• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.367-372
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• 2000

A series of experiment was conducted to investigate the relationship between ammoia removal rate and ammonia loading rates in seawater filtering system using rotating biological contactor (RBC). In this experiment, RBC system was consisted of rotating polyvinyl film disks, which provided $12 m^2$ of total effective surface area in $0.075 m^3$ of volume. $NH_4Cl$ was added by $10{\~}150 g$ as a ammonia nitrogen source to determine ammonia removal rate in RBC system. Relationship between time required for ammonia removal (y: hour) and nitrogen inputted ($x: NH_4-N mg/l$) in RBC system was as followed: $y=3.51+7.76 lnx (r^2=0.936)$. At ammonia concentration $2 mg/l$, it took 10 hour for removal of ammonia in the RBC system. However, at ammonia concentration of $5 and 16.5 mg/l$, it took 16 and 27 hours, respectively. There was a decreasing tencency of an increasing ammonia in the rearing water. Finally, the ammonia removal rate in the RBC system increased with the rise of total ammonia concentration up to $16.5 mg/l$.

• Journal of Veterinary Clinics
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• v.16 no.2
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• pp.300-308
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• 1999

Arthroscopy is a valuable diagnostic and operative tool in equine and human orthopedics. The arthroscope is a difficult instrument to use and requires patience, practice, and persistence in order to obtain good results. This technique was found to be less traumatic than arthrotomy, invasiveness, rapid recovery and the feasibility of surgically correcting many arthropathies. The use of the arthroscope in the dog provides a new dimension in the study and diagnosis of joint derangements. The purpose of this report is to introduce the use of the arthroscope in the dog-more specifically, in the stifle of the dog. A diameter 2.7 mm fore-oblique viewing arthroscope, cold light source, video and video printer are used. With the fore-oblique viewing type it is possible to view directly as well as slightly to the side and the range of viewing can be increased by rotating the arthroscope around the object The scope is connected with a cold light source by means of a fiber-optic light guide. The stifle joint was flexed to 20~30$^{\circ}$. The joint were lavaged with lactated Ringer's solution during arthroscopic examination. Arthroscopy of the stifle was performed prior to arthrotomy in 1 dead dog and 4 healthy dogs, and other 3 dogs was performed only arthroscopic examination. In this study only the conventional approaches were used and in most cases it was possible to view all the intra-articular structures via the lateral infrapatellar approach. In the stifle joint, endoscopic observation was performed to find lateral femoral condyle, patella, medial femoral condyle, trochlear groove, tibia, fat, cranial cruciate ligament, caudal cruciate ligament lateral meniscus, tendon of long digital extensor muscle, medial meniscus, and medial collateral ligament Post-arthroscopic examination, the lameness had disappeared within 12~24 hours. Pain and swelling in the stifle joint had disappeared within 24~36 hours. Post-arthroscopic secondary infection was never encountered in the dogs. In conclusion, arthroscopic insertion technique in canine stifle joint using a diameter 2.7 mm 30$^{\circ}$ arthroscope was established and arthroscopical views of all anatomical structures in the normal stilfe joint were obtained through lateral infrapatellar portal.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.1-10
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• 2015

This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.196-201
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• 1995

The broadband and discrete sources of sound in small cooling fans of propeller type and centrifugal type were investigated to understand the turbulent vortex structures from many bladed fans using ANSI test plenum for small air-moving devices (AMDs). The noise measurement method uses the plenum as a test apparatus to determine the acoustic source spectral density function at each operating conditions similar to real engineering applications based on acoustic similarity laws. The characteristics of fans including the head rise vs. volumetric flow rate performance were measured using a performance test facility. The sound power spectrum is decomposed into two non-dimensional functions: an acoustic source spectral distribution function F(St,.phi.) and an acoustic system response function G(He,.phi.) where St, He, and .phi. are the Strouhal number, the Helmholtz number, and the volumetric flow rate coefficient, respectively. The autospectra of radiated noise measurements for the fan operating at several volumetric flow rates,.phi., are analyzed using acoustical similarity. The rotating stall in the small propeller fan with a bell-mouth guided is mainly due to a leading edge separation. It creates a blockage in the passage and the reduction in the flow rate. The sound power levels with respect to the rotational speeds were measured to reveal the mechanisms of stall and/or surge for different loading conditions and geometries, for example, fans installed with a impinging plate. Lee and Meecham (1993) studied the effect of the large-scale motions like impinging normally on a flat plate using Large-Eddy Simulation(LES) and Lighthill's analogy.[ASME Winter Annual Meeting 1993, 93-WA/NCA-22]. The dipole and quadrupole sources in the fans tested are shown closely related to the vortex structures involved using cross-correlations of the hot-wire and microphone signals.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.191-191
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• 1999

Extended X-ray Absorption Fine Structure (EXAFS)는 일반적으로 널리 사용하는 X선 회절분광기로 분석하기 힘든 chemical 또는 biological system의 structural analyses에 매우 유용한 분석방법이다. 특히 세라믹이나 유전체 비정질 재료의 미세 원자 구조에 관한 정보를 얻는데는 가장 강력한 분석방법중의 하나로 알려져 있다. 현재까지 대부분의 EXAFS 실험은 방사광 가속기를 이용하여 수행하였다. 그런데 신제품 개발의 순환주기가 급속하게 단축되는 현실적인 문제에 부응하기 위하여 실험실에서 EXAFS 실험을 수행할 수 있는 system을 개발하게 되었다. 개발한 XIEES 장비는 rotating anode 형의 18kW X-ray source, Optical system, Detection system, Stepping motor control system, vacuum system, Utility 등으로 구성하였다. Optical system에서의 6개의 Johanson type monochromator를 사용하여 분석가능한 x-ray energy range를 480eV에서 41keV까지 구현하였다. 이는 산소에서 우라늄까지 분석이 가능함을 의미하는 것으로, 산화물 연구에 많이 활용할 것으로 기대한다. XIEES는 투과 및 형광 X-ray를 검출할 수 있는 기능과 X-ray에 의해 여기 되는 모든(광전자, Aiger 전자, 이차전자)들을 검출할 수 있는 기능을 갖추고 있는데 이를 Total Electron Yield 측정이라고 한다. Total Electron Yield 측정은 박막 시료와 같이 투과가 되지 않는 시료를 분석할 뿐만 아니라, 경원소 분석, 낮은 에너지에서 흡수 edge가 나타나는 L-edge 측정을 통한 전자 구조 분석 등에 유용한다. 실험실용 XIEES 장비는 방사광가속기에 비해 x-ray flux가 크게 뒤지는 문제와 Total Electron Yield를 측정하는 데 있어서 source에서 나오는 x-ray beam이 진공용기 안에서 산란되어 이차전자를 여기하고 이 이차전자들이 전자검출기에 유입되어 측정에 영향을 미치는 background 문제 등이 있다. 이 두 가지 문제를 해결하기 위하여 Capillary tube를 사용하였다. 본 연구에서는 실험실용 XIEES 장비를 소개하고 이를 이용하여 Cu standard 시료에서 측정한 EXAFS 결과와 Capillary tube를 사용하여 얻은 x-ray flux 증진 및 background 제거 효과에 대해서 발표한다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.25-31
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• 2000

In this paper, we proposed an algorithm that used a direct method to set an initial value of Broydon-Fletcher-Goldfarb-Shanno(BFGS) method and, accordingly, conducted an experiment in optimal directivity synthesis of adaptive ultrasonic transducer by point source array. To certify the efficiency of this method, quasi-ideal beam with arbitrary beam width, rotating beam, and multi beam, all with the limited side lobe level -30dB, were chosen to check the problem of directivity synthesis that was formed by point source array in the second dimensional sound field. The numerical calculation results showed that the proposed method performed the directivity synthesis faster than the BFGS method did. In addition, the proposed method showed a good error correction for directivity synthesis, and did not demand the choice of initial value. Finally, it is also shown that the proposed method can be used for the adaptive control that was not possible with the direct method alone.

• Korean Journal of Materials Research
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• v.18 no.3
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• pp.148-152
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• 2008

A new cost-effective atomic layer deposition (ALD) technique, known as Proximity-Scan ALD (PS-ALD) was developed and its benefits were demonstrated by depositing $Al_2O_3$ and $HfO_2$ thin films using TMA and TEMAHf, respectively, as precursors. The system is consisted of two separate injectors for precursors and reactants that are placed near a heated substrate at a proximity of less than 1 cm. The bell-shaped injector chamber separated but close to the substrate forms a local chamber, maintaining higher pressure compared to the rest of chamber. Therefore, a system configuration with a rotating substrate gives the typical sequential deposition process of ALD under a continuous source flow without the need for gas switching. As the pressure required for the deposition is achieved in a small local volume, the need for an expensive metal organic (MO) source is reduced by a factor of approximately 100 concerning the volume ratio of local to total chambers. Under an optimized deposition condition, the deposition rates of $Al_2O_3$ and $HfO_2$ were $1.3\;{\AA}/cycle$ and $0.75\;{\AA}/cycle$, respectively, with dielectric constants of 9.4 and 23. A relatively short cycle time ($5{\sim}10\;sec$) due to the lack of the time-consuming "purging and pumping" process and the capability of multi-wafer processing of the proposed technology offer a very high through-put in addition to a lower cost.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.576-584
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• 2003

This paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. Constructing a imaginary second-phase giving time delay to load currents, making single-phase system into the system that has two phases, complex calculation is possible. In the previous method, it made a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle), but in proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used to the second phase. Instantaneous calculation of harmonic current is possible, because two phase have different phase. In this paper, it was done with instantaneous calculation using the rotating reference frames(RRF) that synchronizes with source-frequency, a reference of compensation currents, not applying to instantaneous reactive power theory which uses the existed fixed reference frames. The simulation and experiment about R-L loads using the current source were carried out, and the effect of the proposed method was preyed through the result of this experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.4
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• pp.817-824
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• 2000

This paper presents circuit DQ modeling and analysis of operating characteristics of hybrid cascade multilevel PWM rectifier, especially five-level, without isolation transformers. The circuit DQ transformation changes the original three-phase time varying circuit to stationary equivalent one by employing the synchronously rotating transformation matrix. As a result of circuit DQ modeling, the operating characteristics and some useful design relationships for the system are obtained with ease. That is, the analytic equations for DC voltages and active/reactive power supplied by source with respect to control variables are Presented. Moreover, the DC voltages for the multilevel output generation may be directly built up from AC utility source and the important control equation ensuring 5-level output voltage is obtained. Finally, to confirm the validity of the analysis, MATLAB simulations are carried out and the simulation results show good agreements between analytic predictions and the simulated waveforms.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.215-216
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• 2014

This paper proposes a control algorithm for permanent magnet synchronous generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage offshore wind power system under unbalanced grid conditions. The proposed control algorithm particularly compensates for the unbalanced grid voltage at the point of common coupling in a collector bus of offshore wind power system. This control algorithm has been formulated based on the symmetrical components in positive and negative rotating synchronous reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power are described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of ac input current is injected to the point of common coupling in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm makes it possible to provide a balanced voltage at the point of common coupling resulting in the generated power of high quality from offshore wind power system under unbalanced network conditions.