A wide-band in-air parametric array source composed of a circular plate with steps and a Langevin transducer with a horn

Hwang, Yonghwan,Moon, Wonkyu Elsevier 2018 Applied acoustics Vol.141 No.-

<P><B>Abstract</B></P> <P>Parametric array (PA) sources generate a directional sound beam, via the PA phenomenon. Practical PA sources, such as PA loudspeakers, have high power consumption, low sound quality, and high cost. The stepped-plate transducer, which consists of a Langevin transducer, a horn, and a radiating plate with steps, can provide high-intensity sound and a highly directional sound beam in the acoustic axis. This study investigated the use of a stepped-plate transducer to make a PA source with high directivity and a wide bandwidth. A stepped-plate transducer that had two different resonance frequencies (<I>f</I> <SUB>1</SUB> = 77.5 kHz, <I>f</I> <SUB>2</SUB> = 87.4 kHz) was designed for wide bandwidth, and the three different heights of the steps on the plate (<I>t<SUB>s</SUB> </I> <SUB>1</SUB> = 2.28 mm, <I>t<SUB>s</SUB> </I> <SUB>2</SUB> = 2.14 mm, <I>t<SUB>s</SUB> </I> <SUB>3</SUB> = 2.02 mm) were intended to provide high directivity sound beams. The fabricated stepped-plate transducer demonstrated a 50 ± 3 dB sound pressure level for the difference frequency wave in the 4–19 kHz frequency range (with equalization), and 4.2–5.1° of HPBW was shown for the highly directional sound beam.</P>

Preparation of Pt Films on GaAs by 2-step Electroless Plating

Hungsu Im,Yong Jun Seo,Young Joo Kim,Kai Wang,Sang Sik Byeon,Bon Heun Koo,Ji Ho Chang 한국표면공학회 2009 한국표면공학회지 Vol.42 No.4

Electroless plating is influenced by kinds of parameters including concentrations of electrolyte, plating time, temperature and so on. In this study, the Pt thin films were prepared on GaAs substrate by a 2-step electroless plating depending method. The small Pt catalytic particles by using Pt I bath exhibited islands-morphology dispersed throughout the substrate surface at 65℃, as function as a sensitized thin film, and then a thicker Pt film grew upon the sensitized layer by the second Pt Ⅱ bath. As the growth of Pt film is strongly influenced by the plating time and temperature, the plating time of Pt Ⅱ bath varied from 5 min to 40 min at 60~80℃ after Pt I bath at 60~80℃ for 5 min. It is found that the film grows with the increasing plating time and temperature. The resistivity value of Pt deposited layer was characterized to study the growth mechanism of 2-step plating.

Lateral stiffness of reinforced concrete flat plates with steps under seismic loads

Kim, Sanghee,Kang, Thomas H.K.,Kim, Jae-Yo,Park, Hong-Gun 테크노프레스 2014 Earthquakes and structures Vol.7 No.5

The purpose of this study is to propose a modification factor to reflect the lateral stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analyses. The corner at the step is weak and flexible, and the associated rotational stiffness degradation at the corner of the step is identified through analyses of 6 types of models using a nonlinear finite element program. Then a systematic analysis of stiffness changes is performed using a linear finite element procedure along with rotational springs. The lateral stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied by the other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective slab width.

Preparation of Submicroscale Ag-Coated Cu Particles by Multi-Step Addition of Ag Plating Solution and Antioxidation Properties for Different Ag Shell Thicknesses

Choi, Eun Byeol,Lee, Jong-Hyun De Gruyter Open 2017 Archives of metallurgy and materials Vol.62 No.2

<P>For application as a low-cost conductive filler material, submicroscale Cu@Ag particles were fabricated at room temperature without any reductants by a multi-step addition method using an ethylene glycol-based Ag plating solution. Scanning electron microscopy images of the Ag-coated Cu particles demonstrated the formation of discrete Ag particles less than 100 nm in size as well as a thin Ag coating on Cu particles, during the early addition steps. However, as the thickness of the Ag coating increased, the small Ag particles agglomerated into Ag coatings with an increase in the number of Ag plating steps. Owing to the absence of additives such as surfactants, a comparison between the microstructural images and calculations indicated increased agglomeration between fabricated Ag-coated Cu particles with an increase in the number of Ag plating steps. However, thermogravimetric-differential scanning calorimetry of the agglomerated Ag-coated Cu particles after the fifth addition of the Ag plating solution demonstrated their antioxidation behavior even after 70 min in air at 150 degrees C.</P>

Improvement of formability for fabricating thin continuously corrugated structures in sheet metal forming process

최성우,박상후,박성훈,정호승,하만영,조종래 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.8

A stamping process is widely used for fabricating various sheet metal parts for vehicles, airplanes, and electronic devices by the merit of low processing cost and high productivity. Recently, the use of thin sheets with a corrugated structure for sheet metal parts has rapidly increased for use in energy management devices, such as heat exchangers, separators in fuel cells, and many others. However, it is not easy to make thin corrugated structures directly using a single-step stamping process due to their geometrical complexity and very thin thickness. To solve this problem, a multi-step stamping (MSS) process that includes a heat treatment process to improve formability is proposed in this work: the sequential process is the initial stamping, heat treatment, and final shaping. By the proposed method, we achieved successful results in fabricating thin corrugated structures with an average thickness of 75 μm and increased formability of about 31% compared to the single-step stamping process. Such structures can be used in a plate-type heat exchanger requiring low weight and a compact shape.

An Experimental Study on Structural Performance Evaluation of Steel Wire-Integrated Deck Plate

김성배,강민정,김상섭 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4

Recently, due to the decreased work term and the convenience of construction work, the steel wire-integrated deck plate has been widely used in the construction sites in Korea. Most of all, owing to its good stiffness and economic consideration, the steel wire-integrated deck plate system has become very popular in recent years. This research suggested the new-type shear connector that can perform the roles of vertical bar and shear connector at the same time to obtain safety on construction load of the steel wire-integrated deck plate and improvement on constructability, and used many variables such as the location of lattice end and diameter of the lattice bar to evaluate the structural safety of the steel wire-integrated deck plate in construction step. The test results show that the new-type shear connectors sufficiently perform the roles of the vertical bars.

평지붕 PV거치 시스템의 형태에 따른 풍압영향에 관한 기초연구

윤두영(Yun Doo-Young),이응직(Lee Eung-Jik) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.5

The new renewable energy became popular as a clean and sustainable alternative energy under the circumstances that the entire world is facing severe abnormal climate due to the use of fossil fuel, and among which, solar energy can be obtained anywhere and is not difficult to apply it into the existing buildings, which makes it possible to be widely distributed. However, as PV module is installed into a single plate system, it shows structural weaknesses which are vulnerable to wind load and give loss to design elements in external appearance. Accordingly, this study planned one-step parallel system to complement the problems occurring from a single plate system and used STAR-CCM+V.8 made by CD-Adapco, a computational fluid dynamics(CFD) simulation tool to measure wind load stability and support based on the design standards for a single plate system and one-step parallel system. Building height was limited to less than 10m and wind speed was given when increasing from 35㎧ to 50㎧ by 5㎧ on PV system installed into the flat roof. In this case, our analysis suggested that step-one parallel system was inclass7-9 according to Beaufort’s wind power classification, which did not have an impact on the fixed PV system, and the single plate system is considered to cause risks in designing wind speed in central districts because it is more than wind power class12.

단차가 있는 철근콘크리트 무량판의 강성보정계수에 대한 연구

김상희(Kim, Sang-Hee),강현구(Kang, Thomas H.-K),김재요(Kim, Jae-Yo),홍건호(Hong, Geon-Ho),한규범(Han, Gyu-Beom),송정훈(Song, Jung-Hoon),박홍근(Park, Hong-Gun) 대한건축학회 2014 大韓建築學會論文集 : 構造系 Vol.30 No.3

The purpose of this study is to propose a modification factor to reflect the stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analysis. The corner at the step is weak and flexible, and thus the associated rotational stiffness at the corner of the step is identified through analysis of 6 type models using a nonlinear finite element program. Then a systematic analysis on stiffness changes is performed using a linear finite element procedure along with rotational springs. The stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied each other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective beam width.

혼합촉진장치 적용시 유동장 변화에 의한 탈황효율 연구

정진도 ( J. D. Chung ),김장우 ( J. W. Kim ),서문준 ( J. Seommun ) 한국분무공학회 2010 한국액체미립화학회지 Vol.15 No.4

This paper has designed a mixing enhancement apparatus called Lobed-plate and Step-plate and comparatively calculated desulfurization efficiency of when its shape was changed. The parameters used at this time were the shape, SR ratio and the number of nozzles of the mixing enhancement apparatus and comparatively analyzed desulfurization efficiency according to these parameters. As a result, the Step-plate appeared as more highly by around 4% than Lobed-plate in desulfurization efficiency according to the shape of the mixing promotion apparatus, and when the desulfurization efficiency as a SR ratio is considered, it appeared highly by an average of 5% when the SR ratio is 3 rather than 2. As a result of comparing desulfurization efficiency by fixing the SR ratio and setting the number of nozzles as 4 pieces and 6 pieces, there was no big change in desulfurization efficiency when the SR ratio is 2, but it could be confirmed to improve by around 5% when the SR ratio is 3 when time passed 8 seconds.

고발열 칩 냉각용 Cold plate에서 단차 형상 적용을 이용한 Flow boiling 안정성 향상 설계 연구

이재호(J. Lee),정효재(H. J. Jeong) 한국생산제조학회 2024 한국생산제조시스템학회 학술발표대회 논문집 Vol.2024 No.7