• 한국세라믹학회지
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• 제28권3호
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• pp.234-242
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• 1991

Ti-B system ceramics were prepared by the self-propagating high-temperature synthesis method from the mixture of metal titanium and boron powders The major crystalline phase as a function of boron content was TiB for mixtures containing 0.5 or 1.0mol B, and TiB2 for these containing over 1.3mol B. The combustion mode observed by a high-speed camera was steady-state. The Combustion velocity increased with increasing the boron content. Sintered TiB2 specimen showed the density of 97% of theoretical valve, Vicker's hardness of 2250kg/㎟ for 0.2kg load and three-point-flexure strength of 500MPa.

• 한국재료학회지
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• 제10권5호
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• pp.343-349
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• 2000

자전연소합성(SHS)법을 이용하여 탄소섬유와 티타늄, 지르코늄, 니오븀, 규소, 붕소, 중석, 몰리브덴의 분말로부터 여러 가지 섬유상 탄화물의 합성을 시도하였다. 티타늄과 지르코늄은 예열없이, 그 이외의 경우는 전기로 또는 화학로를 사용하여 예열하여 반응을일으킨 결과, TiC, ZrC, NbC, SiC, $B_4$C, WC,$ Mo_2$C 의 순수한 탄화물의 형성되었다. TiC, ZrC, NbC 및 $B_4$C 탄화물의 형상은 속의 빈 섬유상이었고, SiC는 보다 작은 입자와 미세 휘스커로 이루어진 섬유상을 하고 있었고 WC와 $Mo_2$C 는 비섬유상을 하고 있었다. 여러 가지 형상의 원인에 대하여 합리적 설명을 시도하였으며 정성적 메카니즘을 제안하였다.

• 대한영양사협회학술지
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• 제25권1호
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• pp.30-43
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• 2019

This study compared the predictive models for the growth kinetics of Staphylococcus aureus in ham rice balls. In addition, a semi-quantitative risk assessment of S. aureus on ham rice balls was conducted using FDA-iRISK 4.0. The rice was rounded with chopped ham, which was mixed with mayonnaise (SHM), soy sauce (SHS), or gochujang (SHG), and was contaminated artificially with approximately $2.5{\log}\;CFU{\cdot}g^{-1}$ of S. aureus. The inoculated rice balls were then stored at $7^{\circ}C$, $15^{\circ}C$, and $25^{\circ}C$, and the number of viable S. aureus was counted. The lag phases duration (LPD) and maximum specific growth rate (SGR) were calculated using a Baranyi model as a primary model. The growth parameters were analyzed using the polynomial equation as a function of temperature. The LPD values of S. aureus decreased with increasing temperature in SHS and SHG. On the other hand, those in SHM did not show any trend with increasing temperature. The SGR positively correlated with temperature. Equations for LPD and SGR were developed and validated using $R^2$ values, which ranged from 0.9929 to 0.9999. In addition, the total DALYs (disability adjusted life years) per year in the ham rice balls with soy sauce and gochujang was greater than mayonnaise. These results could be used to calculate the expected number of illnesses, and set the hazard management method taking the DALY value for public health into account.

• 한국환경복원기술학회지
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• 제2권1호
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• pp.1-9
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• 1999

1. 인공식재지반 토양의 배합특성에 따른 켄터키블루글래스의 초기발아율은 버미큘라이트가 사용된 실험구에서 높게 나타났으며, 밭흙의 경우 가장 낮았다. 초장에 있어서는 파종후 약 1개월 후는 "밭흙+버미큘라이트+모래"의 혼합구에서(3.0cm), 2개월 후는 "밭흙+훈탄+모래"의 혼합구(5.0cm)에서 가장 긴 것으로 확인되었다. 그러나 3개월 후부터는 다시 "밭흙+버미큘라이트+모래"의 혼합구(5.0cm)에서 가장 길었다. 피복율은 파종 2개월 후는 "밭흙+버미큘라이트+모래"의 경우가 가장 높았으며, 파종 3개월 후부터는 "밭흙+부숙톱밥+모래"의 혼합구에서 높은 피복율을 나타내었다. 반면 밭흙의 경우 발아율과 마찬가지로 초장 및 피복율에 있어서 가장 불량한 생육상태를 보였다. 즉, 혼합토양의 경우 단일토양 보다 상대적으로 높은 생육상태를 보이고 있었으며, 이는 혼합한 토양개량재의 특성이 식물생육에 영향을 미치고 있음을 반영해 주는 것으로 볼 수 있다. 2. 인공지반상의 토양종류별 시비종류가 식물생육에 미치는 영향정도를 분석한 결과 먼저 밭흙의 경우 유기질비료의 시용구가 우수하였으며, 버미큘라이트 및 "밭흙+버미큘라이트+모래"의 토양구성에서는 초장 및 피복율은 유기질비료의 처리구에서 우세하였다. "밭흙+훈탄+모래"의 혼합구에서는 비료를 시비하지 않은 무처리구에서도 비교적 양호한 생육상태를 보이고 있어, 인공지반상의 식재용토로 사용할 경우 상대적으로 비료 요구도가 덜 한 것을 알 수 있다. "밭흙+부숙톱밥+모래"의 배합토에서는 초기발아율 및 초장, 피복율에 있어 유기질 비료의 처리구에서 우수한 것으로 나타났다. 3. 인공식재지반의 시비방법에 따른 켄터키 블루글래스의 생장을 종합해 볼 때 초기발아율 및 초장, 피복율에서 유기질비료의 처리구가 상대적으로 우수한 것으로 나타났다. 이상의 연구 결과를 종합해 볼 때, 본 실험에 사용된 5종류의 토양중 인공식재지반조성시 "밭흙+부숙톱밥+모래"의 구성이 상대적으로 양호한 생육상태를 나타내고 있었으며, 시비종류에 따른 식물의 생육상태는 유기질 비료를 시용한 실험구가 가장 양호하였다. 토양종류와 시비와의 관계를 살펴보면 무시비구에서는 "밭흙+훈탄+모래", "밭흙+부숙톱밥+모래" 등의 토양에서 생육이 상대적으로 우수하였다. 그러나 버미큘라이트를 사용한 실험구는 화학비료의 영향을 가장 많이 받는 것으로 나타나 인공식재지반용토로 버미큘라이트 등을 사용할 경우 화학비료를 시비해 주는 것이 효과적인 것으로 나타났다. 다만 본 연구에서는 혼합전의 토양과 유기질비료의 몇가지 화학적 특성은 측정되었으나 토양과 비료혼합후의 화학적 특성 등이 구체적으로 규명되지 않아 비료혼합후의 이들의 반응관계에 대한 지속적인 연구가 필요할 것으로 사료된다.

• 한국세라믹학회지
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• 제32권3호
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• pp.341-348
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• 1995

An analysis of the use of temperature profiles in the determination of the kinetic parameters of combustion synthesis of Ti5Si3 were investigated. From profile analysis, an apparent activation energy of 12KJ/mol was calculated. The Maximum heating rate achieved during 10wt% Ti5Si3 reaction by the product dilution method was approximately $1.5\times$104 K/s. Coupling this value with the measured wave velocity of 7.02 cm/s yields a maximum thermal gradient of 2.14$\times$103 K/cm. The value of tr (=t*) was calculated to be 1.2$\times$10-1 s and the value of td (=tx) was calculated to be 32.89 s. Using the definition of t* and the measured wave velocity, the effective thermal diffusivity, $\alpha$, was calculated to be 0.59$\times$10 $\textrm{cm}^2$/s. From these analysis, the power function, G, was also calculated.

• KIEAE Journal
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• 제4권3호
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• pp.129-136
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• 2004

Recently, indoor air pollution has been seriously apprehended, and became a striking issue, due to the airtightness of buildings or the misuse of building materials. Especially, SHS(Sick House Syndrome) and MCS(Multi Chemical Sensitivity) which can have bad influences on the resident in an existing apartment house as well as newly constructed apartment house start to attract public attention. The emission rates of VOCs is sensitively affected by the indoor/outdoor condition, construction materials, construction method, and character of ventilation facilities. Therefore, in this study, by measuring the indoor air pollution substance of the existing apartment house, the problem over this tends to be grasped and it is going to secure an improvement methods.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.148-154
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• 1999

A method to simultaneously synthesize and consolidate $Ti_5Si_4 \;and\; Ti_5Si_3$-20 vol%Nb composite from powders of Ti, Si and Nb was investigated. Combustion synthesis was carried out under the combined effect of an electric field and mechanical pressure. Highly dense $Ti_5Si_4 \;and\; Ti_5Si_3$-20 vol% Nb with relative densities up to 98% was produced from powders of Ti, Si and Nb under the application of 60 MPa pressure and 3000A current on the reactant.

• 한국분말재료학회지
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• 제8권4호
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• pp.231-238
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• 2001

We combined Field-Activated Combustion Synthesis(FACS) with mechanical pressure to produce dense WC-20 vol.%Co composite in one step. The hardness, the fracture toughness and the relative density of the dense WC-20 vol.%Co were investigated. Under the application of 60 MPa pressure and 3000A current on the reactants, the relative density of WC-20 vol.%Co composite was 99.4%. The fracture toughness and hardness were $9.4 MPa.m^{1/2}$ and $1672kg\textrm{mm}^2$ respectively. The fracture toughness and hardness of WC-20 vol.%Co composite produced by FAPACS were lower than that of nanostructured composite, but similar to commercial ones. Therefore we concluded that the FAPACS method which can produce WC-20 vol.%Co within several minutes in one step is superior to conventional ones.

• 분석과학
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• 제35권5호
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• pp.189-196
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• 2022

When cationic basic compounds are chromatographed using hydro-organic mobile phase, the presence of anionic free silanols in the silica-based stationary phases results in broad and asymmetrical peaks. The addition of an ionic reagent to the mobile phase prevents analytes from accessing free silanols, improving peak shape. In this study, the chromatographic behavior of salbutamol sulfate as a basic compound was investigated under various conditions, including the use of different columns, mobile phases, and ion-pair reagents such as triethanolamine (TEA) and sodium heptane sulfonate (SHS). The retention and peak shape of chromatograms were both evaluated. The results show that pre-conditioning the column with TEA and including it in the mobile phase can prevent cationic analytes from accessing anionic silanols, resulting in improved peak shape. Furthermore, buffering the mobile phase is an important factor in keeping the pH constant throughout the process. The chosen method was validated in part. This study could be helpful for researchers and analyst to solve such problems with cationic basic components.

• 한국소음진동공학회논문집
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• 제14권7호
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• pp.551-560
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• 2004

A method how to determine the shock response spectrum from the FRF of the statistical energy analysis( SEA ) is presented here. The system of 3 different Plates connected by bolt joints is selected simulating missile structural sections Joined together. First, the SEA model was rendered by SEA parameters which were determined from experimental SEA method. Then, the mobility power was input to the SEA model and we can verify the validity of the model in the medium to high frequency range checking the reproduction of output average velocity. And, the shock induced shock response spectrum(SRS) was obtained using SEA FRF and arbitrarily chosen experimental FRF. We have compared the thus obtained SRS with actually measured SRS and they were relatively in good agreement. In this paper, we used the measured SEA FRF and therefore we have got the SRS well agreed with actually measured SHS even in the low frequency range. If the SEA FRF of well verified SEA model is used, the good result will come out in SEA effective frequency range which is more important at SRS.