simple closed curve from the viewpoint of a Hausdorff topological structure, i.e. a continuous analogue induced by an algebraic topological approach. However, in digital topology we need to develop a digital topological tool to calculate a digital fundamental group of a given digital space. Finally, the paper [9] firstly developed the notion of a digital covering space and further, the advanced and simplified version was proposed in [21]. Thus the present paper refers the history and the process of calculating a digital fundamental group by using various tools and some utilities of digital covering spaces. Furthermore, we deal with some parts of the preprint [11] which were not published in a journal (see Theorems 4.3 and 4.4). Finally, the paper suggests an efficient process of the calculation of digital fundamental groups of digital images.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.70-78
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• 2001

We have developed a novel driving system of 5' true color FED using voltage controlled PWM method which has current control effect. The proposed method has the advantage of voltage controlled pulse width modulation method and current control method. Also, we propose a new circuit model of FED subpixel for circuit simulation of FED driving circuits, considering some parasitic effects, i.e., cross talk, line coupling effect and leakage current to the adjacent cathode lines. Output stage of the data driving circuit is optimized using the proposed circuit model. In video data processing, FED controller uses the parallel processing of R.G.B input data, so duty ratio is maximized and brightness of FED increases. With this results, no noise and high quality performance is achieved in display of 5' true color FED.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.30-39
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• 2011

In this note, a systematic design of a new robust nonlinear continuous variable structure control system(VSCS) based on the modified state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and matched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear VSCS is presented. The uncertainty of the nonlinear system function is separated into the tow parts, i.e., state dependent term and state independent term for extension of target plants. To be linear in the closed loop resultant dynamics and in order to easily satisfy the existence condition of the sliding mode, the transformed linear sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the linear transformed sliding surface, which will be investigated in Theorem 1. For practical application, the discontinuity of the control input as the inherent property of the VSS is improved dramatically. Through a design example and simulation studies, the usefulness of the proposed controller is verified.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2272-2281
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• 1997

This paepr proposes a shared medium access control protocol for hgih-speed multimedia services of distributed subscriber home and small-sized business ATM networks. This protocol offers not only global fairness for the whole network at the same time, but also local fairness for different prioritytraffics on each node. Considering that the future B-ISDN service si a mixture of real and non-real time traffic data, this protocol is designed to accommodate the real time service, by controlling the priority of the real and non-real time data. The simulation results show that the proposed protocol has better performance than the other protocols.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.3 s.303
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• pp.41-46
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• 2005

In this paper, we proposed noninvasive and continous measurement of blood pressure using pulse transit time(PTT) and physical characteristic parameters and verified its clinical effectiveness. PTT can be obtained by electrocardiogram and phtoplethysmogram. There are many researches for estimating blood pressure using PTT which can be used for individual. However, it is not enough for extracting general regression equation which can estimate blood pressure for unspecified people. In this study, we suggested the regression equatin using PTT and physical characteristic parameters related to blood pressure and did measure blood pressure of many people. we compared the performance between two methods. As the results, we knew that the regressin model using PTT combined with physical characteristic parameters can estimate blood pressure more acurately and is closer to American National Standards Institute of the Association of the Advancement of Medical Instrument(ANSI/AAMI).

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.4
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• pp.49-54
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• 2000

A new functional organic thin film optical waveguide ion sensor is designed, which can select a specific ion, i.e., $Ca^{2+}$ -ion. The sensing membrane was composed of PVC-PVAC-PVA copolymer matrix based on anionic cation-selective chromoionophor(ETH5294), neutral ionophore(K23El), anionic site and plasticizer and it was coated on the etched glass substrate as embeded type optical waveguide itself. The sensor sensitivity dependence on waveguide length and thickness, contence of chromoionophore, and each mode was investigated. And this sensor could detect $Ca^{2+}$ ion in concentrations ranging from 1$\times$10­6~1M(with 0.05M tris-HCI buffer solution of pH7.4) by measuring the absorbance change at 514nm of light. Utilizing thin film membrane, the fast response time and high sensitivity are obtained. Also, it is expected that this sensor can be applied to various biochemical important ions.ons.