• Title/Summary/Keyword: Distribution pattern and Uniformity

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Study on Spray Characteristics of Single-Hole GDI Injector according to Nozzle Hole Diameter - (2) Comparison of Spray Uniformity and Atomization Characteristics (노즐 홀 직경에 따른 단공 GDI 인젝터의 분무 특성 연구 - (2) 분무 균일도 및 미립화 특성 비교)

  • Park, Jeonghyun;Ro, Seungcheon;Chang, Mengzhao;Park, Suhan
    • Journal of ILASS-Korea
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    • v.25 no.4
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    • pp.154-161
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    • 2020
  • A single spray plume is the basic unit of the entire spray plume and is an important factor in understanding the spray characteristics. However, since the multi-hole GDI injector has a narrow spray angle, the superposition of the spray plumes occurs severely. Therefore, the spray uniformity and the spray atomization characteristics of a single spray plume were analyzed in this study using a single-hole GDI injector. Five single-hole GDI injectors with different nozzle hole diameters were used in the experiment. The uniformity of the spray was evaluated through the analysis of the spray pattern images. In addition, the atomization characteristics were compared using the diameter distribution of the spray droplets obtained using PDPA. As a result, the larger diameter of the nozzle hole, the less uniformity of the spray, and the injection pressure did not have a significant effect on the spray uniformity. It is judged that the surface roughness of the injector has a greater effect on spray uniformity than the diameter of the nozzle hole. Also, the size of the spray droplets increased sharply when the diameter of the nozzle hole was 230 ㎛.

A Psychophysical Approach to evaluating the perceived image quality of CRT: White Uniformity Quality (CRT 모니터의 감성품질 정량화를 위한 심물리학적 접근: White Uniformity 품질 평가)

  • Lee, Uk-Gi;Kim, Seong-Hwan;Lee, Seon-Gyu;Lee, Gwang-Hui;Kim, Sang-Su
    • Journal of the Ergonomics Society of Korea
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    • v.20 no.2
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    • pp.59-70
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    • 2001
  • White uniformity is one of the important inspection factors determining the image quality of CRT screen. In the full white pattern, white uniformity means the degree of uniform distribution of white color across the whole screen. To elicit the sensitivity factors affecting the decision of the white uniformity quality, experiments in which participants were confronted with 6 evaluation points embedded in 3 measurement groups on a CRT screen were conducted to gather the psychophysical data that are the level of white uniformity subjects perceived and CA100 produced. These data were used to develop a modified CIE1976 equation for calculating white uniformity. Performance comparison between the original CIE1976 equation and the modified equation was conducted in terms of accuracy test and magnitude estimation. It was concluded the modified equation is more sensitive in the change of white uniformity, compared to the original CIE1976 equation.

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Research of Measurement and Evaluation of White Uniformity Considering Visual Angle on TFT-LCD (TFT-LCD에서 시야각을 고려한 White Uniformity 측정 및 평가에 대한 연구)

  • Chang, Sung-Ho;Seo, Sang-Won
    • Journal of the Ergonomics Society of Korea
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    • v.26 no.4
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    • pp.33-39
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    • 2007
  • In the full white pattern, white uniformity means the degree of uniform distribution of white color and luminance across the whole screen. Among the FPDs(Flat Panel Displays), the TFT-LCD has weak point of viewing angle. The viewing angle considering location and direction can cause different image quality of the TFT-LCD. Therefore, white uniformity of the TFT-LCD must consider viewing angle. Based on international standards, this study proposes an alternative that is realistic and ergonomic measurement of white uniformity of the TFT-LCD.

A Novel Approach for Controlling Process Uniformity with a Large Area VHF Source for Solar Applications

  • Tanaka, T.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.146-147
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    • 2011
  • Processing a large area substrate for liquid crystal display (LCD) or solar panel applications in a capacitively coupled plasma (CCP) reactor is becoming increasingly challenging because of the size of the substrate size is no longer negligible compared to the wavelength of the applied radio frequency (RF) power. The situation is even worse when the driving frequency is increased to the Very High Frequency (VHF) range. When the substrate size is still smaller than 1/8 of the wavelength, one can obtain reasonably uniform process results by utilizing with methods such as tailoring the precursor gas distribution by adjustingthrough shower head hole distribution or hole size modification, locally adjusting the distance between the substrate and the electrode, and shaping shower head holes to modulate the hollow cathode effect modifying theand plasma density distribution by shaping shower head holes to adjust the follow cathode effect. At higher frequencies, such as 40 MHz for Gen 8.5 (2.2 m${\times}$2.6 m substrate), these methods are not effective, because the substrate is large enough that first node of the standing wave appears within the substrate. In such a case, the plasma discharge cannot be sustained at the node and results in an extremely non-uniform process. At Applied Materials, we have studied several methods of modifying the standing wave pattern to adjusting improve process non-uniformity for a Gen 8.5 size CCP reactor operating in the VHF range. First, we used magnetic materials (ferrite) to modify wave propagation. We placed ferrite blocks along two opposing edges of the powered electrode. This changes the boundary condition for electro-magnetic waves, and as a result, the standing wave pattern is significantly stretched towards the ferrite lined edges. In conjunction with a phase modulation technique, we have seen improvement in process uniformity. Another method involves feeding 40 MHz from four feed points near the four corners of the electrode. The phase between each feed points are dynamically adjusted to modify the resulting interference pattern, which in turn modulate the plasma distribution in time and affect the process uniformity. We achieved process uniformity of <20% with this method. A third method involves using two frequencies. In this case 40 MHz is used in a supplementary manner to improve the performance of 13 MHz process. Even at 13 MHz, the RF electric field falls off around the corners and edges on a Gen 8.5 substrate. Although, the conventional methods mentioned above improve the uniformity, they have limitations, and they cannot compensate especially as the applied power is increased, which causes the wavelength becomes shorter. 40 MHz is used to overcome such limitations. 13 MHz is applied at the center, and 40 MHz at the four corners. By modulating the interference between the signals from the four feed points, we found that 40 MHz power is preferentially channeled towards the edges and corners. We will discuss an innovative method of controlling 40 MHz to achieve this effect.

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Uniformity Analysis of Unmanned Aerial Application with Variable Rate Spray System (무인항공 변량방제 시스템의 살포 균일도 분석)

  • Koo, Young Mo;Bae, Yeonghwan
    • Journal of agriculture & life science
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    • v.52 no.6
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    • pp.111-125
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    • 2018
  • In this study, we evaluated the uniformity of deposition rate and particle size distributions of the variable rate application technique using the unmanned rotorcraft by measuring the spray pattern according to path location in the range of spraying flight. The coefficient of variation (CV) of the lateral coverage rate for the overlapped distribution with the spray swath of 3.6 m in both guidance and auto-pilot flight modes maintaining constant flight speed was about 30% and the CV of the coverage rate by the flight path location was extremely small. Therefore, it was assessed that the variable rate application technology compensating for the variation of ground speed was superior in terms of spray uniformity. In addition, the droplet size distributions in both volume median diameter(VMD) and number median diameter(NMD) were adequate for aerial application and uniform in terms of lateral distribution. Thereafter, we intend to contribute to a precise application on small-scaled fields using the unmanned agricultural rotorcraft by the variable rate application.

A study on the thickness distribution and pattern deformation of films in vacuum-assisted thermoforming (열진공성형에서 발생하는 필름의 두께 분포와 패턴 변형에 관한 연구)

  • Seong, Gyeom-Son;Lee, Ho-Sang
    • Design & Manufacturing
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    • v.12 no.2
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    • pp.5-10
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    • 2018
  • Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding(FIM) to parts of complex shape. In this study, the simulations and experiments of thermoforming processes were performed to investigate the effects of process conditions on thickness distribution and printed pattern deformation of films in vacuum-assisted thermoforming. The film thickness uniformity increased with decreasing film heating time, whereas it increased with increasing vacuum delay time. After thermoforming of films with uniform pattern space of 5mm, the maximum space was 9.432mm. Based on the simulation, a modified pattern was calculated to obtain uniform spaces after thermoforming. In the experiments for film with the modified pattern, the maximum space appeared 5.837mm. In, addition. the predicted patterns were in good agreement with the experimental results.

A Study on the Deposit Uniformity and Profile of Cu Electroplated in Miniaturized, Laboratory-Scale Through Mask Plating Cell for Printed Circuit Board (PCBs) Fabrication

  • Cho, Sung Ki;Kim, Jae Jeong
    • Korean Chemical Engineering Research
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    • v.54 no.1
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    • pp.108-113
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    • 2016
  • A miniaturized lab-scale Cu plating cell for the metallization of electronic devices was fabricated and its deposit uniformity and profile were investigated. The plating cell was composed of a polypropylene bath, an electrolyte ejection nozzle which is connected to a circulation pump. In deposit uniformity evaluation, thicker deposit was found on the bottom and sides of substrate, indicating the spatial variation of deposit thickness was governed by the tertiary current distribution which is related to $Cu^{2+}$ transport. The surface morphology of Cu deposit inside photo-resist pattern was controlled by organic additives in the electrolyte as it led to the flatter top surface compared to convex surface which was observed in the deposit grown without organic additives.

Numerical Study on the Effect of Exhaust Flow Pattern under Real Running Condition on the Performance and Reliability of Closed-Coupled Catalyst (실 운전조건에서의 배기유동패턴이 근접장착 촉매변환기의 성능 및 신뢰성에 미치는 영향에 관한 수치적 연구)

  • 정수진;김우승
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.54-61
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    • 2004
  • The engine-out flow is highly transient and hot, and may place tremendous thermal and inertial loads on a closed-coupled catalyst. Therefore, time-dependent and detailed flow and thermal field simulation may be crucial. The aim of this study is to develop combined chemical reaction and multi-dimensional fluid dynamic mathematical model and to study the effect of unsteady pulsating thermal and flow characteristics on thermal reliability of closed-coupled catalyst. The effect of cell density on the conversion performance under real running condition is also investigated. Unlike previous studies, the present study focuses on coupling between the problems of pulsating flow pattern and catalyst thermal response and conversion efficiency. The results are expressed in terms of temporal evolution of flow, pollutant and temperature distribution as well as transient characteristics of conversion efficiency. Fundamental understanding of the flow and thermal phenomena of closed-coupled catalyst under real running condition is presented. It is shown that instants of significantly low values of flow uniformity and conversion efficiency exist during exhaust blowdown and the temporal varaition of flow uniformity is very similar in pattern to one of conversion efficiency. It is also found that the location of hot spot in monolith is directly affected by transient flow pattern in closed-coupled catalyst.

Uniform Side Illumination Generated from LEDs Arranged by an Annealing Algorithm

  • Wang, Xu;Lei, Panling;Qian, Chaoyi;Wang, Zhiping;Xu, Xuefen;Su, Zhouping
    • Current Optics and Photonics
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    • v.6 no.3
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    • pp.332-336
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    • 2022
  • Given a cubic space, it is easy to uniformly illuminate the floor with light sources placed on top. However, little has been reported about uniform illumination on walls with the same configuration of light sources. Here we present a luminaire consisting of nine light-emitting diodes (LEDs) with perfect Lambertian distribution, placed on the top as a 3 × 3 rectangular LED array. The distances between LEDs and tilt angles of each individual LED are adjustable and optimized by an annealing algorithm. After optimization, the array produces a rectangular illumination pattern on one wall with a uniformity of about 89%. Analysis shows that the tilt angles of individual LEDs are key parameters for uniform side illumination. In a scenario that is more practical, the tilt angles of all the LEDs are set to be the same, only decreasing the uniformity to 83%.

Simulation Study of Injection-Molded Light Guide Plates for Improving Luminance Uniformity Based on the Measured Replication Quality of Micro-Patterns for LED TV Backlight

  • Joo, Byung-Yun;Ko, Jae-Hyeon
    • Journal of the Optical Society of Korea
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    • v.19 no.2
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    • pp.159-164
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    • 2015
  • In the injection-molded light guide plate the replication quality, i.e. the reproduction accuracy, of micro-patterns should be high and uniform over the entire surface area. However technical difficulty in meeting the necessary replication quality arises as the plate size becomes large for TV applications. We propose a simulation technique to optimize the distribution of micro-patterns on a 55-inch injection molded light guide plate considering non-ideal replication quality of micro-patterns. The luminance uniformity could be improved by more than 16% by optimizing the pattern distribution in spite of the same replication quality.