• International Journal of Aeronautical and Space Sciences
• /
• 제18권4호
• /
• pp.807-815
• /
• 2017

For liquid rocket engine(LRE)-based space launch vehicles, longitudinal instability, often referred to as the pogo phenomenon in the literature is predicted. In the building block of system-level task, accurate dynamic modeling of a fluid-filled tank is an essential. This paper attempts to apply the virtual mass method that accounts for the interaction of the vehicle structure and the enclosed liquid oxygen to LOX-filled tanks. The virtual mass method is applied in a modal analysis considering the hydroelastic effect of the launch vehicle tank. This method involves an analysis of the fluid in the tank in the form of mass matrix. To verify the accuracy of this method, the experimental modal data of a small hemispherical tank is used. Finally, the virtual mass method is applied to a 1/8-scale space shuttle external tank. In addition, the LOX tank bottom pressure in the external tank model is estimated. The LOX tank bottom pressure is the factor required for the coupling of the LOX tank with the propulsion system. The small hemispherical tank analysis provides relatively accurate results, and the 1/8-scale space shuttle external tank provides reasonable results. The LOX tank bottom pressure is also similar to that in the numerical results of a previous analysis.

• Mass Spectrometry Letters
• /
• 제5권1호
• /
• pp.24-29
• /
• 2014

An advanced and reliable high performance liquid chromatography (HPLC)/ultraviolet detector (UV)/ion-trap time-of-flight (IT-TOF) mass spectrometry was developed for the simultaneous quantification of 19 marker compounds in Bang-poong-tong-sung-san (BPTS), a traditional oriental prescription. Various parameters affecting HPLC separation and IT-TOF detection were investigated, and optimized conditions were identified. The separation was achieved on a Capcell PAK C18 column ($1.5mm{\times}250mm$, $5{\mu}m$ particle size) using a gradient elution of acetonitrile and water containing 0.1% formic acid at a flow rate of 0.1 mL/min. The column temperature was maintained at $40^{\circ}C$ and the injection volume was $2{\mu}L$. IT-TOF system was equipped with an electrospray ion source (ESI) operating in positive or negative ion mode. The optimized electrospray ionization parameters were as follows: ion spray voltage, +4.5 kV (positive ion mode), or -3.5 kV (negative ion mode); drying gas ($N_2$), 1.5 L/min; heat block temperature, $200^{\circ}C$. Automatic $MS^n$ (n = 1~3) analyses were carried out to obtain structural information of analytes. Elemental compositions and their mass errors were calculated based on their accurate masses obtained from a formula predictor software. The marker compounds in BPTS were identified by comparisons between $MS^n$ spectra from standards and those from extracts. Moreover, the libraries of $MS^2$ and $MS^3$ spectra and accurate masses of parent and fragment ions for marker compounds were constructed. The developed method was successfully applied to the BPTS extracts and identified 17 out of 19 marker compounds in the BPTS extracts.

• 천문학회보
• /
• 제38권2호
• /
• pp.79.2-79.2
• /
• 2013

The distributions of Horizontal Branch (HB) star color, temperature, and mass encode a great deal of information on the stellar evolutionary and (possibly) dynamical processes taking place in Globular Clusters (GCs). An accurate physical modeling of the Red Giant Branch (RGB) mass-loss process is key to solving the so-called second parameter problem. In my poster I will present the most recent advancements of an analytical model for mass-loss along the RGB. The model predicts the HB mass distribution with remarkable accuracy over a sample of 4 GCs. These results were submitted as a paper to ApJ (Pasquato et al. 2013, ApJ submitted), but here I expand on them presenting refinements to the model and a comparison with HB masses obtained from Galex ultraviolet observations.

• 전력전자학회논문지
• /
• 제11권2호
• /
• pp.159-163
• /
• 2006

선형 서보 응용분야에서 속도제어기를 정밀하게 조정하기 위해서는 부하 및 가동자의 질량을 항상 정확하게 알고 있어야 한다. 본 논문에서는 선형 영구자석 동기전동기의 가동부 질량을 추정하기 위하여 상수추정 알고리즘으로 최소자승법을 적용한 질량 추정방법을 제안하였다. 먼저 최소자승법을 적용하기 위한 기계적인 동전 시스템에 대한 DARMA(deterministic autoregressive moving average)모델을 유도하고, 유도된 DARMA모델에 최소자승법을 적용한 시뮬레이션 덴 실험 결과를 제시하여 제안한 방법으로 질량을 정밀하게 추정할 수 있음을 보였다.

• 대한기관식도과학회지
• /
• 제7권2호
• /
• pp.168-173
• /
• 2001

Background and Objectives： The introduction of highly sensitive imaging techniques has made it possible to detect many non-palpable nodules, or“incidentaloma”in the thyroid. Discovery of these lesions raises concerns about their malignancy, but the optimal strategy for managing these lesions has not been clearly established. This study was designed to evaluate the usefulness of ultrasonographic exam with new diagnostic criteria and presume the value of mass screening for thyroid cancer. Materials and Methods : Mass screening for thyroid cancer were carried out in conjunction with mass screening for breast cancer. The subjects were 630 women aged 30 years or over. Thyroid glands were examined with 10 MHz transducer ultrasonography by one radiologist. Needle aspiration biopsy were performed when suspicious of malignancy under the new diagnostic criteria. Results and Conclusion : The new ultrasonographic criteria to diagnose thyroid cancer provided useful information and ensured more accurate evaluation. 7 cases of thyroid cancer were discovered and successfully managed. It should be further demonstrated that there is sufficient value of mass screening for thyroid cancer to perform it independently despite early cancer detection.

• Journal of Microbiology and Biotechnology
• /
• 제25권9호
• /
• pp.1537-1541
• /
• 2015

Previous detection methods for Citrobacter are considered time consuming and laborious. In this study, we have developed a rapid and accurate detection method for Citrobacter species in pork products, using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). A total of 35 Citrobacter strains were isolated from 30 pork products and identified by both MALDI-TOF MS and 16S rRNA gene sequencing approaches. All isolates were identified to the species level by the MALDI-TOF MS, while 16S rRNA gene sequencing results could not discriminate them clearly. These results confirmed that MALDITOF MS is a more accurate and rapid detection method for the identification of Citrobacter species.

• Journal of Mechanical Science and Technology
• /
• 제18권2호
• /
• pp.302-312
• /
• 2004

This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.

• 한국대기환경학회지
• /
• 제23권6호
• /
• pp.752-759
• /
• 2007

For an accurate measurement of aerosol particle size distribution using a differential mobility analyser (DMA), a new calculation process, capable of predicting the masses for the various kinds of water cluster ions generated from a bipolar ionizer, was prepared by improving the previous process. The masses for the 5 kinds of positive and negative water cluster ions produced from a SMAC ionizer were predicted by the improved calculation process. The aerosol particle charging ratios calculated by applying the predicted ion masses to particle charging equations were in good accordance with the experimentally measured ones, indicating that the improved calculation process are more reasonable than the previous one in a mass prediction of bipolar water cluster ions.

• 한국대기환경학회지
• /
• 제8권3호
• /
• pp.155-161
• /
• 1992

A simple, fast yet sensitive method is described for the determination of fifty elements in coal by inductively coupled plasma mass spectrometry. The method involves complete dissolution of coal with mixed acid $(HNO_3, HF, HClO_4)$ in hish pressure Teflon bomb and subsequent inductively coupled plasma mass spectrometric(ICP-MS) measurement. The accuracy of the method, being evaluated by the analysis of NIST SRMs (1632a, 1632b) is better than 20% RSD for most elements. The limits of detection defined by two times $\sigma$ (standard deviation of operational blank) are in order of sub-ppm to ppm, which are low enough to quantitate most elements. However, the determiantions for few elements such as V, As, Se are severely interfered by molecular ions such that their accurate determiantions are not possible. Analytical results for twentyon coals from eight countries including six ones world major coal producing, Korea, Japan, China, I.C.S., U.S.A., Canada, Australia, and South Africa are presented. While the results for major elements agree well with the existing ones, those for a few trace elements disagree considerably. The existing values are considerably higher. It is not possible to judge which are more accurate. However, the exisisting values are more likely to be errorous inasmuch as they are obtained without using high purity reagents and clean laboratory techniques.

• 한국대기환경학회지
• /
• 제22권5호
• /
• pp.701-711
• /
• 2006

Sewage treatment plants located near to large cities emit extremely higher concentration of odorous materials. This study evaluated flux profiles of ammonia emitted from the water surface of sewage treatment plants using a dynamic flux chamber. Also, an ammonia overall mass transfer coefficient and a mass transfer model was developed in order to estimate fluxes of ammonia using environment parameters and the flux from the sewage treatment plants. The developed mass transfer model was evaluated through a fitness analysis. Comparison modeled flux applying empirical overall mass transfer coefficients of ammonia and measured ammonia flux show a high linearity with 0.977. The flux ratio of 1.282 demonstrated highly statistical fitness, also. Modeled flux using the mass transfer model was compared with measured flux. In result, it indicated that empirical overall mass transfer coefficients were similar to measured flux. The mass transfer model using the empirical overall mass transfer coefficient developed in this study was proved to be an easy and effective method to make accurate and precise predictions for ammonia flux discharged from sewage treatment plants.