• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.4
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• pp.346-358
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• 2023

Due to the acceleration of climate change or global warming, it is important to predict rice productivity in the future and investigate physiological changes in rice plants. The research aimed to explore how rice adapts to climate change by examining the response of nitrogen absorption and nitrogen use efficiency in rice under elevated levels of carbon dioxide and temperature, utilizing the SPAR system for analysis. The temperature increased by +4.7 ℃ in comparison to the period from 2001 to 2010, while the carbon dioxide concentration was held steady at 800 ppm, aligning with South Korea's late 21st-century RCP8.5 scenario. Nitrogen was applied as fertilizer at rates of 0, 9, and 18 kg 10a^-1, respectively. Under conditions of climate change, there was an 81% increase in the number of panicles compared to the present situation. However, grain weight decreased by 38% as a result of reduction in the grain filling rate. BNUE, indicative of the nitrogen use efficiency in plant biomass, exhibited a high value under climate change conditions. However, both NUEg and ANUE, associated with grain production, experienced a notable and significant decrease. In comparison to the current conditions, nitrogen uptake in leaves and stems increased by 100% and 151%, respectively. However, there was a 25% decrease in nitrogen uptake in the panicle. Likewise, the nitrogen content and NDFF (Nitrogen Derived from Fertilizer) in the sink organs, namely leaves and roots, were elevated in comparison to current levels. Therefore, it is imperative to ensure resources by mitigating the decrease in ripening rates under climate change conditions. Moreover, there seems to be a requirement for follow-up research to enhance the flow of photosynthetic products under climate change conditions.

• Applied Biological Chemistry
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• v.6
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• pp.61-77
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• 1965

In this experiment, Akiochi was studied especially on plant growth on the degraded soils. Besides, such soils were carefully examined on its character and plant body was analysed to know the difference in various mineral contents. For this purpose, paddy cultivation was done with the variety Pal Dal at Suwon, Sosa and Pyungtak. Three plots were chosen at each location as the normal and 2 levels of akiochi, a-the stronger and b-the weaker. Harvests from these 9 plots were measured agronomically and also chemically analysised. As for soil, after an observation on vertical section of soil, samples from each layer were also studied both physically and chemically. The results are summarized as follows. 1. Outer changes in rice plant and changes in yield components. 1) Rice from Akiochi soil showed remarkably shortened culm length, head length, protrusoion length, blade length of boot leaf, and coleoptile length, compared with that from the normal paddy field. 2) There was a tendency for Akiochi rice to have more heads per plant. 3) Akiochi rice showed poorer intercalary growth of upper 3 internodes. The ratio of this upper internode length to total culm length was also smaller in this case. Consquently the ratio of lower internode length to total culm length became larger than that from normal peddy field. 4) Akiochi rice showed significantly fewer first spikelets and attached grains of head at main stem. 5) Maturing rate of both this main seem of whole plant body was remarkably lower than that of normal rice. 6) Akiochi rice showed lower head weight of main stem, total hulled rice weight, total grain yield, 1000-grain weight, straw weight and straw-hulled rice ratio. 2. Physical and chemical study on soil. 1) Akiochi soil showed thinner upper layer and total thickness of upper and lower parts was smaller than that of normal. 2) Akiochi soil of Suwon was mainly composed of sand, while that of Sosa and Pyungtak was composed of heavy clay. 3) Chemical analysis indicated that content of $SiO_2$ in upper layer is always lower than that of normal. But no other common tendencies were found. 4) This analysis further lillustrates lower content of Fe, & Mn at Suwon ; of Mn at Sosa and higher content of Fe at Sosa and organic matters at Pyungtak. 5) Some differences in the content of N in each plot could be marked though irregular. 3. Chemical Composition of plant body. 1) Chemical analysis on grain, boot leaf and straw did not suggest any remarkable differences between normal and Akiochi rice, except that the latter contains less Si in boot leaf and less Mn in straw. 2) Contents of each chemical element were measured in grain and straw to calculate the percentage of element content in grain to that of whole plant body including both grain and straw. Here, Akiochi rice always showed lower value in N, K and Mn. 4. Relationship between chemical composition of plant body and that of soil. Akiochi soil at Sosa marked lower content of Mn. This caused another lower content of this element in grain, boot leaf and straw. But except that, no remarkable relationship could be found in this study.

• Microbiology and Biotechnology Letters
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• v.8 no.3
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• pp.181-191
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• 1980

For the purpose of studies on the citric acid production, some experiments were carried out with isolated strains. The results obtained were as follows. 1) The optimal culture media of the strain M-80 in surface culture contained 140g of sucrose, 3.0g of (N $H_4$)$_2$S $O_4$, 1.5g of K $H_2$P $O_4$, 0.2g of MgS $O_4$.7$H_2O$, 3.0mg of F $e^{++}$, 1.0mg of Z $n^{++}$, 0.5N HCI to a pH of 5.0 and distilled water to 1.0 liter; and that of the strain M-315 in surface culture contained 140g of sucrose, 2.0g of N $H_4$N $O_3$, 1.0g of K $H_2$P $O_4$, 0.25g of MgS $O_4$. 7$H_2O$, 2.0mg of F $e^{++}$, 2.0mg of Z $n^{++}$, 0.05mg of C $u^{++}$, 0.5N HCI to a pH of 4.5 and distilled water to 1.0 liter. While that of the strain M-315 in submerged culture contained 140g of sucrose, 2.5g of N $H_4$N $O_3$, 1.5g of K $H_2$P $O_4$, 0.3g of MgS $O_4$. 7$H_2O$, 3.0mg of F $e^{++}$, 0.1mg of C $u^{++}$, 0.5N HCI to a pH of 4.5 and distilled water to 1.0 liter. The optimal temperature and size of inoculum were mostly 28-3$0^{\circ}C$, 10$^{7}$ -10$^{8}$ spores/50ml, respectively. 2) Through the course of citric acid production, the growth of strains had nearly been completed, pH value was rapidly decreased below 2.0 and the content of sugar was also reduced, while the accumulation of citric acid in media was remarkably begun in about 3-4 days. The yields of citric acid generally reached the maximum level in 8-10 days in surface or submerged fermentation process. 3) Methanol was effective citric acid production when they were added to fermentation media. In the case of surface culture, by addition of 2％ (strain M-80), 3％ (strain M-315), the yields of citric acid was increased 6.5％, 20.6%, respectively and 5.0% yield was increased by addition of 3% methanol in submerged culture media of the strain M-315. 4) Chromatography analysis of culture broth after fermentation under optimal culture conditions detected that the majority of acid in media was citric acid. 72.1mg/ml, 98.1mg/ml, of citric acid were determined in surface culture media by strains of M-80, M-315, and 59.8 mg/ml of citric acid was contained in the submerged culture media by the strain M-315. strain M-315.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.2
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• pp.47-60
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• 1975

For the calculation of population parameter and estimation of recruitment of a fish population, an application of multiple regression method was used with some statistical inferences. Then, the differences between the calculated values and the true parameters were discussed. In addition, this method criticized by applying it to the statistical data of a population of bigeye tuna, Thunnus obesus of the Indian Ocean. The method was also applied to the available data of a population of Pacific saury, Cololabis saira, to estimate its recuitments. A stock at t year and t+1 year is, $N_{0,\;t+1}=N_{0,\;t}(1-m_t)-C_t+R_{t+1}$ where $N_0$ is the initial number of fish in a given year; C, number o: fish caught; R, number of recruitment; and M, rate of natural mortality. The foregoing equation is $$\phi_{t+1}=\frac{(1-\varrho^{-z}{t+1})Z_t}{(1-\varrho^{-z}t)Z_{t+1}}-\frac{1-\varrho^{-z}t+1}{Z_{t+1}}\phi_t-a'\frac{1-\varrho^{-z}t+1}{Z_{t+1}}C_t+a'\frac{1-\varrho^{-z}t+1}{Z_{t+1}}R_{t+1}......(1)$$ where $\phi$ is CPUE; a', CPUE $(\phi)$ to average stock $(\bar{N})$ in number; Z, total mortality coefficient; and M, natural mortality coefficient. In the equation (1) , the term $(1-\varrho^{-z}t+1)/Z_{t+1}$s almost constant to the variation of effort (X) there fore coefficients $\phi$ and $C_t$, can be calculated, when R is a constant, by applying the method of multiple regression, where $\phi_{t+1}$ is a dependent variable; $\phi_t$ and $C_t$ are independent variables. The values of Mand a' are calculated from the coefficients of $\phi_t$ and $C_t$; and total mortality coefficient (Z), where Z is a'X+M. By substituting M, a', $Z_t$, and $Z_{t+1}$ to the equation (1) recruitment $(R_{t+1})$ can be calculated. In this precess $\phi$ can be substituted by index of stock in number (N'). This operational procedures of the method of multiple regression can be applicable to the data which satisfy the above assumptions, even though the data were collected from any chosen year with similar recruitments, though it were not collected from the consecutive years. Under the condition of varying effort the data with such variation can be treated effectively by this method. The calculated values of M and a' include some deviation from the population parameters. Therefore, the estimated recruitment (R) is a relative value instead of all absolute one. This method of multiple regression is also applicable to the stock density and yield in weight instead of in number. For the data of the bigeye tuna of the Indian Ocean, the values of estimated recruitment (R) calculated from the parameter which is obtained by the present multiple regression method is proportional with an identical fluctuation pattern to the values of those derived from the parameters M and a', which were calculated by Suda (1970) for the same data. Estimated recruitments of Pacific saury of the eastern coast of Korea were calculated by the present multiple regression method. Not only spring recruitment $(1965\~1974)$ but also fall recruitment $(1964\~1973)$ was found to fluctuate in accordance with the fluctuations of stock densities (CPUE) of the same spring and fall, respectively.

• Journal of Animal Science and Technology
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• v.55 no.5
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• pp.451-460
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• 2013

The feed value of sesame meal, a main agricultural by-product from the northern area of Gyeongsangbuk-do province, was assessed in Hanwoo steers. A total of twelve Hanwoo steers (average BW = 412.08 kg) were allocated into a Control (fed no sesame meal) or Treatment (fed sesame meal from 14.6 months of age) group, considering BW and ages, and the animals were fed for a total of 480 days. The final BW, total gain and ADG for the Control and Treatment groups were 741.17 kg and 762.67 kg, 331.84 kg and 347.84 kg, and 0.69 kg and 0.72 kg, respectively, showing better performances in sesame meal-fed animals. Feed requirements during the whole experimental period improved by feeding sesame meal (15.31 and 14.87 for Control and Treatment group, respectively). Hanwoo steers fed sesame meal also showed a 22.83 kg heavier cold carcass weight (424.17 kg and 447.00 kg in the Control and Treatment group, respectively), and 2.41% improved dressing percentages (58.60% and 57.22% for the Control and Treatment group, respectively). The area of the M. longissimus dorsi was $91.83cm^2$ and $88.33cm^2$ in the Control and Treatment group, respectively. The final yield of A and B grade meat were 50 : 50% and 33.3 : 66.7% from the Control and Treatment group, respectively. The average marbling score was 4.83 and 5.50, and the numeric values for quality grade was 2.17 and 2.67 for the Control and Treatment group, respectively, showing better beef quality in sesame meal-fed Hanwoo steers. In fact, there were two animals with beef quality $1^{{+}{+}}$ in the sesame meal-fed group. The melting point of lipid extracted from the M. longissimus dorsi of Hanwoo steers was significantly (p<0.05) lower in the Treatment group ($28.28^{\circ}C$) compared to the Control group ($30.65^{\circ}C$). The composition of saturated fatty acids, $C_{14:0}$ (myristic acid) and $C_{16:0}$ (palmitic acid), were significantly lower in sesame meal-fed animals, 4.70% and 2.20% for myristic acid, and 30.55% and 27.12% for palmitic acid, in the Control and Treatment group, respectively. In contrast, there were no significant differences in C18:0 (stearic acid) composition between the groups. The composition of a representative unsaturated fatty acid, $C_{18:1}$ (oleic acid), was significantly higher in Treatment animals (49.89%) than Control animals (44.29%) (p<0.05). The ratio of total monounsaturated fatty acids / saturated fatty acids; M/S) was 1.10 and 1.36 for the Control and Treatment groups, respectively, showing remarkably higher ratios in sesame meal-fed group. The content of glutamic acid, related to beef flavor, was significantly higher in the Treatment group (3.35 mg/100 g) compared to the Control group (1.88 mg/100g) (p<0.05). The tenderness score, evaluated by an eight-point scale in the panel test, and overall palatability (based on juiciness, flavor, oiliness, and umami) were significantly higher in the Treatment group (5.67 and 5.23, respectively) than the Control group (3.83 and 4.60, respectively) (p<0.05). In conclusion, the current results imply that sesame meal could serve as a good supplement for Hanwoo steers for producing high quality beef.

• Journal of Intelligence and Information Systems
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• v.26 no.1
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• pp.135-149
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• 2020

Artificial intelligences are changing world. Financial market is also not an exception. Robo-Advisor is actively being developed, making up the weakness of traditional asset allocation methods and replacing the parts that are difficult for the traditional methods. It makes automated investment decisions with artificial intelligence algorithms and is used with various asset allocation models such as mean-variance model, Black-Litterman model and risk parity model. Risk parity model is a typical risk-based asset allocation model which is focused on the volatility of assets. It avoids investment risk structurally. So it has stability in the management of large size fund and it has been widely used in financial field. XGBoost model is a parallel tree-boosting method. It is an optimized gradient boosting model designed to be highly efficient and flexible. It not only makes billions of examples in limited memory environments but is also very fast to learn compared to traditional boosting methods. It is frequently used in various fields of data analysis and has a lot of advantages. So in this study, we propose a new asset allocation model that combines risk parity model and XGBoost machine learning model. This model uses XGBoost to predict the risk of assets and applies the predictive risk to the process of covariance estimation. There are estimated errors between the estimation period and the actual investment period because the optimized asset allocation model estimates the proportion of investments based on historical data. these estimated errors adversely affect the optimized portfolio performance. This study aims to improve the stability and portfolio performance of the model by predicting the volatility of the next investment period and reducing estimated errors of optimized asset allocation model. As a result, it narrows the gap between theory and practice and proposes a more advanced asset allocation model. In this study, we used the Korean stock market price data for a total of 17 years from 2003 to 2019 for the empirical test of the suggested model. The data sets are specifically composed of energy, finance, IT, industrial, material, telecommunication, utility, consumer, health care and staple sectors. We accumulated the value of prediction using moving-window method by 1,000 in-sample and 20 out-of-sample, so we produced a total of 154 rebalancing back-testing results. We analyzed portfolio performance in terms of cumulative rate of return and got a lot of sample data because of long period results. Comparing with traditional risk parity model, this experiment recorded improvements in both cumulative yield and reduction of estimated errors. The total cumulative return is 45.748%, about 5% higher than that of risk parity model and also the estimated errors are reduced in 9 out of 10 industry sectors. The reduction of estimated errors increases stability of the model and makes it easy to apply in practical investment. The results of the experiment showed improvement of portfolio performance by reducing the estimated errors of the optimized asset allocation model. Many financial models and asset allocation models are limited in practical investment because of the most fundamental question of whether the past characteristics of assets will continue into the future in the changing financial market. However, this study not only takes advantage of traditional asset allocation models, but also supplements the limitations of traditional methods and increases stability by predicting the risks of assets with the latest algorithm. There are various studies on parametric estimation methods to reduce the estimated errors in the portfolio optimization. We also suggested a new method to reduce estimated errors in optimized asset allocation model using machine learning. So this study is meaningful in that it proposes an advanced artificial intelligence asset allocation model for the fast-developing financial markets.

• Korean Journal of Organic Agriculture
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• v.17 no.3
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• pp.371-380
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• 2009

This study was conducted to assess effects of supplying different types of nitrogen sources as fertilizers on productivity and feed values of barley and rye as winter forage crops, and ultimately done to get good quality of organic forages with higher fertilization of soil. For barley, N+P+K plots were significantly (P<0.05) higher in annual dry matter (DM) and total digestible nutrients (TDN) yields than other plots. However, cattle manure plots had significantly (P<0.05) higher annual DM and TDN than P+K and non-fertilizer plots. Plots of 50%-cattle manure and mixed sowing with hairy vetch or forage pea were higher than only 50%-cattle manure plot, particularly, these were significantly higher than non-fertilizer, and their crude protein (CP) yields were much higher than other plots. Crude protein contents were significantly higher in N+P+K and 50%-cattle manure slurry plots than non-fertilizer and P+K plots, and plots of mixed sowing with hairy vetch or forage pea in application of 50%-cattle manure had higher CP content than other plots. ADF content was lowest in 50%-cattle manure+forage pea plots, but highest in 100%-cattle manure plots. NDF content was lowest in legumes-mixed sowing, but highest in 100%-cattle manure plots. TDN content was the highest in forage pea plots, and plots of 50%-cattle manure and legumes-mixed sowing had high RFV, but cattle manure plots rich in ADF and NDF content had the lowest TDN and RFV. For rye, plots of 50%-cattle manure+hairy vetch mixed sowing, and N+P+K application had significantly higher annual DM, CP and TDN than other plots except for cattle manure. DM productive efficiency to nitrogen fertilization was markedly higher for cattle manure plots than for chemical fertilizer. This tendency was more conspicuous in plots of 50% cattle manure+legumes-mixed sowing. CP content was higher for N+P+K plot than for all plots, and plots of 50%-cattle manure + legumes-mixed sowing were significantly higher than other plots. On the contrary, forage pea-mixed sowing plot had the lowest ADF and NDF, but TDN and RFV were significantly (P<0.05) higher than other plots. Grass crop cultivation together with legumes by applying livestock manure to soil may lead to higher palatability of livestock, and better quality of forage. Furthermore, cattle manure application increased production yield per ha and CP contents. Thus, when applying forage crops produced by cattle manure application and mixed sowing to organic livestock production, it was conceived that forages produced might become a substitute for foreign organic grain as protein sources.

• The Korean Journal of Nuclear Medicine Technology
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• v.12 no.3
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• pp.208-213
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• 2008

Purpose: Generally a whole body bone scan has been known as one of the most frequently executed exams in the nuclear medicine fields. Asan medical center, usually use various gamma camera systems - manufactured by PHILIPS (PRECEDENCE, BRIGHTVIEW), SIEMENS (ECAM, ECAM signature, ECAM plus, SYMBIA T2), GE (INFINIA) - to execute whole body scan. But, as we know, each camera's sensitivity is not same so it is hard to consistent diagnosis of patients. So our purpose is when we execute whole body bone scans, we exclude uncontrollable factors and try to correct controllable factors such as inherent sensitivity of gamma camera. In this study, we're going to measure each gamma camera's sensitivity and study about reasonable correction factors of whole body bone scan to follow up patient's condition using different gamma cameras. Materials and Methods: We used the $^{99m}Tc$ flood phantom, it recommend by IAEA recommendation based on general counts rate of a whole body scan and measured counts rates by the use of various gamma cameras - PRECEDENCE, BRIGHTVIEW, ECAM, ECAM signature, ECAM plus, IFINIA - in Asan medical center nuclear medicine department. For measuring sensitivity, all gamma camera equipped LEHR collimator (Low Energy High Resolution multi parallel Collimator) and the $^{99m}Tc$ gamma spectrum was adjusted around 15% window level, the photo peak was set to 140-kev and acquirded for 60 sec and 120 sec in all gamma cameras. In order to verify whether can apply calculated correction factors to whole body bone scan or not, we actually conducted the whole body bone scan to 27 patients and we compared it analyzed that results. Results: After experimenting using $^{99m}Tc$ flood phantom, sensitivity of ECAM plus was highest and other sensitivity order of all gamma camera is ECAM signature, SYMBIA T2, ECAM, BRIGHTVIEW, IFINIA, PRECEDENCE. And yield sensitivity correction factor show each gamma camera's relative sensitivity ratio by yielded based on ECAM's sensitivity. (ECAM plus 1.07, ECAM signature 1.05, SYMBIA T2 1.03, ECAM 1.00, BRIGHTVIEW 0.90, INFINIA 0.83, PRECEDENCE 0.72) When analyzing the correction factor yielded by $^{99m}Tc$ experiment and another correction factor yielded by whole body bone scan, it shows statistically insignificant value (p<0.05) in whole body bone scan diagnosis. Conclusion: In diagnosing the bone metastasis of patients undergoing cancer, whole body bone scan has been conducted as follow up tests due to its good points (high sensitivity, non invasive, easily conducted). But as a follow up study, it's hard to perform whole body bone scan continuously using same gamma camera. If we use same gamma camera to patients, we have to consider effectiveness of equipment's change by time elapsed. So we expect that applying sensitivity correction factor to patients who tested whole body bone scan regularly will add consistence in diagnosis of patients.

• Journal of The Korean Society of Grassland and Forage Science
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• v.13 no.1
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• pp.49-57
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• 1993

The main experiment related to this report was undertaken to assess the effects of two rates of $Ca(OH)_2$ (0, 250 kg/10a only at establishment) and five rates of N-$P_{2}O_{5}$-$K_2O$ (0-0-0, 0-10-10, 6-15-15, 12-20-20, 24-25-20 kg/10a/year) on the pasture establishment, on forage yield and quality, vegetation etc. After this 10-year main experiment, this pasture had been used to assess the effects of the above treatments on the soil characteristics in oversown hilly pasture of a grass-clover sward. This 1st part is concerned with the soil properties of pH-value. OM, T-N, avail. $P_{2}O_{5}$ and $P_{2}O_{5}$ absorption coefficient, and lime requirement by the soil depth. 1. The pH of the topsoil(0~l5 cm) was lowered from pH 5.12 of before the experiment to 4.90 of when $Ca(OH)_2$ was applied and to 4.68 of when $Ca(OH)_2$ was not applied. The pH decrease was more evident with the increase of NPK application rate and in the upper part of the top soil(0.0~7.5 cm). The additional application of lime was necessary in all the experiment blocks due to the strong acidity of the soil, and the amounts of lime requirement were increased with increased application rates of NPK and soil depth. 2. The contents of organic matter and T-N were increased in all the blocks by the establishment of the hilly pasture, and were higher in $Ca(OH)_2$ applied blocks than non-applied blocks. The contents were inversely correlated with the soil depth. No correlation was observed between the contents and the application rates of NPK. 3. The content of available $P_{2}O_{5}$-$K_2O$, was increased with the increased application of P, especially in the upper part of top soil. The content in the upper part(0.0~7.5 cm) was about twice of that in the lower part(7.5~15.0 cm). Since the contents of available $P_{2}O_{5}$$P_{2}O_{5}$/10a/year were applied, respectively), it is necessary to decrease the application rate of $P_{2}O_{5}$, gradually. The $P_{2}O_{5}$ absorption coefficient in topsoil (0.0~15.0 cm) was more or less higher when no lime and less $P_{2}O_{5}$, was applied. No correlation was observed in subsoil. 4. Further studies on the methods, rates, time of additional application of lime, and on the methods of decreased apllication of $P_{2}O_{5}$ should be performed for better management of oversown hilly pasture.

• Tuberculosis and Respiratory Diseases
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• v.43 no.4
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• pp.500-518
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• 1996

Background : The solitary pulmonary nodule(SPN) presents a diagnostic dilemma to the physician and the patient. Many clinical characteristics(i.e. age, smoking history, prior history of malignancy) and radiological characteristics( i.e. size, calcification, growth rate, several findings of computed tomography) have been proposed to help to determine whether the SPN was benign or malignant. However, most of these diagnostic guidelines are based on the data collected before computed tomography(CT) has been introduced and lung cancer was not as common as these days. Moreover, it is not well established whether these guidelines from western populations could be applicable to Korean patients. Methods : We had a retrospective analysis of the case records and radiographic findings in 114 patients presenting with SPN from Jan. 1994 to Feb. 1995 in Seoul National University Hospital, a tertiary referral hospital. Results : We observed the following results ; (1) Out of 113 SPNs, the etiology was documented in 94 SP IS. There were 34 benign SP s and 60 malignant SPNs. Among which, 49 SPNs were primary lung cancers and the most common hi stologic type was adenocarcinoma. (2) The average age of patients with benign and malignant SPNs was $49.7{\pm}12.0$ and $58.1{\pm}10.0$ years, respectively( p=0.0004), and the malignant SPNs had a striking linear propensity to increase with age. (3) No significant difference in the hi story of smoking was noted between the patients with benign SPNs($13.0{\pm}17.6$ pack- year) and those with malignant SPNs($18.6{\pm}25.1$ pack-year) (p=0.2108). (4) 9 out of 10 patients with prior history of malignancy had malignant SPNs. 5 were new primary lung cancers with no relation to prior malignancy. (5) The average size of benign SPNs($3.01{\pm}1.20cm$) and malignant SPNs($2.98{\pm}0.97cm$) was not significantly different(p=0.8937). (6) The volume doubling time could be calculated in 22 SPNs. 9 SPNs had the volume doubling time longer than 400 days. Out of these, 6 were malignant SPNs. (7) The CT findings suggesting malignancy included the lobulated or spiculated border, air- bronchogram, pleural tail, and lymphadenopathy. In contrast, calcification, central low attenuation, cavity with even thickness, well-marginated border, and peri nodular micronodules were more suggestive for benign nodule. (8) The diagnostic yield of percutaneous needle aspiration and biopsy was 57.6%(19/33) of benign SPNs and 81.0%(47/58) of malignant SPNs. The diagnostic value of sputum analysis and bronchoscopic evaluations were relatively very low. (9) 42.3%(11/26) of SPNs of undetermined etiology preoperatively turned out to be malignant after surgical resection. Overall, 75.4%(46/61) of surgically resected SPNs were malignant. Conclusions : We conclude that the likelihood of malignant SPN correlates the age of patient, prior history of malignancy, some CT findings including lobulated or spiculated border, air-bronchogram, pleural tail and lymphadenopathy. However, the history of smoking, the size of the nodule, and the volume doubling time are not helpful to determent whether the SPN is benign or malignant, which have been regarded as valuable clinical parameters previously. We suggest that aggressive diagnostic approach including surgical resection is necessary in patient with SPNs.