• Journal of Electrical Engineering and Technology
• /
• 제9권1호
• /
• pp.1-5
• /
• 2014

When renewable sources are connected to the distribution network in the form of a distributed generators(DGs), the effect of intermittent output appears as voltage fluctuation. The surplus power at the consumer ends results in the reverse power flow to the distribution network. This reverse power flow causes several problems to the distribution network such as overvoltage. Application of the reactive power control equipment and power flow control by means of BTB inverter have been suggested as the general solutions to overcome the overvoltage, but they are not economically feasible since they require high cost devices. Herein, we suggest the feeder loop line switch control method to solve the problem.

• 소음진동
• /
• 제4권2호
• /
• pp.199-208
• /
• 1994

Two-phase cross-flow exists in many shell-tube heat exchangers such as nuclear steam generators, condensers and reboilers. An understanding of damping and of flow-induced vibration excitation mechanisms in necessary to avoid problems due to excessive tube vibration. In this paper, we present the results of experiments on normal-triangular tube bundles of pitch to tube diameter ratio, p/d, 1.22, 1.32 and 1.47. The bundle were subjected to air-water mixtures to simulate realistic mass fluxes and vapour qualities corresponding to void fractions from 5 to 99%. Damping, fluidelastic instability and turbulence- induced excitation are discussed. The behaivior of damping and two vibration mechanisms are different for intermittent flows from for bubbly flows. The effect of pitch to tube diameter ratio and void fraction is dominant on damping and fluidelastic instability.

• Journal of the korean society of oceanography
• /
• 제31권3호
• /
• pp.117-122
• /
• 1996

Oxygen consumption by the Manila clam, Ruditapes philippinarum (Bivalvia: Veneridae) maintained in a culture tank for 7-10 weeks was measured with an automatic intermittent-flow-respirometer (AIFR). There was evidence for an endogenous tidal rhythm of 12.4 h in oxygen consumption, at irregular intervals of between about 7 and 18 hours during experiments of between 22 h 5 min and 70 h 32 min (duration) recording for fasting animals in constant darkness at constant temperatures in the absence of tidal rhythms.

• Journal of Mechanical Science and Technology
• /
• 제16권12호
• /
• pp.1693-1701
• /
• 2002

The intermittent spray characteristics of a multi-hole and a single-hole diesel nozzle were experimentally investigated. The hole number of the multi-hole nozzle was 5, and the hole diameter of the 5-hole and the single-hole nozzle was the same as d$\_$n/=0.32 ㎜ with the constant hole length to diameter ratio(l$\_$n//d$\_$n/=2.81). The droplet diameters of the spray, including the time-resolved droplet diameter, SMD (Sauter mean diameter) and AMD (arithmetic mean diameter) , injected intermittently from the two nozzles into the still ambient were measured by using a 2-D PDPA (phase Doppler particle analyzer). Through the time-resolved evolutions of the droplet diameter, it was found that the structure of the multi-hole and the single-hole nozzle spray consisted of the three main parts : (a) the leading edge affected by surrounding air. and composed of small droplets; (b) the central part surrounded by the leading edge and mixing flow region and scarcely affected by the resistance of air, (c) the trailing edge formed by the passage of the central part. The SMD decreases gradually with the increase in the radial distance, and the constant value is obtained at the outer region of the radial distance (normalized by hole diameter) of 7-8 and 6 for the 5-hole and single-hole nozzle, respectively. The SMD along the centerline of the spray decrease shapely with the increase in the axial distance after showing the maximum value near the nozzle tip. The SMD remains the constant value near the axial distance(normalized by hole diameter) of 150 and 180 for the 5-hole and the single-hole nozzle, respectively.

• 유기물자원화
• /
• 제6권2호
• /
• pp.31-44
• /
• 1998

돈분 슬러리와 톱밥 혼합물을 퇴비화 급속(분해)과정의 파이로트 규모 반응조 성능 평가를 입증하기 위해 간헐통기법으로 퇴비화 처리했다. 계측은 퇴비온도, 산소와 탄산가스농도, 통기량 및 암모니아가스 배출 등의 측정으로 구성됐다. 퇴비화 급속과정의 암모니아 농도는 14일째에 수준이하(I)보다 최적수준(II)부근에서 신속하게 허용범위 34-40ppm 이내로 감소되어 짐을 알 수 있었다. 암모니아가스 저감에 있어서 수분(55-65%), 탄질비(20-40%), 수소이온농도(7-8%) 및 퇴비온도(<$60^{\circ}C$) 등의 최적수준 영향은 상업용 퇴비화에 무시 할 수 없었다.

• Journal of Ginseng Research
• /
• 제46권1호
• /
• pp.167-174
• /
• 2022

Background: 20(S)-protopanaxadiol (20(S)-PPD), one of the main active metabolites of ginseng, performs a broad spectrum of anti-tumor effects. Our aims are to search out new strategies to enhance anti-tumor effects of natural products, including 20(S)-PPD. In recent years, fasting has been shown to be multi-functional on tumor progression. Here, the effects of fasting combined with 20(S)-PPD on hepatocellular carcinoma growth, apoptosis, migration, invasion and cell cycle were explored. Methods: CCK-8 assay, trypan blue dye exclusion test, imagings photographed by HoloMonitorTM M4, transwell assay and flow cytometry assay were performed for functional analyses on cell proliferation, morphology, migration, invasion, apoptosis, necrosis and cell cycle. The expressions of genes on protein levels were tested by western blot. Tumor-bearing mice were used to evaluate the effects of intermittent fasting combined with 20(S)-PPD. Results: We firstly confirmed that fasting-mimicking increased the anti-proliferation effect of 20(S)-PPD in human HepG2 cells in vitro. In fasting-mimicking culturing medium, the apoptosis and necrosis induced by 20(S)-PPD increased and more cells were arrested at G0-G1 phase. Meanwhile, invasion and migration of cells were decreased by down-regulating the expressions of matrix metalloproteinase (MMP)-2 and MMP-9 in fasting-mimicking medium. Furthermore, the in vivo study confirmed that intermittent fasting enhanced the tumor growth inhibition of 20(S)-PPD in H22 tumor-bearing mice without obvious side effects. Conclusion: Fasting significantly sensitized HCC cells to 20(S)-PPD in vivo and in vitro. These data indicated that dietary restriction can be one of the potential strategies of chinese medicine or its active metabolites against hepatocellular carcinoma.

• 멤브레인
• /
• 제13권4호
• /
• pp.283-290
• /
• 2003

BSA 용액을 대상으로 한 dead-end 및 cross-flow 한외여과에서 막모듈에의 초음파 조사가 막성능 향상에 미치는 효과를 연구하였다. 이 결과 막모듈에의 간헐적 또는 연속적 초음파 조사는 막오염의 형성 억제 및 막오염 층의 제거에 상당한 효과가 있음이 확인되었다. 초음파 조사에 의한 막성능 향상 효과는 막오염을 크게 유발시키는 운전조건(도입액 농도와 TMP가 높고, 유량이 낮은 운전조건)일수록 더 컸으며, 막모듈에 초음파를 조사시키면 조사시키지 않은 경우와 비교할 때 dead-end 한외여과에서는 최대 약 1.9배, cross-flow 한외여과에서는 최대 약 1.5배의 투과플럭스 향상을 얻을 수 있었다.

• 환경생물
• /
• 제26권3호
• /
• pp.203-213
• /
• 2008

Benthic macro invertebrate communities were collected at six different sampling sites in the Musucheon stream in Korea from July 2006 to July 2007, and ecological exergy values were calculated based on five different functional feeding groups (collector-gatherer, collector-filterer, predator, scrapper, and shredder) of benthic macro invertebrates. Each sampling site was categorized to three stream types (perennial, intermittent and drought) based on the water flow condition. Exergy values were low at all study sites right after a heavy rain and relatively higher in the perennial stream type than in the intermittent or the drought stream type. Self-Organizing Map (SOM), unsupervised artificial neural network, was implemented to pattern spatial and temporal dynamics of ecological exergy of the study sites. SOM classified samples into four clusters. The classification reflected the effects of floods and droughts on benthic macroinvertebrate communities, and was mainly related with the stream types of the sampling sites. Exergy values of each functional feeding group also responded differently according to the different stream types. Finally, the results showed that exergy is an effective ecological indicator, and patterning changes of exergy using SOM is an effective way to evaluate target ecosystems.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.801-806
• /
• 2000

This experimental study is to investigate the intermittent spray characteristics of a multi-hole nozzle in a heavy-duty DI diesel engine. Multi 8 hole$(d_n=0.25mm)$, Multi 3 hole$(d_n=0.42)$ and Sing hole nozzle$(d_n=0.25mm)$ were used in this experiment. By using the 2-D PDPA(phase Doppler particle analyzer), the droplet diameter and the velocity of a diesel spray injected intermittently from the multi and the single-hole nozzle into a still ambient were measured. In order to calculate the mean values such as mean velocity, SMD, AMD etc. and to analyze the intermittent characteristics, the time-window of 0.15ms were applied. In the spray, the small droplet$(D<10{\mu}m)$ was regarded as an air flow, and the correlation between the fuel droplet$(10{\mu}m and the air (low was examined. The normalized axial droplet-air relative velocity of the 8 hole, the 3 hole and the single hole nozzle was evaluated as 0.081, 0.067, 0.06 and in case of the radial droplet-air relative velocity, the normalized. value is 0.014, 0.013 and 0.008 respectively.

• 한국정밀공학회지
• /
• 제27권2호
• /
• pp.153-159
• /
• 2010

Recently, it has been reported that mechanical stimulation takes a role in improving cell growth. Also, became generally known that skeletal system as bone or cartilage tissues take influence of compression loading. In this study, we fabricated a custom-made bioreactor and analyzed that conditions of compressive loading would influence cell growth. To compare the effect of intermittent compressive loading on cell-encapsulated agarose scaffold, we cultured preosteoblast cell (MC3T3-E1 cells) statically and dynamically. And dynamic culture conditions were produced by changing parameters such as the iteration time and interval delay time. Also, cellencapsulated agarose scaffold were subjected to 10 % dynamic compressive strain at 1㎐ frequency for 7 days. After cell culture, cell proliferation was assessed with PI stain assay for fluorescence images and flow cytometry (FACS).