• Title/Summary/Keyword: Engineering, and physical parameters

Search Result 1,079, Processing Time 0.03 seconds

Fabrication of Microcrystalline NaPbLa(WO4)3:Yb3+/Ho3+ Phosphors and Their Upconversion Photoluminescent Characteristics

  • Lim, Chang Sung;Atuchin, Victor V.;Aleksandrovsky, Aleksandr S.;Denisenko, Yuriy G.;Molokeev, Maxim S.;Oreshonkov, Aleksandr S.
    • Korean Journal of Materials Research
    • /
    • v.29 no.12
    • /
    • pp.741-746
    • /
    • 2019
  • New triple tungstate phosphors NaPbLa(WO4)3:Yb3+/Ho3+ (x = Yb3+/Ho3+ = 7, 8, 9, 10) are successfully fabricated by microwave assisted sol-gel synthesis and their structural and frequency upconversion (UC) characteristics are investigated. The compounds crystallized in the tetragonal space group I41/a and the NaPbLa(WO4)3 host have unit cell parameters a = 5.3927(1) and c = 11.7961(3) Å, V = 343.05(2) Å3, Z = 4. Under excitation at 980 nm, the phosphors have yellowish green emissions, which are derived from the intense 5S2/5F45I8 transitions of Ho3+ ions in the green spectral range and strong 5F55I8 transitions in the red spectral range. The optimal Yb3+:Ho3+ ratio is revealed to be x = 9, which is attributed to the quenching effect of Ho3+ ions, as indicated by the composition dependence. The UC characteristics are evaluated in detail under consideration of the pump power dependence and Commission Internationale de L'Eclairage chromaticity. The spectroscopic features of Raman spectra are discussed in terms of the superposition of Ho3+ luminescence and vibrational lines. The possibility of controlling the spectral distribution of UC luminescence by the chemical content of tungstate hosts is demonstrated.

A Study on the Geomorphologic Synthesis of Hydrologic Response (수문응답의 지형학적 합성방법에 관한 연구)

  • Cho, Hong Je;Lee, Sang Bae
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.10 no.1
    • /
    • pp.99-108
    • /
    • 1990
  • A Synthetic Unit Hydrograph Method was investigated for representation of the effective rainfall-direct runoff hydrograph by using a Geomorphologic Instantaneous Unit Hydrograpb(GIUH) proposed by Gupta et al(1980). The response function of the basin was assumed to be the two-parameter gamma probability density function. The physical parameters of the response function(Nash Model) was determined by using the regression eqs. were parameterized in terms of Horton order ratios and the relations between the basin lag time and time-scale parameter. The capability of the Synthetic Unit Hydrograph to the real basin was tested for the Pyungchang river basin and Wi Stream basin, and its capability to reproduce the hydrologic response was investigate and compared with the Moment Method and the Least Square Method used incomplete gamma function. The representation of the peak flow, the time to peak and the hydrographs the derived Synthetic Unit Hydrograph were tested on some obseved flood data and showed promising, and it was approved to be used for prediction of the ungaged basins.

  • PDF

Procedural Animation Method for Realistic Behavior Control of Artificial Fish (절차적 애니메이션 방법을 이용한 인공물고기의 사실적 행동제어)

  • Kim, Chong Han;Youn, Jae Hong;Kim, Byung Ki
    • KIPS Transactions on Software and Data Engineering
    • /
    • v.2 no.11
    • /
    • pp.801-808
    • /
    • 2013
  • In the virtual space with the interactive 3D contents, the degree of mental satisfaction is determined by how fully it reflect the real world. There are a few factors for getting the high completeness of virtual space. The first is the modeling technique with high-polygons and high-resolution textures which can heighten an visual effect. The second is the functionality. It is about how realistic represents dynamic actions between the virtual space and the user or the system. Although the studies on the techniques for animating and controlling the virtual characters have been continued, there are problems such that the long production time, the high cost, and the animation without expected behaviors. This paper suggest a method of behavior control of animation by designing the optimized skeleton which produces the movement of character and applying the procedural technique using physical law and mathematical analysis. The proposed method is free from the constraint on one-to-one correspondence rules, and reduce the production time by controlling the simple parameters, and to increase the degree of visual satisfaction.

Cost-Driven Optimization of Defect-Avoidant Logic Mapping Strategies for Nanowire Reconfigurable Crossbar Architecture (Nanowire Reconfigurable Crossbar 구조를 위한 결함 회피형 로직 재할당 방식의 분석과 총 비용에 따른 최적화 방안)

  • Lee, Jong-Seok;Choi, Min-Su
    • Journal of KIISE:Computer Systems and Theory
    • /
    • v.37 no.5
    • /
    • pp.257-271
    • /
    • 2010
  • As the end of photolithographic integration era is approaching fast, numerous nanoscale devices and systems based on novel nanoscale materials and assembly techniques are recently emerging. Notably, various reconfigurable architectures with considerable promise have been proposed based on nanowire crossbar structure as the primitive building block. Unfortunately, high-density sys-tems consisting of nanometer-scale elements are likely to have numerous physical imperfections and variations. Therefore, defect-tolerance is considered as one of the most exigent challenges in nanowire crossbar systems. In this work, three different defect-avoidant logic mapping algorithms to circumvent defective crosspoints in nanowire reconfigurable crossbar systems are evaluated in terms of various performance metrics. Then, a novel method to find the most cost-effective repair solution is demonstrated by considering all major repair parameters and quantitatively estimating the performance and cost-effectiveness of each algorithm. Extensive parametric simulation results are reported to compare overall repair costs of the repair algorithms under consideration and to validate the cost-driven repair optimization technique.

Risk Assessment of Fire and Explosion of Methane (메탄의 화재 및 폭발 위험성 평가)

  • Ha Dong-Myeong
    • Journal of the Korean Institute of Gas
    • /
    • v.9 no.2 s.27
    • /
    • pp.1-7
    • /
    • 2005
  • The thermochemical parameters for safe handling, storage, transport, operation and process design of flammable substances are explosive limit, flash point, autoignition temperature, minimum oxygen concentration, heat of combustion etc.. Explosive limit and autoignition temperature are the major physical properties used to determine the fire and explosion hazards of the flammable substances. Explosive limit and autoignition temperature of methane fur LNG process safety were investigated. By using the literatures data, the lower and upper explosive limits of methane recommended 4.8 vol$\%$ and 16 vol$\%$, respectively. Also autoignition temperatures of methane with ignition sources recommended $540^{\circ}C$ at the electrically heated cruicible furnace (the whole surface heating) and recommended about $1000^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosive limits for methane are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

  • PDF

ANALYSES OF ANNULAR LINEAR INDUCTION PUMP CHARACTERISTICS USING A TIME-HARMONIC FINITE DIFFERENCE ANALYSIS

  • Seong, Seung-Hwan;Kim, Seong-O
    • Nuclear Engineering and Technology
    • /
    • v.40 no.3
    • /
    • pp.213-224
    • /
    • 2008
  • The pumping of coolant in a liquid metal fast reactor may be performed with an annular linear induction electro-magnetic (EM) pump. Linear induction pumps use a traveling magnetic field wave created by poly-phase currents, and the induced currents and their associated magnetic field generate a Lorentz force, whose effect can be the pumping of the liquid metal. The flow behaviors in the pump are very complex, including a time-varying Lorentz force and pressure pulsation, because an induction EM pump has time-varying magnetic fields and the induced convective currents that originate from the flow of the liquid metal. These phenomena lead to an instability problem in the pump arising from the changes of the generated Lorentz forces along the pump's geometry. Therefore, a magneto-hydro-dynamics (MHD) analysis is required for the design and operation of a linear induction EM pump. We have developed a time-harmonic 2-dimensional axisymmetry MHD analysis method based on the Maxwell equations. This paper describes the analysis and numerical method for obtaining solutions for some MHD parameters in an induction EM pump. Experimental test results obtained from an induction EM pump of CLIP-150 at the STC "Sintez," D.V. Efremov Institute of Electro-physical Apparatus in St. Petersburg were used to validate the method. In addition, we investigated some characteristics of a linear induction EM pump, such as the effect of the convective current and the double supply frequency (DSF) pressure pulsation. This simple model overestimated the convective eddy current generated from the sodium flow in the pump channel; however, it had a similar tendency for the measured data of the pump performance through a comparison with the experimental data. Considering its simplicity, it could be a base model for designing an EM pump and for evaluating the MHD flow in an EM pump.

A Data Mining Approach for Selecting Bitmap Join Indices

  • Bellatreche, Ladjel;Missaoui, Rokia;Necir, Hamid;Drias, Habiba
    • Journal of Computing Science and Engineering
    • /
    • v.1 no.2
    • /
    • pp.177-194
    • /
    • 2007
  • Index selection is one of the most important decisions to take in the physical design of relational data warehouses. Indices reduce significantly the cost of processing complex OLAP queries, but require storage cost and induce maintenance overhead. Two main types of indices are available: mono-attribute indices (e.g., B-tree, bitmap, hash, etc.) and multi-attribute indices (join indices, bitmap join indices). To optimize star join queries characterized by joins between a large fact table and multiple dimension tables and selections on dimension tables, bitmap join indices are well adapted. They require less storage cost due to their binary representation. However, selecting these indices is a difficult task due to the exponential number of candidate attributes to be indexed. Most of approaches for index selection follow two main steps: (1) pruning the search space (i.e., reducing the number of candidate attributes) and (2) selecting indices using the pruned search space. In this paper, we first propose a data mining driven approach to prune the search space of bitmap join index selection problem. As opposed to an existing our technique that only uses frequency of attributes in queries as a pruning metric, our technique uses not only frequencies, but also other parameters such as the size of dimension tables involved in the indexing process, size of each dimension tuple, and page size on disk. We then define a greedy algorithm to select bitmap join indices that minimize processing cost and verify storage constraint. Finally, in order to evaluate the efficiency of our approach, we compare it with some existing techniques.

Analysis of Irrigation Water Amount Variability based on Crops and Soil Physical Properties Using the IWMM Model (IWMM 모형을 이용한 작물과 토양의 물리적 특성에 따른 관개용수량 변동 특성 분석)

  • Shin, Yongchu
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.59 no.2
    • /
    • pp.37-47
    • /
    • 2017
  • In this study, we analyzed the variability of irrigation water amounts based on the combination of various crops and soil textures using the Irrigation Water Management Model (IWMM). IWMM evaluates the degree of agricultural drought using the Soil Moisture Deficit Index (SMDI). When crops are damaged by the water scarcity under the drought condition indicating that the SMDI values are in negative (SMDI<0), IWMM irrigates appropriate water amounts that can shift the negative SMDI values to "0" to crop fields. To test the IWMM model, we selected the Bandong-ri (BDR) and Jucheon (JC) sites in Gangwon-do and Jeollabuk-do provinces. We derived the soil hydraulic properties using the near-surface data assimilation scheme form the Time Domain Reflectrometry (TDR)-based soil moisture measurements. The daily root zone soil moisture dynamics (R: 0.792/0.588 and RMSE: 0.013/0.018 for BDR/JC) estimated by the derived soil parameters were matched well with the TDR-based measurements for validation. During the long-term (2001~2015) period, IWMM irrigated the minimum water amounts to crop fields, while there were no irrigation events during the rainy days. Also, Sandy Loam (SL) and Silt (Si) soils require more irrigation water amounts than others, while the irrigation water were higher in the order of radish, wheat, soybean, and potato, respectively. Thus, the IWMM model can provide efficient irrigation water amounts to crop fields and be useful for regions at where limited water resources are available.

Monte Carlo simulation of spatial resolution of lens-coupled LYSO scintillator for intense pulsed gamma-ray imaging system with large field of view

  • Guoguang Li;Liang Sheng;Baojun Duan;Yang Li;Dongwei Hei;Qingzi Xing
    • Nuclear Engineering and Technology
    • /
    • v.56 no.7
    • /
    • pp.2650-2658
    • /
    • 2024
  • In this paper, we use a Monte Carlo (MC) simulation based on Geant4 to investigate the influence of four parameters on the spatial resolution of the lens-coupled lutetium yttrium orthosilicate (LYSO) scintillator, including the thickness of the LYSO scintillator, the F-number and minification factor of the lens, and the incident position of the gamma-rays. Simulation results show that when the gamma-rays are incident along the lens axis, the smaller the thickness, the larger the F-number, the larger the minification factor, the higher the spatial resolution, with an isotropic point spread function (PSF). As the incident position of the gamma-rays deviates from the lens axis, the spatial resolution decreases, and the PSF becomes anisotropic. In addition, by analyzing the whole physical process of the lens-coupled LYSO scintillator from gamma-rays to secondary electrons to fluorescence photons, we aim to provide a detailed analysis of the influence of each parameter on the spatial resolution. The results show that the PSF of the secondary electrons energy deposition is almost constant in the simulation, which determines the upper limit of the spatial resolution. Meanwhile, the dispersion process of the fluorescence photons can explain the reason why each parameter affects the spatial resolution.

Numerical Simulation of the Coalescence of Air Bubbles in Turbulent Shear Flow: 2. Model Application (난류전단 흐름에서의 기포응집에 관한 수치모의: 2. 모형의 적용)

  • Jun, Kyung Soo;Jain, Subhash C.
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.14 no.6
    • /
    • pp.1365-1373
    • /
    • 1994
  • A Monte-Carlo simulation model, developed to predict size distribution of air bubbles in turbulent shear flow, is applied to a laboratory-scale problem. Sensitivity to various numerical and physical parameters of the model is analyzed. Practical applicability of the model is explored through comparisons of results with experimental measurements. Bubble size increases with air-water discharge ratio and friction factor. Bubble size decreases with increasing mean flow velocity, but the total bubble surface area in the aeration region remains fairly constant. The effect on bubble size distribution of the longitudinal length increment in the simulation model is negligible. A larger radial length increment yields more small and large bubbles and fewer in between. Bubble size distribution is significantly affected by its initial distribution and the location of air injection. Collision efficiency is introduced to explain the discrepancy between collisions with and without coalescence.

  • PDF