• Journal of Advanced Marine Engineering and Technology
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• 제19권2호
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• pp.20-26
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• 1995

The very rapid cooling problem from $820^{\circ}$C to $20^{\circ}$C on the surface of the steel by thermal conduction including the latent heat of phase transformation of steel and by transient boiling heat transfer of water are considered to principal problem in quenching. The transient boiling process of water at the surface of specimen during the quenching process were experimentally analyzed. Then the heat flux was numerically calculated by the numerical method of inverse heat condition problem. In this report, the simulation program to calculate the cooling curves for large rolls was made using the subcooled transient boiling curve as a boundary condition. By this simulation program, the cooling curves of rolls from D=50mm to D=200mm were calculated and the effects of agitation of circulation of water also investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.463-463
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• 2014

Multi-packet blade systems usually undergo multiple nozzle excitations during operation. For the design of multi-packet blade systems undergoing multiple nozzle excitations, transient characteristics around an operating frequency and resonance frequencies should be identified. In this study the equations of motion of multi-packet blade systems undergoes multiple nozzle excitations are derived. The reliability of the derived equations is verified by obtaining responses at resonance frequencies. Then, using the model, the effects of system parameters on the transient characteristics of the system are investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2235-2237
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• 2005

This paper presents the transient impedance behaviors of grounding systems to lightning impulse current. The potential rise and effective impulse ground impedance of the test grounding electrodes were measured as a function of the rise time of impulse currents and lengths of down conductor. The transient ground impedances strongly depend on the configuration and size of grounding electrodes, the impulse current shapes and lengths of down conductor, and the inductance of reduce of grounding electrode inductance is an important factor to improve the transient ground impedance.

• 생약학회지
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• 제34권4호통권135호
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• pp.335-338
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• 2003

It is thought that highly reactive oxygen species generated after strokes plays a key role in damaging the brain. We examined free radical scavenging activity and neuroprotective effects of several medicinal herbs in a rat model of transient ischemia. Free radical scavenging property of medicinal herbs was examined in vitro using 1,1-diphenyl-2-picrylhydrazyl stable free radical. Transient ischemia was induced by intraluminal occlusion of the right middle cerebral artery for 120 min, followed by reperfusion for 22 hr in rats. Aqueous extracts of 8 medicinal herbs (200 mg/kg) were orally administered twice to transient ischemic rat prior to reperfusion and 2 hr after reperfusion. Total infarction volume in the hemisphere ipsilateral to the ischemia-reperfusion was significantly decreased in 7 groups treated with Sophora flavescens, Lycopus lucidus, Sanguisorba officinalis, Caesalpinia sappan, Albizia julibrissin, Rubia akane, Psoralea corylifolia, or Prunella vulgaris. However, neuroprotective effects of these medicinal herbs were not correlated with their antioxidative activities. These results suggest that these medicinal herbs exert neuroprotection via antioxidative as well as unknown mechanism.

• 한국항행학회논문지
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• 제21권5호
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• pp.459-465
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• 2017

본 논문에서는 간접낙뢰로 인한 항공기 탑재 장비의 손상을 방지하기 위한 간접낙뢰 보호회로의 설계시 고려해야 하는 사항들을 설명한다. 낙뢰로부터 유도된 서지 전압은 항공기 전기 전자장비의 기능 장애나 손상을 가져오는데 이것을 낙뢰의 간접영향이라 한다. 이러한 항공기의 낙뢰 간접영향으로부터 항공전자 장비를 보호하기 위해서는 항공기에 가해진 낙뢰로 인한 영향성을 분석하고 이에 따른 보호 설계를 각각의 장비에 적용한다. 설계된 간접낙뢰 보호회로는 PCB와 TVS다이오드에 기생하는 인덕턴스로 인해 의도치 않은 결과를 가져올 수 있다. 본 논문에서는 간접낙뢰 보호회로를 구성하는 요소들에 기생하는 인덕턴스를 고려한 보호회로 설계 방법을 소개한다. 또한 설계된 보호회로의 유효성 확인을 위해 수행한 낙뢰 간접영향 검증시험 결과를 보인다.

• 대한기계학회논문집B
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• 제40권7호
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• pp.435-440
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• 2016

레이놀즈 수의 시간 증가율이 벽면난류 구조에 미치는 영향을 난류 채널유동에 대한 직접수치모사를 수행하여 조사하였다. 완전 발달된 $Re_{\tau}=180$의 난류 채널유동이 가속을 받게 되어 평균속도로 무차원화된 레이놀즈 수가 5600에서 13600까지 선형적으로 변화하게 된다. 다양한 가속 시간에 대한 계산을 수행하여 벽면난류에 대한 가속율의 효과를 파악하였다. 유량의 증가율이 큰 경우에는 우회 천이와 유사한 현상이 발견되었으며, 유량의 증가율이 낮은 경우에는 우회 천이 현상이 거의 나타나지 않았다. 본 연구 결과는 초기 레이놀즈 수와 최종 레이놀즈 수의 비 보다는 레이놀즈 수의 시간 증가율이 채널 내 과도유동에서의 우회 천이 현상 발생에 주요인자 임을 제시한다.

• The Korean Journal of Physiology and Pharmacology
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• 제16권5호
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• pp.343-348
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• 2012

Blocking or regulating $K^+$ channels is important for investigating neuronal functions in mammalian brains, because voltage-dependent $K^+$ channels (Kv channels) play roles to regulate membrane excitabilities for synaptic and somatic processings in neurons. Although a number of toxins and chemicals are useful to change gating properties of Kv channels, specific effects of each toxin on a particular Kv subunit have not been sufficiently demonstrated in neurons yet. In this study, we tested electro-physiologically if heteropodatoxin2 ($HpTX_2$), known as one of Kv4-specific toxins, might be effective on various $K^+$ outward currents in CA1 neurons of organotypic hippocampal slices of rats. Using a nucleated-patch technique and a pre-pulse protocol in voltage-clamp mode, total $K^+$ outward currents recorded in the soma of CA1 neurons were separated into two components, transient and sustained currents. The extracellular application of $HpTX_2$ weakly but significantly reduced transient currents. However, when $HpTX_2$ was added to internal solution, the significant reduction of amplitudes were observed in sustained currents but not in transient currents. This indicates the non-specificity of $HpTX_2$ effects on Kv4 family. Compared with the effect of cytosolic 4-AP to block transient currents, it is possible that cytosolic $HpTX_2$ is pharmacologically specific to sustained currents in CA1 neurons. These results suggest that distinctive actions of $HpTX_2$ inside and outside of neurons are very efficient to selectively reduce specific $K^+$ outward currents.

• Korean Journal of Acupuncture
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• 제21권1호
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• pp.15-27
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• 2004

Objectives : Acupuncture has been used to prevent and treat the cerebrovascular accident, such as a stroke, and many studies of acupuncture and moxibustion concerning to the stroke have been undertaken in the human and various animals. Also, herbal acupuncture, namely aqua acupuncture has been applied and developed to various diseases including the cerebrovascular accident. FOLIUM ARTEMISIAE ARGYI is the dry leaf of Artemisia argyi Levl. et Vant. collected in summer before the plant blooms and used to moxibustion and has been recommended for use as an analgesic and hemostatic. In this study, effects of FOLIUM ARTEMISIAE ARGYI (艾葉)' herbal acupuncture on the $LR_3$, namely Taechung on neuroprotection after the transient forebrain ischemia were investigated in Sprague-Dawely rats. Methods : Expressions of neuronal nitric oxide synthase (nNOS) protein in the hippocampus and cortex were observed at 2 hrs after transient forebrain ischemia by immunohistochemistry. Results : Expression of nNOS protein was increased in the hippocampus and cortex at 2 hrs after transient forebrain ischemia. However, pretreatment with FOLIUM ARTEMISIAE ARGYI' herbal acupuncture on $LR_3$ significantly decreased expression of nNOS protein protein compared to ischemia group. These features were observed in the motor cortex and the hippocampus. Conclusions : These results suggest that pretreatment with FOLIUM ARTEMISIAE ARGYI' herbal acupuncture on $LR_3$ inhibits the expression of nNOS protein induced by transient forebrain ischemia and may modulate excitatory toxicity of neuron related to neuronal cell death.

• The Korean Journal of Physiology and Pharmacology
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• 제26권1호
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• pp.47-57
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• 2022

Stiripentol is an anti-epileptic drug for the treating of refractory status epilepticus. It has been reported that stiripentol can attenuate seizure severity and reduce seizure-induced neuronal damage in animal models of epilepsy. The objective of the present study was to investigate effects of post-treatment with stiripentol on cognitive deficit and neuronal damage in the cornu ammonis 1 (CA1) region of the hippocampus proper following transient ischemia in the forebrain of gerbils. To evaluate ischemia-induced cognitive impairments, passive avoidance test and 8-arm radial maze test were performed. It was found that post-treatment with stiripentol at 20 mg/kg, but not 10 or 15 mg/kg, reduced ischemia-induced memory impairment. Transient ischemia-induced neuronal death in the CA1 region was also significantly attenuated only by 20 mg/kg stiripentol treatment after transient ischemia. In addition, 20 mg/kg stiripentol treatment significantly decreased ischemia-induced astrocyte damage and immunoglobulin G leakage. In brief, stiripentol treatment after transient ischemia ameliorated transient ischemia-induced cognitive impairment in gerbils, showing that pyramidal neurons were protected and astrocyte damage and blood brain barrier leakage were significantly attenuated in the hippocampus. Results of this study suggest stiripentol can be developed as a candidate of therapeutic drug for ischemic stroke.

• 대한한의학회지
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• 제24권2호
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• pp.66-80
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• 2003

Objectives : Recently, herbal acupuncture has been developed in the Korea since the earlier 1960' applied to various diseases including the cerebrovascular accident. The main characteristics of herbal acupuncture are a combination the merit of acupuncture and herbal medicine. It was not well known the therapeutic effect and the mechanism of herbal acupuncture on transient forebrain ischemic injury, although it has been used frequently in clinics. Ramulus Uncariae Cum Uncis (釣鉤藤) has been claimed to possess sedative, anti-spasmodic actions, and treat childhood epilepsy in oriental medical preparation. Also, it has been stated that Ramulus Uncariae Cum Uncis was antioxidatvie effect and neuroprotection against glutamateinduced neuronal death. Methods : In this study, effects of Ramulus Uncariae Cum Uncis' herbal acupuncture on the $GV_{20}{\;}or{\;}LR_3$, named Baek-hue or Tae-chung, on neuroprotection after the transient forebrain ischemia were investigated in Sprague-Dawely rats. Expressions of cFos, FosB and BDNF protein in the hippocampus and cortex were observed at 2 hrs and 48 hrs after transient forebrain ischemia by immunohistochemistry and ELISA technique. Results : Expression of cFos protein was increased slightly in the hippocampus and cortex at 2 hrs after transient forebrain ischemia, but FosB protein was increased highly comparing to cFos protein. However, pretreatment with Ramulus Uncariae Cum Uncis' herbal acupuncture on $GV_{20}{\;}or{\;}LR_3$ significantly increased expression of cFos protein and significantly decreased expression of FosB protein compared to control group, respectively. These features were observed in the motor cortex and retrosplenial granular cortex as well as the hippocampus. Especially, cFos expression was more increased at the herbal acupuncture on $GV_{20}{\;}than{\;}LR_3$, but FosB expression was more decreased in $LR_3$ group than $GV_{20}$ group. Also, pretreatment with Ramulus Uncariae Cum Uncis' herbal acupuncture on $GV_{20}{\;}or{\;}LR_3$ significantly increased the expression of BDNF protein in the hippocampus ($254.88{\pm}12{\;}pg/ml{\;}in{\;}GV_{20}$ group, $245.93{\pm}44.4{\;}pg/ml{\;}in{\;}LR_3$ group) and the cortex ($85.81{\pm}3.45{\;}pg/ml{\;}in{\;}GV_{20}$ group, $111.51{\pm}15.79{\;}pg/ml{\;}in{\;}LR_3$, group) compared to the hippocampus ($134.07{\pm}2.96{\;}pg/ml$) and the cortex ($61.16{\pm}4.11{\;}pg/ml$) in control group at 48 hrs after transient forebrain ischemia. Conclusion : These results suggest that pretreatment with Ramulus Uncariae Cum Uncis' herbal acupuncture on $GV_{20}{\;}or{\;}LR_3$ has neuroprotective effect on transient forebrain ischemia and the herbal acupunture on $GV_{20}{\;}or{\;}LR_3$ may be related to antioxidative effect and calcium channel block of Ramulus Uncariae Cum Uncis. Also, it could be mentioned there is specificity of acupoints treating ischemic injury through the difference between the herbal acupuncture of $GV_{20}{\;}and{\;}LR_3$.