• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.84-91
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• 2006

A heavy duty hydrogen-natural gas fueled engine can obtain stable operation at ultra lean conditions and reduce emissions extremely. Reduction of $CO_2$ in its engine is one of the most benefit. In this study, rate of hydrogen addition($R_{dH2}$) and compression ratio($\varepsilon$) were investigated including performance of this engine. As results, it was found that phenomenon of pressure oscillation when increasing $R_{dH2}$ and $\varepsilon$, it means occurring knock. It consider that pressure oscillation was increased due to fast burning speed of hydrogen. Even if same compression ratio, pressure oscillation was remarkable increased according to increasing $R_{dH2}$. Therefore, limit compression ratio of knock occurring was reduced by increasing $R_{dH2}$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.1
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• pp.29-39
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• 2013

Fishing vessels have been causing more than 70% of marine casualty in Korea. As a view of the occurring number of marine casualty, it is obvious for fishing vessel to account for the absolute high portion of that in comparison with the non-fishing vessels. That is a natural outcome because fishing vessels have occupied more than 90% of all registered Korean vessels. If we consider it not occurring number, but occurring ratio, we could find out that fishing vessels accounted for 5 times lower than non-fishing vessels in marine casualties. Nevertheless, fishing vessels have not immunity from responsibility for marine casualties at all, because the tendency of it in fishing vessel has been dominating the whole marine casualties in Korea. So for reduction of them, it is indispensable to decrease the casualties of fishing vessel. In this study, the authors tried to carry out many items of them to compare the occurring number with the occurring ratio, and dealt with the casualties of collision and machine damage in detail, because those have not only been occurring most frequently in casualties in Korea, but also led to the death and injury of lives. To reduce the collision and the machine damage, the operator have to keep the watch more strictly and check and keep the machine in good order. And it is necessary for the operator to take more education and training intended to decrease those systematically and continuously, especially for the crews of fishing vessels.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.157-166
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• 2013

PURPOSES : This study is to analyze expected effect of a accident decrease when motorcycle safety inspection is introduced. METHODS : Based on the literature review of effect of 4-wheel vehicle inspection, probability of occurring accidents among defective motorcycles are calculated by using the number of estimated defective motorcycles and accidents resulting from defects of motorcycles. Then, the number of decreased accidents which is resulting from eliminating defects of motorcycles by safety inspection is estimated by using probability of occurring accidents among defective motorcycles. RESULTS : If the ratio of eliminating defects of motorcycles is 95% after motorcycle safety inspection, the effects of accident decrease of motorcycle safety inspection are analyzed from 2005 to 2008. As a result, 46,292 defective motorcycles are repaired and 1,376 accidents are prevented when the probability of occurring accidents among defective motorcycles is 2.97%. CONCLUSIONS : This study suggests the expected effect of motorcycle safety inspection is that the inspection can prevent 1,376 motorcycle accidents. However, the number of preventing motorcycle accidents are small, compared with the total number of motorcycle accidents because there are limitations to investigate the causes of defective motorcycle accidents. A more precise analysis of the expected effect of motorcycle inspection is possible when a systematic investigation of the causes of the accidents is implemented.

• Journal of Fisheries and Marine Sciences Education
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• v.7 no.2
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• pp.173-181
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• 1995

In this paper, marine casualties occurred in Korean coastal and near-coastal seas, from 1989 to 1993, were analysed. The main results obtained were as follows : 1. According to the numerical component ratio of marine casualties, fishing vessels account for higher portion than other vessels and passenger vessels lower portion. On the other hand, in view of the occurring ratio of that, fishing vessels account for very low rate of accidents and passenger vessels very high rate. 2. Most of marine casualties resulted from the human factors such as careless operation and insufficient engine maintenance, etc. Collision accidents took a majority of all marine accidents in all of vessels, but engine trouble accounted for main cause of accidents in fishing vessels. 3. In view of the results on classifying marine casualties into time zone, great number of accidents took place in dawn, but that of fishing vessels in forenoon. 4. According to the view of the occurring ratio of the injury, the rate was 0.33% in total vessels and 0.18% in fishing vessels. 5. In view of the marine casualties by age and shipboard career, crews with 10~20 years shipboard career raised more marine accidents than others.

• Korean Journal of Medicinal Crop Science
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• v.21 no.4
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• pp.289-295
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• 2013

This study was carried out to investigate the cause of leaf discoloration occurring frequently in paddy cultivation. Chemical property of soil and inorganic nutrient component of leaf were analyzed on abnormal fields of 7 regions where leaf discoloration occurred severely and normal fields of 7 regions among ginseng garden. The pH of abnormal fields was strong acidic condition (pH 5.51) compare to normal fields of slightly acid condition (pH 6.42). Calcium and magnesium content in abnormal fields were lower distinctly than that of normal fields, while EC, organic matter, phosphate, and potassium content showed not distinct difference between abnormal and normal fields. Whereas calcium and magnesium content were distinctly high in normal fields, both of potassium and iron content of ginseng leaf were distinctly high in abnormal fields. In particular, iron content of abnormal fields was more 1.94 times in soil, and 3.03 times in leaf than that of normal fields. In soil chemical property, there were significant negative correlation between leaf discoloration ratio and soil pH, and there were also significant positive correlation between leaf discoloration ratio and iron content. In ginseng leaf, there were highly significant negative correlation between leaf discoloration ratio and calcium content, and there were also highly significant positive correlation between leaf discoloration ratio and iron content.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.117-122
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• 2005

Prepacked polymer mortar that is mainly composed of MMA monomer and used for the patching and restoring materials of concrete structures was developed, and its hardening and strength properties were experimentally surveyed. Results of study show that the permeance of binder into the aggregate was excellent for the case of PMMA mixing ratio of below 10%, the surface hardening inferiority was not generated for the case of the ratio of over 5%. Working time of the prepacked polymer mortar and hardening shrinkage tended to decrease as the PMMA mixing ratio increased. On the other hand, the ratio turned out not to decisively affect on compressive and flexural strengths. Regardless of PMMA mixing content, the adhesive strength was about 2.5 MPa. Occurring the desquamation on the substrate of cement concrete showed the adhesive strength of MMA prepact polymer mortar was excellent.

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.81-90
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• 2017

Preceding displacements in tunnel are difficult to predict since the measurements of displacements after excavation can not be performed immediately. In the present study, The longitudinal displacements which can be measured immediately after excavation are used to predict the crown settlements occurring before excavation only if fault is located at the tunnel crown. Three-dimensional finite element analysis was conducted using 28 numerical models with various fault attitudes to analyze the correlation between the longitudinal displacements on tunnel face and preceding crown settlements. The results, $L_{face}/C$ ratio show 2~12% in the drives with dip models and 2~13% in the drives against dip models individually. In addition, each model has a certain $L_{face}/C$ ratio. The result of the regression analysis show that the coefficient of determination is over 0.8 in most models. Therefore, crown settlements occurring before excavation can be predicted by analyzing the longitudinal displacements occurring on tunnel faces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.960-963
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• 2007

In this paper, development of the noise barrier analysis program is described. The upper part of barriers may have complicated shapes like "Y", "T", inverted L, and other shapes. The insertion loss of the barrier is predicted by summation of multiple diffractions occurring at top edge points. In addition, the program considers diffractions occurring at both vertical sides, while reflections from ground due to mirror images are also included. In case of two barriers at both sides of the road, reflections from the other side of barriers are considered, in which magnitudes are decreased by the ratio of absorption coefficient.

• Journal of the Korean Society of Combustion
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• v.17 no.1
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• pp.30-36
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• 2012

Dynamic characteristics of combustion occurring in various combustion devices have been extensively studied since most of high-performance combustion devices are susceptible to hazardous, unstable combustion that deteriorates combustor's lifetime. One of the most severe unstable combustion phenomena is high-frequency combustion instability in which heat release fluctuations from combustion are coupled to resonant modes of the combustor. Here in this study, characteristics of high-frequency combustion instabilities observed in three different combustion devices have been presented. Lean-premixed combustion instability occurs mainly due to equivalence ratio fluctuations which induce large heat release oscillations at lean conditions. Liquid-fueled combustion also shows high-frequency instability from energy coupling between pressure and heat release oscillations.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.2
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• pp.116-122
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• 2003

Pleomorphic adenoma is the most common salivary neoplasm mainly occurring in the major salivary glands - especially in parotid gland, which is characterized by variable histopathologic appearances and high recurrence rate with malignant transformation according to surgical situations. And this benign mixed tumor occurring in minor salivary glands is believed to shows same clinicopathologic appearances and relatively low recurrent rate compared with the case in major salivary glands. But there are few comparative studies of large series of pleomorphic adenoma occurring in minor salivary glands which includes different histopathologic appearance, clinical characteristics, treatment methods, recurrence rate, and malignant transformation. We retrospectively studied the 54 patients who were pathologically confirmed with pleomorphic adenoma occurring in minor salivary glands, and analyzed the clinico-histopathological appearance, surgical methods, recurrent cases. The results obtained are as follows. 1. The incidence of the tumor was most frequent in 4th & 5th decade, and in female. 2. Palate(90%) including hard & soft palate was the most frequent site for pleomorphic adenoma in minor salivary glands. 3. The exact duration could not be known due to asymptomatic slow growth patterns of the tumor. 4. The mean tumor size was 2.3cm. 5. 28 (52%) pleomorphic adenomas were classified as Cellular type (cell-rich), 17 (31%) specimen as Intermediate type(equal cell to stroma ratio), and 9 (17%) as Myxoid type(stroma-rich). 6. Surgically 51 cases (94%) were showed well-encapsulated tumors, but histopathologically only 34 specimen (63%) were wellencapsulated. Therefore pleomorphic adenomas in minor salivary glands also have to be excised more widely, not enucleated. And in case of suspicious malignancy or large tumor, preoperative incisional biopsy can be applied in the center of the tumor for prevention of rupture of tumor cell, and total excision with use of frozen biopsy for detection of malignancy and confirming the excision margin, and closed follow-up according to final histopathologic results is recommended.