• Journal of electromagnetic engineering and science
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• 제17권4호
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• pp.241-243
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• 2017

In this paper, we have presented an equation for estimating the gain of a Fabry-Perot cavity (FPC) antenna with a finite dimension. When an FPC antenna has an infinite dimension and its height is half of a wavelength, the maximum gain of that FPC antenna can be obtained theoretically. If the FPC antenna does not have a dimension sufficient for multiple reflections between a partially reflective surface (PRS) and the ground, its gain must be less than that of an FPC antenna that has an infinite dimension. In addition, the gain of an FPC antenna increases as the dimension of a PRS increases and becomes saturated from a specific dimension. The specific dimension where the gain starts to saturate also gets larger as the reflection magnitude of the PRS becomes closer to one. Thus, it would be convenient to have a gain equation when considering the dimension of an FPC antenna in order to estimate the exact gain of the FPC antenna with a specific dimension. A gain versus the dimension of the FPC antenna for various reflection magnitudes of PRS has been simulated, and the modified gain equation is produced through the curve fitting of the full-wave simulation results. The resulting empirical gain equation of an FPC antenna whose PRS dimension is larger than $1.5{\lambda}_0$ has been obtained.

• 한국산학기술학회논문지
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• 제4권3호
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• pp.164-167
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• 2003

본 연구에서는 무선부품의 일종인 cavity filter금형을 제작하여 도금용 ABS 수지와 PC/ABS alloy 수지를 사용하여 일반사출성형과 금형온도가 높은 MmSH방식, 두 타입으로 성형품을 제작하였다. 성형품의 수축률 변화는 MmSH 방식일 때 ABS 성형품의 단위캐비티 격막부분에서 수축률이 감소되었다. 중량변화는 ABS와 PC/ABS 성형품 모두 MmSH 방식일 때 증가하였고, 성형품 표면 거칠기는 MmSH 방식일 때 모두 거칠기가 감소되었다.

• Design & Manufacturing
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• 제7권1호
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• pp.1-6
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• 2013

The injection molding process is a predominant method for producing plastic parts. In order to maximize productivity and molding quality in a injection mold, it is important that each cavity in a multi-cavity injection mold is identical. This requires that cavity dimensions should be identical and delivery system of melt to each cavity have to be the same. Despite the geometrically balanced layout in multi-cavity injection mold more than 4 cavities, it has been observed that the filling in each cavity results in imbalances. Most of cases, this phenomenon of filling imbalances have a bad effect on dimension accuracy, warpage, molding appearance and strength of molding parts. In this study, experiment were conducted to investigate the effect of filling imbalances on the molding quality(surface gloss, shrinkage, tensile strength) in the multy-cavity injection mold.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.89-94
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• 2008

The injection molding process is a predominant method for producing plastic parts. In order to maximize productivity and molding quality in a injection mold, it is important that each cavity in a multi-cavity injection mold is identical. This requires that cavity dimensions should be identical and delivery system of melt to each cavity have to be the same. Despite the geometrically balanced layout in multi-cavity injection mold more than 4 cavities, it has been observed that the filling in each cavity results in imbalances. Most of cases, this phenomenon of filling imbalances have a bad effect on dimension accuracy, warpage, molding appearance and strength of molding parts. In this study, experiment were conducted to investigate the effect of filling imbalances on the molding quality(surface gloss, shrinkage, tensile strength) in the multy-cavity injection mold.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2003년도 춘계학술발표논문집
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• pp.359-361
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• 2003

본 연구에서는 무선부품의 일종인 cavity filter 금형을 제작하였고, 도금용 ARS 수지와 PC/ARS Alloy 수지를 사용하여 일반사출성형과 금형온도가 높은 MmSH방식, 두 타입으로 성형품을 제작하였다. 성형품의 수축률 변화는 MmSH 방식일 때 ABS 수지로 제작한 성형품의 단위캐비티 격막부분에서 수축률이 감소되었다. 중량변화는 ABS와 PC/ABS Alloy로 제작된 성형품 모두 MmSH 방식일 때 증가하였고. 성형품의 표면 거칠기도 모두 MmSH 방식일 때 거칠기가 감소되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.621-626
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• 2001

Microcellular foaming process was developed at MIT in 1980's to save a quantity of raw materials and improve mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. Of all process variables, part dimension control and shrinkage are the most influential on the post molded dimension. The post molding dimensional change of thermoplastic resins is important to tool designers for predicting the specific difference of molded part vs. actual mold cavity. Generally, articles injection molded are smaller in size than the cavity; hence, the term shrinkage factor is used to define the allowance a designer specifies. It is important to consider the factors that influence molded part dimension. According to ASTM Designation: D 955, shrinkage from mold dimensions of molded plastics was measured. In injection molding, the difference between the dimensions of the mold and of the molded article produced therein from a given material may vary according to the design and operation of the mold. In this paper, shrinkage data of molded plastic parts was obtained. It can be an important information for designing optimum mold system in a microcellular foaming injection molding process.

• Restorative Dentistry and Endodontics
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• 제29권6호
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• pp.532-540
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• 2004

The aim of this study was to measure the cusp deflection during composite restoration for MOD cavity in premolar and to examine the influence of cavity dimension, C-factor and restoration method on the cusp deflection. Thirty extracted maxillary premolar were prepared to four different sizes of MOD cavity and divided into six groups. The width and depth of the cavity were as follows. Group 1; $1.5{\;}{\times}{\;}1{\;}mm$, Group 2; $1.5{\;}{\times}{\;}2{\;}mm$, Group 3; $3{\;}{\times}{\;}1{\;}mm$, and Group 4-6; $3{\;}{\times}{\;}2{\;}mm$ respectively. Group 1-4 were restored using bulk filling method with Z-250 composite. However, Group 5 was restored incrementally, and Group 6 was restored with an indirect resin inlay. The cusp deflection was recorded at the buccal and lingual cusp tips using LVDT probe for 10,000 seconds. The measured cusp deflections were compared between groups, and the relationship between the cube of the length of cavity wall/the cube of the thickness of cavity wall ($L^3/T^3$). C-factor and cusp deflection or % flexure ($100{\;}{\times}$ cuspal deflection / cavity width) was analyzed. The cusp deflection of Group 1-4 were $12.1{\;}\mu\textrm{m},{\;}17.2{\;}\mu\textrm{m},{\;}16.2{\;}\mu\textrm{m}{\;}and{\;}26.4{\;}\mu\textrm{m}$ respectively. The C-factor was related to the % flexure rather than the cusp deflection. There was a strong positive correlationship between the $L^3/T^3$ and the cusp deflection. The cusp deflection of Group 5 and 6 were $17.4{\;}\mu\textrm{m}{\;}and{\;}17.9{\;}\mu\textrm{m}$ respectively, which are much lower value than that of Group 4.

• 한국음향학회지
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• 제30권4호
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• pp.223-230
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• 2011

한국종은 지면으로부터 일정한 간극을 두고 매달리며, 종 아래에 명동이라고 불리는 독특한 음향학적 요소를 갖고 있다. 간극과 명동의 적절한 설계는 공명효과에 의하여 종소리를 극적으로 증폭시킨다. 종체의 내부공동과 간극, 그리고 명동으로 구성된 음향공동계는 공명주파수와 모드를 갖는데, 공명주파수가 종체의 고유진동수에 일치하게 되면, 그 주파수성분이 크게 증폭된다. 이 연구는 성덕대왕신종을 대상으로 간극효과를 고려한 명동의 공명조건을 처음으로 제시한다. 공명조건을 구하기 위하여 신종의 실제 치수를 사용하여 SYSNOISE를 이용한 경계요소해석을 수행하였다. 또한, 계절에 따른 기온의 차이가 공명조건에 어떠한 영향을 미치는가를 규명하고, 가변형 명동의 개념을 제시함으로써, 현장에서 온도차를 보정하여 정확한 공명조건을 구현시킬 수 있는 방안을 제공한다.

• Elastomers and Composites
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• 제52권4호
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• pp.309-316
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• 2017

In injection molding, the quality of an injection molded product varies greatly depending on the molding conditions. Many researche studies have been conducted on the quality analysis of molded parts according to the molding conditions such as injection pressure, injection temperature, and packing pressure. However, there have not been many studies on the V/P switchover timing. It is known that when a large pressure is applied to a cavity in the packing phase, the cavity pressure is most affected by the packing pressure. In addition, depending on the position (timing) of the packing pressure, it can have a direct influence on quality based on the shrinkage and dimensions of the molded parts. In this study, the change in pressure profile in the cavity according to the V/P switchover position is confirmed. A CAE analysis program (Moldflow) was used to simulate and analyze two models using the PC and PBT materials. In order to compare these results with the actual injection molding results, injection molding was performed for each V/P switchover position, and the correlation between simulation and experiment, especially for the shrinkage of molded parts, was evaluated.

• 대한방사선기술학회지:방사선기술과학
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• 제19권1호
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• pp.81-87
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed. This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy Photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and 20.6% for the CO-60, 4 MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions it is, the larger beam reductions we have. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.