• Journal of ILASS-Korea
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• v.27 no.2
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• pp.101-108
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• 2022

Performance and emissions with different diesel injection methods were analyzed in a natural gas-diesel, dual-fuel engine under low-load conditions. Natural gas was supplied to intake port during the intake stoke to form a natural gas-air premixed mixture for all methods. Diesel was injected directly into the cylinder during the compression stroke in three ways: early injections, late injections, and a combination of early and late injections. The early injections had the highest thermal efficiency among the three methods owing to its highest combustion efficiency. The wide dispersion of diesel before the combustion initiation also allowed superior emissions characteristics.

• Biomedical Science Letters
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• v.15 no.1
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• pp.17-23
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• 2009

The prevalence of patent foramen ovale (PFO) in healthy persons was estimated as about $10{\sim}25%$ and was up to 40% in patients with stroke. Transesophageal echocardiography (TEE) was considered to be the most sensitive method to detect PFO and was used as the gold standard. Transcranial doppler sonography (TCD) of the middle cerebral artery (MCA) during a contrast (saline bubble) injection has recently been proposed as an alternative detecting method for PFO. In this study, we would like to know the difference between TCD value and TEE value in subjects with cryptogenic ischemic stroke. We performed TCD and TEE tests to detect PFO on 64 patients (30 women and 34 men, mean age was 59.4 years) with cryptogenic ischemic stroke. PFO prevalence through TCD was 45.3% (29 of 64 patients) and the prevalence through TEE was 34.4% (22 of 64 patients). There was no statistical significance between PFO test and TCD test (P=0.206). But TCD had a sensitivity of 90.9% (20 of 22 patients), specificity of 78.6% (33 of 42 patients), positive predictive value of 69.0% (20 of 29 patients), and negative predictive value of 94.3% (33 of 35 patients). We concluded that TCD was a highly sensitive method for detecting a right-left shunt. Therefore, the non-invasive TCD test is a method more effective than the anti-invasive TEE test in the cost and evaluation of the existence or nonexistence of right to left shunt in addition to the screening method of the cerebrovascular disorder. Considering these points, TCD test could be recommended for patients with cryptogenic ischemic stroke as a useful and convenient method for screening of the existence or nonexistence of a right to left shunt caused by PFO.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.32-38
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• 2004

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC $180^{\circ}C$, fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC $90{\circ}C$ and $60^{\circ}C$, fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.121-126
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• 2006

A gasoline-fueled stratified charge compression ignition (SCCI) engine with both direct fuel injection and intake temperature and compression ratio was examined. The fuel was injected directly by using the high temperature resulting from heating intake port. With this injection strategy, the SCCI combustion region was expanded dramatically without any increase in NOx emissions which were seen in the case of compression stroke injection. Injection timing during the intake temperature was found to be an important parameter that affects the SCCI region width. The effect of mixture stratification and the effect of fuel reformation can be utilized to reduce the required intake temperature for suitable SCCI combustion under each set of engine speed and compression ratio conditions.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.1-7
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• 2010

As world attention has focused on global warming and air pollution, high efficiency diesel engines with low $CO_2$ emissions have become more attractive. Premixed diesel engines in particular have the potential to achieve the more homogeneous mixture in the cylinder which results in lower NOx and soot emission. Early studies have shown that the operation conditions such as the EGR, intake conditions, injection conditions and compression ratio are important to reduce emissions in a PCCI (Premixed Charge Compression Ignition) engine. In this study a modified cam was employed to reduce the effective compression ratio. While opening timing of the intake valve was fixed, closing timing of the intake valve was retarded $30^{\circ}$. Although Atkinson cycle with the retarded cam leads to a low in-cylinder pressure in the compression stroke, the engine work can still be increased by advanced injection timing. On that account, we investigated the effects of various injection parameters to reduce emission and fuel consumption; as a result, lower NOx emission levels and almost same levels of fuel consumption and PM compared with those of conventional diesel engine cam timing could be achieved with the LIVC system.

• The Journal of Korean Medicine
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• v.28 no.1 s.69
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• pp.87-93
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• 2007

Objectives : This study was to assess the effectiveness of Oriental medical treatment on carpal tunnel syndrome, comparing its outcome with that of Western medical treatment. Methods : After being diagnosed with carpal tunnel syndrome by electromyography, subjects were enrolled in Kyung Hee Medical Center from March 2006 to January 2007. We prescribed Kejibokryung-hwan to the Oriental medical therapy group (OM group) and NSAIDS to the Western medical therapy group (WM group). Effectiveness was assessed by degree of pain using visual analog scale (VAS) before and after 3 weeks' treatment. Adverse effects were also monitored. Results : There were 21 patients in the OM group and 19 in the WM group. No statistical significant difference was detected at the baseline assessment. After 3 weeks of medication, pain was reduced about 26% in the OM group and 46% in the WM group. These findings might be explained by that more than half of the WM group received local steroid injection, which has been known to have more rapid analgesic effect that oral medication. Although pain reduction rate was higher in the WM group than in the OM group, we suggest that Oriental medical treatment is still effective, faking into consideration the fact that completely recovered cases were found only in the OM group. No adverse effect was found in either of the groups. Conclusion : This work could help us to understand the effectiveness of Oriental medical treatment on carpal tunnel syndrome.

• The Journal of the Society of Stroke on Korean Medicine
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• v.21 no.1
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• pp.11-20
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• 2020

■ Objectives The purpose of this study is to report on a case that showed improvement in type 2 diabetic patients by using herbal medicine, Yeoldahansotang-gami. ■ Methods Yeoldahansotang-gami was given to patients with type 2 diabetes for 71days. To evaluate the effect, blood glucose was measured 4 times a day. As measured blood sugar, the frequency of hyperglycemia, changes in fasting blood sugar, changes in postprandial blood sugar, and changes in glucose variability were analyzed. The patient's insulin injection dose change was observed, and HbA1c and glycated albumin were measured. Follow-up was performed for 7 months to observe whether the treatment effect was maintained. ■ Results During treatment, the patient's blood sugar control, glucose variability, and HbA1c were improved, and insulin injection dose was gradually reduced and stopped. HbA1c and glycated albumin levels maintained improvement without insulin injection during the follow-up period. ■ Conclusion This study showed the effect of yeoldahansotang-gami on type 2 diabetes patient.

• Investigative Magnetic Resonance Imaging
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• v.6 no.2
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• pp.158-165
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• 2002

Purpose : To evaluate the effect of Gd-DTPA on signal intensity of diffusion-weighted magnetic resonance(MR) image and apparent diffuse coefficient (ADC) in dog brain with hype racute stroke. Materials and methods : Experimental canine model of hyperacute cerebral infarction was made by selective intraarterial embolization with particulate embolic material. Diffusion-weighted MR imaging was performed in five dogs at 1 hour after the embolization of internal carotid artery. After intravenous bolus injection of Gd- DTPA, additional 11 diffusion-weighted MR images were serially obtained from 2 minutes to 90 minutes after injection in each dog. The author evaluated findings of hyperacute cerebral infarction on diffusion-weighted MR imaging, and calculated mean signal intensity and mean ADC in infarcted region and contralateral normal region. Statistical analysis of mean signal intensity, mean ADC and contrast-noise ratio before and after Gd-DTPA injection was performed. Results : Hyperacute cerebral infarction developed in all five dogs on diffusion-weighted MR images obtained 1 hour after embolization. The area of hyperacute infarction had steady increase in signal intensity on diffusion-weighted MR image and decrease in ADC. In normal perfusion area, decrease in signal intensity was observed at 2 minutes the Gd-DTPA injection, whereas ADC did not changed. Conclusion : Intravenous injection of Gd-DTPA had no influence on ADC in both hyperacute infarction and normally perfused are a, but caused initial transient signal reduction in normally perfused area on diffusion-weighted MR image due to susceptibility effect of Gd-DTPA. It is important to calculate ADC in evaluating the effect of diffusion after injection of Gd-DTPA.

• Biomolecules & Therapeutics
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• v.28 no.2
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• pp.152-162
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• 2020

Cerebral ischemia exhibits a multiplicity of pathophysiological mechanisms. During ischemic stroke, the reactive oxygen species (ROS) concentration rises to a peak during reperfusion, possibly underlying neuronal death. Recombinant human erythropoietin (EPO) supplementation is one method of treating neurodegenerative disease by reducing the generation of ROS. We investigated the therapeutic effect of PEGylated EPO (P-EPO) on ischemic stroke. Mice were administered P-EPO (5,000 U/kg) via intravenous injection, and middle cerebral artery occlusion (MCAO) followed by reperfusion was performed to induce in vivo ischemic stroke. P-EPO ameliorated MCAO-induced neurological deficit and reduced behavioral disorder and the infarct area. Moreover, lipid peroxidation, expression of inflammatory proteins (cyclooxygenase-2 and inducible nitric oxide synthase), and cytokine levels in blood were reduced by the P-EPO treatment. In addition, higher activation of nuclear factor kappa B (NF-κB) was found in the brain after MCAO, but NF-κB activation was reduced in the P-EPO-injected group. Treatment with the NF-κB inhibitor PS-1145 (5 mg/kg) abolished the P-EPO-induced reduction of infarct volume, neuronal death, neuroinflammation, and oxidative stress. Moreover, P-EPO was more effective than EPO (5,000 U/kg) and similar to a tissue plasminogen activator (10 mg/kg). An in vitro study revealed that P-EPO (25, 50, and 100 U/mL) treatment protected against rotenone (100 nM)-induced neuronal loss, neuroinflammation, oxidative stress, and NF-κB activity. These results indicate that the administration of P-EPO exerted neuroprotective effects on cerebral ischemia damage through anti-oxidant and anti-inflammatory properties by inhibiting NF-κB activation.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.551-558
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• 2004

Recently, fuel prices have been continually raised in diesel engine. Such a change in the fuel price influences enormously the development trend of marine diesel engines for slow speed, In other words, the focus was shifted from large diameter and high speed to low fuel consumption. Accordingly, more efforts are being made for engine manufacturing and development to develop highly efficient engines. In this study. a single cylinder 4 stroke cycle DI slow speed diesel engine was designed and manufactured, a 4 stroke cycle was configured and basic performances were evaluated. The results are as follows. The optimal fuel injection timing had the lowest value when specific fuel consumption was in BTDC 8~$10^{\circ}$, a little more delayed compared to high speed diesel engines. Cycle variation of engines showed about 5% difference at full loads. This is a significantly small value compared to the cycle variation in which stable operation is possible, showing the high stability of engine operation is good. The torque and brake thermal efficiency of engine increased with an increase of engine 250-450 rpm. but fuel consumption ratio increased from the 450 rpm zone and thermal efficiency abruptly decreased. Mechanical efficiency was maximally 70% at a 400 rpm that was lower than normal engines according to the increase of mechanical frictional loss for cross head part. The purpose of this study was to get more practical engines by comparing the above results with those of slow speed 2 stroke cycle diesel engines.