• 제목/요약/키워드: mesh-free methods

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Characteristics of Particle Separation in Suspension using an Ultrasonic Standing Wave

  • Shin, Beom-Soo;Danao, Mary-Grace C.
    • Journal of Biosystems Engineering
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    • 제37권2호
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    • pp.113-121
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    • 2012
  • Purpose: Particle separation in solution is one of important process in a unit operation as well as in an extract preparation for biosensors. Contrary to centrifuge-type of mesh-type filter, using an ultrasonic standing wave make the filtering process continuous and free from maintenance. It is needed to investigate the characteristics of particle movement in the ultrasonic standing wave field. Methods: Through the computer simulation the effects of major design and driving parameters on the alignment characteristics of particles were investigated, and a cylindrical chamber with up-stream flow type was devised using two circular-shape PZTs on both sides of the chamber, one for transmitting ultrasonic wave and the other for just reflecting it. Then, the system performance was experimentally investigated as well. Results: The speed of a particle to reach pressure-node plane increased as the acoustic pressure and size of particle increased. The maximum allowable up-stream flow rate could be calculated as well. As expected, exact numbers of pressure-node planes were well formed at specific locations according to the wavelength of ultrasonic wave. As the driving frequency of PZT got close to its resonance frequency, the bands of particles were observed clearer, which meant the particles were trapped into narrower space. Higher excitation voltages to the PZT produced a greater acoustic force with which to trap particles in the pressure-node planes, so that the particles gathered could move upwards without disturbing their alignments even at a higher inlet flow rate. Conclusions: This research showed the feasibility of particle separation in solution in the continuous way by an ultrasonic standing wave. Further study is needed to develop a device to collect or harvest those separated particles.

Does the prosthesis weight matter? 3D finite element analysis of a fixed implant-supported prosthesis at different weights and implant numbers

  • Tribst, Joao Paulo Mendes;Dal Piva, Amanda Maria de Oliveira;Borges, Alexandre Luiz Souto;Rodrigues, Vinicius Aneas;Bottino, Marco Antonio;Kleverlaan, Cornelis Johannes
    • The Journal of Advanced Prosthodontics
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    • 제12권2호
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    • pp.67-74
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    • 2020
  • PURPOSE. This study evaluated the influence of prosthesis weight and number of implants on the bone tissue microstrain. MATERIALS AND METHODS. Fifteen (15) fixed full-arch implant-supported prosthesis designs were created using a modeling software with different numbers of implants (4, 6, or 8) and prosthesis weights (10, 15, 20, 40, or 60 g). Each solid was imported to the computer aided engineering software and tetrahedral elements formed the mesh. The material properties were assigned to each solid with isotropic and homogeneous behavior. The friction coefficient was set as 0.3 between all the metallic interfaces, 0.65 for the cortical bone-implant interface, and 0.77 for the cancellous bone-implant interface. The standard earth gravity was defined along the Z-axis and the bone was fixed. The resulting equivalent strain was assumed as failure criteria. RESULTS. The prosthesis weight was related to the bone strain. The more implants installed, the less the amount of strain generated in the bone. The most critical situation was the use of a 60 g prosthesis supported by 4 implants with the largest calculated magnitude of 39.9 mm/mm, thereby suggesting that there was no group able to induce bone remodeling simply due to the prosthesis weight. CONCLUSION. Heavier prostheses under the effect of gravity force are related to more strain being generated around the implants. Installing more implants to support the prosthesis enables attenuating the effects observed in the bone. The simulated prostheses were not able to generate harmful values of peri-implant bone strain.

건조방법을 달리한 유자껍질 티백차의 품질특성 비교 (Quality comparison of hot-water leachate from teabags containing Citrus junos peels dried using different methods)

  • 박한솔;이현정;윤광섭;김동섭;김한수;이영근;성종환;정헌식
    • 한국식품저장유통학회지
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    • 제24권8호
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    • pp.1088-1093
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    • 2017
  • 유자껍질을 이용한 고품질 티백차를 개발하기 위하여, 생유자껍질을 열풍($50^{\circ}C$), 냉풍($30^{\circ}C$), 동결($-45^{\circ}C$) 건조한 후 분쇄하고 종이봉지로 티백 포장한 다음 열수 침출하여 얻은 음용차의 이화학적 품질특성을 조사하여 건조 방법별 비교하였다. 유자껍질 분말의 색도는 $L^*$ 값과 $-a^*$ 값이 동결 건조구에서 유의적으로 가장 높았다. 유자껍질 티백차의 가용성 고형분 함량과 적정산도는 열풍 및 동결건조구 보다 냉풍건조구에서 보다 높은 수준을 나타내었다. 유자껍질 티백차에서 유리당은 fructose, glucose, sucrose 순으로 나타났으며, fructose와 glucose 함량은 건조방법별 뚜렷한 차이를 보이지 않았으나 sucrose 함량은 동결건조구에서 다소 낮음을 보였다. 플라보노이드 함량은 건조방법의 영향을 나타내지 않았으나, DPPH 유리기 소거능은 냉풍건조구에서 유의적으로 가장 높은 수준을 보였다. 이로써, 유자껍질을 이용한 고품질 티백차 제조시 원료의 건조방법으로 냉풍건조법도 유효할 것으로 판단되었다.

무요소법을 이용한 균열진전 문제의 형상 최적설계 (Shape Design Optimization of Crack Propagation Problems Using Meshfree Methods)

  • 김재현;하승현;조선호
    • 한국전산구조공학회논문집
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    • 제27권5호
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    • pp.337-343
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    • 2014
  • 본 논문에서는 재생 커널 기법을 사용하여 혼합모드 균열진전 문제에 대한 연속체 기반의 형상 설계민감도 해석을 수행하였다. 재생 커널 기법은 기존의 유한요소법과 달리 요소망을 재구성할 필요가 없어, 커널 함수의 연속성을 증가시켰을 때 높은 정밀도의 형상함수를 얻을 수 있다는 장점을 가지고 있다. 균열선단 주변에서 J-적분을 수행하기 위해 선형탄성 조건이 고려되었다. 변위장과 응력 확대 계수의 설계변수에 대한 감도해석을 위하여 물질도함수를 도입하였으며 직접 미분법보다 효율적인 애조인 방법을 사용하여 설계민감도를 유도하였다. 수치 예제들을 통해서 재생 커널 기법을 이용한 균열진전 해석결과의 타당성을 확인하였으며 애조인 방법을 이용한 형상 설계민감도 해석 결과를 유한차분법과 비교하여 매우 정확하고 효율적인 결과를 얻을 수 있음을 알 수 있었다. 이를 바탕으로 간단한 모델에 대하여 형상 최적설계를 수행하여 균열이 발생될 수 있는 구조물에 대해서 균열에 의한 피해를 최소화할 수 있도록 균열을 제어할 수 있는 최적의 형상을 도출하였다.

상품성 제고를 위한 고구마 수확 후 관리 및 출하기술 (Postharvest Handling and Marketing Management for Making High Salability of Sweetpotatoes)

  • Jeong, Byeong-Choon
    • 한국식품저장유통학회:학술대회논문집
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    • 한국식품저장유통학회 2001년도 임시총회 및 제18차 학술발표회 발표논문초록집
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    • pp.51-64
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    • 2001
  • The qualities including taste of sweetpotato stored during the winter which can display in the spring market in Korea are affected by availability of storage for the roots. In order to make high storage availability of sweetpotato, the postharvest handlings should be done thoroughly from the moment of harvest until shipping them to the market. A lot of procedures that must be handled carefully for improving postharvest management are as follows; digging, trimming, gathering, putting in storage containers, carrying them from field to house, curing, storing, washing, drying, selecting marketable roots, packing and shipping to the market, etc.. Sweetpotatoes have a high moisture content, and a relatively thin and delicate skin, and are sensitive to chilling, so careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. From now on research has concentrated on the improvement of postharvest conditions to increase yield and lower disease rates. Storage, which makes sweetpotatoes available through out the year, benefits both the producer and the consumer. Seven very important points must be needed in order to get the best quality marketable roots in the storing of sweetpotatos : $\circled1$The storage house must be clean and sanitary, $\circled2$The crop must be harvested before the first frost to avoid low-temperature injury, $\circled3$Particular care must be taken to avoid cutting, bruising, or other injuries of the sweetpotatoes during digging, picking up, grading, placing in containers, and moving to the storage house, $\circled4$Select sound, disease-free roots for storage $\circled5$Sweetpotatoes should be stored in properly stacked containers $\circled6$Cure immediately after harvest, preferably at 32∼33$^{\circ}C$ and 90 to 95 percent relative humidity for 4 to 7 days, After curing the temperature should be reduced to 13$^{\circ}C$ to 16$^{\circ}C$ by ventilating the storage with outside air. $\circled7$Store at 12$^{\circ}C$ to 14$^{\circ}C$ and a relative humidity of 80 to 85 percent. Storage houses should be located on suitable sites and should be tightly constructed and insulated so that temperature and humidity will be uniform. Sweetpotatoes are usually not washed and graded, and lately sometimes washed, graded, waxed, before being shipped to market. Consumer packaging of sweetpotatoes in paper boxes(10-15kg) or film bags is done mainly to aid marketing. The shelf life of washed roots in consumer packs in only 1 to 2 weeks. Weight loss of roots during marketing is much less in perforated film bags than in mesh and paper bags. Perforation of 0.8 to 1kg polyethylene bags with about six 6mm holes is essential ; to lower the internal relative humidity and avoid excessive sprouting, rooting, and dampness. Development and use of better postharvest handling with good storage facilities or marketing methods can minimize sweetpotate losses and has an effect of indirectly increasing productivity and farmer’s income.