• Korean Journal of Microbiology
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• v.46 no.2
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• pp.169-176
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• 2010

A pilot-scale wastewater treatment plant combined with rotating biological contactor and tapered aeration reactors was operated with the wastewater discharged from a food factory for 5 months. The bacterial communities of this plant were investigated by terminal restriction fragment length polymorphism (T-RFLP) and phylogenetic analysis of 16S rRNA genes. In spite of high concentration of nitrogen and phosphorus as well as organic carbon, removal efficiency of chemical oxygen demand, total nitrogen, and total phosphorus was 98%, 93%, and 95%, respectively. Bacterial community at the initial operation stage was clearly distinguished from that of the stable operation stage. The most predominant phylum in the sample of stable stage was Bacteroidetes. Major population of operation period was Haliscomenobacter, Sphaerotilus, and candidate division TM7, which were classified as filamentous bacteria. However, sludge bulking caused by these bacteria was not observed. The population that has a close relationship with Haliscomenobacter increased during the stable operation stage, emerging as the most predominant group. These results suggest that the filamentous bacteria participated in nutrient removal when using rotating biological contactor and tapered aeration reactor.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.289-289
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• 2013

While there are plenty of studies on synthesizing semiconducting germanium nanowires (Ge NWs) by vapor-liquid-solid (VLS) process, it is difficult to inject dopants into them with uniform dopants distribution due to vapor-solid (VS) deposition. In particular, as precursors and dopants such as germane ($GeH_4$), phosphine ($PH_3$) or diborane ($B_2H_6$) incorporate through sidewall of nanowire, it is hard to obtain the structural and electrical uniformity of Ge NWs. Moreover, the drastic tapered structure of Ge NWs is observed when it is synthesized at high temperature over $400^{\circ}C$ because of excessive VS deposition. In 2006, Emanuel Tutuc et al. demonstrated Ge NW pn junction using p-type shell as depleted layer. However, it could not be prevented from undesirable VS deposition and it still kept the tapered structures of Ge NWs as a result. Herein, we adopt $C_2H_2$ gas in order to passivate Ge NWs with carbon sheath, which makes the entire Ge NWs uniform at even higher temperature over $450^{\circ}C$. We can also synthesize non-tapered and uniformly doped Ge NWs, restricting incorporation of excess germanium on the surface. The Ge NWs with carbon sheath are grown via VLS process on a $Si/SiO_2$ substrate coated 2 nm Au film. Thin Au film is thermally evaporated on a $Si/SiO_2$ substrate. The NW is grown flowing $GeH_4$, HCl, $C_2H_2$ and PH3 for n-type, $B_2H_6$ for p-type at a total pressure of 15 Torr and temperatures of $480{\sim}500^{\circ}C$. Scanning electron microscopy (SEM) reveals clear surface of the Ge NWs synthesized at $500^{\circ}C$. Raman spectroscopy peaked at about ~300 $cm^{-1}$ indicates it is comprised of single crystalline germanium in the core of Ge NWs and it is proved to be covered by thin amorphous carbon by two peaks of 1330 $cm^{-1}$ (D-band) and 1590 $cm^{-1}$ (G-band). Furthermore, the electrical performances of Ge NWs doped with boron and phosphorus are measured by field effect transistor (FET) and they shows typical curves of p-type and n-type FET. It is expected to have general potentials for development of logic devices and solar cells using p-type and n-type Ge NWs with carbon sheath.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1182-1190
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• 2001

In this paper, microstrip photonic bandgap (PBG) structure with special perforation patterns etched on the line itself is analyzed and optimized in shape, then used for harmonic tuning of power amplifier. This PBG has an advantage in being fabricated and grounded. The dimension of unit lattice is enlarged vertically, but its input and output line maintain 50 Ω using tapered line. This modification from original structure can lessen possible error in etching PCB. The analysis and design of PBG structure are acquired from using EM simulation. The measured insertion loss of the final structure is 0.3 ∼0.4 dB, and its bandwidth of stopband is 6∼7 GHz. Measured results of improved characteristics by using PBG structure at the output of the power amplifier are 0.72∼0.99 dB in output power, 1.14∼7.8 % in PAE, and 1 dBc in the third IMD.

• Journal of the Optical Society of Korea
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• v.8 no.2
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• pp.90-95
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• 2004

The structure of Ti:LiNbO$_3$optical waveguide with a mode size far different from that of single mode optical fiber has been optimized by tapering the waveguide ends. This work was focused on determining the optimized sets of parameters for the fabrication of low-loss Ti indiffused optical waveguides in LiNbO$_3$. Numerical and analytical modeling were applied to simulate the guiding quality and to determine the mode sizes. Based on these modeling results, new waveguide structures with tapered ends have been defined, fabricated and characterized in the respect of the coupling of fiber to Ti-indiffused LiNbO$_3$waveguide.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.132-136
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• 2017

In this paper, expanded lowest operating frequency by adopting circular slot on ground of balun and balance improved balance performances by stacking dielectric layer balun is proposed. Bandwidth of proposed balun is 1~7 GHz, and electrical length is $0.05{\lambda}$ at 1 GHz. In order to check performances of the proposed balun, simple dipole is integrated with the balun and radiation pattern of dipole is measured.

• Journal of electromagnetic engineering and science
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• v.2 no.1
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• pp.11-15
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• 2002

In this paper, we have proposed the new configuration of wideband antenna using CPW fred lines. The proposed antenna has CPW feed lines and U-slot to achieve wade bandwidth with good impedance matching. The use of CPW feed line can decrease the number of substrates. It is compared with the conventional antenna find by a microstrip fled line. The parameters of CPW fred lines were studied by using the quasi-static approximation which is based on the conformal mapping method. The analysis of CPW discontinuities such as the tapered-step structure and the open ended gap were studied by using the quasi-static approximation which is based on the boundary element method. Also, the equivalent circuit model of multi-layer antenna were proposed using the cavity model. Experiment results of the proposed antenna 7how wide-bandwidth characteristics and good radiation patterns in passband.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.68-75
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• 1998

A one-stage direction and flow control valve was studied theoretically and experimentally. A direction and flow control valve maintains a constant flow rate by changing the spool-orifice area under the variation of valve pressure drop, since the spool-orifice area is varied by the action of flowforces on the spool. A direction and flow control valve has the advantage of simple and low-cost structure compared to a conventional flow control valve utilizing a pressure regulating spool which regulates the pressure drop caused by flow through the metering orifice. The static and dynamic characteristics of a one-stage direction and flow control valve was analyzed. Experimental results on the flow control characteristics of the manufactured valve show satisfactory agreement with simulation results.

• Journal of Plant Biology
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• v.34 no.4
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• pp.311-316
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• 1991

The origin of cambial initials from procambium was studied in the seedling root of Acer saccharinum. In transverse view, the first periclinal divisions of procambial cells occurred just outside of each early metaxylem and resulted in meristematic strips. As root development progressed, the division activities appeared subsequently outside of each late metaxylem and then in pericycle cells opposite the four protoxylem poles. Eventually, such meristematic strips were connected completely each other. Thus, a nearly rectangular shaped meristematic layer in outline was formed outside the xylem in a whole root transectioned. In tangential section, early procambium showed a homogeneous structure consisted of uniform short cells with transverse end walls. However, some of the procambial cells did elongate, whereas others divided transversely. The former become more elongate, tapered, and vacuolated. Finally, they differentiated into fusiform initials. Short cells consisting axial strands divided continuousely in transverse plane and became ray initials, while some short cells elongated and transformed into long cells. The early ontogeny of vascular cambium in Acer saccharinum root was interpreted to be established by a gradual process.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.127-133
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• 2006

Cold expansion method is used to protect a fatigue fracture from fastener hole in the structure and aerospace industry. Cold expansion is that an oversized tapered mandrel goes through the hole and produces a compressive residual stress as well as plastic deformation around the hole. Here, mandrel shapes are one of the factors which are influenced on the residual stress distribution by cold expansion method. This paper, according to mandrel shapes (diameter of mandrel, length of mandrel and length of taper), we are performed a finite element analysis of residual stress distribution by cold expansion method. From this study, it has been found that diameter of mandrel and length of taper are an important factor which was generated a low compressive residual stress surround of fastener hole by cold expansion method.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1273-1274
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• 2015

본 논문에서는 주파수 무관(frequency independence) 특성을 갖는 자기상보 구조(self-complementary structure)로 된 안테나의 급전선로(feed line)로 사용할 수 있는 초광대역 발룬(ultra-wideband balun)을 제안하였다. 발룬을 설계하기 위해 클로펜스타인 테이퍼(Klopfenstein taper)를 사용하여 임피던스 프로파일(impedance profile)을 구하고 이를 평행 스트립 선로(parallel strip line) 구조로 구현하기 위해 등각사상방법(conformal mapping method)을 이용했다. 설계한 발룬을 직접 제작하여 측정한 결과, 대역폭은 반사손실 -10 dB를 기준으로 할 때 0.45~10.53 GHz까지 10.08 GHz로 나타나, UHF(ultra high frequency) 통신대역에서 UWB(ultra-wideband) 통신대역에 이르기까지 매우 넓은 주파수 범위에서 자기상보형 안테나의 입력 임피던스 $188{\Omega}$을 $50{\Omega}$의 특성 임피던스에 정합시킬 수 있음을 확인하였다.