• 제목/요약/키워드: Combined Effects

검색결과 4,197건 처리시간 0.035초

The intrinsic instabilities of fluid flow occured in the melt of Czochralski crystal growth system

  • Yi, Kyung-Woo;Koichi Kakimoto;Minoru Eguchi;Taketoshi Hibiya
    • 한국결정성장학회:학술대회논문집
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    • 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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    • pp.179-200
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    • 1996
  • The intrinsic instabilities of fluid flow occurred in the melt of the Czochralski crystal growth system Czochralski method, asymmetric flow patterns and temperature profiles in the melt have been studied by many researchers. The idea that the non-symmetric structure of the growing equipment is responsible for the asymmetric profiles is usually accepted at the first time. However further researches revealed that some intrinsic instabilities not related to the non-symmetric equipment structure in the melt could also appear. Ristorcelli had pointed out that there are many possible causes of instabilities in the melt. The instabilities appears because of the coupling effects of fluid flow and temperature profiles in the melt. Among the instabilities, the B nard type instabilities with no or low crucible rotation rates are analyzed by the visualizing experiments using X-ray radiography and the 3-D numerical simulation in this study. The velocity profiles in the Silicon melt at different crucible rotation rates were measured using X-ray radiography method using tungsten tracers in the melt. The results showed that there exits two types of fluid flow mode. One is axisymmetric flow, the other is asymmetric flow. In the axisymmetric flow, the trajectory of the tracers show torus pattern. However, more exact measurement of the axisymmetrc case shows that this flow field has small non-axisymmetric components of the velocity. When fluid flow is asymmetric, the tracers show random motion from the fixed view point. On the other hand, when the observer rotates to the same velocity of the crucible, the trajectory of the tracer show a rotating motion, the center of the motion is not same the center of the melt. The temperature of a point in the melt were measured using thermocouples with different rotating rates. Measured temperatures oscillated. Such kind of oscillations are also measured by the other researchers. The behavior of temperature oscillations were quite different between at low rotations and at high rotations. Above experimental results means that the fluid flow and temperature profiles in the melt is not symmetric, and then the mode of the asymmetric is changed when rotation rates are changed. To compare with these experimental results, the fluid flow and temperature profiles at no rotation and 8 rpm of crucible rotation rates on the same size of crucible is calculated using a 3-dimensional numerical simulation. A finite different method is adopted for this simulation. 50×30×30 grids are used. The numerical simulation also showed that the velocity and flow profiles are changed when rotation rates change. Futhermore, the flow patterns and temperature profiles of both cases are not axisymmetric even though axisymmetric boundary conditions are used. Several cells appear at no rotation. The cells are formed by the unstable vertical temperature profiles (upper region is colder than lower part) beneath the free surface of the melt. When the temperature profile is combined with density difference (Rayleigh-B nard instability) or surface tension difference (Marangoni-B nard instability) on temperature, cell structures are naturally formed. Both sources of instabilities are coupled to the cell structures in the melt of the Czochralski process. With high rotation rates, the shape of the fluid field is changed to another type of asymmetric profile. Because of the velocity profile, isothermal lines on the plane vertical to the centerline change to elliptic. When the velocity profiles are plotted at the rotating view point, two vortices appear at the both sides of centerline. These vortices seem to be the main reason of the tracer behavior shown in the asymmetric velocity experiment. This profile is quite similar to the profiles created by the baroclinic instability on the rotating annulus. The temperature profiles obtained from the numerical calculations and Fourier transforms of it are quite similar to the results of the experiment. bove esults intend that at least two types of intrinsic instabilities can occur in the melt of Czochralski growing systems. Because the instabilities cause temperature fluctuations in the melt and near the crystal-melt interface, some defects may be generated by them. When the crucible size becomes large, the intensity of the instabilities should increase. Therefore, to produce large single crystals with good quality, the behavior of the intrinsic instabilities in the melt as well as the effects of the instabilities on the defects in the ingot should be studied. As one of the cause of the defects in the large diameter Silicon single crystal grown by the

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THE LUMINOSITY-LINEWIDTH RELATION AS A PROBE OF THE EVOLUTION OF FIELD GALAXIES

  • GUHATHAKURTA PURAGRA;ING KRISTINE;RIX HANS-WALTER;COLLESS MATTHEW;WILLIAMS TED
    • 천문학회지
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    • 제29권spc1호
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    • pp.63-64
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    • 1996
  • The nature of distant faint blue field galaxies remains a mystery, despite the fact that much attention has been devoted to this subject in the last decade. Galaxy counts, particularly those in the optical and near ultraviolet bandpasses, have been demonstrated to be well in excess of those expected in the 'no-evolution' scenario. This has usually been taken to imply that galaxies were brighter in the past, presumably due to a higher rate of star formation. More recently, redshift surveys of galaxies as faint as B$\~$24 have shown that the mean redshift of faint blue galaxies is lower than that predicted by standard evolutionary models (de-signed to fit the galaxy counts). The galaxy number count data and redshift data suggest that evolutionary effects are most prominent at the faint end of the galaxy luminosity function. While these data constrain the form of evolution of the overall luminosity function, they do not constrain evolution in individual galaxies. We are carrying out a series of observations as part of a long-term program aimed at a better understanding of the nature and amount of luminosity evolution in individual galaxies. Our study uses the luminosity-linewidth relation (Tully-Fisher relation) for disk galaxies as a tool to study luminosity evolution. Several studies of a related nature are being carried out by other groups. A specific experiment to test a 'no-evolution' hypothesis is presented here. We have used the AUTOFIB multifibre spectro-graph on the 4-metre Anglo-Australian Telescope (AAT) and the Rutgers Fabry-Perot imager on the Cerro Tolalo lnteramerican Observatory (CTIO) 4-metre tele-scope to measure the internal kinematics of a representative sample of faint blue field galaxies in the red-shift range z = 0.15-0.4. The emission line profiles of [OII] and [OIII] in a typical sample galaxy are significantly broader than the instrumental resolution (100-120 km $s^{-l}$), and it is possible to make a reliable de-termination of the linewidth. Detailed and realistic simulations based on the properties of nearby, low-luminosity spirals are used to convert the measured linewidth into an estimate of the characteristic rotation speed, making statistical corrections for the effects of inclination, non-uniform distribution of ionized gas, rotation curve shape, finite fibre aperture, etc.. The (corrected) mean characteristic rotation speed for our distant galaxy sample is compared to the mean rotation speed of local galaxies of comparable blue luminosity and colour. The typical galaxy in our distant sample has a B-band luminosity of about 0.25 L$\ast$ and a colour that corresponds to the Sb-Sd/Im range of Hub-ble types. Details of the AUTOFIB fibre spectroscopic study are described by Rix et al. (1996). Follow-up deep near infrared imaging with the 10-metre Keck tele-scope+ NIRC combination and high angular resolution imaging with the Hubble Space Telescope's WFPC2 are being used to determine the structural and orientation parameters of galaxies on an individual basis. This information is being combined with the spatially resolved CTIO Fabry-Perot data to study the internal kinematics of distant galaxies (Ing et al. 1996). The two main questions addressed by these (preliminary studies) are: 1. Do galaxies of a given luminosity and colour have the same characteristic rotation speed in the distant and local Universe? The distant galaxies in our AUTOFIB sample have a mean characteristic rotation speed of $\~$70 km $s^{-l}$ after correction for measurement bias (Fig. 1); this is inconsistent with the characteristic rotation speed of local galaxies of comparable photometric proper-ties (105 km $s^{-l}$) at the > $99\%$ significance level (Fig. 2). A straightforward explanation for this discrepancy is that faint blue galaxies were about 1-1.5 mag brighter (in the B band) at z $\~$ 0.25 than their present-day counterparts. 2. What is the nature of the internal kinematics of faint field galaxies? The linewidths of these faint galaxies appear to be dominated by the global disk rotation. The larger galaxies in our sample are about 2"-.5" in diameter so one can get direct insight into the nature of their internal velocity field from the $\~$ I" seeing CTIO Fabry-Perot data. A montage of Fabry-Perot data is shown in Fig. 3. The linewidths are too large (by. $5\sigma$) to be caused by turbulence in giant HII regions.

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저단백 식이 및 항고혈압제의 투여가 만성신부전증의 진행에 미치는 영향에 관한 실험적 연구 (Renal Effects of a Low Protein Diet and Antihypertensive Drugs on the Progression of Early Chronic Renal Failure in 5/6 Nephrectomized Rats)

  • 김교순;김기혁;김상윤;강용주;맹원재
    • Childhood Kidney Diseases
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    • 제2권2호
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    • pp.125-132
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    • 1998
  • 목 적 : 초기만성신부전증에서 저단백식이를 항고혈압제와 병행 투여하였을 때 저단백식이 단독 투여 때보다 만성신부전의 진행속도 및 혈압조절에 어떠한 영향을 주는지 알기 위하여 저자들은 실험동물 백서를 이용하여 excision remnant kidney model로 만성 신부전을 유발시켰다. 방 법 : 5/6신 절제술로 만성 신부전을 유발시킨 백서를 순술 제 7일부터 무작위로 저단백식이 ($6\%$단백식이) 단독투여군, 저단백식이 enalapril 투여군 (식수 1 L당 50 mg),저단백식이 nicardipine 투여군 (사료 g당 0.2mg)로 나누어 신절제술후 4주, 12주, 16주에 단백뇨의 변화, 신 조직의 mesangial matrix expansion score 및 morphometric analysis로 분석한 사구체용적의 변화를 비교 분석하였다. 결 과 : 1)저단백식이 단독투여군은 신절제술후 계속 혈압이 증가됨을 볼 수 있었으며, 저단백식이 항고혈압제투여군은 신절제술후 8주부터 항고혈압제 투여 7주 후부터 저단백식이 단독투여군에 비해 혈압이 조절되기 시작하였다. 2)신절제술후 16주 째의 24시간 뇨단백은 세군 모두 크게 증가되지 않았으나 저단백식이 enalapril 투여군, 저단백식이 nicardipine투여군은 저단백식이 단독투여군에 비해 24시간 뇨단백의 양이 통계적으로 의미있게 낮았다. 3) 신절제술후 16주째 크레아티닌 청소 율은 저단백식이 단독투여군은 $1.57{\pm}0.11\;mL/min$, 저단백식이 enalapril 투여군 $1.37{\pm}0.14\;mL/min$, 저단백식이 nicardipine 투여군 $1.11{\pm}0.16\;ml/min$ 이었다. 4) 저단백식이 단독투여군의 잔여 신장무게는 신절제술후 4주 $1.33{\pm}0.04g$, 12주 $1.45{\pm}0.05g$, 16주 $1.44{\pm}0.16g$으로 12주 이후 잔여 신장무게의 증가를 관찰할 수 없었다. .신절제술후 16주에 관찰한 저단백식이 단독투여군과 저단백식이 항고혈압제투여군간의 잔여 신장무게는 통계적인 차이는 없었다. 5) 저단백식이 단독투여군의 mesangial matrix expansion score는 12주째 증가소견을 보였고 저단백식이 항고혈압제투여군은 항고혈압제 투여에도 불구하고 12주 이후 mesangial matrix expansion score의 의미있는 증가소견이 없었고 세군 간의 차이도 없었다. 6) 저단백식이 단독투여군의 사구체용적은 12주째 증가소견을 보였고 저단백식이 항고혈압제 투여군은 항고혈압제 투여에도 불구하고 12주 이후 사구체용적의 의미있는 증가소견이 없었고 세군 간의 차이도 없었다. 결 론 : 초기만성신부전증에서 저단백식이는 혈압을 조절시키지 못하였고 저단백식이 항고혈압제투여군은 저단백식이 단독투여군보다 혈압조절 및 단백뇨의 감소 소견은 유의한 차이를 보였으나, mesangial matrix expansion score,대상성 사구체비대는 통계적으로 유의한 차이를 보이지 않았다. 그러므로 만성신부전의 진행을 지연시키는데 있어서 저단백식이와 함께 항고혈압제를 추가하였을 때 항고혈압제에 의한 추가적인 지연 효과는 관찰되지 않았다.

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깔개물질의 종류에 따른 한우-경종 결합 농가의 양분순환 구조 분석 (Analysis of Nutrient Cycling Structure of a Korean Beef Cattle Farm Combined with Cropping as Affected by Bedding Material Types)

  • 임상선;곽진협;박현정;이선일;이동석;김용순;윤봉기;김선우;최우정
    • 한국토양비료학회지
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    • 제41권5호
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    • pp.354-361
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    • 2008
  • 본 연구에서는 깔개물질에 의한 양분 유입 및 축사 내 분뇨 방치 및 퇴비화 과정 중 발생하는 양분손실이 양분순환에 미치는 영향을 조사하기 위해 전남 지역 한우 농가(사육두수 100두, 경지 면적 2.5 ha)를 대상으로 사료$\rightarrow$ 가축 $\rightarrow$ 분뇨 $\rightarrow$ 퇴비 $\rightarrow$ 토양 $\rightarrow$ 사료의 양분순환구조를 분석하였다. 분뇨에 의해 발생한 질소와 인산을 기준으로 비교했을 때, 톱밥을 깔개물질로 사용할 경우 질소 1.6%, 인산 3.1%, 왕겨의 경우 질소의 14.2%와 인산 27.4%가 추가로 공급 되는 것으로 나타났다. 따라서, 양분수지 또는 양분순 환구조 분석에서 깔개물질의 종류와 사용량도 고려할 필요가 있다. 양분순환구조의 가장 큰 특징은 우사내 분뇨의 야적기간(21일)과 퇴비화 기간(90일) 동안에 발생하는 물질과 양분의 손실이었다. 톱밥퇴비의 경우 이 기간 동안 질소의 78.4%, 인산의 9.5%가 손실되었으며, 왕겨퇴비의 경우 각각의 손실률은 81.6%와 10.3%였다. 톱밥 퇴비의 물질 및 양분 손실률이 낮은 것은 톱밥의 C/N 비와 난분해성인 리그닌 함량이 높아서 유기물 분해가 상대적으로 느리게 일어났기 때문으로 판단되었다. 기존의 양분수지 연구는 대부분 분뇨 발생 시점의 양분함량을 기준으로 계산하였지만, 본 연구의 결과에 의하면 분뇨 발생 이후부터 농 경지 시용 이전까지 발생하는 양분손실과 이에 영향 을 미치는 깔개 물질의 특성을 고려하여야만 정확한 양분수지 구명이 가능한 것으로 나타났다.

고추장 추출물을 급여한 Sprague-Dawley-Rat에서의 혈중지질 농도의 변화 양상 (Variation Patterns of the Blood Lipid Levels on the Sprague-Dawley-Rats Fed with Kochujang Extracts)

  • 우용구;김태효;고종호
    • 한국식품영양학회지
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    • 제26권4호
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    • pp.737-744
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    • 2013
  • 오늘날 현대인들의 식생활방식 중 과다한 열량의 영양소 섭취로 인하여 초래되는 비만의 유발 원인 중의 하나로 알려진 고지혈증(hyperlipidemia)에 대한 예방효과가 있는 것으로 알려진 전통방식으로 제조된 고추장의 생리활성 기능성 효과를 분석하고자 하였다. 이 연구에서는 실험동물로서 Sprague-Dawley(SD)-Rat에 대해서 고추장 추출물의 건강증진 효과에 대해서 실험동물을 사용하여 직접 확인하고 시도하였다. 실험군은 실험동물용 일반사료만을 먹인 음성대조군 그룹(N-group)과 일반사료와 고추장 추출물을 동시에 먹인 시험그룹(K-group) 그리고 양성대조군으로 고콜레스테롤 사료만을 먹인 그룹(H-group)으로 구분하여 5주간 사육하면서 건강증진효과의 발현에 대해서 분석하였다. 3그룹의 실험동물을 5주간의 사육 후 해부했을 때 H-group의 모든 동물(100%)에서 공통적으로 심한 지방간(fatty liver) 소견이 관찰되었으나, N-group이나 K-group의 어떠한 동물에서도 지방간 소견은 관찰되지 않았다. 한편, 실험동물의 혈장성분에 대한 혈액생화학적 성적의 비교에서는 고지혈증의 예방에 유익한 성분으로 알려진 HDL의 경우, 고추장 추출물 투여 그룹($25{\pm}8.43mg/d{\ell}$)은 H-group($22.6{\pm}4.16$) 보다 다소간 상승된 수치를 보였으나, 특히 고지혈증을 악화시키는 원인으로 알려진 LDL 경우에는 H-group ($55.8{\pm}44.8mg/d{\ell}$)이 고추장 추출물 투여 그룹($8.6{\pm}1.52mg/d{\ell}$)과 음성대조군인 N-group($9.8{\pm}2.39$)의 성적보다도 유의적으로 높은 수치를 나타냈다. 결과적으로 이 연구에서 SD-Rat에 투여했던 고추장 추출물은 실험동물에서 건강기능 개선효과의 하나인 저지방혈증 효과를 발현한 것으로 사료되었다.

윤환관개의 방법의 차이가 수도생육 및 수량에 미치는 영향과 그 적정시설에 관한 연구 (Studies on the Effects of Variation Methods of Rotation Irrigation Systems Affecting on the Growth, Yield of Rice Plant and its Optimum Facilities)

  • 이창구
    • 기술사
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    • 제2권5호
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    • pp.4-18
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    • 1969
  • This experiment was conducted, making use of the "NONG-RlM 6", a recommended variety of rice for year of 1968. Main purposes of the experiment are to explore possibilities of: a) ways and means of saving irrigation water and, b) overcoming drought at the same time so that an increased yield in rice could be resulted in. Specifically, it was tried to determine the effects of the circulation irrigation method combined with differentiated thickness of lining upon the growth and yield of rice. Some of the major findings are summarized in the following. 1) The different thicknesses show a significant relationship with the weight of 1,000 grains. In the case of 9cm-lined plot, the grain weight is 23.5 grams, the heaviest. Next in order are 3cm-lined plot, 6cm-lined plot, control plot, and wheat straw lined-plot. 2) In rice yield, it is found that there is a considerably moderate significant relationship with both the different thickness of lining and the number of irrigation, as shown in the table. 3) There is little or no difference among different plots in terms of a) physical and chemical properties of solid, b) quality of irrigation water, c) climatic conditions, and rainfalls. 4) It is found that there is a significant relationship between differences in the method of rotation irrigation and the number of ears per hill. The plot irrigated at an interval of 7 days shows 17.4 ears and the plot irrigated at an interval of 6 days, 16.3. 5) In vinyl-treated plots, it is shown that both yield and component element are greatest in the case of the plot with hole of 3$cm/m^2$. Next in order are; the plot with a hole of 2$cm/m^2$; the plot with a hole of 1$cm/m^2$. In the case of the plot with no hole, it is found that both yield and component elements are decreased as compared to the control plot. 6) The irrigation water requirement is measured for the actual irrigation days of 72 which are the number subtracted the days of rainfall of 30 from the total irrigation days of 102. It is found that the irrigation water requirement for the un control plot is 1,590 mm, as compared to 876 mm (44.9% saved) for the 9cm-lined plot, 959mm(39.7% saved) for the 6cm-lined plot, 1,010mm (36% saved) for the 3cm-lined plot, and 1,082mm (32% saved) for the wheat straw lined plot. In the case of the rotation irrigation method, it is found that the water requirement for the plot irrigated at an interval of 8 days is 538mm (65.3% saved), as compared to 617mm (61.1% saved) for the plot irrigated at an interval of 7 days, 672mm (57.7% saved) for the plot irrigated at an interval of 6 days, 746mm (53.0% saved) for the plot irrigated at an interval of 5 days, 890mm (44.0% saved) for to plot irrigated at an interval of 4 days, and 975mm (38.6% saved) for the plot irrigated at an interval of 3 days. 7) The rate of evapo-transpiration is found 2.8 around the end of the month of July, as compared to 2.6 at the begining of August, 3.4 around the end of August, and 2.6 at the begining of September. 8) It is found that the saturaton quantity of 30 mm per day is decreased to 20mm per day through the use of vinyl covering. 9) The husking rate shows 75 per cent which is considered better.

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두경부종양 환자에서 경부 방사선조사가 갑상선기능에 미치는 영향 -75예의 전향적 분석- (The Effects of Neck Irradiation on Thyroid Gland for Tumors of the Head and Neck -A prospective analysis of 75 cases-)

  • 박인규;김상보;윤상모;박준식;전수한;김보완
    • Radiation Oncology Journal
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    • 제12권1호
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    • pp.59-66
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    • 1994
  • 1986년 9월부터 1992년 10월까지 경북대학교병원 치료방사선과에서 방사선치료 단독요법이나 수술 흑은 화학요법과의 병합요법으로 치료받은 두경부종양 환자 75명을 대상으로 경부 방사선조사가 갑상선기능에 미치는 영향을 평가하기 위하여 전향적 조사를 실시하였다. 모든 환자는 방사선치료전 및 방사선치료후에 정기적으로 임상검사 및 갑상선 기능검사를 시행하였다. 갑상선조사선량은 35Gy에서 60Gy였고 그 중앙값은 50Gy였으며 추적관찰기간은 11개월에서 85개월로 중앙추적기간은 30개월 이었다. 결과를 보면 갑상선 기능이상의 빈도는 40$ \% $(30명)이었다. 45명(60$ \% $)은 갑상선 기능이 정상이었으며 2명(3$ \% $)은 임상적 갑상선 기능저하증 이었고 27명(36$ \% $)은 준임상적 갑상선 기능저하증 이었다. 갑상선 기능항진증이 1명(1$ \% $)에서 발견되었으며 갑상선 결절이나 악성종양은 발견되지 알았다. 수술 및 방사선치료군에서 갑상선 기능이상이 다른 치료군에서보다 일찍 발생하였다(p=0.0013). 다변량분석에 따르면 방사선치료후 갑상선 기능이상의 발생빈도에 영향을 주는 위험인자는 여성(p=0.0293) 및 전후두절제술과 방사선치료의 병합요법(p=0.0045)였다. 결론적으로 방사선치료후 정확한 시기에 갑상선 기능이상을 발견하기 위하여 방사선 치료전 및 방사선 치료후에 정기적인 갑상선 기능검사가 필요하며 갑상선 기능이상이 발견되면 즉시 갑상선 호르몬제재 치료를 하여야 하겠다.

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소규모 기업에 있어서 지식소싱 전략이 기업성과에 미치는 영향 고찰 (An Examination of Knowledge Sourcing Strategies Effects on Corporate Performance in Small Enterprises)

  • 최병구
    • Asia pacific journal of information systems
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    • 제18권4호
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    • pp.57-81
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    • 2008
  • Knowledge is an essential strategic weapon for sustaining competitive advantage and is the key determinant for organizational growth. When knowledge is shared and disseminated throughout the organization, it increases an organization's value by providing the ability to respond to new and unusual situations. The growing importance of knowledge as a critical resource has forced executives to pay attention to their organizational knowledge. Organizations are increasingly undertaking knowledge management initiatives and making significant investments. Knowledge sourcing is considered as the first important step in effective knowledge management. Most firms continue to make an effort to realize the benefits of knowledge management by using various knowledge sources effectively. Appropriate knowledge sourcing strategies enable organizations to create, acquire, and access knowledge in a timely manner by reducing search and transfer costs, which result in better firm performance. In response, the knowledge management literature has devoted substantial attention to the analysis of knowledge sourcing strategies. Many studies have categorized knowledge sourcing strategies into intemal- and external-oriented. Internal-oriented sourcing strategy attempts to increase firm performance by integrating knowledge within the boundary of the firm. On the contrary, external-oriented strategy attempts to bring knowledge in from outside sources via either acquisition or imitation, and then to transfer that knowledge across to the organization. However, the extant literature on knowledge sourcing strategies focuses primarily on large organizations. Although many studies have clearly highlighted major differences between large and small firms and the need to adopt different strategies for different firm sizes, scant attention has been given to analyzing how knowledge sourcing strategies affect firm performance in small firms and what are the differences between small and large firms in the patterns of knowledge sourcing strategies adoption. This study attempts to advance the current literature by examining the impact of knowledge sourcing strategies on small firm performance from a holistic perspective. By drawing on knowledge based theory from organization science and complementarity theory from the economics literature, this paper is motivated by the following questions: (1) what are the adoption patterns of different knowledge sourcing strategies in small firms (i,e., what sourcing strategies should be adopted and which sourcing strategies work well together in small firms)?; and (2) what are the performance implications of these adoption patterns? In order to answer the questions, this study developed three hypotheses. First hypothesis based on knowledge based theory is that internal-oriented knowledge sourcing is positively associated with small firm performance. Second hypothesis developed on the basis of knowledge based theory is that external-oriented knowledge sourcing is positively associated with small firm performance. The third one based on complementarity theory is that pursuing both internal- and external-oriented knowledge sourcing simultaneously is negatively or less positively associated with small firm performance. As a sampling frame, 700 firms were identified from the Annual Corporation Report in Korea. Survey questionnaires were mailed to owners or executives who were most erudite about the firm s knowledge sourcing strategies and performance. A total of 188 companies replied, yielding a response rate of 26.8%. Due to incomplete data, 12 responses were eliminated, leaving 176 responses for the final analysis. Since all independent variables were measured using continuous variables, supermodularity function was used to test the hypotheses based on the cross partial derivative of payoff function. The results indicated no significant impact of internal-oriented sourcing strategies while positive impact of external-oriented sourcing strategy on small firm performance. This intriguing result could be explained on the basis of various resource and capital constraints of small firms. Small firms typically have restricted financial and human resources. They do not have enough assets to always develop knowledge internally. Another possible explanation is competency traps or core rigidities. Building up a knowledge base based on internal knowledge creates core competences, but at the same time, excessive internal focused knowledge exploration leads to behaviors blind to other knowledge. Interestingly, this study found that Internal- and external-oriented knowledge sourcing strategies had a substitutive relationship, which was inconsistent with previous studies that suggested complementary relationship between them. This result might be explained using organizational identification theory. Internal organizational members may perceive external knowledge as a threat, and tend to ignore knowledge from external sources because they prefer to maintain their own knowledge, legitimacy, and homogeneous attitudes. Therefore, integrating knowledge from internal and external sources might not be effective, resulting in failure of improvements of firm performance. Another possible explanation is small firms resource and capital constraints and lack of management expertise and absorptive capacity. Although the integration of different knowledge sources is critical, high levels of knowledge sourcing in many areas are quite expensive and so are often unrealistic for small enterprises. This study provides several implications for research as well as practice. First this study extends the existing knowledge by examining the substitutability (and complementarity) of knowledge sourcing strategies. Most prior studies have tended to investigate the independent effects of these strategies on performance without considering their combined impacts. Furthermore, this study tests complementarity based on the productivity approach that has been considered as a definitive test method for complementarity. Second, this study sheds new light on knowledge management research by identifying the relationship between knowledge sourcing strategies and small firm performance. Most current literature has insisted complementary relationship between knowledge sourcing strategies on the basis of data from large firms. Contrary to the conventional wisdom, this study identifies substitutive relationship between knowledge sourcing strategies using data from small firms. Third, implications for practice highlight that managers of small firms should focus on knowledge sourcing from external-oriented strategies. Moreover, adoption of both sourcing strategies simultaneousiy impedes small firm performance.

5가지 (고들빼기, 돌미나리, 메밀, 톳, 생강)혼합식품 물 추출물의 마우스 면역세포 활성화 효과 (Effects of Plant Water Extract Mixture Ixeris Sonchifolia Hance, Oenanthevjavanica, Fagopyrum Esculentum Moench, Hizikia Fusiforme, Zingiber Officinale Roscoe on Mouse Immune Cell Activation Ex vivo)

  • 류혜숙;김현숙;김정희
    • Journal of Nutrition and Health
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    • 제41권2호
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    • pp.141-146
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    • 2008
  • 생체 내 (ex vivo) 실험에서 혼합 (고들빼기, 돌미나리, 메밀, 톳, 생강)시료의 물 추출물을 4주간 격일로 마우스 체중 kg 당 0, 50, 500 mg/kg B.W.의 농도로 마우스에 경구 투여한 후 비장세포 증식능, LPS에 의해 활성화된 복강 대식세포가 분비하는 염증성 사이토카인 ($IL-1{\beta}$, IL-6, $TNF-{\alpha}$)의 생성량을 측정하였다. 그 결과 혼합시료의 물추출물은 ConA나 LPS로 자극하지 않은 경우 50 mg./kg B.W. 농도에서 대조군에 비해 유의적으로 높은 비장 증식능을 보였다. LPS에 의해 활성화된 복강 대식세포의 사이토카인 분비량을 측정한 결과에서도 $IL-1{\beta}$, IL-6, $TNF-{\alpha}$의 분비량은 마우스 체중 kg 당 50 mg/kg B.W. 농도의 투여군에서 높은 생성량을 보여주었으나, 500 mg/kg B.W.의 농도 투여군에서는 IL-6 분비량은 대조군에 비해 높은 반면 $TNF-{\alpha}$의 분비량은 큰 차이를 보이지 않았다. 이상의 결과에 따라 비장세포 증식능과 사이토카인 분비능을 검색한 결과 고들빼기, 도미나리, 메밀, 톳, 생강을 혼합한 혼합시료의 추출물 50 mg/kg B.W. 농도 투여가 면역 세포와 면역 기관의 주요기능을 증진시키리 가능성이 있을 것으로 사료된다. 이러한 연구결과를 토대로 앞으로 혼합식을 통한 기능성 식품 개발에 기초 연구 자료가 될 것으로 기대된다.

조직배양 유래 자생나리 소인경의 온탕 및 저온처리가 맹아 및 비대에 미치는 효과 (Effects of Hot Water and Chilling Treatments of Bulblets Propagated by Tissue Culture on Sprouting and Bulb Development in Korean Native Lilies)

  • 김민희;임영희;오욱;윤해근;김규원
    • 원예과학기술지
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    • 제29권2호
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    • pp.87-94
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    • 2011
  • 본 연구에서는 관상가치가 높은 5종의 자생나리에 있어서 조직배양을 통해 획득한 소인경의 휴면타파 및 비대를 위한 저온 및 온탕처리 효과를 구명하기 위해 실시되었다. 솔나리(L. cernuum), 섬말나리(L. hansonii), 민섬말나리(L. hansonii for. mutatum), 중나리(L. leichtlinii), 하늘말나리(L. tsingtauense)의 소인경을 $4^{\circ}C$에서 0, 4, 8주 저온처리하거나 $35^{\circ}C$의 증류수 또는 $100mg{\cdot}L^{-1}$$GA_3$$GA_{4+7}$ 용액으로 2시간 온탕처리를 하였는데, 저온과 온탕처리는 처리의 선후를 달리하면서 순차적으로 처리한 후 $20^{\circ}C$의 유리온실에서 맹아 및 비대 양상을 조사하였다. 자생나리 5종 모두 기내 소인경은 모두 휴면에 돌입하여 저온 또는 온탕처리 없이는 맹아하지 않았다. 휴면타파를 위한 온탕처리에는 5종 모두 $GA_{4+7}$이 55-96%까지 맹아를 유도한 반면, 증류수나 $GA_3$ 용액은 거의 효과가 없었다. 솔나리와 중나리는 4주간의 저온처리만으로도 50-70%의 맹아를 유도한 반면, 섬말나리, 민섬말나리의 맹아에는 8주간의 저온처리가 필요했다. 온탕과 저온의 연속처리는 맹아 유도에 상승효과를 주었는데, 솔나리와 섬말나리에서 $GA_{4+7}$ 온탕처리 후 4주 저온처리한 것이 역순의 처리보다 맹아를 35-45% 촉진시켰으며, 맹아소요일수도 3-9일까지 앞당겼다. 구근의 비대는 맹아가 촉진된 처리구에서 증가된 경향이었다. 신초는 솔나리에서만 출현하였는데, $GA_{4+7}$ 온탕처리와 저온처리에서 효과적이었으며, 특히 $GA_{4+7}$ 온탕처리 후 저온 8주 처리에서 신초 출현률이 가장 높게 나타났다. 이상의 결과를 종합할 때, 맹아 및 인경비대를 위해 가장 효과적인 휴면타파법은 섬말나리, 민섬말나리와 중나리의 경우에는 $GA_{4+7}$온탕처리 후 4주 저온처리였고, 솔나리와 하늘말나리에서는 $GA_{4+7}$ 온탕처리 후 8주 저온처리구였다.