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Lee, Hyunjun,Han, Manbae,Sohn, Jeongwon,Sunwoo, Myoungho American Society of Mechanical Engineers 2014 Journal of engineering for gas turbines and power Vol.136 No.11
<P>This paper presents a novel method to estimate an exhaust pressure at 357 different steady-state engine operating conditions using a diesel particulate filter (DPF) mass flow model to precisely control the air quantity for a light-duty diesel engine operated with dual-loop exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems. This model was implemented on a 32 bit real-time embedded system and evaluated through a processor-in-the-loop-simulation (PILS) at two transient engine operating conditions. And the proposed model was validated in a vehicle. By applying Darcy's law, the DPF mass flow model was developed and shows a root mean square error (RMSE) of 3.7 g/s in the wide range of the DPF mass flow and above 99% linear correlation with actual values. With such reasonable uncertainties of the DPF mass flow model, the exhaust pressure was estimated via the application of a nonlinear coordinate transformation to the VGT model. The DPF mass flow based exhaust pressure estimation exhibits below 6% error of the exhaust pressure under steady-state conditions. The method was also validated through the PILS and the vehicle test under transient conditions. The results show a reasonable accuracy within 10% error of the exhaust pressure.</P>
Hyunjun Kim,Sang Jun Suh,Ho-Jun Kang,이민석,Yoon-Soo Lee,Jeong-Ho Lee,Dong-Gee Kang 대한신경손상학회 2018 Korean Journal of Neurotrauma Vol.15 No.1
Objective: Patients with traumatic acute subdural hematoma (ASDH) often require surgical treatment. Among patients who primarily underwent craniotomy for the removal of hematoma, some consequently developed aggressive intracranialhypertension and brain edema, and required secondary decompressive craniectomy (DC). To avoid reoperation, we investigated factors which predict the requirement of DC by comparing groups of ASDH patients who did and did not requireDC after craniotomy. Methods: The 129 patients with ASDH who underwent craniotomy from September 2007 to September 2017 were reviewed. Among these patients, 19 patients who needed additional DC (group A) and 105 patients who underwent primarycraniotomy only without reoperation (group B) were evaluated. A total of 17 preoperative and intraoperative factors wereanalyzed and compared statistically. Univariate and multivariate analyses were used to compare these factors. Results: Five factors showed signifcant differences between the two groups. They were the length of midline shifting tomaximal subdural hematoma thickness ratio (magnetization transfer [MT] ratio) greater than 1 (p<0.001), coexistence of intraventricular hemorrhage (IVH) (p<0.001), traumatic intracerebral hemorrhage (TICH) (p=0.001), intraoperative fndingsshowing intracranial hypertension combined with brain edema (p<0.001), and bleeding tendency (p=0.02). An average valueof 2.74±1.52 was obtained for these factors for group A, which was signifcantly different from that for group B (p<0.001). Conclusion: An MT ratio >1, IVH, and TICH on preoperative brain computed tomography images, intraoperative signsof intracranial hypertension, brain edema, and bleeding tendency were identifed as factors indicating that DC would berequired. The necessity for preemptive DC must be carefully considered in patients with such risk factors Objective: Patients with traumatic acute subdural hematoma (ASDH) often require surgical treatment. Among patientswho primarily underwent craniotomy for the removal of hematoma, some consequently developed aggressive intracranialhypertension and brain edema, and required secondary decompressive craniectomy (DC). To avoid reoperation, we investigated factors which predict the requirement of DC by comparing groups of ASDH patients who did and did not requireDC after craniotomy. Methods: The 129 patients with ASDH who underwent craniotomy from September 2007 to September 2017 were reviewed. Among these patients, 19 patients who needed additional DC (group A) and 105 patients who underwent primarycraniotomy only without reoperation (group B) were evaluated. A total of 17 preoperative and intraoperative factors wereanalyzed and compared statistically. Univariate and multivariate analyses were used to compare these factors. Results: Five factors showed signifcant differences between the two groups. They were the length of midline shifting tomaximal subdural hematoma thickness ratio (magnetization transfer [MT] ratio) greater than 1 (p<0.001), coexistence of intraventricular hemorrhage (IVH) (p<0.001), traumatic intracerebral hemorrhage (TICH) (p=0.001), intraoperative fndingsshowing intracranial hypertension combined with brain edema (p<0.001), and bleeding tendency (p=0.02). An average valueof 2.74±1.52 was obtained for these factors for group A, which was signifcantly different from that for group B (p<0.001). Conclusion: An MT ratio >1, IVH, and TICH on preoperative brain computed tomography images, intraoperative signsof intracranial hypertension, brain edema, and bleeding tendency were identifed as factors indicating that DC would berequired. The necessity for preemptive DC must be carefully considered in patients with such risk factors
Lee, Hyunjun,Park, Yeongseop,Sunwoo, Myoungho Professional Engineering Publishing Ltd 2014 Proceedings of the Institution of Mechanical Engin Vol. No.
<P>Exhaust gas recirculation systems are used in diesel engines to reduce nitrogen oxide emissions. Since excessive recirculation in the cylinders may lead to an increase in generation of particulate matter and to unstable combustion, the exhaust gas recirculation rate should be measured correctly and should be controlled precisely. Unfortunately, the harsh conditions of the exhaust gas recirculation path make it difficult to measure the exhaust gas recirculation mass flow rate directly by using the relevant sensors. Therefore, precise control of the exhaust gas recirculation system depends on accurate estimation of the exhaust gas recirculation rate. To estimate accurately the exhaust gas recirculation rate in a turbocharged diesel engine, we propose an observer based on a model reference identification scheme. A linear parameter-varying model of the intake manifold pressure was derived to serve as the observer’s reference model. An update rule of the observer was designed with the model reference identification scheme. The intake and exhaust temperature models were developed through an empirical approach. Convergence of the proposed observer was proven in terms of the Lyapunov stability criterion. The proposed observer was implemented on a real-time embedded system and validated successfully through experiments on the engine.</P>
Lee Hyunjun,Hong Yong Tae 대한후두음성언어의학회 2023 대한후두음성언어의학회지 Vol.34 No.3
Amyloidosis is a idiopathic clinical syndrome caused by deposition of non-soluble protein fibers in the extracellular matrix of organs and tissues. It causes chronic inflammation and destruction of the architecture and functionality of the involved tissue. Amyloidosis occurring in the upper airway tract is rare, accounting for 0.2% to 1.2% of benign tumors of the larynx. In general, the purpose of treatment is reduce the risk of dysphagia and dyspnea. Endoscopic surgery is the mainstream of the treatment because laryngeal preserving is the most important goal of treatment. However, the disadvantage of this treatment is that it can lose voice and may require multiple reoperation. In this article, we report a case in which vertical partial laryngectomy (VPL) in a patient with laryngeal amyloidosis, because the patient want her voice restoration. It was observed that voice restoration and airway patency were maintained for two years without additional surgical treatment after the surgery. Although additional studies are needed, VPL can be a good option for patients who want to preserve their voice.
Development of Weeder Machine to Remove Furrow Weeds by Applying Circle Blade
( Hyunjune Lee ),( Subo Yang ),( Hwanggyu Lee ),( Hongmin Ahn ),( Jinhyun Kim ),( Taewook Kim ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
Removing the weeds from the furrow from the field crop cultivation should be carried out at an appropriate time. Most of the blade currently used in the flat shape and is not suitable for removing weeds from furrow. This research is to develop a weeder machine using a circle blade to efficiently remove weeds in the furrow. The geometric shape of the furrow was designed to develop the weeder machine. Circle blade shapes were based on the depth and width of the furrow from which the field crops were grown. Circle blade shapes were designed to fit the shape and size of the furrow so they would effectively remove weeds in the furrow. Weeder machine driving part is designed to drive a 300mm wheel using a differential gear on the engine’s power extraction device. And the auxiliary wheel was applied to the front of the weeder machine to adjust the height of weeder machine. In the weeding part, a designed by arranging two circle blades in pairs. Depending on the size of the furrow, the angle of placement for the circle blade was designed from 60 to 120 degrees.Power transmission is accomplished by distributing power to both sides using bevel gears. Blade rotation and driving tests were conducted. The optimum circle blades rotation speed of weeder machine drive speed were measured. As a result, it was judgement that the running speed of 4km/h was most suitable at the rotation speed of 3,000~4,000rpm.
Gold nanostar-mediated neural activity control using plasmonic photothermal effects
Lee, Jee Woong,Jung, Hyunjun,Cho, Hui Hun,Lee, Jung Heon,Nam, Yoonkey Elsevier 2018 Biomaterials Vol.153 No.-
<P><B>Abstract</B></P> <P>Nanomaterials have emerged as an essential tool for the understanding of cellular level mechanism in the fields of biology and medical science. Recently, researchers have been studying the regulation of neuronal activity using plasmonic nanoparticles and light, and it has been reported that photothermal effects could lead to both excitation and inhibition of neuronal cells. So far, only a few photothermal transducers have been applied to modulate neural activity. In this paper, we synthesized biocompatible gold nanostars (AuNSs) which generate heat by absorbing near-infrared (NIR) light. And we used the AuNS to inhibit the activity of neurons through light stimulation. We have demonstrated that AuNS inhibits the neural activity by NIR laser in both chip-attached mode and cell-attached mode. We also confirmed the suppression of single neuron signal by using digital micromirror device (DMD) set up. This approach is possible to inhibit the neural firing by controlling the intensity of light, and overcome the disadvantages of conventional electrochemical stimulation methods. This method of NIR-mediated stimulating neurons using light sensitive AuNS will be a powerful tool for neuromodulation researches and neuroscience studies.</P>