• 한국식품영양과학회지
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• 제26권6호
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• pp.1013-1020
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• 1997

To elicit the effect of fermentation on food quality of the watery Chinese cabbage pickles without fish sauce and red pepper paste(Baik-kimchi), changes in physicochemical properties and microstructure of fiber components were studied. Better water holding capacity(WHC) was showed in Baik-kimchi fermented at $25^{\circ}C$ than that of Baik-kimchi fermented at 5$^{\circ}C$. WHC measured at pH 2 and 6 were ranged from 10.18 to 16.79g/g dried sample for Baik-kimchi fermented at $25^{\circ}C$ and 6.51~14.58g/g dried sample for sample for samples at 5$^{\circ}C$, respectively. The higher WHC was resulted in pH controlled freeze-dried sample to pH 6 than that measured in pH 2 sample. The settling volume(SV) and oil adsorption capacity(OAC) increased with fermentation period and kept the same value for a little while, but slightly decreased in the over ripening period. Baik-kimchi fermented at $25^{\circ}C$ exhibited more shrunk microstructure of parenchyma cell and xylem than those of Baik-kimchi fermented at 5$^{\circ}C$. The appearance of SDF of the both Baik-kimchi ripened at 5$^{\circ}C$ and $25^{\circ}C$ could give granular shape, whereas the overripened Baik-kimchi had smooth surface of SDF. On the other hand, the IDF retained the original shape during fermentation.

• 아태비즈니스연구
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• 제10권2호
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• pp.27-41
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• 2019

Following the methodology of Ben-Rephael, Kadan and Wohl (2015), this paper examines whether firm-level liquidity premium exists and whether the premium exhibits a long-term trend in the Korean stock market. The results show that over the whole sample period (1998-2018), a liquidity premium of 0.083% exists in the cross-section of stocks. Interestingly, the pricing of liquidity declines significantly over the sample period. Sub-period analysis indicates that liquidity is priced mainly in the first sub-period (1998-2004) with a significant monthly premium of 0.304%, while the pricing of liquidity becomes weaker or insignificant in the second (2005-2011) and the third (2012-2018) period. I also find that the significance of the liquidity premium in the first period is attributed to small stocks. To explore underlying reasons that might affect the decline in the liquidity premium, I decompose liquidity premium into the product of firm-level liquidity and the sensitivity of expected stock returns on liquidity. The results reveal that the long-term decline is explained by both an increase in firm-level liquidity and a decrease in the sensitivity of expected returns on liquidity.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.279.2-279.2
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• 2016

InGaN/GaN multiple quantum wells (MQWs) have been attracted much attention as light-emitting diodes (LEDs) in the visible and UV regions. Particularly, quantum efficiency of green LEDs is decreased dramatically as approaching to the green wavelength (~500 nm). This low efficiency has been explained by quantum confined Stark effect (QCSE) induced by piezoelectric field caused from a large lattice mismatch between InGaN and GaN. To improve the quantum efficiency of green LED, several ways including epitaxial lateral overgrowth that reduces differences of lattice constant between GaN and sapphire substrates, and non-polar method that uses non- or semi-polar substrates to reduce QCSE were proposed. In this study, graded short-period InGaN/GaN superlattice (GSL) was grown below the 5-period InGaN/GaN MQWs. InGaN/GaN MQWs were grown on the patterned sapphire substrates by vertical-metal-organic chemical-vapor deposition system. Five-period InGaN/GaN MQWs without GSL structure (C-LED) were also grown to compare with an InGaN/GaN GSL sample. The luminescence properties of green InGaN/GaN LEDs have been investigated by using photoluminescence (PL) and time-resolved PL (TRPL) measurements. The PL intensities of the GSL sample measured at 10 and 300 K increase about 1.2 and 2 times, respectively, compared to those of the C-LED sample. Furthermore, the PL decay of the GSL sample measured at 10 and 300 K becomes faster and slower than that of the C-LED sample, respectively. By inserting the GSL structures, the difference of lattice constant between GaN and sapphire substrates is reduced, resulting that the overlap between electron and hole wave functions is increased due to the reduced piezoelectric field and the reduction in dislocation density. As a results, the GSL sample exhibits the increased PL intensity and faster PL decay compared with those for the C-LED sample. These PL and TRPL results indicate that the green emission of InGaN/GaN LEDs can be improved by inserting the GSL structures.

• 한국식품조리과학회지
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• 제24권4호
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• pp.487-493
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• 2008

This study examined barley sprout powder on the quality and preservation of Sulgidduk. An optimized formulation (moisture 18.2%, barley sprout powder 2.0% and sugar 14.8%) was first obtained, and then the affect if incorporating the barley sprout powder as a raw ingredients in the mixture was evaluated in terms of Sulgidduk shelf life and quality. For comparison, a control Sulgidduk sample was prepared using the optimized formulation exclusive of the barley sprout powder. After preparation the samples were stored for 3 days at $20{\pm}1^{\circ}C$. The moisture contents of both samples slightly decreased during storage: however there was no significant difference between the samples. Both samples had decreases in colorimetric L- and a-value attributable to the addition of the barley sprout powder as well as storage. Furthermore the treatment sample had increases in yellowness due to the addition of barley sprout powder and storage while the control sample had decreases in yellowness throughout the storage period. The treatment sample had increasing textural hardness, gumminess, and chewiness as the storage period increased. Finally, the treatment sample had a higher total microbial count for aerobes at the beginning of storage: however, as the storage period progressed the control had greater microbial levels. In conclusion the overall results indicate the addition of barley sprout powder has a preservaion effect on Sulgidduk. This data is expected to contribute to the commercialization of high-quality Sulgidduk products with added nutrition and extended shelf life.

• 한국안전학회지
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• 제7권4호
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• pp.45-53
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• 1992

Sponataneous ignition characteristics for granulated activated carbon were observed by performing experiments at constant ambient temperature and varying the ambient temperature sinusoidally. In case of varying the ambient temperature sinusoidally, the amplitudes of temperature were 5$^{\circ}C$, 1$0^{\circ}C$ and 15$^{\circ}C$ respectively, and the period in each amplitude was varied at an interval of 30minutes from zero to 3hours. As the results of experiments at a constant ambient temperature, the critical spontaneous ignition temperature of the sample decreased as the sample vessel size increased. Apparent activation energy of the sample calculated from the Frank-Kamenetskii's thermal Ignition theory was 38.82［kca1/mo1］ In case of varying the ambient temperature sinusoidally, the critical spontaneous ignition tempera-ture was lower than that at the constant ambient temperature, and the minimum critical spontaneous ignition temperature decreased with the amplitude of heating sinusoidal curve. At the same amplitude, the critical spontaneous ignition temperature decreased until it reached the minimum point and then in-creased as the period increased.

• 한국식품영양과학회지
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• 제24권5호
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• pp.752-757
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• 1995

발효숙성 온도를 달리한 돌산 갓 김치의 저장 중 pH, 산도, 염도, 색도, 비타민 C 등의 이화학적 특성을 알아 보았다. 발효숙성 방법으로는 $4^{\circ}C(A),\;20^{\circ}C(B),\;20^{\circ}C$에서 12시간 숙성시킨 후 $4^{\circ}C$에 저장하는 방법(C), $20^{\circ}C$에서 36시간 숙성시킨 후 $4^{\circ}C$에 저장하는 방법(D)으로 하였다. 돌산 갓 김치 담금 직후의 pH는 5.24이었고, $20^{\circ}C$에서 12시간과 36시간 숙성시킨 후 $4^{\circ}C$에 저장된 C, D군에서 각각 pH 5.13, pH 5.10으로 A군 보다 모두 낮았으며 B군에서는 급속하게 변화하였다. 갓 김치의 적숙기라 할 수 있는 pH 4.6~4.8이 되는 시기는 A군이발효 78~96일, B군은 6~9일, 그리고 C, D군은 모두 68~88일로 같게 나타났다. 총산 함량에 있어서는 담금 직후 0.5%이었고, C, D군은 모두 0.6%으로 A군의 0.5%보다 모두 높게 나타났다. 또한 pH 4.6~4.8이 되는 시기의 총산 함량에 있어서 A군은 0.75~0.82%, B군은 0.65~0.70%, C군은 0.80~0.81%, D군 0.82~0.84%이었다. 갓 김치의 염도는 $20^{\circ}C$인 B군에서 증가폭이 컸고, 다음으로 D > A > C 순으로 나타났다. 도는 발효가 진행됨에 따라 L, a값은 증가했다가 다시 감소하였고 b값은 증가하였다. 특히 B군에서 L값이 적숙기에 증가하여 밝아지는 현상을 나타내었으나, 최종 김치의 색은 C > D > A > B 순으로 좋게 나타났다. 발효숙성일수가 경과함에 따라 총 비타민 C 함량은 9.0~14.0mg%까지 감소하였으며 적숙기에 가서 22.0mg%로 다소 증가 하다가 후기에 서서히 감소하였다. A군은 완만한 감소(25~22 %)를 보인 반면 B군은 다소 감소폭(25~7.0mg%)이 컸다. 발효 후기의 총 비타민 C 보유량에는 A > D > C > B 순으로 높게 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제48권6호
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• pp.896-906
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• 2020

Wood deterioration experiments were carried out for 6 months in an intertidal zone of South Korea to monitor the changes in the chemical properties of two types of species, Korean red pine and sawtooth oak. The results of FT-IR spectra and XRD patterns have shown that the chemical properties of the wood did not change significantly during the 6-month burial period. However, the brightness of the surface decreased after burial; the value of the sawtooth oak sample was lower than that of the Korean red pine sample owing to an accumulation of inorganic compounds in cell lumen as observed by ICP analysis. Among the inorganic compounds, sodium and sulfur concentrations increased significantly over the burial period compared with the control. Further, the maximum moisture content decreased from 199% to 136% in the Korean red pine and 62% to 60% for the sawtooth oak. Nevertheless, the major chemical composition of both the wood species did not change significantly during the 6-month burial period, whereas, the crystallinity decreased with an increasing burial period owing to an accumulation of inorganic compounds in the lumen.

• Journal of the Korean Statistical Society
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• 제29권1호
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• pp.29-44
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• 2000

In this paper, we consider one-level rotation designs with finite rotation groups such that the design satisfies two basic requirements: all rotation groups are included in any given survey period, and overlapping rates depend only on the time lag. First we present the necessary number of rotation groups and a rule for the length of time the sample units are to be in or out of the sample to satisfy the requirements. Second, an algorithm is presented to put rotation groups to proper positions in a panel in order to include all finite rotation groups for any survey period. Third, we define an one-level rotation pattern which is invariant in the survey period and has useful properties in practical sense.

• 농업과학연구
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• 제35권1호
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• pp.1-9
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• 2008

메주를 만들 때 저온숙성의 경우 상온숙성보다 발효 특성과 관련이 있는 pH, 아미노산성 질소 등의 양이 낮았으며 동일한 아미노태 질소 함량에 도달하기까지 숙성기간이 약 2~3배정도 필요한 것으로 나타났고, 된장의 색상이 약 2배정도 밝은 것으로 나타났다. 그리고 숙성초기 낮은 온도로 인해 산성생균의 활동성이 낮아지고 이로 인한 유기산 생성량이 낮아져 상온숙성 된장에 비해 pH가 높고, acidity I이 낮으며, 저온숙성된장은 가수분해 효소에 의한 분해속도의 저하로 낮은 아미노산성 질소 함량을 보였다.

• 한국식품영양과학회지
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• 제30권2호
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• pp.199-203
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• 2001

Chopi, Zanthaxylum piperitum DC., has been used as natural spice traditionally in the Far East countries including Korea. This study was performed with the object of providing basic data, firstly for the decision of the appropriate harvesting time for traditional use of chopi and secondly for developing a new spice satisfying the national dietary custom from chopi as raw material. Concerning the conte수 and its change of the proximate composition, the content of moisture and crude protein decreased in all sample, while the content of fiber and ash tended to increased with the lapse of harvest time. The content of mineral elements tended to increase in every sample with the lapse of harvest time, and contents of K and P were higher than that of Ca, Na and Mg. Every sample showed the highest content of 15~16 components of total amino acids at the first period and the content decreased gradually with the lapse of harvest time. On the basis of the first period, every sample showed the highest content of aspartic acid, the lowest content of methionine and the trace of cysteine. Free amino acids increased considerably with the lapse of harvest time for peels of chopi and minchopi broth, while the amount for leaves increased on the contrary.