• Fisheries and Aquatic Sciences
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• 제26권6호
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• pp.367-379
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• 2023

The rapid expansion of shrimp production requires a huge amount of protein sources from soybeans and wild-caught fishmeal; both are becoming a shortage. Meanwhile, catfish production and processing is a giant industry in Vietnam, which produce hundred thousand tonnes of protein- and lipid-rich by-products, annually. Using catfish by-products to gradually replace the traditional protein sources in shrimp aquaculture may bring triple benefits: 1) reducing pressure on wild fish exploitation for fishmeal, 2) reducing the environmental impacts of catfish by-products, and 3) increasing the value and sustainability of aquaculture production. In this study, we used catfish by-products to produce fish protein hydrolysate (FPH) and nano-hydroxyapatite (HA) as additives in feed for Pacific white shrimp (Litopenaeus vannamei). The supplement mixture of FPH and HA was added into the commercial diet (Charoen Pokphand Group [CP], 38% protein, and 6.5% lipid) to reach 38%, 38.5%, 40%, 43%, and 44% of the crude protein content. The survival and growth of shrimps were weekly assessed to day 55. The results showed that the shrimp growth was highest at 43% crude protein content in the feed as indicated by an increase of 124% and 112% in shrimp weight and length, respectively, compared to the commercial reference diet. No negative effects of adding the mixture of FPH and HA on the water quality were observed. Vibrio density was lower than 6.5 × 10³ CFU/mL, which is the lowest Vibrio density negatively affecting the shrimp growth and development. These findings indicate that the mixture of FPH and HA are promising additive components in feed for post-larval shrimp L. vannamei diets.

• 마이크로전자및패키징학회지
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• 제27권1호
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• pp.45-54
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• 2020

최근 PCB의 소형화, 박형화 및 고밀도화가 크게 요구되면서 MSAP (Modified Semi Additive Process) 기술을 이용한 SLP (Substrate Like PCB) 기술이 큰 주목을 받고 있다. 특히 SLP 기술은 스마트폰의 고용량 배터리 개발과 5G 기술에 꼭 필요한 기술이다. 본 연구에서는 기존의 HDI 기술과 MSAP 기술을 혼합하여 제작한 하이브리드 방식의 SLP의 신뢰성을 실험과 수치해석을 이용하여 분석하였다. 특히 최적의 SLP 설계를 위하여 프리프레그(prepreg)의 물성, 두께, 층수, 마이크로비아(microvia)의 크기 및 misalignment가 마이크로비아의 신뢰성에 미치는 영향을 IST(Interconnect Stress Test) 시험을 이용한 열사이클링 신뢰성 실험과 유한요소 수치해석을 통하여 고찰하였다. SLP 소재인 프리프레그의 열팽창계수가 적을수록 마이크로비아의 신뢰성은 크게 증가하며, 프리프레그의 두께가 얇을수록 신뢰성이 증가된다. 마이크로비아 홀의 크기 및 패드의 크기가 증가하면 응력이 완화되어 신뢰성은 향상된다. 반면 프리프레그의 층수가 증가할수록 마이크로비아의 신뢰성은 감소된다. 또한 misalignment가 크면 신뢰성은 감소하였다. 특히 이들 인자들 중에서 프리프레그의 열팽창계수가 마이크로비아의 신뢰성에 가장 큰 영향을 미친다. 수치 응력해석 결과도 실험 결과와 잘 일치하였으며, 응력이 낮을수록 마이크로비아의 신뢰성은 증가하였다. 본 실험과 수치해석의 결과는 향후 SLP 기판 제작 및 신뢰성 향상을 위한 유용한 설계 가이드라인으로 활용될 것으로 판단된다.

• 예술인문사회 융합 멀티미디어 논문지
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• 제7권6호
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• pp.681-692
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• 2017

최근 들어 사회 간접시설 확충 및 경제발전 계획에 의하여 전국적으로 도로 확포장공사 및 신도시 건설 등 대규모 공사가 이루어지며 이로 인하여 인위적인 사면 훼손이 급격히 증가되고 있다. 기존의 비탈면녹화공법인 식생 기반재 취부공법은 결합력의 부족이나 건조화, 유기물의 부족 등의 문제점들을 보이고 있다. 본 연구에서는 천연부엽토, 바크퇴비, 코코피트, 질석이 포함되어 사용되고 있는 식생 기반재와 친환경적인 토양첨가제를 활용하여 연구수행을 하였다. 토양첨가제의 혼합비율에 따라 압축강도를 측정하였으며 식생 기반재와 토양첨가제를 혼합하여 흙다짐시험방법을 준용하여 몰드높이, 다짐횟수, 다짐방법(층), 양생 조건 등으로 하여 사면 보호용 녹생토 재료특성에 관한 실험을 진행하였다. 실험결과, 석고계 시멘트를 사용한 토양 첨가제에서 우수한 강도 성능이 나타났으며, 성능 향상제와 pH조절제를 사용함으로써 식생 생육기준에 만족하였다. 녹생토와 토양첨가제의 혼합에 따라 강도가 증가하는 것을 확인 할 수 있었으며, 사면 보호 안정성을 높일 수 있을 것으로 판단된다.

• 한국세라믹학회지
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• 제50권1호
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• pp.57-62
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• 2013

We investigated the thermal and electrical properties of the $B_2O_3-ZnO-Bi_2O_3$ glass system as a sealing material in sheath heater modules. A composition with over 90 wt% $Bi_2O_3$ in the $B_2O_3-ZnO-Bi_2O_3$ system was glassified by controlling the cooling rate. The glass transition temperature and thermal expansion coefficient in bismate glass could be controlled by the minor ingredients of ZnO, $SiO_2$, $BaO_2$, and $K_2O$. The $B_2O_3-ZnO-Bi_2O_3$ glass system bonded well to metal, and bismate glass insulating properties were comparable to those of bismate glass $B_2O_3-ZnO-PbO$ glass system in a sheath heater module.

• 한국세라믹학회지
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• 제29권3호
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• pp.232-240
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• 1992

Densification behavior, microstructural evolution, and mechanical properties of hot-pressed specimens using $\beta$-SiC and $\alpha$-SiC powder with Al2O3 additive were studied. Beta-SiC powder was fully densified as 205$0^{\circ}C$, but $\alpha$-SiC powder was at 210$0^{\circ}C$. The maximum flexural strength and the fracture toughness of the specimen hot-pressed using $\beta$-SiC powder were 681 MPa and 6.7 MPa{{{{ SQRT {m } }}, and thosevalues of specimen hot-pressed using $\alpha$-SiC powder were 452 MPa and 4.7 MPa{{{{ SQRT {m } }}, respectively. The strength superiority of specimen hot-pressed using $\beta$-SiC powder was due to the finer grain size, and higher density. The higher toughness of specimen hot-pressed using $\beta$-SiC powder than $\alpha$-SiC powder than $\alpha$-SiC powder was due to the crack deflection mechanism arised from the difference of thermal expansion coefficient between $\alpha$ and $\beta$-SiC phases which were co-existed in the sintered body.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제1권1호
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• pp.74-82
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• 2020

Predictions of suitable habitat areas can provide important information pertaining to the risk assessment and management of alien plants at early stage of their establishment. Here, we predict the invasion potential of Muhlenbergia capillaris (pink muhly) in South Korea using five bioclimatic variables. We adopt four models (generalized linear model, generalized additive model, random forest (RF), and artificial neural network) for projection based on 630 presence and 600 pseudo-absence data points. The RF model yielded the highest performance. The presence probability of M. capillaris was highest within an annual temperature range of 12 to 24℃ and with precipitation from 800 to 1,300 mm. The occurrence of M. capillaris was positively associated with the precipitation of the driest quarter. The projection map showed that suitable areas for M. capillaris are mainly concentrated in the southern coastal regions of South Korea, where temperatures and precipitation are higher than in other regions, especially in the winter season. We can conclude that M. capillaris is not considered to be invasive based on a habitat suitability map. However, there is a possibility that rising temperatures and increasing precipitation levels in winter can accelerate the expansion of this plant on the Korean Peninsula.

• 전자공학회논문지A
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• 제31A권6호
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• pp.1-8
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• 1994

In this paper, in order to apply the idea MDPSK to TCM, we use signal set expansion and set partition by phase differences. Through this we propose the trellis-coded MDPSK. And the Viterbi decoder containing branch metrics of the squared Euclidean distance of the Lth order phase difference as well as the first order phase difference is introduced in order to improve the bit error rate(BER) in the differential detection of the trellis-coded MDPSK. The proposed Viterbi decoder is conceptually same to the sliding multiple symbol dection method which uses the branch metric with the first and Lth order phase differences. We investigate the performance of the uncoded DQPSK and the trallis-coded D8PSK in additive white Gaussian noise (AWGN) through the Monte Carlo simulation under the two cases of using and not using the Lth order phase difference metric. The study shows that trellis-coded 8DPSK is an attractive scheme for power and bandlimited systems while also improving the BER performance when the Viterbi decoder is employed to the Lth order phase order difference metric. This performance improvement has been obtained without sacrificing the bandwidth or the power efficiency.

• 한국세라믹학회지
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• 제55권1호
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• pp.36-43
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• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.

• 한국세라믹학회지
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• 제21권2호
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• pp.105-112
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• 1984

The Effect of Dditives $ZrO_2$ and $TiO_2$ on the enstatite body the composition of which was MgO.$SiO_2$ has been closely investigated on the physical properties and microstructure. $ZrO_2$ and $TiO_2$ as additives were added by weight 5, 10, 15, 20, 25% and 1, 2, 2.5, 5, 10, 20% respectively to the mixture (MgO : SiO2=1:1) and fired at the temperature ranging from 130$0^{\circ}C$ to 145$0^{\circ}C$ and 1275$^{\circ}C$ to 1375$^{\circ}C$. Increasing the add ition or $ZrO_2$ to 20% the physical property became better. In case of $TiO_2$ the sample containing 20% $TiO_2$ had a best effect on the enstastite body. The optimum firing range proved to 14$25^{\circ}C$ for $ZrO_2$ and 1325~135$0^{\circ}C$ for $TiO_2$. The effect of $ZrO_2$ and $TiO_2$ addition on the thermal expansion was observed not ot be remarkable.

• Computers and Concrete
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• 제20권6호
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• pp.705-710
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• 2017

The effectiveness of mineral additives in suppressing alkali-silica reactivity has been studied in this work. Experimentation has been performed in accordance with the procedures prescribed in ASTM C 1567. In the scope of the investigation, a quarry aggregate which was reactive according to ASTM C 1260 was tested. In the experimental program, prismatic mortar specimens measuring $25{\times}25{\times}285mm$ were produced. Ten sets of production, three specimens for each set, were made. Length changes were measured at the end of 3, 7, 14 and 28 days and then expansions in percentage have been calculated. Fly ash, silica fume, and metakaolin have been used as cement replacement in different ratios for the testing of the alkali-silicate reactivity of the aggregate. In the mixes performed, the replacement ratios were 20%, 40%, and 60% for the fly ash, and 5%, 10%, and 15% for the silica fume, and 5%, 10%, and 15% for the metakaolin. Mixes without mineral additives were also produced for comparison. The beneficial effect in suppressing alkali-silica reactivity is highly noticeable as the replacement ratios of the mineral additives increase regardless of the type of the mineral additive used. Being more concise, the optimum concentrations of using silica fume and metakaolin in mortar in suppressing ASR is 10%, respectively, while it is 20% for fly ash.