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Accuracy of HF radar-derived surface current data in the coastal waters off the Keum River estuary (금강하구 연안역에서 HF radar로 측정한 유속의 정확도)

  • Lee, S.H.;Moon, H.B.;Baek, H.Y.;Kim, C.S.;Son, Y.T.;Kwon, H.K.;Choi, B.J.
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.13 no.1
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    • pp.42-55
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    • 2008
  • To evaluate the accuracy of currents measured by HF radar in the coastal sea off Keum River estuary, we compared the facing radial vectors of two HF radars, and HF radar-derived currents with in-situ measurement currents. Principal component analysis was used to extract regression line and RMS deviation in the comparison. When two facing radar's radial vectors at the mid-point of baseline are compared, RMS deviation is 4.4 cm/s in winter and 5.4 cm/s in summer. When GDOP(Geometric Dilution of Precision) effect is corrected from the RMS deviations that is analyzed from the comparison between HF radar-derived and current-metermeasured currents, the error of velocity combined by HF radar-derived current is less than 5.1 cm/s in the stations having moderate GDOP values. These two results obtained from different method suggest that the lower limit of HF radar-derived current's accuracy is 5.4 cm/s in our study area. As mentioned in previous researches, RMS deviations become large in the stations located near the islands and increase as a function of mean distance from the radar site due to decrease of signal-to-noise level and the intersect angle of radial vectors. We found that an uncertain error bound of HF radar-derived current can be produced from the separation process of RMS deviations using GDOP value if GDOP value for each component is very close and RMS deviations obtained from current component comparison are also close. When the current measured in the stations having moderate GDOP values is separated into tidal and subtidal current, characteristics of tidal current ellipses analyzed from HF radar-derived current show a good agreement with those from current-meter-measured current, and time variation of subtidal current showed a response reflecting physical process driven by wind and density field.

Study on the Difference in Intake Rate by Kidney in Accordance with whether the Bladder is Shielded and Injection method in 99mTc-DMSA Renal Scan for Infants (소아 99mTc-DMSA renal scan에서 방광차폐유무와 방사성동위원소 주입방법에 따른 콩팥섭취율 차이에 관한 연구)

  • Park, Jeong Kyun;Cha, Jae Hoon;Kim, Kwang Hyun;An, Jong Ki;Hong, Da Young;Seong, Hyo Jin
    • The Korean Journal of Nuclear Medicine Technology
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    • v.20 no.2
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    • pp.27-31
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    • 2016
  • Purpose $^{99m}Tc-DMSA$ renal scan is a test for the comparison of the function by imaging the parenchyma of the kidneys by the cortex of a kidney and by computing the intake ratio of radiation by the left and right kidney. Since the distance between the kidneys and the bladder is not far given the bodily structure of an infant, the bladder is included in the examination domain. Research was carried out with the presumption that counts of bladder would impart an influence on the kidneys at the time of this renal scan. In consideration of the special feature that only a trace amount of a RI is injected in a pediatric examination, research on the method of injection was also carried out concurrently. Materials and Methods With 34 infants aged between 1 month to 12 months for whom a $^{99m}Tc-DMSA$ renal scan was implemented on the subjects, a Post IMAGE was acquired in accordance with the test time after having injected the same quantity of DMSA of 0.5mCi. Then, after having acquired an additional image by shielding the bladder by using a circular lead plate for comparison purposes, a comparison was made by illustrating the percentile of (Lt. Kidney counts + Rt. Kidney counts)/ Total counts, by drawing the same sized ROI (length of 55.2mm X width of 70.0mm). In addition, in the format of a 3-way stopcock, a Heparin cap and direct injection into the patient were performed in accordance with RI injection methods. The differences in the count changes in accordance with each of the methods were compared by injecting an additional 2cc of saline into the 3-way stopcock and Heparin cap. Results The image prior to shielding of the bladder displayed a kidney intake rate with a deviation of $70.9{\pm}3.18%$ while the image after the shielding of the bladder displayed a kidney intake rate with a deviation of $79.4{\pm}5.19%$, thereby showing approximately 6.5~8.5% of difference. In terms of the injection method, the method that used the 3-way form, a deviation of $68.9{\pm}2.80%$ prior to the shielding and a deviation of $78.1{\pm}5.14%$ after the shielding were displayed. In the method of using a Heparin cap, a deviation of $71.3{\pm}5.14%$ prior to the shielding and a deviation of $79.8{\pm}3.26%$ after the shielding were displayed. Lastly, in the method of direct injection into the patient, a deviation of $75.1{\pm}4.30%$ prior to the shielding and a deviation of $82.1{\pm}2.35%$ after the shielding were displayed, thereby illustrating differences in the kidney intake rates in the order of direct injection, a Heparin cap and the 3-way methods. Conclusion Since a substantially minute quantity of radiopharmaceuticals is injected for infants in comparison to adults, the cases of having shielded the bladder by removing radiation of the bladder displayed kidney intake rates that are improved from those of the cases of not having shielded the bladder. Although there are difficulties in securing blood vessels, it is deemed that the method of direct injection would be more helpful in acquisition of better images since it displays improved kidney intake rate in comparison to other methods.

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The Effect of Corporate Association on the Perceived Risk of the Product (소비자의 제품 지각 위험에 대한 기업연상과 효과: 지식과 관여의 조절적 역활을 중심으로)

  • Cho, Hyun-Chul;Kang, Suk-Hou;Kim, Jin-Yong
    • Journal of Global Scholars of Marketing Science
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    • v.18 no.4
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    • pp.1-32
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    • 2008
  • Brown and Dacin (1997) have investigated the relationship between corporate associations and product evaluations. Their study focused on the effects of associations with a company's corporate ability (CA) and its corporate social responsibility (CSR) on consumers' product evaluations. Their study has found that both of CA and CSR influenced product evaluation but CA association has a stronger effect than CSR associations. Brown and Dacin (1997) have, however, claimed that there are few researches on how corporate association impacts product responses. Accordingly, some of researchers have found the variables to moderate or to mediate the relationship between the corporate association and the product responses. In particular, there has been existed a few of studies that tested the influence of the reputation on the product-relevant perceived risk, but the effects of two types of the corporate association on the product-relevant perceived risk were not identified so far. The primary goal of this article is to identify and empirically examine some variables to moderate the effects of CA association and CSR association on the perceived risk of the product. In this articles, we take the concept of the corporate associations that Brown and Dacin (1997) had proposed. CA association is those association related to the company's expertise in producing and delivering its outputs and CSR association reflected the organization's status and activities with respect to its perceived societal obligations. Also, this study defines the risk, which is the uncertainty or loss of the product and corporate that consumers have taken in a particular purchase decision or after having purchased. The risk is classified into product-relevant performance risk and financial risk. Performance risk is the possibility or the consequence of a product not functioning at some expected level and financial risk is the monetary loss one perceives to be incurring if a product does not function at some expected level. In relation to consumer's knowledge, expert consumers have much of the experiences or knowledge of the product in consumer position and novice consumers does not. The model tested in this article are shown in Figure 1. The model indicates that both of CA association and CSR association influence on performance risk and financial risk. In addition, the effects of CA and CSR are moderated by product category knowledge (product knowledge) and product category involvement (product involvement). In this study, the relationships between the corporate association and product-relevant perceived risk are hypothesized as the following form. For example, Hypothesis 1a($H_{1a}$) is represented that CA association has a positive influence on the performance risk of consumer. Also, the hypotheses that identified some variables to moderate the effects of two types of corporate association on the perceived risk of the product are laid down. One of the hypotheses of the interaction effect is Hypothesis 3a($H_{3a}$), it is described that consumer's knowledges of the product moderates the negative relationship between CA association and product-relevant performance risk. A field experiment was conducted in order to examine our model. The company tested was not real but imagined to meet the internal validity. Water purifiers were used for our study. Four scenarios have been developed and described as the imaginary company: Type A with both of superior CA and CSR, Type B with superior CSR and inferior CA, Type C with superior CA and inferior CSR, and Type D with both inferior of CA and CSR. The respondents of this study were classified into four groups. One type of four scenarios (Type A, B, C, or D) in its questionnaire was given to the respondent who filled out questions. Data were collected by means of a self-administered questionnaire to the respondents, chosen in convenience. A total of 300 respondents filled out the questionnaire but 207 were used for further analysis. Table 1 indicates that the scales in this study are reliable because the range of coefficients of Cronbach's $\alpha$ are from 0.85 to 0.92. The composite reliability is in the range of 0,85 to 0,92 and average variance extracted is in 0.72-0.98 range that is higher than the base level of 0.6. As shown in Table 2, the values for CFI, NNFI, root-mean-square error approximation (RMSEA), and standardized root-mean-square residual (SRMR) are acceptably close to the standards suggested by Hu and Bentler (1999):.95 for CFI and NNFI,.06 for RMSEA, and.08 for SRMR. We also tested discriminant validity provided by Fornell and Larcker (1981). As shown in Table 2, we found strong evidence for discriminant validity between each possible pair of latent constructs in all samples. Given that these batteries of overall goodness-of-fit indices were accurate and that the model was developed on theoretical bases, and given the high level of consistency across samples, this enables us to proceed the previously defined scales. We used the moderated hierarchical regression analysis to test the influence of the corporate association(CA and CSR associations) on product-relevant perceived risk(performance and financial risks) and to identify the variables moderating the relationship between the corporate association and product-relevant performance risk. In this study, dependent variables are performance and financial risk. CA and CSR associations are described the independent variables. The moderating variables are product category knowledge and product category involvement. The results are, as expected, found that CA association has statistically a significant influence on the perceived risk of the product, but CSR association does not. Product category knowledge and involvement moderate the relationship between the CA association and the perceived risk of the product. However, the effect of CSR association on the perceived risk of the product is not moderated by the consumers' knowledge and involvement. For this result, it is necessary for a corporate to inform its customers CA association more than CSR association so that they could be felt to be the reduction of the perceived risk. The important theoretical contribution of this research is the meanings that two types of corporate association that Brown and Dacin(1997), and Brown(1998) have proposed replicated the difference of the effects on product evaluation. According to Hunter(2001), it was an important affair to accomplish the validity of a particular study and we had to take about ten studies to deduce a strict study. Next, there is the contribution of the this study to find that the effects of corporate association on the perceived risk of the product are varied by the moderator variables. In particular, the moderating effect of knowledge on the relationship between corporate association and product-relevant perceived risk has not been tested in Korea. In the managerial implications of this research, we suggest the necessity to stress the ability that corporate manufactures the product well(CA association) than the accomplishment of corporate's social obligation(CSR association). This study suffers from various limitations that imply future research directions. The moderating effects of product category knowledge and involvement on the relationship between corporate association and perceived risk need to be replicated. Next, future research could explore whether the mediated effects of the perceived risk has the relationship between corporate association and consumer's product purchase. In addition, to ensure the external validity of the study will be needed to use realistic company, not artificial.

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A Study of Factors Associated with Software Developers Job Turnover (데이터마이닝을 활용한 소프트웨어 개발인력의 업무 지속수행의도 결정요인 분석)

  • Jeon, In-Ho;Park, Sun W.;Park, Yoon-Joo
    • Journal of Intelligence and Information Systems
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    • v.21 no.2
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    • pp.191-204
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    • 2015
  • According to the '2013 Performance Assessment Report on the Financial Program' from the National Assembly Budget Office, the unfilled recruitment ratio of Software(SW) Developers in South Korea was 25% in the 2012 fiscal year. Moreover, the unfilled recruitment ratio of highly-qualified SW developers reaches almost 80%. This phenomenon is intensified in small and medium enterprises consisting of less than 300 employees. Young job-seekers in South Korea are increasingly avoiding becoming a SW developer and even the current SW developers want to change careers, which hinders the national development of IT industries. The Korean government has recently realized the problem and implemented policies to foster young SW developers. Due to this effort, it has become easier to find young SW developers at the beginning-level. However, it is still hard to recruit highly-qualified SW developers for many IT companies. This is because in order to become a SW developing expert, having a long term experiences are important. Thus, improving job continuity intentions of current SW developers is more important than fostering new SW developers. Therefore, this study surveyed the job continuity intentions of SW developers and analyzed the factors associated with them. As a method, we carried out a survey from September 2014 to October 2014, which was targeted on 130 SW developers who were working in IT industries in South Korea. We gathered the demographic information and characteristics of the respondents, work environments of a SW industry, and social positions for SW developers. Afterward, a regression analysis and a decision tree method were performed to analyze the data. These two methods are widely used data mining techniques, which have explanation ability and are mutually complementary. We first performed a linear regression method to find the important factors assaociated with a job continuity intension of SW developers. The result showed that an 'expected age' to work as a SW developer were the most significant factor associated with the job continuity intention. We supposed that the major cause of this phenomenon is the structural problem of IT industries in South Korea, which requires SW developers to change the work field from developing area to management as they are promoted. Also, a 'motivation' to become a SW developer and a 'personality (introverted tendency)' of a SW developer are highly importantly factors associated with the job continuity intention. Next, the decision tree method was performed to extract the characteristics of highly motivated developers and the low motivated ones. We used well-known C4.5 algorithm for decision tree analysis. The results showed that 'motivation', 'personality', and 'expected age' were also important factors influencing the job continuity intentions, which was similar to the results of the regression analysis. In addition to that, the 'ability to learn' new technology was a crucial factor for the decision rules of job continuity. In other words, a person with high ability to learn new technology tends to work as a SW developer for a longer period of time. The decision rule also showed that a 'social position' of SW developers and a 'prospect' of SW industry were minor factors influencing job continuity intensions. On the other hand, 'type of an employment (regular position/ non-regular position)' and 'type of company (ordering company/ service providing company)' did not affect the job continuity intension in both methods. In this research, we demonstrated the job continuity intentions of SW developers, who were actually working at IT companies in South Korea, and we analyzed the factors associated with them. These results can be used for human resource management in many IT companies when recruiting or fostering highly-qualified SW experts. It can also help to build SW developer fostering policy and to solve the problem of unfilled recruitment of SW Developers in South Korea.

Ammonium Nitrate Explosion Technique for the Establishment of Orchard (산지과수(山地果樹)의 재식(栽植)을 위(爲)한 폭약이용(爆藥利用)에 관(關)한 연구(硏究))

  • Yoo, S.H.;Koh, K.C.;Park, M.E.
    • Korean Journal of Soil Science and Fertilizer
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    • v.12 no.4
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    • pp.169-178
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    • 1980
  • Ammonium nitrate explosion technique was applied to seek a convenient method for the establishment of orchard on the undulating to rolling land or hill side of Pogog clay loam soil (Fine Aquic Fragiudalfs : Planosols) having high bulk density and low permeability. Explosions were made by three ammonium nitrate explosives placed in the bottom of 90cm deep auger hole with every 2m interval (Explosion I) and 4m interval (Explosion II) respectively. The effect of the explosion on physical properties of the soil was investigated and compared with the effect induced by manual digging, excavation of $1m{\times}1m$ in diameter and depth (Manual digging I) and trenching of $1m{\times}1m{\times}25m$ in width, depth, and length (Manual digging II) respectively. The results investigated after 7 months from the treatments are summarized as follows : 1. The explosion or manual digging reduced bulk density and hardness, whereas the treatments increased porosity, hydraulic conductivity, and available moisture-holding capacity of the soil. 2. The explosion of 4 m interval improved physical properties of the soil to optimum level up to 70cm of the distance from the explosion core in the range of depth 0-60cm, while in the case of depth from 60 to 100cm the optimum level was achieved only within 50cm radius. 3. When exploded in 2 m interval, the effect in the 0-60cm depth was overlapped between two explosion cores. The effect in the depth between 60 and 100cm, however, was found to be independent of the explosion intervals. 4. The manual digging was only costly and laborious but effective only within the work-up zone. 5. For the soils having bulk density higher than $1.4g/cm^3$ after the treatments, the field capacity determined 72 hours after a heavy rain was lower than the laboratory estimate at the suction of 1/3 atm. 6. The top growth of apple tree for the first year revealed that the explosion seemed better treatment than the manual digging, even though the difference was insignificant.

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Study on the Improvement of a Grain Harvester (I) -Threshing Force of Rice- (수확기(收穫機)의 성능향상(性能向上)에 관(關)한 연구(硏究)(I) - 수도(水稻)의 탈립저항력(脫粒抵抗力)에 관(關)하여)

  • Lee, Sang Woo;Hur, Yun Kun
    • Korean Journal of Agricultural Science
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    • v.8 no.2
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    • pp.224-230
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    • 1981
  • Threshing forces of seven varieties, that is, three Japonica type varieties-Irri 348, Irri 345, and Milyang 15, and four Indica type varieties-Milyang 23, Irri 342, Suweon 294 and Suweon 287-, which have been cultivated in the standard fertilization field being at Chungnam Provincial Office of Rural Development, Youseong, Chungnam-do, they were measured every other day in the period from September 28 to October 20 which were included the proper harves ting time. Also the threshing forces were checked in three-dimensional directions. Relationships between threshing forces and moisture contents of the unthreshed rice were examined in the laboratory as dried in the natural condition. The results of this study were as follows; 1. The mean threshing force of Japonica type varieties was about 1969r. and that of Indica type varieties was about 113gr. when external force was loaded in the direction parallel to the grain. 2. The threshing force bent to the grain was about 9.8through 28.2gr. equal to 7 through 21 percent to the threshing force parallel to the grain in Indica type varieties meanwhile about 59.8 through 115.0gr equal to 33 through 50 percent in Japonica type varieties. 3. Under the warmer temperature than $0^{\circ}C$, the change of threshing forces was not great in this experimental period on the harvesting dates. 4. The threshing force decreased s lightly as moisture content decreased in natural drying under the shade after cutting. 5. The threshing force of the lower portion was a little biger than that of the upper portion in an ear.

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An experimental study on diameter increase of orthodontic wire by electroplating (전기도금을 이용한 스테인레스 스틸 선재의 직경 증가에 관한 실험적 연구)

  • Cho, Jin-Hyoung;Sung, Young-Eun;Lee, Ki-Heon;Hwang, Hyeon-Shik
    • The korean journal of orthodontics
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    • v.33 no.2 s.97
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    • pp.121-130
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    • 2003
  • The purpose of this study was to evaluate the possibile clinical application of electroplating to increase diameter of an orthodontic wire, through examining the change of physical properties. The diameter of stainless steel orthodontic wire was increased from 0.016 inch to 0.018 inch by electroplating in a bath of nickel sulfate 100g/L, nickel chloride 60g/L, boric acid 30g/L, and sodium chloride 50g/L, under the conditions of 1.7V, $25\~29^{\circ}C\;and\;3.1\~3.3pH$. During the electroplating, the rate of diameter increase was measured every minute. To investigate uniformity, the diameter was measured at three different locations of each wire specimen aster electroplating. An X-ray diffraction test was performed to analyze the nature of the electroplated metal. Following heat treatment to improve adhesion between the wire and electroplated metal, a three-point bending test was conducted to compare stiffness, field strength, and ultimate strength among four wire groups; 0.016 inch, electroplated 016, electroplated and heat-treated 016, and 0.018 inch wires. Through the comparison of each wire group, following results were obtained. 1. In the load-deflection graph, the curve of the electroplated group was Placed between that of the 0.016 inch group and the 0.018 inch group, and the owe was closer to the 0.018 inch group by heat treatment. 2. In the electroplated and heat-treated 016 wire group, the values of stiffness, yield strength and ultimate strength showed higher tendency than in the original 0.016 Inch group. Stiffness and ultimate strength showed statistically significant differences between two groups. 3. Stiffness, yield strength, and ultimate strength of electroplated wire presented lower values than those of 0.018 inch wire group. 4. Stiffness, yield strength, and ultimate strength of electroplated and heat-treated wire showed higher tendency than those of electroplated wire group, and ultimate strength showed statistically significant difference between two groups. 5. After electroplating, the difference in diameter between the three locations was within $0.1\~0.3\%$ variation, and showed no statistical significance.

A study on educational need of nurses for home care (간호사의 가정간호를 위한 교육요구 분석)

  • Moon Jung-Soon
    • Journal of Korean Public Health Nursing
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    • v.5 no.2
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    • pp.5-25
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    • 1991
  • This study was conducted from July to December 1990, in order to diagnose nurses' educational need for home care. The study subjects consisted of 145 nursing educators, and the 3 groups of nurses, namely 250 senior nursing students of diploma and collegiate program, 235 health center nurses, 521 university' hospital nurses in Seoul. Four types of questionaires were formulated by Delphi method. Two questionaires for the nursing educators were designed to measure their expectations of nurses' knowledge and of their skill for home care, and another two questionaires for the nurses to measure their actual home care knowledge and skill. The results of the study were as follows : 1) The mean scores of educators' expectation for home care knowledge were 17.68 for the care of dependence on medical equipment, 17.44 for the care of mobility impairment patient, 16.56 for the care of cardiopulmonary impairment patient, 16.40 for the care of nutrition and elimination impairment patient, '1.20 for the care of psychiatric disorder patient and 9.03 for the care of cancer and terminally ill patient,. 2) The mean scores of nurses' home care knowledge tested by 20 items were 14.36 for the care of mobility impairment patient, 13.28 for the c8;re of dependence on medical equipment, 13.78 for the care of cardiopulmonary impairment patient, 12.92 for the care of nutrition and elimination impairment patient, and those of tested by 10 items were 7.08 for the care of psychologic disorder patient, 7.80 for the care of cancer and terminally ill patient. The sum of means marked 69.23. As for the nurses' home care knowledge categorized by tasks in terms of the group, significant difference were shown in the care of mobility impairment(P=0.00), cancer and terminally ill(P=0.03), nutrition and elimination impairment(P=0.00) and psychologic disorder patient(P=0.00). No significant difference were shown in the care of dependence on medical equipment and cardiopulmonary impairment patient. 3) Regard to educational need of nurses' home care knowledge categorized by task according to the group it was found that all sampled nurses had educational need in the care of mobility impairment, dependence on medical equipment, cardiopulmonary impairment, cancer and terminally ill patient. It was found that health center nurses had educational need in the care of psychologic disorder. No educational need were found in the health center nurses whose career less than 2 years, in the care of mobility impairment, cardiopulmonary impairment and psychologic disorder patient, and in those of career with 2-5 year in the care of psychologic disorder patient. No educational need were found in the hospital nurses whose career more than 15 years, in the care of cardiopulmonary impairment patient and in those of career with 11-15 year, in the care of cancer and terminally ill patient. 4) The mean scores of educators' expectation for home care skill measured by Likert 5 points scale were 4. 21 for assessing, 4.49 for planning, 4.29 for basic care, 4.42 for curative care, 4.40 for rehabilitative care, 4.36 for emergency care, 4.53 for medication, 4.31 for nutritional care, 4.32 for other means for care, and 4.38 for evaluation. 5) Regard to nurses' home care skill measured by Likert 5 points scale of self evaluation, there was a significant difference between the nurses' home care skill and group(P=0.00l). The higher scores reported by students were vital sign checking and basic care while the scores of below medium were curative care and emergency care. The higher scores reported by health center nurses were vital sign checking, other means for care and care of specimen while the scores below medium were curative, emergency and nutritional care. The higher scores reported by hospital nurses were vital sign checking, care of specimen and basic care, while the score below medium was emergency care. 6) Regard to educational need of nurses' home care skill by nursing process activity according to the group it was found that health center nurses had educational need in all nursing skills including vital sign checking, care of specimen, health assessment, socioeconomic assessment, nursing diagnosis, care plan, basic care, curative care, rehabiitative care, psychological care, emergency care, medication, nutritional care, other means for care and evaluation. And students had educational need in all nursing skills except vital sign checking, and hospital nurses had educational need in all nursing skills except vital sign checking, care of specimen and basic care. 7) In short, the result of this study suggests that the curriculum should be organized in accordence with nurses' educational background and their career for the education of nurses for home care. It should be considered to develop the short term educational program focused on curative and rehabilitative care for health center nurse or community health nurse practitioner and which was focused on family care for hospital nurse. Concerning about this field practice for home care nurse, they are required not only community practice but also . clinical practice including emergency, curative and rehabilitative care.

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Comparison of the measurement methods of soil water content by error analysis (토양수분(土壤水分) 함량(含量) 측정방법별(測定方法別) 오차분석(誤差分析)에 의(依)한 비교(比較))

  • Eom, K.C.;Ryu, K.S.;Um, K.T.
    • Korean Journal of Soil Science and Fertilizer
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    • v.21 no.4
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    • pp.367-372
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    • 1988
  • A series of field experiment was conducted to find out error range and to compare precision based on error analysis of soil water content measured with gravimetric, surface & depth neutron and gypsum block methods in a sandy loam soil. The error of soil water content measured with gravimetric (core-sampling), surface and depth neutron method showed quardratic curve, whereas that with gypsum block was exponential curve in relation to soil water content. Within the range of volumetric soil water content from 11 to 33%, the error of soil water content measured with gravimetric, surface neutron, depth neutron and gypsum block method was ranged from 0.28 to 3.49%, 0.71 to 2.63%, 0.52% to 1.01% and 0.05 to 21.89%, respectively. The error of soil water content measured with depth neutron method was lower than those of other methods, when the soil water content was more than 14% in sandy loam soil. The relative number of replicates of soil water measurement for surface neutron, depth neutron and gypsum block method to attain same precision for gravimetric method was 0.6-1.7, 0.07-0.8 and 0.1-125, respectively.

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Studies on the grassland Development in the Forest V. Effect of sharing degrees on the early growth characteristics and winter survival of main grasses (임간초지 개발에 관한 연구 V. 차광정도가 주요 초목의 초기생육과 월동에 미치는 영향)

  • Park, M.S.;Seo, S.;Han, Y.C.;Lee, J.Y.
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.6 no.1
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    • pp.38-43
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    • 1986
  • This field experiment was conducted to determine the effects of shading degrees (0 : full sunlight, 25, 50 and 75%) on the early growth characteristics and winter survival of grasses. For the test different artificial shading houses were established and pasture species used were orchardgrass, timothy and perennial ryegrass. The experiment was performed at Livestock Experiment Station in Suweon, and sowing date was Aug. 25, 1984. The results are summarized as follows : 1. Generally, root length, new root length, number of new root and tillers of grasses were increased at 0% (full sunlight) of shading, followed by 25, 50 and 75% of shading degrees, in that order. Plant length and leaf elongation, however were increased at 50% of shading, followed by 75, 25 and 0%. 2. The percentage of winter killing of grasses was significantly (P<0.05) increased as the shading degrees increased. Also the percentages of winter killing were 10.1% in orchardgrass, 9.5% in timothy and 14.2% in perennial ryegrass, respectively. 3. A significant negative correlations were observed in the relationship between winter killing and tillers, new root length and number of new root of grasses. However, there were positive correlations between winter killing and plant length or leaf elongation under shading conditions. 4. As the shading degrees are increased by 0, 25, 50 and 75%, the NAR of grasses was tended to be decrease to 10.98, 11.52, 9.81 and 6.12 g/$m^2$/day, in that order. Also there was a negative correlation (r=-0.5943*) between winter killing and NAR of grasses, and NAR of orchardgrass, timothy and perennial ryegrass were 8.58, 8.53 and 11.71 g/$m^2$/day, respectively.

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