• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.1950-1957
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• 2015

Modern wind generators (WGs) are forced or encouraged to participate in frequency control in the form of inertial and/or primary control to improve the frequency stability of power systems. To participate in primary control, WGs should perform deloaded operation that maintains reserve power using speed and/or pitch-angle control. This paper proposes an optimization formulation that allocates the required reserve to WGs to maximize the kinetic energy (KE) stored in a wind power plant (WPP). The proposed optimization formulation considers the rotor speed margin of each WG to the maximum speed limit, which is different from each other because of the wake effects in a WPP. As a result, the proposed formulation allows a WG with a lower rotor speed to retain more KE in the WPP. The performance of the proposed formulation was investigated in a 100-MW WPP consisting of 20 units of 5-MW permanent magnet synchronous generators using an EMTP-RV simulator. The results show that the proposed formulation retains the maximum amount of KE with the same reserve and successfully increases the frequency nadir in a power system by releasing the stored KE in a WPP in the case of a disturbance.

• 한국수산과학회지
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• 제40권2호
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• pp.79-83
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• 2007

The maturation and spawning of Shuttles hoppfish Periophthalmus modestus were studied from April to October, 2005 in the mud flat of Suncheon Bay, Korea. The specimens ranged in body length (BL) from 1.5 to 8.4 cm. The gonadosomatic index (GSI) of females was highest in May and decreased until September. The hepatosomatic index (HSI) and fatness index of females were high in April and then decreased to a nadir in July. The data indicate that the spawning season was from April to September. There was no significant difference in the ratio of females to males $(X^2-test,\;p>0.01)$. Over 50% of the females over 5 cm in BL were sexually mature. Fecundity ranged from 1,664 to 13,428. The relationship between fecundity (F) and body length (BL) of the fish was expressed as $F=0.026BL^{2.8638}\;(R^2=0.79)$. The first spawning length was 4.5 cm BL.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제21권4호
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• pp.257-263
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• 2018

Purpose: Studies on the physiology of the transposed stomach as an esophageal substitute in the form of a gastric pull-up or a gastric tube in children are limited. We conducted a study of motility and the pH of gastric esophageal substitutes using manometry and 24-hour pH measurements in 10 such patients. Methods: Manometry and 24 hour pH studies were performed on 10 children aged 24 to 55 months who had undergone gastric esophageal replacement. Results: Six gastric tubes (4, isoperistaltic; 2, reverse gastric tubes) and 4 gastric pull-ups were studied. Two gastric tubes and 4 gastric pull-ups were transhiatal. Four gastric tubes were retrosternal. The mean of the lowest pH at the midpoint of the substitute was 4.0 (range, 2.8-5.0) and in the stomach remaining below the diaphragm was 3.3 (range, 1.9-4.2). In both types of substitute, the difference between the peak and the nadir pH recorded in the intra-thoracic and the sub-diaphragmatic portion of the stomach was statistically significant (p<0.05), with the pH in the portion below the diaphragm being lower. The lowest pH values in the substitute and in the remnant stomach were noted mainly in the evening hours whereas the highest pH was noted mainly in the morning hours. All the cases showed a simultaneous rise in the intra-cavitatory pressure along the substitute while swallowing. Conclusion: The study suggested a normal gastric circadian rhythm in the gastric esophageal substitute. Mass contractions occurred in response to swallowing. The substitute may be able to effectively clear contents.

• Membrane and Water Treatment
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• 제8권1호
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• Geomechanics and Engineering
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• 제12권3호
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• pp.541-560
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• 2017

In this research, experimental and numerical simulations were adopted to investigate the effects of ligament angle on compressive strength and failure mode of rock-like material specimens containing two non-coplanar filled fissures under uniaxial compression. The experimental results show that with the increase of ligament angle, the compressive strength decreases to a nadir at the ligament angle of $60^{\circ}$, before increasing to the maximum at the ligament angle of $120^{\circ}$, while the elastic modulus is not obviously related to the ligament angle. The shear coalescence type easily occurred when ${\alpha}$ < ${\beta}$, although having the same degree difference between the angle of ligament and fissure. Numerical simulations using $PFC^{2D}$ were performed for flawed specimens under uniaxial compression, and the results are in good consistency with the experimental results. By analyzing the crack evolution process and parallel bond force field of rock-like material specimen containing two non-coplanar filled fissures, we can conclude that the coalescence and propagation of crack are mainly derived from parallel bond force, and the crack initiation and propagation also affect the distribution of parallel bond force. Finally, the displacement vectors in ligament region were used to identify the type of coalescence, and the results coincided with that obtained by analyzing parallel bond force field. These experimental and numerical results are expected to improve the understanding of the mechanism of flawed rock engineering structures.

• Asian Pacific Journal of Cancer Prevention
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• 제15권14호
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• pp.5941-5944
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• 2014

Purpose: To highlight the potential factors that could predict the response rate of patients with metastatic colorectal cancer (mCRC) treated with pemetrexed combined chemotherapy after first- or second-line chemotherapy using the FOLFOX regimen. Materials and Methods: Between January 2007 and July 2014, 54 patients diagnosed and pathologically-confirmed with advanced colorectal cancer in Jiangsu Cancer Hospital and Research Institute, were enrolled. They received pemetrexed at a dose of $500mg/m^2$ by 10 minute infusion on day 1, repeated every 3 weeks. Doses were modified depending on nadir counts of blood cells. Combined chemotherapeutic agents included irinotecan, lobaplatin, carboplatin, oxaliplatin, gemcitabine, cis-platinum or bevacizumab. Multiple variables (age, sex, hemoglobin, platinum drugs combined, metastasis sites, LDH, ALP, CEA>40 ug/ml) reported earlier were selected. We used logistic regression analysis to evaluate relationships between these and tumor response. Results: On multivariable analysis, we found that age was significant in predicting the responsiveness to pemetrexed (p<0.05) combined with oxaliplatin. We did not find any other factors which were significantly associated with the response rate to chemotherapy with pemetrexed and irinotecan. Conclusions: By multivariate analysis, we found that age had significant impact on the responsiveness of pemetrexed when combined with oxaliplatin. Additional research based on genomic properties of host and tumors are needed to clarify markers for better selection of patients who could benefit from pemetrexed combined chemotherapy.

• 한국항행학회논문지
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• 제9권2호
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• pp.177-184
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• 2005

본 논문에서는 새로운 간섭 모델, 실제적인 HAPS 시나리오, HAPS 시스템과 FWA 시스템에 대한 안테나 패턴과 같은 파라미터들을 이용하여 HAPS 비행선에서 P-MP FWA 기지국과 P-MP FWA 단말국으로의 간섭 영향을 분석하였다. 분석 결과를 보게 되면, HAPS AS에서 P-MP FWA BS로의 간섭 경우에 두 시스템들 사이의 호환성은 섹터화된 BS 안테나를 이용함으로서 얻어질 수 있었다. 그러나 HAPS AS에서 P-MP FWA TS로의 경우에 동적 채널 할당과 같은 간섭 경감 기법을 이용한 이격 거리가 보장되지 않으면 두 시스템들은 동일한 대역에서 효과적으로 운용될 수 없었다.

• 한국통신학회논문지
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• 제27권8B호
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• pp.819-825
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• 2002

WRC-2000에서 3GHz 이상의 대역에서 운영할 성층권 통신 시스템(HAPS)의 이용에 관한 연구로 Resolution 734가 채택되었다. 이에 새로운 HAPS 시스템과 기존의 지구상의 고정 서비스간의 공유 가능성이 먼저 분석되어야 한다. 본 논문에서는 HAPS 시스템이 무선 중계국에 미치는 간섭 영향을 두 가지의 경우로 나누어서 분석한다. 한가지는 HAPS 비행선의 PFD(Power Flux Density)에 의한 간섭이며, 다른 한가지는 HAPS의 지구국으로부터의 간섭 영향이다. 분석 결과 위성 시스템과는 다른 새로운 PFD 기준 설정이 필요하며, 기존의 FS 시스템과 새로운 HAPS 시스템의 공유를 위한 HAPS nadir 사이의 조정거리는 전송전력밀도가 -50dBW/MHz 일 때 최고 253km에서 최저 60km정도가 요구된다.

• 항공우주기술
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• 제10권2호
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• pp.154-162
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• 2011

다목적실용위성 3호는 고해상도 0.7m 흑백영상을 촬영할 수 있는 PAN 카메라와 2.8m 다중파장대의 칼라 영상을 수집할 수 있는 멀티스펙터럴 카메라를 탑재하고 있다. 이를 통하여 취득한 위성영상은 국토관리, 농업, 환경, 해양감시 및 GIS등의 광범위한 분야에 활용될 예정이다. 다목적실용위성3호의 15km의 관측폭을 가지는 영상을 생성하기 위해, 각 detector의 양 끝단의 20 pixel을 제외하고 24,020 픽셀로 구성된다. 이러한 크기의 CCD를 하나의 CCD로 구성하는 것은 매우 어렵기 때문에 다목적실용위성 3호는 12,080 픽셀로 구성된 두 detector로 구성되며, 따라서 두 detector의 기하학적 특성이 각기 다른 특징을 가지게 된다. 본 연구에서는 다목적실용위성3호의 한 밴드내의 기하학적 특성을 분석하기 위한 시뮬레이션 영상의 생성과정을 서술하고자 한다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.141-144
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• 2006

The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be estimated and used for autonomous satellite operations. For the proposed small satellite mission of the university there will be two GPS receivers onboard the satellite to provide the instantaneous orbital state to the onboard data handling system. In order to meet the power requirements, the satellite will be sun-tracking whenever there is no imaging operation. For imaging activities, the satellite will be maneuvered to nadir-pointing mode. Due to such different modes of orientation the geometry for the GPS receivers will not be favorable at all times and there will be instances of poor geometry resulting in no output from the GPS receivers. Onboard the satellite, the orbital information should be continuously available for autonomous switching on/off of various subsystems. The paper presents the strategies to make use of small arcs of data from GPS receivers to compute the mean orbital parameters and use the updated orbital parameters to calculate the position and velocity whenever the same is not available from GPS receiver. Thus the navigation message from the GPS receiver, namely the position vector in Earth-Centered-Earth-Fixed (ECEF) frame, is used as measurements. As for estimation, two techniques - (1) batch least squares method, and (2) Kalman Filter method are used for orbit estimation (in real time). The performance of the onboard orbit estimation has been assessed based on hardware based multi-channel GPS Signal simulator. The results indicate good converge even with short arcs of data as the GPS navigation data are generally very accurate and the data rate is also fast (typically 1Hz).